JP7352165B2 - Method for producing granular polyarylene sulfide - Google Patents

Description

The present invention relates to a method for producing granular polyarylene sulfide with good yield in the production of granular polyarylene sulfide having a low molecular weight and excellent fluidity properties when melted.

Polyarylene sulfide (hereinafter polyarylene sulfide may be abbreviated as PAS), represented by polyphenylene sulfide, is an engineering plastic with excellent heat resistance, chemical resistance, flame retardance, electrical properties, and mechanical properties. It is widely used for fibers, films, injection molding and extrusion molding. In addition, in recent years, there has been an increase in the demand for thinner and lighter PAS products in the design of PAS products, so there has been an increase in the demand for PAS with excellent flow characteristics when melted.

As a method for producing PAS, for example, a method in which a dihalogenated aromatic compound and an alkali metal sulfide are reacted in an organic polar solvent is known. (For example, see Patent Document 1.). According to this method, the polymerization system at high temperature is generally flashed into a container under normal pressure or reduced pressure, and then the resin is recovered through solvent recovery, washing, and drying, and the final average particle size is A powdered resin having a diameter of several microns to 50 microns can be obtained.

Furthermore, as a method for recovering granular PAS with relatively high bulk density rather than powder, a method has been disclosed in which the reaction system is cooled after the polymerization reaction (see, for example, Patent Documents 2 and 3). In this method, granular PAS can be recovered by adding a precipitating agent to precipitate molten PAS during particle formation, that is, during the cooling stage, or by controlling the temperature.

Furthermore, as another method for increasing the average particle size of granular PAS, a method of controlling the cooling rate after the polymerization reaction has been disclosed (see, for example, Patent Document 4). According to this method, by dividing the post-polymerization cooling process into two stages and cooling each stage at different cooling rates, impurities can be removed even under polymerization reaction conditions where it is difficult to obtain granular PAS in Patent Documents 2 and 3. It is possible to obtain granular PAS with a small content of.

Furthermore, as a method for further improving the productivity of granular PAS production, a method has been disclosed in which a very limited temperature range is selectively slowly cooled in the cooling step after the polymerization reaction (see, for example, Patent Document 5). ). According to this method, by selectively slowly cooling the extremely limited temperature range of the maximum thickening temperature ±1°C, granular PAS with high bulk density and good handling properties during transportation and storage can be produced. It can be produced in relatively short polymerization cycle times.

In addition, as a method to not only increase the average particle size of granular PAS but also improve the product yield, the conversion rate of dihaloaromatic compounds in the presence of less than equimole of alkali metal hydroxide per mole of sulfur source has been proposed. After producing 50% or more of the prepolymer, the polymerization reaction is continued in the presence of at least equimolar alkali metal hydroxide per mole of sulfur source, followed by the presence of at least one auxiliary agent such as a carboxylate salt. A method of performing cooling under the conditions has been disclosed (see, for example, Patent Document 6). According to this method, while suppressing the generation of by-products, it is possible to form hard particles that do not easily become fine or crushed even during transportation and washing, and it is possible to improve the product yield of granular PAS.

In addition, as a method for obtaining granular PAS in a shorter time and with higher yield than conventional methods, a method is disclosed in which the polymerization process is divided into three stages according to temperature and the preferred time for each is specified, thereby shortening the production time of PAS. (For example, see Patent Document 7.). According to this method, not only can granular PAS be efficiently obtained by optimizing the polymerization time, but also 2.0 mol or more and less than 5.5 mol per 1 mol of sulfur component in a state where the monomer consumption reaction is substantially completed. By adding water so that water is present, it is possible to increase the average weight of PAS particles and obtain granular PAS in good yield.

In addition, as a method for obtaining PAS having high melt fluidity and a large weight average particle size, a method for shortening the polymerization time including the time for raising and lowering the temperature in a temperature range of 245°C or higher and lower than 280°C has been disclosed. ing. (For example, Patent Document 8). According to this method, by reacting under specific temperature conditions in the presence of a polymerization aid, it is possible to recover PAS having high melt fluidity to obtain granular PAS in good yield.

Furthermore, as a method for efficiently recovering medium molecular weight PAS as a product, a method has been disclosed in which 50% by mass or more of a phase separation agent is added while the temperature of the reaction product mixture is 245°C or higher (e.g. , Patent Document 9). According to this method, by incorporating medium molecular weight PAS into granular PAS and recovering it, it is possible to improve the yield of granular PAS and obtain granular PAS with improved particle strength.

Japanese Patent Publication No. 52-12240 (Claims) JP-A-59-1536 (Claims) JP-A-60-235838 (Claims) JP2001-089569A (Claims) JP2004-051732A (Claims) JP2017-179255A (Claims) JP2018-083910A (Claims) JP2011-132517A (Claims) International Publication No. 2016/199894 (Claims)

However, the method of Patent Document 1 is a method in which only a powdered resin with a small particle size can be obtained. This form of resin has a low bulk density, which causes problems such as air being drawn in during melt extrusion and reducing the discharge rate, which requires a separate pre-process to pelletize, resulting in poor productivity.

In addition, although the methods of Patent Documents 2 and 3 can recover granular PAS with a relatively high bulk density, conditions that are effective for reducing by-products during the reaction, specifically, polyhalogenation with respect to the amount of organic polar solvent are required. There was a problem in that it was difficult to obtain granular PAS under reaction conditions where the amount of aromatic compounds was large. Furthermore, if the cooling rate is not appropriate, by-products are likely to be incorporated into the granular PAS, which causes a problem of quality deterioration such as an increase in volatile components during heating of the PAS, thermal deterioration, and coloring.

In addition, in the method of Patent Document 4, by optimizing the cooling rate, it is possible to obtain granular PAS with a low content of impurities even under the polymerization reaction conditions in which it is difficult to obtain granular PAS in Patent Documents 2 and 3. Under the conditions for producing low-molecular-weight PAS with excellent flow characteristics when melted, the average particle diameter is not large enough, and some polymer particles pass through the mesh used during recovery, making it difficult to improve product yield. There was room.

Furthermore, in the method of Patent Document 5, it has been clarified that the effect of increasing the particle size due to slow cooling occurs in a specific temperature range, and the method has succeeded in producing granular PAS with high bulk density in a short polymerization cycle time. However, while sufficient effects have been confirmed with high molecular weight PAS, there has been no mention of whether or not low molecular weight PAS can be effective. Furthermore, although it is mentioned that the molecular weight of PAS can be increased by appropriately adjusting the amount of water in the system, there is no mention of the fact that this effect extends to the increase in the particle size of PAS. There wasn't.

In addition, in the method of Patent Document 6, an increase in the average particle diameter and an improvement in particle strength are achieved by cooling the system with phase separation, but the effect tends to be smaller for PAS with a small molecular weight. There was a need for improvement. Furthermore, in the method of Patent Document 6, since it is also necessary to control the amount of alkali metal hydroxide used, there has been a need for a simpler method for increasing the average particle diameter and improving particle strength.

In addition, in the method of Patent Document 7, water is added so that 2.0 mol or more and less than 5.5 mol of water is present per 1 mol of sulfur component in a state where the monomer consumption reaction is substantially completed. Granular PAS has been obtained in good yield by increasing the average weight of the particles, but the efficiency is poor due to the temperature range in which slow cooling is required, or in other words, the time required for slow cooling, and improvements are needed. was. Furthermore, there was no particular mention of whether effects could be obtained with low molecular weight PAS.

Furthermore, in the method of Patent Document 8, the nitrogen content of PAS tends to decrease. Generally, PAS obtained by reacting a sulfidating agent and a dihalogenated aromatic compound in the presence of an alkali metal hydroxide in an organic polar solvent contains nitrogen. This is because the alkali metal alkylaminoalkyl carboxylate produced by the reaction between an organic polar solvent such as NMP and an alkali metal hydroxide reacts with the PAS terminal as a side reaction during polymerization, forming a terminal having a nitrogen atom. It's for a reason. However, if the nitrogen content is extremely low, there is a problem in that the reactivity with various coupling agents used during melt extrusion to increase the toughness and strength of PAS decreases. Another problem was that when the amount of sodium acetate input was large, the wastewater load increased.

In addition, in the method of Patent Document 9, water is added to the reaction system after the first stage polymerization is completed and the reaction is carried out at a temperature of 245°C to 290°C, so the pressure in the reaction system tends to be high and requires expensive pressure-resistant equipment. This tends to be economically disadvantageous as it requires

Therefore, an object of the present invention is to improve the problems of the prior art and to produce granular PAS with good yield in the production of low molecular weight granular PAS that has excellent flow characteristics when melted.

In order to solve the above problems, the present invention provides a method for producing granular PAS having the following features.
[1] A method for producing particulate polyarylene sulfide by reacting a mixture containing at least a sulfidating agent, a dihalogenated aromatic compound, an organic polar solvent, and a polymerization aid, characterized by comprising the following steps 1 to 4. A method for producing granular polyarylene sulfide.
Step 1: A step of heating the mixture at a temperature of 200° C. or higher and lower than 245° C. to cause a reaction. The pressure P1 in the temperature range of Step 1 is 0.1 MPaG or more and 1.0 MPaG or less, and the polymerization time TM1 of Step 1, including temperature raising/lowering time, is 30 minutes or more and 240 minutes or less.
Step 2: Following Step 1, the amount of water in the reaction system is adjusted to 0.1 mol or more and 1.5 mol or less per 1 mol of sulfidation agent , and the reaction is carried out at a temperature of 245°C or more and 290°C or less. A process of heating and reacting. The pressure P2 in the temperature range of Step 2 is 0.5 MPaG or more and 2.0 MPaG or less, and the polymerization time TM2 of Step 2 until the polymerization reaction is completed is 60 minutes or more and 300 minutes or less.
Step 3: Following Step 2, the water content in the reaction system is adjusted to 3.3 mol or more and 6.0 mol or less per 1 mol of sulfidation agent , and the temperature is adjusted to T0 (240°C≦T0≦ 290° C.), and the pressure P3 in the temperature range of step 3 is 1.0 MPaG or more and 2.0 MPaG or less.
Step 4: Following step 3, cool from temperature T0 to T1 (200°C≦T1≦235°C) at a cooling rate S1 (0.2°C/min≦S1≦0.8°C/min), and after cooling to T1. , a step of further cooling by changing the cooling rate to S2 (0.8° C./min<S2≦5° C./min).
[2] The method for producing granular polyarylene sulfide according to [1], wherein the weight average molecular weight Mw of the granular polyarylene sulfide is 5,000 or more and 45,000 or less.
[3] The method for producing granular polyarylene sulfide according to [1] or [2], wherein the average particle diameter of the granular polyarylene sulfide is 500 μm or more and 1,500 μm or less.
[4] As a polymerization aid, organic carboxylate, organic sulfonate, alkali metal halide, alkaline earth metal halide, alkali metal phosphate, alkaline earth metal phosphate, alkali metal sulfate, alkaline earth Using at least one polymerization aid selected from metal oxides [1]
The method for producing granular polyarylene sulfide according to any one of [3].
[5] The granular polyarylene according to any one of [1] to [4], wherein the amount of the dihalogenated aromatic compound in the mixture is 1.04 mol or more and 2.00 mol or less per 1 mol of sulfidation agent. Method for producing sulfide.
[6] The granular polyarylene according to any one of [1] to [5], wherein the amount of the polymerization aid used in the mixture is 0.001 mol or more and 0.4 mol or less per 1 mol of sulfidation agent. Method for producing sulfide.

