US20240018724A1

US20240018724A1 - Method for producing a cellulose-fibre-based drinking straw

Info

Publication number: US20240018724A1
Application number: US18/004,887
Authority: US
Inventors: Lars Goran BERGLUND; Petr Jindra; Elisabeth Schwaiger
Original assignee: Mondi AG
Current assignee: Mondi AG
Priority date: 2020-07-10
Filing date: 2021-07-06
Publication date: 2024-01-18
Also published as: AT523915A4; AT523915B1; WO2022006608A1; EP4179144A1; CN115867706A

Abstract

A method for producing cellulose-fibre-based drinking straws and a drinking straw. The method comprises:

- providing a cellulose material,
- producing at least one aqueous suspension comprising the cellulose material and adding additives to the suspension,
- homogenizing the aqueous suspension and pre-drying to obtain at least one water-containing non-woven web having a first side and a second side,
- drying the water-containing non-woven web in a plurality of drying steps to form at least one paper web having a first side and a second side,
- further processing the paper web or a plurality of paper webs to form a cellulose-fibre-based drinking straw.

At least the first side of the non-woven web 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.

Description

BACKGROUND OF THE INVENTION

The invention relates to a method for producing cellulose-fibre-based drinking straws and a cellulose-fibre-based drinking straw.
The demand for recyclable products is increasing as a result of an increased environmental awareness of the consumers and not least because of legal and normative provisions in relation to disposable products in the packaging and food industry.
In many areas of the packaging and food industry, the replacement of plastic-based products by cellulose-based alternatives is already established. However, the use of cellulose-fibre-based drinking straws instead of plastic-based drinking straws or straws confronts the manufacturer with a number of specific problems. One of the greatest challenges for cellulose-fibre-based drinking straws is to simultaneously provide a water tightness or water resistance, ensured at least during the usage time thereof, whilst at the same time a recycling capability which is as complete as possible or technically not very complex is required.
According to the prior art, papers with coatings are provided so that the necessary water tightness is ensured. Naturally however such coatings are problematic with regard to their recyclability. As an example, mention is made here of WO 2019175470 A1 which provides a drinking straw in which the drinking straw material is basically a recyclable and biologically degradable but coated card. The drinking straw in this case consists of a substantially rectangular sheet-like piece of coated card. However only very little about the properties of the paper or card used is disclosed in WO 2019175470 A1.
The use of papers with at least partial cross-linking of the cellulose fibres is familiar to the person skilled in the art. In order that papers for cellulose-fibre-based drinking straws remain mechanically resistant at least temporarily in moisture or wet, so-called wet strengthening agents are added in paper manufacture. Wet strengthening agents are water-miscible polymer solutions in the processing state which are primarily manufactured from polyamines and epichlorohydrine derivatives. Furthermore, products based on urea formaldehyde or melamine formaldehyde are also feasible as wet strengthening agents but are preferably no longer used for reasons of avoiding health risks. In reaction with cellulose fibres cross-links form between the fibres which result in increased water resistance of the corresponding paper. However, this hydrophobic chain-linking hinders simple or successful recycling. Used drinking draws therefore cannot be returned into a cellulose cycle or only to a limited extent by using high temperatures and/or additional chemicals and additives.
For cellulose-fibre-based drinking straws bleached or unbleached cellulose fibres and mixtures thereof are feasible as starting material.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a method for producing cellulose-fibre-based drinking straws which is as efficient as possible from the technical, economic and ecological viewpoint. In addition, it was the object of the invention to provide cellulose-fibre-based drinking straws which meet the requirements of the consumers—such as neutral taste for example—and the packaging and food industry as well as aspects of durability such as recyclability, compostability and biological degradability in equal measure.
This object is achieved by a method for producing, and a cellulose-fibre-based drinking straw according to the claims.
The method according to the invention for producing cellulose-fibre-based drinking straws comprises the following steps:

- providing a cellulose material,
- producing at least one aqueous suspension comprising the cellulose material and optionally adding additives to the suspension,
- homogenizing the at least one aqueous suspension and pre-drying to obtain at least one water-containing non-woven web having a first side and a second side,
- drying the at least one water-containing non-woven web in a plurality of 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 plurality of paper webs to form a cellulose-fibre-based drinking straw.

