Motor component using cooling medium

Abstract

The present invention provides a motor component which uses a cooling medium, which has excellent thermal shock resistance after an immersion treatment in the cooling medium, and which can be used in even harsh environments in which contact is made with the cooling medium. Provided is a motor component which uses a cooling medium and which is obtained by molding a polyphenylene sulfide resin composition that is obtained by combining (A) a polyphenylene sulfide resin, (B) an elastomer, (C) a fibrous filler, and (D) a non-fibrous filler, said motor component being characterized in that: the tensile elastic modulus of a molded article comprising the polyphenylene sulfide resin composition is 10-21 GPa; and when the tensile strength of the molded article in the resin flow direction is represented as MD and the tensile strength in the direction perpendicular to resin flow direction is represented as TD, MD is not less than 70 MPa and the ratio MD / TD of MD to TD is not more than 1.4.

Description

Motor parts using cooling fluid

[0001] The present invention relates to a motor component that uses a cooling medium and has excellent resistance to thermal shock after being immersed in the cooling medium.

[0002] In recent years, various efforts have been made to reduce the environmental impact of global warming and energy issues. In particular, to reduce carbon dioxide and nitrogen oxide emissions while driving, next-generation automobiles such as electric vehicles, fuel cell vehicles, and hybrid vehicles that use both a gasoline engine and a motor, are becoming more popular.

[0003] In electric vehicles, the increasing capacity of batteries and the increasing power output of motors have led to increased heat generation from batteries and motors. This, in turn, has led to increased heat generation from electrical components that pass high-voltage current, such as inverters and DC-DC converters. Furthermore, to save space and improve efficiency, motors are being integrated with gears and inverters, and even DC-DC converters, power distribution units, PTC heaters, and on-board chargers. Products that include these motors, known as electric axles (also referred to as e-axles), are facing the problem of increased environmental temperatures throughout the system due to increased heat generation and space-saving requirements. Therefore, improving the durability of components against the cooling media used for cooling is crucial to improving the efficiency of thermal management systems and extending the lifespan of the components.

[0004] Meanwhile, thermoplastic resins have traditionally been used for electrical components such as motors, particularly for components with metal inserts, taking into consideration their light weight, good processability, low cost, etc. Furthermore, for resin molded products with metal inserts, such as bus bars as an example of motor components, a resin composition with excellent cold and thermal shock resistance is required so that the metal insert molded product will not crack even when exposed to the temperature fluctuations between the low temperature environment of use in cold regions and the high temperature environment caused by heat generation by the motor.

[0005] Electric vehicles often use polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) resin, which has high heat resistance and chemical resistance at high temperatures. PPS resin is inferior to other engineering plastics in terms of cold and thermal shock resistance and tracking resistance. Therefore, Patent Document 1 describes a resin composition that combines tracking resistance and high and low temperature impact resistance by incorporating a predetermined amount of inorganic filler and olefin copolymer into PPS resin.

[0006] Furthermore, Patent Document 2 describes a resin composition that combines thermal shock resistance, flame retardancy, and tracking resistance by blending a specified amount of modified cross-section glass fiber, a non-fibrous inorganic filler, and an olefin copolymer having an epoxy group into a PPS resin.

[0007] Furthermore, Patent Document 3 describes a heat dissipation member for cooling a motor, which is formed by molding a resin composition having a thermal conductivity of 0.8 W / m·K or more, by incorporating a predetermined amount of magnesium hydroxide and glass fibers with a fiber diameter of 4 to 11 μm into PPS resin, in order to dissipate heat with high efficiency in response to increased motor output.

[0008] JP 2020-105502 A JP 2023-68631 A JP 2012-36386 A

[0009] Thermal management systems for electric vehicle batteries, inverters, and motor components include air-cooled, water-cooled, and oil-cooled systems. Traditionally, motor components have used oil for lubrication and cooling, while batteries and inverters have often used water (coolant), which has high thermal conductivity. In recent years, as heat generation in these systems has increased, components must be durable against the coolant. Furthermore, the use of oil and water (coolant) is increasingly being separated into complex systems, requiring precise control of each refrigerant and the use of multiple coolants. Therefore, components must be highly durable against both coolants. Resin components used in areas exposed to high environmental temperatures due to the rising temperatures of heat sources and coolants must maintain their strength and rigidity, avoid cracking, and maintain their shape even when exposed to the coolant. Therefore, thermoplastic resins used in motor components that use coolants must be resistant to cold and thermal shock after immersion in the coolant.

[0010] However, although the resin compositions disclosed in Patent Documents 1 and 2 have improved resistance to cold and thermal shock, they do not disclose that they are excellent in resistance to cold and thermal shock after immersion in a cooling medium, and are suitable for motor parts that use a cooling medium.

[0011] Although the heat dissipation member for cooling a motor disclosed in Patent Document 3 is a motor component, it is not disclosed that it can be applied to a motor that uses a cooling medium.

[0012] As a result of extensive research aimed at solving the above problems, the present inventors have discovered a previously unknown attribute in which a molded article made from a PPS resin composition containing a PPS resin, an elastomer, a fibrous filler, and a non-fibrous filler has excellent adhesion between the resin and metal and maintains rigidity by satisfying certain properties, resulting in excellent resistance to thermal shock even after heat treatment by immersion in a cooling medium, and have found that molded articles having such attributes are suitable for motor parts that use cooling mediums. (1) A motor part using a cooling medium, which is formed by molding a polyphenylene sulfide resin composition containing (A) a polyphenylene sulfide resin, (B) an elastomer, (C) a fibrous filler, and (D) a non-fibrous filler, wherein the tensile modulus of a molded article made of the polyphenylene sulfide resin composition is 10 GPa or more and 21 GPa or less, and where the tensile strength in the direction of resin flow in the molded article is defined as MD and the tensile strength in the direction perpendicular to the direction of resin flow in TD, the MD is 70 MPa or more, and the ratio of MD to TD, MD / TD, is 1.4 or less. (2) A motor part using a cooling medium according to (1), wherein the polyphenylene sulfide resin composition contains (B-1) an olefin copolymer having an epoxy group as the (B) elastomer, and the polyphenylene sulfide resin composition contains 0.1 parts by mass or more and less than 9 parts by mass of the olefin copolymer having an epoxy group per 100 parts by mass of the polyphenylene sulfide resin (A). (3) A motor part using a cooling medium according to (1) or (2), wherein the polyphenylene sulfide resin composition contains 60 parts by mass or more of a non-fibrous filler (D) per 100 parts by mass of the polyphenylene sulfide resin (A). (4) A motor part using a cooling medium according to any one of (1) to (3), wherein the cooling medium contains at least one selected from the group consisting of long-life coolant (LLC), ethylene glycol, oil, and water. (5) A motor part using a cooling medium according to any one of (1) to (4), wherein the molded article made of the polyphenylene sulfide resin composition is a molded article with a metal insert.(6) A motor component using the cooling medium according to any one of items (1) to (5), which is used in one selected from the group consisting of a stator, a rotor, a slip ring, a current sensor, a bus bar, a rotation angle sensor, a pipe for passing a cooling medium, and a member for spraying a cooling medium. (7) A motor component using the cooling medium according to any one of items (1) to (6), in which the thinnest part of a molded product made of the polyphenylene sulfide resin composition is 0.7 mm or less. (8) A motor component using the cooling medium according to any one of items (1) to (7), in which the MD and TD of a molded product made of the polyphenylene sulfide resin composition are both 80 MPa or more. (9) A method for molding a polyphenylene sulfide resin composition containing (A) a polyphenylene sulfide resin, (B) an elastomer, (C) a fibrous filler, and (D) a non-fibrous filler into a molded article, wherein the molded article has a tensile modulus of elasticity of 10 GPa to 21 GPa, and wherein, where the tensile strength in the resin flow direction of the molded article is defined as MD and the tensile strength in the direction perpendicular to the resin flow direction is defined as TD, the MD is 70 MPa or more and the ratio of MD to TD, i.e., MD / TD, is 1.4 or less. (10) The method according to (9), wherein the polyphenylene sulfide resin composition contains an olefin copolymer having epoxy groups (B-1) as the elastomer (B), and the olefin copolymer having epoxy groups (B-1) is blended in an amount of 0.1 part by mass or more and less than 9 parts by mass per 100 parts by mass of the polyphenylene sulfide resin (A). (11) The method according to item (9) or (10), wherein the polyphenylene sulfide resin composition is obtained by blending 60 parts by mass or more of (D) a non-fibrous filler with 100 parts by mass of (A) polyphenylene sulfide resin. (12) The method according to any one of items (9) to (11), wherein the cooling medium comprises at least one selected from the group consisting of long-life coolant (LLC), ethylene glycol, oil, and water. (13) The method according to any one of items (9) to (12), wherein the molded article made of the polyphenylene sulfide resin composition is a molded article with a metal insert.(14) The method according to any one of items (9) to (13), wherein the motor component using the cooling medium is one selected from the group consisting of a stator, a rotor, a slip ring, a current sensor, a bus bar, a rotation angle sensor, a pipe for passing a cooling medium, and a member for spraying a cooling medium. (15) The method according to any one of items (9) to (14), wherein the thinnest part of the molded article made of the polyphenylene sulfide resin composition is 0.7 mm or less. (16) The method according to any one of items (9) to (15), wherein both the MD and TD of the molded article made of the polyphenylene sulfide resin composition are 80 MPa or more. (17) Use of a molded article, for a motor part using a cooling medium, obtained by molding a polyphenylene sulfide resin composition comprising (A) a polyphenylene sulfide resin, (B) an elastomer, (C) a fibrous filler, and (D) a non-fibrous filler, the molded article having a tensile modulus of elasticity of 10 GPa or more and 21 GPa or less, and where the tensile strength in the resin flow direction of the molded article is defined as MD and the tensile strength in the direction perpendicular to the resin flow direction is defined as TD, the MD is 70 MPa or more and the ratio of MD to TD, MD / TD, is 1.4 or less. (18) Use according to item (17), wherein the polyphenylene sulfide resin composition comprises (B-1) an olefin copolymer having epoxy groups as the (B) elastomer, and the amount of (B-1) an olefin copolymer having epoxy groups is 0.1 part by mass or more and less than 9 parts by mass per 100 parts by mass of the polyphenylene sulfide resin (A). (19) The use according to item (17) or (18), wherein the polyphenylene sulfide resin composition is obtained by blending 60 parts by mass or more of (D) a non-fibrous filler per 100 parts by mass of (A) polyphenylene sulfide resin. (20) The use according to any one of items (17) to (19), wherein the cooling medium comprises at least one selected from the group consisting of long-life coolant (LLC), ethylene glycol, oil, and water. (21) The use according to any one of items (17) to (20), wherein the molded article made of the polyphenylene sulfide resin composition is a molded article with a metal insert.(22) The use according to any one of items (17) to (21), wherein the motor component using the cooling medium is one selected from the group consisting of a stator, a rotor, a slip ring, a current sensor, a bus bar, a rotation angle sensor, a pipe for passing a cooling medium, and a component for spraying a cooling medium. (23) The use according to any one of items (17) to (22), wherein the thinnest part of the molded article made of the polyphenylene sulfide resin composition is 0.7 mm or less. (24) The use according to any one of items (17) to (23), wherein the MD and TD of the molded article made of the polyphenylene sulfide resin composition are both 80 MPa or more.

