Diamine or diamine composition, polyamide, molded article, fiber, membrane or sheet, method for producing diamine and / or dicarboxylic acid, method for producing diamine and / or diamine composition, and method for producing polyamide

Abstract

Provided are: a diamine or diamine composition in which the content of an amino alcohol compound, which is a polymerization inhibition component, in a diamine obtained by depolymerizing a polyamide is low; and a method for producing a diamine and a dicarboxylic acid by which it is possible to obtain the diamine or diamine composition with high efficiency and high purity. This diamine or diamine composition is obtained by depolymerizing a polyamide, in which the amount of an amino alcohol represented by chemical formula (1) is 6.0 * 10 <-5 > mol or less per 1 g of the diamine. Chemical formula (1): H2N-R-OH (In the formula, R represents a residue containing at least one selected from the group consisting of an aliphatic group having 3-12 carbon atoms, an alicyclic group, and an aromatic group. )

Description

Technical Field

[0001] The present invention relates to diamines or diamine compositions, polyamides using the same, and methods for producing diamines and dicarboxylic acids. Background Art

[0002] In recent years, concerns about global environmental problems triggered by the marine plastic issue have been increasing day by day, and the awareness of the need to build a sustainable society has gradually spread. Among global environmental problems, there are problems such as resource depletion and water shortage, with global warming being the leading one. Most global environmental problems are caused by the increased consumption of resources and emissions of global warming gases due to the use of fossil fuels and the rapid development of industry since the Industrial Revolution. Therefore, technologies related to the recycling of fossil resources such as plastics and the reduction of global warming gas emissions have become increasingly important.

[0003] In particular, polyamide 66, which is widely used in various fields such as automotive and electrical / electronic applications, emits a large amount of global warming gases during the production of monomers. Therefore, a technology for recycling products containing polyamide 66 back to monomers is expected.

[0004] As a technology for depolymerizing polyamides formed from diamines and dicarboxylic acids, such as polyamide 66, and recycling them back to monomers, a method of performing hydrolysis in the presence of an inorganic base compound such as sodium hydroxide at a temperature below the melting point of polyamide 66, for example, 220°C, is known (see, for example, Patent Document 1 and Non-Patent Document 1).

[0005] In addition, as a method for depolymerizing polyamides formed from diamines and dicarboxylic acids without using an inorganic base compound, a method of contacting polyamide with high-temperature and high-pressure water to recover diamines and dicarboxylic acids as raw material monomers, and a method of further hydrolyzing polyamide with an enzyme after contacting it with high-temperature water to obtain diamines and dicarboxylic acids have been disclosed (see, for example, Patent Documents 2 to 3 and Non-Patent Document 2).

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. Hei 7-507556

[0009] Patent Document 2: Japanese Patent No. 2001-302597

[0010] Patent Document 3: International Publication No. 2023 / 149514

[0011] Non-Patent Documents

[0012] Non-Patent Document 1: Chemical Abstract 15(1959)14558g

[0013] Non-Patent Document 2: Polymer Degradation and Stability 83(2004)389-393 Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] In the methods for decomposing polyamide 66 using the subcritical state or supercritical state of water disclosed in Patent Document 2 and Non-Patent Document 2, the maximum monomer yield is 25%, and it is difficult to say that it is sufficient to achieve the recycling of resources. In addition, Non-Patent Document 2 states that the reaction mixture contains oligomers. By performing the deamination cyclization reaction of diamine in subcritical water and then performing the decarboxylation cyclization reaction of dicarboxylic acid in supercritical water, the reaction mixture contains cyclic by-products in an amount equal to or greater than that of the monomers. Although the method using an enzyme reaction in Patent Document 3 obtains hexamethylenediamine with a yield of 82% and adipic acid with a yield of 72%, even after two-stage hydrolysis processes, it cannot be said that the yield is sufficiently improved.

[0016] In addition, according to the method for decomposing polyamide 66 disclosed in Patent Document 1, after reacting polyamide 66 in an aqueous sodium hydroxide solution at 220 °C for 6 hours, separation and purification are carried out, whereby hexamethylenediamine is obtained with a yield of 92% and adipic acid is obtained with a yield of 81%. In Non-Patent Document 1, compared with the method of Patent Document 1, the reaction time is shortened to 1 hour, and each monomer is obtained with a yield of 90%, but it still cannot be said to be efficient. Moreover, in Patent Document 1, although it can be confirmed that diamine is generated by depolymerization, it is not disclosed whether the quality can be used as a raw material for polyamide.

[0017] The subject of the present invention is to provide a diamine or diamine composition in which the content of an amino alcohol compound as a polymerization inhibitor component in the diamine obtained by depolymerizing polyamide is small, and a method for manufacturing diamine and / or dicarboxylic acid capable of obtaining it with high efficiency and high purity.

[0018] Means for Solving the Problems

[0019] To solve the above problems, the present invention has the following content.

[0020] [1] A diamine or diamine composition obtained by depolymerizing polyamide, wherein, relative to 1 g of diamine, the amino alcohol represented by the chemical formula (1) is 6.0×10 -5 mol or less.

[0021] Chemical formula (1): H 2 N-R-OH

[0022] In the formula, R is a residue containing at least one selected from aliphatic groups having 3 or more and 12 or less carbon atoms, alicyclic groups, and aromatic groups.

[0023] [2] The diamine composition according to the above [1], wherein the amino alcohol is 0.010×10 -5 mol or more per 1 g of the diamine.

[0024] [3] A polyamide comprising a diamine or a diamine composition obtained by depolymerizing a polyamide as a polymerization raw material, and the terminal structure represented by the chemical formula (2) is 3.0×10 -5 mol / g or less.

[0025] Chemical formula (2): -NH-R-OH

[0026] In the formula, R is a residue containing at least one selected from aliphatic groups having 3 or more and 12 or less carbon atoms, alicyclic groups, and aromatic groups.

[0027] [4] A molded article, fiber, film or sheet formed using the polyamide according to the above [3].

[0028] [5] A method for producing a diamine and / or a dicarboxylic acid, comprising the step of mixing an aqueous solution (B) of a polyamide composition (A) and an alkali (earth) metal compound in a manner that satisfies formula (1), and maintaining at a temperature of 230°C or higher for 0.1 to 45 minutes, wherein the polyamide composition (A) contains the following polyamide, and the polyamide contains X mol of dicarboxylic acid residues; the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates containing Y 1 mol of alkali metal ions and / or Y 2 mol of alkaline earth metal ions, and mixtures containing two or more of them.

[0029] Formula (1): 1.6 ≤ (Y 1 + 2 × Y 2 ) / X < 2.4.

[0030] [6] The method for producing a diamine and / or a dicarboxylic acid according to the above [5], wherein the temperature in the holding step is above the melting point of the polyamide composition (A) determined by differential scanning calorimetry and less than 400°C.

[0031] [7]In the method for producing a diamine and / or a dicarboxylic acid according to [5] above, when the mass ratio of the polyamide composition (A) to the aqueous solution (B) of an alkali (earth) metal compound is set to 1:Z, Z is 1.0 or more and 10.0 or less, and the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them.

[0032] [8]In the method for producing a diamine and / or a dicarboxylic acid according to [5] above, the yields of both the diamine and the dicarboxylic acid derived from the polyamide composition (A) are 70 mol% or more.

