JPH0762330A - Composition for friction material and production of friction material therefrom - Google Patents

Abstract

PURPOSE:To produce a composition which contains water as the solvent, can give a friction material of improved friction performance in improved safety and working environment and to produce a friction material therefrom. CONSTITUTION:This composition comprises a fibrous material as the base material, a friction modifier, a binder, a dispersant, a thickener, a flexibilizer, a surfactant and a water solvent. The production process comprises applying a mixture obtained by dispersing a friction modifier in an aqueous solution of a binder, a dispersant, a flexibilizer and a surfactant to a fibrous material as a base material and molding the base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material composition used for power transmission and braking of automobiles and a method for producing a friction material using the same.

[0002]

Brake linings, disc pads and clutch facings are generally used as friction materials for automobiles and industrial applications. Conventionally, asbestos (asbestos) has been used as a base material, but development of non-asbestos friction materials is desired due to the problem of asbestos pollution. In recent years, the use of organic solvents has been reconsidered in view of the global environment, work environment, safety during production, and the like. At present, friction materials using glass fibers, carbon fibers, aromatic polyamide fibers, rock wool, ceramic fibers, various steel fibers and the like have been developed as substitutes for asbestos, and some of them have been used.

[0003]

However, since these materials have higher elasticity and hardness and lower heat resistance than asbestos, various friction modifiers have been added to improve them. In order to uniformly adhere to the material, a mixture in which a friction modifier is dispersed in a solution prepared by dissolving a composition of rubber and resin in an organic solvent is generally used. In recent years, halogen-based organic solvents are often used as organic solvents in order to prevent combustion and explosion during manufacturing work.However, this organic solvent is regulated in terms of ozone layer destruction, groundwater pollution, etc., Its use has come to be restricted or banned and alternative materials are required. Although it is possible to use water to deal with this, it is difficult to uniformly apply the mixture to the base material with only water, and the friction modifier or binder may be biased or the materials used may be restricted. Therefore, it is difficult to obtain a high-performance friction material.

As a method for producing a friction material which uses an asbestos substitute and does not use an organic solvent at the time of production, there is a method by a papermaking method or a molding method in which a fibrous material of a base material is fibrous. JP-A-61-63797, JP-A-3-210338, etc.). Since this method is a method of manufacturing by mixing a fibrous substance and an admixture (a type of molding method), mechanical strength deterioration and quality variation are likely to occur. In addition, as a method for producing a friction material using a water solvent, there is a method in which a friction modifier is surface-treated so as to be easily attached to a base material (JP-A-3-61732). I can't do it. The present invention solves the above-mentioned problems, can improve the safety and environment at the time of production, and has a friction material composition using water as a solvent, which can improve friction performance, and a method for producing a friction material using this composition. It is provided.

[0005]

The present invention is directed to a friction material composition and a binder comprising a fibrous base material, a friction modifier, a binder, a dispersant, a flexibilizer, a surfactant and an aqueous solvent. The present invention relates to a method for producing a friction material, which comprises applying a mixture of a friction modifier dispersed in an aqueous solution of a dispersant, a flexibilizer and a surfactant to a base material of a fibrous substance and molding the mixture.

In the present invention, the base material of the fibrous material is an inorganic fiber such as glass fiber, carbon fiber, rock wool or ceramic fiber, metal wire such as iron wire, phenol resin fiber, aromatic polyamide resin fiber or the like. One or more kinds of fiber etc. are used, there is no particular limitation, but it is easy to process,
Moreover, since it is cheap, it is preferable to use glass fiber as the main component. The form of the fiber is not particularly limited, such as chopped filament, roving, sheet and mat. When glass fiber is used, the amount thereof is 25 to the friction material in terms of balance of friction characteristics and ease of control.
It is preferable to contain 60% by weight, 30 to 55% by weight
It is more preferable to include it.

Known friction modifiers include known calcium carbonate, magnesium carbonate, zinc oxide, barium sulfate, clay, talc, carbon black, graphite, alumina, mica, fluorite, zirconia, hematite, silica, antimony sulfide, and iron sulfide. Powders of inorganic substances such as molybdenum sulfide and sulfur, powders of metals such as iron, lead and copper, powders of organic substances such as cashew dust, rubber dust, powders of various resin cured products, calcium silicate short fibers and the like are used. The amount of the friction modifier depends on the amount of the glass fibers described above, but it is preferably 10 to 40% by weight based on the friction material. As the binder, a thermosetting resin composition and a rubber latex and / or a rubber solution are used. Examples of the thermosetting resin composition include phenol resin, methylated melamine resin, melamine resin, urea resin, polyamideimide resin, polyimide resin, and epoxy resin. Of these, phenol resins and methylated melamine resins are preferred. The amount of the resin is 10 to 10 in terms of solid content relative to the friction material in terms of the binding force between the fibrous base material and the friction modifier and the relationship between the friction coefficient and the wear rate.
It is preferably 50% by weight. A crosslinkable rubber latex is used as the rubber latex. Examples of latex rubber include natural rubber, chloroprene rubber, nitrile butadiene rubber, acrylic rubber, and styrene butadiene rubber. The rubber solution is a solid rubber such as NBR dissolved in an organic solvent. The amount of the rubber latex or the rubber solution is 5 to 2 with respect to the friction material obtained by the solid content.
It is preferably 0% by weight.

