Inkjet printable multi-layer shrink film

Abstract

The present invention relates to a multi-layer shrink film comprising at least one shrink base layer and an inkjet printable layer, the latter comprising at least one cellulose-based binding agent, to methods of making such a multi-layer shrink film and of providing graphical information by means of such a multi-layer shrink film, to articles provided with such a multi-layer shrink film as well as to the use of a particular cellulose-based binding agent in the inkjet printable layer of an inkjet printable shrink film.

Claims

1. A multi-layer shrink film comprising at least one shrink base layer and an inkjet printable layer, wherein the inkjet printable layer comprises at least 5 wt.-%, based on the weight of the inkjet printable layer, of at least one cellulose-based binding agent selected from the group consisting of esters of cellulose with organic acids, cellulose ethers and mixtures thereof, wherein the inkjet printable layer comprises 40 to 90 wt.-%, of one or more binding agents, and/or 5 to 50 wt.-% of one or more tackifying resins, and/or 5 to 50 wt.-% of one or more plasticizers, and/or 0.1 to 10 wt.-% of organic or inorganic pigments and/or fillers, particulate fillers having a median particle size dv50 of from 0.1 to 50 m, and/or one or more components selected from the group comprising colorants and dyes, heat and/or ultraviolet light stabilizers, UV-absorbers, free radical scavengers, surfactants, dispersing aids, wetting agents, anti-foaming agents, deaerators, rheological additives, substrate wetting and anti-cratering additives, ink fixing agents, flow improvers, antioxidants, brighteners, phosphorescence agents, cross-linking agents, antistatic agents and mixtures thereof.

2. The multi-layer shrink film according to claim 1, wherein the at least one cellulose-based binding agent comprises an ester of cellulose with at least one organic acid.

3. The multi-layer shrink film according to claim 2, wherein the at least one cellulose-based binding agent is selected from the group consisting of mixed cellulose esters comprising a combination of different acyl groups selected from the group consisting of acetyl, butyryl, propionyl and trimellityl groups.

4. The multi-layer shrink film according to claim 2, wherein the at least one cellulose-based binding agent comprises cellulose acetate propionate and cellulose acetate butyrate and mixtures thereof.

5. The multi-layer shrink film according to claim 1, wherein the at least one shrink base layer comprises one or more thermoplastic polymers selected from the group consisting of (co)polyvinyl chloride, (co)polystyrene, (co)polyolefins, (co)polyesters as well as mixtures, blends and copolymers thereof, and, wherein said layer is oriented monoor bidirectionally.

6. The multi-layer shrink film according to claim 5, wherein the one or more thermoplastic polymers are selected from the group consisting of polyvinyl chloride (PVC), glycol-modified polyethylene terephthalate (PETG), polystyrene (PS), styrene-butadiene copolymer, polypropylene (PP), polyethylene (PE) and cyclic olefin copolymer/polyethylene (COC/PE) as well as mixtures, blends and copolymers thereof.

7. The multi-layer shrink film according to claim 1, wherein the inkjet printable layer further comprises at least one tackifying resin and/or at least one plasticizer.

8. The multi-layer shrink film according to claim 1, wherein the fillers comprise particulate fillers having a median particle size dv50 of from 0.1 to 50 m.

9. A multi-layer shrink film comprising at least one shrink base layer and an inkjet printable layer, wherein the inkjet printable layer comprises at least 5wt.-%, based on the weight of the inkjet printable layer, of at least one cellulose-based binding agent selected from the group consisting of esters of cellulose with organic acids, cellulose ethers and mixtures thereof, wherein the inkjet printable layer further comprises at least one tackifying resin, and/or at least one plasticizer, wherein the at least one tackifying resin is a rosin-based tackifying resin, wherein the rosin-based tackifying resin comprises at least one fully or partially hydrogenated rosin or an ester thereof, wherein the at least one plasticizer is selected from the group consisting of oils, epoxidized oils, fatty acids as well as esters thereof, benzoates, glyceryl esters, esters of polycarboxylic acids with linear or branched aliphatic alcohols, (poly)glycol esters, sulfonamides, polymeric plasticizers and mixtures thereof.

