Biodegradable resin composition, molded article, and method for producing the same

Abstract

Provided are: a biodegradable resin composition that is highly stable when being irradiated with non-ultraviolet rays and that exhibits excellent decomposition effect through irradiation with ultraviolet rays; a molded article; and methods for producing the biodegradable resin composition and the molded article. More specifically, provided are: a biodegradable resin composition which is obtained by blending, as essential components, a biodegradable resin (A) having, in the main chain, at least an ester bond or an amide bond, and a biodegradation accelerator (B), and in which the biodegradation accelerator (B) contains a polyarylene sulfide having a weight average molecular weight of 120000 or less; a molded article; and methods for producing the biodegradable resin composition and the molded article.

Description

Technical Field

[0001] The present invention relates to a biodegradable resin composition, a molded article, and a method for producing them.

Background Art

[0002] In recent years, from the viewpoint of preventing environmental pollution, the use of biodegradable resins has been actively studied in a wide range of fields. Conventionally, as biodegradable resins, for example, polylactic acid, polyester-based resins, and polyamide-based resins are known. However, the biodegradation rate and degradation rate of these resins vary depending on their structure, and depending on the usage environment of soil and climate, biodegradability may not be sufficiently exhibited, resulting in a problem of poor degradation.

[0003] To solve such problems, a technique for controlling degradability by blending various decomposition accelerators into biodegradable resins is known. For example, Patent Document 1 discloses a resin composition in which polysaccharides such as starch, cellulose, and chitin are blended with polylactic acid and polybutylene succinate. Further, Patent Document 2 discloses a biodegradable resin composition blended with a biodegradation accelerator containing a polysaccharide and / or monosaccharide having a xylose content of 15% by mass or more. Further, Patent Document 3 discloses a biodegradable resin composition in which a polymer (oligomer) of 3-hydroxyalkanoic acid (such as 3-hydroxybutyric acid) is added at a ratio of 0.1 to 50 parts by weight.

Prior Art Documents

Patent Documents

[0004]

Patent Document !

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since conventional biodegradability accelerators promote the decomposition of biodegradable resins even outside of an ultraviolet irradiation environment, their functions were also exerted during transportation and storage before using the final product made of the biodegradable resin composition. As a result, it has been regarded as a problem that the final product deteriorates before use and the quality assurance period is shortened. In addition, the degree of improvement in decomposition acceleration was also limited.

[0006] Therefore, the problem to be solved by the present invention is to provide a biodegradable resin composition and a molded article that have high stability during non-ultraviolet irradiation and exhibit excellent decomposition effects upon ultraviolet irradiation, as well as methods for producing them.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that by blending a polyarylene sulfide (hereinafter referred to as PAS) having a specific weight average molecular weight as a biodegradability accelerator with a biodegradable resin, it is excellent in both stability in the dark and decomposition acceleration in an ultraviolet irradiation environment, and have thus completed the present invention.

[0008] That is, the present disclosure is a biodegradable resin composition obtained by blending a biodegradable resin (A) having at least an ester bond or an amide bond in the main chain and a biodegradability accelerator (B) as essential components, wherein the biodegradability accelerator (B) contains PAS having a weight average molecular weight of 120,000 or less, and relates to a biodegradable resin composition.

[0009] The present disclosure also relates to a molded article obtained by melt-molding the above-described biodegradable resin composition.

[0010] The present disclosure is also a method for producing a biodegradable resin composition, which comprises blending a biodegradable resin (A) having at least an ester bond or an amide bond in the main chain and a biodegradability accelerator (B) as essential components, and melt-kneading at a temperature equal to or higher than the melting point of the biodegradable resin (A). The present invention relates to a method for producing a biodegradable resin composition, wherein the biodegradability promoter (B) contains PAS having a weight average molecular weight of 120,000 or less.

[0011] The present disclosure also relates to a method for producing a molded article having a step of melt-molding the biodegradable resin composition produced by the method described above.

[0012] In the present disclosure, the dark place refers to an environment where ultraviolet rays are blocked, that is, a non-ultraviolet irradiation environment. For example, the inside of a transport vehicle, the inside of a storage warehouse, a state of being packaged with a material that does not transmit ultraviolet rays, etc. can be mentioned.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a biodegradable resin composition and a molded article having high stability during storage in a dark place and exhibiting an excellent decomposition promoting effect by ultraviolet irradiation, and methods for producing them.

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present disclosure will be described in detail. However, the scope of the present disclosure is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present disclosure. Also, when a plurality of upper limit values and lower limit values are described for a specific parameter, any upper limit value and lower limit value can be combined to form a suitable numerical range.

[0015] <Biodegradable Resin Composition> The biodegradable resin composition according to the present embodiment is formulated by blending a biodegradable resin (A) having at least an ester bond or an amide bond in the main chain and a biodegradability promoter (B) as essential components. Details will be described below.

[0016] ·Biodegradable Resin (A) The biodegradable resin composition according to this embodiment is formulated with a biodegradable resin (A) having at least an ester bond or an amide bond in the main chain (hereinafter sometimes simply referred to as biodegradable resin (A)) as an essential component. The biodegradable resin (A) is not particularly limited as long as the effects of the present invention are not impaired, and known resins can be used. For example, poly(α-hydroxycarboxylic acid) such as polyglycolic acid or polylactic acid, or copolymers thereof, poly(ω-hydroxyalkanoate) such as poly(ε-caprolactone), polyethylene succinate obtained by polycondensation of glycol having 2 to 12 carbon atoms and aliphatic dicarboxylic acid having 2 to 12 carbon atoms, polybutylene succinate, polybutylene adipate, polybutylene succinate lactate, and other aliphatic polyesters, poly(butylene adipate / terephthalate) copolymer and poly(butylene adipate / isophthalate) copolymer obtained by polycondensation of glycol having 2 to 12 carbon atoms, aliphatic dicarboxylic acid having 2 to 12 carbon atoms, and terephthalic acid or isophthalic acid, and other aliphatic polyester resins or polyester resins such as aliphatic-aromatic polyester copolymers; aliphatic polyamide resins (polyamide 6, polyamide 66, polyamide 610, polyamide 11, polyamide 12, polyamide 612, etc.), alicyclic polyamide resins (polymers of bis(aminomethyl)cyclohexane and adipic acid, etc.), aromatic polyamides (polyamide MXD (polymers of xylylenediamine and adipic acid), polymers of trimethylhexamethylenediamine and terephthalic acid, etc.), and copolyamides thereof (copolyamides in which homopolyamide components are copolymerized, for example, copolyamide 6 / 66, copolyamide 6 / 11, copolyamide 66 / 12, etc.) and other polyamide resins are exemplified. In addition, it may be made of polyester amide resin, polyester carbonate resin, polycarbonate resin, or bio-derived raw materials such as polyaspartic acid. Further, the raw materials of the biodegradable resin (A) may include biomass raw materials or biosynthesized raw materials. The above resins may be used alone or in combination of two or more. From the viewpoints of mechanical properties and processability, it is preferable to use polyamide resins and polyester resins.

