Pigment encapsulated latex aqueous colorant dispersions
AssigneeKoh-I-Noor Rapidograph, Inc.
InventorFortunato J. Micale
Life of this patent
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Abstract
A process for modifying colorants which comprise an active ingredient of solid primary particles in the submicron range by an encapsulation with polymer starting materials that are not substantially altered during the process. Writing fluids, textile colorants and cosmetic inks are disclosed wherein the intrinsic physical qualities of a solid active material are modified to create a stable aqueous dispersion with performance and rheology characteristic of the polymer, and not of the active ingredient.
Claims34
A process for producing a colorant comprising a stable aqueous suspension of submicron sized particles of polymer encapsulated active ingredient, wherein a polymer matrix surrounds a core of solid active ingredient, said process comprising the steps of:
- A. Mixing together an organic solvent, a polymer soluble in said solvent but substantially insoluble in water and an active ingredient which substantially is insoluble in water to form a homogeneous mixture, wherein said solvent is characterized by a vapor pressure higher than water and said mixing is continued until said active ingredient has dispersed in said solvent without appreciable agglomeration;
- and
- B. Adding said solvent/polymer/active ingredient mixture to water, in a concentration range of 1.0% to 50.0%, by weight, and dispersing until an emulsion results wherein solvent/polymer/active ingredient comprises a discontinuous phase, having a size less than 4 microns with water as the continuous phase, werein said dispersing step is done under conditions where interfacial tension between the organic solvent and the water is less than approximately 10 dynes/cm.;
- and
- C. Removing substantially all of said solvent to define an aqueous suspension of said particles.
A process for producing a writing fluid comprising a low viscosity aqueous suspension of submicron sized particles of polymer encapsulated pigment, wherein a polymer matrix surrounds a solid core of pigment, said process comprising the steps of:
- A. Mixing together an organic solvent, a film-forming polymer soluble in said solvent but substantially insoluble in water and a pigment comprising submicron sized primary particles, which substantially are insoluble in water, to form a homogeneous mixture, wherein said solvent is characterized by a vapor pressure higher than water and said mixing is continued until said pigment has been dispersed homogeneously as primary particles in said solvent without appreciable agglomeration;
- and
- B. Adding said solvent/polymer/pigment mixture to water, in a concentration range of 1.0% to 50.0%, by weight, and dispersing until an emulsion results wherein solvent/polymer/pigment droplets with an average diameter less than 2 microns comprise a discontinuous phase in water as the continuous phase, wherein said dispersing step is done under conditions where interfacial tension between the organic solvent and the water is less than approximately 10 dynes/cm., and substantially each droplet of discontinuous phase has one or more primary pigment particles therein;
- and
- C. Removing substantially all of said solvent to define an aqueous suspension of submicron-sized particles of pigment with smooth outer polymer surfaces.
A process for creating a textile colorant which comprises creating a polymer matrix that surrounds a core of solid colorant, said process comprising the steps of:
- A. Mixing together an organic solvent, a polymer soluble in said solvent but substantially insoluble in water and colorant primary particles, wherein said solvent is characterized by a vapor pressure higher than water and said mixing is continued until said colorant has been dispersed as primary particles in said solvent without appreciable agglomeration;
- and
- B. Adding said solvent/polymer/colorant mixture to water, in a concentration range of 1.0% to 50.0% by weight, and dispersing until an emulsion results wherein solvent/polymer/colorant comprises a discontinuous droplet phase in water as the continuous phase, wherein said dispersing step is done under conditions where interfacial tension between the organic solvent and the water is less than approximately 10 dynes/cm. and is continued until a stable emulsion of droplets less than 2 microns average diameter results;
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- C. Removing substantially all of said solvent to define encapsulated colorant particles that are adapted to be formed as a film upon a textile surface and then set by application of heat sufficient to raise the polymer encapsulation above its glass transition temperature.
A process for encapsulating submicron sized pigment particles for use in cosmetics, wherein a polymer matrix surrounds a solid pigment particle and the resulting particles are in an aqueous suspension, said process comprising the steps of:
- A. Mixing together an organic solvent, a polymer soluble in said solvent but substantially insoluble in water and a pigment which substantially is insoluble in water to form a homogeneous mixture, wherein said solvent is characterized by a vapor pressure higher than water and said mixing is continued until said active ingredient has dispersed homogeneously in said solvent, without appreciable agglomeration;
- and
- B. Adding said solvent/polymer/pigment mixture, in a concentration range of 1.0% to 50.0%, by weight, to water which contains a nonionic surfactant and dispersing until an emulsion results wherein solvent/polymer/pigment droplets with an average diameter less than 5 microns comprise a discontinuous phase in water as the continuous phase, wherein said dispersing step is done under conditions where interfacial tension between the organic solvent and the water is less than approximately 10 dynes/cm.;
- and
- C. Removing substantially all of said solvents to define an aqueous mixture comprising encapsulated pigment in suspension;
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- D. Concentrating the encapsulated colorant to a desired concentration for admixture with a cosmetic carrier fluid.
Dependencies are inferred from the claim text.