JP6490941B2 - Friction material composition, friction material and friction member - Google Patents

Description

  The present invention relates to a friction material composition suitable for a friction material such as a disc brake pad used for braking of an automobile or the like, and more particularly to a non-asbestos friction material composition containing no asbestos. The present invention also relates to a friction material and a friction member using the friction material composition.

  In automobiles and the like, friction materials such as disc brake pads and brake linings are used for braking. The friction material plays a role of braking by friction with facing materials such as a disk rotor and a brake drum. For this reason, the friction material is required to have a good coefficient of friction, wear resistance (the friction material has a long life), strength, sound vibration (the brake noise and abnormal noise are unlikely to occur), and the like. The friction coefficient is required to be stable regardless of the vehicle speed, deceleration and brake temperature. In recent years, the friction coefficient is less decreased even under severe braking conditions in which the braking temperature is abnormally high due to continuous high-speed (vehicle speed of 200 km / h or higher) and high deceleration (0.8 G or higher) braking. (Fast fade characteristics) is required for the friction material.

  In recent years, copper used in the friction material is scattered as brake powder, causing rivers, lakes, marine pollution, and the like. Copper is blended into the friction material in the form of fibers and powders, and is an effective component for maintaining the friction coefficient under high-temperature braking conditions (fading resistance) and improving wear resistance at high temperatures. Therefore, the composition containing no copper has a problem that the above-mentioned high-speed fade characteristic is extremely deteriorated.

  In a movement that restricts the use of copper, in a composition that does not contain copper, as a measure for improving friction characteristics at high temperature, at least one titanate compound having a plurality of convex shapes, and biosolubility Friction material containing inorganic fiber (Patent Document 1), specific amount of binder, organic fiber, metal sulfide lubricant, carbonaceous lubricant, titanate, mild / hard abrasive, organic friction modifier, A friction material containing a pH adjuster (Patent Document 2) has been proposed.

JP 2013-076058 A JP 2014-156589 A

  Patent Documents 1 and 2 both improve the friction characteristics at high temperatures in a composition that does not contain copper, but these proposed friction materials are effective in improving high-speed fade characteristics at a vehicle speed of 200 km / h or higher. Is still not enough.

  The present invention has been made in view of the above circumstances, and does not contain copper that deteriorates high-speed fade characteristics, or a friction material composition that exhibits high high-speed fade characteristics in a friction material having a copper content of 0.5 mass% or less. In particular, to maintain a sufficient coefficient of friction even in high-speed fade conditions with an abnormal increase in brake temperature by repeating rapid braking at a deceleration of 0.8G from high-speed 200km / h. Is an issue.

  In the high temperature braking in which the temperature of the friction surface is 500 ° C. or higher, the present inventors cause a rapid decomposition of the binding material and generate a decomposition gas in a reducing atmosphere. At this time, certain metal sulfides are decomposed by the decomposition gas in the reducing atmosphere and act as a metal catalyst, promoting the low molecular weight of the binder and forming a strong layer of amorphous carbon in the reducing atmosphere. In addition, the present inventors have found that this strong amorphous carbon layer is effective in maintaining the friction coefficient during high-speed and high-temperature braking, and is effective in maintaining the friction coefficient in high-speed fade conditions even in a composition containing no copper.

  The present invention is based on this finding. Specifically, the friction material composition of the present invention is a friction material composition including a binder, an organic filler, an inorganic filler, and a fiber substrate, and the friction material composition includes the friction material composition. The material composition does not contain copper as an element, or the copper content is 0.5% by mass or less, and is a metal in one or a combination of two or more selected from tin sulfide, bismuth sulfide and molybdenum disulfide It contains 8 to 30% by mass of sulfide.

  In the friction material composition of the present invention, the tin sulfide is preferably tin (II) sulfide, and the tin sulfide is preferably tin (IV) sulfide, and the tin sulfide is tin (II) sulfide and tin sulfide. It may be a mixture of (IV).

