Curing epoxy resins using dicy, imidazole and acid
AssigneeAlliedSignal Inc.
InventorLarry D. Olson
Life of this patent
Estimating the term…
Abstract
A curable epoxide composition consists essentially of curable epoxides, dicyandiamide as a curing agent in an amount less than needed to fully cure the epoxides, an imidazole in an amount exceeding that needed as a catalyst and capable of curing the epoxides in combination with the dicyandiamide, a reactivity controller for the imidazole to reduce the curing speed, and a solvent. The use of undesirable solvents such as DMF is reduced. A glass transition temperature greater than 135.degree. C. is obtained in the cured composition and is maximized by balancing the amounts of dicyandiamide, the imidazole, and the reactivity controller.
Claims19
A curable epoxide composition consisting essentially of
- (a) at least one curable difunctional epoxide, optionally with one or more epoxides having a functionality greater than two;
- (b) as a curing agent, dicyandiamide in an amount less than required to cure the epoxides of (a) but sufficient to provide a gel time greater than about 120.degree. C.;
- (c) an amount of an imidazole sufficient to reduce the gel time below about 120 sec. when added to (a) and (b);
- (d) as a reactivity controller for the imidazole of (c), an acid capable of reacting with said imidazole of (c) in an amount sufficient to obtain a gel time greater than about 120 seconds when added to (a), (b) and (c);
- (e) a solvent sufficient to dissolve dicyandiamide, optionally with at least one additional solvent selected from the group consisting of acetone, methyl ethyl ketone, and ethyl alcohol;
- and
- (f) optionally a chain-extender for said epoxides and a catalyst for reacting said chain extender with said epoxides.
A method of increasing the glass transition temperature (Tg) of a cured epoxy formulation comprising the steps of:
- (a) adding to uncured epoxide resins an mount of dicyandiamide less than required to fully cure said resins but sufficient to provide a gel time greater than about 120.degree. C. and a solvent sufficient to dissolve said dicyandiamide;
- (c) adding to the mixture of epoxy resins and dicyandiamide of (a) an mount of an imidazole sufficient to fully cure said resins in combination with said dicyandiamide and to reduce the gel time below about 120 seconds when added to (a);
- (c) adding to the mixture of epoxy resins, dicyandiamide, and imidazole of (b) an amount of an acid capable of controlling the reactivity of said imidazole and of increasing the gel time above about 120 seconds when added to (a) and (b);
- (d) repeating the steps of (a), (b), and (c) to determine the proportions of said dicyandiamide, imidazole, and acid which provide a predetermined glass transition temperature of said epoxy resins when fully cured.
Dependencies are inferred from the claim text.