JPH0465094B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a non-asbestos friction material used for power transmission and braking in transportation machines such as automobiles.

[Background technology and problems]

Conventionally, asbestos has been mainly used as a reinforcing material for friction materials, and is molded and hardened together with thermosetting resin and reinforcing materials, but as asbestos is a carcinogen, manufacturing There is a growing demand for non-asbestos friction materials due to occupational safety and health issues associated with the increase in airborne dust during use and public health issues. Normally, the requirements for friction materials include a friction coefficient of 0.25 or more, low wear, and
It is said to have high wear resistance and mechanical strength even at temperatures of around 500°C.

Up to now, various types of fiber materials have been tried as reinforcing materials in non-asbestos friction materials. For example, in JP-A-58-113641, flame-resistant fibers obtained by heat-treating acrylic fibers in air at 200-400°C are used, but the tensile strength of these fibers is 1-400°C.
3 g/d, tensile modulus is 50 to 150 g/d,
It is inferior as a reinforcing fiber material. In particular, flame-resistant fibers have a considerably lower tensile modulus than asbestos, and their weight decreases at high temperatures of 500°C, which are required as friction materials. It has the disadvantage of being prone to cracks on the surface of the material. Furthermore, polyacrylonitrile (PAN) based carbon fibers can be considered as the reinforcing fiber material. Usually, PAN-based carbon fibers are fired in an inert gas at 1000°C or higher to have a carbon content of 90% by weight or more and a bound oxygen content of 1 to 8% by weight.
, tensile strength 13g/d or more, tensile modulus 1400~
The fiber has a specific resistance of 1800 g/d and an electrical resistivity of 0.01 Ωcm or less, but when used as a reinforcing material for a friction material, the coefficient of friction is low. Furthermore, due to its high thermal conductivity, PAN-based carbon fiber has the disadvantage of impairing the mechanical properties of the support material in the friction material.

On the other hand, in recent years, pitch-based carbon fibers have been used as reinforcing fiber materials, and this material has a tensile strength of 2 to 6 g/
d, has a tensile modulus of 200 to 300 g/d,
It has been pointed out that its disadvantages include poor properties as a reinforcing material and poor adhesion to the resin used for molding.

[Purpose and structure of the invention]

The object of the present invention is to provide a non-asbestos friction material that does not have the above drawbacks. In order to achieve this objective, a configuration is adopted in which a combination of specific carbon fibers and phosphate fibers are included in a specific amount range as reinforcing fibers.

The present invention is as follows.

When the bound nitrogen content is 14-21% by weight, the tensile modulus is
The carbonaceous fiber and the phosphate fiber having a weight of 500 to 1300 g/d are expressed by the following formulas (1) to (3): 1.5<x+y<30.0...(1) 0.5<x<29.0...(2) 1.0<y<20.0 ...(3) [However, x is the content rate (weight %) of carbonaceous fibers in the friction material, and y is the content rate (weight %) of the same phosphate fibers. ] A thermosetting resin friction material that satisfies all of the following.

In the present invention, the carbonaceous fiber has a bound nitrogen content of 14 to 21% by weight, a tensile modulus of 500 to 1300 g/d,
Preferably it is 600 to 800 g/d.

If the bound nitrogen content is less than 14% by weight, it is not preferable because the friction coefficient of the friction material decreases. If the bound nitrogen content exceeds 21% by weight, the tensile strength and tensile modulus of the fiber will decrease, resulting in a decrease in the strength of the friction material and
This is undesirable because the elastic modulus becomes low.

Furthermore, if the tensile modulus is less than 500 g/d, the coefficient of friction may increase or breakage may occur during measurement.

If it exceeds 1300 g/d, the friction coefficient will be lower than the desired value.

In addition to the above, preferred carbon fibers have a specific gravity of 1.5 or more and a tensile strength of 2 to 15 g/d, especially 5 g/d or more.

Such carbonaceous fibers are obtained by subjecting acrylic fibers produced from acrylonitrile alone or a polymer or copolymer containing 85% or more by weight in air at 200 to 300°C for 0.1 to 4 hours under a tension of 300 mg/d or less. The fiber is oxidized to obtain a flame-resistant fiber, which is then carbonized in nitrogen, an inert gas, or steam at 450 to 900°C for 0.1 to 15 minutes under a tension of 1 to 300 mg/d.

