Polyamide manufacturing method and polyamide manufactured by the same

Abstract

A polyamide manufacturing method for using a diamine and a polyester including a dicarboxylic acid component and a glycol component to manufacture, in a solid-phase state, a polyamide containing a dicarboxylic acid component and a diamine component, the polyamide manufacturing method being characterized in carrying out the following steps (I) to (III) in the sequence listed. (I) Adding a diamine and a polyester having a specific surface area of 100 cm2 / g or above. (II) Performing heating and stirring under normal pressure and at a temperature of between (melting point of the diamine – 100°C) and (melting point of the diamine + 150°C). (III) Then further performing heating and stirring at a temperature equal to or higher than (boiling point of glycol having the highest boiling point from among the glycol components constituting the polyester – 50°C).

Description

[Technical Field]

[0001] The present invention relates to a method for producing polyamide by recycling polyester components. [Background technology]

[0002] From the viewpoint of effective resource utilization and reduction of carbon dioxide emissions as a measure against global warming, many recycling technologies for materials are being considered. Methods for recycling resin materials can be broadly divided into three types: material recycling, in which recovered waste resin is melted and processed again; chemical recycling, in which recovered waste resin is decomposed into monomers and oligomers through chemical reactions and these decomposed materials are then used again for polymerization; and thermal recycling, in which recovered waste resin is used as a heat source. Material recycling is widely used because it is easy to recycle, but there is a problem in that it is difficult for materials obtained by melt-processing again to maintain the same performance as virgin materials due to the influence of impurities and deterioration of resins. Chemical recycling breaks down materials into their raw materials, and the resulting material can be polymerized again to have exactly the same performance as virgin materials. However, because it requires complex processes, it is difficult to use it as a substitute for virgin materials from a cost perspective. Due to these problems, most waste resins are currently recycled thermally, but this is not a desirable method from the perspective of efficient resource utilization and carbon dioxide emissions. Therefore, there is a strong demand for the development of inexpensive chemical recycling technology.

[0003] Various recycling technologies have been developed for polyethylene terephthalate, which is widely used in beverage bottles and other products. Chemical recycling, in particular, involves depolymerizing polyethylene terephthalate to bis-2-hydroxyethyl terephthalate and then repolymerizing it. However, polyester polymerization requires the removal of impurities and water as much as possible, and the purification of the depolymerized monomer is costly.

[0004] Meanwhile, a method for synthesizing polyamides from polyesters and diamines has been developed. This synthesis method utilizes the aminolysis reaction of polyesters with diamines, which is a reaction that proceeds much more easily than the polymerization of polyesters. Patent Document 1 proposes a method in which an aprotic, protophobic polar solvent is added to a polyester and a diamine. Patent Document 2 proposes a method in which a polyester and a diamine are reacted in supercritical water or subcritical water. Both methods use a solvent, which requires removal of the solvent after the reaction. Furthermore, the method of Patent Document 2 requires high temperature and pressure, which results in excessive process costs. Patent Document 3 proposes a method of adding a diamine to a polyester in multiple stages and melt-kneading the mixture. This method requires heating to above the melting point of the aromatic polyamide, which raises concerns about the generation of by-products and gelation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-106504 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-83721 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-11175 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a method for producing polyamide by chemically recycling polyester components, without using solvents, at low temperatures, and while reducing process costs. [Means for solving the problem]

