JPH09278905A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve frictional abrasion characteristics of a friction material to be used in a damping device in an automobile brake, etc. SOLUTION: This friction material is obtained by bonding and molding a mixture composed of a resin and a base material. In the friction material, polycrystal fibers of aluminum-substituted hexatitanic acid potassium barium salt expressed by the formula K2-2 XBaXTi6- YAlYO13 [X is 0.15-0.9; Y is 0.15-0.3] having a tunnel-type crystal structure of potassium hexatitanate are compounded as the base material. A compounding ratio is adjusted in the range of 3-50wt.%. The fibers have the following shapes: fiber length is about 70-400μm; the width is about 20-50μm; the thickness is about 5-10μm; an aspect ratio (length/width) is preferably high and about 5-10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material constituting a sliding surface such as a brake lining, a disc pad, a clutch facing, etc. in 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 a braking device, a resin (phenol resin, epoxy resin, etc.) is used as a binder to disperse a base fiber, and a friction / wear modifier (barium sulfate, etc.) is added if necessary. It is manufactured by binding and molding the above mixture under heat and pressure. Asbestos fibers have been conventionally used as the base fibers, but it has recently been pointed out that asbestos fibers have a carcinogenic problem. Further, although the friction material based on asbestos fiber has a stable friction coefficient in the low temperature range, the wear damage remarkably increases with the temperature rise of the friction surface, and the friction coefficient rapidly decreases and fades. There is a problem that it is easy. To meet the demands for downsizing and weight reduction of automobile brake devices, a friction material having a high coefficient of friction and capable of stably maintaining a high coefficient of friction in a wide temperature range is required. As the friction material, a friction material having potassium titanate fiber as a base material instead of asbestos fiber has been proposed. The potassium titanate fiber has the general formula:
K wherein, n = 2 to 8] ₂ Ti _n O _{2n +1} is a synthetic inorganic compound fibers represented by. Among them, potassium hexatitanate fiber (K ₂ Ti ₆ O ₁₃ ) [which has a tunnel type crystal structure in which K ions are coordinated within a tunnel frame composed of a chain of TiO ₆ octahedra] has a crystal structure The fiber is stable and has excellent wear resistance, heat resistance, and reinforcement, which are necessary as a base material for friction materials. Known industrial methods for producing potassium hexatitanate include firing method, flux method, and melting method. Fibers having a polycrystalline morphology produced by the melting method are characterized by their morphological characteristics such as whiskers. It is preferably used as a base fiber, as compared with the ultrafine single crystal fiber.

[0003]

Potassium hexatitanate fibers make it possible to alleviate the above problems associated with asbestos fiber-based friction materials. However, regarding the use of potassium hexatitanate fiber, the problem of alkali attack has been pointed out. Alkaline attack
This is a phenomenon in which K ions are released from the potassium hexatitanate fiber mixed in the resin and react with the resin to deteriorate and deteriorate the resin, which causes the durability and stability of the friction material to be impaired.
INDUSTRIAL APPLICABILITY The present invention is improved by applying, as a base material, a titanium compound polycrystalline fiber having excellent wear resistance, heat resistance, and reinforcing property based on a tunneling structure of potassium hexatitanate, and reducing and mitigating alkali attack. Another object of the present invention is to provide a friction material capable of ensuring stable friction and wear characteristics.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a friction material obtained by binding and molding a mixture of a base material and a resin, the base material having a tunneling crystal structure of potassium hexatitanate. , formula: _{K 2-2X Ba X Ti 6-Y} Al Y O 13 ... [A] [wherein, X is 0.15 to 0.9, Y is 0.15
0.3] of aluminum-substituted potassium barium hexatitanate polycrystal fiber is blended in an amount of 3 to 50% by weight.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum-substituted potassium barium hexatitanate barium polycrystal fiber of the tunnel type structure represented by the above formula, which is the base fiber of the friction material of the present invention, has a part of Ti ions forming the tunnel frame. It has a structure in which it is replaced with Al ions and at the same time, a part of K ions coordinated in the tunnel frame is replaced with Ba ions. By blending this titanium compound polycrystalline fiber into the resin as the base fiber, the friction coefficient and wear resistance of the friction material are increased, and the K ion content is higher than that when potassium hexatitanate polycrystalline fiber is used. By partially substituting it with Ba ions, the amount of free K ions from the fiber is small, and deterioration and deterioration of the resin due to alkali attack is suppressed and prevented.

