Kinetically controlled in-situ generation of catalytic species for the curing of epoxy/amine compositions
AssigneeThe Dow Chemical Company
InventorsRaymond A. Koenig, Joseph Gan, Richard J. Hayman
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Abstract
A method of preparing epoxy parts wherein the interval of low viscosity of an amine-hardened epoxy system can be extended without sacrifice of cure time. Suitable catalysts for the epoxy-amine hardener reaction are generated in situ. As an advantage, more epoxy articles may be prepared with a given mold capacity having improved wet-out of fiber reinforcement attributed to a larger interval of low viscosity.
Claims12
A method of extending the time for cure of an amine-cured epoxy resin, by an amine curing agent having primal and/or secondary amine functionality, by curing the epoxy resin in the presence of an acid ester capable of alkylating the amino groups of the amine curing agent during cure, under conditions wherein said alkylation occurs and which are sufficient to extend the time of cure as compared to that of the corresponding composition not containing said ester.
The method as claimed in any one of the preceding claims, wherein the epoxy resin is reinforced by a fibrous reinforcing agent.
A method of extending the low viscosity interval of an accelerated epoxy resin system without extending the curing time required for production of an epoxy resin article therefrom comprising:
- (a) preparing an epoxy resin system comprising an epoxide having more than one epoxide group per molecule, and based on 100 parts of said epoxide, from 3 to 70 parts per weight of an amine curing agent having primary and/or secondary amine functionality;
- and from 0.05 to 10.0 parts by weight of the epoxy resin of an acid ester capable of alkylating the amino groups of the amine curing agent during cure;
- (b) maintaining the epoxy resin system at a temperature above the ambient temperature;
- (c) wherein the cured article made therefrom attains a Tg measured as of a demold time from 5 minutes to 30 minutes after start of the completion of Steps (a) and (b) of not more than 20.degree. C. less than the temperature of Step (b);
- (d) wherein the total conversion of epoxide in the epoxy resin at the temperature of Step (b) is 5 or more percent greater, measured at the demold time, than the conversion of epoxide in a corresponding epoxy resin system but without the acid ester according to Step (a);
- (e) and wherein the molar concentration of the ester in Step (a) is more than 1.3 times the molar concentration of the corresponding acid of a corresponding epoxy resin system and wherein the Tg of the cured ester composition is greater than the Tg of the corresponding cured epoxy resin system incorporating the corresponding acid, as measured at the demold time.
Dependencies are inferred from the claim text.