[0013] According to the present invention, it is possible to provide a motor component using a cooling medium, which has excellent resistance to thermal shock even after being immersed in a cooling medium and heat-treated.

[0014] FIG. 1 is a schematic diagram of a molded product used in evaluating thermal shock resistance.

[0015] The present invention has discovered a previously unknown attribute of a molded article made from a PPS resin composition containing PPS resin, elastomer, fibrous filler, and non-fibrous filler, where the molded article has a tensile modulus of elasticity of 10 GPa or more and 21 GPa or less, and where the tensile strength in the direction of resin flow in the molded article is defined as MD and the tensile strength in the perpendicular direction is defined as TD, the MD is 70 MPa or more and the MD / TD is 1.4 or less, and the molded article has excellent resistance to thermal shock even after being immersed in a cooling medium and heat treated.The present invention has also discovered that a molded article made from such a PPS resin composition can be used in a new application such as a motor part that uses a cooling medium.

[0016] Hereinafter, an embodiment of the present invention will be described.

[0017] (A) PPS Resin The (A) polyphenylene sulfide resin used in the present invention is a polymer having a repeating unit represented by the following structural formula.

[0018]

[0019] From the viewpoint of heat resistance, the polyphenylene sulfide resin (A) used in the present invention is preferably a polymer containing 70 mol % or more, more preferably 90 mol % or more, of repeating units represented by the above structural formula. Furthermore, the polyphenylene sulfide resin (A) used in the present invention may be composed of repeating units having the following structure in an amount of less than 30 mol %:

[0020]

[0021] Next, a method for obtaining the polyphenylene sulfide resin (A) used in the present invention will be described. The method for producing the PPS resin preferably comprises a pre-process, a polymerization reaction process, a recovery process, and a post-treatment process, and the resin can be produced by a known method. The raw materials and pre-process used in the production of the PPS resin preferably conform to the method described in JP 2017-155221 A. The polymerization reaction process, recovery process, and post-treatment process will be described below.

[0022] [Polymerization Reaction Step] It is preferable to produce PPS resin powder and granules by reacting a sulfidizing agent with a polyhalogenated aromatic compound in an organic polar solvent at a temperature ranging from 200°C to 290°C.

[0023] To start the polymerization reaction, the sulfidizing agent and the polyhalogenated aromatic compound are added to an organic polar solvent, preferably in an inert gas atmosphere, at a temperature ranging from room temperature to 215°C, and preferably from 100 to 215°C. A polymerization aid may also be added at this stage. These raw materials may be added in any order, or simultaneously.

[0024] The mixture is usually heated to a temperature in the range of 200° C. to 290° C. There are no particular restrictions on the rate of temperature increase, but a rate of 0.01 to 5° C. / min is usually preferably selected, and a range of 0.1 to 3° C. / min is more preferable.

[0025] In general, the temperature is finally raised to 250 to 290° C., and the reaction is carried out at that temperature for usually 0.25 to 50 hours, preferably 0.5 to 20 hours.

[0026] A method in which, before reaching the final temperature, the reaction is carried out for a certain period of time at, for example, 200° C. to 245° C., and then the temperature is raised to 270° C. to 290° C. is effective in obtaining a higher degree of polymerization. In this case, the reaction time at 200° C. to 245° C. is preferably selected from the range of 0.25 to 20 hours, more preferably from 0.25 to 10 hours.

[0027] In order to obtain a polymer with a higher degree of polymerization, it is effective to carry out the polymerization in multiple stages. When carrying out the polymerization in multiple stages, it is effective to raise the temperature to the next stage when the conversion of the polyhalogenated aromatic compound in the system at 245°C reaches 40 mol% or more, preferably 60 mol%.

[0028] [Recovery Step] After the polymerization is completed, solid matter is recovered from the polymerization reaction product containing the polymer, solvent, etc.

[0029] The most preferred method for recovering PPS resin is to perform the recovery under rapid cooling conditions, and one preferred method for this recovery method is the flash method. The flash method is a method of subjecting the polymerization reaction product to high temperature and high pressure (usually 250°C or higher, 8 kg / cm ２ In this method, the polymer is flashed from a state of the above (or above) into an atmosphere of normal pressure or reduced pressure, and the polymer is recovered in powder form at the same time as the solvent is recovered. The "flashing" 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 preferably selected in the range of 150°C to 250°C.

[0030] The flash method is an economical method because it allows the recovery of solids simultaneously with the recovery of solvents and the recovery time is relatively short. In this recovery method, ionic compounds such as sodium and organic low-molecular-weight substances (oligomers) tend to be incorporated into the polymer during the solidification process.

[0031] However, the method for recovering the PPS resin used in the present invention is not limited to the flash method. A method of recovering particulate polymer by slow cooling (quench method) can also be used as long as it satisfies the requirements of the present invention. However, in terms of economy and performance, it is more preferable to use PPS resin recovered by the flash method in the production method of the present invention.

[0032] [Post-Treatment Step (Acid Treatment)] In the present invention, it is preferable to subject the PPS resin obtained through the above-described polymerization reaction step and recovery step to an acid treatment.

[0033] The acid used in the acid treatment is not particularly limited as long as it does not have the effect of decomposing the PPS resin, and examples thereof 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 the PPS resin are not preferred.

[0034] When an aqueous acid solution is used, the water is preferably distilled water or deionized water. The aqueous acid solution preferably has a pH of 1 to 7, more preferably a pH of 2 to 4. A pH of 7 or less is preferred because the metal content of the PPS resin does not increase, and a pH of 1 or more is preferred because the amount of volatile components in the PPS resin can be suppressed.

[0035] The acid treatment method preferably involves immersing the PPS resin in an acid or an aqueous solution of an acid, and stirring and heating can be performed as necessary. The heating temperature is preferably 80 to 250°C, more preferably 120 to 200°C, and even more preferably 150 to 200°C. A temperature of 80°C or higher is preferable because the acid treatment effect can be obtained without increasing the metal content, while a temperature of 250°C or lower is preferable from the perspective of safety because it also suppresses pressure increases. Furthermore, when the PPS resin is immersed in an aqueous acid solution for treatment, the pH is preferably less than 8, more preferably 2 to 8. A pH of less than 8 is preferable because it prevents an increase in the metal content of the resulting PPS resin.

[0036] The acid treatment time is preferably a time sufficient for the reaction between the PPS resin and the acid to reach a sufficient equilibrium, and is preferably 2 to 24 hours when treated at 80°C, and 0.01 to 5 hours when treated at 200°C.

