Method for recovering water-insoluble foreign material composition, and water-insoluble foreign material composition

Abstract

To recover a high-quality water-insoluble foreign material composition in a high yield from a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material.SOLUTION: A solvolysis treatment step of treating a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material in a solvent containing a diol and water at higher than 135 °C and 200 °C or lower in the presence of an alkali, and a step of removing a thermoplastic polyester-derived component from the composition containing the thermoplastic polyester-derived component and the foreign material after the solvolysis treatment step to obtain a water-insoluble foreign material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble foreign material composition is 10% by weight or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for recovering a water-insoluble foreign material composition, and a water-insoluble foreign material composition. [Background technology]

[0002] In recent years, the marine plastic pollution problem has triggered growing interest in global environmental issues, and there is a growing awareness of the need to build a sustainable society. Global environmental issues include global warming, resource depletion, and water shortages, many of which are caused by the increase in resource consumption and greenhouse gas emissions due to the use of fossil fuels and rapid industrial development since the Industrial Revolution. Therefore, in order to build a sustainable society, it is becoming increasingly important to develop technologies that recycle fossil resources such as plastics and reduce greenhouse gas emissions.

[0003] Thermoplastic polyester, a plastic material, is used in clothing by blending it with natural fibers such as cotton to develop properties that cannot be achieved with polyester alone, and in automotive resin moldings by melt-kneading it with inorganic fibers such as glass fiber. In these cases, recycling both thermoplastic polyester and other materials is extremely important from the perspective of resource circulation.

[0004] Patent Document 1 discloses a technique for depolymerizing a blend material of cotton and polyethylene terephthalate, and Patent Document 2 discloses a technique for depolymerizing fibers made of a cellulose component and a polyester component. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 1,137,0895 [Patent Document 2] International Publication No. 2022 / 195433 Summary of the Invention [Problem to be solved by the invention]

[0006] For a blend material of cotton and polyethylene terephthalate, Patent Document 1 describes a technology for recovering cotton by depolymerizing polyethylene terephthalate in subcritical water in the presence of an alkaline component. However, the cotton also deteriorates, resulting in a low cotton recovery rate.

[0007] Furthermore, Patent Document 2 describes a technique for recovering the cellulose component by depolymerizing the polyester component of a fiber made of a cellulose component and a polyester component in a mixed solvent of water and an aqueous organic solvent in the presence of an alkaline component. However, there is no description of differences in the deterioration of the cellulose component or the amount recovered depending on the type of aqueous organic solvent. [Means for solving the problem]

[0008] In order to solve the above problems, the inventors of the present invention conducted extensive research and found that by treating a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble different material in a solvent containing a diol and water within a specific temperature range, the thermoplastic polyester is depolymerized while suppressing deterioration of the water-insoluble different material, and the depolymerization product is dissolved in water, making it possible to recover the water-insoluble different material composition in high yield.

[0009] That is, the present invention has the following configuration. (1) A method for recovering a water-insoluble foreign material composition, comprising: a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material is treated in a solvent containing a diol and water in the presence of an alkali at a temperature above 135°C and not higher than 200°C; and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the foreign material after the solvent treatment step to obtain a water-insoluble foreign material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble foreign material composition is 10% by weight or less. (2) A method for recovering a water-insoluble heterogeneous material composition, comprising: a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble heterogeneous material (excluding cotton) is treated in a solvent containing alcohol and water in the presence of an alkali at 110°C or higher and 350°C or lower; and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the heterogeneous material after the solvent treatment step to obtain a water-insoluble heterogeneous material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble heterogeneous material composition is 10% by weight or lower. (3) A method for recovering a water-insoluble foreign material composition according to (1) or (2) above, wherein the content of the solvent in the solvent treatment step is 100 parts by weight or more and 2000 parts by weight or less per 100 parts by weight of the thermoplastic polyester composition. (4) The method for recovering a water-insoluble foreign material composition according to (1) above, wherein the weight (g) of water in the solvent / weight (g) of diol is 0.1 or more and 100 or less. (5) The method for recovering a water-insoluble foreign material composition according to (2) above, wherein the weight (g) of water in the solvent / weight (g) of alcohol is 0.1 or more and 100 or less. (6) The method for recovering a water-insoluble foreign material composition according to (2) or (5) above, wherein the alcohol is an aliphatic monohydric or dihydric alcohol having 1 to 10 carbon atoms. (7) A method for recovering a water-insoluble foreign material composition according to (1) or (2) above, in which an alkaline component is coexistent in an amount of 25 parts by weight or more and 200 parts by weight or less per 100 parts by weight of the thermoplastic polyester content in the thermoplastic polyester composition. (8) The method for recovering a water-insoluble foreign material composition according to (1) above, wherein in the solvent treatment step, the pressure at a temperature higher than 135°C and lower than 200°C is 0.2 MPa or more and 10 MPa or less. (9) The method for recovering a water-insoluble foreign material composition according to (2) above, wherein the pressure at 110°C or higher and 350°C or lower in the solvent treatment step is 0.1 MPa or higher and 30 MPa or lower. (10) A method for recovering a water-insoluble foreign material composition according to (1) or (2) above, wherein the thermoplastic polyester is one or more selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and copolymers thereof. (11) A method for recovering a water-insoluble heterogeneous material composition according to (1) or (2) above, wherein the lightness L* of the water-insoluble heterogeneous material composition as defined by the CIE 1976 L*a*b* color space is 84.0 or more. (12) A method for recovering a water-insoluble foreign material composition according to (1) above, wherein the water-insoluble foreign material composition is cotton and the weight-average molecular weight of the cotton measured by gel permeation chromatography is 300,000 or more. (13) A method for recovering dicarboxylic acids, diols, and derivatives thereof that are monomers of thermoplastic polyesters, comprising a recovery step of recovering dicarboxylic acids, diols, and derivatives thereof that are monomers of thermoplastic polyesters from components derived from thermoplastic polyesters removed by the method for recovering a water-insoluble foreign material composition described in (1) or (2) above. (14) A method for producing a thermoplastic polyester, comprising a step of polymerizing dicarboxylic acids and diols, which are monomers of a thermoplastic polyester, obtained by separating and purifying components derived from a thermoplastic polyester removed by the method for recovering a water-insoluble foreign material composition described in (1) or (2) above. (15) A water-insoluble heterogeneous material composition obtained by a method for recovering a water-insoluble heterogeneous material composition, the method comprising: a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble heterogeneous material is treated in a solvent containing a diol and water in the presence of an alkali at a temperature above 135°C and not higher than 200°C; and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the heterogeneous material after the solvent treatment step to obtain a water-insoluble heterogeneous material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble heterogeneous material composition is 10% by weight or less. (16) A water-insoluble heterogeneous material composition obtained by a method for recovering a water-insoluble heterogeneous material composition, comprising: a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble heterogeneous material (excluding cotton) is treated in a solvent containing alcohol and water in the presence of an alkali at 110°C or higher and 350°C or lower; and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the heterogeneous material after the solvent treatment step to obtain a water-insoluble heterogeneous material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble heterogeneous material composition is 10% by weight or lower. (17) The water-insoluble heterogeneous composition according to (16) above, wherein the alcohol is an aliphatic monohydric or dihydric alcohol having 1 to 10 carbon atoms. (18) The water-insoluble composition of different materials according to (15) or (16) above, which has a lightness L* defined by the CIE 1976 L*a*b* color space of 84.0 or more. (19) The water-insoluble heterogeneous material composition according to (15) or (16) above, wherein the water-insoluble heterogeneous material comprises natural fibers and / or inorganic fibers. (20) The water-insoluble heterogeneous composition according to (15) above, wherein the water-insoluble heterogeneous composition is cotton, and the weight-average molecular weight of the cotton measured by gel permeation chromatography is 300,000 or more. (21) A fiber, film, or resin molded product comprising the water-insoluble heterogeneous composition according to any one of (15) to (17) or (20) above. [Effects of the Invention]

