Method for producing powder polyamide

Abstract

A method for producing a powdered polyamide according to the present invention comprises: a step 1 in which a polyamide resin composition is heated and dissolved in a metal chloride alcoholic solution containing a metal chloride and an alcohol to obtain a heated polyamide-dissolved solution; a step 2 in which the polyamide heated solution is diluted with an alcohol to obtain an alcohol diluent; and a step 3 in which the alcohol diluent is cooled and the polyamide powder is precipitated. In the step 1, the mass ratio of the metal chloride is 23-35% by mass (inclusive) with respect to 100% by mass of the metal chloride alcoholic solution, and in the step 2, the polyamide heat-dissolved solution contains 0.2-2.5 moles of water with respect to 1 mole of the metal chloride, and in the step 3, the polyamide heat-dissolved solution contains 0.1-2 moles of water with respect to 1 mole of the metal chloride. The polyamide is diluted under the condition that the temperature of the heating solution of the polyamide is not lower than 50 DEG C.

Description

Technical Field

[0001] The present invention relates to a method for producing powdered polyamide.

[0002] In particular, the present invention (I) relates to a method for producing a powdered polyamide. Preferably, it relates to a method for producing a powdered polyamide in which the amount of waste liquid and the energy used are reduced. The present invention (II) relates to a method for producing a recycled polyamide in which the amount of waste liquid is reduced. The present invention (III) relates to a method for producing a recycled polyamide. More specifically, it relates to a method for producing a recycled polyamide using a polyamide base cloth coated with silicone or the like as a raw material. The present invention (IV) relates to a methanol composition that has low metal corrosion and can be used as a solvent with high solubility for polyamide, a method for producing a polyamide composition using the methanol composition, a polyamide composition, and a powder. The present invention (V) relates to a method for producing polyamide. The present invention (VI) relates to a method for producing polyamide, a method for producing polyethylene terephthalate, and a method for producing polyamide and polyethylene terephthalate. The present invention (VII) relates to a method for producing a recycled polyamide. More specifically, it relates to a method for producing a recycled polyamide using a polyamide base cloth coated with urethane or the like as a raw material. Background Art

[0003] Regarding the present invention (I), polyamides represented by nylon 6 and nylon 66, which are representative engineering plastics, have heat resistance and good mechanical properties and are widely used in fibers, automobile parts, electrical product parts, etc., and are one of the irreplaceable materials in modern society.

[0004] In recent years, with the goal of resource conservation and carbon neutrality, technological development for plastic recycling has been carried out, and polyamide is no exception.

[0005] Recycling can be roughly divided into: what is called material recycling, in which a primary molded product is made into pellets again; and what is called chemical recycling, in which monomers are reused by depolymerization. In material recycling, there is a concern about unstable quality due to the deterioration of the polymer contained in the molded product or the residual additives in the recycled polymer. However, since it does not involve chemical reactions and requires few by-products, the resources and energy invested are very small, so material recycling can be selected in cases where the purpose is fixed and the recycling is carried out. In addition, even before chemical recycling is implemented, when additives, coatings, etc. are removed from processed and used polyamides recovered from factories and markets, the process of recovering clean polyamides is also required in the same way as material recycling, so material recycling technology is also a useful technology for chemical recycling.

[0006] In addition, various properties are required for the particles of the obtained polyamide depending on the application. For example, the following examples can be cited: in order to prevent the powder from scattering during handling, a large particle size is preferred; from the perspective of processability and mixing of additives, particles with a small and uniform particle size distribution are preferred; and technologies for controlling these are also being sought.

[0007] In addition, regarding the present invention (II), polyamides represented by nylon 6 and nylon 66, which are representative engineering plastics, have heat resistance and good mechanical properties and are widely used in fibers, automobile parts, electrical product parts, etc., and are one of the irreplaceable materials in modern society.

[0008] In recent years, with the goal of resource conservation and carbon neutrality, technological development for plastic recycling has been carried out, and polyamide is no exception.

[0009] Recycling methods can be roughly divided into: what is called material recycling, in which a primary molded product is made into pellets again; and what is called chemical recycling, in which a polymer is depolymerized and the resulting monomer is reused. In material recycling, there is a concern about unstable quality due to the deterioration of the polymer contained in the molded product and the presence of additives directly in the recycled polymer. On the other hand, since it is not accompanied by a chemical reaction and requires very few by-products, it has the advantage of being able to suppress the resources and energy invested. Therefore, material recycling can be selected in cases where the purpose is fixed and the cycle is carried out. In addition, even before chemical recycling is implemented, in order to remove additives, coatings, etc. from processed and / or used polyamide molded products recovered from factories or markets, the process of recovering clean polyamide is also required in the same way as material recycling, so material recycling technology is also a useful technology for chemical recycling.

[0010] As a physical method for removing impurities from used polyamide molded products to make them clean, there can be cited a method of crushing the recycled molded products and then performing gravity separation (Patent Document 1). This method can be separated with less energy, but it is difficult to separate when the polyamide and the impurities are firmly combined together by, for example, mixing, joining and / or bonding. There is also a method of dissolving and removing part or all of the unnecessary impurities with a solvent. However, the inclusions are usually added or coated on the polyamide, and part or all of them are present inside the structure of the polyamide, and it is difficult to use a solvent to completely dissolve the inclusions and separate them from the polyamide structure.

[0011] As another method, the following method can also be used: the polyamide in the molded product is dissolved with a solvent, and after the inclusions as insolubles are removed, the polyamide is precipitated and recovered by some method. However, the solvents that can dissolve polyamide are strong acids such as formic acid and sulfuric acid, and expensive solvents such as HFIP, etc., which are mostly not suitable for industrial use. As an example of the use of solvents suitable for industrial use, there is a dissolution recovery method based on ethylene glycol (Patent Document 2). However, this method requires a very high temperature reaction, so there is a concern that the polyamide will produce glycolysis, and it is necessary to distill and dry the used solvent from the sorbet-like solid, so a large amount of energy is required together with the heating during the reaction. Therefore, as a method that can be implemented at low temperature using general raw materials, there is also a dissolution method based on an alcohol calcium chloride solution. For example, a proposal has been made for the following method: a cloth-like polyamide molded product coated with silicone is treated with a methanol solution of calcium chloride, and after the polyamide is dissolved, it is diluted with a large amount of water or methanol to obtain the target polyamide in the form of a powder (Patent Document 3).

[0012] In addition, regarding the present invention (III), polyamides represented by nylon 6 and nylon 66, which are representative engineering plastics, have heat resistance and good mechanical properties and are widely used in fibers, automobile parts, electrical product parts, etc., and are one of the irreplaceable materials in modern society. Among them, nylon 66 is particularly important for applications requiring heat resistance and durability in harsh environments.

[0013] In recent years, with the goal of resource conservation and carbon neutrality, technological development for plastic recycling has been carried out, and polyamide is no exception.

[0014] Recycling can be roughly divided into: what is called material recycling, in which a primary molded product is made into pellets again; and what is called chemical recycling, in which monomers are reused by depolymerization. In material recycling, there is a concern about unstable quality due to the deterioration of the polymer contained in the molded product or the residual additives in the recycled polymer. However, since it does not involve chemical reactions and requires few by-products, the resources and energy invested are very small, so material recycling can be selected in cases where the purpose is fixed and the recycling is carried out. In addition, even before chemical recycling is implemented, when additives, coatings, etc. are removed from processed and used polyamides recovered from factories and markets, the process of recovering clean polyamides is also required in the same way as material recycling, so material recycling technology is also a useful technology for chemical recycling.

[0015] As mentioned above, since there are various inclusions in the processed and used polyamide, it is necessary to change the recycling method according to the purpose. The uses of polyamide are diversified. As one of the uses of nylon 66, automotive use requiring high safety can be cited. For example, it is used for parts around the engine that require high heat resistance, and the base fabric of the airbag that requires durability when broken. Among them, the use that deteriorates less and is suitable for material reuse is the base fabric of the airbag. Not only the used airbags can be reused, but also the scraps generated when cutting parts during the manufacture and sewing of the base fabric for the airbag can be reused.

[0016] Generally, the base fabric of the airbag uses a material obtained by coating a woven fabric obtained by spinning and weaving nylon 66 with a silicone resin. Therefore, in order to recycle the material of the airbag base fabric, the coating material needs to be separated from nylon 66.

[0017] In addition, regarding the present invention (IV), polyamides represented by polyamide 6 and polyamide 66, which are representative engineering plastics, have heat resistance and good mechanical properties, and are widely used in fibers, automobile parts, electrical product parts, etc., and are one of the irreplaceable materials in modern society.

[0018] In recent years, the development of plastic recycling technology has been carried out for the purpose of resource conservation and carbon neutrality, and polyamide is no exception. In particular, polyamide 66 (polyhexamethylene adipamide), which is one of the polyamides, has a large production volume and is one of the polyamides that should be prioritized for recycling.

[0019] Recycling can be roughly divided into: what is called material recycling, in which a primary molded product is made into pellets again; and what is called chemical recycling, in which monomers are reused by depolymerization. In material recycling, there is a concern about unstable quality due to the deterioration of the polymer contained in the molded product or the residual additives in the recycled polymer. However, since it does not involve chemical reactions and requires few by-products, the resources and energy invested are very small, so material recycling can be selected in cases where the purpose is fixed and the recycling is carried out. In addition, even before chemical recycling is implemented, when additives, coatings, etc. are removed from processed and used polyamides recovered from factories and markets, the process of recovering clean polyamides is also required in the same way as material recycling, so material recycling technology is also a useful technology for chemical recycling.

[0020] As a physical method for removing impurities from used polyamide to make it clean, there can be cited a method of crushing the recyclables and then performing gravity separation (Patent Document 1). This method can be separated with less energy, but it is difficult to separate in the case where the polyamide and the inclusions are firmly combined by, for example, mixing, joining and / or bonding, such as the coating of the airbag. There is also a method of dissolving and removing part or all of the unnecessary inclusions with a solvent. However, inclusions are usually added or coated on the polyamide, and part or all of them are present inside the structure of the polyamide, making it difficult to completely dissolve the inclusions.

[0021] As another method, it is known that the following method can also be used: dissolve the polyamide with a solvent at one time, remove the inclusions in the form of insoluble matter, and then precipitate the polyamide in a certain way and recover it. However, the solvent for dissolving polyamide is a highly corrosive strong acid such as formic acid and sulfuric acid or a solvent with low availability such as HFIP, which is not suitable as a solvent for industrial use. As an example of the use of a solvent that is easy to use in industry, there is a dissolution recovery method based on ethylene glycol (patent document 2). However, this method requires a very high temperature reaction, so there is a concern that the polyamide will produce glycolysis, and it is necessary to distill and dry the used solvent from the sorbet-like solid, so a large amount of energy is required together with the heating during the reaction. Therefore, as a method using low-temperature and universal raw materials, there is also a dissolution method based on an alcohol solution of metal chlorides such as calcium chloride. For example, the following method is recorded in Patent Document 3: a cloth coated with polyamide coated with silicone is treated with a methanol solution of calcium chloride to dissolve the polyamide, dilute it with a large amount of water or methanol, and obtain the target polyamide in the form of a powder.

[0022] This method is considered to be very useful as a method for recovering polyamide, but the corrosiveness of the calcium chloride methanol solution is very high, and general metals such as carbon steel, stainless steel such as SUS304 and SUS316 are easily corroded. Therefore, it cannot be used as a material for polyamide dissolution equipment using calcium chloride methanol solution, and it is necessary to use a nickel alloy with high chlorine corrosion resistance, such as ALLOY C276, or a device that has been treated with non-metallic glass lining, rubber lining, fluorine lining, etc. From the perspective of availability and processability as a material, it is necessary to use a general material.

[0023] In addition, regarding the present invention (V), polyamide resins have excellent properties and are therefore used in the manufacture of various machines and parts such as automobiles, machinery, and electrical and electronic parts. Among them, polyamide resins are particularly excellent in mechanical properties and wear resistance, and are therefore widely used as molding materials for sliding parts such as gears, cams, and bearings.

[0024] In recent years, with the goal of resource conservation and carbon neutrality, technological development for plastic recycling has been carried out, and polyamide is no exception.

[0025] Recycling can be roughly divided into two types: recycling called material recycling, which is recycling of a primary molded product into pellets again; and recycling called chemical recycling, which is recycling of monomers by depolymerization.

[0026] In material recycling, there is a concern that the quality may be unstable due to deteriorated polymers contained in molded products or additives remaining in the recycled polymers. However, since it does not involve chemical reactions and requires few by-products, the input of resources and energy is very small. Therefore, material recycling can be selected when the purpose is fixed and the recycling is carried out.

[0027] In addition, even before chemical recycling is implemented, when additives, coatings, etc. are removed from processed, used polyamide-containing materials recovered from factories and markets, the process of recovering clean polyamide is also required in the same way as material recycling. Therefore, material recycling technology is also a useful technology for chemical recycling.

[0028] For example, the following examples can be cited: in order to prevent the powder from scattering during handling, a large particle size is preferred; from the perspective of processability and mixing of additives, particles with a small and uniform particle size distribution are preferred; and technologies for controlling these are being sought.

[0029] For example, as a physical method for removing impurities from used polyamide to make it clean, there is a method that dissolves the polyamide in a solvent at once, removes the impurities as insoluble matter, and then precipitates the polyamide by some method to recover it. However, the solvent for dissolving polyamide is a strong acid such as formic acid and sulfuric acid or an expensive solvent such as HFIP, which is often not suitable as a solvent for industrial use.

[0030] As an example of a solvent that is easy to use industrially, a dissolution recovery method based on ethylene glycol can be cited (Patent Document 2). However, the recovery method of Patent Document 2 requires a very high temperature reaction, so there is a concern that polyamide will undergo glycolysis, and the solvent used must be completely distilled off from the sorbet-like solid and dried, so a large amount of energy is required together with the heating during the reaction.

[0031] Therefore, as a method using low-temperature and universal raw materials, there is also a dissolution method based on an alcohol calcium chloride solution. For example, Patent Document 3 discloses the following method: a cloth coated with polyamide of organic silicon is treated with a methanol solution of calcium chloride to dissolve the polyamide, and the polyamide is diluted with a large amount of water or methanol to obtain the target polyamide in the form of powder.

[0032] However, although powdered polyamide can be obtained by the method of Patent Document 3, when diluted with a large amount of solvent, the precipitation rate changes due to the change in the dilution rate over time, so the particle size distribution becomes wider. On the contrary, the method of adding a polyamide solution to a large amount of solvent is expected to reduce the particle size distribution, but if the dilution rate is increased to the extent that the composition change can be ignored, the required solvent will increase, which has the problem of heavy economic and environmental loads.

[0033] As a method for controlling precipitation without increasing the dilution rate, there can be mentioned a recrystallization method described in Patent Document 4, in which the solution is diluted with an aqueous methanol solution in a heated state and then cooled to precipitate.

[0034] However, the technology of Patent Document 4 studies the conditions for obtaining porous powders, but does not describe the crystallization conditions for obtaining good powders and the change in particle size distribution due to the crystallization, and the optimal conditions are unclear.

[0035] In addition, regarding the present invention (VI), polyamide resins and polyethylene terephthalate resins have excellent properties and are therefore used in the manufacture of various machines and parts such as automobiles, machinery, and electrical and electronic parts. Among them, polyamide resins are particularly excellent in mechanical properties and wear resistance and are therefore widely used as molding materials for sliding parts such as gears, cams, and bearings.

[0036] In recent years, with the goal of resource conservation and carbon neutrality, technology development for plastic recycling has been carried out, and polyamide and polyethylene terephthalate are no exception.

[0037] Recycling can be roughly divided into two types: material recycling, which is the process of remaking a primary molded product into pellets; and chemical recycling, which is the process of reusing monomers by depolymerization.

[0038] In material recycling, there is a concern that the quality may be unstable due to deteriorated polymers contained in molded products or additives remaining in the recycled polymers. However, since it does not involve chemical reactions and requires few by-products, the input of resources and energy is very small. Therefore, material recycling can be selected when the purpose is fixed and the recycling is carried out.

[0039] In addition, even before chemical recycling is implemented, when additives, coatings, etc. are removed from processed, used polyamide-containing materials recovered from factories and markets, the process of recovering clean polyamide is also required in the same way as material recycling. Therefore, material recycling technology is also a useful technology for chemical recycling.

[0040] As mentioned above, since there are various inclusions in the processed and used polyamide, it is necessary to change the recycling method according to the purpose. The uses of polyamide are diversified. As one of the uses of nylon 66, automotive use requiring high safety can be cited. For example, it is used for parts around the engine that require high heat resistance, and the base fabric of the airbag that requires durability when broken. Among them, the use that deteriorates less and is suitable for material reuse is the base fabric of the airbag. Not only the used airbags can be reused, but also the scraps generated when cutting parts during the manufacture and sewing of the base fabric for the airbag can be reused.

[0041] Generally, a woven fabric obtained by spinning nylon 66 and polyethylene terephthalate and knitting the two materials individually or by partially mixing and knitting the two materials is used as a base fabric of an airbag.

[0042] Therefore, in order to recycle the airbag base fabric, it is necessary to separate the polyamide and the polyethylene terephthalate.

[0043] Here, as a physical method for removing foreign materials from polyamide containing foreign materials to make it clean, there is a method of crushing a recyclate and then performing gravity separation (Patent Document 1).

[0044] This method can separate with less energy, but is difficult to separate in the case of an airbag base fabric in which polyamide and inclusions are firmly bonded together by mixing, joining, bonding, etc.

[0045] There is also a method of dissolving and removing part or all of unnecessary inclusions such as silicone with a solvent (for example, Patent Document 6).

[0046] However, since silicone is infiltrated into the fibers of polyamide, silicone resin will remain in the recycled polyamide. In addition, the recycled polyamide is recycled in the form of broken cloth. Used airbags and scraps from manufacturing are in various shapes, and it is difficult to directly reuse them in their original shapes or in shapes such as fiber scraps obtained by cutting them. In addition, even if they are melted and reused, they are not suitable as a shape for loading into an extruder, etc.

[0047] Contrary to the above method, it is also known that the polyamide is dissolved in a solvent at once, the inclusions are removed as insoluble matter, and then the polyamide is precipitated by a certain method and recovered.

[0048] However, solvents for dissolving polyamide are strong acids such as formic acid and sulfuric acid or expensive solvents such as HFIP, and many of them are not suitable as solvents for industrial use, and there is a concern that polyethylene terephthalate may be decomposed.

[0049] As an example of using a solvent that is easy to use industrially, there is a dissolution recovery method using ethylene glycol (Patent Document 2).

[0050] However, this method requires a very high temperature reaction, so there is a concern that polyamide and polyethylene terephthalate may undergo glycolysis. In addition, the solvent used must be completely distilled off from the sorbet-like solid and dried, which requires a large amount of energy together with the heating during the reaction.

[0051] Therefore, there is also a dissolution method using an alcoholic calcium chloride solution as a method using a low-temperature and general-purpose raw material.

[0052] For example, Patent Document 3 describes a method in which a cloth coated with polyamide containing silicone is treated with a methanol solution of calcium chloride to dissolve the polyamide, and the polyamide is diluted with a large amount of water or methanol to obtain the target polyamide in the form of powder.

[0053] However, it has been found that the method described in Patent Document 3 actually has the problem of dissolving the silicone-coated polyamide base fabric. Patent Document 3 describes that it is preferable to use calcium chloride dihydrate, which has high solubility for polyamide, or to add water equivalent to the hydrate in addition to anhydrous calcium chloride, because the solubility of polyamide is high in such a composition.

[0054] In addition, regarding the present invention (VII), polyamides represented by nylon 6 and nylon 66, which are representative engineering plastics, have heat resistance and good mechanical properties and are widely used in fibers, automobile parts, electrical product parts, etc., and are one of the irreplaceable materials in modern society. Among them, nylon 66 is particularly important for applications requiring heat resistance and durability in harsh environments.

[0055] In recent years, with the goal of resource conservation and carbon neutrality, technological development for plastic recycling has been carried out, and polyamide is no exception.

[0056] Recycling can be roughly divided into: what is called material recycling, in which a primary molded product is made into pellets again; and what is called chemical recycling, in which monomers are reused by depolymerization. In material recycling, there is a concern about unstable quality due to the deterioration of the polymer contained in the molded product or the residual additives in the recycled polymer. However, since it does not involve chemical reactions and requires few by-products, the resources and energy invested are very small, so material recycling can be selected in cases where the purpose is fixed and the recycling is carried out. In addition, even before chemical recycling is implemented, when additives, coatings, etc. are removed from processed and used polyamides recovered from factories and markets, the process of recovering clean polyamides is also required in the same way as material recycling, so material recycling technology is also a useful technology for chemical recycling.

[0057] As mentioned above, since there are various inclusions in the processed and used polyamide, it is necessary to change the recycling method according to the purpose. The uses of polyamide are diversified. As one of the uses of nylon 66, automotive use requiring high safety can be cited. For example, it is used for parts around the engine that require high heat resistance, and the base fabric of the airbag that requires durability when broken. Among them, the use that deteriorates less and is suitable for material reuse is the base fabric of the airbag. Not only the used airbags can be reused, but also the scraps generated when cutting parts during the manufacture and sewing of the base fabric for the airbag can be reused.

[0058] Generally, the base fabric of the airbag uses a material obtained by coating a resin on a woven fabric obtained by spinning and weaving nylon 66. Therefore, in order to recycle the material of the airbag base fabric, it is necessary to separate the coated material from the nylon 66.

[0059] Prior art literature

[0060] Patent Literature

[0061] Patent Document 1: Japanese Patent No. 5841598

[0062] Patent Document 2: Japanese Patent Application Publication No. 2018-172618

[0063] Patent Document 3: Japanese Patent No. 5110704

[0064] Patent Document 4: Japanese Patent Application Laid-Open No. 60-233129

[0065] Patent Document 5: Japanese Patent Application Laid-Open No. 62-218421

[0066] Patent Document 6: Japanese Patent No. 7024037 Summary of the invention

[0067] Problems to be solved by the invention

[0068] An object of the present invention is to efficiently produce powdered polyamide.

[0069] Regarding the present invention (I), as a physical method for removing the impurities from the used polyamide to make it clean, there can be cited a method of crushing the recyclables and then performing gravity separation (Patent Document 1). This method can be separated with less energy, but it is difficult to separate the polyamide and the impurities when they are firmly combined by mixing, joining, bonding, etc. There is also a method of dissolving and removing part or all of the unnecessary impurities with a solvent. However, the inclusions are usually added or applied to the polyamide, and part or all of them are present inside the structure of the polyamide, making it difficult to dissolve all the impurities, and the obtained polyamide is difficult to fully control the shape, size, etc. in a crushed state.

[0070] As another method, the following method is known: the polyamide is dissolved in a solvent at one time, the inclusions are removed in the form of insoluble matter, and the polyamide is precipitated and recovered by a certain method. However, the solvent for dissolving the polyamide is a strong acid such as formic acid and sulfuric acid or an expensive solvent such as HFIP, which is not suitable as a solvent for industrial use. As an example of the use of a solvent that is easy to use in industry, there is a dissolution recovery method based on ethylene glycol (Patent Document 2). However, this method requires a very high temperature reaction, so there is a concern that the polyamide will produce glycolysis, and the solvent used needs to be completely distilled and dried from the sorbet-like solid, so a large amount of energy is required together with the heating during the reaction.

[0071] Therefore, as a method using low-temperature and universal raw materials, there is also a dissolution method based on an alcohol calcium chloride solution. For example, Patent Document 3 describes the following method: a cloth coated with polyamide of organic silicon is treated with a methanol solution of calcium chloride to dissolve the polyamide, and the polyamide is diluted with a large amount of water or methanol to obtain the target polyamide in the form of powder.

[0072] Industrial production was envisioned and verified for such a method of manufacturing polyamide powder using dissolution and precipitation using a metal chloride alcohol solution. As a result, it was found that although polyamide powder with impurities such as silicone removed can be obtained, it has great problems in industrial implementation. The polyamide powder precipitated from the solvent contains a large amount of solvent when precipitated, and even if it is filtered or centrifuged, the solvent that has entered the solid cannot be easily removed. As a result, in order to remove impurities such as metal chloride in the solid, it is necessary to use a large amount of cleaning solvent for multiple cleaning. Another problem can also be cited: when drying in order to remove the solvent from the cleaned powder, a large amount of energy is also required to remove the large amount of solvent.

[0073] This phenomenon has been studied in depth, and it has been found that the reason for containing a large amount of solvent is the porosity of the particles. As a method for controlling the porosity of polyamide, it is described in Patent Document 4. Patent Document 4 records the following as an invention: if polyamide is dissolved in a metal chloride methanol solution, a methanol aqueous solution with a limited water content is added to the heated polyamide solution, and then cooled and precipitated, porous particles can be obtained. As an example of suppressing porosity, a method of diluting with methanol can be cited. In this invention, the solvent conditions used for precipitation are important. With reference to this invention, a study was conducted to suppress porosity. As a result, although there was a slight inhibitory effect, a porous solid was still obtained, and no significant effect was confirmed.

[0074] From the aspect of particle size control, although powdered polyamide can be obtained by the method described in Patent Document 3, when diluted with a large amount of solvent, the precipitation rate changes due to the change in the dilution rate over time, so the particle size distribution becomes wider. On the contrary, the method of adding a polyamide solution to a large amount of solvent is expected to reduce the particle size distribution, but if the dilution rate is increased to the extent that the composition change can be ignored, the required solvent will increase, which is economically and environmentally burdensome.

[0075] As a method for controlling precipitation without increasing the dilution rate, there can be cited a recrystallization method of diluting with a methanol aqueous solution in a heated state and then cooling and precipitating the solution, as described in Patent Document 4. However, Patent Document 4 studies the conditions for obtaining a porous powder, but does not describe any crystallization conditions for obtaining a good powder and the change in particle size distribution caused by the crystallization, and the optimal conditions are unclear.

[0076] In addition, Patent Document 5 describes a method of dissolving polyamide at a high temperature of 130°C or higher under pressure and slowly cooling at 3 to 20°C / Hr to obtain a powder. However, even at this temperature, there is a concern that the polyamide may be slightly decomposed by alcohol and the additive may be eluted from inclusions, so treatment at high temperature is not ideal. In addition, since slow cooling takes a long time, it is not suitable as an industrial process.

[0077] Therefore, the object of the present invention (I) is to provide a method for producing a powdered polyamide, which reduces the amount of waste liquid and the energy required for drying by suppressing the porosity and reducing the amount of solvent contained. In addition, it is preferred to provide a method for producing a powdered polyamide with a large particle size and a small particle size distribution in a short time.

[0078] In the present invention (II), since the polyamide recovered from the polyamide molded product is molded again after adjusting the composition of additives, etc., it is preferably free of impurities. If the impurities are organic compounds, it is necessary to use a cleaning solution such as an organic solvent for cleaning, and the cleaning of inorganic compounds is preferably carried out by water and / or a cleaning solution containing water. In particular, in the case of a dissolution process using a methanol solution of calcium chloride, calcium chloride used as a solvent and metals such as potassium and copper as additives of the polyamide need to be fully removed by a cleaning process, and if their solubility is considered, the polyamide is preferably finally washed with water.

[0079] The inventor has attempted to recover polyamide by the method of recording in patent documentation 3 using methanol solution of calcium chloride to process polyamide molded articles, and found that, although polyamide can be recovered, a specific phenomenon can be produced during filtration. Specifically, the precipitated polyamide can include a large amount of solvents (including water, methanol, and methanol solution of calcium chloride). The amount of impurities that can be removed by a single cleaning is determined by the dilution rate at which the solvent contained in the precipitated polyamide is diluted by the cleaning solution, so if the amount of solvent contained in the precipitated polyamide is large, the amount of the cleaning solution (representatively water) must also increase proportionally, and as a result, the removal efficiency of impurities is greatly reduced.

[0080] Furthermore, a large amount of energy is required to heat the solution (particularly water) impregnated into the polyamide pellets to be in a stabilized state and remove it by reduced pressure drying. The increase in the solution contained in the polyamide pellets places a very large load on the process.

[0081] Therefore, an object of the present invention (II) is to provide a method for producing recycled polyamide with reduced waste liquid amount.

[0082] Regarding the present invention (III), as a physical method for removing the inclusions from the polyamide containing the inclusions to make it clean, there can be cited a method of crushing the recyclate and then performing gravity separation (Patent Document 1). This method can separate with less energy, but in the case of an airbag base fabric in which the polyamide and the inclusions are firmly combined by mixing, joining, bonding, etc., it is difficult to separate.

[0083] There is also a method of dissolving and removing part or all of the unnecessary inclusions such as silicone with a solvent (for example, Patent Document 6). However, since the silicone is infiltrated into the fibers of the polyamide, the silicone resin remains in the recovered polyamide. In addition, the recovered polyamide is recovered in the form of broken cloth. Used airbags and scraps from manufacturing are in various shapes, and it is difficult to directly reuse them in their original shapes or in shapes such as fiber scraps obtained by cutting them. In addition, even if they are melted and reused, they are not suitable as a shape for loading into an extruder, etc.

[0084] Contrary to the above method, it is known that the following method can also be used: dissolve the polyamide with a solvent at one time, remove the inclusions as insolubles, and then precipitate the polyamide by some method and recover it. However, the solvent for dissolving the polyamide is a strong acid such as formic acid and sulfuric acid or an expensive solvent such as HFIP, which is not suitable as a solvent for industrial use. As an example of the use of a solvent that is easy to use in industry, there is a dissolution recovery method based on ethylene glycol (Patent Document 2). However, this method requires a very high temperature reaction, so there is a concern that the polyamide will produce glycolysis, and the solvent used needs to be completely distilled and dried from the sorbet-like solid, so a large amount of energy is required together with the heating during the reaction.

[0085] Therefore, as a method using low-temperature and universal raw materials, there is also a dissolution method using an alcoholic calcium chloride solution. For example, Patent Document 3 describes the following method: a cloth coated with polyamide of organic silicon is treated with a methanol solution of calcium chloride to dissolve the polyamide, and the polyamide is diluted with a large amount of water or methanol to obtain the target polyamide in the form of powder.

