WO2023214114A1 - Augmenter le rétrécissement et l'extensibilité dans le sens travers d'un produit fibreux - Google Patents

Augmenter le rétrécissement et l'extensibilité dans le sens travers d'un produit fibreux Download PDF

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Publication number
WO2023214114A1
WO2023214114A1 PCT/FI2023/050231 FI2023050231W WO2023214114A1 WO 2023214114 A1 WO2023214114 A1 WO 2023214114A1 FI 2023050231 W FI2023050231 W FI 2023050231W WO 2023214114 A1 WO2023214114 A1 WO 2023214114A1
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WO
WIPO (PCT)
Prior art keywords
web
drying
pattern
fiber
wet
Prior art date
Application number
PCT/FI2023/050231
Other languages
English (en)
Inventor
Elias Retulainen
Jarmo Kouko
Original Assignee
Teknologian Tutkimuskeskus Vtt Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Teknologian Tutkimuskeskus Vtt Oy filed Critical Teknologian Tutkimuskeskus Vtt Oy
Publication of WO2023214114A1 publication Critical patent/WO2023214114A1/fr

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H5/00—Special paper or cardboard not otherwise provided for
    • D21H5/24—Special paper or cardboard not otherwise provided for having enhanced flexibility or extensibility produced by mechanical treatment of the unfinished paper
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
    • D21F11/12—Making corrugated paper or board
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/02—Patterned paper

