Friction material composition, friction material, and friction member

Abstract

This friction material composition contains a fiber base material that contains a cellulose fiber, and an inorganic filler, and the content of aramid fibers is 3 mass% or less with respect to the total amount of the fiber base material.

Description

Friction material composition, friction material, and friction member

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

[0002] Friction materials such as disc brake pads and brake linings are used for braking in automobiles, railway vehicles, various industrial machines, etc. Friction materials perform their braking function by rubbing against opposing materials such as disc rotors and brake drums.

[0003] For example, in order to provide a friction material that achieves both frictional properties and vibration characteristics, a friction material has been disclosed that includes a fibrous base material, a friction modifier, and a binder, and that the content of at least one copper component selected from copper, copper alloys, and copper compounds is 5 mass% or less in terms of elemental copper, and that the friction material includes 2 to 7 mass% elastic graphite, 3 to 10 mass% chromite, and 3 to 15 mass% steel fibers (see, for example, Patent Document 1). Also, in order to provide a friction material composition that reduces brake vibration during high-temperature braking and low-temperature wear, a friction material composition has been disclosed that includes a binder, an organic filler, an inorganic filler, and a fibrous base material, and that does not contain elemental copper in the friction material composition or that contains 0.5 mass% or less copper, that contains 2 to 5 mass% steel fibers with a fiber length of 2500 μm or less, and that contains a titanate with a layered crystal structure (see, for example, Patent Document 2). Furthermore, in order to provide a friction material composition capable of suppressing brake vibration during high-temperature braking, a friction material composition has been disclosed that contains a binder, an organic filler, an inorganic filler, and a fibrous base material, and that the friction material composition does not contain copper as an element or contains copper in an amount of 0.5 mass% or less, and that contains 2 to 5 mass% steel fibers having a fiber length of 2500 μm or less (see, for example, Patent Document 3). Also, in order to provide a friction material capable of suppressing brake vibration during high-temperature braking, a friction material molded from a friction material composition that contains 1 to 4 wt% cashew dust as an organic friction modifier, 7 to 12 wt% muscovite as an inorganic friction modifier, and 0.5 to 5 wt% aluminum particles as an inorganic friction modifier has been disclosed (see, for example, Patent Document 4).

[0004] JP 2015-093935 A JP 2016-121244 A JP 2019-214731 A JP 2021-017521 A

[0005] The friction material compositions and friction materials described in Patent Documents 1 to 4 use aramid fibers as a fiber base material or the like. Friction materials containing a large amount of aramid fibers may experience a decrease in the friction coefficient, known as fade. Furthermore, aramid fibers are derived from petroleum and have recently been facing problems such as rising prices and depletion. Furthermore, it is desirable to reduce the amount of aramid fibers used as part of efforts to achieve carbon neutrality.

[0006] The present disclosure has been made in consideration of the above-described conventional circumstances, and an object of one aspect of the present disclosure is to provide a friction material composition capable of forming a friction material capable of suppressing fade, and a friction material and a friction member using the friction material composition.

[0007] Specific means for achieving the above object are as follows. <1> A friction material composition comprising a fibrous base material containing cellulose fibers and an inorganic filler, wherein the aramid fiber content is 3 mass% or less based on the total amount of the fibrous base material. <2> The friction material composition according to <1>, wherein the cellulose fiber content is 1 mass% or more based on the total amount of the friction material composition. <3> The friction material composition according to <1> or <2>, wherein the aramid fiber content is less than 2 mass% based on the total amount of the fibrous base material. <4> The friction material composition according to any one of <1> to <3>, wherein the cellulose fibers have a fiber length of less than 2000 μm. <5> The friction material composition according to any one of <1> to <4>, wherein the cellulose fiber content is 4 mass% or more based on the total amount of the friction material composition. <6> The friction material composition according to any one of <1> to <5>, wherein the inorganic filler includes zirconia. <7> A friction material formed using the friction material composition according to any one of <1> to <6>. <8> A friction member comprising the friction material according to <7>.

[0008] According to one aspect of the present disclosure, there is provided a friction material composition capable of forming a friction material capable of suppressing fade, and a friction material and a friction member using the friction material composition.

[0009] Hereinafter, embodiments for carrying out the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure.

