JPH0737606B2 - Wet friction material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet friction material applicable to clutches, brakes and the like which are used while being immersed in oil in an automatic transmission of a vehicle.

[0002]

2. Description of the Related Art Conventionally, a wet friction material of this kind has been prepared by forming a paper body by making a mixture of base fiber and additives in water.
It is manufactured by impregnating a papermaking body with a binder and thermally curing it. The heat resistance and abrasion resistance of the friction material formed by this method depend on the characteristics of the base fiber as the main component. Therefore, in order to improve these properties, attempts have been made to appropriately mix heat-resistant organic fibers and inorganic fibers in addition to wood pulp as the base fiber. For example, Japanese Patent Publication No. 60-23774
The publication discloses a friction material containing aromatic polyamide fiber as a base fiber, added with an additive and a friction modifier to make a paper, and impregnated with a phenolic binder in the paper body to be thermoset. ing. Similarly, Japanese Patent Publication No. 1-336
Japanese Patent Laid-Open No. 99 discloses a friction material such as a wet friction material containing pulp-like particles made of a heat-resistant aromatic polymer and inorganic fibers and / or heat-resistant organic fibers. Aromatic polyamides and the like are listed as aromatic polymers having, and aromatic polyamide fibers and the like are listed as heat-resistant organic fibers.

In JP-A-62-106133, a fibrillated acrylic fiber and a filler are blended in an amount of 5 to 50% by weight based on the total amount of base fiber to make a paper, and the paper is heated. There is a disclosure of a wet friction material cured with a binder of a curable resin. The main purpose of this wet friction material is to increase the adhesive strength of the base fiber with the resin binder to improve the breaking strength, and an example in which aromatic polyamide fiber is used in combination (N
o. Although 4) is also disclosed, the blending ratio is 5% by weight of the entire wet friction material (6.8% by weight of the entire papermaking body).

[0004]

As described above, when an aromatic polyamide fiber is used as the base fiber in order to improve the heat resistance and wear resistance of the wet friction material, the friction material is increased in proportion to the addition amount thereof. Heat resistance and wear resistance are improved. Then, in order to sufficiently improve the heat resistance and abrasion resistance, it is preferable to mix the aromatic polyamide fiber in a proportion of 30% or more of the entire papermaking body. However, when the amount of the aromatic polyamide fiber added is increased in this way, the friction caused by deformation such as fatigue due to creep movement of the aromatic polyamide fiber, and changes over time such as reduction of pores on the friction surface due to the deformation. Performance tends to decrease. Therefore, even if the heat resistance and the wear resistance themselves are improved, the durability of the wet friction material cannot be improved sufficiently as a result due to the deterioration of the friction performance due to the deformation such as sag.

When the fibrillated acrylic fiber is used as the main component of the base fiber as disclosed in the above-mentioned Japanese Patent Laid-Open No. 62-106133, the strength of the friction material is improved because of good adhesion to the resin. Although it increases, the melting point is lower than that of the aromatic polyamide fiber having a melting point of 300 ° C. or higher, so that it is not possible to obtain a sufficient effect in improving heat resistance and abrasion resistance.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a wet friction material having excellent heat resistance and wear resistance and high durability.

[0007]

The wet friction material of the present invention comprises:
A base material fiber, a wet friction material formed by impregnating a binder into a papermaking body that is made from a mixture of additives and curing,
The base fiber is 30 to 65% by weight with respect to the entire papermaking body.
Of aromatic polyamide fiber and 5 to 10% by weight of fibrillated acrylic fiber, and the aromatic polyamide fiber and the fibrillated acrylic fiber are in a weight ratio of 1
It is contained at a ratio of 0: 1 to 10: 3.

This wet friction material is formed by binding a papermaking body formed of base fibers and additives with a binder.

Here, the aromatic polyamide fibers are contained in the base fibers constituting the papermaking body, and are generally used in a proportion of 30 to 65% by weight in order to sufficiently improve heat resistance and abrasion resistance. That is, if the proportion of the aromatic polyamide fiber is less than 30% by weight, sufficiently high heat resistance and abrasion resistance cannot be obtained. The upper limit of 65% by weight is
It is practically impossible to set the ratio higher than that in relation to other compounding materials.

