JPH07109448A - Friction material - Google Patents

Abstract

PURPOSE:To improve the heat resistance of a resin binder and obtain stable friction characteristics and abrasion resistance even under a high load. CONSTITUTION:This friction material contains a fibrous substrate, a filler, and a resin binder which is a thermosetting resin comprising 15-30wt.% melamine, 10-25wt.% dicyandiamide, and 5-20wt.% cresole resole modified within an arom.-hydrocarbon-modified maleimide resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used as an automobile, industrial machinery clutch facing, brake lining, etc., and more particularly to a friction material using a specific modified cresol resol as its resin binder. It is a thing.

[0002]

2. Description of the Related Art Conventionally, friction materials such as clutch facings and brake linings for automobiles have been required to have heat resistance and wear resistance, and have stable friction characteristics with little change in friction coefficient even at the time of fade ( Fade resistance) is required.

Therefore, in order to satisfy these various characteristics, the friction material is formed as a composite material. That is, the friction material is generally composed of a fiber base material forming a skeleton, a resin binder for binding and holding the fiber base material, and various fillers dispersed and filled in a matrix of these fibers and the binder. Has been done. And, as the fiber base material, inorganic fiber such as glass fiber, organic fiber such as aramid fiber, metal fiber such as steel fiber, etc. are used, and as the resin binder, thermosetting resin such as phenolic resin is used. A resin or a crosslinkable rubber is used, and as the filler, a body filler such as barium sulfate, a solid lubricant, a friction modifier or other additives are used.

Of these, the resin binder not only affects the heat resistance of the friction material, but also has a great influence on the friction characteristics and wear resistance. As such a resin binder, a phenolic resin has been generally used for a long time. This phenolic resin is a resol-type thermosetting resin obtained by reacting phenols and aldehydes in the presence of an alkaline catalyst, and has high mechanical strength and excellent adhesiveness to a fiber base material. However, pure phenolic resins have drawbacks such as poor fade resistance. Therefore, the phenolic resins used as resin binders are generally modified and used for modification.

The material or compound for such modification is, for example, cashew nut oil, polyvinyl butyral, vegetable oil, melamine, epoxy compound or the like. Further, in JP-A-56-94038, the use of a monoalkylphenol having 4 to 20 carbon atoms is used, and in JP-A-58-217577, an aromatic hydrocarbon resin such as a xylene resin and a triazine-based compound are used. Further, Japanese Patent Application Laid-Open No. 59-77139 discloses the modification of a polyvinyl acetal resin alone or in combination with an aromatic hydrocarbon resin.

Thus, it is known to use various modified phenolic resins as the resin binder. However, among these, the phenolic resin modified with melamine is particularly excellent in stability of friction characteristics (fade resistance) and abrasion resistance. Therefore, the melamine-modified phenolic resin is still generally used as a suitable resin binder for friction materials.

[0007]

By the way, particularly in recent years, along with the performance improvement and long-term warranty of automobiles, friction materials such as clutch facings for automobiles are widely used from light load, medium load to high load. It is strongly desired to be able to meet the conditions and have a long life.

However, although the melamine-modified phenolic resin as a resin binder is excellent in the stability of friction characteristics in light load and medium load regions, and in abrasion resistance, the heat resistance of the resin itself is high in high load region. Due to the lack of properties, there is a problem that the friction coefficient μ decreases and the wear resistance also deteriorates.

In view of this problem, the present inventor has made various investigations and studies on modification of a phenolic resin, and as a result, melamine, dicyandiamine, and aromatic hydrocarbon-modified maleimide are used as modifiers. By using a resin compound in combination, and by modifying each of them at a specific ratio, it is possible to increase the heat resistance, which is a drawback thereof, while maintaining the characteristics due to melamine modification, and the above problems can be advantageously solved. Found.

Therefore, it is an object of the present invention to provide a friction material having stable friction characteristics and wear resistance even in a high load region by increasing the heat resistance of the resin binder.

