Patent Application
20250019903
The invention relates to a multi-layer, in particular, two-layer, paper, in particular, for use for producing corrugated cardboard, according to the preamble of claim 1. The invention further relates to a method for producing such a paper.
In paper production, two different types of fibers have long been used in order to produce therefrom a fibrous material composition, known as pulp, which is then applied in a thin layer to a screen and subsequently dewatered, detached from the screen as a web, and further dewatered and finally dried to form the finished paper. These fibers are at one time what are known as fresh fibers, which are obtained from fresh pulp, typically wood portions or wood chips, and are broken up to such an extent that they form fibrils with which they later enter into a firm bond in the paper. Furthermore, waste paper fibers, i.e., those fibers which are obtained from paper recovered from the recycling circuit, the waste paper, are also used for producing paper. The use of waste paper fibers is advantageous from an environmental perspective, because they enable a second cycle or even a plurality of further cycles of the fiber material. On the one hand, the waste paper can be recycled as a valuable raw material, and, on the other, fewer fresh fibers are required for paper production, and therefore less wood has to be harvested from the natural world for this purpose.
However, a problem in the case of waste paper fibers is that, compared to the fresh fibers, they are usually in smaller parts and therefore, especially if they have already passed through the recycling process several times, result in a poorer bond within the paper, and thus a lower tear strength of the paper.
Therefore, previously, waste paper fibers were often mixed with fresh fibers, in order to thereby reuse the waste paper, while also obtaining sufficient tear strength of the paper material produced.
Nowadays, the waste paper obtained is sorted very carefully into different qualities. For example, a distinction is made between:
This circumstance has, in particular, led to the fact that, nowadays, paper can also be produced from pure waste paper, which, in terms of its properties, not only meets the demands made upon this, e.g., in relation to the tear strength, but is also adjustable in a manner technologically controllable to such an extent that different qualities having particular properties can be produced. Paper produced from pure waste paper is used, for example, in order to subsequently produce corrugated cardboard therefrom in a corrugated cardboard machine.
It is also known to produce paper, including that produced without the use of fresh fibers, in particular, 100% from waste paper, in a multi-layered manner, e.g., two-layered, comprising two or more paper layers of different composition and properties that are couched together. For example, a visible layer or cover layer made of white waste paper can be produced, in order to produce a layer which is visually presentable and suitable for subsequent printing of this layer; a rear layer, on which the visible layer or cover layer is applied, possibly with the interposition of an intermediate layer or a plurality of intermediate layers, can consist of simple brown waste paper which does not have to meet high visual 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 white waste paper is reduced in the case of a multi-layered, in particular, two-layered, production of the paper. In this case, an intermediate layer (or also a plurality of intermediate layers) can be provided in particular in order to prevent the rear layer shining through the cover layer.
In principle, it is also known to use, in addition to waste paper and fresh fibers, other fibers, in particular, grass fibers, in paper production, as a rule as admixture to fresh fibers and/or waste paper fibers. In this case, grass fibers are fibers which are obtained, by appropriate treatment, from dried, semi-dried, or fresh sweet grass and/or sorrel and/or sea grass and/or algae. Since these fibers are significantly shorter compared to fresh fibers or waste paper fibers, and form significantly less strong bonds with one another in a paper layer, the production of paper from 100% of such fibers, in any case up to now, is not possible. However, as already mentioned, grass fibers are added to the fiber compositions in paper production. Compared to fresh fibers, grass fibers have two advantages: firstly, they are more cost-effective than the fresh fibers. According to the current price structure, the price for 1 t fresh fibers is about 800 to 1,000 €, compared to a price for 1 t grass fibers of about 300-400 €. Furthermore, grass fibers are more environmentally friendly than fresh fibers, since they can be obtained from a raw material which grows back significantly more quickly. Compared with waste paper fibers, the advantage is reduced solely to environmental friendliness. Here, the grass fibers are superior to the waste paper fibers in terms of environmental friendliness, since waste paper fibers are often tainted with printing ink residues, and thus, in the paper manufacturing process, introduce chemicals, often chemicals based upon mineral oil, from the printing process, which impact the process, in particular, the waste water. However, a price advantage does not result, since, according to the current price structure, waste paper is still obtainable significantly more cheaply than grass fibers (the current average price for 1 t of waste paper is approximately 80-140 €).
