JP2008231172A - Friction material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a well-balanced friction material that generates no fiber ball even when a chopped strand of a basalt fiber is added to and mixed with a raw material of the friction material and exhibits enhanced effectiveness while reducing attack against a mating surface. <P>SOLUTION: The friction material is obtained by molding and subsequently hardening a friction material composition mainly composed of a fiber base material comprising a chopped strand of a basalt fiber, a binding material and a filler, where the friction material contains the chopped strand of the basalt fiber bundled with at least 0.2 pt.mass and less than 0.5 pt.mass, based on 100 pts.mass of the basalt fiber, of a bundling agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a friction material used for disc brake pads, brake linings, clutch facings and the like of automobiles.

  Metal fiber, organic fiber, inorganic fiber, etc. are used as the fiber base material that constitutes the friction material. However, in recent years, the speed and performance of automobiles have been increased to improve the strength and heat resistance of the friction material as a whole. In order to improve the resistance and secure a high friction coefficient during high-speed braking, it is essential to use chopped strands of inorganic fibers such as glass fibers. The chopped strand is obtained by bundling 50 to 200 cylindrical filaments (single fibers) continuously produced by a melt spinning method with a bundling agent and cutting the filaments into a predetermined length.

  In the friction material, there is a mixing process in which the friction material composition is mixed in the manufacturing process. If the chopped strand has a weak converging force, the chopped strand opens during mixing, and fibers are entangled to form a fiber ball. However, there is a problem of causing poor mixing.

  Therefore, the amount of the bundling agent for bundling the chopped strands is set to 0.5 parts by mass or more with respect to 100 parts by mass of the fibers, and the formation of fiber balls is prevented by giving a sufficient bundling force of the chopped strands. .

  JP-A-58-7475 (Patent Document 1) discloses a friction material containing a glass fiber chopped strand impregnated with 0.5 to 20 parts by mass of a resin or latex.

  Japanese Patent Publication No. 7-72575 (Patent Document 2) describes a glass fiber solidified with 0.5 parts by mass or more of vinyl acetate with respect to the mass of a glass fiber in which 50 to 200 short fibers having a fiber length of 1 to 3 mm are bundled. A friction material containing 5 to 30% by volume of the chopped strand is disclosed.

  Japanese Patent Laid-Open No. 10-280279 (Patent Document 3) discloses an organic polymer obtained by treating a plurality of fibers with a peroxide of 0.5 to 50 parts by mass of a water-soluble organic polymer. Disclosed is a fiber bundle that prevents the formation of fiber balls during mixing.

  On the other hand, further improvement in the strength, heat resistance, and wear resistance of the friction material has been demanded, and as disclosed in Japanese Patent Application Laid-Open No. 2004-331861 (Patent Document 4) as an inorganic fiber replacing the glass fiber. Basalt fiber chopped strands are increasingly being used.

  However, in chopped strands of basalt fibers, adding chopped strands bundled with a sizing agent of 0.5 parts by mass or more to 100 parts by mass of basalt fibers to the friction material prevents the chopped strands from opening during mixing. However, since the mating material (rotor, drum, etc.) is ground in the state of fiber bundles, there is a problem that the face-to-face attack is significantly increased.

JP 58-7475 A Japanese Patent Publication No. 7-72575 Japanese Patent Laid-Open No. 10-280279 JP 2004-331861 A

  The present invention was made in view of the above circumstances, and even when chopped strands of basalt fibers were added to the friction material, there was no generation of fiber balls during mixing, and the effectiveness was improved while reducing the face-to-face attack. An object is to provide a balanced friction material.

  In general, chopped strands of inorganic fibers, such as glass fibers, form fiber balls and cause poor mixing when opened during mixing. However, the strength of the fibers themselves is also reduced. Therefore, it is considered that it is preferable that the fiber is not opened during mixing because it breaks at the time of pressure molding and does not play a role as a fiber base material and the shear strength and wear resistance are significantly reduced. However, as a result of intensive research conducted by the inventor to achieve the above-mentioned problems, chopped strands of basalt fibers among inorganic fibers have high strength and heat resistance, so even if the chopped strands are opened, shear strength and wear resistance The present invention has been completed by discovering that the face-to-face attack is less when the fiber ball is appropriately opened within the range in which fiber balls are not formed during mixing.

