Compositions: coating or plastic – Coating or plastic compositions – Marking
Patent
1997-10-06
1999-08-24
Klemanski, Helene
Compositions: coating or plastic
Coating or plastic compositions
Marking
106412, 106413, C09D 1102
Patent
active
059420286
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for producing printing ink using .beta.-form copper phthalocyanine pigment as a colorant in which the printing ink is produced directly from crude copper phthalocyanine without pigmentation of the .beta.-form copper phthalocyanine. In addition, the present invention relates to a method for producing printing ink of high quality by a simplified process, with the aspect ratio of the primary particles of the pigment in the ink being 1-2.
BACKGROUND OF THE INVENTION
Copper phthalocyanine as synthesized is referred to as crude copper phthalocyanine and is not suitable as a pigment for printing ink since it consists of large .beta.-form crystal particles having a particle size of approximately 10 to 200 .mu. m. The process to reduce the size of this crude copper phthalocyanine to a size (approximately from 0.02 to 0.1 .mu.m) suitable for printing ink is called pigmentation. Printing ink is obtained using pigmentized copper phthalocyanine.
There are various methods for pigmentation. The most common method is salt milling which uses a solvent (hereinafter referred to as a solvent salt milling method). This method is one in which a milling agent such as sodium chloride and an organic solvent which promotes crystal transformation to the .beta.-form are added to crude copper phthalocyanine and the resulting mixture is subjected to the milling process. The .beta.-form copper phthalocyanine pigment produced by this method is suitable for printing ink and is widely used since the aspect ratio of the pigment particle is from 1 to 2 and it has clear greenish hue with strong color strength. However, this method requires an amount of milling agent several times that of the pigment and also consumes considerable time, labor and energy in recovering the milling agent and organic solvent.
An alternative method is known in which crude copper phthalocyanine is dry milled and then treated with an organic solvent. As a portion of the .beta.-form crystals are transformed to .alpha.-form crystals in this process due to the mechanical force applied during milling, the ground material is heat treated with an organic solvent in order to transform the .alpha.-form crystals back to .beta.-form crystals. This method is favourable costwise as compared to the solvent salt milling method but involves problems such as the increase in the aspect ratio of the pigment particle due to acicular growth of the particles during heat treatment in organic solvents, the hue turning reddish and the decrease in fluidity etc. Methods are known for suppressing particle growth by adding pigment derivatives or growth inhibitors but these additives are usually unfavourable ingredients for printing ink.
On the other hand, for production of printing ink from pigments, methods using dry pigments or wet cake pigments which contain 40-70 weight % of water are generally used. The method using wet cake pigments is called flushing method. In the method using dry pigments, the pigment is dispersed using beads mill, three roll mill, etc. after mixing the dry pigment with printing ink varnish, solvents, additives, etc. A large amount of energy is required, however, to disperse the pigment as the primary particles of dry pigments are susceptible to aggregation. In the flushing method, the pigment is converted from the water phase to the varnish phase by mixing the wet cake with printing ink varnish, solvent, additives, etc. Although the energy required for this method is less than that of the dry pigment method, large installations such as a kneader are necessary and drainage occurs during the flushing process.
As indicated above, the process of pigmentation and the production of ink requires a large amount of time and energy for producing printing ink from .beta.-form copper phthalocyanine.
In order to provide low cost ink, production of ink directly from crude copper phthalocyanine without going through the stage of pigmentation may be conceived. However, the milling efficiency is low when printing ink
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Hayashi Mikio
Noguchi Hideto
Tomiya Nobuyuki
Klemanski Helene
Toyo Ink Manufacturing Co. Ltd.
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