A PRINTING INK

Abstract

The invention relates to an inkjet ink comprising: one or more monofunctional (meth)acrylate monomers, including 2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate (MEDA); a pigment; and a photoinitiator.

Claims

1. An inkjet ink comprising: one or more monofunctional (meth)acrylate monomers, including 2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate (MEDA); a pigment; a photoinitiator; and N-vinyl caprolactam.

2. An inkjet ink as claimed in claim 1, wherein the ink comprises at least two monofunctional (meth)acrylate monomers, including MEDA.

3. An inkjet ink as claimed in claim 1, wherein the ink further comprises at least two N-vinyl amide monomers and/or N-(meth)acryloyl amine.

4. An inkjet ink as claimed in claim 1, wherein the ink further comprises one or more di- and/or multifunctional monomers.

5. An inkjet ink as claimed in claim 1, wherein the MEDA is present at 10-45% by weight, based on the total weight of the ink.

6. An inkjet ink as claimed in claim 1, wherein the ink comprises MEDA, isobornyl acrylate (IBOA) and N-vinyl caprolactam (NVC).

7. An inkjet ink as claimed in claim 1, wherein the ink is substantially free of tetrahydrofurfuryl acrylate (THFA).

8. An inkjet ink as claimed in claim 1, wherein the ink further comprises a radiation-curable oligomer.

9. An inkjet ink as claimed in claim 1, wherein the ink further comprises a resin.

10. An inkjet ink as claimed in claim 9, wherein the resin is a chlorinated polyolefin.

11. An inkjet ink as claimed in claim 9, wherein the resin is present at 0.1-5% by weight, based on the total weight of the ink.

12. An inkjet ink as claimed in claim 9, wherein the ink is substantially free of water and volatile organic solvent.

13. A method of inkjet printing, comprising jetting the ink as claimed in claim 9 onto a substrate and curing the ink.

14. A method as claimed in claim 13, wherein the ink contains a chlorinated polyolefin resin and the substrate is composed of polyolefin.

15. A method as claimed in claim 14, wherein the substrate is composed of polypropylene.

Description

EXAMPLES

Example 1

[0042] Two inks were prepared. The inks had formulations as shown in Table 1.

TABLE-US-00001 TABLE 1 Ink formulations Component Ink 1, wt % Ink 2, wt % IBOA 18 18 MEDA 21.88 21.88 NVC 16.5 16.5 DDDA 20 20 UV12 0.2 0.2 CP343-1 2 0 CN964A85 0 2 EPD 0.85 0.85 ITX 0.8 0.8 BP 2.88 2.88 Irgacure 184 1.88 1.88 TPO 8.01 8.01 Cyan pigment dispersion 6 6 Byk 307 1 1 Total 100 100

[0043] IBOA, MEDA, NVC and DDDA are monomers, as defined herein. UV12 is a stabiliser. CP343-1 is a chlorinated polyolefin. CN964A85 is a urethane acrylate oligomer. EPD, ITX, BP, Irgacure 184 and TPO are photoinitiators. The cyan pigment dispersion contains PEA (59.0 wt %), UV12 (1.0 wt %), Solsperse 32000 (10.0 wt %), Heliogen blue (30.0 wt %). BYK307 is a surfactant.

[0044] The inks were prepared by first weighing the monomers into a suitable mixing vessel, placing the vessel under the mixing head of a Silverson stirrer and starting the stirrer. The polyolefin was added, were required, and the mixture stirred until all the polymer particles had dispersed. The temperature was monitored throughout to ensure that the temperature did not exceed 60 C. The remaining components were added to the mixture and the mixture stirred for a further five minutes.

Example 2

[0045] Each of the above ink formulations was coated on to a range of substrates using a K 2 applicator bar (12 m wet film). The resulting films were cured using a standard mercury arc lamp supplied by Jenton, full power 25 m/min2 passes (approximately 2,700 mW/cm.sup.2 and total dose of 764 mJ/cm.sup.2.

[0046] Adhesion of the inks to the substrates were measured by assessing scratch resistance and using a cross hatch tape removal test. The test is as follows. Score surface with an elcometer/blade to form a cross hatch area and apply scotch 3m610 tape across the scored area. After applying pressure, remove the tape and assess for ink removal from the substrate. A good result would typically have no more than 15% of the ink removed by the tape from the substrate. The results are set out in Table 2.

TABLE-US-00002 TABLE 2 Ink adhesion. Substrate Adhesion, ink 1 Adhesion, ink 2 Polycarbonate Good Good PETG Good Good Polystyrene Good Good Fluted polypropylene Good Poor

Example 3

[0047] One ink containing MEDA was prepared, along with a comparative ink containing THFA in place of MEDA, as in Example 1. The inks had formulations as shown in Table 3.