[0033] [9]In the method for producing a diamine and / or a dicarboxylic acid according to [5] above, when the amount of the diamine contained in the reaction mixture (C) obtained by bringing the polyamide composition (A) into contact with the aqueous solution (B) of an alkali (earth) metal compound is set to X'mol and the amount of the amino alcohol represented by the chemical formula (1) is set to Y'mol, Y' / X' is 4.0×10 -3 Hereinafter, the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them.

[0034] Chemical formula (1): H 2 N-R-OH

[0035] In the formula, R is a residue containing at least one selected from aliphatic groups having 3 or more and 12 or less carbon atoms, alicyclic groups, and aromatic groups.

[0036]

[10] In the method for producing a diamine and / or a dicarboxylic acid according to [5] above, the polyamide composition (A) is waste.

[0037]

[11] A method for producing the diamine or diamine composition according to [1] above, which sequentially includes the following steps (1) to (3):

[0038] (1) A step of producing a diamine and a dicarboxylate by bringing the polyamide composition (A) into contact with an aqueous solution (B) of an alkali (earth) metal compound, the alkali (earth) metal compound being selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them;

[0039] (2) A step of separating the diamine and the dicarboxylate produced in step (1);

[0040] (3) A step of distilling the diamine separated in step (2).

[0041]

[12] A method for producing a polyamide, which includes a step of polycondensing a raw material containing the diamine or diamine composition obtained by the method for producing a diamine or diamine composition according to

[11] above.

[0042] Advantages of the Invention

[0043] According to the present invention, a diamine or a diamine composition that can be suitably used as a raw material for repolymerization and has few amino alcohols as polymerization inhibitor components can be provided. Further, for a polyamide composition, by using an aqueous solution of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates of alkali (earth) metal ions containing a specific amount, and a mixture containing two or more of them, and performing a reaction at 230 °C or higher for a short time, a method for reducing the amount of amino alcohol generated and producing diamine and dicarboxylic acid efficiently in a short time can be provided. Detailed Description of the Invention

[0044] Hereinafter, the present invention will be described in detail with reference to embodiments.

[0045] The diamine or diamine composition of the present invention is a diamine or diamine composition obtained by depolymerizing a polyamide, wherein, relative to 1 g of the diamine, the amino alcohol represented by the chemical formula (1) is 6.0×10 -5 mol or less.

[0046] Chemical formula (1): H 2 N-R-OH

[0047] In the formula, R is a residue containing at least one selected from aliphatic groups having 3 or more and 12 or less carbon atoms, alicyclic groups, and aromatic groups.

[0048] Here, the amino alcohol represented by the chemical formula (1) is a specific compound generated when the polyamide is depolymerized. Specifically, it represents a compound generated by converting one amino group of the diamine component contained in the depolymerized polyamide into a hydroxyl group. When the polyamide is depolymerized with high-temperature and high-pressure water, the amino alcohol represented by the chemical formula (1) is likely to be generated.

[0049] In the present invention, as the polyamide to be depolymerized, it is a polymer or copolymer having residues of diamine and dicarboxylic acid as main structural units. Here, "as the main structural unit" means having residues of diamine and dicarboxylic acid in 50 mol% or more of all structural units, and having 80 mol% or more of these residues is a preferred embodiment.

[0050] In the present invention, the polyamide to be depolymerized is preferably a homopolymer or copolymer obtained by polycondensing a diamine and a dicarboxylic acid. Representative examples of the diamine include aliphatic diamines such as tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, 2-methylpentamethylene diamine, nonamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4- / 2,4,4-trimethylhexamethylene diamine, 5-methylnonamethylene diamine; aromatic diamines such as m-xylylenediamine, p-xylylenediamine; alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminopropyl)piperazine, aminoethylpiperazine, etc. In addition, representative examples of the dicarboxylic acid include aliphatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, sodium isophthalate-5-sulfonate, 2,6-naphthalenedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, etc. In the present invention, two or more polyamide homopolymers or copolymers derived from these raw materials can be blended.

[0051] As the structure of R in the compound (1) obtained when depolymerizing the above polyamide, an aliphatic group, an alicyclic group, and an aromatic group having 3 or more and 12 or less carbon atoms can be cited.

[0052] In the present invention, within the range not detrimental to the object of the present invention, the polyamide to be depolymerized may be a polyamide copolymer formed by copolymerizing an amino acid and a lactam, or a substance formed by blending a polyamide homopolymer or copolymer obtained by polycondensing an amino acid and a lactam. Representative examples of the raw materials include amino acids such as 6-aminohexanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, p-aminomethylbenzoic acid; lactams such as ε-caprolactam, ω-laurolactam, etc.

[0053] Specific examples of the above polyamides include polyhexamethylene adipamide (nylon 66), polybutylene adipamide (nylon 46), polybutylene sebacamide (nylon 410), polyhexamethylene glutaramide (nylon 56), polydecamethylene glutaramide (nylon 510), polydecamethylene adipamide (nylon 610), polydodecamethylene adipamide (nylon 612), polyhexamethylene sebacamide (nylon 106), polydecamethylene sebacamide (nylon 1010), polydodecamethylene sebacamide (nylon 1012), polycaprolactam / polyhexamethylene adipamide copolymer (nylon 6 / 66), polycaprolactam / polyhexamethylene terephthalamide copolymer (nylon 6 / 6T), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon 66 / 6T), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6I), polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 6T / 6I), polyhexamethylene terephthalamide / poly-12-lactam copolymer (nylon 6T / 12), polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6T / 6I), polyxylylene adipamide (nylon XD6), polyxylylene sebacamide (nylon XD10), polyhexamethylene terephthalamide / polyhexamethylene glutarate copolymer (nylon 6T / 5T), polyhexamethylene terephthalamide / poly-2-methylhexamethylene glutarate copolymer (nylon 6T / M5T), polyhexamethylene glutarate / polyhexamethylene sebacate copolymer (nylon 5T / 10T), polyhexamethylene nonanediamide (nylon 9T), polyhexamethylene sebacamide (nylon 10T), polyhexamethylene dodecanediamide (nylon 12T), and their copolymers, etc. Two or more of them can also be combined. Here, " / " indicates a copolymer, and the same applies hereinafter.

[0054] The polyamide to be depolymerized in the present invention may be a polyamide composition containing a polymerization catalyst, a thermoplastic resin other than polyamide, a dye, various additives, a fibrous filler, a non-fibrous filler, etc. within a range not detrimental to the object of the present invention. Here, there is no particular limitation on the fibrous filler as long as it has a fibrous shape. Examples of the fibrous filler include glass fiber, carbon fiber, potassium titanate whisker, zinc oxide whisker, aluminum borate whisker, aramid fiber, alumina fiber, silicon carbide fiber, ceramic fiber, asbestos fiber, gypsum fiber, metal fiber, etc. On the other hand, examples of the non-fibrous filler include wollastonite, zeolite, sericite, kaolin, mica, talc, clay, pyrophyllite, bentonite, montmorillonite, asbestos, aluminum silicate, alumina, silica, magnesia, zirconia, titanium oxide, iron oxide, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, glass bead, ceramic bead, boron nitride, silicon carbide, silica, etc. Two or more of them can also be combined.

[0055] The polyamide to be depolymerized in the present invention may be a resin molded article containing polyamide. As the resin molded article containing polyamide, it includes polyamide products, industrial wastes generated during the manufacturing process of polyamide products, or wastes after the use of polyamide products, etc. As specific examples of polyamide products, for example, engine peripheral components such as radiator water tanks and oil pans, automotive components such as gears, electrical / electronic components such as connectors and switches, components for industrial machinery such as fasteners and binding tapes, industrial fiber structures such as airbags, clothing fiber structures, sheets, films, molded articles, etc. can be cited. Moreover, it may also be product scraps, granular scraps, block scraps, etc. generated in these production processes.

