Method for recovering thermoplastic polymer-derived components, thermoplastic polymer-derived components, recycled monomers, method for producing thermoplastic polymers, and thermoplastic polymers

Abstract

To provide a recycling method for recovering thermoplastic polymer-derived components by efficiently separating components that do not melt in the subcritical temperature range from thermoplastic polymer compositions and / or mixtures containing components that do not melt in the subcritical temperature range, using water, which has a low environmental impact, as a solvent. [Solution] The method comprises the steps of mixing a thermoplastic polymer composition and / or mixture containing a thermoplastic polymer and a component that does not melt in the subcritical temperature range with water, and obtaining a thermoplastic polymer-derived component by separating the component that does not melt in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water. A method for recovering components derived from thermoplastic polymers.

Description

Technical Field

[0001] The present invention relates to a method for recovering components derived from thermoplastic polymers, components derived from thermoplastic polymers, recycled monomers, a method for producing thermoplastic polymers, thermoplastic polymers, molded articles, fibers, films, and sheets.

Background Art

[0002] In recent years, triggered by the marine plastic problem, interest in global environmental issues has increased, and the recognition that it is necessary to build a sustainable society has spread. Global environmental issues include global warming, resource depletion, water shortages, etc. Many of the global environmental issues are due to human activities since the Industrial Revolution, caused by the rapid increase in resource consumption and greenhouse gas emissions. Therefore, for building a sustainable society, technologies related to recycling fossil resources such as plastics and reducing greenhouse gas emissions are becoming increasingly important. As one of such technologies, a method has been disclosed for purifying a recovered polymer by bringing it into contact with a fluid solvent at high temperature and high pressure for the purpose of reusing the polymer recovered after consumer or industrial use to obtain properties equivalent to those of virgin products (Patent Document 1).

[0003] Plastics may be used alone or in combination with various materials. For example, plastic molded articles reinforced with glass fibers, polymer alloys blended with other types of plastics, fibers or films coated with a coating agent on the surface, fibers obtained by blending different types of fibers, etc. can be mentioned. When recycling these composite materials, a technique for separating the composite materials is important. As a method, for example, in order to separate a filler from a silicone compound mixed with a filler, it is mixed with alcohol, heated, the silicone compound is decomposed, and the decomposition product of the silicone compound obtained by the decomposition reaction is dissolved to separate the filler and the silicone (Patent Document 2). Also, a method for separating and recovering a non-hydrolyzable polymer from a mixture containing a resin layer containing a hydrolyzable polymer and a resin layer containing a non-hydrolyzable polymer by hydrothermal treatment has been disclosed (Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2018-521186 [Patent Document 2] Japanese Patent Publication No. 2010-47639 [Patent Document 3] Japanese Patent Publication No. 2023-001085 [Overview of the project] [Problems that the invention aims to solve]

[0005] The purification and separation methods for recovered polymers disclosed in Patent Documents 1 or 2 have limitations, such as being limited to polystyrene and silicone plastics, and using organic solvents, which have a high environmental impact.

[0006] The hydrothermal separation and recovery method disclosed in Patent Document 3 utilizes the fact that non-hydrolyzable polymers are immiscible with water when the reaction vessel is opened during recovery. However, if the non-hydrolyzable polymer to be separated has a higher density than water, recovery and separation from hydrolyzable polymers become difficult, limiting the range of substances that can be separated and recovered.

[0007] Therefore, the present invention aims to provide a recycling method for recovering thermoplastic polymer-derived components by efficiently separating components that do not melt in the subcritical temperature range from thermoplastic polymer compositions and / or mixtures containing components that do not melt in the subcritical temperature range, using water, which has a low environmental impact, as a solvent. [Means for solving the problem]

[0008] The inventors of this invention conducted diligent studies to solve the above problems and discovered that in order to separate components that do not have a melting point in the subcritical temperature range, such as inorganic substances, from thermoplastic polymer compositions and / or mixtures, it is important to mix the thermoplastic polymer composition and / or mixture with water and heat it as necessary, and then perform solid-liquid separation while the thermoplastic polymer is dissolved in water. Based on this, the present invention was completed.

[0009] To solve the above problems, the present invention has the following configuration. (1) A step of mixing a thermoplastic polymer composition and / or mixture containing a thermoplastic polymer and a component that does not melt in the subcritical temperature range with water, and a step of obtaining a thermoplastic polymer-derived component by separating the component that does not melt in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water. A method for recovering components derived from thermoplastic polymers. (2) The molten state is formed at a temperature of 200°C or higher. A method for recovering the thermoplastic polymer-derived component described in (1) above. (3) The dissolved state is formed under pressure equal to or greater than the saturated vapor pressure of water at the temperature of the dissolved state. A method for recovering the thermoplastic polymer-derived component described in (1) above. (4) A method for solid-liquid separation of components that do not have a melting point in the subcritical temperature range while the thermoplastic polymer is dissolved in water, including filtration by a filter, A method for recovering the thermoplastic polymer-derived component described in (1) above. (5) The ratio of the thermoplastic polymer a (kg) to water b (kg) is 1 or more. A method for recovering the thermoplastic polymer-derived component described in (1) above. (6) The thermoplastic polymer includes thermoplastic polyamide or thermoplastic polyester. A method for recovering the thermoplastic polymer-derived component described in (1) above. (7) The thermoplastic polymer includes a thermoplastic polyamide or thermoplastic polyester obtained by recovery. The method for recovering components derived from a thermoplastic polymer according to (1) above. (8) Components having no melting point in the temperature range of the subcritical state include metals. The method for recovering components derived from a thermoplastic polymer according to (1) above. (9) Obtained by the method for recovering components derived from a thermoplastic polymer according to (1) above. Components derived from a thermoplastic polymer. (10) Obtained by depolymerizing components derived from a thermoplastic polymer obtained by the method for recovering components derived from a thermoplastic polymer according to (1) above. Recycled monomers. (11) Including the step of polycondensing a raw material containing the recycled monomer according to (10) above. Method for producing a thermoplastic polymer. (12) Obtained by polycondensing a raw material containing the recycled monomer according to (10) above. Thermoplastic polymer. (13) Formed products, fibers, films, or sheets made using the thermoplastic polymer according to (12) above. Molded products, fibers, films, or sheets. [Advantages of the Invention]

