JP7547829B2 - Method for producing polyarylene sulfide - Google Patents

Description

The present invention relates to a method for producing polyarylene sulfide that has an excellent balance between low water absorption and melt stability without impairing the inherent heat resistance, chemical resistance, dimensional stability, etc. of polyarylene sulfide, while at the same time reducing the amount of gas and tar generated during molding and exhibiting high melt fluidity during molding. The present invention relates to a method for producing polyarylene sulfide that is particularly useful for electrical and electronic component applications such as electrical and electronic components or automotive electrical components that require low halogen and low electrolytes.

Polyarylene sulfide is a resin that exhibits excellent properties such as heat resistance, chemical resistance, and dimensional stability, and is widely used in electrical and electronic equipment components, automotive equipment components, and office equipment components, taking advantage of these excellent properties. These polyarylene sulfides are usually produced by carrying out a polymerization reaction between a polyhalogenated aromatic compound such as dichlorobenzene and an alkali metal sulfide such as sodium sulfide in a polar organic solvent such as N-methyl-2-pyrrolidone (hereinafter referred to as NMP). The polyarylene sulfide produced in this manner contains alkali metal salts as by-products in amounts almost equal to the amount of polyarylene sulfide produced. In addition, it is known that various oligomer components are produced as by-products, and it is known that these metal salts and oligomer components reduce the performance of polyarylene sulfide.

As methods for removing these by-products, methods such as heating in an ethylene glycol solvent at a temperature of 200°C or higher and heat treating polyarylene sulfide in an aromatic solvent to reduce the sodium content have been proposed (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 60-210631 Japanese Patent Application Publication No. 59-219331

However, the methods proposed in Patent Documents 1 and 2 are methods for removing alkali metal salts and/or oligomer components contained in an amount of several to several tens of weight percent all at once, and have problems such as poor melt flowability during molding and poor productivity.

The present invention aims to provide a polyarylene sulfide that is produced efficiently, has an excellent balance between low water absorption and melt stability, reduces the amount of gas and tar generated during molding, and has high melt fluidity during molding.

As a result of intensive research into solving the above problems, the inventors discovered that the above problems could be solved by using a manufacturing method in which polyarylene sulfide after polymerization was washed with a specific solvent under specific conditions, and thus completed the present invention.

That is, the present invention relates to a method for producing polyarylene sulfide by a polymerization reaction of a polyhalogenated aromatic compound with an alkali metal sulfide in a polar organic amide solvent, characterized in that the polyarylene sulfide after polymerization is washed with a mixed solvent of water/glycol ether = 70/30 to 95/5 (weight ratio) at a temperature of 160°C to 240°C and a treatment time of 1 hour to 10 hours.

The present invention will be described in detail below.

The method for producing polyarylene sulfide of the present invention involves washing the polyarylene sulfide after polymerization with a mixed solvent of water/glycol ether = 70/30 to 95/5 (weight ratio) under conditions of 160°C to 240°C and 1 hour to 10 hours.

A method for polymerizing polyarylene sulfide is known in which a polyhalogenated aromatic compound and an alkali metal sulfide are polymerized in a polar organic amide solvent, and after polymerization, a mixture consisting of polyarylene sulfide, an alkali metal salt by-product, 4-(N-methyl-chlorophenylamino)butanoate sodium salt, an oligomer component, and an organic amide solvent is obtained. According to the method for producing polyarylene sulfide of the present invention, by controlling the content of the 4-(N-methyl-chlorophenylamino)butanoate sodium salt, it is possible to efficiently produce polyarylene sulfide of excellent quality.

Here, as the organic amide solvent, any solvent that falls within the category of organic amide solvents can be used, such as N-methylpyrrolidone, N-methylcyclohexyl-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylimidazolidinone, etc., and among these, N-methylpyrrolidone is particularly preferred because it makes it easier to obtain polyarylene sulfide with a high molecular weight and excellent mechanical properties.

