Resin composition for sliding bearing and sliding bearing

Abstract

To provide a resin composition for sliding bearings that can provide a molding having stable frictional wear properties both at the room temperature and a high temperature of about 100°C, and a sliding bearing comprising the molding of the resin composition for sliding bearings at its sliding part.SOLUTION: A resin composition for sliding bearings comprises a base resin, a fibrous inorganic filler and a solid lubricant. The base resin is a semi-aromatic polyamide resin primarily composed of terephthalic acid and 1,10-decane diamine, and the fibrous inorganic filler has an average fiber diameter of 3 μm or less and an average fiber length of 2-50 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition for a sliding bearing and a sliding bearing. [Background technology]

[0002] Conventionally, resin materials used in bearings for office equipment, automobiles, machine tools, etc. include polyamide 6 (PA6), polyamide 66 (PA66), polyacetal (polyoxymethylene) (POM), and polyphenylene sulfide (PPS). The friction and wear characteristics of bearings made from these resin materials are stable at room temperature, but tend to deteriorate rapidly at temperatures around 100°C, making them unsuitable for use as bearings. In addition, PA6 and PA66 are highly hygroscopic and have poor dimensional accuracy, and POM can easily decompose during melt molding depending on the type of filler.

[0003] As a solution to this problem, bearings have been proposed that use a polyamide resin containing terephthalic acid and 1,10-decanediamine as the main constituent resin material (see, for example, Patent Documents 1 and 2).

[0004] Patent Document 1 describes a rolling bearing including an inner ring, an outer ring, a plurality of rolling elements interposed between the inner and outer rings, and a cage that holds the rolling elements, the cage being an injection-molded article made of a resin composition containing a polyamide resin made of a dicarboxylic acid component primarily composed of terephthalic acid and a diamine component primarily composed of 1,10-decanediamine, glass fiber or carbon fiber, and a fluororesin, each in a predetermined blending ratio.The document states that having a cage of this configuration makes it possible to provide a rolling bearing cage that has high rigidity (elastic modulus), can reduce deformation even under conditions of high temperature and high speed rotation, can reduce heat generation due to the lubricating effect of the fluororesin, and is able to prevent seizure and damage even when used at high speeds.

[0005] Patent Document 2 describes a semi-aromatic polyamide resin composition containing 100 parts by mass of a semi-aromatic polyamide (A) primarily composed of terephthalic acid and 1,10-decanediamine, 0.5 to 80 parts by mass of a sliding property improver (B), 0.5 to 10 parts by mass of a fibrous reinforcing material (C), and 5 to 60 parts by mass of a flame retardant (D), wherein (A) contains 0.3 to 4.0 mol % of a stearic acid component, based on the total monomers constituting (A). It also describes a molded article of this semi-aromatic polyamide resin composition for use as a sliding member. It also describes that the average fiber diameter and fiber length of the fibrous reinforcing material (C) are preferably 3 to 30 μm and 0.1 to 7 mm, respectively, and that preferred types of fibrous reinforcing material (C) are glass fiber, organic fiber, and carbon fiber. This configuration is said to provide a semi-aromatic polyamide resin composition with improved mechanical properties, heat resistance, and flame retardancy without sacrificing sliding properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6697235 [Patent Document 2] Patent No. 6249711 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 does not particularly mention the average fiber diameter and average fiber length of the glass fibers and carbon fibers used, but gives as specific examples glass fibers with an average fiber diameter of 10 μm and an average fiber length of 3 mm and carbon fibers with an average fiber diameter of 7 μm and an average fiber length of 6 mm. Patent Document 2 gives the above-mentioned preferred ranges for the average fiber diameter and average fiber length of the fibrous reinforcing material (C) used, and gives as specific examples glass fibers with an average fiber diameter of 10 μm and an average fiber length of 3 mm, carbon fibers with an average fiber diameter of 7 μm and an average fiber length of 6 mm, and aramid fibers with an average fiber diameter of 12 μm and an average fiber length of 1 mm.

