MULTI-LAYER FILM

Abstract

It relates to a multi-layer film for seal-peel applications, an article comprising said film and the use of said film.

Claims

1. A multi-layer film for seal-peel application comprising at least two layers, namely a cover layer and a seal layer, whereby the seal layer comprises between 25 and 80 wt. % of EVA and between 20 and 75 wt. % of LLDPE based on the total weight of the layer, whereby the EVA comprises a first EVA and a second EVA.

2. The multi-layer film according to claim 1, wherein the LLDPE has a density between 0.850 and <0.945 g/cm.sup.3.

3. The multi-layer film according to claim 1, wherein the melt flow index of the LLDPE ranges from 0.3 to 15 g/10 min.

4. The multi-layer film according to claim 1, wherein the amount of LLDPE in the seal layer is between 20% and 75% by weight based on the total weight of the layer.

5. The multi-layer film according to claim 1, wherein the amount of EVA in the seal layer is between 25% and 80% by weight based on the total weight of the layer.

6. The multi-layer film according to claim 1, wherein the melt flow index of the EVA ranges from 1 to 35 g/10 min.

7. The multi-layer film according to claim 1, wherein the vinyl acetate content of the EVA is between 4 and 50 wt. %.

8. The multi-layer film according to claim 1, wherein one of the first or second EVAs has a vinyl acetate content below 20 wt. %, while the other one of the first or second EVA has a vinyl acetate content above 20 wt. %, based on the total weight of the respective EVA.

9. The multi-layer film according to claim 1, wherein the seal layer consists of between 25 and 80 wt. % of EVA and between 20 and 75 wt. % of LLDPE based on the total weight of the layer.

10. The multi-layer film according to claim 1, wherein when the EVA content of the seal layer is <50 wt. % the vinyl acetate content of the EVA is >20 wt. % or when the EVA content of the seal layer is >50 wt. % the vinyl acetate content of the EVA is <20 wt. %.

11. The multi-layer film according to claim 1, wherein the EVA with the highest vinyl acetate content and/or the highest melt flow rate of the first and second EVAs is present in the seal layer in amount of between 30 wt. % and 58 wt. %, based on the total weight of the seal layer and/or based on the total weight of EVA in the seal layer.

12. The multi-layer film according to claim 1, wherein the EVA with the lowest vinyl acetate content and/or the lowest melt flow rate of the first and second EVAs is present in the seal layer in amount of between 2 wt. % and 15 wt. %, based on the total weight of the seal layer and/or based on the total weight of EVA in the seal layer.

13. Multi layerThe multi-layer film according to claim 1, wherein the film has a peel strength on PET of between 1 and 20 N/15 mm.

14. Article and/or packaging comprising a the multi-layer film according to claim 1.

15. (canceled)

16. The multi-layer film according to claim 1, wherein the LLDPE has a density between 0.900 to 0.935 g/cm.sup.3, wherein the melt flow index of the LLDPE ranges from 1 to 10 g/10 min, wherein the amount of LLDPE in the seal layer is between 25% and 70% by weight based on the total weight of the layer, wherein the amount of EVA in the seal layer is between 30% and 75% by weight based on the total weight of the layer, wherein the melt flow index of the EVA ranges from 2 to 30 g/10 min, wherein the vinyl acetate content of the EVA is between 8 and 45 wt. %, wherein when the EVA content of the seal layer is <50 wt. % the vinyl acetate content of the EVA may be >20 wt. % and when the EVA content of the seal layer is >50 wt. % the vinyl acetate content of the EVA may be <20 wt. %, and wherein the film has a peel strength on PET of 1.6 and 12 N/15 mm.