Further, in addition to the aromatic polyamide fibers, the base fibers constituting the papermaking body include fibrillated acrylic fibers. The fibrillation of this acrylic fiber is
For example, it can be easily carried out by beating or swelling with a swelling agent, followed by pressing and crushing. The fiber length of this fiber is preferably 0.1 to 3 mm, and the fiber diameter is preferably about 1 to 10 μm, because mixing and dispersion during papermaking becomes easy.

The acrylic fiber mechanically and easily entangles with the aromatic polyamide fiber and other base fibers at the time of papermaking to form a papermaking body based on the characteristic that the fiber is fibrillated. Then, under heat treatment conditions in which the papermaking body is impregnated with a binder and then heat-cured, the fibrils are easily softened and melted and weld-bonded to the base fibers or additives,
It is possible to firmly bond the compounding components together with the binder. Therefore, the fibrillated acrylic fiber can firmly reinforce the aromatic polyamide fiber and suppress the deformation and the change over time due to the creep behavior of the aromatic polyamide fiber.

As described above, the fibrillated acrylic fiber can suppress the deformation of the aromatic polyamide fiber, but the acrylic fiber has a softening start temperature of 15
It is in the range of 0 to 200 ° C and does not have sufficient heat resistance. Therefore, the fibrillated acrylic fiber is used in a minimum ratio necessary for suppressing the deformation of the aromatic polyamide fiber, and is mixed in a ratio of 5 to 10% by weight with respect to the entire paper body. If it is less than 5% by weight, the practically sufficient suppression effect cannot be obtained, and if it is more than 10% by weight, the heat resistance is lowered more than the suppression effect is improved, and as a result, it is sufficiently high. Durability cannot be obtained.

The blending amount of the fibrillated acrylic fiber is also related to the blending amount of the aromatic polyamide fiber. That is, the aromatic polyamide fiber and the fibrillated acrylic fiber are used in a weight ratio of 10: 1 to 10: 3. If the compounding ratio of the fibrillated acrylic fiber is less than this range, it is not possible to sufficiently suppress the deformation of the aromatic polyamide fiber such as the settling and the change with time. On the other hand, if the mixing ratio of the acrylic fiber exceeds the range, the heat resistance is lowered and the durability is lowered, which is not preferable.

As described above, the base fiber constituting the papermaking body contains the aromatic polyamide fiber and the fibrillated acrylic fiber in a specific blending ratio and blending ratio. In addition to the fibers, linter pulp, wood pulp, synthetic pulp, heat resistant organic fibers, inorganic fibers and the like can be blended and used. Additives, which are other constituents of the papermaking body, adjust the frictional properties of the friction material, and include, for example, fillers, silica, clay, wollastonite, mica, talc, diatomaceous known as friction modifiers. Soil, calcium carbonate, magnesium carbonate, cashew dust, graphite and the like can be used alone or in combination of two or more kinds. The amount of these additives is usually 10 to 49% for inorganic additives and 0 to 20 for friction modifiers.
%, In the range of.

The base fiber and the additive are
The slurry of these mixtures is paper-made by a usual method to form a paper-making body. Next, the papermaking body is impregnated with a binder and cured to form a friction material. As the binder used here, a thermosetting resin such as phenol resin, epoxy resin, or melamine resin is used.
The amount used is 20 to 50% with respect to the whole papermaking body, and the amount of impregnation is usually adjusted as a liquid. The impregnated binder is thermoset at a temperature of about 180 to 250 ° C., which is also a temperature near the softening temperature of the fibrillated acrylic fiber, to form a friction material. This friction material is further processed for facing and used.

