Plastic film composite, film packaging and method for the production of packaging containers

Abstract

A plastic film composite for film packaging with an oriented outer film and a sealing film which differs from the outer film, both of which outer film and sealing film are either polyethylene-based or polypropylene-based. The outer film and the sealing film are connected by a polyolefin-based extrusion lamination comprising at least one layer. A film packaging comprising the plastic film lamination and a method for the production of packaging containers uses the plastic film composite.

Claims

1. A plastic film composite for film packaging comprising; an oriented outer film, a sealing film which differs from the outer film, wherein both the oriented outer film and sealing film are polyethylene-based, and a polyolefin-based extrusion lamination comprising at least one layer, wherein the outer film and the sealing film are connected by the extrusion lamination, wherein the extrusion lamination adjoins a contact layer of the outer film either directly or partially via an imprint, wherein the extrusion lamination and the contact layer have as a main constituent a polymer of a polyethylene polymer class and wherein the composite adhesion between the outer film and the sealing film determined in a peel test according to DIN 53357 is greater than 2 N/15 mm, and wherein the extrusion lamination has a layer thickness greater than 10 μm.

2. The plastic film composite according to claim 1, wherein the extrusion lamination comprises a plurality of layers.

3. The plastic film composite according to claim 1, wherein the extrusion lamination directly adjoins the sealing film.

4. The plastic film composite according to claim 3, wherein the extrusion lamination has a maleic anhydride grafted polyolefin copolymer in a layer adjoining the outer film.

5. The plastic film composite according to claim 3, wherein the extrusion lamination has in a layer adjoining the outer film a thermoplastic elastomer (TPE) as admixture in a weight proportion of between 3 and 50% by weight.

6. The plastic film composite according to claim 1, wherein the outer film is formed by flat film extrusion and has a draw ratio of between 1:8 and 1:14.

7. The plastic film composite according to claim 1, wherein the outer film is formed by blown film extrusion and has a draw ratio of between 1:3 and 1:8.

8. The plastic film composite according to claim 1, wherein the outer film has at least one layer with medium-density polyethylene or high-density polyethylene as a main constituent.

9. The plastic film composite according to claim 1, wherein the outer film is coextruded in multiple layers.

10. The plastic film composite according to claim 8, wherein the outer film is coextruded in at least three layers and has cover layers with low-density polyethylene as a main constituent.

11. The plastic film composite according to claim 1, wherein the outer film has a thickness of between 15 μm and 80 μm.

12. The plastic film composite according to claim 1, wherein the outer film is imprinted on an inner side in direction of the extrusion lamination, wherein the imprint extends over 10% to 95% of the surface area of the outer film.

13. The plastic film composite according to claim 1, wherein the sealing film is formed by blown film extrusion.

14. The plastic film composite according to claim 1, wherein the sealing film is coextruded in multiple layers.

15. The plastic film composite according to 1, wherein the sealing film has a thickness of between 30 μm and 140 μm.

16. The plastic film composite according to claim 1, wherein the sealing film is formed based on low-density polyethylene.

17. The plastic film composite according to claim 1, wherein the sealing film contains a pigment.

18. The plastic film composite according to claim 1, wherein the weight proportion of polyolefin relative to all of the polymer constituents amounts to at least 80% by weight.

19. The plastic film composite according to claim 1, wherein the total thickness is between 50 μm and 200 μm.

20. A film packaging comprising a plastic film composite according to claim 1, wherein the outer film forms an outer side, the sealing film faces an interior of the packaging, and wherein the interior of the packaging is bounded by at least one heat-sealing seam formed at the sealing film.

21. The film packaging according to claim 20, wherein the outer film is provided with an imprint not covering an entire surface of the film packaging such that the imprint is omitted at least in an area of the heat-sealing seam.

22. The film packaging according to claim 20, wherein the packaging interior has a fill volume of at least 1 L (liter).

23. The film packaging according to claim 20, wherein the packaging interior is filled with at least 1 kg of a filling material and closed in an airtight manner.

