Friction material composition, friction material, and friction member

Abstract

To provide a friction material composition enabling formation of a friction material that can prevent the fade phenomenon.SOLUTION: This friction material composition contains a fiber base material that contains a cellulose fiber, and an inorganic filler, wherein the content of aramid fibers is 3 mass% or less with respect to the total amount of the fiber base material.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] For automobiles, railway vehicles, various industrial machines, etc., friction materials such as disc brake pads and brake linings are used for braking. The friction material plays a braking role by friction with a facing material such as a disc rotor or a brake drum.

[0003] For example, in order to provide a friction material with compatible friction characteristics and vibration characteristics, a friction material including a fiber base material, a friction modifier, and a binder, wherein the content of at least one copper component selected from copper, copper alloys, and copper compounds is 5% by mass or less in terms of copper element, 2 to 7% by mass of elastic graphite, 3 to 10% by mass of chromite, and 3 to 15% by mass of steel fiber is disclosed (see, for example, Patent Document 1). Further, in order to provide a friction material composition with less brake vibration during high-temperature braking and less low-temperature wear, a friction material composition including a binder, an organic filler, an inorganic filler, and a fiber base material, which does not contain copper as an element or has a copper content of 0.5% by mass or less, and contains 2 to 5% by mass of steel fiber with a fiber length of 2500 μm or less and contains a titanate having a layered crystal structure is disclosed (see, for example, Patent Document 2). Further, in order to provide a friction material composition capable of suppressing brake vibration during high-temperature braking, a friction material composition including a binder, an organic filler, an inorganic filler, and a fiber base material, which does not contain copper as an element or has a copper content of 0.5% by mass or less, and contains 2 to 5% by mass of steel fiber with a fiber length of 2500 μm or less is disclosed (see, for example, Patent Document 3). In order to provide a friction material capable of suppressing brake vibration during high-temperature braking, there is disclosed a friction material formed from a friction material composition characterized by containing 1 to 4% by weight of cashew dust as an organic friction modifier, 7 to 12% by weight of muscovite as an inorganic friction modifier, and 0.5 to 5% by weight of aluminum particles as an inorganic friction modifier (see, for example, Patent Document 4).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the friction material compositions and friction materials described in Patent Documents 1 to 4, aramid fibers are used as a fiber base material or the like. In friction materials containing a large amount of aramid fibers, a decrease in the friction coefficient called fade may occur. In addition, aramid fibers are petroleum-derived fibers, and in recent years, problems such as price increases and depletion have occurred. Furthermore, it is desirable to reduce the usage amount as part of carbon neutrality.

[0006] The present disclosure has been made in view of the above 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 the fade phenomenon, as well as a friction material and a friction member using this friction material composition.

Means for Solving the Problems

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

Advantages of the Invention

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

Modes for Carrying Out the Invention

[0009] Hereinafter, modes 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, the constituent elements (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present disclosure.

[0010] In the present disclosure, in the numerical range indicated by using "~", the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, each component may contain a plurality of corresponding substances. When there are a plurality of substances corresponding to each component in the composition, the content rate or content of each component means the total content rate or content of the plurality of substances present in the composition, unless otherwise specified. In the present disclosure, the particles corresponding to each component may contain a plurality of types of particles. When there are a plurality of types of particles corresponding to each component in the composition, the particle diameter of each component means the value for the mixture of the plurality of types of particles present in the composition, unless otherwise specified. In the present disclosure, the term "layer" includes not only the case where it is formed over the entire region where the layer exists when observing the region where the layer is present, but also the case where it is formed only in a part of the region. The average particle diameter of the particles refers to the 50% (median) diameter (D50) obtained from the volume distribution of the particle size distribution measured by a laser diffraction / scattering type particle size distribution measuring device. The average particle diameter can be measured, for example, with LA-920 (manufactured by Horiba, Ltd.).

[0011] [Friction material composition] The friction material composition of the present disclosure includes a fiber base material containing cellulose fibers and an inorganic filler, and the content rate of aramid fibers is 3% by mass or less with respect to the total amount of the fiber base material. The friction material composition of the present disclosure may contain other components other than the above components.

[0012] The friction material composition of the present disclosure includes a fiber base material containing cellulose fibers, and the content rate of aramid fibers is 3% by mass or less with respect to the total amount of the fiber base material. Cellulose fibers are included as a substitute for aramid fibers, and the usage amount of aramid fibers is reduced. Thereby, a friction material composition capable of forming a friction material capable of suppressing the fade phenomenon is provided.

