FI127456B - Production line for producing special fiber web grades - Google Patents

Abstract

The invention relates to a production line for producing special fiber web grades, especially machine gazed fiber web grades, which production line comprises a forming section comprising a head box (100) and a forming unit (200), a press section (300) a drying section comprising a Yankee dryer (500) and a reel-up (900), which fiber web (W) has a top surface and a bottom surface. The Yankee dryer (50) comprises a reversed Yankee cylinder (50) and the top surface of the fiber web (W) is against the surface of the Yankee cylinder (50) and the press section com-prises at least one metal belt press nip (N2; N3) formed between a press roll (30) and the bottom surface of the fiber web (W) is against the heated metal belt (301).

Description

Production line for producing special fiber web grades

The invention relates generally to producing fiber webs. Particularly the invention relates to a production line for producing special fiber web grades, especially machine glazed fiber web grades, according to the preamble of claim 1.

As known from the prior art in fiber web machines, especially in paper and board machines, the fiber web is produced and treated in an assembly formed by a number of apparatuses arranged consecutively in a process line. A typical production and treatment line comprises a forming section comprising a head box and a forming unit 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 size press, a calender, a coating section. The production and treatment line also comprises typically 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 paper and board webs.

Fiber webs, especially paper and board are available in a wide variety of types 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 m/m². It should be noted that the border20 line 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. The present invention relates especially to production of fiber webs for special paper grades, which are typically paper grades with a specific feature. It is also typically only a minor component in the fi25 nal product. Typical special fiber web grades are: Electrical papers (cable paper, capacitor tissue, transformer board, conductive paper, creped papers), Absorbent lamination papers, furniture papers (absorbent kraft, decor paper, overlay, preimpregnated foils, laminating kraft), Filter papers (engine protection, laboratory and diagnostics, food and beverage, coffee filters, tea bags, vacuum cleaner dust bag), Special strong papers (abrasive base, spinning kraft, hunting cartridge paper), Glassine papers, Release papers (pressure-sensitive labels, posters, signs and manual labels, vinyl casting, cover strips, masking tape), Copy and imaging papers (photographic paper, blueprint diazo paper, carbonless copy, thermal printing paper), Packaging grades (sack kraft, flexible packaging, label papers), Spe35 cialty printing grades, Special fine papers (security papers, artists’ papers, tracing paper, plotting paper, luxury stationery), Building papers (wallpaper, barrier pa20175383 prh 06 -02- 2018 pers), Cigarette papers and Functional papers. In particular the present invention relates to MG (machine glazed)-grades, in production of which Yankee dryer is used typically for improved top side smoothness. The Yankee dryer gives a smooth surface and also closes the surface structure of the fiber web very effi5 ciently. The MG grades are used as specialty papers or boards; as glassine and release papers, for example as wrapping papers and wraps for foodstuffs and as for label paper purposes.

In publication FI20135150 is disclosed a fiber web machine for producing paper grades, which have one smooth surface comprising a head box, a forming unit of fourdrinier type, a press section comprising at least one press nip in a line press, a drying section comprising at least one normal Yankee dryer having at least one nip against the Yankee cylinder and a reel-up. The fiber web is guided directly from the press section to the Yankee cylinder. This fiber web machine is a so called MG machine.

The MG machines are typically used as multi-grades machines i.e. different grades of fiber webs are produced in the machine. One object of the present invention is to create a production line for producing fiber webs of the MG machine type, in which capacity is not limiting the variety of grades to be produced.

In publication US 3079700 is disclosed a method for producing paper, more par20 ticularly a method of drying a wet paper web to produce grades of paper with improved suitability for coating and printing, in which bottom surface of the web is first dried on a Yankee-cylinder to about 80% dry solids content, after which the web is guided onto another Yankee-cylinder, on which the top surface of the web is against the Yankee-cylinder and the web is dried to about 92-96% dry solids content.

In publication WO 2016042198 is disclosed a method for obtaining low weight high quality paper for use as a support layer of a release liner, in which a metal belt press is used and the web is guided as a supported run from the press section to the drying section and the dry solids content of the web is 40-55% when entering the drying section.

An object of the invention is to create a production line for producing special fiber web grades, especially machine glazed fiber web grades in which the disadvantages and problems of prior art are eliminated or at least minimized.