[0010] According to the present invention, a high-quality water-insoluble foreign material composition can be recovered in high yield from a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will now be described in further detail.

[0012] A first aspect of the method for recovering a water-insoluble foreign material composition of the present invention includes a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material is treated in a solvent containing a diol and water in the presence of an alkali at a temperature above 135°C and not higher than 200°C, and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the foreign material after the solvent treatment step to obtain a water-insoluble foreign material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble foreign material composition is 10% by weight or less.

[0013] A second aspect of the method for recovering a water-insoluble foreign material composition of the present invention includes a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material (excluding cotton) is treated in a solvent containing alcohol and water in the presence of alkali at 110°C or higher and 350°C or lower, and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the foreign material after the solvent treatment step to obtain a water-insoluble foreign material composition (excluding cotton), wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble foreign material composition is 10% by weight or lower. Note that in this specification, the "first aspect of the method for recovering a water-insoluble foreign material of the present invention" may be simply referred to as the "first aspect," and the "second aspect of the method for recovering a water-insoluble foreign material of the present invention" may be simply referred to as the "second aspect."

[0014] Thermoplastic polyesters are homopolymers or copolymers obtained by polycondensation of dicarboxylic acids and / or their ester-forming derivatives with diols and / or their ester-forming derivatives as main raw materials. The term "main raw materials" refers to the total content of dicarboxylic acids and their ester-forming derivatives, and diols and their ester-forming derivatives in the raw materials being 50 mol% or more of the total raw materials. This total content is preferably 80 mol% or more, and more preferably 90 mol% or more.

[0015] Examples of the dicarboxylic acid or its ester-forming derivative include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, bis(p-carboxyphenyl)methane, 1,4-anthracenedicarboxylic acid, 1,5-anthracenedicarboxylic acid, 1,8-anthracenedicarboxylic acid, 2,6-anthracenedicarboxylic acid, 9,10-anthracenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-tetrabutylphosphoniumisophthalic acid, and 5-sodiumsulfoisophthalic acid; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, and dimer acid; and alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, as well as ester-forming derivatives thereof. Two or more of these may be used.

[0016] The ester-forming derivatives referred to here include the alkyl esters, acid anhydrides, acid halides, etc. of the dicarboxylic acids mentioned above. Preferred examples of alkyl esters of dicarboxylic acids include methyl esters, ethyl esters, hydroxyethyl esters, and hydroxybutyl esters. Preferred examples of acid anhydrides of dicarboxylic acids include anhydrides of dicarboxylic acids and anhydrides of dicarboxylic acids and acetic acid. Preferred examples of acid halides of dicarboxylic acids include acid chlorides, acid bromides, and acid iodides.

[0017] In the present invention, the dicarboxylic acid is preferably terephthalic acid. When the dicarboxylic acid is terephthalic acid, acid crystallization in the subsequent step becomes easy and polyethylene terephthalate, which is produced in large quantities as a plastic, can be recycled, thereby greatly contributing to resource circulation.

[0018] Examples of the diol or its ester-forming derivative include aliphatic or alicyclic glycols having 2 to 20 carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, cyclohexanedimethanol, cyclohexanediol, and dimer diol; long-chain glycols having a molecular weight of 200 to 100,000, such as polyethylene glycol, poly-1,3-propylene glycol, and polytetramethylene glycol; aromatic dioxy compounds, such as 4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, bisphenol A, bisphenol S, and bisphenol F; and ester-forming derivatives thereof. Two or more of these may be used.

[0019] In the present invention, the diol is preferably at least one selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,4-butanediol. Ethylene glycol, 1,3-propanediol, and 1,4-butanediol can be used to recycle polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate, which are produced in large quantities as plastics, and therefore make a significant contribution to resource circulation.

[0020] Examples of homopolymers or copolymers having a dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative as structural units include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, polypropylene isophthalate, polybutylene isophthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene naphthalate, polycyclohexanedimethylene terephthalate, polyethylene isophthalate / terephthalate, polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polyethylene terephthalate / naphthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polyethylene terephthalate / 5-sodium sulfoisophthalate, and polypropylene terephthalate / 5-sodium Sulfoisophthalate, Polybutylene terephthalate / 5-sodium sulfoisophthalate, Polyethylene terephthalate / Polyethylene glycol, Polypropylene terephthalate / Polyethylene glycol, Polybutylene terephthalate / Polyethylene glycol, Polyethylene terephthalate / Polytetramethylene glycol, Polypropylene terephthalate / Polytetramethylene glycol, Polybutylene terephthalate / Polytetramethylene glycol, Polyethylene terephthalate / Isophthalate / Polytetramethylene glycol, Polypropylene terephthalate / Isophthalate / Polytetramethylene glycol, Polyethylene terephthalate / 1,4-Cyclohexanedimethanol, Polypropylene terephthalate / 1,4-Cyclohexanedimethanol, Polybutylene terephthalate / 1,Examples of aromatic polyester resins include 4-cyclohexanedimethanol, polybutylene terephthalate / succinate, polypropylene terephthalate / adipate, polybutylene terephthalate / adipate, polypropylene terephthalate / sebacate, polybutylene terephthalate / sebacate, polypropylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / succinate, polybutylene terephthalate / isophthalate / adipate, and polybutylene terephthalate / isophthalate / sebacate.

[0021] Here, " / " indicates a copolymer. These homopolymers and copolymers may be used alone or in a mixture of two or more types at any content. Among these, homopolymers or copolymers made primarily from aromatic dicarboxylic acids and / or their ester-forming derivatives, which are produced and consumed in large quantities, and aliphatic diols and / or their ester-forming derivatives are preferred, with the aim of recycling thermoplastic polyesters and promoting the recycling of fossil resources. Examples of preferred polymers include homopolymers or copolymers obtained by polycondensation of at least one selected from terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and their ester-forming derivatives with at least one selected from ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol or their ester-forming derivatives. Among these, it is particularly preferred that the thermoplastic polyester be at least one selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and copolymers thereof.

