Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-08-14
2001-11-06
Huang, Evelyn Mei (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C546S056000, C546S057000, C106S497000, C106S495000, C524S088000, C524S090000
Reexamination Certificate
active
06313300
ABSTRACT:
The present invention relates to a process for the preparation of quinacridone pigments by the catalyzed oxidation of the corresponding 6,13-dihydroquinacridone with air in a selected organic reaction medium.
Quinacridone pigments are known for their attractive red and magenta colors and for their outstanding fastness properties. It is well known in the art to prepare quinacridone pigments by oxidizing the correspondingly substituted 6,13-dihydroquinacridone. U.S. Pat. Nos. 2,821,529; 2,969,366; 3,148,075 and 3,287,457, for example, disclose the oxidation of a 6,13-dihydroquinacridone to the corresponding quinacridone in an alcoholic medium containing a base and a small amount of water using aromatic nitro compounds, e.g., the sodium salt of nitrobenzene sulfonic acid, or similar oxidizing agents.
U.S. Pat. No. 2,821,529 describes a process wherein various 6,13-dihydroquinacridones are oxidized to the corresponding quinacridone by heating a mixture containing the dihydroquinacridone and a mild oxidizing agent in an alkaline reaction medium. The medium is a mixture containing a major portion of an organic solvent, generally an alcohol, and a minor amount of water. The amount of water present in the reaction medium is small relative to the amount of the organic solvent.
The literature also describes processes for oxidizing a dihydroquinacridone to the corresponding quinacridone by utilizing molecular oxygen and a quinone compound as the oxidizing agent. Such a reaction is often referred to as an “air oxidation” because air is a preferred source of the molecular oxygen. In general, such oxidation processes are disclosed as taking place in an alkaline medium, usually an organic solvent containing a minor amount of water, in the presence of a quinone compound and molecular oxygen. The molecular oxygen is introduced to the reaction medium by bubbling an oxygen containing gas through the reaction medium or by blowing the oxygen containing gas above the surface thereof. Although the literature describes the quinone compound both as a catalyst and as an oxidizing agent, U.S. Pat. No. 3,024,239 discloses that the quinone is an oxidizing agent which is reduced to the corresponding leuco compound during the oxidation of the dihydroquinacridone. The molecular oxygen regenerates the quinone so that less than the stoichiometric amount of the quinone is required for the reaction to proceed to completion.
U.S. Pat. No. 3,475,436 discloses an air oxidation process wherein the reaction medium contains a major portion of tetramethylene sulfone and a relatively small amount of water. Similar processes which utilize an alkaline medium containing a major portion of other organic solvents, such as dimethylsulfoxide, dimethylacetamide, alkanediols, C
1
-C
3
alcohols caprolactam and N-alkyl-2-pyrrolidone, usually in the presence of a relatively small amount of water, are also known in the art.
The air oxidation of dihydroquinacridones in an aqueous reaction medium and in the presence of a divalent metal ion or a quaternary ammonium salt is also known. For example, U.S. Pat. No. 3,738,988 discloses a process wherein an aqueous medium is utilized and teaches that the oxidation step should be carried out in the presence of divalent iron, cobalt or nickel ions in order to increase the effectiveness of the oxidation. JP 53/904334 discloses an oxidation media including C
1
-C
3
alcohols and aqueous base, together with air. DE 3,834,748 and U.S. Pat. No. 5,093,497 describe the addition of a quaternary ammonium salt to the oxidation in both aqueous and organic reaction media.
U.S. Pat. No. 5,502,192 describes the conversion of the 6,13-dihydroquinacridone to the corresponding quinacridone in an aqueous medium via an air oxidation process in which the aqueous reaction medium also contains a relatively minor amount of a nonionic, polar organic material which forms a liquid, organic second-phase in the reaction mixture.
In many of the aforementioned processes, the reactants and resulting products are generally not in solution and consequently must be suspended during the oxidation reaction. The resulting pigments are filtered directly from the reaction mixture. The disadvantages encountered with these approaches include incomplete oxidation, long oxidation reaction cycles and particularly the crude nature of the isolated pigments which are relatively large in particle size. Because of the crude nature of the recovered pigment, additional conditioning steps are required to obtain a commercially acceptable strong transparent pigment.
Still other patents disclose the use of N-alkyl-2-pyrrolidone (JP 57/119958) or N-methyl-&egr;-caprolactam (JP 57/108162), or a mixture of polar solvents (JP 58/147459) together with base and preferably nitro compounds such as sodium m-nitrobenzene-sulfonate as the oxidation agent. Although air and oxygen are mentioned as potential oxidizing agents, the yield of quinacridones and substituted quinacridones obtained by such processes are not quantitative due to incomplete oxidation or concomitant over oxidation to quinacridonequinone. Furthermore, the use of solvent mixtures and aromatic nitro compounds requires expensive deposition of the organic reduction products which must be disposed of in an ecologically acceptable manner.
JP 54/135821 discloses the preparation of quinacridone pigments involving the oxidation of 6,13-dihydroquinacridone in dimethylsulfoxide in the presence of water, an alkali and an oxidizing agent such as sodium o-nitrobenzenesulfonate, sodium m-nitrobenzenesulfonate, sulfur powder, selenium, iodine or air, to obtain a quinacridone salt solution, which when diluted with a polar solvent or acid yields a finely divided product. Although this process produces quinacridones directly in pigmentary form, the use of air in such a process requires long reaction times and results in low yields of quinacridones as a consequence of the formation of quinacridonequinone and the presence of residual unoxidized 6,13-dihydroquinacridone. Furthermore, only unsubstituted quinacridones are described as being applicable to this method.
U.S. Pat. No. 5,286,863 describes a process for preparing quinacridone pigments in which 6,13-dihydroquinacridone or a derivative thereof is oxidized at an elevated temperature in the presence of a base, a dimethylsulfoxide medium and a quinone catalyst. This method is described as providing a direct synthesis of pigmentary grade quinacridone that does not require post synthesis conditioning, without the use of organic oxidizing agents or surfactants. U.S. Pat. No. 5,223,624 describes the synthesis of a unique &ggr;
III
form of quinacridone in which 6,13-dihydroquinacridone is oxidized in a dimethylsulfoxide medium.
Applicants have found that the direct oxidation of unsubstituted and/or substituted 6,13-dihydroquinacridones provides corresponding quinacridones in short reaction times and high yields when the oxidation is conducted in a selected organic reaction medium, most preferably a polyalkylene glycol medium, in the presence of an aqueous base, with air or another oxygen-containing gas mixture at a temperature below 100° C., catalyzed by a quinone or quinone derivative. In addition, the resulting solutions, upon subjection to hydrolysis or alcoholysis (drowning), optionally in the presence of an acid, provide quinacridones in a final pigmentary form that requires no post-synthesis particle size reduction procedures.
The use of a selected organic reaction medium allows the direct oxidation of substituted and/or unsubstituted 6,13-dihydroquinacridone to the corresponding quinacridone in an ecologically effective manner, i.e., without the use of organic oxidizing agents or surfactants, such that virtually no waste products are generated. The procedure also allows the introduction of particle growth inhibitors directly in to the reaction mixture whereby small particle size, transparent pigments can be obtained directly from synthesis without requiring mechanical size reduction (e.g., milling).
In addition, it has been unexpectedly found that the a
Ciba Specialty Chemicals Corp.
Crichton David R.
Huang Evelyn Mei
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