SOLVENT-UV HYBRID INKJET INK FOR ALUMINUM BEVERAGE CAN DECORATION

Abstract

A hybrid inkjet ink comprising a water miscible organic solvent, a UV radiation-curable material and appropriate photoinitiator, and an epoxide-containing material and printed decorations produced by applying the inkjet ink images to an aluminum substrate.

Claims

1. A hybrid inkjet ink comprising, in percent by weight based on the weight of the ink: about 3-49% of a water miscible organic solvent; about 3-80% by weight of a UV radiation-curable material and an appropriate photoinitiator; and about 1-30% by weight of an epoxide-containing material.

2. The hybrid inkjet ink of claim 1 in which the water miscible organic solvent is chosen from the group consisting of carbonates, lactones, glycols and glycol ethers.

3. The hybrid inkjet ink of claim 1 in which the organic solvent is a lactone.

4. The hybrid inkjet ink of claim 1 in which the UV radiation-curable material is chosen from the group consisting of: a monofunctional UV radiation-curable monomer, a difunctional UV radiation-curable monomer, and a trifunctional UV radiation-curable monomer.

5. The hybrid inkjet ink of claim 4 including two or more of a monofunctional UV radiation-curable monomer, a difunctional UV radiation-curable monomer, and a trifunctional UV radiation-curable monomer.

6. The hybrid inkjet ink of claim 1 in which the UV radiation-curable material comprises all three of a monofunctional UV radiation-curable monomer, a difunctional UV radiation-curable monomer, and a trifunctional UV radiation-curable monomer.

7. The hybrid inkjet ink of claim 1 in which the UV radiation-curable material monomer is a cycloaliphatic acrylate.

8. The hybrid inkjet ink of claim 7 in which the cycloaliphatic acrylate is isobornyl acrylate and/or 4-tert-butylcyclohexylacrylate.

9. The hybrid inkjet ink of claim 1 in which the UV radiation-curable material is difunctional and is chosen from the group consisting of aliphatic, cycloaliphatic, polyester, polyurethane, and ethylene/propylene glycol diacrylates.

10. The hybrid inkjet ink of claim 9 in which the difunctional UV radiation-curable material is hexanediol diacrylate and/or diprophylene glycol diacrylate.

11. The hybrid inkjet ink of claim 1 in which the radiation-curable material is propoxylated(3)trimethylopropane triacrylate.

12. The hybrid inkjet ink of claim 1 including a resin.

13. The hybrid inkjet ink of claim 12 in which the molecular weight of the resin is less than about 100,000 Daltons.

14. The hybrid inkjet ink of claim 12 in which the molecular weight of the resin is in the range of about 1000-50,000 Daltons.

15. The hybrid inkjet ink of claim 12 in which the resin is chosen from the group consisting of polyols, acrylated polyesters, and acrylated polyurethanes.

16. The hybrid inkjet ink of claim 1 in which the epoxide-containing material is a mono-, di-, or tri-functional epoxide chosen from the group consisting of aliphatic, aromatic, saturated and unsaturated epoxides.

17. The hybrid inkjet ink of claim 1 in which the epoxy-containing material comprises cyclohexyl dimethanol diglycidyl ether and/or neopentyl glycol diglycidyl ether.

18. The hybrid inkjet ink of claim 1 including a colorant.

19. The hybrid inkjet ink of claim 18 in which the colorant is a pigment or dye in combination with a dispersant stabilized using dispersants that are compatible with the remaining components of the inkjet ink.

20. A printed decoration comprising: an aluminum substrate; and an ink composition applied to the aluminum substrate using an inkjet printer, where the inkjet composition comprises, based upon the total weight of the ink, about 3-49% by weight of a water miscible organic solvent, about 3-80% by weight of a UV radiation-curable material and an appropriate photoinitiator and about 1-30% by weight of an epoxide-containing material.

