Friction material composition and friction material

Abstract

To provide a friction material that exhibits superior squeal suppression, along with superior effectiveness and wear resistance during high-speed braking under high temperature conditions.SOLUTION: A friction material composition according to one embodiment of the present invention contains less than 0.5 mass% of copper in terms of elemental copper. The friction material further contains 9 mass% or more of aramid fibers and 26 mass% or more of a titanate, relative to the total amount of the friction material composition.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Friction materials are used in disc brake pads and brake shoes of braking devices such as disc brakes and drum brakes.

[0003] Patent Document 1 discloses a friction material composition including a fiber base material, a binder, and a friction modifier, wherein the copper content in the friction material composition is 0.5% by mass or less and the friction material composition contains fluoropolymer particles.

[0004] Patent Document 2 discloses a friction material obtained by molding a friction material composition for a disc brake pad, which contains a binder, a fiber base material, an inorganic friction modifier, and an organic friction modifier and does not contain a copper component, wherein the friction material composition contains 0.5 to 6% by weight of spherical amorphous α-alumina particles having an average particle diameter of 100 to 300 μm as the inorganic friction modifier based on the total amount of the friction material composition.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] With the advancement of electrification of automobiles, the quietness of brakes, such as improvement of the squeal performance, has become even more important.

[0007] In addition, as the electrification of automobiles progresses, it becomes necessary to install high-weight batteries. For this reason, the total weight of automobiles tends to increase, and the load applied to the brakes becomes higher than that of conventional vehicles, so an improvement in fade performance is required.

[0008] Furthermore, since regulations are being considered due to the environmental impact of dust (Brake wear Particle Emissions: BPE) emitted from brakes, an improvement in the wear performance of brake pads is also required.

[0009] There is room for improvement in these performances in conventional friction materials.

[0010] An object of one aspect of the present invention is to provide a friction material having excellent squeal performance and excellent effectiveness and wear resistance during high-speed braking in a high-temperature range.

Means for Solving the Problems

[0011] As a result of intensive studies to solve the above problems, the inventors have found for the first time that a friction material containing a specific amount of aramid fiber and titanate in a composition in which the copper content in the friction material composition is less than 0.5% by mass as copper element has excellent squeal performance and excellent effectiveness and wear resistance during high-speed braking in a high-temperature range, and have completed the present invention. That is, a friction material composition according to one aspect of the present invention is a friction material composition in which the copper content in the friction material composition is less than 0.5% by mass as copper element, and is configured to contain 9% by mass or more of aramid fiber and 26% by mass or more of titanate with respect to the total amount of the friction material composition.

Effects of the Invention

[0012] According to one aspect of the present invention, it is possible to provide a friction material having excellent squeal performance and excellent effectiveness and wear resistance during high-speed braking in a high-temperature range while the copper content with a high environmental load is less than 0.5% by mass as copper element.

Modes for Carrying Out the Invention

[0013] Hereinafter, one embodiment of the present invention will be described in detail. Unless otherwise specified in this specification, "A to B" representing a numerical range is intended to mean "A or more and B or less". <1. Friction material composition> The friction material composition according to one embodiment of the present invention is a friction material composition in which the copper content in the friction material composition is less than 0.5% by mass as copper element, and the copper content in the friction material composition is less than 0.5% by mass as copper element. With respect to the total amount of the friction material composition, it contains 9% by mass or more of aramid fiber and 26% by mass or more of titanate. The friction material composition according to one embodiment of the present invention is intended to be a composition obtained by blending a friction material raw material containing the above-mentioned components. The friction material composition according to one embodiment of the present invention can be used for forming the friction material described later.

[0014] Since the copper content in the friction material composition according to one embodiment of the present invention is less than 0.5% by mass as copper element, it is environmentally friendly. Furthermore, because it contains specific amounts of aramid fiber and titanate, it can provide a friction material that has excellent screeching performance, good effectiveness during high-speed braking in the high-temperature range, and excellent wear resistance while the copper content is less than 0.5% by mass as copper element, thus achieving an excellent effect.

[0015] The friction material using the friction material composition according to one embodiment of the present invention has excellent screeching performance, and thus can provide a brake with excellent quietness, achieving an excellent effect. Here, in this specification, the "screeching performance" is a performance evaluated based on the friction coefficient (μ) after cold storage, and can be measured by the screeching performance test described in the examples below. The lower the value of the friction coefficient (μ) after cold storage, the better the screeching performance.

