EP4355949A1

EP4355949A1 - Printable, multi-layered paper for packaging and process for production thereof

Info

Publication number: EP4355949A1
Application number: EP22723962.1A
Authority: EP
Inventors: Marvin MÖHLE
Original assignee: Mondi AG
Current assignee: Mondi AG
Priority date: 2021-04-21
Filing date: 2022-04-19
Publication date: 2024-04-24
Also published as: AT524998B1; BR112023021532A2; AT524998A1; WO2022221897A1; AU2022261651A1

Abstract

The invention relates to a process for producing a multi-layered paper for packaging which is printable/intended for printing and to a multi-layered paper for packaging which is printable/intended for printing. The process comprises providing or producing a cellulose fiber-comprising bleached first pulp and providing or producing a cellulose fiber-comprising second pulp. Here, the cellulose fiber-comprising second pulp provided or produced is a mixture consisting of 40% by weight to 80% by weight of unbleached pulp material and 20% by weight to 60% by weight of bleached pulp material, based on 100% by weight of total dry matter of the second pulp.

Description

PRINTABLE MULTI-PLY PAPER FOR PACKAGING AND PROC

REN FOR ITS MANUFACTURE

The invention relates to a method for producing a printable or intended for printing, multi-ply paper for packaging and a printable or intended for printing, multi-ply paper for packaging.

Product manufacturers and/or retailers usually require printable packaging for their products, for example to display graphic representations of the products contained and/or product information for consumers. Such product packaging is now practically used in all sectors, be it for example in the field of food or appliance production or trade. High print quality, in particular high color density, brilliance and contrast of the printed images applied to packaging paper, is increasingly required in order to present the product contained as attractively and as stimulatingly as possible.

On the one hand, printable papers for packaging can be designed as independent packaging papers, such as with outer packaging papers. Alternatively, a generic paper for packaging can also form a component, in particular a printable, outer paper layer of a packaging, as is often the case with cardboard packaging. Generic, multi-ply papers or paper plies are also referred to as liners, paper liners or kraft liners. In this respect, the subject, printable, multi-ply paper for packaging can also be referred to as liner, paper liner or kraft liner.

In order to be able to provide the best possible print quality, in particular high color density and color brilliance as well as contrast, a surface intended for printing with a high degree of whiteness is desirable for the packaging papers in question. For this purpose, bleached pulp is often used to produce printable paper for packaging. On the one hand, printable papers for packaging are known which are produced entirely from bleached cellulose or which exclusively comprise bleached cellulose fiber material. Disadvantageous in such completely bleached Papers are, among other things, a deterioration in the mechanical properties of the resulting packaging due to the chemical treatment of the cellulose and the increased load of process chemicals required and, of course, the associated increased production costs.

Furthermore, multi-layer packaging papers or paper liners are known which have an outer top layer or top layer made of bleached fiber material intended for printing and a carrier layer underneath made of unbleached cellulosic fiber material, including unbleached recycled fiber material. However, depending on the type of unbleached cellulose material used to produce the carrier layer, the surface of the top layer of such multi-layer papers for packaging intended for printing often has a grayish or brownish appearance. This is because the unbleached fiber material of this lower carrier layer shines through the top or cover layer made of bleached fiber material. Of course, this results in disadvantages with regard to the print quality, in particular printed images can appear wrong in color. In order to provide such multilayer packaging papers with a high degree of whiteness, it was previously necessary or known to use a top layer with a very high grammage. However, this in turn has a disadvantageous effect in terms of resource efficiency and manufacturing costs.

A multi-ply paper for packaging or a corresponding (paper) liner is known, for example, from EP 1 392 923 B1.

The object of the present invention was to overcome the remaining disadvantages of the prior art and, on the one hand, to provide an economically and ecologically improved method for producing a printable paper for packaging, by means of which method a paper with good mechanical properties and at the same time good printability, especially high whiteness can be produced. Furthermore, it was an object of the invention to provide a paper for packaging with good mechanical properties and at the same time good printability, which paper can be produced in an improved manner from an economic and ecological point of view.

On the one hand, this object is achieved by a method according to the claims.

The inventive method for producing a printable or intended for printing, multi-ply paper for packaging or packaging paper comprises the steps

- providing or producing a bleached first pulp comprising cellulose fibers and producing a first paper web comprising the first pulp by forming a first pulp comprising the first pulp and dewatering/drying this first pulp,

- providing or producing a second pulp comprising cellulose fibers and producing a second paper web comprising the second pulp by forming a second pulp comprising the second pulp and dewatering/drying this second pulp,

- Connecting the two paper webs to form a multi-layer paper web, so that the first paper web forms an uppermost or outer cover layer and the second paper web forms a carrier layer of the multi-layer paper web that is directly connected to this uppermost cover layer,

- optionally producing one or more additional paper layers and connecting at least one of these additional paper layers to the carrier layer,

- optional further drying of the multi-layer paper web,

- and packaging of the multi-layer paper web.

A mixture consisting of 40% by weight to 80% by weight unbleached cellulose material and 20% by weight to 60% by weight bleached cellulose material is provided as the second pulp comprising cellulose fibers or manufactured.

Here and below, the term pulp means an aqueous suspension of the respective cellulose. As usual, other terms such as pulp, pulp-water suspension, fiber suspension, pulp suspension, etc. can also be used synonymously. For example, an initial consistency of the first and second pulps may be 0.5% to 2%. Optionally, customary auxiliaries can also be added to the first and/or the second pulp in addition to the respective cellulose materials. Examples include bulk starch, PAC (polyaluminum chloride), ASA (alkyl succinic anhydride) or other sizing agents, wet strength agents, bentonite, etc. As is known per se, the proportion by weight of such auxiliary chemicals in the pulps can be small. An unbleached cellulose material is to be understood very generally as a cellulose material which is not bleached in the course of the manufacturing process of the printable, multi-ply paper.

