JPH03152179A - Wet frictional material - Google Patents

Abstract

PURPOSE:To obtain a wet frictional material having a large frictional coefficient and high resistance to seizure containing a specific ratio of an epoxy resin and a granular rubber having reactivity with said epoxy resin as essential ingredients. CONSTITUTION:(A) An epoxy resin preferably as an epi-bis type epoxy resin, phenol.novolak type epoxy resin, alicyclic epoxy resin and/or polyfunctional glycidylamine-type epoxy resin is mixed with (B) a granular rubber having reactivity with said component A preferably as a carboxyl-modified acrylonitrile.butadiene rubber and/or an epoxy-modified acrylic rubber to afford the aimed frictional material suitable as surface-covering material of clutch or brake. The amount of the component A is 1-5wt.% of the total weight and a weight ratio of the component A to the component B is 1/40-2/3.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an organic friction material used as a covering material for clutches and brakes.

(Prior art) An epoxy resin and a rubber that is reactive with the epoxy resin (
The most important prior art for the present invention is Japanese Patent Laid-Open No. 54-1991 (hereinafter referred to as "reactive rubber") as an essential component of the friction material.
66950 (Special Publication No. 57-2733゜U.S. Patent No. 4,1
31.590). This prior art teaches a friction material containing an epoxy resin and a reactive rubber as essential components in a weight ratio of 5 to 40% epoxy resin, 1 to 5 to 40% reactive rubber, and the balance friction filler. The aim is to produce a flexible matrix through copolymerization between an epoxy resin and a rubber that is reactive with the epoxy resin, as stated in the specification.
It is known that this is intended to contain various friction fillers and thereby provide a friction material that has good compatibility with the mating plate.

(Problems to be Solved by the Present Invention) In fact, the friction materials according to the above-mentioned prior art have been well received in the relevant market.

However, according to research conducted by the inventors of the present invention, the friction materials according to the prior art described above do not have sufficient flexibility, which is originally required for this type of friction material. Escape, friction coefficient (hereinafter referred to as μ6)
It was known that the level of friction was low, and at the same time, it was also unsatisfactory in achieving a high coefficient of kinetic friction (referred to as μ), which is naturally required in all applications.

Further, according to research conducted by the inventors of the present invention, it has been found that the major cause of the above-mentioned dissatisfaction is that, among the above-mentioned essential components, the amount of epoxy resin, which becomes a hard component after curing, is too large. Especially when the reactive rubber in the prior art described above remains in the form of particles, the amount of epoxy resin exceeds that required for copolymerization.

This hardens and loses its flexibility, while the reactive rubber does not remain in the form of particles but is dispersed finely (probably in the form of molecules).
It has been found that when a complete copolymerization reaction with an epoxy resin occurs, the product itself loses its flexibility.

(Means for solving problems) The present inventors obtained the following findings from the above-mentioned research.

(If all of the reactive rubber 11 undergoes a polymerization reaction with the epoxy resin, it will lose its flexibility, so it is desirable that some of it remains unreacted.

(2) To achieve this, the reactive rubber remains in the form of granules or blocks (generally flattened due to processing during the process) and reacts with the epoxy only on its surface. Good.

(3) In this case, the amount of epoxy resin required for the reaction should be much smaller than the amount of reactive rubber.

The present invention has been made based on the above findings. That is, in a friction material containing an epoxy resin and a rubber reactive with the epoxy resin as essential components, the reactive rubber is in the form of particles or blocks, and the amount of the epoxy resin is equal to the weight of the entire friction material. The inventors have now invented a wet friction material characterized in that the content of the reactive rubber is 5% or less and 1% or more, and the weight ratio is 1/40 to 2/3 of the amount of the reactive rubber.

Epoxy resins may be of any type, but according to experiments conducted by the inventors, epibis type epoxy resins, phenol/novolak type epoxy resins, alicyclic epoxy resins, and polyfunctional glycidylamine type epoxy resins are used. Epoxy resins are preferred, and one or a combination of two or more selected from this group is used.

The reactive rubber may be of any type as long as it is reactive with the epoxy resin used, but in particular carboxy-modified acrylonitrile/butadiene rubber and/or
Alternatively, epoxy-modified acrylic rubber is preferred.

(Operations and Effects of the Invention) In general, the role of a friction material in a clutch or brake device is to apply an appropriate pressure between two surfaces with a relative speed difference to bring them into contact, generate frictional force, and as a result, In the case of a clutch, it is the transmission of power from one surface to the other, and in the case of a brake, it is to bring it to a standstill. If the pressure applied between both surfaces (surface pressure) is constant,
The magnitude of the frictional force generated is proportional to the true contact area between the two surfaces under the surface pressure. The actual contact area is proportional to the flexibility of the material forming at least one surface. This is one of the reasons why friction materials are required to have flexibility.

As a result of the friction, there is a great deal of heat generation at the real contact surfaces. Therefore, if the actual contact surface is biased toward a portion of the friction surface, the material will be heated beyond its resistance, causing deformation, deterioration, thermal cracking, and other unforeseen accidents. In order to prevent this, extremely precise finishing is required on both sides in order to make the due east contact surface even over the entire friction surface. However, this requirement is technically difficult, and in particular, as the friction surface becomes wider, the difficulty increases with increasing acceleration. As a means to eliminate this difficulty regardless of the degree of surface area, it is possible to utilize the elasticity of the material constituting the friction surface, so that it easily deforms when pressure is applied, and the pressure can be dispersed to other points. This is another reason why friction materials are required to be flexible.

