JP2014141546A - Friction material composition, and friction material and friction member using the friction material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction material composition capable of exhibiting excellent coefficient of friction, stability in the coefficient of friction and wear resistance, and a friction material and a friction member using the friction material composition.SOLUTION: Provided is a friction material composition comprising: a binder; an organic filler; an inorganic filler; and a fiber substrate. The friction material comprises a tetrapod-shaped inorganic substance made of a nuclear part and an acicular crystal part elongating to different four axis directions different from the nuclear part as the fiber substrate. The Mohs hardness of the tetrapod-shaped inorganic matter is preferably 4 or higher. As the inorganic substance, zinc oxide is preferable.

Description

  The present invention relates to a friction material composition. More specifically, the present invention relates to a friction material composition suitable for a friction material such as a disc brake pad and a brake lining used for braking an automobile, and further 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. Therefore, the friction material is required to have a good friction coefficient, stability of the friction coefficient, good wear resistance (long life of the friction material), and the like.

  For forming the friction material, a friction material composition including a binder, a fiber base material, an inorganic filler, an organic filler, and the like is used. A friction material composition in which two or more kinds are combined is used. In order to improve the friction coefficient, a method using a hard inorganic filler (abrasive material) having a high Mohs hardness (Mohs hardness of about 7 to 9), such as alumina, mullite, etc. has been proposed (see, for example, Patent Document 1). . In recent years, a method for improving the coefficient of friction using activated carbon particles has also been proposed (see, for example, Patent Document 2).

  In addition, a large amount of copper, copper alloy, or the like is used for the friction material in order to develop a sufficient friction coefficient and wear resistance. However, it has been suggested that friction materials containing copper or a copper alloy contain copper in the wear powder generated during braking, which may cause pollution of rivers, lakes, oceans, and the like. Therefore, for the purpose of providing a friction material having good friction coefficient, wear resistance, and rotor wear resistance without including metals such as copper and copper alloys, for brakes including a fiber base material, a binder, and a friction adjusting component. A method has been proposed in which the friction material does not contain a heavy metal or a heavy metal compound, magnesium oxide and graphite are contained in an amount of 45 to 80% by volume in the friction material, and the ratio of magnesium oxide and graphite is 1/1 to 4/1. (See Patent Document 3).

International Publication No. 2004/069954 JP 2009-029954 A JP 2002-138273 A

However, with the friction material of Patent Document 1, it is difficult to obtain an excellent friction material that satisfies all of the good friction coefficient, the stability of the friction coefficient, and the good wear resistance. In particular, at high temperatures (during heat fade), the coefficient of friction changes after the thermal history, making it difficult to exhibit stability of the coefficient of friction. The stability of the friction coefficient is important for obtaining the driver's required deceleration, and is an especially important friction characteristic in a control brake such as a cooperative regenerative brake that has been spreading in recent years.
On the other hand, whisker-like titanates are generally used for the purpose of maintaining the coefficient of friction during heat fade or after heat history. The whisker-like titanate has an effect of effectively improving the strength of the friction material at a high temperature or after a high-temperature heat history and maintaining a friction coefficient. However, the whisker-like titanate is preferably not used as a friction material because there is a concern about human harm from the viewpoint of carcinogenicity.

  In view of such a background, the present invention is a case where the content of copper that may cause pollution of rivers, lakes, oceans, etc. is low and the content of whisker-like titanate is low. However, an object of the present invention is to provide a friction material composition that can exhibit an excellent friction coefficient, stability of the friction coefficient, and excellent wear resistance, a friction material using the friction material composition, and a friction member.

  As a result of intensive studies, the inventors of the present invention contain a tetrapod (registered trademark) -like inorganic substance composed of a core part and a needle-like crystal part extending from the core part in different four-axis directions as a fiber base material. It has been found that the above problems can be solved by using the friction material composition, and the present invention has been completed. That is, the present invention is as follows.

