JPH09264356A - Manufacture of rubber dust metallic complex and frictional material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate separation and unevenness caused by the difference of the specific gravity and the difference of the shape in starting materials, by partially exposing metallic powder to be taken as a frictional raw material and burying it in the front surface of a rubber dust to be taken as a raw material of the frictional material. SOLUTION: In a rubber dust as one component of a rubber dust metallic complex 4, all organic particles used as a raw material of a frictional material can be used. Concretely, the particles are made of vulcanized or unvulcanized natural or synthetic rubber. Metal as the other component can use metal used as a raw material of the frictional material, and concretely, it is copper, aluminum, zinc, or alloy of them. The rubber dust complex 4 is completed by burying these metallic particles in the front surface of the rubber dust or forming a film as a thin film. Therefor, the difference of adhesive properties between the rubber dust and the metal is eliminated, dispersibility of starting materials is improved, and a frictional material excellent in mechanical strength, in which various kinds of raw materials are uniformly dispersed can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a friction material used for brakes and clutches of various vehicles and industrial machines, and a starting material for the friction material.

[0002]

BACKGROUND OF THE INVENTION Friction materials widely used for brake pads, brake linings, clutch facings, etc. of various vehicles and industrial machines include fiber materials such as heat-resistant organic fibers, inorganic fibers, and metal fibers, and inorganic / organic fillers. Material, friction modifier and powdered raw material such as thermosetting resin binder are mixed to form a starting raw material at a predetermined pressure while cold (preforming)
Then, it is obtained by subjecting it to a mold set at a predetermined temperature, press-molding, curing (after-cure) and finishing treatment. In the above manufacturing process, it is desirable that the various raw materials be uniformly distributed and present in the friction material, and therefore the various raw materials must be mixed more uniformly when preparing the starting raw material. The method for preparing the starting materials is roughly classified into a wet method in which various raw materials are mixed with a solvent and a dry method in which various raw materials are stirred and mixed as they are.

By the way, the starting materials are composed of various kinds of materials. For example, even friction modifiers are represented by organic particles such as synthetic rubber and cashew resin, graphite, molybdenum disulfide, baryta, calcium carbonate and the like. There are three types of inorganic particles, and metal particles represented by copper, aluminum, zinc and the like. Further, in order to improve the thermal conductivity during braking when used as a friction material, it is generally used as metal particles and organic particles, metal particles and inorganic particles, or a mixture of the three. However, it is difficult to disperse the organic particles and the metal particles uniformly in the starting material, because the organic particles and the metal particles have a large difference in specific gravity and a large difference in shape. Generally, the wet method is superior in dispersibility, but it is inevitable that the metal particles settle in the dispersion medium, and it is difficult to obtain sufficient uniform dispersion even in the wet method. Further, since the difference in specific gravity is large, there is a problem in that the starting materials are easily separated and unevenly distributed during transportation or storage, and in particular, organic material particles or metal particles fall during transportation and a predetermined material composition cannot be obtained. Furthermore, since the organic particles and the metal particles have different adhesiveness with other friction material materials,
The dispersibility of the starting material is further deteriorated. Such poor dispersibility of the starting material causes a reduction in the homogeneity of the friction material as the final product and the resulting mechanical strength.

[0004]

As described above, the prior art has a problem regarding the dispersibility of the starting material, and a method for producing a high-quality friction material in which various constituent materials are uniformly dispersed is desired. . The present invention has been made in view of the above circumstances, and an object thereof is to improve the dispersibility of a starting material and to provide a high-quality friction material in which various constituent materials are uniformly dispersed.

[0005]

Means for Solving the Problems The above objects are as follows: (1) A part of metal powder, which is a raw material of a friction material, is embedded and exposed on a surface of rubber dust, which is a raw material of a friction material. A rubber dust metal composite, and
(2) The present invention is achieved by a rubber dust metal composite characterized in that a thin film of metal, which is a raw material of a friction material, is formed on a surface of rubber dust, which is a raw material of a friction material. The same object is also achieved by a method for producing a friction material, which is characterized in that (3) a starting material containing the rubber dust metal composite according to (1) or (2) above is heat-molded. To be done.

In the rubber dust metal composite according to the present invention, metal particles are partially exposed and embedded on the surface of the rubber dust, or a metal thin film is formed as a film to be integrated. Separation and uneven distribution due to the difference in specific gravity between the two and the difference in shape are eliminated. Moreover, since most of the surface is covered with metal, the metal becomes dominant in contact with other friction material and the difference in adhesiveness between rubber dust and metal is eliminated, and the dispersibility of the starting material is reduced. To further improve. Therefore, the friction material obtained by using this rubber-dust metal composite as a starting material has excellent mechanical strength in which various materials are uniformly dispersed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a rubber dust metal composite according to the present invention and a method for manufacturing a friction material using the rubber dust metal composite will be described in detail. As the rubber dust, which is one component of the rubber dust metal composite of the present invention, all organic particles conventionally used as a raw material of a friction material can be used. Specifically, it is a particle made of vulcanized or unvulcanized natural or synthetic rubber. Examples of the synthetic rubber include SBR (styrene / butadiene rubber) and NBR (nitrile / butadiene rubber).
And the like. The particle size of the rubber dust is not limited as long as it does not hinder the mixing with other friction material materials, and the average particle size is about 100 to 400 μm although it slightly varies depending on the type of rubber. Is preferred.

