The Dexter Corporation

David S Darrow

Polyimide resins, which have reduced anhydride content when molded, are prepared by a novel reaction process that includes reacting an esterified aromatic tetracarboxylic acid or anhydride monomer with a primary aromatic diamine until substantially no free monomer remains to form a polyamide-acid (the molar ratio of esterified monomer to diamine ranging from 1:1 to 1:2); reacting the polyamide-acid with a low molecular weight end-capping agent to form an end-capped polyamide-acid; and heating the end-capped polyamide-acid to form the polyimide.

Polyimide with reduced anhydride content

A coated substrate in which the coating includes abrasion-resistant particles protruding from the hardened surface of a metal matrix and is bonded to the substrate.

Abrasion-resistant coating

A classifying cyclone efficient at removing very fine particles. In preferred embodiments, the cyclone employs an annular bevel ring positioned along the interior wall to redirect separated particles from the wall back into the path of classifying air. A control air deflector is placed in the path of the classifying airstream and adjusted vertically to provide adjustment of the annular orifice through which the classifying air passes. The air deflector is positioned at approximately the height of the bevel ring.

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Portville, NY, United States of America

David S Darrow