JPH0241559B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a friction material composition, and its purpose is to provide a friction material composition useful for use in brake linings, disk pads, clutch facings, etc. of automobiles, railway vehicles, and various industrial machines. It's about doing. In recent years, as vehicles have become larger and faster, and their operating conditions have become more severe, the performance required of brake linings, disk pads, clutch facings, etc. has become increasingly sophisticated. In other words, it is not only necessary to have a high friction coefficient during sliding, but also to have a stable value in response to changes in the temperature, speed, pressure, etc. of the sliding surface, and also to have a long life and a high friction coefficient. Many performance requirements are required, including no abnormal noise during operation and good heat resistance. Conventionally, asbestos has been widely used as one of the main components constituting friction materials, but friction materials made mainly of asbestos suffer from rapid decreases in the coefficient of friction at high temperatures (fade phenomenon) and decreases in the coefficient of friction. This is a major drawback, and it is no longer possible to meet the high-level demands mentioned above. Furthermore, regarding asbestos, (i) the occupational environment and health problems that asbestos dust has on the human body have recently been attracting attention, and there is a possibility that various restrictions will be imposed on its use in the future. (ii) Production is concentrated in specific regions such as Canada, the Union of South Africa, and the Soviet Union, and there are concerns such as difficulty in obtaining it and rising prices due to increased use in developing countries. Various proposals have been made to solve the performance disadvantages of friction materials mainly composed of asbestos and the problems related to asbestos in the occupational environment and hygiene. For example, Japanese Patent Application Laid-open No. 119043, No. 119043,
Publication No. 87549, Japanese Patent Application Publication No. 51-54144, Japanese Patent Application Publication No. 1973
JP-A-153849, JP-A No. 55-86820, JP-A No. 54-25975, etc. describe friction materials mainly composed of glass fibers. However, in these friction materials mainly made of glass fiber,
Although the fade phenomenon is reduced, a new problem arises, the so-called reverse fade phenomenon, in which the coefficient of friction increases as the temperature rises. Furthermore, there are also drawbacks such as insufficient wear resistance, the tendency to generate abnormal noises during sliding, and, especially in clutch facings, insufficient rotational breaking strength. Also, JP-A-54-34351
Although the publication describes a friction material using steel fibers, this friction material also has the same drawbacks as those using glass fibers. As a result of intensive studies to eliminate these drawbacks of the prior art, the present inventors have developed an inorganic fiber and/or inorganic particles other than asbestos, a pulp-like material of a para-oriented aromatic polyamide polymer, and a specific solid lubricant. The friction material, which is blended and bonded with thermosetting resin, has little rapid change in the coefficient of friction due to temperature changes, that is, no fade or reverse fade, and has excellent wear resistance. The present invention was completed based on the findings that there is no abnormal noise when used as a lining or clutch facing, and that mechanical strength such as bending strength and rotational fracture strength in clutch facings is excellent. That is, the present invention comprises (a) 5-70% by weight of inorganic fibers and/or inorganic particles other than asbestos, (b) 5-70% by weight of a pulp-like material of para-oriented aromatic polyamide polymer, and (c) carbon fibers. , carbon black, graphite powder, molybdenum disulfide, tungsten disulfide, boron nitride, fluororesin, nickel iodide, or one or more solid lubricants 1
This is a friction material composition containing ~30% by weight as a main component and substantially free of aromatic polyamide fibers. Inorganic fibers and/or inorganic powder Inorganic fibers and/or inorganic particles referred to in the present invention include, for example, glass fibers (chopped strands, glass wool, milled fibers, etc.),
Cachiline fiber, alumina fiber, silica fiber, silica/alumina fiber, rock wool, mineral wool, titanium oxide fiber, potassium titanate fiber, pauxite fiber, kyanite fiber, boron fiber, gypsum needle crystal fiber, magnesia fiber, metal fiber (iron-based, brass, stainless steel, copper, etc.), dolomite powder, dawsonite (fibrous, granular), calcium silicate (fibrous, granular), gypsum powder, kaolin powder, talc, mica, magnesium oxide and/or magnesium hydroxide , glass powder, metal powder, silica powder, alumina powder, stone powder, barite powder, cryolite powder, calcium carbonate, etc. The size of the inorganic fibers and/or inorganic particles is not particularly limited, but in the case of inorganic fibers, the ratio of fiber length (L) to diameter (D) (L/D) is 5 or more, preferably 10 or more. The diameter is preferably 0.1 μm to 50 μm. In addition, in the case of inorganic particles, the average particle diameter is
It is 500 μm or less, preferably 100 μm or less, more preferably 50 μm or less. The proportion of inorganic fibers and/or inorganic particles in the friction material composition varies depending on the use of the composition, but is 5 to 70% by weight, preferably 10 to 60% by weight.
Weight%. If the proportion of inorganic fibers and/or inorganic particles in the friction material composition is less than about 5% by weight, the addition of inorganic fibers and/or inorganic particles has no effect, and the friction coefficient of the resulting friction material tends to be low. On the other hand, if it exceeds about 70% by weight, the mechanical strength of the friction material decreases, which is undesirable. Pulp-like material of para-oriented aromatic polyamide-based polymer The para-oriented aromatic polyamide-based polymer referred to in the present invention is

