WO2003074783A1 - Procede et calandre permettant de chauffer et de refroidir une bande continue de papier dans une pince de la calandre - Google Patents

Procede et calandre permettant de chauffer et de refroidir une bande continue de papier dans une pince de la calandre Download PDF

Info

Publication number
WO2003074783A1
WO2003074783A1 PCT/FI2003/000160 FI0300160W WO03074783A1 WO 2003074783 A1 WO2003074783 A1 WO 2003074783A1 FI 0300160 W FI0300160 W FI 0300160W WO 03074783 A1 WO03074783 A1 WO 03074783A1
Authority
WO
WIPO (PCT)
Prior art keywords
web
nip
heated
calender
glass transition
Prior art date
Application number
PCT/FI2003/000160
Other languages
English (en)
Inventor
Mika Viljanmaa
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.
Priority to DE10392196T priority Critical patent/DE10392196T5/de
Priority to AU2003211378A priority patent/AU2003211378A1/en
Publication of WO2003074783A1 publication Critical patent/WO2003074783A1/fr

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G1/00—Calenders; Smoothing apparatus
    • D21G1/006—Calenders; Smoothing apparatus with extended nips
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G1/00—Calenders; Smoothing apparatus
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G1/00—Calenders; Smoothing apparatus
    • D21G1/0073—Accessories for calenders
    • D21G1/0093—Web conditioning devices

