JP7413820B2 - Sulfidating agent and method for producing polyarylene sulfide resin - Google Patents

Description

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, it describes a method for separating and purifying a sulfidating agent from wastewater discharged in the manufacturing process of polyarylene sulfide resin, and a method for producing polyarylene sulfide resin by reusing the obtained sulfidating agent as part of the raw material. Regarding the manufacturing method.

Polyarylene sulfide resin (PAS resin), represented by polyphenylene sulfide resin (PPS resin), has excellent heat resistance and chemical resistance, and is widely used in electrical and electronic parts, automobile parts, water heater parts, textiles, film, etc. has been done. In particular, high molecular weight polyarylene sulfide resins have been widely used in recent years for applications such as packing and gasket members for lithium ion batteries because of their excellent toughness and moldability.

Polyarylene sulfide resin is produced by converting a polyhaloaromatic compound into an alkali metal sulfide and/or alkali metal hydrosulfide in an aprotic polar solvent such as N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP). (hereinafter sometimes referred to as a sulfidating agent), along with the target material polyarylene sulfide resin, solvent, alkali metal hydrosulfide and alkali metal sulfide remaining without polymerization reaction. A crude reaction product is obtained which contains by-products such as sulfidating agents such as sulfidizing agents, alkali metal halides such as sodium chloride, other alkali metal-containing inorganic salts, and oligomers and derivatives thereof produced by side reactions. The crude reaction product after the polymerization reaction 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 dryer, filter, or centrifugal separator. (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 byproducts together with the target substance polyarylene sulfide resin, water washing and filtration are repeated. These are removed. In general, there are two methods: washing with water at a temperature below 100°C, and washing with hot water at a temperature of 100°C or higher under high pressure. The polyarylene sulfide obtained after washing with water or hot water is separated using a filter, centrifugal filter, etc., then dried, and if necessary, heat-treated to undergo a crosslinking reaction to produce a product.

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

As a treatment method for reducing COD substances in wastewater, for example, a wastewater treatment method characterized by adding an acidic flocculant to the wastewater to adjust the pH, insolubilizing the COD substances, and separating the insolubilized COD substances. etc. are known (see Patent Document 1). However, in this method, wastewater from the purification process is introduced into a flocculation reaction tank which has a mixing function and is equipped with a pH indicator controller and is capable of pH adjustment and flocculation treatment, and a flocculation reaction tank into which wastewater is introduced from the flocculation reaction tank. Since this method uses a continuous centrifugal separator to separate insolubilized COD substances, the separated COD substances have a high water content and cannot be reused as a raw material for producing polyarylene sulfide resin. Moreover, since the COD substances separated by the acidic flocculant were precipitated in the form of large flocs, they had to be disposed of as industrial waste, which was not desirable.

Therefore, a detailed investigation of the waste water discharged from water washing or hot water washing after the polymerization reaction revealed that the unreacted sulfidating agent remained at about 3 to 5 mol% of the charged amount in terms of sulfur atoms. It is clear that the unreacted sulfidating agent is one of the factors that increases the COD value of wastewater, and that it is also responsible for the loss of sulfur atoms (reducing the raw material consumption rate). became.

Therefore, in addition to the sulfidating agent remaining without polymerization, the wastewater discharged from water washing or hot water washing after the polymerization reaction contains byproducts such as alkali metal halides and oligomers and their derivatives produced by side reactions. The unreacted sulfidating agent is removed and recovered from the wastewater by adding an acid to gasify the unreacted sulfidating agent and then separating and recovering it. It has been proposed that COD can be reduced and that it can be reused as a raw material for producing polyarylene sulfide resin (see Patent Document 2). However, when the recovered material containing this unreacted sulfidating agent was reused as a raw material for producing polyarylene sulfide resin, there was still room for improvement in increasing the molecular weight of the resulting polyarylene sulfide resin.

Japanese Patent Application Publication No. 2003-275773 Japanese Patent Application Publication No. 2015-218214

Therefore, the problem to be solved by the present invention is to provide a method for recovering unreacted sulfidating agent contained in wastewater discharged from water washing or hot water washing after the polymerization reaction of polyarylene sulfide resin, and furthermore, The object of the present invention is to provide a method for producing a polyarylene sulfide resin having a higher molecular weight when a reactive sulfidation agent is reused as a polymerization raw material for the polyarylene sulfide resin.

As a result of various studies, the inventors of the present application found that when unreacted sulfidating agent contained in wastewater discharged from water washing or hot water washing after the polymerization reaction of polyarylene sulfide resin was recovered, the , thiophenol or its derivatives, thereby inhibiting the increase in the molecular weight of polyarylene sulfide resin when the recovered material containing the unreacted sulfidating agent is reused as a raw material for manufacturing polyarylene sulfide resin. We have found a method to reduce the thiophenol concentration in the recovered material easily and with good productivity, and have solved the above problem.

That is, the present invention provides: [1] After contacting the mixture (a) containing at least a polyarylene sulfide resin, an alkali metal halide, a thiophenol derivative, and a sulfidating agent with water, the polyarylene sulfide resin is separated and removed. step (1) of obtaining an aqueous solution (b) containing at least an alkali metal halide, a thiophenol derivative, and a sulfidating agent;
A step (2) of producing hydrogen sulfide by adding an acid to at least an aqueous solution (b) containing an alkali metal halide, a thiophenol derivative, and a sulfidating agent to adjust the pH to a range of 8 or less;
a step (3) of recovering the generated hydrogen sulfide via a thiophenol recovery trap tank having an aqueous solution containing an alkali metal hydroxide or an alkaline earth metal hydroxide, and
a step (4) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide;
The present invention relates to a method for producing a sulfidating agent, characterized by having the following.

Further, the present invention provides that [2] the proportion of thiophenol recovered in the step (3) is less than 100 mol with respect to 100 mol of the thiophenol derivative contained in the aqueous solution (b) in the step (3). The present invention relates to a method for producing a sulfidating agent according to [1] above, which is within the range of [1] above.
Further, the present invention provides [3] The mixture (a) containing at least a polyarylene sulfide resin, an alkali metal halide, a thiophenol derivative, and a sulfidating agent,
At least a polyarylene sulfide resin, an alkali metal halide, the aprotic polar solvent, a thiophenol derivative, and a sulfidation agent obtained after reacting a polyhaloaromatic compound with a sulfidation agent in an aprotic polar solvent. The production method according to [1] or [2], wherein the reaction mixture is a crude reaction mixture containing an agent, or a reaction mixture obtained by solid-liquid separation of the aprotic polar solvent from the crude reaction mixture.
[4] The sulfidating agent used when reacting the polyhaloaromatic compound and the sulfidating agent in an aprotic polar solvent is capable of reacting with water-containing sulfide in the presence of at least the aprotic polar solvent. It relates to the manufacturing method described in [3] above, which is obtained through a dehydration step of dehydrating the dehydrating agent.

Furthermore, the present invention provides the following method: [5] After the step (4) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide, hydrogen sulfide is added to the unreacted alkali metal hydroxide, and the hydrogen sulfide is combined with the hydrogen sulfide. The present invention relates to the production method described in [1] above, which includes the step (5) of reacting the unreacted alkali metal hydroxide.

Furthermore, the present invention provides a sulfide-containing agent, comprising the step of [6] recovering the hydrogen sulfide produced in the dehydration step described in [4] above, and then reacting it with an alkali metal hydroxide to obtain a sulfidating agent. The present invention relates to a method for producing a curing agent.

Furthermore, the present invention provides that after the step of [7] reacting with the alkali metal hydroxide to obtain a sulfidating agent, hydrogen sulfide is added to the unreacted alkali metal hydroxide, and the hydrogen sulfide and the unreacted The method for producing a sulfidating agent according to [6] above, which comprises the step of reacting the sulfidating agent with an alkali metal hydroxide.

Furthermore, the present invention [8] produces a polyarylene sulfide resin by reacting a sulfidating agent obtained by dehydrating a water-containing sulfidizing agent with a polyhaloaromatic compound in the presence of an organic amide solvent. In the method for producing a polyarylene sulfide resin, the sulfidating agent obtained by the production method described in any one of [1] to [5] above and/or the sulfidating agent as the hydrous sulfidating agent or the sulfidating agent. The present invention relates to a method for producing a polyarylene sulfide resin, which comprises a step of adding a sulfidating agent obtained by the production method of [6] or [7].

According to the present invention, it is possible to provide a method for recovering unreacted sulfidating agent contained in waste water discharged from water washing or hot water washing after the polymerization reaction of polyarylene sulfide resin, and further, to recover unreacted sulfidating agent. When reused as a polymerization raw material for polyarylene sulfide resin, it is possible to provide a method for producing a polyarylene sulfide resin having a higher molecular weight.

FIG. 2 is a conceptual diagram of a gas absorption bottle connected to a trap tank among the experimental equipment used in Example (1-2) sulfidating agent manufacturing method (preparation of sodium hydrogen sulfide recovery liquid). Specifically, the gas introduction pipe (2) is guided below the liquid level (2) in the trap tank (1). Furthermore, the hydrogen sulfide bubbled in the trap tank (1) passes through the gas exhaust pipe (3) of the tank (1), the joint part (10), and the gas introduction pipe (7) to the gas absorption bottle (5). The gas is guided below the liquid level (6) in the gas absorption bottle (5), and hydrogen sulfide is absorbed into the aqueous solution in the gas absorption bottle (5).

