JP5691125B2 - Friction material composition, friction material and friction member using the same - Google Patents

Description

  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 of an automobile or the like, and 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 rubbing against a counterpart material such as a disk rotor, a brake drum, etc. for braking, so that not only high friction coefficient and stability of the friction coefficient but also generation of squeal is generated. Less is required.

  Brake squeezing tends to occur especially when braking after leaving at low temperature and high humidity, for example when driving a car that has been left in the morning or overnight, and is quiet. From the viewpoint, reduction of squeal after leaving at low temperature and high humidity has become a major issue.

  As a conventional technique for reducing the brake squeal after being left, several methods for suppressing the coefficient of friction after being left at a low temperature and high humidity have been reported. For example, an example using hydrophobic silica to suppress moisture absorption of the friction material (for example, see Patent Document 1), an example using an aromatic phenol resin as a binder (for example, see Patent Document 2), a silicone-based material Proposed examples using a silicone-impregnated porous body composed of an inorganic porous body impregnated with oil (for example, see Patent Document 3), examples for reducing pores in a friction material (for example, see Patent Document 4), etc. However, there is a problem that the brake squeal cannot be effectively suppressed after being left at a very low temperature of 5 ° C. or less, that is, the condition in which the brake squeal is particularly likely to occur.

  By the way, recent research reports have revealed that the phenomenon of increased brake squeal after leaving at low temperature and high humidity is accompanied by an increase in the friction coefficient and the negative gradient of the friction coefficient with respect to the vehicle speed during one braking. .

The negative gradient of the friction coefficient with respect to the vehicle speed during one braking indicates a negative gradient of μ (friction coefficient) with respect to V (vehicle speed) and is referred to as “μ−V negative gradient”.
Further, in braking after being left at low temperature and high humidity, μ increases as the vehicle speed decreases, and therefore, μ tends to show a negative negative gradient with respect to V. When this negative gradient is large, a brake squeal using self-excited vibration as an excitation force is likely to occur.

  As described above, several methods have been proposed to suppress the brake squeal after leaving at low temperature and high humidity by reducing the coefficient of friction after leaving at low temperature and high humidity. A technique for reducing the V negative slope has not been sufficiently established.

JP 2003-003155 A Japanese Patent Laid-Open No. 11-286676 JP-A-10-245544 JP-A-11-325141

  The present invention has been made in view of the above circumstances. From the viewpoint of reducing the μ-V negative gradient after being left at low temperature and high humidity, it is possible to reduce squeal after being left at low temperature and high humidity compared to conventional products. It is an object to provide a friction material composition, a friction material using the friction material composition, and a friction member.

  In order to achieve the above-mentioned target, the inventors contain 15 to 35% by mass of fine zirconium oxide, and the content of abrasives having a Mohs hardness of 7 or more other than zirconium oxide is set to 2.0% by mass or less. Thus, the friction material sliding surface after the friction with the mating material becomes smooth and the surface of the friction material during one braking after being left at a low temperature and high humidity, that is, at a temperature of -5 ° C to 5 ° C for several hours. It has been found that the increase in the real contact area of the facing material is suppressed, and as a result, the negative squeezing after leaving at low temperature and high humidity is reduced to reduce the brake squeal after leaving at low temperature and high humidity.

Moreover, it discovered that a friction coefficient was suppressed and generation | occurrence | production of a brake squeal was suppressed by using a zirconium silicate as abrasives with Mohs hardness 7 or more other than the above-mentioned zirconium oxide.
Moreover, it discovered that a friction coefficient was suppressed more and the generation | occurrence | production of a brake squeal was suppressed because the 50-% particle size of the above-mentioned zirconium silicate is 10 micrometers or less.

The present invention relates to the following matters.
(1) In a friction material composition including a fiber substrate, an inorganic filler, a binder, an organic filler, and an abrasive,
As the abrasive, 15 to 35% by mass of zirconium oxide having a 50% particle size in the range of 0.1 to 5.0 μm, and 2.0% by mass or less of abrasive having a Mohs hardness of 7 or more other than zirconium oxide Containing friction material composition.
(2) The friction material composition according to (1), wherein the abrasive having a Mohs hardness of 7 or more other than the zirconium oxide is zirconium silicate.
(3) The friction material composition according to (2), wherein the zirconium silicate has a 50% particle size of 10 μm or less.
(4) A friction material obtained by heat-pressing the friction material composition according to any one of (1) to (3) above.
(5) A friction member in which the friction material according to (4) and a back metal are integrated.