  In addition, the friction material of the present invention is formed by molding the friction material composition of the present invention, and the friction member of the present invention is formed by molding the friction material composition of the present invention. It is formed using a friction material and a back metal.

  According to the present invention, a friction material composition, a friction material, and a friction member having a high coefficient of friction under a high-speed fade condition without using copper having a high environmental load when used for a friction material such as an automobile disc brake pad. Can be provided.

  Hereinafter, the friction material composition of the present invention, the friction material using the same, and the friction member will be described in detail. The friction material composition of the present invention is a so-called non-asbestos friction material composition that does not contain asbestos.

[Friction material composition]
The friction material composition of this embodiment does not contain copper, or the content of copper is 0.5 mass% or less even if it contains copper. As mentioned above, copper is an effective component for maintaining the coefficient of friction under high-temperature braking conditions (fading resistance) and improving wear resistance at high temperatures, and does not contain copper or the amount of copper is too small. In this composition, the above-mentioned high-speed fade characteristics are extremely deteriorated. The friction material composition of the present invention uses a specific sulfide to maintain the friction coefficient at a high temperature (fading resistance) and improve the wear resistance at a high temperature.

(Tin sulfide, bismuth sulfide, molybdenum disulfide)
The friction material composition of the present invention contains a metal sulfide in one or a combination of two or more selected from tin sulfide, bismuth sulfide, and molybdenum disulfide. These metal sulfides have a low Mohs hardness of 1 to 2 and are excellent as solid lubricants, and are decomposed in a reducing atmosphere to act as metal catalysts, promoting the low molecular weight of the binder in the friction material. It has the effect of promoting the formation of a strong layer of amorphous carbon and maintaining the friction coefficient at a high temperature, and contributes to the improvement of high-speed fade characteristics.

Tin sulfide may be one of divalent (tin sulfide (II); SnS), tetravalent (tin sulfide (IV); SnS ₂ ), or a mixture of both, but divalent (tin sulfide (II ); SnS) has higher heat resistance and is preferred from the viewpoint of high-speed fade characteristics. The total content of metal sulfides selected from tin sulfide, molybdenum disulfide, and bismuth sulfide is preferably 8 to 30% by mass, and 8 to 20% by mass from the viewpoint of maintaining a friction coefficient and wear resistance under high-speed fade conditions. More preferred. If it is less than 8% by mass, the coefficient of friction under high-speed fade conditions will be drastically reduced, and if it exceeds 30% by weight, the lubrication effect by metal sulfide will be large, and the frictional form will be mainly composed of abrasive wear. Increased rotor wear.

(Binder)
The binder integrates an organic filler, an inorganic filler, a fiber base material, and the like included in the friction material composition to give strength. There is no restriction | limiting in particular as a binder contained in the composition for friction materials of this invention, Usually, the thermosetting resin used as a binder of a friction material can be used.

  Examples of the thermosetting resins include phenol resins; various elastomer-dispersed phenol resins such as acrylic elastomer-dispersed phenol resins and silicone elastomer-dispersed phenol resins; acrylic-modified phenol resins, silicone-modified phenol resins, cashew-modified phenol resins, and epoxy-modified phenols. Various modified phenol resins such as resins and alkylbenzene-modified phenol resins can be used, and these can be used alone or in combination of two or more. In particular, it is preferable to use a phenol resin, an acrylic-modified phenol resin, a silicone-modified phenol resin, or an alkylbenzene-modified phenol resin because good heat resistance, moldability, and friction coefficient are given.

  The content of the binder in the friction material composition of the present invention is preferably 5 to 20% by mass, and more preferably 5 to 10% by mass. By setting the content of the binder in the range of 5 to 20% by mass, it is possible to further suppress the strength reduction of the friction material, and to reduce the porosity of the friction material and to make noise such as squeal due to the increase in the elastic modulus. Vibration performance deterioration can be further suppressed.

(Organic filler)
The organic filler is included as a friction modifier for improving the sound vibration performance and wear resistance of the friction material. The organic filler contained in the friction material composition of the present invention is not particularly limited as long as it can exhibit the above performance, and cashew dust, rubber components, etc., which are usually used as an organic filler can be used. .

