EP4144914A1 - Multi-layer paper containing recycled paper and additional fibres - Google Patents

Abstract

A paper (10) according to the invention is formed from at least two plies couched together with different compositions. A first layer forms a base layer (11). A second layer forms a cover layer (12). In any case, the paper (10) contains waste paper fibers and additional fibers in the form of fibers other than waste paper. The paper is characterized by the fact that the additional fibers contain at least a proportion of fibers from Silphie (Silphium perfoliatum), fibers obtained from the fruit and/or bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus fibers and/or fibers originating from residues of biogas plants. The backing layer contains from 0 to 75% by weight of additional fibers and the top layer contains a minimum proportion of additional fibers of 8% by weight and a maximum proportion of additional fibers of 80% by weight. The proportion of additional fibers in the top layer (12) is higher than the proportion of additional fibers in the base layer (11).

Description

The invention relates to a multi-ply, in particular two-ply, paper, in particular for use in the production of corrugated cardboard, according to the preamble of claim 1. The invention also relates to a method for producing such a paper.

In papermaking, two different types of fibers have long been used to produce a fibrous composition, the so-called pulp, which is then applied to a wire in a thin layer and subsequently dewatered, detached from the wire as a web and made into the finished paper dewatered and finally dried. These fibers are so-called fresh fibers, which are obtained from fresh pulp, typically wood cuttings or wood chips, and are broken up to such an extent that they form fibrils, with which they later enter into a firm connection with one another in the paper. Waste paper fibers are also used for paper production, ie fibers that are obtained from paper recovered from the recycling circuit, the waste paper. The use of waste paper fibers is advantageous from an environmental point of view as it allows a second cycle or even several more cycles of the fiber material. On the one hand, the waste paper can be recycled as a valuable raw material, on the other hand, fewer fresh fibers are required for paper production, so that less wood has to be taken from nature.

The problem with waste paper fibers, however, is that they are usually smaller than fresh fibers and therefore, especially if they have already gone through the recycling process several times, result in poorer binding within the paper, and thus a lower tear strength of the paper.

Therefore, in the past, waste paper fibers were often mixed with fresh fibers in order to reuse the waste paper on the one hand and to obtain sufficient tear strength of the paper material produced on the other.

• recyceltem, zuvor aus Frischfasern hergestelltem Kraftkarton oder Kraftpapier, welches Material besonders lange Zellstofffasern enthält,
• herkömmlichem Papier oder Karton, das bzw. der aus gewerblichen Abfällen stammt,
• unbedrucktem weißen Papier (zum Beispiel aus Druckereien oder Buchbindereien stammende Abschnitte von unbedrucktem Papier aus dem Buchdruck),
• nur mit wenig Druckfarbe bedruckten Abschnitten weißen Papiers und
• gemischtem Altpapier aus Haus- oder Gewerbeabfällen.

Nowadays, the waste paper that is produced is sorted very specifically into different qualities. For example, a distinction is made between:

• Recycled kraft cardboard or paper previously made from virgin fibre, which material contains particularly long cellulose fibres,
• conventional paper or cardboard derived from commercial waste,
• unprinted white paper (e.g. sections of unprinted paper from book printing originating from printers or bookbinders),
• Sections of white paper printed with only a small amount of ink and
• mixed waste paper from household or commercial waste.

This circumstance has led in particular to the fact that nowadays paper can also be made from pure waste paper, the properties of which not only meet the demands placed on it, for example in terms of tear strength, but which can also be adjusted technologically to the extent that different Qualities with special properties can be produced. Paper made from pure waste paper is used, for example, to later produce corrugated cardboard in a corrugated cardboard plant.

It is also known to produce paper, including paper that is made without the use of fresh fibers, in particular 100% from waste paper, in multiple layers, for example two layers, with two or more paper layers couched together and having different compositions and properties. For example, one can The visible layer or top layer can be made of white waste paper in order to produce a visually attractive and suitable layer for later printing of this layer , is applied, consist of simple brown waste paper, which does not have to meet high optical requirements. This is favorable, for example, since white waste paper is a high-priced raw material compared to brown waste paper, the consumption of which is reduced when the paper is produced in multiple layers, in particular in two layers. An intermediate layer (or also several intermediate layers) can be provided in particular in order to prevent the rear layer from showing through the cover layer.

