JP2023080799A - Friction material composition and friction material - Google Patents

Abstract

To provide a friction material effective at a time of high-speed brake in a high temperature region and high in wear resistance and free from defect of a friction material, furthermore, low in rotor polishing property during running in a non-brake state in a usual temperature region.SOLUTION: A friction material composition is a friction material composition in which a content of copper in the friction material composition is less than 0.5 mass% as a copper element, and contains an inorganic filler (A) made of boehmite and another inorganic filler different from the boehmite and has a decomposition temperature of 600°C or higher and a Mohs hardness of 5 or lower, wherein a content of the boehmite in the friction material composition is 1 mass% or more and 24 mass% or less and a content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition is 1 mass% or more and 25 mass% or less.SELECTED DRAWING: None

Description

The present invention relates to friction material compositions and friction materials.

Friction materials are used for disc brake pads and brake shoes of braking devices such as disc brakes and drum brakes.

Patent Document 1 discloses that a friction material containing an alumina hydrate represented by Al ₂ O ₃ ·nH ₂ O can suppress the decomposition of organic materials even in a higher temperature range such as 500 ° C. or higher. is described.

In Patent Document 2, 2 to 7% by volume of calcium oxide and/or calcium hydroxide is used in the total composition as the friction modifier component, and further, zeolite, activated clay, activated alumina, silica gel, A friction material containing 1 to 20% by volume of one or more selected from the group consisting of powdered, granular or fibrous activated carbon and sintered porous material in the total composition has stable friction coefficient and low frequency noise. It is described to be excellent in reduction.

Patent Literature 3 describes that a friction material containing scaly boehmite as a friction modifier has excellent friction and wear characteristics even at high temperatures, as well as excellent productivity and workability.

Japanese Patent Application Laid-Open No. 2009-221400 JP-A-2000-234086 Japanese Patent Application Laid-Open No. 2000-240702

However, the friction materials of the prior art as described above are (i) excellent in effectiveness and wear resistance during high-speed braking in a high-temperature range, (ii) less pad chipping during high-speed braking in a high-temperature range, and (iii) ) low rotor grindability during non-braking running in the normal temperature range. Specifically, the techniques described in Patent Documents 1 and 3 are insufficient in countermeasures against pad chipping during high-speed braking in a temperature range of 600° C. or higher. Since the friction material described in Patent Document 2 contains activated alumina, it absorbs a large amount of moisture, resulting in low rust resistance and low pad strength. In addition, since it contains activated alumina with a Mohs hardness of 6, the friction material described in Patent Document 2 has high rotor grindability during running in a non-braking state in a normal temperature range.

One aspect of the present invention is that the effectiveness and wear resistance are high during high-speed braking in a high temperature range, the friction material is less chipped, and the rotor grindability is low during running in a non-braking state in a normal temperature range. The purpose is to provide materials.

As a result of intensive studies to solve the above problems, the present inventors found that boehmite and another inorganic filler different from the boehmite in a composition having a copper content of less than 0.5% by mass as copper element A friction material containing a predetermined amount of an inorganic filler (A) having a decomposition temperature of 600 ° C. or higher and a Mohs hardness of 5 or less and having a particle size of 1 μm or less is the above-mentioned (i) to (iii) It was discovered for the first time that it has excellent performance in all the characteristics of the above, and the present invention was completed. That is, the friction material composition according to one aspect of the present invention is a friction material composition in which the content of copper in the friction material composition is less than 0.5% by mass as a copper element, and boehmite and the boehmite is another inorganic filler that is different and has a decomposition temperature of 600° C. or higher and a Mohs hardness of 5 or lower, and the content of the boehmite in the friction material composition is 1% by mass or more and 24% by mass or less, and the content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition is 1% by mass or more and 25% by mass or less. be.

According to one aspect of the present invention, although the copper content is less than 0.5% by mass as a copper element, the effectiveness and wear resistance during high-speed braking in a temperature range of 600 ° C. or higher are high, and the friction material is It is possible to provide a friction material that is less chipped and has low rotor grindability during running in a non-braking state in a normal temperature range.

FIG. 2 is a front view of a disc brake that schematically shows the DTV generation mechanism; FIG. 4 is a front view of a single disk rotor in which DTV occurs;

<1. Friction Material Composition>
A friction material composition according to one aspect of the present invention is a friction material composition in which the content of copper in the friction material composition is less than 0.5% by mass as a copper element, and boehmite is different from the boehmite. and an inorganic filler (A) which is another inorganic filler and has a decomposition temperature of 600° C. or higher and a Mohs hardness of 5 or lower, and the content of the boehmite in the friction material composition is 1 mass. % and 24% by mass or less, and the content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition is 1% by mass or more and 25% by mass or less. The friction material composition of this aspect is intended to be a blend of friction material raw materials containing the above-described components. The friction material composition of this aspect can be used to mold a friction material to be described later.

〔feature〕
The friction material composition of this aspect is environmentally friendly because the content of copper in the friction material composition is less than 0.5% by mass as copper element. Furthermore, boehmite and another inorganic filler different from the boehmite, the inorganic filler (A) having a decomposition temperature of 600° C. or more and a Mohs hardness of 5 or less and having a particle size of 1 μm or less are provided. Since it contains a fixed amount, even in a composition with a copper content of less than 0.5% by mass as a copper element, the effectiveness and wear resistance are high during high-speed braking in a temperature range of 600 ° C. or higher, and the friction material does not chip. Furthermore, it is possible to provide a friction material with low rotor grindability during running in a non-braking state in a normal temperature range.

