Friction member, friction material composition, friction material, and vehicle

Abstract

To provide: a friction member having a friction material that satisfies both braking and squeal properties at high levels; a friction material composition with which the friction material can be provided; the friction material; and a vehicle equipped with the friction member or friction material.SOLUTION: A friction member has a friction material and back metal. The friction material contains a metal compound with a Mohs hardness of 5 or more of 30 mass% or more and also contains a component surface-treated with a rubber component of 1.2 mass% or more relative to the total amount of the friction material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a friction member, a friction material composition, a friction material, and a vehicle.

Background Art

[0002] For vehicles such as automobiles, friction materials such as disc brake pads and brake linings are used for braking. These friction materials brake by rubbing against mating members such as disc rotors and brake drums, and converting the kinetic energy of the automobile or the like into thermal energy. Depending on the conversion from kinetic energy to thermal energy, a part may be converted into vibration energy. In this case, since the vibration energy generates vibration or noise, it gives discomfort to the user of the automobile or the like, and the marketability of the friction material is significantly reduced. Therefore, for friction materials, not only a high coefficient of friction (effectiveness) is required, but also it is required that brake noise is difficult to occur (noise characteristics), the friction material has a long life (wear resistance), and the like. However, generally, it has been found that when the coefficient of friction is increased by containing an abrasive having a high Mohs hardness, brake noise is likely to occur. That is, the effectiveness and the noise characteristics are in an antinomic relationship, and in fact, it is very difficult to achieve both the effectiveness and the noise characteristics at a high level.

[0003] Paragraph of Patent Document 1

[0004] In

[0007] , in order to improve the noise characteristics, methods are disclosed in which rubber powder is added or a rubber-modified phenolic resin is used as a binder to impart damping properties to the lining and increase the vibration damping amount. When adding unvulcanized rubber powder as the rubber powder, heat resistance and damping properties cannot be expected much, and since it affects the strength of the brake pad, it cannot be added in large amounts, and it is explained that the effect of preventing the brake noise cannot be expected much. On the other hand, when adding vulcanized rubber powder as the rubber powder, granular vulcanized rubber or rubber powder obtained by pulverizing recycled tires is used, but since the adhesion to the friction material base (friction material matrix) is not very good, it is likely to fall off from the friction surface during braking, wear progresses, and there is a risk that the life of the brake pad will be shortened. Thus, since it is generally not easy to improve the noise characteristics, it can be said that it is even more difficult to improve the noise characteristics while enhancing the effectiveness characteristics.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, an object of the present invention is to provide a friction member having a friction material that achieves both high effectiveness characteristics and noise characteristics, a friction material composition capable of providing the friction material, the friction material, and a vehicle equipped with the friction member or the friction material.

Means for Solving the Problems

[0006] As a result of intensive studies, the inventors of the present invention have found that the above problems can be solved by a friction material containing a metal compound having a predetermined Mohs hardness in a predetermined amount or more and containing a component surface-treated with a rubber component in a predetermined amount or more, and have completed the present invention. That is, the present invention relates to the following [1] to

[24] .

[0007] [1] A friction member having a friction material and a backing metal, wherein the friction material contains 30% by mass or more of a metal compound having a Mohs hardness of 5 or more and contains a component surface-treated with a rubber component in an amount of 1.2% by mass or more based on the total amount of the friction material. [2] The friction member according to [1] above, wherein the component surface-treated with the rubber component is a component surface-treated with a rubber component in an amount of 1.2 to 12% by mass based on the total amount of the friction material. [3] The friction member according to [1] or [2] above, wherein the rubber component is an uncrosslinked rubber that is solid at 25°C. [4] The friction member according to any one of [1] to [3] above, wherein the rubber component is at least one selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, ethylene-propylene-diene rubber, and fluororubber. [5] The friction member according to any one of [1] to [4] above, wherein the rubber component is at least one selected from the group consisting of acrylonitrile-butadiene rubber, butyl rubber, and chlorinated butyl rubber. [6] The friction member according to any one of [1] to [5] above, wherein the component surface-treated with the rubber component contains the metal compound having a Mohs hardness of 5 or more surface-treated with the rubber component. [7] The friction member according to any one of [1] to [6] above, wherein the metal compound having a Mohs hardness of 5 or more contains at least one selected from the group consisting of iron trioxide, alumina, zirconia, zirconium silicate, mullite, magnesium oxide, and titanium oxide. [8] The friction member according to any one of [1] to [7] above, wherein the friction material contains at least one selected from the group consisting of an inorganic filler, an organic filler, a fiber base material, and a binder. [9] The friction member according to any one of [1] to [8] above, wherein the friction material further contains a titanate.

[10] The friction member according to [9] above, wherein the titanate is at least one selected from the group consisting of potassium titanate, lithium potassium titanate, magnesium potassium titanate, and sodium titanate.

[11] The friction member according to any one of [1] to

[10] above, wherein the average coefficient of friction of the friction material at 100 to 300 °C is 0.40 or more.

[12] A vehicle equipped with the friction member according to any one of [1] to

[11] above.

[13] A friction material composition containing a metal compound having a Mohs hardness of 5 or more in an amount of 30% by mass or more and a component surface-treated with a rubber component in an amount of 1.2% by mass or more based on the total amount of the friction material composition.

[14] The friction material composition according to

[13] above, wherein the component surface-treated with the rubber component is a component surface-treated with a rubber component in an amount of 1.2 to 12% by mass based on the total amount of the friction material composition.

[15] The friction material composition according to

[13] or

[14] above, wherein the rubber component is an uncrosslinked rubber that is solid at 25 °C.

[16] The friction material composition according to any one of

[13] to

[15] above, wherein the rubber component is at least one selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, ethylene-propylene-diene rubber, and fluororubber.

[17] The friction material composition according to any one of

[13] to

[16] above, wherein the rubber component is at least one selected from the group consisting of acrylonitrile-butadiene rubber, butyl rubber, and chlorinated butyl rubber.

[18] The friction material composition according to any one of

[13] to

[17] above, wherein the component surface-treated with the rubber component contains the metal compound having a Mohs hardness of 5 or more surface-treated with the rubber component.

[19] The friction material composition according to any one of

[13] to

[18] above, wherein the metal compound having a Mohs hardness of 5 or more contains at least one selected from the group consisting of iron trioxide, alumina, zirconia, zirconium silicate, mullite, magnesium oxide, and titanium oxide.

[20] The friction material composition according to any one of

[13] to

[19] above, wherein the friction material contains at least one selected from the group consisting of an inorganic filler, an organic filler, a fiber base material, and a binder.

[21] The friction material composition according to any one of

[13] to

[20] above, wherein the friction material further contains a titanate.

[22] The friction material composition according to

[21] above, wherein the titanate is at least one selected from the group consisting of potassium titanate, lithium potassium titanate, magnesium potassium titanate, and sodium titanate.

[23] A friction material containing the friction material composition according to any one of

[13] to

[22] above.

[24] A vehicle equipped with the friction material according to

[23] above.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a friction member having a friction material that achieves both high effectiveness characteristics and high squeal characteristics, a friction material composition capable of providing the friction material, a friction material that achieves both high effectiveness characteristics and high squeal characteristics, and a vehicle equipped with the friction member or the friction material.

Brief Description of the Drawings

[0009]

Figure 1

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the friction member, friction material composition, friction material, and vehicle according to the embodiments of the present invention will be described in detail. However, in the following embodiments, the constituent elements are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present invention. In the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. Further, in this specification, the content rate of each component in the friction material composition (or in the friction material) means the total content rate of the plurality of substances present in the friction material composition (or in the friction material) when there are a plurality of substances corresponding to each component, unless otherwise specified. The content rate of each component in the friction material is synonymous with the content rate in the friction material composition. Aspects obtained by arbitrarily combining the matters described in this specification are also included in the present invention.

