Inks

Abstract

A radiation-curable ink comprising (i) a colorant; (ii) a cyclohexyl acrylate of the Formula (1) wherein each R independently is C1-4-alkyl; n has a value of 1, 2 or 3; and Q is H or CH3; (iii) a monoacrylate which comprises a cyclohexyl and/or cyclopentyl ring; and (iv) 0 to 5 wt % of N-vinyl caprolactam; and (v) cyclic trimethylolpropane formal acrylate. ##STR00001##

Claims

1. A radiation-curable ink comprising: (i) a colorant; (ii) a cyclohexyl acrylate of the Formula (1): ##STR00010## wherein: each R independently is C.sub.1-4-alkyl; n has a value of 1, 2 or 3; and Q is H or CH.sub.3; (iii) a monoacrylate which comprises a cyclohexyl and/or cyclopentyl ring; (iv) 0 to 5 wt % of N-vinyl caprolactam; (v) cyclic trimethylolpropane formal acrylate; (vi) a compound having a number average molecular weight of up to 1000 and more than one ethylenically unsaturated group; (vii) an acrylate oligomer having a number average molecular weight greater than 1000; (viii) a photoinitiator; (ix) 2-phenoxyethyl acrylate; and (x) optionally a passive resin.

2. The ink according to claim 1 which is free from N-vinyl caprolactam.

3. The ink according to claim 1 wherein component (ii) comprises t-butylcyclohexyl acrylate and/or trimethyl cyclohexyl acrylate.

4. The ink according to claim 1 which comprises at least 10 wt % of component (ii) and at least 10 wt % of component (iii).

5. The ink according to claim 1 which further comprises one or more of the following ingredients: (x) a passive resin; and (xi) a surfactant.

6. The ink according to claim 1 which is free from tetrahydrofurfuryl acrylate.

7. The ink according to claim 1 wherein component (iii) comprises isobornyl acrylate and/or dihydrodicyclopentadienyl acrylate.

8. The ink according to claim 1 which comprises: 0.1 to 20 wt % of component (i); 5 to 40 wt % of component (ii); 5 to 40 wt % of component (iii); 0 to 5 wt % of component (iv); and 5 to 35 wt % of component (v).

9. The ink according to claim 1 which comprises: 0.1 to 20 wt % of component (i); 5 to 40 wt % of component (ii); 5 to 40 wt % of component (iii); 0 to 5 wt % of component (iv); 5 to 35 wt % of component (v); and 0 to 5 wt % of component (vi) a compound having a number average molecular weight of up to 1000 and more than one ethylenically unsaturated group.

10. The ink according to claim 9 which comprises 0.2 to 2 wt % of component (vi).

11. The ink according to claim 1 which comprises: 0.1 to 20 wt % of component (i); 5 to 40 wt % of component (ii); 5 to 40 wt % of component (iii); 0 to 5 wt % of component (iv); 5 to 35 wt % of component (v); and 0 to 6 wt % of component (vii) an acrylate oligomer having a number average molecular weight greater than 1000.

12. The ink according to claim 11 which comprises 0.25 to 6 wt % of component (vii).

13. The ink according to claim 1 which comprises: 0.1 to 20 wt % of component (i); 5 to 40 wt % of component (ii); 5 to 40 wt % of component (iii); 0 to 5 wt % of component (iv); 5 to 35 wt % of component (v); and 0 to 20 wt % of component (viii) a photoinitiator.

14. The ink according to claim 13 which comprises 10 to 13 wt % of component (viii).

15. The ink according to claim 1 which comprises: 0.1 to 20 wt % of component (i); 5 to 40 wt % of component (ii); 5 to 40 wt % of component (iii); 0 to 5 wt % of component (iv); 5 to 35 wt % of component (v); and 0 to 40 wt % of component (ix) 2-phenoxyethyl acrylate.

16. The ink according to claim 1 which comprises: (i) 0.1 to 20 wt % of a colorant; (ii) 5 to 40 wt % of a cyclohexyl acrylate of the Formula (1): ##STR00011## wherein: each R independently is C.sub.1-4-alkyl; n has a value of 1, 2 or 3; and Q is H or CH.sub.3; (iii) 5 to 40 wt % of a monoacrylate other than component (ii) which comprises a cyclohexyl and/or cyclopentyl ring; (iv) 0 to 5 wt % of N-vinyl caprolactam; (v) 5 to 35 wt % of cyclic trimethylolpropane formal acrylate; (vi) 0 to 5 wt % of a compound having more than one ethylenically unsaturated group; (vii) 0 to 10 wt % of acrylate oligomer; (viii) 0 to 20 wt % of a polymerisation initiator; (ix) 0 to 40 wt % of 2-phenoxyethyl acrylate; (x) 0 to 6 wt % of a passive resin; and (xi) 0 to 5 wt % of a surfactant.