The friction material using the friction material composition of this aspect is excellent in high-speed braking effectiveness and wear resistance in a high temperature range (for example, 600 ° C. or higher, preferably 650 ° C. or higher). It can exhibit excellent performance in vehicles equipped with large batteries, such as hybrid vehicles (HEV). In addition, since the friction material using the friction material composition of this aspect has low rotor grindability during running in a non-braking state in a normal temperature range (for example, 200 ° C. or less), uneven wear of the disk rotor ( The amount of growth of Disk Thickness Variation (DTV) can be kept small. It is known that excessive DTV is one of the causes of brake vibration (see, for example, Japanese Patent Laid-Open No. 2005-273770). Therefore, the disc brake using the friction material using the friction material composition of the present embodiment on the friction surface of the disc brake pad can suppress the amount of growth of DTV during running in the non-braking state in the normal temperature range. Therefore, the excellent effect of reducing the occurrence of brake vibration is exhibited. The growth amount of DTV refers to a value measured by the method described in Examples described later.

[Use]
The friction material composition of this aspect having the characteristics described above is used as a friction material used for the friction surface of disc brake pads for electric vehicles (EV) and hybrid vehicles (HEV) and brake shoes for drum brakes. Therefore, it is particularly useful as a friction material composition. This is because EVs/HEVs are heavier than conventional gasoline vehicles due to their large batteries, and regenerative braking tends to make little contribution to high-speed braking. This is because the temperature of the brake pads or brake shoes tends to rise during high-speed braking, and the frequency of reaching high temperatures increases.

The application of the friction material composition of this embodiment is not particularly limited to EV/HEV, and it is used for friction surfaces such as disc brake pads and drum brake brake shoes used in vehicles in general including motorcycles. It can be suitably used for friction materials.

〔material〕
The raw materials (friction material raw materials) contained in the friction material composition of this embodiment will be described below.

(copper)
A friction material composition according to an aspect of the present invention has a copper content of less than 0.5% by mass as copper element. The friction material composition according to one aspect of the present invention has an extremely low content of copper and copper alloys, which are highly harmful to the environment, and therefore has the effect of providing an environmentally friendly friction material. From the viewpoint of providing an environmentally friendly friction material, the content of copper in the friction material composition is more preferably 0% by mass (copper-free). Copper contained in the friction material composition according to one aspect of the present invention may be derived from copper fibers added as a fiber base material.

(boehmite)
A friction material composition according to an aspect of the present invention contains, as one of inorganic fillers, boehmite in an amount of 1% by mass or more and 24% by mass or less relative to 100% by mass of the friction material composition. Boehmite is also called alumina monohydrate. In the present specification, the category of "boehmite" _includes crystalline boehmite _represented by _the general formula _Al2O3.H2O and general _{formula Al2O3.nH2O} (n exceeds 1 to 3 less than ) and gel-like boehmite with low crystallinity. The former has a boehmite structure as a crystal structure and is usually called boehmite. The latter has a pseudoboehmite structure and is called pseudoboehmite or boehmite gel. Among them, crystalline boehmite represented by Al ₂ O ₃ .H ₂ O having a boehmite structure as a crystal structure is preferable. Boehmite has a Mohs hardness of 3.5-4. Crystalline boehmite and pseudo-boehmite are generally obtained by known production methods such as hydrolysis of aluminum alkoxide such as aluminum isopropoxide, but they may be naturally derived. Crystalline boehmite and pseudo-boehmite can be distinguished by checking powder X-ray diffraction spectra by known methods.

(Action and effect of boehmite)
Boehmite forms a film on the friction surface during high-speed braking in a temperature range of 600° C. or higher. This coating increases the contact area on the friction surface to improve the coefficient of friction (μ), and protects the friction surface to improve wear resistance. As a result, the heat resistance (effectiveness and wear resistance) of the friction material is improved, and chipping of the pad is reduced.

When the content of boehmite in the friction material composition of this embodiment is 1% by mass or more with respect to 100% by mass of the friction material composition, the friction surface is sufficiently protected by the coating of boehmite. Remarkable effects can be obtained in terms of improved heat resistance (efficacy and wear resistance) and less chipping of the pad. Further, when the content of boehmite in the friction material composition of this embodiment is 24% by mass or less with respect to 100% by mass of the friction material composition, pad formability is improved.

Furthermore, as described above, the Mohs hardness of boehmite is 3.5 to 4, and the hardness of the particles is lower than that of alumina (corresponding to Mohs hardness of 9) and activated alumina (corresponding to Mohs hardness of 6). Therefore, by including boehmite in the friction material composition of the present embodiment, the rotor grindability during running in a non-braking state in a normal temperature range can be reduced, and as a result, the occurrence of brake vibration can be reduced. It has the effect of reducing Diaspore is known as an alumina monohydrate having a different crystal form from boehmite. Diaspore has a stronger crystal structure than boehmite and has a Mohs hardness of 6.5-7. From this, it can be said that boehmite is preferable among alumina monohydrates from the viewpoint of lowering rotor grindability during running in a non-braking state in a normal temperature range. Boehmite and diaspore can be distinguished by examining powder X-ray diffraction spectra by known methods.