In particular, due to the environmental friendliness, paper with added grass fibers is currently in high demand, e.g., from the packaging industry, where packaging produced from paper provided with grass fibers, known as grass paper, is used in particular also in the field of the secondary packaging of organic food products. As a result of this type of paper, which has a green appearance on a visible side due to the admixed grass fibers, in some cases the individual grass fibers can still be identified as particles, the customer recognizes the packaging made of this paper as an environmentally friendly and sustainable, and therefore the overall concept of food that has been produced in an environmentally friendly manner and an environmentally friendly and sustainably produced packaging is consistent. This applies in particular if the actual carrier fibers of the paper are not fresh fibers, but, rather, waste paper fibers supporting the recycling concept.
In order to counteract the requirements placed on the paper manufacturers by the users of the grass paper, in particular, from the packaging industry, for an increase in the proportion of grass fibers in paper that is in particular otherwise produced on the basis of waste paper fibers, while additionally obtaining a visually attractive visible surface that can be easily printed and allows the nature of grass paper to be clearly identified, having a high proportion of grass, a procedure has already been proposed in which, in a multi-layer paper system consisting of at least two layers couched together, in any case of a carrier layer and a cover layer, the cover layer is formed with a particularly high proportion of grass. Such a procedure is described, for example, in EP 3 683 357 A1.
The admixtures, otherwise possible only to a limited extent, of grass fibers, which yet further reduce the tear strength of the obtained paper owing to the still smaller fiber length and fibril density, could already be increased in this way, precisely in the production of paper based upon waste paper fibers originating from paper which has reduced fiber lengths and fibril density compared with fresh fibers, and is thus already inherently less durable with respect to tear strength. However, there are still limits here, due to the requirements imposed on the technological properties of the paper.
The inventors have made the object that of developing paper obtained using waste paper fibers and from environmentally friendly, rapidly renewable raw materials, which paper can contain a higher proportion of additional fibers obtained from renewable raw materials upon obtaining the technological properties, such as in particular tear resistance, of the paper, or which makes it possible to achieve improved technological properties of the paper while maintaining the proportion of additional fibers obtained from rapidly renewable raw materials. In the paper obtained, in particular a visible surface should furthermore have an appearance that is attractive and also shows a high proportion of the additional fibers which are obtained from environmentally friendly raw materials that grow back quickly.
According to the invention, this object is achieved by a paper, in particular, for use for producing corrugated cardboard, which is formed of at least two layers of different composition that are couched together. In this cases, a first layer of the paper forms a carrier layer, and a second layer of the paper forms a cover layer. Furthermore, the paper in any case 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 is now that the additional fibers in any case contain a proportion of fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities. The carrier layer may contain no additional fibers, but also a proportion of additional fibers of up to 60 wt %. In each case, additional fibers are contained in the cover layer, at a minimum proportion of 8 wt %. The proportion of additional fibers in the cover layer can be at most 80 wt %. The proportion of additional fibers in the cover layer is in any case higher than the proportion of additional fibers in the carrier layer. It can, for example, be at least 5 wt %, in particular at least 10 wt %, and particularly preferably at least 15 wt % higher than the proportion of additional fibers in the carrier layer. A proportion of additional fibers in the cover layer can, for example, be at least 20 wt %, 30 wt %, 40 wt %, 50 wt %, 60 wt %, or 70 wt %. The maximum proportion of additional fibers in the cover layer can, for example, be 70 wt %, 60 wt %, 50wt %, 40 wt %, or 30 wt %.
In this case, similarly to EP 3 683 357 A1, an at least two-layer system is proposed, in which a first of the layers forms a carrier layer, which also ensures the stability and essential technological properties, such as in particular the tear strength, and in which a second of the layers forms a cover layer which can be formed having a correspondingly increased proportion of additional fibers. Since the cover layer itself does not have to develop any stability that carries the system, but, rather, is carried by the carrier layer, additional fibers having values that are poor per se with regard to fiber length and fibril density can also be used here, such as grass fibers obtained from sweet grass and/or sorrel and/or seagrass and/or algae, such that the cover layer can also form in particular a visible side of the paper that is visually attractive and emphasizes the proportion of additional fibers.
