Primer paint 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 paint composition, a primer layer formed by curing the primer paint composition, and a gasket formed by directly forming the primer layer at least in part.

Background Art

[0002] Conventionally, by laminating a layer on a substrate such as metal or polymer, desired properties are imparted to the substrate. From the viewpoint of workability, paints are widely used for forming layers, and the properties exhibited by the layers vary depending on the components incorporated in the paints.

[0003] Patent Document 1 discloses that by applying a paint composed of an epoxy resin containing inorganic fine particles to an iron alloy body, a layer having uniform width and thickness can be obtained even when heated to a high temperature to cure the coating film. Further, Patent Document 2 discloses that by applying a paint containing a specific urethane resin, a solid lubricant and a solvent in a predetermined ratio to a gasket to coat the elastomer, the adhesion of the elastomer component to the mating material can be prevented without impairing the original sealing property of the gasket.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of other members such as gaskets, etc., where scratches on the base material have a great influence on performance, it is important to provide a primer layer excellent in adhesion and wear resistance on the base material. However, there are few primer paint compositions that are exquisitely designed from such a viewpoint, or even if they exist, the current situation is that sufficient performance has not been obtained.

[0006] An object of the present invention is to provide a primer paint composition that gives a primer layer excellent in adhesion to a base material and excellent in wear resistance and capable of preventing damage to the base material. Another object of the present invention is to provide a primer layer formed by curing the primer paint composition and a gasket in which the primer layer is directly formed at least in part.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have found that by using a primer paint composition containing an epoxy resin and fluororesin fine particles, a primer layer excellent in adhesion to a base material and excellent in wear resistance and capable of preventing damage to the base material can be obtained, and have completed the present invention. That is, the present invention relates to the following.

[0008] [1] A primer paint composition containing an epoxy resin and fluororesin fine particles. [2] The primer paint composition according to [1], wherein the fluororesin fine particles are composed of 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 paint composition according to [1] or [2], which contains 5 to 50 parts by mass of the fluororesin fine particles with respect to 100 parts by mass of the epoxy resin. [4] The primer paint composition according to any one of [1] to [3], wherein the average particle diameter of the fluororesin fine particles is 3 to 18 μm. [5] The primer paint composition according to any one of [1] to [4], which is for application to the surface of a metal material. [6] The primer paint composition according to [5], which is for application to the surface of the metal material of a gasket.

[0009] [7] A primer layer formed by curing the primer paint composition according to any one of [1] to [6]. [8] A gasket in which the primer layer according to [7] is directly formed at least in part.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a primer paint composition that gives a primer layer having excellent adhesion to a substrate and excellent abrasion resistance and capable of preventing damage to the substrate.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the primer paint composition of the present invention, a primer layer formed by curing the primer paint composition, and a gasket in which the primer layer is directly formed at least in part will be described in detail. Note that the present invention is not limited to the embodiments described below. Also, in this specification, a numerical range expressed using "~" includes the numerical values before and after, for example, "P~Q" means "P or more and Q or less".

[0013] <Primer paint composition> The primer paint composition of the present invention contains an epoxy resin and fluororesin fine particles. Thereby, it is possible to provide a primer paint composition that gives a primer layer having excellent adhesion to a substrate and excellent abrasion resistance, and can prevent damage to the substrate.

[0014] [Epoxy resin] The primer paint composition of the present invention contains an epoxy resin. There is no particular limitation 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 resin and bisphenol F type epoxy resin; naphthalene type epoxy resin; biphenyl type epoxy resin; novolak type epoxy resins such as phenol novolak type epoxy resin and cresol novolak type epoxy resin; cycloaliphatic epoxy resin; glycidylamine type resin; heterocyclic epoxy resin; polyfunctional epoxy resin and the like. These may be used alone or in combination of two or more.

[0015] As further specific examples of the epoxy resin, Yucarezine RE-1050 (manufactured by Yoshimura Oil Chemical Co., Ltd.), ECOBOND SEW-47S (manufactured by SNC Chemicals), Adekaresin EM-101-50 (manufactured by Adeka Corporation), Adekaresin 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), Epotote YD014D (manufactured by Nippon Steel Chemical & Material Co., Ltd.), EPONANYANPES-904 (manufactured by Nan Ya Plastics Corporation), etc. can be mentioned.