[0022] In the present invention, the water-insoluble foreign material refers to a material other than thermoplastic polyester that has a solubility of less than 1.0 g in 100 g of water at 20° C. Examples of water-insoluble foreign materials include natural fibers such as wool, silk, cotton, linen, pulp, rayon, and cupra, inorganic fibers such as glass fiber, carbon fiber, and silicon carbide fiber, organic fibers such as aramid fiber, polyparaphenylenebenzoxazole fiber, polyphenylene sulfide fiber, acrylic fiber, and polyethylene fiber, metal fibers such as aluminum fiber, brass fiber, and stainless steel fiber, wollastonite, zeolite, sericite, kaolin, mica, talc, clay, pyrophyllite, bentonite, montmorillonite, hectorite, synthetic mica, asbestos, graphite, aluminosilicate, alumina, silica, magnesium oxide, zirconium oxide, titanium oxide, iron oxide, calcium carbonate, magnesium carbonate, and the like. Examples of suitable inorganic materials include non-fibrous inorganic compounds such as silica, dolomite, calcium sulfate, barium sulfate, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, glass beads, hollow glass beads, ceramic beads, boron nitride, silicon carbide, and wollastonite, and organic polymers such as polyolefin, polystyrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, polyamide, polyurethane, modified polyphenylene ether, polysulfone, polyketone, polyetherimide, polyarylate, polyethersulfone, polyetherketone, polythioetherketone, polyetheretherketone, polyimide, polyamideimide, tetrafluoroethylene, and polyphenylene sulfide. These organic polymers may be crosslinked.

[0023] In the present invention, the water-insoluble different material preferably includes natural fibers and / or inorganic fibers. Natural fibers such as cotton that are blended with thermoplastic polyester for clothing applications, and inorganic fibers such as glass fibers that are melt-kneaded with thermoplastic polyester for resin molding applications, are used in large quantities, so recycling these fibers can greatly contribute to resource circulation.

[0024] In the present invention, the content of the water-insoluble material in the thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble material is preferably 0.1 parts by weight or more and 1,000 parts by weight or less per 100 parts by weight of the thermoplastic polyester. By setting the content within this range, the thermoplastic polyester and the water-insoluble material can be efficiently separated. The content of the water-insoluble material is more preferably 1.0 parts by weight or more, and even more preferably 5.0 parts by weight or more. On the other hand, the content of the water-insoluble material is more preferably 100 parts by weight or less, and even more preferably 50 parts by weight or less.

[0025] The thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble different material may contain additives such as a polymerization catalyst, a nucleating agent, a plasticizer, an ultraviolet resistant agent, a release agent, a flame retardant, a colorant (e.g., a pigment or dye), a lubricant, an antistatic agent, and an antioxidant, in addition to the thermoplastic polyester and the water-insoluble different material.

[0026] In a first embodiment of the method for recovering a water-insoluble foreign material composition of the present invention, a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material is treated in a solvent containing a diol and water in the presence of an alkali in a solvolysis step. The diol may be used alone or in a mixture of two or more diols at any content. It is believed that a metal alkoxide produced by deprotonation of a portion of the diol with an alkali promotes solvolysis. Examples of diols include the thermoplastic polyester raw materials described above. However, ethylene glycol, which has excellent affinity with water, is preferred from the viewpoint of promoting polymer dissolution and hydrolysis. Furthermore, using the same diol as the thermoplastic polyester raw material as the solvent facilitates separation and purification of the thermoplastic polyester monomer after depolymerization of the thermoplastic polyester. However, the diol used in the first embodiment of the present invention does not include diols produced by decomposition of the thermoplastic polyester.

[0027] In a first embodiment of the method for recovering a water-insoluble foreign material composition of the present invention, a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material is treated in the presence of an alkali in the solvent treatment step at a temperature above 135°C and not higher than 200°C. By setting the treatment temperature within the above range, the thermoplastic polyester can be depolymerized and the depolymerized product can be dissolved in water while suppressing deterioration of the water-insoluble foreign material, thereby enabling a high yield of the water-insoluble foreign material to be recovered. The treatment temperature is preferably 138°C or higher, more preferably 140°C or higher. On the other hand, the treatment temperature is preferably 190°C or lower, more preferably 180°C or lower.

[0028] In a second embodiment of the method for recovering a water-insoluble foreign material composition of the present invention, in the solvolysis step, a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material (excluding cotton) is treated in a solvent containing water and an alcohol in the presence of an alkali. Examples of alcohols include aliphatic monohydric alcohols having 1 to 10 carbon atoms, such as methanol, ethanol, 1-propanol, 2-propanol, isobutanol, and tert-butyl alcohol; dihydric alcohols (diols) such as the thermoplastic polyester raw materials described above; and aliphatic trihydric alcohols having 3 to 10 carbon atoms, such as glycerol. The alcohols may be used alone or in a mixture of two or more alcohols at any content. In particular, aliphatic monohydric or dihydric alcohols having 1 to 10 carbon atoms are preferred because of their excellent affinity with water. It is believed that metal alkoxides, generated by deprotonation of a portion of the alcohol with an alkali, promote solvolysis. In particular, tert-butyl alcohol allows solvolysis at lower temperatures. However, the alcohol used in the second embodiment of the present invention does not include dihydric alcohols (diols) produced by decomposition of thermoplastic polyesters.

[0029] In a second embodiment of the method for recovering a water-insoluble foreign material composition of the present invention, a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material (excluding cotton) is treated in the presence of an alkali at 110°C or higher and 350°C or lower in the solvent treatment step. By setting the treatment temperature within the above range, the thermoplastic polyester can be depolymerized and the depolymerized product can be dissolved in water while suppressing deterioration of the water-insoluble foreign material, allowing the water-insoluble foreign material to be recovered in high yield. The treatment temperature is preferably 120°C or higher, more preferably 140°C or higher. On the other hand, the treatment temperature is preferably 300°C or lower, even more preferably 280°C or lower.

[0030] The present invention includes a step of removing the thermoplastic polyester-derived component from a composition containing the thermoplastic polyester-derived component and the foreign material after the solvent treatment step to obtain a water-insoluble foreign material composition. By including this step, it is possible to recover a water-insoluble foreign material composition having a thermoplastic polyester-derived component content of 10 wt% or less. Thermoplastic polyester-derived components refer to thermoplastic polyester polymers, thermoplastic polyester oligomers, thermoplastic polyester monomers, and derivatives thereof. By keeping the content of the thermoplastic polyester-derived component in 100 wt% of the water-insoluble foreign material composition to 10 wt% or less, it is possible to reuse a high-purity water-insoluble foreign material. The content of the thermoplastic polyester-derived component in 100 wt% of the water-insoluble foreign material composition is preferably 5 wt% or less, more preferably 1 wt% or less, and most preferably 0 wt%.

[0031] In the present invention, a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble different material is subjected to a solvolysis treatment in the presence of an alkali. The presence of an alkali component promotes depolymerization of the thermoplastic polyester and improves the solubility of the depolymerized product in water. Examples of alkali components include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as magnesium and calcium; hydroxides such as ammonium; carbonates; bicarbonates; ammonia; and organic amines such as trimethylamine. Among these, alkali metal salts are preferred.

