Friction modifier, friction material composition, friction material, and friction member

Abstract

The present invention provides a friction modifier which, when used in a friction material, can increase the friction coefficient for a high-load region.　Provided is a friction modifier constituted by a titanate, wherein the titanate is a salt of one or more types of element selected from the group consisting of alkali metals and alkali earth metals, and the decomposition rate of the titanate when the titanate is heated for one hour at 800°C in a nitrogen atmosphere is 30-100 mass%.

Description

Friction modifier, friction material composition, friction material, and friction member

[0001] The present invention relates to a friction modifier composed of a titanate, and a friction material composition, a friction material, and a friction member each using the friction modifier.

[0002] Friction materials used in brakes such as disc brakes and drum brakes that constitute braking devices for various vehicles, industrial machinery, etc. are required to have a large and stable friction coefficient, excellent wear resistance, and low attack on mating materials. Such friction materials are classified into three types: semi-metallic materials containing steel fibers such as steel fibers or stainless steel fibers as a fiber base material in a proportion of 30% by mass or more but less than 60% by mass; low-steel materials containing steel fibers in a proportion of 10% by mass or more but less than 30% by mass; and NAO (Non-Asbestos-Organic) materials that do not contain steel fibers. However, friction materials containing trace amounts of steel fibers are also classified as NAO materials.

[0003] In Japan and the United States, where comfort is emphasized, NAO material is mainstream because it is less aggressive to mating materials and has an excellent balance between squeal and wear resistance. In Europe, low-steel material was used to maintain the friction coefficient during high-speed braking, but with a trend toward luxury, NAO material, which is less likely to cause brake squeal, is now being used more often.

[0004] Compositions used in friction materials (hereinafter referred to as "friction material compositions") generally contain copper fibers or copper powder. The primary role of copper is to provide thermal conductivity. Because copper has high thermal conductivity, it diffuses heat generated during braking from the friction interface, thereby reducing friction material wear due to excessive temperature rise and suppressing vibration during braking. The second role of copper is to protect the friction interface during high-temperature braking. Due to the malleability of copper, it spreads to the surface of the friction material during braking and forms a coating. It also migrates to the surface of the mating material and forms an adhesive coating (hereinafter referred to as "transfer film"). These act as protective films, reducing friction material wear during high-temperature braking and enabling the development of a stable friction coefficient. However, friction materials containing copper contain copper in the wear powder generated during braking, which has been suggested to be a cause of river, lake, and ocean pollution. Therefore, state laws have been enacted in the US states of California and Washington that prohibit the sale and installation in new vehicles of friction materials containing 5% or more by mass of copper from 2021 onwards, and 0.5% or more by mass of copper from 2025 onwards.

[0005] Therefore, in NAO materials, titanates have attracted attention as a component other than copper that plays a role in the transfer film. Titanates include titanates with tunnel crystal structures (e.g., potassium hexatitanate) and titanates with layered crystal structures (e.g., lithium potassium titanate and magnesium potassium titanate), and these are used alone or in combination depending on the application of the friction material. For example, a friction material composition containing titanate and barium sulfate with an average particle size of 0.1 μm to 20 μm (Patent Document 1) has been proposed.

[0006] International Publication No. 2018 / 164028

[0007] Hybrid and electric vehicles, which have become increasingly popular in recent years, are equipped with regenerative brakes to recover frictional energy during braking. However, this mechanism does not function when the battery is fully charged, and it is anticipated that the load on the brakes will increase due to the increased vehicle weight caused by the battery. Furthermore, with the spread of heavy, large vehicles such as SUVs, it is becoming increasingly important for friction materials to have a high coefficient of friction in high-load areas. Furthermore, in some mountainous regions, there is an issue of insufficient braking force when overloaded vehicles descend steep roads.

[0008] Potassium hexatitanate, which has a thermally stable crystal structure, is a promising titanate that provides a friction coefficient in the high load range, but its use is being discouraged, particularly in Europe, due to concerns about the inclusion of WHO fibers (fibrous particles with a major axis of 5 μm or more, a minor axis of 3 μm or less, and an aspect ratio of 3 or more) that exceed environmental standards.On the other hand, lithium potassium titanate and magnesium potassium titanate are known as titanates that are free from concerns about the inclusion of WHO fibers, but although they have excellent wear resistance, their friction coefficient in the high load range is an issue.

[0009] An object of the present invention is to provide a friction modifier that, when used in a friction material, can increase the friction coefficient in a high load region, as well as a friction material composition, friction material, and friction member that use the friction modifier.

[0010] The present invention provides a friction modifier composed of the following titanate, as well as a friction material composition, a friction material, and a friction member each using the friction modifier.

[0011] Item 1. A friction modifier comprising a titanate, wherein the titanate is a salt of one or more elements selected from the group consisting of alkali metals and alkaline earth metals, and the decomposition rate of the titanate when heated at 800°C for 1 hour in a nitrogen atmosphere is 30% by mass or more and 100% by mass or less.

[0012] Item 2. The friction modifier according to Item 1, wherein when the titanate is heated at 800°C for 1 hour in a nitrogen atmosphere, a production rate of the titanate having a hollandite crystal structure is 10% by mass or more and 100% by mass or less.

[0013] Item 3. The friction modifier according to Item 1 or 2, wherein the titanate is at least one of lithium potassium titanate and magnesium potassium titanate.

[0014] Item 4. The friction modifier according to any one of Items 1 to 3, wherein the titanate is a plate-like particle.

[0015] Item 5. The friction modifier according to any one of Items 1 to 4, wherein the titanate has an average particle size of 0.1 μm or more and 100 μm or less.

[0016] Item 6: The specific surface area of ​​the titanate is 0.1 m ２ / g or more, 10m ２ Item 6. The friction modifier according to any one of items 1 to 5, wherein the friction modifier has a viscosity of 1 / g or less.

[0017] Item 7. The friction modifier according to any one of Items 1 to 6, wherein the titanate has an alkali metal ion elution rate of 0.01% by mass or more and 15% by mass or less.

[0018] Item 8. A friction material composition comprising the friction modifier according to any one of items 1 to 7 and a binder, wherein the copper content is less than 0.5 mass % in terms of elemental copper.

[0019] Item 9. The friction material composition according to Item 8, wherein the content of the titanate is 1% by mass or more and 40% by mass or less, based on 100% by mass of the total amount of the friction material composition.

