Friction material

Abstract

To provide a friction material which has less tendency to attack counterpart materials and also has excellent rust-removal characteristics.SOLUTION: The present invention relates to a friction material which comprises a friction regulator, a binder and a fiber base material, wherein: alumina fibers are contained as the fiber base material; and the content of the alumina fibers is from 0.1 mass% to 1.0 mass%.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a friction material for use in automobiles, railway vehicles, industrial machines, and the like. [Background technology]

[0002] Conventionally, friction materials are required to have various properties, one of which is rust removal property, which is the ability to scrape off rust that has formed on the surface of the mating material, the disc rotor, due to environmental factors such as rain, and is considered important from the viewpoint of suppressing brake squeal and early wear of the friction material caused by the rust.

[0003] As an example of a friction material with excellent rust removal properties, Patent Document 1 discloses a friction material having as its main components a fiber base material, a filler, and a binder, in which the fiber base material is made from a nonmetallic inorganic material and contains inorganic fibers of medium hardness having a Mohs hardness of 4 to 8, and does not contain inorganic fibers with a length of 5 μm or more, a diameter of 3 μm or less, and an aspect ratio (length / diameter) of more than 3, the filler contains rubber, and the volume ratio of the amount of the inorganic fibers of medium hardness added to the amount of the rubber added is 2:1 to 10:1.

[0004] On the other hand, in recent years, regenerative braking, which is specific to hybrid vehicles and electric vehicles, has become widespread, and part of the braking force is now handled by regenerative braking. Therefore, the proportion of braking force caused by friction and the braking load are lower than those of conventional hydraulic brake systems. As a result, it is difficult to sufficiently remove rust that has developed on the surface of the disc rotor, which is the mating material, with conventional friction materials such as those described in Patent Document 1.

[0005] In view of this, as a friction material with further improved rust removal properties, for example, Patent Document 2 discloses a friction material composition including a fiber matrix, a binder, and a filler, in which the fiber matrix contains at least two types of biosoluble ceramic fibers having different fiber lengths. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-186591 A [Patent Document 2] International Publication No. 2007 / 080975 Summary of the Invention [Problem to be solved by the invention]

[0007] However, according to the inventors' investigations, the friction material described in Patent Document 2 requires a large amount of ceramic fibers, which causes a problem of increased attack on the mating material due to the abrasiveness of the ceramic fibers.

[0008] The present invention has been made in consideration of the above-mentioned conventional circumstances, and an object of the present invention is to provide a friction material that is less aggressive to mating materials and has excellent rust-removing properties. [Means for solving the problem]

[0009] As a result of extensive investigations, the inventors have found that the above-mentioned problems can be solved by adding a specific amount of alumina fibers to the friction material as a fiber base material, and have thus completed the present invention.

[0010] That is, the present invention provides the following <1> ~ <4> This is regarding. <1> A friction material comprising a friction modifier, a binder and a fibrous base material, The fiber base material contains alumina fibers, The friction material has a content of the alumina fibers of 0.1 to 1.0 mass %. <2> The alumina fibers contain Al2O3 and SiO2, The chemical composition ratio of Al2O3 and SiO2 is Al2O3:SiO2=70-80:30-20. <1> The friction material according to claim 1. <3> The average fiber length of the alumina fibers is 50 to 150 μm. <1> or <2> The friction material according to claim 1. <4> Does not contain copper components <1> ~ <3> 13. The friction material according to claim 12, Effect of the Invention

[0011] The friction material of the present invention has low attacking properties against mating materials and has excellent rust-removing properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below, however, these are examples of preferred embodiments and the present invention is not limited to the contents thereof.

[0013] The friction material of the present invention comprises a friction modifier, a binder and a fibrous base material. Each component will be described in detail below.

[0014] <Friction adjustment material> Friction modifiers are used to impart desired friction characteristics, such as wear resistance, heat resistance, and fade resistance, to the friction material.

[0015] Examples of friction modifiers include inorganic fillers, organic fillers, abrasives, lubricants, and metal powders.

[0016] Examples of inorganic fillers include titanates such as potassium titanate, lithium titanate, lithium potassium titanate, sodium titanate, calcium titanate, magnesium titanate, and magnesium potassium titanate, as well as inorganic materials such as barium sulfate, calcium carbonate, calcium hydroxide, vermiculite, and mica. These may be used alone or in combination of two or more.

[0017] The inorganic filler is preferably used in an amount of 30 to 80 mass %, more preferably 40 to 70 mass %, based on the entire friction material.

[0018] Examples of organic fillers include various rubber powders (raw rubber powder, tire powder, etc.), rubber dust, resin dust, cashew dust, tire tread, melamine dust, etc. These may be used alone or in combination of two or more.

[0019] The organic filler is preferably used in an amount of 1 to 15 mass %, more preferably 1 to 10 mass %, based on the entire friction material.

