JP2021008542A - Method for producing polyarylene sulfide - Google Patents

Abstract

To provide a method for producing a polyarylene sulfide (hereinafter, "PAS") with which a PAS having a high molecular weight can be obtained while suppressing a side reaction resulting from an organic polar solvent.SOLUTION: A method for producing a PAS according to the present invention includes: a preparation step in which a mixture is prepared that contains an organic polar solvent containing a pyrrolidone compound represented by formula (1), a sulfur source, water, and a polyhaloaromatic compound; a first polymerization step in which the mixture is heated to initiate a polymerization reaction, producing a prepolymer with a conversion rate of the polyhaloaromatic compound of 50 mol% or more; and a second polymerization step in which, after the first polymerization step, a nonpolar solvent is added to continue the polymerization reaction. In formula (1), R is a hydrocarbon group having at least two carbon atoms.SELECTED DRAWING: None

Description

The present invention relates to a method for producing polyarylene sulfide.

Polyphenylene sulfide (hereinafter, also referred to as "PAS") represented by polyphenylene sulfide (hereinafter, also referred to as "PPS") has heat resistance, chemical resistance, flame retardancy, mechanical strength, electrical properties, and dimensions. It is an engineering plastic with excellent stability. Since PAS can be molded into various molded products, films, sheets, fibers, etc. by general melt processing methods such as extrusion molding, injection molding, and compression molding, it can be used for electrical equipment, electronic equipment, automobile equipment, packaging materials, etc. It is widely used in a wide range of technical fields.

Examples of the method for producing PAS include a method for producing PAS by polymerizing a sulfur source and a dihaloaromatic compound in an organic amide solvent (for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2014-47218 International Publication No. 2006/046748

PAS is widely used as a metal substitute for reducing the weight of automobiles, especially in the field of automobiles. High molecular weight PAS with high toughness is required for automobile applications. However, when the polymerization step is carried out using N-methyl-2-pyrrolidone (hereinafter, also referred to as “NMP”) as the organic polar solvent according to the conventional production method, the by-product derived from NMP reacts with the polymer terminal. Therefore, there is a problem that the production of high-molecular-weight PAS is inhibited.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing PAS capable of obtaining high molecular weight PAS while suppressing side reactions caused by an organic polar solvent.

The present inventors have found that the above object can be achieved by performing a polymerization step using a specific pyrrolidone compound as an organic polar solvent and a non-polar solvent as a phase separation agent, and complete the present invention. I arrived.

（式中、Ｒは、炭素数２以上の炭化水素基である。） The method for producing PAS according to the present invention is
A preparation step for preparing a mixture containing an organic polar solvent containing a pyrrolidone compound represented by the following formula (1), a sulfur source, water, and a polyhaloaromatic compound.
The first polymerization step of heating the mixture to initiate a polymerization reaction to produce a prepolymer having a conversion rate of a polyhalo aromatic compound of 50 mol% or more.
After the first polymerization step, a second polymerization step of adding a non-polar solvent and continuing the polymerization reaction is included.

(In the formula, R is a hydrocarbon group having 2 or more carbon atoms.)

In the method for producing PAS according to the present invention, the R may be a branched or cyclic saturated hydrocarbon group having 3 or more carbon atoms.

In the method for producing PAS according to the present invention, it is preferable that the organic polar solvent does not contain N-methyl-2-pyrrolidone.

In the method for producing PAS according to the present invention, the non-polar solvent may be a hydrocarbon.

In the method for producing PAS according to the present invention, the hydrocarbon may be an aliphatic hydrocarbon.

In the method for producing PAS according to the present invention, the amount of the non-polar solvent may be more than 0.5 mol and 1.5 mol or less with respect to 1 mol of the sulfur source.

According to the present invention, it is possible to provide a method for producing PAS capable of obtaining high molecular weight PAS while suppressing side reactions caused by an organic polar solvent.

An embodiment of the method for producing PAS according to the present invention will be described below. The method for producing PAS in the present embodiment includes a charging step, a first polymerization step, and a second polymerization step as essential steps. The first polymerization step and the second polymerization step may be collectively referred to as a polymerization step. If desired, the method for producing PAS in the present embodiment may include a dehydration step, a cooling step, a post-treatment step, and the like. Hereinafter, each material used in the present invention will be described in detail, and each step will be described in detail.