<1> A friction material composition including a binder, an organic filler, an inorganic filler, and a fiber base material. As the fiber base material, a core part and a needle-like crystal part extending in different four-axis directions from the core part A friction material composition containing a tetrapod-like inorganic substance.
<2> The friction material composition, wherein the tetrapod-like inorganic material has a Mohs hardness of 4 or more.
<3> The friction material composition, wherein the tetrapod-like inorganic substance is zinc oxide.
<4> The friction material composition, wherein the content of copper in the friction material composition is 5% by mass or less as a copper element.
<5> The friction material composition, wherein the content of the tetrapod-like inorganic substance is 1 to 50% by mass.
<6> The friction material composition, wherein an average short fiber length of the needle-like crystal part of the tetrapod-like inorganic substance is 5 to 50 μm.
<7> The friction material composition, wherein an average short fiber diameter of the needle-like crystal part of the tetrapod-like inorganic substance is 0.1 to 10 μm.
<8> The friction material composition, wherein the whisker-like titanate content in the friction material composition is 10% by mass or less.
<9> A friction material formed by molding the friction material composition.
<10> A friction member formed by using a friction material obtained by molding the friction material composition and a back metal.

The friction material composition of the present invention has a low copper content and a low whisker-like titanate content when used in a friction material such as an automobile disc brake pad or brake lining. In addition, it is possible to provide a friction material composition that can exhibit an excellent friction coefficient, stability of the friction coefficient, and excellent wear resistance, and a friction material and a friction member using the friction material composition.
Furthermore, according to the present invention, the friction material composition and the friction material composition exhibiting excellent stability of the friction coefficient by suppressing the change of the friction coefficient after high temperature (during heat fade) and after heat history are used. A friction material and a friction member can be provided.

It is the schematic which shows the tetrapod shape in this invention. It is an electron micrograph of the tetrapod-shaped inorganic substance used in the Example. It is the graph which showed the difference of the friction coefficient before the amount of addition of the tetrapod-like inorganic substance-heat history, and a heat fade in an Example and a comparative example. It is the graph which showed the difference of the friction coefficient before and behind the addition amount of a tetrapod-like inorganic substance in an Example and a comparative example-thermal history. It is the graph which showed the addition amount-pad wear amount of the tetrapod-like inorganic substance in an Example and a comparative example.

  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 non-asbestos friction material composition.

[Friction material composition]
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 base material, and extends as a fiber base material in a different four-axis direction from the core portion. It is a friction material composition containing a tetrapod-like inorganic substance composed of an acicular crystal part.

(Binder)
The binding material integrates an organic filler, an inorganic filler, a fiber base material, and the like contained 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.

  As said thermosetting resin, a phenol resin can be mentioned, for example. The phenol resin may be various elastomer-dispersed phenol resins such as acrylic elastomer-dispersed phenol resin and silicone elastomer-dispersed phenol resin, acrylic-modified phenol resin, silicone-modified phenol resin, cashew-modified phenol resin, epoxy-modified phenol resin, alkylbenzene-modified phenol resin, etc. Various modified phenolic resins can also be used. 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, and 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, wear resistance and the like of the friction material. The organic filler used 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, a rubber component, etc. that 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. From the viewpoint of dispersibility, the average particle size of cashew dust is preferably 850 μm or less, more preferably 750 μm or less, and even more preferably 500 μm or less. In addition, the average particle diameter of cashew dust can be measured using methods, such as a laser diffraction particle size distribution measurement. For example, it can be measured with a laser diffraction / scattering particle size distribution measuring apparatus LA.920 (manufactured by Horiba, Ltd.).

Examples of the rubber component include tire rubber, acrylic rubber, isoprene rubber, NBR (nitrile butadiene rubber), and SBR (styrene butadiene rubber), and these can be used alone or in combination of two or more.
Cashew dust and a rubber component may be used in combination, or cashew dust coated with a rubber component may be used.

  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. Further 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 can be increased, and the deterioration of sound vibration performance such as squeal can be avoided, and the heat resistance is also deteriorated. It is possible to avoid a decrease in strength due to thermal history.

(Inorganic filler)
The inorganic filler is included as a friction modifier for avoiding deterioration of the heat resistance of the friction material.
In the friction material composition of this invention, there will be no restriction | limiting in particular if it is an inorganic filler normally used for a friction material.

  Examples of the inorganic filler include tin sulfide, molybdenum disulfide, iron sulfide, antimony trisulfide, bismuth sulfide, zinc sulfide, calcium hydroxide, calcium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, barium sulfate, dolomite, Coke, graphite, mica, iron oxide, vermiculite, calcium sulfate, granular potassium titanate, plate-like potassium titanate, talc, clay, zeolite, zirconium silicate, zirconium oxide, mullite, chromite, titanium oxide, magnesium oxide, silica, Active alumina such as iron oxide, granular zinc oxide, and γ-alumina, lithium potassium titanate, magnesium potassium titanate, and calcium titanate can be used, and these can be used alone or in combination of two or more. . Of these, antimony trisulfide, calcium oxide, barium sulfate, coke, graphite, zirconium oxide, granular zinc oxide, and granular potassium titanate are preferable from the viewpoint of reducing the aggressiveness to the facing material.

