JP2020070445A - Method for producing granula polyarylene sulfide - Google Patents

Abstract

To provide a method for producing a granular polyarylene sulfide in a good yield in the production of a granular polyarylene sulfide having a low molecular weight which has good fluidity during melting.SOLUTION: There is provided a method for producing a granular polyarylene sulfide, which comprises the following steps 1 to 4 in a method for producing a granular polyarylene sulfide by reacting a mixture containing at least a sulfidation agent, a dihalogenated aromatic compound, an organic polar solvent and a polymerization auxiliary; a step 1 of heating and reacting the mixture at a temperature of 200°C or more and less than 245°C, a step 2 of adjusting the water content in the reaction system in a specific range, followed by heating and reacting the mixture at a temperature of 245°C or more and 290°C or less, a step 3 of adjusting the water content in the reaction system to 3.3 mol or more and 6.0 mol or less per 1 mol of sulfur, followed by setting the temperature to T0 (240°C≤T0≤290°C) and the pressure P3 to a specific value, a step 4 of cooling the temperature from T0 to Ti (200°C≤T1≤235°C) at a cooling rate S1 (0.2°C/min≤S1≤0.8°C/min), after cooling to T1, followed by further cooling by changing the cooling rate to a cooling rate S2 (0.8°C/min<S2≤5°C/min).SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a granular polyarylene sulfide having a low molecular weight, which is excellent in flowability upon melting, in a high yield.

  Polyarylene sulfide represented by polyphenylene sulfide (hereinafter, polyarylene sulfide may be abbreviated as PAS) is an engineering plastic excellent in heat resistance, chemical resistance, flame retardancy, electrical properties and mechanical properties. Yes, it is widely used for fibers, films, injection molding and extrusion. Further, in recent years, there has been an increasing demand for thinner and lighter PAS products in designing, and therefore, there is an increasing demand for a PAS having excellent flow characteristics during melting.

  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. (See, for example, Patent Document 1). According to this method, the polymerization system in a high temperature state is generally taken out by flushing it out into a container under normal pressure or reduced pressure, and then the resin is recovered through solvent recovery, washing and drying to finally obtain an average particle size. A powdery resin with a diameter of a few microns to 50 microns can be obtained.

  In addition, as a method for recovering granular PAS having a relatively high bulk density instead of powder, a method of cooling the reaction system after the polymerization reaction is disclosed (for example, refer to Patent Documents 2 and 3). In this method, granular PAS can be recovered by adding a precipitating agent that causes PAS in a molten state to settle during particle formation, that is, in the cooling step, or by controlling the temperature.

  Further, as another method of increasing the average particle size of the granular PAS, a method of controlling the cooling rate after the polymerization reaction is disclosed (for example, refer to Patent Document 4). According to this method, the cooling step after polymerization is divided into two stages, and the respective steps are cooled at different cooling rates, so that in Patent Documents 2 and 3, even under polymerization reaction conditions where granular PAS is difficult to obtain, impurities It is possible to obtain granular PAS having a small content of.

  Further, as a method of further improving the productivity of the production of granular PAS, a method of gradually cooling a very limited temperature range in the cooling step after the polymerization reaction is disclosed (see, for example, Patent Document 5). ). According to this method, granular PAS having a high bulk density having good handleability in transportation, storage, etc. can be obtained by selectively gradually cooling the extremely limited temperature range of the maximum thickening temperature ± 1 ° C. It can be produced in a relatively short polymerization cycle time.

  Further, as a method of not only increasing the average particle size of the granular PAS but also improving the product yield, the conversion rate of the dihalo aromatic compound in the presence of less than an equimolar amount of alkali metal hydroxide per 1 mol of the sulfur source is used. After producing 50% or more of a prepolymer, the polymerization reaction is continued in the presence of an equimolar amount of an alkali metal hydroxide per mol of a sulfur source, and then the presence of at least one auxiliary agent such as a carboxylate. A method of cooling below is disclosed (for example, refer to Patent Document 6). According to this method, it is possible to suppress the generation of by-products and form hard particles that are less likely to be miniaturized or crushed during transfer / washing, thereby improving the product yield of granular PAS.

  Further, as a method for obtaining granular PAS in a shorter time and a higher yield than in the past, a method is disclosed in which the polymerization step is divided into three stages at different temperatures and the preferable time is defined for each to shorten the PAS production time. (For example, refer to Patent Document 7). According to this method, not only the granular PAS can be efficiently obtained by optimizing the polymerization time, but also 2.0 mol or more and less than 5.5 mol per mol of the sulfur component can be obtained in a state where the monomer consuming 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.

  Further, as a method for obtaining PAS having a high melt fluidity and a large weight average particle diameter, a method of shortening the polymerization time including the temperature raising / lowering time in a temperature range of 245 ° C. or higher and lower than 280 ° C. is disclosed. ing. (For example, patent document 8). According to this method, it is possible to recover PAS having a high melt fluidity in the form of granular PAS with a high yield by reacting under a specific temperature condition in the presence of a polymerization aid.

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

Japanese Patent Publication No. 52-12240 (Claims) Japanese Patent Laid-Open No. 59-1536 (claims) JP-A-60-235838 (claims) JP, 2001-089569, A (claim) Japanese Patent Laid-Open No. 2004-051732 (Claims) JP, 2017-179255, A (claim) JP, 2008-083910, A (claim) JP, 2011-132517, A (claim) International Publication No. 2016/199894 (Claims)

  However, the method of Patent Document 1 is a method in which only a powdery resin having a small particle diameter can be obtained. The resin of such a form has a low bulk density and causes a problem of entraining air during melt extrusion to reduce the discharge amount, and thus a separate pre-process for pelletizing is required, resulting in a problem of poor productivity.

  Further, according to the methods of Patent Documents 2 and 3, although granular PAS having a relatively high bulk density can be recovered, conditions effective for reducing by-products during the reaction, specifically, polyhalogenation with respect to the amount of the organic polar solvent are used. There is a problem that it is difficult to obtain granular PAS under the reaction condition in which the amount of the aromatic compound becomes large. Further, if the cooling rate is not appropriate, there is a problem that the by-product is likely to be entrained in the granular PAS, which causes an increase in volatile components during heating of the PAS, heat deterioration, and quality deterioration such as coloring.

  Further, 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 above. Under the conditions for producing low molecular weight PAS having excellent flow characteristics during melting, the average particle size does not become sufficiently large, and some polymer particles pass through the mesh used during recovery, which improves product yield. There was room.

  Further, in the method of Patent Document 5, it was clarified that the particle size increasing effect by slow cooling is exhibited in a specific temperature range, and succeeded in producing granular PAS having a high bulk density in a short polymerization cycle time. However, while a sufficient effect was confirmed with high molecular weight PAS, no mention was made as to whether or not an effect could be obtained with low molecular weight PAS. Further, although it is mentioned that PAS has a high molecular weight by appropriately adjusting the amount of water in the system, there is no description that the effect extends to the increase of PAS particle size. There wasn't.

  Further, in the method of Patent Document 6, the average particle diameter is increased and the particle strength is improved by cooling the system in a phase-separated state, but the effect tends to be small in PAS having a small molecular weight. There was a need for improvement. Further, in the method of Patent Document 6, since it is also necessary to control the amount of alkali metal hydroxide used, a method that achieves an increase in average particle diameter and an improvement in particle strength by a simpler method has been demanded.

  Further, in the method of Patent Document 7, by adding water such that 2.0 mol or more and less than 5.5 mol of water are present per mol of the sulfur component in a state where the monomer consuming reaction is substantially completed, PAS Although the average weight of the particles is increased to obtain the granular PAS in good yield, the temperature range in which the slow cooling needs to be performed, in other words, the time required for the slow cooling is long, the efficiency is poor, and its improvement is required. Was there. Further, it was not particularly mentioned whether or not the effect was obtained with low molecular weight PAS.

  Further, in the method of Patent Document 8, the nitrogen content of PAS tends to decrease. Generally, PAS obtained by reacting a sulfidizing agent and a dihalogenated aromatic compound in an organic polar solvent in the presence of an alkali metal hydroxide contains nitrogen. This is because an alkali metal alkylaminoalkylcarboxylate produced by a reaction between an organic polar solvent such as NMP and an alkali metal hydroxide reacts with a PAS end as a side reaction during polymerization to form a terminal having a nitrogen atom. This is because. However, if the nitrogen content is extremely low, there is a problem that reactivity with various coupling agents used during melt extrusion in order to enhance the toughness and strength of PAS decreases. There is also a problem that the drainage load increases when the input amount of sodium acetate is large.

