JP2010144085A - Process for producing polyphenylene sulfide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing polyphenylene sulfide which effectively reutilizes unreacted p-dichlorobenzene generated in producing polyphenylene sulfide and reduces the amount of disposal of halides putting a heavy load on the environment. <P>SOLUTION: When the polyphenylene sulfide is produced by polymerizing an alkali metal sulfide and p-dichlorobenzene in N-methyl-2-pyrolidone, the unreacted p-dichlorobenzene recovered as an unreacted substance during the production of polyphenylene sulfide is used for p-dichlorobenzene in the process for producing polyphenylene sulfide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing polyphenylene sulfide (hereinafter referred to as PPS), and more specifically, improves the production efficiency of PPS by recovering and reusing unreacted p-dichlorobenzene generated during the production of PPS. In addition, the present invention relates to a method for producing PPS in which p-dichlorobenzene, which has been disposed of in spite of being a halide having a high environmental load, is reused as a raw material.

  Polyarylene sulfide (hereinafter referred to as PAS) typified by PPS is a resin excellent in heat resistance, molding processability, chemical resistance, flame retardancy, dimensional stability, etc. It has been widely used as a material for automobile equipment parts and chemical equipment parts. These PAS usually undergo a polymerization reaction between a dihaloaromatic compound such as dichlorobenzene and an alkali metal sulfide such as sodium sulfide in an organic amide solvent such as N-methyl-2-pyrrolidone (hereinafter referred to as NMP). It is manufactured by performing (for example, refer patent document 1).

In addition, a method for producing a high molecular weight PAS by a polymerization reaction has been proposed (see, for example, Patent Documents 2 and 3).
Japanese Patent Publication No. 45-3368 Japanese Patent Publication No. 52-12240 Japanese Patent Publication No. 63-33775

  However, the PAS obtained by the method proposed in Patent Document 1 has a low molecular weight and cannot be used for applications such as injection molding as it is, and the low molecular weight PAS is formed into a high molecular weight by heating and oxidative crosslinking in the air. Although it has been used for processing applications, the high molecular weight polymer is inferior in extrudability due to high degree of crosslinking / branching and is difficult to be formed into a film or fiber.

  The PAS obtained by the method proposed in Patent Document 2 has a high molecular weight, but in this method, the addition amount of the polymerization aid is required to be about equimolar with respect to the alkali metal sulfide. In addition, the polymerization aid is expensive, and the polymerization aid is mixed into the treated wastewater after the recovery of the polymer after the polymerization, and has a problem in wastewater treatment.

  Furthermore, in general PAS production methods represented by Patent Documents 1 to 3, when PPS is used, the weight of p-dichlorobenzene, which is a raw material, is suppressed in order to suppress depolymerization of PPS during the polymerization reaction. It is necessary to suppress the reaction conversion rate into a coalescence of about 95%. As a result, unreacted p-dichlorobenzene, which is a halide having a high environmental load remaining in the polymerization solvent, can be separated and recovered and discarded. It was necessary.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have used the unreacted p-dichlorobenzene recovered as an unreacted material as a raw material during the production of PPS, thereby disposing p-dichlorobenzene with a high environmental load. The inventors have found that the amount can be suppressed, and have completed the present invention.

  That is, the present invention uses unreacted p-dichlorobenzene recovered as an unreacted product during PPS production when PPS is produced by carrying out a polymerization reaction between an alkali metal sulfide and p-dichlorobenzene in NMP. It is related with the manufacturing method of the characteristic PPS.

  The present invention is described in detail below.

  In the production method of PPS of the present invention, when a polymerization reaction between an alkali metal sulfide and p-dichlorobenzene is carried out in NMP, unreacted p-dichlorobenzene remaining as an unreacted raw material is separated and recovered, and again the raw material p -Used as dichlorobenzene.