[0016] In addition, the friction material using the friction material composition according to one aspect of the present invention can improve the wear resistance during high-speed braking in a high-temperature range (for example, 640°C), and at the same time achieve an improvement in effectiveness during high-speed braking in the high-temperature range. Further, the improvement in wear resistance during high-speed braking in the high-temperature range means that the strength of the friction material on the friction surface is improved, and thus an improvement in the heat resistance effect of the friction material can also be expected.

[0017] In addition, the friction material using the friction material composition according to one aspect of the present invention is excellent in wear resistance, so that there is little dust released due to wear. As a result, the wheel is less likely to be soiled by dust, and there is an excellent effect that the emissions of PM2.5 and PM10, which have a high environmental load, are small.

[0018] 〔Use〕 The friction material using the friction material composition according to one aspect of the present invention having the above-described characteristics can be applied, for example, as a mating material for a disk brake pad, to a disk rotor made of cast iron, stainless steel, aluminum, carbon ceramics, etc. Further, it is also suitable for a disk rotor having a surface treatment such as a soft nitriding treatment or a treatment of coating tungsten carbide, titanium carbide, etc.

[0019] In addition, the friction material using the friction material composition according to one aspect of the present invention exhibits the above-described effects regardless of the means for generating braking force. For example, it is a hydraulic brake, an air brake, a brake by wire (BBW), an electro-mechanical brake (EMB), etc.

[0020] In addition, the friction material using the friction material composition according to one aspect of the present invention is also suitable, for example, in a vehicle in which the load due to friction braking is relatively small, such as a vehicle equipped with a regenerative brake.

[0021] Moreover, the friction material using the friction material composition according to one aspect of the present invention is also useful as a friction material used, for example, on the friction surfaces of disc brake pads and drum brake brake shoes for electric vehicles (EVs) and hybrid vehicles (HEVs). This is because EVs / HEVs tend to be heavier than conventional gasoline vehicles due to the installation of large batteries, and the contribution of regenerative brakes and regenerative cooperative brakes is low during high-speed braking. Compared with conventional gasoline vehicles, the temperature of the brake pads or brake shoes tends to rise during high-speed braking in the high-temperature range, and the frequency of reaching high temperatures increases.

[0022] The use of the friction material composition according to one aspect of the present invention is not limited to only the uses exemplified above. For example, it can also be suitably used as a friction material used on the friction surfaces of disc brake pads, drum brake brake shoes, etc., adopted in all vehicles including two-wheeled vehicles.

[0023] 〔Raw materials〕 Hereinafter, the raw materials (friction material raw materials) contained in the friction material composition according to one aspect of the present invention will be described.

[0024] (Copper) In the friction material composition according to one aspect of the present invention, the content of copper in the friction material composition is less than 0.5% by mass as copper element. Since the friction material composition according to one aspect of the present invention contains very little copper and copper alloys with high environmental harmfulness, it has the effect of providing an environmentally friendly friction material. From the viewpoint of providing a more environmentally friendly friction material, the content of copper in the friction material composition is more preferably 0% by mass (copper-free). The 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.

[0025] (Aramid fiber) The friction material composition according to one aspect of the present invention contains 9% by mass or more of aramid fiber with respect to 100% by mass of the friction material composition.

[0026] Aramid fiber refers to the fiber of wholly aromatic polyamide and is also called aromatic polyamide fiber. The type of wholly aromatic polyamide constituting the aramid fiber is not particularly limited. The aramid fiber contained in the friction material composition according to one aspect of the present invention may be a meta-type aramid fiber having a meta-type structure or a para-type aramid fiber having a para-type structure. Further, the hydrogen atom of the aromatic group possessed by the wholly aromatic polyamide may be substituted by any substituent.

[0027] (Function and Effect of Aramid Fiber) Aramid fiber contributes to the densification of the friction material surface. The friction material composition according to one aspect of the present invention contains 9% by mass or more of aramid fiber with respect to 100% by mass of the friction material composition, whereby the surface of the friction material becomes denser. As a result, the uptake of rust powder on the disk surface generated by cold storage is suppressed, the increase in the friction coefficient (μ) after cold storage is suppressed, and the squeal performance is improved. Further, since the surface of the friction material becomes dense, the friction surface is stable even during high-speed braking (hereinafter referred to as "high-temperature high-speed braking") in the temperature range of 640°C, and the effectiveness and wear resistance are improved.

