JP2007016142A - Method for manufacturing polyphenylenesulfide resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyphenylenesulfide resin that has a reduced volatile content and is industrially useful, from a polyphenylenesulfide oligomer of 800-20,000 of a weight average molecular weight. <P>SOLUTION: A mixture containing at least a polyhalogenated aromatic compound, a sulfiding agent and an organic polar solvent is heated to polymerize into a polyphenylene sulfide resin, then cooled to 220°C or below to obtain slurry (A) containing at least a granular polyphenylene sulfide resin, a polyphenylene sulfide oligomer, the organic polar solvent, water and a halogenated alkali metal salt. The polyphenylene sulfide oligomer of 800-20,000 weight-average molecular weight is obtained by removing at least the granular polyphenylene sulfide resin, the organic polar solvent, water and the halogenated alkali metal salt from the slurry (A). The polyphenylene sulfide resin is produced by thermal oxidation of the polyphenylene sulfide oligomer at 150-260°C under gas phase oxidizing atmosphere. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an industrially reduced volatile matter characterized in that a polyphenylene sulfide oligomer having a weight average molecular weight of 800 to 20,000 is thermally oxidized at 150 ° C. to 260 ° C. in a gas phase oxidizing atmosphere. The present invention relates to a method for producing a polyphenylene sulfide resin useful for the above and a polyphenylene sulfide resin obtained by the production method.

  Polyphenylene sulfide resin has excellent properties as engineering plastics such as excellent heat resistance, barrier properties, chemical resistance, electrical insulation properties, and heat and humidity resistance, and various electrical and electronic components mainly for injection molding and extrusion molding. Used for machine parts and automobile parts.

  It is already known that a granular polyphenylene sulfide resin can be obtained by polymerizing a polyphenylene sulfide resin and slowly cooling it after polymerization. However, at this time, a particulate solid mainly composed of a low molecular weight polyphenylene sulfide oligomer is also produced as a by-product. In many cases, the particulate solid matter is complicated to handle, and for example, it is collected by filtration with a filter coated with a filter aid, and the mixture of the filter aid and the particulate solid matter has been discarded.

  If it is possible to efficiently recover and reuse the fine solid particles containing the low molecular weight polyphenylene sulfide oligomer as a main component, it is economically advantageous in producing the polyphenylene sulfide resin. However, since this polyphenylene sulfide oligomer generates a large amount of volatile components upon heating, it has a problem in industrial use as it is.

Heat treatment of polyphenylene sulfide oligomer in an oxygen-containing atmosphere has already been disclosed (Patent Document 1). However, in this patent, the molecular weight of the polyphenylene sulfide oligomer before the heat treatment is as extremely low as 600 or less, and the heat treatment temperature is as high as 270 ° C. to 420 ° C. Further, the purpose is to increase the molecular weight of a very low molecular weight PPS oligomer to some extent, and the present invention differs from the present invention in the molecular weight, heat treatment temperature, and purpose of the polyphenylene sulfide oligomer before heat treatment.
U.S. Pat. No. 4,046,749 (Claims)

  An object of the present invention is to obtain an industrially reusable polyphenylene sulfide resin by greatly reducing the volatile matter from a polyphenylene sulfide oligomer which is a by-product in the polymerization of the polyphenylene sulfide resin. .