In this case it is provided that at least the first side of the at least one non-woven web 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.
The at least one-sided compression of the non-woven web has the effect that a cellulose-fibre-based drinking straw fabricated from a non-woven web according to the invention or a paper web produced according to the invention is waterproof or water-resistant at least for the duration of its use. It has been found that the compression of the surface of the non-woven web brings about a smoothing of the cellulose fibres in the near region of the surface. The compression thereby achieved resembles a type of sealing which, however, acts completely without varnishes, coatings or similar adjuvants. As a result of this type of sealing, an undesired or too rapid penetration of liquids into the wall structure of the drinking straw is reduced or even prevented. A premature softening can thus be effectively impeded or at least delayed for a sufficiently long time so that function and shape retention of the drinking straw can be ensured during its usage duration. It has surprisingly been shown that a one-sided compression and a thus optionally associated smoothing of the non-woven web or the paper web is sufficient to achieve this “sealing effect”. Whether a compression on both sides is expedient depends inter alia on the specific case of application.
Since no recyclable additives or the like must be added to achieve these properties, a cellulose-fibre-based drinking straw produced according to the invention is additionally accessible to a recycling or a “repulping”, i.e. a return to an aqueous cellulose suspension in a simple manner. In the case of any additives which are added to the aqueous suspension, care should be taken to ensure that only those additives are contained which, with a view to an aqueous extraction application such as the use of drinking straws constitutes in any case, are harmless for a user and for the environment. This can apply both to cold and also to hot extraction applications.
A cellulose-fibre-based drinking straw produced according to the invention can be supplied to recycling without any increased expenditure or without additional expensive process steps. In particular, if no addition of additives in the form of wet strengthening agents is required by the process according to the invention, an efficient “repulping” can be facilitated.
Furthermore, it can be expedient if at least the first side of the at least one non-woven web is thermally treated in the course of the compression. Preferably this can take place in 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. A thermal treatment taking place in addition to the pressure application can advantageously affect the water resistance of the cellulose-fibre-based drinking straw produced according to the invention. This can be achieved whereby a heat influence can bring about an additional smoothing or a further compression of the surface of the non-woven or paper web.
It can further be provided that at least one non-woven web is compressed by means of a broad-nip calender comprising a heated roller and a shoe roller cooperating with the heated roller and forming a broad nip, wherein the at least one non-woven web is guided through the broad-nip calender with its first side facing the heated roller. Such processing by means of a broad-nip calender which is also designated as shoe calender can usually take place at the end of a drier section.
Furthermore, it can be provided that at least one non-woven web is pressed by means of one or more pressure rollers with its first side onto the surface of a heated drying cylinder, wherein the at least one non-woven web is guided over a large part of the circumference of the drying cylinder and is additionally heated from outside by means of a drying hood which at least partially surrounds the drying cylinder. So-called “MG papers” (“machine-glazed” papers) or also satin papers can also be produced with low grammages and are usually easily printable.
Also advantageous is a manifestation according to which it can be provided 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. Sulphate cellulose is also known to the person skilled in the art under the term Kraft cellulose.
In this case, it can be advantageous if 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, preferably short-fibre sulphate cellulose. A mixture within the given limits has proved particularly advantageous in practice to achieve a good compressibility.
According to a further development, it is possible that at least one sizing agent is added as additive to the at least one suspension 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. The addition of sizing agents to at least one aqueous suspension is also designated as mass sizing.
Furthermore, it can be expedient if 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. The said sizing agents can in particular act advantageously on different properties of the paper web or the cellulose-fibre-based drinking straw. Thus, the addition of this sizing agent can have a positive effect on the contact angle of the paper web.
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 special method by means of which the compression step is carried out, it can be advantageous if the aqueous suspension is produced as a low-consistency suspension having a consistency of 0.15% to 0.30% or as a high-consistency suspension having a consistency of up to 0.70%. The consistency selected in each case can depend on the machine type, the fibrous material mixture, drying power of the machine and other further parameters.
Furthermore it can be provided that in the course of the further processing to form a cellulose-fibre-based drinking straw one or a plurality of paper webs are layered one above the other and joined. The specific structure of such a coating can be adapted to the special requirements of the specific application.
According to a particular manifestation it is possible that in each case the compressed first side of a paper web is contacted with the uncompressed second side of the further paper web layered thereover.
According to an advantageous further development, it can be provided that the paper webs are glued together, wherein one adhesive is applied over the full surface or in sections to the contacting sides of the paper webs. Depending on the type of adhesive, a sectional application can be sufficient for a permanent cohesion during use of the cellulose-fibre-based drinking straw. For hot applications or in the case of repeated use of the drinking straw, however, it can also be advantageous if the adhesive is applied over the full surface or at least to a large part of the contact surface.
It can further be provided that in the course of the further processing to form a cellulose-fibre-based drinking straw, the at least one paper web or a plurality of layered and joined paper webs are assembled to form paper strips, wherein in each case one paper strip is delimited by two longitudinal edges and two transverse edges, and wherein in the region of the two longitudinal edges an overlap region is formed in each case and that by bending a paper strip about a drinking draw axis, a preferably cylindrical hollow body open on both sides is formed, wherein the paper strip is formed in such a manner that by overlap of the two overlap regions, an overlap portion is formed and that the two overlap regions in the overlap portion are glued together.
Furthermore it can be provided that the paper strip is formed in such a manner that its two longitudinal edges run substantially parallel to the drinking straw axis.
Also advantageous is a manifestation according to which it can be provided that the paper strip is formed in such a manner that the two longitudinal edges run substantially in a spiral or helical shape about the drinking straw axis.
Furthermore, it can be expedient if, before the further processing to form a cellulose-fibre-based drinking straw, the first side of the at least one paper web is printed with food-safe and biologically degradable inks. Individual designs, marks etc. can thus be applied to the cellulose-fibre-based drinking straw.
According to the invention, a cellulose-fibre-based drinking straw can also be provided, which is produced in particular according to a method according to one of the claims, and comprises a preferably cylindrical hollow body which is open on both sides having a lateral outer surface and a lateral inner surface. In this case, it is provided that the hollow body is formed by at least one formed paper strip, wherein the at least one paper strip is assembled from at least one paper web having at least one compressed first side.
By using a paper web compressed at least on one side, this has the effect that a cellulose-fibre-based drinking straw fabricated therefrom is waterproof or water-resistant at least for the duration of its use. It has been found that the compression of the surface of the at least one paper web brings about a smoothing of the cellulose fibres in the near region of the surface. The compression thereby achieved resembles a type of sealing which, however, acts completely without varnishes, coatings or similar adjuvants. As a result of this type of sealing, an undesired or too rapid penetration of liquids into the wall structure of the drinking straw is reduced or even prevented. A premature softening can thus be effectively impeded or at least delayed for a sufficiently long time so that function and shape retention of the drinking straw can be ensured during its usage duration. It has surprisingly been shown that a one-sided compression and a thus optionally associated smoothing of the non-woven web or the paper web is fundamentally sufficient to achieve this “sealing effect”. Whether a compression on both sides is expedient depends inter alia on the specific case of application.
Since no recyclable additives or the like must be added to achieve these properties, a cellulose-fibre-based drinking straw produced according to the invention is additionally accessible to a recycling or a “repulping”, i.e. a return to an aqueous cellulose suspension in a simple manner. In the case of any additives which are added to the aqueous suspension, care should be taken to ensure that only those additives are contained which, with a view to an aqueous extraction application such as the use of drinking straws constitutes in any case, are harmless for a user and for the environment. This can apply both to cold and also to hot extraction applications.
A cellulose-fibre-based drinking straw produced according to the invention can be supplied to recycling without any increased expenditure or without additional expensive process steps. In particular, if no addition of additives in the form of wet strengthening agents is required by the process according to the invention, an efficient “repulping” can be facilitated.
Furthermore, it can be provided that the compressed first side of the at least one paper web has a Cobb 1800s value according to ISO 535:2014 from 24 g/m²to 62 g/m².
Since the Cobb 1800s value in accordance with ISO 535:2014 constitutes an absolute value of water absorbency of a paper and the grammage of the paper can play an important role here or can have a substantial influence on this absolute value, for a better comparability between different papers a percentage water content over the entire grammage range can be informative for a characterization of the paper properties. Such a percentage water content can be computed from the ratio between a
Cobb 1800s value in accordance with ISO 535:2014 and the grammage of the paper. In particular, a percentage water content of 35% to 48% can be advantageous for a paper web—this is assuming that 7% of the water in the paper is present as compensating moisture during storage in climatic conditions at 23° C.±1° C. and 50%±2% relative air humidity in accordance with ISO 187:1990. Three calculation examples for different paper webs are given hereinafter for an exemplary explanation:

EXAMPLE 1

Grammage during storage in a normal climate at 23° C.±1° C. and 50% 35 2% relative air humidity in accordance with ISO 187:1990 =40.0 g/m²
Cobb 1800s value in accordance with ISO 535:2014=26. 2 g/m²
Grammage of the paper according to the Cobb 1800s test=66.2 g/m²
Total water content of the paper according to the Cobb 1800s test=((40.0/100*7)+26.2)/66.2*100=43.8%

EXAMPLE 2

Grammage during storage at 23° C.±1° C. and 50%±2% relative air humidity in accordance with ISO 187:1990=60.0 g/m²
Cobb 1800s value in accordance with ISO 535:2014=33.3 g/m²
Grammage of the paper according to the Cobb 1800s test=93.3 g/m²
Total water content in the paper according to the Cobb 1800s test=40.2%

EXAMPLE 3

Grammage during storage in a normal climate at 23° C.±1° C. and 50%±2% relative air humidity in accordance with ISO 187:1990=120.0 g/m²
Cobb 1800s value in accordance with ISO 535:2014=59.7 g/m²
Grammage of the paper according to the Cobb 1800s test=179.7 g/m²
Total water content of the paper according to the Cobb 1800s test=37.9%
It can additionally be expedient if a difference amount of a Cobb 1800s value according to ISO 535:2014 between the compressed first side and the non-compressed or less strongly compressed second side is a maximum of 3 g/m². Less strongly compressed means that the second side is less strongly compressed compared to the first side since this, for example, is not pressed against a smooth surface. According to the methods of manufacture and machine concepts, papers according to the invention having grammages preferably of 22 g/m²to 200 g/m²in accordance with ISO 536:2012 can be used for the production of cellulose-fibre-based drinking straws. Fundamentally however the use of papers having lower, but also having higher grammages is naturally also feasible and optionally expedient.
According to a particular manifestation, it is possible that the compressed first side of the at least one paper web has a Bendtsen roughness according to ISO 8791-2:2013 of 30 ml/min to 250 ml/min.
According to an advantageous further 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 this case, in particular in a manufacturing method using shoe calenders, it can be advantageous if the gloss value according to TAPPI T 480:2015 is 21% to 25%. In the production of MG papers it can be expedient if a gloss value according to TAPPI T 480:2015 is 24% to 33%.
In particular, it can be advantageous if the compressed first side of the at least one paper web has a static contact angle according to ISO 19403-2:2020 using water as test liquid of 100° to 120°.
It can also be advantageous if a difference amount of a static contact angle according to ISO 19403-2:2020 using water as test liquid between the compressed first side and the non-compressed or less strongly compressed second side is a maximum of 6°. Less strongly compressed means that the second side is less strongly compressed compared with the first side since this is not pressed, for example, against a smooth surface.
It can further be provided that at least two paper webs are arranged in such a manner that the first side of the first paper web forms the lateral outer surface of the hollow body and that the first side of the second paper web forms the lateral inner surface of the hollow body.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, this is explained in detail with reference to the following figures.

