Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-06-06
2003-07-29
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031900, C106S031700, C106S031860, C106S031750, C106S031650
Reexamination Certificate
active
06599353
ABSTRACT:
TECHNICAL FIELD
This invention relates to writing compositions, instruments, and methods and, more particularly, to erasable, shear-thinning writing compositions.
BACKGROUND OF THE INVENTION
Erasable, graphite-containing liquid writing compositions have been proposed for use in writing instruments to combine the features of pens and pencils. Writing instruments including these liquid graphite-containing compositions are similar both to pens, in that they require no sharpening, no advancing, and low application pressure, and to pencils, in that they can be used to make markings on a substrate, such as paper, which subsequently can be erased from the substrate.
SUMMARY OF THE INVENTION
According to one aspect of the invention, an erasable, shear-thinning writing composition includes a shear-thinning additive and graphite particles in a liquid.
According to another aspect of the invention, an erasable, shear-thinning writing composition includes a shear-thinning additive and graphite particles dispersed in a liquid, wherein the composition has a shear-thinning index between about 0.01 and 0.8.
In accordance with another aspect of the invention, a writing instrument includes a reservoir containing an erasable, shear-thinning writing composition comprising an aqueous solvent system, a shear-thinning additive, and graphite particles, wherein the graphite particles and the shear-thinning additive are dispersed within the aqueous solvent system. The writing instrument further includes a writing point in fluid communication with the reservoir.
In accordance with an additional aspect of the invention, a method of forming a marking includes making a marking on a substrate with an erasable, shear-thinning writing composition comprising a shear-thinning additive and graphite particles.
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description and appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
One aspect of the invention is an erasable, shear-thinning writing composition comprising a shear-thinning additive and graphite particles in a liquid.
Another aspect of the invention is an erasable, shear-thinning writing composition including a shear-thinning additive and graphite particles dispersed in a liquid wherein the erasable, shear-thinning composition has a shear-thinning index between about 0.01 and about 0.8.
Additional embodiments of these aspects may include one or more of the following features. The erasable, shear-thinning writing composition can have a shear-thinning index between about 0.01 and about 0.8. The erasable, shear-thinning composition also has a viscosity between 200 mPa·sec and 20,000 mPa·sec at a shear rate of about 1.0 sec
−1
, and a viscosity between 10 mPa·sec and 1000 mPa·sec at a shear rate of about 100 sec
−1
. The liquid is an aqueous solvent system. The shear-thinning additive and graphite particles are dispersed within the aqueous solvent system. The shear-thinning additive is a clay, an organoclay, a water-dispersible gum, an acrylic acid-based polymer, or a combination thereof. The clay is a hectorite clay or a bentonite clay. The water-dispersible gum is a polysaccharide, such as, for example, xanthan gum. The composition can include about 0.01 weight percent to about 10 weight percent of the shear-thinning additive, about 0.05 weight percent to about 5 weight percent of the shear-thinning additive, or about 0.1 weight percent to about 2 weight percent of the shear-thinning additive. The composition further comprises at least one water-soluble organic solvent. The composition further comprises at least one water-soluble organic solvent selected from the group consisting of glycols, polyhydric alcohols, glycol ethers, glycol ether esters, amines, amides, and alkanolamides. The water-soluble organic solvent can be a glycol, such as, for example, propylene glycol. The aqueous solvent system comprises water, propylene glycol, and glycerol. The water of the aqueous solvent system is deionized water. The mixture includes from about 0.5 part to about 25 parts water per part water-soluble organic solvent(s). The graphite particles can comprise from about 1 weight percent to about 50 weight percent of the composition, from about 3 weight percent to about 25 weight percent of the composition, or from about 5 weight percent to about 20 weight percent of the composition. The graphite particles have an average thickness of less than about 1 micron, and an average particle diameter between about 1 micron and about 25 microns, or an average thickness of less than about 0.5 micron, and an average particle diameter between about 2 microns and about 15 microns, or an average thickness of less than about 0.25 microns, and an average particle diameter between about 3 microns and about 12 microns. The graphite particles are selected from the group consisting of amorphous graphite, flake natural graphite, primary synthetic graphite, secondary synthetic graphite, and combinations thereof. The erasable, shear-thinning composition further includes one or more dispersants. The dispersant is a water-soluble polymer. The erasable, shear-thinning writing compositions can exhibit an erasability greater than about 80 percent and a line intensity greater than about 25 percent, or an erasability greater than about 95 percent and a line intensity greater than about 30 percent, or an erasability greater than 97 percent and a line intensity greater than about 40 percent. The composition further comprises pigment particles.
Another aspect according to the invention is a writing instrument comprising a reservoir containing an erasable, shear-thinning writing composition comprising an aqueous solvent system, a shear-thinning additive, and graphite particles wherein the graphite particles and the shear-thinning additive are dispersed within the aqueous solvent system. The writing instrument further contains a writing point in fluid communication with the reservoir. The writing instrument can be a pen, such as, for example, a ballpoint pen.
Yet another aspect according to the invention is a method of forming a marking comprising making a marking on a substrate with an erasable, shear-thinning writing composition. The composition comprises a shear-thinning additive and graphite particles.
Embodiments of this aspect of the invention may include one or more of the following features. The method further comprises erasing the marking from the substrate. The erasable, shear-thinning composition further comprises an aqueous solvent system. The erasable, shear-thinning composition has a shear-thinning index between about 0.01 and about 0.8. The erasable, shear-thinning writing composition has a viscosity between 200 mPa·sec and 20,000 mPa·sec at a shear rate of about 1.0 sec
−1
, and a viscosity between 10 mPa·sec and 1000 mPa·sec at a shear rate of about 100 sec
−1
. The substrate is paper. The marking is made with a writing instrument, such as a ballpoint pen.
In another aspect, the invention features an erasable, shear-thinning writing composition including about 30 weight percent to about 99 weight percent of an aqueous solvent system, about 0.01 weight percent to about 10 weight percent of a shear-thinning additive, and about 1 weight percent to about 50 weight percent of graphite particles dispersed within the solvent system.
In other aspects, the invention can also feature an erasable, shear-thinning writing composition including a shear-thinning additive, graphite particles, and pigment particles in a liquid. Examples of pigment particles include, but are not limited to, pearlescent pigments, such as, for example, Afflair 110, available from EM Industries, Inc., located in Hawthorne, N.Y.
Shear-thinning compositions are non-Newtonian liquids that exhibit shear-thinning flow behavior when subjected to shear. Preferred shear-thinning compositions of the invention become thin, readily flowable liquids having a viscosity of no greater than about 500 mPa·sec at shear rates
Czubarow Pawel
Spencer Jean L.
Bell Mark L.
Berol Corporation
Faison Veronica F.
Marshall Gerstein & Borun
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