Regarding the above-mentioned fiber having a tunnel type structure which is mixed with a resin as a base material, the value of X in the above formula [A] is defined in the range of 0.15 to 0.9.
If it is less than 0.15, the effect of substituting K ions with Ba ions (the effect of reducing alkali attack) is small, and if it exceeds 0.9, it becomes difficult to form a tunnel structure. The value of is limited to the range of 0.15 to 0.3 because if it is less than 0.15, the replacement effect of Ti ions by Al ions is poor, and if it exceeds 0.3, the tunnel type structure Is difficult to form.

The fiber morphology of the above-mentioned base fiber is such that the uniform dispersibility in the resin and the reinforcing action are effectively exhibited.
Fiber length: about 70-400 μm, width: about 20-50 μm,
Thickness: about 5-10 μm, aspect ratio (length /
A width of about 5 to 10 having a high aspect ratio and a polycrystalline form is preferably used. The mixing ratio in the resin is
Depending on the application of the friction material and the required friction and wear characteristics, about 3 ~
It is adjusted within the range of 50% by weight. If the amount is less than about 3% by weight, the compounding effect is small. On the other hand, if it exceeds 50% by weight, the effect of improving the friction and wear characteristics is almost saturated, and there is no benefit to increase the amount further.

The friction material of the present invention is used as a base fiber together with the above-mentioned aluminum-substituted potassium barium hexatitanate polycrystal fiber, various known fibers such as polyamide (nylon) fiber, aramid fiber, steel fiber, stainless fiber, and copper. 1 type selected from fiber, brass fiber, carbon fiber, glass fiber, ceramics fiber, rock wool, wood pulp, etc.
Composite of two or more fibers (for example, the total amount of aluminum-substituted potassium barium hexatitanate barium polycrystal fiber: about 10
65% by weight) may be used. These base fibers are silane coupling agents (aminosilane, vinylsilane, epoxysilane, methacryloxylan, mercaptoxylan, etc.) for the purpose of improving dispersibility and binding property with a binder resin, if necessary. ), Or a titanate-based coupling agent (isopropyltriisostearoyl titanate,
Surface treatment (coupling treatment) with di (dioctyl pyrophosphate) ethylene titanate or the like is performed according to a conventional method and used.

If desired, the friction material of the present invention may be a known friction / wear modifier, 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 powder such as barium sulfate, calcium carbonate, metal powder such as copper, aluminum, zinc, iron, alumina, silica, chromium oxide, copper oxide, antimony trioxide, oxidation One or more components selected from oxide powders such as titanium and iron oxide are used in an appropriate amount (for example, 20 to 20) for the purpose of improving friction and wear characteristics (friction coefficient, wear resistance, vibration characteristics, naki, etc.). 70% by weight). Also, it is not different from ordinary friction materials in that various additives, for example, rust preventives, lubricants, abrasives, and the like are blended in an appropriate amount (for example, 50% by weight or less) in accordance with the use and usage mode.

The resin component which is a binder is a commonly used material such as phenol resin, formaldehyde resin,
Examples thereof include thermosetting resins such as epoxy resins and silicone resins, and thermosetting resins thereof (modified with cashew oil and dryness), and rubber resins such as natural rubber, styrene butadiene rubber, and nitrile rubber.

The preparation of the raw material mixture for producing the friction material of the present invention is the same as the conventional friction material except that the polycrystalline fiber having the tunnel structure represented by the above formula is used as the base fiber. In addition, no special condition or limitation is imposed on the manufacturing process. That is, a base fiber is dispersed in a binder resin, and a friction and wear modifier is added as necessary,
And a rust preventive agent, a lubricant, an abrasive, etc. are added and mixed evenly to prepare a raw material composition, and pre-molding is followed by die molding or the like under heating / pressurization (pressing pressure of about 10 to 40 MPa, temperature). Binder molding is performed at about 150 to 200 ° C, and after taking out from the mold, heat treatment is performed in a heating furnace at a temperature of about 150 ° C.
˜200 ° C., holding time: about 1 to 12 hours), and then the molded body is subjected to machining and polishing to finish into a friction material having a predetermined shape. Alternatively, a step of dispersing and suspending the raw material composition in water, etc., making a paper with a paper making net, squeezing water to make sheets, stacking an appropriate number of sheets, and binding-molding under heating and pressure. It is also possible to obtain a predetermined friction material by subjecting the molded body to mechanical processing or polishing processing via the above.

