JP7463838B2 - Method for producing polyarylene sulfide resin and cleaning method - Google Patents

Description

The present invention relates to a method for producing polyarylene sulfide resin. The present invention also relates to a method for cleaning polyarylene sulfide resin.

Polyarylene sulfide resin (hereinafter sometimes abbreviated as PAS resin), typified by polyphenylene sulfide resin (hereinafter sometimes abbreviated as PPS resin), is a thermoplastic polymer with excellent heat resistance and chemical resistance. Molded bodies thereof are used in various molding and processing fields. However, since the production of polyarylene sulfide resin is carried out under harsh polymerization conditions using highly corrosive raw materials, there is a tendency for metallic foreign matter to easily get mixed in from the liquid-contacting parts of the reaction device. For this reason, molded products of polyarylene sulfide resin inevitably contain foreign matter that should not be included as raw materials in terms of design. And this foreign matter could start to cause a decrease in electrical insulation, especially resistance to dielectric breakdown. In addition, the inclusion of impurities could delay crystallization during molding.

Therefore, there is a demand to minimize the amount of foreign matter contained in molded products. For example, various efforts have been made to reduce the inclusion of metallic foreign matter during the production of polyarylene sulfide resin, such as using expensive titanium or zirconium-based reaction equipment (reaction kettle) mainly in the liquid-contacting parts to carry out the polymerization reaction (Patent Document 1). However, these efforts have been insufficient.

JP 2019-104873 A

There are various possible reasons for this, but the inventors believe that the following factors are among them:

Polyarylene sulfide resins are mainly produced by a method in which an organic amide solvent such as N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP) is used as a polymerization solvent, and dichlorobenzene is polymerized with sodium sulfide and/or sodium hydrosulfide, and, if necessary, sodium hydroxide. In this polymerization reaction, a crude reaction product is obtained that contains the polymerization solvent, at least sodium sulfide and/or sodium hydrosulfide that remains unpolymerized, and by-products such as sodium chloride, along with the target polyarylene sulfide resin. After the polymerization reaction, the crude reaction product is taken out into a suitable metal container, and the polymerization solvent in the crude reaction product is removed using a suitable solid-liquid separation device such as a solvent drying device, a filter, or a centrifuge.

The polymerization solvent is separated and removed by the desolvation process, but the sodium sulfide and/or sodium hydrosulfide that remain without undergoing the polymerization reaction and the by-products (hereinafter also referred to simply as "by-products, etc.") remain attached to the surface or encapsulated and are not removed from the target polyarylene sulfide resin. For this reason, after desolvation, the polyarylene sulfide resin containing the by-products, etc. is washed with a washing solvent such as water or an organic solvent.

During this cleaning, when the polyarylene sulfide resin is brought into contact with water and stirred, the polyarylene sulfide resin (powder) has very poor wettability. In other words, due to the hydrophobic nature of the polyarylene sulfide resin, bubbles are generated by the air entrained during stirring and not only adhere to the container wall, but also tend to remain at the adhesion part without flowing even if the slurry is flowing below the liquid surface. The inventors analyzed the components of this foam and found that the above-mentioned by-products are included as components of the foam, and that when such bubbles adhering to the container wall are concentrated and highly concentrated by drying, etc., they corrode the container wall, and the metal components contained in the rust generated as impurities are taken up into the polyarylene sulfide resin, thereby reducing various performances.

The problem that the present invention aims to solve is to provide a method for cleaning polyarylene sulfide resin, or a method for producing polyarylene sulfide resin, which suppresses the amount of impurities such as rust that are generated due to corrosion from bubbles remaining in the liquid-contacting part of the container when the polyarylene sulfide resin is cleaned by contacting and stirring the polyarylene sulfide resin with a cleaning solvent in a metal container.

As a result of further investigations, the inventors of the present application discovered that by suppressing the foaming that occurs when polyarylene sulfide resin is brought into contact with and stirred with a cleaning solvent in a metal container, i.e., by eliminating the foaming, the amount of impurities such as rust that occurs due to corrosion from foam residue in the liquid-contacting part of the container can be suppressed, thereby solving the problem of the present invention.

