JPH0726031A - Friction material - Google Patents

Abstract

PURPOSE:To stably maintain the frictional properties of a molded friction material comprising a base fiber dispersed in and bound with an org. resin by reinforcing an ash layer formed by the combustion of org. components during practical use to thereby prevent disintegration and disappearing of the ash layer. CONSTITUTION:A friction material is prepd. by compounding, as a reinforcement for an ash layer, a suitable amt. (about 10-20vol.%) of an inorg. powder which sinters in the temp. range of ash formation and thus binds and reinforces ash (e.g. titania, zinc oxide, copper oxide, bismuth oxide. molybdenum oxide, antimony oxide, or vanadium oxide). The powder, pref. having a particle size of about 5mum or lower, disperses into openings of ash formed by the combustion of org. components and sinters to bind and reinforce the ash, preventing disintegration and disappearance of the ash layer.

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 brake lining, a disk pad, a clutch facing, etc., which constitutes a braking device for automobiles, railway vehicles, aircrafts, industrial machines and the like.

[0002]

2. Description of the Related Art As a friction material for the above-mentioned braking device, asbestos fibers have been used as base material fibers, which are dispersed in a phenol resin or the like, and a kneaded material to which various friction modifiers are added is heated and pressurized. Binder shaped friction materials have been used. Recently, in order to address the demand for non-asbestos friction materials and improvement of friction and wear characteristics in response to the indication of the harmfulness of asbestos fibers, asbestos fibers have been replaced with heat-resistant organic fibers, metal fibers, glass fibers. Various proposals have been made for friction materials containing synthetic inorganic compound fibers as a base fiber and further mixed with various friction and wear modifiers (for example, JP-A-59-54644, JP-A-1-294553, JP 5-94
62, JP-A-5-32958, etc.).

[0003]

Although many attempts have been made to improve the characteristics of the friction material as described above,
The ashing phenomenon of the friction material has been taken up as a new problem as the braking becomes more severe. The ashing phenomenon of the friction material is a phenomenon in which the organic content of the friction material is burnt and disappears in the high temperature range due to severe friction at high speed and high surface pressure, and a layer of only ash content is formed. Since the front end of the rotary sliding contact is sufficiently in contact with oxygen, ashing is likely to occur. The effect of improving the characteristics of the friction material, which is currently being developed, is largely due to the use of organic fibers, and the strength of the ashing layer is significantly reduced due to the combustion of organic components. The ashing reduces the strength and makes the brittle portion easily collapse, and the newly exposed unashed portion due to the ashing is exposed to sufficient oxygen, and thus ashing is promoted. As ashing progresses in this way,
There is a risk that the characteristics of the friction material will deteriorate and the function of the braking device will be lost. Therefore, the present invention provides a ashing layer with a strength that does not easily collapse even if combustion and ashing of the organic components that make up the friction material occur, and friction that can maintain stable friction characteristics. It is intended to provide wood.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a friction material obtained by binding and molding a kneaded material containing a base fiber with a resin as a binder, and sintering as an ashing layer reinforcing agent in the ashing temperature range. It is characterized by containing a sinterable inorganic compound powder that binds ash.

[0005]

[Function] The ash layer strengthening agent powder compounded in the friction material of the present invention is sintered in the combustion / ash temperature range of organic components due to friction heat under the action of high surface pressure when the friction material is actually used. It causes a reaction and strengthens the binding of ash as a binder. The ashing layer does not easily collapse due to its bond strengthening action, and unlike conventional friction materials, the ashing part is prevented from collapsing / defecting and accompanying ashing is suppressed and prevented. The function of is maintained stable.

The present invention will be described in detail below. The ash layer strengthening agent powder blended in the friction material of the present invention serves to strengthen the ash layer as a binder that binds the ash in the temperature range where the organic components are burned and ashed as described above. Preferable specific examples of the ash layer strengthening agent include titanium oxide (TiO ₂ ), zinc oxide (ZnO), and copper oxide (Cu).
O), molybdenum oxide (MoO ₃ ), bismuth oxide (B
Examples include oxide ceramic powders such as i ₂ O ₃ ), antimony oxide (Sb ₂ O ₃ ), and vanadium oxide (V ₂ O ₅ ).

