JP7552199B2 - Polyphenylene sulfide resin composition and hollow molded article using same - Google Patents

Description

The present invention relates to a polyphenylene sulfide resin composition that has high strength and toughness, and that combines heat aging resistance and blow moldability, and to a blow molded article made using the same.

As a way to improve fuel efficiency in automobiles, the use of resin for ducts and piping in the engine compartment to reduce their weight has become widespread, and polyamide-based materials are currently mainly used.

In recent years, due to the rise in operating environment temperatures caused by the narrowing of engine compartments and exposure to acid from exhaust gas recirculation systems, resin materials need to be designed for use in harsher environments. As a result, attention has been focused on polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) as an engineering plastic with excellent heat resistance, chemical resistance, flame retardancy, and electrical properties.

On the other hand, because PPS resin has a low melt viscosity, drawdown of the parison occurs during blow molding, which is a suitable molding method for ducts and piping, making it difficult to obtain molded products with little thickness deviation. In addition, lack of toughness is also an issue in practical use. For this reason, the mainstream design involves blending an olefin copolymer containing epoxy groups into PPS resin to increase the melt viscosity and improve toughness (for example, Patent Document 1).

However, with the recent development of blow molding technology (e.g., suction blow molding), the design freedom of molded products has increased, such as by making them thinner and thinner, and there are cases where resin materials are required to have even higher strength and toughness, especially resistance to heat aging. For this reason, there have been many reports of studies on improving the blow moldability and material properties of PPS resin by adding organic silane compounds (e.g., Patent Document 2) and by using fiber reinforcement materials (e.g., Patent Document 3).

Japanese Patent Application Publication No. 3-236930 JP 2011-256387 A JP 2016-183316 A

However, since the PPS resin compositions described in Patent Documents 2 and 3 both contain an olefin copolymer containing epoxy groups, if the amount of fiber reinforcement is increased to improve strength while maintaining a high melt viscosity capable of suppressing drawdown, a sudden increase in shear viscosity and shear heat generation will lead to significant deterioration of the olefin copolymer containing epoxy groups, which has low heat resistance, resulting in problems such as reduced mechanical properties, gas generation during molding, and in particular reduced heat aging resistance.

The inventors therefore conducted extensive research to solve the above problems and discovered that in a composition consisting of a polyphenylene sulfide resin, a fiber reinforcing material, an olefin-based copolymer containing epoxy groups, and an organosilane coupling agent, the phosphorus oxoacid metal salt exerts a number of favorable effects to suppress thermal degradation of the olefin-based copolymer containing epoxy groups, thereby achieving both blow moldability and mechanical properties and heat aging resistance.

That is, the present invention has the following configuration.
1. A polyphenylene sulfide resin composition comprising 100 parts by weight of (A) polyphenylene sulfide resin, blended with 1 to 200 parts by weight of (B) reinforcing fiber, 1 to 200 parts by weight of (C) an olefin copolymer containing an epoxy group, 0.01 to 10 parts by weight of (D) an organosilane compound, and 0.01 to 5 parts by weight of (E) a phosphorus oxoacid metal salt , wherein the (E) phosphorus oxoacid metal salt is sodium phosphinate, and the polyphenylene sulfide resin composition has a flexural strength of 100 MPa or more and 300 MPa or less, as measured in accordance with ISO 178 using an ISO (1A) dumbbell test piece obtained by injection molding the polyphenylene sulfide resin composition .
2. The polyphenylene sulfide resin composition according to item 1, wherein the blending amount of the reinforcing fiber (B) is 15% by weight or more and 50% by weight or less, when the total amount of the polyphenylene sulfide resin (A), the reinforcing fiber (B), and the olefin-based copolymer (C) containing an epoxy group is taken as 100% by weight.
3. The polyphenylene sulfide resin composition according to any one of items 1 to 2, having a melt viscosity measured at a temperature of 300° C. and a shear rate of 122/s of 1000 Pa·s or more and 3000 Pa·s or less.
4. The polyphenylene sulfide resin composition according to any one of items 1 to 3, wherein the weight loss rate (%) when pellets of the resin composition are treated in air at 320° C. for 2 hours is 0.3% or more and 3.0% or less.
5. The polyphenylene sulfide resin composition according to any one of items 1 to 4, wherein the (D) organosilane compound is an alkoxysilane compound having an epoxy group or an isocyanate group.
6. A molded article made of the polyphenylene sulfide resin composition according to any one of items 1 to 5 .
7. The molded article according to item 6, which is a hollow molded article.
8. A method for producing a molded article, comprising blow molding the polyphenylene sulfide resin composition according to any one of items 1 to 5 .

According to the present invention, a polyphenylene sulfide resin composition having excellent material strength, toughness, and heat aging resistance, as well as excellent blow moldability, can be obtained. A polyphenylene sulfide resin composition having these properties is suitable for molded products such as ducts around automobile engines and thin-walled piping that are used under high temperatures and vibration.

The present invention will be described in more detail below.

The polyphenylene sulfide resin (A) used in the present invention (hereinafter sometimes abbreviated as PPS resin) is a polymer having a repeating unit represented by the following structural formula:

From the viewpoint of heat resistance, a polymer containing 70 mol % or more, and even more preferably 90 mol % or more, of a polymer containing a repeating unit represented by the above structural formula is preferable. In addition, (A) PPS resin may be composed of repeating units having the following structure, etc., in an amount of less than 30 mol % of the repeating units.

There is no particular limit to the melt viscosity of the (A) PPS resin used in the present invention, but in order to obtain better toughness, the higher the melt viscosity, the better. For example, a range exceeding 30 Pa·s is preferable, 50 Pa·s or more is more preferable, and 100 Pa·s or more is even more preferable. The upper limit is preferably 600 Pa·s or less from the viewpoint of suppressing thermal degradation of the epoxy-containing olefin-based copolymer due to shear heating.

The melt viscosity in this invention is a value measured using a Toyo Seiki Capillograph under conditions of 310°C and a shear rate of 1000/s.

The manufacturing method of the PPS resin (A) used in the present invention is described below, but the manufacturing method is not limited to the following as long as the PPS resin (A) having the above structure can be obtained.

First, we will explain the dihaloaromatic compound, sulfidizing agent, polymerization solvent, molecular weight regulator, polymerization aid, and polymerization stabilizer used in the production method.

[Dihaloaromatic compound]
A dihaloaromatic compound is a compound having two or more halogen atoms in one molecule. Specific examples include p-dichlorobenzene, m-dichlorobenzene, o-dichlorobenzene, and 1,3,5-trichlorobenzene. , 1,2,4-trichlorobenzene, 1,2,4,5-tetrachlorobenzene, hexachlorobenzene, 2,5-dichlorotoluene, 2,5-dichloro-p-xylene, 1,4-dibromobenzene, 1, Examples of the dihaloaromatic compounds include 4-diiodobenzene and 1-methoxy-2,5-dichlorobenzene, and preferably p-dichlorobenzene.

The amount of dihaloaromatic compound added is, for example, in the range of 0.9 to 2.0 moles, preferably 0.95 to 1.5 moles, and more preferably 1.005 to 1.2 moles per mole of sulfidizing agent in order to obtain PPS resin (A) with a viscosity suitable for processing.

[Sulfidizing agent]
The sulfidizing agent includes alkali metal sulfides, alkali metal hydrosulfides, and hydrogen sulfide.

Specific examples of alkali metal sulfides include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, and mixtures of two or more of these, with sodium sulfide being preferred. These alkali metal sulfides can be used as hydrates or aqueous mixtures, or in the anhydrous form.

Specific examples of alkali metal hydrosulfides include sodium hydrosulfide, potassium hydrosulfide, lithium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures of two or more of these, with sodium hydrosulfide being preferred. These alkali metal hydrosulfides can be used as hydrates or aqueous mixtures, or in the anhydrous form.

Alkali metal sulfides prepared in situ in a reaction system from alkali metal hydrosulfides and alkali metal hydroxides can also be used.Alkali metal sulfides can also be prepared from alkali metal hydrosulfides and alkali metal hydroxides, and then 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. Also, an alkali metal sulfide can be prepared from an alkali metal hydroxide such as lithium hydroxide or sodium hydroxide and hydrogen sulfide, and then transferred to a polymerization tank for use.

When some of the sulfidizing agent is lost before the start of the polymerization reaction due to a dehydration operation or the like, the amount of sulfidizing agent charged means the remaining amount obtained by subtracting the loss from the actual charged amount.

It is also possible to use an alkali metal hydroxide and/or an alkaline earth metal hydroxide together with the sulfidizing agent. Specific examples of alkali metal hydroxides include, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, and mixtures of two or more of these. Specific examples of alkaline earth metal hydroxides include, for example, calcium hydroxide, strontium hydroxide, barium hydroxide, etc., and among these, sodium hydroxide is preferably used.