The method for producing a sulfidating agent of the present invention includes contacting a mixture (a) containing at least a polyarylene sulfide resin, an alkali metal halide, a thiophenol derivative, and a sulfidating agent with water, and then adding a polyarylene sulfide resin. Step (1) of separating and removing to obtain an aqueous solution (b) containing at least an alkali metal halide, a thiophenol derivative, and a sulfidating agent;
A step (2) of producing hydrogen sulfide by adding an acid to at least an aqueous solution (b) containing an alkali metal halide, a thiophenol derivative, and a sulfidating agent to adjust the pH to a range of 8 or less;
a step (3) of recovering the generated hydrogen sulfide via a thiophenol recovery trap tank having an aqueous solution containing an alkali metal hydroxide or an alkaline earth metal hydroxide, and
The method is characterized by comprising a step (4) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide.

Step (1) includes contacting the mixture (a) containing at least a polyarylene sulfide resin, an alkali metal halide, a thiophenol derivative, and a sulfidating agent with water to form an alkali metal halide, a thiophenol derivative, and a sulfidizing agent. After separating the aqueous solution (b) containing the agent and the polyarylene sulfide resin, removing the polyarylene sulfide resin to obtain an aqueous solution (b) containing at least an alkali metal halide, a thiophenol derivative, and a sulfidating agent. It is.

The mixture (a) used in step (1) is particularly limited as long as it is a mixture containing at least a polyarylene sulfide resin, an alkali metal halide, a thiophenol derivative such as thiophenol or an alkali metal salt thereof, and a sulfidating agent. However, it is preferable to use a reaction mixture containing at least a polyarylene sulfide resin, an alkali metal halide, the thiophenol derivative, and a sulfidating agent obtained in the method for producing a polyarylene sulfide resin used in the present invention described later. It is preferable to use

The mixture (a) is contacted with water to remove the polyarylene sulfide resin from the mixture (a) to obtain an aqueous solution (b) containing at least an alkali metal halide, a thiophenol derivative, and a sulfidating agent. The method is not particularly limited as long as it does not impair the effects of the present invention, but after contacting with water (hereinafter sometimes referred to as "water washing"), the polyarylene sulfide resin is separated by filtration to form a solid-liquid. Examples of separation methods include:

As a method for solid-liquid separation by bringing the mixture (a) into contact with water and then filtering off the polyarylene sulfide resin, for example, an aprotic aprotic resin may be extracted from the crude reaction mixture obtained in the PAS manufacturing process described below. A method in which water is added to a reaction slurry obtained by solid-liquid separation of a polar solvent, the mixture is stirred, and then filtered using a filtration device. Examples include a method in which water is added to the slurry (abbreviated) again to form a slurry and then filtered, or a method in which water is added again to the slurry while the water-containing cake is held in a filter and filtered.

During the water washing, the amount of water added to the mixture (a) is preferably in the range of 2 to 10 times the theoretical yield of the polyarylene sulfide finally obtained, from the viewpoint of washing efficiency, and the above-mentioned It is preferable to divide the amount of water into 2 to 10 times, preferably 2 to 4 times, for washing. The water washing is carried out under a nitrogen or air atmosphere, preferably at a water temperature of 20°C or higher, more preferably 50°C or higher, even more preferably 70°C or higher, preferably 300°C or lower, more preferably 100°C or lower, even more preferably 90°C. Perform within the following range. The water washing 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, thiophenol derivatives, and sulfidating agents may remain in the filtered polyarylene sulfide resin without being sufficiently washed, the filtered polyarylene sulfide resin may be heated at 100°C to 280°C. After contacting with water in a range of ), which is preferable from the viewpoint of reducing the COD load and suppressing the loss of sulfur atoms (reducing the raw material consumption rate).

The temperature of the hot water washing is preferably in the range of 100°C or higher, more preferably 120°C or higher, and preferably 280°C or lower, more preferably 275°C or lower, to reduce residual alkali metal halides and sulfides in the resin. This is preferable from the viewpoint of improving the extraction efficiency of the curing agent. More specifically, the extraction treatment is performed with hot water at 140 to 260°C under the condition that the pressure of the gas phase in the reactor is increased, preferably 0.2 to 4.6 MPa (gauge pressure, the same applies hereinafter). It is preferable to do this.

A specific method for carrying out such hot water washing includes a method in which the polyarylene sulfide resin filtered out after the water washing is washed with water under stirring in a pressure vessel under predetermined pressure and temperature conditions. The amount of water during hot water washing is 1.5 to 10 times the mass of polyarylene sulfide, from the viewpoint of improving the extraction efficiency of the alkali metal halides, thiophenol derivatives, and sulfidating agents. Preferably, this amount of hot water may be divided into two or more times for hot water washing. For example, when hot water washing is repeated twice, filtration is performed between the first and second hot water washings, and the alkali metal halides, thiophenol derivatives, and sulfidating agents extracted in the first hot water washing are removed. It is preferable to separate the polyarylene sulfide resin by filtration. Alternatively, filtration may be performed after washing with hot water once, and the above-described washing with water may be performed. This operation can also facilitate the separation and removal of the alkali metal halide, thiophenol derivative, and sulfidating agent from the polyarylene sulfide resin. Furthermore, the conditions for the first hot water washing step and the second hot water washing step can be arbitrarily selected from the above conditions, but the temperature for the first hot water washing step is, for example, within the range of 120°C to 200°C. After setting and first filtering and removing the highly alkaline filtrate, the temperature of the second hot water washing step is set to a temperature higher than the temperature of the first hot water washing step, for example, a temperature in the range of 150 ° C. to 275 ° C. It is preferable to carry out the hot water washing from the viewpoint of chemical resistance of the equipment used in the hot water washing.

In addition, in step (1), the pH can be adjusted by adding an acid or a base to the aqueous solution (b), and in particular, the pH after washing with hot water is in the range of 11.0 or more and less than 13.0. It is preferable to control. Examples of acids used in this case include hydrochloric acid, sulfuric acid, carbonic acid, acetic acid, and oxalic acid. 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, or sodium carbonate, ammonium carbonate, and sodium phosphate, and among these, sodium hydroxide is preferred.

In step (1), it is possible to use a washing tank with an agitator and a centrifugal separator for solid-liquid separation, but it is also possible to use a washing tank with an agitator and a centrifugal separator for solid-liquid separation. It can also be carried out in a container with a built-in mixing function. In addition, even for hot water washing exceeding 100°C, it is possible to use a washing tank with an agitator to carry out the hot water washing, and a centrifuge for subsequent filtration at 20 to 100°C. It is also possible to conduct the mixing in a closed type container having wings and a filtration filter disposed at the bottom or a container having a mixing function that can be closed. In the present invention, water washing or hot water washing may be carried out continuously or batchwise.

Examples of the acid used in step (2) include hydrochloric acid, sulfuric acid, carbonic acid, and acetic acid, and among these, hydrochloric acid is preferred. The pH range of the aqueous solution (b) is not particularly limited as long as hydrogen sulfide is produced by adding an acid, but it is preferable to produce more hydrogen sulfide while at the same time suppressing the production of thiophenol. Since the conditions are such that the alkali metal salts are easily produced, the range is 8.0 or less, preferably 1.5 or more, more preferably 2.5 or more, and even more preferably 4.5. The above range is particularly preferably 5.0 or more, preferably 6.5 or less, more preferably 6.0 or less. Further, the addition of the acid is preferably carried out at a temperature of 0°C or higher, more preferably 10°C or higher, preferably 60°C or lower, more preferably 40°C or lower, and the pressure is also in the range of 0 to 1.0 Pa. It is preferable.

Step (3) is a step of recovering the hydrogen sulfide generated in step (2), since it has been evaporated and separated from the aqueous solution (b). At that time, it is first passed through a thiophenol recovery trap tank (hereinafter also simply referred to as "trap tank") containing an aqueous solution (c) containing an alkali metal hydroxide or an alkaline earth metal hydroxide. The proportion of hydrogen sulfide recovered in the step (3) is preferably in the range of 5 moles or more, more preferably in the range of 5 moles or more, based on 100 moles of the sulfidating agent contained in the aqueous solution (b) in the step (2). The range is 20 moles or more, more preferably 50 moles or more, and the upper limit is not particularly limited, but it is preferably 100 moles or less, more preferably 90 moles or less, and even more preferably 80 moles or less. It is in the molar or less range. Moreover, in the step (3), thiophenol may also be recovered. The ratio of the thiophenol derivative recovered in the step (3) is preferably within a range of 70 mol or less, more preferably, with respect to 100 mol of the thiophenol derivative contained in the aqueous solution (b) in the step (2). is in the range of 60 mol or less, more preferably in the range of 50 mol or less, furthermore, although the lower limit is not particularly limited, it is preferably in the range of 0 mol or more, more preferably in the range of 10 mol or more, and even more preferably in the range of 10 mol or more. The range is 20 moles or more. If it is within this range, polymerization inhibition can be suppressed when reusing it as a polymerization raw material for polyarylene sulfide resin, which is preferable.

Furthermore, step (4) is a step of reacting the recovered hydrogen sulfide with an alkali metal hydroxide. Step (3) and step (4) can be performed consecutively, or step (3) and step (4) can be performed separately.

