Partially crosslinked ethylene vinyl acetate copolymers with low melt index values and increased tensile strength
AssigneeExxonMobil Chemical Patents Inc.
InventorsGerd A. Allermann, Hitesh A. Fruitwala
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Abstract
Ethylene vinyl acetate compositions that have been partially crosslinked using organic peroxides are disclosed, as well as methods for their production. The crosslinked compositions have low melt index values and increased tensile strength, leading to flexibility and heat resistant properties.
Claims57
A method for producing an at least partially cross-linked polymer composition, having a melt index (MI) value and a tensile strength, comprising blending from about 0.03 to about 1.0 weight percent of an organic peroxide with an ethylene vinyl acetate (EVA) copolymer, having a MI value and a tensile strength, containing from about 2 to about 80 weight percent units derived from vinyl acetate at a temperature sufficient to initiate cross-linking, wherein:
- a. the MI value of the at least partially cross-linked polymer composition in g/min (190° C., 2.16 kg) is less than or equal to 10% of the MI value of the EVA copolymer, and
- b. the tensile strength of the at least partially cross-linked polymer composition is at least as great as the tensile strength of the EVA copolymer.
An at least partially cross-linked polymer composition comprising the reaction product of an ethylene vinyl acetate (EVA) copolymer containing from about 2 to about 80 weight percent units derived from vinyl acetate and from about 0.03 to about 1.0 weight percent of an organic peroxide, wherein the melt index (MI) value of the at least partially cross-linked polymer composition in g/10 min (190° C., 2.16 kg) is less than or equal to 10% of the MI value of the EVA copolymer and the tensile strength of the at least partially cross-linked polymer composition is at least as great as the tensile strength of the EVA copolymer.
A method for producing at least partially cross-linked polymer compositions comprising:
- a. loading an EVA copolymer having a vinyl acetate content of from about 20 to about 80 weight percent into an extruder;
- b. adding an organic peroxide, organic peroxide solution, organic peroxide masterbatch, or a combination of the foregoing into the extruder;
- c. dispersing the peroxide in the copolymer;
- d. heating the extruder to a temperature suitable to initiate cross-linking of the copolymer;
- and
- e. removing the resulting at least partially cross-linked composition from the extruder.
Dependencies are inferred from the claim text.