MULTI-LAYER PAPER CONTAINING RECYCLED PAPER AND GRASS FIBERS

Description

[0001] The invention relates to a multi-layer, in particular two-layer paper, in particular for use in the production of corrugated cardboard, according to the preamble of claim 1. The invention further relates to a method for producing such a paper.

[0002] In paper production, two different types of fibers have long been used to produce a fiber composition, known as pulp, which is then spread in a thin layer onto a screen and subsequently dewatered, detached from the screen as a web, further dewatered and finally dried to form the finished paper. These fibers are so-called virgin fibers, which are obtained from fresh pulp, typically wood scraps or wood chips, and broken up to the point where they form fibrils with which they later form a strong bond to one another in the paper. Furthermore, waste paper fibers, i.e. fibers obtained from paper recovered from the recycling cycle, i.e. waste paper, are also used in paper production. The use of waste paper fibers is advantageous from an environmental point of view because it enables a second cycle or even several further cycles of the fiber material.On the one hand, waste paper can be recycled as a valuable raw material, and on the other hand, fewer fresh fibers are needed for paper production, meaning that less wood has to be taken from nature.

[0003] The problem with recycled paper fibers, however, is that they are generally smaller than fresh fibers and therefore, especially if they have already been through the recycling process several times, result in poorer bonding within the paper and thus a lower tear resistance of the paper.

[0004] 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 achieve sufficient tear resistance of the produced paper material on the other.

[0005] Nowadays, waste paper is very specifically sorted into different qualities. For example, a distinction is made between: recycled kraft board or kraft paper previously made from virgin fibres, which contains extra-long pulp fibres, conventional paper or board originating from commercial waste, unprinted white paper (for example, offcuts of unprinted paper from book printing originating from printing works or bookbinderies), offcuts of white paper printed with only a small amount of printing ink and mixed waste paper from domestic or commercial waste.

[0006] This circumstance has led, in particular, to the fact that today, even pure waste paper can be used to produce paper whose properties not only meet the demands placed on it, for example, in terms of tear resistance, but which can also be technologically adjusted to such an extent that different qualities with specific properties can be produced. Paper made from pure waste paper is, for example, later used to produce corrugated board in a corrugated board factory.

[0007] It is also known to produce paper, even paper made without the use of virgin fibers, in particular from 100% recycled paper, in multi-layer, for example two-ply, with two or more interleaved paper layers of different compositions and properties. For example, a visible layer or cover layer can be made of white recycled paper to create a visually appealing and suitable layer for later printing on this layer. A backing layer, to which the visible layer or cover layer is applied, possibly with one or more intermediate layers, can consist of simple brown recycled paper, which does not have to meet high optical requirements. This is advantageous, for example, because white recycled paper is a more expensive raw material than brown recycled paper, the consumption of which is reduced when the paper is produced in multiple layers, in particular two layers.An intermediate layer (or several intermediate layers) can be provided in particular to prevent the rear layer from shining through the cover layer.

[0008] In principle, it is also known to use grass fibers in paper production alongside recycled paper and virgin fibers, usually as an additive to virgin fibers and / or recycled paper fibers. An example of a printing substrate that can consist of gas fibers, virgin fibers, and recycled paper fibers is disclosed in DE 20 2018 104 195 U1.

[0009] Grass fibers are fibers obtained through appropriate processing from dried, semi-dried, or fresh sweet and / or sour grass, seaweed, and / or algae. Since these fibers are significantly shorter than virgin fibers or recycled paper fibers and bond much less tightly to one another in a paper layer, the production of paper from 100% such fibers has not been possible, at least not yet. However, as already mentioned, grass fibers are added to the fiber compositions in paper production. Compared to virgin fibers, grass fibers have two advantages: Firstly, they are more cost-effective than virgin fibers. According to current price structures, the price for 1 ton of virgin fiber is approximately €800 to €1,000, compared to a price for 1 ton of grass fibers of approximately €300-400. Furthermore, grass fibers are more environmentally friendly than virgin fibers because they can be obtained from a much faster-renewable raw material.Compared to recycled paper fibers, the advantage is reduced solely to environmental friendliness. Grass fibers are superior to recycled paper fibers in this respect because recycled paper fibers often contain printing ink residues, thus introducing chemicals from the printing process, often mineral oil-based chemicals, into the papermaking process, which pollute the process, particularly the wastewater. However, there is no price advantage, as, based on current pricing, recycled paper is significantly cheaper than grass fibers (the current average price for 1 ton of recycled paper is approximately €80-140).

