Polyphenylene sulfide resin composition and molded article thereof

Abstract

To provide a PPS resin composition which enables manufacture of a molded article that is excellent in mechanical characteristics and abrasion resistance under dry and liquid environments, and a molded article of the same.SOLUTION: A polyphenylene sulfide resin composition used for sliding applications contains a polyphenylene sulfide resin, a PAN-based carbon fiber having tensile strength of 3,000 MPa or more, and an isotropic pitch-based carbon fiber, wherein with respect to 100 pts.wt. of the polyphenylene sulfide resin, a content of the PAN-based carbon fiber having tensile strength of 3,000 MPa or more is 10-40 pts.wt. and a content of the isotropic pitch-based carbon fiber is 5-30 pts.wt., a content of the fluorine resin is 30 pts.wt. or less with respect to 100 pts.wt. of the polyphenylene sulfide resin, and the total of the contents of the isotropic pitch-based carbon fiber and the fluorine resin is 15-60 pts.wt. with respect to 100 pts.wt. of the polyphenylene sulfide resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyphenylene sulfide resin composition and a molded article containing the same. More specifically, the present invention relates to a polyphenylene sulfide resin composition and a molded article thereof that are used for sliding and have high abrasion resistance and excellent strength in dry and liquid environments. [Background technology]

[0002] Polyphenylene sulfide resin (PPS resin) is a highly heat-resistant super engineering plastic. Its mechanical strength, rigidity, flame retardancy, chemical resistance, electrical properties, and dimensional stability make it widely used in a variety of applications, including injection molding, electrical and electronic components, home appliances, automotive components, and machine parts. Among its many applications, PPS resin's excellent chemical resistance and dimensional stability make it widely used in sliding components used in liquids, such as slide valves, gears, and bearing retainers. Sliding components typically incorporate a lubricant at the sliding interface to improve their sliding properties. However, certain conditions can cause the lubricant to dry up during use, leading to equipment failure due to abnormal wear of the sliding components. To maintain good performance, it is important to improve robustness against the presence or absence of lubricant.

[0003] For example, Patent Document 1 proposes a PPS resin composition containing carbon fiber and a sliding property improver in PPS resin as a resin composition with high strength and excellent friction and wear resistance. Patent Document 2 proposes a PPS resin composition containing PAN-based carbon fiber, anisotropic pitch-based carbon fiber, and a fluororesin as a PPS resin composition intended for compressor seal members. Patent Document 3 proposes a PPS resin composition blended with a fibrous filler and a fluororesin as a PPS resin composition intended for valve slide moldings that can withstand high temperatures and high loads. Patent Document 4 proposes a PPS resin composition blended with a matrix synthetic resin, carbon fiber with a specific specific surface area, and a solid lubricant as a resin composition with excellent wear resistance even under sliding conditions without lubricating oil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 9-59592 [Patent Document 2] Patent Publication No. 2001-115976 [Patent Document 3] Patent Publication No. 2002-5316 [Patent Document 4] Patent Publication No. 7-268126 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a demand for better mechanical properties and wear resistance in molded products for sliding components used in liquids.In addition, from the perspective of equipment maintenance, there is a demand for excellent wear resistance both in liquids and in dry environments.

[0006] However, Patent Documents 1, 2, and 3 disclose improved abrasion resistance in environments where lubricating oil or refrigeration oil is present, but have issues with abrasion resistance in dry environments, and Patent Document 4 discloses improved abrasion resistance in lubricating oil and dry environments, but the abrasion resistance in dry environments is not necessarily excellent, and there is an issue of low part strength due to low material strength. Therefore, an object of the present invention is to solve the above-mentioned problems and provide a PPS resin composition and molded article from which molded articles having excellent mechanical properties and abrasion resistance in dry and liquid environments can be obtained. [Means for solving the problem]

[0007] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by adjusting the contents of PPS resin, PAN-based carbon fiber, isotropic pitch-based carbon fiber, and fluororesin in a PPS resin composition to fall within specific ranges, and have thus completed the present invention.

[0008] That is, the present invention provides the following. (1) Polyphenylene sulfide resin, PAN-based carbon fiber with a tensile strength of 3000 MPa or more , etc. tropic pitch-based carbon fiber and fluororesin A polyphenylene sulfide resin composition comprising: The content of PAN-based carbon fiber having a tensile strength of 3000 MPa or more is 10 to 40 parts by weight and the content of isotropic pitch-based carbon fiber is 5 to 30 parts by weight relative to 100 parts by weight of polyphenylene sulfide resin, The content of fluororesin is 100 parts by weight of polyphenylene sulfide resin. 6 parts by weight or more A polyphenylene sulfide resin composition for sliding applications, characterized in that the total content of the isotropic pitch-based carbon fiber and the fluororesin is 15 to 60 parts by weight per 100 parts by weight of the polyphenylene sulfide resin. (2) The polyphenylene sulfide resin composition for sliding applications according to (1), characterized in that the tensile strength is 120 MPa or more. (3) A molded article obtained by molding the polyphenylene sulfide resin composition according to (1) or (2). [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a PPS resin composition having excellent mechanical properties and excellent abrasion resistance in dry and submerged environments, and a molded article thereof. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a wear resistance test (ball-on-disk wear test). DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment for carrying out the present invention (hereinafter, also referred to as "the present embodiment") will be described in detail. However, the present invention is not limited to the following embodiment.

