JPH0125926B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a friction material useful for use in brake linings, disk pads, clutch facings, etc. of automobiles, railway vehicles, and various industrial machines. More specifically, it is a friction material in which fibers made of an aromatic polyamide having a specific structure, which has heat resistance and excellent chemical resistance, are blended as fiber components constituting the friction material. In recent years, as vehicles have become larger and faster, and their operating conditions have become more severe, the performance required of brake linings, disc brake 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 coefficient of friction during sliding. Many performance requirements are required, including no abnormal noise generation and good heat resistance. Currently, asbestos is mainly used as the fiber component that makes up friction materials, but friction materials made mainly of asbestos suffer from rapid decreases in the coefficient of friction at high temperatures (fade phenomenon) and increased wear rates. It has major drawbacks and is no longer able to meet the high demands mentioned above. Various proposals have been made to compensate for the drawbacks of friction materials made mainly of asbestos, and it is known to use certain aromatic polyamide fibers as a fiber component constituting friction materials. For example, JP-A-53-130742 discloses the use of polymetaphenylene isophthalamide fibers together with glass fibers, and in JP-A-54-118448, we disclose that A friction material based on a paper containing 5 to 70% by weight of aromatic polyamide fibers and a binder and a friction performance improver, which is impregnated with a phenolic resin. He then proposed a friction material molded by heating and pressing, and disclosed polymetaphenylene isophthalamide and polyparaphenylene terephthalamide as examples of aromatic polyamide fibers.
However, the above-mentioned Japanese Patent Application Laid-Open No. 53-130742 and Japanese Patent Application Laid-open No. 54
Although the friction material described in Publication No. 118448 has excellent friction properties and wear resistance at high temperatures, its mechanical strength at high temperatures (for example, rotational fracture strength in clutch facings) is still insufficient. The drawback was that the degree of deterioration was large with use. In order to develop a friction material that maintains excellent friction properties and wear resistance at high temperatures and has improved mechanical strength at high temperatures, we continued to study aromatic polyamides and found that (1 ) Fibers obtained from aromatic polyamides having specific structural units have superior chemical resistance such as alkali resistance and acid resistance compared to polymetaphenylene isophthalamide fibers and polyparaphenylene terephthalamide fibers; (2)Friction materials made by blending fibers with excellent chemical resistance obtained from aromatic polyamide having the above-mentioned specific structural units not only have excellent friction properties and wear resistance at high temperatures. The inventors completed the present invention by discovering that the material also has excellent mechanical strength. That is, the present invention includes (i) aromatic polyetheramide fibers 10 to 80% by weight, (ii) friction performance modifier 1 to 40% by weight, and (iii) thermosetting resin 10 to 40% by weight as the main ingredients. It is a friction material. Each component of the present invention will be explained below. Polymer The aromatic polyetheramide fiber used in the present invention is composed of a polymer consisting of repeating units represented by (1) to (4) below. Ar ₁ , Ar ₂ , Ar ₃ Ar ₄ and Ar ₅ are metaphenylene groups or paraphenylene groups, and these may be the same group or different groups. R ₁ , R ₂ , R ₃ , R ₄ and R ₅ in formulas (1) to (4) may be the same or different, and are an alkyl group having 5 or less carbon atoms or a hydrogen atom. Preferably, Ar ₁ , Ar ₂ and Ar ₃ are each a paraphenylene group, and one of Ar ₄ and Ar ₅ is preferably a paraphenylene group and the other is a metaphenylene group. Such aromatic polyether amides are derived from paraphenylene diamine, 3,4'-diaminodiphenyl ether and terephthalic acid chloride. A substituent may be bonded to the carbon atom of the above aromatic carbocyclic residue. For example, halogen groups (e.g. chlorine, bromine, fluorine), lower alkyl groups (e.g. methyl, ethyl group, isopropyl group, n-propyl group), lower alkoxy groups (e.g. methoxy group, ethoxy group), cyano group, acetyl group,
Examples include nitro group, among which chlorine group and methyl group are preferred. The fibers used in the present invention mainly have the above formulas (1) to (4).