[0028] (Fiber Length and Specific Surface Area of Aramid Fiber) From the viewpoint of the manifestation of the above-described effects caused by aramid fiber, the fiber length and specific surface area of the aramid fiber contained in the friction material composition according to one aspect of the present invention are not particularly limited. Therefore, as the aramid fiber, aramid fiber having specifications usually adopted as a fiber base material in the art can be used. For example, aramid fiber having a fiber length of 0.5 to 2 mm and a specific surface area of 3 to 15 m 2 / g can be used. Here, the "fiber length" is a value measured by a method compliant with ISO16065. Further, the "specific surface area" is a value measured by the BET gas adsorption method.

[0029] (Titanate) The friction material composition according to one aspect of the present invention contains 26% by mass or more of titanate with respect to 100% by mass of the friction material composition. The titanate may be added as an inorganic filler.

[0030] (Function and Effect of Titanate) Titanate contributes to the formation of a transfer film on the disk. By including titanate in the friction material composition according to one aspect of the present invention, the transfer film formed on the friction surface during high-temperature and high-speed braking becomes stronger, and the heat resistance (efficacy and wear resistance) of the friction material is further improved. Further, when the content of titanate in the friction material composition is 26% by mass or more, a transfer film is stably generated on the disk by braking. Thereby, the amount of rust powder generated on the disk surface due to cold storage can be suppressed. Also, the friction surface is stabilized even during high-temperature and high-speed braking by the transfer film, and the efficacy and wear resistance are improved.

[0031] (Types of Titanate) The titanate is not particularly limited, and examples thereof include known titanates such as alkali metal titanates and alkali metal - alkaline earth metal titanates. Specific examples of titanate include potassium titanate, sodium titanate, lithium titanate, lithium potassium titanate, magnesium potassium titanate, and the like. From the viewpoint of further improving the squeal performance and high-temperature performance, among these, potassium titanate, lithium potassium titanate, and magnesium potassium titanate are preferable.

[0032] The titanate can be blended alone or in combination of two or more types. From the viewpoint of further improving the squeal performance and high-temperature performance, it is preferable to blend the titanate in combination of two or more types.

[0033] Therefore, from the viewpoint of further improving the squeal performance and high-temperature performance, the friction material composition according to one aspect of the present invention preferably contains at least two types of titanates selected from the group consisting of potassium titanate, lithium potassium titanate, and magnesium potassium titanate as the titanate.

[0034] Examples of combinations of titanates include, for example, a combination of potassium titanate and lithium potassium titanate; a combination of potassium titanate and magnesium potassium titanate; a combination of lithium potassium titanate and magnesium potassium titanate; and a combination of potassium titanate, lithium potassium titanate, and magnesium potassium titanate. From the perspective of further improving the chirping performance and high-temperature performance, among these, potassium titanate, lithium potassium titanate, and magnesium potassium titanate are preferred.

[0035] From the perspective of further improving the chirping performance and high-temperature performance, in one aspect of the friction material composition according to the present invention, as the titanate, it is more preferable to include a combination of lithium potassium titanate and magnesium potassium titanate. When using multiple types of titanates in combination, the content of the titanates specified in this specification means the total content of the titanates.

[0036] When using multiple types of titanates in combination, the ratio of the content of each titanate can be appropriately adjusted and is not particularly limited. Since the effect of the combination is easily obtained, for example, when using two types in combination, it is preferable to use the titanates in such a way that the ratio of the content of one titanate to the content of the other titanate is 1:1 to 1:3.5, more preferably 1:2 to 1:3.5.

[0037] (Particle shape and particle size of titanate) From the perspective of the manifestation of the above-described effects caused by the titanate, the particle shape and particle size of the titanate contained in the friction material composition according to one aspect of the present invention are not particularly limited. Therefore, titanates having particle shapes and particle sizes that are usually employed as inorganic fillers added to the friction material can be appropriately selected.

[0038] For example, titanates having particle shapes such as spherical, granular, plate-like, columnar, rod-like, cylindrical, block-like, porous, and irregular can be used.

[0039] Further, for example, titanate particles having an average particle diameter in the range of 0.1 to 100 μm can be used. The average particle diameter of the titanate shall be the volume-based median diameter (median diameter) obtained by JIS Z 8825 "Particle Size Analysis - Laser Analysis - Scattering Method". When confirming the particle diameter of the titanate after forming the friction material, the average particle diameter of the particles corresponding to the titanate can be measured from the electron microscope image of the cross-section of the friction material by JIS Z 8827-1 "Particle Size Analysis - Image Analysis Method - Part 1: Static Image Analysis Method" to obtain the volume-based particle size distribution, and the median diameter can be determined.