(Organic polar solvents, sulfur sources, and polyhaloaromatic compounds)
As the organic polar solvent, the sulfur source, and the polyhaloaromatic compound, those usually used in the production of PAS can be used as long as the organic polar solvent contains the pyrrolidone compound represented by the following formula (1). Each of the organic polar solvent, the sulfur source, and the polyhaloaromatic compound may be used alone, or two or more kinds may be mixed and used as long as the combination is capable of producing PAS.

In the above formula (1), R is a hydrocarbon group having 2 or more carbon atoms, preferably 2 or more and 20 or less, more preferably 3 or more and 12 or less, and even more preferably 4 or more and 8 or less. When the carbon number of R is 2 or more, the pyrrolidone compound represented by the formula (1) becomes bulkier than the case where the carbon number of R is 1, that is, R is a methyl group, and the formula (1) is used. Since the susceptibility to nucleophilic attack on paradichlorobenzene or the like by the amino group in the ring-opened body of the represented pyrrolidone compound tends to decrease, by-products derived from the pyrrolidone compound are unlikely to occur, and the by-products are polymers. It is less likely that the reaction with the terminal will inhibit the production of high molecular weight PAS. On the other hand, when the carbon number of R is 20 or less, the molecular weight of the pyrrolidone compound does not become too large, and the handleability as an organic polar solvent is easily maintained. From the viewpoint of handleability, availability, etc., the R is a saturated hydrocarbon group having 2 or more carbon atoms, preferably 2 or more and 20 or less, more preferably 3 or more and 12 or less, and even more preferably 4 or more and 8 or less. Is preferable, and since the pyrrolidone compound represented by the formula (1) becomes bulkier, the number of carbon atoms is 3 or more, preferably 3 or more and 20 or less, more preferably 3 or more and 12 or less, still more preferably 4 or more and 8 or less. More preferably, it is a branched or cyclic saturated hydrocarbon group. The R may have a substituent such as a hydroxy group, an amino group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a mercapto group, or the like.

Examples of R include ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, sec-pentyl group, 3-. Pentyl group, tert-pentyl group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, n-hexadecyl group , N-octadecyl group, n-eicosyl group, and other alkyl groups having 2 or more carbon atoms, preferably 2 or more and 20 or less, more preferably 3 or more and 12 or less, and even more preferably 4 or more and 8 or less; cyclopropyl group, cyclobutyl. Group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclodecyl group, cyclododecyl group, cyclooctadecyl group, cycloeicosyl group, etc., having 3 or more carbon atoms, preferably 3 or more and 20 or less carbon atoms, more preferably 3 Cycloalkyl group of 12 or more, more preferably 4 or more and 8 or less; vinyl group, allyl group, 1-propenyl group, isopropenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, 1-methyl -1-Propenyl group, 1-methyl-2-propenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-hexenyl group, 2-hexenyl group, 3-hexenyl group, 4- An alkenyl group having 2 or more carbon atoms, preferably 2 or more and 20 or less, more preferably 3 or more and 12 or less, still more preferably 4 or more and 8 or less, such as a hexenyl group and a 5-hexenyl group; an ethynyl group and a 2-propynyl group. Propargyl group; 1-butylyl group, 2-butynyl group, 3-butynyl group, 1-methyl-2-propynyl group, 1-hexynyl group, 2-hexynyl group, 3-hexynyl group, 4-hexynyl group, 5-hexynyl Alkinyl groups such as groups having 2 or more carbon atoms, preferably 2 or more and 20 or less, more preferably 3 or more and 12 or less, still more preferably 4 or more and 8 or less; phenyl group, o-tolyl group, m-tolyl group, p. -Aryl groups having 6 or more carbon atoms, preferably 6 or more and 20 or less, more preferably 6 or more and 12 or less, still more preferably 6 or more and 8 or less, such as a trill group, a 1-naphthyl group and a 2-naphthyl group; a benzyl group. , Penetyl group, 1-phenylethyl group, 1-phenylpropyl group, 2-phenylpropyl group, 3-phenylpropyl group, 1-methyl-1-phenylethyl group, 1-methyl-2-phenylethyl group, etc. 7 carbon atoms As mentioned above, preferably 7 or more and 20 or less, more preferably 7 or more and 12 or less, still more preferably 7 or 8 aralkyl groups. From the viewpoint of handleability, availability, and the like, R is preferably the above-mentioned alkyl group and the above-mentioned cycloalkyl group. Since the pyrrolidone compound represented by the formula (1) becomes bulkier, R includes an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, an isohexyl group, and a 1-methylheptyl group. 2-Ethylhexyl group, 1-propylpentyl group, 1,1,3,3-tetramethylbutyl group, 2-butyloctyl group, 2-octyldodecyl group, etc., having 3 or more carbon atoms, preferably 3 or more and 20 or less carbon atoms, More preferably 3 or more and 12 or less, still more preferably 4 or more and 8 or less branched alkyl groups; cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclodecyl group, cyclododecyl group, Cycloalkyl groups having 3 or more carbon atoms, preferably 3 or more and 20 or less, more preferably 3 or more and 12 or less, still more preferably 4 or more and 8 or less, such as a cyclooctadecyl group and a cycloeicosyl group, are more preferable. Cycloalkyl groups having 4 or more and 8 or less carbon atoms, such as cyclopentyl group, cyclohexyl group, cycloheptyl group, and cyclooctyl group, are even more preferable, and from the viewpoint of substituent stability, cyclopentyl group, cyclohexyl group, and cycloheptyl group. Is even more preferable.

