Dicarboxylic acid and / or diol, polyester, and methods for producing the same

Abstract

To achieve high-yield recovery of dicarboxylic acids and diols, which are polyester monomers, from a polyester composition containing an acrylic component and / or a silicone component.SOLUTION: The present invention provides dicarboxylic acid and / or diol obtained by a process that involves hydrothermally decomposing a polyester composition including an acrylic component and / or a silicone component and a polyester component, at 180°C or more and 350°C or less in the presence of an alkaline component.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to dicarboxylic acids and / or diols, polyesters, and methods for producing them.

Background Art

[0002] In recent years, triggered by the problem of marine plastics, interest in global environmental problems has increased, and the recognition that it is necessary to build a sustainable society has spread. Global environmental problems include global warming, resource depletion, water shortages, etc., many of which are caused by the use of fossil fuels and the rapid development of industry since the Industrial Revolution, resulting in an increase in resource consumption and greenhouse gas emissions. Therefore, for the construction of a sustainable society, technologies related to the recycling of fossil resources such as plastics and the reduction of greenhouse gas emissions are becoming increasingly important.

[0003] Polyester films and polyester fibers, which are plastic materials, are often mixed with other types of polymers in order to exhibit properties that cannot be achieved by polyester alone. For example, polyester films coated with acrylic polymers or silicone polymers are used as functional films. Also, blended fibers of polyester and acrylic polymers are used as clothing. In particular, when acrylic polymers or silicone polymers are crosslinked, it is difficult to separate them from polyester, which has been a problem when recycling polyester.

[0004] Patent Document 1 discloses a technique for depolymerizing polyethylene terephthalate alone, and Patent Document 2 discloses a technique for depolymerizing an acrylic polymer alone. Also, Patent Document 3 discloses a technique for depolymerizing cellulose fibers containing polyester and acrylic.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] When applying the technology of Patent Document 1 to a composition containing a polyester component and an acrylic component, it can be easily imagined that after removing the acrylic component in advance, only the polyester is depolymerized. However, simultaneous depolymerization of the polyester component and the acrylic component has not been mentioned.

[0007] Also, in Patent Document 2, it has not been described that the decomposition of the acrylic component is promoted by depolymerizing the acrylic component simultaneously with the polyester component.

[0008] Although Patent Document 3 describes a depolymerization technology for cellulose fibers containing a polyester component and an acrylic component, the depolymerization of both the polyester component and the acrylic component was insufficient. Also, the recovery of polyester monomers has not been mentioned. [Means for Solving the Problems]

[0009] To solve the above problems, the inventors of the present invention have conducted intensive studies and found that by subjecting a polyester composition containing an acrylic component and / or a silicone component and a polyester component to hydrothermal decomposition in a specific temperature range in the presence of an alkaline component, dicarboxylic acids and diols, which are polyester monomers, can be recovered in high yields without previously removing the acrylic component or the silicone component. The reason is presumed as follows. That is, since the acrylic component and the silicone component have high affinity with alcohol, by subjecting them to hydrothermal decomposition simultaneously with the polyester under appropriate conditions, the diol generated by the hydrothermal decomposition of the polyester penetrates between the molecular chains of acrylic and silicone, and the alkaline component cuts the molecular chains of acrylic and silicone to promote hydrothermal decomposition and solubilization or low molecular weightization, making it easier to recover particularly dicarboxylic acids among the polyester monomers, and thus it is presumed that dicarboxylic acids and diols can be recovered in high yields.

[0010] That is, the present invention has the following configurations. (1) Dicarboxylic acids and / or diols obtained by subjecting a polyester composition containing an acrylic component and / or a silicone component and a polyester component to hydrothermal decomposition at 180°C or higher and 350°C or lower in the presence of an alkaline component. (2) Dicarboxylic acids and / or diols obtained by subjecting a polyester composition containing an acrylic component and / or a silicone component and a polyester component to hydrothermal decomposition at higher than 135°C and 350°C or lower in the presence of an alcohol and an alkaline component. (3) The dicarboxylic acids and / or diols according to the above (1) or (2), wherein the dicarboxylic acid is terephthalic acid. (4) The dicarboxylic acids and / or diols according to the above (1) or (2), wherein the diol is at least one selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,4-butanediol. (5) The dicarboxylic acid and / or diol according to (1) or (2) above, wherein the polyester composition is a polyester film containing an acrylic component and / or a silicone component. (6) A polyester obtained by polymerizing the dicarboxylic acid and / or diol according to any one of (1) to (5) above. (7) A fiber, film, or resin molded product obtained by processing the polyester according to (6) above. (8) A method for producing a dicarboxylic acid and / or diol, which comprises a step of hydrothermally decomposing a polyester composition containing an acrylic component and / or a silicone component and a polyester component at 180°C or higher and 350°C or lower in the presence of an alkali component. (9) The method for producing a dicarboxylic acid and / or diol according to (8) above, which has a step including acid crystallization after the hydrothermal decomposition step, and the total amount of the acrylic component and the silicone component in the dicarboxylic acid after the step including acid crystallization is 0.1% by weight or less. (10) A method for producing a dicarboxylic acid and / or diol, which comprises a step of hydrothermally decomposing a polyester composition containing an acrylic component and / or a silicone component and a polyester component at higher than 135°C and 350°C or lower in the presence of an alcohol and an alkali component. (11) The method for producing a dicarboxylic acid and / or diol according to (10) above, which has a step including acid crystallization after the hydrothermal decomposition step, and the total amount of the acrylic component and the silicone component in the dicarboxylic acid after the step including acid crystallization is 0.1% by weight or less. (12) The method for producing a dicarboxylic acid and / or diol according to (8) to (11) above, wherein the amount of water is 100 to 1000 parts by weight with respect to a total of 100 parts by weight of the acrylic component, the silicone component, and the polyester component. (13) The method for producing a dicarboxylic acid and / or diol according to (10) or (11) above, wherein the weight (g) of water / the weight (g) of alcohol in the hydrothermal decomposition step is 0.1 or more and 100 or less. (14) The method for producing the dicarboxylic acid and / or diol according to (8) or (9) above, wherein the pressure at 180 °C or higher and 350 °C or lower is 1.0 to 30 MPa. (15) The method for producing the dicarboxylic acid and / or diol according to (10) or (11) above, wherein the pressure above 135 °C and 350 °C or lower is 0.3 to 30 MPa. (16) The method for producing the dicarboxylic acid and / or diol according to any one of (8) to (11) above, wherein 25 to 100 parts by weight of an alkali component coexists with respect to a total of 100 parts by weight of an acrylic component, a silicone component, and a polyester component. (17) The method for producing the dicarboxylic acid and / or diol according to any one of (8) to (11) above, wherein the alkali component is an alkali metal salt and / or an alkaline earth metal salt. (18) The method for producing the dicarboxylic acid and / or diol according to any one of (8) to (11) above, wherein the alkali component is an alkali metal salt with pKa > 4.0 and / or an alkaline earth metal salt with pKa > 4.0. (19) The method for producing the dicarboxylic acid and / or diol according to any one of (8) to (11) above, wherein the polyester composition contains 0.1 to 200 parts by weight of an acrylic component and / or a silicone component with respect to 100 parts by weight of a polyester component. (20) The method for producing the dicarboxylic acid and / or diol according to any one of (8) to (11) above, wherein the polyester component is selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and copolymers thereof. (21) The method for producing the dicarboxylic acid and / or diol according to any one of (8) to (11) above, wherein the polyester composition is a polyester film containing an acrylic component and / or a silicone component. (22) The method for producing a polyester, comprising a step of polymerizing the dicarboxylic acid and / or diol obtained by the method for producing the dicarboxylic acid and / or diol according to any one of (8) to (21) above.

