Allied Chemical Corporation

Ralph W Nussbaum

Harold W Tuller

Omer E Curtis, Jr

Charles T O'Neill

In a process for the production of a low molecular weight polyanhydride having a softening point within the range of about 111.degree. to 156.degree. C. by the mass polymerization reaction of a maleic monomer and at least one alkyl-substituted styrene at a temperature in the range of about 140.degree. to 200.degree. C., the improvement comprising employing an alkali metal bifluoride, preferably potassium bifluoride, as catalyst for the reaction.

Production of low molecular weight polyanhydrides

Epoxy molding compositions useful as semiconductor encapsulants, comprising (a) an epoxide compound; (b) as hardener, a polyanhydride of a maleic monomer and at least one alkyl styrene monomer or prepolymers of the polyanhydride and said epoxide compound; (c) a catalyst; (d) about 1 to 80 percent by weight of a silica filler; (e) about 1 to 80 percent by weight of an additional filler selected from the group consisting of calcined clay, antimony trioxide, antimony tetraoxide, calcium silicate, titanium dioxide, calcium carbonate, zinc oxide, magnesium oxide and mixtures thereof; (f) about 0.05 to 2 percent by weight of a silane coupling agent; and (g) about 0.01 to 2 percent by weight of a lubricant selected from the group consisting of carnauba wax, montanic acid ester wax, polyethylene wax, polytetrafluoroethylene wax and mixtures thereof.

Encapsulant compositions based on anhydride-hardened epoxy resins

Polyanhydrides are produced by a novel bulk polymerization procedure from maleic monomers and alkyl styrenes. The polyanhydrides, of low molecular weight and containing maleic monomer to alkyl styrene in a ratio greater than 1 to 1, are particularly useful as hardeners for epoxy resin-containing compositions and give rise to epoxy compositions which result in cured products exhibiting high heat distortion temperatures and excellent electrical and shelf life properties.

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West Orange, NJ, United States of America

Ralph W Nussbaum