AT504470A2 - METHOD AND ARRANGEMENT FOR PRODUCING PAPER - Google Patents

Description

Method and arrangement for the production of paper

The invention relates to a method for producing different paper grades by the same paper machine, wherein the formed and at least partially dried web is treated in a coating unit (20) by spraying a liquid treating agent onto the surface of the web, the web thereafter being conveyed in a calendering unit (40 ) is affected by heat and compression to at least increase the smoothness of the web and, if desired, its gloss. The invention also relates to an arrangement for producing different paper grades by the same paper machine comprising means for forming a web and at least partially drying the web and a coating unit (20) for treating the web, the coating unit comprising means for spraying a liquid treating agent is on the surface of the web, wherein thereafter in the direction of the formation of the web, a calendering unit (40) is present in order to increase at least the smoothness and, if desired, the gloss of the web by means of heat and compression.

The SC paper grade is conventionally made from wood pulp, one of its particular manufacturing characteristics being intensive calendering by a supercalender. Previously, these supercalenders used almost exclusively filled rolls and cooled rolls, with the web passing through the nip between the rolls. In order to obtain similar properties on both sides of the web, it is possible to: • t ·············································································· «···· · •" i " The so-called reversing nip in the middle of the assembly formed by the rolls is used, with the sides of the cooled and filled rolls being changed at this reversing nip in relation to the web. At present, multi-roll calenders are used instead of the supercalender, with their operating principle being nearly the same, providing stronger polymer-coated rolls instead of the filled rolls. The number of nips treating the web has also changed. Instead of the former 8 to 12 roll nips, there may be the same number of nips, or alternatively different calenders consisting of several sets of rolls, such as those having 3 + 5, 2 + 4, 4 + 5, 3 + 3 nips, etc. In principle, however, the paper quality characteristics remained the same in the sense that the new calenders can also be used to produce paper with similar characteristics as before. SC paper can be subdivided into different subspecies SC-A +, SC-A, SC-B +, SC-B, SC-C, the distinguishing factors being gloss and smoothness, raw material and filler content. The gloss of SC-A is of the order of 46 to 55% and its roughness of 1.0 to 1.3 μπι, while the corresponding values of SC-C from 18 to 27% for gloss and from 1.8 to 2 , 4 μπι amount to roughness. Such large differences are not possible merely by changing the calendering parameters, but, of course, to achieve these values, the constituents contained in the fibrous web differ from each other, with a distinctive constituent being ashes. As an extremely fine-grained ingredient, ash greatly affects the calendering result. In principle, with the increase of its share by calendering a brighter and smoother paper is obtained. Similar to SC quality, LWC (Light Weight Coated) paper is mainly made from wood containing, ie. H. Wood pulp produced. In addition to the sub-processes included in the production of SC grades, this manufacturing process also includes brushing, which is done prior to calendering. A typical spread of LWC paper is 10 g / m2 per side, generally 16-25 g / m2 overall, providing a light and smooth surface that is good at replica pressure. There are a number of different methods, such as, for example, dabbing, sizing, spraying, sizing, curtain coating, etc. In order to provide better qualities, these methods can also be combined, but in the production of good quality basic LWCs, both sides of the web will travel only once be deleted. The publication WO 02/103109 presents a rather versatile selection of factors related to the production of LWC quality.

The purpose of various ways of altering the surface properties of paper is to provide the properties required by the customer of the paper mill, i. H. from the printing house at the time. Typical uses for these grades of paper include various newspapers, advertisements, inserts and catalogs. At the cheaper end of the scale is the pigmented newspaper print, d. H. improved newspaper print quality, which provides the harshest print and has a low ash content, and at the more expensive end is the SC-A gravure paper, which provides the best print quality, and the LWC offset paper.