Advantages of the Invention

[0011] According to the present invention, dicarboxylic acids and diols, which are polyester monomers, can be recovered in high yields.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in more detail.

[0013] A first aspect of the dicarboxylic acids and / or diols of the present invention is obtained by subjecting a polyester composition containing an acrylic component and / or a silicone component and a polyester component to hydrothermal decomposition at 180°C or higher and 350°C or lower in the presence of an alkali component.

[0014] A second aspect of the dicarboxylic acids and / or diols of the present invention is obtained by subjecting a polyester composition containing an acrylic component and / or a silicone component and a polyester component to hydrothermal decomposition at higher than 135°C and 350°C or lower in the presence of an alcohol and an alkali component. In this specification, "the first aspect of the dicarboxylic acids and / or diols of the present invention" may be simply referred to as "the first aspect", and "the second aspect of the dicarboxylic acids and / or diols of the present invention" may be referred to as "the second aspect".

[0015] In the present invention, the polyester composition contains a polyester component.

[0016] The polyester component is a homopolymer or copolymer obtained by polycondensing a dicarboxylic acid and / or its ester-forming derivative and a diol and / or its ester-forming derivative as main raw materials. Here, the main raw materials mean that the total of the dicarboxylic acid and its ester-forming derivative and the diol and its ester-forming derivative in the raw materials is 50 mol% or more in all the raw materials. Preferably 80 mol% or more, more preferably 90 mol% or more.

[0017] 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-tetrabutylphosphonium isophthalic acid, 5-sodium sulfoisophthalic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, dimer acid, alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and ester-forming derivatives thereof. Two or more of these may be used.

[0018] The ester-forming derivative referred to herein is an alkyl ester, acid anhydride, acid halide, etc. of the dicarboxylic acid described above. As the alkyl ester of the dicarboxylic acid, methyl ester, ethyl ester, hydroxyethyl ester, hydroxybutyl ester, etc. are preferably used. As the acid anhydride of the dicarboxylic acid, anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids and acetic acid, etc. are preferably used. As the halide of the dicarboxylic acid, acid chloride, acid bromide, acid iodide, etc. are preferably used.

[0019] In the present invention, it is preferable that the dicarboxylic acid is terephthalic acid. When the dicarboxylic acid is terephthalic acid, in addition to facilitating acid crystallization in the subsequent process, polyethylene terephthalate, which has a large production volume as a plastic, can be recycled, thus making a great contribution to resource circulation.

[0020] Examples of the above 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, dimer diol, long-chain glycols having a molecular weight of 200 to 100,000 such as polyethylene glycol, poly-1,3-propylene glycol, polytetramethylene glycol, aromatic dioxy compounds such as 4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, bisphenol A, bisphenol S, bisphenol F, and ester-forming derivatives thereof. Two or more of these may be used.

[0021] In the present invention, it is preferable that the diol is at least one selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,4-butanediol. Since ethylene glycol, 1,3-propanediol, and 1,4-butanediol have high affinity with acrylic components and silicone components, in addition to promoting their decomposition, polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate, which are produced in large amounts as plastics, can be recycled, thus making a great contribution to resource circulation.

[0022] Examples of homopolymers or copolymers having dicarboxylic acids or their ester-forming derivatives and diols or their ester-forming derivatives as structural units include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, polypropylene isophthalate, polybutylene isophthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene naphthalate, polycyclohexane dimethylene terephthalate, polyethylene isophthalate / terephthalate, polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polyethylene terephthalate / naphthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polyethylene terephthalate / 5-sodium sulfoisophthalate, 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, polybutylene terephthalate / isophthalate / polytetramethylene glycol, polyethylene terephthalate / 1,4-cyclohexanedimethanol, polypropylene terephthalate / 1,4-cyclohexanedimethanol, polybutylene terephthalate / 1,Aromatic polyester resins such as 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, polybutylene terephthalate / isophthalate / sebacate, etc. may be mentioned.,

[0023] Here, " / " represents a copolymer. These homopolymers and copolymers may be used alone or mixed in any content of two or more. Among them, for the purpose of recycling polyester components and promoting the recycling of fossil resources, homopolymers or copolymers mainly composed of aromatic dicarboxylic acids and / or their ester-forming derivatives with a large production and consumption volume and aliphatic diols and / or their ester-forming derivatives are preferred. Examples of the preferred polymers include at least one selected from terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and their ester-forming derivatives, and at least one selected from ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol or their ester-forming derivatives. The homopolymer or copolymer obtained by polycondensation is mentioned, and among them, it is particularly preferable that the polyester component is at least one selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and their copolymers.

[0024] In the present invention, the polyester composition contains an acrylic component and / or a silicone component.

[0025] Examples of the acrylic component include acrylic resins and acrylic fibers. Examples of the acrylic resin include acrylic polymers containing structural units derived from (meth)acrylic acid alkyl esters having an alkyl group having 1 to 18 carbon atoms.