When an alkali metal hydrosulfide is used as the sulfidizing agent, it is particularly preferable to use an alkali metal hydroxide at the same time. The amount used is, for example, 0.95 to 1.20 moles, preferably 1.00 to 1.15 moles, and more preferably 1.005 to 1.100 moles per mole of alkali metal hydrosulfide.

[Polymerization Solvent]
As the polymerization solvent, it is preferable to use an organic polar solvent. Specific examples include N-alkylpyrrolidones such as N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, aprotic organic solvents such as 1,3-dimethyl-2-imidazolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, hexamethylphosphoric triamide, dimethylsulfone, and tetramethylene sulfoxide, and mixtures thereof, all of which are preferably used because of their high reaction stability. Among these, N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP) is particularly preferably used.

The amount of organic polar solvent used is selected from the range of 2.0 to 10 moles, preferably 2.25 to 6.0 moles, and more preferably 2.5 to 5.5 moles per mole of sulfidizing agent.

[Molecular Weight Regulator]
In order to form reactive terminals in the resulting PPS resin (A) or to adjust the polymerization reaction or molecular weight, a monohalogenated compound (which does not necessarily have to be an aromatic compound) can be used in combination with the polyhalogenated aromatic compound.

[Polymerization aid]
In order to obtain a PPS resin (A) with a relatively high degree of polymerization in a short time, it is also a preferred embodiment to use a polymerization aid. Here, the polymerization aid means a substance that has the effect of increasing the viscosity of the resulting PPS resin (A). Specific examples of such polymerization aids include organic carboxylates, water, alkali metal chlorides, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates, and alkaline earth metal phosphates. These can be used alone or in combination of two or more. Among them, organic carboxylates, water, and alkali metal chlorides are preferred, and alkali metal carboxylates are preferred as organic carboxylates, and lithium chloride is preferred as alkali metal chlorides.

The alkali metal carboxylate is a compound represented by the general formula R(COOM) _n (wherein R is an alkyl group, a cycloalkyl group, an aryl group, an alkylaryl group, or an arylalkyl group having 1 to 20 carbon atoms; M is an alkali metal selected from lithium, sodium, potassium, rubidium, and cesium; and n is an integer of 1 to 3). The alkali metal carboxylate can also be used as a hydrate, an anhydride, or an aqueous solution. Specific examples of the alkali metal carboxylate include lithium acetate, sodium acetate, potassium acetate, sodium propionate, lithium valerate, sodium benzoate, sodium phenylacetate, potassium p-toluate, and mixtures thereof.

The alkali metal carboxylate may be formed by adding and reacting an organic acid with one or more compounds selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates in approximately equal chemical equivalents. Of the above alkali metal carboxylates, the lithium salts are highly soluble in the reaction system and have a large auxiliary effect, but are expensive, while the potassium, rubidium, and cesium salts are thought to have insufficient solubility in the reaction system. For this reason, sodium acetate, which is inexpensive and has moderate solubility in the polymerization system, is most preferably used.

When these alkali metal carboxylates are used as polymerization aids, the amount used is usually in the range of 0.01 mol to 2 mol per mol of charged alkali metal sulfide, and in terms of obtaining a higher degree of polymerization, the range of 0.1 mol to 0.6 mol is preferred, and the range of 0.2 mol to 0.5 mol is more preferred.

When water is used as a polymerization aid, the amount added is usually in the range of 0.3 mol to 15 mol per mol of charged alkali metal sulfide, and in terms of obtaining a higher degree of polymerization, the range of 0.6 mol to 10 mol is preferred, and the range of 1 mol to 5 mol is more preferred.

Of course, two or more of these polymerization aids can be used in combination. For example, when an alkali metal carboxylate is used in combination with water, a smaller amount of each is needed to achieve a high molecular weight.

There is no particular designation for the timing of addition of these polymerization aids, and they may be added at any time during the pre-step described below, at the start of polymerization, or during the polymerization, or may be added in multiple batches. However, when an alkali metal carboxylate is used as the polymerization aid, it is more preferable to add it at the start of the pre-step or at the start of polymerization, as this is easier to add. When water is used as the polymerization aid, it is effective to add it during the polymerization reaction after the dihalo aromatic compound has been charged.

[Polymerization stabilizer]
A polymerization stabilizer can be used to stabilize the polymerization reaction system and suppress side reactions. The polymerization stabilizer contributes to the stabilization of the polymerization reaction system and suppresses undesirable side reactions. One of the indicators of side reactions is the generation of thiophenol, and the addition of a polymerization stabilizer can suppress the generation of thiophenol. Specific examples of polymerization stabilizers include compounds such as alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, and alkaline earth metal carbonates. Among them, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide are preferred. The above-mentioned alkali metal carboxylates also act as polymerization stabilizers, and therefore are included in the polymerization stabilizers. In addition, when an alkali metal hydrosulfide is used as a sulfidizing agent, it is particularly preferable to use an alkali metal hydroxide at the same time, as mentioned above, but an excess of an alkali metal hydroxide relative to the sulfidizing agent can also serve as a polymerization stabilizer.

These polymerization stabilizers can be used alone or in combination of two or more. The polymerization stabilizer is usually used in a ratio of 0.02 to 0.2 moles, preferably 0.03 to 0.1 moles, and more preferably 0.04 to 0.09 moles, per mole of charged alkali metal sulfide. If this ratio is too small, the stabilizing effect is insufficient, and conversely, if it is too large, it is economically disadvantageous and the polymer yield tends to decrease.

There is no particular designation for the timing of addition of the polymerization stabilizer, and it may be added at any time during the pre-processing step described below, at the start of polymerization, or during polymerization. It may also be added in multiple portions, but it is more preferable to add it at the start of the pre-processing step or at the start of polymerization at the same time, as this is easier.

Next, a preferred method for producing the PPS resin (A) used in the present invention will be specifically described in order, including the pre-process, polymerization reaction process, recovery process, and post-treatment process, but the method is of course not limited to this method.

[Pre-process]
In the production method for (A) PPS resin, the sulfidizing agent is usually used in the form of a hydrate, and it is preferable to heat a mixture containing an organic polar solvent and a sulfidizing agent and remove excess water from the system before adding a dihalo-aromatic compound.

As described above, the sulfidizing agent may be prepared in situ in the reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide, or in a tank separate from the polymerization tank. There are no particular limitations to this method, but a preferred method is to add an alkali metal hydrosulfide and an alkali metal hydroxide to an organic polar solvent in an inert gas atmosphere at room temperature to 150°C, preferably room temperature to 100°C, and then heat the mixture to at least 150°C or higher, preferably 180 to 260°C, under normal or reduced pressure, to distill off the water. A polymerization aid may be added at this stage. Toluene or the like may be added to promote the distillation of water.

In the polymerization reaction, the amount of water in the polymerization system 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 the amount of water charged to the polymerization system minus the amount of water removed from the polymerization system. The charged water may be in any form, such as water, an aqueous solution, or water of crystallization.

[Polymerization reaction process]
The (A) PPS resin is produced by reacting a sulfidizing agent with a dihaloaromatic compound in an organic polar solvent at a temperature within the range of 200° C. or higher and lower than 290° C.

When starting the polymerization reaction process, the organic polar solvent, the sulfidizing agent, and the dihalo aromatic compound are mixed, desirably in an inert gas atmosphere, at a temperature range of room temperature to 240°C, preferably 100°C to 230°C. A polymerization aid may be added at this stage. These raw materials may be charged in any order, or simultaneously.

The mixture is usually heated to a temperature in the range of 200°C or higher but lower than 290°C. There are no particular restrictions on the heating rate, but a rate of 0.01°C/min to 5°C/min is usually selected, with a range of 0.1°C/min to 3°C/min being more preferred.

Generally, the temperature is finally raised to 250°C or higher but lower than 290°C, and the reaction is carried out at that temperature for usually 0.25 hours to 50 hours, preferably 0.5 hours to 20 hours.

For example, a method of reacting at 200°C to 260°C for a certain period of time before reaching the final temperature and then raising the temperature to 270°C or higher but lower than 290°C is effective in achieving a higher degree of polymerization. In this case, the reaction time at 200°C to 260°C is usually selected to be in the range of 0.25 hours to 20 hours, preferably 0.25 hours to 10 hours.

In order to obtain a polymer with a higher degree of polymerization, it may be effective to carry out the polymerization in multiple stages. When carrying out the polymerization in multiple stages, it is effective that the conversion rate of the dihaloaromatic compound in the system at 245°C is 40 mol% or more, preferably 60 mol%.

The conversion rate of dihalo aromatic compounds (abbreviated as DHA here) is a value calculated by the following formula: The amount of remaining DHA can usually be determined by gas chromatography.
(a) When a dihaloaromatic compound is added in a molar excess relative to an alkali metal sulfide, conversion rate = [charged amount of DHA (moles) - remaining amount of DHA (moles)] / [charged amount of DHA (moles) - excess amount of DHA (moles)]
(b) In cases other than (a) above, conversion rate = [charged amount of DHA (moles) - remaining amount of DHA (moles)] / [charged amount of DHA (moles)].

