WO2019150502A1 - Friction material, friction material composition and friction member - Google Patents

Abstract

The present invention pertains to: a friction material which does not contain copper or when containing copper, contains an amount at which the copper element content constitutes no more than 0.5 mass% thereof, the friction material also containing inorganic fibers (X) which contain 1-10 mass% of iron oxide when calculated by Fe₂O₃ content.

Description

Friction material, friction material composition, and friction member

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

In automobiles, friction materials such as disc brake pads and brake linings are used for braking. These friction materials play a role of braking by friction with a disk rotor, a brake drum, or the like which is a counterpart material. For this reason, friction materials not only require an appropriate coefficient of friction (effectiveness characteristics) according to the conditions of use, but also make it difficult for brake noise to occur (squeal characteristics), and the friction material has a long life (wear resistance). Etc. are required.

Friction materials include semi-metallic materials containing 30 to 60% by mass of steel fibers as a fiber base material, raw steel materials containing less than 30% by mass of steel fibers, and NAO (Non-Asbestos Organic) materials that do not contain steel fibers. Broadly divided. However, friction materials containing a small amount of steel fibers may be classified as NAO materials.

Since NAO material does not contain steel fibers, it has a feature that it is less aggressive to the disk rotor as the counterpart material than semi-metallic material and low steel material. Because of these advantages, NAO materials that are effective in Japan, the United States, etc., and have a good balance between squealing and wear resistance, are currently mainstream. On the other hand, in Europe, low steel materials were often used from the viewpoint of maintaining a coefficient of friction during high-speed braking, but in recent years, in order to respond to the trend toward high-end markets, NAO materials are less prone to tire wheel dirt and brake noise. Are increasingly being used.

The NAO material generally contains copper in a powder or fiber state. However, friction materials containing copper, copper alloys, and the like contain copper in wear powder generated during braking, and thus have been suggested to possibly contaminate rivers, lakes, and the like. For this reason, in California, Washington, etc. in the United States, there is a bill that prohibits the sale of friction materials containing more than 5% by mass of copper after 2021, and the addition of 0.5% by mass of copper after 2023, and the assembly into new cars. In response to this, there is an urgent need to develop a NAO material that does not contain copper or has a low copper content.

One of the typical functions of copper is to impart thermal conductivity. Since copper has high thermal conductivity, wear caused by excessive temperature rise is suppressed by diffusing heat generated during braking from the friction interface.
The second typical function of copper is protection of the friction interface during high-temperature braking.
Since copper has high ductility and malleability, it extends to the friction material surface by braking to form a coating. As a result, it is possible to reduce friction material wear during high-speed and high-temperature braking and to develop a stable friction coefficient. Further, since the copper spreading film can easily hold the abrasive, a good friction coefficient can be expressed even in the low-speed and low-temperature braking region.
Therefore, in order to develop a NAO material that does not contain copper or has a low copper content, a copper replacement technique is required from the viewpoints of improving the thermal conductivity, protecting the interface, and holding the abrasive. .

In such a movement, friction materials that do not contain copper or have a low copper content are being studied (for example, Patent Documents 1 and 2).

JP2015-205959A Japanese Patent Laying-Open No. 2015-059125

In recent years, important issues have arisen from a viewpoint different from the above copper replacement. It is adaptability to a control brake represented by a regenerative brake. In conventional hydraulic brakes, the driver has adjusted the braking force of the vehicle in a timely manner by finely adjusting the input from the brake pedal.
However, in the control brake, since the system side takes part of the braking, if the friction coefficient expressed by the friction material fluctuates extremely, a problem occurs in the control. For example, if the friction coefficient is extremely reduced, the braking distance becomes too long, which may cause an accident in the worst case. Therefore, in order to increase the accuracy of the control brake, it is extremely important that the friction coefficient expressed by the friction material is stable at any time.

A typical example of the friction coefficient variation is a decrease in the friction coefficient in a low-speed and low-temperature braking region in a friction material that does not contain copper. In the friction material not containing copper, it is difficult to form a transfer film on the surface of the disk rotor in the low-speed and low-temperature braking region, and it is difficult to exhibit the effect of holding the abrasive. As a result, the aggressiveness to the disk rotor due to the grinding action and the shear drag generated between the iron component derived from the disk rotor and the disk rotor are reduced, so that the friction coefficient tends to be lower than in the normal case. In this case, as described above, the braking distance becomes long and the braking force is reduced, so that the driver's comfort is impaired.

In addition, an increase in the coefficient of friction variation during one braking in low-speed low-temperature braking is a typical example in which the coefficient of friction varies. The friction material containing no copper has a low ability to discharge wear powder generated during braking, and the wear powder tends to accumulate at the friction interface between the friction material and the disk rotor. As a result, the powder resistance at the friction interface is increased, and the coefficient of variation of the friction coefficient is increased. As a result, problems such as squealing occur when the brake is applied and the driver's comfort is impaired.

From this point of view, the techniques disclosed in Patent Documents 1 and 2 focus only on the high thermal conductivity and high-temperature lubricity of copper, and only complement the friction characteristics during high-speed and high-temperature braking. However, the stability of the friction coefficient in the low-speed low-temperature braking region and other friction characteristics are not taken into consideration.

Therefore, the present invention does not contain copper, or even if it contains copper, the content thereof is 0.5% by mass or less as a copper element, and the composition is low in environmental and human harm, and is excellent in a low-speed low-temperature braking region. It is an object of the present invention to provide a friction material, a friction material composition, and a friction member using the friction material that achieve both stability of the friction coefficient and an excellent friction coefficient in a normal braking range.