  As described in, for example, Japanese Patent Publication Nos. 45-3368, 52-12240, and 63-33775, PPS is a polymerization of alkali metal sulfide and p-dichlorobenzene in NMP. It is produced by a reaction, and in the production, it is preferred to react with p-dichlorobenzene after dehydrating water contained in the alkali metal sulfide in NMP.

  The polymerization conversion rate of the raw material p-dichlorobenzene to PPS during the production of PPS is generally about 95%, which is extremely low as a polycondensation reaction, and in order to suppress depolymerization. -In many cases, polymerization reaction by dichlorobenzene excess system is carried out, and in the production of PPS, halogenated compounds having a low environmental conversion from the polymerization reaction system by p-dichlorobenzene excess system are waste. As a result, problems such as raising raw material costs were caused.

  As the alkali metal sulfide used in the production method of the present invention, any alkali metal sulfide can be used as long as it belongs to the category of alkali metal sulfide, and a general alkali metal sulfide contains crystal water. Examples thereof include hydrates such as sodium sulfide, lithium sulfide, rubidium sulfide, cesium sulfide, potassium sulfide, etc. Among them, the sodium sulfide system that is most stably available is preferable, for example, sodium sulfide. 2.9 water salt, sodium sulfide pentahydrate, sodium sulfide aqueous solution obtained by reacting sodium hydrosulfide aqueous solution and sodium hydroxide aqueous solution can be mentioned. In the dehydration step, these impurities are used in combination with a small amount of alkali metal hydroxide in order to react with alkali metal bisulfide or alkali metal thiosulfate which may be present in a small amount in the alkali metal sulfide. Removal or conversion to sulfide can be achieved.

  Further, as the alkali metal sulfide, it can be used as an alkali metal sulfide having a particularly high purity, and as a result, a high molecular weight PPS can be produced more easily. It is preferable to react an alkali metal hydrosulfide with an alkali metal hydroxide to form an alkali metal sulfide. Examples of the alkali metal hydrosulfide include sodium hydrosulfide, lithium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and potassium hydrosulfide. Examples of the alkali metal hydroxide include sodium hydroxide. , Lithium hydroxide, rubidium hydroxide, cesium hydroxide, potassium hydroxide and the like.

  The production method of the present invention is characterized in that p-dichlorobenzene, which has been discarded as an unreacted product during PPS production, is recovered and used as a raw material again, thereby reducing waste generated during PPS production and PPS production costs. It measures. And in the manufacturing method of this invention, since it becomes possible to manufacture PPS which achieved high molecular weight especially with high production efficiency, it is p-containing 3-50 weight% of unreacted recovery p-dichlorobenzene. It is preferable to use dichlorobenzene as a raw material.

  In addition, as a method for recovering unreacted p-dichlorobenzene during the production of PPS, any method can be used as long as it is possible to separate and recover unreacted p-dichlorobenzene. After the completion of the PPS polymerization reaction, an NMP solution containing unreacted p-dichlorobenzene generated when the PPS is separated and recovered from the PPS polymerization solution is recovered, and the temperature of the recovered NMP solution is raised and azeotroped with water. It is preferable to carry out recovery by distillation. At that time, since the recovery efficiency of p-dichlorobenzene by azeotropic distillation and its workability are excellent, the recovered NMP solution is NMP / water / p-dichlorobenzene = 63 to 84.5 / 15 to 35 / It is preferable that it is in the range of 0.5 to 2 (% by weight), and when adjusting to this range, water is added to the NMP solution after separation and recovery of PPS from the PPS polymerization reaction solution It is possible to adjust by. In addition, when recovering p-dichlorobenzene, it can be recovered using a distillation column or the like, and it is possible to recover unreacted p-dichlorobenzene particularly high in purity and suitable for the production of PPS. Therefore, the tower top temperature is preferably 95 to 105 ° C.

