Method for the production of cellulose fibre-based drinking straws

Abstract

The invention relates to a method for producing cellulose-fibre-based drinking straws (1) and to a cellulose-fibre-based drinking straw (1). The method comprises the following steps: - providing a cellulose material (2), - producing at least one aqueous suspension (3) comprising the cellulose material (2) and optionally adding additives (4) to the suspension (3), - homogenising the at least one aqueous suspension (3) and pre-drying to form at least one water-containing non-woven web (5) having a first side (6) and a second side (7), - drying the at least one water-containing non-woven 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 a plurality of the paper webs (8) to form a cellulose-fibre-based drinking straw (1). According to the invention, at least the first side (6) of the at least one non-woven web (5) is compressed with a line load of 80 kN / m to 500 kN / m before, during or after one of the drying steps and before being further processed to form a cellulose-fibre-based drinking straw (1).

Description

[0001] The invention relates to a method for producing cellulose fiber-based drinking straws, as well as a cellulose fiber-based drinking straw.

[0002] The demand for recyclable products is growing as a result of increased environmental awareness among consumers and, not least, due to legal and regulatory requirements regarding disposable products in the packaging and food industries.

[0003] In many areas of the packaging and food industries, the replacement of plastic-based products with cellulose fiber-based alternatives has become established. However, the use of cellulose fiber-based drinking straws instead of plastic-based ones presents manufacturers with a number of specific problems. One of the biggest challenges for cellulose fiber-based drinking straws is to simultaneously offer watertightness or water resistance—at least for their entire service life—while simultaneously requiring the greatest possible recyclability and minimal technical complexity.

[0004] According to the state of the art, papers are coated to ensure the required water resistance. However, such coatings are inherently problematic with regard to their recyclability. One example is WO 2019175470 A1, which presents a drinking straw in which the straw material, while essentially recyclable and biodegradable, is coated cardboard. The drinking straw consists of a substantially rectangular, sheet-like piece of coated cardboard. However, WO 2019175470 A1 discloses very little about the properties of the paper or cardboard used.

[0005] The use of papers with at least partial cross-linking of the cellulose fibers is also known to those skilled in the art. To ensure that the papers for cellulose-fiber-based drinking straws remain mechanically resistant, at least temporarily, to moisture or wet conditions, so-called wet strength agents are added during paper production. Wet strength agents are, in the processed state, water-miscible polymer solutions, which are primarily made from polyamines and epichlorohydrin derivatives. Urea-formaldehyde or melamine-formaldehyde-based products are also conceivable as wet strength agents, but these are no longer preferred to avoid health risks. Reactions with cellulose fibers result in cross-links forming between the fibers, which increase the water resistance of the corresponding paper. However, this hydrophobic linkage prevents easy or successful recycling.The recycling of used drinking straws into a pulp cycle is therefore not possible or only possible to a limited extent through the use of high temperatures and / or additional chemicals and additives.

[0006] For cellulose fiber-based drinking straws, bleached and / or unbleached cellulose fibers as well as mixtures thereof are conceivable as starting materials.

[0007] The object of the present invention was to provide a process for producing cellulose fiber-based drinking straws that is as efficient as possible from a technical, economic, and ecological perspective. Furthermore, the object of the invention was to provide a cellulose fiber-based drinking straw that equally meets the requirements of consumers—such as taste neutrality—and the packaging and food industries, as well as aspects of sustainability, such as recyclability, compostability, and biodegradability.

[0008] This object is achieved by a manufacturing method and a cellulose fiber-based drinking straw according to the claims.

[0009] The process according to the invention for producing cellulose fiber-based drinking straws comprises the steps: Providing a cellulose material, producing at least one aqueous suspension comprising the cellulose material and without admixing additives in the form of wet strength agents to the suspension (3), homogenizing the at least one aqueous suspension and pre-drying it to form at least one water-containing nonwoven web having a first side and a second side, drying the at least one water-containing nonwoven web in several drying steps to form at least one paper web having a first side and a second side, further processing the at least one paper web or several of the paper webs to form a cellulose fiber-based drinking straw, wherein at least the first side of the at least one nonwoven web is compacted with a line load of 80 kN / m to 500 kN / m before, during or after one of the drying steps and before further processing to form a cellulose fiber-based drinking straw.

[0010] By compacting the nonwoven web at least on one side, a cellulose fiber-based drinking straw made from a nonwoven web according to the invention, or from a paper web produced according to the invention, is water-resistant, or water-resistant, at least for the duration of its use. It has been found that compacting the surface of the nonwoven web smooths the cellulose fibers in the vicinity of the surface. The resulting compaction is equivalent to a type of seal, which, however, works entirely without varnishes, coatings, or similar additives. This type of seal reduces or even prevents unwanted or excessively rapid penetration of liquids into the wall structure of the drinking straw.Premature softening can thus be effectively prevented or at least delayed sufficiently, ensuring the straw's functionality and dimensional stability throughout its service life. Surprisingly, it has been shown that to achieve this "sealing effect," one-sided compaction and, if necessary, the accompanying smoothing of the nonwoven web or paper web is generally sufficient. Whether double-sided compaction is appropriate depends, among other things, on the specific application.

[0011] Because no non-recyclable additives or the like need to be added to achieve these properties, a cellulose fiber-based drinking straw produced according to the invention is also easily amenable to recycling, or rather, "repulping," i.e., returning it to an aqueous pulp suspension. With any additives added to the aqueous suspension, care must be taken to ensure that they only contain additives that are harmless to the user and the environment with regard to an aqueous extraction application, such as the use of drinking straws. This applies to both cold and hot extraction applications.