17. The ink according to claim 16 which comprises: 0.5 to 15 wt % of component (i); 8 to 35 wt % of component (ii); 8 to 35 wt % of component (iii); <1 wt % of component (iv); 5 to 35 wt % of component (v); 0.2 to 2 wt % of component (vi); 0.25 to 6 wt % of component (vii); 10 to 13 wt % of component (viii); 10 to 30 wt % of component (ix); 0.5 to 5 wt % of component (x); and 0.05 to 3 wt % of component (xi).

18. The ink according to claim 1 having a viscosity of 5 to 50 cP when measured at 25 C.

19. The ink according to claim 1 having a surface tension of 20 to 40 mN/m, when measured at 25 C.

20. A process for printing a substrate comprising ink jet printing a radiation-curable ink onto the substrate and curing the ink, wherein the radiation-curable ink is as defined in claim 1.

21. The process according to claim 20 wherein the radiation-curable ink comprises: (i) 0.5 to 15 wt % of a colorant; (ii) 8 to 35 wt % of a cyclohexyl acrylate of the Formula (1): ##STR00012## wherein: each R independently is C.sub.1-4-alkyl; n has a value of 1, 2 or 3; and Q is H or CH.sub.3; (iii) 8 to 35 wt % of a monoacrylate other than component (ii) which comprises a cyclohexyl and/or cyclopentyl ring; (iv) less than 1 wt % of N-vinyl caprolactam; (v) 5 to 35 wt % of cyclic trimethylolpropane formal acrylate; (vi) 0.2 to 2 wt % of a compound having more than one ethylenically unsaturated group; (vii) 0.25 to 6 wt % of acrylate oligomer; (viii) 10 to 13 wt % of a polymerisation initiator; (ix) 10 to 30 wt % of 2-phenoxyethyl acrylate; (x) 0.5 to 5 wt % of a passive resin; and (xi) 0.05 to 3 wt % of a surfactant.

Description

EXAMPLES

(1) The following abbreviations are used in the Tables below: Mogul E is a carbon black pigment, available from Cabot. Heliogen Blue D7110F is a cyan pigment, available from BASF. TBCHA, TMHCA, IBOA, are as hereinbefore defined. CTFA and PEA UV12 is a 30 wt % suspension of an aluminium tris (N-hydroxy-N-nitroso phenylaminato-OO salt in phenoxy ethyl acrylate. Therefore 0.32 parts of UV12 consisted of 0.096 parts of an aluminium tris (N-hydroxy-N-nitroso phenylaminato-OO salt and 0.224 parts of phenoxy ethyl acrylate having one acrylate group. CN2560 is a tetrafunctional polyester acrylate, available from Sartomer. CN964A85 is an aliphatic polyester based urethane diacrylate oligomer blended with 15% SR306, tripropylene glycol diacrylate, obtained from Sartomer. EFKA 7731 is Efka PX 4731 a dispersant available from BASF. Irgacure 819, Irgacure are photoinitiators.
379 and Irgacure 184 ITX is Speedcure ITX (isopropyl thioxanthone). NVC is N-vinyl caprolactam. CN9012 is a difunctional urethane oligomer, available from Sartomer. PRO20169 is a urethane acrylate oligomer from Sartomer. Paraloid DM55 is a passive resin (a 100% solids acrylic resin), available from Dow. Genomer 5695 is a urethane acrylate oligomer, available from Rahn. Dianal BR113 is a 100% solids acrylic copolymer resin from Dianal America Inc. Byk 307 is BYK-307, a polyether modified polydimethylsiloxane dispersant available from Byk. Byk 3575 is BYK-UV 3575, a crosslinkable dispersant from Byk.

Example 1 and Comparative Examples 1 and 2 and (Black Inks)

(2) Inks were prepared as follows:

(3) A black millbase was prepared by milling Mogul E (40 parts, black pigment) with PEA (46.5 parts), parts Efka 7731 (12 parts) and Florstab UV-12 (1.5 parts).