[0011] [Friction Material and Friction Member] The friction member according to this embodiment is a friction member having a friction material and a backing plate, wherein the friction material contains 30% by mass or more of a metal compound having a Mohs hardness of 5 or more and contains a component surface-treated with 1.2% by mass or more of a rubber component based on the total amount of the friction material. Since a large amount of a metal compound having a Mohs hardness of 5 or more is likely to cause noise, generally, it tends to be avoided to contain 30% by mass or more in the friction material. However, in the present invention, by deliberately containing 30% by mass or more of a metal compound having a Mohs hardness of 5 or more and containing a component surface-treated with 1.2% by mass or more of a rubber component based on the total amount of the friction material, it has been successful in suppressing the generation of noise while enhancing the effectiveness characteristics. In addition, as a preferred aspect of the friction material of this embodiment, an aspect containing at least one selected from the group consisting of an inorganic filler, an organic filler, a fiber base material, and a binder can be mentioned. The metal compound having a Mohs hardness of 5 or more is included in the inorganic filler. Hereinafter, each component contained in the friction material of this embodiment will be described in detail.

[0012] The friction material of this embodiment contains a metal compound with a Mohs hardness of 5 or more. Since the metal compound with a Mohs hardness of 5 or more functions as an abrasive, it has the effect of enhancing the braking performance. As the metal compound with a Mohs hardness of 5 or more, one kind may be used alone, or two or more kinds may be used in combination. The metal compound with a Mohs hardness of 5 or more is not particularly limited, but from the viewpoints of braking performance, screeching performance, and wear resistance, metal oxides such as iron trioxide (Mohs hardness: 5.5 - 6), magnesium oxide (Mohs hardness: 6), titanium oxide (Mohs hardness: 7 - 7.5), alumina (Mohs hardness: 5 - 9), zirconia (Mohs hardness: 7), etc.; iron disulfide (Mohs hardness: 6 - 6.5); metal silicates such as zirconium silicate (alias: zircon, Mohs hardness: 7.5), mullite (Mohs hardness: 7.5), etc. It is preferably contained at least one selected from the group consisting of. In particular, from the viewpoints of braking performance and screeching performance, it is more preferably contained at least one selected from the group consisting of alumina, zirconia, iron disulfide, and zirconium silicate, and even more preferably contained at least one selected from the group consisting of alumina, zirconia, and zirconium silicate. Examples of the alumina include α-alumina (Mohs hardness: 9), γ-alumina (Mohs hardness: 5 - 6), etc. As the metal compound with a Mohs hardness of 5 or more, from the viewpoint of braking performance, it is preferably a metal compound with a Mohs hardness of 6 or more, more preferably a metal compound with a Mohs hardness of 7 or more, even more preferably a metal compound with a Mohs hardness of 7.5 or more, and may be a metal compound with a Mohs hardness of 8 or more. There is no particular limitation on the upper limit of the Mohs hardness of the metal compound with a Mohs hardness of 5 or more, but from the viewpoints of screeching performance and wear resistance, a Mohs hardness of 10 or less is preferred, and a Mohs hardness of 9.5 or less is more preferred.

[0013] In the friction material of the present embodiment, from the viewpoint of the effectiveness characteristics, the content of the metal compound with a Mohs hardness of 5 or more is 30% by mass or more, and from the same viewpoint, it is preferably 32% by mass or more, more preferably 34% by mass or more. As the upper limit of the content of the metal compound with a Mohs hardness of 5 or more, from the viewpoint of avoiding exceeding the limit of suppressing the squeal, it is preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less, and particularly preferably 38% by mass or less.

[0014] <Component surface-treated with a rubber component> The friction material of the present embodiment also contains components other than the metal compound with a Mohs hardness of 5 or more. Since the friction material of the present embodiment contains 30% by mass or more of the metal compound with a Mohs hardness of 5 or more, it is in a state where squeal is extremely likely to occur. However, by containing a component surface-treated with a rubber component of 1.2% by mass or more based on the total amount of the friction material, the squeal is effectively suppressed. From the viewpoint of the squeal characteristics, it is preferable to contain a component surface-treated with a rubber component of 1.3% by mass or more based on the total amount of the friction material, more preferably to contain a component surface-treated with a rubber component of 1.4% by mass or more based on the total amount of the friction material, and still more preferably to contain a component surface-treated with a rubber component of 1.5% by mass or more based on the total amount of the friction material. In addition, even if the surface treatment is performed with a rubber component of less than 1.2% by mass based on the total amount of the friction material, when the content of the metal compound with a Mohs hardness of 5 or more is 30% by mass or more as in the present invention, the effect of improving the squeal characteristics is not sufficient. There is no particular limitation on the upper limit of the amount of the rubber component used for the surface treatment. However, from the viewpoints of the effectiveness characteristics and the heat resistance, strength, and abrasion resistance, it is preferably 13% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, particularly preferably 3% by mass or less, and most preferably 2% by mass or less based on the total amount of the friction material. That is, the amount of the rubber component used for the surface treatment is preferably 1.2 to 13% by mass based on the total amount of the friction material, and the lower limit value and the upper limit value in this numerical range can be changed to the above-mentioned usage amounts, respectively.

[0015] The components surface-treated with the rubber component are not particularly limited, and any of the components described later may be surface-treated. However, from the viewpoint of the rattling characteristics, it is preferable to contain at least the metal compound having a Mohs hardness of 5 or more surface-treated with the rubber component. Further, as the component surface-treated with the rubber component, an embodiment containing the inorganic filler surface-treated with the rubber component is also preferable from the viewpoint of the rattling characteristics. Note that it may contain an organic filler surface-treated with the rubber component or a fiber base material surface-treated with the rubber component. Note that the binder is preferably not surface-treated with the rubber component.

[0016] As the rubber component, an uncrosslinked rubber that is solid at 25°C is preferable because it has high adhesiveness. Further, the rubber component may be used alone or in combination of two or more. Examples of the uncrosslinked rubber that is solid at 25°C include natural rubber; synthetic rubbers such as isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, ethylene-propylene-diene rubber, and fluororubber. The rubber component is preferably at least one selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, ethylene-propylene-diene rubber, and fluororubber. From the viewpoint of high adhesiveness at normal temperature and high heat resistance, it is more preferably at least one selected from the group consisting of acrylonitrile-butadiene rubber, butyl rubber, and chlorinated butyl rubber, and even more preferably at least one selected from the group consisting of butyl rubber and chlorinated butyl rubber.

[0017] As described above, the friction material of the present embodiment contains a component surface-treated with the rubber component. On the other hand, when the rubber component is not used for surface treatment of a desired component but is mixed with other components to manufacture a friction material, the dispersion state of the rubber component (especially uncrosslinked rubber solid at 25°C) becomes extremely poor, and the heat resistance, strength, abrasion resistance, and noise characteristics of the friction material become insufficient. In some cases, it may even be difficult to manufacture the friction material itself.

[0018] There is no particular limitation on the method of surface-treating a desired component with the rubber component, and it can be achieved by mixing the component to be surface-treated and the rubber component. At this time, in order to mix sufficiently, it is preferable to use a rubber kneading device. Examples of the rubber kneading device include a pressure kneader, a Banbury mixer, an open roll, etc. In particular, internal mixers (closed kneaders) such as a pressure kneader and a Banbury mixer are preferable because they can uniformly disperse the rubber component (especially uncrosslinked rubber solid at 25°C) in the friction material composition. All of the components to be surface-treated may be surface-treated, or only a part of the components to be surface-treated may be surface-treated. That is, assuming the component to be surface-treated is component A, the friction material of the present embodiment may be such that all of the included component A is surface-treated with the rubber component, or may contain both component A surface-treated with the rubber component and component A not surface-treated with the rubber component. The temperature at the time of surface treatment is not particularly limited, but it can be carried out near room temperature. For example, it can be carried out at 0 to 40°C.