As a result of intensive studies to achieve the above object, the present inventor has found that the friction material containing a specific inorganic fiber has the stability of the friction coefficient in the low-speed and low-temperature braking region and the friction coefficient in the normal braking region. Has been found to be highly compatible. That is, the present invention relates to the following [1] to [17].
[1] An inorganic material that does not contain copper or contains copper, and the content thereof is a friction material having a copper element content of 0.5% by mass or less, and iron oxide in an amount of 1 to 10% by mass in terms of Fe ₂ O ₃ A friction material containing fiber (X).
[2] The friction material according to [1], wherein the content of the inorganic fiber (X) is 5.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total friction material.
[3] The friction material according to [1] or [2], wherein the inorganic fiber (X) has an average fiber length of 100 to 800 μm.
[4] The above [1] to [3], further comprising 4 to 10% by mass of zirconium silicate having an average particle diameter of 0.4 to 2 μm as an inorganic filler with respect to 100% by mass of the total friction material. The friction material according to any one of the above.
[5] The above-mentioned [1], further comprising 15 to 25% by mass of non-acicular titanate having an average particle diameter of 2 to 50 μm as an inorganic filler with respect to 100% by mass of the total friction material. ] To [4].
[6] The friction material according to any one of [1] to [5], further comprising 10 to 20% by mass of zirconium oxide as an inorganic filler with respect to 100% by mass of the total friction material.
[7] The friction material according to any one of [1] to [6], further comprising 2 to 10% by mass of wollastonite as an inorganic filler with respect to 100% by mass of the total friction material.
[8] In any one of the above [1] to [7], the metal powder is not included or the content thereof is 0.5% by mass or less with respect to 100% by mass of the total friction material. The friction material described.
[9] A friction member obtained by integrating the friction material according to any one of [1] to [8] above and a back metal.
[10] A friction material composition that does not contain copper or contains copper, and the content thereof is 0.5% by mass or less as copper element, and contains 1 to 10% by mass of iron oxide in terms of Fe ₂ O ₃ A friction material composition containing inorganic fibers (X).
[11] The friction material according to [10], wherein the content of the inorganic fiber (X) is 5.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total friction material composition. Composition.
[12] The friction material composition according to [10] or [11], wherein the inorganic fiber (X) has an average fiber length of 100 to 800 μm.
[13] The above [10] to [10], further containing 4 to 10 mass% of zirconium silicate having an average particle size of 0.4 to 2 μm as an inorganic filler with respect to 100 mass% of the total amount of the friction material composition. 12]. The friction material composition according to any one of 12).
[14] Further, the inorganic filler contains 15 to 25% by mass of non-acicular titanate having an average particle diameter of 2 to 50 μm with respect to 100% by mass of the total amount of the friction material composition. [10] The friction material composition according to any one of [13].
[15] The friction material according to any one of [10] to [14], further comprising 10 to 20% by mass of zirconium oxide as an inorganic filler with respect to 100% by mass of the total amount of the friction material composition. Composition.
[16] The friction according to any one of [10] to [15], further comprising wollastonite as an inorganic filler in an amount of 2 to 10% by mass relative to 100% by mass of the total amount of the friction material composition. Material composition.
[17] Any of the above-mentioned [10] to [16], wherein the metal powder is not included or the content thereof is 0.5% or less with respect to 100% by mass of the total amount of the friction material composition. The friction material composition according to claim 1.

According to the present invention, copper does not contain, or even if contained, the content is 0.5% by mass or less as a copper element, and the composition is low in environmental and human harm, and is excellent in a low-speed low-temperature braking region. It is possible to provide a friction material, a friction material composition, and a friction member using the friction material, which have both the stability of the friction coefficient and the excellent friction coefficient in the normal braking range.

Hereinafter, although the friction material, friction material composition, and friction member of this embodiment are explained in full detail, this invention is not limited to the following embodiment.
In addition, the friction material and friction material composition of this embodiment do not contain asbestos, and are a so-called non-asbestos friction material and non-asbestos friction material composition.

[Friction material and friction member]
The friction material according to the present embodiment does not contain copper, or even if it contains copper, the content of the friction material is 0.5 mass% or less as a copper element, and iron oxide is 1 to _{2 in} terms of Fe ₂ O _3. It is a friction material containing 10 mass% inorganic fiber (X).

Even if the friction material of this embodiment does not contain copper, the content is 0.5 mass% or less as a copper element, and is very trace amount. For this reason, the friction material of this embodiment becomes a thing with a low environmental hazard and a human body hazard.
In addition, said "copper" is copper element contained in copper, such as a fiber form and a powder form; copper alloy, a copper compound, etc., "copper content" is content with respect to 100 mass% of friction material whole quantity. Show.
The copper content is preferably less than 0.5% by mass, more preferably 0.3% by mass or less, and more preferably 0.1% by mass with respect to 100% by mass of the total amount of the friction material, from the viewpoints of environmental hazards and human injury. % Or less is more preferable, and it is particularly preferable not to contain copper.

<Constituent components of friction material>
It is preferable that the friction material of this embodiment contains 1 or more types selected from the group which consists of a fiber base material, an inorganic filler, an organic filler, and a binder.
Hereinafter, each component which the friction material of this embodiment contains is demonstrated.

<Fiber base>
The friction material according to the present embodiment includes an inorganic fiber (X) (hereinafter, also simply referred to as “inorganic fiber (X)”) containing 1 to 10 mass% of iron oxide in terms of Fe ₂ O ₃ as a fiber base material. contains.
By containing the inorganic fiber (X) whose iron oxide content is in the above range, the stability of the friction coefficient in the normal braking region can be ensured and the friction coefficient in the low-speed and low-temperature braking region can be stabilized.
From the above viewpoint, the content of iron oxide in the inorganic fiber (X) is preferably 2 to 9% by mass, more preferably 4 to 8% by mass, and further preferably 5 to 8% by mass in terms of Fe ₂ O _3. 6 to 8% by mass is preferable.
Note that the iron oxide contained in the inorganic fiber _{(X), FeO,} a _{Fe 2 O 3, Fe 3 O} 4 , etc., the "in terms _{of Fe} 2 _{O 3",} a total Fe content regardless of valence The value converted into the amount of Fe ₂ O ₃ is indicated.
The “inorganic fiber containing 1 to 10% by mass of iron oxide in terms of Fe ₂ O ₃ ” means an inorganic fiber containing the specified amount of iron oxide as a component constituting one fiber. The same applies to each component other than iron oxide described later. Moreover, content of each component in inorganic fiber (X) is content based on 100 mass% of inorganic fiber (X) whole quantity.