[0012] <Polyphenylene sulfide resin> Typical examples of the polyphenylene sulfide resin (PPS resin) used in the present invention include polyarylene sulfide, polyarylene sulfide sulfone, polyarylene sulfide ketone, their random copolymers, block copolymers, and mixtures thereof, among which polyarylene sulfide is particularly preferred. Such polyarylene sulfide is a polymer containing preferably 70 mol % or more, more preferably 90 mol % or more, of repeating units represented by the following structural formula, and when the repeating units are 70 mol % or more, it is preferred in terms of excellent heat resistance.

[0013] [ka]

[0014] Furthermore, such polyarylene sulfide resins can be composed of 30 mol % or less of their repeating units having the following structural formula, and may be random copolymers, block copolymers, or mixtures thereof.

[0015] [ka]

[0016] Such polyarylene sulfide resins can be produced by commonly known methods, i.e., the method for obtaining a polymer having a relatively small molecular weight as described in Japanese Patent Publication No. 45-3368, or the method for obtaining a polymer having a relatively large molecular weight as described in Japanese Patent Publication No. 52-12240 and Japanese Patent Laid-Open No. 61-7332.

[0017] In the method for producing the polyarylene sulfide resin used in the present invention, after the polymerization is completed, a solid is recovered from the polymerization reaction product containing the polymer, the solvent, etc. Any known recovery method may be adopted for the polyarylene sulfide resin used in the present invention.

[0018] For example, after the polymerization reaction is completed, the polymer may be slowly cooled and recovered in particulate form. The cooling rate is not particularly limited, but is typically about 0.1°C / min to 3°C / min. It is not necessary to cool at the same rate throughout the entire cooling process; instead, the polymer may be slowly cooled at a rate of 0.1 to 1°C / min until the polymer particles crystallize and precipitate, and then at a rate of 1°C / min or more.

[0019] Another preferred method is to carry out the recovery under rapid cooling conditions, and a preferred recovery method is the flash method. In the flash method, the polymerization reaction product is subjected to high temperature and high pressure (usually 250°C or higher, 8 kg / cm 2In this method, the polymer is flashed from the above-mentioned state 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. 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 selected in the range of 150 to 250°C.

[0020] In the present invention, the polyarylene sulfide resin obtained as described above can of course be used after being subjected to various treatments such as crosslinking / polymerization by heating in air, heat treatment in an inert gas atmosphere such as nitrogen or under reduced pressure, washing with an organic solvent, hot water, an acid aqueous solution, etc., or activation with a functional group-containing compound such as an acid anhydride, an amine, an isocyanate, or a functional group-containing disulfide compound. However, since crosslinking / polymerization by heating in air leads to oxidative discoloration of the polyarylene sulfide resin, a substantially linear polyarylene sulfide resin that is not crosslinked / polymerized by heating is preferred in order to achieve the target whiteness.

[0021] When washing polyarylene sulfide resin with an organic solvent, any organic solvent can be used as long as it does not decompose the polyarylene sulfide resin. Examples include nitrogen-containing polar solvents such as N-methylpyrrolidone, dimethylformamide, and dimethylacetamide; sulfoxide / sulfone solvents such as dimethyl sulfoxide and dimethyl sulfone; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, and acetophenone; ketone solvents such as dimethyl ether, dipropyl ether, and tetrahydrofuran; halogenated solvents such as chloroform, tetrachloroethane, and chlorobenzene; alcohol / phenol solvents such as methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, phenol, cresol, and polyethylene glycol; and aromatic hydrocarbon solvents such as benzene, toluene, and xylene. These organic solvents can be used alone or in combination.

[0022] Specific methods for washing with such an organic solvent include immersing the polyarylene sulfide resin in the organic solvent, and stirring or heating can be performed as necessary. There are no particular limitations on the washing temperature when washing the polyarylene sulfide resin with an organic solvent, and any temperature between room temperature and about 300°C can be selected. The higher the washing temperature, the higher the washing efficiency tends to be, but usually a washing temperature between room temperature and 150°C will provide sufficient results. Note that the polyarylene sulfide resin that has been washed with an organic solvent is preferably washed several times with water or warm water to remove any remaining organic solvent. The temperature for the water washing is preferably 50 to 90°C, more preferably 60 to 80°C.

