Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-11-20
2003-11-18
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S417000, C106S418000, C106S430000, C106S436000, C106S439000, C106S447000, C106S499000, C428S403000
Reexamination Certificate
active
06648956
ABSTRACT:
SUMMARY OF THE INVENTION
The invention relates to a nondusting, solvent-containing, homogeneous pigment preparation and its use, especially in printing inks.
Industrial processes frequently do not utilize pigments as dry powders, since these dust, which leads to heightened requirements with regard to workplace safety. Furthermore, the incorporation of powders into plastics, base coating systems, etc. is frequently accompanied by an agglomeration of the pigment powder. Homogeneous disbursement of the pigment in the respective matrix is frequently very difficult to achieve, if at all.
Nondusting pigment preparations are used instead of pigment powder. They are
pigmented free-flowing powders having a low moisture content, as known for example from DE-A-41 39 993,
pigmented powders having a higher moisture content, frequently also referred to as pastes because of their flowable consistency, or
pearl luster pigments coated with an alkylene glycol alkyl ether in amounts of 5-20% by weight, as known from U.S. Pat. No. 5,234,496.
Pastes are an industrial alternative to dry or moistened powders, provided they meet the following general conditions:
flowable consistency
very low dilatancy
very high pigment content
The components of the preparation should be such that the preparation is highly compatible with the other components of the particular coating system and readily disperses homogeneously on incorporation.
As well as good compatibility with the other constituents of the coating system, pigment preparations have to have high stability, ie. they must neither tend to phase separate, nor change their overall composition. This requirement is particularly important in the case of pigment preparations based on platelet-shaped pigments, since these tend to phase separate because of their loose structure. For instance, a solvent-containing pigment preparation obtained by pasting up a powder composed of pearl luster pigments, solvent and water will frequently lack stability and the components separate and the upper regions of the fill fall dry.
Pigment preparations that contain excessively volatile substances, for example low-boiling organic solvents, generally have the disadvantage of being instable in composition as a consequence of the volatility of the solvent. Furthermore, pearl luster pigments are difficult to wet with organic substances and solvents because of high surface tension, since these pigments have a sandwich structure and so possess a particularly large number of pores at the surface in particular and these pores are largely also very difficult to access for liquid substances (in contrast to conventional organic and inorganic pigments).
The solvent-containing pearl luster pigment preparations hitherto developed for use in coating systems, and having a pigment fraction >30% by weight and <70% by weight, do not fully meet the requirements described, especially because they tend to shear thicken.
The present invention therefore provides a free-flowing pigment preparation that contains at least 70% by weight of effect pigments. The preparation shall have high stability in storage and possess excellent compatibility with the other components of the coating system.
A particular concern in printing is that, once it has been applied, a printing ink should very quickly be freed of all volatile components, so that there is no detectable odor of these substances in the dry product (Robinson test). Care must therefore also be taken to ensure that the evaporation number does not exceed a certain upper limit.
It has been found that this is achieved by the pigment preparation of the invention.
The invention accordingly provides a nondusting, homogeneous pigment preparation, which includes
≧70% by weight of one or more effect pigments,
0.1-30% by weight of an organic solvent or solvent mixture having an evaporation number (EN) of 10 to 100 and a surface tension (ST) of ≦35 mN/m
and optionally
0-20% by weight of a surface-active substance.
The preparation of the invention is, depending on the moisture content, a free-flowing powder which is particularly suitable for incorporation into printing inks. More particularly, the preparation of the invention shortens the time needed to stir the pigment into the printing ink. Furthermore, it dramatically reduces the problem of foaming on incorporation of the preparation into aqueous printing ink systems. The pigment preparation of the invention likewise has the effect that the “final viscosity” is more quickly reached in the pigmented printing ink. The thusly pigmented printing inks are stable in storage and particularly readily redispersible.
The pigment preparations of the invention are likewise stable in storage and do not tend to separate or change in composition in the storage vessel.
An essential constituent of the pigment preparation according to the invention is effect pigments, for example pearl luster pigments, interference pigments, multilayer pigments, platelet-shaped metal oxides, for example Fe
2
O
3
, TiO
2
, SiO
2
, Al
2
O
3
, coated with one or more metal oxides and/or metal sulfides, holographic pigments, functional pigments based on platelet-shaped substrates and also all luster pigments known to one skilled in the art.
The use of an organic solvent or solvent mixture, preferably the use of an ester, ketone, alcohol, mineral oil or aromatic solvent, provides excellent wetting of the effect pigment, especially in the case of pigments having a high porosity, for example pearl luster pigments. Pearl luster pigments used are pigments based on platelet-shaped, transparent or semitransparent substrates composed for example of sheet-silicates such as, for example, natural or synthetic mica, talcum, sericite, kaolin, composed of glass or other silicatic materials composed of glass or graphite, coated with colored or colorless metal oxides, for example TiO
2
, titanium suboxides, titanium oxynitrides, Fe
2
O
3
, Fe
3
O
4
, SnO
2
, Cr
2
O
3
, ZnO, CuO, NiO and other metal oxides alone or mixed in a single layer or in successive layers. Pearl luster pigments are known for example from German patents and patent applications 14 67 468, 19 59 998, 20 09 566, 22 14 454, 22 15 191, 22 44 298, 23 13 331, 25 22 572, 31 37 808, 31 37 809, 31 51 343, 31 51 354, 31.51 355, 32 11 602, 32 35 017 and P 38 42 330 and commercially available, for example under the mark of Iriodin® from Merck KGaA, Darmstadt, Germany. Particularly preferred pigment preparations contain TiO
2
/mica, Fe
2
O
3
/mica and/or TiO
2
/Fe
2
O
3
mica pigments.
Preference is further given to TiO
2
—and/or Fe
2
O
3
-coated SiO
2
or Al
2
O
3
platelets. The SiO
2
platelets can be coated with one or more metal oxides as described for example in WO 93/08237 (wet-chemical coating) or DE-A 196 14 637 (CVD process). Coated Al
2
O
3
platelets are known for example from EP 0 763 573.
The pigment preparations of the invention may contain one or more effect pigments. Frequently, the use of at least two different effect pigments will provide special color and luster effects.
The pigment preparation of the invention preferably contains ≧70% by weight of effect pigments, especially ≧80% by weight. Very particular preference is given to pigment preparations having an effect pigment content of more than 85% by weight. Preference is given to using one or more pearl luster pigments. The weight percentages are based on the pasted-up pigment preparation.
Organic solvents useful for the pigment preparation of the invention, especially if it is to be used in printing and packaging, include esters, alcohols, di- and trialcohols, ketones, polyols, mineral oils and/or aromatic solvents.
The solvents mentioned have evaporation numbers of 10 to 100 in order to ensure relatively rapid drying in particular in printing, as on high-speed printing presses. Preferably the evaporation number (EN) of the solvent or solvent mixture used is in the range from 12 to 40, especially in the range from 15 to 30 (diethyl ether=1) to ensure rapid drying and to minimize the odour of the print. The su
Hechler Wolfgang
Herget Gerhard
Husseini Brigitte
Schoen Sabine
Bell Mark L.
Hailey Patricia L.
Merck Patent Gesellschaft mit beschraenkter Haftung
Millen White Zelano & Branigan P.C.
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