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
  • D21H23/46—Pouring or allowing the fluid to flow in a continuous stream on to the surface, the entire stream being carried away by the paper
  • D21H23/48—Curtain coaters
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/74—Applying photosensitive compositions to the base; Drying processes therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
  • B05C5/007—Slide-hopper coaters, i.e. apparatus in which the liquid or other fluent material flows freely on an inclined surface before contacting the work
  • B05C5/008—Slide-hopper curtain coaters

Definitions

• the present invention relates to a supporting arrangement in the curtain coating of a paper/board web, wherein a web to be coated is conveyed through a curtain coating station, at which a coating curtain flowing down from an application device proceeds onto the web surface to form a single- or multilayer coating thereon.
• curtain coaters can be categorized in slot-fed and slide-fed coaters.
• a coating is fed by means of a nozzle assembly onto an inclined plane, the coating flowing down towards an edge of the plane constituting a feeding lip, the curtain forming as the coating falls off the feeding lip.
• a coating is pumped by way of a distribution chamber into a narrow vertical slot, the curtain forming at its lip and falling onto a web.
• a coating can be applied in one or more layers.
• the resulting curtain is maintained at a desired width by means of an edge guide which, as suggested by its name, is located along the edge of a feeding slot/feeding lip.
• a multitude of various grades of paper and board are in existence and can be sorted by basis weight in two classes: papers of a single ply and with a basis weight of 25-300 g/m 2 and boards made in multiply technique and with a basis weight of 150-600 g/m 2 .
• papers of a single ply and with a basis weight of 25-300 g/m 2 and boards made in multiply technique and with a basis weight of 150-600 g/m 2 there is a floating line between paper and board, since boards of the lightest basis weight are lighter than the heaviest papers.
• paper is used for printing and board for packaging. Papers and boards can be coated or uncoated.
• Coated magazine paper contains mechanical pulp at 40-60%, bleached softwood pulp at 25-40% and fillers and coatings at 20-35%.
• General values for LWC-paper can considered as follows: basis weight 40-70 g/m 2 , Hunter gloss 50-65%, PPS SlO roughness 0.8-1.5 ⁇ m (offset) and 0.6-1.0 ⁇ m (roto), density 1100-1250 kg/m 3 , brightness 70-75% and opacity 89-94%.
• MFC-paper machine finished coated
• basis weight 50-70 g/m 2 Hunter gloss 25-70%
• PPS SlO roughness 2.2-2.8 ⁇ m PPS SlO roughness 2.2-2.8 ⁇ m
• density 900-950 kg/m 3 brightness 70-75%
• opacity 91-95%
• FCO-paper film coated offset
• basis weight 40-70 g/m 2 Basis weight 40-70 g/m 2
• Hunter gloss 45-55% PPS SlO roughness 1.5-2.0 ⁇ m
• density 1000-1050 kg/m 3 brightness 70-75%
• opacity 91- 95% opacity 91- 95%.
• MWC-paper medium weight coated
• basis weight 70-90 g/m 2 Basis weight 70-90 g/m 2
• Hunter gloss 65-75% PPS SlO roughness 0.6-1.0 ⁇ m
• density 1150-1250 kg/m 3 brightness 70-75%
• opacity 89- 94% opacity 89- 94%.
• HWC heavy weight coated
• HWC has a basis weight of 100-135 g/m 2 and can be coated even more than twice.
• coated pulp-based woodfree printing papers or fine papers the amounts of coating vary to a great extent according to demands and intended use.
• Coated boards make up quite a heterogeneous group, including high-basis weight grades with a basis weight as high as 500 g/m 2 and low-basis weight grades with a basis weight of about 120 g/m 2 , the grades ranging from those based on primary fiber to those based by 100% on recycled fiber and from uncoated ones to those with multiple coating.
• Curtain coating is suitable for making basically all the above-mentioned coatable grades. Curtain coating does not provide a smoothness equal to what is achieved by blade coating, but it is better than blade coating in terms of coverage.
• One problem in curtain coating is to provide a support for the web within a coating curtain impact zone for providing the web with a coating layer which is as consistent as possible in terms of quality.
• the web support over the course of a coating process has been typically implemented in two different techniques: the support is provided in line with a coating curtain impact point or the web is provided with a support by means of supporting elements placed on either side of the impact point.
• the employed supporting element is obviously a roll.
• a wide and/or high-speed web calls for the use of a large-diameter roll, which is a bulky solution.
• a large rotating roll brings along lots of air to the application zone and the angle adjustment of an impact point is not possible in practice.
• the air supplied by the rolls is not usually a major problem, but in certain situations the web vibration may become a problem.
• this solution is likewise bulky.