[0011]

The friction material of the present invention comprises a fibrous base material, a resin binder, and a filler. As the resin binder, 15 to 30% by weight of melamine and 10 to 25% by weight of melamine are used. It contains a thermosetting resin composed of dicyandiamide and cresol resole modified with 5 to 20% by weight of an aromatic hydrocarbon-modified maleimide resin compound.

Here, cresol resole is a liquid resin obtained by condensing cresol and aldehydes such as formaldehyde with an alkali catalyst, and is a thermosetting resin which is cured by heating. Phenol is usually used as such a resole, but in the present invention, a resole of cresol is particularly used because of its excellent curability and flexibility. In the present invention, the thermosetting resin made of cresol resol is modified with melamine, dicyandiamide, and an aromatic hydrocarbon-modified maleimide resin compound. The modified amount of these modified compounds represented by weight% is the ratio with respect to the entire thermosetting resin (solid content) made of modified cresol resol.

Melamine is mainly used for improving the thermal stability (fade resistance) of friction characteristics. And
The modification amount is preferably 15 to 30% by weight. As the amount of melamine modified increases, the minimum friction coefficient μ indicating the stability of the frictional characteristics tends to increase, but on the contrary, the heat resistance of the resin decreases and the abrasion rate tends to increase. If the amount of modification is less than 15% by weight, the effect of improving the fade resistance of the friction material is generally small, and if it exceeds 30% by weight, sufficient abrasion resistance cannot be obtained.

Dicyandiamide is mainly used to accelerate the curing of the modified resole. The modified amount is preferably 10 to 25% by weight. If it is less than 10% by weight, the effect of promoting the curing of the resin is generally small, and the fade resistance is deteriorated. On the other hand, if it exceeds 25% by weight, dicyandiamide is likely to precipitate, and the heat resistance of the resin is remarkably deteriorated.
Abrasion resistance deteriorates. More preferably, the modification amount of this dicindiamide is in the range of 15 to 20% by weight.

The aromatic hydrocarbon-modified maleimide resin compound is an imide compound of maleic acid, which can be obtained, for example, as follows. Aromatic hydrocarbon resinous compounds obtained by reacting aromatic hydrocarbons such as benzene, toluene and xylene with aldehydes such as formaldehyde under strong acidity, and metaphenylenediamine, paraphenylenediamine, 2,2 ' Reacting with an aromatic diamine such as -bis (4-aminophenyl) propane or 4,4'-diaminodiphenylmethane in the presence of an acid catalyst. The reactant is then reacted with maleic anhydride to form a maleimide resin compound. Here, maleic anhydride may be an unsaturated dicarboxylic acid anhydride such as methyl maleic anhydride (citraconic anhydride) or its isomer, itaconic anhydride, and those unsaturated groups are cresol resole and Contribute to the reaction of. As the resinous compound of aromatic hydrocarbon, a xylene formaldehyde resin compound well known as a xylene resin can be preferably used.

The modification of cresol resole with this aromatic hydrocarbon-modified maleimide resin compound has the effect of improving the heat resistance of the thermosetting resin and increasing the wear resistance thereof. The wear rate of the friction material tends to decrease as the amount of modification increases. However, the minimum friction coefficient μ increases with it, but since the curability decreases,
It tends to decrease again with a peak of about 13% by weight. This decrease in curability can be compensated to some extent by increasing the modification amount of dicyandiamide, but there is a limit to that. Therefore, the modified amount of this resin compound is preferably 5 to 20% by weight, and more preferably 10% by weight.
~ 15% by weight.

The modification with these modifying compounds can be carried out by any method, as is well known per se. Melamine and dicyandiamide can be used as a modifier as they are, or can be used by previously reacting with aldehydes. Further, these may be reacted at the same time as the production of cresol resol, or may be mixed and reacted after the formation of cresol resol. The aromatic hydrocarbon-modified maleimide resin compound may also be compounded and reacted during the production of cresol resole, or compounded and reacted after the formation of cresol resole. Alternatively or additionally, it may simply be added to the resole, in which case it will react during the heat curing of the resole.

