JP2000081063A - Raw friction material and friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with water content control of a resin in manufacturing and consideration for humidity conditions at a manufacturing site by using a phenol resin mixed with microcapsules containing hexamethylenetetramine therein as a binder, in a raw friction material consisting of a fiber base material, a binder, and a friction adjustment material. SOLUTION: In manufacturing a friction material, a phenol resin and hexamethylenetetramine are used as a thermosetting resin for a binder and a hardener respectively and the hexamethylenetetramine is mixed with the resin in a state that it is put in microcapsules so that the capsules are broken in thermosetting process to emit the hexamethylenetetramine as a gas. The capsule manufacturing method is that hexamethylenetetramine power is dispersed in cashew oil as a film formation material, its suspension 1 is fed to a drying chamber 2, sprayed in its upper part as droplets from a dispersing device 3, dried in a hot air 5 from a hot air generator 4, and sedimented in a separator 6 so that the capsule 7 coated with a cashew resin film is provided. This constitution can provide a friction material with a high rigidity and sufficiently hardened 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 used for a friction material for a brake of an automobile, a railway vehicle, an industrial machine, and the like, and particularly to a friction material which is not affected by a surrounding atmosphere during manufacturing. TECHNICAL FIELD The present invention relates to a friction material and a friction material capable of stably producing a friction material even when stagnation occurs during production.

[0002]

2. Description of the Related Art Hexamethylenetetramine is mixed (added) as a curing agent in a novolak-type phenol resin currently used as a binder in a friction material. Hexamine is easily affected by moisture, and causes decomposition and chemical change by moisture. Therefore, there is a problem in controlling the moisture content of the phenol resin during the production of the friction material. In particular, when granulating the friction material stirrer, water or ethanol is used as a solvent for dissolving the binder for granulation, and hexamethylenetetramine which is a curing agent in the phenol resin is decomposed by these. As a result, the function as a curing agent may be reduced.

[0003]

However, hexamethylenetetramine added as a curing agent is easily affected by moisture, and is decomposed or changes in chemical structure by moisture. For this reason, when manufacturing friction materials,
Care had to be taken to control the water content of the phenolic resin. The present invention provides a method of manufacturing a friction material using a phenolic resin as a binder, particularly a novolak type phenolic resin, without having to be aware of the moisture management of the phenolic resin and the humidity conditions of the atmosphere at the manufacturing site. It is an object of the present invention to provide a material for a friction material that can be used. An object of the present invention is to reduce the influence of moisture during the production of a friction material using a phenol resin as a binder. Also,
An object of the present invention is to reduce the influence of water and other binder solvents on a phenol resin during granulation of a friction material material. SUMMARY OF THE INVENTION An object of the present invention is to reduce the effect of moisture (spent hexamethylenetetramine) due to stagnation of a friction material.

[0004]

The present invention has solved the above-mentioned problems by the following means. (1) A friction material comprising a fiber base material, a binder, and a friction modifier, wherein a phenol resin containing microcapsules containing hexamethylenetetramine therein is used as the binder. (2) After preforming a mixture of a fiber base material, a binder and a friction modifier into a predetermined shape, and then thermoforming the preformed body, hexamethylenetetramine is used as a binder in the friction material. A friction material obtained by using a phenol resin containing microcapsules contained therein.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the production of a friction material, a thermosetting resin is usually used as a binder, but the present invention relates to a case where a phenol resin is used as the thermosetting resin. As described above, hexamethylenetetramine is used as a curing agent.In this case, the hexamethylenetetramine is not directly mixed with the phenol resin, but is mixed with the phenol resin in a microcapsule. The microcapsules are broken during the thermoforming process so that hexamethylenetetramine is released as a gas.
For this reason, it is necessary to consider the addition amount of hexamethylenetetramine contained in the microcapsules so that the curing reaction of the phenol resin proceeds sufficiently during the thermoforming step.

[0006] Since this hexamethylenetetramine is contained in microcapsules, it is stored in air in a state of being mixed with a phenolic resin, or is mixed with phenolic resin and other raw materials of a friction material. Even when the phenol resin absorbs moisture when stored inside, that is, when the phenol resin absorbs moisture for a certain period of time, the moisture does not act on hexamethylenetetramine to decompose hexamethylenetetramine.

[0007] Microcapsules containing hexamethylenetetramine can be produced by a known microcapsule manufacturing method. Hexamethylenetetramine is prepared by dissolving a film-forming substance in a non-aqueous solvent so as not to come into contact with water. A method is used in which fine particles of hexamethylenetetramine coated with a film-forming substance are produced by dispersing the dispersion liquid into fine droplets and evaporating and removing the solvent from the droplets. For example, hexamethylenetetramine powder is dispersed in cashew oil as a film-forming substance, and the suspension 1 is sent to a drying chamber 2 as shown in FIG. Sprayed as droplets from the disperser 3, dried in hot air 5 from the hot air generator 4, sent to the separator 6 together with the hot air 5, and settled in the separator 6, thereby being coated with a cashew resin film. Microcapsules 7 can be obtained. Rubber dust other than cashew resin can be used as the film-forming substance. Separator 6
A blower 8 is provided at an upper portion of the gas supply port, and discharges the gas 9 after being separated to the outside. The size of the microcapsules is usually in the range of several nanometers to several millimeters, but in this case, it is not necessary to be so small, but if it is too large, there is a concern that many pores will be formed in the friction material. Be unaffected.

