Method for preparing poly-beta-hydroxyalkanoate films

Method for preparing a PHA film comprising the steps of:

• a) mixing a PHA in powder form with the following formula (I):
• wherein:
• each R represents independently a linear or branched alkyl comprising from 1 to 12 carbon atoms,
• n is an integer number greater than or equal to 2 representing the number of units in the PHA,
• and an aqueous solution to obtain a suspension comprising from 0.5 to 15% by weight, preferably from 3 to 10% by weight, PHA with respect to the weight of aqueous solution,
• b) leaving the PHA solution to rest, generally for 10 seconds to 16 hours, by means of which a portion of the PHA settles out and a pellet is obtained, above which floats a supernatant comprising from 0.1 to 1.0% by weight PHA with respect to the weight of aqueous solution,
• c) collecting at least part of the supernatant,
• d) applying the collected supernatant to at least one flat horizontal portion of a surface of a first substrate,
• e) evaporating the water from the applied supernatant,
• f) simultaneously with step e) or after step e), heating at least one region of the portion of the surface of the first substrate to which the supernatant was applied, at a temperature preferably:
• higher than the (specific melting point of PHA+5° C.), preferably higher than the (specific melting point of PHA+15° C.), and
• lower than the (degradation temperature of PHA−10° C.),
• by means of which a first substrate is obtained having said at least one region covered with a PHA film.