  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 80% by mass, and 60 to 80% by mass. Further 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 substrate)
The fiber base material is included for improving the mechanical strength of the friction material. Examples of the fiber substrate used in the present invention include inorganic fibers, metal fibers, organic fibers, carbon fibers, and the like, and these can be used alone or in combination of two or more.

The friction material composition of the present invention contains a tetrapod-like inorganic substance as the inorganic fiber. Here, the tetrapod shape refers to a shape composed of a core portion and needle-shaped crystal portions extending in different four-axis directions from the core portion as shown in FIG.
By containing a tetrapod-like inorganic substance, a good friction coefficient is exhibited without impairing the wear resistance. Further, by containing a tetrapod-like inorganic substance, the coefficient of friction after a high-temperature thermal history is high at the time of thermal fade, and the difference in coefficient of friction under various braking conditions becomes small. That is, a friction material having excellent friction coefficient stability can be obtained.
Furthermore, in the case of a friction material composition having a small content of copper or whisker-like titanate, which will be described later, because it is desired to have a small amount due to environmental impact, by containing a tetrapod-like inorganic substance, The effect is demonstrated remarkably.

As the tetrapod-like inorganic substance, the Mohs hardness is preferably 4 or more from the viewpoint of the friction coefficient, and the Mohs hardness is 6 or less from the viewpoint of improving the wear resistance and the attacking property to the facing material. preferable. As the tetrapod-like inorganic substance, zinc oxide is preferable. Among the tetrapod-like inorganic substances, those that are zinc oxide include commercially available Panatetra (registered trademark) manufactured by Amtec Corporation.
The tetrapod-like inorganic substance is preferably biosoluble. The term “biologically soluble” as used herein refers to being soluble under acidic conditions. If soluble under acidic conditions, even if inhaled into the body, it dissolves and disappears due to acidic conditions caused by macrophages and is unlikely to cause carcinogenic factors such as emphysema.

The average short fiber length of the tetrapod-like inorganic needle-like crystal part is preferably 5 to 50 μm and more preferably 5 to 30 μm from the viewpoint of improving the stability of the friction coefficient and the wear resistance. More preferably, it is 5-20 micrometers. The average short fiber length is the length of part a in FIG.
The average short fiber diameter of the tetrapod-like inorganic needle-like crystal part is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm from the viewpoint of improving the stability of the friction coefficient and the wear resistance. It is more preferable that it is 0.1-3 micrometers. The average short fiber diameter is the length of the portion b (the thickest portion of the acicular crystal portion) in FIG.
The average short fiber length (length a in FIG. 1) and the average short fiber diameter (length b in FIG. 1) are obtained by observing a tetrapod-like inorganic substance with a scanning electron microscope (SEM). Twenty crystals can be selected and the average value can be taken as the average short fiber length and average short fiber diameter.

  The content of the tetrapod-like inorganic substance in the friction material composition of the present invention is preferably 1 to 50% by mass, more preferably 1 to 40% by mass, and 1 to 30% by mass. More preferably. When the content is 1% by mass or more, a good friction coefficient can be imparted to the friction material, and when the content is 50% by mass or less, deterioration of wear resistance due to excessive porosity can be prevented.

The friction material composition of the present invention may contain inorganic fibers other than the tetrapod-like inorganic material. An inorganic fiber refers to a fibrous material whose main component is an inorganic substance other than metals and metal alloys, and is used for improving wear resistance. As the inorganic fiber, for example, ceramic fiber, biosoluble ceramic fiber, mineral fiber, glass fiber, silicate fiber, whisker-like titanate can be used, and one kind or a combination of two or more kinds can be used. Among these inorganic fibers, a mineral fiber having biosolubility containing SiO ₂ , Al ₂ O ₃ , CaO, MgO, FeO, Na ₂ O and the like in an arbitrary combination is preferable, and as a commercial product, LAPINUS FIBERS B . For example, V Roxul series.

  Whisker-like titanates such as whisker-like potassium titanate have been used for conventional friction materials from the viewpoint of suppressing changes in the coefficient of friction during heat fade and after thermal history. From the viewpoint of carcinogenicity, the whisker-like titanate is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably (content 0% by mass). The friction material composition of the present invention exhibits excellent friction coefficient, stability of friction coefficient, and excellent wear resistance even when the copper content is small or whisker-like titanate is not contained. be able to.