• a supporting arrangement of the invention is characterized in that the arrangement comprises supporting elements placed under a web to be coated, including a relatively small-diameter backing roll downstream of the impact point and a bearing element, which is equipped with a sliding surface and located upstream of the roll and which is adjustable for supporting the web optionally either upstream of the impact point, whereby the coating is effected on an unsupported web, or in line with the impact point, whereby the coating is effected on a supported web.
• the inventive solution enables performing the coating either on a supported web or on an unsupported web, as desired. Further benefits of the solution include a compact size and elimination of vibrations resulting from the use of large rolls, as well as less powerful air flows in the vicinity of a coating curtain. In the event of web breaks, the web is not able to stuff itself between the sliding surface and a boundary air remover, which can easily happen when using a roll.
• the backing roll position is preferably adapted to be adjustable in such a way that the impact angle of a curtain relative to the web is variable by shifting the roll's position.
• the sliding surface has its tip preferably adapted to be adjustable to various angular positions, whereby, when coating is effected on a supported web, the impact angle can be varied by modifying the tip's angular position and, if necessary, also by repositioning the roll.
• Fig. 1 shows schematically one embodiment of the invention with the coating effected on a supported web.
• Fig. 1 illustrates one embodiment of the invention, in which a coating curtain 3 flowing down from a nozzle assembly's 1 feeding lip 2 is adapted to strike on the surface of a web W at a location in which the web lies on top of a supporting surface.
• Reference numeral 4 represents an arrangement for removing boundary air carried along with the web W.
• the inventive web supporting arrangement comprises a relatively small- diameter roll 6, which is adapted to support the web W downstream of an impact point 12.
• the roll 6 is adapted to be set at various positions, thus allowing, for example, the modification of an impact angle between the web W and the coating curtain 3.
• the supporting arrangement additionally comprises an adjustable bearing element designated by reference numeral 5, which is mounted on a beam member 11 extending in a cross-web direction.
• the bearing element 5 is provided with sliding means 7, 8 and is pivotable by means of the beam 11 for displacing the sliding means 7, 8 in the direction indicated by an arrow 13.
• the sliding means 7, 8 are preferably designed for an arcuate exterior as regards the sliding surfaces thereof in contact with the underside of the web.
• the sliding means When viewed in the web proceeding direction, the sliding means may also consist of a single-piece block or more than two pieces.
• a tip portion 8 is preferably adapted to pivot as indicated by an arrow 12 for altering the proceeding direction of the web W in view of modifying an impact angle between the web and the coating curtain as desired.
• the roll 6 can also be shifted as called for by the required adjustment of an impact angle.
• a fluid lubrication for example by means of air or another gas, for reducing friction and/or impeding web dusting.
• the sliding surface is preferably designed for low friction and/or wear resistance by using a friction reducing and/or wear resistance enhancing coating or surface treatment or by using a wear resistant material, such as e.g. a ceramic material or stainless steel, for making a sliding-surface containing sliding element or a section thereof.
• the sliding element may consist of a base member made e.g. in stainless steel, having integrated therewith a sliding-surface containing element of a wear resistant material.
• the sliding means have the tip portion 8 thereof adapted to pivot about a fulcrum 9, e.g. by means of a spring-loaded adjustment element 10 shown in the illustrated embodiment. This spring-loaded adjustment element allows the tip portion 8 to flex as necessary, e.g. in response to shocks caused by possible web breaks.
• the distance of the sliding means 7, 8 relative to the boundary air removing equipment 4 is preferably adapted to be adjustable, such that a gap between the coatable web and the boundary air removing equipment can be adjusted to a desired size.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Paper (AREA)
• Coating Apparatus (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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Citations (4)

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• 2005
  • 2005-01-27 FI FI20055040A patent/FI117175B/fi not_active IP Right Cessation
  • 2005-12-02 JP JP2007549921A patent/JP4677456B2/ja active Active
  • 2005-12-02 WO PCT/FI2005/050444 patent/WO2006079679A1/en active Application Filing
  • 2005-12-02 EP EP05813209A patent/EP1841917B1/en active Active

Patent Citations (4)

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