JP2001151984A - Molding material for brake piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a suitable material for brake pistons and the like in place of ceramics and metals that have hitherto been used, which material is not impaired in the resistance to wear and that to brake fluids as compaired with the conventional phenolic molding material and can give a molding material excellent in mechanical strength at room temperature and in high temperature atmosphere. SOLUTION: There is provided a phenolic resin molding material which comprises, as essential components, (a) a high-molecular weight phenolic novolak resin having a weight average molecular weight of 50,000 or more where polystyrene is used as a reference material, (b) a phenolic resol resin having a weight average molecular weight less than 50,000 where polystyrene is used as a reference material, (c) a curing agent of hexamethylenetetramine, and (d) an inorganic filler and/or an organic filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a resin molding material for a disc brake piston which has excellent impact strength, static mechanical strength in normal temperature and high temperature atmospheres, good brake fluid resistance and good wear resistance. Things.

[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, the impact strength, the static mechanical strength in normal temperature and high temperature atmosphere, A molded article having excellent long-term heat resistance can be obtained, and a material suitable for a brake piston for a disc brake or the like can be obtained in place of a conventionally used ceramic or metal.

[0004]

According to the present invention, there are provided (a) a polystyrene as a reference substance having a weight average molecular weight of 50,
A high molecular weight phenol novolak resin having a molecular weight of at least 000 (hereinafter referred to as a high molecular weight novolak resin), and (b) a weight average molecular weight of 50,000 based on polystyrene as a reference substance.
Less than 0 resole type phenol resin (hereinafter, resole resin), (c) hexamethylenetetramine as a curing agent,
And (d) a phenolic resin molding material for a brake piston, comprising an inorganic filler and / or an organic filler as an essential component, wherein the phenolic resin is 10 to 50% by weight, It contains 2 to 10% by weight of methylenetetramine, 45 to 85% by weight of an inorganic filler and / or an organic filler, preferably a wollastonite / glass fiber / clay mixture, and a ratio of the resol resin to the total phenolic resin of 20 to 85%. It is characterized by being 40% by weight.

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.

The resole resin used in the present invention may be either a methylol type or a dimethylene ether type, but preferably has a weight average molecular weight of 50,000 or less. When the weight average molecular weight is 50,000 or more, the viscosity of the resin becomes too high, and it is difficult to take out the resin from the reaction vessel.
This is because the melt viscosity and the curing speed of the molding material increase, and the moldability deteriorates.

According to the present invention, a phenolic resin is used, in particular, by using (a) a high molecular weight novolak resin, and combining (a) the high molecular weight novolak resin with (b) a resole resin and (c) hexamethylenetetramine. Especially, it has excellent mechanical strength in normal temperature and high temperature atmosphere. If the content of the resole resin is less than 20% by weight, the static mechanical strength in a high-temperature atmosphere decreases, and the moldability also deteriorates. When the resole resin exceeds 40% by weight, the effect of improving the impact strength is reduced.

In the present invention, usually, hexamethylenetetramine (c) is 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, and conversely, the decomposition gas will cause molding failure. The mixing ratio of the inorganic filler (d) used in the present invention is not particularly limited, but is preferably 45 to 85% by weight based on the whole molding material. When the amount is less than 45% by weight, heat resistance and dimensional stability are impaired due to a large proportion of the phenolic resin. As the inorganic filler, any of glass fiber, calcium carbonate, talc, aluminum hydroxide and the like may be used, and it is not particularly limited. However, combination use of wollastonite, glass fiber, and clay is 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 wear resistance, a phenolic resin molding material excellent in 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 it is less than 10 μm, the workability at the time of forming a molding material is deteriorated, and if it is 300 μm or more, orientation tends to occur at the time of molding, resulting in an anisotropic difference in mechanical strength and dimensional accuracy. The amount of the glass fiber is preferably 5 to 35% by weight based on the whole molding material. If it is less than 5% by weight, the reinforcing effect is small, and
If the content is more than 10% by weight, an anisotropic difference in mechanical strength occurs due to the orientation of the fibers, or the abrasion resistance decreases. Further, the fiber length is preferably 0.5 to 5 mm. If the thickness is less than 0.5 mm, the reinforcing effect is small, and if it exceeds 5 mm, the productivity is deteriorated. The amount of the clay is 5 to 3 with respect to the entire molding material.
Preferably it is 5% by weight. If it is less than 5% by weight, the effect of imparting heat resistance is small, and if it exceeds 35% by weight, the wear resistance is reduced. Further, the clay used here is not limited to either the fired type or the unfired type.