[0010] According to the present invention, components having no melting point in the temperature range of the subcritical state can be separated using water, which is a solvent with a low environmental impact, and components derived from a thermoplastic polymer can be obtained under relatively mild conditions compared to depolymerization by hydrolysis. [Brief Description of the Drawings]

[0011] [Figure 1] It is a schematic diagram showing an overview of the steps of Example 1. [Figure 2] It is a schematic diagram showing an overview of the steps of Example 2. [Figure 3] It is a schematic diagram showing an overview of the steps of Example 3. [Figure 4] It is a schematic diagram showing an overview of the steps of Comparative Example 3. [Modes for Carrying Out the Invention]

[0012] Hereinafter, the present invention will be described in detail together with embodiments.

[0013] The method for recovering a thermoplastic polymer-derived component of the present invention includes a step of mixing a thermoplastic polymer composition and / or mixture containing a thermoplastic polymer and a component having no melting point in the subcritical temperature range with water, and a step of obtaining a thermoplastic polymer-derived component from which the component having no melting point in the subcritical temperature range is separated by solid-liquid separation in a state where the thermoplastic polymer is dissolved in water.

[0014] (1) Step of mixing a thermoplastic polymer composition and / or mixture containing a thermoplastic polymer and a component having no melting point in the subcritical temperature range with water The method for recovering a thermoplastic polymer-derived component of the present invention includes a step of mixing a thermoplastic polymer composition and / or mixture containing a thermoplastic polymer and a component having no melting point in the subcritical temperature range with water.

[0015] In the present invention, the thermoplastic polymer composition and / or mixture contains a thermoplastic polymer and a component having no melting point in the subcritical temperature range. Here, the thermoplastic polymer composition refers to, for example, a state in which a component having no melting point in the subcritical temperature range is kneaded into the thermoplastic polymer, and the thermoplastic polymer and the component having no melting point in the subcritical temperature range are integrated. The thermoplastic polymer mixture refers to, for example, a component having no melting point in the subcritical temperature range to which no thermoplastic polymer adheres, and a thermoplastic polymer or a thermoplastic polymer composition are mixed, and the thermoplastic polymer and the component having no melting point in the subcritical temperature range are not integrated but are mixed.

[0016] In the present invention, the thermoplastic polymer preferably includes a thermoplastic polyamide or a thermoplastic polyester. Examples of thermoplastic polyamides include polyamide 6 and polyamide 66. Examples of thermoplastic polyesters include polyethylene terephthalate, polybutylene terephthalate, and polycarbonate.

[0017] In the method for recovering components derived from thermoplastic polymers of the present invention, it is preferable that the thermoplastic polymer includes thermoplastic polyamide or thermoplastic polyester obtained by recovery. Thermoplastic polyamide is widely used as engineering plastics and textile products. Thermoplastic polyester is also widely used as general-purpose plastics, bottles, films, and textile products. Therefore, by including thermoplastic polyamide or thermoplastic polyester obtained by recovery as the thermoplastic polymer, a wide range of materials can be recycled. Furthermore, raw material recovery and hydrolysis become easier. In this invention, "obtained by recovery" refers to obtaining materials from reuse after use by consumers or in industry, or from process scraps or waste materials.

[0018] The content of thermoplastic polyamide or thermoplastic polyester in the thermoplastic polymer composition and / or mixture is preferably 30% by weight or more, more preferably 50% by weight or more, and even more preferably 70% by weight or more, based on 100% by weight of the total thermoplastic polymer composition and / or mixture.

[0019] In this invention, a component that does not have a melting point in the subcritical temperature range is defined as a component that, when heated from room temperature to 400°C at a heating rate of 20°C / min under a nitrogen gas atmosphere using a differential scanning calorimeter, does not show an endothermic peak in the temperature range of 130°C to 350°C, or shows an endothermic peak but whose enthalpy change is 5 J / g or less. Peaks due to irreversible thermal decomposition are not included in the above definition. Examples of components that do not have a melting point in the subcritical temperature range include inorganic materials such as glass and metals, and organic materials such as cross-linked polymers, natural fibers, and regenerated fibers.