[Recovery process]
In the method for producing the PPS resin (A), after the polymerization is completed, a solid matter is recovered from the polymerization reaction product containing the polymer, the solvent, etc. As the recovery method, any known method may be adopted.

For example, after the polymerization reaction is completed, the mixture may be slowly cooled to recover the particulate polymer. There is no particular limit to the cooling rate, but it is usually about 0.1°C/min to 3°C/min. It is not necessary to cool at the same rate throughout the entire cooling process, and a method of cooling at a rate of 0.1°C/min to 1°C/min until the polymer particles crystallize and precipitate, and then at a rate of 1°C/min or faster, may be used.

Also, it is a preferred method to carry out the above-mentioned recovery under quenching conditions, and a preferred example of this recovery method is the flash method. The flash method is a method in which the polymerization reaction product is flashed from a high-temperature, high-pressure state (usually 250°C or higher, 8 kg/cm2 or ^higher ) into an atmosphere of normal pressure or reduced pressure, and the polymer is recovered in powder form while the solvent is recovered. The flash method here means that the polymerization reaction product is ejected from a nozzle. Specific examples of the flashing atmosphere include nitrogen or water vapor at normal pressure, and the temperature is usually selected in the range of 150°C to 250°C.

[Post-processing process]
The (A) PPS resin may be one which has been produced through the above-mentioned polymerization and recovery steps, and then subjected to acid treatment, hot water treatment, washing with an organic solvent, or alkali metal or alkaline earth metal treatment.

When acid treatment is performed, it is as follows. There are no particular limitations on the acid used in the acid treatment of (A) PPS resin, so long as it does not have the effect of decomposing (A) PPS resin, and examples of the acid include acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, silicic acid, carbonic acid, and propylic acid. Of these, acetic acid and hydrochloric acid are more preferably used, but acids such as nitric acid that decompose and deteriorate (A) PPS resin are not preferred.

The acid treatment may be carried out by immersing the PPS resin (A) in an acid or an aqueous solution of an acid, and may be carried out with stirring or heating as necessary. For example, when using acetic acid, a sufficient effect can be obtained by immersing the PPS resin powder in an aqueous solution of pH 4 heated to 80°C to 200°C and stirring for 30 minutes. The pH after treatment may be 4 or higher, for example, about pH 4 to 8. The acid-treated PPS resin (A) is preferably washed several times with water or warm water to remove any remaining acid or salt. The water used for washing is preferably distilled water or deionized water, in order not to impair the desired chemical modification effect of the PPS resin (A) by the acid treatment.

When hot water treatment is performed, the procedure is as follows: When hot water treatment is performed on (A) PPS resin, the temperature of the hot water is preferably 100°C or higher, more preferably 120°C or higher, even more preferably 150°C or higher, and particularly preferably 170°C or higher. Temperatures below 100°C are not preferred because the desired chemical modification effect of (A) PPS resin is small.

In order to achieve the desired chemical modification effect of the (A) PPS resin by hot water washing, it is preferable that the water used is distilled water or deionized water. There are no particular limitations on the operation of the hot water treatment, and it can be carried out by adding a specified amount of (A) PPS resin to a specified amount of water, heating and stirring in a pressure vessel, or by continuously carrying out hot water treatment. The ratio of (A) PPS resin to water is preferably higher, but a bath ratio of 200 g or less of (A) PPS resin per 1 liter of water is usually selected.

In addition, since decomposition of the terminal groups is undesirable, it is desirable to carry out the treatment in an inert atmosphere to avoid this. Furthermore, after this hot water treatment operation, it is preferable to wash the (A) PPS resin several times with warm water to remove any remaining components.

When washing with an organic solvent, the procedure is as follows. There are no particular limitations on the organic solvent used to wash the (A) PPS resin, so long as it does not have the effect of decomposing the (A) PPS resin, and examples of the organic solvent include nitrogen-containing polar solvents such as N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, 1,3-dimethylimidazolidinone, hexamethylphosphoramide, and piperazinones, sulfoxide/sulfone solvents such as dimethyl sulfoxide, dimethyl sulfone, and sulfolane, ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, and acetophenone, dimethyl ether, dipropyl ether, dioxane, and tetrahydrofuran. Examples of the organic solvent include ether solvents such as hydrofuran, halogen-based solvents such as chloroform, methylene chloride, trichloroethylene, ethylene dichloride, perchloroethylene, monochloroethane, dichloroethane, tetrachloroethane, perchloroethane, and chlorobenzene, alcohol-phenol solvents such as methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, phenol, cresol, polyethylene glycol, and polypropylene glycol, and aromatic hydrocarbon solvents such as benzene, toluene, and xylene. Among these organic solvents, the use of N-methyl-2-pyrrolidone, acetone, dimethylformamide, and chloroform is particularly preferred. These organic solvents are used alone or in combination of two or more.

Methods for cleaning with an organic solvent include immersing the PPS resin (A) in the organic solvent, and stirring or heating can be performed as necessary. There are no particular limitations on the cleaning temperature when cleaning the PPS resin (A) with an organic solvent, and any temperature between room temperature and about 300°C can be selected. The higher the cleaning temperature, the higher the cleaning efficiency tends to be, but a cleaning temperature between room temperature and 150°C is usually sufficient. It is also possible to clean under pressure in a pressure vessel at a temperature above the boiling point of the organic solvent. There are also no particular limitations on the cleaning time. Although it depends on the cleaning conditions, in the case of batch cleaning, a cleaning time of 5 minutes or more usually produces a sufficient effect. It is also possible to clean in a continuous manner.

Examples of methods for alkali metal treatment and alkaline earth metal treatment include adding an alkali metal salt or alkaline earth metal salt before, during, or after the previous step, adding an alkali metal salt or alkaline earth metal salt to the polymerization kettle before, during, or after the polymerization step, or adding an alkali metal salt or alkaline earth metal salt at the beginning, middle, or end of the washing step. The easiest method is to add an alkali metal salt or alkaline earth metal salt after removing residual oligomers and residual salts by washing with an organic solvent or washing with warm or hot water. The alkali metal or alkaline earth metal is preferably introduced into the PPS resin in the form of an alkali metal ion or alkaline earth metal ion such as acetate, hydroxide, or carbonate. It is also preferable to remove excess alkali metal salt or alkaline earth metal salt by washing with warm water. The alkali metal ion concentration and alkaline earth metal ion concentration when introducing the above alkali metal and alkaline earth metal are preferably 0.001 mmol or more per 1 g of PPS, and more preferably 0.01 mmol or more. The temperature is preferably 50° C. or more, more preferably 75° C. or more, and particularly preferably 90° C. or more. There is no particular upper limit temperature, but from the viewpoint of operability, 280° C. or less is usually preferred. The bath ratio (weight of cleaning solution relative to the weight of dry PPS) is preferably 0.5 or more, more preferably 3 or more, and even more preferably 5 or more.

In the present invention, from the viewpoint of obtaining a polyphenylene sulfide resin composition having excellent toughness, a method is preferred in which residual oligomers and residual salts are removed by repeating washing with an organic solvent and washing with warm water at about 80°C or the above-mentioned hot water several times, and then treatment with an acid or an alkali metal salt or an alkaline earth metal salt, and a method of treatment with an alkali metal salt or an alkaline earth metal salt is particularly preferred.

In addition, (A) PPS resin can be used after the polymerization is completed by heating in an oxygen atmosphere or by a thermal oxidation crosslinking process in which a crosslinking agent such as a peroxide is added and then heated to increase the molecular weight.

When dry heat treatment is performed for the purpose of increasing the molecular weight by thermal oxidation crosslinking, the temperature is preferably 160°C to 260°C, more preferably 170°C to 250°C. The oxygen concentration is preferably 5% by volume or more, and even more preferably 8% by volume or more. There is no particular upper limit to the oxygen concentration, but the limit is about 50% by volume. The treatment time is preferably 0.5 hours to 100 hours, more preferably 1 hour to 50 hours, and even more preferably 2 hours to 25 hours. The heat treatment device may be a normal hot air dryer or a heating device with a rotating or stirring blade, but if efficient and more uniform treatment is required, it is more preferable to use a heating device with a rotating or stirring blade.

It is also possible to carry out a dry heat treatment in order to suppress thermal oxidative crosslinking and remove volatile matter. The temperature is preferably 130°C to 250°C, more preferably 160°C to 250°C. In this case, the oxygen concentration is preferably less than 5% by volume, and even more preferably less than 2% by volume. The treatment time is preferably 0.5 hours to 50 hours, more preferably 1 hour to 20 hours, and even more preferably 1 hour to 10 hours. The heat treatment device may be a normal hot air dryer or a rotary or stirring blade-equipped heating device, but if efficient and more uniform treatment is required, it is more preferable to use a rotary or stirring blade-equipped heating device.