[0026] Examples of the alkyl (meth)acrylate having an alkyl group with 1 to 4 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and the like. Among them, ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred.

[0027] Examples of the alkyl (meth)acrylate having an alkyl group with 5 to 8 carbon atoms include heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and the like. Among them, 2-ethylhexyl acrylate is preferred.

[0028] Examples of the alkyl (meth)acrylate having an alkyl group with 9 to 18 carbon atoms include tridecyl methacrylate, stearyl (meth)acrylate, and the like.

[0029] The above acrylic polymer may contain, if necessary, structural units derived from other copolymerizable polymerizable monomers.

[0030] Examples of the other copolymerizable polymerizable monomers include hydroxyalkyl (meth)acrylate, glycerin dimethacrylate, glycidyl (meth)acrylate, 2-methacryloyloxyethyl isocyanate, (meth)acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, fumaric acid, and the like. These other copolymerizable polymerizable monomers may be used alone or in combination of two or more. Among them, functional monomers having polar functional groups such as hydroxyl groups and carboxyl groups are preferred because it is easy to adjust the gel fraction of the pressure-sensitive adhesive layer by forming a crosslinked structure with a crosslinking agent. The crosslinking agent is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-type crosslinking agents.

[0031] Also, when the acrylic component is acrylic fiber, an acrylic polymer obtained by polymerizing a monomer mixture containing 50% by weight or more of acrylonitrile is preferred.

[0032] As a constituent component other than acrylonitrile that can be used as a raw material for the above acrylic polymer, any vinyl compound may be used. Typical examples include acrylic acid, methacrylic acid, or esters thereof, acrylamide, methacrylamide or N-alkyl substituted products thereof, vinyl esters such as vinyl acetate, vinyl halides or vinylidene halides such as vinyl chloride, vinyl bromide, vinylidene chloride, unsaturated sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid or salts thereof, etc. It is also possible to crosslink using a crosslinking agent.

[0033] The silicone component is a silicone resin containing dimethylsiloxane residues in the main chain or side chain, and a polymer having a curable dimethylsiloxane residue is preferred. Examples of polymers having a curable dimethylsiloxane residue include "addition reaction type" obtained by heat-curing an organohydrogenpolysiloxane and an organohydrogenpolysiloxane containing an alkenyl group under a platinum catalyst, "condensation reaction type" obtained by heat-curing an organohydrogensiloxane and an organopolysiloxane containing a hydroxyl group at the terminal using an organotin catalyst, "UV curable type" obtained by blending a photoinitiator into an organopolysiloxane containing an acryloyl group or a methacryloyl group, or an organopolysiloxane containing an alkenyl group and an organopolysiloxane containing a mercapto group and irradiating with UV light for curing, "cationic polymerization type" obtained by photocycloopening and curing an epoxy group with an onium salt initiator, etc.

[0034] In the present invention, in the polyester composition, the total amount of the acrylic component and / or the silicone component is preferably 0.1 to 200 parts by weight with respect to 100 parts by weight of the polyester component. More preferably, it is 70 parts by weight or less, and even more preferably 50 parts by weight or less. By setting it to 200 parts by weight or less, the acrylic component and the silicone component can be depolymerized more efficiently. When the polyester composition contains either the acrylic component or the silicone component, the content of each component is within the above range. When the polyester composition contains both the acrylic component and the silicone component, the total content of both components is within the above range.

[0035] In the present invention, the polyester composition may contain polymers other than the polyester component, the acrylic component, and the silicone component, as long as the object of the present invention is not impaired. For example, polyamide, polycarbonate, polyolefin, modified polyphenylene ether, polyurethane, polysulfone, polyketone, polyetherimide, polyarylate, polyethersulfone, polyetherketone, polythioetherketone, polyetheretherketone, polyimide, polyamideimide, polytetrafluoroethylene, polyphenylene sulfide, etc. may be mentioned. Two or more of these may be contained. The polymer other than the polyester component, the acrylic component, and the silicone component is preferably 50 parts by weight or less with respect to 100 parts by weight of the polymer component in the polyester composition. More preferably, it is 40 parts by weight or less, and even more preferably 30 parts by weight or less.

[0036] In addition to the above polymers, the polyester composition may contain additives such as polymerization catalysts, fillers, nucleating agents, plasticizers, ultraviolet light resistant agents, mold release agents, flame retardants, colorants (for example, pigments or dyes), lubricants, antistatic agents, antioxidants, etc.

[0037] In the present invention, the polyester composition is hydrothermally decomposed in the presence of an alkali component. By coexisting the alkali component, the polyester component, acrylic component, and silicone component are decomposed, promoting solubilization and reduction in molecular weight. Examples of the alkali component include alkali metals such as lithium, sodium, and potassium, alkaline earth metals such as magnesium and calcium, hydroxides such as ammonium, carbonates, bicarbonates, and organic amines such as ammonia and trimethylamine. Among them, it is preferable that the alkali component is an alkali metal salt and / or an alkaline earth metal salt, and more preferably an alkali metal salt with pKa > 4.0 and / or an alkaline earth metal salt with pKa > 4.0. Here, the pKa refers to the acid dissociation constant of the alkali metal salt and / or alkaline earth metal salt at 25°C. Among alkali metal salts and alkaline earth metal salts, some have multiple pKas, but in the present invention, it is preferable that any pKa exceeds 4.0. By setting pKa > 4.0, the hydrothermal decomposition of the polyester composition is further promoted, and in particular, the dicarboxylic acid becomes more easily solubilized, making it easier to separate the undissolved components with insufficient depolymerization and the dicarboxylic acid. The pKa of the alkali metal salt and / or alkaline earth metal salt is more preferably 6.0 or higher, and even more preferably 10.0 or higher. On the other hand, the pKa of the alkali metal salt and / or alkaline earth metal salt is preferably 16.0 or lower, and more preferably 15.0 or lower.

[0038] Examples of the alkali metal salts include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide; alkali metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, cesium hydrogen carbonate; alkali metal phosphates such as lithium phosphate, sodium phosphate, potassium phosphate, cesium phosphate, dilithium hydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, dilithium hydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, cesium hydrogen phosphate; and alkali metal borates such as lithium borate, sodium borate, potassium borate, cesium borate. Among these, it is preferable that the alkali metal salt is at least one selected from alkali metal hydroxides and alkali metal carbonates. Specifically, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, cesium hydrogen carbonate, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate are more preferable.

