Method for producing cellulose fiber-based drinking straws

Abstract

The invention relates to a method for producing a drinking straw (1) based on cellulose fibers and a drinking straw (1) based on cellulose fibers. The method comprises the following steps. ‑Providing a pulp material (2). ‑Preparing at least one aqueous suspension (3) containing the pulp material (2) and optionally adding an additive (4) to the suspension (3). ‑Homogenizing the at least one aqueous suspension (3) and pre-drying it to form at least one aqueous nonwoven web (5) having a first side (6) and a second side (7). ‑Drying the at least one aqueous nonwoven web (5) in a plurality of drying steps to form at least one paper web (8) having a first side (6) and a second side (7). ‑Further processing the at least one paper web (8) or the plurality of paper webs (8) to form a drinking straw (1) based on cellulose fibers. It is provided that before, during or after one of the drying steps and before further processing into a drinking straw (1) based on cellulose fibers, at least a first side (6) of at least one nonwoven web (5) is pressed with a linear load of 80 kN / m to 500 kN / m.

Description

[0001] The invention relates to a method for manufacturing a drinking straw based on cellulose fibers, and a drinking straw based on cellulose fibers.

[0002] The demand for recyclable products is growing due to increasing environmental awareness among consumers, but also due to legal and regulatory requirements regarding single-use products in the packaging and food industries.

[0003] Cellulose-based alternatives to plastic products are already well established in many areas of the packaging and food industries. However, the use of cellulose-based straws instead of plastic-based straws or drinking straws presents manufacturers with some specific problems. One of the biggest challenges for cellulose-based straws is to simultaneously provide water resistance or water resistance (at least for the duration of their service life) while requiring as complete or technically inexpensive recyclability as possible.

[0004] According to the prior art, paper is provided with a coating, thereby ensuring the required water resistance. However, such coatings naturally present problems with regard to recyclability. By way of example, WO 2019175470 A1 proposes a straw, in which the straw material is in principle recyclable and biodegradable, but is coated cardboard. The straw consists of a substantially rectangular sheet-shaped coated cardboard block. However, WO 2019175470 A1 discloses only very little about the properties of the paper or cardboard used.

[0005] Papers with at least partially crosslinked cellulose fibers are also known to the skilled person. In order to make the paper for drinking straws based on cellulose fibers at least temporarily mechanically resistant to moisture or humidity, so-called wet strength agents are added during the manufacture of the paper. Wet strength agents are water-miscible polymer solutions in the processed state, mainly made of polyamines and epichlorohydrin derivatives. In addition, products based on urea-formaldehyde or melamine-formaldehyde are also conceivable wet strength agents, although these products are no longer preferred for the purpose of avoiding health risks. When reacting with cellulose fibers, crosslinks are formed between the fibers, resulting in an increased water resistance of the corresponding paper. However, this hydrophobic bond hinders simple or successful recycling. Therefore, it is not feasible or only conditionally feasible to return the used drinking straws to the cellulose cycle by using high temperatures and / or additional chemicals and additives.

[0006] For drinking straws based on cellulose fibers, bleached and / or unbleached cellulose fibers and mixtures thereof come into consideration as starting materials.

[0007] The object of the present invention is to provide a method for producing a drinking straw based on cellulose fibers which is as efficient as possible from a technical, economic and ecological point of view. In addition, the object of the present invention is to provide a drinking straw based on cellulose fibers which also meets the requirements of consumers, such as taste neutrality, and the requirements of the packaging and food industry, as well as the requirements of sustainability, such as recyclability, compostability and biodegradability.

[0008] This object is achieved according to the invention by a production method and a drinking straw based on cellulose fibers.

[0009] The method for manufacturing a drinking straw based on cellulose fibers according to the present invention comprises the following steps:

[0010] - providing a pulp material,

[0011] - preparing at least one aqueous suspension comprising pulp material and optionally adding additives to the suspension,

[0012] - homogenizing at least one aqueous suspension and pre-drying it to form at least one aqueous nonwoven web having a first side and a second side,

[0013] - drying at least one aqueous nonwoven web in a plurality of drying steps to form at least one web having a first side and a second side,

[0014] - further processing of the at least one paper web or the plurality of paper webs into a drinking straw based on cellulose fibers.

[0015] It is thus provided that before, during or after one of the drying steps and before further processing to form a drinking straw based on cellulose fibers, at least a first side of at least one nonwoven web is pressed with a linear load of 80 kN / m to 500 kN / m.

[0016] The pressing of the nonwoven fabric web on at least one side ensures that the cellulose fiber-based drinking straw made of the nonwoven fabric web according to the present invention or the paper web manufactured according to the present invention is water-resistant or water-resistant at least during its use. The results show that the pressing of the nonwoven fabric web surface causes the cellulose fibers near the surface to be smooth. The resulting pressing is similar to sealing, but it does not require auxiliary materials such as varnish, coating, etc. at all. This sealing reduces or even prevents liquid from infiltrating the wall structure of the drinking straw undesirably or too quickly. Therefore, premature softening can be effectively prevented, or at least postponed for a long enough time, so that the function and shape stability of the drinking straw can be guaranteed during use. Surprisingly, in order to achieve this "sealing effect", single-sided pressing and, if necessary, the relevant smoothing of the nonwoven fabric web or paper web are basically sufficient. Whether the two-sided pressing is suitable depends, in particular, on the specific application.

[0017] Since no non-recyclable additives or the like need be added to achieve these properties, the cellulose fiber-based straws produced according to the invention can also be recycled or "repulped", i.e. returned to the aqueous slurry suspension, in a simple manner and method. For any additives added to the aqueous suspension, care must be taken to ensure that only such additives are included that are not harmful to the user and the environment for aqueous extraction applications, such as those in which the straws are used in any case. This can apply to both cold extraction and hot extraction applications.