[0056] In the method for producing diamine and / or dicarboxylic acid of the present invention, the polyamide composition (A) is preferably waste. Since the polyamide composition (A) is waste, fossil resources can be recycled. Furthermore, since it is not necessary to incinerate the waste, the emission of global warming gases can be reduced.

[0057] In the diamine or diamine composition of the present invention, relative to 1 g of diamine, the amino alcohol represented by the chemical formula (1) is 6.0×10 -5 mol or less.

[0058] Chemical formula (1): H 2 N-R-OH

[0059] In the formula, R is a residue containing at least one selected from aliphatic groups having 3 or more and 12 or less carbon atoms, alicyclic groups, and aromatic groups.

[0060] When the diamine or diamine composition obtained in the present invention is reused as a polyamide raw material, if it contains a specific amount of the amino alcohol represented by the chemical formula (1), it becomes a capping agent and hinders polymerization. The object of the present invention is to regenerate the above-mentioned diamine or diamine composition into a quality that can be actually used and re-polymerized. By making the amino alcohol represented by the chemical formula (1) contained in the diamine or diamine composition 6.0×10 -5 mol or less relative to 1 g of diamine, the degree of polymerization of the polyamide can be increased to a level that can be actually used. Relative to 1 g of diamine, the amount of amino alcohol is preferably 2.0×10 -5 mol or less, more preferably 1.0×10 -5 mol or less, and further preferably 0.5×10 -5 mol or less. On the other hand, the present inventors found that when the diamine composition contains at least 0.010×10 relative to 1 g of diamine -5When polymerizing the regenerated diamine of amino alcohol at or above mol (the detection limit of gas chromatography described in the examples), the degree of polymerization becomes higher compared to the polyamide formed by polymerizing petroleum-derived diamine under the same conditions. It is considered that this is because the influence of trace amounts of amino alcohol as the above-mentioned capping agent is small, and it acts like a plasticizer, reducing the melt viscosity of the polyamide, thereby increasing the molecular mobility and promoting the polymerization reaction. In the present invention, the amount of the amino alcohol represented by the chemical formula (1) contained in the diamine or diamine composition is determined by quantitative analysis based on gas chromatography (GC) described in the examples.

[0061] The method for producing the diamine or diamine composition of the present invention preferably sequentially includes the following steps (1) to (3).

[0062] (1) A step of producing a diamine and a dicarboxylate by bringing a polyamide composition (A) into contact with an aqueous solution (B) of an alkali (earth) metal compound, wherein the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them;

[0063] (2) A step of separating the diamine and the dicarboxylate produced in step (1);

[0064] (3) A step of distilling the diamine separated in step (2).

[0065] In the present specification, the expression of alkali (earth) metal compound refers to both compounds containing alkali metal atoms such as lithium, sodium, potassium, etc. and compounds containing alkaline earth metal atoms such as magnesium, calcium, barium, etc., and mixtures thereof.

[0066] As the method for producing the diamine and the dicarboxylate in step (1), there is no particular limitation. For example, in the case of carrying out the depolymerization reaction in a batch manner, a reaction mixture containing the alkali (earth) metal salt of the diamine and the dicarboxylic acid can be obtained after the depolymerization reaction. In addition, in the case of carrying out the depolymerization reaction in a continuous manner, a reaction mixture containing the alkali (earth) metal salt of the diamine and the dicarboxylic acid can be obtained while the reaction is proceeding. As the state of the reaction mixture, there is no particular limitation, and examples include aqueous solutions, slurries, pastes, etc.

[0067] As the method for separating diamine and dicarboxylate in step (2), known methods such as extraction and solid-liquid separation can be selected according to the properties of the produced diamine and dicarboxylate. When polyamide 66 is used as the polyamide and an aqueous sodium hydroxide solution is used as the aqueous solution of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them, since both the diamine and the dicarboxylate are water-soluble, separation by extraction is particularly preferred. In addition, if there are water-insoluble components in the reaction mixture, separation can also be performed in advance by known methods such as solid-liquid separation and then provided to step (2). When polyamide 610 is used as the polyamide and sodium hydroxide is used as the aqueous solution of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them, since the dicarboxylate can be precipitated by cooling, separation can also be performed by solid-liquid separation.

[0068] In step (3), it is preferred to distill the diamine separated from the dicarboxylate in step (2) to reduce the content of the amino alcohol represented by Chemical Formula (1). For example, when polyamide 66 is used as the polyamide, the boiling point of hexamethylenediamine as a raw material monomer is 204°C, and the boiling point of 6-amino-1-hexanol, which is an amino alcohol formed by converting one amino group of hexamethylenediamine into a hydroxyl group, is 225°C. By performing distillation purification, the content of the amino alcohol as an inhibitor of polymerization can be reduced, and the quality that can be repolymerized to a practically usable level can be improved, so it is preferred. The thus obtained diamine or diamine composition can be used as a polymerization raw material for polyamide in the same manner as diamine and carboxylic acid produced from petroleum-derived raw materials.

[0069] The polyamide of the present invention contains a diamine or diamine composition obtained by depolymerizing the polyamide as a polymerization raw material, and the terminal structure represented by Chemical Formula (2) is 3.0×10 -5 mol / g or less.

[0070] Chemical Formula (2): -NH-R-OH

[0071] In the formula, R is a residue containing at least one selected from aliphatic groups having 3 or more and 12 or less carbon atoms, alicyclic groups, and aromatic groups.

[0072] In the present invention, for the content of the terminal structure represented by Chemical Formula (2), it can be quantified by analyzing the amino alcohol obtained by hydrolyzing polyamide with hydrochloric acid and then trimethylsilylating it with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA reagent) using gas chromatography (GC). The content of the terminal structure described herein is determined as the molar equivalent of the terminal structure represented by Chemical Formula (2) per 1 g of polyamide. By setting it within this range, polyamide with a high degree of polymerization up to a practically usable level can be obtained. More preferably, it is 1.0×10 -5 mol / g or less, still more preferably 0.5×10 -5 mol / g or less, and most preferably 0 mol / g.

[0073] In the present invention, in the polyamide obtained by polymerizing a diamine composition in which the amino alcohol represented by the above Chemical Formula (1) is about 0.010×10 -5 mol relative to 1 g of diamine, the terminal structure represented by the above Chemical Formula (2) is 0 mol / g (below the detection limit of gas chromatography). Compared with the polyamide shown in Reference Example 1 obtained by polymerizing reagent diamine, an effect of increased degree of polymerization can be confirmed.

[0074] The method for producing the polyamide of the present invention includes a step of polycondensing a raw material containing the diamine or diamine composition of the present invention.

[0075] The polyamide of the present invention can be produced by polycondensing a diamine or diamine composition obtained by depolymerizing polyamide with a component used as a raw material directly or in the form of its salt with a dicarboxylic acid. In the case of producing polyamide, high degree of polymerization is carried out while moderately maintaining the equimolarity of the carboxyl end group amount and the amino end group amount of the monomers. For the purpose of uniformly mixing the diamine and the dicarboxylic acid, it is preferred that the diamine, the dicarboxylic acid, and their salts are uniformly dissolved in the polymerization system. In addition, it is preferred to carry out the polycondensation reaction while heating. As the lower limit of the preferred temperature, 150°C can be exemplified, and as the upper limit of the preferred temperature, 400°C can be exemplified.

