|
(11) | EP 2 682 521 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
||||||||||||||||||||
| (54) | Process and device for treating fiber webs |
| (57) The invention relates to process for treating a fiber web, especially a board web,
in which process fiber web is guided into a processing zone that is created in between
a belt (21) and at least one cylinder or roll (14, 16) and/or in between two belts
(22, 23), in which processing zone the fiber web (w) is treated, advantageously calendered,
during a dwell time. In the process the fiber web is treated in the processing zone
for a long dwell time for at least 200 ms and in moderate temperatures in the range
of 60 - 180 ºC. The processing zone comprises at least three stages in any order:
a short-treatement stage, a loading stage and a long-treatment stage. In the short-treatment
stage the dwell time is less than 200 ms and the load is 0,01- 10 MPa. In the loading
stage the dwell time is 1 ― 20 ms and the load is 0,1 ― 100 MPa. In the long-treatment
stage the dwell time is more than 100 ms and the load is 0,01 ― 10 MPa. The invention
also relates to a device for treating a fiber web.
|
[0001] In general present invention relates to treating fiber webs in a fiber web machine. More especially the present invention relates to a process according to preamble part of claim 1 and to a device according to the preamble part of claim 8.
[0002] As known from the prior art in fiber web producing processes typically comprise an assembly formed by a number of apparatuses arranged consecutively in the process line. A typical production and treatment line comprises a head box, a wire section and a press section as well as a subsequent drying section and a reel-up. The production and treatment line can further comprise other devices and sections for finishing the fiber web, for example, a sizer, a calender, a coating section. The production and treatment line also comprises at least one winder for forming customer rolls as well as a roll packaging apparatus. In this description and the following claims by fiber webs are meant for example a paper, board and tissue webs.
[0003] Calendering is generally carried out in order to improve the properties, like smoothness and gloss, of a web-like material such as a paper or board web. In calendering the web is passed into a nip, i.e. calendering nip, formed between rolls that are pressed against each other, in which nip the web becomes deformed as by the action of temperature, moisture and nip pressure. In the calender the nips are formed for example between a smooth-surfaced press roll such as metal roll and a roll coated with resilient material such as a polymer roll. The resilient-surfaced roll adjusts itself to the forms of the web surface and presses the opposite side of the web evenly against the smooth-surfaced press roll.
[0004] In WO publication 03/064764 is disclosed a processing device and a method applying the same for processing a coated or uncoated fiber web. The device comprises a belt adapted to extend around a guiding element, at least one counter element being disposed outside the belt to provide contact area with the belt such that the belt and the counter element establish there between a web processing zone for passing the web to be processed there through. The processing zone length is defined by means of disposition of the belt's guiding element and/or by means of design of the counter-elements. A contact pressure applied to a web in the processing zone is adapted to be adjustable within the range of about 0,1 MPa to about 70 MPa. In this prior art belt calender the dwell time i.e. the contact time of the web in the processing zone is about 5 - 200 ms, preferably about 20 - 80 ms, and this WO publication 03/064764 mentions that dwell time can be even up to 2 s or even in order of 10 s. This publication does not mention any special uses or advantages for these long dwell times nor describes any examples or embodiments using these long and merely mentions them as farfetched examples and instead focuses to dwell times of 5 - 200 ms for actual implementations of the process and method presented.
[0005] In WO publication 2006/12856 is disclosed a method and equipment for manufacturing fiber web, comprising the formation of at least one layer of fiber web from stock with solids content over 1,5 %, water being removed from the fiber web by first pressing the fiber web to solids content of about 45 to 65 %, then evaporating the fiber web to solids content of about 75 to 95 %, after which the fiber web is treated by means of a pressing contact to increase its smoothness, the fiber web being treated in the manufacturing process before the reeling stage by at least one pressure and heat treatment, wherein the forming pressure exerted on the fiber web is not higher than 20 MPa. In this prior art method dwell time from 20 to 100 ms and mentions as a preferable example for the method that before the pressure and heat treatment, at the evaporation stage of drying the fiber web, the fiber web is treated by means of smooth contact surface, such as a drying cylinder or the cylinder of Yankee dryer so that the total contact time is at least 1000 ms. The pressure and heat treatment equipment comprise a metal belt conveyor, long nip calender, conventional belt calender, and Condebelt dryer or Yankee dryer.