The thermosetting resin composed of the modified cresol resole is a suitable solvent such as N-methyl-
It can be used as a uniform liquid resin by dissolving it in an aprotic polar solvent such as 2-hirolidone or dimethylformamide, a ketone such as acetone or methyl ethyl ketone, or dioxane. Moreover, you may use together another general purpose solvent.

In the friction material of the present invention, the thermosetting resin comprising melamine, dicyandiamine, and cresol resole modified with an aromatic hydrocarbon-modified maleimide resin compound may be used alone or in combination with another resin binder. Generally, 3 to 50% by weight based on the total friction material in combination with
Can be included. However, in the case of the clutch facing in which the crosslinkable rubber is used as the resin binder, the content of the thermosetting resin is preferably 3 to 20% by weight. This is because the wear rate decreases as the content increases, but if the content is too high, the curability at the time of heat molding deteriorates and the fade resistance tends to decrease. And more preferably, it is used in a content of 8 to 15% by weight.

Further, in the friction material of the present invention, as the fiber base material, glass fiber, rock wool, silicate fiber, alumina fiber, carbon fiber, potassium titanate fiber, inorganic fiber such as slag wool, steel fiber, stainless steel, etc. Examples thereof include fibers, metal fibers such as copper fibers, aramid fibers, novoloid fibers, nylon fibers, and organic fibers such as rayon fibers. These can be used alone or in combination as appropriate depending on the specific type or application of the friction material.

Examples of the filler include body fillers such as barium sulfate and calcium carbonate, solid lubricants such as graphite and molybdenum disulfide, organic powders such as cashew dust, abrasive agents such as silica, and other friction performance improving agents. Etc. can be used as appropriate. In addition, various additives other than these fillers can be used as required.

In the present invention, the thermosetting resin composed of the above-mentioned modified cresol resole is used as the resin binder, but other resin binders can be used together if necessary. And as such a resin binder, other modified phenolic resin, epoxy resin,
Examples thereof include melamine-based resins, polyimide-based resins, polyester-based resins, and rubbers such as SBR and NBR.

The friction material of the present invention is manufactured by blending these materials and subjecting the material to heat molding into a predetermined shape or form as a clutch facing, a brake pad or a lining.

[0024]

In the friction material of the present invention, the thermosetting resin comprising cresol resole as the resin binder has its heat resistance increased by being modified with the aromatic hydrocarbon-modified maleimide resin compound, and It is well-balanced with melamine and dicyandiamide. Therefore, the decrease in friction coefficient and deterioration of wear resistance due to insufficient heat resistance of the resin binder are reduced, and stable friction characteristics (fade resistance) and good wear resistance are obtained even under high load. To be

[0025]

EXAMPLE An example in which the present invention is applied to a clutch facing will be described below.

First, the production of the melamine-modified cresol resole for comparison with the modified cresol resole used in the present invention will be described.

[Production of Modified Cresol Resol] The modified cresol resole used in the present invention was produced by the following steps.

(Process 1. Production of xylene-modified aromatic polyamine resin compound) 3000 parts of 4,4'-diaminodiphenylmethane and 300 parts of xylene-formaldehyde resin (Nikanol G, manufactured by Mitsubishi Gas Chemical Co., Inc.) are stirred.
The mixture was placed in a flask equipped with a reflux condenser and a thermometer, the internal temperature was heated to 110 ° C., and when 4,4′-diaminodiphenylmethane was completely dissolved, paratoluenesulfonic acid 4
0 part was added, the temperature was further raised, and the mixture was reacted under reflux for 2 hours.
Furthermore, the reaction was carried out for 2 hours under atmospheric pressure dehydration, and 1000 parts of methyl cellosolve was added while cooling to obtain 4250 parts of an aromatic polyamine solution. The viscosity of this product at 25 ° C was 200 cps, and the nonvolatile content after 1 hour at 135 ° C was 72.
% By weight.