When performing step (3) and step (4) continuously, for example, the volatilized hydrogen sulfide (and the thiophenol if thiophenol is recovered) is removed from the reaction system of step (2). Discharging through a pipe, then guiding the pipe into the aqueous solution (c) contained in a trap tank to cause bubbling, and further positioning the solution above the liquid level of the aqueous solution (c) in the trap tank, The aqueous solution (c) is discharged through piping from an outlet located at a sufficient distance from the liquid surface to the extent that it does not flow out, and introduced into the aqueous solution (d) containing an alkali metal hydroxide by bubbling or the like. ) and at the same time react hydrogen sulfide with an alkali metal hydroxide to produce a sulfidating agent. The trap tank is equipped with a gas inlet pipe and a gas discharge pipe, and the end of the gas inlet pipe (inlet) is introduced below the level of the liquid contained in the tank to enable bubbling. If the structure is such that the bubbled hydrogen sulfide is discharged from the end of the gas exhaust pipe (exhaust port) at the upper part of the tank at a sufficient distance from the liquid surface, it is a known type. can be used.

Examples of the alkali metal hydroxide used in the aqueous solution (c) include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide, strontium hydroxide, barium hydroxide, and the like. Although the amount of alkali metal hydroxide or alkaline earth metal hydroxide used in the aqueous solution (c) cannot be unconditionally determined as it varies depending on temperature and pressure, the volatilized hydrogen sulfide should be absorbed and reacted as much as possible. It is desirable that the amount is such that the unavoidably contained thiophenol can be absorbed or reacted to an alkali metal salt or an alkaline earth metal salt. Generally, at room temperature and normal pressure, per mole of sulfur atoms of hydrogen sulfide volatilized, preferably 0.01 mol or more, more preferably 0.1 mol or more, preferably 0.9 mol or less, More preferably, it is in the range of 0.7 mol or less. The concentration of the alkali metal hydroxide or alkaline earth metal hydroxide in the aqueous solution (c) should be such that it does not absorb or react with hydrogen sulfide as much as possible, and that it can absorb and react with the thiophenol that is inevitably included. Although not limited, the amount of the alkali metal hydroxide or alkaline earth metal is preferably 0.01 wt% or more, more preferably 0.1 wt% or more, preferably 30 wt% or less, more preferably 15 wt% or less. The amount of hydroxide used may be adjusted as appropriate to fall within the range. be. Although the temperature at that time cannot be defined unconditionally as it varies depending on the pressure, it is preferably in the range of 0°C or higher, more preferably 10°C or higher, preferably 200°C or lower, more preferably 150°C or lower. be. Further, the pressure at that time varies depending on the temperature and therefore cannot be defined unconditionally, but is preferably in the range of 0 Pa or more, preferably 1.0 Pa or less, and more preferably 0.5 Pa.

Examples of the alkali metal hydroxide used in the aqueous solution (d) include the aforementioned lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Although the amount of alkali metal hydroxide to be used cannot be specified as it varies depending on the temperature and pressure when absorbing hydrogen sulfide, it must be at least the amount that can sufficiently absorb and react with the entire amount of volatilized hydrogen sulfide. is desirable. Generally, when hydrogen sulfide is absorbed and reacted at room temperature and pressure, it is preferably 1 mole or more, and within the range of 1 to 2 moles, per 1 mole of sulfur atoms in the volatilized hydrogen sulfide. More preferred. The concentration of alkali metal hydroxide in the aqueous solution also varies depending on the temperature and pressure when absorbing and reacting hydrogen sulfide, so it cannot be unconditionally defined, but it is preferably 5 wt% or more, more preferably 10 wt% or more, The amount of the alkali metal hydroxide used may be adjusted as appropriate so that the amount used is preferably 49 wt% or less, more preferably 45 wt% or less. 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 unconditionally specified, but it is preferably 0°C or higher, more preferably 10°C or higher. , preferably 200°C or lower, more preferably 150°C or lower. Further, the pressure at which hydrogen sulfide is absorbed and reacted with an aqueous solution containing an alkali metal hydroxide varies depending on the temperature and cannot be unconditionally defined, but is preferably 0 Pa or more, preferably 1.0 Pa or less, More preferably, the range is up to 0.5 Pa.

On the other hand, when performing step (3) and step (4) separately, for example, the volatilized hydrogen sulfide (and the thiophenol if thiophenol is recovered) is removed from the reaction system of step (2). It is known that hydrogen sulfide is absorbed through piping, then introduced through the piping into the aqueous solution (c) stored in a trap tank to cause bubbling, and further discharged from the trap tank through piping to absorb hydrogen sulfide. After carrying out the step of recovering the hydrogen sulfide by absorption in a solvent such as an organic amide solvent, the aqueous solution (d) is added to the recovered solvent containing hydrogen sulfide to cause the hydrogen sulfide and the alkali metal hydroxide to react, Examples include a method of performing a step of producing an alkali metal hydrosulfide. In this case, solvents known to absorb hydrogen sulfide include organic amide solvents. Further, as organic amide solvents, formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε- Amides such as caprolactam, hexamethylphosphoramide, N-dimethylpropylene urea, 1,3-dimethyl-2-imidazolidinonic acid, and urea can be mentioned, and among these, N-methyl-2-pyrrolidone, 2- Amides having an aliphatic cyclic structure such as pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropylene urea, and 1,3-dimethyl-2-imidazolidinonic acid are preferred; More preferred is N-methyl-2-pyrrolidone.

Although the amount of a solvent known to absorb hydrogen sulfide cannot be specified as it varies depending on the temperature and pressure at which hydrogen sulfide is absorbed, it is sufficient to absorb the entire amount of volatilized hydrogen sulfide. It is desirable that the amount is more than that. Generally, when hydrogen sulfide is absorbed at room temperature and pressure, it is preferable that the amount is in the range of 1 to 30 kg per mole of sulfur atoms in the volatilized hydrogen sulfide. Although the temperature and pressure at which hydrogen sulfide is absorbed into a solvent known to absorb hydrogen sulfide cannot be unconditionally defined, the absorption temperature is preferably in the range of 0 to 200°C, and is preferably in the range of 10 to 150°C. On the other hand, the pressure is preferably in the range of 0 Pa or more, preferably 1.0 Pa or less, more preferably 0.5 Pa or less. Thereafter, the aqueous solution (d) is added to the solvent containing the recovered hydrogen sulfide to cause the hydrogen sulfide and the alkali metal hydroxide to react to produce an alkali metal hydrosulfide. At this time, it is desirable that the amount of alkali metal hydroxide added is at least an amount that can sufficiently react the entire amount of hydrogen sulfide absorbed in the solvent. Generally, when hydrogen sulfide is absorbed at room temperature and pressure, it is preferably 1 mole or more, and may be in the range of 1 to 2 moles, per 1 mole of sulfur atoms in the hydrogen sulfide absorbed in the solvent. It is more preferable. The concentration of alkali metal hydroxide in the aqueous solution (d) added to the solvent also varies depending on the temperature and pressure at which hydrogen sulfide is absorbed, so it cannot be unconditionally defined, but it is preferably 5 wt% or more, more preferably The content ranges from 10 wt% or more to 49 wt% or less, more preferably 45 wt% or less. Further, the temperature at which the hydrogen sulfide absorbed in the solvent and the alkali metal hydroxide are reacted varies depending on the pressure, so it cannot be absolutely specified, but the temperature is preferably 0°C or higher, more preferably The temperature ranges from 10°C or higher, preferably 200°C or lower, more preferably 150°C or lower. Although the pressure cannot be absolutely defined, it is preferably in the range from 0 Pa or more to 1.0 Pa or less, more preferably 0.5 Pa or less.

In the present invention, in order to take advantage of the fact that thiophenol exhibits a higher acid dissociation constant than hydrogen sulfide (thiophenol is more likely to form an alkali metal salt or an alkaline earth metal salt than hydrogen sulfide), step (3) ), the concentration of the alkali metal hydroxide or alkaline earth metal hydroxide in the aqueous solution (c) is low, while the concentration of the alkali metal hydroxide in the aqueous solution (d) in step (4) is high. Compare the amount of alkali metal hydroxide or alkaline earth metal hydroxide used in the aqueous solution (c) with the amount of alkali metal hydroxide used in the aqueous solution (d) by a method such as setting , the former may be set to be low and the latter may be set to be high.
As a result, when thiophenol and hydrogen sulfide are discharged out of the reaction system in step (2), the aqueous solution (c) containing the alkali metal hydroxide can be used as a trap tank for thiophenol in step (3), and The aqueous solution (d) containing the metal hydroxide can be used as the reaction site in step (4), and a higher purity sulfidating agent containing less thiophenol can be obtained.

Step (4) may be carried out either continuously or batchwise. Since the absorption rate of hydrogen sulfide into aqueous solutions of alkali metal hydroxides or organic amide solvents is fast, general equipment such as a packed tower with a circulation pump can be used, and a liquid filling type or bubbling type can also be used. be. Alternatively, for example, after the mixture is transferred to a reaction tank equipped with stirring blades, a vessel, a drum, or the like, an aqueous solution (d) containing an alkali metal hydroxide may be added thereto for reaction.

As mentioned above, step (4) uses an amount of alkali metal hydroxide that is more than enough to absorb and react with the entire amount of recovered hydrogen sulfide, so excess alkali metal hydroxide remains unreacted in the system. It will remain. Therefore, after step (4), hydrogen sulfide is added to the unreacted alkali metal hydroxide measured in advance, and the unreacted alkali metal hydroxide is reacted with the hydrogen sulfide (5). It is preferable to have. The amount of hydrogen sulfide added is preferably in the range of 0.5 to 1 mole per mole of the 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 alkali metal sulfide produced through step (4) or step (5) depends on the amount of alkali metal hydroxide reacted with hydrogen sulfide, reaction time, temperature, and pressure. It is not possible to make a general rule because it varies depending on the factors such as alkali metal hydrosulfide and alkali metal sulfide. Since it is available, the ratio of alkali metal hydrosulfide and alkali metal sulfide may be any ratio within the range of 0/100 to 100/0 on a mass basis.

