Method of producing terephthalic acid and / or 1,4-butanediol, method of producing polyester, and polyester

Abstract

To obtain 1,4-butanediol and / or terephthalic acid in high yield in solvolysis of polyethylene terephthalate.SOLUTION: A method of producing terephthalic acid and / or 1,4-butanediol includes a process of carrying out solvolysis of polyethylene terephthalate or a composition thereof in the presence of an alkali metal salt and / or an alkali earth metal salt of pKa>4.0, and water in a temperature range including a temperature of 180 to 350°C, where a total mol number of a mol number of an alkali metal atom of the alkali metal salt and / or the alkali earth metal salt of pKa>4.0 and a mol number of two times the mol number of an alkali earth metal atom to one mol of terephthalic acid unit in the polybutylene terephthalate is 1.5 to 6.0 mol.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing terephthalic acid and / or 1,4-butanediol, a method for producing a polyester, and a polyester. [Background technology]

[0002] In recent years, interest in global environmental issues has increased, triggered by the marine plastic problem, and awareness of the need to build a sustainable society is spreading. 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 the rapid development of industry since the Industrial Revolution. Therefore, in order to build a sustainable society, technologies for recycling fossil resources such as plastics and reducing greenhouse gas emissions are becoming increasingly important.

[0003] As a method for hydrothermally decomposing polybutylene terephthalate, a method has been disclosed in which polybutylene terephthalate is brought into contact with high-temperature, high-pressure water to recover terephthalic acid, a raw material monomer, and tetrahydrofuran, a cyclized product of 1,4-butanediol (see, for example, Patent Document 1). A method in which depolymerization is performed using only water has the advantage of being a green recycling method since it does not require a catalyst and does not use organic solvents derived from petroleum.

[0004] In the depolymerization using high-temperature, high-pressure water, a method has been disclosed in which a base is added to the water to recover the raw material monomers, terephthalic acid and 1,4-butanediol (see, for example, Non-Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-215676 A [Non-patent literature]

[0006] [Non-Patent Document 1] POLYMER-PLASTICS TECHNOLOGY AND ENGINEERING,Vol.43,No.1,177-198(2004) [Non-Patent Document 2] Chem.Eng.Technol.27,No.7,790-798(2004) Summary of the Invention [Problem to be solved by the invention]

[0007] According to Patent Document 1, when polybutylene terephthalate is depolymerized with high-temperature, high-pressure water, tetrahydrofuran, which is an over-reaction product of terephthalic acid and 1,4-butanediol, which are monomers, is recovered as the main product. Therefore, the method of Patent Document 1 cannot recycle the product as 1,4-butanediol, which is a raw material for polyester.

[0008] In Non-Patent Documents 1 and 2, the depolymerization of polybutylene terephthalate was insufficient, and the monomer yield was low. [Means for solving the problem]

[0009] In order to solve the above problems, the inventors of the present invention have conducted extensive research and have found that by solvolyzing polybutylene terephthalate or a composition thereof under specific conditions in the presence of a specific metal salt and water, the overreaction of the resulting monomer, 1,4-butanediol, can be suppressed and terephthalic acid and 1,4-butanediol can be obtained in high yields.

[0010] That is, the present invention has the following configuration. (1) A method for producing terephthalic acid and / or 1,4-butanediol, comprising a step of solvolyzing polybutylene terephthalate or a composition thereof in the presence of an alkali metal salt and / or an alkaline earth metal salt having a pKa>4.0 and water in a temperature range including a temperature of 180 to 350°C, wherein the total number of moles of the alkali metal atom of the alkali metal salt and / or alkaline earth metal salt having a pKa>4.0 and 2.0 times the mole number of the alkaline earth metal atom is 1.5 to 6.0 moles per mole of terephthalic acid unit in the polybutylene terephthalate. (2) A method for producing terephthalic acid and / or 1,4-butanediol, comprising a step of solvolyzing polybutylene terephthalate or a composition thereof in the presence of an alkali metal salt and / or an alkaline earth metal salt having a pKa>4.0, water, and an alcohol in a temperature range including temperatures of 110 to 350°C, wherein the total number of moles of the alkali metal atoms of the alkali metal salt and / or alkaline earth metal salt having a pKa>4.0 and 2.0 times the number of moles of the alkaline earth metal atoms is 1.5 to 6.0 moles per mole of terephthalic acid unit in the polybutylene terephthalate. (3) The method for producing terephthalic acid and / or 1,4-butanediol according to (1) or (2) above, wherein the solvent is contained in an amount of 100 to 1,000 parts by weight per 100 parts by weight of polybutylene terephthalate. (4) The method for producing terephthalic acid and / or 1,4-butanediol according to (1) above, wherein the pressure at a temperature of 180 to 350° C. is 1.2 to 30 MPa. (5) The method for producing terephthalic acid and / or 1,4-butanediol according to (2) above, wherein the pressure at a temperature of 110 to 350° C. is 0.1 to 30 MPa. (6) The method for producing terephthalic acid and / or 1,4-butanediol according to (1) or (2) above, wherein the alkali metal salt is at least one selected from the group consisting of alkali metal hydroxides and alkali metal carbonates. (7) The method for producing terephthalic acid and / or 1,4-butanediol according to the above (1) or (2), wherein the alkaline earth metal salt is at least one selected from the group consisting of alkaline earth metal hydroxides and alkaline earth metal carbonates. (8) The method for producing terephthalic acid and / or 1,4-butanediol according to (1) or (2) above, in which the yield of 1,4-butanediol is 30% or more. (9) The method for producing terephthalic acid and / or 1,4-butanediol according to (1) or (2) above, wherein polybutylene terephthalate or a composition thereof is a waste product. (10) A method for producing polyester, comprising a step of polymerizing terephthalic acid and / or 1,4-butanediol obtained by the method for producing terephthalic acid and / or 1,4-butanediol according to any one of (1) to (9) above. (11) A polyester obtained by polymerizing terephthalic acid and / or 1,4-butanediol obtained by the method for producing terephthalic acid and / or 1,4-butanediol according to any one of (1) to (9) above. (12) A fiber, film, or resin molded product obtained by processing the polyester described in (11) above. Effect of the Invention

