Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-04-04
2002-04-30
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S412000, C106S493000, C106S494000, C106S495000, C106S496000, C106S497000, C106S498000, C106S499000
Reexamination Certificate
active
06379451
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present disclosure is related to the disclosures provided in the following Japanese patent applications filed prior to the filing of the present application: “METHOD FOR PRODUCING AQUEOUS PIGMENT DISPERSION”, filed as a Japanese Patent Application No. 11-97168; and “PIGMENT COMPOSITION AND AQUEOUS PIGMENT DISPERSION PRODUCT USING THE SAME”, filed as a Japanese Patent Application No. 11-97169; and the disclosures of the aforementioned applications are hereby expressly incorporated by reference herein in their entireties.
The present invention relates to a pigment composition that is easily dispersed in an aqueous medium. Specifically, the present invention relates to a pigment composition that can be produced in a single step without using water and a solvent in large amounts as in the conventional methods; and an aqueous pigment dispersion product comprising the same.
2. Description of the Prior Art
Hitherto, as a method for producing an aqueous dispersion product of a pigment, there has been adopted a method of mixing a pigment treated to be suitable for an aqueous system with dispersing varnish and then dispersing the mixture in an aqueous system in a disperser such as a sand mill or a bead mill with massive energy and time.
The pigment used in such a production of an aqueous dispersion product as above is finished into a pigment that can be used for an aqueous dispersion product after passing through steps requiring a great deal of energy and time. For example, in a pigmentation step based on wet-milling of a crude pigment, the crude pigment is milled in the presence of grinding media by means of a milling apparatus such as a kneader. Such a pigmentation step using mechanical power requires massive kneading energy and time for milling and a great deal of energy and time for separating and purifying the grinding media from the resultant pigment.
Against various processes typically used to produce an aqueous dispersion product of a pigment, as described above, the following methods have been recently suggested: a method of making a milled substance into a pigmentary form in the presence of a surfactant, as disclosed in Japanese Patent Application Laid-Open No. 55-75453; a method of dry-milling a crude pigment and mechanically dispersing a mixture of the dry-milled substance, a resin and an organic solvent, as disclosed in Japanese Patent Application Laid-Open No. 9-217019; and a method of kneading a mixture of crude copper phthalocyanine, a resin and an organic liquid, as disclosed in Japanese Patent Application Laid-Open No. 9-188845.
However, by any one of the above-mentioned methods in the prior art, a pigment composition capable of being dispersed in an aqueous medium with low mechanical energy cannot be economically produced.
SUMMARY OF THE INVENTION
Surprisingly, the present inventors have found out that when, upon the production of the aqueous dispersion of a pigment and a water-soluble resin, a specific surfactant, that is, a nonionic surfactant comprising a compound having in its molecule an acetylenic linkage is added thereto at a suitable timing, the dispersibility of the pigment particles in an aqueous system, particularly in an alkali aqueous solution, can be remarkably improved.
An object of the present invention is to provide a method for producing a pigment composition which is capable of being easily dispersed in an aqueous medium in a single step without using a large amount of water or a solvent.
Another object of the present invention is to provide a pigment composition having an excellent dispersibility as herein-above mentioned, and an aqueous dispersion product thereof.
These and other objects of the invention are satisfied by a pigment composition comprising a dry-milled pigment, a water-soluble resin, and a nonionic surfactant composed of a compound having an acetylenic linkage; and a method for producing a pigment composition, comprising dry-milling a pigment containing coarse particles in the presence of a water-soluble resin and a nonionic surfactant composed of a compound having an acetylenic linkage.
As a production method of the pigment composition, some variations are also possible within the scope of the present invention. One example of such variations is a method comprising the steps of (a) dry-milling a pigment containing coarse particles in the presence of a nonionic surfactant composed of a compound having an acetylenic linkage thereby obtaining an intermediate milled product, and (b) further dry-milling a mixture of the intermediate milled product and a water-soluble resin.
As a method for producing an aqueous pigment dispersion product, one of the most important examples is a method comprising the steps of (a) dry-milling a pigment containing coarse particles in the presence of a water-soluble resin thereby obtaining a milled product, and (b) dispersing the milled product in water in the presence of a nonionic surfactant composed of a compound having an acetylenic linkage.
The water-soluble resin may be water-soluble in the presence of an alkali. Especially, acrylic resin is preferable. One category of pigments applicable to the present invention is those composed of a condensed polycyclic compound. It should be also noted that the present invention can be quite effectively applicable to, though not specifically limited to, a phthalocyanine pigment. The nonionic surfactant may be an acetylene glycol compound such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol or an ethylene oxide adduct thereof.
In the pigment composition according to the invention, the dry-milled pigment may be composed of pigment particles having surfaces coated with the water-soluble resin, which can be readily dispersed into an aqueous medium, especially aqueous solution of sodium hydroxide.
For effectively achieving the objects of the present invention, the water-soluble resin is preferably in an amount of 2 to 50% by weight and the nonionic surfactant is preferably in an amount of 1 to 20% by weight based on an amount of the pigment, in the pigment composition.
The pigment containing coarse particles, which is supposed to be milled, is typically a crude pigment.
In the presence of surfactant, the surfactant produces a surface treating effect on the surface of the pigment particles to improve the hydrophilic properties of the surface thereby significantly improving the affinity of the pigment particles to the resin. In the present invention, a specific compound as above-characterized is used for such surface activating purpose. Along with the surface treating function itself, these compounds also have a high permeability to penetrate into a minute space of material such as pigment particles. Pigment particles are usually composed of smaller particles coagulated each other, namely aggregate of primary particles. Because of this additional property, these compounds can permeate into inside of such an aggregate, and weaken the coagulation force. Wetting and adsorption of the resin to the surface of pigment particles also proceed based on the original surface treating effect. It is reasoned that owing to such double effects produced by the surface treating agent in the present invention, extremely high dispersibility of the pigment composition can be attained.
Therefore, according to the present invention, a pigment can be dispersed in water by a simple operation. According to the present invention, it is possible to provide, at low costs, an aqueous dispersion product having a quality that is equal to or higher than those obtained by the salt milling method using a solvent, which has been adopted as an ordinary pigment-producing method.
DETAILED DESCRIPTION OF THE INVENTION
Examples of the pigment to which the present invention can be applied are, though not specifically limited to, pigments composed of condensed polycyclic compounds such as phthalocyanine pigments, quinacridone pigments, and dioxazine pigments; and azo pigments such as monoazo pigments and bisazo pigments. The pigment that is subjected to dry-milli
Chiba Ataru
Kitamura Kenji
Green Anthony
Toyo Ink Mfg. Co. Ltd.
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