WO2007077296A1

WO2007077296A1 - A method and a device for manufacturing a fibrous web having a matte surface

Info

Publication number: WO2007077296A1
Application number: PCT/FI2006/050575
Authority: WO
Inventors: Reijo PIETIKÄINEN
Original assignee: Metso Paper, Inc.
Priority date: 2006-01-02
Filing date: 2006-12-21
Publication date: 2007-07-12
Also published as: FI117869B; FI20065001A0; DE112006003571T5

Abstract

This specification discloses a method for calendering a low-gloss fibrous web (W), such as paper, board or a corresponding web, so that the fibrous web is passed through a nip zone (Nl to N6) formed by two hard surfaces. The fibrous web (W) to be processed is pressed in said hard nip zone (Nl to N6) formed by at least two hard surfaces. The fibrous web (W) is calendered in at least one hard nip zone (Nl to N6), wherein at least one surface (10; 11; 12; 15) pressing the web is arranged to be a hard matte-surface rough surface manufactured to have an Ra , roughness of 0.2 to 1.0 µm, preferably an Ra roughness of 0.4 to 0.6 µm, in order to calender the fibrous web (W) to be matte-like. Preferably, in the nip zone (Nl to N6) two surfaces (10, 12) pressing the web (W) between them are arranged to be matte surfaces, whereby both surfaces of the fibrous web (W) are calendered to be matte-like in the same nip zone. The specification also discloses a device (100) applying the method.

Description

A METHOD AND A DEVICE FOR MANUFACTURING A FIBROUS WEB HAVING A MATTE SURFACE

The invention relates to a method and a device for manufacturing a matte-surface fibrous web. Particularly, the invention relates to a method and a device for calendering low-gloss paper, board or a corresponding web.

In order to finish a low-gloss matte surface, a method, among others, is known wherein a fibrous web is calendered between two polymer rolls. When this method is used, slight modification can be provided in the fibrous web in the case of a calendering nip formed between two soft rolls. In this method heat is not introduced to the process by means of the polymer rolls. The fibrous web is not glazed significantly. The method produces a relatively poor smoothness in the fibrous web.

In order to finish a low-gloss matte surface, a further method is known wherein a fibrous web is calendered by means of a special matte roll against a soft roll, such as a polymer roll. This method forms an efficient matte modification process, wherein the fibrous web is calendered in a nip between a hard and a soft surface. In this method heat is introduced to the calendering nip by means of the matte roll. The method produces a good smoothness. The matte roll is equipped with a special hard ceramic cover, and duplication of the fine-grained matte surface texture of the matte roll on the fibrous web takes place as a result of compression.

Types of low-gloss webs are included in, among others, wood-containing and woodfree printing papers and boards. Uncoated low-gloss matte papers are used for copying papers, in particular. Coated matte papers are used in objects requiring a high-quality printing surface, such as color printing, photographic and art printing papers, and in special products, such as calendars, calling cards, etc.

Generally, matte-like papers are used for the sake of the pleasant appearance of the surface, even gloss and good readability. With respect to the prior art, reference is made to the international patent specification WO 03/064762, in which belt-calendering solutions are disclosed that allow the use of a wide pressure area and impact time in the modification area of the web.

Papers having a weak formation have a larger grammage variation and floes are clearly above the average density and thickness level. When paper with a weak formation is calendered, thicker floe points in the paper are subjected to the greatest nip pressure and heat transfer. When calendering with a conventional smooth roll, it has been found to be harmful that the floes are glazed more strongly than the remaining area, resulting in gloss-mottled paper.

In the calendering process the outermost surface layer of the paper is modified with respect to small-scale smoothness and optical characteristics by means of a "replication process", or a copying mechanism. Thereby the form of the surface of the roll and particularly the small irregularities in it are duplicated or replicated on the paper in nip contact, if the fibers in the surface layer of the paper are in a sufficiently plastic state.

Thanks to the replication mechanism, a smooth and glossy roll surface provides a smooth and glossy calendering result. Correspondingly, a rough and in a small scale uneven (matte-like) roll surface produces a matte-like final result.

Favorable conditions for replication can be achieved particularly well in a long nip zone of a metal belt calender, wherein, thanks to the sufficiently long nip time, a high temperature is achieved that efficiently plasticizes the paper web.