[0012] A cellulose fiber-based drinking straw produced according to the invention can be recycled without additional effort or complex processing steps. Efficient repulping can be facilitated, particularly if the process according to the invention does not require the addition of additives such as wet strength agents.

[0013] A cellulose fiber-based drinking straw produced according to the invention is essentially characterized in that a pulp mixture consisting of long fiber sulfate pulp and short fiber pulp, preferably short fiber sulfate pulp, with a length-weighted, average fiber length according to ISO 16065-2:2014 of 1.05 mm to 2.50 mm is provided as the pulp material, that the pulp mixture is provided from 20 wt.% to 80 wt.% long fiber sulfate pulp and from 20 wt.% to 80 wt.% short fiber pulp, and that at least the first side of the at least one nonwoven web is thermally treated in the course of the compaction, preferably at a temperature of 90 °C to 97 °C or at a temperature of 200 °C to 295 °C, wherein the compaction of the surface is achieved without varnishes, coatings or similar auxiliary substances. Sulfate pulp is also known to those skilled in the art as kraft pulp.A mixture of long-fiber sulfate pulp and short-fiber pulp within the specified limits has proven particularly advantageous in practice for achieving good compactability. A thermal treatment in addition to the pressurization can have a beneficial effect on the water resistance of the cellulose fiber-based drinking straw produced according to the invention. This can be achieved by applying heat to further smooth or compact the surface of the nonwoven or paper web.

[0014] Furthermore, it can be provided that at least one nonwoven web is compacted by means of an extended nip calender comprising a heating roller and a shoe roll that interacts with the heating roller and forms an extended nip. The at least one nonwoven web is guided through the extended nip calender with its first side facing the heating roller. Such processing by means of an extended nip calender, also referred to as a shoe calender, can usually take place at the end of a dryer section.

[0015] Furthermore, it can be provided that 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. The at least one nonwoven web is guided over a large part of the circumference of the drying cylinder and is additionally heated externally by means of a drying hood that at least partially surrounds the drying cylinder. So-called "MG papers" ("machine-glazed" papers) or satin-finished papers can also be produced with low grammage and are generally easy to print.

[0016] According to a further development, it is possible for at least one sizing agent to be added to the at least one suspension as an additive, based on the active substance of the sizing agent, 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. The addition of sizing agents to the at least one aqueous suspension is also referred to as engine sizing.

[0017] Furthermore, it may be advantageous to add at least one sizing agent selected from a group consisting of alkenylsuccinic anhydride (ASA), alkyl ketene dimer (AKD), resin sizes, or natural sizing agents, or a mixture of sizing agents selected from this group, to the at least one suspension. These sizing agents can have a particularly advantageous effect on various properties of the paper web, or rather, the cellulose fiber-based drinking straw. Thus, the addition of these sizing agents can have a positive effect on the contact angle of the paper web.

[0018] Furthermore, it can be provided that the at least one suspension is produced with a consistency of 0.15% to 0.70%. Depending on the specific process used for the compaction step, it may be advantageous for the aqueous suspension to be produced as a low-consistency suspension with a consistency of 0.15% to 0.30% or as a high-consistency suspension with a consistency of up to 0.70%. The chosen consistency may depend on the machine type, the fiber blend, the drying capacity of the machine, and other parameters.

[0019] Furthermore, during further processing into a cellulose fiber-based drinking straw, one or more of the paper webs can be layered and bonded together. The specific structure of such a layering can be adapted to the specific requirements of the specific application.

[0020] According to a special embodiment, it is possible for the compressed first side of a paper web to be contacted with the uncompressed second side of the further paper web layered above it.

[0021] According to an advantageous development, the paper webs can be glued together, with an adhesive being applied over the entire surface or in sections to the contacting sides of the paper webs. Depending on the type of adhesive, applying it in sections may be sufficient to ensure permanent cohesion during use of the cellulose fiber-based drinking straw. However, for hot applications or repeated use of the drinking straw, it may also be advantageous if the adhesive is applied over the entire surface or at least over a large part of the contact surface.

[0022] Furthermore, it can be provided that the at least one paper web or several layered and connected paper webs are made up into paper strips during further processing to form a cellulose fiber-based drinking straw, wherein a paper strip is delimited by two longitudinal edges and two transverse edges and wherein an overlapping region is formed in the region of each of the two longitudinal edges, and that a preferably cylindrical hollow body which is open on both sides is formed by bending a paper strip around a drinking straw axis, wherein the paper strip is shaped in such a way that an overlapping section is formed by overlapping the two overlapping regions, and that the two overlapping regions are glued to one another in the overlapping section.

[0023] Furthermore, it can be provided that the paper strip is shaped in such a way that its two longitudinal edges run substantially parallel to the drinking straw axis.

[0024] Also advantageous is an embodiment according to which it can be provided that the paper strip is shaped in such a way that the two longitudinal edges run essentially spirally or helically around the drinking straw axis.

[0025] Furthermore, it may be expedient for the first side of the at least one paper web to be printed with food-safe and biodegradable inks before further processing into a cellulose fiber-based drinking straw. This allows individual designs, brands, etc., to be applied to the cellulose fiber-based drinking straw.

[0026] The invention also provides a cellulose fiber-based drinking straw, which is produced in particular by a method according to one of claims 1 to 16 and comprises a preferably cylindrical hollow body open on both sides with an outer shell surface and an inner shell surface. The hollow body is formed by at least one shaped paper strip, wherein the at least one paper strip is made from at least one paper web with at least one compacted first side.