According to the production method of the present invention, in the production of low molecular weight granular PAS with excellent fluidity properties during melting, the average particle diameter can be increased and granular PAS can be produced with good yield.

Embodiments of the present invention will be described below.

(1) Polyarylene sulfide The polyarylene sulfide in the present invention is a homopolymer or copolymer whose main constituent unit is a repeating unit of the formula -(Ar-S)-. Examples of Ar include units represented by the following formulas (A) to (L), among which (A) is particularly preferred.

(R1 and R2 are substituents selected from hydrogen, an alkyl group, an alkoxy group, and a halogen group, and R1 and R2 may be the same or different.) As long as this repeating unit is used as the main constituent unit, the following formula ( M) may contain a small amount of branching units or crosslinking units represented by formula (P) or the like. The amount of copolymerization of these branching units or crosslinking units is preferably in the range of 0 mol % or more and 1 mol % or less per 1 mol of -(Ar-S)- units.

Moreover, the polyarylene sulfide in the present invention may be a random copolymer, a block copolymer, or a mixture thereof containing the above repeating units.

Typical examples of these include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, random copolymers, block copolymers thereof, and mixtures thereof. Particularly preferred polyarylene sulfides include p-phenylene units as the main constituent units of the polymer.

Examples include polyphenylene sulfide, polyphenylene sulfide sulfone, and polyphenylene sulfide ketone containing 90 mol% or more of.

These polyarylene sulfides are originally not particularly limited in their molecular weight, but polyarylene sulfides with a weight average molecular weight Mw of 5,000 to 45,000 have excellent flow characteristics when melted, and can be made thinner and lighter. In the present invention, the polyarylene sulfide having the above-mentioned Mw is defined as a more preferable polyarylene sulfide because it has characteristics that allow it to be preferably used in applications requiring the following. As a more preferable range of the weight average molecular weight Mw, as a lower limit, 10,000 or more is more preferable, and 15,000 or more is even more preferable. Moreover, as an upper limit, 40,000 or less is more preferable, 35,000 or less is still more preferable, and 32,000 or less is even more preferable. Within the above preferred range, it can be used as a PAS with better flow characteristics when melted. Here, the melt viscosity, which is known to be correlated with the weight average molecular weight Mw, is preferably in the range of 1 to 40 Pa·s (320°C, shear rate 1,000/sec) in the present invention from the above-mentioned preferred Mw. , a range of 3 to 30 Pa·s is more preferable, and a range of 5 to 30 Pa·s is even more preferable.

Further, in the present invention, granular polyarylene sulfide is obtained, and the average particle diameter thereof is preferably 500 μm or more and 1,500 μm or less, the lower limit is more preferably 600 μm or more, and the upper limit is more preferably 1,000 μm or less. I can give an example. In such a preferable range, granular polyarylene sulfide can be easily recovered using a general stainless steel sieve, and there are few components lost by passing through the mesh, and granular polyarylene sulfide can be recovered in a high yield. It is possible to do so. Here, the stainless steel sieve can be freely selected in terms of opening and number of meshes, and there are various standards such as JIS and Tyler. Evaluation was performed using a sieve. It should be noted that as 80 mesh sieves, sieves with apertures of 177 to 182 μm are widely known, and there is no major difference between them. Therefore, as long as the sieves have apertures in the above range, they can be evaluated in the present invention without any problems. It can be used for

Here, the average particle diameter of granular polyarylene sulfide in the present invention refers to the volume-based particle size distribution measured under wet conditions using a laser diffraction particle size distribution measuring device and using N-methyl-2-pyrrolidone as a dispersion solvent. This is the value calculated based on Specifically, the particle diameter interval is set to a logarithmic scale, and the arithmetic mean value on the logarithmic scale is determined, and then the result is returned to an average value in normal particle diameter units. In general, parameters such as the mode diameter, which indicates the maximum value of the particle size distribution, and the median diameter, which is the cumulative particle diameter of 50%, are also known, but in the present invention, these parameters are not used, and the average particle diameter is calculated by the arithmetic mean described above. The evaluation will be conducted using the following.

The granular polyarylene sulfide obtained by the present invention is a relatively low molecular weight polyarylene sulfide with excellent flow characteristics when melted as described above, but it is a granular polyarylene sulfide with a large average particle diameter, unlike conventional polyarylene sulfide. This can be said to be extremely significant in that it is possible to achieve both characteristics that were previously difficult to achieve.

(2) Sulfidating agent The sulfidating agent used in the present invention may be any agent that can introduce a sulfide bond into a dihalogenated aromatic compound, and examples thereof include alkali metal sulfides and alkali metal hydrosulfides. Specific examples of the alkali metal sulfide include sodium sulfide, potassium sulfide, lithium sulfide, rubidium sulfide, and cesium sulfide, among which sodium sulfide is preferably used. These alkali metal sulfides can be used as hydrates or aqueous mixtures or in anhydrous form.

Specific examples of the alkali metal bisulfide include sodium bisulfide, potassium bisulfide, lithium bisulfide, rubidium bisulfide, cesium bisulfide, and among these, sodium bisulfide is preferably used. These alkali metal hydrosulfides can be used as hydrates or aqueous mixtures or in anhydrous form.

It is also possible to use an alkali metal hydroxide and/or an alkaline earth metal hydroxide together with the sulfidating agent. Specific examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, etc. Specific examples of alkaline earth metal hydroxides include, for example, hydroxide. Calcium, strontium hydroxide, barium hydroxide, etc. are mentioned, among which sodium hydroxide and magnesium hydroxide are preferably used.

When using an alkali metal hydrosulfide as a sulfidating agent, it is particularly preferable to use an alkali metal hydroxide at the same time, but the amount used is 0.95 mol or more and 1.20 mol or more per 1 mol of the alkali metal hydrosulfide. The range is preferably 1.00 mol or more and 1.15 mol or less, more preferably 1.005 mol or more and 1.100 mol or less. The sulfidating agent may be introduced into the system at any timing, but it is preferably introduced before the dehydration operation described below.

(3) Dihalogenated aromatic compound The dihalogenated aromatic compound used in the present invention is a compound that has an aromatic ring, two halogen atoms in one molecule, and a molecular weight of 1,000 or less. It is about. Specific examples include p-dichlorobenzene, m-dichlorobenzene, o-dichlorobenzene, p-dibromobenzene, m-dibromobenzene, o-dibromobenzene, 1-bromo-4-chlorobenzene, 1-bromo-3-chlorobenzene. Dihalogenated benzenes such as 1-methoxy-2,5-dichlorobenzene, 1-methyl-2,5-dichlorobenzene, 1,4-dimethyl-2,5-dichlorobenzene, 1,3-dimethyl-2, Dihalogenated benzenes containing substituents other than halogen such as 5-dichlorobenzene and 3,5-dichlorobenzoic acid, and 1,4-dichloronaphthalene, 1,5-dichloronaphthalene, 4,4'-dichlorobiphenyl, 4 , 4'-dichlorodiphenyl ether, 4,4'-dichlorodiphenyl sulfone, and 4,4'-dichlorodiphenyl ketone. Dihalogenated aromatic compounds containing benzene as a main component are preferred. Particularly preferably, it contains 80 to 100 mol% of p-dichlorobenzene, more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol% of p-dichlorobenzene. It is also possible to use a combination of two or more different dihalogenated aromatic compounds to produce a cyclic PAS copolymer.

(4) Organic polar solvent In the present invention, an organic polar solvent is used as a reaction solvent, and among them, it is preferable to use an organic amide solvent because of its high reaction stability. Specific examples include N-alkylpyrrolidones such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, 1, Examples include aprotic organic solvents such as 3-dimethyl-2-imidazolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, hexamethylphosphoric triamide, dimethylsulfone, and tetramethylene sulfoxide; A mixture of these can also be used. Among these, N-methyl-2-pyrrolidone is preferably used.

The amount of organic polar solvent to be used in the present invention is preferably 0.5 mol or more and less than 10 mol, preferably 2.5 mol or more per 1 mol of sulfur in the reaction system (polymerization system). The range is selected to be less than 5.5 mol, more preferably 2.7 mol or more and less than 4.5 mol, even more preferably 2.7 mol or more and less than 4.0 mol, and 2.7 mol or more and less than 4.0 mol. A range of less than 5 moles is even more preferred. When the amount of the organic polar solvent is small, undesirable reactions tend to occur, and when the amount is large, it tends to be difficult to increase the degree of polymerization. Here, the amount of organic polar solvent in the reaction system is the amount obtained by subtracting the amount of organic polar solvent removed from the reaction system from the amount of organic polar solvent introduced into the reaction system. Note that there is no problem in introducing the organic polar solvent into the system at any time, but when performing the dehydration operation described below, some of the organic polar solvent tends to scatter out of the system. Preferably, the minimum amount necessary for dehydration is introduced, and after the dehydration operation is completed, an additional amount is introduced to reach the above-mentioned preferred usage amount.

(5) Polymerization aid The polymerization aid used in the present invention is a substance that facilitates the generation of phase separation within the system. When a phase separation state occurs, the polymerization reaction tends to proceed, and when the particles are formed by cooling after the polymerization reaction, the particle size tends to increase.

Specific examples of such polymerization aids include ionic compounds that dissolve in organic polar solvents, such as organic carboxylates, organic sulfonates, alkali metal halides, alkaline earth metal halides, alkali metal phosphates, etc. Examples include salts, alkaline earth metal phosphates, alkali metal sulfates, and alkaline earth metal oxides, but organic carboxylates are preferably used from the viewpoint of cost effectiveness and availability. These may be used alone or in combination of two or more. Furthermore, water also has the effect of promoting phase separation in the same way as the ionic compounds described above, but handling is significantly different from the ionic compounds described above in terms of the preferred usage amount. It is not included in the category of agents, and the effects of water will be discussed in detail separately.