[0010] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another staged numerical range. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, particles corresponding to each component may include multiple types of particles. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified. In the present disclosure, the term "layer" includes cases where the layer is formed over the entire area when the area where the layer is present is observed, as well as cases where the layer is formed only in a part of the area. The average particle size of the particles refers to the 50% (median) diameter (D50) determined from the volume distribution of particle size distribution measured with a laser diffraction / scattering particle size distribution analyzer. The average particle size can be measured, for example, with an LA-920 (manufactured by Horiba, Ltd.).

[0011] [Friction Material Composition] The friction material composition of the present disclosure includes a fibrous base material containing cellulose fibers and an inorganic filler, and the content of aramid fibers is 3 mass% or less based on the total amount of the fibrous base material. The friction material composition of the present disclosure may include other components in addition to the above components.

[0012] The friction material composition of the present disclosure includes a fibrous base material containing cellulose fibers, and the content of aramid fibers is 3 mass% or less based on the total amount of the fibrous base material. The cellulose fibers are used as a substitute for the aramid fibers, thereby reducing the amount of aramid fibers used. This provides a friction material composition that can form a friction material that can suppress the fade phenomenon.

[0013] Furthermore, the friction material composition of the present disclosure reduces the amount of aramid fiber, which is a petroleum-derived fiber, used, and can therefore contribute to carbon neutrality.

[0014] (Fiber base material) The friction material composition of the present disclosure includes a fiber base material containing cellulose fibers. The fiber base material is included to provide a reinforcing effect in the friction material. The fiber base material may or may not include fibers other than cellulose fibers (hereinafter also referred to as "other fibers"). The fiber base material may include one or more types of cellulose fibers, or may include one or more types of fibers other than cellulose fibers.

[0015] Examples of cellulose fibers include natural cellulose fibers, regenerated cellulose fibers, and pulp pulp products. Regenerated cellulose fibers are obtained by chemically dissolving natural cellulose contained in wood pulp, cotton, etc. using a solvent or the like, extracting the cellulose, spinning it, and then remaking it into fibers. Known cellulose fibers can be used.

[0016] Examples of regenerated cellulose fibers include rayon fibers, lyocell fibers, cupra fibers, and polynosic fibers.

[0017] The pulp powder is made by crushing kraft pulp, which has not been spun into fibers by chemical treatment, and any known product can be used. Crushed recycled paper pulp can also be used.

[0018] The fiber length of the cellulose fibers is not particularly limited and may be 5000 μm or less, or from the viewpoint of dispersion, may be less than 2000 μm or may be 1000 μm or less. The lower limit of the fiber length of the cellulose fibers is not particularly limited and may be 500 μm or more.

[0019] The fiber diameter of the cellulose fibers is not particularly limited, and may be 5 μm to 100 μm, 10 μm to 50 μm, or 15 μm to 30 μm.

[0020] The fiber length of cellulose fibers refers to the number-average fiber length, which indicates the average length of cellulose fibers. The fiber length of cellulose fibers refers to the arithmetic average when 50 cellulose fibers are randomly selected and the fiber lengths are measured using an electron microscope. The fiber diameter of cellulose fibers refers to the number-average fiber diameter, which indicates the average diameter of cellulose fibers. The fiber diameter of cellulose fibers refers to the arithmetic average when 50 cellulose fibers are randomly selected and the fiber diameters are measured using an electron microscope.

[0021] When the cellulose fibers are regenerated cellulose fibers, the fiber length or fiber diameter of the cellulose fibers can be adjusted by adjusting the concentration of the spinning dope during the production of the regenerated cellulose, adjusting the spinning conditions, etc.

[0022] The cellulose fiber content is preferably 1% by mass or more of the total friction material composition from the viewpoint of fading suppression. From the viewpoint of formability (e.g., tablet formability) of the friction material composition, it is preferably 4% by mass or more. The cellulose fiber content may be 20% by mass or less, 15% by mass or less, or 10% by mass or less of the total friction material composition.

[0023] Examples of other fibers include inorganic fibers, metal fibers, organic fibers other than cellulose fibers, and carbon-based fibers.

[0024] Examples of inorganic fibers include ceramic fibers, biodegradable ceramic fibers, mineral fibers, glass fibers, potassium titanate fibers, silicate fibers, and wollastonite.