A packaging paper with a high degree of whiteness and, at the same time, good mechanical properties can be produced by means of the specified process. This despite the use of a high proportion of unbleached pulp material. Surprisingly, the grammage or layer thickness of the top layer can also be kept low without compromising too much on the degree of whiteness of the surface of the top layer intended for printing, as will be explained in more detail below using corresponding values for the paper for packaging. Overall, using the specified method, a packaging paper or paper for packaging with good printability, in particular with print images of high quality and color fidelity, can be produced, which also meets the requirements for packaging paper in terms of mechanical robustness and strength.

At the same time, compared to the production of fully bleached packaging paper, the amount of process chemicals used in the process can be reduced. Due to the reduced use of bleached cellulose material and the enabled low grammage of the top layer, the amount of cellulose used can be kept small overall. This and the reduced use of chemicals consequently also have a positive effect on the manufacturing costs for the packaging paper.

The second pulp comprising cellulose fibers can preferably be a mixture consisting of, based on 100% by weight total dry matter of the second pulp, 45% by weight to 75% by weight unbleached pulp material and 25% by weight to 55% by weight bleached pulp material be provided or manufactured.

The unbleached pulp material of the second pulp may preferably be selected from a group consisting of unbleached virgin scavenger pulp material, unbleached recycled fiber pulp material, or a mixture of unbleached pulp materials from this group. Recycled fiber cellulose material is to be understood in particular as a cellulose material obtained by processing waste paper that has already been used. Recycled fiber pulp material is conceptually defined in ISO 4046-4:2016. The term recycled fiber cellulose material does not mean cellulose material discarded or lost in the course of the process for manufacturing the packaging paper as defined in ISO 4046-3, commonly also referred to as broke.

As the bleached pulp material of the second pulp, a mixture of 30% by weight to 80% by weight bleached short-fiber pulp material and 20% by weight to 70% by weight

% bleached long fiber pulp material can be used.

To form the bleached cellulose material of the first cellulose, in particular 70% by weight - 100% by weight of bleached short-fiber cellulose material can be used. Depending on the requirement, up to 30% by weight of long-fiber pulp material can also be used to form the bleached pulp material of the first pulp.

The specified cellulose materials have proven to be particularly well suited for producing a paper for packaging with desired or sufficiently good properties, in particular for achieving good mechanical properties or sufficiently good strength and, at the same time, good printability.

In a further development of the method, it can be provided that immediately before the first paper web and the second paper web are joined, the dry content of the first paper web is adjusted to 3% to 50% and the dry content of the second paper web to 3% to 50%.

As has been found, the two webs of paper can be joined particularly well within the dry contents indicated. As a result, very good adhesion of the top sheet and the backing sheet to each other can also be provided in the paper for packaging. In particular, delamination of the two layers can be effectively prevented.

Furthermore, 100 kg to 150 kg of a white pigment filler per ton of total dry matter of the bleached first pulp can be added to the first pulp or the first paper web. With this measure, the printability of the top layer surface of the paper for packaging can be further improved. The white pigment filler gives the top layer additional opacity or a covering effect on the underlying carrier layer. Surprisingly, it has proven possible to add such a large amount of filler as indicated above without having to accept excessive losses in the mechanical properties of the packaging paper, in particular its mechanical strength. In addition, the production costs for the paper for packaging can be further reduced in this way.

Calcium carbonate or lime can preferably be added to the first pulp or the first paper web as a white pigment filler.

In a preferred method, it can be provided that the multi-layer paper web is produced after complete drying to a final dry content with a basis weight of 75 g/m ² to 120 g/m ² , the top layer having a basis weight of 50 g/m ² to 70 g/m ² is produced, and wherein a ratio of the basis weight of the top layer to a basis weight of the backing layer is adjusted to 1.2:1 to 2:1.

Appropriate basis weights or grammages can, as is known per se, be controlled by controlling various process parameters, such as consistencies in a approach flow section of a paper machine, the quantities of pulp and headbox consistency applied to the headbox of a paper machine, throughput speeds in various areas of a paper machine and so on to be set. A paper with the stated basis weights and basis weight ratios has proven to be particularly suitable for combining good mechanical properties and good printability. Furthermore, the specified measures make it possible overall to provide a paper for packaging that uses little material but nevertheless has good properties.

In a further procedure, the second pulp can be provided or produced with a Schopper-Riegler value according to ISO 5267-1:2000 of 20° SR to 35° SR.

A corresponding cellulose material has proven to be particularly well suited for forming the second cellulose and subsequently for forming the carrier layer of the packaging paper proven. Depending on the starting pulp materials, a pulp within the range given above for the Schopper-Riegler value can be produced, as is known per se, by mechanical beating and/or defibration, in particular in so-called refiners.

Specifically, in a preferred process procedure, the second pulp can be provided or produced with a kappa number of 20 to 65 according to ISO 302:2015.

By using a second pulp with a corresponding kappa number from the specified range, a suitable degree of coloring of the carrier layer of the packaging paper or paper for packaging can be set without having to accept far-reaching losses in terms of the mechanical strength of the packaging paper. As is known per se, a kappa number within the specified range can be set primarily by the selection and/or processing of the appropriate cellulose materials, especially during chemical pulping, and by the composition of cellulose materials for forming the second cellulose.

Furthermore, the first, bleached pulp can be provided or produced with a kappa number according to ISO 302:2015 of 12 or less, preferably 10 or less.

In addition, a smoothing of a surface of the top layer of the multi-layer paper web intended for printing can expediently be provided in the method. In particular, such a smoothing can be carried out by calendering this surface using a calender, such as a hard nip, soft nip, long nip, such as a shoe calender or metal belt calender.

