Primer coating composition and gasket

Abstract

To provide a primer coating composition which gives a primer layer having excellent adhesion to a substrate, having excellent abrasion resistance, and capable of preventing damage to the substrate, and also to provide a primer layer formed by curing the primer coating composition, and a gasket having the primer layer directly formed on at least a portion thereof.SOLUTION: The present invention provides a primer coating composition comprising an epoxy resin and fine fluororesin particles, a primer layer formed by curing the primer coating composition, and a gasket having the primer layer directly formed on at least a portion thereof.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a primer coating composition, a primer layer formed by curing the primer coating composition, and a gasket having the primer layer directly formed at least on a portion thereof. [Background technology]

[0002] Conventionally, desired properties have been imparted to a substrate, such as a metal, a polymer, etc., by laminating layers on the substrate. From the viewpoint of workability, paints are widely used to form the layers, and the properties exhibited by the layers vary depending on the components blended in the paint.

[0003] Patent Document 1 discloses that by applying a coating material made of an epoxy resin containing inorganic fine particles to an iron alloy body, a layer of uniform width and thickness can be obtained even when the coating film is heated to a high temperature to harden it. Patent Document 2 discloses that by applying a coating material containing a specific urethane resin, a solid lubricant, and a solvent in a predetermined ratio to a gasket to coat it with an elastomer, it is possible to prevent the elastomer component from adhering to the mating material without impairing the inherent sealing properties of the gasket. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-036764 [Patent Document 2] JP 2012-219183 A Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, in components in which damage to the substrate has a large effect on performance, such as gaskets, it is important to provide a primer layer with excellent adhesion and abrasion resistance on the substrate. However, there are hardly any primer coating compositions precisely designed from such a viewpoint, and even if they exist, they do not provide sufficient performance.

[0006] An object of the present invention is to provide a primer coating composition that provides a primer layer that has excellent adhesion to a substrate and excellent abrasion resistance and can prevent damage to the substrate. Another object of the present invention is to provide a primer layer obtained by curing the primer coating composition, and a gasket having the primer layer directly formed at least on a portion thereof. [Means for solving the problem]

[0007] As a result of intensive research, the present inventors have found that a primer coating composition containing an epoxy resin and fluororesin fine particles can provide a primer layer that has excellent adhesion to a substrate and excellent abrasion resistance and can prevent the substrate from being scratched, and have completed the present invention.

[0008] [1] A primer coating composition comprising an epoxy resin and fluororesin fine particles. [2] The primer coating composition according to [1], wherein the fluororesin fine particles are at least one selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE). [3] The primer coating composition according to [1] or [2], comprising 5 to 50 parts by mass of the fluororesin fine particles per 100 parts by mass of the epoxy resin. [4] The primer coating composition according to any one of [1] to [3], wherein the average particle size of the fluororesin fine particles is 3 to 18 μm. [5] The primer coating composition according to any one of [1] to [4], which is intended for application to a surface of a metal material. [6] The primer coating composition according to [5], for application to a metal surface of a gasket.

[0009] [7] A primer layer obtained by curing the primer coating composition according to any one of [1] to [6]. [8] A gasket having the primer layer according to [7] directly formed on at least a portion thereof. Effect of the Invention

[0010] According to the present invention, it is possible to provide a primer coating composition which gives a primer layer which has excellent adhesion to a substrate and is also excellent in abrasion resistance so as to prevent damage to the substrate. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the results of a compression-torsion test on evaluation samples of the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The primer coating composition of the present invention, the primer layer formed by curing the primer coating composition, and the gasket having the primer layer directly formed at least partially thereon will be described in detail below. The present invention is not limited to the embodiments described below. In this specification, a numerical range expressed using "to" includes the numerical range before and after the range, for example, "P to Q" means "P or more and Q or less."

[0013] <Primer coating composition> The primer coating composition of the present invention contains an epoxy resin and fluororesin fine particles, and thus it is possible to provide a primer coating composition that provides a primer layer that has excellent adhesion to a substrate and excellent abrasion resistance and can prevent the substrate from being scratched.

