WO2007110474A1 - procédé et configuration permettant de contrôler le poids de revêtement pour enduire une feuille continue - Google Patents

procédé et configuration permettant de contrôler le poids de revêtement pour enduire une feuille continue Download PDF

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Publication number
WO2007110474A1
WO2007110474A1 PCT/FI2007/050154 FI2007050154W WO2007110474A1 WO 2007110474 A1 WO2007110474 A1 WO 2007110474A1 FI 2007050154 W FI2007050154 W FI 2007050154W WO 2007110474 A1 WO2007110474 A1 WO 2007110474A1
Authority
WO
WIPO (PCT)
Prior art keywords
coating material
coat weight
web
moving substrate
coating
Prior art date
Application number
PCT/FI2007/050154
Other languages
English (en)
Inventor
Tapio Anttila
Olli Niemi
Tarmo Sulopuisto
Aleksi Sipilä
Original Assignee
Metso Paper, Inc.
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 Metso Paper, Inc. filed Critical Metso Paper, Inc.
Publication of WO2007110474A1 publication Critical patent/WO2007110474A1/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
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/78—Controlling or regulating not limited to any particular process or apparatus
    • 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
    • D21H19/00—Coated paper; Coating material
    • D21H19/80—Paper comprising more than one coating
    • D21H19/82—Paper comprising more than one coating superposed
    • 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
    • D21H19/00—Coated paper; Coating material
    • D21H19/80—Paper comprising more than one coating
    • D21H19/84—Paper comprising more than one coating on both sides of the substrate
    • 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
    • D21H23/52—Addition to the formed paper by contacting paper with a device carrying the material
    • D21H23/56—Rolls

