| 摘要 |
<p>1463241 Core-shell polymer blends and their use in PVC foams ROHM & HAAS CO 17 Jan 1975 [22 March 1974] 2054/75 Headings C3C and C3P Modifier systems for use in rigid PVC foam comprise an intimate mixture of: (A) a first core-shell polymer, having a shell derived from more than 50 wt. per cent of at least one C 1-4 alkyl methacrylate and having a viscosity average M.W. above 1,500,000, said shell being polymerized in the presence of, but substantially ungrafted to, a cross-linked core derived from more than 50 wt. per cent of at least one C 2-8 alkyl acrylate and 0À1-5 wt. per cent, based on total monomers, of a glycol dimethacrylate cross-linker, the weight ratio of shell to core being from 40 : 60 to 75 : 25; and (B) a second core-shell polymer, having a shell derived from more than 50 wt. per cent of at least one C 1-4 alkyl methacrylate, said shell being polymerized in the presence of, but substantially ungrafted to, a non-cross-linked core derived from more than 50 wt. per cent of at least one C 1-8 alkyl acrylate. Preferably both (A) and (B) are derived wholly from (meth)acrylic monomers. In examples, (A) has a core of butyl acrylate/ 1,3-butylene glycol dimethacrylate and a shell of methyl methacrylate or methyl methacrylate/ethyl acrylate; and (B) has a core of butyl acrylate and a shell of methyl methacrylate; the admixture of the two being obtained by mixing individual emulsions and spray-drying. The above mixtures are used as modifiers in otherwise conventional PVC foam formulations. In Examples V, X and XI foamable blends are formed from PVC, a mixture as above, dimethyltin - S,S<SP>1</SP> - bis(alkyl mercapto - acetate) as stabilizer, TiO 2 as pigment, barium stearate and stearic acid as lubricants, epoxidized soyabean oil as plasticizer, and azo-bis-formamide as blowing agent; and in Examples VI, X and XI these blends were foamed by extrusion,</p> |