[0040] (Preferred content of each component) From the viewpoint of the squeal performance, the content of the aramid fiber in the friction material composition is preferably 10% by mass or more, more preferably 11% by mass or more. Further, from the viewpoint of the manifestation of the effects of the present invention, the upper limit value of the content of the aramid fiber in the friction material composition is not particularly limited. However, since more excellent squeal performance and high-temperature performance can be exhibited, the content of the aramid fiber in the friction material composition is more preferably 13% by mass or less, and further preferably 12% by mass or less.

[0041] Also, from the viewpoint of the squeal performance, the content of the titanate in the friction material composition is preferably 31% by mass or more based on 100% by mass of the friction material composition. Further, from the viewpoint of the manifestation of the effects of the present invention, the upper limit value of the content of the titanate in the friction material composition is not particularly limited. However, since more excellent squeal performance and high-temperature performance can be exhibited, the content of the titanate in the friction material composition is more preferably 36% by mass or less, and further preferably 35% by mass or less.

[0042] In the friction material composition according to one aspect of the present invention, it is preferable that at least one of (a) the content of the aramid fiber and (b) the content of the titanate is the aforementioned preferred content. For example, only (a) or only (b) may be the aforementioned preferred content. Alternatively, both (a) and (b) may be the aforementioned preferred content.

[0043] From the viewpoint of achieving more preferable effects, in one aspect of the present invention, in the friction material composition, the content of the aramid fiber is preferably 9% by mass or more and 12% by mass or less, and the content of the titanate is preferably 31% by mass or more and 35% by mass or less.

[0044] As described above, in the friction material composition according to one aspect of the present invention, by controlling the content of the aramid fiber and the content of the titanate in the friction material composition to predetermined amounts, densification of the friction material surface and formation of the transfer film are performed more efficiently. As a result, a synergistic effect greater than the effects expected from adding aramid fiber alone or titanate alone can be obtained.

[0045] (Other components) In the friction material composition according to one aspect of the present invention, within a range that does not impair the effects of the present invention, in addition to the components described above, other fiber base materials different from aramid fiber, binders, organic fillers, other inorganic fillers different from titanate, and lubricants may be contained as friction material raw materials.

[0046] (Metal materials) Examples of the metal material include metal fibers and metal powders. Examples of the metal fibers and powders include fibers and powders made of single metals such as steel, stainless steel, aluminum, zinc, and tin, and fibers and powders made of their respective alloy metals. The metal material can be used alone or in combination of two or more. Since the metal material is likely to adhere to the disc rotor or drum brake, from the viewpoint of maintaining wear resistance in the normal temperature range, the content of the metal material in the friction material composition is preferably 2.0% by mass or less.

[0047] (Another fiber base material different from aramid fiber) The friction material composition according to one aspect of the present invention may further contain another fiber base material different from aramid fiber as long as the effects of the present invention are not impaired. Examples of another fiber base material different from aramid fiber include organic fibers, inorganic fibers, and the like. These fibers may be natural fibers or synthetic fibers artificially synthesized. Examples of organic fibers include acrylic fibers, cellulose fibers, carbon fibers, and the like. Examples of inorganic fibers include rock wool, slag wool, glass fibers, and the like. Note that it is also possible to define the above-described metal fiber as a fiber base material. The fiber base material can be used alone or in combination of two or more. The content of another fiber base material different from aramid fiber in the friction material composition is not particularly limited, and can be appropriately adjusted so that the total content of the fiber base material together with aramid fiber falls within the range of the content of the fiber base material usually employed in the art.

[0048] (Binder) The binder 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 a binder known in the art can be preferably used. Specific examples of the binder include resins such as phenol resin, epoxy resin, melamine resin, and imide resin. The binder can be used alone or in combination of two or more. The content of the binder in the friction material composition is not particularly limited and can be set to the content usually employed in the art. Further, the binder may contain a modifying component such as silicone rubber, acrylic rubber, and cashew oil.

[0049] (Organic filler) The organic filler has a function as a friction modifier for improving abrasion 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 technical field can be preferably used. Specific examples of the organic filler include rubber powder, tire powder, cashew dust, fluorine-based polymer, melamine cyanurate, polyethylene resin, and the like. The organic filler can be used alone or in combination of two or more kinds. Further, the surface of the organic filler may be coated with phosphoric acid or a fluorine-based polymer. The content of the organic filler in the friction material composition is not particularly limited and can be a content usually adopted in the technical field.