(Preferred boehmite content)
From the viewpoint of further improving the high-speed braking performance (efficacy and wear resistance) of the friction material in a high-temperature range, the content of boehmite in the friction material composition is 3% by mass with respect to 100% by mass of the friction material composition. % or more and 15 mass % or less.

(Preferred particle size of boehmite)
The particle size of boehmite is not limited, but if the boehmite has an average particle size of 50 μm or less, it is possible to uniformly mix the friction material composition without unevenness during production, and when braking, the boehmite particles form the friction surface. Since it is difficult to fall off from the friction material, it is preferable because the effect of improving the performance (efficacy and wear resistance) of the friction material during high-speed braking in a high temperature range can be stably obtained. Further, from the viewpoint of lowering the rotor grindability during running in a non-braking state in a normal temperature range, it is more preferable that the boehmite has an average particle size of 10 μm or less. Moreover, from the viewpoint of handleability during production of the friction material composition, it is preferable that the boehmite has an average particle size of 1 μm or more. The average particle diameter of boehmite is the volume-based median diameter obtained according to JIS Z 8825 "Particle Size Analysis - Laser Analysis/Scattering Method". When confirming the particle size of boehmite after forming the friction material, the average particle size of the particles corresponding to boehmite is determined from the electron microscope image of the cross section of the friction material according to JIS Z 8827-1 "Particle size analysis - Image analysis method - Part 1 : Static image analysis method” to measure the volume-based particle size distribution and obtain the median diameter.

(Preferred particle shape of boehmite)
Examples of the particle shape of boehmite include scale-like, plate-like, granular, cubic, needle-like, and burr-like shapes. The particle shape of boehmite is not particularly limited, but since scale-like or plate-like boehmite has lubricating properties, the particle shape of boehmite should be granular, Cubic or acicular shapes are preferred. Moreover, from the viewpoint of increasing the density of the pad and reducing chipping of the pad, the boehmite particle shape is more preferably granular or cubic. Note that the cubic shape is one aspect of the granular particle shape.

A particle shape with a low aspect ratio (long diameter/thickness) expressed as the ratio of the long diameter to the thickness of the boehmite particles (for example, an aspect ratio (long diameter/thickness) of less than 4) is called granular or cubic. A particle shape having a high thickness (for example, an aspect ratio (length/thickness) of 4 or more) is referred to as scale-like or plate-like. A particle shape with a high aspect ratio (major axis/thickness) and a high aspect ratio (major axis/minor axis) is referred to as needle-like. A particle shape in which a large number of needle-like pieces are bound together to form a burr shape is referred to as a burr shape.

(Inorganic filler (A) having a particle size of 1 μm or less)
The inorganic filler (A) is an inorganic filler different from boehmite, and refers to any inorganic filler having a decomposition temperature of 600° C. or higher and a Mohs hardness of 5 or lower. The friction material composition according to one aspect of the present invention contains boehmite as one of the inorganic fillers in the above-described predetermined amount, and an inorganic filler having a particle size of 1 μm or less with respect to 100% by mass of the friction material composition. (A) is contained in an amount of 1% by mass or more and 25% by mass or less.

(Action and effect of inorganic filler (A) having a particle size of 1 μm or less)
The particles of the inorganic filler (A) having a particle size of 1 μm or less enter the gaps between the particles having a particle size of more than 1 μm in the friction material composition according to one aspect of the present invention, thereby increasing the filling rate of the friction material. and has a dense structure. As a result, the friction material using the friction material composition of this aspect has a dense structure with few voids even when the binder resin decomposes at 600° C. or higher. In addition, the decomposition temperature of the inorganic filler (A) is 600°C or higher, and the inorganic filler (A) itself is not easily decomposed, so that even during high-speed braking in a temperature range of 600°C or higher, a dense structure with few voids can be maintained. can hold. As a result, the friction surface of the friction material does not collapse easily, and excellent effects such as improved effectiveness and wear resistance are achieved.

The content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition of this embodiment is 1% by mass or more with respect to 100% by mass of the friction material composition, so that the filling rate of the friction material is increased. However, since it has a sufficiently dense structure, the friction surface of the friction material does not easily collapse, and remarkable effects can be obtained in terms of improving effectiveness and wear resistance. In addition, the content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition of this embodiment is 25% by mass or less with respect to 100% by mass of the friction material composition, so that the pad formability is good. becomes.

Furthermore, as described above, the inorganic filler (A) has a Mohs hardness of 5 or less. It is possible to lower the rotor grindability during running in the non-braking state in the temperature range of , and as a result, the brake vibration is reduced.

(Example of inorganic filler (A))
The type of the inorganic filler (A) is not particularly limited as long as it has a decomposition temperature of 600° C. or higher and a Mohs hardness of 5 or lower. Examples of inorganic fillers having a decomposition temperature of 600° C. or higher and a Mohs hardness of 5 or lower include barium sulfate, calcium carbonate, and mica. From the viewpoint of making the friction material more dense, the inorganic filler (A) is preferably barium sulfate or calcium carbonate having a low aspect ratio (length/thickness). The inorganic filler (A) can be used singly or in combination. When a plurality of types of inorganic fillers (A) are used in combination, the content of the inorganic fillers (A) having a particle size of 1 μm or less in the friction material composition of this embodiment is the same as the content of the inorganic fillers (A) having a particle size of 1 μm or less. It is the total amount of material (A). Boehmite has a Mohs hardness of 5 or less, but has a decomposition temperature of about 500° C. Therefore, the inorganic filler (A) is an inorganic filler different from boehmite.