That is, the present invention
(1) A method for producing a polyphenylene sulfide resin, wherein a polyphenylene sulfide oligomer having a weight average molecular weight of 800 to 20,000 is thermally oxidized at 150 ° C. to 260 ° C. in a gas phase oxidizing atmosphere,
(2) at least a granular polyphenylene sulfide resin obtained by heating a mixture containing at least a polyhalogenated aromatic compound, a sulfidizing agent and an organic polar solvent to polymerize the polyphenylene sulfide resin and cooling to 220 ° C. or lower; Obtained by removing at least granular polyphenylene sulfide resin, organic polar solvent, water, and alkali metal halide salt from slurry (A) containing polyphenylene sulfide oligomer, organic polar solvent, water, and alkali metal halide salt. A method for producing a polyphenylene sulfide resin, wherein the polyphenylene sulfide oligomer having a weight average molecular weight of 800 to 20,000 is thermally oxidized at 150 ° C. to 260 ° C. in a gas phase oxidizing atmosphere,
(3) A method for separating and recovering the polyphenylene sulfide oligomer from the slurry (A),
(A) An organic polar solvent 0.5-10 mol is added to 1 mol of sulfidizing agents used in the polymerization to the slurry (A) to form a diluted slurry (B),
(B) A granular polyphenylene sulfide resin is recovered from the diluted slurry (B) to obtain a recovered slurry (C) containing at least a polyphenylene sulfide oligomer, an organic polar solvent, water, and an alkali metal halide salt,
(C) Remove at least 50 wt% or more of the organic polar solvent from the recovered slurry (C) to obtain a residue (D),
(D) After adding water to the residue (D), at least residual organic polar solvent and alkali metal halide salt are removed.
A process for producing a polyphenylene sulfide resin according to (2),
(4) The method for producing a polyphenylene sulfide resin according to (3), wherein the granular polyphenylene sulfide resin is recovered by filtration in the step (b),
(5) The method for producing a polyphenylene sulfide resin according to (3) or (4), wherein the organic polar solvent is removed by heating in the step (c),
(6) The method for producing a polyphenylene sulfide resin according to any one of (3) to (5), wherein the residual organic polar solvent and the alkali metal halide salt are removed by filtration in the step (d),
(7) A method for producing the polyphenylene sulfide resin according to any one of (2) to (6), wherein a polymerization aid is used when polymerizing the polyphenylene sulfide resin.
(8) The method for producing a polyphenylene sulfide resin according to any one of (3) to (7), wherein 1 kg or more of water is not added per kg of the polyphenylene sulfide resin in any of the steps (a) and (b),
(9) The method for producing a polyphenylene sulfide resin according to any one of (2) to (8), wherein the organic polar solvent is N-methyl-2-pyrrolidone,
(10) A polyphenylene sulfide resin obtained by subjecting a polyphenylene sulfide oligomer having a weight average molecular weight of 800 to 20,000 to thermal oxidation treatment at 150 ° C. to 260 ° C. in a gas phase oxidizing atmosphere,
(11) The polyphenylene sulfide resin according to (10), wherein the weight loss at 300 ° C. is 0.8% by weight or less when the temperature is increased from room temperature at 20 ° C./min using a thermogravimetric differential thermal analyzer.
Is to provide.

  According to the present invention, an industrially useful and reusable polyphenylene sulfide resin having a reduced volatile content can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail.

(1) Polyphenylene sulfide (hereinafter referred to as PPS) resin The PPS resin referred to in the present invention is a polymer having a repeating unit represented by the following structural formula (I),

From the viewpoint of heat resistance, a polymer containing 70 mol% or more, more preferably 90 mol% or more of a polymer containing a repeating unit represented by the above structural formula is preferred. Moreover, about 30 mol% or less of the repeating unit of the PPS resin may be composed of a repeating unit having the following structure.

  Although there is no restriction | limiting in particular in the melt viscosity of PPS resin superposed | polymerized by this invention, Usually, 5 Pa.s (310 degreeC, shear rate 1000 / s) or more is preferable, and 10 Pa.s or more is further more preferable. The upper limit is preferably 600 Pa · s or less from the viewpoint of maintaining melt fluidity.

  The melt viscosity is a value measured using a capillograph manufactured by Toyo Seiki Co., Ltd. under conditions of 310 ° C. and a shear rate of 1000 / s.

  The PPS oligomer before being thermally oxidized in the present invention is a linear and / or cyclic oligomer having the same structure as the PPS resin.

  The weight average molecular weight is 800 or more, preferably 1000 or more, more preferably 1200 or more, and still more preferably 10,000 or more. Moreover, the upper limit is 20,000, Preferably it is 18,000 or less, More preferably, it is 17,000 or less, More preferably, it is 15,000 or less. If the weight average molecular weight is less than 800, even if the thermal oxidation treatment is performed, the mechanical strength becomes extremely poor, its production is difficult, and it is not suitable for industrial use. Although a polymer having a weight average molecular weight exceeding 20,000 is suitable for industrial use, the main object of the present invention is to obtain a granular high molecular weight PPS resin by polymerizing a PPS resin and gradually cooling it after the polymerization. The low molecular weight PPS oligomer produced as a by-product is effectively used, and the upper limit of the weight average molecular weight of the PPS oligomer thus produced is about 20,000.

  In the present invention, it is possible to polymerize a PPS oligomer having a desired weight average molecular weight by controlling the monomer ratio during polymerization. However, the main object of the present invention is to effectively utilize a low molecular weight PPS oligomer produced as a by-product when a granular high molecular weight PPS resin is obtained by polymerizing a PPS resin and then slowly cooling it after polymerization.

  Hereinafter, the production method of the PPS resin in the present invention will be described. First, the contents of the polyhalogen aromatic compound, sulfidizing agent, polymerization solvent, molecular weight regulator, polymerization aid and polymerization stabilizer used in the production method will be described. explain.