[0014] [Epoxy resin] The primer coating composition of the present invention contains an epoxy resin. There are no particular limitations on the type of epoxy resin, but an epoxy resin having two or more epoxy groups in one molecule is preferred. Examples of preferred epoxy resins include bisphenol type epoxy resins such as bisphenol A type epoxy resins and bisphenol F type epoxy resins, naphthalene type epoxy resins, biphenyl type epoxy resins, novolac type epoxy resins such as phenol novolac type epoxy resins and cresol novolac type epoxy resins, cyclic aliphatic epoxy resins, glycidylamine type resins, heterocyclic epoxy resins, polyfunctional epoxy resins, etc. These may be used alone or in combination of two or more.

[0015] Further specific examples of epoxy resins include Yuka Resin RE-1050 (manufactured by Yoshimura Oil Chemicals Co., Ltd.), ECOBOND SEW-47S (manufactured by SNC Chemicals Co., Ltd.), Adeka Resin EM-101-50 (manufactured by ADEKA Corporation), and Adeka Resin Examples of such resins include EM-0425C (manufactured by ADEKA Corporation), jER1001 (manufactured by Mitsubishi Chemical Corporation), jER1004 (manufactured by Mitsubishi Chemical Corporation), jER1004F (manufactured by Mitsubishi Chemical Corporation), jER1007 (manufactured by Mitsubishi Chemical Corporation), jER4005P (manufactured by Mitsubishi Chemical Corporation), EPICLON1050 (manufactured by DIC Corporation), EPICLON3050 (manufactured by DIC Corporation), EPICLON4050 (manufactured by DIC Corporation), Epotohto YD014D (manufactured by Nippon Steel Chemical & Material Co., Ltd.), and EPONANYANPE-S-904 (manufactured by Nan'a Plastics Co., Ltd.).

[0016] The softening point of the epoxy resin is not particularly limited, but is preferably from 120 to 200°C, more preferably from 140 to 200°C, and even more preferably from 150 to 200°C, from the viewpoint of heat resistance. In addition, the epoxy equivalent of the epoxy resin is not particularly limited, but is preferably 20 to 60, more preferably 20 to 50, and even more preferably 30 to 50, from the viewpoint of abrasion resistance.

[0017] [Fluororesin particles] The primer coating composition of the present invention contains fluororesin fine particles. There is no particular restriction on the type of fluororesin fine particles, but preferred examples of fluororesin fine particles include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE). These may be used alone or in combination of two or more.

[0018] In the primer coating composition of the present invention, the content of the fluororesin fine particles is not particularly limited and can be freely set according to the properties required for the primer coating composition. The content of the fluororesin fine particles is preferably 5 to 50 parts by mass, more preferably 5 to 30 parts by mass, per 100 parts by mass of the epoxy resin.

[0019] It is preferable that the primer coating composition contains 5 parts by mass or more of fluororesin microparticles per 100 parts by mass of epoxy resin, since the abrasion resistance of the resulting primer layer can be improved to a preferred range. It is also preferable that the primer coating composition contains 50 parts by mass or less of fluororesin microparticles per 100 parts by mass of epoxy resin, since the abrasion resistance of the resulting primer layer and its adhesion to the substrate can be both achieved within a preferred range.

[0020] The average particle size of the fluororesin fine particles is not particularly limited and can be freely set depending on the properties required for the primer coating composition. The average particle size of the fluororesin fine particles is preferably 3 to 18 μm, more preferably 3 to 10 μm, and even more preferably 3 to 8 μm. It is preferable that the average particle size of the fluororesin fine particles contained in the primer coating composition is 3 μm or more, since the abrasion resistance of the resulting primer layer can be improved to a preferred range. Also, it is preferable that the average particle size of the fluororesin fine particles contained in the primer coating composition is 18 μm or less, since the abrasion resistance and adhesion to the substrate of the resulting primer layer can be both achieved within a preferred range.

[0021] In this specification, the average particle size of the fluororesin fine particles refers to the 50% particle size (D 50 The average particle size of the fluororesin fine particles is expressed as the equivalent sphere diameter by the laser diffraction / scattering method, and is determined from the particle size distribution measured using a laser diffraction / scattering particle size distribution measuring device.

[0022] By incorporating fluororesin fine particles in the primer coating composition, the strength of the primer layer is increased and the primer layer is less likely to be lost due to wear, thereby preventing damage to the substrate. Furthermore, when the fluororesin fine particles are contained in the primer coating composition, the effect on the smoothness of the outermost surface of the coating film formed on the substrate is small, so that the fluororesin fine particles having a larger average particle size can be used compared to the compositions for forming other layers, and thus the primer coating composition of the present invention can exert a more excellent effect in terms of preventing damage to the substrate.