[0027] By using a paper web that is compacted on at least one side, a cellulose fiber-based drinking straw made from it is water-resistant or water-resistant, at least for the duration of its use. It has been found that compacting the surface of at least one paper web smoothes the cellulose fibers in the immediate vicinity of the surface. The resulting compaction is equivalent to a type of seal, which, however, works entirely without varnishes, coatings, or similar additives. This type of seal reduces or even prevents unwanted or too rapid penetration of liquids into the wall structure of the drinking straw. Premature softening can thus be effectively prevented or at least delayed sufficiently so that the function and dimensional stability of the drinking straw can be guaranteed throughout its service life.Surprisingly, it has been shown that to achieve this "sealing effect," one-sided compaction and, if necessary, the accompanying smoothing of the nonwoven web or paper web is generally sufficient. Whether double-sided compaction is appropriate depends, among other things, on the specific application.

[0028] Because no non-recyclable additives or the like need to be added to achieve these properties, a cellulose fiber-based drinking straw according to the invention is also easily amenable to recycling, or rather, "repulping," i.e., returning it to an aqueous pulp suspension. With any additives added to the aqueous suspension, care must be taken to ensure that they only contain additives that are harmless to the user and the environment with regard to an aqueous extraction application, such as the use of drinking straws. This applies to both cold and hot extraction applications.

[0029] A cellulose fiber-based drinking straw according to the invention can be recycled without additional effort or complex processing steps. In particular, if the process according to the invention does not require the addition of additives such as wet strength agents, efficient repulping can be facilitated.

[0030] Furthermore, it can be provided that the compacted first side of the at least one paper web has a Cobb 1800s value according to ISO 535:2014 of 24 g / m 2< to 62 g / m 2<.

[0031] Due to the fact that the Cobb 1800s value according to ISO 535:2014 represents an absolute value of a paper's water absorption capacity, and the paper's grammage can play a significant role or have a significant influence on this absolute value, a percentage water content across the entire grammage range can also be meaningful for characterizing the paper's properties for better comparability between different papers. Such a percentage water content can be calculated from the ratio between a measured Cobb 1800s value according to ISO 535:2014 and the paper's grammage. In particular, a water content of 35% to 48% can be advantageous for a paper web - this is assuming that 7% water is present in the paper as equilibrium moisture content when stored in a climate of 23 °C ± 1 °C and 50% ± 2% relative humidity according to ISO 187:1990.For illustrative purposes, three calculation examples for different paper webs are given below: Example 1:

[0032] Grammage when stored in standard conditions at 23 °C ± 1 °C and 50 % ± 2 % relative humidity according to ISO 187:1990 = 40.0 g / m 2 < Cobb 1800s value according to ISO 535:2014 = 26.2 g / m 2 < Grammage of the paper according to the Cobb 1800s test = 66.2 g / m 2 < Total water content in the paper according to the Cobb 1800s test = ((40.0 / 100*7)+26.2) / 66.2 *100 = 43.8 % Example 2:

[0033] Grammage when stored in standard conditions at 23 °C ± 1 °C and 50 % ± 2 % relative humidity according to ISO 187:1990 = 60.0 g / m 2 < Cobb 1800s value according to ISO 535:2014 = 33.3 g / m 2 < Grammage of the paper according to the Cobb 1800s test = 93.3 g / m 2 < Total water content in the paper according to the Cobb 1800s test = 40.2 % Example 3:

[0034] Grammage when stored in standard conditions at 23 °C ± 1 °C and 50 % ± 2 % relative humidity according to ISO 187:1990 = 120.0 g / m 2 < Cobb 1800s value according to ISO 535:2014 = 59.7 g / m 2 < Grammage of the paper according to the Cobb 1800s test = 179.7 g / m 2 < Total water content in the paper according to the Cobb 1800s test = 37.9 %

[0035] In addition, it may be expedient if the difference in a Cobb 1800s value according to ISO 535:2014 between the compacted first side and the uncompacted or less highly compacted second side is a maximum of 3 g / m². Less highly compacted means that the second side is less compacted than the first side, for example because it is not pressed against a smooth surface. Depending on the manufacturing processes and machine concepts, papers according to the invention with grammages preferably from 22 g / m² to 200 g / m² according to ISO 536:2012 can be used for the production of cellulose fiber-based drinking straws. In principle, however, the use of papers with lower, but also higher, grammages is of course also conceivable and may be expedient.

[0036] According to a particular embodiment, it is possible for the compacted first side of the at least one paper web to have a Bendtsen roughness according to ISO 8791-2:2013 of 30 ml / min to 250 ml / min.

[0037] According to an advantageous development, it can be provided that the at least one paper web has a gloss value according to TAPPI T 480:2015 of 20% to 35%. In particular, in a production process using shoe calenders, it can be advantageous if a gloss value according to TAPPI T 480:2015 is between 21% and 25%. In the production of MG papers, it can be expedient if a gloss value according to TAPPI T 480:2015 is between 24% and 33%.

[0038] In particular, it may be advantageous if the compacted first side of the at least one paper web has a static contact angle according to ISO 19403-2:2020 with water as the test liquid used of 100° to 120°.

[0039] It can also be advantageous if the difference in a static contact angle according to ISO 19403-2:2020, using water as the test fluid, between the compacted first side and the uncompacted or less compacted second side is a maximum of 6°. Less compacted means that the second side is less compacted than the first side, for example, because it is not pressed against a smooth surface.

[0040] Furthermore, it can be provided that at least two paper webs are arranged such that the first side of the first paper web forms the outer surface of the hollow body and that the first side of the second paper web forms the inner surface of the hollow body.