【formula】

【formula】

[Formula] (-NHNH)- One or more of the constituent units represented by
Polymer containing 80 mol% or more [however, (-NHNH)- is 50 mol% or less], that is, para-oriented aromatic polyamide or para-oriented polyamide hydrazide, such as polyparaphenylene terephthalamide, polypara Examples include lapelsamide, polyterephthalhydrazide, polyparaaminobenzhydrazide terephthalamide, and copolymers thereof, with polyparaphenylene terephthalamide being preferred. Further, the pulp-like substance referred to in the present invention is a fiber produced from the above polymer in a size of 1 to 20 mm, preferably 2 to 20 mm.
After cutting to 8 mm, fibrillated fibers obtained by dry or wet beating and/or shearing using, for example, a disk stiffener, a cone refiner, a beater, etc.
- Publication No. 11851, Japanese Patent Publication No. 37-5732, Japanese Patent Publication No. 11851
As described in Japanese Patent No. 50-138125, it is a so-called fibrid obtained by introducing a solution of a polymer in a solvent into a precipitant that is stirred at high speed and precipitating it as fine particles. Because the pulp-like material has a large number of tentacle-like protrusions that can become mechanically entangled with each other or with other particles, there is no slippage at the interface between the pulp-like material and other components in the friction material. This makes it possible to obtain an ideal reinforcing effect without causing any phenomena. The amount of the pulp-like material of the para-oriented aromatic polyamide polymer in the friction material composition is an important factor in developing the mechanical properties, friction performance, etc. of the friction material, and is 5 to 70% by weight. Preferably it is 10 to 50% by weight. If the pulp-like material is less than about 5% by weight, the resulting friction material will have insufficient mechanical properties, while if it exceeds about 70% by weight, the coefficient of friction tends to decrease, which is not preferable. In addition, when producing a pulp-like material of a para-oriented aromatic polyamide-based polymer, a part or all of the inorganic fibers and/or inorganic particles, and one of the solid lubricants described later are added to a solution in which the polymer is dissolved in a solvent. Inorganic fibers and/or inorganic particles, solid lubricants, and friction performance modifiers can be prepared by adding and mixing part or all of the friction performance modifier, and then introducing it into a precipitant that is being stirred at high speed. A pulp-like material is obtained in which the periphery of the material is coated with a para-oriented aromatic polyamide polymer. This method uses inorganic fibers and/or inorganic particles in friction materials, solid lubricants,
Inorganic fibers and/or inorganic particles, solid lubricants, and friction performance modifiers leak from paper-making wire mesh when improving the dispersion state of friction performance modifiers or manufacturing friction materials through wet papermaking methods. It is effective for preventing Solid Lubricant In the present invention, it is essential to blend a solid lubricant, and it has been found that the reverse fade phenomenon of the friction material can be eliminated by blending the solid lubricant. The solid lubricant used in the present invention is selected from the group consisting of carbon fiber (including graphite fiber), carbon black, graphite powder, molybdenum disulfide, tungsten disulfide, boron nitride, nickel iodide, and fluorine resin. One or more types can be used. The amount of solid lubricant in the composition of the present invention varies depending on the type of solid lubricant, the use of the friction material, etc., but is 1 to 30% by weight, preferably 2 to 20% by weight. If the solid lubricant is less than about 1% by weight, the effect of adding the solid lubricant is small and the reverse fade phenomenon cannot be eliminated, while if it exceeds 30% by weight, the coefficient of friction becomes too low, which is not preferable. Production of Friction Material When producing a friction material using the composition of the present invention, a known method can be employed. For example, inorganic fibers and/or inorganic particles; pulp-like material of para-oriented aromatic polyamide; solid lubricant; thermosetting resin such as phenol resin, epoxy resin, melamine resin, urea resin, polyimide resin; if necessary, A uniform mixture of friction performance modifiers such as cashew dust, non-melting organic fibers, etc. is temporarily molded, placed in a designated mold, and molded at a pressure of 50 kg/cm ² or more, preferably 100 kg/cm ² or more.