[0023] [Optional ingredients] In addition to the epoxy resin and the fluororesin fine particles, the primer coating composition of the present invention may contain the following optional components within limits that do not impair the performance of the composition.

[0024] (solvent) The primer coating composition of the present invention may further contain a solvent as necessary. There is no particular restriction on the type of solvent, and preferred examples of the solvent include aromatic solvents such as toluene, xylene, and mesitylene; alcohols such as propanol, butanol, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; ketones such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and isophorone; esters such as ethyl acetate and butyl acetate; and other organic solvents. In addition to the organic solvent, an aqueous solvent may be used in combination as the solvent. The aqueous solvent may be at least one of water, any aqueous solution, and the like. Only one solvent may be used, or two or more solvents may be used in any ratio and combination.

[0025] When the primer coating composition of the present invention contains a solvent, from the viewpoint of ensuring a film thickness, the content of the solvent is preferably 40 to 70 parts by mass, and more preferably 40 to 60 parts by mass, per 100 parts by mass of the total primer coating composition.

[0026] (Other optional ingredients) The primer coating composition of the present invention may further contain other optional components as necessary. There is no particular restriction on the type of other optional components, but preferred examples of components include plasticizers, curing agents, leveling agents, defoamers, pigment dispersants, silane coupling agents, ultraviolet absorbers, antioxidants, thickeners, vulcanizing agents, fillers such as silica, talc, clay, mica, calcium carbonate, magnesium oxide, calcium hydroxide, wollastonite, and carbon black, stabilizers, and antiblocking agents. These optional components may be used alone or in any combination of two or more in any ratio.

[0027] [Substrate and its uses] The primer coating composition of the present invention can form a primer layer by applying it to the surface of a substrate.

[0028] The substrate to which the primer coating composition of the present invention is applied is not particularly limited, and examples thereof include metal materials selected from metals such as iron, steel, copper, aluminum, tin, zinc, etc. and alloys containing these metals, etc.; and plastic materials selected from polypropylene resins, polycarbonate resins, urethane resins, polyester resins, polystyrene resins, ABS resins, vinyl chloride resins, polyamide resins, etc. The substrate can be appropriately selected depending on the application.

[0029] Before applying the primer coating composition to the metal material, it may be subjected to a surface treatment such as a chromate treatment using trivalent chromium, hexavalent chromium, or the like; a chemical conversion treatment such as a non-chromate treatment such as zinc phosphate treatment or zirconium treatment; or a corona discharge treatment, an ultraviolet light / ozone treatment, a plasma treatment, an oxygen plasma treatment, a flame treatment, a solvent treatment, or the like, as necessary. In addition, before applying the primer coating composition to the plastic material, if necessary, a surface treatment such as corona discharge treatment, ultraviolet light / ozone treatment, plasma treatment, oxygen plasma treatment, flame treatment, solvent treatment, etc. may be performed.

[0030] When the primer coating composition of the present invention is applied to the surface of a metal material as a substrate, it is preferable because it has excellent adhesion to the substrate, excellent abrasion resistance, and more remarkable effect of preventing damage to the substrate. That is, the primer coating composition of the present invention is preferably a primer coating composition for application to the surface of a metal material. From the viewpoint of ensuring the strength of the gasket, the metal material is more preferably a stainless steel material.

[0031] There is no particular limitation on the use of the metal material to which the primer coating composition of the present invention is applied, and it is preferably a metal material for forming a member in which damage to the substrate has a large effect on performance.Such metal materials include, for example, metal materials for gaskets, metal materials for packings, metal materials for screws, metal materials for nuts, etc.Among these, when the primer coating composition of the present invention is applied to the metal materials for gaskets or metal materials for packings, in which damage to the substrate has a large effect on airtightness, particularly the metal materials for gaskets, the effect of the present invention can be more significantly exhibited, which is preferable. That is, the primer coating composition of the present invention is more preferably a primer coating composition for application to the metal surface of a gasket.