(4) The black inks were then prepared by mixing the black millbase (8.5 parts) with the remaining ingredients indicated in Table 1 below. The photoinitiators were incorporated by mixing at 40 C.

(5) TABLE-US-00001 TABLE 1 CEx. 1 CEx. 2 Example 1 Raw Comparison Comparison Invention Component Material Amount (%) Amount (%) Amount (%) Component (i) Mogul E 3.4 3.4 3.4 Component (ii) TBCHA 0 0 25 Component IBOA 40 20 15 (iii) Component (iv) NVC 0 0 0 Component (v) CTFA 20 40 20 Other UV-12 0.6 0.6 0.6 Component CN2560 5 5 5 (vii) CN964A85 3 3 3 Other Efka7731 1 1 1 Component Irgacure 4 4 4 (viii) 819 ITX 4 4 4 Irgacure 3 3 3 184 Irgacure 379 2 2 2 Component (ix) PEA 14 14 14 TOTAL 100 100 100 Cure Pass Fail Pass Adhesion Fail Fail Pass

(6) The inks described in Table 1 were applied to PVC, PS, APET using an RK coating machine fitted with a 6 m wire-wound coating bar.

(7) Each drawdown was cured using a bespoke UV curing unit set at 40 m/min and delivering a dose of 160 mJ/cm.sup.2 per pass with a peak intensity of 1120 mW cm2.

(8) The resultant, cured prints were then tested and scored as follows:

(9) Cure:

(10) The prints which were fully cured after 3 or less passes through the UV curing unit were scored Pass. The prints which were not fully cured after the 3 passes were scored Fail.

(11) Adhesion:

(12) The cross hatch adhesion of the fully cured prints to the various substrates (PVC, PS, APET) was measured as described in ASTM test method D3359-B. Prints where 5% or less was removed were scored Pass. If >5% was removed the score was Fail.

(13) Comparative Examples 1 and 2 both have component (ii) missing and comparison example 1C only has a low amount of component (iii)

(14) Discussion of Results:

(15) Comparative Example 1 failed the adhesion test whereas Comparative Example 2 failed both cure and adhesion tests. In contrast, Inventive Example 1 passed both tests. In conclusion component (ii) is required in the inks of the invention.

Examples 2 and 3 and Comparative Example 3 (Cyan Inks)

(16) A cyan millbase was prepared by milling Heliogen Blue D7110F (30 parts, ex-BASF) in PEA (59 parts), Solsperse 32000 (10 parts) and Florstab UV-12 (1 part).

(17) A passive resin solution was prepared by mixing Paraloid DM55 (35 parts), PEA (64 parts) and Florstab UV-12 (1 part) by stirring at high speed at 50 C.

(18) Inks were then prepared by mixing the cyan millbase, passive resin solution and other ingredients as indicated in Table 2 below. The photoinitiators were added with mixing at 40 C.

(19) TABLE-US-00002 TABLE 2 CEx. 3 Example 2 Example 3 Raw Comparison Invention Invention Component Material Amount (%) Amount (%) Amount (%) Component (i) Heliogen 2.60 2.60 2.60 Blue D7110F Component (ii) TMCHA 0 30.00 0 TBCHA 0 0 30.00 Component IBOA 17.00 17.00 17.00 (iii) DCPA 30.00 0 0 Component (iv) NVC 0 0 0 Component (v) CTFA 17.00 17.00 17.00 Component PRO20169 5.00 5.00 5.00 (vii) Component Irgacure 4.00 4.00 4.00 (viii) 819 Irgacure 3.00 3.00 3.00 184 Irgacure 2.00 2.00 2.00 379 ITX 0.80 0.80 0.80 Benzo- 2.00 2.00 2.00 phenone Component (ix) PEA 13.50 13.50 13.50 Component (x) Paraloid 1.75 1.75 1.75 DM55 UV-12 0.50 0.50 0.50 Solsperse 0.85 0.85 0.85 32000 TOTAL 100.00 100.00 100.00 Cure PASS PASS PASS Adhesion FAIL PASS PASS

(20) The inks were tested as described above, except that the RK coating machine was fitted with a 12 m (instead of 6 m) wire-wound coating bar.

(21) Comparative Example 3 is missing component (ii) whereas inventive Examples 2 and 3 comprise component (ii).

(22) Comparative Example 3 failed the adhesion test. In contrast, inventive Examples 2 and 3 passed both cure and adhesion tests to give an overall satisfactory result.