[0037] The acid treatment is preferably performed while the PPS resin is thoroughly immersed in the acid or acid aqueous solution. The ratio of the PPS resin to the acid or acid aqueous solution in the acid treatment is preferably 0.5 to 500 L, more preferably 1 to 100 L, and even more preferably 2.5 to 20 L per 500 g of PPS resin. Using 0.5 L or more of acid or acid aqueous solution per 500 g of PPS resin is preferable because the PPS resin is thoroughly immersed in the solution, preventing poor cleaning and preventing an increase in the metal content of the PPS resin. Furthermore, using 500 L or less of acid or acid aqueous solution per 500 g of PPS resin is preferable because the amount of solution is not excessive relative to the PPS resin, preventing a significant decrease in production efficiency.

[0038] These acid treatments are carried out by adding a predetermined amount of PPS resin to a predetermined amount of water and acid, heating and stirring the mixture in a pressure vessel, or by continuous acid treatment. Separating the aqueous solution and PPS resin from the treatment solution after acid treatment can be easily achieved by filtration using a sieve or filter, and examples of such methods include natural filtration, pressure filtration, vacuum filtration, and centrifugal filtration. In order to remove the acid and impurities remaining on the surface of the PPS resin separated from the treatment solution, it is preferable to wash the resin several times with water or hot water. Examples of washing methods include filtering the PPS resin while pouring water over it on a filter, or separating the PPS resin from the aqueous solution by adding the separated PPS resin to previously prepared water and then filtering it again. The water used for washing is preferably distilled water or deionized water.

[0039] [Post-treatment step (hot water treatment)] In the present invention, it is preferable to carry out hot water treatment before the acid treatment step, and the method is as follows. The water used in the hot water treatment in the present invention is preferably distilled water or deionized water. The hot water treatment temperature is preferably 80 to 250°C, more preferably 120 to 200°C, and even more preferably 150 to 200°C. A temperature of 80°C or higher can achieve the effects of the hot water treatment and suppress the amount of volatilized gas generated, while a temperature of 250°C or lower suppresses pressure increase, which is preferable from the standpoint of safety.

[0040] The hot water treatment time is preferably a time that allows sufficient extraction of the PPS resin with hot water, and is preferably 2 to 24 hours when treated at 80°C, and 0.01 to 5 hours when treated at 200°C.

[0041] The ratio of PPS resin to water in the hot water treatment is preferably such that the PPS resin is sufficiently immersed in water, with 0.5 to 500 L of water per 500 g of PPS resin being preferred, more preferably 1 to 100 L, and even more preferably 2.5 to 20 L. Using 0.5 L or more of water per 500 g of PPS resin is preferred because the PPS resin is sufficiently immersed in water, preventing poor cleaning and preventing an increase in the amount of volatile gas generated. Furthermore, using 500 L or less of water per 500 g of PPS resin is preferred because the amount of water is not excessive relative to the PPS resin, preventing a significant decrease in production efficiency.

[0042] There are no particular limitations on the operation of these hot water treatments, and they can be carried out by, for example, adding a predetermined amount of PPS resin to a predetermined amount of water and heating and stirring in a pressure vessel, or by continuously performing hot water treatments. There are no particular limitations on the method for separating the aqueous solution and PPS resin from the treatment solution after hot water treatment, but filtration using a sieve or filter is convenient, and examples include natural filtration, pressure filtration, vacuum filtration, and centrifugal filtration. In order to remove impurities remaining on the surface of the PPS resin separated from the treatment solution, it is preferable to wash the PPS resin several times with water or hot water. There are no particular limitations on the washing method, but examples include a method of filtering the PPS resin while pouring water over it on a filter, or a method of separating the aqueous solution and the PPS resin by adding the separated PPS resin to previously prepared water and then filtering it again. The water used for washing is preferably distilled water or deionized water.

[0043] Furthermore, since decomposition of the PPS end groups during these acid treatments and hot water treatments is undesirable, it is desirable to carry out the acid treatments and hot water treatments in an inert atmosphere, such as nitrogen, helium, or argon, with a nitrogen atmosphere being preferred from an economical standpoint.

[0044] [Post-Treatment Step (Washing with Organic Solvent)] In the present invention, a step of washing with an organic solvent may be included before the acid treatment step or the hot water treatment step, and the method is as follows: The organic solvent used for washing the PPS resin in the present invention is not particularly limited as long as it does not have the action of decomposing the PPS resin, and examples thereof 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, tetrahydrofuran, and the like; Examples of suitable organic solvents include ether-based solvents such as chlorofuran, halogen-based solvents such as chloroform, methylene chloride, trichloroethylene, ethylene dichloride, perchloroethylene, monochloroethane, dichloroethane, tetrachloroethane, perchloroethane, and chlorobenzene, alcohol-phenol-based solvents such as methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, phenol, cresol, polyethylene glycol, and polypropylene glycol, and aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene. Among these organic solvents, N-methyl-2-pyrrolidone, acetone, dimethylformamide, and chloroform are particularly preferred. These organic solvents may be used alone or in combination.

[0045] Methods for washing with an organic solvent include immersing the PPS resin in the organic solvent, and stirring or heating can be performed as necessary. There are no particular restrictions on the washing temperature when washing the PPS resin with an organic solvent, and temperatures between room temperature and approximately 300°C can be preferably selected. While higher washing temperatures tend to increase the washing efficiency, a washing temperature between room temperature and 150°C is usually sufficient. Washing can also be performed under pressure in a pressure vessel at a temperature above the boiling point of the organic solvent. There are also no particular restrictions on the washing time. While it depends on the washing conditions, in the case of batch-type washing, washing for 5 minutes or more usually produces a sufficient effect. Continuous washing is also possible.

[0046] The acid treatment, hot water treatment, and washing with an organic solvent can also be carried out in appropriate combination.

[0047] [Post-treatment step (thermal oxidation treatment)] The PPS resin used in the present invention is preferably obtained by carrying out the above-mentioned acid treatment, hot water treatment or washing with an organic solvent followed by a thermal oxidation treatment. The thermal oxidation treatment is a treatment in which the PPS resin is heated in an oxygen atmosphere or immersed in H ２ O ２ The treatment is carried out by adding a peroxide such as HCl or a vulcanizing agent such as S, and then heating. However, heating in an oxygen atmosphere is particularly preferred because of the ease of the treatment.

[0048] The heating device for the thermal oxidation treatment of PPS resin may be a conventional hot air dryer or a rotary or agitator-equipped heating device. However, for efficient and more uniform treatment, it is more preferable to use a rotary or agitator-equipped heating device. The oxygen concentration in the atmosphere during the thermal oxidation treatment is preferably 1% by volume or more, and even more preferably 2% by volume or more. To achieve the effects of the present invention, the upper limit of the oxygen concentration is preferably 5% by volume or less. By performing the thermal oxidation treatment at an oxygen concentration of 5% by volume or less, the thermal oxidation treatment does not proceed excessively, and the toughness of molded products containing the thermally oxidized PPS resin is not impaired. On the other hand, performing the thermal oxidation treatment at an oxygen concentration of 1% by volume or more is preferable because it allows sufficient thermal oxidation treatment and produces PPS resin with a low volatile component content.

[0049] The thermal oxidation treatment temperature for PPS resin is preferably 160 to 270°C, more preferably 160 to 230°C. Conducting the thermal oxidation treatment at 270°C or lower is preferable because the thermal oxidation treatment does not proceed too rapidly and the toughness of a molded article containing the thermally oxidized PPS resin is not impaired. On the other hand, conducting the thermal oxidation treatment at a temperature of 160°C or higher is preferable because the thermal oxidation treatment can proceed at an appropriate rate and a PPS resin that generates a small amount of volatile components can be obtained.

[0050] The treatment time for the thermal oxidation treatment is preferably 0.5 to 30 hours, more preferably 0.5 to 25 hours, and even more preferably 2 to 20 hours. A treatment time of 0.5 hours or more is preferred because sufficient thermal oxidation treatment can be performed and a PPS resin with a low volatile content can be obtained. A treatment time of 30 hours or less is preferred because the crosslinking reaction due to the thermal oxidation treatment can be controlled and the toughness of molded articles containing the PPS resin that has been subjected to the thermal oxidation treatment can be prevented from being impaired.

[0051] The melt flow rate (measured in accordance with ASTM D-1238-70 at a temperature of 315.5°C and a load of 5000 g) of the PPS resin preferably used in the present invention preferably has a lower limit of 100 g / 10 min or more, more preferably 300 g / 10 min or more. The upper limit is preferably 5000 g / 10 min or less, more preferably 3000 g / 10 min or less. A melt flow rate of 100 g / 10 min or more allows for the production of a PPS resin with excellent moldability, and a melt flow rate of 5000 g / 10 min or less allows for the production of a PPS resin with excellent mechanical strength, which are preferred.

