JP2014025014A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction material which is formed by molding a friction material composition of a non-asbestos organic (NAO) material comprising a fiber substrate, a binder, and a friction adjusting material and not containing a copper component, and exhibits sufficient braking performance during high load while ensuring excellent wear resistance.SOLUTION: A part of a friction adjusting material contains, as a decomposition catalyst for a binder, 0.2-5.0 wt.% of one or more selected from potassium carbonate, potassium bicarbonate, sodium carbonate, and sodium bicarbonate based on the total amount of a friction material composition. The decomposition catalyst for the binder is preferably potassium bicarbonate.

Description

The present invention relates to a friction material used for a disc brake pad and a brake shoe of an automobile or the like.

Conventionally, disc brakes and drum brakes are used as braking devices for automobiles, and disc brake pads and brake shoes in which a friction material is bonded to a metal base member such as steel are used as friction members. Yes.

The friction material includes a semi-metallic friction material containing 30% by weight or more and less than 60% by weight of steel fiber as a fiber base material, and steel fiber in a part of the fiber base material. Is classified into low steel friction material containing less than 30% by weight of the total friction material composition and NAO (Non-Asbestos-Organic) material that does not contain steel fibers such as steel fibers and stainless steel as the fiber base material. Yes.

In recent years, there is a demand for friction materials that generate less brake noise. Steel fibers and steel-based fibers are not included, and non-ferrous metal fibers, organic fibers, inorganic fibers and other fiber base materials, thermosetting resins, etc. A friction member using a friction material made of NAO material, which is composed of a friction adjusting material such as a binder, an organic filler, an inorganic filler, an inorganic abrasive, a lubricant, and metal particles, has been widely used.

In consideration of the environment, friction materials that do not contain copper, which is a heavy metal, have been desired, and friction materials made of NAO materials that do not contain copper components such as metallic copper, copper alloys, and copper compounds have been developed. I'm starting.

In Patent Document 1, the binder is 12 to 24% by volume, the fiber is 2 to 10% by volume, the at least one lubricant is 5% by volume or less, and at least one or more abrasives are 15 to 30% by volume. A brake friction material containing 10 to 24% by volume of at least one titanate and substantially free of copper and asbestos, that is, a friction material of NAO material not containing a copper component is described.

In NAO friction materials, copper components, especially copper fibers and particles, are added as essential components to meet the required performance. By removing copper fibers and particles from NAO friction materials, Various problems that have never existed are becoming apparent.

One of the problems is a problem of a decrease in fade resistance. Copper contributes to improving the heat dissipation of the friction material because of its high thermal conductivity. However, if copper is not added to the friction material, the friction material is likely to store heat at a high load, and the thermal decomposition of the phenol resin as the binder is promoted. The so-called fade phenomenon in which the pyrolyzed phenolic resin produces tar-like material, and the tar-like material is interposed between the friction material and the friction surface of the disk rotor or brake drum, which is the counterpart material, and the friction coefficient decreases. Will occur.

US Patent Publication 2010/0084233

A friction material composed of a fiber base material, a binder, and a friction modifier, and formed by molding a friction material composition of NAO material that does not contain a copper component. An object of the present invention is to provide a friction material that exhibits an effective braking effect.

It has been found that when a specific amount of potassium carbonate is added to a friction material made of a fiber base material, a binder, and a friction modifier, and does not contain a copper component, the fade phenomenon is suppressed. When the molecular weight of the phenol resin degradation product is large, tar-like products are produced, but potassium carbonate acts as a phenol resin degradation catalyst, and the phenol resin degradation product is reduced in molecular weight, thus suppressing the production of tar-like products. It is speculated that it was done. Moreover, it discovered that the same effect was acquired also with potassium hydrogencarbonate, sodium carbonate, and sodium hydrogencarbonate.

The present invention relates to a friction material formed of a NAO material friction material composition that includes a fiber base material, a binder, and a friction modifier, and does not contain a copper component. As a catalyst, a specific amount of a compound selected from carbonates or bicarbonates of a specific metal is blended, and is based on the following technique.

