JP2022161190A - Method for producing sulfidizing agent and polyarylene sulfide resin - Google Patents

Abstract

To provide a method for producing a sulfidizing agent having high purity by removing an alkali metal carbonate from waste water discharged when a polyarylene sulfide resin (PAS resin) is subjected to polymerization reaction, and then is washed with water or hot water.SOLUTION: There is provided a method for producing a sulfidizing agent that includes the steps of: bringing a mixture (A) containing at least a PAS resin, an alkali metal halide, an alkali metal carbonate and a sulfidizing agent into contact with water, then solid-liquid separating the mixture, to obtaining an aqueous solution (B); adding a metal salt containing at least one Group-II element to the aqueous solution (B) to produce a water- insoluble carbonate; separating and removing the produced water-insoluble carbonate to obtain an aqueous solution (C); adding an acid to the aqueous solution (C) to produce hydrogen sulfide; recovering the produced hydrogen sulfide; and reacting the recovered hydrogen sulfide with an alkali metal hydroxide. There is also provided a method for producing a PAS resin using the sulfidizing agent.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a method for producing a sulfidating agent and a method for producing a polyarylene sulfide resin using the same. More specifically, a method for removing alkali metal carbonate impurities from wastewater discharged in the production process of polyarylene sulfide resin, separating, purifying, and producing a high-purity sulfidating agent, and the resulting sulfidating agent. It relates to a method for producing a polyarylene sulfide resin that reuses as a part of the raw material.

Polyarylene sulfide resins (hereinafter sometimes abbreviated as PAS resins) typified by polyphenylene sulfide resins (hereinafter sometimes abbreviated as PPS resins) are excellent in heat resistance, chemical resistance, etc., and are used in electrical and electronic parts and automobiles. Widely used for parts, water heater parts, textiles, film applications, etc. In particular, in applications such as lithium-ion battery packing and gasket members, in recent years, high-molecular-weight PAS resins have been widely used because of their excellent toughness and moldability.

PAS resins are prepared by converting polyhaloaromatic compounds into alkali metal sulfides and/or alkali metal hydrosulfides ( hereinafter, it may be abbreviated as a sulfidating agent), and the like. A crude reaction product is obtained which contains by-products such as reagents, alkali metal halides typified by sodium chloride, other alkali metal-containing inorganic salts, oligomers produced by side reactions, and derivatives thereof. After the polymerization reaction, the crude reaction product is taken out into an appropriate container, and the solvent in the crude reaction product is separated by desolvation treatment using an appropriate solid-liquid separation device such as a solvent drying device, a filter, or a centrifugal separator. It is recovered (this operation is called desolvation).

Furthermore, since the reaction product obtained after the solvent removal treatment contains alkali metal halides, other alkali metal-containing inorganic salts and by-products together with the target PAS resin, washing and filtration are repeated, and these removed. Generally, there are a water washing method performed at less than 100° C. and a hot water washing method performed at a temperature of 100° C. or higher and under high pressure. The polyarylene sulfide obtained after washing with water or washing with hot water is separated by a filter, a centrifugal filter, or the like, then dried, and if necessary, subjected to heat treatment and cross-linking reaction to obtain a product.

On the other hand, the waste water obtained after water washing or hot water washing has been treated as industrial waste and has not been effectively utilized. However, since the waste water has a high COD load, it has been desired to reduce the COD substances in order to reduce the environmental load.

A detailed examination of the waste water discharged from washing with water or washing with hot water after the polymerization reaction revealed that the remaining unreacted sulfidating agent, converted to sulfur atoms, remained in an amount of about 3 to 5 mol% of the charged amount. , that the unreacted sulfidating agent is one of the factors that increase the COD value of the wastewater, and that it is the cause of the loss of sulfur atoms (reduction of raw material unit consumption). .

Therefore, a method has been proposed to reduce the COD value of the wastewater by gasifying, separating, and recovering the unreacted sulfidation agent contained in the wastewater (see Patent Document 1). However, in this method, when an acid is added to the wastewater to gasify the unreacted sulfidating agent, even the alkali metal carbonate contained as an impurity in the raw material is gasified at the same time. When the polymerization process using the agent is repeated, there is a problem that alkali metal carbonate, which is an impurity, accumulates in the waste water. In addition, there is a problem from the viewpoint of production, such as clogging of pipes.

JP 2015-218214 A

Therefore, the problem to be solved by the present invention is to reduce the alkali metal carbonate impurities from the aqueous solution (hereinafter sometimes referred to as wastewater) obtained by water washing or hot water washing after the polymerization reaction of the PAS resin, and to obtain a high-purity It is another object of the present invention to provide a method for producing a suitable sulfidating agent. Furthermore, a method for producing a PAS resin is provided in which the sulfidating agent obtained by the above production method is reused as a raw material for polymerization of the PAS resin, thereby suppressing the loss of sulfur atoms (decrease in raw material unit consumption). to provide.

As a result of various investigations by the inventors of the present application, it was found that waste water discharged from water washing or hot water washing after the polymerization reaction contains at least one group 2 element selected from magnesium, calcium, strontium, and barium. By adding a salt to form a water-insoluble carbonate from the alkali metal carbonate that is an impurity, and separating and removing the carbonate from the waste water, the unreacted sulfidation agent is gasified, separated and recovered. The present inventors have found that a sulfidating agent of high purity can be produced, that the COD of waste water can be reduced, and that it can be reused as a raw material for the production of PAS resin, and the above problems have been solved.

That is, the present invention provides [1] contacting a mixture (A) containing at least a PAS resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent with water, and then separating and removing the PAS resin, Step (1) of obtaining an aqueous solution (B) containing at least an alkali metal halide, an alkali metal carbonate and a sulfidating agent;
Step (2) of adding a metal salt containing at least one Group 2 element selected from magnesium, calcium, strontium, and barium to the aqueous solution (B) to form a water-insoluble carbonate;
step (3) of obtaining an aqueous solution (C) containing at least an alkali metal halide and a sulfidating agent by separating and removing the produced water-insoluble carbonate from the aqueous solution (B);
a step (4) of adding an acid to the aqueous solution (C) to generate hydrogen sulfide;
A step (5) of recovering the produced hydrogen sulfide, and
a step (6) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide;
A method for producing a sulfidating agent, characterized by having

[2] After the step (6) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide, hydrogen sulfide is added to the unreacted alkali metal hydroxide to obtain the sulfidation. It relates to the production method according to the above [1], characterized by having a step (7) of reacting hydrogen with an unreacted alkali metal hydroxide.

[3] The mixture (A) containing at least a PAS resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent is
A crude reaction mixture comprising at least a PAS resin, an alkali metal halide, said aprotic polar solvent and a sulfidation agent obtained after reacting a polyhaloaromatic compound with a sulfidation agent in a polar aprotic solvent or the reaction mixture obtained by solid-liquid separation of the aprotic polar solvent from the crude reaction mixture.

