JPH10130628A - Production of facing friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a facing friction material which is excellent in abrasion resistance and frictional characteristics, esp. in μ-V characteristics and durability, and does not need the oil groove machining of a core plate since it is excellent in oil mobility by impregnating a sheet contg. carbon fibers, aramid fibers, a friction modifier, and a filler with a polyamideimide resin liq. and subjecting the sheet to thermal pressing under a high pressure and then to thermal curing. SOLUTION: The sheet is produced by mixing a mixture comprising 25-70wt.% carbon fibers and 75-30wt.% aramid fibers with a friction modifier (e.g. a polytetrafluoroethylene powder, an Mo2 S powder, a carbon powder, or an alumina powder) and a filler (e.g. CaCO3 , SiO2 , or diatomaceous earth) and forming the resultant mixture into a sheet. The sheet is dried, impregnated with a polyamideimide resin liq. (in an amt. of 10-50wt.% of the total sheet wt.), thermally pressed at 130-250 deg.C under a pressure of 51-200kgf/cm<2> , and thermally cured at 200-350 deg.C for 30min to 10hr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a facing friction material, and more particularly, it is useful as a friction member for a device having a friction mechanism, such as a wear-resistant material for machines and home electric appliances, a friction facing material for automobiles and the like. The present invention relates to a method of manufacturing a facing friction material.

[0002]

2. Description of the Related Art This kind of friction material is manufactured by papermaking a composition containing a pulp material and a filler or fiber having frictional performance, or as a paper material formed into a sheet by roll molding or press molding. Have been. This paper material is used as a friction material by being cut and then adhered to a metal plate serving as a core plate.

[0003]

The friction material using the conventional paper-based facing friction material has the following disadvantages.

[0004] It is inferior in wear resistance and heat resistance, and does not show characteristics suitable for recent high-performance specifications. Although fillers are added and mixed in the gaps between the sheets of pulp, the state is uneven and it is difficult to obtain stable friction characteristics.

In order to ensure rapid movement of oil (lubricating oil), it is necessary to use a core plate having a large number of oil grooves formed on a friction surface, but this processing is not easy and the processing cost is low. There is a problem of being expensive. In addition, the pressure on the friction surface increases as the performance of automobiles increases in recent years, and if this oil groove is reduced, sufficient friction characteristics cannot be exhibited. In the case of the facing friction material, the friction coefficient increases as the sliding speed increases, based on the relationship between the sliding speed (V) and the friction coefficient (μ) (hereinafter, this characteristic is referred to as “μ-V characteristic”).
Called. ) Is a necessary condition. Conventional paper-based facing friction materials have a proportional relationship in the relationship between the sliding speed and the friction coefficient, but have poor abrasion resistance and cannot be used under conditions of high surface pressure over a long period of time. As described above, the conventional paper-based facing friction material cannot satisfy the μ-V characteristics, wear resistance, and the like corresponding to the friction mechanism of a recently improved automobile or the like.

The present invention solves the above-mentioned conventional problems, and is excellent in abrasion resistance and friction characteristics, particularly excellent in μ-V characteristics and durability, and also excellent in oil mobility.
It is an object of the present invention to provide a method for manufacturing a facing friction material which can eliminate the need for oil groove machining of a core plate.

[0007]

According to the present invention, there is provided a method for producing a facing friction material, comprising adding a friction modifier and a filler to a mixture of carbon fiber and aramid fiber, mixing the mixture, and forming a sheet. After drying, the sheet is impregnated with a polyamideimide resin liquid, and then 50 kg
After hot pressing at a pressure higher than f / cm ² , a thermosetting treatment is performed.

In the present invention, the friction modifier is at least one member selected from the group consisting of polytetrafluoroethylene powder, MoS ₂ powder, carbon powder and alumina powder, and the filler is CaCO ₃ , SiO ₂ and It is preferable that one or more kinds selected from the group consisting of diatomaceous earth are used.

The mixing ratio of carbon fiber and aramid fiber is 25 to 70% by weight of carbon fiber.
Aramid fiber: 75 to 30% by weight; the mixing ratio of each powder of the friction modifier is 1 to 10% by weight based on the mixture of carbon fiber and aramid fiber; the mixing ratio of the filler is carbon fiber and 5 to 300% by weight based on the mixture with the aramid fiber; the impregnation amount of the polyamide imide resin is 10 to 50% by weight based on the total amount of the carbon fiber, the aramid fiber, the friction modifier, the filler and the polyamide imide resin. Is preferred.