The relationship between the number of moles of these repeating units is essentially (1) + (4) = (2), and (1) + (2) + When (3)+(4)=100 mol%, (3)=
0-90 and (4)=50-5 mol%. Preferably
(4) = 30 to 10 mol%. The polymer can be obtained by reacting diamines, dicarboxylic acid derivatives, and aminocarboxylic acid derivatives corresponding to the repeating units represented by (1) to (4) above in a predetermined ratio. As the dicarboxylic acid derivative, it is preferable to use a dicarboxylic acid halide, particularly a dicarboxylic acid chloride. As the aminocarboxylic acid, it is preferable to use aminocarboxylic acid halide hydrohalide salts, such as aminocarboxylic acid chloride hydrochloride. Polymers can be obtained from these monomers by polymerization using known polymerization methods such as melt polymerization, solid phase polymerization, interfacial polymerization, and solution polymerization. Among these, solution polymerization is preferred. When producing a polymer, various additives can be added before, during, or after polymerization. Additives include inorganic compounds such as lithium chloride, lithium carbonate, calcium oxide, calcium hydroxide, and calcium chloride to neutralize hydrohalides produced as by-products of polymerization reactions and/or to facilitate dissolution of the polymer. , calcium carbonate, etc. Furthermore, a terminal stopper, a light stabilizer, a crosslinking agent, etc. can be added as necessary. Production and Properties of Fibers The fibers used in the present invention are obtained by defoaming and filtering a solution in which the polymer is dissolved, spinning the solution into an aqueous coagulation solution, washing, drying, and hot stretching. As a solvent for the polymer, tetramethylurea, hexalmethylphosphoramide, N,N
-Aprotic amide polar solvents such as -dimethylacetamide, N-methyl-2-pyrrolidone, and N,N-dimethylformamide are preferred. The spinning of the polymer solution may be carried out in a coagulating liquid, or it may be carried out by a dry jet wet spinning method, in which the polymer solution is first spun into a gas and then introduced into a coagulating liquid. A spinning method is preferably used. Further, the hot stretching is preferably carried out at a temperature of 250° C. or higher and 600° C. or lower at a stretching ratio of 2 times or more. Linear aromatic polyamides such as Kevlar, which has high strength and high modulus, are used as friction materials after spinning and drying without heat treatment, or after spinning and drying, for example.
It is sometimes used as a friction material after improving its strength and modulus by heat treatment under tension or relaxation at a temperature of 200°C or higher, generally 300°C or higher. However, the chemical resistance of linearly coordinated aromatic polyamide fibers is inferior to that of fibers made of aromatic polyetheramide having a specific structure used in the present invention. For example, fibers made of linearly coordinated aromatic polyamides such as polyparaphenylene terephthalamide can only be subjected to relaxation heat treatment at a temperature of 200°C or higher or tension heat treatment at a draw ratio of 1.5 times or less. Fibers made of aromatic polyetheramide having a structure are hot-stretched at a temperature of 200° C. or more to a factor of 2 or more times, preferably 5 times or more, and exhibit high strength and modulus as well as high chemical resistance. For example, in a 10% by weight aqueous solution of caustic soda at 95°C.
Comparing the strength retention rate when soaked for 10 hours,
Polyparaphenylene terephthalamide fiber (Kevlar-29), a linear aromatic polyamide
The strength retention rate of the fiber used in the present invention is approximately 95%, whereas the strength retention rate of the fiber used in the present invention is approximately 20%, and the fiber (Kevlar-49) that is further subjected to tension heat treatment is approximately 60%.
% or more, which is very excellent. In addition, the strength retention rates when immersed in a 20% by weight aqueous sulfuric acid solution at 95°C for 20 hours were as follows. Kevlar-29 15% Kevlar-49 50% Fiber used in the present invention 97% The excellent chemical resistance of the fiber used in the present invention is due to the composition of the polymer constituting the fiber and the 200%
It is developed by hot stretching to double or more at a temperature of ℃ or higher. On the other hand, friction materials, such as the disc pads of automobile disc brakes, are used by adhering them to a reinforcing back metal, but this prevents the problem of the disc pad peeling off from the back metal due to rust generated from the adhesive surface between the disc pad and the reinforcing back metal. In order to achieve this, the composition of the disk pad is sometimes chosen to exhibit some degree of alkalinity. There is also a known method of producing a paper-like material using a wet papermaking method and processing this paper-like material to produce, for example, a friction material for clutch facings, but in this case,