As a result, the quality of the surface provided for printing can be improved in the broadest sense, as a result of which the quality of printed images applied to this surface can be further improved. The average person skilled in the art is fundamentally familiar with various control parameters, for example pressure, temperature and residence time, during calendering to achieve the desired surface properties in each case, for example surface roughness.

The object of the invention is also achieved by a printable or intended for printing, multi-ply paper for packaging or packaging paper according to the claims.

The paper for packaging or packaging paper includes - a top cover layer predominantly comprising a first, bleached cellulose fiber material or predominantly consisting of a first, bleached cellulose fiber material,

- and a carrier layer directly connected to the top cover layer, predominantly comprising a second cellulose fiber material or predominantly consisting of a second, bleached cellulose fiber material.

The second cellulosic fiber material is a mixture consisting of, based on 100% by weight total dry matter of the second cellulosic fiber material, 40% by weight to 80% by weight unbleached fiber material and 20% by weight to 60% by weight bleached fiber material educated.

These features make it possible to provide packaging paper that is very easy to print on, which paper has a particularly high degree of whiteness on the top layer surface to be printed, and thus also ensures high color brilliance or color fidelity of print images printed thereon. At the same time, a packaging paper with good mechanical properties can be provided. Surprisingly, a grammage or layer thickness of the top layer can also be kept low without compromising too much the degree of whiteness of the surface of the top layer intended for printing. This is explained in more detail below using the corresponding values for paper for packaging.

In addition, a corresponding packaging paper can be produced using a method as described above, which method is characterized by high efficiency both from an ecological and economic point of view. Preferably, the second cellulosic fiber material can be replaced by a mixture consisting of, based on 100% by weight of the total dry matter of the second cellulosic fiber material, 45% by weight to 75% by weight unbleached fiber material and 25% by weight to 55% by weight % bleached fiber material. An unbleached fiber material is to be understood as meaning a fiber material which was not bleached in the course of the production process of the printable, multi-ply paper or which results from an unbleached cellulose material.

The top layer of the packaging paper or its outwardly facing surface is intended for printing and, when the paper is used, this top layer forms the outside layer of a packaging intended for printing. The paper for packaging In principle, packaging can be used independently for packaging purposes as primary packaging and is also suitable as outer packaging paper for wrapping articles or objects. Another frequent use of paper for packaging is to apply it to or connect it to other primary packaging, such as a packaging box. In particular, it is therefore possible to use the packaging paper as a printable cover paper for cardboard or cardboard packaging, etc. Nevertheless, the paper in question is suitable as part of secondary packaging or as secondary packaging on its own, i.e. as packaging or packaging component of packaging without direct contact with the packaged products.

In a preferred embodiment of the paper for packaging, the unbleached fiber material of the second cellulosic fiber material can be selected from a group consisting of unbleached fresh long fiber material, unbleached recycled fiber material, or a mixture of unbleached fiber materials from this group.

As already discussed above in connection with the term recycled fiber cellulose material, the term recycled fiber material is also to be understood as meaning a fiber material that has been processed from already used waste paper and into new paper, here into the multi-ply paper for packaging. As above, reference is also made to the conceptual definition according to ISO 4046-4:2016 with regard to the term recycled fiber material.

Furthermore, the bleached fiber material of the second cellulosic fiber material can be formed by a mixture of 30% by weight to 80% by weight bleached short fiber material and 20% by weight to 70% by weight bleached long fiber material.

In addition, it can be provided that the bleached fiber material of the first cellulosic fiber material comprises 70% by weight to 100% by weight of bleached short fiber material. Here, the bleached fiber material of the first cellulose fiber material can also comprise up to 30% by weight of bleached long fiber material.

The bleached fiber material of the second cellulosic fiber material can in particular have a kappa number according to ISO 302:2015 of 12 or less, preferably 10 or less and in particular 5 or less. The specified cellulose fiber materials have proven to be particularly well suited for achieving desired or sufficiently good properties, in particular for achieving good mechanical properties or sufficiently good strengths and at the same time good printability.

In a further embodiment of the paper for packaging, its top layer can have a white pigment filler, with an ash residue according to ISO 1762:2015 of the top layer being 10% by weight to 14% by weight.

Thereby, the printability of the top layer surface of the paper for packaging can be further improved. The white pigment filler gives the top layer additional opacity or a covering effect on the underlying carrier layer. Surprisingly, it has been found that with such a high filler content, no excessive losses in the mechanical properties of the packaging paper have to be accepted. Depending on the materials or additives used in the course of production, the measurable ash residue in paper is usually primarily formed by mineral additives or inorganic additives, as is known per se. With regard to the process for manufacturing the paper for packaging, it should be noted for the sake of completeness that there is always an unavoidable loss of inorganic additives used during the dewatering or drying of the pulp or the paper web formed in a paper machine, for example in the course of the process of dewatering on a wire section. This unavoidable loss therefore leads to a reduction in the ash residue that can be measured in the paper compared to the quantities of inorganic additives added in the process.

The white pigment filler can preferably be formed by calcium carbonate or lime.

In a further development of the paper for packaging, the paper can have a Cobb 60 value of 30 g/m ² to 40 g/m ² when its top layer is exposed to water according to ISO 535:2014.

With this feature, the printability of the paper for packaging can be improved. In particular, the absorption of conventional, water-based inks and their drying on the paper can be improved, and in particular an undesirable Penetration of the printing ink can be prevented. As is known per se, the Cobb 60 value can be influenced primarily by the materials used, in particular also by the use of additives such as sizing agents, for example alkenylsuccinic anhydride (ASA).

The paper for packaging may have a basis weight of 75 g/m ² to 120 g/m ² where the liner may have a basis weight of 50 g/m ² to 70 g/m ² and where a ratio of the basis weight of the liner to a basis weight of the carrier layer can be 1.2:1 to 2:1.

