JP4765264B2 - Process for producing polyphenylene sulfide - Google Patents

Description

  The present invention relates to a method for producing polyphenylene sulfide (hereinafter abbreviated as PPS) and PPS obtained by the method, and more particularly relates to a method for efficiently producing high molecular weight PPS in a short time and PPS obtained by the method. Is.

  PPS is an engineering plastic excellent in heat resistance, chemical resistance, flame retardancy, mechanical strength, electrical characteristics and dimensional stability, etc. By various molding methods such as injection molding, extrusion molding and compression molding, Since it can be molded into various molded products, films, sheets, fibers, etc., it is widely used in a wide range of fields such as electric / electronic devices and automobile devices.

  As a method for producing PPS, a method of reacting an alkali metal sulfide such as sodium sulfide with a dihaloaromatic compound such as p-dichlorobenzene in an organic amide solvent such as N-methyl-2-pyrrolidone has been proposed. (For example, refer to Patent Document 1). However, with this method, only PPS having a low molecular weight and a low melt viscosity can be obtained. By heating such low molecular weight PPS in the presence of air after polymerization and oxidative curing (curing), it is possible to increase the molecular weight of PPS. The cured PPS thus obtained has a mechanical property. Is insufficient and is not linear, it is difficult to form a sheet, film, fiber, or the like.

  In recent years, in order to obtain linear and high molecular weight PPS at the time of polymerization, various production methods improved from the above method have been proposed. As a means for improving the polymerization method of PPS, a method of adding various polymerization assistants when reacting an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent is typical. A method using an alkali metal carboxylate (for example, see Patent Document 2), a method using an alkaline earth metal salt of an aromatic carboxylic acid (see, for example, Patent Document 3), and an alkali metal halide. There are proposed a method of using (for example, see Patent Document 4) and a method of using a sodium salt of an aliphatic carboxylic acid (for example, see Patent Document 5).

  According to these methods, it is possible to obtain linear and high molecular weight PPS by polymerization. However, in order to obtain a high degree of polymerization PPS in a shorter time, it is expensive to use lithium acetate or sodium benzoate. However, there is a problem that the polymerization time is long and economically disadvantageous even if an inexpensive polymerization aid such as sodium acetate is simply applied.

  On the other hand, in a method of obtaining PPS by reacting an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent, it has been proposed to employ a specific two-stage polymerization method (see, for example, Patent Document 6). ). That is, in this prepolymerization step, the reaction is carried out at a temperature of 180 to 235 ° C. in the presence of 0.5 to 2.4 mol of water per mol of the charged alkali metal sulfide. After producing a low-viscosity prepolymer with a compound conversion rate of 50 to 98 mol%, 2.5 to 7 mol of water per mol of charged alkali metal sulfide is present in the subsequent polymerization step. In this two-stage polymerization method, water is added to the reaction system and the temperature is raised to a temperature of 245 to 290 ° C. to continue the reaction. However, in this method, since the amount of water present in the reaction system is not appropriate, there is a problem that a considerably long polymerization time is required to obtain a sufficiently high molecular weight PPS.

  Further, there is a method in which polymerization is carried out in the presence of a relatively small amount of 0.001 to 0.20 mole of alkali metal carboxylate in the presence of 0.5 to 2.4 mole of water per mole of alkali metal sulfide. Although disclosed (for example, see Patent Document 7), the main purpose of this method is to precipitate granular PPS to increase the yield, and the use of such a small amount of alkali metal carboxylate. In terms of the amount, it was difficult to obtain PPS having a high degree of polymerization in a short time.

In view of the drawbacks of the prior art as described above, the present inventors have obtained a molar ratio of moisture to a polymerization aid when PPS is obtained by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide solvent. It is proposed to adopt a two-stage polymerization in which is adjusted to a specific range (see Patent Document 8). That is, in this method, the reaction is performed within a temperature range of 200 ° C. or more and less than 245 ° C. so that the conversion rate is 30 to 80 mol%, and a PPS prepolymer is formed. The molar ratio of the polymerization assistant to the moisture in the system [polymerization assistant amount (mole) / water content (mole)] is 0.1 to 0.7 within a temperature range of less than 0 ° C., and the prepolymer is a high molecular weight polyphenylene sulfide However, this method is still insufficient in terms of shortening the polymerization time.
Japanese Examined Patent Publication No. 45-3368 (7-8 pages, Example 1) Japanese Patent Publication No. 52-12240 (Claims) JP 59-219332 A (Claims) U.S. Pat. No. 4,038,263 (Claim 1) Japanese Patent Laid-Open No. 1-161022 (Claims) Japanese Patent Publication No. 63-33775 (Claims) JP-A-6-145355 (Claims) JP 2002-265604 A (Claims 1, 2)

  The present invention has been achieved as a result of studying the solution of the problems in the prior art described above as an issue.

  Accordingly, an object of the present invention is to provide a method for efficiently producing a high molecular weight polyphenylene sulfide in a short time, and a polyphenylene sulfide obtained by the method.