The phosphate fiber combined with this carbonaceous fiber has a chemical composition of calcium sodium metaphosphate, and usually has a specific gravity of 2.5 to 3.0 and a strength of 5 to 3.
15g/d, elastic modulus 300~700g/d, fiber diameter 0.5~
15μm, cotton length 10-500μm, and exhibits excellent long-term heat resistance as a friction material like asbestos.

In the present invention, the carbonaceous fiber and the phosphate fiber are expressed by the following formulas (1) to (3): 1.5<x+y<30.0...(1) 0.5<x<29.0...(2) 1.0<y<20.0... (3) [However, x represents the content rate (weight %) of carbonaceous fiber in the friction material, and y represents the content rate (weight %) of the same phosphate fiber. ] It is necessary to include it within a range that satisfies the following.

The total amount (x+y) of the carbonaceous fiber content x and the phosphate fiber content y is in the range of 1.5 to 30.0% by weight. If it is less than 1.5% by weight, the amount of wear increases, the height of the friction material decreases, and cracks occur when measuring friction characteristics. If it exceeds 30% by weight, the friction coefficient shows an unstable value. Preferably it is 4.0 to 25.0% by weight.
If the carbonaceous fiber content (x) is less than 0.5, the strength of the friction material during molding will be low, cracks will occur when measuring friction characteristics, and the amount of wear will increase. If it exceeds 29.0, the friction coefficient will be lower than the desired value.

On the other hand, the phosphate fiber content (y) is 1.0
If the friction coefficient is less than 1, it is difficult to achieve the desired effect of improving the friction coefficient. If it exceeds 20.0, the friction coefficient may become too high than the desired value, or cracks may occur when measuring friction characteristics.

In the present invention, it is necessary to satisfy all of the above formulas (1) to (3).

In the present invention, in addition to the above two types of fibers, fibers such as aramid fibers, steel fibers, alumina fibers, alumina-silica fibers, potassium titanate fibers, copper fibers, and brass fibers, as well as calcium carbonate and alumina fibers, are used as auxiliary materials. Fillers such as powders, silica powders, etc. can be included.

These are the same auxiliary materials used in conventionally known friction materials. In addition, in order to improve the reinforcing effect and adjust the friction characteristics, we have added aramid fibers (product names Kevlar, Twaron, Technora) from 0.5 to
It is preferable to include 10.0% by weight.

Examples of the thermosetting resin in the present invention include thermosetting resins such as phenol, melamine, cashew, and epoxy, and modified products thereof, such as phenol-modified melamine and epoxy-modified phenol. The content of thermosetting resin is usually 5 to 35
Weight% (to friction material).

The method for making the thermosetting resin friction material of the present invention is as follows:
For example, as follows. The carbon fiber 3mm
Weigh out the predetermined amounts of each cut material, phosphate fiber, calcium carbonate powder, and phenolic resin.
Disperse with a mixer (800 to 10,000 rpm), place in a mold and heat and pressurize to shape. In some cases, the obtained molded product is further post-cured.

There are no particular restrictions on the form of carbonaceous fibers, but in the case of milled fibers and cut fibers, the average cotton length is
Preferably, the diameter is 0.2 to 1000 mm. When used as a yarn, it can also be used in a blended form with other fibers. In this case, the blended yarn may be impregnated with a mixture of phenolic resin and phosphate fibers and then shaped.

〔Effect of the invention〕

Since the thermosetting resin friction material of the present invention is non-asbestos, it is excellent in terms of occupational safety and health and public health, and the friction coefficient has little change over time, and the friction coefficient is the desired 0.30. Not only does it achieve a value of 0.45 or less, but the amount of wear is also low.

For this reason, it exhibits excellent power transmission and braking functions for automobiles and power machinery.

[Example and comparative example]

Example 1 Acrylic fiber made from 93% by weight acrylonitrile and 7% by weight methyl acrylate (tensile strength
4.9/d, tensile modulus 88 g/d, thickness 1.5 d, total 540,000 denier) was treated in air at 245°C under a tension of 60 mg/d for 3.5 hours, resulting in a tensile strength of 2.1 g/d and a tensile modulus of The flame-resistant fiber had a specific gravity of 90 g/d, a specific gravity of 1.42, and a bound oxygen content of 8% by weight.

