Method for producing a polyarylene sulfide oligomer mixture, and method for producing a polyarylene sulfide resin

Abstract

To provide a production method of a polyarylene sulfide (PAS) oligomer mixture which controls a ring opening rate of a cyclic PAS oligomer included in a liquid phase component filtered in a production step of a PAS resin, to concentrate the oligomer.SOLUTION: There is provided a production method of a PAS oligomer mixture which includes the steps of: reacting, in an organic polar solvent, a polyhalo aromatic compound with (i) an alkali metal sulfide or (ii) an alkali metal hydrosulfide and an alkali metal hydroxide to obtain a crude reaction mixture containing a PAS resin, a cyclic PAS oligomer, a chain PAS oligomer, an alkali metal halide and an organic polar solvent; removing a solid-phase component from the mixture to obtain a liquid-phase component (A) containing a PAS oligomer; and concentrating the liquid-phase component (A) at 230°C or lower under a reduced pressure or normal pressure environment to obtain a PAS oligomer mixture (B), wherein a ring opening rate of the cyclic PAS oligomer during concentration is less than 10%. There is also provided a production method of a PAS resin using the mixture.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a polyarylene sulfide oligomer mixture, and a method for producing a polyarylene sulfide resin added with the oligomer mixture with high efficiency.

Background Art

[0002] Polyarylene sulfide (hereinafter sometimes abbreviated as PAS) resins typified by polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) resins are excellent in heat resistance, chemical resistance, etc., and are widely used in electric and electronic parts, automotive parts, hot water supply machine parts, fibers, film applications, etc.

[0003] PPS resins can be obtained by, for example, a method of polymerizing a sulfidizing agent and a polyhaloaromatic compound in a polar organic solvent such as N-methyl-2-pyrrolidone (NMP). At this time, by-products such as PPS oligomers, residual sulfidizing agents, and sodium chloride are also generated simultaneously, but these by-products are regarded as impurities and have not been actively utilized in the past. In particular, most of the PPS oligomers contained in the liquid phase component obtained by solid-liquid separation of the solvent slurry after polymerization are discarded as industrial waste, causing a great loss in production in terms of raw material cost loss and disposal cost.

[0004] So far, a method for recovering the above liquid phase component as a polymerization raw material has been disclosed (see Patent Document 1). However, since impurities (such as phenol) other than PPS oligomers present in the liquid phase component inhibit the polymerization reaction, the reuse rate as a raw material is limited.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, the problem that the present invention aims to solve is to provide a method for producing a composition containing a cyclic PAS oligomer in which the ring-opening rate of the cyclic PAS oligomer is controlled to 10% or less, obtained by solid-liquid separation of the crude reaction mixture after the polymerization reaction of PAS resin. Furthermore, the present invention aims to provide a method for producing PAS resin in which the composition containing the PAS oligomer obtained by the above production method is reused as an additive to PAS resin, thereby improving the reuse rate of the oligomer and reducing loss. [Means for solving the problem]

[0007] As a result of various studies, the inventors of the present invention have found that by separating the reaction mixture obtained after the polymerization reaction of PAS resin into solid and liquid phase components and concentrating the liquid phase component at a reduced pressure or atmospheric pressure environment at a temperature below 230°C, it is possible to produce a composition containing PAS oligomers in which the ring-opening rate of cyclic PAS oligomers contained in the liquid phase component is controlled to less than 10%. Furthermore, they have found that by adding this composition containing PAS oligomers to the production of PAS resin, it is possible to improve the reuse rate of PAS oligomers and suppress the decrease in the thermal stability of the resulting PAS resin, thus completing the present invention.

[0008] In other words, the present invention relates to a method for producing a PAS oligomer mixture, comprising the steps of: (1) reacting a polyhalo-aromatic compound with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent to obtain a crude reaction mixture containing at least a PAS resin, a cyclic PAS oligomer, a chain-like PAS oligomer, an alkali metal halide, and an organic polar solvent; (2) removing a solid phase component from the crude reaction mixture by solid-liquid separation to obtain a liquid phase component (A) containing at least a cyclic PAS oligomer and a chain-like PAS oligomer; and (3) supplying the liquid phase component (A) into an evaporator and concentrating the liquid phase component (A) at a temperature of less than 230°C under reduced pressure or atmospheric pressure to obtain a PAS oligomer mixture (B), wherein in step (3), the ring-opening rate of the cyclic PAS oligomer during concentration is less than 10%.

[0009] Furthermore, the present invention relates to a method for producing PAS resin, characterized by comprising: (2) a step (5) reacting a polyhalo-aromatic compound with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent to obtain a crude reaction mixture containing at least a PAS resin, an alkali metal halide, and an organic polar solvent; (6) adding a PAS oligomer mixture obtained by the production method described in (1) to the crude reaction mixture to obtain a mixture (C) containing at least a PAS resin, a cyclic PAS oligomer, a chain-like PAS oligomer, an alkali metal halide, and an organic polar solvent; (7) separating the mixture (C) from the liquid phase to remove the liquid phase component to obtain a mixture (D) containing at least a PAS resin, a cyclic PAS oligomer, a chain-like PAS oligomer, and an alkali metal halide; and (8) washing the mixture (D) to remove the alkali metal halide.

[0010] Furthermore, the present invention relates to a method for producing PAS resin, characterized by comprising: (3) a step of reacting a polyhalo-aromatic compound with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent to obtain a crude reaction mixture containing at least PAS resin, an alkali metal halide, and an organic polar solvent (5); a step of separating the crude reaction mixture into solid and liquid phases to remove the liquid phase component to obtain a solid (E) containing at least PAS resin and an alkali metal halide (9); a step of adding a PAS oligomer mixture obtained by further contacting the oligomer mixture (B) described in (1) with water to form a slurry to the solid (E) to obtain a mixture (F) containing at least PAS resin, a cyclic PAS oligomer, a chain-like PAS oligomer, and an alkali metal halide (10); and a step of washing the mixture (F) to remove the alkali metal halide (11).

[0011] In this invention, polymer compounds having 2 to 40 repeating units (a mixture of dimers to 40mers) may be referred to as "oligomers." [Effects of the Invention]

[0012] According to the present invention, there can be provided a method for producing an oligomer mixture in which a cyclic PAS oligomer filtered after the polymerization reaction of a PAS resin is concentrated while controlling the ring-opening rate, and further a method for producing a PAS resin in which the PAS oligomer is recovered with higher efficiency.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an embodiment of the present invention will be described in detail. However, the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. Further, when a plurality of upper limit values and lower limit values are described for specific parameters, any upper limit value and lower limit value can be combined to form a suitable numerical range.