As a result of diligent research to solve the above-mentioned problems, the present inventors have succeeded in efficiently reducing polyphenylene sulfide having a high degree of polymerization even when only the polymerization assistant, only the water content, or both are increased at a specific ratio. Although it is difficult to obtain in time, the amount of water in the reaction system is adjusted to be relatively small in the presence of a specific amount of polymerization aid, and the reaction is carried out in a specific temperature range of 250 ° C. or more and less than 265 ° C. After the prepolymer is formed (step 1), the reaction is continued in a specific temperature range of 272 ° C. or higher and lower than 285 ° C. (step 2), and the reaction time in steps 1 and 2 is adjusted to a specific ratio. As a result, it was found that PPS having a high degree of polymerization can be obtained in a short time, and reached the present invention.

  That is, the present invention comprises reacting an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent in the presence of 0.32 to 0.70 moles of polymerization aid per mole of alkali metal sulfide. In the method for producing polyphenylene sulfide, the above-described reaction is carried out at least according to the following steps 1 and 2 and reaction time conditions.

Step 1: Water content in the reaction system is charged under conditions of 0.5 mol or more and less than 1.5 mol per mol of the alkali metal sulfide, and the alkali metal sulfide and the dihaloaromatic compound are 250 ° C. or more and 265 ° C. Reacting within a temperature range of less than to produce a polyphenylene sulfide prepolymer.

  Process 2: The process of making the said prepolymer react within the temperature range of 272 degreeC or more and less than 285 degreeC, and converting into high molecular weight polyphenylene sulfide.

Reaction time condition: While adjusting the ratio (T1 / T2) of the reaction time T1 (min) of the step 1 and the reaction time T2 (min) of the step 2 to 0.50 to 3.0 , it is 200 ° C. or more and 285 ° C. The total reaction time at a temperature below is 300 minutes or less.

  The polyphenylene sulfide production method of the present invention is a method for producing polyphenylene sulfide by reacting an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent in the presence of a specific amount of a polymerization aid. After completion of the reaction, it is particularly useful when it includes a step of recovering the organic amide solvent by evaporation or distillation from the reaction mixture, especially a step of recovering the organic amide solvent by a flash method.

  Furthermore, since the polyphenylene sulfide resin obtained by the production method of the present invention has a sufficiently high melt viscosity and excellent toughness, it is particularly useful as an injection molded product or fiber.

  Further, the method for producing polyphenylene sulfide in the present invention is also useful in that a highly viscous polymer is polymerized in a very short time to improve productivity.

  According to the present invention, high molecular weight PPS can be efficiently produced in a short time. Therefore, the method for producing high molecular weight PPS of the present invention is suitable as a method for producing PPS on an industrial scale safely and economically.

  Hereinafter, for the present invention, alkali metal sulfide, dihaloaromatic compound, molecular weight regulator / branching agent / crosslinking agent, polymerization solvent, polymerization aid, polymerization stabilizer, polymerization reaction, recovery of polymerization solvent, recovery and generation of polymer Details will be described in the order of PPS.

(1) Alkali metal sulfides As the alkali metal sulfides used in the present invention, lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, and a mixture of two or more of these may be mentioned as preferable examples. it can. Particularly preferred is sodium sulfide. These alkali metal sulfides can be used as hydrates or aqueous mixtures or in the form of anhydrides. Further, an alkali metal sulfide prepared in situ in a reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide, or an alkali metal sulfide prepared in another reaction tank before the reaction can be used. . Also, an alkali metal sulfide prepared in situ in a reaction system from an alkali metal hydroxide such as lithium hydroxide or sodium hydroxide and hydrogen sulfide, or an alkali metal sulfide prepared in a separate reaction tank before the reaction Can also be used.

  In the present invention, the amount of charged alkali metal sulfide means the remaining amount obtained by subtracting the loss from the actual charged amount when a partial loss of alkali metal sulfide occurs before the start of the reaction due to dehydration operation or the like. It shall be.

(2) Dihaloaromatic Compound As the dihaloaromatic compound used in the present invention, dihalobenzene such as p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dibromobenzene, and 1-methoxy-2, And dihaloaromatic compounds containing a substituent other than halogen such as 5-dichlorobenzene and 3,5-dichlorobenzoic acid. Especially, the dihalo aromatic compound which has p-dihalobenzene represented by p-dichlorobenzene as a main component is preferable. Particularly preferably, it contains 80 to 100 mol% of p-dichlorobenzene, and more preferably 90 to 100 mol%. It is also possible to combine two or more different dihaloaromatic compounds into a copolymer.

  The use amount (preparation amount) of the dihaloaromatic compound is usually 0.9 to 2.0 mol, preferably 0.95 to 1.5 mol, more preferably 1.0 to 1 mol per mol of the charged alkali metal sulfide. The range of 1.3 mol, more preferably 1.01-1.10 mol, is desirable for obtaining high molecular weight PPS. When this use ratio is less than 0.9 mol or more than 2.0 mol, it tends to be difficult to obtain a high-viscosity (high polymerization degree) PPS suitable for processing.