That is, the present invention provides a method for producing a polyarylene sulfide resin, comprising a step of washing the polyarylene sulfide resin by contacting the polyarylene sulfide resin with a washing solvent and stirring the mixture in a metal container,
The present invention provides a method for producing a polyarylene sulfide resin, characterized in that the washing step is carried out while defoaming any generated bubbles.

The present invention also provides a method for cleaning a polyarylene sulfide resin, comprising contacting and stirring a polyarylene sulfide resin with a cleaning solvent in a metal container, the method comprising the steps of:
The present invention provides a method for cleaning a polyarylene sulfide resin, which is characterized in that the cleaning is carried out while any generated foam is being defoamed.

According to the present invention, a method for cleaning polyarylene sulfide resin, or a method for producing polyarylene sulfide resin, can be provided that suppresses the amount of impurities such as rust generated by corrosion from foam residue when cleaning polyarylene sulfide resin by contacting and stirring the polyarylene sulfide resin with a cleaning solvent in a metal container.

The present invention is a method for producing a polyarylene sulfide resin, which includes a washing step of polyarylene sulfide resin in which the polyarylene sulfide resin is brought into contact with a washing solvent in a metal container and stirred, and is characterized in that the washing step is carried out while defoaming any bubbles that are generated. The present invention is also a method for cleaning a polyarylene sulfide resin, which includes a washing step of polyarylene sulfide resin in which the polyarylene sulfide resin is brought into contact with a washing solvent in a metal container and stirred, and is characterized in that the washing step is carried out while defoaming any bubbles that are generated.

The polyarylene sulfide resin used in the present invention is not particularly limited, and examples thereof include a polyarylene sulfide resin obtained by a process of polymerizing a polyhalo aromatic compound and a sulfidizing agent in the presence of a polymerization solvent (hereinafter also simply referred to as the "polymerization process"), and a process of removing the polymerization solvent from the crude reaction product obtained in the polymerization process, which contains the polyarylene sulfide resin, the polymerization solvent, and at least the unreacted sulfidizing agent and the by-product (hereinafter also referred to as the "desolvation process"), and a polyarylene sulfide resin obtained by microparticulating or porosifying the polyarylene sulfide resin or a product obtained by microparticulating or porosifying the polyarylene sulfide resin, which is obtained by the polymerization process and the desolvation process and contains at least the unreacted sulfidizing agent and the by-product. Preferred examples include polyarylene sulfide resins contained in the reaction product obtained through the polymerization process and the desolvation process, which contains at least the unreacted sulfidizing agent and the by-product.

Here, the polyhaloaromatic compound used in the polymerization step is, for example, a halogenated aromatic compound having two or more halogen atoms directly bonded to an aromatic ring, and specifically includes dihaloaromatic compounds such as p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dibromobenzene, diiodobenzene, tribromobenzene, dibromonaphthalene, triiodobenzene, dichlorodiphenylbenzene, dibromodiphenylbenzene, dichlorobenzophenone, dibromobenzophenone, dichlorodiphenyl ether, dibromodiphenyl ether, dichlorodiphenyl sulfide, dibromodiphenyl sulfide, dichlorobiphenyl, and dibromobiphenyl, and mixtures thereof, and these compounds may be block copolymerized. Among these, dihalogenated benzenes are preferred, and those containing 80 mol% or more of p-dichlorobenzene are particularly preferred. In addition, in order to increase the viscosity of the polyarylene sulfide resin by forming a branched structure, a polyhaloaromatic compound having three or more halogen substituents in one molecule may be used as a branching agent as desired. Examples of such polyhaloaromatic compounds include 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, and 1,4,6-trichloronaphthalene.

The sulfidizing agent used in the polymerization step includes an alkali metal sulfide and/or an alkali metal hydrosulfide. Here, the alkali metal sulfide includes lithium sulfide, sodium sulfide, rubidium sulfide, cesium sulfide, and mixtures thereof. Such an alkali metal sulfide can be used as a hydrate, an aqueous mixture, or an anhydride. The alkali metal hydrosulfide includes lithium hydrosulfide, sodium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures thereof. An alkali metal hydrosulfide and an alkali metal hydroxide can be used in combination. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and sodium hydroxide is particularly preferred. The amount of the alkali metal hydroxide used is preferably 0.8 or more, more preferably 0.9 or more, and preferably 1.2 or less, more preferably 1.1 or less, per mole of the alkali metal hydrosulfide, in order to promote the production of a solid alkali metal sulfide. In addition, a small amount of alkali metal hydroxide may be added to react with the alkali metal hydrosulfide and alkali metal thiosulfate that are usually present in trace amounts in the alkali metal sulfide to form the alkali metal sulfide.