[0023] Specific examples of methods for treating polyarylene sulfide resin with hot water include the following. That is, in order to achieve the desired effect of chemically modifying the polyarylene sulfide resin by hot water washing, the water used is preferably distilled water or deionized water. The hot water treatment is usually carried out by adding a predetermined amount of polyarylene sulfide resin to a predetermined amount of water, and heating and stirring at normal pressure or in a pressure vessel. The ratio of polyarylene sulfide resin to water is preferably higher, and a bath ratio of 200 g or less of polyarylene sulfide resin per 1 liter of water is preferably used.

[0024] As a specific method for acid-treating a polyarylene sulfide resin, the following methods can be exemplified. That is, there are methods such as immersing the polyarylene sulfide resin in an acid or an aqueous solution of an acid, and it is also possible to appropriately stir or heat as necessary. The acid to be used is not particularly limited as long as it does not have an effect of decomposing the polyarylene sulfide resin, and aromatic saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, and butyric acid, halo-substituted aliphatic saturated carboxylic acids such as chloroacetic acid and dichloroacetic acid, aliphatic unsaturated monocarboxylic acids such as acrylic acid and crotonic acid, aromatic carboxylic acids such as benzoic acid and salicylic acid, dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, phthalic acid, and fumaric acid, and inorganic acidic compounds such as sulfuric acid, phosphoric acid, hydrochloric acid, carbonic acid, and silicic acid are used. Among these acids, acetic acid and hydrochloric acid are particularly preferably used. The acid-treated polyarylene sulfide resin is preferably washed several times with water in order to remove the remaining acid or salt. The temperature of the above water washing is preferably 50 to 90 °C, and more preferably 60 to 80 °C. Also, the water used for washing is preferably distilled water or deionized water in order not to impair the effect of the preferable chemical modification of the polyarylene sulfide resin by the acid treatment.

[0025] The melt flow rate (hereinafter sometimes abbreviated as MFR) of the polyarylene sulfide resin used in the present invention is preferably 1000 g / 10 min or less, more preferably 700 g / 10 min or less, and still more preferably 500 g / 10 min or less. When the MFR exceeds 1000 g / 10 min, the degree of polymerization is too low, so the mechanical strength decreases. The lower limit is preferably in the range exceeding 80 g / 10 min, and more preferably 100 g / 10 min or more. Here, the MFR is a value measured according to ASTM-D1238-70 with a temperature of 315.5 °C and a load of 5000 g.

[0026] <PAN-based carbon fiber> PAN-based carbon fibers are primarily composed of filament fibers consisting essentially of carbon, which are produced by insolubilizing and carbonizing fibers made from polyacrylonitrile resin polymerized with acrylonitrile as the primary component. Spinning methods for such PAN-based carbon fibers include wet spinning and dry-wet spinning, and any spinning method can be selected depending on the desired properties.

[0027] The PAN-based carbon fiber used in the present invention must have a tensile strength of 3,000 MPa or more. A tensile strength of 3,000 MPa or more prevents breakage and shedding of the PAN-based carbon fiber at the sliding interface, preventing deterioration of wear resistance. As PAN-based carbon fibers with a tensile strength of 3,000 MPa or more, known PAN-based carbon fibers or commercially available PAN-based carbon fibers with a tensile strength of 3,000 MPa or more can be used. Examples include Toray Industries, Inc.'s Torayca® T300 (tensile strength 3,530 MPa), Torayca® T700SC (tensile strength 4,900 MPa), Torayca® T800SC (tensile strength 5,880 MPa), and Torayca® T1100GC (tensile strength 7,000 MPa), and Teijin Limited's Tenax® Filament HTA40 (tensile strength 4,100 MPa) and Tenax® Filament HTS40 (tensile strength 4,400 MPa). The upper limit of the tensile strength of the PAN-based carbon fiber used in the present invention is not particularly limited, but it is preferably 8000 MPa or less.

[0028] The PAN-based carbon fiber used in the present invention is preferably a PAN-based carbon fiber with a tensile breaking elongation of 1.3% or more. Using a PAN-based carbon fiber with a tensile breaking elongation of 1.3% or more suppresses fiber breakage during the manufacturing process and injection process of the PPS resin composition, allowing the fibers to be maintained for a long time in the resin composition and molded article, resulting in a PPS resin composition and molded article with excellent mechanical properties. The PAN-based carbon fiber preferably has a tensile breaking elongation of 1.5% or more.

[0029] The average fiber diameter of the PAN-based carbon fibers used in the present invention is preferably 1 to 20 μm, and more preferably 3 to 17 μm. If the average fiber diameter is 1 μm or less, it becomes difficult to disperse the carbon fibers in the PPS resin, making it difficult to obtain a sufficient reinforcing effect from the carbon fibers. If the average fiber diameter is 20 μm or more, the number of fibers contained in the PPS resin composition becomes small, making it difficult to obtain a sufficient reinforcing effect.

