JP2007125522A - Method for coating friction member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for coating a friction member which is capable of manufacturing a friction member (a break pad) excellent in the adhesion and corrosion resistance of a coating film. <P>SOLUTION: The method for coating the friction member composed of a metallic pressure plate and a friction material comprises the steps of forming with heat and pressure as overlaying the friction material on the adhesion face of the pressure plate to unify them, making the face to be coated of the pressure plate coarse after the heat and pressure forming process, heat-treating the coarsely faced pressure plate by heating with a superheated steam, and coating the pressure plate face to be coated with a paint. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for coating a friction member used for a friction member for brakes of automobiles, railway vehicles, industrial machines, etc., and in particular, it is possible to produce a friction member having excellent coating film, corrosion resistance and weather resistance, and having stable quality. It relates to a painting method that can be performed.

Regarding the painting of friction members such as brake pads, “Patent Document 1” removes release agent, resin, dirt, dents made during transportation, chemical conversion film deteriorated during heating, etc. attached to the pressure plate by thermoforming. However, as a method of improving the adhesion between the pressure plate and the paint film, shot blasting is performed on the surface to be coated (also referred to as “coating surface”) after thermoforming, heating, or post-blast blast chemical conversion treatment. Is described.
However, in the above method, if there is a stagnation in the processing of the processed product for some reason, such as equipment failure after shot blasting, the shot blasting surface is extremely deteriorated by oxidation. The performance is greatly reduced. In production, it is impossible to build in before painting because rust is generated during storage. In addition, the brake pad that has been finished without any stagnation in the treatment has no underlying coating on the painted surface, so that the corrosion resistance is inferior when compared with the coating with the underlying coating such as chemical conversion treatment.

When performing chemical conversion treatment after shot blasting, it is easy to perform those treatments with the pressure plate alone, but only the painted surface of the pressure plate is subjected to chemical conversion treatment with the friction material stuck after thermoforming → heating. Is technically difficult, and even when the chemical conversion treatment is performed, the pressure plate that has already been treated in the surface treatment process as the pre-bonding treatment is subjected to a duplicate treatment such as shot blasting → chemical conversion treatment → water washing → drying. Will be done.
JP 2003-166574 A

  The present invention performs shot blasting on the surface to be coated after thermoforming, and performs coating after treatment means that does not generate rust even if the subsequent treatment is stagnant, thereby providing adhesion of the coating film. Another object of the present invention is to provide a friction member coating method capable of producing a friction member (brake pad) having excellent corrosion resistance.

The present invention has solved the above problems by the following means.
(1) In a method for coating a friction member made of a metal pressure plate and a friction material, a step of superimposing the friction material on the adhesive surface of the pressure plate and forming it by heat and pressure molding, and the heat and pressure molding A step of roughening the surface to be coated of the pressure plate after the step, a step of heat-treating the roughened pressure plate with superheated steam, and a step of applying a paint to the surface to be coated of the pressure plate A method for painting a friction member.
(2) The friction member according to (1), wherein the step of applying the paint to the coated surface of the pressure plate is electrostatically applied using a powder paint mainly composed of a thermosetting resin. Painting method.
(3) The method for coating a friction member according to (2), wherein the thermosetting resin is any one of an acrylic resin, an epoxy resin, a polyester resin, and an epoxy / polyester composite resin.

  According to the present invention, (a) a friction member having excellent adhesion and corrosion resistance of the coating film is obtained. (B) After thermoforming, the surface to be coated is shot blasted and coated after superheated steam treatment. It is possible to prevent the occurrence of rust when there is a stagnation of the previous treatment, and it is possible to maintain quality such as corrosion resistance and adhesion as a friction material by generating a base coating.

The best mode for carrying out the invention will be described in detail with reference to the drawings.
Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments and examples.

In general, production of a friction material for brake is performed through each step of finishing processing such as blending, mixing, preliminary molding at normal temperature, thermoforming, heat treatment, and polishing.
First, each process will be described by exemplifying the friction member 1 (friction pad of a disc brake). Here, FIG. 1 is a cross-sectional view of a friction member 1 in which a friction material 4 is integrated by press molding with a pressure plate 2 (hereinafter referred to as “P / P”) coated with a primer 5 via an adhesive 3. . P / P processing includes sheet metal pressing, degreasing, primer treatment, and P / P preheating as main processes. In the sheet metal pressing step, a P / P material selected in advance is formed into a P / P having a predetermined shape by pressing or the like. In the degreasing step, oils and fats adhering to the P / P during press working are removed using a cleaning agent.

