High-printability coated paper and method for its production

Description

[0001] The present invention refers to a high-printability coated paper and to a method for its production.

[0002] Nowadays papers are known and widespread upon which special surface treatments are carried out, for example coatings that can confer special effects both in aesthetic and tactile terms.

[0003] Indeed, in the paper sector, new ideas and technical solutions are continually being sought that make it possible to obtain paper products that are innovative and special, and capable of attracting, intriguing and astonishing end users. As indicated above, one of the paths taken by paper makers is to develop new types of paper that have tactile properties which are different from the usual ones, while at the same time maintaining the normal characteristics of the paper substrate.

[0004] In particular it has been found that almost all paper products provided with surface finishings that provide the specific tactile sensations of "plastic effect" or "silk/leather effect" present substantially two types of drawback.

[0005] A first drawback is constituted by the extreme sensitivity of the coating layer to pressure, a phenomenon that leads to adhesiveness between successive coils of coated paper when it is spooled onto a roll or between successive sheets once the paper has been cut and stacked (in the jargon, this phenomenon is known as "blocking").

[0006] A second drawback is related to lower print quality on the above mentioned paper products compared to what can be obtained on traditional papers for graphic uses. Specifically, it has been found that there are difficulties in anchoring the ink, a lack of sharpness of the print typeset, and what is known as "setoff" owing to the ink slow drying speed.

[0007] The aim of the present invention is to obtain a paper, and specifically a high-printability coated paper, that has a tactile sensation which is special and unique, different from other products present on the market.

[0008] Within this aim, an object of the present invention is to make available a high-printability coated paper that can be used for packaging and for printing using the methods normally used for natural or traditional coated papers, including for example offset, embossing, hot stamping, thermal imaging and silk-screen for printing, and cutting, punching, creasing, folding and gluing for packaging operations.

[0009] Another object of the invention is to provide a high-printability coated paper that, specifically, has a surface that is soft and smooth to the touch and which at the same time has an opacity such as to bring to mind the concept of softness, also in visual terms.

[0010] A further object of the invention is to make available a method for producing a new type of high-printability coated paper which is extremely reliable and efficacious.

[0011] A further object of the invention is to develop a high-printability coated paper that allows effective anchoring of the ink during printing and which, at the same time, is less subject to the phenomenon of blocking.

[0012] This aim, as well as these and other objects which will become better apparent hereinafter, are achieved by a high-printability coated paper, comprising a paper substrate that has at least one coated face, characterized in that said coating comprises a layer of substantially uniform thickness of a composition that comprises a polyurethane-based polymeric material in a percentage comprised between 65% and 90% by weight of the total weight and latex in a percentage comprised between 5% and 20% by weight of the total weight.

[0013] The invention also provides a method for producing coated paper, characterized in that the method comprises the step of depositing, by coating, on at least one face of a paper substrate, a composition comprising a polyurethane-based polymeric material in a percentage comprised between 65% and 90% by weight of the total weight and latex in a percentage comprised between 5% and 20% by weight of the total weight.

[0014] Further characteristics and advantages of the invention will become better apparent from the following detailed description of some preferred, but not exclusive, embodiments of a high-printability coated paper, and of its production method, according to the invention.

[0015] In the embodiments that follow, individual characteristics shown in relation to specific examples may in reality be interchanged with other, different characteristics, existing in other embodiments.

[0016] The present invention refers to a coated paper, particularly adapted to printing and packaging, which comprises a paper substrate that has at least one coated face.

[0017] According to the present invention, the coating comprises a layer, of substantially uniform thickness, of a composition that comprises a polyurethane-based polymeric material in a percentage comprised between 65% and 90% by weight of the total weight and latex in a percentage comprised between 5% and 20% by weight of the total weight.

[0018] In particular, such composition is constituted by an aqueous dispersion of polyurethane-based polymeric material and latex.

[0019] Advantageously, the composition also comprises talc in a percentage of less than 20% by weight of the total weight.

[0020] Advisably, the paper substrate has a grammage that is comprised between 85g/m² and 400 g/m², a Bendtsen roughness degree that is comprised between 50 ml/min and 200 ml/min and a water absorption index (Cobb index) that is comprised between 20 g/m² and 25 g/m².

[0021] Obviously, the paper substrates used can be white or mass-coloured.

[0022] More precisely, the polyurethane-based polymeric material comprises a film-forming bonding agent, which comprises dispersions of anionic urethane polymers having aliphatic rigid segments and flexible polyether and polyester segments.

[0023] In this regard, the use of the formula commercially known as "Rolflex 2090", which is made by Lamberti S.p.A. in Gallarate (Varese, Italy) and which comprises, as well as the abovementioned components, silica, formulation auxiliaries and functional additives, has been found to be particularly suitable.