The inventor of the present invention has conducted various studies on additives and manufacturing methods in order to make the paper-based facing friction material exhibit μ-V characteristics, that is, characteristics in which the friction coefficient maintains a tendency to increase as the sliding speed increases. As a result of the superposition, the surface condition of the friction material layer of the facing friction material greatly affects the μ-V characteristics; the surface of the friction material layer has moderate irregularities; and the friction material layer is porous. Μ-
It has been found that this is an important requirement for improving V characteristics.

That is, in order to obtain the friction characteristics desired as a facing friction material, the lubricating oil can be quickly removed from the surface of the friction material layer, the friction material layer itself has some elastic deformation, and the surface has abrasion resistance. It is an essential condition that the tensile strength is large.

In the facing friction material manufactured by the method of the present invention, the friction material layer is porous, and the lubricating oil on the friction surface rapidly moves into the friction material layer at a high sliding speed. As a result, the friction coefficient of the friction surface increases at a high sliding speed, and good μ-V characteristics can be obtained.

In the present invention, carbon fibers and aramid fibers are used in combination in order to improve the performance such as μ-V characteristics. The combined use of carbon fiber and aramid fiber in this way makes it possible to mix large amounts of long fibers, which was impossible in the past, and at the same time the mixing ratio of carbon fiber and aramid fiber and the thickness of the friction material layer Can also be arbitrarily controlled.

The effects of the combined use of carbon fibers and aramid fibers in the present invention are as follows.

Carbon fiber is a short fiber and has high rigidity, and it is impossible to mix a large amount of carbon fiber alone. However, by using aramid fiber in combination, the degree of freedom of mixing is increased, and it is possible to mix a large amount of carbon fiber. Become.

When the carbon fiber and the aramid fiber are formed, the carbon fiber and the aramid fiber are mixed with each other.
Entanglement in a dimension. Then, it is firmly fixed by a polyamide-imide resin as a binder to form a high-strength friction material layer. A fine gap is formed in the friction material layer by the three-dimensional entanglement, so that the oil can move. Further, when the friction adjusting material and the filler enter the gap, the strength of the friction material is improved and the friction characteristics are improved.

The polyamideimide resin firmly and three-dimensionally fixes the fibrous material, the friction modifier and the filler, and effectively acts to increase the strength and maintain the voids. Since the polyamideimide resin is excellent in heat resistance and wear resistance, it is advantageous for improving the characteristics of the facing friction material.

In the present invention, since the polyamide imide resin liquid is impregnated, the impregnation amount can be freely adjusted, and different facing friction materials can be manufactured according to the purpose.

When a friction material is produced by impregnating a polyamideimide resin liquid into a sheet made of a carbon fiber, an aramid fiber, a friction modifier and a filler, a layered material exceeding the amount required for the transfer of lubricating oil is used. May be formed, the strength of the friction material may be reduced, and the durability may be impaired.

Therefore, according to the present invention, coarse gaps are reduced by performing hot-pressing before the sheet impregnated with the polyamide-imide resin liquid is subjected to the thermosetting treatment, thereby increasing the durability of the obtained friction material.

[0021]

Embodiments of the present invention will be described below in detail.

In the present invention, first, carbon fibers and aramid fibers are uniformly mixed. In mixing this fiber material, when the proportion of carbon fiber is large, the wear characteristics of the facing friction material obtained are improved, and when the amount of aramid fiber is large, the entanglement strength of the fiber increases and the friction material strength tends to increase. Therefore, in the present invention, the mixing ratio of these fiber materials is 25 to 70% by weight of carbon fibers, 75 to 30% by weight of aramid fibers, particularly 40 to 60% by weight of carbon fibers, and 60 to 40% by weight of aramid fibers. % By weight.

The fiber diameter of the carbon fiber used is preferably 10 to 20 μm, the fiber length is preferably 0.5 to 3 mm, and the fiber diameter of the aramid fiber is 5 to 100 μm.
m, the fiber length is preferably several mm to 30 mm.

Polytetrafluoroethylene (PTFE) powder, MoS ₂ (molybdenum disulfide powder), carbon powder, and alumina (Al ₂ O ₃ ) powder are used in combination as friction modifiers to be added to and mixed with these mixed fiber materials. Is preferred, but is not necessarily limited to the case of using four types in combination,
Even if one kind is added alone, any two of the four kinds are added.
Types or three types may be added. When four types of friction modifiers are used in combination, the amount of each additive is preferably 1 to 10% by weight, and more preferably 5 to 10% by weight, based on the total of carbon fibers and aramid fibers. In addition,
As for the alumina powder, it is particularly preferable to set it to 1 to 3% by weight. If the ratio of the friction modifier is less than the above range, the compounding effect cannot be sufficiently obtained, and if it exceeds the above range, problems such as difficulty in uniform dispersion and mixing are caused.