[0076] The polyamide thus obtained can be processed into various products such as injection molded products, extrusion molded products, fiber structures, and films in the same manner as polyamides made from petroleum-derived raw materials and used. These products can be used as automotive parts, electrical / electronic parts, industrial machinery applications, industrial fiber structures, clothing fiber structures, sheets, films, or other applications.

[0077] The molded article, fiber, film, or sheet of the present invention is formed using the polyamide of the present invention. The polyamide of the present invention contains a diamine or diamine composition obtained by depolymerizing polyamide as a polymerization raw material. Therefore, the obtained polyamide can become a recycled material with little environmental impact that contributes to resource recycling and reduction of greenhouse gas emissions.

[0078] The method for producing diamine and dicarboxylic acid of the present invention has the following steps: mixing an aqueous solution (B) of a polyamide composition (A) and an alkali (earth) metal compound in a manner that satisfies formula (1), and maintaining at a temperature of 230 °C or higher for 0.1 to 45 minutes. The polyamide composition (A) contains the following polyamide, and the polyamide contains X mol of dicarboxylic acid residues; the alkali (earth) metal compound is selected from those containing Y 1 mol of alkali metal ions and / or Y 2 mol of alkaline earth metal ions, hydroxides, oxides, carbonates, and mixtures containing two or more of them.

[0079] Formula (1): 1.6 ≤ (Y 1 + 2 × Y 2 ) / X < 2.4

[0080] It should be noted that in the present invention, sometimes the temperature during the mixing in the above step and maintaining at the temperature and time within the above range is called the reaction temperature, and the maintaining time is called the reaction time. In addition, sometimes the pressure during the maintaining is called the reaction pressure.

[0081] As described above, the method for producing diamine and / or dicarboxylic acid of the present invention is characterized in that an aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them is mixed with a polyamide composition (A) containing polyamide to produce diamine and dicarboxylic acid, which are monomers of the polyamide constituting the polyamide composition (A).

[0082] Examples of the polyamide composition (A) containing polyamide include compositions formed by mixing the above polyamide to be depolymerized, a polymerization catalyst, a thermoplastic resin other than polyamide, dyes, various additives, fibrous fillers, non-fibrous fillers, and the like.

[0083] An aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures of two or more of them is formed by mixing an alkali (earth) metal compound and water. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, etc. Examples of the alkali metal oxide include lithium oxide, sodium oxide, potassium oxide, magnesium oxide, calcium oxide, barium oxide, etc. The alkali (earth) metal carbonate can be either a normal salt or an acid salt (bicarbonate). Examples of the normal salt include dilithium carbonate, disodium carbonate, dipotassium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, etc. Examples of the alkali metal bicarbonate include lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, barium bicarbonate, etc. In the present invention, two or more selected from these alkali (earth) metal hydroxides, alkali (earth) metal oxides, and alkali (earth) metal carbonates can be used in combination. As the alkali (earth) metal, sodium, potassium, and calcium are preferred from the viewpoint of mineral resource conservation, and sodium and potassium are more preferred from the viewpoint of increasing the production rate of diamine and dicarboxylic acid, and sodium is particularly preferred. In addition, for the purpose of increasing the hydrolysis reactivity with polyamide, the normal salts of hydroxides, oxides, and carbonates are preferred, and hydroxides and oxides are particularly preferred. The water used here is not particularly limited, and any water such as tap water, deionized water, distilled water, well water, etc. can be used. From the viewpoint of suppressing side reactions caused by the influence of coexisting salts, deionized water and distilled water are preferably used as the water.

[0084] The amount of alkali metal ions in the aqueous solution (B) of the alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures of two or more of them is set according to the polyamide content in the polyamide composition (A). Let the dicarboxylic acid residue of the polyamide contained in the polyamide composition (A) be X mol, and let the alkali metal ions contained in the aqueous solution (B) of the alkali (earth) metal compound be Y 1 mol and the alkaline earth metal ions be Y 2 mol, then (Y 1 + 2 × Y 2 ) / X is 1.6 or more and less than 2.4. By controlling (Y 1 + 2 × Y 2 ) / X within this range, in the hydrolysis of the polyamide composition (A), the yields of diamine and dicarboxylic acid can be increased, and the amount of the amino alcohol represented by the above chemical formula (1) can be reduced. (Y 1 + 2 × Y 2 ) / X is preferably 1.8 or more, more preferably 1.9 or more, and particularly preferably 2.0 or more. On the other hand, it is more preferably 2.2 or less.

[0085] The amount of the dicarboxylic acid residue contained in the polyamide composition (A) can be quantified by a spectrum obtained by proton nuclear magnetic resonance spectroscopy ( 1 1H-NMR) using sulfuric acid or hexafluoroisopropanol as a deuterated solvent.

[0086] In the present invention, the yields of diamine and dicarboxylic acid obtained by depolymerizing the polyamide contained in the polyamide composition (A) are each preferably 70 mol% or more. The yield referred to herein is expressed as a mole percentage by setting the number of moles of the diamine residue and the number of moles of the dicarboxylic acid residue contained in the polyamide composition (A) to 100 each, and representing the amounts of the diamine and the dicarboxylic acid contained in the reaction mixture. The above yields are each preferably 80 mol% or more, more preferably each 90 mol% or more, and still more preferably each 95 mol% or more. In the present invention, the yield of diamine is calculated by quantitative analysis based on gas chromatography (GC) described in the examples. Further, in the present invention, the yield of dicarboxylic acid is calculated by quantitative analysis based on ion chromatography (IC) described in the examples. By setting the yields of diamine and dicarboxylic acid within a preferred range, the recovery rate can be increased.

[0087] There is no particular limitation on the amount of the aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures of two or more of them. When the mass ratio of the polyamide composition (A) to the aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures of two or more of them is set to 1:Z, Z is preferably 1 or more. When Z is less than 1, when the polyamide composition (A) is mixed with the aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures of two or more of them at 230°C or higher, there is a tendency for the dispersibility and solubility of the polyamide composition (A) in water to decrease and the reaction efficiency to decrease. It is more preferably 2.0 or more, and still more preferably 3.0 or more. On the other hand, Z is preferably 10 or less, more preferably 8.0 or less, and still more preferably 6.0 or less. The present invention relates to a method for efficiently producing diamine and dicarboxylic acid by depolymerizing a polyamide composition (A) for the purpose of achieving both the recycling of fossil resources and the reduction of greenhouse gas emissions. The specific heat capacity of water is 4.3 kJ / kg·K and the heat of vaporization is 2,250 kJ / kg, which is very high compared to other organic solvents. Therefore, it is important to reduce the amount of water used. By setting the amount of the aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures of two or more of them within a certain range, the production efficiency of diamine and dicarboxylic acid and energy saving can be achieved simultaneously.

[0088] There is no particular limitation on the method for preparing the aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them. The aqueous solution can be prepared by pre-mixing the alkali (earth) metal compound with water, or by mixing the alkali (earth) metal compound with water when it comes into contact with the polyamide composition (A) in the reaction vessel to form an aqueous solution.

[0089] The method for producing diamine and / or dicarboxylic acid of the present invention is characterized in that the polyamide composition (A) is contacted with an aqueous solution (B) of an alkali (earth) metal compound at a temperature of 230 °C or higher for 0.1 to 45 minutes to produce diamine and dicarboxylic acid, and the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them.

