Method for manufacturing corrugated paper webs

Abstract

This invention relates to a method for manufacturing linerboard webs from a fiber suspension, wherein the fiber suspension is at least partially made from waste paper as the fiber raw material. The method includes the following steps: a. feeding waste paper to a preparation facility (3) to generate a waste paper stream (2); b. separating the waste paper stream (2) into a short fiber stream and a long fiber stream in a grading process; c. feeding the short fiber stream to a short fiber stack and further to a mixing tank; d. feeding the long fiber stream to a long fiber stack; e. thickening the long fiber stream to a first material consistency after the long fiber stack; f. pulping the long fiber stream having the first material consistency by high-concentration pulping; g. feeding the long fiber stream to a mixing tank; h. guiding the fiber suspension from the mixing tank to a paper machine via a headstock system to form linerboard webs in the web travel direction; i. subjecting the linerboard webs to shrink-promoting drying in a drying section, preferably with an irregular shape that is transverse to the web travel direction; j. winding up the linerboard webs.

Description

Technical Field

[0001] This invention relates to a method for manufacturing linerboard webs from a fiber suspension, wherein the fiber suspension is at least partially made from waste paper as the fiber raw material. Background Technology

[0002] Linerboard is used to manufacture corrugated board. Corrugated board can consist of three layers. Linerboard serves as the outer layer, and it is separated from the corrugated paper by the so-called corrugated paper. Linerboard made entirely from waste paper is also known as linerboard. Corrugated board is processed into packaging boxes and corrugated board packaging. For this purpose, the corrugated board is grooved and bent along multiple bending lines. Packaging must be stable and protect the packaged goods from mechanical damage. Linerboard makes a significant contribution to this process.

[0003] For both economic and ecological reasons, the use of waste paper as a fiber raw material is constantly increasing in the manufacture of linerboard. Furthermore, increasing recycling rates leads to a decline in the quality of waste paper, which has a particular impact on its strength potential.

[0004] Therefore, when manufacturing packaging boxes and corrugated cardboard packaging, such as in Figure 3 As illustrated in the diagram, at the outer bending radius of the outer carton board, in the area of ​​the bending line, folding breaks occur more and more frequently, which leads to a deterioration in quality or even renders the packaging boxes and corrugated cardboard unusable. Summary of the Invention

[0005] Therefore, the objective of this invention is to describe a method for manufacturing linerboard that is improved in terms of economy and quality, thereby reducing known problems in further processing.

[0006] This task is solved by the features of claim 1. A method for manufacturing linerboard webs from a fiber suspension, wherein the fiber suspension is at least partially made from waste paper as the fiber raw material, is proposed. The method includes the following steps:

[0007] a. Transporting waste paper to the preparation facility to generate a waste paper stream;

[0008] b. In the classification process, waste paper streams are divided into short fiber streams and long fiber streams;

[0009] c. The short fiber stream is conveyed to the short fiber stack tower and further conveyed to the mixing tank;

[0010] d. Convey the long fiber stream to the long fiber stacking tower;

[0011] e. After the long fiber stacking tower, thicken the long fiber stream to the first material consistency;

[0012] f. Pulping a long fiber stream with a first material consistency by high-concentration pulping;

[0013] g. Transport the long fiber stream to the mixing tank;

[0014] h. The fiber suspension is guided from the mixing tank to the paper machine through the konstanter teil to form a linerboard web in the web travel direction;

[0015] i. Drying the linerboard web in the drying section to promote shrinkage, preferably with an irregular shape that is transverse to the web's travel direction;

[0016] j. Roll up the boxboard paper web.

[0017] The inventors recognized that a significant reduction in folding breakage could be achieved through high-concentration beating itself and by placing this method step not before the long-fiber stack, but after it—that is, after conventional material preparation and immediately before the paper machine. High-concentration beating leads to fibrillation of the individual fibers of the fiber raw material, both externally and internally, as well as fiber crimping, and thus results in greater stretchability of the linerboard web, especially in the transverse direction, i.e., across the web travel direction. However, these changes in the fibers are unstable and alter their positive properties over time. Stretchability should be understood as stretching up to the point of breakage.