The particle size of each powder of the friction modifier is 3-5.
It is preferably 0 μm.

As the filler, one or more selected from the group consisting of CaCO ₃ (calcium carbonate), SiO ₂ (silica) and diatomaceous earth can be used. Is preferably 5 to 300% by weight, particularly 100 to 300% by weight, based on the total of If the proportion of the filler is less than 5% by weight, the compounding effect cannot be sufficiently obtained, and if it exceeds 300% by weight, problems such as difficulty in uniform dispersion and mixing occur.

In the present invention, the polyamide imide resin used as the binder is carbon fiber,
10 to 50% by weight, especially 20 to 5% by weight based on the total amount of aramid fiber, friction modifier, filler and polyamideimide resin
It is preferably 0% by weight. When the proportion of the polyamide-imide resin is less than 10% by weight, a sufficient fixing strength by the binder resin cannot be obtained, and when it exceeds 50% by weight, the resin content is too large, the frictional characteristics are reduced, and the lubricating oil is effectively eliminated. Porosity cannot be formed.

In the present invention, in order to disperse the carbon fibers uniformly in the aramid fibers and to sufficiently uniformly mix the friction modifier and the filler in the mixed fiber material, a papermaking method is employed. The obtained sheet is impregnated with a polyamideimide resin liquid.

That is, first, an appropriate amount of carbon fiber and aramid fiber is wet-stirred and mixed, and these fibers are
Disperse sufficiently and uniformly. Usually, water is used as the wet mixed solvent, and the amount of water used is preferably water: fiber material = 50 to 150: 1, particularly preferably about 100: 1 by weight ratio.

If the amount of the fiber material is less than this, there is no effect on the papermaking, but it takes a lot of time to process a large amount of water, which is not preferable. On the other hand, if the proportion of the fiber material is significantly higher than this ratio, it is inconvenient because it is not sufficiently crushed and mixed in water.

Thereafter, a friction modifier and a filler are added and mixed into the fibrous material-dispersed water, followed by stirring and mixing. In addition,
In this mixing, a thickener such as a sulfuric acid band is added as necessary to stabilize each material and secure the viscosity required for papermaking.

The obtained papermaking raw material is formed into a papermaking sheet by a conventional method, and this papermaking sheet is dried.

Next, the sheet after the drying is immersed in a solution in which a polyamideimide resin is dissolved in an appropriate solvent, for example, to impregnate the sheet with the polyamideimide resin solution.
In this impregnation, the amount of polyamideimide resin impregnation can be freely adjusted by adjusting the concentration of polyamideimide resin in the polyamideimide resin liquid, and the sheet is impregnated with polyamideimide resin very uniformly. be able to.

After the impregnation treatment, the sheet is weighed at 50 kgf / cm
^The hot press is performed at a pressure higher than ² , using a uniaxial press at a temperature of 130 to 250 ° C and a pressure of 5 ° C.
It is preferable that the pressure be about 1 to 200 kgf / cm ² . If the pressure is lower than this, there are many gaps in the friction material, the strength is reduced, and the durability is reduced. On the other hand, if the pressure is higher than this, it is impossible to form a porous material effective for removing the lubricating oil.

After the hot pressing, the polyamide-imide resin is completely cured, and the fiber material and various powders are fixed, preferably at a temperature of 200 to 350 ° C. for 30 minutes to 1 hour.
The thermosetting treatment is carried out for about 0 hours.

In the present invention, in particular, the amount of the polyamide-imide resin impregnated and the amount of the filler added are relatively large, and the sheet is hot-pressed before thermosetting to prevent layered gaps. A friction material excellent in durability can be obtained. In other words, the filler fills the layered gap, exhibits a reinforcing effect, and creates fine pores. As the amount of the filler is relatively increased, the amount of the polyamide-imide resin impregnated is increased in order to increase the bonding force. Further, by performing the hot-pressing in such a manner, coarse gaps are reduced, and the strength of the friction material is improved.

In the present invention, a sheet having a thickness of 0.3 to 4 mm is obtained by the above method, dried, impregnated with a polyamideimide resin solution, and subjected to a hot-press and a thermosetting treatment to obtain a sheet having a thickness of 100 mm. It is preferable to use a thermosetting sheet having a thickness of 1000 μm.

The thermosetting sheet thus obtained is
It can be used as a facing material by adhering it to an appropriate core plate. In this case, since the thermosetting sheet has excellent lubricating oil exclusion characteristics, it is not necessary to form a groove in the core plate. Of course, if necessary, the core plate may be used after being subjected to groove processing.

