LINER FILM

Abstract

The invention relates to gusseted plastic film with a thickness of 50 to 200 microns, comprising a polyolefin homopolymer or copolymer, a polyether copolymer and a layer comprising oxygen barrier polymer.

Claims

1. A multilayer plastic film comprising a polyolefin homopolymer or copolymer a polyether copolymer, and an oxygen barrier material.

2. The plastic film of claim 1, wherein the thickness of the film is between 50 and 200 microns.

3. The plastic film of claim 2, wherein the thickness of the film is between 60 and 130 microns.

4. The plastic film of claim 1, wherein the oxygen barrier material is ethylene vinyl alcohol (EVOH).

5. The plastic film of claim 1, wherein the oxygen barrier material is a polyamide.

6. The plastic film of claim 1, wherein the polyolefin homopolymer or copolymer is polyethylene or polypropylene.

7. The plastic film of claim 1, wherein the polyolefin homopolymer or copolymer is ethylene alpha olefin copolymer.

8. The plastic film of claim 7, wherein the polyether copolymer is a block copolymer.

9. The plastic film of claim 1, wherein the polyether copolymer is polyolefin, polyamide or polyester copolymer.

10. The plastic film of claim 1, wherein the polyolefin homopolymer or copolymer and the polyether copolymer are present in the film as a blend.

11. The plastic film of claim 1, wherein the polyether copolymer is contained in at least one of an outer layer or an inner layer.

12. The plastic film of claim 11, wherein 5-25 wt % of polyether copolymers are contained in at least one of the outer layer or the inner layer.

13. A gusseted tubular film comprising the plastic film of claim 1.

14. The plastic film of claim 10, wherein the blend is contained in at least one of the outer layer or the inner layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0047] The present invention in a preferred version is a film comprising [0048] a polyolefin homopolymer or copolymer [0049] a polyether copolymer [0050] an oxygen barrier material.

[0051] In a further preferred version, the film is in the form of gusseted tube.

[0052] In a still further preferred version the average thickness of the film is in the range 50-200 microns, preferably 60-150 microns, more preferably 60-130 microns.

[0053] In a further preferred version the polyolefin homopolymer or copolymer is an ethylene alpha olefin copolymer. In a further preferred version the alpha olefin is butene, hexene or octene. In a further preferred version the ethylene alpha olefin copolymers are produced with metallocene catalysts.

Film Construction

[0054] Preferably the film comprises 5 to 15 layers, more preferably 7 to 12 layers.

[0055] A typical example of the film construction in 7 layer mode is

Outer layer/intermediate layer/tie layer/barrier layer/tie layer/intermediate layer/inner layer

[0056] The film is preferably produced by the hot blown film method and is not heat shrinkable.

Barrier Layer(s)

[0057] The film in a preferable version contains high oxygen barrier materials so that it protects the components of the pack from the detrimental effect of oxygen ingress. EVOH is a preferred option but also polyamide and PVDC are viable alternatives. The EVOH is preferably 24 to 50% ethylene per mol, more preferably 27 to 48%.

[0058] In another preferred version of the invention, the barrier polymer is polyamide. Most suitable polyamides are polyamide 6 and copolymer 6/66 or 6/12.

Intermediate Layer(s)

[0059] Preferably, the intermediate layers comprise different polyolefins. Preferred polyolefins are ethylene alpha olefin copolymers, where alpha olefin is preferably butene, hexene or octene.

[0060] In a preferred version the ethylene alpha olefin copolymers are random copolymers with densities from 0.870 g/cm.sup.3 up to 0.960 g/cm.sup.3. In a further preferred version the molecular weight distribution of the ethylene alpha olefin copolymers are less than 10, preferably less than 5, preferably less than 3.

Tie Layer(s)

[0061] As well known in the art, there is no natural adhesion between polyolefins and oxygen barrier polymers such as EVOH.

[0062] Suitable materials for the tie layer process include maleic anhydride modified EVA, maleic anhydride modified polyethylene, maleic anhydride modified EMA, maleic anhydride modified elastomer, partially saponified EVA copolymer and polyurethane elastomer.

[0063] In the tie layers also polyamides can be used, given the strong natural adhesion between polyamide and EVOH. Preferred polyamides are polyamide 6, polyamide 6/66 and polyamide 6/12.