Specific examples of the pyrrolidone compound represented by the formula (1) include N-ethyl-2-pyrrolidone, Nn-propyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, and Nn-butyl-2-. N-alkylpyrrolidone compounds such as pyrrolidone, N-isobutyl-2-pyrrolidone, Nn-hexyl-2-pyrrolidone, Nn-octyl-2-pyrrolidone; N-cyclohexyl-2-pyrrolidone (hereinafter, "NCP") N-cycloalkylpyrrolidone compounds such as); N-vinyl-2-pyrrolidone; N-phenyl-2-pyrrolidone; N-benzyl-2-pyrrolidone can be mentioned, and from the viewpoint of handleability, availability, etc. The above-mentioned N-alkylpyrrolidone compound and the above-mentioned N-cycloalkylpyrrolidone compound are preferable, and the reactivity of the pyrrolidone compound represented by the formula (1) tends to decrease, and the production of high molecular weight PAS is less likely to be inhibited. Therefore, N-isopropyl -2-Pyrrolidone, N-isobutyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone are preferable, and N-cyclohexyl-2-pyrrolidone is more preferable from the viewpoint of further handleability, availability, and the like.

Examples of the organic polar solvent other than the pyrrolidone compound represented by the formula (1) include an organic amide solvent other than the pyrrolidone compound represented by the formula (1); an aprotic organic polar solvent composed of an organic sulfur compound; a cyclic formula. Examples thereof include an aprotic organic polar solvent composed of an organic phosphorus compound. Examples of the organic amide solvent other than the pyrrolidone compound represented by the formula (1) include amide compounds such as N, N-dimethylformamide and N, N-dimethylacetamide; and N-alkylcaprolactam compounds such as N-methyl-ε-caprolactam. N-Methyl-2-pyrrolidone (hereinafter, also referred to as "NMP"); N, N-dialkylimidazolidinone compounds such as 1,3-dialkyl-2-imidazolidinone; tetraalkylurea such as tetramethylurea. Compounds; Examples thereof include hexaalkylphosphate triamide compounds such as hexamethylphosphate triamide. Examples of the aprotic organic polar solvent composed of an organic sulfur compound include dimethyl sulfoxide and diphenyl sulfone. Examples of the aprotic organic polar solvent composed of the cyclic organic phosphorus compound include 1-methyl-1-oxophosphoran. Among the organic polar solvents other than the pyrrolidone compound represented by the formula (1), the organic amide solvent is preferable in terms of availability, handleability, etc., and the N-alkylcaprolactam compound and the N, N-dialkylimidazolidinone compound are used. More preferred, N-methyl-ε-caprolactam and 1,3-dialkyl-2-imidazolidinone are even more preferred. In the present invention, it is preferable that the organic polar solvent does not contain NMP so that the side reaction caused by the organic polar solvent can be effectively suppressed. From the viewpoint of effectively suppressing side reactions caused by the organic polar solvent, operability, efficiency, etc., the organic polar solvent is composed of the pyrrolidone compound represented by the formula (1), that is, the organic polarity. In the solvent, the proportion of the pyrrolidone compound represented by the formula (1) is preferably 100 mol%.

