Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2002-04-01
2003-10-28
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S415000, C106S418000, C106S447000, C106S460000
Reexamination Certificate
active
06638353
ABSTRACT:
The invention relates to a non-dusting homogeneous pigment preparation notable in that it comprises at least 40% by weight of one or more effect pigments, 0.5-50% by weight of water and/or an organic solvent or solvent mixture, and 0.5-59.5% by weight of a styrene-modified maleate resin having an acid number of >90 mg KOH/g based on the pigment. Pigment preparations of this kind are particularly suitable for producing dry preparations, such as granules or chips, for example. The invention further relates to the production of the pigment preparation and the granules and to the use thereof for pigmenting printing inks.
In industrial processes, pigments are often not employed in the form of dry powders, since such powders produce dust, which results in heightened requirements in terms of workplace safety. In many cases, furthermore, when introducing powders into plastics, printing inks, industrial coatings, basecoat systems, etc., agglomeration of the pigment powder is observed. Homogeneous distribution of the pigment in the respective matrix is frequently difficult if not impossible to achieve.
Instead of the pigment powder, non-dusting pigment formulations or dry preparations are used. These are
free-flowing powders, pearl lustre pigments being coated with polymers, as are described, for example, in DE-C-2603211,
pigmented free-flowing powders having a low moisture content, as are known, for example, from DE-A-4139993,
pigmented powders having a relatively high moisture content, which owing to their flowable consistency are frequently referred to as pastes,
pigment formulations in granule form, in which organic pigments are coated with a resin mixture, as disclosed, for example, in EP 0 897 956 A2, or
dry preparations, such as pellets, granules as precursors for printing inks, as are known, for example, from EP 0 803 552.
Non-dusting homogeneous pigment preparations and dry preparations prepared from them are an industrial alternative to the dry or moistened powders provided that they meet the following general conditions:
flowable consistency
minimal dilatancy
maximum pigment content
The components of the preparation/paste, or of the dry preparations, should be chosen such that the formulation is harmonized very effectively with the other components of the respective coating system and is readily homogeneously distributed following its introduction.
In addition to good compatibility with the other constituents of the coating system, pigment preparations, and the dry preparations produced from them, are required to result in high stability in the coating systems, i.e., they must not tend towards phase separation, or, where this cannot be entirely prevented owing to the low viscosity, the coating systems must be able to be returned easily to a homogeneous state, i.e., the settled sediment must be easy to reagitate. This requirement is particularly important in the case of platelet-shaped pigments, since owing to their structure such pigments have a tendency to undergo “caking” on phase separation and are difficult to reagitate. Pigments based on platelet-shaped substrates give rise to handling problems insofar as, owing to the size and density of the pigments, they readily settle and may then cake together to form a very firm sediment cake. This cake is generally difficult to reagitate. This is particularly so in connection with the storage of varnishes, paints and printing inks, as well as In connection with their processing.
For this reason, numerous methods, inter alia, have been developed in order to solve the problem of the incorporation and handling of platelet-shaped pigments in coating compositions. Reagitation can be facilitated by adding to the coating compositions additives which alternatively bring about controlled flocculation (house of cards effect), pseudoplastic and/or thixotropic behaviour, or steric and/or electrostatic repulsion of the pigments. However, these additives may have an adverse effect on the quality of the coating. In particular, the brilliance in the case of effect pigments, and the uniformity of the coating, may be impaired.
In addition, homogeneous, stable distribution of the redispersants in the pearl lustre pigment powder is difficult to achieve, and/or the redispersant loses some of its activity in the course of mixing.
The effect pigment formulations developed to date for use in coating systems, with a pigment content >30% by weight, frequently do not go far enough towards meeting the requirements described above, especially since they have a tendency towards agglomeration and shear thickening.
The object of the present invention was therefore to provide pigment preparations, especially those in the form of formulations or pastes and dry preparations, which simultaneously can be used very effectively in aqueous, solventborne and solvent-free printing ink and coating systems, possess high stability, are easy to redisperse, and at the same time feature a high level of compatibility with the other components of the coating system. Furthermore, the pigment preparation of the invention ought also to be highly suitable for producing dry preparations in the form, for example, of pellets, granules, etc.
It has surprisingly been found that this object can be achieved by the provision of the pigment preparation of the invention. Styrene-modified maleate resins exhibit, in combination with effect pigments, such as pearl lustre pigments, for example, universal compatibility in aqueous, solventborne and solvent-free printing ink and coating systems. In addition, the formation of the interference effect in the case of pearl lustre pigments is promoted.
The invention therefore provides a non-dusting homogeneous pigment preparation which comprises
≧40% by weight of one or more effect pigments,
0.5-59.5% by weight of a styrene-modified maleate resin having an acid number >90 mg KOH/g,
0.5-50% by weight of water and/or an organic solvent or solvent mixture,
0-10% by weight of neutralizing agent(s), and
0-10% by weight of modifying agent.
Depending on its moisture content, the preparation of the invention is a flowable paste or a moistened, free-flowing powder. Both are highly suitable for producing dry preparations, e.g. granules, pellets, briquettes. The use of styrene-modified maleate resins specifically in the production of non-dusting pigment granules enables better compounding to be achieved than with the polymer resins known from the prior art, as disclosed, for example, in EP 0 803 558 A1. The dry preparations produced from the pigment formulation of the invention are likewise provided by the invention.
Moreover, the products of the invention are non-dusting, readily free-flowing, can be incorporated rapidly into commercially available binder systems, and are compatible therein. In particular, the products are compatible with aqueous, solventborne and also solvent-free printing ink and coating systems. The paints and varnishes produced from the dry preparation, e.g. granules or chips, are suitable for gravure, flexographic and screenprinting, offset overprint varnishes, overprint varnishes (OPVs), and also the various coating systems from the industrial coatings and automotive sector. They are also suitable for colouring plastics.
The pigment preparation of the invention contains preferably 40-98% by weight of effect pigments, especially 45-95% by weight, based on the preparation. Very particular preference is given to pigment preparations having an effect pigment content of more than 50% by weight. The percentages by weight are based in each case on the moist, i.e. undried, pigment preparation.
Effect pigments used are pigments based on platelet-shaped, transparent or semi-transparent substrates comprising, for example, sheet silicates, such as mica, synthetic mica, talc, sericite, kaolin or other silicatic materials, platelet-shaped iron oxide, SiO
2
flakes, TiO
2
flakes, graphite flakes, Fe
2
O
3
flakes, Al
2
O
3
flakes, glass flakes, holographic pigments, which are coated with rare earth metal sulphides such as, e.g., Ce
2
S
3
, co
Griessmann Carsten
Rathschlag Thomas
Koslow C. Melissa
Manlove Shalie
Merck Patent GmbH
Millen White Zelano & Branigan P.C.
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