POLYESTER FILM AND METHOD FOR REPRODUCING POLYESTER CONTAINER USING SAME

Abstract

The embodiments relate to a. polyester film and a process for regenerating a polyester container using the same, which not only solve the environmental problems by improving the recyclability of polyester containers, but also are capable of enhancing the yield and productivity. The polyester film comprises a first layer comprising a first resin comprising a diol component and a dicarboxylic acid component; and a second layer laminated on one side of the first layer and comprising a second resin different from the first resin, wherein when the polyester film is cut with a polyethylene terephthalate container to form flakes and the flakes are thermally treated at a temperature of 200° C. to 220° C. for 60 minutes to 120 minutes, the clumping fraction is 8% or less.

Claims

1. A polyester film to be regenerated with a polyester container, which comprises: a first layer comprising a first resin comprising a diol component and a dicarboxylic acid component; and a second layer laminated on one side of the first layer and comprising a second resin different from the first resin, wherein when the polyester film is cut with a polyethylene terephthalate container to form flakes and the flakes are thermally treated at a temperature of 200° C. to 220° C. for 60 minutes to 120 minutes, the clumping fraction is 8% or less.

2. The polyester film to be regenerated with a polyester container of claim 1, which has a heat shrinkage rate of 30% or more in the main shrinkage direction upon thermal treatment at a temperature of 80° C. for 10 seconds.

3. The polyester film to be regenerated with a polyester container of claim 1, wherein when the second layer is laminated on the first layer with an organic solvent, the bonding force of the laminated portion is 600 gf or more.

4. The polyester film to be regenerated with a polyester container of claim 1, wherein the second resin comprises a resin having a weight average molecular weight of less than 10,000 or a resin having a weight average molecular weight of greater than 12,000.

5. The polyester film to be regenerated with a polyester container of claim 1, wherein the second resin is a polyethylene naphthalate-based resin.

6. The polyester film to be regenerated with a polyester container of claim 1, which further comprises a third layer laminated on the other side of the first layer and comprising a third resin different from the first resin,

7. The polyester film to be regenerated with a polyester container of claim 6, wherein the second resin and the third resin are the same as each other.

8. The polyester film to be regenerated with a polyester container of claim 6, wherein when the second layer is laminated on the third layer with an organic solvent, the bonding force of the laminated portion is 200 gf or more.

9. A process for regenerating a polyester container, which comprises: providing the polyester container and a heat-shrunken polyester film that wraps at least part of the polyester container; crushing the polyester container and the heat-shrunken polyester film to obtain flakes; and thermally treating the flakes to produce regenerated polyester chips, wherein when the flakes are thermally treated at a temperature of 200° C. to 220° C. for 60 minutes to 120 minutes, the clumping fraction is 8% or less, the flakes comprise first flakes obtained by crushing the container and second flakes obtained by crushing the heat-shrunken polyester film, and the heat-shrunken polyester film comprises a first layer comprising a first resin comprising a diol component and a dicarboxylic acid component; and a second layer laminated on one side of the first layer and comprising a second resin different from the first resin,

10. The process for regenerating a polyester container of claim 9, wherein the particle size of the first flakes is 0.1 to 25 mm, and the particle size of the second flakes is 0.1 to 25 min.

11. The process for regenerating a polyester container of claim 9, wherein the container comprises polyethylene terephthalate in an amount of 90% by weight or more.

12. Regenerated polyester chips prepared according to the regeneration process of claim 9.

Description

EXAMPLE

Example 1

[0101] Preparation of a First Resin

[0102] A stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser was charged with 100% by mole of terephthalic acid (TA) as a dicarboxylic acid component and 70% by mole of ethylene glycol (EU) and 30% by mole of cyclohexanedimethanol (CHDM) as a diol component. Then, 0.05% by mole (based on the acid component) of zinc acetate as a transesterification catalyst was added thereto, The transesterification reaction was carried out while methanol was being distilled off. Thereafter, 0.025% by mole (based on the acid component) of antimony trioxide as a polycondensation catalyst was added, and the polycondensation reaction was carried out under a reduced pressure of 26.6 Pa (0.2 Torr) at 280° C. to obtain a first resin.

[0103] Preparation of a Polyester Film

[0104] The first resin was fed to an extruder and then melt-extruded at 280° C. through a T-die, which was cooled. A second resin (PEN 1: polyethylene naphthalate-based resin having a weight average molecular weight of greater than 12,000, Z-690, manufacturer: GOO Chemical) was applied on to the first resin, which was dried to obtain an unstretched sheet. Then, the unstretched sheet was passed through rolls at 75° C. to be stretched by 3.0 to 3.9 times while it was conveyed at a speed of 55 m/min and then preheated at 100° C. to 110° C. for 0.1 minute. Thereafter, the sheet was stretched 4.0 to 4.7 times in the transverse direction at 85° C. and then heat set at 90° C. for 0.1 minute to obtain a polyester film having a thickness of 40 p.m. Here, the thickness of the second layer was 20 μm.