A metal fiber refers to a fibrous material mainly composed of a metal or a metal alloy, and is used for improving crack resistance and wear resistance. Hereinafter, the description will be divided into copper or copper alloy fibers and other metal fibers.
Of the metal fibers used in the friction material composition of the present invention, the metal fibers other than copper or copper alloy are not particularly limited as long as they are usually used in friction materials. For example, aluminum, iron, zinc , Fibers of simple metals such as tin, titanium, nickel, magnesium, and silicon, and fibers in the form of alloys thereof. Moreover, the fiber which has a metal as a main component like cast iron fiber etc. can also be used.

  Among the metal fibers used in the friction material composition of the present invention, examples of copper or copper alloy fibers include copper fibers, brass fibers, bronze fibers, and the like, which can be used alone or in combination of two or more. . In addition, you may use the fiber containing copper, such as copper and a copper alloy, However, From a viewpoint of environmental pollution resistance, content of the whole copper in the friction material composition of this invention is 5 mass% or less as a copper element. It is preferable that it is 0.5% by mass or less, and it is more preferable that the content is not contained (content 0% by mass). The friction material composition of the present invention can exhibit an excellent friction coefficient, stability of the friction coefficient, and excellent wear resistance even when the copper content is low or copper is not included.

  The organic fiber refers to a fibrous material whose main component is an organic material other than carbon-based fibers described later, and is used for improving crack resistance and wear resistance. As an organic fiber, an aramid fiber, a cellulose fiber, an acrylic fiber, a phenol resin fiber can be used, for example, These can be used 1 type or in combination of 2 or more types. Among these, an aramid fiber is preferable from the viewpoint of heat resistance and a reinforcing effect.

  Carbon-based fibers are used to improve crack resistance and wear resistance. As the carbon-based fiber, for example, flame-resistant fiber, pitch-based carbon fiber, PAN-based carbon fiber, and activated carbon fiber can be used, and these can be used alone or in combination of two or more.

  The content of the fiber base material in the friction material composition of the present invention is preferably 1 to 60% by mass, and preferably 5 to 55% by mass in the friction material composition, including tetrapod-like inorganic substances. More preferably, it is more preferably 5 to 40% by mass, and particularly preferably 5 to 30% by mass. By making the content of the fiber base in the range of 1 to 60% by mass, the optimum porosity as a friction material can be obtained, squeal can be prevented, appropriate material strength can be obtained, and wear resistance can be expressed. The moldability can be improved.

(Other materials)
The friction material composition of this invention can mix | blend other materials as needed other than a binder, an organic filler, an inorganic filler, and a fiber base material. For example, metal powders such as copper powder, brass powder, bronze powder, and zinc powder can be blended. However, from the viewpoint of resistance to environmental pollution, the total content of copper in the friction material composition of the present invention is preferably 5% by mass or less as a copper element, and it is more preferable not to contain (content 0% by mass). preferable.
Moreover, organic additives, such as fluorine-type polymers, such as PTFE (polytetrafluoroethylene), can be mix | blended from a viewpoint of abrasion resistance and a heat fade characteristic improvement.

[Friction material]
The friction material of the present invention is formed by molding the friction material composition, and can be used as a friction material for disc brake pads and brake linings for automobiles. Since the friction material of the present invention exhibits an excellent friction coefficient, stability of the friction coefficient, crack resistance, and wear resistance, it is suitable for a friction material for a disk brake pad having a large load during braking.
The friction material of the present invention can be produced by molding the friction material composition of the present invention by a generally used method, and is preferably produced by hot pressing. Specifically, for example, the friction material composition of the present invention is uniformly mixed using a mixer such as a Readyge mixer, a pressure kneader, or an Eirich mixer, and this mixture is preformed in a molding die to obtain a mixture. The obtained preform is molded for 2 to 10 minutes under conditions of a molding temperature of 130 to 160 ° C. and a molding pressure of 20 to 50 MPa, and the obtained 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]
By using the friction material, it is possible to obtain a friction member in which the friction material is formed to be a friction surface. Examples of the friction member that can be formed using the friction material include the following configurations.
(1) Configuration of friction material only.
(2) The structure which has a back metal and the friction material which consists of a friction material composition of this invention used as a friction surface on this back metal.
(3) In the configuration of (2) above, between the back metal and the friction material, a primer layer for the purpose of surface modification for enhancing the adhesion effect of the back metal, and for the purpose of bonding the back metal and the friction material A configuration in which an adhesive layer is further interposed.