[0020] Item 10. The friction material composition according to Item 8 or Item 9, wherein a mass ratio of the titanate to the binder (titanate / binder) is 0.1 or more and 8 or less.

[0021] Item 11. The friction material composition according to any one of Items 8 to 10, wherein the content of the steel fiber is less than 10% by mass, based on 100% by mass of the total amount of the friction material composition.

[0022] Item 12. A friction material, which is a molded product of the friction material composition according to any one of items 8 to 11.

[0023] Item 13. A friction member comprising the friction material according to Item 12.

[0024] According to the present invention, it is possible to provide a friction modifier that, when used in a friction material, can increase the friction coefficient in a high load region, as well as a friction material composition, friction material, and friction member that use the friction modifier.

[0025] Fig. 1 is a graph showing the relationship between the number of braking cycles and the coefficient of friction during fading in a fade test of the friction members obtained in Example 3 and Comparative Example 1. Fig. 2 is a graph showing the relationship between the number of braking cycles and the coefficient of friction during fading in a fade test of the friction members obtained in Example 7 and Comparative Example 2. Fig. 3 is a graph showing the relationship between the change in the coefficient of friction (μ) with respect to rotor temperature and the average coefficient of friction (μ) during fading in a fade test of the friction members obtained in Example 1, Example 3, Example 5, Comparative Example 1, and Reference Example 1.

[0026] Hereinafter, an example of a preferred embodiment of the present invention will be described. However, the following embodiment is merely an example, and the present invention is not limited to the following embodiment.

[0027] 1. Friction Modifier The friction modifier of the present invention is a friction modifier composed of a titanate, which is a salt of one or more elements selected from the group consisting of alkali metals and alkaline earth metals.

[0028] Examples of alkali metals include lithium, sodium, potassium, rubidium, cesium, and francium. Among these, the alkali metal is preferably one or more selected from the group consisting of lithium, sodium, and potassium, from the viewpoint of further improving friction and wear properties.

[0029] Examples of alkaline earth metals include beryllium, magnesium, calcium, strontium, barium, and radium. Among these, magnesium or calcium is preferred as the alkaline earth metal from the viewpoint of further improving friction and wear properties.

[0030] Specific examples of the titanate include potassium titanate, sodium titanate, lithium potassium titanate, magnesium potassium titanate, etc. Among these, from the viewpoint of further improving abrasion resistance and further reducing the risk of containing WHO fiber, the titanate is preferably lithium potassium titanate and / or magnesium potassium titanate.

[0031] In the present invention, the decomposition rate of the titanate is 30% by mass or more and 100% by mass or less when the titanate is heated for 1 hour at 800° C. in a nitrogen atmosphere. The decomposition rate of the titanate can be calculated by measuring the content (% by mass) of undecomposed material (titanate before heating) in powder after heating for 1 hour at 800° C. in a nitrogen atmosphere, and using the following formula (1):

[0032] Decomposition rate (mass%) = 100 - content of undecomposed matter...Equation (1)

[0033] More specifically, the content of undecomposed titanate can be determined by performing X-ray diffraction measurement on a sample before and after heating at 800° C. for 1 hour in a nitrogen atmosphere.

[0034] For example, the X-ray diffraction spectra of the mixture obtained by mixing the sample before and after heating with a standard silicon powder are measured using an X-ray diffraction measurement device. As the standard silicon powder, for example, silicon powder (purity 99.9%) manufactured by Rare Metallic Co., Ltd. can be used. Furthermore, the mass ratio of the sample (powder) after heating to the standard silicon powder can be, for example, sample:silicon = 1:0.1 to 1:1.

[0035] Next, the integrated intensities of the peaks at diffraction angles 2θ=10.9° to 11.6° in the obtained X-ray diffraction pattern, which are attributable to the titanate before heating and the undecomposed product of the titanate after heating, and the peak at diffraction angles 2θ=28.0° to 28.7° in the obtained X-ray diffraction pattern, are measured. The content of the undecomposed product of the titanate after heating can be determined from the ratio of the integrated intensity of the peak of the titanate before heating, normalized with the standard silicon powder, to the integrated intensity of the peak of the undecomposed product of the titanate after heating.

[0036] The X-ray diffraction measurement can be performed by wide-angle X-ray diffraction using CuKα radiation (wavelength 1.5418 Å). As the X-ray diffraction measurement device, for example, Rigaku Corporation's Ultima IV can be used.

[0037] The present inventors have found that by setting the decomposition rate of titanate in the friction modifier within the above range, it is possible to increase the coefficient of friction in the high load region when used in a friction material.

[0038] Specifically, when a titanate whose decomposition rate is within the above range when heated at 800°C for 1 hour in a nitrogen atmosphere is used as a friction modifier, it is believed that a titanate with a hollandite crystal structure will be produced under high-load friction (high-load range). Since particles with a hollandite crystal structure are harder than titanates with other structures, they are thought to act as an abrasive under high-load friction, increasing the friction coefficient. The nitrogen atmosphere is set, for example, assuming the interface state (a state in which oxygen is blocked) when a pad and a rotor are rubbing against each other.

[0039] In the present invention, when the titanate is lithium potassium titanate, the decomposition rate is preferably 40% by mass or more, more preferably 55% by mass or more, and even more preferably 70% by mass or more, from the viewpoint of further improving the stability of the friction coefficient, and is preferably 95% by mass or less, and more preferably 89% by mass or less.

[0040] Furthermore, when the titanate is magnesium potassium titanate, the decomposition rate is preferably 50% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 75% by mass or more, from the viewpoint of further improving the stability of the friction coefficient, and is preferably 95% by mass or less, and more preferably 89% by mass or less.

[0041] In the present invention, the yield of the titanate having a hollandite crystal structure when the titanate is heated in a nitrogen atmosphere at 800° C. for 1 hour is preferably 10% by mass or more and 100% by mass or less. The yield can be obtained by measuring the content (% by mass) of the titanate having a hollandite crystal structure in the powder after heating the titanate in a nitrogen atmosphere at 800° C. for 1 hour.

[0042] More specifically, the content of titanate having a hollandite crystal structure can be determined by heating the titanate at 800°C for 1 hour in a nitrogen atmosphere and then subjecting the resulting powder to X-ray diffraction measurement.