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

[0017] [Fluororesin fine particles] The primer paint composition of the present invention contains fluororesin fine particles. There is no particular limitation on the type of fluororesin fine particles, but examples of preferable 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), etc. These may be used alone or in combination of two or more.

[0018] In the primer paint 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 paint composition. As the content of the fluororesin fine particles, it is preferably 5 to 50 parts by mass, more preferably 5 to 30 parts by mass, based on 100 parts by mass of the epoxy resin.

[0019] When the primer paint composition contains 5 parts by mass or more of the fluororesin fine particles with respect to 100 parts by mass of the epoxy resin, the abrasion resistance of the obtained primer layer can be improved to a preferable range, which is preferable. Further, when the primer paint composition contains 50 parts by mass or less of the fluororesin fine particles with respect to 100 parts by mass of the epoxy resin, the abrasion resistance of the obtained primer layer and the adhesion to the substrate can be made compatible in a preferable range, which is preferable.

[0020] The average particle diameter of the fluororesin fine particles is not particularly limited and can be freely set according to the properties required for the primer paint composition. As the average particle diameter of the fluororesin fine particles, 3 to 18 μm is preferable, 3 to 10 μm is more preferable, and 3 to 8 μm is even more preferable. When the average particle diameter of the fluororesin fine particles contained in the primer paint composition is 3 μm or more, the abrasion resistance of the obtained primer layer can be improved to a preferable range, which is preferable. Further, when the average particle diameter of the fluororesin fine particles contained in the primer paint composition is 18 μm or less, the abrasion resistance of the obtained primer layer and the adhesion to the substrate can be made compatible in a preferable range, which is preferable.

[0021] In addition, the average particle diameter of the fluororesin fine particles referred to in this specification means the 50% particle diameter (D 50 ) on a volume basis, and is determined from the particle size distribution measured using a laser diffraction / scattering type particle size distribution measuring device. The average particle diameter of the above fluororesin fine particles is represented by the sphere equivalent diameter by the laser diffraction / scattering method.

[0022] By incorporating fluororesin fine particles into the primer paint composition, the strength of the primer layer is increased, and it becomes difficult for the primer layer to disappear due to abrasion, thereby preventing damage to the substrate. In addition, when fluororesin fine particles are incorporated into the primer paint composition, since the influence on the smoothness of the outermost surface of the coating film formed on the substrate is low, fluororesin fine particles having a larger average particle size can be used as compared with the composition for forming other layers. Thereby, the primer paint composition of the present invention can exhibit a more excellent effect in preventing damage to the substrate.

[0023] [Optional component] In addition to the epoxy resin and fluororesin fine particles, the primer paint composition of the present invention can contain the following optional components as long as its performance is not impaired.

[0024] (Solvent) The primer paint composition of the present invention can further contain a solvent, if necessary. There is no particular limitation on the type of the solvent. Examples of preferable solvents 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. As the solvent, in addition to the organic solvent, an aqueous solvent may be used in combination. Examples of the aqueous solvent include at least one of water and an arbitrary aqueous solution. The solvent may be used alone, or two or more kinds may be used in an arbitrary ratio and combination.

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

[0026] (Other optional components) The primer paint composition of the present invention can further contain other optional components as necessary. There are no particular restrictions on the types of other optional components, but examples of preferred components include plasticizers; curing agents; leveling agents; defoaming agents; 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, carbon black, etc.; stabilizers; antiblocking agents, and the like. These optional components may be used alone or in any ratio and combination of two or more.

[0027] [Substrate and Its Use] The primer paint composition of the present invention can form a primer layer by being applied to the surface of a substrate.

[0028] There are no particular restrictions on the substrate to which the primer paint composition of the present invention is applied. For example, metal materials selected from metals such as iron, steel, copper, aluminum, tin, zinc, and alloys containing these metals; plastic materials selected from polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, polyamide resin, etc. can be mentioned. The substrate can be appropriately selected according to the use.

[0029] Before applying the primer paint composition, the metal material may be subjected to chemical conversion treatments such as chromate treatment with trivalent chromium, hexavalent chromium, etc.; non-chromate treatments such as zinc phosphate treatment, zirconium treatment, etc.; surface treatments such as corona discharge treatment, ultraviolet / ozone treatment, plasma treatment, oxygen plasma treatment, flame treatment, solvent treatment, etc. as necessary. Also, before applying the primer paint composition, the plastic material may be subjected to surface treatments such as corona discharge treatment, ultraviolet / ozone treatment, plasma treatment, oxygen plasma treatment, flame treatment, solvent treatment, etc. as necessary.