[0008] However, when a fibrous reinforcing material having an average fiber diameter of 3 μm or more and an average fiber diameter of 0.1 mm or more, as disclosed in Patent Documents 1 and 2, is used, the fibrous reinforcing material does not disperse uniformly in the resin composition. Furthermore, when the resin composition is molded into a body, the linear expansion coefficient of the molded body is affected by the fiber orientation, making it difficult to obtain a desired shape with good dimensional accuracy (hereinafter referred to as "shape accuracy"). In particular, it has been found that the degree of deformation of the molded body tends to increase due to the influence of the fiber orientation at temperatures higher than room temperature. Furthermore, it has also been found that, as a result, when the molded body is used in a sliding part, play between the mating material increases, impairing its function as a mechanical part such as a sliding bearing and reducing its friction and wear properties.

[0009] Accordingly, an object of the present invention is to provide a resin composition for a sliding bearing that can provide a molded article that has stable friction and wear properties both at room temperature and at high temperatures of around 100°C, and to provide a sliding bearing that has, in its sliding part, an article molded from this resin composition for a sliding bearing. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have found that the above-mentioned problems can be solved by using a resin composition containing a specific base resin, a specific fibrous inorganic filler, and a solid lubricant. The gist of the present invention is as follows.

[0011] (1) A resin composition for a sliding bearing comprising a base resin, a fibrous inorganic filler, and a solid lubricant, wherein the base resin is a semi-aromatic polyamide resin whose main components are terephthalic acid and 1,10-decanediamine, and the fibrous inorganic filler has an average fiber diameter of 3 μm or less and an average fiber length of 2 to 50 μm. (2) The resin composition for a sliding bearing according to the preceding paragraph (1), wherein the fibrous inorganic filler has a Mohs hardness of 4 or less. (3) A sliding bearing resin composition according to the preceding item (1) or (2), in which the fibrous inorganic filler is at least one type of whisker selected from calcium carbonate whiskers, zinc oxide whiskers, potassium titanate whiskers, and magnesium sulfate whiskers. (4) The sliding bearing resin composition according to any one of (1) to (3) above, wherein the solid lubricant is at least one selected from the group consisting of fluororesin, graphite, molybdenum disulfide, zinc sulfide, metal oxides, and metal carbonates. (5) A resin composition for a sliding bearing according to any one of (1) to (4) above, comprising 55 to 88 mass% of the base resin, 5 to 20 mass% of the fibrous inorganic filler, and 7 to 35 mass% of the solid lubricant. (6) A sliding bearing having, in a sliding part, an article molded from the resin composition for a sliding bearing according to any one of the above items (1) to (5). [Effects of the Invention]

[0012] The present invention can provide a sliding bearing resin composition that can provide a molded article that has stable friction and wear properties both at room temperature and at high temperatures of around 100°C, and a sliding bearing that has an article molded from this sliding bearing resin composition in its sliding part. [Brief explanation of the drawings]

[0013] [Figure 1] 1(a) is a plan view schematically illustrating the dumbbell test pieces prepared in the examples and comparative examples, and FIG. 1(b) is a side view of the plan view shown in FIG. 1(a). DETAILED DESCRIPTION OF THE INVENTION

[0014] A resin composition for a sliding bearing according to an embodiment of the present invention (hereinafter sometimes simply referred to as "resin composition") contains a base resin, a fibrous inorganic filler, and a solid lubricant. The base resin is a semi-aromatic polyamide resin whose main components are terephthalic acid and 1,10-decanediamine. The fibrous inorganic filler has an average fiber diameter of 3 μm or less and an average fiber length of 2 to 50 μm.