[0043] For example, the X-ray diffraction spectrum of the mixture obtained by mixing the heated sample (powder) with standard silicon powder is measured using an X-ray diffraction measurement device. The standard silicon powder may be, for example, silicon powder (purity 99.9%) manufactured by Rare Metallic Co., Ltd. The mass ratio of the heated sample (powder) to the standard silicon powder may be 1:0.1 to 1:1.

[0044] Next, the integrated intensities of the peaks attributable to the undecomposed material (titanate before heating) observed at diffraction angles 2θ=10.9° to 11.6° in the obtained X-ray diffraction pattern, the peaks attributable to the titanate having a hollandite-type crystal structure observed at diffraction angles 2θ=27.5° to 28.0°, and the peaks attributable to the standard silicon powder observed at diffraction angles 2θ=28.0° to 28.7° are measured, and the content (mass%) of the titanate having a hollandite-type crystal structure can be calculated from a calibration curve prepared in advance (a calibration curve of the integrated intensities of the peaks attributable to the standard silicon powder and the peaks attributable to the titanate having a hollandite-type crystal structure).

[0045] In the present invention, when the titanate is lithium potassium titanate, the production rate of the titanate having a hollandite crystal structure is preferably 20% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more, from the viewpoint of further improving the stability of the friction coefficient, and is preferably 90% by mass or less, and more preferably 80% by mass or less.

[0046] Furthermore, when the titanate is magnesium potassium titanate, the production rate of the titanate having a hollandite-type crystal structure is preferably 15% by mass or more, more preferably 30% by mass or more, and is preferably 90% by mass or less, more preferably 75% by mass or less, even more preferably 60% by mass or less, and particularly preferably 45% by mass or less, from the viewpoint of further improving the stability of the friction coefficient.

[0047] In the present invention, the titanate is preferably a non-fibrous particle from the viewpoint of the working environment. Examples of non-fibrous particles include spherical particles (including those with slight surface irregularities and those with a substantially spherical cross section, such as an elliptical cross section), columnar particles (including those with a substantially columnar overall shape, such as a rod, cylinder, prism, strip, substantially cylindrical, or substantially strip), plate-like particles, block-like particles, particles with multiple protrusions (e.g., amoeba-like, boomerang-like, cross-like, or confetti-like), and irregular shapes. Among these, the titanate is preferably a plate-like particle. The titanate may also be a porous particle. These various particle shapes can be arbitrarily controlled by the production conditions, particularly the raw material composition and firing conditions. Furthermore, various particle shapes can be analyzed, for example, by scanning electron microscope (SEM) observation.

[0048] As used herein, "non-fibrous particles" refers to particles having an L / B ratio of 5 or less, where the longest side of the rectangular parallelepiped having the smallest volume among the rectangular parallelepipeds circumscribing the particle (circumscribing rectangular parallelepiped) is the major axis L, the second longest side is the minor axis B, and the shortest side is the thickness T (B > T). Furthermore, "having multiple convex portions" refers to particles whose projected shape on a plane is different from at least a normal polygon, circle, ellipse, etc., and can have convex portions in two or more directions. Specifically, these convex portions refer to the portions corresponding to the protruding parts when a polygon, circle, ellipse, etc. (basic shape) is fitted to a photograph (projection drawing) taken by a scanning electron microscope (SEM).

[0049] In the present invention, the average particle size of the titanate is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. When the average particle size of the titanate is within the above range, the friction characteristics can be further improved when the friction material is produced.

[0050] In this specification, the average particle size refers to the particle size at 50% cumulative volume in the particle size distribution measured by a laser diffraction method. ５０ is the particle size at which the cumulative value reaches 50% when the particle size distribution is calculated on a volume basis and the number of particles is counted from the smallest particle size on a cumulative curve with the total volume set to 100%.

[0051] In the present invention, the specific surface area of ​​the titanate is preferably 0.1 m ２ / g or more, more preferably 0.3m ２ / g or more, more preferably 0.5m ２ / g or more, preferably 10m ２ / g or less, more preferably 6m ２ / g or less, more preferably 5m ２ / g or less, particularly preferably 4m ２ When the titanate is lithium potassium titanate, the specific surface area is preferably 1 m ２ / g or more, preferably 3m ２When the titanate is magnesium potassium titanate, the specific surface area is preferably 2 m ２ / g or more, preferably 4m ２ When the specific surface area of ​​the titanate is within the above range, the friction characteristics of the produced friction material can be further improved. The specific surface area can be measured in accordance with JIS Z8830.

[0052] In the present invention, the alkali metal ion elution rate of the titanate is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less.

[0053] In the present invention, when the titanate is lithium potassium titanate, the alkali metal ion elution rate is preferably 1% by mass or more and preferably 6% by mass or less. When the titanate is magnesium potassium titanate, the alkali metal ion elution rate is preferably 0.5% by mass or more, more preferably 2.6% by mass or more, and preferably 6.0% by mass or less, more preferably 3.5% by mass or less.

[0054] In the curing reaction of novolac phenolic resin, an example of a thermosetting resin used in a friction material composition, the curing agent (or curing accelerator), for example, hexamethylenetetramine, undergoes ring-opening and bonds with hydroxyl groups in the novolac phenolic resin, initiating the curing reaction. However, if alkali metal ions are present during this process, they undergo an ion exchange reaction with the hydrogen ions in the hydroxyl groups in the novolac phenolic resin, which is thought to inhibit the bond between hexamethylenetetramine (the curing agent (or curing accelerator)) and the novolac phenolic resin (thermosetting resin) (curing inhibition). On the other hand, it is thought that the wear and tear of the friction material caused by braking causes alkali components derived from titanates to leach out onto the friction surface.

[0055] Therefore, by setting the alkali metal ion elution rate to the above upper limit or less, it is possible to prevent inhibition of curing of the thermosetting resin during hot and pressure molding, and as a result, it is possible to further improve crack resistance under high temperature and high load. Furthermore, by setting the alkali metal ion elution rate to the above lower limit or more, it is possible to suppress rusting of the rotor even if the friction material using the friction modifier of the present invention is left unused for a long period of time after braking. In other words, by setting the alkali metal ion elution rate within the above range, it is possible to achieve both high levels of crack resistance of the friction material and high levels of suppression of rotor rusting.

[0056] In this specification, the alkali metal ion elution rate refers to the mass ratio of alkali metal ions eluted into water at 80°C from a measurement sample such as a titanate.