10. The multi-layer shrink film according to claim 9, wherein the at least one ester of a fully or partially hydrogenated rosin is selected from the group consisting of ethyl, ethylene glycol, diethylene glycol, glyceryl, methyl, pentaerythrityl and triethylene glycol esters and mixtures thereof.

11. The multi-layer shrink film according to claim 9, wherein the at least one ester of a fully or partially hydrogenated rosin has a softening point from 50 C. to 150 C.

12. The multi-layer shrink film according to claim 9, wherein the at least one plasticizer is selected from the group consisting of epoxidized vegetable oils, oleates, caprates, tallates, glyceryl esters, (poly)glycol esters, alkyl azelates, alkyl citrates, alkyl glutarates, alkyl phthalates, alkyl trimellitates, alkyl adipates, alkyl sebacates, alkyl maleates, alkyl terephthalates, N-(n-butyl) benzene sulfonamide, polymeric plasticizers and mixtures thereof.

13. The multi-layer shrink film according to claim 9, wherein the at least one plasticizer is selected from the group consisting of polyesters of aliphatic dicarbozylic acids.

14. The multi-layer shrink film according to claim 4 comprising one or more additional layer(s) positioned between the shrink base layer and the inkjet printable layer, and/or a protective layer, film or foil over the outer side of the shrink base layer and/or the inkjet printable layer, and/or one or more coating layer(s) over the outer side of the shrink base layer and/or on one or both sides of the protective layer, if present.

15. The multi-layer shrink film according to claim 14, wherein the additional layer(s) is/are selected from the group comprising additional ink receiving layers, adhesive layers, barrier layers, primer layers, seal layers, layers to adapt the color of the multilayer shrink film, layers for enhancing the mechanical and/or thermal resistance of the multilayer shrink film and combinations thereof.

16. The multi-layer shrink film according to claim 1, wherein the shrink base layer has a thickness from 5 to 200 m, and/or the inkjet printable layer has a thickness from 1 to 100 m, and/or the multilayer shrink film has a total thickness in the range of from 30 to 300 m.

17. The multi-layer shrink film according to claim 14, wherein the shrink base layer has a thickness from 20 to 90 m.

18. The multi-layer shrink film according to claim 14, wherein the inkjet printable layer has a thickness from 10 to 55 m.

19. The multilayer shrink film according to claim 1, wherein the multilayer shrink film is provided in form of a sleeve.

20. The multi-layer shrink film according to claim 1, wherein shrinking of the film is at least 5%, in machine direction (MD) and/or transverse direction (TD) immersed in water having a temperature of 95 C. for 15 sec.

21. A method of making the multilayer shrink film according to claim 1, comprising: forming the at least one shrink base layer and the inkjet printable layer, and incorporating the at least one shrink base layer and the ink jet printable layer into the multi-layer shrink film.

22. The method according to claim 21, wherein the shrink base layer and the inkjet printable layer are co-extruded or wherein a coating composition comprising the at least one cellulose-based binding agent is applied over the preformed shrink base layer to form the inkjet printable layer or wherein a preformed inkjet printable layer comprising the at least one cellulose-based binding agent is attached to the preformed shrink base layer, wherein attaching a preformed inkjet printable layer comprising the at least one cellulose-based binding agent to the preformed shrink base layer is preferred.

23. A method of providing graphical information by means of a multilayer shrink film according to claim 1, comprising the step(s) of (i) printing said graphical information onto the inkjet printable layer and/or (ii) attaching such a printed multilayer shrink film to an article by applying heat to said film causing it to shrink and conform to at least a part of the surface of said article.

