Friction material composition, friction material, and friction member

Abstract

To provide a friction material composition that contains biomass-derived materials and can suppress the occurrence of fade phenomena. [Solution] The friction material composition comprises a novolac-type phenolic resin and carboxymethylcellulose or a salt thereof.

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 disk 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 disk rotor or a brake drum.

[0003] In order to provide a friction material composition that can exhibit excellent wear resistance during repeated high-speed braking in a friction material composition that does not contain copper or contains a small amount of copper, there is provided a friction member having a friction material and a backing metal, wherein the friction material contains magnesium oxide and titanate and does not contain copper or, even if it contains copper, the copper content is less than 0.5% by mass as copper element, and the maximum primary particle diameter of the magnesium oxide is 50 μm or more. (For example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] On the other hand, the use of fossil fuels raises concerns about resource depletion and global warming due to increased carbon dioxide (CO2) emissions during incineration. Therefore, from the perspective of reducing the use of fossil fuels and CO2 emissions derived from them, there is a growing movement to replace fossil fuels with carbon-neutral biomass-derived materials (bioplastics) as alternative materials. This disclosure is made in view of the above-mentioned prior circumstances and aims to provide a friction material composition containing biomass-derived materials that can suppress the occurrence of fade phenomena, as well as a friction material and friction member using this friction material composition. [Means for solving the problem]

[0006] The specific means for achieving the aforementioned objectives are as follows: <1> A friction material composition comprising a novolac-type phenolic resin and carboxymethylcellulose or a salt thereof. <2> The content of the carboxymethylcellulose or its salt relative to the total amount of the friction material composition is 0.1% to 8% by mass. <1> The friction material composition described above. <3> The mass loss rate of the carboxymethylcellulose or its salt when heated at a heating rate of 10°C / min to 500°C is 30% to 70% by mass. <1> or <2> The friction material composition described above. <4> The friction material composition further contains cellulose fibers, wherein the content of the cellulose fibers relative to the total amount of the friction material composition is 1% to 20% by mass. <1> ~ <3> A friction material composition according to any one of the items. <5> The friction material composition further contains aramid fibers, wherein the content of the aramid fibers relative to the total amount of the friction material composition is 0.5% to 5% by mass. <1> ~ <4> A friction material composition according to any one of the items. <6> <1> ~ <5> A friction material formed using the friction material composition described in any one of the items. <7> <6> A friction member containing the friction material described above. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a friction material composition that includes biomass-derived materials and can suppress the occurrence of fade phenomena, as well as a friction material and friction member using this friction material composition. [Modes for carrying out the invention]

[0008] The embodiments of this disclosure are described in detail below. However, this disclosure is not limited to the embodiments described below. In the embodiments described below, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit this disclosure.

[0009] In this disclosure, the numerical range indicated using "~" includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance 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 types of substances present in the composition, unless otherwise specified. In this disclosure, each component may include multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified. In this disclosure, the term "layer" includes cases where, when observing the region in which the layer exists, it is formed not only over the entire region but also over only a portion of the region.

[0010] <Friction material composition> The friction material composition of this disclosure comprises a novolac-type phenolic resin and carboxymethylcellulose or a salt thereof (hereinafter sometimes referred to as a CMC compound). The friction material composition of this disclosure may also contain other components besides those described above.

[0011] CMC compounds are water-soluble polymers obtained from natural cellulose and are classified as biomass-derived materials. Therefore, CMC compounds are suitable as alternative materials to fossil resources. As a result of diligent research, the inventors discovered that using CMC compounds as a component of a friction material composition can suppress the occurrence of fade phenomena, thus completing the present invention.

[0012] (Binding material) The friction material composition of this disclosure contains a novolac-type phenolic resin. The novolac-type phenolic resin can function as a binder that combines and integrates the components contained in the friction material composition, giving it a predetermined shape and strength. By using a novolac-type phenolic resin as a binder, it becomes possible to form a friction material that exhibits good heat resistance, moldability, and coefficient of friction. The friction material composition of this disclosure may contain other binders besides novolac-type phenolic resins. Examples of other binders include resol-type phenolic resins, epoxy resins, polyimide resins, and the like. When binders other than novolac-type phenolic resin are used in combination, the proportion of novolac-type phenolic resin in the binder contained in the friction material composition is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The proportion of novolac-type phenolic resin in the binder contained in the friction material composition may be 100% by mass. The proportion of novolac-type phenolic resin in the binder contained in the friction material composition is preferably 50% to 100% by mass.