[0057] In the present invention, in order to further improve adhesion with the binder used in the friction material composition, a treatment layer made of a surface treatment agent may be formed on the surface of the titanate. Examples of the surface treatment agent include silane coupling agents and titanium coupling agents. Among these, silane coupling agents are preferably used, and amino-based silane coupling agents, epoxy-based silane coupling agents, and alkyl-based silane coupling agents are more preferably used. The above surface treatment agents may be used alone or in combination of two or more.

[0058] Examples of amino-based silane coupling agents include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-ethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane.

[0059] Examples of epoxy-based silane coupling agents include 3-glycidyloxypropyl(dimethoxy)methylsilane, 3-glycidyloxypropyltrimethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, triethoxy(3-glycidyloxypropyl)silane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0060] Examples of alkyl silane coupling agents include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexylriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, and n-decyltrimethoxysilane.

[0061] A known surface treatment method can be used to form a treatment layer made of a surface treatment agent on the surface of the titanate, and for example, a wet method can be used in which the surface treatment agent is dissolved in a solvent that promotes hydrolysis (e.g., water, alcohol, or a mixed solvent thereof) to form a solution, and the solution is sprayed onto the titanate.

[0062] The amount of the surface treatment agent used to treat the surface of the titanate is not particularly limited. In the case of a wet method, for example, a solution of the surface treatment agent may be sprayed so that the amount of the surface treatment agent is 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the titanate.

[0063] The titanate used in the present invention may be a granulated titanate treated with the above-mentioned surface treatment agent or a binder described below. The average particle size of the granular titanate is preferably 100 μm or more and preferably 200 μm or less.

[0064] The method for producing the titanate used in the present invention is not particularly limited, and the titanate can be produced, for example, by mixing a titanate having a layered crystal structure as a raw material (hereinafter referred to as "raw titanate") with an acid (acid treatment), and calcining the compound obtained by the acid treatment.

[0065] Examples of the raw titanate include the titanates described in WO 2002 / 010069 and WO 2003 / 037797.

[0066] The acid used in the acid treatment is not particularly limited, and known acids can be used. Examples of the acid used in the acid treatment include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as acetic acid. Two or more acids may be used in combination as needed.

[0067] The acid treatment can be carried out by mixing an acid with an aqueous slurry of the starting titanate. The concentration of the aqueous slurry is not particularly limited and can be appropriately selected from a wide range. In consideration of workability, the concentration of the aqueous slurry may be about 1% by mass to 30% by mass. The amount of acid mixed with the aqueous slurry is, for example, preferably 0.01 to 0.5 equivalents relative to the interlayer element of the starting titanate.

[0068] After the acid treatment, the solid content is separated from the slurry by filtration, centrifugation, etc. The separated solid content can be washed with water and dried, if necessary.

[0069] The calcination can be carried out using an electric furnace or the like, and is preferably maintained at a temperature of 100°C to 600°C, preferably 400°C to 600°C, for 1 to 12 hours, more preferably 1 to 10 hours. After calcination, the resulting powder may be crushed to a desired size or sieved to loosen the particles. In this manner, the titanate used in the present invention can be obtained.

[0070] The titanate prepared by the above method is believed to be able to increase the decomposition rate of the titanate described above in a high-temperature nitrogen atmosphere, to easily produce a titanate with a hollandite-type crystal structure, and to be in an appropriate amount without excessive decomposition of the titanate and production of a titanate with a hollandite-type crystal structure.

[0071] <2. Friction Material Composition> The friction material composition of the present invention contains the friction modifier of the present invention and a binder, and is characterized in that the copper content is less than 0.5 mass % in terms of copper element. The friction material composition of the present invention can also contain other materials as needed. In this specification, the term "friction material composition" refers to a composition used in a friction material.

[0072] The friction material composition of the present invention contains the above-mentioned friction modifier of the present invention, and therefore the coefficient of friction in the high load region of the friction material can be increased.

[0073] Furthermore, by containing less than 0.5 mass % of copper element relative to 100 mass % of the total amount of the friction material composition, or preferably by not containing any copper element, the environmental impact can be reduced compared to conventional friction material compositions. In this specification, "not containing any copper element" means that copper fiber, copper powder, and copper-containing alloys (brass, bronze, etc.) and compounds are not blended as raw materials of the friction material composition.

[0074] According to the friction material composition of the present invention, excellent friction characteristics can be obtained even when no copper component is contained or when the copper component content is reduced.

[0075] The friction material composition of the present invention is preferably an NAO material in which the content of steel fibers, such as steel fibers or stainless steel fibers, is less than 10% by mass relative to 100% by mass of the total amount of the friction material composition, which facilitates the formation of a transfer film on the surface of the mating material and provides excellent friction and wear characteristics.

[0076] (2-1. Binder) The binder integrates the compounding materials contained in the friction material composition and provides strength. There are no particular restrictions on the binder used in the friction material composition of the present invention, and thermosetting resins that are usually used as binders for friction materials can be used.

[0077] Examples of thermosetting resins include phenolic resins; elastomer-dispersed phenolic resins such as acrylic elastomer-dispersed phenolic resins and silicone elastomer-dispersed phenolic resins; modified phenolic resins such as acrylic-modified phenolic resins, silicone-modified phenolic resins, cashew-modified phenolic resins, epoxy-modified phenolic resins, and alkylbenzene-modified phenolic resins; formaldehyde resins; melamine resins; epoxy resins; acrylic resins; aromatic polyester resins; and urea resins. One of these may be used alone, or two or more may be used in combination. Among these, phenolic resins (straight phenolic resins) and modified phenolic resins are preferred as thermosetting resins from the viewpoint of further improving heat resistance, moldability, and friction properties. While both resol-type and novolac-type phenolic resins can be used as phenolic resins, novolac-type phenolic resins are preferred from the viewpoint of production stability and cost. Furthermore, novolac-type phenolic resins may contain additives such as curing agents and curing accelerators (e.g., hexamethylenetetramine) as needed.

[0078] The content of the binder in the friction material composition is preferably 5% by mass or more, more preferably 8% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, based on 100% by mass of the total amount of the friction material composition. By setting the binder content within the above range, an appropriate amount of binder is filled into the gaps in the blended materials, thereby achieving even better friction characteristics.

[0079] (2-2. Titanate) The titanate used in the friction material composition of the present invention constitutes the friction modifier of the present invention described above. The content of the titanate in the friction material composition is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to 100% by mass of the total amount of the friction material composition, and is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. By keeping the titanate content within the above range, even better friction characteristics can be obtained.