[0010] Paper with added grass fibers is currently in high demand, particularly due to its environmental friendliness. This is evident in the packaging industry, for example, where packaging made from paper containing grass fibers, so-called grass paper, is used particularly 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 in some cases allows the individual grass fibers to still be seen as particles, enables customers to recognize packaging made from this paper as environmentally friendly and sustainable, so that the overall concept of environmentally friendly food and environmentally friendly and sustainably produced packaging is consistent. This is especially true when the actual carrier fiber of the paper is not virgin fiber, but rather waste paper fiber, which supports the recycling concept.

[0011] Grass paper users, particularly in the packaging industry, are repeatedly demanding that paper manufacturers increase the proportion of grass fibers in paper, particularly in paper otherwise made from recycled paper fibers, and / or to create visually appealing, easily printable visible surfaces with a high grass content that clearly reflect the character of grass paper.

[0012] However, especially in the production of paper based on waste paper fibres, the addition of grass fibres is only possible to a limited extent, since the waste paper fibres already have shorter fibre lengths and fibril density compared to fresh fibres and thus result in paper that is less resilient in terms of tear strength, so that the addition of grass fibres, which further reduce tear strength, is limited in quantity.

[0013] The inventors have set themselves the task of finding an approach to increase the proportion of grass fibres in a paper based on recycled paper fibres, or of being able to create a visible surface with a clear grass paper appearance in the case of a paper with a grass content.

[0014] According to the invention, this object is achieved by a paper, in particular for use in the production of corrugated cardboard, wherein the paper is formed from at least two layers of different composition which are couched together and wherein the paper contains waste paper fibers and grass fibers, preferably exclusively these two fiber types, and wherein the grass fibers are fibers of sweet and / or sour grass and / or seaweed and / or algae, and wherein the paper is characterized in that a first layer of the paper is designed as a base layer and contains a minimum proportion of waste paper fibers of 70% by weight and a maximum proportion of grass fibers of approximately 30% by weight or no grass fibers, and that a second layer of the paper forms a cover layer with a proportion of grass fibers of at least 20% by weight and a proportion of waste paper fibers of a maximum of 80% by weight.Furthermore, in the paper according to the invention, the proportion of grass fibers in the cover layer is higher, in particular significantly higher, than the proportion of grass fibers in the base layer. In particular, the proportion of grass fibers in the cover layer can be at least 5 wt. %, preferably at least 10 wt. %, in particular at least 15 wt. % higher than the proportion of grass fibers in the base layer, which, within the scope of the invention, can also be produced entirely without the addition of grass fibers.

[0015] A system of at least two layers is therefore deliberately created here, in which the first layer forms a base layer, which ensures stability and essential technological properties, such as tear resistance, and in which the second layer forms a cover layer, which can be formed with a correspondingly increased proportion of grass fibers, since it does not itself have to provide system-supporting stability, but is supported by the base layer. This cover layer can thus, on the one hand, contribute to an increase in the overall proportion of grass fibers in the system compared to the lower proportion of grass fibers in the base layer. On the other hand, it can, in particular, additionally form a visually appealing visible side of the paper, which particularly emphasizes the grass paper appearance.

[0016] It has been found, particularly surprisingly, that the layer forming the cover layer with the high grass fiber content can not only be kept stable in a paper machine until couching with the layer forming the base layer, but also that this layer with the high grass fiber content can nevertheless be sufficiently firmly bonded to the layer forming the base layer by couching, so that manageable splitting strengths 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; for example, one or more intermediate layers can be provided between the base layer and the cover layer.In this case, the couching of the top layer with the base layer is to be understood as a couching of the top layer with the intermediate layer(s), a couching of the intermediate layers with each other, and a couching of the intermediate layer facing the base layer with the base layer. If intermediate layers are used, these can also contain grass fibers and preferably be based at least predominantly on fibers obtained from waste paper, with at most a small, preferably no, proportion of fresh fibers.

[0017] If a proportion of the paper is stated above and below in % by weight, this proportion is to be understood as a proportion measured on a dry mass (after drying in the oven).

