De-inkable inks with high bio-renewable content

Abstract

The present invention relates to a printing ink composition comprising one or more keratin-based pigment(s) and water, wherein the one or more keratin-based pigment(s) has an average particle size of no more than 3000 nm.

Claims

1. A printing ink composition comprising one or more keratin-based pigment(s) and water, wherein the one or more keratin-based pigment(s) has an average particle size of no more than 3000 nm, wherein average particle size is Dv50 measured by dynamic light scattering wherein the keratin-based pigment(s) are milled.

2. The composition according to claim 1, wherein the one or more keratin-based pigment(s) has an average particle size of no more than 2000 nm, preferably no more than 1000 nm, more preferably no more than 600 nm.

3. The composition of claim 1 comprising from about 30% to about 90% (w/w) water, preferably from about 40% to about 80% (w/w) water, more preferably from about 50% to about 70% (w/w) water.

4. The composition of claim 1 comprising from about 5% to about 15% (w/w) of one or more keratin-based pigment(s), preferably from about 7% to about 12% (w/w) of one or more keratin-based pigment(s).

5. The composition of claim 1, comprising an acid-functional binder selected from the group consisting of acrylic, polyurethane, styrene-maleic acid, polycarbonate, styrene-maleic anhydride and co-polymers thereof.

6. The composition of claim 1, wherein the acid-functional binder further comprises hydroxyl groups.

7. The composition of claim 1, wherein the composition comprises no more than 5% (w/w) of a polymeric binder selected from styrene maleic-anhydride, styrene-maleic acid, acrylics, polyurethanes, polycarbonates and co-polymers thereof.

8. The composition of claim 1, wherein the composition is an inkjet ink.

9. The composition of claim 1, wherein the carrier liquid for the ink is water and a humectant derived from a renewable source.

10. The composition of claim 9, wherein the humectant is selected from the group consisting of glycerol, ethylene glycol, diethylene glycol, monopropylene glycol and combinations thereof, preferably wherein the humectant is glycerol.

11. The composition according to claim 1, comprising a preservative is derived from a renewable source.

12. The composition of claim 11, wherein the preservative is selected from the group consisting of 2-phenoxyethanol and sodium benzoate.

13. The composition of claim 1, comprising a wetting agent or dispersant, preferably wherein the wetting agent or dispersant comprises sodium lauryl sulfate.

14. A method of de-inking a substrate comprising the ink composition of claim 1 printed and dried onto the substrate said method comprising immersing the printed substrate in a de-inking solution comprising alkaline water at pH 7.1-14.0, preferably 8.0-12.0, more preferably 10.0-11.0.

15. The method of claim 14, wherein the pH of the de-inking solution is maintained by the use of organic amines selected from the group consisting of primary, secondary and tertiary aliphatic amines.

16. A method of preparing a printing ink composition comprising one or more keratin-based pigment(s) and water, wherein the one or more keratin-based pigment(s) has an average particle size of no more than 3000 nm, said method comprising milling a dispersion comprising water and one or more keratin-based pigment(s), wherein average particle size is Dv50 measured by dynamic light scattering.

17. The method of claim 16, wherein milling is performed for up to 60 minutes, preferably for up to 45 minutes.

18. A method of printing an image on a substrate, wherein said method comprises applying a printing ink composition according to claim 1 onto the substrate and curing.

19. The method of claim 18 wherein the printing ink composition is milled prior to application onto the substrate.

20. The method of claim 18 wherein curing is thermal curing, preferably at a temperature of no more than 220 C.

21. The method of claim 18 wherein the substrate is selected from plastic, textile, paper, metal, glass, polymeric film and ceramic substrates, preferably wherein the substrate is selected from textile and paper.

22. A method of de-inking a substrate comprising: i) applying a printing ink composition according to claim 1 onto the substrate and drying to provide a printed substrate; and ii) immersing said printed substrate into a de-inking solution comprising alkaline water at pH 7.1-14.0, preferably 8.0-12.0, more preferably 10.0-11.0.

23. The method of claim 22 wherein the printing ink composition is milled prior to application onto the substrate.

Description

EXAMPLES

(1) The invention is further described by the following non-limiting examples which further illustrate the invention, and are not intended, nor should they be interpreted to, limit the scope of the invention.

(2) Example 1: A dispersion of the red keratin particles was prepared in solution according to the following process.

(3) TABLE-US-00001 TABLE 1 Example 1 Keratin Pigment Dispersion Formulation Calculated Amount in % In Formulation BRC BRC Ingredient Formulation (Excluding Water) Content Content WS Keratin 23.0 g 90.5% 90% 81.45% Pigment Red.sup.1 Sodium 2.0 g 7.9% 100% 7.9% Lauryl Sulfate Proxel GXL 0.27 g 1.1% 0% 0% Airase 5355 0.15 g 0.6% 0% 0% TOTAL 25.42 g 100% 89.35% (Water) 124.83 g Not Included .sup.1Supplied by Wool Source.