[0086] However, it has been found that the method described in Patent Document 3 actually has the problem of dissolving the silicone-coated polyamide base fabric. Patent Document 3 describes that it is preferable to use calcium chloride dihydrate, which has high solubility for polyamide, or to add water equivalent to the hydrate in addition to anhydrous calcium chloride, because the solubility of polyamide is high in such a composition.

[0087] However, if the polyamide base fabric is actually used to try to dissolve it, the problem becomes clear. The problem lies in the low recovery rate. Even if the polyamide with a saturated solubility of about 23% under the solvent composition is to be dissolved, if the base fabric has a certain area, it will not be possible to dissolve and recover all the polyamide due to the adhesion of the base fabrics to each other and the winding of the base fabrics. The supernatant after dissolution is also turbid, and although it becomes a flowing state, it is difficult to say that it has dissolved. Although there is a method of crushing the base fabric in advance to increase the yield, the tiny fragments of silicone resin will be dispersed in the solution at this time, making it very difficult to recover from the solution.

[0088] An object of the present invention (III) is to provide a method for producing recycled polyamide from a silicone-coated polyamide fabric efficiently and in high yield.

[0089] Regarding the present invention (IV), an object of the present invention (IV) is to provide a solvent having low metal corrosivity and high solubility for polyamide.

[0090] As for the present invention (V), in the techniques of Patent Documents 2 to 4, there is still room for further improvement as a method for recovering polyamide with high efficiency and high yield.

[0091] When polyamide is dissolved using an alcoholic calcium chloride solution as in Patent Document 3, the polyamide is precipitated and recovered, and then the recovered polyamide is usually washed.

[0092] However, it is preferred to avoid excessive washing of the recovered polyamide from the perspectives of production efficiency, cost, environmental considerations, etc. On the other hand, if the recovered polyamide is not sufficiently washed, a part of the polyamide may be melted by the metal chloride attached to the washed polyamide, and the polyamide may be solidified during subsequent drying.

[0093] Therefore, an object of the present invention (V) is to provide a method for producing polyamide, which can recover polyamide with high efficiency and high yield and can obtain high-quality polyamide without excessive washing.

[0094] As for the present invention (VI), the techniques of Patent Documents 1 to 3 and 6 have room for further improvement as a method for recovering polyamide with high efficiency and high yield.

[0095] In addition, when the base fabric of the airbag is a mixture of polyamide and polyethylene terephthalate, the base fabric has a certain area, and it is difficult to effectively recover polyamide and polyethylene terephthalate due to the adhesion of the base fabrics to each other and the winding of the base fabrics, and there is also a problem of reduced recovery rate.

[0096] In order to improve the yield, a method of crushing the base fabric in advance is also considered, but in this case, it is known that there is a problem that the operation becomes complicated, or the polyethylene terephthalate fragments are dispersed in the solution, making recovery very difficult.

[0097] Therefore, an object of the present invention (VI) is to provide a method for producing polyamide, a method for producing polyethylene terephthalate, and a method for producing polyamide and polyethylene terephthalate, wherein the method can recover polyamide and / or polyethylene terephthalate from a mixture of polyamide and polyethylene terephthalate with high efficiency and high yield.

[0098] Regarding the present invention (VII), as a physical method for removing the inclusions from the polyamide containing the inclusions to make it clean, there can be cited a method of crushing the recyclate and then performing gravity separation (Patent Document 1). This method can separate with less energy, but in the case of an airbag base fabric where the polyamide and the inclusions are firmly combined by mixing, joining, bonding, etc., it is difficult to separate.

[0099] In addition, there is a method (for example, patent document 6) in which a part or all of the inclusions such as the unwanted coating resin are dissolved with a solvent and removed. However, since the coating resin is in a state of penetrating into the fiber of the polyamide, the coating resin will remain in the recovered polyamide. In addition, the recovered polyamide is recovered in the form of broken cloth. The scraps of the used airbags and the manufacturing are in various shapes, and it is difficult to directly reuse them in the original shape or in the shape of the fiber scraps obtained by cutting them. In addition, even if it is melted and reused, it is not suitable as a shape to be loaded into an extruder, etc.

[0100] Contrary to the above method, it is known that the following method can also be used: dissolve the polyamide with a solvent at one time, remove the inclusions as insolubles, and then precipitate the polyamide by some method and recover it. However, the solvent for dissolving the polyamide is a strong acid such as formic acid and sulfuric acid or an expensive solvent such as HFIP, which is not suitable as a solvent for industrial use. As an example of the use of a solvent that is easy to use in industry, there is a dissolution recovery method based on ethylene glycol (Patent Document 2). However, this method requires a very high temperature reaction, so there is a concern that the polyamide will produce glycolysis, and the solvent used needs to be completely distilled and dried from the sorbet-like solid, so a large amount of energy is required together with the heating during the reaction.

[0101] Therefore, as a method using low-temperature and universal raw materials, there is also a dissolution method using an alcoholic calcium chloride solution. For example, Patent Document 3 describes a method in which a cloth coated with a polyamide coating resin is treated with a methanol solution of calcium chloride to dissolve the polyamide, and the polyamide is diluted with a large amount of water or methanol to obtain the target polyamide in a powder form.

[0102] However, it has been found that the method described in Patent Document 3 actually has the problem of dissolving the resin-coated polyamide base fabric. Patent Document 3 describes that it is preferable to use calcium chloride dihydrate, which has high solubility for polyamide, or to add water equivalent to the hydrate in addition to anhydrous calcium chloride, because the solubility of polyamide is high under this composition.

[0103] However, if the polyamide base cloth is actually used to try to dissolve it, the problem becomes clear. The problem lies in the low recovery rate. Even if the polyamide with a saturated solubility of about 23% under the solvent composition is to be dissolved, if the base cloth has a certain area, it will not be possible to dissolve and recover all the polyamide due to the adhesion of the base cloths to each other and the winding of the base cloths. The supernatant after dissolution is also turbid, and although it becomes a flowing state, it is difficult to say that it has dissolved. Although there is a method of crushing the base cloth in advance to increase the yield, the tiny fragments of the coated resin will be dispersed in the solution at this time, and it is very difficult to recover from the solution.

[0104] An object of the present invention (VII) is to provide a method for producing recycled polyamide efficiently and in high yield from a urethane-coated polyamide fabric.

[0105] Means for solving problems

[0106] In the present invention (I), the inventors conducted intensive research using a different approach from the prior art and surprisingly found that the composition of the solution during dissolution rather than the composition during precipitation has a significant influence on the porosity. The inventors found that the porosity of the polyamide powder can be suppressed and the amount of solvent contained during precipitation can be significantly reduced by controlling the composition of the solution during dissolution to a specific range, thereby completing the invention.

[0107] That is, the present invention (I) is as follows. [1]

[0109] A method for producing powdered polyamide, characterized in that it comprises the following steps:

[0110] Step 1: a step of heating and dissolving a polyamide resin composition with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated solution;

[0111] Step 2: diluting the heated polyamide solution with alcohol to obtain an alcohol diluted solution; and

[0112] Step 3: Cooling the alcohol dilution to precipitate the powdered polyamide.

[0113] In the above step 1, the mass ratio of the metal chloride is 23 mass % or more and 35 mass % or less relative to 100 mass % of the metal chloride alcohol solution, in the above step 1, the heated polyamide solution contains 0.2 mol or more and 2.5 mol or less of water relative to 1 mol of the metal chloride, and in the above step 2, the polyamide heated solution is diluted without causing the temperature of the heated polyamide solution to fall below 50°C. [2]

[0115] A method for producing powdered polyamide, characterized in that it comprises the following steps:

[0116] Step 1: a step of heating and dissolving a polyamide resin composition with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated solution;

[0117] Step 2: diluting the heated polyamide solution with alcohol to obtain an alcohol diluted solution; and

[0118] Step 3: Cooling the alcohol dilution to precipitate the powdered polyamide.

[0119] In the above step 1, the mass ratio of the metal chloride is 23 mass % or more and 35 mass % or less relative to 100 mass % of the metal chloride alcohol solution, in the above step 1, the polyamide heated solution contains water in an amount of 0.2 mol or more and 2.5 mol or less relative to 1 mol of the metal chloride, and in the above step 2, the mass of the precipitated polyamide is 1 mass % or less relative to the total mass of the polyamide contained in the above polyamide heated solution. [3]

[0121] A method for producing recycled polyamide, using a polyamide resin composition comprising polyamide coated with a silicone resin as a raw material, characterized in that:

[0122] The manufacturing method comprises a dissolving step, wherein a metal chloride alcohol solution containing metal chloride and alcohol is mixed with the polyamide resin composition to dissolve the polyamide to prepare a polyamide dissolved solution.

[0123] In the dissolving step, the mass ratio of the polyamide in the polyamide solution is 5 to 15 mass %. [4]

[0125] A methanol composition comprising a metal chloride at a concentration of 5 to 25%, a hydroxide of the metal at a concentration of 0.001 to 1%, and water at a concentration of 0.001 to 5%. [5]

[0127] A method for producing polyamide, which recovers polyamide from a mixture containing at least polyamide and polyethylene terephthalate, is characterized in that the production method comprises the following steps:

[0128] A step of mixing the mixture with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide solution in which the polyamide is dissolved; and

[0129] The polyamide solution is separated and recovered. [6]

[0131] A method for producing recycled polyamide, using a mixture containing polyamide coated with urethane resin as a raw material, characterized in that:

[0132] The manufacturing method comprises a dissolving step, wherein a metal chloride alcohol solution containing metal chloride and alcohol is mixed with the above mixture to dissolve the polyamide to prepare a polyamide dissolved solution.

[0133] In the dissolving step, the mass ratio of the polyamide in the polyamide solution is 5 to 15 mass %. [7]

[0135] The method for producing a powdered polyamide as described in [1] or [2] further comprises:

[0136] Step 4: a step of washing the powdered polyamide obtained in step 3 once or more using a solvent. [8]

[0138] The method for producing a powdered polyamide as described in [7], wherein the solvent used for the initial washing in the step 4 is the same alcohol as the alcohol used in the step 1. [9]

[0140] The method for producing a powdered polyamide according to [1] or [2], wherein the temperature of the heating and dissolving in the step 1 is 60° C. or higher and 80° C. or lower.

[10]

[0142] The method for producing a powdered polyamide as described in [1] or [2] further comprises:

[0143] Step 5: A step of heating the powdered polyamide precipitated in the above step 3 to obtain heated powdered polyamide.

[11]

[0145] The method for producing a powdered polyamide as described in

[10] , wherein after the above step 5, the method further comprises:

[0146] Step 6: a step of subjecting the heated powdered polyamide obtained in the above step 5 to solid-liquid separation and washing the obtained solid.

[12]

[0148] The method for producing a powdered polyamide according to [1] or [2], wherein the polyamide resin composition comprises polyamide coated with a silicone resin, and the concentration of the polyamide in the heated solution of the polyamide in the step 1 is 5 to 15% by mass.

[13]

[0150] The method for producing a powdered polyamide as described in [1] or [2], wherein the polyamide resin composition comprises polyamide coated with a silicone resin, and the viscosity of the heated solution of the polyamide in the step 1 at 25° C. is 10 to 20,000 mPa·s.

[14]

[0152] A metal chloride alcohol solution, wherein the metal chloride concentration is 23 mass % or more and 35 mass % or less, and contains a hydroxide of the same metal as the metal contained in the metal chloride at a concentration of 0.001 to 1 mass % and water at a concentration of 0.001 to 10 mass %.

[15]

[0154] The method for producing a powdered polyamide as described in [1] or [2], wherein the metal chloride alcohol solution is a metal chloride alcohol solution having a metal chloride concentration of 23 mass % to 35 mass %, containing a hydroxide of the same metal as the metal contained in the metal chloride at a concentration of 0.001 to 1 mass %, and containing water at a concentration of 0.001 to 10 mass %.

[16]

[0156] The method for producing a powdered polyamide as described in [1] or [2] is a method for producing a powdered polyamide containing 0.001 to 1500 ppm of calcium atoms and a molar content of halogen atoms relative to the molar content of calcium atoms of less than 1.

[17]

[0158] The method for producing a powdered polyamide as described in [1] or [2], wherein the polyamide resin composition contains at least polyamide and polyethylene terephthalate.

[18]

[0160] The method for producing a powdered polyamide according to [1] or [2], wherein the polyamide resin composition comprises a polyamide coated with a urethane resin.

[19]

[0162] The method for producing a powdered polyamide as described in [1] or [2], wherein the method further comprises the following step after the above steps 1 to 3:

[0163] Step 7: a step of recovering the precipitated powdered polyamide;

[0164] Step 8: a washing step of washing the recovered polyamide powder; and

[0165] Step 9: Drying the washed polyamide powder by heating.

[0166] The amount of the metal chloride attached to the powdered polyamide after the heat drying in the step 9 is 20 parts by mass or less based on 100 parts by mass of the powdered polyamide.

[0167] In addition, regarding the present invention (II), the inventors have conducted intensive research and various studies on methods for reducing the amount of solvent contained in the precipitated polyamide in order to reduce the amount of cleaning liquid. As a result, it was found that the precipitated polyamide can be modified by heating the polyamide precipitated from the calcium chloride methanol solution, thereby completing the present invention (II). In the present invention (II), since the amount of solvent contained in the precipitated polyamide during cleaning is small, the amount of liquid required for cleaning can be reduced.

[0168] That is, the present invention (II) is as follows.

[0169] [1] A method for producing recycled polyamide, comprising the following steps:

[0170] (i) dissolving polyamide in a calcium chloride methanol solution to obtain a solution containing the dissolved polyamide;

[0171] (ii) a step of precipitating the dissolved polyamide from the solution containing the dissolved polyamide to obtain precipitated polyamide;

[0172] (iii) heating the precipitated polyamide to obtain heated polyamide; and

[0173] (iv) washing the heated polyamide with a washing solution to obtain a regenerated polyamide;

[0174] [2] The production method described in [1], wherein in the step (iii), the precipitated polyamide is heated in the solution during precipitation in the step (ii);

[0175] [3] The production method as described in [1], wherein in the step (ii), the precipitated polyamide is separated from the solution during precipitation to obtain a solid component containing the polyamide, the obtained solid component is washed with an additional washing liquid, and then in the step (iii), the polyamide is heated;

[0176] [4] The production method according to any one of [1] to [3], wherein the regenerated polyamide is in a powder form.

[0177] [5] The production method as described in [1], wherein the polyamide is polyhexamethylene adipamide;

[0178] [6] The production method according to any one of [1] to [5], wherein in the step (ii), after adding a poor solvent to the solution containing the dissolved polyamide, the dissolved polyamide is precipitated from the solution to obtain the precipitated polyamide;

[0179] [7] The production method according to any one of [1] to [5], wherein in the step (ii), no additional solvent is added to the solution containing the dissolved polyamide, and the dissolved polyamide is precipitated from the solution in this state to obtain the precipitated polyamide;

[0180] [8] The production method according to any one of [1] to [7], wherein the cleaning liquid in the step (iv) is water;

[0181] [9] The production method according to any one of [3] to [8], wherein the additional washing liquid in the step (ii) is methanol.

[0182] In addition, regarding the present invention (III), a method for recovering polyamide using a calcium chloride methanol solution was studied intensively, and it was found that the main reason for the reduction in recovery efficiency is the increase in viscosity due to the dissolution of the polyamide. As a result, it was found that the treatment with the composition with the highest solubility is not necessarily a solution composition for recovering polyamide (for example, nylon 66) at a high yield. The dissolving composition was studied, and it was found that metal chlorides other than calcium chloride can be used, and it was found that the yield of the regenerated polyamide can be increased by controlling the viscosity of the polyamide or the solution of the polyamide solution after dissolution, thereby completing the invention.

[0183] That is, the present invention (III) is as follows. [1]

[0185] A method for producing recycled polyamide, using a polyamide resin composition comprising polyamide coated with a silicone resin as a raw material, characterized in that:

[0186] The production method includes a dissolving step of mixing a metal chloride alcohol solution containing a metal chloride and an alcohol with the polyamide resin composition to dissolve the polyamide to prepare a polyamide solution.

[0187] In the dissolving step, the mass ratio of the polyamide in the polyamide solution is 5 to 15 mass %. [2]

[0189] A method for producing recycled polyamide, using a polyamide resin composition comprising polyamide coated with a silicone resin as a raw material, characterized in that:

[0190] The production method includes a dissolving step of mixing a metal chloride alcohol solution containing a metal chloride and an alcohol with the polyamide resin composition to dissolve the polyamide to prepare a polyamide solution.

[0191] In the dissolving step, the viscosity of the polyamide solution at 25° C. is 10 to 20,000 mPa·s. [3]

[0193] The production method as described in [1] or [2], wherein in the dissolving step, the temperature at which the polyamide resin composition and the metal chloride alcohol solution are mixed is 30 to 90°C. [4]

[0195] The production method according to any one of [1] to [3], wherein the polyamide is an aliphatic polyamide. [5]

[0197] The production method according to any one of [1] to [4], wherein the metal chloride is zinc chloride or calcium chloride. [6]

[0199] The production method as described in [5], wherein the metal chloride is calcium chloride. [7]

[0201] The production method according to any one of [1] to [6], wherein the alcohol is methanol. [8]

[0203] The production method according to any one of [1] to [7], wherein the polyamide is nylon 66. [9]

[0205] The production method according to any one of [1] to [8], wherein the metal chloride alcohol solution is a solution produced by separating polyamide from a metal chloride alcohol solution in which polyamide derived from a polyamide-based fabric is dissolved.

[10]

[0207] The production method as described in [9], wherein the metal chloride alcohol solution is a solution obtained by separating the polyamide and then concentrating it.

[0208] In addition, regarding the present invention (IV), a method for inhibiting the corrosion of metals such as the material of the dissolution equipment caused by metal chloride alcohol solutions such as calcium chloride methanol solutions has been studied in depth. The mechanism of metal corrosion caused by metal chlorides such as calcium chloride is due to the destabilization of passivation based on chloride ions. In order to inhibit it, the method of increasing the pH is common. Therefore, in order to increase the pH, it is easy to think of a method of adding an alkaline compound soluble in methanol, but if, for example, sodium hydroxide is added as a base soluble in methanol, the chloride ions react with the sodium hydroxide, and the generated sodium chloride precipitates because it is insoluble in methanol. Such sodium chloride particles are not easy to merge with the solvent, so they are easy to remain in the gaps of the device, etc., resulting in a local increase in the chloride ion concentration, which is easy to cause crevice corrosion, and should therefore be avoided. In addition, since the concentration of metal chlorides such as calcium chloride is reduced overall, the solubility of polyamide is also reduced. From this perspective, various bases were studied, and as a result, it was found that when a hydroxide of the same metal as the metal chloride (hereinafter referred to as "hydroxide of the same metal") such as calcium hydroxide was added, the corrosiveness could be greatly reduced without reducing the solubility of polyamide, thereby completing the invention (IV).

[0209] That is, the present invention (IV) is as follows. [1]

[0211] A methanol composition comprising a metal chloride at a concentration of 5 to 25%, a hydroxide of the metal at a concentration of 0.001 to 1%, and water at a concentration of 0.001 to 5%. [2]

[0213] The methanol composition as described in [1] further comprises a polyamide dissolved in the methanol composition as a solvent. [3]

[0215] The methanol composition as described in [1] or [2], wherein the metal chloride is zinc chloride, and the hydroxide of the same metal is zinc hydroxide. [4]

[0217] The methanol composition as described in [1] or [2], wherein the metal chloride is calcium chloride, and the hydroxide of the same metal is calcium hydroxide. [5]

[0219] A method for producing a polyamide composition, comprising: a step of dissolving a raw material polyamide composition in a solvent to obtain a polyamide solution; and a step of separating polyamide from the obtained polyamide solution, wherein the solvent for dissolving the raw material polyamide composition is the methanol composition described in [1] or [2]. [6]

[0221] The production method as described in [5], wherein the polyamide composition is polyhexamethylene adipamide. [7]

[0223] A polyamide composition obtained by the method described in [5], containing 0.001 to 1000 ppm of metal atoms, wherein the molar content of halogen atoms is less than 2 relative to the molar content of metal atoms. [8]

[0225] The polyamide composition as described in [7] contains 0.001 to 1000 ppm of metal atoms, and the molar content of halogen atoms is less than 1 relative to the molar content of metal atoms. [9]

[0227] The polyamide composition as described in [7], wherein the metal atom is a zinc atom or a calcium atom.

[10]

[0229] The polyamide composition as described in [7] further comprises polyhexamethylene adipamide.

[11]

[0231] A powder comprising the polyamide composition described in [7].

[0232] In addition, regarding the present invention (V), the inventors have repeatedly conducted intensive studies and found that, after a polyamide resin composition is heated and dissolved in a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated solution, polyamide is precipitated from the polyamide heated solution and recovered, and in the subsequent step of washing and drying the recovered polyamide, the amount of metal chloride attached to the heated and dried polyamide is controlled to be 20 parts by mass or less relative to 100 parts by mass of the polyamide. As a result, even without excessive washing, the solidification of the recovered polyamide can be suppressed, thereby completing the present invention (V).

[0233] The present invention (V) has been accomplished based on the above technical ideas, and its gist is as follows.

[0234] [1] A method for producing polyamide, characterized in that it comprises the following steps:

[0235] Step 1: a dissolving step, wherein the polyamide resin composition is heated and dissolved with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated dissolved liquid;

[0236] Step 2: a recovery step, in which the polyamide is precipitated from the heated polyamide solution and recovered;

[0237] Step 3: a cleaning step of cleaning the recycled polyamide; and

[0238] Step 4: Drying step, heating and drying the washed polyamide.

[0239] The amount of the metal chloride attached to the polyamide after the heat drying in the step 4 is 20 parts by mass or less based on 100 parts by mass of the polyamide.

[0240] [2] The method for producing polyamide according to [1] above, wherein the washing step is a control step for controlling the amount of the metal chloride after the heat drying.

[0241] [3] The method for producing a polyamide according to [1] or [2] above, wherein the temperature for heating and dissolving in the step 1 is 30 to 90°C.

[0242] [4] The method for producing a polyamide according to any one of [1] to [3] above, wherein the polyamide concentration in the polyamide heated solution is 5 to 15% by mass.

[0243] [5] The method for producing a polyamide according to any one of [1] to [4] above, wherein the metal chloride is zinc chloride or calcium chloride.

[0244] [6] The method for producing a polyamide according to any one of [1] to [5], further comprising a confirmation step of measuring the amount of metal chloride attached to the polyamide to confirm whether it is within a range.

[0245] [7] The method for producing polyamide according to [6] above, wherein in the confirmation step, a portion of the cleaned polyamide after the cleaning in step 3 is collected to perform the confirmation step.

[0246] [8] The method for producing polyamide as described in [6] above is characterized in that in the step of confirming whether the amount of metal chloride attached to the polyamide is within a range, a part of the polyamide after heat drying in the step 4 is collected to carry out the step.

[0247] [9] The method for producing a polyamide as described in any one of [6] to [8] above, wherein when the amount of the metal chloride attached to the polyamide exceeds 20 parts by mass relative to 100 parts by mass of the polyamide, a second washing step of washing the polyamide again is performed.

[0248] In addition, regarding the present invention (VI), the inventors have discovered that by mixing a mixture of polyamide and polyethylene terephthalate with a metal chloride alcohol solution containing a metal chloride and an alcohol to dissolve and separate the polyamide, polyamide and / or polyethylene terephthalate can be recovered from the mixture, and the efficiency and yield of separation and recovery can be improved, thereby completing the present invention (VI).

[0249] The present invention (VI) has been accomplished based on the above technical ideas, and its gist is as follows.

[0250] [1] A method for producing polyamide, comprising recovering polyamide from a mixture containing at least polyamide and polyethylene terephthalate, the method comprising the following steps:

[0251] A step of mixing the mixture with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide solution in which the polyamide is dissolved; and

[0252] The polyamide solution is separated and recovered.

[0253] [2] A method for producing polyethylene terephthalate, comprising recovering polyethylene terephthalate from a mixture containing at least polyamide and polyethylene terephthalate, characterized in that the method comprises the following steps:

[0254] A step of mixing the mixture with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide solution in which at least the polyamide is dissolved; and

[0255] A step of separating and recovering the polyethylene terephthalate.

[0256] [3] A method for producing polyamide and polyethylene terephthalate, wherein the method recovers polyamide and polyethylene terephthalate from a mixture of polyamide and polyethylene terephthalate, characterized in that the method comprises the following steps:

[0257] A step of mixing the mixture with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide solution in which the polyamide is dissolved; and

[0258] A step of separating and recovering the polyamide solution and the polyethylene terephthalate.

[0259] [4] The manufacturing method as described in [1], [2] or [3] above, characterized in that the above-mentioned mixed material is a woven fabric.

[0260] [5] The manufacturing method as described in [4] above is characterized in that the above-mentioned woven fabric is an airbag component.

[0261] [6] The production method according to any one of [1] to [5] above, wherein the temperature at which the impurity and the metal chloride alcohol solution are mixed is 30 to 90°C.

[0262] [7] The production method according to any one of [1] to [6] above, wherein the metal chloride is zinc chloride or calcium chloride.

[0263] In addition, regarding the present invention (VII), a method for recovering polyamide using a calcium chloride methanol solution was studied intensively, and it was found that the main reason for the decrease in recovery efficiency is the increase in viscosity due to the dissolution of the polyamide. As a result, it was found that the treatment with the composition with the highest solubility is not necessarily a solution composition for recovering polyamide (for example, nylon 66) at a high yield. The dissolving composition was studied, and it was found that metal chlorides other than calcium chloride can be used, and it was found that the yield of the regenerated polyamide can be improved by controlling the polyamide or solution viscosity of the polyamide solution after dissolution, thereby completing the invention (VII).

[0264] That is, the present invention (VII) is as follows. [1]

[0266] A method for producing recycled polyamide, using a mixture containing polyamide coated with urethane resin as a raw material, characterized in that:

[0267] The manufacturing method comprises a dissolving step, wherein a metal chloride alcohol solution containing metal chloride and alcohol is mixed with the above mixture to dissolve the polyamide to prepare a polyamide dissolved liquid;

[0268] In the dissolving step, the mass ratio of the polyamide in the polyamide solution is 5 to 15 mass %. [2]

[0270] A method for producing recycled polyamide, using a mixture containing polyamide coated with urethane resin as a raw material, characterized in that:

[0271] The manufacturing method comprises a dissolving step, wherein a metal chloride alcohol solution containing metal chloride and alcohol is mixed with the above mixture to dissolve the polyamide to prepare a polyamide dissolved liquid;

[0272] In the dissolving step, the viscosity of the polyamide solution at 25° C. is 10 to 20,000 mPa·s. [3]

[0274] The production method described in [1] or [2], wherein in the dissolving step, the temperature at which the mixture and the metal chloride alcohol solution are mixed is 30 to 90°C. [4]

[0276] The production method according to any one of [1] to [3], wherein the polyamide is an aliphatic polyamide. [5]

[0278] The production method according to any one of [1] to [4], wherein the metal chloride is zinc chloride or calcium chloride. [6]

[0280] The production method as described in [5], wherein the metal chloride is calcium chloride. [7]

[0282] The production method according to any one of [1] to [6], wherein the alcohol is methanol. [8]

[0284] The production method according to any one of [1] to [7], wherein the polyamide is nylon 66. [9]

[0286] The production method according to any one of [1] to [8], wherein the metal chloride alcohol solution is a solution produced by separating polyamide from a metal chloride alcohol solution in which polyamide derived from a polyamide-based fabric is dissolved.

[10]

[0288] The production method as described in [9], wherein the metal chloride alcohol solution is a solution obtained by separating the polyamide and then concentrating it.

[0289] Effects of the Invention

[0290] According to the present invention (I), powdered polyamide can be produced efficiently.

[0291] In the present invention (I), a method for producing a powdered polyamide can be provided, which reduces the amount of waste liquid and the energy required for drying by suppressing porosity and reducing the amount of solvent contained. In addition, it is preferred to provide a method for producing a powdered polyamide having a large particle size and a small particle size distribution in a short time.

[0292] Regarding the present invention (II), according to the present invention (II), a method for producing a recycled polyamide with a reduced amount of waste liquid can be provided.

[0293] Regarding the present invention (III), according to the present invention (III), a method for producing a polyamide base fabric efficiently and in high yield from a silicone-coated polyamide base fabric can be provided.

[0294] Regarding the present invention (IV), according to the present invention (IV), a solvent having low corrosiveness and capable of dissolving polyamide can be provided.

[0295] Regarding the present invention (V), according to the present invention (V), there can be provided a method for producing polyamide, which can recover polyamide with high efficiency and high yield, and can obtain high-quality polyamide without excessive washing.

[0296] Regarding the present invention (VI), a method for producing polyamide, a method for producing polyethylene terephthalate, and a method for producing polyamide and polyethylene terephthalate can be provided according to the present invention (VI), wherein the production method can recover polyamide and / or polyethylene terephthalate from a mixture of polyamide and polyethylene terephthalate with high efficiency and high yield.

[0297] Regarding the present invention (VII), according to the present invention (VII), a method for producing a polyamide base fabric efficiently at a high yield from a urethane-coated polyamide base fabric can be provided. DETAILED DESCRIPTION

[0298] A specific embodiment of the present invention (hereinafter referred to as “this embodiment”) will be described in detail below.

[0299] [Invention (I)]

[0300] The present invention (I) is described below. In the present invention (I), the conditions of the present inventions (II) to (VII) can be appropriately incorporated.

[0301] The method for producing a powdered polyamide of the present embodiment (I) includes the following steps: step 1: a step of heating and dissolving a polyamide resin composition with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated dissolved solution; step 2: a step of diluting the above-mentioned polyamide heated dissolved solution with alcohol to obtain an alcohol diluted solution; and step 3: a step of cooling the above-mentioned alcohol diluted solution to precipitate a powdered polyamide, wherein in the above-mentioned step 1, the mass ratio of the metal chloride relative to 100 mass % of the metal chloride alcohol solution is 23 mass % to 35 mass %, in the above-mentioned step 1, the polyamide heated dissolved solution contains 0.2 mol to 2.5 mol of water relative to 1 mol of the metal chloride, and in the above-mentioned step 2, the dilution is performed without causing the temperature of the polyamide heated dissolved solution to be lower than 50°C.