An object of the present invention is to prevent the occurrence of the above- mentioned problems and shortcomings or at least reduce the above-mentioned defects or provide an alternative way of producing a matte-surface fibrous web without gloss mottling. An object of the invention is to create a method and a device for manufacturing a matte-surface fibrous web.

Appended claim 1 discloses the method according to the invention.

Appended claim 12 discloses the device according to the invention.

The invention provides significant advantages compared with known solutions; the following benefits, among others, can be mentioned. According to the invention it is possible to finish the surface of a low-gloss fibrous web, such as paper, board or a corresponding web, by pressing it with a heated rough hard surface against another hard surface so that the surface of the web is modified to be evenly matte-like and with low gloss variation. The matte-like inelastic roll surface presses floes more strongly than the area surrounding the floes, whereby, thanks to the replication phenomenon, the matte modification process becomes more effective and the surface becomes more matte-like than previously also at the floes, and the invention allows reducing the generation of local gloss variation when the fibrous web is pressed in a calendering nip.

The above-mentioned hard and inelastic surface may be a metal surface of a roll, a metal-covered surface of a roll, a ceramic-covered surface of a roll or the surface of a metal belt, for example, so that at least one of the surfaces of a calendering nip zone pressing the web is a matte-surface rough surface. Preferably, two of said surfaces forming the nip zone between them are matte surfaces, whereby both surfaces of the fibrous web are calendered to be matte-like in the same nip zone.

With respect to the other characteristics and advantages of the invention, reference is made to the dependent claims in the set of claims and the special part of the description presented in the following, wherein preferred embodiments of the invention and their implementation possibilities are explained in detail, but only by way of example.

The invention is described in the following by reference to the appended drawings, in which:

Figure 1 schematically shows gloss variation in webs of the same woodfree uncoated (WFU) paper, when two different pressures were used in a test arrangement for five different web modification processes.

Figure 2 schematically shows gloss variation in webs of the same woodfree coated (WFC) paper, when two different pressures were used in the test arrangement for five different web modification processes.

Figure 3 shows a schematic side view of an example implementation of a device according to the invention.

Figure 4a shows a schematic side view of a second example implementation of the device according to the invention.

Figure 4b shows a schematic side view of a third example implementation of the device according to the invention.

Figure 4c shows a schematic side view of a modification of the device according to Figure 4a.

Figure 4d shows a schematic side view of a modification of the device according to Figure 4c.

Figure 5 shows a schematic side view of a fourth example implementation of the device according to the invention. The surface finish of a low-gloss fibrous web, such as paper, board or a corresponding web, was investigated in process tests by pressing the web with a heated rough surface. In these tests, in which the fibrous web was pressed with various matte-surface plates against a smooth hard surface in conditions corresponding to calendering conditions, it was found that it is possible to modify the surface of the web to be evenly matte-like and with low gloss variation. The tests were conducted by pressing the paper web with various matte-like steel bar plates at a temperature of 17O⁰C, using a dwell time and compression pressure corresponding to a calendering nip.

The paper used in the tests was uncoated fine paper (WFU, 80 g/m²), i.e. standard copying paper, and coated fine paper (WFC, 100 g/m²).

In the case of both paper grades, matte press plates VMl, VM2, V3 and V3 were tested, which were hard-coated steel bar plates. The Ra roughness of the bar plate surfaces was VMl 0.6 μm, VM2 0.62 μm, V3 0.48 μm and V4 0.45 μm. The reference bar plate was a smooth steel press, whose Ra roughness was about 0.1 μm. The tested papers were measured for the conventional quality characteristics (density, PPS smoothness, Bendtsen smoothness, Hunter gloss) and the evenness of gloss (gloss variation).

In this context, the result of gloss variation is specified by means of a variation coefficient that describes the relative variation of the gloss. The variation coefficient specifies how many percentage points the standard deviation of the gloss values measured at different points of the same sample deviates from the average gloss of the sample in question. Gloss variation was measured with a measuring device of KCL (KCL = Oy Keskuslaboratorio - Centrallaboratorium Ab, Espoo, Finland). The above-mentioned tests ended up with the result, among others, that the gloss variation of an end-product calendered with a matte-surface roll against a hard- surface roll can be reduced significantly compared with the gloss variation of an end-product calendered with a normal smooth-surface thermo roll. A matte-like inelastic roll surface presses floes more strongly than the area surrounding the floes, whereby the matte modification process becomes more effective and the surface becomes more matte-like than previously also at the floes. The texture and topography of the roll surface are replicated on the paper. Thus, by means of the invention, the generation of local gloss variation can be reduced when the fibrous web is pressed in the calendering nip.