[0018] The cellulose-based straws produced according to the invention can be recycled without additional effort or without additional complex process steps. In particular, effective "repulping" can be promoted if the process according to the invention does not require the addition of additives in the form of wet strength agents.

[0019] Furthermore, it may be suitable that during the pressing process at least the first side of at least one nonwoven web is subjected to a heat treatment. This may preferably be done in one or more steps at a temperature of 90° C. to 97° C. and / or at a temperature of 200° C. to 295° C. In addition to the pressing, the heat treatment may have a favorable effect on the water resistance of the cellulose fiber-based drinking straw produced according to the invention. This may be achieved by the fact that the thermal effect may lead to an additional smoothing or further pressing of the surface of the nonwoven web or paper web.

[0020] Furthermore, it can be provided that at least one nonwoven web is pressed by means of an extended nip calender, which comprises a heated roller and a shoe roller cooperating with the heated roller and forming an extended nip, wherein the at least one nonwoven web is guided through the extended nip calender with its first side facing the heated roller. Such processing by means of an extended nip calender (also known as a shoe calender) can usually be carried out at the end of the drying section.

[0021] Furthermore, it can be provided that the at least one nonwoven web is pressed with its first side against the surface of a heated drying cylinder by means of one or more pressure rollers, wherein the at least one nonwoven web is guided over a large part of the circumference of the drying cylinder and is heated from the outside by a drying hood which at least partially surrounds the drying cylinder. So-called "MG paper" ("machine-made glossy" paper) or calendered paper can also be produced with a low grammage and can generally be printed very well.

[0022] Also advantageous is an embodiment according to which it can be provided that the pulp material is a pulp mixture consisting of long-fiber kraft pulp and short-fiber pulp, preferably short-fiber kraft pulp, whose length-weighted average fiber length is from 1.05 mm to 2.50 mm according to ISO 16065-2:2014. Kraft pulp is also referred to by the skilled person as kraft pulp.

[0023] In this case, it may be advantageous if the pulp mixture provides 20 to 80% by weight of long-fiber kraft pulp and 20 to 80% by weight of short-fiber pulp, preferably short-fiber kraft pulp. In practice, a mixture within the specified range has proven to be particularly advantageous for achieving good compressibility.

[0024] According to a further embodiment, at least one sizing agent can be added as an additive to at least one suspension in an amount of 0.07 wt % to 1.0 wt %, based on 100 wt % of the total dry matter of the at least one suspension. Adding a sizing agent to at least one aqueous suspension is also referred to as batch sizing.

[0025] Furthermore, it can be advantageous to add at least one sizing agent selected from alkenyl succinic anhydride (ASA), alkyl ketone dimer (AKD), resin sizing agents or natural sizing agents or a mixture of sizing agents selected from this group to at least one suspension. The sizing agents mentioned can have a particularly favorable influence on various properties of the paper web or the drinking straw based on cellulose fibers. For example, the addition of these sizing agents can have a positive influence on the contact angle of the paper web.

[0026] Furthermore, it can be provided that at least one suspension is produced with a concentration of 0.15% to 0.70%. Depending on the specific method used for the pressing step, it may be advantageous to produce an aqueous suspension with a concentration of 0.15% to 0.30% as a low-concentration suspension or an aqueous suspension with a concentration of up to 0.70% as a high-concentration suspension. The concentration selected in each case can depend on the type of machine, the fiber mixture, the drying capacity of the machine and other further parameters.

[0027] Furthermore, it can be provided that, during further processing to form a drinking straw based on cellulose fibers, one or more paper webs are stacked and bonded to one another. The specific structure of this stacking can be adapted to the specific requirements of a specific application.

[0028] According to a particular embodiment, a pressed first side of a paper web can in each case be brought into contact with a non-pressed second side of a further paper web stacked thereon.

[0029] According to an advantageous further embodiment, it can be provided that the paper webs are bonded to one another, wherein the adhesive is applied to the contact surfaces of the paper webs over the entire surface or in sections. Depending on the type of adhesive, the sectioned application may be sufficient to provide a permanent cohesive force during the use of the cellulose-based straw. However, in the case of hot-applied or repeatedly used straws, it may also be advantageous to apply the adhesive over the entire surface or at least to a large part of the contact surface.

[0030] Furthermore, it can be provided that, during further processing, at least one paper web or a plurality of stacked and bonded paper webs are configured as a paper strip to form a straw based on cellulose fibers, wherein the paper strip is in each case delimited by two longitudinal edges and two transverse edges, and an overlap region is formed in each case in the region of the two longitudinal edges, and that a hollow body which is open on both sides and is preferably cylindrical is formed by bending the paper strip around the straw axis, wherein the paper strip is shaped in such a way that an overlap section is formed by the overlap of two overlap regions, and the two overlap regions are bonded to one another in the overlap section.

[0031] Furthermore, it can be provided that the paper strip is shaped in such a way that its two longitudinal edges are substantially parallel to the straw axis.

[0032] It is also advantageous to provide an embodiment according to which it can be provided that the paper strip is shaped in such a way that the two longitudinal edges extend substantially in a spiral or wound shape around the straw axis.

[0033] Furthermore, it may be appropriate to print the first side of at least one paper web with food-safe and biodegradable ink before further processing into a cellulose-based drinking straw. Thus, individual designs, brands, etc. may be applied to the cellulose-based drinking straw.

[0034] According to the invention, a drinking straw based on cellulose fibers is also provided, which is produced in particular by the method according to the invention and comprises a hollow body open on both sides, preferably cylindrical, with a jacket outer surface and a jacket inner surface. It is provided that the hollow body is formed by at least one shaped paper web, wherein the at least one paper web is constructed from at least one paper web having at least one embossed first side.