(4) To a glass beaker equipped with a mechanical stirrer was added 124.83 g de-ionised water (conductivity less than 10 microSiemens); followed by 2.0 g Sodium Lauryl Sulphate (dispersant); 0.27 g Proxel GXL (anti-microbial); and 0.15 g Airase 5355 (defoamer). The mixture was stirred whilst 23.0 g of a powder of WS Pigment Red (a keratin pigment having a particle size (Dv50) of 2,032 nm as measured by DLS) was added, with further stirring for 60 minutes to wet out the pigment particles. The resulting pre-mix was then added to an Eiger 50 laboratory mill, fitted with 0.8 mm Ytterbium-Zirconium Oxide grinding media. The mill was started and samples withdrawn periodically to measure the particle size by DLS using a Malvern Zetasizer. After 20 minutes of milling, the Dv50 was 574 nm. After 45 minutes of milling the particle size had increased again to Dv50 1,343 nm and finally after 60 minutes of milling was measured to be 1,543 nm. The dispersion was measured in terms of colour strength compared to the premix. It was found that the colour strength was increased in the dispersion with the smaller particle size. This is a very important result as the colour strength of the final dispersion was found to be significantly higher than the initial colour strength of the pre-mix (prior to milling). The results shown in Table 2 also demonstrate that the colour strength increased with a reduction in the particle size.

(5) Table 2 below shows that the milling time required to reduce the WS Pigment Red particles used in Example 1 down to about 600 nm is only 20 minutes and indeed slightly longer milling times resulted in some increase in particle size. These data demonstrate that a very energy efficient milling process can be used in the present invention to provide pigments having the requisite particle size. The increase in the colour strength after only 20 minutes of milling is also quite remarkable, increasing to over 107% of the original strength. Hence, milling the particles provides keratin-based pigments within increased colour strength.

(6) TABLE-US-00002 TABLE 2 Comparison of Colour Strength and particle size for Example 1 Dispersion with Milling Time Milling Colour Strength (%) Dv50 Particle Size Time (% STR-SWL) (micron) 0 mins 100% 2.032 20 mins 107.21% 0.574 45 mins 106.28% 1.343 60 mins 104.22% 1.543

(7) Further evidence of the increased colour strength of the milled dispersion was obtained by preparing drawdown samples on inkjet coated paper using a No. 6 Kbar. The pre-mix gave a dull shade with some reasonable edge definition. The 45 minutes milled sample showed a very noticeable increase in the colour strength and perfect edge definition. It is hypothesised that the reason for this result is that milling down the pigment particles (preferably to around 600 nm or less although the effect is achieved by milling down to around 1500 nm), results in partial unravelling of the keratin helical structure, which exposes more of the coloured groups on the surface of the keratin.

(8) TABLE-US-00003 TABLE 3 Example 2 Keratin Pigment Dispersion Formulation Amount in % In Formulation BRC Calculated Ingredient Formulation (Excluding Water) Content BRC Content WS Keratin 23.0 g 89.4% 90% 80.46% Pigment Red.sup.1 Sodium Lauryl 2.30 g 8.9% 100% 8.9% Sulfate Proxel GXL 0.27 g 1.1% 0% 0% Airase 5355 0.15 g 0.6% 0% 0% TOTAL 25.72 g 100% 89.36% (Water) 124.83 g .sup.1Supplied by Wool Source.

(9) To a glass beaker equipped with a mechanical stirrer was added 124.83 g de-ionised water (conductivity less than 10 microSiemens); followed by 2.3 g Sodium Lauryl Sulphate (dispersant); 0.27 g Proxel GXL (anti-microbial); and 0.15 g Airase 5355 (defoamer). The mixture was stirred whilst 23.0 g of a powder of WS Pigment Red (a keratin pigment having a particle size (Dv50) of 2,032 nm as measured by DLS) was added, with further stirring for 60 minutes to wet out the pigment particles. The resulting pre-mix was then added to an Eiger 50 laboratory mill, fitted with 0.8 mm Ytterbium-Zirconium Oxide grinding media. The mill was started and samples withdrawn periodically to measure the particle size by DLS using a Malvern Zetasizer. After 30 minutes of milling, the Dv50 was 593 nm. The dispersion was measured in terms of colour strength compared to the premix. It was found that the colour strength was increased in the dispersion with the smaller particle size. This is a very important result as the colour strength of the final dispersion was found to be significantly higher than the initial colour strength of the pre-mix (prior to milling). The results shown in Table 4 also demonstrate that the colour strength increased with a reduction in the particle size. The viscosity of the dispersion was measured using a Brookfield DVII+Pro, fitted with a 00 spindle, and found to 5.13 cP at 32 C.

