Compositions: coating or plastic – Coating or plastic compositions – Marking
Patent
1998-11-05
2000-09-26
Klemanski, Helene
Compositions: coating or plastic
Coating or plastic compositions
Marking
106472, 106478, 4234495, C09D 1102, C09C 156
Patent
active
061237590
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to carbon black useful particularly as a pigment for ink jet ink and writing ink, and a method for its production, as well as a water-base ink containing such oxidation-treated carbon black.
BACKGROUND ART
Ink jet recording has characteristics such that the noise during recording is small, color printing is possible, high speed printing is possible, printing can be made on ordinary paper to have high quality, and it is accordingly widely used for printing by computers irrespective of personal use or office use. Various systems are available for this ink jet printing, including a method wherein an ink in a slender nozzle provided in a recording head, is discharged by static energy, a method wherein an electric current is conducted to a heating zone in a recording head so that bubbles will be formed by the heat generation thereby to discharge the ink from a nozzle to carry out printing.
As an ink to be used for such ink jet recording, it has been common to employ a water-base ink having a dye dissolved or dispersed in water. Such a water-base ink is used also for writing utensils such as fountain pens or ballpoint pens.
The following items may be mentioned as the properties required for a recording ink to be used for such applications. clogging of a pen point or a nozzle in a recording head.
As mentioned above, as an ink for these applications, it has been common to employ an ink having a dye dissolved or dispersed as a coloring agent in water. However, when a dye is employed, there is a problem that bleeding is likely to be observed in the printed or written letters, or discoloration is likely to occur by light. Accordingly, an attention has recently been drawn to an ink which employs carbon black as a black pigment.
However, if such carbon black is used as a pigment for ink, the dispersibility of carbon black in water is poor, since the surface of carbon black is lipophilic, whereby carbon black is likely to cause clogging of a pen point or a nozzle, or aggregates are likely to form during storage, whereby it becomes no longer practically useful. Accordingly, it is required to add various dispersing agent.
Here, as the dispersing agent, a dispersant containing in its molecule both lipophilic groups having good affinity with carbon black and hydrophilic groups having good affinity with water, specifically mainly a resin dispersant, is employed to improve the dispersibility or the dispersion stability.
However, such a resin dispersant is expected to provide its effects as bonded to the surface of carbon black. Accordingly, the dispersing effect can not be obtained unless it is added in an amount in excess of the amount required for bonding to the surface of carbon black. Therefore, an excess dispersant will remain in the liquid, and when the ink at a pen point or in the nozzle, is dried, it turns to a solid which is hardly re-solubilized and which causes clogging. Further, as the dispersant is added, the viscosity of the ink increases, whereby there will be a problem that constant discharge of ink can not be attained.
To overcome these problems, JP-A-8-3498 discloses an attempt to improve the dispersion stability without using a dispersant, by reacting carbon black with a sodium hypochlorite solution to oxidize the carbon black more than the commercial products and to have the surface subjected to hydrophilic treatment. However, by such a method, many chlorine ions and sodium ions used as the oxidizing agent are present in the liquid. Accordingly, to use such a product as an ink, it is necessary that the reaction product is once filtered and then purified by a reverse osmosis membrane or ultra filtration. Further, the oxidation treatment is carried out at a high temperature of 100.degree. C. for a long period of time of 12 hours, whereby humic acid soluble in water, will form.
Further, as a case where commercial carbon black is further subjected to oxidation treatment, JP-A-7-258578 discloses that using a gas phase low concentration ozone, commercial carbon b
REFERENCES:
patent: 3620792 (1971-11-01), Hagopian
patent: 3959008 (1976-05-01), Warner et al.
patent: 3992218 (1976-11-01), Suetsugu et al.
patent: 5184148 (1993-02-01), Suga et al.
patent: 5395435 (1995-03-01), Mizobuchi
patent: 5609671 (1997-03-01), Nagasawa
Hirasa Takashi
Mise Nobutake
Yamada Masahiro
Klemanski Helene
Mitsubishi Chemical Corporation
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