[0013] The content rate of the binder is preferably 4% by mass to 20% by mass, more preferably 5% by mass to 15% by mass, and still more preferably 6% by mass to 10% by mass with respect to the total amount of the friction material composition. By setting the content rate of the binder within the range of 4% by mass to 20% by mass with respect to the total amount of the friction material composition, the decrease in the strength of the friction material can be more suppressed.

[0014] (CMC compound) The friction material composition of the present disclosure contains a CMC compound. By the friction material composition containing the CMC compound, the occurrence of the fade phenomenon can be suppressed. Examples of the CMC compound include carboxymethyl cellulose, sodium carboxymethyl cellulose, calcium carboxymethyl cellulose, ammonium carboxymethyl cellulose, and the like. The CMC compound may be used alone or in combination of two or more.

[0015] The degree of etherification of the CMC compound is not particularly limited. For example, 0.3 to 2.0 is preferable, 0.4 to 1.5 is more preferable, and 0.5 to 1.0 is still more preferable.

[0016] The mass reduction rate (hereinafter, may be referred to as 500 °C thermal weight loss) when the CMC compound is heated at a heating rate of 10 °C / min and reaches 500 °C is preferably 30% by mass to 70% by mass, more preferably 32% by mass to 60% by mass, and still more preferably 34% by mass to 50% by mass. If the 500 °C thermal weight loss of the CMC compound is 30% by mass or more, when forming a friction material using the friction material composition of the present disclosure, appropriate voids are likely to occur in the friction material by the scorch treatment described later, and as a result, the occurrence of the fade phenomenon is more likely to be suppressed. On the other hand, if the 500 °C thermal weight loss of the CMC compound is 70% by mass or less, when forming a friction material using the friction material composition of the present disclosure, the generation of excessive voids in the friction material by the scorch treatment described later is suppressed, and the decrease in the strength of the friction material can be suppressed.

[0017] The 500°C thermal weight loss of the CMC compound is determined as the mass loss rate when 10 mg of the CMC compound is heated from 25°C at a heating rate of 10°C / min using a thermogravimetric analyzer until it reaches 500°C. When two or more CMC compounds are used in combination in the friction material composition of the present disclosure, the 500°C thermal weight loss of the CMC compound refers to the value as a mixture of two or more CMC compounds.

[0018] The content of the CMC compound is preferably 0.1% to 8% by mass, more preferably 1% to 7% by mass, and even more preferably 2% to 6% by mass based on the total amount of the friction material composition. By setting the content of the CMC compound in the range of 0.1% to 8% by mass based on the total amount of the friction material composition, the occurrence of fade phenomenon can be more effectively suppressed.

[0019] (Fiber substrate) The friction material composition of the present disclosure may contain a fiber substrate. The fiber substrate is included to exert a reinforcing effect in the friction material. Examples of the fiber substrate include organic fibers such as cellulose fiber, aramid fiber, acrylic fiber, and phenolic resin fiber which may have a crosslinked structure, inorganic fibers, metal fibers, carbon fibers, etc. The fiber substrate may be used alone or in combination of two or more. Among these, cellulose fiber, aramid fiber, inorganic fiber, etc. are preferable, and cellulose fiber and aramid fiber are more preferable.

[0020] The friction material composition of the present disclosure may contain one or more kinds of cellulose fibers. Examples of the cellulose fiber include natural cellulose fiber, regenerated cellulose fiber, and pulverized pulp. The regenerated cellulose fiber is obtained by chemically dissolving natural cellulose contained in wood pulp, cotton, etc. using a solvent or the like, extracting cellulose and spinning it into fibers again, and known ones can be used.

[0021] Examples of the regenerated cellulose fiber include rayon fiber, lyocell fiber, cupra fiber, polynosic fiber, etc.

[0022] Pulp crushed products refer to kraft pulp that has been crushed and not chemically spun, and any known type can be used. Crushed recycled paper pulp can also be used.

[0023] The fiber length of the cellulose fiber is not particularly limited and may be 5000 μm or less, or from the viewpoint of dispersion, it may be 2000 μm or less, or 1000 μm or less. The lower limit of the fiber length of the cellulose fiber is not particularly limited and may be 500 μm or longer. The fiber length of the cellulose fibers is preferably 500 μm to 5000 μm.

