Polyester-Based Sealant Film

Abstract

Provided is a polyester-based sealant film having highly excellent heat seal strength and excellent recyclability. A polyester-based sealant film of a first aspect of the present invention is a laminated film composed of at least two layers and having a sealing layer and an outermost layer, in which the sealing layer includes a copolymerized polyester formed from a copolymer of terephthalic acid as well as another dicarboxylic acid component and a diol component, the outermost layer includes homopolyethylene terephthalate as a main component, the laminated film has a lamination configuration in which a content proportion (mol %) of the other dicarboxylic acid component in each layer decreases from the sealing layer toward the outermost layer, and a heat seal strength obtainable when the sealing layers of the laminated films are sealed at 0.2 MPa for 1 second in the range of 140° C. to 220° C. is 25 N/15 mm or higher.

Claims

1. A polyester-based sealant film, being a laminated film comprising at least two layers and having a sealing layer and an outermost layer, wherein the sealing layer includes a copolymerized polyester formed from a copolymer of terephthalic acid as well as another dicarboxylic acid component and a diol component, the outermost layer includes homopolyethylene terephthalate as a main component, the laminated film has a lamination configuration in which a content proportion (mol %) of the other dicarboxylic acid component in each layer decreases from the sealing layer toward the outermost layer, and a heat seal strength obtainable when the sealing layers of the laminated films are sealed at 0.2 MPa for 1 second in the range of 140° C. to 220° C. is 25 N/15 mm or higher.

2. A polyester-based sealant film, being a laminated film comprising at least two layers and having a sealing layer and an outermost layer, wherein the sealing layer includes a copolymerized polyester formed from a copolymer of terephthalic acid as well as another dicarboxylic acid component and a diol component, the outermost layer includes homopolyethylene terephthalate as a main component, the laminated film has a lamination configuration in which a content proportion (mol %) of the other dicarboxylic acid component in each layer decreases from the sealing layer toward the outermost layer, the thickness of the laminated film is less than 50 μm, and a heat seal strength obtainable when the sealing layers of the laminated films are sealed at 0.2 MPa for 1 second in the range of 140° C. to 200° C. is 25 N/15 mm or higher.

3. A polyester-based sealant film, being a laminated film comprising at least two layers and having a sealing layer and an outermost layer, wherein each layer includes a copolymerized polyester formed from a copolymer of terephthalic acid as well as another dicarboxylic acid component and a diol component, the laminated film has a lamination configuration in which a content proportion (mol %) of the other dicarboxylic acid component in each layer decreases from the sealing layer toward the outermost layer, and a heat seal strength obtainable when the sealing layers of the laminated films are sealed at 0.2 MPa for 1 second in the range of 160° C. to 200° C. is higher than 25 N/15 mm.

4. The polyester-based sealant film according to claim 1, wherein the polyester-based sealant film has an intermediate layer composed of at least one layer between the sealing layer and the outermost layer.

5. The polyester-based sealant film according to claim 4, wherein the intermediate layer includes a copolymerized polyester formed from a copolymer of terephthalic acid as well as another dicarboxylic acid component and a diol component, and the laminated film has a lamination configuration in which the content proportion (mol %) of the other dicarboxylic acid component in each layer decreases from the sealing layer toward the outermost layer.

6. The polyester-based sealant film according to claim 4, wherein the intermediate layer is a single layer.

7. The polyester-based sealant film according to claim 6, wherein a difference between a proportion of a total content of the other dicarboxylic acid component of the sealing layer and a proportion of a total content of the other dicarboxylic acid component of the intermediate layer is 1 mol % to 20 mol %.

8. The polyester-based sealant film according to claim 6, wherein a difference between a proportion of a total content of the other dicarboxylic acid component of the intermediate layer and a proportion of a total content of the other dicarboxylic acid component of the outermost layer is 5 mol % to 20 mol %.

9. The polyester-based sealant film according to claim 3, wherein the polyester-based sealant film has an intermediate layer composed of at least one layer between the sealing layer and the outermost layer.

10. The polyester-based sealant film according to claim 9, wherein the intermediate layer includes a copolymerized polyester formed from a copolymer of terephthalic acid as well as another dicarboxylic acid component and a diol component, and a content proportion (mol %) of the other dicarboxylic acid component included in the sealing layer is higher than a content proportion (mol %) of the other dicarboxylic acid component included in the intermediate layer.