[0016]

In the wet friction material of the present invention, a relatively large amount of aromatic polyamide fiber having high heat resistance and abrasion resistance is used as the base fiber, and the content of the aromatic polyamide fiber is 30 to 65% by weight based on the whole papermaking body. Therefore, heat resistance and wear resistance are sufficiently improved. Further, since the paper body contains fibrillated acrylic fiber in addition to the aromatic polyamide fiber,
The fibrils of the acrylic fiber are entangled with the aromatic polyamide fiber, melt and bond when the binder is cured, and firmly bond the aromatic polyamide fiber to each other and to other compounding ingredients to reinforce the aromatic polyamide fiber. Deformation such as fatigue due to the creep behavior of the steel sheet, and changes over time such as reduction of pores on the friction surface due to the deformation are suppressed. The fibrillated acrylic fiber having low heat resistance is 5 to 10% by weight with respect to the entire paper body, and the weight ratio of the acrylic fiber to the aromatic polyamide fiber is 1:10.
Since it is contained at a ratio of 3:10 and is a ratio of the minimum necessary minimum, durability is improved without impairing heat resistance and wear resistance.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples.

With the blending composition (parts by weight) shown in Table 1, wet friction materials of Examples and Comparative Examples of the present invention were produced.

[0019]

[Table 1]

Example 1 25 parts by weight of wood pulp as a base fiber, 30 parts by weight of a pulp-like aromatic polyamide fiber, 5 parts by weight of fibrillated acrylic fiber, 30 parts by weight of diatomaceous earth as an additive, and friction. A mixture with 10 parts by weight of a regulator (cashew dust) (total 100 parts by weight) was dispersed and mixed in a large amount of water, and paper was formed by a wet papermaking method to form a papermaking body. The weight ratio of the aromatic polyamide fiber and the fibrillated acrylic fiber is
It is 10: 1.7.

This paper body was impregnated with a resol type phenol resin solution as a binder, air-dried and then cured in a hot air drying oven at 200 ° C. The content of the binder after curing was 30 parts by weight, and the concentration of the phenol resin solution was adjusted by diluting with methanol so that the content would be this content.

Then, a wet friction material facing was formed by press-molding to a required thickness with a uniaxial press machine preheated to 200 ° C. Further, this facing was cut into a required shape and bonded to a core metal.

The wet friction material thus obtained was subjected to a friction performance test (SAE No. 2) to evaluate its durability and the amount of sag. For this durability, the number of engagement cycles until deterioration of friction performance such as fluctuation of friction coefficient due to heat loss or clogging of surface pores was measured. Regarding the amount of squat (%), the thickness of the wet friction material after the durability test was measured, and the amount of decrease in thickness was calculated as a percentage with respect to the initial thickness.
Therefore, the amount of sag is the sum of the amount of crush deformation based on the creep behavior of the base fiber and the amount of wear of the friction material due to repeated friction.

The test conditions for SAE No. 2 are as follows:
Number of friction material surfaces: 4, facing area: 28 cm ² /
Surface, rotation speed (N): 3600 rpm, inertial amount (I):
2.5 kg · cm · sec ² , pressing force (P): 1
0.0 kg / cm ² , test temperature (t): 120 ° C., absorbed energy of friction material / cycle: 4.2 kcal.

As a result of this evaluation test, the wet friction material of Example 1 has durability of 25,000 cycles, and
When the wet friction material after the test was taken out and examined, the amount of sag was 11% of the initial thickness. The results of this evaluation test are shown in Table 1 together with the composition.

Comparative Example 1 30 parts by weight of wood pulp as a base fiber, 30 parts by weight of a pulp-like aromatic polyamide fiber, 30 parts by weight of diatomaceous earth as an additive, and 10 parts by weight of a friction modifier (cashew dust). And a total of 100 parts by weight, and a papermaking body was formed in the same manner as in Example 1 from a mixture of these containing no fibrillated acrylic fiber. Then, a wet friction material was produced from this papermaking machine through the same steps as in Example 1.

When this wet friction material was subjected to a SAE No. 2 friction test under the same conditions as in Example 1, the durability was as short as 10000 cycles, and the friction characteristics were significantly deteriorated and the durability limit was reached. The facing portion after the test had almost no surface pores and was in a clogging state. The amount of sag at this time was 18%, which was larger than that in Example 1.