As the polyhalogenated aromatic compound, any compound that belongs to the category of polyhalogenated aromatic compounds can be used, such as p-dichlorobenzene, m-dichlorobenzene, o-dichlorobenzene, p-dibromobenzene, m-dibromobenzene, o-dibromobenzene, p,p'-dichlorodiphenyl, p,p'-dibromodiphenyl, 2,6-dichloronaphthalene, 2,6-dibromonaphthalene, 1,3,5-trichlorobenzene, and 1,2,4-trichlorobenzene. Among these, p-dichlorobenzene is preferred because it is easier to obtain polyarylene sulfide with a high molecular weight and excellent mechanical properties. It is also possible to use 1,3,5-trichlorobenzene and 1,2,4-trichlorobenzene in combination to obtain polyarylene sulfide with an even higher molecular weight.

As the alkali metal sulfide, any one that belongs to the category of alkali metal sulfides can be used, and examples thereof include sodium sulfides such as anhydrous sodium sulfide, sodium sulfide 2.8 hydrate, and sodium sulfide pentahydrate, lithium sulfide, rubidium sulfide, sodium hydrogen sulfide, and lithium hydrogen sulfide, and among these, sodium sulfide, lithium sulfide, sodium hydrogen sulfide, and lithium hydrogen sulfide are preferred because they make it easier to obtain polyarylene sulfide that has a high molecular weight and excellent mechanical properties. Hydrosulfides such as sodium hydrogen sulfide and lithium hydrogen sulfide can also be used as alkali metal sulfide salts by combining them with alkali metal hydroxide salts.

The polyphenylene sulfide can be recovered from the mixture of polyarylene sulfide obtained after polymerization, the by-product alkali metal salt, 4-(N-methyl-chlorophenylamino)butanoate sodium salt, oligomer components, and organic amide solvent by, for example, recovering the organic amide solvent and then washing the mixture.

In this case, the organic amide solvent can be recovered by distillation, which is highly efficient, for example by flash distillation. The desolvation operation of the organic amide solvent by distillation may be carried out in the reaction vessel, or the mixture after the reaction may be transferred to a separate tank maintained at an equal pressure. The internal pressure of the reaction vessel may be utilized to transfer the mixture to a separate tank and simultaneously flush the mixture to remove the solvent.

After recovering the organic amide solvent, water or a solvent is added to the cake consisting of polyarylene sulfide, alkali metal salt, 4-(N-methyl-chlorophenylamino)butanoate sodium salt, and oligomers, and the alkali metal salt is dissolved and washed, followed by drying to obtain polyarylene sulfide. By controlling the washing conditions, polyarylene sulfide with a reduced content of 4-(N-methyl-chlorophenylamino)butanoate sodium salt can be easily and efficiently produced. The washing conditions are 160°C to 240°C, preferably 170°C to 210°C, 1 hour to 10 hours, preferably 1 hour to 5 hours, and a mixed solvent of water/glycol ether = 70/30 to 95/5 (weight ratio) is used.

If the cleaning temperature is less than 160°C or the treatment time is less than 1 hour, removal of oligomer components and the like will be insufficient. On the other hand, if the temperature exceeds 240°C or the treatment time exceeds 10 hours, degradation of the polyarylene sulfide may occur.

The solvent used for cleaning is a mixed solvent of water/glycol ether = 70/30 to 95/5 (weight ratio). Here, if the water ratio is less than 70/30 (weight ratio), the cleaning efficiency of inorganic impurities and the like will be poor. On the other hand, if the water ratio is more than 95/5, the cleaning efficiency of oligomers and the like will be poor. The water used in this case belongs to the category of normal water, and for example, ion-exchanged water is used. Examples of glycol ethers include ethylene glycol ether, propanediol ether, propylene glycol ether, butanediol ether, diethylene glycol ether, dipropylene glycol ether, and the like. More specifically, examples of the ethylene glycol monomethyl ether include ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propanediol monomethyl ether, propanediol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, butanediol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol dipropyl ether, and dipropylene glycol dibutyl ether.