In principle, it is also known to use other fibers, in particular grass fibers, in addition to waste paper and fresh fibers in paper production, usually as an addition to fresh fibers and/or waste paper fibers. Grass fibers are fibers that are obtained from dried, semi-dried or fresh grass and/or sour grass and/or seaweed and/or algae by appropriate processing. Since these fibers are significantly shorter compared to virgin fibers or waste paper fibers and bond to one another significantly less firmly in a paper layer, the production of paper from 100% such fibers has not been possible, at least up to now. However, as already mentioned, grass fibers are added to the fiber compositions in paper production. Compared to fresh fibres, grass fibers have two advantages: on the one hand they are cheaper than fresh fibres. According to the current price structure, the price for 1 ton of fresh fibers is around €800 to €1000 compared to a price for 1 ton of grass fibers of around €300 to €400. Furthermore, grass fibers are more environmentally friendly than fresh fibers because they can be obtained from a raw material that grows much faster. Compared to waste paper fibres, the advantage is reduced to environmental friendliness alone. Here, the grass fibers are superior to the waste paper fibers in terms of environmental friendliness, since waste paper fibers are often afflicted with ink residues, and thus in the Papermaking process Bring in chemicals, often mineral oil based chemicals, from the printing process that pollute the process, especially the waste water. However, there is no price advantage, because according to the current price structure, waste paper is again significantly cheaper than grass fibers (the current average price for 1 t of waste paper is around €80-140).

Paper with added grass fibers is currently in high demand due to its environmental friendliness, e.g. from the packaging industry, where packaging made from paper provided with grass fibers, so-called grass paper, is used in particular in the secondary packaging of organic food. This type of paper, which has a greenish appearance on one visible side due to the added grass fibers and partially allows the individual grass fibers to be seen as particles, the customer recognizes the packaging made from this paper as environmentally friendly and sustainable, so that the overall concept of food produced in an environmentally friendly manner and environmentally friendly and sustainably manufactured packaging. This applies in particular if the actual carrier fiber of the paper is not fresh fibres, but waste paper fibers that support the idea of recycling.

In order to meet the demands made by the users of grass paper, especially from the packaging industry, to the paper manufacturer for an increase in the proportion of grass fibers in paper, in particular otherwise based on waste paper fibers, while also maintaining a visually appealing, easily printable and the character of a grass paper In order to deal with clearly recognizable visible surfaces with a high grass content, a procedure has already been proposed in which the top layer is formed with a particularly high grass content in a multi-layer paper system from at least two couched layers, at least a base layer and a top layer. Such a procedure is described, for example, in EP 3 683 357 A1 .

The waste paper fibers that are used in the production of paper based on fiber lengths and fibril density that are lower than fresh fibers and therefore result in paper that is less resilient in terms of tear strength otherwise only have limited possible admixtures that reduce the tear strength of the paper obtained because of the even lower fiber length and Fibril denseness, which further reduces grass fibers, could already be increased in this way. However, there are still limits here, which are given by the requirements placed on the technological properties of the paper.

In this respect, the inventors have set themselves the task of developing a paper obtained using waste paper fibers and additional fibers obtained from environmentally friendly, rapidly renewable raw materials, which, while retaining the technological properties, such as in particular tear strength, of the paper has a higher proportion of additional fibers obtained from renewable raw materials can contain, or while maintaining the proportion of additional fibers obtained from rapidly renewable raw materials, improved technological properties of the paper can be obtained. In the paper obtained, a visible surface in particular should continue to have an attractive appearance and also one that shows the high proportion of additional fibers obtained from environmentally friendly, rapidly renewable raw materials.

According to the invention, this object is achieved by a paper, in particular for use in the production of corrugated board, which is formed from at least two layers couched together and having different compositions. A first layer of paper forms a base layer, and a second layer of paper forms a cover layer. In any case, the paper also contains waste paper fibers and additional fibers in the form of fibers other than waste paper fibers. The special feature of the paper according to the invention lies in the fact that the additional fibers contain at least a proportion of fibers from the Silphium perfoliatum ( Silphium perfoliatum ) , fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers from plants of the genus Cannabis- derived fibers and/or from residues of Contain fibers originating from biogas plants. No additional fibers can be contained in the base layer, but it can also contain a proportion of additional fibers of up to 60% by weight. In any case, the top layer contains additional fibers, with a minimum proportion of 8% by weight. The maximum proportion of additional fibers in the top layer can be 80% by weight. In any case, the proportion of additional fibers in the top layer is higher than the proportion of additional fibers in the base layer. It can, for example, be at least 5% by weight, in particular at least 10% by weight, particularly preferably at least 15% by weight, higher than the proportion of additional fibers in the base layer. A proportion of additional fibers in the top layer can be, for example, at least 20% by weight, 30% by weight, 40% by weight, 50% by weight, 60% by weight or 70% by weight. The maximum proportion of additional fibers in the top layer can be, for example, 70% by weight, 60% by weight, 50% by weight, 40% by weight or 30% by weight.

It will be similar here as in the EP 3 683 357 A1 proposed an at least two-layer system, in which a first of the layers forms a base layer, which therefore ensures stability and important technological properties, such as tear resistance in particular, and in which a second of the layers forms a cover layer, which is provided with a correspondingly increased Share of additional fibers can be formed. Since the top layer itself does not have to form the stability that supports the system, but is carried by the base layer, additional fibers with poor values in terms of fiber length and fibril density can also be used here, such as sweet grass and/or sour grass and/or sea grass and/or grass fibers obtained from grass fibers or algae, so the cover layer can in particular also form a visually appealing visible side of the paper that emphasizes the proportion of additional fibers.

