JPS5977139A - Friction material - Google Patents

Abstract

PURPOSE:To improve abrasion resistance of a friction material made of metallic fiber as the basic material, in all operating temperatures, by using a specific modified phenolic resin as an essential ingredient of the bonding agent thereby to enhance the binding force. CONSTITUTION:The suitable modified phenolic resin as the ingredient of the bonding agent to constitute the friction material is polyvinyl acetal resin modified phenolic resin (hereafter to be called the resin A) or aromatic hydrocarbon resin modified polyvinyl acetal resin modified phenolic resin (hereafter to be called the resin B). The resin A can be obtained by first preparing novolac type phenolic resin, through a predetermined period of time of reaction between phenol and aldehyde in the presence of acid catalyst, then adding polyvinyl acetal resin thereto allowing both resin to react with each other, and finally allowing the product of reaction to pass through a dehydrating process. The resin B is obtained by first allowing aromatic hydrocarbon resin and phenol to react with each other in the presence of acid catalyst, then adding polyvinyl acetal resin thereto for further reaction, and finally allowing the product of reaction to pass through a dehydrating process. Using metallic fiber as basic friction material and using the resin A or B as an essential ingredient of the bonding agent, a very useful friction material with abrasion resistance remarkably improved also in low operating temperature can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and useful friction material, and more particularly to a friction material comprising a specific modified phenolic resin as an essential component of a binder.

Friction materials such as brake linings and disc pads have conventionally been produced by using short asbestos fibers as a reinforcing base material, and also by using abrasive and inorganic fillers and bonding them with thermosetting phenolic resin. However, it has been medically proven that such asbestos fibers may cause respiratory system diseases if absorbed into the human body, and during the manufacturing process of the asbestos-based friction material. In recent years, attention has been focused more and more on the impact of asbestos debris on workers.

Under these circumstances, with the aim of ``de-asbestos'', metal fibers are increasingly being seen as a promising alternative base material for the production of various friction materials such as brake linings and disc pads.

This is because the metal fiber itself is cheap and easy to handle, and
Furthermore, this is due to the fact that the technology used for asbestos base materials can be used almost as is, but on the other hand, when this metal fiber is used,
Although it has excellent wear resistance in the high temperature range of 00°C or higher, it has poor wear resistance in the low temperature range of 250°C or lower.
The drawback is that it cannot necessarily be said to be superior to conventional asbestos-based friction materials.

The main reason for this is the weak adhesive bond between the base material and the binder, in other words, the weak adhesive bond between the metal base material and the thermosetting phenolic resin, and this weakness causes friction. It is also conceivable that this may cause problems such as detachment of the base material from the friction pad, and as a result, the amount of wear of the friction pad will increase.

Various thermosetting phenolic resins, such as pure phenolic resin, cashew oil-modified phenolic resin, rubber-modified phenolic resin, or alkylphenol-modified phenolic resin, have been used in combination with these favorite base materials. However, none of these types can be said to be a material that can eliminate the above-mentioned difficulties, that is, solve the problem of improving wear resistance in a low temperature region.

However, based on the above-mentioned technical background, the present inventors have increased the adhesive bonding force between the metal fibers and the binder, improved the abrasion resistance especially in the low temperature range, and further improved the overall temperature resistance as a friction material. As a result of intensive research aimed at improving abrasion resistance in various areas, all of the above-mentioned problems were resolved by incorporating a specific modified phenolic thread resin into the friction material as an essential component of the binder. The inventors have discovered that the object of the present invention can be achieved in a similar manner, and have constructed the present invention.

That is, the present invention provides a friction material comprising a polyvinyl acetal resin or a modified phenolic resin containing polyvinyl acetal resin and an aromatic hydrocarbon resin as an essential component of the binder.