Here, the organic carboxylate refers to the general formula R(COOM), (wherein R is an alkyl group, cycloalkyl group, aryl group, alkylaryl group, or arylalkyl group having 1 to 20 carbon atoms, M is an alkali metal selected from lithium, sodium, potassium, rubidium and cesium). Specific examples include lithium acetate, sodium acetate, potassium acetate, sodium propionate, lithium benzoate, sodium benzoate, sodium phenylacetate, sodium p-toluate, and the like. Organic carboxylic acid salts are organic carboxylic acids and one or more compounds selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates in approximately equal chemical equivalents. It may be formed by adding and reacting. One type of organic carboxylic acid salt or two or more types can be used simultaneously. Among them, lithium acetate and/or sodium acetate are preferably used, and sodium acetate is more preferably used because it is inexpensive and easily available.

In the present invention, the amount of the polymerization aid to be used cannot be clearly defined because the preferred amount changes depending on the amount of the sulfidating agent and the dihalogenated aromatic compound used, but for example, per mole of sulfur of the sulfidating agent, A preferable example is 0.001 mol or more and 0.4 mol or less, a more preferable lower limit is 0.01 mol or more, and an even more preferable example is 0.05 mol or more. The upper limit is more preferably 0.2 mol or less, and even more preferably 0.15 mol or less. When the amount of the polymerization auxiliary used is in the above-mentioned preferred range, the molecular weight of PAS can be easily controlled within the preferred range of the present invention, and the average particle diameter of PAS tends to be increased more easily.

There is no particular restriction on the timing of introducing the polymerization aid into the system, and it may be introduced before the dehydration described below, after dehydration, after dehydration and before the polymerization reaction, during the polymerization reaction, or after the polymerization reaction and before adding water. It can be introduced into the system at any timing, and there is no problem even if it is added in multiple portions, but it is preferable to introduce at least a portion of it into the system before starting the polymerization reaction. This makes it possible to obtain PAS of a desired molecular weight in a shorter time. Furthermore, the polymerization aid may be added in any form such as an anhydride, a hydrate, an aqueous solution, or a mixture with an organic polar solvent.

(6) Water Water in the present invention can promote phase separation by existing in the reaction system at a certain level, and has the effect of strongly bringing out the effects of the polymerization aid. On the other hand, the presence of excess water can reduce the nucleophilicity of the sulfidating agent, delaying the reaction, and increasing the pressure in the system, so the amount used should be adjusted to a preferable range depending on the stage of the reaction. It is important to control. Based on the above, in the present invention, the water present in the system at the end of the polymerization reaction and the water added to the system after the end of the polymerization reaction are treated separately, and the effects and preferable usage amount of water at each stage are discussed. The method for adjusting the water content will be explained below.

In the present invention, the water added into the system after the completion of the polymerization reaction refers to the water added in step 3, which will be described later. The details will be described later in Step 3, but by adjusting the amount of water in the system to an appropriate amount after the polymerization reaction is completed, phase separation can be further promoted and the particle size of the resulting granular polyarylene sulfide can be increased. can get. In step 3, the amount of water in the reaction system is adjusted to 3.3 mol or more and 6.0 mol or less per 1 mol of sulfur. At this time, the amount of water that was present in the system at the end of the polymerization reaction is It is necessary to decide the amount of water to be added to the system after considering this. Here, as a preferable range of the water content of the reaction system in Step 3, the lower limit is more preferably 3.5 mol or more per 1 mol of sulfur. Further, the upper limit is more preferably 5.0 mol or less per 1 mol of sulfur.

In addition, in the present invention, the water present in the system at the end of the polymerization reaction refers to the water that was directly added during the preparation of the raw materials, the sulfidating agent, the dihalogenated aromatic compound, the organic polar solvent, and the polymerization aid that were added. The water distilled out of the system during the dehydration operation is subtracted from the sum of the water introduced during the polymerization reaction and the water produced during the polymerization reaction process. The preferred lower limit of the amount of water present in the system at the end of step 2 and the polymerization reaction is 0.1 mol or more, more preferably 0.5 mol or more per 1 mol of sulfur in the sulfidating agent. Further, the upper limit is 1.5 mol or less, and more preferably 1.3 mol or less. When the amount of water present in the system before the end of the polymerization reaction is in the range described above, the polymerization rate tends to be high and by-products can be suppressed. Furthermore, the pressure increase within the system is suppressed, and the cost associated with introducing high-pressure equipment tends to be reduced.

In the present invention, if the amount of water present in the system at the end of the polymerization reaction exceeds the above-mentioned preferred amount of water, it is also possible to adjust the amount of water by reducing the amount of water in the reaction system by dehydration. be. This dehydration operation is not particularly limited, but for example, a method of heating and removing water by distillation can be exemplified. On the other hand, if the moisture content is less than the above-mentioned range, there is no problem even if water is added so that the moisture content falls within the above-mentioned range.

Here, there is no particular restriction on the method of performing the dehydration operation, such as a method in which the raw materials to be charged are dehydrated in advance, a method using any one of a sulfidating agent, a dihalogenated aromatic compound, an organic polar solvent, a polymerization aid, or A method of dehydrating a mixture in which two or more components are not added, a method of dehydrating a mixture containing a sulfidating agent, a dihalogenated aromatic compound, an organic polar solvent, a polymerization aid, etc. Either method can be adopted, but from the viewpoint of precisely controlling the amount of dihalogenated aromatic compounds used, which tend to scatter when heated, a method in which a mixture in which no dihalogenated aromatic compounds are added is subjected to a dehydration operation. is preferably adopted. At this time, the temperature at which the mixture is heated cannot be clearly specified as it varies depending on the combination of the sulfidating agent and organic polar solvent used, as well as the ratio of water, etc., but the lower limit is 150°C or higher. For example, preferably 160°C or higher, more preferably 170°C or higher. Further, the upper limit can be exemplified as 250°C or lower, preferably 230°C or lower. When the heating temperature during dehydration is in the above-mentioned preferred range, dehydration can be efficiently performed while suppressing the charged sulfidating agent from scattering outside the system as hydrogen sulfide. There are also no particular restrictions on the pressure conditions when dehydrating, and any of normal pressure, reduced pressure, or increased pressure can be used, but normal pressure or reduced pressure is preferable in order to more efficiently distill water off. . Here, normal pressure refers to a pressure near the standard state of the atmosphere, and refers to a temperature of about 25° C. and an atmospheric pressure of about 101 kPa in absolute pressure. In addition, the atmosphere in the system is desirably non-oxidizing, and is preferably an inert gas atmosphere such as nitrogen, helium, or argon. In particular, from the viewpoint of economy and ease of handling, a nitrogen atmosphere is preferable. is more preferable.

Since it is difficult to directly measure the amount of water in the high-pressure system during the polymerization reaction, the method of estimating the amount of water present in the system at the end of the polymerization reaction described above is to add water directly at the time of raw material preparation. Separately estimate the amount of water, the amount of water introduced along with the charged raw materials, the amount of water generated during the polymerization reaction process, and the amount of water distilled out of the system during the dehydration operation, and calculate based on these amounts. Adopt a method.

The water produced during the polymerization reaction may or may not be produced depending on the type of sulfidation agent used, so consider the chemical reaction formula before the polymerization reaction to understand whether water will be produced. It is necessary to keep it. For example, when an alkali metal hydrosulfide and an alkali metal hydroxide, which are the preferred sulfidating agents of the present invention, are used together as the sulfidating agent, an equimolar amount of water is produced as the alkali metal hydrosulfide consumed in the polymerization reaction. do. On the other hand, when an anhydrous alkali metal sulfide is used as the sulfidating agent, no water is produced during the polymerization reaction.

Therefore, when an alkali metal hydrosulfide and an alkali metal hydroxide are used together as a sulfidating agent, the amount of water generated during the polymerization reaction can be estimated by calculating the conversion rate of the sulfidating agent. . In the present invention, the amount of the sulfidating agent remaining in the polymerization reaction solution was estimated by ion chromatography, and the conversion rate of the sulfidating agent was calculated from the ratio to the amount of the sulfidating agent charged. The calculation formula is as follows.
Conversion rate of sulfidating agent (%) = [[Amount of charged sulfidating agent (mol) - Amount of remaining sulfidating agent (mol)]/[Amount of charged sulfidating agent (mol)]] x 100% .

Here, the amount of sulfidating agent charged refers to the amount of sulfidating agent that was present in the system at the time of starting the polymerization reaction, and some of the sulfidating agent was dissolved into hydrogen sulfide by the dehydration operation before the start of the polymerization reaction. When the sulfidating agent is removed from the system as a hydrogen sulfide, estimate the amount of the sulfidating agent present in the system at the start of the polymerization reaction, taking into account the number of moles of hydrogen sulfide scattered.

(7) Method for producing granular polyarylene sulfide The present invention provides a method for producing granular polyarylene sulfide by reacting a mixture containing at least a sulfidating agent, a dihalogenated aromatic compound, an organic polar solvent, and a polymerization aid. , is characterized by including the following steps 1 to 4.
Step 1: A step of heating and reacting at a temperature of 200°C or higher and lower than 245°C. The pressure P1 in the temperature range of Step 1 is 0.1 MPaG or more and 1.0 MPaG or less, and the polymerization time TM1 of Step 1, including temperature raising/lowering time, is 30 minutes or more and 240 minutes or less.
Step 2: Following Step 1, the amount of water in the reaction system is adjusted to 0.1 mol or more and 1.5 mol or less per 1 mol of sulfur, and the reaction is carried out by heating at a temperature of 245°C or more and 290°C or less. process. The pressure P2 in the temperature range of Step 2 is 0.5 MPaG or more and 2.0 MPaG or less, and the polymerization time TM2 of Step 2 until the polymerization reaction is completed is 60 minutes or more and 300 minutes or less.
Step 3: Following Step 2, adjust the water content in the reaction system to 3.3 mol or more and 6.0 mol or less per 1 mol of sulfur, and set the temperature to T0 (240°C≦T0≦290°C). , a step in which the pressure P3 in the temperature range of step 3 is 1.0 MPaG or more and 2.0 MPaG or less.
Step 4: Following step 3, cool from temperature T0 to T1 (200°C≦T1≦235°C) at a cooling rate S1 (0.2°C/min≦S1≦0.8°C/min), and after cooling to T1. , a step of further cooling by changing the cooling rate to S2 (0.8° C./min<S2≦5° C./min).

