JP4011018B2 - Friction material - Google Patents

Description

  The present invention relates to a friction material using a combination of calcined bone powder and calcium carbonate powder, particularly a friction material that suppresses the attack of a counterpart material used in industrial machines, railway vehicles, luggage vehicles, passenger cars, etc., and has improved fade characteristics. More specifically, the present invention relates to brake pads, brake linings, clutch facings, and the like used in the above-mentioned applications.

  Friction materials used in brakes such as disc brakes and drum brakes, or clutches, etc., provide a frictional effect and adjust the friction performance, a fiber base material that reinforces, and these components are integrated. It is made of materials such as binding material. Among them, there are various types of fiber base materials such as metal fibers, inorganic fibers, and organic fibers, each having its own characteristics, and usually two or more types are used in combination.

  On the other hand, there are friction modifiers and solid lubricants as materials that adjust the friction characteristics of the friction material, but these also have inorganic and organic types, each with their own characteristics, usually a combination of two or more types. Have been used. Examples of the friction modifier include inorganic friction modifiers such as alumina, silica, magnesia, zirconia, chromium oxide, and quartz; organic friction modifiers such as synthetic rubber and cashew resin; and solid lubricants such as graphite and And molybdenum disulfide.

As the filler, barium sulfate, calcium carbonate, metal powder, vermiculite, mica, and the like are used.
In addition, various non-asbestos-based friction materials have been proposed as non-asbestos-based friction materials that suppress the aggressiveness of the friction material formed by blending these components against the counterpart material and have improved fade resistance and wear resistance.

Patent Document 1 is a reinforcement other than asbestos for the purpose of providing a non-asbestos-based friction material that is less attacking by the counterpart material, excellent in fading resistance and friction coefficient, and hardly generates noise and low-frequency noise. A non-asbestos-based friction material formed by bonding fibers, organic fillers, inorganic fillers, metal powders, and friction modifiers with a thermosetting resin, is formed by collecting a large number of primary particles as at least part of the filler. Disclosed is a friction material containing secondary particles of magnesia.
For the purpose of providing a fiber-reinforced friction material with improved wear resistance, Patent Document 2 discloses 20 volumes of the total amount of metal powder of a friction material including reinforcing fibers, a filler containing metal powder, and a binder resin. % To 70% by volume is composed of metal powder having a particle diameter exceeding 200 μm, so that metal powder having a small particle diameter is filled between metal powders having a large particle diameter, and the filling efficiency inside the friction material is increased. Although the technique which can reduce the amount of wear of this is disclosed, the compounding example using barium sulfate as an inorganic filler is shown.

Patent document 3 does not contain asbestos as a fiber component, and for the purpose of providing a non-asbestos-based friction material excellent in stability of stability, wear resistance, and face-to-face attack, a fiber component other than asbestos and a phenol resin In a friction material containing a binder component made of a thermosetting resin such as graphite and a filler component such as graphite or barium sulfate, a metal carbonate, hydroxide or the like whose Mohs hardness of the oxide is 4 to 7 A part or all of the inorganic filler composed of powder or fiber of the above is granulated or pelletized with a thermosetting resin as a binder, alone or together with a part of other filler components, and contained as a part of the filler. A friction material is disclosed.
Patent Document 4 shows excellent wear resistance and stable friction performance even when a high load is applied as well as a low load, as well as when used in a medium-sized or large-sized vehicle, and the face-to-face damage is low. For the purpose of providing a non-asbestos-based friction material capable of obtaining a small number of brake pads for disc brakes, filling with a reinforcing fiber other than asbestos and a thermosetting resin such as phenol resin and filling with barium sulfate, etc. In a non-asbestos-based friction material made of a material, a non-asbestos-based friction material containing electrofused magnesia is disclosed as at least a part of the filler.

Each of these friction materials obtained moderately improved performance, but was not fully satisfactory.
By the way, since the fade characteristic of the friction material is greatly influenced by the porosity of the friction material, a material capable of increasing the porosity is required for the filler.
That is, when the porosity of the friction material is increased, the gas pressure generated when the brake is applied can be lowered, so that the fade characteristics can be improved. For this reason, a material capable of increasing the porosity of the friction material is demanded. In the patent document 5, the present inventors have proposed a friction material having improved fade characteristics using 5 to 65% by weight of calcined bone powder as a friction material raw material. Further, Patent Document 6 proposes a friction material that uses 5 to 65% by weight of coral calcium to improve fade characteristics.

JP-A-8-73616 JP-A-9-221658 Japanese Patent Laid-Open No. 5-1278 Japanese Patent No. 2967217 JP 2003-160780 A JP 2003-161339 A

  However, the calcined bone meal disclosed in Japanese Patent Application Laid-Open No. 2003-160780 of Patent Document 5 is a material obtained by calcining animal bones such as cattle, birds and sheep at 600 ° C. to 1100 ° C., and has a porosity of 20 to 60%. This can increase the porosity of the friction material. Further, it is thermally stable up to 1250 ° C., and has a Mohs hardness of 5 and harder than the rotor material (4 to 4.5). For this reason, when the compounding quantity of the calcination bone powder exceeds 25 volume%, there existed a problem that partner material attack property will become large.

