Sliding packings and sliding parts

Abstract

To provide a sliding packing with excellent airtightness, wear resistance, and surface lubricity. [Solution] The sliding packing of the present disclosure comprises a substrate mainly composed of rubber and a coating layer directly laminated on at least a part of the surface of the substrate, wherein the coating layer mainly consists of an electron beam crosslinked fluororesin.

Description

Technical Field

[0001] The present disclosure relates to sliding packings and sliding parts.

Background Art

[0002] Conventionally, for members that require waterproof performance, sliding packings that prevent the intrusion of liquids, gases, etc. from the outside have been used. For example, in pressure devices such as screw bearings, fluid cylinders, and solenoid valves, a sliding packing is attached inside a flow path hole, and the outer peripheral part of a sliding member such as a spool or a piston is arranged to slide inside the flow path hole while abutting against this sliding packing.

[0003] As materials for these sliding packings, relatively soft rubber materials with excellent airtightness such as nitrile rubber, urethane rubber, fluorine rubber, and silicone rubber are widely used (see Patent Document 1). In addition, resin-based materials with excellent surface slipperiness such as polytetrafluoroethylene may be used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The sliding packing of the present disclosure includes a base body mainly composed of rubber and a coating layer directly laminated on at least a part of the surface of the base body, and the coating layer is mainly composed of an electron beam crosslinked body of fluororesin.

Brief Description of the Drawings

[0006] [Figure 1] FIG. 1 is a schematic perspective view showing the sliding packing of the present disclosure. [Figure 2] FIG. 2 is a schematic partial cross-sectional view showing a cross-section along line A-A in the sliding packing of the present disclosure. [Figure 3]Figure 3 is a schematic partial diagram showing the sliding component of the present disclosure. [Modes for carrying out the invention]

[0007] [Issues this disclosure aims to address] Sliding packings used in the applications described above are required to enhance watertightness by reliably sealing the gaps between components. Furthermore, sliding packings are required to have high wear resistance, a long wear life, and excellent surface lubricity on the sliding part (the part that slides with other components). However, when relatively soft, airtight rubber materials are used as the material for sliding packings, problems arise such as poor slipperiness, increased driving torque, and heat generation at the sliding part. On the other hand, when resin-based materials are used as the material for sliding packings, insufficient flexibility prevents adequate airtightness, resulting in poor watertightness. To address these issues, packings coated with polytetrafluoroethylene have been developed, but the adhesion between the rubber material and polytetrafluoroethylene is insufficient, and the solution is merely a matter of coating the entire surface of a rubber O-ring packing with polytetrafluoroethylene. Additionally, sliding components used in applications involving high loads and high-speed rotation face the problem of the polytetrafluoroethylene coating lifting off. Sliding parts used in applications involving high loads and high-speed rotation require further improvements in wear resistance.

[0008] This disclosure aims to provide a sliding packing that is excellent in airtightness, wear resistance, and surface lubricity.

[0009] [Effects of this disclosure] The sliding packing of this disclosure has excellent airtightness, wear resistance, and surface lubricity.

[0010] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0011] (1) The sliding packing of the present disclosure comprises a substrate mainly composed of rubber and a coating layer laminated on at least a part of the surface of the substrate, wherein the coating layer mainly consists of an electron beam crosslinked fluororesin.

[0012] The sliding packing of this disclosure comprises a substrate mainly composed of rubber and a coating layer laminated on at least a portion of the surface of the substrate, wherein the coating layer is mainly composed of an electron beam crosslinked fluororesin, thereby improving wear resistance. Furthermore, when a coating layer mainly composed of an electron beam crosslinked fluororesin is laminated, a crosslinked structure (covalent bond) is formed not only between the fluororesins but also between the fluororesin, which is the main component of the coating layer, and the rubber, which is the main component of the substrate, resulting in adhesive force between the coating layer and the substrate. In addition, the presence of an adhesive would hinder the softness of the layer laminated on the surface of the substrate, leading to a decrease in airtightness, but this sliding packing can obtain high adhesive force between the surface of the substrate and the coating layer without using an adhesive. Therefore, this sliding packing has excellent airtightness, wear resistance, and surface slipperiness. In this disclosure, "main component" refers to the component with the highest content by mass, for example, a component with a content of 90% by mass or more.

