JPH073041A - Production of friction material - Google Patents

Abstract

PURPOSE:To obtain a method for producing a friction material having a burst strength and stable frictional characteristics in a molded friction material using staple fiber glass. CONSTITUTION:This method for producing a friction material is to mix and knead a component for the friction material containing a friction modifier and a binder with a substrate composed of a fibrous material of staple fiber, provide a kneaded material, then knead and extrude the resultant kneaded material by using an extrusion molding machine, prepare stringy preform, arrange and form the prepared preform.

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 power transmission, braking, etc. of an automobile.

[0002]

Brake linings, disc pads, clutch facings and the like are used as friction materials for automobiles. Conventionally, asbestos (asbestos) has been used as a base material, but non-asbestos friction materials are desired due to asbestos pollution. Further, as the performance of automobile engines is improved, it is desired to improve the friction characteristics (friction coefficient, wear rate) and mechanical characteristics of friction materials. In addition, recently, there has been a demand for weight reduction that affects the high-speed rotation strength at high temperatures and the clutch disengagement due to severe operating conditions. Currently, friction materials using glass fiber, carbon fiber, aromatic amide fiber, rock wool, ceramic fiber, various steel fibers, etc. have been developed as alternatives for asbestos.
Used in part. However, since these base materials have higher elasticity and hardness and lower heat resistance than conventional asbestos, various problems occur when used as a friction material, and the above-mentioned required performance is not satisfied.

In order to obtain the above-mentioned required friction material by using an asbestos substitute material, the friction material is subjected to high temperature treatment (for example, JP-A-56-131846, 59-1130).
No. 38, 60-145302, etc.), those to which special friction adjustment is added (for example, JP-A-60-96625, 60-92332, 62-190232, etc.). Although polyimide or the like is disclosed as a binder, there are problems in manufacturing technology, cost, and the like. In addition, there are friction materials manufactured by a molding method that allows flexibility in the addition amount of friction base materials and friction modifiers to improve friction characteristics, but fibrous substances are used to maintain the mechanical strength of the friction materials. In addition. However, it is difficult to uniformly distribute the fibrous substance in the molded product by this method, the molded product becomes non-uniform, and the mechanical strength decreases. In order to make frictional properties and mechanical strength compatible, various reinforcing materials are attached to the back surface of the molded product (for example, Japanese Patent Laid-Open No. 2-1
No. 63529, JP-A No. 62-266239,
JP-A-61-141022 and JP-A-1-14124
No. 2, etc.) Further, at present, a semi-mold type using a coated string which is the mainstream of non-asbestos clutch facings (for example, Japanese Patent Laid-Open No. 62-141328,
JP-A-62-21513, JP-A-62-2662
No. 37), but industrialization is still impossible.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and provides a method for producing a friction material which can produce a friction material having stable friction characteristics and high mechanical strength with good productivity and workability. It is provided.

[0005]

According to the present invention, a composition for a friction material containing a friction modifier and a binder and a base material made of a fibrous substance of short fibers are mixed and kneaded to obtain a kneaded product, Next, the kneaded product is kneaded and extruded by using an extrusion molding machine to prepare a string-shaped preformed product, and the preformed product is arranged and molded.

There are no particular restrictions on the friction modifier used in the present invention, and known ones may be used, and examples thereof include calcium carbonate, magnesium carbonate, barium sulfate, calcium silicate short fibers, clay, talc, graphite, and the like. Carbon black, alumina, mica, fluorite, zirconia, hematite, magnetite, silica, inorganic powder such as antimony sulfide, lead sulfide, iron sulfide, zinc sulfide, molybdenum sulfide, antimony trioxide, metal such as iron, lead and copper And powders of organic substances such as powders of cured products of thermosetting resins such as cashew dust and melamine resins. These are used alone or in combination of two or more.

The binder in the present invention is not particularly limited, and known binders can be used, for example, phenol resin, melamine resin, urea resin, epoxy resin, polyamideimide precursor resin, polyimide precursor resin. And thermosetting resins such as natural rubber, chloroprene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, and acrylic rubber. Among these, a phenol resin and a melamine resin are preferable from the viewpoint of the balance of properties, and among them, a resol type phenol resin and a methylated melamine resin are more preferable. Further, rubber is preferable from the viewpoint of improving heat resistance. When rubber is used, a rubber crosslinking agent (vulcanizing agent) such as sulfur or a vulcanization accelerator such as zinc oxide can be used as required.