The mixture (a) containing at least a polyarylene sulfide resin, an alkali metal halide, a thiophenol derivative, and a sulfidating agent used in the present invention may be obtained by the following method for producing a polyarylene sulfide resin. can. In addition, the alkali metal hydrosulfide and/or alkali metal sulfide obtained through the above steps (1) to (4) or steps (1) to (5) can be used as a sulfidizing agent for the following polyarylenes. In the method for producing a sulfide resin, it can be used as at least a part of the polymerization raw material. At that time, it is possible to reduce or eliminate the thiophenol contained together with the alkali metal hydrosulfide and/or alkali metal sulfide, thereby suppressing polymerization inhibition of the polyarylene sulfide resin. Possible and preferable.

In the PAS polymerization step, that is, the method for producing the polyarylene sulfide resin used in the present invention, an aprotic polar solvent, a polyhaloaromatic compound, and a sulfidation agent are mixed, and the polyhaloaromatic compound is mixed in the aprotic polar solvent. A crude reaction mixture containing at least a polyarylene sulfide resin, a sulfidating agent remaining without polymerization, an alkali metal halide, and an aprotic polar solvent is obtained by polymerizing a group compound and a sulfidating agent. A reaction involving at least a polyarylene sulfide resin, a sulfidating agent remaining without polymerization, and an alkali metal halide obtained by solid-liquid separation of the aprotic polar solvent from the crude reaction mixture. A method that involves a PAS/solvent solid-liquid separation step to obtain a mixture can be mentioned. In this case, the crude reaction mixture or the reaction mixture contains the thiophenol derivative as a by-product.

Here, in the present invention, the polyhaloaromatic compound is, for example, a halogenated aromatic compound having two or more halogen atoms directly bonded to an aromatic ring, and specifically, p-dichlorobenzene, o -Dichlorobenzene, m-dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dibromobenzene, diiodobenzene, tribromobenzene, dibromnaphthalene, triiodobenzene, dichlorodiphenylbenzene, dibromodiphenylbenzene, dichlor Dihaloaromatic compounds such as benzophenone, dibrombenzophenone, dichlorodiphenyl ether, dibromodiphenyl ether, dichlordiphenyl sulfide, dibromodiphenylsulfide, dichlorbiphenyl, dibrombiphenyl, and mixtures thereof are mentioned, and these compounds can be blocked. May be copolymerized. Among these, preferred are dihalogenated benzenes, and particularly preferred are those containing 80 mol% or more of p-dichlorobenzene. Further, for the purpose of increasing the viscosity of the polyarylene sulfide resin by creating a branched structure, a polyhaloaromatic compound having three or more halogen substituents in one molecule may be used as a branching agent as desired. Examples of such polyhaloaromatic compounds include 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, and 1,4,6-trichloronaphthalene. Furthermore, polyhaloaromatic compounds having functional groups with active hydrogen such as amino groups, thiol groups, and hydroxyl groups can be mentioned, and specifically, 2,6-dichloroaniline, 2,5-dichloroaniline, etc. , 2,4-dichloroaniline, dihaloanilines such as 2,3-dichloroaniline; 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 Examples include compounds in which the amino group is replaced with a thiol group or a hydroxyl group in a mixture thereof. In addition, active hydrogen-containing polyhaloaromatic compounds in which the hydrogen atom bonded to the carbon atom forming the aromatic ring in these active hydrogen-containing polyhaloaromatic compounds are substituted with other inert groups, for example, hydrocarbon groups such as alkyl groups. Aromatic compounds can also be used.

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

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; dihalonitrodiphenyl sulfones such as 3,3'-dinitro-4,4'-dichlorodiphenylsulfone; 2,5-dichloro-3-nitropyridine, 2-chloro-3,5 - Mono- or dihalonitropyridines such as dinitropyridine; or various dihalonitronaphthalenes.

Further, in the present invention, examples of the sulfidating agent 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 aqueous mixtures or as anhydrides. Moreover, an alkali metal sulfide can also be derived by a reaction between an alkali metal hydrosulfide and an alkali metal hydroxide. Note that a small amount of alkali metal hydroxide may be added in order to react with alkali metal hydrosulfide and alkali metal thiosulfate, which are usually present in a small amount in the alkali metal sulfide.

Further, the alkali metal hydrosulfide includes lithium hydrosulfide, sodium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures thereof. Such alkali metal hydrosulfides can be used as hydrates or aqueous mixtures or as anhydrides.

Further, the alkali metal hydrosulfide is used together with an alkali metal hydroxide. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, etc. Each of these may be used alone, or two or more types may be used in combination. It may also be used as Among these, lithium hydroxide, sodium hydroxide, and potassium hydroxide are preferred because they are easily available, and sodium hydroxide is particularly preferred.

In addition, as mentioned above, the alkali metal hydrosulfide and/or alkali metal sulfide obtained through the steps (1) to (4) or steps (1) to (5) can also be used as a sulfidating agent in the polyester. It can be reused as a raw material in the polymerization reaction of arylene sulfide resin.

The method for producing the polyarylene sulfide resin used in the present invention can also use a water-containing sulfidating agent as a raw material, in which case, at least in the presence of an aprotic polar solvent, the water-containing sulfidating agent is dehydrated, It is preferable to subject it to a polymerization reaction of polyarylene sulfide resin. In addition, when the amount of the aprotic polar solvent charged is small, for example, when it is less than 1 mol per 1 mol of sulfur atoms of the sulfidating agent, in the presence of the polyhaloaromatic compound, the water-containing sulfidating agent and the non-protic polar solvent are It is preferable 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 sulfidation agent are charged into a reaction vessel equipped with a distillation apparatus, and water is co-extracted. The temperature at which the material is removed by boiling, specifically, from a range of 300°C or lower, preferably 220°C or lower, more preferably 200°C or lower, to a range of preferably 80°C or higher, more preferably 100°C or higher. This is done by discharging water from the system by distillation. In the dehydration step, the amount of water in the system performing the polymerization reaction ranges from 5 mol or less, more preferably 2 mol or less, to preferably 0.01 mol or more per 1 mol of sulfur atoms of the sulfidating agent. It is preferable to dehydrate until it becomes dry.

Further, in the dehydration step, alkali metal sulfides and alkali metal hydrosulfides react with water to generate hydrogen sulfide as a gas in an equilibrium manner. For this reason, it is preferable to collect 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 generated hydrogen sulfide is discharged from the reaction system together with water or the azeotrope, and after separating water or the azeotrope and hydrogen sulfide using a distillation apparatus, the same method as in step (3) is carried out. Preferably, the recovered hydrogen sulfide is reacted with an alkali metal hydroxide in the same manner as in step (4) to produce an alkali metal hydrosulfide and/or an alkali metal sulfide. It is preferable to do so. Further, after the step of producing an alkali metal hydrosulfide and/or an alkali metal sulfide by reacting the hydrogen sulfide recovered in the dehydration step with an alkali metal hydroxide, in the same manner as step (5), It is preferable to include a step of adding hydrogen sulfide to unreacted alkali metal hydroxide and causing the unreacted alkali metal hydroxide to react with the hydrogen sulfide. It is preferable that the alkali metal hydrosulfide and/or alkali metal sulfide obtained in the dehydration step are also used as part of the raw materials in the method for producing a polyarylene sulfide resin as a sulfidizing agent.

In the present invention, examples of the aprotic polar solvent include formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε - Amides, ureas and lactams such as caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropylene urea and 1,3-dimethyl-2-imidazolidinonic acid; sulfolanes such as sulfolane and dimethylsulfolane; benzo Examples include nitriles such as nitrile; ketones such as methylphenylketone; and mixtures thereof; among these, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, Amides having an aliphatic cyclic structure such as hexamethylphosphoramide, N-dimethylpropylene urea, and 1,3-dimethyl-2-imidazolidinonic acid are preferred, and N-methyl-2-pyrrolidone is more preferred.

The polymerization reaction of the polyarylene sulfide resin in the PAS polymerization step involves reacting the alkali metal sulfide as a sulfidating agent with a polyhaloaromatic compound in the presence of these aprotic polar solvents. Alternatively, in the polymerization reaction of the polyarylene sulfide resin, the alkali metal hydrosulfide and alkali metal hydroxide as a sulfidizing agent are reacted with a polyhaloaromatic compound in the presence of these aprotic polar solvents. Polymerization conditions generally range from 200 to 330° C. and pressure should be such as to maintain the polymerization solvent and monomer polyhaloaromatic substantially in the liquid phase, generally 0. It is selected from the range of 1 MPa or more, preferably 20 MPa or less, more preferably 2 MPa or less. The amount of the polyhaloaromatic compound to be charged is from 0.2 mol or more, preferably 0.8 mol or more, more preferably 0.9 mol or more to 5.0 mol, per 1 mol of sulfur atoms of the sulfidating agent. Hereinafter, the amount is preferably adjusted to 1.3 mol or less, more preferably 1.1 mol or less. Further, the amount of the aprotic polar solvent to be charged is from 1.0 mol or more, preferably 2.5 mol or more, to 6.0 mol or less, preferably 4.5 mol or more, per 1 mol of sulfur atom of the sulfidating agent. Adjust so that it is within the range of mol or less. Note that the polymerization reaction is preferably carried out in the presence of a small amount of water, and the ratio is preferably adjusted as appropriate in consideration of the polymerization method, the molecular weight of the resulting polymer, and productivity. Specifically, dehydration is performed so that the amount is 2.0 mol or less, preferably 1.6 mol or less, per 1 mol of sulfur atoms of the sulfidating agent, and further dehydration is performed in the presence of a polyhaloaromatic compound. When performing the operation (for example, the method "5)" in the following specific embodiment), from 0.9 mol or less, preferably 0.3 mol or less, more preferably 0.02 mol or less, preferably 0.05 mol or less. The dehydration operation may be performed so that the amount is at least mol, more preferably at least 0.01 mol.

