Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2002-04-29
2003-04-22
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S415000, C106S417000, C106S418000, C106S474000, C106S502000
Reexamination Certificate
active
06551397
ABSTRACT:
The present invention relates to a pigment preparation essentially consisting of a mixture of BiOCl pigments, luster pigments and spherical particles, and to the use thereof, in particular in printing inks.
Printing inks generally consist of binders, pigments or dyes and additives. In print products for packing prints, labels and high-quality magazines, the requirement to provide a special luster on the imaged articles occurs ever more frequently.
Offset printing inks comprising luster pigments all exhibit the disadvantage that they have problems with production run stability. They tend to build up or sediment rapidly on the inking system, printing plate and rubber blanket, meaning that a problem-free production run of more than 10,000 sheets is generally impossible. A fundamental problem is the strong tendency of luster pigments, in particular pearlescent pigments, due to the platelet-shaped structure and the specific chemical/physical surface properties, to form agglomerates in the printing ink, in which the pigments lie one on top of the other in the manner of a stack and can only be separated with difficulty owing to strong adhesion. Furthermore, the provision of luster on such proofs is generally unsatisfactory, which is attributable to the inadequate amount of pigments transferred to the print product. The ink becomes depleted in pigment on the transport route via inking system, plate and rubber blanket. The pigment accumulates at exposed points on the plate and blanket and results in piling-up.
Pigment preparations comprising pearlescent pigments and spherical particles have already been disclosed in DE-A-4446456. The use of BiOCl pigments in printing inks is described in publications by EM Industries and Mearl Corporation. Preparations comprising pearlescent pigments for offset printing have high luster, but have the disadvantage that the pearlescent pigments exhibit a strong tendency to migrate into the damping solution during printing, depending on the binder used. BiOCl pigments are ground during the printing process, which has the consequence that the optical properties of the pigments are substantially lost.
An object was therefore to provide a pigment preparation, preferably for printing inks, in particular for offset printing inks, which comprises luster pigments, but does not have the above-mentioned disadvantages.
Surprisingly, it has now been found that less pigment migration into the damping solution is observed and the quality of the luster effect and the amount of transferred pigment particles in the printing ink can be increased if a pigment preparation is used which, besides luster pigments, additionally comprises BiOCl pigments and spherical particles.
The pigment preparation according to the invention has the following advantages over the offset preparations from the prior art which comprise only pearlescent pigments or only BiOCl pigments:
higher luster
a more closed print image
better pigment transfer
less pigment migration into the damping solution
better hiding power.
The invention thus relates to a pigment preparation comprising BiOCl pigments, one or more luster pigments, spherical particles and, if desired, additives from the printing sector.
Due to the combination of BiOCl pigments with luster pigments, significantly more coloristic effects can be achieved in the printing inks. The ratio between BiOCl and luster pigment is preferably from 99:1 to 1:99 and in particular from 70:30 to 30:70. The pigment preparation according to the invention preferably comprises from 40 to 99.8% by weight, in particular from 70 to 99.5% by weight, of BiOCl and luster pigments, based on the preparation.
BiOCl pigments for offset printing are commercially available, for example from Engelhard under the name Mearlite Ultra Fine OFS and from Merck KGaA under the name Bi-Flair® 66a. The commercially available BiOCl pigments have particle sizes of 1-50 &mgr;m. For the pigment preparation according to the invention, BiOCl pigments having particle sizes of 5-20 &mgr;m are particularly suitable.
The BiOCl pigments can also be employed in the pigment preparation according to the invention in paste form. Compared with pulverulent BiOCl pigments, these dispersions have significantly higher silver luster, higher transparency and are even easier to disperse. Particularly suitable are BiOCl pastes in castor oil, nitrocellulose, mineral oil and alkyd resin.
A further important constituent of the pigment preparation according to the invention is the luster pigment. The pigment preparation may also comprise a mixture of different luster pigments, in order, for example, to achieve certain color effects.
The luster pigments used are preferably pigments based on platelet-shaped, transparent or semi-transparent substrates of, for example, phyllosilicates, such as, for example, mica, synthetic mica, SiO
2
platelets, glass platelets, TiO
2
platelets, Al
2
O
3
platelets, talc, sericite, kaolin, of glass or other silicate materials which are covered with rare-earth metal sulfides, such as, for example, Ce
2
S
3
, with colored or colorless metal oxides, such as, for example, TiO
2
, titanium suboxides, titanium oxynitrides, pseudobrookite, Fe
2
O
3
, Fe
3
O
4
, SnO
2
, Cr
2
O
3
, ZnO, CuO, NiO and other metal oxides, alone or in a mixture, in a uniform layer or in successive layers (multilayer pigments). Pearlescent pigments are disclosed, for example, in the 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 are commercially available, for example under the trade name Iriodin® from Merck KGaA, Darmstadt, Germany.
Particularly preferred pigment preparations comprise TiO
2
-, Fe
2
O
3
or TiO
2
/Fe
2
O
3
-coated mica, Al
2
O
3
, glass or SiO
2
platelets. The SiO
2
platelets can be coated, for example, as described in WO 93/08237 (wet-chemical coating) or DE-A 196 14 637 (CVD process). Al
2
O
3
platelets are disclosed, for example, in EP 0 763 573 A1. Platelet-shaped substrates which are covered with one or more rare-earth metal sulfides are disclosed, for example, in DE-A 198 10 317.
Also suitable are metal-effect pigments, in particular aluminium platelets modified for water-based or solvent-containing systems, as marketed by Eckart under the trade name Rotovario Aqua® or Stapa Hydroxal® for water-based applications, and Variocrom® and Paliocrom® pigments from BASF, in particular also those from EP-A 0 681 009 A1, EP-A 0 632 110 A1 and EP-A 0 634 458 A1, and LCP (liquid crystal polymer) pigments. Likewise suitable are all holographic pigments and platelet-shaped pigments with metal layers which are known to the person skilled in the art. Pigments of this type are marketed by Flex, BASF, Eckart and Schlenk.
The pigment preparations according to the invention may comprise one or more luster pigments, with it frequently being possible to achieve particular color and luster effects through the use of at least two different luster pigments.
In addition to the pearlescent pigments and BiOCl pigments, the pigment preparation according to the invention may also comprise carbon black particles, fluorescent pigments and/or organic colored pigments. The preparation then preferably consists of 50-100% by weight of BiOCl and luster pigments and 0-50% by weight of carbon black particles, fluorescent pigments and/or colored pigments. However, the content of all pigments in the pigment preparation should preferably not exceed 99.4% by weight. Furthermore, it is possible to add substances and particles which enable product identification (tracers).
The use of spherical particles in offset printing inks has already been disclosed in JP 62-143 984. The spherical resin or wax particles described therein, having a content of 0.1-20% by weight in the printing ink, which comprise neither luster pigments nor BiOCl pigments, are stirred in in order to improve the build-up properties and to prevent picking of the paper by the rubber blanke
Hechler Wolfgang
Weitzel Joachim
Koslow C. Melissa
Manlove Shalie
Merck Patent GmbH
Millen White Zelano & Branigan P.C.
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