Definitions

  • the present invention concerns a method for modifying a fiber network of a fiber web in order to increase the drying shrinkage as well as boost especially the crossmachine direction (CD) extensibility of the fiber web product.
  • the invention also concerns the fiber product thus produced.
  • Packaging materials are constantly being developed, and one major aim is to further reduce the amount of plastics used in this packaging. This typically requires an increase in the amount of cellulose-based materials in said packaging.
  • CD extensibility has also been mentioned in the past, e.g. in US 3220116 A, where an attempt has been made towards improving the CD extensibility via drying the web without restrictive forces after it has been contracted using bowed Mont Hope type of rolls. This is said to cause natural contraction of the web, thus increasing its CD extensibility. However, this contraction takes place through reducing the width of the web, which will change the web dimensions, and will not provide any significant MD extensibility.
  • a method for modifying the fiber network of a fiber web to increase the extensibility of the web in either the machine direction (MD) or in the cross-machine direction (CD), or in both directions.
  • a method involving processing the web before drying, and then allowing the web to shrink under low restraint during the evaporative drying.
  • a method which involves imposing a three-dimensional pattern in the wet fiber web.
  • a fiber product manufactured according to the method of the invention, having an improved extensibility at least in the CD direction, preferably achieved in part via an increased drying shrinkage.
  • the present invention is based on imposing a selected pattern, such as a wavy or corrugated pattern, into a wet fibrous web, such as a paper or board web, and allowing the web to shrink under low restraint during evaporative drying.
  • a selected pattern such as a wavy or corrugated pattern
  • Forming the pattern on a wet web causes local elongations in the web, without affecting the length or width dimensions of the web.
  • the imposed pattern increases the extensibility of the web and also facilitates an advantageous drying shrinkage.
  • the invention thus results in an increase of the extensibility in either the MD or CD directions, or both, due to the imposed pattern, combined with the increased drying shrinkage, particularly in the CD direction.
  • An improved extensibility can be achieved via three different routes, i.e. improving the extensibility behaviour of the wet fiber network before processing, imposing a pattern on the web, and allowing drying shrinkage. Since the pattern has been formed in the wet web, it is achieved through the wet elongation of the web instead of a change in the web dimensions, and during the evaporative drying the pattern can be steepened or flattened. In other words, the pattern reduces the resistance against shrinkage.
  • the corrugations can be crushed or smoothed out, e.g. by any known procedure that increases the MD extensibility, or by crushing. Flattening the pattern will not remove all the achieved benefits, but since the optional crushing of the corrugations will reduce the drying shrinkage, the aim is typically a compromise between the highly extensible corrugated sheet and the flattened planar sheet.
  • FIGURE 1 is a drawing of the corrugation of a sheet in accordance with at least some embodiments of the present invention, also showing exemplary dimensions of the corrugations.
  • FIGURE 2 is a graph showing the tensile strength of various corrugated paper sheets, when the corrugations have been made and crushed at a selected solids contents.
  • FIGURE 3 is a graph showing the drying shrinkage of various corrugated paper sheets, when the corrugations have been made and crushed at a selected solids contents.
  • FIGURE 4 is a graph showing the strain at break of various corrugated paper sheets, when the corrugations have been made and crushed at a selected solids contents.
  • FIGURE 5 is a graph showing the strain at break of various wet corrugated paper sheets, as a function of the shrinkage.
  • the term “extensibility” is used to describe the important characteristic of fibrous products, such as paper or board products, that can be defined as the ability of the fibrous product to increase its linear length upon deformations due to external mechanical forces.
  • the extensibility of the fibrous product is affected, among others, by fiber morphology, interfiber bonding, the structure of the fiber network, drying shrinkage and the straining conditions of the fibrous web.
  • MD extensibility refers to the machine direction extensibility
  • CD extensibility is used to describe the crossmachine direction extensibility.
  • drying shrinkage is intended to define the amount of in-plane shrinkage or contraction that takes place in a sheet or web due to the removal of water from the structure and especially from the swollen wet fibers. It is based on the shrinkage of fibers that takes place almost solely in the transverse direction. The transverse shrinkage of fibers is transmitted to other fibers at the inter- fibre joints. This results also in web shrinkage, but due to the direction, it takes place without affecting the width of the web.
  • the present invention thus relates to a method of modifying a fiber network of a fiber web, including the steps of imposing a three-dimensional pattern in the wet fiber web, e.g. as shown in Fig. 1, and drying the web while allowing it to shrink without major restraints.
  • the invention is particularly characterized by imposing the pattern on the web in the forming section or after the forming section before evaporative drying, while known procedures work on webs that have already undergone some drying or in addition to drying are going through a MD compaction process, thus resulting in an improved MD extensibility, but not affecting the CD extensibility to any considerable level. Due to the pattern on the web being formed while the web is still wet, the pattern of the present invention is achieved through the wet elongation of the web, thereby not affecting its dimensions.
  • the pattern is imposed using wet press rolls, dandy roll or couch roll.
  • the pattern is imposed in the early areas of the drying section, by pressing the web against a patterned drying roll.
  • the pulp used in the web is typically mechanical, chemi-mechanical, thermochemimechanical, semi-chemical or chemical pulp, either bleached or unbleached, from softwood, hardwood or non-wood origin, from either virgin or recycled sources, or their mixture, preferably chemical pulp of softwood origin.
  • the pulp is used in forming a web, preferably with a basis weight of >100g/m 2 , such as 120-250 g/m 2 .
  • An advantageous alternative is to use refined pulp, since unrefined pulp typically results in low strength values and poor elongation at break. Since the patterning requires wet elongation, either low consistency (LC) refined pulp or high consistency (HC) treated pulp can thus be used, or preferably a pulp treated using combination of both methods.
  • LC low consistency
  • HC high consistency
  • HC treated pulps are used for their advantageous effect on the wet elongation values.
  • the wet elongation values are typically >10% for these HC and LC treated pulps, while the drainage resistance values remains on low level (SR number below 30, or CSF values above 400 ml).
  • the shrinkage resistance is important for similar reasons as the drying shrinkage. The latter (the drying shrinkage) is resisted by the straightness and stiffness of fibers, which is avoided by HC and LC refining of fibers and wet patterning of the web, i.e. the patterning increases the drying shrinkage by reducing the shrinkage resistance.