[0014] <Method for Producing PAS Oligomer Mixture> In the present invention, 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 a PAS resin, a cyclic PAS oligomer, a chain-like PAS oligomer, an alkali metal halide, and an organic polar solvent in step (1). In step (2), a solid-phase component is removed from the crude reaction mixture by solid-liquid separation to obtain a liquid-phase component (A) containing at least a cyclic PAS oligomer and a chain-like PAS oligomer, and in step (3), the liquid-phase component (A) is supplied into an evaporator, and the liquid-phase component (A) is concentrated at a temperature lower than 230°C under a reduced pressure or normal pressure environment to obtain a PAS oligomer mixture (B), and in step (3), the ring-opening rate of the cyclic PAS oligomer during concentration is less than 10%. The details are described below.

[0015] Step (1) Step (1) is a step in which a polyhalo-aromatic compound is reacted in an organic polar solvent with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide to obtain a crude reaction mixture containing at least a PAS resin, a cyclic PAS oligomer, a linear PAS oligomer, an alkali metal halide, and an organic polar solvent.

[0016] The mixture used in step (1) is not particularly limited as long as it contains at least a PAS resin, a cyclic PAS ligomer, a linear PAS oligomer, an alkali metal halide, and an organic polar solvent. However, it is preferable to use the crude reaction mixture obtained in step (5) in the method for producing the PAS resin used in the present invention, which will be described later.

[0017] Process (2) Step (2) is a step of removing the solid phase component from the crude reaction mixture by solid-liquid separation to obtain a liquid phase component (A) containing at least a cyclic PAS oligomer and a linear PAS oligomer.

[0018] There are two main types of solid-liquid separation: the flash method and the quench method, which will be described later. The flash method is a method of recovering the solvent by evaporating it from the crude reaction mixture, and simultaneously recovering the solid material. Generally, the crude reaction mixture is flashed from a high-temperature, high-pressure state to an atmosphere of normal pressure or reduced pressure, and the solvent is removed and recovered while the solid material containing the PAS resin is recovered in powder form. A preferred embodiment of the flash method is a method in which the polymer reaction product obtained in the polymerization step, which is at high temperature and high pressure (usually 250°C or higher, 0.8 MPa or higher), is ejected from a nozzle into an atmosphere of nitrogen or water vapor at normal pressure. In the flash method, the solvent can be efficiently recovered by utilizing the heat of vaporization of the solvent when the polymer reaction product is flashed from a high-temperature, high-pressure state to a normal pressure state. The higher the internal temperature during flashing, the more efficient the solvent recovery becomes and the better the productivity. Therefore, the temperature and pressure inside the polymerization system during flashing are usually set to 250°C or higher, preferably in the temperature range of 255 to 280°C and 0.8 MPa or higher, preferably in the pressure range of 1.0 to 5.0 MPa. When flashing under reduced pressure or atmospheric pressure from this state, the ambient temperature is usually in the range of 150-250°C. If solvent recovery from the crude reaction mixture is insufficient, heating may be continued in an atmosphere of 150-250°C after flashing.

[0019] On the one hand, the quench method is a method for recovering particulate PAS resin by cooling the 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 recover the solid content containing PAS resin as granules. There is no particular limitation on the cooling time, 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 speed throughout the entire slow cooling process. A method such as cooling at a rate 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 recover the solid content containing PAS resin. Solid-liquid separation in the quench method includes methods such as separating using a centrifuge such as filtration or a screw decanter, adding water directly to the obtained filtration residue to form a slurry, and then repeating solid-liquid separation, or heating the obtained filtration residue in a non-oxidizing atmosphere to remove the remaining solvent. The quench method is more preferable in this step because it is difficult to incorporate impurities such as the by-products and unreacted raw materials into the polymer particles during crystallization and more PAS oligomers can be recovered.

[0020] Step (3) Step (3) is a step of supplying the liquid phase component (A) into an evaporator and concentrating the liquid phase component (A) at a temperature lower than 230 °C under a reduced pressure or normal pressure environment to obtain a PAS oligomer mixture (B).

[0021] The evaporator used in this step is made of a material resistant to organic polar solvents and is not particularly limited as long as it is a container that can be heated and depressurized, and known ones can be used. Examples include evaporators, autoclaves, thin film evaporators, etc.

[0022] When concentrating the liquid component (A), the temperature in the evaporator is preferably less than 230°C, more preferably 200°C or less. Also, the pressure in the evaporator is preferably normal pressure or less, specifically preferably in the range of 10 to 760 mmHg. By concentrating under such conditions, the ring-opening rate of the cyclic PAS oligomer can be controlled to less than 10%. The ring-opening rate is expressed by the following formula. Ring-opening rate (%) = {1 - (weight fraction of cyclic PAS oligomer with respect to the PAS oligomer contained in the PAS oligomer mixture (B)) / (weight fraction of cyclic PAS oligomer with respect to the PAS oligomer contained in the liquid component (A))} × 100

[0023] Also, when concentrating the liquid component (A), it is desirable to adjust the amount of solvent removed so that the proportion of solids (non-volatile components) contained in the PAS oligomer mixture (B) is in the range of 20 to 100% by mass, preferably 20 to 99.99% by mass, and more preferably 30 to 90% by mass.

[0024] The cyclic PAS oligomer becomes a chain-like PAS oligomer having an active terminal such as a SH group when it is ring-opened by heat or the like. When this chain-like PAS oligomer is added to the PAS resin, it promotes a nucleophilic attack of the chain-like PAS oligomer on the sulfide site of the PAS resin during melting, which causes a decrease in melt stability. In the present invention, by controlling the ring-opening rate of the cyclic PAS oligomer to less than 10%, it is possible to suppress a decrease in the thermal stability of the PAS resin due to the chain-like PAS oligomer.

[0048] The PAS oligomer mixture obtained through steps (1) to (3) may be used as it is, or alternatively, the PAS oligomer may be extracted and purified before use. In that case, a known extraction and purification operation can be performed on the PAS oligomer mixture to obtain a chain-like PAS oligomer and / or a cyclic PAS oligomer.

[0026] Step (4) As step (4), the present invention may further optionally include a step of slurrying by bringing the oligomer mixture (B) into contact with water. By slurrying, when adding to the manufacturing process of the PAS resin, it is possible to improve the charging accuracy of the mixture (B) and reduce the stirring load.

[0027] The amount of water brought into contact with the oligomer mixture (B) is preferably in the range of 0.01 to 10 times the mass of the PAS oligomer. Also, the temperature of the water is preferably room temperature or higher, specifically preferably in the range of 20 to 90°C.