[0080] The mass ratio of titanate to binder (titanate / binder) is preferably 0.1 or more, more preferably 0.5 or more, even more preferably 1.1 or more, and preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less. By setting the mass ratio of titanate to binder within the above range, the formability of the friction material can be further improved, and an appropriate transfer film can be formed.

[0081] (2-3. Other Materials) In addition to the binder and the friction modifier of the present invention, other materials typically used in friction material compositions (such as a fibrous base material, an organic friction modifier, an inorganic friction modifier, a lubricant, a pH adjuster, and a filler) may be blended into the friction material composition of the present invention, as needed.

[0082] The content of the other materials in the friction material composition is preferably 30% by mass or more and preferably 94% by mass or less, based on 100% by mass of the total amount of the friction material composition.

[0083] (2-3-1. Fibrous base material) The fibrous base material exhibits reinforcing properties in the friction material. Examples of the fibrous base material include inorganic fibers, metal fibers, organic fibers, and carbon-based fibers. One of these may be used alone, or two or more may be used in combination.

[0084] Examples of inorganic fibers include glass fibers, rock wool, ceramic fibers, biodegradable ceramic fibers, biodegradable mineral fibers, and biosoluble fibers (SiO ２ -CaO-SrO type fibers, wollastonite fibers, silicate fibers, mineral fibers, etc., and among these, rock wool is preferred.

[0085] When the friction material composition contains rock wool, the content thereof is preferably 1% by mass or more, preferably 10% by mass or less, and more preferably 7% by mass or less, based on 100% by mass of the total amount of the friction material composition. When the rock wool content is within the above range, the friction coefficient during high-load braking can be increased.

[0086] Examples of metal fibers include fibers of simple metals or alloys such as aluminum, iron, zinc, tin, titanium, nickel, magnesium, and silicon (steel fibers, stainless steel fibers, etc.), and straight or curled metal fibers whose main component is metal, such as cast iron fibers.

[0087] Examples of organic fibers include aromatic polyamide (aramid) fibers, fibrillated aramid fibers (aramid pulp), acrylic fibers (fibers of homopolymers or copolymers whose main raw material is acrylonitrile), fibrillated acrylic fibers, cellulose fibers, fibrillated cellulose fibers, and phenolic resin fibers.

[0088] The organic fiber is preferably an aramid fiber, since it provides the friction material with a suitable water absorption property, facilitates the absorption of atmospheric moisture into the friction material, facilitates the elution of the alkali component of the titanate, and is expected to provide a rust prevention effect for the rotor. Furthermore, from the viewpoint of further improving the formability of the friction material and further improving the retention of the filler, the organic fiber is preferably a fibrillated aramid fiber (also called aramid pulp). The specific surface area of ​​the fibrillated aramid fiber is preferably 5 m ２ / g or more, preferably 25m ２ / g or less, more preferably 15m ２ The fiber length of the fibrillated aramid fibers is preferably 0.5 mm or more and preferably 1.2 mm or less.

[0089] When the friction material composition contains fibrillated aramid fibers, the content thereof is preferably 1% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less, based on 100% by mass of the total amount of the friction material composition. When the content of the fibrillated aramid fibers is equal to or greater than the above-mentioned lower limit, crack resistance and wear resistance are improved. On the other hand, when the content of the fibrillated aramid fibers is equal to or less than the above-mentioned upper limit, deterioration of crack resistance and wear resistance due to uneven distribution of the fibrillated aramid fibers and other materials can be more reliably prevented.

[0090] Examples of carbon-based fibers include flame-resistant fibers, PAN-based carbon fibers, pitch-based carbon fibers, activated carbon fibers, and the like.

[0091] (2-3-2. Organic Friction Modifiers) Organic friction modifiers are friction modifiers that are blended with the aim of further improving the noise and vibration performance and wear resistance of friction materials. Examples of organic friction modifiers include unvulcanized or vulcanized rubber powders such as tire rubber, acrylic rubber, isoprene rubber, NBR (nitrile butadiene rubber), SBR (styrene butadiene rubber), chlorinated butyl rubber, butyl rubber, and silicone rubber; cashew dust; rubber-coated cashew dust; melamine dust; and the like. One of these may be used alone, or two or more may be used in combination.

[0092] When the friction material composition contains an organic friction modifier, the content thereof is preferably 0.1% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 6% by mass or less, based on 100% by mass of the total amount of the friction material composition.

[0093] (2-3-3. Inorganic Friction Modifiers) Inorganic friction modifiers (excluding the titanates) are friction modifiers that are blended with the friction material in order to prevent deterioration in heat resistance, improve wear resistance, or further improve the coefficient of friction. Examples of inorganic friction modifiers include abrasives, metal powders, and other inorganic fillers.

[0094] The abrasive can be appropriately selected so that it acts as an abrasive and improves the coefficient of friction depending on the material of the rotor, which is the mating material, and can be selected based on the Mohs hardness of the mating material. From the viewpoint of more effectively exhibiting the coefficient of friction by the abrasive, the Mohs hardness of the abrasive is preferably 6 or more and preferably 8 or less.

[0095] Examples of abrasives include silicon carbide (silicon carbide), titanium oxide, α-alumina, γ-alumina, silica (silicon dioxide), magnesia (magnesium oxide), zirconia (zirconium oxide), zircon (zirconium silicate), chromium oxide, iron oxide (iron trioxide, etc.), chromite, quartz, and iron sulfide. Among these, zirconia (zirconium oxide) and zircon (zirconium silicate) are preferred. The average particle size of zirconia (zirconium oxide) is preferably 1 μm to 14 μm. The average particle size of zirconium silicate is preferably 0.2 μm to 2 μm.

[0096] When the friction material composition contains an abrasive, the content thereof is preferably 0.1 mass % or more, more preferably 5 mass % or more, and is preferably 30 mass % or less, more preferably 25 mass % or less, and even more preferably 18 mass % or less, relative to 100 mass % of the total amount of the friction material composition.

[0097] Examples of the metal powder include powders of simple metals or alloys of aluminum, zinc, iron, tin, etc. One of these may be used alone, or two or more may be used in combination.

[0098] Examples of other inorganic fillers include vermiculite, clay, mica, talc, dolomite, chromite, mullite, calcium silicate, titanates other than the above titanates (hereinafter referred to as "other titanates"), etc. One of these may be used alone, or two or more may be used in combination.

