ENCAPSULATION OF SOLID PARTICLES
A particle composition includes one or more particles comprising a pigment material and a polymeric coating layer at least partially surrounding the pigment particle and stanchions for particle to particle bridging extending from the coating layer. The particle composition can further include discrete particle separators between the particles of pigment material. The stanchions and particle separators contribute to a reduced particle density in the particle composition.
1 . A particle composition comprising:
one or more particles comprising a pigment material and a polymeric coating layer at least partially surrounding the pigment particle; and
stanchions for particle to particle bridging extending from the coating layer.
2 . The particle composition according to claim 1 further comprising discrete particle separators between the particles of pigment material.
3 . The particle composition according to claim 2 , wherein the stanchions for particle to particle bridging are made of a polymeric material, and wherein a polymeric material comprising the polymeric coating layer and the polymeric material of the stanchions are the same or different, and is from 0.01 to 60 wt % based on weight of the polymeric material.
4 . The composition according to claim 1 , wherein the stanchions for particle to particle bridging on average have a measured length between 10 nm (nanometers) and 500 nm.
5 . The composition according to claim 1 , wherein the stanchions for particle to particle bridging measure a width of less than about 2× the radius of a coated particle from which each stanchion extends.
6 . The composition according to claim 1 , wherein an average number of stanchions is from about less than 0.1 to about 6 stanchions per coated particle of the particle composition.
7 . The composition according to claim 1 , wherein the particle has a refractive index, and the polymeric material has a refractive index different than the refractive index of the particle.
8 . The composition according to claim 1 , wherein the pigment material has a brightness value, and the particle composition has a brightness value, as determined by Tappi Test Method T 452 om-08, that is the same or higher than the brightness of the pigment material.
9 . The composition according to claim 1 , wherein the polymeric material is an addition polymerizable polymer selected from alkyl(meth)acrylate.
10 . The composition according to claim 1 , wherein the polymeric material is selected from the group consisting of emulsion polymers consisting of melamine formaldehyde, urea formaldehyde, alkyl(meth)acrylate, styrene, isocyanate and a polyol.
11 . The composition according to claim 1 , wherein the polymeric coating comprises a material selected from the group consisting of gellable colloid, carboxy methyl cellulose, gelatin, gelatin-gum arabic, melamine formaldehyde, methylol melamine, urea formaldehyde, dimethylol urea, methylated dimethylol urea, methylated melamine formaldehyde, methylated methylol melamine, a gelatin-anionic polymer, alkyl acrylate, alkyl methacrylate, alkylacrylate-acrylic acid copolymer, or reaction product with any of the foregoing.
12 . The composition according to claim 1 , wherein the polymeric coating is a reaction product of two wall forming components selected from the group consisting of a diacid and a diol, a diester and a diol, a metal salt of dibasic acid and a dihalide, glycol ester and diacid, diacid chloride and diol, ethylene carbonate and diacid, anhydride and diol, diphenol and diacid, diacetate of diphenol and diacid, alkali metal salt of diphenol and a diacid halogen, a diamine and a dianhydride, or a tetramine and a dianhydride.
13 . The composition according to claim 3 , wherein the discrete particle separators are made of the polymeric material of the stanchions or coating layer.
14 . The composition according to claim 2 , wherein the particle separators have a particle size range between 1 nm to 2 um.
15 . The composition according to claim 2 , wherein the particle separators have a median particle size from 5 nm to 1500 nm.
16 . The composition according to claim 1 , wherein a ratio by weight of polymer to pigment material is from 10 to about 60 wt %.
17 . The composition according to claim 1 , wherein the particle composition comprises a filler for a paper substrate which at loading levels of up to 35% by weight of the substrate results in an opacity value as determined by Tappi method T 425, for the paper substrate which is equal or greater than a paper substrate filled with two times the equivalent weight of pigment without the polymer coating.
18 . The composition to claim 1 , wherein the pigment is selected from the group consisting of titanium dioxide, carbon black, mica, silica, calcium carbonate, barium sulfate, zinc oxide, lead oxide, zinc sulfate, iron oxide, talc, clays, kaolinite, montmorillonite, smectite, illite, and chlorite.
19 . The composition according to claim 18 , wherein the pigment is titanium dioxide.
20 . The composition according to claim 1 , wherein the particle composition has an oil absorption of from 14 to 30 grams oil per 100 grams of the particle composition.
21 . The composition according to claim 1 , wherein the particle composition is selected to have a zeta potential from greater than −180 mV (millivolts) to less than +60 mV.
22 . The composition according to claim 1 , wherein the particle composition is cationic.
23 . A substrate coated with the composition according to claim 3 , wherein a ratio by weight of polymeric material to coated particle composition is from 10 wt % to about 60 wt %, and the substrate with the particle composition has a gloss value higher than a gloss value of the substrate with uncoated pigment material.
24 . The composition according to claim 3 , wherein a ratio by weight of polymeric material to coated particle composition is from 10 wt % to less than 60 wt %, and the particle composition has a density value at least 32% lower than a density value of the pigment particle.
25 . The composition according to claim 1 , wherein the particle composition has a density of less than less than a density of the pigment material when uncoated.