JPS61162537A - Frictional material composition - Google Patents

Abstract

PURPOSE:To produce the titled composition having excellent preformability and improved initial frictional coefficient, and suitable for clutch facing, etc., by compounding a specific amount of a specific unvulcanized rubber powder to a base component composed of an inorganic or organic fiber, an inorganic or organic filler and a resin. CONSTITUTION:The objective composition is produced by compounding (A) 100pts.(wt.) of a base component composed of an inorganic or organic fiber (e.g. asbestos, glass fiber, etc.) an inorganic or organic filler (e.g. barium sulfate, alumina, etc.) and a resin (e.g. a phenolic resin) with (B) 5-50pts. of unvulcanized rubber powder (e.g. NBR, SBR, etc.) having particle diameter of 10mum-3mm. The unvulcanized rubber powder is preferably compounded with 50-150pts. of additives such as vulcanizing agent, softener, etc. per 100pts. of the rubber, and further preferably added with an anticoagulant (e.g. alumina, talc, etc.).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a friction material composition, and more particularly to a friction material composition that provides excellent preformability and an improved initial coefficient of friction.

The friction material composition of the present invention can be used for clutch facings, and the vibration material composition can be used for clutch facings, brake linings, etc.

[Prior Art] Conventional friction materials are composed of inorganic fillers made of inorganic fibers such as asbestos and glass fibers, powders such as barium sulfate and graphite, and binders such as melamine resins and phenolic resins. It is manufactured by preforming at room temperature by wet mixing using an organic solvent or by dry mixing without using an organic solvent, followed by heating and pressing.

[Problems to be Solved by the Invention] Conventional friction material compositions, especially when fibers other than asbestos such as glass fiber or carbon fiber are used as the inorganic msa, have problems when preformed by dry mixing at room temperature. There was a problem in that the molded product lost its shape early. To solve this problem, there are methods such as wet mixing or heating during preforming to increase the adhesiveness of the binder. However, in the case of wet mixing, a drying process to evaporate the organic solvent contained in the preform, a degassing process, etc. are required, and heating energy is also required to heat the preform, resulting in a high cost. There was a problem. Furthermore, in conventional friction materials, the coefficient of friction increases with time of use and reaches a desired value, so there are cases where the desired coefficient of friction cannot be obtained at the beginning of use.

The present invention has been made in view of the above-mentioned problems, and provides a friction material composition that has excellent preformability and provides a friction material with a high coefficient of friction even in the initial stage.

Means for Solving Problem L] The friction material composition of the present invention is characterized by comprising 100 parts by weight of a base component consisting of inorganic/organic fibers, inorganic/organic fillers, resins, and the like.

Here, the term "friction material" refers to clutch facings, brake linings, brake pads, etc., and refers to a material that primarily moves against a metal counterpart and converts kinetic energy into thermal energy through the friction of the friction.

The base component referred to in the present invention is a component that maintains the shape of the friction material and increases sliding frictional resistance, and conventional materials such as inorganic/organic fibers, inorganic/organic fillers, resins, etc. can be used. Inorganic/organic fibers serve as the base material of the friction material, and asbestos, glass fiber, metal fiber, carbon fiber, phenol fiber, etc. can be used alone or in combination of two or more types. Inorganic/organic fillers are mainly blended for the purpose of friction adjustment, and include inorganic powders such as barium sulfate, alumina, calcium carbonate, calcium hydroxide, diatoms, graphite, and dolomite, cashew dust,
Various organic powders such as rubber dust, metal powders such as aluminum, iron, zinc, etc. can be selected and used depending on the purpose. The resin acts as a binder for the above-mentioned cord and filler, maintains the shape of the friction material, and adjusts hardness and friction, and includes phenolic resin, butyral resin,
Phenoxy resin, epoxy resin, etc. can be used. Phenolic 1Ml1# refers to a resin obtained by condensing one or more phenols such as phenol and cresol with formaldehyde or a compound that is a source thereof. Furthermore, modified phenolic resins modified with cashew nut oil, polyvinyl butyral, vegetable oil, melamine, epoxy compounds, etc. may also be used.

In terms of heat resistance, unmodified phenolic resin is excellent.

Note that additives, auxiliaries, etc. other than those mentioned above may also be added to the base component.

The greatest feature of the present invention is that unvulcanized rubber powder is blended into the base component. That is, Fukanon completed the present invention by discovering that by using unvulcanized rubber powder, the preform does not lose its shape even during dry mixing and has good shape retention. This unvulcanized rubber may be NBR, SBR, BR, natural rubber, etc., but is not particularly limited, but NBR and SBR are preferred. Also 1
Not only seeds but also a mixture of two or more types can be used.