The inorganic fiber (X) is preferably a mineral fiber containing 1 to 10% by mass of iron oxide in terms of Fe ₂ O ₃ .
The inorganic fiber (X) preferably further contains other oxides other than the iron oxide. Examples of other oxides include SiO ₂ , Al ₂ O ₃ , CaO, MgO, Na ₂ O, and K _{2. O, TiO 2, P 2 O} 5, MnO and the like. Among _{these, SiO 2, Al 2 O 3} , CaO, preferably contains MgO.
Inorganic fibers (X) _is, when it contains one or more selected from the group consisting of _{SiO 2, Al 2 O 3,} CaO and MgO, the content thereof in the inorganic fibers (X) in are as follows.
The content of SiO ₂ is preferably 30 to 50% by mass, more preferably 35 to 47% by mass, and further preferably 40 to 45% by mass.
The content of Al ₂ O ₃ is preferably 10 to 30% by mass, more preferably 13 to 25% by mass, and further preferably 15 to 20% by mass.
The CaO content is preferably 15 to 30% by mass, more preferably 17 to 25% by mass, and still more preferably 18 to 22% by mass.
The content of MgO is preferably 3 to 20% by mass, more preferably 4 to 15% by mass, and further preferably 5 to 8% by mass.
The total content of CaO and MgO is preferably 18 to 40% by mass, more preferably 22 to 35% by mass, and further preferably 25 to 30% by mass.
The total content of iron oxide, SiO ₂ , Al ₂ O ₃ , CaO and MgO in the inorganic fiber (X) is preferably 90% by mass or more, more preferably 93% by mass or more, and further preferably 95% by mass or more. Further, the total content may be 100% by mass or less, 98% by mass or less, or 97% by mass or less.

In the case where the inorganic fiber (X) further contains one or more selected from the group consisting of Na ₂ O, K ₂ O, TiO ₂ , P ₂ O ₅ and MnO, its inclusion in the inorganic fiber (X) The amounts are as follows.
The content of Na ₂ O is preferably 1 to 5% by mass, more preferably 1.5 to 4% by mass, and still more preferably 2 to 3% by mass.
The content of K ₂ O is preferably 0.1 to 1.5% by mass, more preferably 0.2 to 1.2% by mass, and further preferably 0.4 to 0.8% by mass.
The content of TiO ₂ is preferably 0.2 to 3% by mass, more preferably 0.7 to 2% by mass, and further preferably 1 to 1.5% by mass.
The content of P ₂ O ₅ is preferably 0.01 to 1% by mass, more preferably 0.1 to 0.5% by mass, and further preferably 0.15 to 0.3% by mass.
The content of MnO is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, and further preferably 0.07 to 0.2% by mass.
The total content of one or more selected from the group consisting of Na ₂ O, K ₂ O, TiO ₂ , P ₂ O ₅ and MnO in the inorganic fiber (X) is preferably 0.5 to 10% by mass, It is more preferably 2 to 7% by mass, and further preferably 3 to 5% by mass.

The content of iron oxide and other oxides in the inorganic fiber (X) can be measured by fluorescent X-ray analysis. Moreover, content of the said oxide can be made into content of each oxide converted from content of atoms other than oxygen which forms an oxide.

The average fiber length of the inorganic fiber (X) is preferably from 100 to 800 μm, more preferably from 140 to 500 μm, still more preferably from 170 to 300 μm. When the average fiber length is in the above range, the stability of the friction coefficient can be enhanced without causing adverse effects such as a significant increase in rotor attack.
The average fiber diameter of the inorganic fiber (X) is preferably 1 to 10 μm, more preferably 2 to 8 μm, and further preferably 3 to 6 μm. When the average fiber diameter is in the above range, the stability of the friction coefficient can be improved without causing adverse effects such as a significant increase in rotor attack.
Here, the average fiber length and the average fiber diameter mean a number average fiber length or a number average fiber diameter indicating an average value of the length or diameter of the corresponding fiber. For example, the average fiber length of 200 μm indicates that 50 fibers used as a raw material of the friction material composition are randomly selected, the fiber length is measured with an optical microscope, and the average value is 200 μm.

The content of the inorganic fiber (X) in the friction material of the present embodiment is preferably 5.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total friction material. When the content of the inorganic fiber (X) is in the above range, high friction coefficient stability is obtained in the low-speed and low-temperature braking region, the coefficient of friction fluctuation during one braking is reduced, and excellent friction is obtained in the normal braking region. A coefficient is obtained. In particular, when the content of the inorganic fiber (X) is 5.0% by mass or more, the friction coefficient fluctuation rate during one braking can be reduced while ensuring the friction coefficient stability in the low-speed and low-temperature braking region. Further, when the content of the inorganic fiber (X) is less than 10.0% by mass, the friction coefficient stability in the low-speed and low-temperature braking region is improved while the friction coefficient variation rate during one braking is secured. .
From the same viewpoint, the content of the inorganic fiber (X) in the friction material of the present embodiment is preferably 5.0 to 9.9% by mass with respect to 100% by mass of the total friction material, and 7.0 to 9 0.7% by mass is more preferable, and 8.5 to 9.5% by mass is more preferable.

It is preferable that the friction material of this embodiment contains 1 or more types selected from the group which consists of organic fiber, another inorganic fiber, and metal fiber besides inorganic fiber (X). These fiber base materials exhibit a reinforcing action in the friction material. In addition, organic fiber, other inorganic fiber, and metal fiber may be used individually by 1 type, respectively, and may use 2 or more types together.
In addition, the friction material of this embodiment does not contain the metal fiber from the viewpoint of not excessively increasing the aggressiveness to the disk rotor which is the counterpart material, or the content thereof is 100% by mass of the total friction material. The content is preferably 0.5% by mass or less.