The admixture, according to the invention, of fibers from Silphie ( Silphium perfoliatum), fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or fibers originating from residues of biogas plants Fibers in the additional fibers, which can also be formed entirely by such fibers mentioned above, have this Inventor found out leads to a significant improvement in the technological properties of the paper thus obtained. In this way, either more additional fibers obtained from rapidly renewable raw materials, including in particular plant raw materials to be harvested at least once a year, can be used without impairing the technological properties compared to a known grass paper, or improved properties can be obtained with the same amount of use . It is also conceivable to work with smaller material thicknesses, ie smaller basis weights of the paper while retaining the technological properties in comparison to a known grass paper with a higher basis weight.

As the inventors were able to recognize, this improvement in the technological properties is due to the fact that the fibers mentioned above have significantly longer fibers and a higher fibril density compared to the grass fibers described above in particular. Biogas plants primarily use fast-growing, high-energy plants such as maize. In particular, the cellulose-containing fibers are not converted into biogas in the fermentation process and remain in the fermentation residues. However, the fermentation residues also contain other components, such as proteins not metabolized by the bacteria in the biogas plant. Correspondingly, these fermentation residues must also be further processed once more to separate off the fiber material before this fiber material can then be used in the production of a paper according to the invention. The same applies to the fibers of the silphie ( Silphium perfoliatum). In particular, these can also be obtained from fermentation residues from biogas plants, since this plant is also used as an energy source when feeding biogas plants. However, it is also conceivable to obtain the fibers of this plant from other processes or to process the plant directly after harvesting to obtain fibers for paper production. Since both the residues from biogas plants for the production of paper according to the invention and the fibers of the silphie ( Silphium perfoliatum ) have to be processed, these fiber materials are also currently more expensive to procure as waste paper. Nevertheless, their use is advantageous because it represents an improvement from an ecological point of view.

Fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) have also proven to be advantageous additional fibers, since these too have a longer fiber length and greater fibril density than, in particular, the grass fibers described in more detail above. Correspondingly, these fibers can also improve the technological properties of the paper obtained in this way, or with the use of these fibers higher proportions of rapidly renewable raw materials can be used. The fruits of trees of the genus Adansonia, such as fruits of trees of the species Adansonia digitata (African baobab), have always been used for human nutrition. The fibers contained in the fruit are separated from the actual pulp, which is used for consumption, and are therefore a waste product, so to speak. This can now - after suitable processing - be used in paper production as disclosed here and thus helps to further improve the sustainability of the paper produced. The fibers of the bark of trees of the Adansonia genus can also be harvested sustainably, in particular without weakening the tree itself excessively or even endangering it, and are therefore also suitable for the production of sustainable paper material. The species mentioned above, Adansonia digitata, is not the only one that can be used to obtain fiber from fruit and/or bark. Other species of the Adansonia genus also come into consideration, such as the species Adansonia grandidieri, Adansonia suarezensis, Adansonia gregorii, Adansonia madagascariensis, Adansonia perrieri, Adansonia rubrostipa and/or Adansonia za.

Fibers obtained from plants of the Cannabis genus also have similarly favorable properties in the form of comparatively long fiber lengths and high fibril density. These are types of hemp. In principle, the fibers of plants of all known types of hemp can be used, in particular the type Cannabis sativa in all known variants or subspecies as well as the species Cannabis indica in all known variants or subspecies.

The additional fibers that are used according to the invention and which in any case contain a proportion of fibers from Silphie ( Silphium perfoliatum), fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus Fibers and/or fibers originating from residues of biogas plants may also contain proportions of other fibers, such as, for example, grass fibers obtained from sweet grass and/or sour grass and/or seaweed and/or algae. It is also possible for the additional fibers to contain a proportion of fresh fibers. If grass fibers are used, then they can, for example, as in EP 2 825 699 A1 described, in order to be used in the fiber composition, whereby the grass material does not necessarily have to be pelleted, but can also be added as loose bulk material. A processing of the grass for the production of grass fibers used in the invention can continue according to the DE 10 2013 114 386 A1 take place.

Advantageously, the proportion of fibers from the Silphie ( Silphium perfoliatum ) , fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or from residues of Biogas plants originating fibers in the fiber composition of the top layer at least 5 wt .-%, based on the dry weight of the total fibers introduced in the top layer.

In the case of the paper disclosed here, too, the layer forming the cover layer with the high proportion of additional fibers can not only be kept stable in a paper machine until couched with the layer forming the base layer, but this layer with the high proportion of additional fibers can also be adequate by couching firmly connected to the layer forming the base layer. As a result, and in particular through the use of the fibers silphium ( Silphium perfoliatum), fibers obtained from the fruit and/or bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the genus Cannabis and/or fibers originating from biogas plant residues, which are used in bonding couching is also beneficial, a manageable splitting strength can be achieved for further processing and use of the paper.

