Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-04-08
2003-11-25
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S484000
Reexamination Certificate
active
06653390
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to organic colorant compositions useful for imparting color. Particularly, the present invention relates to methods for preparing a novel class of triarylmethane dyes and to the dyes prepared.
BACKGROUND OF THE INVENTION
There is currently a growing market for water-based inks in the flexographic printing industry, primarily for package and container printing. There is, moreover, a trend toward the use of water-based inks for all types of printing.
Almost all water-based inks and coatings require a basic pH of about 7 to about 12 for dyes of the inks and coatings to be soluble in an aqueous composition. However, at basic pH, the coloristic properties of most dyes are greatly diminished. For example, blue or purple triphenylmethane dyes with ionizable sulfonic acid groups have been utilized for making water-based inks and coatings. The most commonly used dye of this type is Pigment Blue 61:
Pigment Blue 61 is a medium shade blue (&lgr;
max
=600 nm) which has a very high light absorption per unit of weight and is well suited for use in solvent or oil based inks. However, this pigment is sensitive to changes in pH and, at pH values greater than 9, the resulting salt is reddish-brown instead of blue and is coloristically weak when compared to the blue, acid form of the pigment. Accordingly, because almost all water-based inks and coatings are formulated using polymeric resins that require a pH range of about 7 to about 12 to remain solubilized or emulsified, these ink compositions are often unsuitable for use with triphenylmethane pigments such as Pigment Blue 61.
Among commonly used triphenylmethane pigments are the salts of the phenylpararosanilines (PPR's). The sulfate of triphenylpararosaniline (TPPR) is a pigment used in oil-based printing inks and can be prepared by the pigment flushing process. U.S. Pat. No. 4,944,806 discloses two methods of preparation for the salts (sulfate, chloride, nitrate, and phosphate) of the TPPR molecule. The first method involves dissolving the TPPR in an organic solvent, then mixing the solution with a dilute aqueous solution of the acid and a surfactant using a high shear, turbulent mixer, and isolating the product by filtration. The resulting pigment filtercake is converted to a flushed paste ink by vacuum flushing. The second method disclosed involves crushing the solid TPPR and then grinding it to pigmentary size by the use of a high energy media mill, such as an Attritor, in the presence of dilute aqueous acid and a surfactant. The ground pigmentary salt is then isolated by filtration and converted to a flush paste ink by vacuum flushing.
It would thus be desirable to provide colorant compositions that remain solubilized in water-based ink and coating systems. It would be further desirable if the colorant compositions would also remain coloristically strong when solubilized in water-based ink and coating systems.
U.S. Pat. No. 3,671,553 issued to Papenfuss et. al., is directed to the dyestuffs of the monosulfonic acids of the triphenylmethanes. The patent discloses how to make a “color base sulfate ” which is used as an intermediate in the production of the monosulfonated molecule. The 3,671,553 patent does not teach nor suggest a pigmentary form of the “color base sulfate ” molecule and in fact specifically teaches that the color base sulfate remain in solution to aid in the preparation of the sulfonic acid form and is not isolated in a solid or pigmentary form.
U.S. Pat. No. 3,439,004 pertains to the triarylmethane dyes and discloses how to make a “dye product ” stating that these “dye products ” also make excellent pigments. However, this patent is directed specifically at the triaminotriarylurethane compounds which have at least one cyclohexyl sustituent attached to the amino group. It discloses that the dye products, although water-insoluble, have improved solubility in ethyl alcohol and are appropriate for alcohol and polyglycol based inks and coatings.
U.S. Pat. No. 4,321,207 discloses a broad range of triphenylmethane dyes referring to the dyes in their “solid form”. However, it does not disclose the use of the dye solids as a pigment and specifically does not refer to the use of the dye solids as a pigment for use in water-based inks or water-based coatings.
U.S. Pat. No. 3,671,553, issued to Papenfuss et al., is directed to the dyestuffs of monosulfonic acids of the triphenylmethanes. This patent discloses how to make a “color base sulfate ” that is used as an intermediate in the production of the monosulfonated molecule. The 3,671,553 patent specifically teaches that the color base sulfate remains in solution to aid in the preparation of the sulfonic acid form and is not isolated in a solid or pigmentary form.
U.S. Pat. No. 3,439,004 pertains to triarylmethane dyes and discloses how to make a “dye product” stating that these “dye products” also make excellent pigments. This patent, however, is directed specifically at triaminotriarylurethane compounds having at least one cyclohexyl substituent attached to the amino group. It also does not disclose the use of these dyes in water-based ink systems or water-based coatings.
Japanese Patent No. JP 9217019 discloses a method for producing an aqueous pigment dispersion comprising dispersing coarsely ground pigment with an acrylic resin alkali salt in an aqueous solution. In this method, the pigment is never solubilized in the aqueous solution but instead the resin is associated with the pigment surface and serves as a dispersent for the pigment.
SUMMARY OF THE INVENTION
The present invention provides novel colorant compositions useful in water-based ink and coating systems. The novel colorant compositions include pigmentary salts and water soluble or dispersible polymers in which the polymer is present as inclusions in the pigment particles. The term “polymer” as used herein also refers to oligomers and resins. The pigmentary salt may be obtained from saltable colorant dyes suitable for inks and coatings. Preferably the pigmentary salt is formed from a triarylmethane dye, especially triphenylmethane or one of its derivatives. The polymer can be any water soluble or dispersible polymer or resin that aids in solubilizing or dispersing the pigmentary salt in aqueous compositions. Preferably the polymer or resin has acid functionality.
The present invention also provides a process for producing the novel colorant composition. The method includes converting a free unsalted dye to the corresponding pigmentary salt by dissolving the dye in aqueous acid at elevated temperatures, adding the water-soluble or water-dispersible polymer or resin, and then co-precipitating the pigmentary salt with the polymer. The precipitated particles contain mixtures of the resin and the pigment. Colorant compositions thus prepared have greatly increased hydrophilicity, dispersibility, and compatibility with aqueous polymeric ink vehicles.
DETAILED DESCRIPTION
The present invention provides novel colorant compositions that include a pigmentary salt and a water soluble or dispersible polymer or polymeric or oligomeric resin in which the polymer is present as inclusions in the pigment particles. A process for making the novel pigment compositions is also provided. The process includes steps of converting a dye to a pigmentary salt and co-precipitating the salt with a water soluble or dispersible polymer.
In one embodiment, the novel colorant composition of the present invention comprise the salt of a dye, preferably the salt of a triphenylmethane dye having the general formula:
wherein R
1
, R
2
, R
3
, R
4
, and R
5
each independently is H, substituted or unsubstituted alkyl group or phenyl or substituted phenyl. The alkyl group will preferably have 1 to 12 carbon atoms. Preferably, the substituted phenyl has the general formula:
wherein X
1
, X
2
, X
3
, X
4
, and X
5
each independently is any substituent, preferably H, F, Cl, Br, I, CH
3
CH
2
O—, CH
3
O—, NO
2
, or substituted or unsubstituted alkyl including —CH
3
and —CH
2
CH
3
.
In a pref
Ellis Gary Don
Harrison Ashleigh Simms
BASF Corporation
Rajguru U. K
Seidleck James J.
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