(Organic fiber)
Examples of organic fibers include aramid fibers, acrylic fibers, and cellulose fibers. Among these, an aramid fiber is preferable from the viewpoints of heat resistance, a reinforcing effect, and appropriate provision of voids. The aramid fiber can use the well-known thing currently used for the friction material. The average fiber length of the organic fibers is, for example, 650 to 1500 μm, and preferably 1000 to 1300 μm. The method for measuring the average fiber length is the same as described above.
When the friction material of the present embodiment contains organic fibers, the content thereof is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass with respect to 100% by mass of the total friction material, and 2 to 2%. More preferably, 4% by mass.

(Other inorganic fibers)
Examples of other inorganic fibers include ceramic fibers, biodegradable ceramic fibers, mineral fibers, carbon fibers, glass fibers, and potassium titanate fibers. In addition, it is preferable not to contain potassium titanate fiber etc. from a viewpoint of the harmfulness to a human body. Moreover, since rotor attack property will deteriorate notably when the addition amount of the inorganic fiber with high toughness is increased excessively, it is preferable not to contain ceramic fiber and carbon fiber from the viewpoint of toughness of the inorganic fiber.
Moreover, the friction material of this embodiment may not contain other inorganic fibers according to the desired performance.
In the present specification, metal fiber is not included in the definition of inorganic fiber.

The total content of the fiber base material in the friction material of the present embodiment is preferably 6 to 20% by mass, more preferably 7 to 17% by mass, and 8 to 15% by mass with respect to 100% by mass of the total friction material. Further preferred. When the total content of the fiber base is within the above range, higher friction coefficient stability is obtained in the low-speed and low-temperature braking region and the normal braking region.

<Inorganic filler>
The friction material of the present embodiment preferably contains an inorganic filler.
Examples of the inorganic filler include titanate, wollastonite, metal powder, graphite, various oxides used as an abrasive, and other inorganic fillers.
An inorganic filler may be used individually by 1 type, and may use 2 or more types together.
However, the friction material of the present embodiment does not contain metal powder from the viewpoint of not excessively increasing the aggressiveness to the disk rotor as the counterpart material, or the content thereof is 100% by mass of the total friction material. The content is preferably 0.5% by mass or less.

(Titanate)
The friction material of this embodiment preferably contains titanate as an inorganic filler.
Since titanate has a low Mohs hardness of about 4 and a relatively high melting point of 1000 ° C. or higher, an increase in wear of the friction material can be reduced by interposing at the friction interface during high-speed high-temperature braking.
Examples of titanates include 6 potassium titanate, 8 potassium titanate, lithium potassium titanate, magnesium potassium titanate, and sodium titanate. Of these, potassium hexatitanate and potassium potassium titanate are preferable from the viewpoint of the stability of the friction coefficient in the low-speed low-temperature braking region.
One titanate may be used alone, or two or more may be used in combination. From the viewpoint of wear resistance during high-speed high-temperature braking, one type of titanate may be used alone. preferable.

The titanate is preferably not acicular from the viewpoint of human harm. That is, it is preferable that the friction material of this embodiment contains non-acicular titanate. A non-acicular titanate means a plate-like titanate having a polygonal shape, a circle shape, an ellipse shape, or the like, or an indefinite shape titanate.
The average particle size of titanate is preferably 2 to 50 μm, more preferably 2.2 to 40 μm, and even more preferably 2.5 to 30 μm.
In addition, unless otherwise indicated, the average particle diameter in this specification means a median diameter (D50) and can be measured using a method such as laser diffraction particle size distribution measurement. As the measuring device, for example, a laser diffraction / scattering particle size distribution measuring device, trade name: LA-920 (manufactured by Horiba, Ltd.) can be used. Moreover, it can also measure by sieve classification represented by JIS B4130 etc.

When the friction material of this embodiment contains titanate, the content thereof is preferably 15 to 25% by mass, more preferably 15 to 22% by mass, and more preferably 15 to 20% with respect to 100% by mass of the total friction material. More preferred is mass%. When the titanate content is equal to or higher than the above lower limit value, excellent wear resistance during high-speed high-temperature braking is obtained, and a sufficient friction coefficient retention effect is obtained. It is possible to suppress a decrease in the friction coefficient.
In the friction material of this embodiment, from the viewpoint of the stability of the friction coefficient, non-acicular titanate having an average particle diameter of 2 to 50 μm is 15 to 25 mass with respect to 100 mass% of the total friction material. % Content is particularly preferable.

(Wollastonite)
Wollastonite is a silicate mineral represented by CaSiO ₃ and has, for example, a needle shape or a long column shape.
The average aspect ratio (average length / average diameter or thickness) of wollastonite is preferably 3 or more, more preferably 4 to 12, and still more preferably 5 to 8. When the average aspect ratio is 3 or more, the shear strength and crack resistance of the friction material at normal temperature and high temperature can be effectively improved. Here, the average aspect ratio means a D50 value (cumulative median of volume distribution), and can be measured by, for example, a dynamic image analysis method.
The average length of wollastonite is preferably 100 to 500 μm, more preferably 150 to 450 μm, and even more preferably 200 to 400 μm from the viewpoint of imparting strength to the friction material.
When the friction material of this embodiment contains wollastonite, the content thereof is preferably 2 to 10% by mass, more preferably 3 to 8% by mass with respect to 100% by mass of the total friction material, and 4 to 7 More preferred is mass%.

(Grinding material)
The friction material of this embodiment may contain zirconium silicate, triiron tetraoxide, triiron dioxide, bismuth oxide, zirconium oxide, or the like as an abrasive. Among these, zirconium silicate and zirconium oxide are preferable.