Within the scope of the invention, the paper can also contain more than two layers, and in particular one or more intermediate layer(s) can be provided between the base layer and the top layer. In this case, couching the top layer with the base layer is to be understood as couching the top layer with the intermediate layer(s), couching the intermediate layers with one another and couching the intermediate layer facing the base layer with the base layer. If intermediate layers are used, these can also contain additional fibers and are preferably at least predominantly based on fibers obtained from waste paper, and at most have a small, preferably no, proportion of fresh fibers. The base layer does not necessarily have to be an outer layer either; it can also be covered on both sides with further layers and couched with them.

If a proportion of the paper in % by weight or of the additional fibers is given above and below, this proportion is understood as a proportion measured on a dry basis (after drying in the oven).

The material of the additional fibers can be pelleted or used as loose bulk material and added to the process.

As already mentioned, in the case of the paper according to the invention described here, too, the base layer provides the required stability of the paper. It will therefore advantageously have a high proportion of waste paper fibers, in particular those of high fiber quality, and can also consist of 100% waste paper fibers. But you can also have a proportion of additional fibers, the the Additional fibers added to the base layer in turn have a high proportion of fibers from the Silphie ( Silphium perfoliatum), fibers obtained from the fruit and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or fibers from Residues from biogas plants may have fibers that, as the inventors have found, cause better technological properties of the paper due to the longer fiber lengths and/or higher fibril density. In this respect, if additional fibers are added to both the base layer and the top layer, the composition of the additional fibers added can be designed differently in the two layers. For example, in a mixture of additional fibers added to the top layer, proportionally fewer fibers of Silphie ( Silphium perfoliatum ) , fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or fibers originating from residues from biogas plants as a mixture of additional fibers added to the base layer.

The proportion of additional fibers in the base layer can be, for example, between 20% by weight and 50% by weight, but it can also be less. Thus, the maximum proportion of additional fibers in the base layer can also be further limited to, for example, 35% by weight or 30% by weight. As already mentioned, it is also conceivable that no additional fibers are contained in the base layer at all or only small proportions such as 5% by weight, 10% by weight or 15% by weight or only a maximum of one proportion in each case in the specified size. Accordingly, according to a possible embodiment of the invention, a minimum proportion of waste paper fibers in the base layer can be set at 20% by weight, in particular at 40% by weight, particularly preferably at 60% by weight, but also correspondingly higher, in particular as a remaining amount The remainder is 100% by weight, in each case corresponding to the proportions of additional fibers mentioned above. In one embodiment, the base layer and also the cover layer can be produced in particular without the addition of fresh fibers. The proportion of additional fibers and also the proportion of with these added fibers of Silphium ( Silphium perfoliatum ) , fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or fibers originating from residues of biogas plants in the base layer is generally set according to the requirements for the mechanical properties, in particular the tear strength, of the paper on the one hand and for a total proportion of additional fibers in the paper to be set on the other hand. If inexpensive paper is required, the proportion of additional fibers in the base layer is currently rather low, preferably zero, since, as mentioned above, the price for waste paper is currently significantly lower than the price for the material of the additional fibers. If there is a change or even a reversal in price trends, a different prioritization can of course prevail and, from a cost perspective, a high proportion of additional fibers can also be aimed for in the base layer.

According to the invention, the top layer should have as high a proportion as possible, in any case a clearly higher proportion, of additional fibers obtained in particular from rapidly renewable raw materials, in order to be able to increase the total proportion of additional fibers in the paper and/or the top layer should have the appearance of a paper mixed with a high proportion of such additional fibers to rent. However, the top layer also usually requires a proportion of other fibers, preferably waste paper fibers, for minimum strength, in particular also during the manufacturing process. Correspondingly, the maximum proportion of additional fibers, in particular the actual proportion of additional fibers, can be in a range between 20% by weight and 70% by weight. The minimum proportion of additional fibers in the top layer can be, for example, 25% by weight, 30% by weight, 35% by weight or even 40% by weight, depending on the requirements that the subsequent user places on the paper according to the invention. It is possible, for example, to incorporate 40% by weight, 50% by weight or even 60% by weight of additional fibers in the top layer, or proportions reaching up to such proportions as the maximum proportion. The remaining portion is preferably filled with waste paper fibers.

Even if the additional fibers can also contain any proportion of fresh fibers, which can be integrated in the base layer and/or the top layer, according to a particular embodiment, the paper according to the invention can have no fresh fibers or only a small proportion of fresh fibers, typically a maximum of 10 % by weight, in particular a maximum of 5% by weight.

