NZ237125A - Heat-shrinkable multilayer plastics films - Google Patents

Description

237125/239071 NEW ZEALAND PATENTS ACT, 1953 No.: 237 125 & 239 071 Date: 14 February 1991 & 22 July 1991 COMPLETE SPECIFICATION IMPROVEMENTS IN AND/OR RELATING TO MULTILAYER FILMS We, W R Grace & Co.-Conn, a corporation organized and existing under the laws of the state of Connecticut, of 1114 Avenue of the Americas, New York, New York 10035, USA, hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- (followed by page -la-) N.Z. PATENT OPFICE 14 FES 1992 PCCE!V3D 237125/239071 The present invention relates to improvements in and/or relating to multilayer heat shrinkable plastic films, containers (eg bags) or packages using same and to related means and methods.

Multilayer heat shrinkable films have been used for some time for the shrink wrapping of various food products including meat products which will require refrigeration or freezing. Desirable characteristics in such films are their degree of shrinkage under moderate heat and their resistance to abuse.

Currently available in New Zealand are several films useful in the wrapping of products such as meats. These include ionomer based materials, employed in ionomer bags of Trigon Packaging Systems (NZ) Limited of Corner Avalon Drive and Foreman Road, Hamilton, New Zealand and the EVA (ethylene-vinyl acetate copolymer) based materials of WR Grace (NZ) Limited of Prosser Street, Elsdon, Porirua, which are known as their SL3 and SB3 bags.

The abuse resistance of the films if improved would make such containers more useful in the packaging of products having a greater tendency to penetrate or puncture the packaging, such as meat cuts in which bones are retained. It is also desirable for films to have good resistance to external abuse.

It is also desirable for such films to be "high shrink" as this is important with respect to both presentation and consumer appeal.

In this regard, New Zealand Patent Application No. 226 983 of WR Grace (NZ) Limited relates to multilayer films having both good resistance to abuse and heat shrinkabi1ity. These films comprise at least three layers: two outside layers, each comprising VLDPE (very low density polyethylene) or a hlenri of VIDPE/FVA, and an internal layer which is EVA or primarily EVA. - 1Or # :>:r, i2i>/ ^ if071 The present invention is directed to films, containers, packages and methods of producing films, which will go some way towards meeting, at least in part, the above mentioned aims of good abuse resistance and heat shrinkability by different means, or at least provide the public with a useful choice.

As used herein, the term "VLDPE" refers to very low density polyethylene; "EVA" refers to an ethylene-vinyl acetate copolymer; "EMAA" refers to ethylene methacrylic acid copolymer, "EAA" to ethylene acrylic acid copolymer, "PVDC" to vinylidene chloride/vinyl chloride copolymer, and "MA" to vinylidene chloride methyl acrylate copolymer.

Accordingly, in a first aspect the present invention may broadly be said to comprise a heat-shrinkable multilayer film having a measure of resistance to abuse, comprising at least three layers, including: a) a first outside layer selected from the group consisting of EVA, VLDPE and blends of VLDPE and EVA, b) a core or internal layer, comprising an ionomer or a blend thereof with EVA, EMAA or EAA, and c) a second outside layer selected from the group consisting offpfak,^E$^nd 2) a blend of sodium ionomer polymer with EVA, comprising up to about 40% EVA, or The core or internal layer b) preferably comprises either 1) sodium ionomer polymer alone, or ionomers. 237125/ 239071 - 3 - ' 3) a blend of sodium ionomer polymer with EMAA or EAA, comprising up to about 25% of the EMAA or EAA.

For example, a blend of about 93% sodium ionomer polymer (specific gravity 0.94) with about 7% EVA (specific gravity 0.96), or a blend of about 95% sodium ionomer polymer with about 5% EMAA or EAA (specific gravity 0.94) may be used.

The first outside layer a) which is preferably the outer abuse layer, preferably comprises either EVA alone or a blend of VLDPE/EVA comprising from about 0% to 70% EVA, eg a blend of 50% EVA (specific gravity 0.93)/5Q% VLDPE (specific gravity 0.91).