Zirconium silicate has a high Mohs hardness of 6 to 7.5 and is effective in developing a friction coefficient by grinding.
The average particle size of zirconium silicate is preferably 0.2 to 2 μm, more preferably 0.3 to 2 μm, and further preferably 0.4 to 2 μm.
When the friction material of this embodiment contains zirconium silicate, the content thereof is preferably 4 to 10% by mass and more preferably 5 to 10% by mass with respect to 100% by mass of the total friction material.
From the viewpoint of stability of the friction coefficient, the friction material of this embodiment may contain 4 to 10% by mass of zirconium silicate having an average particle size of 0.4 to 2 μm with respect to 100% by mass of the total friction material. Particularly preferred.
In addition, the friction material of this embodiment may not contain a zirconium silicate according to the desired performance.

The average particle diameter of zirconium oxide is preferably 1 to 14 μm, more preferably 5 to 10 μm, and still more preferably 8 to 9 μm.
When the friction material of this embodiment contains zirconium oxide, the content thereof is preferably 10 to 20% by mass, more preferably 12 to 19% by mass, and more preferably 14 to 18% by mass with respect to 100% by mass of the total friction material. % Is more preferable. When the content of zirconium oxide is not less than the above lower limit value, it has excellent wear resistance during high-speed high-temperature braking, and a sufficient friction coefficient retention effect is obtained. A decrease in coefficient can be suppressed.

(graphite)
The friction material of the present embodiment preferably contains graphite. By containing graphite, excellent thermal conductivity can be imparted to the friction material.
The average particle diameter of graphite is preferably 100 to 600 μm, more preferably 200 to 450 μm, and further preferably 300 to 350 μm.
When the friction material of the present embodiment contains graphite, the content thereof is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass with respect to 100% by mass of the total friction material, and 2 to 4%. More preferred is mass%.
When the average particle diameter and content of graphite are in the above ranges, it is possible to achieve both good thermal conductivity imparting to the friction material and retention of the friction coefficient.

(Other inorganic fillers)
Other inorganic fillers include magnesium oxide, antimony trisulfide, zirconium hydroxide, tin sulfide, molybdenum disulfide, bismuth sulfide, zinc sulfide, iron sulfide, calcium hydroxide, calcium oxide, sodium carbonate, calcium carbonate, magnesium carbonate , Barium sulfate, coke, γ alumina, α alumina, mica, vermiculite, calcium sulfate, mullite, chromite, titanium oxide, silica and the like. Among these, zinc sulfide, mica, calcium hydroxide, and barium sulfate are preferable. As these other inorganic fillers, general materials used for friction materials can be used.

When the friction material of this embodiment contains zinc sulfide, the content thereof is preferably 0.5 to 5% by mass and more preferably 1.5 to 3% by mass with respect to 100% by mass of the total friction material.
The average particle diameter of zinc sulfide is preferably 0.05 to 5 μm, more preferably 0.08 to 1 μm, and further preferably 0.1 to 0.3 μm.
When the friction material of this embodiment contains mica, the content is preferably 1 to 10% by mass and more preferably 3 to 7% by mass with respect to 100% by mass of the total friction material.
The average particle diameter of mica is preferably 5 to 100 μm, more preferably 10 to 60 μm, and further preferably 12 to 20 μm.
When the friction material of this embodiment contains calcium hydroxide, the content thereof is preferably 0.01 to 1% by mass, and 0.05 to 0.3% by mass with respect to 100% by mass of the total friction material. More preferred.
The average particle size of calcium hydroxide is preferably 10 to 300 μm, more preferably 30 to 200 μm, and still more preferably 50 to 100 μm.
When the friction material of this embodiment contains barium sulfate, the content thereof is preferably 10 to 35% by mass, and more preferably 12 to 30% by mass with respect to 100% by mass of the total friction material.
The average particle diameter of barium sulfate is preferably 1 to 50 μm, more preferably 3 to 30 μm, and even more preferably 5 to 20 μm.
When the friction material of this embodiment contains other inorganic fillers, the total content thereof is preferably 12 to 50% by mass, more preferably 15 to 40% by mass with respect to 100% by mass of the total friction material. 20 to 35% by mass is more preferable.

The total content of the inorganic filler in the friction material of the present embodiment is preferably 50 to 85% by mass, more preferably 65 to 80% by mass, and 70 to 77% by mass with respect to 100% by mass of the total friction material. Further preferred.

<Organic filler>
The friction material of the present embodiment preferably contains an organic filler. The organic filler is included as a friction modifier for improving the sound vibration performance, wear resistance and the like of the friction material.
An organic filler may be used individually by 1 type, and may use 2 or more types together.
Examples of the organic filler include cashew dust and rubber components.
As the cashew dust, for example, any cashew dust can be used as long as it is usually used for a friction material obtained by pulverizing and curing cashew nut shell oil. The cashew dust is preferably unmodified cashew dust.
The average particle size of cashew dust is preferably 50 to 600 μm, more preferably 70 to 550 μm, and still more preferably 100 to 500 μm.
When the friction material of this embodiment contains cashew dust, the content thereof is preferably 2 to 10% by mass, more preferably 4 to 8% by mass with respect to 100% by mass of the total friction material, and 5 to 7% by mass. % Is more preferable.
When the content of cashew dust is in the above range, sound vibration performance such as squealing due to low elasticity of the friction material can be improved.

As the rubber component, known materials used for friction materials can be used, and examples thereof include tire rubber, acrylic rubber, isoprene rubber, NBR (nitrile butadiene rubber), SBR (styrene butadiene rubber) and the like.
When the friction material of the present embodiment contains a rubber component, the content thereof is preferably 0.2 to 10% by mass, more preferably 0.5 to 5% by mass, with respect to 100% by mass of the total friction material. It is more preferably 1 to 3% by mass.

The friction material of the present embodiment preferably contains one or more selected from the group consisting of cashew dust and a rubber component, and more preferably used in combination with cashew dust and a rubber component. In addition, when cashew dust and a rubber component are used in combination, the cashew dust coated with the rubber component may be used. From the viewpoint of sound vibration performance, the cashew dust and the rubber component may be blended separately. Good.

