JP2001131387A - Molding material for brake piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding material which can have excellent mechanical strengths in high temperature atmospheres in comparison with conventional phenolic molding materials without deteriorating abrasion resistance and brake fluid resistance and is suitable for bake pistons and the like instead of ceramics and metals which have been used. SOLUTION: This phenolic resin molding material containing (a) a high mol.wt. novolak phenol resin having a weight-average mol.wt. of >=50,000 based on polystyrene, (b) hexamethylenetetramine as a curing agent, and (c) an inorganic filler and/or an organic filler as essential components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention provides a phenolic resin molding material for a disc brake piston, which has excellent mechanical strength in a high-temperature atmosphere, good brake fluid resistance and good wear resistance.

[0002]

2. Description of the Related Art Conventionally, brake pistons for disc brakes are required to have heat resistance, wear resistance, brake fluid resistance, mechanical strength in a high-temperature atmosphere, and the like from the usage environment, and ceramic and metal products have been used. However, ceramic and metal products have problems such as heavy weight, time-consuming processing, and high cost. On the other hand, phenolic resin is excellent among thermosetting resins in various points such as heat resistance, chemical resistance, mechanical strength, etc. Especially for molding materials, phenolic resin molding material in which metal parts are reinforced with glass fiber Since the cost can be significantly reduced by substituting the metal material, the demand as an alternative material for various metal parts such as the automobile field is increasing. However, in many cases, conventional molding materials for brake pistons contain glass fiber or silica in order to impart a high degree of heat resistance, but have disadvantages in that the cost is high and the wear resistance is significantly reduced.

[0003]

According to the present invention, it is possible to obtain a molding material having excellent mechanical strength in a high-temperature atmosphere without impairing abrasion resistance and brake fluid resistance as compared with conventional phenol molding materials. Thus, a material suitable for a brake piston or the like can be obtained in place of ceramic or metal conventionally used.

[0004]

According to the present invention, there are provided (a) a polystyrene as a reference substance having a weight average molecular weight of 50,
It contains a high molecular weight novolak phenol resin having a molecular weight of 000 or more (hereinafter, high molecular weight novolak resin), (b) hexamethylenetetramine as a curing agent, and (c) an inorganic filler and / or an organic filler as essential components. Phenolic resin molding material for brake pistons. Preferably, the weight average molecular weight based on (a) polystyrene as a reference substance is 50,
(B) hexamethylenetetramine 2 as a curing agent;
-10% by weight, and (c) 45-75% by weight of inorganic filler
Is a molding material for a brake piston.

The high molecular weight novolak resin (a) used in the present invention is a polycondensate of a trifunctional phenol and formaldehyde, and has a weight average molecular weight of 50,000 or more when polystyrene is used as a reference substance. In order to make the molding material quick-curing, it is preferable that the methylene bond at the ortho-ortho position relative to the phenolic hydroxyl group is 60% or more of all methylene bonds. Further, from the viewpoint of workability in forming a molding material, the weight average molecular weight is 50,000.
~ 200,000 are preferred. In the present invention, if the weight average molecular weight of the high molecular weight novolak resin (a) is less than 50,000, the effect of improving strength in a high-temperature atmosphere cannot be sufficiently obtained. Furthermore, it is preferable to mix 15 to 45% by weight of a high molecular weight novolak resin with respect to the whole molding material. If the amount is less than 15% by weight, the effect of improving the strength in a high-temperature atmosphere will be small, and if it exceeds 45% by weight, the viscosity of the molding material at the time of melting will be high, and the moldability may be reduced.

In the present invention, hexamethylenetetramine (c) is generally used as a curing agent in an amount of 2 to 10% by weight based on the whole molding material. If the amount is less than 2% by weight, the curing will be insufficient, and even if the amount exceeds 10% by weight, the curability will not be improved any more.