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In particular an object of the invention is to provide a new type of production line for producing release-type fiber web grades.

In order to achieve the above mentioned objects the production line according to the invention is mainly characterized by the features of the characterizing clause of claim 1. Advantageous embodiments and features are disclosed in the dependent claims.

In this description and in the claims by term top surface of the fiber web is meant the side of the fiber web which is in the end of production line on top side, so the side which is visible in the reel-up. Thus the bottom surface of the fiber web is the other side of the web, so the side which is hidden in the reel-up. For example in the release papers the top surface of the fiber web is that side of the backing paper which will be treated with release agent (for example silicone) and label paper will be attached to that side of the backing paper.

According to the invention the production line for producing special fiber web grades, especially machine gazed fiber web grades, comprises a forming section comprising a head box and a forming unit, a press section a drying section comprising a Yankee dryer, and a reel-up, which fiber web has a top surface and a bottom surface, and the Yankee dryer comprises a reversed Yankee cylinder and the top surface of the fiber web is against the surface of the Yankee cylinder and the press section comprises at least one metal belt press nip formed between a press roll and a metal belt and the bottom surface of the fiber web is against the metal belt.

According to an advantageous feature of the invention the metal belt is heated by heating means.

According to an advantageous feature of the invention in the press section at least two metal belt press nips are formed, that the first metal belt press nip is formed between a suction press roll and a center press roll, where the fiber web is between a press felt and the metal belt, and that the second metal belt press nip is formed between the shoe press roll and center press roll, where the fiber web (W) is between the press felt and the metal belt.

According to an advantageous feature of the invention the press section comprises at least one press felt at least one press nip, in which water is removed such that the top surface of the fiber web is against the press felt.

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According to an advantageous feature of the invention temperature of the heated metal belt is 70- 120 °C.

According to an advantageous feature of the invention the heating means is a steam heating means or an infra-red heating means.

According to an advantageous feature of the invention drying section of the production line comprises a wire drying part comprising at least one single wire drying group and the wire drying part is in the production line before the Yankee dryer.

According to an advantageous feature of the invention the drying section of the production line comprises a single wire draw cylinder drying part comprising drying cylinders after the Yankee dryer.

According to an advantageous feature of the invention the forming section contains at least one forming unit and one head box and the forming unit is a fourdrinier forming unit or a hybrid forming unit.

According to an advantageous feature of the invention the Yankee dryer compris15 es at least one roll, which forms a press nip against the Yankee cylinder, and a fabric, advantageously a felt, is provided to run through the press nip against the Yankee cylinder such that in the press nip against the Yankee cylinder the fiber web is pressed against the Yankee cylinder with help of the fabric.

According to an advantageous feature of the invention in the production line dry solids content of the fiber web is 45 - 60%, when the fiber web reaches the surface of the Yankee cylinder.

Thus according to the invention in the production line for producing fiber webs a Yankee dryer comprising a Yankee cylinder and around its outer surface located Yankee hoods is used for closing the surface structure of the fiber web and to im25 prove top side smoothness of the fiber web. Advantageously before the Yankee dryer is located at least one drying cylinder group with advantageously single wire draw and after the Yankee dryer is located cylinder drying group with drying cylinders for providing further drying possibility of the fiber web. In the possible wire drying part before the Yankee dryer the bottom side of the fiber web is against the drying cylinders. The Yankee dryer provides for the machine glazed surface of the fiber web and in the Yankee dryer the top surface of the fiber web is against the Yankee cylinder. In the Yankee dryer the Yankee cylinder is a reversed Yankee cylinder, in which the fiber web is first guided downwards along the cylinder sur20175383 prh 06 -02- 2018 face and the rotating direction of the Yankee cylinder is counter-clockwise, when fiber web running direction is from left to right. By this the height of the production line is decreased, which f. ex. saves building costs of the machine hall for the production line. The fiber web is pressed against the cylinder surface of the Yankee cylinder by a drying fabric, advantageously by a drying felt.