  In the production method of PPS of the present invention, since it is possible to produce PPS with excellent production efficiency, when recovered unreacted p-dichlorobenzene is used, in the unreacted p-dichlorobenzene, The thioanisole content is preferably 500 ppm or less, particularly preferably 300 ppm or less. In addition, thioanisole here is a by-product during the production of PPS, and is sometimes accompanied when unreacted p-dichlorobenzene is recovered. Moreover, as a method for measuring the thioanisole content in unreacted p-dichlorobenzene, any method can be used as long as the thioanisole content can be measured. For example, unreacted p-dichlorobenzene can be used as a gas. Examples include methods used for chromatographic analysis.

  Although the manufacturing method of the present invention is specifically shown below, the present invention is not limited to this.

Examples of the method for producing PPS of the present invention include a method through 1) an alkali metal sulfide dehydration step, 2) a PPS polymerization step, 3) a PPS recovery step, 4) an unreacted p-dichlorobenzene recovery step, and the like. 1) Regarding the dehydration process Here, the dehydration process is to dehydrate the crystal water contained in the alkali metal sulfide in order to increase the polymerization efficiency during the polymerization of PPS, and to control the amount of water present in the polymerization reaction system. The amount of water in the system is preferably in the range of 0.5 to 1.5 moles per mole of alkali metal sulfide (in terms of anhydrous state). Further, by setting the dehydration completion temperature at that time to about 180 to 250 ° C., it is possible to adjust the water content in a desired system. In addition, when performing dehydration, it is preferable to perform dehydration in the presence of NMP because stable dehydration is possible.

2) Regarding PPS polymerization process This PPS polymerization process is a p-dioxide containing an alkali metal sulfide whose water content is adjusted by a dehydration process in an NMP solvent and unreacted recovered p-dichlorobenzene or unreacted recovered p-dichlorobenzene. In this process, PPS is produced by reacting with chlorobenzene at a temperature of 180 to 280 ° C., for example. In the present PPS polymerization step, the polymerization reaction may be performed at a constant polymerization temperature, or the polymerization temperature may be controlled in multiple stages in order to achieve a somewhat higher molecular weight of PPS. Furthermore, in order to obtain a higher molecular weight PPS, for example, a polymerization aid represented by water, lithium chloride, sodium acetate, lithium acetate, sodium benzoate, sodium propionate, or the like may be used.

Here, the polymerization conversion rate of p-dichlorobenzene in the production process of PPS can be calculated by the following equation.
(Ii) When p-dichlorobenzene (DCB) is used in excess relative to the alkali metal sulfide, the polymerization conversion rate = (DCB charge-DCB residual amount) / (DCB charge-DCB excess amount) × 100
(B) In cases other than (a) Polymerization conversion rate = (DCB charge−DCB remaining amount) / DCB charge × 100
The amount of p-dichlorobenzene used is preferably 0.9 to 1.1 mol per 1 mol of the alkali metal sulfide, and the reaction proceeds particularly efficiently and depolymerization is efficiently suppressed. Therefore, the amount is preferably 1.02 to 1.09 mol. The polymerization time is preferably 0.5 to 10 hours, and particularly preferably 2 to 7 hours because it is possible to produce with high production efficiency.

3) PPS recovery step This PPS recovery step recovers PPS from the PPS polymerization reaction solution obtained in step 2). Through this step, an NMP solution containing unreacted p-dichlorobenzene is obtained. It is

  In this step, a separator such as a centrifuge, a decanter, or a filter can be used to separate PPS, by-product salt and NMP, NMP-soluble components. Separation can also be performed by a method such as flash distillation.