[0007] As a result of extensive research to solve the above-mentioned problems, the present inventors discovered that the above-mentioned problems could be solved by heating and stirring a polyester having a specific specific surface area and a diamine, thereby synthesizing a polyamide without using a solvent or heating to the melting temperature, and thus arrived at the present invention. The method for producing a polyamide of the present invention is a method for producing a polyamide containing a dicarboxylic acid component and a diamine component in a solid state using a polyester containing a dicarboxylic acid component and a glycol component, and a diamine, and is characterized by carrying out the following steps (I) to (III) in this order: (I) Specific surface area is 100 cm 2 / g or more of polyester and diamine are added to a reactor, (II) Heat and stir the mixture at normal pressure at a temperature between (diamine melting point -100°C) and (diamine melting point +150°C), (III) Thereafter, the mixture is further heated and stirred at a temperature equal to or higher than the boiling point of the glycol having the highest boiling point among the glycol components constituting the polyester minus 50°C. According to the method for producing polyamide of the present invention, it is preferable to use polyethylene terephthalate as the polyester. According to the method for producing polyamide of the present invention, it is preferable to use a fibrous polyester. According to the method for producing polyamide of the present invention, it is preferable to use a particulate polyester. According to the method for producing a polyamide of the present invention, it is preferable to use an aliphatic diamine having 6 to 12 carbon atoms. According to the method for producing polyamide of the present invention, it is preferable to use 1,10-decanediamine. The polyamide of the present invention is produced by the above-mentioned method. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a recycling method that enables chemical recycling of polyester under mild conditions and upgrading of the polyester to a polyamide that is superior in performance, such as heat resistance, hydrolysis resistance, and mechanical strength, compared to the polyester before recycling. Furthermore, when decanediamine, which is derived from a plant-derived material, is used as the diamine, it is possible to provide an unprecedented sustainable resin material that is both a biomass material and a recycled material. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below. In the production method of the present invention, the polyester raw material may be a used polyester or a polyester that has been discarded during the production process. The polyester is not particularly limited as long as it contains a dicarboxylic acid component and a glycol component and has an ester bond in the molecule, and examples of the polyester include aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polypropylene terephthalate, and examples of the aliphatic polyesters such as polybutylene succinate. Polyethylene terephthalate and polybutylene terephthalate are preferred because they can give polyamides with excellent mechanical strength, and polyethylene terephthalate is particularly preferred because it is easily available as a raw material.

[0010] Furthermore, as long as the object of the present invention is not impaired, the polyester may be one in which the components constituting the above polyester are copolymerized with other dicarboxylic acid components, glycol components, oxycarboxylic acid components, or the like, or may be a blend of the above polyesters or a blend of a polyester copolymerized with the above polyester. Examples of other copolymerizable components include dicarboxylic acid components such as isophthalic acid, naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic anhydride, sebacic acid, adipic acid, and succinic acid, and examples of diol components include ethanediol, propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and cyclohexanedimethanol.

[0011] In the present invention, the raw material polyester has a specific surface area of ​​100 cm 2 / g or more, and 500cm 2 / g or more, and 2 / g or more. 2 / g or more, the added diamine is adsorbed onto the surface of the polyester even when melted by heating, so that the aminolysis reaction proceeds quickly and adhesion to the equipment walls and adhesion of polyesters to each other can be suppressed. In addition, the specific surface area of ​​the raw material polyester is set to 40,000 cm or more, because adhesion to the equipment walls and the like can reduce operability. 2 / g or less is preferable.

[0012] The shape of the polyester is not particularly limited as long as the specific surface area is within the above range, and is preferably in the form of a powder or fiber. A powder can be obtained by pulverizing the polyester. A fiber may be cut to a length that can be introduced into a reactor, or may be fed as is without cutting.

[0013] In the production method of the present invention, the diamine as the raw material may be either an aliphatic diamine or an aromatic diamine, and from the viewpoint of efficiently removing the glycol component of the polyester produced by the reaction between the polyester and the diamine, it is preferable that the diamine has a boiling point higher than that of the glycol component of the polyester. For example, when polyethylene terephthalate is used as the raw material polyester, it is particularly preferable to use a diamine having a boiling point higher than that of ethylene glycol (198° C.) Examples of such diamines include aromatic diamines having 6 to 20 carbon atoms, alicyclic diamines having 6 to 20 carbon atoms, and aliphatic diamines having 6 to 12 carbon atoms, such as hexamethylenediamine, 2-methyloctamethylenediamine, trimethylhexamethylenediamine, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane. Among these, from the viewpoints of the balance between the melting point and the boiling point, the uses after recycling, etc., the diamine is preferably an aliphatic diamine having 8 to 12 carbon atoms, and particularly 1,10-decanediamine. 1,10-decanediamine is generally a plant-derived raw material, and therefore polyamide 10T obtained by using this with polyethylene terephthalate has an extremely low environmental impact because the diamine component is a biomass material and the dicarboxylic acid component is a recycled material.

[0014] The method of the present invention for producing a polyamide containing a dicarboxylic acid component and a diamine component is carried out using the above polyester and the above diamine in a solid phase in which the raw material polyester and the reaction product polyamide are not melted, in the following order of steps (I) to (III). (I) Specific surface area is 100 cm 2 / g or more of polyester and diamine are added to a reactor, (II) Heat and stir the mixture at normal pressure at a temperature between (diamine melting point -100°C) and (diamine melting point +150°C), (III) Thereafter, the mixture is further heated and stirred at a temperature equal to or higher than the boiling point of the glycol having the highest boiling point among the glycol components constituting the polyester minus 50°C.

