JPH10316731A - Resin composition for friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin compsn. which enables the steps of molding and baking in a production process of a friction material to be carried out in a short time while preventing blisters and cracks from occurring by incorporating a phenol resin, i.e., a polycondensate resin of a phenol and an aldehyde, having a specified ortho bonding to para bonding ratio of methylene groups into the resin compsn. SOLUTION: At least one phenol selected from among phenol, cresol, xylenol, ethylphenol, catechol, resorcin, hydroquinone, bisphenol A, etc., is used for preparing the phenol resin used. At least one aldehyde selected from among formaldehyde, paraformaldehyde, benzaldehyde, etc., is used. At least one catalyst selected from among metal salts (e.g. lead acetate), oxalic acid, hydrochloric acid, sulfuric acid, diethylsulfuric acid, p-toluenesulfonic acid, etc., can be used. The o/p ratio of the phenol resin is 0.7-1.0. Hexamethylenetetramine in an amt. of 4-17 wt.% of the phenol resin is used as a curative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder used for obtaining a friction material, and relates to a resin composition for a friction material capable of performing molding and firing in a short time in the process of producing the friction material. Things.

[0002]

2. Description of the Related Art Phenolic resins have been used as binders for obtaining friction materials because of their excellent mechanical properties, heat resistance and adhesiveness. However, the conventional phenol resin for a friction material has a problem that curing is slow, and it takes a long time for molding and firing in the process of producing the friction material. In order to solve such a defect, the ratio of the ortho-bond to the para-bond (o / p ratio) in the methylene bond in the phenol resin is increased to 1.0 or more to impart quick-curing property, so that molding time, Studies have been made to reduce the firing time. However, this way o / p
In a resin with a high ratio, only the surface is hardened first during molding of the friction material, there is a problem that the gas generated inside is hard to escape, and swelling, cracks, etc. occur, especially as the size of the friction material becomes larger, Had become.

[0003]

SUMMARY OF THE INVENTION The present invention has been completed as a result of various studies to solve such problems of the phenolic resin. An object of the present invention is to provide a friction material resin composition that can be fired in a short time and that eliminates swelling and cracking of the friction material due to gas generated during molding.

[0004]

The present invention relates to a polycondensate of a phenol and an aldehyde, wherein the ratio of ortho to para bonds (o / p ratio) in the methylene bond in the resin.
A phenolic resin having a ratio of 0.7 to less than 1.0 as an essential component, wherein the o / p ratio of the phenolic resin is 0.
By controlling the friction material to 7 or more and less than 1.0, it is possible to perform molding and firing in a short time without swelling and cracking of the friction material due to gas.

Hereinafter, the present invention will be described specifically.
Phenols used for producing the phenolic resin used in the present invention include phenol, cresol, xylenol, ethylphenol, propylphenol, catechol, resorcin, hydroquinone, bisphenol A
These may be used alone or in combination of two or more. Aldehydes are formaldehyde, paraformaldehyde, benzaldehyde and the like, and these may be used alone or in combination of two or more. As a catalyst for reacting phenols and aldehydes, metal salts such as zinc acetate, and acids such as oxalic acid, hydrochloric acid, sulfuric acid, diethyl sulfate, and paratoluenesulfonic acid can be used alone or in combination of two or more.

[0006] The o / p ratio of the phenol resin is 0.7 or more and less than 1.0, and preferably 0.7 to 0.85. If the o / p ratio is less than 0.7, curing is slow, and a resin having excellent moldability cannot be obtained. Also, when the o / p ratio is 1.
When the resin is 0 or more, the molding surface hardens too quickly during molding, so that gas hardly escapes, and problems such as generation of blisters and cracks occur. Hexamethylenetetramine is used as a curing agent for the phenolic resin composition. The addition amount of hexamethylenetetramine is 4-1 to phenol resin.
7% by weight, preferably 6 to 13% by weight. 4% by weight
If it is less than 10%, the curing of the resin becomes insufficient, and 17% by weight.
If it exceeds 300, the molded product may be blistered or cracked due to the decomposition gas of hexamethylenetetramine.