The amount of the organic polar solvent used is preferably 1 to 30 mol, more preferably 3 to 15 mol, with respect to 1 mol of the sulfur source, from the viewpoint of efficiency of the polymerization reaction and the like.

Examples of the sulfur source include alkali metal sulfide, alkali metal hydrosulfide, and hydrogen sulfide, and alkali metal sulfide and alkali metal hydrosulfide are preferable. The sulfur source can be handled in either an aqueous slurry state or an aqueous solution state, and is preferably in an aqueous solution state from the viewpoint of handleability such as measurable property and transportability. Examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide. Examples of the alkali metal hydrosulfide include lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, and cesium hydrosulfide.

A polyhalo aromatic compound refers to an aromatic compound in which two or more hydrogen atoms directly connected to an aromatic ring are substituted with halogen atoms, and an aromatic compound in which two hydrogen atoms directly connected to an aromatic ring are substituted with halogen atoms. Whether it is a compound (that is, a dihalo aromatic compound) or an aromatic compound in which three or more hydrogen atoms directly connected to an aromatic ring are substituted with halogen atoms (also referred to as "polyhalo aromatic compound having three or more halogen substitutions"). Good.

Examples of the polyhaloaromatic compound include o-dihalobenzene, m-dihalobenzene, p-dihalobenzene, dihalotoluene, dihalonaphthalene, methoxy-dihalobenzene, dihalobiphenyl, dihalobenzoic acid, dihalodiphenyl ether, dihalodiphenylsulfone and dihalo. Dihalo aromatic compounds such as diphenylsulfoxide and dihalodiphenylketone; 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, hexachlorobenzene, 1,2,3 4-Tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,3,5-trichloro-2,4,6-trimethylbenzene, 2,4,6-trichlorotoluene, 1,2,3-trichloronaphthalene , 1,2,4-trichloronaphthalene, 1,2,3,4-tetrachloronaphthalene, 2,2', 4,4'-tetrachlorobiphenyl, 2,2', 4,4'-tetrachlorobenzophenone, Examples thereof include polyhaloaromatic compounds having 3 or more halogen substitutions, such as 2,4,2'-trichlorobenzophenone. The halogen atom refers to each atom of fluorine, chlorine, bromine, and iodine, and two or more halogen atoms in the polyhaloaromatic compound may be the same or different. Among them, p-dichlorobenzene, m-dihalobenzene, and a mixture thereof are preferable, p-dichlorobenzene is more preferable, and p-dichlorobenzene (hereinafter, also referred to as "pDCB") is preferable in terms of availability, reactivity, and the like. Especially preferable.

The amount of the polyhalo aromatic compound used is preferably 0.99 to 1.50 mol, more preferably 0.92 to 1.10 mol, and even more preferably to 1 mol of the sulfur source charge. It is 0.95 to 1.05 mol. When the amount used is within the above range, a decomposition reaction is unlikely to occur, a stable polymerization reaction can be easily carried out, and a high molecular weight polymer can be easily produced.

(Dehydration process)
Prior to the charging step, the dehydration step is carried out from within the system containing an organic polar solvent containing the pyrrolidone compound represented by the above formula (1), a sulfur source, and optionally a mixture containing an alkali metal hydroxide. This is a step of discharging at least a part of the distillate containing water to the outside of the system. The polymerization reaction between the sulfur source and the polyhalo aromatic compound is affected by the amount of water present in the polymerization reaction system, such as being promoted or inhibited. Therefore, it is preferable to reduce the amount of water in the polymerization reaction system by performing a dehydration treatment before the polymerization so that the amount of water does not inhibit the polymerization reaction.

In the dehydration step, it is preferable to perform dehydration by heating in an atmosphere of an inert gas. The water to be dehydrated in the dehydration step is water contained in each raw material prepared in the dehydration step, an aqueous medium of an aqueous mixture, water produced as a by-product by the reaction between each raw material, and the like.

The heating temperature in the dehydration step is not particularly limited as long as it is 300 ° C. or lower, and is preferably 100 to 250 ° C. The heating time is preferably 15 minutes to 24 hours, more preferably 30 minutes to 10 hours.