This unvulcanized rubber is mixed with the base component in a powdered state, and particles having a particle size in the range of 10 μ- to 3 g+s can be used.

If the particle size is smaller than 10 μm, secondary aggregation of the rubber particles tends to occur, making it difficult to obtain a molded article with a uniform rubber composition.

Moreover, if it is larger than 3 mm, the molded body tends to be non-uniform, and the coefficient of friction may differ locally or change over time. Furthermore, the appearance of the friction material is also poor, which is not desirable.

Further, the unvulcanized rubber powder is blended in an amount of 5 to 5011 parts by weight per 100 parts by weight of the base component. When the amount is less than 5 parts by weight, there is almost no effect of increasing the shape retention during preforming and the initial *m coefficient as a friction material, and when it is more than 50 parts by weight, there is a fade phenomenon (continuous braking). This is undesirable because it causes a decrease in the coefficient of friction (when the temperature of the friction surface suddenly increases).

It is desirable to add a compounding agent to the friction material composition of the present invention to adjust the performance of the unvulcanized rubber. For example, unvulcanized rubber is vulcanized during hot-press molding by adding a vulcanizing agent, or carbon is added to impart reinforcing properties. Such compounding agents include conventionally well-known vulcanizing agents, vulcanizing aids,
Various anti-aging agents, fillers, tackifiers, etc. can be selected and used depending on the purpose. These compounding agents are usually mixed in an amount of 50 to 150 parts by weight per 100 parts by weight of unvulcanized rubber. Although these compounding agents can be mixed simultaneously with the base component and unvulcanized rubber powder, they can be mixed in advance into the unvulcanized rubber and used as the base component as unvulcanized compounded rubber powder with a particle size of 10 μII to 3 II m. It is preferable to mix it with However, in this case, it goes without saying that the amount of the compounding agent added must be adjusted.

Unvulcanized rubber powder or unvulcanized compounded rubber powder is usually produced by a method such as freeze-pulverization. For example, a powder can be obtained by kneading unvulcanized rubber and a compounding agent in a heating kneader, Banbury mixer, etc., extruding it into a plate shape, cutting it into eroded strips, and freeze-pulverizing it at -30'C or below. Note that these powder particles may cause problems such as particles sticking to each other and becoming large particles due to the stickiness of the particles themselves at room temperature. To prevent such problems, a very small amount of I (usually 0.5 to 3.0 times the amount of rubber powder) is added to the filler powder of base components such as alumina, talc, calcium carbonate, barium sulfate, and clay. %) to the unvulcanized rubber powder or the unvulcanized compounded rubber powder during the cooling process after the above-mentioned freeze-pulverization. In this case, the filler powder is acting as an anti-agglomeration agent.

In order to manufacture a friction material using the friction material composition of the present invention, conventional methods can be used. However, in order to achieve shape retention during preforming, which is one of the effects of the present invention,
It is desirable to perform preforming after dry mixing without using lj solvent or the like for the base component. That is, the base component and unvulcanized rubber powder or unvulcanized blended rubber powder are thoroughly mixed in a Banbury mixer, Henschel mixer, kneader, V-type blender, high-speed rotating machine, etc. to produce a mixed raw material.

This mixed raw material is filled into a mold and pressed at room temperature to perform preforming to produce a rough shaped material. Next, it is preferable to put the rough shaped material into a heating mold and heat and pressurize it to produce a friction material.

[Function and Effects of the Invention] The friction material composition of the present invention can maintain the shape of a preform for a long time even during dry mixing due to the tackiness of the unvulcanized rubber. Further, by vulcanizing the unvulcanized rubber during heating and pressurization, it is possible to integrally bond with the base component, and a high-strength friction material can be obtained. Furthermore, the initial coefficient of friction can be increased as the amount of unvulcanized rubber is increased. Furthermore, due to the shrinkage of the volume of the unvulcanized rubber powder during vulcanization and the inclusion of air during dry mixing, the resulting friction material has a higher porosity than conventional materials.

Therefore, when organic matter decomposes due to heat generation at **,
It becomes possible for decomposition products to be absorbed into internal pores or released to the outside through pores communicating with the outside. This promotes the decomposition of organic matter, thereby making it possible to stabilize the *m coefficient at an early stage, and the effects of the present invention are significant.

[Example] This will be explained below using examples.

Glass fiber 3 with an average diameter of 8 μm and an average length of 3 ms
0% by weight, Kevlar (15% by weight of aromatic polyamide,
The base component was a mixture consisting of 25% by weight of unmodified phenol resin (straight phenol resin), 10% by weight of cashew dust, and 20% by weight of barium sulfate powder.