(3) Molecular weight regulator / branching agent / crosslinking agent In the present invention, a monohalogen compound (not necessarily an aromatic compound) may be used to form the end of the produced PPS, or to regulate the polymerization reaction or molecular weight. Good) can be used together. In order to form a branched or crosslinked polymer, a trihalogen or higher polyhalogen compound (not necessarily an aromatic compound), an active hydrogen-containing halogenated aromatic compound and a halogenated aromatic nitro compound are used in combination. It is also possible. Specific examples of such polyhalogen compounds include 1,3,5-trichlorobenzene, 1,2,4-trichlorobenzene, 1,2,4,5-tetrachlorobenzene, hexachlorobenzene, 1,4,6-trichloronaphthalene. Among these, 1,3,5-trichlorobenzene and 1,2,4-trichlorobenzene are preferable among these. Examples of such active hydrogen-containing halogenated aromatic compounds include halogenated aromatic compounds having functional groups such as amino groups, mercapto groups, and hydroxyl groups. Specific examples include 2,5-dichloroaniline, 2,4-dichloroaniline, 2,3-dichloroaniline, 2,4,6-trichloroaniline, 2,2′-diamino-4,4′-dichlorodiphenyl ether, Examples include 2,4′-diamino-2 ′, 4-dichlorodiphenyl ether.

  Examples of the halogenated aromatic nitro compound include 2,4-dinitrochlorobenzene, 2,5-dichloronitrobenzene, 2-nitro-4,4′-dichlorodiphenyl ether, and 3,3′-dinitro-4,4′-. Examples include dichlorodiphenyl sulfone, 2,5-dichloro-2-nitropyridine, 2-chloro-3,5-dinitropyridine, and the like.

(4) Polymerization solvent In this invention, an organic amide solvent is used as a polymerization solvent. Examples of the organic amide solvent include N-alkylpyrrolidone such as N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, 1,3-dialkyl-2, and the like. -Aprotic organic amide solvents represented by imidazolidinone, tetraalkylurea, hexaalkylphosphoric triamide and the like, and mixtures thereof are preferably used because of their high reaction stability. Among these, use of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) is particularly preferable. The amount of the polymerization solvent used in the present invention is preferably in the range of 0.2 to 10 mol, more preferably in the range of 2 to 5 mol, per mol of the charged alkali metal sulfide.

(5) Polymerization aid In the present invention, a polymerization aid is used in order to obtain PPS having a high degree of polymerization in a shorter time. Specific examples of such polymerization aids include alkali metal carboxylates and lithium halides that are generally known as polymerization aids for PPS. Particularly preferred are alkali metal carboxylates.

  The alkali metal carboxylate has a general formula R (COOM) n (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. , Lithium, sodium, potassium, rubidium and cesium, and n is an integer of 1 to 3). Alkali metal carboxylates can also be used as anhydrous, hydrated or aqueous solutions. Specific examples of the alkali metal carboxylate include, for example, lithium acetate, sodium acetate, potassium acetate, sodium propionate, lithium valerate, sodium benzoate, sodium phenylacetate, potassium p-toluate, and mixtures thereof. Can be mentioned. Alkali metal carboxylate is an organic acid, an organic acid, and one or more compounds selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates, with approximately equal chemical equivalents. You may form by adding and making it react one by one. Among the alkali metal carboxylates, sodium acetate is particularly preferably used because it is inexpensive and easily available.

  The amount of these polymerization aids used is in the range of 0.32 to 0.70 mol, more preferably in the range of 0.37 to 0.50 mol, with respect to 1 mol of the charged alkali metal sulfide, The range of 0.45 mol is more preferable. If it is less than the above range, the effect of increasing the degree of polymerization is insufficient, and if it exceeds the above range, not only the effect of increasing the degree of polymerization can be obtained, but also the polymerization required to obtain a polymer of the same degree of polymerization. Conversely, the time becomes longer.

  These polymerization auxiliaries should just be contained in the reaction system in a back | latter stage polymerization process (postscript process 2) at least. Therefore, the timing of addition may be before the dehydration step before the start of the pre-stage polymerization, at any point in the middle of the post-stage polymerization from the start of the pre-stage polymerization, or any combination thereof.

(6) Polymerization stabilizer In the present invention, a polymerization stabilizer can also be used in order to stabilize the polymerization reaction system and prevent side reactions. The polymerization stabilizer contributes to stabilization of the polymerization reaction system and suppresses undesirable side reactions. One measure of the side reaction is the generation of thiophenol, and the addition of a polymerization stabilizer can suppress the generation of thiophenol. Specific examples of the polymerization stabilizer include compounds such as alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, and alkaline earth metal carbonates. Among these, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide are preferable. Since the alkali metal carboxylate described above also acts as a polymerization stabilizer, it is one of the polymerization stabilizers used in the present invention.

  These polymerization stabilizers can be used alone or in combination of two or more. The polymerization stabilizer is usually 0.01 to 0.20 mol, preferably 0.02 to 0.15 mol, more preferably 0.03 to 0.10 mol, relative to 1 mol of the charged alkali metal sulfide. Used in. If this ratio is small, the stabilizing effect is insufficient. Conversely, if the ratio is too large, it is economically disadvantageous or the polymer yield tends to decrease. The polymerization stabilizer may be added before the dehydration step before the start of the pre-stage polymerization, at any point during the start of the pre-stage polymerization or in the middle of the post-stage polymerization, or any combination thereof. Preferably, it is before the dehydration step or at the start of the previous stage polymerization. In addition, when a part of alkali metal sulfide decomposes | disassembles at the time of spin-drying | dehydration operation and hydrogen sulfide generate | occur | produces, the alkali metal hydroxide produced | generated as a result can also become a polymerization stabilizer.