(Step 2. Production of xylene-modified maleimide resin compound) 1952 parts of acetone were placed in the same reaction apparatus as described above, 600 parts of maleic anhydride was added and completely dissolved, and then obtained in step 1 while keeping the temperature at 40 ° C. or lower. 825 parts of the obtained aromatic polyamine solution was added dropwise over 90 minutes, and after the completion of the addition, the temperature was kept at the same temperature for 1 hour. Then triethylamine 1
65 parts and 19.5 parts of nickel acetate tetrahydrate were added, 800 parts of acetic anhydride was further added, and the mixture was reacted at a reflux temperature for 2 hours. After the reaction was completed, the solvent was immediately distilled off under vacuum, and the temperature was 70 ° C.
Stir-mix for 10 minutes. Then, the mixture was allowed to stand and the supernatant water tank was removed. Then, after repeating this operation twice, 500 parts of methanol was added, and the mixture was stirred at 70 ° C. for 10 minutes, and then the supernatant was removed.
It was raised to ℃. At this point dimethylformamide 4
110 parts was added and dissolved to obtain 5480 parts of liquid resin. The viscosity of this product at 25 ° C is 3 cps, 135 ° C, 1
The nonvolatile content after 25 hours was 25% by weight.

(Step 3. Production of Cresol Resol) Into a reactor similar to the above, 1000 parts of cresol, 1200 parts of 37% by weight formalin and 5 parts of sodium hydroxide were charged, and the temperature was gradually raised to 100 ° C. The reflux reaction was performed for 1 hour. Then, the temperature in the system was raised to 70 ° C. while dehydrating the system in a vacuum of 680 mmHg. At this point, 1000 parts of methanol was added and dissolved to obtain 2400 parts of a liquid resin. The viscosity of this product at 25 ° C. was 150 cps, and the nonvolatile content after 1 hour at 135 ° C. was 45% by weight.

(Step 4. Modification with melamine and dicyandiamide) 1000 parts of melamine and 8 parts of melamine were added to the same apparatus as above.
0 wt% paraformaldehyde 900 parts, methanol 1
100 parts and 10 parts of sodium hydroxide were charged, the temperature was gradually raised, and after the temperature reached 75 ° C., a reflux reaction was performed for 90 minutes. Next, after adding 2500 parts of methanol, 670 parts of dicyandiamide and 10 parts of sodium hydroxide and reacting at 70 ° C for 1 hour, 2800 parts of the cresol resole obtained in step 3 was added and reacted at 60 ° C for 1 hour to obtain liquid resin 9
000 copies were obtained. The viscosity of this product at 25 ° C is 8c
The nonvolatile content after 1 hour at ps, 135 ° C. was 40% by weight.

(Step 5. Modification with xylene-modified maleimide resin compound) 1000 parts of the modified resole obtained in step 4, 240 parts of xylene-modified maleimide resin compound obtained in step 2, and 565 parts of methyl ethyl ketone were added to the same reaction apparatus as above. And 920 parts of dimethylformamide were charged and reacted at 80 ° C. for 1 hour to obtain 2720 parts of a liquid resin. The viscosity of this product at 25 ° C is 2 cps, 13
The nonvolatile content after 1 hour at 5 ° C. was 20% by weight (amount of modification: xylene-modified maleimide resin compound = 13.0% by weight. Melamine = 24.1% by weight. Dicyandiamide =
16.2% by weight).

[Production of melamine-modified cresol resole] A melamine-modified cresol resole for comparison was produced as follows.

Melamine 1000 in a reactor similar to the above
Parts, 80 parts by weight of paraformaldehyde 900 parts, methanol 1100 parts and sodium hydroxide 10 parts,
The temperature was gradually raised, and after the temperature reached 75 ° C., a reflux reaction was performed for 90 minutes. Then, after adding 3000 parts of methanol and 10 parts of sodium hydroxide and reacting at 70 ° C. for 1 hour, 800 parts of the cresol resol obtained in step 3 was added to
The reaction was carried out at 0 ° C for 1 hour to obtain 6800 parts of a liquid resin. However, the viscosity at 25 ℃ is 3 cps, 135 ℃, 1
The nonvolatile content after 30 hours was 30% by weight (modification amount: melamine = 49.0% by weight).