Definitions

  • the invention relates to a method for controlling machine-directional coat weight in two-sided or double coating of a paper or board web according to the preamble of claim 1.
  • the invention also relates to an arrangement for implementing such a method.
  • either direct or indirect application can be used.
  • di- rect application coating material is spread on the web as it moves past an application area on the surface of a counter roll.
  • indirect application coating material is first spread on a film-transfer roll or other transfer surface from which it is transferred onto the web in a coating nip.
  • Coating material is often applied excessively and the amount of coating that remains on the moving substrate is adjusted, i.e. coating is metered by means of a doctoring element.
  • the doctoring element can be used a doctor blade or a rotating doctor rod, which is pressed against the moving substrate.
  • the load of the doctoring element is provided by means of loading hoses operating with pressure medium or mechanical force driving the doctoring element.
  • Coat weight which means the dry content of coating colour on paper as grams per square metre, is an important measure when evaluating the coating result.
  • the profile of the coating layer is most usually adjusted by changing the load of the doctoring element, hi the cross-direction of the web, the profile of the coating layer is adjusted by changing the load of the doctoring element locally at those points in which there is too much or too little of coating.
  • a prerequisite of the profile control in both machine- and cross-direction is the accurate measurement of coat weight.
  • measuring coat weight is usually used a measuring frame which has a carriage moving over the whole width of the paper web and being provided with sensors.
  • the machine-directional profile of coat weight is controlled by changing the pressure in the pressure-medium hoses which are arranged to press the doctoring element against the moving substrate.
  • the usable adjustment area of the hose pressure is fairly narrow, typically 0.8-2.5 bar. Outside this area, coat weight cannot nowadays be controlled by automatic control. Too low a loading pressure causes runnability problems and too high a pressure speeds up the wear and tear of the doctoring element.
  • the loading pressure of the doctoring element also affects the response of the control of the cross profile of coat weight. A considerable problem is that the pressure of the loading hose very easily drifts away from the optimal operating range.
  • the measurement of coat weight is based on measuring the dry weight of the web before the coating head and after the coating head. In two-sided coating, this way the total coat weight is discovered but not the coat weights applied on different sides of the web. Also in multi-layer coating, there can occur situations in which the coat weight cannot be measured between two successive coating occasions.
  • Controlling the unequal sidedness of coat weight is important also in those ma- chines which have no two-sided measurement of coat weight. Such machines are a great majority of coating machines. Today in these cases, one has to content with solely the control of the total coat weight. Then, coat weight is adjusted by changing the loading pressure of both doctoring elements for the same amount without the knowledge of on which side of the coated web the coat weight devi- ates from the target value.
  • the object of the invention is a control method that gives an opportunity to control the unequal sidedness of coat weight better than before.
  • the idea of the invention is that the total coat weight is still adjusted by changing the loading pressure of both doctoring elements, but simultaneously the unequal sidedness of coating weights is corrected by a separate controller which is ar- ranged to transfer loading pressure from one doctoring element to the other, as required.
  • the controller calculates changes, which are different of their sign but equal of their absolute value, for the loading pressure of each doctoring element. Consequently, this coat weight ratio adjuster will not affect the total coat weight but only how the coat weight is divided onto different sides of the web or, in multi-layer coating, onto layers being applied one upon the other.
  • the consumption of coating material in each application device is measured by means of a measuring device in the machine circulation. Based on mass or volume flow, the consumption of coating material can be calculated on a long period of time extremely accurately.
  • the coat weight can be calculated of the consumption of coating material by means of equation (1):
  • CW m is calculated coat weight
  • Q consumption of coating material
  • d web width
  • v web speed
  • SC dry content of coating material
  • the ratio of coat weights applied on different sides of the web is calculated.
  • the coat weights on the bottom and top surface of the web can be calculated by means of equations (2) and (3):
  • CW mb is calculated coat weight on the bottom side of the web
  • CW m t is calculated coat weight on the top side of the web
  • CWtot is actual coat weight measured from the web
  • CWb is coat weight on the bottom side of the web proportioned to the total coat weight
  • CW t is coat weight on the top side of the web proportioned to the total coat weight.
  • the coat weight ratio adjuster aims at retaining a pre-determined coat weight ratio in the long run.
  • the controller must be tuned slow, because calculation on the basis of the coating ma- terial consumption is not accurate on a very short period of time.
  • the controller must also be locked so that it will not switch on immediately after a production break, because reliable measurement is obtained only when the process is stable enough.
  • the method according to the invention can also be applied in contact-free coating in which no doctoring elements are used.
  • an actuator for metering the coating can be, e.g., a pump or a valve through which the coating material is fed into the application device.
  • the new control method enables optimising and maximising the quality of the product (technical properties of paper) and better uniformity.
  • the new adjusting manner also simplifies the control of the process and decreases the possibility of the machine operator's operating errors.
  • the coating material consumption data has not been, as far as is known, utilised in feedback control of coat weight, because the measurement is slow and the control thus functions with a delay.
  • these problems have been solved by combining the utilisation of the coating material consumption data with the traditional coat weight control which is based on measuring the total coat weight.
  • Fig. 1 shows a system according to the prior art for controlling coat weight in two- sided film-transfer coating.
  • Fig. 2 shows a system according to the invention in which, besides the total coat weight, the ratio of coat weights being applied on different sides of the web is controlled.
  • Fig. 1 schematically shows a coating head which utilises film-transfer technique and is provided with a coat weight control system according to the prior art.
  • the coating head comprises two film-transfer rolls 11, 12, which form a nip through which the web W being coated is carried.
  • Application devices 13, 14 and doctoring elements 15, 16 are shown only as reference.
  • Coating material is carried from a machine circulation 17, 18 via a feed line 17', 18' to the application device 13, 14 which spreads the coating material on the surface of the film-transfer roll 11, 12.
  • the coating film is smoothed and the excess is doctored away by means of the doctoring element 15, 16 which is pressed against the surface of the roll 11, 12.
  • the amount of coating material leaving the application area along with the roll surface is dependent on the load of the doctoring element 15, 16, which is controlled by an actuator 25, 26.
  • the dry basis weight of the web W is measured before the coating head by means of a first measuring frame 19 and after the coating head by means of a second measuring frame 20.
  • Signals G 1 and G 2 describing the dry basis weight are lead to a processor 21 which calculates the coat weight applied on the web.
  • Signal CW describing the total coat weight, produced by the processor 21 is compared with a coat weight set value CW 0 that has been entered via a workstation 22. Based on this comparison, a coat weight controller 23 gives the actuators 25, 26 a command signal S 1 which determines the pressure to be fed in the hoses loading the doctoring elements 15, 16.
  • the actuator 25, 26 can be e.g. a pressure control valve.
  • Coat weight measurement as described above gives information on the total coat weight but it does not reveal how much of coating has been applied on each side of the web. Frequently, one wishes to have different coat weights on the top and bottom surface of the web. Coating materials to be applied on different sides of the web can also be different. The properties of base paper, such as water absorption ability, are frequently different on different sides of the web. As there is no possibility for separate measuring of coat weights, a separate adjustment of the load of the doctoring elements 15, 16 cannot be implemented.
  • the coat weight controller 23 adjusts the total coat weight, whereby a similar control signal Si is given to the actuator 25, 26 controlling the load of each doctoring element 15, 16 irrespective of on which side the possible deviation from the set value of coat weight occurs.
  • Fig. 2 shows an improved system according to the invention, which comprises a coat weight ratio adjuster 24 which monitors and adjusts the coat weights being applied on different sides of the web.
  • the control of the total coat weight takes place in a similar manner as in Fig. 1.
  • the processor 21 calculates, based on the dry basis weights G 1 , G 2 measured of the web W, the total coat weight CW which is compared with the set value CW 0 of coat weight. Based on the comparison, the coat weight controller 23 produces a control signal Si for adjusting the loading pressures of the doctoring elements 15, 16. The change of loading pressure will not, however, be divided equally for both doctoring elements 15, 16, but it is divided in a manner defined by the coat weight ratio adjuster 24.
  • the coat weight ratio adjuster 24 receives information on the total coat weight from the processor 21 and signals Mi, M 2 describing the coating material con- sumption from the machine circulation 17, 18 of each application device 13, 14.
  • the coat weight ratio adjuster 24 calculates the ratio of coat weights applied on the bottom and top surface of the web. This ratio is compared with the set value RWo given to it via a workstation 22. If a deviation occurs, the coat weight ratio adjuster 24 gives the actuators 25, 26 that control the load of the doctoring elements 15, 16 control signals +S 2 and -S 2 , which are equal but with different signs, for correcting the difference. The outcome is that the load of the doctoring elements 15, 16 is changed for an equal amount but in different directions, whereby as the ratio of coat weights changes, the total coat weight remains constant.
  • the method can be applied in both two-sided and double coating in which two coating layers are applied successively on the same side of the web without measuring the coat weight in between.
  • the application method can be direct or indirect.
  • the actuator for metering the coating material can be a doctor blade or a rotating rod which is pressed against a transfer surface or a web by means of compressed-air hoses or other loading devices known as such.
  • the actuator for metering the coating material can be e.g. a pump or a valve.