(Decomposition temperature of inorganic filler (A))
The "decomposition temperature" described in this specification refers to the temperature at which weight loss starts, obtained by thermogravimetry (TG) measurement according to JIS K 0129 "General Rules for Thermal Analysis". The temperature at which the weight starts to decrease is the lowest temperature in the temperature range at which the weight corresponding to the molecule desorbed by heating decreases.

From the viewpoint of enhancing the effect at high temperatures, the inorganic filler (A) preferably has a decomposition temperature of 650° C. or higher, more preferably 700° C. or higher.

(Mohs hardness of inorganic filler (A))
The “Mohs hardness” described herein means a modified Mohs hardness represented by 15 levels of values from 1 to 15. Modified Mohs hardness can be measured according to a known measuring method.

From the viewpoint of DTV growth, the inorganic filler (A) preferably has a Mohs hardness of 4.5 or less, more preferably 4 or less.

(Particle size of inorganic filler (A))
The friction material composition of this aspect may contain the inorganic filler (A) having a particle size of 1 μm or less in the above-described predetermined amount, and the inorganic filler having a particle size of 1 μm or less within a range that does not impair the effects of the present invention. An inorganic filler (A) having a particle size larger than 1 μm may be contained together with the filler (A). The upper limit of the particle size of the inorganic filler (A) having a particle size of more than 1 μm is not particularly limited, and the particle size of inorganic fillers commonly employed in the relevant technical field can be preferably applied.

The amount of the inorganic filler (A) having a particle size of 1 μm or less contained in the friction material composition of this embodiment may be obtained by the following method.
1. The volume-based particle size distribution of the inorganic filler (A) is measured according to JIS Z 8825 "Particle size analysis-laser analysis/scattering method".
2. From the particle size distribution of the obtained inorganic filler (A), an integrated value of particles of 1 μm or less is obtained (unit: %).
3. The particle integrated value obtained in the preceding item "2" indicates the proportion of particles of 1 µm or less contained in the inorganic filler (A). Therefore, the content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material can be calculated by the following formula.
Content of inorganic filler (A) in friction material (% by mass) × Cumulative value of particles of 1 μm or less (%)/100
A similar method can be used to measure the amount of the inorganic filler (A) having a particle size larger than 1 μm contained in the friction material composition of the present embodiment.

(Preferred content of inorganic filler (A) having a particle size of 1 μm or less)
From the viewpoint of further improving the high-speed braking performance (effectiveness and wear resistance) of the friction material in a high temperature range, the content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition is It is preferably 1% by mass or more and 20% by mass or less with respect to 100% by mass of the composition.

(Surface treatment of boehmite and inorganic filler (A))
The boehmite and the inorganic filler (A) may be used after the surfaces of the particles have been surface-treated. By using the surface-treated boehmite and the inorganic filler (A), effects such as improved compatibility with the binder resin and improved water resistance are exhibited.

As the surface treatment method, a known method can be used. For example, the particles of boehmite and the inorganic filler (A) are treated with a coupling agent, phosphoric acid, or the like; A method of forming an inorganic layer of silica, alumina or the like on the surface of particles of the material (A);

(other ingredients)
In addition to the components described above, the friction material composition of this embodiment contains a fiber base material, a binder, an organic filler, and boehmite and an inorganic filler different from the inorganic filler (A) as friction material raw materials. do.

(fiber base material)
Examples of the fiber base material include organic fibers, inorganic fibers, and metal fibers. These fibers may be natural fibers or artificially synthesized synthetic fibers. Examples of organic fibers include aromatic polyamide fibers (aramid fibers), acrylic fibers, cellulose fibers, and carbon fibers. Examples of inorganic fibers include rock wool and glass fibers. Examples of metal fibers include fibers composed of single metals such as steel, stainless steel, aluminum, zinc and tin, and fibers composed of metal alloys thereof. A fiber base material can be used individually by 1 type or in combination of multiple types. The content of the fiber base material in the friction material composition is not particularly limited, and may be a content commonly employed in the technical field.

(Binder)
The binding material has a function of binding the friction material raw materials in the friction material composition. The binder is not particularly limited as long as it can exhibit the above performance, and binders known in the art can be preferably used. Specific examples of binders include resins such as phenol resins, epoxy resins, melamine resins, and imide resins. The binder can be used singly or in combination. The content of the binder in the friction material composition is not particularly limited, and may be the content commonly employed in the technical field. Further, the binder may contain modified components such as silicon rubber, acrylic rubber, cashew oil and the like.

(organic filler)
The organic filler has a function as a friction modifier for improving wear resistance and the like. The organic filler is not particularly limited as long as it can exhibit the above performance, and organic fillers known in the art can be preferably used. Specific examples of organic fillers include cashew dust, rubber powder, tire powder, fluororesin, melamine cyanurate, and polyethylene resin. An organic filler can be used individually by 1 type or in combination of multiple types. Moreover, the surface of the organic filler may be coated with phosphoric acid or fluororesin. The content of the organic filler in the friction material composition is not particularly limited, and may be the content commonly employed in the technical field.