[0035] By using a paper web which is pressed on at least one side, a cellulose-fiber-based drinking straw made therefrom is made water-resistant or water-resistant, at least during use. It has been found that the pressing of at least one surface of the paper web leads to smoothing of the cellulose fibers near the surface. The pressing thus produced is equivalent to a seal, but without any auxiliary materials such as varnish, coating, etc. This type of seal reduces or even prevents unwanted or too rapid penetration of liquid into the wall structure of the drinking straw. Thus, premature softening can be effectively prevented or at least postponed for a sufficiently long time so that the functional and dimensional stability of the drinking straw can be guaranteed during use. Surprisingly, in order to achieve this "sealing effect", a single-sided pressing and, if necessary, the associated smoothing of the nonwoven fabric web or paper web are basically sufficient. Whether the pressing on both sides is suitable depends, in particular, on the specific application.

[0036] Since no non-recyclable additives or the like need be added to achieve these properties, the cellulose fiber based straws according to the invention can also be easily recycled or "repulped", i.e. returned to an aqueous suspension of cellulose. With regard to any additives added to the aqueous suspension, care must be taken to ensure that only those additives are included that are not harmful to the user and the environment for aqueous extraction applications, such as the straws are used in any case. This applies to both cold extraction applications and hot extraction applications.

[0037] According to the invention, drinking straws based on cellulose fibers can be recycled without additional effort or without additional complex process steps. In particular, effective "repulping" can be simplified if the process according to the invention does not require the addition of additives in the form of wet solids.

[0038] Furthermore, it can be provided that the pressed first side of at least one paper web has a density of 24 g / m2 according to ISO 535:2014. 2 Up to 62g / m 2 Cobb 1800s value.

[0039] Due to the fact that the Cobb 1800s value according to ISO 535:2014 represents the absolute value of the water absorption capacity of the paper and that the grammage of the paper has an important influence on this absolute value, the percentage moisture content over the entire grammage range is also meaningful for the description of the paper properties, which allows for better comparability between different papers. Such a percentage moisture content can be calculated based on the ratio between the Cobb 1800s measurement value and the grammage of the paper as specified in ISO 535:2014. In particular, a percentage moisture content of 35% to 48% can be advantageous for the paper web - this assumes that 7% moisture is present in the paper as compensating moisture when stored under climatic conditions of 23°C ± 1°C and 50% ± 2% relative humidity according to ISO 187:1990. For exemplary explanation, three calculation examples for different paper webs are given below.

[0040] Embodiment 1:

[0041] According to ISO 187:1990, at a standard climate of 23°C ± 1°C and 50% ± 2% relative humidity, the grammage during storage = 40.0 g / m 2 .

[0042] According to ISO 535:2014, Cobb 1800s value = 26.2 g / m 2

[0043] According to Cobb 1800s test, the grammage of paper = 66.2g / m 2

[0044] According to the Cobb 1800s test, the total moisture content of the paper = ((40.0 / 100*7)+26.2) / 66.2*100 = 43.8%.

[0045] Embodiment 2:

[0046] According to ISO 187:1990, at a standard climate of 23°C ± 1°C and 50% ± 2% relative humidity, the grammage during storage = 60.0 g / m 2 .

[0047] According to ISO 535:2014, Cobb 1800s value = 33.3 g / m 2

[0048] According to Cobb 1800s test, the grammage of paper = 93.3g / m 2

[0049] Total water content in paper according to Cobb 1800s test = 40.2%.

[0050] Embodiment 3:

[0051] According to ISO 187:1990, when stored in a standard climate of 23°C ± 1°C and 50% ± 2% relative humidity, the grammage = 120.0 g / m 2

[0052] According to ISO 535:2014, Cobb 1800s value = 59.7 g / m 2

[0053] According to Cobb 1800s test, the grammage of paper = 179.7g / m 2

[0054] Total water content in paper according to Cobb 1800s test = 37.9%.

[0055] Furthermore, suitably, the difference in Cobb 1800s values ​​between the pressed first side and the unpressed or less pressed second side according to ISO 535:2014 is at most 3 g / m 2 By weaker pressing is meant that the second side is pressed less strongly than the first side, for example because it is not pressed against a smooth surface. Depending on the manufacturing method and mechanical aspects, the paper according to the invention can be used for producing drinking straws based on cellulose fibers with a grammage of preferably 22 g / m2 to 200 g / m2 according to ISO 536:2012. In principle, however, the use of papers of lower grammage, as well as papers of higher grammage, is conceivable and optionally suitable.

[0056] According to a particular embodiment, it is possible for the pressed first side of at least one paper web to have a Bendtsen roughness according to ISO 87912:2013 of 30 ml / min to 250 ml / min.

[0057] According to an advantageous further embodiment, it can be provided that the gloss value of at least one paper web is from 20% to 35% according to TAPPI T480: 2015. In particular, if in the production process using a shoe calender, it can be advantageous if the gloss value according to TAPPI T 480: 2015 is from 21% to 25%. In the production of MG paper, it can be advantageous if the gloss value according to TAPPI T480: 2015 is between 24% and 33%.

[0058] In particular, it can be advantageous if the pressed first side of the at least one paper web has a static contact angle of 100° to 120° according to ISO 19403-2:2020 with water as test liquid.

[0059] It may also be advantageous if the difference in the static contact angle with water as the test liquid between a pressed first side and a non-pressed or weakly pressed second side is at most 6° according to ISO 19403-2:2020, the so-called weakly pressed second side being less pressed than the first side, because, for example, it is not pressed onto a smooth surface.

[0060] Furthermore, it can be provided that at least two paper webs are arranged such that a first side of a first paper web forms a jacket outer surface of the hollow body and a first side of a second paper web forms a jacket inner surface of the hollow body.

[0061] For a better understanding of the present invention, it will be explained in more detail with reference to the following drawings.

[0062] Each case is represented in a highly simplified schematic diagram.

[0063] Figure 1 An embodiment of a method for producing a nonwoven web and drying it to form a paper web.

[0064] Figure 2 A further embodiment of a method for producing a nonwoven web and drying it to form a paper web is provided.