In the dehydration step, dehydration is performed until the water content is within a predetermined range. That is, in the dehydration step, the amount is preferably 0.5 to 2.4 mol with respect to 1.0 mol of the sulfur source (hereinafter, also referred to as "charged sulfur source" or "effective sulfur source") in the charged mixture (described later). It is desirable to dehydrate until it becomes. When the water content becomes too small in the dehydration step, water may be added in the preparation step prior to the polymerization step to adjust the water content to a desired level.

(Preparation process)
The charging step is a step of preparing a mixture containing an organic polar solvent containing a pyrrolidone compound represented by the formula (1), a sulfur source, water, and a polyhaloaromatic compound. The mixture charged in the charging process is also referred to as "prepared mixture".

When the dehydration step is performed, the amount of sulfur source in the charged mixture (hereinafter, also referred to as "the amount of charged sulfur source" or "the amount of effective sulfur source") is determined from the molar amount of the sulfur source input as a raw material. It can be calculated by subtracting the molar amount of hydrogen sulfide volatilized in.

When the dehydration step is performed, in the preparation step, an alkali metal hydroxide and water can be added to the mixture remaining in the system after the dehydration step, if necessary. In particular, the alkali metal hydroxide can be added in consideration of the amount of hydrogen sulfide produced during dehydration and the amount of alkali metal hydroxide generated during dehydration. As the alkali metal hydroxide, those usually used in the production of PAS can be used. The alkali metal hydroxide may be used alone, or may be used in combination of two or more as long as it is a combination capable of producing PAS. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. The number of moles of the alkali metal hydroxide is the number of moles of the alkali metal hydroxide added as needed in the preparation step, and the alkali added as needed in the dehydration step when the dehydration step is performed. It is calculated based on the number of moles of the metal hydroxide and the number of moles of the alkali metal hydroxide generated with the production of hydrogen sulfide in the dehydration step. When the sulfur source contains alkali metal sulfide, the number of moles of alkali metal hydroxide per mol of sulfur source (charged sulfur source) shall be calculated including the number of moles of alkali metal sulfide. When hydrogen sulfide is used as the sulfur source, the number of moles of alkali metal hydroxide per mole of sulfur source (charged sulfur source) shall be calculated including the number of moles of alkali metal sulfide produced. .. However, the number of moles of alkali metal hydroxide added for other purposes, for example, an embodiment of a combination of an organic carboxylic acid metal salt as a polymerization aid and / or an alkali metal hydroxide with an organic carboxylic acid and an alkali metal hydroxide. When used in, the number of moles of alkali metal hydroxide consumed in reactions such as neutralization shall not be included in the number of moles of alkali metal hydroxide per mole of sulfur source (prepared sulfur source). .. Furthermore, when at least one acid selected from the group consisting of inorganic acids and organic acids is used for some reason, the alkali metal hydroxide required to neutralize the at least one acid. The number of moles shall not be included in the number of moles of alkali metal hydroxide per mole of the sulfur source (charged sulfur source).

In the charged mixture, the amounts of each of the organic polar solvent and the polyhalo aromatic compound used are set, for example, in the range shown in the above description regarding the organic polar solvent and the polyhalo aromatic compound with respect to 1 mol of the charged amount of the sulfur source. ..

(Polymerization process)
The polymerization step is a step of subjecting the charged mixture to a polymerization reaction. In the polymerization step, the sulfur source and the polyhaloaromatic compound are polymerized in an organic polar solvent containing the pyrrolidone compound represented by the formula (1) to generate PAS. When the organic polar solvent contains the pyrrolidone compound represented by the formula (1), a by-product derived from the organic polar solvent is unlikely to be produced, and the by-product reacts with the polymer terminal to inhibit the production of high molecular weight PAS. It is easy to obtain a high-molecular-weight PAS because it is less likely to occur.

In order to obtain high molecular weight PAS, the polymerization reaction is carried out in two or more steps. That is, in the polymerization step, after the first polymerization step of heating the mixture to start the polymerization reaction and producing a prepolymer having a conversion rate of the polyhalo aromatic compound of 50 mol% or more, and after the first polymerization step, A second polymerization step of adding a non-polar solvent and continuing the polymerization reaction is included.