A water-soluble polymer resin is mainly used as the dispersant. As the resin, methyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, polyvinyl ethyl ether, etc., which have a thickening effect, are generally used. From the viewpoint of friction coefficient and mechanical strength, the amount of the dispersant is preferably 10% by weight or less based on the friction material, and is preferably 20% by weight or less based on the solid content of the admixture.
More preferably, it is 10% by weight or less based on the solid content of the mixture.

As the flexibilizer, a substance that is compatible with the water-soluble polymer resin and does not affect the frictional properties is preferable. For example, glycols are suitable. The flexibilizing agent is for facilitating the molding processability of the prepreg coated with the admixture, and is scattered during the molding and post-curing so that it does not exist in the friction material of the actual machine as much as possible. preferable. As a preferable material, lower glycols such as ethylene glycol, propylene glycol and diethylene glycol are preferable. The amount of the flexibilizer depends on the kind of the dispersant, but is preferably 80 to 20% by weight based on the dispersant. The surfactant is used for enhancing the dispersion effect of the friction modifier and the stability of the dispersant, and is not particularly limited, but anionic surfactant or nonionic surfactant is preferably used as an effective surfactant. More preferably, it is a nonionic polyethylene glycol phenyl ether type. The amount of surfactant is usually preferably 1-2% by weight, based on the admixture.

To obtain the friction material, the following method is used.
A flexible agent and a surfactant are added to an aqueous solution of a dispersant, and the mixture is thoroughly stirred to form a uniform solution, and powder of a thermosetting resin is added to the solution to disperse and dissolve it. Then, a friction modifier is added to prepare a uniform dispersion, and rubber latex and water or a rubber solution for adjusting the solid content are further added and mixed with stirring to obtain a mixture.
As the binder, it is not necessary to use all of the thermosetting resin composition, the rubber latex and the rubber solution, and either one may be used. The above mixture is uniformly applied to a fiber base material such as glass roving to give a coated product. The volatile components of the coated product are removed by drying or the like, and then rolled up in a ring to obtain a preform. The obtained annular body is placed in a mold or the like for thermocompression molding, and then the molded product is subjected to heat treatment under predetermined heating conditions to cure the resin. The ratio of the fiber base material to the admixture in the coated product is 30 / by weight of the fiber base material / admixture (solid content).
70-60 / 40 is preferable. If the adhering amount of the admixture is too large, the mechanical strength of the friction material decreases. On the other hand, if the adhesion amount is small, the friction characteristics become unstable, the wear increases, and the strength decreases due to the change of friction with time. The method for applying the mixture is not particularly limited, but dipping and impregnation is preferable. The method of removing water as a solvent is not particularly limited, and care should be taken not to cure the resin component in the mixture.

[0011]

EXAMPLES Examples of the present invention will be described below. The following materials were used in the examples and comparative examples. The base material of the fibrous material is glass roving (made by Fuji Fiber Glass, FER23
10 and 2.3 g / m) were used. The friction modifier is zinc oxide (Wako Pure Chemical Industries, for chemicals) 2% by weight, barium sulfate (Sakai Chemical Co., BC) 40% by weight, carbon black (Mitsubishi Kasei, # 44) 6% by weight, graphite (UK ABRAMWELL
3% by weight, silica powder (Tatsumori, Crystallite) 10
% By weight, calcium silicate short fibers (manufactured by NYCO, USA, trade name Wollastonite) 20% by weight, cashew modified friction dust (manufactured by Cashew Co., Ltd., WD-1350) 14% by weight, and finely divided sulfur (manufactured by Hosoi Chemical Co., Ltd.) 5% by weight. Was uniformly mixed with a V-type blender.

The thermosetting resin composition comprises 50% by weight of a novolac phenol resin (manufactured by Hitachi Chemical Co., Ltd., HD-491, containing 7% by weight of hexamine) and 50% by weight of a methylated melamine resin (manufactured by Nippon Carbide, S-260). Was mixed with a V-type blender to make it uniform. Rubber latex is NBR latex (manufactured by Zeon Corporation, LX513,
The solid content of 45% by weight) and the rubber solution were prepared by adjusting NBR solid rubber (Nippol 1041 manufactured by Nippon Zeon Co., Ltd.) to a solution of 15% by weight with respective solvents of MEK (methyl ethyl ketone) and trichlene (trichloroethylene). The dispersant is polyvinyl alcohol (manufactured by Wako Pure Chemical Industries, degree of polymerization 1500).
10 wt% aqueous solution was used. Ethylene glycol (manufactured by Wako Pure Chemical Industries, for chemicals) was used as the flexible agent. As the surfactant, polyethylene glycol nonylphenol (Emulgen 910, manufactured by Kao Kagaku) was used. As the solvent, ion-exchanged water as water, MEK, and first-class reagent manufactured by Wako Pure Chemical Industries as trichlene were used.