In addition to the above-mentioned friction modifier and binder, the composition for a friction material in the present invention may optionally contain an organic solvent, a solvent such as water, a dispersant, a plasticizer, an adhesion improver and an interface. Additives such as activators can be used.

Examples of the substrate made of a fibrous substance of short fibers in the present invention include inorganic fibers such as glass fiber, carbon fiber, rock wool and ceramic fiber, metal wire such as iron wire, phenol resin fiber and aromatic polyamide. Short fibers (up to 100 mm or less) in shape, such as organic fibers such as resin fibers
What is. Glass fiber is desirable because it is easy to process and cheap, and the maximum length is 50 mm.
The following chopped strands are preferable, and chopped strands having a maximum length of 25 mm or less are more preferable. Strand is 2
Those formed from 0 to 100 filament aggregates are preferable. If the length of the strand is too long, the viscosity of the kneaded product is significantly increased to reduce the kneading efficiency, and excessive shearing force is generated to cut the fiber, which is not preferable.

In the friction material, the weight ratio B of the friction material composition (solid content) A and the base material B made of a fibrous substance of short fibers is used.
/ A is 25/75 to 60/40 (preferably 30/70
It is preferable to mix and knead the friction material composition and the base material made of a fibrous substance of short fibers so as to be about 55/45). This weight ratio B / A is defined as c-b = a from the weight b of the base material made of the fibrous substance of the short fibers used and the weight c of the obtained friction material, and a (friction material composition in friction material If the (solid content) A weight) is obtained, it can be confirmed that B / A = b / a. If B / A is too large or too small, it tends to be difficult to balance the friction characteristics.

The extruder used in the present invention may be any known one without any particular limitation. To obtain the friction material, for example, the following method is used. The friction material composition and a base material made of a fibrous substance of short fibers are mixed and kneaded to obtain a kneaded product, and then, this kneaded product is put into, for example, a uniaxial or biaxial extrusion molding machine and kneaded and extruded to obtain a kneaded product. To obtain a preform of the shape. At this time, the screw of the extruder is preferably a full flight type so that a strong shearing force is not applied.
Next, the obtained cord-shaped preforms are rolled up in an annular shape and arranged, and then placed in a molding die or the like for molding, and after slitting to a predetermined thickness, if necessary, Then, the volatile matter is dried to be put into a mold to be hot-pressed and then heat-treated to be post-cured to obtain a friction material.

[0012]

EXAMPLES The present invention will now be described with reference to examples. Example 1 As a friction modifier, a cured melamine resin powder (cashew
Co., Ltd., melamine dust H-9044) 8 parts by weight, antimony trioxide (Wako Pure Chemical Industries, for chemicals) 6 parts by weight, electrolytic copper powder (Nippon Mining Co., No. 5-2D, 44 μm or less) ) 2 parts by weight, barium sulfate (Sakai Chemical Co., BC) 6.4
4.3 parts by weight of calcium silicate short fibers (produced by NYCO, USA, trade name Wollastonite) and cashew-modified friction dust (produced by Cashew Co., Ltd., WD-135).
0) A total of 28.8 parts by weight of 2.1 parts by weight was prepared. A mixture of 2.4 parts by weight of sulfur powder (manufactured by Hosoi Chemical Co., Ltd., fine sulfur powder) and 0.8 part by weight of zinc oxide (manufactured by Wako Pure Chemical Industries, for chemicals) with a vulcanizing agent and a vulcanization accelerator. Two parts by weight were prepared and mixed with the friction modifier in a V-type mixer to prepare a mixed powder. On the other hand, resole type phenol resin (Dainippon Ink and Chemicals, TD-2040C, solid content 100
% By weight), 1 part by weight of acrylonitrile butadiene rubber (NBR, manufactured by Nippon Zeon, Nippol1041)
53 parts by weight of a 5 wt% MEK (methyl ethyl ketone) solution and 10 parts by weight of MEK were mixed and dissolved to prepare a binder solution. The mixed powder was added to this solution and mixed to obtain a slurry-like composition for friction material. To 110 parts by weight of the composition for friction material (solid content 50% by weight), 22.5 parts by weight of glass chopped strands (up to 50 mm) and 22.5 parts by weight of glass chopped strands (up to 25 mm) were added, and a small kneader (kneader) ) Was mixed and kneaded to obtain a homogenized kneaded product. After heating this kneaded product to volatilize MEK (so that the residual volatile content becomes 15 to 20% by weight), it is put into a single-screw extruder (Toyo Seiki Lab Plastomill, screw is a full flight type). The mixture was kneaded and extruded at a temperature of 40 ° C. to obtain a string-shaped preform having a diameter of 20 mm. This product is wound around a mold with an outer diameter of 200 mm and an inner diameter of 130 mm in an annular shape, and after six-fold winding, it is heated and pressed at a temperature of 70 ° C. to obtain an annular molded product with a thickness of 20 mm, an outer diameter of 200 mm and an inner diameter of 130 mm. It was This molded product is slit into three equal parts and 70-80
MEK is volatilized by drying for about 2 hours at 0 ° C. (so that the residual volatile content becomes 3 to 5% by weight), and then the mold is filled.
Molding was performed at a pressure of 100 kgf / cm ² at 160 ° C. for 15 minutes to obtain a molded body having a thickness of 5 mm. Both sides of this molded body were ground to a thickness of 3.5 mm and heat-treated in the order of 180 ° C. for 1 hour, 210 ° C. for 2 hours and 240 ° C. for 2 hours to obtain an annular friction material.

