Multilayer film for reclosable package with a polyethylene layer obtained by flat sheet coextrusion
A multilayer film comprises an adhesive layer A comprising an HMPSA composition (a); a complexable thin layer B comprising a PolyEthylene (PE) composition (b); and a heat-sealable and breakable layer C comprising a PolyEthylene (PE) composition (c). Layers B and C are bonded together by layer A. The film is characterized in that (i) the melt flow indices of compositions (b) and (c), denoted MFI(b) and MFI(c), respectively, are each between 2.5 and 15 g/10 minutes; and (ii) the melt flow index of composition (a), denoted MFI(a), is such that the ratios MFI(a)/MFI(b) and MFI(a)/MFI(c) are each between 1.5 and 10. A process for manufacturing the film comprises flat sheet coextrusion of composition (a) and of compositions (b) and (c) at a temperature of between 150° C. and 250° C. The multilayer film can be used for the manufacture of resealable packaging.
1. A multilayer film comprising:
an adhesive layer A consisting of an extrudable HMPSA composition (a);
a complexable thin layer B consisting of a PolyEthylene (PE) composition (b) denoted PE (b); and
a heat-sealable and breakable layer C consisting of a PolyEthylene (PE) composition (c) denoted PE (c);
wherein layers B and C are bonded together by layer A and said film is characterized in that:
i. the melt flow indices of compositions (b) and (c), measured in g/10 minutes at a temperature of 190° C. and a total weight of 2.16 kg, and denoted MFI(b) and MFI(c), respectively, are each between 2.5 and 15 g/10 minutes; and
ii. the melt flow index of the HMPSA composition (a), measured in g/10 minutes at a temperature of 190° C. and a total weight of 2.16 kg, and denoted MFI(a), is such that the ratios MFI(a)/MFI(b) and MFI(a)/MFI(c) are each between 1.5 and 10.
2. The multilayer film as claimed in claim 1 , characterized in that the melt flow indices MFI(b) and MFI(c) are each between 3 and 10 g/10 minutes, and the ratios MFI(a)/MFI(b) and MFI(a)/MFI(c) are each between 2 and 9.
3. The multilayer film as claimed in claim 1 , characterized in that the MFI(a) is in a range from 4 to 100 g/10 minutes.
4. The multilayer film as claimed in claim 1 , characterized in that the extrudable HMPSA composition (a) comprises, on the basis of the total weight of said composition:
from 40% to 70% by weight of a composition (a1) of styrene block copolymers comprising at least one elastomer block, said composition (a1) consisting, on the basis of its total weight:
of 10% to 90% by weight of at least one diblock copolymer selected from the group consisting of SI, SBI, SIB, SB, SEB and SEP, and
of 10% to 90% by weight of at least one triblock copolymer selected from the group consisting of SIS, SIBS, SBS, SEBS and SEPS,
wherein the total content of styrene units of said composition (a1) ranges from 10% and 40% by weight on the basis of the total weight of (a1); and
from 30% to 60% by weight of one or more tackifying resins (a2).
5. The multilayer film as claimed in claim 1 , characterized in that compositions (b) and (c) are compositions of the same PolyEthylene PE.
6. The multilayer film as claimed in claim 1 , characterized in that PE (b) and PE (c) are each a low density PE.
7. The multilayer film as claimed in claim 1 , characterized in that composition (b) and (c) consisting of a PE.
8. The multilayer film as claimed in claim 1 , characterized in that compositions (b) and (c) are PE-based compositions which comprise, in addition to said PE, an additive comprising an anti-fogging agent, a processing aid, a slip agent and/or an antiblocking agent.
9. The multilayer film as claimed in claim 1 , characterized in that it consists of three layers A, B and C.
10. The multilayer film as claimed in claim 1 , characterized in that it comprises, in addition to the three layers A, B and C, additional thin layers comprising:
a rigid layer,
a printable layer, and/or
a layer with a barrier effect against oxygen, water vapor or carbon monoxide.
11. The multilayer film as claimed in claim 1 , characterized in that its total thickness varies in a range from 20 to 300 μm.
12. The multilayer film as claimed in claim 1 , characterized in that the thickness of the adhesive layer A varies in a range from 5 to 50 μm and the thickness of the heat-sealable and breakable layer C varies in a range from 5 to 25 μm.
13. A process for manufacturing the multilayer film as defined in claim 1 , comprising flat sheet coextrusion of the HMPSA composition (a) and of compositions (b) and (c) at a temperature of between 150° C. and 250° C.
14. A resealable packaging comprising the multilayer film defined in claim 1 .
15. The resealable packaging of claim 14 , wherein the multilayer film is a cover film of a resealable tray.