[0039] Examples of the alkaline earth metal salts include alkaline earth metal hydroxides such as magnesium hydroxide, calcium hydroxide, barium hydroxide; alkaline earth metal carbonates such as magnesium carbonate, calcium carbonate, barium carbonate; alkaline earth metal phosphates such as magnesium phosphate, calcium phosphate, barium phosphate, magnesium hydrogen phosphate, calcium hydrogen phosphate, barium hydrogen phosphate, dimagnesium hydrogen phosphate, dicalcium hydrogen phosphate, dibarium hydrogen phosphate; and alkaline earth metal borates such as magnesium borate, calcium borate, barium borate. Among these, it is preferable that the alkaline earth metal salt is at least one selected from alkaline earth metal hydroxides and alkaline earth metal carbonates. Specifically, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate, calcium carbonate, barium carbonate are more preferable.

[0040] Among the above alkali metal salts or alkaline earth metal salts, sodium hydrogen carbonate (pKa = 6.6), sodium carbonate (pKa = 6.6, 10.3), sodium dihydrogen phosphate (pKa = 7.2), disodium hydrogen phosphate (pKa = 7.2, 12.3), magnesium hydroxide (pKa = 11.4), sodium hydroxide (pKa = 13), barium hydroxide (pKa = 13.4), lithium hydroxide (pKa = 14), and potassium hydroxide (pKa = 14) are preferred, and sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, sodium carbonate, and magnesium hydroxide are more preferred, and sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, and magnesium hydroxide are even more preferred.

[0041] In the method for producing the dicarboxylic acid and / or diol of the present invention, it is preferable to coexist 25 to 100 parts by weight of an alkali component with respect to 100 parts by weight of the total content of the acrylic component, the silicone component, and the polyester component. By controlling the amount of the coexistent alkali component within this range, the hydrothermal decomposition of the polyester component proceeds, and the generated diol penetrates into the molecular chains of the acrylic component and / or the silicone component to promote decomposition, resulting in solubilization or reduction in molecular weight, so that the dicarboxylic acid and diol, which are polyester monomers, can be easily recovered. It is more preferable to coexist 28 parts by weight or more of the alkali component with respect to 100 parts by weight of the total content of the acrylic component, the silicone component, and the polyester component, and even more preferable to coexist 30 parts by weight or more. On the other hand, it is more preferable to coexist 80 parts by weight or less of the alkali component, and even more preferable to coexist 60 parts by weight or less.

[0042] The second aspect of the dicarboxylic acid and / or diol of the present invention is obtained by subjecting a polyester composition to hydrothermal decomposition in the co-presence of an alcohol and an alkali component. Examples of the alcohol 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 above-described polyester raw materials, and aliphatic trihydric alcohols having 3 to 10 carbon atoms such as glycerol. The alcohol may be used alone or mixed in any content of two or more. It is presumed that a metal alkoxide formed by deprotonation of a part of the alcohol by the above-described alkali promotes hydrothermal decomposition. Particularly in the case of tert-butyl alcohol, hydrothermal decomposition can be carried out at a lower temperature. However, the alcohol used in the second aspect of the present invention does not include a dihydric alcohol (diol) produced by the decomposition of the polyester.

[0043] The first aspect of the dicarboxylic acid and / or diol of the present invention is obtained by the first aspect of the method for producing the dicarboxylic acid and / or diol of the present invention described below. Further, the second aspect of the dicarboxylic acid and / or diol of the present invention is obtained by the second aspect of the method for producing the dicarboxylic acid and / or diol of the present invention described below.

[0044] The first aspect of the method for producing a carboxylic acid and / or a diol of the present invention comprises a step of subjecting a polyester composition containing an acrylic component and / or a silicone component and a polyester component to hydrothermal decomposition at 180°C or higher and 350°C or lower in the presence of an alkali component. By performing hydrothermal decomposition at 180°C or higher and 350°C or lower in the presence of an alkali component, the hydrothermal decomposition of the polyester component proceeds, and the acrylic component and / or the silicone component are decomposed to be solubilized or reduced in molecular weight, whereby dicarboxylic acid and diol, which are polyester monomers, can be recovered in high yields. The temperature is preferably 200°C or higher, more preferably 210°C or higher, and even more preferably 230°C or higher. On the other hand, the temperature is more preferably 320°C or lower, and even more preferably 300°C or lower. The temperature of hydrothermal decomposition may temporarily exceed 350°C as long as the effects of the present invention are not impaired. However, by setting the reaction temperature of hydrothermal decomposition to 350°C or lower, overreaction of the polyester monomer is suppressed, and the yields of dicarboxylic acid and diol tend to improve. Therefore, it is preferable to set the temperature to 350°C or lower at all times during the reaction time of hydrothermal decomposition.

[0045] Further, in the second aspect of the method for producing a dicarboxylic acid and / or a diol of the present invention, a polyester composition containing an acrylic component and / or a silicone component and a polyester component is subjected to hydrothermal decomposition at a temperature exceeding 135°C and 350°C or lower in the presence of an alcohol and an alkali component. By performing hydrothermal decomposition at a temperature exceeding 135°C and 350°C or lower, the hydrothermal decomposition of the polyester component proceeds, and the acrylic component and / or the silicone component are decomposed to be solubilized or reduced in molecular weight, whereby dicarboxylic acid and diol, which are polyester monomers, can be recovered in high yields. The temperature is more preferably 140°C or higher, and even more preferably 160°C or higher. On the other hand, the temperature is more preferably 300°C or lower, and even more preferably 280°C or lower.

[0046] In the hydrothermal decomposition step, the reaction time is preferably from 1 to 120 minutes. The reaction time is more preferably 5 minutes or more, still more preferably 10 minutes or more. On the other hand, it is more preferably 60 minutes or less, still more preferably 30 minutes or less. Note that the reaction time refers to the time when the reaction temperature is 180°C or higher and 350°C or lower in the first aspect. Also, in the second aspect, it refers to the time when the reaction temperature is above 135°C and 350°C or lower.