[0041] For a better understanding of the invention, it is explained in more detail using the following figures.

[0042] They show in a highly simplified, schematic representation: Fig. 1 an embodiment of a process diagram for producing a nonwoven web and drying it to a paper web; Fig. 2 a further embodiment of a process diagram for producing a nonwoven web and drying it to a paper web; Fig. 3 three stacked paper webs in three-dimensional exploded view; Fig. 4 another paper web made up into a paper strip; Fig. 5 a cellulose fiber-based drinking straw in three-dimensional representation; Fig. 6 another cellulose fiber-based drinking straw in three-dimensional representation; Fig. 7 a layered or folded paper web in three-dimensional view.

[0043] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations. The disclosures contained throughout the description can be applied analogously to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and these positional information must be applied analogously to the new position in the event of a change in position.

[0044] The process for producing cellulose fiber-based drinking straws 1 begins, as is known per se, with the production of an aqueous suspension 3 comprising a cellulose material 2 with optional addition of additives 4.

[0045] The person skilled in the art is sufficiently familiar with how the pulp material 2 can be produced, which is why the corresponding possible process steps are not described in detail or illustrated. For the sake of completeness, a possible process sequence is only briefly outlined here. The pulp material 2 can advantageously be a pulp mixture consisting of long-fiber sulfate pulp and short-fiber pulp, preferably short-fiber sulfate pulp, with a length-weighted average fiber length according to ISO 16065-2:2014 of 1.05 mm to 2.5 mm. The pulp mixture can be composed of 20 to 80 wt.% long-fiber sulfate pulp and 20 to 80 wt.% short-fiber sulfate pulp, preferably short-fiber sulfate pulp.The starting material for producing the pulp material 2 can, for example, be a pulp mixture of shredded hardwood as sulfate pulp and shredded softwood as sulfate pulp. Of course, it can also be a mixture of different shredded hardwoods and softwoods. This pulp mixture is prepared by a process comprising chemical treatment of the shredded first and second pulps in a pulp digester. Depending on requirements, it may be expedient to carry out mechanical processing and defibration of an aqueous solid suspension of the pulp mixture in a high-consistency defibrator after the chemical treatment. The consistency of the solid suspension before mechanical processing and defibration in the high-consistency defibrator can be set, for example, to 25% to 40%.Such defibration in a high-consistency defibrator serves, among other things, to reduce the so-called splinter content of the pulp mixture, i.e., to break up any wood-like pulp agglomerates. Furthermore, it can also be expedient to perform mechanical processing and refining of the pulp mixture or an aqueous solid suspension of the pulp mixture in a low-consistency refiner after the initial mechanical processing and defibration in the high-consistency defibrator. The consistency of the solid suspension prior to mechanical processing and refining in the low-consistency refiner can be advantageously set to between 2% and 6%. It is also entirely possible for only mechanical processing of the pulp mixture to be carried out in a high-consistency defibrator.In other cases, however, it may also be advisable to omit defibration in a high-consistency defibrator and simply perform mechanical processing of the pulp blend in a low-consistency refiner. The specific refining performance of the individual refining stages must be adapted to the selected pulp blend and the desired paper parameters.

[0046] The description of the Figures 1 and 2 is presented below as far as possible in summary form to avoid unnecessary repetition, using the same reference symbols for the same parts. Figures 1 and 2 each show an embodiment of a process diagram for producing a nonwoven web 5 and drying it to a paper web 8.

[0047] Regardless of how the pulp mixture is prepared to provide a pulp material 2, at least one aqueous suspension 3 comprising the pulp material 2 is produced for further processing of the pulp material 2. This process step is described, for example, in Figure 1 and 2by means of a tank 28 with a stirrer. In particular, various additives 4 or aggregates and auxiliaries customary in paper technology, such as fillers, starch, etc., can be added to this at least one aqueous suspension 3. At least one sizing agent, based on the active substance of the sizing agent, can be added to the at least one suspension 3 as an additive 4 in an amount of 0.07 wt.% to 1.0 wt.% based on 100 wt.% total dry matter of the at least one suspension 3. Sizing agents can be selected from a group consisting of alkenyl succinic anhydride (ASA), alkyl ketene dimer (AKD), resin sizes or natural sizing agents, or a mixture of sizing agents selected from this group.

[0048] Independently of this, a consistency 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%, before the homogenization and pre-drying to form at least one water-containing nonwoven web 5 with a first side 6 and a second side 7. The further processing of this at least one aqueous suspension 3 can then be carried out as known per se by means of a paper machine 29, as will be described below with reference to the Figures 1 and 2is described roughly schematically. Paper machines 29 can usually comprise a wire section 30, a press section 31 and a dryer section 32, each of these process steps being a drying or dewatering process. According to the invention, at least the first side 6 of the at least one nonwoven web 5 is compacted with a line load of 80 kN / m to 500 kN / m before, during or after one of the drying steps and before further processing into a cellulose fiber-based drinking straw 1. This compaction step can be carried out either in a single nip, i.e. compaction step, or in several nips arranged one behind the other, each with the specified line loads. In addition, it can be expedient if at least the first side 6 of the at least one nonwoven web 5 is thermally treated during this compaction.In other words, this means that thermal influence can occur in the same process step at the same time as pressure is applied.