The proportion of the inorganic filler (c) used in the present invention is not particularly limited, but is preferably 45 to 75% by weight based on the whole molding material. When the amount of the inorganic filler is less than 45% by weight, heat resistance and dimensional stability are impaired due to a large proportion of the phenolic resin. Tends to occur. As the inorganic filler (c), any of glass fiber, calcium carbonate, talc, aluminum hydroxide and the like may be used, and it is not particularly limited. preferable.
Since the wollastonite used here is a needle-like crystal, it has excellent wear resistance as compared with glass fiber or silica, and can be reinforced without impairing the wear resistance even in a large amount. Clay is also excellent in heat resistance and chemical resistance. Further, by blending glass fibers within a range that does not affect the wear resistance, a phenol resin molding material having excellent mechanical strength, wear resistance, brake fluid resistance and heat resistance in a high-temperature atmosphere can be obtained. The amount of wollastonite is preferably 35 to 65% by weight based on the whole molding material. If it is less than 35% by weight, the wear resistance and dimensional accuracy may be insufficient, and if it exceeds 65% by weight, the workability at the time of materialization deteriorates. The particle size of wollastonite is preferably from 10 to 300 μm. If the particle size is less than 10 μm, the workability at the time of forming a molding material is deteriorated. The compounding amount of the clay is preferably 5 to 35% by weight based on the whole molding material. If the amount is less than 5% by weight, the effect of imparting heat resistance is small, and if it exceeds 35% by weight, the abrasion resistance is reduced. Further, the clay used here is not limited to either the fired type or the unfired type. The amount of glass fiber is 5 to 5
Preferably it is 35% by weight. If the compounding amount is less than 5% by weight, the reinforcing effect is small, and if it exceeds 35% by weight, an anisotropic difference in mechanical strength occurs due to the orientation of the fiber or the abrasion resistance decreases. The fiber length of the glass fiber is preferably 0.5 to 5 mm. If the fiber length is less than 0.5 mm, the reinforcing effect is small, and if it exceeds 5 mm, the productivity is reduced.

If necessary, an organic filler may be used in addition to the inorganic filler. The organic filler is not particularly limited, but aramid fiber or the like is preferably used.

In the present invention, in order to obtain a molding material, the mixture is uniformly mixed with a curing aid, another filler, a releasing agent, a pigment, etc., kneaded by heating in a kneader, and then cooled and pulverized. Is common. As the kneader, a twin-screw roll, a kneader, a twin-screw extruder or the like may be used alone or in combination. Furthermore, granulation into pellets may be performed using a twin-screw extruder, a single-screw extruder, or the like, or granulation may be performed using a high-speed rotary mixer such as a Henschel mixer having rotating blades.

[0010]

The present invention will be described below with reference to examples and comparative examples. In each case, a homogeneous mixture having the composition shown in Table 1 was kneaded with a heated biaxial roll, cooled, and pulverized to obtain a desired phenolic resin molding material. In the measurement of the weight average molecular weight in the present invention, a gel permeation chromatography (GPC) method using an ultraviolet absorption spectrum detector using polystyrene as a standard substance was used. Further, various test pieces were prepared by transfer molding using the obtained molding materials, and the evaluation results are shown in Table 2.

EXAMPLE 1 22.0 kg of phenol was placed in a 50 L high-pressure reactor having a heat exchanger, a heating device and a two-stage turbine type stirring blade of the same diameter, heated to 180 ° C., and heated to 0 ° C. with nitrogen gas. .8
After pressurizing to MPa, the formic acid content was previously reduced to 50P by ion exchange resin treatment with a diaphragm type high pressure metering pump.
13.3Kg of 40% formalin reduced to PM to 60
The mixture was added sequentially from the lower part of the reactor over a period of minutes to cause an addition condensation reaction. The temperature and the addition rate of the jacket of the reactor were adjusted so that the reaction temperature during this time was 180 to 200 ° C. After completion of the addition, the temperature was maintained for 5 minutes, and after confirming that self-heating did not occur, a dehydration reaction was performed while returning to normal pressure over 30 minutes via a heat exchanger while heating to further maintain the temperature at 220 to 230 ° C. Was. Thereafter, the pressure was reduced to 1.3 KPa, and the unreacted phenol was removed for 30 minutes. The unreacted phenol was taken out on a cooling vat, and a novolak-type phenol resin having a weight average molecular weight of 52,000 in terms of polystyrene 20.0%
Kg was obtained. The novolak resin having a weight average molecular weight of 52,000, hexamethylenetetramine, a filler, a curing aid, a lubricant, a colorant, and the like were blended in the proportions shown in Table 1 and melt-kneaded with a biaxial roll to obtain a molding material. .