When the friction material of this embodiment contains an organic filler, the content thereof is preferably 2 to 20% by mass, more preferably 3 to 12% by mass with respect to 100% by mass of the total amount of the friction material. More preferred is mass%.
When the content of the organic filler is within the above range, sound vibration performance such as squealing due to low elasticity of the friction material is improved, and deterioration in heat resistance and strength reduction due to thermal history can be avoided.

<Binder>
The friction material of this embodiment preferably further contains a binder. The binding material provides strength by integrating an organic filler, a fiber base material, and the like contained in the friction material.
A binder may be used individually by 1 type and may be used in combination of 2 or more type.
As the binder, a thermosetting resin usually used for a friction material can be used.
Examples of the thermosetting resin include various modified phenol resins such as phenol resin, acrylic rubber-modified phenol resin, silicone-modified phenol resin, cashew-modified phenol resin, epoxy-modified phenol resin, and alkylbenzene-modified phenol resin. Among these, a silicone-modified phenol resin is preferable from the viewpoint of improving the water repellency at the friction interface. As the silicone-modified phenol resin, a phenol resin in which silicone oil or silicone rubber is dispersed is preferable. The silicone-modified phenol resin may be used alone, but may be used in combination with a thermosetting resin other than the above-described silicone-modified phenol resin, and is preferably used in combination with an acrylic rubber-modified phenol resin.

The content of the binder in the friction material of the present embodiment is preferably 5 to 10% by mass, more preferably 6 to 10% by mass, and even more preferably 7 to 9% by mass with respect to 100% by mass of the total friction material.
When the content of the binder is within the above range, it is possible to further suppress a decrease in strength of the friction material, and it is possible to suppress deterioration in sound vibration performance such as squeal due to a decrease in the porosity of the friction material and an increase in the elastic modulus. .

<Other ingredients>
The friction material of the present embodiment may contain other materials other than the above components as necessary.

<Friction material manufacturing method>
The friction material of this embodiment can be manufactured by a generally used method.
As a manufacturing method of the friction material of this embodiment, the method of heat-pressing and manufacturing the friction material composition which satisfies the composition of the friction material of this embodiment is mentioned, for example. Specifically, for example, the friction material composition of the present embodiment to be described later is uniformly mixed using a mixer such as a Laedige (registered trademark) mixer, a pressure kneader, an Eirich (registered trademark) mixer, and the mixture is mixed. Preliminary molding is performed with a molding die, and the obtained preform is molded under conditions of a molding temperature of 140 to 150 ° C., a molding pressure of 30 to 45 MPa, and a molding time of 3 to 6 minutes. A heat treatment method at 3 ° C. for 3 to 4 hours can be mentioned. In addition, you may perform a coating, a scorch process, a grinding | polishing process, etc. as needed.

<Application of friction material>
The friction material of this embodiment is used in the following aspects (1) to (3), for example.
(1) Friction material only configuration (2) Friction member having a back metal and the friction material of the present embodiment to be a friction surface formed on the back metal (3) In the above configuration (2), the back metal A structure in which a primer layer for the purpose of surface modification for enhancing the adhesion effect of the backing metal and an adhesive layer for the purpose of bonding the backing metal and the friction member are further interposed between the friction member and the friction member. As in (2) or (3), it is preferable to be used as a friction member formed by integrating the friction material and the back metal of the present embodiment.
The backing metal is used to improve the mechanical strength of the friction member. Examples of the material include metals such as iron and stainless steel; fiber reinforced plastics such as inorganic fiber reinforced plastics and carbon fiber reinforced plastics. .
The primer layer and the adhesive layer may be those used for friction members such as brake shoes.

The friction material of this embodiment is suitable as a friction material for disc brake pads and brake linings for automobiles. Moreover, the friction material of this embodiment can be used also as friction materials, such as a clutch facing, an electromagnetic brake, a holding brake, by giving processes, such as a shaping | molding, a process, and a sticking, to a target shape.
Furthermore, the friction material of this embodiment is suitable for a brake pad for a passenger car mounted on a control brake such as a regenerative brake because it can exhibit a stable friction coefficient in a low-speed low-temperature braking region. That is, according to the present invention, it is possible to provide a passenger vehicle such as an electric vehicle or a hybrid vehicle equipped with a control brake using the friction material of the present embodiment.
Furthermore, since the friction material of the present embodiment is excellent in stability of friction coefficient, wear resistance at high temperature, etc., it is useful as a “upholstery material” for friction members such as disc brake pads and brake linings. It can also be molded and used as a “underlaying material” for the member. The “upper material” is a friction material that becomes the friction surface of the friction member, and the “underlay material” is a friction material that is interposed between the friction material that becomes the friction surface of the friction member and the back metal. It is a layer for the purpose of improving the shear strength and crack resistance in the vicinity of the adhesion part with the back metal.

[Friction material composition]
The friction material composition according to the present embodiment does not contain copper, or even if it contains copper, the content thereof is a friction material composition of 0.5% by mass or less as a copper element, and iron oxide is Fe ₂ O _3. The friction material composition contains inorganic fiber (X) in an amount of 1 to 10% by mass in terms of conversion.
The kind of each component contained in the friction material composition of this embodiment, and its manufacturing method are demonstrated similarly to the friction material of the said embodiment, The suitable aspect is altogether the same. In addition, the preferable range of the content of each component in the friction material composition is the same as the preferable range described in the friction material of the present embodiment, but the reference of the content is “100% by mass of the total friction material composition”. And
Furthermore, this invention also provides the friction material formed by shape | molding the friction material composition of this embodiment. The friction material formed by molding the friction material composition of the present embodiment includes, for example, a method of hot-pressing a preform formed by preforming the friction material composition of the present embodiment, and the friction material composition of the present embodiment. It can be produced by a method such as direct hot pressing, heat treatment as necessary, and thermosetting the binder. The specific manufacturing method is as described in the manufacturing method of the friction material of the present embodiment and the examples described later.

Hereinafter, the friction material and the friction material composition of the present embodiment will be described in more detail by way of examples, but the present invention is not limited to these.