Furthermore, the present invention provides [4] the sulfidating agent used in the reaction of the polyhaloaromatic compound and the sulfidating agent in an aprotic polar solvent, at least in the presence of the aprotic polar solvent. It relates to the production method according to the above [3], characterized in that it is obtained through a dehydration step of dehydrating the sulfidating agent.

Furthermore, the present invention has a step of obtaining a sulfidating agent by reacting it with an alkali metal hydroxide after recovering the hydrogen sulfide produced in the dehydration step of [5] above [4]. The present invention relates to a method for producing a sulfidating agent.

[6] After the step of reacting with an alkali metal hydroxide to obtain a sulfidating agent, hydrogen sulfide is added to the unreacted alkali metal hydroxide, and the unreacted hydrogen sulfide and The method for producing the sulfidating agent according to the above [5], characterized in that it has a step of reacting with an alkali metal hydroxide.

[7] A PAS resin is produced by reacting a sulfidation agent obtained by dehydrating a hydrous sulfidation agent in the presence of an organic amide solvent with a polyhaloaromatic compound in the presence of an organic amide solvent. In the method for producing a PAS resin, a sulfidation agent obtained by the production method according to any one of [1] to [4] as a hydrous sulfidation agent or a sulfidation agent and / or [5] or It relates to a method for producing a PAS resin, characterized by including a step of adding a sulfidating agent obtained by the production method of [6].

According to the present invention, the alkali metal carbonate contained in the waste water discharged from the water washing or hot water washing after the polymerization reaction of the PAS resin is efficiently removed, the unreacted sulfidating agent is recovered, and the COD value of the waste water is reduced. A method can be provided to reduce it. Furthermore, it is possible to provide a method for producing a PAS resin in which the recovered unreacted sulfidating agent is reused as a raw material for polymerization of the PAS resin, thereby suppressing the loss of sulfur atoms (decrease in raw material unit consumption). can.

Method for producing sulfidating agent The method for producing the sulfidating agent of the present invention comprises:
After contacting the mixture (A) containing at least a PAS resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent with water, the PAS resin is separated and removed to obtain at least an alkali metal halide, an alkali step (1) of obtaining an aqueous solution (B) containing a metal carbonate and a sulfidating agent;
A metal salt containing at least one Group 2 element selected from magnesium, calcium, strontium and barium is added to an aqueous solution (B) containing at least an alkali metal halide, an alkali metal carbonate and a sulfidating agent to obtain water. step (2) of producing a carbonate insoluble in
step (3) of obtaining an aqueous solution (C) containing at least an alkali metal halide and a sulfidating agent by separating and removing the produced water-insoluble carbonate from the aqueous solution (B);
Step (4) of adding an acid to an aqueous solution (C) containing at least an alkali metal halide and a sulfidating agent to generate hydrogen sulfide;
A step (5) of recovering the produced hydrogen sulfide, and
a step (6) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide;
characterized by having

Step (1)
In step (1), a mixture (A) containing at least a PAS resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent is brought into contact with water, and then at least the alkali metal halide and alkali metal carbonate and an aqueous solution (B) containing a sulfidating agent and a PAS resin, the PAS resin is removed to obtain an aqueous solution (B) containing at least an alkali metal halide, an alkali metal carbonate and a sulfidating agent (hereinafter referred to as wastewater) is obtained.

The mixture (A) used in step (1) is not particularly limited as long as it is a mixture containing at least a PAS resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent, but is preferably described later. It is preferable to use a reaction mixture containing at least a PAS resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent obtained in the method for producing the PAS resin used in the present invention.

A method of contacting the mixture (A) with water to remove the PAS resin from the mixture (A) to obtain an aqueous solution (B) containing at least an alkali metal halide, an alkali metal carbonate and a sulfidating agent. Although it is not particularly limited as long as it does not impair the effects of the present invention, a method of solid-liquid separation by filtering the PAS resin after contacting with water (hereinafter sometimes referred to as "washing"). can be mentioned.

The method of solid-liquid separation by washing the mixture (A) with water and then filtering the PAS resin includes, for example, solid-liquid separation of the aprotic polar solvent from the crude reaction mixture obtained in the PAS production process described below. A method of adding water to the reaction slurry obtained by adding water to the obtained reaction slurry, stirring it, and then filtering it using a filtering device, and again to the filtration residue containing water obtained by the above-described filtration (hereinafter abbreviated as “water-containing cake”). Examples include a method of adding water to form a slurry and then filtering, or a method of adding water again and filtering while the water-containing cake is held in a filter.

When washing with water, the amount of water added to the mixture (A) is preferably in the range of 2 to 10 times the theoretical yield of the finally obtained PAS resin from the viewpoint of washing efficiency. It is preferable to divide the amount of water into 2 to 10 times, preferably 2 to 4 times, and subject it to water washing. The water washing is preferably carried out in a nitrogen or air atmosphere at a water temperature of 20°C to 300°C, and more preferably at a temperature of 50°C to 100°C in order to improve the washing efficiency. Furthermore, it is most preferable to carry out within the range of 70°C to 90°C. The washing with water can be repeated once or multiple times. When water washing is repeated multiple times, the atmosphere and temperature conditions may be the same or different.

Since trace amounts of alkali metal halides and sulfidating agents may remain in the filtered PAS resin without being sufficiently washed, the PAS resin was further brought into contact with water in the range of 100°C to 280°C. After solid-liquid separation (hereinafter sometimes referred to as “hot water washing”), the PAS resin is separated and removed by filtration or the like, and the resulting filtrate can be added to the aqueous solution (B) to reduce the COD load. It is preferable from the viewpoint of reduction and suppressing the loss of sulfur atoms (decrease in raw material unit consumption).

The hot water washing temperature is, for example, preferably in the range of 100 to 280° C., and more preferably in the range of 120 to 275° C., because the extraction efficiency of alkali metal halides and sulfidating agents remaining in the resin is good. preferred from More specifically, the extraction treatment can be performed with hot water of 140 to 260° C. under the condition that the pressure of the gas phase in the reactor is increased, more preferably 0.2 to 4.6 MPa (gauge pressure). preferable.

A specific method for performing such hot water washing includes a method in which the PAS resin filtered off after the water washing is washed with water under predetermined pressure and temperature conditions in a pressure vessel while stirring. The amount of water during hot water washing is preferably 1.5 to 10 times the mass of the polyarylene sulfide from the viewpoint of good extraction efficiency of the alkali metal halide and sulfidating agent. Hot water washing may be performed by dividing the water into two or more times. For example, when the hot water washing is repeated twice, filtration is performed between the first hot water washing and the second hot water washing, and the alkali metal halide and sulfidating agent extracted by the first hot water washing are combined with the PAS resin. Filtering off is preferred. Moreover, after performing hot water washing once, filtering may be performed and the above-mentioned water washing may be performed. This operation also facilitates the separation and removal of the alkali metal halide and sulfidating agent from the PAS resin. The conditions for the first hot water washing process and the second hot water washing process can be arbitrarily selected from the above conditions. After first filtering off the highly alkaline filtrate, the temperature of the second hot water washing step is set to a temperature higher than that of the first hot water washing step, for example a temperature in the range of 150°C to 275°C. From the viewpoint of the chemical resistance of the equipment used in the hot water washing, it is preferable to carry out the washing with water.