[0030] When the primer paint composition of the present invention is applied to the surface of a metal material as a base material, it has excellent adhesion to the base material, excellent wear resistance, and can more significantly exert the effect of preventing damage to the base material. Therefore, it is preferable. That is, the primer paint composition of the present invention is preferably a primer paint composition for application to the surface of a metal material. Also, from the viewpoint of ensuring the strength as a gasket, stainless steel is more preferable as the metal material.

[0031] There is no particular limitation on the use of the metal material to which the primer paint composition of the present invention is applied. It is preferably a metal material for constituting a member in which damage to the base material has a great influence on the performance. Examples of such metal materials include a metal material for a gasket, a metal material for a packing, a metal material for a screw, and a metal material for a nut. Among these, when the primer paint composition of the present invention is applied to a metal material for a gasket or a metal material for a packing in which damage to the base material has a significant influence on airtightness, particularly to a metal material for a gasket, the effects of the invention can be more significantly exerted, so it is preferable. That is, the primer paint composition of the present invention is more preferably a primer paint composition for application to the surface of a metal material for a gasket.

[0032] [Manufacturing method of primer paint composition] The primer paint composition of the present invention can be manufactured by any method. Examples of the manufacturing method include mixing each component contained in the primer paint composition. For the mixing of 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 disper, a kneader, etc. can be used.

[0033] [Primer layer] The present invention also relates to a primer layer formed by curing the above-described primer paint composition.

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

[0035] There is no particular limitation on the thickness of the primer layer of the present invention, and it can be appropriately changed according to the purpose, application, etc. From the viewpoints of sealing of 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 even more preferably 15 to 20 μm.

[0036] The primer layer of the present invention can be produced by any method. Examples of the production method include applying the primer paint composition of the present invention to the surface of the substrate by methods such as spraying, dipping, brushing, roll coating, etc., and drying and / or baking and curing under drying conditions and / or baking conditions suitable for each; printing processes such as screen printing, etc.

[0037] <Gasket> The present invention also relates to a gasket in which at least a part of the above-mentioned primer layer is directly formed. Since the gasket of the present invention has a primer layer that is directly formed at least in part and is excellent in adhesion to the gasket surface and excellent in wear resistance, preventing damage to the gasket surface, it is excellent in durability, reliability, and crack resistance, and reduces the attack on the engine. The components contained in the primer layer formed on the gasket of the present invention and its preferred embodiments are the same as those described for the above-mentioned primer layer. Also, the constituent material of the gasket and its preferred embodiments are the same as those described for the above-mentioned substrate.

[0038] [Additional Layer] The gasket of the present invention may further include a layer on the surface opposite to the gasket-side surface of the primer layer. The additional layer is not particularly limited and can be appropriately selected according to the purpose and environment in which the gasket is used. Examples of the additional layer include a rubber layer; a lubricating layer, etc. The additional layer may be formed of only one layer, or may be formed in any combination of two or more layers.

[0039] (Rubber layer) The rubber layer can serve to improve heat resistance and micro-sealing properties. For the rubber layer, a rubber known for its high heat resistance can be used. Examples of rubbers rich in heat resistance include synthetic rubbers such as fluororubber and silicone rubber, and fluororubber is preferred.

[0040] When the rubber layer is present, its thickness is not particularly limited and can be appropriately changed according to the purpose and application, etc. The thickness of the rubber layer is preferably 3 to 15 μm.

[0041] (Lubricating layer) The lubricating layer only needs to have excellent lubricity, and known solid lubricants can be used. Examples of the solid lubricant include fine particles such as fluororesin, molybdenum disulfide, and graphite. The lubricating layer can be composed of only the solid lubricant, but a binder may be used as a binder to enhance the adhesion to the lower layer. The lubricating layer may be composed of a combination of an epoxy resin and fluororesin fine particles as a binder.

[0042] When the lubricating layer is present, its thickness is not particularly limited and can be appropriately changed according to the purpose and 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 attack on the engine. Therefore, it can be suitably used in internal combustion engines such as vehicle engines; pipes, etc.

