COMPOSITE POLYMERIC FILM

Abstract

A composite film comprising a of amide substrate layer having a first and second surface, and a primer coating layer disposed on the first surface of the substrate layer, wherein the primer coating layer is derived from a composition comprising an acid copolymer resin, an organic crosslinker and an acid catalyst. A heat-sealable coating is applied on the primer.

Claims

1. A composite film comprising a polyamide substrate layer having a first and second surface; a primer coating layer disposed on the first surface of the substrate layer, wherein the primer coating layer is derived from a composition comprising an acid copolymer resin, an organic crosslinker and an acid catalyst; and a heat-sealable polymeric coating layer disposed on the primer coating layer.

2. (canceled)

3. A method for manufacturing a composite film comprising: (i) disposing a primer coating layer composition comprising an acid copolymer resin, an organic crosslinker and an acid catalyst in a coating vehicle onto a surface of a polyamide substrate; (ii) drying the primer coating layer composition; (iii) heating the dried primer coating layer composition to form a cured primer layer; and (iv) disposing a heat-sealable polymeric coating layer comprising a heat-sealable polymeric material in a second coating vehicle onto the cured primer layer; and (v) drying and/or heating the heat-sealable polymeric coating layer.

4. A composite film according to claim 1, or a method according to claim 3, wherein the polyamide substrate is uniaxially or biaxially oriented, preferably biaxially oriented.

5. A composite film according to claim 1, wherein the polyamide is a thermoplastic crystallisable linear aliphatic polyamides, preferably selected from: nylon 6,6; nylon 6; nylon 6.66; nylon 6,10; nylon 6,4; and blends and mixtures thereof.

6. A composite film according to claim 1, wherein the thickness of said polyamide substrate is from about 5 to about 150 μm, preferably from 10 to about 100 μm, preferably from about 11 to about 50 μm and preferably from about 12 to about 30 μm.

7. A composite film according to claim 1, wherein the acid copolymer resin is selected from ethylene/acrylic acid (EAA) copolymers; ethylene acrylate copolymers functionalized with COOH groups; ethylene/methacrylic acid (EMAA) copolymers; methyl acrylate/acrylic acid (MAAA) copolymers; and ethylene/vinyl acetate (EVA) copolymers functionalized with COOH groups; and mixtures thereof.

8. A composite film according to claim 1, wherein the primer coating layer comprises from 60% to 99.9%, preferably from 75 to 99%, preferably from 92 to 95% by weight of the acid copolymer resin based on the total weight of the primer coating layer.

9. A composite film according to claim 1, wherein the organic crosslinker is selected from melamine crosslinking agents, polyisocyanate crosslinking agents, polycarbodiimide crosslinking agents, crosslinkers comprising multiple oxazoline groups, crosslinkers comprising multiple aziridine groups, and mixtures thereof.

10. A composite film according to claim 1, wherein the organic crosslinker is one or more melamine crosslinking agent(s).

11. A composite film according to claim 1, wherein the primer coating layer is derived from a composition comprising from 0.05% to 25%, preferably from 0.5% to 20%, preferably from 5 to 12% by weight of the organic crosslinker based on the total weight of the primer coating layer.

12. A composite film according to claim 1, wherein the acid catalyst is selected from an organic sulfonic acid, sulphuric acid and ammonium nitrate.

13. A composite film according to claim 1, wherein the acid catalyst is an organic sulfonic acid, wherein the organic sulfonic acid is selected from p-toluenesulfonic acid and dodecylbenzenesulfonic acid.

14. A composite film according to claim 1, wherein the primer coating layer is derived from a composition comprising from 0.01% to 2%, preferably from 0.05% to 1.8%, preferably from 0.3 to 1.3% by weight of the acid catalyst based on the total weight of the primer coating layer.

15. A composite film according to claim 1, wherein the primer coating layer further comprises a slip-aid, an anti-blocking agent and/or a tackifying resin.