[0015] There are no particular limitations on the reactor that can be used in the production method of the present invention, but in order to maintain a solid-phase state, i.e., a solid (powder) state, throughout, a device that can uniformly stir even a solid is preferred.

[0016] In step (I), the amount of diamine added to the polyester is preferably 1.00 to 1.50 mol per 1 mol of repeating unit of the polyester. If the amount of diamine added is less than 1.00 mol, the resulting polyamide will be a copolymer with residual glycol components, which may result in reduced physical properties. On the other hand, if the amount of diamine added exceeds 1.50 mol, the amount of diamine will be excessive relative to the dicarboxylic acid components of the polyester, and the resulting polyamide may not have a high degree of polymerization.

[0017] In step (II), the mixture is heated and stirred under normal pressure. The temperature in step (II) must be (melting point of diamine - 100°C) to (melting point of diamine + 150°C), preferably (melting point of diamine - 50°C) to (melting point of diamine + 150°C), and more preferably (melting point of diamine) to (melting point of diamine + 120°C). If the temperature in step (II) is lower than (diamine melting point - 100°C), the reaction between the diamine and polyester will not proceed smoothly, making it difficult to obtain a polyamide. If the temperature in step (II) is higher than (diamine melting point + 150°C), the diamine will be close to its boiling point and will vaporize and be eliminated from the system before reacting with the polyester, making it difficult to obtain a high-molecular-weight polyamide. Even if the temperature in step (II) is equal to or higher than the melting point of the diamine, the polyester used in the present invention can be 2 / g or more, the diamine is adsorbed onto the polyester surface as soon as it melts, and the entire system can be maintained in a solid state.

[0018] Following step (II), in step (III), heating and stirring are further carried out. The temperature in step (III) must be (the boiling point of the glycol having the highest boiling point among the glycol components constituting the polyester - 50°C) or higher. If the temperature in step (III) is lower than (the boiling point of the glycol having the highest boiling point among the glycol components constituting the polyester - 50°C), the glycol component produced cannot be sufficiently removed, and the resulting polyamide will be a copolymer consisting of a dicarboxylic acid component, a diamine component, and a glycol component. The temperature in step (III) is preferably 280° C. or lower. If the temperature in step (III) is higher than 280° C., the polyamide may gel, or the diamine component may volatilize and be discharged outside the system, preventing an increase in the degree of polymerization.

[0019] The above steps (I) to (III) are carried out substantially in a solid phase. A method carried out in a solid phase is economically advantageous because it does not require complicated equipment and does not require a step for removing solvents, etc. However, if necessary, a step of washing the polyamide with a low-boiling point solvent may be added after step (III) for the purpose of removing reaction by-products. In this case, it is necessary to remove the washing solvent and dry the polyamide.

[0020] The method for producing a polyamide of the present invention may be carried out by blending, as necessary, an antioxidant, an antistatic agent, a flame retardant, a flame retardant assistant, a heat stabilizer, a light stabilizer, a colorant, a lubricant, a reinforcing material, a filler, a pigment, or the like.

[0021] The polyamide obtained by the above steps (I) to (III) has a diamine component substituted for the glycol component of the polyester. The polyamide produced by the method of the present invention has an amide group conversion rate, expressed as the ratio of amide bonds to all bonds, of preferably 90% or more, more preferably 95% or more, and even more preferably 99% or more.

[0022] The polyamide produced by the method of the present invention can be processed into various molded articles, films, sheets, fibers, etc. by known methods such as injection molding, extrusion molding, blow molding, compression molding, or by known film-forming methods or spinning methods. [Example]

[0023] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0024] 1.Measurement method The physical properties of the polyamide were measured by the following methods.

[0025] (1) Melting point Using a differential scanning calorimeter (PerkinElmer DSC-7), the sample was heated to 360°C at a rate of 20°C / min, held at 360°C for 5 minutes, cooled to 25°C at a rate of 20°C / min, held at 25°C for a further 5 minutes, and then heated again at a rate of 20°C / min. The top of the endothermic peak was taken as the melting point (Tm).