[0090] In the method for producing diamine and / or dicarboxylic acid of the present invention, the reaction time between the polyamide composition (A) and the aqueous solution (B) of the alkali (earth) metal compound is 0.1 to 45 minutes, and the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them. As described above, the reaction time in the present invention refers to the total time maintained at a temperature of 230 °C or higher. For the heating process until reaching the reaction temperature and the cooling process after the reaction at the reaction temperature, the time for mixing the polyamide composition (A) and the aqueous solution (B) of the alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them in the reaction vessel at a temperature of 230 °C or higher is also included in the reaction time. When the reaction time exceeds 45 minutes, the yields of diamine and dicarboxylic acid decrease and the amount of amino alcohol formed increases, so it is not preferred. It is preferably 45 minutes or less, more preferably 40 minutes or less, and further preferably within 35 minutes. On the other hand, if the reaction time is less than 0.1 minute, the depolymerization reaction cannot proceed sufficiently and the yields of diamine and dicarboxylic acid decrease. It is preferably 0.1 minute or more, more preferably 1 minute or more, and further preferably 3 minutes or more.

[0091] By contacting the polyamide composition (A) with the aqueous solution (B) of the alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them for the reaction time within the above preferred range, the amount of the amino alcohol represented by the chemical formula (1) can be reduced. It is considered that the amino alcohol is formed by the transformation of one NH 2 group of the diamine, which is a depolymerization product of the polyamide composition (A), into an OH group through a nucleophilic substitution reaction. Regarding the amount of the amino alcohol represented by the chemical formula (1) in the present invention, when the amount of the diamine contained in the depolymerized reaction mixture (C) is set to X'mol and the amount of the amino alcohol represented by the chemical formula (1) is set to Y'mol, it is preferred that Y' / X' is 4.0×10 -3Hereinafter, more preferably 3.0×10 -3 or less, further preferably 2.0×10 -3 , particularly preferably 1.0×10 -3 or less. The amounts of the diamine and the amino alcohol represented by the chemical formula (1) can be calculated by the quantitative analysis based on gas chromatography (GC) described in the Examples. If the amount of the amino alcohol represented by the chemical formula (1) is within the preferred range, the polyamide obtained by repolymerizing the diamine or the diamine composition obtained by subsequent purification can achieve high molecular weight.

[0092] The reaction temperature in the method for producing the diamine and / or dicarboxylic acid of the present invention is 230°C or higher. The reaction temperature is the temperature during the contact of the polyamide composition (A) with an aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them in a reaction vessel with temperature control, and can be a constant temperature or a temperature that changes with time. It should be noted that there are no particular restrictions on the temperature during the heating process until the reaction temperature is reached and the cooling process after the reaction at the reaction temperature as long as it is below 230°C. By setting the reaction temperature to 230°C or higher, the time required for the hydrolysis reaction of the polyamide composition (A) can be shortened, and the production efficiency of the diamine and dicarboxylic acid can be improved.

[0093] Furthermore, the reaction temperature is preferably a temperature that is equal to or higher than the melting point of the polyamide composition (A) determined by differential scanning calorimetry and lower than 400 °C. By setting the reaction temperature to be equal to or higher than the melting point of the polyamide composition (A), the polyamide composition (A) can be easily dispersed and dissolved in water, thereby improving the reaction efficiency. When the pressure of water rises to 22.1 MPa and the temperature rises to 374.2 °C, water exhibits a state that is neither liquid nor gas. Water in this state is called supercritical water. Due to its characteristics of both the solubility of a liquid and the diffusivity of a gas, it has attracted attention as a reaction site for decomposing polymers. In addition, hot water in the vicinity of the critical point at a temperature and pressure slightly lower than the critical point of water is called subcritical water. Although subcritical water is water, it has the characteristics of (i) low dielectric constant and (ii) high ionic product. The dielectric constant and ionic product of subcritical water depend on the temperature and the partial pressure of water and can be controlled. By reducing the dielectric constant, even water becomes an excellent solvent for organic compounds. By increasing the ionic product, the concentrations of hydrogen ions and hydroxide ions become higher, and thus it has excellent hydrolysis. By setting the reaction temperature to be lower than 400 °C, when the polyamide resin (A) is mixed and reacted with an aqueous solution (B) of an alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them, a reaction site with the excellent characteristics of supercritical water or subcritical water can be utilized, and undesirable reactions such as thermal decomposition can be suppressed. In addition, by setting the reaction temperature to be lower than 374.2 °C, the ionic product can be well controlled using the subcritical state of water, so the reaction efficiency can be improved and the reaction time can be shortened, which is therefore preferred. Furthermore, in order to suppress the excessive reaction of diamine and dicarboxylic acid, the reaction temperature is more preferably lower than 350 °C, and further preferably lower than 300 °C. On the other hand, in order to promote the depolymerization reaction, it is more preferably 250 °C or higher, and further preferably 270 °C or higher.

[0094] The melting point of the polyamide composition (A) in the present invention mentioned herein is the temperature of the endothermic peak that appears when heating from 40 °C to 300 °C at a heating rate of 10 °C / minute under a nitrogen gas flow using a differential scanning calorimeter manufactured by TA Instruments. Among them, when two or more endothermic peaks are detected, the temperature of the endothermic peak detected on the highest temperature side is taken as the melting point. When the melting point of the polyamide composition (A) exceeds 400 °C, thermal decomposition reactions of the polyamide composition (A) etc. occur, and the recovery rates of diamine and dicarboxylic acid decrease, so it is not preferred. There is no particular limitation on the lower limit of the melting point of the polyamide composition (A). As a preferred lower limit, 50 °C can be exemplified. When the melting point of the polyamide composition (A) is 50 °C or higher, the polyamide becomes a solid at room temperature, and thus the operability is excellent.

[0095] In addition, as the reaction pressure, it is preferable to exemplify a pressure higher than the saturated vapor pressure. By making the reaction pressure higher than the saturated vapor pressure, water can be maintained in a liquid state and the reaction can proceed easily. Therefore, as the pressure of the aqueous solution (B) of the alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them, a pressure higher than the saturated vapor pressure is preferable. In addition, there is no particular limitation on the upper limit of the reaction pressure, and 22.1 MPa or less can be exemplified. By being in such a pressure range, the ionic product of the above water tends to increase, which is therefore preferable. As a method of bringing the reaction pressure into this pressure range, a method of pressurizing and sealing the inside of the pressure vessel can be cited. In order to pressurize the inside of the pressure vessel, in addition to the polyamide composition (A) and the aqueous solution (B) of the alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them, a gas may be enclosed. Examples of the enclosed gas include air, argon, and nitrogen. From the aspect of suppressing side reactions such as oxidation reactions, nitrogen or argon is preferably used as the enclosed gas. In addition, the inside of the pressure vessel can also be pressurized by introducing high-pressure water. In the case of using high-pressure water, it can also be set in a state where there is no gas in the pressure vessel. As the degree of gas pressurization, it is set to achieve the target pressure and there is no particular limitation, and 0.3 MPa or more can be cited.

[0096] The mixing of the polyamide composition (A) and the aqueous solution (B) of the alkali (earth) metal compound selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them in the present invention can adopt various known reaction methods such as batchwise and continuous methods. For example, in the case of batchwise, 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, etc. can be cited. In the case of continuous, 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, etc. can be cited. In addition, the atmosphere during manufacturing is preferably a non-oxidizing atmosphere, more preferably carried out in an inert atmosphere such as nitrogen, helium, and argon, and further preferably a nitrogen atmosphere from the aspects of economy and ease of operation.