[0052] The PPS resin used in the present invention preferably has a residue amount of 4.0% by mass or less when dissolved in 20 times the mass of 1-chloronaphthalene at 250°C for 5 minutes and hot-pressurized filtered through a PTFE membrane filter with a pore size of 1 μm. A residue amount exceeding 4.0% by mass indicates excessive thermal oxidative crosslinking of the PPS resin, resulting in an increase in gelled matter in the resin. A residue amount of 4.0% by mass or less is preferable because it inhibits the progression of thermal oxidative crosslinking of the PPS resin, allowing the PPS resin to maintain its toughness and thermal shock resistance. There is no particular lower limit for the residue amount, but it is preferably 1.5% by mass or more, and more preferably 1.7% by mass or more. A residue amount of 1.5% by mass or more indicates a moderate state of thermal oxidative crosslinking, and the volatile components do not decrease significantly upon melting, potentially resulting in a small effect on reducing volatile components.

[0053] The residue amount was measured using a sample of PPS resin pressed into a film approximately 80 μm thick, in a high-temperature filtration apparatus and a stainless steel test tube equipped with a pneumatic cap and collection funnel. Specifically, a membrane filter with a pore size of 1 μm was first placed in a stainless steel test tube, and then the PPS resin pressed into a film approximately 80 μm thick and 20 times the mass of 1-chloronaphthalene were weighed and sealed. This was then placed in a high-temperature filtration apparatus at 250°C and heated and shaken for 5 minutes. Next, an air-filled syringe was connected to the pneumatic cap, and the syringe piston was pushed out to perform hot filtration using pneumatic pressure. The residue amount was determined by calculating the difference between the mass of the membrane filter before filtration and the mass of the membrane filter vacuum-dried at 150°C for 1 hour relative to the charged mass of the pressed PPS resin.

[0054] (B) Elastomer The polyphenylene sulfide resin composition used in the present invention contains an elastomer (B). The lower limit of the amount of the elastomer (B) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and most preferably 6 parts by mass or more, per 100 parts by mass of the polyphenylene sulfide resin (A) from the viewpoint of improving toughness and thermal shock resistance after immersion in a cooling medium. The upper limit is preferably less than 20 parts by mass, more preferably 14 parts by mass or less, and most preferably 10 parts by mass or less, per 100 parts by mass of the polyphenylene sulfide resin (A) from the viewpoint of flame retardancy.

[0055] In the present invention, it is desirable to blend (B-1) an olefin copolymer having an epoxy group as the elastomer (B) from the viewpoint of resistance to cold and thermal shock after immersion in a cooling medium.

[0056] Examples of the olefin copolymer (B-1) having an epoxy group include a (co)polymer obtained by polymerizing an α-olefin such as ethylene, propylene, 1-butene, 1-pentene, 1-octene, 4-methyl-1-pentene, or isobutylene, or by polymerizing two or more of these α-olefins; a copolymer of an α-olefin with an α,β-unsaturated acid or an alkyl ester thereof, such as acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, or butyl methacrylate; and copolymers obtained by introducing a monomer component having an epoxy group (a functional group-containing component) into such copolymers. Examples of functional group-containing components include epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, glycidyl itaconate, and glycidyl citraconate. The method for introducing these functional group-containing components is not particularly limited, and methods such as copolymerization during copolymerization of an olefin (co)polymer or grafting into an olefin (co)polymer using a radical initiator can be used. Particularly useful examples of olefin copolymers having epoxy groups obtained by introducing a functional group-containing component into an olefin (co)polymer include ethylene / propylene-g-glycidyl methacrylate copolymer ("g" represents graft, the same applies hereinafter), ethylene / 1-butene-g-glycidyl methacrylate copolymer, ethylene / glycidyl acrylate copolymer, ethylene / glycidyl methacrylate copolymer, ethylene / methyl acrylate / glycidyl methacrylate copolymer, and ethylene / methyl methacrylate / glycidyl methacrylate copolymer. Alternatively, epoxy group-containing olefin copolymers containing other monomers as essential components in addition to an α-olefin such as ethylene or propylene and a glycidyl ester of an α,β-unsaturated acid can also be suitably used.

[0057] Among the (B-1) olefin copolymers having epoxy groups, from the viewpoints of improving toughness and resistance to thermal shock after immersion in a cooling medium, preferred are olefin copolymers containing a structure derived from a glycidyl ester of an α,β-unsaturated acid, and more preferred are ethylene / methyl acrylate / glycidyl methacrylate copolymers.

[0058] The lower limit of the blending amount of the olefin copolymer having epoxy groups (B-1) is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the polyphenylene sulfide resin (A) from the viewpoint of obtaining thermal shock resistance after immersion treatment in a cooling medium. The upper limit of the blending amount of the olefin copolymer having epoxy groups (B-1) is preferably less than 9 parts by mass, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the polyphenylene sulfide resin (A) from the viewpoint of obtaining flame retardancy.

[0059] Furthermore, it is preferable to use, as the elastomer (B), a combination of an olefin copolymer (B-1) having an epoxy group and an elastomer (B-2) having no polar functional group in order to obtain excellent moldability and even better thermal shock resistance. Although there are no particular restrictions on the ratio between these, a mass ratio of (B-1) / (B-2) of 5 / 95 to 95 / 5 is preferred, in terms of the amount of each compounded relative to 100 parts by mass of the polyphenylene sulfide resin (A), and a range of (B-1) / (B-2) of 10 / 90 to 90 / 10 is more preferred, as this provides an excellent balance between moldability and thermal shock resistance after immersion in a cooling medium.

[0060] On the other hand, as the elastomer (B-2) having no polar functional group, a copolymer similar to the olefin copolymer constituting the olefin copolymer having an epoxy group (B-1) is preferred, and among them, an ethylene / butyl acrylate copolymer is preferred from the viewpoint of resistance to thermal shock after immersion in a cooling medium.

[0061] (C) Fibrous Filler The polyphenylene sulfide resin composition used in the present invention contains (C) a fibrous filler. Examples of (C) a fibrous filler include glass fiber, milled glass fiber, carbon fiber, modified cross-section glass fiber, cut glass fiber, stainless steel fiber, metal fibers such as aluminum fiber and brass fiber, organic fibers such as aromatic polyamide fiber and Kevlar (registered trademark) fibril, gypsum fiber, ceramic fiber, asbestos fiber, zirconia fiber, alumina fiber, silica fiber, titanium oxide fiber, silicon carbide fiber, carbon nanotube, carbon nanohorn, and cellulose nanofiber.

[0062] Among the (C) fibrous fillers, it is preferable to use at least one selected from glass fiber and irregular cross-section glass fiber in terms of mechanical strength and thermal shock resistance after immersion in a cooling medium. Among them, irregular cross-section glass fiber is most preferable because it reduces the MD / TD ratio, which is the ratio of the tensile strength in the resin flow direction (MD) to the tensile strength in the direction perpendicular to the resin flow direction (TD), in a molded product, thereby suppressing the anisotropy of strength during thermal shock, thereby providing excellent thermal shock resistance after immersion in a cooling medium. The irregular cross-section glass fiber is a glass fiber having a flat cross-section, and in the cross-section when the glass fiber is cut perpendicular to the length, the ratio of the major axis (the longest linear distance in the cross-section) to the minor axis (the longest linear distance perpendicular to the major axis) (major axis / minor axis, hereinafter sometimes abbreviated as "flatness") is preferably 1.3 or more and 10 or less. It is preferably 1.5 or more and 7 or less, and more preferably 1.5 or more and 5 or less. When the aspect ratio is 1.3 or more, the resin composition has good resistance to cold and thermal shock, and when it is 10 or less, the resin composition has good mechanical strength. The aspect ratio is a value determined by observing 50 randomly selected glass fibers with a scanning electron microscope, measuring the major axis and minor axis of the cross section, calculating the ratio, and calculating the number average.

[0063] The fibrous filler (C) used in the present invention is preferably treated with a sizing agent or a surface treatment agent. Examples of the sizing agent or surface treatment agent include functional compounds such as epoxy compounds, isocyanate compounds, silane compounds, and titanate compounds. Epoxy compounds with a high epoxy content are particularly preferred from the viewpoints of improving the reactivity of the fibrous filler and suppressing a decrease in strength due to immersion in a cooling medium.

[0064] In the present invention, the lower limit of the amount of the fibrous filler (C) to be blended is preferably 60 parts by mass or more, more preferably more than 80 parts by mass, and most preferably 100 parts by mass or more, relative to 100 parts by mass of the polyphenylene sulfide resin (A) from the viewpoint of mechanical strength and resistance to thermal shock after immersion in a cooling medium. The upper limit is preferably 150 parts by mass or less, more preferably 130 parts by mass or less, relative to 100 parts by mass of the polyphenylene sulfide resin (A) from the viewpoint of flame retardancy.