[0047] In the method for producing a dicarboxylic acid and / or a diol of the present invention, the water content is preferably 100 to 1000 parts by weight with respect to 100 parts by weight of the total content of the acrylic component, the silicone component, and the polyester component. By setting it within this range, it is possible to suppress the environmental load by suppressing the consumption of energy for heating water, and at the same time, the hydrothermal decomposition of the polyester can proceed sufficiently. The water content is more preferably 150 parts by weight or more, still more preferably 200 parts by weight or more. On the other hand, the water content is more preferably 800 parts by weight or less, still more preferably 600 parts by weight or less. Note that the water content in the first aspect refers to the content at the time when the reaction temperature reaches 200°C. Also, the water content in the second aspect refers to the content at the time when the reaction temperature exceeds 135°C.

[0048] In the second aspect of the present invention, in the hydrothermal decomposition step, the weight (g) of water / the weight (g) of alcohol is preferably 0.1 or more and 100 or less. By controlling within this range, the hydrothermal decomposition of the polyester component proceeds, and the acrylic component and / or the silicone component are decomposed to be solubilized or reduced in molecular weight, so that the dicarboxylic acid and diol, which are polyester monomers, can be recovered in a high yield. The weight (g) of water / the weight (g) of alcohol is more preferably 1.0 or more, still more preferably 3.0 or more. On the other hand, the weight (g) of water / the weight (g) of alcohol is more preferably 70 or less, still more preferably 50 or less.

[0049] In the first aspect of the method for producing a dicarboxylic acid and / or a diol of the present invention, the pressure at a temperature of 180°C or higher and 350°C or lower is preferably 1.0 to 30 MPa. In the second aspect, the pressure at a temperature exceeding 135°C and 350°C or lower is preferably 0.3 to 30 MPa. Depending on each aspect, by setting the pressure within this range, the hydrothermal decomposition of the polyester composition proceeds, and the acrylic component and / or the silicone component are decomposed to be solubilized or have a lower molecular weight, and the dicarboxylic acid and diol, which are polyester monomers, can be recovered in a high yield. The pressure in the first aspect is more preferably 1.1 MPa or higher, and even more preferably 2.0 MPa or higher. On the other hand, the pressure is more preferably 25 MPa or lower, and even more preferably 20 MPa or lower. Also, the pressure in the second aspect is more preferably 0.5 MPa or higher, and even more preferably 2.0 MPa or higher. On the other hand, it is more preferably 25 MPa or lower, and even more preferably 20 MPa or lower.

[0050] In the present invention, in the method for producing a dicarboxylic acid and / or a diol having a step including acid crystallization after the step of hydrothermal decomposition, the total amount of the acrylic component and the silicone component in the dicarboxylic acid obtained is preferably 0.1% by weight or less. By setting it within the above range, crosslinking and polymerization inhibition due to impurity mixing can be avoided during repolymerization. The total amount of the acrylic component and the silicone component is more preferably 0.08% by weight or less, even more preferably 0.05% by weight or less, and most preferably zero.

[0051] In the method for producing a dicarboxylic acid and / or a diol of the present invention, various known reaction methods such as batch type and continuous type can be employed for the hydrothermal decomposition of a polyester composition containing an acrylic component and / or a silicone component. Examples of the apparatus used when adopting the batch type include an autoclave equipped with a stirrer and a heating function, a vertical or horizontal reactor, and a vertical or horizontal reactor equipped with a compression mechanism such as a cylinder in addition to a stirrer and a heating function. Examples of the apparatus used when adopting the continuous type include an extruder equipped with a heating function, a tubular reactor, a tubular reactor equipped with a mixing mechanism such as a baffle, a line mixer, a vertical or horizontal reactor, a vertical or horizontal reactor equipped with a stirrer, and a tower.

[0052] The atmosphere in the hydrothermal decomposition step is preferably a non-oxidizing atmosphere, more preferably an inert atmosphere such as nitrogen, helium, and argon, and even more preferably a nitrogen atmosphere from the viewpoints of economy and ease of handling.

[0053] In the method for producing a dicarboxylic acid and / or a diol according to the present invention, after the step of hydrothermal decomposition, there is a step including acid crystallization, and it is preferable that the total amount of the acrylic component and the silicone component in the dicarboxylic acid after the step including acid crystallization is 0.1% by weight or less. The preferable range of the total amount of the acrylic component and the silicone component in the dicarboxylic acid is as described above. The dicarboxylic acid salt generated by hydrothermal decomposition can be converted into a dicarboxylic acid by acid crystallization. In the present invention, since the acrylic component and / or the silicone component is solubilized or depolymerized after hydrothermal decomposition, separation from the dicarboxylic acid salt and the diol becomes easy. On the other hand, when the decomposition of the acrylic component and / or the silicone component is insufficient and the viscosity is high, the dicarboxylic acid salt and the diol are incorporated into the acrylic component and the silicone component, and it becomes difficult to recover the polyester monomer in a high yield. As a method for separating and purifying each component from the reaction mixture after hydrothermal decomposition, for example, it can be achieved by combining known methods such as solvent extraction, solid-liquid separation, distillation, and crystallization. The present invention is particularly effective when recovering a dicarboxylic acid by a step including acid crystallization after hydrothermal decomposition.

[0054] Acid crystallization is a step of converting and recovering terephthalic acid by adding an acid to a dicarboxylic acid salt such as an alkali metal salt or an alkaline earth metal salt of the dicarboxylic acid contained in the reaction mixture. The acid used here is not particularly limited as long as it can neutralize an alkali, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, and phosphoric acid. By setting the addition amount of this acid to be equal to or more than the amount necessary for neutralizing the alkali component used in hydrothermal decomposition, the dicarboxylic acid can be recovered in a high yield. In order to further purify the dicarboxylic acid, methods such as washing the recovered dicarboxylic acid with water or an organic solvent, dissolving the dicarboxylic acid in a solvent in which it dissolves and recrystallizing, esterifying the dicarboxylic acid to convert it into a dialkyl dicarboxylate, distillation purification, and then converting it back into the dicarboxylic acid can be mentioned.

[0055] In addition, as a method for purifying the diol, it can be combined with purification methods such as precision distillation, vacuum distillation with the addition of a small amount of sodium hydroxide, activated carbon treatment, ion exchange treatment, and recrystallization. By these methods, impurities that are difficult to separate by distillation separation can also be efficiently removed.