The polymerization solvent used in the polymerization step includes organic amide solvents (also called amide-based solvents). Examples of organic amide solvents include amide-based organic inhibitor solvents such as formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropyleneurea, and 1,3-dimethyl-2-imidazolidinoic acid, as well as mixtures thereof. Among these, N-methyl-2-pyrrolidone is preferred.

In the polymerization step, the polymerization conditions may be general conditions, and the temperature is preferably in the range of 200°C or more and preferably 330°C or less. The pressure should be in a range that keeps the polymerization solvent and the polyhalo aromatic compound, which is the polymerization monomer, substantially in the liquid phase, and is preferably selected from the range of 0.1 MPa or more and preferably 20 MPa or less, more preferably 2 MPa or less. The amount of the polyhalo aromatic compound charged is preferably in the range of 0.2 mol or more and preferably 5.0 mol or less, preferably in the range of 0.8 to 1.3 mol, and more preferably in the range of 0.9 to 1.1 mol, relative to 1 mol of sulfur atoms of the sulfidizing agent. The amount of the polymerization solvent to be charged varies depending on the type of compound used and the water content in the system, and cannot be generally determined; however, in order to maintain a viscosity of the reaction system that allows a uniform polymerization reaction and to maintain a certain level of productivity, the amount is preferably 1.0 mole or more, more preferably 1.2 moles or more, and even more preferably 1.5 moles or more, to preferably 6.0 moles or less, more preferably 5.0 moles or less, and even more preferably 4.5 moles or less, per mole of sulfur atom in the sulfidizing agent.

The crude reaction mixture obtained after the polymerization of the polyarylene sulfide resin is completed contains the polyarylene sulfide resin, the polymerization solvent, and at least the unreacted sulfidizing agent and the by-products.

Then, the desolvation step is a step in which the polymerization solvent is separated from the obtained crude reaction mixture into solid and liquid, and the liquid phase component is separated and removed. The solid phase component obtained by the desolvation step is preferably taken out into a metal container described below. The solid phase component obtained after the desolvation step contains the target substance, polyarylene sulfide resin, and at least the unreacted sulfidizing agent and the by-product as components that remain without being separated and removed.

The solid-liquid separation is broadly divided into two types, the flash method and the quench method, which will be described later. The flash method is a method in which the polymerization solvent is evaporated to recover the solvent and simultaneously recover the solid matter. It is generally carried out by heating under reduced pressure, preferably at 130°C or higher and preferably at 200°C or lower, to distill off the solvent. The solvent temperature immediately after the solvent recovery by the flash method is generally in the range of 90°C or higher and 190°C or lower.

On the other hand, the Quench method is a method of recovering particulate polyarylene sulfide resin by slowly cooling the polymerization reaction product. In general, the reaction slurry is cooled in a reaction vessel (inside a kettle) while adding poor solvent as necessary, and the polyarylene sulfide resin is crystallized and then solid-liquid separation is performed. In the Quench method, solid-liquid separation can be performed by separating the polyarylene sulfide resin using a centrifuge such as a filter or a screw decanter, adding water directly to the obtained filtration residue to form a slurry, and then repeatedly performing solid-liquid separation, or by heating the obtained filtration residue in a non-oxidizing atmosphere to remove the remaining solvent. The solvent temperature immediately after the solvent is recovered by the Quench method is generally in the range of 90°C or higher to 190°C or lower. The Flash method is preferable because it is relatively easy to recover solids, and the Quench method is preferable because it is easy to control the particle size of the polyarylene sulfide resin and because it is difficult for alkali metal-containing inorganic salts and other impurities to be incorporated into the polymer particles during crystallization, making it easy to obtain a high-purity polymer.