[0006] In WO publication 2007/110472 is disclosed a method producing coated paper or board. In the method the fiber web is conveyed to a precalendering device before coating and the paper or board is dried in one or more stages and dried after coating in at least one coating stage. In the method is used a precalender and/or intermediate calender which is selected from a group comprising a metal belt calender and a long nip calender. In this prior art method dwell time of the fiber web on the nip or in the calendering zone is 10 ms.
[0007] In prior art no special focus has been given to longer dwell times for example to dwell times over 200 ms since this is sufficient when prior art type belt calendering process is used and it has not been an attractive alternative due to long belt contact zone required for fast production speeds.
[0008] Paper and board are available in a wide variety of grades and can be divided according to basis weight in two grades: papers with a single ply and a basis weight of 25 - 300 g/ m2 and boards manufactured in multi-ply technology and having a basis weight of 150 - 600 g/ m2. It should be noted that the borderline between paper and board is flexible since board grades with lightest basis weights are lighter than the heaviest paper grades. Generally speaking, paper is used for printing and board for packaging.
[0009] The subsequent descriptions are examples of some values presently applied for fibrous webs, and there may be considerable variations from the disclosed values. The descriptions are mainly based on the source publication Papermaking Science and Technology, section Papermaking Part 3, edited by Jokio, M., published by Fapet Oy, Jyväskylä 1999, 362 pages.
[0010] Mechanical-pulp based, i.e. wood-containing printing papers include newsprint, uncoated magazine and coated magazine paper.
[0011] Newsprint is composed either completely of mechanical pulp or may contain some bleached softwood pulp (0 - 15 %) and/or recycled fiber to replace some of the mechanical pulp. General values for newsprint can be regarded as follows: basis weight 40 - 48,8 g/m2, ash content (SCAN-P 5:63) 0 - 20 %, PPS s10 roughness (SCAN-P 76:95) 3,0 - 4,5 µm, Bendtsen roughness (SCAN-P 21:67) 100 - 200 ml/min, density 200 - 750 kg/m3, brightness (ISO 2470:1999) 57 - 63 %, and opacity (ISO 2470:1998) 90 - 96 %.
[0012] Uncoated magazine paper (SC=supercalendered) usually contains mechanical pulp to 50 - 70 %, bleached softwood pulp to 10 - 25 %, and fillers to 15 - 30%. Typical values for calendered SC paper (containing e.g. SC-C, SC-B. SC-A/A+) include basis weight 40 - 60 g/m2, ash content (SCAN-P 5:63) 0 - 35 %, Hunter gloss (ISO/DIS 8254/1) < 20 - 50 %, PPS s10 roughness (SCAN-P 76:95) 1,2 - 2,5 µm, Bendtsen roughness (SCAN-P 21:67) 100 - 200 ml/min, density 700 - 1250 kg/m3, brightness (ISO 2470:1999) 62 - 70 %, and opacity (ISO 2470:1998) 90 - 95 %.
[0013] Coated magazine paper (LWC = light weight coated) contains mechanical pulp to 40 - 60 %, bleached softwood pulp to 25 - 40 %, and fillers and coaters to 20 - 35 %. General values for LWC paper can be regarded as follows: basis weight 40 - 70 g/m2, Hunter gloss 50 - 65 %, PPS s10 roughness 0,8 - 1,5 µm (offset), 0,6 - 1,0 µm (roto), density 1100 - 1250 kg/m3, brightness 70 - 75 %, and opacity 89 - 94 %.
[0014] General values for MFC (machine finished coated) can be regarded as follows: basis weight 50 - 70 g/m2, Hunter gloss 25 - 70 %, PPS s10 roughness 2,2 - 2,8 µm, density 900 - 950 kg/m3, brightness 70 - 75 %, and opacity 91 - 95 %.