The admixture, according to the invention, of fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities, into the additional fibers, which can also be formed completely by such fibers mentioned above, leads, as the inventors have found, to a significant improvement in the technological properties of the paper thus obtained. Thus, either more additional fibers obtained from raw materials that grow back quickly, 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 used. It is also conceivable to work with lower material thicknesses, i.e., lower basis weights of the paper, while preserving the technological properties compared to a known grass paper having a higher basis weight.
This improvement of the technological properties is, as the inventors were able to recognize, due to the fact that the aforementioned fibers have significantly longer fibers and a higher fibril density compared in particular to the grass fibers described above. In biogas facilities, primarily energy-rich plants, such as corn, which grow rapidly, are used. In this case, in particular the cellulose-containing fibers are also not converted into biogas in the fermentation process and remain in the fermentation residues. However, further components, e.g., proteins not metabolized by the bacteria in the biogas facility, are also contained in the fermentation residues. Accordingly, these fermentation residues must also be further processed once again for separating the fiber material before this fiber material can then be used in the production of a paper according to the invention. The same applies for fibers of the cup plant (Silphium perfoliatum). These can in particular also be obtained from fermentation residues from biogas facilities, since this plant is also used as an energy carrier in the charging of biogas facilities. However, it is also conceivable to obtain the fibers of this plant from other processes, or to process the plant directly, after harvesting, for producing fibers for paper production. Since both the residues from biogas facilities and the fibers of the cup plant (Silphium perfoliatum) have to be processed for obtaining for the production of paper according to the invention, these fiber materials are also currently more expensive to procure than waste paper. Nevertheless, the use thereof is advantageous, since 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) also have proven to be advantageous additional fibers, since they also have a longer fiber length and greater fibril density than, in particular, the grass fibers described in more detail above. Accordingly, these fibers can also improve the technological properties of the paper obtained in this way, or higher proportions of rapidly renewable raw materials can be used when these fibers are used. The fruits of trees of the genus Adansonia, i.e., for example, fruits of trees of the species Adansonia digitata (African baobab), have also been used forever for human nutrition. In this case, the fibers contained in the fruits are separated from the actual flesh of the fruit, which is used for eating, and thus accumulate similarly as a waste product. This can now be used, after suitable processing, as disclosed here, in paper production, and thus helps to yet further improve the sustainability of the paper produced. The fibers of the bark of trees of the genus Adansonia can also be sustainably harvested, in particular, without unduly weakening the tree or even endangering it, and are therefore also suitable for the production of sustainable paper material. The aforementioned species Adansonia digitata is not the only one that can serve for obtaining fibers from fruits and/or bark. Other species of the genus Adansonia are also equally possible, for example, the species Adansonia grandidieri, Adansonia suarezensis, Adansonia gregorii, Adansonia madagascariensis, Adansonia perrieri, Adansonia rubrostipa, and/or Adansonia za.
Fibers obtained from plants of the genus Cannabis also have similarly favorable properties in the form of comparatively long fiber lengths and high fibril density. These are species of hemp. In principle, the fibers of plants of all known species of hemp can be used, in particular, of the species Cannabis sativa in all known variants or subspecies, as well as the species Cannabis indica in all known variants or subspecies, as well as Cannabis indica in all known variants or subspecies.
The additional fibers which are used according to the invention and which in any case have a proportion of fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities, can also have proportions of further fibers, such as in particular also grass fibers obtained from sweet grass and/or sorrel and/or seagrass and/or algae. It is also possible for the additional fibers to contain a proportion of fresh fibers. If grass fibers are used, these can be prepared for example as described in EP 2 825 699 A1, in order to be used in the fibrous material composition, wherein the grass material does not necessarily have to be pelletized, but, rather, is also able to be added as a loose bulk material. Processing of the grass for obtaining grass fibers used within the scope of the invention can furthermore take place according to DE 10 2013 114 386 A1.
The proportion of the fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities, in the fiber composition of the cover layer, is advantageously at least 5 wt %, relative to the dry weight of the fibers introduced overall in the cover layer.