Advantageously at least one nip is located at the Yankee cylinder formed by a roll pressing against the Yankee cylinder surface. Advantageously two pressing nips are formed against the Yankee cylinder by rolls, one of which is a smooth roll or a grooved roll or a perforated roll and the other is advantageously a grooved roll. In the first nip the fiber web is thus attached to the cylinder surface and in the other nip, which is advantageously the nip with the grooved roll, properties of the fiber web are improved, in case the grooved roll is used it is applied for marking the fiber web. At least in the first nip the fiber web is pressed against the cylinder surface of the Yankee cylinder by a drying fabric, advantageously by a felt. Also in the other nip formed against the Yankee cylinder a drying fabric can be used.

According to an advantageous feature of the invention the dry solids content of the fiber web is 45 - 60%, when the fiber web reached the surface of the Yankee cylinder. By this good attachment for the fiber web to the Yankee cylinder surface is achieved and good adherence during the run of the fiber web on the Yankee cylin20 der surface is achieved and the fiber web is unfastened only at the end run on the Yankee cylinder surface.

The fiber web is advantageously guided to and from the Yankee cylinder as a supported run, i.e. the fiber web is supported by a fabric during its run. The fiber web may have a free run from the press section to the wire drying part located be25 fore the Yankee dryer.

Advantageously from the Yankee cylinder of the Yankee dryer the fiber web is guided to the cylinder drying part with single wire draw, in which the wire drying part is descending i.e. center line of a first drying cylinder in respect the center line of its successive drying cylinder is at higher position. The advantageous, additional wire drying parts provide drying variation needed in multi-grade production and also provide for flexibility for dry capacity content variation as the drying capacity of a cylinder drying part is effectively variable by adjusting the drying capacity of the drying cylinders. Cylinder drying groups provide good runnability of the fiber web.

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The forming unit in the forming section is advantageously a fourdrinier forming unit or a hybrid forming unit, in which the fine substances in the fiber web concentrate on the side of the top surface of the fiber web and do not drain away with the white waters. Also the desired formation of the fiber web is achievable. Typically the forming section contains only one head box and one forming unit and the singleply forming is applied. In some cases it is possible to use also crescent type gap former.

The press section comprises advantageously a center roll with two press nip in which a smooth roll is against the bottom surface of the fiber web. Against the top surface of the fiber web advantageously a shoe press nip is located. In connection with each nip a felt is advantageously used as press fabric. In the press section good density of the fiber web is provided.

In the production line for producing fiber webs the production begins from a head box, type of which is advantageously a dilution head box but other types of head boxes can be used as well. Typically a one layer head box is used.

After drying in the production line for producing fiber webs the fiber web is calendered in a calender comprising at least one calender nip and at the end the full width fiber web is reeled to a parent roll in a reel-up. In the calender advantageously a thermo roll of the calendering nip will be against the top side of the fiber web. Depending on the final use of the fiber web further treatments can be provided and the full width web is typically before sending to customers formed to customer rolls in a slitter-winder and packed in roll packaging apparatus.

As is clear from the above by the production line according to the invention many advantages are achieved and for example in the forming section a fine substance rich top side of the fiber web is created and in the press section the top surface receives good density and in the Yankee cylinder the by the forming section created fine substance rich top side of the fiber web is against the cylinder and additionally the reversed Yankee cylinder also provides for cost savings due to the decreased height of the production line.

In the following the invention is explained in detail with reference to the accompanying drawing to which the invention is not to be narrowly limited.

In figure 1 is shown schematically an advantageous example of a production line for producing fiber webs according to the invention.

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During the course of the following description and in the figure like numbers and signs will be used to identify like elements which illustrate the invention and its advantageous examples. In the figure some repetitive reference signs have been omitted for clarity reasons. In the figures rolls and cylinders provided with a drive are denoted by a black center circle.

In the example of figure the production line for producing fiber webs comprises a forming section comprising a head box 100 and a forming unit 200 and a press section 300 as well as a subsequent drying section comprising a drying cylinder part 400, a Yankee dryer 500 and another wire drying part 550 followed by a pre10 calender 600, a coating section 700 with a wire drying unit, a final calender 800 and a reel-up 900.

The head box 100 in the example of the figures is a dilution head box but other types of head boxes are applicable in the production line. From the head box mass is fed on to a wire 20 of the forming unit 200.