[0015] General values for FCO (film coated offset) can be regarded as follows: basis weight 40 - 70 g/m2, Hunter gloss 45 - 55 %, PPS s10 roughness 1,5 - 2,0 µm, density 1000 - 1050 kg/m3, brightness 70 - 75 %, and opacity 91 - 95 %.
[0016] General values for MWC (medium weight coated) can be regarded as follows: basis weight 70 - 90 g/m2, Hunter gloss 65 - 75 %, PPS s10 roughness 0,6 - 1,0 µm, density 1150 - 1250 kg/m3, brightness 70 - 75 %, and opacity 89 - 94 %.
[0017] HWC (heavy weight coated) has a basis weight of 100 - 135 g/m2 and can be coated even more than twice.
[0018] Wood free printing papers or fine papers include uncoated - and coated - pulp-based printing papers, in which the portion of mechanical pulp is less than 10 %.
[0019] Uncoated pulp-based printing papers (WFU) contain bleached birchwood pulp to 55 - 80 %, bleached softwood pulp 0 - 30 %, and fillers to 10 - 30 %. The values with WFU have a large variation: basis weight 50 - 90 g/m2, Bendtsen roughness 250 - 400 ml/min, brightness 86 - 92 %, and opacity 83 - 98 %.
[0020] In coated printing papers (WFC), the amounts of coating vary widely in accordance with requirements and intended application the following are typical values for once- and twice-coated, pulp-based printing paper: once-coated basis weight 90 g/m2, Hunter gloss 65 - 80 %, PPS s10 roughness 0,75 - 2,2 µm, brightness 80 - 88 %, and opacity 91 - 94 %, and twice-coated basis weight 130 g/m2, Hunter gloss 70 - 80 %, PPS s10 roughness 0,65 -0,95 µm, brightness 83 - 90 %, and opacity 95 - 97 %.
[0023] Board making makes use of chemical pulp, mechanical pulp and/or recycled pulp. Boards can be divided e.g. in the following main groups cartonboards, containerboards and specialty boards. Cartonboards are mainly used for consumer product packaging and they comprise boxboards, used for making boxes, cases, which boxboards include e.g. liquid packaging boards; FBB = folding boxboard, WLC = white-lined chipboard, SBS = solid bleached sulfate board, SUS = solid unbleached sulfate board and LPB = liquid packaging board. Containerboards comprise f. ex. linerboard, fluting board and other corrugated boards and specialty boards comprise wallpaper base, plaster board etc. Graphic boards are used for making e.g. cards, files, folders, cases, covers, etc. and wallpaper bases. Each end use sets its own demands on the mechanical and functional properties of boards. Basically a certain mechanical strength and stiffness, especially bending stiffness is required, and in the optimum structure middle-ply is very bulky and top and back plies have high modulus of elasticity. Often also purity and cleanliness requirements are very high and also almost all boards have defined printing properties and for example the printing requirements of folding box board are usually very high and also high bulkiness is required of folding box board.
[0024] One problem in production of boards is that due to their thickness in treatment of board the effect is not deep enough in the web. For example with calendering of thick board grades the penetration of heat is incomplete and thus the surface structure can be of defective tightness and of incomplete depth, particularly at higher speeds this problem is pronounced.
[0025] An object of the invention is to create a process for treating fiber webs and a device for treating a fiber web, especially paper or board webs, in which good quality fiber web, especially a board web, is produced in an energy efficient and cost effective process.
[0026] Another object if the invention is to further develop the prior art and to eliminate or at least to minimize the disadvantages of prior art especially relating to short heat transfer and influencing times, as well as relating to temperature, moisture and curling control.
[0027] Another object of the invention is to enhance heat transfer and/or drying and/or calendering, particularly at higher speeds.
[0028] One object of the present invention is to solve at least part of the disadvantages and problems relating to production of board, especially solving the problems relating to heat treatment of board and to quality.
[0029] To achieve the objects mentioned above and later the process according to the invention is mainly characterized by the features of the characterizing part of claim 1.