In the figures in each case in a highly simplified schematic view:

FIG. 1 shows an exemplary embodiment of a process diagram to produce a non-woven web and its drying to form a paper web;

FIG. 2 shows a further exemplary embodiment of a process diagram to produce a non-woven web and its drying to form a paper web;

FIG. 3 shows three paper webs layered one above the other in a three-dimensional exploded view;

FIG. 4 shows a further paper web assembled to form a paper strip;

FIG. 5 shows a cellulose-fibre-based drinking straw in three-dimensional view;

FIG. 6 shows a further cellulose-fibre-based drinking straw in three-dimensional view;

FIG. 7 shows a paper web layered one above the other or folded, in three-dimensional view.

DETAILED DESCRIPTION OF THE INVENTION

Firstly it should be noted that in the variously described embodiments the same parts are provided with the same reference numbers or the same component designations, wherein the disclosures contained in the entire description can be applied accordingly to the same parts with the same reference numbers or the same component designations. The positional information selected in the description such as top, bottom, laterally etc. are related to the figure described directly and depicted, and in the event of a change in position this positional information can be applied accordingly to the new position.
The method for producing cellulose-fibre-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.
The person skilled in the art is sufficiently aware of how the cellulose material 2 can be produced which is why the corresponding possible process steps are not described in detail or are not depicted in figures. For the sake of completeness one possible process sequence is only briefly outlined at this point. Advantageously 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 can be provided as cellulose material 2. The cellulose mixture can be composed of 20 to 80 wt. % long-fibre sulphate cellulose and of 20 to 80 wt. % short-fibre cellulose, preferably short-fibre sulphate cellulose. For example, a cellulose mixture of comminuted hard wood as sulphate cellulose and of comminuted soft wood as sulphate cellulose can be used as starting material to produce the cellulose material 2. Naturally this can also comprise a mixture of various comminuted hard woods and soft woods. This cellulose mixture is prepared by a process comprising chemical treatment of the comminuted first and second cellulose in a pulp digester. Depending on the requirement, it can be expedient if, after the chemical treatment, a mechanical treatment and defibration of an aqueous solid suspension of the cellulose mixture is carried out in a high-consistency defibrator. A consistency of the solid suspension before the mechanical treatment and defibration in the high-consistency defibrator can, for example be set to 25% to 40%. Such a defibration in a high-consistency defibrator is used, inter alia, to reduce the so-called splinter fraction of the cellulose mixture, i.e. the dissolution of still-wood-like cellulose agglomerates. In addition, it can also be expedient if, after the first mechanical processing and defibration in the high-consistency defibrator, a mechanical treatment and grinding of the cellulose mixture or an aqueous cellulose suspension of the cellulose mixture is carried out in a low-consistency refiner. A consistency of the solid suspension before the mechanical treatment and grinding in the low-consistency refiner can expediently be set to 2% to 6%. It can certainly be provided that only a mechanical treatment of the cellulose mixture is carried out in a high-consistency defibrator. In precisely the same way, in other cases however it can also be expedient if a defibration in a high-consistency defibrator is omitted and only a mechanical treatment of the cellulose mixture in a low-consistency refiner is carried out. The specific grinding powers of the individual grinding stages should be adapted to the selected cellulose mixture of the desired paper parameters.
The description of FIGS. 1 and 2 is provided hereinafter as far as is appropriate and possible in a combined view in order to avoid unnecessary repetitions, wherein the same reference numbers are used for the same parts. FIGS. 1 and 2 each show an exemplary embodiment of a process diagram to produce a non-woven web 5 and its drying to form a paper web 8.
Regardless of how preparation of the cellulose mixture to form a cellulose material 2 is carried out, production of at least one aqueous suspension 3 comprising the cellulose material 2 is carried out for further processing of the cellulose material 2. This process step is illustrated, for example, in FIGS. 1 and 2 by means of a tank 28 with agitator. In particular, various usual additives 4 in paper technology or aggregates and adjuvants such as fillers, starch etc. can be added to this at least one aqueous suspension 3. At least one strengthening agent can be added to the at least one suspension 3 as additive 4 relative to the active substance of the sizing agent in an amount of 0.07 wt. % to 1.0 wt. % relative to 100 wt. % total dry mass of the at least one suspension 3. Sizing agents in this case can be selected from a group consisting of alkenyl succinic acid anhydride (ASA), alkyl ketene dimer (AKD), resin sizing agents or natural sizing agents or a mixture of sizing agents selected from this group.
Regardless of this, before the homogenization and pre-drying to form at least one water-containing non-woven web 5 having a first side 6 and a second side 7, a consistency of the at least one aqueous suspension 3 can be set to a value of 0.15% to 0.8%, preferably of 0.3% to 0.7%. The further processing of this at least one aqueous suspension 3 can then be accomplished, as is known per se, by means of a paper machine 29, as is described roughly schematically hereinafter with reference to FIGS. 1 and 2 . Usually paper machines 29 comprise a wire section 30, a press section 31 and a drier section 32, wherein each of these process steps comprises drying or dewatering processes. According to the invention, it is provided that 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 and after one of the drying steps and before the further processing to form a cellulose-fibre-based drinking straw 1. This compression step can either be produced in a single nip, i.e. compression step, or in a plurality of consecutively arranged nips each having the specified line loads. In addition, it can be expedient if at least the first side 6 of the at least one non-woven web 5 is thermally treated in the course of this compression. In other words, this means that a thermal influencing can take place in the same process steps at the same time as the pressure application.