The forming unit 200 in the example of figure 1 is a hybrid type former comprising the wire 20, which runs as a continuous loop guided by guide rolls 21 located inside the wire loop 20, some rolls 23 are provided with a drive. Tension of the wire 20 is adjusted by outside the loop located tension roll 22. The wire 20 forms a continuous planar surface onto which the mass is fed form the head box 100 and be20 low the planar run are located suction boxes 25 form removing water. The hybrid forming unit 200 of the example of figure 1 also comprises above the planar section located suction box 28 with a wire loop 21 with inside the loop located guide rolls 23. In this example water can also be removed upwards and thus the fine contents on the top layer can be further adjusted by the suction box 28. The form25 ing unit 200 provides for the fine substances in the fiber web W concentrate on the side of the top surface of the fiber web W and the desired formation of the fiber web W is achieved. The forming unit 200 may also comprise a breast roll 26 with a shaker known as such from prior art. The forming unit 200 can also be provided with adjustable or loadable foils. From the forming unit 200 the fiber web W is guided to the press section 300. Also other types of forming units, for example fourdrinier type formers or crescent type gap formers are applicable in the production line.

For pick-up of the fiber web W from the forming section to the press section a roll 31, advantageously a suction roll is provided. The press section 300 is a Sym35 Press™-type press section, in which the fiber web W is first guided between two

20175383 prh 06 -02- 2018 press fabrics, advantageously upper and lower press felts 34. Each press felt 34 is formed as a continuous loop guided by guide rolls 35, and tension adjustment of which felt 34 is provided by tension rolls 35. The first press nip N1 is formed between press rolls 37, 38 and upper press roll 37 is provided by a suction sector for turning the run of the fiber web W and guiding the fiber web W to following press nips N2, N3, which are metal belt press nips. Typically the press roll 38 is a deflection compensated roll. The first metal belt press nip N2 is formed between suction press roll 37 and a center press roll 30 where fiber web is between the press felt 34 and the metal belt 301. The second metal belt press nip N3 is formed between the shoe press roll 32 and center press roll 30 where fiber web is between the press felt 34 and the metal belt 301. The metal belt 301 forming the metal belt press nips N2, N3 is heated by heating means 302, which are advantageously steam heating means, but also for example infra-red heating means can be used. The metal belt 301 is a continuous belt loop circumventing around press roll 30 and a guide roll 303. The heated metal belt 301 is against the bottom surface of the fiber web W. In the press section 300 good surface smoothness on to the bottom side of the fiber web W and good density of the fiber web W is provided. The heated metal belt also improves dry content of the web substantially, depending on the production rate, dry content can improve up to 10 percentage point and therefore the drying section before the Yankee cylinder can be shorten. This gives big benefit in investment costs regarding to machinery and building costs. From the press section 300 the fiber web W is guided to the a subsequent drying section comprising a wire drying part 400, a Yankee dryer 500 and another wire drying part 550. The fiber web W may have a free run from the press section 300 to the wire drying part 400 located before the Yankee dryer 500 or the fiber web W may be transferred from the press section to the wire drying part by closed transfer.

In the first wire drying part 400 before the Yankee dryer 500 the fiber web W is dried in a drying group of single wire draw, comprising a drying wire 40, heated drying cylinders 41 in the top row and reversing cylinders 42 in the bottom row.

The fiber web W that is being dried runs on support of the drying wire 40 such that the drying wire 40 presses the fiber web W on a drying cylinders 41 against heated cylinder surfaces, and the fiber web W remains at the side of the outside curve of reversing cylinders 42 located between drying cylinders 41. The drying wires 40 run as continuous loops guided by guide rolls 48 located inside the loop and ten35 sion of the wires 40 can be adjusted by outside the loop located tension roll 49. In the wire drying part 400 before the Yankee dryer 500 the bottom side of the fiber web W is in contact with the surface of the drying cylinders 41. From the first wire

20175383 prh 06 -02- 2018 drying section the fiber web W is guided as a free run assisted by runnability components 43 to the Yankee dryer 500. Advantageously the first wire drying part 400 contains only single wire draw drying group I groups and the wire drying part 400 is in the production line before the Yankee dryer 500. The fabric 45 forms a con5 tinuous loop guided by guide rolls 46 located inside the loop and tensions of which can be adjusted by the outside the loop located tension roll 47. In the wire drying part before the Yankee dryer the fiber web W is dried to the dry solids content of the fiber web is 45 - 60% and thus the fiber web reaches the surface of the Yankee cylinder in this dry solid content. By this good attachment for the fiber web W to the Yankee cylinder surface is achieved and good adherence during the run of the fiber web W on the Yankee cylinder surface is achieved.