[0011] According to the present invention, in the solvolysis of polybutylene terephthalate, tetrahydrofuran, which is an over-reacted product of 1,4-butanediol, can be significantly reduced to obtain 1,4-butanediol and / or terephthalic acid. The 1,4-butanediol and / or terephthalic acid can then be polymerized to obtain polyester. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will now be described in further detail.

[0013] A first embodiment of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention is a method for producing terephthalic acid and / or 1,4-butanediol, comprising a step of solvolyzing polybutylene terephthalate or a composition thereof in the presence of an alkali metal salt and / or alkaline earth metal salt having a pKa>4.0 and water in a temperature range including a temperature of 180 to 350°C, in which the total number of moles of the alkali metal atoms of the alkali metal salt and / or alkaline earth metal salt having a pKa>4.0 and 2.0 times the number of moles of the alkaline earth metal atoms is 1.5 to 6.0 moles per mole of terephthalic acid unit in polybutylene terephthalate.

[0014] The second aspect of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention is a method for producing terephthalic acid and / or 1,4-butanediol, which comprises a step of solvolyzing polybutylene terephthalate or a composition thereof in the presence of an alkali metal salt and / or an alkaline earth metal salt having a pKa>4.0, water, and an alcohol at a temperature range including a temperature of 110 to 350°C, and the total number of moles of the alkali metal atom of the alkali metal salt and / or alkaline earth metal salt having a pKa>4.0 and 2.0 times the number of moles of the alkaline earth metal atom is 1.5 to 6.0 moles per mole of terephthalic acid unit in polybutylene terephthalate. In this specification, the "first aspect of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention" may be simply referred to as the "first aspect", and the "second aspect of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention" may be simply referred to as the "second aspect".

[0015] The polybutylene terephthalate used in the present invention is a polymer or copolymer containing, as structural units, a residue of a dicarboxylic acid or its ester-forming derivative, which has a residue of terephthalic acid as the main structural unit, and a residue of a diol or its ester-forming derivative, which has a residue of 1,4-butanediol as the main structural unit. Here, the term "residue" refers to a structural unit derived from a certain (co)polymerization component in the polymer. In addition, "main structural unit" refers to the presence of at least one selected from the group consisting of residues of terephthalic acid and its ester-forming derivatives, and at least one selected from the group consisting of residues of 1,4-butanediol and its ester-forming derivatives, each of which accounts for 25 mol% or more of all structural units, and it is preferable to have them at 40 mol% or more.

[0016] Other dicarboxylic acids or ester-forming derivatives thereof, and / or other diols or ester-forming derivatives thereof can also be used as copolymerization components with terephthalic acid and / or 1,4-butanediol. In this case, examples of the other dicarboxylic acid or its ester-forming derivative include aromatic dicarboxylic acids such as 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, and 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, and dimer acid; alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, and ester-forming derivatives thereof.

[0017] The ester-forming derivatives referred to here are the alkyl esters, acid anhydrides, acid halides, etc. of the dicarboxylic acids mentioned above. As the alkyl esters of dicarboxylic acids, methyl esters, ethyl esters, hydroxyethyl esters, hydroxybutyl esters, etc. are preferably used. As the acid anhydrides of dicarboxylic acids, anhydrides of dicarboxylic acids and anhydrides of dicarboxylic acids and acetic acid, etc. are preferably used. As the halides of dicarboxylic acids, acid chlorides, acid bromides, acid iodides, etc. are preferably used.

[0018] Examples of the other diols or ester-forming derivatives thereof include aliphatic or alicyclic glycols having 2 to 20 carbon atoms, such as ethylene glycol, propylene glycol, 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.