[0028] <Method for producing PAS resin> The method for producing a PAS resin of the present invention comprises 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 a PAS resin, an alkali metal halide, and an organic polar solvent (step (5)); adding the PAS oligomer mixture obtained by the production method described in [1] to the crude reaction mixture to obtain a mixture (C) containing at least a PAS resin, a cyclic PAS oligomer, a chain PAS oligomer, an alkali metal halide, and an organic polar solvent (step (6)); subjecting the mixture (C) to solid-liquid separation to remove the liquid phase component to obtain a mixture (D) containing at least a PAS resin, a cyclic PAS oligomer, a chain PAS oligomer, and an alkali metal halide (step (7)); and washing the mixture (D) to remove the alkali metal halide (step (8)).

[0029] Alternatively, the present invention provides a method for producing PAS resin, comprising the steps of: (5) reacting a polyhalo-aromatic compound with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent to obtain a crude reaction mixture containing at least PAS resin, an alkali metal halide, and an organic polar solvent; (9) separating the crude reaction mixture into solid and liquid phases to remove the liquid phase component to obtain a solid (E) containing at least PAS resin and an alkali metal halide; (10) adding a PAS oligomer mixture obtained by further contacting the oligomer mixture (B) described in [1] with water to form a slurry to the solid (E) to obtain a mixture (F) containing at least PAS resin, a cyclic PAS oligomer, a chain-like PAS oligomer, and an alkali metal halide; and (11) washing the mixture (F) to remove the alkali metal halide. Further details are provided below.

[0030] Process (5) Step (5) is a step in which a polyhalo-aromatic compound is reacted in an organic polar solvent with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide, to obtain a crude reaction mixture containing at least a PAS resin, an alkali metal halide, and an organic polar solvent.

[0031] In this invention, the polyhalo-aromatic compound is, for example, a halogenated aromatic compound having two or more halogen atoms directly bonded to an aromatic ring. Specifically, examples include dihalo-aromatic compounds such as p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dibrombenzene, diiodobenzene, tribrombenzene, dibromnaphthalene, triiodobenzene, dichlorodiphenylbenzene, dibromdiphenylbenzene, dichlorobenzophenone, dibrombenzophenone, dichlorodiphenyl ether, dibromdiphenyl ether, dichlorodiphenyl sulfide, dibromdiphenyl sulfide, dichlorobiphenyl, and dibrombiphenyl, as well as mixtures thereof. These compounds may be block copolymerized. Among these, dihalogenated benzenes are preferred, and those containing 80 mol% or more of p-dichlorobenzene are particularly preferred. Furthermore, in order to increase the viscosity of the PAS resin by creating a branched structure, polyhalo-aromatic compounds having three or more halogen substituents in one molecule may be used as branching agents as desired. Examples of such polyhalo-aromatic compounds include 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, and 1,4,6-trichloronaphthalene. Furthermore, examples include polyhalo-aromatic compounds having functional groups with active hydrogens such as amino groups, thiol groups, and hydroxyl groups. Specifically, these include dihaloanilines such as 2,6-dichloroaniline, 2,5-dichloroaniline, 2,4-dichloroaniline, and 2,3-dichloroaniline; trihaloanilines such as 2,3,4-trichloroaniline, 2,3,5-trichloroaniline, 2,4,6-trichloroaniline, and 3,4,5-trichloroaniline; dihaloaminodiphenyl ethers such as 2,2'-diamino-4,4'-dichlorodiphenyl ether and 2,4'-diamino-2',4-dichlorodiphenyl ether, and compounds in which the amino group is replaced with a thiol group or a hydroxyl group in mixtures thereof.Furthermore, active hydrogen-containing polyhalo-aromatic compounds can also be used in which the hydrogen atoms bonded to the carbon atoms forming the aromatic ring in these active hydrogen-containing polyhalo-aromatic compounds are substituted with other inert groups, such as hydrocarbon groups like alkyl groups.

[0032] Among these various active hydrogen-containing polyhalo-aromatic compounds, the preferred is an active hydrogen-containing dihalo-aromatic compound, and the most preferred is dichloroaniline.

[0033] Examples of polyhaloaromatic compounds having a nitro group include mono- or dihalonitrobenzenes such as 2,4-dinitrochlorobenzene and 2,5-dichloronitrobenzene; dihalonitrodiphenyl ethers such as 2-nitro-4,4'-dichlorodiphenyl ether; dihalonitrodiphenyl sulfones such as 3,3'-dinitro-4,4'-dichlorodiphenyl sulfone; mono- or dihalonitropyridines such as 2,5-dichloro-3-nitropyridine and 2-chlor-3,5-dinitropyridine; and various dihalonitronaphthalenes.

[0034] Furthermore, in the present invention, alkali metal sulfides or alkali hydrosulfides and alkali metal hydroxides (hereinafter sometimes referred to as sulfidating agents) are used as raw materials.

[0035] In the present invention, the alkali metal sulfide includes lithium sulfide, sodium sulfide, rubidium sulfide, cesium sulfide, and mixtures thereof. Such alkali metal sulfides can be used as hydrates, aqueous mixtures, or anhydrous forms. Alkali metal sulfides can also be obtained by the reaction of alkali metal hydroxides with alkali metal hydroxides. In addition, it is acceptable to add a small amount of alkali metal hydroxide to react with the alkali metal hydroxides and alkali metal thiosulfates that are usually present in trace amounts in the alkali metal sulfides.

[0036] Furthermore, the alkali metal hydrosulfides include lithium hydrogen sulfide, sodium hydrogen sulfide, rubidium hydrogen sulfide, cesium hydrogen sulfide, and mixtures thereof. Such alkali metal hydrosulfides can be used as hydrates, aqueous mixtures, or anhydrous products.

[0037] Furthermore, the alkali metal hydroxide is used together with an alkali metal hydroxide. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, which may be used individually or in combination of two or more. Among these, lithium hydroxide, sodium hydroxide, and potassium hydroxide are preferred due to their availability, with sodium hydroxide being particularly preferred.

[0038] The present invention's method for producing PAS resin can also use a hydrated sulfidating agent as a raw material. In this case, it is preferable to dehydrate the hydrated sulfidating agent in the presence of at least an aprotic polar solvent before subjecting it to the polymerization reaction of the PAS resin. Furthermore, if the amount of aprotic polar solvent charged is small, for example, less than 1 mole per mole of sulfur atoms in the sulfidating agent, it is preferable to dehydrate the hydrated sulfidating agent and the aprotic polar solvent in the presence of a polyhalo-aromatic compound.

