Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1993-06-22
1994-06-07
Klemanski, Helene
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106495, 546 49, C09B 4800
Patent
active
053186265
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for converting a 2,9-dimethylquinacridone compound into a pigment. More specifically, it relates to a process for converting a 2,9-dimethylquinacridone compound into a pigment which particularly has the form of crystal grains having a length:width average ratio of 2:1-5:1 and a specific surface area of 50-90 m.sup.2 /g, which has a crystal spacing and relative intensity of a so-called blue color tone pigment when measured by X-ray diffractometry and which has advantageous surface properties and various practically advantageous properties.
TECHNICAL BACKGROUND
As a process for producing a crude 2,9-dimethylquinacridone compound, for example, Japanese Patent Publication No. 36-13833 discloses a production process in which 2,9-dimethyl-6,13-dihydroquinacridone is oxidized in an alkaline alcoholic solvent in the presence of sodium nitrobenzenesulfonate or sodium polysulfide, or Japanese Patent Publication No. 38-26487 discloses a production process in which 2,5-di(p-toluidino)terephthalic acid is heated in polyphosphoric acid. A 2,9-dimethylquinacridone compound is known to be a substance in a solid form when it is a crude one. However, the following is also known. It is not much useful as a pigment when it is used directly. When its powder is used as a component for a coating composition, there is only obtained a product which is inferior from the commercial point of view. That is, this product is poor in dispersibility, liable to degenerate due to heat and light, unstable in a solvent, and dull in color tone. Attempts have been hitherto made to convert this substance into a useful pigment for obtaining 2,9-dimethylquinacridone having a desirable color tone.
Japanese Patent Publication No. 41-11348 discloses a treatment method in which a crude substance is pretreated, or not pretreated, with a solvent such as dimethylformamide, a lower alcohol, dimethylsulfoxide or xylene, and milled with a ball mill while it is immersed in a solvent such as xylene. It has been already revealed that 2,9-dimethylquinacridone is converted into two different crystal forms by this treatment. One having the first crystal form is obtained when the above pretreatment is not carried out, and it is called a blue color tone pigment. One having the second crystal form is obtained through the above pretreatment, and it is called a yellow color tone pigment. These pigments in these crystal forms are both stable at high temperatures, and particularly, the yellow color tone pigment is stable at high temperatures even in the presence of a solvent. However, these pigments obtained by the above pigment-forming method are both non-uniform in particle size, and when used in a coating composition, they have no satisfactory dispersibility.
Japanese Patent Publication No. 41-11348 proposes a third crystal form. One having this crystal form is obtained by adding a glycol, finely milled common salt and flakes-shaped common salt to a crude substance of 2,9-dimethylquinacridone or the yellow color tone pigment described in Japanese Patent Publication No. 41-11348 and milling with a milling apparatus to cause extreme shear deformation. However, it is required to fully mix common salt in an amount 2.25-15 times the weight of the pigment and a glycol in an amount 0.75 to 3 times the weight of the pigment with the pigment, and in this case, a considerable amount of energy is required. Further, after the milling, it is required to separate the added common salt and glycol by washing. Thus, the above pigment is not suitable for commercial production.
For producing 2,9-dimethylquinacridone, in Japanese Patent Publication No. 44-22419, Japanese Patent Publication No. 52-43497 and Japanese Laid-open Patent Publication No. 55-48250, 2,9-dimethylquinacridone is synthesized from 2,5-di(p-toluidino)terephthalic acid as a raw material in the presence of polyphosphoric acid or polyphosphoric acid ester as a solvent or a cyclization agent, and then separated while preventing the solidification of polyphosp
REFERENCES:
patent: 3607336 (1971-09-01), Jaffe
patent: 3686009 (1972-08-01), West
patent: 4212975 (1980-07-01), Kroh et al.
patent: 4400515 (1983-08-01), Fuchs et al.
Kato Shigeki
Maki Hitoshi
Hertzog Scott L.
Klemanski Helene
Toyo Ink Manufacturing Co. Ltd.
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