For further technological adjustment of the paper and also for obtaining different properties of the surface showing the base layer and the surface showing the top layer, it can also be provided in particular that the said layers contain different types of waste paper fibers. For example, the top layer can contain waste paper fibers obtained from white waste paper. In order to obtain a printable appearance, the base layer can contain brown waste paper fibers that are obtained from a less expensive raw material. However, if a brown appearance is desired, the top layer can also contain waste paper fibers from brown waste paper. The waste paper fibers of the base layer can, for example, also be fibers obtained from kraft cardboard or kraft paper, which give the base layer particularly good strength. When choosing such waste paper fibers for the base layer, for example, a particularly high proportion of additional fibers can also be integrated in the base layer.

The paper according to the invention can be produced in particular as a paper web in a paper machine. As already mentioned above, it is preferably produced as a paper which is used for use in the further manufacture of corrugated cardboard. For this purpose, but also for other purposes, it can in particular have a basis weight of 80 g/m ² to 200 g/m ² , preferably 125 to 175 g/m ² .

Of this total grammage of the paper, which is reflected in the thickness of the paper in a known manner, typically the larger portion, indeed often the significantly larger portion, is accounted for by the backing layer. In the case of the paper according to the invention, this can in particular have a basis weight of 60-170 g/m ² . This ensures that the base layer can guarantee the sufficient technological properties of the multi-ply, in particular two-ply, paper. In the case of the paper according to the invention, the cover layer can typically have a weight per unit area of 30-50 g/m ² . In a typical multi-, in particular two-ply, paper according to the invention, the top layer makes up about 1/4 to 1/3 of the total thickness of the paper, the backing layer contributes about 2/3 to 3/4 of the total thickness of the paper.

A firm connection of the couched layers is important for the paper according to the invention. In this respect, it is preferred for the paper according to the invention that it has a splitting strength, determined according to the International Scott Bond Test according to DIN ISO 16260, of 180 to 300 J/m ² , in particular of 220-300 J/m ² .

In order to achieve good printability of the top layer, it is preferred that the paper according to the invention has a Cobb ₆₀ value determined according to DIN EN ISO 535 of at most 40 g/m ² , in particular less than 35 g/m ² , preferably less than 30 g/m 2 . m ² . The Cobb ₆₀ value, which is a measure of the water absorption of the paper, is set in the manner known in papermaking by adding glue and/or starch to the still wet or damp paper web before drying, which is typically carried out in a pass over drying cylinders . For certain applications, a high absorbency of the paper is required, i.e. a high Cobb ₆₀ value. This is required, for example, for corrugated medium, i.e. the paper layer that forms the intermediate layer in corrugated board. Higher Cobb ₆₀ values can then also be set for such a paper, and in particular it is possible to work without any addition of glue or starch. A paper according to the invention can be produced in particular in a paper machine. For this purpose, the fiber materials used are first introduced in a manner known per se into separate pulpers, at least one for the material of the base layer and another for the material of the cover layer, in this case at least waste paper fibers are introduced into the pulper for forming the base layer, possibly also Additional fibers and waste paper as well as additional fibers in the pulper for forming the top layer. The Additional fibers can be further treated before they are placed in the pulper or pulpers, in particular ground up in a fibrillating manner. In the paper machine, a first fibrous composition, which is taken from a first of the pulpers and which may have been sifted again in further separators, refiners and/or chests, and which contains water, waste paper fibers and any additional fibers, but to a maximum Share of 50 wt .-%, based on the dry matter contains applied to a first screen. This fiber composition forms a first layer, the base layer. In this fibrous composition, the proportion of waste paper fibers can be, in particular, at least 60% by weight, based on the dry mass.

At the same time, in the process, a second fibrous composition, which is taken from a second of the pulpers and which may have been sifted again in further separators, refiners and/or chests and which contains the waste paper fibers in a maximum proportion of less than 80% by weight , based on the dry matter, and additive fibers in a minimum proportion of 20% by weight, based on the dry matter, but in any case a higher proportion of additive fibers than the first fiber composition, applied to a second sieve. The webs formed from the fiber masses on the two wires are brought together after optional initial dewatering and couched to form a two-ply paper web. It can also be provided within the scope of the invention that a fibrous material composition applied to a further wire forms a further web, for example as an intermediate layer, which, after optional initial dewatering, is brought together with the two webs described above. Several such further webs can also be formed and brought together accordingly with the two webs described above. The resulting two- or multi-ply paper web is then further dewatered and finally dried in a manner known in the papermaking process, in particular with drying while passing through drying cylinders. The resulting web-shaped paper is then wound up into a roll and can then be transported and used for further processing. In an appropriately adjusted setting of the proportions by weight in the fibrous material compositions, a paper with the proportions by weight of waste paper fibers or additional fibers indicated above can then be achieved. Furthermore, in the production process, in particular a processing of the reject, which is known per se, and a return of the fibers obtained from the reject to the feed of the fibrous composition can be carried out.

