JP2020164630A - Friction material and friction material composition - Google Patents

Abstract

To provide a friction material that does not contain copper (or has a reduced copper content), which has a high damping property, suppresses the occurrence of squeal, and also suppresses brake vibration.SOLUTION: A friction member of an embodiment is a friction material having a copper content of 0.5 wt% or less, and includes a cashew dust having the content of 6 wt.% or more and 9 wt.% or less, an acrylic elastomer-dispersed phenolic resin having the content of 5 wt.% or more and 7 wt.% or less, a rubber having the content of 1 wt.% or less, a fiber substrate, and an inorganic filler, and in which the average particle size of the cashew dust is 100 to 400 μm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a friction material and a friction material composition.

In recent years, from the viewpoints of river pollution, marine pollution, and adverse effects on the human body, the demand for environmental compatibility with the materials contained in brake pads is becoming stricter.
Therefore, it is desired to develop a brake pad (friction material) that does not contain copper (or has a reduced copper content).

Japanese Unexamined Patent Publication No. 2016-188378

By the way, a friction material using rubber has excellent damping properties, but when braking under a high load, it may be used beyond the decomposition temperature of rubber, giving a thermal history exceeding the decomposition temperature of rubber. In that case, it may be difficult to maintain the performance.
Further, the damping property is effective for the squeal of the brake, but not so effective for the vibration of the brake. Brake vibration is mainly caused by partial wear of the brake disc and the difference in wall thickness of the brake disc due to thermal molding, and the difference in wall thickness causes frictional force fluctuation between the friction material and the brake disc. Leads to vibration. In order to suppress fluctuations in frictional force when a difference in wall thickness of the brake disc occurs, it is effective to reduce the storage elastic modulus of the friction material against brake vibration.

Therefore, an object of the present invention is to provide a friction material that does not contain copper (or has a reduced copper content), has high damping property, can suppress the occurrence of squeal, and can also suppress brake vibration. It is an object of the present invention to provide a friction material composition.

In order to solve the above problems, the friction member of the embodiment is a friction material having a copper content of 0.5 wt% or less, cashew dust having a copper content of 6 wt% or more and 9 wt% or less, and a content of 5 wt%. Acrylic elastomer-dispersed phenolic resin having a content of 7 wt% or less, rubber having a content of 1 wt% or less, a fiber base material, and an inorganic filler are provided, and the average particle size of cashew dust is 100 to 400 μm.
According to the above configuration, the damping property is high, the occurrence of squeal can be suppressed, and the brake vibration can also be suppressed.

In the above configuration, the blending amount of cashew dust may be 7.5 wt% or more.
According to this configuration, the storage elastic modulus can be further reduced and the brake vibration can be further suppressed.

In the above configuration, the content of the acrylic elastomer-dispersed phenolic resin may be 6 wt% or less.
According to this configuration, the damping property is high, and the occurrence of squeal can be suppressed.

In the above configuration, the rubber content may be 0.5 wt% or more.
According to this configuration, the damping property can be maintained high and the occurrence of squeal can be suppressed.

In the above structure, the fiber base material may be made of a material other than metal fibers.
According to this configuration, the storage elastic modulus can be easily maintained below a desired value.

The composition for a friction material of the embodiment is a composition for a friction material having a copper content of 0.5 wt% or less, and is a thermosetting bond of a base fiber (excluding metal fibers), a lubricant, and a thermosetting material. A material, cashew dust having a content of 6 wt% or more and 9 wt% or less, an acrylic elastomer-dispersed phenol resin having a content of 5 wt% or more and 7 wt% or less, rubber having a content of 1 wt% or less, and an inorganic filler. The average particle size of cashew dust is 100 to 400 μm.
According to the above configuration, it is possible to obtain a friction material which has high damping property, can suppress the occurrence of squeal, and can also suppress brake vibration.

FIG. 1 is an explanatory diagram of performance evaluation results of Examples and Comparative Examples.

Next, exemplary embodiments of the present invention will be described in detail with reference to the drawings.
The configurations of the embodiments shown below, as well as the actions and results (effects) brought about by the configurations, are examples. The present invention can also be realized by configurations other than those disclosed in the following embodiments. Further, according to the present invention, it is possible to obtain at least one of various effects (including derivative effects) obtained by the configuration.