  • the shrinkage resistance is additionally reduced by reducing the flatness and buckling resistance of the structure, which is, also, achieved with the help of the patterning.
  • the fiber web has thus been formed from a fiber pulp that has been mechanically pre-treated by one or more steps selected from high- consistency refining, kneading or other high consistency treatment, or middle or low- consistency refining, the pre-treatment steps preferably containing at least one high- consistency treatment step that induces fiber deformations, such as curl, kinks, dislocations or microcompressions.
  • the three-dimensional pattern of the invention is imposed on the web for example by moulding, preferably by pressing the web between two surfaces of which one or both surfaces are shaped, such as forming or wet pressing fabrics, belts or wet pressing rolls on a paper machine, or their combination.
  • the optional smooth surface of the belt or roll may for example be made of an elastic material that flexes with the pattern.
  • the pattern can be a machine-direction (MD) corrugation of the web, or another similar pattern that provides waves and ridges in the web, particularly in the machine-direction.
  • the pattern can be formed of wave-shaped corrugations or of a folded pattern.
  • the pattern is formed of wave-shaped smooth corrugations having a flute height of about 0.7mm and a wave length of 2-4mm, such as about 2.7mm.
  • the dimensions of the pattern are adjusted to be sufficient to cause local buckling of the web or fibers, so that they no longer prevent the drying shrinkage.
  • the dry matter content of the web during the formation of the pattern is 20-60% by weight, or even 10-60% by weight Preferred contents are 35-50% by weight, while even a content as low as 20-40% by weight can be considered advantageous, since it provides the highest wet elongation.
  • the lower end of the range, i.e. 20-30% by weight, is particularly suitable for formation of the pattern on the forming wire.
  • one or more chemical pre-treatment steps can be carried out, e.g. by addition of said one or more chemicals to the pulp suspension, or by applying them on or impregnating them in the wet web, or applying them as mixtures of multilayers, or as cellulose solvents, the chemicals being selected from natural or modified polymeric materials with or without cross-linking agents, like micro- or nanofibrillated cellulose material, hemicellulose or cellulose, carboxymethylated cellulose, dialcohol cellulose, starch, xyloglucan, alginate, gelatin, agar, chitosan, guargum, polyamideamine epichlorohydrin (PAE), polyurethane, polylactic acid (PLA), polyvinylacetate (PVAc), polyvinylamine (PVAm), polyethyleneimine (PEI), or polyacrylamide (PAM), preferred chemicals being cellulose microfibrils or nanofibrils (CMF, CNF
  • the drying step of the method is carried out as an evaporative drying in an unrestrained manner, i.e. while avoiding shrinkage restraints, particularly in the cross machine direction. This will facilitate shrinkage. Shrinkage can, however, also be facilitated further by using chemicals or rollers, or by utilizing stretching in transverse direction. Such a stretching will decrease the MD extensibility, but may increase the CD shrinkage.
  • the evaporative drying is achieved by cylinder drying, impingement drying, or air flotation drying, preferably until a solids content of >80% by weight is achieved, more preferably a solids content of >90%.
  • the drying-induced shrinkage is boosted using contracting rollers.
  • the drying shrinkage is boosted using water-soluble or water-swelling chemicals, that have low gel point such as water-soluble or waterswelling natural or modified polymeric materials with or without cross-linking agents, like micro- or nanofibrillated cellulose material, hemicellulose or cellulose, carboxymethylated cellulose, dialcohol cellulose, starch, xyloglucan, alginate, gelatin, agar, chitosan or guargum.
  • water-soluble or water-swelling chemicals that have low gel point such as water-soluble or waterswelling natural or modified polymeric materials with or without cross-linking agents, like micro- or nanofibrillated cellulose material, hemicellulose or cellulose, carboxymethylated cellulose, dialcohol cellulose, starch, xyloglucan, alginate, gelatin, agar, chitosan or guargum.
  • drying shrinkage is a type of web shrinkage which, conventionally, is restricted by the axial stiffness of fibers, but this stiffness can, as described above, be reduced by HC and LC refining. Additionally, web shrinkage is, conventionally, restricted by the flatness and bending stiffness of the web. However, as described above, this stiffness is effectively reduced by the pattern imposed on the web.
  • the dried web can be used as such, or the formed pattern can be smoothed out.
  • the corrugations are typically smoothed out at least partly during the elongation of the web e.g. in 3D moulding.
  • smoothening of a non-strained web, to obtain a planar web can be achieved e.g. by crushing.
  • the crushing can, in turn, take place by using a machine-direction (MD) compacting step, or the crushing step is combined with a machine-direction (MD) compacting step, said MD compacting step preferably being a step, wherein the fiber web is placed in contact with a contracting surface, such as in the Clupak or Expanda process.
  • MD machine-direction
  • MD machine-direction
  • the smoothing step can take place before drying, during drying or after drying. However, it is preferred to smooth out the pattern when the web has a dry matter content of 55-95% by weight, more preferably 65-75% by weight.
  • the smoothing step maintains the advantages achieved by elongation, thus also maintaining the extensibility potential.
  • the smoothing of the pattern reduces the drying shrinkage, a suitable compromise is required between obtaining a smooth product surface and obtaining a particularly advantageous extensibility.
  • Example 1 Preparing corrugated and optionally crushed paper sheets
  • wet paper sheets of 140 g/m 2 were prepared from pulp refined first at high consistency (HC) and then at low consistency (LC). The sheets were wet pressed to a solids content of about 50%. Some sheets were also moisturized to lower solids contents of 30% and 40%. The sheets had a wet strain at break of 10.4%, while the strain at break of wet sheets made of LC refined pulp is typically 2-4%.
  • Example 1 The sheets prepared in Example 1 were tested for their tensile strength, their drying shrinkage and their strain at break.
  • the applied corrugating and crushing did not essentially weaken the paper sheets, as shown in Fig. 2.
  • the weakest paper was the corrugated, freely dried sheet, which had a tensile index of 41 Nm/g.
  • the amount of drying shrinkage of the sheets is shown in Fig. 3.
  • the shrinkage varied from 5% to 16% in a freely dried sheet.
  • a reference sheet without corrugations was found to shrink 7.3%.
  • the corrugations thus increased the drying shrinkage considerably.
  • crushing the corrugations again decreased the drying shrinkage.
  • the results do also indicate that a higher solids content during crushing resulted in a higher drying shrinkage, and that a lower solids content during the corrugation resulted in a higher drying shrinkage.
  • the optimal alternative is to use a low solids content during the corrugating and a high solids content during the crushing.
  • strain at break values are shown in Fig. 4. Generally, these results are explained by the preceding results for the drying shrinkage and the imposed corrugation pattern. Also here the low solids content during corrugation and a high solids content during crushing was found to be beneficial.
  • the present method can be used to prepare cellulose-based fiber products having an increased potential in replacing plastics in packaging products.
  • the prepared material is useful in increasing the CD extensibility in such cellulose-based materials.

