Coating processes – Heat decomposition of applied coating or base material – Base material decomposed or carbonized
Patent
1999-09-13
2000-09-19
Cameron, Erma
Coating processes
Heat decomposition of applied coating or base material
Base material decomposed or carbonized
427353, 427381, 427382, B05D 302, D01F 914, D01F 916, D01F 1112
Patent
active
061208418
DESCRIPTION:
BRIEF SUMMARY
This is the national stage of International Application No. PCT/FR98/00504, filed Mar. 12, 1998.
1. Field of the Invention
The present invention relates to making activated fabrics out of carbon fibers.
Such fabrics are usable in particular for filtering fluids, e.g. for processing gaseous or liquid waste.
2. Background of the Invention
Various methods are known for making carbon fiber fabrics starting from a cellulose fiber fabric which is impregnated with a liquid composition containing an ingredient whose function is to promote dehydration of the cellulose, prior to being subjected to heat treatment at a temperature which is high enough to transform the cellulose fibers essentially into carbon fibers.
Such ingredients that promote the dehydration of cellulose are also known as fire-proofing agents for cellulose. They enable the cellulose precursor to be carbonized with better efficiency and at a faster rate.
The making of an activated fabric out of carbon fibers then includes activation treatment of the carbon fiber fabric by the action of an oxidizing gas, e.g. carbon dioxide, water vapor, or air, at a temperature greater than 500.degree. C., typically in the range 600.degree. C. to 1000.degree. C., i.e. at a temperature higher than the carbonizing temperature. A technique for activating a carbon fabric in an oven is described in document FR-A-2 741 363.
Reference can also be made to the following documents: "Database WPI, Derwent Publications Ltd.", London, 4B, No. AN96-299 267 (TW-A-274 567), No. AN77-52947Y (JP-A-52-070121), No. AN85-287 343 (JP-A-60-198 166), No. AN83-49756K (JP-1-56-167716), and "Patents Abstracts of Japan", Vol. 4, No. 38 (C-004) (JP-A-55-010472) which describe the activation of carbon fiber fabrics previously obtained by carbonizing a cellulose precursor to which there has been added a cellulose dehydration promoter (ammonium chloride, phosphoric acid, zinc chloride, . . . ).
Those activation techniques require special heat treatment. Their overall mass efficiency is relatively low compared with the cellulose fiber fabric, since the activation treatment has the effect of creating an array of micropores by eliminating carbon. Cost price is relatively high since the carbon fiber fabrics to which activation is applied are themselves expensive. In addition, activation has a major effect on the mechanical qualities of the carbon fibers, and it can be seen that the above-mentioned documents do not, in general, mention the mechanical properties of activated carbon fibers.
OBJECTS AND BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a method enabling activated fabrics of carbon fibers to be obtained starting from cellulose type carbon-precursor fibers, and to do so in a manner that is less expensive and with much greater efficiency than in the prior art.
Another object of the invention is to provide a method enabling activated fabrics of carbon fibers to be obtained having good strength and conserving a high degree of flexibility, enabling them to be shaped, e.g. by being draped.
The invention provides a method of making an activated fabric of carbon fibers, the method comprising the steps that consist in providing a fabric of fibers of a carbon-precursor cellulose material, impregnating the fabric with a composition containing at least one inorganic ingredient having a function of promoting dehydrating of cellulose, and performing heat treatment on the impregnated fabric at a temperature which is sufficient to cause the precursor cellulose to be transformed essentially into carbon, and obtaining a fabric of carbon fibers, which method is characterized in that the heat treatment consists in raising temperature at a speed lying in the range 1.degree. C./min to 15.degree. C./min followed by keeping the temperature constant in the range 350.degree. C. to 500.degree. C., and followed by a step of washing the fabric, thereby directly obtaining an activated fabric of carbon fibers having a specific surface area of not less than 600 m.sup.2 /g, without subsequ
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Fontarnou Veronique
Ouvry Ludovic
Parmentier Philippe
Cameron Erma
Messier-Bugatti
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