Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1997-02-07
2002-04-09
Copenheaver, Blaine (Department: 1771)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S377000, C106S037000, C260SDIG031
Reexamination Certificate
active
06369128
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an aqueous ink composition containing a water soluble, poly(oxyalkylene) substituted colorant and a water soluble polymer or latex binder. The ink composition is water resistant once it is applied to a substrate and dried.
Water soluble, poly(oxyalkylene) substituted organic chromophores are known in the art for use as fugitive tints, as disclosed in Kuhn U.S. Pat. No. 3,157,633 for textile fibers; and Brendle U.S. Pat. No. 5,387,745 for agricultural chemicals. The poly(oxyalkylene) substituted colorants have also found utility for use in washable inks as exemplified by Kluger et al. U.S. Pat. No. 4,981,516 and Kluger et al. U.S. Pat. No. 5,043,013.
For some applications, it has been desirable to limit the water solubility of the poly(oxyalkylene) substituted colorants by incorporating a relatively high proportion of propylene oxide and/or butylene oxide adducts in the poly(oxyalkylene) substituent, as shown in Kuhn U.S. Pat. No. 4,091,034 and Hauser et al. U.S. Pat. No. 4,113,721. Inks made by dissolving a thermoplastic resin in an organic solvent and blending in a poly(oxyalkylene) substituted colorant are exemplified in Baumgartner U.S. Pat. No. 4,812,141. Alternatively, the solubility of the poly(oxyalkylene) substituted colorants may be modified by an ester cap, as disclosed in Brendle U.S. Pat. No. 4,167,510.
An aqueous ink composition containing a poly(oxyalkylene) substituted colorant is disclosed in Moore et al. U.S. Pat. No. 5,176,745. The poly(oxyalkylene) substituent is esterfied, with, for example, a cyclic acid anhydride, to provide a terminal carboxylic acid group. A counter ion is present in the ink composition to solubilize the colorant. Aqueous ink compositions having an anionic dye which is solubilized by a volatile alkali component is disclosed in Fujita, U.S. Pat. No. 5,536,761.
SUMMARY OF THE INVENTION
Therefore, the objects of the invention include providing an aqueous based ink composition; an ink composition having a water soluble colorant; an ink composition which is water resistant once applied to a substrate; an ink composition having an aqueous based binder; and an ink composition with little or no volatile organic compounds (VOC's).
Accordingly, an ink composition is provided having an aqueous solvent with an organic colorant dissolved in the solvent and a binder which is either (i) an alkali soluble acrylic polymer or copolymer dissolved in the solvent, or (ii) a polymer latex suspended in the solvent. The organic colorant has one or more poly(oxyalkylene) substituents, but is free from any metal salts of a carboxylic or sulfonic acid substituent. Preferably, the colorant is free from any carboxylic or sulfonic acid substituents, or their salts.
The poly(oxyalkylene) substituent enhances the water solubility of the colorant, when the colorant is dissolved in the aqueous composition. Without being bound to a particular theory, it is believed that the colorant, which has a relatively higher molecular weight and linear structure by virtue of the poly(oxyalkylene) substituent, is immobilized by the binder when the ink is applied to a substrate and dried. By avoiding water solubilizing substituents on the colorant, such as metal salts of carboxylic and sulfonic acid groups, one further improves the bleed resistance of the ink.
DETAILED DESCRIPTION OF THE INVENTION
Without limiting the scope of the invention, the preferred embodiments and features are hereinafter set forth. Unless otherwise indicated, all parts and percentages are by weight and conditions are ambient, i.e. one atmosphere of pressure and 25° C. Unless otherwise specified, aliphatic hydrocarbons and radicals thereof are from one to twelve carbon atoms in length.
All of the United States patents cited in the specification are hereby incorporated by reference.
The ink composition is comprised of an aqueous solvent, a colorant dissolved in the solvent and a binder dissolved or suspended in the solvent. The aqueous solvent may include a water miscible organic co-solvent, such as C
1-8
alcohols, glycol ethyl ether e.g. Cellosolve™ and acetates. Preferably, the organic co-solvent is less than 10 wt % of the aqueous solvent, most preferably less than 1% of the aqueous solvent. In applications where it is desirable to minimize VOC's, the ink composition can be provided without an organic co-solvent.