(7) Polymerization Reaction In the present invention, the polymerization reaction is carried out by the following polymerization reaction 1 or polymerization reaction 2.

(7-1) Polymerization reaction 1
In the present invention, the polymerization reaction 1 is a reaction between an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent in the presence of 0.32 to 0.70 mol of polymerization aid per mol of the alkali metal sulfide. In the method for producing PPS, the above-described reaction is performed at least according to the following steps 1 and 2 and reaction time conditions, but there are additional steps such as a pretreatment step and a posttreatment step. Also good.

  Step 1: Water content in the reaction system is charged to 245 ° C. or more and 272 ° C. under conditions of 0.5 mol or more and less than 1.5 mol per mol of alkali metal sulfide charged. Reacting within a temperature range of less than to produce a polyphenylene sulfide prepolymer.

  Process 2: The process of making the said prepolymer react within the temperature range of 272 degreeC or more and less than 285 degreeC, and converting into high molecular weight polyphenylene sulfide.

  Reaction time condition: While adjusting the ratio (T1 / T2) of the reaction time T1 (min) of the step 1 and the reaction time T2 (min) of the step 2 to 0.45 to 4.50, the reaction time is 200 ° C. or more and 285 ° C. The total reaction time at a temperature below is 300 minutes or less.

    When starting Step 1 above, the alkali metal sulfide and the dihaloaromatic compound are added to the organic amide solvent in an inert gas atmosphere, preferably from room temperature to 220 ° C., preferably from 100 to 220 ° C. . A polymerization aid may be added at this stage. The order in which these raw materials are charged may be out of order or may be simultaneous. Alkali metal sulfides are usually used in the form of hydrates, but if the water content is less than 0.5 moles per mole of charged alkali metal sulfides, the necessary amount must be added and replenished. There is. If the alkali metal sulfide content is too high, before adding the dihaloaromatic compound, the mixture containing the organic amide solvent and the alkali metal sulfide is heated to remove excess water out of the system. Needed (dehydration process). In addition, when water is removed excessively by this operation, it is necessary to add and replenish the shortage.

  As alkali metal sulfide, alkali metal sulfide prepared in situ in the reaction system from alkali metal hydrosulfide and alkali metal hydroxide, or alkali metal sulfide prepared in another reaction tank before the reaction Can also be used. Although there is no particular limitation on this method, desirably, an alkali metal hydrosulfide and an alkali metal hydroxide are added to an organic amide solvent in an inert gas atmosphere at a temperature ranging from room temperature to 150 ° C., preferably from room temperature to 100 ° C. A method in which the temperature is raised to at least 150 ° C. or higher, preferably 180 to 250 ° C. under normal pressure or reduced pressure, to distill off water (dehydration step). A polymerization aid may be added at this stage. Moreover, in order to accelerate | stimulate distillation of a water | moisture content, you may react, adding toluene etc.

  The amount of coexisting water in the reaction system in Step 1 is in the range of 0.5 to less than 1.5 mol, preferably 0.8 to 1.2 mol, per mol of the charged alkali metal sulfide. By defining the amount of coexisting water in step 1 in such a relatively small range, PPS having a high degree of polymerization can be obtained in a shorter time.

The reaction temperature of step 1 is Ru der than 2 50 ° C. or higher 265 ° C..

  The amount of coexisting water in the reaction system in Step 2 is 0.5 to 1.5 mol, preferably 0.8 to 1.2 mol, per mol of the alkali metal sulfide charged. However, for the purpose of obtaining PPS having a higher degree of polymerization, not limited to this, water may be added to the reaction system in an arbitrary amount. In this case, the addition timing of the water may be any of the start time, the intermediate time, and the end time of the above step 2, but it is preferable to start the addition before half the reaction time of the above step 2.

  The reaction temperature in the above step 2 is 272 ° C. or more and less than 285 ° C., and more preferably 274 ° C. or more and less than 282 ° C. A reaction temperature exceeding the above range is not preferable because the inside of the reaction system tends to decompose.

  The reaction in the above steps 1 and 2 may be performed with the reaction temperature kept constant within the above temperature range, or may be performed by gradually raising the temperature within the above temperature range.

  In the present invention, the reaction time T1 in the above step 1 is preferably in the range of 60 to 150 minutes, more preferably in the range of 80 to 130 minutes, from the viewpoint of economically obtaining a sufficient degree of polymerization.

  The reaction time T2 in the above step 2 is preferably in the range of 40 to 120 minutes, more preferably in the range of 60 to 100 minutes, from the viewpoint of economically obtaining a sufficient degree of polymerization.

In order to achieve a sufficiently high degree of polymerization in the polymerization reaction 1, the ratio (T1 / T2) of the reaction time T1 in step 1 to the reaction time T2 in step 2 is 0 . Area by Der of 5 to 3.0.

  Furthermore, in the present invention, it is desirable that the total reaction time in the temperature range of 200 ° C. or more and less than 285 ° C. is 300 minutes or less, more preferably 250 minutes or less. Even if the reaction time is continued further, not only a sufficiently high polymerization degree effect is not recognized, but it becomes economically disadvantageous. About the minimum of total reaction time, it is preferable that it is 100 minutes or more, More preferably, it is 150 minutes or more.