[0032] Examples of alkali metal salts include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; alkali metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium hydrogencarbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, and cesium hydrogencarbonate; alkali metal phosphates such as lithium phosphate, sodium phosphate, potassium phosphate, cesium phosphate, dilithium hydrogenphosphate, dipotassium hydrogenphosphate, dicesium hydrogenphosphate, lithium monohydrogenphosphate, sodium monohydrogenphosphate, potassium monohydrogenphosphate, and cesium monohydrogenphosphate; and alkali metal borates such as lithium borate, sodium borate, potassium borate, and cesium borate. Among these, it is preferable that the alkali metal salt be at least one selected from alkali metal hydroxides and alkali metal carbonates. Specifically, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydrogencarbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, lithium carbonate, sodium carbonate, and potassium carbonate are more preferable.

[0033] In the present invention, the alkaline component is preferably present in an amount of 25 parts by weight or more and 200 parts by weight or less per 100 parts by weight of the thermoplastic polyester in the thermoplastic polyester composition. Controlling the amount of the alkaline component within this range can promote depolymerization of the thermoplastic polyester while suppressing deterioration of the water-insoluble other material. The alkaline component is more preferably present in an amount of 30 parts by weight or more, and even more preferably 35 parts by weight or more, per 100 parts by weight of the thermoplastic polyester in the thermoplastic polyester composition. Meanwhile, the alkaline component is more preferably present in an amount of 160 parts by weight or less, and even more preferably 130 parts by weight or less, per 100 parts by weight of the thermoplastic polyester in the thermoplastic polyester composition.

[0034] The preferred treatment temperature for depolymerizing the thermoplastic polyester varies depending on the type of alkaline component. When an alkali metal hydroxide is used as the alkaline component, the treatment temperature in the first and second embodiments is preferably 160°C or lower from the viewpoint of suppressing deterioration of the water-insoluble other material. On the other hand, when an alkali metal carbonate is used as the alkaline component, the treatment temperature in the first embodiment is preferably 170°C or higher, and in the second embodiment is preferably 150°C or higher from the viewpoint of promoting depolymerization of the thermoplastic polyester. In the first embodiment, the treatment temperature may temporarily exceed 200°C as long as the effects of the present invention are not impaired. However, by keeping the treatment temperature at 200°C or lower, deterioration of the water-insoluble other material can be suppressed, and therefore, it is preferable to keep the treatment temperature at 200°C or lower throughout the treatment time. In the second embodiment, the treatment temperature may temporarily exceed 350°C as long as the effects of the present invention are not impaired. However, by keeping the treatment temperature at 350°C or lower, deterioration of the water-insoluble other material (excluding cotton) can be suppressed, and therefore, it is preferable to keep the treatment temperature at 350°C or lower throughout the treatment time.

[0035] In the present invention, when the alkali component is an alkali metal hydroxide, the treatment time is preferably 1 to 120 minutes. The treatment time is more preferably 5 minutes or more, and even more preferably 10 minutes or more. On the other hand, the treatment time is more preferably 90 minutes or less, and even more preferably 60 minutes or less. When the alkali component is an alkali metal carbonate, the treatment time is preferably 1 to 240 minutes or less. The treatment time is more preferably 5 minutes or more, and even more preferably 10 minutes or more. On the other hand, the treatment time is more preferably 180 minutes or less, and even more preferably 120 minutes or less. In the first embodiment, the treatment time refers to the time during which the treatment temperature is higher than 135°C and lower than 200°C. In the second embodiment, the treatment time refers to the time during which the treatment temperature is higher than 135°C and lower than 200°C.

[0036] In the present invention, the content of the solvent in the solvent addition treatment step is preferably 100 parts by weight or more and 2000 parts by weight or less, relative to 100 parts by weight of the thermoplastic polyester composition. By setting the content within the above range, the energy required for heating can be minimized, the environmental impact can be reduced, and depolymerization of the thermoplastic polyester can be sufficiently promoted. In the first aspect, the content of the solvent containing a diol and water is more preferably 150 parts by weight or more, and even more preferably 200 parts by weight or more. On the other hand, the content of the solvent containing a diol and water is more preferably 1500 parts by weight or less, and even more preferably 1000 parts by weight or less. Note that the content of the solvent containing a diol and water refers to the content at the time when the treatment temperature exceeds 135°C. Furthermore, in the second aspect, the content of the solvent containing an alcohol and water is more preferably 150 parts by weight or more, and even more preferably 200 parts by weight or more. On the other hand, the content of the solvent containing an alcohol and water is more preferably 1500 parts by weight or less, and even more preferably 1000 parts by weight or less. The content of the solvent containing alcohol and water refers to the content at the time when the treatment temperature reaches 110°C.

[0037] In the first aspect of the present invention, the ratio (g) of water (weight) to (g) of diol in the solvent is preferably 0.1 or more and 100 or less. In the second aspect, the ratio (g) of water (weight) to (g) of alcohol in the solvent is preferably 0.1 or more and 100 or less. In each aspect, controlling the ratio within this range allows the depolymerization of the thermoplastic polyester to proceed while suppressing deterioration of the water-insoluble foreign material, improving the solubility of the depolymerized product in water, and thereby enabling the recovery of the water-insoluble foreign material with a high yield. In the first aspect, the ratio (g) of water (weight) to (g) of diol is more preferably 1.0 or more, even more preferably 3.0 or more. Meanwhile, the ratio (g) of water (weight) to (g) of diol is more preferably 70 or less, even more preferably 50 or less. In the second aspect, the ratio (g) of water (weight) to (g) of alcohol is more preferably 1.0 or more, even more preferably 3.0 or more. Meanwhile, the ratio (g) of water (weight) to (g) of alcohol is more preferably 70 or less, even more preferably 50 or less.

[0038] In the solvent treatment step of the first aspect of the present invention, the pressure at temperatures above 135°C and below 200°C is preferably 0.2 MPa or more and 10 MPa or less. Furthermore, in the solvent treatment step of the second aspect, the pressure at temperatures above 110°C and below 350°C is preferably 0.1 MPa or more and 30 MPa or less. By controlling the pressure within this range depending on each aspect, it is possible to suppress deterioration of the water-insoluble foreign material while promoting depolymerization of the thermoplastic polyester and improving the solubility in water of the depolymerized product, thereby enabling high recovery of the water-insoluble foreign material. In the first aspect, the pressure is more preferably 0.3 MPa or more, even more preferably 0.4 MPa or more. Meanwhile, the pressure is more preferably 8.0 MPa or less, even more preferably 6.0 MPa or less. Furthermore, in the second aspect, the pressure is more preferably 0.3 MPa or more, even more preferably 2.0 MPa or more. Meanwhile, the pressure is more preferably 25 MPa or less, even more preferably 20 MPa or less.