These steps will be explained below.

(7-1) Process 1
Step 1 is a step in which a mixture containing at least a sulfidating agent, a dihalogenated aromatic compound, an organic polar solvent, and a polymerization aid is heated at a temperature of 200° C. or higher and lower than 245° C. to react. This step is characterized in that the pressure P1 in the temperature range of Step 1 is 0.1 MPaG or more and 1.0 MPaG or less, and the polymerization time TM1 of Step 1 including temperature raising/lowering time is 30 minutes or more and 240 minutes or less.

The pressure of the reaction system also changes depending on the raw materials constituting the mixture, the composition, the reaction temperature, and the degree of progress of the reaction. Here, the pressure P1 is the maximum pressure (gauge pressure) in the system in the temperature range of Step 1 (200° C. or higher and lower than 245° C.). The lower limit of the pressure P1 is 0.1 MPaG, and a more preferable example is 0.25 MPaG or more. Further, the upper limit is 1.0 MPaG or less, more preferably 0.9 MPaG or less. By keeping the pressure in the reaction system within the range mentioned above, the sulfidating agent and dihalogenated aromatic compound, which are the raw materials, tend to be quickly consumed by reaction, and the use of expensive pressure-resistant equipment tends to be avoided. . Here, in order to maintain the pressure within the reaction system within the above-mentioned preferred range, the inside of the reaction system may be pressurized with an inert gas at any stage such as before or during the reaction, preferably before starting the reaction. I don't mind. Note that gauge pressure here refers to relative pressure with atmospheric pressure as a reference, and is the same as the pressure difference obtained by subtracting atmospheric pressure from absolute pressure.

Here, the lower limit of the polymerization time TM1 in step 1 including the temperature raising time is 30 minutes, preferably 60 minutes or more, and more preferably 80 minutes or more. The upper limit of TM1 is 240 minutes, more preferably 180 minutes or less. If TM1 is too short, the conversion rate of the dihalogenated aromatic compound described below will be too low, and the unreacted sulfidating agent will cause decomposition of the prepolymer in step 2, causing volatilization when the resulting PAS is heated and melted. The sexual component tends to increase. Moreover, if TM1 is too long, it will be economically disadvantageous due to a decrease in production efficiency.

(7-2) Process 2
Step 2 is the next step to step 1, in which the amount of water in the reaction system is adjusted to 0.1 mol or more and 1.5 mol or less per 1 mol of sulfur, and heated at a temperature of 245°C or more and 290°C or less. This is a reaction step. This step is characterized in that the pressure P2 in the temperature range of step 2 is 0.5 MPaG or more and 2.0 MPaG or less, and the polymerization time TM2 of step 2 until the polymerization reaction is completed is 60 minutes or more and 300 minutes or less.

Here, the temperature at which the mixture is heated to react needs to be 245°C or more and 290°C or less. If the temperature at which the mixture is heated and reacted is lower than 245° C., the polymerization rate becomes slow and PAS cannot be efficiently obtained. Furthermore, if the temperature at which the mixture is heated and reacted exceeds 290° C., the PAS produced will be denatured by the influence of the organic solvent, making it difficult to obtain PAS exhibiting normal physical properties. In addition, as a preferable range of the temperature at which the mixture is heated to react, a preferable lower limit is 250° C. or higher, and a preferable upper limit is 280° C. or lower. When the temperature at which the mixture is heated and reacted is within the above preferred range, PAS exhibiting normal physical properties can be obtained more efficiently.

Here, when the temperature at which the mixture is heated to react exceeds the reflux temperature of the mixture under normal pressure, methods of heating at such temperature include, for example, a method of heating the mixture under pressure exceeding normal pressure, An example is a method of heating the mixture in a closed container. Note that normal pressure refers to a pressure near the standard state of the atmosphere, and the standard state of the atmosphere refers to a temperature of about 25° C. and an atmospheric pressure condition of about 101 kPa in absolute pressure. Further, the reflux temperature is a temperature at which the liquid component of the mixture repeatedly boils and condenses. Furthermore, although the reaction in the present invention is carried out at a temperature of 245°C or higher and 290°C or lower, it is also possible to carry out a reaction at a constant temperature, a multi-step reaction in which the temperature is raised stepwise, or a reaction in which the temperature is continuously changed. Either is fine.

Here, the pressure P2 is the maximum pressure (gauge pressure) in the system in the temperature range of step 2 (245° C. or higher and 290° C. or lower). The lower limit of the pressure P2 is 0.5 MPaG or more, preferably 0.7 MPaG or more, more preferably 0.8 MPaG or more, and even more preferably 1.0 MPaG. Moreover, the upper limit is 2.0 MPaG or less, more preferably 1.95 MPaG or less, and even more preferably 1.9 MPaG or less. When the pressure within the reaction system is in the above-mentioned range, the sulfidating agent and the dihalogenated aromatic compound, which are the raw materials, tend to be rapidly consumed by reaction, and the use of expensive pressure-resistant equipment tends to be avoided.

Here, the amount of water in the reaction system in Step 2 needs to be adjusted to 0.1 mol or more and 1.5 mol or less per 1 mol of sulfur. If the amount of water in the reaction system exceeds 1.5 mol per mol of sulfur, the pressure in the system will become significantly high, leading to safety problems. Here, as a preferable range of the amount of water in the reaction system in Step 2, a preferable lower limit is 0.5 mol or more per 1 mol of sulfur, and a preferable upper limit is 1.3 mol or less per 1 mol of sulfur. can. When the amount of water in the reaction system in Step 2 is within the above-described preferred range, it is possible to keep the pressure in the system lower. A method for adjusting the amount of water in the reaction system in step 2 so that it is 0.1 mol or more and 1.5 mol or less per 1 mol of sulfur is a method of adjusting the amount of water in the reaction system in step 3, which will be described later. This can be done in a similar way.

Here, the lower limit of the polymerization time TM2 in step 2 until the polymerization reaction is completed is 60 minutes, and more preferably 90 minutes or more. The upper limit of TM2 is 300 minutes or less, more preferably 240 minutes or less, even more preferably 180 minutes or less, and even more preferably 150 minutes or less. If TM2 is too short, it becomes difficult to control the reaction and undesirable reactions are likely to occur, and if TM2 is too long, it becomes economically disadvantageous.

Here, the preferred amount of the dihalogenated aromatic compound used in the mixture changes depending on the amount of the polymerization aid used. For example, if the amount of polymerization aid used is less than 0.085 mol per mol of sulfidating agent, the amount of dihalogenated aromatic compound used in the mixture is 0.085 mol per mol of sulfur of the sulfidating agent. The amount is preferably .95 mol or more and 2.00 mol or less. Further, a more preferable lower limit is 1.00 mol or more per 1 mol of sulfur in the sulfidating agent, and a more preferable upper limit is 1.50 mol or less per 1 mol of sulfur in the sulfidating agent, and 1.20 mol or less is more preferable. More preferably, 1.10 mol or less is even more preferable. On the other hand, when the amount of the polymerization aid used is 0.085 mol or more per 1 mol of sulfur of the sulfidating agent, the amount of the dihalogenated aromatic compound used in the mixture is 1 mol or more per 1 mol of sulfur of the sulfidating agent. The amount is preferably .04 mol or more and 2.00 mol or less. Further, a more preferable lower limit is 1.043 mol or more per 1 mol of sulfur in the sulfidating agent, and a more preferable upper limit is 1.50 mol or less per 1 mol of sulfur in the sulfidating agent, and 1.20 mol or less is more preferable. More preferably, 1.10 mol or less is even more preferable. When the amount of the dihalogenated aromatic compound used is within the above-mentioned preferred range, the molecular weight of the PAS can be easily controlled within the preferred range of the present invention, and a PAS that generates a small amount of gas upon heating can be obtained.

Note that the dihalogenated aromatic compound may be introduced into the system at any timing, but it is preferable to introduce it after performing the dehydration operation described below. Further, as a preparation method, not only a method of preparing the entire amount at once but also a method of introducing it in stages can be adopted.

Here, in the present invention, Step 3 is carried out after the polymerization reaction of Step 2 is completed, and this "completion of the polymerization reaction" means heating until the conversion rate of the charged dihalogenated aromatic compound reaches 97% or more. This refers to the state in which a reaction occurs. After converting the dihalogenated aromatic compound to such a conversion rate, the molecular weight of PAS can be controlled within the preferred range of the present invention by carrying out step 3, which will be described later. The average particle size can be increased. In addition, in the present invention, the polymerization reaction is considered to have ended when the conversion rate of the dihalogenated aromatic compound reaches 97% or more, but there is also a method of further increasing the conversion rate of the dihalogenated aromatic compound by continuing the reaction. Preferably adopted. In this case, the lower limit of the conversion rate of the dihalogenated aromatic compound in the polymerization reaction is more preferably 98% or more, and even more preferably 98.5% or more. When the conversion rate is equal to or higher than this preferable lower limit, there is a tendency that contamination of unreacted monomers into the granular PAS can be suppressed in the recovery of the granular PAS described later. On the other hand, due to the calculation formula below, the upper limit may exceed 100% and varies depending on the amount of the dihalogenated aromatic compound used, so it cannot be absolutely defined, but if all the dihalogenated aromatic compounds used are The conversion rate in the case of conversion can be said to be the preferable upper limit. When the conversion rate of the dihalogenated aromatic compound is within the above-described preferred range, it is easier to control the molecular weight of PAS within the preferred range of the present invention, and there is a tendency to increase the average particle size of granular PAS. In the present invention, the remaining amount of the dihalogenated aromatic compound in the polymerization reaction solution is estimated by gas chromatography, and the amount of the dihalogenated aromatic compound is estimated from the ratio to the amount of the charged sulfidating agent or the charged dihalogenated aromatic compound. Calculate the conversion rate of the compound. The calculation formula is as follows.
(a) When dihalogenated aromatic compound is used in excess molar ratio to sulfidation agent Conversion rate of dihalogenated aromatic compound (%) = [Amount of charged dihalogenated aromatic compound (mol) - Dihalogenation Remaining amount of aromatic compound (mol)]/Amount of charged sulfidating agent (mol) x 100
(b) Cases other than the above (a) Conversion rate of dihalogenated aromatic compound (%) = [Amount of charged dihalogenated aromatic compound (mol) - Remaining amount of dihalogenated aromatic compound (mol)] / Charged Amount of dihalogenated aromatic compound (mol) x 100.