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., heated and kneaded by a kneader, 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.

[0011]

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 1.

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 having the same diameter, heated to 180 ° C., and heated to 180 ° 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 removed and taken out on a cooling vat, and 20.0 kg of a high molecular weight novolak resin having a weight average molecular weight of 52,000 in terms of polystyrene was obtained.
I got Also, 100 kg of phenol (P) and 62 kg of 87% paraformaldehyde (F) (F / P molar ratio of 1.7)
0), 0.5 kg of zinc acetate was added to a reflux condenser stirrer,
Put into a 300 liter reactor equipped with a heating device, a vacuum dehydrator, and a resin circulation device with a static mixer,
The reflux reaction was performed for 4 hours. The phenol conversion at this point was 94%. Then, while dehydrating, 115 ° C
After heating to 115 ° C and maintaining the vacuum degree of 100 torr for 1 hour, the reaction was taken out and placed on a cooling vat.
117 kg of a dimethylene ether type resole resin (solid) having a weight average molecular weight of 22,000 in terms of polystyrene was obtained. This high molecular weight novolak resin having a weight average molecular weight of 52,000 and a dimethylene ether type resole having a weight average molecular weight of 22,000 were obtained. A resin, 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 put 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. The reaction was carried out in the same manner as in Example 1 to obtain 27.0 kg of a novolak-type phenol resin having a weight average molecular weight of 102,000 in terms of polystyrene. This weight average molecular weight 102,
2,000 high molecular weight novolak resin, a dimethylene ether type resole resin having a weight average molecular weight of 22,000 obtained by reacting with the same method as in Example 1, hexamethylenetetramine, a filler, a curing aid, a lubricant, and a colorant. And the like were blended in the ratio shown in Table 1, and were 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) and a dimethylene ether type resole resin having a weight average molecular weight of 22,000 obtained by reacting in the same manner as in Example 1, 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.

From the obtained molding material, a test piece was molded by transfer molding (molding conditions: temperature: 175 ° C., time: 3 minutes), and Charpy impact strength, bending strength at 25 ° C. and 200 ° C., brake fluid resistance, Heat resistance and abrasion resistance were evaluated. Table 1 shows the obtained results. (Note) Test method Impact strength: Bending strength according to JIS K7111 (normal temperature & 200 ° C): According to JIS K7203 Brake fluid resistance: Bending strength retention at room temperature after treatment in 200 ° C brake fluid for 500 hours, dimensional / weight change rate Heat resistance: Measured for bending strength retention and dimensional change at room temperature after treatment in a 250 ° C. atmosphere for 500 hours Abrasion resistance: By sliding wear test (partner material: S55C)

[0016]

[Table 1]

[0017]

As is evident from the results obtained by the above Examples and Comparative Examples, the molding material for a brake piston of the present invention is particularly superior in impact strength, room temperature and high temperature atmosphere to conventional phenolic resin molding materials. It has excellent medium mechanical strength and good abrasion resistance and brake fluid resistance.

Claims (4)

[Claims] 1. A phenolic resin molding material,
(A) a high molecular weight novolak type phenol resin having a weight average molecular weight of 50,000 or more when polystyrene is used as a reference substance, and (b) a resol type having a weight average molecular weight of less than 50,000 when polystyrene is used as a reference substance. A molding material for a brake piston, comprising a phenolic resin, (c) hexamethylenetetramine as a curing agent, and (d) an inorganic filler and / or an organic filler as essential components. 2. The compounding amount of a phenol resin is 10 to 50% by weight based on the whole molding material, and (c) 2 to 10% by weight of hexamethylenetetramine as a curing agent; and (d) an inorganic filler. 2. The composition according to claim 1, which contains 45 to 85% by weight.
The molding material for a brake piston according to the above. 3. The weight average molecular weight of (b) polystyrene as a reference substance is 50,0 based on the entire phenolic resin.
Resol type phenolic resin of less than 00 20 to 40% by weight
The molding material for a brake piston according to claim 1 or 2, comprising: 4. 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.