Method of visbreaking polypropylene
AssigneeHercules Incorporated
InventorDonald E. Boynton
Life of this patent
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Abstract
A process for preparing an environmentally stable plastic composition having narrow molecular weight distribution by visbreaking a propylene polymer using an activated portion of the propylene polymer as a prodegradant. The process includes forming the prodegradant by activating a portion of the propylene polymer either by exposure to ionizing radiation or by oxidation.
Claims13
A process for preparing an environmentally stable plastic composition by visbreaking a propylene polymer to controllably reduce its molecular weight, using an activated portion of said propylene polymer as a prodegradant, which process comprises:
- forming a prodegradant by activating a first portion of propylene polymer by exposure to ionizing radiation;
- incorporating said prodegradant into a second portion of propylene polymer, wherein said second portion is at least as large as said first portion;
- adding to the mixture of said first and second portions of said propylene polymer a stabilizing amount of an antioxidant;
- and
- visbreaking said mixture by shear mixing in an extruder while heating said mixture to an extrusion temperature between about 200.degree. C. and 300.degree. C. to controllably lower the molecular weight of said mixture and narrow the molecular weight distribution, while substantially retaining the stabilizing effect of said antioxidant stabilizer.
A process for preparing an environmentally stable plastic composition by visbreaking a propylene polymer to controllably reduce its molecular weight, using an activated portion of said propylene polymer as a prodegradant, which process comprises:
- forming a prodegradant by activating a first portion of propylene polymer by exposure to ionizing radiation;
- incorporating said prodegradant into a second portion of propylene polymer, wherein said second portion is at least as large as said first portion and said second portion contains a stabilizing amount of at least one reactive antioxidant stabilizer;
- visbreaking said mixture by shear mixing in an extruder while heating said mixture to an extrusion temperature between about 200.degree. C. and 300.degree. C. to controllably lower the molecular weight of said mixture, while substantially retaining the stabilizing effect of said antioxidant stabilizer.
Dependencies are inferred from the claim text.