[0065] (D) Non-fibrous Filler The polyphenylene sulfide resin composition used in the present invention contains (D) a non-fibrous filler. Examples of (D) non-fibrous fillers include fullerene, talc, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, 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, glass beads, glass flakes, glass powder, ceramic beads, boron nitride, silicon carbide, carbon black, silica, and graphite. These may be hollow, and two or more of these non-fibrous fillers may be used in combination. These non-fibrous fillers may also be used after being pretreated 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.

[0066] Among these, calcium carbonate is preferred from the viewpoint of mechanical strength and resistance to thermal shock after immersion in a cooling medium.

[0067] The lower limit of the amount of the non-fibrous filler (D) used in the present invention is preferably 40 parts by mass or more, more preferably 60 parts by mass or more, relative to 100 parts by mass of the polyphenylene sulfide resin (A) from the viewpoints of flame retardancy and tracking resistance, and the upper limit is preferably 140 parts by mass or less, more preferably 110 parts by mass or less, relative to 100 parts by mass of the polyphenylene sulfide resin (A) from the viewpoints of mechanical strength and thermal shock resistance after immersion in a cooling medium.

[0068] [Other Additives] Furthermore, a silane-based compound may be optionally added to the PPS resin composition used in the present invention for the purpose of improving mechanical strength, toughness, etc., within the range that does not impair the effects of the present invention. Examples of silane compounds include isocyanate group-containing alkoxysilane compounds such as γ-isocyanate propyl triethoxysilane, γ-isocyanate propyl trimethoxysilane, γ-isocyanate propyl methyl dimethoxysilane, γ-isocyanate propyl methyl diethoxysilane, γ-isocyanate propyl ethyl dimethoxysilane, γ-isocyanate propyl ethyl diethoxysilane, and γ-isocyanate propyl trichlorosilane; epoxy group-containing alkoxysilane compounds such as γ-glycidoxypropyl trimethoxysilane, γ-glycidoxypropyl triethoxysilane, and β-(3,4-epoxycyclohexyl)ethyl trimethoxysilane; amino group-containing alkoxysilane compounds such as γ-(2-aminoethyl)aminopropyl methyl dimethoxysilane, γ-(2-aminoethyl)aminopropyl trimethoxysilane, and γ-aminopropyl trimethoxysilane; and silane compounds such as modified silicone oils having epoxy groups, amino groups, isocyanate groups, and hydroxyl groups. Among these, alkoxysilanes having an epoxy group, an amino group, an isocyanate group, or a hydroxyl group are particularly suitable for achieving excellent mechanical strength and resistance to cold and thermal shock. The preferred amount of such silane compounds to be added is preferably selected from the range of 0.05 to 3 parts by mass per 100 parts by mass of the PPS resin (A).

[0069] Furthermore, the PPS resin composition used in the present invention may be blended with other resins as long as the effects of the present invention are not impaired. There are no particular restrictions on the resins that can be blended, but specific examples include polyamide, polyethylene terephthalate, polyether ether ketone resin, and vinyl aromatic compound-based block copolymers.

[0070] Furthermore, in order to maintain high heat resistance and thermal stability, the PPS resin composition of the present invention preferably contains one or more antioxidants selected from phenolic compounds and phosphorus-based compounds, within a range that does not impair the effects of the present invention. The amount of such antioxidant added is preferably 0.01 parts by mass or more, particularly 0.02 parts by mass or more, per 100 parts by mass of the PPS resin (A) from the viewpoint of improving heat resistance, and is preferably 5 parts by mass or less, particularly 1 part by mass or less, from the viewpoint of reducing gas components generated during molding. Furthermore, using a phenolic antioxidant and a phosphorus-based antioxidant in combination is particularly effective in maintaining heat resistance and thermal stability, and is therefore preferred.

[0071] [Method for Preparing PPS Resin Composition] The method for preparing the PPS resin composition of the present invention is not particularly limited. Representative examples include feeding the raw materials to a commonly known melt mixer, such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a mixing roll, and kneading them at a temperature of 280 to 380°C. The order in which the raw materials are mixed is also not particularly limited. Any of the following methods may be used: blending all the raw materials and then melt-kneading them using the method described above; blending some of the raw materials and then melt-kneading them using the method described above, followed by blending and melt-kneading the remaining raw materials; or blending some of the raw materials and then melt-kneading them using a side feeder while melt-kneading them in a single-screw or twin-screw extruder. Furthermore, minor additive components can be added to the mixture before molding after the other components have been kneaded and pelletized using the method described above.

[0072] The PPS resin composition of the present invention thus obtained can be subjected to various molding processes such as injection molding, extrusion molding, blow molding and transfer molding, but is particularly suitable for injection molding.

[0073] [Molded Article Made of PPS Resin Composition] The tensile modulus of a molded article made of the PPS resin composition of the present invention, measured in accordance with ISO 527-1, -2 (2012), must be 10 GPa or more and 21 GPa or less. This makes the molded article of the PPS resin composition, even one that has been immersed in a cooling medium, excellent in resistance to cold and thermal shock, and applicable to products with complex shapes that are prone to cracking, such as motor parts.

[0074] The lower limit of the tensile modulus must be 10 GPa or more, preferably 12 GPa or more, and more preferably 16 GPa or more. If it is less than 10 GPa, the rigidity is likely to decrease during immersion in a cooling medium, and the difference in linear expansion coefficient with the metal is likely to increase, leading to a decrease in thermal shock resistance after immersion in a cooling medium. The upper limit of the tensile modulus must be 21 GPa or less, preferably 20 GPa or less. If it exceeds 21 GPa, the toughness after immersion in a cooling medium is not excellent and the thermal shock resistance is deteriorated.

[0075] The tensile modulus of a molded article made from the PPS resin composition of the present invention can be made 10 GPa or more by blending (C) a fibrous filler or (D) a non-fibrous filler, which has a high effect of increasing rigidity, with (A) the PPS resin, or by reducing the blending amount of a highly flexible thermoplastic resin other than (A) the PPS resin. The tensile modulus of a molded article made from the PPS resin composition of the present invention can be made 21 GPa or less by blending (B) an elastomer, which has a low tensile modulus, with (A) the PPS resin, or by not blending too much of the (C) a fibrous filler or (D) a non-fibrous filler, which has high rigidity.

[0076] In a molded article made from the PPS resin composition of the present invention, if the tensile strength in the direction of resin flow is defined as MD and the tensile strength in the direction perpendicular to the direction of resin flow is defined as TD, then MD must be 70 MPa or more, and the ratio of MD to TD, MD / TD, must be 1.4 or less. This allows the tensile strength to be maintained at a high level even after immersion in a cooling medium, and by reducing MD / TD and suppressing the anisotropy of strength during thermal shock, the cooling medium is less likely to penetrate between the metal and the resin even after immersion in the cooling medium, resulting in excellent resistance to thermal shock.

[0077] The lower limit of MD must be 70 MPa or more, and preferably 80 MPa or more. If it is less than 70 MPa, the tensile strength after immersion in a cooling medium decreases, resulting in a decrease in thermal shock resistance after immersion in a cooling medium. There is no particular upper limit for MD, and the higher the upper limit after immersion in a cooling medium, the better the thermal shock resistance.

[0078] The lower limit of TD is preferably 60 MPa or more, more preferably 80 MPa or more. By setting it to 60 MPa or more, a decrease in tensile strength after immersion in a cooling medium can be suppressed, and thermal shock resistance after immersion in a cooling medium can be maintained, which is preferable.

[0079] There is no particular limit to the lower limit of MD / TD, which is the ratio of MD to TD. In general molded products, MD tends to be larger than TD, but TD may be larger than MD when the molded product is thick and the orientation of the glass fibers is likely to be random. In practice, the lower limit of MD / TD is preferably 0.7 or more. The upper limit of MD / TD must be 1.4 or less, and preferably 1.2 or less. If MD / TD is greater than 1.4, the anisotropy of strength during thermal shock increases, making it easier for the cooling medium to penetrate between the metal and the resin after immersion in the cooling medium, resulting in reduced thermal shock resistance. Furthermore, the closer MD / TD is to 1, the more preferable it is, with 1 being most preferable. If MD / TD is 1, it can be determined that there is no anisotropy.

[0080] Achieving an MD of 70 MPa or more is possible by blending (A) a fibrous filler (C) that is highly effective in increasing mechanical strength with the PPS resin, by not blending too much thermoplastic resin with weak mechanical strength other than the PPS resin (A), or by using (D) a non-fibrous filler such as calcium carbonate that does not impair mechanical strength.

[0081] The reason for the increased MD / TD is that blending (C) fibrous filler with (A) PPS resin makes it easier for the fibrous filler to orient in the direction of resin flow, but not blending (C) fibrous filler reduces mechanical strength. Achieving an MD / TD ratio of 1.4 or less can be achieved by using (D) a non-fibrous filler with a small irregularity ratio, such as calcium carbonate, in addition to (C) fibrous filler with (A) PPS resin, by not blending too much (C) fibrous filler, which causes increased anisotropy, or by using a fibrous filler with a high anisotropy-suppressing effect, such as irregular cross-section glass fiber, as the (C) fibrous filler.