24. A method for the production of packaging containers, comprising: a) extruding an outer film and orienting the outer film after extrusion in a separate method step with a draw ratio of between 1:3 and 1:12 along a production direction, b) imprinting the outer film, c) forming a sealing film by blown film extrusion, wherein the outer film and the sealing film are both polyethylene-based, d) feeding the oriented outer film and the sealing film to a roll nip and connecting the outer film and sealing film to form a plastic composite by means of an extrusion lamination comprising at least one layer and based on polyethylene, wherein the extrusion lamination adjoins a contact layer of the outer film either directly or partially via the imprint, and wherein the composite adhesion between the outer film and the sealing film determined in a peel test according to DIN 53357 is greater than 2 N/15 mm, e) forming film packaging bags from the plastic composite by forming heat-sealing seams, and f) filling and closing the film packaging bags, wherein the extrusion lamination has a layer thickness greater than 10 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in the following referring to figures which are merely exemplary. The drawings show:

(2) FIG. 1 a plastic film composite according to the prior art;

(3) FIG. 2 a film packaging bag according to the prior art which is split at a sealing seam;

(4) FIG. 3 a detailed view showing the breaking of the plastic film composite according to the prior art at a seam root of the sealing seam;

(5) FIG. 4 a plastic film composite according to the invention with front-side printing on the outer side;

(6) FIG. 5 a plastic film composite according to the invention with reverse printing on the inner side;

(7) FIG. 6 a section corresponding to FIG. 3 for a film packaging bag according to the invention; and

(8) FIG. 7 a method step for forming the plastic composite.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(9) FIG. 1 shows a possible layer construction corresponding to the prior art. The following Table 1 is referred to in this respect. The plastic film composite comprises an outer film 1 of HDPE which is oriented in machine direction (MDO-HDPE) and has a thickness of 50 μm.

(10) TABLE-US-00001 TABLE 1 Thickness/Weight per unit area Material Outer film 50 μm MDO-HDPE Laminating adhesive 2 g/m.sup.2 2K PUR (solvent-free) Sealing film 20 μm LLDPE + LDPE (coex. blown film, 20 μm LMDPE + LDPE + TiO.sub.2 total thickness 60 μm 20 μm LLDPE + LDPE

(11) The plastic film composite according to the prior art further comprises a sealing film 2 which is coextruded as blown film with a total thickness of 60 μm. In the depicted embodiment example, sealing film 2 comprises three layers 2a, 2b, 2c with a respective thickness of 20 μm. While the layer 2b arranged in the middle in sealing film 2 contains a blend of LMDPE and LDPE with an addition of titanium dioxide (TiO.sub.2) as white batch, the rest of the layers 2a, 2c of the sealing film are formed from a blend of LLDPE and LDPE.

(12) In the configuration according to the prior art, outer film 1 and sealing film 2 are connected by laminating adhesive 3 which is applied at a weight per unit area of 2 g/m.sup.2. Taking into account typical densities, the layer of laminating adhesive consequently also has a thickness of approximately 2 μm. A polyurethane-based, solvent-free two-component adhesive (2K PUR) is provided as laminating adhesive 3.

(13) Outer film 1 is usually provided with an imprint 4 which can be provided on the exposed outer side of outer film 1 as front-side printing or on the inner side on the side of outer film 1 facing the laminating adhesive 3 as reverse printing. FIG. 1 shows an exemplary embodiment of the imprint 4 as front-side printing.

(14) Laminating adhesive 3 achieves a laminating strength sufficient to safeguard against a delamination between outer film 1 and sealing film 2 under normal load. In practice, however, it may come about especially under large mechanical loads that a film packaging 5 formed from the plastic film composite by heat-sealing seams 6 can burst unintentionally in an uncontrolled manner.

(15) FIG. 2 shows an exemplary film packaging 5 of this kind in the form of a film packaging bag which is split open in a bottom area during a drop test so that filling material 7 exits in an uncontrolled manner and is no longer protected. It will be appreciated that an unwanted bursting of this kind must be prevented unconditionally in practice although a compromise must always be found between cost and the stability of the film packaging 5.

(16) Upon close inspection of film packaging 5, it will be noted that an unwanted bursting often occurs due to tearing of the plastic film composite adjacent to the heat-sealing seam 6 rather than by a separation of the heat-sealing seam 6.