[0049] As in the Figures 1 and 2As shown, the at least one aqueous suspension 3 comprising the cellulose material 2 can be applied, as is known per se, to a rotating endless screen 33 of a screen section 30. In such a screen section 30, the at least one aqueous suspension 3 is made uniform and pre-dried to form at least one water-containing nonwoven web 5. The endless screen 33 can be guided over dewatering means 34 of the screen section 30, which dewatering means 34 can be formed, for example, by suction bars. In principle, dewatering in a screen section 30 can also take place solely by means of gravity. In addition, however, depending on the design of a screen section 30, the dewatering or pre-drying of the at least one nonwoven web 5 can be assisted by generating a negative pressure. The at least one first nonwoven web 5 comprising the cellulose material 2 can be dewatered by means of the screen section 30, for example, to a water content of 75 wt.-% to 85 wt.% pre-dried.

[0050] Subsequently, the at least one nonwoven web 5 can be formed as shown in the Figures 1 and 2 shown by means of a press section 31, further dewatered or dried. The nonwoven web 5 can be Figure 1 between rollers 35 of the press section 31 and are thereby further dewatered under pressure. In addition, further drying can be supported by absorbent support material 36. For this purpose, felt mats, for example, can be used, as is known per se. A press section 31 according to Figure 1 As is known per se, it can comprise more than just two rollers 35; in particular, several pairs of rollers formed by rollers 35 can be arranged one after the other. The water content of the nonwoven web 5 after passing through a press section 31 can, for example, be approximately 45% to 65% by weight, based on the total mass of the nonwoven web 5.

[0051] After the press section 31, according to Figure 1 A so-called slalom dryer 37 may be arranged as a drying section 32 or as part of a drying section 32. A slalom dryer 37 may be arranged as shown in the Figure 1 illustrated comprise numerous rotating drying cylinders 15 over which the at least one nonwoven web 5 can be guided. The drying cylinders 15 can be heated directly. For example, heating channels (not shown in detail) can be designed to conduct hot steam into the drying cylinder 15. Alternatively, it is also possible, for example, to heat the drying cylinders 15 by means of an electrical resistance heater. A temperature of the drying cylinders 15 of a drying section 32 can, for example, rise successively in the direction of passage of the at least one nonwoven web 5. The nonwoven web 5 can be dried by means of the slalom dryer 37, for example, to a water content of 1 wt.% to 10 wt.%.

[0052] For compaction according to the invention with a line load of preferably 210 kN / m to 370 kN / m, a so-called wide-nip calender 9 or shoe calender with a shoe length of, for example, 50 mm and a shoe tilt of 24% can be provided in the drying section 32 downstream of a slalom dryer 37 for further drying and compaction of the nonwoven web 5. For compaction according to the invention with a line load of preferably 380 kN / m to 490 kN / m, a shoe length of, for example, 75 mm and a shoe tilt of 24% can also be provided in a shoe calender.

[0053] An extended nip calender 9 can essentially be formed by a heating roller 10 and a shoe roller 12 interacting with the heating roller 10. The shoe roller 12 can act as a flexible counterpressure element to the heating roller 10 and have a circumferential sleeve 38. This circumferential sleeve 38 interacts with the heating roller 10 and forms an extended nip 11. The first side 6 of the at least one nonwoven web 5 facing the heating roller 10 is satinized by passing it between the heating roller 10 and the shoe roller 12. This means that the nonwoven web 5 is simultaneously compressed with increased pressure and subjected to an elevated temperature. Temperatures on the surface of the heating roller can, for example, range from approximately 250°C to 295°C. This temperature can be achieved, for example, using a thermal oil with a correspondingly higher oil flow temperature.To further stabilize the surface temperatures, other heating elements, such as induction heating, can also be provided. It is also conceivable, although not illustrated, that a second, advantageously structurally identical wide-nip calender 9 is provided, which is arranged in the paper machine 29 in such a way that a so-called calendering of the second side 7 can be performed in addition to the calendering of the first side 6 of the at least one nonwoven web 5.

[0054] It is also conceivable that a process-technical combination of press section 31 and dryer section 32 is provided after the wire section 30, by means of which the compaction according to the invention can take place with a line pressure of approximately 80 kN / m in a first shoe press, in a second calender press with approximately 90 kN / m and in a third calender press with approximately 100 kN / m. The surface temperature of the calender cylinder can be, for example, approximately 94 °C. This conceivable embodiment is Figure 2 shown schematically. Alternatively to the design variant according to Figure 1 is through the Figure 2 Dewatering, compaction, or pressurization by means of a so-called Yankee cylinder 39 is shown. Papers produced using such or a similar arrangement are commonly referred to in the art as "machine-glazed" or "MG papers." As a component of a paper machine 29, Figure 2Thus, a combined press section 31 and dryer section 32 in the form of a Yankee cylinder 39 with a dryer hood 16 or gas dryer hood attached. The at least one nonwoven web 5, adhering to a take-off felt, is pressed with its first side 6 against the surface 14 of the steam-heated Yankee cylinder 39 by two pressure rollers 13 and further dried or completely dried by additional blowing of hot air by means of the dryer hood 16.

[0055] The completion of the exemplary paper machines 29 according to the Figures 1 and 2 represents a winder 40, by means of which the finished at least one paper web 8 can be wound onto a roll. However, it is also conceivable and possibly also expedient for the at least one paper web 8 to be fed directly to further processing or finishing.

[0056] Depending on the design of a paper machine 29, the at least one suspension 3 can be produced with a consistency of 0.15% to 0.70%. Arrangements based on Figure 1 With a wide nip calender 9 both high-consistency and low-consistency suspensions 3 can be used, while for an arrangement based on the Figure 2 with a Yankee cylinder 39, a low-consistency suspension 3 with a consistency of 0.15% to 0.30% may be more appropriate.