[0020] Among the components that do not have a melting point in the subcritical temperature range, examples of inorganic materials include fibrous fillers, non-fibrous fillers, and metals.

[0021] Fibrous fillers are fillers that have a fibrous shape. Specifically, examples include glass fibers, polyacrylonitrile (PAN) and pitch-based carbon fibers, stainless steel fibers, metal fibers such as aluminum fibers and brass fibers, gypsum fibers, ceramic fibers, asbestos fibers, zirconia fibers, alumina fibers, silica fibers, titanium oxide fibers, silicon carbide fibers, rock wool, potassium titanate whiskers, silicon nitride whiskers, wollastenite, alumina silicate, and various other fibers or whisker-shaped fillers, as well as glass fibers or carbon fibers coated with one or more metals selected from the group consisting of nickel, copper, cobalt, silver, aluminum, iron, and alloys thereof.

[0022] Specific examples of non-fibrous fillers include non-swelling silicates such as talc, warlastenite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, bentonite, asbestos, alumina silicate, and calcium silicate; swelling layered silicates such as Li-type fluoroteniolite, Na-type fluoroteniolite, Na-type tetrasilicon fluorimica, and Li-type tetrasilicon fluorimica; metal oxides such as silicon oxide, magnesium oxide, alumina, silica, diatomaceous earth, zirconium oxide, titanium oxide, iron oxide, zinc oxide, calcium oxide, tin oxide, and antimony oxide; calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, and Examples include metal carbonates such as romite and hydrotalcite, metal sulfates such as calcium sulfate and barium sulfate, metal hydroxides such as magnesium hydroxide, calcium hydroxide, aluminum hydroxide, and basic magnesium carbonate, smectite-type clay minerals such as montmorillonite, bydelite, nontronite, saponite, hectorite, and souconite, and various clay minerals such as vermiculite, halloysite, kanemite, kenyaite, zirconium phosphate, and titanium phosphate, as well as glass beads, glass flakes, ceramic beads, boron nitride, aluminum nitride, silicon carbide, calcium phosphate, carbon black, and graphite. In the above-mentioned swollen layered silicates, the exchangeable cations present between the layers may be exchanged with organo-onium ions. Examples of organo-onium ions include ammonium ions, phosphonium ions, and sulfonium ions.

[0023] Specific examples of metals include nickel, copper, cobalt, silver, aluminum, iron, and alloys thereof. Metals are included in thermoplastic polymer compositions and / or mixtures, for example, as metals inserted into thermoplastic polymer molded products or as metals that were not completely removed when thermoplastic polymers were recovered and sorted as recycled waste.

[0024] Specific examples of crosslinked polymers include acrylic polymers crosslinked using a crosslinking agent and cured silicone polymers.

[0025] Examples of natural fibers include cotton, silk, linen, and wool.

[0026] Specific examples of regenerated fibers include cellulose fibers such as rayon, ponosic, cupro, and lyocell.

[0027] Components that do not have a melting point in the subcritical temperature range may be, for example, crosslinked silicone polymers coated on processed thermoplastic polymer fibers or films, or components compounded during the processing of thermoplastic polymers, such as cellulose fibers blended with thermoplastic polymer fibers.

[0028] The thermoplastic polymer composition and / or mixture of the present invention may contain two or more components that do not have a melting point in the subcritical temperature range. Preferably, the content of components that do not have a melting point in the subcritical temperature range is 1 to 200 parts by weight per 100 parts by weight of the thermoplastic polymer.

[0029] In the method for recovering components derived from thermoplastic polymers of the present invention, it is preferable that the component that does not have a melting point in the subcritical temperature range contains a metal. Thermoplastic polymers are used in automotive parts and other applications, and metals are often mixed in during recovery. On the other hand, completely separating the mixed metals during the raw material recovery process is difficult and costly. Therefore, including a metal makes raw material recovery easier and more economical.

[0030] In the present invention, it is preferable that the component that does not have a melting point in the subcritical temperature range includes a fibrous filler, and more preferably glass fibers. Thermoplastic polymers containing fibrous fillers are widely used, as exemplified by glass fiber reinforced resins. Therefore, including a fibrous filler facilitates resource recovery.

[0031] The thermoplastic polymer compositions and / or mixtures of the present invention may contain various additives, etc., to the extent that they do not impair the objectives of the present invention. Specific examples of various additives include antioxidants and heat stabilizers (hindered phenols, hydroquinones, phosphates and their derivatives, copper halides, iodine compounds, etc.), weathering agents (resorcinols, salicylates, benzotriazoles, benzophenones, hindered amines, etc.), mold release agents and lubricants (aliphatic alcohols, aliphatic amides, aliphatic bisamides, bisurea and polyethylene wax, etc.), pigments (cadmium sulfide, phthalocyanine, carbon black, etc.), dyes (nigrosine, aniline black, etc.), plasticizers (octyl p-oxybenzoate, N-butylbenzenesulfonamide, etc.), and bands. Examples of additives include antistatic agents (alkyl sulfate type anionic antistatic agents, quaternary ammonium salt type cationic antistatic agents, nonionic antistatic agents such as polyoxyethylene sorbitan monostearate, betaine-type amphoteric antistatic agents, etc.) and flame retardants (hydroxides such as melamine cyanurate, magnesium hydroxide, and aluminum hydroxide, phosphorus-based flame retardants such as ammonium polyphosphate, melamine polyphosphate, and phosphinate metal salts, brominated polystyrene, brominated polyphenylene oxide, brominated polycarbonate, brominated epoxy resin, or combinations of these brominated flame retardants with antimony trioxide, etc.). When these additives are included, their content is preferably 10 parts by weight or less, and more preferably 1 part by weight or less, per 100 parts by weight of thermoplastic polymer.