A paper with the specified basis weights and basis weight ratios has proven to be particularly well suited to combining good mechanical properties and good printability. What is surprising here is that the weight per unit area or grammage of the cover layer can be kept so low, and good printability can nevertheless be provided.

In a further embodiment of the paper for packaging, a bursting pressure index of the paper according to ISO 2758:2014 can be from 3.5 kPa*m ² /g to 4.5 kPa*m ² /g.

As a result, a paper with sufficiently good mechanical strength for packaging purposes can be provided.

In addition, a Scott Bond value according to TAPPE ANSI T 569 om-14 of the paper for packaging can be from 250 J/m ² to 450 J/m ² .

With this feature, a packaging paper can be provided with good adhesion of the top sheet and the base sheet to each other, and delamination of these two sheets can be suppressed in the course of using the paper for packaging applications.

Preferably, the linerboard of the packaging paper may have an ISO 2471:2008 opacity greater than 75%.

Furthermore, a surface of the top layer of the paper for packaging can preferably have a whiteness according to ISO 2470-1:2016 of more than 70%. In addition, for the paper for packaging, the surface of the top layer can have an L* value in the CIELab color space according to ISO 5631-2:2015 of more than 65.

Through these features, the print quality of printed images applied to the surface of the top layer of the paper can be further increased, in particular the color fidelity of such printed images can be improved.

In a development of the paper for packaging, it can also be provided that it has a strip compression resistance index according to ISO 9895:2008 as a geometric mean of 15 Nm/g to 30 Nm/g. The Strip Crush Resistance Index expressed as a geometric mean according to ISO 9895:2008 is, as is well known, the square root of the product of the corresponding machine direction (MD) and cross direction (CD) measurements.

This mechanical characteristic value is particularly important for packaging paper, since the strip compression resistance of a paper is suitable for counteracting the stresses that frequently occur in packaging. Therefore, the resistance of the paper and thus also of the packaging, which is formed by the paper or includes the paper as a component, can be further improved by the specified feature.

A Bendtsen roughness according to ISO 8791-2:2013 of the surface of the top layer of the paper intended for printing can be from 100 mF/min to 300 mF/min.

This can also further improve the printability of the paper. A corresponding Bendtsen roughness can be set, as already explained above, for example by means of calendering.

Furthermore, it can be advantageous if a Dennison wax pick resistance of the paper according to TAPPI T459 OM-13 is at least 14 as the critical wax strength number.

Such a configuration of the paper for packaging can be particularly advantageous when using certain printing processes, for example printing on the packaging paper by means of offset printing processes can be improved.

For a better understanding of the invention, it will be explained in more detail, also with reference to the following figures. They each show in a greatly simplified, schematic representation:

1 shows an exemplary embodiment of a method step for connecting two paper webs by wet pressing;

Fig. 2 gene an embodiment of a printable, multi-ply paper for Verpackun.

As an introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numbers or the same component designations, and the disclosures contained throughout the description can be transferred to the same parts with the same reference numbers or the same component designations. The position information selected in the description, such as top, bottom, side, etc., refers to the figure directly described and shown and these position information are to be transferred to the new position in the event of a change in position.

The process for producing the paper in question can, in principle, be carried out using standard process steps using a paper machine. The process relates to the production of a printable, multi-ply paper for packaging, i.e. a paper with at least two paper plies, which has at least one surface intended for printing. Since the process steps carried out on a paper machine, and in particular the dewatering and drying steps, are well known to the person skilled in the art, a detailed description of these basic process steps with the aid of figures can be omitted here and below, and these basic processes carried out on a paper machine become steps are only mentioned below. The present paper for packaging can be produced using paper machine parameters that are customary per se in paper production.

Since the product of this production process has at least two layers of paper, the process comprises, on the one hand, provision or production of a bleached first pulp comprising cellulose fibers and, on the other hand, provision or production of a second pulp comprising cellulose fibers. Accordingly, as is usual in papermaking on a paper machine, a first paper web comprising the bleached first pulp is produced and a second paper web comprising the second pulp is produced. For this purpose, first a first pulp is produced comprising the first cellulose and a second pulp is produced comprising the second cellulose. For this purpose, the two pulps can be suspended in an aqueous liquid, as is known per se. An initial consistency of the first and the second pulp can be, for example, 0.5% to 2%. As is also usual in papermaking, the first pulp, the second pulp or both pulps can also contain other auxiliaries in addition to the respective cellulose.

Bulk starch, PAC (polyaluminum chloride) or alum, ASA (alkyl succinic anhydrides) or other sizing agents, bentonite or talc, pH adjusters, retention aids, etc. may be mentioned as examples of such auxiliaries. The type and amount of such auxiliary substances can be selected by a person skilled in the art in the technical field in question, for example on the basis of desired detailed properties of the multi-ply packaging paper and/or also adapted to a specific design of a paper machine or adapted to a specific process .

As is known, the first pulp and the second pulp can each be fed into or applied to a paper machine on or by means of a so-called headbox(es). For the sake of completeness, it should be defined at this point that the term pulp means an aqueous suspension of the respective cellulose. As usual, other terms such as pulp, pulp-water suspension, fiber suspension, pulp suspension, etc. can also be used synonymously.

As is well known to those skilled in the art, a paper web is usually formed in a paper machine by successive dewatering and drying of pulp introduced via a headbox. A paper web can be formed, for example, in a first dewatering step by means of a so-called wire section and at least thickened, with further drying of a paper web formed in a paper machine being able to take place in further drying steps.