[Preparation of Clutch Facing] Clutch facings of Examples and Comparative Examples were prepared using the modified cresol resole manufactured as described above.

First, a clutch facing as an example of the present invention was manufactured as follows.

Bulk-processed 6 μm glass fiber 30
10 parts by weight of cresol resole modified with the above-mentioned melamine, dicyandiamide, and xylene-modified maleimide resin compound (simply referred to as the modified cresol resole of the present invention) was impregnated into the parts by weight, and then the brass wire 3
Parts by weight were combined. And to this, rubber (SBR) 20
By weight, 32 parts by weight of an additive such as a filler and 5 parts by weight of a vulcanizing agent (sulfur) were mixed (a total amount of 100 parts by weight).

Next, this was wound into a ring shape, placed in a mold, heated and pressure-molded under the conditions of a pressure of 160 kg / cm ² and a temperature of 165 ° C., heat treated, and then polished to a predetermined thickness. I got the clutch facing. The composition (% by weight) of this clutch facing is shown in FIG.

Similarly, a clutch facing of Comparative Example was prepared by using the above-mentioned melamine-modified cresol resole in the same weight ratio in place of the modified cresol resole of the present invention. The composition (% by weight) of the clutch facing of this comparative example is the same as that of the example except for the modified cresol resole, as shown in FIG.

[Friction Test] A friction test was conducted on the thus prepared clutch facings of Examples and Comparative Examples, and the minimum friction coefficient μ and wear rate of each were measured.

The friction test was carried out under the following conditions with the clutch facing mounted on a full size dynamo tester.

Rotational speed: 1800 rpm Inertial amount: 0.5 kg · m · sec ² Number of engagements: 2000 times Temperature: 200 ° C. The measurement results are shown in the lower column of FIG.

As shown in FIG. 1, the minimum friction coefficient μ indicating the stability of frictional characteristics was 0.20 in the comparative example corresponding to the prior art, whereas the modified cresol resol of the present invention was used. In the examples described above, it was 0.32, and the decrease in the friction coefficient μ was considerably small.

The wear rate (× 10 ⁻⁴ mm ³ / kg · m) was 14.1 in the comparative example, whereas it was 6.6 in the example, and the wear rate was considerably lowered. showed that.

From these measurement results, it was confirmed that the use of the modified cresol resol of the present invention makes it possible to obtain a clutch facing having a small decrease in friction coefficient and a small wear rate even in a high load region.

[0046]

As described above, the friction material of the present invention contains 15 to 30% by weight of melamine and 10 to 2 as a resin binder.
It contains a thermosetting resin consisting of 5% by weight of dicyandiamide and 5 to 20% by weight of cresol resole modified with an aromatic hydrocarbon-modified maleimide resin compound. Therefore, the thermosetting resin made of cresol resol is particularly improved in heat resistance by being modified with an aromatic hydrocarbon-modified maleimide resin compound,
Moreover, since it is modified in a well-balanced manner with melamine and dicyandiamide, the friction material of the present invention containing this as a resin binder has stable friction characteristics (resistance to resistance) not only in the light load and medium load regions but also in the high load region. (Fade property) and abrasion resistance. As a result, the friction material of the present invention can be advantageously used as a clutch facing of an automobile or the like.

[Brief description of drawings]

FIG. 1 is a table showing compositions (wt%) of clutch facings in Examples and Comparative Examples of the present invention, and measurement results of minimum friction coefficient and wear rate.

Claims (1)

[Claims] 1. A friction material comprising a fibrous base material, a resin binder and a filler, wherein the resin binder is 15 to 30.
A friction material containing a thermosetting resin consisting of melamine in an amount of 10% by weight, dicyandiamide in an amount of 10 to 25% by weight, and cresol resole modified with an aromatic hydrocarbon-modified maleimide resin compound in an amount of 5 to 20% by weight. .