Abstract: Acyl-ethyleneurea terminated compounds based on the reaction of ethyleneurea with dibasic acids or methyl esters of dibasic acids or cyclic anhydrides are useful as modifying agents, cure accelerators and blocking agents with tertiary amine catalysts for epoxy resins. As epoxy modifiers, they react with epoxy resins at 120 degrees C. without a catalyst to produce modified epoxies having increased viscosity and increased reactivity and solvent power. When combined with a suitable tertiary amine catalyst, they are useful as cure accelerators at a low cure temperature of about 80 degrees C. When combined with a tertiary amine, they form complexes which provide superior latency of the epoxy-hardener mixture at 20 degrees C. Heat-curable epoxy-based compositions treated with the materials of the invention and processes whereby the various novel compositions of the invention are made, are also described.
Abstract: An epoxy-hardener system is provided having relatively long latency periods combined with relatively short cure times at low cure temperatures. The hardeners of the present invention are ureidoamines and their derivatives, which are chelates of ureido compounds and amines. The ureidoamines are prepared by reacting an amine with the ureido compound and aqueous formaldehyde without a catalyst. Complexes of ureidoamine hardeners with various blocking agents are prepared in the melt. The hardener is prevented from curing the epoxy by the reaction between the hardener and the blocking agent. The blocked hardener is then blended with the epoxy, usually by warming the mixture briefly at about 50-60 degrees C.
Abstract: Hardeners are provided for curing epoxies at lower temperatures than currently available hardeners while retaining superior mechanical and thermal properties. A first component is selected from imidazole, dicyandiamide, or a mixture of polyamines and tertiary amines. A poiyol mixture is then selected. The first component is combined with the polyol mixture to form a hardener. The hardener is combined with epoxy resin and is cured. A method for selecting a hardener to yield an epoxy-hardener system with good properties after curing at a specified temperature and time includes selecting components for the hardener so the glass transition temperature of the cured epoxy-hardener system is not significantly lower than 45° C. above the cure temperature. The method includes steps for adjusting and controlling the ultimate glass transition temperature to maximize the mechanical properties of the epoxy-hardener system. The method regularly produces hardened epoxy systems having about 90% or more epoxy groups reactect.
Abstract: An epoxy resin hardener having a cure temperature of between about 60° C. and 100° C. comprises a mixture of:
a) an imidazole or a trihydric compound having methylol groups at the 2- and 6-positions formed by reacting a 4-alkylphenol with 2 moles of formaldehyde,
b) trimethylopropane, and
c) tetramethylguanidine or a tetramethylguanidine derived from the reaction of a monepoxide, a diepoxide, a phenol and formaldehyde, or a dihydric phenol and formaldehyde.