As one example of a conventionally known method for producing a friction material, a process for producing a disc pad for a disc brake will be described. That is, in the manufacturing process of a disc pad for a disc brake, a pressure plate formed into a predetermined shape by a sheet metal press, subjected to a degreasing process and a primer process, and coated with an adhesive, is heat-resistant organic fiber or inorganic fiber. , A fiber material such as a metal fiber, and a powder material such as an inorganic / organic filler, a friction modifier and a thermosetting resin binder (a phenol resin in the present invention) are blended, and the raw material sufficiently homogenized by stirring is cooled to room temperature. In a thermoforming step, the preformed body produced by molding (preliminary molding) at a predetermined pressure is thermoformed at a predetermined temperature and pressure to fix the two members together, after-cure, and finally It comprises a step of performing a finishing treatment.

A conventional thermoforming process will be described with reference to the drawings. As shown in FIG.
A thermoforming apparatus 10 is used in which a thermoforming mold 14 including a lower mold 13 is provided between an upper heating plate 15 having a heater 17 and a lower heating plate 16. A preformed body 18 composed of a friction material and a pressure plate is put between the upper mold 11 and the lower mold 13, a heater 17 is energized, and the preformed body 18 is heated by the heating plate 15 and the heating plate 16. To do. Thermoforming is performed by applying pressure from above and below the heating plate 15 and the heating plate 16 so that heating and pressing are performed simultaneously. A temperature sensor 19 is provided on the lower mold 13 and the like,
Control the heating temperature.

As the material of the friction material, those conventionally used can be used. Examples of the organic fibers include aromatic polyamide fibers (eg, aramid fibers) and acrylic fibers. Examples of the inorganic fibers include ceramic fibers such as potassium titanate fibers and alumina fibers, glass fibers, carbon fibers, and rock wool. Examples of the metal fibers include copper fibers and steel fibers. Examples of the inorganic filler include scaly inorganic substances such as vermiculite and mica, and particles such as barium sulfate and calcium carbonate. Examples of the organic filler include synthetic rubber and cashew resin.
As the thermosetting resin binder, a phenol resin (including various modified phenol resins such as straight phenol resin and rubber) is used in the present invention, but if necessary, other resins such as melamine resin, polyimide resin, BT resin, etc. May be added and used in combination. Examples of the friction modifier include metal oxides such as alumina and silica, magnesia, zirconia, chromium oxide, and quartz. Examples of the solid lubricant include graphite and molybdenum disulfide.

[0011]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

[Production Example of Microcapsule]-Method for producing microcapsule (spray drying method)-A microcapsule was prepared using cashew resin as a film material. Cashew oil, formaldehyde (HCHO) 3
0: 1 (weight ratio). With respect to the powdered hexamethylenetetramine compound, (mixture of): (hexamethylenetetramine)
= 5: 2 (weight ratio), and stirred so that the hexamethylenetetramine powder is well dispersed in the mixture. The mixture (suspension) is spray-dried with a spray dryer (B) and the formulation is cured. The conditions at that time are in a nitrogen atmosphere at 300 ° C. Nitrogen is used to prevent oxidation and decomposition of hexamethylenetetramine. Thus, hexamethylenetetramine microcapsules (C) using cashew dust as a film material are prepared.

Example 1 The microencapsulated product prepared according to the above production example was used.
Novola with hexamethylenetetramine 10 wt%
Phenolic resin, together with other friction materials,
Mix and stir as shown in the table. Preform at room temperature. Is placed in a thermoforming mold and heated at a temperature of 150
° C, surface pressure 550kg / cm ^TwoFriction material with 6 minutes pressurization time
Is molded.

[0014]

[Table 1]

Example 2 Influence of stagnation (compared with Comparative Example 2)
Comparison) Hexamethylenetetraminema prepared by Production Example
Novolak-type ferrite containing 10% by weight of microcapsules
Nol resin is absorbed at a temperature of 25 ° C and a humidity of 70% (summer
(Station conditions) in a constant temperature and humidity chamber for 30 days. Novolac-type phenolic resin
Is blended and stirred together with the friction material raw materials as shown in Table 1. Preform at room temperature. Is placed in a thermoforming mold and heated at a temperature of 150
° C, surface pressure 550kg / cm ^TwoFriction material with 6 minutes pressurization time
Is molded.

Example 3 Granulation (Compared with Comparative Example 3) A novolak-type phenol resin blended with 10% by weight of hexamethylenetetramine microcapsules prepared according to the production example was mixed with other friction material materials as shown in Table 1. Mix and stir. Is stirred by a high-speed rotary stirrer using a 4 wt% aqueous solution of polyvinyl alcohol as a binder. Is put into a thermoforming mold, and a friction material is formed at a temperature of 150 ° C., a surface pressure of 550 kg / cm ² and a pressing time of 6 minutes.