[Polyhalogenated aromatic compounds]
The polyhalogenated aromatic compound used in the present invention refers to a compound having two or more halogen atoms in one molecule. Specific examples include p-dichlorobenzene, m-dichlorobenzene, o-dichlorobenzene, 1,3,5-trichlorobenzene, 1,2,4-trichlorobenzene, 1,2,4,5-tetrachlorobenzene, hexa Polyhalogenated aromatics such as chlorobenzene, 2,5-dichlorotoluene, 2,5-dichloro-p-xylene, 1,4-dibromobenzene, 1,4-diiodobenzene, 1-methoxy-2,5-dichlorobenzene Group compounds, and preferably p-dichlorobenzene is used. Further, it is possible to combine two or more different polyhalogenated aromatic compounds into a copolymer, but it is preferable to use a p-dihalogenated aromatic compound as a main component.

  The amount of the polyhalogenated aromatic compound used is 0.9 to 2.0 mol, preferably 0.95 to 1.5 mol, per mol of the sulfidizing agent, from the viewpoint of obtaining a PPS resin having a viscosity suitable for processing. More preferably, the range of 1.005 to 1.2 mol can be exemplified.

[Sulfiding agent]
Examples of the sulfidizing agent used in the present invention include alkali metal sulfides, alkali metal hydrosulfides, and hydrogen sulfide.

  Specific examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide and a mixture of two or more of these, and sodium sulfide is preferably used. These alkali metal sulfides can be used as hydrates or aqueous mixtures or in the form of anhydrides.

  Specific examples of the alkali metal hydrosulfide include, for example, sodium hydrosulfide, potassium hydrosulfide, lithium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide and a mixture of two or more of these. Preferably used. These alkali metal hydrosulfides can be used as hydrates or aqueous mixtures or in the form of anhydrides.

  In addition, an alkali metal sulfide prepared in situ in a reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide can also be used. Moreover, an alkali metal sulfide can be prepared from an alkali metal hydrosulfide and an alkali metal hydroxide and transferred to a polymerization tank for use.

  Alternatively, 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 can also be used. Moreover, an alkali metal sulfide can be prepared from an alkali metal hydroxide such as lithium hydroxide or sodium hydroxide and hydrogen sulfide, and transferred to a polymerization tank for use.

  In the present invention, the amount of the sulfidizing agent charged means the residual amount obtained by subtracting the loss from the actual charged amount when a partial loss of the sulfiding agent occurs before the start of the polymerization reaction due to dehydration operation or the like. Shall.

  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 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 sulfiding agent, it is particularly preferable to use an alkali metal hydroxide at the same time, but the amount used is 0.95 to 1. A range of 20 mol, preferably 1.00 to 1.15 mol, more preferably 1.005 to 1.100 mol can be exemplified.

[Polymerization solvent]
In the present invention, an organic polar solvent is used as a polymerization solvent. Specific examples include N-alkylpyrrolidones such as N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, and 1,3-dimethyl-2-imidazolide. Non-, N, N-dimethylacetamide, N, N-dimethylformamide, hexamethylphosphoric acid triamide, dimethyl sulfone, tetramethylene sulfoxide and the like, and mixtures thereof, and the like are all included. It is preferably used because of its high reaction stability. Of these, N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP) is particularly preferably used.

  The amount of the organic polar solvent used in the polymerization is in the range of 2.0 to 10 mol, preferably 2.25 to 6.0 mol, more preferably 2.5 to 5.5 mol per mol of the sulfidizing agent. Selected.

[Molecular weight regulator]
In the present invention, a monohalogen compound (not necessarily an aromatic compound) is used as the polyhalogenated aromatic for the purpose of forming the end of the PPS resin to be produced or adjusting the polymerization reaction or molecular weight. Can be used in combination with a compound.

[Polymerization aid]
In the present invention, in order to obtain a granular PPS resin in a shorter time, it is one of preferred embodiments to use a polymerization aid. Here, the polymerization assistant means a substance having an action of increasing the viscosity of the obtained polyphenylene sulfide resin. Specific examples of such polymerization aids include, for example, organic carboxylates, water, alkali metal chlorides, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates and alkaline earths. Metal phosphates and the like. These may be used alone or in combination of two or more. Of these, organic carboxylates and / or water and lithium chloride are preferably used.

The alkali metal carboxylate is 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). M is an alkali metal selected from lithium, sodium, potassium, rubidium and cesium, and n is an integer of 1 to 3). Alkali metal carboxylates can also be used as hydrates, anhydrides 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.

  The alkali metal carboxylate is an organic acid and one or more compounds selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates, and are allowed to react by adding approximately equal chemical equivalents. You may form by. Among the alkali metal carboxylates, lithium salts are highly soluble in the reaction system and have a large auxiliary effect, but are expensive, and potassium, rubidium and cesium salts are insufficiently soluble in the reaction system. Therefore, sodium acetate, which is inexpensive and has an appropriate solubility in the polymerization system, is most preferably used.

