Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-05-19
2002-05-28
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S206000, C524S555000, C524S556000, C427S221000, C428S407000
Reexamination Certificate
active
06395805
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a dispersion composition utilizable in fields in which granular materials insoluble in organic solvents are utilized by dispersion in the organic solvents, for example, the fields of coating materials, printing inks, liquid developers (liquid toners) and jet printing inks in which pigments or dyes are utilized as granular materials by dispersion, fields in which drugs are utilized as granular materials by dispersion, and fields in which catalysts, polymerization initiators or the like are utilized as granular materials by dispersion; and a process for producing said dispersion composition. In addition, the present invention relates to a dispersion composition utilizable also in the fields of coloring materials obtained by incorporating a granular material into a high-molecular weight compound by drying, such as dry toners and powder coating materials, plastics, etc.; and a process for producing this dispersion composition.
In the fields in which pigments or dyes insoluble in organic solvents are utilized by dispersion in the organic solvents, the diameter of dispersed particles of the dye or pigment have been made very small and various improvements have been made in the storage stability of the resulting dispersion. For example, British Patent No. 2001083 has proposed specific polyester amines as a pigment-dispersing agent in a coating material or ink. JP-A-10-265728 has proposed a pigment coated with a thin film of a thermosetting polymer having methylol groups, as a coloring composition for ink jet. JP-A-8-30040 has proposed a liquid developer obtained by dispersing, in a nonaqueous solvent, coloring resin particles in the form of urethane-based microcapsules containing a pigment or a dye. Further, Japanese Patent Application Kohyo No. 11-501353 has proposed a dispersion ink for ink jet printer which contains a dispersant containing basic groups or acidic groups and a neutralizing agent for said groups in such an amount that the neutralizing agent does not destabilize the dispersion.
However, in the case of dispersion compositions obtained by using a conventional dispersion stabilizer or the above-mentioned pigment-dispersing agent, the kinds of organic solvents and pigments are limited. The dispersion of the pigment is stabilized by the steric repulsion of resin, but because of an insufficient amount of electric charge generated on the pigment surface, a dilute pigment dispersion undergoes precipitation when stored for a long period of time, namely, it is poor in dispersion stability. Moreover, when the coloring composition of a pigment coated with a thermosetting polymer or the coloring resin particles in the form of urethane-based microcapsules are used as a liquid developer, the coloring composition or the coloring resin particles involve the precipitation problem when stored for a long period of time, because the diameter of dispersed particles is as large as 0.5 &mgr;m or more.
On the other hand, the dispersion ink for ink jet printer obtained by using a dispersant containing basic groups or acidic groups and a neutralizing agent for said groups is not always satisfactory n storage stability because the dispersant is in a dissolved state in a solution, so that the amount of the dispersant adsorbed is small. Moreover, the dispersion ink is poor also in charge stability because the adsorption and desorption of the dispersion are repeated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a dispersion composition which is free from the precipitation problem because of the improved dispersion stability of a granular material contained in the composition, is free also from the charge stability problem, permits employment of various kinds of organic solvents and insoluble granular materials, is widely utilizable, and is useful as, in particular, a liquid developer or a jet printing ink, in which electrostatic force is utilized.
The present inventors earnestly investigated in order to solve the problems described above, and consequently found that by providing a dispersion composition comprising a dispersion of a granular material in an organic solvent and further comprising at least a high-molecular weight compound having acidic groups and a high-molecular weight compound having basic groups, at least a part of said high-molecular weight compounds being insoluble in said organic solvent, and said high-molecular weight compounds being adsorbed on said granular material, the following effects can be obtained: the mutual steric repulsion among particles of the granular material can be increased owing to the large amounts of the high-molecular weight compounds adsorbed; the precipitation of the granular material is prevented by its atomization, so that the dispersion stability is improved; and electric charge can be generated on the surface of the granular material and can be stably maintained. Thus, the present invention has been accomplished.
In addition, as a process for producing the dispersion composition of the present invention, there is provided a process for producing the above-mentioned dispersion composition by mixing a dispersion prepared by dispersing a granular material in an organic solvent by the use of a high-molecular weight compound having acidic groups, with a solution or dispersion prepared by dissolving or dispersing a high-molecular weight compound having basic groups in an organic solvent incapable of dissolving the high-molecular weight compound having acidic groups, to adsorb the high-molecular weight compound having acidic groups and/or the high-molecular weight compound having basic groups on the granular material; or a process for producing the above-mentioned dispersion composition by mixing a dispersion prepared by dispersing a granular material in an organic solvent by the use of a high-molecular weight compound having basic groups, with a solution or dispersion prepared by dissolving or dispersing a high-molecular weight compound having acidic groups in an organic solvent incapable of dissolving the high-molecular weight compound having basic groups, to adsorb the high-molecular weight compound having basic groups and/or the high-molecular weight compound having acidic groups on the granular material.
DETAILED DESCRIPTION OF THE INVENTION
The dispersion composition of the present invention comprises a granular material, a high-molecular weight compound having acidic groups and a high-molecular weight compound having basic groups, and it is absolutely necessary that at least a part of the high-molecular weight compounds is insoluble in an organic solvent used in the dispersion composition. In addition, the total amount of the high-molecular weight compound having acidic groups and the high-molecular weight compound having basic groups which are adsorbed on the granular material ranges preferably from 20 to 10,000 parts by weight, more preferably from 40 to 5,000 parts by weight, per 100 parts by weight of the granular material. When this adsorbing amount is less than 20 parts by weight, the dispersion stability is not sufficient. When the adsorbing amount is more than 10,000 parts by weight, the content of the granular material in the dispersion composition is decreased, so that it becomes difficult to attain a sufficient concentration of the granular material to utilize the dispersion composition as a coating material, ink, toner or the like.
In the dispersion composition of the present invention, the total amount of the high-molecular weight compound having acidic groups and the high-molecular weight compound having basic groups which are adsorbed on the granular material ranges preferably from 30 to 10,000 parts by weight per 100 parts by weight of the granular material.
The number average molecular weight of the high-molecular weight compound having acidic groups ranges preferably from 1,000 to 50,000. When the number average molecular weight is less than 1,000, the acid strength of the acidic groups is increased, so that the high-molecular weight compound h
Birch & Stewart Kolasch & Birch, LLP
Hitachi Maxell Ltd.
Yoon Tae H.
LandOfFree
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