[0015] The resin composition contains a fibrous inorganic filler having an average fiber diameter equal to or smaller than that of conventional fibrous reinforcing materials such as glass fiber or carbon fiber, and a shorter average fiber length. This facilitates uniform dispersion of the fibrous inorganic filler within the resin composition and its molded body, and also suppresses the orientation of the fibrous inorganic filler, thereby improving the shape precision of the molded body. Furthermore, as described below, the specific semi-aromatic polyamide resin used as the base resin has a glass transition temperature (Tg) of 120°C or higher and can maintain good mechanical properties even at high temperatures of around 100°C. The solid lubricant can impart low friction properties. Thus, by using the specific fibrous inorganic filler, in combination with the functions of the specific semi-aromatic polyamide resin and the solid lubricant, the resin composition is believed to be able to provide a molded body with stable friction and wear properties both at room temperature and at high temperatures of around 100°C.

[0016] The semi-aromatic polyamide resin serving as the base resin is primarily composed of terephthalic acid, a dicarboxylic acid component, and 1,10-decanediamine, a diamine component, such as a polycondensate of a dicarboxylic acid component and a diamine component. Examples of such semi-aromatic polyamide resins that can be used include those described in Patent Documents 1 and 2, and Japanese Patent No. 5804313.

[0017] Terephthalic acid is preferably contained in an amount of 50 mol% or more, more preferably 95 mol% or more, and even more preferably 100 mol% in the dicarboxylic acid component. The dicarboxylic acid component may contain aromatic dicarboxylic acids and aliphatic dicarboxylic acids other than terephthalic acid. Examples of other semi-aromatic dicarboxylic acids include phthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid.

[0018] The diamine component preferably contains 1,10-decanediamine at 50 mol% or more, more preferably 95 mol% or more, and even more preferably 100 mol%. The diamine component may contain aliphatic diamine components, alicyclic diamine components, and aromatic diamine components other than 1,10-dodecanediamine. Examples of other aliphatic diamine components include 1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine. Examples of alicyclic diamine components include cyclohexanediamine. Examples of aromatic diamine components include xylylenediamine.

[0019] The semi-aromatic polyamide resin may be (a) a polycondensation product of the dicarboxylic acid component and the diamine component described above, or (b) one or more components selected from an aminocarboxylic acid component and a lactam component that can be condensed with the dicarboxylic acid component and the diamine component described above. In these cases, the content of units composed of terephthalic acid and 1,10-decanediamine in the semi-aromatic polyamide resin is preferably 50 to 100 mol %, more preferably 95 to 100 mol %, and particularly preferably 100 mol % in the case of (a), and preferably 50 to 98 mol %, more preferably 95 to 98 mol % in the case of (b).

[0020] The Tg of the semi-aromatic polyamide resin described above is preferably 120° C. or higher. The Tg of the semi-aromatic polyamide resin can be measured using a differential scanning calorimeter (DSC) in accordance with JIS K7121. A measurement sample is prepared by rapidly cooling the semi-aromatic polyamide resin from a heated molten state to room temperature in an inert gas atmosphere, and the baseline shift temperature appearing in the resulting DSC curve when the measurement sample is measured by DSC can be taken as the Tg.

[0021] The weight average molecular weight of the semi-aromatic polyamide resin is preferably 15,000 to 50,000, more preferably 26,000 to 50,000, from the viewpoints of mechanical properties and moldability.

[0022] Using terephthalic acid as the main component can impart good heat resistance and high rigidity to the semi-aromatic polyamide resin. Using 1,10-decanediamine as the main component, coupled with the use of an aromatic carboxylic acid, can impart good low moisture absorption to the semi-aromatic polyamide resin. This allows for good shape precision and dimensional stability to be achieved in molded articles. Because both terephthalic acid and 1,10-decanediamine have highly symmetric chemical structures, using them as the main components can enhance crystallinity. As a result, crystallization during molding is rapid, shortening the molding cycle and improving demoldability. Thus, semi-aromatic polyamide resins containing terephthalic acid and 1,10-decanediamine as the main components are well suited for producing molded articles. Furthermore, 1,10-decanediamine is preferably derived from castor oil, which is obtained from the inedible plant known as castor bean. By using plant-based biomass-derived materials in this way, environmentally friendly resin compositions and sliding bearings can be provided.