  Further, in the method of Patent Document 9, since water is added to the reaction system after the completion of the first-stage polymerization and the reaction is carried out at a temperature of 245 ° C. to 290 ° C., the pressure of the reaction system tends to be high and expensive pressure resistant equipment Therefore, it tends to be economically disadvantageous.

  Therefore, an object of the present invention is to improve the problems of the prior art, and to produce granular PAS with a high yield in the production of low-molecular-weight granular PAS having excellent flow characteristics during melting.

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 a granular polyarylene sulfide by reacting a mixture containing at least a sulfidizing agent, a dihalogenated aromatic compound, an organic polar solvent, and a polymerization aid, including the following steps 1 to 4 And 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 the reaction. The pressure P1 in the temperature range of the step 1 is 0.1 MPaG or more and 1.0 MPaG or less, and the polymerization time TM1 of the step 1 including the temperature raising / lowering time is 30 minutes or more and 240 minutes or less.
Step 2: After Step 1, the water content in the reaction system is adjusted to be 0.1 mol or more and 1.5 mol or less per 1 mol of sulfur, and the reaction is performed by heating at a temperature of 245 ° C. or more and 290 ° C. or less. The process of making. 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 completion of the polymerization reaction is 60 minutes or more and 300 minutes or less.
Step 3: After Step 2, the water content in the reaction system is adjusted to be 3.3 mol or more and 6.0 mol or less per mol of sulfur, and the temperature is set to T0 (240 ° C. ≦ T0 ≦ 290 ° C.). The step of setting the pressure P3 in the temperature range of step 3 to 1.0 MPaG or more and 2.0 MPaG or less.
Step 4: Subsequent to Step 3, cooling 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 to a cooling rate 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 size 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 The method for producing a granular polyarylene sulfide according to any one of [1] to [3], wherein at least one polymerization aid selected from metal oxides is used.
[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 sulfur of the sulfidizing 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 sulfur of the sulfidizing agent. Method for producing sulfide.

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

  Hereinafter, embodiments of the present invention will be described.

(1) Polyarylene Sulfide The polyarylene sulfide in the present invention is a homopolymer or copolymer having a repeating unit of the formula — (Ar—S) — as a main constituent unit. Examples of Ar include units represented by the following formulas (A) to (L) and the like, and among them, (A) is particularly preferable.

(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 the main constituent unit, the following formula ( It may contain a small amount of branching units or crosslinking units represented by the formula (P) or the like from M). The copolymerization amount of these branch units or crosslinking units is preferably in the range of 0 mol% or more and 1 mol% or less per 1 mol of the-(Ar-S)-unit.

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

  Typical examples thereof include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, random copolymers thereof, block copolymers and mixtures thereof. Particularly preferred polyarylene sulfides are 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

  The molecular weight of these polyarylene sulfides is not particularly limited, but the polyarylene sulfides having a weight average molecular weight Mw of 5,000 or more and 45,000 or less have excellent fluidity characteristics at the time of melting, and are thin and lightweight. In the present invention, the above-mentioned Mw polyarylene sulfide is defined as a more preferable polyarylene sulfide, since it has a characteristic that it is preferably used for the use required. As a more preferable range of the weight average molecular weight Mw, the lower limit is more preferably 10,000 or more, and further preferably 15,000 or more. Further, the upper limit is more preferably 40,000 or less, further preferably 35,000 or less, and further preferably 32,000 or less. Within the above preferred range, it can be used as a PAS that is more excellent in the flow characteristics during melting. Here, regarding the melt viscosity known to correlate with the weight average molecular weight Mw, the range of 1 to 40 Pa · s (320 ° C., shear rate 1,000 / sec) is preferable in the present invention from the above-mentioned preferable Mw. The range of 3 to 30 Pa · s is more preferable, and the range of 5 to 30 Pa · s is more preferable.

  Further, in the present invention, granular polyarylene sulfide can be obtained, but the average particle size thereof can be preferably exemplified by 500 μm or more and 1,500 μm or less, and the lower limit is more preferably 600 μm or more and the upper limit is more preferably 1,000 μm or less. It can be illustrated. In such a preferable range, the granular polyarylene sulfide can be easily recovered using a general stainless steel sieve, the components that pass through the mesh are small, and the granular polyarylene sulfide can be recovered in good yield. It is possible to Here, as for the sieve made of stainless steel, the mesh size and the number of meshes can be freely selected, and various standards such as JIS and Tyler are known, but in the present invention, the mesh size is 177 μm, 80 mesh, and the Tyler standard. The evaluation was performed using a sieve. As the 80-mesh sieve, sieves having an opening of 177 to 182 μm are widely known, and there is no big difference between the sieves. Therefore, if the opening has a sieve in the above range, evaluation in the present invention is not particularly problematic. Can be used for.

  Here, the average particle size of the granular polyarylene sulfide in the present invention means a volume-based particle size distribution measured by a laser diffraction type particle size distribution measuring device under wet conditions using N-methyl-2-pyrrolidone as a dispersion solvent. It is a value calculated based on the above. Specifically, the section of the particle diameter is set to a logarithmic scale, the arithmetic mean value on the logarithmic scale is obtained, and then the result is returned to the average value having a normal unit of the particle diameter for calculation. In general, parameters such as a mode diameter showing a maximum value of the particle size distribution and a median diameter which is a particle diameter of 50% of integration are known, but in the present invention, those parameters are not used, and the average particle diameter calculated by the above-mentioned arithmetic mean is used. Will be used for evaluation.

  The granular polyarylene sulfide obtained in the present invention is a relatively low molecular weight polyarylene sulfide having excellent fluidity characteristics during melting as described above, but is a granular polyarylene sulfide having a large average particle diameter, It can be said that it is very significant in that it is possible to achieve the features that were difficult to achieve at the same time.

(2) Sulfidating agent The sulfiding 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 them, sodium sulfide is preferably used. These alkali metal sulfides can be used as hydrates or aqueous mixtures or in the form of anhydrides.

  Specific examples of the alkali metal hydrosulfide include, for example, sodium hydrosulfide, potassium hydrosulfide, lithium hydrosulfide, rubidium hydrosulfide, and cesium hydrosulfide. Among them, sodium hydrosulfide is preferably used. These alkali metal hydrosulfides can be used as hydrates or aqueous mixtures or in the anhydrous form.

  It is also possible to use an alkali metal hydroxide and / or an alkaline earth metal hydroxide together with the sulfidizing agent. Specific examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide, and specific examples of the alkaline earth metal hydroxide include hydroxide. Calcium, strontium hydroxide, barium hydroxide and the like can be mentioned, of which sodium hydroxide and magnesium hydroxide are preferably used.

  When an alkali metal hydrosulfide is used as the sulfidizing agent, it is particularly preferable to use the alkali metal hydroxide at the same time, but the amount used is 0.95 mol or more and 1.20 mol per 1 mol of the alkali metal hydrosulfide. It is preferably not more than mol, more preferably not less than 1.00 mol and not more than 1.15 mol, and still more preferably not less than 1.005 mol and not more than 1.100 mol. There is no problem in introducing the sulfidizing agent into the system at any time, but it is preferable to introduce the sulfidizing agent before performing the dehydration operation described later.

(3) Dihalogenated aromatic compound The dihalogenated aromatic compound used in the present invention is a compound having an aromatic ring, having two halogen atoms in one molecule, and having a molecular weight of 1,000 or less. That is. Specific examples include p-dichlorobenzene, m-dichlorobenzene, o-dichlorobenzene, p-dibromobenzene, m-dibromobenzene, o-dibromobenzene, 1-bromo-4-chlorobenzene, 1-bromo-3-chlorobenzene. Such as dihalogenated benzene, and 1-methoxy-2,5-dichlorobenzene, 1-methyl-2,5-dichlorobenzene, 1,4-dimethyl-2,5-dichlorobenzene, 1,3-dimethyl-2, 5-dichlorobenzene, dihalogenated benzene also containing a substituent other than halogen such as 3,5-dichlorobenzoic acid, 1,4-dichloronaphthalene, 1,5-dichloronaphthalene, 4,4′-dichlorobiphenyl, 4 , 4'-dichlorodiphenyl ether, 4,4'-dichlorodiphenyl sulfone, 4,4'-di Examples thereof include dihalogenated aromatic compounds such as lorodiphenyl ketone. Among them, dihalogenated aromatic compounds containing p-dihalogenated benzene represented by p-dichlorobenzene as a main component are preferable. Particularly preferably, p-dichlorobenzene is contained in an amount of 80 to 100 mol%, further preferably 90 to 100 mol%, and further preferably, p-dichlorobenzene is contained in an amount of 95 to 100 mol%. It is also possible to use two or more different dihalogenated aromatic compounds in combination in order to produce a cyclic PAS copolymer.