[0018] The grass fibers used here are those from sweet and / or sour grass, seaweed, and / or algae. These can be obtained from dried, semi-dried, or fresh material. The grass fibers can be processed, for example, as described in EP 2 825 699 A1 for use in the fiber composition. However, it is not absolutely necessary for the grass material to be pelletized in a single process step. The grass material can also be used as loose bulk material. Grass processing for the production of grass fibers can also be carried out in accordance with DE 10 2013 114 386 A1.The fiber compositions used for the production of the two layers, base layer and cover layer, of the two- or multi-layer paper can, for example, correspond to those described in principle in DE 10 2012 107 193 A1, wherein preferably no fresh fibers or only a small proportion of fresh fibers, typically max. 10 wt.%, in particular max. 5 wt.%, are used for the paper according to the invention.

[0019] As already mentioned, the base layer provides the necessary stability for the paper, so that it can only contain a limited maximum proportion of grass fibers. This can be, for example, between 20% and 30% by weight, but also less. The maximum proportion of grass fibers in the base layer can also be further limited to, for example, 25% or 20% by weight. As already mentioned, it is also conceivable for the base layer to contain no grass fibers at all, or only small proportions such as 5%, 10%, or 15% by weight, or only a maximum of one proportion of the specified size. Accordingly, the minimum proportion of recycled paper fibers in the base layer is 70% by weight, but can also be correspondingly higher, in particular as a remainder to 100% by weight, in each case corresponding to the aforementioned proportions of grass fibers, i.e. in a design without the addition of fresh fibers.The proportion of grass fibers in the base layer will generally be adjusted according to the requirements for the mechanical properties, particularly tensile strength, of the paper on the one hand, and the total proportion of grass fibers in the paper to be adjusted on the other. If cost-effective paper is required, the proportion of grass fibers in the base layer will currently be selected to be low, preferably zero, since, as mentioned above, the price of recycled paper is currently significantly lower than that of grass material. If there is a change or even a reversal in the price trend, a different prioritization may naturally prevail and, if necessary, a high proportion of grass fibers in the base layer may also be aimed for from a cost perspective.

[0020] According to the invention, the cover layer should have as high a proportion of grass fibers as possible, or at least a significantly higher proportion, in order to be able to increase the overall proportion of grass fibers in the paper and / or to give the cover layer the appearance of grass paper with a high proportion of grass fibers. However, the cover layer also requires a proportion of other fibers, preferably waste paper fibers, to achieve a minimum level of strength, particularly during the manufacturing process. Accordingly, the maximum proportion of grass fibers, and in particular the actual proportion of grass fibers, can be in a range between 30% by weight and 70% by weight. The minimum proportion of grass fibers in the cover 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. For example, it is possible to have 40% by weight, 50% by weight or even 60% by weight in the cover layer.-% or up to such proportions as the maximum proportion of grass fibers. The remaining portion is preferably filled with recycled paper fibers.

[0021] For further technological adjustment of the paper and also to obtain different properties of the surface showing the base layer and the surface showing the cover layer, it can also be provided in particular that the two layers contain different types of recycled paper fibers. For example, the cover layer can contain recycled paper fibers obtained from white recycled paper; to achieve a good printable appearance, the base layer can contain brown recycled paper fibers obtained from a more cost-effective raw material. However, if a brown appearance is desired, the cover layer can also contain recycled paper fibers from brown recycled paper. The recycled paper fibers of the base layer can also be fibers obtained from kraft board or kraft paper, for example, which give the base layer particularly good strength.When choosing such waste paper fibers for the base layer, a particularly high proportion of grass fibers can also be integrated into the base layer.

[0022] 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 for use in the further production of corrugated board. 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 .

[0023] Of this total grammage of the paper, which is reflected in the thickness of the paper in a known manner, the larger proportion, indeed often the significantly larger proportion, is typically attributable to the base layer. In the case of the paper according to the invention, this can in particular have a basis weight of 60-170 g / m². This ensures that the base layer can guarantee the sufficient technological properties of the multi-layer, in particular two-layer, paper. The cover layer in the case of the paper according to the invention can typically have a basis weight of 30-50 g / m². In a typical multi-layer, in particular two-layer, paper according to the invention, the cover layer makes up approximately 1 / 4 to 1 / 3 of the total thickness of the paper, while the base layer contributes approximately 2 / 3 to 3 / 4 to the total thickness of the paper.