11. The polyester-based sealant film according to claim 9, wherein a content proportion (mol %) of the other dicarboxylic acid component included in the intermediate layer is equal to or higher than a content proportion (mol %) of the other dicarboxylic acid component included in the outermost layer.

12. The polyester-based sealant film according to claim 9, wherein the intermediate layer is a single layer.

13. The polyester-based sealant film according to claim 12, wherein a difference between a proportion of a total content of the other dicarboxylic acid component of the sealing layer and a proportion of a total content of the other dicarboxylic acid component of the intermediate layer is 1 mol % to 20 mol %.

14. The polyester-based sealant film according to claim 12, wherein a difference between a proportion of a total content of the other dicarboxylic acid component of the intermediate layer and a proportion of a total content of the other dicarboxylic acid component of the outermost layer is 0 mol % to 17 mol %.

15. The polyester-based sealant film according to claim 4, wherein the intermediate layer includes homopolyethylene terephthalate.

16. The polyester-based sealant film according to claim 1, wherein the other dicarboxylic acid component includes isophthalic acid and/or sebacic acid.

17. The polyester-based sealant film according to claim 1, wherein the outermost layer includes inorganic particles.

18. The polyester-based sealant film according to claim 3, wherein the outermost layer includes homopolyethylene terephthalate.

19. The polyester-based sealant film according to claim 1, wherein the polyester-based sealant film has a barrier layer on the outermost layer.

20. A packaging material comprising the polyester-based sealant film according to claim 1.

Description

EXAMPLES

[0243] Hereinafter, an example of the Examples of the present invention will be described. However, the present invention is not intended to be limited to the Examples that will be described below.

[0244] <Evaluation Methods>

[0245] Measurement of Heat Seal Strength

[0246] Heat seal strength was measured according to JIS Z1707. The sealing surfaces of films were joined together and heat-sealed at 0.2 MPa for 1 second at each temperature (140° C. to 220° C.) to form a sealed part, the sealed part was cut to have a width of 15 mm, and the peeling strength of the sealed part was measured with a tensile tester at a tensile rate of 300 mm/min.

[0247] Measurement of Breaking Strength

[0248] A sample film having a size of 1.5 cm×15 cm was pulled at a rate of 200 mm/min by using a tensile tester, and the strength when the sample was cut (broken) (value obtained by dividing the tensile load value by the cross-sectional area of the test specimen) was designated as breaking strength (MPa).

[0249] Measurement of Piercing Strength

[0250] The piercing strength (N) was measured according to JIS 21707, and a value obtained by dividing the piercing strength (N) by the film thickness was designated as unit piercing strength (N/mm).

[0251] Measurement of Shrinkage Ratio

[0252] A sample film having a size of 1.5 cm×15 cm was heat-treated for 5 minutes in a tensionless state in a hot air type oven maintained at a predetermined temperature (100° C.), the lengths of the sample film before and after the heat treatment were measured, and the shrinkage ratio was calculated as follows (Formula 1). Incidentally, the shrinkage ratio was measured in each of the longitudinal direction (MD) and the width direction (TD) of the film.

Shrinkage ratio (%)={(Sample length before heat treatment)−(sample length after heat treatment)}÷(sample length before heat treatment)×100  (Formula 1)

[0253] Measurement of Haze

[0254] The haze was measured according to JIS K7136 by using a haze meter DH-2000 manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD.

[0255] <Materials Used>

[0256] [Adjustment of Polyester Raw Materials]

[0257] The composition of each polyester used for the present invention is shown in Table 1. In Table 1, TPA is terephthalic acid, IPA is isophthalic acid, EG is ethylene glycol, and DEG is diethylene glycol.

[0258] Incidentally, at the time of production of polyester B, SiO.sub.2 (SL310 manufactured by FUJI SILYSIA CHEMICAL LTD.) as a lubricating agent was added to the polyester at a proportion of 6000 ppm.

TABLE-US-00001 TABLE 1 Amount of Raw material composition of polyester (mol %) addition of Polyester Dicarboxylic acid Diol lubricating raw component component agent material TPA IPA EG DEG (ppm) A 100 0 96 4 0 B 100 0 98 2 6000 C 76 24 97 3 0

[0259] <First or Second Aspect>

Example 1-1

[0260] Polyester A and polyester B were mixed at a mass ratio of 50:50 as a raw material of an outermost layer, polyester A and polyester C were mixed at a mass ratio of 50:50 as a raw material of an intermediate layer, and polyester B and polyester C were mixed at a mass ratio of 15:85 as a raw material of a sealing layer.