16. A composite film according to claim 1, wherein the primer coating layer is derived from a composition further comprising a coating vehicle, preferably wherein the coating vehicle is an organic solvent, preferably toluene, xylene and/or chlorobenzene.

17. A composite film according to claim 1, wherein the primer coating layer has a dry thickness of 0.1 to 1.0 μm.

18. A composite film according to claim 1, wherein the heat-sealable polymeric coating layer is formed from polyvinylidene chloride (PVDC), ethylene vinyl acetate (EVA), polyolefins, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and mixtures thereof.

19. A composite film according to claim 18, wherein the heat-sealable polymeric coating layer is formed from EVA polymer having a vinyl acetate content in the range of 9% to 40%.

20. A composite film according to claim 1, wherein the heat-sealable polymeric coating layer has a thickness of between from 2 to 6 μm, preferably from 2 to 4 μm.

21. A composite film according to claim 1, wherein the composite film has a total thickness of no more than 60 μm, preferably of no more than 35 μm.

22. A sealed container comprising a receptacle containing a food product, particularly an ovenable meal, and a lid formed from a composite film as defined in any one of claim 1, particularly wherein the receptacle is made from CPET or a polyolefin, preferably PP.

23. Use of a composite film as defined in claim 1, as a lid in the packaging of an ovenable meal, said packaging further comprising a receptacle, particularly wherein the receptacle is made from CPET or a polyolefin, preferably PP.

24. A sealed bag containing a food product, wherein the bag is formed from a composite film as defined in claim 1.

25. Use of a composite film as defined in claim 1 as a bag for packaging of a food product.

Description

EXAMPLES

[0119] The materials noted in Table 1 were used to prepare composite films:

TABLE-US-00001 TABLE 1 Raw Material Supplier Description Elvax ® 4260 DuPont EVA (28 wt % VA, 1 wt % methacrylic acid) Nucrel ® 960 DuPont E/MAA (15 wt % methacrylic acid) Bynel ® 2022 DuPont Acid-modified ethylene acrylate Bynel ® 3101 DuPont Acid/acrylate-modified EVA Cymel XW 3106 Allnex Water insoluble, specifically alkylated high solids melamine resin p-Toluenesulfonic Sigma-Aldrich Acid catalyst (5% solution in THF) acid Nacure ® 5076 King Industries, Inc. Acid catalyst based on DDBSA Nacure ® 5925 King Industries, Inc. Amine neutralized DDBSA catalyst Sulphuric acid Sigma-Aldrich Acid catalyst Elvax ® 3185 DuPont EVA (32 wt % VA) Piccolyte ® M115 Pinova Solutions Poly terpene resin, softening point 111-119° C. Kemamide EZ PMC Biogenix Fatty amide slip-aid Syloid ® 620 W.R. Grace Amorphous silica anti-blocking agent Capran 1200 AdvanSix Biaxially oriented nylon 6 film, 12 μm

Comparative Examples 1 to 2; Examples 3 to 12

[0120] A biaxially oriented nylon 6 film was obtained (Capran 1200, available from AdvanSix). The nylon 6 film thickness was 12 μm. A substrate of A4 size was prepared.

[0121] A range of composite films were prepared by coating a primer coating layer having the compositions shown in Table 2 onto one surface of the nylon 6 film as described above. For instance, the primer coating layer of Example 3 was prepared by dissolving 9.45 g of Elvax® 4260 in 89.05 g of toluene at 60° C., followed by adding 0.05 g of p-Toluenesulfonic acid monohydrate and 0.5 g of Cymel XW 3106.

[0122] The amounts of the components of the coating formulation shown in Table 2 are the amounts by weight of each component in the finished primer coating layer (i.e. the dry weight of the primer coating layer). The coating formulations in Table 2 were prepared at 10 wt % in toluene. The coating was conducted off-line using a Meyer coating rod at a coat weight of 0.7 g/m.sup.2 to one surface of the nylon 6 film. The primer coating layer composition was transferred to a forced air oven preset at 150° C. for drying and curing for 3 min. The composite film was cooled down to room temperature.

