Patent ID: 8252856

Claim:
A method for manufacturing white plastic film comprising: providing a first particulate polyester material and second particulate polyester material; subjecting said first particulate polyester material to solid state polymerization to prepare a first polyester resin having the intrinsic viscosity of 0.65˜0.90 and the oligomer content of less than 0.5%; providing a master batch composition comprising the second particulate polyester material −5[˜]-25 parts by weight of an amorphous polyester resin and 50[˜]150 parts by weight of barium sulfate, each based on 100 parts by weight of the second particulate polyester material; subjecting the master batch composition to solid state polymerization to prepare a second polyester resin having an oligomer content of less than 0.5% within the second polyester resin, and a melt viscosity of 500[˜]-3,000 Poise in the full range of shear rate 100[˜]-5,000 l/s after melting at 280° C. for 5 minutes; preparing a mixture of the first polyester resin and the second polyester resin, subjecting the mixture to melt-extrusion to prepare a sheet; drawing the sheet to produce a film; heat-treating the drawn film; and heat-setting the heat-treated film to provide the white plastic film, wherein, the white plastic film has an oligomer content of less than 0.8% in the final film, and a crystallization speed of 20˜180 seconds when measured under the isothermal condition of 210° C. after melting at 280° C. for 5 minutes by using differential scanning calorimetry.