[0039] A first aspect of the water-insoluble heterogeneous material composition of the present invention can be obtained by the first aspect of the method for recovering a water-insoluble heterogeneous material composition of the present invention. A second aspect of the water-insoluble heterogeneous material composition of the present invention can be obtained by the second aspect of the method for recovering a water-insoluble heterogeneous material composition of the present invention. The water-insoluble heterogeneous material composition of the present invention includes a case where the composition is composed of only one type of water-insoluble heterogeneous material.

[0040] In the present invention, the lightness L* of the water-insoluble heterogeneous material composition is preferably 84.0 or more as defined by the CIE 1976 L*a*b* color space. The lightness of the solid material of the present invention is measured by filling the solid material into a borosilicate glass container with a body diameter of 35 mm to a height of 10 mm and shining a C light source from the bottom of the glass container using the SCI method. A lightness L* of 84.0 or more allows for the reuse of high-quality water-insoluble heterogeneous materials. The lightness L* of the water-insoluble heterogeneous material composition is more preferably 85.0 or more, and even more preferably 85.5 or more.

[0041] In the present invention, the water-insoluble heterogeneous composition is cotton, and the weight-average molecular weight of the cotton measured by gel permeation chromatography is preferably 300,000 or more. A weight-average molecular weight of 300,000 or more allows for the reuse of high-quality cotton. The weight-average molecular weight of the cotton is more preferably 400,000 or more, and even more preferably 500,000 or more. On the other hand, the weight-average molecular weight of the cotton is preferably 5,000,000 or less, and even more preferably 3,000,000 or less.

[0042] The fiber, film, or molded resin article of the present invention contains the water-insoluble composition of different materials of the present invention. When the water-insoluble composition of different materials is a natural fiber such as cotton, it can also be used as a raw material for bioethanol.

[0043] In the present invention, various known reaction methods, such as batch and continuous methods, can be used to treat a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble different material in the solvolysis step. Examples of equipment used in batch processes include autoclaves equipped with a stirrer and a heating function, vertical or horizontal reactors, and vertical or horizontal reactors equipped with a stirrer, a heating function, and a compression mechanism such as a cylinder. Examples of equipment used in continuous processes include extruders equipped with a heating function, tubular reactors, tubular reactors equipped with a mixing mechanism such as baffles, line mixers, vertical or horizontal reactors, vertical or horizontal reactors equipped with a stirrer, and towers.

[0044] The atmosphere in the solvolysis step is preferably a non-oxidizing atmosphere, more preferably an inert atmosphere such as nitrogen, helium, or argon, and even more preferably a nitrogen atmosphere from the standpoints of economy and ease of handling.

[0045] As a method for removing the thermoplastic polyester-derived component from the composition containing the thermoplastic polyester-derived component and the foreign material after the solvolysis step, various known separation methods using filters, screens, centrifugation, etc. can be used. Specific examples of fixed filters include cartridge filters, leaf filters, filter presses, and Nutsche filters. Fixed strainers include basket strainers, cartridge strainers, T-type strainers, and Y-type strainers. Moving strainers include belt filters, centrifugal filters, screen changers, and drum filters. Screens include fixed screens such as bar screens, vibrating screens, in-plane sieves, rotary sieves, and conveyor-type screens. To increase the recovery rate of the water-insoluble foreign material, preferred methods include narrowing the mesh size of the filter material and performing multiple filtering operations.

[0046] The present invention preferably includes a recovery step of recovering dicarboxylic acids, diols, and their derivatives, which are the monomers of thermoplastic polyesters, from thermoplastic polyester-derived components removed from a composition containing a thermoplastic polyester-derived component and a different material. Examples of dicarboxylic acid and diol derivatives include alkali metal dicarboxylic acid salts, alkaline earth metal dicarboxylic acid salts, ammonium dicarboxylic acid salts, bishydroxyalkyl dicarboxylic acid diesters (e.g., bishydroxyalkyl terephthalate when the thermoplastic polyester is polyethylene terephthalate), and monohydroxyalkyl dicarboxylic acid esters (e.g., monohydroxyalkyl terephthalate when the thermoplastic polyester is polyethylene terephthalate). This recovery step enables chemical recycling of thermoplastic polyesters. Separation and purification of thermoplastic polyester-derived components can be achieved by known methods, such as solvent extraction, solid-liquid separation, distillation, and crystallization, or a combination of these methods. In the separation and purification step, dicarboxylic acid and diol derivatives can also be converted to dicarboxylic acids and diols.

[0047] A thermoplastic polyester can be produced by polymerizing a dicarboxylic acid and / or a diol separated and purified from a component derived from a thermoplastic polyester. The process for obtaining the thermoplastic polyester can be carried out, for example, through a first step consisting of an esterification reaction between a dicarboxylic acid and a diol, followed by a second step of a polycondensation reaction. Alternatively, a thermoplastic polyester can be produced through a first step consisting of a transesterification reaction between a dialkyl dicarboxylate obtained by chemically converting a dicarboxylic acid and a diol, followed by a second step of a polycondensation reaction.

[0048] Furthermore, the thermoplastic polyester produced by polymerizing the dicarboxylic acid and / or diol can be processed to obtain fibers, films, or molded resin articles. Examples of methods for processing the thermoplastic polyester to obtain the fibers or films include melt spinning, melt film formation, and melt extrusion molding. Examples of methods for obtaining the molded resin articles include injection molding, blow molding, and extrusion molding. These fibers, films, and molded resin articles are useful for agricultural materials, horticultural materials, fishing materials, civil engineering and construction materials, industrial films, sheets, stationery, medical supplies, clothing, automotive parts, electrical and electronic parts, and other applications. [Example]

[0049] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0050] In each example, the following thermoplastic polyester composition containing a thermoplastic polyester and a different water-insoluble material was used.

[0051] [Thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble material] Raw material A: A blended fiber consisting of 82% polyethylene terephthalate (PET) and 18% cotton by weight. Raw material B: Molded product of polybutylene terephthalate (PBT) resin composition containing 30% by weight of glass fiber Raw material C: A blended fiber consisting of 83% by weight of polyethylene terephthalate (PET) and 17% by weight of polyurethane.

[0052] [Yield of water-insoluble heterogeneous composition] The aqueous solution containing the water-insoluble heterogeneous composition, obtained after solvent treatment of raw material A, raw material B, or raw material C under specific conditions, was filtered to obtain a residue. The residue was washed with water (100 mL) and then dried under vacuum at 80°C for 8 hours to obtain the water-insoluble heterogeneous composition. The yield (%) of the water-insoluble heterogeneous composition was calculated as follows: Yield (%) of water-insoluble foreign material composition = weight (g) of water-insoluble foreign material composition / theoretical weight (g) of water-insoluble foreign materials other than thermoplastic polyester contained in the raw material × 100.