[0025] The carbon fiber referred to here may be flame-resistant fiber, pitch-based carbon fiber, PAN (polyacrylonitrile)-based carbon fiber, activated carbon fiber, or the like.

[0026] The mineral fiber referred to here refers to an artificial inorganic fiber that is melt-spun using blast furnace slag such as slag wool, basalt such as basalt fiber, or other natural rocks as the main component. The mineral fiber is preferably a fiber derived from a natural mineral containing Al. Specifically, SiO ２ , Al ２ O ３ , CaO, MgO, FeO, Na ２ Among these, those containing Al element can be preferably used as the mineral fiber.

[0027] The mineral fiber is preferably biosoluble. The biosoluble mineral fiber referred to here is a mineral fiber that, even if taken into the human body, is characterized by being partially decomposed and excreted from the body within a predetermined time. Specifically, it refers to a fiber whose chemical composition has a total content of alkali metal oxides and alkaline earth metal oxides (total content of oxides of sodium, potassium, calcium, magnesium, and barium) of 18% by mass or more, and which satisfies the following conditions: in a short-term bio-permanence test by respiration, the mass half-life of fibers 20 μm or larger is 40 days or less, there is no evidence of excessive carcinogenicity in an intraperitoneal test, or there is no related pathogenicity or tumorigenesis in a long-term respiration test (Nota Q (carcinogenicity exemption) of EU Directive 97 / 69 / EC). Such biosoluble mineral fibers include SiO ２ -Al ２ O ３ -CaO-MgO-FeO-Na ２ O-based fibers, etc., and SiO ２ , Al ２ O ３ , CaO, MgO, FeO, Na ２ Examples of commercially available products include the Roxul series manufactured by Lapinus Fibers B.V. "Roxul" includes fibers containing SiO ２ , Al ２ O ３ , CaO, MgO, FeO, Na ２ O and the like are included.

[0028] As the metal fibers, copper or copper alloy fibers can be used to improve crack resistance and abrasion resistance. Examples of copper or copper alloy fibers that can be used include copper fibers, brass fibers, and bronze fibers.

[0029] Furthermore, metal fibers other than copper and copper alloys may be used as the metal fibers. Metal fibers other than copper and copper alloys may be contained from the viewpoint of improving the coefficient of friction and crack resistance.

[0030] Examples of metal fibers other than copper and copper alloys include fibers of simple metals or alloys such as aluminum, iron, zinc, tin, titanium, nickel, magnesium, and silicone, and fibers primarily composed of metals such as cast iron fibers.

[0031] Examples of organic fibers include aramid fibers, acrylic fibers, and phenolic resin fibers which may have a crosslinked structure.

[0032] The friction material composition of the present disclosure may or may not contain aramid fibers as the fibrous base material. In the friction material composition of the present disclosure, the aramid fiber content may be 3% by mass or less relative to the total amount of the fibrous base material. From the viewpoint of suitably forming a friction material that can suppress fade, the aramid fiber content is preferably less than 2% by mass, more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0% by mass.

[0033] The content of the fibrous base material is preferably 5% by mass to 40% by mass, more preferably 5% by mass to 30% by mass, and even more preferably 6% by mass to 20% by mass, based on the total amount of the friction material composition.

[0034] The content of cellulose fibers in the fiber substrate may be 10% by mass to 100% by mass, 15% by mass to 80% by mass, or 20% by mass to 60% by mass, based on the total amount of the fiber substrate.

[0035] (Inorganic Filler) The friction material composition of the present disclosure contains an inorganic filler. The inorganic filler may be used alone or in combination of two or more.

[0036] Examples of inorganic fillers include graphite, zirconia (zirconium dioxide), metal sulfides, mica, titanates, coke, calcium hydroxide (slaked lime), calcium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, barium sulfate, dolomite, iron oxide, vermiculite, calcium sulfate, talc, clay, zeolite, zirconium silicate, mullite, chromite, titanium oxide, magnesium oxide, silica, iron oxide, garnet, aluminas such as α-alumina and γ-alumina, and silicon carbide.

[0037] Examples of graphite include artificial graphite such as petroleum pitch-based and coal pitch-based graphite, and natural graphite.

[0038] Examples of metal sulfides include antimony trisulfide, tin sulfide, tin disulfide, molybdenum disulfide, iron sulfide, iron disulfide, bismuth sulfide, zinc sulfide, and tungsten disulfide.