[0017] Biodegradation accelerator (B) The biodegradation promoter (B) according to this embodiment contains, as an essential component, a PAS having a molecular weight of 120,000 or less.

[0018] -Polyarylene sulfide PAS has a resin structure in which a repeating unit is a structure in which an aromatic ring and a sulfur atom are bonded, and specifically, PAS is represented by the following general formula (1):

[0019] [ka] (In the formula, R 1 and R 2 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a nitro group, an amino group, a phenyl group, a methoxy group, or an ethoxy group, and, if necessary, a structural portion represented by the following general formula (2):

[0020] [ka] The resin has a trifunctional structural moiety represented by formula (2) and a repeating unit represented by formula (3). The trifunctional structural moiety represented by formula (2) is preferably present in an amount of 0.001 to 3 mol %, and particularly preferably in an amount of 0.01 to 1 mol %, based on the total number of moles of the trifunctional structural moiety and other structural moieties.

[0021] Here, the structural moiety represented by the general formula (1) is particularly R 1 and R 2 is preferably a hydrogen atom from the viewpoint of the mechanical strength of the PAS resin, and in that case, examples include those bonded at the para position represented by the following formula (3) and those bonded at the meta position represented by the following formula (4).

[0022] [ka] Among these, a structure in which the sulfur atom is bonded to the aromatic ring in the repeating unit at the para position, as represented by the general formula (3), is particularly preferred in terms of the heat resistance of the PAS.

[0023] In addition, the PAS may contain not only the structural moieties represented by the general formulas (1) and (2) but also the following structural formulas (5) to (8)

[0024] [Chemical formula] and may contain the structural moieties represented by the following at 30 mol% or less of the total of the structural moieties represented by the general formula (1) and the general formula (2). In particular, in the present disclosure, it is preferable from the viewpoints of heat resistance and mechanical strength of the PAS that the structural moieties represented by the general formulas (5) to (8) are 10 mol% or less. When the PAS resin contains the structural moieties represented by the general formulas (5) to (8), their bonding modes may be any of a random copolymer and a block copolymer.

[0025] In addition, the PAS may have a naphthyl sulfide bond or the like in its molecular structure, but it is preferably 3 mol% or less, particularly preferably 1 mol% or less, based on the total number of moles with other structural moieties.

[0026] (Molecular weight) The weight average molecular weight (Mw) of the PAS applicable to the present embodiment is 120,000 or less. In such a range, excellent compatibility with the biodegradable resin can be exhibited. Incidentally, from the viewpoints of better compatibility and the decomposition rate of the biodegradable resin, it is preferably 100,000 or less, more preferably 50,000 or less, still more preferably 30,000 or less, and particularly preferably 10,000 or less. The weight average molecular weight (Mw) in the present disclosure can be determined by gel permeation chromatography by the method described in the examples.

[0027] The PAS applicable to this embodiment only needs to have a weight average molecular weight of 120,000 or less, and thus can contain oligoarylene sulfide (hereinafter referred to as PAS oligomer). There are linear and cyclic forms of the PAS oligomer, but the blending ratio of the linear and cyclic forms in the PAS oligomer used in this embodiment is not particularly limited. The number of repetitions of the PAS oligomer is not particularly limited as long as the effects of the present invention are not impaired, but from the viewpoint of excellent melt stability, it is preferably a tetramer or more, more preferably a pentamer or more, and still more preferably a hexamer or more. Further, the PAS oligomer may be a PAS oligomer having a single number of repetitions, or any mixture of PAS oligomers having different numbers of repetitions. In the present disclosure, the PAS oligomer refers to PAS (dimer to 40-mer) having 2 to 40 repeating units.

[0028] (Thermal properties) The thermal properties of the PAS applicable to this embodiment are not particularly limited, but from the viewpoints of processability and stability, it is preferable to include those having a melting point of 285°C or lower. Further, from the viewpoint of suppressing thermal decomposition of the biodegradable resin, it is more preferable to include those having a melting point of 270°C or lower, and still more preferable to include those having a melting point of 260°C or lower. Further, from the viewpoint of processability, those having a glass transition point of 100°C or lower are preferable. The melting point and glass transition point can be measured using a differential scanning calorimeter by the method described in the examples.

[0029] (Melt viscosity) The melt viscosity (V6) of the PAS applicable to this embodiment is not particularly limited, but from the viewpoint of being more excellent in compatibility with the biodegradable resin, those of 600 Pa·s or less are preferable, those of 300 Pa·s or less are more preferable, those of 50 Pa·s or less are still more preferable, and those of 2 Pa·s or less are particularly preferable. However, the melt viscosity (V6) is measured using a flow tester, CFT-500D manufactured by Shimadzu Corporation, for the PAS resin, and is the measured value of the melt viscosity measured after holding at 300°C, load: 1.96×10 6 Pa, L / D = 10 (mm) / 1 (mm) for 6 minutes.

[0030] (Manufacturing method)The method for producing the PAS is not particularly limited. For example, (Production Method 1) a method of polymerizing a dihalogenoaromatic compound in the presence of sulfur and sodium carbonate, and adding a polyhalogenoaromatic compound or other copolymerization components if necessary; (Production Method 2) a method of polymerizing a dihalogenoaromatic compound in a polar solvent in the presence of a sulfidizing agent or the like, and adding a polyhalogenoaromatic compound or other copolymerization components if necessary; (Production Method 3) a method of self-condensing p-chlorothiophenol and adding other copolymerization components if necessary; (Production Method 4) a method of melt-polymerizing a diiodoaromatic compound and elemental sulfur while reducing the pressure in the presence of a polymerization inhibitor which may have a functional group such as a carboxyl group or an amino group, etc. may be mentioned. Among these methods, the method of (Production Method 2) is general and preferable. During the reaction, an alkali metal salt of a carboxylic acid or a sulfonic acid, or an alkali hydroxide may be added to adjust the degree of polymerization. Among the above (Production Method 2) methods, a hydrous sulfidizing agent is introduced into a mixture containing a heated organic polar solvent and a dihalogenoaromatic compound at a rate at which water can be removed from the reaction mixture, and the dihalogenoaromatic compound and the sulfidizing agent in the organic polar solvent are added with a polyhalogenoaromatic compound if necessary and reacted, and the amount of water in the reaction system is controlled within the range of 0.02 to 0.5 mol per 1 mol of the organic polar solvent to produce PAS (see JP-A-07-228699), or in the presence of a solid alkali metal sulfide and an aprotic polar organic solvent, a dihalogenoaromatic compound and, if necessary, a polyhalogenoaromatic compound or other copolymerization components are added, and an alkali metal hydrosulfide and an alkali metal organic acid salt are reacted while controlling the amount of the alkali metal organic acid salt in the range of 0.01 to 0.9 mol per 1 mol of the sulfur source and the amount of water in the reaction system within the range of 0.02 mol or less per 1 mol of the aprotic polar organic solvent (see WO2010 / 058713 pamphlet), and those obtained by such methods are particularly preferable.Specific examples of the dihalogenoaromatic compound and the polyhalogeno-structured compound include p-dihalobenzene, m-dihalobenzene, o-dihalobenzene, 2,5-dihalotoluene, 1,4-dihalonaphthalene, 1-methoxy-2,5-dihalobenzene, 4,4'-dihalobiphenyl, 3,5-dihalobenzoic acid, 2,4-dihalobenzoic acid, 2,5-dihalonitrobenzene, 2,4-dihalonitrobenzene, 2,4-dihaloanisole, p,p'-dihalodiphenyl ether, 4,4'-dihalobenzophenone, 4,4'-dihalodiphenyl sulfone, 4,4'-dihalodiphenyl sulfoxide, 4,4'-dihalodiphenyl sulfide, and compounds having an alkyl group with 1 to 18 carbon atoms in the aromatic ring of each of the above compounds. Examples of the polyhalogenoaromatic compound include 1,2,3-trihalobenzene, 1,2,4-trihalobenzene, 1,3,5-trihalobenzene, 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,4,6-trihalonaphthalene, and the like. Further, the halogen atoms contained in each of the above compounds are preferably chlorine atoms and bromine atoms.