24. An article comprising the multilayer shrink film according to claim 1.

25. The multi-layer shrink film according to claim 2, wherein the ester of cellulose with at least one organic acid is selected from the group consisting of mixed cellulose esters.

26. The multi-layer shrink film according to claim 7, wherein the at least one tackifying resin is a rosin-based tackifying resin.

27. The multi-layer shrink film according to claim 26, wherein the inkjet printable layer further comprising one or more binding agent in addition to the at least one cellulose-based binding agent.

28. The multi-layer shrink film according to claim 9, wherein the inkjet printable layer further comprising one or more binding agent in addition to the at least one cellulose-based binding agent.

29. The multi-layer shrink film according to claim 28, wherein the one or more further binding agent(s) is/are selected from the group consisting of acrylic (co)polymers, polyurethanes, polyvinyl alcohols, polyvinyl acetates, polyvinyl butyrals as well as blends, mixtures and copolymers thereof.

30. The multi-layer shrink film according to claim 14, wherein the protective layer, film or foil is positioned at least over the inkjet printable layer.

31. The multi-layer shrink film according to claim 16, wherein the shrink base layer has a thickness from 10 to 150 m, and/or the inkjet printable layer has a thickness from 2.5 to 75 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates an exemplary multi-layer shrink film 1 according to the present invention comprising a shrink base layer 2 and an inkjet printable layer 3. In the specific embodiment shown in the figure, an additional layer 4, e.g. an adhesive layer, is positioned between these to layers. Further, the inkjet printable layer 3 is covered with a removable protective layer 5 and said protective layer 5 and the backside of the shrink base layer 2 each are provided with a coating layer 6 and 7, respectively, for stabilizing the shrink film and/or the respective layer and/or imparting particular properties to them.

(2) FIG. 2 illustrates the shrinking behavior (dimensional change ) of a multi-layer shrink film according to the present invention, which is further described in Example 1 and comprises a shrink base layer attached to an inkjet printable layer by means of an intermediate adhesive layer, in comparison to the shrinking behavior of the shrink base layer alone according to ASTM 2732-14 in a water bath having defined temperatures (T) for 15 sec in TD and MD. The dotted lines show the shrinking behavior of the shrink base layer alone, i.e. without having an inkjet printable layer attached thereto, in MD (curve 1) and TD (curve 2). The solid lines show the shrinking behavior of a multi-layer shrink film according to the present invention comprising said shrink base layer in combination with an inkjet printable layer as described in Example 1 in MD (curve 3) and TD (curve 4).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(3) Test Methods

(4) Heat Shrink Properties:

(5) Shrinkage or dilation of shrink films used as base shrink layers as well as the multi-layer shrink films of the present invention are determined according to ASTM 2732-14 by measuring the difference of sample lengths in transverse or machine web direction before and after immersing the respective film for 15 sec into hot water having a temperature of 95 C., unless otherwise specified. Shrinkage or dilation is defined as the relative length difference =(L2L1)/L1100, wherein both the length before immersion (L1) and after immersion (L2) in one of both web directions are calculated as mean value of two measurements. As specimens 200 mm200 mm sheets of the films are used. A digital caliper meter (MIB-Messzeuge GmbH, Spangenberg, Germany) according to DIN 862 is used.

(6) Haze:

(7) The haze of transparent films is measured according to ASTM D 1003 (Haze-gard Plus C; Byk-Gardner, Geretsried, Germany).

(8) Print Quality:

(9) A Roland printer comprising Eco-Sol MAX inks is used for print quality tested. A diagnostic test chart with 200 color patches is printed and evaluated concerning coalescence (uneven area fill of colored patches), pigment cracking (cracking of a homogeneously printed patches while drying the ink) and/or bronzing (bronzing is a phenomenon where, when an image is viewed from an angle, part of the image seems to disappear or take on a undesired metallic tone in appearance. It occurs because of some of the ink laid on the film coating is not properly absorbed into the coating, but remains on top of it. Even though the effect is only visible at certain angles, the perceived appearance is quite unattractive.). Furthermore the optical density of a blue color patch (100 parts magenta+100 parts cyan) as well as a black color patch (100 parts magenta+40 parts cyan+100 parts yellow+100 parts black) is measured by a SpectroEye spectrophotometer/densitometer (X-Rite Europe GmbH, Regensdorf, Switzerland).