[0099] Other titanates include potassium hexatitanates such as TERRACESS JSL, TERRACESS JSL-R, TERRACESS DP-R, TERRACESS DP-A, and TERRACESS DP-AS manufactured by Otsuka Chemical Co., Ltd., TXAX-MA and TXAX-A manufactured by Kubota Corporation, and TOFIX-S and TOFIX-SNR manufactured by Toho Titanium Co., Ltd.; sodium hexatitanates such as TERRACESS DSR manufactured by Otsuka Chemical Co., Ltd.; potassium octatitanates such as TERRACESS TF-SS, TERRACESS TF-S, TERRACESS TF-L, and TERRACESS JP manufactured by Otsuka Chemical Co., Ltd.; and TERRACESS PM and TERRACESS and lithium potassium titanate such as TERRACESS L, TERRACESS L-SS, and TERRACESS JSM-M manufactured by Otsuka Chemical Co., Ltd. Preferred examples of other titanates include sodium hexatitanate, potassium octatitanate, magnesium potassium titanate, and lithium potassium titanate.

[0100] When the friction material composition contains the other titanate, the mass ratio of the other titanate to the friction modifier of the present invention (other titanate / friction modifier of the present invention) is preferably 0.1 or more and preferably 3 or less, from the viewpoint of the friction coefficient in the high load region.

[0101] (2-3-4. Lubricant) The lubricant is preferably a solid lubricant, and examples thereof include carbon-based lubricants, metal sulfide-based lubricants, polytetrafluoroethylene (PTFE), etc. One of these may be used alone, or two or more may be used in combination. The lubricant is preferably one or more selected from the group consisting of carbon-based lubricants and metal sulfide-based lubricants.

[0102] When the friction material composition contains a lubricant, the content thereof is preferably 0.1 mass % or more, more preferably 1 mass % or more, and is preferably 20 mass % or less, more preferably 10 mass % or less, and even more preferably 5 mass % or less, relative to 100 mass % of the total amount of the friction material composition.

[0103] Examples of the carbon-based lubricant include synthetic or natural graphite, flake graphite, phosphate-coated graphite, carbon black, coke, activated carbon, and elastic graphitized carbon, with synthetic graphite and natural graphite being preferred in terms of being able to more reliably impart thermal conductivity. Examples of the metal sulfide-based solid lubricant include antimony trisulfide, molybdenum disulfide, tin sulfide, iron sulfide, zinc sulfide, bismuth sulfide, and tungsten disulfide, with tin sulfide and molybdenum disulfide being preferred in terms of being less harmful to the human body.

[0104] (2-3-5. pH Adjuster) Examples of the pH adjuster include inorganic bases such as calcium hydroxide (slaked lime), sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, trisodium phosphate, disodium hydrogen phosphate, tripotassium phosphate, and dipotassium hydrogen phosphate, and organic bases such as imidazole, histidine, and hexamethylenediamine. From the viewpoints of cost and hygroscopicity, the pH adjuster is preferably an inorganic base. One of these may be used alone, or two or more may be used in combination. The pH adjuster may also be used to prevent rust adhesion between the friction material and the mating material (rotor).

[0105] When the friction material composition contains a pH adjuster, the content thereof is preferably 0.1% by mass or more and preferably 8% by mass or less, based on 100% by mass of the total amount of the friction material composition.

[0106] (2-3-6. Filler) Examples of the filler include barium sulfate and calcium carbonate. Preferably, barium sulfate can be used as the filler. One of these may be used alone, or two or more may be used in combination.

[0107] Barium sulfate comes in two forms: elutriated barium sulfate (baryte powder), which is obtained by crushing a mineral called barite, washing it to remove iron, and elutriating it, and artificially synthesized precipitated barium sulfate. The particle size of precipitated barium sulfate can be controlled by the synthesis conditions, allowing for the production of fine barium sulfate with a low content of the desired coarse particles. It is preferable to use precipitated barium sulfate in order to further reduce impurities and achieve a more uniform particle size distribution of the barium sulfate particles.

[0108] (2-4. Method for Producing Friction Material Composition) The friction material composition of the present invention can be produced by (1) a method of mixing the components using a mixer such as a Loedige mixer ("Loedige" is a registered trademark), a pressure kneader, or an Eirich mixer ("Eirich" is a registered trademark); or (2) a method of preparing granules of the desired components and, if necessary, mixing other components using a mixer such as a Loedige mixer, a pressure kneader, or an Eirich mixer.

[0109] The content of each component in the friction material composition of the present invention can be appropriately selected depending on the desired friction characteristics, and the composition can be produced by the above-mentioned production method.

[0110] The friction material composition of the present invention may also be prepared by preparing a masterbatch containing a specific component at a high concentration, and then adding and mixing a thermosetting resin or the like to this masterbatch.

[0111] <3. Friction Material and Friction Member> In the present invention, the friction material composition is pre-molded at room temperature (20°C), and the resulting pre-molded body is subjected to heat and pressure molding (molding pressure of 10 MPa to 40 MPa, molding temperature of 150°C to 200°C). If necessary, the resulting molded body is subjected to heat treatment in a heating furnace (150°C to 220°C, held for 1 hour to 12 hours), and then the molded body is subjected to machining and polishing, thereby producing a friction material having a predetermined shape.

[0112] The friction material of the present invention is used as a friction member formed from the friction material to form a friction surface. Examples of friction members that can be formed using the friction material include (1) a structure consisting of only the friction material, and (2) a structure having a substrate such as a backing metal and the friction material of the present invention provided on the substrate to provide a friction surface.

[0113] The substrate is used to further improve the mechanical strength of the friction member. Examples of the material for the substrate include metal and fiber-reinforced resin. Examples of metal and fiber-reinforced resin include iron, stainless steel, glass fiber-reinforced resin, and carbon fiber-reinforced resin.

[0114] Friction materials usually have many fine pores formed inside, which act as escape routes for decomposition products (gases and liquids) at high temperatures, preventing a decrease in friction characteristics, and also preventing squealing by reducing the rigidity of the friction material and improving damping. In ordinary friction materials, the material blend and molding conditions are controlled so that the porosity is preferably 5% to 30%, and more preferably 10% to 25%.