17. The multi-layer film according to claim 1, wherein the LLDPE has a density between 0.915 to 0.927 g/cm.sup.3, wherein the melt flow index of the LLDPE ranges from 2 to 6 g/10 min, wherein the amount of LLDPE in the seal layer is between 51 and 70% by weight based on the total weight of the layer, wherein the amount of EVA in the seal layer is between 30 and 49% by weight based on the total weight of the layer, wherein the melt flow index of the EVA ranges from 2 to 20 g/10 min, wherein one of the first or second EVAs has a vinyl acetate content below 10 wt. %, while the other one of the first or second EVA may have a vinyl acetate content above 30 wt. %, based on the total weight of the respective EVA, wherein when the EVA content of the seal layer is <50 wt. % the vinyl acetate content of the EVA may be >20 wt. %, and wherein when the EVA content of the seal layer is >50 wt. % the vinyl acetate content of the EVA may be <20 wt. %.

18. The multi-layer film according to claim 1, wherein the LLDPE has a density between 0.915 to 0.927 g/cm.sup.3, wherein the melt flow index of the LLDPE ranges from 2 to 6 g/10 min, wherein the seal layer consists of between 25 and 80 wt. % of EVA and between 20 and 75 wt. % of LLDPE based on the total weight of the layer, wherein when the EVA content of the seal layer is <50 wt. % the vinyl acetate content of the EVA may be >20 wt. %, wherein when the EVA content of the seal layer is >50 wt. % the vinyl acetate content of the EVA may be <20 wt. %, wherein the EVA with the highest vinyl acetate content and/or the highest melt flow rate of the first and second EVAs is present in the seal layer in amount of between 37 wt. % and 50 wt. % based on the total weight of the seal layer and/or based on the total weight of EVA in the seal layer, wherein the EVA with the lowest vinyl acetate content and/or the lowest melt flow rate of the first and second EVAs is present in the seal layer in amount of between 3 wt. % and 10 wt. %. based on the total weight of the seal layer and/or based on the total weight of EVA in the seal layer, and wherein the film has a peel strength on PET of between 1 and 20 N/15 mm.

19. The multi-layer film according to claim 1, wherein the melt flow index of the EVA ranges from 2 to 3 g/10 min or from 10 to 20 g/10 min.

Description

EXAMPLES

[0049] As shown in Table 1 below, the seal layer was compounded in a ZSK-26MC twin screw extruder from W&P. Maximum extrusion temperature was 170 and 160 C. for NT and LT conditions respectively. Similarly melt temperature was 175 C. and 162 C., screw speed was 300 rpm and 250 rpm again for NT and LT conditions respectively. Output was 15 kg/hour in both NT and LT conditions.

TABLE-US-00001 TABLE 1 Parameters UOM *NT *LT Feed (Zone 0) Temp C. 50 50 Zone 1 Temp C. 100 100 Zone 2 Temp C. 130 130 Zone 3 Temp C. 140 130 Zone 4 Temp C. 150 130 Zone 5 Temp C. 160 125 Zone 6 Temp C. 160 125 Zone 7 Temp C. 160 125 Zone 8 Temp C. 160 115 Zone 9 Temp C. 160 110 Zone 10 Temp C. 160 100 Die Temp C. 170 160 Screw speed rpm 300 250 Throughput kg/hr 15 15 Tmelt % 175 162

[0050] Normal temperature conditions (NT) and lower temperature conditions (LT) for the compounding are reported in Table 1 above.

[0051] Five different seal layers 1, 2, 3a, 3b and 4 were obtained with the compositions as presented in Table 2 below. 1, 2, 3a and 3b are comparative, while 4 is according to the present invention.

TABLE-US-00002 TABLE 2 EVA PE Compound EVA PE parameter No. Grade wt % Grade wt % MI Processing 1 ELVAX 460 69 6318BE 31 2.65 NT 2 EVAFLEX 35 6318BE 65 7.2 NT EV250 3.a EVAFLEX 44 6318BE 56 8.28 NT EV250 3.b EVAFLEX 44 6318BE 56 8.28 LT EV250 4 LEVAMELT 45/5 6318BE 50 2.84 NT 450/ELVAX 760A

[0052] As EVAs, three Dupont grades ELVAX460, LEVAMELT 450 and EVAFLEX EV250 (Dupont-Mitsui) were used. Moreover, LEVAMELT 450 from Lanxess was also used as EVA. The EVAs used are presented in Table 5 below. As LLDPE SABIC grade 6318BE was used. Seal layer 3b has been produced using lower temperature (LT) compounding conditions as reported above in Table 1.

