Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2002-12-18
2003-11-11
Rotman, Alan L. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C546S036000, C106S498000
Reexamination Certificate
active
06646126
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
The present invention is described in the German priority application No. DE-1 000 5186.3, filed May 2, 2000, which is hereby incorporated by reference as is fully disclosed herein.
FIELD OF THE INVENTION
The present invention relates to a particularly environment-friendly and economic process for preparing transparent perylene-3,4,9,10-tetracarboxylic diimide pigments of formula (I):
in which
u is a number from 0 to 8 and, if u>0,
E is a chlorine or bromine atom and, where u>1, may be a combination thereof.
BACKGROUND OF THE INVENTION
In the pigmentation of automotive finishes, especially the metallic finishes, there is a need for pigments which with a high transparency and clean hue give strongly colored and highly glossy finishes. The pigment concentrates and the paints must be of low viscosity and must not exhibit pseudoplasticity. Moreover, very good fastness properties are demanded, especially good weather fastness.
Depending on the synthesis route, organic pigments are obtained in coarsely crystalline or finely divided form. Crude pigments obtained in coarsely crystalline form require fine division before being used. Examples of such fine division processes are grinding on roll mills or vibratory mills, which may be performed wet or dry, with or without grinding aids such as salt, for example; kneading, revatting, reprecipitation from sulfuric acid or polyphosphoric acid, for example (acid pasting), and suspending in sulfuric acid or polyphosphoric acid, for example (acid swelling).
In the case of perylene-3,4,9,10-tetracarboxylic diimide (referred to below as perylimide), neither the prepigments obtained from a synthesis nor the prepigments obtained in finely divided form from a fine division known to date may be used directly as pigments, since in the course of processing and especially in the course of drying they have a very strong tendency to form aggregates and agglomerates, leading to poor dispersibility, which results, for example, in a loss of color strength. Moreover, perylimide pigments exhibit a very strong tendency to flocculate in paints. Both phenomena result in performance properties which no longer satisfy the present-day requirements.
Perylimide has been used for a long time as an organic brown to reddish violet pigment (C.I. Pigment Violet 29, C.I. No. 71129). The suitability of the halogenated derivatives as pigments is also known. The crude pigment is prepared either by reacting 1,8-naphthalenedicarboximide in alkali metal hydroxide melts and then oxidizing the resultant leuco form, as described for example in EP-A-0 123 256, or by condensing perylene-3,4,9,10-tetracarboxylic acid or its anhydrides or carboxylic salts (called peracid below) with ammonia, as described for example in DE-A-386 057. The preparation of the halogenated derivatives is described, for example, in EP-A-0 260 648. The following processes are described for converting the resultant perylimides into a coloristically useful pigment form:
DE-A-16 19 531 describes the conversion of crude perylimide into a pigment by grinding in inert organic solvents and drying to remove the solvent. The process is costly since it necessitates a high level of expenditure on apparatus; furthermore, the solvent must be regenerated.
DE-A-20 43 820 describes a wet grinding process in an aqueous-alkaline medium. The pigments obtained under the stated conditions, however, no longer satisfy present-day requirements.
DE-A-23 16 536 describes a two-stage process for preparing perylimide pigments by means of dry grinding of the crude pigment followed by a deagglomeration and recrystallization step, either by finishing in the presence of amines or amides, or by suspending the millbase in sulfuric acid (acid swelling). The amines or amides used may lead to incompatibilities in certain applications, so that the pigments are not universally applicable.
DE-A-28 51 752 describes a multistage process for conditioning organic pigments; perylimide, among others, is mentioned as an example: dry grinding is conducted in the presence of small amounts of acid, followed in a second step by a solvent finish comprising recrystallization of the agglomerates formed in the course of grinding. Dry grinding in the presence of acid imposes extreme requirements on the material of the milling equipment used; furthermore, it is virtually impossible in practice to prevent dust contamination of operating personnel and of the environment.
EP-A-0 039 912 discloses a process for preparing perylimides and halogenation products derived from them in pigment form by purifying the crude pigment via the sulfate stage and finely dividing it, then carrying out dry grinding for the purpose of deagglomeration, and then, if desired, conducting a solvent finish. This is a multistage process in the course of which large amounts of sulfuric acid are produced and must be disposed of.
EP-A-0 366 062 discloses a process for preparing halogenated perylimides and mixed crystals of halogenated perylimides of high hiding power.
According to DE 40 07 728, finely divided perylimide pigments are subjected to conditioning in the presence of organic solvents. This is a two-stage process. The preferred embodiment describes the use of carboxylic esters which following the finish are saponified and passed off into the wastewater.
EP-A-0 678 559 describes a two-stage process for the fine division of crude pigments. First of all a dry grinding operation is conducted, followed by wet grinding. The latter is required in order to disperse the agglomerated millbase. The two-stage procedure leads to increased costs and to long production cycles, dry grinding being hampered by the disadvantages described.
There was a need to prepare transparent perylimide pigments in a simple, cost-effective and environmentally friendly manner.
SUMMARY OF THE INVENTION
It has now been found that transparent perylimide pigments of formula (I) having advantageous coloristic and rheological properties may be prepared in a simple and environmentally friendly way from crude perylimide pigments by means of a special beadmilling operation with high energy density.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a process for preparing transparent perylimide pigments of the formula (I):
in which
u is a number from 0 to 8 and, if u>0,
E is a chlorine or bromine atom and, where u>1, may be a combination thereof, which comprises wet-grinding a crude perylimide pigment in a liquid medium in a stirred ballmill operated at a power density of from 1.0 kW per liter of milling space and at a stirrer peripheral speed of more than 12 m/s under the action of grinding media having a diameter of less than or equal to 0.9 mm, and isolating the resulting pigment.
The crude perylimide pigments for this process may have been prepared either by the route of the reaction of 1,8-naphthalenedicarboximide in alkali metal hydroxide melts with subsequent oxidation of the leuco form or by condensation from peracid, as defined above, with ammonia.
The crude, coarsely crystalline perylimide pigments obtainable from the synthesis, or finely crystalline perylimide prepigments, may be supplied in powder form or advantageously, with or without isolation beforehand, as a suspension, or in the form of an as-synthesized moist presscake, without further drying, to the wet grinding operation. It is also possible to purify the crude perylimide pigments, for example, by recrystallization or by extractive stirring with, for example, sulfuric acid.
The preparation of transparent perylimide pigments in accordance with the invention is surprisingly achieved without dry grinding beforehand. Examples of stirred ballmills which are suitable for conducting the wet grinding of the invention are those which are designed for batchwise and continuous operation, which have a cylindrical or hollow-cylindrical milling chamber in horizontal or vertical construction, which can be operated at a specific power density of more than 1.0 kW per liter of milling space, and whose st
Böhmer Martin
Dietz Erwin
Urban Manfred
Weber Joachim
Wilker Gerhard
Bisulca Anthony A.
Clariant GmbH
Coppins Janet L
Rotman Alan L.
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