[0302] In addition, another method for producing a powdered polyamide according to the present embodiment (I) includes the following steps: step 1: a step of heating and dissolving a polyamide resin composition with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated dissolved solution; step 2: a step of diluting the above-mentioned polyamide heated dissolved solution with alcohol to obtain an alcohol diluted solution; and step 3: a step of cooling the above-mentioned alcohol diluted solution to precipitate a powdered polyamide, wherein in the above-mentioned step 1, the mass ratio of the metal chloride relative to 100 mass% of the metal chloride alcohol solution is 23 mass% to 35 mass%, in the above-mentioned step 1, the polyamide heated dissolved solution contains water in an amount of 0.2 mol to 2.5 mol relative to 1 mol of the metal chloride, and in the above-mentioned step 2, the mass of the precipitated polyamide is 1 mass% or less relative to the total mass of the polyamide contained in the above-mentioned polyamide heated dissolved solution.

[0303] The production method of the present embodiment may be a method having only steps 1 to 3, or may further include other steps.

[0304] The compounds and the like used in the production method of this embodiment will be described.

[0305] <Polyamide>

[0306] As the polyamide, a polymer obtained by polymerization via an amide bond, such as a polymer obtained by condensation polymerization of a diamine compound and a dicarboxylic acid compound or a polymer obtained by ring-opening polymerization of a cyclic lactam, can be used.

[0307] The diamine compound is not particularly limited, and examples thereof include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonanediamine, methylpentamethylenediamine, and p-phenylenediamine.

[0308] The dicarboxylic acid compound is not particularly limited, and examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid.

[0309] The cyclic lactam is not particularly limited, and examples thereof include ε-caprolactam, undecyl lactam, and lauryl lactam.

[0310] There is no particular limitation on the combination of the diamine compound, the dicarboxylic acid compound, and the cyclic lactam compound, and a plurality of compounds of each type may be used in combination. Polyhexamethylene adipamide composed of hexamethylenediamine and adipic acid has high solubility and is suitable for a powdering process.

[0311] The method for measuring the particle size and particle size distribution of the powdered polyamide is not particularly limited, and examples thereof include a laser diffraction method, a laser scattering method, a centrifugal sedimentation method, a particle tracking method, and a dynamic scattered light method.

[0312] <Polyamide resin composition>

[0313] Additives may be added to the polyamide resin composition to achieve the effects shown during use and processing as the final purpose. As additives, heat stabilizers, pigments, dyes, plasticizers, etc. may be cited, but are not limited to them. Each additive may also be any one of an inorganic salt and an organic compound.

[0314] The polyamide resin composition may also include polyamide coated with resins other than polyamide. The resin for coating is not limited, and examples thereof include polyolefin resins, polyurethanes, acrylic resins, silicone resins, RFL (resorcinol formaldehyde latex) adhesives, etc. From the perspective of separability, it is preferred to include polyamide coated with silicone resin. It may be a composition consisting only of polyamide coated with silicone resin, or it may further include other components.

[0315] Among them, from the perspective of the production efficiency of the powdered polyamide, the mass ratio of the polyamide coated with the silicone resin relative to 100 mass % of the polyamide resin composition is preferably 30 to 100 mass %, more preferably 60 mass % or more, further preferably 70 mass % or more, and particularly preferably 80 mass % or more.

[0316] The silicone resin is not particularly limited, and examples thereof include methyl silicone and phenyl silicone resins. The silicone resin may be a mixture of these resins, or may be a product obtained by mixing and curing the respective raw materials.

[0317] The polyamide coated with the silicone resin may be coated with other coatings besides the silicone resin. The type of other coating is not particularly limited, and examples thereof include polyethylene, polypropylene, polyester, fluororesin, etc. Preferably, the polyamide is a material that does not dissolve in the metal chloride alcohol solution used for dissolution.

[0318] The polyamide coated with the silicone resin can be a recycled raw material of polyamide, for example, engineering scraps and wastes of molded products such as fibers, automobile parts, and electrical product parts using polyamide as a raw material. Specifically, engineering scraps and wastes such as clothing, airbags, tire cords, engine compartment or intake system, fuel system parts, connectors, fishing nets, UD tapes, etc. can be cited.

[0319] The composition of the RFL adhesive is not particularly limited, and may be an RFL adhesive commonly used for bonding polyamide fibers and rubber for tire cords.

[0320] Examples of the polyamide coated with polyurethane or acrylic resin include base fabrics used for clothing and the like, and the types of polyurethane or acrylic resin are not particularly limited.

[0321] The polyamide resin composition may contain sewing thread. The material of the sewing thread is not particularly limited, but is preferably made of the same polyamide as the base fabric because it can be recovered as recycled polyamide.

[0322] The polyamide resin composition may be composed of the polyamide alone or may contain the polyamide and other components. For example, impurities such as other resins and metals may be mixed, attached, or coated on the polyamide as other components.

[0323] From the perspective of the recovery rate of the polyamide, the mass ratio of the above-mentioned polyamide relative to 100 mass% of the above-mentioned polyamide resin composition is preferably 30 to 100 mass%, more preferably 70 mass% or more, further preferably 80 mass% or more, further preferably 85 mass% or more, and particularly preferably 100 mass%.

[0324] In the case of impurities other than polyamide, the process of separating the polyamide from these impurities may be included. There is no particular limitation on the separation method. If the impurities are insoluble in the state where the polyamide resin composition has been dissolved, separation can be performed by filtration, centrifugal separation, sedimentation separation, etc. In the case of being dissolved in a solvent together with the polyamide, separation by extraction separation, membrane separation, separation based on electrodialysis, etc. in a dissolved state, or separation of the polyamide by a precipitation process described later and then washing may be considered.

[0325] The polyamide resin composition may contain at least polyamide and polyethylene terephthalate, and may further contain other components.

[0326] As other components, there can be mentioned components for coating a mixture of polyamide and polyethylene terephthalate, components for coating, etc. As the component for coating, there can be mentioned resin, and silicone resin, urethane resin, etc. can be mentioned as examples. As the component for coating, there can be mentioned lubricating oil, etc.

[0327] Regarding the shape of the above-mentioned polyamide resin composition containing polyamide and polyethylene terephthalate, from the perspective of being able to further enjoy the effects brought about by the present invention, it is preferably a woven fabric (water jet loom, air jet loom, rapier loom, base fabric for airbags, etc.), and more preferably an airbag component. In the case of a high-density fabric such as a base fabric for an airbag, the fibers composed of polyamide and the fibers composed of polyethylene terephthalate are entangled, and it is difficult to fully separate them using existing separation methods. On the other hand, in this embodiment, by dissolving and separating the polyamide, polyamide and / or polyethylene terephthalate can be recovered from the mixture of polyamide and polyethylene terephthalate, and even if it is a woven fabric, polyamide and / or polyethylene terephthalate can be recovered with high efficiency and high yield.

[0328] Examples of the polyethylene terephthalate (PET) include resins having the following structures.

[0329] [Chemistry 1]

[0330]

[0331] The polyethylene terephthalate may be composed of polyethylene terephthalate alone, or may be a polyethylene terephthalate resin composition containing the polyethylene terephthalate and other components. For example, impurities such as other resins and metals may be mixed, attached, or applied to the polyethylene terephthalate as other components.

[0332] The polyethylene terephthalate may be contained in the polyamide resin composition as PET fibers. The PET fibers may be obtained by further solid phase polymerization and spinning of a PET resin.

[0333] It should be noted that since polyethylene terephthalate is insoluble in the metal chloride alcohol solution described later, only polyamide can be melt-separated in step 1. Therefore, polyamide and polyethylene terephthalate can be separated efficiently and at a high yield simply by mixing the polyamide resin composition containing polyamide and polyethylene terephthalate with a predetermined metal chloride alcohol solution, and polyamide can be recovered.

[0334] Regarding polyethylene terephthalate, the polyethylene terephthalate remaining without dissolving can be separated and recovered. As a method for separating and recovering the polyethylene terephthalate, the polyethylene terephthalate remaining without dissolving in the polyamide heated solution can be taken out by filtration or the like, thereby separating and recovering.

[0335] The polyamide resin composition preferably includes polyamide coated with a urethane resin.

[0336] From the perspective of the production efficiency of the powdered polyamide, the mass ratio of the polyamide coated with the urethane resin relative to 100 mass % of the polyamide resin composition is preferably 30 to 100 mass %, more preferably 60 mass % or more, further preferably 70 mass % or more, and particularly preferably 80 mass % or more.

[0337] The polyurethane resin is obtained by a reaction between a polyol component and a polyisocyanate component, and examples of the polyol component include polycarbonate polyol, polyester polyol, and polyether polyol.

[0338] The urethane resin is not particularly limited, and examples thereof include polyester polyurethane resins, polyether polyurethane resins, polycarbonate polyurethane resins, etc. The urethane resin may be added with a crosslinking agent composed of epoxy resin, melamine, polyfunctional isocyanate, etc., a carbodiimide anti-hydrolysis agent, a phenolic, aromatic amine antioxidant, or a salicylic acid, benzophenone, benzotriazole derivative, etc. UV absorber, and a flame retardant such as thiourea.

[0339] The polyamide coated with the urethane resin may be coated with other coatings in addition to the urethane resin. The types of other coatings are not particularly limited, and examples thereof include polyethylene, polypropylene, polyester, fluororesin, silicone resin, etc. Preferably, the coating resin is not soluble in the metal chloride alcohol solution used for dissolution. Preferably, the coating resin does not contain silicone resin.

[0340] The polyamide coated with the urethane resin can be a recycled raw material of polyamide, for example, engineering scraps and wastes of molded products such as fibers, automobile parts, and electrical product parts using polyamide as a raw material. Specifically, engineering scraps and wastes such as clothing, airbags, tire cords, engine compartment or intake system, fuel system parts, connectors, fishing nets, and UD tapes can be cited.

[0341] As a method for separating the urethane resin, there can be cited a method of scooping up the urethane resin from the dissolved layer, filtration, centrifugal separation, sedimentation separation, etc., or a combination thereof. Since fine fragments of the urethane resin may be generated when the polyamide is heated and dissolved, it is preferred to remove the fine fragments by filtration or a combination of filtration methods.

[0342] It is also preferred that other coatings of the polyamide coated with the urethane resin are removed simultaneously with the urethane resin.

[0343] Regarding the separated urethane resin and other coatings, since the solution containing polyamide is attached, it is preferred to clean and recycle the solution containing polyamide. The solvent for cleaning is not particularly limited, and calcium chloride methanol solution is preferred. There is no particular limitation on the cleaning method, and stirring cleaning in a tank reactor, circulation cleaning in a filter, etc. can be cited.

[0344] <Metal chloride alcohol solution>

[0345] The metal chloride alcohol solution contains a metal chloride and an alcohol, and may further contain a hydroxide of the same metal as the metal chloride and other components.

[0346] Among them, from the viewpoint of the solubility of polyamide, the total mass ratio of the metal chloride and the alcohol is preferably 80 mass % or more, more preferably 90 mass % or more, based on 100 mass % of the metal chloride alcohol solution.

[0347] Examples of the alcohol include methanol, ethanol, linear or branched propanol, linear or branched butanol, and combinations thereof, etc. Among them, methanol, ethanol, or a combination thereof is preferred, and methanol is more preferred, from the viewpoint of the solubility of the polyamide.

[0348] The mass ratio of the metal chloride relative to 100 mass % of the metal chloride alcohol solution is preferably 23 to 35 mass %, more preferably 25 to 33 mass %, and particularly preferably 27 to 31 mass %. If the mass ratio is less than 23 mass %, the amount of polyamide dissolved is small, and a large amount of solvent is required. In addition, if the mass ratio exceeds 35 mass %, the metal chloride is likely to have insoluble matter remaining, and is likely to be mixed as an impurity.

[0349] Examples of the metal chloride include zinc chloride, magnesium chloride, calcium chloride and the like, among which zinc chloride and calcium chloride are preferred, and calcium chloride is most preferred.

[0350] The above-mentioned metal chloride can be added in the form of an anhydrate or a hydrate.

[0351] The mass ratio of water in the metal chloride alcohol solution is preferably 30 mass % or less, more preferably 15 mass % or less, further preferably 10 mass % or less, and particularly preferably contains no water.

[0352] The metal chloride alcohol solution may be a solution containing an alcohol, a metal chloride, a hydroxide of the same metal as the metal chloride (sometimes referred to as “hydroxide of the same metal” in this specification), and water.

[0353] Examples of the metal constituting the above-mentioned hydroxide of the same metal include zinc (i.e., the metal chloride is zinc chloride and the hydroxide of the same metal is zinc hydroxide) and calcium (i.e., the metal chloride is calcium chloride and the hydroxide of the same metal is calcium hydroxide), and calcium is preferred.

[0354] The concentration of the hydroxide of the same metal is preferably 0.001 to 1 mass %, more preferably 0.001 to 0.1 mass %, and even more preferably 0.001 to 0.01 mass % relative to 100 mass % of the metal chloride alcohol solution. The hydroxide of the same metal does not necessarily need to be completely dissolved in the alcohol such as methanol, and may be partially undissolved.

[0355] The mass ratio of water relative to 100 mass % of the metal chloride alcohol solution is preferably 0.001 to 10 mass %, more preferably 0.001 to 5 mass %, further preferably 0.001 to 1 mass %, particularly preferably 0.01 to 0.1 mass %.

[0356] Each step in the production method of this embodiment will be described.

[0357] <Step 1: Obtaining a Polyamide Heated Dissolved Liquid>

[0358] The polyamide resin composition is dissolved in a metal chloride alcohol solution.

[0359] In the step 1, the polyamide resin composition and the metal chloride alcohol solution are mixed and heated to dissolve.

[0360] The temperature for heating and dissolving is not particularly limited, but is preferably 30 to 90° C., more preferably 60 to 80° C. Alternatively, it may be 40 to 60° C. If the temperature is low, dissolution will be slow, and if it is higher than 90° C., the temperature becomes higher than the boiling point, which is not preferred from the perspective of corrosiveness and decomposition.

[0361] In the above step 1, the temperature may be fixed or may be varied within the above range.

[0362] The dissolution may be carried out in a batch manner or in a continuous manner.

[0363] In the case of a batch method, stirring is not particularly limited, but stirring is preferably performed. Stirring increases the dissolution rate of the polyamide.

[0364] In the case of a continuous method, the solvent may be continuously passed through the solid or the solution may be circulated. Circulation is preferred because the amount of solvent used can be reduced.

[0365] The shape of the container used when the above-mentioned polyamide resin composition and the metal chloride alcohol solution are heated and dissolved is not particularly limited, and any shape such as a trough type and a circulation type can be used. In addition, the material of these containers and pipes is not particularly limited, and SUS316, SUS316L, SUS329J4L, SUS444, etc. can be cited. In addition, the surface of these materials can also be lined, coated, etc., and glass, fluorine resin, rubber, epoxy resin, etc. can be cited. From the aspect of corrosion resistance, glass and fluorine resin are preferred. It should be noted that when the processing of lining and coating is implemented, the material of the container and the pipe itself can be selected without considering the corrosiveness.

[0366] The heating and dissolution time is not particularly limited, but is preferably 5 minutes to 100 hours.

[0367] The mass ratio of the polyamide resin composition to the metal chloride alcohol solution used in step 1 is not particularly limited, but is preferably 5 to 15 mass %, more preferably 7 to 13 mass %. If it is less than 5 mass %, too much solvent is required, and if it is more than 15 mass %, the viscosity increases, resulting in a prolonged dissolution time and deterioration of workability.

[0368] Moreover, for the same reason as described above, the mass ratio of the polyamide in the polyamide heated solution is preferably 5 to 15 mass %, and more preferably 7 to 13 mass %.

[0369] In the polyamide heated solution, the molar ratio of water is preferably 0.2 to 2.5 moles, more preferably 0.5 to 2.0 moles, and even more preferably 1 to 1.5 moles relative to 1 mole of the metal chloride in order to suppress the liquid content of the precipitate obtained by crystallization. Although the principle is not clear, it is believed that it has the following effects: the water present during the dissolution affects the state of hydrogen bonding of the polyamide in the metal chloride alcohol solution, and adjusts the microscopic solubility and dispersibility that cannot be evaluated in the macroscopic dissolved state. It is believed that if it is less than 0.2 moles, the dispersibility of calcium chloride in alcohol is reduced, and it becomes difficult to interact with polyamide; if it is more than 2.5 moles, the solubility of polyamide in water is low, so it is not easy for polyamide to be evenly dispersed in the solution.

[0370] When the polyamide resin composition comprises polyamide coated with a silicone resin, the mass ratio of the polyamide in 100 mass% of the polyamide heated solution is preferably 5 to 15 mass%, more preferably 7 to 13 mass%. If it is less than 5 mass%, too much solvent is required, and if it is more than 15 mass%, the viscosity increases, thereby prolonging the dissolution time and deteriorating the workability.

[0371] When the polyamide resin composition comprises polyamide coated with a silicone resin, the viscosity of the heated polyamide solution at 25° C. is preferably 10 to 20,000 mPa·s, more preferably 10 to 10,000 mPa·s, and further preferably 10 to 3,000 mPa·s. The higher the viscosity, the higher the concentration of the polymer, but the dissolution efficiency of the polyamide is reduced due to adhesion of the base fabric, etc.

[0372] When the polyamide resin composition comprises polyamide coated with silicone resin, the method for separating the silicone resin from the polyamide heated solution is not particularly limited, and may include a method of scooping up the silicone resin from the dissolved layer, filtration, centrifugal separation, sedimentation separation, etc., or a combination thereof. Since fine fragments of silicone may be generated when polyamide is heated and dissolved, it is preferred to remove the fine fragments by filtration or a combined filtration method.

[0373] It is also preferred that other coatings of the polyamide coated with the silicone resin are removed simultaneously with the silicone resin.

[0374] Since the separated organosilicon resin and other coatings are attached with a solution containing polyamide, it is preferred to wash and recycle the solution containing polyamide. The solvent for washing is not particularly limited, and calcium chloride methanol solution is preferred. There is no particular limitation on the washing method, and stirring washing in a tank reactor, circulation washing in a filter, etc. can be cited.

[0375] The polyamide heated solution obtained in step 1 is preferably used continuously in step 2.

[0376] <Step 2: Step of Obtaining Alcohol Diluted Liquid>

[0377] Step 2 is a step of diluting the heated polyamide solution obtained in step 1 with alcohol.

[0378] The alcohol used in step 2 may be methanol, ethanol, linear or branched propanol, linear or branched butanol, or a combination thereof. From the perspective of ease of recovery when the solvent is reused, the alcohol is preferably the same as the alcohol contained in the above-mentioned metal chloride alcohol solution.

[0379] The method of diluting the polyamide heated solution will be described in detail.

[0380] The dilution rate based on alcohol is preferably 1.5 to 5 times. The dilution rate in this specification is defined as the value obtained by dividing the mass of the alcohol dilution liquid after dilution by the mass of the polyamide heated solution during dissolution. At this time, even if precipitation occurs in the alcohol dilution liquid after dilution, the weight including the precipitate is used as the mass of the alcohol dilution liquid after dilution. When the dilution rate is less than 1.5 times, the particle size becomes smaller because the amount of polyamide precipitation is small and the particles are not fully grown. If the dilution rate is greater than 5 times, precipitation is likely to occur during dilution, and the particle size distribution becomes wider.

[0381] In step 2, from the perspective of suppressing the liquid content of the precipitate obtained by crystallization, it is preferred to dilute the polyamide heated solution so that the temperature does not fall below 50° C. Although the principle is not clear, it is believed that by maintaining the temperature at a high level during the dilution stage, rapid precipitation can be avoided and the properties of the precipitate can be made uniform from the initial stage to the final stage of precipitation.

[0382] The temperature when diluting with alcohol is not particularly limited, but is preferably 30 to 90° C. When diluting at a temperature lower than 30° C., the particle size becomes smaller due to precipitation during dilution. When diluting at a temperature higher than 90° C., non-uniform precipitation is likely to occur near the liquid surface due to volatilization and condensation of alcohol, making it difficult to control the particle size distribution.

[0383] From the perspective of obtaining a powdered polyamide with a larger particle size and a smaller particle size distribution in a short time, the temperature from the production of the polyamide heating solution to the acquisition of the alcohol dilution solution is preferably within the range of ±10°C of the temperature for heating and dissolving in step 1, and more preferably within the range of ±5°C.

[0384] The dilution rate of the alcohol is not particularly limited, but it is preferably added at a rate that does not cause abrupt changes in concentration or temperature during dilution to cause precipitation of polyamide.

[0385] The amount of polyamide precipitated during dilution (i.e., the mass of the polyamide precipitated in step 2) is preferably 1% by mass or less, more preferably less than 1% by mass, relative to the total mass of the polyamide contained in the polyamide heated solution obtained in step 1. The polyamide precipitated during dilution and the polyamide precipitated during cooling have different microscopic separation mechanisms when precipitated from the solvent. If the amount of polyamide precipitated during dilution increases, the liquid content of the precipitate increases. In addition, if there are a large number of particles that cannot be controlled in particle size due to the particles generated by the rapid composition change, the particle size control in the cooling precipitation process described later becomes difficult.

[0386] The temperature of the alcohol used for dilution is not particularly limited, but is preferably 15 to 90° C. If it is lower than 15° C., local precipitation is easily caused during dilution, and if it is higher than 90° C., it is higher than or close to the boiling point of the alcohol, so it is necessary to handle under pressure.

[0387] The water content of the alcohol used for dilution is not particularly limited, but is preferably 0.005 to 50% by mass, more preferably 0.005 to 1% by mass. If the water content increases, the polyamide will rapidly precipitate in the aqueous solution due to its low solubility. Since the precipitation property varies depending on the type of polyamide, the amount of water can be changed within the above range according to the polyamide.

[0388] The dilution method is not particularly limited and may be either a batch method or a continuous method.

[0389] In the case of a batch method, stirring is not particularly limited, but stirring is preferably performed. By stirring, the temperature and concentration become uniform.

[0390] The shape of the container for diluting the above-mentioned polyamide heating solution with the above-mentioned alcohol is not particularly limited, and any shape such as a trough type and a circulation type can be used. The same container as in step 1 can also be used. In addition, the material of these containers and piping is not particularly limited, and SUS316, SUS316L, SUS329J4L, SUS444, etc. can be cited. In addition, lining, coating and other treatments can also be implemented on the surface of these materials, and glass, fluorine resin, rubber, epoxy resin, etc. can be cited. From the aspect of corrosion resistance, glass and fluorine resin are preferred. It should be noted that when implementing the treatment of lining and coating, the material of the container and piping itself can be selected without considering the corrosiveness.

[0391] <Step 3: Step of Precipitating Powdered Polyamide>

[0392] Step 3 is a step of cooling the alcohol dilution obtained in step 2 to precipitate polyamide.

[0393] When the alcohol dilution is cooled, it is preferably stirred. By stirring, the temperature and concentration become uniform, and the particle size is easily controlled. It is preferred that the stirring is performed under conditions that do not easily cause destruction or shearing of the particles due to stirring, depending on the equipment and method used in the stirring.

[0394] The cooling rate is not particularly limited, but is preferably 10 to 100°C / Hr, more preferably 20 to 70°C / Hr, and still more preferably 40 to 68°C / Hr. If it is less than 10°C / Hr, the time taken becomes longer; if the cooling rate exceeds 100°C / Hr, the particle size becomes smaller due to rapid precipitation. The particle size can be controlled by changing the cooling rate.

[0395] The temperature after cooling is not particularly limited, but is preferably 10° C. or more lower than the temperature during dilution. If the temperature difference is less than 10° C., precipitation is reduced and particles are less likely to grow.

[0396] The precipitated solid is preferably recovered by solid-liquid separation.

[0397] The method for solid-liquid separation is not particularly limited, and examples thereof include filtration, centrifugal separation, sedimentation separation, etc. Any of the methods may be batch-wise or continuous.

[0398] The solid obtained by solid-liquid separation is preferably washed with a solvent. There is no particular limitation on the washing solvent, but it is preferred to use a solution composed of the liquid portion during precipitation or a good solvent, or a solvent that can dissolve metal chlorides, etc. Alcohols such as methanol and ethanol and water are preferred, and they may also be combined.

[0399] The washing method is not particularly limited, and examples thereof include a batch washing method, a continuous washing method in which a washing solvent is passed through a solid-liquid separation device such as a filter or a centrifuge, and a combination thereof.

[0400] The washed polyamide can be heated and / or reduced in pressure to distill off the washing solvent and made into a dry solid, thereby obtaining a powdered polyamide.

[0401] The production method of the present embodiment preferably includes step 4 of washing the powdered polyamide obtained in step 3 with a solvent once or more. The washing may be performed once or multiple times.

[0402] In the above-mentioned washing, the above-mentioned solvent used in the initial washing is preferably the same alcohol as the alcohol used in the above-mentioned step 1 from the aspects of washing efficiency and reuse of raw materials. That is, it is preferably the same alcohol as the alcohol contained in the above-mentioned metal chloride alcohol solution in the above-mentioned step 1. The solution contained in the polyamide after crystallization contains the metal chloride used for dissolution. By using the same alcohol as the alcohol used in the above-mentioned step 1, the filtered filtrate after crystallization is concentrated together with the above-mentioned washing liquid, and it is reused as a dissolving liquid, which can reduce the waste amount of metal chloride. In addition, if a different solvent is used, the change in affinity between the polyamide and the solvent is increased, and the washing efficiency is reduced.

[0403] The production method of this embodiment preferably includes step 5 of heating the powdered polyamide obtained in step 3 to obtain heated powdered polyamide. The precipitated powdered polyamide solid component can be heated and modified to reduce the content of the solvent (representatively a metal chloride alcohol solution such as a calcium chloride methanol solution) in the powdered polyamide solid component.

[0404] The step 5 may heat the powdered polyamide washed in the step 4, that is, the step 5 may be provided after the step 4. Alternatively, after obtaining the heated powdered polyamide in the step 5, the heated powdered polyamide may be washed in the step 4.

[0405] It should be noted that the above step 5 may be the step (iii) of the present invention (II) described later.

[0406] The heating in step 5 may be performed in the atmosphere or in an inert gas. In the heating, drying may be performed in addition to heating, or drying may be performed together with heating. For example, after washing the powdered polyamide in step 4, the powdered polyamide may be heated and dried in step 5.

[0407] Although not intended to be bound by any theory, it is believed that the powdered polyamide can be modified as follows due to heating. That is, assuming that swelling occurs in a state where a solvent (representatively a metal chloride alcohol solution such as a calcium chloride methanol solution) penetrates into the powdered polyamide during precipitation, it is believed that heating in this state can dry the metal chloride alcohol solution as a solvent and / or reduce the space for capturing the metal chloride alcohol solution. Therefore, it is believed that the amount of the residual metal chloride alcohol solution can be reduced, and the impurity removal efficiency during subsequent cleaning can also be improved.

[0408] The heating temperature in step 5 is not particularly limited, and is, for example, 20° C. to 100° C. If the heating temperature is too low, the reforming effect is reduced, and if the heating temperature is too high, solid fusion occurs due to the solution, making the treatment difficult.

[0409] There are no particular limitations on stirring during heating in the step 5, but stirring is preferably performed to avoid local heating.

[0410] There is no particular limitation on the pressure during heating in the above step 5, and the heating may be performed under pressure or under reduced pressure. If the pressure is reduced to below the atmospheric pressure and the heating is performed, the solvent (representatively, a metal chloride alcohol solution such as a calcium chloride methanol solution) can be distilled off, the amount of the residual metal chloride alcohol solution can be reduced, and the impurity removal efficiency during subsequent washing can be improved, which is preferred.

[0411] The production method of the present embodiment preferably includes a step 6 of performing solid-liquid separation on the heated powdered polyamide obtained in the step 5, and washing the solid obtained by the solid-liquid separation.

[0412] The method for solid-liquid separation is not particularly limited, and examples thereof include filtration, centrifugal separation, and sedimentation separation. A washing liquid is added to the solid component obtained by the solid-liquid separation to dissolve and remove impurities.

[0413] As the cleaning solution, water, and alcohols such as ethanol, n-propanol, and isopropanol can be cited, and they can be used in combination. In addition, acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and acetic acid, and alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate can be added to the cleaning solution according to the type of impurities. In order to avoid residues after cleaning, the final cleaning is preferably carried out with water, and most preferably, all cleaning is carried out in water.

[0414] The amount of the cleaning liquid used in the step 6 is not particularly limited, but is preferably determined so that the amount of impurities remaining after cleaning is reduced to a target residual amount.

[0415] The cleaning method in step 6 is not particularly limited, and examples thereof include a method of performing batch cleaning only as many times as necessary, a method of performing continuous cleaning by circulating a cleaning liquid in a state where solids are added to a filter or a centrifugal separator, and a combination of these methods.

[0416] After washing, the solid component may be dried as necessary. For example, when a solid component of polyamide is obtained by water washing, water is distilled off from the solid component by heating and / or reducing pressure to obtain a dry solid.

[0417] The manufacturing method of this embodiment preferably includes the following steps after steps 1 to 3:

[0418] Step 7: a step of recovering the precipitated powdered polyamide;

[0419] Step 8: a washing step of washing the recovered polyamide powder; and

[0420] Step 9: Drying the washed polyamide powder by heating.

[0421] The amount of the metal chloride attached to the powdered polyamide after the heat drying in the step 9 is 20 parts by mass or less relative to 100 parts by mass of the powdered polyamide recovered in the step 7.

[0422] The method for producing polyamide of the present embodiment may further include a recovery step (step 7) of recovering the precipitated polyamide powder after the step 3. For example, the polyamide powder may be recovered after washing in the step 4, the polyamide powder may be recovered after heating in the step 5, or the polyamide powder may be recovered after washing the solid obtained in the solid-liquid separation in the step 6.

[0423] The production method of this embodiment preferably includes a washing step (step 8) of washing the powdered polyamide recovered in the above step 7. This step can remove impurities such as metal chloride from the polyamide recovered in step 7.