[0050] The friction material composition according to one aspect of the present invention may contain a fluorine-based polymer. However, among fluorine-based polymers, perfluoroalkyl compounds and polyfluoroalkyl compounds (so-called "PFAS") are of concern for adverse effects on the environment and human health, and thus restrictions on their use in products are being considered. Since the friction material composition according to one aspect of the present invention can provide a friction material excellent in chirping performance and high-temperature performance without relying on a fluorine-based polymer, from the viewpoint of providing a more environmentally and human-friendly friction material, the content of the fluorine-based polymer in the friction material composition is preferably 1% by mass or less, and more preferably 0% by mass (fluorine-based polymer-free).

[0051] (Another inorganic filler different from titanate) The friction material composition according to one aspect of the present invention may further contain another inorganic filler different from the titanate as long as the effects of the present invention are not impaired. As another inorganic filler different from the titanate, inorganic materials known in the art can be preferably used, and examples thereof include barium sulfate, mica, iron oxide (ferrous oxide, ferric oxide, etc.), calcium hydroxide, calcium carbonate, and the like. These inorganic fillers can be used alone or in combination of two or more. The content of another inorganic filler different from the titanate in the friction material composition is not particularly limited, and can be appropriately adjusted so that the total content of the inorganic filler other than the titanate falls within the range of the content of the inorganic filler adopted in the art.

[0052] Further, the particle size of another inorganic filler different from the titanate is not particularly limited, and an inorganic material having an average particle size usually adopted in the art can be preferably used.

[0053] (Lubricant) The friction material composition according to one aspect of the present invention may further contain a lubricant as long as the effects of the present invention are not impaired. The lubricant is not particularly limited, and lubricants known in the art can be preferably used. Specific examples of the lubricant include coke, graphite, carbon black, graphite, metal sulfides, and the like. Examples of the metal sulfide include tin sulfide, antimony trisulfide, molybdenum disulfide, bismuth sulfide, iron sulfide, zinc sulfide, tungsten sulfide, and the like. These lubricants can be used alone or in combination of two or more. The content of the lubricant is not particularly limited and can be the content usually adopted in the art.

[0054] (Method for manufacturing friction material composition) The friction material composition according to one aspect of the present invention can be manufactured by a manufacturing method including a mixing step of blending the above-described friction material raw materials and mixing them. From the viewpoint of uniformly mixing the friction material raw materials, the mixing step is preferably a step of mixing the 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 a method known in the art can be adopted. For example, using a known mixer such as a Fenschel mixer or a Lodige mixer, the friction material raw materials may be mixed at room temperature for about 10 minutes. In the mixing step, while mixing, the mixture of the friction material raw materials may be cooled by a known cooling method so that the temperature of the friction material raw materials during mixing does not rise.

[0055] (Method for determining the blending amount of the friction material composition) When controlling the blending amounts of the aramid fiber and the titanate to the predetermined amounts described above, the appropriate blending amounts of the respective components of the friction material composition can be appropriately determined from viewpoints such as the balance between the screeching performance and the high-temperature performance and the performance of other friction materials; and the blending balance between the aramid fiber and the titanate and other components contained in the friction material composition. For example, the appropriate blending amounts of the respective components of such a friction material composition can be determined using a data analysis method. Examples of the data analysis method include known regression analysis methods such as linear regression, decision tree, random forest, neural network, and Gaussian process regression.

[0056] The present invention has the effect of being able to provide a friction material that is excellent in screeching performance and excellent in effectiveness and wear resistance during high-speed braking in a high-temperature range within the above-described numerical ranges. However, by using the above-described analysis method, it may be possible to determine the types and blending amounts of components that result in a friction material composition useful even outside the scope of the present invention.

[0057] <2. Friction material> The friction material according to one aspect of the present invention is formed by molding the friction material composition according to one aspect of the present invention. Regarding the friction material composition according to one aspect of the present invention in the friction material according to one aspect of the present invention, since it has already been described as above, the description will not be repeated here.

