Process for preparing polycarbonate copolymer foam pattern suitable for lost foam casting, pre-expanded polymer beads therefor and method of forming said beads.

摘要

The evaporative casting of molten metals has been shown to produce castings having smooth surfaces without any sign of carbon deposits thereon by using a copolymer polycarbonate in making patterns for the lost foam casting process, said copolymer polycarbonate being selected from: (A) those comprising repeating units of the structure <CHEM> wherein in each unit n is 3, 4 or 5; (B) those comprising repeating units of the structure <CHEM> and (C) those comprising repeating units of the structure - CH2 - @H - O - CO - O- (III) and repeating units of the structure <CHEM> wherein in each unit (III) R is hydrogen, methyl or ethyl, and in each unit (IV) z is 3 or 4 and the ratio of the number of units (III) to the number of units (IV) in the polymer is between 1:9 and 2:1.