The above materials were mixed in the following order according to the blending ratio shown in Table 1 to prepare a mixture. That is, in the case of the example, the flexing agent and the surfactant were added to the polyvinyl alcohol aqueous solution of the dispersant, and the mixture was well stirred to obtain a uniform solution, and the powder of the thermosetting resin was added thereto. A solution of a thermosetting resin composition was prepared, and a dispersant (Comparative Examples 3 and 4) and a flexibilizer (Comparative Example 5) were added or left as they were (other Comparative Examples), and in each case, a high-speed mixer was used. The mixture was stirred and mixed to obtain a uniform solution. Then, a friction modifier was added and stirred to uniformly disperse. After that, the stirring was changed to propeller stirring, and rubber latex or a rubber solution was added except for Comparative Examples 1 and 4, and the mixture was stirred without adding a solvent for adjusting the solid content so that the solid content was 50% by weight, and a predetermined mixture was mixed. I got a thing. The amount of glass roving (base material of fibrous substance) shown in Table 2 was dipped and impregnated in this mixture to adhere a predetermined amount of the mixture, and the mixture was dried by a dryer at 135 ° C. to apply the mixture. I got a string. This coated string was applied to a scatter winding machine to obtain an annular preform having an outer diameter of 200 mm and an inner diameter of 130 mm. Put this preform in the mold and press at 160 ℃
For 10 minutes at 4.9 × 10 ⁶ Pa (50 kgf / cm) ² by thermocompression molding, then heat treatment at 205 ° C. for 4 hours to cure the resin, then polish both sides to obtain a thickness. A friction material of 3.5 mm was obtained.

[0014]

[Table 1]

[0015]

[Table 2]

In each of the above-mentioned Examples and Comparative Examples, the quality of the working environment, workability, properties of the admixture, properties of the friction material, etc. were tested as follows. The test results are shown in Table 3. A part of the mixture obtained in each Example and each Comparative Example was sampled in a test tube, and the sedimentation property and thickening property of the mixture solution after standing at room temperature for 5 days were examined to determine the stability of the mixture. Further, the adhesiveness to the glass roving when the mixture was applied to the glass roving and the adhesive property after drying were examined to determine the adhesiveness to the glass roving. The working environment and safety were evaluated from the odor and the volatility of the solvent during the coating work of each example and each comparative example. The preformability was judged from the ease and formability of the scatter winding operation of the coated cord obtained in each of the examples and each of the comparative examples. A drill hole having a diameter of 8 mm was drilled in the annular friction material obtained in each of the examples and each comparative example, and the workability was evaluated from chipping, crevices and the like around the hole.
Further, a test piece was prepared by cutting out a part from an annular friction material, and the test piece was attached to a constant speed abrasion tester specified in JIS-D4411 for operation, and the pressing pressure was 4.9 × 10 ⁵ Pa (5 kgf
/ Cm ² ) wear rate at 350 ° C (cm ³ / kgf ・ m × 10)
^-7 ) was measured. Furthermore, an annular friction material was attached to the rotary fracture strength tester and the temperature was set to 200 ° C. for 5 minutes at 250
It was rotated at 0 rpm, then the number of revolutions was increased at a rate of 100 revolutions per second, and the number of revolutions at break was examined to obtain the burst strength.

[0017]

[Table 3]

In Table 3, ◯ marks, Δ marks and X marks indicate the following. Odor: ○: No odor, ×: Odorous Explosion risk: ○: No explosion risk, ×: Explosion risk Mixture stability: ○: Aggregation, thickening No phenomenon, Δ mark does not aggregate but thickens, and X mark causes aggregation and thickening. Adhesion of admixture… ○ mark is good, △ mark is partly bad, × mark is bad Preformability… ○ mark is good, △ mark is difficult to form Drill hole workability… ○ mark is good, △ mark As shown in Table 3, the work environment and safety are better by using the water solvent than by using the conventional organic solvent. Further, the stability of the admixture of the example, the adhesion of the admixture, the preformability and the processability are improved as compared with those of the comparative example. Further, it is shown that the friction material of the example has a smaller wear rate and a higher burst strength than the friction material of the comparative example.

[0019]

According to the present invention, the working environment and safety at the time of manufacturing the friction material are improved. Further, the obtained friction material has a high burst strength and a low wear rate.

Claims (2)

[Claims] 1. A friction material composition containing a fibrous base material, a friction modifier, a binder, a dispersant, a flexibilizer, a surfactant and a water solvent. 2. A fibrous base material is coated with a mixture prepared by dispersing a friction modifier in an aqueous solution of a binder, a dispersant, a flexibilizing agent, and a surfactant, and molded. Method of manufacturing friction material.