  According to the present invention, a friction material composition capable of reducing brake squeal after being left at a low temperature and high humidity, particularly after being left at a very low temperature, compared with a conventional product, a friction material using this friction material composition, and A friction member can be provided.

Hereinafter, the friction material composition of the present invention will be described in detail.
The friction material composition of the present invention is a friction material composition including a fiber substrate, an inorganic filler, a binder, an organic filler and an abrasive, and the abrasive has a 50% particle size of 0.1 to 5. A friction material composition comprising 15 to 35% by mass of zirconium oxide in the range of 0 μm and 2.0% by mass or less of an abrasive having a Mohs hardness of 7 or more other than zirconium oxide. By containing a large amount of zirconium oxide with a small diameter, the friction material surface after rubbing with the counterpart material becomes smooth on the order of several tens to several hundreds of microns.

  As a result, even in a state where the elastic modulus of the friction material is high after standing at a low temperature, that is, in a state where the true contact area is small at the initial stage of braking and the true contact area is increased due to the presence of wear powder in the late stage of braking. From the end of braking to the late stage of braking, the change in the true contact area of the friction interface is reduced, and the μ-V negative gradient is reduced.

If the content of zirconium oxide is 15% by mass or more, the effect of reducing the μ-V negative gradient is not small, and if it is 35% by mass or less, not only after leaving at low temperature and high humidity but also during normal braking. In addition, the problem that the friction coefficient increases and the occurrence of brake squealing is less likely to occur. A more preferable content of zirconium oxide having a 50% particle size in the range of 0.1 to 5.0 μm is 20 to 35% by mass.
In addition, the 50% particle size of zirconium oxide is defined to be in the range of 0.1 to 5.0 μm by setting it to 0.1 μm or more, and by setting it to 5.0 μm or less, after being left at low temperature and high humidity. This is because it is possible to reduce the reduction in the negative μ-V gradient and suppress brake noise.

  At the same time, the content of abrasives having a Mohs hardness of 7 or more other than zirconium oxide must be 2.0 mass% or less. An abrasive with a Mohs hardness of 7 or more tends to scrape the counterpart during braking, and its scratch resistance decreases as the speed increases.

In a friction material composition containing 15 to 35% by mass of zirconium oxide having a 50% particle size in the range of 0.1 to 5.0 μm, the content of abrasives having a Mohs hardness of 7 or more other than zirconium oxide is 2.0% by mass. % Or less, the negative μ-V slope after leaving at low temperature and high humidity will not increase, and not only after low temperature and high humidity standing but also during normal braking, the brake squeal will be caused by a high coefficient of friction. Can be reduced. The content of the abrasive having a Mohs hardness of 7 or more other than zirconium oxide is 0.1 to 1.5% by mass.
As an abrasive having a Mohs hardness of 7 or more other than zirconium oxide, zirconium silicate, alumina, silicon carbide, or the like can be used.

  In the friction material composition containing 15 to 35% by mass of zirconium oxide having a 50% particle size in the range of 0.1 to 5.0 μm, the above-mentioned abrasive having a Mohs hardness of 7 or more contained as a friction modifier is silicic acid. Zirconium is preferred. Zirconium silicate has a relatively low face-to-face attack among abrasives with a Mohs hardness of 7 or more, and it is difficult to increase the coefficient of friction. Therefore, zirconium oxide having a 50% particle size of 0.1 to 5.0 μm is 15 to 35 mass. % Of the friction material composition is preferable as an abrasive component.

  The 50% particle size of the zirconium silicate is preferably 10 μm or less. Zirconium silicate having a 50% particle size of 10 μm or less has a relatively low face-to-face attack among abrasives having a Mohs hardness of 7 or more, and it is difficult to increase the friction coefficient. In the friction material composition containing 15 to 35% by mass of 0 μm zirconium oxide, it is preferable as an abrasive component.

Examples of the fiber substrate used in the present invention include metal fibers, inorganic fibers, and organic fibers.
Among these, as a metal fiber, a copper fiber, a brass fiber, a bronze fiber, an iron fiber, a titanium fiber, a zinc fiber, an aluminum fiber, etc. can be used, and it can be used 1 type or in combination of 2 or more types.