Specific embodiments of polymerizing the sulfidating agent and the polyhaloaromatic compound in the presence of the aprotic polar solvent described above 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 carrying out a polymerization reaction in the presence of a small amount of water, and then adding water and further polymerizing;
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 refluxing it to a liquid phase;
5) In the presence of a polyhaloaromatic compound, an alkali metal sulfide, or a hydrous alkali metal hydrosulfide and an alkali metal hydroxide, and an amide, urea, or lactam having an aliphatic cyclic structure are reacted while being dehydrated. After producing the slurry, a polar organic solvent such as NMP is further added and water is distilled off to perform dehydration. In the resulting slurry, a polyhaloaromatic compound, an alkali metal hydrosulfide, and an alkali metal salt of the hydrolyzate of an amide, urea, or lactam having an aliphatic cyclic structure are mixed in 1 mol of a polar organic solvent such as NMP. On the other hand, there is a method for producing a polyarylene sulfide resin which has as an essential production step a step of performing polymerization by reacting at a water content of 0.02 mol or less existing in the reaction system.

Among these, when producing a polyarylene sulfide resin by the polymerization method of 1) to 5), especially 1) to 4), the aprotic polar solvent as a production raw material is, for example, N-methyl-2-pyrrolidone. , when the polyhaloaromatic compound is p-dichlorobenzene, the following general formula (1) is used as a side reaction product of the polymerization reaction.

（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、ポリアリーレンスルフィド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、前記水溶液（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、さらに工程（３）、（４）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。

A carboxyalkylamino group-containing compound represented by (wherein, X represents an alkali metal atom or a hydrogen atom) may be contained in the crude reaction mixture. The present invention does not particularly limit the production method of polyarylene sulfide resin as long as it is a known method, and depending on the production method, the carboxyalkylamino group-containing compound may not be produced, so it is not an essential component. . However, for example, if the carboxyalkylamino group-containing compound is produced by the polymerization methods 1) to 5), especially 1) to 4), the carboxyalkylamino group-containing compound is mixed with the crude reaction mixture and has an aprotic polarity. Through the PAS/solvent solid-liquid separation step of the solvent, it is contained in the reaction mixture, further through the step (1) of the present invention, contained in the aqueous solution (a), and further through the step (2) of the present invention. , is contained in the aqueous solution (b), and is further separated from hydrogen sulfide in steps (3) and (4). That is, it migrates in the same way 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 polyarylene sulfide resin obtained through the above PAS polymerization step, the alkali metal hydrosulfide and/or alkali metal sulfide remaining as an unreacted sulfidating agent, the alkali metal halide, and the thiophenol derivative. , and an aprotic polar solvent can be used as the mixture (a).

Next, the PAS/solvent solid-liquid separation step removes at least the polyarylene sulfide resin obtained through the PAS polymerization step, and the alkali metal hydrosulfide and/or alkali metal sulfide remaining as an unreacted sulfidizing agent. The crude reaction mixture containing an alkali metal halide and an aprotic polar solvent is then obtained by solid-liquid separation of the aprotic polar solvent from the crude reaction mixture to obtain at least a polyarylene sulfide resin and an alkali metal halogen. This is a step of obtaining a reaction mixture containing a compound, a thiophenol derivative, and an alkali metal hydrosulfide and/or an alkali metal sulfide. The obtained 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 polyarylene sulfide resin by gradually cooling the polymerization reaction product. Generally, after cooling the reaction slurry in a reaction vessel, the polyarylene sulfide resin is crystallized. A method of solid-liquid separation after solid-liquid separation is mentioned. Solid-liquid separation in the quench method is performed by separating using filtration or a centrifugal separator such as a screw decanter, then adding water directly to the resulting filtration residue to form a slurry, and then repeating solid-liquid separation, or by repeatedly performing solid-liquid separation. For example, the remaining solvent may be removed by heating the filtration residue under a non-oxidizing atmosphere. The flash method is preferable because solid matter can be recovered relatively easily, and the quench method is preferable because it allows easy control of the particle size of the polyarylene sulfide resin and the addition of alkali metal halides and sulfidating agents to the polymer particles during crystallization. This is preferable in that it is difficult to incorporate impurities such as, and a highly pure polymer can be obtained.

Subsequently, the reaction mixture is separated into the polyarylene sulfide resin and an aqueous solution containing at least an alkali metal halide and a sulfidating agent through the water washing or hot water washing purification process of the present invention. The purification step can be performed in the same manner as step (1), and when producing a polyarylene sulfide resin, the filtered polyarylene sulfide resin may be recovered.

The filtered polyarylene sulfide resin is collected and then dried as it is and used as a polyarylene sulfide resin powder, or after further washing treatment, solid-liquid separation and drying are performed to form powder or granules. It can also be prepared as a polyarylene sulfide resin.

As mentioned above, the polyarylene sulfide resin polymerized by reusing the sulfidating agent obtained through steps (1) to (4) of the present invention as at least a part of the raw material may impair the effects of the present invention. Additives such as a mold release agent, a coloring agent, a heat stabilizer, an ultraviolet stabilizer, a foaming agent, a rust preventive agent, a flame retardant, a lubricant, a coupling agent, a filler, etc. can be contained within a certain range. Furthermore, the following synthetic resins and elastomers may 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, Examples of the elastomer include polydifluoroethylene, polystyrene, ABS resin, epoxy resin, silicone resin, phenol resin, urethane resin, and liquid crystal polymer. Examples of the elastomer include polyolefin rubber, fluorine rubber, and silicone rubber.

Furthermore, the polyarylene sulfide resin polymerized by reusing the sulfidating agent obtained through steps (1) to (4) as at least a part of the raw material can be used for injection molding, extrusion molding, compression molding, and blow molding. By various melt processing methods such as the above, it is possible to produce molded products having excellent heat resistance, moldability, dimensional stability, etc., and particularly excellent adhesion to epoxy resins. For this reason, for example, electrical and electronic parts such as connectors, printed circuit boards, and molded seals, automobile parts such as lamp reflectors and various electrical components, interior materials for various buildings, aircraft, and automobiles, and OA equipment parts and It can be widely used as injection molded and compression molded products such as precision parts such as camera parts and watch parts, as well as extrusion molded and pultruded molded products such as fibers, films, sheets, and pipes.

According to the present invention, by separating and recovering alkali metal hydrosulfide remaining as an unreacted sulfidating agent in a reusable state from wastewater obtained after washing with water or hot water in the manufacturing process of polyarylene sulfide resin, It is possible to reduce the COD value of wastewater, reduce the environmental load by reducing industrial waste, suppress the loss of sulfur atoms (reduce the raw material consumption rate), and improve the productivity of polyarylene sulfide resin. Furthermore, when the recovered unreacted sulfidating agent is reused as a polymerization raw material for polyarylene sulfide resin, a polyarylene sulfide resin having a higher molecular weight can be produced.

The present invention will be specifically described below with reference to Examples. These examples are illustrative and not limiting.

(Measurement method 1 Melt viscosity measurement method)
Polyphenylene sulfide resin was tested using a Shimadzu flow tester, CFT-500D, at 300°C, load: 1.96 x 10 ⁶ Pa, L/D = 10 (mm)/1 (mm), after being held for 6 minutes. It was measured.

(Measurement method 2: Measuring method for scattered hydrogen sulfide (splattered S) and sulfur in unreacted sulfidating agent)
0.5 g of the sample was accurately weighed in a beaker, and then 70 ml of pure water and 4 ml of 1 wt % sodium hydroxide aqueous solution were added, and titrated with 0.02 mol/L silver nitrate aqueous solution using a potentiometric automatic titrator while stirring.

(Measurement method 3: Measuring method of first neutralization point (soda sulfide + soda carbonate))
10 g of the sample was accurately weighed in a beaker, then 70 ml of pure water was added, and titrated with 0.1 mol/L hydrochloric acid using an automatic potentiometric titrator while stirring.

(Measurement method 4: Method for measuring pH in wastewater)
"Personal pH Meter PH72" manufactured by Yokogawa Electric Corporation was used. After pH calibration using pH4 and pH7 standard solutions, the attached electrode "PH72" was immersed in wastewater to measure the pH.

(Measurement method 5 Measuring method of sodium hydrogen sulfide concentration and sodium sulfide concentration in recovered liquid)
Precisely weigh 90 g of a 110-fold diluted aqueous solution of the sample, perform neutralization titration with 0.5 mol/L hydrochloric acid using a potentiometric automatic titrator while stirring, and calculate the sodium sulfide concentration from the titration at the first equivalent point. Then, the sodium hydrogen sulfide concentration was calculated from the difference between the titration amount at the second equivalence point and the titration amount at the first equivalence point. The recovery rate (%) of sodium bisulfide and/or sodium sulfide (sulfidating agent) is (mole part of hydrogen sulfide scattered during dehydration and molar part of sulfidating agent transferred to the sodium bisulfide recovery liquid) ÷ (wastewater It was calculated as (molar parts of the sulfidating agent in) x 100.