(4) Organic Polar Solvent In the present invention, an organic polar solvent is used as the reaction solvent, but it is preferable to use an organic amide solvent having high reaction stability. Specific examples include N-alkyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-alkylpyrrolidones such as N-cyclohexyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, 1, Aprotic organic solvents represented by 3-dimethyl-2-imidazolidinone, N, N-dimethylacetamide, N, N-dimethylformamide, hexamethylphosphoric triamide, dimethyl sulfone, tetramethylene sulfoxide, and the like can be given. Can also be used as a mixture thereof. Among these, N-methyl-2-pyrrolidone is preferably used.

  The amount of the organic polar solvent used in the present invention is preferably such that the amount of the organic polar solvent in the reaction system (polymerization system) is 0.5 mol or more and less than 10 mol, and preferably 2.5 mol or more, per 1 mol of sulfur of the sulfidizing agent. The range of 5.5 mol or less is selected, the range of 2.7 mol or more and less than 4.5 mol is more preferable, the range of 2.7 mol or more and less than 4.0 mol is further preferable, and the range of 2.7 mol or more and 3. A range of less than 5 mol is even more preferred. If the amount of the organic polar solvent is small, an undesired reaction is likely to occur, and if it is large, the degree of polymerization tends to be difficult to increase. Here, the amount of the organic polar solvent in the reaction system is the amount obtained by subtracting the amount of the organic polar solvent removed outside the reaction system from the amount of the organic polar solvent introduced into the reaction system. It should be noted that the organic polar solvent may be introduced into the system at any timing, but when the dehydration operation described below is performed, a part of the organic polar solvent tends to scatter out of the system, and therefore, before the dehydration operation. In addition, a method in which the minimum amount necessary for dehydration is introduced and then the amount is additionally introduced so that the above-mentioned preferable amount is used after completion of the dehydration operation is preferably adopted.

(5) Polymerization Aid The polymerization aid used in the present invention is a substance that easily causes a phase separation state in the system. When a phase-separated state occurs, the polymerization reaction easily proceeds, and when the particles are formed by cooling after the polymerization reaction, the particle size tends to increase.

  Specific examples of such a polymerization aid include ionic compounds which are soluble in an organic polar solvent, and include, for example, organic carboxylates, organic sulfonates, alkali metal halides, alkaline earth metal halides, alkali metal phosphates. Examples thereof include salts, alkaline earth metal phosphates, alkali metal sulfates, alkaline earth metal oxides, etc. From the viewpoint of cost effectiveness and availability, organic carboxylates are preferably used. These may be used alone or in combination of two or more. Further, water also has the effect of promoting the phase separation state similarly to the above-mentioned ionic compound, but since the handling is significantly different from the above-mentioned ionic compound in terms of the preferred amount of use, in the present invention, water is a polymerization aid. It is not included in the category of agents, and the effect of water will be described in detail separately.

  Here, the organic carboxylic acid salt is a general formula R (COOM), (wherein R is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, an aryl group, an alkylaryl group or an arylalkyl group, M Is an alkali metal selected from lithium, sodium, potassium, rubidium and cesium.). Specific examples thereof include lithium acetate, sodium acetate, potassium acetate, sodium propionate, lithium benzoate, sodium benzoate, sodium phenylacetate, sodium p-toluate, and the like. The organic carboxylic acid salt is an organic carboxylic acid and one or more compounds selected from the group consisting of alkali metal hydroxides, alkali metal carbonates and alkali metal bicarbonates in an organic polar solvent, in approximately equal chemical equivalents. You may form by adding and making it react. The organic carboxylates may be used alone or in combination of two or more. Among them, lithium acetate and / or sodium acetate is 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 used cannot be clearly defined because the preferred amount varies depending on the amount of the sulfidizing agent and the dihalogenated aromatic compound used. The amount is preferably 0.001 mol or more and 0.4 mol or less, and the lower limit is preferably 0.01 mol or more, more preferably 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 aid used is in the above-mentioned preferred range, the molecular weight of PAS tends to be controlled within the preferred range of the present invention, and the average particle size of PAS tends to increase more easily.

  Incidentally, there is no particular limitation on the time of introducing the polymerization aid into the system, before performing dehydration described below, during dehydration, after dehydration and before polymerization reaction, during polymerization reaction, after polymerization reaction and before addition of water, any of It can be introduced into the system at a timing, and there is no problem if it is added in a plurality of times, but it is preferable to introduce at least a part thereof into the system by the time the polymerization reaction is started. This makes it possible to obtain PAS having a desired molecular weight in a shorter time. Further, 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 without any problem.

(6) Water Water in the present invention can promote a phase separation state by being present in a certain amount or more in the reaction system, and has an effect of strongly drawing out the effect of the polymerization aid. On the other hand, the presence of excess water lowers the nucleophilicity of the sulfidizing agent and delays the reaction, or may increase the pressure in the system, so that the amount used may 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 completion of the polymerization reaction are handled separately, and the effect of water at each stage and a preferable amount used, The method of adjusting the water content will be described below.

  In the present invention, the water added to the system after the completion of the polymerization reaction is the water added in step 3 described later. As will be described in detail later in the section of step 3, the effect of increasing the particle size of the obtained granular polyarylene sulfide by further promoting phase separation by adjusting the amount of water in the system to an appropriate amount after the completion of the polymerization reaction. 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 mol of sulfur. At this time, the amount of water present in the system at the end of the polymerization reaction is adjusted. It is necessary to determine the amount of water to be added to the system after considering it. 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 mol of sulfur. The upper limit is more preferably 5.0 mol or less per mol of sulfur.

  Further, in the present invention, the water present in the system at the end of the polymerization reaction refers to water added directly at the time of charging the raw materials, the sulfidizing agent charged, the dihalogenated aromatic compound, the organic polar solvent, and the polymerization aid. The total amount of water introduced during the polymerization reaction and the amount of water generated during the polymerization reaction, minus the water distilled out of the system by the dehydration operation. A preferable range of the amount of water present in the system at the end of the step 2 and the polymerization reaction is, as a lower limit, 0.1 mol or more per mol of the sulfidizing agent, and 0.5 mol or more can be more preferably exemplified. The upper limit is 1.5 mol or less, and 1.3 mol or less can be more preferably exemplified. When the amount of water present in the system before the completion of the polymerization reaction is within the above range, the polymerization rate is high and by-products tend to be suppressed. Furthermore, the pressure rise in the system is suppressed, and the cost associated with the introduction of high-voltage equipment tends to be reduced.

  In the present invention, when the amount of water present in the system at the end of the polymerization reaction exceeds the above preferred amount of water, it is also possible to perform an operation of reducing the amount of water in the reaction system by dehydration to adjust the amount of water. is there. The dehydration operation is not particularly limited, but a method of removing water by distillation by heating can be exemplified. On the other hand, when the water content is less than the above range, it does not matter even if water is added so that the water content falls within the above range.