Definitions

  • the present invention relates to a calendering method according to the preamble of claim 1, in which method a web is passed into a calender nip comprising a first member and a second member adapted to form a contacting nip with each other. At least one surface of the web is heated in the nip to a temperature at least so high as to reach the glass transition temperature of the polymeric compounds contained in the heated surface, whereupon the web is passed out from the nip.
  • the invention also relates to a calender for implementing the method.
  • the function of calendering is to increase the smoothness and gloss of paper and paperboard webs as well as to improve other qualities of a printing surface.
  • the web is subjected to deformation in a nip formed by two opposed rolls.
  • the rolls may have a hard- or soft-covered surface.
  • the surface material of soft-covered rolls is paper or other fibrous material or a polymer coating.
  • Hard-surfaced thermorolls are generally made from cast iron permitting heating or cooling of the rolls with oil, steam or other methods such a induction heating.
  • One of the nip rolls can be replaced by an alternative member such as a press shoe or belt.
  • the deformability of the web being calendered can be improved by elevating the web temperature and/or moisture content.
  • the web is heated by a heatable thermoroll. Additionally, the web may be wetted and heated with steam before the web enters the nip. Slippage of the web on the roll surfaces may also cause deformation of fiber thus improving the smoothing effect.
  • the deformability of the web being calendered is improved substantially when the polymeric components of the web reach the glass transition temperature.
  • the glass transition temperature of their polymeric components varies from room temperature (e.g., the coating mix polymers) to about 250 °C (for polymeric compounds of wood fiber).
  • the glass transition temperature of polymers drops with a higher moisture content of the web.
  • the temperature of the outer layers of the web is desirably elevated above the glass transition temperature of their polymeric compounds.
  • the web is worked in a nip formed by calender rolls, whereby the hot superficial layers of the web are deformed more than the middle portion of the web.
  • a recovery phenomenon known as re-swelling occurs resulting in coarser roughness of the web. Re-swelling is caused by dimensional recovery taking place in different magnitude at different points of the web. Re-swelling is particularly vigorous when the temperatures incurred in calendering remain lower than the glass transition temperature of the polymeric components of the web.
  • Web roughness also increases when the web is calendered at a temperature above the glass transition temperature of the polymeric components and is cooled after the nip to a temperature below the glass transition temperature.
  • the desired smoothness of the web can be attained only by carrying out calendering in multiple successive nips, running the calendering equipment at a slower speed or using a higher lineal nip pressure.
  • Patent publication US 5,245,920 describes a calendering method wherein the object is to reduce the re-swelling of the web after its leaves the press nip.
  • the web is heated in the nip to a temperature above the glass transition temperature.
  • the web is rapidly cooled to a temperature below the glass transition temperature of the polymeric compounds of the web. Cooling is carried out with the help of a cooling device located immediately downstream from the nip.
  • a cooling device located immediately downstream from the nip.
  • Such a rapid cooling reduces the re-swelling of the web.
  • a disadvantage of this embodiment is that the web is cooled after its departure from the nip, whereby no pressing force capable of preventing re-swelling is any more imposed on the web.
  • the cooling device increases the footprint need and cost of the calender.
  • the goal of the invention is attained by way of heating a substantial portion the poly- meric compounds of at least one surface of the web being calendered at the ingoing side of the calender nip into a plastic state, i.e., to a temperature not lower than the glass transition temperature of the polymeric compounds in the web surface layer. Subsequently, a substantial portion of the polymeric compounds heated to their glass transition temperature is cooled at the outgoing side of the nip still under the pressure of the nip to a temperature lower than the glass transition temperature.
  • the calender according to the invention comprises heating means for heating at least one surface of the web at the ingoing side of the calender nip to a temperature not lower than the glass transition temperature of the polymeric com- pounds of the heated web surface layer.
  • the heating means may comprise, e.g., a heated belt.
  • the calender also comprises cooling means for cooling the web surface heated to the glass transition temperature at the outgoing side of the nip to a temperature lower than the glass transition temperature of the polymeric compounds of the heated web surface layer.
  • the cooling means may comprise, e.g., a cooled roll.
  • the calender according to the invention is characterized by what is stated in the characterizing part of claim 8.
  • the invention offers significant benefits.
  • a major portion of the polymeric compounds of the web that are heated to the glass transition temperature is cooled down to a temperature below the glass transition temperature simultaneously as the web is being worked in the calender nip.
  • This arrangement reduces the substantial increase of web roughness as the web leaves the nip thus allowing the desired smoothness of the web surface to be attained using a lesser number of successive calendering nips. Hence, savings are attained in both equipment investment and energy consumption costs.
  • the belt calender shown in the diagram comprises a nip 6 formed by a first member 1 and a second member 4 running in a nip contact during the operation of the calender.
  • the first member is a rotating roll 1 and the second member is an endless- loop belt 4 passing over a backing roll 2 and about guide rolls 3 adapted on both sides and below the backing roll 2.
