Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-03-03
2002-06-04
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S412000, C106S413000, C106S472000, C106S476000, C106S493000, C106S494000, C106S495000, C106S496000, C106S497000, C106S498000
Reexamination Certificate
active
06398858
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing colored pigments and aqueous compositions containing the same and, more particularly, to preparing surface-modified colored pigments and ink compositions useful for imaging applications, such as ink jet inks.
2. Discussion of the Related Art
Aqueous systems are increasingly being used in many applications such as automotive and industrial coatings, paints, papers, inks, toners, adhesives, latexes, etc. as manufacturers face increased pressure to replace conventional solvent based systems. Such aqueous systems are known and generally contain a colorant, such as a dye, which is soluble in the aqueous vehicle, such as water or a mixture of water and a water-soluble or water-miscible organic solvent.
Although dye-based compositions are readily utilized, dyes have several disadvantages when used in aqueous ink systems. For example, dyes, being water-soluble in a water/organic mixture, may dissolve and run when exposed to moisture or water. Dye images may further smear or rub off on contact with felt pen markers or upon being rubbed or touched by a finger. Dyes also exhibit poor light stability when exposed to visible or ultraviolet light.
Pigments are also known as colorants in aqueous compositions but have not received a wide degree of acceptance in aqueous systems, such as ink jet inks, because of problems associated with the performance and reliability of the composition, i.e., print properties, stability, latency, and the like. Examples of such pigments include carbon black, titanium dioxide white, cobalt blue (CoO—Al
2
O
3
), phthalocyanine blue, phthalocyanine green, and chrome yellow (PbCrO
4
).
U.S. Pat. No. 5,837,045, to Johnson et al. describes novel surface-modified colored pigments and aqueous compositions containing such surface-modified colored pigments. Although such surface-modified colored pigments are a considerable improvement over dye-based or traditional pigment systems (i.e. pigments requiring stabilization with a polymer or surfactant compositions), a continuing need exists for improved surface-modified colored pigments and processes for making the same, as well as aqueous or solvent based compositions containing such surface-modified colored pigments, especially for use in ink compositions which require long term colloidal stability and lightfastness. It is also desirable to produce improved aqueous ink compositions which exhibit improved latency and recoverability in their respective printing systems while providing good print properties. A further need exists for improved aqueous ink compositions which generate print images having improved waterfastness.
SUMMARY OF THE INVENTION
The present invention relates to a process for preparing surface-modified colored pigments. The process includes the steps of: preparing a reaction batch comprising a treating agent and a diazotizing agent; adding a colored pigment to the batch; and mixing the colored pigment and the batch under high shear conditions to form a reaction product comprising a surface-modified colored pigment. The treating agent has an organic group which comprises at least one diazotizable group. In a preferred embodiment the diazotizable group comprises a) at least one aromatic group, at least one C
1
-C
20
alkyl group, or mixtures thereof; and b) at least one ionic group, ionizable group, nonionic group, or mixtures thereof.
The present invention is further directed to a process for preparing ink compositions incorporating the surface-modified colored pigments described above.
The surface-modified color pigments prepared by the process of the present invention may be used in aqueous or solvent based compositions containing conventional pigments. Such compositions include, for example, automotive and industrial coatings, printing plates, paints, papers, toners, inks (particularly, ink jet ink compositions), adhesives, latexes, textiles and fibers. The surface-modified colored pigments may be tailored to provide compatibility with the particular aqueous or solvent based system and provide easier, more complete dispersion, improved colloidal stability and greater color intensity and shades.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to a process for preparing surface-modified colored pigments. The process includes the steps of: preparing a reaction batch comprising a treating agent and a diazotizing agent; adding a colored pigment to the batch; and mixing the colored pigment and the batch under high shear conditions to form a reaction product comprising a surface-modified colored pigment.
The treating agent for use in the process of the present invention comprises an organic group which comprises at least one diazotizable group. For purposes of the present invention, a “diazotizable group” means a nitrogen containing compound which, in the presence of a diazotizing agent, will react to form a diazonium salt. The “diazotizing agent” means any compound which will donate a nitrogen atom during the reaction with the diazotizable group to form the diazonium salt. In a preferred embodiment the diazotizable group comprises a) at least one aromatic group, at least one C
1
-C
20
alkyl group, and mixtures thereof; and b) at least one ionic group, ionizable group, nonionic group, and mixtures thereof.
A diazotizable group comprising at least one aromatic group includes, but is not limited to, unsaturated cyclic hydrocarbons containing one or more rings and may be substituted or unsubstituted, for example with alkyl groups. Aromatic groups include aryl groups (for example, phenyl, naphthyl, anthracenyl, and the like) and heteroaryl groups (for example, imidazolyl, pyrazolyl, pyridinyl, thienyl, thiazolyl, furyl, triazinyl, indolyl, and the like). A diazotizable group comprising at least one C
1
-C
20
alkyl group may be branched or unbranched, substituted or unsubstituted. In a preferred embodiment, at least one aromatic group or at least one C
1
-C
20
alkyl group of the diazotizable group is directly attached to the colored pigment.
A preferred set of diazotizable groups which may be used are organic groups substituted with an ionic group, an ionizable group or an nonionic group as a functional group. An ionizable group is one capable of forming a ionic group in the medium of use. The ionic group may be an anionic group or a cationic group and the ionizable group may form an anion or cation. The nonionic group is a group which does not possess or is not capable of possessing a charge. Alternatively, the nonionic group may include a zwitterion (i.e. carrying both a positive and negative charge), thereby forming an overall neutral group.
Ionizable functional groups forming anions or anionic groups include, for example, acidic groups or salts of acidic groups. The organic groups, therefore, include groups derived from organic acids. Preferably, when an organic group contains an ionizable group forming an anion, such an organic group has a) an aromatic group or a C
1
-C
20
alkyl group and b) at least one acidic group having a pK
a
of less than 11, or at least one salt of an acidic group having a pK
a
of less than 11, or a mixture of at least one acidic group having a pK
a
of less than 11 and at least one salt of an acidic group having a pK
a
of less than 11. The pK
a
of the acidic group refers to the pK
a
of the organic group as a whole, not just the acidic substituent. More preferably, the pK
a
is less than 10 and most preferably less than 9. Preferably, the aromatic group of the organic group is directly attached to the colored pigment. The aromatic group may be further substituted or unsubstituted, for example, with alkyl groups. More preferably, the organic group is a phenyl or a naphthyl group and the acidic group is a sulfonic acid group, a sulfinic acid group, a phosphonic acid group, or a carboxylic acid group. Most preferably, the organic group is a substituted or unsubstituted sulfophenyl group or a salt thereof; a substituted or unsubstituted carboxyphe
Amici Robert M.
Gambale Ronald J.
Yu Yuan
Cabot Corporation
Green Anthony
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