Petroleum pitch-based carbon foam

Abstract

Petroleum or coal tar pitch-based cellular or porous products having a density of preferably between about 0.1 g / cm<3 >and about 0.8 g / cm<3 >are produced by the controlled heating of mesophase carbon materials derived from coal tar or petroleum pitch having a softening point in excess of about 300° C. and preferably between about 300 and about 400° C. in a "mold" and under a non-oxidizing atmosphere. The porous product thereby produced, preferably as a net shape or near net shape, can be machined, adhered and otherwise fabricated to produce a wide variety of low cost, low density products.

Description

[0001] The present invention relates to carbon foam materials, and more particularly to such materials derived from petroleum pith starting materials.[0002] U.S. patent application Ser. No. 09 / 453,729 filed Dec. 2, 1999 and entitled, "Coal-Based Carbon Foams", describes a family of high strength and abrasion resistant carbon foams having densities of preferably between about 0.1 g / cm.sup.3 and about 0.8 g / cm.sup.3 that are produced by the controlled heating of low cost, coal particulate, preferably up to 1 / 4 inch in diameter, in a "mold" and under a non-oxidizing atmosphere. Because of the relatively low cost of the starting material, and the significantly high strength and other properties of these materials, such foams are highly economically desirable[0003] So called, "carbonaceous mesophase" materials are nematic forms of carbon commonly derived from isotropic petroleum or coal tar pitches using a variety of well known techniques. Such materials take the physical form of very fi...

AI Technical Summary

Benefits of technology

"The present invention provides a method for producing carbon foam from isotropic petroleum or coal tar pitch using mesophase carbon materials with a softening point above about 300. The method involves heating the mesophase carbon material in a \"mold\" under a non-oxidizing atmosphere at a controlled heating rate of from about 1 to about 20.degree. C. per minute to a temperature of between about 300 and 700. The resulting foam can be machined, adhered, or fabricated into various low-cost, low-density products such as filters, heat or electrical insulators, or used as a carbon foam for molding or casting. The foam exhibits high compressive strengths and can be further improved through the addition of strengthening additives or carbonization. The method is simple, economical, and commercially viable."

Problems solved by technology

While such feedstocks are relatively inexpensive, they often and generally do contain insoluble carbon solids that decrease the mechanical properties of carbon fibers manufactured therefrom, and are therefore considered highly inferior for this purpose.

While more suited to the preparation of carbon fibers, these materials are considerably more expensive than those derived from petroleum or coal tar pitch and therefore not economically suitable for many applications, such as the production of carbon foam, due to cost.

The application of processes similar to those used to obtain coal-based carbon foams from coal particulate to the production of low softening point pitch-based mesophase carbon materials has proven problematic.

.), the application of foaming processes such as those described In aforementioned U.S. patent application Ser. No. 09 / 453,729 is very difficult and attempts to foam them in this fashion have generally failed.

Such failure is primarily due to the fact that, although the mesophase materials derived from such "low softening point" petroleum and coal tar pitches, as just described, can be "foamed" using processes similar to those described in connection with the production of coal-based carbon foams, they tend to "slump" or collapse upon themselves during the foaming process resulting in a relatively dense, if somewhat porous, mass, unless extremely tight process controls are applied.

Even when such care is taken, the variability of such petroleum and coal tar pitches often results in failure of the foaming operation.

Thus such foams have not until now been found highly useful as low density and high strength structural, insulating, ablation resistant or abrasive foam materials.