(Measurement method 6 Measuring method of thiophenol concentration)
Accurately weigh 0.5 g of the sample and 2.5 g of methyl isobutyl ketone into a vial with a lid, and then slowly dropwise add 1.5 g of 5M hydrochloric acid under an ice bath. Add 0.1 g of monochlorobenzene and 8 g of acetone into the same vial, cover with a lid, and stir the contents thoroughly. The thiophenol concentration of the supernatant liquid of the obtained slurry was measured using a gas chromatograph manufactured by Shimadzu Corporation. The recovery rate (%) of thiophenol was calculated as (molar parts of thiophenol transferred to the sodium hydrogen sulfide recovery liquid)/(molar parts of thiophenol derivatives in wastewater)×100.

Example 1
<Example (1-1)> PPS polymerization and wastewater production A condenser, a pressure gauge, a thermometer, a decanter, and a rectification column were connected to a gas absorption bottle containing 2.90 kg of a 15 wt% aqueous sodium hydroxide solution in advance. In an autoclave equipped with stirring blades, 33.20 kg (226 mol) of p-dichlorobenzene (hereinafter abbreviated as p-DCB), 2.28 kg (23.00 mol) of NMP, and 27.30 kg of a 47.23% by mass NaSH aqueous solution (230 sulfur atoms) were placed in an autoclave equipped with a stirring blade. 18.34 kg (228 mol) of a 49.21% by mass NaOH aqueous solution were charged, and heated to 173°C under a nitrogen atmosphere for 5 hours with stirring. The temperature was raised to distill out 27.21 kg of water. Hydrogen sulfide scattered during dehydration was absorbed into a sodium hydroxide aqueous solution using a gas absorption bottle to obtain a sodium hydroxide aqueous solution (1) that had absorbed hydrogen sulfide. The aqueous sodium hydroxide solution (A) that had absorbed hydrogen sulfide was subjected to silver nitrate titration (measurement method 2). The results are shown in Table 1.

Thereafter, the pot was sealed, and DCB distilled azeotropically during dehydration was separated in a decanter and returned to the pot as needed. After the dehydration was completed, fine particulate anhydrous sodium sulfide composition was dispersed in the DCB inside the pot. After the dehydration step was completed, the internal temperature was cooled to 160°C, 47.49 kg (479 mol) of NMP was charged, and the temperature was raised to 185°C. When the pressure reached 0.00 MPa, the valve connected to the rectification column was opened, and the internal temperature was raised to 200° C. over 1 hour. At this time, cooling and valve opening were controlled so that the temperature at the outlet of the rectifying column was 110° C. or less. The distilled mixed vapor of DCB and water was condensed in a condenser, separated in a decanter, and the DCB was returned to the pot. The amount of distilled water was 414 g. The internal temperature was raised from 200°C to 230°C over 3 hours, stirred for 2 hours, then raised to 250°C, and stirred for 1 hour. The final pressure was 0.48 MPa.

After the slurry obtained after the reaction was cooled to room temperature, it was dried using a vacuum dryer at 150° C. under reduced pressure for 3 hours to distill off N-methyl-2-pyrrolidone. Next, 142 kg of 70° C. hot water was added, stirred, and then filtered. Further, 81 kg of 70° C. hot water was added and filtered, and the filtrate was collected to obtain 209 kg of waste water (1). Wastewater (1) was titrated with silver nitrate (measurement method 2) to determine the amount (mol) of sulfidating agent (sodium sulfide and sodium hydrogen sulfide) from the concentration of sodium sulfide and sodium hydrogen sulfide, and the amount (mol) of thiophenol from the concentration of thiophenol. ) was sought. The results are shown in Table 1.

<Example (1-2)> Method for producing sulfidating agent (preparation of sodium bisulfide recovery liquid)
The hydrogen sulfide obtained in Example (1-1) was absorbed into a closed container equipped with a stirrer, a pH meter, a gas inlet pipe, a gas discharge pipe, and a dropping funnel through the gas discharge pipe and a trap tank. A gas absorption bottle containing an aqueous sodium hydroxide solution (1) was connected. The trap tank was charged with 2.00 kg of a 2.30 wt % aqueous sodium hydroxide solution (0.1 mol per mol of sulfur in wastewater (1)).
209 kg of waste water (1) was placed in the airtight container, and then stirred while introducing _N2 gas (50 ml/min). Hydrochloric acid equivalent to 1.20 mol was added dropwise to adjust the pH (measurement method 4) to 3.3. Stirring was performed for 60 minutes to generate hydrogen sulfide gas, which was absorbed into an aqueous sodium hydroxide solution (1) in a glass absorption bottle via a trap tank to obtain a sodium hydrogen sulfide recovery liquid (1). The obtained sodium bisulfide recovery liquid (1) was measured to determine the amount (mol) of the sulfidating agent from the sodium bisulfide concentration and the sodium sulfide concentration (Measurement Methods 5 and 6). The results are shown in Table 2.

<Example (1-3)> PPS production using the sulfidating agent obtained in Example (1-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, 172.70 g (1.46 mol) of a 47.23% by mass NaSH aqueous solution, and an autoclave with stirring blades connected to a rectification column. 14.58 g (4.50 x 10 ^-2 mol) of the obtained sodium bisulfide recovery solution (1), the proportion of recovered sodium bisulfide used in relation to the total mole of sodium bisulfide charged was 3.0 mol%, thiophenol 2.84 x 10 ^-4 mol per mol of NaSH) and 119.10 g (1.47 mol) of a 49.21% by mass NaOH aqueous solution were charged, and the temperature was raised to 173°C over 5 hours under a nitrogen atmosphere with stirring. It was heated and 186.20 g of water was distilled out.

Thereafter, the pot was sealed, and DCB distilled azeotropically during dehydration was separated in a decanter and returned to the pot as needed. After the dehydration was completed, fine particulate anhydrous sodium sulfide composition was dispersed in the DCB inside the pot. After the dehydration step was completed, the internal temperature was cooled to 160°C, 309.73 g (3.13 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. At this time, cooling and valve opening were controlled so that the temperature at the outlet of the rectifying column was 110° C. or less. The distilled mixed vapor of DCB and water was condensed in a condenser, separated in a decanter, and the DCB was returned to the pot. The amount of distilled water was 2.70 g. The internal temperature was raised from 200°C to 230°C over 3 hours, stirred for 2 hours, then raised to 250°C, and stirred for 1 hour. The final pressure was 0.48 MPa.

After the slurry obtained after the reaction was cooled to room temperature, it was dried using a vacuum dryer at 150° C. under reduced pressure for 3 hours to distill off N-methyl-2-pyrrolidone. Next, 920g of 70°C warm water was added and stirred, then filtered, and 1200g of 70°C warm water was added, stirred for 10 minutes, filtered, and 1200g of 70°C ion-exchanged water was added to the filtered cake to wash the cake. . The obtained water-containing cake and 460 g of ion-exchanged water were placed in a 0.5 liter autoclave and stirred at 150° C. for 30 minutes. After cooling to room temperature, it was filtered, and 1200 g of 70° C. ion-exchanged water was added to the filtered cake to wash the cake. The obtained water-containing cake and 460 g of ion-exchanged water were placed in a 0.5 liter autoclave and stirred at 220° C. for 30 minutes. After the slurry was cooled to room temperature, it was filtered, and 70° C. ion exchange water (1200 g) was added to the filtered cake to wash the cake. Thereafter, it was dried at 120° C. for 4 hours to obtain a PPS resin with a melt viscosity of 57 Pa·s (measurement method 1). The results are summarized in Table 3.

Example 2
<Example (2-1)> PPS polymerization and wastewater production Example (1) except that the amount of 15 wt% sodium hydroxide aqueous solution charged in advance in the gas absorption bottle was changed from 2.90 kg to 2.50 kg. -1) The same operation was performed. The aqueous sodium hydroxide solution that has absorbed hydrogen sulfide obtained in Example (2-1) is referred to as the aqueous sodium hydroxide solution that has absorbed hydrogen sulfide (2). Furthermore, the wastewater obtained in Example (2-1) is referred to as wastewater (2). The results are shown in Table 1.

<Example (2-2)> Method for producing sulfidating agent (preparation of sodium bisulfide recovery liquid)
Example except that the concentration of 2.00 kg of sodium hydroxide aqueous solution charged to the trap tank was changed from 2.30 wt% to 4.60 wt% (0.2 mol per 1 mol of sulfur in wastewater (2)). The same operation as (1-2) was performed. The obtained sodium bisulfide recovery liquid is referred to as a sodium bisulfide recovery liquid (2).
The sodium hydrogen sulfide recovery liquid (2) was measured (Measurement methods 5 and 6). The results are shown in Table 2.