[0024] The fiber diameter of the cellulose fiber is not particularly limited and may be 5 μm to 100 μm, 10 μm to 50 μm, or 15 μm to 30 μm.

[0025] The fiber length of a cellulose fiber refers to the number-mean fiber length, which is the average length of the cellulose fibers. Specifically, it is the arithmetic mean obtained when 50 randomly selected cellulose fibers are measured using an electron microscope. The fiber diameter of cellulose fibers refers to the number-mean fiber diameter, which is the average of the diameters of cellulose fibers. Specifically, it is the arithmetic mean obtained when 50 randomly selected cellulose fibers are measured using an electron microscope.

[0026] When 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 solution and the spinning conditions during the production of regenerated cellulose.

[0027] From the viewpoint of suppressing fade, the cellulose fiber content is preferably 1% by mass or more relative to the total amount of the friction material composition. From the viewpoint of the moldability of the friction material composition (e.g., tablet moldability), it is preferably 4% by mass or more. The cellulose fiber content may be 20% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total amount of the friction material composition. The cellulose fiber content is preferably 1% to 20% by mass relative to the total amount of the friction material composition.

[0028] The friction material composition of this disclosure may contain one or more types of aramid fibers. The fiber length of the aramid fiber is not particularly limited and may be 5000 μm or less, or from the viewpoint of dispersion, it may be 2000 μm or less, or 1500 μm or less. The lower limit of the fiber length of the aramid fiber is not particularly limited; it may be 500 μm or longer, or 800 μm or longer. The fiber length of the aramid fiber is preferably 500 μm to 5000 μm.

[0029] The fiber diameter of the aramid fiber is not particularly limited and may be 5 μm to 100 μm, 10 μm to 50 μm, or 15 μm to 30 μm.

[0030] The fiber length of aramid fibers refers to the number-mean fiber length, which is the average length of aramid fibers. Specifically, it is the arithmetic mean obtained when 50 aramid fibers are randomly selected and their lengths are measured using an electron microscope. The fiber diameter of aramid fibers refers to the number-mean fiber diameter, which is the average of the diameters of aramid fibers. Specifically, it is the arithmetic mean obtained when 50 aramid fibers are randomly selected and their diameters are measured using an electron microscope.

[0031] From the viewpoint of suppressing the fade phenomenon, the aramid fiber content may be 0.5% to 5% by mass, 1% to 4% by mass, 1.2% to 3% by mass, 1.5% to 2.5% by mass, or 1.7% to 2.3% by mass, relative to the total amount of the friction material composition.

[0032] Examples of inorganic fibers include ceramic fibers, biodegradable ceramic fibers, mineral fibers, glass fibers, potassium titanate fibers, silicate fibers, and wollastonite.

[0033] Mineral fibers refer to artificial inorganic fibers produced by melt-spun from blast furnace slag such as slag wool, basalt such as basalt fiber, and other natural rocks as the main components. Preferably, the mineral fibers are derived from natural minerals containing the element Al. Specifically, SiO2, Al2O3, CaO, MgO, FeO, Na2O, etc., can be used individually or in combination of two or more elements, and more preferably, those containing the element Al can be used as mineral fibers.

[0034] Mineral fibers are preferably biosoluble. Biosoluble mineral fibers, as used here, are those that, even when taken into the human body, are partially decomposed and excreted within a predetermined time. Specifically, these are fibers that have 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 in their chemical composition, and that satisfy the following criteria: in a short-term bio-persistence test by respiration, the mass half-life of fibers 20 μm or larger is within 40 days, or there is no excessive evidence of carcinogenicity in an intraperitoneal test, or there is no related pathogenicity or tumor development in a long-term respiratory test (Nota Q (exemption from carcinogenicity) of EU Directive 97 / 69 / EC). Examples of such biosoluble mineral fibers include SiO2-Al2O3-CaO-MgO-FeO-Na2O system fibers, and include fibers containing SiO2, Al2O3, CaO, MgO, FeO, Na2O, etc. in any combination. Examples of commercially available products include the Roxul series from LAPINUS FIBERS BV. "Roxul" contains SiO2, Al2O3, CaO, MgO, FeO, Na2O, etc.

