Note: Descriptions are shown in the official language in which they were submitted.
CA 02524042 2005-10-27
WO 2004/099500 PCT/EP2004/004222
METHOD FOR PRODUCING COATED PAPER WITH PEARLESCENT
EFFECT
Technical Field
The present invention relates to a method for producing coated paper
with pearlescent effect.
Background Art
Currently, coated papers are increasingly important in the graphic
sector.
In particular, so-called ivory or embossed coated papers are rather
widespread and are produced by combining the traditional processes for
producing coated papers with the methods for obtaining the so-called ivory
or embossed effect.
However, currently it is not easy to obtain a coated paper with
pearlescent effect by using conventional processes.
The pearlescent effect, according to current knowledge, can in fact be
obtained either by depositing, by means of a stiff blade, the pearlescent
pigments on the paper medium on which the coating has been spread
beforehand, or by mixing the pearlescent pigments with the coating and then
spreading the resulting mixture onto the paper medium.
However, it has been found that the products obtained with the
methods described above are very poor.
The dimensions of the pearlescent pigments are in fact distinctly
larger (by approximately ten times) than those of conventional coatings, and
it is therefore practically impossible to obtain a uniform mixture.
Furthermore, in order to allow pearlescent pigments to express their
characteristic effect, they must remain completely on the surface, whereas if
they are mixed with the coating they also distribute proximate to the paper
medium.
Finally, it should be noted that if the pearlescent pigments are
deposited by means of a stiff blade, since they are, as mentioned,
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considerably larger than the pigments that constitute the coating, they form
streaks and/or lines.
Disclosure of the Invention
The aim of the present invention is to provide a method for producing
coated paper with pearlescent effect that is capable of eliminating or in any
case drastically reducing the drawbacks noted above of conventional
methods.
Within this aim, an object of the invention is to provide a method for
producing coated paper with pearlescent effect that allows to obtain a paper
with high printability.
Another object of the present invention is to provide a technological
solution that allows to provide a range of coated papers with pearlescent (or
slightly pearlescent) effect while maintaining a high brightness, so as to
allow their use in the most disparate sectors, from graphics to packaging and
covering to advertising.
Another object of the invention is to provide a method for producing
coated paper with pearlescent effect that allows to obtain coated papers with
pearlescent effect on one or both sides of the paper medium.
This aim and these and other objects that will become better apparent
hereinafter are achieved by a method for producing coated paper with
pearlescent effect, characterized in that it sequentially comprises the steps
of.
-- performing a first deposition, on at least one side of a paper
medium, of at least one first layer of coating;
-- performing a second deposition, over the first layer of coating, of a
coating with pearlescent effect by means of a
rotogravure/flexographic device.
Advantageously the coating with pearlescent effect comprises at least
nitrocellulose resins, mica-based pigments, and a solvent.
According to another aspect, the present invention provides a coated
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paper with pearlescent effect, which is characterized in that it comprises a
paper medium that has, at at least one side, at least one first layer of
coating
and, over the first layer of coating, at least one layer of coating having a
pearlescent effect.
Brief Description of the Drawings
Further aspects and advantages of the invention will become better
apparent from the present detailed description of some currently preferred
examples of embodiments, given merely by way of non-limiting example
with reference to the accompanying drawings, wherein:
Figure 1 is a perspective view of a coated paper with pearlescent
effect according to the invention;
Figure 2 is a perspective view of a deposition cylinder;
Figure 3 is an enlarged-scale side elevation view of the outer surface
of the deposition cylinder shown in Figure 2; and
Figure 4 is a sectional view, taken along the line IV-IV of Figure 3.
Ways of carrying out the Invention
In the examples of embodiments that follow, individual
characteristics, given in relation to specific examples, may actually be
interchanged with other different characteristics that exist in other examples
of embodiments.
Moreover, it is noted that anything found to be already known during
the patenting process is understood not to be claimed and to be the subject
of a disclaimer.
As shown by the figures, the present invention relates to a method for
producing coated paper having a pearlescent effect, generally designated by
the reference numeral 1.
In particular, the production process according to the invention
provides that at least one deposition of at least one layer 3a of coating is
performed at at least one side 2a of a paper medium 2, first of all, by way of
per se known devices or systems.
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Also according to the invention, the method for producing coated
paper with pearlescent effect provides for an additional deposition of a
pearlescent coating 3b over the coating layer 3a.
In particular, the additional deposition of pearlescent coating 3b is
performed by using rotogravure (or flexographic) devices (or systems),
constituted for example by a deposition roller 4, which has a plurality of
deposition cells 5 at its outer side wall 4a.
In greater detail, a method for producing coated paper having a
pearlescent effect, merely by way of example, can provide for a first
deposition of a layer of conventional coating approximately 6-12 microns
thick on both sides (2a and 2b) of a paper medium 2 that has a thickness of
approximately 100 microns.
Then, according to a preferred embodiment, an additional layer of
coating of approximately 1-8 microns per side is deposited on both sides.
It is evident that after these depositions (of "conventional" coating),
the thickness of the medium will be approximately 116-140 microns.
According to the invention, a layer of pearlescent coating is then
applied on one or both sides of the resulting medium by way of a system or
device of the rotogravure/flexographic type, constituted for example by a
deposition roller 4.
By way of example, this deposition or these depositions of layers of
pearlescent coating is(are) performed by placing the medium, or rather both
faces of the medium, in contact with the outer side wall 4a of the deposition
roller 4.
According to a preferred embodiment, the coating layer(s) containing
the pearlescent pigments deposited by the deposition roller 4 has(have) a
thickness of approximately 2-6 microns, which accordingly brings the total
thickness of the resulting paper to 120-152 microns.
Naturally, nothing forbids the use of initial paper media of different
thickness, or the deposition of thicknesses of coating (or pearlescent
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coating) having thicknesses that differ from those indicated in the method
described above.
Advantageously, the pearlescent coating comprises at least
nitrocellulose resins, mica-based pigments, and a suitable solvent.
5 According to another aspect, the present invention provides a coated
paper with pearlescent effect 1, which is constituted by a paper medium 2
that has, at at least one side 2a, at least one coating layer 3a and, above
the
coating layer 3a, at least one coating layer 3b with pearlescent effect.
All the characteristics of the invention described above as being
advantageous, convenient or the like may also be omitted or replaced with
equivalents.
All the details may further be replaced with other technically
equivalent elements.
The materials and the dimensions may be various according to
requirements.
