Method for producing polyarylene sulfide resin

Abstract

To provide a method for recovering highly efficiently a polyarylene sulfide (PAS) oligomer generated by polymerization reaction of a PAS resin in the PAS resin.SOLUTION: There is provided a production method of a PAS resin which includes the steps of: subjecting at least a polyhalo aromatic compound and a sulfidizing agent as raw materials in an organic polar solvent to polymerization reaction to obtain a crude reaction mixture; cooling a reaction container to 200°C or lower and adding a byproduct-containing organic polar solvent (A) to the crude reaction mixture to obtain a mixture (B); and purifying the mixture (B). The method is characterized in, in addition to comprising said steps, that: the solvent (A) is an organic polar solvent obtained by reacting a polyhalo aromatic compound with a sulfidizing agent in an organic polar solvent to obtaining a crude reaction mixture, and then removing a solid-phase component by solid-liquid separation.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a polyarylene sulfide resin, which efficiently recovers polyarylene sulfide oligomers contained in a by-product-containing organic polar solvent obtained in the production process of the polyarylene sulfide resin into a product.

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 applications such as electric and electronic parts, automotive parts, hot water supply machine parts, fibers, and films.

[0003] PPS resins are obtained by a method such as a polymerization reaction of 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 unreacted raw materials also exist in the liquid phase component, it is difficult to adjust the raw material ratio. In addition, impurities (such as phenol) other than PPS oligomers present in the liquid phase component inhibit the polymerization reaction, so the recycling rate is limited.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] Therefore, the problem that the present invention aims to solve is to provide a method for efficiently recovering PAS oligomers generated in the polymerization reaction of PAS resin into PAS resin, thereby improving the reuse rate of oligomers and reducing losses. [Means for solving the problem]

[0007] As a result of various studies, the inventors of the present invention have found that by cooling the reaction vessel containing the crude reaction mixture obtained after the polymerization reaction of PAS resin to 200°C and adding an organic polar solvent containing by-products including PAS oligomers, the oligomers can be recovered into the PAS resin with high efficiency while suppressing the deterioration of the physical properties of the PAS resin due to side reactions that produce impurities, etc., thus completing the present invention.

[0008] In other words, the present invention is a method for producing PAS resin, Step (1) involves polymerizing a polyhalo-aromatic compound and (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide, in an organic polar solvent in a reaction vessel to obtain a crude reaction mixture containing PAS resin, an alkali metal halide, and an organic polar solvent. Step (2) involves cooling the reaction vessel to 200°C or below, adding a by-product-containing organic polar solvent (A) to the crude reaction mixture to obtain a mixture (B) containing at least PAS resin, PAS oligomer, alkali metal halide, and organic polar solvent, and The process includes a step (3) of purifying the aforementioned mixture (B), and The aforementioned by-product-containing organic polar solvent (A) 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 PAS oligomer, and an organic polar solvent. After removing the solid-phase components by solid-liquid separation, the present invention relates to a method for producing a PAS resin, which is an organic polar solvent containing at least a PAS oligomer.

[0009] In the present invention, a high molecular compound having repeating units of 2 to 40 (a mixture of dimers to 40-mers) may sometimes be referred to as an "oligomer".

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a method for producing a PAS resin, in which the oligomers contained in the organic polar solvent containing by-products can be efficiently recovered into the PAS resin, and further, the decrease in the thermal stability of the obtained PAS resin is suppressed.

Embodiments for Carrying Out the Invention

[0011] 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. Also, 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.

[0012] <Method for Producing PAS Resin> The method for producing a PAS resin of the present invention is In a reaction vessel, at least a polyhaloaromatic compound and (i) an alkali metal sulfide or (ii) an alkali metal hydrosulfide and an alkali metal hydroxide are used as raw materials, and a polymerization reaction is carried out in an organic polar solvent to obtain a crude reaction mixture containing a PAS resin, an alkali metal halide, and an organic polar solvent (step 1). Step (2) involves cooling the reaction vessel to 200°C or below, adding a by-product-containing organic polar solvent (A) to the crude reaction mixture to obtain a mixture (B) containing at least PAS resin, PAS oligomer, alkali metal halide, and organic polar solvent, and The process includes a step (3) of purifying the aforementioned mixture (B).