[0097] The method for recovering diamine and dicarboxylic acid produced by the method of the present invention is not particularly limited, and any method can be adopted. For example, when the depolymerization reaction is carried out batchwise, after the depolymerization reaction, a reaction mixture (C) of diamine and dicarboxylic acid alkali (earth) metal salt can be obtained. In addition, when the depolymerization reaction is carried out continuously, the reaction mixture (C) of diamine and dicarboxylic acid alkali (earth) metal salt can be obtained while the reaction is being carried out. The obtained reaction mixture (C) can separate the diamine and the dicarboxylic acid alkali (earth) metal salt by known methods such as extraction, and the separated dicarboxylic acid alkali (earth) metal salt is converted into dicarboxylic acid under acidic conditions, and then the diamine and dicarboxylic acid are respectively recovered by known methods such as distillation-solid-liquid separation. In addition, if there are components insoluble in water in the reaction mixture (C), they can also be separated in advance by known methods such as solid-liquid separation and provided to the recovery process of diamine and dicarboxylic acid. For the purpose of reducing the content of amino alcohol in the diamine, it is particularly preferred to distill and purify the diamine.

[0098] In addition, in order to obtain higher purity diamine and dicarboxylic acid, they can be further purified by known methods.

[0099] The diamine and dicarboxylic acid obtained by the method for producing diamine and / or dicarboxylic acid of the present invention can be used as polymerization raw materials for polyamide in the same manner as diamine and carboxylic acid produced from petroleum-derived raw materials. For polyamide, polyamide resin can be produced by directly heating and polycondensing diamine and / or dicarboxylic acid, or by heating and polycondensing its salt. In the present invention, by repolymerizing the diamine and / or dicarboxylic acid obtained by depolymerizing polyamide, polyamide can be regenerated, and thus it can become a recycling material with little environmental impact that contributes to resource recycling and reduction of greenhouse gas emissions.

[0100] In addition, the polyamide thus obtained can be processed into various products such as injection molded products, extrusion molded products, fiber structures, and films in the same manner as polyamide produced from petroleum-derived raw materials and used. These products can be used as automotive parts, electrical / electronic parts, industrial machinery applications, industrial fiber structures, clothing fiber structures, sheets, films, or other applications.

[0101] Examples

[0102] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited by these examples.

[0103] The following raw materials are used in each example.

[0104] (A-1) Polyamide 66: "Amilan" (registered trademark) manufactured by Toray Industries, Inc., CM3001-N, melting point 262 °C

[0105] (A-2) Polyamide 66 waste: Polyamide 66 airbag base fabric recycled from scrapped vehicles

[0106] (A-3) Polyamide 66 waste: Organosilicon-coated airbag base fabric made of polyamide 66 recycled from scrapped vehicles, with an estimated organosilicon adhesion amount of 25 g / m 2

[0107] (A-4) Polyamide 66 waste: GF30% reinforced polyamide 66 molding chips (broken pieces of sprue and runner)

[0108] Sodium hydroxide: Manufactured by Kanto Chemical Co., Inc., reagent special grade

[0109] Sodium carbonate: Manufactured by Kanto Chemical Co., Inc., reagent special grade

[0110] Sodium bicarbonate: Manufactured by FUJIFILM Wako Pure Chemical Corporation, first grade

[0111] Adipic acid: Manufactured by FUJIFILM Wako Pure Chemical Corporation, special grade

[0112] Hexamethylenediamine: Manufactured by FUJIFILM Wako Pure Chemical Corporation, first grade.

[0113] 《Evaluation Method》

[0114] (Amount of amino alcohol in diamine composition (GC))

[0115] The amount of amino alcohol in the diamine composition is calculated by quantitative analysis using gas chromatography (GC).

[0116] Apparatus: GC-2010 manufactured by Shimadzu Corporation

[0117] Column: DB-5 manufactured by Agilent Technologies, 0.32 mm × 30 m (0.25 μm)

[0118] Carrier gas: Helium

[0119] Detector: Flame ionization detector (FID)

[0120] Sample: Take about 0.02 g of the diamine composition, dilute it with about 10 g of deionized water, and separate and remove the components insoluble in deionized water by filtration to prepare a gas chromatography measurement sample.

[0121] Quantification of amino alcohol: The amount of amino alcohol is quantified by the absolute standard curve method.

[0122] (Diamine yield, amount of amino alcohol in reaction mixture (GC))

[0123] The amounts of diamine and amino alcohol in the reaction mixture (C) were quantitatively analyzed by gas chromatography (GC) and calculated, and the diamine yield was determined from the calculated amount of diamine.

[0124] Apparatus: GC-2010 manufactured by Shimadzu Corporation

[0125] Column: DB-5, 0.32 mm × 30 m (0.25 μm) manufactured by Agilent Technologies

[0126] Carrier gas: Helium

[0127] Detector: Flame ionization detector (FID)

[0128] Sample: Approximately 0.15 g of the reaction mixture was taken, diluted with approximately 10 g of deionized water, and the components insoluble in deionized water were separated and removed by filtration to prepare a sample for gas chromatography measurement.

[0129] Quantification of diamine: The amount of diamine was quantified by the absolute standard curve method.

[0130] Quantification of amino alcohol: The amount of amino alcohol was quantified by the absolute standard curve method.

[0131] (Yield of dicarboxylic acid (IC))

[0132] The dicarboxylic acid yield was calculated by quantitatively analyzing the sodium dicarboxylate in the reaction mixture (C) by ion chromatography (IC).

[0133] Apparatus: HIC-20Asuper manufactured by Shimadzu Corporation

[0134] Column: Shim-pack IC-SA2 (250 mm × 4.6 mm ID) manufactured by Shimadzu Corporation

[0135] Detector: Conductivity detector (suppressor)

[0136] Eluent: 4.0 mM sodium bicarbonate / 1.0 mM sodium carbonate aqueous solution

[0137] Flow rate: 1.0 ml / minute

[0138] Injection volume: 50 μl

[0139] Column temperature: 30 °C

[0140] Sample: Approximately 0.02 g of the reaction mixture was taken, diluted with approximately 10 g of deionized water, and the components insoluble in deionized water were separated and removed by filtration to prepare a sample for ion chromatography measurement.

[0141] Quantification of dicarboxylic acid: The amount of sodium dicarboxylate was quantified by the absolute standard curve method.

[0142] (Melting point of polyamide (DSC))

[0143] Using a differential thermal analyzer (TG / DTA7200 manufactured by Hitachi High-Tech Science), approximately 5.0 mg of polyamide was heated from 40 °C to 300 °C at a heating rate of 10 °C / min under a nitrogen stream, and the temperature of the endothermic peak that appeared at this time was taken as the melting point. However, in the case where two or more endothermic peaks were detected, the temperature of the endothermic peak detected on the highest temperature side was taken as the melting point.

[0144] (Molecular weight of polyamide)

[0145] Approximately 2.5 mg of the polyamide obtained from each example and comparative example was dissolved in 4 ml of hexafluoroisopropanol (added with 0.005 N sodium trifluoroacetate), and the resulting solution was filtered through a 0.45 μm filter. Using the resulting solution, the number average molecular weight (Mn) was determined by GPC. The measurement conditions are as follows.