[0424] The cleaning liquid used in the cleaning of step 8 is not particularly limited, and for example, a solution composed of the liquid part during precipitation, a good solvent, and a solvent capable of dissolving calcium chloride, etc., can be used. The additional cleaning liquid used here is, for example, water, and alcohols such as methanol, ethanol, n-propanol, and isopropanol. The additional cleaning liquid is preferably methanol. Cleaning can be performed multiple times as needed.

[0425] The washing method is not particularly limited, and examples thereof include a batch washing method, a continuous washing method in which water is passed through a solid-liquid separation device such as a filter or a centrifuge, and a combination thereof.

[0426] It should be noted that the above-mentioned step 8 is preferably a control step for controlling the amount of the metal chloride after heat drying in the step 9 described later.

[0427] The amount of the metal chloride after drying in step 9 can be controlled by adjusting the type, concentration, cleaning time, etc. of the cleaning liquid so that the amount of the metal chloride after drying in step 9 is within a specific range.

[0428] The production method of this embodiment may include a drying step (step 9) of heating and drying the polyamide washed in step 8. In step 9, the washing solvent can be distilled off from the washed polyamide to obtain a dry solid, thereby obtaining the polyamide.

[0429] Furthermore, in the method for producing polyamide of the present embodiment, the amount of the metal chloride attached to the polyamide after the heat drying in the step 9 is preferably 20 parts by mass or less relative to 100 parts by mass of the polyamide.

[0430] Regarding the cleaning of the recovered polyamide, it is preferred to avoid excessive cleaning from the perspectives of manufacturing efficiency, cost, and environmental considerations. On the other hand, if the recovered polyamide is not sufficiently cleaned, there is a problem that a portion of the polyamide melts due to the metal chloride attached to the cleaned polyamide, and solidifies during subsequent drying.

[0431] Therefore, the metal chloride concentration can be controlled within a range that can suppress the melting of the polyamide by setting the amount of the metal chloride attached to the polyamide after the heat drying in the step 9 to 20 parts by mass or less relative to 100 parts by mass of the polyamide obtained in the step 9. In addition, from the viewpoint of avoiding excessive washing, the amount of the metal chloride attached to the polyamide after the heat drying in the step 9 is preferably 0.01 parts by mass or more relative to 100 parts by mass of the polyamide.

[0432] From the same viewpoint, the amount of the metal chloride attached to the polyamide after heat drying in the step 9 is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, based on 100 parts by mass of the polyamide.

[0433] The method for measuring the amount of metal chloride attached to the polyamide after heat drying in the above step 9 is not particularly limited, and examples thereof include the following methods: sampling a portion and 1) measuring the amount by X-ray fluorescence analysis after drying; 2) measuring the amount by ICP-AES after heat decomposition with nitric acid; 3) extracting the metal chloride with water and measuring the amount by ion chromatography; and the like.

[0434] It should be noted that the measurement of the amount of metal chloride attached to the polyamide after the heat drying in the above step 9 may be performed after the heat drying in the above step 9 or after the washing of the polyamide in the above step 8 .

[0435] Regarding the measurement of the amount of the metal chloride, a known method can be appropriately used.

[0436] From the perspective of reusing the metal chloride alcohol solution, the production method of the present embodiment may further include a step of concentrating the metal chloride alcohol solution.

[0437] For example, the metal alcohol solution containing the metal chloride and the alcohol obtained in the above-mentioned polyamide recovery step can be concentrated and reused.

[0438] Examples of the concentration method include concentration by heating.

[0439] As described above, according to the manufacturing method of this embodiment, when a polyamide useful as an engineering plastic is dissolved and precipitated to manufacture a powdered polyamide, the liquid content of the precipitated polyamide can be reduced by controlling the metal chloride and water contents of the metal chloride alcohol solution used for dissolving the polyamide to be within specific ranges, and controlling the temperature during dilution or the precipitation amount during dilution to be within specific ranges, thereby providing a manufacturing method for powdered polyamide with reduced washing solvent amount and drying energy.

[0440] <Powdered polyamide>

[0441] The powdered polyamide obtained by the production method of the present embodiment has a large particle size and a small particle size distribution.

[0442] The median diameter of the powdered polyamide is preferably 20 μm or more, more preferably 30 to 70 μm. The median diameter can be measured by the method described in the examples below.

[0443] The particle size distribution of the powdered polyamide is represented by the following formula (1): S, 10 to the power of S = 10 S That is, the span is preferably 5 or less, more preferably 4 or less, and further preferably 3 or less.

[0444] S=log(d90 / d10) / log(d50)···(1)

[0445] (Here, in the above formula (1), dn (n represents 10, 50 or 90) means the particle size when the number of particles having a particle size smaller than dn is n% relative to the total number of particles when the particle size distribution of the above powdered polyamide is measured by laser diffraction / scattering method.)

[0446] The particle size distribution can be measured by the method described in the examples below.

[0447] The above-mentioned powdered polyamide may contain metal atoms and halogen atoms.

[0448] The metal atom may be a metal atom derived from a metal chloride and / or a hydroxide of the same metal contained in the metal chloride alcohol solution, for example, a zinc atom and a calcium atom, preferably a calcium atom.

[0449] The powdered polyamide preferably contains 0.001 to 1500 ppm of calcium atoms, and the molar content of halogen atoms is less than 1 relative to the molar content of calcium atoms.

[0450] The metal atom content in the powdered polyamide is preferably 0.001 to 1500 ppm, more preferably 0.001 to 1000 ppm, further preferably 0.001 to 700 ppm, particularly preferably 0.001 to 500 ppm.

[0451] The calcium atom content in the powdered polyamide is preferably 0.001 to 1500 ppm, more preferably 0.001 to 1000 ppm, further preferably 0.001 to 700 ppm, particularly preferably 0.001 to 500 ppm.

[0452] The ratio of the molar content of halogen atoms (e.g., mol / L) to the molar content of metal atoms (e.g., mol / L) in the above-mentioned powdered polyamide (molar content of halogen atoms / molar content of metal atoms) is preferably less than 2, more preferably less than 1, and further preferably less than 0.5.

[0453] The element not derived from silicon and polyamide contained in the powdered polyamide is not particularly limited, and examples thereof include calcium and zinc (for example, in the form of a calcium compound or a zinc compound).

[0454] The amount of calcium contained in the powdered polyamide is preferably 1500 ppm or less, more preferably 1000 ppm or less, further preferably 700 ppm or less, particularly preferably 500 ppm or less, in terms of calcium atom content quantified by X-ray fluorescence analysis.

[0455] The amount of zinc contained in the powdered polyamide is preferably 1500 ppm or less, more preferably 1000 ppm or less, further preferably 700 ppm or less, particularly preferably 500 ppm or less, in terms of zinc atom content quantitatively determined by X-ray fluorescence analysis.

[0456] Calcium and zinc have little influence on clogging during spinning, but these compounds easily absorb water and melt the powdered polyamide in a water-containing state to cause hydrolysis, thereby reducing the molecular weight and the durability of the molded product.

[0457] (Spinning of polyamide fibers)

[0458] The spinning temperature during melt spinning is preferably 290° C. to 310° C. The spinning temperature is preferably set to 310° C. or less, because thermal decomposition of the polyamide is suppressed. The spinning temperature is more preferably set to 300° C. or less, and further preferably set to 295° C. or less. On the other hand, the spinning temperature is preferably set to 290° C. or more, because the polyamide exhibits sufficient melt fluidity, the discharge amount between the discharge holes is uniform, and high-ratio stretching can be achieved.

[0459] The shorter the residence time (the time from when the polyamide resin melts until it is discharged from the spinning nozzle) in the melt spinning process, the better. The residence time is preferably 30 minutes or less, more preferably 15 minutes or less, and further preferably 0.5 minutes or more and 7 minutes or less. A short time is preferred because the cyclopentanones in the polymer increase at the melting temperature.

[0460] In order to achieve thermal stability in a high temperature and high humidity environment, it is preferred to add a copper compound in a manner such that the copper concentration relative to the polyamide is 1 to 500 ppm, and the copper concentration is more preferably 30 to 500 ppm. In this way, even if the polyamide is left for a long time in a high temperature and high humidity environment, or is exposed to an environment containing a large amount of ozone for a long time, the reduction in mechanical properties can be extremely effectively suppressed. If the above copper content is less than 30 ppm, the heat resistance strength retention rate is reduced, and if the addition amount exceeds 500 ppm, the strength is reduced.

[0461] As the copper compound, there is no particular limitation on its type, for example, organic copper salts such as cupric acetate, or copper halides such as cuprous chloride and cupric chloride can be preferably used. The copper compound is more preferably used in combination with a metal halide. As the metal halide, for example, potassium iodide, potassium bromide, potassium chloride, etc. can be cited. The preferred combination in this embodiment is cuprous iodide and potassium iodide, and cupric acetate and potassium iodide. It should be noted that the copper content in the polyamide can be measured by atomic absorption spectrometry, colorimetry, etc.

[0462] Although not limited to the following, as stabilizers, organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, and phosphorus antioxidants, heat stabilizers, hindered amine-based, benzophenone-based, and imidazole-based light stabilizers, and ultraviolet absorbers can be added. The amount of addition can be selected appropriately, and 1 to 1000 ppm can be added relative to the polyamide. These additives can be used not only alone but also in combination of multiple types.

[0463] In the melt spinning step, a single-screw or twin-screw extruder is preferably used in the melting section. The extruder can apply an appropriate pressure to the polyamide resin and simultaneously introduce it into the polymer pipe, gear pump, and spinning pack.

[0464] In addition, it is preferred to filter the polyamide resin using a metal fiber nonwoven fabric filter, gravel, or the like before discharge from the spinning nozzle because the spinning operation can be stabilized.

[0465] The shape of the nozzle hole of the spinning nozzle can be selected according to the cross-sectional shape of the single fiber constituting the manufactured filament. The spun yarn from the spinning nozzle is solidified by cooling air, given an engineering oil and pulled, and then stretched and heat-treated to obtain a polyamide fiber.

[0466] The oil agent adhesion rate of the polyamide fiber is preferably 0.5 to 1.5 wt%. If the oil agent adhesion rate is 1.5 wt% or less, the weft yarn will hardly fly away due to stickiness (adhesion), and the air or water as the weft yarn conveying medium will not lose the weft yarn conveying power due to the monofilament bundling being too good to exceed the monofilament bundling degree based on interweaving and the reduction of the apparent cross-sectional area, and the weft yarn conveying power will be good. On the other hand, if the oil agent adhesion rate is 0.5 wt% or more, the weft yarn can be smoothly supplied due to the appropriate friction reduction effect, so there is no weaving stop and the productivity is excellent.

[0467] (Polyamide base fabric)

[0468] In weaving, a water jet loom, an air jet loom, a rapier loom, etc. can be used as a loom. The base fabric for airbags is a high-density fabric, and it is preferably manufactured with increased warp tension and good process performance in the warping process and weaving process. The warp tension is set high during weaving to create effective weft beating conditions, thereby forming a high-density fabric.

[0469] The woven fabric can be subjected to a scouring process to remove the engineering oil of the polyamide fiber.

[0470] The scouring step may be performed with warm water, pressurized hot water, or the like, and the treatment step may be a single-stage treatment or a multi-stage treatment of two or more stages. In addition, it is also preferred to perform scouring by applying a conventionally known scouring agent.

[0471] The fabric is preferably heat-set in a heat-setting process. The heat-setting temperature is preferably 110°C to 200°C, and the heat-setting time is appropriately selected in the range of 0.1 to 30 minutes. In the heat-setting process, the fabric is preferably dried while being stretched so that the shrinkage force is maintained at a predetermined strength. If the fabric is heat-set, the process of the subsequent resin coating process can be stabilized.

[0472] The fabric after the scouring step can be subjected to a drying treatment before the heat setting step as needed. The drying temperature is preferably in the range of 80°C to 130°C, more preferably in the range of 100°C to 120°C. In addition, the treatment time is preferably appropriately selected within the range of 0.1 minute to 30 minutes. Drying can be performed in a relaxed state or in a tensioned state.

[0473] The polyamide base fabric can be used as an uncoated base fabric after a heat setting process, but can also be coated with a coating agent such as silicone or urethane or heat-laminated into a thin film or the like.

[0474] As a method for coating the surface of the fabric, the following methods can be used: a method of immersing the fabric in a resin solution tank, and then using a squeezer, a vacuum machine, and then a coating blade to coat and evenly coat the excess resin; a rod coating method using a comma coater, etc., a method of blowing the resin using a spray device or a foaming device, etc. Among these, the method of applying the resin uniformly and in small amounts is preferably a method of coating with a blade.

[0475] Coating amount is 5g / m 2 Above 100g / m 2 Less than 10 g / m 2 Above 70g / m 2 Below, more preferably 15g / m 2 Above 30g / m 2 Below, use 5g / m 2The above coating amount can obtain the required airtightness. On the other hand, using 100g / m 2 The following coating amounts can make the coated fabric soft and have good storage properties, while reducing the weight of the entire airbag.

[0476] <Airbag>

[0477] The airbag can be appropriately selected from commonly used airbags for the driver's seat, front passenger seat, side (including side air curtain), rear seat, etc. The bag body of the airbag can be cut into any shape such as circular, oblong, elliptical, rectangular, polygonal or a combination thereof, as long as the desired deployment shape is met.

[0478] The stitch shape includes a single straight line or multiple parallel straight lines, a zigzag shape, a combination of a straight line and a zigzag shape, a straight line and an oblique line, etc. The stitching method may be a commonly used stitching method such as a flat stitch or a double-thread lock stitch, and the stitch spacing may be selected from a range of 20 to 60 times / 10 cm. In addition, the thread thickness may be selected from 420d to 3000d, and the thread material may be a commercially available thread such as polyamide fiber, polyester fiber, vinylon-based fiber, aramid-based fiber, glass fiber, etc.

[0479] [Invention (II)]

[0480] The present invention (II) is described below. In the present invention (II), the conditions of the present invention (I) and (III) to (VII) can be appropriately incorporated.

[0481] The present invention (II) relates to a method for producing regenerated polyamide by precipitating dissolved polyamide in a solvent. The production method is characterized in that it includes a step of heating the precipitated polyamide and then washing it with a washing liquid.

[0482] The method for producing the regenerated polyamide in the present invention (II) comprises the following steps:

[0483] (i) a step of dissolving polyamide in a calcium chloride methanol solution to obtain a solution containing the dissolved polyamide;

[0484] (ii) a step of precipitating the dissolved polyamide from the solution containing the dissolved polyamide to obtain precipitated polyamide;

[0485] (iii) heating the precipitated polyamide to obtain heated polyamide; and

[0486] (iv) A step of washing the heated polyamide with a washing liquid to obtain a regenerated polyamide.

[0487] In this specification, the term "method for producing recycled polyamide" has the same meaning as the terms "method for recovering polyamide", "method for separating polyamide", "method for purifying polyamide" and "method for regenerating polyamide", and can be used interchangeably. In the present invention, polyamide is recovered, separated and / or purified from polyamide molded products, specifically, processed polyamide molded products or used polyamide molded products, for the purpose of reuse. Therefore, the term "recycled polyamide" in this specification refers to polyamide obtained through such treatment.

[0488] <Polyamide>

[0489] In this specification, polyamide includes polymers polymerized via amide bonds, such as those obtained by polycondensation of diamine compounds and dicarboxylic acid compounds and those obtained by ring-opening polymerization of cyclic lactams. Polyamide includes those having only an aliphatic skeleton, those having only an aromatic skeleton, and those having both an aliphatic skeleton and an aromatic skeleton. In the production method of the present invention, the polyamide preferably has only an aliphatic skeleton.

[0490] The diamine compound is not particularly limited, and examples thereof include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonanediamine, methylpentamethylenediamine, and p-phenylenediamine.

[0491] The dicarboxylic acid compound is not particularly limited, and examples thereof include oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid.

[0492] The cyclic lactam is not particularly limited, and examples thereof include ε-caprolactam, undecyl lactam, and lauryl lactam.

[0493] The combination of the diamine compound, the dicarboxylic acid compound, and the cyclic lactam compound is not particularly limited, and a plurality of compounds of each type may be used in combination.

[0494] The polyamide is preferably polyhexamethylene adipamide. Polyhexamethylene adipamide composed of hexamethylene diamine and adipic acid has high solubility and is suitable for the process based on the production method of the present invention. In addition, due to its high solubility, it is also easy to powderize.

[0495] <Step (i): Polyamide Dissolution Step>

[0496] In this step, polyamide is dissolved in the calcium chloride methanol solution to obtain a solution containing dissolved polyamide. In this step, polyamide is dissolved in the calcium chloride methanol solution to perform a dissolution treatment of polyamide.

[0497] The concentration of calcium chloride in the calcium chloride methanol solution is not particularly limited, for example, 10% to 25% by weight, preferably 12% to 22% by weight, and more preferably 15% to 20% by weight. If the concentration of calcium chloride in the calcium chloride methanol solution is too low, the amount of polyamide dissolved is small, and a large amount of solvent is required. On the other hand, if the concentration of calcium chloride in the calcium chloride methanol solution is too high, calcium chloride is prone to have insoluble matter remaining, and is easily mixed in as an impurity.

[0498] The calcium chloride methanol solution may further contain a solvent other than methanol. The solvent other than methanol is not particularly limited, and examples thereof include water, and alcohols such as ethanol, n-propanol, and isopropanol. When the calcium chloride methanol solution contains the solvent, the solution containing the dissolved polyamide also contains these solvents.

[0499] The calcium chloride used as a raw material of the calcium chloride methanol solution preferably is anhydrous because the solubility of the polyamide decreases when mixed with water. However, the calcium chloride may be mixed with a dihydrate within a range within which the solubility is allowed.

[0500] When calcium chloride is dissolved, heating may be performed or not. The heating temperature is not particularly limited, and is, for example, 20° C. to 100° C., preferably 25° C. to 80° C. If the temperature is lower than 20° C., the dissolution rate is reduced, and if the temperature is higher than 100° C., the decomposition reaction is accelerated, and the yield is reduced.

[0501] The dissolving of calcium chloride can be carried out by any mode in batch mode or continuous mode. In the case of batch mode, stirring can be performed or not stirring can be performed, preferably stirring is performed. By stirring, the dissolution rate of the polyamide solid is improved. In the case of continuous mode, the solid can be continuously circulated with solvent, and the solution can also be circulated, and from the aspect of reducing the solvent used, the solution is preferably circulated.

[0502] The shape of the container for dissolving calcium chloride is not particularly limited, and any shape such as a tank type or a circulation type can be used.

[0503] The dissolution time is not particularly limited, and is, for example, 5 minutes to 48 hours.

[0504] In this process, the concentration of polyamide relative to the solvent (specifically, calcium chloride methanol solution) is not particularly limited, and is, for example, 1 to 20%, preferably 5 to 15%. If the concentration of polyamide relative to the solvent is too low, too much solvent is required, while if the concentration of polyamide relative to the solvent is too high, the viscosity increases and the dissolution takes time.

[0505] The polyamide molded article provided for dissolution, specifically, the processed polyamide molded article or the used polyamide molded article, etc., may be composed only of polyamide or may contain impurities. Impurities are, for example, other resins and metals. In the polyamide provided for dissolution, the impurities may be in a mixed, attached and / or coated state. In the case where impurities coexist, the polyamide and the impurities may be separated as needed. There is no particular limitation on the separation method. If impurities are to be removed in a state where the polyamide has been dissolved, separation may be performed by methods such as filtration, centrifugal separation and sedimentation separation. In the case where the polyamide is dissolved in a solvent together with the impurities, separation may be performed by, for example, extraction separation, membrane separation and electrodialysis in a dissolved state, or the polyamide may be precipitated in the precipitation step described later and then washed.

[0506] <Step (ii): Precipitation Step>

[0507] In this step, the dissolved polyamide obtained in step (i) is precipitated from the solution containing the dissolved polyamide to obtain the precipitated polyamide. In this step, the precipitated polyamide solid content can be separated from the above solution.

[0508] The method for precipitating the dissolved polyamide from the solution is not particularly limited, and several precipitation methods are possible depending on the state after the dissolution.

[0509] When dissolving by heating, precipitation by cooling using the temperature dependence of the solubility of the polyamide can be considered. In this case, no additional solvent is added to the solution containing the dissolved polyamide, and the dissolved polyamide is precipitated from the solution in this state to obtain the precipitated polyamide.

[0510] When the temperature dependence of the solubility during dissolution is small, the polyamide can be precipitated by mixing it with a poor solvent for the polyamide, thereby reducing the solubility. In this case, after adding a poor solvent to a solution containing the dissolved polyamide, the dissolved polyamide is precipitated from the solution to obtain the precipitated polyamide. The poor solvent is not particularly limited, and for example, water, and alcohols such as ethanol, n-propanol and isopropanol can be cited. As a method for adding a poor solvent to the polyamide, it can be any one of a method for adding a polyamide solution to a poor solvent or a method for adding polyamide in a poor solvent, and the addition rate, temperature and stirring rate during addition are not particularly limited.

[0511] When the temperature dependence of the solubility during dissolution is small, the solubility of the polyamide can be reduced by reducing the concentration of calcium chloride.

[0512] As described above, in this process, the precipitated polyamide solid component can be separated from the solution before the subsequent heating process. As a method for solid-liquid separation, for example, filtration, centrifugal separation and sedimentation separation can be cited. Any method can adopt any mode of batch type and continuous type.

[0513] The solid component obtained by solid-liquid separation can be washed with an additional cleaning solution. Specifically, the precipitated polyamide can be separated from the solution during precipitation to obtain a solid component containing polyamide. After the obtained solid component is washed with an additional cleaning solution, the polyamide is heated in step (iii). The additional cleaning solution is not particularly limited. For example, a solution composed of the liquid part during precipitation, a good solvent, and a solvent capable of dissolving calcium chloride, etc. can be used. The additional cleaning solution used here is, for example, water, and alcohols such as methanol, ethanol, n-propanol and isopropanol. The additional cleaning solution is preferably methanol. Cleaning can be performed multiple times as needed. In addition, in the case where the additional cleaning solution needs to be removed by decompression in the heating step described later, the boiling point of the additional cleaning solution used in the cleaning is preferably less than 100°C. If the boiling point of the additional cleaning solution is too high, the energy required to remove the cleaning solution will increase.

[0514] <Step (iii): Heating Step>

[0515] In this step, the precipitated polyamide obtained in step (ii) is heated to obtain heated polyamide. The precipitated polyamide solid component is heated and reformed to reduce the content of the solvent (typically, a calcium chloride methanol solution) in the polyamide solid component.

[0516] When the solid content of the precipitated polyamide is not separated from the solution in step (ii), the solid content is heated in the solution in this step. That is, the polyamide precipitated in step (ii) is heated in the solution at the time of precipitation in step (ii).

[0517] In addition, in the case where the solid component after precipitation is separated from the solution at the time of precipitation in step (ii), heating is performed in, for example, the atmosphere or an inert gas. In the heating of this step, in addition to heating, drying can also be performed, or drying can be performed with heating. For example, as described above, in step (ii), the precipitated polyamide is separated from the solution at the time of precipitation to obtain a solid component containing polyamide, and the obtained solid component is cleaned with additional cleaning liquid, and in this step, the polyamide can be heated.

[0518] Although not intended to be constrained by any theory, it is believed that, by heating, polyamide is modified as follows. That is, assuming that the state infiltrating into the polyamide with a solvent (representatively calcium chloride methanol solution) swells when precipitating, it can be believed that by heating in this state, the calcium chloride methanol solution as a solvent can be dried and / or the space for capturing the calcium chloride methanol solution can be reduced. Therefore, it is believed that liquids such as cleaning solutions can be made to be difficult to penetrate into the polyamide again, reduce the amount of the residual calcium chloride methanol solution, and then the impurity removal efficiency during subsequent cleaning (operation (iv)) can also be improved.

[0519] The heating temperature is not particularly limited, and is, for example, 20° C. to 100° C. If the heating temperature is too low, the reforming effect is reduced, and if the heating temperature is too high, solid fusion occurs due to the solution, making the treatment difficult.

[0520] Stirring during heating is not particularly limited, but stirring is preferably performed to avoid local heating.

[0521] The pressure during heating is not particularly limited, and can be pressurized and heated, or can be heated under reduced pressure. In the case of solid-liquid separation in operation (ii), if the pressure is reduced to below the atmospheric pressure and heated, the solvent (representatively calcium chloride methanol solution) is distilled off, and the efficiency of the cleaning (operation (iv)) described later improves, thereby preferably.

[0522] <Step (iv): Cleaning Step>

[0523] In this step, the heated polyamide obtained in step (iii) is washed with a washing liquid to obtain a regenerated polyamide. That is, this step is a step of washing the modified polyamide solid content.

[0524] In the case where solid-liquid separation is not performed in step (ii) and the precipitated solution is subjected to a heating step, solid-liquid separation is first performed. There is no particular limitation on the method for solid-liquid separation, and examples thereof include filtration, centrifugation, and sedimentation separation. A cleaning solution is added to the solid component obtained by solid-liquid separation to dissolve and remove impurities.

[0525] As the cleaning solution used in this process, water, and alcohols such as ethanol, n-propanol and isopropanol can be cited, and they can be used in combination. In addition, acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, and alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate can be added to the cleaning solution according to the type of impurities. In order to avoid residues after cleaning, the final cleaning is preferably carried out with water, and most preferably all cleaning is carried out in water. That is, in a preferred embodiment, the cleaning solution in step (iv) is water.

[0526] The amount of the cleaning liquid used in this step is not particularly limited, but is preferably determined so that the amount of impurities remaining after cleaning is reduced to a target residual amount.

[0527] The washing method in this step is not particularly limited, and examples thereof include a method of performing batch washing only a necessary number of times, a method of performing continuous washing by passing a washing liquid through a filter or a centrifugal separator with solids added thereto, and a combination of these methods.

[0528] After washing, the solid component may be dried as necessary. For example, when a solid component of polyamide is obtained by water washing, water is distilled off from the solid component by heating and / or reducing pressure to obtain a dry solid.

[0529] The regenerated polyamide obtained in this step is in the form of a solid, preferably a powder.

[0530] As described above, according to the present invention, when regenerating polyamide useful as an engineering plastic, the amount of waste liquid generated in the washing process (e.g., water washing process) required for removing impurities can be reduced. In addition, it is believed that by reducing the amount of waste liquid, the amount of energy used during drying can be reduced. This can be expected to reduce the amount of energy required in the polyamide recycling process and reduce the load on the process.

[0531] [Invention (III)]

[0532] The present invention (III) is described below. In the present invention (III), the conditions of the present inventions (I) to (II) and (IV) to (VII) can be appropriately incorporated.

[0533] The method for producing recycled polyamide of the present embodiment (III) is a method for producing recycled polyamide using a polyamide resin composition comprising polyamide coated with a silicone resin as a raw material, which comprises a dissolution step of dissolving the polyamide to prepare a polyamide solution by mixing a metal chloride alcohol solution comprising a metal chloride and an alcohol with the polyamide resin composition, wherein the mass proportion of the polyamide in the polyamide solution is 5 to 15 mass %.

[0534] In addition, another method for producing recycled polyamide of the present embodiment (III) is a method for producing recycled polyamide using a polyamide resin composition comprising polyamide coated with a silicone resin as a raw material, which includes a dissolution step of dissolving the polyamide to prepare a polyamide solution by mixing a metal chloride alcohol solution comprising a metal chloride and an alcohol with the above-mentioned polyamide resin composition, wherein the viscosity of the above-mentioned polyamide solution at 25°C is 10 to 20,000 mPa·s.

[0535] The production method of the present embodiment (III) may be, for example, a method for producing recycled polyamide by the step of dissolving and extracting polyamide from a silicone-coated polyamide base fabric using a metal chloride alcohol solution having a controlled water content.

[0536] The compounds and the like used in the production method of this embodiment (III) are described.

[0537] <Polyamide resin composition>

[0538] As the polyamide in the present embodiment, a polymer obtained by polymerization via an amide bond, such as a polymer obtained by polycondensation of a diamine compound and a dicarboxylic acid compound or a polymer obtained by ring-opening polymerization of a cyclic lactam, can be used.

[0539] The diamine compound is not particularly limited, and examples thereof include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonanediamine, methylpentamethylenediamine, and p-phenylenediamine.

[0540] The dicarboxylic acid compound is not particularly limited, and examples thereof include oxalic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid.

[0541] The cyclic lactam is not particularly limited, and examples thereof include ε-caprolactam, undecyl lactam, and lauryl lactam.

[0542] The combination of the diamine compound, the dicarboxylic acid compound, and the cyclic lactam compound is not particularly limited, and a plurality of compounds of each type may be used in combination.

[0543] Among them, the polyamide is preferably an aliphatic polyamide, and most preferably nylon 66, from the viewpoint of high solubility in a metal chloride alcohol solution (for example, calcium chloride methanol).

[0544] The polyamide resin composition includes polyamide coated with a silicone resin. The polyamide resin composition may be a composition consisting only of polyamide coated with a silicone resin, or may further include other components.

[0545] Among them, from the perspective of the production efficiency of the recycled polyamide, the mass ratio of the polyamide coated with the silicone resin relative to 100 mass % of the polyamide resin composition is preferably 30 to 100 mass %, more preferably 60 mass % or more, further preferably 70 mass % or more, and particularly preferably 80 mass % or more.

[0546] The silicone resin is not particularly limited, and examples thereof include methyl silicone and phenyl silicone resins. The silicone resin may be a mixture of these resins, or may be a product obtained by mixing and curing the respective raw materials.

[0547] The polyamide coated with the silicone resin may be coated with other coatings besides the silicone resin. The type of other coating is not particularly limited, and examples thereof include polyethylene, polypropylene, polyester, fluororesin, etc. Preferably, the polyamide is a material that does not dissolve in the metal chloride alcohol solution used for dissolution.

[0548] The polyamide coated with the silicone resin can be a recycled raw material of polyamide, for example, engineering scraps and wastes of molded products such as fibers, automobile parts, and electrical product parts using polyamide as a raw material. Specifically, engineering scraps and wastes such as clothing, airbags, tire cords, engine compartment or intake system, fuel system parts, connectors, fishing nets, UD tapes, etc. can be cited.