Accordingly, the present method also provides for the production or formation of a first paper web by dewatering/drying the first pulp, and the production or formation of a second paper web by dewatering/drying the second pulp. A process step for connecting the first paper web and the second paper web is of course also provided for the production of the multi-ply paper for packaging. Such joining can in principle take place with different degrees of drying or consistencies of the two paper webs, ie also for example at different points in a paper machine or for example after or in the course of different dewatering or drying stages in a paper machine.

Accordingly, connecting the two paper webs is also provided in the present method, ie connecting the first and the second paper web to form a multi-layer paper web to form a multi-layer paper web. An exemplary embodiment of such a connection process is greatly simplified and is shown schematically in FIG. 1.

The exemplary embodiment shown in FIG. 1 illustrates a joining of the first paper web 1 formed with the second paper web 2 formed in the course of drying by means of a so-called press section 3 of a paper machine, as is preferably carried out. The exemplary embodiment according to FIG. 1 shows only a section of a press section for the purpose of illustrating the joining of the paper webs 1, 2. As is known per se, a press section 3 can form a drying stage of a paper machine following the wire section.

It should be mentioned again at this point that the two paper webs 1, 2 can in principle also be connected at another point or at other points in time in the process. Thus, a joining of the two paper webs 1, 2 from two different headboxes is also possible already in the course of or on a wire section which is usually connected upstream of the press section. In the same way, the first and second paper webs 1, 2 can be joined by gluing, laminating, etc. after previous drying to a final dry content or at least approximately the final dry content of the paper webs.

In the embodiment shown in FIG. 1, the two paper webs 1, 2 can be connected, as illustrated, by pressing the two paper webs 1, 2 together using press rollers 4, 5. As illustrated further with reference to the exemplary embodiment in FIG. 1, the paper webs 1, 2 are connected to form a multi-layer paper web 6 in such a way the fact that the first paper web 1 forms a top cover layer 7 and the second paper web 2 forms a carrier layer 8 or support layer of the multi-layer paper web 6 directly connected to this top cover layer 7 .

A dry content of the first paper web 1 can preferably be set to 3% to 50% and a dry content of the second paper web 2 to 3% to 50% immediately before the first paper web 1 and the second paper web 2 are connected. A corresponding dry content is in the range of a water content of paper webs that is usual in a press section.

In principle, it is of course also possible to produce one or more additional paper layers and connect them to form the multi-layer paper web 6 , with at least one of these additional paper layers possibly being connected to the carrier layer 8 to form a multi-layer paper web 6 . This option is not shown in Figure 1 for reasons of clarity, but is self-explanatory to one of ordinary skill in the papermaking art. Additional layers of paper to form the multi-layer packaging paper can be useful depending on the intended use or requirements, but a two-layer packaging paper and thus the formation of a two-layer paper web 6 for its production, as illustrated schematically in FIG. 1, can be completely sufficient in most cases and also be desirable for reasons of material savings and with regard to the simplest possible process control.

Regardless of the number of layers of paper connected to form the multi-layered paper web 6, this paper web 6 can be dried further after the connection, for example in subsequent stages of the press section 3 shown only in part in FIG. As is known, subsequent to a press section 3, a final drying can be carried out by means of a so-called drying section to the desired final moisture content.

Finally, the multi-layer, completely dried paper web 6 is made up. Customary making-up can be done, for example, by rolling up the ready dried, multi-layer paper web 6 onto a carrier roll. Alternatively, confection can, for example, also include cutting the multi-ply paper web 6 to a respectively desired dimension of a multi-ply packaging paper and stacking the correspondingly cut pieces of packaging paper. The method provides that the second pulp comprising cellulose fibers is a mixture consisting of, based on 100% by weight of the total dry matter of the second pulp, 40% by weight to 80% by weight unbleached pulp material and 20% by weight to 60% by weight % bleached pulp material is provided or produced. An unbleached cellulose material is to be understood here as meaning a cellulose material which is not bleached in the course of the production process of the printable, multi-ply paper.

In the above context, the wording “consisting of” is to be understood in absolute terms relative to 100% by weight of the total dry matter of the second pulp. The specified weight % ranges therefore do not include, for example, added additives and/or also unavoidable, small amounts of impurities introduced. The second pulp comprising cellulose fibers can preferably be a mixture consisting of, based on 100% by weight total dry matter of the second pulp, 45% by weight to 75% by weight unbleached pulp material and 25% by weight to 55% by weight bleached pulp material are provided or manufactured.

The unbleached pulp material of the second pulp may preferably be selected from a group consisting of unbleached virgin long fiber pulp material, unbleached recycled fiber pulp material, or a mixture of unbleached pulp materials from this group.

% bleached long fiber pulp material can be used.

Preferably, at least 70% by weight and up to 100% by weight of bleached short fiber pulp material can be used to form the bleached pulp material of the first pulp. Furthermore, to form the bleached cellulose material of the first cellulose, up to 30% by weight of long-fiber cellulose material can also be used.

The term short-fiber cellulose material can be understood in particular as cellulose material obtained from hardwoods, which is characterized by short average fiber lengths of the cellulose fibers. The term long-fiber pulp material can be understood in particular pulp material obtained from softwoods, which through distinguishes comparatively longer mean fiber lengths of the cellulose fibers. The relevant relationships are familiar to those of ordinary skill in the papermaking art. As is known per se, such cellulose materials can be produced by crushing the corresponding wood and mechanical and/or chemical digestion to remove lignin components, hemicellulose components and other wood components, as well as any other processing methods such as mechanical post-treatment, for example wet grinding or wet defibration in so-called refiners.

In particular, it can be expedient in the method if the second pulp is provided or produced with a Schopper-Riegler value according to ISO 5267-1:2000 of 20° SR to 35° SR. This can be accomplished by processing the pulp, for example by mechanical beating or defibration in refiners, as already mentioned above.