[0065] Figure 3 3D exploded image of three sheets of paper stacked on top of each other.

[0066] Figure 4 Make another strip of paper.

[0067] Figure 5 3D illustration of a cellulose fiber-based drinking straw.

[0068] Figure 6 is a 3D illustration of another cellulose fiber based drinking straw.

[0069] Figure 7 A three-dimensional image of paper webs stacked or folded on top of each other.

[0070] As an introduction, it should be pointed out that in the different described embodiments, identical components are provided with the same reference symbols or the same component names, whereby the disclosure contained in the entire description can be transferred mutatis mutandis to the identical components having the same reference symbols or the same component names. In addition, selected position indications in the description, such as top, bottom, side, etc., are related to the figures directly described and illustrated, and these position indications are transferred mutatis mutandis to the new positions in case of a change of position.

[0071] The method for producing a drinking straw 1 based on cellulose fibers, as known per se, firstly involves producing an aqueous suspension 3 containing a pulp material 2 and optionally adding additives 4 .

[0072] The skilled person is fully aware of how to achieve the production of pulp material 2, so that the corresponding possible method steps are not described or illustrated in detail. For the sake of completeness, only a possible process is briefly described here. Advantageously, as pulp material 2, a pulp mixture consisting of long-fiber kraft pulp and short-fiber pulp, preferably short-fiber kraft pulp, can be provided, whose length-weighted average fiber length according to ISO 16065-2:2014 is 1.05 mm to 2.50 mm. The pulp mixture can consist of 20 to 80 wt% of long-fiber kraft pulp and 20 to 80 wt% of short-fiber pulp, preferably short-fiber kraft pulp. For example, a pulp mixture of hardwood kraft pulp and softwood kraft pulp can be used as starting material for producing pulp material 2. Of course, it can also be a mixture of hardwood and softwood with different crushing. The pulp mixture is prepared by the following process: it includes chemically treating the crushed first and second pulps in a pulp digester. Depending on the requirements, it may be suitable to subject the water-based solid suspension of the pulp mixture to mechanical processing and deslagging in a high-consistency cleaner after the chemical treatment. Before the mechanical processing and deslagging in the high-consistency cleaner, the concentration of the solid suspension may be adjusted to, for example, 25% to 40%. Such deslagging in the high-consistency cleaner may, in particular, also reduce the so-called chip content in the pulp mixture, i.e. dissolved pulp lumps that are still woody. Furthermore, it may also be advantageous to subject the pulp mixture or the water-based solid suspension of the pulp mixture to mechanical processing and grinding in a low-consistency refiner after the first mechanical processing and deslagging in the high-consistency cleaner. Before the mechanical processing and grinding in the low-consistency refiner, the concentration of the solid suspension may be appropriately adjusted to 2% to 6%. It is also conceivable to subject the pulp mixture to mechanical processing only in the high-consistency refiner. In other cases, however, it may be preferred not to perform vibration in the high-consistency refiner and to subject the pulp mixture to mechanical processing only in the low-consistency refiner. The specific grinding capacities of the individual grinding stages must be adapted to the selected pulp mixture for the desired paper parameters.

[0073] To avoid unnecessary repetition, Figure 1 and Figure 2 The description of the invention is given below, where reasonable and possible, in summary form, in which like reference numerals are used for like parts. Figure 1 and Figure 2 In each case an exemplary embodiment of a method for producing a nonwoven web 5 and drying it to form a paper web 8 is shown.

[0074] Independently of this, the preparation of the pulp mixture to provide the pulp material 2 requires the production of at least one aqueous suspension 3 containing the pulp material 2 for further processing of the pulp material 2. This processing step is for example carried out in Figure 1 and Figure 22 is illustrated with the aid of a tank 28 with a stirrer. In particular, various additives 4 or additives and auxiliary materials customary in papermaking technology, such as fillers, starches, etc., can be added to the at least one aqueous suspension 3. At least one sizing agent can be added as additive 4 to the at least one suspension 3 in an amount of 0.07% to 1.0% (based on 100% by weight of the total dry matter of the at least one suspension 3), based on the active substance of the sizing agent. The sizing agent can be selected from the group consisting of alkenyl succinic anhydride (ASA), alkyl ketone dimer (AKD), resin sizing agent or natural sizing agent or a mixture of sizing agents selected from this group.

[0075] Independently of this, the concentration of the at least one aqueous suspension 3 can be adjusted to a value of 0.15% to 0.8%, preferably 0.3% to 0.7%, and then homogenized and predried to at least one aqueous nonwoven web 5 having a first side 6 and a second side 7. The further processing of the at least one aqueous suspension 3 can be carried out by a paper machine 29, which is known per se, and is described below with reference to Figure 1 and Figure 2 Described schematically. Typically, the paper machine 29 may include a screen section 30, a pressing section 31 and a drying section 32, each of these method steps being a drying or dewatering operation. According to the invention, it is designed that before, during or after one of the drying steps and before further processing into a cellulose fiber-based straw 1, the first side 6 of at least one nonwoven fabric web 5 is pressed with a linear load of 80 kN / m to 500 kN / m. The pressing step can be produced either in a single pressing zone (Nip), i.e. a pressing step, or in a plurality of successively arranged pressing zones, each of which has a specified linear load. In addition, it may be appropriate that during the pressing process, the first side 6 of at least one nonwoven fabric web 5 is heat treated. In other words, this means that in the same method step, thermal influence can occur simultaneously with pressurization.

[0076] like Figure 1 and Figure 2As shown, at least one aqueous suspension 3 comprising pulp material 2 can be applied to a circulating endless screen 33 of a screen section 30, which is known per se. In such a screen section 30, the at least one aqueous suspension 3 is homogenized and pre-dried to form at least one water-containing nonwoven web 5. In this case, the endless screen 33 can be guided to a dewatering device 34 of the screen 30, which can be formed by, for example, an extruder. In principle, the dewatering in the screen section 30 can also be carried out only by gravity. In addition, however, depending on the design of the screen section 30, the dewatering or pre-drying of at least one nonwoven web 5 can be supported by generating a negative pressure. At least one first nonwoven web 5 consisting of pulp material 2 can be pre-dried by the screen section 30, for example, to a moisture content of 75 wt.% to 85 wt.%.