EXAMPLES

Example 1

(10) 50 g cellulose acetate butyrate (CAB-381-20, Eastman Chemical Company), 20 g of a glycerol ester of partially hydrogenated rosin and 23 g of acetyl triethyl citrate as well as 0.3 g Propyltex 270S (polypropylene pigment with a mean particle size of 20 m, Micro Powders Inc.) were dissolved in 300 g methyl ethyl ketone (MEK). The solution was cast onto a siliconized paper liner (Sappi Ultracast Adva Patent, Sappi Fine Paper Europe SA, Brussels, Belgium) by means of a bar coater (Erichsen Coatmaster 510, Erichsen GmbH & Co. KG, Hermer, Germany) with a gap of 200-250 m. After drying at 105 C. in a laboratory oven a dry coating weight of 45 g/m.sup.2 was achieved. Onto this dry film a dry laminating adhesive comprising an adhesive polymer emulsion and a di-isocyanate cross-linking component (13 g/m.sup.2 of LOCTITE LIOFOL LA 29-208/LA 5804, polyurethane based 2K lamination adhesive, Henkel, Dusseldorf, Germany) was coated. Subsequently, the adhesive was dried in a laboratory oven at 70 C. The dry coating weight of the adhesive layer was 10 g/m.sup.2. A commercially available 40 m thick, in transverse direction oriented PETG shrink film (Pentalabel Rigid PETG LF-TG10F22-T52 made by Klckner Pentaplast GmbH, Burgkirchen, Germany) was laminated in a lamination press onto the sticky adhesive surface. After curing the multi-layer shrink film for 1 day at room temperature, the siliconized paper liner was removed.

(11) The multi-layer shrink film was shrunk in a water bath having different temperatures of up to 95 C. for 15 sec in each case. At 95 C., the level of shrinkage was 70% in TD and 8% in MD (FIG. 2). The base film without any inkjet coating showed a shrinkage of 76% in TD and 1% in MD.

(12) The inkjet printable layer was printed with an image using a Roland printer equipped with Eco-Sol MAX inks including white and metallic inks. The image quality obtained was excellent, particularly showing high brilliance, high color gamut and no coalescence. After drying the printed multi-layer shrink film comprising the shrink layer, the printed inkjet layer and the intermediate adhesive layer was cut to form a label. Said label was tightly wrapped around a PET bottle with the printed side facing the PET bottle and fixed by applying a strip of adhesive between the two opposing edges of the wrapped around label in order to hold the printed multi-layer shrink film in position. As the PET bottle has a 3-dimensional contoured shape, parts of the label still were not in close contact with the surface of the bottle. Next the prefixed film was heated by a hot air fan to a temperature of about 90 C. in order to achieve shrinking of the multi-layer shrink film tightly around the shaped PET bottle. After about 2 min of heating the multi-layer shrink film from all positions around the bottle, the film including the printed inkjet layer shrank uniformly around the bottle. The printed image was very colorful and vibrant without any printing artifacts like e.g. cracks, adhesion issues or color changes.