[0031] As a method for post-treating the reaction mixture containing PAS obtained by the coincidence process, there are no particular restrictions, but for example, (post-treatment 1) after the polymerization reaction is completed, first, the reaction mixture is left as it is, or after adding an acid or a base, the solvent is distilled off under reduced pressure or normal pressure, and then the solid obtained after solvent distillation is washed one or more times with solvents such as water, the reaction solvent (or an organic solvent having the same solubility as the low molecular polymer), acetone, methyl ethyl ketone, and alcohols, and then neutralized, washed with water, filtered, and dried; or (post-treatment 2) after the polymerization reaction is completed, a solvent such as water, acetone, methyl ethyl ketone, alcohols, ethers, halogenated hydrocarbons, aromatic hydrocarbons, and aliphatic hydrocarbons (a solvent that is soluble in the polymerization solvent used and is a poor solvent at least for PAS) is added as a precipitant to precipitate solid products such as PAS and inorganic salts, and these are filtered off, washed, and dried; or (post-treatment 3) after the polymerization reaction is completed, the reaction solvent (or an organic solvent having the same solubility as the low molecular polymer) is added to the reaction mixture and stirred, then filtered to remove the low molecular weight polymer, and then washed one or more times with solvents such as water, acetone, methyl ethyl ketone, and alcohols, and then neutralized, washed with water, filtered, and dried; (post-treatment 4) after the polymerization reaction is completed, water is added to the reaction mixture for washing with water, filtering, and if necessary, an acid is added during washing with water for acid treatment and then dried; (post-treatment 5) after the polymerization reaction is completed, the reaction mixture is filtered, and if necessary, washed one or more times with the reaction solvent, and then further washed with water, filtered, and dried, etc. Among these methods, the method of (post-treatment 4) is preferable because a PAS resin having a carboxyl group at the molecular terminal of PAS can be obtained.

[0032] In addition, in the post-treatment methods exemplified in the above (post-treatment 1) to (post-treatment 5), the drying of PAS may be carried out in a vacuum, or in air or an inert gas atmosphere such as nitrogen.

[0033] In addition, as the PAS used in this embodiment, newly polymerized PAS by the above method can be used, or recycled PAS can also be used. For example, PAS recovered from a PAS resin composition or a PAS resin molded product can be used. Specifically, examples include PAS obtained by performing the above post-treatment on a solution obtained by heating a PAS resin composition or a PAS resin molded product in an organic polar solvent to dissolve the contained PAS.

[0034] When using a PAS oligomer as PAS, for example, in an organic polar solvent, a polyhaloaromatic compound is reacted with (i) an alkali metal sulfide or (ii) an alkali metal hydrosulfide and an alkali metal hydroxide to obtain a crude reaction mixture containing at least oligoarylene sulfide, an alkali metal halide, and an organic polar solvent in step (1). In step (2), the solid-phase component is removed from the crude reaction mixture by solid-liquid separation to obtain a liquid-phase component (A) containing at least oligoarylene sulfide and an organic polar solvent. It can be produced by a method having step (3) of removing the organic polar solvent from the liquid-phase component (A) to obtain a reaction mixture (B).

[0035] - Step (1)- Step (1) is a step of reacting a polyhaloaromatic compound with (i) an alkali metal sulfide or (ii) an alkali metal hydrosulfide and an alkali metal hydroxide in an organic polar solvent to obtain a crude reaction mixture containing at least oligoarylene sulfide, an alkali metal halide, and an organic polar solvent.

[0036] As the polyhaloaromatic compound, the same compounds as the dihalogenoaromatic compounds and polyhalogeno-structured compounds described above can be used. In the production method, an alkali metal sulfide or an alkali metal hydrosulfide and an alkali metal hydroxide (hereinafter sometimes referred to as a sulfidizing agent) are used as raw materials.

[0037] Examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, rubidium sulfide, cesium sulfide, and mixtures thereof. The alkali metal sulfide can be used as a hydrate, an aqueous mixture, or an anhydride. Further, the alkali metal sulfide can also be obtained by reacting an alkali metal hydrosulfide with an alkali metal hydroxide. Usually, a small amount of an alkali metal hydroxide may be added to react with trace amounts of an alkali metal hydrosulfide and an alkali metal thiosulfate present in the alkali metal sulfide.

[0038] Examples of the alkali metal hydrosulfide include lithium hydrosulfide, sodium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures thereof. Such an alkali metal hydrosulfide can be used as a hydrate, an aqueous mixture, or an anhydride.

[0039] The alkali metal hydrosulfide is used in combination with the alkali metal hydroxide. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, etc. These may be used alone or in combination of two or more. Among these, lithium hydroxide, sodium hydroxide, and potassium hydroxide are preferred because they are easily available, and sodium hydroxide is particularly preferred. [[ID=##**REMOVED**##]]

[0040] [[ID=##**REMOVED**##]] [[ID=##**REMOVED**##]] In the production method, a hydrous sulfiding agent can also be used as a raw material. In that case, it is preferable to subject the hydrous sulfiding agent to a dehydration step in the presence of at least an aprotic polar solvent and then use it in the polymerization reaction of the PAS resin. Further, when the charged amount of the aprotic polar solvent is small, for example, less than 1 mol per 1 mol of the sulfur atom of the sulfiding agent, it is preferable to dehydrate the hydrous sulfiding agent and the aprotic polar solvent in the presence of a polyhaloaromatic compound.