Outer Layer

[0064] The outer layer of the film preferably comprises ethylene alpha olefin copolymers and/or low density polyethylene (LDPE) produced by Ziegler Natta or metallocene catalyst. Polypropylene is also possible.

Inner Layer

[0065] The inner layer of the film would be able to seal the film to itself to secure that no leakers and oxygen influx is allowed. This could be detrimental to the product packed.

[0066] Suitable materials for the inner layer include different polyolefins, preferable ethylene alpha olefin copolymers, low density polyethylene or polypropylene.

[0067] In general, the above layers may comprise further well known in the art additives such as antiblock, slip, antifog, polymer processing enhancers and others.

Polyether Copolymers

[0068] We have unexpectedly noticed that by adding 5-25%, preferably 5-20% of polyether copolymers in at least one of outer and inner layers in a blend with polyolefin homopolymer or copolymer compounds, there is substantial improvement in the gussetability of the film. The film is nicely transformed inline to a gusseted tube without any creasing during the whole rotation of the collapsing frame.

[0069] Without wanted to be bound to any theory, we suspect that the addition of polyether copolymers to polyolefins improve the melt strength thus allowing easier gusset formations even with higher rotation ratio of the collapsing frame and blown film tower.

[0070] Preferred polyether copolymers are copolymers with polyolefins, polyamides or polyester. Typical materials are PEBAX from Arkema, IRGASTAT from BASF and PELESTAT from Sanyo.

[0071] In a preferred version the melting points of the polyether copolymers are in the range 100-180° C., preferably 110-170° C. If the melting temperatures are lower the gussetability is compromised by the higher friction due to polymer tackiness while if the melting temperatures are higher the sealing properties (often required) are compromised.

EXAMPLE 1

[0072] From a commercial hot blown film line we produced the following film [0073] Outer layer, thickness 30 microns [0074] Intermediate layer 1, thickness 10 microns [0075] Tie layer 1, thickness 8 microns [0076] EVOH 38%, thickness 8 microns [0077] Tie layer 2, thickness 8 microns [0078] Intermediate layer 2, thickness 20 microns [0079] Inner layer, thickness 12 microns.

[0080] Outer layer was a blend of [0081] 89% LDPE+10% polyether polyamide copolymer+1% slip antiblock masterbatch. [0082] LDPE density was 0.923 while MFI was 0.75 under 190C/2.16 kilos

[0083] Intermediate layer 1 was a blend of [0084] 60% ethylene hexene copolymer+40% LDPE [0085] The density of ethylene hexene copolymer was 0.919 while MFI was 1 under 190° C./2.16 kilos [0086] LDPE was same as used in the outer layer.

[0087] Tie layer 1 was maleic anhydride LLDPE based copolymer

[0088] Tie layer 2 was similar to tie layer 1

[0089] Intermediate layer 2 was exactly the same as intermediate layer 1.

[0090] Inner layer was a blend of [0091] 89% metallocene LLDPE+10% polyether polyamide copolymer+1% slip antiblock masterbatch [0092] Metallocene LLDPE had a density of 0.918 while MFI was 1 under 190° C./2.16 kilos

[0093] Polyether copolymer used was PEBAX 1074SA01, a copolymer of polyether and polyamide.

EXAMPLE 2

[0094] In the case of example 2 the LDPE used in the outer layer was replaced by the ethylene hexene copolymer used in intermediate layer 1.

EXAMPLE 3

[0095] In this example, the EVOH 38% was replaced by 32% which is stiffer and thought to be more difficult to form gusset.

Comparative Example

[0096] The comparative example was like example 1 but with the polyether copolymer removed and replaced by LDPE (in the case of outer layer) and metallocene LLDPE in the case of inner layer.

Examining System

[0097] On the tower of the blown film line two gusset boards were mounted as known in the art. Each example structure ran in production for 2 hours and the number of creases was monitored. As the creases tend to come along in timely intervals, we recorded “creasing instances”, meaning we recorded any incident when more than 3 creases passed from the nip section of the blown film line.

[0098] The rotation speed was kept constant during all this experiment.

Results Example 1 presented 0 creasing incident during the two hours production. Example 2 presented 1 creasing incidents. Example 3 presented 3 incidents.

[0099] The comparative example presented 12 incidents during the two hours production.