(1) A friction material composed of a fiber base material, a binder, and a friction modifier, and formed by molding a friction material composition of NAO material that does not contain a copper component. As a decomposition catalyst for the binder in a part of the friction modifier. Friction material characterized by containing 0.2 to 5.0 wt% of one or more selected from potassium carbonate, potassium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate with respect to the total amount of the friction material composition .

(2) The friction material according to (1), wherein the decomposition catalyst for the binder is potassium hydrogen carbonate.

According to the present invention, a friction material formed of a fiber base material, a binder, a friction modifier, and a NAO material friction material composition containing no copper component, while ensuring sufficient wear resistance, A friction material with good fade resistance can be provided.

FIG. 1 is a diagram showing an example of a manufacturing process of a disc brake pad using the friction material of the present invention. FIG. 2 is a perspective view showing an example of a disc brake pad using the friction material of the present invention. FIG. 3 is a diagram showing an example of a manufacturing process of a brake shoe using the friction material of the present invention. FIG. 4 is a perspective view showing an example of a brake shoe using the friction material of the present invention.

In the present invention, a friction material comprising a fiber base material, a binder, and a friction modifier, and formed by molding a friction material composition of a NAO material that does not contain a copper component. As the catalyst, one or more selected from potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate are blended in an amount of 0.2 to 5.0% by weight based on the total amount of the friction material composition.

If the blending amount of the cracking catalyst is less than 0.2% by weight based on the total amount of the friction material composition, the action of the binder as the cracking catalyst is insufficient, and the effect of suppressing the fade phenomenon is not exhibited, and the blending amount of the cracking catalyst If it exceeds 5.0% by weight with respect to the total amount of the friction material composition, it becomes a factor that inhibits the curing reaction of the phenol resin in the manufacturing process of the friction material, resulting in a problem that the wear resistance of the friction material is lowered.

The decomposition catalyst can be used alone or in combination of two or more selected from potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate.

Potassium carbonate and sodium carbonate have a function as a decomposition catalyst, but have deliquescence, so that strict storage management is required, which is disadvantageous in terms of cost.

Non-deliquescent potassium bicarbonate and sodium bicarbonate do not cause the above-mentioned problems and release carbon dioxide only when the friction material is exposed to high temperature by braking, respectively potassium carbonate and sodium carbonate. To function as a decomposition catalyst. For these reasons, it is preferable to use potassium hydrogen carbonate and sodium hydrogen carbonate as the decomposition catalyst, and it is more preferable to use more effective potassium hydrogen carbonate.

Further, the friction material of the present invention includes, in addition to the decomposition catalyst for the above-mentioned binder, fiber base materials such as metal fibers, organic fibers, and inorganic fibers used for ordinary friction materials, and a binder such as a thermosetting resin. And a friction material composition including an organic filler, an inorganic filler, an inorganic abrasive, a friction modifier such as a lubricant and metal particles.

Examples of the fiber substrate include metal fibers such as steel fibers and stainless steel fibers, organic fibers such as aramid fibers and acrylic fibers, and inorganic fibers such as carbon fibers, ceramic fibers, rock wool, and wollastonite. The content of the fiber base material is preferably 5 to 20% by weight with respect to the total amount of the friction material composition in order to ensure sufficient mechanical strength.

Examples of the binder include phenol resins, resins obtained by modifying phenol resins with cashew oil, silicone oil, various elastomers, and the like, resins obtained by dispersing various elastomers, fluoropolymers, and the like in phenol resins. In order to ensure sufficient mechanical strength and wear resistance, the content of the binder is preferably 4 to 15% by weight with respect to the total amount of the friction material composition.

Examples of friction modifiers other than the decomposition catalyst for the binder include organic fillers such as cashew dust, rubber dust (pulverized tire tread rubber), various unvulcanized rubber particles, and various vulcanized rubber particles, sulfuric acid Inorganic fillers such as barium, calcium hydroxide, vermiculite, mica, inorganic abrasives such as iron oxide, aluminum oxide, zirconium silicate, magnesium oxide, lubricants such as graphite, coke, metal sulfide, tin particles, Examples thereof include metal particles such as zinc particles. The content of the friction modifier is preferably 65 to 90% by weight based on the total amount of the friction material composition, depending on the desired friction characteristics.