[0058] (Manufacturing method of friction material) The friction material according to one aspect of the present invention 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 the friction material composition according to one aspect of the present invention can be molded into a predetermined shape, and a method known in the art can be adopted. For example, the friction material composition according to one aspect of the present invention can be molded by pressing it with a press or the like. As the molding method by pressing, either a hot press method in which the friction material composition according to one aspect of the present invention is heated and pressed to be molded or a normal temperature press method in which the friction material composition according to one aspect of the present invention is pressed and molded at normal temperature without heating can be preferably adopted. When molding by the hot press method, for example, the molding temperature is set to 140°C or higher and 200°C or lower (preferably 160°C), the molding pressure is set to 10 MPa or higher and 40 MPa or lower (preferably 20 MPa), and the molding time is set to 3 minutes or longer and 15 minutes or shorter (preferably 10 minutes), whereby the friction material composition according to one aspect of the present invention can be molded into a friction material. When molding by the normal temperature press method, for example, the molding pressure is set to 50 MPa or higher and 200 MPa or lower (preferably 100 MPa), and the molding time is set to 5 seconds or longer and 60 seconds or shorter (preferably 15 seconds), whereby the friction material composition according to one aspect of the present invention can be molded into a friction material. Further, if necessary, a polishing step of polishing the surface of the friction material to form a friction surface may be performed.

[0059] <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. As the friction member, it can be configured to include only the friction material according to one aspect of the present invention, or to integrate a plate-like member such as a metal plate as a back plate and the friction material according to one aspect of the present invention. Regarding the friction material according to one aspect of the friction member according to one aspect of the present invention, since it has already been described as above, the description will not be repeated here.

[0060] When the friction member according to one aspect of the present invention has a configuration in which a plate-like member and the friction material according to one aspect of the present invention are integrated, the friction material according to one aspect of the present invention and the plate-like member can be clamped and then heat-treated to bond the friction material according to one aspect of the present invention and the plate-like member. The conditions for the clamping process are not particularly limited. For example, they can be, for example, 180°C, 1 MPa, and 10 minutes. Also, the conditions for the heat treatment after the clamping process are not particularly limited. For example, they are 150°C or higher, 250°C or lower, 5 minutes or longer, and 180 minutes or shorter, and preferably 230°C and 3 hours.

[0061] 〔Summary〕 [1] The friction material composition according to Aspect 1 of the present invention is a friction material composition in which the copper content in the friction material composition is less than 0.5% by mass as copper element, and contains 9% by mass or more of aramid fiber and 26% by mass or more of titanate with respect to the total amount of the friction material composition.

[0062] According to such a configuration, although the copper content is less than 0.5% by mass as copper element, it is possible to provide a friction material that is excellent in squeal performance and has excellent effectiveness and wear resistance during high-speed braking in a high-temperature range as compared with conventional friction materials.

[0063] [2] In the friction material composition according to Aspect 2 of the present invention, in the above Aspect 1, the content of the titanate in the friction material composition is preferably 31% by mass or more.

[0064] According to such a configuration, there is an effect that the howling performance, as well as the effectiveness and wear resistance during high-speed braking in a high-temperature range, are further improved.

[0065] [3] The friction material composition according to Aspect 3 of the present invention may be configured not to contain a fluorine-based polymer in the above-described Aspect 1 or 2.

[0066] The friction material composition according to one aspect of the present invention provides a friction material that is excellent in howling performance and also excellent in effectiveness and wear resistance during high-speed braking in a high-temperature range, even in a composition that does not contain a fluorine-based polymer, which raises concerns about adverse effects on the environment and human health, compared to conventional friction materials. Therefore, according to such a configuration, there is an effect that a friction material considering the environment and human health can be provided.

[0067] [4] The friction material composition according to Aspect 4 of the present invention preferably contains at least two types of titanates selected from the group consisting of potassium titanate, lithium potassium titanate, and magnesium potassium titanate as the titanate in any one of the above-described Aspects 1 to 3.

[0068] According to such a configuration, there is an effect that the howling performance, as well as the effectiveness and wear resistance during high-speed braking in a high-temperature range, are further improved.

[0069] [5] The friction material composition according to Aspect 5 of the present invention preferably contains lithium potassium titanate and magnesium potassium titanate as the titanate in any one of the above-described Aspects 1 to 4.

[0070] According to such a configuration, there is an effect that the howling performance, as well as the effectiveness and wear resistance during high-speed braking in a high-temperature range, are further improved.

[0071] [6] According to Aspect 6 of the present invention, in any one of the above Aspects 1 to 5, the content of the aramid fiber in the friction material composition is 9% by mass or more and 12% by mass or less, and the content of the titanate in the friction material composition is preferably 31% by mass or more and 35% by mass or less.

