| 摘要 |
1355012 Emulsion or suspen ion polymerization of ethylene and vinyl esters WACKER-CHEMIE GmbH 15 March 1972 [17 March 1971] 11989/72 Heading C3P An aqueous dispersion of a copolymer of a vinyl ester and 5-50 wt. per cent of ethylene is prepared by polymerization in emulsion with a redox initiator, in the presence of a protective colloid and/or an amulsifier, wherein the vinyl ester and reducing agent are initially added to the aqueous system in the reaction vessel, and a peroxy compound is then metered in in such a way that whilst fully utilizing the cooling capacity of the reaction vessel, a constant polymerization temperature of from 0-100 ‹C. is maintained. Where the reaction vessel is water cooled, the temperature of the reaction mixture and the water issuing from the cooling system are both constant. The ethylene pressure is preferably 3-150 atm., and is preferably maintained at a constant level until a predetermined amount of the vinyl ester has polymerized, preferably all of said ester. In the examples vinyl acetate and ethylene are polymerized alone or with acrylic acid and acrylamide, or vinyl chloride, using redox systems comprising Na 2 SO 3 / t - butyl hydroperoxide, FeSO 4 / Na 2 SO 3 / t - butyl hydroperoxide, Na formaldehyde sulphoxylate / t - butyl hydroperoxide, and palladium sol/H 2 /K 2 S 2 O 8 ; and emulsifiers and/or protective colloids selected from polyvinylalcohol, polyvinylalcohol / sodium alkyl sulphonate / nonyl phenol polyethylene oxide, and hydroxy ethyl cellulose / polyvinylpyrrolidone / nonyl phenol polyethylene oxide / sodium dodecyl benzene sulphonate. |