[0032] [Method of manufacturing primer coating composition] The primer coating composition of the present invention can be produced by any method. For example, the production method includes mixing each component contained in the primer coating composition. For mixing each component, for example, a mixer disperser such as a roller mill, a ball mill, a bead mill, a pebble mill, a sand grind mill, a pot mill, a paint shaker or a disperser, a kneader, etc. can be used.

[0033] <Primer layer> The present invention also relates to a primer layer formed by curing the above-mentioned primer coating composition.

[0034] The components contained in the primer layer of the present invention and their preferred embodiments are the same as those described for the primer coating composition above. However, among the components contained in the primer coating composition, components that volatilize or disappear when the primer layer is formed, such as solvents, are not contained in the primer layer.

[0035] The thickness of the primer layer of the present invention is not particularly limited and can be appropriately changed depending on the purpose, application, etc. From the viewpoint of sealing water, oil, and combustion gas of the engine and improving the wear resistance of the gasket, the thickness of the primer layer is preferably 5 to 20 μm, more preferably 10 to 20 μm, and further preferably 15 to 20 μm.

[0036] The primer layer of the present invention can be produced by any method, for example, by applying the primer coating composition of the present invention to the surface of a substrate by spraying, immersion, brushing, roll coating, or other methods, and then drying and / or baking under suitable drying and / or baking conditions to cure the composition; printing such as screen printing, etc.

[0037] <Gasket> The present invention also relates to a gasket having the above-mentioned primer layer formed directly on at least a portion thereof. The gasket of the present invention has a primer layer formed directly on at least a portion thereof, which has excellent adhesion to the gasket surface, excellent abrasion resistance, and can prevent the gasket surface from being scratched, and therefore has excellent durability, reliability, and crack resistance, and is less susceptible to attacking the engine. The components contained in the primer layer formed on the gasket of the present invention and preferred embodiments thereof are the same as those described above for the primer layer, and the constituent materials of the gasket and preferred embodiments thereof are the same as those described above for the substrate.

[0038] [Further Layers] The gasket of the present invention may include an additional layer on the surface opposite to the gasket side surface of the primer layer. There is no particular limitation on the additional layer, and it can be appropriately selected depending on the purpose and environment in which the gasket is used. Examples of the additional layer include a rubber layer and a lubricating layer. The additional layer may be formed as only one layer, or may be formed as any combination of two or more layers.

[0039] (Rubber layer) The rubber layer can have the role of improving heat resistance and providing micro-sealing properties. The rubber layer can be made of a known rubber having excellent heat resistance. Examples of rubber having excellent heat resistance include synthetic rubbers such as fluororubber and silicone rubber, and fluororubber is preferred.

[0040] When a rubber layer is present, there is no particular limitation on its thickness, and it can be appropriately changed depending on the purpose, application, etc. The thickness of the rubber layer is preferably 3 to 15 μm.

[0041] (lubricating layer) The lubricating layer may be made of any known solid lubricant as long as it has excellent lubricity. Examples of solid lubricants include fine particles of fluororesin, molybdenum disulfide, and graphite. The lubricating layer may be made of only a solid lubricant, but a binder may be used as a binding agent to improve adhesion to the lower layer. The lubricating layer may be made of a combination of epoxy resin and fine particles of fluororesin as a binding agent.

[0042] When the lubricating layer is present, there is no particular limitation on its thickness, and it can be appropriately changed depending on the purpose, application, etc. The thickness of the lubricating layer is preferably 5 to 15 μm.

[0043] [Application] The gasket of the present invention is excellent in durability, reliability and crack resistance, and can reduce the risk of attack on the engine, and therefore can be suitably used in internal combustion engines such as vehicle engines; piping, and the like. EXAMPLES

[0044] <Production Example 1: Preparation of base coating composition A> Base coating composition A was prepared by uniformly dissolving 100 parts by mass of bisphenol A type epoxy resin (YD-014, manufactured by Nippon Steel Chemical & Material Co., Ltd.), 20 parts by mass of an amine-based curing agent (Jeffamine D-230, manufactured by Huntsman Co., Ltd.), 10 parts by mass of carbon black (N762, manufactured by Cabot Corporation), 30 parts by mass of talc (P-3, manufactured by Nippon Talc Co., Ltd.), 20 parts by mass of calcium carbonate (Escalon #2000, manufactured by Sankyo Flour Milling Co., Ltd.), and 10 parts by mass of silica (Aerosil #200, manufactured by Nippon Aerosil Co., Ltd.) in isophorone to a solids content of 30%.