(13) The coating compositions used for the inkjet printable layer in the examples are specified in Table 1. Herein, the following abbreviations and trade names are used:

(14) MEK=methyl ethyl ketone

(15) Dowanol PM=propylene glycol monomethyl ether (The Dow Chemical Company, Midland, Mich., USA)

(16) CAB=cellulose acetate butyrate (Eastman Chemical Company, Kingsport, Tenn., USA)

(17) ATBC=acetyl tributyl citrate

(18) ATEC=acetyl triethyl citrate

(19) Propyltex 270S=dispersible polypropylene pigment (Micro Powders Inc., Tarrytown, N.Y., USA)

(20) Elvacite 2014=methyl methacrylate copolymer (Lucite International, Newton Aycliffe, UK)

(21) Estane 5750=polyurethane (Lubrizol Advanced Materials, Cleveland, Ohio, USA)

Example 2

(22) Example 1 was reproduced except that the shrink film was facing the PET bottle instead of the printed inkjet layer. After about 2 min of heating the multi-layer shrink film from all positions around the bottle, the film including the printed inkjet layer shrank uniformly around the bottle. The printed image was very colorful and vibrant without any printing artifacts like e.g. cracks, adhesion issues or color changes.

Example 3

(23) Example 1 was reproduced except that a water based pressure sensitive adhesive (Acronal V212, BASF, Ludwigshafen, Germany) was used. After about 2 min of heating the multi-layer shrink film from all positions around the bottle, the film including the printed inkjet layer shrank uniformly around the bottle. The printed image was very colorful and vibrant without any printing artifacts like e.g. cracks, adhesion issues or color changes.

(24) The multi-layer shrink film was also shrunk in a water bath having a temperature of 95 C. for 15 sec. The level of shrinkage was 72% in TD and 5% in MD.

Example 4

(25) Example 1 was reproduced except that the shrink film used was a TD-oriented transparent 40 m thick rigid PVC for Shrink Sleeve Label application (Pentalabel Rigid PVC LF-T145/01-T02) and the shrink temperature was increased to approximately 110 C. After about 2 min of heating the multi-layer shrink film from all positions around the bottle, the film including the printed inkjet layer shrank uniformly around the bottle. The printed image was very colorful and vibrant without any printing artifacts like e.g. cracks, adhesion issues or color changes.

(26) In addition, the multi-layer shrink film was shrunk in a water bath having a temperature of 95 C. for 15 sec. The level of shrinkage was 48% in TD and 3% in MD.

Example 5

(27) Example 1 was reproduced except that the coating solution was cast directly onto a 40 m thick transparent shrink film based on MD-oriented polypropylene (Label-Lyte 40LR210 ROSO, OPP film; Jindal Films, New Delhi, India) after corona treatment of the coating side. Drying in a lab oven was accomplished at 40 C. The obtained multi-layer shrink film was placed around the bottle in such a way that the shrink base layer was facing the bottle, so that the printed image was visible as a label. After about 2 min of heating the multi-layer shrink film from all positions around the bottle with hot air, the film including the printed inkjet layer shrank uniformly around the bottle. The printed image was very colorful and vibrant without any printing artifacts like e.g. cracks, adhesion issues or color changes.

(28) In addition the multi-layer shrink film was shrunk in a water bath having a temperature of 95 C. for 15 sec. The level of shrinkage was 15% in MD and 1% in TD.

Example 6

(29) Example 1 was reproduced except that the coating solution was cast directly onto a 50 m thick transparent TD-oriented polyolefin shrink film (Label-Lyte 50TD200; Jindal Films, New Delhi, India) after corona treatment of the coating side. Drying in a lab oven was accomplished at 40 C. The obtained multi-layer shrink film was placed around the bottle in such a way that the shrink base layer was facing the bottle, so that the printed image was visible as a label. After about 2 min of heating the multi-layer shrink film from all positions around the bottle with hot air, the film including the printed inkjet layer shrank uniformly around the bottle. The printed image was very colorful and vibrant without any printing artifacts like e.g. cracks, adhesion issues or color changes.

(30) In addition, the multi-layer shrink film was shrunk in a water bath having a temperature of 95 C. for 15 sec. The level of shrinkage was 50% in TD and 0% in MD.