First, the principle of the embodiment will be described.
In friction materials, rubber is known to increase loss tangent (tan δ).
However, it has been found that when a thermal history in a high temperature range exceeding 200 ° C. is given, decomposition / deterioration is irreversibly promoted, the viscosity is lost, and the loss tangent is rather lowered.
Therefore, it is desirable that rubber is not used as much as possible in the friction material.

Therefore, consider a case where the compounding amount of rubber is 1 wt% or less.
The inventors maintain the loss tangent tan δ to be a preferable value of 0.05 or more as a friction material when the amount of rubber compounded is 1 wt% or less in the temperature range of the assumed actual use temperature of -20 ° C to 300 ° C. In order to do so, it was found that it is effective to add 6 wt% or more of cashew dust as a lubricant.

On the other hand, when the lining is molded only by the blending amount of rubber and cashew dust and the molding pressure, the loss positive contact tan δ can be maintained at 0.05 or more, but the storage elastic modulus exceeds 1 GPa and the wall thickness difference of the brake disc is large. When it occurs, the frictional force fluctuation due to the difference in wall thickness becomes large, which causes brake vibration.

In order to suppress the influence of the wall thickness difference of the brake disc, that is, to suppress the storage elastic modulus to less than 1 GPa and to maintain the loss tangent tan δ of 0.05 or more, the inventors use it as a base fiber. By blending acrylic elastomer-dispersed phenolic resin as a binder (binder) without using metal fibers made of copper or copper alloy, the lining of the brake pad has flexibility (viscoelasticity) and the storage elastic modulus is 1 GPa. I found that I could keep it below.

Here, it was found that the smaller the content of the binder, the lower the storage elastic modulus and the more the deterioration due to heat is suppressed, so that the loss tangent tan δ becomes larger.
Based on these, as a result of sharp research, it was found that the content of the binder is preferably 5 wt% to 7 wt%, but it is caused by cracks due to molding defects and the absence of metal fibers made of copper or copper alloy. There was a possibility that cracks would occur due to the decrease in strength.

As a source of this crack, a gap around cashew dust can be considered as a lubricant.
Therefore, in order to suppress this gap, the average particle size of cashew dust was set to 100 to 400 μm, the blending amount was set to 6 to 9% by weight, and the molding pressure was set to 10 to 25 MPa to suppress the occurrence of cracks.

As a result, in the friction material containing no copper (or the copper content is reduced), the damping material is high, the squeal is good, and the wall thickness of the brake disc is high in the actual operating temperature range of -20 ° C to 300 ° C. Even when a difference occurred, the frictional force fluctuation could be suppressed and the brake vibration could be reduced.

More specifically, suitable friction materials of the embodiment are friction materials having a copper content of 0.5 wt% or less, cashew dust having a content of 6 wt% or more and 9 wt% or less, and a content of 5 wt%. A friction material comprising an acrylic elastomer-dispersed phenolic resin having a content of 7 wt% or less, a rubber having a content of 1 wt% or less, a fiber base material, and an inorganic filler, and having an average particle size of cashew dust of 100 to 400 μm. is there.

The reason for the above configuration is that if the cashew dust content is less than 6 wt%, the desired loss tangent tan δ (for example, 0.05 or more) cannot be obtained. Further, when the content of cashew dust exceeds 9 wt%, the desired strength cannot be obtained and the durability is lowered.

Further, if the average particle size of cashew dust is less than 100 μm, it becomes difficult to uniformly disperse it in the lining, and stable performance cannot be obtained. Further, if the average particle size of the cashew dust is more than 400 μm, the gap around the cashew dust becomes large, cracks may occur, the desired strength cannot be obtained, and the durability is lowered.

Further, if the content of the acrylic elastomer-dispersed phenolic resin is less than 5 wt%, cracks may occur due to molding defects, a desired storage elastic modulus cannot be obtained, and brake vibration cannot be suppressed. Further, if the content of the acrylic elastomer-dispersed phenolic resin exceeds 7 wt%, the storage elastic modulus becomes too large, which causes a decrease in the brake feeling.

Next, a method for manufacturing a brake pad including a specific friction material (lining) will be described.
First, a predetermined raw material is mixed to obtain a mixed powder (friction material composition).

