Solid sheared polymer blends and process for their preparation
AssigneeDSM Copolymer, Inc.
InventorsErrol J. Olivier, Robert T. Patterson, Peter N. Nugara
Life of this patent
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Abstract
A blend and a process for producing that blend in which a high ethylene content ethylene-propylene polymer and a lower ethylene content ethylene-propylene polymer are subjected to simultaneous blending and shearing to reduce their molecular weights and molecular weight distribution and to yield a product that can be recovered as a solid using conventional plastic processing equipment. The sheared blend of polymers can function as a shear stable viscosity index improver with improved lower temperature properties.
Claims18
An ethylene-propylene polymer blend having a number average molecular weight within the range of about 20,000 to about 150,000 and a molecular weight distribution within the range of about 1.5 to about 5 prepared by the process of simultaneously in the absence of solvent blending and shearing:
- (a) an essentially amorphours low ethylene content ethylene-propylene polymer containing an ethylene to propylene mole ratio within the range of 35/65 to 65/35, having a number average molecular weight within the range of about 40,000 to about 250,000 and a molecular weight distribution within the range of about 2 to 7;
- (b) a partially crystalline higher ethylene content ethylene-propylene polymer containing an ethylene to propylene molar ratio within the range of about 65/35 to about 85/15, having a number average molecular weight within the range of about 40,000 to about 250,000 and a molecular weight distribution within the range of about 2 to 7;
- whereby the blending and shearing is carried out under conditions of heat and mechanical work sufficient to create high shear conditions for a time sufficient to reduce the molecular weight and molecular weight distribution of the blend of (a) and (b), wherein the weight ratio of low ethylene content ethylene-propylene polymer (a) to the higher ethylene-propylene polymer (b) is within the range of about 80/20 to about 50/50.
Dependencies are inferred from the claim text.