[0023] The fibrous inorganic filler has an average fiber diameter of 3 μm or less and an average fiber length of 2 to 50 μm. As described above, this configuration allows the fibrous inorganic filler to be uniformly dispersed in the resin composition, suppressing the influence of fiber orientation. This, combined with the excellent shape precision and dimensional stability of the semi-aromatic polyamide resin, allows the molded article to have excellent shape precision. It can also provide a reinforcing effect to the molded article. The average fiber diameter and average fiber length can be measured and calculated using an electron microscope or an optical microscope.

[0024] Here, the orientation of fibers (fibrous inorganic fillers) in a molded body is speculated as follows, but is not limited to this speculation. The orientation of fibers in a molded body tends to be affected by the flow direction of the resin composition during melt molding. For example, the length direction of fibers tends to be oriented parallel to the flow direction of the molten resin composition during molding. Therefore, while the fibers suppress linear expansion in the direction parallel to the flow direction of the resin composition, the fiber's linear expansion suppression effect tends to be insufficient in the direction perpendicular to the flow direction. As a result, when the temperature rises from room temperature to about 100°C, the difference in linear expansion coefficient between the flow direction and the perpendicular direction in the molded body increases, resulting in significant deformation, reduced dimensional stability, and an inability to ensure shape precision. For example, fibrous reinforcing materials such as glass fibers and carbon fibers described in Patent Documents 1 and 2 are strongly affected by fiber orientation due to their large average fiber diameters and average fiber lengths, which is thought to reduce the dimensional stability of the molded body and make it difficult to ensure shape precision. In contrast, the specific fibrous inorganic filler described above has a predetermined size and is smaller than conventional ones, so it is thought that the orientation of the fibrous inorganic filler in the molded body is significantly suppressed as described above. Furthermore, large fibers like those in conventional fibrous reinforcing materials have low dispersibility and are unevenly distributed in the molded body, which, together with the orientation of the fibers, causes large deformation.

[0025] There are no particular limitations on such fibrous inorganic fillers, as long as they have the average fiber diameter and fiber length described above. However, from the perspective of aggressiveness against mating materials when the molded article is used as the sliding part of a sliding bearing, fillers with a Mohs hardness of 4 or less are preferred. Glass fiber and general carbon fiber have Mohs hardnesses greater than 5. Therefore, when a fibrous inorganic filler with a Mohs hardness of 4 or less is used, aggressiveness against mating materials in the sliding part of a sliding bearing, which occurs when using conventional fibrous reinforcing materials such as glass fiber and general carbon fiber, can be suppressed, while at the same time, a certain degree of reinforcing effect can be imparted to molded articles containing the fibrous inorganic filler. Furthermore, when whiskers, as described below, are included as a fibrous inorganic filler with a Mohs hardness of 4 or less, the anisotropy of the thermal expansion coefficient caused by conventional fibrous reinforcing materials can be more effectively suppressed in injection-molded articles of the resin composition.

[0026] Specific examples of fibrous inorganic fillers include whiskers, such as calcium carbonate whiskers, zinc oxide whiskers, potassium titanate whiskers, and magnesium sulfate whiskers.

[0027] The above-mentioned fibrous inorganic fillers may be used alone or in combination of two or more. When whiskers are used as the fibrous inorganic filler, the fibrous inorganic filler is preferably at least one selected from calcium carbonate whiskers, zinc oxide whiskers, potassium titanate whiskers, and magnesium sulfate whiskers.

[0028] The solid lubricant can be one that can improve the sliding properties of the compact, and examples thereof include fluororesin, graphite, molybdenum disulfide, zinc sulfide, metal oxides, metal carbonates, etc. The form of the solid lubricant is not particularly limited as long as it can impart lubricity, and examples thereof include powder.