The matte roll is equipped with a special hard ceramic cover, and duplication of the fine-grained matte surface texture of the matte roll takes place on the fibrous web as a result of compression.

In the above-mentioned process tests 80 g/m² WFU and 100 g/m² WFC paper webs were pressed with five different types of surfaces against a smooth hard surface and thereafter the gloss variation of the fibrous web was determined. The five different types of surfaces are presented in the same order as the columns representing the gloss variation values measured from the webs pressed with these surfaces are successively ordered in the diagrams of Figures 1 and 2. The four first surfaces, VMl, VM2, V3 and V4, are different rough matte surfaces that correspond to matte-surface heatable thermo rolls in the calendering process. The fifth surface is a smooth heatable surface that corresponds to a normal smooth heatable thermo roll in the calendering process. Gloss variation was measured in three different variation wavelength ranges, less than 1 mm, 1 mm to 5 mm and more than 5 mm, which are described on the horizontal axis of the diagrams. The gloss variation results provided in the fibrous web by pressing with each surface VMl, VM2, V3 and V4 and the smooth surface against a hard surface in a certain variation wavelength are presented as columns whose height describes gloss variation. Thus gloss variation is described on the vertical axis of the diagrams. The calendering pressures used in the test arrangements were 3 MPa in the upper diagrams of Figures 1 and 2 and 9 MPa in the lower diagrams.

In the upper diagrams of Figure 1, when the compression pressure of 3 MPa was used, the value of the variation coefficient of gloss variation provided in the WFU web by pressing with the matte surfaces VMl, VM2, V3, V4 was about 3 at the variation wavelength of < 1 mm, whereas gloss variation with the smooth surface was about 9. Further, at the pressure of 3 MPa, the corresponding values of the variation coefficient of gloss variation were about 2 to 3 and about 6 at the variation wavelength range of 1 mm to 5 mm, and correspondingly about 2 and about 3 at the variation wavelength of more than 5 mm.

In the lower diagrams of Figure 1, when the compression pressure of 9 MPa was used, the value of the variation coefficient of gloss variation provided in the WFU web by pressing with the matte surfaces VMl, VM2, V3, V4 was about 4 to 5 at the variation wavelength of < 1 mm, whereas gloss variation with the smooth surface was about 23. Further, at the pressure of 9 MPa, the corresponding values of the variation coefficient of gloss variation were about 2 to 3 and about 13 at the variation wavelength range of 1 mm to 5 mm, and correspondingly about 2 and about 7 at the variation wavelength of more than 5 mm.

It can be seen from Figure 1 that, when pressure is increased, the gloss mottling of WFU caused by the normal thermo roll increases, but the gloss mottling caused by the matte rolls VMl, VM2, V3, V4 remains constant or decreases. A more effective matte modification process can be observed at the floe points.

In the upper diagram of Figure 2, when the compression pressure of 3 MPa was used, the value of the variation coefficient of gloss variation provided in the WFC web by pressing with the matte surfaces VMl, VM2, V3, V4 was about 9 to 12 at the variation wavelength of < 1 mm, whereas with the smooth surface gloss variation was about 21. Further, at the pressure of 3 MPa, the corresponding values of the variation coefficient of gloss variation were about 3 and about 12 at the variation wavelength range of 1 mm to 5 mm, and correspondingly about 2 to 3 and about 7 at the variation wavelength of more than 5 mm.

In the lower diagrams of Figure 2, when the compression pressure of 9 MPa was used, the value of the variation coefficient of gloss variation provided in the WFC web by pressing with the matte surfaces VMl, VM2, V3, V4 was about 9 to 11 at the variation wavelength of < 1 mm, whereas with the smooth surface the gloss variation was about 49. Further, at the pressure of 9 MPa, the corresponding values of the variation coefficient of gloss variation were about 3 to 4 and about 22 at the variation wavelength range of 1 mm to 5 mm, and correspondingly about 2 to 3 and about 15 at the variation wavelength of more than 5 mm.