The drying conditions for recovering polyarylene sulfide are such that the moisture is removed, and there is no need to increase the temperature more than necessary. The final drying temperature is preferably in the range of 100°C to 150°C.

In the method for producing the polyarylene sulfide of the present invention, heat curing may be further performed in an air or nitrogen atmosphere at an atmospheric temperature of 240°C or higher. The apparatus used for heat curing is not particularly limited, and examples thereof include calcination apparatuses such as ribbon blender types and rotary kiln types. There is also no particular limit to the method for supplying air or nitrogen as long as it can be efficiently supplied to the inside of the apparatus.

The polyarylene sulfide produced by the polyarylene sulfide production method of the present invention is a polyarylene sulfide that is particularly well-balanced between low water absorption, melt stability, and moldability, and therefore preferably contains 1500 ppm or less, and particularly 300 ppm or more and 1500 ppm or less, of 4-(N-methyl-chlorophenylamino)butanoate sodium salt represented by the following general formula (1).

The above-mentioned 4-(N-methyl-chlorophenylamino)butanoate sodium salt is a by-product produced during the production of polyarylene sulfide, and by controlling its content to 1,500 ppm or less, a polyarylene sulfide is obtained that has an excellent balance between low water absorption and melt stability, while at the same time reducing the amount of gas and tar generated during molding, and furthermore has high melt fluidity during molding.

The polyarylene sulfide used in the production method of the present invention may be any polyarylene sulfide that falls within the category known as polyarylene sulfide, such as polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, polyphenylene sulfide ether, etc., and of these, polyphenylene sulfide is preferred.

In the manufacturing method of the present invention, it is possible to efficiently remove oligomers and the like, and to manufacture polyarylene sulfide that has excellent stability of melt viscosity after curing. Therefore, after washing with the above-mentioned mixed solvent, it is preferable to further wash with hot water under conditions of 165°C to 245°C, 1 hour to 10 hours, and particularly under conditions of 175°C to 215°C, 1 hour to 5 hours. The hot water in this case belongs to the category of water, and examples thereof include ion-exchanged water. In addition, it is preferable to use hot water at a temperature of +5°C or more, particularly +10°C or more, relative to the washing temperature with the mixed solvent.

The polyarylene sulfide obtained by the manufacturing method of the present invention has low and excellent water absorption, and therefore preferably has a water absorption rate of 1% by weight or less.

In addition, the polyarylene sulfide obtained by the manufacturing method of the present invention may be made into a polyarylene sulfide composition by blending it with a filler that is blended into a general resin composition. Examples of the filler include fibrous fillers such as glass fibers, carbon fibers, potassium titanate whiskers, zinc oxide whiskers, aluminum borate whiskers, aramid fibers, alumina fibers, silicon carbide fibers, asbestos fibers, gypsum fibers, metal fibers, etc., and among these, glass fibers are preferred because they result in a polyarylene sulfide composition that has particularly excellent mechanical strength. Examples of non-fibrous fillers include silicates such as wollastonite, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, talc, and alumina silicate; oxides such as aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, titanium oxide, zinc oxide, and iron oxide; carbonates such as calcium carbonate, magnesium carbonate, and dolomite; sulfates such as calcium sulfate and barium sulfate; nitrides such as silicon nitride, boron nitride, and aluminum nitride; glass flakes, glass beads, and the like. Among these, mica, clay, talc, calcium carbonate, glass flakes, and glass beads are preferred because they provide a polyarylene sulfide composition with particularly excellent dimensional stability. Furthermore, the filler may be surface-treated with an isocyanate-based compound, a silane-based coupling agent, a titanate-based coupling agent, an epoxy compound, and the like, because they provide a polyarylene sulfide composition with high mechanical strength. Furthermore, the polyarylene sulfide obtained by the present invention may be a polyarylene sulfide composition containing a lubricant to improve the mold releasability and appearance when molded into a molded product, and examples of the lubricant include carnauba wax and carboxylic acid amide wax. As the carnauba wax, a general commercially available product can be used, and examples thereof include (product name) Refined Carnauba No. 1 Powder (manufactured by Nikko Fine Products). In addition, the carboxylic acid amide wax is a polycondensate of higher aliphatic monocarboxylic acid, polybasic acid, and diamine, and any wax that falls within this category can be used, and examples thereof include (product name) Light Amide WH-255 (manufactured by Kyoeisha Chemical Co., Ltd.), which is a polycondensate of stearic acid, sebacic acid, and ethylenediamine.