[0019] Examples of copolymers using other dicarboxylic acids or their ester-forming derivatives, and / or other diols or their ester-forming derivatives as copolymerization components include aromatic polyester resins such as polybutylene terephthalate / naphthalate, polybutylene terephthalate / decanedicarboxylate, polybutylene terephthalate / 5-sodium sulfoisophthalate, polybutylene terephthalate / polyethylene terephthalate, polybutylene terephthalate / polyethylene glycol, polybutylene terephthalate / polytetramethylene glycol, polybutylene terephthalate / isophthalate / polytetramethylene glycol, polybutylene terephthalate / succinate, polybutylene terephthalate / adipate, and polybutylene terephthalate / sebacate.

[0020] Here, " / " indicates a copolymer. These copolymers may be used alone or in combination of two or more at any content. The content of these copolymer components is preferably 50 mol % or less, more preferably 20 mol % or less, based on the total structural units.

[0021] In the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the polybutylene terephthalate composition may contain a polymer other than polybutylene terephthalate. For example, polyamide, polyethylene terephthalate, polypropylene terephthalate, polycarbonate, polyolefin, modified polyphenylene ether, polyurethane, polysulfone, polyketone, polyetherimide, polyarylate, polyethersulfone, polyetherketone, polythioetherketone, polyetheretherketone, polyimide, polyamideimide, polyethylene tetrafluoride, polyphenylene sulfide, etc. may be included. Two or more of these may be included. The polymer other than polybutylene terephthalate is preferably 50 parts by weight or less relative to 100 parts by weight of the polymer component in the polybutylene terephthalate composition. More preferably, it is 40 parts by weight or less, and even more preferably, it is 30 parts by weight or less.

[0022] In addition to the polymer, the polybutylene terephthalate composition may contain additives such as fillers, nucleating agents, plasticizers, UV-resistant agents, release agents, flame retardants, colorants (e.g., pigments or dyes), lubricants, antistatic agents, and antioxidants.

[0023] Examples of the filler include glass fibers, carbon fibers, potassium titanate whiskers, zinc oxide whiskers, aluminum borate whiskers, aramid fibers, alumina fibers, silicon carbide fibers, ceramic fibers, asbestos fibers, gypsum fibers, metal fibers, glass sheets, 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, dolomite, calcium sulfate, barium sulfate, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, glass beads, hollow glass beads, ceramic beads, boron nitride, silicon carbide, and wollastonite.

[0024] From the viewpoint of the separability after solvolysis, the fibrous filler is preferably glass fiber or carbon fiber. The cross-sectional shape of the fibrous filler is not particularly limited, and may be either a circular or flat fiber. In the present invention, the content of the fibrous filler in the polybutylene terephthalate composition is preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less in the composition.

[0025] In the present invention, an alkali metal salt and / or an alkaline earth metal salt having a pKa>4.0 is blended with polybutylene terephthalate or a composition thereof. The pKa here is the acid dissociation constant of the alkali metal salt and / or the alkaline earth metal salt at 25°C. Some alkali metal salts and alkaline earth metal salts have multiple pKas, but in the present invention, it is necessary that all pKas exceed 4.0. By making the pKa>4.0, the solvolysis of polybutylene terephthalate can be promoted and the yield of terephthalic acid and 1,4-butanediol can be improved. The pKa of the alkali metal salt and / or the alkaline earth metal salt is more preferably 6.0 or more, and even more preferably 10.0 or more. On the other hand, the pKa of the alkali metal salt and / or the alkaline earth metal salt is preferably 16.0 or less, and more preferably 15.0 or less.

[0026] Examples of the alkali metal salt 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 hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and cesium hydrogen carbonate; alkali metal phosphates such as lithium phosphate, sodium phosphate, potassium phosphate, cesium phosphate, dilithium hydrogen phosphate, dipotassium hydrogen phosphate, dicesium hydrogen phosphate, lithium monohydrogen phosphate, sodium monohydrogen phosphate, potassium monohydrogen phosphate, and cesium monohydrogen phosphate; and alkali metal borates such as lithium borate, sodium borate, potassium borate, and cesium borate. Among them, 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, and cesium carbonate are more preferable.

[0027] Examples of the alkaline earth metal salt include alkaline earth metal hydroxides such as magnesium hydroxide, calcium hydroxide, and barium hydroxide, alkaline earth metal carbonates such as magnesium carbonate, calcium carbonate, and 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, and dibarium hydrogen phosphate, and alkaline earth metal borates such as magnesium borate, calcium borate, and 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, and barium carbonate are more preferable.

[0028] Of the above alkali metal salts or alkaline earth metal salts, sodium hydrogencarbonate (pKa=6.6), sodium carbonate (pKa=6.6, 10.3), sodium dihydrogenphosphate (pKa=7.2), disodium hydrogenphosphate (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, with sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogencarbonate, sodium carbonate, and magnesium hydroxide being more preferred, and sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, and magnesium hydroxide being even more preferred.