As the metal which is the other component of the rubber dust metal composite of the present invention, all the metals conventionally used as a raw material for friction materials can be used. Specifically, copper, aluminum, zinc and alloys thereof are used. Then, particles of these metals are embedded in the surface of the rubber dust or formed into a thin film to complete the rubber dust composite.

Here, when the metal particles are embedded in the rubber dust surface, for example, as shown in FIG. 1, the vessel 1 having an elliptical inner diameter and the rotor 2 having an elliptic outer diameter are rotated about the same center. The mixer 3 which is freely arranged is used. Then, a predetermined amount of each of the rubber dust and the metal particles is weighed and put into the space between the vessel 1 and the rotor 2, and the vessel 1 and the rotor 2 are rotated in opposite directions for a predetermined time, whereby a rubber dust composite is obtained. To be At this time, the clearance (CL = (D−d) / 2), which is the difference between the minor axis diameter D of the vessel 1 and the major axis diameter d of the rotor 2, the rotation speed of the bezel 1 and the rotor 2, and the processing time are rubber dust. It is appropriately set in consideration of the type and size of the metal, the particle size of the metal particles, and the like. The higher the rotation speed of the vessel 1 and the rotor 2 and the longer the processing time, the more the amount of metal particles embedded in the rubber dust surface tends to increase. The clearance can be changed by appropriately selecting the size of the rotor 2 (major axis diameter d), and the smaller the clearance, the stronger the adhesion strength of the metal particles.

By the way, since the thermal conductivity of the friction material increases as the amount of metal particles increases, it is preferable that the amount of metal particles embedded in the rubber dust composite is large. Therefore, it is advantageous that the particle size of the metal particles is small, and the average particle size is preferably about 5 to 30 μm. For the same reason, it is preferable that the amount of the metal particles is large also in the compounding ratio of the rubber dust and the metal particles, and the metal particles are preferably at least 10% by weight of the total amount of the rubber dust composite. However, when it exceeds 50% by weight, the lubrication adjusting function of the other component, rubber dust, the density adjusting function during preforming, the noise absorbing effect when used as a friction material, and the like are not sufficiently exhibited.

The appearance of the obtained rubber dust composite is shown in FIG. Here, the portions shown in white in the drawing are metal particles, and the portions shown in black in the drawing are rubber dust. As shown in the figure, it can be seen that the metal particles are dispersed and embedded so as to cover almost the entire surface of the rubber dust. The morphological effect of the rubber dust composite is to eliminate the separation and uneven distribution of the rubber dust and the metal in the starting material due to the difference in specific gravity and the shape of the metal. It is sufficient that the friction material is kept on the surface of the rubber dust at the time of preparing the starting material, preferably at the time of press loading for preforming. The adhesion strength of the metal particles can be adjusted by the clearance of the mixer.

On the other hand, when a metal is formed as a thin film,
Electroless plating and vapor deposition are performed according to a conventional method. The film thickness of the metal thin film is not particularly limited, but it is preferable that the metal thin film be a thick film in consideration of the thermal conductivity of the friction material. The thickness is preferably 5 to 20 μm. The metal thin film does not need to completely cover the entire surface of the rubber dust, and no special consideration is required for the film forming operation. Also, the adhesion strength of the metal thin film is
For the same reason as in the case of embedding metal particles, it need not be so strong.

The present invention is further characterized in that a friction material is produced from a starting material containing the rubber dust metal composite. The manufacturing process will be described below. First, a composite of rubber dust and metal is prepared as described above. And
Other friction material raw materials, for example, fiber raw materials such as organic fibers, inorganic fibers, and metal fibers, inorganic / organic fillers, thermosetting resin binders, and the like are mixed with stirring to prepare starting materials. Here, as the organic fiber, for example, by using a heat-resistant organic fiber such as aromatic polyamide fiber (aramid fiber: commercially available product manufactured by Dupont Co., trade name “Kevlar”, etc.), flame-resistant acrylic fiber, etc. The heat resistance of the friction material can be improved. Further, as the inorganic fiber, a ceramic fiber such as potassium titanate fiber or alumina fiber,
Glass fiber, carbon fiber, rock wool, etc. can be used. Copper fibers and steel fibers can be typically used as the metal fibers. As a filler,
Scale-like inorganic substances such as vermiculite and mica, barium sulfate, calcium carbonate and the like can be used. Examples of the thermosetting resin binder include phenol resin (including straight phenol resin and various modified phenol resins such as rubber), melamine resin, epoxy resin, cyanate ester resin and the like. In addition,
Friction modifiers such as metal oxides such as alumina, silica and zirconia, and solid lubricants such as graphite and molybdenum disulfide can be added.

