JPH10245434A - Production of polyarylene sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing the deterioration of the properties of a produced polyarylene sulfide(PAS) and improving the productivity of PAS, by increasing the filtration speed of a PAS slurry in a production of PAS, in which the PAS is recovered by filtering the PAS slurry after reaction. SOLUTION: In the production of polyarylene sulfide by reacting an alkali metal sulfide with a dihaloromatic compound in an organic amide solvent, an acid and/or a salt, which exhibits an acidic property in an aqueous solution is added to a polyarylene sulfide slurry after the reaction in an amount of 0.05-2.5mol% based on 1mol of the charged alkali metal sulfide and then the polyarylene sulfide slurry is filtered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polyarylene sulfide, and more particularly, to a method for recovering polyarylene sulfide from a reacted polyarylene sulfide slurry by filtration.

[0002]

2. Description of the Related Art Polyarylene sulfide (hereinafter, referred to as polyarylene sulfide)
PAS) is a production method, for example,
JP-B-45-3368 discloses a method of producing a PAS by reacting an alkali metal sulfide with a dihalo-aromatic compound in an organic amide solvent described in JP-B-45-3368.
No. 4,038,263, a method using a polymerization aid such as lithium halide described in US Pat. No. 4,038,263.
JP-A-88719, a method using a cross-linking agent such as a polyhalo aromatic compound, JP-B-63-33775, a method using a multi-step reaction in the presence of different amounts of water, and JP-A-5-222196. In the method for producing a PAS by reacting an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent described in JP-A No. Various methods are known, such as a method of condensing a part of a gaseous phase and refluxing it in a liquid phase. A common feature of these methods is that a slurry is formed after the reaction including the produced PAS and various by-products, unreacted substances, and a polar organic solvent, and from the slurry, a PAS as a final product is obtained. PA
S is to be recovered.

[0003] As a method for recovering PAS, a solvent flush method is generally employed. However, in this method, it is difficult to separate the PAS oligomer from the recovered powdery resin by filtration, and the oligomer remains in the resin and causes problems such as gas generation during molding.

Various proposals have been made to solve such a problem. For example, JP-A-60-235838 discloses that the solubility of an organic solvent is reduced by lowering the temperature of an organic solvent solution of PAS and / or by adding a precipitant, and dissolving at a temperature of 150 to 300 ° C. There is disclosed a method for obtaining a high molecular weight PAS in which a high molecular weight fraction of PAS is precipitated, and the fraction is recovered from the generated slurry. JP-A-59-1536 discloses a slurry containing particulate PAS by lowering the temperature of a mixture, which is higher than the temperature at which PAS forms a molten phase, from a reacted PAS slurry containing a phase separating agent. A method for recovering particulate PAS, characterized in that a particulate PAS is formed.

[0005] Further, a method of recovering PAS after filtering a PAS slurry after the reaction to remove a part of oligomers, a solvent and the like is known to those skilled in the art. In this method, filtration is an important step, and the amount of impurities such as oligomers and alkali metal halides (eg, NaCl) in the obtained PAS is determined by the quality of the filter. Poor filterability
The amount of impurities in the AS increases, resulting in problems such as generation of gas at the time of molding and deterioration of electrical characteristics and dimensional stability of the molded product. In addition, the time spent for filtration at the time of manufacturing becomes longer, which causes a decrease in productivity.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for preparing P after reaction.
In a PAS production method for filtering an AS slurry to recover a PAS, the filtration rate of the PAS slurry is increased to prevent deterioration of the properties of the obtained PAS and to reduce the PAS.
It is intended to provide a method for improving productivity.

[0007]

Means for Solving the Problems The present inventors have found that it is necessary to lower the viscosity of the PAS slurry in order to increase the filtration rate of the PAS slurry. Various studies were conducted to develop an effective means for lowering. As a result, P
The present inventors have found that the addition of a predetermined amount of acid and / or a salt exhibiting acidity in an aqueous solution to an AS slurry can unexpectedly lower the viscosity of the slurry and significantly increase the filtration rate, thereby completing the present invention. .

That is, the present invention relates to (1) a method for producing a polyarylene sulfide by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide-based solvent, wherein an acid is added to the polyarylene sulfide slurry after the reaction. And / or adding an acid salt in an aqueous solution in an amount of 0.05 to 2.5 mol% with respect to 1 mol of the charged alkali metal sulfide, and then filtering the slurry. It is a manufacturing method.