[0024] A strong bond between the couched layers is important for the paper according to the invention. In this respect, it is preferred that the paper according to the invention has a splitting strength determined according to the International Scott Bond Test according to DIN ISO 16260 of 180 to 300 J / m², in particular of 220 to 300 J / m².

[0025] In order to achieve good printability of the cover layer, it is preferred that the paper according to the invention has a Cobb 60 value determined in accordance with DIN EN ISO 535 of a maximum of 40 g / m 2< , in particular of less than 35 g / m 2<, preferably less than 30 g / m 2<. The Cobb 60 value, which is a measure of the water absorption of the paper, is adjusted in the manner known in paper production by adding glue and / or starch to the still wet or moist paper web before drying, which is typically carried out in a continuous run 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 corrugating medium, i.e. the paper layer that forms the intermediate layer in corrugated board. For such a paper, higher Cobb 60 values ​​can then also be adjusted and, in particular, work can be carried out 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—in this case, waste paper fibers and grass fibers—are first introduced in a manner known per se into separate pulpers, one for the material of the base layer and one for the material of the cover layer. Before being fed into the pulper, the grass fibers can be treated in the manner known from the described prior art, in particular by fibrillation. In the paper machine, a first fiber composition, which is taken from a first pulper, which may have been further screened in further separators, refiners, and / or vats, and which contains water, grass fibers in a maximum proportion of 30% by weight, based on the dry matter, and waste paper fibers, is then applied to a first screen. This fiber composition forms a first layer, the base layer.In this fiber composition, the proportion of waste paper fibers is in particular at least 70% by weight, based on the dry mass.

[0026] In parallel, a second fiber composition, taken from a second pulper, which may have been further screened in additional separators, refiners, and / or vats, and which contains grass fibers in a minimum proportion of 20% by weight, based on the dry matter, but in any case a higher proportion of grass fibers than the first fiber composition, and which contains waste paper fibers in a maximum proportion of less than 80% by weight, based on the dry matter, is applied to a second screen. The webs formed from the fiber masses on the two screens are combined after initial dewatering, if required, and couched to form a two-ply paper web.Within the scope of the invention, it can also be provided that a fiber composition applied to a further screen forms a further web, for example as an intermediate layer, which, after optionally first dewatering, is brought together with the two webs described above. Several such further webs can also be formed and correspondingly brought together with the two webs described above. The two- or multi-layer paper web thus produced is then further dewatered and finally dried in a manner known in the paper industry, in particular by drying in a passage through drying cylinders. The web-shaped paper thus produced is finally wound into a roll and can then be transported and used for further processing.By adjusting the weight proportions in the fiber compositions accordingly, a paper with the weight proportions of waste paper fibers or grass fibers specified above can be produced. The manufacturing process also includes a conventional processing of the reject and a return of the fibers obtained from the reject to the fiber composition feed.

[0027] The proportions of grass fibres and / or waste paper fibres in the fibre compositions for the production of the two webs for the base layer and the cover layer can be selected according to the requirements and in particular with the weight proportions mentioned above in the description of the paper according to the invention.

[0028] For example, a two-ply paper according to the invention can contain a total of over 30% grass fibers while still demonstrating sufficient stability, particularly tear resistance, if the base layer contains 75% by weight of recycled paper fibers and 25% by weight of grass fibers in the base layer, and the base layer accounts for 110 g / m 2 of a total paper basis weight of 150 g / m 2 , the cover layer contributes 40 g / m 2 and contains 50% by weight of grass fibers, the paper can contain a total of over 30% by weight of grass fibers and still demonstrate sufficient stability, particularly tear resistance. In addition, the cover layer with its particularly high proportion of grass fibers makes the addition of this material particularly visible and has an appearance that emphasizes the paper's properties as grass paper.

[0029] It can therefore be seen here that the invention provides a novel paper and a production process for such a paper, which in the combination of waste paper fibers and grass fibers in the use for the production of such a paper enables a high proportion of grass fibers to be used without jeopardizing the required technological properties, in particular the stability and tear resistance of the paper, and / or in which the side of the paper showing the cover layer has an appearance which makes the character of the grass paper particularly recognizable.

[0030] Further advantages and features of the invention will become apparent from the following description and the figures referenced therein. These show: Fig. 1 is a schematic representation of the production of a paper web containing grass fibers as a single web according to the prior art, and Fig. 2 is a schematic representation of the production of a two-layer paper web according to the invention composed of a base layer and a cover layer containing a high proportion of grass fibers.