  Here, there is no particular limitation on the method of performing the dehydration operation, and a method of previously dehydrating the raw materials to be charged, any one of a sulfidizing 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 after preparing a mixture containing a sulfidizing agent, a dihalogenated aromatic compound, an organic polar solvent and a polymerization aid, Either method can be adopted, but from the viewpoint of precisely controlling the amount of the dihalogenated aromatic compound that is easily scattered by heating, a method of performing dehydration operation on the mixture in which the dihalogenated aromatic compound is not added Is preferably adopted. At this time, the temperature for heating the mixture cannot be clearly specified because it varies variously depending on the combination of the sulfidizing agent and the organic polar solvent used, and the ratio with water, but the lower limit is 150 ° C or higher. It can be exemplified, preferably 160 ° C. or higher, more preferably 170 ° C. or higher. The upper limit may be 250 ° C or lower, preferably 230 ° C or lower. When the heating temperature at the time of dehydration is within the above-mentioned preferable range, the dehydration can be efficiently performed while suppressing the scattering of the charged sulfidizing agent as hydrogen sulfide to the outside of the system. Further, the pressure condition for dehydration is not particularly limited, and any condition of normal pressure, reduced pressure, and increased pressure can be adopted, but normal pressure or reduced pressure is preferable in order to distill off water more efficiently. .. Here, the atmospheric pressure is a pressure in the vicinity of a standard state of the atmosphere, and is a temperature of about 25 ° C. and an atmospheric pressure condition of an absolute pressure of about 101 kPa. The atmosphere in the system is preferably a non-oxidizing condition, and is preferably an inert gas atmosphere such as nitrogen, helium, and argon. Particularly, from the viewpoint of economy and ease of handling, the nitrogen atmosphere is Is more preferable.

  Since it is difficult to directly measure the amount of water in the high-pressure system during the polymerization reaction, as a method for estimating the amount of water present in the system at the end of the above-mentioned polymerization reaction, it was added directly when the raw materials were charged. Estimate separately the amount of water, the amount of water introduced along with the charged raw materials, the amount of water generated during the polymerization reaction, and the amount of water distilled out of the system during the dehydration operation, and calculate based on those amounts. Adopt the method.

  Here, water generated in the course of the polymerization reaction may or may not be generated depending on the type of the sulfidizing agent used.Therefore, it is necessary to consider the chemical reaction formula before the polymerization reaction to determine whether water is generated. Need to be kept. For example, when the alkali metal hydrosulfide and the alkali metal hydroxide, which are the preferred sulfidizing agents of the present invention, are used together as the sulfidizing agent, water having an equimolar amount to the alkali metal hydrosulfide consumed in the polymerization reaction is produced. To do. On the other hand, when an alkali metal sulfide anhydride is used as the sulfidizing agent, water is not generated in the course of the polymerization reaction.

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

  Here, the amount of the sulfidizing agent charged refers to the amount of the sulfidizing agent present in the system at the start of the polymerization reaction. When removed outside the system, the amount of the sulfidizing agent present in the system at the start of the polymerization reaction is estimated in consideration of the number of moles of hydrogen sulfide scattered.

(7) Method for producing granular polyarylene sulfide In the present invention, in a method for producing a granular polyarylene sulfide by reacting a mixture containing at least a sulfidizing agent, a dihalogenated aromatic compound, an organic polar solvent, and a polymerization aid. The following steps 1 to 4 are included.
Step 1: A step of reacting by heating 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 the 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 be 0.1 mol or more and 1.5 mol or less per mol of sulfur, and the reaction is performed by heating at a temperature of 245 ° C. or more and 290 ° C. or less. The process of making. 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 completion of the polymerization reaction is 60 minutes or more and 300 minutes or less.
Step 3: After Step 2, the water content in the reaction system is adjusted to be 3.3 mol or more and 6.0 mol or less per mol of sulfur, and the temperature is set to T0 (240 ° C. ≦ T0 ≦ 290 ° C.). The step of setting the pressure P3 in the temperature range of step 3 to 1.0 MPaG or more and 2.0 MPaG or less.
Step 4: Following Step 3, cooling 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 to a cooling rate S2 (0.8 ° C./min<S2≦5° C./min).

  Hereinafter, these steps will be described.

(7-1) Step 1
Step 1 is a step in which a mixture containing at least a sulfidizing 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 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 the 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 0.25 MPaG or more can be more preferably exemplified. Further, the upper limit is 1.0 MPaG or less, and more preferably 0.9 MPaG or less. By setting the pressure in the reaction system within the above range, the sulfidizing agent as a raw material and the dihalogenated aromatic compound tend to be rapidly reacted and consumed, and the use of expensive pressure resistant equipment tends to be easily avoided. .. Here, in order to set the pressure in the reaction system to the above-mentioned preferable range, even if the reaction system is pressurized with an inert gas at any stage such as before the reaction starts or during the reaction, preferably before the reaction is started. I don't care. Here, the gauge pressure is a relative pressure based on the atmospheric pressure, and is synonymous with the pressure difference obtained by subtracting the atmospheric pressure from the 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 longer, and more preferably 80 minutes or longer. The upper limit of TM1 is 240 minutes, and 180 minutes or less is more preferable. If TM1 is too short, the conversion rate of the dihalogenated aromatic compound described below is too low, so that the unreacted sulfidizing agent causes decomposition of the prepolymer in step 2 and volatilization occurs when the obtained PAS is heated and melted. The sex component tends to increase. Further, if TM1 is too long, it is economically disadvantageous because the production efficiency is lowered.

(7-2) Step 2
What is Step 2? After Step 1, the amount of water in the reaction system is adjusted to be 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 higher and 290 ° C or lower. This is a step of 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 completion of the polymerization reaction is 60 minutes or more and 300 minutes or less.

  Here, the temperature at which the mixture is heated for reaction needs to be 245 ° C. or higher and 290 ° C. or lower. If the temperature at which the mixture is heated to cause the reaction is lower than 245 ° C, the polymerization rate becomes slow and PAS cannot be efficiently obtained. When the temperature at which the mixture is heated to react exceeds 290 ° C., the PAS produced is denatured due to the influence of the organic solvent, making it difficult to obtain PAS having normal physical properties. In addition, as a preferable range of the temperature for heating and reacting the mixture, the lower limit is preferably 250 ° C. or higher, and the upper limit is preferably 280 ° C. or lower. When the temperature at which the mixture is heated to cause the reaction is within the above-mentioned preferred range, PAS exhibiting normal physical properties can be obtained more efficiently.

  Here, when the temperature for heating the mixture to react exceeds the reflux temperature under normal pressure of the mixture, as a method of heating at such temperature, for example, a method of heating the mixture under a pressure higher than normal pressure, The method of heating a mixture in a closed container can be illustrated. Note that the atmospheric pressure is a pressure in the vicinity of the standard state of the atmosphere, and the standard state of the atmosphere is 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 is repeatedly boiled and condensed. Further, the reaction in the present invention is carried out at 245 ° C. or higher and 290 ° C. or lower, but a reaction carried out 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 It doesn't matter which one.

  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 higher, preferably 0.7 MPaG or higher, more preferably 0.8 MPaG or higher, and even more preferably 1.0 MPaG. 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 in the reaction system is within the above-mentioned range, the sulfidizing agent as a raw material and the dihalogenated aromatic compound tend to be rapidly reacted and consumed, and use of expensive pressure resistant equipment tends to be avoided.

  Here, it is necessary to adjust the amount of water in the reaction system in step 2 to be 0.1 mol or more and 1.5 mol or less per mol of sulfur. When the amount of water in the reaction system exceeds 1.5 mol per mol of sulfur, the pressure in the system becomes extremely high, which causes a safety problem. Here, as a preferable range of the amount of water in the reaction system in Step 2, the lower limit is preferably 0.5 mol or more per mol of sulfur, and the upper limit is preferably 1.3 mol or less per mol of sulfur. it can. When the amount of water in the reaction system in step 2 is within the above-described preferable range, the pressure in the system can be suppressed to be lower. As a method for adjusting the amount of water in the reaction system in step 2 to be 0.1 mol or more and 1.5 mol or less per mol of sulfur, a method of adjusting the amount of water in the reaction system in step 3 described later. It can be carried out in the same manner as.

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

  Here, the amount of the dihalogenated aromatic compound used in the mixture varies depending on the amount of the polymerization aid used. For example, when the amount of the polymerization aid used is less than 0.085 mol per mol of the sulfiding agent, the amount of the dihalogenated aromatic compound in the mixture is 0 per mol of the sulfiding agent. It is preferably not less than 0.95 mol and not more than 2.00 mol. Further, the lower limit is more preferably 1.00 mol or more per mol of the sulfiding agent, and the upper limit is more preferably 1.50 mol or less per mol of the sulfiding agent, and 1.20 mol or less. More preferably, 1.10 mol or less can be exemplified even more preferably. On the other hand, when the amount of the polymerization aid used is 0.085 mol or more per mol of the sulfiding agent, the amount of the dihalogenated aromatic compound used in the mixture is 1 per mol of the sulfiding agent. It is preferably 0.04 mol or more and 2.00 mol or less. Further, the lower limit is more preferably 1.043 mol or more per 1 mol of sulfur of the sulfidizing agent, and the upper limit is more preferably 1.50 mol or less per 1 mol of sulfur of the sulfiding agent, and 1.20 mol or less. More preferably, 1.10 mol or less can be exemplified even more preferably. When the amount of the dihalogenated aromatic compound used is within the above-mentioned preferred range, it is possible to easily control the molecular weight of PAS within the preferred range of the present invention and to obtain PAS with a small amount of gas generated during heating.