(7-2) Polymerization reaction 2
In the present invention, the polymerization reaction 2 is a reaction between an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent in the presence of 0.32 to 0.70 mol of polymerization aid per mol of the alkali metal sulfide. In the method for producing PPS, the above-described reaction is performed at least according to the following steps 1 and 2 and reaction time conditions, but there are additional steps such as a pretreatment step and a posttreatment step. Also good.

  Step 1: Water content in the reaction system is charged to 245 ° C. or more and 255 ° C. between alkali metal sulfide and dihaloaromatic compound under conditions of 0.5 mol or more and less than 1.5 mol per mol of the alkali metal sulfide charged. Reacting within a temperature range of less than to produce a polyphenylene sulfide prepolymer.

  Process 2: The process of making the said prepolymer react within the temperature range of 275 degreeC or more and less than 285 degreeC, and converting into high molecular weight polyphenylene sulfide.

  Reaction time condition: While adjusting the ratio (T3 / T4) of the reaction time T3 (min) in the above step 1 to the reaction time T4 (min) in the step 2 to 0.15 to 1.7, the reaction time is 200 ° C. or more and 285 ° C. The total reaction time at a temperature below is 300 minutes or less.

  When starting Step 1 above, the alkali metal sulfide and the dihaloaromatic compound are added to the organic amide solvent in an inert gas atmosphere, preferably from room temperature to 220 ° C., preferably from 100 to 220 ° C. . A polymerization aid may be added at this stage. The order in which these raw materials are charged may be out of order or may be simultaneous. Alkali metal sulfides are usually used in the form of hydrates, but if the water content is less than 0.5 moles per mole of charged alkali metal sulfides, the necessary amount must be added and replenished. There is. If the alkali metal sulfide content is too high, before adding the dihaloaromatic compound, the mixture containing the organic amide solvent and the alkali metal sulfide is heated to remove excess water out of the system. Needed (dehydration process). In addition, when water is removed excessively by this operation, it is necessary to add and replenish the shortage.

  As alkali metal sulfide, alkali metal sulfide prepared in situ in the reaction system from alkali metal hydrosulfide and alkali metal hydroxide, or alkali metal sulfide prepared in another reaction tank before the reaction Can also be used. Although there is no particular limitation on this method, desirably, an alkali metal hydrosulfide and an alkali metal hydroxide are added to an organic amide solvent in an inert gas atmosphere at a temperature ranging from room temperature to 150 ° C., preferably from room temperature to 100 ° C. A method in which the temperature is raised to at least 150 ° C. or higher, preferably 180 to 250 ° C. under normal pressure or reduced pressure, to distill off water (dehydration step). A polymerization aid may be added at this stage. Moreover, in order to accelerate | stimulate distillation of a water | moisture content, you may react, adding toluene etc.

  The amount of coexisting water in the reaction system in Step 1 is in the range of 0.5 to less than 1.5 mol, preferably 0.8 to 1.2 mol, per mol of the charged alkali metal sulfide. By defining the amount of coexisting water in step 1 in such a relatively small range, PPS having a high degree of polymerization can be obtained in a shorter time.

  The reaction temperature in Step 1 is 245 ° C. or higher and lower than 255 ° C., and more preferably 245 ° C. or higher and lower than 253 ° C.

  The amount of coexisting water in the reaction system in Step 2 is 0.5 to 1.5 mol, preferably 0.8 to 1.2 mol, per mol of the alkali metal sulfide charged. However, for the purpose of obtaining PPS having a higher degree of polymerization, not limited to this, water may be added to the reaction system in an arbitrary amount. In this case, the addition timing of the water may be any of the start time, the intermediate time, and the end time of the above step 2, but it is preferable to start the addition before half the reaction time of the above step 2.

  The reaction temperature in the above step 2 is 275 ° C. or more and less than 285 ° C., and more preferably 278 ° C. or more and less than 282 ° C. A reaction temperature exceeding the above range is not preferable because the inside of the reaction system tends to decompose.

  The reaction in the above steps 1 and 2 may be performed with the reaction temperature kept constant within the above temperature range, or may be performed by gradually raising the temperature within the above temperature range.

  In the polymerization reaction 2, the reaction time T3 in the above step 1 is preferably in the range of 30 to 100 minutes, more preferably in the range of 50 to 90 minutes, from the viewpoint of economically obtaining a sufficient degree of polymerization.

  As reaction time T4 of the said process 2, the range for 60 to 150 minutes is preferable from the viewpoint of obtaining sufficient polymerization degree effect economically, and the range for 70 to 120 minutes is more preferable.

  Moreover, ratio (T3 / T4) of reaction time T3 of the said process 1 in the polymerization reaction 2 and reaction time T4 of the process 2 is 0.15-1.7, and is the range of 0.2-1.7. The range of 0.3 to 1.3 is more preferable.