The reaction mixture obtained after the solvent removal step contains a polyarylene sulfide resin. In addition, a portion of the crude reaction product contains unreacted sulfidizing agent and the by-products as residues.

In the present invention, the washing step involves washing the polyarylene sulfide resin by contacting it with a washing solvent in a metal container and stirring it, while defoaming any bubbles that may form during the washing process.

In the washing step, for example, a washing solvent is added to the polyarylene sulfide resin (solid content) obtained after the solvent removal step, and the mixture is stirred and then filtered using a filtration device, or a washing solvent is added again to the filtration residue containing the washing solvent obtained by the above-mentioned filtration (hereinafter also referred to as "solvent-containing cake") to form a slurry, which is stirred and then filtered. In either case, when the washing solvent is added, bubbles that are generated during stirring are suppressed, i.e., defoamed.

A known defoaming device (also called a defoaming device or bubble remover) can be used to defoam. For example, a method of sucking and removing bubbles on the liquid surface using a shear type defoaming/defoaming device or a centrifugal defoaming device is preferred. After suction, the bubbles are liquefied in the defoaming device and reused as a slurry.

When using a shear type foam defoamer, the bubbles on the liquid surface are sucked into the shear type foam defoamer through a suction port by a blower, where the bubbles are destroyed by the shear force acting in the gap between a rotating disk and an orifice plate.
When using a centrifugal separator, the bubbles on the liquid surface are sucked in through a suction port by a blower and drawn into the centrifugal separator, where the bubbles are destroyed by the centrifugal force of the internal rotor.

When the foam on the liquid surface is removed by suction using a defoamer, the foam suction speed is not particularly limited, but is preferably in the range of 10 liters or more, more preferably 50 liters or more, and preferably 1,000 liters or less, more preferably 500 liters or less, per minute per ^m2 of liquid surface.

The bubbles destroyed by the defoaming device, i.e., the liquefied cleaning solvent, are directly returned as a slurry from the outlet of the defoaming device to the metallic container, or are discharged into a container or the like for use in the next cleaning step, and then returned from the container or the like to the metallic container, thereby being reused to thoroughly clean the entirety. The amount of the liquefied cleaning solvent returned to the metallic container is not particularly limited, but is preferably in the range of 0.5 liters or more, more preferably 2.5 liters or more, and preferably 50 liters or less, more preferably 25 liters or less per minute per ^m2 of liquid surface.

According to the present invention, when the polyarylene sulfide resin is contacted with and stirred in a metal container to wash the polyarylene sulfide resin, it is possible to suppress the amount of impurities such as rust generated by corrosion from the foam retained matter. The amount of metal contained in the polyarylene sulfide resin is not particularly limited, but preferably, the amount of eluted metal contained in the polyarylene sulfide resin obtained after the washing step can be 50 ppm or less, and more preferably, 30 ppm or less.
Furthermore, by removing the bubbles by washing, the by-products that did not flow along with the bubbles and remained at the adhesion portion can also be sufficiently removed, and the by-products remaining in the polyarylene sulfide resin can also be reduced, which is preferable because it improves various performance properties that the polyarylene sulfide resin inherently possesses.

Here, the cleaning solvent may be one that is miscible with the polymerization solvent and is a poor solvent for the polyarylene sulfide resin within the temperature range during cleaning. For example, alcohol solvents and phenol solvents such as methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, phenol, cresol, and polyethylene glycol; halogen solvents such as chloroform, bromoform, methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane, chlorobenzene, and 2,6-dichlorotoluene; hydrocarbon solvents such as pentane, hexane, heptane, octane, cyclohexane, cyclopentane, benzene, toluene, and xylene; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, methyl butyl ketone, and acetophenone; methyl acetate, ethyl acetate, and pentyl acetate; Examples include carboxylate solvents such as octyl acetate, methyl butyrate, ethyl butyrate, pentyl butyrate, methyl salicylate, and ethyl formate, and water. Among these, methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, chloroform, methylene chloride, 1,2-dichloroethane, pentane, hexane, heptane, octane, cyclohexane, cyclopentane, acetone, methyl acetate, ethyl acetate, and water are preferred, and methanol, ethanol, propanol, ethylene glycol, chloroform, methylene chloride, 1,2-dichloroethane, acetone, ethyl acetate, and water are particularly preferred, methanol, acetone, and water are even more preferred, and water is particularly preferred. These solvents can be used alone or as a mixture of two or more types.