Next, it was fired for 2.5 minutes at 600° C. under a tension of 30 mg/d in a nitrogen gas atmosphere to obtain a carbonaceous fiber. This fiber had a bound nitrogen content of 18% by weight, a carbon content of 71% by weight, a tensile strength of 8.2 g/d, a tensile modulus of 550 g/d, and an electrical resistivity of 3.6×10 ⁵ Ωcm.

The carbon fiber was cut into a length of 3 mm using a guillotine cutter. 17.0% by weight of the obtained cut fiber (x), 3.0% by weight of phosphate fiber (y), 50.0% by weight of calcium carbonate, and 30.0% by weight of phenolic resin were mixed in a Lodeige mixer, and the resulting mixture was heated at 170°C. Place it in a circular mold and apply a pressure of 20kgf/
^cm2 , compression molded for 30 minutes, outer diameter 100mm, inner diameter 60
mm, 10 mm thick molded product [x+y=20.0, x=
17.0, y=3.0, therefore all of equations (1) to (3) are satisfied. ] was obtained.

Friction characteristics of this molded product were measured using the following equipment and conditions.

Testing machine: Dynamo testing machine with inertia of 0.1kgf/msec ² Mating material: FC-25 (JIS G5501) Initial sliding speed: 10m/sec Surface pressure: 20kgf/cm ² As a result, the friction coefficient is 0.28 to 0.32, The amount of wear is
When measured at 0.5mg/stop, the torque curve showed extremely stable friction characteristics with maximum and minimum torques within ±8% of the average torque.

Example 2 The same carbonaceous fiber as in Example 1 was cut into a length of 1 mm using a guillotine cutter. 20.0% by weight of the obtained cutlet fiber (x), 5.0% by weight of phosphate fiber (manufactured by Monsanto) (y), 45.0% by weight of calcium carbonate powder, and phenolic resin powder.
30.0% by weight was mixed in a Lodeige mixer and molded in the same manner as in Example 1 [x+y=25.0,
x=20.0, y=5.0, therefore all of equations (1) to (3) are satisfied. ] was obtained.

As a result of measuring the friction properties of the obtained molded product, the friction coefficient was 0.31 to 0.35, and the amount of wear was 10 mg/
At stop, the torque curve during measurement showed very stable friction behavior with maximum and minimum torques within ±9% of the average torque.

Example 3 The same carbonaceous fiber as in Example 1 was cut into a length of 3 mm using a guillotine cutter. Example 1: 2.5% by weight of the obtained cut fiber (x), 12.5% by weight (y) of phosphate fiber (manufactured by Monsanto), 55.0% by weight of calcium carbonate, and 30.0% by weight of phenol resin were mixed in a Lodeige mixer.
Molded in the same manner as [x+y=15, x=
2.5, y=12.5, therefore all of equations (1) to (3) are satisfied. ] Obtained. As a result of measuring the friction characteristics of the obtained molded product, the friction coefficient was 0.35 to 0.38, and the amount of wear was
40mg/stop, the torque curve showed extremely stable friction behavior with maximum and minimum torques within ±10% of the average torque.

Comparative Example 1 (Lack of Phosphate Fiber) The same carbonaceous fiber as in Example 1 was cut into a length of 3 mm using a guillotine cutter. 20.0% by weight of the obtained cutlet fiber, calcium carbonate
50.0% by weight of the phenol resin and 30.0% by weight of the phenolic resin were mixed in a Henshil mixer and molded in the same manner as in Example 1 to obtain a molded product.

As a result of measuring the friction properties of the obtained molded product, the friction coefficient was 0.25 to 0.31, and the amount of wear was 10 mg/
stop, the minimum torque was within 10% of the average torque, but as the number of tests increased, the maximum torque exceeded 25% of the average torque, causing a reverse fade phenomenon.

Comparative Example 2 (lack of carbonate fiber) Phosphate fiber 10.0% by weight, calcium carbonate
60.0% by weight and 30.0% by weight of phenolic resin were stirred in a Lodeige mixer and molded under the same conditions as in the example.

