Method of preparing encapsulated pigment dispersions which include polyurethane dispersions
First Claim
1. A method of making an encapsulated pigment comprising steps of:
- a) dispersing a pigment using a polymeric dispersant in an aqueous vehicle wherein the polymeric dispersant is selected from the group consisting of acrylic dispersant comprising acrylic and acrylate monomers and polyurethane dispersant and mixtures thereof and wherein the polymeric dispersant has a number average molecular weight of 2,000 to 9,500 daltons;
b) adding at least one encapsulation monomer and at least one aqueous polyurethane dispersion to the aqueous vehicle of step (a) to form a first dispersed pigment/encapsulation monomer/polyurethane dispersion/aqueous mixture and wherein the encapsulation monomer comprises acrylate monomers;
c) dispersing the encapsulation monomer/aqueous mixture using high shear mixing to form a second dispersed pigment/encapsulation monomer/aqueous polyurethane dispersion /aqueous mixture; and
d) polymerizing the encapsulation monomer by adding a polymerization initiator to the second dispersed pigment/encapsulation monomer/aqueous polyurethane dispersion/aqueous mixture.
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Abstract
A process for encapsulating pigment dispersions is provided where a pigment is dispersed with a polymeric dispersant in an aqueous solvent system. An acrylate monomer and a polyurethane dispersion are added and the resultant mixture is polymerized. Optionally, the acrylate monomer/polyurethane mixture may be emulsified in water with an added surfactant or polymeric dispersant and up to 20% acrylic or other vinyl monomers based on the acrylate may be added to the acrylate monomer/polyurethane mixture before polymerization. Such encapsulated pigment dispersions may be used in inkjet inks and are stable to heat, aging test conditions, and solvent challenges. Prints from these inks have better durability.
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Citations
22 Claims
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1. A method of making an encapsulated pigment comprising steps of:
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a) dispersing a pigment using a polymeric dispersant in an aqueous vehicle wherein the polymeric dispersant is selected from the group consisting of acrylic dispersant comprising acrylic and acrylate monomers and polyurethane dispersant and mixtures thereof and wherein the polymeric dispersant has a number average molecular weight of 2,000 to 9,500 daltons; b) adding at least one encapsulation monomer and at least one aqueous polyurethane dispersion to the aqueous vehicle of step (a) to form a first dispersed pigment/encapsulation monomer/polyurethane dispersion/aqueous mixture and wherein the encapsulation monomer comprises acrylate monomers; c) dispersing the encapsulation monomer/aqueous mixture using high shear mixing to form a second dispersed pigment/encapsulation monomer/aqueous polyurethane dispersion /aqueous mixture; and d) polymerizing the encapsulation monomer by adding a polymerization initiator to the second dispersed pigment/encapsulation monomer/aqueous polyurethane dispersion/aqueous mixture. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 20, 21)
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18. A method of making an encapsulated pigment comprising the steps of:
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a) dispersing a pigment using a first polymeric dispersant in an aqueous vehicle, wherein the first polymeric dispersant comprises acrylic and acrylate monomers and wherein the first polymeric dispersant has a number average molecular weight of 2000 to 9500 daltons; b) preparing an aqueous emulsion comprising at least one encapsulation monomer, and least one aqueous polyurethane dispersion and a surfactant or a second polymeric dispersant, wherein the second polymeric dispersant comprises acrylic and acrylate monomers and wherein the encapsulation monomer comprises acrylate monomers; c) adding the aqueous emulsion of step (b) to the aqueous vehicle of step (a) to form a first dispersed pigment/encapsulation monomer/aqueous polyurethane dispersion/aqueous mixture; d) dispersing the encapsulation monomer/aqueous polyurethane dispersion/aqueous mixture using high shear mixing to form a second dispersed pigment/encapsulation monomer/aqueous mixture; and e) polymerizing the encapsulation monomer by adding a polymerization initiator to the second dispersed pigment/encapsulation monomer/aqueous mixture. - View Dependent Claims (19, 22)
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Specification