Comparative Example 1 (Normal Production Method) A novolak-type phenol resin containing 10% by weight of hexamethylenetetramine is mixed and stirred with other friction material materials as shown in Table 1. Is preformed at room temperature. Is placed in a thermoforming mold and heated at a temperature of 150
C., a surface pressure of 550 kg / cm ² , and a pressing time of 6 minutes to form a friction material. Comparative Example 2 Influence of stagnation (compared with Example 2) A novolak-type phenol resin containing 10% by weight of hexamethylenetetramine was absorbed in a constant temperature and humidity chamber of 25 ° C. and 70% humidity (summer conditions) for absorbing moisture. Stagnate for days. Is mixed and stirred with other friction material materials as shown in Table 1. Is preformed at room temperature. Is placed in a thermoforming mold and heated at a temperature of 150
C., a surface pressure of 550 kg / cm ² , and a pressing time of 6 minutes to form a friction material.

Comparative Example 3 Granulation (Compared with Example 3)
The novolak-type phenol resin blended with wt% is blended and stirred with other friction material raw materials as shown in Table 1. Is stirred by a high-speed rotary stirrer using a 4 wt% aqueous solution of polyvinyl alcohol as a binder. Is poured into a thermoforming mold, and molded into a friction material at a temperature of 150 ° C., a surface pressure of 550 kg / cm ² and a pressing time of 6 minutes.

Test Examples The friction materials manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 were examined for their hardness, acetone extraction, and the like. This test was conducted to determine whether the friction material obtained by the present invention reached a practical level. Table 2 shows the test results. According to the test results, Example 1
Was the same level as Comparative Example 1 in hardness and acetone extraction. In other words, it can be determined that Example 1 has been cured to the same level as that obtained by mixing hexamethimementeramine which is not contained in microcapsules (Comparative Example 1).

In Example 2 and Comparative Example 2, a friction material was manufactured by blending a stagnant and moisture-absorbing resin under the same conditions. On the other hand, the hardness of Comparative Example 2 was lower than that of Comparative Example 1, and the amount of acetone extracted was large.
In other words, in Comparative Example 2, the phenol resin was insufficiently cured,
In Example 2, it can be said that the resin is cured to the same degree as Comparative Example 1. From these results, it is understood that the present invention can prevent decomposition and chemical change of hexamethimetetramine due to stagnation of resin and moisture absorption. Example 3 and Comparative Example 3 examine how water (polyvinyl alcohol aqueous solution) used at the time of granulation has an effect on hexamethymentetetramine. In Example 3, it can be said that it is cured to the same degree as Comparative Example 1. Comparative Example 3 was lower in hardness than Comparative Example 1, and the amount of acetone extracted was larger. That is, in Comparative Example 2, the phenol resin was insufficiently cured. From these results, it can be seen that the present invention can prevent the decomposition and chemical change of hexamethimetetramine even when the friction material is granulated using water.

[0021]

[Table 2]

[0022]

According to the present invention, since the hardening agent hexamethylenetetramine is protected by the microcapsules, the phenol resin stagnation causes a change with time (decomposition and chemical change of hexamethylenetetramine) and a solvent during granulation. Hardly affected by (water, alcohol) (decomposition and chemical change of hexamethylenetetramine). For this reason,
In the production of friction materials using phenolic resin as a binder,
Even if the phenol resin stagnates, a friction material having high hardness and sufficiently hardened phenol resin can be obtained.

[Brief description of the drawings]

FIG. 1 shows a schematic diagram of an apparatus for producing microcapsules of hexamethylenetetramine.

FIG. 2 is a longitudinal sectional view of a thermoforming apparatus used in a thermoforming method of a friction material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suspension 2 Drying room 3 Sprayer 4 Hot air generator 5 Hot air 6 Separator 7 Microcapsule 8 Blower 9 Exhaust gas 10 Thermoforming device 11 Upper mold 12 Medium mold 13 Lower mold 14 Thermoforming mold 15 Heating plate 16 Heating plate 17 Heater 18 Preform 19 Temperature sensor

Continued on front page F term (reference) 3J058 BA61 EA31 FA01 FA11 FA21 GA54 GA55 GA64 GA65 GA68 GA92 4J002 AC003 BG002 CC031 CC185 CL062 CM045 DA017 DA029 DA077 DA087 DE079 DE099 DE147 DE149 DE187 DE238 DG029 DG048 DJ019 DJ047 FB088 GN00 HA05

Claims (2)

[Claims] 1. A friction material comprising a fiber base material, a binder, and a friction modifier, wherein a phenol resin containing microcapsules containing hexamethylenetetramine therein is used as the binder. . 2. A friction material obtained by preforming a mixture of a fibrous base material, a binder and a friction modifier in a predetermined shape, and then thermoforming the preform, wherein hexamethylene is internally contained as a binder. A friction material obtained by using a phenol resin containing microcapsules containing tetramine.