  There is no problem in introducing the dihalogenated aromatic compound into the system at any timing, but it is preferable to introduce the dihalogenated aromatic compound after performing the dehydration operation described later. Further, as a charging method, not only a method of charging the entire amount in a batch but also a method of introducing stepwise can be adopted.

Here, in the present invention, the step 3 is carried out after the completion of the polymerization reaction in the step 2, but the term “end of the polymerization reaction” means that heating is performed until the conversion rate of the charged dihalogenated aromatic compound becomes 97% or more. It refers to the state of reacting. After the conversion of the dihalogenated aromatic compound to such a conversion rate, the molecular weight of PAS can be controlled in the preferable range of the present invention by carrying out the step 3 described later, and further, the granular PAS can be controlled. The average particle size can be increased. In the present invention, it is considered that the polymerization reaction is completed when the conversion rate of the dihalogenated aromatic compound is 97% or more, but a method of further continuing the reaction to further increase the conversion rate of the dihalogenated aromatic compound is also available. It is preferably adopted. In that case, as a more preferable range of the conversion rate of the dihalogenated aromatic compound in the polymerization reaction, the lower limit is more preferably 98% or more, and further preferably 98.5% or more. When the conversion rate is equal to or higher than this preferable lower limit, there is a tendency that in the recovery of granular PAS described later, the unreacted monomer can be prevented from being mixed into the granular PAS. On the other hand, the upper limit may exceed 100% for the sake of convenience of the following calculation formula, and cannot be unconditionally specified because it changes depending on the amount of the dihalogenated aromatic compound used, but all the dihalogenated aromatic compounds used are It can be said that the conversion rate in the case of conversion is a preferable upper limit. When the conversion rate of the dihalogenated aromatic compound is in the above-mentioned preferred range, it is easier to control the molecular weight of PAS in the preferred range of the present invention, and it is easier to increase the average particle size of the granular PAS. In the present invention, the residual amount of the dihalogenated aromatic compound in the polymerization reaction liquid is estimated by gas chromatography, and the dihalogenated aromatic compound is calculated from the ratio with the amount of the charged sulfidizing agent or the charged dihalogenated aromatic compound. The conversion of the compound is calculated. The calculation formula is as follows.
(A) When the dihalogenated aromatic compound is used in excess with respect to the sulfidizing agent in a molar ratio: Conversion rate of dihalogenated aromatic compound (%) = [amount of charged dihalogenated aromatic compound (mol) -dihalogenation Amount of remaining aromatic compound (mol)] / amount of sulfidizing agent charged (mol) × 100
(B) In 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 (mol) of dihalogenated aromatic compound × 100.

  Here, the amount of the sulfidizing agent charged refers to the amount of the sulfidizing agent present in the system at the start of the polymerization reaction. When removed outside the system, the amount of the sulfidizing agent present in the system at the start of the polymerization reaction is estimated in consideration of the number of moles of hydrogen sulfide scattered.

  The amount of the dihalogenated aromatic compound charged refers to the amount of the dihalogenated aromatic compound that was present in the system at the start of the polymerization reaction. When the group compound is removed to the outside of the system, the amount of the dihalogenated aromatic compound present in the system at the start of the polymerization reaction is estimated in consideration of the number of moles scattered.

(7-3) Step 3
In step 3, after the completion of the polymerization reaction, the water content in the reaction system is adjusted so as to be not less than 3.3 mol and not more than 6.0 mol per mol of sulfur, and the temperature is 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 considered that this operation further promotes the phase separation state in the system. Here, T0 corresponds to the temperature at which the slow cooling operation is started in step 4 performed after step 3, and is not the temperature immediately after the adjustment of the water content is completed in step 3. From the viewpoint of improving the efficiency of the manufacturing time cycle, it is preferable to control the temperature so as to reach T0 when the adjustment of the water content is completed in step 3, but if the adjustment of the water content is completed, it is not within the range of T0. In this case, the temperature may be adjusted to T0 before the slow cooling operation of step 4 is started. However, when the amount of the organic polar solvent used is within the preferred range of the present invention, in order to obtain PAS particles having a large particle size, it is important to control the temperature not to fall below 240 ° C. in step 3. Here, the water content in the reaction system is the total of water existing in the system at the end of the polymerization reaction and water added to the system after the completion of the polymerization reaction. It is necessary to determine the amount of water added to the system, taking into consideration the amount of water present. When the amount of water in the system at the end of the polymerization reaction exceeds 6.0 mol per mol of sulfur, the amount of water in the system becomes 3.3 mol or more and 6.0 mol or less per mol of sulfur. To dehydrate. For this dehydration operation, for example, a method of heating to remove water by distillation can be exemplified.

  When the amount of water in the reaction system is less than 3.3 mol per mol of sulfur, phase separation in the system is difficult to be promoted, and when cooling is performed in the subsequent step 4, the average particle size of PAS particles is sufficiently increased. It is difficult to increase. Further, if the water content in the reaction system exceeds 6.0 mol per mol of sulfur, the pressure in the system becomes extremely high, which causes a safety problem. Here, as a preferable range of the amount of water in the reaction system in Step 3, the lower limit is preferably 3.5 mol or more per mol of sulfur, and the upper limit is preferably 5.0 mol or less per mol of sulfur. it can. When the amount of water in the reaction system in step 3 is within the above-mentioned preferable range, it is possible to further increase the average particle size of the granular PAS while suppressing the pressure in the system to a lower level.

  As described in Patent Document 6, it has been conventionally known that the average particle size of granular PAS is increased by adding water at the end of the polymerization reaction to cause phase separation in the system, but the effect is that of PAS. It was not known that the molecular weight varied. It is presumed that PAS having a large molecular weight is easily affected by phase separation even with a small amount of water, and grows to a certain particle size without strictly controlling the cooling rate, so that it is easy to obtain a granular PAS in good yield. However, in order to obtain the same effect with PAS having a small molecular weight, precise control of both the water content and the cooling rate is required. The inventors of the present invention have conducted intensive studies to clarify the conditions of the amount of water and the cooling rate at which the average particle diameter of the polymer can be sufficiently grown even in the production of low molecular weight PAS, and the present invention has been completed. ..

  When step 3 is carried out to promote the phase separation in the system, not only the average particle size of the obtained granular PAS increases but also the hardness of the particles tends to increase. It is more preferable that the hardness of the particles is increased, because it is possible to suppress the fineness due to the crushing of the particles in the recovery operation of the granular PAS. Although there are various methods for measuring the hardness of the particles, in the present invention, the granular PAS whose average particle diameter was measured is first added to N-methyl-2-pyrrolidone at a concentration of 10% by weight. The resulting dispersion was shaken with a shaker (Azuwan TUBE MIXER TRIO HM-1N, scale 10) at room temperature for 5 minutes, the average particle size after the treatment was measured again, and the average particle size after the treatment was measured. It was estimated by calculating a value (%) obtained by dividing by the original average particle diameter.

  In step 3, the method of adding water to the system is not particularly limited, and a known addition method such as a method using a liquid addition pump or a method using shower spraying can be adopted. Further, 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 when T0 <240 ° C., PAS tends to be precipitated as fine particles at the time of step 3. Therefore, it is difficult to sufficiently increase the average particle diameter of PAS particles even when the subsequent step 4 is performed. Further, when T0> 290 ° C., the pressure in the system becomes extremely high, which causes 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 system may be cooled by the operation of adding water. Therefore, in order to control T0 within the above range, it is preferable to continue heating even in step 3. A preferable range of T0 is preferably 240 ° C. ≦ T0 ≦ 260 ° C. When T0 is in the above-described preferred range, the time required for the slow cooling operation in the subsequent Step 4 can be shortened, and the granular PAS can be efficiently produced in a shorter time.