  In the primer treatment step, a resin-based primer is spray-coated on the entire surface of the degreased P / P, dried, heated at 180 to 200 ° C. for about 1 hour, and the primer is cured to form a primer layer. As the primer 5, a general primer can be used, for example, vinyl / phenolic resins (vinyl acetal, polyvinyl formal, polyvinyl butyral, copolymerized polyamide as vinyl elastomer), nitrile rubber / phenolic resin, silane. Examples include γ-aminopropyltriethoxysilane and urethane primers.

On the other hand, the preforming of the friction material 4 is mainly performed by measuring, blending, mixing, and preforming raw materials. Each of these steps can follow conventional friction material manufacturing techniques. For example, reinforcing fibers such as heat-resistant organic fibers, inorganic fibers, and metal fibers and powder raw materials such as inorganic fillers, friction modifiers, solid lubricants, and thermosetting resin binders are blended at a predetermined ratio and mixed. To prepare a starting material with sufficient homogenization. In the above, examples of the reinforcing fibers include organic fibers such as aromatic polyamide fibers and flame-resistant acrylic fibers, copper fibers, metal fibers such as steel fibers, inorganic materials such as potassium titanate fibers and Al ₂ O ₃ —SiO-based ceramic fibers. Fiber. Examples of the inorganic filler include inorganic particles such as barium sulfate and calcium carbonate, and scale-like inorganic substances such as vermiculite and mica. Examples of the thermosetting resin binder include a phenol resin (including various modified phenol resins such as a straight phenol resin and rubber), a melamine resin, an epoxy resin, and a polyimide resin. Examples of the friction modifier include inorganic friction modifiers such as alumina, silica, magnesia, zirconia, and chromium oxide; organic friction modifiers such as synthetic rubber and cashew resin; and solid lubricants such as graphite and disulfide. Molybdenum etc. can be mentioned. As the composition of the friction material, various composition ratios can be adopted. That is, these may be blended singly or in combination of two or more according to the friction characteristics required for the product, for example, friction coefficient, wear resistance, vibration characteristics, squeal characteristics, and the like.

  Next, this starting material is put into a molding die and molded at room temperature and with a surface pressure of about 10 to 100 MPa to produce a preform 4a of the friction member 1 as shown in FIG. 1, for example. The P / P and friction material preform 4a processed as described above is transferred to a thermoforming process. In the thermoforming process, first, preheated P / P is set in a press machine while maintaining a high temperature, and the preformed body 4a is placed thereon and matured.

The present invention is characterized by performing shot blasting and superheated steam treatment after thermoforming.
Shot blasting is preferably performed so that the surface roughness of the surface is Rz = 6 to 35 μm. By performing shot blasting after thermoforming, the release agent, resin, oxidatively deteriorated film and impurities are removed to form a clean surface, and then a dense oxide film passivated by heat treatment in a superheated steam atmosphere is formed. Can be generated. Since this film has a corrosion resistance equal to or higher than that of the chemical conversion treatment (iron phosphate coating) and is excellent in affinity with the paint, it can be a suitable ground treatment before coating.

The heat treatment in the superheated steam atmosphere is effective as a base treatment before coating, but can also improve the fade resistance against the friction material.
The heat treatment conditions in the superheated steam atmosphere, including the effect of the friction material, are possible at 225 to 800 ° C. and 15 to 60 minutes, but preferably 300 to 400 ° C. and 15 to 60 minutes. In addition, since the superheated steam has a degreasing ability, it is possible to remove mineral oils and animal and vegetable oils that have adhered after shot blasting.