Normally, the PAS slurry after the reaction has a high basicity, and the molecular terminals of the PAS are in the form of -SNa or the like. Therefore, the affinity with the solvent is strong and the slurry viscosity is high. In the present invention, by adding an acid and / or a salt exhibiting acidity in an aqueous solution, the molecular terminal of such a PAS is converted into a -SH form, thereby lowering the affinity with a solvent, The viscosity of the PAS slurry can be reduced.

In a preferred embodiment, (2) the acid and / or a salt exhibiting acidity in an aqueous solution is added in an amount of 0.1 to 1.5 mol% based on 1 mol of the charged alkali metal sulfide. (3) The method according to the above (1) or (2), wherein the filterability of the slurry after adding an acid and / or a salt exhibiting acidity in an aqueous solution is 0.5 g / sec or more,
(4) The above (1) to (1), wherein the pH of the slurry after the addition of an acid and / or a salt exhibiting acidity in an aqueous solution is 7.0 or more.
The method described in any one of (3) can be mentioned.

Further, the present inventors have found that if the PAS slurry after the reaction is diluted with the solvent used in the polymerization reaction, the slurry viscosity can be remarkably reduced by adding a very small amount of the solvent, and the filtration speed is extremely high. Was also found to be achieved.

That is, the present invention relates to (5) a method for producing a polyarylene sulfide by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide-based solvent. After adding the solvent used in the reaction in such an amount that the concentration of the slurry after the reaction is reduced by up to 10% by weight,
A method for producing polyarylene sulfide, which comprises filtering the slurry.

In a preferred embodiment, (6) the solvent used in the polymerization reaction is mixed with a slurry having a concentration of 0.5 after the reaction.
The method according to the above (5), wherein the solvent used in the polymerization reaction is added in an amount such that the concentration is reduced by 0.5 to 5.0% by weight.
The method described in the above (5) in which the compound is added in such an amount as to be reduced can be used.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing PAS of the present invention, first, an acid and / or a salt exhibiting acidity in an aqueous solution is added to the PAS slurry after the reaction in an amount of 0.05 to 1 mol of the charged alkali metal sulfide. ~ 2.5 mol%, preferably 0.1
To 1.5 mol%, particularly preferably 0.1 to 1.2 mol%
Add in. When the amount is less than the lower limit, the effect of lowering the viscosity of the slurry by the addition is small, and even when the amount exceeds the upper limit, the lowering of the slurry viscosity is sufficiently achieved by the upper limit, and there is almost no effect on the addition. Therefore, it is not preferable.

The PAS slurry after the addition of the acid and / or the salt exhibiting acidity in the aqueous solution has a filterability of preferably 0.5 g / sec or more, particularly preferably 0.8 g / sec or more. is there. If it is less than the above lower limit, a long time is required for filtration, deterioration of properties of the obtained PAS cannot be sufficiently prevented, and PAS productivity cannot be improved. Here, the filterability means that 100 g of the PAS slurry after the reaction
The filtration time and the amount of the filtrate when suction filtration (filter paper used: No. 5C, retained particles 1 micron, diameter 40 mm, degree of reduced pressure: 500 mmHg) were measured, and calculated by the following formula.

[0016]

## EQU1 ## The filterability (gram / second) = filtrate amount (gram) / filtration time (second) Further, the pH of the PAS slurry after the addition of the acid and / or the salt exhibiting acidity in the aqueous solution is preferably used. Is 7.0
Above, more preferably 7.0 to 12.0, particularly preferably 7.5 to 11.5. Below the lower limit, PAS
Of the main chain of the polymer and the molecular weight of the PAS is undesirably reduced.

The acid used in the present invention is not particularly limited. For example, acetic acid, formic acid, oxalic acid, phthalic acid, hydrochloric acid, phosphoric acid, sulfuric acid, sulfurous acid, nitric acid, boric acid, carbonic acid and the like are used, and acetic acid is preferred. In addition, a salt exhibiting acidity in an aqueous solution can be used, and preferred examples include zinc chloride, calcium chloride, magnesium chloride, barium chloride, and sodium hydrogen sulfate.