Example 7

(31) Example 1 was reproduced except that the coating solution was cast directly onto a 50 m thick TD-oriented white shrink film Bonpet 7M based on PETG (BONSET America Corporation, Brown Summit, N.C., USA) after corona treatment of the coating side. Drying in a lab oven was accomplished at 40 C. The obtained multi-layer shrink film was placed around the bottle in such a way that the shrink base layer was facing the bottle, so that the printed image was visible as a label. After about 2 min of heating the multi-layer shrink film from all positions around the bottle, the film including the printed inkjet layer shrank uniformly around the bottle. The printed image was very colorful and vibrant without any printing artifacts like e.g. cracks, adhesion issues or color changes.

(32) The multi-layer shrink film was in addition shrunk in a water bath having a temperature of 95 C. for 15 sec. The level of shrinkage was 78% in TD and 1% in MD.

Example 8

(33) Example 1 was essentially reproduced except for the changes in composition shown in Table 1, in particular that a polyurethane (Estane 5750, Lubrizol Deutschland GmbH, Ritterhude, Deutschland) was added to the coating composition for forming the inkjet printable layer comprising CAB, acetyl tributyl citrate as a plasticizer and partially hydrogenated rosin ester. Print quality as well as shrink properties are excellent.

(34) The multi-layer shrink film was shrunk in a water bath having a temperature of 95 C. for 15 sec. The level of shrinkage was 70% in TD and 3% in MD.

Example 9

(35) Example 1 was essentially reproduced except for the changes in composition shown in Table 1, in particular that a polyacrylate (Elvacite 2014, Lucite International Specialty Polymers & Resins Ltd, Newton Aycliffe, United Kingdom) was added to the coating composition for forming the inkjet printable layer comprising CAB, acetyl tributyl citrate as a plasticizer and partially hydrogenated rosin ester. Print quality as well as shrink properties are excellent.

(36) The multi-layer shrink film was shrunk in a water bath having a temperature of 95 C. for 15 sec. The level of shrinkage was 72% in TD and 3% in MD.

Example 10

(37) Example 1 was essentially reproduced except for the changes in composition shown in Table 1, in particular that the formulation of Example 1 was varied concerning a higher content of CAB and a different rosin-based tackifying resin. Print quality as well as shrink properties are excellent.

(38) The multi-layer shrink film was shrunk in a water bath having a temperature of 95 C. for 15 sec. The level of shrinkage was 74% in TD and 0% in MD.

Comparative Example 11

(39) Example 5 was reproduced except that a typical aqueous PVA-based inkjet coating was applied to the shrink base layer and dried slowly at temperatures of 50 C. at most. The coating composition comprised 8 wt.-% Mowiol 26/88 (Kuraray Europe GmbH, Germany), 2 wt.-% polyvinylpyrrolidone K90 (ISP GmbH, Cologne, Germany) and 2 wt.-% diethylene glycol in water. This coating was printed using a Roland printer equipped with Eco-Sol MAX inks. The inks did not penetrate into the coating so that the image did not dry within 30 minutes. As the ink stayed on top of the coating, the image quality was very poor since ink coalescence and uncontrolled mixing of the colors took place.

(40) TABLE-US-00001 TABLE 1 Glycerol ester of Methyl partially ester of Dowanol CAB CAB hydroge- hydroge- Propyl- Elvacite Estane Example MEK PM 381-20 551-0.2 ATBC ATEC nated rosin nated rosin tex 270S 2014 5750 1-7 300.0 50.0 23.0 20.0 0.3 8 200.0 43.7 8.8 5.0 6.3 9 170.0 30.0 38.00 12.0 3.0 12.0 10 200.0 40.0 10.00 8.0 5.0

A. LIST OF REFERENCE SIGNS

(41) 1 multi-layer, inkjet printable shrink film 2 shrink base layer 3 inkjet printable layer 4 optional additional layer 5 optional protective layer 6 optional coating layer 7 optional coating layer