Dry blending with fibers

Details Dry blending with fibers Dry blending with fibers

1988-08-17

1990-08-28

Simone, Timothy F.

Agitating

Having specified feed means

Agitation of material in feeder or supply reservoir

366 30, 366 76, 366165, 366290, 366292, B01F 1502

Patent

active

049531352

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The field of this invention relates to compounding of fibrous components in a binder matrix. More specifically, this invention relates to the use of carbon fibers in particulate binder matrices.


PRIOR ART

Brake pads are conventionally made by resin reinforced materials and then machined into appropriate shapes. Examples of appropriate resins that are used in brake pads are phenolic resins. Necessary attributes of brake pads are their ability to withstand mechanical compression, maintain their shape, withstand high temperatures, and distribute friction uniformly.
Currently, the fibrous reinforcement for brake pads is usually provided by asbestos. However, in light of asbestos' hazards and the need for work place safety for employees, substitutes for asbestos are in demand. Primary characteristics that make asbestos a useful fibrous reinforcement material in brake pads are its high temperature, performance, high strength and light weight.
It is these same characteristics that make carbon fiber a particularly attractive partial substitute. Unfortunately, the carbon fibers which produce the best results tend to be those which are most uniform in terms of diameter and length. This is unfortunate because it is precisely the uniformity of length and diameter which tends to result in a phenomena which for purposes for this specification will be referred to as the "balling tendency".
In a mix of dry fibrous carbon fibers, there is a tendency for the carbon fibers to clump together in spheroidal particles. These particles are made up of clumped and intertwined discrete carbon fibers. Once carbon fibers have formed tightly agglomerated closely interacting bundles of carbon fibers, they do not uniformly distribute throughout a dry binder matrix during stirring.
European patent application, having publication No. 0125511 and application No. 84104229.4 with a date of filing Apr. 13, 1984, entitled "Carbon Fiber--Reinforced Gypsum Models and Forming Molds, Gypsum Powdered Materials for Making Such Models and Molds, and a Method for Producing Them", discloses usefulness of carbon fibers as reinforcement materials. Also disclosed is the fact that carbon fibers are apt to form lumps. To insure uniform dispersion of carbon fibers having lengths ranging from 5 to 100 mm, prior to addition to a gypsum slurry, bundles of carbon fibers are separated into single fibers by dispersing them in water with supersonic agitation. Once the carbon fibers have been uniformly dispersed in a gypsum slurry, they will tend to remain separated provided the ratio of amount of the carbon fibers to gypsum is very small.
The following patents are examples of technology relating to friction elements of the type which are often employed in brakes of automotive vehicles. U.S. Pat. No. 2,428,298 of R. E. Spokes et al. entitled "Friction Element", discloses use of finely divided dust-like materials composed essentially of vulcanizable synthetic rubber-like elastoprenes of the butadiene-acrylonitrile copolymer type compounded with about 5% to about 10%, by weight, of sulfur. These materials provide useful friction-controlling or friction-stabilizing agents in friction elements.
U.S. Pat. No. 3,007,890 of S. B. Twiss et al., entitled "Friction Elements and Method of Making Same", discloses the use of high molecular weight, high acrylonitrile content, butadiene-acrylonitrile copolymer, synthetic rubber-like elastoprenes give superior stable friction elements with a high level of friction coefficient at high temperatures in over a wide range of temperatures.
U.S. Pat. No. 3,007,549 of B. W. Kline, entitled "Friction Controlling Means", discloses a multi component, friction producing device.
U.S. Pat. No. 2,685,551 of R. E. Spokes, entitled "Friction Elements and Methods of Making Same", discloses friction elements employing synthetic rubber is the principal ingredient in the bonding agent. Bonding agents commonly comprise thermosetting resins and/or a synthetic rubber.
It has been observed that carbon fibers that have undergo

REFERENCES:
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patent: 2428298 (1947-09-01), Spokes et al.
patent: 2685551 (1954-08-01), Spokes
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patent: 3007890 (1961-11-01), Twiss et al.
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patent: 3314398 (1967-04-01), Legourd
patent: 4242841 (1981-01-01), Ushakor et al.
patent: 4427645 (1984-01-01), Frenken et al.
patent: 4501047 (1985-02-01), Wrassman
patent: 4514093 (1985-04-01), Coch et al.
patent: 4669887 (1987-06-01), Lee

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