JP2011111548A - Method for continuously recovering alkali metal halide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for continuously recovering an alkali metal halide in the production of a polyarylene sulfide and a cyclic polyarylene sulfide. <P>SOLUTION: In recovering an alkali metal halide from a mixture including at least a polyarylene sulfide, a cyclic polyarylene sulfide, an alkali metal halide, water and an organic polar solvent, the continuous recovery of the alkali metal halide is achieved by performing sedimentation separation under a pressure higher than the vapor pressure of the mixture at the recovery temperature and at the same time the polyarylene sulfide and the cyclic polyarylene sulfide can be recovered with high efficiency. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for producing polyarylene sulfide, and more particularly to a method for continuously recovering an alkali metal halide from a reaction mixture containing at least polyarylene sulfide, cyclic polyarylene sulfide, alkali metal halide, water and an organic polar solvent.

  Polyarylene sulfide (hereinafter sometimes abbreviated as PAS) represented by polyphenylene sulfide (hereinafter also abbreviated as PPS) has excellent heat resistance, barrier properties, chemical resistance, electrical insulation properties, and heat and humidity resistance. It is a resin having properties suitable as an engineering plastic such as flame retardancy. In addition, it can be molded into various molded parts, films, sheets, fibers, etc. by injection molding and extrusion molding, and widely used in fields that require heat resistance and chemical resistance, such as various electrical / electronic parts, mechanical parts, and automotive parts. It has been.

  As a specific method for producing this PAS, a method of reacting an alkali metal sulfide such as sodium sulfide with a polyhaloaromatic compound such as p-dichlorobenzene in an organic amide solvent such as N-methyl-2-pyrrolidone is proposed. This method is widely used as an industrial production method for PAS. Since the polymerization reaction in this production method is a desalting polycondensation mechanism, a large amount of by-product salt such as sodium chloride is generated. Therefore, a by-product salt removal step is necessary after the polymerization reaction, but it is difficult to completely remove the by-product salt by ordinary treatment, and in a commercially available general-purpose PPS product, the alkali metal content is several thousand ppm. The degree is contained. As described above, when the alkali metal salt remains in the produced polymer, there arises a problem that the physical properties such as electric characteristics are lowered. Therefore, when applying a molded product using such PAS as a raw material to the field of electric / electronic parts, the deterioration of the electrical characteristics due to the alkali metal in PAS becomes a major obstacle.

  The above-mentioned problems in PAS, that is, methods for reducing the amount of metal contained in PAS have been variously studied so far. For example, PPS containing 1000 ppm or more of alkali metal obtained by the above method is heated at 120 ° C. or less for a long time. A method of repeatedly carrying out water washing (for example, see Patent Document 2), a reaction product containing PPS obtained by reacting sodium hydrosulfide, sodium hydroxide and p-dichlorobenzene in N-methyl-2-pyrrolidone. After repeatedly washing with water and warm water, further washing with an acidic aqueous solution followed by washing with ion-exchanged water (see, for example, Patent Document 3), a method of repeatedly washing PPS in the presence of a surfactant (for example, Patent Document) 4, etc.). Regarding the removal of the metal compound (by-product salt) generated in the reaction generation stage of PAS, in these methods, a mixture containing solid PAS and the metal compound is brought into contact with water, and the metal compound is dissolved in water to dissolve the PAS. Therefore, several steps of long-time water washing using a large amount of water are necessary to remove metal impurities, and thus a very large and complicated process is required. Furthermore, it is necessary to treat a large amount of aqueous wastewater generated in this washing process, which is a process with extremely high process cost and environmental load.

  On the other hand, as a simple method for separating the metal component from the PAS component, for example, after filtering the reaction solution generated after polymerization in the production of polyphenylene sulfide through a pressure filter at a temperature at which the polyphenylene sulfide dissolves, the filtrate is put into water or a water-containing medium. A method of recovering the polyarylene sulfide component by precipitation by introduction (see, for example, Patent Document 5), and in the production process of the polysulfide arylene, the polysulfide arylene is dissolved at a temperature at which the polysulfide arylene is dissolved in the reaction solvent. By separating the metal salt formed as a by-product, a solution containing polysulfide arylene is recovered, and after removing the solvent from this solution and isolating the polysulfide arylene, the polysulfide arylene in the molten state is mixed with water. Polysulfide after contact, and through vacuum extrusion A method for isolating rylene (see, for example, Patent Document 6), a temperature at which polyphenylene sulfide dissolves sodium chloride produced by polymerization after polymerizing sodium sulfide monomer and dichlorobenzene monomer in N-methyl-2-pyrrolidone And then recovering polyarylene sulfide by adding carbon dioxide until a high pressure state of 15 MPa or higher is obtained (see, for example, Patent Document 7). When sodium chloride is separated according to these methods, it is possible to separate the alkali metal halide from the PAS component. However, in order to reduce the loss of the PAS component in the sodium chloride separation step, it is still large and complicated. Therefore, a special and expensive apparatus is required, and many problems to be improved still remain.