The second outside layer c), is preferably a sealing layer, which in use will contact a product to be packaged by the film, and comprises either EMAA, EAA or sodium ionomer polymer.

The films of the present invention may also comprise an oxygen barrier layer, such as vinylidene chloride vinyl chloride copolymer, vinylidene chloride methyl acrylate copolymer, ethylene vinyl alcohol copolymer or polyamide, located between the first outside layer a) and the internal layer b). In addition, polymeric adhesive layers (eg EMAA) may be included, between the first outside layer and the internal layer, or, if a barrier layer is included, between the barrier layer and the first outside layer and/or between the barrier layer and the internal layer b).

In a further aspect the present invention comprises a multilayer film having a measure of resistance to abuse, comprising at least two layers, including: YsSy ' Z3flcr\ l a) a first outside layer selected from the group consisting of VLDPE, EVA and blends of VLDPE and EVA; and c) a second outside layer comprising EMAA.

Preferably a core or internal layer b) is also included, which is preferably as hereinbefore described. Alternatively the core layer may comprise cross-linked EVA.

Preferably the first outside layer is as hereinbefore described.

Barrier and/or adhesive layers as hereinbefore described may also be included in this form of the present invention.

In a further aspect the present invention comprises a process of making a heat-shrinkable multilayer film, comprising: (i) co-extruding as a multilayer film precursor laminate, at least three layers, including: a) a first outside layer selected from the group consisting of EVA, VLDPE and blends of VLDPE and EVA, b) a core or internal layer,comprising an ionomer or a blend thereof with EVA, EMAA or EAA, and c) a second outside layer selected from the group consisting of EMAA, EAA and ionomers; and o y iC (ii) subsequently treating the precursor to provide the multilayer/^ •i film ;. 6 APRW® I - " Preferably said precursor laminate is stretched by racking and/or blowing to a desired film thickness to thereby provide the heat shrinkable film.

Preferably said precursor laminate is stretched by first heating it to softening point, then expanding it by blowing a vertical bubble to stretch the laminate, cooling the laminate into thin film, and collapsing the bubble onto converging rollers, then winding the film under tension into roll form.

Preferably said stretching is to about 5 to 9 times the surface area of the film precursor.

Preferably said precursor laminate has a total thickness of from about 400 microns to about 820 microns. Preferably said second outside layer c) of said precursor laminate has a thickness of about 75 to about 155 microns.

Preferably said core or internal layer b) of said precursor laminate has a thickness of from about 200 to about 410 microns.

Preferably said first outside layer a) of said precursor laminate has a thickness of from about 125 to about 255 microns.

Preferably said multilayer film has a resultant total thickness of about 60 to about 120 microns.

In a further aspect the present invention comprises a process of niakinq a multilayer film, comprising: 1 23Tl~V23907i (i) co-extruding as a multilayer film precursor laminate at least two layers, including: a) a first outside layer selected from the group comprising VLDPE, EVA and blends of VLDPE and EVA, c) a second outside layer comprising EMAA; and (ii) subsequently treating the precursor to provide the multilayer film.

Preferably a core layer b) is also co-extruded with layers a) and c).

Preferably said multilayer film is as herein described.

The present invention will now be described in more detail, with reference to the accompanying drawings.

Figure 1 shows a three layer multilayer heat shrinkable film such as can be produced by extrusion, for convenience all film thicknesses being shown substantially identical. It will be appreciated that it is not essential that the film of the present invention has three layers - from two to four or more layers may be used.

Figure 2 is a diagrammatic view of a three-layer precursor laminate showing how it is to be blown down to a film.

In one preferred form of the present invention the multilayer film has three layers. Layer a) is preferably the so-called outside layer, which in use (when the film is used as a wrapping, or to define a container or package) will be that surface which does not contact ' 237125 j 239071 the product. Layer c) is preferably the inner sealing layer, which in use will be that surface likely to contact the foodstuff. Layer b) is the core or internal layer.