In the cleaning step, there is no particular restriction on the atmosphere when the polyarylene sulfide resin is brought into contact with the cleaning solvent, but if the polyarylene sulfide resin or the cleaning solvent is oxidized and deteriorated due to the temperature, time, and other conditions during contact, it is desirable to carry out the cleaning step in a non-oxidizing atmosphere. There is no particular restriction on the temperature when the polyarylene sulfide resin is brought into contact with the cleaning solvent, but since it is preferable to carry out the cleaning step under atmospheric pressure, it is desirable to set the upper limit temperature to the reflux temperature of the solvent used under atmospheric pressure or lower, and when the above-mentioned preferred solvent is used, the range is preferably 20°C or higher, more preferably 30°C or higher, and more preferably 70°C or higher in terms of cleaning efficiency, and preferably 100°C or lower, more preferably 90°C or lower.

In the washing step, the method for contacting the polyarylene sulfide resin with the washing solvent may be a known general method, and is not particularly limited. For example, the washing solvent may be added to the polyarylene sulfide resin continuously or in several divided portions and stirred.
The amount of the washing solvent used when the polyarylene sulfide resin is brought into contact with the washing solvent is not particularly limited, but is preferably in the range of 2 times or more to 100 times or less, based on the mass of the theoretical yield of the polyarylene sulfide resin. In the case of such a ratio range, the polyarylene sulfide resin and the washing solvent can be mixed uniformly, and the unreacted sulfidizing agent and by-products can be washed away while efficiently defoaming. In addition, when the polyarylene sulfide resin is repeatedly brought into contact with the washing solvent, that is, when washing is repeatedly performed, a smaller ratio may be sufficient, and sufficient effects can often be obtained.

An embodiment of washing using water as a washing solvent will be described in detail below.
When washing is performed using water as a washing solvent (hereinafter referred to as "water washing"), the amount of water added to the polyarylene sulfide resin is preferably in the range of 2 to 10 times the theoretical yield of the polyarylene sulfide resin finally obtained on a mass basis from the viewpoint of washing efficiency, and the above amount of water is preferably divided into a range of preferably 2 or more, preferably 10 or less, more preferably 4 or less, and then subjected to water washing. The water washing is performed under a nitrogen or air atmosphere, and the solvent temperature is preferably in the range of 20°C or more, more preferably 30°C or more, and more preferably 70°C or more, preferably 100°C or less, more preferably 90°C or less from the viewpoint of washing efficiency. The water washing can be performed once or repeatedly a plurality of times. When washing with water is performed repeatedly a plurality of times, the atmosphere and temperature conditions may be the same or different.

When washing with water is performed, most of the remaining unreacted sulfidizing agent and by-products are removed, but some remain and cannot be completely removed, so it is preferable to further contact the product with water in the range of 100°C or higher and 275°C or lower, followed by solid-liquid separation (hereinafter sometimes referred to as "hot water washing").

The temperature of the hot water washing is preferably in the range of, for example, 120°C or higher and 275°C or lower. More specifically, it is preferable to carry out the extraction process with hot water in the range of 140°C or higher and 260°C or lower under conditions in which the pressure of the gas phase in the reactor is 0.2 MPa or higher and 4.6 MPa or lower.

A specific method for performing such hot water washing includes a method in which the polyarylene sulfide resin filtered after the water washing is washed by adding hot water under predetermined pressure and temperature conditions in a pressure vessel and further stirring. The amount of water during hot water washing is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, and even more preferably 200 parts by mass or more, and preferably 10,000 parts by mass or less, more preferably 5,000 parts by mass or less, and even more preferably 1,000 parts by mass or less, relative to 100 parts by mass of polyarylene sulfide resin. It is preferable that the amount of hot water is in the range of up to 100 parts by mass, and hot water washing may be performed by dividing this amount of hot water into two or more times. For example, when hot water washing is repeated twice, it is preferable to perform filtration between the first and second hot water washings, add hot water, and then perform the second stirring. In addition, filtration may be performed after one hot water wash, and the above-mentioned water washing may be performed. In addition, although the conditions for the first hot water washing step and the second hot water washing step can be selected arbitrarily from the above conditions, it is preferable to set the temperature of the first hot water washing step to a temperature in the range of, for example, 120°C or more and 200°C or less, and to first filter and remove the highly alkaline filtrate, and then set the temperature of the second hot water washing step to a temperature higher than the temperature of the first hot water washing step, for example, a temperature in the range of 150°C or more and 275°C or less, from the viewpoint of reducing impurities from the metal container used in the hot water washing.