[0039] The dehydration step of the hydrated sulfidating agent is carried out by charging at least an aprotic polar solvent and a hydrated alkali metal sulfide or hydrated alkaline aqueous sulfide and alkali metal hydroxide as the hydrated sulfidating agent into a reaction vessel equipped with a distillation apparatus, heating to a temperature at which water is removed by azeotropy, specifically in the range of 300°C or less, preferably in the range of 80 to 220°C, more preferably in the range of 100 to 200°C, and then discharging the water from the system by distillation. In the dehydration step, it is preferable to dehydrate until the amount of water in the system carrying out the polymerization reaction is 5 moles or less, more preferably in the range of 0.01 to 2.0 moles, per mole of sulfur atoms of the sulfidating agent.

[0040] In addition, examples of organic polar solvents in the present invention include amides, ureas and lactams 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, and 1,3-dimethyl-2-imidazolidinonic acid; sulfolanes such as sulfolane and dimethylsulfolane; nitriles such as benzonitrile; ketones such as methylphenyl 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-imidazolidinonic acid are preferred, and N-methyl-2-pyrrolidone is even more preferred.

[0041] In the PAS polymerization process, the polymerization reaction of the PAS resin involves reacting the alkali metal sulfide and the polyhalo-aromatic compound as sulfidating agents in the presence of these organic polar solvents. Alternatively, the polymerization reaction of the PAS resin involves reacting the alkali metal hydroxide and alkali metal hydroxide as sulfidating agents with the polyhalo-aromatic compound in the presence of these organic polar solvents. The polymerization conditions are generally in the temperature range of 200 to 330°C, and the pressure should be in a range that substantially maintains the polymerization solvent and the polyhalo-aromatic compound, which is the polymerization monomer, in the liquid phase, and is generally selected from the range of 0.1 to 20 MPa, preferably from 0.1 to 2 MPa. The amount of polyhalo-aromatic compound to be charged is prepared in the range of 0.2 moles to 5.0 moles, preferably from 0.8 to 1.3 moles, and more preferably from 0.9 to 1.1 moles, per mole of sulfur atoms of the sulfidating agent. Furthermore, the amount of aprotic polar solvent charged is adjusted to be in the range of 1.0 to 6.0 moles, preferably 2.5 to 4.5 moles, per mole of sulfur atoms of the sulfidating agent. The polymerization reaction is preferably carried out in the presence of a small amount of water, and the proportion is preferably adjusted as appropriate in consideration of the polymerization method, the molecular weight of the obtained polymer, and productivity. Specifically, the dehydration operation is carried out so that the amount of water is in the range of 2.0 moles or less, preferably 1.6 moles or less, per mole of sulfur atoms of the sulfidating agent. However, if the dehydration operation is carried out in the presence of a polyhalo-aromatic compound (for example, the method in "5)" in the specific embodiment below), the amount of water should be in the range of 0.9 moles or less, preferably 0.05 to 0.3 moles, more preferably 0.01 to 0.02 moles or less.

[0042] Specific embodiments of polymerizing a sulfidating agent and a polyhalo-aromatic compound in the presence of the aforementioned aprotic polar solvent include, for example, 1) A method using polymerization aids such as alkali metal carboxylates or lithium halides. 2) A method using branching agents such as aromatic polyhalogen compounds, 3) A method in which polymerization is carried out in the presence of a small amount of water, and then water is added to further polymerize the molecule. 4) A method in which, during the reaction of an alkali metal sulfide with an aromatic dihalogen compound, the gas phase portion of the reaction vessel is cooled to condense a portion of the gas phase inside the reaction vessel and reflux it into the liquid phase. 5) A method for producing PAS resin, which includes the essential steps of: producing a slurry containing solid alkali metal sulfide by reacting an alkali metal sulfide, or a hydrated alkali metal hydroxide and alkali metal hydroxide, with an amide, urea, or lactam having an aliphatic cyclic structure while dehydrating it in the presence of a polyhalo-aromatic compound; further dehydrating the slurry by adding a polar organic solvent such as NMP and distilling off the water; and then polymerizing the slurry obtained through the dehydration step by reacting a polyhalo-aromatic compound, an alkali metal hydroxide, and an alkali metal salt of the hydrolysis product of the amide, urea, or lactam having an aliphatic cyclic structure, at a rate of 0.02 moles or less of water present in the reaction system per mole of a polar organic solvent such as NMP.

[0043] Thus, by polymerizing a dihalo-aromatic compound with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent, PAS resin can be obtained as a product. In addition, cyclic PAS oligomers and chain-like PAS oligomers may also be produced as by-products. Substances contained after the reaction may also include by-products such as alkali metal-containing inorganic salts, carboxyalkylamino group-containing compounds, terminal SH group-containing compounds, unreacted raw materials, and water.

[0044] Process (6) Step (6) is a step of adding the PAS oligomer mixture obtained by the manufacturing method described in [1] to the crude reaction mixture to obtain a mixture (C) containing at least PAS resin, PAS oligomer, alkali metal halide and organic polar solvent.

[0045] The amount of PAS oligomer mixture added to the crude reaction mixture is not particularly limited, but it is preferable to adjust it so that the amount of PAS oligomer is 0.1% by mass or more relative to the PAS resin (theoretical yield) contained in the crude reaction mixture, and more preferably 3% by mass or more. Furthermore, it is preferable to adjust it to be 40% by mass or less, and more preferably 10% by mass or less.

[0046] Process (7) Step (7) is a step in which a mixture (C) containing at least PAS resin, a cyclic PAS oligomer, a linear PAS oligomer, an alkali metal halide, and an organic polar solvent is subjected to solid-liquid separation by a flash method to obtain a mixture (D) containing at least PAS resin, a PAS oligomer, and an alkali metal halide.

[0047] Solid-liquid separation using the flash method in this process can be carried out in the same manner as in process (2). By using the flash method to separate the solid and liquid phases and recover the liquid phase components, oligomers can be recovered into the product with high efficiency.

[0048] Process (8) Step (8) is a step of washing a mixture (D) containing at least PAS resin, cyclic PAS oligomer, linear PAS oligomer, and alkali metal halide to remove the alkali metal halide.

[0049] In this process, the mixture (D) is washed by washing with water or hot water. After washing with water, methods for solid-liquid separation by filtering the PAS resin include, for example, a method in which a reaction slurry obtained by solid-liquid separation of an aprotic polar solvent from the crude reaction mixture obtained in the PAS manufacturing process described later is mixed with water and then filtered using a filtration device; a method in which water is added again to the water-containing filtration residue obtained by the above filtration (hereinafter abbreviated as "hydrated cake") to form a slurry and then filtered; or a method in which water is added again while the hydrated cake is held in the filter and then filtered.