[0019] As described above, the friction material of the present embodiment may contain at least one selected from the group consisting of an inorganic filler, an organic filler, a fiber base material, and a binder. Any of these components may be surface-treated with the rubber component. Hereinafter, these components will be described in detail.

[0020] <Inorganic filler> The inorganic filler can exhibit a function as a friction modifier for avoiding deterioration of the heat resistance, wear resistance, stability of the friction coefficient, etc. of the friction material. Here, in the present invention, the inorganic filler does not include fibrous ones (that is, the inorganic fibers described later). Since the hardness of the disk rotor that is the mating material of the friction material is generally cast iron with a Mohs hardness of about 4.5, an inorganic filler with a Mohs hardness of 5 or more has an effect of increasing the friction coefficient and can act as an abrasive. In particular, in the friction material of the present embodiment, as described above, it contains at least a metal compound with a Mohs hardness of 5 or more. The inorganic filler may be used alone or in combination of two or more. Hereinafter, inorganic fillers other than metal compounds with a Mohs hardness of 5 or more will be described.

[0021] Examples of the inorganic filler include titanates such as potassium titanate, lithium potassium titanate, sodium titanate, and magnesium potassium titanate; metal sulfides such as bismuth sulfide, tin sulfide, molybdenum disulfide, zinc sulfide, tungsten sulfide, and manganese sulfide; calcium hydroxide, mica, graphite, coke, calcium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, dolomite, vermiculite, calcium sulfate, talc, clay, zeolite, chromite, zinc oxide, barium sulfate; and metal powder. It is preferable that the inorganic filler contains at least one selected from these, and from the viewpoints of heat resistance, wear resistance, stability of the friction coefficient, and chirping characteristics, it is more preferable to contain at least one selected from the group consisting of titanates, metal sulfides, calcium hydroxide, mica, graphite, coke, barium sulfate, and metal powder, and it is even more preferable to contain at least one selected from the group consisting of titanates, calcium hydroxide, mica, graphite, coke, tin sulfide, zinc sulfide, barium sulfate, and metal powder.

[0022] From the viewpoints of the heat resistance, abrasion resistance, and stability of the friction coefficient of the friction material, the content rate of the inorganic filler in the friction material of the present embodiment is preferably 40 to 90% by mass, more preferably 45 to 85% by mass, still more preferably 50 to 85% by mass, and particularly preferably 60 to 80% by mass with respect to the total amount of the friction material. Hereinafter, the above-mentioned preferable inorganic fillers will be described in detail in order.

[0023] (Titanate) Since the titanate has a low Mohs hardness of about 4 and a relatively high melting point of 1,000 °C or higher, it can improve the abrasion resistance of the friction material by intervening in the friction interface during high-speed and high-temperature braking. In addition, the titanate has an effect of improving the stability of the friction coefficient. As the titanate, for example, it preferably contains at least one selected from the group consisting of potassium titanate (6-potassium titanate, 8-potassium titanate), lithium potassium titanate, magnesium potassium titanate, and sodium titanate, and more preferably contains at least one selected from the group consisting of potassium titanate and lithium potassium titanate. The shape of the titanate is not particularly limited, but from the viewpoint of avoiding harmfulness to the human body, it is preferably non-needle-shaped. The non-needle-shaped titanate means plate-shaped titanate having a shape such as a polygon, a circle, or an ellipse; flaky titanate; columnar titanate; irregular-shaped titanate, etc. Among these, flaky titanate is preferable. The shape of the titanate can be analyzed, for example, by observation with a scanning electron microscope (SEM).

[0024] Also, although not particularly limited, from the viewpoints of abrasion resistance, stability of the friction coefficient, and improvement of the squeal characteristics, titanates having a layered crystal structure and titanates having a tunnel crystal structure are preferable, and it is more preferable to use a layered crystal structure titanate and a tunnel crystal structure titanate in combination. Both the titanate having a layered crystal structure and the titanate having a tunnel crystal structure are preferably flaky. As the titanate having a layered crystal structure, lithium potassium titanate and magnesium potassium titanate can be used. As the titanate having a tunnel-shaped crystal structure, potassium octatitanate, potassium hexatitanate, and sodium titanate can be used.

[0025] The average particle diameter of the titanate is not particularly limited, but is preferably 1 to 50 μm, more preferably 1.5 to 40 μm, and even more preferably 2.0 to 30 μm. In this specification, the average particle diameter means the value of d50 (median diameter of volume distribution, cumulative median) measured using the method of measuring laser diffraction particle size distribution, and the same applies hereinafter. The average particle diameter can be measured, for example, with a laser diffraction / scattering type particle size distribution measuring device, trade name: LA·920 (manufactured by Horiba, Ltd.).

[0026] When the friction material of this embodiment contains a titanate, its content is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, even more preferably 1 to 10% by mass, and particularly preferably 1.5 to 8% by mass with respect to the total amount of the friction material. When the content of the titanate is at least the lower limit value, the effectiveness characteristics during high-speed and high-temperature braking tend to be good, and when it is at most the upper limit value, the decrease in the effectiveness characteristics during low-speed and low-temperature braking can be suppressed.

[0027] (Calcium hydroxide) Calcium hydroxide increases the pH of the friction material, and the aramid fiber described later tends to be easily decomposed. Therefore, when used together with the aramid fiber described later, it is preferable to pay attention to the usage amount so that the pH does not become too high. When the friction material contains calcium hydroxide, the content of calcium hydroxide is preferably 0.5 to 10% by mass, more preferably 1.0 to 9% by mass, even more preferably 2.5 to 8% by mass, and particularly preferably 2.5 to 5.5% by mass with respect to the total amount of the friction material. The average particle diameter of calcium hydroxide is not particularly limited, but is preferably 1 to 70 μm, more preferably 3 to 60 μm, and even more preferably 5 to 50 μm.

[0028] (Mica) By including mica in the friction material of the present embodiment, the effectiveness characteristics, crack resistance, and wear resistance of the friction material can be improved, and the flexibility can be further improved. Examples of mica include phlogopite, biotite, muscovite, and synthetic mica. Mica may be used alone or in combination of two or more. Phlogopite is known as soft mica, and its composition formula is KMg3AlSi3O 10 (OH)2. Also, biotite is a substance in which part of the Mg in phlogopite is replaced by Fe (composition formula: K(Mg,Fe)3AlSi3O 10 (OH)2), and it is a continuous solid solution of phlogopite and annite (composition formula: KFe3AlSi3O 10 (OH)2). Phlogopite and biotite have a Mohs hardness of 2.0 to 2.5 and are relatively soft among micas. The molar ratio (Mg / Fe) of Mg and Fe in biotite is not particularly limited, preferably 50 / 50 or more, more preferably 60 / 40 or more, and even more preferably 80 / 20 or more. Since the case where the molar ratio (Mg / Fe) is 100 / 0 is phlogopite, the upper limit of the preferable range of the molar ratio (Mg / Fe) is less than 100 / 0. Muscovite (white mica, composition formula: KAl2(AlSi3)O 10 (OH)2), known as hard mica, has a Mohs hardness of 2.5 to 3.5, and the Mohs hardness of synthetic mica (Synthetic Mica, for example, composition formula: KMg3(AlSi3)O 10 F2) is 3.4, and these are hard among micas. There is no particular limitation on the average particle size of mica, but from the viewpoints of chirping characteristics, wear resistance, crack resistance, etc., it is preferably 10 to 500 μm, more preferably 20 to 200 μm, even more preferably 30 to 100 μm, and particularly preferably 30 to 80 μm.