[0029] In the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the total number of moles of the alkali metal atom of the alkali metal salt and / or alkaline earth metal salt having pKa>4.0 and the number of moles 2.0 times the number of moles of the alkaline earth metal atom is 1.5 to 6.0 moles. By setting the total number of moles in this range, the solvolysis of polybutylene terephthalate can be promoted, and the overreaction of the monomer can be suppressed, thereby improving the yield of terephthalic acid and 1,4-butanediol. The total number of moles is more preferably 1.7 moles or more, and even more preferably 1.9 moles or more. On the other hand, the total number of moles is more preferably 5.0 moles or less, even more preferably 4.0 moles or less, and particularly preferably 3.0 moles or less. In the first embodiment of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the total number of moles refers to the total number of moles at the time when the reaction temperature reaches 180°C. In the second embodiment, the total number of moles refers to the total number of moles at the time when the reaction temperature reaches 110°C.

[0030] The first embodiment of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention has a step of solvolyzing polybutylene terephthalate or a composition thereof in a temperature range including a temperature of 180 to 350°C. By carrying out solvolysis in which the temperature range of the reaction temperature includes all or part of the temperature range of 180 to 350°C, the solvolysis of polybutylene terephthalate is promoted, and the overreaction of monomers is suppressed, and the yield of terephthalic acid and 1,4-butanediol can be improved. The temperature is more preferably 190°C or higher, even more preferably 210°C or higher, particularly preferably 230°C or higher, and even more particularly preferably 250°C or higher. On the other hand, the temperature is more preferably 320°C or lower, and even more preferably 300°C or lower. When the reaction temperature of solvolysis is 350°C or lower, the overreaction of monomers is suppressed, and the yield of terephthalic acid and 1,4-butanediol tends to be improved, so it is preferable to set the reaction temperature of solvolysis to 350°C or lower in the entire temperature range of the reaction temperature of solvolysis.

[0031] In the second embodiment of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the reaction is carried out in the presence of water and alcohol, so that solvolysis can be carried out at 110°C to 350°C. The reason why solvolysis can be carried out at a lower temperature in the presence of water and alcohol is unclear, but it is presumed that, for example, a metal alkoxide produced by deprotonating a part of the alcohol with an alkali becomes a strong alkali, so that solvolysis of polybutylene terephthalate or a composition thereof can be carried out at a lower temperature. The temperature is preferably 120°C or higher, more preferably 140°C or higher. On the other hand, the temperature is preferably 320°C or lower, more preferably 300°C or lower.

[0032] 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; aliphatic dihydric alcohols having 2 to 10 carbon atoms, such as ethylene glycol, propylene glycol, and 1,4-butanediol; and aliphatic trihydric alcohols having 3 to 10 carbon atoms, such as glycerol. These alcohols may be used alone or in combination of two or more at any content. However, the alcohol used in the present invention does not include 1,4-butanediol produced by decomposition of polybutylene terephthalate.

[0033] The alcohol is preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, isobutanol, tert-butyl alcohol, and 1,4-butanediol. When methanol, ethanol, 1-propanol, 2-propanol, isobutanol, or tert-butyl alcohol is used as the alcohol, it can be easily separated from 1,4-butanediol produced by decomposition of polybutylene terephthalate in the purification step after solvolysis. When 1,4-butanediol is used as the alcohol, it can be recovered simultaneously with 1,4-butanediol produced by decomposition of polybutylene terephthalate.

[0034] In the second embodiment of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the weight (g) of water / weight (g) of alcohol is preferably 0.1 or more and 100 or less. By setting it in this range, the solvolysis of polybutylene terephthalate is promoted, and the over-reaction of the product is suppressed, so that terephthalic acid and 1,4-butanediol can be obtained in high yields. The weight of water / weight of alcohol is more preferably 1.0 or more, and even more preferably 3.0 or more. On the other hand, the weight of water / weight of alcohol is more preferably 70.0 or less, and even more preferably 50.0 or less.

[0035] In the solvolysis step, the reaction time is preferably 1 to 120 minutes. The reaction time is more preferably 5 minutes or more, and even more preferably 10 minutes or more. On the other hand, it is more preferably 60 minutes or less, and even more preferably 30 minutes or less. In the first embodiment of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the reaction time refers to the time during which the reaction temperature is 180°C or more. In the second embodiment, the reaction time refers to the time during which the reaction temperature is 110°C or more.

[0036] In the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, it is preferable to contain 100 to 1000 parts by weight of the solvent relative to 100 parts by weight of polybutylene terephthalate. The solvent used in the present invention may be a water solvent alone, a mixed solvent of water and the above-mentioned alcohol, or the above-mentioned solvent may further contain another solvent. By containing 100 to 1000 parts by weight of the solvent, it is possible to obtain 1,4-butanediol in a higher yield while suppressing the consumption of energy for heating the solvent and suppressing the environmental load. The content of the solvent is more preferably 150 parts by weight or more, more preferably 200 parts by weight or more. On the other hand, it is more preferably 800 parts by weight or less, and more preferably 600 parts by weight or less. In the first embodiment of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the content of the solvent refers to the content at the time when the reaction temperature reaches 180° C. In addition, in the second embodiment, the content of the solvent refers to the content at the time when the reaction temperature reaches 110° C.