As a method for adding an acid and / or an acid salt in an aqueous solution to the PAS slurry after the reaction, a known method can be used. For example, there is a method in which a predetermined amount of an acid and / or the above-mentioned salt is added to a slurry cooled after completion of the reaction, followed by stirring. Here, the temperature of the PAS slurry at the time of adding the acid and / or the salt is preferably room temperature to 200 ° C, particularly preferably 50 to 180 ° C.
It is. If the addition exceeds 200 ° C., a side reaction with a solvent or the like is liable to occur, and if it is lower than room temperature, the fluidity of the PAS slurry is extremely poor and mixing cannot be performed sufficiently. After the addition, in order to uniformly mix the PAS slurry and the acid and / or salt, it is preferable to continue stirring for preferably 10 minutes to 48 hours, particularly preferably 30 minutes to 36 hours.

In another embodiment of the present invention, the solvent (eg, N-methylpyrrolidone) used in the polymerization reaction described in detail below can be added to the PAS slurry after the reaction. The solvent has a concentration of the PAS slurry after the reaction of at most 10% by weight, preferably 0.5 to 7.
0% by weight, particularly preferably 0.5 to 5.0% by weight. PAS exceeding the above upper limit
The total amount of the slurry is remarkably increased, which not only increases the time required for filtration, but also lowers productivity due to an increase in the throughput of the filtrate. As a method for adding the solvent, a known method can be used. For example, a method in which a predetermined amount of a solvent is added to the slurry immediately after the reaction is completed, or a method in which the slurry is cooled after the reaction is completed, and the solvent is added and stirred.
The temperature of the PAS slurry at the time of adding the solvent is preferably from room temperature to 275 ° C, particularly preferably from 50 to 260 ° C. If the temperature exceeds 275 ° C., the PAS is liable to be decomposed. After the addition, in order to sufficiently mix the PAS slurry and the solvent, it is preferable to perform stirring for preferably 10 minutes to 48 hours, particularly preferably 30 minutes to 36 hours. When a solvent is added after the reaction is completed and before PAS is crystallized, water may be used in combination with the addition of water to improve the particle size of the PAS particles. The amount of water to be added is 0.01 to 1. 1 mol per mol of the charged alkali metal sulfide.
It is 5 mol%, preferably 0.1 to 1.0 mol%. The addition of the solvent as described above can be used in combination with the addition of the acid and / or salt.

The PAS slurry to which the acid and / or the salt is added or the PAS slurry to which the solvent is added is then filtered to separate the solvent-containing filter cake and the solvent. For the purpose of reducing oligomers, the solvent may be further filtered using the solvent used in the polymerization reaction.

Thereafter, the solvent-containing filter cake is washed according to a conventional method to remove by-product salts. Preferably, the filter cake is washed with water by dispersing it in water, and then the PAS is washed by repeating the filtration operation. For example, the filter cake is put into water, preferably 1 to 5 times by weight, and stirred and mixed at room temperature to 90 ° C., preferably for 5 minutes to 10 hours, and then filtered. The stirring and mixing and filtration operations are preferably repeated 2 to 10 times to remove the solvent and by-product salts attached to the PAS, thereby completing the water washing.

Preferably, the solvent-containing filter cake obtained is heated at a temperature of 150 to 250 ° C. in a non-oxidizing gas atmosphere to remove the solvent, and then the PAS is washed by water washing. Can also. For example, the filter cake is obtained in a stream of a non-oxidizing gas such as helium, argon, hydrogen or nitrogen, preferably in a stream of nitrogen gas having an oxygen concentration of less than 5.0% by volume, preferably at 150 to 250 ° C., particularly preferably at 180 ° C. At a temperature of ~ 230 ° C, preferably 0.5 ~ 2
Heating is carried out for 0 hour, particularly preferably 1 to 10 hours. The heating is preferably performed under reduced pressure to 3 atm, particularly preferably at normal pressure. When the heating temperature is lower than the above lower limit, it takes a long time to remove the solvent, and the productivity is reduced. Exceeding the upper limit is not preferable because the PAS is significantly colored. By performing the above-described solvent removal by heating, compared to a method of removing the solvent by water washing, steps such as water washing can be simplified, and the recovery rate of the solvent can be significantly improved. High cost is advantageous.