However, from the viewpoint of exhibiting excellent toughness, it is preferable that the (A) PPS resin of the present invention is a substantially linear PPS resin that has not been subjected to high molecular weight by thermal oxidation crosslinking treatment, or a semi-crosslinked PPS resin that has been lightly oxidative crosslinked. On the other hand, a PPS resin that has been subjected to thermal oxidation crosslinking treatment is preferable from the viewpoint of suppressing creep strain to a small value, and it is possible to use it by mixing it with a linear PPS resin as appropriate. In addition, in the present invention, a mixture of multiple (A) PPS resins with different melt viscosities may be used.

The reinforcing fibers (B) used in the present invention include glass fibers, carbon fibers, carbon nanotubes, carbon nanohorns, potassium titanate whiskers, zinc oxide whiskers, calcium carbonate whiskers, wollastonite whiskers, aluminum borate whiskers, aramid fibers, alumina fibers, silicon carbide fibers, ceramic fibers, asbestos fibers, gypsum fibers, and metal fibers, with glass fibers being preferred in terms of the balance between the effect of improving the mechanical strength of the resin composition and cost.

It is also preferable to pre-treat the surface of the (B) reinforcing fiber with a coupling agent such as an isocyanate compound, an organic silane compound, an organic titanate compound, an organic borane compound, or an epoxy compound, from the viewpoints of improving the bundling ability of the (B) reinforcing fiber, its dispersibility when compounded with the resin, and the adhesion between the glass fiber and the resin.

The shape of the (B) reinforcing fibers cannot be generally defined because it varies depending on the type of fiber used, but the fiber diameter is preferably 1 to 50 μm, more preferably 3 to 30 μm, and even more preferably 5 to 20 μm. The length is preferably 30 μm to 10 mm, and more preferably 50 μm to 5 mm. By setting the fiber cross-sectional diameter and fiber length within the above ranges, the mechanical strength of the resin composition can be improved, which is preferable.

The amount of the (B) reinforcing fiber should be in the range of 1 to 200 parts by weight per 100 parts by weight of the (A) polyphenylene sulfide resin in order to obtain a strength improving effect, and is preferably 10 parts by weight or more, more preferably 30 parts by weight or more, and particularly preferably 50 parts by weight or more. The upper limit of the amount is preferably 150 parts by weight or less, and more preferably 120 parts by weight or less. If the amount of (B) reinforcing fiber is less than 1 part by weight, excellent mechanical strength cannot be obtained, and if it exceeds 200 parts by weight, the melt viscosity increases significantly, leading to a decrease in moldability and toughness, which is not preferable.

The epoxy group-containing olefin copolymer (C) used in the present invention includes olefin copolymers having glycidyl esters, glycidyl ethers, glycidyl diamines, etc. in the side chains, and olefin copolymers having double bonds in which the double bond portion is epoxy-oxidized. Among these, olefin copolymers in which a monomer having an epoxy group is copolymerized are preferred, and in particular, olefin copolymers whose main components are α-olefins and glycidyl esters of α,β-unsaturated acids are preferably used.

Specific examples of such α-olefins include ethylene, propylene, butene-1, 4-methylpentene-1, hexene-1, decene-1, and octene-1, among which ethylene is preferably used. Two or more of these can also be used simultaneously.

On the other hand, glycidyl esters of α,β-unsaturated acids are represented by the general formula

(where R is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms), and specific examples include glycidyl acrylate, glycidyl methacrylate, and glycidyl ethacrylate, with glycidyl methacrylate being the most preferred.

Such an olefin-based copolymer having as its main components an α-olefin and a glycidyl ester of an α,β-unsaturated acid may be a random, block, or graft copolymer of the α-olefin and the glycidyl ester of an α,β-unsaturated acid.

In an olefin-based copolymer mainly composed of an α-olefin and a glycidyl ester of an α,β-unsaturated acid, the copolymerization amount of the glycidyl ester of the α,β-unsaturated acid is preferably 0.5 to 40% by weight from the viewpoint of the effect on the intended effect, the polymerizability, gelation, heat resistance, fluidity, strength, etc. The lower limit is preferably 1.0% by weight or more from the viewpoint of obtaining a sufficient melt viscosity and toughness improvement effect, more preferably 3.0% by weight or more, and particularly preferably 5.0% by weight or more. The upper limit is preferably 20% by weight or less from the viewpoint of suppressing an excessive reaction and the shear heat generated by the reaction, more preferably 15% by weight or less, and particularly preferably 10% by weight or less.

In the present invention, as the olefin copolymer containing an epoxy group, an olefin copolymer containing an epoxy group, which contains, in addition to an α-olefin (1) and a glycidyl ester of an α,β-unsaturated acid (2), a monomer (3) represented by the following general formula as an essential component, is also preferably used.

(wherein, ^R1 represents hydrogen or an alkyl group having 1 to 5 carbon atoms, X represents a group selected from the group consisting of ^--COOR2 , --CN, and aromatic groups, and ^R2 represents an alkyl group having 1 to 10 carbon atoms.)

The details of the α-olefin (1) and the glycidyl ester of α,β-unsaturated acid (2) used in such an olefin-based copolymer are the same as those in the above-mentioned (C) olefin-based copolymer containing epoxy groups.

On the other hand, specific examples of monomer (3) include α,β-unsaturated carboxylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, and isobutyl methacrylate, acrylonitrile, styrene, α-methylstyrene, styrene in which the aromatic ring is substituted with an alkyl group, and acrylonitrile-styrene copolymers, and two or more of these can be used simultaneously.

Such an olefin copolymer containing an epoxy group may be any of the copolymerization modes, such as a random copolymer, block copolymer, or graft copolymer of an α-olefin (1), a glycidyl ester of an α,β-unsaturated acid (2), and a monomer (3), or a copolymer obtained by copolymerizing these copolymers. For example, it may be a copolymer in which two or more copolymerization modes are combined, such as a random copolymer of an α-olefin (1) and a glycidyl ester of an α,β-unsaturated acid (2) that is graft-copolymerized with a monomer (3).

The copolymerization ratio of the epoxy group-containing olefin copolymer is preferably selected in the range of α-olefin (1)/glycidyl ester of α,β-unsaturated acid (2) = 60% to 99% by weight/40% to 1% by weight from the viewpoints of the effect on the intended effect, polymerizability, gelation, heat resistance, fluidity, strength, etc. The copolymerization ratio of the monomer (3) is preferably selected in the range of 5% to 60% by weight of the monomer (3) relative to the total amount of α-olefin (1) and glycidyl ester of α,β-unsaturated acid (2) of 95% to 40% by weight. It is also possible to adjust the melt viscosity and toughness of the polyphenylene sulfide resin composition by using these epoxy group-containing olefin copolymers with different copolymerization ratios in combination.

The amount of the epoxy group-containing olefin copolymer (C) cannot be generally specified because it depends on the amount of copolymerization of the glycidyl ester of α,β-unsaturated acid in the olefin copolymer mainly composed of α-olefin and glycidyl ester of α,β-unsaturated acid. However, from the viewpoint of obtaining excellent toughness and a melt viscosity suitable for blow molding, the amount should be in the range of 1 to 200 parts by weight per 100 parts by weight of the polyphenylene sulfide resin (A), preferably 5 parts by weight or more, and more preferably 10 parts by weight or more. The upper limit of the amount is preferably 150 parts by weight or less, more preferably 100 parts by weight or less, and particularly preferably 70 parts by weight or less. If the epoxy group-containing olefin copolymer (C) is less than 1 part by weight, excellent toughness and blow moldability cannot be obtained, and if it exceeds 200 parts by weight, the melt viscosity increases significantly, leading to the formation of a gel and a decrease in toughness, which is not preferable.

In the present invention, excellent toughness can be obtained by using an unmodified olefin copolymer together with the olefin copolymer containing the epoxy group (C) described above.

Specific examples of unmodified olefin copolymers include ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, polybutene, ethylene-propylene-diene copolymers, styrene-butadiene copolymers, polybutadiene, butadiene-acrylonitrile copolymers, polyisoprene, butene-isoprene copolymers, and SBS, SIS, SEBS, SEPS, etc. Among these, ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, and ethylene-propylene-diene copolymers are particularly preferred from the viewpoint of compatibility with the olefin copolymer containing epoxy groups (C).