(Another inorganic filler different from boehmite and inorganic filler (A))
The friction material composition of this aspect may contain an inorganic filler other than boehmite and the inorganic filler (A) within a range that does not impair the effects of the present invention. As another inorganic filler different from boehmite and the inorganic filler (A), inorganic substances known in the art can be preferably used, for example, zirconium oxide, iron oxide (ferrous oxide, ferric oxide iron, etc.), silicate compounds such as titanates, calcium hydroxide, calcium silicate and zirconium silicate, and carbonate compounds such as magnesium carbonate and potassium carbonate. Examples of titanates include alkali metal titanates, alkali metal titanates/group II salts, and specific examples include potassium titanate, sodium titanate, lithium titanate, and lithium potassium titanate. , magnesium potassium titanate, and the like. These inorganic fillers can be used singly or in combination. The content of the inorganic filler different from the boehmite and the inorganic filler (A) is not particularly limited, and the total content of the inorganic filler combined with the boehmite and the inorganic filler (A) is adopted in the art. The content of the inorganic filler may be appropriately adjusted so as to fall within the range of the content of the inorganic filler.

By containing zirconium oxide or titanate as another inorganic filler different from boehmite and the inorganic filler (A), a film is formed on the friction surface during high-speed braking in a temperature range of 600° C. or higher. It is preferable because it becomes stronger and the heat resistance (effectiveness and wear resistance) of the friction material is further improved. In this case, the upper limit of the content of zirconium oxide and titanate is not particularly limited, and the total content of inorganic fillers combined with boehmite and inorganic filler (A) is the amount of inorganic fillers employed in the art. The content may be adjusted as appropriate. The higher the content of zirconium oxide and titanate, the more improved the heat resistance of the above-described friction material, which is preferable.

In addition, the particle size of the inorganic filler other than boehmite and the inorganic filler (A) is not particularly limited, and an inorganic substance having an average particle size commonly employed in the technical field can be preferably used. As described above, the particles of the inorganic filler (A) having a particle size of 1 μm or less enter the gaps between the particles having a particle size of more than 1 μm, thereby increasing the filling rate of the friction material and forming a dense structure. Considering that the boehmite and another inorganic filler different from the inorganic filler (A) preferably contain particles with a particle size greater than 1 μm, mostly particles with a particle size greater than 1 μm, particles More preferably, it does not substantially contain particles with a particle size of 1 μm or less. “Substantially free of particles with a particle size of 1 μm or less” means that the content of particles with a particle size of 1 μm or less is 20% by mass or less, 10% by mass or less, preferably 5% by mass or less, or more. It means that it is preferably 2% by mass or less, more preferably 1% by mass or less. The content of inorganic fillers having a particle size larger than 1 μm in the friction material composition of this embodiment is the total content of inorganic fillers combined with boehmite and inorganic fillers (A), which is adopted in the art. The content of the inorganic filler may be appropriately adjusted so as to fall within the range.

(lubricant)
The friction material composition of this aspect may further contain a lubricant within a range that does not impair the effects of the present invention. Lubricants are not particularly limited, and lubricants known in the art can be preferably used. Specific examples of lubricants include coke, graphite, carbon black, graphite, and metal sulfides. Examples of metal sulfides include tin sulfide, antimony trisulfide, molybdenum disulfide, bismuth sulfide, iron sulfide, zinc sulfide, and tungsten sulfide. These lubricants can be used singly or in combination. The content of the lubricant is not particularly limited, and may be the content commonly employed in the technical field.

(Method for producing friction material composition)
The friction material composition of this aspect can be produced by a production method including a mixing step of blending the friction material raw materials described above and mixing them. From the viewpoint of uniformly mixing the friction material raw materials, the mixing step is preferably a step of mixing powdery friction material raw materials. The mixing method and mixing conditions in the mixing step are not particularly limited as long as the friction material raw materials can be uniformly mixed, and methods known in the art can be adopted. For example, the friction material raw materials may be mixed at room temperature for about 10 minutes using a known mixer such as a Fenchel mixer or Loedige mixer. In the mixing step, the mixture of friction material raw materials may be mixed while being cooled by a known cooling method so that the temperature of the friction material raw materials during mixing does not rise.

<2. Friction Material>
A friction material according to one aspect of the present invention is obtained by molding the friction material composition according to one aspect of the present invention. The effect, application, etc. of the friction material of this aspect are as described for one aspect of the friction material composition of the present invention, and will not be repeated here.

(Method for manufacturing friction material)
The friction material of this aspect can be manufactured by a manufacturing method including a molding step of molding the friction material composition according to one aspect of the present invention. The molding method and molding conditions in the molding step are not particularly limited as long as one aspect of the friction material composition of the present invention can be molded into a predetermined shape, and methods known in the art can be adopted. For example, one aspect of the friction material composition of the present invention can be molded by pressing or the like. As the molding method by press, there is a hot press method in which one embodiment of the friction material composition of the present invention is heated and compacted to be molded, and one embodiment of the friction material composition of the present invention is compacted at room temperature without heating. Any cold pressing method for molding can be suitably employed. When molding by the hot press method, for example, the molding temperature is 140 ° C. or higher and 200 ° C. or lower (preferably 160 ° C.), the molding pressure is 10 MPa or higher and 40 MPa or lower (preferably 20 MPa), and the molding time is 3 minutes. As described above, one aspect of the friction material composition of the present invention can be molded into a friction material by setting the time to 15 minutes or less (preferably 10 minutes). When molding by a normal temperature press method, for example, the molding pressure is 50 MPa or more and 200 MPa or less (preferably 100 MPa), and the molding time is 5 seconds or more and 60 seconds or less (preferably 15 seconds). One aspect of the friction material composition can be molded into a friction material. Furthermore, if necessary, a polishing step may be performed to polish the surface of the friction material to form a friction surface.

