E.i. Dupont De Nemours and Company

Other

Maria Spinu

Lin Wang

Joel David Citron

Steven Raymond Lustig

Robert Ray Burch

Thomas M Ford

Alexa A Dembek

Blends of two or more polyethylenes are made by reacting ethylene with an oligomerization catalyst that forms &#x3b1;-olefins, and two polymerization catalysts, one of which under the process conditions copolymerizes ethylene and &#x3b1;-olefins, and the other of which under process conditions does not readily copolymerize ethylene and &#x3b1;-olefins. The blends may have improved physical properties and/or processing characteristics.

Manufacture of polyethylenes

Blends of two or more polyethylenes are made by reacting ethylene with an oligomerization catalyst that forms &agr;-olefins, and two polymerization catalysts, one of which under the process conditions copolymerizes ethylene and &agr;-olefins, and the other of which under process conditions does not readily copolymerize ethylene and &agr;-olefins. The blends may have improved physical properties and/or processing characteristics.

This invention concerns a process for polymerizing cyclic oligomers to homopolymers or copolymers, conducted in the presence of one or more linear polymers.

Polymerizations based on cyclic oligomer

Linear stereo block copolymers are disclosed. The polymers comprise a plurality of alternating polymeric blocks of amorphous copolymers of L-lactide and D-lactide with semicrystalline blocks of either L-lactide homopolymer or D-lactide homopolymer. The molecular weight can be built up by either of two techniques. The first technique is to use a chain extending agent such as a diacyl chloride or a diisocyanate to link a plurality of the preformed block copolymers. The second technique is to polymerize additional alternating amorphous and semicrystalline segments or blocks onto the original alternating block copolymers.

L,d-polylactide copolymers with controlled morphology

Polyvinyl alcohol esterified by lactic is produced by dissolving polyvinyl alcohol and lactic acid in water, and removing the water by volatilization at a temperature of 75.degree. C. to 175.degree. C. The lactic acid esterified polyvinyl alcohol is useful as a molding resin, and in films, fibers and adhesives.

Polyvinyl alcohol esterified with lactic acid and process therefor

Polylactide stereocomplex is formed by mixing poly-D-lactide and L-lactide or poly-L-lactide and D-lactide and a lactide polymerization catalyst, and heating to polymerize the monomeric lactide, preferably under pressure. The parts are useful in medical devices such as bone screws.

Manufacture of polylactide stereocomplexes

Linear block copolymers are disclosed. The polymers comprise a plurality of alternating polymeric blocks of amorphous copolymers of L-lactide and D-lactide with semicrystalline blocks of either L-lactide homopolymer or D-lactide homopolymer. The molecular weight can be built up by either of two techniques. The first technique is to use a chain extending agent such as a diacyl chloride or a diisocyanate to link a plurality of the preformed block copolymers. The second technique is to polymerize additional alternating amorphous and semicrystalline onto the original alternating block copolymers.

L-Dpolylactide copolymers with controlled morphology

Star-shaped poly (hydroxyacid) chains and the process for preparing them are disclosed. The star shaped polymers have the residue of a central polyfunctional compound having at least 5 hydroxyl or amino groups and 5 to 100 carbon atoms with polymeric arms attached to the functional groups. The polymeric arms are formed from lactide, glycolide or caprolactone. In a preferred aspect the inner segment of the arms are an amorphous copolymer of D-lactide and L-lactide and the outer segment of the arms are a semicrystalline polymer of one of L-lactide or D-lactide.

Star-shaped hydroxyacid polymers

Environmentally benign closed cell compositions made by foaming star-shaped polymers with a plurality of poly(hydroxy acid) chains attached to a central polyfunctional compound having a plurality of hydroxyl and/or amino groups.

Degradable foam materials

Polymers of the general formula R--(A-B-A-I)-.sub.x A-B-A-R and their preparation are disclosed. In the general formula, -A- is a polyhydroxy acid residue preferably a polymer of either 98 to 100% L-lactide or 98 to 100% D-lactide having a molecular weight of 500 to 40,000 and preferably 2,000 to 20,000, -B- is an oligomeric diol or diamine residue, having a number average molecular weight of 500 to 20,000 and preferably 2,000 to 8,000. The polymers are prepared by polymerizing a lactone onto the diol or diamine followed by reacting the resulting polymeric H-A-B-A-H with an diisocyanate or diacyl chloride to form the -L- chain extending units in the general formula.

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Wilmington, DE, United States of America

Maria Spinu