[0549] The polyamide resin composition may contain sewing thread. The material of the sewing thread is not particularly limited, but is preferably made of the same polyamide as the base fabric because it can be recovered as recycled polyamide.

[0550] <Metal chloride alcohol solution>

[0551] As the solvent for dissolving the polyamide, a metal chloride alcohol solution was used.

[0552] The metal chloride alcohol solution comprises a metal chloride and an alcohol, and may further comprise other components. The total mass ratio of the metal chloride and the alcohol relative to 100 mass % of the metal chloride alcohol solution is preferably 80 mass % or more, more preferably 90 mass % or more, and further preferably 100 mass %.

[0553] The metal chloride is not particularly limited, and examples thereof include zinc chloride, magnesium chloride, calcium chloride, etc., among which zinc chloride and calcium chloride are preferred, and calcium chloride is most preferred.

[0554] The metal chloride used as the raw material may be an anhydrous form or a hydrate form.

[0555] The mass ratio of the metal chloride is preferably 10 to 25 mass % relative to 100 mass % of the metal chloride alcohol solution. If it is less than 10 mass %, the amount of polyamide dissolved is small and a large amount of solvent is required. If it is more than 25 mass %, the metal chloride is likely to have insoluble matter remaining and is likely to be mixed as an impurity.

[0556] The amount of water in the metal chloride alcohol solution is not particularly limited, but is preferably 4 mol or less per mol of the metal chloride in the solution.

[0557] Examples of the alcohol include methanol, ethanol, n-propanol, 2-propanol, etc. Among them, methanol is preferred from the viewpoint of the solubility of the polyamide.

[0558] There is no particular limitation on the method for mixing the metal chloride and the alcohol. However, if the mixture is mixed in batches, stirring is preferred. Calcium chloride will dissolve even without stirring, but this takes time and may cause local deviations in the composition.

[0559] The metal chloride alcohol solution used in the dissolution of polyamide is preferably a solution produced by separating polyamide from a metal chloride alcohol solution in which polyamide from a polyamide base fabric is dissolved. In the case where the concentration and composition change during the separation and recovery of polyamide, separation from unnecessary components based on extraction, distillation, etc.; concentration based on distillation; concentration adjustment based on the addition of metal chloride and / or alcohol; etc. can be performed. For example, the metal chloride alcohol solution after separation of polyamide can be concentrated and used in the manufacturing method of this embodiment. Since alcohol and metal chloride are not discarded, the environmental load is small, and the polyamide remaining in the supernatant during the separation and recovery of polyamide can also be recovered, so the recovery rate is improved.

[0560] Each step in the production method of this embodiment will be described below.

[0561] <Step 1 Dissolution Step>

[0562] The dissolving step is a step of mixing a polyamide resin composition containing a silicone-coated polyamide (e.g., a silicone-coated polyamide base fabric) with a metal chloride alcohol solution to dissolve the polyamide. By mixing the polyamide resin composition with the metal chloride alcohol solution, the polyamide can be dissolved from the silicone-coated polyamide in the polyamide resin composition.

[0563] In this specification, the solution obtained by mixing the polyamide resin composition and the metal chloride alcohol solution is referred to as a "polyamide solution". The polyamide solution contains dissolved polyamide, silicone coated with polyamide, etc. By separating the coating such as silicone from the polyamide solution, a "solution containing polyamide" can be obtained.

[0564] There is no particular limitation on the shape of the polyamide base fabric used in the dissolution. The base fabric may be added directly in the shape of scraps from the fabric manufacturing process or a used air bag, or it may be cut according to the size of the device used in the dissolution.

[0565] The temperature when the polyamide resin composition and the metal chloride alcohol solution are mixed is not particularly limited, but is preferably 30 to 90° C., more preferably 40 to 90° C., and even more preferably 40 to 60° C. If the temperature is lower than 30° C., dissolution becomes slow, and if the temperature is higher than 90° C., the temperature is higher than the boiling point, which is not preferred from the viewpoint of corrosiveness and decomposition.

[0566] The dissolution may be carried out in either a batch or continuous manner.

[0567] In the case of a batch method, stirring is not particularly limited, but stirring is preferably performed. Stirring increases the dissolution rate of the polyamide solid.

[0568] In the case of a continuous method, the solvent may be continuously passed through the solid or the solution may be circulated. Circulation is preferred because the amount of solvent used can be reduced.

[0569] The shape of the container used in the dissolution step is not particularly limited, and any shape such as a tank type or a circulation type can be used.

[0570] The time for mixing the polyamide resin composition and the metal chloride alcohol solution is not particularly limited, but is preferably 5 minutes to 100 hours.

[0571] The mass ratio of the polyamide in 100 mass % of the polyamide solution is preferably 5 to 15 mass %, more preferably 7 to 13 mass %. If it is less than 5 mass %, too much solvent is required, and if it is more than 15 mass %, the viscosity increases, resulting in a prolonged dissolution time and deterioration of workability.

[0572] In addition, the mass ratio of the polyamide in 100 mass % of the above-mentioned solution containing polyamide is preferably 5 to 15 mass %, more preferably 7 to 13 mass %. If it is less than 5 mass %, too much solvent is required, and if it is more than 15 mass %, the viscosity increases, resulting in a longer mixing time and deterioration of workability.

[0573] The viscosity of the polyamide solution at 25° C. is preferably 10 to 20,000 mPa·s, more preferably 10 to 10,000 mPa·s, and even more preferably 10 to 3,000 mPa·s. The higher the viscosity, the higher the polymer concentration, but the dissolution efficiency of the polyamide decreases due to adhesion of the base fabric.

[0574] The viscosity of the solution containing polyamide at 25° C. is preferably 10 to 20,000 mPa·s, more preferably 10 to 10,000 mPa·s, and even more preferably 10 to 3,000 mPa·s.

[0575] There is no particular limitation on the method for separating the silicone resin from the polyamide solution, and examples include a method of scooping up the silicone resin from the dissolved layer, filtration, centrifugal separation, sedimentation separation, etc., or a combination thereof. Since fine fragments of silicone may be generated when polyamide is dissolved, it is preferred to remove the fine fragments by filtration or a combination of filtration methods.

[0576] It is also preferred that other coatings of the polyamide coated with the silicone resin are removed simultaneously with the silicone resin.

[0577] Since the separated organosilicon resin and other coatings are attached with a solution containing polyamide, it is preferred to wash and recycle the solution containing polyamide. The solvent for washing is not particularly limited, and calcium chloride methanol solution is preferred. There is no particular limitation on the washing method, and stirring washing in a tank reactor, circulation washing in a filter, etc. can be cited.

[0578] <Polyamide recycling process>

[0579] The polyamide recovery step is a step of recovering polyamide from the polyamide-containing solution from which the silicone resin has been removed and obtained in the dissolving step.

[0580] Although the polyamide can be recovered from the polyamide solution, it is preferred to recover the polyamide from the solution containing the polyamide after removing the covering material such as a silicone resin in order to further improve the recovery efficiency.

[0581] As a method for recovering polyamide from a solution containing polyamide, a method of precipitating polyamide can be mentioned. The method of precipitating polyamide from the solution containing polyamide is not particularly limited, and several precipitation methods can be used depending on the state after dissolution.

[0582] When dissolving by heating, precipitation by cooling using the temperature dependence of the solubility of the polyamide can be considered. In this case, no additional solvent is added to the solution containing the dissolved polyamide, and the dissolved polyamide is precipitated from the solution in this state to obtain the precipitated polyamide.

[0583] When the temperature dependence of the solubility during dissolution is small, the solubility can be reduced by mixing a solution containing polyamide with a poor solvent for polyamide to precipitate it. In this case, after adding a poor solvent to a solution containing dissolved polyamide, the dissolved polyamide is precipitated from the solution to obtain the precipitated polyamide. The poor solvent is not particularly limited, and for example, water, and alcohols such as ethanol, n-propanol and isopropanol can be cited. As a method for adding a poor solvent to polyamide, it can be any method of adding a solution containing polyamide to a poor solvent or adding a poor solvent to a solution containing polyamide, and the addition rate, temperature and stirring rate during addition are not particularly limited.

[0584] The amount of the poor solvent added is not particularly limited, but is preferably 0.5 to 50 times the mass of the solution containing the polyamide, and more preferably 1 to 10 times the mass. The smaller the amount added, the lower the recovery rate, and the larger the amount added, the larger the amount of solution, which requires time and energy for processing.

[0585] When the temperature dependence of the solubility during dissolution is small, the solubility of the polyamide can also be reduced by reducing the concentration of calcium chloride. There is no particular limitation on the method of adding methanol to reduce the concentration of calcium chloride, and it can be a method of adding a solution containing polyamide to methanol or a method of adding methanol to a solution containing polyamide. There is no particular limitation on the addition rate, temperature, stirring rate, etc. during addition.

[0586] The shape of the container is not particularly limited, and any shape such as a trough type or a circulation type can be used.

[0587] The precipitated polyamide is preferably recovered by solid-liquid separation. Examples of solid-liquid separation methods include filtration, centrifugal separation, and sedimentation separation. Any of the methods may be batch or continuous.

[0588] The polyamide obtained by solid-liquid separation is preferably washed with a solvent. The washing liquid is not particularly limited, and for example, a solution composed of the liquid part during precipitation, a good solvent, and a solvent capable of dissolving calcium chloride, etc. are used. The additional washing liquid used here is, for example, water, and alcohols such as methanol, ethanol, n-propanol, and isopropanol. The additional washing liquid is preferably methanol. Washing can be performed multiple times as needed.

[0589] The washing method is not particularly limited, and examples thereof include a method of performing batch washing, a method of performing continuous washing by passing water in a state where solids are placed in a solid-liquid separation device such as a filter or a centrifuge, and a method combining these methods.

[0590] The washed polyamide can be heated and / or reduced in pressure to distill off the washing solvent and made into a dry solid, thereby obtaining a powdered polyamide.

[0591] As described above, according to the present embodiment, it is possible to provide a method for producing recycled polyamide at a high yield from a composition in which polyamide useful as an engineering plastic is coated with silicone.

[0592] <Step of Concentrating the Metal Chloride Alcohol Solution>

[0593] The production method of the present embodiment may further include a step of concentrating the metal chloride alcohol solution from the viewpoint of reusing the metal chloride alcohol solution.

[0594] For example, the metal alcohol solution containing the metal chloride and the alcohol obtained in the above-mentioned polyamide recovery step may be concentrated and reused.

[0595] Examples of the concentration method include concentration by heating.

[0596] <Recycled polyamide>

[0597] There is no particular limitation on the shape of the recycled polyamide produced by the manufacturing method of this embodiment, and examples include a shape in which the polyamide is melted during regeneration to form pellets; a shape in which the polyamide is temporarily dissolved in a solvent and then precipitated to form a powder; a shape in which the powder is agglomerated in accordance with the treatment conditions to form a flat plate; and the like.

[0598] The above-mentioned recycled polyamide can be used as a raw material for polyamide fibers, polyamide base fabrics, airbags, etc.

[0599] (Spinning of polyamide fibers)

[0600] The spinning temperature during melt spinning is preferably 290° C. to 310° C. The spinning temperature is preferably set to 310° C. or less, because thermal decomposition of the polyamide can be suppressed; the spinning temperature is more preferably 300° C. or less, and further preferably 295° C. or less. On the other hand, the spinning temperature is preferably set to 290° C. or more, because the polyamide exhibits sufficient melt fluidity, the discharge amount between the discharge holes is uniform, and high-ratio stretching can be achieved.

[0601] The shorter the residence time (the time from when the polyamide resin melts until it is discharged from the spinning nozzle) in the melt spinning process, the better. The residence time is preferably 30 minutes or less, more preferably 15 minutes or less, and further preferably 0.5 minutes or more and 7 minutes or less. A short time is preferred because the cyclopentanones in the polymer increase at the melting temperature.

[0602] In order to achieve thermal stability in a high temperature and high humidity environment, it is preferred to add a copper compound in a copper concentration of 1 to 500 ppm relative to the polyamide, and the copper concentration is more preferably 30 to 500 ppm. In this way, even if the polyamide is placed for a long time in a high temperature and high humidity environment, or is exposed to an environment containing a large amount of ozone for a long time, the reduction in mechanical properties can be extremely effectively suppressed. If the above copper content is less than 30 ppm, the heat resistance strength retention rate is reduced; if the addition amount is more than 500 ppm, the strength is reduced.

[0603] As the copper compound, there is no particular limitation on its type, for example, organic copper salts such as cupric acetate, or copper halides such as cuprous chloride and cupric chloride can be preferably used. The copper compound is more preferably used in combination with a metal halide. As the metal halide, for example, potassium iodide, potassium bromide, potassium chloride, etc. can be cited. The preferred combination in this embodiment is cuprous iodide and potassium iodide, and cupric acetate and potassium iodide. It should be noted that the copper content in the polyamide can be measured by atomic absorption spectrometry, colorimetry, etc.

[0604] Although not limited to the following, as stabilizers, organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, and phosphorus antioxidants, heat stabilizers, hindered amine-based, benzophenone-based, and imidazole-based light stabilizers, and ultraviolet absorbers can be added. The amount of addition can be selected appropriately, and 1 to 1000 ppm can be added relative to the polyamide. These additives can be used not only alone but also in combination of multiple types.

[0605] In the melt spinning step, a single-screw or twin-screw extruder is preferably used in the melting section. The extruder can apply an appropriate pressure to the polyamide resin and simultaneously introduce it into the polymer pipe, gear pump, and spinning pack.

[0606] In addition, it is preferred to filter the polyamide resin using a metal fiber nonwoven fabric filter, gravel, or the like before discharge from the spinning nozzle because the spinning operation can be stabilized.

[0607] The shape of the nozzle hole of the spinning nozzle can be selected according to the cross-sectional shape of the single fiber constituting the manufactured filament. The spun yarn from the spinning nozzle is solidified by cooling air, given an engineering oil and pulled, and then stretched and heat-treated to obtain a polyamide fiber.

[0608] The oil agent adhesion rate of the polyamide fiber is preferably 0.5 to 1.5 wt%. If the oil agent adhesion rate is 1.5 wt% or less, the weft yarn will hardly fly away due to stickiness (adhesion), and the air or water as the weft yarn conveying medium will not lose the weft yarn conveying power due to the monofilament bundling being too good to exceed the monofilament bundling degree based on interweaving and the reduction of the apparent cross-sectional area, and the weft yarn conveying power will be good. On the other hand, if the oil agent adhesion rate is 0.5 wt% or more, the weft yarn can be smoothly supplied due to the appropriate friction reduction effect, so there is no weaving stop and the productivity is excellent.

[0609] (Polyamide base fabric)

[0610] In weaving, a water jet loom, an air jet loom, a rapier loom, etc. can be used as a loom. The base fabric for airbags is a high-density fabric, and it is preferably manufactured with increased warp tension and good process performance in the warping process and weaving process. The warp tension is set high during weaving to create effective weft beating conditions, thereby forming a high-density fabric.

[0611] The woven fabric can be subjected to a scouring process to remove the engineering oil of the polyamide fiber.

[0612] The scouring step may be performed with warm water, pressurized hot water, or the like, and the treatment step may be a single-stage treatment or a multi-stage treatment of two or more stages. In addition, it is also preferred to perform scouring by applying a conventionally known scouring agent.

[0613] The fabric is preferably heat-set in a heat-setting process. The heat-setting temperature is preferably 110°C to 200°C, and the heat-setting time is appropriately selected in the range of 0.1 to 30 minutes. In the heat-setting process, the fabric is preferably dried while being stretched so that the shrinkage force is maintained at a predetermined strength. If the fabric is heat-set, the process of the subsequent resin coating process can be stabilized.

[0614] The fabric after the scouring step can be subjected to a drying treatment before the heat setting step as needed. The drying temperature is preferably in the range of 80°C to 130°C, more preferably in the range of 100°C to 120°C. In addition, the treatment time is preferably appropriately selected within the range of 0.1 minute to 30 minutes. Drying can be performed in a relaxed state or in a tensioned state.

[0615] The polyamide base fabric can be used as an uncoated base fabric after a heat setting process, but can also be coated with a coating agent such as silicone or urethane or heat-laminated into a thin film or the like.

[0616] As a method for coating the surface of the fabric, the following methods can be used: a method of immersing the fabric in a resin solution tank, and then using a squeezer, a vacuum machine, and then a coating blade to coat and evenly coat the excess resin; a rod coating method using a comma coater, etc., a method of blowing the resin using a spray device or a foaming device, etc. Among these, the method of applying the resin uniformly and in small amounts is preferably a method of coating with a blade.

[0617] Coating amount is 5g / m 2 Above 100g / m 2 Less than 10 g / m 2 Above 70g / m 2 Below, more preferably 15g / m 2 Above 30g / m 2 Below, use 5g / m2 The above coating amount can obtain the required airtightness. On the other hand, using 100g / m 2 The following coating amounts can make the coated fabric soft and have good storage properties, while reducing the weight of the entire airbag.

[0618] <Airbag>

[0619] The airbag can be appropriately selected from commonly used airbags for the driver's seat, front passenger seat, side (including side air curtain), rear seat, etc. The bag body of the airbag can be cut into any shape such as circular, oblong, elliptical, rectangular, polygonal or a combination thereof, as long as the desired deployment shape is met.

[0620] The stitch shape includes a single straight line or multiple parallel straight lines, a zigzag shape, a combination of a straight line and a zigzag shape, a straight line and an oblique line, etc. The stitching method may be a commonly used stitching method such as a flat stitch or a double-thread lock stitch, and the stitch spacing may be selected from a range of 20 to 60 times / 10 cm. In addition, the thread thickness may be selected from 420d to 3000d, and the thread material may be a commercially available thread such as polyamide fiber, polyester fiber, vinylon-based fiber, aramid-based fiber, glass fiber, etc.

[0621] [Invention (IV)]

[0622] The present invention (IV) is described below. In the present invention (IV), the conditions of the present inventions (I) to (III) and (V) to (VII) can be appropriately incorporated.

[0623] The present invention (IV) relates to a solvent having low corrosiveness and capable of dissolving polyamide.

[0624] <Low Corrosive Solvent (Methanol Composition)>

[0625] The solvent in the present invention (IV) is a methanol composition containing a metal chloride, a hydroxide of the same metal, and water at predetermined concentrations.

[0626] The concentration of the metal chloride in the present solvent is 5 to 25%, preferably 10 to 23%, and more preferably 15 to 22%. The concentration of the metal chloride is defined as a weight concentration relative to the entire methanol composition. The lower the concentration of the metal chloride, the lower the solubility of the polyamide. The solubility of the metal chloride in methanol is 25%, and an excess of the metal chloride absorbs moisture, increases the water content in the methanol composition, and as a result, reduces the solubility of the polyamide.

[0627] The mass ratio of the metal chloride relative to 100 mass % of the solvent is also preferably 23 to 35 mass %, more preferably 25 to 33 mass %, and particularly preferably 27 to 31 mass %.

[0628] The metal constituting the metal chloride and the hydroxide of the same metal is not particularly limited, and examples thereof include zinc (i.e., the metal chloride is zinc chloride and the hydroxide of the same metal is zinc hydroxide) and calcium (i.e., the metal chloride is calcium chloride and the hydroxide of the same metal is calcium hydroxide), and calcium is preferred.

[0629] The metal chloride used in the preparation of the solvent is preferably an anhydrous form, but a hydrate may be used within a range in which the solubility of the polyamide can be maintained.

[0630] The solvent of the present invention contains a hydroxide of the same metal as a base to reduce corrosion caused by metal chloride. By making the solvent of the present invention contain a hydroxide of the same metal, metal corrosivity can be reduced without reducing the solubility of polyamide in the methanol solution of the metal chloride.

[0631] The concentration of the hydroxide of the same metal is 0.001 to 1%, preferably 0.001 to 0.1%, and more preferably 0.001 to 0.01%. The concentration of the hydroxide of the same metal is defined as the weight concentration of the hydroxide of the same metal relative to the entire methanol composition. The hydroxide of the same metal does not need to be completely dissolved in methanol, and a part of it may not be dissolved.

[0632] The mass ratio of water relative to 100 mass % of the metal chloride alcohol solution is preferably 0.001 to 10 mass %, more preferably 0.001 to 5 mass %, further preferably 0.001 to 1 mass %, particularly preferably 0.01 to 0.1 mass %.

[0633] The metal chloride alcohol solution of this embodiment preferably has a metal chloride concentration of 23 mass % to 35 mass %, contains a hydroxide of the same metal as the metal contained in the metal chloride at a concentration of 0.001 to 1%, and contains water at a concentration of 0.001 to 10%.

[0634] <Solution containing polyamide>

[0635] In addition, the methanol composition may be a polyamide-containing solution further comprising polyamide dissolved in the methanol composition as a solvent. Such a polyamide-containing solution can reduce corrosiveness.

[0636] <Polyamide>

[0637] The polyamide in the present invention refers to a polymer obtained by polymerization via an amide bond, such as a product obtained by polycondensation of a diamine compound and a dicarboxylic acid compound or a product obtained by ring-opening polymerization of a cyclic lactam.

[0638] The diamine compound is not particularly limited, and examples thereof include hexamethylenediamine, nonanediamine, methylpentanediamine, and p-phenylenediamine.

[0639] The dicarboxylic acid compound is not particularly limited, and examples thereof include adipic acid, sebacic acid, terephthalic acid, and isophthalic acid.

[0640] The cyclic lactam is not particularly limited, and examples thereof include ε-caprolactam, undecyl lactam, and lauryl lactam.

[0641] There are no particular limitations on the combination of the diamine compound, the dicarboxylic acid compound, and the cyclic lactam compound, and a plurality of compounds of each type may be used in combination. Polyhexamethylene adipamide composed of hexamethylenediamine and adipic acid is preferably used because of its high solubility.

[0642] The polyamide is not particularly limited and examples thereof include those containing aliphatic polyamides such as polyamide 66 (polyhexamethylene adipamide), polyamide 6, polyamide 610, polyamide 6T, and polyamide 6I. Those containing aliphatic polyamides are preferred, and those containing polyamide 66 (polyhexamethylene adipamide) are most preferred.

[0643] <Method for producing polyamide composition>

[0644] The method for producing a polyamide composition using the low-corrosive solvent of the present invention will be described in detail below, but the following description does not limit the method for producing a polyamide composition.

[0645] <Step 1: Polyamide Dissolution Step>

[0646] Step 1 is a step of dissolving a raw material polyamide composition serving as a raw material of polyamide.

[0647] As the solvent for dissolving the raw material polyamide composition, the above-mentioned low-corrosive solvent is used.

[0648] The temperature for dissolving is not particularly limited, but is preferably 40 to 90° C., more preferably 40 to 60° C. If it is lower than 40° C., dissolution becomes slow, and if it is higher than 90° C., the temperature is higher than the boiling point, which is not preferred in terms of corrosiveness and decomposition.

[0649] The dissolution may be carried out in either a batch or continuous manner.

[0650] In the case of a batch method, there is no particular limitation on whether stirring is performed, but stirring is preferably performed. Stirring increases the dissolution rate of the polyamide solid.

[0651] In the case of a continuous method, the solvent may be continuously passed through the solid or the solution may be circulated. Circulation is preferred because the amount of solvent used can be reduced.

[0652] The shape of the container is not particularly limited, and any shape such as a trough type or a circulation type can be used.

[0653] The dissolution time is not particularly limited, but is preferably 5 minutes to 100 hours.

[0654] The concentration of polyamide in the solvent is not particularly limited, but is preferably 5 to 15%, more preferably 7 to 13%. If it is less than 5%, too much solvent is required, and if it is more than 15%, the viscosity increases, resulting in a prolonged dissolution time and poor workability.

[0655] The raw material polyamide composition used as the raw material for dissolving may be composed of polyamide alone, or may be in a state of being mixed, attached, or coated with impurities such as other resins and metals. In the case where impurities other than polyamide coexist, a process for separating the polyamide and these impurities is required. There is no particular limitation on the separation method. If impurities are to be removed in a state where the polyamide has been dissolved, separation can be performed by methods such as filtration, centrifugation, and sedimentation separation. In the case of being dissolved in a solvent together with polyamide, separation can be performed by extraction separation, membrane separation, electrodialysis, etc. in a dissolved state, or by washing after the polyamide is precipitated in a precipitation process described later.

[0656] <Step 2 Dilution Step>

[0657] Step 2 is an optional step in which the polyamide dissolved in the solvent in step 1 is diluted with methanol.

[0658] The method of diluting the polyamide solution will be described in detail.

[0659] The dilution rate based on methanol is preferably 1.5 to 5 times. The dilution rate in this specification is defined as the value obtained by dividing the weight of the diluted polyamide solution by the weight of the polyamide solution when dissolved. At this time, even if precipitation occurs in the diluted polyamide solution, the weight including the precipitate is used as the weight of the diluted polyamide solution. When the dilution rate is less than 1.5, the particle size becomes smaller because the amount of polyamide precipitation is small and the particles are not fully grown. If the dilution rate is greater than 5 times, precipitation is likely to occur during dilution, and the particle size distribution becomes wider.

[0660] The temperature when diluting with methanol is not particularly limited, but is preferably 40 to 90° C. When diluting at a temperature lower than 40° C., precipitation is likely to occur during dilution. When diluting at a temperature higher than 90° C., non-uniform precipitation is likely to occur near the liquid surface due to the volatilization and condensation of methanol, making it difficult to control the particle size distribution.

[0661] The dilution rate of methanol is not particularly limited, but it is preferably added at a rate that does not cause abrupt changes in concentration or temperature during dilution to cause precipitation of polyamide.

[0662] The temperature of methanol used for dilution is not particularly limited, but is preferably 15 to 90° C. If it is lower than 15° C., local precipitation is likely to occur during dilution, and if it is higher than 90° C., it is higher than the boiling point of methanol, so it is necessary to treat under pressure.

[0663] The water content of methanol used for dilution is not particularly limited, but is preferably 0.005 to 1%. If the water content is high, polyamide rapidly precipitates in the aqueous solution due to low solubility.

[0664] The dilution method is not particularly limited and may be either a batch method or a continuous method.

[0665] In the case of a batch method, stirring is not particularly limited, but stirring is preferably performed. By stirring, the temperature and concentration become uniform.

[0666] The shape of the container is not particularly limited, and any shape such as a trough type or a circulation type can be used.

[0667] <Step 3 Separation Step (Cooling and Precipitation Step)>

[0668] Step 3 is a step of separating polyamide from the polyamide solution. The separation of polyamide can be performed, for example, by cooling the polyamide solution to precipitate the polyamide and subjecting the precipitated solid polyamide to solid-liquid separation from the polyamide solution.

[0669] There are no particular limitations on the cooling method, and the cooling may be performed in a batch or continuous manner.

[0670] In the case of batch method, there is no particular limitation on whether stirring is performed, but stirring is preferably performed. By stirring, the temperature and concentration become uniform. Preferably, stirring is performed under conditions where the particles are not easily destroyed or sheared due to stirring, depending on the equipment and method used in stirring.

[0671] The cooling rate is not particularly limited, but is preferably 10 to 100°C / Hr, more preferably 20 to 50°C / Hr. If it is lower than 10°C / Hr, the time taken becomes longer, and if the cooling rate is higher than 100°C / Hr, the particle size becomes smaller due to rapid precipitation. The particle size can be controlled by changing the cooling rate.

[0672] The temperature during cooling is not particularly limited, but is preferably 10° C. or more lower than the temperature during dilution. If the temperature difference is less than 10° C., precipitation is reduced and particles are less likely to grow.

[0673] The precipitated solid is preferably recovered by solid-liquid separation.

[0674] The method for solid-liquid separation is not particularly limited, and examples thereof include filtration, centrifugal separation, sedimentation separation, etc. Any of the methods may be batch-wise or continuous.

[0675] The solid obtained by solid-liquid separation is preferably washed with a solvent. The washing solvent is not particularly limited, but a solution of the liquid component during precipitation, a good solvent, or a solvent capable of dissolving metal chlorides or the like is preferably used.

[0676] As the washing solvent, alcohol such as methanol and ethanol, and water are preferred.

[0677] The washing method is not particularly limited, and examples thereof include a method of performing batch washing, a method of performing continuous washing by passing water in a state where solids are placed in a solid-liquid separation device such as a filter or a centrifuge, and a method combining these methods.

[0678] The washed polyamide can be heated and / or reduced in pressure to distill off the washing solvent to obtain a dry solid, thereby obtaining a polyamide composition.

[0679] In the method for producing a polyamide composition of the present invention, the polyamide composition can be obtained in the form of a powder (powdered polyamide composition).

[0680] <Polyamide composition>

[0681] In the polyamide composition obtained by the production method of the present invention, as polyamide, aliphatic polyamides such as polyamide 66 (polyhexamethylene adipamide), polyamide 6, polyamide 610, polyamide 6T, and polyamide 6I can be cited, preferably aliphatic polyamides, and most preferably polyamide 66 (polyhexamethylene adipamide). The polyamide composition obtained by the production method of the present invention may contain metal atoms and halogen atoms. The metal atom is a metal atom derived from a metal chloride and / or a hydroxide of the same metal contained in the low-corrosive solvent (methanol composition) used in the production method of the present invention, and examples thereof include zinc atoms and calcium atoms, preferably calcium atoms. The metal atom content of the polyamide composition obtained by the production method of the present invention is preferably 0.001 to 1000 ppm, more preferably 0.001 to 700 ppm, and further preferably 0.001 to 500 ppm. The molar content of halogen atoms in the polyamide composition obtained by the production method of the present invention is preferably less than 2, more preferably less than 1, and further preferably less than 0.5 relative to the molar content of metal atoms. The polyamide composition obtained by the production method of the present invention may be in the form of powder.

[0682] <Application of polyamide composition>

[0683] The polyamide composition obtained by the manufacturing method of the present invention can be used as a material for polyamide fibers. By spinning the polyamide fibers, regenerated fibers can be obtained. By weaving the regenerated fibers of this embodiment, regenerated woven fabrics can be obtained. The regenerated woven fabrics of this embodiment can be used to regenerate polyamide base fabrics for airbags.