[0039] Examples of titanates include potassium titanate, lithium potassium titanate, sodium titanate, and magnesium potassium titanate.

[0040] The inorganic filler may include at least one selected from the group consisting of graphite, zirconia, metal sulfide, titanate, barium sulfate, calcium hydroxide, and alumina.

[0041] The content of the inorganic filler may be 30% by mass to 85% by mass, 50% by mass to 80% by mass, or 60% by mass to 80% by mass, based on the total amount of the friction material composition.

[0042] The inorganic filler may contain zirconia. The zirconia content is preferably 40% by mass or less, more preferably 10% to 35% by mass, and even more preferably 15% to 30% by mass, based on the total amount of the friction material composition. The mass ratio of zirconia to cellulose fiber (zirconia:cellulose fiber) may be 25:1 to 25:15, or 25:2 to 25:10. The average particle size of the zirconia is preferably 1 μm to 10 μm, and more preferably 1 μm to 5 μm.

[0043] The inorganic filler may contain a titanate (preferably potassium titanate). The content of the titanate (preferably potassium titanate) is preferably 40 mass% or less, more preferably 10 mass% to 35 mass%, and even more preferably 15 mass% to 30 mass%, based on the total amount of the friction material composition. The mass ratio of the titanate (preferably potassium titanate) to the cellulose fiber (titanate:cellulose fiber) may be 26:1 to 26:15, or may be 26:2 to 26:10.

[0044] The inorganic filler may contain barium sulfate. The content of barium sulfate is preferably 20% by mass or less, more preferably 5% by mass to 15% by mass, and even more preferably 5% by mass to 12% by mass, based on the total amount of the friction material composition. The mass ratio of barium sulfate to cellulose fiber (barium sulfate:cellulose fiber) may be 10:0.5 to 10:15, or may be 10:1 to 10:10.

[0045] (Organic Filler) The friction material composition of the present disclosure may contain an organic filler. Examples of the organic filler include friction dust and cashew dust. The organic filler may be used alone or in combination of two or more.

[0046] The content of the organic filler may be 4% by mass to 20% by mass, 5% by mass to 15% by mass, or 6% by mass to 10% by mass, based on the total amount of the friction material composition.

[0047] (Binder) The friction material composition of the present disclosure may contain a binder. The binder binds and integrates the components contained in the friction material composition, thereby giving the composition a predetermined shape and strength. There are no particular restrictions on the binder contained in the friction material composition of the present disclosure, and any known thermosetting resin used as a binder for friction materials can be used.

[0048] Examples of thermosetting resins include phenolic resins (resol-type phenolic resins and novolac-type phenolic resins), epoxy resins, and polyimide resins. Further examples include various 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. These may be used alone or in combination of two or more. It is particularly preferable to use at least one selected from the group consisting of phenolic resins, acrylic-modified phenolic resins, silicone-modified phenolic resins, and alkylbenzene-modified phenolic resins, as these resins provide good heat resistance, moldability, and coefficient of friction.

[0049] The binder content is preferably 4% by mass to 20% by mass, more preferably 5% by mass to 15% by mass, and even more preferably 6% by mass to 10% by mass, based on the total amount of the friction material composition. By setting the binder content within the range of 4% by mass to 20% by mass, based on the total amount of the friction material composition, a decrease in the strength of the friction material can be further suppressed.

[0050] (Other Materials) The friction material composition of the present disclosure may contain other materials in addition to the above-described components, as necessary. Examples of other materials include fluorine-based polymers such as PTFE (polytetrafluoroethylene), rubber powder, etc. The other materials may be used alone or in combination of two or more.

[0051] Examples of rubber components constituting the rubber powder include tire rubber, natural rubber, acrylonitrile-butadiene rubber (NBR), acrylic rubber, isoprene rubber, polybutadiene rubber (BR), styrene butadiene rubber (SBR), silicone rubber, etc. The rubber powder may be tire powder composed of tire rubber.

[0052] The shape of the friction material composition of the present disclosure is not particularly limited, and may be in the form of powder, tablet, or the like.

[0053] [Friction Material] The friction material of the present disclosure is formed using the friction material composition of the present disclosure. The friction material of the present disclosure can be used as a friction material for disc brake pads, brake linings, and the like used in automobiles, etc.