[0056] The method for producing a polyester according to the present invention includes a step of polymerizing a dicarboxylic acid and / or a diol obtained by the method for producing a dicarboxylic acid and / or a diol according to the present invention to obtain a polyester. The step of obtaining the polyester can produce a polyester, for example, through a first step consisting of an esterification reaction between a dicarboxylic acid and a diol, followed by a second step of polycondensation reaction. Further, for example, a polyester can also 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 polycondensation reaction.

[0057] In the present invention, it is preferable that the polyester composition is a polyester film containing an acrylic component and / or a silicone component, and more preferably a polyester film coated with an acrylic component and / or a silicone component. By using the present invention, even if the functional layer of the acrylic component and / or the silicone component is not removed in advance from a laminated film or the like, or even if a trace amount of the functional layer remains, it can be depolymerized simultaneously with the polyester. Other examples of the polyester composition include blended fibers of acrylic fibers and polyester fibers. By depolymerizing the waste of the polyester composition to obtain monomers and then repolymerizing them to regenerate the polyester, resources can be recycled and the emission of greenhouse gases can be reduced.

[0058] The polyester of the present invention is obtained by polymerizing the dicarboxylic acid and / or diol of the present invention. Further, the fiber, film, or resin molded article of the present invention is obtained by processing the polyester of the present invention. Examples of methods for processing the polyester of the present invention to obtain the fiber or film of the present invention include melt spinning, melt film formation, and melt extrusion molding. Examples of methods for processing the polyester of the present invention to obtain the resin molded article of the present invention include injection molding, blow molding, and extrusion molding. These fibers, films, and resin molded articles are useful as agricultural materials, horticultural materials, fishery materials, civil engineering and construction materials, industrial films, sheets, stationery, medical supplies, clothing, automotive parts, electrical and electronic parts, or other applications.

Examples

[0059] Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[0060] The following commercially available raw materials were used as the polyester composition in each example.

[0061] [Raw materials] Raw material A: NSA32T (a PET film manufactured by Sun Ace Chemical Research Co., Ltd., with an acrylic polymer (unknown thickness) coated on one side of a polyethylene terephthalate (PET) substrate with a thickness of 25 μm) Raw material B: No. 31B (total thickness 80 μm) (a PET film manufactured by Nitto Denko Corporation, with an acrylic polymer with a thickness of 30 μm coated on one side of a PET substrate with a thickness of 50 μm) Raw material C: No. 31B (total thickness 53 μm) (a PET film manufactured by Nitto Denko Corporation, with an acrylic polymer with a thickness of 28 μm coated on one side of a PET substrate with a thickness of 25 μm) Raw material D: A mixture of 2.0 g of raw material A and 8.0 g of PET pellets (a polyethylene terephthalate resin (melting point 254 °C) manufactured by Toray Industries, Inc.) Raw material E: PET75X1-V series (a PET film manufactured by Nippa Co., Ltd., with a silicone-based polymer with a thickness of 1 μm or less coated on one side of a PET substrate with a thickness of 75 μm).

[0062] [Content of acrylic component or silicone component in the polyester composition] HFIP (1,1,1,3,3,3 - hexafluoro - 2 - propanol, manufactured by Fujifilm Wako Pure Chemical Corporation, 30 mL) was added to raw material A (1.0 g), and the mixture was stirred at room temperature for 1 hour. The reaction solution was filtered, methanol (100 mL) was added to the filtrate, and reprecipitation was carried out (on the other hand, the filter residue was vacuum - dried at 80 °C overnight. The filter residue was 0.24 g, and since no peak corresponding to the melting point of PET could be confirmed by differential scanning calorimetry, the filter residue was judged to be the acrylic component). This solution was filtered, the filter residue was washed with methanol, and the filter residue was vacuum - dried at 80 °C overnight. When the filter residue was analyzed by NMR, it was confirmed to be PET. 0.76 g of PET was obtained as a white solid.

[0063] For raw materials B to E as well, in the same manner as for raw material A, the content of the PET component and the acrylic component or silicone component was calculated. The results are shown in Table 1.

[0064]

Table 1

[0065] ≪Evaluation method≫ [Yield of ethylene glycol (GC)] The calculation of the ethylene glycol yield (GC) was carried out by gas chromatography measurement. The measurement conditions are as follows. Apparatus: GC - 2010 manufactured by Shimadzu Corporation Column: DB - 5 0.32 mm × 30 m (0.25 μm) manufactured by Agilent Technologies Carrier gas: Helium Detector: Flame ionization detector (FID) Sample: The reaction mixture was concentrated, the dried solid was washed with isopropanol. 10 μL of this isopropanol solution was measured, and diluted with about 10 g of methanol. A gas chromatography measurement sample was prepared by separating and removing the components insoluble in methanol by filtration. Yield of ethylene glycol: Quantified by the absolute calibration curve method, the molar yield of ethylene glycol was calculated with the ethylene glycol residues contained in PET as 100 mol%.

[0066] [Yield of terephthalic acid (HPLC)] The yield of terephthalic acid (HPLC) was calculated by high performance liquid chromatography measurement. The measurement conditions are as follows. Apparatus: LC-10Avp series manufactured by Shimadzu Corporation Column: Mightysil RP-18GP150-4.6 Detector: Photodiode array detector (UV, wavelength 254 nm) Flow rate: 1 mL / min Column temperature: 40 °C Mobile phase: 0.1% aqueous acetic acid solution / acetonitrile Sample: Approximately 0.1 g of the reaction mixture was weighed and diluted with approximately 10 g of water. The high performance liquid chromatography measurement sample was prepared by separating and removing insoluble components by filtration. Terephthalic acid yield: Quantified by the absolute calibration curve method (however, in this example, although terephthalic acid metal salts may be formed after the hydrothermal reaction, they are converted to terephthalic acid by the acid contained in the mobile phase), the molar yield of terephthalic acid was calculated with the terephthalic acid residues contained in the PET mixture as 100 mol%.

[0067] [Appearance of the reaction mixture after hydrothermal reaction] After the hydrothermal reaction, 20.0 g of deionized water was added to the reaction mixture, and the presence or absence of insolubles was visually confirmed and evaluated according to the following criteria. A: No insoluble components can be confirmed in the reaction mixture. B: Insoluble components can be confirmed in the reaction mixture.