Example 2 8 parts by weight of acrylonitrile-butadiene rubber (NBR, manufactured by Nippon Zeon Co., Nippol 1041) was kneaded in a solid state with a kneader while adding 20 parts by weight of MEK for mastication, and then resorphenol resin (large After adding 15 parts by weight of TD-2040C (manufactured by Nippon Ink Chemical Co., Ltd., solid content: 100% by weight) and further kneading, the same amount as the mixed powder prepared in Example 1 was further added and further kneading. 45 parts by weight of glass chopped strand (maximum 25 mm) was added and kneaded to obtain a clay-like composition for friction material.
This friction material composition was put into an extrusion molding machine (same as in Example 1) and kneaded and extruded at 40 ° C. to obtain a cord-shaped molded body having a diameter of 20 mm and a uniform density. This molded body was molded and heat treated in the same manner as in Example 1 to obtain an annular friction material.

Comparative Example 1 A kneaded product similar to that of Example 1 was dried at 40 to 60 ° C.,
Fill a mold with an outer diameter of 200 mm and an inner diameter of 130 mm in an annular shape 7
It was preformed at a temperature of 0 ° C. and a pressure of 50 kgf / cm ² . Then, it was dried at 70 to 80 ° C. for about 2 hours to volatilize MEK (so that the residual volatile content was 3 to 5% by weight). Fill this into a mold and press at 100kgf / cm ² at 160 ℃.
Molding was performed for 15 minutes to obtain a molded body having a thickness of 5 mm. The molded body was polished on both sides to a thickness of 3.5 mm, and then heat-treated in the order of 180 ° C. for 1 hour, 210 ° C. for 2 hours and 240 ° C. for 2 hours to obtain an annular friction material.

Comparative Example 2 A kneaded product similar to that used in Example 2 was dried at 40 to 60 ° C., then put into a kneader again, kneaded and pulverized to obtain a powder, which was 200 mm in outer diameter and 130 mm in inner diameter. Then, the mold and the heat treatment were performed in the same manner as in Comparative Example 1 to obtain an annular friction material.

Characteristic Evaluation (1) Burst Strength The annular friction materials produced in the examples and comparative examples were subjected to 200 ° C.
After maintaining at 2500 rpm for 5 minutes in the atmosphere, the rotation speed was increased at 100 rotations / second to obtain the rotation speed at break. (2) Friction characteristics (friction coefficient and wear rate) 25 mm from the annular friction material produced in the examples and comparative examples
The corner test piece was cut out, and the friction coefficient and the wear rate at each temperature of 150 ° C., 250 ° C. and 350 ° C. were obtained by a low speed friction tester according to JIS D4411.

[0017]

[Table 1]

In the comparative example, the burst strength is low, the friction coefficient is not stable, and the wear rate is high. On the other hand, since the examples have stable high burst strength and stable friction coefficient and low wear rate, it can be seen that they are excellent friction materials.

[0019]

The method for producing a friction material of the present invention has excellent productivity and workability, and the friction material obtained by this production method has high burst strength and stable friction characteristics.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location // B29B 7/00 9350-4F

Claims (1)

[Claims] 1. A composition for friction material containing a friction modifier and a binder and a base material made of a fibrous substance of short fibers are mixed and kneaded to form a kneaded product, and then this kneaded product is extruded. Kneading and extruding using a machine to produce a string-shaped preform,
A method of manufacturing a friction material, which comprises arranging and arranging these.