[0684] <Spinning of polyamide fibers>

[0685] The spinning temperature during melt spinning is preferably 290° C. to 310° C. The spinning temperature is preferably set to 310° C. or less, because thermal decomposition of the polyamide can be suppressed; the spinning temperature is more preferably 300° C. or less, and further preferably 295° C. or less. On the other hand, the spinning temperature is preferably set to 290° C. or more, because the polyamide exhibits sufficient melt fluidity, the discharge amount between the discharge holes is uniform, and high-ratio stretching can be achieved.

[0686] The shorter the residence time (the time from when the polyamide resin melts until it is discharged from the spinning nozzle) in the melt spinning process, the better. The residence time is preferably 30 minutes or less, more preferably 15 minutes or less, and further preferably 0.5 minutes or more and 7 minutes or less. A short time is preferred because the cyclopentanones in the polymer increase at the melting temperature.

[0687] In order to achieve thermal stability under high temperature and high humidity environment, it is preferred to add copper compound in a manner that the copper concentration relative to the polyamide is 1 to 500 ppm, and the copper concentration is more preferably 30 to 500 ppm. In this way, even if the product of the present invention is placed for a long time under high temperature and high humidity environment, or is exposed to an environment containing a large amount of ozone for a long time, the reduction of mechanical properties can be extremely effectively suppressed. If the above copper content is less than 30 ppm, the heat resistance strength retention rate is reduced, and if the addition amount exceeds 500 ppm, the strength is reduced.

[0688] As the copper compound, there is no particular limitation on its type, for example, organic copper salts such as cupric acetate, or copper halides such as cuprous chloride and cupric chloride can be preferably used. The copper compound is more preferably used in combination with a metal halide. As the metal halide, for example, potassium iodide, potassium bromide, potassium chloride, etc. can be cited. The preferred combination in this embodiment is cuprous iodide and potassium iodide, and cupric acetate and potassium iodide. It should be noted that the copper content in the polyamide can be measured by atomic absorption spectrometry, colorimetry, etc.

[0689] Although not limited to the following, as stabilizers, organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, and phosphorus antioxidants, heat stabilizers, hindered amine-based, benzophenone-based, and imidazole-based light stabilizers, and ultraviolet absorbers can be added. The amount of addition can be selected appropriately, and 1 to 1000 ppm can be added relative to the polyamide. These additives can be used not only alone but also in combination of multiple types.

[0690] In the melt spinning step, a single-screw or twin-screw extruder is preferably used in the melting section. The extruder can apply an appropriate pressure to the polyamide resin and simultaneously introduce it into the polymer pipe, gear pump, and spinning pack.

[0691] In addition, it is preferred to filter the polyamide resin using a metal fiber nonwoven fabric filter, gravel, or the like before discharge from the spinning nozzle because the spinning operation can be stabilized.

[0692] The shape of the nozzle hole of the spinning nozzle can be selected according to the cross-sectional shape of the single fiber constituting the manufactured filament. The spun filaments from the spinning nozzle are solidified with cooling air, given an engineering oil and drawn, and then stretched and heat-treated to obtain the polyamide fiber used in the present invention.

[0693] The oil agent adhesion rate of the polyamide fiber is preferably 0.5 to 1.5 wt%. If the oil agent adhesion rate is 1.5 wt% or less, the weft yarn will hardly fly away due to stickiness (adhesion), and the air or water as the weft yarn conveying medium will not lose the weft yarn conveying power due to the monofilament bundling being too good to exceed the monofilament bundling degree based on interweaving and the reduction of the apparent cross-sectional area, and the weft yarn conveying power will be good. On the other hand, if the oil agent adhesion rate is 0.5 wt% or more, the weft yarn can be smoothly supplied due to the appropriate friction reduction effect, so there is no weaving stop and the productivity is excellent.

[0694] <Polyamide base fabric>

[0695] In weaving, a water jet loom, an air jet loom, a rapier loom, etc. can be used as a loom. The base fabric for airbags is a high-density fabric, and it is preferably manufactured with increased warp tension and good process performance in the warping process and weaving process. The warp tension is set high during weaving to create effective weft beating conditions, thereby forming a high-density fabric.

[0696] The woven fabric can be subjected to a scouring process to remove the engineering oil of the polyamide fiber.

[0697] The scouring step may be performed with warm water, pressurized hot water, or the like, and the treatment step may be a single-stage treatment or a multi-stage treatment of two or more stages. In addition, it is also preferred to perform scouring by applying a conventionally known scouring agent.

[0698] The fabric is preferably heat-set in a heat-setting process. The heat-setting temperature is preferably 110°C to 200°C, and the heat-setting time is appropriately selected in the range of 0.1 to 30 minutes. In the heat-setting process, the fabric is preferably dried while being stretched so that the shrinkage force is maintained at a predetermined strength. If the fabric is heat-set, the process of the subsequent resin coating process can be stabilized.

[0699] The fabric after the scouring step can be subjected to a drying treatment before the heat setting step as needed. The drying temperature is preferably in the range of 80°C to 130°C, more preferably in the range of 100°C to 120°C. In addition, the treatment time is preferably appropriately selected within the range of 0.1 minute to 30 minutes. Drying can be performed in a relaxed state or in a tensioned state.

[0700] The polyamide base fabric can be used as an uncoated base fabric after a heat setting process, but can also be coated with a coating agent such as silicone or urethane or heat-laminated into a thin film or the like.

[0701] As a method for coating the surface of the fabric, the following methods can be used: a method of immersing the fabric in a resin solution tank, and then using a squeezer, a vacuum machine, and then a coating blade to coat and evenly coat the excess resin; a rod coating method using a comma coater, etc., a method of blowing the resin using a spray device or a foaming device, etc. Among these, the method of applying the resin uniformly and in small amounts is preferably a method of coating with a blade.

[0702] Coating amount is 5g / m 2 Above 100g / m 2 Less than 10 g / m 2 Above 70g / m 2 Below, more preferably 15g / m 2 Above 30g / m 2 Below, use 5g / m 2 The above coating amount can obtain the required airtightness. On the other hand, using 100g / m 2 The following coating amounts can make the coated fabric soft and have good storage properties, while reducing the weight of the entire airbag.

[0703] <Airbag>

[0704] The airbag can be appropriately selected from commonly used airbags for the driver's seat, front passenger seat, side (including side air curtain), rear seat, etc. The bag body of the airbag can be cut into any shape such as circular, oblong, elliptical, rectangular, polygonal or a combination thereof, as long as the desired deployment shape is met.

[0705] The stitch shape includes a single straight line or multiple parallel straight lines, a zigzag shape, a combination of a straight line and a zigzag shape, a straight line and an oblique line, etc. The stitching method may be a commonly used stitching method such as a flat stitch or a double-thread lock stitch, and the stitch spacing may be selected from a range of 20 to 60 times / 10 cm. In addition, the thread thickness may be selected from 420d to 3000d, and the thread material may be a commercially available thread such as polyamide fiber, polyester fiber, vinylon-based fiber, aramid-based fiber, glass fiber, etc.

[0706] As described above, the present invention can provide a solvent that has low corrosiveness and can dissolve polyamide, and this solvent can also be used to dissolve and precipitate polyamide useful as an engineering plastic to produce a powdered polyamide.

[0707] [Invention (V)]

[0708] The present invention (V) is described below. In the present invention (V), the conditions of the present inventions (I) to (IV) and (VI) to (VII) can be appropriately incorporated.

[0709] <Production Method of Polyamide>

[0710] The method for producing polyamide according to the present embodiment (V) (hereinafter sometimes referred to as “the method for producing polyamide according to the present embodiment” or “the method for producing polyamide according to the present embodiment”) includes the following steps:

[0711] Step 1: a dissolving step of heating and dissolving the polyamide resin composition with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated solution;

[0712] Step 2: a recovery step of precipitating polyamide from the polyamide heated solution and recovering the polyamide;

[0713] Step 3: a washing step of washing the recovered polyamide; and

[0714] Step 4: A drying step of heating and drying the washed polyamide.

[0715] It should be noted that the production method of the present embodiment may include only steps 1 to 4, or may further include other steps.

[0716] (Polyamide)

[0717] First, the polyamide and the polyamide resin composition used in the production method of the present embodiment will be described.

[0718] As the polyamide, a polymer obtained by polymerization via an amide bond, such as a polymer obtained by condensation polymerization of a diamine compound and a dicarboxylic acid compound or a polymer obtained by ring-opening polymerization of a cyclic lactam, can be used.

[0719] The diamine compound is not particularly limited, and examples thereof include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonanediamine, methylpentamethylenediamine, and p-phenylenediamine.

[0720] The dicarboxylic acid compound is not particularly limited, and examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid.

[0721] The cyclic lactam is not particularly limited, and examples thereof include ε-caprolactam, undecyl lactam, and lauryl lactam.

[0722] There is no particular limitation on the combination of the diamine compound, the dicarboxylic acid compound and the cyclic lactam compound, and a plurality of compounds of each type may be used in combination. Polyhexamethylene adipamide (for example, polyhexamethylene adipamide composed of hexamethylenediamine and adipic acid) has high solubility and is suitable for the method for producing polyamide of this embodiment.

[0723] Examples of the polyamide include polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), polybutylene adipamide (nylon 46), polybutylene sebacate (nylon 410), polypentamethylene adipamide (nylon 56), polypentamethylene sebacate (nylon 510), polyhexamethylene sebacate (nylon 610), polyhexamethylene dodecanoyl (nylon 612), polydecanediamide (nylon 106), polydecanediamide (nylon 101 0), polydecanediamide (nylon 1012), polyundecanamide (nylon 11), polydodecaneamide (nylon 12), polycaprolactam / polyhexamethylene adipamide copolymer (nylon 6 / 66), polycaprolactam / polyhexamethylene terephthalamide copolymer (nylon 6 / 6T), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon 66 / 6T), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6I), poly Hexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 6T / 6I), polyhexamethylene terephthalamide / polyundecanamide copolymer (nylon 6T / 11), polyhexamethylene terephthalamide / polydodecaneamide copolymer (nylon 6T / 12), polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6T / 6I), polyphenylene adipamide (nylon XD6), polyphenylene sebacate (nylon X D10), polyhexamethylene terephthalamide / polypentamethylene terephthalamide copolymer (nylon 6T / 5T), polyhexamethylene terephthalamide / poly-2-methylpentamethylene terephthalamide copolymer (nylon 6T / M5T), polypentamethylene terephthalamide / polydecamethylene terephthalamide copolymer (nylon 5T / 10T), polynonane terephthalamide (nylon 9T), polydecamethylene terephthalamide (nylon 10T), polydodecane terephthalamide (nylon 12T), etc. It should be noted that the " / " mentioned here represents a copolymer. These polyamides can be used alone or in combination of two or more.

[0724] Among these, as the polyamide, one selected from the group consisting of polyamide 6, polyamide 66, polyamide 46, polyamide 610 and polyamide 612 is preferably used, and polyamide 66 is particularly preferably used. Polyamide 66 itself is a generally known polyamide resin, and is generally produced by polycondensation of hexamethylenediamine and adipic acid. Alternatively, polyamide 66 may be a copolymer containing less than 30% by mass of at least one monomer unit selected from the group consisting of lactam, aminocarboxylic acid, and a combination of other diamines and dicarboxylic acids, relative to the total mass of all monomer units.

[0725] In addition, these polyamides can use commercial products or can be produced using known methods. As the production method of polyamide, specifically, but not particularly limited to, for example, a method of ring-opening polymerization of lactam, a method of self-condensation of ω-aminocarboxylic acid, a method of condensing diamine and dicarboxylic acid, etc. can be cited.

[0726] In addition, in the above polyamide, the value [NH2] / [COOH] obtained by dividing the amount of amino terminal groups by the amount of carboxyl terminal groups is preferably 0.5 or more and 0.9 or less. By making [NH2] / [COOH] within the above range, the interaction between the surface of the glass fiber and the polyamide terminal is more fully increased during melt kneading, and the physical properties of the obtained composition are fully improved. The amount of amino terminal groups and the amount of carboxyl terminal groups can be, for example, 1 The measurement was performed by H-NMR.

[0727] The polyamide may be composed of polyamide alone, or may be used as a polyamide resin composition containing the polyamide and other components.

[0728] For example, impurities such as other resins and metals may be mixed as other components, attached to, or applied to the polyamide.

[0729] From the perspective of obtaining a powdered polyamide having a larger particle size and a smaller particle size distribution in a short time, the mass ratio of the above-mentioned polyamide relative to 100 mass% of the above-mentioned polyamide resin composition is preferably 30 to 100 mass%, more preferably 70 mass% or more, further preferably 80 mass% or more, further preferably 85 mass% or more, and particularly preferably 100 mass%.

[0730] It should be noted that, in the case of impurities other than the above-mentioned polyamide, the process of separating the polyamide from these impurities may be included. There is no particular limitation on the separation method. In the state where the polyamide resin composition has been dissolved, if the impurities are insoluble, they can be separated by methods such as filtration, centrifugation, sedimentation separation, etc. In the case where the impurities are dissolved in a solvent together with the polyamide, it can be considered to separate by extraction separation, membrane separation, electrodialysis, etc. in a dissolved state, or to separate the polyamide in a precipitation process described later and then wash it.

[0731] (Step 1: Polyamide Heating Dissolved Liquid Obtaining Step)

[0732] Furthermore, the recovery method of the present embodiment includes a dissolving step (step 1) of heating and dissolving the polyamide resin composition with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated dissolved liquid.

[0733] According to this step, only the polyamide can be melt-separated from the polyamide resin composition, so that subsequent recovery of the polyamide becomes easy.

[0734] Furthermore, since only the polyamide can be melt-separated simply by mixing the polyamide resin composition with a predetermined metal chloride alcohol solution, the polyamide can be recovered efficiently at a high yield.

[0735] The metal chloride alcohol solution used for heating and dissolving the polyamide contains metal chloride and alcohols. It should be noted that it may further contain components other than metal chloride and alcohols as required.

[0736] From the viewpoint of the solubility of the polyamide, the total mass ratio of the metal chloride and the alcohol is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass% relative to 100 mass% of the metal chloride alcohol solution.

[0737] As the above-mentioned alcohols, methanol, ethanol, linear or branched propanol, linear or branched butanol, and combinations thereof can be cited. Among them, methanol, ethanol, or a combination thereof is preferred from the aspect of the solubility of the polyamide, and methanol is more preferred. In addition, as the above-mentioned alcohols, various glycols can be further included as needed.

[0738] The mass ratio of the metal chloride is preferably 10 to 50 mass %, more preferably 15 to 25 mass % relative to 100 mass % of the metal chloride alcohol solution. If the mass ratio is less than 10 mass %, the amount of polyamide dissolved is small and a large amount of solvent is required. On the other hand, if the mass ratio is more than 50 mass %, the metal chloride is likely to have insoluble matter remaining and is likely to be mixed as an impurity.

[0739] Examples of the metal chloride include zinc chloride, magnesium chloride, calcium chloride and the like, among which zinc chloride and calcium chloride are preferred, and calcium chloride is most preferred.

[0740] The metal chloride is preferably anhydrous. If mixed with water, the solubility of the polyamide decreases. However, a hydrate (for example, a dihydrate in the case of calcium chloride) may be mixed within a range within which the solubility is allowed.

[0741] The mass ratio of water in the metal chloride is preferably 30 mass % or less, more preferably 1 mass % or less, further preferably 0.1 mass % or less, and particularly preferably no water is contained.

[0742] The temperature for heating and dissolving is not particularly limited, but is preferably 30 to 90° C., more preferably 40 to 60° C., from the perspective of solubility and other aspects. It should be noted that if the temperature is low, the dissolution will be slow, and if it is higher than 90° C., the temperature is higher than the boiling point, which is not preferred from the perspective of corrosiveness and decomposition.

[0743] It should be noted that the above temperature may be fixed or may vary within the above range.

[0744] The polyamide may be dissolved in a batch manner or in a continuous manner.

[0745] In the case of a batch method, stirring is not particularly limited, but stirring is preferably performed. Stirring increases the dissolution rate of the polyamide.

[0746] In the case of a continuous method, the solvent may be continuously passed through the solid or the solution may be circulated. Circulation is preferred because the amount of solvent used can be reduced.

[0747] The shape of the container used when heating and dissolving the polyamide is not particularly limited, and any shape such as a tank type and a circulation type can be used.

[0748] The dissolution time of the polyamide is not particularly limited, but is preferably 5 minutes to 100 hours.

[0749] In the step 1, the mass ratio of the polyamide resin composition to the metal chloride alcohol solution is not particularly limited, but is preferably 3 to 15 mass %, and more preferably 5 to 13 mass %. If it is less than 3 mass %, too much solvent is required, and if it is more than 15 mass %, the viscosity of the polyamide heated solution increases, resulting in a prolonged dissolution time and deterioration of workability.

[0750] (Step 2: Polyamide precipitation and recovery step)

[0751] The method for producing polyamide of the present embodiment further includes, after the step 1, a recovery step (step 2) of precipitating and recovering polyamide from the polyamide heated solution.

[0752] Through this step, the polyamide contained in the polyamide heated solution can be separated and recovered.

[0753] The method for precipitating the polyamide heated solution is not particularly limited. For example, the polyamide may be precipitated by cooling the polyamide heated solution.

[0754] It should be noted that the step of separating and recovering the polyamide heated dissolved liquid may be performed after the dissolution step of obtaining the polyamide heated dissolved liquid, and may be performed after the step of obtaining the alcohol diluted liquid described later.

[0755] It should be noted that there is no particular limitation on the cooling method, and it may be a batch method or a continuous method.

[0756] In the case of batch method, there is no particular limitation on whether stirring is performed, but stirring is preferably performed. By stirring, the temperature and concentration become uniform. Depending on the equipment and method used in stirring, stirring is preferably performed under conditions that do not easily cause destruction or shearing of particles due to stirring.

[0757] The cooling rate is not particularly limited, but is preferably 10 to 100°C / Hr, more preferably 20 to 50°C / Hr. If it is lower than 10°C / Hr, the cooling time becomes longer, and if it is higher than 100°C / Hr, the particle size becomes smaller due to rapid precipitation. The particle size can be controlled by changing the cooling rate.

[0758] The temperature during cooling is not particularly limited, but is preferably 10° C. or more lower than the temperature during dilution. If the temperature difference is less than 10° C., precipitation is reduced and particles are less likely to grow.

[0759] The precipitated solid is preferably recovered by solid-liquid separation.

[0760] The method for solid-liquid separation is not particularly limited, and examples thereof include filtration, centrifugal separation, sedimentation separation, etc. Any of the methods may be batch-wise or continuous.

[0761] The solid obtained by solid-liquid separation is preferably washed with a solvent. The washing solvent is not particularly limited, but a solution of the liquid component during precipitation, a good solvent, or a solvent capable of dissolving metal chlorides or the like is preferably used.

[0762] It should be noted that, when the temperature dependence of the solubility during dissolution is small, the polyamide can be heated and dissolved by mixing with a poor solvent for the polyamide to reduce the solubility and precipitate the polyamide. In this case, after adding a poor solvent to a solution containing the dissolved polyamide, the dissolved polyamide is precipitated from the solution to obtain the precipitated polyamide.

[0763] The above-mentioned poor solvent is not particularly limited, and examples thereof include water, and alcohols such as ethanol, n-propanol, and isopropanol. As a method for adding the poor solvent to the polyamide, it can be a method of adding a solution containing polyamide to the poor solvent, or a method of adding the poor solvent to a solution containing polyamide, and the addition rate, temperature, stirring rate, etc. during addition are not particularly limited.

[0764] The amount of the poor solvent added is not particularly limited, but is preferably 0.5 to 50 times the mass of the solution containing the polyamide, and more preferably 1 to 10 times the mass. The smaller the amount added, the lower the recovery rate, and the larger the amount added, the more the solution volume increases, requiring time and energy for processing.

[0765] In addition, when the temperature dependence of the solubility during dissolution is small, the solubility of the polyamide can also be reduced by reducing the concentration of the calcium chloride. There is no particular limitation on the method of adding methanol to reduce the concentration of calcium chloride, and it can be any method of adding a solution containing polyamide to methanol or adding methanol to a solution containing polyamide. There is no particular limitation on the addition rate, temperature, stirring rate, etc. during addition.

[0766] It should be noted that the shape of the container is not particularly limited, and any shape such as a trough type or a circulation type can be used.

[0767] (Step 3: Polyamide cleaning step)

[0768] The method for producing polyamide according to the present embodiment further includes a washing step (step 3) of washing the polyamide recovered in the step 2.

[0769] This process can remove impurities such as metal chloride from the recycled polyamide.

[0770] The cleaning liquid used in the above cleaning is not particularly limited, and for example, a solution composed of the liquid part during precipitation, a good solvent, and a solvent capable of dissolving calcium chloride, etc., can be used. The additional cleaning liquid used here is, for example, water, and alcohols such as methanol, ethanol, n-propanol, and isopropanol. The additional cleaning liquid is preferably methanol. Cleaning can be performed multiple times as needed.

[0771] The washing method is not particularly limited, and examples thereof include a batch washing method, a continuous washing method in which water is passed through a solid-liquid separation device such as a filter or a centrifuge, and a combination thereof.

[0772] It should be noted that the above step 3 is preferably a control step for controlling the amount of the metal chloride after drying in the step 4 described later.

[0773] The amount of the metal chloride after drying in step 4 described later can be controlled by adjusting the type, concentration, cleaning time, etc. of the cleaning liquid so that the amount of the metal chloride after drying in step 4 described later is within a specific range.

[0774] (Step 4: Polyamide heating and drying step)

[0775] The method for producing polyamide according to the present embodiment further includes a drying step of heating and drying the washed polyamide.

[0776] By distilling off the washing solvent from the washed polyamide in this step and converting the washed polyamide into a dry solid, the polyamide can be obtained.

[0777] Furthermore, in the method for producing polyamide of the present embodiment, the amount of the metal chloride attached to the polyamide after the heat drying in the step 4 is set to 20 parts by mass or less based on 100 parts by mass of the polyamide.

[0778] Regarding the washing of the recovered polyamide, it is preferred to avoid excessive washing from the perspectives of manufacturing efficiency, cost, and environmental considerations. On the other hand, if the recovered polyamide is not sufficiently washed, there is a problem that a portion of the polyamide melts due to the metal chloride attached to the washed polyamide, and solidifies during subsequent drying.

[0779] Therefore, by setting the amount of the metal chloride attached to the polyamide after the heat drying in the step 4 to 20 parts by mass or less relative to 100 parts by mass of the polyamide, the metal chloride concentration can be controlled within a range that can suppress the melting of the polyamide. In addition, from the aspect of avoiding excessive washing, the amount of the metal chloride attached to the polyamide after the heat drying in the step 4 is preferably 0.01 parts by mass or more relative to 100 parts by mass of the polyamide.

[0780] From the same viewpoint, the amount of the metal chloride attached to the polyamide after heat drying in the step 4 is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, based on 100 parts by mass of the polyamide.

[0781] The method for measuring the amount of metal chloride attached to the polyamide after heat drying in the above step 4 is not particularly limited, and examples thereof include the following methods: sampling a portion and 1) measuring the amount by X-ray fluorescence analysis after drying; 2) measuring the amount by ICP-AES after heat decomposition with nitric acid; 3) extracting the metal chloride with water and measuring the amount by ion chromatography; and the like.

[0782] It should be noted that the amount of metal chloride attached to the polyamide after heat drying in the above step 4 may be measured after heat drying in the above step 4 or after washing the polyamide in the above step 3.

[0783] Regarding the measurement of the amount of the metal chloride, a known method can be appropriately used.

[0784] (Metal chloride amount measurement and confirmation step, second cleaning step)

[0785] The method for producing polyamide of the present embodiment preferably further comprises a confirmation step of measuring the amount of metal chloride attached to the polyamide after heat drying in the step 4 to confirm whether it is within a predetermined range (20 parts by mass or less relative to 100 parts by mass of the polyamide).

[0786] This is because, by going through this step, the amount of metal chloride attached to the polyamide after heat drying can be confirmed, and the conditions for the above-mentioned washing and the like can be appropriately adjusted.

[0787] For example, when the amount of metal chloride attached to the polyamide after washing in the above step 3 or after heat drying in the above step 4 is confirmed and is less than 0.01 parts by mass relative to 100 parts by mass of the above polyamide, the washing in the above step 3 may become excessive washing, and therefore the washing conditions (washing time, concentration of the washing liquid, etc.) may be relaxed.

[0788] On the other hand, when the amount of metal chloride attached to the polyamide after washing in the above step 3 or after heat drying in the above step 4 is confirmed and is higher than 20 parts by mass relative to 100 parts by mass of the above polyamide, it is considered that the amount of metal chloride attached to the polyamide after washing is large and there is a possibility of solidification after heat drying, and therefore a second washing step of washing again may be implemented.

[0789] It should be noted that whether the amount of metal chloride attached to the polyamide is within the range can be confirmed by sampling a portion of the washed polyamide after washing in the above step 3, or sampling a portion of the polyamide after heat drying in the above step 4 and measuring the amount of metal chloride attached to the polyamide.

[0790] (Recycled polyamide)

[0791] It should be noted that there is no particular limitation on the shape of the recovered polyamide, and examples include a shape in which the polyamide is melted to form pellets; a shape in which the polyamide is temporarily dissolved in a solvent and then precipitated to form a powder; a shape in which the powder is agglomerated in accordance with the treatment conditions to form a flat plate; and the like.

[0792] The powdered polyamide obtained by the production method of the present embodiment has a large particle size and a small particle size distribution.

[0793] The median diameter of the powdered polyamide is preferably 20 μm or more, more preferably 30 to 70 μm. The median diameter can be measured by the method described in the examples below.

[0794] The particle size distribution of the powdered polyamide is represented by the following formula (1): S, 10 to the power of S = 10 S That is, the span is preferably 5 or less, more preferably 4 or less, and further preferably 3 or less.

[0795] S=log(d90 / d10) / log(d50)···(1)

[0796] (Here, in the above formula (1), dn (n represents 10, 50 or 90) means the particle size when the number of particles having a particle size smaller than dn is n% relative to the total number of particles when the particle size distribution of the above powdered polyamide is measured by laser diffraction / scattering method.)

[0797] The particle size distribution can be measured by the method described in the examples below.

[0798] Alternatively, the obtained polyamide may be melt-spun to produce polyamide fibers.

[0799] The spinning temperature during melt spinning is preferably 290° C. to 310° C. The spinning temperature is preferably set to 310° C. or less, because thermal decomposition of the polyamide is suppressed. The spinning temperature is more preferably set to 300° C. or less, and further preferably set to 295° C. or less. On the other hand, the spinning temperature is preferably set to 290° C. or more, because the polyamide exhibits sufficient melt fluidity, the discharge amount between the discharge holes is uniform, and high-ratio stretching can be achieved.

[0800] The shorter the residence time (the time from when the polyamide resin melts until it is discharged from the spinning nozzle) in the melt spinning process, the better. The residence time is preferably 30 minutes or less, more preferably 15 minutes or less, and further preferably 0.5 minutes or more and 7 minutes or less. A short time is preferred because the cyclopentanones in the polymer increase at the melting temperature.

[0801] In order to achieve thermal stability in a high temperature and high humidity environment, it is preferred to add a copper compound in a manner such that the copper concentration relative to the polyamide is 1 to 500 ppm, and the copper concentration is more preferably 30 to 500 ppm. In this way, even if the polyamide is left for a long time in a high temperature and high humidity environment, or is exposed to an environment containing a large amount of ozone for a long time, the reduction in mechanical properties can be extremely effectively suppressed. If the above copper content is less than 30 ppm, the heat resistance strength retention rate is reduced, and if the addition amount exceeds 500 ppm, the strength is reduced.

[0802] As the copper compound, there is no particular limitation on its type, for example, organic copper salts such as cupric acetate, or copper halides such as cuprous chloride and cupric chloride can be preferably used. The copper compound is more preferably used in combination with a metal halide. As the metal halide, for example, potassium iodide, potassium bromide, potassium chloride, etc. can be cited. The preferred combination in this embodiment is cuprous iodide and potassium iodide, and cupric acetate and potassium iodide. It should be noted that the copper content in the polyamide can be measured by atomic absorption spectrometry, colorimetry, etc.

[0803] Although not limited to the following, as stabilizers, organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, and phosphorus antioxidants, heat stabilizers, hindered amine-based, benzophenone-based, and imidazole-based light stabilizers, and ultraviolet absorbers can be added. The amount of addition can be selected appropriately, and 1 to 1000 ppm can be added relative to the polyamide. These additives can be used not only alone but also in combination of multiple types.

[0804] In the melt spinning step, a single-screw or twin-screw extruder is preferably used in the melting section. The extruder can apply an appropriate pressure to the polyamide resin and simultaneously introduce it into the polymer pipe, gear pump, and spinning pack.

[0805] In addition, it is preferred to filter the polyamide resin using a metal fiber nonwoven fabric filter, gravel, or the like before discharge from the spinning nozzle because the spinning operation can be stabilized.

[0806] The shape of the nozzle hole of the spinning nozzle can be selected according to the cross-sectional shape of the single fiber constituting the manufactured filament. The spun yarn from the spinning nozzle is solidified by cooling air, given an engineering oil and pulled, and then stretched and heat-treated to obtain a polyamide fiber.

[0807] In addition, it is preferred to filter the polyamide resin using a metal fiber nonwoven fabric filter, gravel, or the like before discharge from the spinning nozzle because the spinning operation can be stabilized.

[0808] The shape of the nozzle hole of the spinning nozzle can be selected according to the cross-sectional shape of the single fiber constituting the manufactured filament. The spun yarn from the spinning nozzle is solidified by cooling air, given an engineering oil and pulled, and then stretched and heat-treated to obtain a polyamide fiber.