[0026] (2) Amide group conversion rate A high-resolution nuclear magnetic resonance spectrometer (JEOL ECA500NMR, resolution: 500 MHz, solvent: trifluoroacetic acid, temperature: 25°C) was used. 1 By H-NMR analysis, the ratio of amide bonds to all bonds was calculated from the peak intensity area ratios of dicarboxylic acid components, diamine components, glycol components, terminal carboxyl groups, terminal hydroxyl groups, and terminal amino groups, and this was taken as the amide group conversion rate. Because all bonds before the reaction were ester bonds, the amide group conversion rate was 0%.

[0027] 2.Raw materials The raw materials used in the examples and comparative examples are shown below.

[0028] (1) Polyester PET-1 Fiber waste (fineness 3.0 dtex, density 1.38, specific surface area 1742 cm) discharged during the manufacturing process of polyethylene terephthalate (PET) fiber 2 / g) PET-2 Fiber waste (fineness 10.0 dtex, specific gravity 1.38, specific surface area 954 cm) discharged during the PET fiber manufacturing process 2 / g) PET-3 The collected PET bottles were cut into pieces of approximately 5 mm with scissors and then crushed in a crusher (volume average particle size 95 μm, specific gravity 1.38, specific surface area 458 cm). 2 / g) PET-4 The collected PET bottles were cut into 5 mm pieces with scissors (specific surface area 54 cm 2 / g)

[0029] (2) Diamine Decanediamine (DDA, melting point 62°C, boiling point above 260°C) Hexamethylenediamine (HMDA, melting point 42°C, boiling point 205°C) Nonanediamine (NDA, melting point 37°C, boiling point 260°C) Butanediamine (BDA, melting point 30°C, boiling point 160°C)

[0030] Example 1 6.00 g of PET-1 was weighed out, and 1.10 mol of DDA was weighed out per 1 mol of the repeating unit of PET-1, and these were charged into a reactor equipped with a stirrer (step (I)). In a nitrogen atmosphere, the mixture was heated and stirred at 170°C for 3 hours as step (II), and then heated and stirred at 250°C for 9 hours as step (III). After the reaction was completed, the temperature was returned to room temperature and the reaction product was taken out of the reactor to obtain a white polyamide powder.

[0031] Examples 2 to 7, Comparative Examples 1 to 3 A white polyamide powder was obtained in the same manner as in Example 1, except that the type of polyester, the type and amount of diamine, the temperature and time of step (II), and the temperature of step (III) were as shown in Table 1.

[0032] Table 1 shows the conditions for producing the polyamide, and the results of measuring the melting point and amide group conversion rate of the obtained polyamide.

[0033] [Table 1]

[0034] In Examples 1 to 7, the diamine that melted at the beginning of the reaction was immediately adsorbed onto the polyester and then maintained in a dry solid state, and the obtained polyamide had a high amide group conversion rate.

[0035] In Comparative Example 1, the specific surface area of ​​the polyester was too low, so the reaction with the diamine did not proceed efficiently, and the polyester was in a viscous state in step (II). In Comparative Example 2, the temperature in step (II) was too high, so that the diamine was vaporized, and the obtained polyamide had a low amide group conversion rate. In Comparative Example 3, the temperature in step (III) was too low, so that the glycol component could not be sufficiently removed, and the obtained polyamide had a low amide group conversion rate.

Claims

1. A method for producing a polyamide containing a dicarboxylic acid component and a diamine component in a solid state using a polyester containing a dicarboxylic acid component and a glycol component, and a diamine, characterized in that the method comprises the steps (I) to (III) below in this order to obtain a polyamide having an amide group conversion rate of 90% or more. (I) Specific surface area is 100 cm ２ / g or more of polyester and diamine are added to a reactor, (II) Heating and stirring the mixture at a temperature of (diamine melting point -100°C) to (diamine melting point +150°C) under normal pressure; (III) Thereafter, the mixture is further heated and stirred at a temperature of (the boiling point of the glycol having the highest boiling point among the glycol components constituting the polyester - 50°C) or higher and 280°C or lower.

2. 2. The method for producing polyamide according to claim 1, wherein polyethylene terephthalate is used as the polyester.

3. 3. The method for producing polyamide according to claim 1, wherein the polyester is in the form of a fiber.

4. 3. The method for producing polyamide according to claim 1, wherein the polyester is in the form of powder or granule.

5. 5. The method for producing a polyamide according to claim 1, wherein an aliphatic diamine having 6 to 12 carbon atoms is used.

6. 5. The method for producing a polyamide according to claim 1, wherein 1,10-decanediamine is used.

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