[0032] In the present invention, the thermoplastic polymer composition and / or mixture may be waste from a resin molded product. The fact that the thermoplastic polymer composition and / or mixture is waste from a resin molded product increases the amount of resources available for recovering thermoplastic polymer-derived components.

[0033] When the thermoplastic polymer is a thermoplastic polyamide, waste of resin molded articles containing thermoplastic polyamide includes polyamide products, industrial waste generated during the manufacturing process of polyamide products, or used polyamide products. Examples of polyamide products include textile structures for clothing such as used clothes, uniforms, sportswear and innerwear; industrial textile structures such as curtains, carpets, ropes, nets, belts, sheets, seat belts and airbags; automotive parts; molded parts for housing materials; electrical and electronic molded parts; aircraft parts; industrial machinery parts; film products; extruded products; in-situ polymerized products; and RIM molded products. Furthermore, product scraps, pellet scraps, lump scraps, and cutting chips generated during these production processes are also considered waste.

[0034] When the thermoplastic polymer is thermoplastic polyester, waste from resin molded articles containing thermoplastic polyester includes thermoplastic polyester products, industrial waste generated during the manufacturing process of thermoplastic polyester products, and used thermoplastic polyester products. Examples of thermoplastic polyester products include containers such as beverage bottles and condiment bottles, sheet products such as food trays, blister packs, food dividers, and industrial trays, film products such as packaging films, optical functional films, magnetic tapes, and insulating materials, textile structures for clothing such as used clothes, uniforms, sportswear, and underwear, industrial textile structures such as curtains, carpets, nets, belts, sheets, seat belts, and airbags, and molded articles such as automobile parts, electrical and electronic components, building materials, daily necessities, household goods, and hygiene products. Furthermore, product scraps, pellet scraps, and lump scraps generated during these production processes are also considered waste.

[0035] The present invention relates to a method for recovering components derived from thermoplastic polymers, comprising the step of mixing a thermoplastic polymer composition and / or mixture with water.

[0036] There are no particular restrictions on the water used in this invention; any type of water may be used, such as tap water, deionized water, distilled water, or well water. Deionized water or distilled water is preferred from the viewpoint of suppressing side reactions caused by impurities such as salts of unknown type and content.

[0037] In the present invention, the ratio b / a of thermoplastic polymer a (kg) to water b (kg) is preferably 1 or more, and more preferably 3 or more. By setting b / a to 1 or more, the viscosity of the mixture of thermoplastic polymer and water is reduced, making it easier to separate components that do not have a melting point in the subcritical temperature range. On the other hand, it is preferable to set b / a to 10 or less. Setting it to 10 or less reduces the energy required to heat to the subcritical state and the energy required for the purification of recycled monomers. It is more preferable for b / a to be 8 or less, and even more preferable for it to be 6 or less.

[0038] Depending on the type of thermoplastic polymer composition and / or mixture, alkali (earth) metal salts may be added to water to promote the dissolution of the thermoplastic polymer in water. In this specification, the term alkali (earth) metal salt means both salts containing alkali metal atoms, such as lithium, sodium, and potassium, and salts containing alkaline earth atoms, such as magnesium, calcium, and barium, and mixtures thereof.

[0039] The mixing method is not particularly limited, and known methods can be used. Specifically, examples include mixing by molecular diffusion or mixing by rotating a stirring blade provided in the reaction vessel.

[0040] (2) A process to obtain thermoplastic polymer-derived components by separating components that do not have a melting point in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water. The present invention provides a method for recovering thermoplastic polymer-derived components, comprising the step of obtaining thermoplastic polymer-derived components by separating components that do not have a melting point in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water. Here, thermoplastic polymer-derived components refer to thermoplastic polymers and their decomposition products (including oligomers, monomers, and their derivatives).

[0041] In the method for recovering thermoplastic polymer-derived components of the present invention, the dissolved state is preferably formed at 200°C or higher, more preferably at 220°C or higher, and even more preferably at 240°C or higher. By setting the temperature at which the dissolved state is formed to 200°C or higher, the viscosity of the mixture of thermoplastic polymer and water decreases, making it easier to separate components that do not have a melting point in the subcritical temperature range. The upper limit of the temperature is preferably 320°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower. By setting the temperature to 320°C or lower, the energy required to heat to the dissolved state can be reduced, and energy can be further saved when separating components that do not have a melting point in the subcritical temperature range.