[0029] Examples of fluororesins that can be used for the fluororesin include those described in Patent Documents 1 and 2. Examples include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF). Among these, PTFE, PFA, and FEP are preferred, with PTFE being particularly preferred. While virgin PTFE may be used, from the standpoint of moldability, a powder of a fired virgin material, such as recycled PTFE, is preferred.

[0030] Examples of metal oxides include silica, magnesium oxide, and zinc oxide.

[0031] Examples of metal carbonates include calcium carbonate, barium carbonate, potassium carbonate, and sodium carbonate.

[0032] The solid lubricant is preferably at least one selected from fluororesin, graphite, molybdenum disulfide, zinc sulfide, metal oxides, and metal carbonates, and more preferably at least fluororesin.

[0033] The contents of each of the above-mentioned components can be determined as appropriate depending on factors such as the application of the sliding bearing; however, from the perspective of factors such as friction and wear characteristics and shape precision when used in the sliding part of a sliding bearing, it is preferable for the resin composition to contain 55 to 88 mass% of base resin, 5 to 20 mass% of fibrous inorganic filler, and 7 to 35 mass% of solid lubricant, relative to the total amount of the resin composition.

[0034] In addition to the above-mentioned components, the resin composition may contain other components as needed. Examples of such components include elastomers, colorants, flame retardants, weathering agents, antioxidants, heat stabilizers, mold release agents, lubricants, nucleating agents, plasticizers, and antistatic agents. The total content of such optional components can be, for example, 0.1 to 5% by mass based on the total amount of the resin composition.

[0035] The resin composition described above can be obtained by mixing and kneading the components according to a standard method. After kneading, the resin composition can be formed into various forms, such as pellets or powder, as needed. For example, the components constituting the resin composition can be mixed using a general-purpose mixer, and the resulting mixture can be melt-kneaded using a melt extruder such as a single-screw kneading extruder or a twin-screw kneading extruder. The resulting molten material can be extruded into strands and pelletized to obtain pellets for molding. Alternatively, a molten mixture obtained by a predetermined method can be hot-cut or underwater-cut into pellets to obtain pellets for molding. Alternatively, the molten mixture can be extruded into a block shape, and the molded product can be pulverized into a powder to obtain a molding powder.

[0036] A sliding bearing according to an embodiment of the present invention has a sliding part made of a molded article made from the aforementioned resin composition for a sliding bearing. The molding method for the molded article is not particularly limited, but injection molding is preferred. The structure of the injection molding mold is also not particularly limited, and examples include a single-point side gate mold, a multi-point pin gate mold, and a disk gate mold. With the aforementioned resin composition, molded articles with good shape precision can be obtained even with a single-point side gate mold, which has a simple mold structure and is cost-effective but is generally prone to welds in molded articles. When welds form in a molded article, the orientation of the fibers in the vicinity of the weld becomes disordered, reducing shape precision. However, the aforementioned specific fibrous inorganic filler can suppress the effects of orientation, thereby preventing a reduction in shape precision.

[0037] The shape precision of an injection-molded article obtained by injection molding a resin composition can be confirmed, for example, by the ratio (TD / MD) of the linear expansion coefficient in the flow direction (MD) of the resin composition in the injection-molded article to the linear expansion coefficient in the direction perpendicular to the flow direction (TD). When the linear expansion coefficient ratio (TD / MD) is 1.00 to 1.50, the shape precision tends to be good. As a result, the molded article tends to have stable friction and wear properties both at room temperature and at high temperatures of around 100°C. This ratio can be calculated, for example, by measuring the linear expansion coefficient using the method described in the Examples section below.

[0038] The shape of the sliding part (molded article) that constitutes the sliding bearing can be determined as appropriate depending on the intended application, and examples include cylindrical shapes such as bushings, U-shapes, etc. Of these, the resin compositions described above can be suitably used for cylindrical shapes such as bushings, which particularly require dimensional stability at high temperatures of around 100°C and shape precision (roundness).