These fiber base materials, binders, and friction modifiers can be used in appropriate combinations according to desired quality, mechanical properties, and friction and wear properties.

The friction material of the present invention comprises a mixing step in which a predetermined amount of the above-mentioned binder decomposition catalyst, fiber base material, binding material, and friction modifier are mixed uniformly using a mixer, and the resulting friction material raw material mixture Into a preforming mold, pressurizing and pre-molding, pre-molding process, putting the obtained preform into a thermo-molding mold, heating and press-molding process to mold, It is manufactured through a heat treatment step (post-curing step) for completing the curing reaction of the binder by heating and a polishing step for forming a friction surface.

If necessary, a granulation process for granulating the friction material raw material mixture is performed before the preforming process, and a coating process, a paint baking process, and a scorch process are performed after the heat and pressure molding process.

When manufacturing a disc brake pad, in the heat and pressure molding process, heat and pressure molding is performed in a state in which the preform is overlapped with a metal back plate such as steel that has been previously washed, surface-treated, and coated with an adhesive. Is given.

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

[Methods for Producing Friction Materials of Examples 1 to 8 and Comparative Examples 1 to 3] Friction material compositions having the compositions shown in Table 1 were mixed for 5 minutes with a Redige mixer, and 1 at 30 MPa in a preforming mold. Partial pressurization was performed to obtain a preform.

This preform was overlaid on a steel back plate that had been washed, surface-treated, and coated with adhesive in advance, and was heat-pressed and molded in a thermoforming mold for 6 minutes at a molding temperature of 150 ° C. and a molding pressure of 30 MPa. Thereafter, heat treatment (post-curing) was performed at 200 ° C. for 4 hours, and polishing was performed to produce a disc brake pad for a passenger car (Examples 1 to 8, Comparative Examples 1 to 3). The fade resistance and wear resistance of these disc brake pads were evaluated under the following conditions. The evaluation results are shown in Tables 1 and 2.

[Evaluation] <Fade Resistance> The minimum friction coefficient μ in the first fade test was measured in accordance with JASO C406 “passenger car-brake device-dynamometer test method”. The evaluation criteria are as follows. ◎: 0.3 or more ○
: 0.25 or more and less than 0.30 △: 0.20 or more and less than 0.25 ×: Less than 0.20

<Abrasion resistance> In accordance with JASO C427 “Automobile-brake lining and disc brake pad-dynamometer wear test method”, braking initial speed 50 km / h, braking deceleration 0.3 G, number of times of braking, brake temperature before braking 200 The friction material wear amount (mm) was measured under the condition of ° C., converted into the wear amount per 1000 times of braking, and then evaluated according to the following criteria. ◎: Less than 0.15 ○: 0.15 or more and less than 0.20 △: 0.20 or more and less than 0.50 ×: 0.50 or more

From the results of Tables 1 and 2, it is understood that the friction material of the present invention has good fade resistance while ensuring wear resistance.

According to the present invention, a friction material composed of a fiber base material, a binder, and a friction modifier, and formed by molding a friction material composition of a NAO material that does not contain a copper component, while ensuring sufficient wear resistance and fading resistance. As a friction material used for a disc brake or a drum brake, which is a braking device for an automobile, a practical effect is extremely high.

1 Disc brake pad 2 Back plate 3 Friction material 4 Brake shoe 5 Brake shoe body 6 Friction material (lining)

Claims (2)

In a friction material formed of a NAO material friction material composition comprising a fiber base material, a binder, and a friction modifier, and containing no copper component, carbon dioxide is used as a decomposition catalyst for the binder in a part of the friction modifier. A friction material comprising 0.2 to 5.0% by weight of one or more selected from potassium, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate based on the total amount of the friction material composition. The friction material according to claim 1, wherein the decomposition catalyst for the binder is potassium hydrogen carbonate.