  Further, in step 3, the rate of adding water to the system cannot be clearly specified because it affects the scale of the reaction system, but it is preferable to set an appropriate rate to maintain the above temperature. .. Further, from the viewpoint of productivity, it is important to shorten the time required for water addition, and therefore, for example, 1 minute or more and 2 hours or less, preferably 10 minutes or more and 1 hour or less, and more preferably 10 minutes or more and 45 minutes or less. A water addition rate at which the target amount of water can be completely added within the time can be preferably exemplified.

  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, even more preferably 1.2 MPaG or more. 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 in the reaction system is within the above-mentioned range, the sulfidizing agent as a raw material and the dihalogenated aromatic compound tend to be rapidly reacted and consumed, and use of expensive pressure resistant equipment tends to be avoided.

(7-4) Step 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) and further cooling is performed. By this operation, PAS in a dissolved state is precipitated and its particle size grows large. Here, S1 is the cooling rate in the slow cooling operation which is important for precipitating PAS and increasing the particle size thereof, and T1 is the temperature at which the slow cooling operation is completed at the cooling rate S1. Further, S2 is the cooling rate in the rapid cooling operation for cooling to a temperature suitable for recovering the granular PAS.

  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 start point to the temperature determined as the end point by the total time required for cooling the temperature difference. To do. However, regarding the cooling rate S1 of the slow cooling operation that has a great influence on the growth of PAS particles, the cooling rate per minute time, so-called instantaneous cooling rate is also important, and with respect to this instantaneous cooling rate, the regulation of S1 should be as much as possible. It is preferable to satisfy. Specifically, in the time required for the slow cooling operation for cooling at the cooling rate S1, preferably 90% or more, more preferably 95% or more, the instantaneous cooling rate satisfies the regulation of S1 Is preferable, and 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 in which the instantaneous cooling rate is out of the regulation of S1. However, it can be said that there is no problem unless the object of the present invention is essentially impaired. As an example of the state in which the instantaneous cooling rate deviates from the regulation, not only an example in which the cooling rate is simply deviated but also an example in which the temperature rises for a short time due to heat generated when the PAS is crystallized or the like can be allowed.

  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 is significantly lengthened and the productivity is reduced. Further, when S1> 0.8 ° C./min, the average particle size of the granular PAS does not sufficiently increase, and the PAS yield decreases. 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. It can be illustrated. When S1 is in the above-described preferred range, the average particle size of PAS particles can be further increased, and granular PAS tends to be obtained with high 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 is remarkably lengthened and the productivity is lowered. Further, when T1> 235 ° C., the average particle diameter of the granular PAS does not sufficiently increase, and PAS yield and quality are deteriorated. A preferable range of T1 is 210 ° C. ≦ T1 ≦ 235 ° C. When T1 is within the above-described preferable range, the time required for the slow cooling operation in step 2 can be shortened, and the granular PAS can be efficiently produced in a shorter time.

  As described in Patent Document 5, conventionally, a technique for obtaining granular PAS having a high bulk density by selectively gradually cooling the extremely limited temperature range of maximum thickening temperature ± 1 ° C. has been known. However, it has not been known that the effect is difficult to be obtained in a low molecular weight PAS having a high affinity with a solvent and a low cohesive force between particles. Since PAS having a large molecular weight has a low affinity with a solvent and a high cohesive force between particles, even if the time for slow cooling is short, particle growth due to coagulation proceeds in the subsequent quenching step, and It is estimated that it is easy to obtain granular PAS efficiently. However, when trying to obtain the same effect with PAS having a small molecular weight, it is considered that it is necessary to grow a single particle to a large size by setting a longer time for slow cooling because the cohesive force is small. The inventors of the present invention have conducted diligent verification and found that even in the production of PAS having a low molecular weight, particles can be sufficiently grown by continuing slow cooling to a temperature of 200 ° C. ≦ T1 ≦ 235 ° C. The invention has been completed.

  In step 4, after gradually cooling from T0 to T1 at the cooling rate S1, the cooling rate is changed to the cooling rate S2 (0.8 ° C./min<S2≦5° C./min) to perform further rapid cooling. When S2 ≦ 0.8 ° C./min, the time required for the step 4 is remarkably lengthened and the productivity is lowered. Further, when S2> 5 ° C./min, there is a concern that a sudden temperature change may adversely affect the device. As a preferable range of S2, 1.5 ° C./min≦S2≦4° C./min can be exemplified. When S2 is within the above-described preferable range, the time required for the quenching operation in step 4 can be shortened, and the granular PAS can be efficiently produced in a shorter time.

  Here, the temperature at which the rapid cooling operation starts at the cooling rate S2 is T1, but there is no particular limitation on the temperature at which the rapid cooling operation ends. For example, in order to recover the polymerization reaction liquid once, it may be rapidly cooled to around room temperature, or in the case of shifting to the recovery operation of the granular PAS without recovering the polymerization reaction liquid, quenching is performed at the temperature at which the granular PAS is recovered. You may stop. Therefore, the temperature at which the quenching operation ends can not be specified unconditionally, but a temperature of 15 ° C. or higher and 170 ° C. or lower can be exemplified.

  Generally, PAS obtained by reacting a sulfidizing agent and a dihalogenated aromatic compound in an organic polar solvent in the presence of an alkali metal hydroxide contains nitrogen. This is because an alkali metal alkylaminoalkylcarboxylate produced by a reaction between an organic polar solvent such as NMP and an alkali metal hydroxide reacts with a PAS end as a side reaction during polymerization to form a terminal having a nitrogen atom. This is because. The PAS obtained in the present invention has a nitrogen content of 600 ppm or more and 1500 ppm or less. When the nitrogen content is significantly lower than 600 ppm, the reactivity with various coupling agents used in melt extrusion for increasing the toughness and strength of PAS decreases. As a lower limit, the nitrogen content of PAS for that purpose is more preferably 650 ppm or more, and further 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 large, the amount of volatile components will become excessive during injection molding of PAS, which will likely cause defects in the appearance of the molded product and increase the amount of impurities attached to the mold. Or the workability in molding is significantly reduced.

  The method for adjusting the nitrogen content of PAS to the above-mentioned preferred range is not particularly limited as long as such PAS can be obtained. For example, the polymerization time in Step 2 until the completion of the polymerization reaction is 60 minutes or more. It is preferably 300 minutes or less. The nitrogen content of PAS is measured by thermally decomposing / oxidizing a sample at a final temperature of 900 ° C. using a horizontal reactor, and supplying the generated nitric oxide to a nitrogen detector ND-100 manufactured by Mitsubishi Chemical Analytech. be able to.

(8) Other Post-Treatment The granular PAS thus obtained is a PAS having a low molecular weight, but its average particle size is 500 μm or more and 1,500 μm or less, and a granular PAS having a sufficiently large particle size can be obtained. 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. Granular PAS having such a particle size can be easily filtered by, for example, a stainless steel sieve or the like. It can be recovered.

  As described above, in the present invention, the evaluation is performed using a sieve having a mesh size of 177 μm, 80 mesh, and Tyler standard. Here, the granular PAS obtained by filtering with a sieve or the like as described above may be subjected to other post-treatments such as washing with an organic solvent and / or water and drying. By performing such a post-treatment, the organic polar solvent, ionic compound, oligomer component, unreacted monomer and the like contained in the granular PAS tend to be removed, and higher quality granular PAS tends to be obtained.

  Here, the organic solvent used for washing is not particularly limited as long as it does not have a function of decomposing PAS, and for example, a nitrogen-containing polar solvent such as N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide and the like. , 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, dichloride Halogen-based solvents such as ethylene, dichloroethane, tetrachloroethane, chlorobenzene, methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol Lumpur, phenol, cresol, alcohol phenol based solvents such as polyethylene glycol, benzene, toluene, and aromatic hydrocarbon solvents such as xylene. Among these organic solvents, it is preferable to use N-methyl-2-pyrrolidone, acetone, dimethylformamide, chloroform and the like. Further, these organic solvents are used alone or in a mixture of two or more kinds.

  As a method of washing with an organic solvent, there is a method of immersing PAS in an organic solvent, and it is also possible to appropriately stir or heat if necessary.

