Process of polyesters
AssigneeMonsanto Company
InventorsJohn Jamieson Liggat, Gregory O'Brien
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Abstract
Method of retarding age embrittlement of polyester comprising heat treating the polyester after preparation by cooling below 90.degree. C. and then heating at 90.degree. C. to 160.degree. C. within 24 hours of preparation, and a polyester composition in which ageing is substantially retarded compared to the non-heat treated polyester. The invention encompasses the polyester composition which has been subjected to the method.
Claims8
In a process of producing a shaped article at least partly made of a polyhydroxyalkanoate selected from the group consisting of poly-(R)-3-hydroxybutyrate and poly-(R)-3-hydroxybutyrate-co-(R)-valerate by the steps of:
- (a) shaping by injection molding, compression molding, melting, sintering, extrusion of fiber or film or profile, gas-current spinning, tack spinning, coating of melt onto substrate, coating latex onto substrate, or shaping solution in volatile solvent;
- (b) allowing the shaped article to cool below 90 deg C.;
- and
- (c) heat treating at 90-160 deg C. without substantial change of shape;
- the improvement wherein step (c) is performed within 24 hours of the end of step (a), whereby the resulting shaped article is characterized by its resistance to brittleness on aging.
In a process of producing a shaped article at least partly made of poly-(R)-3-hydroxybutyrate-co-(R)-valerate by the steps of:
- (a) shaping by injection molding, compression molding, melting, sintering, extrusion of fibre or film or profile, gas-current spinning, tack spinning, coating of melt onto substrate, coating latex onto substrate, or shaping solution in volatile solvent;
- (b) allowing to cool below 90.degree. C.;
- and
- (c) heat treating at 90.degree.-160.degree. C. without substantial change of shape;
- the improvement which comprises performing step (c) within 24 hours of the end of step (a) whereby the resulting shaped article is characterised by its resistance to brittleness on ageing.
Dependencies are inferred from the claim text.