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The use of pearlescent pigments in printing inks.

Offset Inks high quality, very easy to work with and fast work and turn. An object was therefore to find an offset printing ink preparation which contains pearlescent pigments, but nevertheless has none of the above-mentioned disadvantages. All offset printing inks containing pearlescent pigments have a disadvantage in that they have problems with stability during continuous printing. They tend to accumulate rapidly on the printing inks system, printing plate and blanket, so that problem-free continuous printing of more than 10,000 sheets is generally impossible. Furthermore, the glossing of such prints is generally unsatisfactory, due to the inadequate amount of pigments transferred to the print products. The concentration of pigment in the ink drops over the transport path over inking system, plate and blanket. The pigment accumulates at exposed areas on the plate and blanket and results in piling and caking. In general, only pearlescent pigments having a very small mean particle size are suitable, since the particle size is critical for pigment transfer in offset printing. Such pigments only exist for pearl-white and pastel-shaded inkings, but not for gold, silver, bronze and copper shades, in which there is a great deal of interest. It has hitherto not been possible to produce such shades satisfactorily in the offset method using pearlescent pigments.

The use of pearlescent pigments in printing inks for offset printing is described in DE 29 03 212, which discloses the pigmenting of a commercial oil-based printer's varnish containing a preferably very finely divided pearlescent pigment. The offset printer's varnish preparation described therein is distinguished by the fact that the proportion of pearlescent pigments is very high, the upper limit of the pigment concentration in the suspension essentially being limited only by the mixture flowability required. The proportion of pearlescent pigments is in the range up to 65% by weight. Varnishes having such a high proportion of pigments are very viscous and may have to be made more flowable using a thinner so as to be processable in conventional offset printing machines. Experiments have shown that, in contrast to the teaching of DE 29 03 212, the transfer of pigment from inking system to the substrate is adversely affected at such high pigment levels.

The main advantage of including offset inks the ability of high speed press, low cost and eliminate oil. Dark asphalt content, may be fed to animals, indeed, the fatty acids are edible. Discovered letterpress, offset printing ink viscosity range from 20 to 1000 unique may be appropriate. Looks like 1000 unique cap signature when cylinder actual contact ink reservoir. Ink viscosity is very difficult to pump used in some of the modern media. Ink viscosity, of course, the density and thickness of the paper stock page, and the speed of the news. Surprisingly, it has been found that the quality of the pearlescent effect and the amount of transferred pigment particles becomes optimum at printing ink viscosities <15 Pas. The novel pigmented printing ink has viscosities <12 Pas, preferably <8 Pas. The printing inks show no problems with splashing from the inking roller systems, even at printing rates of 10,000 sheets per hour. For optimum pigment transfer from inking system to the substrate, the pearlescent pigment:nonvolatile ink component ratio is important. The ratio should not be too high, since otherwise the pigment may be transported in an unsatisfactory manner. The pigment:nonvolatile ink component ratio is preferably <0.40, in particular <030.