As shown in FIGS. 1 and 2 , the at least one aqueous suspension 3 comprising the cellulose material 2 can be applied, as is known per se, to a circulating continuous screen 33 of a wire section 30. A homogenization of the at least one aqueous suspension 3 and its pre-drying to form at least one water-containing non-woven web 5 takes place in such a wire section 30. The continuous screen 33 can in this case be guided over dewatering agents 34 of the wire section 30 which dewatering agents 34 can, for example, be formed by suction strips. Fundamentally a dewatering in a wire section 30 can also take place merely by means of gravity. In addition, however, for example depending on the design of a wire section 30, the dewatering or pre-drying of the at least one non-woven web 5 can be assisted by producing a vacuum. The at least one first non-woven web 5 comprising the cellulose material 2 can be pre-dried by means of the wire section 30, for example, to a water content of 75 wt. % to 85 wt. %.
Hereinafter, as shown in FIGS. 1 and 2 , the at least one non-woven web 5 can be further dewatered or further dried by means of a press section 31. According to FIG. 1 , the non-woven web 5 can be guided between rollers 35 of the press section 31 and thereby further dewatered under pressure. In addition, the further drying can be assisted by means of absorbent support material 36. For this purpose, as is known per se, felt mats can be used for example. A press section 31 according to FIG. 1 can comprise more than only two rollers 35, as is known per se, in particular a plurality of roller pairs formed by rollers 35 can be arranged consecutively. A water content of the non-woven web 5 after passing through a press section 31 can, for example, be about 45 wt. % to 65 wt. % relative to the total mass of the nonwoven web 5.
A so-called slalom drier 37 can be arranged after the press section 31 according to FIG. 1 as drier section 32 or as part of a drier section 32. As shown in FIG. 1 , a slalom drier 37 can comprise numerous rotating drying cylinders 15 over which the at least one non-woven web 5 can be guided. The drying cylinder 15 can be heated directly. For example, heating channels not shown in detail can be formed to guide hot steam into the drying cylinders 15. Alternatively, for example, it is also possible to heat the drying cylinder 15 by means of an electrical resistance heater. A temperature of the drying cylinder 15 of a drying section 32 can, for example, increase successively in the direction of guidance of the at least one non-woven web 5. The non-woven web 5 can be dried by means of the slalom drier 37, for example, to a water content of 1 wt. % to 10 wt. %.
For compression according to the invention with a line load of preferably 210 kN/m to 370 kN/m, a so-called broad-nip calender 9 or also shoe calender having a shoe length of, for example, 50 mm and a shoe tilt of 24% can be provided in the drier section 32 following a slalom drier 37 for further drying and compression of the non-woven web 5. For compression according to the invention with a line load of preferably 380 kN/m to 490 kN/m, for example, a shoe length of 75 mm and a shoe tilt of 24% can be provided in a shoe calender.
A broad-nip calender 9 can be formed substantially by a heated roller 10 and by a shoe roller 12 cooperating with the heated roller 10. The shoe roller 12 can act as a flexible counter-pressure element to the heated roller 10 and have a circulating jacket 38. This circulating jacket 38 cooperates with the heated roller 10 and forms a broad nip 11. The first side 6 of the at least one non-woven web 5 facing the heated roller 10 is finished by passing between heated roller 10 and shoe roller 12. This means that the non-woven web 5 is at the same time compressed with elevated pressure and exposed to an elevated temperature. Temperatures at the surface of the heated roller can, for example, be about 250° C. to 295° C. The temperature can be achieved, for example, by means of a thermal oil having a correspondingly higher oil flow temperature. Other heating elements such as, for example, an induction heater can be provided for further stabilization of the surface temperatures. Fundamentally it is also feasible but not shown in the figures that a second, advantageously identically constructed broad nip calender 9 is provided, which is arranged in the paper machine 29 in such a manner that a so-called satin finishing of the second side 7 in addition to the satin finishing of the first side 6 of the at least one non-woven web 5 can take place.
It is also feasible that a process-technical combination of press section 31 and drier section 32 is provided after the wire section 30 by means of which the compression according to the invention with a line pressure of about 80 kN/m can take place in a first shoe press, in a second smoothing press at about 90 kN/m and in a third smoothing press at about 100 kN/m. The surface temperature of the smoothing cylinder can, for example, be about 94° C. This feasible design is shown roughly schematically by FIG. 2 . Alternatively to the design variant according to FIG. 1 , FIG. 2 shows a dewatering, compression or pressure application by means of a so-called Yankee cylinder 39. Papers which are produced by means of such an arrangement or a comparable one are usually designated in technical circles as “machine-glazed” or “MG papers”. As part of a paper machine 29 FIG. 2 thus shows a combined press section 31 and drier section 32 in the configuration of a Yankee cylinder 39 with drying hood 16 or gas drying hood placed thereon. The at least one non-woven web 5 adhering to a removal felt is pressed with the first side 6 thereof by two pressing rollers 13 onto the surface 14 of the steam-heated Yankee cylinder 39 and further or finish dried by additional blowing of hot air by means of the drying hood 16.