[0029] When the friction material of the present embodiment contains mica, its content is preferably 1 to 10% by mass, more preferably 1.5 to 8% by mass, still more preferably 3 to 8% by mass, and particularly preferably 4 to 6.5% by mass with respect to the total amount of the friction material. If the content of mica is equal to or higher than the lower limit value, rotor wear tends to be good, and if it is equal to or lower than the upper limit value, a decrease in effectiveness characteristics tends to be suppressed.

[0030] (Graphite; Lubricant) The friction material of the present embodiment preferably contains graphite. Graphite functions as a lubricant, and the wear resistance of the friction material is improved by the friction material containing graphite. Furthermore, the thermal conductivity of the friction material can also be increased by graphite. Graphite is not particularly limited, and any known graphite, that is, either natural graphite or artificial graphite can be used. The average particle diameter of graphite is not particularly limited, but is preferably 50 to 1,000 μm, more preferably 80 to 800 μm, and still more preferably 100 to 800 μm. Graphite having different average particle diameters may be used in combination of two or more kinds. If the average particle diameter of graphite is equal to or lower than the upper limit value, the thermal conductivity is improved, the curing of the binder during molding is promoted, and the strength of the friction material tends to be improved.

[0031] When the friction material of the present embodiment contains graphite, its content is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, still more preferably 1 to 10% by mass, and particularly preferably 1 to 5% by mass with respect to the total amount of the friction material. If the content of graphite is equal to or higher than the lower limit value, the thermal conductivity is improved and the pad wear at high temperature tends to be good, and if it is equal to or lower than the upper limit value, a decrease in the friction coefficient tends to be easily suppressed.

[0032] (Coke; Lubricant) The friction material of the present embodiment preferably contains coke. Coke functions as a lubricant, and the wear resistance of the friction material is improved by the friction material containing coke. Coke is roughly classified into coal coke and petroleum coke, and either can be used. Coal coke is expensive because it uses high-quality coal as a raw material, but petroleum coke has little variation in quality, a low price, and can be easily obtained. Therefore, it is preferable to use petroleum coke.

[0033] More specifically, examples of coke include (1) coke for ironmaking obtained by carbonizing coal at about 1,300°C, (2) delayed coke obtained by thermally decomposing petroleum, coal tar, or pitch at 400 to 500°C, and (3) calcined coke obtained by calcining the delayed coke at about 1,300°C. However, the coke for ironmaking has many impurities because coal is carbonized as it is. The delayed coke undergoes thermal decomposition during heat treatment at 500°C or higher, and its hardness varies depending on the final treatment temperature, but it becomes an extender for the fired product of the binder. For the calcined coke, a mechanically pulverized product with a desired particle size can be used, and it can efficiently improve the lubricating performance of the friction material. Any of these cokes can be used, but delayed coke and calcined coke are preferred.

[0034] There is no particular limitation on the average particle size of the coke, but it is preferably 5 to 400 μm, more preferably 10 to 100 μm, and even more preferably 15 to 60 μm. If the average particle size of the coke is 150 μm or more, the abrasion resistance tends to be improved in the high-temperature range, and if it is 400 μm or less, segregation is less likely to occur, and cracks and wrinkles are less likely to occur in the friction material during molding.

[0035] When the friction material of this embodiment contains coke, the content is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, and even more preferably 2 to 5% by mass based on the total amount of the friction material. If the content of coke is at least the lower limit value, the abrasion resistance tends to be improved, and if it is at most the upper limit value, the decrease in the friction coefficient is likely to be suppressed.

[0036] (Metal sulfide; Lubricant) The friction material of the present embodiment preferably contains a metal sulfide. The metal sulfide functions as a lubricant, and by containing the metal sulfide in the friction material, wear resistance can be imparted to the friction material. Examples of the metal sulfide include bismuth sulfide, tin sulfide, molybdenum disulfide, zinc sulfide, tungsten sulfide, manganese sulfide, etc., and it is preferably at least one selected from the group consisting of these. Among these, from the viewpoint of stabilizing the friction coefficient without excessively reducing the friction coefficient, it is preferable to contain at least one selected from the group consisting of bismuth sulfide, tin sulfide, and zinc sulfide. From the viewpoint of stabilizing the friction coefficient while suppressing the decrease in the friction coefficient, it is more preferable to contain tin sulfide. Note that iron disulfide, which is one of the metal sulfides, has a Mohs hardness of 6 to 6.5 and corresponds to the above-mentioned "metal compound with a Mohs hardness of 5 or more". Therefore, in the present invention, tin disulfide is not included in the metal sulfide. The metal sulfide may be used alone or in combination of two or more.

[0037] When the friction material of the present embodiment contains a metal sulfide, its content is preferably 0.1 to 10% by mass, more preferably 0.5 to 6% by mass, still more preferably 1.0 to 5% by mass, and particularly preferably 1.5 to 4% by mass with respect to the total amount of the friction material. If the content of the metal sulfide is at least the lower limit value, rotor wear can be suppressed, and if it is at most the upper limit value, a decrease in effectiveness characteristics can be suppressed.

[0038] (Metal powder) The friction material of the present embodiment preferably contains metal powder. By containing the metal powder, it is possible to suppress a decrease in the friction coefficient over time in the friction material. Examples of the metal powder include copper powder, iron powder, cast iron powder, aluminum powder, nickel powder, tin powder, zinc powder, and alloy powders containing at least one metal selected from the group consisting of copper, iron, cast iron, aluminum, nickel, tin, and zinc. Among these, as the metal powder, it is preferable to contain at least one selected from the group consisting of iron powder, cast iron powder, aluminum powder, tin powder, and zinc powder, and it is more preferable to contain tin powder. The metal powder is not particularly limited in terms of particle size, shape, etc., as long as it does not cause extreme deterioration of properties. For example, the shape of the metal powder may be spherical produced by a general atomization method or the like, or may be columnar produced by a general cutting method or the like. Also, the purity as a metal is preferably 90% or more, but there is no problem even if the surface of the metal powder changes to a metal oxide or the like.

[0039] When the friction material of the present embodiment contains metal powder, its content is preferably 0.1 to 10% by mass, more preferably 0.5 to 6% by mass, still more preferably 1.0 to 5% by mass, and particularly preferably 1.5 to 4% by mass with respect to the total amount of the friction material. If the content of the metal powder is at least the lower limit value, the decrease in the friction coefficient can be effectively suppressed, and if it is at most the upper limit value, the aggressiveness to the disk rotor as the mating material is not increased too much.

[0040] (Barium sulfate) The average particle diameter of barium sulfate is not particularly limited, but is preferably 1 to 100 μm, more preferably 5 to 75 μm, and still more preferably 10 to 50 μm. Note that barium sulfate serves as merely a filler for adjusting the volume of the friction material. That is, the content of barium sulfate depends on the content of other components, and the balance for making the friction material a predetermined amount can be supplemented with barium sulfate.

[0041] <Organic filler> The friction material of this embodiment preferably contains an organic filler. The organic filler is included as a friction modifier for improving the screeching characteristics, wear resistance, etc. of the friction material. Here, in the present invention, the organic filler does not include fibrous ones (i.e., the organic fibers described later). One type of organic filler may be used alone, or two or more types may be used in combination. Examples of the organic filler include cashew particles and rubber components.