Molding is carried out at 130-290°C, preferably 170-250°C.
After the molded product has cooled, it is finished using a polishing machine if necessary. Further, after molding, heat treatment may be performed for the purpose of completing the curing reaction of the thermosetting resin in a state taken out from the mold. Also,
In particular, when manufacturing clutch facings, inorganic fibers and/or inorganic particles, a para-oriented aromatic polyamide pulp, and a solid lubricant are uniformly mixed in water, and then paper is made and then impregnated with thermosetting resin. There is also a method of manufacturing through processes such as preliminary drying, pressurized heat molding, and punching using a crank press or the like. The proportion of thermosetting resin in the friction material is 10
~40% by weight, preferably 15-35% by weight, and 10
If it is less than 40% by weight, the mechanical properties of the friction material will be insufficient, while if it exceeds 40% by weight, it tends to become brittle, which is not preferable. As described above, according to the composition of the present invention, the resulting friction material has little change in friction coefficient due to temperature, excellent wear resistance, and high mechanical strength, and is suitable for use in brake linings, disc pads, and clutch surfaces. It is useful for things such as sing. Hereinafter, the present invention will be explained in detail with reference to Examples. Incidentally, unless otherwise specified, parts or percentages are based on weight. Example 1 Preparation of pulp-like material of para-oriented aromatic polyamide polymer 20 parts of polyparaphenylene terephthalamide with an intrinsic viscosity of 2.4 and 10 parts of lithium chloride were mixed with 300 parts of hexamethylphosphoramide and N-methyl- A solution was obtained by dissolving in a mixed solvent with 500 parts of 2-pyrrolidone.
The above solution was added at 15/hr and water at 200/hr in a pipe stirring type mixer consisting of a combination of rotor and stator.
A slurry containing a pulp-like material of polyparaphenylene terephthalamide was obtained by simultaneously feeding at a flow rate of Hr. The slurry was passed through a Nutstier vacuum filter and thoroughly washed with ion-exchanged water to obtain a pulp-like material of polyparaphenylene terephthalamide. Manufacture of friction material (i) 20 parts of the above pulp-like substance (ii) 40 parts of glass fiber (diameter 10 μ, length 5 mm) (iii) Graphite powder 10 parts (iv) Cashew dust 10 parts (v) Phenol resin 15 parts (vi) ) Brass powder 5 parts The above (i) to (vi) were mixed uniformly by stirring in water, and then filtered through a filter. Then 80℃
It was preformed after drying at a temperature of . The preformed product was placed in a mold and compression molded at 170℃ and 150Kg/ ^cm2 for 10 minutes, then taken out of the mold and heat treated in a hot air oven at 200℃ for 5 hours to induce the curing reaction of the phenolic resin. made complete. Cool after heat treatment,
The properties of the friction materials obtained by subsequent polishing were as shown in Table 1, and all were good. (JISD4311)
)

[Table] Example 2 (i) Pulp material prepared in Example 1 25 parts (ii) Rock wool 15 parts (iii) Kaolin fiber (Kao wool manufactured by Isolite Industries) 15 parts (iv) Brass fiber (diameter 30μ, length 6mm) 5 parts (v) Carbon fiber (Beshuite manufactured by Toho Bethlon)
10 parts After dispersing the above (i) to (v) in water to a concentration of 0.2%, paper was made and dried using a Fourdrinier paper machine to obtain a sheet-like product. The sheet-like material was impregnated with a liquid mixture of phenolic resin and cashew dust, and dried in a dryer at a temperature of 110°C. 70 parts of the sheet-like material was impregnated with 20 parts of phenol resin and 10 parts of cashew dust. Next, this was cut into a 20 mm tape with a slitter, wound into a spiral shape, and then placed in a mold and heated to a temperature.
Pressing was carried out under the conditions of 160°C, pressure of 250 kg/cm ² and time of 7 minutes. Further, the material was heated at 190° C. for 2 hours and polished to obtain a friction material for clutch facing. The performance of the friction material for clutch facings thus obtained was as shown in Table 2, and all were excellent.