<Example (2-3)> PPS production using the sulfidating agent obtained in Example (2-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, 172.70 g (1.46 mol) of a 47.23% by mass NaSH aqueous solution, and an autoclave with stirring blades connected to a rectification column. 14.58 g (4.50 × 10 ^-2 mol) of the obtained sodium hydrogen sulfide recovery solution (2), the proportion of recovered sodium hydrogen sulfide used with respect to the total mole of sodium hydrogen sulfide charged was 3.0 mol%, thiophenol The amount was 1.56 x 10 ^-4 mol per mol of NaSH) and 119.10 g (1.47 mol) of a 49.21% by mass NaOH aqueous solution, and the temperature was raised to 173°C over 5 hours under a nitrogen atmosphere with stirring. Upon heating, 186.22 g of water was distilled out.
From then on, the same operations as in Example (1-3) were performed. The melt viscosity of the obtained PPS resin was 68 Pa·s (Measurement method 1). The results are summarized in Table 3.

Example 3
<Example (3-1)> PPS polymerization and wastewater production -1) The same operation was performed. Note that the aqueous sodium hydroxide solution that has absorbed hydrogen sulfide obtained in Example (3-1) is referred to as an aqueous sodium hydroxide solution that has absorbed hydrogen sulfide (3). Furthermore, the wastewater obtained in Example (3-1) is referred to as wastewater (3). The results are shown in Table 1.

<Example (3-2)> Method for producing sulfidating agent (preparation of sodium hydrogen sulfide recovery liquid)
Example except that the concentration of 2.00 kg of sodium hydroxide aqueous solution charged to the trap tank was changed from 2.30 wt% to 17.24 wt% (0.75 mol per 1 mol of sulfur in wastewater (3)). The same operation as (1-2) was performed. The obtained sodium bisulfide recovery liquid is referred to as a sodium bisulfide recovery liquid (3).
The sodium hydrogen sulfide recovery liquid (3) was measured (Measurement methods 5 and 6). The results are shown in Table 2.

<Example (3-3)> PPS production using the sulfidating agent obtained in Example (3-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, 142.43 g (1.20 mol) of a 47.23% by mass NaSH aqueous solution, and an autoclave with stirring blades connected to a rectification column. 98.94 g (3.00 × 10 ^-1 mol) of the obtained sodium hydrogen sulfide recovered solution (3), the proportion of recovered sodium hydrogen sulfide used with respect to the total mole of sodium hydrogen sulfide charged was 20 mol%, and the amount of thiophenol was 2.76 x 10 ^-4 mol per mol of NaSH) and 119.10 g (1.47 mol) of a 49.21% by mass NaOH aqueous solution were charged, and the temperature was raised to 173°C over 5 hours under a nitrogen atmosphere while stirring. 237.28 g of water was distilled out.
From then on, the same operations as in Example (1-3) were performed. The melt viscosity of the obtained PPS resin was 58 Pa·s (Measurement method 1). The results are summarized in Table 3.

Example 4
<Example (4-1)> PPS polymerization and wastewater production Example (1) except that the amount of 15 wt % sodium hydroxide aqueous solution charged in advance in the gas absorption bottle was changed from 2.90 kg to 0.480 kg. -1) The same operation was performed. Note that the aqueous sodium hydroxide solution that has absorbed hydrogen sulfide obtained in Example (4-1) is referred to as an aqueous sodium hydroxide solution that has absorbed hydrogen sulfide (4). Furthermore, the wastewater obtained in Example (4-1) is referred to as wastewater (4). The results are shown in Table 1.

<Example (4-2)> Method for producing sulfidating agent (preparation of sodium bisulfide recovery liquid)
Example except that the concentration of 2.00 kg of sodium hydroxide aqueous solution charged to the trap tank was changed from 2.30 wt% to 19.54 wt% (0.85 mol per 1 mol of sulfur in wastewater (4)). The same operation as (1-2) was performed. The obtained sodium bisulfide recovery liquid is referred to as a sodium bisulfide recovery liquid (4).
The sodium hydrogen sulfide recovery liquid (4) was measured (Measurement methods 5 and 6). The results are shown in Table 2.

<Example (4-3)> PPS production using the sulfidating agent obtained in Example (4-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, and 498.41 g (1.4 mol) of the obtained sodium hydrogen sulfide recovery liquid (4) were placed in an autoclave equipped with stirring blades connected to a rectification column. 50 mol, the proportion of recovered sodium hydrogen sulfide used with respect to the charged mol of total sodium hydrogen sulfide is 100 mol%, the amount of thiophenol is 2.14 × 10 ^-4 mol per 1 mol of NaSH), and 49.21 mass % NaOH aqueous solution 119.10 g (1.47 mol) was charged, and the temperature was raised to 173° C. over 5 hours under a nitrogen atmosphere while stirring, and 479.39 g of water was distilled out. No 47.23% by mass NaSH aqueous solution was charged.
From then on, the same operations as in Example (1-3) were performed. The melt viscosity of the obtained PPS resin was 63 Pa·s (Measurement method 1). The results are summarized in Table 3.

Example 5
<Example (5-1)> PPS polymerization and wastewater production The same operations as in Example (2-1) were performed. Note that the aqueous sodium hydroxide solution that has absorbed hydrogen sulfide obtained in Example (5-1) is referred to as an aqueous sodium hydroxide solution that has absorbed hydrogen sulfide (5). Furthermore, the wastewater obtained in Example (5-1) is referred to as wastewater (5). The results are shown in Table 1.

<Example (5-2)> Method for producing sulfidating agent (preparation of sodium bisulfide recovery liquid)
Except that the pH (measurement method 4) was adjusted to 5.5 by dropping hydrochloric acid equivalent to 0.90 mol per 1 mol of first neutralization point (measurement method 3) + sulfur content in wastewater (5). , the same operation as in Example (1-2) was performed. The obtained sodium bisulfide recovery liquid is referred to as a sodium bisulfide recovery liquid (5).
The sodium hydrogen sulfide recovery liquid (5) was measured (Measurement methods 5 and 6). The results are shown in Table 2.

<Example (5-3)> PPS production using the sulfidating agent obtained in Example (5-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, 172.70 g (1.46 mol) of a 47.23% by mass NaSH aqueous solution, and an autoclave with stirring blades connected to a rectification column. 14.76 g (4.50 x 10 ^-2 mol) of the obtained sodium hydrogen sulfide recovery solution (5), the proportion of recovered sodium hydrogen sulfide used in relation to the total mole of sodium hydrogen sulfide charged was 3.0 mol%, thiophenol 1.84 x 10 ^-4 mol per mol of NaSH) and 119.10 g (1.47 mol) of a 49.21% by mass NaOH aqueous solution were charged and heated to 173°C over 5 hours under a nitrogen atmosphere with stirring. Upon heating, 186.34 g of water was distilled out.
From then on, the same operations as in Example (1-3) were performed. The melt viscosity of the obtained PPS resin was 65 Pa·s (Measurement method 1). The results are summarized in Table 3.

Example 6
<Example (6-1)> PPS polymerization and wastewater production Example (1) except that the amount of 15 wt% sodium hydroxide aqueous solution charged in advance in the gas absorption bottle was changed from 2.90 kg to 0.540 kg. -1) The same operation was performed. The aqueous sodium hydroxide solution that has absorbed hydrogen sulfide obtained in Example (6-1) is referred to as the aqueous sodium hydroxide solution that has absorbed hydrogen sulfide (6). Furthermore, the wastewater obtained in Example (6-1) is referred to as wastewater (6). The results are shown in Table 1.

<Example (6-2)> Method for producing sulfidating agent (preparation of sodium bisulfide recovery liquid)
Except that the pH (measurement method 4) was adjusted to 7.1 by dropping hydrochloric acid equivalent to 0.25 mole per 1 mole of first neutralization point (measurement method 3) + sulfur content in wastewater (6). , the same operation as in Example (1-2) was performed. The obtained sodium bisulfide recovery liquid is referred to as a sodium bisulfide recovery liquid (6).
The sodium hydrogen sulfide recovery liquid (6) was measured (Measurement methods 5 and 6). The results are shown in Table 2.

<Example (6-3)> PPS production using the sulfidating agent obtained in Example (6-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, and 491.42 g (1.4 mol) of the obtained sodium hydrogen sulfide recovery liquid (6) were placed in an autoclave equipped with stirring blades connected to a rectification column. 50 mol, the proportion of recovered sodium hydrogen sulfide used with respect to the charged mol of total sodium hydrogen sulfide is 100 mol%, the amount of thiophenol is 2.15 × 10 ^-4 mol per 1 mol of NaSH), and 49.21 mass % NaOH aqueous solution 119.10 g (1.47 mol) was charged, and the temperature was raised to 173° C. over 5 hours under a nitrogen atmosphere while stirring, and 474.60 g of water was distilled out. No 47.23% by mass NaSH aqueous solution was charged.
From then on, the same operations as in Example (1-3) were performed. The melt viscosity of the obtained PPS resin was 63 Pa·s (Measurement method 1). The results are summarized in Table 3.

Example 7
<Example (7-1)> PPS polymerization and wastewater production The same operations as in Example (2-1) were performed. The aqueous sodium hydroxide solution that has absorbed hydrogen sulfide obtained in Example (7-1) is referred to as the aqueous sodium hydroxide solution that has absorbed hydrogen sulfide (7). Furthermore, the wastewater obtained in Example (7-1) is referred to as wastewater (7). The results are shown in Table 1.

<Example (7-2)> Method for producing sulfidating agent (preparation of sodium bisulfide recovery liquid)
The 2.00 kg of liquid charged in the trap tank was changed from 2.30 wt% sodium hydroxide aqueous solution to 4.25 wt% calcium hydroxide aqueous solution (0.1 mol per 1 mol of sulfur content in wastewater (7)). Except for this, the same operation as in Example (1-2) was performed. The obtained sodium bisulfide recovery liquid is referred to as a sodium bisulfide recovery liquid (7).
The sodium hydrogen sulfide recovery liquid (7) was measured (Measurement methods 5 and 6). The results are shown in Table 2.