The colorant is a poly(oxyalkylene) substituted organic chromophore, which is free from metal salts of a carboxylic or sulfonic acid substituent. For example, the colorant does not contain carboxylic or sulfonic acid substituents in the form of a metal salt with alkali metals, alkaline earth metals or zinc. In a preferred embodiment of the invention, the colorant is free from any carboxylic or sulfonic acid substituents, whether in the form of an acid or salt. Most preferably, the colorant is free from any anionic substituents which render the colorant water insoluble when the anionic substituent is in the acid form and water soluble when it forms a salt. The colorant is dissolved in the aqueous solvent and, is preferably water soluble, defined herein as a minimun solubility of 1 part per 100 parts of water, and preferably the colorant has a minimum solubility of 5 parts per 100 parts of water.
A wide variety of organic chromophores are suitable for use in the present invention. Examples of useful chromophores include: nitroso, nitro, azo and polyazo, diarylmethane, triarylmethane, xanthene, acridine, quinoline, methine, thiazole, indamine, indophenol, lactone, aminoketone, hydroxyketone, stilbene, azine, oxazine, thiazine, anthraquinone, phthalocyanine and indigoid chromophore groups. Of particular interest are azo, methine, triarylmethane and anthraquinone chromophore groups.
One or more poly(oxyalkylene) substituents are covalently bonded to the organic chromophore. The poly(oxyalkylene) substituent may be characterized as a straight or branched chain of from 2 to 200 residues of C
2
-C
4
alkylene oxides. In a preferred embodiment, the poly(oxyalkylene) substituents are primarily comprised of from 3 to 100, most preferably 4 to 50 residues of ethylene oxide, propylene oxide or random and block copolymers thereof. Minor amounts of glycidol, butylene oxide and other compatible monomers may also be incorporated into the substituent. For example, glycidol monomers may be incorporated into the poly(oxyalkylene) substituent to promote branching. When enhanced branching is desired, preferably from 2 to 10 glycidol units are provided per poly(oxyalkylene) chain. The water solubility of the colorant is enhanced by providing a poly(oxyalkylene) substituent having 35% or more, preferably 50% or more, most preferably 75% or more ethylene oxide residues relative to the total number of alkylene oxide residues.
The chromogen is covalently bonded to the poly(oxyalkylene) substituent by a linking group, for example by a group selected from N, NR, O, S, S
2
, SO
2
N, SO
2
NR, CO
2
, CON or CONR, where R is H, C
1
-C
12
alkyl, phenyl or benzyl. Preferably, the linking group is N, NR, O, SO
2
N or SO
2
NR. Two poly(oxyalkylene) substituents may be bonded to the chromophore through a trivalent linking group. The number of poly(oxyalkylene) chains per chromophore may be from 1 to 6, preferably 1 to 4, most preferably 1, 2 or 3.
The precise identity of the terminal group of the poly(oxyalkylene) substituent is not believed to be critical, insofar as the functioning of the colorant is concerned, but may have an affect on solubility. By way of example, the end group may be selected from thio, hydroxyl and amine groups, or may be ester, amide or hydroxyl capped, provided that the terminal group of the poly(oxyalkylene) substituent is not a carboxylic or sulfonic acid or salt thereof. Preferably, the poly(oxyalkylene) substituent has a hydroxyl or amine terminal group.
Synthesis of organic chromophores containing poly(oxyalkylene) substituents are disclosed in Kuhn U.S. Pat. No. 3,157,633, Brendle U.S. Pat. No. 4,167,510, Cross et al. U.S. Pat. No. 4,284,72
Brown Steven E.
Hunt Michael O.
Mahaffey Robert L.
Starks Leonard L.
Copenheaver Blaine
Guarriello John J.
Milliken & Company
Monahan Timothy J.
Moyer Terry T.
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