[0077] Then, if Figure 1 and Figure 2 As shown, at least one nonwoven web 5 can be further dewatered and respectively further dried by a pressing section 31. Figure 1 The nonwoven web 5 can be passed between the rollers 35 of the pressing section 31, thereby further dewatering under pressure. In addition, further drying can be supported by an absorbent support material 36. It is well known that, for example, a felt pad can be used for this purpose. As is known per se, according to Figure 1 The pressing section 31 can include more than two rollers 35, in particular, several pairs of rollers formed by rollers 35 can be arranged in succession. For example, after passing through the pressing section 31, the moisture content of the nonwoven fabric 5 relative to the total mass of the nonwoven fabric 5 can be about 45% by weight to 65% by weight.

[0078] according to Figure 1 A so-called rotary dryer 37 can be arranged after the pressing section 31 as the drying section 32 or as a part of the drying section 32. Figure 1 As shown, the rotary dryer 37 may include many rotating drying cylinders 15, on which the at least one nonwoven fabric web 5 may be guided. The drying cylinder 15 may be directly heated. For example, a heating channel may be formed, which is not shown in more detail, for introducing superheated steam into the drying cylinder 15. In addition, for example, it is also possible to heat the drying cylinder 15 by means of a resistance heater. For example, the temperature of the drying cylinder 15 of the drying section 32 may increase successively along the passing direction of at least one nonwoven fabric 5. The nonwoven fabric 5 may be dried by means of the rotary dryer 37, for example, being dried to a moisture content of 1 wt % to 10 wt %.

[0079] For the pressing according to the invention, the line load is preferably 210 kN / m to 370 kN / m, and a so-called wide nip calender 9 or also a shoe calender with a shoe length of, for example, 50 mm and a shoe inclination of 24% can be provided in the drying section 32 downstream of the rotary dryer 37 to further dry and press the nonwoven web 5. For the pressing according to the invention, the line load is preferably 380 kN / m to 490 kN / m, and a shoe calender can also be provided, for example, with a shoe length of 75 mm and a shoe inclination of 24%.

[0080] The wide nip calender 9 can be formed essentially by a heating roller 10 and a shoe roller 12 cooperating with the heating roller 10. The shoe roller 12 can serve as a flexible counterpressure element for the heating roller 10 and has a surrounding sheath 38. The surrounding sheath 38 cooperates with the heating roller 10 to form a wide nip 11. At least one nonwoven web 5 is calendered with its first side 6 facing the heating roller 10 passing between the heating roller 10 and the shoe roller 12. This means that the nonwoven web 5 is simultaneously pressed with an increased pressure and loaded with an increased temperature. The temperature of the heating roller surface can be, for example, from about 250° C. to 295° C. This temperature can be achieved, for example, by means of a heat transfer oil with a correspondingly high oil flow temperature. In order to further stabilize the surface temperature, further heating elements, such as induction heating, can also be provided. In principle, it is also conceivable, but not shown, to provide a second advantageous identical wide-nip calender 9 which is arranged in the paper machine 29 in such a way that, in addition to calendering the first side 6 of the at least one nonwoven web 5, calendering of the so-called second side 7 can also be performed.

[0081] It is also conceivable that after the screen section 30, a process combination of a pressing section 31 and a drying section 32 is provided, with which the pressing according to the invention can be carried out at a line pressure of about 80 kN / m in the first shoe press, at about 90 kN / m in the second smoothing press, and at about 100 kN / m in the third smoothing press. For example, the surface temperature of the Yankee dryer can be about 94° C. This conceivable solution is Figure 2 A rough outline is given. Figure 1 An alternative to the scheme variant of Figure 2 The dewatering, pressing or pressurizing is shown by means of a so-called Yankee dryer 39. Paper produced by this arrangement or similar arrangements is generally referred to in the industry as "machine-made waxed" or "MG paper". As part of the paper machine 29, Figure 2A combined pressing section 31 and drying section 32 is shown in the form of a Yankee dryer 39 with an attached drying cap 16 or gas drying cap. At least one nonwoven web 5 adhering to a release felt is pressed with its first side 6 by two pressing rollers 13 against the surface 14 of the steam-heated Yankee dryer 39 and is further or completely dried by additional blowing of hot air with the aid of the drying cap 16.

[0082] Figure 1 and Figure 2 The end of the exemplary paper machine 29 shown in the figure is represented in each case by a rewinder 40, by means of which the at least one finished paper web 8 can be wound onto a roll. Alternatively, however, it is also conceivable and, if necessary, suitable to feed the at least one paper web 8 directly to further processing or finishing.

[0083] Depending on the configuration of the paper machine 29, at least one suspension 3 can be prepared with a concentration of 0.15% to 0.70%. Figure 1 With the arrangement of the wide nip calender 9, both high and low concentration suspensions 3 can be used, and for similar Figure 2 With the arrangement of the Yankee dryer 39, a low-concentration suspension 3 with a concentration of 0.15% to 0.30% may be more suitable.

[0084] A large number of different methods for producing drinking straws 1 based on cellulose fibers from at least one paper web 8 are sufficiently known to the person skilled in the art that possible method steps are not discussed in detail.

[0085] Advantageously, one, but also several, preferably three or even four, of the paper webs 8 produced according to the invention can be further processed to form a drinking straw 1 based on cellulose fibers. In the further processing, one or more paper webs 8 produced from the same pulp material 2, i.e. several identical paper webs 8, can be stacked on top of one another. However, it is also conceivable and has proven to be particularly advantageous to stack and combine several paper webs 8 produced from different pulp materials 2 and thus having different process properties.

