Printing process

Abstract

A process for printing on a water-soluble material using a self-dispersible pigment which comprises a carboxy-functional dispersant crosslinked around a pigment core by a crosslinking agent having at least two groups selected from oxetane, carbodiimide, hydrazide, oxazoline, aziridine, isocyanate, N-methylol, keteneimine, isocyanurate and epoxy groups. Also inks, ink-sets, printed material and ink-jet printers.

Claims

1. A process for printing on a water-soluble material using an ink comprising (1.sup.1) 2.5 to 7.5 parts of a self-dispersible pigment which comprises a carboxy-functional dispersant crosslinked around a pigment core by a crosslinking agent having at least two groups selected from oxetane, carbodiimide, hydrazide, oxazoline, aziridine, isocyanate, N-methylol, keteneimine, isocyanurate and epoxy groups; (2.sup.1) 1 to 10 parts of glycerol; (3.sup.1) 0.5 to 5 parts of ethylene glycol; (4.sup.1) 1 to 10 parts of 2-pyrrolidone; (5.sup.1) 0.2 to 2 parts of an acetylenic surfactant; (6.sup.1) 0.001 to 2 parts of biocide; (7.sup.1) 1 to 15 parts of polyethylene glycol 20,000; (8.sup.1) the balance to 100 parts water.

2. The process for printing on a water-soluble material as claimed in claim 1 wherein the self-dispersible pigment comprises one or more of Carbon Black; Pigment Blue 15:3; Pigment Yellow 74 and Pigment Red 122.

3. The process for printing on a water-soluble material as claimed in claim 1 wherein the carboxy-functional dispersant comprises benzyl methacrylate.

4. The process for printing on a water-soluble material as claimed in claim 1 wherein the carboxy-functional dispersant is a copolymer comprising: (i) from 75 to 97 parts of one or more hydrophobic ethylenically unsaturated monomers comprising at least 50 parts of benzyl methacrylate; (ii) from 3 to 25 parts of one or more hydrophilic ethylenically unsaturated monomers having one or more carboxy groups; and (iii) 0 to 1 part of hydrophilic ethylenically unsaturated monomers having one or more hydrophilic non-ionic groups; wherein the parts are by weight.

5. The process for printing on a water-soluble material as claimed in claim 1 wherein the crosslinking agent has at least two epoxy groups.

6. The process for printing on a water-soluble material as claimed in claim 1 wherein the water-soluble material is a polyvinyl alcohol film.

7. The process for printing on a water-soluble material as claimed in claim 1 wherein the process for printing is an ink-jet printing process.

8. A water-soluble material printed by an ink-jet printing process as described in claim 7.

9. A water-soluble material printed by a process as described in claim 1.

10. The water-soluble material as claimed in claim 9 which is a unit-dose pouch either prior to or after filling the unit-dose pouch.

11. The process for printing on a water-soluble material as claimed in claim 1 wherein the ink further comprises 2 to 6 parts of a styrene butadiene latex binder.

12. An ink-jet ink comprising: (1.sup.1) 2.5 to 7.5 parts of a self-dispersible pigment which comprises a carboxy-functional dispersant crosslinked around a pigment core by a crosslinking agent having at least two groups selected from oxetane, carbodiimide, hydrazide, oxazoline, aziridine, isocyanate, N-methylol, keteneimine, isocyanurate and epoxy groups; (2.sup.1) 1 to 10 parts of glycerol; (3.sup.1) 0.5 to 5 parts of ethylene glycol; (4.sup.1) 1 to 10 parts of 2-pyrrolidone; (5.sup.1) 0.2 to 2 parts of an acetylenic surfactant; (6.sup.1) 0.001 to 2 parts of biocide; (7.sup.1) 1 to 15 parts of polyethylene glycol 20,000; (8.sup.1) the balance to 100 parts water.