Landscapes

  • Coating Apparatus (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Paper (AREA)

Abstract

Pour enduire une feuille de papier ou de carton, on étale le matériau de revêtement au moyen de deux dispositifs d'application (13, 14) sur les deux surfaces de la feuille au moyen de deux rouleaux de transfert de film (11, 12), après quoi le poids de revêtement total de la feuille revêtue (W) est mesuré. La quantité de matériau de revêtement consommé par chaque dispositif d'application (13, 14) est mesurée et, sur la base des données, on calcule le rapport de poids de revêtement appliqué sur les différentes surfaces de la feuille. Le dosage du matériau de revêtement sur les différentes surfaces de la feuille est ajusté pour conserver le rapport des poids de revêtement et le poids de revêtement total à une valeur désirée. Un premier contrôleur (23) régule la charge d'éléments de raclage (15, 16) pour maintenir le poids de revêtement total à une valeur désirée. Un processeur (24) reçoit des informations (M1, M2) sur la consommation de matériau de revêtement de chaque dispositif d'application (13, 14) et calcule le rapport des poids de revêtement appliqué sur les différentes surfaces de la feuille. Un second contrôleur (24) modifie, si besoin est, la charge de chaque élément de raclage (15, 16) de sorte que le rapport de poids de revêtement appliqué présente une valeur désirée, le poids de revêtement total restant au niveau défini par le premier contrôleur (23).
PCT/FI2007/050154 2006-03-24 2007-03-22 procédé et configuration permettant de contrôler le poids de revêtement pour enduire une feuille continue WO2007110474A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20065193 2006-03-24
FI20065193A FI118304B (fi) 2006-03-24 2006-03-24 Menetelmä ja sovitelma päällystemäärän hallitsemiseksi kuiturainan päällystyksessä