  Further, a method for producing a high-quality polyarylene sulfide having a reduced metal content (for example, see Patent Document 8) has been disclosed. When alkali metal halide is removed according to this method, Although the metal halide can be separated and a high-quality polyarylene sulfide having a reduced metal content and oligomer component can be obtained, there is a problem that continuous operation is difficult and production efficiency is low.

Japanese Patent Publication No. 45-3368 JP-A-55-156342 JP-A-61-220446 Japanese Patent Laid-Open No. 62-185718 JP-A-62-86022 JP-A-4-318027 JP-A-10-265576 Japanese Patent Laid-Open No. 21-167395

  An object of the present invention is to provide a method for continuously recovering an alkali metal halide in order to solve the above-described problems of the prior art and to efficiently obtain a high-quality polyarylene sulfide having a reduced metal content.

The present invention employs the following means in order to solve such problems.
That is, the present invention
(1) At least a polyarylene sulfide, a cyclic polyarylene sulfide, an alkali metal halide, water and an organic polar solvent obtained by bringing a sulfidizing agent and a dihalogenated aromatic compound into contact with each other in an organic polar solvent. A method for continuously recovering alkali metal halides, characterized in that when recovering the alkali metal halide from the reaction mixture (a), the alkali metal halide is recovered by settling under a pressure equal to or higher than the vapor pressure of the reaction mixture (a) at the recovery temperature ( 2) The method for continuously recovering alkali metal halides according to (1), wherein the sedimentation separation is performed using a decanter centrifuge as a separator when the sedimentation separation is performed.
(3) The alkali according to (1) or (2), wherein the amount of water contained in the reaction mixture (a) when performing sedimentation separation is 3 parts by weight or less with respect to 100 parts by weight of the organic polar solvent. (4) The metal halide is continuously recovered. (4) The amount of water contained in the reaction mixture (a) during the precipitation separation is 1 part by weight or less with respect to 100 parts by weight of the organic polar solvent. Any one of (1) to (4), wherein the method for continuously recovering alkali metal halides according to any one of (3) to (5) is characterized in that the precipitation separation is carried out in a temperature range in which the polyarylene sulfide is soluble. A method for continuously recovering alkali metal halides as described above.

  According to the present invention, alkali metal halide is continuously recovered from a reaction mixture containing polyarylene sulfide, cyclic polyarylene sulfide, alkali metal halide, water and an organic polar solvent, and the metal content is reduced. A high-quality polyarylene sulfide can be obtained efficiently.

Hereinafter, the present invention will be described in detail.

(1) Cyclic polyarylene sulfide The cyclic polyarylene sulfide in the present invention is a cyclic compound having a repeating unit of the formula:-(Ar-S)-as a main structural unit, and preferably the repeating unit is 80 It is a compound such as the following formula (A) containing at least mol%.

  Here, examples of Ar include units represented by the following formulas (A) to (S), among which the formulas (A) to (SA) are preferable, and the formulas (A) and (U) are preferable. More preferably, formula (I) is particularly preferred (wherein R1 and R2 are substituents selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and a halogen group). , R1 and R2 may be the same or different.

  In addition, in cyclic polyarylene sulfide, repeating units, such as said Formula (I)-Formula (S), may be included at random, may be included in a block, and any of those mixtures may be sufficient. Typical examples of these include cyclic polyarylene sulfide, cyclic polyphenylene sulfide sulfone, cyclic polyphenylene sulfide ketone, cyclic random copolymers containing these, cyclic block copolymers, and mixtures thereof. It is done. Particularly preferred cyclic polyarylene sulfides include p-phenylene sulfide units as the main structural unit.