  Coral calcium disclosed in Japanese Patent Application Laid-Open No. 2003-161339 of Patent Document 6 is a porous material produced by pulverizing uplifted weathered reef coral (porosity of about 12%). The main component of coral calcium is calcium carbonate, which does not have sufficient heat resistance, so that the friction material for the disc brake, which tends to have a high temperature, has a disadvantage that it is preferably up to 20% by volume.

  The main characteristics originally required for a friction material for braking are stable friction characteristics, heat resistance, wear resistance, and the like. Among these required characteristics, the friction characteristics are improved to a level that can be almost satisfied by the prior art, and particularly, the friction material based on the fiber exhibits good performance. However, recently, it has been strongly desired to supply a low-cost friction material with good fading characteristics, low attacking property of the counterpart material, improved noise characteristics. In addition, there is a strong demand for maintaining friction performance and improving wear resistance at high temperatures, which are particularly stable up to a higher temperature range. In addition, there is a strong demand for a friction material that has good fading characteristics, low attack on the counterpart material, and low environmental impact.

  In order to provide a friction material having the above-mentioned characteristics, the present invention has conventionally been applied to particles having irregular irregularities as an inorganic filler, large porosity, and easily generating inter-particle voids, and part of the inorganic filler. By using a material that is not used and excellent in properties, the high porosity makes it possible to obtain good fade characteristics, as well as reliable friction performance and wear resistance up to high temperatures. It is intended to obtain a friction material that is secured and also capable of reducing the environmental load. That is, the present invention provides a friction material that has a low attack on the counterpart material, good fade characteristics, noise and low cost, friction characteristics at high temperatures, heat resistance, and wear resistance, and also has a low environmental impact. The task is to do.

The inventors of the present invention are a calcium compound and a porous material having a higher porosity than conventional calcium carbonate derived from limestone due to the above problems, and exhibiting good fade characteristics, and improve the fade characteristics At the same time, we researched various materials to reduce environmental impact. And calcium carbonate produced by pulverizing uplifted weathered reef-building coral has a higher porosity and easily forming voids between particles than calcium carbonate produced by pulverizing limestone, and cows, horses The calcined bone meal obtained by calcining bones of livestock such as pigs and birds and fish and fish is a porous material mainly composed of Ca ²⁺ deficient type hydroxyapatite and having a porosity of 20 to 60%. The present invention has been achieved by paying attention to the fact that it has selectivity for ions and the like and high ion exchange capacity, and can improve the fade characteristics of the friction material and reduce the load on the global environment.

That is, the present invention has solved the above problems by the following means.
(1) In a friction material composed of a fiber base material, a friction modifier, a binder, and an inorganic filler, at least one kind of calcined bone meal of livestock and fish as a component of the inorganic filler is 15 to 25 volumes of the entire friction material. %, And calcium carbonate powder obtained by pulverizing uplifted weathered reef-building coral is used in combination with 5-20% by volume of the entire friction material.

  According to the present invention, the obtained friction material is a combination of calcium carbonate (coral calcium) produced from uplifted weathered reef coral as part of the inorganic filler component and at least one calcined bone meal of livestock and fish. The friction material obtained therefrom has a high porosity, so that the fading characteristics are improved, the wear resistance is large, and the aggressiveness of the counterpart material is suppressed.

Embodiments of the present invention will be described below. What is necessary is just to use what was described in Unexamined-Japanese-Patent No. 2003-161339 previously shown as patent document 6 as the uplift weathering reef-building coral used in this invention.
The reason why the preferable proportion of the coral calcium used in the friction material is 5 to 25% by volume is that if it is less than 5% by volume, it is difficult to satisfy the criterion for determining whether or not the fade rate is 85% or more, which is a criterion for determining whether or not the fade is acceptable. It is. On the other hand, even if the proportion of coral calcium exceeds 25% by volume, the target value of the fade rate was not satisfied. Uplifted weathered reef coral is pulverized and blended as powdered coral calcium. The average particle size of the powder varies depending on the purpose, but for example, an average particle size of 3 μm is used.

  As the calcined bone powder used in the present invention, two types are mainly known, which are calcined beef bone and bone ash. As these, those described in Japanese Patent Application Laid-Open No. 2003-160780 previously shown as Patent Document 5 can be used.

  The reason why the preferable blending ratio of the above-mentioned calcined bone powder is set to 15 to 25% by volume is that if it is less than 5% by volume, it is difficult to satisfy the criterion for determining whether or not the fade rate is 85% or more, which is a criterion for determining whether or not to fade. On the other hand, if the blending of the calcined bone powder exceeds 25% by volume, the amount of wear of the rotor increases and the target value is not satisfied. As the calcined bone powder, those having an average particle diameter of 1 to 200 μm are preferably used.