[0086] It is also possible to further process the individual paper webs 8, for example, by corresponding single or also multiple folding. For example, the individual paper webs 8 can be folded several times in a zigzag or curved shape, thereby forming a quasi-multi-layer or mutually superimposed paper web 8. This conceivable embodiment is Figure 7 In the case of such a fold, the pressed first sides 6 are in contact with each other and the unpressed second sides 7 are in contact with each other. Figure 4The exemplary sketch and the subsequent description of the embodiment can also be subsequently produced according to this embodiment. This folded paper strip consisting of the paper according to the invention can be fixed in its position by means of adhesive 17 via correspondingly selected adhesive points. Adhesive 17 - in Figure 7 It is not explicitly shown in the example - for example, it can be applied across the entire surface, in dots or in strips between the folded layers.

[0087] Figure 3 In a three-dimensional exploded view, three paper webs 8 stacked one on top of another are shown. Of course, a smaller or larger number of paper webs 8 can also be provided. In this case, it can be suitable that the uppermost of the three paper webs 8 shown has been pressed on a paper machine 29 with a wide nip calender 9, and the middle and lower paper webs 8 have been pressed on an MG machine by a Yankee dryer 39. It can also be suitable to arrange three stacked paper webs 8, wherein the upper paper web 8 is pressed by a Yankee dryer 39 and the middle and lower paper webs 8 are pressed by a wide nip calender 9. Here, as shown in FIG. Figure 3 As shown, the paper webs 8 can be stacked on top of each other in such a way that the pressed first side 6 of one paper web 8 in each case contacts the unpressed second side 7 of the other paper web 8 stacked thereon. In addition, but not shown, it is also advantageous if the paper webs 8 are stacked on top of each other in such a way that the pressed first side 6 of each of the two outer paper webs 8 is located on the outside. It should be noted here that the unpressed second side 7 can also be the less pressed side compared to the pressed first side 6.

[0088] In addition, but also not shown, it can also be advantageous if, in the arrangement of a plurality of paper webs 8, at least one layer is a paper product produced according to the invention. In particular, it can also be advantageous if, in particular, one of the two outer paper webs 8, i.e. one of the two paper webs 8 that are in direct contact with the drinking liquid, is produced according to the method according to the invention. However, it can also be advantageous if both outer paper webs 8 of the finished cellulose-based drinking straw 1 are produced according to the method according to the invention. In this case, it can be advantageous if the pressed first side 6 is in direct contact with the liquid. By means of a targeted arrangement of the paper webs 8, various parameters or product properties, such as optical properties such as gloss, printability, tactile sensation, etc., can be adjusted accordingly in an advantageous manner.

[0089] The paper webs 8 can be bonded to one another, ie adhesive 17 can be applied to the contact surfaces 6 , 7 of the paper webs 8 over the entire surface or in sections. Figure 3, it is shown that the adhesive 17 can be applied in strips and approximately symmetrically on one side 6, 7 of each paper web 8. Of course, depending on the requirements and the adhesive strength, it is also conceivable that the adhesive 17 can be applied over the entire surface and can also be applied only selectively or along the edges of the sheet on each contact surface 6, 7. In particular, in order to obtain food certification for the cellulose-based straw 1 and taking into account that the cellulose-based straw may leach components when in contact with cold and / or hot liquids, it may be important to use food-safe, biodegradable glues of animal and / or plant origin as adhesive 17. Different legal requirements and recommendations apply to the safe use of paper, cartons and paperboard for direct contact with food. To name a few relevant examples, reference should be made, for example, to Recommendation No. XXXVI of the Federal Institute for Risk Assessment and also Recommendation No. XXXVI / 1 on cooking and hot filter papers. In this regard, reference should also be made to Regulation (EC) No. 1935 / 2004 and the Food, Commodities and Feed Act. More national regulations are Decreto Minis teriale 21 March 1973, Code of Federal Regulations, Food and Drugs (FDA), 21 CFR Ch.I (April 1, 2019 edition), §§176.170 and 176.180, Regulation of the Minis ter von Volksgezondheid, Standard of Practice von 14 March 2014, kenmerk 328583-117560-VGP, Warehouse management, Mercosure and Chinese regulations.

[0090] During further processing into a drinking straw 1 based on cellulose fibers, the individual paper webs 8 can also be Figure 3 The stacked paper web 8 shown is formed into a paper strip 18. To illustrate the problem, Figure 4 A further paper web 8 is shown which is further formed into a paper strip 18. In each case, a paper strip 18 can be defined by two longitudinal edges 19 and two transverse edges 20, wherein an overlap region 21 can be formed in each region of the two longitudinal edges 19. The length 41 of such a paper strip 18 can correspond to a multiple of the length 25 of the finished cellulose-fiber-based drinking straw 1. Figure 3 The dashed lines in show possible positions of subsequent cutting areas. It is also possible to print the first side 6 of at least one paper web 8 with a food-safe and biodegradable ink before further processing into a drinking straw 1 based on cellulose fibers.

[0091] Figure 5 and Figure 6Two conceivable embodiments of a drinking straw 1 based on cellulose fibers are further shown in a three-dimensional representation, wherein the drinking straw 1 based on cellulose fibers comprises a hollow body 23 open on both sides, preferably cylindrical, having a jacket outer surface 26 and a jacket inner surface 27. It is provided here that the hollow body 23 is formed by at least one shaped paper web 18, wherein the at least one paper web 18 is composed of at least one paper web 8 having at least one embossed first surface 6. For example, as an alternative to a cylindrical hollow body 23, a drinking straw 1 with a rolled edge or a polygonal cross section is also conceivable.