<Examples 1 to 12 and Comparative Examples 1 to 4>
[Production of disc brake pads]
The materials were blended according to the blending amount (% by mass) shown in Table 1, and the friction material compositions of Examples 1 to 12 and Comparative Examples 1 to 4 were obtained.
Next, the friction material composition is mixed with a Ladige (registered trademark) mixer (manufactured by Matsubo Co., Ltd., trade name: Ladige mixer M20), and the mixture is preformed with a molding press (manufactured by Oji Machinery Co., Ltd.). did. Next, the obtained preform is molded using a molding press (manufactured by Sanki Seiko Co., Ltd.) under the conditions of a molding temperature of 150 ° C., a molding pressure of 30 MPa, and a molding time of 5 minutes, and a backing metal (manufactured by Hitachi Automotive Systems). Together with heating and pressing. Subsequently, the obtained molded product was heat-treated at 200 ° C. for 4 hours, polished using a rotary polishing machine, subjected to scorch treatment at 500 ° C., and a disc brake pad (friction material thickness 9 mm, friction material projected area). 52 cm ² ) was obtained.

The details of various materials used in the examples and comparative examples are as follows.

[Binder]
Resin A: Silicone-modified phenolic resin (PR54529 manufactured by Sumitomo Bakelite Co., Ltd.)
Resin B: Acrylic rubber modified phenolic resin (PR55291A manufactured by Sumitomo Bakelite Co., Ltd.)

[Organic filler]
Cashew dust: average particle size of 100 to 500 μm (FF2600 manufactured by Tohoku Kako Co., Ltd.)
・ Rubber component (tire rubber powder): Powder TPA manufactured by Carquest Co., Ltd.

[Fiber base]
Copper fiber: Average fiber length 3000 μm
・ Aramid fiber: Average fiber length 1170μm
Mineral fiber A:
Average fiber length: 230 ± 50 μm
Average fiber diameter: 5.5 μm
Fe ₂ O ₃ (7.9% by mass)
Other components: SiO ₂ (42.5 mass%), Al ₂ O ₃ (18.0 mass%), CaO (21.3 mass%), MgO (6.0 mass%), TiO ₂ (1.5 Mass%), Na ₂ O (2.0 mass%), K ₂ O (0.5 mass%), P ₂ O ₅ (0.2 mass%), MnO (0.1 mass%)
Mineral fiber B:
Average fiber length: 650 ± 150 μm
Average fiber diameter: 5.5 μm
Fe ₂ O ₃ (7.9% by mass)
Other components: SiO ₂ (42.5 mass%), Al ₂ O ₃ (18.0 mass%), CaO (21.3 mass%), MgO (6.0 mass%), TiO ₂ (1.5 Mass%), Na ₂ O (2.0 mass%), K ₂ O (0.5 mass%), P ₂ O ₅ (0.2 mass%), MnO (0.1 mass%)
・ Mineral fiber C:
Average fiber length: 125 ± 25 μm
Average fiber diameter: 5.5 μm
Fe ₂ O ₃ (7.9% by mass)
Other components: SiO ₂ (42.5 mass%), Al ₂ O ₃ (18.0 mass%), CaO (21.3 mass%), MgO (6.0 mass%), TiO ₂ (1.5 Mass%), Na ₂ O (2.0 mass%), K ₂ O (0.5 mass%), P ₂ O ₅ (0.2 mass%), MnO (0.1 mass%)
Mineral fiber D: Superwool fiber (Al ₂ O ₃ —SiO ₂ —ZrO ₂ —K ₂ O system) manufactured by Morgan Advanced Materials
Average fiber length: 300 ± 100 μm
Average fiber diameter: 3.3 μm
Iron oxide content: less than 1% by mass Mineral fiber E:
Average fiber length: 300 ± 50 μm
Average fiber diameter: 5.5 μm
Fe ₂ O ₃ (13.5% by mass)
Other components: SiO ₂ (40.5 mass%), Al ₂ O ₃ (15.3 mass%), CaO (21.0 mass%), MgO (6.0 mass%), TiO ₂ (0.9 Mass%), Na ₂ O (2.0 mass%), K ₂ O (0.5 mass%), P ₂ O ₅ (0.2 mass%), MnO (0.1 mass%)

[Inorganic filler]
Potassium titanate A: Potassium titanate 8 (average particle size 3.5 μm, shape: irregular)
-Potassium titanate B: Potassium titanate (average particle size 6 μm, shape: columnar)
-Potassium titanate C: Potassium titanate 6 (average particle size 27 μm, shape: irregular)
Potassium titanate D: Potassium titanate 6 (average particle size 30 μm, shape: irregular)
-Potassium titanate E: Potassium titanate 6 (average particle diameter 46 μm, shape: irregular)
・ Lithium potassium titanate: average particle size 2.5 μm, shape: plate shape, wollastonite: average length 300 μm, aspect ratio: 6
Graphite: average particle size 300 to 350 μm (4058 manufactured by TIMCAL)
・ Zirconium oxide: Average particle size 8-9μm
・ Zirconium silicate A: average particle size of 1 to 2 μm (MZ1000B, manufactured by Daiichi Elemental Chemical Co., Ltd.)
Zirconium silicate B: average particle size 0.4 to 0.6 μm, maximum particle size 1.1 μm (A-PAX UF manufactured by Kinsei Matec Co., Ltd.)
・ Zinc sulfide: Average particle size 0.2μm
・ Mica: average particle size 16-17μm
・ Calcium hydroxide: average particle size 50-70μm
Barium sulfate: average particle size 12.5μm

Various performances of the disc brake pads obtained in each example were evaluated using a brake dynamo tester (manufactured by Shin Nippon Toki Co., Ltd.). In the experiment, a general pin slide type collet caliper and a ventilated disc rotor (FC250 (gray cast iron)) manufactured by Kiriu Co., Ltd. were used, and the evaluation was performed with an inertia moment of 50 kgm ² .