In the paper disclosed here, too, the layer forming the cover layer and having the high additional fiber content can be kept stable not only in a paper machine until it is couched with the layer forming the carrier layer, but, rather, this layer having the high proportion of additional fibers can nevertheless also be bonded sufficiently firmly to the layer forming the carrier layer by the couching. As a result, and in particular by the use of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities, which is additionally conducive to the bonding by means of couching, interlaminar strengths that are easy to manage for the further processing and the use of the paper can be achieved.
In the context of the invention, the paper can also contain more than two layers; for example, one or more intermediate layer(s) can in particular be provided between the carrier layer and the cover layer. In this case, the couching of the cover layer to the carrier layer is to be understood overall as a couching of the cover layer to the intermediate layer(s), a couching of the intermediate layers to one another, and a couching of the intermediate layer facing the carrier layer to the carrier layer. If intermediate layers are used, these can also contain additional fibers and preferably be based at least predominantly upon fibers obtained from waste paper, and comprise at most a small proportion of fresh fibers, preferably none. The carrier layer also does not necessarily have to be an external layer; it can also be covered on both sides with further layers and can be couched to them.
If a proportion of the paper is specified above and in the following in wt % or in terms of the additional fibers, this proportion is understood as a proportion measured based upon a dry mass (after drying in the furnace).
The material of the additional fibers can be pelletized, or also used and added to the process as loose bulk material.
As already mentioned, in the paper according to the invention described here, too, the carrier layer provides the required stability of the paper. It will therefore advantageously consist of a high proportion of waste paper fibers, in particular, those of high fiber quality, and can also consist of 100% waste paper fibers. However, it can also have a proportion of additional fibers, wherein the additional fibers added to the carrier layer in turn have a high proportion of fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities, which, as the inventors have found, bring about better technological properties of the paper due to the greater fiber lengths and/or higher fibril density. In this respect, if additional fibers are added both to the carrier layer and to the cover layer, the composition of the added additional fibers in both layers can be designed differently. For example, a mixture of additional fibers added to the cover layer can contain proportionally fewer fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities, than a mixture of additional fibers added to the carrier layer.
The proportion of additional fibers in the carrier layer can, for example, be between 20 wt % and 50 wt %, but also below this. The maximum proportion of additional fibers in the carrier layer can thus also be further limited to, for example, 35 wt % or 30 wt %. As already mentioned, it is also conceivable that no additional fibers at all be contained in the carrier layer, or only small proportions, e.g., 5 wt %, 10 wt %, or 15 wt %, or in each case only at most a proportion in the indicated size. Correspondingly, according to one possible embodiment of the invention, a minimum proportion of waste paper fibers in the carrier layer can be fixed at 20 wt %, in particular 40 wt %, and particularly preferably 60 wt %, but also correspondingly higher, in particular, also as a remainder up to 100 wt %, in each case corresponding to the aforementioned proportions of additional fibers. In one embodiment, the carrier 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 these admixed fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities, in the carrier layer, are generally set according to the requirements for the mechanical properties, in particular, the tear strength, of the paper on the one hand, and a total proportion of additional fibers, to be set in the paper, on the other. If a cost-effective paper is required, the proportion of additional fibers in the carrier layer is currently selected to be rather low, and 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 a change or even a trend reversal of the prices results here, then a different prioritization can naturally prevail and, if necessary, a high proportion of additional fibers can also be sought in the carrier layer, out of cost considerations.
According to the invention, the cover layer should have as high a proportion as possible, and in any case a clearly higher proportion of additional fibers obtained from rapidly renewable raw materials, in order to be able to increase the total proportion of additional fibers in the paper and/or to give the cover layer the appearance of a paper admixed with a high proportion of such additional fibers. However, the cover layer also usually requires a proportion of other fibers, preferably waste paper fibers, for a minimum strength, in particular, also in the production process. Accordingly, the maximum proportion of additional fibers, in particular, the actual proportion of additional fibers, can be in a range between 20 wt % and 70 wt %. The minimum proportion of additional fibers in the cover layer can, for example, be 25 wt %, 30 wt %, 35 wt %, or also 40 wt %, depending upon the requirement that the later user places on the paper according to the invention. In this case, it is possible, for example, to incorporate into the cover layer 40 wt %, 50 wt %, or also 60 wt %, or up to such proportions, as proportions reaching a maximum proportion of additional fibers. The remaining proportion is preferably filled with waste paper fibers.