  When using these alkali metal carboxylates as polymerization aids, the amount used is usually in the range of 0.01 to 2 moles per mole of charged alkali metal sulfide, and in the sense of obtaining a higher degree of polymerization. The range of 0.1-0.6 mol is preferable, and the range of 0.2-0.5 mol is more preferable.

  Moreover, the addition amount in the case of using water as a polymerization aid is usually in the range of 0.3 mol to 15 mol with respect to 1 mol of the charged alkali metal sulfide, and in the sense of obtaining a higher degree of polymerization, 0.6 to The range of 10 mol is preferable, and the range of 1 to 5 mol is more preferable.

  Of course, two or more kinds of these polymerization aids can be used in combination. For example, when an alkali metal carboxylate and water are used in combination, a higher molecular weight can be obtained in a smaller amount.

  There is no particular designation as to the timing of addition of these polymerization aids, which may be added at any time during the previous step, polymerization start, polymerization in the middle to be described later, or may be added in multiple times. When an alkali metal carboxylate is used as a polymerization aid, it is more preferable that it is added at the start of the previous step or at the start of the polymerization because the addition is easy. When water is used as a polymerization aid, it is effective to add the polyhalogenated aromatic compound during the polymerization reaction after charging.

[Polymerization stabilizer]
In the present invention, a polymerization stabilizer may be used 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. In addition, when an alkali metal hydrosulfide is used as a sulfidizing agent, it has been described above that it is particularly preferable to use an alkali metal hydroxide at the same time. Oxides can also be polymerization stabilizers.

  These polymerization stabilizers can be used alone or in combination of two or more. The polymerization stabilizer is usually in a proportion of 0.02 to 0.2 mol, preferably 0.03 to 0.1 mol, more preferably 0.04 to 0.09 mol, relative to 1 mol of the charged alkali metal sulfide. Is preferably used. 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 addition timing of the polymerization stabilizer is not particularly specified, and may be added at any time during the previous step, at the start of polymerization, or during the polymerization described later, or may be added in multiple times. It is more preferable to add at the start of the process or at the start of the polymerization from the viewpoint of easy addition.

  Next, the production method of the PPS resin in the present invention will be specifically described in the order of the pre-process, the polymerization reaction process, the recovery process, and the post-treatment process.

[pre-process]
In the method for producing a PPS resin in the present invention, the sulfidizing agent is usually used in the form of a hydrate. Before adding the polyhalogenated aromatic compound, the mixture containing the organic polar solvent and the sulfidizing agent is increased. It is preferable to warm and remove excess water out of the system.

As described above, a sulfidizing agent prepared from an alkali metal hydrosulfide and an alkali metal hydroxide in situ in the reaction system or in a tank different from the polymerization tank is also used as the sulfidizing agent. Can do. Although there is no particular limitation on this method, desirably an alkali metal hydrosulfide and an alkali metal hydroxide are added to the organic polar solvent in an inert gas atmosphere at a temperature ranging from room temperature to 150 ° C., preferably from room temperature to 100 ° C. In addition, there is a method in which the temperature is raised to at least 150 ° C. or more, preferably 180 to 260 ° C. under normal pressure or reduced pressure, and water is distilled off. A polymerization aid may be added at this stage. Moreover, in order to accelerate | stimulate distillation of a water | moisture content, you may react by adding toluene etc.

  The amount of water in the polymerization system in the polymerization reaction is preferably 0.3 to 10.0 moles per mole of the charged sulfidizing agent. Here, the amount of water in the polymerization system is an amount obtained by subtracting the amount of water removed from the polymerization system from the amount of water charged in the polymerization system. In addition, the water to be charged may be in any form such as water, an aqueous solution, and crystal water.

[Polymerization reaction step]
In the present invention, a PPS resin is produced by reacting a sulfidizing agent and a polyhalogenated aromatic compound in an organic polar solvent within a temperature range of 200 ° C. or higher and lower than 290 ° C.

  When starting the polymerization reaction step, the organic polar solvent, the sulfidizing agent, and the polyhalogenated aromatic compound are desirably mixed in an inert gas atmosphere at room temperature to 240 ° C., preferably 100 to 230 ° 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.

  The mixture is usually heated to a temperature in the range of 200 ° C to 290 ° C. Although there is no restriction | limiting in particular in a temperature increase rate, Usually, the speed of 0.01-5 degreeC / min is selected, and the range of 0.1-3 degreeC / min is more preferable.

  In general, the temperature is finally raised to a temperature of 250 to 290 ° C., and the reaction is usually carried out at that temperature for 0.25 to 50 hours, preferably 0.5 to 20 hours.