<3. Friction member>
A friction member using the friction material according to one aspect of the present invention as a friction surface is also included in the scope of the present invention. The friction member may have a configuration that includes only one aspect of the friction material of the present invention, or a configuration that integrates a plate-like member such as a metal plate as a back plate with one aspect of the friction material of the present invention. . The effect, application, etc. of the friction member of this aspect are as described for one aspect of the friction material composition of the present invention, and will not be repeated here.

In the case where the friction member of this aspect is configured such that the plate-like member and the one aspect of the friction material of the present invention are integrated, the one aspect of the friction material of the present invention and the plate-like member are clamped, and then The one aspect of the friction material of the present invention and the plate member can be adhered by heat treatment. The clamping conditions are not particularly limited, but are, for example, 180° C., 1 MPa, and 10 minutes. The conditions for the heat treatment after the clamping process are not particularly limited, but are, for example, 150° C. or more and 250° C. or less, 5 minutes or more and 180 minutes or less, preferably 230° C. and 3 hours.

〔summary〕
A friction material composition according to aspect 1 of the present invention is a friction material composition in which the content of copper in the friction material composition is less than 0.5% by mass as a copper element, and boehmite is different from the boehmite. and an inorganic filler (A) which is another inorganic filler and has a decomposition temperature of 600° C. or higher and a Mohs hardness of 5 or lower, and the content of the boehmite in the friction material composition is 1 mass. % or more and 24 mass % or less, and the content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition is 1 mass % or more and 25 mass % or less. . According to such a configuration, even though the copper content is less than 0.5% by mass as a copper element, the effectiveness and wear resistance during high-speed braking in the temperature range of 600 ° C. or higher are high, and the friction material is not chipped. It is possible to provide a friction material that has a low rotor grinding performance during running in a non-braking state in a normal temperature range.

In the friction material composition according to aspect 2 of the present invention, in aspect 1, it is preferable that the boehmite has an average particle size of 10 μm or less. According to such a configuration, it is possible to provide a friction material with lower rotor grindability during running in a non-braking state in a normal temperature range.

In the friction material composition according to aspect 3 of the present invention, in aspect 1 or 2, the content of the boehmite in the friction material composition is 3% by mass or more and 15% by mass or less, and the friction The content of the inorganic filler (A) having a particle size of 1 μm or less in the material composition is preferably 1% by mass or more and 20% by mass or less. According to such a configuration, it is possible to provide a friction material with higher effectiveness and wear resistance during high-speed braking in a temperature range of 600° C. or higher.

In the friction material composition according to aspect 4 of the present invention, in any one of aspects 1 to 3, the boehmite is preferably granular boehmite. According to such a configuration, it is possible to increase the denseness of the pad and reduce chipping of the pad.

A friction material according to aspect 5 of the present invention is formed by molding the friction material composition according to any one of aspects 1 to 4 above.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

<Raw material for friction material>
The main friction material raw materials used in the examples and comparative examples are as follows.

Boehmite (Al ₂ O ₃ ·H ₂ O): average particle size 1 μm, 8 μm, and 50 μm; particle shape is granular (aspect ratio (length/thickness) 1.5)
・Activated alumina: average particle size 8 μm
- Barium sulfate (inorganic filler (A)): Two kinds of barium sulfate containing no particles with a particle size exceeding 1 µm and barium sulfate containing no particles with a particle size of 1 µm or less were used.

- Calcium carbonate (inorganic filler (A)): Two types of calcium carbonate containing no particles having a particle size of 1 µm or less and calcium carbonate containing no particles having a particle size of 1 µm or less were used in the same manner as barium sulfate.

• Aluminum hydroxide and alumina (Al ₂ O ₃ ): Aluminum hydroxide and alumina were used that did not contain particles with a particle size greater than 1 µm.

• Zirconium oxide, mica (inorganic filler (A)), iron oxide (composition: Fe ₂ O ₃ ), and calcium hydroxide: raw materials containing no particles with a particle size of 1 μm or less were used.

Raw materials other than the friction raw materials described above were those commonly used in this technical field.

Table 1 summarizes the physical properties of the following inorganic fillers used in Examples and Comparative Examples as inorganic fillers having a particle size of 1 μm or less.

これらの無機充填材の粒径が１μｍよりも大きい粒子も、粒径１μｍ以下の粒子と物性は同じである。

Particles of these inorganic fillers having a particle size larger than 1 μm have the same physical properties as particles having a particle size of 1 μm or less.

[Example 1]
<Production of brake pads>
Each raw material was blended according to the blending ratio shown in Table 2, and mixed at room temperature (20° C.) for about 10 minutes using a Loedige mixer to obtain a friction material composition. In addition, the unit of the compounding amount of each raw material in Table 2 is % by mass in the friction material composition.

Using a molding press, the friction material composition was heated and compacted by a hot press method to obtain a molded article. The molding conditions by the hot press method were as follows:
Molding temperature: 160°C
Molding pressure: 20MPa
Molding time: 10 minutes The surface of the obtained molded article was polished using a polishing machine to form a friction surface, thereby obtaining a friction material. A brake pad of Example 1 was produced using this friction material, and a high temperature test and an evaluation of DTV growth after the test were performed. The brake pad produced in Example 1 had a thickness of the friction material of 12.5 mm and a projected area of the friction material of 55 cm ² .