13. An ink-set comprising two or more different coloured ink-jet inks as described in claim 12.

14. An ink-set comprising a black ink, a cyan ink, a yellow ink and a magenta ink wherein the inks are as described in claim 12 and wherein the pigment in the black ink is carbon black; in the cyan ink is Pigment Blue 15:3; in the yellow ink is Pigment Yellow 74; and in the magenta ink is Pigment Red 122.

15. An ink-set comprising a black ink, red ink, and a white ink wherein the black ink and red ink are as described in claim 12 and wherein the pigment in the black ink is Carbon Black and in the red ink is a mixture of Pigment Red 122 and Pigment Yellow 74 and the white ink comprises a dispersible form of titanium dioxide.

16. The ink-jet ink as claimed in claim 12 wherein the ink further comprises 2 to 6 parts of a styrene butadiene latex binder.

Description

EXAMPLES

(1) The present invention will now be illustrated by the following examples in which all parts are by weight unless stated to the contrary.

(2) Preparation of the Self-Dispersible Pigment

(3) Preparation of the Dispersant

(4) The dispersant was prepared by solution copolymerisation of benzyl methacrylate and methacrylic acid at weight proportions of 78.5 to 21.5 respectively. The dispersant was isolated in the form of a dry solid and had an acid value of 2.5 mmoles of acid groups/g of dispersant.

(5) Preparation of the Dispersant Solution

(6) The dispersant (200 parts) was dissolved in water to make up to 1000 parts and neutralised with potassium hydroxide aqueous solution to give an aqueous solution having a pH of about 9.

(7) Preparation of Mill-Bases

(8) Black Mill-Base

(9) Pigment powder (90 parts of a Carbon Black pigment) and the dispersant solution (180 parts) were mixed together to form a pre-mixture. Water was added to the pre-mixture as appropriate to provide a suitable viscosity for mixing and milling.

(10) The premixture was thoroughly mixed together. After mixing the mixture was transferred to a bead mill containing milling beads. The mixture was then milled for several hours until the desired particle size of approximately 110 nm had been reached. The particle size was the Z averaged particle size as measured by a Malvern Zetasizer

(11) The milling beads were then removed from the milled mixture to give the Black Mill-base.

(12) Magenta Mill-Base

(13) The Magenta Mill-base was prepared in the same way as the Black Mill-base except that a magenta pigment (85 parts of C.I. Pigment 122) and dispersant solution (1) (127.5 parts) were used. For the Magenta Mill-base the milling was continued for several hours until a particle size of approximately 120 nm had been obtained. The particle size was the Z averaged particle size as measured by a Malvern Zetasizer.

(14) The milling beads were then removed from the milled mixture to give the Magenta Mill-base.

(15) Yellow Mill-Base

(16) The Yellow Mill-base was prepared in the same way as the Black Mill-base except that a yellow pigment (100 parts of C.I. Pigment Yellow 74) and dispersant solution (250 parts) were used. For the Yellow Mill-base the milling was continued for several hours until a particle size of approximately 120 nm had been obtained. The particle size was the Z averaged particle size as measured by a Malvern Zetasizer.

(17) The milling beads were then removed from the milled mixture to give the Yellow Mill-base.

(18) Cyan Mill-Base

(19) The Cyan Mill-base was prepared in the same way as the Black Mill-base except that a cyan pigment (150 parts of a C.I. Pigment Blue 15:3) and dispersant solution (225 parts) were used. For the Cyan Mill-base the milling was continued for several hours until a particle size of approximately 120 nm had been obtained. The particle size was the Z averaged particle size as measured by a Malvern Zetasizer.

(20) The milling beads were then removed from the milled mixture. This resulted in Cyan Mill-base (1).

(21) Preparation of Encapsulated Pigment

(22) The mill-bases prepared above were adjusted to a solids content of about 10% by weight by the addition of pure water.