The friction characteristics of the obtained molded product were measured in the same manner as in Example 1, and the friction coefficient was 0.38 to 0.40.
The amount of wear was 150 mg/stop, which was a high value for both, and the torque curve fluctuated greatly.

Comparative Example 3 The same carbonaceous fiber as in Example 1 was cut into a length of 3 mm using a guillotine cutter. The obtained cut fiber 20.0% by weight (x), phosphate fiber 15.0% by weight (y), calcium carbonate 35.0% by weight, and phenol resin 30.0% by weight were stirred in a Lodeige mixer and molded under the same conditions as Example 1. Then, the molded product [(x) + (y) = 35.0, (x) = 20.0,
(y)=15.0, therefore, formula (1) is not satisfied. ] was obtained.

The friction characteristics of the obtained molded product were measured in the same manner as in Example 1, and the friction coefficient was 0.35 to 0.38.
Wear amount is 120mg/stop, maximum and minimum torque is ±
Although it was very stable within 10%, the amount of wear was large.

Comparative Example 4 The same carbonaceous fiber as in Example 1 was cut into a length of 3 mm using a guillotine cutter. 2.5% by weight of the obtained cut fiber (x), 0.3% by weight of phosphate fiber (y), 67.2% by weight of calcium carbonate, and 30% by weight of phenol resin were mixed in a Lodeige mixer and molded in the same manner as in Example 1. Therefore, the molded product [x+y=2.8, x=2.5, y=0.3, therefore
Equation (3) is not satisfied. ] was obtained.

When an attempt was made to measure the obtained molded product using the same dynamo tester as in Example 1, the molded product was damaged during the measurement and measurement was impossible.

Comparative Example 5 The same carbonaceous fiber as in Example 1 was cut into a length of 3 mm using a guillotine cutter. Obtained cutlet fiber 0.3% by weight (x), phosphate fiber 25% by weight (y), calcium carbonate 44.7% by weight,
30% by weight of phenolic resin was mixed in a Lodeige mixer and molded in the same manner as in Example 1 to obtain a molded product [x+y=25.3, x=0.3, y=25, therefore (2)
and (3) are not satisfied. ] was obtained.

As a result of measuring the friction properties of the obtained molded product, the friction coefficient was 0.45 to 0.48, and the amount of wear was 210 mg/
stop and both are high, and the maximum torque is the average torque.
It was over 25%.

Comparative Example 6 The same carbon fiber as in Example 1 was cut into a length of 3 mm using a guillotine cutter. Obtained fiber 33% by weight (x), phosphate fiber 0.5
Weight% (y), 36.5% by weight of calcium carbonate, and 30% by weight of phenolic resin were mixed in a Lodeige mixer, and molded in the same manner as in Example 1 to obtain a molded product [x
+y=33.5, (x)=33, y=0.5, therefore (1)
~ (3) does not satisfy all of the expressions. ] was obtained.

As a result of measuring the frictional properties of the obtained molded product, it was found that the coefficient of friction was 0.18 to 0.22, which tended to be too low.

Comparative Example 7 The same carbon fiber as in Example 1 was cut into a length of 3 mm using a guillotine cutter. The obtained cut fiber fibers were 33% by weight (x), phosphate fibers were 18% by weight (y), calcium carbonate was 19% by weight,
30% by weight of the phenol resin was mixed in a Lodeige mixer and molded in the same manner as in Example 1, and the molded product [x+y=51, x=33, y=18, therefore, formula (1) and (2 ) does not satisfy the expression. ] was obtained.

An attempt was made to measure the frictional properties of the obtained molded product, but the molded product was damaged during the measurement, making it impossible to measure the friction coefficient and amount of wear.

Claims (1)

[Scope of Claims] 1. A carbon fiber having a bound nitrogen content of 14 to 21% by weight and a tensile modulus of 500 to 1300 g/d and a phosphate fiber according to the following formulas (1) to (3) 1.5<x+y <30.0 ...(1) 0.5<x<29.0 ...(2) 1.0<y<20.0 ...(3) [However, x is the content of carbon fiber in the friction material (weight%), and y is the content of the same phosphate Represents the fiber content (% by weight). ] A thermosetting resin friction material that satisfies all of the following.