Also, 50 parts by weight of unvulcanized NBR rubber, 2 parts of carbon black
3 parts by weight, 107,111 parts by weight of sulfur, 10 parts by weight of talc,
A mixture consisting of 5 parts by weight of zinc oxide and 2 parts by weight of anti-aging agent was extruded at 110°C into a mixed M plate shape and cut into strips.
Freeze-pulverization was performed at 0°C to obtain unvulcanized compounded rubber powder with a particle size of 0.1 to 1.0H. The base component and the unvulcanized rubber component in the unvulcanized compounded rubber powder are in a vertical ratio of 100:1.
The friction material composition of Example 1 was obtained.

Next, the base component and the unvulcanized compounded rubber powder had the same composition as in Example 1, and the base component and the unvulcanized rubber component in the unvulcanized compounded rubber powder were mixed in a weight i ratio of 100:45. The friction material composition of Example 2 was obtained.

Furthermore, the base component and the unvulcanized compounded rubber powder were mixed with the unvulcanized rubber component in the example rubber powder at a weight ratio of 100:2.5 and 100:55, respectively, for Comparative Example 1 and Comparative Example 2.
A friction material composition consisting of only a base component without blending unvulcanized compounded rubber powder was used as a conventional example.

[Test Example] Using the friction material compositions of Example 1, Example 2, and the conventional example, each was kneaded at room temperature using a V-type blender, and then preformed to have an outer diameter of 236cm-1, an inner diameter of 1501L, and a thickness of 101I. Fill the mold to obtain the body, and apply a surface pressure of 250 at room temperature.
Each preform was created by applying pressure at kQ/c12. Two pressurization times of 1 minute and 5 minutes were selected, and two preforms were created for each friction material composition using these two pressurization times. The thickness of the obtained preform immediately after it was taken out of the mold and the thickness after it was left to stand for 5 minutes were measured, and the results are shown in the bar graphs of FIGS. 1 and 2. In the case of this test example, the thickness is 12.5
It has been found that if m- is exceeded, it becomes impossible to maintain the shape of the preform.

Figure 1 shows that the thickness of the preformed body made from the conventional friction material composition is 13.7 mm when it is left for 5 minutes after being pressurized for 1 minute.
This makes it difficult to maintain the shape, and as shown in Figure 2, even after 5 minutes of pressurization and 5 minutes of standing, the temperature is 11°7, which is a dangerous area for maintaining the shape. In comparison, the preforms made of the friction material compositions of Examples 1 and 2 had extremely excellent shape retention, with a thickness of 10.3 to 10.8 mm after being left for 5 minutes even when pressurized for 1 minute. .

Next, a test example of friction characteristics will be explained. .

5 of each friction material composition at a surface pressure of 250 kQ/am2.
Immediately after forming a preform, a surface pressure of 100 kg was applied.
/cwt, and was molded using a compression molding machine at 160°C. Note that the time required for heat molding was 3 minutes. After this molding, heat treatment was performed at 200° C. for 4 hours, and the front and back surfaces were polished to produce respective dry clutch facings.

The dry flat facings obtained from the friction material compositions of the above Examples, Comparative Examples, and Conventional Examples were subjected to 2000 joint tests using a clutch dynamometer, and the friction coefficients were measured. The results are shown in Figure 3. The conditions in this test were: jib inertia, 3 kam s'', and rotation speed 150 rpm.

The temperature was 200°C, and cast iron was used as the mating material.

It is clear from FIG. 3 that the initial coefficient of friction increases as the amount of unvulcanized rubber added increases. Further, in Comparative Example 1 and the conventional example, approximately 80 joints are required until the friction coefficient becomes stable, whereas in Example 1 and Actual Example 12, the number of joints is as small as approximately 60 times. Furthermore, in Comparative Example 2, a fading phenomenon in which the friction coefficient decreases due to continuous jointing appears.

From the above test examples, it is clear that the jI friction material compositions of Examples 1 and 2 have excellent shape retention during preforming, and the friction materials obtained thereby also have excellent friction properties. .

[Brief explanation of drawings]

Figures 1, 2 and 3 show the results of test examples, Figures 1 and 2 are bar graphs showing changes in the thickness of the preform, and Figure 3 shows changes in friction coefficient depending on the number of joints. This is a graph showing. Figure 1

Claims (3)

[Claims] (1) Friction characterized by consisting of 100 parts by weight of a base component consisting of inorganic/organic fibers, inorganic/organic fillers, resins, etc., and 5 to 50 parts by weight of unvulcanized rubber powder with a particle size of 10 μm to 3 mm. material composition. (2) The friction material composition according to claim 1, wherein the unvulcanized rubber powder is an unvulcanized compounded rubber mixed with rubber compounding agents such as a vulcanizing agent and a softening agent. (3) The friction material composition according to claim 1, wherein an anti-agglomeration agent is attached to the surface of the unvulcanized rubber powder.