Heat-shrinkable polyester-based single-layer film
The present invention relates to a heat-shrinkable polyester-based single-layer film which has superior shrinkability and color, and thus provides aesthetic enhancement to the product to which the film is attached when the film is printed. Therefore, the polyester-based single-layer film of the present invention can be valuably used as a label film as it can replace labels made of paper, and can be easily peeled off by means of hot water, thus contributing to the recycling of bottles.
1. A heat-shrinkable polyester-based single-layer film, comprising a polyester-based resin matrix including a repeating unit of 2,2-dimethyl(-1,3-propylene)terephthalate and particles dispersed in the resin matrix, wherein the film has a haze of 80 95%, a haze deviation of within ±5% of an average haze over an entire width of a film roll, a shrinkage of 40 80% in a maximum shrinking direction upon treatment with warm water at 90° C. for 10 sec, and a shrinkage deviation of within ±5% of an average shrinkage in the maximum shrinking direction,
wherein the heat-shrinkable polyester-based single-layer film is manufactured by a method of extruding and stretching a polyester-based resin, comprising: compounding particles having an average particle size of 0.1-5 μm and a 2,2-dimethyl(-1,3-propane)diol copolyester resin having an intrinsic viscosity of at least 0.6 dl/g to give a polyester-based resin master batch containing the particles, wherein the particles are included in an amount of 10-70 wt % based on a total weight of the master batch; mixing and extruding the polyester-based resin master batch containing the particles and additional 2,2-dimethyl(-1,3-propane)diol copolyester resin to produce an unstretched polyester-based sheet, wherein the particles are included in an amount of 2-10 wt % based on a total weight of the sheet; preheating the extruded polyester-based sheet; and stretching the sheet in a transverse direction at 65-100° C., and
wherein the manufacturing the master batch comprises: providing a mixture of the 2,2-dimethyl(-1,3-propane)diol copolyester and the particles; placing the mixture in a twin-screw extruder or a kneader so that the mixture is melted and mixed to give polyester-based master batch chips containing the particles; rubbing the master batch chips with each other to form minute roughness on at least a portion of a surface thereof; and drying the master batch chips having minute roughness on at least the portion of the surface thereof.
2. The heat-shrinkable polyester-based single-layer film of claim 1 , wherein the particles have an average particle size of 0.1-5 μm.
3. The heat-shrinkable polyester-based single-layer film of claim 1 , wherein the particles are titanium oxide, and are included in an amount of 2-10 wt % based on a total weight of the film.
4. A method of manufacturing a heat-shrinkable polyester-based single-layer film by extruding and stretching a polyester-based resin, comprising:
compounding particles having an average particle size of 0.1-5 μm and a 2,2-dimethyl(-1,3-propane)diol copolyester resin having an intrinsic viscosity of at least 0.6 dl/g, thus manufacturing a polyester-based resin master batch containing particles, wherein the particles are included in an amount of 10-70 wt % based on a total weight of the master batch;
mixing and extruding the polyester-based resin master batch containing particles and a 2,2-dimethyl(-1,3-propane)diol copolyester resin, thus manufacturing an unstretched polyester-based sheet, wherein the particles are included in an amount of 2-10 wt % based on a total weight of the film;
preheating the extruded polyester-based sheet; and
stretching the sheet in a transverse direction at 65-100° C.;
wherein the manufacturing the master batch comprises mixing the 2,2-dimethyl(-1,3-propane)diol copolyester and the particles to create a mixture; placing the mixture in a twin-screw extruder or a kneader so that the mixture is melted and mixed, thus obtaining polyester-based master batch chips containing particles; rubbing the master batch chips with each other to form minute roughness on at least a portion of a surface thereof; and drying the master batch chips having minute roughness on at least the portion of the surface thereof.
5. The method of claim 4 , wherein the mixing the master batch and the 2,2-dimethyl(-1,3-propane)diol copolyester resin comprises providing a separation means in a feeding section for feeding the master batch and the resin into an extruder, so that the 2,2-dimethyl(-1,3-propane)diol copolyester resin is fed into one portion of the feeding section divided by the separation means, and the master batch chips are fed into the other portion of the feeding section using a quantitative feeding section, thus melting and mixing the master batch and the 2,2-dimethyl(-1,3-propane)diol copolyester resin at a feeding section of the extruder via rotation of a screw of the extruder.
6. The method of claim 4 , wherein the stretching in the transverse direction is performed at a stretching ratio of 3.5-5.0 times.
7. The method of claim 4 , wherein the particles of the polyester-based resin master batch are titanium oxide.