[0041] It seems there were some tags removed in the provided translation task as there are some "##**REMOVED**##" marked lines in the original text tags which are not present in the translation. If you have any further clarifications or corrections regarding this, feel free to let me know.The dehydration process of the aqueous sulfiding agent involves charging at least an aprotic polar solvent, an aqueous alkali metal sulfide or aqueous alkali hydrosulfide as the aqueous sulfiding agent, and an alkali metal hydroxide into a reaction vessel equipped with a distillation apparatus, and heating to a temperature at which water is removed by azeotropy, specifically in the range of 300°C or lower, preferably in the range of 80 to 220°C, more preferably in the range of 100 to 200°C, and discharging water out of the system by distillation. In the dehydration process, it is preferable to dehydrate until the amount of water in the system where the polymerization reaction is carried out is in the range of 5 moles or less, more preferably in the range of 0.01 to 2.0 moles, per mole of sulfur atom of the sulfiding agent.

[0042] Examples of the organic polar solvent include amides such as formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropyleneurea, 1,3-dimethyl-2-imidazolidinone; sulfolanes such as sulfolane and dimethyl sulfolane; nitriles such as benzonitrile; ketones such as methyl phenyl ketone; and mixtures thereof. Among these, amides having an aliphatic cyclic structure such as N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropyleneurea, and 1,3-dimethyl-2-imidazolidinone are preferred, and N-methyl-2-pyrrolidone is more preferred.

[0043] In the PAS polymerization process, the polymerization reaction of the PAS resin is carried out by reacting the alkali metal sulfide as a sulfidizing agent with the polyhaloaromatic compound in the presence of these organic polar solvents. Alternatively, the polymerization reaction of the PAS resin is carried out by reacting the alkali metal hydrosulfide and alkali metal hydroxide as sulfidizing agents with the polyhaloaromatic compound in the presence of these organic polar solvents. The polymerization conditions generally range from 200 to 330 °C in temperature, and the pressure should be in a range that substantially maintains the polymerization solvent and the polyhaloaromatic compound, which is the polymerization monomer, in the liquid phase. Generally, it is selected from the range of 0.1 to 20 MPa, preferably from the range of 0.1 to 2 MPa. The charged amount of the polyhaloaromatic compound is adjusted to be in the range of 0.2 mol to 5.0 mol, preferably in the range of 0.8 to 1.3 mol, and more preferably in the range of 0.9 to 1.1 mol, per 1 mol of the sulfur atom of the sulfidizing agent. Also, the charged amount of the aprotic polar solvent is adjusted to be in the range of 1.0 to 6.0 mol, preferably in the range of 2.5 to 4.5 mol, per 1 mol of the sulfur atom of the sulfidizing agent. Note that the polymerization reaction is preferably carried out in the presence of a small amount of water, and the ratio is preferably adjusted as appropriate in consideration of the polymerization method, the molecular weight of the resulting polymer, and productivity. Specifically, a dehydration operation is carried out so that it is 2.0 mol or less, preferably 1.6 mol or less, per 1 mol of the sulfur atom of the sulfidizing agent. However, when the dehydration operation is further carried out in the presence of the polyhaloaromatic compound (for example, the method of "5)" in the following specific embodiments), the dehydration operation may be carried out so that it is 0.9 mol or less, preferably 0.05 to 0.3 mol, and more preferably 0.01 to 0.02 mol or less.

[0044] As a specific embodiment of polymerizing the sulfidizing agent and the polyhaloaromatic compound in the presence of the above-mentioned aprotic polar solvent, for example, 1) A method using a polymerization aid such as an alkali metal carboxylate or lithium halide; 2) A method using a branching agent such as an aromatic polyhalogen compound; 3) A method of carrying out the polymerization reaction in the presence of a small amount of water and then adding water to further polymerize; 4) A method of cooling the gas phase portion of a reaction kettle during the reaction between an alkali metal sulfide and an aromatic dihalogen compound to condense a part of the gas phase in the reaction kettle and reflux it to the liquid phase. 5) In the presence of a polyhaloaromatic compound, a step of reacting an alkali metal sulfide, or a hydrous alkali metal hydrosulfide and an alkali metal hydroxide, with an amide, urea or lactam having an aliphatic cyclic structure while dehydrating to produce a slurry containing a solid alkali metal sulfide. After producing the slurry, further adding a polar organic solvent such as NMP and distilling off water to perform dehydration. Then, in the slurry obtained through the dehydration step, reacting a polyhaloaromatic compound, an alkali metal hydrosulfide, and an alkali metal salt of a hydrolysis product of the amide, urea or lactam having the aliphatic cyclic structure in a reaction system where the amount of water present per 1 mol of the polar organic solvent such as NMP is 0.02 mol or less to perform polymerization. A method for producing a PAS resin having this as an essential production step is mentioned.

[0045] Thus, by subjecting a dihaloaromatic compound and (i) an alkali metal sulfide or (ii) an alkali metal hydrosulfide and an alkali metal hydroxide to a polymerization reaction in an organic polar solvent, a mixture such as a PAS resin and a PAS oligomer is obtained as a product. Substances contained after the reaction may also include, among others, by-products such as alkali metal-containing inorganic salts, carboxyalkylamino group-containing compounds, terminal SH group-containing compounds, unreacted raw materials, and water.

[0046] - Step (2)- Step (2) is a step of removing the solid phase component by solid-liquid separation from the crude reaction mixture to obtain a liquid phase component (A) containing at least a PAS oligomer and an organic polar solvent.

[0047] The solid-liquid separation is roughly divided into two types: the flash method and the quench method described later. In this step, the quench method is preferred from the perspective of yield.

[0048] The quenching method is a method for separating particulate PAS resin by cooling a crude reaction mixture, and generally, after gradually cooling the crude reaction mixture from a high temperature and high pressure state to crystallize the PAS resin in the reaction system, solid-liquid separation is performed by filtration or the like to separate the solid content containing the PAS resin as granules. Generally, as the molecular weight of a polymer increases, the interaction between polymers becomes stronger, so the solubility in a solvent deteriorates. Therefore, in this step, the PAS resin precipitates to become a solid, while cyclic PAS and oligomers remain dissolved in the solvent. There is no particular limitation on the cooling time in quenching, but usually a range of 0.1 °C / min to 3 °C / min is preferred. Also, it is not necessary to cool at the same rate throughout the entire slow cooling process. A method such as cooling in the range of 0.1 °C / min to 1 °C / min until particulate PAS resin crystallizes and then cooling at a rate of 1 °C / min or more is also preferred. Finally, it is preferably cooled to 70 °C or higher, preferably 100 °C or higher and 200 °C or lower, and then solid-liquid separation is performed to remove the solid content containing the PAS resin. Solid-liquid separation in the quenching method includes separating using a centrifuge such as filtration or a screw decanter, adding water directly to the obtained filter residue to form a slurry, and then repeating solid-liquid separation, or heating the obtained filter residue in a non-oxidizing atmosphere to remove the remaining solvent, etc.