[0082] In the present invention, a molded article made of the polyphenylene sulfide resin composition has been found to have an unknown attribute of excellent resistance to cold and thermal shock even after being immersed in a cooling medium and heat-treated, and it has also been found that a molded article made of such a PPS resin composition can be used in a new application, such as a motor part that uses a cooling medium.

[0083] The present invention also provides a method for molding a PPS resin composition containing a PPS resin, an elastomer, a fibrous filler, and a non-fibrous filler into a molded article, wherein the molded article has a tensile modulus of elasticity of 10 GPa or more and 21 GPa or less, and, where the tensile strength in the direction of resin flow in the molded article is defined as MD and the tensile strength in the direction perpendicular to the direction of resin flow in TD, the MD has a tensile strength of 70 MPa or more and the ratio of MD to TD, MD / TD, is 1.4 or less. The method is for forming a motor component that uses a cooling medium.

[0084] [Cooling Medium] The cooling medium used for motor components is important for preventing a decrease in motor life and improving motor drive efficiency by cooling the motor. The cooling medium used for motor components in the present invention preferably contains at least one selected from the group consisting of long-life coolant (LLC), ethylene glycol, oil, and water, and is more preferably oil. The oil used as the cooling medium may also contain unintentional water contamination. Oil has a higher volume resistivity than long-life coolant (LLC) or water and offers excellent insulation properties. In particular, EV cooling oils have superior insulation properties and metal corrosion prevention compared to conventional ATF oils. Therefore, they can be used to cool not only drive motors but also batteries and inverters, reducing the number of cooling mediums required, simplifying heat management, and reducing the number of parts, thereby enabling weight reduction. Oils with a resistivity of 30 MΩ·m or higher measured at 90°C in accordance with IEC 60247 are preferred because they have excellent insulation properties and suppress deterioration of motor components. Furthermore, oils with a thermal conductivity of 0.1 W / m·K or higher, measured in an 80°C environment according to ASTM D2717, are preferred because they can efficiently cool components. Among these, e-Axle-specific oils developed specifically for e-Axles are preferred. Commercially available EV oils include those available from Castrol under the trade name BOT805C EV. Compared to general ATF oils, these have lower viscosity and better fluidity, making them capable of more effectively improving motor cooling performance and offering excellent corrosion resistance and insulating properties for copper components.

[0085] As a heat treatment method after immersion in the cooling medium, it is desirable to endure a durability test of 2000 hours in an environment of 150°C, which is the upper limit temperature to which motor parts can be exposed.

[0086] Molded articles made from the PPS resin composition of the present invention preferably have excellent thermal shock resistance in thin-walled and corner sections after immersion in a cooling medium. In thin-walled and corner sections, stress generated by the difference in linear expansion coefficients between the resin and the metal tends to concentrate during thermal shock resistance tests. Furthermore, the cooling medium tends to penetrate between the resin and the metal, resulting in poor thermal shock resistance after immersion in a cooling medium. Molded articles made from a PPS resin composition that have excellent thermal shock resistance in thin-walled and corner sections after immersion in a cooling medium can also be used in motor parts used in environments with a wide temperature range from low to high temperatures, as well as motor parts that include thin-walled sections designed for weight reduction. To achieve excellent thermal shock resistance in thin-walled and corner sections after immersion in a cooling medium, the molded article must be made from the polyphenylene sulfide resin composition of the present invention. This prevents the decrease in strength due to immersion in a cooling medium, and also suppresses the anisotropy of strength during thermal shock, making it difficult for the cooling medium to penetrate between the metal and resin even after immersion in the cooling medium, resulting in excellent resistance to thermal shock.

[0087] The flame retardancy of a molded article made from the PPS resin composition of the present invention after immersion in a cooling medium, i.e., the flame retardancy measured in accordance with UL94, is preferably V-0 for test specimens with a thickness of 0.7 mmt or less. This makes the molded article made from the PPS resin composition applicable to motor parts that require flame retardancy and that come into contact with a cooling medium, including thin-walled parts for the purpose of weight reduction. In order to achieve a V-0 flame retardancy after immersion in a cooling medium for test specimens with a thickness of 0.7 mmt or less, this can be achieved by increasing the amount of the non-combustible component (D) non-fibrous filler or by reducing the amount of the combustible component (B) elastomer. However, it is desirable to do so to an extent that does not reduce thermal shock resistance after immersion in a cooling medium.

[0088] Molded articles made from the PPS resin composition of the present invention preferably have a tracking resistance of 175 V or more after immersion in a cooling medium, i.e., a tracking resistance measured in accordance with IEC 60112 (2003). IEC 60664 states that for products such as automotive parts, materials with a tracking resistance of less than 175 V are undesirable (and should be considered for use in contamination level 3 locations in product usage environments where the rated voltage of the product exceeds 630 V). Therefore, molded articles made from resin compositions with a tracking resistance of 175 V or more after immersion in a cooling medium can also be used for motor parts that are subjected to high voltage and come into contact with the cooling medium. A tracking resistance of 175 V or more after immersion in a cooling medium can be achieved by reducing the amount of polyphenylene sulfide resin, which inherently has low tracking resistance, and incorporating a large amount of (C) fibrous filler or (D) non-fibrous inorganic filler. However, it is desirable to achieve a level that does not reduce thermal shock resistance after immersion in a cooling medium.

[0089] The present invention also relates to the use of a molded article obtained by molding a PPS resin composition comprising a PPS resin, an elastomer, a fibrous filler, and a non-fibrous filler, the molded article having a tensile modulus of elasticity of 10 GPa or more and 21 GPa or less, and, where the tensile strength in the direction of resin flow in the molded article is defined as MD and the tensile strength in the direction perpendicular to the direction of resin flow in TD, the MD is 70 MPa or more and the ratio of MD to TD, MD / TD, is 1.4 or less, for a motor part that uses a cooling medium.

[0090] Molded articles made from the PPS resin composition of the present invention exhibit excellent resistance to cold and thermal shock after immersion in a cooling medium, making them suitable for use in motor parts that use cooling mediums and can be used in harsh environments where they come into contact with the cooling medium. Examples of motor parts suitable for use in motor parts that use a cooling medium selected from the group consisting of stators, rotors, slip rings, current sensors, bus bars, rotation angle sensors, piping through which the cooling medium passes, and components for spraying the cooling medium. In particular, because of their excellent resistance to cold and thermal shock after immersion in a cooling medium, they are suitable for use in motor parts with metal inserts. Furthermore, as motor parts aimed at weight reduction, molded articles made from the PPS resin composition are suitable for use in motor parts in which the thinnest portion is 0.7 mm or less.

[0091] Examples of applications to which molded articles made from the PPS resin composition of the present invention can be applied include electrical and electronic parts such as sensors, LED lamps, consumer connectors, sockets, resistors, relay cases, switches, coil bobbins, capacitors, variable capacitor cases, oscillators, various terminal boards, transformers, plugs, printed circuit boards, tuners, speakers, microphones, headphones, small motors, magnetic head bases, semiconductors, liquid crystal displays, FDD carriages, FDD chassis, motor brush holders, parabolic antennas, and computer-related parts; and parts for household and office electrical appliances such as VTR parts, television parts, irons, hair dryers, rice cooker parts, microwave oven parts, acoustic parts, audio equipment parts such as audio equipment, laser discs (registered trademark), and compact discs; lighting parts, refrigerator parts, air conditioner parts, typewriter parts, and word processor parts.Other products include office computer parts, telephone parts, facsimile parts, copier parts, cleaning tools, lighters, typewriters, and other machinery-related parts; optical equipment and precision machinery parts such as microscopes, binoculars, cameras, and clocks; plumbing parts such as water faucet tops, mixer taps, pump parts, pipe joints, water flow control valves, relief valves, hot water temperature sensors, water flow sensors, and water meter housings; valves, alternator terminals, alternator connectors, IC regulators, light dimmer potentiometer bases, various valves such as exhaust gas valves, various pipes for fuel, exhaust, and intake systems, air intake nozzles, snorkels, intake manifolds, fuel pumps, engine coolant joints, carburetor main bodies, carburetor spacers, exhaust gas sensors, coolant sensors, oil temperature sensors, and throttle position sensors. Preferred examples of the applications include automobile and vehicle-related parts such as sensors, crankshaft position sensors, air flow meters, brake pad wear sensors, air conditioner thermostat bases, heating hot air flow control valves, brush holders for radiator motors, water pump impellers, water pump housings, engine cooling modules, 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 insulating plates, lamp sockets, lamp reflectors, lamp housings, brake pistons, solenoid bobbins, engine oil filters, ignition device cases, vehicle speed sensors, and cable liners.