[0261] The respective mixed raw materials of the outermost layer, the intermediate layer, and the sealing layer were introduced into separate twin-screw extruders, and the mixed raw materials of the outermost layer and the intermediate layer were melted at 280° C., while the mixed raw material of the sealing layer was melted at 270° C. Each of the raw materials was co-extruded onto a cooling roll set at 15° C. to be cooled and solidified, and thus, three kinds of unstretched laminated films of three layers (outermost layer/intermediate layer/sealing layer) were obtained.

[0262] Next, the obtained unstretched laminated film was stretched 3.3 times in the longitudinal direction (MD) at 85° C. with a roll stretching machine. Furthermore, the film was preheated to 95° C. in a tenter and then stretched 4.2 times in the width direction (TD) at 110° C. Lastly, the film was subjected to a heat treatment at 225° C., and a laminated film having a thickness of 36 μm (outermost layer: 5 μm, intermediate layer: 26 μm, sealing layer: 5 μm) was obtained.

[0263] The characteristics of the obtained laminated film were evaluated by the above-described methods. The evaluation results are presented in Table 2.

Example 1-2

[0264] A laminated film having a thickness of 50 μm (outermost layer: 7 μm, intermediate layer: 36 μm, sealing layer: 7 μm) was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer as in Example 1-1. The evaluation results are presented in Table 2.

Example 1-3

[0265] A laminated film having a thickness of 75 μm (outermost layer: 10 μm, intermediate layer: 55 μm, sealing layer: 10 μm) was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer as in Example 1-1. The evaluation results are presented in Table 2.

Example 1-4

[0266] Polyester A and polyester C were mixed at a mass ratio of 40:60 as a raw material of the intermediate layer. A laminated film having a thickness of 75 μm (outermost layer: 10 μm, intermediate layer: 55 μm, sealing layer: 10 μm) was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer other than the intermediate layer as in Example 1-1. The evaluation results are presented in Table 2.

Example 1-5

[0267] A laminated film having a thickness of 75 μm (outermost layer: 5 μm, intermediate layer: 60 μm, sealing layer: 10 μm) was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer as in Example 1-1. The evaluation results are presented in Table 2.

Example 1-6

[0268] Polyester A and polyester C were mixed at a mass ratio of 52:48 as a raw material of the intermediate layer, and polyester B and polyester C were mixed at a mass ratio of 7:93 as a raw material of the sealing layer. A laminated film having a thickness of 75 μm (outermost layer: 14 μm, intermediate layer: 47 μm, sealing layer: 14 μm) was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer other than the intermediate layer as in Example 1-1. The evaluation results are shown in Table 2.

Example 1-7

[0269] A laminated film having a thickness of 49.9 μm (outermost layer: 9.3 μm, intermediate layer: 31.3 μm, sealing layer: 9.3 μm) was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer as in Example 1-6. The evaluation results are presented in Table 2.

Example 1-8

[0270] A laminated film having a thickness of 38 μm (outermost layer: 7 μm, intermediate layer: 24 μm, sealing layer: 7 μm) was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer as in Example 1-6. The evaluation results are presented in Table 2.

Comparative Example 1-1

[0271] As a raw material of the intermediate layer, only polyester A was used. A laminated film having a thickness of 75 μm (outermost layer: 5 μm, intermediate layer: 60 μm, sealing layer: 10 μm) was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer other than the intermediate layer as in Example 1-1. The evaluation results are presented in Table 2.