[0115] The friction member of the present invention is made of the friction material composition of the present invention, and therefore can obtain excellent friction characteristics even when it does not contain a copper component or when the copper component content is reduced. Therefore, the friction member of the present invention can be suitably used in brake systems in general, such as disc pads, brake linings, and clutch facings that constitute braking devices for various vehicles and industrial machinery, and can be suitably used particularly as a friction member for regenerative cooperative brakes.

[0116] The present invention will now be described in further detail with reference to specific examples.

[0117] The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the present invention.

[0118] <Production of Titanate> (Synthesis Example 1) A 20 mass% aqueous slurry of magnesium potassium titanate (KTMO, manufactured by Otsuka Chemical Co., Ltd., product name: TERRACESS PM) was prepared, and 0.34 equivalents of sulfuric acid relative to the potassium in the magnesium potassium titanate was mixed with the aqueous slurry and stirred for 2 hours at room temperature (20° C.). This aqueous slurry was suction filtered and washed with deionized water to separate the cake (solid content). This cake was dried at 110° C. for 12 hours, calcined at 500° C. for 1 hour in an electric furnace, and then slowly cooled. The calcined product was passed through a 20-mesh sieve to obtain the target titanate 1.

[0119] Synthesis Example 2 Titanate 2 was obtained in the same manner as in Synthesis Example 1, except that the equivalent of sulfuric acid was changed to 0.27 equivalents and the baking time was changed to 12 hours.

[0120] Synthesis Example 3 Titanate 3 was obtained in the same manner as in Synthesis Example 1, except that the equivalent of sulfuric acid was changed to 0.27 equivalents.

[0121] Synthesis Example 4 Titanate 4 was obtained in the same manner as in Synthesis Example 1, except that the equivalent of sulfuric acid was changed to 0.22 equivalents.

[0122] Synthesis Example 5 Titanate 5 was obtained in the same manner as in Synthesis Example 1, except that the equivalent of sulfuric acid was changed to 0.16 equivalents.

[0123] Synthesis Example 6 Potassium magnesium titanate (KTMO, manufactured by Otsuka Chemical Co., Ltd., trade name: TERRACESS PM) was used as titanate 6 as it was.

[0124] Synthesis Example 7 A 20% by mass aqueous slurry of lithium potassium titanate (KTLO, manufactured by Otsuka Chemical Co., Ltd., product name: TERRACESS L) was prepared, and 0.24 equivalents of sulfuric acid relative to the potassium in the lithium potassium titanate was mixed with the aqueous slurry and stirred for 2 hours at room temperature (20° C.). The aqueous slurry was suction filtered and washed with deionized water to separate a cake (solid content). The cake was dried at 110° C. for 12 hours, calcined at 500° C. for 1 hour in an electric furnace, and then slowly cooled. The calcined product was passed through a 20-mesh sieve to obtain the target titanate 7.

[0125] Synthesis Example 8 Titanate 8 was obtained in the same manner as in Synthesis Example 7, except that the equivalent of sulfuric acid was changed to 0.19 equivalents.

[0126] Synthesis Example 9 Titanate 9 was obtained in the same manner as in Synthesis Example 7, except that the equivalent of sulfuric acid was changed to 0.05 equivalents.

[0127] Synthesis Example 10 Potassium lithium titanate (KTLO, manufactured by Otsuka Chemical Co., Ltd., trade name: TERRACESS L) was used as titanate 10 as it was.

[0128] <Measurement of Physical Properties of Titanates> The physical properties of Titanate 1 to Titanate 10 were measured as follows, and the results are shown in Table 1.

[0129] (Heating test) 3 g of sample was placed in an alumina furnace tube under a nitrogen atmosphere and heated at 800 ° C for 1 hour using an electric tubular furnace. 1 g of the heated sample was mixed with 0.5 g of standard silicon powder (Rare Metallic Co., Ltd., silicon powder (purity 99.9%)) to obtain a mixture, and the X-ray diffraction spectrum of the mixture was measured using an X-ray diffractometer (Rigaku Corporation, product number "Ultima IV"). The integrated intensities of the peaks derived from the undecomposed material (titanate before heating) observed at diffraction angles 2θ = 10.9 ° to 11.6 °, the peaks derived from titanate with a hollandite crystal structure observed at diffraction angles 2θ = 27.5 ° to 28.0 °, and the peaks derived from the standard silicon powder observed at diffraction angles 2θ = 28.0 ° to 28.7 ° in the obtained X-ray diffraction pattern were measured, and the content (mass%) of the undecomposed material (titanate before heating) and the titanate with a hollandite crystal structure was calculated from a previously prepared calibration curve. The decomposition rate of titanate and the production rate of titanate with a hollandite crystal structure were also determined.

[0130] (Average particle size) Measurement was performed using a laser diffraction particle size distribution analyzer (Shimadzu Corporation, product number "SALD-2300"), and the particle size at 50% cumulative volume in the obtained particle size distribution was taken as the average particle size.

[0131] (Specific Surface Area) Measurement was carried out using an automatic specific surface area measuring device (manufactured by Micromeritics, product number "TriStar II 3020").

[0132] (Particle Shape) The particle shape was confirmed using a field emission scanning electron microscope (manufactured by Hitachi High-Tech Corporation, product number "S-4800").

[0133] (Alkali Metal Ion Elution Rate) The mass (X) of the sample was measured, and then the sample was added to ultrapure water to prepare a 1% by mass slurry. After stirring at 80°C for 4 hours, the solid content was removed using a membrane filter with a pore size of 0.2 µm to obtain an extract. The mass (Y) of the alkali metal ions in the obtained extract was measured using an ion chromatograph (manufactured by Dionex Corporation, product number "ICS-1100"). Next, using the values ​​of the masses (X) and (Y) g, the alkali metal ion elution rate (mass %) was calculated based on the formula [(Y) / (X)] x 100.

