Abstract This invention relates to copolymerizing vinyl acetate and ethylene in aqueous emulsion in contact with a pressurized ethylene gas phase and in particular to a method of copolymerizing substantially larger amounts of ethylene into the copolymer than have heretofore been copolymerized at equivalent temperature and pressure, said method comprising adding vinyl acetate to an aqueous emulsifying composition containing initiator and maintained under ethylene pressure, the rate of vinyl acetate addition during copolymerization being such as to maintain the concentration of unpolymerized vinyl acetate at a level not exceeding about 3.5 percent by weight of the aqueous emulsifying composition. The resulting latexes of this invention are useful as adhesives and bases for paints and paper coatings.
The method of claim 1 wherein said aqueous emulsifying composition contains a latex, prior to said addition of vinyl acetate to said emulsifying composition, said latex prepared by the method of claim 1, the quantity of said latex being sufficient to provide between about 5 percent and about 25 percent of the total copolymer in the final product.
Claim 2
Dependent Claim
75 words
The method of claim 1 wherein the latex is prepared in two steps by first adding to the aqueous emulsifying composition, in one portion, vinyl acetate corresponding to between about 5 percent and 25 percent of the total amount of vinyl acetate used in the completed preparation, and copolymerizing this vinyl acetate with ethylene to form a latex and secondly by continuing the copolymerization of vinyl acetate with ethylene under the conditions of claim 1.
Claim 3
Independent Claim
100 words
A method of preparing a stable latex of a copolymer of vinyl acetate with ethylene, which method comprises maintaining ethylene pressure of between about 30 and about 1,000 p.s.i. on contact with an aqueous emulsifying phase, adding to said phase a free radical donating initiator, maintaining the temperature of said emulsifying phase between about 0* and 70* C. and then gradually adding thereto vinyl acetate at a rate such as to maintain the concentration of unpolymerized vinyl acetate at a level not exceeding about 3.5 percent by weight of the aqueous emulsion phase during the addition of said vinyl acetate.
Claim 4
Independent Claim
108 words
A method of preparing a stable latex of a vinyl acetate ethylene copolymer containing up to about 20 percent ethylene by weight of copolymer, which method comprises maintaining about 145-155 p.s.i. ethylene pressure in contact with an aqueous emulsifying phase, adding a free radical donating initiator to said emulsifying phase, maintaining, said emulsifying phase at a temperature between about 20 and 30* C., and Then gradually adding vinyl acetate to said emulsifying phase at a rate to maintain the concentration of unpolymerized vinyl acetate at a level not exceeding about 3.5 percent by weight of the aqueous emulsion phase while simultaneously polymerizing said ethylene with the vinyl acetate.