In the present invention, the PAS obtained as described above may be further subjected to an acid treatment. The acid treatment is carried out at a temperature of 100 ° C or lower, preferably at a temperature of 40 to 80 ° C. If the temperature exceeds the above upper limit, the PAS molecular weight after the acid treatment decreases, which is not preferable. On the other hand, when the temperature is lower than 40 ° C., the remaining inorganic salt precipitates out and lowers the fluidity of the slurry, which hinders the continuous treatment process, which is not preferable. The concentration of the acid solution used for the acid treatment is preferably 0.01 to 5.0% by weight. Further, the pH of the acid solution after the acid treatment is preferably 4.0 to 5.0. By adopting the above concentration and pH, most of the -SA (A represents an alkali metal) terminal in the PAS to be treated can be converted to the -SH terminal, and corrosion of plant equipment and the like can be achieved. This is preferable because it can prevent The time required for the acid treatment depends on the temperature of the acid treatment and the concentration of the acid solution.
Minutes or more, particularly preferably 10 minutes or more. If the amount is less than the above, -SA terminal in PAS cannot be sufficiently converted to -SH terminal, which is not preferable. In the acid treatment, for example, acetic acid,
Formic acid, oxalic acid, phthalic acid, hydrochloric acid, phosphoric acid, sulfuric acid, sulfurous acid, nitric acid, boric acid, carbonic acid and the like are used, and acetic acid is particularly preferred. By performing the treatment, an alkali metal such as sodium which is an impurity in the PAS can be reduced. Therefore, elution of alkali metal such as sodium during use of the product and deterioration of electrical insulation can be suppressed.

The method for producing PAS by reacting an alkali metal sulfide with a dihalo aromatic compound in an organic amide solvent is not particularly limited. For example, Japanese Patent Publication No. 45-336
8, a method using an alkali metal carboxylate described in JP-B No. 52-12240, a method using a polymerization aid such as lithium halide described in U.S. Pat. No. 3,038,263, Japanese Patent Publication No. 54-871
It can be produced by a method using a cross-linking agent such as a polyhalo aromatic compound described in JP-A-9, a method using a multi-step reaction in the presence of different amounts of water described in JP-B-63-33775, and the like.

Preferably, in the method described in JP-A-5-222196 for producing PAS by reacting an alkali metal sulfide with a dihalo aromatic compound in an organic amide-based solvent, a reaction vessel during the reaction is preferably used. By cooling the gaseous phase part of the reaction vessel, a part of the gaseous phase in the reaction vessel can be condensed, and this can be refluxed to a liquid phase. By using this method, P having a relatively high melt viscosity V ₆ can be obtained.
AS can be manufactured, and therefore, PAS having high mechanical strength such as tensile strength and impact strength can be obtained, which is preferable.

In this method, the refluxed liquid has a higher water content than the liquid phase bulk due to the vapor pressure difference between water and the amide solvent. The reflux liquid having a high water content forms a layer having a high water content at the upper portion of the reaction solution. As a result, a large amount of residual alkali metal sulfide (eg, Na ₂ S), alkali metal halide (eg, NaCl), oligomers, and the like are contained in the layer. In the conventional method, 2
At a high temperature of 30 ° C. or more, when the produced PAS is uniformly mixed with raw materials such as Na ₂ S and by-products, not only can a high molecular weight PAS not be obtained, but also a solution of the produced PAS can be obtained. Polymerization also occurs, and by-products of thiophenol are observed. However, in the present invention, the above disadvantageous phenomenon can be avoided by actively cooling the gas phase portion of the reaction vessel and returning a large amount of the water-rich reflux liquid to the upper part of the liquid phase so as to inhibit the reaction. It can be considered that such factors can be effectively eliminated and a high molecular weight PAS can be obtained. However, the present invention is not limited only by the effect of the above phenomenon, and a high molecular weight PAS can be obtained by various effects caused by cooling the gas phase portion.

In this method, it is not necessary to add water during the reaction as in the conventional method. However, this does not preclude the addition of water at all. However, if the operation of adding water is performed, some of the advantages of the present invention are lost. Therefore, preferably, the total water content in the polymerization reaction system is constant throughout the reaction.

The gas phase portion of the reactor can be cooled either externally or internally, and can be cooled by a cooling means known per se. For example, a method of flowing a cooling medium through an internal coil installed at an upper part in a reaction can, a method of flowing a cooling medium through an external coil or a jacket wrapped around the upper part of the reaction can, and using a reflux condenser installed at the upper part of the reaction can A method such as spraying water or blowing a gas (air, nitrogen, etc.) on the upper portion of the outside of the reaction vessel is conceivable, but any method can be used as long as it has the effect of increasing the amount of reflux in the vessel as a result. May be used. If the outside air temperature is relatively low (for example, normal temperature), appropriate cooling can be performed by removing a heat insulating material conventionally provided on the upper part of the reaction vessel. In the case of external cooling, water condensed on the reactor wall
The amide-based solvent mixture enters the upper layer of the liquid phase along the reaction vessel wall. Thus, the water-rich mixture accumulates at the top of the liquid phase, keeping the water content relatively high. In the case of internal cooling, the mixture condensed on the cooling surface likewise travels along the cooling device surface or the reactor wall and into the liquid phase.