[0039] The sliding parts that make up the sliding bearing have an article molded from the resin composition described above, and therefore have good shape precision and dimensional stability in the temperature range from room temperature to high temperatures of around 100°C. This allows for stable sliding against the mating material, and ensures stable friction and wear characteristics both at room temperature and at high temperatures of around 100°C. Consequently, sliding bearings that have this sliding part are suitable for use in office equipment, automobiles, electric motors, medical equipment, home appliances, industrial equipment, and other applications that use bushings and other components. [Example]

[0040] Hereinafter, embodiments of the present invention will be described based on examples.

[0041] (Examples 1 to 12, Comparative Examples 1 to 8) The components in the formulations shown in Tables 1 and 2 were dry mixed and then kneaded using a twin-screw kneading extruder (TEM-26SX, manufactured by Shibaura Machine Co., Ltd.) to obtain pellets of a resin composition for a sliding bearing. The obtained pellets of the resin composition for a sliding bearing were placed in a hot-air drying oven (PHH-201, manufactured by Espec Corporation) and dried at 120°C for 16 hours. After that, an injection molding machine (PS60E5H, manufactured by Nissei Plastic Industrial Co., Ltd.) was used to prepare various test pieces to be used for the various evaluations described below. The molding temperatures were all 310°C for the cylinder temperature and 150°C for the mold temperature.

[0042] The components shown in Tables 1 and 2 are as follows: (1) Base resin PA10T Unitika Ltd., XecoT (registered trademark) XN400, semi-aromatic polyamide mainly composed of terephthalic acid and 1,10-decanediamine, Tg: 121°C, PA66 Leona, polyamide 66, manufactured by Asahi Kasei Corporation, Tg: 50°C, PPS DIC Corporation, FZ2100, polyphenylene sulfide, Tg: 90°C, (2) Solid lubricant Polytetrafluoroethylene Kitamura Co., Ltd., KTL-620, powder of baked PTFE (recycled PTFE), ·graphite Nippon Graphite Industries Co., Ltd., CPB, (3) Fibrous inorganic filler (referred to as "inorganic filler" in Tables 1 and 2) Calcium carbonate whiskers Maruo Calcium Co., Ltd., Whiscal, average fiber diameter: 1.0 μm, average fiber length: 20 μm, Mohs hardness: 3 or less, Zinc oxide whiskers Amtec Co., Ltd., Panatetra, average fiber diameter: 1.5 μm, average fiber length: 20 μm, Mohs hardness: 4 or less, (4) Fibrous reinforcement Glass fiber Asahi Fiberglass Co., Ltd., 03JAFT692, average fiber diameter: 10 μm, average fiber length: 3 mm, Mohs hardness: 6.5 Aramid fiber Teijin Limited, product name: Conex, average fiber diameter: 12 μm, average fiber length: 1 mm,

[0043] (evaluation) <Friction characteristics and wear resistance> The pellet-shaped resin compositions obtained in the above-mentioned Examples and Comparative Examples were molded into cylindrical test pieces with a diameter of 5 mm using the above-mentioned injection molding machine. A pin-on-disk test was carried out using a pin-on-disk friction and wear tester (Auto Pin Disk APD-101, manufactured by Starlite Industrial Co., Ltd.), the dynamic friction coefficient of each test piece was measured, and the specific wear rate was calculated. The test conditions were as follows: Surface pressure (load on sample): 2.0 MPa Speed ​​(set value): 1.0 m / s Counter disc temperature: 25°C and 100°C Lubrication: No lubrication Counterpart disc: SUS303 (surface roughness before test: Rz ≒ 1.5 to 2.5 μm)

