Method for manufacturing polyester film having laminated structure

A method for manufacturing a polyester film having a laminated structure comprising at least a white polyester film layer and a black polyester film layer, the method comprising:

• obtaining a recycled polyester material;
• physically recycling a part of the recycled polyester material by melting the recycled polyester material;
• selectively adding at least one black additive selected from carbon black powder, graphite powder, nano carbon black, carbon nanotubes, and graphene when preparing chips for the black polyester film layer;
• and granulating the same to obtain a plurality of physically recycled polyester chips;
• wherein black additive is added only to the physically recycled polyester chips for preparing the black polyester film layer;
• chemically recycling another part of the recycled polyester material and granulating the same to obtain a plurality of chemically recycled polyester chips,
• wherein at least a portion of the chemically recycled polyester chips are chemically recycled electrostatic pinning polyester chips prepared by:
• de-polymerizing the another part of the recycled polyester material to obtain a chemically de-polymerized material mixture that includes ester monomers and oligomers, each of the ester monomers being bis(2-hydroxyethyl) terephthalate (BHET) formed by two diol units and one dibasic acid unit;
• subsequent to the de-polymerizing, adding electrostatic pinning additives to at least a part of the chemically de-polymerized material mixture prior to re-polymerization, and not adding the electrostatic pinning additives during the step of physically recycling, wherein the electrostatic pinning additives are at least one selected from the group consisting of magnesium acetate (Mg(CH3COO)2) and lithium acetate (CH3COOLi);
• re-polymerizing the chemically de-polymerized material mixture containing the electrostatic pinning additives and granulating the same to obtain the chemically recycled electrostatic pinning polyester chips, wherein a content of the electrostatic pinning additives in the chemically recycled electrostatic pinning polyester chips is between 0.01% and 0.3% by weight;
• and
• mixing and melting 50 to 95 parts by weight of the physically recycled polyester chips, 5 to 35 parts by weight of the chemically recycled electrostatic pinning polyester chips, and no greater than 10 parts by weight of virgin polyester chips to respectively form the white polyester film layer and the black polyester film layer;
• and
• laminating the white polyester film layer and the black polyester film layer,
• wherein the white polyester film layer contains at least one white additive selected from the group consisting of titanium dioxide (TiO2) particles, barium sulfate (BaSO4) particles, and calcium carbonate (CaCO3) particles;
• and wherein the black polyester film layer is formed from the physically recycled polyester chips containing the black additive and the chemically recycled polyester chips, wherein the black additive is included in the physically recycled polyester chips and not in the chemically recycled polyester chips.