Encapsulated pigment for ink-jet ink formulations nad methods of producing same

Abstract

Encapsulated pigment for use in ink-jet ink formulations, improved ink-jet ink formulations using the encapsulated pigment, and methods for producing same. The pigment particles are pretreated with a polymer that is soluble in organic solvents, but substantially insoluble in water. The pigment particles are added to a solution of polymer/organic solvent, mixed to form a paste then collected after driving off the solvent. The encapsulated pigment can be used to prepare an ink-jet ink formulation by grinding it in a water carrier with a conventional polymer dispersant.

What is claimed is:  
     
         1 . Encapsulated pigment particles for use in ink-jet ink formulations, which pigment particles are at least partially encapsulated with one or more polymer materials, which polymer materials are at least partially soluble in an organic solvent, but substantially insoluble in water, and which polymer materials have at least one polar segment and at least one non-polar segment.  
     
     
         2 . The encapsulated pigment particles of  claim 1  wherein the monomer contributing to the non-polar segment of the polymer material is selected from the group consisting of polydimethylsiloxane, propoxylated allyl methacrylate, nonylphenyl polypropylene glycol acrylate, stearyl methacrylate, ethylene glycol, ether methacrylate and alkyl(meth) acrylates.  
     
     
         3 . The encapsulated pigment particles of  claim 1  wherein the monomer contributing to the polar segment of the polymer material is selected from the group consisting of hydroxyethyl methacrylate, hydroxy terminated monomer, combined with or without acid-amine monomers.  
     
     
         4 . The encapsulated pigment particles of  claim 1  wherein the average pigment particle is substantially totally encapsulated with said polymer material.  
     
     
         5 . The encapsulated pigment particles of  claim 2  wherein the monomer contributing to the polar segment of the polymer material is selected from the group consisting of hydroxyethyl methacrylate, a hydroxy terminated monomer, combined with or without acid-amine monomers, and the encapsulated pigment particles are substantially totally encapsulated with said polymer material.  
     
     
         6 . The encapsulated pigment particles of  claim 1  wherein the monomer contributing to the non-polar segment is selected from the alkyl(meth) acrylates, nonylphenyl polypropylene glycol, and 2-(2′hydroxy-5′-methacryloxyethyl-phenyl)-2H-benzotriazole.  
     
     
         7 . The encapsulated pigment particles of  claim 6  wherein the monomer contributing to the polar segment is hydroethyl methacrylate.  
     
     
         8 . A method for producing encapsulated pigment particles suitable for ink-jet ink formulations, which method comprising: a) dissolving an organic soluble polymer material in an organic solvent, which polymer material is comprised of at least one polar segment and at least one non-polar segment; b) introducing an effective amount of pigment particles into the resulting polymer/solvent solution, thereby forming a slurry; and c) mixing the slurry at effective conditions to form a paste containing at least partially encapsulated pigment particles.  
     
     
         9 . The method of  claim 8  wherein the monomer contributing to the non-polar segment of said polymer material is selected from the group consisting of polydimethylsiloxane, propoxylated allyl methacrylate, nonylphenyl ppg acrylate, stearyl methacrylate, ethylene glycol, ether methacrylate and alkyl(meth) acrylates.  
     
     
         10 . The method of  claim 8  wherein the monomer contributing to the polar segment of said polymer material is selected from the group consisting of hydroxyethyl methacrylate, hydroxy terminated monomer, combined with or without acid-amine monomers.  
     
     
         11 . The method of  claim 8  wherein the organic solvent is selected from the group consisting of acetone, isopropyl alcohol, ethylene glycol, pyrrolidane and propylene glycol.  
     
     
         12 . The method of  claim 8  wherein the paste of step c) is washed with water and dried.  
     
     
         13 . The method of  claim 8  wherein the organic solvent is also used as a humectant in a final ink formulation and thus is not driven off.  
     
     
         14 . The method of  claim 8  wherein the monomer contributing to the non-polar segment is selected from the alkyl(meth)acrylates, nonylphenyl polypropylene glycol, and 2-(2′hydroxy-5′-methacryloxyethyl-phenyl)-2H-benzotriazole.  
     
     
         15 . The method of  claim 14  wherein the monomer contributing to the polar segment is hydroethyl methacrylate.  
     
     
         16 . The method of  claim 14  wherein the monomer contributing to the non-polar segment is an alkyl(meth )acrylate.  
     
     
         17 . The method of  claim 16  wherein the alkyl(meth) acrylate is selected from n-butyl acrylate and methyl methacrylate.  
     
     
         18 . The method of  claim 14  wherein: i) the monomer contributing to the polar segment of said polymer material is selected from the group consisting of hydroxyethyl methacrylate, a hydroxy terminated monomer, combined with or without acid-amine monomers; and ii) the organic solvent is selected from the group consisting of acetone, isopropyl alcohol, ethylene glycol, pyrrolidane and propylene glycol.  
     
     
         19 . The method of  claim 18  wherein the organic solvent is also used as a humectant in a final ink formulation and thus is not driven off.  
     