[0092] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to the descriptions of these examples.

[0093] [Methods for evaluating PPS resins produced in Reference Examples] (1) Melt flow rate (MFR) Measurement was carried out at a temperature of 315.5° C. under a load of 5000 g in accordance with a method in accordance with ASTM-D1238-70.

[0094] (2) Residue Amount A pre-weighed PTFE membrane filter with a pore size of 1 μm was placed in a Senshu Scientific SUS test tube equipped with a pneumatic cap and collection funnel. 100 mg of PPS resin pressed into a film approximately 80 μm thick and 2 g of 1-chloronaphthalene were weighed and then sealed. This was inserted into a Senshu Scientific SSC-9300 high-temperature filtration device and heated and shaken at 250°C for 5 minutes to dissolve the PPS resin in 1-chloronaphthalene. A 20 mL syringe containing air was connected to the pneumatic cap, and the piston was pushed out to filter the solution through the membrane filter. The membrane filter was removed, vacuum dried at 150°C for 1 hour, and then weighed. The residue amount (% by mass) was determined as the difference between the mass of the membrane filter before and after filtration relative to the charged mass of the pressed PPS resin.

[0095] Reference Example: Preparation of PPS A 70-liter autoclave equipped with a stirrer and a bottom stop valve was charged with 8.27 kg (70.00 mol) of 47.5% sodium hydrosulfide, 2.91 kg (69.80 mol) of 96% sodium hydroxide, 11.45 kg (115.50 mol) of N-methyl-2-pyrrolidone (NMP), 1.89 kg (23.10 mol) of sodium acetate, and 10.5 kg of ion-exchanged water. The mixture was gradually heated to 245°C over approximately 3 hours under atmospheric pressure while passing nitrogen through it. 14.78 kg of water and 0.28 kg of NMP were distilled off, and the reaction vessel was then 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 released was 0.02 mol per mole of charged alkali metal sulfide.

[0096] The mixture was then cooled to 200°C, and 10.45 kg (71.07 mol) of p-dichlorobenzene and 9.37 kg (94.50 mol) of NMP were added. The reaction vessel was sealed under nitrogen gas and heated from 200°C to 270°C at a rate of 0.6°C / min while stirring at 240 rpm. After reacting at 270°C for 100 minutes, the bottom stopper valve of the autoclave was opened, and the contents were flushed into a vessel equipped with a stirrer over 15 minutes while pressurizing with nitrogen, and the mixture was stirred for a while at 250°C to remove most of the NMP.

[0097] The obtained solid and 76 liters of ion-exchanged water were placed in an autoclave equipped with a stirrer, washed at 70°C for 30 minutes, and then suction-filtered through a glass filter. Next, 76 liters of ion-exchanged water heated to 70°C was poured into the glass filter and suction-filtered to obtain a cake.

[0098] The obtained cake and 90 liters of ion-exchanged water were charged into an autoclave equipped with a stirrer, and acetic acid was added to adjust the pH to 7. After the inside of the autoclave was purged with nitrogen, the temperature was raised to 192°C and maintained at that temperature for 30 minutes. Thereafter, the autoclave was cooled, and the contents were removed.

[0099] The contents were filtered with a glass filter under suction, and then 76 liters of ion-exchanged water at 70°C was poured into the filter and filtered under suction to obtain a cake. The obtained cake was dried at 120°C under a nitrogen stream to obtain a dried PPS.

[0100] The obtained PPS had an MFR of 600 g / 10 min and a residue amount of 0.7% by mass.

[0101] The raw materials used in the examples and comparative examples are shown below.

[0102] (A) PPS Resin PPS-1: A PPS resin polymerized by the method described in Reference Example was subjected to thermal oxidation treatment at an oxygen concentration of 2% at 220°C for 12 hours. The resulting PPS had an MFR of 400 g / 10 min and a residue amount of 1.9% by mass.

[0103] (B) Elastomer B-1: Ethylene-glycidyl methacrylate-methyl acrylate copolymer (Bondfast 7M manufactured by Sumitomo Chemical Co., Ltd., 67% by mass of ethylene, 6% by mass of glycidyl methacrylate, 27% by mass of methyl acrylate).

[0104] B-2: Ethylene / n-butyl acrylate copolymer (Lotril 35BA40 manufactured by Arkema K.K.).

[0105] (C) Fibrous Filler C-1: irregular cross section glass fiber (T-760FGF, flatness 4, manufactured by Nippon Electric Glass Co., Ltd.).

[0106] C-2: Circular cross section glass fiber (T-760H manufactured by Nippon Electric Glass Co., Ltd., aspect ratio 1).

[0107] (D) Non-fibrous filler D-1: heavy calcium carbonate (Escalon #800 manufactured by Sankyo Flour Milling Co., Ltd.).

[0108] D-2: Magnesium hydroxide (KISUMA5EU manufactured by Kyowa Chemical Industry Co., Ltd.).

[0109] [Methods for measuring and evaluating molded articles made from resin compositions] The methods for measuring and evaluating the molded articles in the present examples and comparative examples are as follows.

[0110] (1) Tensile modulus The resin composition pellets were fed into an injection molding machine (SE-50D) manufactured by Sumitomo Heavy Industries, Ltd., set at a cylinder temperature of 310 ° C. and a mold temperature of 145 ° C., and injection molded using a mold having a type A1 test piece shape as specified in ISO 20753 (2008) under conditions of a filling time of 0.8 s and a holding pressure of 75% of the filling pressure to obtain a test piece for evaluation. After conditioning this test piece for 16 hours under conditions of 23 ° C. and 50% relative humidity, the tensile modulus was measured in accordance with ISO 527-1, -2 (2012) under conditions of an atmosphere of 23 ° C. and 50% relative humidity, a gripper distance of 115 mm, and a test speed of 5 mm / min.

[0111] (2) Tensile strength in the flow direction (MD), tensile strength perpendicular to the flow direction (TD) The resin composition pellets were fed into an injection molding machine (SE50DUZ-C160) manufactured by Sumitomo Heavy Industries, Ltd., with a cylinder temperature of 320 ° C. and a mold temperature of 130 ° C., and injection molded using a mold for a square plate (80 mm × 80 mm × 3.0 mmt) under conditions of a filling time of 0.5 s and a holding pressure of 50% of the filling pressure to obtain a square plate (80 mm × 80 mm × 3.0 mmt). This square plate was cut into a Type 3 shape as defined in ISO 8256 so that the long sides were in the flow direction (injection direction) and the direction perpendicular to the flow direction, and used as test pieces for measuring the tensile strength in the flow direction (MD) and the tensile strength perpendicular to the flow direction (TD). The test piece was conditioned for 16 hours at 23°C and a relative humidity of 50%, and then the tensile strength was measured in an atmosphere of 23°C and a relative humidity of 50%, with a gauge length of 10 mm and a test speed of 1 mm / min.

[0112] (3) Thermal Shock Resistance After LLC Immersion Treatment The resin composition pellets were fed into an injection molding machine (SE-50DUZ) manufactured by Sumitomo Heavy Industries, Ltd., with a cylinder temperature of 320 ° C. and a mold temperature of 130 ° C. A metal block (carbon steel S45C) was set in the mold and injection molded under the conditions of an injection speed of 100 mm / s, an injection pressure of 5 MPa added to the injection pressure when filled to the tip of the test piece, and an injection time of 12 s, to obtain the metal insert test piece shown in Figure 1. This test piece was immersed in a 50% by mass aqueous solution of Toyota genuine S-LLC diluted with distilled water in a pressure-resistant container and subjected to a heat treatment of 150 ° C. x 2000 hours. The test piece after LLC immersion treatment was subjected to a thermal shock treatment consisting of 130 ° C. x 1 hour treatment followed by -40 ° C. x 1 hour treatment, which constituted one cycle. The presence or absence of cracks was visually confirmed every 10 cycles. This test specimen is thin, with a thickness of 0.6 mm at its thinnest point, and is prone to stress concentration at the corners, so it was designed to simulate the thermal shock resistance of the thin-walled and corner parts. The thermal shock resistance was evaluated based on the number of cycles at which cracks were observed. If cracks did not occur for 100 cycles or more, it can be said that the product is at a level that is acceptable for practical use, but the more cycles until cracks occur, the better the thermal shock resistance and the more preferable it is.