The paper machines 29 shown as examples according to FIGS. 1 and 2 are each terminated by a winder 40 by means of which the finished at least one paper web 8 can be wound onto a roll. However, it is alternatively also feasible and optionally also expedient if at least one paper web 8 is supplied directly to a further processing or assembly.
Depending on how a paper machine 29 is constructed, the at least one suspension 3 can be produced with a consistency of 0.15% to 0.70%. In this case, both high-consistency and also low-consistency suspensions 3 can be used for arrangements based on FIG. 1 with a broad-nip calender 9 whereas a low-consistency suspension 3 with a consistency of 0.15% to 0.30% can be more expedient for an arrangement based on FIG. 2 with a Yankee cylinder 39.
The person skilled in the art is familiar with a plurality of different methods for producing cellulose-fibre-based drinking straws 1 from at least one paper web 8 which is why the possible process steps are not discussed in detail.
Advantageously one but also more, preferably three or even four of the paper webs 8 produced according to the invention can be further processed to form a cellulose-fibre-based drinking straw 1. In the course of the further processing, one or more paper webs 8 produced from the same cellulose material 2, i.e. a plurality of identical paper webs 8 can be layered one above the other. However, it is also feasible and has proved particularly advantageous if paper webs 8 produced from various cellulose materials 2 and therefore different with regard to their technical properties are layered one above the other and joined.
A single paper web 8 can, for example, also be further processed by a corresponding single or multiple folding. Thus, a single paper web 8 can, for example, be multiply folded so that it runs in a zigzag manner or in a meander shape so that a paper web 8 that is quasi-multi-layered or layered one above the other is formed. This feasible embodiment is shown by FIG. 7 in a schematic three-dimensional view. With such folding in each case the compressed first side 6 and the uncompressed second side 7 contact one another. From this exemplary embodiment, a similar paper strip 18 as depicted as an example by FIG. 4 and described hereinafter can be fabricated subsequently. Such a folded paper strip consisting of the paper according to the invention can be fixed in its position by means of suitably selected adhesive points. An adhesive 17—which is not shown explicitly in FIG. 7 —can be applied for example over the entire surface, in a punctuate manner or also in a strip form between the folded layers.
FIG. 3 shows the paper webs 8 layered one above the other in a three-dimensional exploded view. Naturally, a smaller or higher 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 was compressed on a paper machine 29 with a broad nip calender 9 and if the middle and the lower paper web 8 were compressed 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 compressed by means of a Yankee cylinder 39 and with middle and lower paper webs 8 compressed by means of a broad nip calender 9 can also be expedient. In this case, as shown in FIG. 3 , the paper webs 8 are layered one above the other in such a manner that in each case the compressed first side 6 of a paper web 8 contacts the uncompressed second side 7 of the further paper web 8 layered thereover. Alternatively, however but not shown in the figures, it can also be advantageous if the paper webs 8 are layered one above the other in such a manner that in each case the compressed first side 6 of the two outer paper webs 8 lies on the outside. At this point, it should be noted that an uncompressed second side 7 can also be a less strongly compressed side compared to the compressed first side 6.
Alternatively but also not shown in the figures, it can also be advantageous if at least one layer of the paper produced according to the invention is fabricated in an arrangement of several paper webs 8. In particular, it can also be expedient if in particular one of the two exterior paper webs 8, i.e. one of the two directly in contact with a drinking liquid is produced according to the method according to the invention. However, it can also be advantageous that both the finished cellulose-fibre-based drinking straw 1 exterior paper webs 8 are produced according to the method according to the invention. In this case, it can be expedient if in each case, 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 or product properties such as, for example, optical properties such as gloss, printability, haptics and the like can be set accordingly in an advantageous manner.
The paper webs 8 can be glued together, wherein an adhesive 17 is applied over the full surface or in sections to the contacting sides 6, 7 of the paper webs 8. FIG. 3 shows that the adhesive 17 can be applied in a strip shape and approximately symmetrically to respectively one side 6, 7 of a paper web 8. Naturally, according to requirements and adhesive power, it is also feasible that the adhesive 17 can be applied over the full surface and to each contacting side 6, 7 or also only in a punctuate manner or along the sheet edges. In particular, in order to achieve a food licence for the cellulose-fibre-based drinking straw 1 and with a view to any leaching of contents from the cellulose-fibre-based drinking straw on contact with cold and/or hot liquids, it can be important if a food-safe, biologically degradable glue of animal and/or vegetable origin is used as adhesive 17. Various legal requirements and recommendations apply for a safe use for papers, boards and cardboards which are provided for direct contact with food. In order to mention just a few relevant ones, for example, the recommendation XXXVI of the Federal Institute for Risk Assessment and further the recommendations XXXVI/1 for cooking and hot filter papers should be used here, for example. At this point, for example, mention should also be made of the Regulation (EC) No. 1935/2004 and the Food, Consumer Goods and Animal Feed Code. As national regulations, mention is further made of the Decreto Ministeriale 21 marzo 1973, Code of Federal Regulations, Food and Drugs (FDA), 21 CFR Ch. I (edition 1 April 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.