[0105] Preparation of a Polyester Container wrapped with a polyester film The outer surface of a polyethylene terephthalate container (PET container, 30 g) was wrapped with the polyester film (1 g) prepared above using an acrylate-based is adhesive. The polyester film was shrunken in hot air at a temperature of 90° C. to obtain a polyester container wrapped with a heat-shrunken polyester film.

[0106] Process for Regenerating a Polyester Container

[0107] The container wrapped with the polyester film was crushed with a. crusher to obtain flakes. The flakes were washed with water and then washed for 15 minutes with a corrosion washing solution (a mixture of a solution of 0.3% by weight of Triton X-100 and a solution of 1.0% by weight of NaOH) stirred in a bath at 85° C. to 90° C. at 880 rpm. Thereafter, the flakes were washed with water at room temperature to remove the residual corrosion washing solution, dried at 160° C. for 20 minutes, and then thermally treated at 210° C. to produce regenerated polyester chips.

Examples 2 to 9 and Comparative Example

[0108] Regenerated polyester chips were prepared in the same manner as in Example 1, except that the components and contents were changed as shown in Table 1. below and that the first resin and the second resin or the first resin to the third resin were co-extruded through respective extruders and laminated in Examples 2, 4, 7, and 9. The same resin. was used for the second resin and the third resin.

TABLE-US-00001 TABLE 1 Second layer and third layer No. of Thickness laminations First layer (% by mole) Process (μm) Resin Ex. 1 2 layers NPG (30% by mole), Coating 20 PEN 1 — EG (70% by mole) (100%) Ex. 2 CHDM (30% by mole), Co-extrusion 20 PEN 1 — EG (70% by mole) (100%) Ex. 3 NPG (30% by mole), Coating 20 PEN 1 PEN 2 EG (70% by mole) (40%) (60%) Ex. 4 CHDM (30% by mole), Co-extrusion 20 PEN 1 PEN 2 EG (70% by mole) (60%) (40%) Ex. 5 CHDM (30% by mole), Coating 20 — PEN 2 EG (70% by mole) (100%) Ex. 6 3 layers NPG (30% by mole), Coating 20 PEN 1 — EG (70% by mole) (100%) Ex. 7 CHDM (30% by mole), Co-extrusion 20 PEN 1 — EG (70% by mole) (100%) Ex. 8 NPG (30% by mole), Coating 20 PEN 1 PEN 2 EG (70% by mole) (40%) (60%) Ex. 9 CHDM (30% by mole), Co-extrusion 20 PEN 1 PEN 2 EG (70% by mole) (60%) (40%) C. Ex. 1 Single CHDM (30% by mole), — — — — layer EG (70% by mole) * 2-layer laminated structure: first layer / second layer * 3-layer laminated structure: third layer / first layer / second layer * PEN 2: polyethylene naphthalate-based resin having a weight average molecular weight of less than 10,000 (Z-760, manufacturer: GOO Chemical)

Test Example 1

Measurement of Clumping

[0109] The flakes prepared above were passed through a 0.625″-sieve. 1 kg of the flakes thus sieved (in which the first flakes and the second flakes were mixed at a ratio of 97:3) was exposed in an oven at 210° C. for 90 minutes. The flakes were cooled to room temperature and passed through a 0.625″-sieve. The weight of the aggregates thus filtered out was measured and calculated as a percentage of the total weight of the flakes.

Test Example 2

Measurement of Bonding Force

[0110] Tetrahydrofuran as an organic solvent was applied on to the surface of the first polyester film prepared above. Then, the second polyester film prepared in the same manner was bonded. The bonded film was aged for 1 hour at a load of 2 kg. Thereafter, Is it was cut in the direction in which the organic solvent was applied by 30 mm and in the perpendicular direction by 90 mm at room temperature, which was measured for the force when the bonded surfaces were detached at a speed of 300 mm/min as the bonding force (gf).

[0111] The results of Test Examples 1 and 2 are shown in Table 2 below.

TABLE-US-00002 TABLE 2 No. of Clumping fraction Bonding force laminations (%) (gf) Ex. 1 2 layers 7.8 849 Ex. 2 7.4 1,010 Ex. 3 8.0 1,048 Ex. 4 7.9 1,205 Ex. 5 8.0 1,450 Ex. 6 3 layers 5.6 450 Ex. 7 4.1 604 Ex. 8 6.7 690 Ex. 9 5.8 871 C. Ex. 1 Single layer 10 1,820

[0112] As shown in Table 2, the polyester films prepared in Examples 1 to 9 and the regenerated polyester chips prepared by the process for regenerating a polyester container using the same had a low clumping fraction and excellent bonding force.