The proportions of additional fibers and/or waste paper fibers in the fibrous compositions for the production of the two webs for the base layer and the top layer can be selected according to the requirements and in particular with the weight proportions mentioned above in the context of the description of the paper according to the invention.

A two-ply paper according to the ^invention can, for example, contain 75 wt ² , the top layer contributes 40 g/m ² of basis weight and contains 50% by weight of additional fibers, contains a total of more than 30% by weight of additional fibers and still shows sufficient stability, in particular tear strength. In addition, the top layer with the particularly high proportion of additional fibers shows the addition of this material particularly well and has a corresponding appearance that emphasizes the property of the paper as paper made with such additional fibers obtained from rapidly renewable raw materials.

It can therefore be seen here that the invention provides a new type of paper and a production method for such a paper, which in the combination of waste paper fibers and additional fibers in the use for the production of such paper due to the use of the stability compared to grass fibers cheaper fibers of Silphie ( Silphium perfoliatum ) , fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or from residues of Biogas plants originating fibers allows to use an even higher proportion of additional fibers than from the prior art according to the EP 3 683 357 A1 was known without jeopardizing the required technological properties, in particular the stability and tear strength of the paper, and/or in which the side of the paper showing the top layer shows the character of the paper made with fibers made from rapidly renewable raw materials particularly well has optics.

Fig. 1

eine schematische Darstellung der Herstellung einer aus einer Tragschicht und einer einen hohen Anteil an Zusatzfasern enthaltenden Deckschicht zusammengefügten, zweilagigen Papierbahn gemäß der Erfindung; und

Fig. 2

in einer tabellarischen Darstellung mögliche Kombinationen von Zusammensetzungen des Papiers jeweils in der Tragschicht (auch als "Unterlage" bezeichnet) und in der Deckschicht (auch als "Decke" bezeichnet).

Further advantages and features of the invention result from the following description and from the figures referred to therein. show:

1

a schematic representation of the production of a combined from a base layer and a top layer containing a high proportion of additional fibers, two-ply paper web according to the invention; and

2

a tabular representation of possible combinations of compositions of the paper in the base layer (also referred to as "base") and in the top layer (also referred to as "cover").

In figure 1 a procedure for the production of a paper according to the invention is shown schematically.

There, a paper web 10 is produced in multiple layers, here in two layers. For this purpose, a first paper layer, a base layer 11, is formed by applying a first fibrous composition to a first wire of a paper machine, for example to a bottom wire. At the same time, a second paper layer, a cover layer 12, is formed by applying a second fiber composition to a second wire of a paper machine, for example to an upper wire. The base layer 11 contains a high proportion of waste paper fibers, for example waste paper fibers in a proportion of at least 60% by weight, based on the dry matter. The top layer 12, on the other hand, is characterized by a high proportion of additional fibers, viz at least 20% by weight in dry matter. The proportion of additional fibers in the cover layer 12 can in particular be between 30 and 70% by weight. The base layer 11 can also contain additional fibers, but this does not necessarily have to be the case. The proportion of additional fibers in the top layer should be limited to a maximum of 50% by weight, preferably to a maximum of 35% by weight, in particular a maximum of 30% by weight. In any case, the proportion of additional fibers in the top layer 12 is higher, in particular significantly higher, than a proportion of additional fibers in the base layer 11.

In any case, the additional fibers used contain fibers from Silphium ( Silphium perfoliatum), fibers obtained from the fruit and/or bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or fibers from residues of biogas plants. Furthermore, the additional fibers can also contain fractions of grass fibers in the form of fibers from sweet grass and/or sour grass and/or seaweed and/or algae and/or fresh fibers. The fact that the additional fibers are fibers of Silphium ( Silphium perfoliatum), fibers obtained from the fruit and/or bark of trees of the Adansonia genus, fibers obtained from plants of the Cannabis genus and/or fibers from residues of Containing biogas plants leads to a clearly improved stability, in particular tear strength, of the paper made with these fibers compared to the addition of pure grass fibers. This is due to the longer fibers and higher fibril density of these particular fibers.

If additional fibers are added to the base layer 11, the remainder of the dry mass in the base layer 11 can preferably be formed entirely by waste paper fibers. In this way, the base layer 11 is formed with sufficient stability to be able to meet the tear strength and also other properties required of the paper of the paper web 10 .

In the cover layer 12, the proportion of fibers not formed by additional fibers is preferably also completely realized by waste paper fibers.

Virgin fibers are preferably avoided in both layers, the base layer and the top layer. However, such fresh fibers can be contained in the layers, in particular as components of the additional fibers. But then the proportion of fresh fibers in the mass of additional fibers is selected to be low, in particular it is already at most 10% by weight or even significantly lower, e.g. below 5% by weight, so that the proportion of such fresh fibers in corresponding to the paper obtained.

