Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1999-10-14
2001-08-07
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S447000, C106S491000, C106S504000, C106S501100, C106S169410, C106S169560
Reexamination Certificate
active
06270563
ABSTRACT:
The invention relates to a non-dusting homogeneous pigment composition, its preparation and its use in paints, varnishes, printing inks and plastics and as a precursor for printing inks.
BACKGROUND OF THE INVENTION
Pigments in industrial processes are often used not in the form of dry powders, since such powders form dust, which leads to increased requirements in terms of workplace safety. In addition, the incorporation of powders into plastics, basecoat systems, etc., is frequently observed to be accompanied by agglomeration of the pigment powder. Homogeneous distribution of the pigment in the respective matrix is, however, difficult if not impossible to achieve.
Instead of the pigment powder, non-dusting pigment preparations are used, as known from DE-C 36 27 329 and DE-A 41 39 993. These are readily dispersible pearl luster pigment preparations, in which a platelet-shaped pearl luster pigment is coated with a polymer resin with or without plasticizers, solvents and surfactants. DE-A 41 39 993 discloses pigmented free-flowing powders with a low moisture content.
Pastes and dry preparations prepared from them, as known, for example, from EP 0 803 552, are an industrial alternative to the dry or moistened powders provided that they meet the following general conditions:
flowable consistency
minimal dilatency
at maximum pigment content
The components of the preparation/paste should be chosen such that the preparation/paste is tailored to suit the other components of the respective coating system and, once incorporated, lends itself readily to homogeneous distribution.
In addition to good compatibility with the other components of the coating system, pigment preparations are required to exhibit high stability; that is, they must not tend towards phase separation. This requirement is particularly important in the case of pigment preparations based on platelet-shaped pigments, since owing to their structure such pigments have a tendency to undergo caking on phase separation and are difficult to reagitate. Homogeneous distribution of the pigment in the respective matrix is difficult, if not impossible, to achieve. For example, an aqueous pigment preparation obtained by forming an aqueous paste from a powder comprising platelet-shaped pearl luster pigments exhibits inadequate stability.
Coating compositions, such as varnishes, paints, printing inks, etc., comprising pigments based on platelet-shaped substrates are subject to handling problems insofar as the pigments, owing to their size and density, settle readily and may then become compacted to form an extremely solid sediment cake. This cake can generally be reagitated only with very great difficulty. This situation affects in particular the storage of varnishes, paints and printing inks and their processing.
Thus, numerous methods have been developed, inter alia, to solve the problem of the incorporation and handling of platelet-shaped pigments in coating compositions.
DE 36 27 329 and the EPs 0 306 056 and 0 268 918 disclose that modified platelet-shaped substrates with a polymer coating and, respectively, following treating with coupling reagents such as organotitanates, or organosilanes in covering compositions, exhibit improved settling and reagitation characteristics.
Furthermore, reagitation can be facilitated by treating the coating compositions with additives which bring about controlled flocculation (house of cards effect), pseudoplastic and/or thixotropic behavior, steric repulsion and/or electrostatic repulsion of the pigments.
Additives with thixotropic characteristics are described in EP 0 198 519 and DE-A 18 05 693. DE-A 39 22 178 discloses that mixing a suspension of a platelet-shaped substrate with spherical particles such as SiO
2
, TiO
2
and ZrO
2
, for example, produces deagglomerated and readily dispersible pigments.
In EP 0 523 357, pearl luster pigments are treated with diurea derivatives, while EP 0 515 928 discloses the surface modification of pigments with polyacrylates. EP 0 650 144 discloses the coating of pearl luster pigments with SiO
2
/Al
2
O
3
and SiO
2
/ZrO
2
.
The pigment preparations that are based on platelet-shaped pigments and have been developed to date for use in aqueous and organic coating systems often fail to comply to a sufficient extent with the requirements as described.
SUMMARY OF THE INVENTION
An object of the present invention was therefore to provide pigment compositions, based on platelet-shaped pigments, which
can be used in aqueous and organic coating systems,
exhibit high stability, and
are characterized by a high level of compatibilty with the other components of the coating system.
It has been found that this object can be achieved by the provision of the pigment composition of the invention.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.
The invention therefore provides a non-dusting homogeneous pigment composition comprising:
at least 50% by weight of one or more effect pigments,
0.1-50% by weight of plasticizer or a mixture of plasticizer
itrocellulose, and
0-49.9% by weight of a solvent or solvent mixture.
The invention also provides a process for preparing the pigment composition, characterized by the dry mixing of the effect pigments with the plasticizer or plasticizer
itrocellulose mixture and, if used, with the solvent or solvent mixture in a mixing vessel.
Also surprising is the observation that the pigment preparation is not permanently affected in its optical properties. The concentration in which the plasticizer or plasticizer
itrocellulose mixture is used is 0.1-50% by weight; preferably, however, it is 5-30% by weight, in particular 10-25% by weight, based on the pigment. The weight ratio of plasticizer to nitrocellulose is variable but is preferably from 1:1 to 1:9.
The pigment preparation according to the invention is also notable for its good compatibility with the other components of coating systems, and for its good processability, high level of freedom from dust, and stability. In connection with the ease of incorporation of the pigment preparation into formulations, a delayed settling behavior and an improved reagitation behavior of any sediment are observed. Furthermore, depending on the moisture content, the pigment composition is a flowable paste or a moistened free-flowing powder highly suitable for the production of dry preparations, such as pellets, granules, briquettes, etc., for example. The dry preparations produced from the pigment preparation of the invention are likewise provided by the invention.
An essential constituent of the composition is pigments. The effect pigments used are preferably interference pigments based on platelet-shaped, transparent or semitransparent substrates of, for example, sheet silicates, such as, for instance, natural or synthetic mica, talc, kaolin, or of glass or other silicatic materials, which are coated with one or more layers of at least one metal oxide or metal oxide hydrate. In such an arrangement at least one of these layers comprises preferably one or more metal oxides and/or metal oxide hydrates of high refractive index, selected from the following group: titanium dioxide, titanium suboxide, tin oxide, zirconium oxide, zirconium dioxide, zinc oxide, iron oxide (Fe
2
O
3
, Fe
2
,O
4
), chromium oxide, nickel oxide, cobalt oxide and the corresponding oxide hydrates.
It is also possible to use platelet-shaped metal oxides such as, for example, platelet-shaped iron oxide, aluminum oxide, titanium dioxide, silicon dioxide, LCPs (liquid crystal polymers), holographic pigments or bismuth oxichloride in the pigment preparations of the invention.
As the platelet-shaped pigments it is also possible to use metal flakes, which can be uncoated or else covered with one or more metal oxide layers; preference is given, for example, to Al, Cr, Fe, Au, Ag and steel flakes. Where metal flakes susceptible to corrosion, such as Al, Fe or steel flakes, for example, are to be used uncoated, they are preferably
Griessmann Carsten
Hechler Wolfgang
Herget Gerhard
Faison Veronica F.
Koslow C. Melissa
Merck Patent GmbH
Millen White Zelano & Branigan
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