JP2004510897A - Apparatus and method for web calendering a material including a long nip calender - Google Patents

Abstract

The invention relates to a method and calender arrangement for calendering a material web (W), especially a paper or board web, in a long-nip calender, in which the backing roll (11) of the long-nip roll (15) is a heated, chilled-surface roll. The length of the long nip (N) in the direction of travel of the material web (W) is within the range from approximately 10 mm to 500 mm. In the invention, as a long-nip roll (15) is used a roll, the belt mantle (30) of which is made of metal at least as concerns its calendering, longitudinal, central area (31). In the method, a nip pressure within the range from 0.1 MPa to about 50 MPa is directed at the material web (W), and the surface temperature of the rolls (11, 15) before the nip (N) is adjusted to a value from about 60 DEG C to about 350 DEG C.

Description

[0001]
The present invention relates to a method for calendering a material web and a calendering apparatus for realizing the method.
[0002]
It is an object of the present invention, particularly in a long nip calender wherein the backing roll of the long nip roll is a hot roll and the nip length in the running direction of the material web is in the range of about 10 mm to 500 mm. It is an object of the present invention to provide a method for calendering a material web which is a paper or paperboard web. The invention also relates to a calender for calendering a material web, in particular a paper or paperboard web, the calender comprising a long nip calender wherein the backing roll of the long nip roll is a hot roll of metal surface. And a long nip is formed between the rolls, and the length of the nip in the running direction of the material web is in a range of about 10 mm to 500 mm.
[0003]
In order to improve the quality of calendering, in fact, increasing the number of calendering nips has been proposed as the only possibility, but in this case the complexity of the calendering structure and the control of the paper web and the threading It causes difficulty. In an attempt to solve these problems, various belts and shoe calenders have been used to increase the calendering nip and improve nip operation. For example, paper calendered by a belt calender is conveyed by an endless belt so as to make initial contact with a hot calender roll, thereby enabling a steep temperature gradient effective for calendering. With a belt, the effective length of the nip is reduced due to the initial contact, since there is no problem arising from heat-induced deformation and it is possible to use a polymer that is more flexible than the roll coating as the belt material. To increase. A longer nip than in a supercalender or soft calender makes it possible to increase the pressure impact directed at the paper without the pressure peaks becoming too large and to suppress the onset of bulk.
[0004]
A belt calender solution is disclosed, for example, in Finnish Patent No. 955061, in which a calendering nip is formed between a hard roll of heat and a metal belt supported by calender rolls having an elastic coating. Is done. One disadvantage of this solution is that the maximum nip pressure is insufficient for some paper grades that require a high degree of calendering.
[0005]
It is an object of the present invention to achieve a solution that can perform calendering between two solid surfaces without the disadvantages associated with conventional mechanical calendering, such as relatively large gloss variations and reduced bulk. It is in.
[0006]
In order to achieve the object of the invention, the method according to the invention is characterized in that a roll having a belt mantle in which at least a central longitudinal region for calendering is made of metal is used as the long nip roll, and the method comprises the steps of: A nip pressure of 1 MPa to about 50 MPa acts on the material web, and the temperature of the roll before the nip position is adjusted from about 60 ° C to about 350 ° C. The nip pressure is preferably in the range of 0.2 MPa to about 15 MPa, and the surface temperature before the nip position is preferably in the range of about 120 ° C to about 300 ° C. Compared with machine calendering, the solution according to the invention achieves, inter alia, a more uniform gloss, a maintenance of bulk and a good smoothness.
[0007]
The calendar device according to the present invention is characterized in that the belt mantle of the long nip roll is formed of a metal at least in a longitudinal central region for calendering.
[0008]
The present invention will now be described in detail with reference to the accompanying drawings.
[0009]
Referring to FIG. 1, the calendar device according to the present invention includes a shoe roll 15, in which a load member 17 is disposed on a fixed axle 16 at a nip N position. Includes a shoe portion 19 that extends beyond the width of the nip (the width in the longitudinal direction of the roll), and a piston 20 applies a load to the shoe portion 19. A belt mantle 30 runs around the shoe 19, and the belt mantle 30 is formed of a metal at least in a calendering area, as shown in FIG.
[0010]
In the embodiment shown in FIG. 2, the central region of the belt mantle 30 comprises a steel belt 31 extending over the entire length of the shoe 19, the steel belt 31 having an elastic material such as polymer, rubber, silicon or the like. An end 32 made of a material is connected. The end 32 is connected to the steel belt 31 in an elastic manner by, for example, an adhesive or vulcanization (curing). The connection is made outside the shoe section 19 so that no fatigue loads are directed at the steel belt.
[0011]
The steel belt 31 can also be made entirely of metal by providing an elastic seal ring at the end of the belt mantle, the elastic seal ring being as disclosed in Finnish Patent No. 66932 Is mounted to rotate with the mantle.
[0012]
FIG. 3 shows that the thin metal cylinder 41 is fitted on the polymer belt 40 of the shoe roll 15 and the cylinder 41 is tightened to a predetermined position by the internal air pressure of the roll (it is securely fitted). A solution is shown. The length of the cylinder 41 is the same as the length of the material web and is not fixed to the end structure of the shoe roll, so that loads which cause fatigue of the metallic material are prevented in the edge region of the shoe.
[0013]
A long nip N is formed between the long nip roll 15 and the hot backing roll 11 on the metal surface, through which the material web W is guided for calendering. The web is subjected to a nip pressure in the range of about 0.1 MPa to about 50 MPa, preferably in the range of about 0.2 MPa to about 15 MPa, used in normal mechanical calendering, where the nip pressure is on the order of 100 MPa. Much less than the pressure that is applied. The roll surface temperature before the nip N position can be a value from about 60 ° C. to about 350 ° C. when the surface temperature used in conventional mechanical calendering is typically in the range of about 60 ° C. to about 120 ° C. Preferably, it is adjusted to a value of about 120 ° C to about 300 ° C.
[0014]
The length of the nip N in the direction of travel of the material web is preferably in the range from about 10 mm to about 500 mm. The surface roughness Ra of both the outer surface of the backing roll 11 and the steel belt 30 of the long nip roll 15 is preferably less than 0.3 μm, so that the material web W can undergo a gloss treatment. It becomes. The calender according to the present invention uses a sufficiently high Ra value for the surface of the steel belt and / or the backing roll, for example, by using an Ra value in the range of about 0.4 to 2.0 μm. Applicable to single-sided or double-sided matte drives.
[0015]
The solution according to the invention is applicable for both online use and offline use. For the preliminary calendering before the coating machine (coating machine) and for the final calendering after the coating machine, for example on a pressurizing unit for drying the material web, the calendering device according to the invention is used. Can be used.
[0016]
When using the apparatus according to the invention in the dryer section of a paper machine, the paper machine can be shortened by omitting a part of the drying cylinder.
[Brief description of the drawings]
FIG.
1 is a schematic view of a long nip calender according to the present invention when viewed from an end.
FIG. 2
It is a perspective view showing roughly one example of a belt mantle of a long nip roll applicable to a calendar device concerning the present invention.
FIG. 3
FIG. 7 is a perspective view schematically showing another embodiment of a belt mantle of a long nip roll applicable to the calendering device according to the present invention when viewed from an end.

