JP2001240847A - Frictional material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frictional material without using asbestos, suppressing the use pf an inorganic fiber such as a potassium titanate fiber to a small amount for avoiding the problems of working environmental hygiene and also sufficiently improving its frictional characteristics (the efficiency at a high speed, fade, squeak and friction) and strength. SOLUTION: This frictional material consisting of a reinforcing fiber, friction- adjusting material and binder is characterized by blending a polypara- phenylenebenzobisoxazole fiber(PBO fiber) as a reinforcing fiber without containing asbestos fiber. It is preferable to blend the above PBO fiber by 1-30 wt.% of the total of the frictional material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material, and more particularly to a friction material used in industrial machines, railway vehicles, luggage vehicles, passenger cars, and the like, and more specifically, to a friction material used in the above-mentioned applications. And friction materials such as brake pads, brake linings and clutch facings.

[0002]

2. Description of the Related Art As a friction material mainly used for brake pads, etc., reinforcing fibers are used as one of the materials in order to enhance the strength, and glass fibers, steel fibers, aramid fibers, and titanium are used as substitute fibers for asbestos. Potassium acid fibers and the like are used, and since these have their respective characteristics, several types are used in combination. Among these fibers, potassium titanate fiber is a hard inorganic inorganic fiber that not only improves the overall strength and heat resistance of the friction material and improves wear resistance, but also increases the friction coefficient of the friction material due to its grindability. In particular, it is highly evaluated as being able to secure a high friction coefficient under a high load such as high-speed braking.

[0003]

However, potassium titanate fibers which have been used as substitute fibers for asbestos have a diameter of 0.2-1 μm called whisker.
It is made of a needle-like single crystal having a length of 10 to 20 μm, and it is not preferable to use it in a large amount in view of working environment hygiene. Therefore, at present, the friction material mainly uses aramid fiber as the reinforcing fiber. However, since the reinforcing fiber of the friction material is required to have both the strength against heat and stress and the flexibility related to the squealing property, the aramid fiber is used in combination with the inorganic fibers such as potassium titanate fiber and ceramic fiber. Have been.

[0004] The present invention can reduce the amount of inorganic fibers used while using flexible organic fibers as a friction material, and yet achieve the same frictional action and strength as when a large amount of the inorganic fibers are used. It is an object of the present invention to obtain a friction material which has excellent squeal characteristics.

[0005]

SUMMARY OF THE INVENTION According to the above-mentioned object, the present inventor has sought to use a small amount of inorganic fibers having high strength but low flexibility as much as possible, and yet have the same frictional effect as when using a large amount of the inorganic fibers. Various researches have been made on organic fibers for reinforcement that give friction and strength to friction materials. When polyparaphenylene benzobisoxazole fiber (hereinafter also referred to as “PBO fiber”) is used as the reinforcing fiber, attention can be paid to the fact that the same frictional action, strength and squealing characteristics as when a large amount of the inorganic fiber are used can be obtained. Thus, the present invention has been reached.

That is, the present invention has solved the above-mentioned problems by the following means. (1) A friction material comprising a reinforcing fiber, a friction modifier, and a binder, wherein a polyparaphenylene benzobisoxazole fiber is blended as a reinforcing fiber without asbestos fiber. (2) The friction material according to the above (1), wherein the polyparaphenylene benzobisoxazole fiber is blended in an amount of 1 to 30% by weight of the whole friction material.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A friction material is composed of a reinforcing fiber, a friction adjusting material, a binder and the like. In the present invention, as a matter of course, asbestos is not used as the reinforcing fiber, and the PBO fiber is used. Thus, only a small amount of inorganic fiber, for example, potassium titanate fiber which is considered to be unfavorable in working environment hygiene, can be used. The PBO fiber used in the present invention is one of polybenzazoles, which is a heterocycle-containing polymer. The polymer dope obtained by polycondensing terephthalic acid and diaminoresorcinol in a polyphosphoric acid solvent is subjected to dry-wet spinning. It is manufactured by PBO fiber is about 2 of aramid fiber.
It shows twice the strength and modulus of elasticity, and in particular, the modulus of elasticity has an extreme value as a linear polymer. Furthermore, it shows heat resistance comparable to glass fiber, reflecting the rigidity of the molecular chain. Therefore, the present invention improves the friction characteristics (high-speed efficacy, fade, squeal, abrasion) and strength by adding PBO fiber to the friction material or using it as a substitute for unfavorable hygiene fiber.

Generally, the fiber diameter of the PBO fiber is preferably around 1.5 denier as single yarn denier. The amount of the fibers used in the friction material is from 1 to 30% by weight of the whole friction material. If it is less than 1% by weight, it is difficult to disperse the fibers uniformly during mixing and stirring, and the desired effect cannot be obtained. If the amount is more than 30% by weight, the cost becomes high, and the wear characteristics at fade and high temperature deteriorate. Preferably, the content is 5 to 30% by weight.

In order to produce the friction material of the present invention, the above-mentioned raw materials are blended in a friction material comprising a reinforcing fiber, a friction modifier, a lubricant and a binder, and the blend is preformed according to a usual production method. It can be manufactured by thermoforming.