  • the belt 4 is pressed against the roll 1 by a backing roll 2.
  • the roll 1 is advantageously a hard-surfaced thermoroll adapted heatable or chillable by means of a liquid circulated in the interior of the roll 1.
  • the web 5 being calendered travels via a nip 6 formed between the roll 1 and the belt 4.
  • the travel direction of web 5 is marked with an arrow in the diagram.
  • the length of the calender nip 6 may be adjusted by changing the position of the guide rolls 3. For instance, when both guide rolls 3 at the opposite sides of the backing roll 2 are elevated upward, the belt 4 can be guided to travel a longer distance on the periphery of the thermoroll 1, whereby the length of the nip 6 increases.
  • the length of the calender nip 6 according to the invention can be increased up to about 95 % of the circumference of roll 1.
  • the nip length must be understood to refer to the travel distance along which both ones of members 1, 4 forming the nip 6 are in contact with the web 5 so as to press the web 5.
  • the temperature of the web 5 entering the calender varies from about 30 °C (off-line calenders) to 100 °C (on-line calenders).
  • An essential portion of one side of web 5 is heated in the nip 5 to a temperature not lower than the glass transition temperature of the polymeric compounds contained in the heated surface.
  • a substantial quantity of the polymeric compounds contained in the surface being heated is gradually brought to a temperature not lower than their glass transition temperature.
  • the polymeric compounds contained in the inner portion of web 5, yet close to the surface layer being heated are heated to their glass transition temperature.
  • a substantial portion of the heated surface layer with its polymeric compounds heated in nip 6 to their glass transition temperature is cooled to a temperature below the glass transition temperature. As the cooling of the polymeric compounds below their glass transition temperature takes place in the nip 6 under a pressing force, the re- swelling of web 5 after leaving nip 6 remains minimal.
  • the heating and cooling of web 5 in nip 6 is implemented, e.g., so that the web 5 pressing surface of the second member 4 is made from a material of low thermal capacity.
  • the surface temperature of the second member 4 pressing the web 5 is kept at the ingoing end of nip 6 higher than the glass transition temperature of the polymeric compounds contained in the surface layer of web 5 facing the pressing member.
  • the thermal conductivity of the surface of the second member 4 pressing web 5 must be high in order to achieve rapid transfer of the heat content of the member from its surface to the surface of web 5 thus allowing the surface layer of web 5 and the polymeric compounds thereof to reach at least their glass transition temperature in the ingoing end of nip 6.
  • the heat content of the surface pressing web 5 can be kept so small that the temperature of the second member 4 pressing web 5, together with the surface temperature of web 5, can fall below the glass transition temperature of the polymeric compounds contained in the surface layer of web 5 by the time the web reaches the outgoing end of nip 6.
  • a preferred embodiment of the invention is carried out using a belt calender such as the one shown in the diagram comprising a nip 6 formed between a belt 4 dimensioned to fulfill the above-described requirement and cooperating with a cooled roll 1.
  • the outer surface of roll 1 can be cooled by way of, e.g., circulating chilled cooling liquid in the interior of the roll perimeter.
  • the roll 1 may also be of an uncooled type.
  • the outer surface of belt 4 is heated with the help of a heater device 7 at a point exterior to the nip 6.
  • the belt 4 is preferably heated as close as possible to the point where the web 5 is taken into nip 6, whereby the outer surface of belt 4 is prevented from cooling substantially prior to its entry into nip 6.
  • the temperature of the outer surface of belt 4 at its entry point into nip 6 is in the range of 70-400 °C.
  • the belt entry point into nip 6 must be understood to refer to the point where both members 1 , 4 forming nip 6 come into contact with web 5.
  • Heat stored in belt 4 is transferred to web 5 in the ingoing end of nip 6 wherein a substantial quantity of polymeric compounds contained in the surface web 5 facing belt 4 is heated so as to reach a plastic state.
  • web 5 is subjected to pressing in nip 6 formed between belt 4 and roll 1.
  • a portion of the heat transferred from the surface of belt 4 to the surface of web 5 is conducted through web 5 to the cooled surface of roll 1.
  • a substantial quantity of the polymeric compounds of web 5 heated into a plastic state is again cooled within the outgoing end of nip 6 to a temperature below the glass transition temperature of the polymeric compounds.
  • the belt 4 can be fabricated from a thermally insulating material having its outer surface, that is, the surface facing the web 5, covered with a thin layer of a material of high thermal conductivity.
  • a thermally insulating material having its outer surface, that is, the surface facing the web 5, covered with a thin layer of a material of high thermal conductivity.
  • Such an outer layer may be of a metallic material, for instance.
  • the invention may also be carried out using embodiments different from those described above.
  • the above-discussed treatment wherein the surface of the web 5 is heated to a temperature not lower than the glass transition temperature of the poly- meric compounds contained in the web surface layer and thereupon is cooled below the glass transition temperature in nip 6, may be carried out simultaneously on both sides of the web 5.
  • both members 1, 4 forming the nip 6 are dimensioned to meet these requirements.
  • the surface of the web 5 before its entry into the ingoing side of the nip 6 may be heated with the help of a preheater 8 to a temperature lower than the glass transition temperature of polymeric compounds contained in the web surface layer.
  • the web 5 may also be wetted just prior to calendering in order to reduce the glass transition temperature of the polymeric compounds.
  • any other calender type of sufficiently long nip may be used, such as a shoe calender, for instance.