Is a cyclic polyphenylene sulfide containing 80 mol% or more, particularly 90 mol% or more.

  Although there is no restriction | limiting in particular in the repeating unit number m in the said Formula (a) formula of cyclic polyarylene sulfide, 2-50 are preferable, 2-25 are more preferable, and 3-20 can be illustrated as a still more preferable range.

  The cyclic polyarylene sulfide may be either a single compound having a single repeating unit number or a mixture of cyclic polyarylene sulfides having different repeating unit numbers.

(2) Polyarylene sulfide In the present invention, the polyarylene sulfide is a linear homopolymer containing a repeating unit of the formula-(Ar-S)-as a main constituent unit, preferably containing 80 mol% or more of the repeating unit. A linear copolymer. Ar includes units represented by the above formulas (a) to (su), among which the formula (a) is particularly preferred (wherein R1 and R2 are hydrogen, from 1 carbon atom). 6 is an alkyl group having 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and a substituent selected from a halogen group, and R1 and R2 may be the same or different.

  As long as this repeating unit is a main structural unit, it can contain a small amount of branching units or crosslinking units represented by the following formulas (C) to (H). The amount of copolymerization of these branched units or cross-linked units is preferably in the range of 0 to 1 mol% with respect to 1 mol of-(Ar-S)-units.

  In addition, the polyarylene sulfide in the present invention may be any of a random copolymer, a block copolymer and a mixture thereof containing the above repeating unit.

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

In addition to polyphenylene sulfide containing 80 mol% or more, particularly 90 mol% or more, polyphenylene sulfide sulfone and polyphenylene sulfide ketone.

  Although there is no restriction | limiting in particular in the molecular weight of various polyarylene sulfide in this invention, As a weight average molecular weight of general polyarylene sulfide, 2000-1 million can be illustrated, 2500-500000 are preferable and 5000-100000 are more preferable. In general, polyarylene sulfide having a weight average molecular weight within the above range is particularly excellent in properties such as mechanical strength and chemical resistance. Here, the weight average molecular weight is a value calculated in terms of polystyrene by gel permeation chromatography (GPC).

(3) Sulfidation agent The sulfidation agent in the present invention may be any as long as it can introduce a sulfide bond into a dihalogenated aromatic compound, and examples thereof include alkali metal sulfides, alkali metal hydrosulfides, and hydrogen sulfide. .

  Specific examples of the alkali metal hydrosulfide include, for example, lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, and a mixture of two or more of these, and lithium sulfide and / or sodium sulfide are preferable. Sodium sulfide is more preferably used. These alkali metal sulfides can be used as hydrates or aqueous mixtures or in the form of anhydrides. The aqueous mixture refers to an aqueous solution, a mixture of an aqueous solution and a solid component, or a mixture of water and a solid component. Since generally available inexpensive alkali metal sulfides are hydrates or aqueous mixtures, it is preferable to use such forms of alkali metal sulfides.

  Specific examples of the alkali metal sulfide include lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide and a mixture of two or more thereof, among them lithium hydrosulfide and / or Alternatively, sodium hydrosulfide is preferable, and sodium hydrosulfide is more preferably used.

  Moreover, the alkali metal sulfide prepared in a reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide can also be used. Further, an alkali metal sulfide prepared by previously contacting an alkali metal hydrosulfide and an alkali metal hydroxide can also be used. These alkali metal hydrosulfides and alkali metal hydroxides can be used as hydrates or aqueous mixtures, or in the form of anhydrides. From the viewpoint of availability and cost of hydrates or aqueous mixtures. preferable.

  Furthermore, alkali metal sulfides prepared in the reaction system from alkali metal hydroxides such as lithium hydroxide and sodium hydroxide and hydrogen sulfide can also be used. Further, alkali metal sulfides prepared by previously contacting alkali metal hydroxides such as lithium hydroxide and sodium hydroxide with hydrogen sulfide can also be used. Hydrogen sulfide can be used in any form of gas, liquid, and aqueous solution.

  In the present invention, the amount of the sulfidizing agent is subtracted from the actual charge when the loss of the sulfidizing agent partially occurs before the start of the reaction with the dihalogenated aromatic compound due to dehydration operation or the like. It shall mean the remaining amount.