The amount of the unmodified olefin copolymer is preferably in the range of 1 to 200 parts by weight of the total of (C) the olefin copolymer containing epoxy groups and the unmodified olefin copolymer per 100 parts by weight of (A) polyphenylene sulfide resin. The lower limit of the amount is preferably 5 parts by weight or more, more preferably 10 parts by weight or more. The upper limit of the amount is preferably 150 parts by weight or less of the total of (C) the olefin copolymer containing epoxy groups and the unmodified olefin copolymer, more preferably 100 parts by weight or less, and particularly preferably 70 parts by weight or less. By making the total of (C) the olefin copolymer containing epoxy groups and the unmodified olefin copolymer 1 part by weight or more, toughness and blow moldability are obtained, and when it is 200 parts by weight or less, the coarse dispersion of the unmodified olefin copolymer is suppressed, and toughness can be maintained.

When the total of (A) polyphenylene sulfide resin, (B) reinforcing fiber, and (C) olefin-based copolymer containing epoxy groups is taken as 100% by weight, the blending amount of (B) reinforcing fiber is preferably 15% by weight or more from the viewpoint of obtaining sufficient mechanical strength, more preferably 20% by weight or more from the viewpoint of obtaining practical strength in a thin-walled molded product, and particularly preferably 25% by weight or more from the viewpoint of increasing the rigidity of the parison to suppress drawdown and obtain uniformity in thickness, and particularly preferably 30% by weight or more. By making it 15% by weight or more, sufficient mechanical strength can be obtained. The upper limit is preferably 70% by weight or less, more preferably 60% by weight or less, and particularly preferably 50% by weight or less from the viewpoint of obtaining an excellent appearance of the molded product, and most preferably 40% by weight or less. By making it 70% by weight or less, it is possible to suppress shear heat generation due to an increase in melt viscosity caused by the significant entanglement of (B) reinforcing fiber, and suppress thermal decomposition of the polymer.

In the polyphenylene sulfide resin composition of the present invention, it is essential to add an organic silane compound (D) from the viewpoint of obtaining excellent toughness and excellent blow moldability by adjusting the melt viscosity. The above effect is similar to that of the olefin copolymer containing an epoxy group (C), but it is superior in that it does not involve a decrease in mechanical strength. As the organic silane compound (D), it is preferable that it has at least one functional group selected from an epoxy group, an isocyanate group, an amino group, a hydroxyl group, a mercapto group, a ureido group, and an alkoxy group. Among them, from the viewpoint of reactivity with the polyphenylene sulfide resin (A), the reinforcing fiber (B), and the olefin copolymer containing an epoxy group (C), an alkoxysilane compound having an epoxy group or an isocyanate group is preferable. Specific examples include isocyanate-modified silicone, epoxy-modified silicone, amino-modified silicone, carbinol-modified silicone, carboxyl-modified silicone, mercapto-modified silicone, ureido-modified silicone, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyl Preferred examples of the silane include diethoxysilane, N-phenylaminomethyltrimethoxysilane, N-phenylaminopropyltrimethoxysilane, dimethoxymethyl-3-piperazinopropylsilane, 3-piperazinopropyltrimethoxysilane, 3-isocyanatepropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, 3-isocyanatepropylmethyldimethoxysilane, 3-isocyanatepropylmethyldiethoxysilane, 3-isocyanatepropylethyldimethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptomethyldimethoxysilane, γ-ureidopropyltrimethoxysilane, etc. Among these, from the viewpoint of reactivity and handling, 3-isocyanatepropyltriethoxysilane, 3-aminopropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane are preferred. In addition, the (D) organic silane compound can be used alone or in the form of a mixture of two or more types.

The amount of the (D) organosilane compound must be 0.01 to 10 parts by weight per 100 parts by weight of the (A) polyphenylene sulfide resin, preferably 0.1 to 5 parts by weight, and more preferably 0.3 to 3 parts by weight. If the amount of the (D) organosilane compound exceeds 10 parts by weight, the melt viscosity increases significantly, which is undesirable as it leads to the formation of a gelled product and a decrease in toughness, and if it is less than 0.01 part by weight, sufficient blow moldability cannot be obtained, which is undesirable.

In the polyphenylene sulfide resin composition of the present invention, it is essential to incorporate (E) a phosphorus oxoacid metal salt in order to suppress thermal degradation of (C) the olefin copolymer containing epoxy groups, suppress gas generation during molding, and obtain excellent mechanical strength, toughness, and heat aging resistance.

(E) Phosphorus oxoacid metal salt can suppress the thermal oxidation of (C) epoxy group-containing olefin copolymer by known reducing action. In addition, the present inventors have newly discovered that (E) phosphorus oxoacid metal salt suppresses shear heat generation during melt kneading in a resin composition consisting of (A) polyphenylene sulfide resin, (B) reinforcing fiber, (C) epoxy group-containing olefin copolymer, and (D) organosilane compound while maintaining the same melt viscosity. This action makes it possible to suppress shear heat generation and thermal deterioration of (C) epoxy group-containing olefin copolymer even if the amount of (B) reinforcing fiber is increased while maintaining a high melt viscosity that allows blow molding, and can suppress gas generation during molding, as well as obtain a polyphenylene sulfide resin composition having excellent mechanical strength, toughness, and especially heat aging resistance. The mechanism by which this action occurs is unclear, but it is presumed to control the reactivity of (B) reinforcing fiber.

As the (E) metal salt of phosphorus oxo acid, a metal salt of an acid selected from phosphorous acid, phosphoric acid, phosphinic acid, phosphonic acid, diphosphoric acid, and triphosphoric acid is preferred, and a metal salt of phosphinic acid is more preferred. Specific examples include potassium phosphinate, sodium phosphinate, calcium phosphinate, aluminum phosphinate, aluminum diethylphosphinate, zinc phosphinate, and magnesium phosphinate. Among these, from the viewpoints of phosphorus concentration and handling, a metal salt of phosphinic acid is preferred, and sodium phosphinate is more preferred.

These (E) phosphorus oxoacid metal salts can be used alone or in the form of a mixture of two or more kinds.

The amount of the phosphorus oxoacid metal salt (E) must be 0.01 to 5 parts by weight per 100 parts by weight of the polyphenylene sulfide resin (A), and is preferably 0.05 parts by weight or more, and more preferably 0.1 parts by weight or more. The upper limit of the amount is preferably 3 parts by weight or less, and more preferably 1 part by weight or less. If the amount of the phosphorus oxoacid metal salt (E) exceeds 5 parts by weight, it will cause a large amount of gas to be generated, and if it is less than 0.01 part by weight, a sufficient shear heat suppression effect will not be obtained.

In the present invention, additives, other thermoplastic resins, fillers, etc. may be added as necessary to the extent that the properties are not impaired.

Additives that can be blended include phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, plasticizers such as organophosphorus compounds, nucleating agents such as organophosphorus compounds and polyether ether ketone, montanic acid waxes, metal soaps such as lithium stearate and aluminum stearate, release agents such as ethylenediamine-stearic acid-sebacic acid polycondensates and silicone compounds, as well as other conventional additives such as water, lubricants, UV inhibitors, colorants, and foaming agents.

The amount of the additives to be added is preferably 0.1 to 10 parts by weight, and more preferably 0.2 to 5 parts by weight, per 100 parts by weight of polyphenylene sulfide resin (A).

Other thermoplastic resins include polyketone resins, polyarylate resins, liquid crystal polymers, polyetherketone resins, polythioetherketone resins, polyetheretherketone resins, polyethersulfone resins, polyethylene tetrafluoride resins, and ethylene tetrafluoroethylene copolymers.

As fillers, fullerene, talc, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, silica, bentonite, asbestos, silicates such as alumina silicate, metal compounds such as silicon oxide, magnesium oxide, alumina, zirconium oxide, titanium oxide, and iron oxide, carbonates such as calcium carbonate, magnesium carbonate, and dolomite, sulfates such as calcium sulfate and barium sulfate, hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide, glass beads, glass flakes, glass powder, ceramic beads, boron nitride, silicon carbide, carbon black, and non-fibrous fillers such as silica and graphite are used. These inorganic fillers may be hollow, and two or more types may be used in combination. These inorganic fillers may also be pretreated with coupling agents such as isocyanate compounds, organosilane compounds, organotitanate compounds, organoborane compounds, and epoxy compounds before use. Among these, calcium carbonate, silica, and carbon black are preferred in terms of their corrosion prevention, lubricant, and electrical conductivity properties.

The amount of any of the other components listed above that exceeds 20% by weight of the total composition is undesirable because the original properties will be impaired, and it is best to add no more than 10% by weight, preferably no more than 5% by weight.

The melt viscosity of the polyphenylene sulfide resin composition of the present invention is preferably 1000 Pa·s or more, more preferably 1300 Pa·s or more, from the viewpoint of suppressing drawdown during blow molding. Also, from the viewpoint of obtaining a uniform wall thickness of the blow molded product, 1500 Pa·s or more is particularly preferable. The upper limit is preferably 3000 Pa·s or less, more preferably 2500 Pa·s or less, from the viewpoint of maintaining melt fluidity. By setting the melt viscosity to 1000 Pa·s or more, molding defects such as the occurrence of drawdown and loss of uniformity in wall thickness can be suppressed.