[0113] (4) Thermal shock resistance after oil immersion treatment The resin composition pellets were fed into an injection molding machine (SE-50DUZ) manufactured by Sumitomo Heavy Industries, Ltd., set at a cylinder temperature of 320 ° C. and a mold temperature of 130 ° C. A metal block (carbon steel S45C) was set in the mold, and injection molding was performed under the conditions of an injection speed of 100 mm / s, an injection pressure of 5 MPa added to the injection pressure when filled to the tip of the test piece, and an injection time of 12 s, to obtain a metal insert test piece for evaluation as shown in FIG. 1. This test piece was immersed in EV cooling oil (CASTROL BOT805C EV) in a pressure-resistant container and subjected to a heat treatment of 150 ° C. × 2000 hours. The test piece after oil immersion treatment was subjected to a thermal shock treatment, with one cycle consisting of a 130 ° C. × 1 hour treatment followed by a -40 ° C. × 1 hour treatment, and the presence or absence of cracks was confirmed visually every 10 cycles. This test specimen is thin, with a thickness of 0.6 mm at its thinnest point, and is prone to stress concentration at the corners, so it was designed to simulate the thermal shock resistance of the thin-walled and corner parts. The thermal shock resistance was evaluated based on the number of cycles at which cracks were observed. If cracks did not occur for 100 cycles or more, it can be said that the product is at a level that is acceptable for practical use, but the more cycles until cracks occur, the better the thermal shock resistance and the more preferable it is.

[0114] (5) Flame retardancy after oil immersion treatment The resin composition pellets were fed into an injection molding machine (SE-50D) manufactured by Sumitomo Heavy Industries, Ltd., set at a cylinder temperature of 320 ° C. and a mold temperature of 145 ° C., and injection molding was performed using a mold having a UL test piece shape specified in UL94 under the conditions of an injection speed of 120 mm / s, an injection pressure of 5 MPa added to the injection pressure when filled to the tip of the test piece, an injection time of 8 s, and a cooling time of 10 s to obtain a test piece for evaluation. This test piece was immersed in EV cooling oil (CASTROL BOT805C EV) in a pressure-resistant container and subjected to a heat treatment of 150 ° C. x 2000 hours. The flame retardancy was evaluated in accordance with the UL94 vertical test using the test piece after oil immersion treatment. Flame retardancy is ranked in descending order of V-0 > V-1 > V-2, and those that do not meet V-2 are indicated as V-out. The test piece used is 0.7 mm thick, and it is preferable that a test piece thickness of 0.7 mm or less shows V-0.

[0115] (6) Tracking Resistance After Oil Immersion Treatment The resin composition pellets were fed into an injection molding machine (SE50DUZ-C160) manufactured by Sumitomo Heavy Industries, Ltd., with a cylinder temperature of 320 ° C and a mold temperature of 130 ° C., and injection molded using a mold for a square plate (80 mm x 80 mm x 3.0 mmt) under conditions of a filling time of 0.5 s and a holding pressure of 50% of the filling pressure to obtain a square plate (80 mm x 80 mm x 3.0 mmt). This test piece was immersed in EV cooling oil (CASTROL BOT805C EV) in a pressure-resistant container and subjected to a heat treatment of 150 ° C x 2000 hours. Using the test piece after oil immersion treatment, the maximum voltage at which tracking breakdown did not occur was measured in accordance with IEC 60112 (2003). A 0.1% aqueous ammonium chloride solution was used as the electrolyte. The higher this maximum voltage, the better the tracking resistance, with 175 V or higher being preferred.

[0116] Examples 1 to 6, Comparative Examples 1 to 7 Using a twin-screw extruder (TEM-26SS, manufactured by Toshiba Machine Co., Ltd.) with a 26 mm diameter intermediate addition port and a cylinder temperature set to 320°C and a screw rotation speed set to 400 rpm, (B) elastomer and (D) non-fibrous filler were added to 100 parts by mass of (A) PPS resin through the raw material supply port in the mass ratios shown in Tables 1 and 2 to form a molten state, and (C) fibrous filler was supplied through the intermediate addition port in the mass ratio shown in Tables 1 and 2, followed by melt-kneading at a discharge rate of 30 kg / hour to obtain PPS resin composition pellets. The PPS resin composition pellets were used to evaluate the above-mentioned properties. The results are shown in Tables 1 and 2.

[0117]

[0118]

[0119] In Examples 1 to 6, the components (A) to (D) were blended, and the molded articles had a tensile modulus of elasticity of 10 GPa or more and 21 GPa or less, and when the tensile strength of the resin in the molded article in the flow direction is defined as MD and the tensile strength in the direction perpendicular to the flow direction is defined as TD, the MD was 70 MPa or more and the MD / TD was 1.4 or less. This meant that the molded articles had excellent resistance to thermal shock (100 cycles or more) after being immersed in a refrigerant and heat-treated, and were therefore suitable for motor parts that use a cooling medium.

[0120] From Comparative Examples 1 and 3, it was found that when MD / TD was greater than 1.4, the thermal shock resistance after heat treatment by immersion in a refrigerant was poor.

[0121] From Comparative Example 2, it was found that when the tensile modulus was greater than 21 GPa and the MD / TD ratio was greater than 1.4, the thermal shock resistance after heat treatment by immersion in a refrigerant was poor.

[0122] From Comparative Example 4, it was found that when the tensile modulus was less than 10 GPa and the MD was less than 70 MPa, the thermal shock resistance after heat treatment by immersion in a refrigerant was poor.

[0123] From Comparative Example 5, it was found that when MD was less than 70 MPa and MD / TD was greater than 1.4, the thermal shock resistance after heat treatment by immersion in a refrigerant was poor.

[0124] From Comparative Examples 6 and 7, it was found that when the MD was less than 70 MPa, the thermal shock resistance after immersion in a refrigerant and heat treatment was poor.

[0125] This resin exhibits excellent resistance to cold and thermal shock after immersion in a cooling medium without significantly compromising the excellent flame retardancy inherent to polyphenylene sulfide resin, making it suitable for motor parts that come into contact with the cooling medium, have metal inserts, and use cooling mediums, such as bus bars and current sensors.

[0126] 1. Insert metal 2. Gate 3. Metal insert molding

Claims

1. A motor part using a cooling medium, which is formed by molding a polyphenylene sulfide resin composition containing (A) polyphenylene sulfide resin, (B) an elastomer, (C) a fibrous filler, and (D) a non-fibrous filler, wherein the tensile modulus of a molded article made of said polyphenylene sulfide resin composition is 10 GPa or more and 21 GPa or less, and where the tensile strength in the direction of resin flow in said molded article is defined as MD and the tensile strength in the direction perpendicular to the direction of resin flow is defined as TD, then MD is 70 MPa or more and the ratio of MD to TD, MD / TD, is 1.4 or less.

2. A motor part using a cooling medium according to claim 1, wherein the polyphenylene sulfide resin composition is prepared by blending (B-1) an olefin copolymer having an epoxy group as the elastomer (B), and the polyphenylene sulfide resin composition is prepared by blending 0.1 parts by mass or more and less than 9 parts by mass of (B-1) an olefin copolymer having an epoxy group per 100 parts by mass of the polyphenylene sulfide resin (A).

3. A motor part using a cooling medium according to claim 1 or 2, wherein the polyphenylene sulfide resin composition is obtained by blending 60 parts by mass or more of (D) a non-fibrous filler with 100 parts by mass of (A) polyphenylene sulfide resin.

4. A motor component using a cooling medium according to claim 1 or 2, wherein the cooling medium includes at least one selected from the group consisting of long-life coolant (LLC), ethylene glycol, oil, and water.

5. A motor part using the cooling medium according to claim 1 or 2, wherein the molded article made of the polyphenylene sulfide resin composition is a molded article with a metal insert.

6. A motor component using the cooling medium according to claim 1 or 2, which is used in one selected from the group consisting of a stator, a rotor, a slip ring, a current sensor, a bus bar, a rotation angle sensor, a pipe through which the cooling medium passes, and a member for spraying the cooling medium.

7. A motor part using the cooling medium according to claim 1 or 2, wherein the thinnest part of the molded article made of the polyphenylene sulfide resin composition is 0.7 mm or less.

8. A motor part using the cooling medium according to claim 1 or 2, wherein the MD and TD of the molded article made of the polyphenylene sulfide resin composition are both 80 MPa or more.

9. A method for molding a polyphenylene sulfide resin composition containing (A) polyphenylene sulfide resin, (B) an elastomer, (C) a fibrous filler, and (D) a non-fibrous filler into a molded article, wherein the molded article has a tensile modulus of elasticity of 10 GPa or more and 21 GPa or less, and wherein the tensile strength in the direction of resin flow in the molded article is defined as MD and the tensile strength in the direction perpendicular to the direction of resin flow in the molded article is defined as TD, the MD is 70 MPa or more, and the ratio of MD to TD, MD / TD, is 1.4 or less.

10. Use of a molded article made by molding a polyphenylene sulfide resin composition containing (A) polyphenylene sulfide resin, (B) elastomer, (C) fibrous filler, and (D) non-fibrous filler, wherein the molded article has a tensile modulus of elasticity of 10 GPa or more and 21 GPa or less, and wherein the tensile strength in the direction of resin flow in the molded article is defined as MD and the tensile strength in the direction perpendicular to the direction of resin flow in TD, the MD is 70 MPa or more, and the ratio of MD to TD, MD / TD, is 1.4 or less, for a motor part that uses a cooling medium.

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