[0146] Pump: e-Alliance GPC system (manufactured by Waters)

[0147] Detector: Differential refractive index detector Waters 2414 (manufactured by Waters)

[0148] Column: Shodex HFIP-806M (2 pieces) + HFIP-LG

[0149] Solvent: Hexafluoroisopropanol (added with 0.005 N sodium trifluoroacetate)

[0150] Flow rate: 1 ml / min

[0151] Sample injection volume: 0.1 ml

[0152] Temperature: 30 °C

[0153] Molecular weight reference substance: Polymethyl methacrylate.

[0154] (Amount of amino alcohol at the end of polyamide (GC))

[0155] Accurately weigh approximately 50 mg of the polyamide resin obtained in each example and comparative example, add it to a glass ampoule with an internal volume of 16 ml, add 8 ml of 6N hydrochloric acid aqueous solution, and then seal the ampoule. Place it in a pressure-resistant container, heat it at 180 °C for 20 hours for hydrolysis treatment. After cooling, take out the ampoule, concentrate the content to dryness. Furthermore, after removing hydrochloric acid, conduct drying, and trimethylsilylate the resulting dry solid with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA reagent). Dilute the reaction product with dehydrated acetonitrile to prepare a gas chromatography measurement sample. The measurement conditions are as follows.

[0156] Apparatus: GC-2010 manufactured by Shimadzu Corporation

[0157] Column: DB-5 manufactured by Agilent Technologies, 0.32 mm × 30 m (0.25 μm)

[0158] Carrier gas: Helium

[0159] Detector: Flame ionization detector (FID)

[0160] Quantification of amino alcohol: Quantify the amount of amino alcohol by the absolute standard curve method of trimethylsilylated reagent amino alcohol.

[0161] [Example 1]

[0162] In a SUS316L autoclave equipped with a stirrer, add polyamide 66 (A-1) with a melting point of 262 °C and aqueous sodium hydroxide solution in the amounts recorded in Table 1. The amount of polyamide 66 in moles is X, and the amount of sodium hydroxide in moles is Y 1 The molar ratio Y 1 / X is 2.11.

[0163] Replace the air in the reaction vessel with nitrogen, close it under nitrogen pressure of 0.5 MPa, and react while stirring at 200 rpm and maintaining at 280 °C for 15 minutes. During the reaction, the pressure inside the system is 6.5 MPa. After the reaction, cool to room temperature and recover the reaction mixture. At 230 °C or higher, the total time for mixing the polyamide composition and aqueous sodium hydroxide solution in the reaction vessel is 40 minutes.

[0164] The diamine yield (X’) calculated by gas chromatography measurement of the recovered reaction mixture is 98 mol%, and the dicarboxylic acid yield calculated by high-performance liquid chromatography measurement is 95 mol%. The amount of amino alcohol (Y’) is 0.14 mol%, and Y’ / X’ is 1.4×10 -3 .

[0165] [Examples 2-9, Comparative Examples 1-3]

[0166] Appropriately change the type of raw polyamide, the amount and concentration of the sodium hydroxide aqueous solution, the amount of deionized water, the reaction temperature, and the reaction time, and depolymerize the polyamide using the same method as in Example 1. It should be noted that in Comparative Example 3, the reaction was carried out at a temperature lower than 230°C, so the reaction time was set to the time for treatment at 220°C (60 minutes).

[0167] [Examples 10 and 11]

[0168] Change sodium hydroxide to sodium carbonate or sodium bicarbonate, and depolymerize the polyamide using the same method as in Example 1.

[0169] The reaction conditions, the yields of the reaction products, and the quantitative analysis results of Examples 1 to 11 and Comparative Examples 1 to 3 are shown in Tables 1 and 2.

[0170]

[0171] Table 2

[0172]

[0173] As can be seen from Examples 1 to 11, by contacting the polyamide with an aqueous solution containing a preferred amount of an alkali metal hydroxide or an alkali metal carbonate, hydrolysis can proceed sufficiently, the yields of diamine and dicarboxylic acid can be increased, and the amount of the amino alcohol represented by Chemical Formula (1) can be reduced.

[0174] In Comparative Example 1 where Y 1 / X is greater than the preferred range, compared with Example 1 where the reaction is carried out under substantially the same conditions except for Y 1 / X, the yield of diamine is reduced and the amount of amino alcohol produced becomes larger. When the amount of the alkali metal hydroxide is excessive, even if the reaction temperature and reaction time conditions are satisfied, both diamine and dicarboxylic acid cannot be obtained in good yield, and the amount of amino alcohol produced increases.

[0175] On the other hand, in Comparative Example 2 where the reaction is carried out for a long time exceeding the preferred range, compared with Example 1 where the reaction is carried out under substantially the same conditions except for the reaction time, the amount of amino alcohol produced becomes larger. In Comparative Example 3 where the reaction temperature is lower than 230°C, by setting the reaction time to 60 minutes, diamine and dicarboxylic acid can be obtained in good yield, but the amount of amino alcohol produced is still large.

[0176] From this, it can be seen that by bringing the polyamide composition into contact with an aqueous solution containing a preferred amount of alkali metal hydroxide and / or alkali metal carbonate at a temperature above 230°C for 0.1 to 45 minutes, hydrolysis can proceed sufficiently, the yields of diamine and dicarboxylic acid can be increased, and the amount of the amino alcohol represented by Chemical Formula (1) can be reduced. In addition, when the reaction temperature is lower than the preferred range, as described in Patent Document 1 and Non-Patent Document 1, not only does the reaction require a long time, but the amount of amino alcohol is also larger compared to the case of reacting at the preferred reaction temperature.

[0177] When polyamide 66 is selected as the polyamide, the boiling point of 6-amino-1-hexanol, which is the amino alcohol derived from the hexamethylenediamine residue, is 225°C, close to the boiling point of hexamethylenediamine at 204°C. Therefore, it is considered that when the amount of amino alcohol in the reaction mixture is large, the difficulty of separation and removal by distillation increases, making it difficult to be used for recycling.

[0178] [Reference Example 1]

[0179] 5.15 g of hexamethylenediamine and 6.47 g of adipic acid were dissolved in 12.6 g of deionized water to prepare a salt solution. The salt solution was charged into a reaction vessel and sealed, and nitrogen replacement was carried out. The set temperature of the heater located outside the reaction vessel was set to 290°C, and heating was started. After the pressure in the tank reached 1.75 MPa, while discharging water outside the system, the pressure in the tank was maintained at 1.75 MPa, and the temperature was raised until the temperature in the tank reached 237°C. After the temperature in the tank reached 237°C, the pressure in the tank was adjusted to atmospheric pressure over 1 hour (the temperature in the tank when reaching atmospheric pressure: 257°C). Then, nitrogen was circulated in the tank (nitrogen flow) while maintaining for 60 minutes to obtain polyamide 66 (the highest temperature reached: 274°C). The number average molecular weight of the obtained polyamide 66 was 14,300 g / mol, and the melting point was 262°C.

[0180] [Example 12]

[0181] Diamine was extracted from the reaction mixture obtained by performing the same operation as in Example 1 with isobutanol, concentrated using an evaporator, and distilled at 84 to 90°C and 3 ± 1 hPa to obtain a crude diamine composition. The crude diamine composition was distilled again at 84 to 90°C and 3 ± 1 hPa to obtain a diamine composition. The content of amino alcohol in the diamine composition relative to 1 g of diamine was 0.80×10 -5 mol.