[0007]

The present invention will be described below with reference to examples. However, the present invention is not limited by these examples. Further, “parts” described in Examples and Comparative Examples
And "%" all indicate "parts by weight" and "% by weight".

EXAMPLE 1 After 1000 parts of phenol, 630 parts of 37% formalin and 5 parts of zinc acetate were charged into a reactor equipped with a stirrer, a reflux condenser and a thermometer, the temperature was gradually raised to reach 100 ° C. After that, a reflux reaction was performed for 120 minutes. Internal temperature is 110 ° C
Atmospheric pressure dehydration until reaching, then vacuum dehydration,
When the temperature in the system was raised to 160 ° C., the contents were taken out of the reactor to obtain 1070 parts of a phenol resin composition which was solid at room temperature.

Comparative Example 1 1000 parts of phenol and 10 parts of oxalic acid were charged into the same reactor as in Example 1, then the temperature was gradually raised until the temperature reached 100 ° C., and 630 parts of 37% formalin were added in portions over 60 minutes. Then, a reflux reaction was performed for 120 minutes. Internal temperature is 110
Dehydration under normal pressure was performed until the temperature reached ° C, and then vacuum dehydration was performed. When the temperature in the system was raised to 160 ° C, the contents were taken out of the reactor to obtain 1070 parts of a phenol resin composition which was solid at normal temperature. .

Comparative Example 2 A reaction was carried out in the same manner as in Example 1 except that the charged amount of zinc acetate was changed to 10 parts, and a phenol resin composition 1070 solid at room temperature was obtained.
Got a part.

100 parts of hexamethylenetetramine was separately added to 1000 parts of the phenol resin solid at room temperature obtained in Example 1 and Comparative Examples 1 and 2, and pulverized to obtain 1089 parts of a powder phenol resin. Next, the respective phenol resins were mixed in the mixing ratio shown below. Formulation Formulation amount (% by weight) Glass fiber 20 Calcium carbonate 70 Resin 10

[0012] This composition is heated at a temperature of 160 ° C and a pressure of 200k.
g / cm ² , molding into a size of 150 mm × 150 mm × 20 mm, measurement of moldable time, and 18
The molded state of the test piece fired at 0 ° C. for 3 hours was observed. For each phenolic resin, the o / p ratio,
The gelation time, which is a curing characteristic of the resin, was measured. o /
The p ratio uses an infrared absorption spectrum and is 730 to 770 cm
^-1 absorbance at 800-1 and 840 cm ^-1
Was determined by the ratio of the absorbance of the para bond appearing in the above.

Example 1 Comparative Example 1 Comparative Example 2 ────────────────────── o / p ratio 0.76 0.59 1.73 Gelation time (165 ° C.sec) 33 56 14 Moldable time (min) 5 8 5 Molding condition Good Good Bad ──────────────────────────────

As is clear from Table 2, Example 1 has o /
As a result of controlling the p ratio, the curing speed was suitable for molding the friction material, the molding time was 5 minutes, and the molding conditions after firing were good. On the other hand, in Comparative Example 1, the o / p ratio was low, the gelation time was short, and the curing was slow, so that the molding time was long. In Comparative Example 2, since the o / p ratio was high, the gelation time was short, the curing was fast, and molding was possible in 5 minutes, but swelling occurred during firing.

[0015]

The resin composition for a friction material of the present invention can be molded and fired in a short time while maintaining good moldability in the process of producing the friction material.

Claims (2)

[Claims] 1. A polycondensate of a phenol and an aldehyde, wherein the ratio of the ortho bond to the para bond (o / p ratio) in the methylene bond in the resin is 0.7 or more and less than 1.0. A resin composition for a friction material, comprising a resin as an essential component. 2. The resin composition for a friction material according to claim 1, wherein hexamethylenetetramine is contained in an amount of 4 to 17% by weight based on the phenol resin.