A single paper web 8 but also in the sense of FIG. 3 , layered paper webs 8 can be assembled in the course of the further processing to form a cellulose-fibre-based drinking straw 1 to form paper strips 18. To illustrate this, FIG. 4 shows a further paper web 8 assembled to form a paper strip 18. A paper strip 18 can be delimited in each case by two longitudinal edges 19 and two transverse edges 20, wherein respectively one overlap region 21 can be formed in the 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 a finished cellulose-fibre-based drinking straw 1. Possible positions for subsequent cutting regions are shown by dashed lines in FIG. 3 . It can also be the case that the first side 6 of the at least one paper web 8 is printed with food-safe and biologically degradable inks before the further processing to form a cellulose-fibre-based drinking straw 1.
FIGS. 5 and 6 further show two feasible embodiments of cellulose-fibre-based drinking straws 1 in three-dimensional view, wherein the cellulose-fibre-based drinking straws 1 comprise a preferably cylindrical hollow body 23 which is open on both sides having a lateral outer surface 26 and a lateral inner surface 27. in this case, it is provided that 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 with at least one compressed first side 6. Alternatively to hollow bodies 23, for example, drinking straws 1 having a tilted or polygonal cross-section are also feasible.
By bending a paper strip 18 about a drinking straw axis 22, a preferably cylindrical hollow body 23 open on both sides can be folded, wherein the at least one paper strip 18 can be formed in such a manner that an overlap portion 24 is formed by overlap of the two overlap 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. In this case, the at least one paper strip 18 can be formed in such a manner that its two longitudinal edges 19 can run substantially parallel to the drinking straw axis 22 as shown schematically by FIG. 5 . Alternatively it is shown in FIG. 6 that it is also feasible that the two longitudinal edges 19 run substantially spirally or in a helical shape about the drinking straw axis 22. Advantageously the two overlap regions 21 can be glued together in the overlap portion 24.
At least two paper webs 8 can be arranged in such a manner that the first side 6 of the first paper web 8 forms the lateral outer surface 26 of the hollow body 23 and that the first side 6 of the second paper web 8 forms the lateral inner surface 27 of the hollow body 23. It can be the case here that one or more further paper webs 8 are formed between the two outer, i.e. between the first and the second paper web 8. These interior or interposed paper webs 8 can comprise both paper webs 8 according to the invention and also different types of further papers with possibly additional advantageous properties. It can also be the case that at least two paper webs 8 are arranged in such a manner that the uncompressed or less strongly compressed second side 7 of the first paper web 8 compared to the first side 6 forms the lateral outer surface 26 of the follow body 23 and that the uncompressed or less strongly compressed second side 7 of the second paper web 8 compared to the first side 6 forms the lateral inner surface 27 of the hollow body 23.
The compressed first side 6 of the at least one paper web 8 or the paper webs 8 can have a Cobb 1800s value in accordance with ISO 535:2014 of 24 to 62 g/m². A difference amount of a Cobb 1800s value in accordance with ISO 535:2014 between the compressed first side 6 and the non-compressed or less strongly compressed second side 7 can advantageously be a maximum of 4 g/m². In addition, the compressed first side 6 of the paper web(s) 8 can have a Bendtsen roughness in accordance with 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 in accordance with TAPPI 480 of 20 to 35%. Furthermore, the compressed first side 6 of the paper web(s) 8 can have a static contact angle in accordance with ISO 19403-2:2020 with water as test liquid of 100° to 120°. A difference amount of a static contact angle in accordance with 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 can be a maximum of 6°.
The exemplary embodiments show possible design variants wherein at this point it is noted that the invention is not restricted to specially depicted design variants of the same but on the contrary, diverse combinations of individual design variants amongst one another are possible and this scope for variation lies within the ability of the person skilled in the art active in this technical field as a result of the teaching on the technical action by the specific invention.
The scope of protection is determined by the claims. The description and the drawings should however be used to interpret the claims. Individual features or combinations of features from the depicted and described various exemplary embodiments can form independent inventive solutions by themselves. The object forming the basis of the independent inventive solutions can be deduced from the description.
All the information on ranges of values in the specific description should be understood such that these cover arbitrary and all partial ranges thereof, e.g. the information 1 to 10 should be understood such that all partial ranges starting from the lower limit 1 and the upper limit 10 are covered, i.e. all partial ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7 or 3.2 to 8.1 or 5.5 to 10.
For the sake of good order it should finally be pointed out that for better understanding of the structure elements are shown in some cases not to scale and/or enlarged and/or reduced.