The composition of the starting material may be the same as the composition of the normal friction material. For example, 2 to 10 parts by weight of rubber dust metal composite, 5 to 20 parts by weight of fiber raw material, 30 to 60 parts by weight of filler, and 5 to 20 parts by weight of thermosetting resin binder are weighed and mixed by stirring to obtain a starting material. To be

Next, after preforming the above-mentioned starting material into a tablet shape, it is put into a hot press in which a pressure plate is set and thermoformed into a molded article having a predetermined thickness and density, after-curing, Finishing process is performed to complete the friction material integrated with the pressure plate. These series of steps can be performed according to a conventional method, for example, preforming is performed at a surface pressure of 100 to 500 Kgf / cm ² ,
Thermoforming is performed at a temperature of 130 to 180 ° C and a surface pressure of 200 to 1000.
Kgf / cm ² is performed for about ³ to 15 minutes, and after-curing is performed at a temperature of 150 to 300 ° C. for about 1 to 15 hours. If desired, scorch treatment may be performed after after-cure. In this scorch treatment, for example, the surface of the friction material is flame-treated for 30 to 300 sec using a burner, or a hot plate heated to 400 to 700 ° C. is heated for 30 to 300 se.
The surface is baked by contacting with c.

[Examples] The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. SBR (average particle size 300 μm) and NBR (average particle size 1 as rubber dust
50 μm) and copper powder (average particle size 20 μm) and zinc powder (average particle size 10 μm) 2 as metal particles.
Various types of rubber dust and metal particles were mixed and the compounding ratio thereof was changed as shown in Table 1, and the mixture was charged into the mixer shown in FIG. Mixing is done at a vessel rotation speed of 50 rp
m, rotor speed 3000 rpm, clearance (C
L) The test was performed for 15 minutes under the condition of 1.0 mm. The obtained rubber dust metal composite 4 had an appearance in which metal powder was dispersed and embedded on the surface thereof as shown in FIG. 2, although there was a difference depending on the blending amount of metal particles. In particular, in the rubber dust metal composites of sample symbols SC40 and ZN40, the metal particles were embedded so as to cover almost the entire surface of the rubber dust, and the surface state was the best.

The above processing conditions are obtained from the experimental results shown in Table 2. That is, in order to find the optimum treatment conditions, 70% by weight of NBR and 30% by weight of copper powder are used in FIG.
The rubber dust metal composite was prepared by charging the mixer shown in Table 2 and changing the vessel rotation speed, rotor rotation speed, clearance (CL) and mixing time as shown in Table 2. And
When the surface condition was observed, the condition Nos. 8 and 9 were the best as the surface condition because the metal particles were embedded on the entire surface of the rubber dust. From this, as processing conditions, the vessel rotation speed was 50 rpm and the rotor rotation speed was 3
000 rpm, clearance (CL) 1.0 mm, mixing time 15 minutes were required. Further, from the above experiment, it was found that the higher the vessel rotation speed and the rotor rotation speed and the longer the mixing time, the larger the amount of metal particles on the rubber dust surface. Furthermore, condition No. 5,
From 6, it was found that the amount of metal particles on the surface of the rubber dust may be reduced depending on the selection of the clearance even if the Bessel rotation speed, rotor rotation speed and mixing time are the same.

[0018]

[Table 1]

[0019]

[Table 2]

In addition, the sample symbols SC40 and ZN40, which had the best surface condition in the formulations of Table-1, were blended in place of the rubber dust of the current friction material, and agitated according to a conventional method.
A friction material was prepared by weighing, preforming, thermoforming, after-curing, polishing and grooving. This friction material had good dispersibility of various raw materials and excellent mechanical strength as compared with the current friction material.

[0021]

As described above, in the rubber dust metal composite according to the present invention, metal particles are partially exposed and embedded on the surface of the rubber dust, or a metal thin film is formed and integrated. Therefore, the separation and uneven distribution due to the difference in specific gravity and the difference in shape in the starting material are eliminated. Moreover, since most of the surface is covered with metal, the metal becomes dominant in contact with other friction material and the difference in adhesiveness between rubber dust and metal is eliminated, and the dispersibility of the starting material is reduced. To further improve. Therefore, the friction material obtained by using this rubber-dust metal composite as a starting material has excellent mechanical strength in which various materials are uniformly dispersed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a mixer used in the present invention.

FIG. 2 is a diagram showing the appearance of the rubber dust metal composite of the present invention.

[Explanation of symbols]

 1 Vessel 2 Rotor 3 Mixer 4 Rubber dust metal composite

Claims (3)

[Claims] 1. A rubber dust surface which is a raw material of a friction material,
A rubber dust metal composite characterized in that a metal powder as a friction material raw material is partially exposed and embedded. 2. A rubber dust surface which is a raw material of a friction material,
A rubber dust metal composite characterized in that a thin film of a metal as a friction material raw material is formed. 3. A method for producing a friction material, which comprises heat-molding a starting material containing the rubber dust metal composite according to claim 1.