The melt viscosity of the polyphenylene sulfide resin composition of the present invention can be increased, for example, by selecting a high-viscosity polyphenylene sulfide resin (A) or by increasing the amount of reinforcing fiber (B), olefin copolymer containing epoxy groups (C), and organosilane compound (D). The melt viscosity of the resin composition of the present invention is measured using a Capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd. under conditions of 300°C and a shear rate of 122/s.

The weight loss rate of the polyphenylene sulfide resin composition of the present invention is preferably 3.0% by weight or less, more preferably 2.5% by weight or less, from the viewpoint of suppressing the inclusion of voids in the molded product, and particularly preferably 2.0% by weight or less, most preferably 1.5% by weight or less, from the viewpoint of suppressing the decrease in strength of a thin-walled molded product due to the inclusion of voids. The weight loss rate of the resin composition in the present invention is the ratio of the weight change before and after the drying process to the weight before the drying process when pellets of the resin composition are treated in air at 320°C for 2 hours. In other words, the weight loss rate is also an index representing the amount of gas generated from the resin composition. The method of making the weight loss rate of the polyphenylene sulfide resin composition 3.0% by weight or less is not particularly limited as long as such a resin composition can be obtained, but for example, a method of suppressing the shear heat generation during melt-kneading of the polyphenylene sulfide resin composition to lower the resin temperature, and a method of suppressing the thermal degradation of the olefin-based copolymer containing an epoxy group (C) by adding an antioxidant can be mentioned.

The polyphenylene sulfide resin composition of the present invention must have a bending strength of 100 MPa or more and 300 MPa or less, measured according to ISO178 on an ISO dumbbell test piece (1A) obtained by injection molding. From the viewpoint of obtaining practical strength in a thinner molded product, 150 MPa or more is preferable, and 200 MPa or more is more preferable. If the bending strength exceeds 300 MPa, it becomes difficult to achieve compatibility with blow moldability, which is not preferable. The bending strength of the polyphenylene sulfide resin composition can be increased by increasing the amount of reinforcing fiber (B). Furthermore, from the viewpoint of obtaining durability in a high-temperature environment, it is preferable that the ISO dumbbell test piece (1A) has a bending strength of 100 MPa or more and 300 MPa or less even after being treated at 180 ° C for 500 hours. In order to suppress the decrease in bending strength after heat treatment at 180°C for 500 hours, for example, it is preferable to suppress the shear heat generation during melt kneading of the polyphenylene sulfide resin composition to lower the resin temperature, and to add an antioxidant to suppress the thermal deterioration of the epoxy group-containing olefin copolymer (C). Furthermore, from the viewpoint of obtaining durability in an environment where the polyphenylene sulfide resin composition comes into contact with a coolant mainly composed of ethylene glycol used to cool automobile engines and motors, it is preferable that the ISO dumbbell test piece (1A) has a bending strength of 100 MPa or more and 300 MPa or less even after being treated for 500 hours at 150°C in a liquid obtained by mixing LLC (Toyota Super Long Life Coolant (product number 08889-01005) manufactured by Toyota Motor Corporation) and ion-exchanged water at a weight ratio of 1:1. In order to suppress the decrease in bending strength after heat treatment at 150°C for 500 hours in LLC, for example, it is preferable to make the chemical bond formed between the polyphenylene sulfide resin (A) and the reinforcing fiber (B) a bond with higher hydrolysis resistance.

The polyphenylene sulfide resin composition of the present invention preferably has a tensile elongation at break of 3.0% or more and 20.0% or less, as measured according to ISO 527-1 and -2 on an ISO dumbbell test piece (1A) obtained by injection molding. From the viewpoint of obtaining practical toughness in a thinner molded product, 3.5% or more is preferable, 4.0% or more is more preferable, and 4.5% or more is particularly preferable. The tensile elongation at break of the polyphenylene sulfide resin composition can be increased by increasing the blending amount of (C) an olefin copolymer containing an epoxy group or (D) an organic silane compound. Furthermore, from the viewpoint of obtaining durability in a high-temperature environment, it is preferable that the ISO dumbbell test piece (1A) has a tensile elongation at break of 3.0% or more and 20.0% or less after being treated at 180°C for 500 hours. In order to suppress the decrease in the tensile elongation at break after heat treatment at 180°C for 500 hours, for example, it is preferable to suppress the shear heat generation during melt-kneading of the polyphenylene sulfide resin composition to lower the resin temperature, and also to suppress the thermal deterioration of the epoxy group-containing olefin copolymer (C) by adding an antioxidant. Furthermore, from the viewpoint of obtaining durability in an environment where the composition comes into contact with a coolant mainly composed of ethylene glycol used to cool automobile engines and motors, it is preferable that the ISO (1A) dumbbell test piece has a tensile elongation of 3.0% or more and 20.0% or less after being treated at 150°C for 500 hours in a mixture of LLC (Toyota Super Long Life Coolant (product number 08889-01005) manufactured by Toyota Motor Corporation) and ion-exchanged water in a weight ratio of 1:1. In order to suppress the decrease in tensile elongation at break after heat treatment in LLC at 150°C for 500 hours, it is preferable, for example, to make the chemical bond formed between (A) polyphenylene sulfide resin and (B) reinforcing fiber a bond with higher hydrolysis resistance.

There are no particular limitations on the method for producing the polyphenylene sulfide resin composition of the present invention. Representative examples include a method in which raw materials are supplied to a commonly known melt kneader such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a mixing roll, and melt kneaded so that the resin temperature is the melting peak temperature of the polyphenylene sulfide resin (A) +5°C to +100°C. Among these, melt kneading using a twin-screw extruder is preferred.

The ratio (L/D) of the screw length L (mm) to the screw diameter D (mm) of the twin-screw extruder is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. The upper limit of L/D for twin-screw extruders is usually 60. If L/D is less than 10, kneading tends to be insufficient, making it difficult to obtain sufficient melt viscosity and toughness.

In this case, there is no particular restriction on the order in which the raw materials are mixed. Any of the following methods may be used: after all the raw materials are mixed, they are melt-kneaded by the above method; after some of the raw materials are mixed, they are melt-kneaded by the above method, and then the remaining raw materials are mixed and melt-kneaded; or after some of the raw materials are mixed, the remaining raw materials are mixed using a side feeder halfway through the melt-kneading by the extruder. From the viewpoint of obtaining sufficient material strength, it is preferable to mix the reinforcing fibers (B) using a side feeder.

It is also preferable to suppress gelation of the extrusion gut due to overreaction of (A) polyphenylene sulfide resin, (B) reinforcing fiber, (C) olefin copolymer containing epoxy groups, and (D) organosilane compound, and the associated decrease in toughness. To achieve this, it is preferable to use a stirring screw with a notch. Here, the "notch" refers to a part of the crest of the screw flight that is cut off. The stirring screw with a notch can increase the resin filling rate. When the molten resin passes through the kneading section to which the stirring screw is connected, it is easily affected by the extruder cylinder temperature. By using a stirring screw with a notch, the molten resin that is heated by shear during kneading is efficiently cooled, making it possible to lower the resin temperature during kneading. In addition, the stirring screw with a notch can perform kneading mainly by stirring and stirring, unlike the conventional method of grinding the resin, and therefore it is possible to further suppress thermal deterioration of the resin due to heat generation.

From the viewpoint of improving the cooling efficiency of the molten resin by filling it with resin and improving kneading, it is preferable for the stirring screw to have a notched portion, with the screw pitch length being in the range of 0.1D to 0.3D, where D (mm) is the screw diameter, and with 10 to 15 notches per pitch. Here, "screw pitch length" refers to the screw length between the screw crests when the screw rotates 360 degrees.

For stirring screws with cutouts, it is preferable to introduce them so that they make up 3% or more of the total length L (mm) of the screw, and more preferably 5% or more. The upper limit is preferably 20% or less, and more preferably 15% or less.

The cylinder temperature of the extruder depends on the melting point of the polyphenylene sulfide resin (A) used, so it is difficult to generalize, but a preferable range is, for example, 280°C or higher and 320°C or lower.

From the viewpoint of suppressing thermal degradation of the (C) epoxy group-containing olefin copolymer, the resin temperature during melt kneading is preferably 350°C or less, more preferably 340°C or less, and particularly preferably 330°C or less. The resin temperature during melt kneading in the present invention is the temperature measured by a thermometer provided on the extruder die head.