[0037] In the first embodiment of the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the pressure at a temperature of 180 to 350°C is preferably 1.2 to 30 MPa. In the second embodiment, the pressure at a temperature of 110 to 350°C is preferably 0.1 to 30 MPa. By setting the pressure within this range according to each embodiment, the solvolysis of polybutylene terephthalate is promoted, and the overreaction of the product is suppressed, so that the yield of terephthalic acid and 1,4-butanediol can be further improved. In the first embodiment, the pressure is more preferably 2.0 MPa or more, and more preferably 4.5 MPa or more. On the other hand, it is more preferably 25 MPa or less, and more preferably 20 MPa or less. In the second embodiment, the pressure is more preferably 0.3 MPa or more, and more preferably 2.0 MPa or more. On the other hand, it is more preferably 25 MPa or less, and more preferably 20 MPa or less.

[0038] In the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, various known reaction methods such as batch and continuous methods can be used for the solvolysis of polybutylene terephthalate or a composition thereof. Examples of the apparatus used in the batch method include an autoclave equipped with a stirrer and a heating function, a vertical or horizontal reactor, a vertical or horizontal reactor equipped with a compression mechanism such as a cylinder in addition to a stirrer and a heating function, and the like. Examples of the apparatus used in the continuous method 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, a tower, and the like.

[0039] 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 standpoint of economy and ease of handling.

[0040] In the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, the 1,4-butanediol yield is preferably 30% or more. The 1,4-butanediol yield is more preferably 50% or more, and even more preferably 80% or more. The upper limit of the yield of 1,4-butanediol is not particularly limited, but is preferably 100%. Here, the 1,4-butanediol yield refers to the yield in the reaction mixture. The reaction mixture refers to a reaction mixture of an alkali metal salt of terephthalic acid and / or an alkaline earth metal salt of terephthalic acid obtained by solvolysis of polybutylene terephthalate or a composition thereof, and 1,4-butanediol. The method for producing terephthalic acid and / or 1,4-butanediol of the present invention can solve the problem of low yield of 1,4-butanediol, which could not be solved by conventional hydrothermal reaction, and therefore can obtain a high 1,4-butanediol yield as described above.

[0041] Separation and purification of each component from the reaction mixture of the alkali metal salt of terephthalic acid and / or the alkaline earth metal salt of terephthalic acid obtained by solvolysis and 1,4-butanediol can be achieved by combining known methods such as solvent extraction, solid-liquid separation, distillation, crystallization, etc. The alkali metal salt of terephthalic acid and / or the alkaline earth metal salt of terephthalic acid can be converted to terephthalic acid by adding an acid such as hydrochloric acid and recovered. In order to purify terephthalic acid, a method of washing the recovered terephthalic acid with water or an organic solvent, a method of recrystallization, etc. can be used.

[0042] Methods for purifying 1,4-butanediol include a method of subjecting recovered 1,4-butanediol to precision distillation, a method of adding a small amount of sodium hydroxide and distilling under reduced pressure, and the like.

[0043] In the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, when additives and the like are contained in the polybutylene terephthalate or the composition thereof, they can be removed by a method such as activated carbon treatment, coagulation sedimentation treatment, ion exchange treatment, etc. in the above-mentioned separation and purification process.

[0044] In the method for producing terephthalic acid and / or 1,4-butanediol of the present invention, polybutylene terephthalate or a composition thereof may be a waste. The waste is preferably a waste of a composition containing at least polybutylene terephthalate. Examples of waste of a composition containing polybutylene terephthalate include polybutylene terephthalate products, industrial waste generated in the production process of polybutylene terephthalate, and used waste of polybutylene terephthalate products. Examples of polybutylene terephthalate products include resin molded products such as automobile parts, electric and electronic parts, building parts, various containers, daily necessities, household goods, and sanitary products, fibers, films, and sheets. In addition, product scraps, pellet scraps, and lump scraps generated in these production processes are also subject to waste. Waste of resin molded bodies, fibers, films, and sheets containing polybutylene terephthalate may be subjected to the depolymerization method of the present invention together with products other than polybutylene terephthalate or its composition within a range that does not impair the effects of the present invention.

[0045] The method for producing the polyester of the present invention includes a step of polymerizing terephthalic acid and / or 1,4-butanediol obtained by the method for producing terephthalic acid and / or 1,4-butanediol of the present invention. The polyester of the present invention is also obtained by polymerizing terephthalic acid and / or 1,4-butanediol obtained by the method for producing terephthalic acid and / or 1,4-butanediol of the present invention. The terephthalic acid and / or 1,4-butanediol obtained by the method for producing terephthalic acid and / or 1,4-butanediol of the present invention can be used as a polymerization raw material for polyester, similar to 1,4-butanediol and terephthalic acid produced from petroleum-derived raw materials. The polyester of the present invention can be produced, for example, by subjecting 1,4-butanediol and / or terephthalic acid to a known polycondensation reaction as it is or as an ester-forming derivative thereof.

[0046] The polyester of the present invention, like polyesters produced from petroleum-derived raw materials, can be processed and used into various products such as fibers, films, bottles, sheets, resin molded products, etc. These products are suitably used as agricultural materials, horticultural materials, fishing materials, civil engineering and construction materials, clothing materials, stationery, medical supplies, automobile parts, automobile interior parts, electric and electronic parts, and other applications.