TABLE-US-00003 TABLE 3 Ink formulations Component Ink 3, wt % Comparative ink 1, wt % IBOA 12 12 MEDA 34.9 0 THFA 0 34.9 NVC 24 24 UV12 0.4 0.4 Photomer 6210 10.5 10.5 ITX 4.0 4.0 BAPO 2.8 2.8 TPO 2.8 2.8 Cyan pigment dispersion 8.6 8.6 Total 100 100

[0048] IBOA, MEDA, THFA and NVC are monomers, as defined herein. UV12 is a stabiliser. Photomer 6210 is an aliphatic urethane diacrylate oligomer. ITX, BAPO and TPO are photoinitiators. The cyan pigment dispersion contains PEA (59.0 wt %), UV12 (1.0 wt %), Solsperse 32000 (10.0 wt %), Heliogen blue (30.0 wt %).

Example 4

[0049] Each of the above ink formulations was coated on to a range of substrates using a K 2 applicator bar (12 m wet film). The resulting films were cured using a standard mercury arc lamp supplied by Jenton, full power 25 m/min2 passes (approximately 2,700 mW/cm.sup.2 and total dose of 764 mJ/cm.sup.2).

[0050] Adhesion of the inks to the substrates was measured by measuring the % area of ink removed using Scotch 3M 600 tape according to the ISO Standard Method BS EN ISO 2409 as described in Example 2. The results are set out in Table 4.

TABLE-US-00004 TABLE 4 Ink adhesion. Substrate Adhesion, ink 3 Adhesion, comparative ink 1 PVC banner Good Good Semi-rigid PVC Good Good Self-adhesive vinyl Good Good Polyester Good Poor

[0051] Therefore THFA, which has good adhesion to these substrates, can be replaced by MEDA with no loss in adhesion performance. In fact, adhesion to polyester is better for the ink of the invention containing MEDA than the comparative ink containing THFA.

Example 5

[0052] Four inks were prepared, one of the invention (ink 4) and three comparative inks (comp. inks 2-4), as in Example 1. The inks had formulations as shown in Table 5.

TABLE-US-00005 TABLE 5 Ink formulations Comp. ink 2, Comp. ink 3, Comp. ink 4, Component Ink 4, wt % wt % wt % wt % IBOA 12 12 12 12 NVC 24 24 24 24 MEDA 35.1 0 0 0 PEA 0 34.9 35.1 0 THFA 0 0 0 35.1 Photomer 9.5 10.5 9.5 9.5 6210 UV12 0.4 0.4 0.4 0.4 Cyan pigment 0 8.6 0 0 dispersion Black pigment 6.5 0 6.5 6.5 dispersion Darocur TPO 8.5 2.8 8.5 8.5 Irgacure 819 0 2.8 0 0 ITX 4 4 4 4 Total 100 100 100 100

[0053] IBOA, NVC, MEDA, PEA and THFA are monomers, as defined herein. Photomer 6210 is an aliphatic urethane diacrylate oligomer. UV12 is a stabiliser. Darocur TPO, Irgacure 819 and ITX are photoinitiators. The cyan pigment dispersion contains PEA (59.0 wt %), UV12 (1.0 wt %), Solsperse 32000 (10.0 wt %), Heliogen blue (30.0 wt %). The black pigment dispersion contains PEA (46.5 wt %), UV12 (1.5 wt %), Efka 7731 (12.0 wt %) and carbon black (40.0 wt %). Efka 7731 is a high molecular weight dispersant.

Example 6

[0054] Inks 3 and 4 and comparative inks 1-4 were printed onto a Banner PVC substrate and cured using a Mimaki UJF3042 benchtop printer, in 8-pass mode, equipped with a 385 nm UV-LED lamp (500 mW/cm.sup.2 output and total dose of 120 mJ/cm.sup.2).

[0055] Adhesion of the inks to the substrates was measured by measuring the % area of ink removed using Scotch 3M 600 tape according to the ISO Standard Method BS EN ISO 2409 as described in Example 2. The results are set out in Table 6.

TABLE-US-00006 TABLE 6 Ink adhesion Ink 3, Ink 4, Comp. ink Comp. ink Comp. ink Comp. ink wt % wt % 1, wt % 2, wt % 3, wt % 4, wt % % ink 0 0 0 11 30 0 removed

[0056] As can be seen from Table 6, inks 3 and 4 containing MEDA perform equally to comparative inks 1 and 4 containing THFAall of the ink remains intact, showing that MEDA is a good substitute for THFA. In contrast, comparative inks 2 and 3 containing PEA, are less adhesive than comparative inks 1 and 4 containing THFA, showing that PEA is not a good substitute for THFA.