  An alkali metal hydroxide and / or an alkaline earth metal hydroxide can be used in combination with the sulfidizing agent. Specific examples of the alkali metal hydroxide include, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, and a mixture of two or more thereof. Specific examples of the metal hydroxide include, for example, calcium hydroxide, strontium hydroxide, barium hydroxide, and sodium hydroxide is preferably used.

  When an alkali metal hydrosulfide is used as the sulfidizing agent, it is particularly preferable to use an alkali metal hydroxide at the same time, but the amount used is from 0.95 mol to 1 per mol of the alkali metal hydrosulfide. A range of .50 mol, preferably 1.00 mol to 1.25 mol, and more preferably 1.005 mol to 1.200 mol can be exemplified. When hydrogen sulfide is used as the sulfiding agent, it is particularly preferable to use an alkali metal hydroxide at the same time. In this case, the amount of the alkali metal hydroxide used is from 2.0 to 3. A range of 0 mol, preferably 2.01 mol to 2.50 mol, more preferably 2.04 mol to 2.40 mol can be exemplified.

(4) Dihalogenated aromatic compound In the present invention, as a preferred method for preparing a mixture comprising at least polyarylene sulfide, cyclic polyarylene sulfide, alkali metal halide, water and an organic polar solvent, (i) at least a sulfidizing agent, dihalogen A method of heating and reacting a mixture containing a halogenated aromatic compound and an organic polar solvent, and (ii) a method of heating and reacting a mixture containing at least a polyarylene sulfide, a sulfidizing agent, a dihalogenated aromatic compound and an organic polar solvent. As a dihalogenated aromatic compound used here, p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dibromobenzene, o-dibromobenzene, m-dibromobenzene 1-bromo-4- Dihalogenated benzene such as chlorobenzene, 1-bromo-3-chlorobenzene, and 1-methoxy-2,5-dichlorobenzene, 1-methyl-2,5-dichlorobenzene, 1,4-dimethyl-2,5-dichlorobenzene And dihalogenated aromatic compounds having substituents other than halogen such as 1,3-dimethyl-2,5-dichlorobenzene and 3,5-dichlorobenzoic acid. Especially, the dihalogenated aromatic compound which has p-dihalogenated benzene represented by p-dichlorobenzene as a main component is preferable. Particularly preferably, it contains 80 to 100 mol%, more preferably 90 to 100 mol% of p-dichlorobenzene. It is also possible to use two or more different dihalogenated aromatic compounds in combination in order to produce a cyclic polyarylene sulfide copolymer.

(5) Organic polar solvent Although the mixture (a) in this invention contains an organic polar solvent, an organic amide solvent is preferable especially. Specific examples include N-alkylpyrrolidones such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and N-cyclohexyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, Aprotic organic solvents represented by 3-dimethyl-2-imidazolidinone, N, N-dimethylacetamide, N, N-dimethylformamide, hexamethylphosphoric triamide, and mixtures thereof are preferably used because of their high stability. It is done. Among these, N-methyl-2-pyrrolidone and / or 1,3-dimethyl-2-imidazolidinone are preferable, and N-methyl-2-pyrrolidone is particularly preferably used.

  Here, the amount of the organic polar solvent used is preferably 50 liters or less, more preferably 20 liters or less, and even more preferably 15 liters or less with respect to 1 mole of the sulfur component of the sulfidizing agent. With such a preferable amount of the organic polar solvent used, the reaction of the sulfidizing agent and the dihalogenated aromatic compound can proceed with a high yield in a short time, and PAS and cyclic polyarylene sulfide having a low molecular weight can be efficiently produced. Here, the amount of solvent used is based on the volume of the solvent under normal temperature and pressure. Moreover, the usage-amount of an organic polar solvent is the quantity which deducted the organic polar solvent removed out of the reaction system from the organic polar solvent introduce | transduced in the reaction system.

(6) Alkali metal halide The alkali metal halide in the present invention includes all alkali metal halides present in the reaction mixture (a). Alkali metal halides include any combination of alkali metals, i.e. lithium, sodium, potassium, rubidium and cesium, and halogens, i.e. fluorine, chlorine, bromine, iodine and astatine. Lithium, sodium chloride, potassium chloride, lithium bromide, cesium fluoride and the like can be exemplified, and sodium chloride, potassium chloride, sodium bromide and potassium bromide can be exemplified as preferred, and sodium chloride is more preferred. .