The polyarylene sulfide may also contain one or more additives, such as heat stabilizers, antioxidants, ultraviolet absorbers, crystal nucleating agents, foaming agents, mold corrosion inhibitors, flame retardants, flame retardant assistants, colorants such as dyes and pigments, and antistatic agents, within the scope of the object of the present invention.

Furthermore, the polyarylene sulfide of the present invention can be used in combination with one or more of various thermosetting resins and thermoplastic resins, such as epoxy resins, cyanate ester resins, phenolic resins, polyimides, silicone resins, polyesters, polyamides, polyphenylene oxides, polycarbonates, polysulfones, polyetherimides, polyethersulfones, polyetherketones, and polyetheretherketones, within the scope of the object of the present invention.

When the above-mentioned fillers, additives, etc. are blended to prepare a polyarylene sulfide composition, they may be blended with the polyarylene sulfide without any restrictions on the blending method. Among them, it is preferable to manufacture the composition by melt kneading, since this is particularly efficient when blending.

As the device for melt kneading, any device capable of melt kneading can be used, for example, a single-screw or twin-screw extruder, a kneader, a mill, a Brabender, or other heating melt kneading device. It is preferable to use a single-screw extruder or twin-screw extruder, since this allows for efficient production of polyarylene sulfide with particularly excellent quality. In addition, there is no particular restriction on the kneading temperature for melt kneading, and it can be selected from the range of 270 to 400°C, for example.

Polyphenylene sulfide can be molded into any shape using various molding machines such as injection molding machines, extrusion molding machines, transfer molding machines, and compression molding machines.

The present invention relates to a method for producing polyarylene sulfide that has an excellent balance between low water absorption and melt stability without impairing the inherent heat resistance, chemical resistance, dimensional stability, etc. of polyarylene sulfide, while at the same time reducing the amount of gas and tar generated during molding and exhibiting high melt fluidity during molding. More specifically, the present invention relates to a method for producing polyarylene sulfide that is particularly useful for use in electrical and electronic parts such as electrical and electronic parts or automotive electrical components.

Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Synthesis Example 1
In a 15-liter autoclave equipped with a stirrer, 1842 g of flake sodium sulfide (Na ₂ S.2.9H ₂ O), 25 g of 30% caustic soda solution (30% NaOHaq), and 3679 g of N-methyl-2-pyrrolidone were charged, and the temperature was gradually raised to 200° C. while stirring under a nitrogen stream, and 375 g of water was distilled off. After cooling to 190° C., 2151 g of p-dichlorobenzene and 985 g of N-methyl-2-pyrrolidone were added, and the system was sealed under a nitrogen stream. The system was heated to 225° C. over 2 hours, polymerized at 225° C. for 1 hour, then heated to 250° C. over 25 minutes, and further polymerized at 250° C. for 2 hours. After polymerization, N-methyl-2-pyrrolidone was removed from the polymerization slurry by distillation under reduced pressure. The final temperature was 170°C and the pressure was 4.7 kPa. Hot water at 80°C was added to the obtained cake to make the slurry concentration 20%, which was then recovered and centrifuged for solid-liquid separation to obtain a cake. The obtained cake was used as crude polyarylene sulfide (hereinafter referred to as PPS (A-1)). PPS (A-1) was dried overnight at 105°C to obtain PPS (A-2).