[0030] In this embodiment, the PAN-based carbon fiber content is 10 to 40 parts by weight relative to 100 parts by weight of the PPS resin. When the PAN-based carbon fiber content is in the range of 10 to 40 parts by weight relative to 100 parts by weight of the PPS resin, a molded article containing the PAN-based carbon fiber exhibits an excellent balance between abrasion resistance and strength in a dry environment and in a liquid environment, which is required for the molded article.

[0031] If the amount of PAN-based carbon fiber is less than 10 parts by weight, the mechanical strength of the molded product will be poor. On the other hand, if the amount of PAN-based carbon fiber is more than 40 parts by weight, the mechanical strength will be high, but the wear resistance in dry and liquid environments will be reduced due to the presence of PAN-based carbon fiber that falls off during wear at the sliding interface.

[0032] <Isotropic pitch-based carbon fiber> Isotropic pitch-based carbon fibers are carbon fibers made from isotropic pitch as a carbon precursor. Isotropy refers to optical isotropy, which indicates that molecules or molecular clusters are randomly oriented. Carbon precursors refer to a series of carbonization intermediates that precede the desired final carbon product.

[0033] Pitch, a carbon precursor, is a solid substance at room temperature obtained by heat treatment and polymerization of liquid tar obtained during the carbonization of wood, coal, etc., bitumen obtained from oil sands, oil obtained by the carbonization of oil shale, residual oil from crude oil distillation, tar produced by cracking petroleum fractions, etc. Specific examples include coal-based pitch, petroleum-based pitch, and synthetic pitch obtained by polymerizing aromatic compounds such as naphthalene. Chemically, pitch is a mixture of countless condensed polycyclic aromatic compounds. An example of coal-based pitch obtained from coal as a raw material is pitch obtained by heat treatment of coal tar produced in coke ovens.

[0034] In the present invention, the isotropic pitch used as the raw material is not particularly limited, but coal-based isotropic pitch is preferred.

[0035] The method for producing isotropic pitch-based carbon fibers consists of the steps of spinning molten pitch, insolubilizing it, and carbonizing it. In the spinning step, a vortex method can be used to first impart a swirling flow to the molten pitch, and then the molten pitch is discharged from an outlet nozzle. The pitch is spun and deposited on a table to form a pitch fiber mat.

[0036] The insolubilization process is a process in which oxygen is introduced into the surface of pitch fiber to oxidize it. The insolubilization process can be performed in an air or NOx atmosphere, and a mat-like isotropic pitch-based carbon fiber can be obtained by the insolubilization process.

[0037] A PPS resin composition can be obtained by cutting and pulverizing a mat-shaped isotropic pitch-based carbon fiber to a desired length and then kneading it with a PPS resin. Methods for cutting and pulverizing the mat fiber include, for example, pulverization using a jet mill, hammer mill, pin mill, etc., or cutting using a roving cutter, guillotine cutter, cross cutter, low-speed shear screen pulverizer, etc.

[0038] Although there are no particular limitations on the average fiber diameter of isotropic pitch-based carbon fibers, those of approximately 10 to 20 μm are generally available. Most commercially available products have a fiber diameter of 13 to 18 μm, and among these, those with a smaller fiber diameter are preferred because they provide better dispersibility in PPS resin.

[0039] Isotropic pitch-based carbon fibers have a crystalline structure in which the carbon hexagonal mesh planes are arranged non-oriented in the fiber axial direction, making them susceptible to shear and exhibiting cleavage properties when subjected to sliding. Therefore, resin compositions containing isotropic pitch-based carbon fibers have good wear resistance in dry environments.

[0040] Since isotropic pitch-based carbon fibers can absorb liquids such as moisture, resin compositions containing isotropic pitch-based carbon fibers can retain the liquid that acts as a lubricant when sliding in liquid at the sliding interface without expelling it, and therefore have good wear resistance even in liquid environments.

[0041] In this embodiment, the content of the isotropic pitch-based carbon fiber is 5 to 30 parts by weight relative to 100 parts by weight of the PPS resin. When the content of the isotropic pitch-based carbon fiber is in the range of 5 to 30 parts by weight relative to 100 parts by weight of the PPS resin, the molded article containing the fiber exhibits excellent abrasion resistance in dry and liquid environments.

[0042] If the amount of isotropic pitch-based carbon fiber is less than 5 parts by weight, the effect of cleavage of the crystalline structure of the isotropic pitch-based carbon fiber on abrasion resistance is insufficient, and the abrasion resistance of the molded product in a liquid environment is poor. On the other hand, if the amount of isotropic pitch-based carbon fiber is more than 30 parts by weight, the mechanical properties of the PPS resin composition are reduced, and the PPS resin composition becomes significantly embrittled, resulting in poor abrasion resistance in both dry and liquid environments.