[0050] During the washing process, the amount of water added to the mixture (D) is preferably in the range of 2 to 10 times the theoretical yield of the PAS resin that will ultimately be obtained, which is preferable from the viewpoint of washing efficiency. It is preferable to divide the above amount of water into 2 to 10 washes, preferably 2 to 4 washes. The washing is preferably carried out under a nitrogen or air atmosphere at a water temperature in the range of 20°C to 300°C. From the viewpoint of good washing efficiency, it is more preferable to carry out the washing in the range of 50°C to 100°C, and most preferably in the range of 70°C to 90°C. The washing can be carried out once or multiple times. When washing is repeated multiple times, the atmosphere and temperature conditions may be the same or different.

[0051] Since trace amounts of alkali metal halides and sulfidating agents may remain in the filtered PAS resin due to insufficient washing, it can be further subjected to solid-liquid separation (hereinafter sometimes referred to as "hot water washing") after contact with water in the range of 100°C to 280°C.

[0052] The temperature for hot water washing is preferably in the range of 100 to 280°C, and more preferably in the range of 120 to 275°C, as this allows for good extraction efficiency of alkali metal halides and sulfidating agents remaining in the resin. More specifically, it is preferable to perform the extraction treatment with hot water at 140 to 260°C under conditions of pressurized gas phase pressure in the reactor, more preferably 0.2 to 4.6 MPa (gauge pressure).

[0053] A specific method for performing such hot water washing is to wash the PAS resin, which has been filtered after the aforementioned water washing, with water under agitation in a pressure vessel under predetermined pressure and temperature conditions. The amount of water used during hot water washing is preferably 1.5 to 10 times the mass of the PAS resin, as this improves the extraction efficiency of the alkali metal halides and sulfidating agents. This amount of hot water may be divided into two or more washings. For example, when hot water washing is repeated twice, it is preferable to filter between the first and second hot water washings to separate the alkali metal halides and sulfidating agents extracted in the first hot water washing from the PAS resin. Alternatively, filtration may be performed after one hot water washing, followed by the aforementioned water washing. This operation can also further promote the separation and removal of the alkali metal halides and sulfidating agents from the PAS resin. Furthermore, although the conditions for the first and second hot water washing processes can be arbitrarily selected from the above conditions, it is preferable from the viewpoint of chemical resistance of the apparatus used in the hot water washing to first filter and remove the highly alkaline filtrate by setting the temperature of the first hot water washing process to a higher temperature than the temperature of the first hot water washing process, for example, in the range of 150°C to 275°C, and then carry out the second hot water washing process.

[0054] In the process of performing this hot water washing, the pH can be adjusted by adding an acid or base during washing, and it is particularly preferable to control the pH after hot water washing to be in the range of 9.5 or more and less than 13.5, preferably 11.0 or more and less than 13.0, and even more preferably 12.0 or more and less than 13.0. Examples of acids that can be used in this case include hydrochloric acid, sulfuric acid, carbonic acid, acetic acid, oxalic acid, etc., with carbonic acid, acetic acid, and oxalic acid being preferred among these. Alternatively, carbon dioxide may be introduced and brought into contact under normal pressure or under pressure. On the other hand, examples of bases include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, or sodium carbonate, ammonium carbonate, sodium phosphate, etc., with sodium hydroxide being preferred among these.

[0055] Furthermore, in the process of performing this hot water washing, a PAS oligomer mixture obtained by the manufacturing method described in [1] or [2] may be added. The amount of PAS oligomer mixture to be added is preferably 0.1% by mass or more, more preferably 3% by mass or more, relative to the PAS resin contained in the mixture (D). It is also preferably 40% by mass or less, and more preferably 10% by mass or less.

[0056] Furthermore, in this process, hot water washing and solid-liquid separation can be repeated. In that case, the pH can be individually adjusted so that it is different after each hot water washing.

[0057] In this process, it is possible to use a washing tank with a stirrer and a centrifugal separator for solid-liquid separation, but it can also be carried out in a container with a mixing function that has stirring blades inside and a filtration filter at the bottom. Similarly, for hot water washing at temperatures exceeding 100°C, it is possible to use a washing tank with a stirrer for hot water washing and a centrifugal separator for subsequent filtration at 20-100°C, but it can also be carried out in a sealed or sealable container with a mixing function that has stirring blades inside and a filtration filter at the bottom. In this invention, water washing or hot water washing may be carried out continuously or in batches.

[0058] The filtered PAS resin is recovered and can then be dried and used as PAS resin powder, or it can be further washed, separated into solid and liquid forms, and dried to prepare it as powdered or granular PAS resin. Furthermore, the obtained powdered or granular PAS resin can be heat-treated to produce crosslinked PAS resin.

[0059] Process (9) Step (9) is a step in which a crude reaction mixture containing at least PAS resin, alkali metal halide, and organic polar solvent is subjected to solid-liquid separation by a flash method to obtain a solid component (E) containing at least PAS resin and alkali metal halide. The solid-liquid separation using the flash method in this step can be carried out in the same manner as in step (2). By using the flash method to separate the solid and liquid components and recovering the liquid phase components, the oligomer can be recovered into the product with high efficiency.

[0060] Process (10) Step (10) is a step of adding the PAS oligomer mixture obtained by the manufacturing method described in [2] above to a solid component (E) containing at least PAS resin and alkali metal halide to obtain a mixture (F) containing at least PAS resin, PAS oligomer and alkali metal halide. By using a slurryed PAS oligomer mixture, improvements in preparation accuracy and reduction of stirring load can be achieved.

[0061] The amount of PAS oligomer mixture added to the solid (E) is preferably 0.1% by mass or more, more preferably 3% by mass or more, relative to the PAS resin contained in the solid (E). Furthermore, 40% by mass or less is preferred, and 10% by mass or less is more preferred.

[0062] Process (11) Step (11) is a step of washing a mixture (F) containing at least PAS resin, PAS oligomer, and alkali metal halide to remove the alkali metal halide. The washing in this step can be carried out in the same manner as in step (8). The filtered PAS resin is recovered and can then be dried as is and used as PAS resin powder, or it can be further washed, followed by solid-liquid separation and drying to prepare it as powdered or granular PAS resin. Furthermore, the obtained powdered or granular PAS resin can be heat-treated to produce crosslinked PAS resin.

[0063] <Composition / Applications, etc.> The PAS resin obtained by the above manufacturing method may contain additives such as mold release agents, colorants, heat stabilizers, UV stabilizers, foaming agents, rust inhibitors, flame retardants, lubricants, coupling agents, and fillers, as long as they do not impair the effects of the present invention. As fillers, known and conventional materials may be used as long as they do not impair the effects of the present invention. Examples include inorganic fillers of various shapes, such as fibrous materials and non-fibrous materials such as granular or plate-shaped materials. Specifically, fibrous fillers such as glass fibers, carbon fibers, silane glass fibers, ceramic fibers, aramid fibers, metal fibers, potassium titanate, silicon carbide, calcium silicate, wollastonite, and other fibers and natural fibers can be used. Non-fibrous fillers such as glass beads, glass flakes, barium sulfate, clay, pyrophyllite, bentonite, sericite, mica, talc, attapulgite, ferrite, calcium silicate, calcium carbonate, glass beads, zeolite, milled fiber, and calcium sulfate can also be used.