(7) Preparation method of reaction mixture (a) The adjustment method of the reaction mixture (a) in the present invention is a method of reacting a sulfidizing agent and a dihalogenated aromatic compound in an organic polar solvent, or polyarylene as a raw material. It is obtained by heating and reacting the four components added with sulfide.

  These reaction methods are not particularly limited as long as a reaction mixture containing at least polyarylene sulfide, cyclic polyarylene sulfide, alkali metal halide, water and an organic polar solvent can be obtained, and known methods can be employed. As this method, for example, a mixture of the above raw materials is usually heated to a temperature of 120 to 300 ° C., preferably 180 to 280 ° C. for 0.1 to 40 hours, preferably 0.5 to 20 hours, more preferably It is preferable that the reaction is carried out by heating for 1 to 10 hours. In such a temperature range, the reaction tends to proceed in a short time, and the reaction tends to proceed uniformly and easily. The reaction may be either a one-step reaction performed 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. In order to suppress it, after carrying out some reaction at 120-240 degreeC, the method of superposing | polymerizing at 240-300 degreeC can also be illustrated as a preferable method. In addition, the reaction time depends on the type and amount of the raw material used or the reaction temperature, and thus cannot be defined unconditionally. However, the amount of unreacted components can be sufficiently reduced within the above time range, so that the polyarylene as the target product can be reduced. The sulfide component tends to be recovered with good yield and efficiency.

  In the method for continuously recovering an alkali metal halide according to the present invention, the water content in the reaction mixture (a) containing at least polyarylene sulfide, cyclic polyarylene sulfide, alkali metal halide, water and an organic polar solvent is organic polar. The amount is preferably 3 parts by weight or less, more preferably 1 part by weight or less based on 100 parts by weight of the solvent. When the amount of water in the reaction mixture (a) exceeds the above range, an operation of reducing the amount of water can be performed before starting the reaction, during the reaction and / or after preparing the mixture. It is possible to add an additional organic polar solvent to the mixture so that the amount of water with respect to the organic polar solvent is within the above-mentioned preferred range after preparation, but in particular, the amount of water is reduced before starting the reaction and / or after preparing the mixture. It is preferable to perform an operation, and it is more preferable to perform an operation to reduce the amount of water before starting the reaction. When components other than water are removed before starting the reaction or during the operation to reduce the amount of water, additional sulfidizing agent, dihalogenated aromatic compound and organic polar solvent are added as necessary. It is also possible to perform the operation of returning the removed component again.

  There is no particular problem with any method as long as the amount of water can be reduced to the above-mentioned preferable range as the operation for reducing the amount of water. Preferred methods include distillation of water under reduced pressure or pressure, and removal of water by flash transfer. Among them, a method of distilling water under reduced pressure or under pressure is preferable. In addition, when water is distilled under reduced pressure or under pressure, an inert gas such as nitrogen, helium, or argon may be used as a carrier gas.

  In addition, in the method of reacting by heating a mixture containing at least polyarylene sulfide, a sulfidizing agent, a dihalogenated aromatic compound and an organic polar solvent in the present method, various known polymerization methods such as a batch method and a continuous method, a reaction A scheme can be adopted. In addition, the atmosphere in the production is preferably a non-oxidizing atmosphere, preferably in an inert gas atmosphere such as nitrogen, helium, and argon. From the viewpoint of economy and ease of handling, a nitrogen atmosphere is preferable.

(8) Continuous recovery method of alkali metal halide In order to efficiently obtain a high-quality polyarylene sulfide having a reduced metal content from the reaction mixture (a) adjusted to a preferable water content as described above, an alkali metal halogen is used. Collect the chemicals.

  For recovery of alkali metal halides, it is possible to employ sedimentation separation by standing, centrifugal sedimentation separation using a cyclone or decanter, or a combination of these, but centrifugal sedimentation using a cyclone or decanter is preferred. Further, centrifugal sedimentation using a decanter is more preferable. In such an alkali metal halide separation method, continuous operation becomes possible by not using a filter during solid-liquid separation, and there is no fear of filter loss or filter clogging due to thermal expansion. Stable operation is possible.