[0053] The melt flow index of the compound may be determined using ASTM-D1238 (190 C/2.16 KG).

[0054] 3 layer films were produced on a Labtech, LF400COEX multilayer extrusion blow film machine as indicated below in Table 3, BUR was 2, die gap was 2.0, total thickness was 50 micron.

[0055] A second cover layer comprising 30 wt. % of low density polyethylene of SABIC grade 2201H0W and 70 wt. % of linear low density polyethylene of SABIC grade 6118NSF is arranged in contact with the first cover layer. A first cover layer of low density polyethylene of SABIC grade 2201HOW is arranged in contact with the seal layer.

[0056] The thicknesses of second cover layer, the first cover layer and the seal layer were 17.5 microns, 17.5 microns and 15 microns respectively. The extrusion temperatures for the second cover layer, the first cover layer and the seal layer were 210 C., 210 C. and 175 C., respectively.

TABLE-US-00003 TABLE 3 Layer Profile Layer Adaptor Barrel 4 Barrel 3 Barrel 2 Barrel 1 information (%) C. Pipe C. C. C. C. C. C. Second 35 210 210 210 210 210 190 170 cover layer First 35 210 210 210 210 210 190 170 cover layer Seal layer 30 210 175 175 175 175 175 125

[0057] After a corona treatment with a CTP-2000K Plasma generator provided on the 3 layer films, the 3 layers film above was laminated to a 15 micron biaxially oriented nylon film with an adhesive substance, namely Liofol LA2788, using a FM380 lamination machine from Simeile. The coating weight was 2.85 g/m2.

[0058] Table 4 shows the peel strength values in N/15 mm for different seal temperatures obtained with the 3 layer films above (see Table 3) with different seal layers 1, 2, 3a and 3b (see Table 2).

TABLE-US-00004 TABLE 4 peel strength values (N/15 mm) Seal temperature 80 C. 90 C. 110 C. 130 C. 150 C. Seal layer No. 1 1.99 1.76 6.43 8.11 10.86 Seal layer No. 2 0.79 3.68 4.50 3.50 4.92 Seal layer No. 3a 0.91 1.93 3.52 3.00 4.10 Seal layer No. 3b 0.43 0.72 5.60 4.60 6.14 Seal layer No. 4 2.81 4.01 5.72 5.00 7.07

[0059] Peel strength has been measured according to ASTM F88 method C, after keeping under room temperature 72 hours, the film was sealed to a 250 micron PET film with a strip width of 15 mm by a HSG-C seal machine from Brugger. The standard testing condition was follow: dwell time was 1.5 second, pressure was 4 bar, width and length of sealing bar size was 10 mm*150 mm, sealing temperature was from 80 C. to 150 C., separation rate 200 mm/min. As can be seen above, the sealing temperature window at which heat sealing on a PET substrate may be achieved to get a seal strength with a strip width of 15 mm and a separation rate of 200 mm/min of between 2.5 and 8 N/15 mm, preferably between 2.7 to 8 N/15 mm as determined by ASTM F88 method C is broadened for seal layer 4 according to the invention compared to seal layers 1, 2, 3a and 3b, as comparative examples. Especially a higher peel strength may be achieved with a sealing temperature between 80 C. and 90 C., preferably with a sealing temperature of 80 C. and/or 90 C.

TABLE-US-00005 TABLE 5 EVAs used VA content Grade Vendor MI (wt. %) density ELVAX460 Dupont 2.5 18 0.941 EVAFLEX Dupont-Mitsui 15 28 0.950 EV250 LEVAMELT Lanxess 3 45 0.99 450 ELVAX 760A Dupont 2 9.3 0.93