[0012]

【Example】

(1) Fabrication of friction material The following raw material composition was prepared by using the fiber A or the fiber B as the base fiber and preformed (pressing force: 14.7 MPa).
= 150Kg / cm ² , temperature: room temperature, time: 1 minute), and then binding molding with a die (pressing force: 14.7MPa = 150Kg / cm ² ,
Temperature: 170 ℃, pressurizing and holding time: 5 minutes), after molding, mold release and heat treatment in a drying oven (hold at 180 ℃ for 3 hours). After that, it was cut into a predetermined size and subjected to polishing to obtain a disk pad A (base fiber: A) and a disk pad B (base fiber: B). [Base Fiber] Fiber A: Aluminum-substituted potassium barium hexatitanate fiber K _0.8 Ba _0.6 Ti _5.85 Al _0.15 O ₁₃ [By reference example described below] Fiber B: Potassium hexatitanate fiber (K ₂ Ti ₆ O ₁₃ ) Fiber size (Average) is 300 μm in length and 40 in width
The thickness is 7 μm and the aspect ratio is 7. [Composition of raw material composition] Base fiber (fiber A or B) ... 30% by weight Binder resin (phenol resin) ... 20% by weight Friction modifier (barium sulfate) ... 50% by weight

(2) Friction and Wear Test Disk Pad A (Invention Example) and Disk Pad B
Regarding (Comparative Example), the friction coefficient and the specific wear rate (cm ³ / N · m) were measured by a constant speed friction wear test specified in JIS D4411 “Brake lining for automobiles”, and the results shown in FIGS. 1 and 2 were obtained. Got Disc friction surface: FC25 gray cast iron, surface pressure: 10Kg / cm ² , friction speed: 7m / s.

As shown in FIG. 1 (friction coefficient) and FIG. 2 (wear rate), the friction material A containing aluminum-substituted potassium barium hexatitanate polycrystal fiber as the base fiber is potassium hexatitanate polycrystal fiber. Compared to the friction material B having the base fiber of, the friction coefficient is high even in a high temperature range, and the abrasion resistance is excellent.

[0015]

[Reference example]

 [Aluminum-substituted potassium barium hexatitanate by the melting method
Production of polycrystalline fiber] (Raw material preparation) Calcium carbonate, barium carbonate, titanium oxide
K and alumina powder _TwoCO_Three/ BaCO
_Three/ Al_TwoO_Three/ TiO_Two= 4: 1: 0.125: 8.75
Mixed at the same ratio. (Heat melting and solidification treatment) Raw material at 1200 ° C for 1H
r Heat to melt, pour the melted product into a cooling container,
It is cooled and solidified to obtain a lump. The lumps are crystalline fibers (
Lumi-substituted barium dititanate fiber)
You.

(Elution / defibration treatment) The weight ratio of the fiber mass is 10
After immersing in 0 times the amount of water and allowing to stand overnight, industrial sulfuric acid is added to adjust the pH, and K and Ba are eluted and defibrated with stirring for 5 hours under propeller stirring. (Baking treatment) Fibers (hydrates) recovered from the treatment liquid were dehydrated and dried, and then heat-treated (crystal structure conversion) at 1150 ° C. for 2 hours to obtain the following composition (by fluorescent X-ray analysis) and tunnel-type crystal structure ( Aluminum substituted potassium barium hexatitanate barium fibers (polycrystalline) having X-ray powder diffraction) were obtained. K _0.8 Ba _0.6 Ti _5.85 Al _0.15 O ₁₃ (X in the formula [A]
= 0.6, Y = 0.15) Fiber size (average): length 300 μm, width 40 μm, thickness 7
μm, aspect ratio (length / width) 7 (scanning electron microscope).

[0017]

EFFECTS OF THE INVENTION The friction material of the present invention stably maintains a high friction coefficient and high wear resistance from a low temperature range to a high temperature range as a blending effect of aluminum-substituted potassium barium hexatitanate barium polycrystal fiber. Moreover, deterioration and deterioration of the resin due to alkali attack is reduced and alleviated. It is useful as a brake lining, a disc pad, a clutch facing, etc. that composes a braking system for automobiles, vehicles, aircraft, and various industrial machines. It enables the downsizing and weight reduction of the braking system and improves the braking function. -The effects such as stabilization and improvement of durability can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a measurement result of a friction coefficient of a friction material.

FIG. 2 is a graph showing a measurement result of a specific wear rate of a friction material.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F16D 69/02 F16D 69/02 K

Claims (1)

[Claims] 1. A friction material obtained by binding-molding a mixture of a resin and base fibers, wherein the base fibers have a tunnel hexagonal crystal structure of potassium hexatitanate.
_2-2X Ba _X Ti _6-Y Al _Y O ₁₃ [wherein, X is 0.15 to 0.9, and Y is 0.15 to
0.3] aluminum-substituted potassium barium hexatitanate polycrystal fiber is blended in an amount of 3 to 50% by weight.