[0049] At that time, if necessary, it may have a step of removing part or most of the organic polar solvent in the crude reaction mixture by distillation. After performing this step, a solid-liquid separation operation by filtration may be performed on the crude reaction mixture to remove the solid phase component. Also, it may have a step of washing by bringing water or an organic polar solvent into contact with the crude reaction mixture, or preferably, the solid content (slurry) obtained after solid-liquid separation.

[0050] - Step (3) - Step (3) is a step of obtaining a reaction mixture (B) by removing the organic polar solvent from the liquid phase component (A).

[0051] In step (3), methods for removing the organic polar solvent include, for example, the flash method in which the solvent is distilled off by flashing from a high-temperature and high-pressure state into an atmosphere of normal pressure or reduced pressure, the method of distilling off the solvent by heating, and the removal of the solvent using a membrane. When removing the organic polar solvent, it is desirable to remove the solvent such that the proportion of the solid matter (non-volatile content) is in the range of 20 to 100 parts by mass, preferably 20 to 99.99 parts by mass, and more preferably 30 to 90 parts by mass. Since the temperature for removing the solvent by heating depends on the properties of the solvent used, it cannot be uniquely limited, but usually, a range of 20 to 150 °C, preferably 40 to 120 °C can be selected. Also, the pressure for removing the solvent is preferably below normal pressure, which enables the removal of the solvent at a lower temperature.

[0052] In the present embodiment, for the purpose of further removing impurities or adjusting the content of the oligoarylene sulfide, a step of contacting the reaction mixture (B) with water at a temperature above 100 °C and a pH of 6 or higher (see Japanese Patent Application Laid-Open No. 2020-007490) may be included as step (4). If necessary, as a pretreatment, after subjecting the reaction mixture (B) to a treatment of contacting with water (water washing treatment) under conditions in the range of 100 °C or lower, preferably 20 to 100 °C, it can be contacted with water at a temperature above 100 °C and a pH of 6 or higher.

[0053] The reaction mixture (B) obtained through the above steps (1) to (3) and, if necessary, further through step (4) can be used as it is as a biodegradability promoter if the PAS oligomer content is 90 parts by mass or more. When the PAS oligomer content is 90 parts by mass or less, further, the reaction mixture (B) can be washed or dried, or the PAS oligomer can be extracted and purified for use. In that case, known extraction, purification operations, and drying can be performed.

[0054] The biodegradability promoter (B) applicable to this embodiment preferably has a PAS content of 90 parts by mass or more, more preferably 92 parts by mass or more, and even more preferably 95 parts by mass or more. In such a range, it exhibits an excellent decomposition promoting effect on the biodegradable resin. In the present disclosure, the content of PAS in the biodegradability promoter can be measured by the method described in the examples. Further, although the volatile content of the biodegradability promoter (B) is not particularly limited, from the viewpoint of processability, those having 10% or less are preferable, and those having 5% or less are more preferable.

[0055] In addition, the components other than PAS contained in the biodegradability promoter (B) are not particularly limited as long as the effects of the present invention are not impaired. For example, alkali metal-containing inorganic salts, carboxyalkylamino group-containing compounds, terminal SH group-containing compounds, etc., which are by-products generated during PAS polymerization, as well as unreacted raw materials, organic solvents, water, etc. may be included.

[0056] Further, the biodegradability promoter (B) applicable to this embodiment may, in addition to the above components, optionally contain known and commonly used additives such as plasticizers, fillers, silane coupling agents, dispersants, colorants, antistatic agents, antioxidants, heat stabilizers, ultraviolet stabilizers, ultraviolet absorbers, foaming agents, flame retardants, flame retardant aids, mold release agents, antibacterial agents, nucleating agents, hydrolysis inhibitors, and rust preventives as optional components. These additives are not essential components and may be appropriately adjusted and used according to the purpose and application so as not to impair the effects of the present invention. When the biodegradability promoter (B) contains these optional components, it may be pre-dry blended and mixed with PAS, or may be further melt-kneaded with an extruder or the like after mixing.

[0057] In the biodegradable resin composition according to this embodiment, the blending amount of the biodegradability promoter (B) is preferably 0.001 to 50 parts by mass, more preferably 0.01 to 40 parts by mass, and even more preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the biodegradable resin (A). In such a range, while maintaining the mechanical properties of the biodegradable resin, it is excellent in the balance between biodegradability control and processability of the resin composition.

[0058] The biodegradability promoter (B) incorporated into the biodegradable resin composition according to this embodiment is difficult to decompose in an environment where it is not exposed to ultraviolet rays, such as during product distribution or storage before use. Therefore, the presence or absence of the incorporation does not affect the quality retention period of the resin composition or the molded article. And because it exhibits an excellent effect of promoting the decomposition of biodegradable resin by ultraviolet irradiation, it is possible to rapidly promote the decomposition of the biodegradable resin by irradiating it with ultraviolet rays when used outdoors, after use, or when composted. The reason for obtaining such an effect is not necessarily clear, but it is presumed to be due to the following mechanism. First, PAS in the state added to the biodegradable resin is considered to exist stably in the composition as PAS and not to affect the biodegradable resin as long as it is not exposed to ultraviolet rays. On the other hand, in an ultraviolet environment, molecular cleavage occurs in the S-benzene bond that constitutes PAS, and sulfonic acid is generated through subsequent oxidation reactions and hydrogen adsorption. This sulfonic acid serves as a hydrolysis catalyst for the ester bonds and amide bonds that make up the biodegradable resin, and by acting simultaneously with the moisture in the use environment, it rapidly reduces the molecular weight of the resin to a molecular weight that can be metabolized by microorganisms, leading to the promotion of biodegradability. Such a mechanism is not limited to the atmosphere, and it is considered that the same decomposition behavior occurs as long as ultraviolet rays are irradiated in an aqueous solution (for example, seawater). It should be noted that the above mechanism is only speculative, and even if the effects of the present invention are achieved for other reasons, they are included in the technical scope of the present invention.

[0059] ·Optional component The biodegradable resin composition according to this embodiment may, as an optional component if necessary, be blended with known and commonly used additives such as plasticizers, fillers, silane coupling agents, dispersants, colorants, antistatic agents, antioxidants, heat stabilizers, ultraviolet stabilizers, ultraviolet absorbers, foaming agents, flame retardants, flame retardant aids, mold release agents, antibacterial agents, nucleating agents, hydrolysis inhibitors, and rust preventives as optional components. These additives are not essential components and may be appropriately adjusted and used according to the purpose and application so as not to impair the effects of the present invention.

[0060] <Method for producing biodegradable resin composition> The manufacturing method of the biodegradable resin composition according to this embodiment has a step of blending the above essential components and melt-kneading them in a temperature range equal to or higher than the melting point of the biodegradable resin (A). The method for manufacturing the resin composition used in the present invention is not particularly limited, but it is a method of blending the essential components and optional components as required and then melt-kneading them. More specifically, it is a method of uniformly dry-blending with a tumbler or a Henschel mixer as required, and then charging it into a twin-screw extruder for melt-kneading.