  In the stage before reaching the final temperature, for example, a method of reacting at 200 to 260 ° C. for a certain time and then raising the temperature to 270 to 290 ° C. is effective in obtaining a higher degree of polymerization. Under the present circumstances, as reaction time in 200 to 260 degreeC, the range of 0.25 to 20 hours is normally selected, Preferably the range of 0.25 to 10 hours is selected.

  In order to obtain a polymer having a higher degree of polymerization, it may be effective to perform polymerization in multiple stages. When the polymerization is carried out in a plurality of stages, it is effective that the conversion rate of the polyhalogenated aromatic compound in the system at 245 ° C. reaches 40 mol% or more, preferably 60 mol%.

The conversion rate of the polyhalogenated aromatic compound (herein abbreviated as PHA) is a value calculated by the following formula. The residual amount of PHA can usually be determined by gas chromatography.
(A) When polyhalogenated aromatic compound is added excessively in a molar ratio with respect to the alkali metal sulfide Conversion rate = [PHA charge (mol) −PHA remaining amount (mol)] / [PHA charge (mol) -PHA excess (mole)]
(B) In cases other than the above (a) Conversion rate = [PHA charge (mol) −PHA remaining amount (mol)] / [PHA charge (mol)]

[Polymer recovery process]
In the method for producing a PPS resin in the present invention, solids are recovered from a polymerization reaction product containing a polymer, a solvent and the like after completion of polymerization. Any known recovery method may be used for the PPS resin used in the present invention. However, in order to obtain a granular PPS resin, a method of gradually cooling after the polymerization reaction and recovering the particulate polymer is preferable. . Although there is no restriction | limiting in particular in the slow cooling rate in this case, Usually, it is about 0.1 degreeC / min-3 degreeC / min. There is no need for slow cooling at the same rate in the entire process of the slow cooling step, and a method of slow cooling at a rate of 0.1 to 1 ° C./minute until the polymer particles crystallize and then 1 ° C./minute or more is used. It may be adopted. Finally, it is cooled to 220 ° C. or lower. In addition, a method of venting the polymerization tank after crystallization of the polymer particles and removing part or all of the water in the polymerization tank in advance is a preferable method in terms of simplifying the subsequent solvent recovery step.

[Method for recovering PPS oligomer before thermal oxidation]
In the present invention, as a method for obtaining a PPS oligomer before thermal oxidation treatment, a slurry obtained in a polymerization reaction step, that is, a slurry containing at least a granular PPS resin, a PPS oligomer, an organic polar solvent, water, and an alkali metal halide salt ( A method of removing at least the granular PPS resin, the organic polar solvent, water, and the alkali metal halide from A) is mentioned as a preferred method.

  Preferred examples of the slurry (A) here are granular PPS resins having a particle size of 0.04 to 4 mm, preferably 0.1 to 2 mm, finely divided PPS oligomers, organic polar solvents, water, alkali halides. Examples thereof include those containing at least a metal salt, further a polymerization aid, and a by-product during polymerization.

  In addition, preferred methods for recovering PPS oligomers (a) to (d) are shown below.

  (A) In the present invention, the slurry (A) is first diluted with an organic solvent to form a diluted slurry (B). By diluting, the viscosity of the slurry (A) decreases, and the recovery efficiency of the PPS resin by filtration in the following step (b) increases. At this time, the amount of the organic polar solvent used for dilution is in the range of 0.5 to 10 mol, preferably in the range of 0.7 to 5 mol, with respect to 1 mol of the sulfidizing agent used for polymerization. The organic polar solvent species used for dilution is preferably the same as the polymerization solvent. In addition, sulfoxide and sulfone solvents such as dimethyl sulfoxide, dimethyl sulfone, and sulfolane, ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, and acetophenone, ether solvents such as dimethyl ether, dipropyl ether, dioxane, and tetrahydrofuran, chloroform, and methylene chloride , Halogen solvents such as trichloroethylene, ethylene dichloride, perchlorethylene, monochloroethane, dichloroethane, tetrachloroethane, perchlorethane, chlorobenzene, methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, phenol , Cresol, polyethylene glycol, polypropylene glycol, etc. However, if diluted with a solvent other than the polymerization solvent such as water, separation from the polymerization solvent is required, and if a solvent having a high affinity with the polymerization solvent such as water is used, the separation of the two will be significant. It is economically disadvantageous because it requires a lot of energy.