The present invention
<1> In a friction material obtained by molding and then curing a friction material composition containing a basalt fiber chopped strand as a main component, a binder, and a filler as a main component, 100 parts by mass of basalt fiber is 0 A friction material comprising chopped strands of basalt fibers bundled with a sizing agent in an amount of 2 parts by mass or more and less than 0.5 parts by mass;
<2> The friction material according to <1>, containing 1 to 20% by volume of chopped strands of the basalt fiber,
It is.

According to the present invention,
<1> Occurrence (mixing failure) of fiber balls of chopped strands of basalt fiber can be eliminated.
<2> A well-balanced friction material with improved effectiveness can be provided while reducing the face-to-face attack on the rotor or drum.

  The friction material of the present invention is formed by molding and then curing a friction material composition mainly composed of a fiber base material excluding asbestos, a binder, and a filler. Here, the present invention is characterized by containing chopped strands of basalt fibers bundled with a sizing agent in an amount of 0.2 parts by mass or more and less than 0.5 parts by mass with respect to 100 parts by mass of the basalt fibers as the fiber base material.

When the sizing agent is 0.2 parts by mass or more and less than 0.5 parts by mass with respect to 100 parts by mass of the basalt fiber, the chopped strands of the basalt fiber are appropriately opened without forming fiber balls during mixing. Aggressiveness can be reduced.
Further, when the amount of the sizing agent is less than 0.2 parts by mass with respect to 100 parts by mass of the basalt fiber chopped strand, the basalt fiber chopped strand is excessively opened at the time of mixing, and a fiber ball is formed, resulting in poor mixing. In addition, when the amount of the sizing agent is 0.5 parts by mass or more with respect to 100 parts by mass of the basalt fiber, the chopped strands of the basalt fiber are not opened at the time of mixing.

  As the sizing agent, latex and synthetic resin can be preferably used. Examples of the latex include acrylic, SBR, and NBR. Examples of synthetic resins include phenolic resins, epoxy resins, polyester resins, and vinyl acetate.

  Examples of the fiber base material that may be further contained in addition to the chopped strands of the basalt fiber include fiber base materials other than asbestos (asbestos) that are usually used for friction materials. For example, metal fibers such as steel, copper, brass, bronze, aluminum and stainless steel; ceramic fibers, potassium titanate fibers, glass fibers, rock wool, artificial mineral fibers, inorganic fibers such as wollastonite, sepiolite, attapulgite; aramid fibers, Organic fibers such as carbon fiber, polyimide fiber, phenol fiber, cellulose fiber, acrylic fiber; These can be used alone or in combination of two or more. The added amount of the fiber base material is preferably 10 to 40% by volume with respect to the total amount of the friction material.

  As the binding material described above, a known material usually used for a friction material can be used. For example, phenol resin, phenol aralkyl resin, NBR rubber-modified high-orthophenol resin, NBR rubber-modified phenol resin, acrylic rubber-modified resin, melamine resin, epoxy resin, NBR, acrylic rubber and the like can be mentioned. These can be used alone or in combination of two or more. The amount of the binder added is preferably 5 to 30% by volume based on the total amount of the friction material.

  Examples of the filler described above include organic fillers and inorganic fillers. Examples of the organic filler include cashew dust, tire liquor, rubber dust (rubber powder, particles), nitrile rubber (unvulcanized product), acrylic rubber dust (vulcanized product), graphite, coke and the like. These can be used alone or in combination of two or more. The addition amount of the organic filler is preferably 5 to 30% by volume with respect to the total amount of the friction material. On the other hand, examples of the inorganic filler include barium sulfate, calcium carbonate, graphite, mica, and metal powders such as iron, copper, and aluminum. These can be used alone or in combination of two or more. This inorganic filler is 20-75 volume% with respect to the friction material whole quantity.

