EP0104731A2 — 3-Hydroxybutyrate polymers

Claim 1

Independent Claim 188 words

A process for the production of an oriented shaped article from a polymer containing at least 40 mole % of 3-hydroxybutyrate residues in the polymer chain comprising uni-or bi- axially drawing a preform of said hydroxybutyrate polymer in a partially crystalline state at a temperature between the glass transition temperature, Tg, and the melting point of the hydroxybutyrate polymer into said shaped article, and then increasing the degree of crystallinity of the hydroxybutyrate polymer by subjecting the drawn preform, while in the drawn condition, to a temperature between the glass transition temperature and the drawing temperature until the drawn article is non-rubbery, the amount of said uni- or bi- axial drawing being such that, after said step of increasing the degree of crystallinity, at least one dimension of the preform has increased by at least 200%, said hydroxybutyrate polymer having a degree of crystallinity, at the time of drawing, such that the preform is not so brittle that it breaks before achieving said increase in said at least one dimension, and such that the drawn article does not break during the step of increasing the degree of crystallinity.

Claim 2

Dependent Claim 188 words

A process for the production of an oriented shaped article from a polymer containing at least 40 mole % of 3-hydroxybutyrate residues in the polymer chain comprising uni-or bi- axially drawing a preform of said hydroxybutyrate polymer in a partially crystalline state at a temperature between the glass transition temperature, Tg, and the melting point of the hydroxybutyrate polymer into said shaped article, and then increasing the degree of crystallinity of the hydroxybutyrate polymer by subjecting the drawn preform, while in the drawn condition, to a temperature between the glass transition temperature and the drawing temperature until the drawn article is non-rubbery, the amount of said uni- or bi- axial drawing being such that, after said step of increasing the degree of crystallinity, at least one dimension of the preform has increased by at least 200%, said hydroxybutyrate polymer having a degree of crystallinity, at the time of drawing, such that the preform is not so brittle that it breaks before achieving said increase in said at least one dimension, and such that the drawn article does not break during the step of increasing the degree of crystallinity.

Claim 3

Dependent Claim 46 words

A process as claimed in claim 1 wherein the partially crystalline hydroxybutyrate polymer preform is produced by subjecting an amorphous EB polymer preform to a temperature within 30 0 C of the temperature at which the rate of crystallisation of the hydroxybutyrate polymer is a maximum.

Claim 4

Dependent Claim 58 words

A process as claimed in claim 1 or claim 2 wherein the hydroxybutyrate polymer is melt extruded into the desired configuration to form an amorphous preform which is then passed through a quenching/crystallisation zone maintained at a temperature below the melting point of the hydroxybutyrate polymer to solidify the polymer and to effect the desired degree of crystallisation.

Claim 5

Dependent Claim 21 words

A process as claimed in claim 3 wherein the preform is fed directly from said quenching/crystallisation zone to the drawing stage.

Claim 6

Dependent Claim 29 words

A process as claimed in any one of claims 1 to 4 wherein the drawing is conducted at a temperature above that at which the preform is partially crystallised.

Claim 7

Dependent Claim 32 words

A process as claimed in any one of claims 1 to 5 wherein the drawing is conducted at a temperature between 30 and 80°C below the melting point of the hydroxybutyrate polymer.

Claim 8

Dependent Claim 47 words

A process as claimed in any one of claims 1 to 6 wherein the degree of crystallinity of the drawn preform is increased by subjecting the drawn preform to a temperature within 20 0 C of the temperature at which the rate of crystallisation is a maximum.

Claim 9

Dependent Claim 55 words

A process as claimed in any one of claims 1 to 7 wherein the drawn preform is allowed to relax, during the further crystallisation step, by up to 10% of the drawn value, (before any such relaxation) of the at least one dimension that has been increased by at least 20% during the drawing step.

3-Hydroxybutyrate polymers

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