[0068] [Total amount of acrylic and silicone components contained in terephthalic acid] The terephthalic acid recovered from the reaction mixture after hydrothermal decomposition through a purification process including an acid crystallization step was dissolved in N,N-dimethylformamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and the solution was filtered to separate insoluble matters. The insoluble matters were vacuum dried at 80 °C for 8 hours to measure the weight of the insoluble matters, and the total amount of the acrylic component and the silicone component contained in the terephthalic acid was calculated. Total amount (wt%) of acrylic component and silicone component = weight of insoluble matters (g) / weight of the above terephthalic acid (g) × 100.

[0069] [Example 1] As shown in Table 2, raw material A, deionized water, and sodium hydroxide were added to an autoclave made of SUS316L equipped with a stirrer. The nitrogen replacement in the reaction vessel was carried out, and under nitrogen pressurization of 0.5 MPa and sealed, it was stirred at 200 rpm at the temperature and for the time shown in Table 2. The pressure inside the system during the reaction was as shown in Table 2. After the reaction, it was cooled to room temperature, and the reaction mixture was recovered. The results of analyzing the reaction mixture are shown in Table 2.

[0070] [Example 2] Raw material E was hydrothermally decomposed in exactly the same manner as in Example 1, except that the type of polyester composition and the addition amount of sodium hydroxide were changed. The results are shown in Table 2. [Comparative Examples 1 and 2] Raw material A or raw material E was hydrothermally decomposed in exactly the same manner as in Example 1 or 2, except that sodium hydroxide was not added. The results are shown in Table 2.

[0071]

Table 2

[0072] *: The insoluble acrylic component or silicone component adheres to the terephthalic acid, and it is impossible to calculate the yield of terephthalic acid alone.

[0073] By comparing Example 1 with Comparative Example 1 and Example 2 with Comparative Example 2, it can be seen that by adding sodium hydroxide, the acrylic component or the silicone component can be solubilized or reduced in molecular weight, and terephthalic acid (sodium terephthalate is formed in Examples 1 and 2), which is a monomer of PET, and ethylene glycol can be obtained in high yields. In Comparative Examples 1 and 2, terephthalic acid adhered to the acrylic component or silicone component that is insoluble in water and was incorporated inside, so the yield could not be calculated.

[0074] [Examples 3 - 5] Except for changing the addition amount of the polyester composition and the addition amount of sodium hydroxide, raw materials A and E were hydrothermally decomposed in the same manner as in Example 1. The results are shown in Table 3.

[0075]

Table 3

[0076] From Examples 1 and 3 - 5, it can be seen that by setting the water content relative to 100 parts by weight of raw material A to a specific amount, terephthalic acid and ethylene glycol can be obtained in high yields.

[0077] [Examples 6 - 8 and Comparative Example 3] Except for changing the reaction temperature, raw material A was hydrothermally decomposed in the same manner as in Example 1. The results are shown in Table 4.

[0078]

Table 4

[0079] By comparing Examples 1, 6 - 8 with Comparative Example 3, it can be seen that by setting the reaction temperature to a specific temperature or higher, terephthalic acid and ethylene glycol can be obtained in high yields.

[0080] [Examples 9 - 12] Except for changing the type and addition amount of the metal salt, raw material A was hydrothermally decomposed in the same manner as in Example 1. The results are shown in Table 5.

[0081]

Table 5

[0082] From Examples 1 and 9 to 12, it can be seen that when an alkali metal salt with pKa > 4.0 such as sodium hydroxide, potassium hydroxide, or sodium carbonate, or an alkaline earth metal salt with pKa > 4.0 such as magnesium hydroxide is used, terephthalic acid and ethylene glycol can be obtained in high yields.

[0083] [Examples 13 and 14] Except for changing the addition amount of sodium hydroxide, raw material A was hydrothermally decomposed in the same manner as in Example 1. The results are shown in Table 6.

[0084]

Table 6

[0085] By comparing Examples 1, 13, and 14, it can be seen that by setting the metal salt to a specific amount or more, terephthalic acid and ethylene glycol can be obtained in high yields. The reason for the slightly lower terephthalic acid yield in Example 13 is presumably that the content of sodium hydroxide was low, and a part of the terephthalic acid produced after the hydrothermal decomposition of raw material A could not be converted into water-soluble disodium terephthalate.

[0086] [Examples 15 to 17] Except for changing the type of polyester composition, the polyester composition was hydrothermally decomposed in the same manner as in Example 1. The results are shown in Table 7.

[0087]

Table 7

[0088] From Example 1 and Examples 15 to 17, it can be seen that by setting a specific amount of the acrylic component, the insoluble acrylic component is solubilized in water, and terephthalic acid and ethylene glycol can be obtained in high yields.

[0089] [Example 18] Into an SUS316L autoclave equipped with a stirrer, raw material A, deionized water, ethylene glycol, and sodium hydroxide were added as shown in Table 8. The nitrogen replacement in the reaction vessel was carried out, and under nitrogen pressurization of 0.5 MPa, it was stirred at 200 rpm at the temperature and for the time shown in Table 8 under sealing. During the reaction, the pressure in the system was as shown in Table 8. After the reaction, it was cooled to room temperature, and the reaction mixture was recovered. The results of analyzing the reaction mixture are shown in Table 8.

[0090] [Examples 19 to 21] Raw material A was hydrothermally decomposed in exactly the same manner as in Example 18, except that ethylene glycol was changed to 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 8.

[0091]

Table 8

[0092] From Examples 18 to 21, it can be seen that when alcohols such as ethylene glycol, 2-propanol, and tert-butyl alcohol are blended, the polyester component is hydrothermally decomposed at a lower temperature, the acrylic component is solubilized in water, and terephthalic acid and ethylene glycol can be obtained in high yields.

[0093] [Examples 22, 23] Raw material A was hydrothermally decomposed in exactly the same manner as in Example 18, except that the reaction temperature was changed. The results are shown in Table 9.

[0094]

Table 9

[0095] From Examples 18, 22, and 23, it can be seen that by setting the reaction temperature to a specific temperature or higher, terephthalic acid and ethylene glycol can be obtained in high yields.