4) Unreacted p-dichlorobenzene recovery step This unreacted p-dichlorobenzene recovery step is a step of recovering p-dichlorobenzene from the NMP solution separated in step 3), and recovering unreacted p-dichlorobenzene. Examples of the method include a method in which a recovered NMP solution is introduced into a distillation column, the temperature is increased, and recovery is performed by azeotropic distillation. And when performing the collection | recovery by a distillation tower, since it becomes possible to collect | recover especially p-dichlorobenzene excellent in purity and efficiency, it collect | recovers through the process of the following (1) and (2) at least. It is preferable.
(1): A step of introducing the NMP solution into a distillation tower set at a tower top temperature of 95 to 105 ° C. and a tower bottom temperature of 110 to 130 ° C., and recovering unreacted p-dichlorobenzene from the tower top.
(2); The NMP solution obtained from the bottom of the step (1) is introduced into a distillation column set at a tower top temperature of 95 to 105 ° C. and a tower bottom temperature of 200 to 210 ° C. A process for recovering chlorobenzene.

  In addition, after the azeotropic distillation, the unreacted p-dichlorobenzene is solidified by cooling the system, so that it can be easily separated and recovered from water.

  Furthermore, in the method for producing PPS of the present invention, NMP solution obtained by separating and recovering unreacted p-dichlorobenzene is further introduced into a distillation column, and NMP is purified by distillation to separate by-products such as phenol. It is also possible to carry out this process, and by accompanying this step, it is possible to reuse NMP as a polymerization solvent.

  The PPS obtained by the production method of the present invention can be used for various purposes by blending conventional additives. Examples of the additives include fibrous fillers such as glass fibers, carbon fibers, and potassium titanate whiskers. Agents; inorganic fillers such as calcium carbonate, mica, talc, silica, kaolin; mold release agents such as wax; silane and titanate coupling agents; antioxidants; thermal stabilizers; ultraviolet absorbers; Colorants; resins such as polyamide, polyethylene, polypropylene, polyphenylene oxide, polytetrafluoroethylene, and the like.

  According to the production method of the present invention, the unreacted p-dichlorobenzene generated during the production of PPS is recovered and reused to increase the production efficiency of PPS and to be discarded despite being a halide having a high environmental impact. The p-dichlorobenzene that has been used can be reused as a raw material, and the effect is extremely great in terms of reducing environmental impact.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these Examples.

~ Measurement of melt viscosity of PPS ~
Measurement was performed with a Koka type flow tester (manufactured by Shimadzu Corporation) equipped with a die having a diameter of 1 mm and a length of 2 mm under the conditions of a measurement temperature of 315 ° C. and a load of 10 kg.

Example 1
A 50 liter autoclave equipped with a stirrer is charged with 6214 g of flaky sodium sulfide (Na ₂ S · 2.9H ₂ O) and 17000 g of NMP, and gradually heated to 205 ° C. with stirring under a nitrogen stream, to 1355 g of water. Distilled off. After cooling this system to 140 ° C., 7160 g of p-dichlorobenzene and 5000 g of NMP were added, and the system was sealed under a nitrogen stream. This system was heated to 225 ° C. over 2 hours and polymerized at 225 ° C. for 2 hours, then heated to 250 ° C. over 30 minutes, and further polymerized at 250 ° C. for 3 hours. At this time, the polymerization conversion rate of p-dichlorobenzene was 96.2%. After completion of the polymerization, the mixture was cooled to room temperature and the polymer was isolated using a centrifuge. The solid content was repeatedly washed with warm water and dried at 100 ° C. for a whole day and night to obtain PPS having a melt viscosity of 280 poise.

  Separately, 4200 g of distilled water is added to 23400 g of the NMP separation solution after centrifugation, and an NMP solution of NMP / water / p-dichlorobenzene = 80/19/1 (wt%) is used. It was introduced into a distillation column set at 0 ° C., p-dichlorobenzene-water was recovered from the top of the column by azeotropy with water, and 350.8 g of p-dichlorobenzene was recovered (4.9 g of charged p-dichlorobenzene). %.) The thianisole content in p-dichlorobenzene at that time was 291 ppm as confirmed by gas chromatography analysis. Then, the NMP solution obtained from the tower bottom is introduced into a distillation tower set at a tower top temperature of 100 ° C. and a tower bottom temperature of 205 ° C., and p-dichlorobenzene-water is recovered from the tower top by azeotropy with water, 35.8 g of p-dichlorobenzene was recovered and discarded. After the azeotropic distillation, the distillation temperature was further raised to purify N-methyl-2-pyrrolidone. Furthermore, NMP obtained from the bottom of the column was introduced into a vacuum distillation column to purify NMP.