[0061] The melt-kneading can be carried out by heating to a temperature range in which the resin temperature is equal to or higher than the melting point of the biodegradable resin (A), preferably a temperature range of the melting point + 10°C or higher, more preferably the melting point + 10°C or higher, still more preferably the melting point + 20°C or higher, and preferably up to the melting point + 150°C or lower, more preferably up to the melting point + 80°C or lower.

[0062] From the viewpoints of dispersibility and productivity, a twin-screw kneading extruder is preferable as the melt-kneading machine. For example, it is preferable to carry out melt-kneading while appropriately adjusting the range of the discharge amount of the resin component of 5 to 500 (kg / hr) and the range of the screw rotation speed of 50 to 500 (rpm), and it is more preferable to carry out melt-kneading under the condition that the ratio (discharge amount / screw rotation speed) is in the range of 0.02 to 5 (kg / hr / rpm). In addition, the addition and mixing of each component to the melt-kneading machine may be carried out simultaneously or separately. For example, when adding a fibrous filler as required, it is preferable to charge it into the extruder from the side feeder of the twin-screw kneading extruder from the viewpoint of dispersibility. The position of such a side feeder is preferably such that the ratio of the distance from the resin charging part (top feeder) of the twin-screw kneading extruder to the side feeder to the total length of the screw of the extruder is 0.1 or more, more preferably 0.3 or more. Also, such a ratio is preferably 0.9 or less, more preferably 0.7 or less.

[0063] The biodegradable resin composition according to the present disclosure obtained by melt-kneading as described above is a melt mixture containing the above essential components, optional components added as necessary, and their derived components. Therefore, the biodegradable resin composition of the present disclosure has a morphology in which the biodegradable resin (A) forms a continuous phase and the biodegradability promoter (B) and other optional components are dispersed.

[0064] The biodegradable resin composition according to this embodiment, after the melt-kneading, is preferably processed into forms such as pellets, chips, granules, powders, etc. after extruding the resin composition in a molten state into strands by a known method, and then pre-dried in a temperature range of 60 to 150 °C as necessary.

[0065] In addition, the manufacturing method of the biodegradable resin composition according to this embodiment includes a method for manufacturing a PAS resin composition in which the biodegradable resin composition obtained by the manufacturing method described above is used as a masterbatch and further diluted with a biodegradable resin. That is, as one of the other embodiments of the present disclosure, there is a method for manufacturing a biodegradable resin composition having a step of using the biodegradable resin composition obtained by the manufacturing method described above as a masterbatch and further diluting it with a biodegradable resin. As a method for diluting the biodegradable resin composition, dry blending may be used, or it may be melt-kneaded again under the same conditions as the manufacturing method of the above resin composition. The biodegradable resin used for dilution is not particularly limited as long as the effects of the present invention are not impaired, and it may be the same as the resin blended in the masterbatch, or another type of biodegradable resin, and various selections can be made according to the processing conditions and applications. From the viewpoint of efficiently decomposing the resin, the blending amount of the biodegradability promoter (B) with respect to 100 parts by mass of the resin composition obtained after dilution is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and still more preferably 0.1 part by mass.

[0066] <Molded article, manufacturing method of molded article> The molded article according to this embodiment is obtained by melt-molding a biodegradable resin composition. Further, the method for manufacturing the molded article according to this embodiment includes a step of melt-molding the biodegradable resin composition produced by the method described above. Therefore, the molded article according to this embodiment has a morphology in which the biodegradable resin (A) forms a continuous phase and the biodegradable accelerator (B) and optional components are dispersed.

[0067] The biodegradable resin composition according to this embodiment can be used for various moldings such as injection molding, compression molding, composite, sheet, pipe extrusion molding, co-extrusion molding, drawing molding, blow molding, transfer molding, non-woven fabric molding, etc. However, when manufacturing a plate-like or sheet-like molded body, for example, methods of melt-molding using an extrusion molding method, a flat press, a profile extrusion molding method, a blow molding method, a compression molding method, a vacuum molding method, an injection molding method, etc. can be mentioned. Further, when manufacturing a film-like molded article, for example, a melt extrusion method, a solution casting method, an inflation film molding, a cast molding, an extrusion lamination molding, a calender molding, a sheet molding, a fiber molding, a blow molding, an injection molding, a rotational molding, a coating molding can be mentioned. These films may be further stretch-molded.

[0068] In addition, various known and publicly used secondary processes can also be performed on the molded article according to this embodiment for the purpose of imparting functions to the surface such as chemical functions, electrical functions, magnetic functions, mechanical functions, wear-resistant functions, etc. Examples of secondary processes include, for example, painting, adhesion, plating, various surface treatments (hydrophilic treatment, antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating, etc.), printing, machining, embossing, etc.

[0069] The molded article according to this embodiment includes a remolded article obtained by recycling a molded article formed by melt-molding the biodegradable resin composition. Specifically, for example, sprues or runners generated during the production of molded articles, articles recovered as off-specification molded articles, or molded articles once used as products are washed as necessary and then pulverized and remelted at a temperature equal to or higher than the melting point of the biodegradable resin (A) to obtain the molded articles. When recycling, it is preferable from the viewpoint of mechanical properties to mix and use the pulverized molded articles with the biodegradable resin composition. The size of the molded article when pulverized is not particularly limited, but from the viewpoints of mixability and processability, it is preferably about the same size as the biodegradable resin composition to be mixed. Further, the mixing ratio is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less of the pulverized molded article with respect to 100 parts by mass of the biodegradable resin composition. Within such a range, recyclability can be improved without impairing the effects exhibited by the biodegradable resin composition of the present disclosure.

[0070] <Use> Since the resin composition and the molded article according to this embodiment are characterized by having little change over time when stored in the dark and exhibiting an excellent decomposition promotion effect by ultraviolet irradiation, agricultural materials such as greenhouse films, multilayer films, coating materials, coating materials for fertilizers, seedling pots, vegetation nets, water retention sheets, etc.; fishing materials such as fishing nets, nori nets, aquaculture nets, fishing lines, fishing bait bags, etc.; packaging materials such as trays, cutlery, stretch films, shrink films, bottles, bags, etc. and food applications; building materials such as curing sheets, construction forms, piles, etc. It can be suitably used for such uses. Furthermore, it can also be used for other general uses.

Examples

[0071] Hereinafter, examples and comparative examples will be used for explanation, but the present invention is not limited to these examples. In the following, unless otherwise specified, “%” and “parts” are based on mass.