[0031] In Figure 1First, a conventional procedure for the production of a single-ply paper is shown in a very schematic representation. A paper web 1 is produced in a conventional manner in a paper machine by applying fiber mass based on waste paper to a screen and first dewatering and subsequent drying, and then wound onto a paper reel. It is known that a proportion of grass fibers is added to the paper thus produced as paper web 1, or more precisely to the fiber composition. The possible proportion of added grass fibers is limited, however, since grass fibers are even shorter than the already not particularly long fibers of waste paper, and thus can provide less strength to the fiber composite of the paper.In order to maintain the required tear strength and other technological properties of the paper, the addition of grass fibers to a fiber mixture for paper production that is otherwise based on waste paper is limited, typically to a maximum of 20 to 30 wt.%.

[0032] In order to meet the demands of the customers and users of such paper, who, due to ecological considerations, on the one hand strive for a higher total proportion of grass fibers in the paper and, on the other hand, also require an appearance of the paper, at least on a visible or cover surface, which clearly shows the grass fibers contained in the paper, i.e. a "grass paper character", the inventors have now devised a different procedure for the production of such paper, which Figure 2 is shown schematically.

[0033] There, a paper web 10 is produced in multiple layers, here two layers. For this purpose, a first paper layer, a base layer 11, is formed by applying a first fiber composition to a first wire of a paper machine, e.g. to a lower wire. In parallel, a second paper layer, a cover layer 12, is formed by applying a second fiber composition to a second wire of a paper machine, e.g. to an upper wire. The base layer 11 contains a high proportion of waste paper fibers, e.g. waste paper fibers in a proportion of at least 70 wt.%, based on the dry mass. The cover layer 12, on the other hand, is characterized by a high proportion of grass fibers, namely at least 20 wt.% in the dry mass. The proportion of grass fibers in the cover layer 12 can in particular be between 30 and 70 wt.%. The base layer 11 can also contain grass fibers, wherein the proportion of grass fibers there is a maximum of 30 wt.-%, preferably to a maximum of 25 wt.%, in particular a maximum of 20 wt.%, and wherein the proportion of grass fibers in the cover layer 12 is in any case higher, in particular significantly higher, than a proportion of grass fibers in the base layer 11. Preferably, the remainder of the dry mass in the base layer 11 is formed entirely by waste paper fibers. However, fresh fibers can also be contained therein - preferably, however, only in a small proportion. In this way, the base layer 11 is formed to be sufficiently stable in order to be able to meet the tear resistance and other properties required of the paper of the paper web 10.

[0034] In the cover layer 12, the portion of fibers not formed by grass fibers is preferably also entirely made up of recycled paper fibers, although a—preferably small—portion of fresh fibers may also be included here. Due to the high proportion of grass fibers, the cover layer 12 is not sufficiently stable in this way and, as such, does not meet the technological properties required of the paper in the paper web 10.

[0035] By joining the two webs consisting of base layer 11 and cover layer 12 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 – exhibits the required technological properties. This paper web 10 is typically wound onto a paper roll 14 after further dewatering and drying.

[0036] The paper web 10 can, in particular, have a basis weight of 80 to 200 g / m 2 . The paper can, for example, be one that is later used in the production of corrugated cardboard.

[0037] The base layer 11 can, in particular, have a basis weight of 60 to 170 g / m². The cover layer 12 can, in particular, have a basis weight of 30 to 50 g / m². By adjusting the ratio of the thicknesses, i.e., basis weights, of the base layer 11 and the cover layer 12, the required technological properties and, furthermore, the proportion of grass fibers in the two-layer paper web 10 can be adjusted (with preset proportions of grass fibers in the cover layer 12 and, if applicable, also in the base layer 11).

[0038] The two-layer paper web 10 preferably 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 to 300 J / m 2< .

[0039] For the cover layer 12, a Cobb 60 value according to DIN EN ISO 535 of a maximum of 40 g / m 2 , in particular less than 35 g / m 2 , preferably less than 30 g / m 2 , is preferably set. This is achieved by a conventional addition of glue and / or starch.

[0040] To achieve 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. Especially in a white-based cover layer, the greenish grass fibers are clearly visible and are thus easily perceived by viewers of a final product made from the paper according to the invention, which has the cover layer 12 as a visible surface.