[0134]

[0135] <Production of Friction Members> (Examples 1-14, Comparative Examples 1-2, and Reference Example 1) The materials were blended according to the blending ratios listed in Tables 2 and 3 and mixed for 3 minutes using an Eirich mixer. The resulting mixture was pressurized at 15 MPa for 5 seconds at room temperature (20°C) to produce a temporary compact. The temporary compact was fitted into the cavity of a hot-molding die heated to 150°C, and with a back plate (made of steel) placed on top, the mixture was pressurized at 10 MPa to 40 MPa for 300 seconds so that the porosity of the compact was 15%. Five degassing treatments were performed between 5 and 70 seconds measured from the start of pressurization. The resulting compact was placed in a constant-temperature dryer heated to 220°C and held there for 2 hours to fully harden, yielding a friction member. The materials used in Tables 2 and 3, other than titanates 1-10, were as follows:

[0136] (Titanate 11) Titanate 11: 6 potassium titanate (6KT), columnar particles, average major axis 65 μm, average minor axis 13 μm

[0137] (Titanate 12) Titanate 12: 6 Sodium titanate, porous spherical particles, average particle diameter 21.2 μm, manufactured by Otsuka Chemical Co., Ltd. (trade name: TERRACESS DSR)

[0138] (Titanate 13) Titanate 13: 6 Potassium titanate, porous spherical particles, average particle diameter 60.1 μm, manufactured by Otsuka Chemical Co., Ltd. (trade name: TERRACESS DP-AS)

[0139] (Titanate 14) Titanate 14: 6 Potassium titanate, columnar particles, average particle diameter 36 μm, manufactured by Otsuka Chemical Co., Ltd. (trade name: TERRACESS JSL)

[0140] (Binder) Phenolic resin: Hexamethylenetetramine-blended novolac-type phenolic resin powder

[0141] (Other materials) Barium sulfate: average particle diameter 1.6 μm Natural mica: average particle diameter 180 μm Cashew dust: average particle diameter 200 μm Iron oxide: average particle diameter 0.3 μm, Mohs hardness 6 Zirconium silicate: average particle diameter 1.1 μm, Mohs hardness 7.5 Antimony trisulfide: average particle diameter 1.5 μm Synthetic graphite: average particle diameter 730 μm Aramid fiber: fibrillated para-aramid fiber (aramid pulp), fiber length 0.89 mm, specific surface area 9.8 m ２ / g Slaked lime: average particle size 0.2 μm Rock wool: average fiber length 125 μm, maximum shot content (125 μm or more) 5.0%

[0142] <Evaluation of Friction Member> The Rockwell hardness and fade test of the friction members prepared above were evaluated as follows.

[0143] (Rockwell Hardness) The Rockwell hardness of the surface of the friction member was measured according to the method of JIS D4421. The hardness scale used was the S scale. The results are shown in Table 2 below.

[0144] (Fade Test) The surface (friction surface) of the friction member was polished to 1.0 mm, and a braking effectiveness test was performed based on JASO C406. However, the first fade test conditions were changed to a speed of 160 km / h, which is assumed to be a high load, and the braking effectiveness test was performed. The rotor used was a cast iron rotor that conforms to ASTM standard number A48 / A48M.

[0145] FIG. 1 is a graph showing the relationship between the number of braking cycles and the coefficient of friction during fading in the fading test of the friction members obtained in Example 3 and Comparative Example 1.

[0146] From Figure 1, it can be seen that Example 3, which used magnesium potassium titanate with a decomposition rate of 30% or more, had a larger friction coefficient in the high load range and better stability of the friction coefficient than Comparative Example 1, which used magnesium potassium titanate with a decomposition rate of less than 30%.

[0147] FIG. 2 is a graph showing the relationship between the number of braking cycles and the coefficient of friction during fading in the fading test of the friction members obtained in Example 7 and Comparative Example 2.

[0148] From Figure 2, it can be seen that Example 7, which used lithium potassium titanate with a decomposition rate of 30% or more, had a larger friction coefficient in the high load range and better stability of the friction coefficient than Comparative Example 2, which used lithium potassium titanate with a decomposition rate of less than 30%.

[0149] 3 is a graph showing the relationship between the change in friction coefficient (μ) with respect to rotor temperature and the average friction coefficient (μ) during fade in the fade test of the friction members obtained in Examples 1, 3, 5, Comparative Example 1, and Reference Example 1. The average friction coefficient (μ) during fade was determined from the average value (average μ) of 10 braking cycles in the first fade test results.

[0150] From Figure 3, it can be seen that in Examples 1, 3, and 5, which used magnesium potassium titanate with a decomposition rate of 30% or more, the friction coefficients were equal to or greater than those of Reference Example 1, which used potassium hexatitanate, and the stability of the friction coefficient was also improved.

[0151] For all Examples, Comparative Examples, and Reference Examples, the average value (average μ) of the 10 braking cycles in the first fade test results and Δμ (maximum - minimum) were calculated from the difference between the maximum μ and minimum μ during the first fade. The results are shown in Tables 2 and 3 below.

[0152]

[0153]

Claims

1. A friction modifier composed of titanate, the titanate is a salt of one or more elements selected from the group consisting of alkali metals and alkaline earth metals, A friction modifier, wherein a decomposition rate of the titanate when heated at 800°C for 1 hour in a nitrogen atmosphere is 30% by mass or more and 100% by mass or less.

2. 2. The friction modifier according to claim 1, wherein a production rate of the titanate having a hollandite crystal structure when the titanate is heated at 800°C for 1 hour in a nitrogen atmosphere is 10% by mass or more and 100% by mass or less.

3. 3. The friction modifier according to claim 1, wherein the titanate is at least one of lithium potassium titanate and magnesium potassium titanate.

4. 3. The friction modifier according to claim 1, wherein the titanate is in the form of plate-like particles.

5. 3. The friction modifier according to claim 1, wherein the titanate has an average particle size of 0.1 μm or more and 100 μm or less.

6. The specific surface area of ​​the titanate is 0.1 m ２ / g or more, 10m ２ 3. The friction modifier according to claim 1, wherein the friction modifier has a viscosity of 1 / g or less.

7. 3. The friction modifier according to claim 1, wherein the titanate has an alkali metal ion elution rate of 0.01% by mass or more and 15% by mass or less.

8. A friction modifier according to claim 1 or 2, and a binder, A friction material composition having a copper content of less than 0.5 mass % in terms of elemental copper.

9. 9. The friction material composition according to claim 8, wherein the content of the titanate is 1% by mass or more and 40% by mass or less, relative to 100% by mass of the total amount of the friction material composition.

10. 9. The friction material composition according to claim 8, wherein a mass ratio of the titanate to the binder (titanate / binder) is 0.1 or more and 8 or less.

11. 9. The friction material composition according to claim 8, wherein the content of the steel fibers is less than 10% by mass, based on 100% by mass of the total amount of the friction material composition.

12. A friction material which is a molded product of the friction material composition according to claim 8.

13. A friction member comprising the friction material according to claim 12.