[0072] <Reference Examples 1-2, Examples 1-8 and Comparative Examples 1-6> According to the components and compounding amounts described in Tables 1 to 3, each material was compounded. Then, these compounded materials were charged into a twin-screw extruder "TEX-30α (product name)" with a vent, manufactured by Japan Steel Works, Ltd., and melt-kneaded at a resin component discharge rate of 30 kg / hr, a screw rotation speed of 200 rpm, and a set resin temperature of 260 °C to obtain pellets of the resin composition. The obtained pellets were pressed with a NF-37HH type press machine manufactured by Kando Metal Industry Co., Ltd. with the mold temperature set at 190 °C after being preheated for 1 minute to obtain a pressed sheet with a thickness of about 1 mm. Using the obtained pressed sheet as a test piece, it was kept at 55 °C and 50% RH for 200 hours in the dark or under ultraviolet irradiation (60 W / m 2 ) respectively, and then the following tests were conducted.

[0073] <Evaluation>

[0074] (1) Evaluation of Intrinsic Viscosity (IV) Retention For each sample of each test piece before storage in the dark, after storage in the dark, and after ultraviolet irradiation in the air, a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (mass ratio 1 / 1) was used as the solvent for viscosity measurement, and the intrinsic viscosity (IV) was measured at a temperature of 30 °C and a sample concentration of 1.00×10 -2 kg / L solution using a fully automatic solution viscometer ("2CH type DJ504" manufactured by Sentech Co., Ltd.). The retention rate was calculated from the value after the test with respect to the initial value using the following formula. The results are shown in Tables 1 to 3. Retention rate (%) = value after the test (dL / g) / initial value (dL / g) × 100

[0075] (2) Evaluation of Melt Viscosity (MFR) Retention For each sample of each test piece before storage in the dark, after storage in the dark, and after ultraviolet irradiation in the air, the melt viscosity (MFR) was measured using a flow tester "CFT-500D" manufactured by Shimadzu Corporation after holding for 6 minutes. For the test piece using A-1 as the biodegradable resin, the measurement was carried out at a temperature of 190 °C and a load of 2 kg, and for the test piece using A-2, the measurement was carried out at a temperature of 320 °C and a load of 20 kg. In both cases, an orifice with L / D = 10 (mm) / 1 (mm) was used. The retention rate was calculated from the obtained values using the following formula. The retention rate was calculated from the value after the test with respect to the initial value using the following formula. The results are shown in Tables 1 to 3. Retention rate (%) = Value after test (Pa·s) / Initial value (Pa·s) × 100

[0076] (3) Evaluation of soil biodegradability Each sample of each test piece at the initial stage, after storage in the dark, and after ultraviolet irradiation in the air was cryogenically pulverized into a powder. Using 120 mg of each obtained powder, the biodegradability (%) after 60 days was measured from the amount of carbon dioxide generated by the metabolism of microorganisms according to the test method compliant with ISO14855-1. The results are shown in Tables 1 to 3.

[0077] (4) Evaluation of biodegradability in seawater Each sample of each test piece at the initial stage and after ultraviolet irradiation in the air was cryogenically pulverized into a powder. Using 100 mg of each obtained powder, the biodegradability (%) after 60 days was measured from the amount of carbon dioxide generated by the metabolism of microorganisms according to the test method compliant with ISO23977-2. The results are shown in Tables 1 to 3.

[0078] (5) Evaluation of PAS content in the biodegradation promoter Approximately 8.0 mg of the biodegradation promoter obtained in each production example was placed in a Pt pan for TG-DTA measurement, and the mass was accurately measured. The Pt pan was heated with a TG-DTA (TG-DTA6200, manufactured by SII NanoTechnology Inc.) from room temperature (23°C) to 350°C at a heating rate of 50°C / min under a nitrogen stream, and held at 350°C for 30 minutes to thermally decompose and volatilize components other than PAS. The PAS content of the biodegradation promoter was calculated from the difference between the weight after holding and the weight at room temperature (23°C).

[0079] (6) Evaluation of thermal properties of PAS in the biodegradation promoter After melting the biodegradation promoter obtained in each production example at 350°C, it was rapidly cooled to prepare an amorphous film. Approximately 4 mg was taken from this film, and the melting point of PAS was measured using a differential scanning calorimeter (DSC8500 manufactured by Perkin Elmer). When multiple melting points were measured, they were recorded in the form of "lowest melting point to highest melting point".

[0080] (7) Evaluation of the molecular weight of PAS in the biodegradation promoter The weight-average molecular weight of the PAS containing the biodegradation promoter was measured by gel permeation chromatography under the following measurement conditions. Calibration was performed using six types of monodisperse polystyrenes. Apparatus: Ultra-high temperature polymer molecular weight distribution measuring apparatus “SSC-7000” manufactured by Senshu Science Co., Ltd. Column: UT-805L (manufactured by Showa Denko K.K.) Column temperature: 210 °C Solvent: 1-chloronaphthalene Measurement method: UV detector (360 nm)

[0081]

Table 1

[0082]

Table 2

[0083]

Table 3

[0084] In addition, the blending ratios of the blending components in Tables 1 to 3 were as follows. · Biodegradable resin (A) A-1: Polyester resin “(product number) BioPBS FZ-71PB” manufactured by Mitsubishi Chemical Corporation A-2: Polyamide resin “(product number) ULTRAMID A3W” manufactured by BASF Japan Ltd. · Biodegradation promoter (B) B-1: 99 parts by mass of PAS content, weight-average molecular weight of PAS 20,000, melting point 282 °C, melt viscosity 10 Pa·s B-2: 99 parts by mass of PAS content, weight-average molecular weight of PAS 2,000, melting point about 140 to 250 °C, melt viscosity 3 Pa·s B-3: PBS masterbatch containing 50 parts by mass of 99 parts by mass of PAS content, weight-average molecular weight of PAS 2,000, melting point about 140 to 250 °C, melt viscosity 3 Pa·s B-4: PAS content 99 parts by mass, weight-average molecular weight of PAS 60,000, melting point 282 °C, melt viscosity 400 Pa·s b-5: PAS content 99 parts by mass, weight-average molecular weight of PAS 150,000, melting point about 282 °C, melt viscosity 1500 Pa·s b-6: Poly[(R)-3-hydroxybutyric acid] (PHB) manufactured by Sigma-Aldrich Japan