<Example (7-3)> PPS production using the sulfidating agent obtained in Example (7-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, 172.70 g (1.46 mol) of a 47.23% by mass NaSH aqueous solution, and an autoclave with stirring blades connected to a rectification column. 14.76 g (4.50 x 10 ^-2 mol) of the obtained sodium hydrogen sulfide recovery solution (7), the proportion of recovered sodium hydrogen sulfide used with respect to the total mole of sodium hydrogen sulfide charged was 3.0 mol%, thiophenol 1.40 x 10 ^-4 mol per mol of NaSH) and 119.10 g (1.47 mol) of a 49.21% by mass NaOH aqueous solution were charged, and the temperature was raised to 173°C over 5 hours under a nitrogen atmosphere with stirring. Upon heating, 186.35 g of water was distilled out.
From then on, the same operations as in Example (1-3) were performed. The melt viscosity of the obtained PPS resin was 69 Pa·s (Measurement method 1). The results are summarized in Table 3.

Comparative example 1
<Comparative Example (1-1)> PPS polymerization and wastewater production Example (1) except that the amount of 15 wt % sodium hydroxide aqueous solution charged in advance in the gas absorption bottle was changed from 2.90 kg to 3.20 kg. -1) The same operation was performed. Note that the aqueous sodium hydroxide solution that has absorbed hydrogen sulfide obtained in Comparative Example 1-1 is referred to as an aqueous sodium hydroxide solution that has absorbed hydrogen sulfide (C1). Furthermore, the wastewater obtained in Comparative Example (1-1) is referred to as wastewater (C1). The results are shown in Table 4.

<Comparative Example (1-2)> Method for producing sulfidating agent (preparation of sodium bisulfide recovery liquid)
The same operation as Example (1-1) except that the hydrogen sulfide gas generated from the wastewater (C1) after dropping hydrochloric acid was directly absorbed into the sodium hydroxide aqueous solution (C1) without going through a trap tank. I did it. The obtained sodium bisulfide recovery liquid is referred to as a sodium bisulfide recovery liquid (C1).
The obtained sodium hydrogen sulfide recovery liquid (C1) was measured (Measurement methods 5 and 6). The results are shown in Table 5.

<Comparative Example (1-3)> PPS production using the sulfidating agent obtained in Comparative Example (1-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, 172.70 g (1.46 mol) of a 47.23% by mass NaSH aqueous solution, and an autoclave with stirring blades connected to a rectification column. 14.45 g (4.50 x 10 ^-2 mol) of the obtained sodium bisulfide recovery solution (2), the proportion of recovered sodium bisulfide used in relation to the total mole of sodium bisulfide charged was 3.0 mol%, thiophenol 4.63 x 10 ^-4 mol per mol of NaSH) and 119.10 g (1.47 mol) of a 49.21% by mass NaOH aqueous solution were charged and heated to 173°C over 5 hours under a nitrogen atmosphere with stirring. It was heated and 186.08 g of water was distilled out.
From then on, the same operations as in Example (1-3) were performed. The melt viscosity of the obtained PPS resin was 43 Pa·s (Measurement method 1). The results are shown in Table 6.

Comparative example 2
<Comparative Example (2-1)> PPS polymerization and wastewater production The same operations as in Comparative Example (1-1) were performed. Note that the aqueous sodium hydroxide solution that has absorbed hydrogen sulfide obtained in Comparative Example (2-1) is referred to as an aqueous sodium hydroxide solution that has absorbed hydrogen sulfide (C2). Furthermore, the wastewater obtained in Comparative Example (2-1) is referred to as wastewater (C2). The results are shown in Table 4.

<Comparative Example (2-2)> Method for producing sulfidating agent (preparation of sodium bisulfide recovery liquid)
The same operation as in Example (1-2) was performed except that the 2.00 kg of liquid charged in the trap tank was changed from a 2.30 wt % sodium hydroxide aqueous solution to pure water. The obtained sodium bisulfide recovery liquid is referred to as a sodium bisulfide recovery liquid (C2).
The obtained sodium hydrogen sulfide recovery liquid (C2) was measured (Measurement methods 5 and 6). The results are shown in Table 5.

<Comparative Example (2-3)> PPS production using the sulfidating agent obtained in Comparative Example (2-2) A condenser connected to a gas absorption bottle containing an aqueous sodium hydroxide solution, a pressure gauge, a thermometer, a decanter, 216.53 g (1.47 mol) of p-DCB, 14.87 g (0.15 mol) of NMP, 172.70 g (1.46 mol) of a 47.23% by mass NaSH aqueous solution, and an autoclave with stirring blades connected to a rectification column. 14.72 g (4.50 x 10 ^-2 mol) of the obtained sodium bisulfide recovery solution (2), the proportion of recovered sodium bisulfide used in relation to the total mole of sodium bisulfide charged was 3.0 mol%, thiophenol 4.73 x 10 ^-4 mol per mol of NaSH) and 119.10 g (1.47 mol) of a 49.21% by mass NaOH aqueous solution were charged, and the temperature was raised to 173°C over 5 hours under a nitrogen atmosphere with stirring. Upon heating, 186.26 g of water was distilled out.
From then on, the same operations as in Example (1-3) were performed. The melt viscosity of the obtained PPS resin was 42 Pa·s (Measurement method 1). The results are summarized in Table 6.

※「←」印は左記に同様。

*The "←" mark is the same as the one on the left.

From the above results, in comparison with Comparative Examples 1 and 2, in Examples 1 to 5, thiophenol was reduced from the sulfidating agent used as a raw material for producing polyphenylene sulfide resin, and it remained unreacted. It has become clear that it can be recovered as a recovery liquid containing a large amount of sulfidating agent, and that even if it is reused as a raw material for PPS polymerization, a higher molecular weight PPS resin can be produced.

1 Trap tank 2 Gas introduction pipe 3 Gas discharge pipe 4 Liquid level 5 Gas absorption bottle 6 Liquid level 7 Gas introduction pipe 8 Gas discharge pipe 9 Stirrer 10 Joint

Claims (7)

After contacting the mixture (a) containing at least a polyarylene sulfide resin, an alkali metal halide, a thiophenol derivative, and a sulfidating agent with water, the polyarylene sulfide resin is separated and removed, and at least the alkali metal halide step (1) of obtaining an aqueous solution (b) containing a compound, a thiophenol derivative and a sulfidating agent;
A step (2) of producing hydrogen sulfide by adding an acid to at least an aqueous solution (b) containing an alkali metal halide, a thiophenol derivative, and a sulfidating agent to adjust the pH to a range of 8 or less;
a step (3) of recovering the generated hydrogen sulfide via a thiophenol recovery trap tank having an aqueous solution containing an alkali metal hydroxide or an alkaline earth metal hydroxide, and
a step (4) of reacting the recovered hydrogen sulfide with an alkali metal hydroxide;
has
The ratio of thiophenol recovered in the step (3) is in a range of less than 70 mol per 100 mol of the thiophenol derivative contained in the aqueous solution (b) in the step (2). A method for producing a sulfidating agent.
(However, the sulfidating agent refers to an alkali metal sulfide and/or an alkali metal hydrosulfide.) The mixture (a) containing at least a polyarylene sulfide resin, an alkali metal halide, and a sulfidating agent,
At least a polyarylene sulfide resin, an alkali metal halide, the aprotic polar solvent, a thiophenol derivative, and a sulfidation agent obtained after reacting a polyhaloaromatic compound with a sulfidation agent in an aprotic polar solvent. 2. The production method according to claim 1 , wherein the reaction mixture is a crude reaction mixture containing an agent, or a reaction mixture obtained by solid-liquid separation of the aprotic polar solvent from the crude reaction mixture. The sulfidating agent used when the polyhaloaromatic compound and the sulfidating agent are reacted in an aprotic polar solvent is used in a dehydration step of dehydrating the water-containing sulfidating agent at least in the presence of an aprotic polar solvent. The manufacturing method according to claim 2 , which is obtained through the following steps. After the step (4) of reacting the recovered hydrogen sulfide with the alkali metal hydroxide, hydrogen sulfide is added to the unreacted alkali metal hydroxide, and the hydrogen sulfide and the unreacted alkali metal hydroxide are combined. The manufacturing method according to claim 1, comprising a step (5) of reacting with a substance. A method for producing a sulfidating agent, comprising the step of recovering hydrogen sulfide produced in the dehydration step according to claim 3 , and then reacting it with an alkali metal hydroxide to obtain a sulfidating agent. After the step of reacting with the alkali metal hydroxide to obtain the sulfidating agent, hydrogen sulfide is added to the unreacted alkali metal hydroxide, and the unreacted alkali metal hydroxide is combined with the hydrogen sulfide. The method for producing a sulfidating agent according to claim 5 , comprising the step of reacting. A polyarylene sulfide resin, which is produced by producing a polyarylene sulfide resin by reacting a sulfidating agent obtained by dehydrating a water-containing sulfidating agent with a polyhaloaromatic compound in the presence of an organic amide solvent. In the production method, the sulfidation agent obtained by the production method according to any one of claims 1 to 4 and/or the sulfidation agent according to claim 5 or 6 is used as the hydrous sulfidation agent or at least a part of the sulfidation agent. A method for producing a polyarylene sulfide resin, comprising the step of adding a sulfidating agent obtained by the production method.

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