The polyphenylene sulfide resin composition of the present invention can be applied to various molding methods, such as extrusion molding, injection molding, hollow molding, calendar molding, compression molding, vacuum molding, foam molding, blow molding, and rotational molding. In particular, the polyphenylene sulfide resin composition of the present invention is useful for blow molding applications because it can suppress drawdown during molding and obtain molded products with little thickness deviation. Examples of blow molding include extrusion blow molding and injection blow molding, and examples of blow molding include multi-layer blow such as direct blow and exchange blow, multi-dimensional blow such as suction blow, injection blow, and injection stretch blow. In addition, air can be used as the air used to blow up the parison during blow molding, and in terms of suppressing thermal oxidation deterioration, it is preferable to use an inert gas such as nitrogen or helium, and nitrogen is particularly preferable in terms of cost.

Applications of molded products obtained by extrusion and blow molding include round bars, square bars, sheets, films, tubes, and pipes. More specific applications include electrical insulating materials for water heater motors, air conditioner motors, and drive motors, film capacitors, speaker diaphragms, magnetic tape for recording, printed circuit board materials, peripheral parts for printed circuit boards, semiconductor packages, semiconductor transport trays, process and release films, protective films, automotive film sensors, insulating tape for wire cables, insulating washers in lithium-ion batteries, tubes for hot water, cooling water, and chemicals, automotive fuel tubes, hot water piping, chemical piping in chemical plants, piping for ultrapure water and ultra-high purity solvents, automotive piping, automotive cooling piping, piping pipes for freon and supercritical carbon dioxide refrigerants, and workpiece retaining rings for polishing equipment. Other examples include coated molded articles for windings for motor coils in hybrid and electric vehicles, railways, and power generation equipment, heat-resistant electric cables for home appliances, wire harnesses and control wires such as flat cables used for wiring inside automobiles, and coated molded articles for windings of signal transformers or on-board transformers for communication, transmission, high frequency, audio, measurement, etc. Among these, the polyphenylene sulfide resin composition of the present invention is useful as various pipes and ducts for fuel-related, exhaust, intake, and cooling systems of automobiles exposed to high-temperature environments, such as hybrid and electric vehicles and automobiles equipped with turbo mechanisms, taking advantage of its excellent characteristics of heat aging resistance and chemical resistance.

The polyphenylene sulfide resin composition of the present invention has the characteristics of high strength, high toughness, and excellent heat aging resistance, making it possible to design molded products that are thin while maintaining their strength, and can be used to reduce the weight and diameter of molded products.

Applications of molded products obtained by injection molding include generators, electric motors, transformers, current transformers, voltage regulators, rectifiers, inverters, relays, power contacts, switches, circuit breakers, knife switches, multi-pole rods, electrical component cabinets and other electrical equipment parts, sensors, LED lamps, connectors, sockets, resistors, relay cases, small switches, coil bobbins, capacitors, variable capacitor cases, optical pickups, oscillators, various terminal boards, transformers, plugs, printed circuit boards, tuners, speakers, microphones, headphones, small motors, magnetic head bases, power modules, semiconductors, liquid crystal displays, FDD carriages, FDD chassis, motor brush holders, parabolic antennas, computers electronic components such as VTR parts, television parts, irons, hair dryers, rice cooker parts, microwave oven parts, audio parts, audio equipment parts such as audio, laser discs (registered trademark), compact discs, lighting parts, refrigerator parts, air conditioner parts, typewriter parts, word processor parts, and other household and office electrical appliance parts; office computer parts, telephone parts, facsimile parts, copier parts, cleaning jigs, motor parts, lighters, typewriters, and other machine-related parts; microscopes, binoculars, cameras, watches, and other optical and precision machinery-related parts; alternator terminals, alternator connectors, IC registers regulators, potentiometer bases for light dimmers, various valves such as exhaust gas valves, automotive cooling piping, various pipes and ducts for fuel, exhaust systems and intake systems, turbo ducts, air intake nozzle snorkels, intake manifolds, fuel pumps, engine coolant joints, carburetor main bodies, carburetor spacers, exhaust gas sensors, coolant sensors, oil temperature sensors, brake pad wear sensors, throttle position sensors, crankshaft position sensors, air flow meters, brake pad wear sensors, thermostat bases for air conditioners, heating hot air flow control valves, brush holders for radiator motors, water heater ... Examples include turbo pump impellers, turbine vanes, wiper motor-related parts, distributors, starter switches, starter relays, transmission wire harnesses, windshield washer nozzles, air conditioner panel switch boards, coils for fuel-related electromagnetic valves, fuse connectors, horn terminals, electrical component insulation plates, step motor rotors, lamp sockets, lamp reflectors, lamp housings, brake pistons, solenoid bobbins, engine oil filters, ignition device cases and other automobile and vehicle-related parts, as well as gaskets for primary or secondary batteries in mobile phones, notebook computers, video cameras, hybrid cars, electric cars, etc.

The effects of the present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. Basic evaluations of each example and comparative example were performed using the following method.

(1) Melt Viscosity Measurement The resin composition pellets obtained in each of the Examples and Comparative Examples were measured using a Capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd. under conditions of a test temperature of 300° C., a shear rate of 122/s, a capillary length of 10 mm, and a capillary diameter of 1 mm.

(2) Measurement of the amount of generated gas 10 g of the resin composition pellets obtained in each Example and Comparative Example was weighed into an aluminum cup, treated for 2 hours in an Espec PHH202 hot air dryer heated to 320° C., and allowed to cool at room temperature. The weight was then measured, and the weight reduction rate (%), which is the ratio of the weight change before and after the drying treatment to the weight before the drying treatment, was taken as the amount of generated gas.

(3) Injection Molding From the resin composition pellets obtained in each of the Examples and Comparative Examples, an ISO (1A) dumbbell test piece was injection molded using an injection molding machine SE75-DUZ manufactured by Sumitomo Heavy Industries, with a cylinder temperature of 310°C and a mold temperature of 140°C.

(4) Initial Mechanical Properties The tensile properties of the ISO (1A) dumbbell test pieces injection molded under the conditions described in (3) were evaluated at 23°C using an Autograph AG-Xplus 20 kN testing machine in accordance with ISO527-1 and -2 under conditions of a support distance of 114 mm and a tensile speed of 5 mm/min.
Next, the bending properties were evaluated according to ISO178 under conditions of a support distance of 64 mm and a bending speed of 2 mm/min.

(5) Mechanical properties after heat treatment at 180°C for 500 hours ISO (1A) dumbbell test pieces injection molded under the conditions described in (3) were treated in an Espec PHH202 hot air dryer heated to 180°C for 500 hours, and then allowed to cool at room temperature for 24 hours.

Then, the tensile and bending properties were evaluated using the same method as described in (4).

(6) Mechanical Properties after LLC Treatment at 150°C for 500 Hours ISO (1A) dumbbell test pieces injection molded under the conditions described in (3) were immersed in an autoclave filled with a mixture of LLC (Toyota Super Long Life Coolant (product number 08889-01005) manufactured by Toyota Motor Corporation) and ion-exchanged water in a weight ratio of 1:1, and treated for 500 hours in an Espec PHH202 hot air dryer heated to 150°C, and then allowed to cool at room temperature for 24 hours.

Then, the tensile and bending properties were evaluated using the same method as described in (4).

(7) Blow Molding The resin composition pellets obtained in each of the Examples and Comparative Examples were subjected to a blow molding machine, and a hollow molded body having a wall thickness of 3 mm, φ40 mm and a length of 200 mm and a thin-walled hollow molded body having a wall thickness of 1 mm, φ40 mm and a length of 200 mm were molded at a cylinder temperature of 320°C.

(8) Evaluation of thickness uniformity For the blow molded hollow molded bodies and thin-walled hollow molded bodies described above, the thicknesses of five arbitrary positions on the circumference of the upper part (30 mm from the upper end) and the lower part (30 mm from the lower end) of the molded products were measured, and the thickness uniformity was calculated according to the following formula.
Thickness uniformity=((average thickness at five points on the bottom−average thickness at five points on the top)/(average thickness at five points on the top))×100(%)

(9) Pressure Repetition Test The blow molded hollow molded body and the thin-walled hollow molded body were subjected to 1000 cycles of pressurization by introducing compressed air so that the internal pressure was changed from 0 MPa to 1 MPa. The test was evaluated according to the number of times that pressure leakage occurred, as follows.
◎: No pressure leakage even after 1000 cycles ○: 300 to less than 1000 cycles ×: Less than 300 cycles

The raw materials used in each example and comparative example are listed below.

[Reference Example 1] (A) Polyphenylene sulfide resin 8.27 kg (70.00 mol) of 47.5% sodium hydrosulfide, 2.94 kg (70.63 mol) of 96% sodium hydroxide, 11.45 kg (115.50 mol) of N-methyl-2-pyrrolidone (NMP), 1.89 kg (23.1 mol) of sodium acetate, and 5.50 kg of ion-exchanged water were charged into a 70-liter autoclave equipped with a stirrer and a bottom plug valve, and the mixture was gradually heated to 245°C over about 3 hours while passing nitrogen through the mixture at normal pressure. After distilling out 9.77 kg of water and 0.28 kg of NMP, the reaction vessel was cooled to 200°C. The amount of water remaining in the system per mole of charged alkali metal sulfide was 1.06 mol, including the water consumed in the hydrolysis of NMP. The amount of hydrogen sulfide scattered was 0.02 mol per mole of charged alkali metal sulfide.