[0064] The PAS resin obtained by the above manufacturing method can also be used by mixing it with the following synthetic resins and elastomers, to the extent that the effects of the present invention are not impaired. Examples of these synthetic resins include polyester, polyamide, polyimide, polyetherimide, polycarbonate, polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, polyetherketone, polyarylene, polyethylene, polypropylene, polytetrafluoroethylene, polydifluoroethylene, polystyrene, ABS resin, epoxy resin, silicone resin, phenolic resin, urethane resin, liquid crystal polymer, etc. Examples of elastomers include polyolefin rubber, fluororubber, silicone rubber, etc.

[0065] Furthermore, the PAS resin of the present invention exhibits excellent heat resistance, moldability, and dimensional stability when subjected to various melting processes such as injection molding, extrusion molding, compression molding, and blow molding. For this reason, it can be widely used as, for example, electrical and electronic components such as connectors, printed circuit boards, and encapsulated molded products; automotive parts such as lamp reflectors and various electrical components; interior materials for various buildings, aircraft, and automobiles; injection-molded and compression-molded products such as precision parts such as OA equipment parts, camera parts, and watch parts; or extrusion-molded and pultruded products such as fibers, films, sheets, and pipes. [Examples]

[0066] The present invention will be specifically described below with reference to examples. These examples are illustrative and not limiting. Unless otherwise specified, "%" and "parts" refer to mass.

[0067] <Rating>

[0068] (1) Evaluation of the ring-opening rate of PPS oligomers Water was added to the liquid phase component containing PPS oligomers (hereinafter referred to as "NMP filtrate") and the concentrate of the filtrate (hereinafter referred to as "NMP filtrate concentrate") to form aqueous slurries. Each aqueous slurry was subjected to solid-liquid separation, washing, and drying to obtain powders. 5.0000 g of the obtained powder was taken, 75 mL of chloroform was added, and the mixture was refluxed at 65°C for 1 hour. The residue after extraction was measured by weight as linear PPS oligomers, and the solid matter contained when the obtained chloroform extract was slowly cooled to room temperature was measured by weight as cyclic PPS oligomers. The PPS oligomer content in the NMP filtrate and NMP filtrate concentrate was calculated. From the obtained values, the ring-opening rate of cyclic PPS oligomers in the NMP filtrate concentration process was calculated using the following formula. The results are shown in Tables 1 and 2. W1 = Amount of cyclic PPS oligomer in 5g of PPS oligomer contained in NMP filtrate Amount of cyclic PPS oligomers in 5g of PPS oligomers contained in W2=NMP filtrate concentrate Ring opening rate (%)=(1-W2 / W1)×100

[0069] (2) Evaluation of melt viscosity and melt stability Using a Shimadzu CFT-500D flow tester, the temperature was set to 300°C and the load to 20 kgf / cm². 2 The melt viscosity was measured after holding for 6 minutes or 30 minutes at L / D = 10(mm) / 1(mm). Melt stability was compared using the viscosity change rate α. The viscosity change rate α was defined as follows: A smaller value of α indicates a smaller viscosity change rate of the resin and superior melt stability. V6 viscosity refers to the melt viscosity after holding for 6 minutes, and V30 viscosity refers to the melt viscosity after holding for 30 minutes. The measurement results are shown in Tables 1 and 2. α = |{(V30-V6) / V6}| × 100

[0070] (3) Determination of weight loss A 4.0000 g sample of PPS powder was weighed into an aluminum petri dish using a precision balance. The sample was left in a drying oven set to 150°C for 1 hour, then the petri dish was removed, allowed to cool to room temperature, and weighed again. Next, the same petri dish was left in a drying oven set to 370°C for 1 hour, then the petri dish was removed, allowed to cool to room temperature, and weighed again. The weight loss for each sample was calculated using the following formula. The measurement results are shown in Tables 1 and 2. {(Weighing value after heating at 150°C) - (Weighing value after heating at 370°C)} ÷ (Weighing value after heating at 150°C) × 100

[0071] <Example 1> Process (1) In a 150-liter autoclave equipped with a stirring blade and bottom valve, connected to a pressure gauge, thermometer, and condenser, 19.413 kg (150 moles) of flake sodium sulfide (60.3 wt% Na2S) and 45.0 kg (454 moles) of N-methyl-2-pyrrolidone (NMP) were charged. The mixture was heated to 209°C while stirring under a nitrogen atmosphere, and 4.644 kg of water was distilled off (the remaining water content was 1.13 moles per mole of sodium sulfide). Subsequently, the autoclave was sealed and cooled to 180°C, and 21.631 kg (147 mol) of p-dichlorobenzene (hereinafter abbreviated as p-DCB) and 18.0 kg (182 mol) of NMP were charged. At a liquid temperature of 150°C, the gauge pressure was increased to 0.1 MPa using nitrogen gas to start heating. The liquid temperature was raised to 240°C over 135 minutes and held for 30 minutes. Then, the liquid temperature was raised to 250°C over 40 minutes and held for 73 minutes to complete the reaction. After that, the autoclave was cooled.

[0072] Process (2) The bottom valve of the autoclave was opened at 100°C, and the reaction slurry was transferred to a 150-liter plate filter and pressure filtered at 120°C. 48.0 kg of NMP was added, and the mixture was pressure washed and filtered again. The recovered NMP filtrate (1) weighed 80.0 kg and contained 1.091 kg of PPS oligomers (0.763 kg of cyclic PPS oligomers and 0.328 kg of linear PPS oligomers).

[0073] Process (3) The NMP filtrate was charged into an evaporator with a boiler wall temperature of 150°C, and the NMP was removed by distillation under reduced pressure of 50 mmHg to obtain 3.78 kg of a brown solid residue with a non-volatile content of 45% by mass. The residue contained 0.763 kg of cyclic PPS oligomers and 0.328 kg of linear PPS oligomers, and the ring-opening rate of the cyclic PPS oligomers was 0.00%.