21. A method of producing a printed decoration to an aluminum substrate comprising: providing an aluminum substrate; providing an inkjet ink composition comprising, based on the total weight of the ink, about 3-49% by weight of water miscible organic solvent, about 3-80% by weight of a UV radiation-curable component, and an appropriate photoinitiator; and about 1-30% by weight of an epoxide-containing material; applying the inkjet composition to the aluminum substrate using an inkjet printer to form an image on the substrate; irradiating the image with UV light to achieve a partial cure of the UV curable component of the ink, pinning the image to the substrate while leaving unevaporated solvent in place within the image; applying an overprint varnish coating to intermix with the unevaporated solvent in the image; and heating the image to drive off the solvent and produce a full cure of the image as a decoration on the aluminum substrate.

22. The method of claim 21 in which the overprint varnish includes an aqueous carrier.

23. The method of claim 21 in which the overprint varnish includes an organic carrier.

24. The method of claim 21 in which the aluminum substrate is the outer surface of an aluminum beverage can.

25. The hybrid inkjet ink of claim 21 in which the printed decorations have a thickness exclusive of overprint varnish of about 1 to 12 μm.

26. The hybrid inkjet ink of claim 21 in which the printed decorations have a thickness exclusive of overprint varnish of about 1-8 μm.

Description

EXAMPLES

[0036] The following examples are presented for purposes of illustration and are not intended to be exhaustive or limiting of any embodiment of the invention.

[0037] 1. Adhesion to Aluminum Substrate

[0038] The test specimens were successfully necked cans with inkjet-applied decoration and an overprint varnish top coat. An ASTM standard test method D3359-09 was used to measure and examine the adhesion of inkjet-applied hybrid ink. A hard metal straight edge was used to make straight cuts with a sharp razor blade to form intersecting 7 to 8 crosshatched cuts in selected areas of the body and neck of the cans. The tape applied was a 0.75″ wide transparent Scotch® Brand Tape, Cat 600.

[0039] The crosshatch adhesion tests on both the necked areas of the can specimens and on the bodies of the can specimens for CMYK image hybrid coatings did not show any adhesion failure and had outstanding adhesion ratings of 4B- 5B, before and after pasteurization.

[0040] 2. Gloss Level

[0041] An ASTM standard test method D523-08 was used to measure the specular gloss of nonmetallic specimens for glossmeter geometries of 20, 60, and 85° using two specimens: 1) a hybrid black ink prepared in accordance with embodiments of the invention and applied using an inkjet printer, and 2) a commercial black beverage can coating prepared using conventional offset printing. A black hybrid inkjet ink as follows was used:

TABLE-US-00001 Material Type Percent by Weight 4-tert-butylcyclohexyl acrylate (monomer) 13 2-phenoxyethyl acrylate (monomer) 4 Propoxylated (3) Trimethylopropane Triacrylate 6 (trifunctional monomer) Resin 12 Amine Synergist 8 Antioxidant and thermal stabilizer blend 1 Surfactant 1 Photoinitiator Norrish Type I 3.5 Photoinitiator Norrish Type II 3.5 Black Pigment Dispersion (colorant) 15 Gamma-butyrolactone (solvent) 20 Neopentyl glycol diglycidyl ether (epoxide) 13 100

[0042] The 20° geometry is advantageous for comparing specimens having 60° gloss values higher than 70. The 60° geometry is used for inter-comparing most specimens and for determining when the 20° geometry may be more applicable. The 85° geometry is used for comparing specimens for sheen or near-grazing shininess; it is most frequently applied when specimens have 60° gloss values lower than 10.

[0043] The following results were obtained:

TABLE-US-00002 Gloss Level Commercial Hybrid Angle Black Black 20° 57.6 66.7 60° 87.4 89.9 85° 96.6 94.4

[0044] This data demonstrates that the hybrid inkjet black ink coating can produce gloss levels commensurate with those achieved using conventional offset printing processes. In other words, the new hybrid ink is shown here to enable inkjet printing on aluminum cans to produce gloss levels commensurate with those achieved in conventional offset printing processes thereby delivering all of the benefits of inkjet printing to the can printing process.