Even if any desired proportion of fresh fibers can also be contained in the additional fibers, which proportion can be incorporated into the carrier layer and/or the cover layer, according to a particular embodiment, the paper according to the invention cannot comprise any fresh fibers, or only a small proportion of fresh fibers, typically at most 10 wt %, and in particular at most 5 wt %.
For further technological adjustment of the paper and also for obtaining different properties of the surface displaying the carrier layer and the surface displaying the cover layer, it can in particular also be provided that the mentioned layers contain different types of waste paper fibers. Thus, for example, waste paper fibers obtained from white waste paper can be contained in the cover layer, in order to obtain a readily printable appearance; brown waste paper fibers, which are obtained from a more cost-effective raw material, can be contained in the carrier layer. However, if a brown appearance is desired, the cover layer can also contain waste paper fibers from brown waste paper. The waste paper fibers of the carrier layer can, for example, also be fibers obtained from craft cardboard or craft paper, which provide the carrier layer with particularly good strength. When selecting such waste paper fibers for the carrier layer, a particularly high proportion of additional fibers can for example then also be integrated into the carrier layer.
The paper according to the invention can in particular be produced as a paper web in a paper machine. As already mentioned above, it is preferably produced as a paper which is implemented for use in the further production of corrugated cardboard. For this purpose, but also for other purposes, it can in particular have a basis weight of 80 g/m2 up to 200 g/m2, and preferably of 125 to 175g/m2.
From this overall grammage of the paper, which is portrayed in a known manner in the thickness of the paper, the larger proportion, and indeed often the substantially larger proportion, is typically dispensed with on the carrier layer. In the paper according to the invention, this can in particular have a basis weight of 60-170 g/m2.
This ensures that the carrier layer can ensure the sufficient technological properties of the multi-layer, in particular, two-layer, paper. In the paper according to the invention, the cover layer 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 about 1/4 to 1/3 of the total thickness of the paper, and the carrier layer contributes approximately 2/3 to 3/4 to the total thickness of the paper.
A firm bonding 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 have an interlaminar strength according to the International Scott Bond Test according to DIN ISO 16260 of 180 to 300 J/m2, in particular, of 220-300J/m2.
In order to achieve good printability of the cover layer, it is preferred that the paper according to the invention have a Cobb60 value, determined according to DIN EN ISO 535, of at most 40 g/m2, in particular of less than 35 g/m2, and preferably less than 30 g/m2. Setting the Cobb60 value, which is a measure of the water absorption of the paper, is carried out in the manner known in paper production, by adding glue and/or starch into the still wet or moist paper web, before the drying, which is typically carried out in a continuous pass over drying cylinders. For certain applications, a high absorbency of the paper is required, i.e., a high Cobb60 value. This is required, for example, for corrugated material, i.e., the paper layer which forms the intermediate layer in corrugated cardboard. For such paper, higher Cobb60 values can then also be set; in particular, it is possible to work without any addition of glue or starch. A paper according to the invention can in particular be produced in a paper machine. For this purpose, first, in a manner known per se, the fiber materials used are introduced into separate pulpers, in any case one for the material of the carrier layer and a further one for the material of the cover layer, thus, here, in any case waste paper fibers into the pulper for forming the carrier layer, optionally also additional fibers, and waste paper and additional fibers into the pulper for forming the cover layer. Before they are added to the pulper(s), the additional fibers can be further treated, in particular, milled to form fibrils. In the paper machine, a first fibrous material composition, which is removed from a first of the pulpers and which has optionally been sifted once again in further separators, refiners, and/or butts, and which contains water, waste paper fibers, and, optionally, additional fibers, but in a maximum proportion of 50 wt %, relative to the dry mass, is then applied to a first screen. This fibrous material composition forms a first layer, the carrier layer. In this fibrous material composition, the proportion of waste paper fibers can be in particular at least 60 wt %, relative to the dry mass.
