MULTILAYER BLOCKED FILM COMPOSITE

Abstract

A polyolefin-based film composite has a uniaxially stretched first film layer and a second film layer bonded directly or indirectly to the first film layer. The second film layer is unstretched and has at least two integrally blocked film sublayers. A third film layer between the first and second layers can act as a barrier.

Claims

1. A polyolefin-based film composite comprising: a uniaxially stretched first film layer; and a second film layer bonded directly or indirectly to the first film layer, the second film layer being unstretched and having at least two integrally blocked film sublayers.

2. The film composite according to claim 1, wherein the first film layer carries indicia or printing.

3. The film composite according to claim 1, further comprising: at least one third film layer.

4. The film composite according to claim 1, wherein the second film layer is on an outer face of the film composite and is a seal layer.

5. The film composite according to claim 4, wherein the seal layer has a weight content of at least 30% of high-density polyethylene.

6. The film composite according to claim 5, wherein the high-density polyethylene is exclusively in one or more core sublayers.

7. The film composite according to claim 4, wherein the seal layer itself has at least one seal sublayer comprising at least 20% by weight of polyethylene having a density of not more than 0.905 g/cm.sup.3.

8. The film composite according to claim 7, wherein the seal layer contains at least 70% by weight of polyethylene with a density of not more than 0.92 g/cm.sup.3.

9. The film composite according to claim 4, wherein the seal layer is at least 30% by weight formed by a polyethylene plastomer.

10. The film composite according to claim 1, wherein all film layers are based on polyethylene.

11. The film composite according to claim 1, wherein all film layers are based on polypropylene.

12. The film composite according to claim 1, wherein the film layers each have at least two film sublayers integrally blocked with one another.

13. The film composite according to claim 1, wherein at least one of the film layers is of multilayer structure including a barrier sublayer of ethylene-vinyl alcohol copolymer.

14. The film composite according to claim 13, wherein the barrier sublayer has a thickness of at most 10 m.

15. The film composite according to claim 1, wherein the first film layer has a thickness between 20 m and 50 m.

16. The film composite according to claim 1, wherein the second film layer has a thickness of between 100 m and 180 m.

17. The film composite according to claim 16, wherein the first film layer and the second film layer have a total thickness of between 120 m and 200 m.

18. A packaging bag having an interior space defined by a sheet of a film formed by the composite of claim 1.

Description

SPECIFIC DESCRIPTION OF THE INVENTION

[0103] As shown in the drawing, a film composite 1 according to the invention has a first film layer 2 stretched uniaxially in a machine direction and a second film layer 3 indirectly connected to the first film layer 2.

[0104] The first film layer 2 is carries indicia or printing 4 on its face turned toward the second film layer 3. This printing 4 is a mixture of a binder and pigments.

[0105] Furthermore, the first film layer 2 is a three-layer coextruded film laminate with a first outer sublayer 2a made of a mixture containing HDPE and LMDPE, a core sublayer 2b of a mixture of HDPE, LLDPE and MDPE, and an inner sublayer 2c carrying the printing 4 and consisting of a 7 μm thick mixture of HDPE and LMDPD. The total thickness a of the first film layer 2 is 25 μm with an overall density of 0.94 g/cm.sup.3.

[0106] A third film layer 5 is a barrier between the first film layer 2 and the second film layer 3. This barrier layer 5 is a symmetrical five-layer coextruded film laminate with 9 μm thick outer first and fifth film sublayers 5a and 5e made of polyethylene. Adhesion second and fourth promoter sublayers 5b and 5d, are made of a polyethylene grafted with maleic anhydride, and are next to the respective sublayers 5a and 5e. The core of the barrier layer 5 is formed by a 4 μm thick oxygen and grease barrier sublayer 5c made of EVOH with an ethylene content of 32 wt. %. The first and fifth film sublayers 5a and 5e are fully positioned on the respective first layer 2 and the second layer 3 via respective polyurethane-based laminating adhesive sublayers 6a and 6b.

[0107] The second film layer 3 is opposite the first film layer 2 on an outer face of the film composite 1 and is formed as a seal. It is formed from a collapsed three-layer extruded film tube to form a six-layer laminate in which the first film sublayer 3a is turned toward and positioned on the barrier layer 5. This sublayer 3a and the sixth outwardly turned film sublayer 3f of the second film layer 3 are formed from a mixture of 65 wt. % PE-LLD-m and 35 wt. % of a PE plastomer with a thickness of 16 μm. Second and fifth core sublayers 3b and 3a of the seal layer 3 are each 52 m thick and made of a mixture of 60 wt % PE-HD, 25 wt % of a bimodal LMDPE and 15 wt % of a LLDPE. The particularly high HDPE content improves the strength and rigidity of the seal layer 3.

[0108] According to the invention, the second film layer 3 has a third film sublayer 3a and a fourth film sublayer 3d that are integrally blocked with each other according to the invention. The third film sublayer 3a and the fourth film sublayer 3d are formed from 100% by weight EVA with a VA content of 18% by weight. This high VA content improves them adhesiveness, especially when heated and being laminated together. The two EVA sublayers 3a and 3d bonded together each have a thickness of 12 m for a total thickness of 24 m.

[0109] In the illustrated embodiment, the first film layer 2 has the thickness a of 25 m. The second film layer 3 has a thickness b of 160 m. The barrier layer 5 has a thickness c of 30 m.