(23) In conclusion, component (ii) is required in the inks of the invention.

Example 4 and Comparative Examples 4 and 5 (Cyan Inks)

(24) Cyan millbases and inks were prepared and tested for cure as described above for Examples 2 and 3 and Comparative Example 2. The resultant inks and the cure results are described in Table 3 below:

(25) TABLE-US-00003 TABLE 3 CEx. 4 CEx. 5 Example 4 Raw Comparison Comparison Invention Component Material Amount (%) Amount (%) Amount (%) Component (i) Heliogen 2.60 2.60 2.60 Blue D7110F Component (ii) TMCHA 12.50 20.00 12.50 TCBHA 12.50 20.00 12.50 Component IBOA 0 0 25.00 (iii) Component (iv) NVC 0 0 0 Component (v) CTFA 30.00 18.20 18.20 Component CN9012 5.00 5.00 5.00 (vii) Component Irgacure 4.00 4.00 4.00 (viii) 819 Irgacure 3.00 3.00 3.00 184 Irgacure 2.00 2.00 2.00 379 ITX 0.80 0.80 0.80 Benzo- 2.00 2.00 2.00 phenone Component (ix) PEA 23.10 19.90 9.90 Component (x) Dianal 1.20 1.20 1.20 BR113 Other Solsperse 0.80 0.80 0.80 32000 UV-12 0.50 0.50 0.50 TOTAL 100.00 100.00 100.00 Cure PASS PASS PASS Wallace Rub FAIL FAIL PASS Test

(26) The Wallace rub test was performed using a Wallace rub tester. This indicated the rub/abrasion resistance of the cured inks. The Wallace rub tester comprised a rotating head holding a circular piece of Avery SAV which is applied to the sample under a defined load and number of revolutions The rub or abrasion resistance is determined by the extent of damage to the cured ink or by the extent of colour or print transfer to the piece of corrugated paper board. The scores were rated 1 to 5, where 5 is no damage (i.e. good abrasion/rub resistance) and 1 is substantial poor damage (i.e. very poor abrasion/rub resistance). A score of less than 4 was a Fail.

(27) Comparative Examples 4 and 5 comprise component (ii) but component (iii) is absent.

(28) Inventive Example 4 comprises all of components (i), (ii), (iii) and (iv).

(29) Both of Comparative Examples 4 and 5 failed both the Wallace Rub test. In contrast, Inventive Example 4 passed both the cure test and the Wallace Rub Test.

(30) In conclusion, component (iii) is required in the inks of the invention.

Examples 5 and 6 and Comparative Example 6 (Cyan Inks)

(31) Cyan millbases and inks were prepared and tested for cure as described above for Examples 2 and 3 and Comparative Example 2.

(32) The resultant inks and the cure results are described in Table 4 below:

(33) TABLE-US-00004 TABLE 4 CEx. 6 Example 5 Example 6 Raw Comparison Invention Invention Component Material Amount (%) Amount (%) Amount (%) Component (i) Heliogen 2.50 2.60 2.60 Blue D7110F Component (ii) TMCHA 0 13.00 14.00 TBCHA 0 12.50 0 Component IBOA 11.90 17.50 17.50 (iii) DCPA 0 0 12.50 Component (iv) NVC 16.50 0 0 Component (v) CTFA 22.90 17.50 17.50 Component CN9012 0 5.00 4.00 (vii) Genomer 2.00 0 0 5695 Component Irgacure 2.00 4.00 4.00 (viii) 819 Irgacure 2.85 3.00 3.00 184 Irgacure 0 2.00 2.00 379 ITX 0 0.80 0.80 Benzo- 0 2.00 2.00 phenone TPO 2.00 0 0 Component (ix) PEA 32.55 16.70 16.70 Component (x) Dianal 2.50 1.00 1.00 BR113 Other UV-12 0.50 0.55 0.55 Solsperse 0.80 0.85 0.85 32000 Byk307 1.00 0 0 Byk 3575 0 1.00 1.00 TOTAL 100.00 100.00 100.00 Cure PASS PASS PASS Adhesion PASS PASS PASS Mar PASS PASS PASS Resistance Embrittle- FAIL PASS PASS ment

(34) In order to perform the tests described in Table 4 above, the inks described in Table 4 were first printed onto substrates using an Accuity Advance HS 3545 UV inkjet printer and cured using Lamp 7. This provided samples of printed substrate carrying cured ink for assessment.