Publications (1)

Publication Number Publication Date
WO2007110474A1 true WO2007110474A1 (fr) 2007-10-04

Family

ID=36192038

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI2007/050154 WO2007110474A1 (fr) 2006-03-24 2007-03-22 procédé et configuration permettant de contrôler le poids de revêtement pour enduire une feuille continue

Country Status (2)

Country Link
FI (1) FI118304B (fr)
WO (1) WO2007110474A1 (fr)

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4732776A (en) * 1987-02-24 1988-03-22 Measurex Corporation Apparatus and method for controlling the thickness of coatings on paper or other materials
US5162131A (en) * 1990-06-12 1992-11-10 Valmet Paper Machinery Inc. Method and equipment for measurement and regulation of quantity of coating
EP0829575A1 (fr) * 1996-09-12 1998-03-18 Voith Sulzer Papiermaschinen GmbH Procédé et dispositif pour l'application directe ou indirecte d'un médium liquide ou pasteux sur une bande de matérial mouvante
WO2000052265A1 (fr) * 1999-03-04 2000-09-08 Metso Paper, Inc. Procede permettant de gerer l'humidite dans le sens machine d'une bande en cours d'enduction sur une machine a enduire
WO2001059435A1 (fr) * 2000-02-10 2001-08-16 Metso Paper Automation Oy Procede et appareil pour mesurer un revetement
US20030124244A1 (en) * 2001-09-04 2003-07-03 J. M. Huber Corporation Method of predicting optical properties and physical characteristics to formulate optimum coating system
WO2003087814A1 (fr) * 2002-04-16 2003-10-23 Metso Automation Oy Procede et appareil de mesure d'une quantite de revetement sur une bande de papier
EP1559835A1 (fr) * 2004-01-22 2005-08-03 Voith Paper Patent GmbH Dispositif et procédé pour enduire deux faces d'une bande de matériau en mouvement avec un medium fluide ou pâteux, en particulier du papier ou du carton, ainsi qu'un procédé adapté lié pour déterminer des enductions separées relatives à la surface

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4732776A (en) * 1987-02-24 1988-03-22 Measurex Corporation Apparatus and method for controlling the thickness of coatings on paper or other materials
US5162131A (en) * 1990-06-12 1992-11-10 Valmet Paper Machinery Inc. Method and equipment for measurement and regulation of quantity of coating
EP0829575A1 (fr) * 1996-09-12 1998-03-18 Voith Sulzer Papiermaschinen GmbH Procédé et dispositif pour l'application directe ou indirecte d'un médium liquide ou pasteux sur une bande de matérial mouvante
WO2000052265A1 (fr) * 1999-03-04 2000-09-08 Metso Paper, Inc. Procede permettant de gerer l'humidite dans le sens machine d'une bande en cours d'enduction sur une machine a enduire
WO2001059435A1 (fr) * 2000-02-10 2001-08-16 Metso Paper Automation Oy Procede et appareil pour mesurer un revetement
US20030124244A1 (en) * 2001-09-04 2003-07-03 J. M. Huber Corporation Method of predicting optical properties and physical characteristics to formulate optimum coating system
WO2003087814A1 (fr) * 2002-04-16 2003-10-23 Metso Automation Oy Procede et appareil de mesure d'une quantite de revetement sur une bande de papier
EP1559835A1 (fr) * 2004-01-22 2005-08-03 Voith Paper Patent GmbH Dispositif et procédé pour enduire deux faces d'une bande de matériau en mouvement avec un medium fluide ou pâteux, en particulier du papier ou du carton, ainsi qu'un procédé adapté lié pour déterminer des enductions separées relatives à la surface

Also Published As

Publication number Publication date
FI20065193A0 (fi) 2006-03-24
FI118304B (fi) 2007-09-28

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