The pressure at the time of recovering the alkali metal halide is not particularly limited as long as it is equal to or higher than the vapor pressure of the reaction mixture (a), but the specific pressure range is 2.0 MPa or less, preferably absolute pressure. Illustrative is 1.0 MPa or less, more preferably an absolute pressure of 0.1 MPa or more and 0.7 MPa or less. By recovering the alkali metal halide under a pressure higher than the vapor pressure, not only the evaporation of water and the organic polar solvent in the apparatus is suppressed and the concentration of the reaction mixture (a) is suppressed, but also the polyarylene which is the target component. It suppresses the adhesion of sulfide and cyclic polyarylene sulfide by evaporation on the inner wall of the apparatus, and has the effect of reducing the loss of the target component.
The temperature at the time of recovering the alkali metal halide is not particularly limited as long as the polyarylene sulfide contained in the reaction mixture (a) is soluble, but it is 280 ° C. or lower. The polyarylene sulfide or the cyclic polyarylene sulfide is not easily decomposed or altered, and the organic polar solvent tends to be hardly decomposed or altered.

  It is important to adjust the amount of water contained in the reaction mixture (a) in order to keep the temperature and pressure range as described above, and the water vapor partial pressure increases when the amount of water contained in the organic polar solvent is large. In order to maintain the pressure under high temperature, it becomes heavy equipment and is not realistic. On the other hand, when the water content in the reaction mixture (a) is 3 parts by weight or less, more preferably 1 part by weight or less with respect to 100 parts by weight of the organic polar solvent, the vapor of the reaction mixture (a) at 280 ° C. or less. The pressure can be set to a desired pressure, and a commercially available decanter centrifuge can be used.

  By using a decanter type centrifuge for the recovery of the alkali metal halide here, it is possible to continuously recover the majority of the alkali metal halide as a solid content, preferably after the alkali metal halide is recovered. The alkali metal halide can be recovered as a solid content until the concentration of alkali metal halide contained in the mixture is 1.0% by weight or less, more preferably 0.5% by weight or less, and even more preferably 0.1% by weight or less. Decanter centrifuges are generally commercially available, and these commercially available ones can be used in the present invention. For example, a vertical decanter TRV manufactured by Sakai Kogyo Co., Ltd. can be used. By recovering alkali metal halide using a decanter type centrifuge in this way, not only can the semi-continuous and inefficient process of production be improved as in the prior art, but also alkali metal halide from the reaction mixture (a). It became possible to remove the chemicals efficiently.

  As described above, reducing the concentration of chloride ions contained in the reaction mixture (a) by making the amount of water contained in the reaction mixture (a) or by removing the alkali metal halide. Can do. Chloride ions can be cited as one of the causes of equipment corrosion, but due to the reduction of corrosion-causing components, the material of equipment related to the metal halide recovery process or subsequent processes is represented by JIS standards SUS316 and SUS316L. Austenitic stainless steel such as SUS329J1, SUS329J2L, and SUS329J4L, which are known for producing polyarylene sulfide, Carpenter (registered trademark), Hastelloy (registered trademark) ), An effect that a high-grade material such as titanium is unnecessary is also obtained.

[Example 1]
In a 10 L reaction vessel made of JIS standard SUS316 equipped with a stirrer and a rectifying column, 2.46 kg of sodium hydrogen sulfide 48 wt% aqueous solution, 1.84 kg of sodium hydroxide 48 wt% aqueous solution, N-methyl-2-pyrrolidone (NMP ) 4.43 kg was charged and the temperature was raised under nitrogen gas for dehydration. The amount of water evaporated at this time was 2.21 kg. Into a 70 L reaction vessel made of JIS standard SUS316 equipped with a stirrer, the mixture excluding water was added, 50.19 kg of NMP and 3.15 kg of p-dichlorobenzene (p-DCB) were added, and the reaction vessel was placed under nitrogen gas. Sealed. The mixture was heated with stirring and kept at 250 ° C. for 2 hours to obtain a reaction mixture. At this time, the amount of water contained in the reaction mixture was 0.72 parts by weight with respect to 100 parts by weight of NMP.

  To preheat a vertical decanter TRV085 (manufactured by Sakai Kogyo Co., Ltd.) to 250 ° C., set the rotation speed of a bowl provided for causing sedimentation separation to 5000 rpm, and to discharge the separated and separated product from the decanter The rotational speed of the provided screw conveyor was adjusted so that the speed difference from the bowl rotational speed was 15 rpm. Next, the reaction mixture obtained using a metering pump was supplied to a decanter, and 54.4 kg of the filtrate and 3.38 kg of the separated product were recovered. The amount of metal halide contained in the separated product was 2.36 kg, and almost the entire amount was recovered. On the other hand, the loss of polyarylene sulfide and cyclic polyarylene sulfide was 1.83% by weight based on the total amount of polyarylene sulfide to be obtained.