It can be seen from Figure 2 that, when pressure is increased, the gloss mottling of WFC caused by the normal thermo roll increases radically, but the gloss mottling caused by the matte roll VMl, VM2, V3, V4 remains constant or decreases. A more effective matte modification process can be observed at the floe points.

As shown by Figures 1 and 2, it can be observed that the gloss variation produced by a matte roll is only 20 to 50% of the gloss variation produced by a smooth- surface roll with WFU and WFC grades. In the test arrangements said types of fibrous webs were calendered in the same calendering conditions to have the same bulk and approximately the same surface roughness level. The same calendering conditions here also refer to the standardization of humidity, temperature and dwell time in the test arrangement.

By considering Figures 1 and 2 it can further be observed that the greater the calendering pressure, the more significant becomes the advantage for the matte surface. This is significant for matte grades that are calendered to be high-density. This also means that an even-quality matte process can be implemented particularly well with a hard nip and/or nip zone, which is arranged in a machine calender or metal belt calender or the roll stack of a multiroll calender, for example. The advantage of using a hard nip/nip zone is its simplicity and the possibility to use two matte surfaces on both sides. In a double-sided process that is formed by two or at least two matte hard inelastic pressing surfaces, the surface characteristics of both sides of the paper can be efficiently improved to be matte- like, avoid the generation of local gloss variation during calendering, adjust the thickness of the paper to provide an end-product of a suitable density and even out the thickness profile of the paper in order to provide even reels in reeling.

A hard matte processing zone may be a nip, such as a roll/roll nip or a roll/belt nip or a belt/belt nip, or a zone, such as a roll/roll zone or roll/belt zone or belt/belt zone. Preferably, the hard matte processing zone is any of the nip zones of a device 100 shown in Figures 3 to 5, such as a matte roll / matte roll nip shown in Figure 3, a matte roll / metal belt zone shown in Figure 4a, a matte roll / metal belt nip shown in Figure 4b, a matte roll / metal belt zone shown in Figures 4c; 4d, or a metal belt / metal belt zone shown in Figure 5. When a metal belt is used, in particular, the profiling of the calendering nip can be arranged by means of an additional loading roll arranged within the belt circulation, which additional loading roll may be a deflection-compensated roll, for example, which is possible in the manner presented in Figures 4b, 4c and 4d, for example.

Figure 3 shows a schematic side view of an example implementation of the device 100, whereby the device comprises at least one hard nip zone Nl according to Figure 3, through which a fibrous web W to be processed is passed, and in which nip zone at least one of the surfaces pressing the web W is a hard matte-like rough surface manufactured to have an R_a roughness of 0.2 to 1.0 μm, preferably an R₃ roughness of 0.4 to 0.6 μm. In Figure 3 the device preferably comprises the nip zone Nl formed by two matte-surface hard thermo rolls 10 and 11, whereby the modification area of the web W is the hard matte roll / matte roll nip Nl. Optionally, one of the hard rolls of the hard nip zone Nl, the thermo roll 11, for example, might be a smooth-surface roll, such as a smooth-surface thermo roll. Figure 4a shows a schematic side view of another example implementation of the device 100 according to the invention, whereby the device comprises at least one hard nip zone N2 according to Figure 4a, through which the fibrous web W to be processed is passed. Here the hard nip zone N2 and thus the modification area of the web W is formed by a matte-surface thermo roll 10 and a metal belt 12, between which the fibrous web W is passed during calendering. Compression is provided in the nip zone N2 by means of the tension of the metal belt 12. In the nip zone N2 at least one of the surfaces pressing the web W is a hard matte- surface rough surface manufactured to have an R₃ roughness of 0.2 to 1.0 μm, preferably an Ra roughness of 0.4 to 0.6 μm. In Figure 4a the device comprises the nip zone N2 formed by the matte-surface hard thermo roll 10 and the matte- surface metal belt 12, whereby the modification zone of the web W is the hard matte roll / metal belt zone N2, whose length enables a longer dwell time. Optionally, one of the hard surfaces of the hard nip zone N2, the metal belt 12 or the thermo roll, for example, might have a smooth surface.