On the other hand, the temperature of the liquid phase bulk is maintained at a predetermined constant temperature or controlled according to a predetermined temperature profile. 230-275 for constant temperature
It is preferred to carry out the reaction at a temperature of ° C for 0.1 to 20 hours. More preferably, the temperature is 240 to 265 ° C for 1 to 6 hours. In order to obtain a higher molecular weight PAS, it is preferable to use two or more reaction temperature profiles. This 2
When performing a step operation, the first step is preferably performed at a temperature of 195 to 240 ° C. If the temperature is low, the reaction rate is too low, which is not practical. If the temperature is higher than 240 ° C., the reaction rate is too high, so that not only a sufficiently high molecular weight PAS cannot be obtained, but also the side reaction rate is significantly increased. The end of the first phase,
The residual ratio of the dihalo aromatic compound in the polymerization reaction system is 1 mol% to 40 mol%.
It is preferable to carry out the reaction at a time point when the molar% is within the range of 3,000 to 20,000. More preferably, the residual ratio of the dihalo aromatic compound in the polymerization reaction system is in the range of 2 mol% to 15 mol%, and the molecular weight is in the range of 5,000 to 15,000. Residual rate is 40 mol%
If it exceeds 200, side reactions such as depolymerization are likely to occur in the second stage reaction, while if it is less than 1 mol%, high molecular weight P
It is hard to get AS. Thereafter, the temperature is raised, and the reaction in the final stage is preferably carried out at a reaction temperature of 240 to 270 ° C. for 1 to 10 hours. PAS with sufficiently high molecular weight at low temperature
When the temperature is higher than 270 ° C., side reactions such as depolymerization are liable to occur, making it difficult to stably obtain a high molecular weight product.

As an actual operation, first, under an inert gas atmosphere, dehydration or water addition is performed as necessary so that the water content of the polymerization system becomes a predetermined amount. The water content is preferably
0.5 to 1.39 mol per mol of alkali metal sulfide,
Particularly, it is 0.8 to 1.2 mol. If it exceeds 1.39 mol, the total amount of water added at the time of pH adjustment exceeds 1.4 mol per mol of alkali metal sulfide.
When the zinc compound is added, an operation such as flushing and adjusting the water in the system in advance occurs, which complicates the operation. 0.5
If the amount is less than the mole, the reaction rate is too high to obtain a product having a sufficient high molecular weight, and undesirable reactions such as side reactions occur.

In the case of a one-stage reaction at a constant temperature, the cooling of the gas phase during the reaction is preferably carried out from the start of the reaction, but it must be carried out at least in the course of raising the temperature to 250 ° C. or lower. In the multi-stage reaction, it is preferable to perform cooling from the first-stage reaction, but it is preferable to perform cooling at the latest after the completion of the first-stage reaction. The degree of the cooling effect is usually the most suitable index of the pressure in the reactor. The absolute value of the pressure varies depending on the characteristics of the reaction vessel, the stirring state, the amount of water in the system, the molar ratio of the dihalo aromatic compound to the alkali metal sulfide, and the like. However, when the pressure in the reaction vessel is reduced as compared with the case where the reaction vessel is not cooled under the same reaction conditions, the amount of the reflux liquid increases, which means that the temperature at the gas-liquid interface of the reaction solution decreases. It is considered that the relative degree of decrease indicates the degree of separation between a layer having a high water content and a layer having no water content. Therefore, it is preferable to perform cooling to such an extent that the internal pressure of the reaction vessel is lower than that in the case where no cooling is performed. The degree of cooling can be appropriately set by those skilled in the art according to the equipment used, operating conditions, and the like.

The organic amide solvents used in the process are known for PAS polymerization, for example N-methylpyrrolidone (NMP), N, N-dimethylformamide, N, N-dimethyl (or diethyl) acetamide , N-methyl (or ethyl) caprolactam, 1,3
-Dimethyl-2-imidazolidinone, formamide, acetamide, hexamethylphosphoramide, tetramethylurea, N, N'-ethylene-2-pyrrolidone, 2-
Pyrrolidone, ε-caprolactam, diphenylsulfone, and the like, and mixtures thereof can be used, with NMP being preferred. They all have a lower vapor pressure than water.

