| 摘要 |
High molecular weight copolymers containing beta -hydroxybutyric acid residue, i.e. units of the formula - O.CH(CH3).CH2.CO - and up to 50 mole % of residues of other hydroxy acids, viz units of the formula - O.CR<1>R<2>.(CR<3>R<4>)n.CO - where n is 0 or 1 and, if n = 1 and R<2>, R<3>, and R<4> = H, R<2> is not methyl. The copolymers are made microbiologically: for part of the cultivation the micro-organism is under conditions of limitation of a nutrient, e.g. nitrogen source, required for growth but not polyester accumulation. For at least part of this period of growth limitation the substrate is an acid or a salt thereof that tives the comonomer units. Propionic acid, which gives polymers where n = 1, R<2>=R<3>=R<4>=H and R<1> = C2H5, is the preferred acid. |