In the method for producing a friction material of the present invention, the above components are uniformly mixed using a mixer such as a Henschel mixer, a Redige mixer, or an Eirich mixer, and preformed in a molding die, and the preform is molded. Molding is performed at a temperature of 140 to 180 ° C. and a molding pressure of 20 to 50 MPa for 5 to 15 minutes.
Next, the obtained molded product is heat-treated (post-cured) for 2 to 48 hours at a temperature of 140 to 250 ° C., and then subjected to spray coating, baking, and polishing treatment as necessary to obtain a finished product.

  When manufacturing disc pads for automobiles, etc., a preform is placed on an iron or aluminum plate that has been pre-washed, surface-treated, and coated with an adhesive, and molded in a thermoforming mold in this state. Then, it can be manufactured by heat treatment, spray coating, baking and polishing.

  The friction material of the present invention can be widely used for various applications such as disc brake pads, brake linings, and clutch facings for automobiles.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, it is not restrict | limited to the description.

  Friction material compositions having the compositions shown in Table 1 were mixed for 5 minutes with a Redige mixer, and pre-molded by pressurizing at 10 MPa in a molding die for 1 minute. This preform was molded in a thermoforming mold for 10 minutes under the conditions of a molding temperature of 150 ° C. and a molding pressure of 40 MPa, and then heat-treated at 200 ° C. for 5 hours (post-curing) and polished to produce a friction material ( Examples 1 to 7, Comparative Examples 1 and 2). The friction material was evaluated for mixing properties, face-to-face attack (rotor wear) and efficacy (friction coefficient), and the results are shown in Table 1.

評価については、下記基準にて行った。なお、評価不能とは、混合時にファイバーボールが形成され、性能評価できる摩擦材を得られなかったことを意味する。
（１）混合性：混合後のファイバーボール形成の有無を目視にて確認した。判定基準は下記の通り。
○：ファイバーボール形成無し
×：ファイバーボール形成有り
（２）対面攻撃性：テストピース型対面攻撃性試験機を使用し、スケールイナーシャ０．３５Ｋｇｍ2、初速６０ｋｍ/ｈ、終速４０ｋｍ/ｈ、ロータ温度８０℃、面圧１．５ＭＰａ、制動回数２０００回後の対面（ロータ）の最大摩耗量を測定した。判定基準は下記の通り。
◎：５μｍ未満
○：５μｍ以上１０μｍ未満
△：１０μｍ以上３０μｍ未満
×：３０μｍ以上
（３）効力（摩擦係数）：ＪＡＳＯ Ｃ４０６ 準拠。第２効力の平均値を求めた。判定基準は下記の通り。
◎：０．４２以上
○：０．３７以上０．４２未満
△：０．３２以上０．３７未満
×：０．３２未満

The evaluation was performed according to the following criteria. Inability to evaluate means that a fiber ball was formed at the time of mixing, and a friction material capable of evaluating performance could not be obtained.
(1) Mixability: The presence or absence of fiber ball formation after mixing was visually confirmed. Judgment criteria are as follows.
○: No fiber ball formed ×: Fiber ball formed (2) Face-to-face attack: Using a test piece type face-to-face attack tester, scale inertia 0.35 kgm2, initial speed 60 km / h, final speed 40 km / h, rotor temperature The maximum wear amount of the facing (rotor) after 80 ° C., surface pressure of 1.5 MPa, and 2000 brakings was measured. Judgment criteria are as follows.
A: Less than 5 μm ○: 5 μm or more and less than 10 μm Δ: 10 μm or more and less than 30 μm X: 30 μm or more (3) Efficacy (coefficient of friction): Conforms to JASO C406. The average value of the second efficacy was determined. Judgment criteria are as follows.
◎: 0.42 or more ○: 0.37 or more and less than 0.42 Δ: 0.32 or more and less than 0.37 ×: less than 0.32

Claims (2)

In the friction material formed by molding and then curing the friction material composition containing the basalt fiber chopped strand as a main component, a binder, and a filler,
A friction material comprising chopped strands of basalt fibers bundled with a sizing agent in an amount of 0.2 parts by mass or more and less than 0.5 parts by mass with respect to 100 parts by mass of basalt fibers. The friction material according to claim 1, comprising 1 to 20% by volume of chopped strands of the basalt fiber.