[0044] The evaluation criteria for the frictional properties are as follows: ○: Friction coefficient at 25℃ and 100℃ is 0.30 or less, ×: Friction coefficient at 25°C or 100°C is greater than 0.30 The evaluation criteria for abrasion resistance are as follows. ○: Specific wear rate at 25°C and 100°C is 1.5 [× 10 -6 mm 3 / N m] or less ×: Specific wear rate at 25°C or 100°C is 1.5 [×10 -6 mm 3 / N·m]

[0045] The specific wear rate was calculated from the wear progress curve, which shows the change in wear rate (height) over time, using the following formula (1): In this experiment, T' was set to 6 hours (21,600 s) after the start of the test, and T was set to 2 hours (7,200 s) after the start of the test. K = (H'-H) / {P·V·(T'-T)} (1) K: specific wear amount [mm 3 / N·m] H': Wear amount (height) at test time T' [mm] H: Wear amount (height) at test time T [mm] P: Surface pressure [N / mm 2 ] V: Velocity [m / s] T': Test time in steady state [s] T: Test time in steady state [s] Steady state: After the test time, the wear rate stabilizes

[0046] <Shape accuracy (roundness)> Using the pellet-shaped resin compositions obtained in the above-mentioned Examples and Comparative Examples, dumbbell test specimens conforming to ISO 527 were molded using the above-mentioned injection molding machine with a fan-gate type, single-side gate injection mold. As shown in Figures 1(a) and 1(b), immediately after demolding from the fan-gate type, single-side gate injection mold, dumbbell test specimen 1 has gate 2 connected to runner 3. Gate 2 is located at one end of dumbbell test specimen 1 in the longitudinal direction, and one end of runner 3 is connected to dumbbell test specimen 1 via gate 2. The dimensions of the main parts of dumbbell test specimen 1 are as shown in Figures 1(a) and 1(b). Dimensions in Figure 1 are in millimeters. As shown in Figure 1(a), in relation to the gate position, the length (long axis) direction of the dumbbell test specimen 1 is the flow direction (MD) of the molten resin composition (the direction of the arrow indicated by the reference numeral 4 in Figure 1(a)), and the direction perpendicular to the length direction, i.e., the flow direction, in the planar direction of the dumbbell test specimen 1 is the normal direction (TD) (the direction of the arrow indicated by the reference numeral 5 in Figure 1(a)). The gate 2 and runner 3 were cut out to obtain the dumbbell test specimen 1. From the obtained dumbbell test specimen 1, rectangular column-shaped test specimens measuring 4 mm x 5 mm x 10 mm were cut out in the flow direction (MD) and the normal direction (TD), respectively, and analyzed using a thermomechanical analyzer (TMA) (EXSTAR, manufactured by Hitachi High-Tech Science Corporation) in accordance with JIS K7197. The linear expansion coefficient was measured at 25°C to 100°C using a tester (TMA / SS6100). The evaluation criteria for shape precision (roundness) are as follows. The closer the ratio of linear expansion coefficients TD / MD is to 1.00, the higher the shape precision (roundness). ○: Ratio of linear expansion coefficient TD / MD is 1.00 or more and 1.50 or less ×: The ratio of linear expansion coefficients TD / MD is greater than 1.50

[0047] <Aggression of opponents> After the pin-on-disk test conducted in the evaluation of the friction characteristics and wear resistance described above, the contact surface with the mating disc test piece was measured for ten-point average roughness (Rz) in accordance with JIS B0601-1982 using a surface roughness tester (SURFCOM 1500DX3, manufactured by Tokyo Seimitsu Co., Ltd.). The test conditions were as follows: Measurement length: 8,000 mm (Evaluation length: 5,000 mm) ·Measuring speed: 0.300mm Shape removal: least squares straight line

[0048] The evaluation criteria for opponent aggression are as follows: ○: Ten-point average roughness (Rz) after pin-on-disk testing at 25℃ and 100℃ is 10 or less ×: Ten-point average roughness (Rz) after pin-on-disk test at 25°C or 100°C is greater than 10