[0042] In the method for recovering components derived from thermoplastic polymers according to the present invention, it is preferable that the dissolved state is formed under pressure equal to or greater than the saturated vapor pressure of water at the temperature of the dissolved state. By having a pressure in the reaction vessel equal to or greater than the saturated vapor pressure of water at the above temperature, the proportion of water in a gaseous state in the reaction vessel decreases, and the efficiency of dissolving the thermoplastic polymer is further improved, making it easier to separate components that do not have a melting point in the subcritical temperature range. Typically, a subcritical state is defined as a temperature range of 130°C to 350°C and a pressure range equal to or greater than the saturated vapor pressure of water at that temperature. Furthermore, whether or not the thermoplastic polymer is dissolved in water can be confirmed by the method described in Reference Example 1.

[0043] In the method for recovering thermoplastic polymer-derived components of the present invention, it is preferable that the dissolved state is a subcritical state. Being in a subcritical state makes the thermoplastic polymer more easily soluble in water.

[0044] When a thermoplastic polymer is dissolved in water, a method for solid-liquid separation of components that do not have a melting point in the subcritical temperature range is preferably one that includes filtration. In addition to conventional filters, devices such as screen changers, laser filters, and drum filters can also be used as filters, provided that they can be used while maintaining a subcritical state. The mesh size and area of ​​the filter are appropriately selected depending on the type and amount of components that do not have a melting point in the subcritical temperature range.

[0045] When performing filtration using a filter, it is preferable to create a pressure difference between the primary and secondary sides of the filter. This pressure difference generates a driving force for the fluid to pass through the filter, improving the filtration speed and stabilizing the filtration efficiency. Furthermore, it is expected to improve the capture performance of fine particles and impurities, and suppress filter clogging. In particular, maintaining a high pressure on the primary side stabilizes the fluid inflow and creates a uniform flow throughout the filter, reducing variations in filtration performance and making it easier to suppress clogging due to localized particle accumulation. Methods for creating a pressure difference include, if possible while maintaining a subcritical state, utilizing gravity by positioning the primary side at a higher position and the secondary side at a lower position, injecting an inert gas (e.g., nitrogen, argon), partially evacuating the secondary side, or utilizing the difference in saturated vapor pressure by changing the heating temperature between the primary and secondary sides. When creating a pressure difference, it is preferable that the difference is 0.01 MPa or greater, and more preferably 0.1 MPa or greater.

[0046] In the method for recovering thermoplastic polymer-derived components of the present invention, the thermoplastic polymer-derived components, from which components without a melting point have been separated in the subcritical temperature range, may be recovered while maintaining a mixed state with water, or the water may be removed before recovery. If water is removed, the thermoplastic polymer-derived components may be heated above their melting point to maintain a molten state. If solidified, they may be cut or crushed to an appropriate size at the time of solidification to facilitate recovery, or they may be crushed or pulverized after solidification.

[0047] The thermoplastic polymer-derived component of the present invention is obtained by the method for recovering the thermoplastic polymer-derived component of the present invention. Since the thermoplastic polymer-derived component of the present invention is free of components that do not have a melting point in the subcritical temperature range and cannot be recycled monomers, it can reduce transport costs compared to thermoplastic polymer compositions and / or mixtures.

[0048] (3) Recycled monomers The recycled monomer of the present invention is obtained by depolymerizing a thermoplastic polymer-derived component obtained by the thermoplastic polymer-derived component recovery method of the present invention. Known depolymerization methods can be used as the depolymerization method.

[0049] Specific depolymerization methods include, for example, hydrolysis using subcritical water.

[0050] The recycled monomers obtained after the depolymerization reaction can be purified by known methods such as distillation and crystallization. It is preferable to reuse the purified recycled monomers as a composition containing a thermoplastic polymer by repolymerization.

[0051] (4) Method for manufacturing thermoplastic polymers, thermoplastic polymers, and molded articles, etc. The method for producing the thermoplastic polymer of the present invention includes a step of polycondensing raw materials containing the recycled monomer of the present invention. The thermoplastic polymer of the present invention is obtained by polycondensing raw materials containing the recycled monomer of the present invention. Known polycondensation methods can be used as the polycondensation method. Since thermoplastic polymers can be regenerated by polycondensing raw materials containing the recycled monomer of the present invention, they can become environmentally friendly recycled materials that contribute to resource recycling and the reduction of greenhouse gas emissions.

[0052] The molded articles, fibers, films, or sheets of the present invention are made using the thermoplastic polymer of the present invention. The thermoplastic polymer of the present invention can be processed and used in various products such as molded articles, fibers, films, or sheets, similar to thermoplastic polymers produced from petroleum-derived raw materials.

[0053] Examples of molded products include injection-molded products and extruded products. More specifically, examples include automotive parts, electrical and electronic components, and industrial machinery parts.

[0054] Examples of fibers include fiber structures. More specifically, examples include industrial fiber structures and clothing fiber structures. [Examples]

[0055] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0056] The following raw materials were used in each example.

[0057] Polyamide 6: "Amilan" (registered trademark), CM1017, manufactured by Toray Industries, Inc. Glass fiber (GF) reinforced polyamide 6: Toray Industries, Inc.'s "Amiran" (registered trademark) CM1011G30 (GF 30% reinforced polyamide 6). Melting point 220°C, GF melting point 500°C or higher. Polyamide 6 was used as the thermoplastic polymer, and GF was used for the component that does not have a melting point in the subcritical temperature range.