In order to produce the friction material of the present invention, various materials for friction material consisting of a fiber base material, a friction modifier, a lubricant, a filler, and a binder are blended, and the blend is preformed according to a normal manufacturing method, It can be manufactured by thermoforming. In the above, examples of the fiber base material include organic fibers such as aromatic polyamide fiber and flame-resistant acrylic fiber, copper fibers, metal fibers such as steel fibers, potassium titanate fibers, Al ₂ O ₃ —SiO ₂ ceramic fibers, and the like. Inorganic fiber. Examples of the inorganic filler include metal particles such as copper, aluminum and zinc, scaly inorganic materials such as vermiculite and mica, barium sulfate and calcium carbonate.

  Examples of the binder include thermosetting resins such as phenol resins (including various modified phenol resins such as straight phenol resins and rubbers), melamine resins, epoxy resins, and polyimide resins. Examples of the friction modifier include inorganic friction modifiers such as alumina, silica, magnesia, zirconia, and chromium oxide; organic friction modifiers such as synthetic rubber and cashew resin; and solid lubricants such as graphite and molybdenum dioxide. Etc. As the composition of the friction material, various composition ratios can be adopted. That is, these may be blended singly or in combination of two or more according to the friction characteristics required for the product, for example, friction coefficient, wear resistance, vibration characteristics, squeal characteristics, and the like.

  The manufacturing process of a brake pad for a disc brake is formed into a predetermined shape by a sheet metal press, subjected to a degreasing process and a primer process, and a pressure plate coated with an adhesive, heat resistant organic fibers, metal fibers, etc. Created by blending reinforcing fibers and raw materials for friction materials such as inorganic and organic fillers, friction modifiers, and binders, and then molding (pre-molding) raw materials that are sufficiently homogenized by stirring at room temperature. The preformed body is thermoformed at a predetermined temperature and pressure in a thermoforming process, and both members are fixed together, aftercured, and finally subjected to a finishing treatment. It is the same as the conventional method.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to only these examples.

Examples 1-4 and Comparative Examples 1-4
1) Formulation of friction material Based on the base material that was used with the blending ratio of the inorganic filler of the friction material unified to 40% by volume, a friction material was used in combination with calcined bone meal and coral calcium. Further, barium sulfate was used in order to evaluate the blending amount of the inorganic filler at a constant level. Since barium sulfate is not a porous material, there is no effect of improving the porosity. The blending contents are shown in Table 1.

2) Manufacturing method The above-mentioned blended material was subjected to normal steps such as stirring, preforming, thermoforming, heating (aftercuring), polishing, and the like to obtain a finished friction material.
3) Measurement of porosity The porosity (oil impregnation method, JIS D4418) was measured with respect to the friction material obtained by the Example and the comparative example. The measurement results are shown in Table 2.

4) Fade characteristics A performance test (according to JASO C406) was performed using a test piece inertia type scale tester, and the fade rate during the first fade test was measured. Here, the fade rate was defined as follows.
Fade rate (%) = [minimum μ in the fade test / μ (60 ° C.) at the first braking in the fade test] × 100
The test results are shown in Table 2.

5) Measurement of rotor wear amount After the performance test was completed, the wear amount of the rotor was measured to evaluate the rotor aggression (partner material aggression). The results are shown in Table 2. The target values of the friction material this time are a fade rate of 85% or more and a rotor wear amount of 7 μm or less.

  Comparative Example 1 in which the calcined bone powder was used in an amount of 25% by volume or more showed good fade characteristics, but the amount of rotor wear was large and the target value was not satisfied. Further, Comparative Example 2 in which only 25% by volume of the calcined bone meal was used without using coral calcium showed good rotor attack, but the fade rate did not reach the target value. On the other hand, Examples 1 to 3 in which the calcined bone powder and 5% by volume or more coral calcium were used in combination suppressed rotor attack and exhibited good fade characteristics.

However, Comparative Example 3 containing 25% by volume of coral calcium did not satisfy the target value of the fade rate. This is because coral calcium is decomposed and carbon dioxide gas is generated. From this, it is understood that 5 to 20% by volume of coral calcium is good.
Further, Comparative Example 4 in which 20% by volume (maximum) of coral calcium and 10% by volume of calcined bone powder did not satisfy the target value of the fade rate, whereas Example 4 in which 15% by volume of calcined bone powder was blended. Had good fade characteristics and rotor attack. From this, it can be seen that 15 to 25% by volume of the calcined bone meal is good.

  According to the present invention, the obtained friction material is a combination of coral calcium and calcined bone powder, and has a high porosity, so that the fade characteristics are improved and the noise generation is excellent. Therefore, it is particularly useful for brake pads, brake linings, clutch facings and the like used for industrial machines, railway vehicles, luggage vehicles, passenger cars and the like.

Claims (1)

In the friction material composed of the fiber base material, the friction modifier, the binder, and the inorganic filler, at least one kind of calcined bone meal of livestock and fish as one component of the inorganic filler is 15 to 25% by volume of the entire friction material , A friction material , characterized in that calcium carbonate powder obtained by crushing uplifted weathered reef coral is combined with 5 to 20% by volume of the entire friction material.