Layer c), the inner sealing layer, may comprise EMAA, EAA, or an ionomer. EMAA is especially preferred, since use of EMAA copolymer provides the film with very good sealability properties, important when there may be contamination of the material, for example by particulates, and/or pleats or folds in the material. A layer c) of an ionomer also confers reasonably good sealability properties on the film, although a non-ionised form of EMAA is preferred in this respect.

Layer b), the core or internal layer, may comprise either an ionomer (preferably sodium ionomer polymer) or a blend thereof with EVA, EMAA or EAA. For example, the internal layer could comprise a blend of sodium ionomer polymer with up to about 40% EVA, more preferably up to 20% EVA, or a blend of sodium ionomer polymer with up to about 25% EAA or EMAA, more preferably from about 1% to about 10% by weight of EMAA or EAA. The ionomer provides the film with high shrink and high clarity properties. It is also possible for this layer to comprise some other heat-shrinkable material, such as cross-linked EVA. Layers c) and b) also give the film good resistance to internal puncturing.

Layer a) (the "outside layer"), in one preferred form of the invention, may be a blend of about 50% VLDPE with about 50% of EVA copolymer, although blends of VLDPE and EVA containing up to about 70% EVA, or even EVA alone, may also be used. This layer provides the 237125/ 230071 -8- ' film with good external abuse resistance properties, while at the same time having a glossy appearance when shrunk, and a smooth printable surface finish.

It is also possible for there to be an additional layer, for example an oxygen barrier layer, to ensure that the film is substantially impermeable to gas transmission (mainly oxygen). The barrier layer could comprise any of the well known resins useful in enhancing oxygen barrier properties in a film or bag. These include vinylidene chloride vinylchloride copolymer, vinylidene chloride methyl acrylate copolymer, ethylene vinyl alcohol copolymer and polyamide.

Adhesive layers may be used either to adhere the outside VLDPE/EVA layer to the core (preferably ionomer) layer, and/or to adhere an oxygen barrier layer, such as PVDC or MA, to the other layers. Appropriate materials for adhesive layers which may be used include EVA, EMAA, EAA or ionomer. Possible structures which include the use of adhesive layers (with or without a barrier layer) may be: (1) a 6-layer structure: VLDPE/EMAA/PVDC/EMAA/IONOMER/EMAA a b c d e f a = outside layer b = adhesive layer c = barrier layer d = adhesive layer e = internal layer f = inner sealing layer or (2) a 4-layer structure: ;'.

VLDPE/EMAA/IONOMER/EMAA a b c d a = outside layer b = adhesive layer c = internal layer d - inner son 1 incj layer 237125/239071 In these structures, EAA may be used instead of EMAA.

Table 1 shows the structures of 3 different multilayer (three-layer) films made in accordance with the present invention.

TABLE 1: THE PACKAGING STRUCTURES STRUCTURE NO. 1 2 3 LAYER c) (inside) Resin (see below) A C C Thickness (micron) Tolerance +/-10 90 +/-10 90 +/-10 90 +/-10 LAYER b) (core or internal) Resin (see below) A A D Thickness (micron) Tolerance +/-20 235 +/-20 235 +/-20 235 +/-20 LAYER a) (outside) Resin (see below) B B B Thickness (micron) Tolerance +/-20 145 +/-20 145 +/-20 145 +/-20 TOTAL THICKNESS OF PRECURSOR LAMINATE: (micron) 470 Tolerance +/-50 470 +/-50 470 +/-50 470 +/-50 BLOW UP RATIO: 6.76 6.76 6.76 RESULTANT FILM THICKNESS (micron): Tolerance +1-5 80 +/-5 80 +/-5 80 +/-5 RESINS: A = Sodium Ionomer Polymer, specific gravity (sg) 0.94 B = Blend of 50% by weight of Very Low Density Polyethylene (VLDPE), sg 0.91, with 50% of Ethylene Vinyl Acetate (EVA) Copolymer, sg 0.93.

C = Ethylene Methacrylic Acid Copolymer(EMAA),sg 0.94.

D = Blend of 93% of Sodium Ionomer Polymer, sg 0.94, with 7% of EVA Copolymer, sg 0.96. 237125 10071 The general properties of the final packaging structures are: a. Percent Shrink at 85°C: LD (longitudinal direction) = 35 to 45 TD (transverse direction) = 50 to 60 b. Tensile Strength in kg/sq cm: LD = 400 to 550 TD = 400 to 600 c. Percent Elongation: LD = 120 to 180 ' : ' ■"•i'-'W TD = 150 to 250 The packaging performance characteristics of each layer in each structure are dependent on the resins being used. These characteristi may be generalised as follows: STRUCTURE 1: Layers c) and b) - Easy sealability through contamination and pleats.

High clarity and high shrink.

Good resistance to internal puncturing. 237125/ 23907 11- Layer a) - Glossy appearance when shrunk.

Good resistance to external abuse puncturing. Smooth printable surface finish.

STRUCTURE 2: Layer c) Easy sealability at low temperatures through contamination and pleats.

High clarity.

Good resistance to internal puncturing.

Layer b) - High clarity and high shrink.

Good resistance to internal puncturing.

Layer a) - Same as Structure 1.

STRUCTURE 3: Layer c) - Same as Structure 2.

Layer b) - Same as Structure 2.

Layer a) - Same as Structure 1.

Table 2 shows examples of alternative structures of multi-layer films in accordance with the present invention, in which layer a) (the outside layer) comprises EVA copolymer alone. In these structures, layer c) (the inside sealing layer) comprises EMAA or EAA (specific gravity = 0.94); layer b) (the core layer) comprises sodium ionomer blended with EMAA or 23'*25/2300 EAA at a ratio of 5% by weight of EMAA or EAA (ionomer specific gravity = 0.94); and layer a) (the outside layer) comprises EVA copolymer (specific gravity = 0.96).

Table 2 Further Packaging Structures Structure No. 4 6 7 Layer c) (inside) Resin (see below) Thickness (micron) Tolerance +/-10 C 90 C 90 D 90 D 90 Layer b) (core) Resin (see below) Thickness (micron) Tolerance +/-20 E 200 G 200 E 200 G 200 Layer a) (outside) Resin (see below) Thickness (micron) Tolerance +/-20 F 180 F 180 F 180 F 180 Total thickness of precursor laminate (micron) Tolerance +/-50 470 470 470 470 Blow Up Ratio 6.76 6.76 6.76 6.76 Resultant film thickness (micron) Tolerance +/-50 80 80 80 80 RESINS: C = Ethylene Methacrylic Acid Copolymer (EMAA), sg. 0.94 D = Ethylene Acrylic Acid Copolymer (EAA), sg. 0.94 E = Blend of 95% sodium ionomer polymer with 5% EMAA copolymer (ionomer s.g. 0.94) F = EVA copolymer G = Blend of 95% sodium ionomer polymer with 5% EAA copolymer, s.g. 0.94 The precursor laminates may be made by using a three layer coextrusion process - examples of the resins and preferred layer thicknesses are specified in Tables 1 and 2. The thicknesses of the 237125/231)071 various layers are chosen so as to provide an overall multilayer film thickness that is desired. The total thickness of the precursor laminate is preferably in the range of about 400 to 820 microns.

After the precursor laminate has been formed, it is oriented by first heating it to softening point, then expanding it by blowing a vertical bubble. This stretches the laminate into a thin film which is cooled. The bubble is collapsed by converging rollers then wound under tension into roll form. In this regard, Figure 2 shows how the precursor laminate is to be blown down to film.

Alternatively, tenter frame stretching may be used to stretch the precursor laminate.

The stretching process orientates the polymer molecules into longitudinal and transverse directions (LD and TD). The amount of stretch is the Blow Up Ratio which is specified in Table 1. The preferred Blow Up Ratio is about 6.76. The total thickness of the final film (after coextrusion and orientation) is preferably from about 60 to 120 microns.

Other processes known in the art such as extrusion coating, and conventional lamination, may also be used to make the precursor laminates.

Optionally, when the inner sealing layer comprises EMAA or EAA, and the core layer is not an ionomer (eg when the core layer comprises EVA) the sealing layer, the core layer, and any additional layers located between the core and sealing layers, may be cross-linked, using, for example, irradiation. 237i2.V239071 -13a- It is believed that a multilayer film in accordance with the present invention will provide a multilayer film having good abuse resistance properties, both to internal and external puncturing (due to the presence of a layer comprising a blend of VLDPE/EVA or EVA), while at the same time having good heat shrinkabi1ity , high clarity and good sealability. 23" 12! 23? o"II

Claims (66)

WHAT WE CLAIM IS:

1. A heat-shrinkable multilayer film having a measure of resistance to abuse, comprising at least three layers, including: a) a first outside layer selected from the group consisting of EVA, VLDPE and blends of VLDPE and EVA, b) a core or internal layer, comprising an ionomer or a blend thereof with EVA, EMAA or EAA, and c) a second outside layer selected from the group consisting of EMAA, EAA, and ionomers.

2. A multilayer film as claimed in claim 1 wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EMAA copolymer, and wherein the blend comprises from 0% to 25% EMAA copolymer by weight.

3. A multilayer film as claimed in claim 1 or 2, wherein the core or internal layer b) comprises a blend of about 95% by weight sodium ionomer polymer with about 5% weight EMAA copolmer.

4. A multilayer film as claimed in claim 1, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer ° with EAA copolymer, and wherein the blend comprises from 0% V'® £ APR 19? to 25% EAA copolymer by weight. 23 7 1 2 5 2390 7 1

5. A multilayer film as claimed in claim 1 or 4 wherein the core or internal layer b) comprises a blend of about 95% by weight sodium ionomer polymer with about 5% by weight EAA copolymer.

6. A multilayer film as claimed in claim 1, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EVA, and wherein the blend comprises from 0% to 40% EVA by weight.

7. A multilayer film as claimed in claim 1 or 6, wherein the core or internal layer b) comprises a blend of about 93% by weight sodium ionomer polymer with about 7% by weight eva copolymer.

8. A multilayer film as claimed in claim 1, wherein the core or internal layer b) comprises sodium ionomer polymer alone.

9. A multilayer film as claimed in claim 6 wherein said sodium ionomer polymer has a specific gravity of about 0.94, and said EVA in the core or internal layer has a specific gravity of about 0.96.

10. A multilayer film as claimed in any preceding claim wherein the first outside layer a) comprises a blend of VLDPE and EVA, and wherein said blend comprises from 0% to 70% EVA by weight.

11. A multilayer film as claimed in claim 10 wherein the first outside layer a) comprises a blend of about 50% by weight VLDPE and about 50% by weight of EVA. o\s " -JULJ99J r'i 23 9 0 7 1

12. A multilayer film as claimed in any one of claims 1 to 9 wherein the first outside layer a) comprises EVA alone.

13. A multilayer film as claimed in any one of claims 1 to 11 wherein said VLDPE has a specific gravity of about 0.91.

14. A multilayer film as claimed in any one of claims 1 to 13 wherein said EVA of said first outside layer has a specific gravity of about 0.93,

15. A multilayer film as claimed in any one of the preceding claims wherein the second outside layer c) is a sealing layer which in use will contact a product to be packaged by the film.

16. A multilayer film as claimed in claim 15 wherein the sealing layer c) comprises EMAA.

17. A multilayer film as claimed in claim 15 wherein the sealing layer c) comprises EAA.

18. A multilayer film as claimed in any one of the preceding claims wherein the EMAA or EAA in the second outside layer (c) has a specific gravity of about 0.94.

19. A multilayer film as claimed in claim 15 wherein the sealing layer comprises a sodium ionomer polymer.

20. A multilayer film as claimed in any preceding claim which further includes an oxygen barrier layer located between the ttrst outside ^ ^ * ' ^ 1 o v layer a) and the internal layer b). •v ' / T<? JUL '"" -17- 23fo~7/

21. A multilayer film as claimed in claim 20 wherein the barrier layer comprises PVDC or MA.

22. A multilayer film as claimed in any one of claims 1 to 19 which further includes an adhesive layer between the first outside layer a) and the internal layer.

23. A multilayer film as claimed in claim 20 or 21 which further includes one or more adhesive layers between the barrier layer and the first outside layer a), and/or between the barrier layer and the internal layer b).

24. A multilayer film having a measure of resistance to abuse, comprising at least two layers, including: a) a first outside layer selected from the group consisting of VLDPE, EVA and blends of VLDPE and EVA; and c) a second outside layer comprising EMAA.

25. A multilayer film as claimed in claim 24, further including a core or internal layer b).

26. A multilayer film as claimed in claim 25, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EMAA copolymer, and wherein the blend comprises from 0% ( to 25% EMAA copolymer b.y weight. 23 7 125 23 90 71

27. A multilayer film as claimed in claim 25 or 26, wherein the core or internal layer b) comprises a blend of about 95% by weight sodium ionomer polymer with about h% bv weiaht EMAA cop.ol.ymer.

28. A multilayer film as claimed in claim 25, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EAA copolymer, and wherein the blend comprises from 0% to 25% EAA copolymer bv weiqht.

29. A multilayer film as claimed in claim 25 or 28, wherein the core or internal layer b) comprises a blend of about 95% bv weiqht sodium ionomer polymer with about 5% by weight eaa copolymer.

30. A multilayer film as claimed in claim 25, wherein the core or internal layer b) comprises a blend of a sodium ionomer polymer with EVA, and wherein the blend comprises from 0% to 40% EVA by weight.

31. A multilayer film as claimed in claim 25 or 30, wherein the core or internal layer b) comprises a blend of about 93% by weight sodium ionomer polymer with about 7% by weight EVA copolymer.

32. A multilayer film as claimed in claim 25, wherein the core or internal layer b) comprises sodium ionomer polymer alone.

33. A multilayer film as claimed in claim 31 wherein said sodium ionomer polymer has a specific gravity of about 0.94, and said EVA in the core layer (b) has a specific - '<*•' <_ qravity of about 0.96. W i w x ^ 19 JULD53 ' 19 - 23 7 125 23 9 0 7 1

34. A multilayer film as claimed in claim 25, wherein said internal layer b) comprises cross-linked EVA.

35. A multilayer film as claimed in claim 25, wherein the first outside layer a) comprises a blend of VLDPE and EVA, and wherein

36. A multilayer film as claimed in claim 35, wherein the first outside layer a) comprises a blend of about 50% by weight VLDPE and about 50% by weight of EVA.

37. A multilayer film as claimed in any one of claims 25 to 34 wherein the first outside layer a) comprises EVA alone.

38. A multilayer film as claimed in any one of claims 25 to 36 wherein said VLDPE has a specific gravity of about 0.91.

39. A multilayer film as claimed in any one of claims 25 to 38 wherein said EVA of said first outside layer has a specific gravity of about 0.93.

40. A multilayer film as claimed in any one of claims 24 to 39, wherein the second outside layer c) is a sealing layer, which in use will contact a product to be packaged by said film.

41. A multilayer film as claimed in any one of claims 24 to 40, wherein said EMAA in the second outside layer (c) has a specific gravity of about 0.94. said blend comprises from 0% to 70% EVA by weight. h !iu \\* 19 JUL •o* ... » r» <-y rV • / - 20 -

42. A multilayer film as claimed in any one of claims 25 to 41 which further includes an oxygen barrier layer located between the first outside layer a) and the internal layer b).

43. A multilayer film as claimed in claim 42 wherein the barrier layer comprises PVDC or MA.

44. A multilayer film as claimed in any one of claims 25 to 41 which further includes an adhesive layer between the first outside layer a) and the internal layer b).

45. A multilayer film as claimed in claim 42 or 43 which further includes one or more adhesive layers between the barrier layer and the first outside layer a), and/or between the barrier layer and the internal layer b).

46. A process of making a heat-shrinkable multilayer film, comprising: (i) co-extruding as a multilayer film precursor laminate, at least three layers, including: a) a first outside layer selected from the group consisting of EVA, VLDPE and blends of VLDPE and EVA, b) a core or internal layer,comprising an ionomer or a blend thereof with EVA, EMAA or EAA, and c) a second outside layer selected from the group consisting of EMAA, EAA, and ionomers; and (ii) subsequently treating the precursor to provide th multilayer film. 2 3 -< 1 :i n / ziiom

47. A process as claimed in claim 46 wherein said precursor laminate is stretched by racking and/or blowing to a desired film thickness to thereby provide the multilayer film.

48. A process as claimed in claim 47 wherein said stretching is to 5 to 9 times the surface area of the film precursor. \

49. A process as claimed in any one of claims 46 to 48 wherein said precursor laminate has a total thickness of from 400 to 820 microns.

50. A process as claimed in any one of claims 46 to 49 wherein said layer c) of said precursor laminate has a thickness of 75 to 155 microns.

51. A process as claimed in any one of claims 46 to 50 wherein said layer b) of said precursor laminate has a thickness of 200 to 410 microns.

52. A process as claimed in any one of claims 46 to 51 wherein said layer a) of said precursor laminate has a thickness of 125 to 255 microns.

53. A process as claimed in any one of claims 46 to 52 wherei id„ •, multilayer film has a resultant total thickness of 120 microns.

54. A multilayer film as claimed in any one of claims 1 to 23 when produced by a process as claimed in any one of claims 46 to 53, - 22 - 237 125 239071

55. A process of making a multilayer film comprising: (i) co-extruding as a multilayer film precursor laminate at least two layers, including: a) a first outside layer selected from the group consisting of VLDPE, EVA and blends of VLDPE and EVA, c) a second outside layer comprising EMAA; and (ii) subsequently treating the precursor to provide the multilayer film.

56. A process as claimed in claim 55 wherein a core or internal layer b) is co-extruded with layers a) and c) to form the multilayer film precursor laminate, said layer b) comprising either cross-linked EVA or an ionomer or a blend thereof with EVA, EMAA or EAA.

57. A process as claimed in claim 55 or 56 wherein said precursor laminate is stretched by racking and/or blowing to a desired film thickness to thereby provide the multilayer film.

58. A process as claimed in claim. 57 wherein said stretching is to 5 to 9 times the surface area of the film precursor.

59. A process as claimed in any one of claims 56 to 58 wherein said precursor laminate has a total thickness of from 400 to 820 microns. o c \\ 19 JUU993 :i a ■; 12 n / ^ - 23 - 2noi i

60. A process as claimed in any one of claims 56 to 59 wherein said layer c) of said precursor laminate has a thickness of from 75 to 155 microns.

61. A process as claimed in any one of claims 56 to 60 wherein said layer b) of said precursor laminate has a thickness of 200 to 410 microns.

62. A process as claimed in any one of claims 56 to 61 wherein said layer a) of said precursor laminate has a thickness of 125 to 255 microns.

63. A process as claimed in any one of claims 57 to 62 wherein said multilayer film has a resultant total thickness of 60 to 120 microns.

64. A multilayer film as claimed in any one of claims 24 to 45 when produced by a process as claimed in any one of claims 55 to 63.

65. A multilayer film substantially as herein described with reference to the examples and/or the accompanying drawings.

66. A process of making a multilayer film substantially as herein described with reference to the examples and/or the accompanying "i ' J *T T.'\- drawings. _ - ' ■ • •"-> l£> (Z GpCK Co -6 8y tfWHar/ThelrAutl A. J. RpK &Mn