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  • Paper (AREA)

Abstract

La présente invention concerne un procédé de modification d'un réseau de fibres d'une bande de fibres, typiquement constituée d'une pâte à papier à base de cellulose, afin d'augmenter le rétrécissement au séchage ainsi que d'augmenter l'extensibilité dans le sens travers (CD) du produit fibreux ainsi préparé. Le procédé comprend les étapes consistant à imposer un motif tridimensionnel dans la bande de fibres humides, et à sécher la bande à l'aide d'un séchage par évaporation tout en permettant à la bande de rétrécir sans contraintes importantes. Le motif est imposé sur la bande dans la section de formation ou après la section de formation, avant le séchage par évaporation, tout en utilisant l'allongement humide de la bande pour les formes du motif, ce qui n'affecte pas la largeur de la bande humide. L'invention concerne également le produit fibreux formé présentant une extensibilité CD accrue.
PCT/FI2023/050231 2022-05-02 2023-04-27 Augmenter le rétrécissement et l'extensibilité dans le sens travers d'un produit fibreux WO2023214114A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20225377 2022-05-02
FI20225377A FI20225377A1 (en) 2022-05-02 2022-05-02 To enhance transverse shrinkage and extensibility of a fiber product

Publications (1)

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WO2023214114A1 true WO2023214114A1 (fr) 2023-11-09

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3220116A (en) 1962-10-02 1965-11-30 Clupak Inc Increasing cross machine direction extensibility of paper webs
US3630837A (en) 1969-02-17 1971-12-28 Clupak Inc Compacting apparatus for fibrous webs
EP1047837A1 (fr) * 1997-12-22 2000-11-02 Kimberly-Clark Worldwide, Inc. Feuille de papier a etirabilite accrue en sens transversal
US20060090867A1 (en) * 2004-11-02 2006-05-04 Hermans Michael A Paper manufacturing process
US20170274616A1 (en) * 2016-03-22 2017-09-28 Scorrboard, Llc System and method for inducing fluting in a paper product by embossing with respect to machine direction

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3220116A (en) 1962-10-02 1965-11-30 Clupak Inc Increasing cross machine direction extensibility of paper webs
US3630837A (en) 1969-02-17 1971-12-28 Clupak Inc Compacting apparatus for fibrous webs
EP1047837A1 (fr) * 1997-12-22 2000-11-02 Kimberly-Clark Worldwide, Inc. Feuille de papier a etirabilite accrue en sens transversal
US20060090867A1 (en) * 2004-11-02 2006-05-04 Hermans Michael A Paper manufacturing process
US20170274616A1 (en) * 2016-03-22 2017-09-28 Scorrboard, Llc System and method for inducing fluting in a paper product by embossing with respect to machine direction

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Publication number Publication date
FI20225377A1 (en) 2023-11-03

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