Patent ID: 7128863

Claim:
A method for producing a heat-shrinkable co-polyester film having terephthalic acid and ethylene glycol as main components and containing 1,4-cyclohexanedimethanol at the amount of 3–40 mol %, comprising the steps of: introducing raw materials comprising 1,4-cyclohexanedimethanol co-polymer (PETG), polyethylene terephthalate (PET), and polybutylene terephtalate (PBT) synthesized from said terephthalic acid, ethylene glycol and 1,4 cyclohexanedimethanol into raw material feeders without pre-drying or pre-crystallization; melting and extruding said raw materials with the removal of water at high vacuum levels and then solidifying; and drawing to 2–5 times in a longitudinal or transverse direction, thereby producing the co-polyester film having a crystallization temperature of 80–220° C., a heat shrinkage (%) higher than 30% in at least one direction of longitudinal and transverse directions in 90° C. hot water, and a maximum shrinkage stress lower than 3 kg/mm 2 .