JP5410087B2 - Binder resin composition for friction material and friction material for brake - Google Patents

Description

  The present invention relates to a binder resin composition for a friction material and a brake friction material using the same. More specifically, the present invention provides a friction material binder resin composition with good flowability and moldability, which gives a friction material with improved moldability, quality stability, heat resistance and wear resistance, and the composition. The present invention relates to a brake friction material having the above properties.

  Non-asbestos brake friction materials used for brake pads of automobiles, etc., for example, a base material made of metal fibers such as steel and copper, ceramics, inorganic fibers such as carbon, organic fibers such as aramid fibers, graphite, Blends lubricants such as antimony trisulfide and molybdenum disulfide, fillers such as swellable clay minerals, barium sulfate, calcium carbonate and calcium hydroxide, and friction modifiers such as cashew dust, ceramic powder and metal powder, and These components are prepared by blending a binder resin (binding material) with these components, sufficiently stirring and mixing, and then performing compression molding while heating.

  And as a binder resin, a phenol resin and an epoxy resin have been frequently used so far. However, in a friction material using a phenol resin, molding defects such as cracks and blisters occur due to the gas generated due to the curing agent hexamethylenetetramine in the thermoforming process, and the production yield is reduced. There is also concern about environmental pollution caused by ammonia, which is the main component of. Moreover, the epoxy resin has a problem that heat resistance is insufficient.

  Therefore, as a binder resin for a friction material that replaces a phenol resin or an epoxy resin, use of a polybenzoxazine resin that does not generate gas during the thermosetting process and can provide a friction material having excellent heat resistance and strength has been attempted. . For example, in a friction material comprising a heat-resistant resin as a binder, a reinforcing fiber as a base material, and graphite, metal powder, inorganic filler, etc., the heat-resistant resin is a resin containing a dihydrobenzoxazine ring (polybenzoxazine resin). A friction material is disclosed (see, for example, Patent Document 1).

  Among them, the polybenzoxazine resin based on p-aminophenol has been attracting attention as a resin having high heat resistance and excellent wear resistance. However, the flowability of the resin is poor, and a friction material using it as a binder resin. However, there are concerns about moldability and quality stability.

JP-A-8-74896

  Under such circumstances, the present invention gives a friction material having improved moldability, quality stability, heat resistance and wear resistance, and has a good flowability and moldability, and a binder resin composition for a friction material. Another object of the present invention is to provide a brake friction material having the above properties using the composition.

As a result of intensive studies to achieve the above object, the present inventors have found that a polybenzoxazine resin, which is a polycondensation reaction product of p-aminophenol and formaldehyde, and 2,2-bis (4-hydroxy). It was found that the purpose can be achieved by a resin composition containing a polybenzoxazine resin, which is a polycondensation reaction product of (phenyl) propane , primary amines and formaldehyde, in a predetermined ratio. Based on this, the present invention has been completed.

That is, the present invention
(1) (A) polybenzoxazine resin that is a polycondensation reaction product of p-aminophenol and formaldehyde , (B) 2,2-bis (4-hydroxyphenyl) propane , primary amines, Binder resin composition for friction material, comprising polybenzoxazine resin, which is a polycondensation reaction product with formaldehyde, in a mass ratio of 95: 5 to 50:50, and ( 2 ) 1 ) A friction material for a brake, characterized by being obtained using the binder resin composition for a friction material described in 1 ) ,
Is to provide.

  According to the present invention, a binder resin composition for a friction material having good flowability and moldability, which gives a friction material with improved moldability, quality stability, heat resistance and wear resistance, and the composition are used. A brake friction material having the above properties can be provided.

First, the binder resin composition for a friction material of the present invention will be described.
[Binder resin composition for friction material]
The binder resin composition for a friction material of the present invention (hereinafter sometimes simply referred to as “binder resin composition” or “resin composition”) is a polybenzoxazine resin based on (A) p-aminophenol. And (B) 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) based polybenzoxazine resin in a mass ratio of 95: 5 to 50:50 .

((A) Polybenzoxazine resin based on p-aminophenol)
In the resin composition of the present invention, examples of the polybenzoxazine resin based on p-aminophenol used as the component (A) include a polycondensation reaction product of p-aminophenol and formaldehyde.
Examples of the formaldehydes include formalin, paraformaldehyde, and trioxane.

  By polycondensation reaction of p-aminophenol and the above formaldehydes, the following formula (1)

（式中、ｎは重合度を示す。）
で表される、ｐ−アミノフェノールをベースとするポリベンゾオキサジン樹脂が得られる。

(In the formula, n represents the degree of polymerization.)
A polybenzoxazine resin based on p-aminophenol is obtained.

((B) Polybenzoxazine resin based on bisphenol A)
In the resin composition of the present invention, examples of the polybenzoxazine resin based on bisphenol A used as the component (B) include polycondensation reaction products of bisphenol A, primary amines, and formaldehydes. it can.

