JPH1036522A - Production of friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and economically produce a friction material without using a resin impregnation operation with an organic solvent. SOLUTION: This friction material contains a phenolic resin and one or more substances selected from para-type aromatic polyamide fiber and para-type aromatic polyamide pulp. The friction material is produced by making a paper sheet from a crosslinkable fibrous phenolic resin together with one or more substances selected from the above fiber and pulp, forming the sheet to a prescribed form and crosslinking and curing the phenolic 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, particularly to a wet friction material used for clutch facing of an automatic transmission. In the friction material, fibers and / or pulp of para-aromatic polyamide (hereinafter sometimes abbreviated as para-aramid) are widely used as a reinforcing base material, and phenol resin is widely used as a binder.

[0002]

2. Description of the Related Art As a friction material used for clutch facing of an automatic transmission, a composite material in which a reinforcing fiber material, a friction modifier, and other fillers are combined with a binder such as a phenol resin is generally used. I have. Conventionally, asbestos has often been used as a reinforcing fiber, but since its use has been regulated due to carcinogenicity, pulp such as glass fiber, carbon fiber, aramid fiber and linter pulp has been used instead. There are many examples used in combination. Among them, aramid fibers and aramid pulp have high strength, and are excellent in heat resistance and friction and abrasion performance. Therefore, as the demand for the heat resistance of the facing becomes higher, it is used more frequently. Various thermosetting resins are used as the binder, and among them, a phenol resin is often used.

[0003] Since these friction materials are used in oil, they are generally called wet friction materials. These wet friction materials are generally produced by a papermaking method as disclosed in Japanese Patent Application Laid-Open No. 4-339888. Manufactured. Specifically, a reinforcing fiber or pulp, a friction modifier, various fillers, and the like are dispersed in water to form a slurry mixture, which is made into a paper to obtain a base paper. On this base paper,
A prepreg sheet is obtained by impregnating a resin solution in which a phenol resin is dissolved in a solvent such as alcohol and drying the resin to make the resin semi-cured. Next, the prepreg sheet is punched into a desired shape, and then heated and pressed to sufficiently crosslink and cure the thermosetting resin to obtain a desired friction material.

Since it is uneconomical to carry out papermaking and resin impregnation in separate steps as described above, attempts have been made to simultaneously blend a binder resin during papermaking. However, even if a resin in the form of a solution, a particle, or a powder is mixed into a papermaking slurry, it is difficult to fix 100% of the resin to the paper, and a part of the resin flows out into papermaking wastewater. For this reason, extra treatment of wastewater is required, and economic efficiency is impaired.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a friction material, particularly a wet friction material, only by a paper making process that does not require a resin treatment and does not require a special wastewater treatment. It is an object to provide a manufacturing method.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a friction material containing at least one selected from para-aromatic polyamide fibers and para-aromatic polyamide pulp and a phenolic resin. A method comprising making a sheet by making a phenolic resin together with at least one selected from the fibers and the pulp, forming the sheet into a predetermined shape, and crosslinking and curing the phenolic resin.

Hereinafter, the present invention will be described in detail. In the present invention, the para-aromatic polyamide (hereinafter, may be referred to as para-aramid) is obtained by polycondensation of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid, and the amide bond has an aromatic ring. Para-position or an alignment position corresponding thereto (for example, 4,4′-biphenylene, 1,
It consists essentially of repeating units which are linked in opposite directions, coaxial or parallel, such as 5-naphthalene, 2,6-naphthalene and the like.

Specific examples thereof include polyparaphenylene terephthalamide, poly 4,4'-benzanilide terephthalamide, polyparaphenylene-4'4-biphenylenedicarboxylic acid amide, polyparaphenylene-3,
4'-diphenyl ether terephthalamide and the like can be mentioned.

The paraamide fiber described in the present invention is in a form that can be used in ordinary papermaking methods, and preferably has a fiber diameter of 0.5 denier to 5 denier and a length of 0.2 mm to 30 mm. And more preferably a short fiber of 0.5 mm or more and 15 mm or less. Para-aramid pulp has a highly fibrillated shape of para-aramid fiber, and its specific surface area measured by the BET method indicates 3 to 25 m ² / g. Pulp freeness test method ", the freeness value measured by the Canadian standard method is 40
の も の 700 ml.

The crosslinkable fibrous phenolic resin described in the present invention is, for example, a phenolic resin such as a phenol-formaldehyde resin or a cresol-formaldehyde resin melted and extruded from a die at 50 to 200 ° C., and this is wound up or collected. It is manufactured by doing. The phenol resin may be either a novolak type or a resol type.

The crosslinkable fibrous phenolic resin thus obtained can be used as it is, but it can also be partially cured if necessary.
Partially cured is obtained by treating uncured fibers in an aqueous solution containing an acid and formaldehyde, such as hydrochloric acid, to cure some of the fibers and leave the other uncured.

