Amidines as initiators for converting acrylic fibers into carbon fibers
OwnerKenneth Wilkinsoninventor
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Abstract
A method of preparing PANOX fibers useful in the production of superior carbon fiber material; the method based on the concept that the true initiators in the preparation of superior carbon fiber are amidines.
Claims19
A precursor fiber for preparing carbon fiber comprising a chemically treated solid acrylonitrile polymer wherein the polymer comprises cyano and amidine pendant groups and wherein the amidine groups are present in an amount of about 1-10 mole percent, based on total amount of functional groups.
A process of making a precursor fiber for preparing carbon fiber comprising:
- (a) preparing a suspension of a solid acrylonitrile polymer in a solvent;
- (b) adding to the suspension a liquid or gaseous chemical treating agent which is a member selected from the group consisting of a primary organic amine, a secondary organic amine, ammonia and mixtures thereof;
- (c) spinning the suspension to obtain a fiber;
- (d) heating the fiber to obtain a precursor which comprises a chemically treated solid acrylonitrile polymer wherein the treated polymer comprises cyano and amidine pendant groups;
- and
- (e) separating the precursor fiber from the suspension whereby the precursor fiber contains amidine groups in an amount of about 1-10 mole percent, based on total amount of functional groups.
A process according to claim 11 wherein the acrylonitrile copolymer is prepared
- from acrylonitrile monomer and a co-monomer selected from the group consisting of itaconic acid, acrylic acid, methacrylic acid, crotonic acid, maleic anhydride, p-vinyl benzoic acid, itaconic anhydride, and mixtures thereof.
A process for making a precursor fiber for preparing carbon fiber comprising:
- (a) placing in a heating zone a fiber comprising an acrylonitrile copolymer comprising at least 90 mole percent acrylonitrile units, and about 1 mole percent to about 10 mole percent nitrogen-containing compound as neutralizing cation for carboxylate groups, said compound incorporated into the polymer by copolymerization of one or more copolymerizable, carboxylate containing co-monomers;
- (b) heating the fiber in air at a temperature of about 200° C. to about 250° C. for a time of about 3 minutes to about 15 minutes;
- and
- (c) withdrawing a precursor fiber wherein the precursor fiber contains amidine groups in an amount of about 1-10 mole percent, based on total amount of functional groups.
A method of selecting a precursor fiber for preparing a carbon fiber, the method comprising the steps of:
- (a) obtaining a fiber comprising a chemically treated solid acrylonitrile polymer which is the reaction product of solid polyacrylonitrile and a nitrogen-containing compound, the nitrogen-containing compound being in the liquid or gaseous state,
- (b) analyzing the fiber by means of an infrared spectrophotometer;
- (c) removing the fiber to a heating zone;
- (d) heating the fiber in air at a temperature of about 250° C. to about 275° C. for a time of about 3-10 minutes;
- (e) withdrawing the fiber from the heating zone;
- (f) cooling the fiber;
- (g) analyzing the cooled fiber by means of an infrared spectrophotometer;
- (h) calculating the amount of reduction of nitrile absorbance based on the IR scans of the original unheated fiber and the heated fiber;
- and
- (i) selecting the fiber for preparing carbon fiber when the nitrile absorbance is reduced by about 15% to about 25%.
Dependencies are inferred from the claim text.