Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1998-05-04
2001-01-09
Marcheschi, Michael (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S482000, C106S492000, C423S335000, C423S339000
Reexamination Certificate
active
06171384
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a high surface area amorphous silicate pigment, and a method of making the same. More particularly, the invention relates to a high surface area amorphous silicate pigment which is useful in a variety of recording media coatings, especially coatings for ink jet printer recording sheets, and a method of making the same.
BACKGROUND OF THE INVENTION
Ink jet printing systems can generally be divided into two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The ink stream is then perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field which adjusts the trajectory of each droplet, thereby directing the droplet to a gutter for recirculation or to a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled in drop-on-demand systems unless it is to be placed on the recording medium.
Ink jet inks may be water-based, or may employ an alkylene glycol or other solvent base. Regardless of the type of ink used, the surface chemistry of the recording medium largely determines the print quality. Therefore, recording media for ink jet and other printing systems have utilized pigment-containing coatings to sorb the solvent of the ink (i.e., dry the ink) and hold its dye-component to maximize the color development and visual effect of the ink. It is known that highly porous, high surface area pigments are especially effective in this regard, as such pigments maximize the amount of ink dye positioned in the path of light reflected from the substrate to the eye, while at the same time minimizing the dye absorbed in the pigment layer or paper substrate.
The drawback of these highly porous, high surface area pigments has been that they also rapidly build viscosity in aqueous systems and coating compositions as loading levels increase. Consequently, coating suspensions of known highly porous/high surface area pigments can only achieve about 10-20% pigment solids before their viscosities exceed practical levels for processing and application. This disadvantageously limits the amount of high surface area pigment that can be effectively utilized in recording media coatings, thereby lowering the solids content and reducing the weight of the coatings. Coating performance suffers as a consequence.
OBJECTS OF THE INVENTION
It is accordingly an object of the invention to provide a high porosity, high surface area amorphous silicate pigment which can be loaded at high levels into coatings for ink jet recording media and other recording media.
Other objects will become apparent from the detailed description of the invention provided below.
SUMMARY OF THE INVENTION
Briefly, the invention is an amorphous silicate pigment having a pore volume of at least about 4.0 ml/g as measured by mercury intrusion, a BET surface area of at least about 300 m
2
/g, preferably about 400 to 500 m
2
/g, and an Al
2
O
3
content of about 2.0 to 10.0 wt %, preferably about 3.0 to 7.0 wt %. The invention preferably has a linseed oil absorption of about 180 to 250 cc/100 g, more preferably about 190 to 220 cc/100 g. The invention preferably has a pore volume as measured by mercury porosimetry of about 4 to 7 cc Hg/g with a pore size maximum of about 0.005 to 0.030 &mgr;m diameter, more preferably a pore volume of about 5 to 6 cc Hg/g with a pore size maximum of about 0.014±0.003 &mgr;m diameter. The invention preferably has an average particle size as measured by laser light scattering of about 2 to 8 &mgr;m, more preferably about 4 to 6 &mgr;m. The invention preferably exhibits a CTAB surface area of about 150 to 300 m
2
/g, more preferably about 170 to 250 m
2
/g.
The method of the invention involves the addition of a reactive source of aluminum to a reaction medium during the precipitation of a silicate pigment. The temperature of the reaction medium during the precipitation reaction is controlled between about 50 to 85° C. Preferably, the reactive source of aluminum is sodium aluminate, aluminum chloride and/or aluminum sulfate (alum), and is more preferably alum.
The invention also encompasses a coating for a print recording substrate, the coating containing a binder and an amorphous silicate pigment having the physical characteristics described above. Preferably, the coating is in the form of an aqueous slurry containing at least 30% pigment solids of an amorphous silicate pigment having the physical characteristics described above such that the Brookfield viscosity of the pigment slurry at 10 rpm is less than about 10,000 cps.
The invention further encompasses a print recording medium comprising a print recording substrate and an amorphous silicate pigment having the physical characteristics described above.
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Conley Donald P.
Loock Gary W.
Preston Barry W.
Withiam Michael C.
Crimaldi Kenneth
J. M. Huber Corp.
Koons, Jr. Robert A.
Marcheschi Michael
Pepper Hamilton LLP
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