[0020] Examples of the abrasive include zirconium oxide, alumina, silica, magnesium oxide, zirconia, zirconium silicate, chromium oxide, iron oxide trioxide (Fe3O4), chromite, etc. These may be used alone or in combination of two or more.

[0021] The abrasive is preferably used in an amount of 1 to 20 mass %, more preferably 3 to 15 mass %, based on the total mass of the friction material.

[0022] Examples of lubricants include graphite, coke, antimony trisulfide, molybdenum disulfide, tin sulfide, polytetrafluoroethylene (PTFE), etc. These may be used alone or in combination of two or more.

[0023] The lubricant is preferably used in an amount of 1 to 20 mass %, more preferably 3 to 15 mass %, based on the total mass of the friction material.

[0024] Examples of metal powders include powders of aluminum, tin, zinc, etc. These may be used alone or in combination of two or more.

[0025] The metal powder is preferably used in an amount of 1 to 10 mass %, more preferably 1 to 5 mass %, based on the entire friction material.

[0026] From the viewpoint of imparting the above-mentioned desired friction characteristics to the friction material sufficiently, the friction modifier is used in an amount of preferably 60 to 90 mass %, and more preferably 70 to 90 mass %, of the entire friction material.

[0027] <Binding material> As the binder, various commonly used binders can be used, specifically, thermosetting resins such as phenolic resin, various modified phenolic resins such as elastomers, melamine resin, epoxy resin, and polyimide resin can be mentioned.

[0028] Examples of elastomer-modified phenolic resins include acrylic rubber-modified phenolic resins, silicone rubber-modified phenolic resins, nitrile rubber (NBR)-modified phenolic resins, etc. These may be used alone or in combination of two or more.

[0029] From the viewpoint of formability of the friction material, the binder is preferably used in an amount of 1 to 20 mass %, more preferably 3 to 15 mass %, of the entire friction material.

[0030] <Fiber base material> The friction material of the present invention contains alumina fibers as a fiber base material. The content of the alumina fibers in the friction material of the present invention is 0.1 to 1.0 mass %. By containing 0.1 to 1.0 mass % of alumina fibers in the friction material of the present invention, rust generated on the surface of the disk rotor, which is the mating material, can be effectively removed.

[0031] In addition, the grindability of the friction material of the present invention can be suppressed by controlling the sintering temperature during the manufacturing process of the alumina fibers, and the aggressiveness of the friction material of the present invention to the mating material can be reduced by selecting an appropriate blending amount of the alumina fibers. Therefore, the friction material of the present invention can have low aggressiveness to the mating material and excellent rust removal properties.

[0032] The content of the alumina fibers in the entire friction material is preferably 0.1 to 0.8 mass %, and more preferably 0.2 to 0.5 mass %.

[0033] The alumina fiber is an artificial mineral fiber containing alumina (Al2O3) and silica (SiO2) as main components. The chemical composition ratio of Al2O3 and SiO2 in the alumina fiber is preferably Al2O3:SiO2=70-80:30-20, and more preferably Al2O3:SiO2=70:30.

[0034] The alumina fibers preferably have an average fiber length of 50 to 150 μm and an average fiber diameter of 1 to 10 μm. In the present invention, the average fiber length and average fiber diameter of the alumina fibers can be measured by observation using a microscope or the like.

[0035] Alumina fibers can be produced by a conventional method, for example, a precursor fiber method in which an organic polymer is added to a solution of aluminum salts to thicken the solution, which is then mechanically formed into fibers and calcined.

[0036] In addition to the above, examples of the fibrous substrate include organic fibers, inorganic fibers, etc. Each of the fibrous substrates may be used alone or in combination of two or more kinds.

[0037] Examples of organic fibers include aromatic polyamide (aramid) fibers and flame-resistant acrylic fibers.

[0038] Examples of inorganic fibers include biosoluble inorganic fibers, ceramic fibers, glass fibers, carbon fibers, rock wool, etc. Examples of biosoluble inorganic fibers include biosoluble ceramic fibers such as SiO2-CaO-MgO fibers, SiO2-CaO-MgO-Al2O3 fibers, and SiO2-MgO-SrO fibers, and biosoluble rock wool.

[0039] From the viewpoint of ensuring the strength of the friction material, the fibrous base material is used in an amount of preferably 3 to 30 mass %, and more preferably 5 to 20 mass %, of the entire friction material.

[0040] From the viewpoint of reducing the environmental load, it is preferable that the friction material of the present invention does not contain a copper component.

[0041] <Method of manufacturing friction material> The friction material of the present invention can be produced by a known production process. For example, the above-mentioned components are mixed, and the mixture is subjected to steps such as preforming, thermoforming, heating, and polishing according to a conventional manufacturing method to produce the friction material.