Here, the amount of sulfidating agent charged refers to the amount of sulfidating agent that was present in the system at the time of starting the polymerization reaction, and some of the sulfidating agent was dissolved into hydrogen sulfide by the dehydration operation before the start of the polymerization reaction. When the sulfidating agent is removed from the system as a hydrogen sulfide, estimate the amount of the sulfidating agent present in the system at the start of the polymerization reaction, taking into account the number of moles of hydrogen sulfide scattered.

In addition, the amount of dihalogenated aromatic compound charged refers to the amount of dihalogenated aromatic compound that was present in the system at the time of starting the polymerization reaction. When the group compound is removed from the system, the amount of the dihalogenated aromatic compound present in the system at the start of the polymerization reaction is estimated, taking into account the number of moles dispersed.

(7-3) Process 3
In step 3, after the polymerization reaction is completed, the water content in the reaction system is adjusted to 3.3 mol or more and 6.0 mol or less per 1 mol of sulfur, and the temperature is adjusted to T0 (240°C≦T0≦290°C). The pressure P3 in the temperature range of step 3 is 1.0 MPaG or more and 2.0 MPaG or less. It is thought that this operation further promotes the phase separation state within the system. Here, T0 corresponds to the temperature at which the slow cooling operation is started in Step 4, which is carried out following Step 3, and is not the temperature immediately after the adjustment of the moisture content in Step 3 is completed. From the viewpoint of streamlining the manufacturing time cycle, it is preferable to control the temperature so that it reaches T0 when the moisture content adjustment is completed in step 3, but if the temperature is not within the T0 range when the moisture content adjustment is completed. In this case, the temperature may be adjusted to T0 before starting the slow cooling operation in step 4. However, when the amount of the organic polar solvent used is within the preferred range of the present invention, it is important to control the temperature in step 3 so that it does not fall below 240°C in order to obtain PAS particles with a large particle size. Here, the amount of water in the reaction system is the sum of the water present in the system at the end of the polymerization reaction and the water added to the system after the end of the polymerization reaction. It is necessary to determine the amount of water to be added to the system, taking into account the amount of water that was present. In addition, if the water content in the system at the end of the polymerization reaction exceeds 6.0 mol per 1 mol of sulfur, the water content in the system will be 3.3 mol or more and 6.0 mol or less per 1 mol of sulfur. Perform the dehydration operation as follows. An example of this dehydration operation is a method of heating and removing water by distillation.

If the amount of water in the reaction system is less than 3.3 moles per mole of sulfur, phase separation in the system is difficult to promote, and when cooling is performed in the subsequent step 4, the average particle diameter of the PAS particles is Difficult to increase. Furthermore, if the amount of water in the reaction system exceeds 6.0 moles per mole of sulfur, the pressure in the system will become significantly high, leading to safety problems. Here, as a preferable range of the amount of water in the reaction system in step 3, a preferable lower limit is 3.5 mol or more per 1 mol of sulfur, and a preferable upper limit is 5.0 mol or less per 1 mol of sulfur. can. When the amount of water in the reaction system in step 3 is in the above-described preferred range, it is possible to further increase the average particle diameter of the granular PAS while keeping the pressure in the system lower.

As described in Patent Document 6, it has been known that the average particle diameter of granular PAS increases by adding water at the end of the polymerization reaction to cause phase separation in the system. It was not known that it differs depending on the size of the molecular weight. It is assumed that PAS with a large molecular weight is easily affected by phase separation even with a small water content and grows to a certain particle size without strictly controlling the cooling rate, making it easier to obtain granular PAS with a high yield. However, if a similar effect is to be obtained using PAS with a small molecular weight, precise control of both the water content and the cooling rate is required. Through intensive verification, the inventors of the present invention have clarified the conditions of water content and cooling rate that can sufficiently grow the average particle size of the polymer even in the production of low molecular weight PAS, and have completed the present invention. .

Note that when step 3 is performed to promote phase separation in the system, not only the average particle diameter of the resulting granular PAS increases, but also the hardness of the particles tends to increase. It is more preferable that the hardness of the particles increases because it is possible to suppress the reduction in size due to particle crushing during the recovery operation of granular PAS. There are various methods for measuring the hardness of this particle, but in the present invention, first, the granular PAS whose average particle diameter has been measured is added to N-methyl-2-pyrrolidone at a concentration of 10% by weight. The dispersion was shaken at room temperature for 5 minutes using a shaker (Azu One TUBE MIXER TRIO HM-1N, scale 10), and the average particle size after the treatment was measured again. It was estimated by calculating the value (%) when divided by the original average particle diameter.

In step 3, there is no particular restriction on the method of adding water into the system, and any known addition method such as a method using a liquid addition pump or a method using shower spraying can be employed. Moreover, it is preferable to add water while stirring the inside of the reaction system.

Here, in step 3, water is added to bring the temperature to T0 (240°C≦T0≦290°C), but if T0<240°C, PAS tends to precipitate as fine particles at the time of step 3. Therefore, even if the subsequent step 4 is performed, it is difficult to sufficiently increase the average particle diameter of the PAS particles. Furthermore, if T0>290°C, the pressure within the system becomes significantly high, which poses a safety problem. Therefore, T0 needs to be 240°C≦T0≦290°C. Note that depending on the temperature of the water to be added, the inside of the system may be cooled by the water addition operation, so it is preferable to continue heating in step 3 in order to control T0 within the above range. In addition, as a preferable range of T0, the range of 240 degreeC<=T0<=260 degreeC can be illustrated preferably. When T0 is in the above-described preferable range, the time required for the slow cooling operation in the subsequent step 4 can be shortened, and granular PAS can be efficiently produced in a shorter time.

In addition, in step 3, the rate at which water is added to the system cannot be clearly specified because it also affects the scale of the reaction system, but it is preferable to set an appropriate rate in order to maintain the above temperature. . In addition, from the viewpoint of productivity, it is important to shorten the time required for water addition. A preferable example is a water addition rate that allows the target amount of water to be added within a certain amount of time.

Here, the pressure P3 is the maximum pressure (gauge pressure) in the system in the temperature range of step 3. The lower limit of the pressure P3 is 1.0 MPaG or more, more preferably 1.1 MPaG or more, and even more preferably 1.2 MPaG or more. Moreover, the upper limit is 2.0 MPaG or less, more preferably 1.95 MPaG or less, and even more preferably 1.9 MPaG or less. When the pressure within the reaction system is in the above-mentioned range, the sulfidating agent and the dihalogenated aromatic compound, which are the raw materials, tend to be rapidly consumed by reaction, and the use of expensive pressure-resistant equipment tends to be avoided.

(7-4) Process 4
In step 4, following step 3, cooling is performed from temperature T0 to T1 (200°C≦T1≦235°C) at a cooling rate S1 (0.2°C/min≦S1≦0.8°C/min) until temperature T1. After cooling, the cooling rate is changed to S2 (0.8° C./min<S2≦5° C./min) for further cooling. By this operation, PAS which was in a dissolved state is precipitated and its particle size increases. Here, S1 is the cooling rate in the slow cooling operation, which is important for precipitating PAS and increasing its particle size, and T1 is the temperature at which the slow cooling operation ends at the cooling rate S1. Moreover, S2 is the cooling rate in the rapid cooling operation for cooling the granular PAS to a temperature suitable for recovering it.

The cooling rates S1 and S2 in the present invention refer to the average cooling rate, and are calculated by dividing the temperature difference from the temperature determined as the starting point to the temperature determined as the end point by the total time required for cooling the temperature difference. do. However, regarding the cooling rate S1 of the slow cooling operation, which has a large effect on the growth of PAS particles, the cooling rate per minute time, the so-called instantaneous cooling rate, is also important, and regarding this instantaneous cooling rate, the regulation of S1 should be kept as much as possible. It is preferable to meet the requirements. Specifically, a state in which the instantaneous cooling rate satisfies the regulation of S1 for preferably 90% or more, more preferably 95% or more of the time required for the slow cooling operation to perform cooling at cooling rate S1. When the instantaneous cooling rate is controlled at such a preferable rate, it is possible to further increase the average particle diameter of the PAS particles. Conversely, if the time required for the slow cooling operation is preferably less than 10%, more preferably less than 5%, there is a time when the instantaneous cooling rate deviates from the specification of S1. However, it can be said that there is no problem as long as the purpose of the present invention is not essentially impaired. Examples of situations in which the instantaneous cooling rate deviates from the specifications are not only cases where the cooling rate simply deviates, but also cases in which the temperature rises for a short period of time due to heat generation when PAS crystallizes, etc. are acceptable.

Here, the cooling rate S1 needs to be 0.2°C/min≦S1≦0.8°C/min. When S1<0.2° C./min, the time required for cooling becomes significantly longer and productivity decreases. Further, when S1>0.8° C./min, the average particle diameter of granular PAS does not increase sufficiently, and a decrease in PAS yield is observed. A preferable range of S1 is 0.2°C/min≦S1≦0.7°C/min, and a more preferable range is 0.2°C/min≦S1≦0.6°C/min. I can give an example. When S1 is within the above-mentioned preferred range, it is possible to further increase the average particle diameter of the PAS particles, and there is a tendency for granular PAS to be obtained with better productivity and high yield.

Further, T1 in the present invention needs to be 200°C≦T1≦235°C. When T1<200° C., the time required for cooling becomes significantly longer and productivity decreases. Moreover, when T1>235°C, the average particle diameter of granular PAS does not increase sufficiently, and a decrease in PAS yield and quality is observed. In addition, as a preferable range of T1, 210 degreeC<=T1<=235 degreeC can be illustrated. When T1 is in the above-described preferable range, the time required for the slow cooling operation in step 2 can be shortened, and granular PAS can be efficiently produced in a shorter time.

As described in Patent Document 5, the technique of obtaining granular PAS having a high bulk density by selectively slow cooling in an extremely limited temperature range of the maximum thickening temperature ±1°C has been known in the past. However, it was not known that this effect is difficult to obtain with low molecular weight PAS, which has high affinity with solvents and low cohesive force between particles. PAS, which has a large molecular weight, has a low affinity with solvents and a high cohesive force between particles, so even if slow cooling is performed for a short time, particle growth due to aggregation progresses in the subsequent rapid cooling process, resulting in poor yield. It is estimated that granular PAS can be easily obtained. However, when trying to obtain the same effect with PAS having a small molecular weight, it is considered necessary to grow a single particle to a large size by setting a longer slow cooling time because the cohesive force is small. Through intensive verification, the inventors of the present invention discovered that even in the production of low molecular weight PAS, particles can be grown sufficiently by continuing slow cooling to a temperature of 200°C≦T1≦235°C. The invention has been completed.