[0033] Alkali metal sulfides are also known, for example, lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide and mixtures thereof. These hydrates and aqueous solutions may be used. Hydrosulfides and hydrates corresponding to these can be used after being neutralized with the corresponding hydroxides.
Inexpensive sodium sulfide is preferred.

Dihaloaromatic compounds are described in, for example,
It can be selected from those described in JP-A-5-3368, but is preferably p-dichlorobenzene. Further, a copolymer can be obtained by using one or more kinds of para-, meta- or ortho-dihalides of diphenyl ether, diphenyl sulfone or biphenyl in a small amount (20 mol% or less). For example, o-dichlorobenzene, p, p'-dichlorodiphenyl ether, m, p'-dichlorodiphenyl ether, m, m'-dichlorodiphenyl ether, p, p '
-Dichlorodiphenylsulfone, m, p'-dichlorodiphenylsulfone, m, m'-dichlorodiphenylsulfone, p, p'-dichlorobiphenyl, m, p'-dichlorobiphenyl, m, m'-dichlorobiphenyl.

In order to further increase the molecular weight of PAS,
For example, 1,3,5-trichlorobenzene, 1,2,4-
The polyhalo compound such as trichlorobenzene can be used in an amount of preferably 0.005 to 1.5 mol%, particularly preferably 0.02 to 0.75 mol%, based on 1 mol of the alkali metal sulfide.

The PAS produced by the method of the present invention is
Oligomers or alkali metal halides (eg, NaC
It has a small amount of impurities such as 1) and is useful as a material for automobile equipment parts, electric / electronic equipment parts, chemical equipment parts and the like.

When the PAS of the present invention is processed, conventional additives such as powdered fillers such as carbon black, calcium carbonate, silica and titanium oxide, or carbon fibers, glass fibers, asbestos fibers and polyaramid fibers And other fibrous fillers.

Further, if necessary, additives such as an antioxidant, a heat stabilizer, a lubricant, a release agent, and a coloring agent can be added.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0040]

EXAMPLES Each characteristic value in the examples was measured as follows. <Melt viscosity V _6> Shimadzu flow tester CFT-
Using 500C, 300 ℃, load 20kgf / c
The viscosity (poise) measured after holding for 6 minutes at m ² and L / D = 10/1. <Filterability> No. 5C diameter 4
The measurement was performed using a 0 mm filter paper. <Slurry viscosity> The viscosity of the slurry after the reaction was measured using a B-type viscometer (model BM, manufactured by Tokyo Keiki Co., Ltd.). The measured value 4 minutes after the start of the measurement at 25 ° C. was defined as the slurry viscosity (centipoise). <Slurry pH> The pH of the slurry is measured with a pH meter F-
21 (trademark, manufactured by Horiba, Ltd.).

Synthesis Example 1 In a 150-liter autoclave, 19.381 kg of flaky sodium sulfide (60.4% by weight Na ₂ S) and N
45.0 kg of -methyl-2-pyrrolidone (hereinafter abbreviated as NMP) was charged. The temperature was raised to 209 ° C. while stirring under a nitrogen stream to distill 4.640 kg of water (the amount of remaining water was 1.12 per mole of sodium sulfide).
Mol). Thereafter, the autoclave was sealed and cooled to 180 ° C., and paradichlorobenzene (hereinafter referred to as p-DCB) was used.
22.185 kg and NMP18.
0 kg was charged. 1 at a liquid temperature of 150 ° C using nitrogen gas
The temperature was increased by applying pressure to kg / cm ² G. Liquid temperature 260
The reaction was allowed to proceed while stirring at 3 ° C. for 3 hours, and the autoclave was cooled by sprinkling water on the top. Next, the temperature was lowered and the cooling at the top of the autoclave was stopped. During the cooling of the upper part of the autoclave, the liquid temperature was kept constant so as not to drop.
The maximum pressure during the reaction was 8.52 kg / cm ² G.

After cooling, the obtained post-reaction slurry (S-
A part (1) (200 g) of 1) was filtered, and washing with hot water and filtration were repeated according to a conventional method to obtain PPS as a white powder. The melt viscosity V ₆ of the obtained PPS was 620 poise.