The printing processes place different demands on paper qualities. In gravure printing, the ink is transferred from trays on the surface of the printing drum of the printing press to the surface of the paper to be printed. With this method, the smoothness of the printed surface is quite significant for providing good print quality. If the surface is uneven, the ink is unevenly transferred from the shell, air bubbles remain under the ink, and the print character is not repeated as it is on the surface of the pressure roller. In offset printing, first, different ink colors and patterns are built up on the surface of the printing roll by means of chemical adhesion, the ink then being removed therefrom after it has been pressure-adhered to the surface of the paper. In particular, since the surface must withstand the tearing of tacky ink from the surface of the printing roll, this printing process requires surface strength of the printed surface. Therefore, the ink should come down from the interface between the ink and the rubber coating of the press roll. If the printing paper is unsuitable, the paper delaminates on its surface after pressing, d. H. the surface layer of the paper is transferred to the surface of the press roll, causing a failure in printing.

In US 2003 / 0056920A1 a method and equipment for on-line calendering of SC-A in a paper production line is presented. The publication suggests that by positioning a moistening device to moisten the surface of the web from 0.6 to 1.2 seconds prior to the first nip of a multi-roll calender, paper having the desired surface properties can be made. The moistening device produces fine droplets having a mean droplet size of less than 50 μτη or less. The publication states that the humidity after moistening is from 7 to 11%, ie. H. its solids content is from 89 to 93%. ······· ······

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WO 02/103109 presents a process, a paper machine and a base paper for the production of a once coated LWC. The publication shows the selection of suitable components for different structural groups, thereby allowing the use of certain parameters in order to achieve the best possible quality in the product being manufactured. The publication also describes the effect of moistening and brushing parameters on the properties of the product produced.

The object of the invention is to provide a manufacturing method and a paper machine which can be used for the production of printing papers of top quality for different purposes according to the circumstances in an easily selectable manner. In the paper market, the demand for different grades of paper varies greatly according to the terms and conditions and the like, and the object of the invention is to provide an arrangement which enables the full utilization of papermaking investment in the midst of different market conditions. Another object is to extend the quality selection that may be provided by a paper machine to cover the different SC grades from SC-A + to SC-C, and different LWC grades such as offset and roto grades ,

The object of the method is also to provide a versatile arrangement for a wide selection of paper for the so-called gradient calendering of paper, wherein the moisture profile of each paper quality to be produced individually and optimally in the direction of the thickness or in the Z direction before calendering ··· · ····················································································································································································

Make full use of the basic document.

The method according to the invention is characterized in that in the method: the paper quality to be produced is selected, wherein a liquid treatment agent is selected according to the paper quality affecting the web and the characteristics of the paper quality being produced, the liquid processing agent enables one Group of water, water with additives, surface size and pigmented paint and mixtures thereof, a desired solids content of the web is selected before the calendering unit 40, a drying process 30 is selected to obtain the desired solids content, wherein in the dry process 30 Dry process and dry performance, which differ from each other, can be selected between the coating unit 20 and the calendering unit 40, wherein the drying performance of a caused by a gap, natural drying up to a by a e combination of multiple dryers 30, 321, 361 can be selected, wherein the desired solids content of the web is from 85 to 92%, when the liquid treating agent is water, and from 90 to 95%, preferably 92%, when the liquid Treatment agent is the pigment-containing coating agent.

The arrangement according to the invention is in turn characterized in that it comprises: a control unit which enables the selection of paper quality to be produced, wherein the liquid treatment agent can be selected according to the paper quality, the liquid treatment agent enabling the characteristics of the paper quality concerned; the features can be recorded in the memory of the control unit; a coating unit 20 having means for spraying different liquid processing agents, wherein the liquid processing agent can be selected from a group of water, water with additives, surface size and pigmented coating agent and the mixtures thereof, a drying unit 30 implementing different drying processes in order to obtain the desired solids content before the calendering unit, different drying processes and drying powers being selectable in the drying unit, the drying capacity of natural drying caused by a gap up to one obtained by a combination of several dryers 30, 321, 361, so that the desired solids content of the web thus obtained is from 85 to 92% when the liquid treating agent is water and from 90 to 95%, preferably 92%, when the liquid Sige treatment agent is the pigment-containing coating agent. es ··········································································