Examples of the primary amines include aliphatic amines and aromatic amines. When aliphatic amines are used, the resulting polybenzoxazine resin has poor heat resistance, and aromatic amines are preferred. Examples of the aromatic amine include aniline, toluidine, xylidine, and anisidine.
On the other hand, the formaldehydes are as described above.

  By using aniline as a primary amine and subjecting bisphenol A, aniline and the formaldehyde to a polycondensation reaction, the following formula (2)

で表される、ビスフェノールＡをベースとするポリベンゾオキサジン樹脂が得られる。

A polybenzoxazine resin based on bisphenol A is obtained.

  The polybenzoxazine resin of the component (A) and the component (B) is, for example, heated at a temperature of about 120 to 300 ° C. to open the dihydrobenzoxazine ring and self-crosslink, or a crosslinkable compound Is present, it self-crosslinks and crosslinks and cures the crosslinkable compound. Therefore, no volatile by-product is generated during curing.

  In the binder resin composition of the present invention, the content ratio of the polybenzoxazine resin based on the p-aminophenol as the component (A) and the polybenzoxazine resin based on the bisphenol A as the component (B). Requires a mass ratio of 95: 5 to 50:50. When the content ratio of the component (B) is less than 5% by mass with respect to the total amount of the component (A) and the component (B), the flowability improving effect of the resin composition is not sufficiently exhibited, and the desired molding is performed. Therefore, the object of the present invention cannot be achieved. On the other hand, when the content ratio of the component (B) exceeds 50% by mass with respect to the total amount of the component (A) and the component (B), the curing time of the resin composition becomes long, and the moldability is poor. The object of the present invention cannot be achieved. The content ratio of the component (A) and the component (B) is a mass ratio, preferably 90:10 to 60:40, more preferably 90:10 to 65:35.

  In this way, a binder resin composition for a friction material having good flowability and moldability is obtained which gives a friction material having improved moldability, quality stability, heat resistance and wear resistance.

Next, the brake friction material of the present invention will be described.
[Brake friction material]
The brake friction material of the present invention (hereinafter sometimes simply referred to as “friction material”) is obtained by using the above-described binder resin composition for a friction material of the present invention.

  In order to produce the friction material of the present invention, first, a friction material forming material is prepared. Examples of the friction material forming material include materials including the binder resin composition for a friction material of the present invention, a fibrous reinforcing material, a lubricant, a friction adjusting material, and various fillers.

(Fibrous reinforcement)
As the fibrous reinforcing material in the friction material forming material, both organic fibers and inorganic fibers can be used. Examples of organic fibers include high-strength aromatic polyamide fibers (aramid fibers; manufactured by DuPont, trade name “Kevlar”, etc.), flame-resistant acrylic fibers, polyimide fibers, polyacrylate fibers, polyester fibers, and the like. On the other hand, as inorganic fibers, in addition to potassium titanate fibers, basalt fibers, silicon carbide fibers, glass fibers, carbon fibers, wollastonite, etc., ceramic fibers such as alumina silica fibers, stainless fibers, copper fibers, brass fibers, Examples thereof include metal fibers such as nickel fibers and iron fibers. These fibrous substances may be used alone or in combination of two or more.

(Lubricants, friction modifiers, other fillers)
There is no restriction | limiting in particular as a lubricant in the said friction material formation material, Arbitrary things can be suitably selected from the well-known things currently used as a lubricant in the friction material. Specific examples of this lubricant include graphite, fluorinated graphite, carbon black, metal sulfides such as tin sulfide and tungsten disulfide, and polytetrafluoroethylene (PTFE), boron nitride, and the like. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Moreover, there is no restriction | limiting in particular as a friction modifier in the said friction material formation material, Arbitrary things can be suitably selected from the well-known things used as a friction modifier in the conventional friction material. Specific examples of the friction modifier include metal oxides such as alumina, silica, magnesia, zirconia and iron oxide; zirconium silicate; silicon carbide; metal powders such as copper, brass, zinc and iron, and titanate powder. And inorganic friction modifiers such as rubber dust such as NBR, SBR and tire tread, and organic friction modifiers such as organic dust such as cashew dust. These may be used individually by 1 type and may be used in combination of 2 or more type.

In the friction material forming material, clay minerals can be contained as other fillers such as a reinforcing material and a friction adjusting material. Examples of the clay mineral include kaolin, talc, smectite, vermiculite, and mica.
Further, calcium carbonate, barium sulfate, calcium hydroxide and the like can be contained.

  In the friction material forming material, the inorganic filler among the lubricant, the friction modifier and other fillers, in order to make the dispersibility in the friction material forming material good, A filler treated with an organic compound can be used.

  Examples of fillers treated with organic compounds include clay minerals, calcium carbonate, barium sulfate, magnesia, alumina, zirconia, silica, aluminum powder, copper powder, zinc powder, graphite, tin sulfide, tungsten disulfide, and other organic materials. The thing processed with a compound can be mentioned.