Here, the modified phenolic resin which is a binder component constituting the friction material of the present invention means that polyvinyl acetal resin is used as a modifier component, or (・&1 this polyvinyl alcohol lid l) W and an aromatic compound. Polyvinyl acecool resin modified phenolic resin (hereinafter referred to as resin resin) or aromatic hydrocarbon resin modified - Polyvinyl acecool resin modified phenolic resin (hereinafter also referred to as resin (B)), these modified phenolic yarns mtlIv+1
It can be obtained as follows.

In other words, I am particular about it (ha)! -First, phenols and aldehydes are reacted in the presence of an acidic catalyst for a predetermined period of time, and then (
・Polyvinyl acetal resin is added to the novolac type phenolic resin obtained by force and combing, and the resin is obtained through a dehydration process after reaction. Polyvinyl acetal resin is obtained by reacting polyvinyl acetal resin under an acidic catalyst, then reacting with polyvinyl acetic resin, and then dehydrating the resin. Some of the hydroxyl groups in the saponified product are acetalized by condensation with aldehydes, and typical examples include polyvinyl formal and polyvinyl butyral.

In the polyvinyl acetal resin, the residual hydroxyl group of the polyvinyl alcohol unit becomes a functional group and is modified by a condensation reaction with a phenol.
The amount of denaturation of the sac 1 is 1 to 7 with respect to the raw material phenols.
A range of 0% by weight is suitable, preferably a range of 5 to 60% by weight.

If the amount of this modification exceeds 70 Tc, the adhesive strength with the metal fibers will be strengthened, but the heat resistance of the resin (Al itself will deteriorate, and in addition, the abrasion resistance at high temperatures will be impaired. If the amount is less than 1 kg by weight, the desired effects of the present invention cannot be obtained, so both are not preferred.

Typical examples of the above phenols include phenol, cresol, xylenol, and other alkylphenols, and typical examples of the aldehydes include formaldehyde, paraform, and glyoxal, and hexamethylenetetramine and the like. Materials that emit formaldehyde, such as, can be used as well.

On the other hand, the aromatic hydrocarbon resin is a resin produced by reacting an aromatic hydrocarbon such as benzene, toluene or xylene with an aldehyde in the presence of an acidic catalyst. If so, benzene
These include formaldehyde disintegration, toluene-containing formaldehyde resin, and mixed alkylbenzene/formaldehyde resin obtained from xylene.

The amount of the aromatic hydrocarbon resin to be used is preferably 5 to 100% by weight, preferably 10 to 8% by weight, based on the raw material phenol.

If the amount used exceeds 100%, resin (B
Molten: It becomes slow-curing, reducing the productivity of the friction material, and conversely, if it is less than 5% by weight, the desired effect for the present invention cannot be obtained, so both are not preferred.

Furthermore, typical acidic catalysts include sulfuric acid,
Examples include inorganic acids such as hydrochloric acid and nitric acid, and organic acids such as para-toluenesulfonic acid, oxalic acid and acetic acid, and mixtures thereof can also be used.

Thus, the friction material of the present invention is obtained by finely pulverizing each a-modified novolak type phenol resin, which is obtained using a main raw material compound such as a submerged one, together with 1 to 30% by weight of hexamethylenetetramine. Next, the pulverized product thus obtained is mixed uniformly with a so-called friction base material, a friction modifier, and other fillers in a mixer, then molded using a hot pressure molding machine, and then fired and polished. This product is extremely useful because it exhibits a high coefficient of friction with excellent abrasion resistance over the entire temperature range of use, and is also excellent in stability.

Here, typical friction base materials include metal fibers such as iron fibers and brass fibers, but further known and commonly used fibers such as asbestos staple fibers may also be used.

Typical friction modifiers include cashew dust, which is a gelled product of cashew grain oil, and carbon or graphite powder.Other fillers include calcium carbonate, barium sulfate, alumina powder, and starch powder. Or zinc oxide powder is a typical example.

When hot-pressing molding is performed to obtain the friction material of the present invention, the temperature may be sufficient as long as the temperature is sufficient to crosslink the resin (B) or resin (B) as the binder component. -Could you give an example of a mold @ temperature condition of 140~220℃ and
A pressure condition of ky/cl' is given.

