KR100644262B1 - Non-asbestos friction materials - Google Patents

Abstract

Provided is a non-asbestos brake pad for automobiles which is free from an antimony-based compound or a sulfide compound, is excellent in braking performance and is reduced in the generation of noise. The brake pad comprises an organic fiber; a metal fiber; an inorganic fiber; a binder; 0.5-10 vol% of titanium dioxide (TiO2) as an abrasive; 0.2-10 vol% of a carbon nanofiber as a lubricant; 0.5-10 vol% of molybdenum oxide (MoO3) as a friction modifier; and a filler. Preferably the organic fiber is an aramid fiber or an acrylic fiber; the metal fiber is a steel fiber, a copper fiber or an aluminum fiber; the inorganic fiber is asbestos, sepiolite or rock wool; and the binder is a phenolic resin.

Description

Non-asbestos friction materials

Figure 1 is an electron micrograph to show the structure of the needle-like metal fibers.

Figure 2 is an electron micrograph to show the structure of the needle-like inorganic fibers.

Figure 3 is an electron micrograph to show the structure of the fibrous nano-carbon fibers.

4 is a graph showing the high speed braking characteristics (before fade) of the examples and comparative examples of the present invention.

5 is a graph showing the high speed braking characteristics (after padding) of the examples of the present invention and the comparative example.

6 is a graph showing the noise characteristics of Examples and Comparative Examples of the present invention.

The present invention relates to a non-asbestos friction material. More specifically, the present invention relates to an environmentally friendly non-asbestos friction material that does not use antimony or emulsions.

Brake pads for automobiles have the function of decelerating or stopping a driving car by converting kinetic energy into thermal energy by causing friction with a counterpart disc. More than 200 raw materials can be used for the friction material having such a function, and are manufactured using 10 to 30 kinds of raw materials.

Friction materials are largely divided into fibers, resins, and fillers, and again, fillers may be classified into inorganic fillers and organic fillers. Raw materials used in friction materials have been used regardless of whether they are environmentally friendly, but when looking at recent development trends, the use of environmentally friendly raw materials is a mainstream.

The representative environmentally friendly friction material development is the development of non-asbestos friction material using asbestos replacement fiber without using asbestos used as fiber. Friction materials using asbestos replacement fibers are called non-asbestos friction materials (NAO, Non-Asbestos Organics), and are classified into semi-metallic, low steel, and non-metal.

Asbestos replacement fibers are as follows.

-Metal fiber: Iron fiber, copper fiber, aluminum fiber

-Inorganic Fibers: Rockwool, Haepostone

Organic fiber: aramid fiber, acrylic fiber, cellulose fiber, carbon fiber, etc.

Carbon fiber is a kind of organic fiber and is widely used for aircraft brake pads or disc rotors due to its high temperature stability, and is widely used as disc rotors or pads of racing cars with high braking speed at high speed. Carbon fiber has a needle-like short fiber form and is used as a carbon fiber reinforced carbon composite material (C / C) using a thermosetting resin as a matrix. However, the nano carbon fiber has the advantage of improving the braking performance because the component can act as a lubricant with the same component as the conventional carbon-based lubricant, and the needle-like fiber has a fibrous structure.

Development of environmentally friendly friction materials focuses on developing eco-friendly raw materials for raw materials used in friction materials as well as non-asbestos friction materials using asbestos replacement fibers. Representative raw materials are antimony compounds of Sb ₂ O ₃ or Sb ₂ O ₃ which are widely used as lubricants and abrasives, and the other is emulsions.

Jans et al. Reported that MoS ₂ reacts with oxygen and water in the air to form sulfuric acid (H ₂ SO ₄ ), which leads to acid corrosion, increasing disk wear (SAE Paper 982235).

Representative methods for eco-friendly friction material development technology are as follows.

First, as disclosed in Akebono Patent Publication No. 2003-322183, it does not contain Cu-based metals or heavy metals, and develops a friction material having excellent braking performance and mechanical strength at high temperatures. The ratio of MgO / graphite was adjusted and carbon fiber and alumina-silica ceramic fiber were used.

Second, as in Nisshinbo Publication No. 2003-313312, it is a friction material development that does not contain antimony (Sb) and lead (Pb) compounds. Some sulfur compounds such as zinc emulsified copper, copper emulsified stone, manganese sulphur, and iron emulsified oil are used.

And the technique using nano carbon fiber is disclosed by Unexamined-Japanese-Patent No. 2004-308776. In case of using carbon fiber as reinforcing material, nano carbon fiber or fullerene was used in addition to the carbon fiber, and in case of using carbon material as reinforcing material (C / C), Fullan was used.

Accordingly, an object of the present invention is to provide a low noise automobile friction material which is excellent in braking performance and does not generate noise without using an antimony compound or an emulsion.

The present invention is a friction material consisting of organic fibers, metal fibers, inorganic fibers, binders, abrasives, lubricants, friction modifiers, fillers, 0.2 to 10% by volume of nano carbon fibers as a lubricant, molybdenum oxide as a friction modifier ( MoO ₃ ) 0.5 to 10% by volume, it is characterized in that the non-asbestos friction material prepared by replacing 0.5 to 10% by volume of titanium oxide (TiO ₂ ) as an abrasive.

Antimony compounds (Sb ₂ O ₃ , Sb ₂ S ₃ ) and emulsions (Sb ₂ S ₃ , MoS ₂ , FeS) are mainly used as a lubricant, noise is likely to occur if they are not used as a raw material of the friction material.

Nano carbon fiber to be used in the present invention is made of carbon, which is the same component as graphite used as a conventional lubricant has a lubricating effect, it can replace the lubricant of the harmful emulsion. In addition, the carbon nanofibers have a fibrous structure and have an effect of improving wear resistance as well as excellent lubrication properties.