[0035] For the metal fibers, copper or copper alloy fibers can be used to improve crack resistance and wear resistance. As the copper or copper alloy fibers, copper fibers, brass fibers, bronze fibers, etc., can be used.

[0036] Furthermore, metal fibers other than copper and copper alloys may be used as the metal fibers. Other metal fibers other than copper and copper alloys may be included from the viewpoint of improving the coefficient of friction and crack resistance.

[0037] Other metal fibers besides copper and copper alloys include fibers in the form of individual metals or alloys such as aluminum, iron, zinc, tin, titanium, nickel, magnesium, and silicone, as well as fibers whose main component is metal, such as cast iron fibers.

[0038] From the viewpoint of reducing the burden on the environment, the total content of metal fibers is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, based on the total amount of the friction material composition. The friction material composition does not have to contain metal fibers.

[0039] As carbon fibers, flame-resistant fibers, pitch-based carbon fibers, PAN (polyacrylonitrile)-based carbon fibers, activated carbon fibers, etc., can be used.

[0040] The total content of the fiber base material is preferably 5% to 40% by mass, more preferably 5% to 30% by mass, and even more preferably 6% to 20% by mass, based on the total amount of the friction material composition.

[0041] (Inorganic filler) The friction material composition of this disclosure may contain an inorganic filler. Inorganic fillers may be used individually or in combination of two or more types.

[0042] 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, zircon (zirconium silicate), mullite, chromite, titanium dioxide, magnesium oxide, silica, garnet, alumina such as α-alumina and γ-alumina, and silicon carbide.

[0043] Examples of graphite include artificial graphite such as petroleum pitch and coal pitch, as well as natural graphite.

[0044] If the friction material composition of this disclosure contains graphite, the graphite content may be 1% to 12% by mass, 2% to 10% by mass, or 3% to 8% by mass, based on the total amount of the friction material composition.

[0045] Examples of metal sulfides include antimony trisulfide, tin sulfide, tin disulfide, molybdenum disulfide, iron sulfide, iron disulfide, bismuth sulfide, zinc sulfide, and tungsten disulfide.

[0046] Examples of titanates include potassium titanate, lithium potassium titanate, sodium titanate, and magnesium potassium titanate.

[0047] The inorganic filler may contain at least one selected from the group consisting of graphite, zirconia, metal sulfides, titanates, barium sulfate, calcium hydroxide, zircon, and alumina.

[0048] The inorganic filler may contain titanates (preferably potassium titanate, lithium potassium titanate, or magnesium potassium titanate). The content of titanate (preferably potassium titanate, lithium potassium titanate, or magnesium potassium titanate) 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.

[0049] The inorganic filler may contain barium sulfate. The barium sulfate content is preferably 50% by mass or less, more preferably 10% to 45% by mass, and even more preferably 15% to 35% by mass, based on the total amount of the friction material composition.

[0050] The inorganic filler content may be 30% to 85% by mass, 50% to 80% by mass, or 60% to 80% by mass, based on the total amount of the friction material composition.

[0051] (organic filler) The friction material compositions of this disclosure may include organic fillers. Examples of organic fillers include cashew particles. Organic fillers may be used individually or in combination of two or more types.

[0052] The content of the organic filler may be 3% to 20% by mass, 4% to 15% by mass, or 5% to 10% by mass, based on the total amount of the friction material composition.

[0053] (Other materials) The friction material compositions of this disclosure may optionally contain other materials in addition to the components described above. Other materials include fluorine-based polymers such as PTFE (polytetrafluoroethylene), rubber powder, and metal powder. Other materials may be used individually or in combination of two or more.

[0054] Examples of rubber components that make up rubber powder include tire rubber, natural rubber, acrylonitrile-butadiene rubber (NBR), acrylic rubber, isoprene rubber, polybutadiene rubber (BR), styrene-butadiene rubber (SBR), and silicone rubber. The rubber powder may also be tire powder composed of tire rubber.

[0055] The shape of the friction material composition of this disclosure is not particularly limited and may be in the form of a powder, a tablet, or the like.

[0056] <Friction material> The friction material of this disclosure is a component formed using the friction material composition of this disclosure. The friction material of this disclosure can be used as a friction material for disc brake pads, brake linings, etc., used in automobiles and the like.