Claims (10)

The backing roll of the long nip roll is a hot roll, especially a paper or paperboard web in a long nip calender where the nip length in the running direction of the material web is in the range of about 70 mm to 270 mm. A method of calendering a material web,
A roll having a belt mantle with at least a central longitudinal region for calendering made of metal is used as a long nip roll, wherein a nip pressure of about 0.1 MPa to about 50 MPa acts on the material web, A method wherein the temperature of the roll before the nip is adjusted from about 60 ° C to about 350 ° C. The method of claim 1, wherein the nip pressure is in a range from 0.2 MPa to about 15 MPa, and the surface temperature before the nip position is in a range from about 120C to about 300C. 3. The method according to claim 1, wherein a roll having a surface roughness Ra of the outer surface of the mantle smaller than 0.3 [mu] m is used. 4. The method according to claim 1, wherein a long nip roll is used in which the belt mantle is made entirely of metal. A calender for calendering a material web, preferably a paper or paperboard web,
The backing roll of the long nip roll (15) is a hot roll (11) with a metal surface, a long nip is formed between the rolls (11, 15), and the length of the nip in the running direction of the material web. A long nip calender having a length in the range of about 70 mm to 270 mm,
A calender device, characterized in that the belt mantle (30) of the long nip roll (15) is formed of metal at least in a central longitudinal region for calendering. The central region of the belt mantle (30) comprises a steel belt (31), the edge of which is flexibly connected to an end (32) made of a resilient non-metallic material. The calendar device according to claim 5, wherein: The calender according to claim 6, characterized in that the end (32) is connected to the steel belt (31) by gluing or vulcanization. A calender according to claim 5, characterized in that the belt mantle (30) is made entirely of metal. A calender for calendering a material web, preferably a paper or paperboard web,
The backing roll of the long nip roll (15) is a hot roll (11) with a metal surface, a long nip is formed between the rolls (11, 15), and the length of the nip in the running direction of the material web. A long nip calender having a length in the range of about 10 mm to 500 mm,
A calender device, wherein a belt mantle of a long nip roll (15) is made of a polymer belt, and a thin metal cylinder (41) is fitted on the belt mantle. The metal cylinder (41) is fitted in place by the air pressure inside the roll, or is glued or vulcanized to the polymer belt (40) so as to rotate with the polymer belt (40). The calendar device according to claim 9, wherein the calendar device is used.