[0013] Furthermore, in the friction material composition of the present disclosure, since the usage amount of aramid fiber, which is a petroleum-derived fiber, is reduced, it can contribute to carbon neutralization.

[0014] (Fiber substrate) The friction material composition of the present disclosure includes a fiber substrate containing cellulose fibers. The fiber substrate is included to play a reinforcing role in the friction material. The fiber substrate may or may not contain fibers other than cellulose fibers (hereinafter also referred to as "other fibers"). The fiber substrate may contain one or more cellulose fibers, and may also contain one or more fibers other than cellulose fibers.

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

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

[0017] Pulverized pulp is obtained by pulverizing kraft pulp and has not been spun by chemical treatment, and known ones can be used. Also, pulverized waste paper pulp can be used.

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

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

[0020] The fiber length of the cellulose fiber refers to the number average fiber length indicating the average value of the lengths of the cellulose fibers. The fiber length of the cellulose fiber refers to the arithmetic mean when 50 cellulose fibers are randomly selected and the fiber lengths are measured with an electron microscope. The fiber diameter of the cellulose fiber refers to the number average fiber diameter indicating the average value of the diameters of the cellulose fibers. The fiber diameter of the cellulose fiber refers to the arithmetic mean when 50 cellulose fibers are randomly selected and the fiber diameters are measured with an electron microscope.

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

[0022] From the viewpoint of fading suppression, the content of the cellulose fiber is preferably 1% by mass or more based on the total amount of the friction material composition. From the viewpoint of the moldability (for example, tablet moldability) of the friction material composition, it is preferably 4% by mass or more. The content of the cellulose fiber may be 20% by mass or less, may be 15% by mass or less, or may be 10% by mass or less based on the total amount of the friction material composition.

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

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

[0025] Here, as the carbon fiber, flame-resistant fiber, pitch-based carbon fiber, PAN (polyacrylonitrile)-based carbon fiber, activated carbon fiber, etc. can be used.

[0026] In addition, the mineral fiber referred to here means artificial inorganic fiber obtained by melt spinning with blast furnace slag such as slag wool, basalt such as basalt fiber, and other natural rocks as the main components. As the mineral fiber, it is more preferable that it is a fiber derived from a natural mineral containing Al element. Specifically, SiO2, Al2O3, CaO, MgO, FeO, Na2O, etc. are mentioned, and preferably those containing Al element among these can be preferably used as the mineral fiber.

[0027] The mineral fiber is preferably bio-soluble. The bio-soluble mineral fiber referred to here is a mineral fiber that has the characteristic of being partially decomposed and discharged outside the body within a predetermined time even when taken into the human body. Specifically, the total content rate of alkali metal oxides and alkaline earth metal oxides (total content rate of oxides of sodium, potassium, calcium, magnesium, and barium) as the chemical composition is 18% by mass or more, and in the short-term bio-persistence test by respiration, the mass half-life of fibers of 20 μm or more is within 40 days, or there is no evidence of excessive carcinogenicity in the intraperitoneal test, or there is no related pathogenicity and tumorigenesis in the long-term respiration test (Nota Q (exclusion of carcinogenicity application) of EU Directive 97 / 69 / EC). Examples of such bio-soluble mineral fibers include SiO2-Al2O3-CaO-MgO-FeO-Na2O-based fibers, etc., and fibers containing SiO2, Al2O3, CaO, MgO, FeO, Na2O, etc. in any combination. Commercially available products include the Roxul series manufactured by LAPINUS FIBERS B.V. "Roxul" contains SiO2, Al2O3, CaO, MgO, FeO, Na2O, etc.

[0028] As the metal fiber, in order to improve crack resistance and wear resistance, fibers of copper or copper alloy can be used. As the fibers of copper or copper alloy, copper fibers, brass fibers, bronze fibers, etc. can be used.

[0029] Further, as the metal fiber, other metal fibers other than copper and copper alloy may be used. Other metal fibers other than copper and copper alloy may be contained from the viewpoints of improving the friction coefficient and crack resistance.

[0030] Examples of other metal fibers other than copper and copper alloy include fibers in the form of simple metals or alloys such as aluminum, iron, zinc, tin, titanium, nickel, magnesium, and silicon, and fibers mainly composed of metals such as cast iron fibers.

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

[0032] The friction material composition of the present disclosure may or may not contain aramid fiber as a fiber base material. In the friction material composition of the present disclosure, the content of aramid fiber may be 3% by mass or less with respect to the total amount of the fiber base material, and preferably less than 2% by mass, more preferably 1.5% by mass or less, still more preferably 1.0% by mass or less, and particularly preferably 0% by mass from the viewpoint of preferably forming a friction material capable of suppressing the fade phenomenon.