[Examples 2 to 10]
Brake pads of Examples 2 to 10 were produced in the same manner as in Example 1, except that each raw material was blended according to the blending ratio shown in Table 2.

[Comparative Examples 1 to 10]
Brake pads of Comparative Examples 1 to 10 were produced in the same manner as in Example 1, except that each raw material was blended according to the blending ratio shown in Table 3.

<High temperature test>
An AMS fade test (evaluation conditions published in the German automobile magazine auto motor und sport: vehicle speed 130 km/h, maximum rotor temperature 600°C or higher) was performed, and the brake pads of Examples 1 to 10 and Comparative Examples 1 to 10 were tested as follows. was evaluated. The maximum rotor temperature for each test was 650-670°C.

(Minimum friction coefficient)
The lowest coefficient of friction during the AMS fade test was measured by the following method.

(Method for measuring minimum friction coefficient)
Using the minimum torque during one braking, the coefficient of friction for each braking was calculated according to the formula described in JIS D 0106. The lowest coefficient of friction in the test was taken as the lowest coefficient of friction.

The measurement result of the lowest coefficient of friction was evaluated with a score of 5 grades from A to E according to the criteria shown below.
A: More than 20% improvement relative to Comparative Example 1 B: 10% or more, 20% or less improvement relative to Comparative Example 1 C: Same or equivalent to Comparative Example 1 D: 10 relative to Comparative Example 1 % or more and 20% or less deterioration E: More than 20% deterioration with respect to Comparative Example 1 Here, the minimum friction coefficient of the brake pad to be evaluated is 10% or more with respect to the minimum friction coefficient of the brake pad of Comparative Example 1. When it increased, it was evaluated as "improved", and when the minimum friction coefficient of the brake pad to be evaluated decreased by 10% or more from the minimum friction coefficient of the brake pad of Comparative Example 1, it was evaluated as "worse". If the change in the minimum friction coefficient of the brake pad to be evaluated was less than 10% with respect to the minimum friction coefficient of the brake pad of Comparative Example 1, it was evaluated as the same as or equivalent to Comparative Example 1.

(amount of wear)
The wear amount of the brake pad after the AMS fade test was measured by the following method.

(Method for measuring amount of wear)
JASO C4276. The amount of wear was measured according to the measurement method.

After the test, the amount of pad wear was measured at eight points per brake pad, and the average value was taken as the "amount of pad wear."

The measurement results of the amount of wear were evaluated with a five-level score from A to E according to the criteria shown below.
A: More than 20% improvement relative to Comparative Example 1 B: 10% or more, 20% or less improvement relative to Comparative Example 1 C: Same or equivalent to Comparative Example 1 D: 10 relative to Comparative Example 1 % or more and 20% or less deterioration E: More than 20% deterioration compared to Comparative Example 1 Here, the amount of wear of the brake pad to be evaluated decreased by 10% or more compared to the amount of wear of the brake pad of Comparative Example 1. When the wear amount of the brake pad to be evaluated increased by 10% or more relative to the wear amount of the brake pad of Comparative Example 1, it was evaluated as "worse". If the increase or decrease in the amount of wear of the brake pad to be evaluated was less than 10% of the amount of wear of the brake pad of Comparative Example 1, it was evaluated as the same as or equivalent to Comparative Example 1.

(Presence or absence of chipping)
The appearance of the brake pads after the AMS fade test was visually observed to confirm the presence or absence of cracks in the brake pads.

<Measurement of post-test DTV growth amount (μm)>
Non-uniform wear (hereinafter simply referred to as DTV) is, as schematically shown in FIG. ), the braking friction material 12a of the inner pad 12 and the braking friction material 13a of the outer pad 13 are brought into contact with each friction surface 11a of the disc rotor 11 with a very light surface pressure compared to that during braking. , 11b, and the contact portions are scraped off by the brake friction materials 12a, 13a of the pads 12, 13 and grow. This DTV is generally represented by the difference between the maximum thickness To and the minimum thickness T1 or T2 of the disk rotor 11 shown in FIG.

Using a bench tester, set the initial amount of deflection S of the disk rotor (see FIG. 1) to 100 μm, and rub it 50 times (vehicle speed 65 km / hour → vehicle speed 0 km / hour, deceleration 3.5 m / s ² , pad temperature 90°C before braking), then idle at a vehicle speed of 100 km / hour for 1 hour, braking at a vehicle speed of 100 km / hour → vehicle speed of 60 km / hour, and braking 10 times in succession. A cycle was performed, compared with the initial DTV, and the difference was taken as the post-test DTV growth amount (μm).

The measurement results of the amount of DTV growth after the test were evaluated with a three-level score from A to C according to the criteria shown below.
A: Equivalent to or improved from Comparative Example 1 B: 10% or more, 20% or less worse than Comparative Example 1 C: More than 20% worse than Comparative Example 1 Discs to be evaluated here If the post-test DTV growth amount in the rotor decreased by 10% or more from the post-test DTV growth amount in the disk rotor of Comparative Example 1, it was evaluated as "improved", and the post-test DTV growth amount in the disk rotor to be evaluated was evaluated as "improved". When the amount of DTV growth after the test in the disk rotor of Comparative Example 1 increased by 10% or more, it was evaluated as "deteriorated". If the increase or decrease in the post-test DTV growth amount in the disk rotor to be evaluated was less than 10% with respect to the post-test DTV growth amount in the disk rotor of Comparative Example 1, it was evaluated as the same as or equivalent to Comparative Example 1. If the post-test DTV growth amount score is A, it means that the post-test DTV growth amount can be suppressed to a small amount. I can say there is.