[0053] [Content of thermoplastic polyester-derived components in the water-insoluble heterogeneous material composition recovered after solvent treatment of raw material A or raw material B] HFIP (1,1,1,3,3,3-hexafluoro-2-propanol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 30 mL) was added to 1.0 g of the recovered water-insoluble heterogeneous material composition, and the mixture was allowed to stand overnight at room temperature. This solution was filtered, and the filtrate was concentrated and then dried under vacuum at 80°C for 8 hours to dryness. NMR measurement of the dried product confirmed that it was a component derived from thermoplastic polyester. The content (wt%) of the component derived from thermoplastic polyester was calculated as follows: Content (wt %) of thermoplastic polyester-derived component = weight (g) of thermoplastic polyester-derived component / weight (g) of water-insoluble foreign material composition × 100.

[0054] [Content of thermoplastic polyester-derived components in the water-insoluble heterogeneous material composition recovered after solvent treatment of raw material C] N-methylpiperidone (100 mL, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 1.0 g of the recovered water-insoluble heterogeneous material composition and stirred at 110°C for 3 hours. This solution was air-cooled to 80°C and filtered at 80°C. N-methylpiperidone was added to the filtered cake, and the above procedure was repeated twice. After this procedure, the recovered cake was dried under vacuum at 80°C for 8 hours to obtain a dried product. NMR measurement of the dried product confirmed that the dried product was a component derived from thermoplastic polyester. The content (wt%) of the component derived from thermoplastic polyester was calculated as follows: Content (wt %) of thermoplastic polyester-derived component = weight (g) of thermoplastic polyester-derived component / weight (g) of water-insoluble foreign material composition × 100.

[0055] [Lightness of water-insoluble heterogeneous material composition] A portion of the water-insoluble heterogeneous composition was sampled and filled to a height of 10 mm into a borosilicate glass container (for the SE-2000 spectrophotometer, manufactured by Nippon Denshoku Industries Co., Ltd.) with a body diameter of 35 mm and a height of 15 mm. Measurements were performed from the bottom of the glass container using the SE-2000 spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd.) using the SCI method with illuminant C, and the lightness L*(1) defined by the CIE 1976 L*a*b* color system was calculated. Another portion of the water-insoluble heterogeneous composition was sampled, and the lightness L*(2) was calculated using the same method as above. The same procedure was repeated to calculate the lightness L*(3). The average lightness L* (= ((1) + (2) + (3)) / 3) of the three measurements was calculated and used as the lightness of the water-insoluble heterogeneous composition.

[0056] [Yield of terephthalic acid (HPLC)] The yield of terephthalic acid (HPLC) was calculated by high performance liquid chromatography under the following measurement conditions.

[0057] Equipment: Shimadzu LC-10Avp series Column: Mightysil RP-18GP150-4.6 Detector: Photodiode array detector (UV, wavelength 254 nm) Flow rate: 1mL / min Column temperature: 40℃ Mobile phase: 0.1% acetic acid aqueous solution / acetonitrile Sample: Approximately 0.1 g of the aqueous solution after the solvent treatment step (excluding water-insoluble foreign material components) was weighed out and diluted with approximately 10 g of water. The insoluble components were separated and removed by filtration to prepare a sample for high-performance liquid chromatography measurement.

[0058] Terephthalic acid yield: Quantitative determination was performed by the absolute calibration curve method (however, in this example, although a metal terephthalate was produced after the hydrothermal reaction, it was converted to terephthalic acid by the acid contained in the mobile phase), and the molar yield of terephthalic acid was calculated by taking the theoretical value of the terephthalic acid residues constituting the thermoplastic polyester contained in the raw material as 100 mol %.

[0059] [Weight average molecular weight measurement of cotton (GPC)] Using gel permeation chromatography, 0.01 g of the water-insoluble heterogeneous composition (cotton) that had been separated into solid and liquid after the solvent treatment step was dissolved in 15 ml of dimethylacetamide (with 8 wt% lithium chloride added), and the solution obtained by filtering through a 0.45 μm filter was measured under the following measurement conditions.

[0060] Equipment: Shimadzu Nexera GPC system Column: PLgel 20 μm MIXED-A (φ7.5 mm × 30 cm, Polymer Laboratories) Detector: Differential refractive index detector RI (Showa Denko RI-71, sensitivity 16) Flow rate: 0.5mL / min Column temperature: 23℃ Mobile phase: Dimethylacetamide (8% by weight lithium chloride added) Standards: Pullulan from Showa Denko and Sigma Aldrich, maltopentaose from Hayashibara.

[0061] [Yield of ethylene glycol and 1,4-butanediol (GC)] The yields (GC) of ethylene glycol and 1,4-butanediol were calculated by gas chromatography under the following conditions.

[0062] Equipment: Shimadzu GC-2010 Column: Agilent Technologies DB-5 0.32 mm x 30 m (0.25 μm) Carrier gas: Helium Detector: Flame ionization detector (FID) Sample: The reaction mixture was concentrated, and the resulting solid was washed with isopropanol. 10 μL of this isopropanol solution was weighed out and diluted with approximately 10 g of methanol. Components insoluble in methanol were removed by filtration to prepare a sample for gas chromatography measurement.

[0063] Ethylene glycol yield: Quantitatively determined using the absolute calibration curve method, the molar yield of ethylene glycol was calculated by taking the ethylene glycol residues contained in the PET as 100 mol%. When ethylene glycol was added for solvolysis, the molar yield of ethylene glycol was calculated by subtracting the weight of the added ethylene glycol from the weight of the recovered ethylene glycol.

[0064] Yield of 1,4-butanediol: Quantitative analysis was performed using the absolute calibration curve method. The molar yield of 1,4-butanediol was calculated by taking the 1,4-butanediol residues in PBT as 100 mol%. When 1,4-butanediol was added for solvolysis, the molar yield of 1,4-butanediol was calculated by subtracting the weight of the added 1,4-butanediol from the weight of the recovered 1,4-butanediol.

[0065] [Example 1] A SUS316L autoclave equipped with a stirrer was charged with 6.0 g of raw material A, 58 g of deionized water, 2.0 g of EG (ethylene glycol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 2.1 g of NaOH (sodium hydroxide, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The atmosphere inside the reaction vessel was replaced with nitrogen, and the mixture was stirred at 200 rpm at 140°C for 30 minutes under a nitrogen pressure of 0.3 MPa while sealed. The pressure inside the system was 0.4 MPa during the reaction. After the reaction, the mixture was cooled to 80°C, and the aqueous solution containing the water-insoluble heterogeneous material composition was filtered. The residue (water-insoluble heterogeneous material composition) and filtrate (aqueous solution) were recovered. The analysis results of the residue and filtrate are shown in Table 1.

[0066] [Comparative Example 1] Except for changing the amounts of water and EG added, raw material A was treated in exactly the same manner as in Example 1. The results are shown in Table 1.

[0067] Comparative Example 2 Except for changing the temperature, raw material A was treated in exactly the same manner as in Comparative Example 1. The results are shown in Table 1.