In this way, the present invention particularly uses a metal substrate as the friction base material, and a novolak type phenolic thread resin as a binder, either alone or with a polyvinyl acetal resin and an aromatic hydrocarbon resin. By using resin (A) or resin (B) as an essential component, which is obtained by modifying resin (A) or resin (B), the adhesive bonding force with such metal fibers is strengthened, which has been a drawback of conventional friction materials. An extremely useful friction material with significantly improved abrasion resistance in low temperature ranges can be obtained.

As mentioned above, the basic performance required of such friction materials includes even higher wear resistance at high temperatures, a high coefficient of friction, and stability, but under recent harsh braking conditions. Now, various characteristics in such a high temperature region are also becoming important, and the friction material of the present invention will be highly evaluated as meeting the demands of this era.

Many of the properties exhibited in these high-temperature ranges are due to the resin (B), which is composed only of phenol nuclei, substituted benzene nuclei, and methylene bonds, and has excellent heat resistance. This may be due to the fact that it has the characteristics of being excellent in hardness and flexibility, and on the other hand, the friction material of the present invention solves the problem of wear resistance in low temperature ranges, which is considered to be a drawback or difficulty of conventional friction materials. This is thought to be due to the phenolic resin obtained using polyvinyl acetal resin as a modifier, and also to the fact that metal fibers are used as an essential component of the friction base material.

The friction material of the present invention obtained in this way can be used in a wide range of temperatures over the entire temperature range from low to high temperatures, so it can be used not only as a friction material for brake linings and disc pads, but also for brake linings for industrial machinery. It can also be used in a wide range of fields.

Next, the present invention will be explained in detail with reference to Examples and Comparative Examples. Unless otherwise specified, all parts and parts are based on weight.

Example 1 930 parts of phenol was charged into a reaction vessel equipped with a reflux cooling device, a stirring device, and a normal pressure/vacuum distillation device, and 0.96 parts of 98-thiosulfuric acid was added, and the temperature was increased from 7 to 1.
When the temperature reached 00℃, commercially available 37.21 formalin 6
After 30 parts were gradually added dropwise and reacted for 1 hour under reflux, 186 parts of Denka Formal 30HJ (polyvinyl formal manufactured by Denki Kagaku Kojo) was added and further reacted for 1 hour under reflux. .

Next, after neutralizing by adding 1.3 parts of commercially available 25 thiammonia water, dehydration was immediately started by closed pressure distillation, and the end point of closed pressure distillation was reached when the temperature inside the reaction pot reached 160°C. At the same time, the vacuum distillation circuit was switched to, the degree of vacuum was gradually increased, and the end point of the vacuum distillation was when the softening point of the bamboo resin produced reached 114°C, at which point the produced resin was taken out. Collected electricity is 1100 copies).

After subjecting the resulting Senso to nitrogen resistance, it was roughly pulverized, and 77 parts of hexamethylenetetramine was added and finely pulverized to obtain a powdered resin with a particle size of 94% that passed through 200 meshes. Hereinafter, this will be abbreviated as resin (A-1).

Next, the desired friction material is prepared using this resin (A-1) with the formulation shown below. First, each compounded raw material is mixed uniformly in a mixer, and then put into a hot pressure molding machine. The mold temperature was set to 165°C, and the press pressure was set to 300°C.
/cII? The molded product was sealed and held under these conditions for 10 minutes to be molded, and then the molded product was fired at 180° C. for 8 hours and then polished to obtain a friction material.

The results of measuring the friction coefficient and wear rate of this friction material according to JIS D-4411 are summarized in Table 1.

Iron-based fiber 50cm Resin (A-1) 10cm Dust 5qb Copper
Powder 10-barium sulfate
10th grade graphite (graphite) 1
5qb Example 2 The same operation as in Example 1 was repeated without using "Denka Formal 30H" to perform neutralization, followed by dehydration by atmospheric distillation, the distillate decreased and the temperature inside the pot increased, and 15
When the temperature reached 0'C, 186 parts of I°Denka Butyral IO Rho 1' (product of the same company) was added for the first time, and after reacting at the same temperature for 1 hour, the temperature was gradually raised to 160°C and the temperature was increased to normal pressure. Distillation was performed, and when the same temperature was reached, switching to vacuum distillation was performed.