In parallel, in the method, a second fibrous material composition which has been removed from a second of the pulpers and which has optionally been sifted once again in further separators, refiners, and/or butts, and which contains the waste paper fibers in a maximum proportion of less than 80 wt %, relative to the dry mass, and additional fibers in a minimum proportion of 20 wt %, relative to the dry mass, but in any case a higher proportion of additional fibers than the first fibrous material composition, is applied to a second screen. The webs formed from the fibrous materials on the two screens are brought together after optionally first dewatering, and couched to form a two-layer paper web. In the context of the invention, it can also be provided that a fibrous material composition applied to a further screen form a further web, e.g., as an intermediate layer, which is brought together with the two webs described above after optional first dewatering. A plurality of such further webs can also be formed and accordingly combined with the two webs described above. The two-layer or multi-layer paper web formed in this way is then further dewatered and finally dried, in a manner known in paper production, in particular, by means of drying in a pass through drying cylinders. The web-like paper formed in this way is finally wound into a roll and can then be transported and used for further processing. A paper having the weight fractions of waste paper fibers or additional fibers referred to above can then be achieved with correspondingly adapted adjustment of the weight fractions in the fibrous material compositions. In the production method, furthermore, in particular a preparation of the reject, which is known per se, and a return of the fibers obtained from the reject into the supply of the fibrous material composition, can be carried out.
The proportions of additional fibers and/or waste paper fibers in the fibrous material compositions for the production of the two webs for the carrier layer and the cover layer can be selected according to the requirements and in particular with the weight fractions mentioned above in the context of the description of the paper according to the invention.
A two-layered paper according to the invention can, for example, if it contains 75 wt % waste paper fibers and 25 wt % additional fibers in the carrier layer, and the carrier layer, at a total basis weight of the paper of 150 g/m2, makes up a proportion of 110 g/m2, the cover layer makes up 40 g/m2 in terms of basis weight, and contains a proportion of additional fibers of 50 wt %, contain in total over 30 wt % of additional fibers, and in this case still exhibit sufficient stability, in particular, tear strength. In addition, the cover layer having the particularly high proportion of additional fibers makes it possible to recognize the addition of this material particularly well, and has a visual appearance which correspondingly emphasizes the property of the paper as paper produced comprising such additional fibers obtained from rapidly renewable raw materials.
It can thus be seen here that the invention specifies a novel paper and a production method for such paper which makes it possible, in the combination of waste paper fibers and additional fibers in the use for the production of such a paper, owing to the use of the fibers, which are significantly more favorable for the stability compared with grass fibers, of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or of fibers originating from residues of biogas facilities, to use a yet higher proportion of additional fibers than was known from the prior art according to EP 3 683 357 A1, without in the process endangering the required technological properties, in particular, the stability and tear strength of the paper, and/or in which the side of the paper displaying the cover layer has a visual appearance that makes it possible to particularly clearly identify the nature of the paper produced using fibers obtained from rapidly renewable raw materials.
Further advantages and features of the invention emerge from the following description and from the figures referred to in this case, in which:
Here, a paper web 10, in this case, two-layered, is produced. For this purpose, a first paper layer, a carrier layer 11, is formed by applying a first fibrous material composition on a first screen of a paper machine, for example, on a lower screen. In parallel, a second paper layer, a cover layer 12, is formed by applying a second fibrous material composition on a second screen of a paper machine, for example, on an upper screen. In this case, the carrier layer 11 contains a high proportion of waste paper fibers, e.g., waste paper fibers in a proportion of at least 60 wt %, relative to the dry mass. In contrast, the cover layer 12 is characterized by a high proportion of additional fibers, specifically, at least 20 wt % in the dry mass. The proportion of additional fibers in the cover layer 12 can in particular be between 30 and 70 wt %. The carrier layer 11 can also contain additional fibers, but does not necessarily have to. The proportion of additional fibers in the cover layer should be limited to at most 50 wt %, preferably to at most 35 wt %, and in particular at most 30 wt %. In any case, the proportion of additional fibers in the cover layer 12 is higher, in particular, significantly higher, than a proportion of additional fibers in the carrier layer 11.
In any case, the additional fibers used contain fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or from residues of biogas facilities. Furthermore, the additional fibers can also contain proportions of grass fibers in the form of fibers of sweet grass and/or sorrel and/or seagrass and/or algae, and/or of fresh fibers. The fact that the additional fibers contain fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or from residues of biogas facilities, leads to a stability, in particular, tear strength, of the paper produced using these fibers that is clearly improved compared to the addition of pure grass fibers. This is due to the longer fibers and the higher fibril density of these particular fibers.