Example 2 20.0 kg of phenol was placed in a reactor, 8.9 kg of 88% paraformaldehyde was used as aldehydes, and this paraformaldehyde was previously mixed with 8.0 kg of phenol to form a suspension. Except that the liquid was supplied from the lower part of the reactor with a plunger-type high-pressure metering pump, unreacted phenol was not removed under reduced pressure, and the reaction temperature was 200 to 220 ° C. 27.0 Kg of a novolak-type phenol resin having a weight average molecular weight of 102,000 in terms of polystyrene reacted in the same manner as in Example 1 was obtained. This weight average molecular weight 10
2,000 novolak resins, hexamethylenetetramine, fillers, curing aids, lubricants, coloring agents, and the like were blended in the proportions shown in Table 1 and melt-kneaded with a biaxial roll to obtain a molding material.

Comparative Example 1 A novolak resin having a weight average molecular weight of 14,000 in terms of polystyrene (PR-5073 manufactured by Sumitomo Durez Co., Ltd.)
1), filler, hexamethylenetetramine, curing aid,
A lubricant, a colorant, and the like were blended in the proportions shown in Table 1 and melt-kneaded with a biaxial roll to obtain a molding material.

From the obtained molding material, test specimens were molded by transfer molding (molding conditions: temperature: 175 ° C., time: 3 minutes), and flexural strength at 25 ° C. and 200 ° C., brake fluid resistance, heat resistance and resistance Abrasion was evaluated. Table 1 shows the obtained results. (Note) Test method Bending strength (normal temperature & 200 ° C): According to JIS K7203 Brake fluid resistance: Measured the flexural strength retention rate and dimensional / weight change rate at normal temperature after treatment in 200 ° C brake fluid for 500 hours Heat resistance: 250 Measurement of bending strength retention and dimensional change at room temperature after treatment in a 500 ° C. atmosphere for 500 hours Abrasion resistance: By sliding wear test (partner material: S55C)

[0015]

[Table 1]

[0016]

As is clear from the results obtained by the above Examples and Comparative Examples, the molding material for a brake piston of the present invention is superior to the conventional phenolic resin molding material in the mechanical strength particularly in a high-temperature atmosphere. It is also excellent in wear resistance and brake fluid resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16D 65/20 F16D 65/20 B F16J 1/01 F16J 1/01 F term (Reference) 3J044 AA02 AA08 AA20 BA06 BC01 DA12 3J058 AA41 BA32 BA41 BA46 EA13 4J002 CC041 DE147 DE237 DJ007 DJ039 DJ047 DL008 EN046 FA048 FD017 FD018 FD019 FD146 GM03

Claims (3)

[Claims] 1. A phenolic resin molding material,
(A) a high molecular weight novolak phenol resin having a weight average molecular weight of 50,000 or more when polystyrene is used as a reference substance; (b) hexamethylenetetramine as a curing agent; and (c) an inorganic filler and / or an organic filler. Material for brake piston, characterized by containing as an essential component 2. The weight average molecular weight of the whole molding material is (a) 50,0, based on polystyrene as a reference substance.
High molecular weight novolak type phenol resin having a molecular weight of 00 or more 1
5 to 45% by weight, (b) 2 to 10% by weight of hexamethylenetetramine as a curing agent, and (c) 45 to 45% of an inorganic filler.
2. The molding material for a brake piston according to claim 1, comprising 75% by weight. 3. The compounding ratio of each component of the inorganic filler is 35 to 65% by weight of wollastonite, 5 to 35% by weight of glass fiber, and 5 to 35% by weight of clay based on the whole molding material.
Or a molding material for a brake piston according to 2.