[0047] The fiber, film, or resin molded article of the present invention is obtained by processing the polyester of the present invention. Examples of the method 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 the method 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, fishing materials, civil engineering and construction materials, industrial films, sheets, stationery, medical supplies, clothing, automotive parts, electric and electronic parts, and other applications. EXAMPLES

[0048] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0049] The following raw materials were used in each example. PBT: Commercially available polybutylene terephthalate pellets, melting point 224°C PET: Commercially available polyethylene terephthalate pellets, melting point 254°C PBT composition: Molded product of polybutylene terephthalate composition containing 30% by weight of glass fiber

[0050] Here, the melting point was determined as the temperature of an endothermic peak that appeared when polybutylene terephthalate or polyethylene terephthalate was cooled from a molten state to 30° C. at a rate of 20° C. / min in a nitrogen gas atmosphere using a differential scanning calorimeter, and then heated to the melting point + 40° C. at a rate of 20° C. / min. However, when two or more endothermic peaks were detected, the temperature of the endothermic peak with the greatest peak intensity was determined as the melting point.

[0051] Evaluation method (1,4-butanediol, tetrahydrofuran and ethylene glycol yields (GC)) The yields of 1,4-butanediol, tetrahydrofuran and ethylene glycol (GC) were calculated by gas chromatography under the following measurement conditions. Equipment: Shimadzu GC-2010 Column: Agilent Technologies DB-5 0.32mm x 30m (0.25μm) Carrier gas: Helium Detector: Flame ionization detector (FID) Sample: Approximately 1.2 g of the reaction mixture was weighed out and diluted with approximately 5 g of methanol. Components insoluble in methanol were separated and removed by filtration to prepare a sample for gas chromatography measurement.

[0052] Yields of 1,4-butanediol and tetrahydrofuran: Quantitative determination was performed by the absolute calibration curve method, and the molar yields of 1,4-butanediol and tetrahydrofuran were calculated by taking the 1,4-butanediol residue contained in PBT as 100 mol %.

[0053] Ethylene glycol yield: Quantitatively determined by 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 %.

[0054] (Yield of terephthalic acid and monohydroxyethyl terephthalate (hereinafter, MHET) (HPLC)) The yields (HPLC) of terephthalic acid and MHET were calculated by high performance liquid chromatography under the following measurement conditions. Equipment: Shimadzu LC-10Avp series Column: Mightysil RP-18GP150-4.6 Detector: Photodiode array detector (UV=254nm) Flow rate: 1mL / min Column temperature: 40℃ Mobile phase: 0.1% acetic acid aqueous solution / acetonitrile Sample: Approximately 0.1 g of the reaction mixture was weighed out and diluted with approximately 10 g of water. Insoluble components were separated and removed by filtration to prepare a sample for high performance liquid chromatography measurement.

[0055] Yields of terephthalic acid and MHET: Quantitatively determined by the absolute calibration curve method (however, in this example, although some metal terephthalates were produced after the hydrothermal reaction, they were converted to terephthalic acid by the acid contained in the mobile phase). The molar yields of terephthalic acid and MHET were calculated by taking the terephthalic acid residues contained in PBT or the PBT / PET mixture as 100 mol %.

[0056] [Example 1] 20.0 g of polybutylene terephthalate resin (PBT), 60.0 g of deionized water, and 7.3 g of sodium hydroxide were added to a SUS316L autoclave equipped with a stirrer. The atmosphere in the reaction vessel was replaced with nitrogen, and the mixture was stirred at 200 rpm at 280°C for 15 minutes under a nitrogen pressure of 0.5 MPa while sealed. The pressure in the system during the reaction was 6.2 MPa. After the reaction, the mixture was cooled to room temperature, and the reaction mixture was recovered. The analysis results of the reaction mixture are shown in Table 1.

[0057] [Comparative Example 1] Except for not adding sodium hydroxide, polybutylene terephthalate was solvolyzed in the same manner as in Example 1. The results are shown in Table 1.

[0058] [Table 1]

[0059] A comparison between Example 1 and Comparative Example 1 reveals that the addition of sodium hydroxide, which is an alkali metal salt with a pKa of >4.0, suppresses the production of tetrahydrofuran (THF), an over-reaction product of 1,4-butanediol, and enables the production of 1,4-butanediol in high yield.

[0060] [Examples 2 to 4] Except for changing the amounts of PBT and sodium hydroxide added, polybutylene terephthalate was solvolyzed in the same manner as in Example 1. The results are shown in Table 2.

[0061] [Table 2]

[0062] It is clear from Examples 1 to 4 that terephthalic acid and 1,4-butanediol can be obtained in high yields by setting the content of the solvent to 200 to 1000 parts by weight relative to 100 parts by weight of PBT.

[0063] [Examples 5 to 10 and Comparative Example 2] Except for changing the reaction temperature, polybutylene terephthalate was solvolyzed in the same manner as in Example 1. The results are shown in Table 3.

