Chopped carbon fiber preform processing method using coal tar pitch binder

Abstract

A procedure for forming a chopped carbon fiber preform using a coal tar pitch binder and the product thereof.

Description

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 10 / 476,017 filed Oct. 23, 2003 and claims the benefit under 35 USC 119(e) of U.S. Provisional Application Ser. No. 60 / 475,107 filed May 30, 2003.FIELD OF THE INVENTION [0002] The present invention relates to friction material preforms using a coal tar-pitch binder, and more specifically, a chopped carbon fiber preform using a coal tar pitch binder and the method of making thereof. BACKGROUND OF THE INVENTION [0003] Coal tar is a primary by-product material produced during the destructive distillation or carbonization of coal into coke. While the coke product is utilized as a fuel and reagent source in the steel industry, the coal tar material is distilled into a series of fractions, each of which are commercially viable products in their own right. A significant portion of the distilled coal tar material is the pitch residue. This material is utilized in the production of anodes for aluminum smelti...

AI Technical Summary

Benefits of technology

[0023] Generally, at least one presently preferred embodiment of the present invention broadly contemplates output coal tar pitch having a high softening point greater than 170° C. used as a “modifier” in the formation of carbon / graphite products. The utilization of high softening point pitch product of the present invention addresses the problems associated with evolution of volatiles during production by yielding a lower number of volatiles. The lower volatiles yield means there are fewer organic compounds to capture or destroy, and the product produced has a higher density with resulting superior properties of the finished carbon / graphite product. Also, the high softening point coal tar pitch portion of the resulting carbon / graphite product shrinks thereby improving product density and strength. The resulting product exhibits increased efficiency to conduct heat and electricity.

[0025] Further, at least one presently preferred embodiment of the present invention broadly contemplates high softening point coal tar pitch used as a saturant in the formation of aircraft brakes. The saturation of carbon fiber preforms can be performed with the high softening point pitch of the present invention resulting in a 95% saturation of the carbon fiber preform in about one hour. This preliminary quick saturation has the potential to reduce the time necessary for complete carbon saturation of the preform by many hours. Also, dynamometer testing results of the finished aircraft brakes produced using high softening point pitch have shown superior friction characteristics.

[0026] Additionally, at least one presently preferred embodiment of the present invention broadly contemplates high softening point coal tar pitch used in the production of rubber products. Rubber formulations containing the pitch of this invention have exhibited superior adhesive properties.

[0027] Further, at least one presently preferred embodiment of the present invention broadly contemplates distillate used to make mesophase pitch. The distillate product of this invention is a quinoline insolubles free coal tar derived material which has been shown to produce high quality mesophase. Also, the economics for mesophase production of the present invention result in a product with a much lower cost.

Problems solved by technology

The other is a declining supply of crude coal tar from the coke-making process.

No commercially attractive substitute for coal tar pitch in the aluminum industry has been developed, however.

Although higher softening points of up to 170° C. can be reached using batch distillation, the combination of high heat and longer residence time can often lead to decomposition of the coal tar pitch and the formation of unwanted mesophase pitch.

The major problem experienced with pitch in the process is evolution of volatiles during the carbonization step.

Volatiles evolution causes two major problems: 1) emissions of organic compounds, and 2) reduction of the density of the finished baked product.

The reduction of the density of the carbon / graphite product results in an inferior product with reduced strength, increased reactivity, and increased electrical resistivity.

One of the major problems experienced with automobile brakes is a characteristic called fade.

It is believed that fade is caused by the heat instability of the phenolic resin binder of the friction material.

This gas layer causes a loss of friction resulting in the need to push harder on the brake pedal.

The chemical vapor infiltration process is very time consuming with about 600 hours of processing time required to produce a finished product.

Significant work has been performed to produce mesophase pitch from coal tar pitch with limited success because of the quinoline insolubles content of the pitch.

It has been shown that the quinoline insolubles particles in coal tar pitch hinder coalescence of the mesophase spheres causing a poor quality mesophase to be formed.

While these processes work quite well and allow for production of a high quality mesophase, they result in a very high cost of the mesophase product.

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