Further, in step 4, after slow cooling is performed from T0 to T1 at a cooling rate S1, the cooling rate is changed to S2 (0.8° C./min<S2≦5° C./min) and further rapid cooling is performed. If S2≦0.8° C./min, the time required for step 4 becomes significantly longer and productivity decreases. Furthermore, if S2>5° C./min, there is a concern that the rapid temperature change may have an adverse effect on the device. Note that a preferable range of S2 is 1.5°C/min≦S2≦4°C/min. When S2 is in the above-mentioned preferred range, the time required for the rapid cooling operation in step 4 can be shortened, and granular PAS can be efficiently produced in a shorter time.

Here, the temperature at which the rapid cooling operation at the cooling rate S2 is started is T1, but there is no particular restriction on the temperature at which the rapid cooling operation is ended. For example, in order to recover the polymerization reaction liquid, it may be rapidly cooled to around room temperature, or when proceeding to the recovery operation of granular PAS without recovering the polymerization reaction liquid, it may be rapidly cooled at the temperature at which the granular PAS is recovered. You can stop. Therefore, the temperature at which the quenching operation ends cannot be absolutely defined, but for example, a temperature of 15° C. or higher and 170° C. or lower can be exemplified.

Generally, PAS obtained by reacting a sulfidating agent and a dihalogenated aromatic compound in the presence of an alkali metal hydroxide in an organic polar solvent contains nitrogen. This is because the alkali metal alkylaminoalkyl carboxylate produced by the reaction between an organic polar solvent such as NMP and an alkali metal hydroxide reacts with the PAS terminal as a side reaction during polymerization, forming a terminal having a nitrogen atom. It's for a reason. The nitrogen content of the PAS obtained in the present invention is 600 ppm or more and 1500 ppm or less. If the nitrogen content is significantly less than 600 ppm, the reactivity with various coupling agents used during melt extrusion to increase the toughness and strength of PAS will decrease. The lower limit of the nitrogen content of PAS for this purpose is more preferably 650 ppm or more, and even more preferably 700 ppm or more. The upper limit is preferably 1400 ppm or less, more preferably 1300 ppm or less. If the nitrogen content derived from impurities is too high, the amount of volatile components will be excessive when PAS is injection molded, which may easily cause defects in the appearance of the molded product or increase the amount of impurities attached to the mold. Otherwise, the workability during molding process will be significantly reduced.

The method for bringing the nitrogen content of PAS into the above preferred range is not particularly limited as long as such PAS can be obtained, but for example, the polymerization time in step 2 until the polymerization reaction is completed is 60 minutes or more. It is preferable to set it as 300 minutes or less. The nitrogen content of PAS is measured by thermally decomposing and oxidizing the sample at a final temperature of 900°C using a horizontal reactor, and applying the generated nitrogen monoxide to a nitrogen detector ND-100 manufactured by Mitsubishi Chemical Analytech. be able to.

(8) Other Post-Processing The granular PAS thus obtained has an average particle size of 500 μm or more and 1,500 μm or less, although it is a low molecular weight PAS, and it is possible to obtain a granular PAS with a sufficiently large particle size. The lower limit of the particle size is more preferably 600 μm or more, and the upper limit is more preferably 1,000 μm or less. Particulate PAS with such a particle size can be easily separated by, for example, filtering with a stainless steel sieve. It is recoverable.

As described above, in the present invention, evaluation is performed using a sieve with an opening of 177 μm, 80 mesh, and the Tyler standard. Here, the granular PAS obtained by filtering through a sieve or the like as described above may be washed with an organic solvent and/or water and dried as other post-treatments. By performing such a post-treatment, organic polar solvents, ionic compounds, oligomer components, unreacted monomers, etc. contained in the granular PAS are removed, and a higher quality granular PAS tends to be obtained.

Here, the organic solvent used for cleaning is not particularly limited as long as it does not have the effect of decomposing PAS, but for example, nitrogen-containing polar solvents such as N-methyl-2-pyrrolidone, dimethylformamide, and dimethylacetamide. , sulfoxide/sulfone solvents such as dimethyl sulfoxide and dimethyl sulfone, ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, and acetophenone, ether solvents such as dimethyl ether, dipropyl ether, and tetrahydrofuran, chloroform, methylene chloride, trichloroethylene, and dichloride. Halogenated solvents such as ethylene, dichloroethane, tetrachloroethane, chlorobenzene, alcohol/phenolic solvents such as methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, phenol, cresol, polyethylene glycol, benzene, toluene , aromatic hydrocarbon solvents such as xylene, etc. Among these organic solvents, N-methyl-2-pyrrolidone, acetone, dimethylformamide, chloroform and the like are preferably used. Further, these organic solvents may be used alone or in combination of two or more.

As a method for washing with an organic solvent, there is a method such as immersing the PAS in an organic solvent, and it is also possible to stir or heat as appropriate if necessary.

Although there is no particular restriction on the cleaning temperature when cleaning PAS with an organic solvent, for example, a temperature from room temperature to 300° C. or less can be exemplified. Although cleaning efficiency tends to increase as the cleaning temperature increases, sufficient effects can usually be obtained by cleaning at temperatures from room temperature to 150° C. or lower. As for the ratio of PAS to organic solvent, it is preferable that the amount of organic solvent is large, but usually a bath ratio of 300 g or less of PAS to 1 liter of organic solvent is selected. Furthermore, it is preferable that the PAS that has been washed with an organic solvent be washed several times with water or hot water in order to remove the remaining organic solvent.

When washing PAS with water or warm water, there is a method such as immersing PAS in water or warm water, and it is also possible to stir or heat as necessary.

There is no limit to the temperature at which PAS is washed with water or hot water, but it is preferably carried out at a temperature of 20°C or more and 220°C or less, more preferably 50°C or more and 200°C or less. If the cleaning temperature is less than 20°C, it will be difficult to remove by-products, and if it exceeds 220°C, high pressure will result, which is unfavorable from a safety standpoint.

The water used for water or hot water cleaning is preferably distilled water or deionized water, but if necessary, formic acid, acetic acid, propionic acid, butyric acid, chloroacetic acid, dichloroacetic acid, acrylic acid, crotonic acid, benzoic acid, Organic acidic compounds such as salicylic acid, oxalic acid, malonic acid, succinic acid, phthalic acid, and fumaric acid; their alkali metal and alkaline earth metal salts; inorganic acidic compounds such as sulfuric acid, phosphoric acid, hydrochloric acid, carbonic acid, and silicic acid; and ammonium ions. You may use the aqueous solution containing etc.

The hydrothermal treatment is usually carried out by adding a predetermined amount of PAS to a predetermined amount of water, heating and stirring at normal pressure or in a pressure vessel. As for the ratio of PAS to water, the more water the better, but usually a bath ratio of 200 g or less of PAS to 1 liter of water is selected.

(9) Characteristics of granular PAS obtained by the present invention The granular PAS obtained by the method of the present invention has excellent heat resistance, chemical resistance, flame retardance, electrical properties, and mechanical properties, and has a low by-product content. It can be used as a PAS with excellent moldability since it produces less gel and gas during molding. Furthermore, it can be used not only for injection molding, but also for a wide range of extrusion molded products such as fibers, sheets, films, and pipes. Furthermore, while the PAS obtained by the present invention has the above-mentioned excellent characteristics, it also has particularly excellent flow characteristics when melted, so it is easy to consider thinning and weight reduction in designing PAS products. Furthermore, the effect of shortening the solidification time, that is, the molding cycle time, by making the product thinner can be expected.

In addition, the PAS obtained in the present invention may be used alone or, if desired, may include glass fibers, carbon fibers, inorganic fillers such as titanium oxide, calcium carbonate, antioxidants, heat stabilizers, ultraviolet rays, etc. Absorbers, colorants, etc. can also be added, such as polyamide, polysulfone, polyphenylene, polycarbonate, polyether sulfone, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene, epoxy group, carboxyl group, carboxylic acid ester. It is also possible to blend resins such as olefin copolymers, polyolefin elastomers, polyether ester elastomers, polyether amide elastomers, polyamideimides, polyacetals, and polyimides having functional groups such as groups and acid anhydride groups.

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

<Analysis of sulfidating agent>
The determination of the sulfidating agent (for example, the determination of hydrogen sulfide and sodium bisulfide) in the dehydration distillate and the polymerization reaction solution was carried out using ion chromatography under the following conditions.
Equipment: Shimadzu HIC-20Asuper
Column: Shimadzu Shim-pack IC-SA2 (250mm x 4.6mm ID)
Detector: Electric conductivity detector (suppressor)
Eluent: 4.0mM sodium bicarbonate/1.0mM sodium carbonate aqueous solution Flow rate: 1.0ml/min Injection volume: 50 microliters Column temperature: 30°C.

After adding hydrogen peroxide solution to the sample to oxidize the sulfide ions contained in the sample, it was quantified as sulfate ion by the above analysis, and when an untreated sample without adding hydrogen peroxide solution was analyzed. The amount of sulfide ions in the sample was calculated by subtracting the quantitative value of sulfate ions. The amount of sulfide ions calculated here was taken as the amount of the remaining sulfidating agent, and the conversion rate of the sulfidating agent was calculated from the ratio of the amount of the sulfidating agent charged. The calculation formula is as follows.
Conversion rate of sulfidating agent (%) = [[Amount of charged sulfidating agent (mol) - Amount of remaining sulfidating agent (mol)]/[Amount of charged sulfidating agent (mol)]] x 100% .

Here, the amount of sulfidating agent charged refers to the amount of sulfidating agent present in the system at the start of polymerization, and the amount of hydrogen sulfide removed from the system by dehydration etc. before the start of polymerization. If it exists, calculate it by taking into consideration the number of moles scattered.

<Analysis of dihalogenated aromatic compounds>
Quantification of dihalogenated aromatic compounds in the reaction solution (for example, quantification of p-dichlorobenzene) was carried out using gas chromatography (GC) under the following conditions.
Equipment: Shimadzu GC-2010
Column: J&W DB-5 0.32mm x 30m (0.25μm)
Carrier gas: Helium Detector: Flame ionization detector (FID).

<Yield of granular PAS>
The yield of granular PAS was calculated as the ratio of the yield of granular PAS to the weight (theoretical amount) assuming that all the sulfidating agent present in the system was converted to PAS after the dehydration operation.