[0013] (2) In (1) above, the rubber may be silicone rubber or fluororubber, and the fluororesin may be polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. In the sliding packing, if the rubber is silicone rubber or fluororubber, the airtightness of the substrate can be improved while the durability can be improved. Furthermore, if the fluororesin is polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, the abrasion resistance of the coating layer can be further improved, and the heat resistance and chemical resistance can also be improved.

[0014] (3) The sliding component of the present disclosure further comprises a sliding packing as described in (1) or (2) above and a sliding member, wherein the coating layer of the sliding packing is arranged to abut against the sliding surface of the sliding member. Since the coating layer of the sliding packing, which has excellent airtightness, wear resistance and surface slipperiness, is arranged to abut against the sliding surface of the sliding member, the parts of the sliding component are reliably sealed, providing excellent watertightness and improving the durability of the sliding component.

[0015] [Details of the embodiments of this disclosure] The sliding packing and sliding parts according to the embodiments of this disclosure will be described in detail below with reference to the drawings.

[0016] <Sliding packing> The sliding packing comprises a base material mainly composed of rubber and a coating layer directly laminated on at least a portion of the surface of the base material. The sliding packing can be suitably used, for example, in bearings of engines for automobiles and other industrial machinery, drive components in the automotive sector, fluid cylinders, solenoid valves and other pressure equipment.

[0017] Figure 1 is a schematic perspective view showing the sliding packing 1. Figure 2 is a schematic partial cross-sectional view showing the cross-section of the sliding packing 1 along line AA. The sliding packing 1 shown in Figures 1 and 2 comprises a base body 2 and a coating layer 3 that is directly laminated on at least a portion of the surface of the base body 2.

[0018] Figure 1 shows an example where the overall shape is annular and a coating layer is provided on the inner surface of the annular body. However, the shape of the sliding packing 1 is not particularly limited, and the shape in plan view may be, for example, circular, elliptical, semicircular, triangular, square, hexagonal, trapezoidal, roughly X-shaped, roughly U-shaped, roughly Y-shaped, or a partially constricted gourd shape.

[0019] [Base] Examples of the rubber that is the main component of the base body 2 include silicone rubber, fluororubber (FKM), urethane rubber, isoprene rubber (IR), butyl rubber (IIR), ethylene propylene rubber (EPM), butadiene rubber (BR), 1,2-polybutadiene rubber (1,2-BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (acrylonitrile-butadiene rubber; NBR), styrene-ethylene-butylene-styrene rubber (SEBS), styrene-ethylene-propylene-styrene rubber (SEPS), ethylene propylene diene rubber (EPDM), acrylic rubber (ACR), epichlorohydrin rubber, chlorostyrenated polyethylene rubber (CSM), epichlorohydrin rubber (CO), and natural rubber (NR). Among these, from the viewpoint of improving the airtightness of the base body while enhancing the durability, silicone rubber or fluororubber may be used.

[0020] The lower limit of the rubber content in the base body 2 may be 90% by mass, 95% by mass, 98% by mass, or 100% by mass.

[0021] The average thickness of the base body 2 can be appropriately set according to the use of the sliding packing 1. For example, it may be 1 mm or more and 10 mm or less. Here, the "average thickness" means the value obtained by measuring the thickness at five points at an arbitrary location and averaging them.

[0022] (Coating layer) The coating layer 3 is directly laminated on the surface of the base body 2 and mainly composed of an electron beam crosslinked body of a fluororesin. Since the coating layer 3 is mainly composed of an electron beam crosslinked body of a fluororesin, it is excellent in wear resistance and surface slipperiness.

[0023] Electron beam crosslinked fluororesins are obtained by irradiating fluororesins with electron beams. Here, "fluororesin" refers to a polymer in which at least one hydrogen atom bonded to a carbon atom forming the polymerization unit of the polymer chain is substituted with a fluorine atom or an organic group containing a fluorine atom (hereinafter also referred to as a "fluorine atom-containing group"). A fluorine atom-containing group is a linear or branched organic group in which at least one hydrogen atom is substituted with a fluorine atom, and examples include fluoroalkyl groups, fluoroalkoxy groups, and fluoropolyether groups.

