FIBC liner film

Abstract

The invention relates to plastic film preferably with a thickness of 50 to 300 microns, comprising a polyolefin homopolymer or copolymer, a polyether copolymer having a melting point between 100° C. and 120° C. and a layer comprising oxygen barrier polymer.

Claims

1. A plastic film comprising an inner layer comprising a blend of a polyolefin homopolymer or copolymer and a polyether copolymer having a melting point in the range of 100° C. to 120° C., wherein the inner layer is a layer that comes in direct contact with a product to be packed; and a layer comprising an oxygen barrier material.

2. The plastic film of claim 1, where the thickness of the film is between 50 and 300 microns.

3. The plastic film of claim 2, where the thickness of the film is between 60 and 150 microns.

4. The plastic film of claim 2, where the oxygen barrier material is ethylene vinyl alcohol (EVOH).

5. The plastic film of claim 2, where the oxygen barrier material is a polyimide.

6. The plastic film of claim 2, where the polyolefin homopolymer or copolymer is polyethylene or polypropylene.

7. The plastic film of claim 2, where the polyolefin homopolymer or copolymer is an ethylene alpha olefin copolymer.

8. The plastic film of claim 2, where the polyether copolymer is a polyolefin, polyamide or polyester copolymer.

9. The plastic film of claim 2, where the polyether copolymer is contained in both inner and outer layers.

10. A gusseted tubular film made of a plastic film of claim 2.

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

12. The plastic film of claim 1, where the oxygen barrier material is a polyimide.

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

14. The plastic film of claim 1, where the polyolefin homopolymer or copolymer is an ethylene alpha olefin copolymer.

15. The plastic film of claim 14, where the polyether copolymer is a block copolymer.

16. The plastic film of claim 1, where the polyether copolymer is a polyolefin, polyamide or polyester copolymer.

17. The plastic film of claim 1, where the polyether copolymer is contained in both inner and outer layers.

18. A gusseted tubular film made of a plastic film of claim 1.

Description

DETAILED DESCRIPTION

(1) The present invention relates to a film comprising a polyolefin homopolymer or copolymer a polyether copolymer having melting point in the range of 100° C. to 120° C. an oxygen barrier material.

(2) In a preferred embodiment, the film is in the form of gusseted tube.

(3) In a further preferred embodiment, the average thickness of the film is in the range 50-300 microns, preferably 60-150 microns, more preferably 60-130 microns.

(4) In a further preferred embodiment, the polyolefin homopolymer or copolymer is an ethylene alpha olefin copolymer. In a further preferred embodiment, the alpha olefin is butene, hexene or octene. In a further preferred embodiment, the ethylene alpha olefin copolymers are produced with metallocene catalysts.

FILM CONSTRUCTION

(5) Preferably the film comprises 5 to 15 layers, more preferably 7 to 12 layers.

(6) 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

(7) The film is preferably produced by the hot blown film method and is not heat shrinkable.

(8) Barrier Layer(s)

(9) The film in a preferable embodiment contains high oxygen barrier materials so that it protects the components of the pack from the detrimental effect of oxygen ingress.

(10) EVOH is a preferred option but also polyamide and PVDC are viable alternatives. The EVOH comprises preferably 24% to 50% ethylene per mol, more preferably 27% to 48%.

(11) In another preferred embodiment of the invention, the barrier polymer is polyamide. Most suitable polyamides are polyamide 6 and copolymer 6/66 or 6/12.

(12) Intermediate Layer(s)

(13) Preferably, the intermediate layers comprise different polyolefins. Preferred polyolefins are ethylene alpha olefin copolymers, where alpha olefin is preferably butene, hexene or octene.

(14) In a preferred embodiment 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 embodiment, the molecular weight distribution MWD (M.sub.w/M.sub.n) as measured by GPC of the ethylene alpha olefin copolymers is less than 10, preferably less than 5, preferably less than 3.

(15) Tie Layer(s)

(16) As well known in the art, there is no natural adhesion between polyolefins and oxygen barrier polymers such as EVOH.

(17) 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.

(18) 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.

(19) Outer Layer

(20) 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, ethylene vinyl acetate, ethylene methyl acrylate, ethylene butyl acrylate, ionomer, polyester and polyamide is also possible.

(21) Inner Layer

(22) 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.