[0058] ≪Evaluation Method≫ [Remaining percentage of components without a melting point in the subcritical temperature range and polymer recovery rate] The components separated outside the filter were recovered, dried in a vacuum oven set to 80°C for 12 hours, and weighed. The components separated outside the filter after drying were accurately weighed to approximately 1 g, and ash was obtained by calcining in an electric furnace set to 600°C in a crucible for 3 hours. From the weight of the components separated outside the filter after drying and the ash, the residual rate of components that do not have a melting point in the subcritical temperature range and the polymer recovery rate were calculated. Percentage of remaining components (by weight) that do not have a melting point in the subcritical temperature range = [Amount of ash generated (g)] / [Amount of components separated from the filter after drying, accurately weighed in the crucible (g)] × 100 Polymer recovery rate (weight %) = [Amount of thermoplastic polymer in the components separated outside the filter after drying (g)] / [Amount of thermoplastic polymer present in the thermoplastic polymer composition and / or mixture before separation (g)] × 100.

[0059] [Reference example 1] Approximately 660 mg of polyamide 6 pellets and approximately 2000 mg of heavy water were sealed in high-temperature, high-pressure reaction tubes, and neutron imaging experiments were performed. Measurements were taken over a 9-second integration period, varying the measurement temperature from 30 to 350°C. The results showed that the polyamide 6 pellets melted at around 140°C. Furthermore, mixing of the polyamide 6 phase and the heavy water phase was observed at around 220-230°C. This suggests that polyamide 6 dissolves in water within this temperature range.

[0060] [Example 1] The separation was carried out by filtration using a cylindrical 100-mesh SUS304 filter placed inside an autoclave. 8.6 g of polyamide 6 pellets containing 30% by weight of glass fiber were placed inside the 100-mesh SUS304 filter cylinder in the autoclave, and 58.7 g of deionized water was added to the autoclave. The autoclave was purged with nitrogen, sealed with a nitrogen pressure of 0.5 MPa or less, and then heated to 240°C and held for 20 minutes. The pressure inside the system at 240°C was 3.1 MPa. After that, the system was cooled to room temperature, the container was opened, and the polyamide solids separated outside the filter and the solids remaining inside the filter were recovered. At this time, the remaining percentage of components that do not have a melting point in the subcritical temperature range in the polyamide solids separated outside the filter was 0.7% by weight, and the polymer recovery rate was 19% by weight.

[0061] Figure 1 shows an overview of the process in Example 1. The process in Figure 1 is an example of a process to obtain thermoplastic polymer-derived components by separating components that do not have a melting point in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water. Pressure vessel 1 was used as a pressure vessel for mixing a thermoplastic polymer composition and / or mixture containing the thermoplastic polymer and components that do not have a melting point in the subcritical temperature range with water. A cylindrical filter 2 was used as a means to obtain thermoplastic polymer-derived components by separating components that do not have a melting point in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water. The cylindrical filter 2, which contains polyamide 6 pellets 3 containing 30% by weight of glass fibers, and deionized water 4 were sealed in pressure vessel 1 and purged with nitrogen (Figure 1A). The entire apparatus was heated to 240°C, and when the thermoplastic polymer was dissolved in water, components that do not have a melting point in the subcritical temperature range were separated into the filter (Figure 1B). After cooling to room temperature and opening the apparatus, the solid material 5 separated by solid-liquid separation and the polyamide solid material 6 separated by passing through the filter were recovered (Figure 1C).

[0062] [Comparative Example 1] Unlike Example 1, this study was conducted without placing a cylindrical filtration filter (100 mesh) made of SUS304 in the autoclave. 8.6 g of polyamide 6 pellets containing 30% by weight of glass fiber and 60.0 g of deionized water were placed in the autoclave. The autoclave was purged with nitrogen, sealed with a nitrogen pressure of 0.5 MPa or less, and then heated to 250°C and held for 20 minutes. The pressure in the system at 250°C was 4.0 MPa. After cooling to room temperature and opening the container, the glass fiber and polyamide 6 were found to be integrated, and separation of the glass fiber and polyamide 6 was difficult while the polyamide 6 was not dissolved in water.

[0063] [Comparative Example 2] Similar to Comparative Example 1, the study was conducted without placing a cylindrical filtration filter (100 mesh) made of SUS304 in the autoclave. 8.6 g of polyamide 6 pellets containing 30% by weight of glass fiber and 60.0 g of deionized water were placed in the autoclave. The autoclave was purged with nitrogen, sealed with a nitrogen pressure of 0.5 MPa or less, and then heated to 140°C and held for 20 minutes. The pressure in the system at 140°C was 0.7 MPa. After cooling to room temperature and opening the container, the glass fiber and polyamide 6 were found to be integrated, and separation of the glass fiber and polyamide 6 was difficult.

[0064] Reference Example 1 shows that at a heating temperature of 140°C, polyamide 6 is melted but not dissolved in water. In other words, in order to separate glass fibers from a polyamide 6 pellet containing 30% by weight of glass fibers, the polyamide 6 needs to be dissolved in water.