  As the inorganic fiber, ceramic fiber, biodegradable ceramic fiber, mineral fiber, carbon fiber, glass fiber, potassium titanate fiber, silicate fiber and the like can be used, and one kind or a combination of two or more kinds can be used. However, it is preferable not to contain attractive potassium titanate fibers or ceramic fibers from the viewpoint of reducing environmental substances.

As an organic fiber, an aramid fiber, an acrylic fiber, a cellulose fiber, a phenol resin fiber, etc. can be used, and it can be used 1 type or in combination of 2 or more types.
Moreover, it is preferable to contain 5-30 mass% of fiber base materials in a composition, and it is more preferable to contain 10-20 mass%.

Examples of the inorganic filler used in the present invention include antimony trisulfide, tin sulfide, molybdenum disulfide, iron sulfide, bismuth sulfide, zinc sulfide, calcium hydroxide, calcium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, and sulfuric acid. Barium, dolomite, coke, graphite, mica, iron oxide, vermiculite, granular potassium titanate, calcium sulfate, plate-like potassium titanate, talc, clay, zeolite, etc. can be used, and these can be used alone or in combination of two or more. Can be used in combination.
The content of the inorganic filler is preferably 20 to 80% by mass, and more preferably 30 to 60% by mass in the friction material composition.

  As the binder contained in the friction material composition of the present invention, a thermosetting resin usually used for a friction material can be used. Examples of the thermosetting resin include various modified phenol resins such as phenol resin, acrylic modified phenol resin, silicone modified phenol resin, cashew modified phenol resin, epoxy modified phenol resin, and alkylbenzene modified phenol resin. Resins, acrylic-modified phenol resins, and silicone-modified phenol resins are preferred, and these can be used alone or in combination of two or more.

  Examples of the organic filler contained in the friction material composition of the present invention include cashew dust, tire rubber powder, acrylic rubber powder, isoprene rubber, NBR powder, SBR powder, and the like. Used in combination.

  The friction material composition of the present invention can be used as a friction material for disc brake pads, brake linings, etc. of automobiles, or by subjecting the friction material composition of the present invention to a target shape by subjecting it to steps such as molding, processing, and pasting. It can also be used as a friction material for electromagnetic brakes and holding brakes.

  Moreover, the friction material composition of this invention can mix | blend other materials as needed other than the said material, for example, metal powders, such as copper powder, zinc powder, brass powder, etc. Can do.

  Moreover, the friction material composition of the present invention can be produced by using a generally used method, and can be produced by heating and pressing the friction material composition of the present invention. 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 at 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. The friction material can be obtained. In addition, you may perform a coating, a scorch process, a grinding | polishing process etc. as needed.

The friction material composition of the present invention can be used as a friction member itself that becomes a friction surface to obtain a friction material. Examples of the friction material using the friction material include, for example, (1) the configuration of only the friction member, (2) the back metal, and the friction member formed on the back metal and made of the friction material composition of the present invention which becomes the friction surface; (3) In the configuration of (2) above, a primer layer for the purpose of surface modification for enhancing the adhesion effect of the back metal and the adhesion of the back metal and the friction member between the back metal and the friction member Examples include a configuration in which the intended adhesive layer is further interposed.
As the backing metal, primer layer, and adhesive layer, those usually used for friction materials can be used.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these.
<Examples 1-4 and Comparative Examples 1-4>
(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 4 and Comparative Examples 1 to 4 were obtained.

  This friction material composition was mixed with a Readyge mixer (manufactured by Matsubo Co., Ltd., trade name: Ladyge mixer M20), and this mixture was preformed with a molding press (Oji Machinery Co., Ltd.). The preform was subjected to heat and pressure molding using a molding press (manufactured by Sanki Seiko Co., Ltd.) for 5 minutes under conditions of a molding temperature of 145 ° C. and a molding pressure of 30 MPa.

The obtained 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. to obtain a disc brake pad. In this example, a disc brake pad having a friction material projection area of 52 cm ² was produced.