[0045] <Production Example 2: Preparation of Base Coating Composition B> Base coating composition B was prepared by uniformly dissolving 100 parts by mass of fluororubber (vinylidene fluoride-hexafluoropropylene copolymer) (Chemours, Viton A-200), 20 parts by mass of carbon black (Cabot, N762), 6 parts by mass of calcium hydroxide (Ohmi Chemical Industry Co., Ltd., Caldic #1000), 3 parts by mass of magnesium oxide (Kyowa Chemical Industry Co., Ltd., Kyowamag 150), 2 parts by mass of a vulcanizing agent (Chemours, Curative #20), and 4 parts by mass of a vulcanizing agent (Chemours, Curative #30) in isophorone to a solids content of 30%.

[0046] <Production Example 3: Preparation of lubricant layer-forming composition 1> Lubricant layer-forming composition 1 was prepared by uniformly dissolving 100 parts by mass of bisphenol A type epoxy resin (YD-014, manufactured by Nippon Steel Chemical & Material Co., Ltd.), 20 parts by mass of an amine-based curing agent (Jeffamine D-230, manufactured by Huntsman), 5 parts by mass of carbon black (N762, manufactured by Cabot Corporation), 15 parts by mass of talc (P-3, manufactured by Nippon Talc Co., Ltd.), 10 parts by mass of calcium carbonate (Escalon #2000, manufactured by Sankyo Flour Milling Co., Ltd.), and 100 parts by mass of fluororesin fine particles (polytetrafluoroethylene (PTFE, average particle size: 6 μm, Fluo300, manufactured by Micropowder Co., Ltd.)) in isophorone to a solid content of 30%.

[0047] <Production Example 4: Preparation of rubber layer forming composition 1> To 100 parts by mass of base coating composition B, 20 parts by mass of fluororesin fine particles (polytetrafluoroethylene (PTFE, average particle size: 6 μm, manufactured by Micropowder Co., Ltd., Fluo300)) were added and mixed uniformly to prepare rubber layer forming composition 1.

[0048] <Example 1: Preparation of primer coating composition 1> Fluorine resin fine particles (polytetrafluoroethylene (PTFE, average particle size: 6 μm, manufactured by Micropowder Co., Ltd., Fluo300)) were added to 100 parts by mass of base coating composition A and mixed uniformly to prepare primer coating composition 1. The content of the fluororesin fine particles was 20 parts by mass relative to 100 parts by mass of bisphenol A type epoxy resin.

[0049] <Comparative Example 1: Preparation of primer coating composition 2> Base coating composition A was used as primer coating composition 2 without adding the fluororesin fine particles.

[0050] <Example 2-1: Production of Gasket 1> On a flat substrate (stainless steel SUS301H treated with chromate; dimensions 100 mm x 100 mm x 0.2 mm), the primer coating composition 1 was printed by a screen printer to form a primer layer having a thickness of 10.5 μm. On the obtained primer layer, the rubber layer forming composition 1 was printed by the screen printer to form a rubber layer having a thickness of 7.5 μm. On the obtained rubber layer, the lubricant layer forming composition 1 was printed by the screen printer to form a lubricant layer having a thickness of 10.0 μm, and a gasket 1 was obtained. The obtained gasket 1 was laminated in the order of the primer layer, rubber layer, and lubricant layer from the substrate side, and the thickness of the entire layer excluding the substrate was 28.0 μm.

[0051] <Example 2-2: Production of Gasket 2> A gasket 2 was obtained in the same manner as in Example 2-1, except that the thickness of the primer layer was 17.5 μm, the thickness of the rubber layer was 7.5 μm, and the thickness of the lubricating layer was 7.5 μm. The obtained gasket 2 had the primer layer, the rubber layer, and the lubricating layer laminated in this order from the substrate side, and the total thickness of the layers excluding the substrate was 32.5 μm.