  The washing temperature when washing PAS with an organic solvent is not particularly limited, and examples thereof include a temperature from room temperature to 300 ° C. or lower. The higher the cleaning temperature, the higher the cleaning efficiency tends to be, but normally, cleaning at a temperature from room temperature to 150 ° C. or lower is sufficient to obtain the effect. The ratio of PAS to the organic solvent is preferably such that the amount of the organic solvent is large, but usually, a bath ratio of 300 g or less is selected for 1 liter of the organic solvent. The PAS that has been washed with an organic solvent is preferably washed several times with water or warm water in order to remove the remaining organic solvent.

  As a method for washing PAS with water or warm water, there is a method of immersing PAS in water or warm water, and it is also possible to appropriately stir or heat as necessary.

  The temperature at which the PAS is washed with water or warm water is not limited, but it is preferably carried out at a temperature of 20 ° C or higher and 220 ° C or lower, more preferably 50 ° C or higher and 200 ° C or lower. If the washing temperature is lower than 20 ° C., it becomes difficult to remove by-products, and if it exceeds 220 ° C., the pressure becomes high, which is not preferable for safety.

  Water or water used for washing with warm water 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, and their alkali metals, alkaline earth metal salts, sulfuric acid, phosphoric acid, hydrochloric acid, carbonic acid, silicic acid and other inorganic acidic compounds and ammonium ions You may use the aqueous solution containing these.

  The operation of the hot water treatment is usually carried out by adding a predetermined amount of PAS to a predetermined amount of water and heating and stirring at normal pressure or in a pressure vessel. The ratio of PAS to water is preferably as much as possible, 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 is excellent in heat resistance, chemical resistance, flame retardancy, electrical properties and mechanical properties, and has a by-product content. It can be used as a PAS which has a small amount of gel and gas at the time of molding and is excellent in moldability. Further, not only for injection molding, but also by extrusion molding, it can be widely used as extrusion molded articles of fibers, sheets, films and pipes. Further, since the PAS obtained in the present invention has the above-mentioned excellent characteristics and is particularly excellent in the flow characteristics at the time of melting, it is easy to study thinning and weight reduction in the design of PAS products. Furthermore, the effect of shortening the solidification time due to the thinning of the product, that is, the molding cycle time can be expected.

  The PAS obtained in the present invention may be used alone or, if desired, an inorganic filler such as glass fiber, carbon fiber, titanium oxide or calcium carbonate, an antioxidant, a heat stabilizer, and an ultraviolet ray. It is also possible to add absorbents, colorants, etc., polyamide, polysulfone, polyphenylene, polycarbonate, polyether sulfone, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene, epoxy group, carboxyl group, carboxylic acid ester. Compounding resins such as olefin-based copolymers, polyolefin-based elastomers, polyetherester elastomers, polyetheramide elastomers, polyamide-imides, polyacetals, and polyimides that have functional groups such as groups and acid anhydride groups. It can be.

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

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

When hydrogen peroxide solution was added to the sample to oxidize the sulfide ions contained in the sample and then quantified as sulfate ion by the above analysis, when an untreated sample containing no hydrogen peroxide solution was analyzed. The amount of sulfide ion in the sample was calculated by the method of subtracting the quantitative value of sulfate ion. The amount of the sulfide ion calculated here was used as the amount of the remaining sulfidizing agent, and the conversion rate of the sulfiding agent was calculated from the ratio with the amount of the sulfidizing agent charged. The calculation formula is as follows.
Conversion rate of sulfidizing agent (%) = [[amount of sulfiding agent charged (mol) -amount of remaining sulfiding agent (mol)] / [amount of sulfiding agent charged (mol)]] × 100% ..

  Here, the amount of the sulfidizing agent charged refers to the amount of the sulfidizing agent present in the system at the start of the polymerization, and hydrogen sulfide removed outside the system by performing a dehydration operation before the start of the polymerization. If it is present, calculate it after considering the number of moles scattered.

<Analysis of dihalogenated aromatic compounds>
The quantification of the dihalogenated aromatic compound in the reaction solution (for example, quantification of p-dichlorobenzene) was carried out under the following conditions using gas chromatography (GC).
Device: Shimadzu Corporation GC-2010
Column: J & W DB-5 0.32 mm × 30 m (0.25 μm)
Carrier gas: Helium detector: Hydrogen 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) that was assumed to convert all of the sulfidizing agent present in the system into 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).

Granular PAS (5 mg) was added to 1-chloronaphthalene (5 g), heated to 250 ° C., dissolved, filtered through a membrane filter having a pore size of 0.1 μm, and the filtrate was cooled to room temperature to obtain a slurry-like solution. The obtained solution was used as a sample and analyzed under the following conditions to calculate the number average molecular weight (Mn) and the weight average molecular weight (Mw) in terms of polystyrene.
Device: Senshu Scientific Co., Ltd. SSC-7110
Column name: Shodex UT806Mx2
Eluent: 1-chloronaphthalene Detector: Differential refractive index detector Column temperature: 210 ° C
Pre-constant bath temperature: 250 ℃
Pump bath temperature: 50 ° C
Detector temperature: 210 ℃
Flow rate: 1.0 mL / min
Sample injection volume: 300 μL.

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

<Measurement of particle hardness>
The hardness of the particles is measured by first dispersing the granular PAS, the average particle diameter of which has been measured, in N-methyl-2-pyrrolidone to a concentration of 10% by weight, and dispersing the dispersion in a shaker (Azuwan TUBE MIXER TRIO). Shake for 5 minutes at room temperature with HM-1N, scale 10), re-measure the average particle size after treatment, and calculate the value (%) when the average particle size after treatment is divided by the original average particle size. I estimated it by doing.

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

[Example 1]
An apparatus for distillation and an alkali trap were connected to an autoclave equipped with a stirrer, and 117 g (1.00 mol) of a 47.7% sodium hydrosulfide aqueous solution and 81.2 g (1.02%) of a 49.5% sodium hydroxide aqueous solution. 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 replaced with nitrogen.

  A distillation column was attached to the upper part of the autoclave through a valve, and the mixture was gradually heated to 237 ° C. over 3 hours with stirring under nitrogen at 240 rpm under normal pressure to remove liquid, and 103 g of a distillate was obtained. When the distillate was analyzed by gas chromatography, the composition of the distillate was 101 g of water and 2 g of N-methyl-2-pyrrolidone. At this stage, 1.9 g of water (0.11 mol) was contained in the reaction system. ) It was found that 162 g of N-methyl-2-pyrrolidone remained. The hydrogen sulfide scattered from the reaction system through the dehydration operation was 0.02 mol. As a result, the amount of the polymerization aid used in the mixture was 0.09 mol per mol of the sulfiding agent sulfur.

  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 sufficiently replaced with nitrogen. And sealed. As a result, the amount of the dihalogenated aromatic compound used in the mixture was 1.047 mol per mol of the sulfiding agent. The internal temperature dropped to 130 ° C by the charging operation. Then, it heated up from 130 degreeC to 200 degreeC, stirring at 400 rpm.

  The temperature was raised from 200 ° C to just before reaching 245 ° C over 91 minutes (step 1). The polymerization time TM1 of the step 1 including the temperature rising / falling time of the step 1 was 91 minutes, and P1 was 0.6 MPaG.

  Subsequently, the temperature was raised to 275 ° C. over 40 minutes, and further held 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 mol per mol of sulfur together with the mol of water generated during the polymerization (= mol of the sulfidizing agent consumed by the reaction; see Reference Example 1). During this period, a liquid addition pump was connected via a valve of the autoclave.

  After the completion of the polymerization reaction, 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 was 3.9 mol per mol of sulfur together with the mol of water generated during the polymerization (= mol of the sulfidizing agent consumed by the reaction, see Reference Example 1). It was The temperature control by the heater was continued during the addition of water, and the internal temperature was controlled so as not to fall below 240 ° C. At the end of the 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 S2 was changed to 4 ° C./min, further cooling to 170 ° C., and then rapid cooling to room temperature.

  Then, the contents were taken out, diluted with 210 g of N-methyl-2-pyrrolidone, the solvent and the solid were filtered off with an 80-mesh stainless sieve (opening 177 μm), and the obtained particles were washed with 1 liter of warm water. It 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 size of the polymer was 647 μm, and the nitrogen content was 9 × 10 2 ppm.