The method and paper machine according to the invention can be used to expand the quality selection produced by the same paper machine from the conventional, relatively small quality selection to a considerably larger one. In this way, it is easy to meet different market conditions and demands imposed thereby without time-consuming changes that would almost inevitably cause a temporary deterioration of the efficiency and often the performance of the paper machine. When using the invention, it is therefore appropriate to use different ··· ···· ··· ι ·· ···· ······· # ·· ····· ·

To produce paper grades that are, however, of the highest quality for their respective paper grades. The required changes are already integrated into the paper machine, which is why they do not have to be operated in a conventional manner. In this way, a versatile arrangement for a wide selection of paper for the so-called Gradientenkalandrierung of paper is provided, the moisture profile of each paper quality to be produced individually and optimally adjustable in the direction of the thickness or in the Z direction before calendering to the calendering properties of the Make full use of the basic document. This object is implemented by conveniently selecting a combination of the liquid treating agent, drying and residence time, and then, when it comes to the calendering unit, the properties of the web are optimal for the final calendering result.

A preferred feature of the invention is characterized in that the web is treated with the liquid treating agent in a coating unit having at least one means for spraying liquid processing agents having viscosities which differ from one another. The object of the invention was to produce a very extensive paper quality selection which in practice would require the use of different liquid treatment agents. Conventionally, different water spray systems are used for SC paper grades. For the production of LWC paper grades pigment-containing coating compositions are used which can be sprayed onto the surface of the web by means of a spray-coating unit. The liquids comprising water used in the SC paper grades and pigmented brushing agent used in the LWC paper grades differ considerably, especially in their viscosities and as many others

Properties, such as surface tension,

Abrasion and solidification and drying properties. It is advantageous to arrange at least one replaceable nozzle for these different types of liquid treatment agents so that a layer of liquid treatment agent which properly covers and has uniform patterns can be sprayed onto the passing web.

In order to reduce the energy consumed by the process, to reduce web breaks, and to provide the best possible quality of the paper produced, it is preferable that the treatment of the web with the liquid treating agent minimizes the reduction of the total solids content of the web however, such that at least the gloss and smoothness of the web after the calendering unit are indicative of the selected paper grade. One way to implement this is to influence the total solids content of the web after the coating unit by affecting the amount of liquid processing agent that is supplied and the solids content of the liquid processing agent.

The invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a diagram of a possible mode of operation illustrating the invention;

Fig. 2 is a diagram of another possible mode of operation illustrating the invention;

Fig. 3 is a diagram of an alternative embodiment of the coating unit 20; and

Pig. 4 illustrates the characteristics of different paper grades or sub-grades examined for gloss and roughness.

In Fig. 1 is a diagram of the operating mode according to the invention is shown, wherein the processing of the web in the direction of the arrow progresses. In the process, the web, i. H. the SC or LWC base paper to be produced is molded to a sufficient solids content and dried by a paper machine 10 having all the processing equipment necessary to make the base paper. The coating unit 20 comprises all the devices necessary for spraying the liquid processing agent onto the surface of the moving web during production. The drying unit 30 ensures that the web dries to a suitable solids content, i. H. conversely, to suitable moisture in front of the calendering unit 40. In the calendering unit 40, the web is formed by heat and compression to increase at least the smoothness and, if desired, the gloss of the web. A web take-up unit 50 rolls the web onto a roll which can then be conveyed, for example, into a longitudinal cutter, for further processing. Measuring units 60 control the quality characteristics of the web among other things in suitable stages. One method of implementation is to measure preferably the solids content of the web prior to the coating unit 20, immediately after the coating unit 20 and after the calendering unit 40, the measurement being preferably carried out on both surfaces of the web and through the web, the solids content of the web Surface of the web on both sides and the total solids content of the web can be distinguished. A breakpoint or retainer 70 ensures good equipment runnability by maintaining proper web tension at each point. The breakpoint 70 is preferably on the route of