In general, so-called kraft cellulose materials can preferably be provided or produced as short- and long-fiber cellulose materials, ie cellulose materials produced by means of the kraft process or kraft pulping. Such kraft pulps are also often referred to as sulfate pulp materials. The term recycled pulp material is self-explanatory.

The process of bleaching to produce bleached cellulosic materials includes, as known to those of ordinary skill in the art, further chemical digestion to at least substantially remove residual lignin and other coloring substances. Corresponding bleaching is suitable both for removing residual lignin and, in principle, also for removing coloring substances, for example from recycled cellulose material.

In addition, the method can provide or produce the second pulp having a kappa number of 20 to 65 according to ISO 302:2015. A kappa number within the specified range can be adjusted primarily through the selection and/or preparation of the relevant pulp materials, especially during chemical pulping, as well as through the composition of pulp materials to form the second pulp, as would be apparent to those of ordinary skill in the art is known in the technical field of papermaking. In a preferred procedure, the first pulp or the first paper web can be admixed with 1100 kg to 150 kg of a white pigment filler per ton of total dry matter of the bleached first pulp. A corresponding white pigment filler can therefore be added to the first pulp before the start of dewatering and formation of the first paper web 1 or also after at least a first dewatering step or a first dewatering stage of the first paper web 1 formed. Calcium carbonate can preferably be added to the first pulp or the first paper web 1 as a white pigment filler.

As already mentioned above, other auxiliaries customary in papermaking, such as modified or native starch, sizing agents, retention aids, fixing agents, wet strength agents, etc., can of course also be added or used, depending on the need or intended use of the multi-ply, printable packaging paper in the course of its manufacture .

In the method, the multi-layer paper web 6 can be produced after complete drying to a final dry content with a basis weight of 75 g/m ² to 120 g/m ² . In this context, the top layer 7 of the multi-layer paper web 6 can be produced with a basis weight of 50 g/m ² to 70 g/m ² , and a ratio of the basis weight of the top layer 7 to a basis weight of the carrier layer 8 can be 1.2: 1 to 2:1 can be set.

Appropriate basis weights or grammages can, as is known per se, be achieved by controlling various process parameters, such as consistencies in pulp preparation and in the approach flow of the paper machine, the quantities of pulp applied to the headbox of a paper machine and their consistency, throughput speeds in various areas of a paper machine and so on.

In addition, a smoothing of an upper surface of the top layer 7 of the multi-layer paper web 6 intended for printing can be provided in the method. Specifically, such smoothing can be performed by calendering this surface by means of a calender such as hard nip, soft nip, long nip, such as shoe calender or metal belt calender. The person skilled in the art is known to control or vary various settings during calendering, such as pressure, temperature and dwell time, in order to achieve the desired surface properties, for example a specific surface roughness. An embodiment of a physical, printable and multi-ply paper 9 for packaging is shown in FIG.

As can be seen from Fig. 2, the multi-layer, printable packaging paper 9 in question comprises a top cover layer 10 and a carrier layer 11 directly connected to the top cover layer 10. The top cover layer 10 predominantly comprises a first, bleached cellulose fiber material and the carrier layer 11 predominantly comprises a second cellulosic fiber material. This second cellulose fiber material of the carrier layer 11 is made up of a mixture consisting of, based on 100% by weight of the total dry mass of the second cellulose fiber material, 40% by weight to 80% by weight unbleached fiber material and 20% by weight to 60% by weight % bleached fiber material formed.

The packaging paper 9 shown in FIG. 2 is ultimately formed or manufactured by connecting the paper webs 1, 2 shown in FIG.

The second cellulosic fiber material can preferably be bleached by a mixture consisting of 45% to 75% by weight unbleached fiber material and 25% to 55% by weight, based on 100% by weight total dry matter of the second cellulosic fiber material be formed tes fiber material.

The terms cellulose fiber material and fibrous material for the packaging paper in question were chosen because the terms cellulose and cellulose material are not commonly used for finished paper, but instead the term cellulose is used more as a designation for a starting material for paper production. However, in this sense and in the first place, the chosen different material designations are only of a formal nature, and this fact is not to be understood as any kind of material conversion in the course of the manufacturing process, in particular not as a chemical conversion to a chemically different material. On the contrary, no significant material transformations, at least in the chemical sense, are to be expected in the course of paper manufacture on a paper machine with pulp as the starting material, as is well known to the person skilled in the art. Processes in a paper machine are known to include primarily mechanical and physical processes, such as an at least partially wise orientation of the cellulosic fibers and dewatering processes, etc. The matters just explained apply throughout this document. Furthermore, an unbleached fibrous material is to be understood as meaning a fibrous material which was not bleached in the course of the production process of the printable, multi-ply paper or which results from an unbleached cellulose material.

The packaging paper 9 shown in FIG. 2 can, for example, be used as an independent outer packaging paper for products as primary packaging, but also as secondary packaging. However, the present paper 9 for packaging can also form just one component of a packaging, in particular a topmost or outward-facing layer of a packaging, as is usual, for example, with cardboard packaging.

Irrespective of this, the packaging paper 9 in question has at least one surface which is intended for printing or can be printed on, which, as illustrated in FIG. 2, is formed by the outwardly facing surface 12 of the cover layer 10.

The unbleached fibrous material of the second cellulosic fibrous material can be selected from a group consisting of unbleached, fresh scavenged fibrous material, unbleached recycled fibrous material, or a mixture of unbleached fibrous materials from this group.

In this context, it can be advantageous for certain applications if only virgin fiber material is used as the fiber material in all layers 10, 11, 13 of the packaging paper. In this case, the packaging paper in question can also be suitable as packaging with direct contact with the product for dry, moist and greasy product if all legal requirements are observed, for example with regard to any auxiliary substances. When using recycled fiber material, there may be limited suitability associated with additional expense in this respect, with the use of recycled fiber material being quite expedient and advantageous outside of the area of primary packaging for Febenmittel.