Synthesis Example 2 A reaction slurry (S-2) was obtained in the same manner as in Synthesis Example 1 except that 22.732 kg of p-DCB was used and the upper part of the autoclave was not cooled.

The melt viscosity V ₆ of the obtained PPS was 240 poise.

Synthesis Example 3 0.033 kg of 1,2,4-trichlorobenzene (0.12 mol% based on sodium sulfide) simultaneously with p-DCB
Was added, and the mixture was stirred at a liquid temperature of 220 ° C. for 4 hours. Then, the temperature was raised again and the reaction was allowed to proceed while stirring at a liquid temperature of 260 ° C. for 3 hours.
The reaction was carried out in the same manner as in Synthesis Example 1 except that the upper part of the autoclave was cooled by sprinkling water.
3) was obtained.

The melt viscosity V ₆ of the obtained PPS was 1930
Poise.

[0047]

Example 1 Slurry after reaction obtained in Synthesis Example 2 (S-
2) 2 grams of a 1% by weight aqueous acetic acid solution per 250 grams (the amount of acetic acid added was 0.09 per mole of sodium sulfide charged)
Mol%. ) And stirred, then the pH of the slurry,
The viscosity and filterability were measured.

[0048]

Example 2 The same procedure as in Example 1 was carried out except that 5 g of a 1% by weight aqueous acetic acid solution (the amount of acetic acid added was 0.2 mol% based on 1 mol of sodium sulfide charged). did.

[0049]

Example 3 The same procedure as in Example 1 was carried out except that 20 g of a 1% by weight aqueous acetic acid solution (the amount of acetic acid added was 0.9 mol% with respect to 1 mol of sodium sulfide charged). did.

[0050]

Example 4 Slurry after reaction obtained in Synthesis Example 1 (S-
The procedure was performed in the same manner as in Example 3 except that 1) was used.

[0051]

Example 5 The same procedure as in Example 4 was carried out except that 1 g of a 1% by weight aqueous acetic acid solution (the amount of acetic acid added was 0.05 mol% with respect to 1 mol of sodium sulfide charged). did.

[0052]

Example 6 Slurry after reaction obtained in Synthesis Example 3 (S-
The procedure was performed in the same manner as in Example 3 except that 3) was used.

[0053]

Example 7 One gram of a 50% by weight aqueous solution of zinc chloride (the amount of zinc chloride added was 1.0 to 1 mol of sodium sulfide charged).
0 mol%. ) Was carried out in the same manner as in Example 1 except that) was added.

[0054]

EXAMPLE 8 5 g of a 15% by weight aqueous oxalic acid solution (the amount of oxalic acid added was 2.2 mol% per mol of sodium sulfide charged) was added to adjust the pH of the slurry after the reaction to 4.
Except having set it as 8, it carried out similarly to Example 7.

[0055]

Example 9 Slurry after reaction obtained in Synthesis Example 2 (S-
(2, Slurry concentration 35%) NMP 19 g was added to 250 g and stirred to lower the slurry concentration by 2.5%, and then the pH, viscosity and filterability of the slurry were measured.

[0056]

Example 10 The same operation as in Example 10 was carried out except that 42 g of NMP was added and stirred, and the slurry concentration was diluted by 5%.

[0057]

EXAMPLE 11 3 g of a 1% by weight aqueous acetic acid solution (the amount of acetic acid added was 0.13 mol% based on 1 mol of sodium sulfide charged).
It is. ) And 42 grams of NMP were added.

[0058]

Comparative Example 1 Slurry after reaction obtained in Synthesis Example 1 (S-
1) 250 grams were used to measure the pH, viscosity and filterability of the slurry without addition of acid and solvent.

[0059]

Comparative Example 2 Slurry after reaction obtained in Synthesis Example 2 (S-
The procedure was performed in the same manner as in Comparative Example 1 except that 2) was used.

[0060]

Comparative Example 3 Slurry after reaction obtained in Synthesis Example 3 (S-
The procedure was performed in the same manner as in Comparative Example 1 except that 3) was used.

[0061]

Comparative Example 4 The same procedure as in Example 4 was carried out except that 0.5 g of a 1% by weight aqueous acetic acid solution (the amount of acetic acid added was 0.02 mol% with respect to 1 mol of sodium sulfide charged). It was carried out.

The above results are shown in Tables 1 and 2.