In the step (1), an acid or a base can be added to the aqueous solution (B) to adjust the pH. Control is preferred. Acids used in this case include, for example, hydrochloric acid, sulfuric acid, carbonic acid, acetic acid, oxalic acid, etc. Among these, carbonic acid, acetic acid, and oxalic acid are preferred. Alternatively, carbon dioxide gas may be introduced and brought into contact under normal pressure or increased pressure. On the other hand, examples of the base include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide, sodium carbonate, ammonium carbonate, sodium phosphate and the like, among which sodium hydroxide is preferred.

In step (1), it is possible to use a washing tank with a stirrer and a centrifuge for solid-liquid separation. It can also be carried out in a vessel with a controlled mixing function. In addition, even in hot water washing exceeding 100 ° C., it is possible to use a washing tank with a stirrer for hot water washing, and a centrifuge for filtering at 20 to 100 ° C., but stirring is performed inside the container. It is also possible to carry out in a closed or sealable mixing container having wings and a filtering filter at the bottom. In the present invention, water washing or hot water washing may be carried out continuously or batchwise.

Step (2)
Step (2) comprises adding at least one of magnesium, calcium, strontium and barium from group 2 of the periodic table to an aqueous solution (B) containing at least an alkali metal halide, an alkali metal carbonate and a sulfidating agent. In this step, a metal salt containing an element is added to form a water-insoluble carbonate, which is deposited in the aqueous solution (B). The metal salt used at this time is not particularly limited as long as it is a metal salt containing at least one Group 2 element in the periodic table of magnesium, calcium, strontium, and barium. oxides, bromides, acetates and the like. Among these, chlorides are preferable, and calcium chloride and barium chloride are more preferable. The amount of the metal salt to be added is not particularly limited as long as it is within a range in which a water-insoluble carbonate is formed by addition, but it is preferable relative to 1 mol of the alkali metal carbonate in the aqueous solution (B). is in the range of 0.1 mol or more, more preferably in the range of 0.3 mol or more, preferably in the range of 5 mol or less, more preferably in the range of 3 mol or less.

Step (3)
Step (3) is a step of separating and removing the produced water-insoluble carbonate from the aqueous solution (B) to obtain an aqueous solution (C) containing at least an alkali metal halide and a sulfidating agent. The method for separating and removing the formed water-insoluble carbonate is not particularly limited as long as the effect of the present invention is not impaired, but solid-liquid separation is performed by filtering out the formed water-insoluble carbonate. You can mention how to do it. Examples of the method for solid-liquid separation by filtering out the produced carbonate that is insoluble in water include, for example, a method of filtering using a filtration device, and a filtration residue containing water obtained by the above-described filtration (hereinafter “hydrous abbreviated as "cake".) to form a slurry and then filter, or a method of adding water again while the water-containing cake is held in a filter and filtering. Through step (3), 90% by mass or more of the carbonate produced and precipitated in the aqueous solution (B) in step (2) can be separated and removed.

Step (4)
Step (4) is a step of adding an acid to the aqueous solution (C) containing at least an alkali metal halide and a sulfidating agent to generate hydrogen sulfide.
Acids used in this case include hydrochloric acid, sulfuric acid, carbonic acid, acetic acid, etc. Among them, hydrochloric acid is preferred. The pH range of the aqueous solution (C) is not particularly limited as long as hydrogen sulfide is generated by adding an acid. 0.5 is preferable, and 3.5 to 4.5 is more preferable. Further, the acid addition is preferably carried out in the range of 0 to 60° C., more preferably in the range of 10 to 40° C., and in the pressure range of 0 to 1.0 Pa (gauge pressure). preferable.

Steps (5) and (6)
The step (5) is a step of recovering the hydrogen sulfide produced in the step (4) because the hydrogen sulfide produced in the step (4) is volatilized as a gas. Furthermore, step (6) is a step of reacting the obtained hydrogen sulfide with an alkali metal hydroxide. Steps (5) and (6) can be performed simultaneously or separately.

When step (5) and step (6) are performed simultaneously, for example, volatilized hydrogen sulfide is discharged out of the system, absorbed by an aqueous solution containing an alkali metal hydroxide and recovered, and at the same time, hydrogen sulfide and A method of producing a sulfidating agent by reacting with an alkali metal hydroxide can be mentioned. In this case, as the alkali metal hydroxide to be used, the same one as used in the PAS polymerization step can be used. The amount of alkali metal hydroxide to be used varies depending on the temperature and pressure when hydrogen sulfide is absorbed, so it cannot be categorically specified, but it should be at least the amount that can sufficiently absorb and react with the total amount of volatilized hydrogen sulfide. is desirable. In general, when hydrogen sulfide is absorbed and reacted at normal temperature and pressure, it is preferably 1 mol or more with respect to 1 mol of sulfur atoms of volatilized hydrogen sulfide, and if it is in the range of 1 to 2 mol more preferred. The concentration of alkali metal hydroxide in the aqueous solution also varies depending on the temperature and pressure when hydrogen sulfide is absorbed and reacted, so it cannot be defined unconditionally, but it is preferably in the range of 5 to 49 wt%, and 10 to More preferably, it is in the range of 45 wt%. In addition, the temperature at which hydrogen sulfide is absorbed and reacted with an aqueous solution containing an alkali metal hydroxide varies depending on the pressure, so it cannot be defined unconditionally, but it is preferably in the range of 0 to 200 ° C., and 10 to 150 ° C. is more preferred. In addition, since the pressure at which hydrogen sulfide is absorbed and reacted with an aqueous solution containing an alkali metal hydroxide varies depending on the temperature, it cannot be defined unconditionally, but the range of 0 to 1.0 Pa (gauge pressure) is preferable. , 0 to 0.5 Pa (gauge pressure) is more preferable.

On the other hand, when the step (5) and the step (6) are performed separately, for example, the volatilized hydrogen sulfide is discharged out of the system, and a solvent known to absorb hydrogen sulfide, such as an organic amide, is used. After performing the step of absorbing and recovering with a solvent, an alkali metal hydroxide is added to the recovered solvent containing hydrogen sulfide, and the hydrogen sulfide and the alkali metal hydroxide are reacted to generate an alkali metal hydrosulfide. and a method of performing the step of causing. In this case, solvents known to absorb hydrogen sulfide include organic amide solvents. Furthermore, organic amide solvents include formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε- Mention may be made of caprolactam, hexamethylphosphoramide, N-dimethylpropylene urea, amides such as 1,3-dimethyl-2-imidazolidinoic acid, urea, among these N-methyl-2-pyrrolidone, 2- Amides having an aliphatic cyclic structure of pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropylene urea, and 1,3-dimethyl-2-imidazolidinoic acid are preferred, More preferred is N-methyl-2-pyrrolidone.