In the friction material of the present invention, as the reinforcing fibers, one or more of inorganic fibers, metal fibers and other heat-resistant organic fibers can be used in combination with the PBO fibers. Examples of the inorganic fibers include glass fibers, rock wool, ceramic fibers such as potassium titanate fibers and alumina fibers, and carbon fibers. Examples of the metal fibers include copper fibers and steel fibers.
As other heat-resistant organic fibers, aromatic polyamide fibers (aramid fibers, aramid pulp), flame-resistant acrylic fibers, and the like can be preferably used. Examples of the aramid fiber include Kevlar (trade name) manufactured by DuPont and Twaron (trade name) manufactured by Twaron Products.

Examples of the inorganic filler include metal particles such as copper, aluminum, and zinc; scaly inorganic substances such as vermiculite and mica; and barium sulfate and calcium carbonate. Examples of the binder include thermosetting resins such as phenolic resins (including various modified phenolic resins such as straight phenolic resins and rubbers), melamine resins, epoxy resins, and polyimide resins. Examples of the friction modifier include inorganic friction modifiers such as alumina and silica, magnesia, zirconia, chromium oxide, and quartz; organic friction modifiers such as synthetic rubber and cashew dust; and solid lubricants such as graphite and silica. Molybdenum disulfide and the like can be mentioned. As the composition of the friction material, various composition ratios can be adopted. That is, these may be used alone or in combination of two or more in accordance with the friction characteristics required for the product, for example, the friction coefficient, abrasion resistance, vibration characteristics, and squeal characteristics.

In the manufacturing process of the brake pad, a pressure plate, which is formed into a predetermined shape by a sheet metal press, subjected to a degreasing process and a primer process, and is coated with an adhesive, a reinforcing fiber, an inorganic / organic filler, , Blended with powder raw materials such as friction modifier and thermosetting resin binder,
A preform of a friction material formed by forming (preforming) the raw material sufficiently homogenized by stirring at room temperature at a predetermined pressure and thermoforming at a predetermined temperature and pressure in a thermoforming step. Are fixed together, after-cured, and finally subjected to a finishing treatment, but the steps up to that are the same as the conventional method.

[0013]

The present invention will be described in detail with reference to the following examples. However, the present invention is not limited to only these examples.

EXAMPLES (Materials of Friction Material Sample) The following materials were used as friction material materials when producing friction material samples, and when preparing as samples, the materials were selected from those materials and blended. Was changed. Binders ・ ・ Phenolic resin Organic friction modifier ・ ・ Cashew dust filler ・ ・ Barium sulfate (powder, average particle size 8μ)
m) Abrasive ・ ・ Zirconia (powder, average particle size 11μ)
m) Solid lubricant ・ ・ Graphite (powder, average particle size 60 μm) Reinforcement fiber ・ ・ PBO fiber (fiber diameter 1.5 denier) / copper fiber (fiber diameter 90 μm) / aramid fiber (fiber diameter 13.5 μm) / ceramics Fiber (alumina-silica fiber fiber length 700 μm, fiber diameter 2.8 μm) / potassium titanate fiber (fiber diameter 0.4 μm)

(Composition of Friction Material Sample) Examples 1 to 3 were prepared with the composition ratio of the friction material used in producing the friction material sample as shown in Table 1 below.
In addition, the thing which does not use PBO fiber (comparative example 1) was also produced for comparison. (Preparation of Brake Pad Sample) A brake pad of a friction material sample having the above composition was prepared by a conventional manufacturing method.

[0016]

[Table 1]

(Test Method) The following test was performed using a disk brake using a rotor. (1) JASO efficacy evaluation Initial speed 50 km / h, initial speed 100 km / h, deceleration α =
The friction coefficient and the JASO efficacy were evaluated under the condition of 5.88 m / s ² . (2) JASO first fade minimum μ (3) JASO wear speed 50 km / h, deceleration 2.94 m / s ² , 100
Pad wear per 1000 ° C, 200 ° C, 400 ° C, 1000 times. (4) Squeal test with actual vehicle (5) Bending strength (Test results) The test results are shown in Table 2. According to Table 2, it can be seen that the friction material of the present invention has a small amount of wear in a friction test at a high temperature, and has a large coefficient of friction at a high speed and exhibits excellent characteristics. The more the amount of the PBO fiber used, the better the characteristics.

[0018]

[Table 2]

[0019]

According to the present invention, a friction material having sufficiently improved friction characteristics (high-speed effect, fade, squeal, wear) and strength by using a PBO fiber excellent in strength, elasticity and heat resistance. Can be obtained. According to the present invention, the use amount of inorganic fibers such as potassium titanate fibers can be suppressed to a small amount without using asbestos, so that problems in working environment hygiene caused when using the fibers and the like are avoided. can do.

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Claims (2)

[Claims] 1. A friction material comprising a reinforcing fiber, a friction adjusting material and a binder, wherein a polyparaphenylene benzobisoxazole fiber is blended as a reinforcing fiber without asbestos fiber. 2. The friction material according to claim 1, wherein the polyparaphenylene benzobisoxazole fiber is blended in an amount of 1 to 30% by weight of the whole friction material.