  Furthermore, in the present invention, it is desirable that the total reaction time in the temperature range of 200 ° C. or more and less than 285 ° C. is 300 minutes or less, more preferably 250 minutes or less. Even if the reaction time is continued further, not only a sufficiently high polymerization degree effect is not recognized, but it becomes economically disadvantageous. About the minimum of total reaction time, it is preferable that it is 100 minutes or more, More preferably, it is 150 minutes or more.

(8) Recovery of polymerization solvent In the present invention, recovery of the organic amide solvent after the completion of polymerization can be carried out by a conventional method. For example, the organic amide solvent can be directly evaporated or distilled from a reaction mixture containing PPS, an organic amide solvent, a polymerization aid, and a by-product alkali metal halide. Alternatively, the cooled reaction mixture may be filtered as it is or after diluting with water or the like, and after the filtrate is extracted, the organic amide solvent may be evaporated or distilled.

  When the organic amide solvent is recovered directly from the reaction mixture by evaporation or distillation, the polymerization reaction product in a high temperature state is evaporated or distilled, or the polymerization reaction mixture is heated and evaporated as necessary. be able to. In particular, the flash method is more preferable because the recovery of the organic amide solvent and the produced polymer is easy and the recovery cost of the organic amide solvent is low. The flash method can be performed by a known method that is generally well known. Specifically, for example, after completion of the polymerization step 2, the reaction mixture in a high temperature state is introduced into a flash tank through a pipe, and the organic amide solvent evaporated in the flash tank is supplied to the organic amide solvent recovery tank. to recover. At this time, in order to increase the recovery rate of the organic amide solvent, the flash tank can be heated with a heating medium or the like. For example, when NMP is used as the organic amide solvent, it is 200 ° C. or higher, preferably 220 ° C. It is desirable to heat the flash tank in a temperature range of ~ 240 ° C. In order to further increase the recovery rate of the organic amide solvent, an inert gas can be circulated through the flash tank. Examples of the inert gas include water vapor, nitrogen gas, carbon dioxide gas, etc. Among them, water vapor is preferable in terms of cost. In order to further increase the recovery rate of the organic amide solvent, the flash tank can be evacuated or reduced in pressure.

  When the polymerization solvent is recovered by the flash method, most of the obtained PPS is in the form of powder, so that in the subsequent polymer recovery process, it is difficult to remove impurities such as by-product alkali metal halides and PPS oligomers by washing. is there. On the other hand, after the polymerization is completed, the reaction mixture is gradually cooled at a specific cooling rate, and when the organic amide solvent is recovered, since most of the obtained PPS is obtained in a granular form, by-product alkali metal halide, PPS oligomer, etc. Although the removal can be easily performed, the removal of the PPS oligomer has a problem that the polymer yield is reduced by 5 to 10% as compared with the flash method. In the method for producing polyphenylene sulfide in the present invention, high molecular weight PPS can be efficiently obtained in a high yield in a short time even when the polymerization solvent is recovered by a flash method.

(9) Polymer Recovery In the present invention, the polymer recovery after the completion of the polymerization reaction can be performed by a conventional method. For example, after completion of the polymerization reaction, the organic amide solvent as a polymerization solvent is removed by flashing, or the cooled product slurry is diluted as it is or diluted with water and filtered, and then washed and filtered repeatedly. By-product alkali metal halide, PPS oligomer, etc. remaining in the polymer are removed. Regarding the washing of the polymer with water, it is desirable to carry out washing at least once at a temperature of 120 ° C. or higher, preferably 150 ° C. to 200 ° C. In addition, after washing with water and collecting the polymer by filtration and further replacing with washing water, the efficiency of washing with water is improved.

  Washing with water can be performed batchwise, continuously, or any combination thereof. When the washing is batch type, the amount of water used for one washing is 2 to 20 g, preferably 5 to 15 g, per 1 g of the polymer. Moreover, the time required for one washing | cleaning is 5 to 60 minutes, Preferably it is 10 to 30 minutes. Further, after the above filtration and sieving, the PPS may be washed with the same organic amide solvent as the polymerization solvent, or an organic solvent such as ketones or alcohols. PPS can also be treated with an acid such as acetic acid or hydrochloric acid or a salt such as ammonium chloride.

  In the present invention, the polymer after washing and filtration can be dried by a conventional method. The drying method is not particularly limited, but it is more preferable to perform the drying at a temperature of 100 ° C. or higher, preferably in a temperature range of 120 to 180 ° C., under an inert gas atmosphere or under vacuum or reduced pressure. Drying may be performed batchwise, continuously, or any combination thereof.

(10) Generated PPS
By the method of the present invention, a high molecular weight PPS can be obtained in a high yield in a short time. Since the PPS obtained by the method of the present invention has a high molecular weight in a linear form, it can be molded not only into injection molded products but also into extruded products such as sheets, films, fibers and pipes by extrusion molding. it can.