[0018] Therefore, it is advantageous to keep the residence time of the fibers between the end of step f) and the start of the paper machine as short as possible. In possible embodiments, the residence time is less than 45 minutes, i.e., less than 0.75 hours, especially less than 35 minutes, and preferably less than 25 minutes. For example, the residence time can be affected by the size of the tank or by partially canceling the passage through the tank after high-concentration pulping. The smaller the pipeline and tank volume between step f) and the paper machine, the shorter the residence time.

[0019] Another advantage of the invention is achieved through drying in the paper machine that promotes shrinkage in the transverse direction of the web's travel. The inventors recognize that this also improves the stretchability of the linerboard web, i.e., stretching in the transverse direction until breakage, and thus reduces the problem of folding breakage when the corrugated board is bent.

[0020] The drying process of a paper machine is known to produce an uneven variation in transverse shrinkage across the width of the paper web. This variation is also known as the "bathtub effect." The edges of the web experience greater transverse shrinkage than the middle. This also results in varying degrees of stretchability of the linerboard web in the transverse direction. In further processing of the linerboard web, this difference has led to varying degrees of folding breakage, depending on whether the linerboard originates from the middle or the edges of the produced linerboard web.

[0021] In a preferred embodiment, drying in step i) is performed without mechanical stretching and / or shrinking, i.e., compression, of the linerboard web transverse to the web travel direction of the paper machine, and the linerboard web is preferably manufactured at a paper machine production speed greater than 1200 m / min, preferably greater than 1300 m / min, and especially greater than 1400 m / min. Equipment and methods for improving the stretchability of the paper web during mechanical compression transverse to the web travel direction are known. In the conventional so-called "Clupak (micro-crease stretching) method," the paper web is mechanically shrinked, i.e., mechanically compressed or wrinkled, in the web travel direction by a rubber sheet, thereby creating high stretchability of the paper web in the longitudinal direction. This is used, for example, in the manufacture of kraft paper bags. This method can also be used for mechanical shrinking in the transverse direction. However, this method is limited in terms of speed. When used for manufacturing linerboard, it is almost impossible to achieve the desired production. Additionally, the quality of the linerboard may be compromised. Therefore, the manufacturing process of linerboard is preferably free from any mechanical shrinkage, which is the case, for example, according to the principle of the "Clupak method".

[0022] Corrugated board webs can have a thickness of 60 g / m². 2 Up to 300g / m 2 Within the range, especially at 70g / m 2 Up to 160g / m 2 Weight per unit area within the specified range.

[0023] Advantageously, the waste paper has an ash content of 10% to 25%, and preferably has... The pulping degree is between 50°SR and 50°SR, and preferably has a water retention capacity between 95% and 130%.

[0024] In possible practical design schemes, the consistency of the first material is greater than 10%, especially greater than 15%, and preferably greater than 20%. Therefore, high-concentration pulping has a particularly advantageous effect on reducing folding and breakage.

[0025] Furthermore, it is advantageous to use 80 kWh / t in the high-concentration pulping according to step f). 长纤维 and 350kWh / t 长纤维 Between, preferably greater than 150 kWh / t 长纤维 Energy within a certain range.

[0026] In a possible improvement, immediately following step f), 100% or at least a portion of the long fiber stream is diluted and preferably piled up.

[0027] In practical cases where possible, the long fiber stream is diluted to a material consistency preferably less than 5%, and then subjected to low-concentration pulping.

[0028] In the actual improved version, in step h), a linerboard web is formed on at least one screen, and the screen is oscillated back and forth transverse to the web's direction of travel using a oscillating device. This, in particular, reduces the "bathtub effect." The shrinkage difference between the web's edges and the middle of the web is reduced, and the quality of the linerboard web becomes more uniform.

[0029] The drying section may have a pre-drying section and a post-drying section, and starch-glued linerboard webs are preferably used between them, on one or both sides. Gluing can be performed using a gluing press or a film press. This improves the strength potential of the fiber suspension containing waste paper, and thus also increases the production efficiency of the paper machine.

[0030] In a favorable improvement, the linerboard web is immediately deflected without contact and / or dried by impact flow immediately after gluing, preferably in conjunction with a felt-free drying drum in a subsequent drying section. Impact flow drying is preferably configured to be irregularly shaped transverse to the web's direction of travel.