<Measurement of molecular weight>
The molecular weight was calculated by gel permeation chromatography (GPC), which is a type of size exclusion chromatography (SEC).

5 mg of granular PAS was added to 5 g of 1-chloronaphthalene, heated to 250° C., dissolved, filtered through a membrane filter with a pore size of 0.1 μm, and the filtrate was cooled to room temperature to obtain a slurry solution. The obtained solution was analyzed as a sample under the following conditions, and the number average molecular weight (Mn) and weight average molecular weight (Mw) were calculated in terms of polystyrene.
Equipment: SSC-7110 manufactured by Senshu Kagakusha
Column name: Shodex UT806M x 2
Eluent: 1-chloronaphthalene Detector: Differential refractive index detector Column temperature: 210°C
Pre constant temperature bath temperature: 250℃
Pump constant temperature bath temperature: 50℃
Detector temperature: 210℃
Flow rate: 1.0mL/min
Sample injection volume: 300 μL.

<Measurement of average particle diameter>
The average particle diameter was measured using a laser diffraction particle size distribution analyzer under wet conditions using N-methyl-2-pyrrolidone as a dispersion solvent.
Equipment: Laser particle size distribution analyzer (SALD-2100) manufactured by Shimadzu Corporation.

<Measurement of particle hardness>
To measure the hardness of particles, first, the granular PAS whose average particle diameter was measured was dispersed in N-methyl-2-pyrrolidone to a concentration of 10% by weight, and the dispersion was placed in a shaker (As One TUBE MIXER TRIO). Shake at room temperature for 5 minutes using HM-1N (scale 10), re-measure the average particle size after treatment, and calculate the value (%) of the average particle size after treatment divided by the original average particle size. I estimated it by doing this.

<Nitrogen content>
The sample was thermally decomposed and oxidized using a horizontal reactor at a final temperature of 900°C, and the nitrogen monoxide produced was subjected to a nitrogen detector ND-100 manufactured by Mitsubishi Chemical Analytech Co., Ltd. to measure the nitrogen content in the polymer.

[Example 1]
A distillation device and an alkali trap were connected to an autoclave equipped with a stirrer, and 117 g (1.00 mol) of a 47.7% aqueous sodium hydrogen sulfide solution and 81.2 g (1.02 mol) of a 49.5% aqueous sodium hydroxide solution were added. mol), 164 g (1.65 mol) of N-methyl-2-pyrrolidone, and 7.30 g (0.09 mol) of sodium acetate were charged, and the inside of the reaction vessel was sufficiently purged with nitrogen.

A distillation column was attached to the upper part of the autoclave via a valve, and the autoclave was gradually heated to 237° C. over 3 hours while stirring at 240 rpm and nitrogen was passed under normal pressure to remove the liquid, thereby obtaining 103 g of distillate. Analysis of this distillate by gas chromatography revealed that the composition of the distillate was 101 g of water and 2 g of N-methyl-2-pyrrolidone. At this stage, 1.9 g (0.11 mol) of water was present in the reaction system. ), and it was found that 162 g of N-methyl-2-pyrrolidone remained. Note that 0.02 mole of hydrogen sulfide was scattered from the reaction system during the dehydration operation. As a result, the amount of polymerization aid used in the mixture was 0.09 mol per 1 mol of sulfidation agent.

Next, after cooling the autoclave to 160°C or lower, 152 g (1.03 mol) of p-dichlorobenzene and 127 g (1.29 mol) of N-methyl-2-pyrrolidone were charged, and the inside of the reaction vessel was again thoroughly purged with nitrogen. and sealed. As a result, the amount of dihalogenated aromatic compound used in the mixture was 1.047 mol per 1 mol of sulfidation agent. Note that the internal temperature decreased to 130° C. during the charging operation. Subsequently, the temperature was raised from 130°C to 200°C while stirring at 400 rpm.

The temperature was increased over 91 minutes from 200°C to just before reaching 245°C (Step 1). The polymerization time TM1 of Step 1 including the temperature raising/lowering time of Step 1 was 91 minutes, and P1 was 0.6 MPaG.

Subsequently, the temperature was raised to 275°C over 40 minutes, and the temperature was further maintained at 275°C for 70 minutes to cause a reaction (Step 2). The polymerization time TM2 until the end of the polymerization reaction in the temperature range of Step 2 was 110 minutes, and P2 was 1.1 MPaG. Here, it was confirmed from Reference Example 1 below that the conversion rate of the dihalogenated aromatic compound was 98.6%. The amount of water in the system in Step 2 was 1.1 moles per mole of sulfur, including the moles of water produced during polymerization (= moles of the sulfidating agent consumed in the reaction, see Reference Example 1). During this time, a liquid addition pump was connected via the autoclave valve.

After the polymerization reaction was completed, 49.6 g of water was added into the autoclave over 30 minutes using a liquid addition pump (Step 3). As a result, the amount of water in the system in step 3 is 3.9 moles per mole of sulfur, including the moles of water produced during polymerization (= moles of the sulfidating agent consumed in the reaction, see Reference Example 1). Ta. Note that the temperature control by the heater was continued even during the addition of water, and the internal temperature was controlled so as not to fall below 240°C. At the end of water addition, the internal temperature was 240°C and P3 was 1.6 MPaG.

After the addition of water was completed, a slow cooling operation was performed from T0 = 240°C to T1 = 215°C at a cooling rate S1 = 0.4°C/min (Step 4). After cooling to 215°C, the cooling rate was changed to S2 = 4°C/min, and further cooling was performed to 170°C, and then rapidly cooled to room temperature.

After that, the contents were taken out and diluted with 210 g of N-methyl-2-pyrrolidone, and the solvent and solids were filtered through an 80-mesh stainless steel sieve (openings 177 μm). The mixture was washed twice and filtered to obtain polymer particles. This was dried under reduced pressure at 120°C.

The yield of the obtained granular polyphenylene sulfide was 84%, the weight average molecular weight Mw was 25,000, the average particle diameter of the polymer was 647 μm, and the nitrogen content was 9×10^2 ppm.

In addition, when the particle hardness of the obtained polymer was measured, the average particle diameter after the shaking treatment was 631 μm, and the value obtained by dividing the average particle diameter after the treatment by the original average particle diameter was 98%. .

[Reference example 1]
After polymerization was carried out in the same manner as in Example 1, in step 3, the autoclave was cooled by air cooling without adding water, and the polymerization reaction liquid was collected after cooling. When the polymerization reaction solution was analyzed for the sulfidating agent, the conversion rate of the sulfidating agent was 97%. Therefore, the amount of water produced during polymerization can be calculated to be 0.96 mol, and when added to the 0.11 mol of water remaining in the system before the start of polymerization, the amount of water present in the system at the end of polymerization is 1. The total amount is 0.7 mole. (1.1 mol per 1 mol of sulfur) Furthermore, when the dihalogenated aromatic compound was analyzed for the polymerization reaction solution, the conversion rate of the dihalogenated aromatic compound was 98.6%.

[Comparative example 1]
After completion of the polymerization reaction in Step 2, granular polyphenylene sulfide was produced in the same manner as in Example 1, except that the amount of water added in Step 3 was changed to 38.1 g. (The amount of water in the system after water addition is 3.2 moles per mole of sulfur, including the moles of water produced during polymerization.) The pressure P3 in step 3 was 1.4 MPaG.

As a result, the yield of the obtained granular polyphenylene sulfide was 80%, the weight average molecular weight Mw was 24,000, the average particle diameter of the polymer was 449 μm, and the nitrogen content was 9×10^2 ppm.

In addition, when the particle hardness of the obtained polymer was measured, the average particle diameter after the shaking treatment was 388 μm, and the value obtained by dividing the average particle diameter after the treatment by the original average particle diameter was 86%. .

[Comparative example 2]
Granular polyphenylene sulfide was produced in the same manner as in Example 1, except that the cooling from T0 = 240 °C to T1 = 215 °C after the completion of water addition was performed at a cooling rate of S1 = 4.0 °C / min. .

As a result, the yield of the obtained granular polyphenylene sulfide was 72%, the weight average molecular weight Mw was 25,000, the average particle diameter of the polymer was 350 μm, and the nitrogen content was 9×10^2 ppm.

[Example 2]
After completion of the polymerization reaction in Step 2, granular polyphenylene sulfide was produced in the same manner as in Example 1, except that the amount of water added in Step 3 was changed to 66.0 g. (The amount of water in the system after water addition is 4.8 mol per 1 mol of sulfur, including the mole of water produced during polymerization.) The pressure P3 in step 3 was 1.9 MPaG.

As a result, the yield of the obtained granular polyphenylene sulfide was 90%, the weight average molecular weight Mw was 25,000, the average particle diameter of the polymer was 642 μm, and the nitrogen content was 9×10^2 ppm.

In addition, when the particle hardness of the obtained polymer was measured, the average particle diameter after the shaking treatment was 636 μm, and the value obtained by dividing the average particle diameter after the treatment by the original average particle diameter was 99%. .

[Example 3]
After completion of the polymerization reaction in step 2, granular polyphenylene sulfide was produced in the same manner as in Example 1, except that the slow cooling start temperature T0 was set to 250°C and the slow cooling operation was performed at a cooling rate S1 = 0.2°C/min. was carried out. The pressure P3 in step 3 was 1.8 MPaG.

As a result, the yield of the obtained granular polyphenylene sulfide was 84%, the weight average molecular weight Mw was 25,000, the average particle diameter of the polymer was 750 μm, and the nitrogen content was 9×10^2 ppm.

[Example 4]
After completion of the polymerization reaction in step 2, granular polyphenylene sulfide was produced in the same manner as in Example 1, except that the slow cooling start temperature T0 was set to 250°C and the slow cooling end temperature T1 was set to 235°C. The pressure P3 in step 3 was 1.8 MPaG.

As a result, the yield of the obtained granular polyphenylene sulfide was 84%, the weight average molecular weight Mw was 25,000, the average particle diameter of the polymer was 700 μm, and the nitrogen content was 9×10^2 ppm.

[Comparative example 3]
After completion of the polymerization reaction in step 2, granular polyphenylene sulfide was produced in the same manner as in Example 1, except that the slow cooling start temperature T0 was set to 250°C and the slow cooling operation was performed at a cooling rate S1 = 0.9°C/min. was carried out. P3 in step 3 was 1.8 MPaG.

As a result, the yield of the obtained granular polyphenylene sulfide was 80%, the weight average molecular weight Mw was 25,000, the average particle diameter of the polymer was 400 μm, and the nitrogen content was 9×10^2 ppm.