  The PPS obtained by the method of the present invention can be used alone, but various inorganic fillers, fibrous fillers, various synthetic resins and the like can be blended and used as desired. Specific examples of such inorganic fillers include silicates such as talc, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, bentonite, asbestos, alumina silicate, silicon oxide, magnesium oxide, alumina, oxidation Metal compounds such as zirconium, titanium oxide and iron oxide, carbonates such as calcium carbonate, magnesium carbonate and dolomite, sulfates such as calcium sulfate and barium sulfate, hydroxides such as calcium hydroxide, magnesium hydroxide and aluminum hydroxide , Glass beads, glass flakes, glass powder, ceramic beads, boron nitride, silicon carbide, carbon black and silica, graphite and the like. Specific examples of the fibrous filler include glass fiber, carbon fiber, potassium titanate whisker, zinc oxide whisker, calcium carbonate whisker, wollastonite whisker, aluminum borate whisker, aramid fiber, alumina fiber, silicon carbide fiber, ceramic fiber, Examples include asbestos fiber, stone koji fiber, and metal fiber. Specific examples of the synthetic resin include polyamide resin, polybutylene terephthalate resin, polyethylene terephthalate resin, modified polyphenylene ether resin, polysulfone resin, polyallyl sulfone resin, polyketone resin, polyetherimide resin, polyarylate resin, and liquid crystal polymer. , Polyether sulfone resin, polyether ketone resin, polythioether ketone resin, polyether ether ketone resin, polyimide resin, polyamideimide resin, and tetrafluoropolyethylene resin. In particular, for the purpose of improving the flexibility and impact resistance of PPS, in addition to the synthetic resin, an epoxy group-containing olefin copolymer and an ethylene / α-olefin copolymer may be used alone or arbitrarily. It can mix | blend and use in the ratio of. Examples of the epoxy group-containing olefin copolymer include an ethylene / propylene-g-glycidyl methacrylate copolymer (“g” represents a graft, the same shall apply hereinafter), an ethylene / butene-1-g-glycidyl methacrylate copolymer. Α- such as ethylene / glycidyl acrylate copolymer, ethylene / glycidyl methacrylate copolymer, ethylene / methyl acrylate / glycidyl methacrylate copolymer, ethylene / methyl methacrylate / glycidyl methacrylate copolymer, etc. Preferred are olefin copolymers containing olefin and glycidyl ester of α, β-unsaturated carboxylic acid as essential copolymerization components. Of these, ethylene / glycidyl methacrylate copolymer, ethylene / methyl acrylate / glycidyl methacrylate copolymer, and ethylene / methyl methacrylate / glycidyl methacrylate copolymer are particularly preferable. Examples of the ethylene / α-olefin copolymer include copolymers having ethylene and at least one α-olefin having 3 to 20 carbon atoms as constituent components. Specific examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1 -Dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1 -Hexene, 3-ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, 12-ethyl-1-tetradecene and combinations thereof To be mentioned.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The physical properties were measured according to the following methods.

(1) Polymer Yield Based on the weight (theoretical amount) assumed that all sodium sulfide in the autoclave after the dehydration step was converted to PPS. If sodium sulfide is charged in excess of the dihaloaromatic compound, it may not be converted to PPS at all, but even in that case, the amount of sodium sulfide should be considered as a standard.

(2) Melt viscosity of polymer Using a melt indexer (orifice length 8 mm, load 5000 g) manufactured by Toyo Seiki Co., Ltd., measurement was performed under the conditions of 315 ° C. and a residence time of 5 minutes, and the melt flow rate of the polymer was compared.

[Example 1]
(Dehydration process)
In an autoclave equipped with a stirrer and a valve at the bottom, 118 g (1.00 mol) of 47.4% sodium hydrosulfide, 42.9 g (1.03 mol) of 96% sodium hydroxide, N-methyl-2 -198 g (2.00 mol) of pyrrolidone (NMP), 31.3 g (0.38 mol) of sodium acetate and 150 g of ion-exchanged water were charged and gradually heated to 240 ° C. over about 3 hours while passing nitrogen at normal pressure. After distilling 210 g of water and 4 g of NMP, the reaction vessel was cooled to 160 ° C. The amount of water remaining in the system per mole of the alkali metal sulfide charged was 1.15 mol including the water consumed for the hydrolysis of NMP. The amount of hydrogen sulfide scattered was 2 mol%.

(Process 1)
Next, 147 g (1.00 mol) of p-dichlorobenzene (p-DCB) and 92.1 g (0.93 mol) of NMP were added, the reaction vessel was sealed under nitrogen gas, and the mixture was stirred at 240 rpm. From 250 to 250 ° C. at a rate of 0.8 ° C./min and held at 250 ° C. for 70 minutes. Next, the temperature was raised to 272 ° C. at a rate of 0.8 ° C./min.

(Process 2)
Subsequently, the temperature was raised from 272 ° C. to 278 ° C. at a rate of 0.8 ° C./min, and held for 78 minutes. After 78 minutes at 278 ° C., the extraction valve provided at the bottom of the autoclave was opened, the contents were flushed, and rapidly cooled to near room temperature.

(Recovery process)
After diluting the flushed contents with 1.0 liter of warm ion-exchanged water, the liquid part and the solid part are separated by a glass filter, and the resulting solid part is washed several times with 1.0 liter of warm ion-exchanged water. And filtered off. Next, the solid portion separated by filtration and 1.2 liters of ion exchange water were charged into an autoclave equipped with a stirrer and purged with nitrogen, and then heated to 195 ° C. and held for 30 minutes. After 30 minutes, the autoclave was rapidly cooled to 90 ° C., and the contents were filtered off with a glass filter to obtain PPS polymer particles. This was dried at 120 ° C. under a nitrogen stream.