The ash layer strengthening agent powder is preferably a fine powder. Even if the sintering temperature is high, the fine grain size enhances the sinterability under pressure, and the sinterability for strengthening the ash bond in the ashing temperature range when the friction material is actually used. Is expressed. Therefore, the particle size of the ashing layer reinforcing agent powder is preferably ultrafine particles of about 5 μm or less. The ratio of the ashing layer reinforcing agent powder to be mixed is not strict depending on the type of the base fiber and the friction modifier, but the ratio in the friction material can be about 10 to 20% by volume to obtain good results. .

The composition of the friction material of the present invention is the same as that of the conventional friction material except that the ashing layer reinforcing agent powder is mixed, and the raw material composition for producing the friction material is
It is prepared by blending the ashing layer reinforcing agent powder according to the present invention with a mixture of a base fiber, a binder resin, and an optional friction modifier. As the constituent material of the raw material composition, various known kinds of materials can be appropriately selected and used as follows.

The base fibers are, for example, organic fibers such as polyamide (nylon) fibers and aramid fibers, steel fibers,
Metal fibers such as stainless fibers, copper fibers, brass fibers, carbon fibers, glass fibers, ceramic fibers, rock wool,
Inorganic fibers such as potassium titanate fibers (potassium hexatitanate fibers, potassium tetratitanate fibers, etc.), and these fibers may be used alone or in combination of two or more. May be used for. The base fiber is a surface with a silane coupling agent or a titanate coupling agent, etc. for the purpose of improving dispersibility and adhesion with a resin binder, etc. prior to preparation of the raw material composition, if necessary. The treatment is carried out according to a conventional method.

The binder resin is, for example, a thermosetting resin such as a phenol resin, an epoxy resin, a polyester resin, a polyamide resin, an alkyd resin, a silicone resin or a polyimide resin, or a modified resin thereof, or a natural rubber or styrene butadiene. Various resins used as a binding resin for the friction material such as rubber and nitrile rubber are appropriately used.

The friction and wear modifier is, for example, vulcanized or unvulcanized natural / synthetic rubber powder, cashew resin powder, resin dust, organic powder such as rubber dust, natural / artificial graphite, molybdenum disulfide, antimony trisulfide, Inorganic powders such as barium sulfate, calcium carbonate and xonotlite, flaky inorganic fillers such as mica and vermiculite, metal powders such as copper, aluminum, zinc, iron and stainless steel,
A composition in which a single or a combination of two or more types is blended according to the frictional characteristics, vibration characteristics, pear, etc. required for the product, and an appropriate amount of an auxiliary material such as a rust preventive agent and an abrasive is blended as necessary. It is also the same as that of the conventional friction material.

In the friction material of the present invention, a composition obtained by mixing the above-mentioned base fiber, binder resin, friction modifier, and ash layer reinforcing agent powder in a required mixing ratio and uniformly kneading the mixture is prepared by a conventional method. It is manufactured by binding and molding under heat and pressure by die molding or the like, and then mechanically processing the molded body to finish it into a predetermined shape and size. Alternatively, the raw material composition may be dispersed and suspended in water or the like, made up on a making net, squeezed to make paper or sheet, and then binding-formed under heat and pressure. You can also

[0013]

【Example】

[1] Production of test friction material (1) Preparation of raw material composition: base fiber, resin, friction modifier,
And the ash layer strengthening agent powder, etc., and knead uniformly with an Erich mixer. Composition A (friction material of the invention) Binder resin (phenolic resin) 10% by volume Base fiber Kevlar pulp 10% by volume Copper fiber 7% by volume Potassium titanate fiber 20% by volume Friction and wear modifier Cashew dust 10% by volume Graphite 8% by volume Barium sulfate 25% by volume Ashing layer strengthening agent 10% by volume Component composition B (friction material of comparative example) Binder resin (phenolic resin) 10% by volume Base fiber Kevlar pulp 10% by volume Copper fiber 7% by volume Titanium Potassium acid fiber 20% by volume Friction and wear modifier Cashew dust 10% by volume Graphite 8% by volume Barium sulphate 35% by volume Ash layer strengthening agent None

The raw materials used for the preparation of the above kneaded material are as follows. Phenolic resin: "HP309NS" manufactured by Hitachi Chemical Co., Ltd. Kevlar pulp: "IF302" manufactured by DuPont Potassium titanate fiber: "TXAX-A" manufactured by Kubota (potassium hexatitanate fiber, fiber diameter 10 to 30 µm, length) 8
0-350 μm) Cashew dust: “H102” manufactured by Cashew Co., Ltd. Barium sulfate: “BA” manufactured by Sakai Chemical Industry Co., Ltd., average particle size 4.5 μm Ashing layer strengthening agent powder: See Table 1 (both purity 99 .5%
Above, the particle size is 2 to 3 μm.