[0068] [Table 1]

[0069] Comparison of Example 1 with Comparative Examples 1 and 2 reveals that using a water-EG mixed solvent enables PET depolymerization at a lower reaction temperature than using water alone, suppressing cotton degradation and enabling high-yield cotton recovery with high brightness and weight-average molecular weight. Furthermore, it also reveals that PET monomers, terephthalic acid and EG, can be recovered in high yield. The weight-average molecular weight of the cotton before depolymerization was 2,440,000. It is believed that sodium ethylene glycol, a stronger base than sodium hydroxide, generated during the reaction allowed PET to depolymerize at a lower reaction temperature than using water alone. In Comparative Example 1, PET depolymerization was insufficient, resulting in a PET-derived component content of more than 10 wt% in the water-insoluble cotton. Therefore, the brightness and weight-average molecular weight of the water-insoluble mixed-material composition were not measured.

[0070] [Examples 2 to 4] Except for changing the amounts of water and EG added, raw material A was treated in exactly the same manner as in Example 1. The results are shown in Table 2.

[0071] Comparative Example 3 Except for changing EG to MeOH (methanol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), raw material A was treated in exactly the same manner as in Example 3. The results are shown in Table 2.

[0072] [Table 2]

[0073] The results of Examples 1 to 4 demonstrate that high-brightness cotton, terephthalic acid, and EG can be recovered in high yields even when the water-to-EG ratio is changed. Furthermore, a comparison of Example 3 and Comparative Example 3 reveals that replacing EG with MeOH reduces the brightness and yield of cotton. According to reports in J. Am. Chem. Soc. 82(4)795-798 (1960) and J. Chem. Educ. 94,690-695 (2017), the acid dissociation constant of ethylene glycol is pKa = 15.1, and the acid dissociation constant of methanol is pKa = 15.5, and the base strength is lower than that of sodium ethylene glycol. Therefore, we speculate that sodium methoxide, a stronger base than sodium ethylene glycol, generated during the reaction accelerated the degradation of cotton, resulting in a decrease in recovery rate and brightness.

[0074] [Examples 5 and 6] Except for changing the amount of raw material A used and the amount of base added, raw material A was treated in exactly the same manner as in Example 1. The results are shown in Table 3.

[0075] [Table 3]

[0076] Examples 1, 5 and 6 show that even if the content of the solvent relative to 100 parts by weight of the thermoplastic polyester composition is changed, cotton, terephthalic acid and EG having high brightness can be obtained in high yield.

[0077] [Example 7, Comparative Example 4] Except for the temperature change, raw material A was treated in exactly the same manner as in Example 1. The results are shown in Table 4.

[0078] [Example 8] A SUS316L autoclave equipped with a stirrer was charged with 6.0 g of raw material A, 58 g of deionized water, 2.0 g of EG (ethylene glycol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 4.3 g of NaHCO3 (sodium bicarbonate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). The atmosphere inside the reaction vessel was replaced with nitrogen, and the mixture was stirred at 200 rpm at 180°C for 30 minutes under a nitrogen pressure of 0.3 MPa in a sealed container. The pressure inside the system was 1.6 MPa during the reaction. After the reaction, the mixture was cooled to 80°C and the reaction solution was filtered. The residue (referred to in the table as "Water-insoluble foreign material composition (cotton)") and the filtrate (referred to in the table as "Thermoplastic polyester depolymerized product") were collected. The analysis results of the residue and filtrate are shown in Table 4.

[0079] [Example 9] Except for the temperature change, raw material A was treated in exactly the same manner as in Example 8. The results are shown in Table 4.

[0080] [Table 4]

[0081] A comparison of Examples 1, 7, and Comparative Example 4 reveals that when the alkali is sodium hydroxide, high-brightness cotton, terephthalic acid, and EG can be recovered in high yields by setting the reaction temperature above 135°C (e.g., 140°C, 160°C, etc.). At a reaction temperature of 120°C, depolymerization of raw material A was insufficient, and the content of PET-derived components in the water-insoluble cotton was greater than 10 wt%, so the brightness of the water-insoluble heterogeneous composition was not measured. The results of Examples 8 and 9 reveal that high-brightness cotton can be recovered in high yields by setting the reaction temperature to 180°C or 200°C when the alkali is sodium bicarbonate. It is speculated that a higher reaction temperature than that of sodium hydroxide is required to produce sodium ethylene glycol, which promotes the depolymerization of raw material A. On the other hand, because hydrothermal decomposition proceeds under weakly basic conditions, cotton degradation is suppressed even at high temperatures.

[0082] [Examples 10 and 11] Except for changing the type and amount of alkali, raw material A was treated in exactly the same manner as in Example 8. The results are shown in Table 5.

[0083] [Example 12] Except for changing the type and amount of alkali, raw material A was treated in exactly the same manner as in Example 1. The results are shown in Table 5.

[0084] [Table 5]

[0085] Examples 1, 8, and 10 to 12 show that even if various alkali metal salts such as sodium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate, and potassium hydroxide are used, it is possible to obtain highly bright cotton, terephthalic acid, and EG in high yields.

[0086] [Examples 13 and 14] Except for changing the amount of alkali added, raw material A was treated in exactly the same manner as in Example 1. The results are shown in Table 6.

[0087] [Table 6]

[0088] Examples 1, 13 and 14 show that even if the amount of alkali component added relative to 100 parts by weight of thermoplastic polyester is changed, it is possible to recover highly bright cotton, terephthalic acid and EG in high yields.

[0089] [Example 15] A SUS316L autoclave equipped with a stirrer was charged with 6.0 g of raw material B, 58 g of deionized water, 2.0 g of BDO (1,4-butanediol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 1.5 g of NaOH. The atmosphere inside the reaction vessel was replaced with nitrogen, and the mixture was stirred at 200 rpm at 140°C for 30 minutes under a nitrogen pressure of 0.3 MPa while sealed. The pressure inside the system was 0.4 MPa during the reaction. After the reaction, the mixture was cooled to 80°C, and the reaction solution was filtered. The residue (listed in the table as "Water-insoluble foreign material composition (glass fiber)") and the filtrate (listed in the table as "Thermoplastic polyester depolymerized product") were collected. The analysis results of the residue and filtrate are shown in Table 7.

[0090] [Examples 16 to 18] Raw material B was treated in exactly the same manner as in Example 15, except that BDO was replaced with methanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 2-propanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), or tert-butyl alcohol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.). The results are shown in Table 7.

[0091] [Table 7]

[0092] Examples 15 to 18 show that when BDO and an alcohol such as methanol, 2-propanol, or tert-butyl alcohol are blended, PBT undergoes solvolysis at a reaction temperature of 140°C, and high-brightness glass fibers, terephthalic acid (a PBT monomer), and BDO can be recovered in high yields from the PBT composition containing glass fibers.

[0093] [Examples 19 and 20 and Comparative Example 5] Except for changing the reaction temperature, raw material B was treated in exactly the same manner as in Example 18. The results are shown in Table 8.

[0094] [Table 8]

[0095] A comparison of Examples 19 and 20 with Comparative Example 5 shows that by setting the reaction temperature at a specific temperature or higher, it is possible to recover high-brightness glass fibers, terephthalic acid, and BDO in high yields. In Comparative Example 5, the depolymerization of PBT was insufficient, and the content of PBT-derived components in the water-insoluble cotton was greater than 10 wt %, so the brightness of the water-insoluble mixed-material composition was not measured.