[0043] <Fluoropolymer> The fluororesin content in this embodiment is based on 100 parts by weight of PPS resin. 6 parts by weight or more 30 parts by weight or less 。

[0044] Fluorine resins include tetrafluoroethylene (TFE), vinylidene fluoride, chlorotrifluoroethylene, vinyl fluoride, hexafluoropropylene, hexafluoroisobutene, and CH2=CX. 1 (CF2) n X 2 (In the formula, X 1 is H or F, X 2 is H, F or Cl, and n is an integer of 1 to 10), 1 (In the formula, Rf 1 represents a perfluoroalkyl group having 1 to 8 carbon atoms), and perfluoro(alkyl vinyl ether) represented by CF2=CF-OCH2-Rf 2 (In the formula, Rf 2 It is preferable that the fluororesin has polymerization units based on at least one fluorine-containing monomer selected from the group consisting of alkyl perfluorovinyl ether derivatives represented by (a perfluoroalkyl group having 1 to 5 carbon atoms), trifluoroethylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, and iodine-containing fluorinated vinyl ethers. The fluororesin may be a homopolymer of the above-mentioned fluorine-containing monomer, or a modified fluororesin (a copolymer obtained by copolymerizing the above-mentioned fluorine-containing monomer with a comonomer to an extent that does not impair the effects of the present invention). . Current The fluororesin is preferably a homopolymer of a fluorine-containing monomer.

[0045] In a dry environment, when the fluororesin falls off from the PPS resin composition (sliding member) due to sliding, it can remain on the surface of the sliding member and can be transferred to the surface of the sliding counterpart member, so that the fluororesin is present at the sliding interface, which may result in good wear resistance. However, as will be described later, in the present invention, by controlling the content of PAN-based carbon fiber or isotropic pitch-based carbon fiber (particularly the content of isotropic pitch-based carbon fiber) within a predetermined range, good wear resistance can be obtained even without incorporating the fluororesin into the PPS resin composition.

[0046] Furthermore, the fluororesin content in this embodiment must be 30 parts by weight or less per 100 parts by weight of PPS resin. If the fluororesin content is more than 30 parts by weight, the fluororesin will inhibit the lubricating action of the liquid at the sliding interface in a liquid environment, or the fluororesin will flow out of the sliding surface due to the liquid, resulting in poor wear resistance in liquid.

[0047] From the viewpoint of the appearance of the resulting molded article, the melting point of the fluororesin is preferably 140 to 340° C., more preferably 150 to 330° C. The melting point is the temperature corresponding to the maximum value on the heat of fusion curve when the temperature is increased at a rate of 10° C. / min using a differential scanning calorimeter (DSC).

[0048] The fluororesin preferably has a melt flow rate (MFR) of 0.3 to 300 g / 10 min at 372°C. If the MFR is too low, the low friction and non-stick properties may be poor, while if the MFR is too high, the abrasion resistance may be poor. The above MFR is a value obtained in accordance with ASTM D 1238 at a temperature of 372°C and a load of 5 kg.

[0049] <Relationship between isotropic pitch-based carbon fiber and fluororesin content> The present inventors have found that when the total content of the isotropic pitch-based carbon fiber and the fluororesin is within a certain range, the resulting molded article has particularly excellent abrasion resistance in dry and submerged environments.

[0050] That is, in the present invention, it is important that the total content of the isotropic pitch-based carbon fiber and the fluororesin is 15 to 60 parts by weight relative to 100 parts by weight of the PPS resin. The reason why the wear resistance of the resulting molded article in dry and liquid environments is improved by setting the total content of the isotropic pitch-based carbon fiber and the fluororesin within the above range is not clear, but is presumed to be as follows.

[0051] When a sliding member slides against a counter member (e.g., a metal part) in a dry environment, the sliding member wears, causing the isotropic pitch-based carbon fiber and fluororesin to fall off. Isotropic pitch-based carbon fiber easily falls off due to shear stress. Furthermore, because isotropic pitch-based carbon fiber has cleavage properties, it significantly reduces the amount of wear at the sliding interface between the sliding member and the counter member. Wear at the sliding interface between the sliding member and the counter member is reduced by the cleavage properties of the isotropic pitch-based carbon fiber, and this performance correlates with the amount of isotropic pitch-based carbon fiber blended. Therefore, the amount (content) of the isotropic pitch-based carbon fiber has the aforementioned lower limit. Furthermore, when a PPS resin composition contains a fluororesin, the fluororesin may also fall off the sliding member and transfer to the counter member, forming a fluororesin layer at the sliding interface. This lubricating effect may reduce wear, similar to that of isotropic pitch-based carbon fiber. When the PPS resin composition contains an appropriate amount of isotropic pitch-based carbon fiber and fluororesin, the above effects work together and may produce a synergistic effect.

