JPS5980440A - Method for preventing reduction in friction coefficient of cork-based friction material - Google Patents

Abstract

PURPOSE:To prevent the reduction in friction coefficient of friction materials at a low cost and further squeal and slippage of the friction materials, by applying an inorganic powder as a friction performance modifying and improving agent to the surfaces of simple cork particles, and kneading and coating the resultant coated particles with a nitrile rubber material as a binder. CONSTITUTION:An inorganic powder, e.g. red iron oxide, calcium carbonate or diatomaceous earth, having <=60mu particle diameter as a friction coefficient modifying and improving agent is previously applied to the surfaces of simple cork particles to keep the porous structure of a corky material, and the resultant coated particles are then kneaded and coated with a nitrile rubber consisting of a copolymer of preferably butadine and acrylonitrile to prevent the reduction in friction coefficient of cork-based friction materials. Preferably, the composition of the incorporated components is as follows; 20-80pts.wt. simple cork particles, 15-60pts.wt. friction performance modifying and improving agent and 10-60pts.wt. binder. USE:Friction plates operating in oil in wet multiple plate clutch devices used for bicycles.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a friction plate that operates in oil in a wet multi-plate clarifier device used for automobiles, etc., especially motorcycles, and more particularly relates to a method for producing a friction material. This is an improved invention.

Conventionally, in this type of wet friction device, friction plates are manufactured using a friction material that is coated with a copolymer with nitrile rubber as a binder and coated with cork, filler, and a vulcanizing agent. was used as the mainstream. The heat resistance of this nitrile rubber (NBR) itself is 100~
Since the temperature limit is set at approximately 110°C (Mr. This has caused problems such as a decrease in the value and the occurrence of burnt, slippery, etc. defects in the clutch, which can lead to problems such as poor cutting. In the background of these conventional techniques and trends, the disadvantages of the conventional techniques,
The present inventors have chosen to solve the problem as the purpose of their research and development, and the responses of the prior art will be specifically described below.

A friction material based on cork is disclosed in Japanese Patent Application Laid-Open No. 50-12
Publication No. 8043 describes a friction material made by kneading cork particles, carbon powder, a vulcanizing agent, and acrylic rubber as a base material, and pressurizing and heating the mixture into a sheet shape, and using general nitrile rubber as a binder. The reason for this is that in friction materials that use general nitrile rubber as a binder, active sulfur contained in additives in the oil is extracted as thermal decomposition as the oil temperature rises, and this causes damage to the rubber surface. This causes the rubber to react and harden as a result of rubber deterioration, thereby reducing friction performance.Acrylic rubber is said to have less of this reduction.

Next, as a similar cork-based friction material, JP-A-Sho 5ft-
No. 147878 discloses animal leather fiber as a base material,
There is a proposal to improve moisture absorption resistance (no aggressiveness) and improve squealing noise by using cork powder coated with rubber, vegetable fiber, and organic fiber instead of animal leather powder.

Furthermore, Japanese Patent Application Laid-open No. 54-41340 discloses that the surface of cork particles is coated with graphite or molybdenum disulfide, and iron powder is further mixed into the cork to make it ferromagnetic. A friction material bonded with a phenol powder binder has been proposed to prevent clutch plate squeal and improve wear resistance.

In contrast to the conventional techniques described in these three publications, the present invention has developed technical improvements and new processes that no one had thought of before, with the ultimate goal of achieving lower cost, economic efficiency, and eliminating problems. In other words, we established a method for preventing a decrease in the coefficient of friction by taking the following measures without damaging the porous structure of cork itself.

First, in response to JP-A-50-128043, we proposed that there is a method that can maintain durability by using a generally inexpensive nitrile rubber binder without using acrylic synthetic rubber as a binder. It is something to do.

In order to prevent the temperature of the oil (friction oil) from rising excessively, this method uses a cork base (porous structure) in which the oil on the friction surface is convected away from the friction surface through the inside of the facing itself. Then, a significant minimum amount of inorganic solid powder (friction performance adjustment improver) is impregnated and coated, and then coated with a nitrile rubber binder in the next step. It can be maintained without closing the opening. This is one of the basic configurations of the present invention.

In short, when the conventional cork base material and rubber binder are mixed and coated all at once, the porous structure of the cork single particles is sealed, so the penetration of oil amount and the circulation of oil on the friction surface are eliminated, which in turn helps increase the oil temperature. become. Therefore, the conventional process has problems and drawbacks because the hardening phenomenon caused by the deterioration of the rubber surface lowers the friction performance, and the new process of the present invention is an improvement on this problem.