The amount of solvent that is known to absorb hydrogen sulfide varies depending on the temperature and pressure at which hydrogen sulfide is absorbed. Amount or more is desirable. In general, when hydrogen sulfide is absorbed at normal temperature and pressure, it is preferably in the range of 1 to 30 kg with respect to 1 mol of sulfur atoms of volatilized hydrogen sulfide. Although the temperature and pressure at which hydrogen sulfide is absorbed by a solvent known to absorb hydrogen sulfide cannot be defined unconditionally, the absorption temperature is preferably in the range of 0 to 200 ° C., and 10 to 150 ° C. range is more preferred, while the pressure is preferably in the range of 0 to 1.0 Pa (gauge pressure), more preferably in the range of 0 to 0.5 Pa (gauge pressure). Thereafter, an alkali metal hydroxide is added to the recovered solvent containing hydrogen sulfide to react the hydrogen sulfide and the alkali metal hydroxide to produce an alkali metal hydrosulfide. At that time, the amount of the alkali metal hydroxide to be added is desirably an amount or more that can sufficiently react the total amount of hydrogen sulfide absorbed by the solvent. In general, when hydrogen sulfide is absorbed at normal temperature and pressure, it is preferably 1 mol or more with respect to 1 mol of sulfur atoms of hydrogen sulfide absorbed by the solvent, and may be in the range of 1 to 2 mol. is preferred. The concentration of the alkali metal hydroxide in the alkaline aqueous solution added to the solvent also varies depending on the temperature and pressure when hydrogen sulfide is absorbed, so it cannot be defined unconditionally, but it is preferably in the range of 5 to 49 wt%. More preferably, it is in the range of 10 to 45 wt%. In addition, since the temperature at which the hydrogen sulfide absorbed by the solvent and the alkali metal hydroxide are reacted varies depending on the pressure, the temperature cannot be defined unconditionally, but the temperature is preferably in the range of 0 to 200 ° C. A range of ~150°C is more preferred. Also, although the pressure cannot be defined unconditionally, it is preferably in the range of 0 to 1.0 Pa (gauge pressure), more preferably in the range of 0 to 0.5 Pa (gauge pressure).

The step (5) may be performed either continuously or batchwise. Since the absorption rate of hydrogen sulfide in an aqueous solution of alkali metal hydroxide or an organic amide solvent is fast, a general type such as a packed tower with a circulating pump can be used, and a liquid filling type or bubbling type can also be used sufficiently. be. Further, when step (5) and step (6) are performed simultaneously, step (6) can be performed in the same apparatus as step (5), and step (5) and step (6) can be performed separately. In this case, even if step (6) was carried out in the same apparatus as step (5), the hydrogen sulfide recovered in step (5) was transferred to another apparatus, such as a reactor equipped with stirring blades, a vessel, or a drum. An alkali metal hydroxide may be added later and allowed to react.

Step (7)
As described above, in steps (5) and (6), an amount of alkali metal hydroxide that can sufficiently absorb and react with the total amount of recovered hydrogen sulfide is used. remains in the system. Therefore, after the step (6), a step (7) of adding hydrogen sulfide to the unreacted alkali metal hydroxide and reacting the unreacted alkali metal hydroxide with the hydrogen sulfide is included. is preferred. The amount of hydrogen sulfide to be added is preferably in the range of 0.5 to 1 mol per 1 mol of alkali metal hydroxide remaining unreacted. By reacting with hydrogen sulfide in this range, 0.5 to 1 mol of alkali metal hydrosulfide and/or alkali metal sulfide is produced per 1 mol of residual alkali metal hydroxide.

The ratio of the alkali metal hydrosulfide and the alkali metal sulfide produced through step (6) or step (7) depends on the amount of alkali metal hydroxide to be reacted with hydrogen sulfide, the reaction time, temperature, and pressure. etc., and cannot be categorically defined, and both alkali metal hydrosulfides and alkali metal sulfides can be reused as sulfidation agents that are raw materials for polymerization of PAS resins described later. Therefore, the ratio of the alkali metal hydrosulfide and the alkali metal sulfide may be any ratio within the range of 0/100 to 100/0 on the mass basis.

Method for Producing PAS Resin As the mixture (A) containing at least a PAS resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent, one obtained by the following method for producing a PAS resin can be used. Further, the alkali metal hydrosulfide and / or alkali metal sulfide obtained through the above steps (1) to (6) or steps (1) to (7) are used as a sulfidating agent, the following PAS resin can be used as at least a part of the raw material for polymerization in the production method of

PAS polymerization step That is, the method for producing the PAS resin used in the present invention comprises mixing an aprotic polar solvent, a polyhaloaromatic compound, and a sulfidating agent, and a PAS polymerization step of polymerizing a sulfidating agent to obtain a crude reaction mixture containing at least a PAS resin, a sulfidating agent remaining without polymerization, an alkali metal halide, and an aprotic polar solvent; PAS/solvent to obtain a reaction mixture containing at least a PAS resin, a sulfidating agent remaining without polymerization, and an alkali metal halide, obtained by solid-liquid separation of an aprotic polar solvent from the crude reaction mixture A method through a solid-liquid separation step can be mentioned.

Here, the polyhaloaromatic compound in the present invention is, for example, a halogenated aromatic compound having two or more halogen atoms directly bonded to an aromatic ring, specifically p-dichlorobenzene, o -Dichlorobenzene, m-dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dibrombenzene, diiodobenzene, tribrombenzene, dibromnaphthalene, triiodobenzene, dichlorodiphenylbenzene, dibromodiphenylbenzene, dichlor Dihaloaromatic compounds such as benzophenone, dibromobenzophenone, dichlorodiphenyl ether, dibromodiphenyl ether, dichlorodiphenyl sulfide, dibromodiphenyl sulfide, dichlorobiphenyl, dibromobiphenyl and mixtures thereof, and block these compounds. It may be copolymerized. Among these, dihalogenated benzenes are preferred, and those containing 80 mol % or more of p-dichlorobenzene are particularly preferred. For the purpose of increasing the viscosity of the PAS resin by forming a branched structure, a polyhaloaromatic compound having 3 or more halogen substituents in one molecule may be used as a branching agent, if desired. Examples of such polyhaloaromatic compounds include 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, 1,4,6-trichloronaphthalene and the like. Furthermore, polyhaloaromatic compounds having functional groups with active hydrogen such as amino groups, thiol groups, and hydroxyl groups can be mentioned. Specifically, 2,6-dichloroaniline and 2,5-dichloroaniline. , 2,4-dichloroaniline, 2,3-dichloroaniline and other dihaloanilines; 2,3,4-trichloroaniline, 2,3,5-trichloroaniline, 2,4,6-trichloroaniline, 3, trihaloanilines such as 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 an amino group is replaced with a thiol group or a hydroxyl group in a mixture thereof. In addition, active hydrogen-containing polyhalo aromatic compounds 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 such as alkyl groups. Aromatic compounds can also be used.

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

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

In the present invention, examples of sulfidating agents include alkali metal sulfides and/or alkali metal hydrosulfides.