[0074] Process (5) A 150-liter autoclave equipped with stirring blades and connected to a pressure gauge, thermometer, condenser, decanter, and rectification column was charged with 33.222 kg (226 mol) of p-DCB, 2.280 kg (23 mol) of NMP, 27.300 kg (230 mol) of 47.23% by mass NaSH aqueous solution, and 18.533 kg (228 mol) of 49.21% by mass NaOH aqueous solution. The mixture was heated to 173°C over 5 hours under a nitrogen atmosphere while stirring, and 27.300 kg of water was distilled off, after which the autoclave was sealed. The p-DCB distilled off by azeotrope during dehydration was separated in the decanter and returned to the autoclave as needed. After dehydration, the autoclave contained particulate anhydrous sodium sulfide composition dispersed in p-DCB. After the above dehydration process was completed, the internal temperature was cooled to 160°C, 47.492 kg (479 mol) of NMP was charged, and the temperature was raised to 185°C. When the pressure reached 0.00 MPa, the valve connected to the rectification column was opened, and the internal temperature was raised to 200°C over 1 hour. During this time, the temperature at the outlet of the rectification column was controlled by cooling and valve opening to keep it below 110°C. The distilled DCB and water mixture vapor was condensed in a condenser, separated in a decanter, and the DCB was returned to the vessel. The amount of water distilled was 179 g. The internal temperature was raised from 200°C to 230°C over 3 hours, stirred for 1 hour, then raised to 250°C, stirred for 1 hour. The final pressure was 0.48 MPa.

[0075] Process (6) After the autoclave cooled to room temperature, 260 g was taken from the 101.53 kg of slurry obtained. 10.49 g of the brown residue obtained in step (3) was added to it.

[0076] Process (7) The NMP contained in the slurry was removed by vacuum drying at 150°C for 2 hours under reduced pressure.

[0077] Process (8) After removing NMP, 360g of ion-exchanged water at 70°C was added to the mixture and stirred for 10 minutes, then filtered. 480g of ion-exchanged water at 70°C was added to the filtered cake to wash it, and solid-liquid separation was performed to obtain a solid component (hydrated cake). The obtained hydrated cake and 180g of ion-exchanged water were placed in a 0.5-liter autoclave and stirred at 150°C for 30 minutes. After cooling to room temperature, the mixture was filtered, and 480g of ion-exchanged water at 70°C was added to the filtered cake to wash it, and solid-liquid separation was performed to obtain a solid component (hydrated cake). The obtained hydrated cake and 180g of ion-exchanged water were again placed in a 0.5-liter autoclave, a 48% NaOH aqueous solution was added to adjust the pH to 11.9, and the mixture was stirred at 200°C for 30 minutes. After cooling to room temperature, the mixture was filtered. The pH of the filtrate was 12.2. 480g of ion-exchanged water at 70°C was added to the filtered cake to wash it, and solid-liquid separation was performed to obtain a solid component (hydrated cake). The resulting hydrated cake was dried at 120°C for 4 hours to obtain 63.57 g of powder (1). The added oligomer amounted to 5.0% by mass relative to the PPS resin.

[0078] <Example 2> Steps (1) to (3) and step (5) were carried out in the same manner as in <Example 1>.

[0079] Process (4) 3.97 kg of ion-exchanged water at 70°C was added to the brown residue obtained in step (3) to obtain 7.75 kg of residue water slurry.

[0080] Process (9) After the autoclave cooled to room temperature, 260 g of the resulting slurry was taken out, and the NMP contained therein was removed by vacuum drying at 150°C for 2 hours under reduced pressure.

[0081] Process (10) To the mixture after NMP removal, 360 g of ion-exchanged water at 70°C and 21.50 g of the residue water slurry obtained in step (4) were added.

[0082] Process (11) The obtained aqueous slurry was stirred for 10 minutes and then filtered. 480g of ion-exchanged water at 70°C was added to the filtered cake to wash it, and solid-liquid separation was performed to obtain a solid component (hydrated cake). The obtained hydrated cake and 180g of ion-exchanged water were placed in a 0.5-liter autoclave and stirred at 150°C for 30 minutes. After cooling to room temperature, it was filtered, and 480g of ion-exchanged water at 70°C was added to the filtered cake to wash it, and solid-liquid separation was performed to obtain a solid component (hydrated cake). The obtained hydrated cake and 180g of ion-exchanged water were placed in a 0.5-liter autoclave, a 48% NaOH aqueous solution was added to adjust the pH to 11.9, and it was stirred at 200°C for 30 minutes. After cooling to room temperature, it was filtered. The pH of the filtrate was 12.2. 480g of ion-exchanged water at 70°C was added to the filtered cake to wash it, and solid-liquid separation was performed to obtain a solid component (hydrated cake). The resulting hydrated cake was dried at 120°C for 4 hours to obtain 63.57 g of powder (2). The added oligomer amounted to 5.0% by mass relative to the PPS resin.

[0083] <Example 3> In step (6), the procedure was carried out in the same manner as in Example 1, except that the amount of brown residue added was 20.97 g, and 66.59 g of powder (2) was obtained. The amount of added oligomer was 10.0% by mass relative to the PPS resin.

[0084] <Example 4> In step (10), the process was carried out in the same manner as in Example 2, except that the amount of residual water slurry added was 43.00 g, and 66.59 g of powder (4) was obtained. The amount of oligomer added was 10.0% by mass relative to the PPS resin.

[0085] <Example 5> In step (6), the procedure was carried out in the same manner as in Example 1, except that the amount of brown residue added was 41.95 g, and 72.65 g of powder (5) was obtained. The amount of oligomer added was 20.0% by mass relative to the PPS resin.

[0086] <Example 6> In step (10), the process was carried out in the same manner as in Example 2, except that the amount of residual water slurry added was 85.99 g, and 72.65 g of powder (6) was obtained. The amount of oligomer added was 20.0% by mass relative to the PPS resin.

[0087] <Example 7> In step (6), the procedure was carried out in the same manner as in Example 1, except that the amount of brown residue added was 62.92 g, and 78.70 g of powder (7) was obtained. The amount of oligomer added was 30.0% by mass relative to the PPS resin.

[0088] <Example 8> In step (10), the process was carried out in the same manner as in Example 2, except that the amount of residual water slurry added was 128.99 g, and 78.70 g of powder (8) was obtained. The amount of oligomer added was 30.0% by mass relative to the PPS resin.

[0089] <Example 9> In step (3), the NMP filtrate was concentrated at a can wall temperature of 210°C and atmospheric pressure. 3.78 kg of a brown solid residue with a non-volatile content of 45% by mass was obtained. The residue contained 0.760 kg of cyclic PPS oligomers and 0.331 kg of chain-like PPS oligomers, and the ring-opening rate of the cyclic PPS oligomers was 0.39%. Otherwise, the procedure was carried out in the same manner as in Example 1, and 63.57 g of powder (9) was obtained. The amount of oligomer added was 5.0% by mass relative to the PPS resin.

[0090] <Example 10> In step (3), the NMP filtrate was concentrated at a can wall temperature of 210°C under atmospheric pressure, and the procedure was carried out in the same manner as in Example 2, yielding 63.57 g of powder (10). The amount of added oligomer was 5.0% by mass relative to the PPS resin.