(10) TABLE-US-00004 TABLE 4 Comparison of Colour Strength and particle size with Milling Time Colour Strength (%) Milling Time (% STR-SWL) Dv50 Particle Size (micron) 0 mins 100% 2.032 30 mins 105.17% 0.593

(11) This second example with an optimised milling time for particle size liberated particles with a Dv50 particle size of 593 nm, again demonstrating s significant increase in colour strength of the dispersion after milling.

(12) TABLE-US-00005 TABLE 5 Example 3 Finished Ink Formulation Calculated Amount in % In Formulation BRC BRC Ingredient Formulation (Excluding Water) Content Content Example 2 25.0 g 71.4% 89.36% 63.80% Dispersion (RR4415-45) Glycerine 10.0 g 28.6% 100% 28.60% TOTAL 35.0 g 100% 92.40%

(13) Preparation of a simple ink for subsequent evaluation by inkjet printing was performed using the following process. To 25 g of a separate sample of the Example 2 dispersion was added 10 g of glycerine. The particle size of the input material was measured at 593 nm by DLS. The mixture was stirred using a magnetic stirrer in a glass beaker for about 60 minutes and then the physical properties of the ink were measured.

(14) The viscosity of the ink was measured using a Brookfield DVII+Pro, fitted with a 00 spindle, and found to 6.57 cP at 32 C. and 6.08 cP at 35 C.

(15) The resulting Example 3 ink was then loaded into a Dimatix DMP print cartridge and the printer set so the print head temperature was 32 C. and the print head angle was 2.5. The print resolution was set to 1,700 DPI. A 2 cm2 cm print block was achieved in a single pass. The printed image on Panama cotton showed a very well resolved edge, with a good, uniform colour saturation across the block of printed colour and good wetting of the cotton weave. Furthermore, the edges and the corners for the square block were very well resolved indicating that the print quality was good.

(16) The resulting prints were then heat cured at 160 C. for two minutes using a standard thermal heat press.

(17) Films of the ink from Example 3 were also produced by drawdown, using a 24-micron ink film which was applied to PET and then transfer printed onto Panama cotton and dried for five minutes at 150 C. The ink coverage of such drawdown generated samples replicates closely the same ink laydown expected from inkjet printing.

(18) Washfastness of the drawdown printed Panama cotton was tested as follows. Under very aggressive test conditions, using a 1% solution of standard washing detergent (Persil, Unilever), the pigment was partially removed from Panama cotton, and was awarded a washfastness rating of 2-3, where 4 is completely fixed and 1 is completely removed. This is an average rating for a textile pigment ink. It should be noted that this inventive example did not contain any additional optional binder.

(19) The Resolubility of the inks was measured using the standard method of casting a film of the ink on a glass slide, allowing the ink to air dry for at least one hour, and then immersing the ink in either deionised water or a 1% solution of Tergitol 15-S-7 in deionised water. In both cases, the resolubility was awarded 4 by visual inspection, in that the dried ink was removed from the glass slides as small flakes which were still present as flakes in the washing solution after 60 minutes. In this context, perfect resolubility is 4 and no Resolubility is 1. The Resolubility test is developed to mimic what would happen in an inkjet printing head if the ink is permitted to dry out in the air, and then could be permanently damaged if the ink which has dried is not resoluble. A Resolubility rating of 4 indicates a very good fit for industrial textile printing.

(20) The de-inking was tested by submerging the fabrics (in this case Panama cotton) into a basic solution for 2 hours at 60 C. Three basic solutions were examined with pH 10-13. In all cases, facile de-inking was observed. In particular, when using pH 10, 11.5 and 13.0, the de-inking after 2 hours was awarded a 4 rating. The de-inking is rated as 4 being completely removed and leaving a pristine white surface (as though the ink had been bleached from the surface) and 1 being absolutely no removal of the ink.

(21) TABLE-US-00006 TABLE 6 Resistance Properties Wet Rub Dry Rub Ink Fastness.sup.2 Fastness Resolubility De-inkability Example 3 2-3 2-3 4 4 Keratin-based pigment ink Comparative Ink.sup.1 2-3 4-5 2-3 1 .sup.1538PIKY1 Xennia Emerald Red (Sun Chemical) based on standard organic pigment that has been optimized for inkjet printing. The comparative ink is also water-based and comprises glycol co-solvents. .sup.2The test methods for wet and dry rub fastness are taken from physical rub tests (ISO 105 X12 and ASTM D 5264).

(22) As demonstrated by the results in Table 6, the inks of the present invention provide improved resolubility and de-inkability compared with the comparative ink.