The bleached fiber material of the second cellulosic fiber material can be formed by a mixture of 30% by weight to 80% by weight bleached short fiber material and 20% by weight to 70% by weight bleached capture fiber material. The bleached fiber material of the first cellulosic fiber material may preferably comprise 70% to 100% by weight bleached short fiber material, but may also comprise up to 30% by weight bleached long fiber material.

As described above, corresponding fiber materials can be formed or formed by using or producing corresponding cellulose materials in the production process also already described above.

Depending on the intended use or requirements, paper 9 for packaging can also include further paper layers, with at least one such optional, further paper layer being connected to the carrier layer 11 . Such an optional, additional paper layer 13 is shown in broken lines in FIG.

The top layer 10 of the packaging paper 9 in question can have a white pigment filler in particular as an additive. In this context, an ash residue according to ISO 1762:2015 of the top layer 10 can be from 10% to 14% by weight. The white pigment filler may preferably be calcium carbonate.

Depending on the materials or additives used in the course of production, the measurable ash residue in paper is usually primarily formed by mineral additives or inorganic aggregates, as is known per se. In addition, however, cellulose itself can also contain a small amount of ash, which can vary depending on the type of cellulose. With regard to the process for producing the paper for packaging, it should be noted for the sake of completeness that there is always an unavoidable loss of inorganic additives used during the dewatering/drying of the pulp or the paper web formed in a paper machine, for example during the Dewatering on a wire section. This unavoidable loss can therefore lead to a reduction in the ash residue that can be measured in the paper compared to the amounts of inorganic additives added in the process.

Furthermore, the paper for packaging may have a basis weight of 75 g/m ² to 120 g/m ² , the liner may have a basis weight of 50 g/m ² to 70 g/m ² , and a basis weight ratio of the top layer to a basis weight of the carrier layer can be 1.2:1 to 2:1. In the following, some, particularly preferred properties of the paper 9 in question for packaging are explained in more detail, primarily on the basis of characteristic values.

The packaging paper 9 can have a Cobb 60 value of 30 g/m ² to 40 g/m ² when its top layer 10 is exposed to water according to ISO 535:2014. A corresponding Cobb 60 value can be set primarily through the materials used, in particular through the use of additives such as sizing agents.

In addition, a bursting pressure index of the subject packaging paper 9 according to ISO 2758:2014 can be from 3.5 kPa*m ² /g to 4.5 kPa*m ² /g.

A Scott Bond value according to TAPPE ANSI T 569 om-14 of paper 9 for packaging can be from 250 J/m ² to 450 J/m ² . The Scott-Bond value describes the tendency of papers to delaminate from paper layers, in the present case relating to the cover layer 10 and the carrier layer 11.

The packaging paper 9 per se can have a strip crush resistance index according to ISO 9895:2008 as a geometric mean of 15 Nm/g to 30 Nm/g. As is known to those skilled in the art, the strip crush resistance index expressed as a geometric mean according to ISO 9895:2008 is the square root of the product of the corresponding measurements in the machine direction (MD) and the cross direction (CD).

Regarding characteristic values with regard to the optical appearance and, in this context, the printability of the packaging paper 9 in question, its top layer 10 can have an opacity of more than 75% according to ISO 2471:2008.

Furthermore, the surface 12 of the top layer 10 of the packaging paper 9 intended for printing can have a degree of whiteness of more than 70% according to ISO 2470-1:2016.

In addition, the surface 12 of the topsheet 10 of the subject paper 9 may have an L* value greater than 65 in the CIELab color space according to ISO 5631-2:2015. A packaging paper with these optical characteristics is characterized by very good printability and is particularly suitable for printing with colored print images of ho her quality and color fastness.

Furthermore, a Bendtsen roughness according to ISO 8791-2:2013 of the surface of the top layer of the paper intended for printing can be from 100 mL/min to 300 mL/min.

In addition, a Dennison Wax Pick of the paper according to TAPPI T459 OM-13 can be at least 14 as a critical wax strength number.

The exemplary embodiments show possible variants, it being noted at this point that the invention is not limited to the specifically illustrated variants of the same, but rather that various combinations of the individual variants are also possible with one another and these possible variations are based on the teaching of technical action the present invention is within the skill of a person skilled in the art working in this technical field.

The scope of protection is determined by the claims. However, the description and drawings should be used to interpret the claims. Individual features or combinations of features from the different exemplary embodiments shown and described can represent independent inventive solutions. The task on which the independent inventive solutions are based can be found in the description.

All information on value ranges in the present description is to be understood in such a way that it also includes any and all sub-ranges, e.g. the information 1 to 10 is to be understood as including all sub-ranges, starting from the lower limit 1 and the upper limit 10 i.e. all sub-ranges start with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

Finally, for the sake of clarity, it should be pointed out that some elements are shown not to scale and/or enlarged and/or reduced in order to better understand the structure. List of reference numbers Paper web Paper web Press section Press roll Press roll Paper web Cover layer Support layer Paper Cover layer Support layer Surface of paper layer

Claims

P atentClaims

Claims 1. A method for producing a printable, multi-ply paper (9) for packaging, comprising

- providing or producing a bleached first pulp comprising cellulose fibers and producing a first paper web (1) comprising the first pulp by forming a first pulp comprising the first pulp and dewatering/drying this first pulp,

- providing or producing a second pulp comprising cellulose fibers and producing a second paper web (2) comprising the second pulp by forming a second pulp comprising the second pulp and dewatering/drying this second pulp,

- Joining the two paper webs (1, 2) to form a multi-layer paper web (6), so that a top cover layer (7) is directly connected through the first paper web (1) and a top cover layer (7) is directly connected through the second paper web (2). Carrier layer (8) of the multi-layered paper web (6) is formed,

- optionally producing one or more additional paper layers and connecting at least one of these additional paper layers to the carrier layer (8),

- optional further drying of the multi-layer paper web (6),

- Making up the multi-ply paper web (6), characterized in that the second pulp comprising cellulose fibers is a mixture consisting of, based on 100% by weight of the total dry matter of the second pulp, 40% by weight to 80% by weight of unbleached pulp material and 20% to 60% by weight bleached pulp material is provided or produced.

