Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1999-12-15
2002-08-13
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C546S037000
Reexamination Certificate
active
06432193
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a novel continuous process for preparing perylene pigments having controllable particle shape, size, and size distribution. Of particular interest is the more desirable oval particle having a particle size between 15 nm and 75 nm and a narrow size distribution. Peryienes, particularly the diimides and dianhydrides of perylene-3,4,9,10-tetracarboxylic acid, can be unsubstituted or substituted (for example, with one or more alkyl, alkoxy, halogens such as chlorine, or other substituents typical of perylene pigments), including those that are substituted at imide nitrogen atoms with chemically reasonable groups such as alkyl. Crude perylenes can be prepared by methods known in the art by alkaline fusion of naphthalimides. For example, perylene melts can be prepared by mixing a naphthalimide in molten mixtures of caustic (usually caustic potash) and alkali metal carboxylates (usually sodium acetate) at high temperatures to form the non-pigmentary leuco form of a perylene tetracarboxylic diimide as a metal salt. This melt is usually drowned batchwise in water and then oxidized with air at elevated temperatures to give the pigment. E.g., W. Herbst and K. Hunger,
Industrial Organic Pigments,
2nd ed. (New York: VCH Publishers, Inc., 1997), page 476; H. Zollinger,
Color Chemistry
(VCH Verlagsgessellschaft, 1991), pages 227-228; and BIOS Final Report, 1484, page 21. The particles formed using this general procedure usually range from submicron size to several microns in size with a very wide size distribution.
Continuous processes for the preparation of perylene pigments are known. For example, U.S. Pat. No. 5,247,088 discloses a process in which the leuco form of perylene tetracarboxylic diimide is formed continuously and then drowned and oxidized batchwise. However, the reported processes do not disclose a continuous drowning and oxidation step that forms pigmentary perylenes while at the same time allowing control of particle size. The preparation of pigments having small particle sizes and a narrow size distribution is not achievable by conventional drowning processes, which generally give much larger particle sizes and very wide size distributions. The present invention overcomes such disadvantages.
SUMMARY OF THE INVENTION
This invention relates to a continuous process for preparing perylenes comprising
(a) continuously mixing a melt of the leuco form of a perylene tetracarboxylic diimide obtained by alkaline fusion of naphthalimide with a continuous water-containing stream comprising
(1) 2 to 50 parts by weight (preferably 4 to 20 parts by weight) of water per part by weight of the melt,
(2) 0 to X
1
moles of oxidizing agent per mole of the leuco form of the perylene tetracarboxylic diimide,
(3) 0 to Y
1
parts by weight of processing additives, based on the leuco form of the perylene tetracarboxylic diimide, and
(4) 0 to Z
1
parts by weight of an acid, based on the leuco form of the perylene tetracarboxylic diimide, to form a slurry;
(b) optionally mixing the slurry in one or more continuous or batchwise steps with a second stream comprising
(1) 0 to 10 parts by weight of water, based on the weight of the slurry,
(2) 0 to X
2
moles of oxidizing agent per mole of the leuco form of the perylene tetracarboxylic diimide, with the proviso the total of X
1
and X
2
represents at least the molar amount (preferably from 1 to 10 times the molar amount, more preferably from 2 to 6 times the molar amount) of oxidizing agent theoretically needed to oxidize all of the leuco form of the perylene tetracarboxylic diimide,
(3) 0 to Y
2
parts by weight of processing additives, based on the leuco form of the perylene tetracarboxylic diimide, with the proviso that the total of Y
1
and Y
2
is from 0 parts by weight (i.e., no additives are present) to 50 parts by weight (preferably 0 to 5 parts by weight), and
(4) 0 to Z
2
parts by weight of an acid, based on the leuco form of the perylene tetracarboxylic diimide, to give a perylene pigment;
(c) optionally, isolating the perylene pigment; and
(d) optionally, conditioning the perylene pigment.
DETAILED DESCRIPTION OF THE INVENTION
The process of the invention is accomplished by continuously mixing a melt of the leuco form of a perylene tetracarboxylic diimide with a drowning medium in one or more steps, at least the first of which is carried out using a continuous aqueous stream and at least one of which includes an amount of oxidizing agent theoretically sufficient to oxidize all of the leuco form of the perylene tetracarboxylic diimide.
Suitable oxidizing agents are capable of oxidizing the leuco form of the perylene tetracarboxylic diimide to form the desired pigment form, preferably without causing significant decomposition. Examples of suitable oxidizing agents include oxygen (including substantially pure O
2
, air and other gas mixtures containing oxygen, or ozone), persulfates (such as potassium persulfate), nitrobenzenesulfonic acid salts (such as the sodium salt), nitrates, chlorates, hydrogen peroxide (preferably in a concentration between 0.5% and 10%), adducts of hydrogen peroxide and borates, hypochlorites, and other known oxidizing agents.
The leuco form of a perylene tetracarboxylic diimide is obtained as a melt by alkaline fusion of naphthalimide using known methods. A method is described in U.S. Pat. No. 5,247,088, which is herein incorporated by reference.
In the first step of the process of the invention, the leuco-form melt is continuously mixed with a stream of liquid (“the drowning medium”) containing from 2 to 50 parts by weight of water per part by weight of the melt to form a slurry. The drowning medium used in the first step can optionally contain all or part of the oxidizing agent theoretically needed to oxidize the leuco form to the colored form as long as the total theoretical amount is added at some step in the overall process.
The drowning liquid used in the first step can also include various processing additives that help maintain particle size and prevent agglomeration, as well as enhance the efficiency of the oxidation process. It is also possible to add processing additives in later steps as long as the total amount of the additives does not exceed 50 parts by weight (preferably 0 to 5 parts by weight) based on the leuco form of the perylene tetracarboxylic diimide. Suitable processing additives include dispersants or surfactants, metal salts, and various pigment derivatives. Examples of suitable dispersants include anionic compounds, such as fatty acids (e.g., stearic or oleic acid), fatty acid salts (i.e., soaps such as alkali metal salts of fatty acids), fatty acid taurides or N-methyltaurides, alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylphenol polyglycol ether sulfates, naphthenic acids or resin acids (such as abietic acid); cationic compounds, such as quaternary ammonium salts, fatty amines, fatty amine ethylates, and fatty amine polyglycol ethers; and nonionic compounds, such as fatty alcohol polyglycol ethers, fatty alcohol polyglycol esters, and alkylphenol polyglycol ethers. Examples of suitable metal salts include various salts of alkali metals (such as lithium, sodium, and potassium), alkaline earth metals (such as magnesium, calcium, and barium), aluminum, transition and other heavy metals (such as iron, nickel, cobalt, manganese, copper, and tin), including, for example, the halide (especially chloride), sulfate, nitrate, phosphate, polyphosphate, sulfonate (such as methanesulfonate or p-toluenesulfonate, or even known quinacridone sulfonate derivatives), and carboxylate salts, as well as the oxides and hydroxides. Examples of suitable pigment additives include organic pigments having one or more sulfonic acid groups, sulfonamide groups, carboxylic acid, carboxamide, and/or (hetero)aryl-containing (cyclo)aliphatic groups.
The drowning liquid used in the first step can also include an acid to neutralize all or part of the alkali from the alkaline melt or can even be used in excess to acidify the mixture. The acid can even hel
Faubion Richard Kent
Feldhues Ulrich
Flatt Thomas R.
Putnam Mark A.
Vogel Richard A.
Bayer Corporation
Gil Joseph C.
Green Anthony J.
Henderson Richard E. L.
Roy Thomas W.
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