Due to the high proportion of additional fibers, the top layer 12 per se is not sufficiently stable in such a way and as such does not meet the technological properties that are required of the paper in the paper web 10 .

By bringing the two webs of base layer 11 and cover layer 12 together at position 13 and couching the two webs there, the two-ply paper web 10 is obtained, which - primarily due to the properties of the base layer 11, but also due to the proportion of fibers in the Silphie ( Silphium perfoliatum) growing through, fibers obtained from the fruit and/or bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or residues from biogas plants in the additional fibers - the required technological has properties. After further dewatering and drying, this paper web 10 is typically wound up on a paper roll 14 .

The paper web 10 can in particular have a basis weight of 80 to 200 g/m ² . The paper can, for example, be of a type that is subsequently used in the production of corrugated cardboard.

The base layer 11 can in particular have a basis weight of 60 to 170 g/m ² . The cover layer 12 can in particular have a basis weight of 30 to 50 g/m ² . By adjusting the ratio of the strengths, ie basis weights, the base layer 11 and the top layer 12, a setting of the required technological properties and also a Adjustment of the proportion of additional fibers in the two-ply paper web 10 take place (with preset proportions of additional fibers in the top layer 12 and possibly also the base layer 11).

The two-ply paper web 10 preferably has a splitting strength, determined according to the International Scott Bond Test according to DIN ISO 16260, from 180 to 300 J/m ² , in particular from 220 to 300 J/m ² .

A Cobb ₆₀ value according to DIN EN ISO 535 of at most 40 g/m ² , in particular less than 35 g/m ² , preferably less than 30 g/m ² , is preferably set for the cover layer 12 . This is obtained by adding glue and/or starch, which is known per se.

In order to obtain a specific appearance of the cover layer 12, it can be provided, for example, that the waste paper fibers used there are fibers obtained from white waste paper. The usually greenish or greenish-brownish or brownish additional fibers can be easily recognized in a white-ground cover layer in particular and are thus well perceived by the viewer of an end product made from the paper according to the invention, which has the cover layer 12 as the visible surface.

AP:

Altpapierfasern,

Sil o. Bio:

Fasern der Durchwachsenen Silphie, aus Rückständen von Biogasanlagen stammenden Fasern oder aus Früchten und/oder der Rinde von Bäumen der Gattung der Affenbrotbäume (Adansonia) gewonnene Fasern,

Hanf:

aus Pflanzen der Gattung Cannabis gewonnene Fasern,

Gras:

aus getrocknetem, halbgetrocknetem oder frischem Süß- und/oder Sauergras und/oder Seegras und/oder Algen gewonnene Grasfasern.

In the figure 2 are in a matrix-like representation, or are tabular, possible combinations of base layer, referred to as "underlay" in the figure, and cover layer, referred to as "cover" in the figure, illustrated. The abbreviations used designate the following fiber components in the layers:

AP:

waste paper fibers,

Sil or Bio:

fibers of silphium that has grown through, fibers originating from residues from biogas plants or fibers obtained from the fruit and/or bark of trees of the baobab genus (Adansonia) ,

Hemp:

Fibers obtained from plants of the Cannabis genus,

Grass:

grass fibers obtained from dried, semi-dried or fresh grass and/or sour grass and/or seaweed and/or seaweed.

In the overview 2 nine combination ranges of base layers and surface layers are indicated by the crosses placed in the respective cells. Three different possible composition ranges of base layers are listed, namely, each starting from a base layer consisting of 100% waste paper, such a base layer composed of waste paper and grass fibers (top line), a base layer made of waste paper, grass and other fibers, also possibly Fibers derived from plants of the Cannabis genus, composite base layer (middle row) and a base layer composed of waste paper, hemp and grass fibers (bottom row).

The respective proportions of the fibers in the base layers with different compositions are given in % by weight of the composition in the layer and as proportions in the dry mass, with possible ranges.

Furthermore, three possible composition ranges of the top layer are shown, in the left column with proportions of waste paper, grass and other fibers as well as fibers possibly obtained from plants of the Cannabis genus. In the middle column, a top layer with a composition of waste paper, grass and other fibers is shown. The right-hand column shows a composition range of the top layer made of waste paper, grass and possibly fibers obtained from plants of the Cannabis genus.

The respective proportions of the fibers in the differently composed top layers are given in % by weight of the composition in the layer and as proportions in the dry mass, with possible ranges.

From the preceding description it has become clear once again what advantages the paper according to the invention and the process for its production have. In particular, it has become clear that the use of fibers from Silphie ( Silphium perfoliatum), fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or from residues from biogas plants, on the one hand, the total proportion of additional paper fibers in a paper based on waste paper fibers paper produced can be increased and adjusted in a very freely configurable manner, so that in particular a cover layer can also be obtained, which can later serve in particular as a visible surface, in which there is a higher proportion of additional fibers obtained from rapidly renewable raw materials than in the known material is involved, which has a corresponding optics.