Example

[0044] <Production Example 1: Preparation of Base Paint Composition A> 100 parts by mass of bisphenol A type epoxy resin (manufactured by Nippon Steel Chemical & Material Co., Ltd., YD-014), 20 parts by mass of amine curing agent (manufactured by Huntsman, Jeffamine D-230), 10 parts by mass of carbon black (manufactured by Cabot, N762), 30 parts by mass of talc (manufactured by Nippon Talc Co., Ltd., P-3), 20 parts by mass of calcium carbonate (manufactured by Sankyo Flour Milling Co., Ltd., Escaron #2000), and 10 parts by mass of silica (manufactured by Nippon Aerosil Co., Ltd., Aerosil #200) were uniformly dissolved in isophorone so that the solid content became 30%, and Base Paint Composition A was prepared.

[0045] <Production Example 2: Preparation of Base Paint Composition B> 100 parts by mass of fluororubber (vinylidene fluoride - hexafluoropropylene copolymer) (manufactured by Chemours, Viton A-200), 20 parts by mass of carbon black (manufactured by Cabot, N762), 6 parts by mass of calcium hydroxide (manufactured by Omi Chemical Industry Co., Ltd., Calcidic #1000), 3 parts by mass of magnesium oxide (manufactured by Kyowa Chemical Industry Co., Ltd., Kyowamag 150), 2 parts by mass of vulcanizing agent (manufactured by Chemours, Curative #20), and 4 parts by mass of vulcanizing agent (manufactured by Chemours, Curative #30) were uniformly dissolved in isophorone so that the solid content became 30%, and Base Paint Composition B was prepared.

[0046] <Production Example 3: Preparation of Composition 1 for Forming Lubricating Layer> 100 parts by mass of bisphenol A type epoxy resin (manufactured by Nippon Steel Chemical & Material Co., Ltd., YD-014), 20 parts by mass of amine curing agent (manufactured by Huntsman, Jeffamine D-230), 5 parts by mass of carbon black (manufactured by Cabot, N762), 15 parts by mass of talc (manufactured by Nippon Talc Co., Ltd., P-3), 10 parts by mass of calcium carbonate (manufactured by Sankyo Flour Milling Co., Ltd., Escaron #2000), and 100 parts by mass of fluororesin fine particles (polytetrafluoroethylene (PTFE, average particle size: 6 μm, manufactured by Micro Powder Inc., Fluo300)) were uniformly dissolved in isophorone so that the solid content became 30%, and Composition 1 for Forming Lubricating Layer was prepared.

[0047] <Production Example 4: Preparation of Rubber Layer Forming Composition 1> To 100 parts by mass of the base paint composition B, 20 parts by mass of fluororesin fine particles (polytetrafluoroethylene (PTFE, average particle size: 6 μm, manufactured by Micro Powder Inc., Fluo300)) were added and then uniformly mixed to prepare Rubber Layer Forming Composition 1.

[0048] <Example 1: Preparation of Primer Paint Composition 1> To 100 parts by mass of the base paint composition A, fluororesin fine particles (polytetrafluoroethylene (PTFE, average particle size: 6 μm, manufactured by Micro Powder Inc., Fluo300)) were added and then uniformly mixed to prepare Primer Paint Composition 1. The content of the fluororesin fine particles was 20 parts by mass with respect to 100 parts by mass of the bisphenol A type epoxy resin.

[0049] <Comparative Example 1: Preparation of Primer Paint Composition 2> Without adding fluororesin fine particles, the base paint composition A was used as Primer Paint Composition 2 as it was.

[0050] <Example 2 - 1: Production of Gasket 1> On a flat substrate (stainless steel SUS301H subjected to chromate treatment; dimensions 100 mm × 100 mm × 0.2 mm), Primer Paint Composition 1 was printed by a screen printing machine to form a primer layer with a thickness of 10.5 μm. On the obtained primer layer, Rubber Layer Forming Composition 1 was printed by the screen printing machine to form a rubber layer with a thickness of 7.5 μm. On the obtained rubber layer, Lubricating Layer Forming Composition 1 was printed by the screen printing machine to form a lubricating layer with a thickness of 10.0 μm, and Gasket 1 was obtained. The obtained Gasket 1 had a primer layer, a rubber layer, and a lubricating layer laminated in this order from the substrate side, and the total thickness of the layers excluding the substrate was 28.0 μm.