(23) Suitable materials for the inner layer include different polyolefins, preferably ethylene alpha olefin copolymers, low density polyethylene, polypropylene, ethylene vinyl acetate, ethylene methyl acrylate, ionomer, ethylene butyl acrylate and the like.

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

(25) Polyether Copolymers

(26) We have unexpectedly noticed that by adding polyether copolymers having a melting point of 100° C. to 120° C. in the inner layer, the seal initiation temperature of the film drops to 120° C. while the gussetability of the film remains very good. The film is nicely transformed inline to a gusseted tube without any creasing during the whole rotation of the collapsing frame. Preferably, the polyether copolymers having a melting point of 100° C. to 120° C. are added in the inner layer, in an amount of 5% to 20% by weight.

(27) Preferred polyether copolymers are copolymers with polyolefins, polyamides or polyester. A typical example of a polyether copolymer useful for the invention is Pelestat LM230 from Sanyo Chemical.

(28) In a preferred embodiment the melting points of the polyether copolymers are in the range 100° C. to 120° C., preferably 110° C. to 120° C. If the melting temperature is lower the gussetability is compromised by the higher friction due to polymer tackiness while if the melting temperatures are higher the sealing initiation temperature increases.

(29) The preferred melt flow index (MFI) of the polyether copolymer is more than 12 at 190° C. and 21.18 N measured according to ASTM D 1238.

SEAL INITIATION TEMPERATURE

(30) This term as used in the present application is defined as the lower sealing temperature which allows the average sealing strength (measured according to ASTM F88) to be at least 25N/15 mm seal width when the sealing time is 2 seconds, sealing pressure is 4 bars and the sealing station is impulse type. Films of the present invention have seal initiation temperature less than 130° C., preferably less than 125° C., preferable less than 120° C., preferably less than 115° C.

MELTING POINT OF POLYETHER COPOLYMER

(31) The melting point of the polyether copolymer is measured by DSC (=differential scanning calorimetry) as well known in the art. The polyether copolymer used in the present invention has a melting point between 100° C. and 120° C.

(32) The preferred method for producing the film of the present invention is how blown film as well known in the art.

EXAMPLES

Example 1

(33) From a commercial hot blown film line we produced the following film Outer layer, thickness 30 microns Intermediate layer 1, thickness 10 microns Tie layer 1, thickness 8 microns EVOH 38%, thickness 8 microns Tie layer 2, thickness 8 microns Intermediate layer 2, thickness 20 microns Inner layer, thickness 12 microns.

(34) Outer layer was a blend of

(35) 89% LDPE+10% polyether copolymer+1% slip antiblock masterbatch.

(36) LDPE density was 0.923 while MFI was 0.75 under 1900/2.16 kilos

(37) Intermediate layer 1 was a blend of

(38) 60% ethylene hexene copolymer+40% LDPE

(39) The density of ethylene hexene copolymer was 0.919 while MFI was 1 under 190° C./2.16 kilos

(40) LDPE was same as used in the outer layer.

(41) Tie layer 1 was maleic anhydride LLDPE based copolymer

(42) Tie layer 2 was similar to tie layer 1

(43) Intermediate layer 2 was exactly the same as intermediate layer 1.

(44) Inner layer was a blend of

(45) 89% metallocene LLDPE +10% polyether copolymer+1% slip antiblock masterbatch Metallocene LLDPE had a density of 0.918 while MFI was 1 under 190° C./2.16 kilos

(46) Polyether copolymer used was Pelestat LM230 from Sanyo Chemical.

Example 2

(47) 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

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

COMPARATIVE EXAMPLE

(49) The comparative example was like example 1 but with the polyether copolymer removed and replaced by MV PEBAX 1074 SA01. This material has a melting point of 158° C. as measured by differential scanning calorimetry (DSC).

EXAMINING SYSTEM

(50) 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.

(51) The rotation speed was kept constant during all experiments.

RESULTS

(52) Examples 1 and 2 recorded 2 instances while example 3 recorded 3.

(53) The comparative example recorded 2 instances.

(54) Therefore, the invention keeps the good gussetability of the prior art.

SEAL INITIATION

(55) Test of the seal initiation was done in a Toss sealing machine, keeping the sealing time at 2 seconds and seal pressure at 4 bars. Sealing was done inner side to inner side.

(56) The measured seal initiation temperature of example 1 was found to be 120° C. while for the comparative example a seal initiation temperature of 170° C. has been measured.