[0091] <Comparative Example 1> In step (3), the NMP filtrate was concentrated at a can wall temperature of 250°C and atmospheric pressure. 3.78 kg of a brown solid residue with 45% non-volatile content was obtained. The residue contained 0.534 kg of cyclic PPS oligomers and 0.556 kg of chain-like PPS oligomers, with a ring-opening rate of 30.0% for the cyclic PPS oligomers. The rest of the procedure was the same as in Example 1, yielding 63.57 g of powder (C1). The amount of added oligomers was 5.0% by mass relative to the PPS resin.

[0092] <Comparative Example 2> In step (3), the NMP filtrate was concentrated at a can wall temperature of 250°C under atmospheric pressure, and the procedure was carried out in the same manner as in Example 2, yielding 63.57 g of powder (C2). The amount of added oligomer was 5.0% by mass relative to the PPS resin. <Comparative Example 3> In step (3), the NMP filtrate was concentrated at a can wall temperature of 270°C and atmospheric pressure. 3.78 kg of a brown solid residue with 45% by mass of non-volatile content was obtained. The amount of cyclic PPS oligomer in the residue was 0.311 kg, and the amount of chain-like PPS oligomer was 0.780 kg. The ring-opening rate of the cyclic PPS oligomer was 59.3%. The rest of the procedure was the same as in Example 1, yielding 63.57 g of powder (C3). The amount of added oligomer was 5.0% by mass relative to the PPS resin.

[0093] <Comparative Example 4> In step (3), the NMP filtrate was concentrated at a can wall temperature of 270°C under atmospheric pressure, and the procedure was carried out in the same manner as in Example 2 to obtain 63.57 g of powder (C4). The amount of oligomer added was 5.0% by mass relative to the PPS resin.

[0094] <Reference example (1)> Steps (1) to (4) were omitted, and only steps (5) to (11) were performed in the same manner as in Example 1 to obtain powder (R1) with an oligomer addition rate of 0%.

[0095] [Table 1]

[0096] [Table 2]

[0097] The results in Tables 1 and 2 show that the examples exhibited a smaller viscosity change rate and less weight loss compared to the comparative examples, indicating that oligomers can be recovered efficiently and PPS with excellent thermal stability can be obtained.

Claims

1. Step (5) to obtain a crude reaction mixture containing at least a polyarylene sulfide resin, an alkali metal halide, and an organic polar solvent by reacting a polyhalo-aromatic compound with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent. Step (6) involves adding the polyarylene sulfide oligomer mixture obtained in steps (1) to (3) below to the crude reaction mixture to obtain a mixture (C) containing at least a polyarylene sulfide resin, a cyclic polyarylene sulfide oligomer, a linear polyarylene sulfide oligomer, an alkali metal halide, and an organic polar solvent. Step (7) involves separating the mixture (C) using a flash method to obtain a mixture (D) containing at least a polyarylene sulfide resin, a cyclic polyarylene sulfide oligomer, a linear polyarylene sulfide oligomer, and an alkali metal halide, The process includes step (8) of washing the mixture (D) to remove alkali metal halides, Steps (1) to (3) are, Step (1): A step in which a polyhalo-aromatic compound is reacted in an organic polar solvent with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide to obtain a crude reaction mixture containing at least a polyarylene sulfide resin, a cyclic polyarylene sulfide oligomer, a linear polyarylene sulfide oligomer, an alkali metal halide, and an organic polar solvent. Step (2) involves removing the solid phase component from the crude reaction mixture by solid-liquid separation to obtain a liquid phase component (A) containing at least a cyclic polyarylene sulfide oligomer and a linear polyarylene sulfide oligomer, and Step (3) involves supplying the liquid phase component (A) into an evaporator and concentrating the liquid phase component (A) at a temperature below 230°C under reduced pressure or atmospheric pressure to obtain a polyarylene sulfide oligomer mixture (B), and, A method for producing polyarylene sulfide resin, wherein in step (3), the ring-opening rate of the cyclic polyarylene sulfide oligomer during concentration is less than 10%. (However, the ring-opening rate (%) of the cyclic polyarylene sulfide oligomer in step (3) is = {1 - (weight fraction of cyclic polyarylene sulfide oligomer relative to polyarylene sulfide oligomer contained in polyarylene sulfide oligomer mixture (B)) / (weight fraction of cyclic polyarylene sulfide oligomer relative to polyarylene sulfide oligomer contained in liquid phase component (A))} × 100.)

2. Step (5) to obtain a crude reaction mixture containing at least a polyarylene sulfide resin, an alkali metal halide, and an organic polar solvent by reacting a polyhalo-aromatic compound with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide in an organic polar solvent. Step (9) to separate the crude reaction mixture by a flash method to obtain a solid (E) containing at least polyarylene sulfide resin and alkali metal halide. Step (10) involves adding the polyarylene sulfide oligomer mixture obtained by the manufacturing method described in steps (1) to (4) below to the solid content (E) to obtain a mixture (F) containing at least a polyarylene sulfide resin, a cyclic polyarylene sulfide oligomer, a linear polyarylene sulfide oligomer, and an alkali metal halide, The process includes a step (11) of washing the mixture (F) to remove alkali metal halides, Steps (1) to (4) are Step (1): A step in which a polyhalo-aromatic compound is reacted in an organic polar solvent with (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide to obtain a crude reaction mixture containing at least a polyarylene sulfide resin, a cyclic polyarylene sulfide oligomer, a linear polyarylene sulfide oligomer, an alkali metal halide, and an organic polar solvent. Step (2): Remove the solid phase component from the crude reaction mixture by solid-liquid separation to obtain a liquid phase component (A) containing at least a cyclic polyarylene sulfide oligomer and a linear polyarylene sulfide oligomer. Step (3) involves supplying the liquid phase component (A) into an evaporator and concentrating the liquid phase component (A) at a temperature below 230°C under reduced pressure or atmospheric pressure to obtain a polyarylene sulfide oligomer mixture (B), and The step (4) involves contacting the oligomer mixture (B) with water to form a slurry, and A method for producing polyarylene sulfide resin, wherein in step (3), the ring-opening rate of the cyclic polyarylene sulfide oligomer during concentration is less than 10%. (However, the ring-opening rate (%) of the cyclic polyarylene sulfide oligomer in step (3) is = {1 - (weight fraction of cyclic polyarylene sulfide oligomer relative to polyarylene sulfide oligomer contained in polyarylene sulfide oligomer mixture (B)) / (weight fraction of cyclic polyarylene sulfide oligomer relative to polyarylene sulfide oligomer contained in liquid phase component (A))} × 100.)

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