[0054] The friction material of the present disclosure can be produced by molding the friction material composition of the present disclosure using a commonly used method. Preferably, it is produced by hot-press molding. Specifically, the friction material composition of the present disclosure is mixed using a mixer such as a Lödige mixer, a pressure kneader, or an Eirich mixer, and the mixture is preformed in a molding die. The resulting preform is heated and molded at a molding temperature of 140°C to 160°C and a molding pressure of 20 MPa to 50 MPa for 4 to 10 minutes, and the resulting molded product is then heat-treated at 180°C to 250°C for 2 to 10 hours. Furthermore, painting, scorching, polishing, etc. may be performed as necessary.

[0055] [Friction Member] The friction member of the present disclosure includes the friction material of the present disclosure. In the friction member of the present disclosure, it is preferable that the friction material of the present disclosure constitutes the friction surface of the friction member. Examples of the friction member of the present disclosure include the following configurations: (1) A configuration consisting of only the friction material; (2) A configuration having a backing metal and the friction material of the present disclosure that forms the friction surface provided on the backing metal; (3) A configuration in which, in the configuration (2) above, a primer layer for surface modification to enhance the adhesive effect of the backing metal to the friction material and an adhesive layer for bonding the backing metal to the friction material are further interposed between the backing metal and the friction material.

[0056] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples in any way.

[0057] [Preparation of disc brake pads] Materials were blended according to the blending ratios (mass%) shown in Table 1 to obtain friction material compositions of Examples and Comparative Examples. The blend amount of each component in Table 1 is expressed in mass% of the friction material composition. In Table 1, "-" indicates that the corresponding component is not contained. Details of the cellulose 1 and cellulose 2 used are as follows: - Cellulose 1 - Fiber length: 900 μm, fiber diameter: 20 μm, bulk density: 20 to 40 g / L - Cellulose 2 - Fiber length: 2200 μm, fiber diameter: 35 μm, bulk density: 25 to 50 g / L

[0058] This friction material composition was mixed in a Loedige mixer (manufactured by Matsubo Corporation, product name: Loedige mixer M20), and this mixture was preformed in a molding press (manufactured by Oji Machinery Co., Ltd.). The resulting preform was hot-pressed together with a steel backing metal using a molding press (manufactured by Sanki Seiko Co., Ltd.) at a molding temperature of 150°C and a molding pressure of 20 MPa to 40 MPa for 5 minutes. The resulting molded product was heat-treated at 200°C to 300°C, polished using a rotary polisher, and subjected to a scorch treatment to produce a disc brake pad (friction material thickness 11 mm, friction material projected area 52 cm). ２ ) was obtained.

[0059] The general performance test was conducted in accordance with JASO C406. Specifically, the test was conducted using a 1 / 5 scale tester (inertia 3.0 kg m ２ ) and 18 mm x 44 mm test pieces cut out from the disc brake pads produced in each Example and Comparative Example were used to determine the minimum value (Min.min.μ) of the average friction coefficient μ in the 1st Fade test, which is an index of fade suppression. JASO performance wear in Table 1 means the average pad wear (mm) after the test was completed. The higher the fade suppression value in Table 1, the more the fade phenomenon was suppressed.

[0060]

[0061] As is clear from the evaluation results in Table 1, the brake pads formed using the friction material compositions of the Examples were able to suppress the fade phenomenon compared to the brake pads formed using the friction material compositions of the Comparative Examples.

[0062] The disclosure of Japanese Patent Application No. 2023-215214, filed on December 20, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A friction material composition comprising a fibrous base material containing cellulose fibers and an inorganic filler, wherein the content of aramid fibers is 3 mass% or less based on the total amount of the fibrous base material.

2. The friction material composition according to claim 1, wherein the content of the cellulose fibers is 1 mass % or more based on the total amount of the friction material composition.

3. The friction material composition according to claim 1, wherein the content of the aramid fiber is less than 2 mass% based on the total amount of the fiber base material.

4. The friction material composition according to claim 1, wherein the cellulose fibers have a fiber length of less than 2000 μm.

5. The friction material composition according to claim 1, wherein the content of the cellulose fibers is 4 mass% or more based on the total amount of the friction material composition.

6. The friction material composition according to claim 1, wherein the inorganic filler contains zirconia.

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

8. A friction member comprising the friction material according to claim 7.

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