[0031] Non-contact deflection can be achieved by providing an air cushion between the paper web and the blowing element for blowing out preferably hot air. This non-contact deflection and impingement flow drying promotes shrinkage of the fiber web, and thus reduces the risk of fold breakage. Drying on a feltless drying drum further enhances this advantage, as the paper web is dried without shrinkage inhibition due to the absence of drying felt or drying screens.

[0032] In a preferred improvement, the drying section comprises single-row and double-row drying groups, and the number of drying cylinders in the double-row drying groups accounts for 10% to 70%, preferably 30% to 80%, and especially >50% of the total number of drying cylinders. Shrink drying of the linerboard web is also promoted in the double-row drying groups. Therefore, the number of drying cylinders in the double-row drying groups should be as large as possible relative to the total number of drying cylinders.

[0033] The fiber suspension can be manufactured from more than 50%, especially more than 70%, preferably more than 80%, and particularly preferably more than 90% waste paper as fiber raw material.

[0034] In certain cases, the fiber suspension may be manufactured using waste paper and fresh fiber pulp as fiber raw materials. This is advantageous for improving the strength and production efficiency of linerboard webs. Preferably, the fresh fibers are selected from wood pulp, cellulose, and fibers from annual plants.

[0035] In a preferred embodiment, the fiber suspension is made from 100% waste paper as the fiber raw material.

[0036] The gluing of the linerboard web is preferably performed at a dry content between 60% and 80%.

[0037] In practical cases, gluing is performed such that, after gluing, the moisture content of the linerboard web is between 25% and 50%. This, in particular, combined with drying that promotes shrinkage, results in fewer folding breaks.

[0038] If the subsequent drying section has a final single-row drying group before the two-row drying groups, and the final drying screen suction roller is equipped with a nozzle wetter preferably irregularly shaped in the transverse direction for wetting the linerboard web, then this advantageous effect can also be achieved and enhanced. After wetting the linerboard web, the linerboard web is shrunk and dried in the subsequent double-row drying group, thus reducing the formation of folds and breaks.

[0039] The present invention also explicitly relates to the following embodiments, which are not given by combination of features of the explicitly cited claims, to which the disclosed features of the present invention (provided that this is technically meaningful) may be combined with each other in any way. Attached Figure Description

[0040] Other features and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings. Wherein:

[0041] Figure 1 A simplified method diagram illustrates an embodiment of the method according to the present invention;

[0042] Figure 2 A simplified illustration shows a segment of the drying section of a paper machine.

[0043] Figure 3 A simplified illustration shows a curved corrugated cardboard. Detailed Implementation

[0044] Figure 1A simplified method diagram illustrates an embodiment of the method according to the invention. Corrugated board webs are manufactured in manufacturing facility 1 from a fiber suspension, which is at least partially made from waste paper 2.1 as the fiber raw material. In this example, the fiber raw material 100% comes from waste paper 2.1. However, alternatively, fresh fibers 13.1 may also be mixed in. Here, the fresh fiber stream 13 is formed from the fresh fibers 13.1 prepared in the fresh fiber preparation unit 14. The fresh fiber stream 13 is conveyed to the mixing tank 10. Waste paper is supplied, for example, in the form of waste paper bales 2.1, and prepared as waste paper stream 2 in preparation facility 3. This step is known to include, for example, stripping, dissolving, and cleaning. Waste paper stream 2 is now separated into short fiber stream 5.1 and long fiber stream 6.1 in grading 4. Subsequently, short fiber stream 5.1 is stacked in short fiber stacking tower 5, while long fiber stream 6.1 is stacked in long fiber stacking tower 6. Stacking towers 5 and 6 represent the end of a conventional material preparation facility for manufacturing corrugated board. The short fiber stream 5.1 is further guided from the short fiber stack 5 to the mixing tank 10. Conversely, the long fiber stream 6.1 is thickened to a first material consistency greater than 10%, particularly greater than 15%, preferably greater than 20%, after the long fiber stack 6 and is conveyed to the high-concentration pulping 8. Energy in the range of 80 kWh / t to 350 kWh / t is used in the high-concentration pulping. Then, in the stacking and / or dilution step 9, the long fiber stream 6.1 can be conveyed to the stacking tank and optionally diluted again. This is done before being conveyed to the mixing tank 10 and mixed with the short fiber stream 5. In another optional step, the long fiber stream 6.1 can be diluted to a second concentration of less than 5% after the high-concentration pulping 8 and then pulped in the low-concentration pulping 11 before being guided to the mixing tank 10. This second pulping step further suppresses the occurrence of fold breakage. The fiber suspension in mixing tank 10 is conveyed to paper machine 15 via a so-called headstock system 12 to form linerboard webs. The linerboard webs can have a g / m² content of 60 g / m². 2 Up to 300g / m 2 Weight per unit area within the specified range.