[0013] Furthermore, the by-product-containing organic polar solvent (A) The organic polar solvent is characterized by being obtained 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 to obtain a crude reaction mixture containing at least a PAS resin, a PAS oligomer, and an organic polar solvent, and then removing the solid phase component by solid-liquid separation, thereby obtaining an organic polar solvent containing at least a PAS oligomer. Further details are provided below.

[0014] Process (1) Step (1) is a step of polymerizing a polyhalo-aromatic compound and (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 PAS resin, an alkali metal halide, and an organic polar solvent.

[0015] 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.In addition, active hydrogen-containing polyhaloaromatic compounds in which the hydrogen atoms bonded to the carbon atoms forming the aromatic rings in these active hydrogen-containing polyhaloaromatic compounds are substituted with other inert groups, such as hydrocarbon groups like alkyl groups, can also be used.

[0016] Among these various active hydrogen-containing polyhaloaromatic compounds, preferred are active hydrogen-containing dihaloaromatic compounds, and particularly preferred is dichloroaniline.

[0017] 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-chloro-3,5-dinitropyridine; or various dihalonitronaphthalenes and the like.

[0018] In the present invention, an alkali metal sulfide or an alkali hydrosulfide and an alkali metal hydroxide (hereinafter sometimes referred to as a sulfidizing agent) are used as raw materials.

[0019] 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 anhydrides. Also, the alkali metal sulfide can be prepared by the reaction of an alkali metal hydrosulfide and an alkali metal hydroxide. Incidentally, usually, in order to react with trace amounts of alkali metal hydrosulfide and alkali metal thiosulfate present in the alkali metal sulfide, a small amount of alkali metal hydroxide may be added without any problem.

[0020] In addition, examples of the alkali metal hydrosulfide include lithium hydrosulfide, sodium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures thereof. The alkali metal hydrosulfide can be used as a hydrate, an aqueous mixture, or an anhydride.

[0021] The alkali metal hydrosulfide is used in combination with an alkali metal hydroxide. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, etc. These may be used alone or in combination of two or more. Among these, lithium hydroxide, sodium hydroxide, and potassium hydroxide are preferred because they are easily available, and sodium hydroxide is particularly preferred.

[0022] In the method for producing the PAS resin of the present invention, a hydrous sulfiding agent can also be used as a raw material. In that case, it is preferable to subject the hydrous sulfiding agent to a dehydration step in the presence of at least an aprotic polar solvent and then use it in the polymerization reaction of the PAS resin. When the charged amount of the aprotic polar solvent is small, for example, less than 1 mol per 1 mol of the sulfur atom of the sulfiding agent, it is preferable to dehydrate the hydrous sulfiding agent and the aprotic polar solvent in the presence of a polyhaloaromatic compound.

[0023] In the dehydration step of the hydrous sulfiding agent, at least an aprotic polar solvent, a hydrous alkali metal sulfide or a hydrous alkali metal hydrosulfide as the hydrous sulfiding agent, and an alkali metal hydroxide are charged into a reaction vessel equipped with a distillation apparatus, and the temperature at which water is removed by azeotropy, specifically, in the range of 300°C or lower, preferably in the range of 80 to 220°C, more preferably in the range of 100 to 200°C, and water is discharged out of the system by distillation. In the dehydration step, it is preferable to dehydrate until the amount of water in the system for carrying out the polymerization reaction is in the range of 5 mol or less, more preferably in the range of 0.01 to 2.0 mol, per 1 mol of the sulfur atom of the sulfiding agent.

[0024] 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.

[0025] 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.

[0026] 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 has the following essential manufacturing steps: 1) 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 in the presence of a polyhalo-aromatic compound, while dehydrating, to produce a slurry containing a solid alkali metal sulfide; 2) After producing the slurry, adding a polar organic solvent such as NMP and removing the water by distillation to dehydrate the slurry; and 3) 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 in the slurry obtained through the dehydration step, 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, to carry out polymerization.

[0027] 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 is obtained as a product, but PAS oligomers are also 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.