In the first polymerization step, the conversion of the polyhalo aromatic compound is preferably 50 to 98 mol%, more preferably 60 to 97 mol%, still more preferably 65 to 96 mol%, and particularly preferably 70 to 95 mol%. is there. The conversion rate of the polyhalo aromatic compound is calculated based on the amount of the polyhalo aromatic compound remaining in the reaction mixture determined by gas chromatography, the residual amount, the amount of the polyhalo aromatic compound charged, and the amount of the sulfur source charged. Can be done.

In the second polymerization step following the first polymerization step, the degree of polymerization of the prepolymer increases. In the second polymerization step, after the first polymerization step, a non-polar solvent is added to continue the polymerization reaction. The non-polar solvent is added as a phase separation agent. A high molecular weight PAS can be obtained by going through the second polymerization step. When the carbon number of R in the pyrylolidone compound represented by the formula (1) increases, the compatibility with water decreases. Therefore, a non-polar solvent compatible with the pyrrolidone compound represented by the formula (1) is selected as the phase separation agent. By adding the phase separation agent, the reaction between the prepolymers increases and the degree of polymerization increases.

Examples of the non-polar solvent include hydrocarbons, and in order to promote the reaction between prepolymers, it is easier to obtain a high-molecular-weight PAS when the non-polar solvent does not dissolve the prepolymer. Therefore, an aliphatic hydrocarbon Is preferable, alkanes (paraffinic hydrocarbons) are more preferable, and linear alkanes are even more preferable. The number of carbon atoms of hydrocarbons, aliphatic hydrocarbons, alkanes, and linear alkanes is particularly limited as long as hydrocarbons, aliphatic hydrocarbons, alkanes, and linear alkanes can be used as solvents in the second polymerization step. However, for example, 6 to 24 are mentioned, and from the viewpoint of handleability and the like, 7 to 20 is preferable, 8 to 18 is more preferable, 9 to 16 is even more preferable, and 10 to 14 is particularly preferable. Specific examples of the non-polar solvent include n-hexane, n-heptane, n-octane, isooctane, n-nonane, n-decane, n-dodecane, n-tetradecane, n-hexadecane, n-octadecan, and n-icosane. , N-Tetracosane and the like, and since it is easy to obtain a higher molecular weight PAS and is excellent in handleability, availability, etc., isooctane, n-decane, and n-tetradecane are preferable, and n-decane and n-tetradecane are preferable. More preferred.

The amount of the non-polar solvent used is preferably more than 0.5 mol and 1.5 mol or less, more preferably 0.7 to 1.4 mol, and further preferably 0.9 to 1.3 mol with respect to 1 mol of the sulfur source. More preferably, 1.0 to 1.2 mol is particularly preferable. When the amount of the non-polar solvent used exceeds 0.5 mol, the molecular weight of the obtained PAS tends to increase, and the high molecular weight PAS tends to be obtained. When the amount of the non-polar solvent used is 1.5 mol or less, the yield of high molecular weight PAS tends to be improved.

In the second polymerization step, a phase separation agent other than the non-polar solvent may be added in addition to the non-polar solvent, but since it is easy to obtain a high molecular weight PAS, it is necessary not to add a phase separation agent other than the non-polar solvent. preferable. The phase separating agent other than the non-polar solvent is not particularly limited, and for example, water, an organic carboxylic acid metal salt, an organic sulfonic acid metal salt, an alkali metal halide, an alkaline earth metal halide, and an alkaline earth of an aromatic carboxylic acid. At least one selected from the group consisting of metal salts, alkali metal phosphates, and alcohols can be mentioned. Of these, water is preferable because it is inexpensive and easy to post-treat. In addition, the above-mentioned salts may have a mode in which the corresponding acid and base are added separately. The amount of the phase separation agent other than the non-polar solvent used varies depending on the type of the compound used, but may be in the range of 0.01 to 20 mol with respect to 1 kg of the organic polar solvent. In particular, when water is added as a phase separation agent, the amount of water in the reaction system may be more than 4 mol and 20 mol or less per 1 kg of the organic polar solvent, and may be 4.1 to 14 mol, or 4.2 to 10 mol. It may be.