  The cashew dust is not particularly limited as long as it is obtained by pulverizing a hardened cashew nut shell oil and is usually used for a friction material.

  Examples of the rubber component include tire rubber, acrylic rubber, isoprene rubber, NBR (nitrile butadiene rubber), SBR (styrene butadiene rubber), chlorinated butyl rubber, butyl rubber, silicone rubber, and the like. Used in combination of more than one type.

  The content of the organic filler in the friction material composition of the present invention is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, and 3 to 8% by mass. Particularly preferred. By setting the content of the organic filler in the range of 1 to 20% by mass, the elastic modulus of the friction material is increased, deterioration of sound vibration performance such as squealing can be avoided, heat resistance deterioration, heat It is possible to avoid a decrease in strength due to history.

(Inorganic filler)
The inorganic filler is included as a friction modifier that is added for the purpose of improving the friction coefficient in order to avoid deterioration of the heat resistance of the friction material or to improve the wear resistance. If the composition for friction materials of this invention is an inorganic filler normally used for a friction material, there will be no restriction | limiting in particular.

  Examples of the inorganic filler include iron sulfide, antimony trisulfide, and zinc sulfide as metal sulfides other than tin sulfide, molybdenum disulfide, and bismuth sulfide. Calcium hydroxide, calcium oxide, sodium carbonate, barium sulfate, coke, graphite, mica, vermiculite, calcium sulfate, talc, clay, zeolite, mullite, chromite, titanium oxide, magnesium oxide, silica, dolomite, calcium carbonate, carbonic acid Magnesium, granular or plate-like titanate, zirconium silicate, γ-alumina, manganese dioxide, zinc oxide, iron tetroxide, cerium oxide, zirconia, etc. can be used alone or in combination of two or more. Can be used. As the granular or plate-like titanate, potassium 6 titanate, 8 potassium titanate, lithium potassium titanate, magnesium potassium titanate, sodium titanate, or the like can be used.

  The content of the inorganic filler in the friction material composition of the present invention is preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and 50 to 60% by mass. Particularly preferred. By making content of an inorganic filler into the range of 30-80 mass%, deterioration of heat resistance can be avoided and it is preferable also at the point of content balance of the other component of a friction material.

(Fiber base)
The fiber base material exhibits a reinforcing action in the friction material.

  In the friction material composition of the present invention, inorganic fibers, metal fibers, organic fibers, carbon fibers, etc., which are usually used as fiber base materials, can be used, and these are used alone or in combination of two or more. be able to.

As said inorganic fiber, a ceramic fiber, a biodegradable ceramic fiber, a mineral fiber, glass fiber, a silicate fiber etc. can be used, It can use 1 type or in combination of 2 or more types. Among these inorganic fibers, biodegradable mineral fibers containing SiO ₂ , Al ₂ O ₃ , CaO, MgO, FeO, Na ₂ O and the like in any combination are preferable, and commercially available products manufactured by LAPINUS FIBERS BV Examples include the Roxul series.

  The metal fiber is not particularly limited as long as it is usually used for a friction material. For example, a metal or an alloy such as aluminum, iron, cast iron, zinc, tin, titanium, nickel, magnesium, silicon, copper, brass, etc. Can be used. These metals or alloys may be contained in the form of powder in addition to the fiber form. However, copper and the alloy containing copper are made into 0.5 mass% or less as copper content from a viewpoint of environmental hazard.

  As said organic fiber, an aramid fiber, a cellulose fiber, an acrylic fiber, a phenol resin fiber etc. can be used, These can be used individually or in combination of 2 or more types.

  As the carbon-based fiber, flame-resistant fiber, pitch-based carbon fiber, PAN-based carbon fiber, activated carbon fiber, or the like can be used, and these can be used alone or in combination of two or more.