[0030] By the invention a new process for treating, advantageously calendering a fiber web is provided in which long dwell times in the processing zone, advantageously calendering contact zone are used and in which moderate temperatures are used. The long dwell times are at least 200 ms, preferably 200 - 5000 ms, more preferably 200 - 1500 ms. The temperatures used are in the range of 60 - 180 ºC, preferably in the range of 80 - 120 ºC. By this long contact zone and moderate temperatures very good processing and calendering results are achieved. The long dwell time provides for the web to be throughout heat treated.
[0031] Long dwell time is provided by combination of the length of the processing zone and the running speed of the fiber web and in advantageous cases for board webs the length of the processing zone is 1 - 10 m, advantageously 2 - 4 m and the running speed of the web is 300 - 800 m/min for thick board grades, 800 - 1200 m/min for medium thick board grades, for example liners, and over 1200 m/min for paper grades.
[0032] According to the invention the processing zone has at least three stages: short-treatment stage, loading stage and long-treatment stage in any order: in the short-treatment stage the dwell time is long and the load is small, in the loading the dwell time is short and the load is heavy and in the long-treatment stage the dwell time again is long and the load is small. Also the temperature in different stages may vary. The loading stage can be profiling in the cross direction of the web. The loading stage can be created by a loading element that is a loadable element for example a loadable roll located on at least one cylinder or roll guiding the belt. The loading element can also be a hydrodynamically loaded shoe or a pressure chamber.
[0036] The temperature in the short-treatment stage, in the loading stage and in the long-treatment stage can be same in all stages or it can be different in at least one of the stages. Advantageously temperature is 80 - 120 °C. According to an advantageous feature at least one of the stages comprises a temperature control device.
[0037] According to one aspect of the invention the short-treatment stage and the long-treatment stage can be in opposite process order and even the loading stage can be the first or last stage in process order followed or preceded by the short-treatment and long-treatment stages in any order.
[0038] According to an advantageous feature of the invention in connection with the short-treatment stage and/or the long-treatment stage a temperature control device is used, which can be a heating or a cooling device with for example separately controllable temperature zones in the running direction of the web.
[0039] The process according to the invention is used in connection of treating of a fiber web such as paper or board, advantageously of board web and advantageously in connection of calendering, in precalendering or for example in end calendering of special products of pulp. It can also be used for processing and drying purposes, especially for thicker webs when effective heating is required.
[0040] According to the invention the processing zone with long dwell time is provided in between at least one belt, advantageously at least one metal belt, and at least one cylinder or between at least one belt, advantageously at least one metal belt, and at least another belt, advantageously at least one metal belt. The belt/belts are advantageously arranged as continuous, endless loops and the loops are guided by guide rolls and corresponding guide elements known as such to one skilled in the art. The cylinder of the processing zone has advantageously a diameter in the range of 0,5 - 6 m, preferably 1,8 - 5 m. The belt is advantageously metal or metal with a layer of synthetic material but also synthetic materials such as plastics, for example PU (polyurethane), PEEK (polyether ether ketone), PFD (polyphenylenediene), Teflon and rubber are suitable to be used as belt materials. Also the synthetic material may have a metal layer. Further the belt may be of material that has strengthening fibers, for example of glass, aramid or metal. The belt may also comprise several layers of different or same material. The processing zone created of at least three stages, the first stage the web is treated in between the belt and its counter surface formed by a roll, in the second stage in addition another roll is provided for further load and in the third stage again the web is treated in between the belt and the roll. The belt may also be a felt, a wire and any corresponding fabric.
[0041] The invention is advantageously used in production of fiber webs as precalendering process or as a new process replacing precalendering. The process is advantageously used in production of coated fiber webs. The process according to the invention is also very advantageous in connection with board webs of higher thickness of over 250 µm, especially in connection with board webs of grammage over 100 g/m2, advantageously over 200 g/m2.
[0042] Advantageously the process according to the invention is combined with contactless coating, such as curtain or spray coating by which uniform coverage is achieved but require smooth surface which by the long contact zone is achieved. Also other coating methods can be used. The process according to the invention can also be combined with drying such that the contact zone also has a drying effect.