[0024] The coating layer 3 does not need to be laminated over the entire surface of the substrate 2; it is sufficient if it is laminated over at least a portion of the surface of the substrate 2. For example, if the substrate 2 is in the shape of an O-ring as shown in Figure 1, the coating layer 3 may be directly laminated only on the inner circumferential surface of the substrate 2, or it may be directly laminated only on the outer circumferential surface of the substrate 2.

[0025] The coating layer 3 may be a coated layer or formed from a film. Forming the coating layer 3 from a coated layer or a film facilitates precise control of the surface roughness and average thickness of the coating layer 3.

[0026] Examples of the above-mentioned fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), fluoroolefin-vinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer. From the viewpoint of abrasion resistance, chemical resistance, and heat resistance, among these, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer may be used. The above-mentioned fluororesins can be used individually or in combination of two or more.

[0027] Polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer may contain polymerization units derived from other copolymerizable monomers, to the extent that the effects of the present disclosure are not impaired, for example, they may contain polymerization units of perfluoro(alkyl vinyl ether), (perfluoroalkyl)ethylene, or chlorotrifluoroethylene. The upper limit of the content of polymerization units derived from the above-mentioned other copolymerizable monomers can be, for example, 3 mol%.

[0028] The above-mentioned fluororesin may contain structural units derived from other copolymerizable monomers, to the extent that it does not impair the effects of the present disclosure. For example, PTFE may contain structural units such as perfluoro(alkyl vinyl ether), hexafluoropropylene, (perfluoroalkyl)ethylene, and chlorotrifluoroethylene. The upper limit of the content of structural units derived from the above-mentioned other copolymerizable monomers is, for example, 3 mol% of the total structural units in the above-mentioned fluororesin.

[0029] The lower limit of the electron beam crosslinked fluororesin content in the coating layer 3 may be 90% by mass, 95% by mass, 98% by mass, or 100% by mass. Furthermore, the electron beam crosslinked fluororesin content may be 100% by mass. If the electron beam crosslinked fluororesin content is less than the lower limit, the wear resistance of the sliding packing 1 may be insufficient.

[0030] The lower limit of the average thickness of the coating layer 3 may be 1 μm, 5 μm, or 10 μm. An average thickness of 1 μm or more of the coating layer 3 maintains good strength and abrasion resistance, improving durability. On the other hand, the upper limit of the average thickness of the coating layer 3 may be 500 μm, 300 μm, or 100 μm. While a thinner average thickness of the coating layer 3 improves airtightness between the coating layer 3 and the substrate 2, it tends to decrease durability due to reduced abrasion resistance of the coating layer 3. Therefore, the average thickness of the coating layer may be between 5 μm and 300 μm, or between 10 μm and 100 μm.

[0031] The coating layer 3 may contain other optional components as long as they do not impair the effects of the present disclosure. Examples of these optional components include solid lubricants and reinforcing materials. By including solid lubricants and reinforcing materials in the coating layer 3, the lubricity can be further improved. An example of the solid lubricant is molybdenum disulfide. Examples of the reinforcing materials include inorganic fillers such as calcium carbonate, talc, silica, alumina, and aluminum hydroxide, glass fillers such as glass fibers and spherical glass, and carbon fibers.

[0032] The lower limit of the critical PV value of the surface of the coating layer 3 measured in a ring-on-disk type abrasion test in accordance with JIS-K7218:1986 may be 10 MPa·m / min, 100 MPa·m / min, or 1000 MPa·m / min. A critical PV value of 10 MPa·m / min or higher improves the abrasion resistance of the coating layer 3, and a critical PV value of 1000 MPa·m / min or higher increases the abrasion resistance of the coating layer 3, resulting in better durability of the sliding packing 1. The upper limit of the critical PV value of the surface of the coating layer 3 is not particularly limited and may be, for example, 1500 MPa·m / min.

[0033] The upper limit of the dynamic friction coefficient of the surface of the coating layer 3, measured in accordance with JIS-K7125:1999, may be 0.15 or 0.10. A dynamic friction coefficient of 0.15 or less improves the slipperiness of the surface of the sliding packing 1, thereby reducing the sliding torque of the sliding member in contact with the sliding packing 1. The lower limit of the dynamic friction coefficient of the surface of the coating layer 3 is not particularly limited and may be 0.