(23) The dispersants in each of the mill-bases were then cross-linked using a cross-linking agent, (Denacol EX-321 obtained from Nagase ChemteX, with weight per epoxy=140, hereafter abbreviated as EX-321). This cross-linked the carboxylic acid groups in the dispersant and thereby encapsulated the pigment. The cross-linking reaction was controlled by the presence of a small amount of boric acid (obtained from Aldrich). The cross-linking reaction was effected by heating the above described mixture to a temperature of about 65 C. for 5 hours. This prepared a range of different Encapsulated pigments with the references as indicated in column 1 of Table 1.

(24) TABLE-US-00001 TABLE 1 Cross-linking Encapsulated Cross-linking Boric acid pigment Mill-base (parts) agent (parts) parts EPS 1 Cyan Mill-base 1 EX321 2.78 (3) (6.3) EPS 2 Magenta Mill-base 1 EX321 1.58 (3) (3.57) EPS 3 Yellow Mill-base 1 EX321 2.16 (3) (4.9) EPS 4 Black Mill-base 1 EX321 2.23 (3) (5.04)
Purification of the Encapsulated Pigment

(25) The encapsulated pigments prepared above in were each purified by means of ultrafiltration. The encapsulated pigment dispersions were diafiltered with pure water. The ultrafiltration membrane was then used to concentrate the encapsulated dispersion back to a solids content of around 10 to 13% by weight.

(26) Example Inks

Example 1

(27) The present invention will now be illustrated by the following examples in which all parts are by weight unless stated to the contrary.

(28) The self-dispersible pigment used were the Pro-Jet APD 1000 pigment dispersions which are available from FUJIFILM Imaging Colorants Limited.

(29) Surfynol 440 is an acetylenic surfactant from Air Products.

(30) Rovene 4111 is a styrene butadiene dispersion from Mallard Creek Polymers. The Tg of Rovene 6102 is 20 C. and the acid number is 50 mgKOH/g. 1,2-Benzisothazolin-3-one was obtained as Proxel GXL (20% solution) from Lonza.

(31) PEG 20K is polyethylene glycol 20,000.

(32) Ink Example 1Red Ink

(33) TABLE-US-00002 Formulation At 100% Active (Wt %) Component Projet APD 1000 Magenta 3.35 Projet ADP 1000 Yellow 0.65 Glycerol 3.75 Ethylene glycol 1.25 2 Pyrrolidone 95% 5.00 Surfynol 440 0.24 1,2-Benzisothazolin-3-one 0.015 Rovene 4111 5.50 PEG 20K 7.00 DI Water to 100 Properties pH 8.84 Viscosity at 32 C. cP 12.68 Surface Tension D/cm 34.48
Ink Example 2Black Ink

(34) TABLE-US-00003 Formulation At 100% Active (Wt %) Component Projet APD 1000 Black 4.00 Glycerol 3.75 Ethylene glycol 1.25 2 Pyrrolidone 95% 5.00 Surfynol 440 0.24 1,2-Benzisothazolin-3-one 0.015 Rovene 4111 5.50 PEG 20K 6.45 DI Water to 100 Properties pH 8.85 Viscosity at 32 C. cP 12.68 Surface Tension D/cm 35.8

(35) The inks were printed through a StarFire SG1024 re-circulating print head from FUJIFILM Dimatix. The StarFire SG1024 re-circulating print head is commonly only used with non-aqueous inks due to a tendency of its face plate to wet when used with aqueous inks, thus adversely effecting printer performance.

(36) However the example ink printed without any problems. The print head was photographed with a JetXpert drop watcher. There was no evidence of any face plate wetting with any of the inks of the present invention.

(37) The sustainability of the inks when printed through the StarFire SG1024 print head was evaluated by printing an image with a nozzle check pattern combined with a solid block. The solid block of color measured 30 mm in length, this value is later used in calculating the longer term feathering/latency effect. The nozzle test pattern is used to quantify nozzles which drop out over the course of the test.

(38) After 15 minutes no significant degradation was observed and no missing nozzles were observed.

(39) The latency of the inks in the StarFire SG1024 print head was evaluated by printing an image file that consists of a series of lines and block. Each block is timed to print 1 second from the previous block, the last block representing 6 seconds. For each block, the top portion should be clearly printed as it represent a baseline if there are latency problems the lower section will have a feathered appearance.