The alkali metal sulfides include lithium sulfide, sodium sulfide, rubidium sulfide, cesium sulfide and mixtures thereof. Such alkali metal sulfides can be used as hydrates or as aqueous mixtures or as anhydrates. Alkali metal sulfides can also be derived from the reaction between alkali metal hydrosulfides and alkali metal hydroxides. A small amount of alkali metal hydroxide may be added to react with alkali metal hydrosulfide and alkali metal thiosulfate, which are usually present in trace amounts in alkali metal sulfide.

Also, the alkali metal hydrosulfide includes lithium hydrogen sulfide, sodium hydrogen sulfide, rubidium hydrogen sulfide, cesium hydrogen sulfide and mixtures thereof. Such alkali metal hydrosulfides can be used as hydrates or as aqueous mixtures or as anhydrates.

Also, the alkali metal hydrosulfide is used together with the alkali metal hydroxide. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. These may be used alone, or two or more of them may be mixed. You can use it as Among these, lithium hydroxide, sodium hydroxide and potassium hydroxide are preferred because they are readily available, and sodium hydroxide is particularly preferred.

As described above, the alkali metal hydrosulfides and/or alkali metal sulfides obtained through the steps (1) to (6) or the steps (1) to (7) are also used as sulfidating agents in the PAS resin. can be reused as a raw material in the polymerization reaction of

The method for producing the PAS resin used in the present invention can also use a hydrous sulfidation agent as a raw material. is preferably subjected to the polymerization reaction of Further, when the amount of the aprotic polar solvent charged is small, for example, when it is less than 1 mol with respect to 1 mol of sulfur atoms in the sulfidation agent, in the presence of the polyhaloaromatic compound, the hydrous sulfidation agent and the non- It is preferred to dehydrate the protic polar solvent.

In the dehydration step, at least an aprotic polar solvent and a hydrous alkali metal sulfide or a hydrous alkali hydrosulfide and an alkali metal hydroxide as a hydrous sulfidating agent are charged into a reaction vessel equipped with a distillation apparatus, and water is coexisted. The temperature to be removed by boiling, specifically, the range of 300 ° C. or less, preferably the range of 80 to 220 ° C., more preferably the range of 100 to 200 ° C. is heated, and the water is discharged out of the system by distillation. by doing. In the dehydration step, dehydration is performed until the amount of water in the system in which the polymerization reaction is performed is 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 sulfidating agent. is preferred.

In the dehydration step, alkali metal sulfides and alkali metal hydrosulfides react with water to generate hydrogen sulfide as gas in equilibrium. Therefore, it is preferable to recover the generated hydrogen sulfide and then react it with an alkali metal hydroxide to obtain an alkali metal hydrosulfide and/or an alkali metal sulfide. Specifically, the produced hydrogen sulfide is discharged out of the reaction system together with water or the azeotrope, and the water or the azeotrope and hydrogen sulfide are separated by a distillation apparatus, and then the same method as in the step (5). Further, the recovered hydrogen sulfide is reacted with an alkali metal hydroxide in the same manner as in the step (6) to produce an alkali metal hydrosulfide and / or an alkali metal sulfide. preferably. Further, after the step of reacting the hydrogen sulfide recovered in the dehydration step with an alkali metal hydroxide to produce an alkali metal hydrosulfide and/or an alkali metal sulfide, in the same manner as in step (7) and adding hydrogen sulfide to the unreacted alkali metal hydroxide to react the unreacted alkali metal hydroxide with the hydrogen sulfide. The alkali metal hydrosulfide and/or alkali metal sulfide obtained in the dehydration step is also preferably used as a sulfidating agent as a part of raw materials in the method for producing a PAS resin.

In the present invention, the aprotic polar solvent includes formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε. - Amides such as caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropylene urea, 1,3-dimethyl-2-imidazolidinoic acid, urea and lactams; sulfolane such as sulfolane, dimethylsulfolane; benzo nitriles such as nitriles; ketones such as methylphenylketone and mixtures thereof, among which N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, Hexamethylphosphoramide, N-dimethylpropylene urea, and amides having an aliphatic ring structure of 1,3-dimethyl-2-imidazolidinoic acid are preferred, and N-methyl-2-pyrrolidone is more preferred.

In the PAS polymerization step, the PAS resin is polymerized by reacting the alkali metal sulfide as a sulfidating agent with the polyhaloaromatic compound in the presence of these aprotic polar solvents. Alternatively, the PAS resin is polymerized by reacting the alkali metal hydrosulfide and alkali metal hydroxide as sulfidating agents with the polyhaloaromatic compound in the presence of these aprotic polar solvents. Polymerization conditions generally range in temperature from 200 to 330° C., and the pressure should be such that the polymerization solvent and the polyhaloaromatic compound, which is the polymerization monomer, are substantially maintained in the liquid phase, generally 0.5. It is selected from the range of 1 to 20 MPa, preferably from the range of 0.1 to 2 MPa. The amount of the polyhaloaromatic compound charged is in the range of 0.2 mol to 5.0 mol, preferably in the range of 0.8 to 1.3 mol, more preferably in the range of 0.8 to 1.3 mol, per 1 mol of the sulfur atom of the sulfidating agent. It is prepared so as to be in the range of 0.9 to 1.1 mol. In addition, the amount of the aprotic polar solvent charged is in the range of 1.0 to 6.0 mol, preferably in the range of 2.5 to 4.5 mol, per 1 mol of the sulfur atom of the sulfidating agent. adjust. The polymerization reaction is preferably carried out in the presence of a small amount of water, and the proportion thereof is preferably adjusted appropriately in consideration of the polymerization method, the molecular weight of the resulting polymer, and productivity. Specifically, the dehydration operation is carried out so that the amount becomes 2.0 mol or less, preferably 1.6 mol or less per 1 mol of the sulfur atom of the sulfidation agent, and the dehydration is performed in the presence of the polyhaloaromatic compound. When the operation is performed (for example, the method of "5)" in the specific embodiment below), it is 0.9 mol or less, preferably 0.05 to 0.3 mol, more preferably 0.01 to 0.02 mol or less. Dehydration operation may be performed so that the range of

Specific embodiments of polymerizing the sulfidating agent and the polyhaloaromatic compound in the presence of the aprotic polar solvent include, for example:
1) A method using a polymerization aid such as an alkali metal carboxylate or lithium halide,
2) A method using a branching agent such as an aromatic polyhalogen compound,
3) a method of conducting a polymerization reaction in the presence of a small amount of water and then adding water to further polymerize;
4) a method of cooling the gas phase portion of the reaction vessel during the reaction between the alkali metal sulfide and the aromatic dihalogen compound to condense a portion of the gas phase in the reaction vessel and reflux it to the liquid phase;
5) reacting an alkali metal sulfide, or a hydrous alkali metal hydrosulfide and an alkali metal hydroxide with an amide, urea or lactam having an aliphatic cyclic structure in the presence of a polyhaloaromatic compound while dehydrating; a step of producing a slurry containing a solid alkali metal sulfide, a step of adding a polar organic solvent such as NMP after producing the slurry, distilling off water to dehydrate, and then a dehydration step. In the resulting slurry, a polyhaloaromatic compound, an alkali metal hydrosulfide, and an alkali metal salt of the hydrolyzate of the amide, urea or lactam having an aliphatic cyclic structure are added to 1 mol of a polar organic solvent such as NMP. and a method for producing a PAS resin comprising, as an essential production step, a step of polymerizing by reacting with the amount of water present in the reaction system being 0.02 mol or less.