Then, it was cooled to 200°C, 10.42 kg (70.86 mol) of p-dichlorobenzene and 9.37 kg (94.50 mol) of NMP were added, the reaction vessel was sealed under nitrogen gas, and the temperature was raised from 200°C to 270°C at a rate of 0.6°C/min while stirring at 240 rpm, and the reaction was carried out at 270°C for 140 minutes. After that, 2.40 kg (133 mol) of water was injected while cooling from 270°C to 250°C over 15 minutes. Next, it was gradually cooled from 250°C to 220°C over 75 minutes, after which it was rapidly cooled to near room temperature and the contents were removed.

The contents were diluted with about 35 liters of NMP, stirred at 85°C for 30 minutes as a slurry, and filtered through an 80-mesh wire mesh (0.175 mm mesh size) to obtain a solid. The obtained solid was washed and filtered with about 35 liters of NMP in the same manner. The obtained solid was diluted with 70 liters of ion-exchanged water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh to recover the solid. This operation was repeated three times in total. The obtained solid and 32 g of acetic acid were diluted with 70 liters of ion-exchanged water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh. The obtained solid was further diluted with 70 liters of ion-exchanged water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh to recover the solid. The solid thus obtained was dried at 120°C under a nitrogen stream to obtain a dried PPS.

[Other ingredients]
(B) Reinforcing fiber: Glass fiber (T-747H manufactured by Nippon Electric Glass Co., Ltd.), 3 mm long, average fiber diameter 10.5 μm
(C) Epoxy group-containing olefin copolymer: ethylene-glycidyl methacrylate copolymer ("Bondfast" E, manufactured by Sumitomo Chemical Co., Ltd.). Amount of glycidyl methacrylate copolymerized: 12 wt %.
Unmodified olefin copolymer: ethylene/1-butene copolymer ("Tafmer" A4085, manufactured by Mitsui Chemicals)
Polyamide: Nylon 66 with a relative viscosity of 3.0 ("Amilan" manufactured by Toray)
(D) Organic silane compound-1: 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (manufactured by Shin-Etsu Silicones: KBM303)
(D) Organic silane compound-2: 3-isocyanatepropyltriethoxysilane (Shin-Etsu Silicone: KBE9007N)
(E) Phosphorus oxoacid metal salt: manufactured by Wako Pure Chemical Industries, Ltd.: sodium phosphinate monohydrate Phenol-based antioxidant: 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane ("ADEKA STAB" AO80 manufactured by ADEKA Corporation)
Phosphorus-based antioxidant: 3,9-bis(2,6-di-t-butyl-4-methylphenoxy)2,4,8,10-tetraoxa-3,9-diphosphapyro[5.5]undecane ("ADEKA STAB" PEP36 manufactured by ADEKA)

[Examples 1 to 4, Comparative Examples 1 to 6]
The raw materials were dry-blended in the ratios shown in Table 1, and then melt-kneaded using a Japan Steel Works TEX30α type twin-screw extruder (L/D = 45, two kneading sections) equipped with a vacuum vent at a cylinder temperature of 280°C and a screw rotation speed of 300 rpm, and pelletized using a strand cutter.

The pellets were then dried overnight at 130°C and injection molded, and the resulting test pieces were evaluated for various physical properties. The pellets were then dried overnight at 130°C and direct blow molded using the method described above, to obtain a hollow molded product with a wall thickness of 3 mm and a thin-walled hollow molded product with a wall thickness of 1 mm. The hollow molded products were then subjected to a pressure cycle test.

The results of the Examples and Comparative Examples in Table 1 above will be compared and explained.
As shown in Examples 1 to 4, (A) polyphenylene sulfide resin, (B) reinforcing fiber, (C) olefin-based copolymer containing epoxy groups, (D) organosilane compound, and (E) phosphorus oxoacid metal salt were melt-kneaded, and the resulting composition maintained a high melt viscosity capable of suppressing drawdown, while exhibiting a small amount of gas generation and excellent initial mechanical properties, as well as excellent heat aging resistance in the mechanical properties after treatment at 180°C for 500 hours.

In particular, in Examples 2 to 4, a large amount of (B) reinforcing fiber was blended, resulting in excellent bending strength. As a result, no pressure leakage was observed even in repeated pressure tests on thin-walled hollow molded products with a wall thickness of 1 mm.

Comparative Example 1 had a lower melt viscosity than Example 1, and drawdown was observed during blow molding of a thin-walled hollow molded product with a wall thickness of 1 mm, resulting in a thin-walled hollow molded product with an uneven wall thickness that was not worthy of a pressure cycle test. In Comparative Example 2, compared to Example 1, no phosphorus oxoacid metal salt (E) was added, resulting in insufficient control of the reactive extrusion and a significant increase in the resin temperature during melt kneading. As a result, an increase in the amount of gas generated, a decrease in initial mechanical properties, and a significant decrease in the tensile elongation at break and bending strength after treatment at 180°C for 500 hours were observed. As a result, although a thin-walled hollow molded product was obtained, the molded product had many voids, and pressure leakage was observed in less than 300 cycles in a pressure cycle test.

In Comparative Example 3, the melt viscosity was lower than in Example 2, so drawdown was observed even during blow molding of a hollow molded product with a wall thickness of 3 mm, and the obtained hollow molded product had an uneven wall thickness and was not worthy of a pressure cycle test. In Comparative Example 4, (E) the phosphorus oxoacid metal salt was not added, so the reactive extrusion control was insufficient and the resin temperature during melt kneading increased significantly. As a result, an increase in the amount of gas generated, a decrease in initial mechanical properties, and a significant decrease in tensile elongation at break and bending strength after treatment at 180°C for 500 hours were observed. As a result, although a thin-walled hollow molded product was obtained, the molded product had many voids, and pressure leakage was observed in less than 300 cycles in the pressure cycle test.

In Comparative Example 5, a phenolic antioxidant and a phosphorus-based antioxidant were added instead of the phosphorus oxoacid metal salt (E) compared to Example 2, but the reactive extrusion was not well controlled, and the result was similar to Comparative Example 4. As a result, although a thin-walled hollow molded product was obtained, the molded product had many voids, and pressure leakage was observed in less than 300 cycles in a pressure cycle test.

In Comparative Example 6, a polyamide was melt-kneaded instead of the olefin copolymer containing epoxy groups (C), and a decrease in melt viscosity was observed. As a result, drawdown was observed even during blow molding of a hollow molded article with a wall thickness of 3 mm, and the obtained hollow molded article had an uneven wall thickness and was not worthy of a pressure cycle test. It is clear that the olefin copolymer containing epoxy groups (C) is essential for applying a polyphenylene sulfide resin composition to blow molding.

Claims (8)

A polyphenylene sulfide resin composition comprising 100 parts by weight of (A) polyphenylene sulfide resin, 1 to 200 parts by weight of (B) reinforcing fiber, 1 to 200 parts by weight of (C) an olefin-based copolymer containing an epoxy group, 0.01 to 10 parts by weight of (D) an organosilane compound, and 0.01 to 5 parts by weight of (E) a metal salt of a phosphorus oxoacid, wherein the metal salt of a phosphorus oxoacid (E) is sodium phosphinate, and the polyphenylene sulfide resin composition has a flexural strength of 100 MPa or more and 300 MPa or less, as measured in accordance with ISO 178 using an ISO (1A) dumbbell test piece obtained by injection molding the polyphenylene sulfide resin composition . The polyphenylene sulfide resin composition according to claim 1, in which the amount of the reinforcing fiber (B) is 15% by weight or more and 50% by weight or less when the total of the polyphenylene sulfide resin (A), the reinforcing fiber (B), and the olefin-based copolymer containing an epoxy group (C) is taken as 100% by weight. The polyphenylene sulfide resin composition according to any one of claims 1 to 2, having a melt viscosity of 1000 Pa·s or more and 3000 Pa·s or less, measured at a temperature of 300°C and a shear rate of 122/s. A polyphenylene sulfide resin composition according to any one of claims 1 to 3, in which the weight loss rate (%) when pellets of the resin composition are treated in air at 320°C for 2 hours is 0.3% or more and 3.0% or less. The polyphenylene sulfide resin composition according to any one of claims 1 to 4, wherein the (D) organic silane compound is an alkoxysilane compound having an epoxy group or an isocyanate group. A molded article made of the polyphenylene sulfide resin composition according to any one of claims 1 to 5 . The molded article according to claim 6, which is a hollow molded article. A method for producing a molded article, comprising blow molding the polyphenylene sulfide resin composition according to any one of claims 1 to 5 .