[Example 2]
In a 70 L reaction vessel made of JIS SUS316 equipped with a stirrer and a rectifying column, 2.46 kg of 48% by weight aqueous solution of sodium hydrosulfide, 1.84 kg of 48% by weight aqueous solution of sodium hydroxide, 52.55 kg of NMP, 3.15 kg of p-DCB Was sealed under nitrogen gas. The mixture was heated with stirring and maintained at 250 ° C. for 2 hours. Subsequently, the dehydration operation was performed from the reaction tank through the rectification column so that the amount of water contained in the reaction mixture was 1 part by weight with respect to 100 parts by weight of NMP. The amount of water evaporated at this time was 2.07 kg.

  A vertical decanter TRV085 (manufactured by Sakai Kogyo Co., Ltd.) was preheated to 250 ° C. in advance, and the rotational speed of the rotating cylinder was 5000 rpm, and the differential speed from the screw conveyor was 15 rpm. Next, the reaction mixture with the water content adjusted using a metering pump was supplied to a decanter, and 54.55 kg of the filtrate and 3.38 kg of the separated product were recovered. The amount of metal halide contained in the separated product was 2.36 kg, and almost the entire amount was recovered. On the other hand, the loss of polyarylene sulfide and cyclic polyarylene sulfide was 1.82% by weight based on the total amount of polyarylene sulfide to be obtained.

[Comparative Example 1]
A 1 L autoclave made of JIS SUS316 equipped with a stirrer and a rectifying column was charged with 23.36 g of a 48 wt% aqueous solution of sodium hydrosulfide, 17.50 g of a 48 wt% aqueous solution of sodium hydroxide, 500 g of NMP, and 29.99 g of p-DCB. Sealed under nitrogen gas. Heating was carried out with stirring and maintained at 250 ° C. for 2 hours. Thereafter, the mixture was passed through a rectification column and dehydrated so that the amount of water contained in the reaction mixture was 1 part by weight with respect to 100 parts by weight of NMP, and cooled to room temperature. The amount of water evaporated at this time was 19.71 g. Next, 100 g of the cooled reaction solution was charged into a SUS316 pressure vessel equipped with a bottom plug valve and a glass filter (average opening 10 μm) at the bottom. The vessel was placed in a nitrogen atmosphere and heated to 250 ° C. with stirring under normal pressure, and then the bottom plug valve was opened to perform filtration. The filtrate was recovered while introducing nitrogen at an absolute pressure of 0.4 MPa into the container at the stage when the filtration rate was lowered. By this operation, about 92 g of the filtrate and about 8 g of the separated product were recovered. The amount of metal halide contained in the separated product was 3.9 g, and almost the entire amount was recovered. On the other hand, the loss of polyarylene sulfide and cyclic polyarylene sulfide was 4.10% by weight based on the total amount of polyarylene sulfide to be obtained.

Claims (5)

A reaction mixture comprising at least a polyarylene sulfide, a cyclic polyarylene sulfide, an alkali metal halide, water and an organic polar solvent, obtained by contacting a sulfidizing agent with a dihalogenated aromatic compound in an organic polar solvent. A method for continuously recovering alkali metal halides, wherein when recovering alkali metal halides from (a), precipitation separation is performed under a pressure equal to or higher than the vapor pressure of the reaction mixture (a) at the recovery temperature. 2. The method for continuously recovering an alkali metal halide according to claim 1, wherein the sedimentation separation is performed using a decanter centrifuge as a separator when the sedimentation separation is performed. The continuous alkali metal halide according to claim 1 or 2, wherein the amount of water contained in the reaction mixture (a) during the sedimentation separation is 3 parts by weight or less with respect to 100 parts by weight of the organic polar solvent. Collection method. The alkali metal according to any one of claims 1 to 3, wherein the amount of water contained in the reaction mixture (a) during the sedimentation separation is 1 part by weight or less with respect to 100 parts by weight of the organic polar solvent. Method for continuous recovery of halides. The method for continuously recovering an alkali metal halide according to any one of claims 1 to 4, wherein the sedimentation separation is performed in a temperature range in which the polyarylene sulfide is soluble.