.delta.-indanthrone blue pigment and manufacturing method theref

Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...

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106400, 106401, 544339, 544340, C08K 500

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057887594

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BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a .delta.-indanthrone blue pigment which exhibits a more reddish blue color than .alpha.-indanthrone blue pigment and to a manufacturing method thereof.
2. Description of the Related Art
According to PB Report 85172 and THE JOURNAL OF JAPAN SOCIETY OF COLOUR MATERIAL (Vol 43, pp 560-561, 1979) which introduced the contents of the PB Report, there are 4 types of crystal form known for indanthrones, .alpha., .beta., .gamma., and .delta.. These indanthrones are used as dye stuffs, and their crystalline properties have only been of secondary importance. In addition, it is reported that, of these crystalline forms, .alpha. is the most stable crystal form, the others are reported to change crystal form to .alpha. when heated to 250.degree. C. .delta.-indanthrone is made by dissolving indanthrone in concentrated sulfuric acid and then slowly adding water. In addition, it is stated that its particle diameter is large, and that its color is greenish gray.
In addition, it is stated in Japanese Patent Application, First Publication, Sho. 53-98334 that indanthrone exists in 4 polymorphic crystal forms called .alpha.-, .beta.-, .gamma.-, and .delta.-transformations; .alpha.- and .beta.- crystal forms give a blue coloring which has a greenish tone; .gamma.-crystal form gives a blue coloring which has a reddish tone; and .delta.-crystal form has no value from the point of view of color. Furthermore, it is stated that, within the indanthrone crystal forms, the .alpha.-form is the most stable, and, for this reason, it is good for use as a pigment for coloring varnish and composition resins; and that the .gamma.-form is obtained by oxidizing leuco indanthrone at 50.degree. C., and then the filtration residue is dried carefully in a vacuum.
The .alpha.-indanthrone blue pigment, as a beautiful reddish blue pigment is used mainly in the automobile paint field because it gives a reddish blue color of high weather resistance that copper phthalocyanine cannot satisfactorily possess.
However, .alpha.-indanthrone blue pigment has a problem for coloring such as flip-flop phenomenon, for example, when .alpha.-indanthrone blue pigment is used in metallic paint for automobile use, when observed from a vertical angle to the paint panel, it looks reddish blue but it is on the greenish side, in the reddish blue range the reddishness is not strong, in contrast, when the metallic paint panel is observed from the bottom angle, the reddishness appears strong. This problem can be improved by making the particles of .alpha.-indanthrone blue pigment smaller, however, the hue becomes even greener causing a new problem.
Because the hue of .beta.-indanthrone blue pigment has about the same degree of reddish blue color as the .alpha.-indanthrone blue pigment, it has no value over .alpha.-indanthrone blue pigment, and, in addition, it has a problem of being unstable as a pigment.
The .gamma.-indanthrone blue pigment exhibits a more reddish blue color than .alpha.-indanthrone blue, but, because it is unstable in terms of its crystal properties, a stable pigment cannot be obtained.
The above-mentioned public literature has a description to the effect that .delta.-indanthrone blue has no value from the point of coloring as a pigment, and also among pigment manufacturers, .delta.-indanthrone blue is considered to have no value from the point of view of color. In addition, .delta.-indanthrone lacks stability as a coloring material because it has an unstable crystal form, and when used as a paint, it was thought to cause problems such as heat discoloration, and discoloration over time.
For this reason, it has not been possible to make a tone of strong reddish blue color except by employing, for example, a method of mixing blue pigments of phthalocyanine with other violet pigments, or red pigments.
Furthermore, methods which use pigments of different chemical structure together have not been able to provide colors which can satisfy the various problems such as inferiorit

REFERENCES:
patent: 4167634 (1979-09-01), Hoch et al.
"Chemical Abstracts", vol. 93, Abstract No. 48538 of DE 2854190, Mar. 1980.
Derwent Abstract, "WPIDS", No. 80-23803C of DE 2854190, Mar. 1980.

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