[0028] Process (2) Step (2) is a step in which the reaction vessel is cooled to 200°C or below, and by adding an organic polar solvent (A) containing by-products to the crude reaction mixture to obtain a mixture (B) containing at least PAS resin, PAS oligomer, alkali metal halide, and organic polar solvent.

[0029] • By-product-containing organic polar solvent (A) The by-product-containing organic polar solvent (A) used in step (2) is an organic polar solvent containing at least a PAS oligomer, obtained 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 to obtain a crude reaction mixture containing at least a PAS resin, a PAS oligomer, and an organic polar solvent, and then removing the solid phase component by solid-liquid separation.

[0030] A method for obtaining a crude reaction mixture containing at least a PAS resin, a PAS oligomer, 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 is not particularly limited, but an example is the same method as in step (1).

[0031] As described above, there are two main methods for removing solid-phase components from a crude reaction mixture containing at least PAS resin, PAS oligomer, and organic polar solvent by 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, it is a method in which the crude reaction mixture is flashed from a high-temperature, high-pressure state to an atmosphere of normal pressure or reduced pressure to remove and recover the solvent by distillation, while simultaneously recovering the solid material containing PAS resin 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 within the polymerization system during flashing are typically set to 250°C or higher, preferably in the range of 255-280°C, and 0.8 MPa or higher, preferably in the range of 1.0-5.0 MPa. When flashing from this state under reduced pressure or atmospheric pressure, the ambient temperature is typically 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.

[0032] On the other hand, the Quench method is a method for recovering particulate PAS resin by slowly cooling the crude reaction mixture. Generally, the crude reaction mixture is gradually cooled from a high-temperature, high-pressure state to crystallize the PAS resin in the reaction system, and then the solid component containing the PAS resin is recovered as granules by solid-liquid separation using filtration or the like. There are no particular restrictions on the cooling time, but it is usually in the range of 0.1°C / min to 3°C / min. Furthermore, it is not necessary to cool at the same rate throughout the entire slow cooling process. It is also preferable to cool at a rate of 0.1°C / min to 1°C / min until the granular PAS resin crystallizes, and then cool at a rate of 1°C / min or higher. Finally, it is preferable to cool to 70°C or higher, preferably 100°C or higher and 200°C or lower, and then recover the solid component containing the polyarylene sulfide resin by solid-liquid separation. In the Quench process, solid-liquid separation can be achieved by following methods such as filtration or separation using a centrifuge like a screw decanter, followed by adding water directly to the resulting filtration residue to form a slurry, and then repeating the solid-liquid separation process; or by heating the resulting filtration residue in a non-oxidizing atmosphere to remove any remaining solvent.

[0033] To obtain an organic polar solvent containing at least a PAS oligomer from the crude reaction mixture, it is preferable to remove the solid phase component by solid-liquid separation using the Quench method, as this allows for highly efficient recovery of the liquid phase component.

[0034] In step (2), the amount of by-product-containing organic polar solvent (A) added to the crude reaction mixture is preferably such that the amount of PAS oligomer contained in the by-product-containing organic polar solvent (A) is 0.1% by mass or more, more preferably 3% by mass or more, relative to the PAS resin (theoretical yield) contained in the crude reaction mixture. Furthermore, it is preferably 40% by mass or less, and more preferably 10% by mass or less.

[0035] The amount of PAS oligomer contained in the by-product-containing organic polar solvent (A) can be quantified by weighing the residue obtained by washing and drying the solids dissolved in the solvent (A).

[0036] The by-product-containing organic polar solvent (A) may also contain terminal SH group-containing compounds in addition to PAS oligomers. Examples of terminal SH group-containing compounds include the following general formula (1):

[0037] [ka] Examples of compounds are shown below (where n is an integer between 4 and 30).

[0038] When the reaction vessel temperature is above 200°C and an organic polar solvent (A) containing by-products is added, the terminal SH group-containing compound may decompose the PAS resin, resulting in a decrease in the resin's molecular weight, an increase in gas generation, and a decrease in thermal stability. This can be suppressed by cooling the reaction vessel temperature to below 200°C before adding the organic polar solvent (A) containing by-products.