The details of zirconium oxides (1) to (3) and zirconium silicates (1) and (2) in Table 1 are as follows.
Zirconium oxide (1): manufactured by Daiichi Rare Element Chemical Co., Ltd., trade name: BR-3QZ, D50% particle size = 2.0 μm
Zirconium oxide (2): manufactured by Daiichi Rare Element Chemical Co., Ltd., trade name: BR-QZ, D50% particle size = 6.5 μm
Zirconium oxide (3): manufactured by Daiichi Rare Element Chemical Co., Ltd., trade name: BR-12QZ, D50% particle size = 8.5 μm
Zirconium silicate (1): manufactured by Daiichi Rare Element Chemical Co., Ltd., trade name: MZ-1000B, D50% particle size = 1.5 μm
Zirconium silicate (2): manufactured by Daiichi Rare Element Chemical Co., Ltd., trade name: MZ-50B, D50% particle size = 17.0 μm

(Evaluation of brake squeal and μ-V negative slope after standing at low temperature)
The disc brake pads of Examples 1 to 4 and Comparative Examples 1 to 4 produced by the above method were evaluated for brake squeal after being left at a low temperature using a brake dynamo tester. In the experiment, a general pin-slide type collet caliper and a ventilated disc rotor (FC250) manufactured by Kiriu Corporation were used, and evaluation was performed based on the moment of inertia of the Nissan Skyline V35.
Further, in order to remarkably generate squeal after standing at low temperature, the disc brake pad was tested without using a damping shim that is generally mounted to prevent squeal.

  After slicing according to JASO C427 (initial speed 50km / h, deceleration 0.3G, brake temperature 100 ° C before braking, 200 times of braking), left for 4 hours in environment of temperature 5 ° C and humidity 40% RH Then, braking at a vehicle speed of 10 km / h and a brake hydraulic pressure of 0.5 MPa was repeated 50 times at intervals of 120 seconds.

  Thereafter, the vehicle was left for 4 hours in an environment at a temperature of −5 ° C., and braking at a vehicle speed of 10 km / h and a brake hydraulic pressure of 0.5 MPa was repeated 50 times at an interval of 120 seconds. In this test, the occurrence rate of the brake squeal measured at a sound pressure of 75 dB or higher in braking at a low speed reduction speed after being left in an environment of 5 ° C. and −5 ° C. is shown in Examples 1-4 and Comparative Examples 1-4. Disc brake pads were evaluated.

  In addition, a change in the friction coefficient with respect to the vehicle speed in the latter half of the braking was first-order approximated, and the gradient was defined as a μ-V gradient. The value of this μ-V gradient indicates that a larger negative value has a greater increase in the coefficient of friction in the latter half of braking, which is disadvantageous for brake squeal. The μ-V gradient was calculated as an average value of 50 brakings after being left in an environment of 5 ° C. and −5 ° C., respectively.

※ 表１の配合量は、摩擦材組成物全体に対する質量％である。

* The blending amount in Table 1 is mass% with respect to the entire friction material composition.

  As shown in Table 1, when the friction material composition for brake pads for passenger cars of the present invention is used as a friction material, it is left at a low temperature as compared with the friction material composition of the comparative example, particularly after being left at a very low temperature. It is clear to reduce the brake squeal.

Claims (5)

In a friction material composition comprising a fiber substrate, an inorganic filler, a binder, an organic filler and an abrasive ,
Before SL inorganic filler, antimony trisulfide, tin sulfide, molybdenum disulfide, iron sulfide, bismuth sulfide, zinc sulfide, calcium hydroxide, calcium oxide, sodium carbonate, calcium carbonate, magnesium carbonate, barium sulfate, dolomite, coke, graphite, mica, iron oxide, vermiculite, granular potassium titanate, seen containing calcium sulfate, plate-like potassium titanate, talc, at least one member selected from the group consisting of clay and zeolite,
Containing 10 to 20% by mass of the fiber substrate in the friction material composition;
Containing 30-60 mass% of the inorganic filler in the friction material composition,
Wherein as the abrasive, 50% particle size containing 20-35% by mass of zirconium oxide in the range of 0.1~5.0μm in the friction material composition,
A friction material composition having a content of an abrasive having a Mohs hardness of 7 or more other than zirconium oxide of 2.0% by mass or less in the friction material composition.
The friction material composition according to claim 1, wherein the abrasive having a Mohs hardness of 7 or more other than zirconium oxide contains zirconium silicate.   The friction material composition according to claim 2, wherein the zirconium silicate has a 50% particle size of 10 μm or less.   The friction material which heat-press-molded the friction material composition as described in any one of Claims 1-3.   A friction member in which the friction material according to claim 4 and a back metal are integrated.