Method for producing polyhydroxyalkanoic acid and its use

Abstract

To obtain PHA with high strength and good handleability by a simple method using a twin screw extruder.SOLUTION: A method for producing polyhydroxyalkanoic acid includes the steps of: (a) preparing a wet powder of polyhydroxyalkanoic acid containing 10-25 wt.% of an aqueous solvent with a pH of 7 or more and (b) granulating by heating the wet powder of polyhydroxyalkanoic acid wet powder within a twin screw extruder to a preset temperature of 60-110°C for granulation.SELECTED DRAWING: None

Claims

1. (a) A step of preparing a polyhydroxyalkanoic acid wet powder containing 10 to 25% by weight of an aqueous solvent with a pH of 7 or less, based on 100% by weight of the total polyhydroxyalkanoic acid wet powder, and (b) A method for producing polyhydroxyalkanoic acid, comprising the step of heating the polyhydroxyalkanoic acid wet powder prepared in step (a) in a twin-screw extruder at a set temperature of 60 to 110°C to granulate it.

2. A method for producing polyhydroxyalkanoic acid according to claim 1, wherein the molecular weight retention rate (%) shown by the following formula (1) is 80 to 100%. Formula (1): Molecular weight retention rate (%) = (Weight-average molecular weight of polyhydroxyalkanoic acid granulated in step (b) / Weight-average molecular weight of polyhydroxyalkanoic acid in the polyhydroxyalkanoic acid wet powder subjected to step (b)) × 100

3. The method for producing polyhydroxyalkanoic acid according to claim 1 or 2, wherein in step (b), the set temperature in the twin-screw extruder is 60 to 95°C.

4. The method for producing polyhydroxyalkanoic acid according to claim 1 or 2, wherein at least a portion of the screws of the twin-screw extruder is a screw having a kneading action.

5. A method for producing polyhydroxyalkanoic acid according to claim 1 or 2, further comprising the step (c) of drying the granulated polyhydroxyalkanoic acid obtained in step (b).

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