AQUEOUS INKJET INK FOR NON-ABSORBENT PRINTING SUBSTRATES AND PRINTING PROCESS

Abstract

An inkjet ink includes pigment, dispersing agent, fixing agent, binder and water. The binder is selected from polyurethanes of a low acid value, the dispersing agent has a low acid value, and the fixing agent is a multivalent calcium salt used in a low concentration. The inkjet ink is easy to apply by using commercial inkjet printing presses, has high storage stability, adheres to surfaces that do not absorb water, exhibits high resistance to wiping and is very advantageously capable of being overprinted by other water-based inkjet inks. A printing process is also provided.

Claims

1. An inkjet ink, comprising: a) at least one pigment; b) at least one dispersing agent having an acid value of less than 20 mg KOH/g relative to an entirety of said at least one dispersing agent; c) at least one fixing agent selected from multivalent calcium salts, an amount of said at least one fixing agent ranging between 0.05 and 5 percent by weight relative to an entirety of the inkjet ink; d) at least one binder selected from polyurethanes with an acid value of less than 20 mg KOH/g relative to an entirety of the at least one binder; and e) water; the inkjet ink having a viscosity of less than 30 mPa.Math.s as measured by a cone plate viscometer at 25° C.

2. The inkjet ink according to claim 1, wherein the inkjet ink has a viscosity of less than 20 mPa.Math.s as measured by a cone plate viscometer at 25° C.

3. The inkjet ink according to claim 1, wherein the inkjet ink has a viscosity of less than 10mPa.Math.s as measured by a cone plate viscometer at 25° C.

4. The inkjet ink according to claim 1, wherein said at least one binder is selected from non-ionic and anionic polyurethanes.

5. The inkjet ink according to claim 1, wherein said at least one fixing agent is selected from calcium chloride, calcium acetate, calcium nitrate, and mixtures of calcium chloride, calcium acetate and calcium nitrate.

6. The inkjet ink according to claim 5, wherein said at least one fixing agent is calcium chloride.

7. The inkjet ink according to claim 1, wherein an amount of said at least one binder ranges between 1 and 20 percent by weight relative to an entirety of the inkjet ink.

8. The inkjet ink according to claim 1, wherein an amount of said at least one dispersing agent ranges between 0.1 and 10 percent by weight relative to an entirety of the inkjet ink.

9. The inkjet ink according to claim 1, wherein an amount of said at least one pigment ranges between 1 and 30 percent by weight relative to an entirety of the inkjet ink.

10. The inkjet ink according to claim 1, wherein said at least one pigment is selected from white pigments.

11. The inkjet ink according to claim 1, wherein an amount of the water ranges between 30 and 90 percent by weight relative to an entirety of the inkjet ink.

12. A printing process, comprising: i) providing a printing substrate; ii) printing at least one inkjet ink according to claim 1 onto the printing substrate in an inkjet printing process; iii) drying the inkjet ink printed in step ii); iv) printing at least one further inkjet ink in an inkjet printing process onto the inkjet ink dried in step iii); and v) drying the inkjet ink printed in step iv).

13. The printing process according to claim 12, which further comprises carrying out the drying in steps iii) and v) by heating.

14. The printing process according to claim 12, which further comprises providing the printing substrate with a water absorption capacity of less than 10 g of water per kg of printing substrate.

15. The printing process according to claim 12, which further comprises carrying out step ii) by printing on a plastic surface, a metal surface, or combinations of a plastic surface and a metal surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0058] Utilized Substances

Pigment 1: KRONOS® 2066 95% titanium dioxide)
Pigment 2: TIOXIDE® RDIS (95% titanium dioxide)
Dispersing agent 1: ZETASPERSE® 3800 (polymeric, slightly anionic dispersing agent)
Dispersing agent 2: DISPERBYK-190 (aqueous solution of a high-molecular block copolymer with pigment affine groups, acid value 10 mg KOH/g)
Dispersing agent 3 DISPERBYK-2010 (aqueous emulsion of a structured acrylate polymer with pigment affine groups)
Fixing agent 1: calcium chloride