[0042] A method for manufacturing a brake pad having a friction material generally includes the following steps. (a) A process of forming a pressure plate into a desired shape using a sheet metal press. (b) A process of degreasing, chemical conversion and primer treatment on the pressure plate, and applying an adhesive. (c) A process of blending raw materials such as friction modifiers, binders, and fiber base materials, thoroughly homogenizing them by mixing, and molding them at room temperature under a predetermined pressure to produce a preform. (d) A thermoforming process in which the preform and the pressure plate coated with adhesive are bonded together by applying a predetermined temperature and pressure (molding temperature: 130 to 180°C, molding pressure: 30 to 80 MPa, molding time: 2 to 10 minutes). (e) After-curing (150-300°C, 1-5 hours) and final finishing such as polishing, scorching, and painting. EXAMPLES

[0043] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples in any way.

[0044] (Examples 1 to 8, Comparative Examples 1 to 4) The ingredients shown in Table 2 were all charged into a mixer and mixed at room temperature for 4 minutes to obtain a mixture.

[0045] The following alumina fibers were used. Alumina fiber A Al2O3:SiO2=70:30 (chemical composition ratio), average fiber length 50μm Alumina fiber B Al2O3:SiO2=70:30 (chemical composition ratio), average fiber length 100μm Alumina fiber C Al2O3:SiO2=70:30 (chemical composition ratio), average fiber length 150μm Alumina fiber D Al2O3:SiO2=80:20 (chemical composition ratio), average fiber length 100μm The resulting mixture was subjected to the following steps of (i) preforming, (ii) thermoforming, and (iii) heat treatment and scorching to produce a friction material.

[0046] (i) Preforming The mixture was placed in a mold of a preforming press and molded at room temperature at 20 MPa for 10 seconds to prepare a preforming body. (ii) Thermoforming This preform was placed in a thermoforming mold, and a metal plate (pressure plate) to which an adhesive had been applied was placed on top of it, followed by heat and pressure molding at 150° C. and 40 MPa for 5 minutes. (iii) Heat treatment, scorch This hot-pressed compact was heat-treated at 250° C. for 3 hours, and then the surface was polished. Next, the surface of this hot-pressed molded product was subjected to a scorch treatment and then finished with a coating to obtain a friction material.

[0047] The friction materials obtained in Examples 1 to 8 and Comparative Examples 1 to 4 were evaluated for rust removal properties and attacking properties against counterpart materials by the following methods. The results are shown in Table 2.

[0048] <Rust removal properties> Using the friction material obtained above, a new rotor, and a rusted disc rotor, a rust removal test was carried out under the test conditions shown in Table 1 using a 1 / 7 scale tester. During the rust removal test, the amount of wear of the disk rotor was measured at the following braking cycles. Before the test (0 times), 10 times, 30 times, 50 times, 100 times, 150 times, 200 times

[0049] The rusted disc rotor was obtained by the following procedure. (a) A 5% by mass salt solution was sprayed onto the disk rotor. (b) The disk rotor (a) above was left in a thermo-hygrostat chamber maintained at a temperature of 50°C±1°C and a humidity of 95±1% in accordance with JIS D4419 for 3 hours and 15 minutes, and then dried for 2 hours and 30 minutes under conditions of 70±1°C and a humidity of 15±1%. (c) The above step (b) was repeated until the rust thickness reached 70 μm.

[0050] [Table 1]

[0051] The rust removal rate after 100 braking cycles was calculated based on the following formula.

[0052]

number

[0053] The calculated rust removal rate was evaluated based on the following criteria. ◎: 100% or more ○: 90% or more but less than 100% △: 80% or more but less than 90% ×: Less than 80%

[0054] <Aggression against opposing materials> The friction material obtained above was processed into a test piece, which was pressed against a disk rotor with a surface pressure of 0.08 MPa and subjected to a test at a speed of 60 km / h. The amount of wear of the disk rotor after 40 hours was measured.

[0055] The measured wear amount of the disk rotor was evaluated based on the following criteria. ◎: Less than 10μm ○: 10μm or more and less than 15μm △: 15μm or more and less than 20μm ×: 20μm or more

[0056] [Table 2]

[0057] From the results in Table 2, it was found that the friction materials according to Examples 1 to 8 had low attacking properties against the mating material and excellent rust removal properties.

Claims

1. A friction material comprising a friction modifier, a binder and a fiber base material, The fiber base material contains alumina fibers, The content of the alumina fibers is 0.1 to 1.0 mass %, The alumina fibers contain Al 2 O 3 and SiO 2 ; A friction material having a chemical composition ratio of Al 2 O 3 and SiO 2 of Al 2 O 3 :SiO 2 =70-80:30-20.

2. 2. The friction material according to claim 1, wherein the alumina fibers have an average fiber length of 50 to 150 μm.

3. 3. The friction material according to claim 1, which does not contain a copper component.

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