[0092] By bending the paper strip 18 around the straw axis 22, a preferably cylindrical hollow body 23 open on both sides can be formed, wherein at least one paper strip 18 can be formed in such a way that an overlap section 24 is formed by the overlap of two overlap regions 21. The cylindrical hollow body 23 can then be cut approximately or substantially in the radial direction of the straw axis 22 to a finished length 25, for example 5 cm to 50 cm. In this case, at least one paper strip 18 can be formed in such a way that its two longitudinal sides 19 extend substantially parallel to the straw axis 22, such as Figure 5 Alternatively, Figure 6 As shown, it is also conceivable that the two longitudinal edges 19 extend substantially in a spiral or winding manner around the straw shaft 22. Advantageously, the two overlapping regions 21 can be bonded to one another in the overlapping section 24.

[0093] At least two paper webs 8 can be arranged in such a way that the first side 6 of the first paper web 8 forms the outer jacket surface 26 of the hollow body 23 and the first side 6 of the second paper web 8 forms the inner jacket surface 27 of the hollow body 23. It is possible here to form one or more further paper webs 8 between the two outer paper webs, i.e. between the first and second paper webs 8. These attached or interposed paper webs 8 can be paper webs 8 according to the invention or further papers of different types with optional additional advantageous properties. It is also possible to arrange at least two paper webs 8 in such a way that the second side 7 of the first paper web 8, which is not pressed or is pressed less than the first side 6, forms the outer jacket surface 26 of the hollow body 23 and the second side 7 of the second paper web 8, which is not pressed or is pressed less than the first side 6, forms the inner jacket surface 27 of the hollow body 23.

[0094] The at least one paper web 8 or the pressed first side 6 of the paper web 8 has a Cobb 1800s value of 24 to 62 g / m2 according to ISO 535:2014. The difference in Cobb 1800s value between the pressed first side 6 and the unpressed or less pressed second side 7 according to ISO 535:2014 is preferably at most 4 g / m2. 2. Furthermore, the pressed first side 6 of the paper web 8 can have a Bendtsen roughness of 30 to 250 ml / min according to ISO 8791-2:2013. It can also be advantageous if the paper web 8 has a gloss value of 20-35% according to TAPPI 480. Furthermore, the static contact angle of the pressed first side 6 of the paper web 8 with water as a test liquid can be 100° to 120° according to ISO 19403-2:2020. The difference in the static contact angle with water as a test liquid between the pressed first side 6 and the unpressed or less pressed second side 7 according to ISO 19403-2:2020 is at most 6°.

[0095] The embodiments show possible implementation variants, and it should be pointed out that the present invention is not limited to the implementation variants specifically described, but various combinations of the various implementation variants are also possible. Due to the teaching of the present invention on technical actions, the possibility of such changes lies within the capabilities of technicians active in this technical field.

[0096] The scope of protection is determined by the claims. However, reference should be made to the description and the drawings when interpreting the claims. Individual features or combinations of features in the various embodiments shown and described may constitute independent inventive solutions in themselves. The tasks on which the independent inventive solutions are based can be derived from the description.

[0097] All numerical ranges in this specification should be understood to include any and all sub-ranges thereof, for example, the indication of 1 to 10 should be understood to include all sub-ranges, starting from a lower limit of 1 and an upper limit of 10, that is, all sub-ranges start with a lower limit of 1 or greater and end with an upper limit of 10 or less, for example, 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0098] Finally, for the sake of order, it should be pointed out that some elements are not shown to scale and / or are enlarged and / or reduced in size for a better understanding of the structure.

[0099] Reference Mark List

[0100] 1. Cellulose-based drinking straw

[0101] 2. Pulp material

[0102] 3 Suspension

[0103] 4 Additives

[0104] 5Nonwoven fabric width

[0105] 6 Narrow side

[0106] 7 wide noodles

[0107] 8 paper widths

[0108] 9 Wide Nip Calender

[0109] 10 Heating roller

[0110] 11 Wide pressure zone (Brei tnip)

[0111] 12 shoe rollers

[0112] 13 Pressing roller

[0113] 14 Surface

[0114] 15 Drying cylinder

[0115] 16 Drying hood

[0116] 17 Adhesives

[0117] 18 paper tape

[0118] 19 vertical edge

[0119] 20 horizontal edge

[0120] 21 Overlapping Area

[0121] 22 straw shaft

[0122] 23 Hollow body

[0123] 24 Overlapping segments

[0124] 25 long

[0125] 26 Outer surface of sheath

[0126] 27 Inner surface of sheath

[0127] 28 cans

[0128] 29Paper Machine

[0129] 30 Screen part

[0130] 31 Suppression part

[0131] 32 Drying part

[0132] 33 Endless Screen

[0133] 34 Dehydration device

[0134] 35 rollers

[0135] 36 Support Materials

[0136] 37 Rotary Dryer

[0137] 38 sheath

[0138] 39 Yankee Dryer

[0139] 40 rewinding machine

[0140] 41 long

Claims

1. A method for manufacturing a drinking straw (1) based on cellulose fibers, comprising the following steps: - providing a pulp material (2), - preparing at least one aqueous suspension (3) comprising pulp material (2), and adding at least one sizing agent as an additive (4) to the at least one suspension (3), the sizing agent being used in an amount of 0.07% by weight to 1.0% by weight, based on the active substance of the sizing agent, based on 100% by weight of the total dry matter of the at least one suspension (3), - homogenizing at least one aqueous suspension (3) and pre-drying it to form at least one aqueous nonwoven web (5) having a first side (6) and a second side (7), - drying at least one aqueous nonwoven web (5) in a plurality of drying steps to form at least one paper web (8) having a first side (6) and a second side (7), - further processing of at least one paper web (8) or a plurality of paper webs (8) to form a drinking straw (1) based on cellulose fibers, wherein at least a first side (6) of at least one nonwoven web (5) is pressed with a linear load of 80 kN / m to 500 kN / m before, during or after one of the drying steps and before further processing into a drinking straw (1) based on cellulose fibers, Features The pulp material (2) provided is a pulp mixture consisting of long-fiber kraft pulp and short-fiber pulp having a weighted average fiber length of 1.05 mm to 2.50 mm according to ISO 16065-2:2014, and During the pressing process, at least a first side (6) of at least one nonwoven web (5) is heat treated.