Preferably, if additional fibers are added to the carrier layer 11, the remainder of the dry mass in the carrier layer 11 can be formed completely by waste paper fibers. The carrier layer 11 is thus formed in a manner sufficiently stable to be able to fulfill the tear strength and also further properties required of the paper of the paper web 10.
In the cover layer 12, the proportion of fibers that is not formed by additional fibers is preferably also completely realized by waste paper fibers.
Fresh fibers are preferably avoided in both layers, the carrier layer and the cover layer. However, such fresh fibers can be contained in the layers, in particular, as components of the additional fibers. However, the proportion of fresh fibers in the mass of the additional fibers is then selected to be low, and is in particular already at most 10 wt % here, or even significantly lower, e.g., below 5 wt %, such that the proportion of such fresh fibers in the paper obtained is also correspondingly low.
Due to the high proportion of additional fibers, the cover layer 12 itself is not sufficiently stable in such a manner, and does not as such comply with the technological properties required by the paper in the paper web 10.
By bringing together the two webs of the carrier layer 11 and cover layer 12 at position 13, and the couching of the two webs performed there, the two-layer paper web 10 is then obtained which, primarily as a result of the properties of the carrier layer 11, but also due to the proportion of fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or from residues of biogas facilities, exhibits the required technological properties. After further dewatering and drying, this paper web 10 is typically wound onto a paper roll 14.
The paper web 10 can in particular have a basis weight of 80 to 200 g/m2. The paper can, for example, be of a type that is implemented in a subsequent use in the production of corrugated cardboard.
The carrier 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 strengths, i.e., the basis weights, of the carrier layer 11 and the cover layer 12, it is possible to adjust the required technological properties and furthermore also to adjust the proportion of additional fibers in the two-layer paper web 10 (in the case of preset proportions of additional fibers in the cover layer 12 and possibly also the carrier layer 11).
The two-layer paper web 10 preferably has an interlaminar strength, determined according to the International Scott Bond Test according to DIN ISO 16260, of 180 to 300 J/m2, and in particular of 220 to 300 J/m2.
A Cobb60 value according to DIN EN ISO 535 of at most 40 g/m2, in particular of less than 35 g/m2, and preferably less than 30 g/m2, is preferably set for the cover layer 12. This is obtained by an addition, known per se, of glue and/or starch.
In order to obtain a particular look of the cover layer 12, it can be provided, for example, that the waste paper fibers used there be fibers obtained from white waste paper. Especially in a white-based cover layer, the generally greenish or green/brownish or brownish additional fibers can be easily recognized and are thus easily perceived by the observers of a final product produced from the paper according to the invention, which has the cover layer 12 as a visible surface.
In the overview according to
The respective proportions of the fibers in the differently assembled carrier layers are specified in wt % of the composition in the layer and as proportions in the dry mass, with possible ranges.
Furthermore, three possible composition ranges of the cover layer are shown, in the left-hand column with proportions of waste paper, grass, and further fibers, and, optionally, fibers obtained from plants of the genus Cannabis. In the middle column, a cover layer having a composition of waste paper, grass, and further fibers is shown. In the right-hand column, a composition range of the cover layer consisting of waste paper fibers, grass fibers, and, optionally, fibers obtained from plants of the genus Cannabis is shown.
The respective proportions of the fibers in the differently assembled cover layers are specified in wt % of the composition in the layer and as proportions in the dry mass, with possible ranges.
The advantages inherent in the paper according to the invention and the method for the production thereof are once again clear from the above description. In particular, it has become clear that the use of fibers of the cup plant (Silphium perfoliatum), of fibers obtained from fruits and/or the bark of trees of the baobab genus (Adansonia), of fibers obtained from plants of the genus Cannabis, and/or from residues of biogas facilities, firstly increases the total proportion of additional paper fibers in a paper produced on the basis of waste paper fibers, and can be adjusted in a manner that can be very freely tailored, such that, in this case in particular, a cover layer can also be obtained, which can later serve in particular as a visible surface, in which a high proportion of additional fibers obtained from rapidly renewable raw materials, which proportion is increased yet again compared with known materials, is incorporated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21195241.1 | Sep 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/071240 | 7/28/2022 | WO |