(17) FIG. 3 correspondingly shows a typical fracture pattern of the plastic film composite according to the prior art lateral to the sealing seam 6, i.e., at the root of the heat-sealing seam 6.

(18) FIG. 4 shows a plastic film composite according to the invention in which outer film 1 and sealing film 2 are connected by an extrusion lamination 8 comprising at least one layer. As in FIG. 1, outer film 1, sealing film 2 and extrusion lamination 8 are shown separately for the sake of clarity but, of course, form a composite with directly joining layers.

(19) The outer film 1 and the sealing film can be constructed as described above referring to FIG. 1. However, outer film 1 and sealing film 2 are not joined by a laminating adhesive 3 based on 2 K-PUR but by an extrusion lamination 8 which then forms at least one corresponding intermediate layer in the plastic film composite.

(20) The production of the plastic film composite by extrusion lamination is shown merely schematically in FIG. 7, wherein the premade outer film 1, after orientation in machine direction, and the premade sealing film 2 are fed to a roll nip 9 and laminated in the roll nip 9 with extrusion lamination 8 to form the plastic film composite.

(21) Extrusion lamination 8 can comprise one or more layers. FIG. 4 shows an exemplary multiple-layered configuration with layers 8a, 8b of extrusion lamination 8.

(22) Three embodiment examples differing only with respect to the material of the extrusion lamination 8 are given in Tables 2 to 4 for a layer sequence according to FIG. 4.

(23) TABLE-US-00002 TABLE 2 Thickness/Weight per unit area Material Outer film 45 μm MDO-HDPE Extrusion lamination 6 g/m.sup.2 90 wt. % EAA-MAH (Lotader 4503) 10 wt. % SEBS-MAH (Kraton FG1901GT) 14 g/m.sup.2 LDPE (Lupolen 2420K) sealing film 20 μm LLDPE + LDPE (coex. blown film, 20 μm LMDPE + LDPE + TiO.sub.2 total thickness 60 μm 20 μm LLDPE + LDPE

(24) TABLE-US-00003 TABLE 3 Thickness/Weight per unit area Material Outer film 45 μm MDO-HDPE Extrusion lamination 6 g/m.sup.2 50 wt. % LLDPE(M)- C6 (Exceed 2018HA) + 50 wt. % LDPE (Lupolen 2420K) 14 g/m.sup.2 LDPE (Lupolen 2420K) Sealing film 20 μm LLDPE + LDPE (coex. blown film, 20 μm LMDPE + LDPE + TiO.sub.2 total thickness 60 μm 20 μm LLDPE + LDPE

(25) TABLE-US-00004 TABLE 4 Thickness/Weight per unit area Material Outer film 45 μm MDO-HDPE Extrusion lamination 6 g/m.sup.2 HDPE (Borealis CG 8410) 14 g/m.sup.2 LDPE (Borealis CT 7200) Sealing film 20 μm LLDPE + LDPE (coex. blown film, 20 μm LMDPE + LDPE + TiO.sub.2 total thickness 60 μm 20 μm LLDPE + LDPE

(26) According to the first embodiment example, outer film 1 is formed from MDO-HDPE with a thickness of 45 μm. An outer film 1 formed by flat film extrusion with a draw ratio of between 1:8 and 1:14, particularly with a draw ratio of between 1:10 and 1:12, is preferred. Sealing film 2 has a total thickness of 80 μm and is formed as coextruded blown film with three layers 2a, 2b, 2c. The middle layer of the sealing film 2b comprises a blend of LMDPE and LDPE with an addition of titanium dioxide (TiO.sub.2) as white batch. The rest of the layers 2a, 2c of the sealing film with a thickness of 20 μm and 30 μm, respectively, comprise a blend of LLDPE and LDPE.

(27) In all of the embodiment examples, the layers of extrusion lamination 8a, 8b are formed by way of example with the same weight per unit area of 6 g/m.sup.2 and 14 g/m.sup.2. Taking into account typical densities, the amount of the weight per unit area in g/m.sup.2 approximately corresponds to the amount of the thickness in μm.

(28) According to the first embodiment example, the layer 8a of extrusion lamination 8 that directly adjoins the outer film has 90% by weight of EAA-MAH (Lotader 4503) and 10% by weight SEBS-MAH (Kraton FG1901GT). The layer 8b of extrusion lamination that adjoins sealing film 2 is formed from LDPE (Lupolen 2420 K).