TABLE-US-00002 TABLE 2 Example Example Example Example Example Example Example Example Comparative 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 Example 1-1 Thickness Outermost layer 5 7 10 10 5 14 9.3 7 5 (μm) Intermediate layer 26 36 55 55 60 47 31.3 24 60 Sealing layer 5 7 10 10 10 14 9.3 7 10 Total thickness 36 50 75 75 75 75 49.9 38 75 Other Outermost layer 0 0 0 0 0 0 0 0 0 dicarboxylic Intermediate layer 12 12 12 14 12 11 11 11 0 acid component Sealing layer 20 20 20 20 20 22 22 22 20 (mol %) Heat seal 140° C. 29 40 33 29 38 25 41 34 13 strength 160° C. 31 38 38 58 50 43 45 35 12 (N/15 mm) 180° C. 25 39 61 56 53 45 35 28 11 200° C. 28 26 65 34 58 52 37 27 12 220° C. 31 33 63 27 68 49 37 22 12 Breaking MD 88 92 91 75 69 106 108 110 201 strength TD 114 117 117 80 109 114 116 125 230 (MPa) Unit piercing strength (N/mm) 214 214 208 164 199 225 224 228 479 Shrinkage MD 1.6 1.7 1.3 1.4 1.8 1.4 2.0 2.1 0.5 ratio (%) TD −0.7 −0.4 −0.3 −0.3 −0.9 −0.5 −0.8 −0.7 0.1 Haze (%) 4.3 5.0 5.7 5.6 5.3 6.9 5.8 5.3 5.4

[0272] <Third Aspect>

Example 2-1

[0273] Polyester A, polyester B, and polyester C were mixed at a mass ratio of 25:50:25 as a raw material of the outermost layer, polyester A and polyester C were mixed at a mass ratio of 50:50 as a raw material of the intermediate layer, and polyester B and polyester C were mixed at a mass ratio of 15:85 as a raw material of the sealing layer.

[0274] The respective mixed raw materials of the outermost layer, the intermediate layer, and the sealing layer were introduced into separate twin-screw extruders, and the mixed raw materials of the outermost layer and the intermediate layer were melted at 280° C., while the mixed raw material of the sealing layer was melted at 270° C. Each of the raw materials was co-extruded onto a cooling roll set at 15° C. to be cooled and solidified, and thus, three kinds of unstretched laminated films of three layers (outermost layer/intermediate layer/sealing layer) were obtained.

[0275] Next, the obtained unstretched laminated film was stretched 3.3 times in the longitudinal direction (MD) at 85° C. with a roll stretching machine. Furthermore, the film was preheated to 95° C. in a tenter and then stretched 4.2 times in the width direction (TD) at 110° C. Lastly, the film was subjected to a heat treatment at 225° C., and a laminated film having a thickness of 75 μm (outermost layer: 10 μm, intermediate layer: 55 μm, sealing layer: 10 μm) was obtained.

[0276] The characteristic of the obtained laminated films were evaluated by the above-described methods. The evaluation results are presented in Table 3.

Example 2-2

[0277] Polyester B and polyester C were mixed at a mass ratio of 50:50 as a raw material of the outermost layer. A laminated film was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer other than the outermost layer as in Example 2-1. The evaluation results are presented in Table 3.

Comparative Example 2-1

[0278] Polyester A and polyester C were mixed at a mass ratio of 60:40 as a raw material of the intermediate layer. A laminated film was obtained by adopting the same raw material mass ratio and film-forming conditions for each layer other than the intermediate layer as in Example 2-2. The evaluation results are presented in Table 3.

TABLE-US-00003 TABLE 3 Example Example Comparative 2-1 2-2 Example 2-1 Thickness Outermost layer 10 10 10 (μm) Intermediate layer 55 55 55 Sealing layer 10 10 10 Total thickness 75 75 75 Other Outermost layer 6 12 12 dicarboxylic Intermediate layer 12 12 10 acid component Sealing layer 20 20 20 (mol %) Heat seal 140° C. 20 30 22 strength 160° C. 32 29 23 (N/15 mm) 180° C. 27 28 22 200° C. 26 37 22 220° C. 16 40 18 Breaking MD 86 85 106 strength TD 122 113 136 (MPa) Unit piercing strength (N/mm) 212 221 304 Shrinkage MD 1.8 2.4 1.9 ratio (%) TD −0.9 −1.4 −1.0 Haze (%) 7.3 10.0 10.9

INDUSTRIAL APPLICABILITY

[0279] The polyester-based sealant film of the present invention has sufficient mechanical characteristics such as low shrinkability, breaking strength, and piercing strength necessary for use as a sealant.

[0280] In addition, the polyester-based sealant film of the present invention has highly excellent heat seal strength.

[0281] Therefore, according to the present invention, since a packaging material based on a single material system composed of a polyester material can be realized by, for example, laminating another polyester-based base material film such as a transparent barrier vapor deposition PET, or by combining high barrier vapor deposition and printing processing technologies for polyester-based films, a packaging material having excellent recyclability can be provided.