The predetermined raw material referred to here is a base fiber, a binder, an organic filler, a lubricant, an inorganic filler and the like.
In this case, examples of the base fiber include aramid fiber, inorganic fiber and the like (excluding metal fiber).

Examples of the binder include a phenol resin which is a thermosetting resin and the acrylic elastomer-dispersed phenol resin described above.

Examples of the organic filler include cashew dust and rubber powder.
Examples of the lubricant include graphite.
Examples of the inorganic filler include titanate, iron oxide, zirconium oxide, zirconium silicate, calcium hydroxide, mica, and barium sulfate.

In this case, mica has cleavability and functions as a lubricant.
In addition, calcium hydroxide (slaked lime) functions as a pH adjuster.

Next, a method of manufacturing the brake pad will be described.
First, after the predetermined raw materials are sufficiently mixed, premolding is performed by a preforming step. In this pre-molding, molding is performed to such an extent that the mixture of friction materials can be placed on a predetermined back plate.

Subsequently, the preformed lining is set in the pressurizing and heating mold of the thermoforming apparatus with the preformed lining arranged at a predetermined position on the back plate, and thermoforming is performed in the first temperature zone (for example, less than 200 ° C.). Do.

This thermoforming is performed to maintain the shape of the lining (or brake pad) in the heat treatment performed in the subsequent stage by sufficiently melting and then curing the binder (binder) added as a raw material. With the back plate placed in the mold, a predetermined raw material is put into the mold, and pressurization (molding pressure = 10 to 25 MPa) and heating are performed.

In this state, the brake pad provided with the back plate and the lining is in a pressurized state to suppress deformation, and is in a second temperature zone (for example, 200 to 240 ° C.) higher than the first temperature zone for a predetermined time (for example, 200 to 240 ° C.). Heat treatment is performed to cure the lining by heating (for example, 1 to 2 hours).

Subsequently, the brake pad after the heat treatment is subjected to a predetermined finishing process to become a product.

According to the present embodiment, a friction material having a copper content of 0.5 wt% or less, cashew dust having a copper content of 6 wt% or more and 9 wt% or less, and an acrylic elastomer having a copper content of 5 wt% or more and 7 wt% or less. A lining (friction material) comprising a dispersed phenol resin, a rubber having a content of 1 wt% or less, a fiber base material containing no metal fibers, and an inorganic filler, and having an average particle size of cashew dust of 100 to 400 μm. Is obtained.

According to this lining, in the actual operating temperature range of -20 ° C to 300 ° C, the loss tangent tan δ is 0.05 or more, the excitation frequency is 1 to 50 Hz, and the actual operating temperature range of -20 ° C to 300 ° C. In, a characteristic with a storage elastic modulus of less than 1 GPa can be obtained.
Therefore, according to the friction member of the present embodiment, the damping property is high, the squeal is good, and even if a difference in the wall thickness of the brake disc occurs, the frictional force fluctuation can be suppressed and the brake vibration can be reduced. Become.

Next, an embodiment will be described in detail.
FIG. 1 is an explanatory diagram of an example, a comparative example, and a performance evaluation.
[1] Example [1.1] First Example First, the compounding composition of the first example (referred to as Example 1 in FIG. 1; the same applies hereinafter) will be described.
The compounding composition of the examples is roughly classified into a fiber base material, a binder, an elastomer powder, a lubricant and an inorganic filler.

Hereinafter, the compounding composition of the first example will be described in detail.
In the first embodiment, 5 wt% of aramid fiber and 1 wt% of inorganic fiber are blended as the fiber base material, and the metal fiber (copper fiber in this example) is not blended.
In the first embodiment, 2 wt% of phenol resin and 5 wt% of acrylic elastomer-dispersed phenol resin were blended as a binder.

In the first embodiment, 1 wt% of rubber powder and 6 wt% of cashew dust were blended as the organic filler. In this case, the average particle size of cashew dust is 100 to 400 μm.
In the first embodiment, 6 wt% of graphite was blended as a lubricant.

In the first embodiment, as the filler (inorganic filler), titanium acid salt is 20 wt%, iron oxide is 4 wt%, zirconium oxide is 2 wt%, zirconium silicate is 1 wt%, calcium hydroxide is 3 wt% and mica. Was blended in 15 wt%, and barium sulfate was blended in the balance to make a total of 100 wt%.