(29) As mentioned previously, the embodiment examples according to the invention differ only with respect to the material of the extrusion lamination. According to the second embodiment example shown in Table 3, the layer 8a of extrusion lamination 8 that faces outer film 1 has 50% by weight LLDPE(M)-C6 (Exceed 2018 HA) and 50% by weight LDPE (Lupolen 2420 K). The layer 8b of extrusion lamination 8 that adjoins sealing film 2 comprises LDPE (Lupolen 2420 K).

(30) According to the third embodiment example shown in Table 4, the layer 8a of extrusion lamination 8 that faces outer film 1 is formed from HDPE (Borealis CG 8410) and the layer 8b of the extrusion lamination that faces sealing film 2 is formed by LDPE (Borealis CT 7200).

(31) In all of the embodiment examples, there is an appreciably stronger composite adhesion compared with lamination by means of laminating adhesive 3, which surprisingly also causes a substantial improvement in the stability of the plastic packaging with respect to tearing under compressive loading. This insight is surprising because the composite adhesion ultimately specifies the forces acting in thickness direction between the individual layers, while in case of bursting (see FIG. 2 and FIG. 3) which is sometimes unavoidable in the prior art, the plastic film composite tears along the thickness direction so that it must be assumed that the strength in the plane of the film (that is, transverse to the thickness direction) is decisive.

(32) According to FIG. 4, an imprint 4 is provided as front-side printing such that the imprint 4 is located on the outer film 1 opposite extrusion lamination 8 and on the sealing film 2 adjoining the latter. The plastic film composites in all of the embodiment examples are suitable for a front-side printing. However, for reasons of cost, the embodiment examples 2 and 3 according to Tables 3 and 4 are preferred.

(33) With reverse printing, on the other hand, there is the risk that the comparatively strong composite adhesion within the framework of the invention will be impaired. In particular, with a reverse printing the extrusion lamination 8 or the layer 8a facing the outer film 1 may not intimately bond with the material of the outer film 1 and, in particular, fuses to the material of outer film 1.

(34) However, an exemplary reverse printing shown in FIG. 5 is possible particularly when the imprint 4 is not provided over the entire surface. In particular, according to FIG. 6, the area of the plastic film composite at which the heat-sealing seams 6 are generated when the film packaging 5 is formed can be left blank. Accordingly, there is an area 10a of greater composite adhesion in this location. Additional areas 10b with increased laminating strength can be generated as anchor points or anchor surfaces through further omission of imprint 4.

(35) When the imprint 4 is not arranged over the entire surface in case of a reverse printing and, in particular, the areas of the heat-sealing seams 6 are left blank and/or are provided with the imprint 4 only on a small portion of the total surface area, the plastic film composites according to the three embodiment examples are well suited, an improved bonding being achieved by the polar groups provided in the extrusion lamination 8 according to the first embodiment example (Table 2).

(36) While the composite adhesion between outer film 1 and sealing film 2 in the comparison example according to Table 1 is approximately 1 N/15 mm in a peel test according to DIN 53357, a laminating strength of greater than 3 N/15 mm is always observed in plastic film composites provided with front-side printing according to embodiment examples 1 to 3. Tests with filled film packaging 5 in the form of film packaging bags further show that the risk of tearing of the plastic film composite, particularly adjacent to a heat-sealing seam 6, is substantially reduced in embodiment examples 1 to 3 so that bursting is prevented or the risk of bursting can at least be substantially reduced also when the film packaging bag is unintentionally dropped, in case of shocks and impacts during transport and storage, or under other sudden loads.

(37) When an imprint 3 is provided as reverse printing which also extends into the area of the heat-sealing seams according to a variant of the plastic film composite according to the invention, sufficient values can still be achieved for the composite adhesion depending on the printing ink and the material of the extrusion lamination 8 when the materials are suitably adapted to one another. Accordingly, it is expected that acceptable values for a composite adhesion can be achieved at least with the extrusion lamination 8 according to the first embodiment example (Table 2) with a polyvinylbutyral-based ink.