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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/22—Addition to the formed paper
  • D21H23/70—Multistep processes; Apparatus for adding one or several substances in portions or in various ways to the paper, not covered by another single group of this main group
• • 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
  • D21F11/02—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type
  • D21F11/04—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type paper or board consisting on two or more layers
• • 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
  • D21H25/005—Mechanical treatment
• • 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
  • D21H27/30—Multi-ply
• • 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
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/16—Sizing or water-repelling agents
• • 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
  • D21H27/10—Packing paper

Definitions

• the invention relates to the management of a surface moisture level required for example in a finishing process for liquid packaging board by using two or more different adhesives for the treatment of various layers.
• One problem is that, in preparation for calendering, the paper surface should be enabled to absorb water for more effective calendering, and a sizing method generally applied in the process of making liquid packaging board practically blocks the absorption of water in paper surface. Therefore, it is difficult to achieve a good calendering result.
• the sizing of a central layer and/or a back layer is performed with a hydrophobic and fast-setting adhesive and the sizing of a topliner with an adhesive which is hydrophilic during its setting period, such that, during the process of surface wetting, the water sorption essentially occurs into the desired topliner only.
• the topliner is enabled to absorb water, and the hydrophobic sizing of the inner ply blocks the absorption of water deeper than the board surface.
• the strength is improved during a calendering process and the susceptibility to breaking is reduced, since only the surface is moist.
• the inventive method is used for example for making three-layer board, such that each layer emerges from its own wet end.
• the central layer pulp is admixed for example with a fast-setting resin adhesive and the topliners with a slow-curing AKD adhesive (alkylketyldimer).
• AKD adhesive alkylketyldimer
• the layers are pressed together and, at that point, the resin adhesive of the central layer has had time to set prior to wetting and has developed into a highly hydrophobic central layer in board.
• the AKD adhesive of the topliner is still undeveloped and hence hydrophilic.
• the adhesive for all layers is thus admixed within the pulp.
• Wetting can be preferably effected for example as a spray wetting.
• Surface sizing in general Surface sizing is usually effected in a paper machine in a film size press, which is positioned at such a distance on a dryer section that the paper will have a sufficient dryness to withstand the sizing process.
• a size press can be used for applying a starch solution, CMC, an adhesive or other chemicals to the surface of paper. Even fillers can be admixed in the solution. Coating with these substances, as opposed to admixing within the pulp, results in a total retention and a dense material layer for web surfaces. Thus, surface strength is improved and dusting is reduced. Paper or board will have more strength and smoothness, and the subsequent coating will be more successful.
• Surface sizing is used for fine papers, coating raw stock, and board.
• a web surface is supplied with a mixed adhesive (e.g. starch or AKD) by using a film size press.
• a mixed adhesive e.g. starch or AKD
• a function of the adhesive is to bond raw materials contained in the web with itself.
• starch the adhesive qualities of starch are based on its basic structure, on numerous OH groups contained in glucose units and capable of forming hydrogen bonds. In solution, the hydrogen bonds form between water molecules and starch.
• the starch functions as an adhesive.
• insoluble adhesives for example resin adhesives, ASA (alkylsuccinic anhydride), or AKD adhesives.
• the moisture of paper downstream of a size press is 40-50%, its strength being seriously impaired and its susceptibility to breaking being increased.
• the prior used size presses are currently replaced with sizing equipment making use of a film transfer method.
• the film size press is used to apply no more than the exactly desired amount of adhesive with applicator devices for a thin film on roll surfaces, and the rolls are used to transfer the adhesive to paper.
• the sizing is performed two or even more times. After the sizing of inner layers, the board no longer becomes soaked through, which is why it has a high wet strength in the calendering process.
• Coating is used for improving the printing qualities of paper and board - primarily smoothness, gloss and brightness.
• properties of base paper are also crucial for those of coated papers and boards.
• Finishing methods for paper and board can be divided according to the amount of a material transferring to the surface and the composition of a finishing or glazing agent in three different methods, surface sizing, pigmenting, and coating.
• a coating paste which contains pigment (e.g. kaolin, talc, carbonate) and a binder (e.g. starch, latexes).
• Paste is spread, i.e. applied, to the surface of paper or board in excess.
• the coating amount is adjusted as desired by removing excess paste.
• the coating is still dried.
• Printing quality can be improved by coating paper or board several times. High-grade printing papers can be coated up to three times.