In the second polymerization step, the amount of alkali metal hydroxide is preferably 1.00 to 1.10 mol, more preferably 1.01 to 1.08 mol, and even more preferably 1 with respect to 1 mol of the sulfur source. It is 0.02 to 1.07 mol. When the amount of the alkali metal hydroxide is within the above range, the molecular weight of the obtained PAS is likely to increase, and the high molecular weight PAS is more likely to be obtained. In the second polymerization step, the reaction mixture is adjusted so that the final amount of the alkali metal hydroxide is within the above range based on the amount of the alkali metal hydroxide present in the reaction mixture after the first polymerization step. Alkali metal hydroxide is added to the water.

In the polymerization step, it is preferable to carry out the polymerization reaction under heating at a temperature of 170 to 300 ° C. from the viewpoint of the efficiency of the polymerization reaction and the like. The polymerization temperature in the polymerization step is more preferably in the range of 180 to 280 ° C. in order to suppress side reactions and decomposition reactions. In particular, in the first polymerization step, from the viewpoint of the efficiency of the polymerization reaction, the polymerization reaction is started under heating at a temperature of 170 to 270 ° C. to produce a prepolymer having a conversion rate of a polyhaloaromatic compound of 50 mol% or more. Is preferable. The polymerization temperature in the first polymerization step is preferably selected from the range of 180 to 265 ° C. in order to suppress side reactions and decomposition reactions.

The polymerization reaction in this polymerization step may be carried out in a batch manner or continuously. For example, at least the supply of an organic polar solvent, a sulfur source, and a polyhalo aromatic compound, the formation of PAS by polymerization of the sulfur source and the polyhalo aromatic compound in the organic polar solvent, and the recovery of the reaction mixture containing PAS. , Can be carried out in parallel to carry out the polymerization reaction continuously.

(Cooling process)
The cooling step is a step of cooling the reaction mixture after the polymerization step. The specific operation in the cooling step is as described in, for example, Japanese Patent No. 6062924.

(Post-treatment process (separation process, cleaning process, recovery process, etc.))
In the method for producing PAS in the present embodiment, the post-treatment step after the polymerization reaction can be carried out by a conventional method, for example, by the method described in JP-A-2016-0562332.

(Obtained PAS)
The PAS obtained by the method for producing PAS in the present embodiment preferably has a weight average molecular weight of 35,000 or more, more preferably 38,000 or more, and even more preferably 40,000 or more. , 41,000 or more is even more preferable, and 42,000 or more is particularly preferable. When the weight average molecular weight is 35,000 or more, the toughness of PAS tends to be high. The upper limit of the weight average molecular weight is not particularly limited, and may be 60,000 or less, 55,000 or less, 50,000 or less, or 46,000 or less. In the present specification, the weight average molecular weight means a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography.

The PAS obtained by the method for producing PAS in the present embodiment can be used as it is, or after being oxidatively crosslinked, it can be used alone or, if desired, by blending various inorganic fillers, fibrous fillers and various synthetic resins, and various injection moldings. It can be molded into products or extruded products such as sheets, films, fibers, and pipes.

In the method for producing PAS in the present embodiment, PAS is not particularly limited and is preferably PPS.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims, and the embodiment obtained by appropriately combining the disclosed technical means is also the present invention. Included in the technical scope. In addition, all the documents described in the present specification are incorporated by reference.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the examples.

1. 1. Measurement method: Nitrogen content (index of by-product generation)
The nitrogen content of about 10 mg of the dried polymer was measured using a trace nitrogen-sulfur analyzer (manufactured by Astec Co., Ltd., model "ANTEK7000"). Nitrogen content is shown as a sample (polymer) conversion value (ppm, mass basis).

2. 2. About the first polymerization step [Reference Example 1]
(Preparation process)
In a 1 L autoclave, 73.9 g of anhydrous sodium sulfide (purity 98% by mass, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) (NaOH / effective S = 1.00 (mol / mol)), p-dichlorobenzene (hereinafter, "pDCB") Abbreviation) 139.1 g (pDCB / effective S = 1.02 (mol / mol)), N-cyclohexyl-2-pyrrolidone (hereinafter abbreviated as "NCP") 347.8 g (NCP / effective S = 375 in a can) (G / mol)) and 25.1 g of water (total amount of water in the can / effective S = 1.50 (mol / mol)) were added and replaced with nitrogen.

