Heat-shrinkable polyester film
The blocking phenomenon at the time of recycling can be effectively suppressed. Provided is a heat-shrinkable polyester film derived from a first polyester resin and a second polyester resin as a plurality of polyester resins having different crystallinity, the heat-shrinkable polyester film satisfying the following characteristics (A) to (E). (A) and (B): The first polyester resin includes terephthalic acid, in which a reaction amount of ethylene glycol is in the range of 50 mol % or more and below 90 mol %, and the second polyester resin includes terephthalic acid, in which a reaction amount of ethylene glycol is 90 mol % or more. (C) and (D): When predetermined isothermal crystallization measurement is performed, an exothermic peak appears within 12 minutes from the start, including a cooling process time, and the heat quantity of the exothermic peak is 5 to 35 J/g. (E): The thermal shrinkage ratio in the main shrinkage direction as measured under predetermined conditions is 20% to 60%.
1 . A heat-shrinkable polyester film being produced from a first polyester resin and a second polyester resin the first and second polyester resins having different crystallinity,
90% or more by weight of the film being produced from the first and second polyester resins,
a weight-based mixing proportion of the first polyester resin/second polyester resin having a value within the range of 20/80 to 80/20,
wherein the heat-shrinkable polyester film satisfies the following characteristics (A) to (E):
(A) the first polyester resin is an amorphous polyester resin that is a reaction product of a first polyvalent carboxylic acid and a first polyalcohol,
the first polyvalent carboxylic acid comprises terephthalic acid, when a total amount of the first polyvalent carboxylic acid is taken as 100 mol %, terephthalic acid is 90 mol % or more,
the first polyalcohol comprises ethylene glycol, 1,4-cyclohexanedimethanol and/or diethylene glycol, and when a total amount of the first polyalcohol is taken as 100 mol %, ethylene glycol is 50 mol % or more and below 90 mol %, the remaining balance of the first polyalcohol is 1,4-cyclohexanedimethanol and/or diethylene glycol;
(B) the second polyester resin is a crystalline polyester resin that is a reaction product of a second polyvalent carboxylic acid and a second polyalcohol,
the second polyvalent carboxylic acid comprises terephthalic acid, when a total amount of the second polyvalent carboxylic acid is taken as 100 mol %, terephthalic acid is 90 mol % or more,
the second polyalcohol comprises ethylene glycol, and when a total amount of the second polyalcohol is taken as 100 mol %, ethylene glycol is 90 mol % or more;
(C) the heat-shrinkable polyester film is a heat-shrinkable polyester film in which when isothermal crystallization measurement at 150° C., including a cooling process at a constant temperature, is performed by DSC, an exothermic peak appears within 12 minutes from the start, including the cooling process time;
(D) the heat-shrinkable polyester film is a heat-shrinkable polyester film in which when isothermal crystallization measurement at 150° C., including a cooling process at a constant temperature, is performed by DSC, a heat quantity corresponding to an obtained exothermic peak area is within the range of 5 to 35 J/g; and
(E) the heat-shrinkable polyester film is a heat-shrinkable polyester film in which a thermal shrinkage ratio in a main shrinkage direction as measured under thermal shrinkage conditions of being immersed in hot water at 80° C. for 10 seconds, is within the range of 20% to 60%.
2 . The heat-shrinkable polyester film according to claim 1 , wherein the first polyalcohol includes at least 1,4-cyclohexanedimethanol.
3 . The heat-shrinkable polyester film according claim 1 , wherein the second polyester resin is a homopolyester resin and a post-consumer recycled polyester resin, or either one of them.
4 . The heat-shrinkable polyester film according to claim 1 , wherein when a total amount of the first polyester resin and the second polyester resin is taken as 100 parts by weight, the heat-shrinkable polyester film contains a lubricating agent in an amount within the range of 0.01 to 5 parts by weight.
5 . The heat-shrinkable polyester film according to claim 1 , further satisfying the following characteristic (F):
(F) a thermal shrinkage ratio in a direction orthogonally intersecting the main shrinkage direction as measured under the thermal shrinkage conditions of being immersed in hot water at 80° C. for 10 seconds, is within the range of −3% to 10%.
6 . The heat-shrinkable polyester film according to claim 1 , further satisfying the following characteristic (G):
(G) a thermal shrinkage stress in the main shrinkage direction as measured under the thermal shrinkage conditions at 80° C. for 10 seconds, is 8 MPa or less.
7 . The heat-shrinkable polyester film according to claim 1 , wherein the second polyalcohol comprises ethylene glycol alone or both ethylene glycol and diethylene glycol, and in a case where the second polyalcohol comprises both ethylene glycol and diethylene glycol, when the total amount of the second polyalcohol is taken as 100 mol %, ethylene glycol is 90 mol % or more and diethylene glycol is 1 mol % to 10 mol %.
8 . The heat-shrinkable polyester film according to claim 1 , wherein the film comprises 0.01 to 10% by weight of at least one additive selected from an oxidation inhibitor, a weather-resistant stabilizer, an antistatic agent, an antifogging agent, a metallic soap, a wax, an antifungal agent, an antibacterial agent, a nucleating agent, a flame retardant, and a lubricating agent.
9 . The heat-shrinkable polyester film according to claim 1 , wherein the first polyalcohol is ethylene glycol, 1,4-cyclohexanedimethanol and diethylene glycol.