[0064] [Table 3]

[0065] Comparing Examples 1 and 5 to 10 with Comparative Example 2, it is understood that by setting the reaction temperature to 180° C. or higher, terephthalic acid and 1,4-butanediol can be obtained in high yields.

[0066] [Examples 11 to 13, Comparative Example 3] Except for changing the amount of sodium hydroxide added, polybutylene terephthalate was solvolyzed in the same manner as in Example 1. The results are shown in Table 4.

[0067] [Table 4]

[0068] Comparing Examples 1 and 11 to 13 with Comparative Example 3, it is found that terephthalic acid and 1,4-butanediol can be obtained in high yields by setting the amount of Na per 1 mol of terephthalic acid units in PBT to 1.5 mol or more.

[0069] [Examples 14 to 17] Except for changing the type and amount of the metal salt, polybutylene terephthalate was solvolyzed in the same manner as in Example 1. The results are shown in Table 5.

[0070] [Table 5]

[0071] From Example 1 and Examples 14 to 17, it can be seen that terephthalic acid and 1,4-butanediol can be obtained in high yields when an alkali metal salt having a pKa>4.0, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, or sodium carbonate, or an alkaline earth metal salt having a pKa>4.0, such as magnesium hydroxide, is used.

[0072] [Example 18] In a SUS316L autoclave equipped with a stirrer, 10.0 g of polybutylene terephthalate resin (PBT), 10.0 g of polyethylene terephthalate resin (PET), 60.0 g of deionized water, and 7.8 g of sodium hydroxide were added. The atmosphere in the reaction vessel was replaced with nitrogen, and the mixture was stirred at 200 rpm at 280°C for 15 minutes under a sealed condition with a nitrogen pressure of 0.5 MPa. The pressure in the system during the reaction was 6.2 MPa. After the reaction, the mixture was cooled to room temperature, and the reaction mixture was recovered. The analysis results of the reaction mixture are shown in Table 6.

[0073] [Comparative Example 4] Except for not adding sodium hydroxide, the polybutylene terephthalate composition was solvolyzed in the same manner as in Example 18. The results are shown in Table 6.

[0074] [Comparative Example 5] A polybutylene terephthalate composition was solvolyzed in the same manner as in Example 18, except that the temperature was 160° C. and the pressure was 1.5 MPa. The results are shown in Table 6.

[0075] [Table 6]

[0076] A comparison between Example 18 and Comparative Example 4 shows that the addition of sodium hydroxide, an alkali metal salt with a pKa>4.0, to a mixture of PBT and PET suppressed the production of monohydroxyethyl terephthalate (MHET), a partial depolymerization product of PET. As a result, terephthalic acid, 1,4-butanediol, and ethylene glycol were obtained in high yields. A comparison between Example 18 and Comparative Example 5 shows that the depolymerization of PBT and PET was low at 160°C, and the yields of terephthalic acid, 1,4-butanediol, and ethylene glycol were low.

[0077] [Example 19] In a SUS316L autoclave equipped with a stirrer, 20.0 g of polybutylene terephthalate resin (PBT), 58.0 g of deionized water, 2.0 g of 1,4-butanediol, and 7.3 g of sodium hydroxide were added. The atmosphere in the reaction vessel was replaced with nitrogen, and the mixture was stirred at 200 rpm at 140°C for 15 minutes under a nitrogen pressure of 0.5 MPa while sealed. The pressure in the system during the reaction was 0.9 MPa. After the reaction, the mixture was cooled to room temperature, and the reaction mixture was recovered. The analysis results of the reaction mixture are shown in Table 7.

[0078] [Examples 20 to 22] Except for changing the type of alcohol, polybutylene terephthalate was solvolyzed in the same manner as in Example 19. The results are shown in Table 7.

[0079] [Table 7]

[0080] From Examples 19 to 22, it can be seen that when alcohols such as 1,4-butanediol, methanol, 2-propanol, and tert-butyl alcohol are blended, polybutylene terephthalate undergoes solvolysis at a reaction temperature of 140°C, and terephthalic acid and 1,4-butanediol are obtained in high yields.

[0081] [Examples 23 and 24, Comparative Example 6] Except for changing the reaction temperature, polybutylene terephthalate was solvolyzed in the same manner as in Example 22. The results are shown in Table 8.

[0082] [Table 8]

[0083] A comparison of Examples 22 to 24 with Comparative Example 6 shows that terephthalic acid and 1,4-butanediol can be obtained in high yields by setting the reaction temperature to 120° C. or higher.

[0084] [Examples 25 and 26] Except for changing the weight amounts of water and alcohol, polybutylene terephthalate was solvolyzed in the same manner as in Example 22. The results are shown in Table 9.

[0085] [Table 9]

[0086] From Examples 22, 25 and 26, it is seen that terephthalic acid and 1,4-butanediol can be obtained in high yields by setting the weight ratio of water to alcohol to 1.0 or more.