[0057] The friction material of this disclosure can be manufactured by molding the friction material composition of this disclosure using a commonly used method. Preferably, it is manufactured by heat-pressure molding. Specifically, the friction material composition of this disclosure is mixed using a mixer such as a Redigge mixer, a pressure kneader, or an Eich mixer, and this mixture is pre-molded in a molding die. The resulting pre-molded product is then heated and molded at a molding temperature of 140°C to 160°C and a molding pressure (molding surface pressure) of 20 MPa to 50 MPa for 4 minutes to 10 minutes, and the resulting molded product is heat-treated at 180°C to 300°C for 0.5 hours to 10 hours. In addition, painting, scorching, polishing, etc. may be performed as needed.

[0058] <Friction component> The friction member of this disclosure includes the friction material of this disclosure. In the friction member of this disclosure, it is preferable that the friction material of this disclosure constitutes the friction surface of the friction member. Examples of the friction members of this disclosure include the following configurations. (1) Composition consisting only of friction material (2) A configuration comprising a backing plate and a friction material of the present disclosure which forms a friction surface provided on the backing plate. (3) In the configuration of (2) above, a primer layer for surface modification to enhance the adhesive effect of the backing plate on the friction material, and an adhesive layer for bonding the backing plate and the friction material are further interposed between the backing plate and the friction material. [Examples]

[0059] The present disclosure will be described in further detail below with reference to examples, but the present disclosure is not limited in any way by these examples.

[0060] [Manufacturing of disc brake pads] The materials were blended according to the mixing ratios shown in Table 1 to obtain the friction material compositions of the examples and comparative examples. The units for the amount of each component in Table 1 are in mass % of the friction material composition. In Table 1, "-" means that the component is not present.

[0061] The following components were used as cellulose fibers. The following components were used as CMC compounds. • Cellulose fiber; fiber length: 900 μm, fiber diameter: 20 μm • CMC-1 Loss of weight at 500℃: 38% by mass, Degree of etherification: 0.8 • CMC-2: Loss of weight at 500°C: 55% by mass, degree of etherification: 0.7

[0062] This friction material composition was mixed in a Redigge mixer (manufactured by Matsubo Co., Ltd., product name: Redigge Mixer M20), and the mixture was pre-formed at 30 MPa. The resulting pre-formed material was then heated and pressurized together with an iron backing plate (6 mm thick) for 5 minutes at a molding temperature of 150°C and a molding surface pressure of 20 MPa to 40 MPa. The resulting molded product was heat-treated for 2 hours and polished using a rotary polishing machine. Next, a scorching treatment was performed to create a product with a thickness of 10 mm and a projected area of ​​60 cm². 2 We manufactured a disc brake pad equipped with the following friction material.

[0063] General performance tests were conducted in accordance with JASO C406. Specifically, a 1 / 5 scale tester (inertia 3.0 kg·m) was used. 2Using 18mm x 44mm test pieces cut from the disc brake pads prepared in each example and comparative example, the average friction coefficient μ (Min. Avg. μ) and minimum value (Min. min. μ) of the 1st Fade test, which is an indicator of fade suppression, were determined. In Table 1, a higher value for fade suppression indicates that the fade phenomenon is suppressed.

[0064] [Table 1]

[0065] 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 more effectively than the brake pads formed using the friction material composition of the comparative examples.

Claims

1. A friction material composition comprising a novolac-type phenolic resin and carboxymethylcellulose or a salt thereof.

2. The friction material composition according to claim 1, wherein the content of carboxymethylcellulose or a salt thereof in relation to the total amount of the friction material composition is 0.1% by mass to 8% by mass.

3. The friction material composition according to claim 1, wherein the mass loss rate of the carboxymethylcellulose or a salt thereof when heated at a heating rate of 10°C / min to 500°C is 30% by mass to 70% by mass.

4. The friction material composition according to claim 1, further comprising cellulose fibers, wherein the content of the cellulose fibers relative to the total amount of the friction material composition is 1% by mass to 20% by mass.

5. The friction material composition according to claim 1, further comprising aramid fibers, wherein the content of the aramid fibers relative to the total amount of the friction material composition is 0.5% by mass to 5% by mass.

6. A friction material formed using the friction material composition described in any one of claims 1 to 5.

7. A friction member comprising the friction material described in claim 6.

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