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US 2012/0129976 A1Published application
Polyoxymethylene Polymer Compositions Having Improved Creep
AssigneeE.I.Du Pont De Nemours and Company
InventorRamabhadra Ratnagiri
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Abstract
Processes of making articles of a melt mixed polyoxymethylene composition comprising polyoxymethylene polymer and polyoxymethylene terpolymer in which the melt mixed composition is maintained above the crystallization temperature of the polyoxymethylene polymer. Such processes impart improved creep resistance compared to that of articles made of the same melt mixed composition but which has been cooled below crystallization temperature of the polyoxymethylene polymer during manufacture. These articles are useful for making plastic gears having high heat resistance.
Claims16
A process comprising:
- i) melt mixing a polyoxymethylene polymer composition comprising
- a) 95-99 weight percent of a polyoxymethylene selected from the group consisting of homopolymer and copolymer, and
- b) 1-5 weight percent of a polyoxymethylene terpolymer, by heating the polyoxymethylene above its crystallization temperature;
- ii) maintaining the melt mixed composition above the crystallization temperature of the polyoxymethylene;
- and
- iii) molding the composition into an article;
- wherein the article has a time to 5 percent tensile strain that is at least 20 percent greater than that of an article made by the steps of melt mixing, cooling the polyoxymethylene below its crystallization temperature, reheating the polyoxymethylene composition above its crystallization temperature, and then molding the composition.
4 more elements
A process comprising:
- i) melt mixing a composition comprising
- a) 95-99 weight percent of a polyoxymethylene selected from the group consisting of homopolymer and copolymer, and
- b) 1-5 weight percent of a polyoxymethylene terpolymer, by heating the polyoxymethylene above its crystallization temperature;
- ii) maintaining the melt mixed composition above the crystallization temperature of the polyoxymethylene;
- and
- iii) molding the composition into an article;
- wherein the article has a time to 7 percent tensile strain that is at least 20 percent greater than that of an article made by the steps of melt mixing, cooling the polyoxymethylene below its crystallization temperature, reheating the polyoxymethylene composition above its crystallization temperature, and then molding the composition.
4 more elements
Dependencies are inferred from the claim text.