[0087] [Example 27] 20.0 g of PBT composition, 60.0 g of deionized water, and 5.1 g of sodium hydroxide were added to a SUS316L autoclave equipped with a stirrer. The atmosphere in the reaction vessel was replaced with nitrogen, and the mixture was stirred at 200 rpm at 180°C for 15 minutes under a nitrogen pressure of 0.5 MPa while sealed. The pressure in the system during the reaction was 1.2 MPa. After the reaction, the mixture was cooled to room temperature, and the reaction mixture was recovered. The analysis results of the reaction mixture are shown in Table 10.

[0088] [Example 28] In a SUS316L autoclave equipped with a stirrer, 20.0 g of PBT composition, 58.0 g of deionized water, 2.0 g of butanediol, and 5.1 g of sodium hydroxide were added. The atmosphere in the reaction vessel was replaced with nitrogen, and the mixture was stirred at 200 rpm at 140°C for 15 minutes under a nitrogen pressure of 0.5 MPa while sealed. The pressure in the system during the reaction was 0.9 MPa. After the reaction, the mixture was cooled to room temperature, and the reaction mixture was recovered. The analysis results of the reaction mixture are shown in Table 10.

[0089] [Table 10]

[0090] From Examples 27 and 28, it is seen that terephthalic acid and 1,4-butanediol can be obtained in high yields even in the case of a PBT composition containing glass fibers.

[0091] [Reference Example 1] Hydrothermal decomposition of polybutylene terephthalate resin (repeated experiment of Non-Patent Document 2) In a 300mL round-bottomed single-necked flask, 10.0g of polybutylene terephthalate resin (PBT), 4mL of cyclohexylamine, 50.0g of deionized water, and 8.0g of sodium hydroxide were added. The mixture was stirred at 200 rpm for 120 minutes at 140°C under a nitrogen atmosphere. After the reaction, the mixture was cooled to room temperature and the reaction mixture was recovered. The analysis results of the reaction mixture are shown in Table 11.

[0092] [Table 11]

[0093] Comparison of Example 1 and Reference Example 1 shows that the method described in Non-Patent Document 2 provides low yields of terephthalic acid and 1,4-butanediol.

Claims

1. A method for producing terephthalic acid and / or 1,4-butanediol, comprising a step of solvolyzing polybutylene terephthalate or a composition thereof in the presence of an alkali metal salt and / or an alkaline earth metal salt having a pKa > 4.0 and water in a temperature range including a temperature of 180 to 350°C, wherein the total number of moles of the alkali metal atoms of the alkali metal salt and / or alkaline earth metal salt having a pKa > 4.0 and 2.0 times the number of moles of the alkaline earth metal atoms is 1.5 to 6.0 moles per mole of terephthalic acid units in the polybutylene terephthalate.

2. A method for producing terephthalic acid and / or 1,4-butanediol, comprising a step of solvolyzing polybutylene terephthalate or a composition thereof in the presence of an alkali metal salt and / or an alkaline earth metal salt having a pKa of > 4.0, water, and an alcohol, in a temperature range including a temperature of 110 to 350°C, wherein the total number of moles of the alkali metal atoms of the alkali metal salt and / or alkaline earth metal salt having a pKa of > 4.0 and 2.0 times the number of moles of the alkaline earth metal atoms is 1.5 to 6.0 moles per mole of terephthalic acid unit in the polybutylene terephthalate.

3. 3. The method for producing terephthalic acid and / or 1,4-butanediol according to claim 1, wherein the solvent is contained in an amount of 100 to 1,000 parts by weight based on 100 parts by weight of polybutylene terephthalate.

4. The method for producing terephthalic acid and / or 1,4-butanediol according to claim 1, wherein the pressure at a temperature of 180 to 350° C. is 1.2 to 30 MPa.

5. The method for producing terephthalic acid and / or 1,4-butanediol according to claim 2, wherein the pressure at a temperature of 110 to 350° C. is 0.1 to 30 MPa.

6. The method for producing terephthalic acid and / or 1,4-butanediol according to claim 1 or 2, wherein the alkali metal salt is at least one selected from the group consisting of alkali metal hydroxides and alkali metal carbonates.

7. 3. The method for producing terephthalic acid and / or 1,4-butanediol according to claim 1 or 2, wherein the alkaline earth metal salt is at least one selected from the group consisting of alkaline earth metal hydroxides and alkaline earth metal carbonates.

8. The method for producing terephthalic acid and / or 1,4-butanediol according to claim 1 or 2, wherein the yield of 1,4-butanediol is 30% or more.

9. The method for producing terephthalic acid and / or 1,4-butanediol according to claim 1 or 2, wherein the polybutylene terephthalate or a composition thereof is a waste product.

10. A method for producing a polyester, comprising a step of polymerizing terephthalic acid and / or 1,4-butanediol obtained by the method for producing terephthalic acid and / or 1,4-butanediol according to any one of claims 1 to 9.

11. A polyester obtained by polymerizing terephthalic acid and / or 1,4-butanediol obtained by the method for producing terephthalic acid and / or 1,4-butanediol according to any one of claims 1 to 9.

12. A fiber, film, or resin molded product obtained by processing the polyester according to claim 11.

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