Reference List

10

paper web

11

base course

12

top layer

13

position

14

paper roll

Claims (19)

Paper (10), in particular for use in the production of corrugated board, the paper (10) being formed from at least two couched layers of different composition, a first layer of the paper (10) forming a base layer (11) and a second layer of the paper (10) forms a top layer (12) and the paper (10) in any case contains waste paper fibers and additional fibers in the form of fibers other than waste paper fibers, characterized in that the additional fibers contain at least a proportion of fibers of the Silphie ( Silphium perfoliatum) , fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the cannabis genus and/or fibers originating from residues from biogas plants, with a proportion of additional fibers in the base layer of 0 to 75% by weight is contained, and the top layer contains a minimum proportion of additional fibers of 8 % by weight and a maximum proportion of additional fibers of 80% by weight, the proportion of additional fibers in the cover layer (12) being higher than the proportion of additional fibers in the base layer (11). Paper (10) according to Claim 1, characterized in that the proportion of additional fibers in the top layer (12) is at least 5% by weight, in particular at least 10% by weight, particularly preferably at least 15% by weight higher than the proportion of additional fibers in the base layer (11). Paper (10) according to one of the preceding claims, characterized in that the base layer also contains additional fibers, in particular in a proportion of at least 5% by weight. Paper (10) according to one of the preceding claims, characterized in that the proportion of additional fibers in the base layer (11) is at most 80% by weight, in particular at most 60% by weight. Paper (10) according to one of the preceding claims, characterized in that the proportion of additional fibers in the top layer (12) is 20 to 70% by weight. Paper (10) according to one of the preceding claims, characterized in that the minimum proportion of additional fibers in the top layer (12) is 25% by weight, in particular 30% by weight, preferably 35% by weight, particularly preferably 40% by weight. -%, amounts to. Paper (10) according to any one of the preceding claims, characterized in that the base layer has a minimum proportion of waste paper fibers of 20% by weight, in particular 40% by weight, more preferably 60% by weight. Paper (10) according to one of the preceding claims, characterized in that the additional fibers also contain a proportion of fresh fibers and/or a proportion of grass fibers in the form of fibers from sweet and/or sour grass and/or seaweed and/or algae. Paper (10) according to any one of the preceding claims, characterized in that the proportion of fibers of the Silphie ( Silphium perfoliatum), fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , from plants of the Fibers from the genus Cannabis and/or fibers originating from residues from biogas plants make up at least 5% by weight of the fiber composition of the top layer, based on the dry weight of the total fibers introduced into the top layer. Paper (10) according to any one of the preceding claims, characterized in that it contains no fresh fibers. Paper (10) according to any one of the preceding claims, characterized in that the base layer contains different types of waste paper fibers than the top layer. Paper (10) according to Claim 11, characterized in that the top layer (12) contains waste paper fibers obtained from white waste paper and that the base layer (12) contains brown waste paper fibers. Paper (10) according to one of the preceding claims, characterized in that the backing layer (11) contains waste paper fibers made from kraft paper or kraft cardboard. Paper (10) according to one of the preceding claims, characterized in that it has a basis weight of 80 to 200 g/m ² , in particular 125 to 175 g/m ² . Paper (10) according to one of the preceding claims, characterized in that the base layer (11) has a basis weight of 60 to 170 g/m ² . Paper (10) according to one of the preceding claims, characterized in that the top layer (12) has a basis weight of 30 to 50 g/m ² . Paper (10) according to one of the preceding claims, characterized by a splitting strength, determined according to the International Scott Bond Test according to DIN ISO 16260, of 180 to 300 J/m ² , in particular of 220 to 300 J/m ² . Paper (10) according to one of the preceding claims, characterized by a Cobb ₆₀ value of the top layer (12) according to DIN EN ISO 535 of at most 40 g/m ² , in particular less than 35 g/m ² , preferably less than 30 g/m 2 ^m2 . Method for producing a paper according to one of the preceding claims, comprising the following steps carried out in a paper machine: • Web application of a first fibrous composition containing water, waste paper fibers and possibly additional fibers in the form of fibers other than waste paper in a maximum proportion of 50% by weight or less, based on the dry matter, and on a first sieve; • Web application of a second fiber composition containing water, waste paper fibers in a maximum proportion of 80% by weight, based on the dry matter, and additional fibers in the form of fibers other than waste paper in a minimum proportion of 20% by weight, based on the dry matter second wire, wherein the second fiber composition has a higher proportion of filler fibers than the first fiber composition; • Couching the webs formed on the screens into an at least two-ply paper web; • drying of the paper web, where the additional fibers contain at least a proportion of fibers from the Silphie ( Silphium perfoliatum), fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia) , fibers obtained from plants of the Cannabis genus and/or fibers from residues contain fibers originating from biogas plants.

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