[0034] (hardness) The upper limit of the Shore D hardness of the sliding packing 1, measured in accordance with Type D of JIS-K7215:1986, may be 40 or 20. Having a Shore D hardness of the sliding packing 1 below this upper limit ensures good airtightness. On the other hand, the lower limit of the Shore D hardness of the sliding packing 1 may be 5 or 10. Having a Shore D hardness of the sliding packing 1 above this lower limit reduces deformation under high load.

[0035] [Manufacturing method for sliding packing] The method for manufacturing the sliding packing comprises the steps of directly laminating a coating layer mainly composed of fluororesin onto the surface of a substrate mainly composed of rubber, and irradiating the coating layer with an electron beam.

[0036] (Lamination process) In this process, a coating layer mainly composed of fluororesin is directly laminated onto the surface of a substrate mainly composed of rubber.

[0037] Methods for lamination include, for example, powder coating, electrostatic coating, and dipping coating using a paint mainly composed of fluororesin, or thermocompression bonding of a film mainly composed of fluororesin to the substrate. By using powder coating, electrostatic coating, dipping coating, or thermocompression bonding of a film to the substrate in the lamination process, it becomes easier to control the arithmetic mean roughness of the surface of the coating layer to a good range.

[0038] When performing powder coating, electrostatic coating, or dip coating using a paint primarily composed of fluororesin, the paint primarily composed of fluororesin is applied to the outer surface of the substrate. Examples of paints primarily composed of fluororesin include paints in which a fluororesin composition is dispersed in a solvent, or paints in which a fluororesin composition is dissolved. As the solvent, a mixture of water and an emulsifier, water and alcohol, water and acetone, or water, alcohol, and acetone can be used to efficiently disperse the fluororesin.

[0039] The lower limit of the solid content concentration of the above-mentioned paint may be 5% by mass, 25% by mass, or 40% by mass. On the other hand, the upper limit of the solid content concentration of the above-mentioned paint may be 60% by mass, 50% by mass, or 45% by mass. By setting the solid content concentration of the above-mentioned paint within the above range, the applicability can be improved, and as a result, a coating film with fewer coating defects can be easily and reliably formed.

[0040] After performing the above-mentioned powder coating, electrostatic coating, or dipping coating, or heat-pressing of a film, the substrate is placed in a heating furnace and heated to bake the fluororesin. The heating temperature when baking the fluororesin layer can be, for example, 320°C to 400°C, but a lower temperature above the melting point of the fluororesin is preferable to reduce thermal degradation of the substrate. For example, if the fluororesin is PFA with a melting point of 310°C, the heating temperature range should be 320°C to 360°C. The heating time when baking the coating can be, for example, 10 minutes to 60 minutes, but it may be 20 minutes or less to reduce thermal degradation of the substrate. By setting the heating temperature and heating time within the above range, a film with excellent density can be formed while reducing the decomposition of the fluororesin. Furthermore, if the baking of the coating is performed simultaneously with the subsequent electron beam irradiation step, thermal degradation of the substrate can be further reduced. Finally, a coating layer is formed on the surface of the substrate by cooling the sintered coating.

[0041] As mentioned above, the coating layer does not need to be laminated over the entire surface of the substrate; it is sufficient if it is laminated at least on the sliding surface of the substrate.

[0042] (Process of irradiating with an electron beam) In this process, the coating layer and the substrate are irradiated with an electron beam. The electron beam irradiation process crosslinks the fluororesin and simultaneously allows it to bond with the substrate. In this process, the coating layer is irradiated with an electron beam in a low-oxygen atmosphere at a temperature above the melting point of the fluororesin. This irradiation causes the fluororesin to have a crosslinked structure, and covalent bonds are formed between it and the rubber, which is the main component of the substrate, so that a high adhesive strength can be obtained between the surface of the substrate and the coating layer.

[0043] The lower limit of the electron beam irradiation temperature is preferably 5°C higher than the melting point of the fluororesin, and more preferably 10°C higher than the melting point. On the other hand, the upper limit of the temperature is preferably 50°C higher than the melting point of the fluororesin, and more preferably 30°C higher than the melting point. Irradiating with an electron beam at the above temperatures can reduce the severance of the main chain of the fluororesin while promoting intermolecular crosslinking. If the temperature exceeds the upper limit, the fluororesin may decompose. Here, "melting point of resin" refers to the melting point peak temperature measured by a differential scanning calorimeter (DSC) in accordance with JIS-K7121:2012 "Method for measuring transition temperature of plastics".

[0044] The heating temperature during electron beam irradiation is, for example, 280°C to 300°C if the fluororesin is FEP (melting point: 270°C), 337°C to 357°C if the fluororesin is PTFE (melting point: 327°C), and 320°C to 340°C if the fluororesin is PFA (melting point: 310°C).

[0045] In this disclosure, a low-oxygen atmosphere specifically refers to a vacuum (5.0 × 10⁻⁴ Torr or less) or an inert gas atmosphere such as nitrogen. The upper limit of the oxygen concentration in the low-oxygen atmosphere may be 100 ppm, 10 ppm, or 5 ppm. By keeping the oxygen concentration at 100 ppm or less, the decomposition of the fluororesin by electron beam irradiation can be prevented.

[0046] The lower limit of the electron beam irradiation dose may be 50 kGy or 100 kGy. On the other hand, the upper limit of the irradiation dose may be 500 kGy or 1,000 kGy. An irradiation dose of 50 kGy or more can improve the progress of the crosslinking reaction of the fluororesin. An irradiation dose of 1,000 kGy or less can reduce the cleavage of the main chain of the fluororesin. Therefore, by keeping the irradiation dose within the above range, electron beam crosslinking can be reliably performed while reducing the cleavage of the main chain of the fluororesin. Whether or not crosslinking has occurred can be confirmed by NMR (nuclear magnetic resonance analysis). Furthermore, the lower limit of the acceleration voltage may be 0.5 MeV, 0.7 MeV, or 1.0 MeV. An acceleration voltage of 10 MeV or more can ensure that electron beam crosslinking can be reliably performed over the entire range. The upper limit of the acceleration voltage may be 10 MeV or 4.0 MeV. By keeping the accelerating voltage below the above upper limit, the extent to which bridging occurs in the deeper parts of the substrate can be reduced.

[0047] The specific configuration of the substrate and the coating layer is as described above.

[0048] This sliding packing offers excellent airtightness, wear resistance, and surface lubricity.

[0049] <Sliding parts> In sliding components used in pressure equipment such as fluid cylinders, pumps, and solenoid valves, a sliding packing is installed in a flow path hole, and the outer circumference of a sliding member such as a spool or piston is arranged to slide within the flow path hole while in contact with the sliding packing. The sliding component comprises the aforementioned sliding packing and a sliding member. Specifically, the sliding component is arranged within the flow path hole such that the coating layer of the aforementioned sliding packing is in contact with the sliding surface of the sliding member.

[0050] Figure 3 is a schematic partial diagram showing the sliding component 50. A sliding member 10, which is made up of a sliding shaft such as a piston, is slidably supported on the support member 15 of the sliding component 50 along its central axis. Between the support member 15 and the sliding member 10, the covering layer 3 of the sliding packing 1, which is O-ring shaped (annular), is placed in the flow path hole so as to abut against the outer circumferential surface, which is the sliding surface of the sliding member 10. In other words, in the sliding component 50, the sliding packing 1 is placed in the flow path hole so as to abut against the outer circumferential surface of the sliding member 10, and the sliding member 10 is provided to slide through the hole in the center of the sliding packing 1. Furthermore, a fluid is in contact with the first surface of the sliding packing 1, and air is in contact with the second surface of the sliding packing 1. In the sliding component 50, the fluid in contact with the first surface is sealed by the sliding packing 1 so as not to penetrate toward the second surface. In the sliding part 50, the sliding packing 1 is positioned so that the coating layer 3, which mainly consists of an electron beam crosslinked fluororesin, contacts the sliding surface of the sliding member 10. As a result, the gaps between the members of the sliding part 50 are reliably sealed, providing excellent watertightness. Furthermore, the sliding packing 1 has high wear resistance, resulting in excellent durability, and its surface has good lubricity, thus reducing sliding torque.

[0051] Since the sliding part is positioned so that the coating layer of the sliding packing, which has excellent airtightness, wear resistance, and surface lubricity, comes into contact with the sliding surface of the sliding member, the gap between the members of the sliding part is reliably sealed, providing excellent watertightness and improving the durability of the sliding part.

[0052] [Other embodiments] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is not limited to the configurations of the embodiments described above, but is indicated by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Examples]

[0053] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples.

[0054] <Sliding Packing No. 1> A silicone rubber sheet with an average thickness of 1 mm was powder-coated with PFA powder (MJ-103, manufactured by Mitsui Chemours Fluoroproducts Co., Ltd.) on one side, and the powder-coated substrate was fired (lamination process). Furthermore, the test sample (laminated body) formed by the lamination process was irradiated with an electron beam (electron beam irradiation process). In the electron beam irradiation process, the sample was heated at 330°C for 10 minutes under a nitrogen atmosphere with an oxygen concentration of 5 ppm, and then irradiated from above with an electron beam using an electron beam accelerator (Sagatron, manufactured by Nissin Electric Co., Ltd.). The irradiation conditions were an acceleration voltage of 1 MeV and an irradiation dose of 100 kGy. In this way, a coating layer was laminated on one side of the substrate, and a sliding packing No. 1 with an average coating layer thickness of 30 μm was obtained.

[0055] Next, a grid test was performed on sliding packing No. 1 in accordance with JIS-K5400-8.5:1990 (JIS-D0202:1988) to evaluate the adhesion between the substrate and the coating layer. Here, the grid test specifically involves making 100 grid-like scratches on the surface of the coating layer, applying tape over them, and then peeling it off. The number of grid marks that remain intact is then counted. For example, a grid test result of "99 / 100" means that 99 out of 100 grid marks remained intact. The evaluation results are shown in Table 1.

[0056] <Sliding Packing No. 2> Sliding packing No. 2 was manufactured in the same manner as sliding packing No. 1, except that the electron beam irradiation process was omitted.

[0057] <Sliding packing No. 3 to No. 7> Sliding packings No. 3 to No. 7 were manufactured using the same materials as shown in Table 1 for the base material, except that a coating layer was not laminated, as was done with sliding packing No. 1.

[0058] Next, sliding packings No. 1 to No. 7 were evaluated for wear resistance using a ring-on-disk type abrasion test, surface slipperiness using the coefficient of dynamic friction, and airtightness using hardness. The results are shown in Table 1.

[0059] (Critical PV value based on ring-on-disc type wear test) The ring-on-disk abrasion test is a test method compliant with JIS-K7218:1986, in which a ring-shaped tip is pressed perpendicularly against the sliding surface of the test material while the sliding surface is rotated, causing circular sliding. Specifically, a ring-shaped mating material made of S45C (carbon steel) with an outer diameter of Φ11.4 mm, an inner diameter of 7.4 mm, and a surface roughness of Ra 0.28 μm was used. This ring-shaped mating material was placed on the top surface of the test sample, and at the same time, a load of 10 MPa was applied, and the table on which the test sample was placed was rotated at high speed. The limit PV value [MPa·m / min] of the surface of each test sample was measured to evaluate the abrasion resistance. For the above measurements, an A&D friction and abrasion tester "EFM-III1010" was used as the test apparatus. Furthermore, the test samples for sliding packings No. 1 and No. 2 were laminates consisting of a base and a coating layer. Since the adhesive strength between the base and the coating layer was insufficient for abrasion testing, the test samples for sliding packings No. 1 and No. 2 were constructed by laminating a coating layer with an average thickness of 1 mm onto a 1 mm aluminum plate under the same conditions as for No. 1 and No. 2. For test samples No. 1 and No. 2, the PV value just before the aluminum plate was exposed was used as the limit PV value. In addition, since test sample No. 3 did not have a coating layer, the PV value of the base just before the table on which it was placed was exposed was used as the limit PV value. For sliding packings No. 4 to No. 7, measurement was not possible because the limit PV values ​​were below the measurement limit.