Comparing the structure of the nano carbon fiber structure and the conventional fibers used are as shown in Figs. 1 is a needle-shaped metal fiber, FIG. 2 is a needle-shaped inorganic fiber, and FIG. 3 is a fibrous nano carbon fiber.

Titanium oxide (TiO ₂ ) used in the present invention is a chemically and physically very stable material, has excellent corrosion resistance and is widely used as a white pigment, and there are two kinds of rutile (Rutile) and anatase (Anmatase). It is a raw material which also has a function of an abrasive with hardness of 5.5-7.0.

In the present invention, aramid fiber, acrylic fiber, carbon fiber as an organic fiber as a general friction material component, iron fiber (Steel Fiber), copper fiber, aluminum fiber as a metal fiber, asbestos, haemulseok, rock wool as an inorganic fiber (Rock) Wool) etc. are used.

In addition, a phenol resin is used as a binder, and unmodified resin or modified resin may be used, but a modified resin is more preferable. As the friction modifier, rubber powder, Cashwew Dust, and Cokes are used, and as the filler, barium sulfate (BaSO ₄ ) and calcium hydroxide [Ca (OH ₂ )] are preferably used.

The method of manufacturing the friction material will vary depending on the raw materials. In the case of using a liquid raw material, a cold molding method may be used, and in the case of using a solid raw material, a dry molding method may be applied. In the present invention, a friction material is manufactured by applying a dry molding method, and the raw materials are first mixed, preformed, and then thermoformed, heat-treated, polished and inspected, and then packaged.

In the above process, the friction material is mainly used by the Eirich Mixer, the Rodige Mixer, and the Henschel Mixer, and it is preferable to divide the mixture by using the Henschel mixer. In order to disperse the nano carbon fiber, the organic material is mixed with the organic fiber in the first mixing, and the remaining raw materials are mixed in the second. In this case, the nano carbon fibers are uniformly dispersed.

Hereinafter, it will be described in more detail based on the embodiment of the present invention.

Example

The friction material was prepared by mixing according to the ingredient list of the following Table 1. In the first mixing, the nano-carbon fibers were added together with the organic fibers, and the mixture was mixed using a Henschel mixer, and the remaining raw materials were put in the second mixture.

Friction coefficient and noise evaluation of the friction material produced in this example was evaluated using a scale tester (Scale Tester). The scale tester has FFT (Fast Fourier Transform) as well as coefficient of friction during braking, so it can evaluate noise every braking. The evaluation mode was evaluated based on JASO C406 Mode.

Comparative example

The friction material was prepared by mixing according to the ingredient list of the following Table 1. In the first mixing, the nano-carbon fibers were added together with the organic fibers, and the mixture was mixed using a Henschel mixer, and the remaining raw materials were put in the second mixture.

Friction coefficient and noise evaluation of the friction material produced in this comparative example were evaluated using a scale tester. The scale tester has FFT (Fast Fourier Transform) as well as coefficient of friction during braking, so it can evaluate noise every braking. The evaluation mode was evaluated based on JASO C406 Mode.

Table 1

ingredient Example Comparative example Organic Fiber (Kevlar, Acryl Fiber) 8 8 Steel Fiber (Al Fiber) 5 5 Inorganic Fiber (Rock Wool) 20 20 Nano carbon fiber 2 0 Binder (rubber modified resin) 15 15 Sb ₂ O ₃ 0 2 TiO ₂ 2 0 MoO ₃ 2 0 Sb ₂ S ₃ 0 2 MoS ₂ 0 2 Friction modifiers (polishing agents, lubricants, etc.) 31 31 BaSO ₄ 15 15 Sum 100 100

(Unit: Volume%)

Friction coefficient and noise evaluation results by the scale tester for the friction material produced in the above Examples and Comparative Examples are as follows.

Table 2

division Example Comparative example Coefficient of friction (average) 0.414 0.416 Friction Coefficient (100 kph, 0.3g) 0.424 0.447 Fade * minimum coefficient of friction 0.325 0.347 Frequency of noise (more than 50 dB) 0 times 7th

* Fade phenomenon: the friction coefficient decreases rapidly during friction

According to the embodiment of the present invention, the average friction coefficient of the environmentally friendly friction material using nano carbon carbon and titanium oxide (TiO ₂ ) as the non-asbestos friction material showed the same level as the friction material containing harmful substances such as Sb ₂ S. In addition, the high speed (100 km / h) braking performance is less stable friction coefficient according to the deceleration showed a more stable characteristics than the friction material containing harmful substances (see Figs. 4, 5), the noise generated during braking of the comparative example It showed a reduced appearance compared to the product (see FIG. 6). 4 is a graph showing a comparison of the high speed braking characteristics (before the fade) of the embodiment of the present invention and the comparative example, Figure 5 is a comparison of the high speed braking characteristics (after the fade) of the embodiment of the present invention and the comparative example 6 is a graph showing the comparison of the noise characteristics of the Examples and Comparative Examples of the present invention.

Therefore, the non-asbestos friction material of the present invention has an effect of excellent braking performance and less noise by using nano carbon fibers and titanium oxide without using antimony compounds or emulsions.

Claims (1)

In a friction material composed of organic fibers, metal fibers, inorganic fibers, binders, abrasives, lubricants, friction modifiers and fillers, 0.2 to 10% by volume of nano carbon fibers as a lubricant, and molybdenum oxide (MoO ₃ ) as a friction modifier. A non-asbestos friction material having excellent braking performance and low noise, which is manufactured by replacing 0.5 to 10% by volume and 0.5 to 10% by volume of titanium oxide (TiO ₂ ) as an abrasive.

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