Among these, in the case of producing a PAS resin by the polymerization methods 1) to 5), particularly 1) to 4), the production raw materials include, for example, NMP as an aprotic polar solvent and p- In the case of dichlorobenzene, as a side reaction product of the polymerization reaction, the following general formula (1)

（式中、Ｘはアルカリ金属原子または水素原子を表す。）で表されるカルボキシアルキルアミノ基含有化合物が該粗反応混合物に含まれる場合がある。本発明は、ＰＡＳ樹脂を製造方法について公知の方法であれば特に限定するものではないため、製造方法によっては該カルボキシアルキルアミノ基含有化合物が生成しない場合もあることから必須の成分ではない。しかし、例えば、１）～５）、特に１）～４）の重合方法で、前記カルボキシアルキルアミノ基含有化合物が生成した場合は、当該カルボキシアルキルアミノ基含有化合物は粗反応混合物と非プロトン性極性溶媒のＰＡＳ／溶媒固液分離工程を経て、反応混合物中に含まれ、さらに本発明の工程（１）を経て、前記混合物（Ａ）中に含まれ、さらに本発明の工程（２）を経て、前記水溶液（Ｂ）中に含まれ、（３）、（４）を経て、前記水溶液（Ｃ）中に含まれ、さらに工程（５）、（６）において硫化水素と分離されることとなる。すなわち、アルカリ金属ハロゲン化物と同様に移行する。このため、アルカリ金属水硫化物を生成する反応には関与せず、必須の成分ではない。

(wherein X represents an alkali metal atom or a hydrogen atom) may be contained in the crude reaction mixture. The present invention is not particularly limited as long as the PAS resin is produced by a known method, and the carboxyalkylamino group-containing compound may not be produced depending on the production method, so it is not an essential component. However, for example, when the carboxyalkylamino group-containing compound is produced by the polymerization methods of 1) to 5), particularly 1) to 4), the carboxyalkylamino group-containing compound is mixed with the crude reaction mixture and the aprotic polar included in the reaction mixture through the PAS/solvent solid-liquid separation step of the solvent, further included in the mixture (A) through the step (1) of the present invention, and further through the step (2) of the present invention , contained in the aqueous solution (B), passed through (3) and (4), contained in the aqueous solution (C), and further separated from hydrogen sulfide in steps (5) and (6). . That is, they migrate in the same manner as alkali metal halides. Therefore, it does not participate in the reaction that produces alkali metal hydrosulfides and is not an essential component.

At least the PAS resin, alkali metal hydrosulfide and/or alkali metal sulfide remaining as an unreacted sulfidating agent, alkali metal halide, and alkali metal carbonate obtained through the above PAS polymerization step; A crude reaction mixture containing an aprotic polar solvent can be used as said mixture (A).

PAS/solvent solid-liquid separation step At least the PAS resin obtained through the PAS polymerization step, the alkali metal halide, the alkali metal hydrosulfide and/or alkali metal sulfide remaining as an unreacted sulfidating agent, and the alkali A crude reaction mixture comprising a metal carbonate and an aprotic polar solvent is then subjected to solid-liquid separation of the aprotic polar solvent from the crude reaction mixture to produce at least a PAS resin, an alkali metal halide, an alkali A step of obtaining a reaction mixture containing a metal carbonate and a sulfidating agent. The resulting reaction mixture can also be used as the mixture (A).

The solid-liquid separation is roughly divided into two types, a flash method and a quench method, which will be described later. The flash method is a method of recovering the solvent by evaporating the solvent and recovering the solid at the same time, and is generally carried out by distilling off the solvent by heating under reduced pressure.

On the other hand, the quench method is a method of recovering particulate PAS resin by slowly cooling the polymerization reaction product. A method of liquid separation is mentioned. Solid-liquid separation in the quench method is performed by filtering or separating using a centrifuge such as a screw decanter, then adding water directly to the resulting filtration residue to make a slurry, and then repeating solid-liquid separation. and a method of heating the filtered residue in a non-oxidizing atmosphere to remove the remaining solvent. The flash method is preferable in that the solids can be recovered relatively easily, and the quench method is preferable in that the particle size of the PAS resin can be easily controlled, and the addition of alkali metal halides, sulfidating agents, etc. to the polymer particles during crystallization. Since it becomes difficult to incorporate impurities, it is preferable in that a high-purity polymer can be obtained.

Subsequently, the reaction mixture undergoes the purification step of the present invention by washing with water or washing with hot water, and is separated into a PAS resin and an aqueous solution containing at least an alkali metal halide and a sulfidating agent. The purification step can be performed in the same manner as the step (1), and in the case of producing a PAS resin, the filtered PAS resin may be collected.

The filtered PAS resin may be recovered and then dried as it is to be used as PAS resin powder. Alternatively, it may be further washed, separated into solids and liquids, and dried to be powdered or granular PAS resin. can also be prepared.

Composition, use, etc. As described above, the sulfidation agent obtained through steps (1) to (6) or steps (1) to (7) of the present invention is reused as at least a part of the raw material. The PAS resin polymerized by this method may contain a release agent, a coloring agent, a heat stabilizer, an ultraviolet stabilizer, a foaming agent, a rust inhibitor, a flame retardant, a lubricant, a coupling agent, a filler, and a filler within a range that does not impair the effects of the present invention. Additives such as lumber can be included. Furthermore, synthetic resins and elastomers such as those described below can also be mixed and used in the same manner. These synthetic resins include polyester, polyamide, polyimide, polyetherimide, polycarbonate, polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, polyetherketone, polyarylene, polyethylene, polypropylene, polytetrafluoroethylene, Polyethylene difluoride, polystyrene, ABS resins, epoxy resins, silicone resins, phenol resins, urethane resins, liquid crystal polymers and the like can be mentioned, and elastomers can include polyolefin rubbers, fluororubbers, silicone rubbers and the like.

Furthermore, the PAS resin polymerized by reusing the sulfidating agent obtained through steps (1) to (6) or steps (1) to (7) as at least a part of the raw material can be injection molded, Excellent heat resistance, molding processability, dimensional stability, etc. by various melt processing methods such as extrusion molding, compression molding, and blow molding. For this reason, for example, electrical and electronic parts such as connectors, printed circuit boards, and sealed molded products, automotive parts such as lamp reflectors and various electrical parts, interior materials for various buildings, aircraft, automobiles, etc., OA equipment parts, It can be widely used as injection molding/compression molding products such as precision parts such as camera parts and watch parts, or extrusion molding/pultrusion molding such as fibers, films, sheets and pipes.