[0809] It should be noted that the oil agent adhesion rate of the polyamide fiber is preferably 0.5 to 1.5 wt%. If the oil agent adhesion rate is 1.5 wt% or less, the weft yarn will hardly fly away due to stickiness (adhesiveness), and the air or water as the weft yarn conveying medium will not lose the weft yarn conveying power due to the monofilament bundling being too good to exceed the monofilament bundling degree based on interweaving and the reduction of the apparent cross-sectional area, and the weft yarn conveying power will be good. On the other hand, if the oil agent adhesion rate is 0.5 wt% or more, the weft yarn can be smoothly supplied due to the appropriate friction reduction effect, so there is no weaving stop and the productivity is excellent.

[0810] (Polyamide fabric)

[0811] Alternatively, the polyamide obtained by the production method of the present embodiment may be melt-spun to produce a polyamide-based fabric.

[0812] In weaving, a water jet loom, an air jet loom, a rapier loom, etc. can be used as a loom. The base fabric for airbags is a high-density fabric, and it is preferably manufactured with increased warp tension and good process performance in the warping process and weaving process. The warp tension is set high during weaving to create effective weft beating conditions, thereby forming a high-density fabric.

[0813] The woven fabric can be subjected to a scouring process to remove the engineering oil of the polyamide fiber.

[0814] The scouring step may be performed with warm water, pressurized hot water, or the like, and the treatment step may be a single-stage treatment or a multi-stage treatment of two or more stages. In addition, it is also preferred to perform scouring by applying a conventionally known scouring agent.

[0815] The fabric is preferably heat-set in a heat-setting process. The heat-setting temperature is preferably 110°C to 200°C, and the heat-setting time is appropriately selected in the range of 0.1 to 30 minutes. In the heat-setting process, the fabric is preferably dried while being stretched so that the shrinkage force is maintained at a predetermined strength. If the fabric is heat-set, the process of the subsequent resin coating process can be stabilized.

[0816] The fabric after the scouring step can be subjected to a drying treatment before the heat setting step as needed. The drying temperature is preferably in the range of 80°C to 130°C, more preferably in the range of 100°C to 120°C. In addition, the treatment time is preferably appropriately selected within the range of 0.1 minute to 30 minutes. Drying can be performed in a relaxed state or in a tensioned state.

[0817] The polyamide base fabric can be used as an uncoated base fabric after a heat setting process, but can also be coated with a coating agent such as silicone or urethane or heat-laminated into a thin film or the like.

[0818] As a method for coating the surface of the fabric, the following methods can be used: a method of immersing the fabric in a resin solution tank, and then using a squeezer, a vacuum machine, and then a coating blade to coat and evenly coat the excess resin; a rod coating method using a comma coater, etc., a method of blowing the resin using a spray device or a foaming device, etc. Among these, the method of applying the resin uniformly and in small amounts is preferably a method of coating with a blade.

[0819] Coating amount is 5g / m 2 Above 100g / m 2 Less than 10 g / m 2 Above 70g / m 2 Below, more preferably 15g / m 2 Above 30g / m 2 Below, use 5g / m 2 The above coating amount can obtain the required airtightness. On the other hand, using 100g / m 2 The following coating amounts can make the coated fabric soft and have good storage properties, while reducing the weight of the entire airbag.

[0820] [Invention (VI)]

[0821] The present invention (VI) is described below. In the present invention (VI), the conditions of the present inventions (I) to (V) and (VII) can be appropriately incorporated.

[0822] <Method for producing polyamide and / or polyethylene terephthalate>

[0823] The method for producing polyamide, the method for producing polyethylene terephthalate, and the method for producing polyamide and polyethylene terephthalate (hereinafter sometimes also referred to as the "production method of the present embodiment") based on the present embodiment (VI) are methods for recovering polyamide and / or polyethylene terephthalate from a mixture of polyamide and polyethylene terephthalate to produce polyamide and / or polyethylene terephthalate, and the methods include the following steps: a step of mixing the mixture with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide dissolved solution containing the polyamide; and a step of separating and recovering the polyamide dissolved solution and / or the polyethylene terephthalate.

[0824] (mixture of polyamide and polyethylene terephthalate)

[0825] First, the mixture used in the production method of this embodiment will be described.

[0826] The mixture used as the material of the production method of this embodiment is a mixture of polyamide and polyethylene terephthalate. It should be noted that the mixture only needs to contain at least polyamide and polyethylene terephthalate, and may contain other components as needed.

[0827] The other components are not particularly limited, and may include components for coating a mixture of polyamide and polyethylene terephthalate, components for coating, etc. As the component for coating, resin may be mentioned, and silicone resin, urethane resin, etc. may be mentioned as examples, but are not limited thereto. As the component for coating, lubricating oil, etc. may be mentioned.

[0828] Here, there is no particular limitation on the shape of the above-mentioned mixture, but from the perspective of further enjoying the effects of the present invention, it is preferably a woven fabric (water jet loom, air jet loom, rapier loom, base fabric for airbags, etc.), and more preferably an airbag component.

[0829] In the case where the above-mentioned mixed material is a high-density fabric such as a base fabric for an airbag, the fibers composed of the above-mentioned polyamide and the fibers composed of the above-mentioned polyethylene terephthalate are entangled, and it is difficult to fully separate them using the existing separation method. On the other hand, in this embodiment, polyamide and / or polyethylene terephthalate can be recovered from the mixed material by dissolving and separating the polyamide, so even if the above-mentioned mixed material is a woven fabric, polyamide and / or polyethylene terephthalate can be recovered with high efficiency and high yield.

[0830] Polyamide

[0831] As the polyamide, a polymer obtained by polymerization via an amide bond, such as a polymer obtained by polycondensation of a diamine compound and a dicarboxylic acid compound or a polymer obtained by ring-opening polymerization of a cyclic lactam, can be used.

[0832] The diamine compound is not particularly limited, and examples thereof include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonanediamine, methylpentamethylenediamine, and p-phenylenediamine.

[0833] The dicarboxylic acid compound is not particularly limited, and examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid.

[0834] The cyclic lactam is not particularly limited, and examples thereof include ε-caprolactam, undecyl lactam, and lauryl lactam.

[0835] There is no particular limitation on the combination of the diamine compound, the dicarboxylic acid compound and the cyclic lactam compound, and a plurality of compounds of each type may be used in combination. Polyhexamethylene adipamide (for example, polyhexamethylene adipamide composed of hexamethylenediamine and adipic acid) has high solubility and is suitable for the method for producing polyamide of this embodiment.

[0836] The method for measuring the particle size and particle size distribution of the powdered polyamide is not particularly limited, and examples thereof include a laser diffraction method, a laser scattering method, a centrifugal sedimentation method, a particle tracking method, and a dynamic scattered light method.

[0837] Examples of the polyamide include polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), polybutylene adipamide (nylon 46), polybutylene sebacate (nylon 410), polypentamethylene adipamide (nylon 56), polypentamethylene sebacate (nylon 510), polyhexamethylene sebacate (nylon 610), polyhexamethylene dodecanoyl (nylon 612), polydecanediamide (nylon 106), polydecanediamide (nylon 101 0), polydecanediamide (nylon 1012), polyundecanamide (nylon 11), polydodecaneamide (nylon 12), polycaprolactam / polyhexamethylene adipamide copolymer (nylon 6 / 66), polycaprolactam / polyhexamethylene terephthalamide copolymer (nylon 6 / 6T), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon 66 / 6T), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6I), poly Hexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 6T / 6I), polyhexamethylene terephthalamide / polyundecanamide copolymer (nylon 6T / 11), polyhexamethylene terephthalamide / polydodecaneamide copolymer (nylon 6T / 12), polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6T / 6I), polyphenylene adipamide (nylon XD6), polyphenylene sebacate (nylon X D10), polyhexamethylene terephthalamide / polypentamethylene terephthalamide copolymer (nylon 6T / 5T), polyhexamethylene terephthalamide / poly-2-methylpentamethylene terephthalamide copolymer (nylon 6T / M5T), polypentamethylene terephthalamide / polydecamethylene terephthalamide copolymer (nylon 5T / 10T), polynonane terephthalamide (nylon 9T), polydecamethylene terephthalamide (nylon 10T), polydodecane terephthalamide (nylon 12T), etc. It should be noted that the " / " mentioned here represents a copolymer. These polyamides can be used alone or in combination of two or more.

[0838] Among these, as the polyamide, one selected from the group consisting of polyamide 6, polyamide 66, polyamide 46, polyamide 610 and polyamide 612 is preferably used, and polyamide 66 is particularly preferably used. Polyamide 66 itself is a generally known polyamide resin, and is generally produced by polycondensation of hexamethylenediamine and adipic acid. Alternatively, polyamide 66 may be a copolymer containing less than 30% by mass of at least one monomer unit selected from the group consisting of lactam, aminocarboxylic acid, and a combination of other diamines and dicarboxylic acids relative to the total mass of all monomer units.

[0839] In addition, these polyamides can use commercial products or can be produced using known methods. As the production method of polyamide, specifically, but not particularly limited to, for example, a method of ring-opening polymerization of lactam, a method of self-condensation of ω-aminocarboxylic acid, a method of condensing diamine and dicarboxylic acid, etc. can be cited.

[0840] In addition, in the above polyamide, the value [NH2] / [COOH] obtained by dividing the amount of amino terminal groups by the amount of carboxyl terminal groups is preferably 0.5 or more and 0.9 or less. By making [NH2] / [COOH] within the above range, the interaction between the surface of the glass fiber and the polyamide terminal is more fully increased during melt kneading, and the physical properties of the obtained composition are fully improved. The amount of amino terminal groups and the amount of carboxyl terminal groups can be, for example, 1 The measurement was performed by H-NMR.

[0841] The polyamide may be composed of polyamide alone or may be a polyamide resin composition containing the polyamide and other components. For example, impurities such as other resins and metals may be mixed, attached, or coated on the polyamide as other components.

[0842] From the perspective of obtaining a powdered polyamide having a larger particle size and a smaller particle size distribution in a short time, the mass ratio of the polyamide relative to 100 mass% of the above-mentioned polyamide is preferably 30 to 100 mass%, more preferably 70 mass% or more, further preferably 80 mass% or more, further preferably 85 mass% or more, and particularly preferably 100 mass%.

[0843] It should be noted that, in the case of impurities other than the above-mentioned polyamide, the process of separating the polyamide from these impurities may be included. There is no particular limitation on the separation method. In the state where the polyamide resin composition has been dissolved, if the impurities are insoluble, they can be separated by methods such as filtration, centrifugation, sedimentation separation, etc. In the case where the impurities are dissolved in a solvent together with the polyamide, it can be considered to separate by extraction separation, membrane separation, electrodialysis, etc. in a dissolved state, or to separate the polyamide in a precipitation process described later and then wash it.

[0844] Polyethylene terephthalate

[0845] Polyethylene terephthalate (PET) constituting the above-mentioned mixture generally has the structure shown below.

[0846] [Chemistry 2]

[0847]

[0848] It should be noted that, in the above-mentioned mixture, the above-mentioned polyethylene terephthalate may be present in the form of fibrous PET. The fibrous PET can be obtained by further solid phase polymerization and spinning of PET resin.

[0849] It should be noted that the polyethylene terephthalate may be composed of polyethylene terephthalate alone, or may be a polyethylene terephthalate resin composition comprising the polyethylene terephthalate and other components. For example, impurities such as other resins and metals may be mixed, attached, or coated on the polyethylene terephthalate as other components.

[0850] (Step of Obtaining Polyamide Dissolved Liquid)

[0851] Furthermore, the production method of the present embodiment includes the step of mixing the above-mentioned mixture with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide dissolved solution in which the above-mentioned polyamide is dissolved.

[0852] According to this process, only the polyamide can be melt-separated from the mixture of the polyamide and polyethylene terephthalate, so that the subsequent recovery of the polyamide and / or the polyethylene terephthalate becomes easy. In addition, since only the polyamide can be melt-separated simply by mixing the mixture with a predetermined metal chloride alcohol solution, the polyamide and / or the polyethylene terephthalate can be recovered efficiently and at a high yield.

[0853] The metal chloride alcohol solution used for dissolving the polyamide contains metal chloride and alcohols. It should be noted that it may further contain components other than metal chloride and alcohols as required.

[0854] From the viewpoint of the solubility of the polyamide, the total mass ratio of the metal chloride and the alcohol is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass% relative to 100 mass% of the metal chloride alcohol solution.

[0855] As the above-mentioned alcohols, methanol, ethanol, linear or branched propanol, linear or branched butanol, and combinations thereof can be cited. Among them, methanol, ethanol, or a combination thereof is preferred from the aspect of the solubility of the polyamide, and methanol is more preferred. In addition, as the above-mentioned alcohols, various glycols can be further included as needed.

[0856] The mass ratio of the metal chloride is preferably 10 to 50 mass %, more preferably 15 to 25 mass % relative to 100 mass % of the metal chloride alcohol solution. If the mass ratio is less than 10 mass %, the amount of polyamide dissolved is small and a large amount of solvent is required. On the other hand, if the mass ratio is more than 50 mass %, the metal chloride is likely to have insoluble matter remaining and is likely to be mixed as an impurity.

[0857] Examples of the metal chloride include zinc chloride, magnesium chloride, and calcium chloride. Zinc chloride and calcium chloride are preferred, and calcium chloride is most preferred.

[0858] The metal chloride is preferably anhydrous. If mixed with water, the solubility of the polyamide decreases. However, a hydrate (for example, a dihydrate in the case of calcium chloride) may be mixed within a range within which the solubility is allowed.

[0859] The mass ratio of water in the metal chloride is preferably 30 mass % or less, more preferably 1 mass % or less, further preferably 0.1 mass % or less, and particularly preferably no water is contained.

[0860] In the step of obtaining the polyamide solution, the temperature when the impurity and the metal chloride alcohol solution are mixed is preferably 30 to 90° C., more preferably 40 to 60° C. It should be noted that if the temperature is low, the dissolution becomes slow, and if it is higher than 90° C., the temperature is higher than the boiling point, which is not preferred from the viewpoint of corrosiveness and decomposition.

[0861] It should be noted that the above temperature may be fixed or may vary within the above range.

[0862] The polyamide may be dissolved in a batch manner or in a continuous manner.

[0863] In the case of a batch method, stirring is not particularly limited, but stirring is preferably performed. Stirring increases the dissolution rate of the polyamide.

[0864] In the case of a continuous method, the solvent may be continuously passed through the solid or the solution may be circulated. Circulation is preferred because the amount of solvent used can be reduced.

[0865] The shape of the container used when mixing the mixture of polyamide and polyethylene terephthalate with the metal chloride alcohol solution to dissolve the polyamide is not particularly limited, and any shape such as a tank type or a circulation type can be used.

[0866] The dissolution time of the polyamide is not particularly limited, but is preferably 5 minutes to 100 hours.

[0867] In the step of obtaining the polyamide solution, the mass ratio of the polyamide in the mixture to the metal chloride alcohol solution is not particularly limited, but is preferably 3 to 15 mass %, more preferably 5 to 13 mass %. If it is less than 3 mass %, too much solvent is required, and if it is more than 15 mass %, the viscosity of the polyamide solution increases, resulting in a prolonged dissolution time and deterioration of operability.

[0868] (Step of separating and recovering the polyamide solution)

[0869] The method for producing polyamide and the method for producing polyamide and polyethylene terephthalate according to the present embodiment further includes a step of separating and recovering the polyamide solution after the step of obtaining the polyamide solution.

[0870] By this step, the polyamide contained in the polyamide solution and the polyethylene terephthalate remaining without being dissolved can be separated and recovered.

[0871] The method for separating and recovering the polyamide solution is not particularly limited. The polyethylene terephthalate remaining in the polyamide solution and not dissolved in the polyamide solution may be removed by filtration or the like, thereby separating and recovering only the polyamide.

[0872] It should be noted that the step of separating and recovering the polyamide solution can be performed after the step of obtaining the polyamide solution, or after the step of obtaining the alcohol dilution solution described later. For example, there are the following situations: diluting at a high temperature, separating in a state where the polyamide is not precipitated, and then cooling to recover the polyamide, etc.

[0873] It should be noted that in the production method of the present embodiment, from the perspective of reusing the metal chloride alcohol solution, the metal chloride alcohol solution may be further concentrated.

[0874] For example, the metal alcohol solution containing the metal chloride and the alcohol obtained in the polyamide recovery step may be concentrated and reused. Examples of the concentration method include concentration by heating.

[0875] (Step of separating and recovering polyethylene terephthalate)

[0876] The method for producing polyethylene terephthalate and the method for producing polyamide and polyethylene terephthalate according to the present embodiment further comprises a step of separating and recovering the polyethylene terephthalate after the step of obtaining the polyamide solution.

[0877] By this step, the polyethylene terephthalate remaining without being dissolved can be separated from the polyamide contained in the polyamide solution and recovered.

[0878] The method for separating and recovering the polyethylene terephthalate is not particularly limited, and the polyethylene terephthalate remaining in the polyamide solution without being dissolved can be separated and recovered by taking out the polyethylene terephthalate by filtration or the like.

[0879] It should be noted that the step of separating and recovering the polyethylene terephthalate may be performed after the step of obtaining the polyamide solution, and may be performed after the step of obtaining the alcohol diluted solution described later.

[0880] (Polyamide precipitation and recovery process)

[0881] Furthermore, the production method of the present embodiment preferably further includes a step of precipitating and recovering polyamide after the step of obtaining the polyamide solution or after the step of separating and recovering the polyamide solution and / or the polyethylene terephthalate.

[0882] The polyamide may be recovered from the polyamide solution. However, in order to further improve the recovery efficiency, it is preferred to recover the polyamide after precipitating the polyamide from the polyamide solution.

[0883] As a method for recovering polyamide from the solution containing polyamide, there can be mentioned a method of precipitating polyamide. The method of precipitating polyamide from the solution containing polyamide is not particularly limited, and several precipitation methods can be used depending on the state after dissolution.

[0884] When dissolving by heating, precipitation by cooling using the temperature dependence of the solubility of the polyamide can be considered. In this case, no additional solvent is added to the solution containing the dissolved polyamide, and the dissolved polyamide is precipitated from the solution in this state to obtain the precipitated polyamide.

[0885] When the temperature dependence of the solubility during dissolution is small, the solubility can be reduced and the polyamide can be precipitated by mixing a solution containing the polyamide with a poor solvent for the polyamide. In this case, after adding a poor solvent to a solution containing the dissolved polyamide, the dissolved polyamide is precipitated from the solution to obtain the precipitated polyamide. The poor solvent is not particularly limited, and examples thereof include water, and alcohols such as ethanol, n-propanol, and isopropanol. As a method for adding a poor solvent to the polyamide, any method of adding a solution containing the polyamide to a poor solvent or a method of adding a poor solvent to a solution containing the polyamide can be used, and the addition rate, temperature, stirring rate, etc. during addition are not particularly limited.

[0886] The amount of the poor solvent added is not particularly limited, but is preferably 0.5 to 50 times the mass of the solution containing the polyamide, and more preferably 1 to 10 times the mass. The smaller the amount added, the lower the recovery rate, and the larger the amount added, the larger the amount of solution, which requires time and energy for processing.

[0887] When the temperature dependence of the solubility during dissolution is small, the solubility of the polyamide can also be reduced by reducing the concentration of calcium chloride. There is no particular limitation on the method of adding methanol to reduce the concentration of calcium chloride, and it can be either a method of adding a solution containing polyamide to methanol or a method of adding methanol to a solution containing polyamide. There is no particular limitation on the addition rate, temperature, stirring rate, etc. during addition.

[0888] It should be noted that the shape of the container is not particularly limited, and any shape such as a trough type or a circulation type can be used.

[0889] It should be noted that the precipitated polyamide is preferably recovered by solid-liquid separation. As a method for solid-liquid separation, for example, filtration, centrifugal separation and sedimentation separation can be cited. For any method, any method of batch type and continuous type can be adopted.

[0890] The polyamide obtained by solid-liquid separation is preferably washed with a solvent. The washing liquid is not particularly limited, and for example, a solution composed of the liquid part during precipitation, a good solvent, and a solvent capable of dissolving calcium chloride, etc. are used. The additional washing liquid used here is, for example, water, and alcohols such as methanol, ethanol, n-propanol, and isopropanol. The additional washing liquid is preferably methanol. Washing can be performed multiple times as needed.

[0891] The washing method is not particularly limited, and examples thereof include a method of performing batch washing, a method of performing continuous washing by passing water in a state where solids are placed in a solid-liquid separation device such as a filter or a centrifuge, and a method combining these methods.

[0892] The washed polyamide can be heated and / or reduced in pressure to distill off the washing solvent and made into a dry solid, thereby obtaining a powdered polyamide.

[0893] It should be noted that there is no particular limitation on the shape of the recovered polyamide, and examples include a shape in which the polyamide is melted to form pellets; a shape in which the polyamide is temporarily dissolved in a solvent and then precipitated to form a powder; a shape in which the powder is agglomerated in accordance with the treatment conditions to form a flat plate; and the like.

[0894] (Spinning of polyamide fibers)

[0895] Alternatively, the obtained polyamide may be melt-spun to produce polyamide fibers.

[0896] The spinning temperature during melt spinning is preferably 290° C. to 310° C. The spinning temperature is preferably set to 310° C. or less, because thermal decomposition of the polyamide is suppressed. The spinning temperature is more preferably set to 300° C. or less, and further preferably set to 295° C. or less. On the other hand, the spinning temperature is preferably set to 290° C. or more, because the polyamide exhibits sufficient melt fluidity, the discharge amount between the discharge holes is uniform, and high-ratio stretching can be achieved.

[0897] The shorter the residence time (the time from when the polyamide resin melts until it is discharged from the spinning nozzle) in the melt spinning process, the better. The residence time is preferably 30 minutes or less, more preferably 15 minutes or less, and further preferably 0.5 minutes or more and 7 minutes or less. A short time is preferred because the cyclopentanones in the polymer increase at the melting temperature.

[0898] In order to achieve thermal stability in a high temperature and high humidity environment, it is preferred to add a copper compound in a manner such that the copper concentration relative to the polyamide is 1 to 500 ppm, and the copper concentration is more preferably 30 to 500 ppm. In this way, even if the polyamide is left for a long time in a high temperature and high humidity environment, or is exposed to an environment containing a large amount of ozone for a long time, the reduction in mechanical properties can be extremely effectively suppressed. If the above copper content is less than 30 ppm, the heat resistance strength retention rate is reduced, and if the addition amount exceeds 500 ppm, the strength is reduced.

[0899] As the copper compound, there is no particular limitation on its type, for example, organic copper salts such as cupric acetate, or copper halides such as cuprous chloride and cupric chloride can be preferably used. The copper compound is more preferably used in combination with a metal halide. As the metal halide, for example, potassium iodide, potassium bromide, potassium chloride, etc. can be cited. The preferred combination in this embodiment is cuprous iodide and potassium iodide, and cupric acetate and potassium iodide. It should be noted that the copper content in the polyamide can be measured by atomic absorption spectrometry, colorimetry, etc.

[0900] Although not limited to the following, as stabilizers, organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, and phosphorus antioxidants, heat stabilizers, hindered amine-based, benzophenone-based, and imidazole-based light stabilizers, and ultraviolet absorbers can be added. The amount of addition can be selected appropriately, and 1 to 1000 ppm can be added relative to the polyamide. These additives can be used not only alone but also in combination of multiple types.

[0901] In the melt spinning step, a single-screw or twin-screw extruder is preferably used in the melting section. The extruder can apply an appropriate pressure to the polyamide resin and simultaneously introduce it into the polymer pipe, gear pump, and spinning pack.

[0902] In addition, it is preferred to filter the polyamide resin using a metal fiber nonwoven fabric filter, gravel, or the like before discharge from the spinning nozzle because the spinning operation can be stabilized.

[0903] The shape of the nozzle hole of the spinning nozzle can be selected according to the cross-sectional shape of the single fiber constituting the manufactured filament. The spun yarn from the spinning nozzle is solidified by cooling air, given an engineering oil and pulled, and then stretched and heat-treated to obtain a polyamide fiber.

[0904] In addition, it is preferred to filter the polyamide resin using a metal fiber nonwoven fabric filter, gravel, or the like before discharge from the spinning nozzle because the spinning operation can be stabilized.

[0905] The shape of the nozzle hole of the spinning nozzle can be selected according to the cross-sectional shape of the single fiber constituting the manufactured filament. The spun yarn from the spinning nozzle is solidified by cooling air, given an engineering oil and pulled, and then stretched and heat-treated to obtain a polyamide fiber.

[0906] [Invention (VII)]

[0907] The present invention (VII) is described below. In the present invention (VII), the conditions of the present inventions (I) to (VI) can be appropriately incorporated.

[0908] The method for producing regenerated polyamide of the present embodiment (VII) is a method for producing regenerated polyamide using a mixture comprising polyamide coated with a urethane resin as a raw material, which comprises a dissolution step, mixing a metal chloride alcohol solution comprising a metal chloride and an alcohol with the above mixture to dissolve the polyamide to prepare a polyamide solution, wherein in the above dissolution step, the mass proportion of the polyamide in the above polyamide solution is 5 to 15 mass %.

[0909] In addition, another method for producing regenerated polyamide of the present embodiment (VII) is a method for producing regenerated polyamide using a mixture of polyamide coated with a carbamate resin as a raw material, which includes a dissolution step, mixing a metal chloride alcohol solution containing a metal chloride and an alcohol with the above mixture to dissolve the polyamide to prepare a polyamide solution, and in the above dissolution step, the viscosity of the above polyamide solution at 25°C is 10 to 20,000 mPa·s.

[0910] The production method of the present embodiment (VII) may be, for example, a method for producing recycled polyamide including a step of dissolving and extracting polyamide from a urethane-coated polyamide base fabric using a metal chloride alcohol solution having a controlled water content.

[0911] The compounds and the like used in the production method of this embodiment (VII) are described.

[0912] <Mixture>

[0913] (Polyamide)

[0914] As the polyamide, a polymer obtained by polymerization via an amide bond, such as a polymer obtained by polycondensation of a diamine compound and a dicarboxylic acid compound or a polymer obtained by ring-opening polymerization of a cyclic lactam, can be used.

[0915] The diamine compound is not particularly limited, and examples thereof include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonanediamine, methylpentamethylenediamine, and p-phenylenediamine.

[0916] The dicarboxylic acid compound is not particularly limited, and examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid.

[0917] The cyclic lactam is not particularly limited, and examples thereof include ε-caprolactam, undecyl lactam, and lauryl lactam.

[0918] There is no particular limitation on the combination of the diamine compound, the dicarboxylic acid compound and the cyclic lactam compound, and a plurality of compounds of each type may be used in combination. Polyhexamethylene adipamide (nylon 66) (for example, polyhexamethylene adipamide composed of hexamethylenediamine and adipic acid) has high solubility and is suitable for the method for producing polyamide of the present embodiment.

[0919] The mixture contains polyamide coated with urethane resin. The mixture may be composed of only polyamide coated with urethane resin, or may further contain other components.

[0920] Among them, from the perspective of the production efficiency of the recycled polyamide, the mass ratio of the polyamide coated with the urethane resin relative to 100 mass% of the mixture is preferably 30 to 100 mass%, more preferably 60 mass% or more, further preferably 70 mass% or more, and particularly preferably 80 mass% or more.

[0921] The polyurethane resin is obtained by a reaction between a polyol component and a polyisocyanate component, and examples of the polyol component include polycarbonate polyol, polyester polyol, and polyether polyol.

[0922] The urethane resin is not particularly limited, and examples thereof include polyester polyurethane resins, polyether polyurethane resins, polycarbonate polyurethane resins, etc. The urethane resin may be added with a crosslinking agent composed of epoxy resin, melamine, polyfunctional isocyanate, etc., a carbodiimide anti-hydrolysis agent, a phenolic, aromatic amine antioxidant, or a salicylic acid, benzophenone, benzotriazole derivative, etc. UV absorber, and a flame retardant such as thiourea.

[0923] The polyamide coated with the urethane resin may be coated with other coatings in addition to the urethane resin. The type of other coatings is not particularly limited, and polyethylene, polypropylene, polyester, fluororesin, etc. may be cited. It is preferred that the coating resin does not dissolve in the metal chloride alcohol solution used for dissolution. It is preferred that the coating resin does not contain silicone resin.

[0924] The polyamide coated with the urethane resin can be a recycled raw material of polyamide, for example, engineering scraps and wastes of molded products such as fibers, automobile parts, and electrical product parts using polyamide as a raw material. Specifically, engineering scraps and wastes such as clothing, airbags, tire cords, engine compartment or intake system, fuel system parts, connectors, fishing nets, and UD tapes can be cited.

[0925] The mixture may contain sewing thread. The material of the sewing thread is not particularly limited, but is preferably made of the same polyamide as the base fabric because it can be recovered as recycled polyamide.

[0926] <Metal chloride alcohol solution>

[0927] As the solvent for dissolving the polyamide, a metal chloride alcohol solution was used.

[0928] The metal chloride alcohol solution comprises a metal chloride and an alcohol, and may further comprise other components. The total mass ratio of the metal chloride and the alcohol relative to 100 mass % of the metal chloride alcohol solution is preferably 80 mass % or more, more preferably 90 mass % or more, and further preferably 100 mass %.

[0929] The metal chloride is not particularly limited, and examples thereof include zinc chloride, magnesium chloride, calcium chloride, etc., among which zinc chloride and calcium chloride are preferred, and calcium chloride is most preferred.

[0930] The metal chloride used as the raw material may be an anhydrous form or a hydrate form.

[0931] The mass ratio of the metal chloride is preferably 10 to 25 mass % relative to 100 mass % of the metal chloride alcohol solution. If it is less than 10 mass %, the amount of polyamide dissolved is small and a large amount of solvent is required. If it is more than 25 mass %, the metal chloride is likely to have insoluble matter remaining and is likely to be mixed as an impurity.

[0932] The amount of water in the metal chloride alcohol solution is not particularly limited, but is preferably 4 mol or less per mol of the metal chloride in the solution.

[0933] Examples of the alcohol include methanol, ethanol, n-propanol, 2-propanol, etc. Among them, methanol is preferred from the viewpoint of the solubility of the polyamide.

[0934] There is no particular limitation on the method for mixing the metal chloride and the alcohol. However, if the mixture is mixed in batches, stirring is preferred. Calcium chloride will dissolve even without stirring, but this takes time and may cause local deviations in the composition.

