Method of making sacrificial coating for an intermediate transfer member of indirect printing apparatus
View Patent ↗A method of making a sacrificial coating composition is disclosed. The method comprises emulsifying an oil with surfactant to form an oil-in-water emulsion; and combining ingredients comprising (i) at least one polymer, (ii) at least one hygroscopic material, (iii) the oil-in water emulsion and (iv) water to produce the sacrificial coating composition. The at least one polymer is selected from the group consisting of a hydrophilic polymer, a latex comprising polymer particles dispersed in a continuous liquid phase, or mixtures thereof.
1. An method of making a sacrificial coating composition, the method comprising:
emulsifying an oil with surfactant and water to form an oil-in-water emulsion, the oil being selected from the group consisting of a silicone oil, a perfluoroether oil and a hydrocarbon oil and mixtures thereof and the surfactant comprising a branched secondary alcohol ethoxylate with 6 to 12 moles of ethylene oxide (EO);
combining ingredients comprising (i) at least one polymer, (ii) at least one hygroscopic material, (iii) the oil-in water emulsion and (iv) water to produce the sacrificial coating composition,
wherein the at least one polymer is polyvinyl alcohol.
2. The method of claim 1 , wherein combining ingredients comprises mixing the at least one polymer, the at least one hygroscopic material and water to form a polymer mixture and then combining the polymer mixture and the oil-in-water emulsion.
3. The method of claim 1 , wherein the emulsifying comprises mixing the oil and surfactant at a high shear speed of at least 6000 RPM.
4. The method of claim 1 , wherein the oil is loaded in the surfactant at a concentration ranging from about 0.1 wt % to about 15 wt %, relative to the combined weight of the oil and surfactant.
5. The method of claim 1 , wherein the method further comprises heating the polyvinyl alcohol in water to a temperature of at least about 80° C. for a time ranging from about 30 minutes to about 90 minutes prior to combining ingredients to dissolve the polyvinyl alcohol.
6. The method of claim 1 , wherein the polyvinyl alcohol has a hydrolysis degree ranging from about 75% to about 99.5% and weight average molecular weight ranging from about 8000 to about 30,000 g-mole −1 .
7. The method of claim 6 , wherein the viscosity of the polyvinyl alcohol in a DI water solution at 20° C. ranges from about 3 cps to about 100 cps, wherein the solution contains 4% by weight polyvinyl alcohol relative to the total weight of polyvinyl alcohol and DI water in the solution.
8. The method of claim 1 , wherein the sacrificial coating composition further comprises a waxy maize starch.
9. The method of claim 8 , wherein the waxy maize starch comprises more than 90 weight percent amylopectin.
10. The method of claim 1 , wherein the at least one hygroscopic material is selected from the group consisting of glycerol, sorbitol, glycols, vinyl alcohols, xylitol, maltitol, polymeric polyols, glyceryl triacetate, glycouril, ionic liquids and mixtures thereof.
11. The method of claim 1 , wherein the surfactant is a nonionic surfactant with hydrophile lipophile balance (HLB) value of from 4 to 15.
12. The method of claim 1 , wherein the surfactant comprises a mixture of a first surfactant and a second surfactant that is different from the first surfactant, the first surfactant having a hydrophile lipophile balance (“HLB”) value ranging from about 8 to about 15 and the second surfactant having an HLB value ranging from about 4 to about 10, the HLB value for the first surfactant being higher that the HLB value for the second surfactant.
13. The method of claim 1 , wherein the oil is selected from the group consisting of a silicone oil, a perfluoroether oil and mixtures thereof.