[0060] (Coefficient of kinetic friction) Using a surface texture measuring instrument (TYPE-HEIDON-14, manufactured by Shinto Kagaku Co., Ltd.), a 10mmΦ steel ball was pressed against the surface of each sliding packing with a load of 1N and slid at a speed of 150mm / min. The resulting load was measured, and the coefficient of dynamic friction was measured in accordance with JIS-K7125:1999. However, for sliding packings No. 4 to No. 7, the coefficient of friction was too high, preventing the steel ball from moving relative to the sample surface, and therefore measurement was not possible.

[0061] (hardness) The hardness of each sliding packing was measured using a Shore D hardness tester in accordance with JIS-K7215:1986 Type D. Hardness is related to the airtightness of the sliding packing, and the airtightness of the sliding packing can be evaluated by the measured hardness.

[0062] (Judgment criteria) Airtightness, abrasion resistance, and surface slipperiness were evaluated on a three-point scale (A: very good, B: good, C: poor) based on the measurement results. The specific evaluation criteria are as follows. An evaluation of A or B is considered acceptable. (1) Airtightness A: Shore D hardness 20 or less B: Shore D hardness between 20 and 40 C: Shore D hardness over 40 (2) Abrasion resistance A: The limit PV value is 500 MPa·m / min or higher. B: Limit PV value is 100 MPa·m / min or more and less than 500 MPa·m / min C: Limit PV value is less than 100 MPa·m / min (3) Surface slipperiness A: The coefficient of kinetic friction is less than 0.3 B: The coefficient of kinetic friction is 0.3 or greater and less than 0.6. C: The coefficient of kinetic friction is 0.6 or higher.

[0063] [Table 1]

[0064] As shown in Table 1, in sliding packing No. 1, which has a coating layer mainly composed of an electron beam crosslinked polytetrafluoroethylene, it can be seen that the substrate and the coating layer are strongly bonded. Furthermore, sliding packing No. 1 has a high limit PV value and excellent wear resistance, as well as a low Shore D hardness and dynamic friction coefficient, and excellent airtightness and surface slipperiness.

[0065] On the other hand, sliding packing No. 2, which has a coating layer mainly composed of non-crosslinked fluororesin, has a low Shore D hardness and coefficient of dynamic friction, and excellent airtightness and surface slipperiness, but poor wear resistance and adhesion, and is considered unsuitable for high-speed sliding and high loads. Sliding packing No. 3, which does not have a coating layer and has only a substrate mainly composed of non-crosslinked fluororesin, has a low coefficient of dynamic friction and excellent surface slipperiness, so it can reduce sliding torque even under sliding conditions of high load and high rotation, but it has a low limit PV value, resulting in poor wear resistance, and its high Shore D hardness makes it difficult to maintain airtightness. In sliding packing No. 4, which lacks a coating layer and consists only of a base material mainly composed of silicone rubber, the Shore D hardness is very low and it is thought to have excellent airtightness. However, the limiting PV value is extremely low and the coefficient of dynamic friction is extremely high, resulting in very poor wear resistance and surface lubricity. Therefore, it is found that it is not suitable for sliding parts that rotate at high speeds under high loads. Even in sliding packings No. 5 to No. 7, which lack a coating layer and consist only of a base material mainly composed of various rubbers, the limit PV value is extremely low, the coefficient of dynamic friction is extremely high, and the wear resistance and surface lubricity are very poor, making them unsuitable for sliding parts that rotate at high speeds under high loads. Therefore, only Example 1 could simultaneously satisfy all of the required characteristics of a sliding packing: adhesion to the substrate, airtightness, wear resistance, and surface lubricity.

[0066] The results above demonstrate that the sliding packing exhibits excellent airtightness, wear resistance, and surface lubricity. [Explanation of symbols]

[0067] 1. Sliding packing 2 Base 3 Covering layer 10 Sliding member 15 Support member 50 Sliding parts

Claims

1. A substrate mainly composed of rubber, A coating layer directly laminated on at least a portion of the surface of the above substrate and Equipped with, A sliding packing in which the above-mentioned coating layer is mainly composed of an electron beam crosslinked fluororesin.

2. The above rubber is silicone rubber or fluororubber. The sliding packing according to claim 1, wherein the fluororesin is polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

3. A sliding packing according to claim 1 or claim 2, Sliding member and Equipped with, A sliding component in which the coating layer of the sliding packing is positioned to contact the sliding surface of the sliding member.

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