  Further, when the hardness of particles 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, the autoclave was cooled by air cooling without adding water in step 3, and the polymerization reaction liquid was recovered after cooling. When the sulfidizing agent was analyzed for the polymerization reaction liquid, the conversion rate of the sulfiding agent was 97%. Therefore, the amount of water generated during the polymerization can be calculated to be 0.96 mol, and when added to 0.11 mol of the water remaining in the system before the start of the polymerization, the amount of water existing in the system at the end of the polymerization was 1. It becomes 07 mol. (1.1 mol per mol of sulfur) Furthermore, when the dihalogenated aromatic compound was analyzed in the polymerization reaction liquid, the conversion rate of the dihalogenated aromatic compound was 98.6%.

[Comparative Example 1]
After the completion of the polymerization reaction in Step 2, the production of granular polyphenylene sulfide was carried out 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 the addition of water is 3.2 mol per mol of sulfur together with the mol of water generated during the 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 size of the polymer was 449 μm, and the nitrogen content was 9 × 10 ^ 2 ppm.

  Further, when the hardness of particles 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]
The production of granular polyphenylene sulfide was carried out in the same manner as in Example 1 except that the cooling rate from T0 = 240 ° C. to T1 = 215 ° C., which was carried out after the addition of water, was changed to the cooling rate 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 size of the polymer was 350 μm, and the nitrogen content was 9 × 10 ^ 2 ppm.

[Example 2]
After the completion of the polymerization reaction in step 2, the production of granular polyphenylene sulfide was carried out in the same manner as in Example 1 except that the amount of water added in step 3 was 66.0 g. (The amount of water in the system after the addition of water was 4.8 mol per mol of sulfur, including the mol of water generated during the 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 size of the polymer was 642 μm, and the nitrogen content was 9 × 10 ^ 2 ppm.

  Further, when the hardness of particles 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]
Production of granular polyphenylene sulfide in the same manner as in Example 1 except that the temperature T0 for starting slow cooling after the completion of the polymerization reaction in Step 2 was 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 size 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, the production of granular polyphenylene sulfide was carried out in the same manner as in Example 1 except that the temperature T0 at which slow cooling was started was 250 ° C and the slow cooling end temperature T1 was 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 size of the polymer was 700 μm, and the nitrogen content was 9 × 10 ^ 2 ppm.

[Comparative Example 3]
After the completion of the polymerization reaction in step 2, the temperature T0 at which gradual cooling is started was set to 250 ° C., and the gradual cooling operation was performed at a cooling rate S1 = 0.9 ° C./min to produce granular polyphenylene sulfide as in Example 1. Was carried out. P3 in the process 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 size of the polymer was 400 μm, and the nitrogen content was 9 × 10 ^ 2 ppm.

[Comparative Example 4]
After the completion of the polymerization reaction in step 2, the production of granular polyphenylene sulfide was carried out in the same manner as in Example 1 except that the temperature T0 at which slow cooling was started was 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 size of the polymer was 450 μm, and the nitrogen content was 9 × 10 2 ppm.

[Comparative Example 5]
After the completion of the polymerization reaction in step 2, the production of granular polyphenylene sulfide was carried out in the same manner as in Example 1 except that the temperature T0 for starting slow cooling was 250 ° C. and the end temperature T1 for slow cooling 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 size of the polymer was 450 μm, and the nitrogen content was 9 × 10 2 ppm.

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

  A distillation column was attached to the upper part of the autoclave through a valve, and the mixture was gradually heated to 220 ° C. over 2.5 hours with stirring under nitrogen at 240 rpm under normal pressure to remove liquid, and 202.5 g of water, N-methyl- 2-Pyrrolidone distilled off 2 g. 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 in the reaction system. The hydrogen sulfide scattered from the reaction system through the dehydration operation was 0.02 mol. As a result, the amount of the polymerization aid used in the mixture was 0.010 mol per mol of the sulfurizing agent.

  Then, after cooling the autoclave to 160 ° C. or lower, 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 sufficiently replaced with nitrogen. And sealed. Thereby, the amount of the dihalogenated aromatic compound used in the mixture was 1.02 mol per mol of the sulfiding agent. Then, it heated up to 200 degreeC.

  The temperature was raised from 200 ° C to just before reaching 245 ° C over 147 minutes (step 1). The polymerization time TM1 of the step 1 including the temperature rising / falling time of the step 1 was 147 minutes, and P1 was 0.7 MPaG.

  Then, it heated up to 270 degreeC over 31 minutes (process 2). The polymerization time TM2 until the completion 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 mol of sulfur, including the mol of water generated during polymerization (= mol of sulfidizing agent consumed by the reaction). During this period, a liquid addition pump was connected via a valve of the autoclave.

  Immediately after reaching 270 ° C, the mixture was 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 mol per mol of sulfur, including the mol of water generated during the polymerization (= mol of the sulfidizing agent consumed by 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, further cooling to 170 ° C., and then rapidly cooling to room temperature.

  The subsequent treatment was performed 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 size of the polymer was 432 μm, and the nitrogen content was 4 × 10 2 ppm.

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

  A distillation column was attached to the upper part of the autoclave through a valve, and the mixture was gradually heated to 220 ° C. over 2.5 hours with stirring under nitrogen at 240 rpm under normal pressure to remove liquid, 202 g of water and N-methyl-2- 2 g of pyrrolidone was discharged. 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 in the reaction system. The hydrogen sulfide scattered from the reaction system through the dehydration operation was 0.014 mol.

  Then, after cooling the autoclave to 160 ° C. or lower, 152 g (1.04 mol) of p-dichlorobenzene, 112 g (1.13 mol) of N-methyl-2-pyrrolidone, and 1.9 g (0% of a 48% aqueous sodium hydroxide solution). 0.02 mol) and 5 g of water were charged, and the inside of the reaction vessel was sufficiently replaced with nitrogen again, sealed, and the temperature was raised to 200 ° C. As a result, the amount of the dihalogenated aromatic compound used in the mixture was 1.05 mol per mol of the sulfiding agent sulfur.

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

  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 injected under pressure over 10 minutes using a liquid addition pump. After water pressure injection, the temperature was raised to 265 ° C. over 10 minutes and the reaction was performed for 2 hours (step 2). The polymerization time TM2 until the completion 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 mol per mol of sulfur, including the mol of water generated during the polymerization (= mol of the sulfiding agent consumed by the reaction).

  After the completion of the polymerization reaction, injection of 3.6 g of water was started at 265 ° C., and injection was completed at 264 ° C. The amount of water in the system in step 3 was 2.8 mol per mol 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 S2 was changed to 4 ° C./min, further cooling to 170 ° C., and then rapid cooling to room temperature.

  The subsequent treatment was performed 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 size of the polymer was 450 μm.

  The above results are shown in Table 1.

Claims (6)

A method for producing a granular polyarylene sulfide by reacting a mixture containing at least a sulfidizing agent, a dihalogenated aromatic compound, an organic polar solvent, and a polymerization aid, the method comprising the following steps 1 to 4 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 the reaction. The pressure P1 in the temperature range of the step 1 is 0.1 MPaG or more and 1.0 MPaG or less, and the polymerization time TM1 of the step 1 including the temperature raising / lowering time is 30 minutes or more and 240 minutes or less.
Step 2: After Step 1, the water content in the reaction system is adjusted to be 0.1 mol or more and 1.5 mol or less per 1 mol of sulfur, and the reaction is performed by heating at a temperature of 245 ° C. or more and 290 ° C. or less. The process of making. 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 completion of the polymerization reaction is 60 minutes or more and 300 minutes or less.
Step 3: After Step 2, the water content in the reaction system is adjusted to be 3.3 mol or more and 6.0 mol or less per mol of sulfur, and the temperature is set to T0 (240 ° C. ≦ T0 ≦ 290 ° C.). The step of setting the pressure P3 in the temperature range of step 3 to 1.0 MPaG or more and 2.0 MPaG or less.
Step 4: Subsequent to Step 3, cooling 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 to a cooling rate S2 (0.8 ° C./min<S2≦5° C./min). The method for producing granular polyarylene sulfide according to claim 1, wherein the weight average molecular weight Mw of the granular 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 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 metal oxide The method for producing a granular polyarylene sulfide according to any one of claims 1 to 3, wherein at least one polymerization aid selected from the above is used. 5. The production of granular polyarylene sulfide according to claim 1, 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 sulfidizing 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 sulfidizing agent.