[0033] The content of the fiber base material is preferably 5% to 40% by mass, more preferably 5% to 30% by mass, and still more preferably 6% to 20% by mass with respect to the total amount of the friction material composition.

[0034] The content of the cellulose fiber in the fiber base material may be 10% to 100% by mass, 15% to 80% by mass, or 20% to 60% by mass with respect to the total amount of the fiber base material.

[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 the inorganic filler include graphite, zirconia (zirconium dioxide), metal sulfide, mica, titanate, 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, α-alumina, alumina such as γ-alumina, silicon carbide, and the like.

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

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

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

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

[0041] The content rate of the inorganic filler may be 30% by mass to 85% by mass, may be 50% by mass to 80% by mass, or may be 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 content rate of the zirconia is preferably 40% by mass or less, more preferably 10% by mass to 35% by mass, and still more preferably 15% by mass 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 may be 25:2 to 25:10. The average particle diameter of zirconia is preferably 1 μm to 10 μm, 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% by mass or less, more preferably 10% by mass to 35% by mass, and still more preferably 15% by mass to 30% by mass with respect to 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 still more preferably 5% by mass to 12% by mass with respect to the total amount of the friction material composition. The mass ratio of barium sulfate to the 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, cashew dust, and the like. 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, may be 5% by mass to 15% by mass, or may be 6% by mass to 10% by mass with respect to 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 to give a predetermined shape and strength. There is no particular limitation on the binder contained in the friction material composition of the present disclosure, and known thermosetting resins used as binders for friction materials can be used.

[0048] Examples of the thermosetting resin include phenolic resins (resole type phenolic resins and novolak type phenolic resins), epoxy resins, polyimide resins, etc. Furthermore, 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 are also included. These can be used alone or in combination of two or more. In particular, it is 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 because they give good heat resistance, moldability, and friction coefficient.

[0049] The content of the binder 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 content of the binder in 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 more effectively suppressed.

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

[0051] Examples of the rubber component 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 it may be in the form of powder, tablet, etc.

[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 such as a disc brake pad, brake lining, etc. used in automobiles and the like.

[0054] The friction material of the present disclosure can be manufactured by molding the friction material composition of the present disclosure by a generally used method. Preferably, it is manufactured by hot press molding. Specifically, the friction material composition of the present disclosure is mixed using a mixer such as a Lodige mixer, a pressure kneader, an Ehrlich mixer, etc., the mixture is preformed in a molding die, and the obtained preform is heated and molded for 4 to 10 minutes under the conditions of a molding temperature of 140°C to 160°C and a molding pressure of 20 MPa to 50 MPa, and the obtained molded product is heat treated at 180°C to 250°C for 2 to 10 hours. Also, painting, scorch treatment, polishing treatment, etc. are 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 in the friction member. Examples of the friction member of the present disclosure include the following configurations. (1) Configuration consisting only of a friction material (2) Configuration having a back plate and the friction material of the present disclosure serving as a friction surface provided on the back plate (3) In the configuration of (2) above, a primer layer for the purpose of surface modification to enhance the adhesion effect of the backing metal on the friction material and an adhesive layer for the purpose of adhering the backing metal and the friction material are further interposed between the backing metal and the friction material.

Example

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

[0057] [Fabrication of Disc Brake Pad] Materials were blended according to the blending ratios (mass %) shown in Table 1 to obtain friction material compositions for the examples and comparative examples. The unit of the blending amount of each component in Table 1 is mass % in the friction material composition. Also, in Table 1, “-” means that the corresponding component is not contained. The 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 - 40 g / L - Cellulose 2 - Fiber length: 2200 μm, fiber diameter: 35 μm, bulk density: 25 - 50 g / L

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

[0059] The general performance test was carried out in accordance with JASO C406. Specifically, a 1 / 5 scale tester (inertia 3.0 kg·m 2)Using 18 mm × 44 mm test pieces cut out from the disk brake pads produced in each example and each comparative example, the minimum value (Min.min.μ) of the average friction coefficient μ of the 1’st Fade test, which is an index of fade suppression, was determined. The wear on JASO performance in Table 1 means the average pad wear (mm) after the test. The higher the value of fade suppression in Table 1, the more the fade phenomenon is suppressed.

[0060]

Table 1

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

Claims

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

2. The friction material composition according to claim 1, wherein the content of the cellulose fibers is 1% by 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 fibers is less than 2% by mass based on the total amount of the fiber substrate.

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

5. The friction material composition according to claim 1, wherein the content of the cellulose fibers is 4% by 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 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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