Figure 4b shows a schematic side view of a third example implementation of the device 100 according to the invention, whereby the device comprises at least one hard nip zone N3 according to Figure 4b, through which the fibrous web W to be processed is passed. Here the hard nip zone N3 and thus the modification area of the web W is formed by a matte-surface hard thermo roll 10 and a metal belt 12, between which the fibrous web W is passed during calendering, and by a nip roll 13 that supports the metal belt 12 and presses it towards the thermo roll 10 in order to subject the web W to be modified to an additional compression force. The nip roll 13 of the nip zone N3 may preferably be a deflection-compensated roll. In the nip zone N3 at least one of the surfaces pressing the web W is a hard matte- surface rough surface manufactured to have an R₈ roughness of 0.2 to 1.0 μm, preferably an R₅ roughness of 0.4 to 0.6 μm. In Figure 4b the device comprises the nip zone N3 formed by the matte-surface hard thermo roll 10 and the smooth- surface metal belt 12, whereby the modification area of the web W is the hard matte roll / metal belt nip N3. Optionally, the metal belt 12 may have a matte surface.

Figure 4c shows a schematic side view of a modification of the device 100 according to Figure 4a, whereby the device comprises at least one hard nip zone N4 according to Figure 4c, through which the fibrous web W to be processed is passed. Here the hard nip zone N4 and thus the modification area of the web W is formed by a matte-surface hard thermo roll 10 and a metal belt 12, between which the fibrous web W is passed during calendering. Compression of the web W is provided in the nip zone N4 by means of the tension of the metal belt 12 and a nip roll 13, which is used to press the metal belt 12 towards the thermo roll 10 and subject the web W to be modified to an additional compression force. Preferably, the nip roll 13 of the nip zone N4 may be a deflection-compensated roll. In the nip zone N4 at least one of the surfaces pressing the web W is a hard matte-surface rough surface manufactured to have an R₃ roughness of 0.2 to 1.0 μm, preferably an R₃ roughness of 0.4 to 0.6 μm. In Figure 4c the device comprises the nip zone N4 formed by the matte-surface hard thermo roll 10, the matte-surface metal belt 12 and the nip roll 13, whereby the modification area of the web W is the hard matte roll / metal belt zone N4, whose length enables a longer dwell time and the nip roll 13 used as a pressing element enables making the form of the pressure impulse as desired. Optionally, one of the hard surfaces of the hard nip zone N4, the metal belt 12, for example, may have a smooth surface. It is also possible that a smooth-surface roll and a matte-surface belt form the hard nip zone between them.

Figure 4d shows a schematic side view of a modification of the device according to Figure 4c, whereby the device comprises at least one hard nip zone N5 according to Figure 4c, through which the fibrous web W to be processed is passed. Here the hard nip zone N5 and thus the modification area of the web W is formed by a matte-surface hard thermo roll 10 and a metal belt 12, through which the fibrous web W is passed during calendering. Compression is provided in the nip zone N5 by means of the tension of the metal belt 12 and a long nip roll 14 supporting the metal belt 12, which long nip roll 14 is used to subject the web W to be modified to an additional compression force. Preferably, the long nip roll 14 of the nip zone N5 is a deflection-compensated roll, a "shoe roll", for example. In the nip zone N5 at least one of the surfaces pressing the web W is a hard matte- surface rough surface manufactured to have an R₈ roughness of 0.2 to 1.0 μm, preferably an R₁ roughness of 0.4 to 0.6 μm. In Figure 4d the device comprises the nip zone N5 formed by the matte-surface hard thermo roll 10, the matte-surface metal belt 12 and the long nip roll 14, whereby the modification area of the web W is the hard matte roll/ metal belt zone N5, whose length enables a longer dwell time and the long nip roll 14 used as a pressing element enables making the form of the pressure impulse as desired. Optionally, one of the hard surfaces of the nip zone N5, the metal belt 12, for example, may have a smooth surface.