(40) After 6 seconds no latency problems were seen with either ink.

(41) PVA Dissolution Test

(42) The printed PVA substrate was dissolved in water with continuous stirring. The solution was dissolved and filtered using a 0.3 micron filter paper. The particles on the filter paper were assessed by examination under a microscope and particle size measurements were carried out on the dispersed particles.

(43) Rub Test

(44) A lint free wipe was soaked in Persan detergent and then gently rubbed against the PVA print sample (5 to 7 times). No significant transfer was observed.

(45) Print Robustness Against Detergent

(46) The PVA print was soaked in Persan detergent at 5 C., 25 C., 40 C. and 60 C. respectively. A comparative PVA print was printed using a white ink minus the latex component.

(47) While the Example inks showed an excellent performance the white ink lacking latex binder peeled off from the substrates within a few hours.

(48) Ink Stain Test

(49) A test image was printed on PVA substrates using the different ink samples. The printed sample was stapled between 2 pieces of fabric and stapled. The sample was placed in water at 5 C. in water in the presence or 2 ml/L detergent solution with continuous stirring for 30 minutes. When the PVA substrate had dissolved the test fabric was evaluated for any visual stain. The test was repeated at different temperatures; 25 C., 40 C. and 60 C.

(50) The fabrics used had a dimension of 411 cm and were obtained from Testfabrics, inc., PA, USA. Twelve different fabrics were evaluated. They were Filament Acetate, SEF (Modacrylic), Filament Triacetate, Bleached Cotton, Creslan 61 (Acrylic), Dacron 54 (Polyester), Dacron 64 (Polyester), Nylon 66 (Polyamide), Orlan 75 (Acrylic), Spun Silk, Polypropylene (Polyolefin), Viscose (Rayon) and Wool (Worsted). A black test fabric was used to test the staining for white ink.

(51) Image Quality

(52) PVA films typically have a matt and glossy side. The red Example Ink 1 and black Example Ink 2 were printed onto the glossy and matt sides of M8630 PVA from Monosol. The print quality was then evaluated and there was no discernible difference between the L*a*b* parameters of the prints on the matt and glossy sides.

(53) Ink-Set Example

(54) An ink set was prepared using the inks shown in Table 1. The inks of the ink-set were printed onto various PVA films sourced from Monosol and Aicello using an ink-jet printer with a StarFire SG1024 print head. All prints were of an acceptable quality.

(55) TABLE-US-00004 TABLE 1 Ink Set Example Component Black Ink Cyan Ink Magenta Ink Yellow Ink Red Ink White Ink PEG 20K 6.45 6.50 6.50 6.50 7.00 6.30 2-Pyrrolidone 5.00 5.00 5.00 5.00 5.00 5.00 Ethylene Glycol 1.25 1.25 1.25 1.25 1.25 1.25 Glycerol 3.75 3.75 3.75 3.75 3.75 3.75 Surfynol 440 0.24 0.24 0.24 0.24 0.20 0.30 Proxel GXL 0.015 0.015 0.015 0.015 0.015 0.015 Pigment Dispersion I 4.00 4.00 5.00 4.00 3.35 12.00 Pigment Dispersion II 0.65 Rovene 4111 (Tg = 69 C.) 4.00 4.00 4.00 4.00 4.00 4.00 DI Water to 100% to 100% to 100% to 100% to 100% to 100%

(56) TABLE-US-00005 TABLE 2 Ink set ink properties Component Black Ink Cyan Ink Magenta Ink Yellow Ink Red Ink White Ink Foam No No No No No No pH 8.90 8.89 8.92 8.75 8.84 8.48 Surface Tension (Dyne/cm) 33.29 33.75 33.49 32.90 34.48 33.62 Viscosity (cPs) @ 32 C. 11.0-13.0 15.88 15.51 14.47 15.45 15.34 15.14