[0039] The aforementioned by-product-containing organic polar solvent (A) also contains, in addition to the PAS oligomer, the following general formula (2):

[0040] [ka] The compound represented by (wherein X represents an alkali metal atom or a hydrogen atom) may be included (this compound is sometimes abbreviated as "CP-MABA").

[0041] The aforementioned CP-MABA is one of the factors that inhibits the polymerization reaction during the polymerization process of PAS resin. Therefore, when an organic polar solvent (A) containing by-products including CP-MABA is used as a polymerization raw material, a decrease in the molecular weight of the resin, an increase in gas generation, and a decrease in thermal stability may occur. This can be suppressed by cooling the reaction vessel to 200°C or below in step (2) before adding the organic polar solvent (A) containing by-products.

[0042] Process (3) Step (3) is a step of purifying the mixture (B). The purification method is not particularly limited, but for example, it may involve a solvent-solid-liquid separation step and a purification step by washing with water or hot water.

[0043] As mentioned above, there are two main types of solvent-solid-liquid separation processes: the flash method and the Quench method. However, the solvent-solid-liquid separation process in this step preferably includes a step (3-1) in which the organic polar solvent is separated and removed from the mixture (B) by the flash method to obtain a mixture (C) containing at least PAS resin, PAS oligomer, and alkali metal halide.

[0044] The mixture (B) or the mixture (C) is purified by a washing step using the water washing or hot water washing method of the present invention (step 3-2). After washing with water, methods for separating the solid and liquid by filtering off the PAS resin include, for example, filtering using a filtration device, adding water again to the water-containing filtration residue obtained by the above filtration (hereinafter abbreviated as "water-containing cake") to form a slurry and then filtering, or adding water again while the water-containing cake is held in a filter and then filtering.

[0045] During the washing process, the amount of water added to the mixture (C) 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.

[0046] 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.

[0047] 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).

[0048] 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 PAS, 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.

[0049] In this process, the pH can be adjusted by adding an acid or base during washing, and it is particularly preferable to control the pH so that it is in the range of 11.0 to less than 13.0 after washing with hot water. Examples of acids that can be used include hydrochloric acid, sulfuric acid, carbonic acid, acetic acid, and oxalic acid, with carbonic acid, acetic acid, and oxalic acid being preferred among these. Alternatively, carbon dioxide may be introduced and brought into contact under normal or pressurized pressure. On the other hand, examples of bases include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, or sodium carbonate, ammonium carbonate, and sodium phosphate, with sodium hydroxide being preferred among these.

[0050] 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.

[0051] 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.

[0052] <Composition / Applications, etc.> As described above, the PAS resin obtained through steps (1) to (3) of the present invention may contain additives such as mold release agents, colorants, heat stabilizers, UV stabilizers, foaming agents, rust inhibitors, flame retardants, lubricants, coupling agents, and fillers, to the extent that they do not impair the effects of the present invention. Furthermore, the following synthetic resins and elastomers may also be mixed and used in the same manner. 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, and liquid crystal polymer, while examples of elastomers include polyolefin rubber, fluororubber, and silicone rubber.

[0053] Furthermore, the PAS resin obtained through steps (1) to (3) 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, an electrical and electronic component such as connectors, printed circuit boards, and encapsulated molded products; an automotive part such as lamp reflectors and various electrical components; an interior material for various buildings, aircraft, and automobiles; an injection-molded or compression-molded product such as an OA equipment part, camera part, or watch part; or an extrusion-molded or pultruded product such as a fiber, film, sheet, or pipe; or a 3D-printed product.

[0054] This invention makes it possible to reduce the environmental burden by reducing industrial waste and suppress the decrease in raw material cost by recovering oligomers generated in the manufacturing process of PAS resin into the product, thereby improving the productivity of PAS resin. [Examples]

[0055] 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.

[0056] <Rating>

[0057] (1) 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. Furthermore, 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. α = |{(V30-V6) / V6}| × 100

[0058] (2) Determination of weight loss A 4.0000g sample of PPS powder was weighed into an aluminum petri dish using a precision balance. The sample was left to stand 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 to stand 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. {(Weighing value after heating at 150°C) - (Weighing value after heating at 370°C)} ÷ (Weighing value after heating at 150°C) × 100

[0059] (3) Determination of PPS oligomers Ten g of by-product-containing organic polar solvent was separated, water was added, and a water slurry sample was prepared. The sample was subjected to solid-liquid separation, washing, and drying. The amount of PPS oligomer contained in the by-product-containing organic polar solvent was calculated from the weight of the obtained powder (PPS oligomer) and the total weight of the by-product-containing organic polar solvent.