  (B) Next, the PPS resin is recovered from the diluted slurry (B). At this time, in the diluted slurry (B), the PPS resin exists in a solid state, and the PPS oligomer, water, and the alkali metal halide are dispersed in the organic solvent. It can be recovered. At this time, the diluting slurry (B) may optionally contain a polymerization aid contained in the slurry (A), a by-product during polymerization, and the like. The PPS resin is preferably collected by filtration. The granular PPS resin is separated by filtration to obtain a recovered slurry (C) containing at least a PPS oligomer, an organic polar solvent, water, an alkali metal halide salt and, optionally, a polymerization aid and by-products. Although there is no restriction | limiting in particular in the temperature of the slurry (B) in the case of filtration, Usually, the range of 50-200 degreeC is selected, and the range of 60-150 degreeC is more preferable. It is necessary to select a filter medium used at this time that can separate granular PPS resin, and a slurry containing a PPS oligomer, an organic polar solvent, water, a by-product, and an alkali metal halide salt passes therethrough. Usually, a mesh of about 10 mesh (aperture 1.651 mm) to 200 mesh (aperture 0.074 mm), preferably 48 mesh (aperture 0.295 mm) to 100 mesh (aperture 0.147 mm) is preferable. Examples of the filter include, but are not limited to, a centrifugal filter and a vibrating screen.

  (C) The organic polar solvent is removed from the recovered slurry (C) obtained in (b) above. The organic polar solvent is preferably removed by heating and treating under normal pressure or reduced pressure. The removal of the organic polar solvent volatilizes and removes at least 50 wt% or more, preferably 70 wt% or more, more preferably 90 wt% or more of the organic polar solvent. As the temperature at that time, the range of 120 ° C to 300 ° C is usually selected, and 140 ° C to 250 ° C is more preferable. At this time, water contained in the recovered slurry (C) is also volatilized and removed. A method of reducing the pressure when removing the organic polar solvent can also be employed.

  (D) Next, water is added to the residue (D) obtained in the step (c), and the residue (D) is slurried in water. Alkali metal salts, optionally some by-products and polymerization aids are removed to obtain PPS oligomers. The amount of water to be added at this time is preferably selected in the range of 0.5 to 5 g with respect to 1 g of the recovered slurry (C), and preferably in the range of 0.7 to 2.5 g. If the amount of water is too small, it takes too much time for filtration, and if it is too large, the amount of waste liquid increases, which is not preferable. Although there is no restriction | limiting in particular in the temperature of the water slurry in the case of filtration, Usually, the range of 50-200 degreeC is selected, and the range of 60-100 degreeC is more preferable. The filter medium used at the time of filtration is selected to have a mesh size that allows PPS oligomers to be recovered by filtration, and is usually about 1 μm to 100 μm, preferably about 2 μm to 50 μm. Examples of the filter include a suction filter and a pressure filter, but are not limited thereto.

  In the above methods (a) to (d), it is one of preferred embodiments that 1 kg or more of water per 1 kg of the dry PPS resin is not added to the slurry (A) or the diluted slurry (B) at a temperature of 220 ° C. or less. It is. This is because, as described above, when a polymerization solvent and a large amount of water are mixed, a great deal of energy is required to separate them, which is economically disadvantageous.

  The granular PPS resin recovered in the step (b) is reslurried once or more with an organic polar solvent, filtered off, and the filtrate is mixed with the first filtrate to obtain the above (b) to (d ) Is an effective means for obtaining a higher-purity PPS resin. At this time, for example, when slurrying twice, the method of using the filtrate for the first slurry after filtering the second slurry is an effective method in terms of reducing the amount of organic polar solvent used. .

  Slurry the PPS oligomer obtained in the step (d) once more into water slurry and filter it is an effective method for obtaining a PPS oligomer with higher purity. In this case, for example, when slurrying twice, the method of using the filtrate for the first slurry after filtering the second slurry is an effective method in terms of reducing the amount of water used.

[Thermal oxidation treatment of PPS oligomer]
The PPS oligomer thus obtained contains a large amount of volatile matter. The volatile content mentioned here is a PPS containing a large amount of volatile matter by using a thermogravimetric differential thermal analyzer, a dry sample amount of about 10 mg, a temperature increase from room temperature to 20 ° C./minute, and a weight loss at 300 ° C. It is very difficult to reuse oligomers industrially. In the present invention, it has been found that the volatile matter can be greatly reduced by subjecting such a PPS oligomer to thermal oxidation treatment in a gas phase oxidizing atmosphere. The term “gas phase oxidizing atmosphere” as used herein means a gas atmosphere containing oxygen. Specifically, the oxygen concentration is preferably 5% by volume or more, and more preferably 8% by volume or more. Although there is no restriction | limiting in particular in the upper limit of oxygen concentration, About 50 volume% is a limit. The temperature of the thermal oxidation treatment is in the range of 150 to 260 ° C, and more preferably in the range of 170 to 250 ° C. The treatment time is preferably 0.5 to 100 hours, more preferably 1 to 50 hours, and further preferably 2 to 25 hours. The heat treatment apparatus may be a normal hot air dryer or a heating apparatus with a rotary blade or a stirring blade. However, for efficient and more uniform treatment, a heating device with a rotary blade or a stirring blade is used. Is more preferable. The PPS resin thus obtained can be confirmed by measuring the weight reduction amount of the PPS resin using a thermogravimetric differential thermal analyzer to determine whether the volatile content in the PPS resin has been reduced. A preferable example of the thermogravimetric differential thermal analyzer is a thermogravimetric differential thermal analyzer TG / DTA200 manufactured by Seiko Instruments Inc. In the present invention, when the PPS resin is heated from room temperature at 20 ° C./min, the weight loss at 300 ° C. is 0.8% by weight or less, preferably 0.5% by weight or less.

