Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-03-03
2002-08-27
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S494000, C106S495000, C106S496000, C106S497000, C106S498000
Reexamination Certificate
active
06440207
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to processes of preparing readily dispersible organic pigments by milling such pigments in the presence of aromatic polyalkylene oxide dispersants.
Crude organic pigments as obtained after chemical synthesis are generally unsuitable for use as pigments in coating formulations. Therefore, crude organic pigments undergo one or more finishing steps that modify particle size, particle shape, surface characteristics, and/or crystal structure of the pigment in such a way that provides a pigment having good pigmentary quality. See, for example, W. Carr, “Improving the Physical Properties of Pigments” in
Pigment Handbook
, Vol. III (New York: John Wiley & Sons, Inc., 1973), pages 29-35; W. Herbst and K. Hunger,
Industrial Organic Pigments
(New York: VCH Publishers, Inc., 1993), pages 205-207; R. B. McKay, “The Development of Organic Pigments with Particular Reference to Physical Form and Consequent Behavior in Use” in
Rev. Prog. Coloration
, 10, 25-32 (1979); and R. B. McKay, “Control of the application performance of classical organic pigments” in
JOCCA
, 89-93 (1989) herein incorporated by reference. In some finishing processes, one or more of the finishing steps can include a strong mineral acid, followed by precipitation of the pigment, and/or milling the crude pigment. A pigment conditioning process that avoids a strong acid step would be desirable because elimination of such a step would significantly reduce environmental and health risks associated with caustic chemicals and lower costs associated with pigment conditioning processes. Crude organic pigments having undergone a pigment conditioning process are called conditioned organic pigments and are typically sold commercially.
Various dispersants have been used to disperse and maintain, in a dispersed state, conditioned organic pigments in coating systems. Included among the known dispersants for this use are polyalkylene oxide-based compounds such as those described in U.S. Pat. Nos. 4,186,029, 4,373,930, 4,403,077, 4,436,522, 4,872,916, 4,927,463, 5,073,585, 5,266,622, 5,466,482, 5,494,511, 5,855,662, 5,935,272, 5,922,122, and 5,935,315, British Patent 2,090,876, German Offenlegungsschriften 2,414,455 and 19,811,791, Polish Patent 127,761, and PCT Application WO 99/49963. The resultant pigment dispersions or pastes can be combined with other components (such as resins and other additives) to form paints and other coatings. However, such dispersants have not been described as being used for milling crude organic pigments that are isolated as dry powders before being used in paints or other coatings.
U.S. Pat. No. 5,466,482 discloses the use of certain phosphate ester dispersants for surface treatment of organic pigments that, after isolation, are readily dispersible even in the absence of additional dispersant. This patent, however, does not disclose the use of such dispersants during milling or other conditioning processes.
U.S. Pat. No. 5,472,494 discloses pigment preparations containing organic pigments, certain perylene sulfonate or carboxylate derivatives, and optional additives, including dispersants, that can be mixed before, during, or after pigment conditioning. Aromatic polyalkylene oxide dispersants are not disclosed.
PCT Application WO 99/38920 discloses pigment compositions containing an isoindoline pigment, certain alkylenedicarboxylic acid dialkyl esters, and, optionally, fatty acid esters of polyhydroxyalkanes that can have one or more ether groups. Aromatic polyalkylene oxide dispersants are not disclosed.
U.S. Pat. No. 5,626,662 discloses a two-step milling method for preparing finely divided organic pigments by first dry milling coarsely crystalline pigments and then wet milling the resultant finely divided prepigments in aqueous suspension in a stirred ball mill at a power density of more than 2.5 kW per liter and a peripheral stirrer speed of more than 12 m/s using a grinding medium of no more than 1 mm. Milling auxiliaries, including surfactants, can be added in quantities of up to 10% by weight relative to the crude pigment during either milling step. The resultant milled pigment is collected by filtration and the resultant filtercake is then washed and dried. Both milling steps must be carried out to achieve desirable pigment properties.
It has now been found that pigments obtained according to the present invention after milling in the presence of aromatic polyalkylene oxide dispersants, unlike pigments dispersed in a conventional manner, are stir-in pigments that are readily dispersible in aqueous media and do not settle out upon standing. As a result, pigments prepared according to the invention are particularly suitable for use in water-based coating systems, such as coating compositions, paints, and printing inks.
SUMMARY OF THE INVENTION
The present invention relates to a process for preparing dispersible organic pigments comprising
(a) milling a mixture comprising
(1) one or more organic pigments,
(2) at least about 1% by weight, relative to the organic pigment, of one or more aromatic polyalkylene oxide dispersants,
(3) 0 to about 10 parts by weight, relative to the organic pigment, of a milling liquid in which the organic pigment is substantially insoluble,
(4) 0 to about 50% by weight, relative to the organic pigment, of one or more milling additives other than dispersant (2), and
(5) 0 to about 20% by weight, relative to the organic pigment, of one or more surface treatment additives;
(b) optionally, adding to the milled pigment
(6) one or more liquids in which the organic pigment is substantially insoluble in amounts such that the total solids content is not reduced below about 10%, and
(7) one or more multivalent metal salts and/or one or more quaternary ammonium salt; and
(c) isolating the milled organic pigment (preferably by methods other than filtration).
DETAILED DESCRIPTION OF THE INVENTION
In the process of the present invention, an organic pigment is milled with one or more aromatic polyalkylene oxide dispersants, an optional milling liquid, and optionally one or more milling additives, followed by isolation. The components of the milling mixture may be added or combined in any order such that preferably (but not necessarily) all are present at the start of the milling. The resultant organic pigments contain readily dispersible individual particles or loosely bound aggregates.
Organic Pigments
Suitable organic pigments for use in the practice of the present invention include perylenes, quinacridones, phthalocyanines, 1,4-diketopyrrolopyrroles, isoindolines, indanthrones, dioxazines (that is, triphenedioxazines), anthrapyrimidines, anthanthrones, flavanthrones, indanthrones, isoindolines, perinones, pyranthrones, thioindigos, 4,4′-diamino-1,1′-dianthraquinonyl, and azo compounds, as well as substituted derivatives thereof. Preferred organic pigments are perylene, quinacridone, phthalocyanine, 1,4-diketopyrrolopyrroles, and isoindoline pigments. Mixtures, including solid solutions, may also be prepared. The organic pigments can be used as crude organic pigments that have not been modified after chemical synthesis or as pigments that have been conditioned or otherwise treated by methods other than the process of the present invention.
Perylene pigments used in the practice of the present invention may be unsubstituted or substituted. Substituted perylenes may be substituted at imide nitrogen atoms for example, and substituents may include an alkyl group of 1 to 10 carbon atoms, an alkoxy group of 1 to 10 carbon atoms and a halogen (such as chlorine) or combinations thereof. Substituted perylenes may contain more than one of any one substituent. The diimides and dianhydrides of perylene-3,4,9,10-tetracarboxylic acid are preferred. Crude perylenes can be prepared by methods known in the art. Please review, W. Herbst and K. Hunger,
Industrial Organic Pigments
(New York: VCH Publishers, Inc., 1993), pages 9 and 467-475, H. Zollinger,
Color Chemistry
(VCH Verlagsgessellschaft, 1991), pages 227-228 and 297-298,
Bayer Corporation
Gil Joseph C.
Green Anthony J.
Roy Thomas W.
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