Imperial Chemical Industries Limited

Peter J Barham

Alan Selwood

Jeffrey A Odell

Frank M Willmouth

Paul A Holmes

Andrew Webb

Sally J Organ

Hydroxyalkanoate polymer composition

A solvent-free preform of a 3-hydroxybutyric acid polymer is subjected to a compression step to reduce its thickness by at least 5% and the compressed preform is then drawn uni- or bi- axially to induce orientation.

3-Hydroxybutyric acid polymers

The invention provides a method of heat-treating a biaxially oriented polyolefin film by constraining the film against shrinkage, heating the constrained film to at least the minimum stress relaxation temperature of the polyolefin, and thereafter cooling the treated film to a temperature below the alpha-relaxation temperature of the polyolefin. The film is preferably heated rapidly to the required temperature and cooled rapidly therefrom. The resultant films exhibit good modulus and thermal shrinkage characteristics. The heat-treatment may be supplemented by a conventional heat-setting operation to improve heat-sealing characteristics of the treated films.

Heat-treating coated polyolefin films

.beta.-Hydroxybutyric acid polymers are extracted from micro-organism cells by contact with a solvent, such as 1,2-dichloroethane which is a poor solvent for the polymer once it has been precipitated. The solution obtained by extraction is caused to gel and then solvent is expelled by subjecting the gel to a deformation process. Expelled solvent is recovered for extraction of polymer from a further quantity of cells.

Extraction of poly(.beta.-hydroxybutyric acid)

A process of forming shaped articles comprising forming a free draining gel from a solution of a crystallizable, high molecular weight polymer under conditions which cause crystallization of the polymer and subjecting the gel to a non-random deformation process so that the associated solvent is expressed. Some residual solvent may be present and can assist in subsequent fabrication processes but the solvent may also be completely removed for such processes. The resulting products have good physical properties, particularly in modulus after uniaxial or biaxial drawing.

Removal of solvent from gels of high molecular weight crystalline

A process of forming shaped articles comprising forming a free draining gel from a solution of poly(hydroxybutyrate) in a poor solvent under conditions which cause crystallization of the polymer and subjecting the gel to a non-random deformation process so that the associated solvent is expressed. Some residual solvent may be present and can assist in subsequent fabrication processes but the solvent may also be completely removed for such processes. The resulting products have good physical properties, after uniaxial or biaxial drawing.

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Bristol, United Kingdom

Peter J Barham