[0123] A heat-sealable polymeric coating layer was then coated onto the cured primer layer of the range of composite films as described above. The heat-sealable polymeric coating composition was prepared by dissolving 31 g of Elvax® 3185, 0.3 g of Syloid® 620 and 0.5 g of Kemamide EZ in 200 mL of toluene at 60° C. The coating was conducted off-line using a Meyer coating road at a coat-weight of 6.5 g/m.sup.2. The heat-sealable polymeric coating layer composition was transferred to a forced air oven preset at 115° C. for drying for 2 min.

[0124] The final composite film was heat-sealed (350° F.; dwell time 0.5 second; pressure 80 psi) to itself, to a PP substrate and to a C-PET substrate and the peel strengths of the composite films were tested as described herein. The results are provided in Table 2.

[0125] The composite films according to the present invention exhibited an easy and clean peel when peeled from the container substrate. In contrast, the films of Comparative Examples 1 and 2 left a coating residue on the substrate after peeling.

[0126] In addition, the inventive examples were found to exhibit superior peel strength across all peel strengths tested compared to the composite film of Comparative Example 1 (no organic crosslinker or acid catalyst in the primer coating layer) and to the composite film of Comparative Example 2 (no acid catalyst in the primer coating layer).

Comparative Example 3; Example 13

[0127] The composite film of Comparative Example 3 was prepared by disposing the heat-sealable polymeric coating composition directly on the polyamide substrate. Thus, the comparative composite film did not comprise a primer coating layer. The peelability of the composite film to a PP substrate and to a CPET substrate was evaluated as shown in FIGS. 2A and 2B respectively. The composite film did not exhibit a clean peel when manually peeled from the substrates, which can be seen by the spotting and residue of the heat-sealable coating layer visible on the surface of the PP and CPET substrate.

[0128] A composite film of Example 13 was provided wherein the primer coating layer was disposed on the first surface of the polyamide substrate and then the heat-sealable polymeric coating layer was disposed on the primer coating layer. The peelability of the composite film to itself, to a CPET substrate and to a PP substrate was evaluated, as shown in FIG. 3 (left to right).

[0129] The composite film exhibited a clean peel when manually peeled from the substrates, as illustrated by the absence of spotting and the absence of any residue of the heat-sealable coating layer visible on the surface of the substrates.

[0130] The coating/coating peel test (i.e. wherein the composite film was heat-sealed to itself) exhibited cohesive failure within the heat-sealable coating, indicating advantageously high adhesion strength between the heat-sealable coating layer and the primer coating layer.

TABLE-US-00002 TABLE 2 1 (C) 2 (C) 3 4 5 6 7 8 9 10 11 12 Acid copolymer resin: Elvax 4260 100% .sup. 95% 94.50% 98.9% 99.89% 62.00% 63.90% 89.00% 94.50% Nucrel 960 99.45% Bynel 2022 99.45% Bynel 3101 99.45% Organic crosslinker: CYMEL  0%  5.0% 5.00% 1.0% 0.10% 5.00% 1.00% 10.00% 5.00% 0.50% 0.50% 0.50% XW 3106 Acid catalyst: p-Toluene-  0% 0.00% 0.50% 0.1% 0.01% 0.50% 0.05% 0.05% 0.05% sulfonic acid (PTSA) NACURE 0.50% 5076 NACURE 1.00% 5925 Sulfuric 0.10% Acid Other Ingredients: Piccolyte 32.00% 35.00% C115 Syloid 0.50% 620 Peel strength (g/25.4 mm) Coating- 683* 702* 1492 1589 1247 1392 1309 1605 1806 1055 1288 1153 coating Peel 516* 439* 766 750 643 721 684 748 812 686 801 792 strength to CPET Peel 390* 422* 634 676 571 823 860 580 626 578 652 690 strength to PP *coating residue observed on the substrate after peeling