[0042] (Cashew particles) The cashew particles are, for example, obtained by pulverizing a polymerized and cured cashew nut shell oil, and are sometimes generally referred to as cashew dust. The cashew particles are preferably unmodified cashew particles. The cashew particles are generally classified into tea-based, tea-black-based, black-based, etc. according to the type of curing agent used in the curing reaction. By adjusting the molecular weight, etc., of the cashew particles, it is possible to easily control the heat resistance, screeching characteristics, and film-forming property on the rotor as the mating material. From the viewpoint of dispersibility, the average particle diameter of the cashew particles is preferably 850 μm or less, more preferably 750 μm or less, still more preferably 600 μm or less, and particularly preferably 350 μm or less. There is no particular limitation on the lower limit value of the average particle diameter of the cashew particles, and it may be 10 μm or more, or 30 μm or more. Needless to say, the numerical range obtained by arbitrarily combining the upper limit value and the lower limit value is also included in the preferred embodiments of the average particle diameter of the cashew particles. Commercially available products can be used as the cashew particles. One type of cashew particle may be used alone, or two or more types may be used in combination.

[0043] When the friction material of the present embodiment contains cashew particles, the content rate is preferably 1 to 16% by mass, more preferably 1.5 to 10% by mass, still more preferably 1.5 to 7% by mass, and particularly preferably 1.5 to 5% by mass with respect to the total amount of the friction material. When the content rate of the cashew particles is within the above range, the squeal characteristics tend to be easily improved due to the reduction of the elasticity of the friction material.

[0044] (Rubber component) As the rubber component, known ones used in friction materials can be used, and examples thereof include natural rubber and synthetic rubber. Examples of the synthetic rubber include acrylonitrile-butadiene rubber (NBR), acrylic rubber, isoprene rubber, polybutadiene rubber (BR), styrene-butadiene rubber (SBR), silicone rubber, and pulverized tire tread rubber. In addition, since the friction material of the present embodiment contains a component surface-treated with a rubber component as described above, the rubber component may or may not be separately contained.

[0045] The friction material of the present embodiment preferably contains one or more selected from the group consisting of cashew particles and a rubber component, and more preferably contains cashew particles.

[0046] When the friction material of the present embodiment contains an organic filler, the content rate (however, the total content rate including the rubber component used for the surface treatment of the above components) is preferably 1 to 20% by mass, more preferably 2 to 10% by mass, and still more preferably 2 to 6% by mass with respect to the total amount of the friction material. When the content rate of the organic filler is equal to or higher than the lower limit value, the squeal characteristics tend to be easily improved due to the reduction of the elasticity of the friction material, and when it is equal to or lower than the upper limit value, it tends to be easy to avoid the deterioration of heat resistance and the strength reduction due to the heat history.

[0047] <Fiber substrate; organic fiber and inorganic fiber> The friction material of this embodiment preferably contains a fiber base material. The fiber base material exhibits a reinforcing effect. Examples of the fiber base material include organic fibers and inorganic fibers. The fiber base material may be used alone or in combination of two or more kinds.

[0048] -Organic fibers- The friction material of this embodiment preferably contains organic fibers. Organic fibers are fibrous materials mainly composed of organic substances. Examples of the organic fibers include hemp, cotton, aramid fiber, cellulose fiber, acrylic fiber, phenolic resin fiber (having a crosslinked structure), etc. The organic fibers may be used alone or in combination of two or more kinds. From the viewpoint of heat resistance, aramid fiber is preferable as the organic fiber. Also, from the viewpoint of improving the strength of the friction material, it is preferable to contain fibrillated organic fibers as the organic fiber, and more preferably to contain fibrillated aramid fibers. Fibrillated organic fibers are organic fibers that are fibrillated and have fluffiness, and can be commercially obtained.

[0049] When the friction material of this embodiment contains organic fibers, the content is not particularly limited, but is preferably 1 to 15% by mass, more preferably 1 to 10% by mass, still more preferably 1.5 to 6% by mass, and particularly preferably 1.5 to 4% by mass with respect to the total amount of the friction material. If it is above the lower limit value, good shear strength, crack resistance and wear resistance tend to be exhibited. If it is below the upper limit value, the deterioration of shear strength and crack resistance due to the uneven distribution of organic fibers (fibrillated organic fibers) and other materials in the friction material composition can be effectively suppressed.

[0050] -Inorganic fibers- Inorganic fibers can exhibit the effect of improving the mechanical strength and wear resistance of the friction material. Examples of the inorganic fiber include mineral fiber, metal fiber, glass fiber, carbon fiber, ceramic fiber, biodegradable ceramic fiber, sepiolite (α-type sepiolite and β-type sepiolite), attapulgite, potassium titanate fiber, silica alumina fiber, flame-resistant fiber, and the like. The inorganic fiber is preferably a fibrous material mainly composed of an inorganic substance other than a metal and a metal alloy, and mineral fiber and metal fiber are more preferable. The inorganic fiber may be used alone or in combination of two or more.

[0051] (Mineral fiber) The mineral fiber is a man-made inorganic fiber obtained by melt spinning using blast furnace slag such as slag wool, basalt such as basalt fiber, and other natural rocks as main components. Examples of the mineral fiber include mineral fibers containing SiO2, Al2O3, CaO, MgO, FeO, Na2O, etc., or mineral fibers containing one or more of these compounds. As the mineral fiber, a mineral fiber containing an aluminum element is preferable, a mineral fiber containing Al2O3 is more preferable, and a mineral fiber containing Al2O3 and SiO2 is even more preferable. Examples of the mineral fiber include wollastonite, rock wool, and the like. The mineral fiber may or may not be surface-treated, and a mode of using a surface-treated mineral fiber and a non-surface-treated mineral fiber in combination is also preferable.

[0052] From the viewpoint of shear strength, the average fiber length of the mineral fiber is preferably 500 μm or less, more preferably 100 to 400 μm, and even more preferably 120 to 340 μm.

[0053] Mineral fibers are preferably biopersoluble from the perspective of harmfulness to the human body. The biopersoluble mineral fibers referred to here are mineral fibers that have the characteristic of being partially decomposed and discharged outside the body in a short time even when taken into the human body. Specifically, the chemical composition is such that the total amount of alkali oxides and alkaline earth oxides (the total amount of oxides of sodium, potassium, calcium, magnesium, and barium) is 18% by mass or more, and (a) in the in-vivo durability test by short-term inhalation exposure, the half-life of fibers with a length exceeding 20 μm is less than 10 days, (b) in the in-vivo durability test by short-term intratracheal injection, the half-life of fibers with a length exceeding 20 μm is less than 40 days, (c) there is no significant carcinogenicity in the intraperitoneal administration test, or (d) there are no pathological findings or tumor formations associated with carcinogenicity in the long-term inhalation exposure test (refer to Nota Q (excluding carcinogenicity application) of EU Directive 97 / 69 / EC). Examples of such biodegradable mineral fibers include SiO2-Al2O3-CaO-MgO-FeO(-K2O-Na2O) based fibers, etc., and mineral fibers containing at least two selected from SiO2, Al2O3, CaO, MgO, FeO, K2O, Na2O, etc. in any combination are included.

[0054] When the friction material of the present embodiment contains mineral fibers, the content is not particularly limited, but it is preferably 0.5 to 15% by mass, more preferably 2 to 10% by mass, and even more preferably 3 to 8% by mass with respect to the total amount of the friction material. By setting the content of the mineral fibers within this range, the stability of the friction coefficient, wear resistance, and shear strength tend to be further improved.

[0055] (Metal fiber) By containing metal fibers in the friction material of the present embodiment, the wear resistance and toughness can be improved. Examples of the metal fibers include fibers in the form of simple metals or alloys such as aluminum, iron, zinc, tin, titanium, nickel, magnesium, etc., and fibers mainly composed of metals such as cast iron. Examples of the fibers in the form of alloys (alloy fibers) include copper alloy fibers, iron alloy fibers, aluminum alloy fibers, etc. The metal fibers may be used alone or in combination of two or more kinds. From the viewpoint of improving crack resistance and wear resistance, copper fibers, copper alloy fibers, iron fibers, and iron alloy fibers are preferable, and considering the chirping characteristics, copper fibers and copper alloy fibers are more preferable. As the copper alloy fibers, brass fibers are preferable.