  Powder coating is used for the coating of the present invention. There are electrostatic coating method and fluidized immersion method for powder coating. The electrostatic coating method is based on the principle of electrostatic coating method using powder coating. It adheres to the object grounded by electrostatic attraction. The coating material applied to the object to be coated is ripened in a baking oven, melted and cured to form a continuous film. The oversprayed powder paint is collected and reused. There are roughly two types of electrostatic coating methods using powder coatings.

a. Electrostatic spraying method Powder paint is sent to the spray gun by air from the paint supply tank. The powder coating is negatively charged by the high voltage (usually −40 KV to −90 KV) obtained by the high-voltage electrostatic generator. On the other hand, the object to be coated is grounded, and the powder paint discharged from the tip of the gun adheres to the surface of the object to be coated by electrostatic attraction. At this time, the negatively charged powder particles strongly act on the portion having a high potential and adhere to the object to be coated. As the powder particles adhere thickly, negative charges accumulate on the coating film, and the thickness exceeds a certain level. Then, electrostatic repulsion occurs and it becomes difficult to adhere. Part of the powder coating that does not go straight to the object is attached to the back side. By these phenomena, a uniform coating film can be obtained with a certain thickness, and the film thickness is limited. In addition, the tribocharging spray coating, which applies the principle of triboelectric charging, is a coating method that is advantageous in that it does not require a high-pressure generator, has good throwing power and penetration, and does not easily generate electrostatic repulsion. .

b. Electrostatic dipping method The bottom plate of the dipping tank filled with the powder coating is made of a perforated plate, and electrodes are arranged at regular intervals. The powder coating in the tank becomes fluidized by the air blown up from the porous bottom plate. On the other hand, a high voltage of −40 KV to −90 KV is applied to the electrode from the high-voltage electrostatic generator and floats in the ionized air. The powder particles are negatively charged, move up in the tank, and adhere to the grounded object. Particles that do not adhere to the object to be coated fall by gravity, rise as charged particles again, and reattach to the object to be coated.

In the fluid immersion method, powder is air-flowed in a fluid tank with a porous plate at the bottom, and the preheated coating is immersed in the floating powder, and the powder adheres to the surface of the coating. Is a method of forming a continuous film by melting and melting.
Since no special equipment is required, the equipment cost is relatively low, there is almost no paint loss, and a film with a high film thickness of 250 μm to 1000 μm and excellent edge cover properties can be easily obtained. The size and shape of the material are restricted, and preheating (250 to 300 ° C.) of the object is an essential condition.

  The powder coating composition used in the present invention has an average particle size of 15 to 35 μm, and particles having a particle size of 50 μm or more are 30% by mass or less. More preferably, particles having a particle size of 100 μm or more are 5% by mass or less, while particles having a particle size of 5 μm or less are 15% by mass or less. Thus, by making the average particle size small and making the particle size uniform, the coating film thickness is thin and the scorch processability is excellent.

As the resin for powder coating used in the powder coating, thermosetting resins such as acrylic resin, epoxy resin, polyester resin, and epoxy / polyester composite resin are used. In the present invention, epoxy resin is the main component. A powder paint is preferably used.
Specific examples of epoxy resins include glycidyl ester resins; glycidyl ether type resins such as condensation reaction products of bisphenol A and epichlorohydrin and condensation reaction products of bisphenol F and epichlorohydrin; alicyclic epoxy resins Aliphatic epoxy resins; bromine-containing epoxy resins; phenol-novolac type or cresol-novolac type epoxy resins, etc., preferably a condensation reaction product of bisphenol A and epichlorohydrin, or bisphenol F and epichlorohydride It is a glycidyl ether type resin such as a condensation reaction product with phosphorus.

  Specifically, “Epototo YD903N, YD128, YD14, PN639, CN701, NT114, ST-5080, ST-5100, ST-4100D” manufactured by Toto Kasei Co., Ltd., “EITPA3150” manufactured by Daicel Chemical Industries, Ciba-Geigy "Aldite CY179, PT810, PT910, GY6084" manufactured by Nagase Chemicals, "Teconal EX711" manufactured by Nagase Chemical Co., Ltd. "Epicron 4055RP, N680, HP4032, N-695, HP7200H" manufactured by Dainippon Ink, Inc. “Epicoat 1001, 1002, 1003, 1004, 1007”, “DER662” manufactured by Dow Chemical Co., “EPPN201, 202, EOCN1020, 102S” manufactured by Nippon Kayaku Co., Ltd., and the like.