[1.2] Second Example The difference in the compounding composition of the second example from the compounding composition of the first example is that 6 wt% of acrylic elastomer-dispersed phenolic resin is compounded with respect to the compounding of the binder and organic filling. Regarding the material, 7.5 wt% of cashew dust was blended.
Other compounding compositions are the same as in the first embodiment.

[1.3] Third Example The difference in the compounding composition of the third example from the compounding composition of the first example is that 7 wt% of acrylic elastomer-dispersed phenolic resin is compounded with respect to the compounding of the binder and organic filling. Regarding the material, 9 wt% of cashew dust was blended.
Other compounding compositions are the same as in the first embodiment.

[1.4] Fourth Example The difference in the compounding composition of the fourth example from the compounding composition of the first example is that 7 wt% of the acrylic elastomer-dispersed phenolic resin is compounded with respect to the compounding of the binder.
Other compounding compositions are the same as in the first embodiment.

[1.5] Fifth Example The difference in the compounding composition of the fifth example from the compounding composition of the first example is that 9 wt% of cashew dust is blended with respect to the organic filler.
Other compounding compositions are the same as in the first embodiment.

[2] Comparative Example Next, a comparative example will be described.
Similar to the compounding composition of the example, the compounding composition of the comparative example is roughly classified into a fiber base material, a binder, an organic filler, a lubricant and an inorganic filler.

[2.1] First Comparative Example First, the compounding composition of the first comparative example (referred to as Comparative Example 1 in FIG. 1; the same applies hereinafter) will be described.
The compounding composition of the first comparative example is different from the compounding composition of the first example described above in that the acrylic elastomer-dispersed phenolic resin as a binder is not blended, and 2 wt% of rubber powder is blended with respect to the organic filler. It is a point and a point where 4 wt% of cashew dust is mixed.
Other compounding compositions are the same as in the first embodiment.

[2.2] 2nd Comparative Example The compounding composition of the 2nd Comparative Example is different from the compounding composition of the 1st Example described above in that the acrylic elastomer-dispersed phenolic resin as a binder is not blended, and the organic filler. Regarding, 2 wt% of rubber powder was blended and 5 wt% of cashew dust was blended.
Other compounding compositions are the same as in the first embodiment.

[2.3] 3rd Comparative Example The compounding composition of the 3rd Comparative Example is different from the compounding composition of the 1st Example described above in that the acrylic elastomer-dispersed phenolic resin as a binder is not blended, and the organic filler. Regarding the above, 2 wt% of rubber powder was blended, 5 wt% of cashew dust was blended, and 3 wt% of graphite was blended with respect to the lubricant.
Other compounding compositions are the same as in the first embodiment.

[2.4] 4th Comparative Example The compounding composition of the 4th Comparative Example is different from the compounding composition of the 1st Example described above in that the organic filler contains 2 wt% of rubber powder and 4 wt% of cashew dust. It is a compounded point.
Other compounding compositions are the same as in the first embodiment.

[2.5] Fifth Comparative Example The compounding composition of the fifth comparative example is different from the compounding composition of the first embodiment described above in that 4 wt% of cashew dust is blended with respect to the organic filler.
Other compounding compositions are the same as in the first embodiment.

[2.6] 6th Comparative Example The compounding composition of the 7th Comparative Example is different from the compounding composition of the 1st Example described above in that the organic filler contains 2 wt% of rubber powder and 5 wt% of cashew dust. It is a compounded point.
Other compounding compositions are the same as in the first embodiment.

[2.7] 7th Comparative Example The compounding composition of the 7th Comparative Example is different from the compounding composition of the 1st Example described above in terms of the base fiber, 11 wt% of the same fiber, and the organic filler. , 2 wt% of rubber powder and 4 wt% of cashew dust.
Other compounding compositions are the same as in the first embodiment.

[3] Performance Evaluation Next, the performance evaluation results of each of the above Examples and Comparative Examples will be described again with reference to FIG.
As the performance evaluation, the loss tangent tan δ and the storage elastic modulus were evaluated.

[3.1] Loss tangent tan δ
The loss tangent tan δ was evaluated by obtaining the minimum value (Min. Value) in the range of −20 ° C. to 300 ° C. as the actual operating temperature range.

