Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-07-19
2003-11-04
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031430, C106S031860, C106S031870, C106S499000
Reexamination Certificate
active
06641653
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ink compositions comprising a liquid vehicle and a modified colored pigment. The modified colored pigment comprises the product of a colored pigment having at least one leaving group and a treating agent. The present invention further relates to the modified colored pigments and to processes for preparing them.
2. Description of the Related Art
In general, an ink composition consists of a colorant, such as a dye or pigment, and a liquid vehicle, which functions as a carrier. Pigments offer advantages over dyes, including print durability and lightfastness. However, pigments alone are generally not readily dispersible in liquid vehicles. Thus, dispersants are used to provide stable pigment-based ink compositions.
Colored pigments have been modified in order to obtain improved pigment performance. For example, U.S. Pat. No. 3,981,734 discloses the use of a stabilizing compound of the formula Pc-(X—A)
n
, wherein Pc is metallized or unmetallized phthalocyanine radical, X is O,S, or —NH—, and A is 4-20 carbon straight or branched chain alkyl, an unsubstituted aryl, or an aryl substituted by halogen, trifluoromethyl, alkyl, or alkoxy. The modified pigments are shown to improve the stability of unmodified phthalocyanine pigments towards phase transformations.
Recently, modified colored pigments have also been developed which provide ink compositions with improved properties, such as dispersibility. The methods of modification involve the reaction of a pigment with a diazonium treating agent. For example, U.S. Pat. No. 5,851,280 discloses methods for the attachment of organic groups onto pigments including, for example, attachment via a diazonium reaction wherein the organic group is part of the diazonium salt. The resulting surface-modified pigments can be used in a variety of applications, such as inks, inkjet inks, coatings, toners, plastics, rubbers, and the like.
While these efforts provide modified colored pigments with improved properties, there remains a need for improved pigment-based ink compositions.
SUMMARY OF THE INVENTION
The present invention relates to an ink composition comprising a liquid vehicle and a modified colored pigment. The modified colored pigment comprises the product of: a) a colored pigment having at least one leaving group, wherein the leaving group is selected from the group consisting of: halogens, substituted or unsubstituted alkyl or aryl sulfonates, substituted or unsubstituted acylates, substituted or unsubstituted benzoates, and mixtures thereof, and b) a treating agent having the formula B-R-Q, wherein B is a nucleophilic group, R is an alkylene or arylene group, and Q is an ionic or ionizable group. The present invention further relates to the modified colored pigment itself, as described herein.
The present invention also relates to an ink composition comprising a liquid vehicle and a modified colored pigment. In this embodiment, the modified colored pigment comprises the product of: a) a colored pigment having at least one leaving group, wherein the leaving group is selected from the group consisting of: halogens, substituted or unsubstituted alkyl or aryl sulfonates, substituted or unsubstituted acylates, substituted or unsubstituted benzoates, and mixtures thereof, and b) a treating agent having the formula B-R-AO, wherein B is a nucleophilic group, R is bond, an alkylene group, or an arylene group, and AO is an alkylene oxide group. The present invention further relates to the modified colored pigment itself, as described herein.
The present invention also relates to an ink composition comprising a liquid vehicle and a modified colored pigment. In this embodiment, the modified colored pigment comprises the product of: a) a colored pigment having at least one leaving group; and b) a sulfite treating agent. The invention further relates to the modified pigment itself.
The present invention further relates to a process for preparing a modified colored pigment comprising the steps of: a) combining, in any order, a colored pigment having at least one leaving group, a treating agent having at least one nucleophilic group, a solvent A, and a solvent B; and b) heating for a time and a temperature sufficient to produce a modified colored pigment. In this process, solvent A is a non-solvent for the colored pigment whereas solvent B is a solvent for the colored pigment. The treating agents are described herein. When the treating agent is a sulfite treating agent, solvent B is optional. In one embodiment, a base is also combined in step a).
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to ink compositions comprising a liquid vehicle and a modified colored pigment, as well as the modified colored pigment itself and processes for preparing the modified colored pigment. The modified colored pigment comprises the product of a colored pigment having at least one leaving group and a treating agent.
Ink compositions can be categorized into various classifications. These include, for example, printing inks, ultraviolet cure inks, ball-point pen inks, and stamp pad or marking inks. As described above, in general, an ink composition consists of a vehicle, which functions as a carrier, and a colorant such as a dye or pigment. Additives and/or cosolvents can be incorporated in order to adjust the ink to attain the desired performance.
The vehicle for the ink compositions of the present invention may be either an aqueous or a non-aqueous vehicle. Preferably, the vehicle is an aqueous vehicle and the ink composition is an aqueous ink composition. The ink composition of the present invention is preferably an inkjet ink composition.
The ink compositions of the present invention comprise a modified colored pigment. This composition can be formed with a minimum of additional components (additives and/or cosolvents) and processing steps. The modified colored pigment is present in the ink compositions in an amount effective to provide the desired image quality (for example, optical density) without detrimentally affecting the performance of the ink. For example, typically, the modified colored pigment will be present in an amount ranging from about 0.1% to about 20% based on the weight of the ink. It is also within the bounds of the present invention to use a formulation containing a mixture of the modified colored pigments described herein and unmodified pigments, other modified pigments, or both.
Suitable additives may also be incorporated into these ink compositions to impart a number of desired properties while maintaining the stability of the compositions. For example, surfactants may be added to further enhance the colloidal stability of the composition. Other additives are well known in the art and include humectants, biocides, binders, drying accelerators, penetrants, and the like. The amount of a particular additive will vary depending on a variety of factors but are generally present in an amount ranging between 0% and 40%.
Additionally, the ink compositions of the present invention may further incorporate dyes to modify color balance and adjust optical density. Such dyes include food dyes, FD&C dyes, acid dyes, direct dyes, reactive dyes, derivatives of phthalocyanine tetrasulfonic acids, including copper phthalocyanine derivates, tetra sodium salts, tetra ammonium salts, tetra potassium salts, tetra lithium salts, and the like.
The ink compositions can be purified and/or classified using methods such as those described below for the modified pigments and dispersions thereof. An optional counterion exchange step can also be used. In this way, unwanted impurities or undesirable large particles can be removed to produce an ink with good overall properties.
The ink compositions of the present invention comprise a modified colored pi
Bell Mark L.
Cabot Corporation
Faison Veronica F.
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