  The content of the fiber substrate in the friction material composition of the present invention is preferably 5 to 40% by mass, more preferably 5 to 20% by mass, and 5 to 15% by mass in the friction material composition. It is particularly preferred that By setting the content of the fiber base in the range of 5 to 40% by mass, an optimum porosity as a friction material can be obtained, squeal can be prevented, an appropriate material strength can be obtained, and wear resistance can be exhibited. The moldability can be improved.

[Friction material]
The friction material of the present embodiment can be manufactured by molding the friction material composition of the present invention by a generally used method, and is preferably manufactured by hot pressing. In detail, for example, the friction material composition of the present invention is uniformly applied using a mixer such as a Laedige mixer (“Laedige” is a registered trademark), a pressure kneader, an Eirich mixer (“Eirich” is a registered trademark), or the like. This mixture is preformed with a molding die, and the obtained preform is molded under conditions of a molding temperature of 130 to 160 ° C., a molding pressure of 20 to 50 MPa, and a molding time of 2 to 10 minutes. The molded product is heat-treated at 150 to 250 ° C. for 2 to 10 hours. Furthermore, it is manufactured by performing coating, scorch treatment, and polishing treatment as necessary.

[Friction material]
The friction member of the present embodiment uses the friction material of the present embodiment as a friction material that becomes a friction surface. Examples of the friction member include the following configurations.
(1) Configuration of only friction material (2) Configuration having a back metal and a friction material made of the friction material composition of the present invention which becomes a friction surface on the back metal (3) In the above configuration (2), the back metal A primer layer for the purpose of surface modification to enhance the adhesion effect of the back metal and an adhesive layer for the purpose of bonding the back metal to the friction material

  The backing metal is usually used as a friction member to improve the mechanical strength of the friction member, and the material is metal or fiber reinforced plastic, specifically iron, stainless steel, inorganic fiber reinforced plastic. And carbon fiber reinforced plastics. The primer layer and the adhesive layer may be those used for friction members such as brake shoes.

  The friction material composition of this embodiment is particularly useful as an upper material for disc brake pads and brake linings for automobiles and the like because it is excellent in high-speed fading characteristics, etc., but is used as a lower material for friction members. You can also. The “upper material” is a friction material that becomes the friction surface of the friction member, and the “underlay material” is a friction material that is interposed between the friction material that becomes the friction surface of the friction member and the back metal. It is a layer for the purpose of improving the shear strength, crack resistance, etc. in the vicinity of the bonded portion with the back metal.

  Hereinafter, although the friction material composition, the friction material, and the friction member of the present invention will be described in more detail with reference to Examples and Comparative Examples, the present invention is not limited thereto.

[Examples 1 to 15 and Comparative Examples 1 to 9]
(Production of disc brake pad)
The materials were blended according to the blending ratios shown in Table 1 and Table 2, and the friction material compositions of Examples 1 to 15 and Comparative Examples 1 to 9 were obtained. As the tin sulfide used in Examples and Comparative Examples, “Frenostannid” (SnS) manufactured by Tribotecc GmbH and “Stannolube” manufactured by Tribotecc GmbH (a mixture of SnS and SnS ₂ ) were used. As the bismuth sulfide, “BIS 83” (Bi ₂ S ₃ ) manufactured by Tribotecc GmbH was used. As the molybdenum disulfide, “Superfine” manufactured by Climax Molybdenum Company was used. This friction material composition was mixed with a Laedige mixer (manufactured by Matsubo Co., Ltd., trade name: Ladige mixer M20), and the resulting mixture was preformed with a molding press (manufactured by Oji Machinery Co., Ltd.). The preform is obtained by using a molding press (manufactured by Sanki Seiko Co., Ltd.) under the conditions of a molding temperature of 140 to 160 ° C., a molding pressure of 30 MPa, and a molding time of 5 minutes. Together with heating and pressing. The obtained molded product was heat treated at 200 ° C. for 4.5 hours, polished using a rotary polishing machine, subjected to scorch treatment at 500 ° C., and the disc brake pads of Examples 1-15 and Comparative Examples 1-9 were prepared. Obtained. In Examples and Comparative Examples, a disc brake pad having a backing metal thickness of 6 mm, a friction material thickness of 11 mm, and a friction material projection area of 52 cm ² was produced. In addition, the mixture ratio in visiting China is mass%.