Next, regarding the disclosure of Japanese Patent Application Laid-open No. 513-147878,
Typical basic formulations include cork powder coated with rubber, aromatic polyamide fibers, vegetable pulp fibers, friction modifiers, metal powder, thermosetting resin, and this formulation is thoroughly stirred. The mixture is mixed, placed in a designated mold, and heated and molded.

The mixture of cork powder and rubber is made by kneading a viscous liquid of NBR synthetic rubber into cork powder using a rubber kneading roll, etc., and then going through a powder process to prepare cork powder coated with rubber. be.

What is especially important is that the mixing process is not only well-stirred and mixed, but also that the order of the mixing process is a technical means that can prevent a decrease in the coefficient of friction, which is an effect of the function of the composition. This is a big problem because it is different.

This is the main point of the present invention, and is achieved by coating cork particles with powder as a friction performance adjustment improver in a step prior to the step of mixing the rubbery liquid.

By the way, the friction performance adjustment improver referred to in the present invention is Bengara,
This is achieved by an inorganic powder of one or more substances selected from calcium carbonate, magnesium carbonate, barium sulfate, silica, diatomite, etc., with a particle size of 80 microns or less, and more preferably diatom. is good.

The difference between the present invention and JP-A-54-4940 is that this publication uses a liquid material that is used in electromagnetic clutches and brakes, particularly industrial sewing machines, etc., and requires hydrophobicity and lubricity. and iron powder are mixed in a mixer, and at the same time, a phenol powder binder is mixed uniformly, and the cork molded product containing the ferromagnetic powder is obtained by pressing and compacting, and this is then coated with a coating agent as a base material. . The material of the present invention is fundamentally different because it uses a cork base as a base material and is made by first coating cork single particles with a friction performance adjustment improver and then coating them with a rubbery binder. The same applies to its uses.

When the present invention is compared with the prior art, the above-mentioned differences become apparent and can be cited as deficiencies of the prior art. [In bulk mixing molding with rubber, the pores of the cork material's own porous structure are closed, and due to this phenomenon, the friction material in the oil no longer has the role of convection through the oil. In addition, there was a defect in which the oil temperature rose, resulting in the friction material squealing and slipping.

The purpose and reason of the present invention is to correct and eliminate this problem.

Next, as a function of the friction performance adjustment improver, fine particles enter the pores by coating them with the porous pores of single cork particles, and when the rubber material is coated in the next step, the pores are covered with the pores of the hollow part. Less likely to be blocked due to air expansion. This porous structure allows the oil on the friction surface to pass through the inside of the facing itself and be removed from the friction surface, so it hardens into a dense state by simply coating the base cork with a minimum amount of friction performance adjustment improver. Provides a better coefficient of friction than molded asbestos friction plates. A large amount of oil is retained within the pores of the facing, and the oil moves under external influences (compression deformation, etc.), so frictional heat can be effectively absorbed, greatly improving wear resistance. . Also, problems caused by abrasion particles of the facing are less likely to occur.

As the rubbery binder, styrene-butadiene rubber (S
(N B R), which is a copolymer of butadiene and acrylonitrile, is more often used than B R).

The reason is that the former uses rosin acid soap as an emulsifier and has excellent adhesive processability, abrasion resistance, tensile strength,
#Although it has excellent aging resistance, it does not have oil resistance and does not become light colored due to the influence of staining stabilizers. In addition, the latter has excellent oil resistance, which is its greatest feature, and it is known that there is a correlation with the amount of bonded nitrile, and other characteristics are also related to the distribution of the amount of nitrile added, and generally oil resistance is high. This results in improved wear resistance and improved heat resistance. The tensile strength also increases, the anti-fracture elasticity decreases, and the cold resistance also deteriorates.

In short, NBR is better than SBH for wet multi-disc clutches.
is widely used because of its good heat resistance, which is why it is also used in the present invention.

Examples will be described below.

Example 1 Four cork powder particles with an average diameter of 0.5 to 1.5 mmφ were
0 parts by weight and the average diameter of diatoms as a friction performance adjustment improver to maintain the porous structure of this cork powder particle.
30 parts by weight of Micron were placed in a Henshil mixer and mixed for 5 minutes until uniform. The obtained mixture was transferred to a mixing roll, and 5 parts by weight of cashew resin powder and 25 parts by weight of tolyl butadiene copolymer (hereinafter referred to as NBR) were mixed with rubber as a binder, and an appropriate amount of general A vulcanization accelerator that is commonly used as a vulcanizing agent and sulfur as a vulcanizing agent were added and kneaded. Next, stretch the above-mentioned mixed wire into a sheet shape, make it into a plate shape, and then shape it into a predetermined shape (circular ring).
The core metals coated with adhesive in advance are sandwiched together and bonded together using a hot press machine, followed by heating and pressure molding. Pressurized at 175℃ for 150s
It is vulcanized and molded by EC heating. Thereafter, heat treatment at 185° C. for 30 minutes was carried out using a drying oven as an unvulcanized treatment. In this way, a friction material of the present invention was obtained.