  The PPS resin obtained by heat-treating the PPS oligomer in a gas-phase oxidizing atmosphere as described above has suppressed generation of volatile matter, and various molded products can be obtained by molding by injection molding or extrusion molding. In addition, it can be applied to various uses such as a fluidity improver of a higher molecular weight PPS resin or a coating application. In addition, the present PPS resin can be reused as a raw material for producing the PPS resin.

The present invention will be described more specifically with reference to the following examples.

[Molecular Weight Measurement] Preparation of Eluent Activated alumina (1/20 weight relative to 1-CN) was added to 1-chloronaphthalene (hereinafter abbreviated as 1-CN), stirred for 6 hours, and then filtered through a G4 glass filter. This was deaerated using an aspirator while applying an ultrasonic cleaner.
Sample Preparation (1) About 5 mg of PPS sample and about 5 g of 1-CN were weighed into a sample bottle.
(2) It put into the high temperature filtration apparatus (SSC-9300 by Senshu Scientific) set to 210 degreeC, and heated for 5 minutes (1 minute preheating, 4 minutes stirring).
(3) The product was taken out from the high temperature filtration device and left to reach room temperature.
GPC measurement condition equipment: Senshu Science SSC-7100
Column name: Senshu Science GPC3506 × 1
Eluent: 1-chloronaphthalene (1-CN)
Detector: Differential refractive index detector Detector sensitivity: Range 8
Detector polarity: +
Column temperature: 210 ° C
Pre-temperature bath temperature: 250 ° C
Pump bath temperature: 50 ° C
Detector temperature: 210 ° C
Sample-side flow rate: 1.0 mL / min
Reference side flow rate: 1.0 mL / min
Sample injection amount: 300 μL
Calibration curve preparation sample: Polystyrene

[Measurement of volatile matter]
Using a thermogravimetric differential thermal analyzer TG / DTA200 manufactured by Seiko Instruments Inc. as the apparatus, the temperature was increased from a dry sample amount of about 10 mg at room temperature to 20 ° C./min, and the weight loss at 300 ° C. was measured.

[Reference example]
Polymerization of PPS (PPS-1)
In a 70 liter autoclave equipped with a stirrer, 8267.37 g (70.00 mol) of 47.5% sodium hydrosulfide, 2957.21 g (70.97 mol) of 96% sodium hydroxide, N-methyl-2-pyrrolidone (NMP ) 11434.50 g (115.50 mol), sodium acetate 2583.00 g (31.50 mol), and ion-exchanged water 10500 g, gradually heated to 245 ° C. over about 3 hours under nitrogen at normal pressure, After distilling out 14780.1 g of water and 280 g of NMP, the reaction vessel was cooled to 160 ° C. The residual water content in the system per 1 mol of the charged alkali metal sulfide was 1.06 mol including the water consumed for the hydrolysis of NMP. The amount of hydrogen sulfide scattered was 0.02 mol per mol of the charged alkali metal sulfide.

  Next, 10235.46 g (69.63 mol) of p-dichlorobenzene and 900.00 g (91.00 mol) of NMP were added, the reaction vessel was sealed under nitrogen gas, and stirred at 240 rpm while stirring at 0.6 ° C. / The temperature was raised to 238 ° C. at a rate of minutes. After reacting at 238 ° C. for 95 minutes, the temperature was raised to 270 ° C. at a rate of 0.8 ° C./min. After performing the reaction at 270 ° C. for 100 minutes, 1260 g (70 mol) of water was injected over 15 minutes and cooled to 250 ° C. at a rate of 1.3 ° C./minute. Thereafter, it is cooled to 200 ° C. at a rate of 1.0 ° C./min, and then rapidly cooled to near room temperature, granular PPS resin, PPS oligomer, organic polar solvent, water, alkali metal halide salt, polymerization aid, auxiliary agent A slurry (A) containing organisms was obtained.