[0045] To maintain the positive effect of high-concentration beating 8 on fold breakage, it is advantageous to keep the residence time of fibers between the end of high-concentration beating 8 and the start of the paper machine 15 as short as possible. In possible embodiments, the residence time is less than 45 minutes, especially less than 35 minutes, and preferably less than 25 minutes. For example, the residence time can be affected by partially eliminating the tank after high-concentration beating 8, depending on the size of the tank or line. The smaller the volume of the line and tank between high-concentration beating 8 and the paper machine, the shorter the residence time.

[0046] The linerboard web is formed on at least one screen in the forming zone of the paper machine 15, and the screen is oscillated back and forth transversely to the web travel direction 29 by means of an oscillating device. This reduces the shrinkage difference between the edges and the middle of the web, thus making the quality of the linerboard web more uniform. The forming zone may include a long screen, a mixing former, or a clamping former. By using a short residence time between the fibers in the high-concentration beating 8 and the fibers being fixed in the forming zone, the state achieved by the high-concentration beating 8 can be frozen and maintained, reducing the occurrence of folding breaks. After the forming zone, the linerboard web is dewatered and dried in the extrusion section and subsequently the drying section. Drying is carried out by shrinkage-promoting drying of the linerboard web in the drying section. The drying step can be performed by a drying process that can be irregularly configured transversely to the web travel direction. For example, drying can be performed differently in sections along the width. This reduces the negative impact of the width-specific characteristics of the linerboard web during further processing. Drying section 16 may have a pre-drying section 17 and a post-drying section 18, and between these sections, the linerboard web may preferably be starch-bonded on one or both sides. Bonding 19 may be performed using a bonding press or a film press. This improves the strength potential of the fiber suspension containing waste paper, and thus also increases the production efficiency of the paper machine. After drying section 16, the paper web is wound up.

[0047] Figure 2 A simplified illustration shows a segment of the drying section of a paper machine. Drying section 16 includes a pre-drying section 17 and a post-drying section 18 located downstream of the web travel direction 29. The end of the pre-drying section 17 and the beginning of the post-drying section 18 are shown in this segment. The linerboard web passes through the final drying unit of the pre-drying section 17, which is implemented as a two-column drying unit with upper and lower drying cylinders 20. Unlike a single-column drying unit, the paper web is dried to facilitate shrinkage. Subsequently, using starch, the linerboard web is glued on one and / or both sides at a dry content between 60% and 80%. Through this process step, the linerboard web is wetted to a moisture content of 25% to 50%. Gluing is performed using a film press.

[0048] Immediately following gluing 19, non-contact deflection 23 and / or impact flow drying 22, in conjunction with a feltless drying drum 20.1, are performed on the linerboard web. This arrangement also enables shrinkage-promoting drying of the linerboard web because there are no drying screens or drying felts to impede shrinkage. The web is then dried in a single-row drying group with a lower drying screen suction roller 21 and subsequently in two additional rows of drying groups. The impact flow drying can be irregularly arranged transverse to the web travel direction 29. Non-contact deflection 23 can be achieved by providing an air cushion between the web and the blowing element for preferably hot blowing. Non-contact deflection 23 and impact flow drying 22 promote shrinkage of the fiber web and thus reduce the risk of fold breakage. Drying on a feltless drying drum further enhances this advantage because the web is dried without shrinkage inhibition due to the absence of drying felts or drying screens. The drying section comprises single-row and double-row drying units, with the number of drying cylinders in the double-row drying units accounting for 10% to 70%, preferably 30% to 80%, and especially >50% of the total number of drying cylinders. Shrink drying of the linerboard web is also promoted in the double-row drying units. Therefore, the number of drying cylinders in the double-row drying units relative to the total number of drying cylinders should be as large as possible.