[0052] When a sliding member slides against a mating member (e.g., a metal part) in a liquid environment, generally, the liquid stays at the sliding interface and acts as a lubricant. However, at locations with large irregularities, the sliding member contacts the mating member and wears, similar to the dry environment. At the contacted locations, the isotropic pitch-based carbon fibers are likely to shear off. However, due to their liquid-absorbing property, the isotropic pitch-based carbon fibers can retain the liquid acting as a lubricant at the sliding interface between the sliding member and the mating member without repelling it, thus obtaining good wear resistance. The wear at the sliding interface portion between the sliding member and the mating member can be reduced by the liquid-absorbing property of the isotropic pitch-based carbon fibers, and the performance correlates with the blending amount of the isotropic pitch-based carbon fibers. Therefore, there is a lower limit value as described above for the blending amount (content) of the isotropic pitch-based carbon fibers. Also, when the PPS resin composition contains a fluororesin, the fluororesin may peel off from the sliding member and adhere to the mating member, and in some cases, the amount of wear can be reduced by the action of the fluororesin layer formed at the sliding interface. And when the PPS resin composition contains an appropriate amount of isotropic pitch-based carbon fibers and fluororesin, the above effects may combine and exhibit a synergistic effect.

[0053] In the present invention, it is important that the total content of the isotropic pitch-based carbon fibers and the fluororesin is 15 to 60 parts by weight with respect to 100 parts by weight of the PPS resin. When the total amount of the isotropic pitch-based carbon fibers and the fluororesin is less than 15 parts by weight, the lubricant effect due to the splitting of the isotropic pitch-based carbon fibers at the sliding interface between the sliding member and the mating member in the dry environment is insufficient, and even with the synergistic effect with the fluororesin, the wear increases.

[0055] On the other hand, when the total amount of the pitch-based carbon fibers and the fluororesin is greater than 60 parts by weight, in the liquid environment, the fluororesin inhibits the lubricating action of the liquid at the sliding interface, and the wear increases.

[0056] <PPS resin composition> In addition to the above components, the PPS resin composition of the present invention can further contain other ordinary additives used during the production (mixing) and molding of the resin composition, as long as its physical properties are not impaired.

[0057] <Properties of PPS resin composition> In the present invention, the tensile strength of the PPS resin composition is preferably 120 MPa or more. When the tensile strength is 120 MPa or more, local fracture is not caused by the stress generated from the relative movement in the contact state with the mating member due to the sliding member, and thus the wear amount may be suppressed. For example, by containing 10 parts by weight or more of PAN-based carbon fiber with respect to 100 parts by weight of the PPS resin, the tensile strength of the PPS resin composition can be made 120 MPa or more.

[0058] <Manufacturing method of PPS resin composition> The PPS resin composition of the present embodiment can be manufactured by blending PPS resin, PAN-based carbon fiber, isotropic pitch-based carbon fiber, fluororesin, and other additives as necessary. As the blending method, known techniques can be used.

[0059] For example, a method of melt-kneading each raw material can be mentioned. The blending order of each component is not particularly limited. Taking the case of melt-kneading using a twin-screw extruder as an example, for example, a method of supplying PPS resin and fluororesin from the main feeder and supplying PAN-based carbon fiber and isotropic pitch-based carbon fiber from the side feeder of the twin-screw extruder can be mentioned.

[0060] <Manufacturing method of molded product> By molding the above PPS resin composition, the molded product of the present invention can be obtained. The molding method is not particularly limited, and for example, known methods such as injection molding method, injection compression molding method, extrusion molding method, profile extrusion method, transfer molding method, blow molding method, extrusion blow molding method, multilayer molding method, two-color molding method, insert molding method, foam molding method, pressure molding method, etc. can be used. From the viewpoints of shape freedom and productivity, the injection molding method and the injection compression molding method are preferable.

[0061] <Uses of PPS resin composition and molded product> The PPS resin composition of this embodiment and molded articles obtained by molding it have good mechanical properties and good abrasion resistance in dry and liquid environments, and are therefore suitable for a variety of applications, including various electronic and electrical parts, home appliance parts, building components, sanitary products, and automobile parts. In particular, the PPS resin composition of this embodiment is particularly suitable for sliding applications, and molded articles can be suitable for use as various sliding members.

[0062] Examples of sliding components in electrical and electronic components, home appliance components, building components, and sanitary products include, but are not limited to, gears, cams, bearing retainers, bearings, pulleys, end face materials for mechanical seals, valve seats, V-rings, impellers, vanes, pump casings, pipe joints, water control valves, hot water temperature sensors, and water volume sensors.

[0063] The sliding members for automobile parts can be suitably used for, but are not limited to, members that slide in dry and liquid environments, such as gears, actuators, bearing retainers, bearings, chain guides, chain tensioners, switches, pistons, packings, rollers, and belts. [Example]

[0064] The present invention will be described in detail below with reference to examples, but the gist of the present invention is not limited to the following examples.