[Comparative example 4]
After completion of the polymerization reaction in step 2, granular polyphenylene sulfide was produced in the same manner as in Example 1, except that the temperature T0 at which slow cooling was started was set to 235°C. The pressure P3 in step 3 was 1.8 MPaG.

As a result, the yield of the obtained granular polyphenylene sulfide was 81%, the weight average molecular weight Mw was 25,000, the average particle diameter of the polymer was 450 μm, and the nitrogen content was 9×10^2 ppm.

[Comparative example 5]
After completion of the polymerization reaction in step 2, granular polyphenylene sulfide was produced in the same manner as in Example 1, except that the slow cooling start temperature T0 was 250°C and the slow cooling end temperature T1 was 242°C. The pressure P3 in step 3 was 1.8 MPaG.

As a result, the yield of the obtained granular polyphenylene sulfide was 81%, the weight average molecular weight Mw was 25,000, the average particle diameter of the polymer was 450 μm, and the nitrogen content was 9×10^2 ppm.

[Comparative Example 6]
A distillation device and an alkali trap were connected to an autoclave equipped with a stirrer, and 116.8 g (1.00 mol) of a 48% aqueous sodium hydrogen sulfide solution and 84.1 g (1.01 mol) of a 48% aqueous sodium hydroxide solution were added. , 164 g (1.65 mol) of N-methyl-2-pyrrolidone, 8.0 g (0.10 mol) of sodium acetate, and 100 g of water were charged, and the inside of the reaction vessel was sufficiently purged with nitrogen.

A distillation column was attached to the upper part of the autoclave via a valve, and the liquid was removed by gradually heating to 220°C over 2.5 hours while stirring at 240 rpm under nitrogen at normal pressure, and 202.5 g of water, N-methyl- 2g of 2-pyrrolidone was distilled out. At this stage, it was found that 2.0 g (0.11 mol) of water remained in the reaction system and 162 g of N-methyl-2-pyrrolidone remained. Note that 0.02 mole of hydrogen sulfide was scattered from the reaction system during the dehydration operation. As a result, the amount of polymerization aid used in the mixture was 0.010 mol per 1 mol of sulfidation agent.

Next, after cooling the autoclave to below 160°C, 147 g (1.0 mol) of p-dichlorobenzene and 132 g (1.33 mol) of N-methyl-2-pyrrolidone were charged, and the inside of the reaction vessel was again thoroughly purged with nitrogen. and sealed. As a result, the amount of dihalogenated aromatic compound used in the mixture was 1.02 mol per 1 mol of sulfidation agent. Subsequently, the temperature was raised to 200°C.

The temperature was increased over 147 minutes from 200°C to just before reaching 245°C (Step 1). The polymerization time TM1 of Step 1 including the temperature raising/lowering time of Step 1 was 147 minutes, and P1 was 0.7 MPaG.

Subsequently, the temperature was raised to 270° C. over 31 minutes (Step 2). The polymerization time TM2 until the end of the polymerization reaction in the temperature range of Step 2 was 31 minutes, and P2 was 1.2 MPaG. Here, it was confirmed that the conversion rate of the dihalogenated aromatic compound was 91%. The amount of water in the system in Step 2 was 1.0 mol per 1 mol of sulfur, including the mole of water produced during polymerization (=mol of sulfidating agent consumed by reaction). During this time, a liquid addition pump was connected via the autoclave valve.

After reaching 270°C, it was immediately cooled to 250°C over 15 minutes. At that time, using a liquid addition pump in the system, 35.6 g of water was added into the autoclave over 15 minutes (Step 3). As a result, the amount of water in the system in Step 3 was 3.0 moles per mole of sulfur, including the moles of water produced during polymerization (= moles of the sulfidating agent consumed in the reaction). P3 was 1.5 MPaG.

After the addition of water was completed, a slow cooling operation was performed from T0 = 250°C to T1 = 220°C at a cooling rate S1 = 0.4°C/min (Step 4). After cooling to 220°C, the cooling rate was changed to S2 = 4°C/min, and further cooling was performed to 170°C, and then rapidly cooled to room temperature.

The subsequent treatments were carried out in the same manner as in Example 1.

The yield of the obtained granular polyphenylene sulfide was 83%, the weight average molecular weight Mw was 27,000, the average particle diameter of the polymer was 432 μm, and the nitrogen content was 4×10^2 ppm.

[Comparative Example 7]
A distillation device and an alkali trap were connected to an autoclave equipped with a stirrer, and 116.8 g (1.00 mol) of a 48% aqueous sodium hydrogen sulfide solution and 82.6 g (0.99 mol) of a 48% aqueous sodium hydroxide solution were added. , 268.5 g (2.71 mol) of N-methyl-2-pyrrolidone were charged, and the inside of the reaction vessel was sufficiently purged with nitrogen.

A distillation column was attached to the upper part of the autoclave via a valve, and the liquid was removed by gradually heating to 220°C over 2.5 hours while stirring at 240 rpm through nitrogen at normal pressure, and 202 g of water, N-methyl-2- 2 g of pyrrolidone leaked out. At this stage, it was found that 2.0 g (0.11 mol) of water remained in the reaction system and 266.5 g of N-methyl-2-pyrrolidone remained. Note that 0.014 mole of hydrogen sulfide was scattered from the reaction system during the dehydration operation.

Next, after cooling the autoclave to below 160°C, 152 g (1.04 mol) of p-dichlorobenzene, 112 g (1.13 mol) of N-methyl-2-pyrrolidone, and 1.9 g (0.0 mol) of a 48% aqueous sodium hydroxide solution were added. 02 mol) and 5 g of water were charged, and the inside of the reaction vessel was again sufficiently purged with nitrogen, sealed, and heated to 200°C. As a result, the amount of dihalogenated aromatic compound used in the mixture was 1.05 mol per 1 mol of sulfidation agent.

The temperature was increased over 150 minutes from 200°C to just before reaching 245°C (Step 1). The polymerization time TM1 of Step 1 including the temperature raising/lowering time of Step 1 was 150 minutes, and P1 was 0.9 MPaG. During this time, a liquid addition pump was connected via the autoclave valve.

Subsequently, the temperature was raised to 265° C. over 30 minutes, and while stirring the contents of the autoclave at 400 rpm, 22.0 g of water was pressure-injected over 10 minutes using a liquid addition pump. After injecting water, the temperature was raised to 265° C. over 10 minutes and reacted for 2 hours (Step 2). The polymerization time TM2 until the end of the polymerization reaction in the temperature range of Step 2 was 170 minutes, and P2 was 2.0 MPaG. Here, it was confirmed that the conversion rate of the dihalogenated aromatic compound was 92%. The amount of water in the system in Step 2 was 2.6 moles per mole of sulfur, including the moles of water produced during polymerization (= moles of the sulfidating agent consumed in the reaction).

After the polymerization reaction was completed, 3.6 g of water was started to be injected at 265°C, and the injection was completed at 264°C. The amount of water in the system in Step 3 was 2.8 moles per mole of sulfur. P3 was 2.4 MPaG.

After the addition of water was completed, a slow cooling operation was performed from T0 = 264°C to T1 = 215°C at a cooling rate S1 = 0.8°C/min (Step 4). After cooling to 215°C, the cooling rate was changed to S2 = 4°C/min, and further cooling was performed to 170°C, and then rapidly cooled to room temperature.

The subsequent treatments were carried out in the same manner as in Example 1.

The yield of the obtained granular polyphenylene sulfide was 86%, the weight average molecular weight Mw was 30,000, and the average particle diameter of the polymer was 450 μm.

The above results are shown in Table 1.

Claims (6)

A method for producing granular polyarylene sulfide by reacting a mixture containing at least a sulfidating agent, a dihalogenated aromatic compound, an organic polar solvent, and a polymerization aid, the method comprising the following steps 1 to 4. A method for producing polyarylene sulfide.
Step 1: A step of heating the mixture at a temperature of 200° C. or higher and lower than 245° C. to cause a reaction. The pressure P1 in the temperature range of Step 1 is 0.1 MPaG or more and 1.0 MPaG or less, and the polymerization time TM1 of Step 1, including temperature raising/lowering time, is 30 minutes or more and 240 minutes or less.
Step 2: Following Step 1, the amount of water in the reaction system is adjusted to 0.1 mol or more and 1.5 mol or less per 1 mol of sulfidation agent , and the reaction is carried out at a temperature of 245°C or more and 290°C or less. A process of heating and reacting. The pressure P2 in the temperature range of Step 2 is 0.5 MPaG or more and 2.0 MPaG or less, and the polymerization time TM2 of Step 2 until the polymerization reaction is completed is 60 minutes or more and 300 minutes or less.
Step 3: Following Step 2, the water content in the reaction system is adjusted to 3.3 mol or more and 6.0 mol or less per 1 mol of sulfidation agent , and the temperature is adjusted to T0 (240°C≦T0≦ 290° C.), and the pressure P3 in the temperature range of step 3 is 1.0 MPaG or more and 2.0 MPaG or less.
Step 4: Following step 3, cool from temperature T0 to T1 (200°C≦T1≦235°C) at a cooling rate S1 (0.2°C/min≦S1≦0.8°C/min), and after cooling to T1. , a step of further cooling by changing the cooling rate to S2 (0.8° C./min<S2≦5° C./min). The method for producing particulate polyarylene sulfide according to claim 1, wherein the weight average molecular weight Mw of the particulate polyarylene sulfide is 5,000 or more and 45,000 or less. The method for producing granular polyarylene sulfide according to claim 1 or 2, wherein the average particle diameter of the granular polyarylene sulfide is 500 μm or more and 1,500 μm or less. As polymerization aids, organic carboxylates, organic sulfonates, alkali metal halides, alkaline earth metal halides, alkali metal phosphates, alkaline earth metal phosphates, alkali metal sulfates, alkaline earth metal oxides. The method for producing granular polyarylene sulfide according to any one of claims 1 to 3, wherein at least one polymerization aid selected from the following is used. The production of granular polyarylene sulfide according to any one of claims 1 to 4, wherein the amount of the dihalogenated aromatic compound used in the mixture is 1.04 mol or more and 2.00 mol or less per 1 mol of sulfur of the sulfidating agent. Method. The method for producing granular polyarylene sulfide according to any one of claims 1 to 5, wherein the amount of the polymerization aid used in the mixture is 0.001 mol or more and 0.4 mol or less per 1 mol of sulfur of the sulfidating agent.