[0049] To illustrate the problem on which this invention is based, Figure 3 A segment of corrugated board 24, bent for the manufacture of corrugated board packaging, is shown. In this example, corrugated board 24 comprises an upper linerboard 25, a lower linerboard 26, and a corrugated board 27 located between them, bonded to both linerboards 25 and 26. Due to the bending, the lower linerboard 26 may, for example, tear at least partially in the bent area 28. This is known as fold breakage. The risk of fold breakage is particularly high when using 100% waste paper as raw material. The lower the quality of the waste paper, the greater the risk of fold breakage of the linerboard, which is also known as lining linerboard when using 100% waste paper.

[0050] The different features described in the embodiments are not limited to the corresponding embodiments, but can be explicitly combined or interchanged with each other, as long as no contradiction arises. Similarly, the embodiments do not limit the scope of protection of the present invention. Possible combinations or partial combinations of the features described in the present invention should be considered within the scope of the present invention. Corresponding elements in the embodiments in the drawings are given the same reference numerals. Unless otherwise stated, the functions of these elements in the various figures correspond to each other and do not lead to contradictions. Therefore, repeated descriptions are omitted.

[0051] List of reference numerals

[0052] 1 Manufacturing facilities

[0053] 2 Waste paper flow

[0054] 2.1 Waste paper bales

[0055] 3. Preparation facilities

[0056] 4. Grading

[0057] 5 Short Fiber Stacking Tower

[0058] 5.1 Short Fiber Flow

[0059] 6 Long Fiber Stacking Tower

[0060] 6.1 Long Fiber Flow

[0061] 7. Thickening

[0062] 8. High-concentration pulping

[0063] 9. Material stacking and dilution

[0064] 10 Mixing tank

[0065] 11. Low-concentration pulping

[0066] 12. Slurry system

[0067] 13 Fresh fiber flow

[0068] 13.1 Fresh Fiber

[0069] 14. Preparation of Fresh Fiber

[0070] 15. Paper machine

[0071] 16 Drying Section

[0072] 17 Pre-drying section

[0073] 18 Post-drying section

[0074] 19. Gluing

[0075] 20 Drying drum

[0076] 20.1 Felt-free drying drum

[0077] 21 Drying screen suction roller

[0078] 22 Impact flow drying

[0079] 23 Non-contact deflection

[0080] 24 Corrugated cardboard

[0081] 25. The cardboard above.

[0082] 26. The cardboard below

[0083] 27 Corrugated paper

[0084] 28. Curved area

[0085] 29. Direction of travel of the sheath

Claims

1. Method for manufacturing a containerboard web from a fibre suspension, which fibre suspension is manufactured at least partly from waste paper as a fibre raw material, the method comprising the following steps: a. conveying waste paper to a preparation plant (3) to produce a waste paper stream (2); b. separating the waste paper stream (2) into a short fibre stream and a long fibre stream in a fractionation; c. conveying the short fibre stream to a short fibre stock tower and further to a mixing chest; d. conveying the long fibre stream to a long fibre stock tower; e. thickening the long fibre stream to a first material consistency after the long fibre stock tower; f. beating the long fibre stream having the first material consistency by high consistency beating; g. conveying the long fibre stream to the mixing chest; h. leading the fibre suspension from the mixing chest through a flow system to a paper machine to form a containerboard web in the direction of web travel; i. promoting shrinkage drying of the containerboard web differently in zones in the width in a drying section; j. winding up the containerboard web.

2. The method according to claim 1, characterized in that the drying in step i) is performed without mechanical stretching and / or mechanical shrinking of the containerboard web transversely to the direction of web travel of the paper machine.

3. The method according to claim 2, characterized in that the containerboard web is manufactured at a production speed of the paper machine greater than 1200 m / min.

4. The method according to claim 2, characterized in that the containerboard web is manufactured at a production speed of the paper machine greater than 1300 m / min.