(First polymerization step)
The temperature was raised to 240 ° C. with stirring, and the reaction was carried out as it was for 7 hours. The conversion rate of pDCB was 86.12 mol%. Table 1 shows the results of measuring the characteristics of a part of the obtained polymer.

[Reference example 2]
The operation was carried out in the same manner as in Reference Example 1 except that NMP was used instead of NCP and the reaction time after raising the temperature to 240 ° C. was changed from 7 hours to 1 hour.

3. 3. About the second polymerization step [Example 1]
(Second polymerization step)
Following Reference Example 1, 208 g of tetradecane (hereinafter, also referred to as “TD”) (TD / effective S = 1.13 (mol / mol)) and 2.49 g of sodium hydroxide (NaOH / effective) as phase separation agents. S = 1.065 (mol / mol)) was added, the temperature was raised to 260 ° C., and the reaction was carried out as it was for 3 hours.

(Post-treatment process)
After the reaction mixture after the completion of the second polymerization step was cooled to room temperature, the polymer (granular polymer) was sieved through a screen of 100 mesh (opening 150 μm). The separated polymer was washed with acetone three times, washed with water three times, washed with 0.3% by mass acetic acid, and further washed with water four times to obtain a washed polymer. The washed polymer was dried at a temperature of 120 ° C. for 4 hours. The properties of the granular polymer thus obtained are shown in Table 1.

[Comparative Example 1]
(Second polymerization step)
Following Reference Example 2, 18.9 g of water (H ₂ O / effective S = 2.63 (mol / mol)) and 2.49 g of sodium hydroxide (NaOH / effective S = 1.065 (NaOH / effective S = 1.065)) as a phase separation agent. Mol / mol)) was added, the temperature was raised to 260 ° C., and the reaction was carried out as it was for 3 hours.

(Post-treatment process)
The operation was performed in the same manner as in Example 1.

[Comparative Example 2]
The procedure was the same as in Comparative Example 1 except that 208 g of tetradecane (TD / effective S = 1.13 mol / mol) was used instead of 18.9 g of water as the phase separation agent.

[Comparative Example 3]
The procedure was the same as in Example 1 except that 18.9 g of water (H ₂ O / effective S = 2.63 (mol / mol)) was used instead of 208 g of tetradecane as the phase separation agent. Since the obtained polymer was pulverized, it is presumed that it was not phase-separated.

4. Discussion In Example 1, by performing the polymerization step using NCP as the organic polar solvent and tetradecane as the phase separation agent, PPS having a low nitrogen content and a large weight average molecular weight can be obtained. It was. On the other hand, in Comparative Examples 1 to 3 in which the polymerization step was carried out using NMP instead of NCP as the organic polar solvent and / or water as the phase separation agent, the obtained PPS had a high nitrogen content. The weight average molecular weight was small. As described above, in the present invention, the organic polar solvent is caused by performing the polymerization step using an organic polar solvent containing the pyrrolidone compound represented by the formula (1) and using a non-polar solvent as a phase separation agent. It was confirmed that a high-molecular-weight PAS can be obtained while suppressing the side reaction.

Claims (6)

A preparation step for preparing a mixture containing an organic polar solvent containing a pyrrolidone compound represented by the following formula (1), a sulfur source, water, and a polyhaloaromatic compound.
The first polymerization step of heating the mixture to initiate a polymerization reaction to produce a prepolymer having a conversion rate of a polyhalo aromatic compound of 50 mol% or more.
A method for producing polyarylene sulfide, which comprises a second polymerization step of adding a non-polar solvent after the first polymerization step and continuing the polymerization reaction.

(In the formula, R is a hydrocarbon group having 2 or more carbon atoms.) The method according to claim 1, wherein R is a branched or cyclic saturated hydrocarbon group having 3 or more carbon atoms. The method according to claim 1 or 2, wherein the organic polar solvent does not contain N-methyl-2-pyrrolidone. The method according to any one of claims 1 to 3, wherein the non-polar solvent is a hydrocarbon. The method according to claim 4, wherein the hydrocarbon is an aliphatic hydrocarbon. The method according to any one of claims 1 to 5, wherein the amount of the non-polar solvent is more than 0.5 mol and 1.5 mol or less with respect to 1 mol of the sulfur source.