[3.2] Storage elastic modulus The storage elastic modulus was evaluated by obtaining the maximum value (Max. Value) in the range of −20 ° C. to 300 ° C. as the actual operating temperature range.

[3.3] Evaluation result [3.3.1] Loss tangent tan δ
As shown in FIG. 1, in each of the first to fifth embodiments, good results satisfying the loss tangent tan δ = 0.05 or more, which is practically sufficient, were obtained.
Therefore, according to the first to fifth examples, it was found that the damping property is high and the occurrence of squeal can be suppressed.

On the other hand, among the first comparative examples to the seventh comparative examples, only the second comparative example satisfies the loss tangent tan δ = 0.05 or more, which is practically sufficient, and the other comparative examples are practical. It turned out to be scarce.

[3.3.2] Storage elastic modulus As shown in FIG. 1, in all of the first to fifth embodiments, good results satisfying the storage elastic modulus of less than 1 MPa, which is practically sufficient, were obtained. It was.
Therefore, according to the first to fifth embodiments, it was found that even when the disc thickness difference occurs, the frictional force fluctuation can be absorbed and the brake vibration can be suppressed.
On the other hand, among the first to seventh comparative examples, only the fourth comparative example satisfies the storage elastic modulus of less than 1 MPa, which is practically sufficient, and the other comparative examples are said to be poor in practicality. It turned out.

[3.3.3] Comprehensive evaluation Based on the above explanation, the friction material has a copper content of 0.5 wt% or less, and has a cashew dust content of 6 wt% or more and 9 wt% or less. Friction with an acrylic elastomer-dispersed phenolic resin of 5 wt% or more and 7 wt% or less, rubber having a content of 1 wt% or less, a fiber base material, and an inorganic filler, and an average particle size of cashew dust of 100 to 400 μm. According to the first to fifth embodiments of the material, it was found that the brake pad has high damping property, can suppress the occurrence of squeal, and can also suppress the brake vibration.
In particular, according to the fifth embodiment, it was demonstrated that the brake pad is a high-performance brake pad having a sufficiently large loss tangent tan δ and a sufficiently small storage elastic modulus.

[4] Modifications of the Embodiment In the above description, only one type of the first abrasive is described, but the same as the second abrasive, a plurality of types may be blended. Is also possible.
By adopting such a configuration, it is possible to maintain the friction coefficient more stably even if the environmental conditions, braking conditions, and the like fluctuate.

In the above description, the use of the brake pad is not limited, but in addition to the floating type as a disc brake, the pistons as pressing members are arranged to face each other, and the pistons arranged to face each other are a pair of brake pad pad sets. The so-called opposed type (opposed piston type) having a structure in which the solid body is pressed against the disc rotor (friction material) can also be applied in the same manner.

In the above description, the brake pad (lining) for the disc brake has been described, but the same can be applied to the brake shoe of the drum brake that comes into contact with the brake drum (friction material).

Claims (6)

A friction material with a copper content of 0.5 wt% or less.
Cashew dust with a content of 6 wt% or more and 9 wt% or less,
Acrylic elastomer-dispersed phenolic resin with a content of 5 wt% or more and 7 wt% or less,
Rubber with a content of 1 wt% or less and
With fiber base material
With an inorganic filler,
The average particle size of the cashew dust is 100 to 400 μm.
Friction material. The blending amount of the cashew dust is 7.5 wt% or more.
The friction material according to claim 1. The content of the acrylic elastomer-dispersed phenolic resin is 6 wt% or less.
The friction material according to claim 1 or 2. The content of the rubber is 0.5 wt% or more.
The friction material according to any one of claims 1 to 3. The fiber base material is composed of a material other than metal fibers.
The friction material according to claim 1 to 4. A composition for a friction material having a copper content of 0.5 wt% or less.
Base fiber (excluding metal fiber) and
Lubricant and
With thermosetting binder
Cashew dust with a content of 6 wt% or more and 9 wt% or less,
Acrylic elastomer-dispersed phenolic resin with a content of 5 wt% or more and 7 wt% or less,
Rubber with a content of 1 wt% or less and
With an inorganic filler,
The average particle size of the cashew dust is 100 to 400 μm.
Composition for friction material.

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