Low shrinkage low oligomer polyester film and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-11732097-B2
Application number	US-202017034279-A
Country	US
Kind code	B2
Filing date	Sep 28, 2020
Priority date	Feb 19, 2020
Publication date	Aug 22, 2023
Grant date	Aug 22, 2023

Abstract

A low shrinkage low oligomer polyester film and a method for manufacturing the same are provided. The method includes forming at least one polyester composition into an unstretched polyester thick film and stretching the unstretched polyester thick film in a machine direction (MD) and a transverse direction (TD) at a stretch ratio of two to six times. The polyester composition includes 94% to 99.974% by weight of a polyester resin, 0.01% to 1% by weight of a primary antioxidant, 0.01% to 1% by weight of a secondary antioxidant, 0.003% to 2% by weight of a nucleating agent, and 0.003% to 2% by weight of a flow aid. The polyester resin has an intrinsic viscosity between 0.60 dl/g and 0.80 dl/g.

First claim

The invention claimed is:

1. A manufacturing method of a polyester film, comprising:
forming at least one polyester composition into an unstretched polyester film, wherein the at least one polyester composition includes:
94% to 99.974% by weight of a polyester resin having an intrinsic viscosity between 0.60 dl/g and 0.80 dl/g;
0.01% to 1% by weight of a primary antioxidative agent;
0.01% to 1% by weight of a secondary antioxidative agent;
0.003% to 2% by weight of a nucleating agent; and
0.003% to 2% by weight of a flow aid; and

stretching the unstretched polyester film in a machine direction (MD) and a transverse direction (TD) at a stretch ratio of 2 to 6 times to form a biaxially stretched polyester film that includes a substrate layer and at least one surface layer formed on the substrate layer;
wherein a thickness of the biaxially stretched polyester film is between 15 μm and 350 μm, and a thickness of the at least one surface layer is 4% to 15% of the thickness of the biaxially stretched polyester film.

2. The manufacturing method according to claim 1 , further comprising pre-shrinking the biaxially stretched polyester film in the machine direction (MD) and/or the transverse direction (TD).

3. The manufacturing method according to claim 1 , wherein the unstretched polyester film is sequentially stretched in the machine direction (MD) and the transverse direction (TD), a stretch in the machine direction (MD) is performed at a temperature from 70° C. to 145° C., and a stretch in the transverse direction (TD) is performed at a temperature from 90° C. to 160° C.

4. The manufacturing method according to claim 1 , wherein the unstretched polyester film is simultaneously stretched in the machine direction (MD) and the transverse direction (TD) at a stretch ratio of 2 to 6 times and at a temperature from 70° C. to 160° C.

5. The manufacturing method according to claim 2 , further comprising: before forming the unstretched polyester film, performing a crystallizing and drying process on the at least one polyester composition at a temperature from 120° C. to 180° C.

6. The manufacturing method according to claim 5 , wherein a process time of the crystallizing and drying process is between 3 and 8 hours.

7. The manufacturing method according to claim 1 , wherein the at least one polyester composition further includes 0.5% to 2% by weight of slipping agent particles each having a particle size between 1 μm and 5 μm.

8. The manufacturing method according to claim 1 , wherein the polyester resin has an intrinsic viscosity between 0.65 dl/g and 0.78 dl/g.

9. A polyester film, comprising:
a substrate layer; and
at least one surface layer formed on at least one surface of the substrate layer;
wherein the substrate layer and the at least one surface layer are each formed of a polyester composition, and the polyester composition includes: wherein the substrate layer and the at least one surface layer are each formed of a polyester composition, and the polyester composition includes:
94% to 99.974% by weight of a polyester resin having an intrinsic viscosity between 0.60 dl/g and 0.80 dl/g;
0.01% to 1% by weight of a primary antioxidative agent;
0.01% to 1% by weight of a secondary antioxidative agent;
0.003% to 2% by weight of a nucleating agent; and
0.003% to 2% by weight of a flow aid;

wherein a thickness of the polyester film is between 15 μm and 350 μm, and a thickness of the at least one surface layer is 4% to 15% of the thickness of the polyester film.

10. The film according to claim 9 , wherein the polyester composition forming the at least one surface layer further includes 0.5% to 2% by weight of slipping agent particles each having a particle size between 1 μm and 5 μm.

11. The film according to claim 9 , wherein the polyester resin has an intrinsic viscosity between 0.65 dl/g and 0.78 dl/g.

12. The film according to claim 9 , wherein the film has a thermal shrinkage rate less than 1% in each of the machine direction (MD) and the transverse direction (TD) at a temperature of 210° C.

Assignees

• Nan Ya Plastics Corp

Inventors

• Liao Te-Chao
• Yang Wen-Cheng
• Cheng Wen-Jui
• HSIAO Chia-Yen

Classifications

• C08J5/18 Primary

  Manufacture of films or sheets · CPC title

• B29C48/0018

  combined with shaping by orienting, stretching or shrinking, e.g. film blowing (B29C48/0017 takes precedence) · CPC title

• B29C48/022

  characterised by the choice of material · CPC title

• B29C48/08

  flexible, e.g. films · CPC title

• B29C55/005

  characterised by the choice of materials · CPC title