# US 2014/0155535 A1 · Method of preparing encapsulated pigment dispersions with minimal free polymer

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- Number: US 2014/0155535 A1
- Document ID: US20140155535A1
- Status: Published application
- Kind: A1
- Application number: 14/117,897
- Filed: 2011-12-15
- Published: 2014-06-05
- Earliest claimed: 2011-07-14
- Assignees: E. I. Du Pont de Nemours and Company
- Inventors: Hee Hyun Lee; Michael Joseph Otley; Michael Stephen Wolfe; Tristan Williams
- Web page: https://patentgrep.com/patent/US20140155535A1

## CPC

- C09C 3/10: Treatment with macromolecular organic compounds {(C09C3/006 takes precedence)}
- C08G 18/0823: {containing carboxylate salt groups or groups forming them}
- C08G 18/12: using two or more compounds having active hydrogen in the first polymerisation step
- C08G 18/348: {Hydroxycarboxylic acids}
- C08G 18/44: Polycarbonates
- C08G 18/664: {with compounds of group C08G18/3203}
- C08G 18/7614: {containing only one aromatic ring}
- C09B 67/0013: {with polymeric coatings}
- C09D 11/322: Pigment inks
- C09D 11/326: characterised by the pigment dispersant
- C09D 175/04: Polyurethanes
- C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer
- C01P 2004/84: one phase coated with the other
- C08F 220/1807: {C7-(meth)acrylate, e.g. heptyl (meth)acrylate or benzyl (meth)acrylate}
- C08L 33/10: Homopolymers or copolymers of methacrylic acid esters
- C09C: TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES (treatment of materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone C04B14/00, C04B18/00, C04B20/00); PREPARATION OF CARBON BLACK {; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS}
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C09B: ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES {, e.g. PIGMENTS}; MORDANTS; LAKES (fermentation or enzyme using processes to synthesise a desired chemical compound C12P)
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

A process for encapsulating pigment dispersions is provided where a pigment is dispersed with a polymeric dispersant in an aqueous solvent system. The free polymer dispersant in the pigment dispersion is limited to less than 0.12 grams per gram of pigment. This dispersed pigment is then encapsulated by adding acrylate monomers and optionally acrylic and vinyl monomers and polymerizing. In the encapsulated pigment dispersion the weight ratio of final free polymer to polymer found to the final encapsulated pigment is less than 0.9. The free polymer dispersant is measured by a centrifugation method and the final free polymer is measured by a density gradient centrifugation method. 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.

## Claims

### Claim 1

A method of making an encapsulated pigment dispersion comprising steps of
a) dispersing a pigment using a polymeric dispersant in an aqueous vehicle wherein the polymeric dispersant not bound to the pigment is less than 0.12 grams per gram of pigment in the pigment dispersion, and the polymer dispersant bound to the pigment is less than 0.33 grams per gram of pigment, where the polymeric dispersant not bound to the pigment is measured by a centrifugation method;
b) adding at least one encapsulation monomer to the aqueous vehicle of step (a) to form a first dispersed pigment/encapsulation monomer/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 mixture;
d) polymerizing the encapsulation monomer by adding a polymerization initiator to the second dispersed pigment/encapsulation monomer/aqueous mixture;
wherein for the final encapsulated pigment dispersion the weight ratio of final free polymer to bound polymer is less than 0.9 and the final free polymer is measured by a density gradient centrifugation method.

### Claim 2 (depends on 1)

The method of claim 1 where the weight ratio of free polymer to polymer bound in the final encapsulated pigment is less than 0.75 as measured by the density gradient centrifugation method.

### Claim 3 (depends on 1)

The method of claim 1 where the weight ratio of free polymer to polymer bound in the final encapsulated pigment is less than 0.60 as measured by the density gradient centrifugation method.