Sulfate band is often used as a fixing agent in order to reduce the leakage of fillers, friction performance modifiers, etc. from the entire paper mesh. In this case, the clutch facing friction material may become acidic. Therefore, it is of great significance to use the fibers of the present invention, which have excellent chemical resistance such as alkali resistance and acid resistance, as fibers constituting friction materials. This makes it possible to obtain an excellent friction material. The fiber used in the present invention has a single fiber fineness of 0.5 to 15 deniers, preferably 1 to 10 deniers. or,
It is preferable to cut the fibers and use them as short fibers. In this case, the length of the fibers varies greatly depending on the fineness of the fibers, their proportion in the friction material, the manufacturing method of the friction material, etc., but the length of the fibers is 100 mm or less, preferably 60 mm. It is as follows. Furthermore, the fibers of the present invention and other fibers may be mixed and used as necessary. In this case, other fibers include asbestos fiber, glass fiber, ceramic fiber, silica fiber, alumina fiber, potassium titanate fiber, titanium oxide fiber, bauxite fiber, kyanite fiber, boron fiber, magnesia fiber, rock wool, mineral wool, and metal. Examples include inorganic fibers such as fibers, gypsum fibers, and dawsonite fibers; non-melting organic fibers such as cotton, wool, linen, rayon, aromatic polyamide fibers, carbon fibers, and phenol fibers. When the fibers used in the present invention are mixed with other fibers, the mixing ratio should be selected depending on the intended use and required characteristics. Further, the fibers made of aromatic polyamide fibers having a specific structure used in the present invention can be used after partially or most of the fibers are fibrillated by shearing force in a dry or wet process. Furthermore, pulp-like particles made of aromatic polyamide can also be mixed and used. Manufacture of Friction Material When manufacturing the friction material of the present invention, known methods can be employed. For example, a mixture of a fiber component, a friction performance modifier, and a thermosetting resin is pre-molded, placed in a predetermined mold, and molded at a pressure of 50 kg/cm ² or more, preferably 100 kg/cm ² or more, at a molding temperature of 130~ 290℃ preferably 170~
Mold at 250℃. After the molded product is cooled, it is finished using a polishing machine. 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. In particular, when manufacturing clutch facings, the fiber components and friction performance modifiers are uniformly mixed and dispersed in water, followed by paper making, impregnation with thermosetting resin, pre-drying, pressure and heat molding, and crank press. There is also a method of manufacturing through a process such as punching. Furthermore, a fiber component and a friction performance modifier are blended and made into a yarn using a well-known yarn manufacturing method, followed by impregnation with a thermosetting resin, pre-drying, winding into a loop, pressurizing and heating forming, It can also be manufactured through processes such as heat treatment. Furthermore, there is also a method in which a fiber component and a friction performance modifier are blended, the felt is made into a felt shape using a well-known felt manufacturing method, and then the product is manufactured through processes such as impregnation with a thermosetting resin, preliminary drying, pressurized heat molding, and punching. be. Examples of the friction performance modifier used in producing the friction material of the present invention include the following. Alumina, silica, talc, kaolin, mica,
Metal oxides such as chromium oxide, magnesium oxide, and titanium oxide; Metals such as copper or copper alloys, zinc, iron, and aluminum; Inorganic compounds such as barium sulfate, quicklime, calcium phosphate, calcium fluoride, and carborundum; Clay, and beryl Minerals such as , mullite, and chromite; abrasive friction performance modifiers such as ceramic powder and hardened resin particles called friction dust; non-abrasive friction performance modifiers such as rubber powder; carbon black; graphite, etc. Conditioners can be used.
Further, thermosetting resins used in the production of the friction material of the present invention include phenolic, melamine, urea, epoxy, and polyimide resins, and phenolic resins are often used. In the case of phenolic resins, liquid or solid products such as novolac-type phenolic resins, resol-type phenolic resins, and modified phenolic resins such as melamine-modified phenolic resins, cresol-modified phenolic resins, and cashew-modified phenolic resins can be used. Next, in manufacturing the friction material of the present invention, the blending ratios of the fiber component, friction performance modifier, and thermosetting resin will be described. The proportion of the fiber component in the total formulation is 10 to 80% by weight, preferably 20 to 70% by weight. Similarly, the total amount of frictional performance modifiers is 1 to 40% by weight, preferably 5 to 20% by weight. Further, the amount of the thermosetting resin is 10 to 40% by weight, preferably 15 to 35% by weight. The present invention will be explained in detail with reference to Examples below. Incidentally, unless otherwise specified, parts or percentages are based on weight. Example 1 N-methyl-2
- Polymerization in pyrrolidone followed by neutralization with calcium hydroxide until the concentration of aromatic polyetheramide is 6
% spinning solution was obtained. This solution has a pore size of 0.2 mm.