  The slurry (A) was diluted with 26300 g of NMP to obtain a diluted slurry (B). 200 g of slurry (B) heated to 70 ° C. was filtered off with a sieve (80 mesh, opening 0.175 mm) to obtain 150 g of PPS resin and recovered slurry (C). The filtration time was 9 minutes. The recovered slurry (C) was charged into a rotary evaporator and treated under reduced pressure at 160 ° C. for 1 hour, and then treated with a vacuum dryer at 160 ° C. for 1 hour. The amount of NMP in the obtained solid was 3% by weight.

To this solid, 180 g of ion-exchanged water (1.2 times the amount of recovered slurry (C)) was poured and stirred at 70 ° C. for 30 minutes to make a slurry again. The slurry was subjected to suction filtration with a glass filter having a filtration area of 9.6 cm ² (aperture 10 to 16 μm) to obtain a PPS oligomer having a weight average molecular weight of 13,600.

[Comparative Example 1]
When the volatile content of the PPS oligomer obtained in Reference Example 1 was measured, the weight reduction rate was 1.7% by weight.

[Example 1]
The PPS oligomer obtained in Reference Example 1 was subjected to thermal oxidation treatment at 220 ° C. for 5 hours using a hot air dryer, and the volatile content of the obtained sample was measured. The weight reduction rate was 0.35% by weight. It was.

[Example 2]
The PPS oligomer obtained in Reference Example 1 was subjected to thermal oxidation treatment at 240 ° C. for 7 hours using a hot air dryer, and the volatile content of the obtained sample was measured. The weight loss rate was 0.30% by weight. It was.

[Comparative Example 2]
The PPS oligomer obtained in Reference Example 1 was treated at 220 ° C. for 5 hours under a nitrogen stream (oxygen concentration of 1% or less), and the volatile content of the obtained sample was measured. % By weight.

Claims (11)

A method for producing a polyphenylene sulfide resin, wherein a polyphenylene sulfide oligomer having a weight average molecular weight of 800 to 20,000 is thermally oxidized at 150 ° C. to 260 ° C. in a gas phase oxidizing atmosphere. At least granular polyphenylene sulfide resin, polyphenylene sulfide obtained by heating a mixture containing at least a polyhalogenated aromatic compound, a sulfidizing agent and an organic polar solvent to polymerize the polyphenylene sulfide resin and cooling to 220 ° C. or lower. It was obtained by removing at least granular polyphenylene sulfide resin, organic polar solvent, water, and alkali metal halide from the slurry (A) containing the oligomer, organic polar solvent, water, and alkali metal halide. A method for producing a polyphenylene sulfide resin, wherein a polyphenylene sulfide oligomer having a weight average molecular weight of 800 to 20,000 is thermally oxidized at 150 ° C. to 260 ° C. in a gas phase oxidizing atmosphere. A method for separating and recovering the polyphenylene sulfide oligomer from the slurry (A),
(A) An organic polar solvent 0.5-10 mol is added to 1 mol of sulfidizing agents used in the polymerization to the slurry (A) to form a diluted slurry (B),
(B) A granular polyphenylene sulfide resin is recovered from the diluted slurry (B) to obtain a recovered slurry (C) containing at least a polyphenylene sulfide oligomer, an organic polar solvent, water, and an alkali metal halide salt,
(C) Remove at least 50 wt% or more of the organic polar solvent from the recovered slurry (C) to obtain a residue (D),
(D) After adding water to the residue (D), at least residual organic polar solvent and alkali metal halide salt are removed.
The method for producing a polyphenylene sulfide resin according to claim 2, which is a method. The method for producing a polyphenylene sulfide resin according to claim 3, wherein the granular polyphenylene sulfide resin is recovered by filtration in the step (b). The method for producing a polyphenylene sulfide resin according to claim 3 or 4, wherein the organic polar solvent is removed by heating in the step (c). The method for producing a polyphenylene sulfide resin according to any one of claims 3 to 5, wherein the residual organic polar solvent and the alkali metal halide salt are removed by filtration in the step (d). The method for producing a polyphenylene sulfide resin according to any one of claims 2 to 6, wherein a polymerization aid is used when polymerizing the polyphenylene sulfide resin. The method for producing a polyphenylene sulfide resin according to any one of claims 3 to 7, wherein 1 kg or more of water is not added per 1 kg of the polyphenylene sulfide resin in any of the steps (a) and (b). The method for producing a polyphenylene sulfide resin according to any one of claims 2 to 8, wherein the organic polar solvent is N-methyl-2-pyrrolidone. A polyphenylene sulfide resin obtained by thermally oxidizing a polyphenylene sulfide oligomer having a weight average molecular weight of 800 to 20,000 at 150 ° C. to 260 ° C. in a gas phase oxidizing atmosphere. 11. The polyphenylene sulfide resin according to claim 10, wherein the weight loss at 300 ° C. when the temperature is raised from room temperature at 20 ° C./min using a thermogravimetric differential thermal analyzer is 0.8 wt% or less.