[0052] <Comparative Example 2: Manufacture of Gasket 3> On a flat substrate (stainless steel SUS301H treated with chromate; dimensions 100 mm x 100 mm x 0.2 mm), the primer coating composition 2 was printed by a screen printer to form a primer layer having a thickness of 11.5 μm. On the obtained primer layer, the rubber layer forming composition 1 was printed by the screen printer to form a rubber layer having a thickness of 13.5 μm. On the obtained rubber layer, the lubricant layer forming composition 1 was printed by the screen printer to form a lubricant layer having a thickness of 10.0 μm, and a gasket 3 was obtained. The obtained gasket 3 was laminated in the order of the primer layer, rubber layer, and lubricant layer from the substrate side, and the thickness of the entire layer excluding the substrate was 35.0 μm.

[0053] <Gasket evaluation: Compression torsion test> A ring-shaped test jig (aluminum alloy A2618; diameter φ: 60 mm, hollow diameter φ: 30 mm, thickness: 30 mm; processed by our company) was placed on the lubricating layer of the obtained gasket to prepare an evaluation sample, and was set in a compression torsion tester (manufactured by Shimadzu Corporation). The compression torsion tester was set so that a load of 200 MPa was applied to the evaluation sample at a temperature of 200 ° C., and a test was performed in which the sample was repeatedly slid at 10 Hz within an angle range of 1 degree. After 18,000 cycles, the test jig was removed from the evaluation sample, and the evaluation sample surface was visually observed and evaluated as follows. In the following evaluation, when a resin layer remained on the evaluation sample surface, it was determined that at least the primer layer remained in a state of adhesion to the substrate. The results are shown in Table 1. A (Good): Primer layer remains on 75% or more (area ratio) of the substrate surface B (No problem): Primer layer remains on 50% to less than 75% (area ratio) of the substrate surface C (Poor): Primer layer remains on less than 50% (area ratio) of the substrate surface

[0054] FIG. 1 shows the relationship between the number of cycles in the compression-torsion test and the coefficient of friction.

[0055] [Table 1]

[0056] As shown in Table 1, the evaluation samples made from the gaskets of Examples 2-1 and 2-2 using the primer coating composition according to the present invention had high primer layer remnants even after the compression torsion test. This shows that the primer layers contained in the gaskets of Examples 2-1 and 2-2 have excellent adhesion to the substrate and excellent abrasion resistance, and can prevent the substrate from being scratched. In contrast, the evaluation samples made from the gaskets of Comparative Example 2 using a primer coating composition different from the present invention had low remnants after the compression torsion test.

[0057] In addition, as shown in FIG. 1, the evaluation samples made from the gaskets of Examples 2-1 and 2-2 using the primer coating composition according to the present invention required many cycles before the friction coefficient started to increase, whereas the evaluation sample made from the gasket of Comparative Example 2 using a primer coating composition different from the present invention had a relatively small number of cycles before the friction coefficient started to increase. The friction coefficient of the evaluation sample is kept low while the fluororesin fine particles remain between the substrate and the test jig, and starts to increase when they are lost. Therefore, the evaluation sample that requires more cycles before the friction coefficient starts to increase has excellent adhesion to the substrate and excellent abrasion resistance, and can prevent the substrate from being scratched. In particular, it was found that the evaluation sample made from the gasket of Example 2-2, which has a thick primer layer using the primer coating composition according to the present invention, required a very large number of cycles before the friction coefficient started to increase. [Industrial Applicability]

[0058] The primer coating composition of the present invention can provide a primer layer that has excellent adhesion to a substrate and excellent abrasion resistance, thereby preventing damage to the substrate, and can therefore be suitably used, for example, to form a primer layer for a gasket.

Claims

1. A primer coating composition comprising an epoxy resin and fluororesin fine particles.

2. The primer coating composition according to claim 1, wherein the fluororesin fine particles are at least one selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE) and ethylene-chlorotrifluoroethylene copolymer (ECTFE).

3. The primer coating composition according to claim 1, comprising 5 to 50 parts by mass of the fluororesin fine particles per 100 parts by mass of the epoxy resin.

4. The primer coating composition according to claim 1, wherein the average particle size of the fluororesin fine particles is 3 to 18 μm.

5. The primer coating composition according to claim 1, for application to a metal surface.

6. The primer coating composition according to claim 5, which is for application to a metal surface of a gasket.

7. A primer layer obtained by curing the primer coating composition according to any one of claims 1 to 6.

8. A gasket having the primer layer according to claim 7 directly formed at least on a portion thereof.

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