In the present invention, by configuring the friction material as described in the previous section, a large frictional force can be obtained with a small surface pressure, and the contact surface of the mouth and bottom is evenly distributed over the entire friction surface, resulting in a large coefficient of friction. , provides a friction material with high seizure resistance. According to experimental results, the amount of epoxy resin added is preferably less than 5%.

Furthermore, if the amount of epoxy resin added is less than 1%, the rubber will occupy a relatively large portion of the binder and the heat resistance will be significantly lowered, which is not desirable. The amount of rubber that is reactive with epoxy resin depends on the type of filler to be added, but if it is more than 40 times the amount of epoxy resin added, the amount of rubber added may be too large and may impair heat resistance or may act as a binder. If the temperature is too high, problems such as fluctuations in μ due to plastic flow will occur.

If it is less than +3/21 times the amount of epoxy resin added, the μ is sufficient.
S cannot be obtained or the desired resistance rate cannot be obtained.

Furthermore, according to the claims described in the present invention, high μ
By selecting not only the S material but also an appropriate filler, a friction material with low static friction characteristics with little difference between μd and μS and a very high load capacity can be obtained. In order to obtain the elastic modulus necessary for uniform contact over the entire friction surface, it is possible to add less binder component than conventional products, and because of this, the filler component is relatively large, causing phenomena such as plastic flow. This is to suppress friction and increase heat resistance and seizure resistance on the friction surface.

In addition to the essential components shown in the claims, the wet friction material of the present invention contains 0.01% or more and less than 5% of a curing agent and a curing accelerator for crosslinking resin and rubber, and the remainder is a friction filler material (filler). ) is suitable. Generally recommended curing agents and curing accelerators are used, but polyvarahydroxystyrene phenol resin is particularly used as a curing agent.

1 selected from phenol/aralkyl resins and acid anhydrides
When using seeds or a mixture of two or more types.

Improves the heat resistance and oil resistance of the binder, and improves stable friction coefficient, abrasion resistance, seizure resistance, and durability. If the amount of the curing agent or curing accelerator added is less than 0.01%, the reaction will be insufficient or the heat resistance will be poor. Moreover, if it exceeds 5%, the elasticity of the material will be impaired or it will be wasteful.

(Example) Examples of the present invention will be described below. This example is an example of an experiment conducted to confirm the effect of the present invention and confirm the scope of application, and the scope of the claims is not limited by the example.

The compositions shown in Table 1 below were kneaded using a roll or kneader until each component was uniformly dispersed, and calendered to form a sheet. The sheet was cut into a desired shape, heat-cured, adhered to a steel core plate material, and an oil groove was cut to prepare a test sample.

Examples 1 to 3 have high μS, and Examples 4 to 7 have μS, μ
This is an example of a high-load low static material with a relatively low load. As a comparative example, a commercially available CTBN-epoxy friction material was partially used.

Figure 1 shows diesel engine oil, S-3, IOW 120.
As for the swelling when immersed in ℃ temperature for a long time, it can be seen that the value of the Example is about 174 compared to the commercial product used as a comparison, which shows that the oil resistance is greatly improved.

Figure 2 shows the change over time in the tensile strength of Example 2 at 100°C in air, Figure 3 shows the P-μs curve as the result of the inertial friction test, and Figure 4 shows the results of the 10,000 cycle durability test. , stable physical properties, high μS of 0, 2 or more, and long-term stable friction characteristics.

FIG. 5 shows the results of a durability test conducted at an absorbed energy IQI (gfm/ca+1, absorbed power of 14 kgfm/cm"sec). It can be seen that stable friction characteristics are exhibited under high load conditions.

Like Example 1.3 and Example 2, and Example 5.6.7 as well as Example 4, they were effective over the conventional products.

[Brief explanation of the drawing]

Figure 1 is a curve diagram showing the relationship between the number of days of immersion and the rate of change in thickness in the swelling test for the friction material of the present invention and a wet friction material for comparison. A curve diagram showing the relationship between IIm dew opening time and tension in the deterioration test, Figure 3 is a curve diagram showing the relationship between surface pressure and escape friction coefficient, and Figures 4 and 5 are curve diagrams showing the relationship between the friction cycle and the tension. FIG. 3 is a curve diagram showing the relationship between friction coefficient and wear rate.

Claims (3)

[Claims] (1) In a friction material containing an epoxy resin and a rubber reactive with the epoxy resin (reactive rubber) as essential components, the reactive rubber is in the form of particles, and the amount of the epoxy resin is determined based on the entire friction material. A wet friction material characterized in that the content thereof is 5% or less and 1% or more by weight, and the weight ratio is 1/40 to 2/3 with respect to the amount of the reactive rubber. (2) The reactive rubber is carboxy-modified acrylonitrile.
The wet friction material according to claim 1, characterized in that it is at least one selected from butadiene rubber and epoxy-modified acrylic rubber. (3) A patent claim characterized in that the epoxy resin is at least one selected from the group of epibis type epoxy resin, phenol/novolac type epoxy resin, alicyclic epoxy resin, and polyfunctional glycidylamine type epoxy resin. Wet friction material according to scope 1.