[0060] <Example 1> • Production of by-product-containing organic polar solvents 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 stream, and 4.644 kg of water was distilled off (the remaining water content was 1.13 moles per mole of sodium sulfide). The autoclave was then sealed and cooled to 180°C, and 21.631 kg (147 moles) of p-dichlorobenzene (hereinafter abbreviated as p-DCB) and 18.0 kg (182 moles) of NMP were charged. At a liquid temperature of 150°C, the mixture was pressurized to a gauge pressure of 0.1 MPa using nitrogen gas, and heating was started. The mixture was heated to 240°C over 135 minutes and held for 30 minutes. The liquid temperature was then raised to 250°C over 40 minutes and maintained at that temperature for 73 minutes to complete the reaction. After that, the autoclave was cooled. Next, the temperature was lowered and the cooling of the top of the autoclave was stopped. While the top of the autoclave was cooling, the liquid temperature was kept constant to prevent it from dropping. The maximum pressure during the reaction was 0.85 MPa. After the reaction, it was cooled. 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 weight of the recovered NMP filtrate (organic polar solvent containing by-products) was 80.0 kg, and it contained 1.09 kg of PPS oligomer and 0.365 kg of Na-type CP-MABA.

[0061] ·Process (1) A 150-liter autoclave equipped with stirring blades and connected to a pressure gauge, thermometer, condenser, decanter, and rectification column was charged with 21.667 kg (147 mol) of p-DCB, 1.487 kg (15 mol) of NMP, 17.804 kg (150 mol) of 47.23% by mass NaSH aqueous solution, and 12.087 kg (149 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 17.804 kg of water was distilled off, after which the autoclave was sealed. The 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 DCB. After the above dehydration process was completed, the internal temperature was cooled to 160°C, 30.973 kg (312 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 117 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. Fresh NMP was used in this process.

[0062] ·Process (2) The reaction vessel was slowly cooled until it reached 150°C, at which point 34.061 kg of organic polar solvent containing by-products was added. The amount of oligomer added at this time was 3.0% by mass relative to the PPS resin. The mixture was then stirred and cooled to room temperature.

[0063] ·Process (3) NMP contained in 260g of the slurry was removed by vacuum distillation at 150°C for 2 hours. 360g of ion-exchanged water at 70°C was added to this mixture and stirred for 10 minutes, then filtered. 480g of ion-exchanged water at 70°C was added to the filtered cake for cake washing. The resulting 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 for cake washing. The resulting hydrated cake and 169g of ion-exchanged water were placed in a 0.5-liter autoclave and stirred at 200°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 for cake washing. The mixture was then dried at 120°C for 4 hours to obtain 39.98g of powder (1).

[0064] <Example 2> In step (2), the procedure was carried out in the same manner as in Example 1, except that the amount of by-product-containing organic polar solvent added was changed from 34.061 kg to 56.769 kg, and 32.60 g of powder (2) was obtained. The added oligomer was 5.0% by mass relative to the PPS resin.

[0065] <Example 3> The procedure was carried out in the same manner as in Example 1, except that in step (1), the amount of NaSH added was changed from 150 moles to 100 moles, and the amounts of p-DCB, NMP, and NaOH added were also changed in the same ratio as NaSH, and in step (2), the amount of by-product-containing organic polar solvent added was changed from 34.061 kg to 75.692 kg. 22.30 g of powder (3) was obtained. The added oligomer was 10.0% by mass relative to the PPS resin.