[Table] In Table 2, the friction coefficient and wear rate are as follows:
Measured based on JISD4311. In addition, the rotational breaking strength is 200mm in outer diameter, 130mm in inner diameter,
A sample with a thickness of 3.5 mm was rotated at increased speed in an atmosphere at a temperature of 200°C, and the number of rotations at the time of failure was measured. Example 3 Same as Example 1 except that the solid lubricant shown in Table 3 below was used instead of 10 parts of graphite powder.
A friction material was obtained in exactly the same manner as above. All of the obtained friction materials were excellent as in Example 1.

[Table] Example 4 The procedure was exactly the same as in Example 2, except that inorganic fibers and/or inorganic particles shown in Table 4 below were used instead of 15 parts of rock wool and 15 parts of kaolin fiber (30 parts in total). The friction material obtained was almost the same as that of the friction material obtained for clutch facings and was excellent.

[Table] In Table 4, No. 3 and No. 4, 10 p.
The test was carried out by adding pm polymer flocculant (polyacrylamide nonionic type). Example 5 Polyparaphenylene terephthalamide fiber (du Pont, Kevlar, single filament fineness 1.5 denier) was cut into a length of 7 mm and dispersed in water to a concentration of 1.0%. This aqueous dispersion was repeatedly passed through Discliff Eye Iner (manufactured by Kumagai Riki Kogyo) five times to fibrillate the fibers to obtain a pulp-like material. Next, the aqueous dispersion containing the pulp-like material was filtered, dried, and then used to produce a friction material. (i) 20 parts of the above pulp-like substance of polyparaphenylene terephthalamide (ii) 35 parts of glass fiber (diameter 10 μ, length 5 mm) (iii) Graphite powder 10 parts (iv) Cashew dust 15 parts (v) Phenol resin 15 parts (vi) Brass powder 5 parts The above (i) to (vi) were added to water and stirred to mix uniformly, and then filtered through a filter. Then 80℃
It was preformed after drying at a temperature of . The preformed product was placed in a mold and compression molded at 180℃, 150Kg/cm ² for 8 minutes, then taken out from the mold and heat treated in a hot air oven at 180℃ for 5 hours to induce the curing reaction of the phenolic resin. was made complete. The performance of the friction material obtained by cooling after the heat treatment and then polishing was as shown in Table 5, and all were good.

[Table] Example 5 A para-oriented aromatic polyamide copolymer (intrinsic viscosity 5.5) with a copolymerization molar ratio of polyterephthalhydrazide units, polyparabenzamide units, and polyparaphenylene terephthalamide units of 35/35/30 was prepared. A solution was obtained by dissolving in N-methyl-2-pyrrolidone. A pulp-like material was made from this solution in the same manner as in Example 1, and a friction material was further obtained in the same manner as in Example 1. The performance of the obtained friction material was as excellent as that of the friction material obtained in Example 1. Comparative Example 1 The friction coefficient and wear rate measured using the JISD4311 method, and the rotational fracture strength at 200°C measured using the same method as in Example 2, of clutch facings made using asbestos using a known method. It is shown in Table 6. The problem was a decrease in the coefficient of friction and an increase in the wear rate at 250°C, which was not desirable. Furthermore, the rotational fracture strength at 200°C is not sufficient.

【table】

Claims (1)

[Scope of Claims] 1 (a) 5 to 70% by weight of inorganic fibers and/or inorganic particles other than asbestos, (b) 5 to 70% by weight of a pulp-like material of para-oriented aromatic polyamide polymer, and (c) ) At least one solid lubricant selected from the group consisting of carbon fiber, carbon black, graphite powder, molybdenum disulfide, tungsten disulfide, boron nitride, nickel iodide, and fluorine resin.
A composition for a friction material, characterized in that it contains 30% by weight as a main compounding component and substantially does not contain aromatic polyamide fibers. 2. The composition for a friction material according to claim 1, wherein the para-oriented aromatic polyamide is polyparaphenylene terephthalamide.