REFERENCE NUMBERS

1 Cellulose fibre-based drinking straw
2 Cellulose material
3 Suspension
4 Additive
Non-woven web
6 First side
7 Second side
8 Paper web
9 Broad-nip calender
10 Heated roller
11 Broad nip
12 Shoe roller
13 Press roller
14 Surface
15 Drying cylinder
16 Drying hood
17 Adhesive
18 Paper strip
19 Longitudinal edge
20 Transverse edge
21 Overlap region
22 Drinking straw axis
23 Hollow body
24 Overlap section
25 Length
26 Lateral outer surface
27 Lateral inner surface
28 Tank
29 Paper machine
30 Wire section
31 Press section
32 Drier section
33 Endless screen
34 Dewatering agent
35 Roller
36 Support material
37 Slalom drier
38 Jacket
39 Yankee cylinder
40 Winder
41 Length

Claims

1. Method for producing cellulose-fibre-based drinking straws comprising the steps:

providing a cellulose material,

producing at least one aqueous suspension comprising the cellulose material and adding additives to the suspension,

homogenizing the at least one aqueous suspension and pre-drying to obtain at least one water-containing non-woven web having a first side and a second side,

drying the at least one water-containing non-woven web in a plurality of 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 plurality of paper webs to form a cellulose-fibre-based drinking straw,

wherein at least the first side of the at least one non-woven web 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 the cellulose-fibre-based drinking straw,

wherein

a cellulose mixture consisting of long-fibre sulphate cellulose and short-fibre cellulose is provided as the cellulose material, and that at least the first side of the at least one non-woven web is thermally treated in the during the compression.

2. The method according to claim 1, wherein the at least one non-woven web is compressed of a broad-nip calender comprising a heated roller and a shoe roller cooperating with the heated roller and forming a broad nip, wherein the at least one non-woven web is guided through the broad-nip calender with its first side facing the heated roller.

3. The method according to claim 1, wherein the at least one non-woven web is pressed by means of one or more pressure rollers with its first side onto the surface of a heated drying cylinder, wherein the at least one non-woven web is guided over a large part of the circumference of a drying cylinder and is additionally heated from outside by means of a drying hood which at least partially surrounds the drying cylinder.

4. The method according to claim 1, wherein 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.

5. The method according to claim 1, wherein at least one sizing agent is added as an additive to the at least one suspension relative to the active substance of a 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.

6. The method according to claim 5, wherein 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.

7. The method according to claim 1, wherein the at least one suspension is produced with a consistency of 0.15% to 0.70%.

8. The method according to claim 1, wherein during the further processing to form a cellulose-fibre-based drinking straw, one or a plurality of the paper webs are layered one above the other and joined.

9. The method according to claim 8, wherein a compressed first side of the at least one paper web is contacted with an uncompressed second side of a further paper web layered thereover.

10. The method according to claim 8, wherein the paper webs are glued together, wherein one adhesive is applied over the full surface or in sections to contacting sides of the paper webs.

11. The method according to claim 1 in the course of the further processing to form a cellulose-fibre-based drinking straw, the at least one paper web or a plurality of layered and joined paper webs are assembled to form paper strips, wherein in each case one paper strip is delimited by two longitudinal edges and two transverse edges, and wherein in the region of the two longitudinal edges an overlap region is formed in each case and that by bending the paper strip about a drinking straw axis, a cylindrical hollow body open on both ends is formed, wherein the paper strip is formed by overlapping the two overlap regions and the two overlap regions are glued together.

12. The method according to claim 11, wherein the paper strip is formed so that its two longitudinal edges run substantially parallel to the axis of the drinking straw.

13. The method according to claim 11, wherein the paper strip is formed so that the two longitudinal edges run substantially in a spiral or helical shape about the axis of the drinking straw axis.

14. The method according to claim 1, wherein before further processing to form the cellulose-fibre-based drinking straw the first side of the at least one paper web is printed with food-safe or biologically degradable inks.

15. A cellulose-fibre-based drinking straw produced according to method according to claim 1, comprising a cylindrical hollow body which is open on both ends having a lateral outer surface and a lateral inner surface, wherein the cylindrical hollow body is formed by at least one formed paper strip, wherein the at least one paper strip is assembled from at least one paper web having at least one compressed first side, wherein the compressed first side of the at least one paper web has a Cobb 1800s value according to ISO 535:2014 from 24 g/m²to 62 g/m².

16. The cellulose-fibre-based drinking straw according to claim 15, wherein a difference amount of a Cobb 1800s value according to ISO 535:2014 between the compressed first side and the non-compressed or less strongly compressed second side is a maximum of 3 g/m².

17. The cellulose-fibre-based drinking straw according to claim 15, wherein the compressed first side of the at least one paper web has a Bendtsen roughness according to ISO 8791-2:2013 of 30 ml/min to 250 ml/min.

18. The cellulose-fibre-based drinking straw according to claim 15, wherein the at least one paper web has a gloss value according to TAPPI T 480:2015 of 20 to 35%.

19. The cellulose-fibre-based drinking straw according to claim 15, wherein the compressed first side of the at least one paper web has a static contact angle according to ISO 19403-2:2020 using water as test liquid of 100° to 120°.

20. The cellulose-fibre-based drinking straw according to claim 15, wherein a different amount of a static contact angle according to ISO 19403-2:2020 using water as test liquid between the compressed first side and the non-compressed or less strongly compressed second side is a maximum of 6°.

21. The cellulose-fibre-drinking drinking straw according to claim 15, wherein at least two paper webs are arranged so that the first side of a first paper web forms the lateral outer surface of the hollow body and that a first side of the second paper web forms the lateral inner surface of the hollow body.