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US 4,395,514 AGranted
Process for preparing a carbon fiber reinforced composite article which utilizes a polyimide matrix
AssigneeCelanese Corporation
InventorRobert Edelman
Life of this patent
Estimating the term…
Abstract
The present invention provides an improvement in a process for preparing carbon fiber reinforced polyimide compositions from a mixture of monomers by the application of heat in two stages. The improvement comprises incorporating a cyclic peroxyketal catalyst, such as 3,6,6,9,9,-pentamethyl-3-(ethylacetate)-1,2,4,5-tetraoxycyclononane, into the monomer mixture prior to reaction.
Claims7
A process for preparing a carbon fiber reinforced composite article wherein a polyimide constitutes the continuous phase which comprises:
- (1) providing a polyimide forming catalyst-monomer mixture comprising:
- (a) at least one ester of the formula:
- ##STR16## wherein R.sub.3 is a tetravalent aryl radical, and R.sub.4 is selected from the group consisting of a lower alkyl radical having 1 to 4 carbon atoms, and hydrogen, with two R.sub.4 groups being alkyl and two R.sub.4 groups being hydrogen;
- (b) at least one amine of the formula:
- H.sub.2 N--R.sub.5 --NH.sub.2
- wherein R.sub.5 is a divalent aryl radical;
- and
- (c) at least one ester of the formula:
- ##STR17## wherein R.sub.4 is selected from the group consisting of a lower alkyl radical having 1 to 4 carbon atoms, and hydrogen with one R.sub.4 group being alkyl and one R.sub.4 group being hydrogen, and R.sub.6 is a divalent radical of the formula:
- ##STR18## wherein Y, which is the same or different, is selected from the group consisting of hydrogen, and methyl and X is an alkylidene radical of from 1 to 6 carbon atoms;
- wherein monomers (a), (b) and (c) are present in said mixture at a molar ratio of n:(n+x):y respectively, wherein n is an integer of from about 1 to about 20, x is an integer of from about 0.5 to about 1, and y is an integer of from about 1.5 to about 2, and from about 0.5 to about 15%, by weight, based on the weight of the monomer mixture, of at least one peroxide catalyst represented by the structural formula:
- ##STR19## wherein R, which is the same or different, is a lower alkyl group having from 1 to about 3 carbon atoms, and R.sub.1 is an alkyl acetate group of the formula:
- ##STR20## wherein R.sub.2 is an alkyl group having from 1 to about 4 carbon atoms;
- (2) impregnating at least one carbon fiber lamina with said polyimide forming catalyst-monomer mixture of step (1);
- (3) reacting said polyimide forming catalyst-monomer mixture in the presence of the at least one carbon fiber lamina at a temperature of from about 250.degree. to about 350.degree. F. for a period of from about 0.5 to about 3 hours and at a pressure of from about 2 to about 30 in.Hg to form a prepolymer;
- and
- (4) curing the prepolymer to form a carbon fiber reinforced composite article while employing a short cure procedure which comprises the steps of heating the prepolymer to a temperature of from about 375.degree. to about 425.degree. F. at a continuous or intermittent pressure of from about 175 to about 225 psi;
- raising the temperature of the prepolymer to a temperature of from about 450.degree. to about 625.degree. F. while under a continuous or intermittent pressure of from about 175 to about 225 psi;
- and maintaining the temperature of the prepolymer thereat for a period of about 10 to about 120 minutes.
16 more elements
A process for preparing a carbon fiber reinforced composite article wherein a polyimide constitutes the continuous phase which comprises:
- (1) providing a polyimide forming catalyst-monomer mixture comprising:
- (a) at least one ester of the formula:
- ##STR22## wherein R.sub.3 is a tetravalent aryl radical, and R.sub.4 is selected from the group consisting of a lower alkyl radical having 1 to 4 carbon atoms, and hydrogen, with two R.sub.4 groups being alkyl and two R.sub.4 groups being hydrogen;
- (b) at least one amine of the formula:
- H.sub.2 N--R.sub.5 --NH.sub.2
- wherein R.sub.5 is a divalent aryl radical;
- and
- (c) at least one ester of the formula:
- ##STR23## wherein R.sub.4 is selected from the group consisting of a lower alkyl radical having 1 to 4 carbon atoms, and hydrogen with one R.sub.4 group being alkyl and one R.sub.4 group being hydrogen, and R.sub.6 is a divalent radical of the formula:
- ##STR24## wherein Y, which is the same or different, is selected from the group consisting of hydrogen, and methyl and X is an alkylidene radical of from 1 to 6 carbon atoms;
- wherein monomers (a), (b) and (c) are present in said mixture at a molar ratio of n:(n+x):y respectively, wherein n is an integer of from about 1 to about 20, x is an integer of from about 0.5 to about 1, and y is an integer of from about 1.5 to about 2, and from about 0.5 to about 15%, by weight, based on the weight of the monomer mixture, of at least one peroxide catalyst represented by the structural formula:
- ##STR25## wherein R, which is the same or different, is a lower alkyl group having from 1 to about 3 carbon atoms, and R.sub.1 is an alkyl acetate group of the formula:
- ##STR26## wherein R.sub.2 is an alkyl group having from 1 to about 4 carbon atoms;
- (2) impregnating at least one carbon fiber lamina with said polyimide forming catalyst-monomer mixture of step (1);
- (3) reacting said polyimide forming catalyst-monomer mixture in the presence of the at least one carbon fiber lamina at a temperature of about 250.degree. to about 350.degree. F. for a period of from about 0.5 to about 3 hours and at a pressure of from about 2 to 30 in.Hg to form a prepolymer;
- and
- (4) curing the prepolymer to form a carbon fiber reinforced composite article while employing a low temperature cure procedure which comprises the steps of heating the prepolymer to a temperature of from about 300.degree. to about 330.degree. F. while under a continuous or intermittent pressure of from about 2 to about 30 in.Hg;
- raising the temperature of the prepolymer therefrom until a temperature of from about 375.degree. to about 390.degree. F. is attained;
- maintaining the temperature of the prepolymer thereat for a period of from about 4 to about 10 hours to form a polyimide.
16 more elements
Dependencies are inferred from the claim text.