[0072] According to such a configuration, there is an effect that a friction material having more excellent squeal performance, effectiveness during high-speed braking in a high-temperature range, and abrasion resistance can be provided.

[0073] [7] The friction material according to Aspect 7 of the present invention has a configuration formed by molding the friction material composition according to any one of the above Aspects 1 to 6.

[0074] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in each embodiment are also included in the technical scope of the present invention.

Examples

[0075] <Friction material raw materials> The main friction material raw materials used in the examples and comparative examples are as follows.

[0076] (Aramid fiber) Aramid fibers with a fiber length of 0.65 to 1.2 mm and a specific surface area of 5 to 12 m 2 / g were used.

[0077] (Titanate) · Potassium titanate: Plate-like potassium titanate was used. · Lithium potassium titanate: Amorphous lithium potassium titanate was used. · Magnesium potassium titanate: Plate-like magnesium potassium titanate was used.

[0078] As raw materials other than the above-described friction raw materials, those commonly used in the art were used.

[0079] <Fabrication of Brake Pad> Each raw material was blended according to the blending ratios shown in Tables 1 to 3, and using a Lodige mixer, it was mixed at room temperature (20 °C) for about 10 minutes to obtain a friction material composition. The unit of the blending amount of each raw material in the table is mass % in the friction material composition.

[0080] Using a molding press, the friction material composition was heated and compacted by the hot press method to form a molded product. The molding conditions by the hot press method were as follows: Molding temperature: 160 °C Molding pressure: 20 MPa Molding time: 10 minutes.

[0081] The surface of the obtained molded product was polished using a polishing machine to form a friction surface, thereby obtaining a friction material. Using this friction material, a brake pad was fabricated, and a squeal performance test and a high-temperature test were conducted. The fabricated brake pad had a friction material thickness of 12.5 mm and a friction material projected area of 55 cm 2 It was.

[0082] <Squeal Performance Test> For the fabricated brake pad, the following tests were conducted. As the rubbing, at a vehicle speed of 65 km / h and a braking start temperature of 120 °C, after 200 brakings, it was left for 240 minutes under the conditions of an environment of 10 °C and 80%. Thereafter, water was sprayed onto the disk brake surface, and braking was performed 10 times at a vehicle speed of 10 km / h, and the highest friction coefficient was recorded.

[0083] (Highest Friction Coefficient) The highest friction coefficient during the squeal performance test was measured by the following method.

[0084] (Measurement Method of Highest Friction Coefficient) Using the highest torque during one braking, the friction coefficient of each braking was calculated by the calculation formula described in JIS D 0106. The highest friction coefficient during the test was taken as the highest friction coefficient.

[0085] The measurement results of the maximum friction coefficient were evaluated with a three - level score of 0 to 2 according to the following criteria. 2: The maximum friction coefficient is 0.55 or less 1: The maximum friction coefficient is 0.55 or more and less than 0.60 0: The maximum friction coefficient is 0.60 or more Here, a score of 1 was evaluated as having excellent squeal performance, and a score of 2 was evaluated as having particularly excellent squeal performance. On the other hand, a score of 0 was evaluated as having poor squeal performance.

[0086] <High - temperature test> A fade test (vehicle speed 130 km / h, number of braking operations 10 times, maximum disk temperature 640 °C) was carried out, and the following evaluations were made.

[0087] (Minimum friction coefficient) The lowest friction coefficient during the fade test was measured by the following method.

[0088] (Measurement method of the minimum friction coefficient) 1. Using the lowest torque during braking, the friction coefficient of each braking was calculated by the formula described in JIS D 0106. The lowest friction coefficient during the test was taken as the minimum friction coefficient.

[0089] The measurement results of the minimum friction coefficient were evaluated with a three - level score of 0 to 2 according to the following criteria. 2: The minimum friction coefficient is 0.25 or more 1: The minimum friction coefficient is 0.20 or more and less than 0.25 0: The minimum friction coefficient is less than 0.20 Here, a score of 1 was evaluated as having excellent effectiveness during high - speed braking in the high - temperature range, and a score of 2 was evaluated as having particularly excellent effectiveness during high - speed braking in the high - temperature range. On the other hand, a score of 0 was evaluated as having poor effectiveness during high - speed braking in the high - temperature range.

[0090] (Wear amount) The wear amount of the brake pad after the fade test was measured by the following method.

[0091] (Measurement method of the wear amount) The wear amount was measured in accordance with the measurement method of JASO C427 6.