Therefore, comparing Example 1 with Comparative Example 1, even in the base fiber system containing wood pulp and aromatic polyamide fiber, the wet friction material has improved durability due to the addition of the fibrillated acrylic fiber, It also indicates that the amount of sagging has decreased.

Example 2 As the base fiber, 55 parts by weight of pulp-like aromatic polyamide fiber and 10 parts by weight of fibrillated acrylic fiber (weight ratio 10: 1.8) were used without using wood pulp. Further, 30 parts by weight of diatomaceous earth and 5 parts by weight of a friction modifier were used as additives, a mixture of these (100 parts by weight in total) was made into paper, and the wet friction material was produced through the same steps as in Example 1.

When this wet friction material was subjected to a SAE No. 2 friction test under the same conditions as in Example 1, it was found to be 3
The durability of 5000 cycles was shown. Further, the amount of sag of the friction material at this time was 13%. The results are shown in Table 1.

Comparative Example 2 Only a pulp-like aromatic polyamide fiber was used as the base fiber, and a mixture of 65 parts by weight of this, 30 parts by weight of diatomaceous earth and 5 parts by weight of a friction modifier (total 100 parts by weight). Was used to make a paper, and the wet friction material was produced through the same steps as in Example 1.

When this wet friction material was subjected to the SAE No. 2 friction test under the same conditions as in Example 1, the friction characteristics were significantly deteriorated in just 8000 cycles and the durability limit was reached. Also, the facing part after this test is
There was almost no surface porosity and it was in a clogged state. The sag amount at this time was as high as 21%, and sag deformation due to creep of the aromatic polyamide fiber was confirmed.

Therefore, these Example 2 and Comparative Example 2
By contrast, by blending the fibrillated acrylic fiber in the base fiber system of the aromatic polyamide fiber, it is possible to suppress the fatigue deformation of the aromatic polyamide fiber due to creep and further improve the durability of the wet friction material. I understand.

From the comparison between Example 1 and Example 2,
Under the prescribed proportion of fibrillated acrylic fibers, increasing the proportion of aromatic polyamide fibers improves the heat resistance and wear resistance of the wet friction material, thereby improving its durability. It can be seen that it can be further increased.

[0035]

As described above, the wet friction material of the present invention is
A base material fiber, a wet friction material formed by impregnating a binder into a papermaking body that is made from a mixture of additives and curing,
The base fiber is 30 to 65% by weight with respect to the entire papermaking body.
Of the aromatic polyamide fiber and 5 to 10% by weight of fibrillated acrylic fiber, and the aromatic polyamide fiber and the fibrillated acrylic fiber are in a weight ratio of 10: 1 to 10: 3. It is included in.

Therefore, this wet friction material contains a large amount of aromatic polyamide fibers having high heat resistance and abrasion resistance, and the content of acrylic fibers having relatively low heat resistance is reduced to the minimum required. Therefore, excellent heat resistance and wear resistance can be obtained. In addition, the fibrillated acrylic fiber is entangled with the aromatic polyamide fiber,
When the binder is cured, it melts and adheres, and the aromatic polyamide fibers are strongly bonded to each other and other compounding ingredients to reinforce, so that deformation such as sag based on the creep behavior of the aromatic polyamide fibers, Since the change over time such as the decrease of pores on the friction surface due to the deformation is suppressed, the durability can be improved.

Therefore, according to the present invention, there is an effect that it is possible to obtain a wet friction material having excellent heat resistance and abrasion resistance and high durability.

Claims (1)

[Claims] 1. A wet friction material formed by impregnating a papermaking body, which is made from a mixture of a base fiber and an additive, with a binder, and hardening the papermaking medium , wherein the base fiber is formed on the entire papermaking body. To
30 to 65% by weight of aromatic polyamide fiber and 5 to 10
% Of fibrillated acrylic fiber , said aromatic polyamide fiber and said fibrillated acrylic
A wet friction material characterized by containing fibers in a weight ratio of 10: 1 to 10: 3.