     
         20 . The method of  claim 18  wherein the paste of step c) is washed with water and dried.  
     
     
         21 . An ink-jet ink formulation comprising: a) an aqueous carrier; b) an effective amount of pigment particles that are at least partially encapsulated with a first polymer material, which first polymer material is at least partially soluble in organic solvent but which is substantially insoluble in water and which first polymer material contains at least one polar segment and at least one non-polar segment; and c) a second polymer material dispersant that is at least partially soluble or miscible in water, and which is comprised of a polar segment and a non-polar segment.  
     
     
         22 . The ink formulation of  claim 21  wherein the monomer contributing to the non-polar segment of said first polymer material is selected from the group consisting of polydimethylsiloxane, propoxylated allyl methacrylate, nonylphenyl ppg acrylate, stearyl methacrylate, ethylene glycol, ether methacrylate and alkyl(meth) acrylates.  
     
     
         23 . The ink formulation of  claim 21  wherein the monomer contributing to the polar segment of said first polymer material is selected from the group consisting of hydroxyethyl methacrylate, hydroxy terminated monomer, combined with or without acid-amine monomers.  
     
     
         24 . The ink formulation of  claim 21  wherein the monomer contributing to the non-polar segment is selected from the alkyl(meth)acrylates, nonylphenyl polypropylene glycol, and 2-(2′hydroxy-5′-methacryloxyethyl-phenyl)-2H-benzotriazole.  
     
     
         25 . The ink formulation of  claim 21  wherein the monomer contributing to the polar segment is hydroethyl methacrylate.  
     
     
         26 . The ink formulation of  claim 24  wherein the monomer contributing to the non-polar segment is an alkyl(meth ) acrylate.  
     
     
         27 . The ink formulation of  claim 26  wherein the alkyl(meth) acrylate is selected from n-butyl acrylate and methyl methacrylate.  
     
     
         28 . The ink formulation of  claim 21  wherein there is also present at least one additive selected from the group consisting of co-solvents, humectants, biocides, penetrants, surfactants, anti-coagulation agents, anti-curling agents, buffers, chelating agents, and anti-bleed agents.  
     
     
         29 . A method for preparing an ink-jet ink formulation comprising: a) dissolving an organic soluble first polymer material in an organic solvent, which first polymer material contains at least one polar segment and at least one non-polar segment; b) introducing an effective amount of pigment particles into the resulting polymer/solvent solution thereby forming a slurry of pigment particles in the polymer/solvent solution; c) mixing the slurry at effective conditions to form a paste; d) driving off at least a portion of the solvent, thereby resulting in pigment particles that are at least partially encapsulated with the first polymer material; and e) grinding the encapsulated pigment particles in a water carrier with a water soluble or water miscible second polymer material for an effective amount of time to result in a final particle size from about 100 to 300 nm, which second polymer material is comprised of a polar segment and a non-polar segment and which second polymer material is a dispersant with respect to the pigment particles  
     
     
         30 . The method of  claim 29  wherein the monomer contributing to the non-polar segment of said polymer material is selected from the group consisting of polydimethylsiloxane, propoxylated allyl methacrylate, nonylphenyl ppg acrylate, stearyl methacrylate, ethylene glycol, ether methacrylate and alkyl(meth) acrylate.  
     
     
         31 . The method of  claim 29  wherein the monomer contributing to the polar segment of said polymer material is selected from the group consisting of hydroxyethyl methacrylate, hydroxy terminated monomer, combined with or without acid-amine monomers.  
     
     
         32 . The method of  claim 30  wherein the monomer contributing to the non-polar segment is an alkyl(meth ) acrylate.  
     
     
         33 . The method of  claim 32  wherein the alkyl(meth) acrylate is selected from n-butyl acrylate and methyl methacrylate.  
     
     
         34 . The method of  claim 29  wherein the organic solvent is selected from the group consisting of acetone, isopropyl alcohol, ethylene glycol, 2-pyrrolidone and propylene glycol.  
     
     
         35 . The method of  claim 29  wherein the paste of step c) is washed with water and dried.  
     
     
         36 . The method of  claim 29  wherein the organic solvent is also used as a humectant in a final ink formulation and thus is not driven off.  
     
     
         37 . The method of  claim 21  wherein: i) the monomer contributing to the polar segment of said polymer material is selected from the group consisting of hydroxyethyl methacrylate, hydroxy terminated monomer, combined with or without acid-amine monomers; and ii) the organic solvent is selected from the group consisting of acetone, isopropyl alcohol, ethylene glycol, 2-pyrrolidone and propylene glycol.  
     
     
         38 . The method of  claim 37  wherein the monomer contributing to the non-polar segment is an alkyl(meth ) acrylate.  
     
     
         39 . The method of  claim 38  wherein the paste of step c) is washed with water and dried.  
     
     
         40 . The method of  claim 37  wherein the organic solvent is also used as a humectant in a final ink formulation and thus is not driven off.