[0065] [Example 2] Two cylindrical pressure-resistant pipes made of SUS304 stainless steel, each open at one end, were connected to form a sealed system, and a sintered metal filter was installed at the connection point between the two pipes. 2.4 g of polyamide 6 pellets containing 30% by weight of glass fiber and 12.0 g of deionized water were placed in the lower pressure-resistant pipe. After purging the entire apparatus with nitrogen, it was sealed under a nitrogen pressure of 0.5 MPa or less, and while the entire apparatus was heated to 220°C, only the lower pressure-resistant pipe was locally heated to 240°C. The internal pressure of the system while maintaining 240°C was 3.0 MPa.

[0066] Subsequently, the apparatus was inverted while maintaining the heating state, and filtration separation was performed using the pressure difference of 0.7 MPa caused by the temperature difference between the upper and lower parts. After processing, the container was cooled to room temperature and opened. Components insoluble in subcritical water were separated at the top of the filter, and the polyamide solids separated from the water were recovered in the pressure-resistant tube at the bottom. At this time, the residual rate of components that do not have a melting point in the subcritical temperature range in the polyamide solids recovered at the bottom was 1.1% by weight, and the polymer recovery rate was 88% by weight.

[0067] Figure 2 shows an overview of the process in Example 2. The process in Figure 2 is an example of a process to obtain thermoplastic polymer-derived components by separating components that do not have a melting point in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water. Pressure vessel 1 was used as a pressure vessel for mixing a thermoplastic polymer composition and / or mixture containing the thermoplastic polymer and components that do not have a melting point in the subcritical temperature range with water. As a means of obtaining thermoplastic polymer-derived components by separating components that do not have a melting point in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water, a filter 7 was installed inside pressure vessel 1 and used. Polyamide 6 pellets 3 containing 30% by weight of glass fibers and deionized water 4 were sealed in the lower part of pressure vessel 1 and nitrogen purged (E in Figure 2). At this time, the lower part of the container containing the polyamide 6 pellets 3 containing 30% by weight of glass fibers and deionized water 4 was designated as the primary side of the filter 7, and the upper part of the container was designated as the secondary side. The primary side was heated to 240°C and the secondary side to 220°C to dissolve the thermoplastic polymer in water (Figure 2, F). By maintaining the heating state and inverting the container, filtration proceeded due to the differential pressure caused by the difference in heating temperatures. The thermoplastic polymer dissolved in subcritical water passed through the filter 7, and components that do not have a melting point in the subcritical temperature range were separated onto the filter (Figure 2, G). After cooling to room temperature and opening the apparatus, the solid material 5 separated by solid-liquid separation and the polyamide solid material 6 separated by passing through the filter could be recovered (Figure 2, H).

[0068] [Example 3] Two cylindrical pressure-resistant pipes made of SUS304 stainless steel, each open at one end, were connected to form a sealed system, and a sintered metal filter was installed at the connection point between the two pipes. 2.4 g of polyamide 6 pellets containing 30% by weight of glass fiber and 12.0 g of deionized water were placed in the lower pressure-resistant pipe. After purging the entire apparatus with nitrogen, it was sealed under a nitrogen pressure of 0.5 MPa or less, and the entire apparatus was uniformly heated to 240°C. The internal pressure of the system while maintaining 240°C was 3.0 MPa.

[0069] Subsequently, the apparatus was inverted, but since there was no temperature difference between the top and bottom, no pressure difference was generated, and separation through the filtration filter proceeded only slightly. After processing, when the container was opened after cooling to room temperature, a large amount of polyamide solids and water were observed at the top of the filter, indicating insufficient separation. At this time, the residual rate of components that do not have a melting point in the subcritical temperature range in the polyamide solids recovered at the bottom was 1.0% by weight, and the polymer recovery rate was 17% by weight.

[0070] Figure 3 shows an example of a process performed using the apparatus shown in Figure 2, without creating a temperature difference between the upper and lower parts of the container. Because there is no temperature difference between the top and bottom of the container, no differential pressure is generated due to the saturated vapor pressure difference, and the driving force to promote filtration is small. As a result, although the solid-liquid separation efficiency of components that do not have a melting point in the subcritical temperature range decreases, separation still proceeds, albeit in small quantities.

[0071] [Comparative Example 3] Two cylindrical pressure-resistant pipes made of SUS304 stainless steel, each open at one end, were connected to form a sealed system, and a sintered metal filter was installed at the connection point between the two pipes. 2.4 g of polyamide 6 pellets containing 30% by weight of glass fiber and 12.0 g of deionized water were placed in the upper pressure-resistant pipe. After purging the entire apparatus with nitrogen, it was sealed under a nitrogen pressure of 0.5 MPa or less, and while the entire apparatus was heated to 220°C, only the upper pressure-resistant pipe containing the contents was locally heated to 240°C.

[0072] During heating, a pressure difference was created due to the temperature difference between the top and bottom before the polyamide dissolved, and filtration proceeded through the filter. However, because the polyamide that was not dissolved in water was highly viscous, it could not pass through the filter at this pressure difference (0.7 MPa), and only water was separated as filtrate in the pressure-resistant tube at the bottom. After processing, when the container was opened after cooling to room temperature, undissolved or highly viscous polyamide remained at the top of the filter, indicating that the separation was incomplete. At this time, the residual rate of components that do not have a melting point in the subcritical temperature range in the polyamide solid recovered at the bottom was 0.1% by weight or less, and the polymer recovery rate was 3% by weight.