[0049] [Table 1]

[0050] [Table 2]

[0051] Tables 1 and 2 show that a resin composition for a sliding bearing containing the specified components has good friction properties and wear resistance at 25°C and 100°C, and also has good shape precision (roundness). It is therefore clear that the resin composition for a sliding bearing has good friction and wear properties from the normal temperature of 25°C to around 100°C, making it suitable as a component of a sliding bearing. In particular, it is presumed that the inclusion of the above-mentioned fibrous inorganic filler in the resin composition for a sliding bearing suppresses the effects of fiber orientation in the molded product, resulting in good maintenance of shape precision (roundness).

[0052] Furthermore, because the base resin contains a specific biomass-derived semi-aromatic polyamide resin, it is possible to provide an environmentally friendly resin composition and sliding bearing.Furthermore, it has been found that the use of a fibrous inorganic filler with a Mohs hardness of 4 or less, combined with the lubricating properties of the fluororesin, which is a solid lubricant, makes it possible to provide a resin composition and sliding bearing that also suppresses aggressiveness toward mating surfaces. [Explanation of symbols]

[0053] 1 dumbbell specimen 2 Gate 3 Runner 4 Flow direction 5 vertical direction

Claims

1. A resin composition for a sliding bearing comprising a base resin, a fibrous inorganic filler, and a solid lubricant, the base resin is a semi-aromatic polyamide resin containing terephthalic acid and 1,10-decanediamine as main components, the fibrous inorganic filler has an average fiber diameter of 3 μm or less, an average fiber length of 2 to 50 μm, and a Mohs hardness of 4 or less, and is at least one type of whisker selected from calcium carbonate whiskers, zinc oxide whiskers, potassium titanate whiskers, and magnesium sulfate whiskers; the solid lubricant is at least one selected from the group consisting of fluororesin, graphite, molybdenum disulfide, zinc sulfide, metal oxides, and metal carbonates; The composition contains 55 to 88 mass % of the base resin, 5 to 20 mass % of the fibrous inorganic filler, and 7 to 35 mass % of the solid lubricant, The resin composition for a sliding bearing has a friction coefficient of 0.3 or less and a specific wear rate of 1.5×10 −6 mm 3 / N·m or less at 100°C, as measured under the test conditions described below using an injection-molded article of the resin composition for a sliding bearing. Test conditions: A pin-on-disc test was carried out under the following conditions using a pin-on-disc friction and wear tester (Auto Pin Disk APD-101, manufactured by Starlite Industrial Co., Ltd.), the dynamic friction coefficient of the test piece was measured, and the specific wear rate was calculated from the wear progress curve based on the following formula (1). Test piece: φ5 mm cylindrical injection molded body Surface pressure (load on sample): 2.0 MPa Speed ​​(set value): 1.0 m / s ・Matching disc temperature: 100℃ Lubrication: No lubrication Counterpart disc: SUS303 (surface roughness before test: Rz ≒ 1.5 to 2.5 μm) ・K=(H'-H) / {P・V・(T'-T)} (1) K: specific wear rate [mm 3 / N·m] H': wear amount (height) at test time T' [mm] H: Amount of wear (height) at test time T [mm] P: Surface pressure [N / mm 2 ] V: Velocity [m / s] T': Test time [s] in the steady state, 6 hours (21600 s) after the start of the test T: Test time in steady state [s], 2 hours (7200 s) after the start of the test Steady state: After the test time, the rate of wear has stabilized

2. A resin composition for sliding bearings according to claim 1, wherein the friction coefficient at 25°C measured under the test conditions (with the exception of mating disc temperature of 25°C) using an injection-molded article of the resin composition for sliding bearings is 0.3 or less, and the specific wear rate is 1.5 x 10-6 mm3 / N・m or less.

3. A sliding bearing having, in a sliding part, an article molded from the resin composition for sliding bearings according to claim 1 or 2.

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