[0935] The metal chloride alcohol solution used in the dissolution of polyamide is preferably a solution produced by separating polyamide from a metal chloride alcohol solution in which polyamide from a polyamide base fabric is dissolved. In the case where the concentration and composition change during the separation and recovery of polyamide, separation from unnecessary components based on extraction, distillation, etc.; concentration based on distillation; concentration adjustment based on the addition of metal chloride and / or alcohol; etc. can be performed. For example, the metal chloride alcohol solution after separation of polyamide can be concentrated and used in the manufacturing method of this embodiment. Since alcohol and metal chloride are not discarded, the environmental load is small, and the polyamide remaining in the supernatant during the separation and recovery of polyamide can also be recovered, so the recovery rate is improved.

[0936] Each step in the production method of this embodiment will be described below.

[0937] <Step 1 Dissolution Step>

[0938] The dissolving step is a step of mixing a mixture containing urethane-coated polyamide (e.g., urethane-coated polyamide base fabric) with a metal chloride alcohol solution to dissolve the polyamide. By mixing the mixture with the metal chloride alcohol solution, the polyamide can be dissolved from the urethane-coated polyamide in the mixture.

[0939] In this specification, the solution obtained by mixing the above mixture and the above metal chloride alcohol solution is referred to as "polyamide solution". The above polyamide solution contains dissolved polyamide, carbamate coated with polyamide, etc. By separating the coating such as carbamate from the polyamide solution, a "solution containing polyamide" can be obtained.

[0940] There is no particular limitation on the shape of the polyamide base fabric used in the dissolution. The base fabric may be added directly in the shape of scraps from the fabric manufacturing process or a used air bag, or it may be cut according to the size of the device used in the dissolution.

[0941] The temperature when the mixture and the metal chloride alcohol solution are mixed is not particularly limited, but is preferably 30 to 90° C., more preferably 40 to 90° C., and even more preferably 40 to 60° C. If the temperature is lower than 30° C., dissolution becomes slow, and if the temperature is higher than 90° C., the temperature is higher than the boiling point, which is not preferred from the viewpoints of corrosiveness and decomposition.

[0942] The dissolution may be carried out in either a batch or continuous manner.

[0943] In the case of a batch method, stirring is not particularly limited, but stirring is preferably performed. Stirring increases the dissolution rate of the polyamide solid.

[0944] In the case of a continuous method, the solvent may be continuously passed through the solid or the solution may be circulated. Circulation is preferred because the amount of solvent used can be reduced.

[0945] The shape of the container used in the dissolution step is not particularly limited, and any shape such as a tank type or a circulation type can be used.

[0946] The time for mixing the mixture and the metal chloride alcohol solution is not particularly limited, but is preferably 5 minutes to 100 hours.

[0947] The mass ratio of the polyamide in 100 mass % of the polyamide solution is preferably 5 to 15 mass %, more preferably 7 to 13 mass %. If it is less than 5 mass %, too much solvent is required, and if it is more than 15 mass %, the viscosity increases, resulting in a prolonged dissolution time and deterioration of workability.

[0948] In addition, the mass ratio of the polyamide in 100 mass % of the above-mentioned solution containing polyamide is preferably 5 to 15 mass %, more preferably 7 to 13 mass %. If it is less than 5 mass %, too much solvent is required, and if it is more than 15 mass %, the viscosity increases, resulting in a longer mixing time and deterioration of workability.

[0949] The viscosity of the polyamide solution at 25° C. is preferably 10 to 20,000 mPa·s, more preferably 10 to 10,000 mPa·s, and even more preferably 10 to 3,000 mPa·s. The higher the viscosity, the higher the polymer concentration, but the dissolution efficiency of the polyamide decreases due to adhesion of the base fabric.

[0950] The viscosity of the solution containing polyamide at 25° C. is preferably 10 to 20,000 mPa·s, more preferably 10 to 10,000 mPa·s, and even more preferably 10 to 3,000 mPa·s.

[0951] There is no particular limitation on the method for separating the carbamate resin from the polyamide solution, and examples thereof include a method of scooping up the carbamate resin from the dissolved layer, filtration, centrifugal separation, sedimentation separation, etc., or a combination thereof. Since fine fragments of the carbamate resin may be generated when the polyamide is dissolved, it is preferred to remove the fine fragments by filtration or a combination of filtration methods.

[0952] It is also preferred that other coatings of the polyamide coated with the urethane resin are removed simultaneously with the urethane resin.

[0953] Regarding the separated urethane resin and other coatings, since the solution containing polyamide is attached, it is preferred to clean and recycle the solution containing polyamide. The solvent for cleaning is not particularly limited, and calcium chloride methanol solution is preferred. There is no particular limitation on the cleaning method, and stirring cleaning in a tank reactor, circulation cleaning in a filter, etc. can be cited.

[0954] <Polyamide recycling process>

[0955] The polyamide recovery step is a step of recovering polyamide from the polyamide-containing solution from which the urethane resin has been removed and obtained in the dissolving step.

[0956] Although the polyamide can be recovered from the polyamide solution, it is preferred to recover the polyamide from the solution containing the polyamide after removing the coating such as the urethane resin in order to further improve the recovery efficiency.

[0957] As a method for recovering polyamide from a solution containing polyamide, a method of precipitating polyamide can be mentioned. The method of precipitating polyamide from the solution containing polyamide is not particularly limited, and several precipitation methods can be used depending on the state after dissolution.

[0958] When dissolving by heating, precipitation by cooling using the temperature dependence of the solubility of the polyamide can be considered. In this case, no additional solvent is added to the solution containing the dissolved polyamide, and the dissolved polyamide is precipitated from the solution in this state to obtain the precipitated polyamide.

[0959] When the temperature dependence of the solubility during dissolution is small, the solubility can be reduced and the polyamide can be precipitated by mixing a solution containing the polyamide with a poor solvent for the polyamide. In this case, after adding a poor solvent to a solution containing the dissolved polyamide, the dissolved polyamide is precipitated from the solution to obtain the precipitated polyamide. The poor solvent is not particularly limited, and examples thereof include water, and alcohols such as ethanol, n-propanol, and isopropanol. As a method for adding a poor solvent to the polyamide, any method of adding a solution containing the polyamide to a poor solvent or a method of adding a poor solvent to a solution containing the polyamide can be used, and the addition rate, temperature, stirring rate, etc. during addition are not particularly limited.

[0960] The amount of the poor solvent added is not particularly limited, but is preferably 0.5 to 50 times the mass of the solution containing the polyamide, and more preferably 1 to 10 times the mass. The smaller the amount added, the lower the recovery rate, and the larger the amount added, the larger the amount of solution, which requires time and energy for processing.

[0961] When the temperature dependence of the solubility during dissolution is small, the solubility of the polyamide can also be reduced by reducing the concentration of calcium chloride. There is no particular limitation on the method of adding methanol to reduce the concentration of calcium chloride, and it can be a method of adding a solution containing polyamide to methanol or a method of adding methanol to a solution containing polyamide. There is no particular limitation on the addition rate, temperature, stirring rate, etc. during addition.

[0962] The shape of the container is not particularly limited, and any shape such as a trough type or a circulation type can be used.

[0963] The precipitated polyamide is preferably recovered by solid-liquid separation. Examples of solid-liquid separation methods include filtration, centrifugal separation, and sedimentation separation. Any of the methods may be batch or continuous.

[0964] The polyamide obtained by solid-liquid separation is preferably washed with a solvent. The washing liquid is not particularly limited, and for example, a solution composed of the liquid part during precipitation, a good solvent, and a solvent capable of dissolving calcium chloride, etc. are used. The additional washing liquid used here is, for example, water, and alcohols such as methanol, ethanol, n-propanol, and isopropanol. The additional washing liquid is preferably methanol. Washing can be performed multiple times as needed.

[0965] The washing method is not particularly limited, and examples thereof include a method of performing batch washing, a method of performing continuous washing by passing water in a state where solids are placed in a solid-liquid separation device such as a filter or a centrifuge, and a method combining these methods.

[0966] The washed polyamide can be heated and / or reduced in pressure to distill off the washing solvent and made into a dry solid, thereby obtaining a powdered polyamide.

[0967] As described above, according to the present embodiment, it is possible to provide a method for producing recycled polyamide at a high yield from a mixture in which polyamide useful as an engineering plastic is coated with urethane.

[0968] <Step of Concentrating the Metal Chloride Alcohol Solution>

[0969] The production method of the present embodiment may further include a step of concentrating the metal chloride alcohol solution from the viewpoint of reusing the metal chloride alcohol solution.

[0970] For example, the metal alcohol solution containing the metal chloride and the alcohol obtained in the above-mentioned polyamide recovery step may be concentrated and reused.

[0971] Examples of the concentration method include concentration by heating.

[0972] <Recycled polyamide>

[0973] There is no particular limitation on the shape of the recycled polyamide produced by the manufacturing method of this embodiment, and examples include a shape in which the polyamide is melted during regeneration to form pellets; a shape in which the polyamide is temporarily dissolved in a solvent and then precipitated to form a powder; a shape in which the powder is agglomerated in accordance with the treatment conditions to form a flat plate; and the like.

[0974] The above-mentioned recycled polyamide can be used as a raw material for polyamide fibers, polyamide base fabrics, airbags, etc.

[0975] (Spinning of polyamide fibers)

[0976] The fibers of the above-mentioned regenerated polyamide can be spun to produce polyamide-based fabrics.

[0977] The spinning temperature during melt spinning is preferably 290° C. to 310° C. The spinning temperature is preferably set to 310° C. or less, because thermal decomposition of the polyamide is suppressed; the spinning temperature is more preferably set to 300° C. or less, and further preferably set to 295° C. or less. On the other hand, the spinning temperature is preferably set to 290° C. or more, because the polyamide exhibits sufficient melt fluidity, the discharge amount between the discharge holes is uniform, and high-ratio stretching can be achieved.

[0978] The shorter the residence time (the time from when the polyamide resin melts until it is discharged from the spinning nozzle) in the melt spinning process, the better. The residence time is preferably 30 minutes or less, more preferably 15 minutes or less, and further preferably 0.5 minutes or more and 7 minutes or less. A short time is preferred because the cyclopentanones in the polymer increase at the melting temperature.

[0979] In order to achieve thermal stability in a high temperature and high humidity environment, it is preferred to add a copper compound in a manner such that the copper concentration relative to the polyamide is 1 to 500 mass ppm, and the copper concentration is more preferably 30 to 500 mass ppm. In this way, even if the polyamide is left for a long time in a high temperature and high humidity environment, or is exposed to an environment containing a large amount of ozone for a long time, the reduction in mechanical properties can be extremely effectively suppressed. If the above copper content is less than 30 mass ppm, the heat resistance strength retention rate is reduced; if the addition amount is more than 500 mass ppm, the strength is reduced.

[0980] As the copper compound, there is no particular limitation on its type, for example, organic copper salts such as cupric acetate, or copper halides such as cuprous chloride and cupric chloride can be preferably used. The copper compound is more preferably used in combination with a metal halide. As the metal halide, for example, potassium iodide, potassium bromide, potassium chloride, etc. can be cited. The preferred combination in this embodiment is cuprous iodide and potassium iodide, and cupric acetate and potassium iodide. It should be noted that the copper content in the polyamide can be measured by atomic absorption spectrometry, colorimetry, etc.

[0981] Although not limited to the following, as stabilizers, organic antioxidants such as hindered phenol antioxidants, sulfur antioxidants, and phosphorus antioxidants, heat stabilizers, hindered amine-based, benzophenone-based, and imidazole-based light stabilizers, and ultraviolet absorbers can be added. The amount of addition can be selected appropriately, and 1 to 1000 mass ppm can be added relative to the polyamide. These additives can be used not only alone but also in combination of multiple types.

[0982] In the melt spinning step, a single-screw or twin-screw extruder is preferably used in the melting section. The extruder can apply an appropriate pressure to the polyamide resin and simultaneously introduce it into the polymer pipe, gear pump, and spinning pack.

[0983] In addition, it is preferred to filter the polyamide resin using a metal fiber nonwoven fabric filter, gravel, or the like before discharge from the spinning nozzle because the spinning operation can be stabilized.

[0984] The shape of the nozzle hole of the spinning nozzle can be selected according to the cross-sectional shape of the single fiber constituting the manufactured filament. The spun yarn from the spinning nozzle is solidified by cooling air, given an engineering oil and pulled, and then stretched and heat-treated to obtain a polyamide fiber.

[0985] The oil agent adhesion rate of the polyamide fiber is preferably 0.5 to 1.5 wt%. If the oil agent adhesion rate is 1.5 wt% or less, the weft yarn will hardly fly away due to stickiness (adhesion), and the air or water as the weft yarn conveying medium will not lose the weft yarn conveying power due to the monofilament bundling being too good to exceed the monofilament bundling degree based on interweaving and the reduction of the apparent cross-sectional area, and the weft yarn conveying power will be good. On the other hand, if the oil agent adhesion rate is 0.5 wt% or more, the weft yarn can be smoothly supplied due to the appropriate friction reduction effect, so there is no weaving stop and the productivity is excellent.

[0986] (Polyamide fabric)

[0987] In weaving, a water jet loom, an air jet loom, a rapier loom, etc. can be used as a loom. The base fabric for airbags is a high-density fabric, and it is preferably manufactured with increased warp tension and good process performance in the warping process and weaving process. The warp tension is set high during weaving to create effective weft beating conditions, thereby forming a high-density fabric.

[0988] The woven fabric can be subjected to a scouring process to remove the engineering oil of the polyamide fiber.

[0989] The scouring step may be performed with warm water, pressurized hot water, or the like, and the treatment step may be a single-stage treatment or a multi-stage treatment of two or more stages. In addition, it is also preferred to perform scouring by applying a conventionally known scouring agent.

[0990] The fabric is preferably heat-set in a heat-setting process. The heat-setting temperature is preferably 110°C to 200°C, and the heat-setting time is appropriately selected in the range of 0.1 to 30 minutes. In the heat-setting process, the fabric is preferably dried while being stretched so that the shrinkage force is maintained at a predetermined strength. If the fabric is heat-set, the process of the subsequent resin coating process can be stabilized.

[0991] The fabric after the scouring step can be subjected to a drying treatment before the heat setting step as needed. The drying temperature is preferably in the range of 80°C to 130°C, more preferably in the range of 100°C to 120°C. In addition, the treatment time is preferably appropriately selected within the range of 0.1 minute to 30 minutes. Drying can be performed in a relaxed state or in a tensioned state.

[0992] The polyamide base fabric can be used as an uncoated base fabric after a heat setting process, but can also be coated with a coating agent such as silicone or urethane or heat-laminated into a thin film or the like.

[0993] As a method for coating the surface of the fabric, the following methods can be used: a method of immersing the fabric in a resin solution tank, and then using a squeezer, a vacuum machine, and then a coating blade to coat and evenly coat the excess resin; a rod coating method using a comma coater, etc., a method of blowing the resin using a spray device or a foaming device, etc. Among these, the method of applying the resin uniformly and in small amounts is preferably a method of coating with a blade.

[0994] Coating amount is 5g / m 2 Above 100g / m 2 Less than 10 g / m 2 Above 70g / m 2 Below, more preferably 15g / m 2 Above 30g / m 2 Below, use 5g / m 2 The above coating amount can obtain the required airtightness. On the other hand, using 100g / m 2 The following coating amounts can make the coated fabric soft and have good storage properties, while reducing the weight of the entire airbag.

[0995] <Airbag>

[0996] The airbag can be appropriately selected from commonly used airbags for the driver's seat, front passenger seat, side (including side air curtain), rear seat, etc. The bag body of the airbag can be cut into any shape such as circular, oblong, elliptical, rectangular, polygonal or a combination thereof, as long as the desired deployment shape is met.

[0997] The stitch shape includes a single straight line or multiple parallel straight lines, a zigzag shape, a combination of a straight line and a zigzag shape, a straight line and an oblique line, etc. The stitching method may be a commonly used stitching method such as a flat stitch or a double-thread lock stitch, and the stitch spacing may be selected from a range of 20 to 60 times / 10 cm. In addition, the thread thickness may be selected from 420d to 3000d, and the thread material may be a commercially available thread such as polyamide fiber, polyester fiber, vinylon-based fiber, aramid-based fiber, glass fiber, etc.

[0998] Example

[0999] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[1000] Examples of the present invention (I) are described below.

[1001] The analysis methods used in Examples and Comparative Examples are as follows.

[1002] <Particle Size Distribution>

[1003] (1) Particle size distribution measuring device

[1004] Measuring device: MT3300EX (Microtrac MRB)

[1005] Permeability: Permeable

[1006] Solvent: Water

[1007] Distribution: Volume

[1008] According to the analysis results, the median diameter is expressed as the particle size. The median diameter refers to the particle size at which the number of particles larger than the particle size is equal to the number of particles smaller than the particle size for a certain powder. In addition, when the value derived from the following general formula (1) is used as S, the median diameter is expressed as “10 S The numerical value represented by " is used as a span, which is shown as an index of the particle size distribution. The closer the value is to 1, the narrower the particle size distribution is.

[1009] S=log(d90 / d10) / log(d50)···(1)

[1010] (Here, in the above formula (1), dn (n represents 10, 50 or 90) means the particle size when the number of particles with a particle size smaller than dn is n% relative to the total number of particles when the particle size distribution of the obtained powdered polyamide is measured by laser diffraction / scattering method.)

[1011] It should be noted that d50 is the median diameter.

[1012] [Example 1]

[1013] In a 300mL three-necked flask equipped with a stirrer, 10g of polyamide 66 pellets and 100g of a 25wt% calcium chloride methanol solution as a metal chloride alcohol solution (25.0g of calcium chloride, 8.1g of water content (molar amount of water / molar amount of calcium chloride = 2)) were added, placed in an 80°C oil bath, and polyamide 66 was dissolved while stirring for 12 hours by magnetic stirring to obtain a polyamide heated solution. The viscosity of the obtained polyamide heated solution at 25°C was 4200mPa·s. While stirring the polyamide heated solution, 220.0g of methanol was added to dilute it. During the addition, the internal temperature was maintained above 65°C. After adding methanol, it was lifted from the oil bath and cooled. After 1 hour, the stirring was stopped when it reached 30°C, and the solid precipitate was recovered by pressure filtration using a 10μm membrane filter. The weight of the filtrate in a wet state was 43g. 50g of methanol was added to the filter, and pressure filtration was performed again. The amount of calcium chloride in the filtrate was analyzed by ion chromatography, and the residual amount of calcium chloride in the polyamide was calculated. The operation from the addition of methanol to the calculation of the residual amount of calcium chloride was repeated, and the cleaning was terminated when the residual amount reached less than 1000 ppm. The number of cleanings was 7 times, and the amount of cleaning liquid was 350 g. The mass (g) of the cleaning liquid was 35 relative to the mass (g) of the raw material polyamide 66 pellets. The solid precipitate after cleaning was heated and dried in a vacuum dryer at 80°C to obtain 9.8 g of powdered polyamide 66 (yield 98.0%). The energy required for drying calculated from the amount of solvent contained was 3.6 kJ per 1 g of polyamide 66. The mass (g) of the solution contained in the powdered polyamide 66 obtained per 1 g is 3.3.

[1014] [Examples 2 to 8] [Comparative Examples 1 to 4]

[1015] The results are shown in Table 1.

[1016]

[1017] [Example 9]

[1018] In a 300mL three-necked flask equipped with a stirrer, 10g of polyamide 66 pellets and 100g of a 25wt% calcium chloride methanol solution (calcium chloride 25.0g, water content 8.1g (molar amount of water / molar amount of calcium chloride = 2)) as a metal chloride alcohol solution were added, placed in an 80°C oil bath, and polyamide 66 was dissolved while stirring for 12 hours by magnetic stirring to obtain a polyamide heated solution. The viscosity of the obtained polyamide heated solution at 25°C was 4200mPa·s. While stirring the polyamide heated solution, 220.0g of methanol was added to dilute it. During the addition, the internal temperature was lowered to 45°C. At this time, the supernatant was sampled and the content of the precipitated polyamide was calculated. The result was that the precipitated amount at this time was 0.7% by weight of the polyamide 66 used in the raw material. After adding methanol, it was lifted out of the oil bath and cooled. After 1 hour, when the temperature reaches 30°C, stirring is stopped, and the solid precipitate is recovered by pressure filtration using a 10μm membrane filter. The weight of the wet filtrate is 43g. 50g of methanol is added to the filter and pressure filtration is performed again. The amount of calcium chloride in the filtrate is analyzed by ion chromatography, and the residual amount of calcium chloride in the polyamide is calculated. The operation from the addition of methanol to the calculation of the residual amount of calcium chloride is repeated, and the cleaning is terminated when the residual amount reaches less than 1000ppm. The number of cleanings is 6 times, and the amount of cleaning liquid is 300g. The cleaned solid precipitate is heated and dried in a vacuum dryer at 80°C to obtain 9.8g of powdered polyamide 66 (yield 98.0%). The energy required for drying calculated from the amount of solvent contained is 3.6kJ per 1g of polyamide 66.

[1019] [Example 10]

[1020] In a 300mL three-necked flask equipped with a stirrer, 10g of polyamide 6 pellets and 100g of a 25wt% calcium chloride methanol solution (calcium chloride 25.0g, water content 8.1g (molar amount of water / molar amount of calcium chloride = 2)) as a metal chloride alcohol solution were added, placed in an 80°C oil bath, and polyamide 6 was dissolved while stirring for 12 hours by magnetic stirring to obtain a polyamide heated solution. The viscosity of the obtained polyamide heated solution at 25°C was 2500mPa·s. While stirring the polyamide heated solution, methanol aqueous solution (150.0g of methanol, 60.0g of water) was added to dilute it. During the addition, the internal temperature was maintained above 65°C. After adding the methanol aqueous solution, it was lifted out of the oil bath and cooled. After 1 hour, when it reached 30°C, the stirring was stopped, and the solid precipitate was recovered by pressure filtration using a 10μm membrane filter. The weight of the filtrate in a wet state was 41g. Add 50g of methanol to the filter and filter under pressure again. Analyze the amount of calcium chloride in the filtrate by ion chromatography and calculate the residual amount of calcium chloride in the polyamide. Repeat the operation from adding methanol to calculating the residual amount of calcium chloride, and end the cleaning when the residual amount reaches less than 1000ppm. The number of cleanings is 6 times and the amount of cleaning liquid is 300g. The solid precipitate after cleaning is heated and dried in a vacuum dryer at 80°C to obtain 9.8g of powdered polyamide 66 (yield 98.0%). The energy required for drying calculated from the amount of solvent contained is 3.4kJ per 1g of polyamide 66.

[1021] [Example 11]

[1022] In a 300mL three-necked flask equipped with a stirrer, 10g of polyamide 66 pellets and 100g of a 25wt% calcium chloride ethanol solution as a metal chloride alcohol solution (25.0g of calcium chloride, 8.1g of water content (molar amount of water / molar amount of calcium chloride = 2)) were added, placed in an 80°C oil bath, and polyamide 66 was dissolved while stirring for 12 hours by magnetic stirring to obtain a polyamide heated solution. The viscosity of the obtained polyamide heated solution at 25°C was 4100mPa·s. While stirring the polyamide heated solution, 220.0g of ethanol was added to dilute it. During the addition, the internal temperature was maintained above 65°C. After adding ethanol, it was lifted from the oil bath and cooled. After 1 hour, when it reached 30°C, the stirring was stopped, and the solid precipitate was recovered by pressure filtration using a 10μm membrane filter. The weight of the filtrate in a wet state was 44g. 50g of methanol was added to the filter, and pressure filtration was performed again. The amount of calcium chloride in the filtrate was analyzed by ion chromatography, and the residual amount of calcium chloride in the polyamide was calculated. The operation from the addition of ethanol to the calculation of the residual amount of calcium chloride was repeated, and the cleaning was terminated when the residual amount reached less than 1000 ppm. The number of cleanings was 6 times, and the amount of cleaning liquid was 300 g. The solid precipitate after cleaning was heated and dried in a vacuum dryer at 80°C to obtain 9.8 g of powdered polyamide 66 (yield 98.0%). The energy required for drying calculated from the amount of solvent contained was 3.6 kJ per 1 g of polyamide 66.

[1023] [Example 12]

[1024] In a 300mL three-necked flask equipped with a stirrer, 10g of polyami...

Claims

1. A method for producing a powdered polyamide, characterized in that: It includes the following steps: Step 1: a step of heating and dissolving a polyamide resin composition with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated solution; Step 2: diluting the heated polyamide solution with alcohol to obtain an alcohol diluted solution; and Step 3: Cooling the alcohol dilution to precipitate the powdered polyamide. In the step 1, the mass ratio of the metal chloride is 23 mass % to 35 mass % relative to 100 mass % of the metal chloride alcohol solution, in the step 1, the heated polyamide solution contains 0.2 mol to 2.5 mol of water relative to 1 mol of the metal chloride, and in the step 2, the polyamide heated solution is diluted without causing the temperature of the heated polyamide solution to fall below 50°C.

2. A method for producing a powdered polyamide, characterized in that: It includes the following steps: Step 1: a step of heating and dissolving a polyamide resin composition with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide heated solution; Step 2: diluting the heated polyamide solution with alcohol to obtain an alcohol diluted solution; and Step 3: Cooling the alcohol dilution to precipitate the powdered polyamide. In the step 1, the mass ratio of the metal chloride is 23 mass % to 35 mass % relative to 100 mass % of the metal chloride alcohol solution, in the step 1, the polyamide heated solution contains water in an amount of 0.2 mol to 2.5 mol relative to 1 mol of the metal chloride, and in the step 2, the mass of the precipitated polyamide is 1 mass % or less relative to the total mass of the polyamide contained in the polyamide heated solution.

3. A method for producing recycled polyamide, using a polyamide resin composition comprising polyamide coated with a silicone resin as a raw material, characterized in that: The manufacturing method comprises a dissolving step, wherein a metal chloride alcohol solution containing metal chloride and alcohol is mixed with the polyamide resin composition to dissolve the polyamide to prepare a polyamide dissolved solution. In the dissolving step, the mass ratio of the polyamide in the polyamide solution is 5 mass % to 15 mass %.

4. A methanol composition comprising a metal chloride at a concentration of 5% to 25%, a hydroxide of the metal at a concentration of 0.001% to 1%, and water at a concentration of 0.001% to 5%.

5. A method for producing polyamide, comprising recovering polyamide from a mixture containing at least polyamide and polyethylene terephthalate, characterized in that: The manufacturing method comprises the following steps: A step of mixing the mixture with a metal chloride alcohol solution containing a metal chloride and an alcohol to obtain a polyamide solution in which the polyamide is dissolved; and A step of separating and recovering the polyamide solution.

6. A method for producing recycled polyamide, using a mixture containing polyamide coated with urethane resin as a raw material, characterized in that: The manufacturing method comprises a dissolving step, wherein a metal chloride alcohol solution containing metal chloride and alcohol is mixed with the mixture to dissolve the polyamide to prepare a polyamide dissolved solution. In the dissolving step, the mass ratio of the polyamide in the polyamide solution is 5 mass % to 15 mass %.

7. The method for producing a powdered polyamide according to claim 1 or 2, further comprising: Step 4: a step of washing the powdered polyamide obtained in step 3 once or more using a solvent.

8. The method for producing a powdered polyamide according to claim 7, wherein: The solvent used for the initial washing in the step 4 is the same alcohol as the alcohol used in the step 1.

9. The method for producing a powdered polyamide according to claim 1 or 2, wherein: The temperature of the heating and dissolving in the step 1 is 60° C. or higher and 80° C. or lower.

10. The method for producing a powdered polyamide according to claim 1 or 2, further comprising: Step 5: A step of heating the powdered polyamide precipitated in the step 3 to obtain heated powdered polyamide.

11. The method for producing a powdered polyamide according to claim 10, wherein: After step 5, the method further comprises: Step 6: a step of subjecting the heated powdered polyamide obtained in the step 5 to solid-liquid separation and washing the obtained solid.

12. The method for producing a powdered polyamide according to claim 1 or 2, wherein: The polyamide resin composition includes polyamide coated with a silicone resin, and the concentration of the polyamide in the polyamide heated solution in the step 1 is 5% by mass to 15% by mass.

13. The method for producing a powdered polyamide according to claim 1 or 2, wherein: The polyamide resin composition includes polyamide coated with a silicone resin, and the viscosity of the polyamide heated solution in the step 1 at 25° C. is 10 mPa·s to 20000 mPa·s.

14. A metal chloride alcohol solution, wherein: The metal chloride concentration is 23 mass % or more and 35 mass % or less, and contains a hydroxide of the same metal as the metal contained in the metal chloride at a concentration of 0.001 mass % to 1 mass %, and contains water at a concentration of 0.001 mass % to 10 mass %.

15. The method for producing a powdered polyamide according to claim 1 or 2, wherein: The metal chloride alcohol solution has a metal chloride concentration of 23 mass % to 35 mass %, contains a hydroxide of the same metal as the metal contained in the metal chloride at a concentration of 0.001 mass % to 1 mass %, and contains water at a concentration of 0.001 mass % to 10 mass %.

16. The method for producing a powdered polyamide according to claim 1 or 2, which is a method for producing a powdered polyamide containing 0.001 ppm to 1500 ppm of calcium atoms and a molar content of halogen atoms relative to the molar content of calcium atoms being less than 1.

17. The method for producing a powdered polyamide according to claim 1 or 2, wherein: The polyamide resin composition contains at least polyamide and polyethylene terephthalate.

18. The method for producing a powdered polyamide according to claim 1 or 2, wherein: The polyamide resin composition includes polyamide coated with a urethane resin.

19. The method for producing a powdered polyamide according to claim 1 or 2, wherein: The following steps are included after steps 1 to 3: Step 7: a step of recovering the precipitated powdered polyamide; Step 8: a washing step of washing the recovered powdered polyamide; and Step 9: a drying step of heating and drying the washed powdered polyamide. The amount of the metal chloride attached to the powdered polyamide after the heat drying in the step 9 is 20 parts by mass or less based on 100 parts by mass of the powdered polyamide.

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