5. The method according to claim 2, characterized in that the containerboard web is manufactured at a production speed of the paper machine greater than 1400 m / min.

6. The method according to any one of claims 1 to 5, characterized in that The boxboard web has a basis weight in the range of 60 g / m 2 to 300 g / m 2 .

7. The method according to any one of claims 1 to 5, characterized in that The boxboard web has a basis weight in the range of 70 g / m 2 to 160 g / m 2 .

8. The method according to any one of claims 1 to 5, characterized in that the waste paper has an ash content of 10 to 25 %.

9. The method according to claim 8, characterized in that The waste paper has a beating degree of between 0 and 50°SR.

10. The method according to claim 8, characterized in that the waste paper has a water retention capacity of between 95 to 130 %.

11. The method according to any one of claims 1 to 5, characterized in that the first material consistency is greater than 10 %.

12. The method according to any one of claims 1 to 5, characterized in that the first material consistency is greater than 15 %.

13. The method according to any one of claims 1 to 5, characterized in that the first material consistency is greater than 20 %.

14. The method according to any one of the preceding claims 1 to 5, characterized in that In the high consistency beating according to step f) an energy in the range between 80 kWh / t 长纤维 and 350 kWh / t 长纤维 is used.

15. The method according to any one of the preceding claims 1 to 5, characterized in that In the high consistency beating according to step f) an energy in the range of more than 150 kWh / t 长纤维 is used.

16. The method according to any one of the preceding claims 1 to 5, characterized in that after step f) 100 % of the long fibre stream or at least a part of the long fibre stream is diluted.

17. The method according to any of the preceding claims 1 to 5, characterized in that after step f) 100 % of the stream of long fibres or at least a part of the stream of long fibres is diluted and piled.

18. The method according to claim 16, characterized in that the stream of long fibres is diluted to a certain consistency and then subjected to low consistency beating.

19. The method according to claim 18, characterized in that the stream of long fibres is diluted to a consistency of less than 5 %.

20. The method according to any of the preceding claims 1 to 5, characterized in that in step h) the containerboard web is formed on at least one screen and the screen is shaken back and forth transversely to the web travel direction by means of a shaking device.

21. The method according to any of the preceding claims 1 to 5, characterized in that the drying section has a pre-drying section and a post-drying section and between them the containerboard web is glued on one or both sides.

22. The method according to claim 21, characterized in that the containerboard web is glued with starch.

23. The method according to claim 21, characterized in that immediately after gluing the containerboard web is deflected contactlessly and / or dried in the post-drying section by impingement flow drying.

24. The method according to claim 21, immediately after gluing dried in the post-drying section by impingement flow drying in cooperation with a feltless drying cylinder.

25. The method according to claim 24, characterized in that the impingement flow drying is profiled transversely to the web travel direction.

26. The method according to any of the preceding claims 1 to 5, characterized in that the drying section comprises single and double drying groups and the share of the number of drying cylinders of the double drying groups from the total number of drying cylinders is 10 to 70 %.

27. The method according to the preceding claim 26, characterized in that the share is 30 to 80 %.

28. The method according to the preceding claim 26, characterized in that the share is > 50 %.

29. The method according to any of the claims 1 to 5, characterized in that the fibre suspension is manufactured from more than 50 % of waste paper as fibre raw material.

30. The method according to any of the claims 1 to 5, characterized in that the fibre suspension is manufactured from more than 70 % of waste paper as fibre raw material.

31. The method according to any of the claims 1 to 5, characterized in that the fibre suspension is manufactured from more than 80 % of waste paper as fibre raw material.

32. The method according to any of the claims 1 to 5, characterized in that the fibre suspension is manufactured from more than 90 % of waste paper as fibre raw material.

33. The method according to any of the preceding claims 1 to 5, characterized in that the fibre suspension is manufactured from waste paper and fresh fibre pulp as fibre raw material.

34. The method according to claim 33, characterized in that the fresh fibre is selected from wood pulp, cellulose and fibres of annual plants.

35. The method according to any one of claims 1 to 5, characterized in that the fiber suspension is produced from 100% of waste paper as a fiber raw material.

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