[0043] In an advantageous example of the invention a process for fiber web is provided in which a web-like product of new type with low cost is produced by using cheaper raw materials: pulp, coating paste. For example a by the invention first a smooth surface is provided for liner- or fluting-type base and then the product is coated by curtain coating. In this example a new product replacing board of white-top-liner (WTL) type is achieved. In another example in a fiber web or one of its plies cheaper fiber material is used than in corresponding web according to prior art. The cheaper fiber material may comprise greater amount of filler or recycled fiber or less grounded fiber.
[0044] The invention is utilizable also in connection with production of special materials, for example foils, fiber web comprising nanosellulose, barrier-layers, fine material layering on the surfaces and in connection with their calendering, laminating, processing where long dwell times are required in belt contact zone.
[0045] In the process according to the invention is provided good total thermal transmission in connection with required varying load due to simultaneous high thermal coefficient and long dwell time and the stage-wise treatment of the web in at least three stages. Especially in connection with thicker webs the invention is very advantageous as inner thermal conductivity limits the thermal transfer and thus longer dwell times result better total thermal transmission while lower temperatures can be used. Better thermal transmission results, better softening, better plasticization, better forming, better compression, better smoothing of the surfaces of the web are achieved but requiring less load when compared to prior art methods. The short dwell time in the high load stage provides for good surface properties in connection with high bulkiness.
[0047] By the invention many advantages are achieved:
- calendering results are very good, especially in smoothness of large scale (Bendtsen roughness 100 - 300 ml)
- both sides of the web will be smoothened simultaneously to good smoothness values and high symmetricity
- long dwell time increases the effect of heating and thus lower pressure (belt tightness) can be used and thus bulk is saved
- coating methods that require smooth surface, such as curtain or spray coating, can be used for coating which methods are contactless and also have good runnability properties
- moderate process temperature is used and still good end result is achieved. Temperatures under 100 ºC can be used and thus energy costs will be reduced, for example low pressure steam can be used and thus the hot oil system can be omitted. Also when moderate temperatures are used also the heat losses are smaller. By this also significantly lower energy cost is achieved.
[0048] In the following the invention is discussed in more detail by reference to figures of accompanying drawings.
Figure 1 shows schematically an example of an embodiment of the invention.
Figure 2 shows schematically another example of an embodiment of the invention.
Figure 3 shows schematically a further example of an embodiment of the invention.
Figure 4 shows schematically a further example of an embodiment of the invention.
Figure 5 shows schematically a further example of an embodiment of the invention.
[0049] In the following description same reference signs designate for respective components etc. unless otherwise mentioned and it should be understood that the examples are susceptible of modification in order to adapt to different usages and conditions within the frames of a belt dying device.
[0050] In the example of figure 1 the fiber web is guided to the processing zone, which is provided in between a belt, advantageously a metal belt 21 and a cylinder or roll 14. In which processing zone the fiber web has long dwell time. The cylinder 14 and/or the belt 21 are heated and the diameter of the cylinder 14 is 0,5 - 6 m, advantageously 1,8 - 5 m. The metal belt 21 is formed as a continuous loop and its run is guided by rolls 15. In this example the fiber web W is treated in the processing zone, for example a calendering zone while it is between the surface if the cylinder 14 and the metal belt 21. According to the invention the processing zone has been divided into three stages I, II, III by a loadable roll 20. In the three stages I, II, III i.e. in short-treatment stage I, profiling nip II i.e. loading stage II and long-treatment stage III: in the first stage I the dwell time is long and the load is small, in the second stage II the dwell time is short and the load is heavy and in the third stage III the dwell time again is long and the load is small. Also the temperature in different stages may vary. In the first stage dwell time is less than 200 ms, advantageously less than 100 ms, load is 0,01- 10 MPa. In the second stage dwell time is 1 - 20 ms, load is 0,1 - 100 MPa. In the third stage dwell time is more than 100 ms, load is 0,01 - 10 MPa.