• Surface adhesive does not contain any pigment at all, and only a very small amount (1,0-2,0 g/m 2 ) of coating transfers to the surface of paper or board in the pigmenting process.
• the most common coating method is blade coating in its various forms.
• the coating can also be effected e.g. with a rod coater, a film transfer coater, and an air brush coater.
• Pigment coating can be performed at the mill either with a paper or board machine (on-machine coating) or with a separate coating machine (off- machine coating).
• Stuff sizing is effected by admixing adhesive in wet-end pulp.
• the web will be sized throughout its thickness.
• the sizing of a topliner and the sizing of a central layer are thus performed by joining for example three layers together, the central position being occupied by a fast drying layer which is hydrophobic after drying.
• the surface layers are sized with a hydrophilic adhesive, which is uncured during wetting and calendering.
• the inventive method can naturally be also used for making just a one-sided surface layer. In this case, the reverse side is hydrophobic during wetting.
• the inventive method enables an improvement of calendering and coating properties and an improvement of runnability by virtue of reduced susceptability to breaking.
• the surface is quickly absorbed with water, and the water-soluble coating layers have a high adhesion.
• wetting is almost nonexistent with regard to the already cured base and/or back element sized with a quick-setting adhesive and, thus, it retains a high strength despite wetting.
• a web emerging from the dryer section of a board machine is not applicable as such to its ultimate application, but it requires further treatment.
• the most common further treatment is calendering. Calendering is performed by passing the web through a nip system established by two or more rolls. Board can be calendered:
• Calendering could be said to have three principal functions:
• Machine calendering The type of calendering effected on a board machine immediately after drying is referred to as machine calendering.
• machine calendering the web is passed through one or more nips established by hard-surfaced cast iron or steel rolls.
• the board machine can be provided with an intermediate calender. It is located on the dryer section, generally upstream of the final dryer group.
• the intermediate calender includes a single hard nip.
• Soft calender refers to a mechanism, wherein at least one of the rolls establishing a nip is an elastic, polymer-coated roll, and each nip is separately loaded. Indeed, soft calenders are mostly on-line machines, i.e. integrally built in a paper, board or coating machine. The number of nips in soft calenders ranges from one to four.
• Long nip calendering is based on the utilization of very soft coating belts and shoe press technology. Long nip calendering is particularly applicable to board calendering, wherein saving of bulk is especially important.
• one of the rolls is a so-called shoe roll or belt solution and the other is a thermal roll.
• the width of a nip does not depend on loading or roll diameters, but it is constant. This enables the optimization of a nip time and a nip pressure regardless of each other. Background of the invention, general information regarding manufacture of liquid packaging boards
• Liquid packaging boards are sized with wet strength adhesives for limiting the liquid absorption thereof.
• the sizing is effected with ASA, AK13, and resin adhesives, as well as combinations thereof.
• ASA and resin sizing develop to an almost full strength as early as on the dryer section of a paper machine.
• paper reaches a full sizing degree at the end of a dryer section.
• the product's water sorption potential falls substantially.
• AKD sizing does not develop fully until a few days after the manufacture of paper. Downstream of the dryer section, paper is practically unsized, and its water sorption can be at the level of 200Cobb.
• the inventive procedure is used to block the penetration of water deeper than the topliner of liquid packaging board.
• the central and back layers of board are sized with ASA or ASA-resin sizing.
• the adhesive can be admixed in pulps at the initial stage of manufacture.
• the central and back layers are totally hydrophobic during a surface wetting process.
• the board surface is sized with AKD (or some other corresponding stuff sizing agent of the type AK13 and/or a derivative thereof).
• AKD or some other corresponding stuff sizing agent of the type AK13 and/or a derivative thereof.
• the topliner will be hydrophilic during a surface wetting process.
• the topliner absorbs water very quickly.
• the topliner has its saturation degree rising, yet water is not able to penetrate deeper than the above-mentioned top layer.
• the inventive method enables the use of lower pressures, it is respectively possible, by virtue of smaller masses in the machine and improved management thereof, to increase the machine speed, while improving the quality of resulting board.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=8562520

Family Applications (1)

Country Status (5)

Families Citing this family (1)

Family Cites Families (13)

• 2001
  • 2001-12-19 FI FI20012511A patent/FI117761B/sv active IP Right Grant
• 2002
  • 2002-12-13 WO PCT/FI2002/001021 patent/WO2003052204A1/en not_active Application Discontinuation
  • 2002-12-13 EP EP02785476A patent/EP1458931A1/en not_active Withdrawn
  • 2002-12-13 AU AU2002350781A patent/AU2002350781A1/en not_active Abandoned
  • 2002-12-13 US US10/497,345 patent/US20050072541A1/en not_active Abandoned

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events