GB1340026A - Graftlinked heteropolymer film - Google Patents

Abstract

1340026 Multi-stage graft polymers ROHM & HAAS CO 19 April 1971 [13 April 1970] 26742/71 Heading C3G A film-forming composition comprises heteropolymer latex particles comprising 35-50% by weight of a first-stage, rubbery, cross-linked polymer having a Tg below 10‹ C. and the balance a second-stage, thermoplastic polymer having a Tg of at least 60‹ C. polymerized directly thereon and attached thereto, said heteropolymer particles being formed by the steps of: (1) emulsion polymerizing, to an average particle size of less than 1300 Š, a monomer mixture comprising: (a) a principal monomer system of at least one C 1 -C 8 alkyl acrylate or mixtures of more than 50% by weight of one or more of said alkyl acrylates and less than 50% by weight of one or more of C 1 -C 8 alkoxy acrylates, cyanoethyl acrylate, acrylamide, hydroxy C 1 -C 8 alkyl acrylates, hydroxy C 1-8 alkyl methacrylates, acrylic acid, methacrylic acid, and acrylonitrile; (b) a polyfunctional cross-linking monomer for said principal monomer system; and, as a graft linker; (c) at least one allyl ester of an α,#-unsaturated carboxylic acid to form said first-stage polymer, the relative proportions of (b) and (c) being sufficient to substantially uniformly cross-link said principal monomer system and to provide a level of attachment of said first-stage polymer to said second-stage polymer of at least 20%; and (2) attaching said second-stage polymer to said first-stage polymer particles by emulsion polymerizing to an average molecular weight of 80,000-300,000, and in the presence of said particles a monomer system comprising at least 80% by weight of at least one C 1 -C 4 alkyl methacrylate, the balance, if any, being at least one C 1 -C 8 alkyl acrylate, C 1 -C 8 alkoxy acrylate, cyanoethyl acrylate, acrylamide, hydroxy C 1 -C 8 alkyl acrylate, hydroxy C 1 -C 8 alkyl methacrylate, acrylic acid, methacrylic acid or acrylonitrile. The first stage polymer is preferably composed of butyl acrylate, butylene glycol diacrylate and allyl methacrylate and the second-stage polymer comprises methyl methacrylate and butyl acrylate units. In the examples use is also made of allyl acrylate and diallyl maleate as graft linkers. The two-stage sequential emulsion polymerization may be carried out at 0-125‹ C. and the polymerization medium may contain a chain transfer agent such as tertiary dodecyl mercaptan. The polymerization medium in each stage contains a free radical generator which is activated either thermally or by redox reaction. Conventional emulsifiers are also present. Films and sheets may be formed from the composition which may also contain conventional fillers, pigments, dyes and stabilizers.