Figure 5 shows a schematic side view of a fourth example implementation of the device 100 according to the invention, whereby the device 100 comprises at least one hard nip zone N6 according to Figure 5, through which the web W to be processed is passed during calendering. Here the hard nip zone N6 and thus the modification area of the web W is formed by a matte-surface metal belt 12 and another matte-surface metal belt 15, between which the fibrous web W is passed during calendering. The belts 12; 15 are supported by means of guide rolls 17. Compression is provided in the nip zone N6 by means of the tension of the metal belts 12 and 15 and by means of optional nip rolls 16, 16' supporting/pressing the metal belts 12; 15. The nip rolls 16, 16' shown by means of dashed lines in Figure 5 may together form a nip and they can be used to support the metal belts and subject the web W to be modified to an additional compression force. In Figure 5 the nip zone N6 between the two metal belts is presented to be planar, but it may equally well be a nip zone between two metal belts of some other form, a nip formed between two metal belts, for example. In the nip zone N6 at least one of the surfaces pressing the web W is a hard matte-surface rough surface manufactured to have an R₃ roughness of 0.2 to 1.0 μm, preferably an Ra roughness of 0.4 to 0.6 μm. In Figure 5 the device 100 comprises the nip zone N6 formed by the matte-surface metal belt 12 and the second matte-surface metal belt 15 between them, whereby the modification area of the web W is the hard metal belt / metal belt zone N6, whose length enables a longer dwell time, and moreover, the optional nip rolls 16, 16' used as pressing elements enable making the form of the pressure impulse as desired. Optionally, one of the hard surfaces of the hard nip zone N6, the metal belt 12, for example, may have a smooth surface.

The temperature of the matte surface of the rolls and belts shown in Figures 3 to 5 can be arranged to be in the range of about 80 to 220°C, particularly preferably in the range of about 140 to 200°C when the web W is calendered. According to one embodiment, the magnitude of the pressure maximum in the nip zones Nl to N6 is about 0.2 to 40 MPa, particularly preferably about 5 to 20 MPa.

According to one embodiment, the fibrous web W shown in Figures 3 to 5 is woodfree uncoated paper, such as copying paper or color copying paper (WFU), whose bulk is 1.1 to 1.4 and smoothness is 6.0 to 4.0 PPS or about 50 to 200 ml/min Bendtsen or better than said smoothness values.

According to one embodiment, the fibrous web W shown in Figures 3 to 5 is wood-containing uncoated paper.

According to one embodiment, the fibrous web shown in Figures 3 to 5 is woodfree coated paper, such as fine paper (WFC) that is suitable for use in high- quality printed products, such as brochures, art printed products, etc., whose bulk is about 0.8 to 1.0 and smoothness about 0.8 to 1.2 PPS.

According to one embodiment, the fibrous web W shown in Figures 3 to 5 is wood-containing coated paper. According to one embodiment, the fibrous web W shown in Figures 3 to 5 is board.

At least one hard nip and/or nip zone shown in Figures 3 to 5 may be arranged in a machine calender, a metal belt calender or the roll stack of a multiroll calender.

The invention has been described above by using a metal roll, particularly a matte-surface thermo roll, as an example of a hard roll surface, but another hard inelastic roll surface may be used, such as a metal coated roll surface. It is preferable to use a special ceramic coated matte-surface roll. Likewise, the invention has been described above by using a metal belt as an example of a hard belt surface; it is preferable to use a heatable matte-surface belt, such as a metal belt, but another hard inelastic belt surface may be used.

The invention has been specified above by way of example by reference to the figures of the appended drawings. However, the invention is not limited to what has been described in the description and figures, but different embodiments of the invention may vary within the framework of the inventive idea defined in the appended claims.

Claims

1. A method of calendering a low-gloss fibrous web (W), such as paper, board or a corresponding web, so that the fibrous web is passed through a nip zone (Nl to N6) formed by two hard surfaces so that the fibrous web (W) to be processed is pressed in said hard nip zone (Nl to N6) formed by at least two hard surfaces, characterized in that the fibrous web (W) is calendered in at least one hard nip zone (Nl to N6), in which nip zone at least one surface (10, 11, 12, 15) pressing the web is arranged as a hard matte-surface rough surface manufactured to have an Ra roughness of 0.2 to 1.0 μm, preferably an R_a roughness of 0.4 to 0.6 μm, in order to calender the fibrous web (W) to be matte-like.

2. A method as claimed in claim 1, characterized in that, in the nip zone (Nl to N6), at least one surface pressing the web (W) is arranged to be the surface of a matte-surface thermo roll (10, 11).

3. A method as claimed in claim 1, characterized in that, in the nip zone (Nl to N6), at least one surface pressing the web (W) is arranged to be the surface of a matte-surface metal belt (12, 15).