[0096] [Example 24] Into a SUS316L autoclave equipped with a stirrer, raw material E, deionized water, ethylene glycol, and sodium hydroxide were added as shown in Table 10. The nitrogen in the reaction vessel was replaced, and under nitrogen pressure of 0.5 MPa and sealed, stirring was carried out at 200 rpm at the temperature and for the time shown in Table 10. During the reaction, the pressure in the system was as shown in Table 10. After the reaction, it was cooled to room temperature, and the reaction mixture was recovered. The results of analyzing the reaction mixture are shown in Table 9.

[0097] [Example 25] Except for changing the reaction temperature, raw material E was hydrothermally decomposed in exactly the same manner as in Example 24. The results are shown in Table 10.

[0098]

Table 10

[0099] From Examples 24 and 25, it can be seen that even in raw material E containing a silicone component, terephthalic acid and ethylene glycol can be obtained in high yields at a specific temperature or higher.

[0100] [Example 26] The reaction mixture obtained by repeating the operation of hydrothermally decomposing raw material A three times in exactly the same manner as in Example 1 was filtered. The filtrate was distilled under reduced pressure to distill off water and ethylene glycol. 150 mL of water was added to the residue to dissolve the residue, and further 4.0 g of an aluminum-based flocculant was added. After stirring at room temperature for 3 hours, it was allowed to stand overnight. The solution was filtered to remove the flocs, and then subjected to activated carbon treatment and subsequently ion exchange treatment. 1M hydrochloric acid was added to the solution for acid crystallization, and the filtrate was recovered as terephthalic acid. The results of analyzing the terephthalic acid are shown in Table 11.

[0101] [Examples 27 - 29] Terephthalic acid was recovered in the same manner as in Example 26, except that starting material A or starting material E was pyrolyzed in the same manner as in Example 2, 18 or 24. The results of the analysis of the terephthalic acid are shown in Table 11.

[0102] [Table 11]

[0103] From Examples 26 to 29, it can be seen that the total amount of the acrylic component and the silicone component contained in the terephthalic acid is not more than a specific amount.

Claims

1. A dicarboxylic acid and / or a diol obtained by hydrothermally decomposing a polyester composition containing an acrylic component and / or a silicone component and a polyester component at 180° C. or higher and 350° C. or lower in the presence of an alkali component.

2. A dicarboxylic acid and / or a diol obtained by hydrothermally decomposing a polyester composition containing an acrylic component and / or a silicone component and a polyester component at a temperature of more than 135°C and not more than 350°C in the presence of an alcohol and an alkali component.

3. 3. The dicarboxylic acid and / or diol according to claim 1 or 2, wherein the dicarboxylic acid is terephthalic acid.

4. 3. The dicarboxylic acid and / or diol according to claim 1 or 2, wherein the diol is at least one selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,4-butanediol.

5. The dicarboxylic acid and / or diol according to claim 1 or 2, wherein the polyester composition is a polyester film containing an acrylic component and / or a silicone component.

6. A polyester obtained by polymerizing the dicarboxylic acid and / or the diol according to any one of claims 1 to 5.

7. A fiber, film, or resin molded product obtained by processing the polyester according to claim 6.

8. A method for producing a dicarboxylic acid and / or a diol, comprising a step of hydrothermally decomposing a polyester composition containing an acrylic component and / or a silicone component and a polyester component at 180° C. or higher and 350° C. or lower in the presence of an alkali component.

9. 9. The method for producing a dicarboxylic acid and / or a diol according to claim 8, further comprising a step including acid crystallization following the hydrothermal decomposition step, wherein the total amount of an acrylic component and a silicone component in the dicarboxylic acid following the step including acid crystallization is 0.1% by weight or less.

10. A method for producing a dicarboxylic acid and / or a diol, comprising a step of hydrothermally decomposing a polyester composition containing an acrylic component and / or a silicone component and a polyester component at a temperature of more than 135°C and not more than 350°C in the presence of an alcohol and an alkali component.

11. The method for producing a dicarboxylic acid and / or a diol according to claim 10, further comprising a step including acid crystallization subsequent to the hydrothermal decomposition step, wherein the total amount of an acrylic component and a silicone component in the dicarboxylic acid after the step including acid crystallization is 0.1% by weight or less.

12. The method for producing a dicarboxylic acid and / or a diol according to any one of claims 8 to 11, wherein the amount of water is 100 to 1000 parts by weight per 100 parts by weight of the total of the acrylic component, the silicone component, and the polyester component.

13. The method for producing a dicarboxylic acid and / or a diol according to claim 10 or 11, wherein the weight (g) of water / weight (g) of alcohol in the hydrothermal decomposition step is 0.1 or more and 100 or less.

14. The method for producing a dicarboxylic acid and / or a diol according to claim 8 or 9, wherein the pressure at 180° C. or higher and 350° C. or lower is 1.0 to 30 MPa.

15. The method for producing a dicarboxylic acid and / or a diol according to claim 10 or 11, wherein the pressure at a temperature higher than 135° C. and not higher than 350° C. is 0.3 to 30 MPa.

16. The method for producing a dicarboxylic acid and / or a diol according to any one of claims 8 to 11, wherein an alkali component is coexisted in an amount of 25 to 100 parts by weight per 100 parts by weight of the total of the acrylic component, the silicone component, and the polyester component.

17. The method for producing a dicarboxylic acid and / or a diol according to any one of claims 8 to 11, wherein the alkali component is an alkali metal salt and / or an alkaline earth metal salt.

18. The method for producing a dicarboxylic acid and / or a diol according to any one of claims 8 to 11, wherein the alkali component is an alkali metal salt having a pKa > 4.0 and / or an alkaline earth metal salt having a pKa > 4.

0.

19. The method for producing a dicarboxylic acid and / or a diol according to any one of claims 8 to 11, wherein the polyester composition contains 0.1 to 200 parts by weight of an acrylic component and / or a silicone component based on 100 parts by weight of the polyester component.

20. The method for producing a dicarboxylic acid and / or a diol according to any one of claims 8 to 11, wherein the polyester component is selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and copolymers thereof.

21. The method for producing a dicarboxylic acid and / or a diol according to any one of claims 8 to 11, wherein the polyester composition is a polyester film containing an acrylic component and / or a silicone component.

22. A method for producing a polyester, comprising a step of polymerizing a dicarboxylic acid and / or a diol obtained by the method for producing a dicarboxylic acid and / or a diol according to any one of claims 8 to 21.

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