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Web transfer between the coating unit 20 and the calendering unit 40 for controlling the tension of the web in the coating unit 20 and before the calendering unit 40. The tension of the web on different sides of the contact point between the web and the holding member may vary as production progresses during a conventional production, the holding member and the web are in substantially non-sliding contact with each other. liquid supplied

In Fig. 1, the drying unit 30 is also shown in detail, which represents a solution as a possible embodiment, the three different Bahnübertragungsrouten 32, 34 and 36 contains. Therefore, the residence time of the web between the coating unit 20 and the calendering unit 40 in this document can be selected from at least two alternatives 32, 34, 36 having different web transfer routes. By selecting the residence time, the moisture profile in the direction of the thickness of the web is influenced for its part so that between the highest and lowest moisture in the direction of the thickness of the web a greater difference by a shorter residence time, and a smaller difference by a longer residence time provided. Of these web transfer routes, the one shown by reference numeral 34 is an abbreviation on which no separate dryers are present, but the web is dried in a moderately low circumference, the drying being caused by a clearance. In this alternative route, the residence time between the coating unit and the calendering unit is as short as possible, with the moisture contribution in the direction of the thickness of the web deviating from the uniformity. The solids content of the surface of the web after the coating unit can be determined by the hydrophobicity between the .sym.,...,...,...,. ······· 12 · ♦ • ♦ • · • ·

Treatment agent and the web are affected. This chemical process can be easily used to tailor the absorption of the liquid into the web. The web transfer routes 32 and 36 are alternatives that include dry solutions that differ from one another. The drying process 30 may include performance adjustable fluidized bed dryers or other through-dry machines, infrared dryers, interstices and dryer combinations thereof; wherein the dryer combinations may include one or more of the dryers 30, 321, 361. It is also possible to use cylinder dryers or corresponding dryers based on a contact. The lengths of the web transfer routes 32 and 36 may vary depending on the desired run parameter range. In Fig. 2, a drying unit 30 is shown in a corresponding location containing a web transfer route, but with the different drying processes and services required by the different liquid processing agents, by switching on / off different dryers and adjusting the power the dryer can be implemented if necessary. This is a preferred embodiment if the length of the web transfer route between the coating and calendering units remains short enough for the production of SC grades and, on the other hand, sufficient dry performance is obtained for the heaviest end production of the LWC grades.

The coating unit 20 in FIG. 1 is presented as being similar to that in FIG. 2, wherein the coating unit 20 includes two sets of spray heads 22 and 24. The liquid processing agent to be sprayed on the web is supplied from a container T by means of a pressure generating instrument 26. The tubing includes closure devices 25 that are used to direct the liquid processing agent to a desired spray head. In Fig. 3, another possible embodiment is shown, which contains two systems for the liquid treatment agent, including two containers T and two sets of pressure generating devices 26. A particular advantage of this solution is that the qualities can be changed very quickly without the system has to be washed in between, especially in the transition from the production of LWC to that of SC. Another advantage is that the sizing of the tubing and pumps is easier to logically implement as one works closer to the optimal flow situation of each liquid treating agent in relation to the pressures and volume flow rates. One disadvantage, of course, is the larger initial investment.

In the calendering unit 40, the web is affected by heat and compression in at least one nip, preferably by means of a plurality of nips; wherein the nip may be formed by means of rollers, metal bands or bands made of an elastic material or combinations thereof.

The method and arrangement are controlled by a controller based on a model or a multivariable controller, preferably by means of a learning multivariable controller based on a model.

A product provided by the method and arrangement may include SC and LWC paper grades; more specifically, the paper grades from SC-A + to SC-C, new grades and LWC offset and LWC Roto grades, by changing the spray head 22, 24 of the coating unit and possibly the web transfer route 32, 34, 36 between the coating unit 20 and the calendering unit 40, and the control parameter, such as the drying process, which changes are integrated into the paper machine and can be activated by the control system.