As described above, since DTV may be one of the causes of brake vibration, it can be said that the score of the evaluation result of the measurement result of DTV growth amount after the test represents the likelihood of occurrence of brake vibration. That is, the three graded scores from A to C of the measurement result of the post-test DTV growth express the likelihood of occurrence of the following brake vibration.
A: Equivalent to Comparative Example 1, or less brake vibration than Comparative Example 1.
B: Slightly more brake vibration occurs than in Comparative Example 1.
C: Much more brake vibration occurs than in Comparative Example 1.

<Results>
Tables 2 and 3 show the evaluation results in the high-speed test and the evaluation results in the post-test DTV growth measurement.

表２中の太線で囲った実施例は、実施例の中でも特に高温試験および試験後ＤＴＶ成長量の測定の評価結果が良好であったものである。表２に示すとおり、実施例１～１０のブレーキパッドは、無機充填材として摩擦材組成物中に（ｉ）ベーマイトを１質量％以上、２４質量％以下、および（ｉｉ）粒径が１μｍ以下の無機充填材（Ａ）を１質量％以上、２５質量％以下、含有することにより、比較例１のブレーキパッドと比較して、６００℃以上の温度域での高速制動時に効きおよび耐摩耗性が高く且つ摩擦材の欠けが少なく、さらに、試験後ＤＴＶ成長量が減少することが確認された。

Among the examples, the examples surrounded by a thick line in Table 2 had particularly good evaluation results in the high temperature test and the measurement of the amount of DTV growth after the test. As shown in Table 2, the brake pads of Examples 1 to 10 contained (i) 1% by mass or more and 24% by mass or less of boehmite as an inorganic filler in the friction material composition, and (ii) a particle size of 1 μm or less. By containing 1% by mass or more and 25% by mass or less of the inorganic filler (A) of Comparative Example 1, compared to the brake pad of Comparative Example 1, effectiveness and wear resistance during high-speed braking in a temperature range of 600 ° C. or higher It was confirmed that the DTV growth amount was reduced after the test, and the chipping of the friction material was small.

From the results shown in Comparative Examples 1 to 6, in order to exhibit the effects of high braking effectiveness and wear resistance at high speed braking in a temperature range of 600 ° C. or higher and less chipping of the friction material, the content and grain size of boehmite It was confirmed that both the content of the inorganic filler (A) having a diameter of 1 μm or less and the content of the inorganic filler (A) must be contained in predetermined amounts.

In addition, as shown in Comparative Examples 2, 7 and 8, a predetermined amount of another inorganic filler different from the inorganic filler (A) having a particle size larger than 1 μm or the inorganic filler (A) having a particle size of 1 μm or less Since the desired effect cannot be obtained even if it is contained, the effect of high braking effectiveness and wear resistance at high speed braking in the temperature range of 600 ° C. or higher and less chipping of the friction material requires the particle size It was confirmed that the inorganic filler (A) with a diameter of 1 µm or less must be contained.

Further, as shown in Comparative Example 9, even if a predetermined amount of activated alumina (Al ₂ O ₃ ) is contained instead of boehmite (Al ₂ O ₃ ·H ₂ O), the desired effect cannot be obtained. Boehmite, which is an alumina hydrate, is used to achieve the effects of high braking effectiveness and wear resistance at high speed braking in a temperature range of 600° C. or higher, less chipping of the friction material, and a decrease in the amount of DTV growth after the test. It was confirmed that (Al ₂ O ₃ .H ₂ O) must be included.

From the above results, (i) 1% by mass or more and 24% by mass or less of boehmite and (ii) 1% by mass of an inorganic filler (A) having a particle size of 1 µm or less in the friction material composition as an inorganic filler. As described above, by containing 25% by mass or less, even though the copper content is less than 0.5% by mass as a copper element, the effectiveness and wear resistance during high-speed braking in a temperature range of 600 ° C. or higher are high and It has become clear that it is possible to provide a friction material that is less chipped and has low rotor grindability during running in a non-braking state in a normal temperature range.

INDUSTRIAL APPLICABILITY The friction material composition and the friction material according to one aspect of the present invention can be suitably used as friction members in braking devices for vehicles such as automobiles.

REFERENCE SIGNS LIST 11 disk rotor 12 outer pad 13 inner pad 12a, 13a brake friction material θ rotation angle S amount of rotation

Claims (5)

A friction material composition in which the content of copper in the friction material composition is less than 0.5% by mass as copper element,
boehmite and
an inorganic filler (A) which is another inorganic filler different from the boehmite and has a decomposition temperature of 600° C. or higher and a Mohs hardness of 5 or lower;
The content of the boehmite in the friction material composition is 1% by mass or more and 24% by mass or less, and the content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition is , 1% by mass or more and 25% by mass or less, the friction material composition. 2. The friction material composition according to claim 1, wherein said boehmite has an average particle size of 10 [mu]m or less. The content of the boehmite in the friction material composition is 3% by mass or more and 15% by mass or less, and the content of the inorganic filler (A) having a particle size of 1 μm or less in the friction material composition is , 1% by mass or more and 20% by mass or less, the friction material composition according to claim 1 or 2. The friction material composition according to any one of claims 1 to 3, wherein the boehmite is granular boehmite. A friction material obtained by molding the friction material composition according to any one of claims 1 to 4.

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