Patent GB-1005045-A (GB)
Title: Process for preparing foamed polymeric materials
IPC: C08J9/02
Filed: 1964-02-03
Abstract: Foamed polymeric material is prepared by heating a mixture of a thermoplastic polymeric material or its monomeric or pre-polymer precursor with a blowing agent comprising a b -propiolactone of the formula <FORM:1005045/C3/1> wherein R1 is hydrogen or a lower (C1-C8) alkyl radical, R2 is hydrogen or a methyl, phenyl, lower alkenyl or lower carboxyalkyl radical, or R1 and R2 together constitute the radical <FORM:1005045/C3/2> the b -propiolactone having a decomposition temperature below the decomposition temperature of the thermoplastic polymeric material but above its softening temperature, the heating being sufficient to decompose the b -propiolactone into carbon dioxide and a polymerizable substance.  Suitable polymeric material is normally solid thermoplastic macromolecular polymeric material having a decomposition temperature above 200 DEG  C. and a softening temperature below 150 DEG  C., e.g. natural and synthetic rubber, polystyrene, polymethylstyrene, polymethylacrylate, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, polyethylene, chlorinated polyethylene, polypropylene, polyesters such as those derived from phthalic and maleic anhydrides and propylene glycol, polyamides, polyacrylates, polyacrylonitrile and polymers of chlorofluoroethylenes.  Examples of suitable b -propiolactones are b -phenyl-b -propiolactone, b -vinyl-b -propiolactone, b -methyl-b -carboxy-methyl-b -propiolactone, b -isovalerolactone, b -propiolactone, b -butyrolactone, b -methyl b -valerolactone, b -d -dimethyl-b -caprolactone and b -n-caprolactone.  The particular b -propiolactone used may be selected to yield a polymerizable monomer identical with or different from that of the monomer of the material with which it is incorporated. Additives such as dyes, pigments, plasticizers, stabilizers and flame-retardants may also be incorporated in the compositions. The foams are useful for low temperature insulation, in the preparation of linings for clothing, as cushioning material, as cores between paper lines, as beach toys, and in architectural panels.ALSO:b -Propiolactones may be prepared by the condensation of a ketene with a carbonyl compound such as an aldehyde in the presence of zinc or aluminium chloride.  Example 1 includes a description of the preparation of b -phenyl - b  - propiolactone by passing gaseous ketene through a liquid mixture of benzaldehyde and zinc chloride.  In Example 2 acetone and ketene are reacted to prepare b -isovalerolactone.ALSO:Cloth or paper is coated with a mixture of a vinyl plastisol and a b -propiolactone of the formula:  <FORM:1005045/B1-B2/1> wherein R1 is hydrogen or a lower alkyl radical, R2 is hydrogen or a methyl, phenyl, lower alkenyl or lower carboxyalkyl radical or R1 and R2 together constitute the radical:  <FORM:1005045/B1-B2/2> and the mixture heated to form the vinyl resin which simultaneously is foamed by the gases released by the b -propiolactone.  The vinyl plastisol may be, for example, a mixture of solid polyvinyl chloride particles suspended in a plasticizer such as diallyl phthalate or a dialkyl phthalate mixed with other liquid plasticizers such as diaryl phosphates, alkylated benzene or epoxidized drying oils.