Binder 1: PrintRite DP 380

[0059] Binder 2: PrintRite DP 375 (aqueous polyurethane dispersion with a solid proportion of 30 to 34%, pH value from 4 to 8)

Binder 3: XW-UM3

[0060] Binder 4: NeoRez® R-9340 (aqueous non-ionic polyester urethane dispersion with a solid proportion of 40%, pH value of 6.8)

Binder 5: NeoRez® D-2301

[0061] Binder 6: Takelac W-6355 (aqueous polycarbonate polyurethane dispersion)
Binder 7: Lupasol® PN 60 (modified polyethylenimine) (COMPARISON)
Binder 8: Antara 430 (styrene N-vinylpyrrolidone copolymer) (COMPARISON)
Binder 9: Luviskol® VA73W (vinylpyrrolidone vinyl alcohol copolymer)

(COMPARISON)

[0062] Wetting agent 1: TEGO® Twin 4000 (siloxane-based wetting agent)
Wetting agent 2: TEGO® Twin 4100 (siloxane-based wetting agent)
Wetting agent 3: TEGO® Twin 4200 (siloxane-based wetting agent)
Wetting agent 4: TEGO® Wet 280 (siloxane-based wetting agent)
Wetting agent 5: TRITON HW-1000 (non-ionic wetting agent)
Defoaming agent 1: SURFYNOL® ADO1
Humectant 1: ethylene glycol
Humectant 2: 1,3-butanediol

[0063] General Methodology

Pigment, dispersing agent, defoaming agent, and water were combined and mixed with a mixer of a high shear force. The mixing continued until no reduction in particle size occurred any longer. Then fixing agent, binder, wetting agent, and humectant were added and mixed again with the mixer of a high shear force until the mixture was homogeneous.
Viscosity was measured at 25° C. each time by using a cone plate viscometer, based on DIN ISO 3219.
Redispersibility of the sediments was measured by rolling the sample container for five minutes at room temperature.
Particle size was measured by using dynamic light scattering.

[0064] Measurements on Storage Stability

Redispersibility of the sediments was measured after a test period of 28 days at 60° C. in a temperature-control cabinet. Only total redispersibility was acceptable.
Changes in viscosity, pH value, and particle size were likewise measured after a 28-day test period at 60° C. in a temperature-control cabinet using the measuring methods described above. Viscosity changes of up to ±1 mPa.Math.s were acceptable. pH value changes of up to −1 were acceptable. Particle size changes of not more than ±80 nm were acceptable.

Example 1

[0065] 15 percent by weight of pigment 1
1.5 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 1
1 percent by weight of wetting agent 1
0.25 percent by weight of defoaming agent 1
10 percent by weight of humectant 1
66.25 percent by weight of water
Viscosity: 3.1 mPa.Math.s
pH value: 8.1
Change in viscosity after test period: +0.4 mPa.Math.s
Change in pH value after test period: −0.1
Sediments redispersible after test period: yes
Change in particle size after test period: acceptable

Example 2

[0066] 15 percent by weight of pigment 1
1.5 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 1
1 percent by weight of binder 2
0.25 percent by weight of defoaming agent 1
10 percent by weight of humectant 1
66.25 percent by weight of water
Viscosity: 2.7 mPa.Math.s
pH value: 8.2
Change in viscosity after test period: +0.4 mPa.Math.s
Change in pH value after test period: −0.1
Sediments redispersible after test period: yes
Change in particle size after test period: acceptable

Example 3

[0067] 15 percent by weight of pigment 1
1.5 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 1
1 percent by weight of wetting agent 3
0.25 percent by weight of defoaming agent 1
10 percent by weight of humectant 1
66.25 percent by weight of water
viscosity: 2.9 mPa.Math.s
pH value: 8.1

[0068] Change in viscosity after test period: 0 mPa.Math.s Change in pH value after test period: 0 Sediments redispersible after test period: yes Change in particle size after test period: acceptable

Example 4

[0069] 15 percent by weight of pigment 1
1.5 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 1
1 percent by weight of wetting agent 4
0.25 percent by weight of defoaming agent
10 percent by weight of humectant 1
66.25 percent by weight of water
Viscosity: 2.9 mPa.Math.s
pH value: 8.3
Change in viscosity after test period: +0.2 mPa.Math.s
Change in pH value after test period: −0.1
Sediments redispersible after test period: yes
Change in particle size after test period: acceptable