[0056] When the friction material of the present embodiment contains metal fibers, the content is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass based on the total amount of the friction material.

[0057] (Glass fibers) Glass fibers refer to fibers produced by melting and spinning glass. As the glass fibers, those with raw materials such as E glass, C glass, S glass, D glass, etc. can be used. Among these, from the viewpoint of particularly high strength, it is preferable to use glass fibers containing E glass or S glass. Also, for improving the affinity with the binder, glass fibers whose surfaces are treated with aminosilane or epoxysilane, etc. are preferable. Further, from the viewpoint of improving the handleability of the raw materials and the friction material composition, glass fibers aggregated with a urethane resin, an acrylic resin, a phenolic resin, etc. can be used, and the number of aggregated fibers is preferably 50 to 1,000, and more preferably 50 to 500 from the viewpoint of the balance between dispersibility and handleability.

[0058] The average fiber length of the glass fiber is not particularly limited, but is preferably 80 to 6,000 μm, more preferably 150 to 5,000 μm, still more preferably 300 to 5,000 μm, particularly preferably 1,000 to 5,000 μm, and most preferably 2,000 to 4,000 μm. If the average fiber length is equal to or greater than the lower limit value, the strength of the friction material tends to improve, and if it is equal to or less than the upper limit value, the decrease in dispersibility tends to be suppressed. Further, the average fiber diameter of the glass fiber is preferably 5 to 20 μm, more preferably 7 to 15 μm. If the average fiber diameter is equal to or greater than the lower limit value, it is possible to suppress breakage of the glass fiber during mixing of the friction material composition, and if it is equal to or less than the upper limit value, the strength of the friction material tends to improve.

[0059] When the friction material of the present embodiment contains glass fiber, its content is not particularly limited, but is preferably 0.5 to 10% by mass, more preferably 2 to 6% by mass, based on the total amount of the friction material. By setting the content of the glass fiber within this range, toughness can be imparted without impairing the handleability of the friction material composition after mixing, and the strength of the friction material tends to be easily improved. On the other hand, the friction material of the present embodiment may not contain glass fiber.

[0060] When the friction material of the present embodiment contains inorganic fiber, its content is preferably 3 to 35% by mass, more preferably 4 to 30% by mass, still more preferably 6 to 20% by mass, particularly preferably 8 to 15% by mass, based on the total amount of the friction material.

[0061] <Binder> The friction material of the present embodiment preferably further contains a binder. The binder integrates organic fillers, fiber base materials, etc. contained in the friction material and imparts strength to the friction material. One type of binder may be used alone, or two or more types may be used in combination. As the binder, a thermosetting resin usually used for friction materials can be used. Examples of the thermosetting resin include various modified phenol resins such as phenol resins (e.g., straight novolak phenol resins), acrylic rubber-modified phenol resins, silicone-modified phenol resins, cashew-modified phenol resins, epoxy-modified phenol resins, and alkylbenzene-modified phenol resins. Among these, phenol resins (e.g., straight novolak phenol resins) and acrylic rubber-modified phenol resins are preferred, and from the perspective of flexibility, an acrylic rubber-modified phenol resin may be selected.

[0062] When the friction material of the present embodiment contains a binder, its content is preferably 4 to 20% by mass, more preferably 5 to 15% by mass, and even more preferably 6 to 10% by mass with respect to the total amount of the friction material. If the content of the binder is equal to or higher than the lower limit value, the strength reduction of the friction material can be suppressed, and if it is equal to or lower than the upper limit value, the porosity of the friction material decreases, and the deterioration of the squeal characteristics due to the increase in the elastic modulus can be suppressed.

[0063] <Other components> The friction material of the present embodiment may contain other components other than the above components as necessary. Examples of other components include curing agents such as hexamethylenetetramine, hexamethoxymethylol melamine, and resol resins; and curing accelerators such as p-toluenesulfonic acid. When the friction material of the present embodiment contains the above other components, their contents are preferably 5% by mass or less, more preferably 3% by mass or less, respectively, with respect to the total amount of the friction material, and the friction material may not contain other components.

[0064] [Manufacturing method of friction material] Since the friction material of the present embodiment contains components surface-treated with the predetermined amount of rubber component, the manufacturing method thereof includes a step of surface-treating the desired components with the rubber component. Although not particularly limited, the friction material of the present embodiment can be manufactured, for example, by a manufacturing method including the following steps. (i) A step of mixing a rubber component corresponding to 1.2 mass% or more based on the total amount of the friction material (friction material composition) with a desired component and performing surface treatment [hereinafter referred to as surface treatment step (i)]. (ii) A step of preparing a friction material composition by mixing the component surface-treated with the rubber component obtained in the surface treatment step (i) with the component that has not undergone the surface treatment step (i) [hereinafter referred to as mixing step (ii)]. (iii) A step of using the friction material composition obtained in the mixing step (ii) to produce a preform in a molding die, and then molding the preform under conditions of preferably a molding temperature of 130 to 170 °C, preferably a molding pressure of 15 to 50 MPa, and preferably a molding time of 3 to 10 minutes to obtain a molded body [hereinafter referred to as molding step (iii)]. (iv) A step of heat-treating the molded body obtained in the molding step (iii) preferably at 180 to 250 °C to cure the binder in the molded body to obtain a friction material [hereinafter referred to as heat treatment step (iv)]. Hereinafter, each step will be described in order.

[0065] (Surface treatment step (i)) The surface treatment step (i) is a step of mixing a rubber component corresponding to 1.2 mass% or more based on the total amount of the friction material (friction material composition) with a desired component and performing surface treatment. When using an uncrosslinked rubber that is solid at 25 °C, particularly butyl rubber, as the rubber component, since its adhesiveness is extremely high, it is extremely difficult to perform sufficient mixing of butyl rubber with all components. Therefore, it is preferable to limit the components to be surface-treated to some extent. In this step, it is preferable to perform surface treatment by mixing a desired component containing a metal compound with a Mohs hardness of 5 or more and a rubber component. Note that the component is considered to be surface-treated when the rubber component adheres to the surface of the desired component. By mixing only the desired components such as metal compounds with a Mohs hardness of 5 or more with the rubber component and performing surface treatment, it becomes easier to carry out the mixing step (ii) of mixing the surface-treated components with the remaining components that have not been surface-treated. Since the surface treatment step (i) can be carried out, for example, at 0 to 50 °C, it may be carried out at room temperature. Further, there is no particular limitation on the mixing time, and sufficient surface treatment can be performed, for example, by mixing for 5 to 30 minutes. The surface treatment step (i) can be carried out using a general rubber kneading apparatus. Examples of the rubber kneading apparatus include a pressure kneader, a Banbury mixer, an open roll, etc. In particular, internal mixers (closed kneaders) such as a pressure kneader and a Banbury mixer are preferable because they can sufficiently mix the rubber component and the component to be surface-treated. From the viewpoint of suppressing segregation of the materials, it is preferable to mix the rubber component after previously mixing the component to be surface-treated. In addition, since heat may be generated during mixing of each component in the surface treatment step (i), it is preferable to carry out the step in the absence of the binder so that the reaction between the binder and the rubber component does not proceed.

[0066] (Mixing step (ii)) The mixing step (ii) is a step of preparing a friction material composition by mixing the component surface-treated with the rubber component obtained in the surface treatment step (i) with the component that has not undergone the surface treatment step (i). When mixing each component in the mixing step (ii), as in the case of the surface treatment step (i), it can be carried out using a general rubber kneading apparatus. Examples of the rubber kneading apparatus include a pressure kneader, a Banbury mixer, an open roll, etc. As described above, the binder is preferably used as the "component that has not undergone the surface treatment step (i)" in this step. Since the mixing step (ii) can be carried out, for example, at 0 to 50 °C, it may be carried out at room temperature. Further, there is no particular limitation on the mixing time, and a friction material composition in which each component is sufficiently mixed can be obtained, for example, by mixing for 5 to 30 minutes.