[0057] For the production of cellulose fiber-based drinking straws 1 from at least one paper web 8, a large number of different processes are sufficiently known to the person skilled in the art, which is why the possible process steps will not be discussed in detail.

[0058] Advantageously, one, but also several, preferably three or even four, of the paper webs 8 produced according to the invention can be further processed into a cellulose fiber-based drinking straw 1. During further processing, one or more paper webs 8 produced from the same pulp material 2, i.e., several identical paper webs 8, can be layered one on top of the other. However, it is also conceivable and has proven particularly advantageous if several paper webs 8 produced from different pulp materials 2 and thus differing in terms of their technical properties are layered one on top of the other and joined.

[0059] A single paper web 8 can, for example, also be further processed by a corresponding single or multiple folding. For example, a single paper web 8 can be folded several times in a zigzag or meander shape, so that a quasi multi-layered or stacked paper web 8 is formed. This conceivable embodiment is characterized by the Figure 7 shown in a schematic three-dimensional view. With such a folding, the compressed first side 6 and the uncompressed second side 7 contact each other. From this embodiment, a similar paper strip 18 can also be subsequently produced, as shown by the Figure 4sketched as an example and described below. A folded paper strip consisting of the paper according to the invention can be fixed in its position by means of appropriately selected adhesive points with the aid of an adhesive 17. An adhesive 17 - which in the Figure 7 not explicitly shown - can be applied, for example, over the entire surface, in dots, or in strips between the folded layers.

[0060] The Figure 3shows three paper webs 8 layered one above the other in a three-dimensional exploded view. Of course, a smaller or larger number of paper webs 8 can also be provided. In this case, it can be expedient if the uppermost of the three paper webs 8 shown was compacted on a paper machine 29 with a wide nip calender 9 and if the middle and lower paper webs 8 were compacted on an MG machine by means of a Yankee cylinder 39. An arrangement of three layered paper webs 8 with an uppermost paper web 8 compacted by means of a Yankee cylinder 39 and with a middle and lower paper web 8 each compacted by means of a wide nip calender 9 can also be expedient. In this case, the paper webs 8 can be as in Figure 3shown, they are layered one on top of the other in such a way that the compressed first side 6 of each paper web 8 contacts the uncompressed second side 7 of the additional paper web 8 layered thereon. Alternatively, although not shown in the figure, it can also be advantageous if the paper webs 8 are layered one on top of the other in such a way that the compressed first side 6 of each of the two outer paper webs 8 is on the outside. It should be noted at this point that an uncompressed second side 7 can also be a side that is less strongly compressed than the compressed first side 6.

[0061] Alternatively, but also not shown in the figure, it can also be advantageous if, in an arrangement of several paper webs 8, at least one layer is made from the paper produced according to the invention. In particular, it can also be expedient if, above all, one of the two outer paper webs 8, i.e. one of the two paper webs 8 in direct contact with a drinking liquid, is produced according to the method according to the invention. However, it can also be advantageous if both paper webs 8 on the outside of the finished cellulose fiber-based drinking straw 1 are produced according to the method according to the invention. In this case, it can be expedient if the compressed first side 6 is in direct contact with a liquid. By means of a targeted arrangement of the paper webs 8, various parameters orProduct properties, such as optical properties such as gloss, printability, haptics and the like, can be adjusted accordingly.

[0062] The paper webs 8 can be glued together, whereby an adhesive 17 can be applied over the entire surface or in sections to the contacting sides 6, 7 of the paper webs 8. In the Figure 3It is shown that the adhesive 17 can be applied in strips and approximately symmetrically to one side 6, 7 of a paper web 8. Of course, depending on the requirements and adhesive strength, it is also conceivable for the adhesive 17 to be applied over the entire surface and to each contacting side 6, 7, or only selectively or along the sheet edges. In particular, to achieve food approval for the cellulose fiber-based drinking straw 1 and with regard to possible leaching of ingredients from the cellulose fiber-based drinking straw upon contact with cold and / or hot liquids, it can be important if a food-safe, biodegradable glue of animal and / or plant origin is used as the adhesive 17. Various legal requirements and recommendations apply to safe use for paper, cardboard and paperboard intended for direct food contact.To name just a few relevant ones, these include Recommendation XXXVI of the Federal Institute for Risk Assessment (BfR) and Recommendation XXXVI / 1 for cooking and heat-treated filter papers. Regulation (EC) No. 1935 / 2004 and the Food, Consumer Goods, and Feed Code are also examples. Other national regulations include Decreto Ministeriale 21 Marzo 1973, Code of Federal Regulations, Food and Drugs (FDA), 21 CFR Ch. I (edition April 1, 2019), §§ 176.170 and 176.180, Regeling von de Minister von Volksgezondheid, Welzijn von 14 Maart 2014, kenmerk 328583-117560-VGP, Warenwetregeling, Mercosure, and Chinese regulations.

[0063] A single paper web 8, but also in the sense of Figure 3Layered paper webs 8 can be made into paper strips 18 during further processing into a cellulose fiber-based drinking straw 1. For illustration purposes, Figure 4 a further paper web 8 made up into a paper strip 18 is shown. A paper strip 18 can be delimited by two longitudinal edges 19 and two transverse edges 20, wherein an overlapping area 21 can be formed in the area 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 a finished cellulose fiber-based drinking straw 1. Possible positions for later cutting areas are shown in the Figure 3 represented by dashed lines. It is also possible that the first side 6 of the at least one paper web 8 is printed with food-safe and biodegradable inks before further processing into a cellulose fiber-based drinking straw 1.