[0066] <Example 4> Except for the following changes, the procedure was carried out in the same manner as in Example 1: in step (1), the amount of NaSH added was changed from 150 moles to 30 moles, and the amounts of p-DCB, NMP, and NaOH added were also changed in the same ratio as NaSH, and the capacity of the autoclave was changed from 150 liters to 100 liters; in step (2), the amount of by-product-containing organic polar solvent added was changed from 34.061 kg to 68.123 kg; and in step (3), the amount of slurry to be dried was changed from 260 g to 500 g. 18.95 g of powder (4) was obtained. The added oligomer was 30.0% by mass relative to the PPS resin. <Reference example 1> The procedure was carried out in the same manner as in Example 1, except that the by-product-containing organic polar solvent was not added in step (2), and 60.54 g of powder (R1) was obtained.

[0067] <Comparative Example 1> The procedure was carried out in the same manner as in Reference Example 1, except that the solvent charged into the reaction vessel after dehydration in step (1) was changed from 32.460 kg of fresh NMP to 34.061 kg of by-product-containing organic polar solvent, yielding 59.11 g of powder (C1). The added oligomer amounted to 3.0% by mass relative to the PPS resin.

[0068] <Comparative Example 2> The procedure was carried out in the same manner as in Comparative Example 1, except that the amount of by-product-containing organic polar solvent charged in step (1) was changed from 34.061 kg to 56.769 kg, and 44.28 g of powder (C2) was obtained. The added oligomer was 5.0% by mass relative to the PPS resin.

[0069] <Comparative Example 3> The procedure was carried out in the same manner as in Comparative Example 1, except that the amount of by-product-containing organic polar solvent charged in step (1) was changed from 34.061 kg to 75.692 kg, and 27.22 g of powder (C3) was obtained. The added oligomer was 10.0% by mass relative to the PPS resin.

[0070] <Comparative Example 4> The procedure was carried out in the same manner as in Example 1, except that the temperature inside the reaction vessel when adding the by-product-containing organic polar solvent in step (2) was changed from 150°C to 250°C (immediately after the end of polymerization), and 32.60 g of powder (C4) was obtained. The added oligomer was 5.0% by mass relative to the PPS resin.

[0071] [Table 1]

[0072] The results in Table 1 show that the examples exhibited a lower viscosity change rate and less weight loss compared to the comparative examples, indicating that PPS with excellent thermal stability can be obtained.

Claims

1. Step (1) involves polymerizing a polyhalo-aromatic compound and (i) an alkali metal sulfide, or (ii) an alkali metal hydroxide and an alkali metal hydroxide, in an organic polar solvent in a reaction vessel to obtain a crude reaction mixture containing a polyarylene sulfide resin, an alkali metal halide, and an organic polar solvent. Step (2) involves cooling the reaction vessel to 200°C or below, adding a by-product-containing organic polar solvent (A) to the crude reaction mixture to obtain a mixture (B) containing at least a polyarylene sulfide resin, a polyarylene sulfide oligomer, an alkali metal halide, and an organic polar solvent, and The process includes a step (3) of purifying the aforementioned mixture (B), and The aforementioned by-product-containing organic polar solvent (A) 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 polyarylene sulfide oligomer, and an organic polar solvent. The solid phase component is then removed by solid-liquid separation to obtain an organic polar solvent containing at least a polyarylene sulfide oligomer. A method for producing polyarylene sulfide resin, characterized in that, in step (2), the amount of polyarylene sulfide oligomer contained in the by-product-containing organic polar solvent (A) is 3% by mass or more and 10% by mass or less, relative to the polyarylene sulfide resin (theoretical yield) contained in the crude reaction mixture.

2. The method for producing a polyarylene sulfide resin according to claim 1, wherein the by-product-containing organic polar solvent (A) further contains a terminal SH group-containing compound.

3. The aforementioned by-product-containing organic polar solvent (A) further comprises the following general formula (1) 【Chemistry 1】 A method for producing a polyarylene sulfide resin according to claim 1 or 2, comprising a compound represented by (wherein X represents an alkali metal atom or a hydrogen atom).

4. The above step (3) is, Step (3-1) to separate and remove the organic polar solvent from the mixture (B) by flushing to obtain a mixture (C) containing at least a polyarylene sulfide resin, a polyarylene sulfide oligomer, and an alkali metal halide, A method for producing a polyarylene sulfide resin according to claim 1 or 2, comprising the step (3-2) of washing the mixture (C) with water to remove alkali metal halides and obtaining a polyarylene sulfide resin containing at least a polyarylene sulfide oligomer.

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