(Production of friction material)
In order to produce the friction material of the present invention, the material for forming the friction material is filled in a mold or the like, preliminarily molded at a normal temperature of about 5 to 30 MPa, and then at a temperature of 150 to 300 ° C. and a pressure of 10 to 10. After performing compression molding for about 2 to 20 minutes under a condition of about 100 MPa, a desired friction material can be produced by performing after-curing treatment at a temperature of about 200 to 300 ° C. for about 1 to 10 hours as necessary. .

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
The performance of the friction material binder and the friction material obtained in each example was evaluated according to the following methods.

<Binder for friction material>
(1) Resin flowability In accordance with JIS K 6911 5.3.2 disk flow measurement method, the resin flowability was measured at a disk temperature of 200 ° C., and the resin flowability was measured.
(2) Curing characteristics While kneading 1 g of the resin powder on a 200 ° C. hot plate, the time until the yarn was not pulled (gel time) was measured.
(3) Gas generation status Gas generation during molding was judged by visual observation and odor.

<Friction material>
(4) Bending strength A test piece of 80 × 10 × 4 mm was cut out from each friction material, and the bending strength was measured according to JIS K 7171.
(5) Resin curing degree Rockwell hardness (HRS) was measured according to JIS D 4421.
(6) Fade test A test piece was cut out from each friction material, and a test piece friction tester was used to perform a fade test in accordance with JASO-C406-82. The minimum friction coefficient of the first fade and the friction after the test The amount of material wear was measured.

Examples 1-2 and Comparative Examples 1-4
(1) Manufacture of binder for friction material (a) Synthesis of p-aminophenol type polybenzoxazine resin (p-AP-PBO) Four-neck flask containing 400 g of p-aminophenol, 234 g of paraformaldehyde, and 200 g of tetrahydrofuran (THF) The mixture was stirred and uniformly mixed, and then subjected to a polycondensation reaction at 40 ° C. for 1 hour, 50 ° C. for 1 hour, and 75 ° C. under reflux for 4 hours. After completion of the reaction, the product was dried under reduced pressure in a vacuum oven at 100 ° C. for 10 hours to obtain a p-aminophenol type polybenzoxazine resin.

(B) Synthesis of bisphenol A-type polybenzoxazine resin (Bis-A-PBO) 480 g of bisphenol A, 390 g of aniline, 270 g of paraformaldehyde, and 480 g of methyl ethyl ketone (MEK) were placed in a four-necked flask and stirred and mixed uniformly. The polycondensation reaction was carried out at 40 ° C. for 1 hour, 50 ° C. for 1 hour, and 80 ° C. for 5 hours. After completion of the reaction, the inside of the flask system was depressurized to perform dehydration and desolvation to obtain a bisphenol A type polybenzoxazine resin.

(C) Preparation of Binder for Friction Material Using the p-AP-PBO, Bis-A-PBO and phenol novolac resin [trade name “2075” manufactured by Cashew Co., Ltd.] obtained above, a mixer at the ratio shown in Table 1 To prepare a powdery binder for friction material.
The performance of this binder for friction material was evaluated. The results are shown in Table 2.

(2) Preparation of friction material sample Friction by mixing the powdery binder for friction material obtained in the above (1) and each component shown in Table 1 at a blending ratio shown in Table 1 by a mixer. A material forming material was prepared.

This friction material forming material was put into a preforming die and compressed at room temperature and 30 MPa to perform preforming. Next, the pre-formed body and a pressure plate pre-applied with an adhesive were set in a thermoforming mold, and heat compression molding was performed at 200 ° C., 50 MPa for 600 seconds. After thermoforming, heating was performed at 300 ° C. for 3 hours to obtain a friction material sample.
The performance of this friction material sample was evaluated. The results are shown in Table 2.

表１および表２から、下記のことが分かる。

From Tables 1 and 2, the following can be understood.

(1) In Comparative Example 2, the curing time of the resin is too long and molding is impossible. (2) No gas generation is observed even when a mixture of two types of polybenzoxazine resins is used. (3) In Examples 1 and 2 , by adding Bis-A-PBO to p-AP-PBO, the flowability of the resin is improved and the gel time is increased. In addition, the improved flowability of the resin increases the bending strength and Rockwell hardness of the friction material. (4) A mixture of p-AP-PBO and Bis-A-PBO is more excellent in wear resistance than a mixture of Bis-A-PBO and a phenol novolac type resin.

  The binder resin composition for a friction material of the present invention has good flowability and moldability, and can provide a friction material having improved quality stability, moldability, heat resistance, and wear resistance.

Claims (2)

(A) polybenzoxazine resin which is a polycondensation reaction product of p-aminophenol and formaldehyde , (B) 2,2-bis (4-hydroxyphenyl) propane , primary amines, and formaldehydes And a polybenzoxazine resin, which is a polycondensation reaction product, at a mass ratio of 95: 5 to 50:50. A brake friction material obtained using the binder resin composition for a friction material according to claim 1 .