[0041] The foregoing description once again demonstrates the advantages inherent in the paper according to the invention and the process for its production. In particular, it has become clear that, firstly, the total proportion of grass paper fibers in a paper produced from recycled paper fibers can be increased and adjusted in a very freely configurable manner. At the same time, a cover layer can be obtained, which can later serve in particular as a visible surface, incorporating a particularly high proportion of grass fibers, which has an appearance that clearly reflects the "grass paper character" of the paper. List of reference symbols

[0042] 1Paper web 2Paper roll 10Paper web 11Base layer 12Cover layer 13Position 14Paper roll

Claims

1. Paper (10), in particular for use in the manufacture of corrugated cardboard, the paper (10) being formed from at least two layers of different composition which are bonded together and the paper (10) containing recycled paper fibres and grass fibres, the grass fibres being fibres of sweet and / or sour grass and / or seaweed and / or algae, characterised in that a first layer of the paper (10) is designed as a base layer (11) and contains a minimum proportion of recycled paper fibres of 70% by weight and a maximum proportion of grass fibres of 30% by weight or no grass fibres, in that a second layer of the paper (10) forms a top layer (12) with a minimum proportion of grass fibres of% by weight and a maximum proportion of grass fibres of 30 % by weight or no grass fibres, in that a second layer of the paper (10) forms a top layer (12) with a minimum proportion of grass fibres of 20 % by weight and a maximum proportion of recycled paper fibres of 80 % by weight, and in that the proportion of grass fibres in the top layer (12) is higher than the proportion of grass fibres in the base layer (11).

2. Paper (10) according to claim 1, characterised in that the proportion of grass fibres 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 grass fibres in the base layer (11).

3. Paper (10) according to one of the preceding claims, characterised in that the proportion of grass fibres in the base layer (11) is at most 25% by weight, in particular at most 20% by weight.

4. Paper (10) according to one of the preceding claims, characterised in that the proportion of grass fibres in the top layer (12) is 20 to 70% by weight.

5. Paper (10) according to one of the preceding claims, characterised in that the minimum proportion of grass fibres in the top layer (12) is 25% by weight, in particular 30% by weight, preferably 35% by weight, particularly preferably 40% by weight.

6. Paper (10) according to one of the preceding claims, characterised in that it contains no virgin fibres.

7. Paper (10) according to one of the preceding claims, characterised in that the two plies contain different types of recycled paper fibres.

8. Paper (10) according to claim 7, characterised that the top layer (12) contains recycled paper fibres obtained from white recycled paper and that the base layer (12) contains brown recycled paper fibres.

9. Paper (10) according to one of the preceding claims, characterised in that the base layer (11) contains recycled paper fibres from kraft paper or kraft board.

10. Paper (10) according to one of the preceding claims, characterised in that it has a basis weight of 80 to 200 g / m2, in particular of 125 to 175 g / m2.

11. Paper (10) according to one of the preceding claims, characterised in that the base layer (11) has a basis weight of 60 to 170 g / m2.

12. Paper (10) according to one of the preceding claims, characterised in that the cover sheet (12) has a basis weight of 30 to 50 g / m2.

13. Paper (10) according to one of the preceding claims, characterised by a splitting strength determined according to the International Scott Bond Test according to DIN ISO 16260 of 180 to 300 J / m2, in particular of 220 to 300 J / m2.

14. Paper (10) according to one of the preceding claims, characterised by a Cobb60 of the top layer (12) according to DIN EN ISO 535 of at most 40 g / m2, in particular of less than 35 g / m2, preferably less than 30 g / m2.

15. A method of manufacturing a paper according to any of the preceding claims, comprising the following steps carried out in a paper machine: • Web-shaped application of a first pulp composition containing water, optionally grass fibres in a maximum proportion of 30% by weight or less, based on the dry mass, and recycled paper fibres in a proportion of at least 70% by weight, based on the dry mass, to a first wire; • Web-like application of a second pulp composition containing water, grass fibres in a minimum proportion of 20% by weight, based on the dry mass, and recycled paper fibres in a maximum proportion of 80% by weight, based on the dry mass, to a second wire, the second pulp composition having a higher proportion of grass fibres than the first pulp composition; • The webs formed on the sieves are smothered to form a paper web with at least two layers; • Drying the paper web, wherein the grass fibres are fibres of fresh and / or sour grass and / or seaweed and / or algae.