PACKING BAND AND MANUFACTURE THEREOF

摘要

PROBLEM TO BE SOLVED: To provide outstanding transparency, mechanical strength and heat resistance and impart good decomposition properties by stretching a lactic acid polymer at a specific stretching magnification in the longer direction in the temperature range from the glass transition temperature to the melting point of the polymer. SOLUTION: The packing band made of a lactic acid polymer is manufactured by stretching the polymer at a stretching magnification of 3-15x in the longer direction by 1-5 step stretch and in the temperature range from the glass transition temperature to the melting point of the polymer. The lactic acid polymer is such as (1) polylactic acid, (2) a copolymer of lactic acid with another fatty hydroxy-carboxylic acid, (3) a copolymer of lactic acid, aliphatic polyvalent alcohol and an aliphatic polybasic acid and (4) a mixture of components selected from (1)-(3) or the like. The lactic acid is such as L-lactic acid, D-lactic acid, DL-lactic acid or a mixture of these lactic acids or lactide which is the cyclic dimer of lactic acid. The molecular weight of the lactic acid polymer is preferably 10,000-5,000,000 in general, in terms of weight average molecular weight. The heating process at the time of stretching is by either of a water tank, an oven, a heating roll or the like.