Fig. 4 illustrates the typical characteristics of the different sub-qualities of the SC paper grade produced by the method and the paper machine according to the invention, and is distributed in terms of gloss and roughness. It can be seen from the figure that there is a considerable difference between the roughness and gloss between SC-A + and SC-C, which allows for the best print quality and newspaper qualities (newspaper print). The difference between these sub-qualities is not unique, but for the sub-qualities presented, the order of magnitude is shown in FIG. -15: - -15: -

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The reference numerals in the figures: 10 Paper Machine 20 Coater 22 Spray Head / Spray Nozzles 2 4 Spray Head / Spray Nozzles 25 Closures 26 Pressure Generator 30 Drying Unit 32 Web Transfer Route 321 Drying Devices of the Railway Transfer Route 32 34 Rail Route 36 Rail Route 361 Dryers of the Rail Route 36 40 Calendering Unit 50 Web Rolling Unit 60 Measuring Unit, Quality Measurements 70 Breakpoint / Retainer T Container

Claims (23)

A method for producing different grades of paper by the same paper machine, wherein the formed and at least partially dried web is treated in a coating unit (20) by spraying a liquid treating agent onto the surface of the web, the web thereafter heat-treated in a calendering unit (40) and compression is controlled to increase at least its smoothness and, if desired, the gloss of the web, characterized in that the paper quality to be produced is selected, wherein a liquid treatment agent is selected according to the paper quality which influences the web and the web Characteristics of the paper quality of the paper grade being produced enables the liquid treating agent to be selected from a group of water, water with additives, surface size and pigmented paint and mixtures thereof, a desired solid dry process (30) is selected to obtain the desired solids content, wherein in the drying process (30) drying process and drying performance, which differ from each other, between the coating unit (20) and the Calendering unit (40), wherein the drying performance is provided by spaced, natural drying provided by a combination of multiple dryers (30,321,361), wherein the desired solids content of the web is from 85 to 92%, the liquid treating agent being water is, and is from 90 to 95%, preferably 92%, wherein the liquid treatment agent is the pigment-containing coating agent. 2. The method according to claim 1, characterized in that the web is treated with the liquid treatment agent in a coating unit (20) having at least one means for spraying liquid processing agents having viscosities differing from one another. 3. The method according to claim 1, characterized in that the residence time of the web between the coating unit (20) and the calendering unit (40) can be selected from at least two alternatives having different web transfer routes (32,34,36). Method according to claims 1 and 3, characterized in that, by selecting the residence time, the moisture profile in the direction of the thickness of the web is influenced for its part such that between the highest and lowest humidities in the direction of the thickness of the web a larger difference is provided by a shorter dwell time, and a smaller difference by a longer dwell time. 5. The method according to claim 1, characterized in that in the treatment of the web, the reduction of the total solids content of the web by the liquid treatment ♦ ····················································· * Medium is minimized, but so that at least the gloss and smoothness of the web after the calendering unit (40) are indicative of the selected paper grade. A process according to claims 1 and 5, characterized in that the total solids content of the web after the coating unit (20) is influenced by acting on the amount of liquid processing agent which is supplied and on the solids content of the liquid processing agent. 7. The method according to claim 1, characterized in that the solids content of the surface of the web after the coating unit (20) can be influenced by the hydrophobicity between the supplied liquid treatment agent and the web. A method according to claim 1, characterized in that the drying process (30) may include power adaptable fluidized bed dryers or other through-going dryers, infrared dryers, spacers and dryer combinations thereof, wherein the dryer combination may include one or more of the dryers (30,321,361). 9. The method according to claim 1, characterized in that the solids content of the web is preferably measured before the coating unit (20), directly after the coating unit (20) and after the calendering unit (40), wherein the measurement preferably on both surfaces of the web and through the web, the solids content of the surface of the web being distinguishable on both sides, and the total solids content of the web. 10. The method according to claim 1, characterized in that on the web transfer route between the coating unit and the calendering a holding element (70) is arranged in contact with the web, wherein the tension of the web on different sides of the contact point between the web and the holding element at progressively may be different, wherein during a conventional production, the holding member and the web in a substantially non-sliding contact with each other. 