Patent Application
20190040583
The present invention refers to a paper material (paper/card) and to the relative manufacturing method.
In the paper sector, there is a constant search for new types of paper having particular characteristics and finishes, especially papers designed for packing, packaging, realizing illustrative material, quality printing, etcetera.
However, it is not uncommon that the achievement of special effects is detrimental to other characteristics of the paper, such as printability.
A technical task of the present invention is to provide a paper material that has a different optical effect from conventional paper materials, while also being printable with high printing quality.
This technical task is solved by a paper material comprising a base support, made up of a mixture of cellulose fibres containing at least one polymeric substance, which is adapted to give the mixture of fibres mechanical strength, and an inorganic filler, said base support having at least one surface treated with at least one surface adhesive and at least one coating applied on said treated surface, characterized in that said coating comprises at least pearlescent pigments of high lightfastness.
The present invention also discloses a method for manufacturing the paper material, comprising the steps of:
preparing an aqueous pulp of cellulose fibres, containing at least one polymeric substance adapted to give the mixture of fibres mechanical strength, and an inorganic filler;
removing water from the pulp so as to form a base support of the paper material;
treating at least one surface of the base support with at least one surface adhesive;
performing a smoothing process on the treated surface of the base support;
applying a coating comprising at least pearlescent pigments of high lightfastness to the smoothed treated surface.
In a preferred embodiment the pearlescent pigments are borosilicates or aluminosilicates and in particular micas.
In a preferred embodiment the pearlescent pigments are transparent borosilicates or aluminosilicates coated with metal oxides such as iron oxides, titanium oxides or tin oxides.
In a preferred embodiment the pearlescent pigments are of various colours, particle sizes and shapes.
In a preferred embodiment the coating comprises one or more binder polymers and/or waxes, in a mixture with said pearlescent pigments.
In a preferred embodiment the coating comprises one or more binder polymers and/or waxes, in a mixture with said pearlescent pigments and with magnetic or diamagnetic metallic pigments.
In a preferred embodiment the metallic pigments are of various colours, particle sizes and shapes.
In a preferred embodiment the metallic effect pigments of the coating are those normally used for exterior grade paint.
Therefore the coating contains pearlescent pigments and can optionally contain metallic pigments as well as the pearlescent pigments.
Furthermore, the coating may also contain organic and inorganic pigments in addition to the pearlescent pigments and the metallic pigments.
There may also be organic or inorganic pigments contained in the base support which may be coloured.
The invention therefore provides a pearlescent paper material (paper/card) of high lightfastness, thanks to a specially designed pulp and a specific surface coating treatment.
The paper material of the invention also proves to be perfectly printable with high printing quality and makes it possible to achieve particular graphic effects that are difficult to achieve with conventional coated papers.
In detail, the paper material of the invention comprises a base support made up of a mixture of cellulosic fibres and it contains at least one polymeric substance, adapted to give the mixture of fibres mechanical strength (when dry or wet), and an inorganic filler, adapted to give the material good machinability characteristics.
The base support has at least one surface (face) treated with at least one surface adhesive to which a coating is applied, so that, due to the combined effect of the composition of the base support and the surface treatment, the paper material has a pearlescent effect with various colours. Clearly, both faces of the base support may be treated in the same way.
Preferably, the polymeric substance included in the base support comprises one or more colophony-based and/or alkyl-ketene-dimer-based and/or acetylsuccinic-acid-based and/or epochlorohydrin-based resins, and/or modified starches; and the inorganic filler is a mineral filler comprising one or more substances selected from the group constituted by carbonates, kaolins, talc and mixtures thereof.
The surface adhesive is for example an adhesive based on starch and/or polyvinyl alcohol- and/or acrylic-, polyurethane- and/or styrene-butadiene-based polymers. As mentioned, the paper material according to the invention is provided with a coating, applied on the treated surface and clearly, the paper material may have both surfaces treated and provided with a coating.
In particular, the coating is formed by one or more binder polymers (e.g. polyurethane- and/or silicone-, and/or acrylic-, styrene-butadiene-, polyvinyl acetate-, polyvinyl alcohol-based polymers and the like) and/or waxes, in a mixture with dyes and pigments, e.g. pearlescent pigments of various colours, particle sizes and shapes with the characteristic of being stable to the exposure of the UV component of sunlight.
The quantity of polymer per face is preferably comprised between 5% by weight and 100% by weight with respect to the pigments; the paper basis weight of the paper material is comprised between about 90 and about 450 g/m2; the quantity of coating spread onto each face is comprised between about 5 and about 20 g/m2.
The coating may be coloured and/or spread onto a coloured base support; preferably, coloured pastes and organic or inorganic pigments are used.
In accordance with a further aspect of the present invention, the paper material described hereinabove is realized using the following method.
The base support is realized first, using a substantially known paper-forming technique, for example on a continuous machine for manufacturing paper.
In essence, an aqueous pulp comprising a mixture of cellulose fibres and containing the polymeric substance (colophony-based and/or alkyl-ketene-dimer-based and/or acetylsuccinic-acid-based and/or epochlorohydrin-based resins, and/or modified starches) and the inorganic filler (carbonates, kaolins, talc, etcetera) is prepared.
Subsequently, water is removed from the pulp so as to form a base support of the paper material.
This is followed by a step of surface treatment of one or both faces of the base support with an aqueous solution of surface adhesive, for example made up of a 10% by weight aqueous solution of starch, and/or 5% by weight of acrylic adhesive, or similar adhesives.
After the surface treatment with adhesive, the method then comprises a smoothing step of the base support, wherein the base support is smoothed up to Bendtsen ISO 2494 roughness values of less than approximately 450 ml/min., preferably of less than approximately 400 ml/min. and approximately around 350 ml/min, followed by an application step of the coating previously described.
Preferably, the application of the coating takes place by spreading with an air knife or a smoothing blade, roto-offset, rotographic and flexographic techniques.
This is followed by step of drying the coating, carried out in an infrared and/or hot-air oven at a temperature within the range of 100° C. approximately to 180° C. approximately and with an oven time ranging between 0.5 and 4 minutes.
Lastly, the method comprises a step of mechanically treating the surface provided with the coating, particularly a smoothing and/or an embossing step.
It remains understood that modifications and variants that are not beyond the scope of the invention as defined in the appended claims, may be made concerning the paper material and the relative manufacturing method disclosed and illustrated herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102016000010127 | Feb 2016 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/052094 | 2/1/2017 | WO | 00 |
