Surface treatment of ethylene-based polymer pellets to improve blocking resistance
AssigneeE. I. Du Pont de Nemours and Company
InventorBrian Thomas Roach
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Abstract
The method of this invention for raising the stick temperature of pellets of ethylene-based copolymers with an acid content at least 5 weight percent has the steps of contacting the pellets with an aqueous solution of a water-soluble metal salt of an aliphatic acid having fewer than 12 carbon atoms, and drying the pellets. The resulting ethylene-based copolymers have a stick temperature of above 25° C. and preferably at least 5° C. above that of the untreated pellets.
Claims14
A process for forming free-flowing pellets of ethylene-based, copolymers comprising repeating polymerized units of
- (i) at least 50% by weight, based on the weight of the copolymer, of ethylene,
- (ii) 5 to 30% by weight, based on the weight of the copolymer, of an ethylenically unsaturated acid selected from the group consisting of acrylic acid and methacrylic acid;
- and
- (iii) 0 to 40% by weight, based on the weight of the copolymer, of an alkyl (meth)acrylate, wherein the copolymer has 0-100% of the acid groups neutralized with one or more metal cations,
- the process comprising the steps of
- (i) contacting the pellets with an aqueous solution of a sufficient amount of one or more metal salts of an aliphatic acid having fewer than 12 carbon atoms to increase the stick temperature to a temperature at least 5° C. higher than the stick temperature of the pellets before being contacted;
- and,
- (ii) drying the pellets.
Pellets of high-stick-temperature, ethylene-based copolymer comprising
- a. ethylene-based copolymer having repeating polymerized units of
- (i) at least 50% by weight, based on the weight of the copolymer, of ethylene,
- (ii) 5 to 30% by weight, based on the weight of the copolymer, of an ethylenically unsaturated acid selected from the group consisting of acrylic acid and methacrylic acid;
- and
- (iii) 0 to 40% by weight, based on the weight of the copolymer, of an alkyl(meth)acrylate, wherein the copolymer has 0-100% of the acid groups neutralized with metal cations, and
- b. a sufficient amount of a surface coating comprising one or more metal salts of an aliphatic acid having fewer than 12 carbon atoms to increase the copolymer stick temperature to a temperature at least 5° C. above the temperature of the pellets without the coating.
Dependencies are inferred from the claim text.