Example 2 A friction material was produced in the same manner as in Example 1, except that 30 parts by weight of calcium carbonate powder (average particle size: 9 microns) was mixed in place of the diatomaceous diatomaceous material in Example 1. Obtained. In addition, the blending materials and blending ratios are as follows.

O Rubber (NBR) 25 parts by weight Cork powder 40 tt Cashew resin 5 // Calcium carbonate 30 // Other vulcanization accelerators, vulcanizing agents Comparative Example 1 Friction material compound rubber (NBR) 25 parts by weight Cork powder 40 tt Cashew resin 5 〃 Gainudo 30 〃 Other vulcanization accelerators, vulcanizing agents The total amount of the above composition is mixed at once with a Henshil mixer, then mixed with a mixing roll, and the mixed material is rolled out into a sheet and made into a plate. This is punched out into a predetermined shape, and a core metal coated with adhesive is sandwiched between the metal cores and the metal cores are simultaneously bonded using a hot press machine, followed by heating and pressure forming. The following steps are Example 1
It was carried out under the same conditions. A comparative test product was obtained in this way.

A comparative test was conducted on the friction materials obtained in Example 1, Example 2, and Comparative Example 1. In order to test the excellent effects of the product of the present invention, the porosity was measured using a mercury porosimeter. The average pore size of the pores was confirmed and the porosity rate was measured in the same way.The conditions for this test were to immerse the sample in 8Hγ in a 90°C atmosphere with torque converter (for automatic transmission) oil to check the oil-impregnated porosity. The results of measuring the impregnated porosity of torque converter oil are shown below.

Porosity measurement results Next, the friction materials obtained in Comparative Example 1, Example 1, and Example 2 described above were adhered as lining materials to both surfaces of the metal base material for testing, and a friction test was performed for 5000 cycles using an SAE #2 tester. carried out. An outline of the SAE #2 tester and test conditions is as follows. The short plate type SAE #2 tester has a single piece of friction material glued on the same axis and has a rotational inertia mass of 2.518Kg.

cm, 5ec2. It is rotated at a rotational speed of 3800 times/min, and the mating member (fixed) that engages with the lining material is braked to a stop with a clutch pressing load of 313 kg, and its rotational energy (carrying amount 17813 kgcm) is absorbed. The operation was set at 120°C (Ford type, A
TRn type F) The test was repeated in oil at a rate of once every 30 seconds.

Figure 1 shows the relationship between the number of tests and the coefficient of dynamic friction obtained with the SAE #2 tester. The vertical axis in FIG. 1 is the coefficient of dynamic friction, and the horizontal axis is the number of tests.

In addition, 70- in the figure is the product of the present invention (obtained in Example 1)
2X- in the figure shows the results of the friction material of the present invention (obtained in Example 2), and ■-・- shows the results of the friction material of Comparative Example 1 (obtained in Example 2).
The results are shown for the friction material used as a conventional product.

From FIG. 1, it can be seen that the friction material of the present invention has excellent friction characteristics with less decrease in the initial dynamic friction coefficient than the friction material of Comparative Example 1 (prior art quantity).

As a result of the above, as an effect of the present invention, a method for preventing a decrease in the initial friction coefficient of a friction material has been established by discovering a new manufacturing process for a cork-based friction material at low cost by using members similar to conventional products. Ta. Therefore, this new method is widely available to industry.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the number of frictional engagements and the coefficient of dynamic friction of the friction materials of Example 1, Example 2, and Comparative Example 1, and Figure 2 is a diagram showing the relationship between the amount of wear and the number of engagements. It is a diagram showing the relationship, and in the first illustration and the second illustration, -o- indicates Example 1. -x- indicates Example 2, and -.- indicates Comparative Example. Patent applicant Aisin Kako Co., Ltd.4

Claims (2)

[Claims] (1) In order to maintain the porous structure of cork, the first step is to coat the surface of single cork particles with inorganic powder as a friction performance adjustment improver, and then apply nitrile rubber (NBR) as a binder. A method for preventing a decrease in the coefficient of friction of a cork-based friction material, the main step being a second step of kneading and coating as a binder. (2) 70~70~ of cork single particles based on the total weight of the friction agent
80 parts by weight, and 15 to 60 parts by weight of a friction performance adjustment improver.
parts by weight, 10 to 60 parts by weight of nitrile rubber (NBR) as a binder for coating the above, and further parts by weight of thermosetting resins F, D, and resin '1-ham. A method for preventing a decrease in the coefficient of friction of a cork-based friction material according to claim 1, characterized in that: