COLLATION SHRINK FILM PRINTABLE WITH A DIGITAL PRINTING PROCESS

Abstract

Multi-layer collation shrink film comprising a main layer based on a polyethylene mixture comprising 75 to 85 wt.-% low density polyethylene and 15 to 25 wt.-% high density polyethylene or linear low density polyethylene and a skin layer based on a polar ethylene copolymer with vinyl acetate or alkyl (meth)acrylate with a vinyl acetate or alkyl (meth)acrylate content of at least 15 wt.-% and containing 5000 to 20000 ppm silica and a slip agent, use of the film in multi-layer packaging films and method for packaging objects together with the multi-layer collation shrink film including printing the skin layer with a digital ink printing process before or after packaging the objects.

Claims

1-15. (canceled)

16. A multi-layer collation shrink film comprising: a main layer based on a polyethylene mixture comprising 75 to 85 wt.-% low density polyethylene and 15 to 25 wt.-% high density polyethylene or linear low density polyethylene and a skin layer based on a polar ethylene copolymer with vinyl acetate or alkyl (meth)acrylate with a vinyl acetate or alkyl (meth)acrylate content of at least 15 wt.-% and containing 5000 to 20000 ppm silica and a slip agent.

17. The multi-layer collation shrink film according to claim 16, wherein the content of silica ranges from 5000 to 15000 ppm.

18. The multi-layer collation shrink film according to claim 16, wherein the content of vinyl acetate or alkyl (meth)acrylate in the ethylene copolymer ranges from 15 to 28 wt.-% of the total ethylene copolymer weight.

19. The multi-layer collation shrink film according to claim 16, wherein the alkyl (meth)acrylate is a C.sub.1-C.sub.4-alkyl (meth)acrylate.

20. The multi-layer collation shrink film according to claim 16, wherein the ethylene copolymer is ethylene vinyl acetate.

21. The multi-layer collation shrink film according to claim 16, wherein the skin layer comprises a slip agent selected from unsaturated fatty acid primary amides.

22. The multi-layer collation shrink film according to claim 16, wherein the slip agent is present in an amount from 0.01 to 0.15 wt.-%.

23. The multi-layer collation shrink film according to claim 16, wherein the film contains an inner layer.

24. The multi-layer collation shrink film according to claim 16, wherein the thickness of the film ranges from 20 to 150 m.

25. The multi-layer collation shrink film according to claim 16, wherein the main layer makes up 40 to 80% of the film thickness.

26. The multi-layer collation shrink film according to claim 16, wherein the film has at least one of: a shrinkage in transverse direction according to ASTM D 2732 at 150 C. of 10 to 25% a tear resistance according to ASTM D1922 of at least 35 N/mm a gloss according to ASTM D2457 of at least 100 (60 deg.) or below 30 a haze according to ASTM D1003 below 10.

27. A method for packaging objects together with a multi-layer collation shrink film comprising a main layer based on a polyethylene mixture comprising 75 to 85 wt.-% low density polyethylene and 15 to 25 wt.-% high density polyethylene or linear low density polyethylene and a skin layer based on a polar ethylene copolymer with vinyl acetate or alkyl (meth)acrylate with a vinyl acetate or alkyl (meth)acrylate content of at least 15 wt.-% and containing 5000 to 20000 ppm silica and a slip agent, comprising the steps: arranging the objects adjacent to each other to form a bundle, wrapping the multi-layer collation shrink film around the bundle, sealing the edges of the film together, exposing the bundle to a temperature sufficient to shrink the multi-layer collation shrink film to form a package, and cooling the package, wherein the multi-layer collation shrink film is printed with a digital ink printing process onto its skin layer before wrapping around the bundle and/or after cooling of the package.

28. The method according to claim 29, wherein from 2 to 30 objects are packed.

29. The method according to claim 30, wherein 4, 6, 8, 9, 10, 12, 15, 20, or 24 objects are packed.

30. The method according to claim 29, wherein beverage or food containers are packed.

31. The method according to claim 30, wherein beverage bottles or cans are packed.

32. The method according to claim 29, wherein the alkyl(meth)acrylate is ethyl methacrylate or butyl acrylate.

33. The method according to claim 29, wherein the content of silica ranges from 7000 to 11000 ppm, the content of vinyl acetate or alkyl(meth)acrylate ranges from 16 to 20 wt.-%, and an amount of slip agent ranges from 0.05 to 0.1 wt.-%.

34. The method according to claim 29, wherein the slip agent is oleamide or erucamide.

35. The method according to claim 33, wherein the content of silica ranges from 7000 to 11000 ppm, the content of vinyl acetate or alkyl(meth)acrylate ranges from 16 to 20 wt.-%, and an amount of slip agent ranges from 0.05 to 0.1 wt.-%.

36. The multi-layer collation shrink film according to claim 18, wherein the content of silica ranges from 7000 to 11000 ppm and an amount of slip agent ranges from 0.05 to 0.1 wt.-%.

37. The multi-layer collation shrink film according to claim 19, wherein a content of vinyl acetate or alkyl(meth)acrylate ranges from 16 to 20 wt.-%.

38. The multi-layer collation shrink film according to claim 22, wherein the slip agent is oleamide or erucamide.

39. The multi-layer collation shrink film according to claim 16, wherein an amount of slip agent ranges from 0.05 to 0.1 wt.-%.

40. The multi-layer collation shrink film according to claim 23, wherein the inner layer based on low density polyethylene.

41. The multi-layer collation shrink film according to claim 26, wherein thickness of the film ranges from 30 to 70 m.

42. The multi-layer collation shrink film according to claim 26, wherein the main layer makes up 50 to 75% of the film thickness.

Description

EXAMPLES

[0029] The materials listed in the following table 1 have been used.

TABLE-US-00001 TABLE 1 material description HDPE1 density 937 kg/m.sup.3, MI 0.55 (190 C./2.16 kg) HDPE2 density 961 kg/m.sup.3, MI 0.7 (190 C./2.16 kg) LDPE1 density 926 kg/m.sup.3, MI 0.3 (190 C./2.16 kg) LDPE2 density 918 kg/m.sup.3, MI 1.0 (190 C./2.16 kg) LDPE3 density 933 kg/m.sup.3, MI 2.2 (190 C./2.16 kg) EVA 17% vinyl acetate density 941 kg/m.sup.3, MI 0.4 (190 C./2.16 kg) EBA 17% butyl acrylate density 924 kg/m.sup.3, MI 7.0 (190 C./2.16 kg) EMA 11.5% ethyl methacrylate density 930 kg/m.sup.3, MI 1.5 (190 C./2.16 kg) silica silica masterbatch with 15% silica in LDPE additive1 slip masterbatch with 5% erucamide in LDPE additive2 Antistatic additive additive3 processing aid masterbatch with 15% fluorochemical in LDPE

[0030] Several films were made with the layers listed in table 2. The components for the layers were fed into extruders and films made on a blown film coextrusion line with the following settings: temperature 180-210 C., output 200 kg/h, blow-up-ratio 3.4. The layer thicknesses were in each film 42 m for the main layer and 9 m each for the skin layer and inner layer. The skin layer surface was treated with a corona discharge 40-46 DYN prior to printing.

TABLE-US-00002 TABLE 2 sample skin layer main layer inner layer Inv 1 92.5% EVA 78% LDPE1 55.5% LDPE3 1.5% additive1 20% HDPE1 40% LDPE2 6% silica (9000 ppm) 2% additive2 1.5% additive1 1% additive3 2% silica Comp 1 65% EVA 78% LDPE1 55.5% LDPE3 31.5% LDPE3 20% HDPE1 40% LDPE2 1.5% additive 1 2% additive2 1.5% additive1 2% silica 1% additive3 2% silica Comp 2 65% EBA 78% LDPE1 40% LDPE2 31.5% LDPE3 20% HDPE2 55.5% LDPE3 1.5% additive1 2% additive2 1.5% additive1 2% silica 1% additive3 2% silica Comp 3 96.5% EMA 20.0% HDPE1 40% LDPE2 1.5% additive 78.0% LDPE1 55.5% LDPE3 2% silica 2.0% additive2 1.5% additive1 1% additive3 2% silica Comp 4 55.8% LDPE3 78.5% LDPE1 55.8% LDPE3 40% LDPE2 20% HDPE2 40% LDPE2 0.7% additive1 1.5% additive2 1.5% additive1 2.5% silica 1% additive3 2.5% silica

[0031] The films obtained were tested for ink adhesion (by applying a self-adhesive tape and stripping it off), shrink in transverse direction by ASTM D 2732 at 150 C. and tear resistance according to ASTM D1922. The results are reported in table 3.

TABLE-US-00003 TABLE 3 sample Ink Adhesion shrink TD tear resistance MD observations Inv 1 Good 22% >35 N/mm No curling Comp 1 Limit case 18% >35 N/mm Some curling Comp 2 Limit case 16% >35 N/mm Curling Comp 3 Limit case 16% >35 N/mm Some curling Comp 4 No adhesion 15% >35 N/mm No curling

[0032] As can be seen, standard collation shrink film Comp 4 from poly-ethylenes could not be printed in the HP Indigo 20000, the ink was completely stripped off from the surface when a self-adhesive tape was applied onto it and removed again. In contrast, using a skin layer from EVA with 17% vinyl acetate and containing 9000 ppm silica (Inv 1) provided good printability. Furthermore, the film showed appropriate shrink and no curling.

[0033] The comparison films with a skin layer from a blend of EVA having 17% vinyl acetate with LDPE or a blend of EBA with 17% butyl acrylate with LDPE or from EMA with 11.5% ethyl methacrylate could not be run in a packing line. With a too small amount of silica the films curled after cutting before the wrapping process. The small amount of polar comonomer in the polymer material of the skin layer also resulted in a less than optimal ink adhesion.