[0073] Figure 4 shows an example of a process in the apparatus shown in Figure 2, where a difference in heating temperature is applied to the upper and lower parts of the container while the polyamide is not dissolved in water, and the process is carried out without inverting the container. Polyamide 6 pellets 3 containing 30% by weight of glass fiber and deionized water 4 are sealed in the upper part of the container and nitrogen purging is performed. At this time, the upper part of the container containing 3 and 4 is designated as the primary side of the filter 7, and the lower part of the container is designated as the secondary side. The primary side is heated to 240°C and the secondary side to 220°C, but only water passes through the filter before the thermoplastic polymer dissolves in water, and the viscosity is not reduced enough for the thermoplastic polymer to pass through the filter without dissolving in water. As a result, the solid-liquid separation efficiency of components that do not have a melting point in the subcritical temperature range decreases.

[0074] [Example 4] 20.0 g of polyamide 6 resin, from which glass fibers had been separated, and 60.0 g of deionized water were charged into a SUS316L autoclave equipped with a stirrer. The weight ratio of water to polyamide 6 was 3:1. The reaction vessel was purged with nitrogen, sealed under nitrogen pressure of 0.5 MPa, and the reaction was carried out at 320°C for 15 minutes while stirring at 200 rpm. The final pressure during the reaction was 11.9 MPa. After the reaction was complete, the mixture was cooled to room temperature and the depolymerized recycled lactam was recovered.

[0075] Water was added to the recycled lactam to form a 90% by weight caprolactam aqueous solution, which was placed in a polymerization tank. The raw materials were heated while being stirred in a sealed state. When the internal pressure of the tank reached 1 MPa, water vapor was distilled out and the pressure was maintained at that level. When the internal liquid temperature reached 250°C, the internal pressure of the tank was gradually reduced to atmospheric pressure over 70 minutes. At that time, the internal liquid temperature was 260°C. After that, nitrogen was flowed into the gas phase inside the tank for 60 minutes while maintaining the internal liquid temperature at 260°C to complete the polymerization. After polymerization was complete, the molten nylon 6 was extruded in a gut-like manner from the bottom of the polymerization tank, cooled with water, and then cut with a pelletizer to form pellets. Low molecular weight impurities were extracted from these pellets with hot water to obtain chemically recycled polyamide 6 resin pellets. [Industrial applicability]

[0076] The present invention can be suitably used in the chemical recycling of thermoplastic polymer compositions and / or mixtures. For example, it can be suitably used to separate additives such as glass fibers from thermoplastic polyamide products and thermoplastic polyester products, and to depolymerize the polymers. When the present invention is used in chemical recycling, it is possible to achieve both resource recycling and reduction of greenhouse gas emissions. [Explanation of symbols]

[0077] 1: Pressure vessel 2: Cylindrical filtration filter 3: Polyamide 6 pellets containing 30% by weight of glass fiber 4: Deionized water 5: Solids separated by solid-liquid separation 6: Polyamide solids separated after passing through the filter 7: Filtration filter

Claims

1. The method comprises the steps of mixing a thermoplastic polymer composition and / or mixture containing a thermoplastic polymer and a component that does not have a melting point in the subcritical temperature range with water, and obtaining a thermoplastic polymer-derived component by separating the component that does not have a melting point in the subcritical temperature range by solid-liquid separation while the thermoplastic polymer is dissolved in water. A method for recovering components derived from thermoplastic polymers.

2. The aforementioned molten state is formed at a temperature of 200°C or higher. A method for recovering components derived from thermoplastic polymers as described in claim 1.

3. The aforementioned dissolved state is formed under pressure equal to or greater than the saturated vapor pressure of water at the temperature of the dissolved state. A method for recovering components derived from thermoplastic polymers as described in claim 1.

4. A method for separating components that do not have a melting point in the subcritical temperature range from a thermoplastic polymer dissolved in water includes filtration using a filter. A method for recovering components derived from thermoplastic polymers as described in claim 1.

5. The ratio b / a of the thermoplastic polymer a (kg) to water b (kg) is 1 or greater. A method for recovering components derived from thermoplastic polymers as described in claim 1.

6. The thermoplastic polymer includes thermoplastic polyamide or thermoplastic polyester. A method for recovering components derived from thermoplastic polymers as described in claim 1.

7. The thermoplastic polymer includes a thermoplastic polyamide or thermoplastic polyester obtained by recovery. A method for recovering components derived from thermoplastic polymers as described in claim 1.

8. The component that does not have a melting point in the aforementioned subcritical temperature range includes metals. A method for recovering components derived from thermoplastic polymers as described in claim 1.

9. Obtained by the method for recovering thermoplastic polymer-derived components described in claim 1, Components derived from thermoplastic polymers.

10. The thermoplastic polymer-derived component obtained by the method for recovering the thermoplastic polymer-derived component described in claim 1 is obtained by depolymerizing the thermoplastic polymer-derived component, Recycled monomer.

11. The process includes polycondensation of a raw material containing the recycled monomer described in claim 10, A method for producing thermoplastic polymers.

12. Obtained by polycondensation of a raw material containing the recycled monomer described in claim 10, Thermoplastic polymer.

13. Using the thermoplastic polymer described in claim 12, Molded products, fibers, films, or sheets.

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