The fiber of the crosslinkable fibrous phenolic resin preferably has a diameter of 1.5 to 5 deniers and a length of 2 to 50 mm, more preferably 2 to 30 mm.

As a method for making para-aromatic polyamide paper from para-aromatic polyamide fibers and / or pulp and a crosslinkable fibrous phenol resin as raw materials, a conventional round-mesh or long-mesh paper-making method is used. Can be used as it is. The mixing of the raw materials is performed by measuring a required amount of the raw materials, dispersing them in water, and obtaining a mixed slurry. In the present invention, substantially all of the fibrous phenolic resin remains in the paper made. It hardly flows out into the waste liquid of papermaking like a particulate binder or a solution binder.

The para-aramid fibers or pulp can be used alone or in combination. The strength of the paper can be increased as the proportion of the fiber to the pulp is increased, but the dispersibility deteriorates, so that it is difficult to obtain a paper having a good formation. The amount of the para-aramid fiber or pulp can be freely selected in the range of 1 to 60% (% by weight, the same applies hereinafter) depending on the required performance of the intended friction material. From the viewpoint of holding the molten phenolic resin in the sheet and preventing sticking to the heating roll, etc. during drying after papermaking, 5% (% by weight, the same applies hereinafter) or more of para-aramid pulp is blended into the sheet. It is desirable to do so.

The proportion of the phenolic resin in the sheet can be freely selected depending on the purpose, but is preferably from 10% to 50%.

According to the purpose, other fiber components, friction modifiers and other fillers can be incorporated into the composition. Examples of the fiber component include inorganic fibers such as glass fibers and carbon fibers, organic fibers such as cellulose fibers, various pulp such as cellulose, and whiskers such as potassium titanate. Examples of the friction modifier include cashew dust, graphite and the like. Examples of the filler include diatomaceous earth, alumina, kaolin and the like.

The crosslinkable phenolic resin can be cured by heating or chemically crosslinked, but a curing aid such as hexamethylenetetramine (hexamine) should be added for more effective curing. Can also.
The amount of the curing aid is 3% or more based on the phenol resin.
0% or less is appropriate. As a method of compounding, a method of mixing into a slurry at the time of papermaking, a method of dipping a sheet after papermaking in a solution of a curing aid, a method of dropping or spraying a solution of a curing aid on a sheet, and the like can be used.

Usually, the formed sheet is first dried by heating to form a prepreg sheet. At this time, if the temperature is raised above the melting point of the phenol resin, the resin will melt and contaminate the equipment,
Since the crosslinking of the resin proceeds, it is necessary to perform the reaction at a temperature lower than the melting point of the phenol resin.

Next, the prepreg sheet is formed into a desired shape by, for example, punching, and then heated and pressed by a hot press or a heating roll to melt-crosslink the resin and integrate the components to form a friction material. Conditions such as temperature, pressure and time
It varies depending on the raw material composition, type of phenolic resin, product shape, required performance, and the like. In a wet friction material such as clutch facing, it is necessary that a molded product has a certain porosity. This is achieved by controlling the thickness of the compact during molding.

The molding is generally performed using a dried prepreg, but an undried prepreg can be used as it is. In this case, drying and molding are performed simultaneously, which is more economical.

[0021] The friction material after molding further advances the crosslinking and hardening of the phenolic resin to obtain a higher strength friction material. For this purpose, heat treatment can be performed at a temperature of 150 ° C. or more for 10 minutes or more, or immersion treatment in a mixed aqueous solution of a basic catalyst such as ammonia and an aldehyde.

According to the present invention, a friction material can be easily and economically manufactured only by a papermaking and molding step without using a resin impregnation step using an organic solvent.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[0024]

EXAMPLES Each physical property value in the examples was measured by the following methods. 1. Fiber length The fiber length of para-aramid pulp was measured by a laser projection method using a Kajaani fiber length measuring instrument FS-200 (Valmet Automation). 2. COD of papermaking filtrate COD is 100 in accordance with JIS K0102.17.
It was measured by the KMnO ₄ method of ℃. 3. Fixing rate of phenolic resin during paper making Fixing rate of phenolic resin was calculated by the following equation, assuming that all para-aramid pulp remains in the paper. The weight of diatomaceous earth was determined from the residue after firing the friction material at 900 ° C.

Fixing rate of phenol resin [%] = {(dry weight of friction material−prepared amount of para-aramid pulp−diatomaceous earth weight)} / (prepared amount of phenol resin) × 10
0 4. Tensile shear strength of friction material Tensile shear of a friction material was measured under the following conditions, with the friction material interposed between GFRPs.