(Evaluation of high-speed fade characteristics)
The disk brake pads of Examples 1 to 15 and Comparative Examples 1 to 9 prepared by the above method were evaluated for high-speed fade characteristics using a brake dynamo testing machine. In the experiment, a general pin-slide type collet caliper and a ventilated disc rotor (FC190) manufactured by Kiriu Corporation were used, and the evaluation was performed with the moment of inertia of the Skyline V35 manufactured by Nissan Motor Co., Ltd.

  After high speed fade test (initial speed 200 km / h) after performing sizing according to JASO C427 (initial speed 50 km / h, final speed 0 km / h, deceleration 0.3 G, brake temperature 100 ° C before braking, number of brakings 200 times) h, final speed 80km / h, deceleration 0.8G, braking temperature 100 ° C before first braking, 10 brakings at 60 second intervals), and the minimum value of friction coefficient in high-speed fade test (one braking) The average value of the average friction coefficient was measured.

(Evaluation of rotor wear)
A test piece of 25 mm × 25 mm × 8 mm was cut out from the friction material surface of the disc brake pad manufactured with the friction material composition of Examples 1 to 15 and Comparative Examples 1 to 9, and this was rotated at a peripheral speed equivalent to 130 km · h. The amount of wear of the rotor was measured after pressing the disc at a pressure of 73.5 kPa and dragging it for 22 hours. As the disk rotor, a ventilated disk rotor (FC190) manufactured by Kiriu Corporation was used.

  When the total amount of metal sulfides selected from tin sulfide, bismuth sulfide, and molybdenum disulfide is 8% by mass or more, even in a composition that does not contain copper, high-speed fade characteristics equivalent to or higher than that of Comparative Example 2 containing copper are exhibited. The high-speed fade characteristics were good with respect to Comparative Examples 1 and 3 to 5 that contained no metal sulfide and had a total metal sulfide content of 8% by mass or less. On the other hand, Comparative Examples 6 to 9 in which the total amount of metal sulfide exceeds 30% by mass has a very large amount of rotor wear. From the above, it is clear that Examples 1 to 15 in which the total amount of metal sulfide is 8 to 30% by mass are friction material compositions excellent in high-speed fade characteristics and rotor wear even when copper is not contained.

  Since the friction material composition of the present invention does not contain copper having a high environmental load compared to conventional products and has a high coefficient of friction under high-speed fade conditions, the friction material composition can be used for brake pads for passenger cars, etc. Suitable for friction material and friction member.

Claims (10)

A friction material composition comprising a binder ,
The friction material composition does not contain copper as an element, or the copper content is 0.5% by mass or less,
A friction material comprising 8-30% by mass of one or more metal sulfides selected from tin sulfide, bismuth sulfide and molybdenum disulfide , and containing granular or plate-like titanate. Composition.   2. The friction material composition according to claim 1, wherein the tin sulfide is tin (II) sulfide.   The friction material composition according to claim 1, wherein the tin sulfide is tin (IV) sulfide.   2. The friction material composition according to claim 1, wherein the tin sulfide is a mixture of tin (II) sulfide and tin (IV) sulfide. The friction material composition in any one of Claims 1-4 containing an organic filler, an inorganic filler, and a fiber base material. The friction material composition according to any one of claims 1 to 5, comprising a mineral fiber. The friction material composition according to any one of claims 1 to 6, wherein a content of the metal sulfide is 10 to 30% by mass. A friction material composition for high temperature braking, comprising the friction material composition according to any one of claims 1 to 7, wherein the friction surface has a temperature of 500 ° C or higher. Friction material composition or friction material made by molding the hot braking friction material composition according to claim 8 according to any one of claims 1-7. A friction member formed using the friction material according to claim 9 and a back metal.