[0065] (PPS resin (A)) A 70-liter autoclave equipped with a stirrer and bottom stop valve was charged with 8.27 kg (70.00 mol) of 47.5% sodium hydrosulfide, 2.96 kg (71.1 mol) of 96% sodium hydroxide, 11.43 kg (115.50 mol) of N-methyl-2-pyrrolidone (NMP), 1.72 kg (21.00 mol) of sodium acetate, and 10.5 kg of ion-exchanged water. The mixture was gradually heated to 230°C over approximately 3 hours under atmospheric pressure while passing nitrogen through it. After distilling off 14.78 kg of water and 0.28 kg of NMP, the reactor was cooled to 160°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 0.017 mol per mole of charged alkali metal sulfide.

[0066] Next, 10.36 kg (70.5 mol) of p-dichlorobenzene and 9.08 kg (91.7 mol) of NMP were added, and the reaction vessel was sealed under nitrogen gas. The mixture was stirred at 240 rpm and heated to 270°C at a rate of 0.6°C / min, and held at 270°C for 140 minutes. Subsequently, 2.52 kg (140 mol) of ion-exchanged water was pressure-charged into the autoclave while cooling to 250°C at a rate of 1.3°C / min. The mixture was then cooled to 200°C at a rate of 1.0°C / min, and then rapidly cooled to near room temperature.

[0067] The contents were removed and diluted with 26.3 kg of NMP. The solvent and solids were separated using a sieve (80 mesh). The resulting particles were washed with 31.9 kg of NMP and filtered. These were washed several times with 56 kg of ion-exchanged water and filtered, and then washed with 70 kg of a 0.05 wt% aqueous acetic acid solution and filtered. After washing with 70 kg of ion-exchanged water and filtering, the resulting hydrous PPS particles were dried with hot air at 80°C and then dried under reduced pressure at 120°C to obtain dried PPS resin (A). The MFR of the resulting polymer was 210 g / 10 min.

[0068] (PAN-based carbon fiber (B)) Toray Industries, Inc.'s Torayca(R) T700SC.

[0069] (Isotropic pitch-based carbon fiber (C)) DonaCarbo S-242 manufactured by Osaka Gas Chemicals Co., Ltd.

[0070] (Fluorine resin (D)) Polytetrafluoroethylene (Lubron L-5 manufactured by Daikin Industries, Ltd.), melting point: 328°C.

[0071] [Measurement and evaluation method] The measurement and evaluation methods in the present examples and comparative examples are as follows.

[0072] (Tensile strength of PPS resin composition) The pellets obtained in each example and comparative example were injection molded using an injection molding machine (SE50DUZ-C160, manufactured by Sumitomo Heavy Industries, Ltd.) under the conditions specified in JIS K7315 to prepare 4.0 mm thick ISO dumbbell test pieces, type 1A. These test pieces were conditioned for 16 hours at 23°C and 50% relative humidity, and then subjected to a tensile test in accordance with ISO 527 using an Instron 5581 tensile tester (manufactured by Instron) at a crosshead speed of 5 mm / min. Five measurements were taken, and the average value was calculated as the tensile strength.

[0073] (Tensile strength of PAN-based carbon fiber) The tensile strength of PAN-based carbon fibers can be determined according to the resin-impregnated strand test method of JIS-R-7608 (2004). The resin formulation used is Celloxide (registered trademark: 2021P, manufactured by Daicel Chemical Industries, Ltd.) / boron trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / acetone = 100 / 3 / 4 (parts by weight), and the curing conditions are 130°C and 30 minutes.

[0074] (Wear resistance in dry environments, wear resistance in liquid environments (ball-on-disk wear test)) The pellets obtained in each example and comparative example were molded into test specimens using an injection molding machine (SE50DUZ-C160 manufactured by Sumitomo Heavy Industries, Ltd.) in accordance with the ball-on-disk wear test method specified in JIS R 1613. A ball-on-disk friction and wear test was performed on each of the test specimens.

[0075] Figure 1 shows a schematic diagram of the ball-on-disk test equipment used to evaluate wear depth. First, a ball (φ6 mm) made of SUJ-2 chrome steel (1) was prepared and fixed to a holder (2). Then, ball (1) fixed to holder (2) was brought into contact with the upper surface of test specimen (3). A load of 20 N was applied from the ball toward the test specimen (direction B in Figure 1), while the test specimen was rotated at a speed of 0.3 m / s in a circular direction (direction A in Figure 1: test specimen rotation). Tests were conducted under two conditions: dry conditions at room temperature and atmospheric pressure, and submerged conditions at room temperature and in water. After rotating the test specimens of each example and comparative example for 3 hours, the wear depth of the test specimens was measured using a laser microscope (Keyence VK-X100). The wear depth indicates the amount of wear due to sliding, and a shallower wear depth indicates better wear resistance.

[0076] Example 3 ~13, Comparative Examples 1~17) The (A) PPS resin and (D) fluororesin shown in the table were melted and fed into the raw material feed port of a TEX-44α II twin-screw extruder manufactured by Japan Steel Works, Ltd., with the cylinder temperature set at 15°C above the melting point of the PPS resin. The raw material feed port was connected to the upstream end of the screw segment at position 0, where the total length of the screw is 1.0. Subsequently, the (B) PAN-based carbon fiber and (C) isotropic pitch-based carbon fiber shown in the table were fed into the twin-screw extruder through a side feeder and melt-mixed at a throughput rate of 60 kg / h. The guts discharged from the die were immediately cooled in a water bath and processed into pellets using a strand cutter.