The evaluation and measurement methods for the obtained polyarylene sulfide are shown below.

Measurement of 4-(N-methyl-chlorophenylamino)butanoate, sodium salt (hereinafter sometimes referred to as SMCAB)
SMCAB was extracted from polyarylene sulfide with a solvent and measured by HPLC (HPLC8020 system (trade name) manufactured by Tosoh Corporation).

～Melt viscosity measurement～
The melt viscosity was measured at a measurement temperature of 315° C. and a load of 10 kg using a high-performance flow tester (manufactured by Shimadzu Corporation, product name: CFT-500) equipped with a die having a diameter of 1 mm and a length of 2 mm. The melt viscosity value obtained was divided by the melt viscosity value of PPS (A-2) obtained in Synthesis Example 1 to obtain a melt viscosity ratio, and a melt viscosity ratio of less than 0.85 was determined to have excellent fluidity.

～Water absorption rate～
An ASTM D-638 No. 1 test piece was prepared by injection molding, and the test piece was placed in a 2 L autoclave containing 18 g of water. The autoclave was placed in an oven at 121°C and left to stand for 100 hours. After 100 hours, the autoclave was cooled to room temperature, the test piece was removed, and the moisture adhering to the test piece was wiped off. The weight difference from before the test was taken as the amount of water absorption, and the water absorption rate was measured. A water absorption rate of 1.0 wt% or less was determined to be low water absorption.

～Melt Viscosity Measurement (2)～
Before and after heat curing, the melt viscosity was measured at a measurement temperature of 315° C. and a load of 10 kg using a high-performance flow tester (manufactured by Shimadzu Corporation, product name: CFT-500) equipped with a die having a diameter of 1 mm and a length of 2 mm. The melt viscosity ratio (2) was determined by dividing the melt viscosity value after heat curing by the melt viscosity value before heat curing, and a melt viscosity ratio (2) of 2.00 or less was determined to have excellent fluidity.

Example 1
6.2 kg of PPS (A-1) (including 2.5 kg of water), 11.7 kg of water, and 1.6 kg of diethylene glycol monomethyl ether were charged into a 30-liter autoclave, and the system was sealed under a nitrogen stream. The system was heated to 190°C and washed for 2 hours. After washing, the system was cooled to 80°C and polyarylene sulfide was recovered. The recovered polyarylene sulfide was dried at 105°C for 24 hours to obtain polyarylene sulfide containing 1200 ppm of SMCAB.

The polyarylene sulfide was placed in the hopper of an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd., product name: SE75) with the cylinder temperature heated to 310°C, and test pieces for measuring the water absorption rate were molded and evaluated. The results are shown in Table 1.

Examples 2 to 4
Polyarylene sulfide was prepared in the same manner as in Example 1, except that the cleaning temperature, cleaning time, amount of hot water, and water/glycol ether mixed solvent were set as shown in Table 1, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

All of the polyarylene sulfides obtained had low water absorption and melt viscosity ratios, and were excellent in low water absorption and melt fluidity.

Comparative Examples 1 to 4
Polyarylene sulfide was prepared in the same manner as in Example 1, except that the cleaning temperature, cleaning time, amount of hot water, and water/glycol ether mixed solvent were set as shown in Table 2, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

The polyarylene sulfides obtained in Comparative Examples 1 and 3 were poor in both water absorption and melt fluidity.

The polyarylene sulfide obtained in Comparative Example 2 had a high water absorption rate and poor water absorption.

The polyarylene sulfide obtained in Comparative Example 4 had a high melt viscosity ratio and poor melt fluidity.