[0067] (Forming step (iii)) Forming step (iii) is a step of producing a preform using the friction material composition obtained in the mixing step (ii) in a molding die, and then molding the preform under conditions of preferably a molding temperature of 130 to 170°C, preferably a molding pressure of 15 to 50 MPa, and preferably a molding time of 3 to 10 minutes to obtain a formed body. The molding temperature is more preferably 140 to 160°C. The molding pressure is more preferably 15 to 45 MPa, and even more preferably 20 to 40 MPa. The molding time is more preferably 3 to 8 minutes.

[0068] (Heat treatment step (iv)) Heat treatment step (iv) is a step of heat-treating the formed body obtained in the forming step (iii) preferably at 180 to 250°C to cure the binder in the formed body and obtain a friction material. If the heat treatment temperature is 180°C or higher, the binder tends to cure sufficiently, and if it is 250°C or lower, the deterioration of the rubber component can be prevented. From the same viewpoint, the heat treatment temperature is more preferably 180 to 230°C. In this step, although not particularly limited, from the viewpoint of suppressing the expansion of the friction material, it is preferable to pressurize the friction material at a low pressure during heat treatment. The friction material thus obtained may be subjected to painting, scorch treatment, polishing treatment, etc. as necessary.

[0069] [Applications of the friction material] The friction material of this embodiment is used, for example, in the following aspects (1) to (3). (1) Configuration of only the friction material. (2) A friction member having a backing metal and the friction material of this embodiment formed on the backing metal to serve as a friction surface. (3) In the configuration of (2) above, a primer layer for the purpose of surface modification to enhance the adhesion effect of the backing metal or an adhesive layer for the purpose of adhering the backing metal and the friction member is further interposed between the backing metal and the friction member. Among these, it is preferable to be used as a friction member having the friction material and the backing metal of this embodiment as in (2) or (3) above. The above backing metal is used to improve the mechanical strength of the friction member, and examples of its material include metals such as iron and stainless steel; fiber-reinforced plastics such as inorganic fiber-reinforced plastics and carbon fiber-reinforced plastics. As the primer layer and the adhesive layer, those usually used for friction members such as brake shoes may be used.

[0070] The friction material of the present embodiment is useful as a friction member such as a disc brake pad and a brake lining. Referring to FIG. 1, a specific embodiment of the friction member using the friction material of the present embodiment will be described. It is composed of a back plate 1, a friction material (also referred to as an upper layer material in the case of FIG. 1) 2, and a lower layer material 3. The friction material (upper layer material) 2 is fixed to the surface 11 (here, the upper surface of the back plate 1) of the back plate 1 where the friction material is disposed via the lower layer material 3. The friction material of the present invention can be used as the "upper layer material" or the "lower layer material", but it is preferably used as the "upper layer material". Here, the "upper layer material" is the friction material that becomes the friction surface of the friction member, and the "lower layer material" is a layer provided between the friction material that becomes the friction surface of the friction member and the backing metal, for the purpose of improving the shear strength and crack resistance near the adhesive portion between the friction material and the backing metal.

[0071] The friction material of the present embodiment is suitable as a friction material such as a disc brake pad and a brake lining for automobiles and the like. Further, the friction material of the present embodiment can also be used as a friction material such as a clutch facing, an electromagnetic brake, and a holding brake by performing processes such as molding, processing, and attaching to a target shape.

[0072] [Friction Material Composition] The friction material composition according to the present embodiment is a friction material composition containing 30% by mass or more of a metal compound having a Mohs hardness of 5 or more and containing a component surface-treated with a rubber component of 1.2% by mass or more based on the total amount of the friction material composition. The types of the respective components contained in the friction material composition of the present embodiment and its manufacturing method are the same as those described for the friction material of the present embodiment, and all of their preferred embodiments are also the same. Note that the preferred range of the content ratio of each component in the friction material composition is the same as the preferred range described for the friction material of the present embodiment, but the reference for the content ratio is "the total amount of the friction material composition". Furthermore, the present invention also provides a friction material containing the friction material composition of the present embodiment. The friction material containing the friction material composition of the present embodiment can be manufactured with reference to the manufacturing method of the friction material of the present embodiment and the manufacturing method described in the examples described later.

[0073] [Vehicle] The present invention also provides a vehicle equipped with the friction member of the present embodiment. For example, vehicles in which the friction member of the present invention is used for a disc brake pad, a brake lining, a clutch facing, an electromagnetic brake, a holding brake, etc. can be mentioned. Examples of vehicles include various automobiles including four-wheel vehicles and two-wheel vehicles such as large-sized automobiles, medium-sized automobiles, ordinary automobiles, large-sized special automobiles, small-sized special automobiles, large-sized two-wheel motorcycles, and ordinary two-wheel motorcycles. [Examples]

[0074] Hereinafter, the friction material and the friction material composition of the present embodiment will be described in more detail with reference to examples, but the present invention is not limited to these in any way.

[0075] [Examples 1 to 6 and Comparative Examples 1 and 3] [Production of Disc Brake Pad] Each component shown in Table 1 was used in each blending amount, and each friction material composition was obtained according to the following steps. (Surface Treatment Step (i)) Among the components described in Table 1, the cashew particles and the inorganic filler were kneaded with chlorinated butyl rubber (manufactured by JSR Corporation, trade name: CHLOROBUTYL1066) at room temperature for 30 minutes using a pressure kneader to perform surface treatment on each component. (Mixing Step (ii)) Next, the component surface-treated with the rubber component obtained in the above surface treatment step (i) and the remaining untreated components (binder and fiber base material) were mixed and dry-mixed for 9 minutes using a mixer to obtain a friction material composition.

[0076] (Forming step (iii)) Using the friction material composition obtained in the above mixing step (ii), a preform was produced by preforming at room temperature. Subsequently, a backing plate (made of iron) was set in a mold, the preform was put into the mold, and heat and pressure molding was performed at 150 °C and 20 MPa for 5 minutes to produce a molded body. (Heat treatment step (iv)) The molded body obtained in the above forming step (iii) was heat-treated in an electric furnace at 225 °C for 4 hours to cure the binder and obtain a friction material. The surface was polished using a rotary polishing machine, and a scorch treatment at 500 °C was performed to obtain a disc brake pad (thickness of the friction material; 11 mm, projected area of the friction material; 65 cm 2 ) was obtained.

[0077] <Comparative Example 2> [Production of Disc Brake Pad] All the components in Table 1 were mixed and dry-mixed for 9 minutes using a mixer to obtain a friction material composition, and a preform was produced by preforming at room temperature. Next, a backing plate (made of iron) was set in a mold, the preform was put into the mold, and heat and pressure molding was performed at 150 °C and 20 MPa for 5 minutes to produce a molded body. The molded body thus obtained was heat-treated in an electric furnace at 225 °C for 5 hours to cure the binder and obtain a friction material. The surface was polished using a rotary polishing machine, and a scorch treatment at 500 °C was performed to obtain a disc brake pad (thickness of the friction material; 11 mm, projected area of the friction material; 65 cm 2 ) was obtained.