In the present invention, the metal material constituting the core plate is not particularly limited, and the present invention can be applied to any metal material core plate. Iron alloys or lightweight aluminum alloys.

[0040]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 to 6 Carbon fiber (average fiber diameter: 13 μm, average fiber length: 1 mm) and aramid fiber (average fiber diameter: 10 μm, average fiber length: 15 mm) were blended in the proportions shown in Table 1 and mixed in water. And mixed uniformly by forced stirring. In this stirring and mixing, water was used in an amount of 10 liters per 100 g of fibers in total, and stirring was performed for 60 minutes. Next, for a total of 100 g of fibers, PT
FE powder (average particle size 10 μm), MoS ₂ (average particle size 1
0 μm), carbon powder (average particle size: 40 μm), alumina powder (average particle size: 5 μm), and diatomaceous earth (average particle size: 10 μm) as a filler were added and mixed at the ratios shown in Table 1, and further stirred and mixed for 10 minutes. . At this time, a small amount of a sulfuric acid band was added while observing the state of mixing to increase the viscosity.

The mixed solution was dehydrated by a paper machine to obtain a sheet having a thickness of about 1 mm. The sheet was dried, impregnated with a polyamideimide resin solution in which a polyamideimide resin was dissolved in an N-methylpyrrolidone solvent at a concentration shown in Table 1, and then impregnated so as to have an impregnation amount shown in Table 1.
After hot pressing at 50 ° C. and a pressure of 100 kgf / cm ² , a thermosetting treatment was carried out at 300 ° C. for 1 hour.

The obtained sheet (thickness: 0.3 mm) was adhered to a flat iron plate (disc) which had not been grooved to form a facing material.

Using the facing material thus obtained, abrasion resistance (500 minutes or 10 minutes with a disc material of S45C steel as a mating material)
The wear amount (μm) when the sliding test was performed at a speed of 50 minutes at 50 RPM and the μ-V characteristics (the relationship between the sliding speed and the coefficient of friction measured by a SAE tester) were examined. The results are shown in Table 1. Was.

The durability was judged from the above-mentioned wear amount and the result of observation of the friction member, and the results are shown in Table 1.

Comparative Example 1 A conventional paper-based facing friction material (paper-based friction material having a thickness of 0.5 mm) was examined for wear resistance, μ-V characteristics, and durability in the same manner as in Example 1, and the results were tabulated. 1 is shown.

Comparative Example 2 A facing material was produced in the same manner as in Example 1 except that the hot pressing conditions were 150 ° C. and a pressure of 40 kgf / cm ^2, and abrasion resistance, μ-V characteristics and The durability was examined, and the results are shown in Table 1.

[0048]

[Table 1]

From Table 1, it is clear that the facing friction material of the present invention has excellent wear resistance, good μ-V characteristics, and excellent durability.

[0050]

As described above in detail, according to the method for producing a facing friction material of the present invention, the abrasion resistance is remarkably good. Excellent μ-V characteristics. Excellent heat resistance and durability. There is no change with time in the coefficient of friction and it is stable for a long time. Oil groove machining of the core plate can be eliminated, and labor and machining cost can be reduced. In addition, there is no problem of a decrease in friction characteristics due to wear of the groove. It is possible to reliably manufacture a facing friction material having target characteristics without variation in performance. A facing friction material having such excellent characteristics as described above is provided.

Claims (3)

[Claims] Claims 1. A mixture of carbon fiber and aramid fiber, a friction modifier and a filler are added and mixed, followed by papermaking. After drying the resulting paper sheet, the sheet is impregnated with a polyamideimide resin liquid. Then, 50kgf / c
A method for producing a facing friction material, which comprises hot-pressing at a pressure higher than m ² , followed by heat curing. 2. The method according to claim 1, wherein the friction modifier is at least one member selected from the group consisting of polytetrafluoroethylene powder, MoS ₂ powder, carbon powder and alumina powder, and the filler is CaCO 2. _3, the manufacturing method of the facing friction material, characterized in that it is SiO ₂ and one or more selected from the group consisting of diatomaceous earth. 3. The method according to claim 1, wherein the mixing ratio of the carbon fiber and the aramid fiber is 75 to 30% by weight of the aramid fiber with respect to 25 to 70% by weight of the carbon fiber. The mixing ratio of the powder is 1 to 10% by weight based on the mixture of the carbon fiber and the aramid fiber.
Wherein the mixing ratio of the filler is 5 to 300% by weight based on the mixture of the carbon fiber and the aramid fiber, and the amount of the polyamide imide resin impregnated is carbon fiber, aramid fiber, a friction modifier, a filler and A method for producing a facing friction material, comprising 10 to 50% by weight based on the total amount of the polyamideimide resin.