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  • Paper (AREA)

Abstract

L'invention concerne un procédé et une calandre permettant de calandrer une bande continue de papier ou de carton. Dans ce procédé, une bande continue (5) est passée dans la pince (6) de la calandre et est travaillée dans celle-ci. Au moins une surface de la bande (5) est chauffée dans la pince (6) à une température qui n'est pas inférieure à la température de transition vitreuse des composés polymères renfermés dans la surface de la bande chauffée. La surface de la bande (5) chauffée à la température de transition vitreuse des composés polymères renfermés dans la surface chauffée est refroidie dans la pince (6) de manière à atteindre une température inférieure à la température de transition vitreuse des composés polymères renfermés dans la surface chauffée.
PCT/FI2003/000160 2002-03-07 2003-03-04 Procede et calandre permettant de chauffer et de refroidir une bande continue de papier dans une pince de la calandre WO2003074783A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE10392196T DE10392196T5 (de) 2002-03-07 2003-03-04 Verfahren und Kalander zum Erwärmen und Kühlen einer Papierbahn in einem Kalanderwalzenspalt
AU2003211378A AU2003211378A1 (en) 2002-03-07 2003-03-04 Method and calender for heating and cooling a paper web in a calender nip

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20020442 2002-03-07
FI20020442A FI111282B (fi) 2002-03-07 2002-03-07 Kalanterointimenetelmä ja kalanteri

Publications (1)

Publication Number Publication Date
WO2003074783A1 true WO2003074783A1 (fr) 2003-09-12

Family

ID=8563463

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI2003/000160 WO2003074783A1 (fr) 2002-03-07 2003-03-04 Procede et calandre permettant de chauffer et de refroidir une bande continue de papier dans une pince de la calandre

Country Status (4)

Country Link
AU (1) AU2003211378A1 (fr)
DE (1) DE10392196T5 (fr)
FI (1) FI111282B (fr)
WO (1) WO2003074783A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1887131A1 (fr) 2006-08-09 2008-02-13 Voith Patent GmbH Agencement de calendre

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4277524A (en) * 1978-12-27 1981-07-07 Mitsubishi Paper Mills, Ltd. Method and apparatus for finishing coated papers
US5245920A (en) * 1988-12-22 1993-09-21 Sulzer Escher Wyss Gmbh Method of calendering a paper web
US5318670A (en) * 1991-08-08 1994-06-07 Sulzer-Escher Wyss Gmbh Method for the generation of smoothness and gloss of a paper web
WO1998044196A1 (fr) * 1997-04-02 1998-10-08 Valmet Corporation Procede de calandrage et calandre utilisant ledit procede
DE10157688C1 (de) * 2001-11-24 2003-02-13 Voith Paper Patent Gmbh Kalander zum Glätten einer Bahn aus Faserstoff

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4277524A (en) * 1978-12-27 1981-07-07 Mitsubishi Paper Mills, Ltd. Method and apparatus for finishing coated papers
US5245920A (en) * 1988-12-22 1993-09-21 Sulzer Escher Wyss Gmbh Method of calendering a paper web
US5318670A (en) * 1991-08-08 1994-06-07 Sulzer-Escher Wyss Gmbh Method for the generation of smoothness and gloss of a paper web
WO1998044196A1 (fr) * 1997-04-02 1998-10-08 Valmet Corporation Procede de calandrage et calandre utilisant ledit procede
DE10157688C1 (de) * 2001-11-24 2003-02-13 Voith Paper Patent Gmbh Kalander zum Glätten einer Bahn aus Faserstoff

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1887131A1 (fr) 2006-08-09 2008-02-13 Voith Patent GmbH Agencement de calendre

Also Published As

Publication number Publication date
FI20020442A0 (fi) 2002-03-07
DE10392196T5 (de) 2005-02-17
FI111282B (fi) 2003-06-30
AU2003211378A1 (en) 2003-09-16

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