  Examples of the epoxy resin curing agent include blocked isocyanate type and triglycidyl isocyanurate (TGIC) type. Particularly preferred are blocked isocyanate compounds.

As pigments or extender pigments that are appropriately blended in the coating composition of the present invention, titanium oxide, bengara, iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, quinacridone pigments, azo pigments and other colored pigments, talc, Examples include extender pigments such as silica, alumina, calcium carbonate, and precipitated barium sulfate, and rust preventive pigments such as chromium pigments, phosphate pigments, and molybdenum pigments.
Moreover, as a leveling agent (surface conditioner) mix | blended suitably, there exist silicones, such as dimethyl silicone and methyl silicone, an acrylic oligomer, etc., specifically, "CF-1056" by Toshiba Silicone Co., Ltd. “Modaflow” manufactured by Monsanto Kasei Co., Ltd., “Acronal 4F” manufactured by BASF, “BYK-360P” manufactured by BYKchemie, “Chipalon PL540” manufactured by Enomoto Kasei, and the like.

In the present invention, the coating on the superheated steam-treated surface can be applied without any problem under normal conditions for both liquid and powder (corona charging method, tribo charging method), and the wettability with the paint is due to surface irregularities due to shot blasting, This is even better than the case of superheated steam treatment on a smooth surface.
As described above, in summary, a coating film having excellent adhesion and corrosion resistance can be produced by roughening after thermoforming and coating after heat treatment in a superheated steam atmosphere. The paint is preferably a powder paint.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by these examples.
Example 1 and Comparative Example 1
Friction members were prepared and evaluated by the processing steps of Example 1 and Comparative Example 1 shown in FIG.

The superheated steam treatment of Example 1 was performed at an oxygen concentration of less than 0.3% and 400 ° C. × 30 minutes, and it was confirmed that a dense oxide film having a thickness of 2 to 3 μm was generated with an optical microscope.
Comparative Example 1 was prepared by a method of shot blasting the coated surface after thermoforming and heating.
The shot blasting was set to Rz = 20 to 30 μm (10-point average roughness) in both Example 1 and Comparative Example 1. The coating was a powder coating (tribo-charging method) with a difference in adhesion, and an epoxy resin powder coating was used and the thickness was 30 μm.
Evaluation is performed by the following salt spray test, and the results are shown in Table 1. It was confirmed that Example 1 was superior to Comparative Example 1 in corrosion resistance and adhesion.

(Test method)
A crosscut was put on the painted surface, and after 72 hours of spraying with salt water (JIS standard), the cellophane tape was brought into close contact with the crosscut portion, and after 10 minutes, the cellophane tape was peeled off and evaluated according to the following evaluation criteria.
(Test results)
Peeling within 2mm on one side from cross cut part: ○
Peeling within 5mm on one side from the cross cut part: △
Peeling of 5 mm or more on one side from the cross cut part: ×

  INDUSTRIAL APPLICABILITY The present invention is expected to be implemented as a friction member coating method that is excellent in corrosion resistance and adhesion and that can provide a product of uniform quality in the manufacturing process of brake friction materials such as automobiles, railway vehicles, and industrial machines.

It is a schematic diagram which shows the layer structure (cross section) of a friction member (brake pad). The flow sheet of each process in the coating method of the friction member in Example 1 and Comparative Example 1 is shown.

Explanation of symbols

1 friction member 2 pressure plate 3 adhesive 4 friction material 4a preform 5 primer

Claims (3)

  In a method for coating a friction member comprising a metal pressure plate and a friction material, a step of superimposing the friction material on the adhesive surface of the pressure plate and integrating by heating and pressing, and a step after the heating and pressing step Including a step of roughening a coated surface of the pressure plate, a step of heating the roughened pressure plate by heating with superheated steam, and a step of applying a paint to the coated surface of the pressure plate. A characteristic friction member coating method.   2. The method for coating a friction member according to claim 1, wherein the step of applying the paint to the surface to be coated of the pressure plate is electrostatically applied using a powder paint mainly composed of a thermosetting resin.   3. The method for coating a friction member according to claim 2, wherein the thermosetting resin is any one of an acrylic resin, an epoxy resin, a polyester resin, and an epoxy / polyester composite resin.

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