4. A method as claimed in any one of claims 1 to 3, characterized in that, in the nip zone (Nl to N6), two surfaces (10, 12) pressing the web (W) between them are arranged to be matte surfaces, whereby in the same nip zone both surfaces of the fibrous web (W) are calendered to be matte-like.

5. A method as claimed in any one of claims 1 to 4, characterized in that, in the nip zone (Nl to N6), the temperature of the matte surface is arranged to be about 80 to 22O⁰C, preferably about 140 to 200⁰C.

6. A method as claimed in any one of claims 1 to 5, characterized in that, in the nip zone (Nl to N6), the pressure maximum is arranged to be about 0.2 to 40 MPa, preferably about 5 to 20 MPa.

7. A method as claimed in any one of claims 1 to 6, characterized in that the method is used to calender woodfree uncoated paper (W), such as copying paper or color copying paper (WFU) whose bulk is 1.1 to 1.4 and whose smoothness is 6.0 to 4.0 PPS or about 50 to 200 ml/min Bendtsen or better.

8. A method as claimed in any one of claims 1 to 6, characterized in that the method is used to calender wood-containing uncoated paper.

9. A method as claimed in any one of claims 1 to 6, characterized in that the method is used to calender woodfree coated paper, such as fine paper (WFC) whose bulk is about 0.8 to 1.0 and smoothness about 0.8 to 1.2 PPS.

10. A method as claimed in any one of claims 1 to 6, characterized in that the method is used to calender wood-containing coated paper.

11. A method as claimed in any one of claims 1 to 6, characterized in that the method is used to calender board.

12. A device (100) for calendering a low-gloss fibrous web (W), such as paper, board or a corresponding web, which device comprises a hard nip zone (Nl to N6), which is formed between at least two hard surfaces for passing the fibrous web (W) through said hard nip zone (Nl to N6) and pressing it, characterized in that the device (100) comprises at least one hard nip zone (Nl to N6), wherein at least one surface pressing the web is a hard matte-surface rough surface manufactured to have an Ra roughness of 0.2 to 1.0 μm, preferably an R₃ roughness of 0.4 to 0.6 μm, in order to calender the fibrous web (W) to be matte- like.

13. A device (100) as claimed in claim 12, characterized in that, in the nip zone (Nl to N6), at least one surface pressing the web (W) is the surface of a matte- surface roll (10, 11).

14. A device (100) as claimed in claim 13, characterized in that the matte-surface roll (10, 11) is a thermo roll.

15. A device (100) as claimed in claim 12, characterized in that, in the nip zone (Nl to N6), at least one surface pressing the web (W) is the surface of a matte- surface belt (12, 15).

16. A device (100) as claimed in claim 15, characterized in that the matte-surface belt (12, 15) is heatable.

17. A device (100) as claimed in any one of claims 12 to 16, characterized in that, in the nip zone (Nl to N6), two surfaces (10, 12) pressing the web (W) between them are matte surfaces, whereby both surfaces of the fibrous web (W) are calendered to be matte-like in the same nip zone.

18. A device (100) as claimed in any one of claims 12 to 17, characterized in that, in the nip zone (Nl to N6), the matte surface is heatable to the temperature of about 80 to 22O⁰C, preferably about 140 to 200°C.

19. A device (100) as claimed in any one of claims 12 to 18, characterized in that, in the nip zone (Nl to N6), the magnitude of the pressure maximum is about 0.2 to 40 MPa, preferably about 5 to 20 MPa.

20. A device as claimed in any one of claims 12 to 19, characterized in that the nip zone (Nl to N6) is a belt/roll nip (N3), a belt/roll zone (N2; N4; N5), a belt/belt nip or a belt/belt zone (N6).

21. A device (100) as claimed in any one of claims 12 to 19, characterized in that the nip zone (Nl to N6) is a roll/roll nip (Nl) or a roll/roll zone.

22. A device (100) as claimed in any one of claims 12 to 19, characterized in that the nip zone (Nl to N6) is a nip or zone of a metal belt calender.

23. A device (100) as claimed in any one of claims 12 to 19, characterized in that the nip zone (Nl to N6) is a nip or zone of a machine calender or a long nip calender.

24. A device (100) as claimed in any one of claims 12 to 19, characterized in that the nip zone (Nl to N6) is a nip or zone of a multiroll calender.