[0063]

[Table 1]

[0064]

[Table 2] Each symbol in each of the above tables indicates the following. * 1: Ac indicates a 1% by weight acetic acid aqueous solution. * 2: Zc indicates a 50% by weight aqueous solution of zinc chloride. * 3: Ox indicates a 15% by weight oxalic acid aqueous solution. * 4: Value calculated by the following equation.

[0065]

## EQU2 ## Viscosity reduction rate (%) = [(slurry viscosity before acid and / or solvent addition)-(slurry viscosity after acid and / or solvent addition)] × 100 / (before acid and / or solvent addition) Slurry viscosity) In Examples 1 to 3, the addition amount of the acetic acid aqueous solution was changed within the range of the present invention. When the amount of the acetic acid aqueous solution is increased, the slurry viscosity becomes lower and the filterability increases. Further, there was no change in the melt viscosity V ₆ of PPS before and after the addition of the acid. Example 4 was performed in the same manner as Example 3 except that a slurry containing PPS having a higher V ₆ was used. Filterability was good, the change in V ₆ of the PPS also was little. In Example 5, the addition amount of the acetic acid aqueous solution was changed within the scope of the present invention under the same conditions as Example 4. It was found that the filterability was improved even when the addition amount was extremely small. Example 6 is the same as Example 4, except that a slurry containing an even higher PPS of V ₆ was used. Filterability was good, the change in V ₆ of the PPS also was little. In Example 7, the aqueous zinc chloride solution was used for 1.
The same operation as in Example 1 was performed except that 0 mol% was added. Similarly good results were obtained. Example 8 is the same as Example 6 except that 2.2 mol% of the oxalic acid aqueous solution was added.
The same was done. The pH value of the slurry after the addition of oxalic acid was extremely low at 4.8. Filtration of the slurry is improved, V ₆ of the obtained PPS is compared to V ₆ of PPS before acid addition is significantly reduced, it was found that the degradation of the polymer backbone is generated. Examples 9-1
0 is a value obtained by adding NMP, which is a polymerization solvent, to the slurry after the reaction to reduce the slurry concentration by 2.5% by weight and 5.0% by weight, respectively. In all cases, the addition of a very small amount of NMP significantly reduced the viscosity. In Example 11, acetic acid addition and NMP addition were used in combination. When used together, it was found that the viscosity of the slurry was significantly reduced as compared with the case where each was used alone.

On the other hand, in Comparative Examples 1 to 3, each of the PPS slurries (S-1 to 3) used in Examples was filtered without adding any acid or solvent. The filterability was significantly poorer than the corresponding examples. In Comparative Example 4, the addition amount of the acetic acid aqueous solution was set to be less than the range of the present invention under the same conditions as in Example 4. The rate of decrease in slurry viscosity was low, and the filterability was poor.

[0067]

According to the present invention, there is provided a PAS production method for recovering PAS by filtering a PAS slurry after the reaction.
The PA obtained by increasing the filtration rate of the slurry
Provided is a method for preventing deterioration of S properties and improving PAS productivity.

Claims (6)

[Claims] 1. A method for producing a polyarylene sulfide by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide-based solvent, wherein the polyarylene sulfide slurry after the reaction is acidified in an acid and / or an aqueous solution. A method for producing a polyarylene sulfide, which comprises adding a salt of the formula (1) at a concentration of 0.05 to 2.5 mol% based on 1 mol of the charged alkali metal sulfide, and filtering the slurry. 2. An acid and / or a salt showing an acidity in an aqueous solution is added in an amount of 0.1 to 1 mol per mol of the charged alkali metal sulfide.
2. The method according to claim 1, wherein the addition is at 1.5 mol%. 3. The method according to claim 1, wherein the slurry has a filterability of 0.5 g / sec or more after adding an acid and / or a salt exhibiting acidity in an aqueous solution. 4. The method according to claim 1, wherein the pH of the slurry after adding an acid and / or a salt exhibiting acidity in an aqueous solution is 7.0 or more. 5. A method for producing a polyarylene sulfide by reacting an alkali metal sulfide and a dihalo aromatic compound in an organic amide solvent, wherein the solvent used in the polymerization reaction is added to the polyarylene sulfide slurry after the reaction. A method for producing polyarylene sulfide, which comprises adding the slurry in an amount such that the concentration of the slurry after the reaction is reduced by at most 10% by weight, and then filtering the slurry. 6. The method according to claim 5, wherein the solvent used in the polymerization reaction is added in such an amount that the concentration of the slurry after the reaction is reduced by 0.5 to 7.0% by weight.