[0092] After the test, the pad wear amounts at 8 locations for each brake pad were measured, and the average value was defined as the "average pad wear amount".

[0093] The measurement results of the wear amount were evaluated with a 3 - level score of 0 - 2 according to the criteria shown below. 2: The wear amount is less than 0.5 mm 1: The wear amount is 0.5 mm or more and less than 1.0 mm 0: The wear amount is 1.0 mm or more Here, a score of 1 was evaluated as excellent wear resistance during high - speed braking in the high - temperature range, and a score of 2 was evaluated as particularly excellent wear resistance during high - speed braking in the high - temperature range. On the other hand, a score of 0 was evaluated as inferior wear resistance during high - speed braking in the high - temperature range.

[0094] <Results> The evaluation results (scores) in the squeal test and the evaluation results (scores) in each high - temperature test are shown in Tables 1 - 3.

[0095]

Table 1

[0096]

Table 2

[0097]

Table 3

[0098] The brake pads of Examples 1 to 26 have (i) the content of aramid fiber in the friction material composition being 9% by mass or more, and (ii) the content of titanate in the friction material composition being 26% by mass or more. Compared with the brake pads of the comparative examples, it was confirmed that they are excellent in squeal performance and are excellent in effectiveness during high-speed braking in the high-temperature range and in abrasion resistance. From the comparison between Examples 1 to 3 and Examples 24 to 26, it was confirmed that when both (i) and (ii) are satisfied, excellent squeal performance and high-temperature performance can be exhibited regardless of the presence or absence of fluoropolymer particles.

[0099] On the other hand, from the comparison between Comparative Example 1 and Comparative Examples 2 to 3, when both (i) and (ii) are not satisfied, it was confirmed that when containing fluoropolymer particles, the squeal performance and high-temperature performance tend to be better than when not containing fluoropolymer particles. However, compared with Examples 1 to 26, the squeal performance and high-temperature performance of Comparative Example 1 were inferior.

[0100] Also, from the comparison between Examples 1 to 6 and Comparative Examples 4 to 9, when either (i) or (ii) is not satisfied, it was confirmed that either the squeal performance or the high-temperature performance tends to deteriorate.

[0101] From these results, by controlling the contents of aramid fiber and titanate in the friction material composition to predetermined amounts, densification of the friction material surface and formation of a transfer film are more efficiently performed. Therefore, it was considered that a synergistic effect greater than the effects expected from adding aramid fiber alone or titanate alone can be obtained.

[0102] Furthermore, by having (iii) the content of aramid fiber in the friction material composition being 9 to 13% by mass, and (iv) the content of titanate in the friction material composition being 31 to 35% by mass, it was confirmed that even more excellent squeal performance and high-temperature performance can be exhibited (for example, Examples 1 to 6, 13 to 15, 19, 20, 24 to 26).

[0103] In addition, it was confirmed that by using different types of titanates in combination as the titanate, better chirping performance and high-temperature performance can be exhibited than when blending one type of titanate (for example, comparison between Example 3 and Example 13). Further, it was confirmed that when using different types of titanates in combination, even better chirping performance and high-temperature performance can be exhibited by the combination of lithium potassium titanate and magnesium potassium titanate (for example, comparison between Example 1 and Example 2).

Industrial Applicability

[0104] The friction material composition and the friction material according to one aspect of the present invention can be suitably used for friction members in braking devices of vehicles such as automobiles.

Claims

1. A friction material composition in which the copper content in the friction material composition is less than 0.5% by mass as elemental copper, relative to the total amount of the friction material composition, aramid fiber is 9% by mass or more, and titanate is 26% by mass or more contained, a friction material composition.

2. The friction material composition according to claim 1, wherein the content of the titanate in the friction material composition is 31% by mass or more.

3. The friction material composition according to claim 1, which does not contain a fluorine-based polymer.

4. The friction material composition according to claim 1, wherein the titanate includes at least two types of titanates selected from the group consisting of potassium titanate, lithium potassium titanate, and magnesium potassium titanate.

5. The friction material composition according to claim 4, wherein the titanate includes lithium potassium titanate and magnesium potassium titanate.

6. The content of the aramid fiber in the friction material composition is 9% by mass or more and 12% by mass or less, and the content of the titanate in the friction material composition is 31% by mass or more and 35% by mass or less, the friction material composition according to claim 1.

7. A friction material formed by molding the friction material composition according to any one of claims 1 to 6.

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