[Evaluation of friction coefficient stability in low-speed low-temperature braking range and coefficient of friction fluctuation during one braking]
The test environment is 25 ° C. and 30% humidity, 40 km / h, 0.15 G braking is performed 1500 times, and the rate of change of the friction coefficient from the 500th braking coefficient to the 1500th braking coefficient is expressed as “ The coefficient of friction stability in the low-speed and low-temperature braking range ”was evaluated based on the following evaluation criteria. The results are shown in Table 1.
(Evaluation criteria)
A: Change rate within ± 5% B: Change rate + 5% + 10% or less, or -10% or more and less than −5% C: Change rate 10% or more and less than −10%

Further, the coefficient of friction variation during one braking at the number of braking times of 1500 was defined as “friction coefficient coefficient of variation during one braking”, and evaluation was performed based on the following calculation method and the following evaluation criteria. The results are shown in Table 1.
(Calculation method)
Friction coefficient fluctuation rate during braking (%) = ((friction coefficient at time X2−friction coefficient at time X3) × 100) / (X2−X3)
Braking start time (seconds): X1
Braking end time (seconds): X2
Midpoint of actual braking time (seconds): X3 = (X1 + X2) / 2
(Evaluation criteria)
A: Fluctuation rate 3% or less B: Fluctuation rate 3% or more and 5% or less C: Fluctuation rate 5%

[Evaluation of friction coefficient in normal braking range]
The test environment was implemented under conditions of 25 ° C. and a humidity of 30%, and in accordance with JASO C406, the friction coefficient at 200 km / h, 0.6 G braking in the second efficacy test was measured and evaluated based on the following evaluation criteria. The results are shown in Table 1.
(Evaluation criteria)
A: 0.38 or more, less than 0.41 B: 0.35 or more, less than 0.38 C: less than 0.35

The friction materials of Examples 1 to 12 containing inorganic fiber (X) had a better friction coefficient in the normal braking region than Comparative Example 2 containing copper. In addition, Examples 1 to 12 are superior to Comparative Examples 1 and 3 in which the content of iron oxide in the inorganic fiber (X) is less than 1% by mass, and have excellent friction coefficient stability in a low-speed and low-temperature braking region. The friction coefficient in the normal braking region was superior to that of Comparative Example 4 in which the content of iron oxide in the fiber (X) exceeded 10% by mass. From this result, it is understood that the friction materials of Examples 1 to 12 are highly compatible with the friction coefficient stability in the low-speed and low-temperature braking region, the friction coefficient fluctuation rate during one braking, and the friction coefficient in the normal braking region. .

The friction material, friction material composition and friction member of the present invention can express a stable coefficient of friction in a low-speed and low-temperature braking region without using copper having a high environmental load compared to conventional products, and are excellent in a normal braking region. Since it has a friction coefficient, it is suitable not only for general passenger cars but also for brake pads for passenger cars equipped with a control brake such as a regenerative brake.

Claims (17)

1. Inorganic fiber (X) containing no or even copper, the friction material having a copper element content of 0.5% by mass or less and containing iron oxide in an amount of 1 to 10% by mass in terms of Fe ₂ O ₃ ) Containing friction material.
2. The friction material according to claim 1, wherein the content of the inorganic fiber (X) is 5.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total amount of the friction material.
3. The friction material according to claim 1 or 2, wherein an average fiber length of the inorganic fibers (X) is 100 to 800 µm.
4. 4. The inorganic filler according to claim 1, further comprising 4 to 10% by mass of zirconium silicate having an average particle diameter of 0.4 to 2 μm with respect to 100% by mass of the total friction material. The friction material described.
5. Further, the inorganic filler contains 15 to 25% by mass of non-acicular titanate having an average particle diameter of 2 to 50 μm with respect to 100% by mass of the total friction material. The friction material according to any one of claims.
6. The friction material according to any one of claims 1 to 5, further comprising 10 to 20% by mass of zirconium oxide as an inorganic filler with respect to 100% by mass of the total amount of the friction material.
7. The friction material according to any one of claims 1 to 6, further comprising 2-10% by mass of wollastonite as an inorganic filler with respect to 100% by mass of the total amount of the friction material.
8. The friction material according to any one of claims 1 to 7, wherein the friction material does not contain metal powder or contains 0.5% by mass or less with respect to 100% by mass of the total friction material. .
9. A friction member formed by integrating the friction material according to any one of claims 1 to 8 and a back metal.
10. Inorganic fiber which does not contain copper or is a friction material composition containing 0.5% by mass or less as copper element and containing 1 to 10% by mass of iron oxide in terms of Fe ₂ O _3. A friction material composition containing (X).
11. The friction material composition according to claim 10, wherein the content of the inorganic fiber (X) is 5.0% by mass or more and less than 10.0% by mass with respect to 100% by mass of the total friction material composition.
12. The friction material composition according to claim 10 or 11, wherein an average fiber length of the inorganic fibers (X) is 100 to 800 µm.
13. The inorganic filler further comprises 4 to 10% by mass of zirconium silicate having an average particle size of 0.4 to 2 μm with respect to 100% by mass of the total friction material composition. The friction material composition according to item.
14. Further, the inorganic filler contains 15 to 25% by mass of non-acicular titanate having an average particle diameter of 2 to 50 μm with respect to 100% by mass of the total amount of the friction material composition. 14. The friction material composition according to any one of items 13.
15. The friction material composition according to any one of claims 10 to 14, further comprising, as an inorganic filler, zirconium oxide in an amount of 10 to 20% by mass with respect to 100% by mass of the total friction material composition.
16. The friction material composition according to any one of claims 10 to 15, further comprising wollastonite as an inorganic filler in an amount of 2 to 10% by mass with respect to 100% by mass of the total amount of the friction material composition.
17. The metal powder is not contained or the content thereof is 0.5 mass% or less with respect to 100 mass% of the total amount of the friction material composition, even if it is contained, according to any one of claims 10 to 16. Friction material composition.