2. The method according to claim 1, characterized in that The short fiber pulp is short fiber sulfate pulp.

3. The method according to claim 1, characterized in that During the pressing process, at least the first side (6) of at least one nonwoven web (5) is heat treated at a temperature of 90° C. to 97° C. and / or at a temperature of 200° C. to 295° C.

4. The method according to claim 1, characterized in that At least one nonwoven web (5) is pressed by means of a wide nip calender (9), the wide nip calender (9) comprising a heating roller (10) and a boot roller (12) cooperating with the heating roller (10) and forming a wide nip (11), wherein the at least one nonwoven web (5) is guided through the wide nip calender (9) while the first side (6) of the nonwoven web faces the heating roller (10).

5. The method according to claim 1 or 4, characterized in that A first side (6) of at least one nonwoven web (5) is pressed against a surface (14) of a heated drying cylinder (15) by means of one or more pressure rollers (13), wherein the at least one nonwoven web (5) is guided over a large part of the circumference of the drying cylinder (15) and is further heated from the outside by means of a drying hood (16) which at least partially surrounds the drying cylinder (15).

6. The method according to claim 1, characterized in that A pulp mixture consisting of 20 to 80 wt. % long fiber kraft pulp and 20 to 80 wt. % short fiber pulp is provided.

7. The method according to claim 6, characterized in that The short fiber pulp is short fiber sulfate pulp.

8. The method according to claim 1, characterized in that At least one sizing agent selected from the group consisting of alkenyl succinic anhydride (ASA), alkyl ketone dimer (AKD), resin sizing agent or natural sizing agent, or a mixture of sizing agents selected from this group, is added to at least one suspension (3).

9. The method according to claim 1, characterized in that At least one suspension (3) is prepared at a concentration of 0.15% to 0.70%.

10. The method according to claim 1, characterized in that During further processing to form a drinking straw (1) based on cellulose fibers, one or more paper webs (8) are stacked one on top of the other and bonded.

11. The method according to claim 10, characterized in that In each case, a pressed first side (6) of a paper web (8) is in contact with a non-pressed second side (7) of a further paper web (8) stacked one above the other.

12. The method according to claim 10, characterized in that Paper webs (8) are bonded to one another, wherein an adhesive (17) is applied fully or partially to the contact surfaces (6, 7) of the paper webs (8).

13. The method according to claim 1, characterized in that During further processing to form a drinking straw (1) based on cellulose fibers, at least one paper web (8) or a plurality of layered and bonded paper webs (8) are combined into a paper strip (18), wherein one paper strip (18) is in each case delimited by two longitudinal edges (19) and two transverse edges (20) and wherein in each case an overlap region (21) is formed in the region of the two longitudinal edges (19), and a hollow body (23) open on both sides is formed by bending the paper strip (18) around a straw axis (22), wherein the paper strip (18) is shaped in such a way that an overlap section (24) is formed by overlapping two overlap regions (21) and the two overlap regions (21) are bonded to one another in the overlap section (24).

14. The method according to claim 13, characterized in that The hollow body (23) is cylindrical.

15. The method according to claim 12, characterized in that The paper strip (18) is formed in such a way that its two longitudinal edges (19) extend parallel to the straw axis (22).

16. The method according to claim 13, characterized in that The paper strip (18) is formed in such a way that the two longitudinal edges (19) extend in a spiral or wound manner around the straw shaft (22).

17. The method according to claim 1, characterized in that Prior to further processing into a cellulose-fiber-based drinking straw (1), a first side (6) of at least one paper web (8) is printed with a food-safe and biodegradable ink.

18. A drinking straw (1) based on cellulose fibers, produced by a method according to any one of claims 1 to 17, comprising a double-open hollow body (23) having a sheathing outer surface (26) and a sheathing inner surface (27), wherein: The hollow body (23) is formed by at least one shaped paper web (18), wherein the at least one paper web (18) is composed of at least one paper web (8) having at least one pressed first side (6), characterized in that the pressed first side (6) of the at least one paper web (8) has a density of 24 g / m2 according to ISO 535:2014. 2 Up to 62g / m 2 Cobb 1800s value.

19. A drinking straw (1) based on cellulose fibers according to claim 18, characterised in that The hollow body (23) is cylindrical.

20. The drinking straw (1) based on cellulose fibers according to claim 18, characterized in that According to ISO 535:2014, the difference in Cobb 1800s value between the pressed first side (6) and the unpressed or less pressed second side (7) is at most 3 g / m 2 .

21. A drinking straw (1) based on cellulose fibers according to claim 18 or 20, characterised in that The pressed first side (6) of the at least one paper web (8) has a Bendtsen roughness of 30 mL / min to 250 mL / min according to ISO 8791-2:2013.

22. A drinking straw (1) based on cellulose fibers according to claim 18 or 20, characterised in that The at least one paper web (8) has a gloss value of 20 to 35% according to TAPPI T480:2015.

23. A drinking straw (1) based on cellulose fibers according to claim 18 or 20, characterised in that According to ISO 19403-2:2020, the static contact angle of the pressed first side (6) of the at least one paper web (8) with water as test liquid is between 100° and 120°.

24. A drinking straw (1) based on cellulose fibers according to claim 18 or 20, characterised in that According to ISO 19403-2:2020, the difference in the static contact angle with water as test liquid between the pressed first side (6) and the unpressed or less pressed second side (7) is at most 6°.

25. A drinking straw (1) based on cellulose fibers according to claim 18 or 20, characterised in that At least two paper webs (8) are arranged in such a way that the first side (6) of the first paper web (8) forms the outer jacket surface (26) of the hollow body (23) and the first side (6) of the second paper web (8) forms the inner jacket surface (27) of the hollow body (23).

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