The material was once extruded into the air through a spinning nozzle with 1000 holes, passed through an air layer of about 2 cm, and then introduced into an aqueous coagulation solution, thoroughly washed in a water washing bath, and then dried with a drying roller. The dried fibers
Stretched 11.0 times on a hot plate at 510°C, coated with oil and wound, single yarn fineness 1.5 denier, tensile strength 430 kg/
mm ² and an initial modulus of 7.5×10 ³ Kg/mm ² . The thus obtained fibers were cut into a length of 51 mm to be used as fibers for a friction material, and a clutch facing was prepared as follows. Aromatic polyetheramide fiber 40 length fiber asbestos (Quebec Standard 3 class)
10 parts The above two components were opened into a felt, the felt was impregnated with a liquid mixture of a phenol resin and a friction performance modifier, and dried in a dryer at a temperature of 120°C for 40 minutes. Fifty parts of the felt was impregnated with 20 parts of phenolic resin and 30 parts of a friction performance modifier. Next, this was cut into a tape with a width of 20 mm using a slitter, and a brass wire was wound around the tape in a spiral shape from one end to the other. Put it in the press at the temperature
It was pressed at 160° C., pressure 170 kg/cm ² for 6 minutes, taken out, heated at 200° C. for 60 minutes, and then polished to obtain a clutch facing. The performance of the clutch facing thus obtained was as shown in Table 1.

[Table] In Table 1, the friction coefficient and wear rate are
Conducted based on JISD4311. In addition, the rotational breaking strength is 200 mm in outer diameter, 130 mm in inner diameter,
After leaving a 3.5mm thick sample at 200℃ for 24 hours, the temperature was 200℃.
It was rotated at increased speed in an atmosphere at ℃, and the number of rotations at the time of failure was measured. Comparative Example 1 Clutch facing was carried out in exactly the same manner as in Example 1 except that polyparaphenylene terephthalamide fiber (duPont Kevlar-29) was used instead of the aromatic polyetheramide fiber. I got it. The friction coefficient and wear rate of this clutch facing were almost the same as in Example 1, which was good, but the rotational fracture strength was 16000 r.
It was inferior to P.M. Comparative Example 2 A clutch facing was obtained in exactly the same manner as in Example 1 except that long fiber asbestos was used instead of the aromatic polyetheramide fiber. Table 2 shows the performance of the obtained clutch facing.

[Table] The wear rate and rotational fracture strength at 200°C were insufficient. Example 2 After polymerization in N-methyl-2-pyrrolidone using 15 mol% paraphenylene diamine, 15 mol% 3.4′-diaminodiphenyl ether, 20 mol% chlorparaphenylene diamine, and 50 mol% terephthalic acid chloride, A solution for spinning with a polymer concentration of 6% was obtained by neutralization with calcium hydroxide. Using this solution, fibers were obtained in exactly the same manner as in Example 1. The obtained fiber had a single yarn fineness of 1.5 denier, a tensile strength of 395 Kg/mm ² , and an initial modulus of 9.7×
It was ¹⁰³ Kg/ ^mm2 . The fiber thus obtained was cut into a length of 5 mm to be used as a friction material. (1) 30 parts of the above aromatic polyetheramide fiber (2) Short fiber asbestos 15 parts (3) Phenol resin 20 parts (4) Cashew powder 15 parts (5) Barium sulfate 10 parts (6) Inorganic powder filler 10 parts The mixture obtained by uniformly mixing the above (1) to (6) was preformed, then put into a mold, compression molded at 170°C, 230Kg/cm ² for 5 minutes, and then further heated in a hot air oven at 190°C. The resin was heat-treated for 5 hours to complete the curing reaction of the phenolic resin. The performance of the friction material thus obtained is shown in Table 3, and all were good.

[Table] In Table 3, the bending strength of the friction material at 200℃ is
After heat aging treatment for 24 hours, cool to room temperature.
Although it was measured using the method specified in JISD4311,
Even after thermal treatment at 200°C for 24 hours, it exhibited a bending strength of 6 kg/mm ² and had sufficient mechanical strength. Comparative Example 3 In Example 2, a friction material was obtained in exactly the same manner as in Example 1, except that polyparaphenylene terephthalamide fiber (duPont, Kevlar) was used instead of aromatic polyetheramide fiber. . The friction coefficient and wear rate of the friction material thus obtained were almost the same as in Example 2, and were good.
The bending strength measured in the same manner as in Example 1 was poor at 4 Kg/mm ² .

Claims (1)

[Claims] 1 (i) Aromatic polyetheramide fiber
10 to 80% by weight (ii) Friction performance modifier 1 to 40% by weight (iii) Thermosetting resin 10 to 40% by weight A friction material whose main compounding components are 10 to 80% by weight. 2. The aromatic polyetheramide fiber is a polyetheramide fiber derived from paraphenylene diamine, 3,4'-diaminodiphenyl ether, and terephthalic acid chloride, and
Claim 1, which is a fiber drawn at a draw ratio of 2 times or more at a temperature of ℃ to 600℃
Friction material described in section.