[0182] 15 mL of 35% aqueous hydrochloric acid was added to the aqueous solution of dicarboxylic acid from which diamine had been removed by extraction to obtain a slurry solution in which dicarboxylic acid precipitated. The slurry solution was heated in an oil bath at 80 °C, and after forming a homogeneous solution, it was allowed to stand at room temperature for 12 hours, whereby crude adipic acid precipitated. Deionized water in an amount twice the mass of the crude adipic acid was added to the crude adipic acid recovered by vacuum filtration, and it was again heated in an oil bath at 80 °C. After forming a homogeneous solution, it was allowed to stand at room temperature for 12 hours, and the precipitated adipic acid was recovered by vacuum filtration and dried in a vacuum oven set at 110 °C for 12 hours, whereby adipic acid was obtained.

[0183] Using 5.14 g of the diamine composition and 6.50 g of adipic acid thus obtained as polymerization raw materials, in addition, the same operation as in Reference Example 1 was carried out to produce polyamide 66. The number-average molecular weight of the obtained recycled polyamide 66 was 15,300 g / mol, the melting point was 262 °C, and the amount of amino alcohol end groups was 0.41×10 -5 mol / g.

[0184] [Example 13]

[0185] The reaction mixture obtained by carrying out the same operation as in Example 3 was subjected to the same distillation as in Example 12 twice to obtain a diamine composition. The content of amino alcohol in this diamine composition was 0.010×10 -5 mol relative to 1 g of diamine. In addition, adipic acid and polyamide 66 were produced by the same method as in Example 12. The number-average molecular weight of the obtained recycled polyamide 66 was 15,000 g / mol, the melting point was 262 °C, and the amount of amino alcohol end groups was 0 mol / g (below the detection limit of gas chromatography).

[0186] [Comparative Example 4]

[0187] From the reaction mixture obtained by carrying out the same operation as in Comparative Example 1, a diamine composition and adipic acid were produced in the same manner as in Example 12. The content of amino alcohol in the diamine composition was 6.4×10 -5 mol relative to 1 g of diamine. Using this diamine composition and adipic acid as polymerization raw materials, in addition, polyamide 66 was produced in the same manner as in Reference Example 1. The number-average molecular weight of the obtained recycled polyamide 66 was 11,000 g / mol, the melting point was 261 °C, and the amount of amino alcohol end groups was 3.3×10 -5 mol / g.

[0188] Therefore, from Reference Example 1, Example 12, and Example 13, it can be seen that the number-average molecular weight of the polyamide obtained by repolymerizing the diamine composition of the present invention obtained by depolymerizing polyamide and adipic acid is greater than the number-average molecular weight of the polyamide obtained by polymerizing reagent diamine and reagent dicarboxylic acid.

[0189] On the other hand, from Reference Example 1 and Comparative Example 4, it can be seen that for a diamine composition in which the content of amino alcohol is more than 6.0×10 -5 mol with respect to 1 g of diamine, the polyamide obtained by repolymerization has a structure derived from amino alcohol of 3.0×10 -5 mol / g or more at the end, and the number average molecular weight becomes smaller. It is speculated that the amino alcohol in the diamine composition hinders the polymerization. It is considered that the boiling point of 6-amino-1-hexanol, which is an amino alcohol derived from hexamethylenediamine residue, is 225°C, close to the boiling point of hexamethylenediamine of 204°C. Therefore, the amount of amino alcohol in the reaction mixture is large, making it difficult to remove by distillation.

[0190] Industrial availability

[0191] Since the diamine composition of the present invention has few impurities, it can be suitably used as a raw material for repolymerization of polyamide. In addition, particularly by depolymerizing polyamide to obtain the diamine composition of the present invention, it can contribute to resource recycling and reduction of greenhouse gas emissions.

Claims

1. A diamine or diamine composition obtained by depolymerizing a polyamide, wherein, relative to 1 g of the diamine, the amino alcohol represented by the chemical formula (1) is 6.0×10 -5 mol or less. Chemical formula 1: H 2 N-R-OH In the formula, R is a residue containing at least one selected from aliphatic groups, alicyclic groups, and aromatic groups having 3 to 12 carbon atoms.

2. The diamine composition according to claim 1, wherein the amino alcohol is 0.010×10 -5 mol or more per 1 g of diamine.

3. A polyamide comprising a diamine or a diamine composition obtained by depolymerizing the polyamide as a polymerization raw material, and the terminal structure represented by Chemical Formula (2) is 3.0×10 -5 mol / g or less, Chemical formula (2): -NH-R-OH In the formula, R is a residue containing at least one selected from aliphatic groups, alicyclic groups, and aromatic groups having 3 to 12 carbon atoms.

4. A molded article, fiber, film, or sheet formed from the polyamide according to claim 3.

5. Process for producing diamine and / or dicarboxylic acid, comprising the step of mixing an aqueous solution (B) of a polyamide composition (A) and an alkali (earth) metal compound in a manner satisfying formula (1) and maintaining the mixture at a temperature of 230 °C or higher for 0.1 to 45 minutes, wherein the polyamide composition (A) contains the following polyamide, the polyamide containing X mol of dicarboxylic acid residues; the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates containing Y 1 mol of alkali metal ions and / or Y 2 mol of alkaline earth metal ions, and mixtures containing two or more of them; Formula (1): 1.6 ≤ (Y 1 + 2 × Y 2 ) / X < 2.4 6. The method for producing a diamine and / or dicarboxylic acid according to claim 5, wherein the temperature in the holding step is equal to or higher than the melting point of the polyamide composition (A) determined by differential scanning calorimetry and lower than 400 °C.

7. The method for producing a diamine and / or dicarboxylic acid according to claim 5, wherein when the mass ratio of the polyamide composition (A) to the aqueous solution (B) of an alkali (earth) metal compound is set to 1:Z, Z is 1.0 or more and 10.0 or less, and the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them.

8. The method for producing a diamine and / or dicarboxylic acid according to claim 5, wherein the yields of the diamine and dicarboxylic acid derived from the polyamide composition (A) are both 70 mol% or more.

9. In the method for producing a diamine and / or a dicarboxylic acid according to claim 5, when the amount of the diamine contained in the reaction mixture (C) obtained by bringing the polyamide composition (A) into contact with an aqueous solution (B) of an alkali (earth) metal compound is set to X' mol and the amount of the amino alcohol represented by the chemical formula (1) is set to Y' mol, Y' / X' is 4.0×10 -3 Hereinafter, the alkali (earth) metal compound is selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them; Chemical formula 1: H 2 N-R-OH In the formula, R is a residue containing at least one selected from aliphatic groups, alicyclic groups, and aromatic groups having 3 to 12 carbon atoms.

10. The method for producing a diamine and / or dicarboxylic acid according to claim 5, wherein the polyamide composition (A) is a waste product.

11. A method for producing the diamine or diamine composition according to claim 1, which sequentially includes the following steps (1) to (3): (1) A step of producing a diamine and a dicarboxylate by bringing the polyamide composition (A) into contact with an aqueous solution (B) of an alkali (earth) metal compound, the alkali (earth) metal compound being selected from hydroxides, oxides, carbonates, and mixtures containing two or more of them; (2) A step of separating the diamine and the dicarboxylate produced in step (1); (3) A step of distilling the diamine separated in step (2).

12. A method for producing a polyamide, which includes a step of polycondensing a raw material containing a diamine or a diamine composition, the diamine or diamine composition being obtained by the method for producing a diamine or a diamine composition according to claim 11.

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