2. The method according to claim 1, characterized in that the unbleached cellulose material of the second pulp is selected from a group consisting of unbleached, fresh long fiber cellulose material, unbleached recycled fiber cellulose material, or a mixture of unbleached cellulose materials from this group.

3. The method according to claim 1 or 2, characterized in that a mixture of 30% by weight to 80% by weight of bleached short-fiber cellulose material and 20% by weight to 70% by weight of bleached long-fiber cellulose material is used as the bleached cellulose material of the second cellulose is used.

4. The method according to any one of claims 1 to 3, characterized in that 70% by weight - 100% by weight of bleached short-fiber cellulose material is used to form the bleached cellulose material of the first cellulose.

5. The method according to any one of claims 1 to 4, characterized in that immediately before the connection of the first paper web (1) and the second paper web (2), a dry content of the first paper web (1) to 3% to 50% and a dry content of the second paper web (2) is set to 3% to 50%.

6. The method according to any one of claims 1 to 5, characterized in that the first pulp or the first paper web (1) 100 kg to 150 kg of a white pigment filler per ton of total dry matter of the bleached first pulp is admixed.

7. The method according to claim 6, characterized in that calcium carbonate is added as the white pigment filler.

8. The method according to any one of claims 1 to 7, characterized in that the multi-layer paper web (6) is produced after complete drying to a final dry content with a basis weight of 75 g/m ² to 120 g/m ² , the top layer ( 7) is produced with a basis weight of 50 g/m ² to 70 g/m ² and wherein a ratio of the basis weight of the cover layer (7) to a basis weight of the carrier layer (8) is set to 1.2:1 to 2:1 becomes.

9. The method according to any one of claims 1 to 8, characterized in that the second pulp is provided or produced with a Schopper-Riegler value according to ISO 5267-1:2000 of 20°SR to 35°SR.

10. The method according to any one of claims 1 to 9, characterized in that the second pulp is provided or produced with a kappa number according to ISO 302:2015 from 20 to 65.

11. Printable, multi-ply paper (9) for packaging comprising,

- a top cover layer (10) predominantly comprising a first, bleached cellulose fiber material,

- a carrier layer (11) directly connected to the top cover layer (10) and predominantly comprising a second cellulose fiber material, characterized in that the second cellulose fiber material consists of a mixture consisting of, based on 100% by weight of the total dry mass of the second cellulose fiber material, 40% to 80% by weight unbleached fiber material and 20% to 60% by weight bleached fiber material.

12. Paper (9) according to claim 11, characterized in that the unbleached fiber material of the second cellulose fiber material is selected from a group consisting of unbleached, fresh long fiber material, unbleached recycled fiber material, or a mixture of unbleached fiber materials from this group.

13. Paper (9) according to claim 11 or 12, characterized in that the bleached fiber material of the second cellulose fiber material consists of a mixture of 30% by weight to 80% by weight bleached short fiber material and 20% by weight to 70% by weight. bleached long fiber material is formed.

14. Paper (9) according to any one of claims 11 to 13, characterized in that the bleached fiber material of the first cellulosic fiber material comprises 70% by weight to 100% by weight bleached short fiber material.

15. Paper (9) according to one of Claims 11 to 14, characterized in that the top layer (10) has a white pigment filler, with an ash residue according to ISO 1762:2015 of the top layer (10) being from 10% by weight to 14% by weight . % amounts to.

16. Paper (9) according to claim 15, characterized in that the white pigment filler is formed by calcium carbonate.

17. Paper (9) according to one of Claims 11 to 16, characterized in that the paper (9) has a Cobb-60 value of 30 g/m ² to 40 g/m 2 to 40 g/m 2 when the top layer (10) is exposed to water according to ISO 535:2014 g/m ² .

18. Paper (9) according to one of Claims 11 to 17, characterized in that it has a basis weight of 75 g/m ² to 120 g/m ² , the top layer (10) having a basis weight of 50 g/m ² to 70 g/m ² , and wherein a ratio of the weight per unit area of the cover layer (10) to the weight per unit area of the carrier layer (11) is 1.2:1 to 2:1.

19. Paper (9) according to any one of claims 11 to 18, characterized in that a

Burst pressure index according to ISO 2758:2014 is from 3.5 kPa*m ² /g to 4.5 kPa*m ² /g.

20. Paper (9) according to one of claims 11 to 19, characterized in that a Scott Bond value according to TAPPI/ANSI T 569 om-14 is from 250 J/m ² to 450 J/m ² .

21. Paper (9) according to any one of claims 11 to 20, characterized in that the top layer (10) has an opacity according to ISO 2471:2008 of more than 75%.

22. Paper (9) according to one of claims 11 to 21, characterized in that a surface (12) of the top layer (10) has a degree of whiteness according to ISO 2470-1:2016 of more than 70%.

23. Paper (9) according to any one of claims 11 to 22, characterized in that a surface (12) of the top layer (10) has an L* value in the CIELab color space according to ISO

5631-2:2015 of more than 65.

24. Paper (9) according to one of Claims 11 to 23, characterized in that it has a strip compression resistance index according to ISO 9895:2008 as the geometric mean of 15 Nm/g to 30 Nm/g.