[0078] Details of the various materials used in each example and each comparative example are as follows. Also, the various materials used in the examples and comparative examples were the same. [Binder] · Phenolic resin

[0079] [Fiber substrate] - Organic fiber - · Aramid fiber - Inorganic fiber - · Mineral fiber · Brass fiber (metal fiber)

[0080] [Organic filler] · Cashew particle · Chlorinated butyl rubber (for surface treatment)

[0081] [Inorganic filler] · Titanate A: Potassium titanate · Titanate B: Lithium potassium titanate · Calcium hydroxide · Mica · Barium sulfate · Graphite (lubricant) · Coke (lubricant) · Tin sulfide (lubricant)

[0082] [Metal powder] · Tin powder

[0083] [Metal compound with Mohs hardness of 5 or more] · Zirconia: Mohs hardness 7 · Zirconium silicate: Mohs hardness 7.5 · γ - Alumina: Mohs hardness 5 - 6 · Iron disulfide: Mohs hardness 6 - 6.5

[0084] [Evaluation test] For the disc brake pads obtained in each example, the following performance evaluations were carried out using a brake dynamometer tester. In the performance evaluation test, a general pin - slide type collet caliper and a ventilated disc rotor (FC250 (gray cast iron)) were used.

[0085] (1. Evaluation of the average coefficient of friction (μ) at 100 - 300 °C) Vehicle speed 60 km / h, deceleration 3.0 m / s 2, braking was performed 500 times at each of the braking temperatures of 100°C, 150°C, 200°C, 250°C, and 300°C, and the average friction coefficient was determined. Evaluation was carried out according to the following criteria. It is preferably B or higher. A (excellent): μ is 0.45 or more B (good): μ is 0.40 or more and less than 0.45 C (poor): μ is 0.35 or more and less than 0.40 D (unsuitable): μ is less than 0.35

[0086] (2. Evaluation of the frequency of occurrence of noise) Vehicle speeds of 20 km / h, 40 km / h, 60 km / h, deceleration 1.0 m / s 2 , 2.0 m / s 2 , 3.0 m / s 2 , 4.0 m / s 2 , a matrix of conditions of braking temperatures of 50°C, 100°C, 150°C, 200°C, 250°C, and 300°C was created, and the number of occurrences of noise under the matrix conditions was counted in a total of 3 sections: (1) before heat treatment, (2) after heat treatment at 350°C, and (3) after heat treatment at 400°C. The number of occurrences of noise relative to the total number of brakings was defined as the frequency of occurrence of noise, and evaluation was carried out according to the following criteria. It is preferably B or higher. A (excellent): No occurrence B (good): 0.1% or more and less than 1.0% C (poor): 1.0% or more and less than 2.0% D (unsuitable): 2.0% or more

[0087]

Table 1

[0088] In Examples 1 to 6, the effectiveness characteristics and the noise characteristics are compatible at a high level. On the other hand, in Comparative Example 1 where the content of the abrasive having a Mohs hardness of 5 or more was less than 30% by mass, the average coefficient of friction was insufficient. Even when the content of the abrasive having a Mohs hardness of 5 or more was 30% by mass or more, in Comparative Example 2 which did not contain a component surface-treated with a rubber component, and in Comparative Example 3 which contained a component surface-treated with a rubber component of less than 1.2% by mass, the squeal characteristics could not be brought to a high level.

Industrial Applicability

[0089] Since the friction material, friction material composition, and friction member of the present invention achieve both high braking performance and high squeal characteristics, they are suitable for vehicle applications such as various automobiles.

Explanation of Reference Numerals

[0090] 1 Back plate 11 Surface on which the friction material of the back plate is disposed 12 Other surface of the back plate 2 Friction material (top sheet) 3 Bottom sheet

Claims

1. A friction member having a friction material and a backing plate, wherein the friction material contains 30% by mass or more of a metal compound having a Mohs hardness of 5 or more, and contains a component surface-treated with a rubber component of 1.2% by mass or more based on the total amount of the friction material, and the rubber component is an uncrosslinked rubber that is solid at 25°C, a friction member, wherein the component surface-treated with the rubber component contains an inorganic filler (including the metal compound having a Mohs hardness of 5 or more) surface-treated with a rubber component of 1.2 to 13% by mass based on the total amount of the friction material.

2. The friction member according to claim 1, wherein the component surface-treated with the rubber component is a component surface-treated with a rubber component of 1.2 to 12% by mass based on the total amount of the friction material.

3. The friction member according to claim 1 or 2, wherein the rubber component is an uncrosslinked rubber that is solid at 25°C.

4. The friction member according to any one of claims 1 to 3, wherein the rubber component is at least one selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, ethylene-propylene-diene rubber, and fluororubber.

5. The friction member according to any one of claims 1 to 4, wherein the rubber component is at least one selected from the group consisting of acrylonitrile-butadiene rubber, butyl rubber, and chlorinated butyl rubber.

6. The friction member according to any one of claims 1 to 5, wherein the component surface-treated with the rubber component contains the metal compound having a Mohs hardness of 5 or more surface-treated with the rubber component.

7. The friction member according to any one of claims 1 to 6, wherein the metal compound having a Mohs hardness of 5 or more contains at least one selected from the group consisting of iron trioxide, alumina, zirconia, zirconium silicate, mullite, magnesium oxide, and titanium oxide.

8. The friction member according to any one of claims 1 to 7, wherein the friction material contains at least one selected from the group consisting of an organic filler, a fiber base material, and a binder.

9. The friction member according to any one of claims 1 to 8, wherein the friction material further contains a titanate.

10. The friction member according to claim 9, wherein the titanate is at least one selected from the group consisting of potassium titanate, lithium potassium titanate, magnesium potassium titanate, and sodium titanate.

11. The friction member according to any one of claims 1 to 10, wherein the average coefficient of friction of the friction material at 100 to 300 °C is 0.40 or more.

12. A vehicle equipped with the friction member according to any one of claims 1 to 11.

13. Containing 30% by mass or more of a metal compound with a Mohs hardness of 5 or more, and containing a component surface-treated with a rubber component of 1.2% by mass or more based on the total amount of the friction material composition, the rubber component being an uncrosslinked rubber that is solid at 25 °C. The friction material composition, wherein the component surface-treated with the rubber component contains an inorganic filler (including the metal compound with a Mohs hardness of 5 or more) surface-treated with a rubber component of 1.2 to 13% by mass based on the total amount of the friction material.

14. The friction material composition according to claim 13, wherein the component surface-treated with the rubber component is a component surface-treated with a rubber component of 1.2 to 12% by mass based on the total amount of the friction material composition.

15. The friction material composition according to claim 13 or 14, wherein the rubber component is an uncrosslinked rubber that is solid at 25 °C.

16. The friction material composition according to any one of claims 13 to 15, wherein the rubber component is at least one selected from the group consisting of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, chlorinated butyl rubber, ethylene-propylene-diene rubber, and fluororubber.

17. The friction material composition according to any one of claims 13 to 16, wherein the rubber component is at least one selected from the group consisting of acrylonitrile-butadiene rubber, butyl rubber, and chlorinated butyl rubber.

18. The friction material composition according to any one of claims 13 to 17, wherein the component surface-treated with the rubber component contains the metal compound with a Mohs hardness of 5 or more surface-treated with the rubber component.

19. The friction material composition according to any one of claims 13 to 18, wherein the metal compound with a Mohs hardness of 5 or more contains at least one selected from the group consisting of iron trioxide, alumina, zirconia, zirconium silicate, mullite, magnesium oxide, and titanium oxide.

20. The friction material composition according to any one of claims 13 to 19, containing at least one selected from the group consisting of an organic filler, a fiber base material, and a binder.

21. The friction material composition according to any one of claims 13 to 20, further containing a titanate.

22.

23. The friction material composition according to claim 21, wherein the titanate is at least one selected from the group consisting of potassium titanate, lithium potassium titanate, magnesium potassium titanate, and sodium titanate.

24.

25. A friction material comprising the friction material composition according to any one of claims 13 to 22.

26.

27. A vehicle equipped with the friction material according to claim 23.

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