In addition, when washing with hot water, an acid or a base can be added before, during, or after the washing with hot water to adjust the pH. In particular, in a carboxyalkylamino group-containing compound that may be contained as a secondary component in the polyarylene sulfide resin, the carboxy group becomes an alkali metal salt, which makes it easier to extract into water. For this reason, it is preferable to control the pH after washing with hot water to be in the range of 10.0 or more to less than 13.0. Examples of acids used in this case include hydrochloric acid, sulfuric acid, carbonic acid, acetic acid, and oxalic acid, and among these, carbonic acid, acetic acid, and oxalic acid are preferred. Carbon dioxide gas may also be introduced and contacted under normal pressure or pressure. On the other hand, examples of bases include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, or sodium carbonate, ammonium carbonate, and sodium phosphate, and among these, sodium hydroxide is preferred.

The metal container used in the cleaning process is not particularly limited as long as it is used in the production of polyarylene sulfide resin, but examples include containers in which at least the liquid-contacting parts are made of corrosion-resistant metals such as stainless steel, titanium material, zirconium material, and nickel alloys containing chromium, molybdenum, etc., such as Hastelloy alloy.
The metal vessel may be equipped with various mechanisms. For example, a metal vessel having an agitator or a metal vessel equipped with a centrifugal separation mechanism for solid-liquid separation may be used, and further, a metal vessel having an agitator blade inside and a mixing function with a filtration filter disposed at the bottom may be used. In addition, washing with hot water exceeding 100°C may be performed using a water washing tank having an agitator or a centrifuge for solid-liquid separation, but it may be performed in a sealed or sealable vessel having a mixing function with an agitator blade inside and a filtration filter disposed at the bottom. In the present invention, washing may be performed continuously or batchwise.

The polyarylene sulfide resin obtained through the washing process can then be dried to prepare a powdered or granular polyarylene sulfide resin. Alternatively, the polyarylene sulfide resin may be oxidatively crosslinked by heat treatment in air, oxygen-enriched air, or under reduced pressure. The temperature of this heat treatment is preferably in the range of 180°C to 270°C, although it varies depending on the target crosslinking treatment time and the treatment atmosphere. The heat treatment may be performed in a molten state of the polyarylene sulfide resin at a temperature equal to or higher than the melting point of the polyarylene sulfide resin using an extruder or the like, but it is preferable to perform the heat treatment at a temperature equal to or lower than the melting point plus 100°C, since this increases the possibility of thermal degradation of the polyarylene sulfide resin.

The polyarylene sulfide resin obtained by the present invention can be used as a polyarylene sulfide resin composition in combination with various fillers in order to further improve the strength, heat resistance, dimensional stability, and other properties. The filler is not particularly limited, but examples thereof include fibrous fillers and inorganic fillers. As fibrous fillers, glass fibers, carbon fibers, silane glass fibers, ceramic fibers, aramid fibers, metal fibers, potassium titanate, silicon carbide, calcium sulfate, calcium silicate, and natural fibers such as wollastonite can be used. As inorganic fillers, barium sulfate, calcium sulfate, clay, biloferrite, bentonite, sericite, zeolite, mica, talc, atalpulgite, ferrite, calcium silicate, calcium carbonate, magnesium carbonate, glass beads, and the like can be used. In addition, various additives such as release agents, colorants, heat stabilizers, ultraviolet stabilizers, foaming agents, rust inhibitors, flame retardants, and lubricants can be added as additives during molding.

