Diepoxides manufactured by epoxidation of diacetals or diketals from .DELTA..sup.3 -cyclohexene-1,1-dimethanol or its homologues and dialdehydes or diketones which apart from the two aldehyde groups or keto groups only contain hydrocarbon radicals, for example the diepoxide of the formula ##SPC1## The new diepoxides couple good mechanical properties with a significantly higher heat distortion point according to Martens than the known epoxidised diacetals of similar constitution, in which the acetal groups are interrupted by an alkylene-oxyalkylene chain instead of by an alkylene chain which is free of ether oxygen.

The invention relates to a process for the preparation of powder coatings, in which a mixture of A) a binder comprising an epoxide group-containing synthetic resin or a mixture of epoxide group-containing synthetic resins, and B) a crosslinking agent comprising a compound which contains on statistical average at least two carboxyl groups and at least one acid anhydride group per molecule, or a mixture of such compounds, is admixed before or during the melt homogenization process with C) a polyol or a mixture of polyols in such an amount that from 0.1 to 0.9 hydroxyl groups of component C) are present per acid anhydride group of component B). The mixture is homogenized in the molten state and the resulting homogenized melt, after having cooled and solidified, is powdered.

A non-shrinking, strain-free, dimensionally-stable modified epoxy resin is disclosed for use in the fabrication of composite, structural laminates. The uniqueness of product preparation is that the optimum amount of the lactone compound can be copolymerized with the epoxy resin since equimolar amounts of each monomer do not necessarily need to be copolymerized to achieve the optimum shrink resistance. By varying the ratio of shrink-resistant monomer and epoxy in a resin blend, a means is available for controlling the shrinkage, and, in this manner, it would be possible to produce a laminate with a matrix so tailored so that reinforcing fibers would not undergo breakage, or pull out of the matrix on being stressed. The modified epoxy resin is the reaction product produced from reacting a compound selected from 6-hexanolactone and 5-norbornene-2,2-dimethanol with the diglycidyl ether of bisphenol A and cured with the curing agent hexahydrophthalic acid. The ratio of the modified-epoxy composition to epoxy can be varied to achieve the desired volume change or desired shrinkage control in the matrix resin when used in a lamination process which employs fibers selected from glass, graphite and poly-p-ethylene terephthalamide as required for high brust strength pressure uses.

A cleavable epoxy resin composition suitable for encapsulating electronic chips and a method for making the composition comprises the cured reaction product of a diepoxide; a cyclic dicarboxylic anhydride curing agent mixture; a 1,3-diaza compound having two nitrogen atoms present with one nitrogen atom doubly bonded to the central carbon and singly bonded to one other carbon, and the other nitrogen atom singly bonded to the central carbon and singly bonded to another carbon and singly bonded to a hydrogen. The 1,3-diaza compound serves either as the sole catalyst or in combination with a tertiary amine catalyst different from the diaza compound. The composition may include an optional hydroxy functional compound capable of reacting with the cyclic anhydrides to form a half ester thereby initiating the reaction between the diepoxide and the cyclic dicarboxylic anhydride curing agent. The resin can be used for the encapsulation of electronic parts, but can be removed by a solvent. This feature allows electronic components to be recycled.

A cleavable epoxy resin composition suitable for encapsulating electronic chips comprising the cured reaction product of a diepoxide containing a cyclic anhydride curing agent and an amine promoter.