Example 5

[0070] 15 percent by weight of pigment 2
1.5 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 4
0.25 percent by weight of defoaming agent 1
10 percent by weight of humectant 2
67.25 percent by weight of water
Viscosity: not determined
pH value: 8.5
Change in viscosity after test period: not determined
Change of ph value after test period: −0.8
Sediments redispersible after test period: yes
Change in particle size after test period: acceptable

Example 6

[0071] 15 percent by weight of pigment 2
1.5 percent by weight of dispersing agent 3
1 percent by weight of fixing agent 1
5 percent by weight of binder 2
0.25 percent by weight of binder 1
5 percent by weight of humectant 1
72.25 percent by weight of water
Viscosity: 4.5 mPa.Math.s
pH value: 8.1
Change in viscosity after test period: 0 mPa.Math.s
Change in pH value after test period: −1
Sediments redispersible after test period: yes
Change in particle size after test period: acceptable

Example 7

[0072] 15 percent by weight of pigment 1
1.5 percent by weight of dispersing agent 2
1 percent by weight of fixing agent 1
5 percent by weight of binder 5
0.25 percent by weight of defoaming agent 1
5 percent by weight of humectant 1
72.25 percent by weight of water
Viscosity: 3.5 mPa.Math.s
pH value: 8.7
Change in viscosity after test period: 0 mPa.Math.s
Change in pH value after test period: −0.6
Sediments redispersible after test period: yes
Change in particle size after test period: acceptable

Example 8

[0073] 15 percent by weight of pigment 1
1.2 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 3
1 percent by weight of wetting agent 5
0.25 percent by weight of defoaming agent 1
10 percent by weight of humectant 1
66.55 percent by weight of water
Viscosity: 2.3 mPa.Math.s
pH value: 8.1
Change in viscosity after test period: +0.1 mPa.Math.s
Change in pH value after test period: −0.2
Sediments redispersible after test period: yes
Change in particle size after test period: acceptable

Example 9

[0074] 15 percent by weight of pigment 2
1.2 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 6
3 percent by weight of wetting agent 5
0.25 percent by weight of defoaming agent 1
10 percent by weight of humectant 1
64.55 percent by weight of water
Viscosity: 5.1 mPa.Math.s
pH value: 8.1
Change in viscosity after test period: not determined
Change in pH value after test period: —0.3
Sediments redispersible after test period: yes
Change in particle size after test period: acceptable

Comparative Example 1

[0075] 15 percent by weight of pigment 1
1.5 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 8
0.25 percent by weight of defoaming agent 1
10 percent by weight of humectant 1
67.25 percent by weight of water
Viscosity: 11.6 mPa.Math.s
pH value: 8.4
Change in viscosity after test period: +12.9 mPa.Math.s
Change in pH value after test period: −0.3
Sediments redispersible after test period: no sediments
Change in particle size after test period: polydisperse mix

Comparative Example 2

[0076] 15 percent by weight of pigment 2
1.5 percent by weight of dispersing agent 2
5 percent by weight of binder 7
5 percent by weight of binder 3
0.25 percent by weight of defoaming agent 1
10 percent by weight of humectant 1
63.25 percent by weight of water
Viscosity: 8.5 mPa.Math.s
pH value: 8.2
Change in viscosity after test period: −0.8 mPa.Math.s
Change in pH value after test period: −0.4
Sediments after test period redispersible: yes
Change in particle size after test period: inacceptable

Comparative Example 3

[0077] 15 percent by weight of pigment 1
1.2 percent by weight of dispersing agent 1
1 percent by weight of fixing agent 1
5 percent by weight of binder 9
0.25 percent by weight of defoaming agent
10 percent by weight of humectant 1
67.55 percent by weight of water
Viscosity: 5 mPa.Math.s
pH value: 8.4
Change in viscosity after test period: +3.2 mPa.Math.s
Change in pH value after test period: −2.1
Sediments redispersible after test period: yes
Change in particles size after test period: unacceptable