Example 5
6.2 kg of PPS (A-1) (including 2.5 kg of water), 11.7 kg of water, and 1.6 kg of diethylene glycol monomethyl ether were charged into a 30-liter autoclave, and the system was sealed under a nitrogen stream. The system was heated to 190°C, and washed for 2 hours. After washing, the system was cooled to 80°C to recover polyarylene sulfide. Next, 8.6 kg of water was charged into a 30-liter autoclave, and the system was sealed under a nitrogen stream. The system was heated to 195°C, and washed for 1 hour. After washing, the system was cooled to 80°C to recover polyphenylene sulfide. The recovered polyarylene sulfide was dried at 105°C for 24 hours to obtain polyarylene sulfide containing 600 ppm of SMCAB.

The resulting polyphenylene sulfide was then subjected to a heat curing treatment at 240°C in a nitrogen atmosphere.

The polyarylene sulfide was placed in the hopper of an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd., product name: SE75) with the cylinder temperature heated to 310°C, and test pieces for measuring the water absorption rate were molded and evaluated. The results are shown in Table 3.

Examples 6 to 8
Polyarylene sulfide was prepared in the same manner as in Example 5, except that the mixed solvent washing temperature, washing time, and water/glycol ether mixed solvent in step [1], and the washing temperature, washing time, and amount of hot water in step [2] were set to the conditions shown in Table 3, and evaluated in the same manner as in Example 5. The evaluation results are shown in Table 3.

All of the polyarylene sulfides obtained had low water absorption and melt viscosity ratios, and were excellent in low water absorption and melt fluidity.

Comparative Examples 5 and 6
Polyarylene sulfide was prepared in the same manner as in Example 5, except that the mixed solvent washing temperature, washing time, and water/glycol ether mixed solvent in step [1], and the washing temperature, washing time, and amount of hot water in step [2] were set to the conditions shown in Table 4, and evaluated in the same manner as in Example 5. The evaluation results are shown in Table 4.

The polyarylene sulfide obtained in Comparative Example 6 had poor melt fluidity.

The polyarylene sulfide obtained from Comparative Example 5 had a high water absorption rate and melt viscosity ratio, but was poor in water absorption and melt fluidity.

The method for producing polyarylene sulfide of the present invention can efficiently provide polyarylene sulfide that has an excellent balance between low water absorption and melt stability without compromising heat resistance, chemical resistance, dimensional stability, etc., while at the same time reducing the amount of gas and tar generated during molding and having high melt fluidity during molding, and is particularly useful for electrical and electronic parts such as electrical and electronic parts or automotive electrical parts that also require low halogen and low electrolytes.

Claims (5)

A method for producing polyarylene sulfide by polymerization of a polyhalogenated aromatic compound with an alkali metal sulfide in a polar organic amide solvent, comprising washing the polyarylene sulfide after polymerization with a mixed solvent of water/glycol ether= 80/20 to 95/5 (weight ratio) at 160° C. or higher and 200° C. or lower for 1 hour or longer and 6 hours or shorter , wherein the glycol ether is any one selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, butanediol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, and dipropylene glycol monobutyl ether . The method for producing polyarylene sulfide described in claim 1, characterized in that 185 to 1900 parts by weight of the mixed solvent are used per 100 parts by weight of polyarylene sulfide. 3. The method for producing polyarylene sulfide according to claim 1 or 2, characterized in that the method is a method for producing polyarylene sulfide containing 300 ppm or more and 1500 ppm or less of 4-(N-methyl-chlorophenylamino)butanoate sodium salt represented by the following general formula (1):
(1) The method for producing a polyarylene sulfide according to any one of claims 1 to 3, characterized in that after washing with the mixed solvent, washing with hot water is further carried out under conditions of 165°C to 245°C and 1 hour to 10 hours. 5. The method for producing polyarylene sulfide according to claim 4, wherein 185 to 1900 parts by weight of hot water is used per 100 parts by weight of polyarylene sulfide.