Organic compounds -- part of the class 532-570 series – Organic compounds – Acyclic carbon bonded directly to three benzene rings or to...
Reexamination Certificate
2000-01-18
2002-01-29
Pryor, Alton (Department: 1616)
Organic compounds -- part of the class 532-570 series
Organic compounds
Acyclic carbon bonded directly to three benzene rings or to...
C106S031430, C106S031280, C106S031270
Reexamination Certificate
active
06342616
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to triphenylmethane compounds for aqueous ink formulations which are storage stable for prolonged periods of time under alkaline conditions. Preferably, these compounds are either dyestuffs or polymeric colorants. Methods of making and using such aqueous inks are also contemplated within this invention.
DISCUSSION OF THE PRIOR ART
Triphenylmethane chromophore-based inks, particularly those dyes or colorants capped with cyclic anhydride, are well known for their excellent ability for coloring and shading within the printing industry. Problems exist, however, during the storage of such triphenylmethanes. Upon contact with an alkaline storage environments, chemical rearrangement may occur rendering undesirable shades. For instance, with triphenylmethane colorants, this degradation of color apparently occurs due to the presence of terminal carboxylic anions of a polymeric chromophore neutralized with hydroxide, ammonia, ethanolamine, diethanolamine, or other unhindered amines. This degradation of color results in very short storage time or requires refrigerated storage, all of which increases the costs associated with colorant storage. An improved cost-effective method of storing such colorants with substantially no shade degradation is thus necessary within the printing industry.
Triphenylmethane dyes and colorants, and, again, particularly those which are capped with cyclic anhydride, are well known within the printing industry and have been taught within U.S. Pat. Nos. 4,871,371, to Harris, and 5,310,887, to Moore et al., the disclosures of which are herein entirely incorporated by reference. Such compounds, as noted above, must undergo neutralization of their terminal carboxylic acids with a counter ion in order to provide solubility within an aqueous medium. Again, the problem with such a step is the degradation of suitable printing shades after reaction with common alkaline counter ions. It is believed that this undesired reaction is the result of interference from the primary or secondary amine moieties of the counter ion (neutralizing compound), such as diethanolamine, monoethanolamine, and the like, for example, or the strong nucleophilicity of alkali metal hydroxide ions, alkaline earth metal hydroxide ions, ammonium ions, and zinc ammonium complexes, or the resultant carboxylates of these ions and complexes, all being present in stoichiometric proportions, when used as such a counter ion. Thus, again, there is a need to provide a relatively inexpensive storage stable aqueous ink composition comprising triphenylmethane polymeric colorants, including cyclic anhydride capped colorants. The prior art has not accorded such an improvement to the printing industry.
DESCRIPTION OF THE INVENTION
It is thus an object of the invention to provide an improved aqueous ink composition comprising triphenylmethane dyes or colorants. A further object of the invention is to provide a relatively inexpensive, improved, storage-stable (particularly under alkaline conditions) triphenylmethane-based polymeric colorant for the printing industry. Another object of the invention is to provide a printing ink having pleasing coloring and shading characteristics and having substantially no color degradation after a prolonged storage period, particularly under standard alkaline conditions. Yet another object of this invention is to provide a process for making such an improved coloring composition, as well as a method of using such a triphenylmethane polymeric colorant for printing cellulose-based writing surfaces, particularly newspapers, commercial inserts, folding cartons, household paper products, multiwall paper bags, and corrugated containers, merely as examples. One further object is to provide an improved long-lasting storage-stable aqueous printing ink composition comprising cyclic anhydride-capped triphenylmethane polymeric colorants and methods of making and using such a composition.
Accordingly, this invention concerns an aqueous ink composition comprising a triphenylmethane dye or colorant neutralized with a sterically hindered amine counter ion. Preferably, the triphenylmethane compound is a polymeric colorant containing carboxylic acid groups neutralized with a sterically hindered amine counter ion. The term polymeric is meant to include those colorants which have alkylene oxide chains reacted with cyclic anhydrides and attached to nucleophilic groups bonded to the triphenylmethane backbone. The preferred alkylene oxides are ethylene oxide, propylene oxide, and butylene oxide, and any mixtures thereof Ethylene oxide provides greater degrees water solubility for the colorant. Lower levels of such solubility are possible with greater numbers of longer chain alkylene oxide moieties. Preferred nucleophilic bridging groups include amino, hydroxyl, thio, or any other well known bridging group for alkylene oxides to a chromophore, such as those listed within U.S. Pat. No. 5,310,887. Preferred cyclic anhydrides are those ranging in chain length from about C
2
to about C
30
.
The sterically hindered amine is one of a low molecular weight fagitive tertiary amine. The tertiary structure of the amine counter ion decreases its ability to act as a strong nucleophilic agent attacking any reactive centers of the chromophore. This fugitive tertiary amine is generally selected from the group consisting of one or more of di(C
1
-C
10
-alkyl)ethanolamine. Examples of such amines include and are preferably N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dipropylethanolamine, N-methyl-N-ethylethanolamine, N-methyl-N-propylethanolamine, and the like. This list is not meant to limit the invention in any way as any number of other low molecular weight fugitive sterically hindered amines may be suitable as counter ions. The low molecular weight and fugitivity requirement for such a tertiary amine counter ion facilitates its evaporation upon utilization in a standard printing method. In order to produce water fast colors on a cellulose-based substrate (i.e., paper), the triphenylmethane polymeric colorants must be effectively free of their counter ions. The term fugitivity means the removal of amine counter ion which is accomplished through evaporation upon long-term presence within a dry environment, through neutralization of the amine on the cellulose-based substrate itself (i.e., paper surfaces are generally acidic due to the presence of alum), or through the migration of the counter ion within the paper substrate. The removal of counter ion is accomplished through any of these three processes. Nowhere within the prior art is such a sterically hindered amine counter ion either taught or fairly suggested as a manner to reduce the effect of alkaline degradation upon the coloring and shading ability of a triphenylmethane polymeric colorant.
Any triphenylmethane dye or colorant is contemplated within this invention; however, the preferred types are those which are polymeric colorants and capped with cyclic anhydride. Particularly preferred cyclic anhydride capped triphenylmethane polymeric colorants are taught within U.S. Pat. No. 5,310,887, to Moore et al., mentioned above, and are represented by the formula:
A—{Y—X—C(O)—R—C(O)O
−
}
p
wherein A is a triphenylmethane organic chromophore; Y is a polyoxyalkylene substituent; X is a radical of a reactive hydroxyl, amino, or thio group; R is C
2-30
, substituted or unsubstituted alkylene, alkyenylene, or phenylenealkylene; and p is from 1 to 4, and preferably 4. In general, when in aqueous composition, the sterically hindered fugitive amine counter ion is present in an amount of from about 0.01 to about 15% by parts of the entire amount of the triphenylmethane dye or colorant within the composition; preferably this amount is from about 1 to about 12%; more preferably from about 4 to about 8%; and most preferably from about 5 to about 7%.
Any other standard ink composition additives, such as resins, preservatives, other colorants, dyes, pigments, surfactants, and antistatic compounds may also be in
Milleken & Company
Moyer Terry T.
Parks William S.
Pryor Alton
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