According to the present invention, the alkali metal hydrosulfide remaining as an unreacted sulfidating agent in a reusable state with high purity is separated and recovered from the wastewater obtained after washing with water or after washing with hot water in the manufacturing process of the PAS resin. , the COD value of waste water can be reduced, the environmental load can be reduced by reducing industrial waste, the loss of sulfur atoms (decrease in raw material unit consumption) can be suppressed, and the productivity of PAS resin can be improved.

EXAMPLES The present invention will be specifically described below with reference to examples. These examples are illustrative and not limiting. In the following, unless otherwise specified, "%" and "parts" are based on mass.

<Evaluation>

(1) Determination of sodium carbonate concentration, sodium hydrogen sulfide concentration, and sodium sulfide concentration in the waste water and the sulfidating agent recovery liquid After adding an aqueous barium chloride solution and confirming the precipitation of barium carbonate, the slurry solution was subjected to neutralization titration with 0.5 mol/L hydrochloric acid using a potentiometric automatic titrator. Calculate the sodium sulfide concentration from the titration amount at the first equivalence point, then calculate the sodium hydrogen sulfide concentration from the difference between the titration amount at the second equivalence point and the titration amount at the first equivalence point, and calculate the third equivalence point and The sodium carbonate concentration was calculated from the difference between the second equivalence points.

(2) Measurement of pH when hydrochloric acid is added to wastewater In each sulfidating agent recovery process of each example and comparative example, the pH when hydrochloric acid is added to wastewater was measured using a “personal pH meter” manufactured by Yokogawa Electric Corporation. PH72” was used. Electrode calibration was performed using pH 4 and pH 7 standard solutions.

<Examples 1 to 9, Comparative Examples 1 to 4>

Example (1-1) PPS polymerization and production of wastewater A condenser connected to a gas absorption bottle charged with 1.88 kg of a 20 wt% sodium hydroxide aqueous solution in advance, a pressure gauge, a thermometer, a stirring blade connected to the condenser, and a bottom valve. In a 150 liter autoclave, 19.403 kg of 60.33 wt% Na ₂ S flake raw material (150 mol of sulfur atoms, "60% sodium sulfide product" manufactured by Nagao Co., Ltd., sodium carbonate content of 0.35 wt%) and 45.0 kg of NMP ( 454 mol) were charged. The temperature was raised to 209° C. while stirring under a nitrogen stream to distill 4.815 kg of water. Hydrogen sulfide scattered during dehydration was absorbed in an aqueous sodium hydroxide solution using a gas absorption bottle. After that, the autoclave was closed and cooled to 180° C., and 22.185 kg (151 mol) of p-dichlorobenzene and 18.0 kg (182 mol) of NMP were charged. At a liquid temperature of 150° C., nitrogen gas was used to pressurize the liquid to a gauge pressure of 0.1 MPa to start heating. The reaction was allowed to proceed with stirring at a liquid temperature of 260° C. for 3 hours, and the upper part of the autoclave was cooled by sprinkling water. Next, the temperature was lowered and the cooling of the upper part of the autoclave was stopped. After the slurry obtained after the reaction was cooled to room temperature, it was dried at 150° C. under reduced pressure for 3 hours using a vacuum dryer to distill off NMP. Next, 93 kg of hot water at 70°C was added and stirred, followed by filtration, and then 53 kg of hot water at 70°C was added and filtered. Each filtrate was collected to obtain 136 kg of waste water (1a-1). Concentrations of sodium carbonate and sulfidating agents (sodium hydrogen sulfide and sodium sulfide) contained in the wastewater (1a-1) were measured by neutralization titration. Table 1 shows the results.

Example (1-2) Filtration of wastewater and recovery of sulfidation agent contained in wastewater To wastewater (1a-1), 0.50 mol of calcium chloride is added to 1 mol of dissolved sodium carbonate to generate The resulting white precipitate was filtered to obtain 136 kg of wastewater (1a-2). Waste water (1a-2) was neutralized and titrated to determine the amount of sodium carbonate and sulfidating agent. Table 1 shows the results. After that, a gas absorption bottle containing the sodium hydroxide aqueous solution absorbing hydrogen sulfide obtained in Example (1-1) was connected to a container equipped with a stirrer, a pH meter, a gas inlet tube and a dropping funnel. 136 kg of waste water (1a-2) was charged into the container, stirred while introducing N ₂ gas (50 ml/min), hydrochloric acid was added to adjust the pH to 3.0, stirred for 60 minutes, and hydrogen sulfide generated a gas containing The generated hydrogen sulfide gas was absorbed in an aqueous sodium hydroxide solution to obtain 2.17 kg of a sulfidating agent recovery liquid (1a). The sulfidating agent recovery liquid (1a) was measured by neutralization titration to determine the concentrations of sodium carbonate and sulfidating agent. Table 2 shows the results.

Example (1-3) PPS production using sulfidating agent recovery liquid The raw material to be charged into the autoclave was changed to "60.33 wt% Na ₂ S flakes" instead of "19.413 kg of 60.33 wt% Na ₂ S flake raw material". 18.918 kg of raw material (146.25 mol of sulfur atoms) and 0.997 kg of sulfidating agent recovery liquid (1a) (3.75 mol of sulfur atoms, using sulfidating agent recovery liquid with respect to the charged mole number of all sulfur atoms) The ratio is 2.5 mol%) and 49.21 wt% sodium hydroxide 0.259 kg (3.18 mol) "mixture" was performed in the same manner as in Example (1-1). -1) was obtained. Table 3 shows the amounts of sulfidation agent and sodium carbonate in the raw materials charged in the production of PPS.

Example (1-4) Filtration of wastewater and recovery of sulfidation agent contained in wastewater (second time)
In the same procedure as in Example (1-2), 0.50 mol of calcium chloride is added to 1 mol of sodium carbonate in the wastewater (1b-1), and the resulting white precipitate is filtered. to obtain waste water (1b-2). Thereafter, hydrochloric acid was added to the obtained wastewater (1b-2), and the generated gas containing hydrogen sulfide was absorbed into an aqueous sodium hydroxide solution to obtain a sulfidating agent recovery liquid (1b). The sulfidating agent recovery solution (1b) was measured by neutralization titration to determine the concentrations of sodium carbonate and the sulfidating agent. Table 4 shows the results.

Example (1-5) Repeated test After that, PPS production using the sulfidating agent recovery liquid in the same manner as in Example (1-3) and the same wastewater filtration as in (1-4) and the sulfidating agent contained in the wastewater collection was repeated. In each process, sulfidating agent recovery liquids (1c) to (1j) were obtained, respectively. The concentration of sodium carbonate and sulfidating agent contained in each sulfidating agent recovery solution was determined by neutralization titration. Table 4 shows the results.

Examples (2-1 to 2-5)
Example (1) except that in Example (1-3), the ratio of the sulfidating agent recovery liquid used to the charged moles of all sulfur atoms was set to 5.0 mol% instead of 2.5 mol%. went as well. The obtained results are shown in Tables 1-4.