Furthermore, the polyarylene sulfide resin obtained by the present invention may be used as a polyarylene sulfide resin composition by blending it with synthetic resins such as polyester, polyamide, polyimide, polyetherimide, polycarbonate, polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, polyetherketone, polyarylene, polyethylene, polypropylene, polytetrafluoroethylene, polydifluoroethylene, polystyrene, ABS resin, epoxy resin, silicone resin, phenolic resin, urethane resin, liquid crystal polymer, or elastomers such as polyolefin rubber, fluorine rubber, silicone rubber, etc., depending on the application.

The polyarylene sulfide resin and its composition obtained by the manufacturing method of the present invention can be processed into molded products having excellent heat resistance, moldability, dimensional stability, etc., by various known melt molding methods such as injection molding, extrusion molding, compression molding, and blow molding.

The polyarylene sulfide resin obtained by the manufacturing method of the present invention has a low metal foreign matter content, and it is possible to further increase the melt viscosity, and in addition to the various properties inherent to polyarylene sulfide resin such as heat resistance and dimensional stability, it is possible to further improve the mechanical strength, and the molded products thereof are widely useful as materials for various molding processes such as injection molding or compression molding of precision parts such as office automation equipment parts, camera parts, and watch parts, extrusion molding of composites, sheets, pipes, etc., or pultrusion molding, or as materials for fibers or films.

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

[Comparative Example 1]
Synthesis Example 1
(Polymerization step) Polymerization step of polyphenylene sulfide 33.222 kg (226 mol) of p-dichlorobenzene (hereinafter abbreviated as DCB), 2.280 kg (23 mol) of NMP, 27.300 kg (230 mol) of 47.23 mass% sodium hydrosulfide, and 18.533 kg (228 mol) of 49.21 mass% caustic soda were charged into a 150 L autoclave equipped with a pressure gauge, a thermometer, a condenser, and a decanter, and the temperature was raised to 173 ° C. over 5 hours under a nitrogen atmosphere while stirring, and 27.3 kg of water was distilled, and the kettle was sealed. The DCB distilled by azeotropy during dehydration was separated in a decanter and returned to the kettle as needed, and the kettle after completion of dehydration was in a state in which the anhydrous sodium sulfide composition was dispersed in DCB. Further, the inside temperature was cooled to 160 ° C., 47.492 kg (479 mol) of NMP was charged, and the temperature was raised to 185 ° C. The distilled mixed vapor of DCB and water was condensed in a condenser, separated in a decanter, and DCB was returned to the kettle. The amount of distilled water was 179 g. Next, the inside temperature was raised from 200 ° C. to 230 ° C. over 3 hours, stirred for 1 hour, then heated to 250 ° C. and stirred for 1 hour to complete the reaction. After opening the bottom valve of the autoclave, the mixture was flashed in a 150-liter vacuum stirring dryer (desolvent jacket temperature 120 ° C.) with a stirring blade while in a reduced pressure state to extract N-methyl-2-pyrrolidone, cooled to room temperature, and sampled to obtain a PPS mixture with a non-volatile content of 58%.

(Refining process)
Next, 36 kg of the mixture cooled to room temperature was decompressed in a vacuum dryer at 150°C for 2 hours, NMP was distilled off to obtain a solid residue, and the mixture was transferred to a stainless steel container (diameter 585 mm x height 898 mm, the height from the bottom surface is indicated on the wall surface). Next, 600 parts by mass of 70°C ion-exchanged water was added to 100 parts by mass of the obtained solid residue. At that time, the liquid level was used as the reference point. After that, the mixture was stirred for 10 minutes to foam, and the highest position of the wall surface to which the generated foam reached was measured from the addition of the ion-exchanged water to the end of the stirring, and the height from the reference point was calculated.

After that, it was filtered, and 70°C ion-exchanged water was added to the filtered wet cake in a ratio of 600 parts by mass per 100 parts by mass of the solid residue, and stirred for 10 minutes. From the time the ion-exchanged water was added until the end of stirring, the highest point on the wall reached by the generated bubbles was measured, and the height from the reference point was calculated. This operation was repeated nine times.