  The backing metal is usually used as a friction member in order to improve the mechanical strength of the friction member. As the material, metal, fiber reinforced plastic, etc. can be used. For example, iron, stainless steel, inorganic fiber Examples include reinforced plastic and carbon fiber reinforced plastic. The primer layer and the adhesive layer may be those used for friction members such as brake shoes.

The friction material composition of the present invention has a high friction coefficient, is excellent in stability of the friction coefficient, and is excellent in wear resistance. Therefore, the friction material composition is useful as a “upper material” of the friction member. Can also be used.
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 and crack resistance in the vicinity of the adhesion part with the back metal.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Examples 1 to 11 and Comparative Examples 1 to 4]
(Production of disc brake pad)
The materials were blended according to the blending ratio shown in Table 1, and the friction material compositions of Examples 1 to 11 and Comparative Examples 1 to 4 were obtained. This friction material composition is mixed with a ladyge mixer (manufactured by Matsubo Co., Ltd., trade name: ladyge mixer M20), and this mixture is preformed with a molding press (manufactured by Oji Machinery Co., Ltd.). The pre-molded product was heat-pressed with a backing metal manufactured by Hitachi Automotive Systems, Ltd. using a molding press (manufactured by Sanki Seiko Co., Ltd.) for 5 minutes at a molding temperature of 145 ° C. and a molding pressure of 30 MPa. The molded product was heat treated at 200 ° C. for 4.5 hours, polished using a rotary polishing machine, and subjected to scorch treatment at 500 ° C., and the disc brake pads of Examples 1 to 11 and Comparative Examples 1 to 4 (of the back metal) A thickness of 6 mm, a friction material thickness of 11 mm, and a friction material projection area of 52 cm ² were prepared.

The various materials used in the examples and comparative examples are as follows.
(Binder)
・ Phenolic resin: manufactured by Hitachi Chemical Co., Ltd. (trade name: HP491UP)
(Organic filler)
・ Cashew dust: manufactured by Tohoku Kako Co., Ltd. (trade name: FF-1056)
(Inorganic filler)
-Barium sulfate: manufactured by Sakai Chemical Co., Ltd. (trade name BA)
・ Granular potassium titanate: Otsuka Chemical Co., Ltd. (trade name Terraces TF-S)
・ Graphite: TIMCAL (trade name KS75)
・ Coke: TIMCAL (trade name FC250-1500)
・ Granular zinc oxide: manufactured by Tokyo Kasei Co., Ltd. (trade name: 1 type of zinc oxide)
(Fiber substrate)
・ Aramid fiber (organic fiber): manufactured by Toray DuPont Co., Ltd. (trade name: 1F538)
Copper fiber (metal fiber): manufactured by Sunny Metal (trade name SCA-1070)
Mineral fiber (inorganic fiber): LAPINUS FIBERS B. Made of V (Brand name RB240 Roxul 1000, average fiber length 300μm)
Tetrapod-like inorganic substance: manufactured by Amtec Co., Ltd. (trade name: Panatetra, component zinc oxide, Mohs hardness 4, average short fiber length of needle crystal part 7 μm, average short fiber diameter of needle crystal part 0.5 μm (SEM 20 were selected from the images observed in the above, and the average value of the short fiber length and short fiber diameter measured on the image was taken as the average short fiber length and average short fiber diameter), biosolubility, electron micrograph 2)
-Whisker-like potassium titanate: manufactured by Otsuka Chemical Co., Ltd. (trade name: Tismo D)

(Evaluation of friction coefficient and wear resistance)
The disc brake pad friction coefficient and abrasion resistance of the produced Examples 1 to 11 and Comparative Examples 1 to 4 were evaluated by a friction test in accordance with the Japan Society of Automotive Engineers Standard JASO C406 using a brake dynamo. The friction test using the brake dynamo was evaluated with an inertia of 7 kgf · m · s ² . Moreover, it was carried out using a ventilated disc rotor (manufactured by Kiriu Co., Ltd., material FC190) and a general pin slide type collet type caliper. The results are shown in Table 1.
<Coefficient of friction>
・ Friction coefficient before thermal history:
It is the average value of the friction coefficient in the second efficacy test (normal braking).
・ Friction coefficient during thermal fade:
Of the friction coefficients generated during 10 brakings in the first fade, the smallest value was evaluated.
・ Friction coefficient after thermal history:
It is the average value of the coefficient of friction in the third efficacy test (after heat history).
<Stability of friction coefficient>
・ Difference in friction coefficient before heat history and heat fade:
It was calculated from (friction coefficient before heat history) − (friction coefficient at the time of heat fade).
・ Difference in friction coefficient before and after thermal history:
(Friction coefficient before thermal history) − (Friction coefficient after thermal history)
<Abrasion resistance>
Pad wear amount (mm): For the inner and outer pads of the disc brake pad, the difference in pad thickness before and after the test was measured, and the average value was calculated.