[0096] [Examples 21 and 22] Except for changing the weights of water and alcohol, raw material B was treated in exactly the same manner as in Example 22. The results are shown in Table 9.

[0097] [Table 9]

[0098] Examples 18, 21 and 22 show that by setting the weight ratio of water to alcohol to a specific ratio or more, it is possible to recover glass fibers with high brightness, terephthalic acid and BDO in high yields.

[0099] [Example 23] A SUS316L autoclave equipped with a stirrer was charged with 6.0 g of raw material C, 58 g of deionized water, 2.0 g of EG, and 2.1 g of NaOH. The reactor was purged with nitrogen, and the mixture was sealed and stirred at 200 rpm at 140°C for 30 minutes under a nitrogen pressure of 0.3 MPa. The pressure inside the system was 0.4 MPa during the reaction. After the reaction, the mixture was cooled to 80°C and the reaction solution was filtered. The residue (listed in the table as "Water-insoluble foreign material composition (polyurethane)") and the filtrate (listed in the table as "Thermoplastic polyester depolymerization product") were collected. The analysis results of the residue and filtrate are shown in Table 10.

[0100] [Example 24] The raw material C was treated in exactly the same manner as in Example 23, except that EG was replaced with tert-butyl alcohol. The results are shown in Table 10.

[0101] [Table 10]

[0102] Examples 23 and 24 show that when alcohols such as EG and tert-butyl alcohol are blended, PET undergoes solvolysis, and polyurethane fibers, terephthalic acid, and EG can be recovered in high yields from the PET composition containing polyurethane fibers.

Claims

1. A method for recovering a water-insoluble foreign material composition, comprising: a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble foreign material is treated in a solvent containing a diol and water in the presence of an alkali at a temperature above 135°C and not higher than 200°C; and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the foreign material after the solvent treatment step to obtain a water-insoluble foreign material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble foreign material composition is 10% by weight or less.

2. A method for recovering a water-insoluble different material composition, comprising: a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble different material (excluding cotton) is treated in a solvent containing alcohol and water in the presence of an alkali at 110°C or higher and 350°C or lower; and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the different material after the solvent treatment step to obtain a water-insoluble different material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble different material composition is 10% by weight or lower.

3. A method for recovering a water-insoluble foreign material composition as described in claim 1 or 2, wherein the content of the solvent in the solvent treatment process is 100 parts by weight or more and 2000 parts by weight or less per 100 parts by weight of the thermoplastic polyester composition.

4. The method for recovering a water-insoluble foreign material composition according to claim 1, wherein the weight (g) of water in the solvent / weight (g) of diol is 0.1 or more and 100 or less.

5. The method for recovering a water-insoluble foreign material composition according to claim 2, wherein the weight (g) of water / weight (g) of alcohol in the solvent is 0.1 or more and 100 or less.

6. The method for recovering a water-insoluble foreign material composition according to claim 2 or 5, wherein the alcohol is an aliphatic monohydric or dihydric alcohol having 1 to 10 carbon atoms.

7. A method for recovering a water-insoluble foreign material composition as described in claim 1 or 2, in which an alkaline component is coexisted in an amount of 25 parts by weight or more and 200 parts by weight or less per 100 parts by weight of the thermoplastic polyester content in the thermoplastic polyester composition.

8. The method for recovering a water-insoluble foreign material composition according to claim 1, wherein in the solvent treatment step, the pressure at a temperature higher than 135°C and lower than 200°C is 0.2 MPa or more and 10 MPa or less.

9. The method for recovering a water-insoluble foreign material composition according to claim 2, wherein the pressure at 110°C or higher and 350°C or lower in the solvent treatment step is 0.1 MPa or higher and 30 MPa or lower.

10. A method for recovering a water-insoluble foreign material composition according to claim 1 or 2, wherein the thermoplastic polyester is one or more selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and copolymers thereof.

11. 3. The method for recovering a water-insoluble foreign material composition according to claim 1 or 2, wherein the lightness L* of the water-insoluble foreign material composition as defined by the CIE 1976 L*a*b* color space is 84.0 or more.

12. 2. The method for recovering a water-insoluble foreign material composition according to claim 1, wherein the water-insoluble foreign material composition is cotton, and the weight average molecular weight of the cotton measured by gel permeation chromatography is 300,000 or more.

13. A method for recovering dicarboxylic acids, diols, and their derivatives, which are monomers of thermoplastic polyesters, comprising a recovery step of recovering dicarboxylic acids, diols, and their derivatives, which are monomers of thermoplastic polyesters, from thermoplastic polyester-derived components removed by the method for recovering a water-insoluble foreign material composition described in claim 1 or 2.

14. A method for producing a thermoplastic polyester, comprising a step of polymerizing dicarboxylic acids and diols, which are monomers of a thermoplastic polyester obtained by separating and purifying components derived from a thermoplastic polyester removed by the method for recovering a water-insoluble foreign material composition according to claim 1 or 2.

15. A water-insoluble different material composition obtained by a method for recovering a water-insoluble different material composition, the method comprising: a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble different material is treated in a solvent containing a diol and water in the presence of an alkali at a temperature above 135°C and not higher than 200°C; and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the different material after the solvent treatment step to obtain a water-insoluble different material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble different material composition is 10% by weight or less.

16. A water-insoluble heterogeneous material composition obtained by a method for recovering a water-insoluble heterogeneous material composition, which includes a solvent treatment step in which a thermoplastic polyester composition containing a thermoplastic polyester and a water-insoluble heterogeneous material (excluding cotton) is treated in a solvent containing alcohol and water in the presence of an alkali at 110°C or higher and 350°C or lower, and a step in which the thermoplastic polyester-derived component is removed from the composition containing the thermoplastic polyester-derived component and the heterogeneous material after the solvent treatment step to obtain a water-insoluble heterogeneous material composition, wherein the content of the thermoplastic polyester-derived component in 100% by weight of the water-insoluble heterogeneous material composition is 10% by weight or less.

17. The water-insoluble heterogeneous composition according to claim 16, wherein the alcohol is an aliphatic monohydric or dihydric alcohol having 1 to 10 carbon atoms.

18. The water-insoluble composition of different materials according to claim 15 or 16, having a lightness L* defined by the CIE 1976 L*a*b* color space of 84.0 or more.

19. 17. The water-insoluble heterogeneous composition according to claim 15 or 16, wherein the water-insoluble heterogeneous material comprises natural fibers and / or inorganic fibers.

20. 16. The water-insoluble heterogeneous composition according to claim 15, wherein the water-insoluble heterogeneous composition is cotton, and the weight average molecular weight of the cotton measured by gel permeation chromatography is 300,000 or more.

21. A fiber, film, or resin molded product comprising the water-insoluble heterogeneous material composition according to any one of claims 15 to 17 or 20.

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