11. The method according to claim 1, characterized in that the web in the calendering unit (40) is influenced by heat and compression in at least one nip, preferably by means of a plurality of nips, wherein the nip by means of rolls, metal strips or tapes made of an elastic material or Combinations of which may be formed. 12. The method according to claim 1, characterized in that the method is controlled by means of a control based on a model or a multivariable control, preferably by means of a learning multivariable control based on a model. A product provided by the method of claim 1, characterized by comprising SC and LWC paper grades; more specifically, the paper grades from SC-A + to SC-C, new.. ϊ. ::: grades and LWC offset and LWC Roto qualities, by changing the spray head (22, 24) of the coating unit and possibly the web transfer route (32, 34, 36) between the coating unit (20) and the calendering unit (40) , and the control parameter, such as the drying process, where the changes are integrated into the paper machine and can be activated by the control system. 14. Arrangement for producing different paper grades by the same machine having means for forming a web and at least partially drying the same, and having a coating unit (20) for the treatment of the web, wherein the coating unit comprises means for spraying a liquid treatment agent thereafter comprising a calendering unit (40) in the direction of manufacture of the web, to provide at least smoothness and, if desired, glossiness of the web by means of heat and compression, characterized in that the assembly comprises: a Control unit, which allows the selection of the paper quality produced, wherein the liquid treatment agent can be selected according to the paper quality, wherein the liquid treatment agent provides the characteristics of the paper quality concerned, the features in the memory of the control unit can be drawn; a coating unit (20) having means for spraying different liquid processing agents, said liquid processing agent being selected from a group of water, water with additives, surface size and pigmented coating, and the mixtures thereof, ··· ·· «· ··········· ··· a drying unit (30) through which different processes can be implemented to obtain the desired solids content prior to the calendering unit, whereby different drying processes and drying powers are selectable in the drying unit, the drying capacity being caused by a distance, natural drying to a drying provided by a combination of several dryers (30,321,361) is selectable such that the desired solids content of the web thus obtained from 85 to 92% when the liquid treating agent is water, and from 90 to 95%, preferably 92%, when the liquid treating agent is the pigment-containing coating agent. 15. An arrangement according to claim 14, characterized in that it comprises at least one coating unit (20) for treating the web with a liquid treatment agent, wherein the coating unit (20) comprises means for at least spraying liquid processing agents having viscosities differing from each other. 16. Arrangement according to claims 14 and 15, characterized in that at least replaceable nozzles (22,24) are arranged in the coating unit for the different types of liquid treatment agents. An assembly according to claim 14, characterized in that the length of the web transfer route (32, 34, 36) is such that the travel time is selectable upwards at the available production rate of 0.3 seconds; when the next longest rail transfer route is selected, • · The length is preferably doubled or more than doubled compared to a shorter path transmission route. An assembly according to claim 14, characterized in that the dryers (30, 321, 361) may include power adaptable fluidized bed dryers or other through-going dryers, infrared dryers and spaces, a dryer combination thereof, which may contain one or more of the dryers. 19. Arrangement according to claim 14, characterized in that it has a device (60) for determining the solids content of the web, the device preferably before the coating unit (20), directly after the coating unit (20) and after the calendering unit (40). The determination may preferably be made on both surfaces of the web and through the web to determine the solids content of the three different layers in the direction of the thickness of the web. An assembly according to claim 14, characterized in that there is a breakpoint (70) on the path of the web transfer between the coating unit (20) and the calendering unit (40) to detect the tension of the web in the coating unit (20) and before to control the calendering unit (40). 21. Arrangement according to claim 14, characterized in that in the calendering unit (40) at least one nip, preferably a plurality of nips are present, which by means of rollers, metal strips or of an elastic ······· t »Μ Μ • · · ···································································································································································································· Arrangement according to claim 14, characterized in that it comprises a control system based on a model or a multivariable control, preferably on a learning multivariable control based on a model. An assembly according to claim 14, characterized in that it comprises a variable spray unit (22, 24) of the coating unit integrated in the paper machine and activatable by the control system to produce SC and LWC paper grades; more specifically, the paper grades from SC-A + to SC-C and the LWC offset and LWC Roto grades.