[0064] The Figures 5 and 6 further show two conceivable embodiments of cellulose fiber-based drinking straws 1 in three-dimensional representation, wherein the cellulose fiber-based drinking straws 1 comprise a preferably cylindrical hollow body 23 open on both sides with an outer shell surface 26 and an inner shell surface 27. It is provided that the hollow body 23 is formed by at least one shaped paper strip 18, wherein the at least one paper strip 18 is made up of at least one paper web 8 with at least one compacted first side 6. As an alternative to cylindrical hollow bodies 23, drinking straws 1 with a folded or polygonal cross-section are also conceivable.

[0065] By bending a paper strip 18 around a drinking straw axis 22, a preferably cylindrical hollow body 23 open on both sides can be formed, wherein the at least one paper strip 18 can be shaped such that an overlapping section 24 is formed by the overlapping of the two overlapping regions 21. The cylindrical hollow body 23 can then be cut approximately or largely radially to the drinking straw axis 22 into a finished length 25 of, for example, 5 cm to 50 cm. The at least one paper strip 18 can be shaped such that its two longitudinal edges 19 run essentially parallel to the drinking straw axis 22, as is shown by the Figure 5 is shown schematically. Alternatively, Figure 6It has been shown that it is also conceivable for the two longitudinal edges 19 to extend substantially spirally or helically around the drinking straw axis 22. Advantageously, the two overlapping areas 21 can be glued together in the overlapping section 24.

[0066] At least two paper webs 8 can be arranged such that the first side 6 of the first paper web 8 forms the outer surface 26 of the hollow body 23 and that the first side 6 of the second paper web 8 forms the inner surface 27 of the hollow body 23. It is possible that one or more further paper webs 8 are formed between the two outer ones, i.e. between the first and the second paper web 8. These inner or intermediately layered paper webs 8 can be either paper webs 8 according to the invention or different types of further papers with optionally additional, advantageous properties.It is also possible for at least two paper webs 8 to be arranged such that the uncompacted or less strongly compressed second side 7 of the first paper web 8 forms the outer shell surface 26 of the hollow body 23 and that the uncompacted or less strongly compressed second side 7 of the second paper web 8 forms the inner shell surface 27 of the hollow body 23.

[0067] The compacted first side 6 of the at least one paper web 8, or of the paper webs 8, can have a Cobb 1800s value according to ISO 535:2014 of 24 to 62 g / m 2 . A difference in a Cobb 1800s value according to ISO 535:2014 between the compacted first side 6 and the uncompacted or less densely compacted second side 7 can advantageously be a maximum of 4 g / m 2 . In addition, the compacted first side 6 of the paper web(s) 8 can have a Bendtsen roughness according to ISO 8791-2:2013 of 30 to 250 ml / min. It can also be advantageous if the paper web(s) 8 have a gloss value according to TAPPI 480 of 20 to 35%. Furthermore, the compacted first side 6 of the paper web(s) 8 can have a static contact angle according to ISO 19403-2:2020 with water as the test liquid of 100° to 120°.The difference in a static contact angle according to ISO 19403-2:2020 using water as the test liquid between the compacted first side 6 and the non-compacted or less compacted second side 7 may not exceed 6°. Reference symbol list 1 Cellulose fiber-based drinking straw 34 Dehydrating agents 2 Pulp material 35 roller 3 suspension 36 Support material 4 Additive 37 Slalom dryer 5 Nonwoven web 38 Coat 6 first page 39 Yankee cylinder 7 wide side 40 Rewinder 8 Paper web 41 length 9 Wide nip calender 42 10 heating roller 11 Broad nip 12 shoe roller 13 pressure roller 14 surface 15 Drying cylinder 16 Drying hood 17 Glue 18 Paper strips 19 Longitudinal edge 20 transverse edge 21 Overlap area 22 Drinking straw axis 23 hollow body 24 Overlap section 25 length 26 Outer shell surface 27 Shell inner surface 28 tank 29 Paper machine 30 Wire section 31 Press section 32 Dry section 33 Endless screen

Claims

1. Method for producing cellulose-fibre-based drinking straws (1) comprising the steps: - providing a cellulose material (Fehler! Verweisquelle konnte nicht gefunden werden.), - producing at least one aqueous suspension (3) comprising the cellulose material (2) and and without adding additives in the form of wet strength agents to the suspension - homogenizing the at least one aqueous suspension (3) and pre-drying to obtain at least one water-containing non-woven web (5) having a first side (6) and a second side (7), - drying the at least one water-containing non-woven 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 plurality of paper webs (8) to form a cellulose-fibre-based drinking straw (Fehler! Verweisquelle konnte nicht gefunden werden.), wherein at least the first side (6) of the at least one non-woven web (5) is compressed with a line load of 80 kN / m to 500 kN / m before, during or after one of the drying steps and before the further processing to form a cellulose-fibre-based drinking straw (1), characterized in that a cellulose mixture consisting of long-fibre sulphate cellulose and short-fibre cellulose, preferably short-fibre sulphate cellulose having a length-weighted, average fibre length in accordance with ISO 16065-2:2014 of 1.05 mm to 2.50 mm is provided as cellulose material (2), that the cellulose mixture is prepared from 20 wt.% to 80 wt.% long-fibre sulphate cellulose and from 20 wt.% to 80 wt.% short-fibre cellulose, and that at least the first side (6) of the at least one non-woven web (5) is thermally treated in the course of the compression, preferably at a temperature of 90°C to 97°C or at a temperature of 200°C to 295°C, wherein the compression of the surface is achieved without varnishes, coatings or similar adjuvants.