[0051] <Example 2 - 2: Production of Gasket 2> 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 a primer layer, a rubber layer, and a 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: Production of Gasket 3> On a flat substrate (stainless steel SUS301H subjected to chromate treatment; dimensions 100 mm × 100 mm × 0.2 mm), primer coating composition 2 was printed using a screen printing machine to form a primer layer with a thickness of 11.5 μm. On the obtained primer layer, rubber layer-forming composition 1 was printed using the screen printing machine to form a rubber layer with a thickness of 13.5 μm. On the obtained rubber layer, lubricating layer-forming composition 1 was printed using the screen printing machine to form a lubricating layer with a thickness of 10.0 μm, and gasket 3 was obtained. The obtained gasket 3 had a primer layer, a rubber layer, and a lubricating layer laminated in this order from the substrate side, and the total thickness of the layers excluding the substrate was 35.0 μm.

[0053] <Evaluation of Gasket: Compression Torsion Test> A ring-shaped test jig (aluminum-based alloy A2618; diameter φ: 60 mm, diameter of the hollow part φ: 30 mm, thickness: 30 mm; processed by our company) was placed on the lubricating layer of the obtained gasket to serve as an evaluation sample, and it was set in a compression torsion testing machine (manufactured by Shimadzu Corporation). The compression torsion testing machine 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 conducted in which it was repeatedly slid at 10 HZ within a range of 1 degree of angle. After 18,000 cycles, the test jig was removed from the evaluation sample, and the surface of the evaluation sample was visually observed and evaluated as follows. In the following evaluation, when a resin layer remained on the surface of the evaluation sample, it was determined that at least the primer layer remained in a state of being adhered to the substrate. The results are shown in Table 1. A (Good): The primer layer remains on 75% or more (area ratio) of the substrate surface. B (Good): The primer layer remains on 50% or more but less than 75% (area ratio) of the substrate surface. C (Bad): The primer layer remains on less than 50% (area ratio) of the substrate surface.

[0054] Also, the relationship between the number of cycles and the friction coefficient in the compression torsion test is shown in Fig. 1.

[0055]

Table 1

[0056] As shown in Table 1, the evaluation samples prepared from the gaskets of Examples 2-1 and 2-2 using the primer paint composition according to the present invention had high residual properties of the primer layer even after the compression torsion test. From this, it was found that the primer layers contained in the gaskets of Examples 2-1 and 2-2 were excellent in adhesion to the substrate and excellent in wear resistance, and could prevent damage to the substrate. On the other hand, the evaluation sample prepared from the gasket of Comparative Example 2 using a primer paint composition different from the present invention had low residual properties after the compression torsion test.

[0057] Also, as shown in Fig. 1, the evaluation samples prepared from the gaskets of Examples 2-1 and 2-2 using the primer paint composition according to the present invention required a large number of cycles until the friction coefficient started to increase. In contrast, the evaluation sample prepared from the gasket of Comparative Example 2 using a primer paint composition different from the present invention started to increase the friction coefficient at a relatively small number of cycles. The friction coefficient of the evaluation sample was maintained at a low value while the fluororesin fine particles remained between the substrate and the test jig, and started to increase when this was lost. Therefore, the more cycles required for the friction coefficient to start to increase for an evaluation sample, the better the adhesion to the substrate and the better the wear resistance, meaning that damage to the substrate can be prevented. In particular, it was found that the evaluation sample prepared from the gasket of Example 2-2 with a thick primer layer using the primer paint composition according to the present invention had a very large number of cycles until the friction coefficient started to increase.

Industrial Applicability

[0058] The primer paint composition of the present invention is excellent in adhesion to a substrate and can provide a primer layer excellent in abrasion resistance and capable of preventing damage to the substrate. Therefore, it can be suitably used, for example, for forming a primer layer of a gasket.

Claims

1. A primer paint composition for coating on the surface of a metal material of a gasket, which contains an epoxy resin and fluororesin fine particles, does not contain a phenolic resin, and the average particle diameter of the fluororesin fine particles is 3 to 18 μm.

2. The primer paint composition according to Claim 1, wherein the fluororesin fine particles are composed of 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 paint composition according to Claim 1, which contains 5 to 50 parts by mass of the fluororesin fine particles with respect to 100 parts by mass of the epoxy resin.

4. A gasket in which a primer layer formed by curing the primer paint composition according to any one of Claims 1 to 3 is directly formed at least in part.

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