Thereafter, the softening point of the resin obtained in the same manner as in Example 1 was 123 ° C., the yield was 1100 parts, and hexamethylenetetramine was then added to the coarsely pulverized material and finely pulverized. Table 1 also shows the measurement results of the friction coefficient and wear rate for the resin having a particle size of 94 inches.

Example 6 200 xylene-formaldehyde resin manufactured by Shikagaku ■
and 500 parts of phenol, and further added 16 parts of 49-thiosulfuric acid and reacted at 120° C. for 2.5 hours.

Next, the temperature was lowered to 90°C, and 312 parts of 37.21 formalin and 4.2 parts of 49 sulfuric acid were added, and the mixture was heated to 100°C.
After reacting for 1 hour and neutralizing by adding 6.15 parts of 25% aqueous ammonia, [Denka Butyral 3000-I
After adding 120 parts of J and reacting for 30 minutes, the resin with a softening point of 119°C was treated in the same manner as in Example 1.
I got 00 copies.

Thereafter, a powdered resin was obtained in the same manner as in Example 1, and then a friction material was obtained. The friction coefficient and wear rate of this friction material are as shown in Table 1.

Example 4 The same procedure as in Example 6 was carried out, except that the amount of "Nicanol H" used was 400 parts, and the amount of "Denka Butyral, 15000-IJ" was changed to 60 parts.
1140 parts of resin having a temperature of 12° C. was obtained.

Thereafter, a powder resin was obtained using this resin in the same manner as in Example 1, and then a friction material was obtained (the measurement results of the friction coefficient and wear rate of the obtained friction material are shown in Table 1). That's right.

Comparative Example 1 Into the same reaction pot as in Example 1, 1000 parts of phenol and 2 parts of 98-thiosulfuric acid were charged, heated to 100°C, and further! + 644 parts of 7.2% formalin was added dropwise at the same temperature, and the reaction was continued for 2 hours after the completion of one drop. Then, 2.8 parts of 25% ammonia water was added to neutralize, and then atmospheric distillation was started. After dehydration was carried out until the temperature of the reaction system reached 160°C, vacuum distillation was also carried out to obtain 1000 parts of a control resin having a softening point of 109°C.

A finely ground powdered resin was obtained in the same manner as in Example 1, except that the amount of hexamethylenetetramine was changed to 70 parts, and then a friction material was obtained. The rate results are shown in Table 1.

Comparative example 2 Added an extra 150 parts of cashew shell polymerized oil.

120 U parts of cashew oil-modified novolac tsukusa with a softening point of 105° C. was obtained in the same manner as in Comparative Example 1, except that the amount of formalin to be added was changed to 695 parts.

Thereafter, a powdered resin was obtained in the same manner as in Comparative Example 1, and then a friction material for weight u was obtained.

The results of measuring the friction coefficient and wear rate for this #rubbing are shown in Table 1.

As is clear from the results in Table 1, the friction material of the present invention in which a polyvinyl acetal resin-modified phenolic resin or an aromatic hydrocarbon resin-polyvinyl acetal resin-modified phenolic resin is an essential component of the binder is a conventional phenolic resin. Compared to typical pure phenolic resins or cashew oil-modified phenolic resins, it exhibits a particularly remarkable improvement in wear resistance, and also has a high commercial friction coefficient and stability. Therefore, it is known that the friction system of the present invention is extremely useful.

It goes without saying that each of the modified phenol resins used in the present invention is also useful as a binder for friction materials based on asbestos base materials.

Claims (1)

[Claims] A friction material comprising a modified phenolic resin obtained by using polyvinyl acetal resin alone or in combination with an aromatic hydrocarbon resin as a deforming agent, as an essential component of a binder.