(2) Molding of molded body: A kneaded product is filled in a mold, preformed, thermoformed in the mold, taken out from the mold after thermoforming, and heat treated to obtain a friction material. . Preforming: Pressure 15 MPa Thermoforming: Temperature 180 ° C. × Pressure 30 MPa × 10 minutes Heat treatment: Temperature 180 ° C. × 3 Hr

[2] Friction and Wear Test Test pieces were cut out from each of the friction materials (A1 to A8) of the invention examples and the friction materials (B1, B2) of the comparative examples, and JI
SD 4411 "Brake lining for automobiles" was subjected to a constant-speed friction and wear test, and the ashed portion generated at the front end of the rotating contact with the disc of the test piece (see Fig. 1) was observed to evaluate the ashing status. did. Test conditions Disc material type: FC25 gray cast iron Disc temperature: 500 ° C Test time: 1 hour

[3] Test Results The test results are shown in the column "Ashed layer quality" in Table 1. Each mark in the table is as follows. ○: No damage (cracks, defects) in the ash layer △: Very small amount of defects at the end of the ash layer (no cracks) ×: Disintegration disappeared at the end of the ash layer In Comparative Example B1 corresponding to the conventional material, the edge portion collapsed and disappeared because the ashed portion became brittle due to the decrease in strength, whereas the invention examples A1 to A8
Then, as a reinforcing effect of the ashed portion, the edge portion is not damaged and the member shape is maintained. In Comparative Example B2, since the ashing layer strengthening agent powder is blended, there is no collapse and disappearance of the edge portion as in Comparative Example B1, but since the addition amount is small,
The reinforcing effect of the ashed part is slightly less, and a slight amount of defect is generated. According to the scanning electron microscope observation of the ashed portion performed on the invention example A1 and the comparative example B1, the ashed portion of the invention example A1 is different from the ashed portion of the comparative example B1 in the ashed layer reinforcing agent powder. It is observed that the fine particles of (titania powder) are dispersed in the minute gaps of the ash and sintered in a state of being clogged to strengthen the bond of the ash.

FIGS. 2 (1) and 2 (2) show the shapes of the edge portions of the test pieces of Inventive Example A1 and Comparative Example B1 after the test, and the organic components (represented by the amount of carbon) obtained by EPMA surface analysis. ) Schematically shows the concentration distribution [(1) in the figure shows invention example A1 and (2) in the figure shows comparative example B1]. The density of the scatter pattern indicates high and low carbon concentrations, and the higher the density of the scatter, the lower the degree of combustion and ashing of the organic matter. Comparing Invention Example A1 with Comparative Example B1, Comparative Example B1 (see FIG.
In (2)), the end of the ashed test piece collapsed / missed (and the unashed layer was exposed), so the ashing reaction proceeded to a wider area. Invention Example A1
In (Fig. 2 (1)), there is no loss of the edge of the ashed portion,
The progress of the ashing reaction is suppressed, and the ashing reaction remains in a narrow area.

[0019]

[Table 1]

[0020]

EFFECTS OF THE INVENTION The friction material of the present invention has a conventional structure in which the ash content is strengthened by the ashing layer strengthening agent even if the organic content is burned out by frictional heat in actual use under high surface pressure. Unlike the friction material of No. 1, the ashing layer is unlikely to collapse and disappear, the friction function can be stably maintained for a long period of time, and the reliability of the friction material subjected to severe usage conditions is enhanced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a test piece for a friction and wear test.

FIG. 2 Shape of test piece and EPMA after friction and wear test
It is explanatory drawing which shows typically the carbon concentration distribution by surface analysis.

Claims (1)

[Claims] 1. A friction material obtained by binding and molding a kneaded material containing a base fiber using a resin as a binder, and as a ashing layer reinforcing agent, sinterability for binding ash content by sintering in an ashing temperature range. A friction material containing an inorganic compound powder.