(35) The substrate in the Cure test referred to in Table 4 was PVC and two sheets were printed using Quality and FineArt print modes respectively. The cure test was performed by rubbing the printed PVC with a finger. If prints in both modes were tack-free the cure was scored Pass, whereas a tacky print in either or both modes was scored Fail.

(36) The substrates in the Adhesion test referred to in Table 4 were PVC, PS, PET, Acrylic, PC and Coroplast (PC). Seven sheets were printed with ink using Quality mode. The adhesion of the printed substrates was evaluated as described above in Examples 1 and 2.

(37) The substrate in the Mar Resistance test referred to in Table 4 was Avery SAV and one sheet was printed with ink using Quality mode. The Mar Resistance test referred is an abrasion resistance test. Each of the samples of printed substrate was secured on the reciprocatable table of a Taber Reciprocating Abraser Model 5900 such that the path defined by contact with the looped stylus along the platform stroke length could be accommodated over a clean, clear area of print. A 2N weight was attached to the Taber test arm above the looped stylus and the number of reciprocating cycles was set to 5. After the completion of 5 cycles, the path made by the looped stylus on each sample was examined for damage and scored Pass or Fail.

(38) The Embrittlement test referred to in Table 4 was performed as follows. Each ink was printed onto three, A4 sheets of white PVC of (22 m thickness) as described above, using FineArt mode. After 24 hours, each print was rolled lengthways into a cylinder and struck three times against the top edge of a shelf. Each print was then assessed for any splitting of the print and scored Pass (no splitting) or Fail (visible splitting).

(39) Component (ii) is missing from Comparative Example 6 and NVC is also present in an amount of >5 wt %. In contrast, inventive Examples 5 and 6 both contained component (ii) and were free from NVC.

(40) Comparative Example 6 failed the embrittlement test. In contrast, Inventive Examples 2 and 6 both passed both the embrittlement test.

(41) In conclusion, component (ii) is required in the inks of the invention and the inks of the invention passed the cure, adhesion and mar resistance test (in addition to the embrittlement test) even though they did not contain any NVC.

Example 7 and Comparative Examples 7 and 8 (Magenta Inks)

(42) A magenta millbase was prepared by milling Cinquasia Magenta L4540 (30 parts magenta pigment) with PEA (56.5 parts), Solsperse 32000 (12 parts) and Florstab UV-12 (1.5 parts). Magenta inks were then prepared by mixing the magenta millbase (15 parts) with the remaining ingredients necessary to obtain the formulations described in Table 5 below. The photoinitiators were incorporated by mixing with the other components at 40 C.

(43) TABLE-US-00005 TABLE 5 CEx. 7 CEx. 8 Example 7 Raw Comparison Comparison Invention Component Material Amount (%) Amount (%) Amount (%) Component (i) Cinquasia 5 5 5 Magenta L4540 Component (ii) TMCHA 22 40 16 Component IBOA 22 0 16 (iii) DCPA 20 0 14 Component (iv) NVC 0 0 0 Component (v) CTFA 0 25 20 Component CN9012 2 2 2 (vii) Component Irgacure 3 3 3 (viii) 819 ITX 1 1 1 Esacure 4 4 4 KIP160 Speed- 2 2 2 cure EDB Component (ix) PEA 15 15 15 Component (x) Dianal 1 1 1 BR113 Other UV-12 1 1 1 Solsperse 2 2 2 32000 Byk 3575 1 1 1 TOTAL 100 100 100 Cure Fail Pass Pass Fingernail Fail Fail Pass scratch Film tack Fail Fail Pass

(44) The inks described in Table 5 were applied to Avery Self-adhesive Vinyl using a RK coating machine fitted with a 12 m wire-wound coating bar. Each drawdown was cured using a bespoke UV curing unit set at 40 m/min and output set at 850 W (100 W/cm) and consisted of three layers; the first two layers were cured with 1 pass and the third layer was cured with three passes. The resultant, cured prints were then tested and scored as follows:

(45) The fingernail scratch test was performed by scratching across the cured print with a fingernail. Prints that did not show damage were scored Pass. Prints that showed damage were scored Fail.

(46) The film tack test was performed as follows: 24 hours after curing, a finger was pressed onto the print. Prints that showed no tack were scored Pass, prints that had tack were scored Fail.

(47) The cure was also assessed and rated pass or fail.

(48) Comparative Example 7 is missing Component (v). Comparative Example 8 is missing Component (iii).