  Then, PPS and recovered p-dichlorobenzene were obtained in the same manner as described above, except that 7160 g of p-dichlorobenzene containing 350.8 g of recovered p-dichlorobenzene was used instead of 7160 g of p-dichlorobenzene. .

  By repeating these steps 60 times, 290.5 kg of PPS was obtained. At that time, 2.14 kg of p-dichlorobenzene was treated as waste.

Example 2
Except that 35.8 g of p-dichlorobenzene recovered by the second distillation column was not discarded and the whole amount of recovered p-dichlorobenzene was used again for the production of PPS, the PPS was recovered in the same manner as in Example 1. Manufactured. The obtained PPS was 290.5 kg, and there was no treatment of p-dichlorobenzene as waste.

Comparative Example 1
PPS was produced in the same manner as in Example 1 except that azeotropic recovery of p-dichlorobenzene was not performed and all unreacted p-dichlorobenzene was discarded.

  At that time, the obtained PPS was 290.5 kg, but the amount of p-dichlorobenzene treated as waste was 23.2 kg.

Claims (7)

  When producing polyphenylene sulfide by carrying out a polymerization reaction between an alkali metal sulfide and p-dichlorobenzene in N-methyl-2-pyrrolidone, unreacted p-dichlorobenzene recovered as an unreacted product during the production of polyphenylene sulfide is used. A process for producing polyphenylene sulfide, characterized in that   The method for producing polyphenylene sulfide according to claim 1, wherein p-dichlorobenzene containing 3 to 50% by weight of the unreacted p-dichlorobenzene is used.   The method for producing polyphenylene sulfide according to claim 1 or 2, wherein the unreacted p-dichlorobenzene has a thioanisole content of 500 ppm or less.   The unreacted p-dichlorobenzene recovered from the N-methyl-2-pyrrolidone solution obtained by separating the polyphenylene sulfide from the polyphenylene sulfide polymerization reaction solution after completion of the polymerization reaction by azeotropy with water is used. The manufacturing method of the polyphenylene sulfide in any one of.   Use of unreacted p-dichlorobenzene recovered by azeotropy with water from a water-adjusted N-methyl-2-pyrrolidone solution to which water is further added to the N-methyl-2-pyrrolidone solution according to claim 4 A process for producing polyphenylene sulfide, characterized in that   The N-methyl-2-pyrrolidone solution according to claim 4 or the water-adjusted N-methyl-2-pyrrolidone solution according to claim 5 is N-methyl-2-pyrrolidone / water / p-dichlorobenzene = 63. A process for producing polyphenylene sulfide, characterized in that it comprises ˜84.5 / 15 to 35 / 0.5 to 2 (% by weight). When using p-dichlorobenzene recovered by azeotropy with water from the N-methyl-2-pyrrolidone solution according to claim 4 or the water-adjusted N-methyl-2-pyrrolidone solution according to claim 5, A method for producing polyphenylene sulfide, characterized in that at least the unreacted p-dichlorobenzene recovered from the top of the distillation column in the following steps (1) and (2) is used.
(1): The N-methyl-2-pyrrolidone solution or the moisture-adjusted N-methyl-2-pyrrolidone solution is introduced into a distillation column set at a tower top temperature of 95 to 105 ° C and a tower bottom temperature of 110 to 130 ° C. Recovering unreacted p-dichlorobenzene from the top of the tower.
(2); The N-methyl-2-pyrrolidone solution obtained from the bottom of the column in step (1) is introduced into a distillation column set at a tower top temperature of 95 to 105 ° C. and a tower bottom temperature of 200 to 210 ° C. A step of recovering more unreacted p-dichlorobenzene.