The obtained wet cake was dried at 120° C. for 4 hours using a hot air dryer to obtain a white powdery polymer. The melt viscosity of the obtained polymer was 45 Pa·s.
The heights from the reference point measured in the purification step were calculated as an arithmetic average, and the average is shown in Table 1. The iron atom content in the resulting polymer was also measured, and the total amount is shown in Table 1.

[Example 1]
(Polymerization process)
In the same manner as in Comparative Example 1, a PPS mixture having a non-volatile content of 58% was obtained.
(Refining process)
Next, 36 kg of the mixture cooled to room temperature was decompressed at 150 ° C. for 2 hours in a vacuum dryer, and NMP was distilled off to obtain a solid residue. Then, it was transferred to the stainless steel container equipped with a shear type defoamer ("Disc Defoamer" manufactured by Techno Eye Co., Ltd.). Next, 600 parts by mass of 70 ° C. ion exchange water was added to 100 parts by mass of the obtained solid residue. At that time, the liquid level was used as the reference point. Then, it was stirred for 10 minutes to foam, and the highest position of the wall surface where the generated foam reached was measured from the addition of the ion exchange water to the end of stirring, and the height from the reference point was calculated. From the addition of the ion exchange water to the end of stirring, the shear type defoamer was operated, and the generated foam was sucked from the suction port of the shear type defoamer at a rate of 200 liters / min per 1 m ² of liquid surface, thereby defoaming the foam on the slurry liquid surface. Suction was performed at a rate at which the liquefied foam returned to the stainless steel container at a rate of 5 liters / min. During the period from the addition of ion-exchanged water to the end of stirring, the highest point on the wall that the generated bubbles reached was measured, and the height from a reference point was calculated.

After that, the mixture was filtered, and ion-exchanged water at 70° C. was added to the filtered wet cake in a ratio of 600 parts by mass per 100 parts by mass of the solid residue, and the mixture was stirred for 10 minutes. From the addition of the ion-exchanged water to the end of the stirring, the shear type foaming device was operated, and the generated foam was sucked from the suction port of the shear type foaming device, thereby defoaming the foam on the surface of the slurry. The suction was performed at a rate at which the liquefied foam returned to the stainless steel container at a rate of 5 liters/minute. From the addition of the ion-exchanged water to the end of the stirring, the highest position of the wall surface reached by the generated foam was measured, and the height from the reference point was calculated. This operation was performed nine times.
The obtained wet cake was filtered using a centrifugal filter and then dried at 120° C. for 4 hours using a hot air dryer to obtain a white powdery polymer. The melt viscosity of the obtained polymer was 45 Pa·s.
The heights from the reference point measured in the purification step were calculated as an arithmetic average, and the average is shown in Table 1. The iron content in the resulting polymer was also measured, and the total amount is shown in Table 1.

[Example 2]
The same procedure as in Example 1 was repeated, except that a centrifugal defoamer ("Babkes II" manufactured by Toyooki Kogyo Co., Ltd.) was used instead of a shear defoamer. As in Example 1, the heights from the reference points measured in the purification step were arithmetically averaged, and the results are shown in Table 1. The iron content in the obtained polymer was also measured, and the total amount is shown in Table 1.

(Measurement Example) Measurement of iron content The obtained polymer was calcined at 500° C., and then calcined at 530° C. for 6 hours. The ash obtained by calcining was dissolved in hydrochloric acid and measured with an atomic absorption spectrophotometer (manufactured by Shimadzu Corporation, “AA-6300”).

Claims (4)

A method for producing a polyarylene sulfide resin, comprising a step of washing the polyarylene sulfide resin by contacting the polyarylene sulfide resin with a washing solvent and stirring the mixture in a metal container, comprising:
The method for producing a polyarylene sulfide resin is characterized in that the washing step is carried out while defoaming any generated bubbles. The method for producing a polyarylene sulfide resin according to claim 1, in which the generated bubbles are removed from the metal container by suction. The method for producing the polyarylene sulfide resin according to claim 2, in which the aspirated bubbles are broken down, liquefied, and returned to the metal container. A method for cleaning a polyarylene sulfide resin, comprising contacting and stirring a polyarylene sulfide resin with a cleaning solvent in a metal container, the method comprising the steps of:
A method for cleaning a polyarylene sulfide resin, comprising the step of defoaming any foam that is generated during the cleaning.