Examples (3-1 to 3-5)
Example (1) except that in Example (1-2), the amount of calcium chloride added to the wastewater was 1.00 mol instead of 0.50 mol with respect to 1 mol of sodium carbonate. went as well. The obtained results are shown in Tables 1-4.

Examples (4-1 to 4-5)
Example (2) except that in Example (2-2), the amount of calcium chloride added to the wastewater was 1.00 mol instead of 0.50 mol with respect to 1 mol of sodium carbonate. went as well. The obtained results are shown in Tables 1-4.

Examples (5-1 to 5-5)
Example (2) except that in Example (2-2), the amount of calcium chloride added to the wastewater was 2.00 mol instead of 0.50 mol with respect to 1 mol of sodium carbonate. went as well. The obtained results are shown in Tables 1-4.

Examples (6-1 to 6-5)
Example (4-2) was carried out in the same manner as in Example (4), except that calcium acetate was used instead of calcium chloride as the metal salt added to the wastewater. The obtained results are shown in Tables 1-4.

Examples (7-1 to 7-5)
Example (4-2) was carried out in the same manner as in Example (4), except that calcium hydroxide was used instead of calcium chloride as the metal salt added to the wastewater. The obtained results are shown in Tables 1-4.

Examples (8-1 to 8-5)
Example (4-2) was carried out in the same manner as in Example (4), except that barium chloride was used instead of calcium chloride as the metal salt added to the waste water. The obtained results are shown in Tables 1-4.

Examples (9-1 to 9-5)
Example (4-2) was carried out in the same manner as in Example (4), except that strontium chloride was used instead of calcium chloride as the metal salt added to the waste water. The obtained results are shown in Tables 1-4.

Comparative example (1-1 to 1-5)
Example (1-2) was carried out in the same manner as in Example (1), except that the hydrochloric acid treatment was performed without adding metal salt to the wastewater. The obtained results are shown in Tables 1-4.

Comparative example (2-1 to 2-5)
Example (2-2) was carried out in the same manner as in Example (2), except that the hydrochloric acid treatment was performed without adding metal salt to the waste water. The obtained results are shown in Tables 1-4. In the fourth production of the sulfidating agent, the concentration of sodium carbonate exceeded 10 wt%, and due to concerns about precipitation of sodium carbonate, subsequent PPS production was discontinued.

Comparative example (3-1 to 3-5)
Example (4-2) was carried out in the same manner as in Example (4), except that calcium carbonate was used instead of calcium chloride as the metal salt added to the wastewater. The obtained results are shown in Tables 1-4. In the fourth production of the sulfidating agent, the concentration of sodium carbonate exceeded 10 wt%, and due to concerns about precipitation of sodium carbonate, subsequent PPS production was discontinued.

Comparative example (4-1 to 4-5)
Example (4-2) was carried out in the same manner as in Example (4), except that potassium chloride was used instead of calcium chloride as the metal salt added to the wastewater. No sediment was observed in the waste water after addition of potassium chloride. Hydrochloric acid was therefore added without subsequent filtration. The obtained results are shown in Tables 1-4. In the fourth production of the sulfidating agent, the concentration of sodium carbonate exceeded 10 wt%, and due to concerns about precipitation of sodium carbonate, subsequent PPS production was discontinued.

From the results in Table 1, it was confirmed that the examples can reduce the concentration of sodium carbonate in the wastewater after filtration compared to the comparative examples. From the results in Table 2, since the wastewater of Examples has a low sodium carbonate concentration, when hydrogen sulfide gas generated by adding hydrochloric acid to the wastewater is recovered in an aqueous sodium hydroxide solution, carbon dioxide derived from sodium carbonate is generated together. It was found that there was little sodium carbonate in the sulfidating agent recovery solution. It is clear from Table 4 that when PPS production is repeated by reusing the sulfidating agent recovery liquid in the amount shown in Table 3, the sodium carbonate concentration in the sulfidating agent recovery liquid remains low in the examples. .

Claims (7)

After the mixture (A) containing at least a polyarylene sulfide resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent is brought into contact with water, the polyarylene sulfide resin is separated and removed to obtain at least the alkali metal Step (1) of obtaining an aqueous solution (B) containing a halide, an alkali metal carbonate and a sulfidating agent;
Step (2) of adding a metal salt containing at least one Group 2 element selected from magnesium, calcium, strontium, and barium to the aqueous solution (B) to form a water-insoluble carbonate;
step (3) of obtaining an aqueous solution (C) containing at least an alkali metal halide and a sulfidating agent by separating and removing the produced water-insoluble carbonate from the aqueous solution (B);
a step (4) of adding an acid to the aqueous solution (C) to generate hydrogen sulfide;
A step (5) of recovering the produced hydrogen sulfide, and
a step (6) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide;
A method for producing a sulfidating agent, characterized by having After the step (6) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide, hydrogen sulfide is added to the unreacted alkali metal hydroxide to convert the hydrogen sulfide and the unreacted alkali metal hydroxide. 2. The method for producing a sulfidation agent according to claim 1, comprising the step (7) of reacting with a substance. The mixture (A) comprising at least a polyarylene sulfide resin, an alkali metal halide, an alkali metal carbonate and a sulfidating agent,
A crude product obtained after reacting a polyhaloaromatic compound with a sulfidating agent in an aprotic polar solvent, comprising at least a polyarylene sulfide resin, an alkali metal halide, the aprotic polar solvent and a sulfidating agent 2. The method for producing a sulfidation agent according to claim 1, wherein the reaction mixture is a reaction mixture or a reaction mixture obtained by solid-liquid separation of the aprotic polar solvent from the crude reaction mixture. A dehydration step of dehydrating a hydrous sulfidating agent, in the presence of at least an aprotic polar solvent, for use in reacting a polyhaloaromatic compound with a sulfidating agent in an aprotic polar solvent. The method for producing a sulfidating agent according to claim 3, characterized in that it is obtained through 5. A method for producing a sulfidation agent, comprising a step of recovering hydrogen sulfide produced in the dehydration step according to claim 4 and then reacting it with an alkali metal hydroxide to obtain a sulfidation agent. After the step of reacting with an alkali metal hydroxide to obtain a sulfidating agent, hydrogen sulfide is added to the unreacted alkali metal hydroxide to convert the hydrogen sulfide and the unreacted alkali metal hydroxide. 6. The method for producing a sulfidating agent according to claim 5, comprising a step of reacting. A polyarylene sulfide resin, which is produced by reacting a sulfidating agent obtained by dehydrating a hydrous sulfiding agent in the presence of an organic amide solvent with a polyhaloaromatic compound in the presence of an organic amide solvent to produce a polyarylene sulfide resin. In the manufacturing method of
A sulfidating agent obtained by the method for producing a sulfidating agent according to any one of claims 1 to 4 and/or the method for producing a sulfidating agent according to claim 5 or 6 as at least a part of a hydrous sulfidating agent or a sulfidating agent. A method for producing a polyarylene sulfide resin, comprising the step of adding the sulfidating agent obtained by.