  The melt flow rate of the obtained PPS was 200 g / 10 min, and the yield was 98% (Table 1).

[Comparative Example 1]
Polymerization and recovery operations were performed in the same manner as in Example 1 except for the following points.

  The reaction in (Step 1) was heated from 200 ° C. to 250 ° C. at a rate of 0.8 ° C./min, held at 250 ° C. for 70 minutes, and then from 250 ° C. to 270 ° C. at 0.8 ° C./min. The temperature was raised at a rate of.

  Subsequently, the reaction in (Step 2) was maintained at 270 ° C. for 78 minutes, and then the temperature was increased from 270 ° C. to 278 ° C. at a rate of 0.8 ° C./minute to flush the contents.

  The melt flow rate of the obtained PPS was 288 g / 10 min, and the yield was 98% (Table 1). From this, it can be seen that the constant temperature reaction temperature in (Step 2) is 278 ° C., which is superior in increasing the degree of polymerization.

[Comparative Example 2]
Polymerization and recovery operations were performed in the same manner as in Example 1 except that the amount of sodium acetate charged in (dehydration step) was 24.1 g (0.29 mol).

  The melt flow rate of the obtained PPS was 355 g / 10 min, and the yield was 99% (Table 1). From this, it can be seen that if the amount of the polymerization aid used for the polymerization is too small, the resulting PPS has a low degree of polymerization.

[Example 2]
The reaction in (Step 1) was heated from 200 ° C. to 260 ° C. at a rate of 0.8 ° C./min, held at 260 ° C. for 70 minutes, and then from 260 ° C. to 272 ° C. at a rate of 0.8 ° C./min. Polymerization and recovery operations were carried out in the same manner as in Example 1 except that the temperature was raised.

  The melt flow rate of the obtained PPS was 180 g / 10 min, and the yield was 98% (Table 1). It can be seen that when the constant temperature reaction temperature in (Step 1) is 260 ° C., PPS having a higher degree of polymerization is more easily obtained.

[Example 3]
Polymerization and recovery operations were performed in the same manner as in Example 1 except that the holding time at 250 ° C. in (Step 1) was 50 minutes and the holding time at 278 ° C. in (Step 2) was 98 minutes.

  The melt flow rate of the obtained PPS was 220 g / 10 min, and the yield was 99% (Table 1). It can be seen that the degree of polymerization of the resulting PPS differs depending on the distribution of the reaction time T1 of 245 ° C. or more and less than 272 ° C. in (Step 1) and the reaction time T2 of 272 ° C. or more and less than 285 ° C. in (Step 2).

[Example 4]
The holding time at 250 ° C. in (Step 1) was 100 minutes, and the reaction in (Step 2) was heated from 272 ° C. to 275 ° C. at a rate of 0.8 ° C./min and held at 275 ° C. for 85 minutes. Except for the above, polymerization and recovery operations were carried out in the same manner as in Example 1.

  The melt flow rate of the obtained PPS was 210 g / 10 min, and the yield was 98% (Table 1).

[Comparative Example 3]
After completion of (dehydration step) (at the beginning of (step 1)), polymerization and recovery operations were performed in the same manner as in Example 4 except that 0.5 mol of water was added.

  The melt flow rate of the obtained PPS was 454 g / 10 min, and the yield was 98% (Table 1). From this, it is understood that PPS having a high degree of polymerization cannot be obtained when the amount of water in (Step 1) is large.

Claims (4)

Process for producing polyphenylene sulfide by reacting an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent in the presence of 0.32 to 0.70 mole of a polymerization aid per mole of alkali metal sulfide The method for producing polyphenylene sulfide, wherein the reaction is carried out at least in the following steps 1 and 2 and reaction time conditions.
Step 1: Water content in the reaction system is charged to a temperature of 250 ° C. or more and 265 ° C. between the alkali metal sulfide and the dihaloaromatic compound under the conditions of 0.5 mol or more and less than 1.5 mol per mol of the alkali metal sulfide charged. Reacting within a temperature range of less than to produce a polyphenylene sulfide prepolymer.
Process 2: The process of making the said prepolymer react within the temperature range of 272 degreeC or more and less than 285 degreeC, and converting into high molecular weight polyphenylene sulfide.
Reaction time condition: While adjusting the ratio (T1 / T2) of the reaction time T1 (min) of the step 1 and the reaction time T2 (min) of the step 2 to 0.5 to 3.0, it is 200 ° C. or more and 285 ° C. The total reaction time at a temperature below is 300 minutes or less. The reaction time condition is such that the ratio (T1 / T2) of the reaction time T1 (minute) in the step 1 and the reaction time T2 (minute) in the step 2 is adjusted to 0.65 to 1.34, and is 200 ° C. or higher. 2. The method for producing polyphenylene sulfide according to claim 1, wherein the total reaction time at a temperature lower than 285 [deg.] C. is from 150 minutes to 300 minutes. Wherein after step 2 termination method for producing a polyphenylene sulfide according to claim 1 or 2 comprising the step of recovering the organic amide solvent is evaporated or distilled from the reaction mixture. The method for producing polyphenylene sulfide according to claim 3 , wherein the organic amide solvent is recovered by a flash method.