[0051] In the example of figure 2 the fiber web is guided to the processing zone, which is provided in between a belt, advantageously a metal belt 21 and a cylinder or roll 14. In which processing zone the fiber web has long dwell time. The cylinder 14 and/or the belt 21 are heated and the diameter of the cylinder 14 is 0,5 - 6 m, advantageously 1,8 - 5 m. The metal belt 21 is formed as a continuous loop and its run is guided by rolls 15. In this example the fiber web W is treated in the processing zone, for example a calendering zone while it is between the surface if the cylinder 14 and the metal belt 21. According to the invention the processing zone has been divided into two sections with three stages I, II, III by a loadable rolls 20. The last stage III of the first section is simultaneously the first stage I of the second section. In the three stages I, II, III of short-treatment stage I, profiling nip II i.e. loading stage and long-treatment stage III: in the first stage I the dwell time is long and the load is small, in the second stage II the dwell time is short and the load is heavy and in the third stage III the dwell time again is long and the load is small. Also a heating / cooling device 30 can be used for further heating or cooling of belt 21 and by the means of the belt to heat or cool the web W.
[0052] In figure 3 an example is shown in which the processing zone is provided in two sequences, which sequences of the processing zone are created between the belt 21 and two rolls or cylinders 14. The belt 21 is advantageously a metal belt formed as an endless loop which is guided by rolls 14, 15, 16. One of the rolls 16 can be heatable and/or a heating device 25 can be located in connection with the belt 21 for heating. The heating device 25 is advantageously a steam heater or induction heater and its temperature is advantageously 90 - 120 ºC. Also rolls 14 can be heatable. This example can be used for example for treating moist fiber web W that has solids content in the range of 55 - 75 % as between the sequences of the processing zone evaporation can occur which evaporation can be further intensified by heating the roll 16. According to the invention the processing zone has been divided into two sections with three stages I, II, III by a loadable rolls 20. In the three stages I, II, III of short-treatment stage I, profiling nip II i.e. loading stage II and long-treatment stage III: in the first stage I the dwell time is long and the load is small, in the second stage II the dwell time is short and the load is heavy and in the third stage III the dwell time again is long and the load is small. Also a heating / cooling device 30 can be used for further heating or cooling of belt 21 and by the means of the belt to heat or cool the web W.
[0053] In the example of figure 4 the processing zone has been created between two belts 22, 23, advantageously metal belts of which at least one belt 23 is heated. Both belts 22, 23 are formed as continuous, endless loops that are guided by rolls and/or cylinders 14, 15, 16. Advantageously rolls or cylinders 14 are heatable and a heating device 26 is provided for heating the belt 23. The heating device is for example an induction heater or a steam heater. Also a blow device 27 located in connection with one of the processing zones for intensifying the evaporation. According to the invention the processing zone has been divided into two sections with three stages I, II, III by a loadable rolls 20. In the three stages I, II, III of short-treatment stage I, profiling nip II i.e. loading stage II and long-treatment stage III: in the first stage I the dwell time is long and the load is small, in the second stage II the dwell time is short and the load is heavy and in the third stage III the dwell time again is long and the load is small. Also the temperature in different stages may vary. Also heating / cooling devices 30 can be used for further heating or cooling of belts 22, 23 and by the means of the belt to heat or cool the web W.
[0054] In the example of figure 5 the fiber web is guided to the processing zone, which is provided in between a belt, advantageously a metal belt 21 and a cylinder or roll 14. In which processing zone the fiber web has long dwell time. The cylinder 14 and/or the belt 21 are heated and the diameter of the cylinder 14 is 0,5 - 6 m, advantageously 1,8 - 5 m. The metal belt 21 is formed as a continuous loop and its run is guided by rolls 15. In this example the fiber web W is treated in the processing zone, for example a calendering zone while it is between the surface if the cylinder 14 and the metal belt 21. According to the invention the processing zone has been divided into four stages II, III, II, I by loadable rolls 20. The four stages II, III, II, I comprise two loading stages II, one long treatment stage III and one short-treatment stage I. Also the temperature in different stages may vary. In the short-treatment stage I dwell time is less than 200 ms, advantageously less than 100 ms, load is 0,01- 10 MPa. In the loading stages II dwell time is 1 - 20 ms, load is 0,1 - 100 MPa. In the long-treatment stage III dwell time is more than 100 ms, load is 0,01 - 10 MPa.