[0024] Advantageously, the composition is applied to such at least one face of the paper substrate in a quantity comprised between 3 g/m² and 15 g/m², preferably between 5 g/m² and 10 g/m².

[0025] It has also been found to be particularly useful to ensure that the talc added to the composition has an average diameter of 2.0 microns and a granulometric distribution such that at least 45%, preferably at least 48%, of the particles have a diameter of less than 2 microns.

[0026] Advisably, the latex used is of the SBR (Styrene-Butadiene-Rubber) type, but obviously there is no reason why other types of latex such as, for example, acrylic-based latexes should not be used, even though experimental results for such latexes have not been shown to be as satisfactory.

[0027] Obviously it is possible to add coloured pigments to the composition, if desired, to give more intense colourings to the coated surface.

[0028] According to another aspect, the present invention provides a method for producing coated paper which provides for the deposition, by coating, on at least one face of a paper substrate, of a composition comprising a polyurethane-based polymeric material in a percentage comprised between 65% and 90% by weight of the total weight and latex in a percentage comprised between 5% and 20% by weight of the total weight.

[0029] Advisably, the composition comprises talc in a percentage of less than 20% by weight of the total weight.

[0030] By way of example, the coating comprises an air knife coating.

[0031] According to a particularly important aspect, the temperature of the ribbon of coated paper should be kept at a temperature lower than 30°C.

[0032] Specifically, the production method makes use of one or more spreading rollers to take the coating that has a composition comprising polyurethane-based polymeric material, latex and possibly talc, in the percentages indicated above from a containment receptacle and to transfer it onto a ribbon of paper substrate upon which the coating is to be executed.

[0033] The quantity of coating applied exceeds the desired end result and the operation to remove the excess quantity is carried out by means of a "calibrated air blast" or air knife located immediately downstream of the applicator rollers.

[0034] Subsequently there is a drying phase which takes place by means of various different technologies such as, for example, radiation drying using infrared rays, convection drying using hot-air hoods, or conduction drying using steam-heated cylinders.

[0035] This phase can be followed by an identical sequence of operations if it is desired to apply a coating to the other side of the paper substrate as well.

[0036] Lastly, any accessory operations (for example cooling, coating, smoothing) can be performed before spooling the paper in rolls.

[0037] It has been found by experimental analysis of the coated paper according to the invention that the tactile effect obtained is, in effect, extremely unusual and original and able to convey the concept of "softness", also in visual terms.

[0038] From tests carried out, it has also been verified that the "blocking" phenomenon is greatly reduced by the combined action of the latex. The optional addition of talc has also produced a degree of printability that is substantially similar to that of papers for graphic uses.

[0039] In addition, all the details can be replaced by other technically equivalent elements.

[0040] The disclosures in Italian Patent Application No. VR2009A000054 from which this application claims priority are incorporated herein by reference.

[0041] Where the technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A high-printability coated paper, comprising a paper substrate that has at least one coated face, characterized in that said coating comprises a layer of substantially uniform thickness of a composition comprising a polyurethane-based polymeric material in a percentage comprised between 65% and 90% by weight of the total weight and latex in a percentage comprised between 5% and 20% by weight of the total weight.

2. The high-printability coated paper according to claim 1, characterized in that said composition comprises talc in a percentage below 20% by weight of the total weight.

3. The high-printability coated paper according to claim 1, characterized in that said polyurethane-based polymeric material comprises a film-forming bonding agent, which comprises dispersions of anionic urethane polymers having aliphatic rigid segments and flexible polyether and polyester segments.

4. The high-printability coated paper according to one or more of the preceding claims, characterized in that said composition is applied on said at least one face in a quantity comprised between 3 g/m² and 15 g/m², preferably between 5 g/m² and 10 g/m².

5. The high-printability coated paper according to one or more of the preceding claims, characterized in that said paper substrate has a grammage comprised between 85 g/m² and 400 g/m².

6. The high-printability coated paper according to one or more of claims 2 to 5, characterized in that said talc has an average diameter of 2.0 microns and a particle size distribution such that at least 45% of the particles have a diameter of less than 2 microns.

7. The high-printability coated paper according to one or more of the preceding claims, characterized in that said latex is of the SBR (Styrene-Butadiene-Rubber) type.

8. A method for producing high-printability coated paper, characterized in that it comprises the step of depositing, by coating, on at least one face of a paper substrate, a composition comprising a polyurethane-based polymeric material in a percentage comprised between 65% and 90% by weight of the total weight and latex in a percentage comprised between 5% and 20% by weight of the total weight.

9. The method according to claim 8, characterized in that said composition comprises talc in a percentage of less than 20% by weight of the total weight.

10. The method according to one or more of claims 8 and 9, characterized in that said coating comprises an air knife coating.

11. The method according to one or more of claims 8 and 9, characterized in that the temperature of the ribbon of coated paper is kept below 30°C.