### Claim 4 (depends on 1)

The method of claim 1 where the polymeric dispersant not bound to the pigment is less than 0.1 grams per gram of pigment in the pigment dispersion where the polymeric dispersant is measured by a centrifugation method; and the weight ratio of free polymer to polymer bound to the final encapsulated pigment is less than 0.6 as measured by the density gradient centrifugation method.

### Claim 5 (depends on 1)

The method of claim 1, wherein the weight ratio of encapsulation monomer to pigment is from 0.1 to 10.

### Claim 6 (depends on 1)

The method of claim 1, wherein the weight ratio of encapsulation monomer to pigment is from 0.15 to 5.

### Claim 7 (depends on 1)

The method of claim 1, wherein the weight ratio of encapsulation monomer to pigment is from 0.25 to 1.

### Claim 8 (depends on 1)

The method of claim 1 wherein the final free polymer bound to the final encapsulated pigment is less than 0.25 grams per gram of pigment as measured by the density gradient centrifugation method.

### Claim 9 (depends on 1)

The method of claim 1, wherein the polymeric dispersant is selected from the group consisting of acrylic dispersant comprising acrylic and acrylate monomers and polyurethane dispersant and mixtures thereof.

### Claim 10 (depends on 1)

The method of claim 1 wherein the polymeric dispersant is substituted with crosslinkable moieties where the crosslinkable moieties are selected from the group consisting of acetoacetoxy, acid, amine, epoxy, hydroxyl, blocked isocyanates and mixtures thereof.

### Claim 11 (depends on 10)

The method of claim 10 wherein the polymeric dispersant with substituted with crosslinkable moieties is reacted with a crosslinking agent where the crosslinking agent is chosen from acetoacetoxy, acid, amine, anhydride, epoxy, hydroxyl, isocyanates, blocked isocyanates and mixtures thereof.

### Claim 12 (depends on 1)

The method of claim 1 where the polymeric dispersant is crosslinked after the pigment is dispersed and before the encapsulation monomer is added.

### Claim 13 (depends on 1)

The method of claim 1 wherein the pigment dispersion of step (a) is purified prior to step (b).

### Claim 14 (depends on 1)

The method of claim 1, wherein the encapsulation monomer is selected from the group consisting of benzyl methacrylate, butyl methacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, lauryl methacrylate, stearyl methacrylate, phenyl methacrylate, phenoxyethyl methacrylate, methacrylonitrile, glycidyl methacrylate, p-tolyl methacrylate, sorbyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, phenyl acrylate, phenoxyethyl acrylate, glycidyl acrylate, p-tolyl acrylate, sorbyl acrylate, ethoxytriethyleneglycol methacrylate, 2-(2-ethoxyethoxy) ethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-ethoxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, di- and tri-methacrylates, and mixtures thereof.

### Claim 15 (depends on 1)

The method of claim 1, wherein the encapsulation monomer further comprises an acrylic monomer that is at most 20 weight percent of the acrylate monomer.

### Claim 16 (depends on 7)

The method of claim 7, wherein the acrylic monomer is selected from the group consisting of methacrylic acid, acrylic acid, maleic acid, maleic acid monoester, itaconic acid, itaconic acid monoester, crotonic acid, crotonic acid monoester, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate, N,N-diethylaminoethyl acrylate, t-butylaminoethyl methacrylate, t-butylaminoethyl acrylate and mixtures thereof.

### Claim 17 (depends on 1)

The method of claim 1, wherein the encapsulation monomer further comprises at least one vinyl monomer which is at most 50 weight percent of the acrylate monomer, said vinyl monomer is selected from the group consisting of styrene, alpha-methyl styrene, substituted styrenes, N-alkyl acrylamides, N-alkyl methacrylamides, vinyl acetate, vinyl butyrate, vinyl benzoate, and mixtures thereof.

### Claim 18 (depends on 1)

The method of claim 1, wherein the polymeric dispersant is a structured polymeric dispersant selected from the group consisting of block polymer dispersant, branched polymer dispersant, graft star polymer dispersant, and mixtures thereof.