[0055] In connection with the examples of figures 1 - 5 there may be a cooling device before and/or after the processing zone.
[0056] In one test fluting base fiber web that had basis weight was 125 g/m2 was tested in a belt calender that had contact zone between belt and thermo roll. The dwell time 500 ms, temperature of thermo roll 100 ºC, temperature of belt 80 ºC was used and thus the process corresponded to precalendering with long dwell time and moderate temperature. The end result was a very smooth and good quality web when compared with a reference in which machine calendering was used. Bendtsen roughness of upper side 235 ml/min and of lower side 285 ml/min, bulk 1.3 properties were measured from the web produced in accordance with the invention. The reference test with machine calender resulted Bendtsen roughness of upper side 300 ml/min and of lower side 470 ml/min, bulk 1.3. The sensing smoothness was very good, which means that the topography of the surface is smooth. Porosity values of both web tests were at same level.
1. Process for treating a fiber web, especially a board web, in which process fiber web
is guided into a processing zone that is created in between a belt (21) and at least
one cylinder or roll (14, 16) and/or in between two belts (22, 23), in which processing
zone the fiber web (w) is treated, advantageously calendered, during a dwell time
characterized in, that in the process the fiber web is treated in the processing zone for a long dwell time
for at least 200 ms and in moderate temperatures in the range of 60 - 180 ºC,
that the processing zone comprises at least three stages in any order:
that the processing zone comprises at least three stages in any order:
a short-treatement stage, a loading stage and a long-treatment stage,
that in the short-treatment stage the dwell time is less than 200 ms and the load is 0,01- 10 MPa,
that in the loading stage the dwell time is 1 - 20 ms and the load is 0,1 - 100 MPa and
that in the long-treatment stage the dwell time is more than 100 ms and the load is 0,01 - 10 MPa.
2. Process according to claim 1, characterized in that in the process the fiber web is treated in the processing zone for a long dwell time
for 200 - 5000 ms and in temperatures in the range of 80 - 120 ºC.
3. Process according to claim 1, characterized in, that the loading stage is created by a loadable roll (20), which is located on at least
one cylinder or roll (14), or by a loading element.
4. Process according to claim 1, characterized in, that at least one of the stages comprises a temperature control device.
5. Process according to claim 1, characterized in, that in the process for a board web long dwell time is provided by combination of the
length of the processing zone and 1 - 10 m, advantageously 2 - 4 m, and the running
speed of the web is 300 - 800 m/min for thick board grades, 800 - 1200 m/min for medium
thick board grades and over 1200 m/min for paper grades.
6. Process according to claim 1, characterized in that in the process the long dwell time in the processing zone is in connection of precalendering
of the fiber web.
7. Process according to claim 1, characterized in, that the processing zone is one continuous processing zone.
8. Device for treating a fiber web, especially a board web, in which device comprises
means for guiding the fiber web into a processing zone that is created in between
a belt (21) and at least one cylinder or roll (14, 16) and/or in between two belts
(22, 23), in which processing zone the fiber web (w) is treated, advantageously calendered,
during a dwell time, characterized in, that in the processing zone is provided for threating the fiber web in the processing
zone for a long dwell time for at least 200 ms and in moderate temperatures in the
range of 60 - 180 ºC, that the processing zone comprises at least three stages in
any order: a short-treatement stage, a loading stage and a long-treatment stage,
that in the short-treatment stage the dwell time is less than 200 ms and the load is 0,01- 10 MPa,
that in the loading stage the dwell time is 1 - 20 ms and the load is 0,1 - 100 MPa and
that in the long-treatment stage the dwell time is more than 100 ms and the load is 0,01 - 10 MPa.
that in the short-treatment stage the dwell time is less than 200 ms and the load is 0,01- 10 MPa,
that in the loading stage the dwell time is 1 - 20 ms and the load is 0,1 - 100 MPa and
that in the long-treatment stage the dwell time is more than 100 ms and the load is 0,01 - 10 MPa.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description
Non-patent literature cited in the description
- Papermaking Science and TechnologyFapet Oy19990000362 pages- [0009]