[0085] (Production Example 1) Manufacturing method of B-1 Into a 150 L autoclave equipped with a stirrer blade and a bottom valve connected to a force gauge, a thermometer, and a condenser, 14.148 kg of 45% sodium hydrosulfide (47.55 wt% NaSH), 9.541 kg of 48% caustic soda (48.8 wt% NaOH), and 38.0 kg of N-methyl-2-pyrrolidone (NMP) were charged. While stirring under a nitrogen stream, the temperature was raised to 209 °C, and 12.150 kg of water was distilled off (the remaining water content was 1.13 moles per mole of NaSH). Then, the autoclave was sealed and cooled to 180 °C, and 17.874 kg of p-dichlorobenzene (p-DCB) and 16.0 kg of NMP were charged. Using nitrogen gas, the pressure was increased to 0.1 MPa at a gauge pressure at a liquid temperature of 150 °C, and the temperature increase was started. When the temperature reached 260 °C, the upper part of the autoclave was sprinkled with water for cooling, and the reaction was carried out at 260 °C for 2 hours. During the cooling of the upper part of the autoclave, the liquid temperature was kept constant so that it did not drop. Next, the temperature was lowered and the cooling of the upper part of the autoclave was stopped. The maximum pressure during the reaction was 0.87 MPa. After the reaction, it was cooled, the bottom valve was opened at 100 °C, and the reaction slurry was transferred to a 150 L flat plate filter and pressure-filtered at 120 °C. 50 kg of warm water at 70 °C was added to the obtained cake and stirred, then filtered, and another 25 kg of warm water was added and filtered. Next, the operation of adding 25 kg of warm water, stirring for 1 hour, filtering, and then adding 25 kg of warm water and filtering was repeated twice. The obtained cake was dried at 120 °C for 15 hours using a hot air circulation dryer to obtain a biodegradation promoter (B-1).

[0086] (Production Example 2) Manufacturing method of B-2 Into a 150 L autoclave equipped with a pressure gauge, a thermometer, a stirring blade connected to a condenser, and a bottom valve, 19.413 kg (150 mol) of flaky sodium sulfide (60.3 wt% Na2S) and 45.0 kg (454 mol) of NMP were charged. While stirring under a nitrogen stream, the temperature was raised to 209 °C, and 4.644 kg of water was distilled off (the remaining water content was 1.13 mol per mol of sodium sulfide). Then, the autoclave was sealed and cooled to 180 °C, and 21.631 kg (147 mol) of p-DCB and 18.0 kg (182 mol) of NMP were charged. Using nitrogen gas, the pressure was increased to 0.1 MPa gauge pressure at a liquid temperature of 150 °C, and the temperature increase was started. The temperature was raised to 240 °C over 135 minutes and held for 30 minutes. Then, the temperature was raised to 250 °C over 40 minutes and held for 73 minutes to complete the reaction. Then, the autoclave was cooled. The bottom valve of the autoclave was opened at 100 °C, and the reaction slurry was transferred to a 150 L plate filter and pressure-filtered at 120 °C. 48.0 kg of NMP was added, and the pressure cake was washed and filtered again. The weight of the recovered NMP filtrate was 80.0 kg. After adding water to the obtained NMP filtrate to form a water slurry, solid-liquid separation and water washing were repeated twice, and then it was dried in a hot air dryer at 120 °C for 4 hours to obtain a powdery biodegradation promoter (B-2).

[0087] (Production Example 3) Method for producing B-3 Based on 100 parts by mass of the biodegradable resin (A-1), the biodegradation promoter (B-2) obtained in Production Example 2 was blended so that it became 100 parts by mass, and a resin composition (masterbatch) was obtained by melt-kneading using a twin-screw extruder with a vent in the same manner as the production method of the above resin composition. This masterbatch was used in Example 6 as the biodegradation promoter (B-3).

[0088] (Production Example 4) Method for producing B-4 [Step 1] Into a 150 L autoclave equipped with a temperature sensor, a capacitor, a dropping tank, a dropping pump, a distillate separation tank, a stirring blade, and a bottom valve, 22.05 kg (150.0 mol) of p-DCB, 59.49 kg (600 mol) of NMP, and 1.08 kg (60.0 mol) of water were charged at room temperature. While stirring, the temperature was raised to 100 °C over 20 minutes under a nitrogen atmosphere, the system was closed, and the temperature was further raised to 220 °C over 40 minutes. At this temperature, the internal pressure was controlled to 0.22 MPa (gauge pressure). Then, a mixed solution containing 18.00 kg of pre-prepared flaky sodium hydrosulfide (Na2S: 58.9 wt%, NaSH: 1.3 wt%), 2.7 kg of hydrated flaky sodium hydrosulfide (NaSH: 71.2 wt%, Na2S: 2.7 wt%), 2.90 kg (68.3 mol) of lithium chloride, and 5.1 kg of water was added dropwise over 3 hours. During the dropwise addition, a dehydration operation was performed simultaneously, water was removed outside the system, and p-DCB that distilled out with water was continuously returned to the autoclave. The dehydration operation and the operation of returning p-DCB were carried out until the temperature reached 240 °C, and the system was sealed when the temperature rise was completed. [Step 2] After that, it was held at the same temperature and pressure for 1 hour, then the internal temperature was raised to 240 °C over 1 hour while lowering the internal pressure to 0.17 MPa, held at this temperature for 1 hour to complete the reaction, and cooled to room temperature. [Step 3] 30 L of water was added to 6.0 kg of the obtained reaction slurry, stirred at 80 °C for 1 hour, and then filtered. This cake was stirred again with 15 L of warm water for 1 hour, filtered, acetic acid was added to adjust the pH to 4.0, stirred for 30 minutes, and then filtered. Further, 15 L of warm water was added to the filter cake, stirred for 30 minutes and filtered, and then filtered. This operation was repeated 3 times. After filtration, it was dried at 120 °C for 10 hours in a hot air dryer to obtain a powdery biodegradation promoter (B-4).

[0089] (Production Example 5) Method for producing b-5 A powdery biodegradation promoter (b-5) was obtained in the same manner as in Production Example 4 except that 6.96 kg (163.8 mol) of lithium chloride was used.

[0090] From Tables 1 to 3, when comparing Examples 1 to 8 with Comparative Examples 1, 3, and 5, it was shown that by using a biodegradation accelerator containing PAS having a specific weight average molecular weight, the melt viscosity and intrinsic viscosity decreased significantly under ultraviolet irradiation, indicating that the degradation was promoted. Also, it was shown that the biodegradability was improved in soil and seawater. Further, when comparing Examples 1 to 8 with Comparative Examples 2 and 4, it was shown that the biodegradation accelerator of the present disclosure can improve the biodegradability under ultraviolet irradiation with a smaller addition amount. Also, when comparing Examples 1 to 8 with Comparative Example 6, it was shown that the resin composition of the present disclosure suppresses the promotion of degradation in the dark and improves the biodegradability only under ultraviolet irradiation. From Example 9, it can be seen that the biodegradability promoter of the present disclosure does not limit the resin type and can improve the biodegradation of polyamide resins as well.

Claims

1. A hydrolysis acceleration method for promoting the hydrolysis of a biodegradable resin having at least an ester bond or an amide bond in the main chain by blending a polyarylene sulfide having a weight average molecular weight of 120,000 or less in an ultraviolet irradiation environment.

2. A method of using a polyarylene sulfide having a weight average molecular weight of 120,000 or less as a hydrolysis accelerator for a biodegradable resin having at least an ester bond or an amide bond in the main chain in an ultraviolet irradiation environment.

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