2. Method according to claim 1, characterized in that at least one non-woven web (5) is compressed by means of a broad-nip calender (9) comprising a heated roller (10) and a shoe roller (12) cooperating with the heated roller (10) and forming a broad nip (11), wherein the at least one non-woven web (5) is guided through the broad-nip calender (9) with its first side (6) facing the heated roller (10).

3. Method according to one of claims 1 or 2, characterized in that at least one non-woven web (5) is pressed by means of one or more pressure rollers (13) with its first side (6) onto the surface (14) of a heated drying cylinder (15), wherein the at least one non-woven web (5) is guided over a large part of the circumference of the drying cylinder (15) and is additionally heated from outside by means of a drying hood (16) which at least partially surrounds the drying cylinder (15).

4. Method according to any one of claims 1 to 3, characterized in that at least one sizing agent is added as additive (4) to the at least one suspension (3) relative to the active substance of the sizing agent in a quantity of 0.07 wt.% to 1.0 wt.% relative to 100 wt.% of total dry mass of the at least one suspension (3).

5. Method according to any one of claims 1 to 4, characterized in that at least one sizing agent selected from a group consisting of alkenyl succinic acid anhydride (ASA), alkyl ketene dimer (AKD), resin sizes or natural sizing agents or a mixture of sizing agents selected from this group is added to the at least one suspension (3).

6. Method according to one of the preceding claims, characterized in that the at least one suspension (3) is produced with a consistency of 0.15% to 0.70%.

7. Method according to one of the preceding claims, characterized in that in the course of the further processing to form a cellulose-fibre-based drinking straw (1) one or a plurality of paper webs (8) are layered one above the other and joined.

8. Method according to Claim 7, characterized in that in each case the compressed first side (6) of a paper web (8) is contacted with the uncompressed second side (7) of the further paper web (8) layered thereover.

9. Method according to one of Claims 7 or 8 characterized in that the paper webs (8) are glued together, wherein one adhesive (17) is applied over the full surface or in sections to the contacting sides (6, 7) of the paper webs (8).

10. Method according to one of the preceding claims, characterized in that in the course of the further processing to form a cellulose-fibre-based drinking straw (1), the at least one paper web (8) or a plurality of layered and joined paper webs (8) are assembled to form paper strips (18), wherein in each case one paper strip (18) is delimited by two longitudinal edges (19) and two transverse edges (20), and wherein in the region of the two longitudinal edges (19) an overlap region (21) is formed in each case and that by bending a paper strip (18) about a drinking straw axis (22), a preferably cylindrical hollow body (23) open on both sides is formed, wherein the paper strip (18) is formed in such a manner that by overlap of the two overlap regions (21), an overlap portion (24) is formed and that the two overlap regions (21) in the overlap portion (24) are glued together.

11. Method according to Claim 9, characterized in that the paper strip (18) is formed in such a manner that its two longitudinal edges (19) run substantially parallel to the drinking straw axis (22).

12. Method according to Claim 10, characterized in that the paper strip (18) is formed in such a manner that the two longitudinal edges (19) run substantially in a spiral or helical shape about the drinking straw axis (22).

13. Method according to one of the preceding claims, characterized in that before the further processing to form a cellulose-fibre-based drinking straw (1) the first side (6) of the at least one paper web (8) is printed with food-safe or biologically degradable inks.

14. Cellulose-fibre-based drinking straw (1) produced according to a method according to one of Claims 1 to 13, comprising a preferably cylindrical hollow body (23) which is open on both sides having a outer shell surface (26) and an inner shell surface (27), wherein the hollow body (23) is formed by at least one formed paper strip (18), wherein the at least one paper strip (18) is assembled from at least one paper web (8) having at least one compressed first side (6), characterized in that the compressed first side (6) of the at least one paper web (8) has a Cobb 1800s value according to ISO 535:2014 from 24 g / m2 to 62 g / m2.

15. Cellulose-fibre-based drinking straw (1) according to Claim 14, characterized in that a difference of a Cobb 1800s value according to ISO 535:2014 between the compressed first side (6) and the non-compressed or less strongly compressed second side (7) is a maximum of 3 g / m2.

16. Cellulose-fibre-based drinking straw (1) according to one of Claims 14 or 15, characterized in that the compressed first side (6) of the at least one paper web (8) has a Bendtsen roughness according to ISO 8791-2:2013 of 30 ml / min to 250 ml / min.

17. Cellulose-fibre-based drinking straw (1) according to one of Claims 14 to 16, characterized in that the at least one paper web (8) has a gloss value according to TAPPI T 480:2015 of 20 to 35%.

18. Cellulose-fibre-based drinking straw (1) according to one of Claims 14 to 17, characterized in that the compressed first side (6) of the at least one paper web (8) has a static contact angle according to ISO 19403-2:2020 using water as test liquid of 100° to 120°.

19. Cellulose-fibre-based drinking straw (1) according to one of Claims 14 to 18, characterized in that a difference amount of a static contact angle according to ISO 19403-2:2020 using water as test liquid between the compressed first side (6) and the non-compressed or less strongly compressed second side (7) is a maximum of 6°.

20. Cellulose-fibre-based drinking straw (1) according to one of claims 14 to 19, characterized in that at least two paper webs (8) are arranged in such a manner that the first side (6) of the first paper web (8) forms the outer shell surface (26) of the hollow body (23) and that the first side (6) of the second paper web (8) forms the inner shell surface (27) of the hollow body (23).

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