Shear area of test piece: 25 × 30 mm Loading speed: 10 mm / min Shear mode: I

[0027]

Example 1 Para-aramid pulp, Twaron 1097
(Nippon Aramid Co., Ltd., BET specific surface 6.5 m ² / g,
The fiber length is 1.4 mm), and the dry weight is 12.5 g.
-0206 (fiber diameter 2 denier, fiber length 6 mm).
3 g and 13.5 g of diatomaceous earth were weighed and dispersed in 1.5 liters of water, and then made into a 250 mm square wire mesh using a square sheet machine (Kumaya Riki Co., Ltd.), and then dewatered. Thus, a model sheet (wet paper) of a wet friction material having a composition ratio of para-aramid pulp, diatomaceous earth and a phenolic resin of 60/40/35 was obtained. At this time, the fixing rate of the phenol resin (kainol fiber) was 100%, and the COD value of the filtrate was 2 ppm. The difference between the charge ratio and the composition ratio of the papermaking sheet is that the fixing ratio of diatomaceous earth is 10%.
Because it is not 0%. To this model sheet, 10% hexamine per phenol resin was added by dripping a required amount of a 3% aqueous solution of hexamine evenly over the entire surface of the sheet. Next, after drying this sheet in a 50 ° C. oven for 5 hours, a hot press at 200 ° C.
While controlling the thickness using a 0.6 mm spacer, 6
Press molding was performed at a pressure of 0 kgf / cm ² for 5 minutes. Thereafter, post-curing was performed in an oven at 200 ° C. for 3 hours to obtain a wet friction material model sheet having a thickness of 0.6 mm. It has a porosity of 50% and a tensile shear strength of 18 kgf.
/ Cm ² .

[0028]

Comparative Example 1 A friction material was made by impregnating a sheet with a phenolic resin according to a conventional method. After weighing 12.5 g of para-aramid pulp and Twaron 1097 by dry weight and 13.4 g of diatomaceous earth and dispersing them in 1.5 liters of water, using a square sheet machine (Kumaya Riki Co., Ltd.) 2
Paper was made on a 50 mm square wire mesh, and then dehydrated and dried to obtain a model sheet of a wet friction material having a composition ratio of para-aramid pulp and diatomaceous earth of 60/40. The CDD value of the filtrate is 5
Met. The incompatibility between the charge ratio and the composition ratio of the papermaking sheet is due to the fact that the diatomaceous earth fixing rate is 100%. Next, a modified resol type phenol resin [PR-SCI-
3, Sumitomo Durez Co., Ltd.] and a 11.25% methanol solution having a pulp / diatomaceous earth / resin composition ratio of 60/4.
The sheet was uniformly impregnated so as to be 0/35, and then dried at 50 ° C. for 20 minutes to obtain a prepreg sheet. The thickness of this sheet was controlled by a hot press at 200 ° C. while controlling the thickness using a 0.6 mm spacer, and the thickness was controlled to 60 kgf / c.
Press molding was performed at a pressure of m ² for 5 minutes. Thereafter, post-curing was performed in an oven at 200 ° C. for 3 hours to obtain a wet friction material model sheet having a thickness of 0.6 mm. Its porosity is 4
9%, and the tensile shear strength was 18 kgf / cm ² .

[0029]

COMPARATIVE EXAMPLE 2 Para-aramid pulp, Twaron 1097, 12.5 g by dry weight, and granular uncured phenol resin [Bellpearl BP-S890, Kanebo Co., Ltd.]
1 g of diatomaceous earth and 13.5 g of diatomaceous earth were weighed and dispersed in 1.5 liters of water, and then made into a 250 mm square wire mesh using a square sheet machine (Kumaya Riki Co., Ltd.), and then dehydrated. Thus, a model sheet (wet paper) of a wet friction material having a composition ratio of para-aramid pulp, diatomaceous earth and phenolic resin of 60/40/35 was obtained. At this time, the fixing rate of the phenol resin (Bellpearl) was 80%, and the CO
The value of D was 5 ppm. The reason why the charge ratio and the composition ratio of the papermaking sheet do not match is that the fixing rate of diatomaceous earth is not 100%. Next, the sheet was dried in an oven at 50 ° C. for 5 hours, and then heated with a hot press at 200 ° C. for 0.2 hour.
60K while controlling the thickness using a 6mm spacer
Press molding was performed at a pressure of gf / cm ² for 5 minutes. Then 2
Post-cured in an oven at 00 ° C for 3 hours to a thickness of 0.6
Thus, a model sheet of a wet friction material having a thickness of 1 mm was obtained. This has a porosity of 49% and a tensile shear strength of 18 kgf / cm.
^{Was 2} .

[0030]

According to the present invention, a friction material used for clutch facing of an automatic transmission, etc. can be easily and economically manufactured only by papermaking and molding steps without using a resin impregnation operation requiring an organic solvent. it can.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display F16D 69/02 F16D 69/02 A

Claims (1)

[Claims] 1. A method for producing a friction material comprising at least one selected from para-aromatic polyamide fibers and para-aromatic polyamide pulp and a phenolic resin, wherein the crosslinkable fibrous phenolic resin is mixed with the fibers and the phenolic resin. A method comprising making a sheet by making paper together with at least one selected from pulp, shaping the sheet into a predetermined shape, and crosslinking and curing the phenolic resin.