[0077] Using the obtained pellets, the tensile strength and the wear depth after ball-on-disk wear tests in a dry environment and in a liquid environment were evaluated by the method shown in Reference Examples. The evaluation results are shown in the table. In Examples 1 to 13, the PPS resin was mixed with 100 parts by weight of PPS resin, 10 to 40 parts by weight of PAN-based carbon fiber, 5 to 30 parts by weight of isotropic pitch-based carbon fiber, and fluororesin. 6~The material contains 30 parts by weight of isotropic pitch-based carbon fiber and fluororesin, and the total amount of isotropic pitch-based carbon fiber and fluororesin is 15 to 60 parts by weight per 100 parts by weight of PPS resin. This shows that the wear depth is small in dry and submerged environments, and that the material is highly robust against environmental conditions. Furthermore, its high tensile strength makes it suitable for various sliding parts.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] [Table 4]

[0082] [Table 5]

[0083] [Comparative Examples 1 and 3] It can be seen that Comparative Example 1 shown in the table does not contain isotropic pitch-based carbon fibers, which inhibits the lubricating effect due to the cleavage of the isotropic pitch-based carbon fibers in a dry environment, resulting in poor wear resistance.

[0084] [Comparative Examples 2, 4, 6, and 9] In Comparative Examples 2, 4, 6 and 9 shown in the table, the sum of the blending amounts of isotropic pitch-based carbon fiber and fluororesin was low, so no lubricant effect was obtained and the wear resistance in a dry environment was poor.

[0085] [Comparative Examples 5, 7, and 11] Comparative Examples 5, 7, and 11 shown in the table have poor wear resistance because the amount of isotropic pitch-based carbon fiber blended is low, which inhibits the lubricating effect of the isotropic pitch-based carbon fiber cleavage in a liquid environment and repels the liquid that acts as a lubricant from the sliding interface.

[0086] Comparative Example 8 It is clear that Comparative Example 8 shown in the table has a high blending amount of PAN-based carbon fiber, and therefore its stiffness means that it has poor abrasion resistance in both dry and submerged environments.

[0087] Comparative Example 10 It can be seen that Comparative Example 10 shown in the table has a low blending amount of PAN-based carbon fiber, which causes localized fracture due to stress generated at the sliding interface, resulting in poor wear resistance in a dry environment.

[0088] [Comparative Examples 12, 13, and 15] Comparative Examples 12, 13, and 15 shown in the table contain a high amount of fluororesin, which inhibits the lubricating action of the liquid at the sliding interface and causes the fluororesin to flow out of the sliding surface due to the liquid, resulting in poor wear resistance in a liquid environment.

[0089] [Comparative Examples 14 and 16] Comparative Examples 14 and 16 shown in the table contain a high amount of isotropic pitch-based carbon fiber, which reduces the tensile strength of the PPS resin composition, and therefore the abrasion resistance is poor in dry and liquid environments.

[0090] Comparative Example 17 Comparative Example 17 shown in the table does not contain PAN-based carbon fiber, which reduces the tensile strength of the PPS resin composition, and therefore is found to have poor abrasion resistance in a dry environment. [Industrial Applicability]

[0091] The polyphenylene sulfide resin composition of the present invention and its molded article are applicable to all applications requiring high friction resistance and strength in dry and liquid environments and involving sliding. [Explanation of symbols]

[0092] Ball Holder Test specimens A. Rotation direction of the test piece B.Load

Claims

1. A polyphenylene sulfide resin composition comprising a polyphenylene sulfide resin, a PAN-based carbon fiber having a tensile strength of 3000 MPa or more, an isotropic pitch-based carbon fiber, and a fluororesin, The content of the PAN-based carbon fiber having a tensile strength of 3000 MPa or more is 10 to 40 parts by weight and the content of the isotropic pitch-based carbon fiber is 5 to 30 parts by weight relative to 100 parts by weight of the polyphenylene sulfide resin, A polyphenylene sulfide resin composition for sliding applications, characterized in that the content of the fluororesin is 6 parts by weight or more and 30 parts by weight or less per 100 parts by weight of the polyphenylene sulfide resin, and the total content of the isotropic pitch-based carbon fiber and the fluororesin is 15 to 60 parts by weight per 100 parts by weight of the polyphenylene sulfide resin.

2. 2. The polyphenylene sulfide resin composition for sliding applications according to claim 1, wherein the polyphenylene sulfide resin composition has a tensile strength of 120 MPa or more.

3. A molded article obtained by molding the polyphenylene sulfide resin composition according to claim 1 or 2.

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