  Moreover, the difference of the friction coefficient of Examples 1, 2, 8-11 and Comparative Examples 1 and 3 and the amount of pad wear were plotted in FIGS.

Examples 1 to 11 containing a tetrapod-like inorganic material are excellent in friction coefficient and wear resistance, have little change in friction coefficient before and after thermal history, and in heat fade, and are excellent in friction coefficient stability. Could get.
It turned out that stability of a friction coefficient is inferior when Examples 1-11 do not contain a tetrapod-like inorganic substance like comparative example 1.
Moreover, when there are few copper fibers like the comparative example 2, and when a copper fiber is not included like the comparative example 3, there exists a tendency for stability of a friction coefficient to deteriorate or abrasion resistance to deteriorate. However, when a tetrapod-like inorganic substance is used, even when the copper content is 5% by mass or less as in Example 3, or when copper is not substantially included as in Examples 4 to 11, A friction material having excellent friction coefficient and wear resistance and excellent friction coefficient stability could be obtained.
In addition, in Comparative Example 4 in which granular zinc oxide was used instead of tetrapod-shaped zinc oxide, which is a tetrapod-shaped inorganic substance, the stability of the friction coefficient could not be improved.
Moreover, when it does not contain whisker-like potassium titanate like Comparative Examples 2-4, there exists a tendency for stability of a friction coefficient to deteriorate. However, even when the whisker-like potassium titanate is 10% by mass or less as in Example 7 and when the whisker-like potassium titanate is not substantially contained as in Examples 8 to 11, the tetrapot In Examples 7-11, the friction material which was excellent in the friction coefficient and abrasion resistance, and excellent in the stability of a friction coefficient was able to be obtained by containing a fibrous inorganic substance.
From the above, it is clear that the friction material using the friction material composition of the present invention containing a tetrapod-like inorganic substance is excellent in the friction coefficient, the stability of the friction coefficient, and the wear resistance.
As can be seen from FIGS. 3 to 5, when a friction material composition containing no copper and not containing a whisker-like titanate is used, the effect of the stability of the friction coefficient is more remarkably exhibited. did.

  The friction material composition of the present invention is superior in friction coefficient, friction coefficient stability and wear resistance compared to conventional products, and the effect of the present invention is a whisker-like titanate having a carcinogenic problem, The friction material composition is suitable for a friction material such as a brake pad for a passenger car and a friction member because the friction material composition is particularly prominent in a composition having a small amount of copper which is harmful to the environment.

Claims (10)

  A friction material composition comprising a binder, an organic filler, an inorganic filler, and a fiber base material. The fiber base material includes a core and a tetragonal crystal part extending from the core in different four-axis directions. A friction material composition containing a pod-like inorganic substance.   The friction material composition according to claim 1, wherein the tetrapod-like inorganic substance has a Mohs hardness of 4 or more.   The friction material composition according to claim 1 or 2, wherein the tetrapod-like inorganic substance is zinc oxide.   The friction material composition according to claim 1, wherein the content of copper in the friction material composition is 5% by mass or less as a copper element.   The friction material composition according to any one of claims 1 to 4, wherein a content of the tetrapod-like inorganic substance is 1 to 50% by mass.   The friction material composition according to any one of claims 1 to 5, wherein an average short fiber length of the needle-like crystal part of the tetrapod-like inorganic substance is 5 to 50 µm.   The friction material composition according to any one of claims 1 to 6, wherein the tetrapod-like inorganic needle-like crystal part has an average short fiber diameter of 0.1 to 10 µm.   The friction material composition according to claim 1, wherein the content of whisker-like titanate in the friction material composition is 10% by mass or less.   The friction material formed by shape | molding the friction material composition in any one of Claims 1-8.   The friction member formed using the friction material formed by shape | molding the friction material composition in any one of Claims 1-8, and a back metal.