The Yankee dryer 500 comprises a heated Yankee cylinder 50 and around its outer surface located Yankee hoods 51 and the top surface of the fiber web W is against the surface of the Yankee cylinder 50. The Yankee dryer 500 closes the surface structure of the fiber web W and improves top side smoothness of the fiber web W. The Yankee dryer 500 also provides for the machine glazed surface of the fiber web W. In the Yankee dryer the top surface of the fiber web W is dried against the Yankee cylinder 50. In the Yankee dryer 500 the Yankee cylinder is a reversed Yankee cylinder, in which the fiber web W is first guided downwards along the cylinder surface and the rotating direction of the Yankee cylinder is counter-clockwise, when the running direction of the fiber web W is from left to right. The fiber web W is pressed against the cylinder surface of the Yankee cylinder 50 by a drying fabric, advantageously by a drying felt. At least one nip is located at the Yankee cylinder formed by a roll 52, 53 pressing against the Yankee cyl25 inder surface by a drying fabric, advantageously by a felt. Advantageously two pressing nips are formed against the Yankee cylinder by rolls 52, 53, first one 52 of which is a smooth roll or a grooved roll or a perforated roll and the other 53 is advantageously a grooved roll. In the first nip the fiber web W is attached to the cylinder surface and in the other nip, which is advantageously the nip with the grooved roll 53, properties of the fiber web W are improved, in case the grooved roll 53 is used it is applied for marking the fiber web. In connection with the Yankee cylinder 50 a web tray 54 is located for collecting the fiber web W in case of a web break. The Yankee hoods 51 blow hot air towards the fiber web W on the area of Yankee cylinder 50.

After the Yankee dryer 500 the fiber web W is guided by a support fabric 55, guided by guide rolls 57 and tension rolls 58 and aided by runnability devices 56 to a

20175383 prh 06 -02- 2018 cylinder drying section 550 of single wire draw having one drying cylinder group with drying cylinders 59 and as drying wire 55 functioning support fabric 55 and its guide rolls 57 and tension rolls 58 for providing further drying possibility of the fiber web W and in which both sides of the fiber web W is in contact with the surface of the drying cylinders 59 one at the time. Advantageously the cylinder drying part 550 contains only single wire draw drying group I groups and the cylinder drying part 550 is in the production line after the Yankee dryer 500.

After the wire drying part 550 the fiber web W is guided in a free run to the precalender 600. In the pre-calender 600 the fiber web W is calendered in a calender nip formed between two calender rolls 61,62 on which one is a thermo roll 61 that is against the top side of the fiber web W.

From the pre-calender 600 the fiber web W is guided to the coating section 700 comprising a coating unit having a coating nip formed between two coating rolls 71, 72 with coating supplying means 73, 74 for coating the fiber web W two15 sidedly and a drying unit with wire, advantageously single wire draw, drying. The drying unit comprises drying cylinders 76. For transferring and turning the run of the fiber web W from the coating unit to the drying unit a turn-up, advantageously a contactless turn-up, device 75 is provided.

After the wire drying unit of the coating section 700 the fiber web W is guided in a free run to the final calender 800. In the final calender 800 the fiber web W is calendered in a calender nip formed between two calender rolls 81,82 on which one is a thermo roll 81 that is against the top side of the fiber web W. From the final calender 800 the fiber web W is guided to the reel-up 900.

In the reel-up 900 the full width fiber web W is reeled to a parent roll 90.

Above only some advantageous examples of the inventions has been described to which examples the invention is not to be narrowly limited and many modifications and alterations are possible within the invention.

Claims (8)

A production line for making special types of fiber webs, in particular Yankee polished fiber webs, comprising a forming part comprising a head box (100) and a forming unit (200), a press section (300), a drying section comprising a Yankee dryer (500) and a roller lower surface, characterized in that the Yankee dryer comprises (50) an inverted Yankee cylinder (50), that the upper surface of the fiber web (W) is against the surface of the Yankee cylinder (50) and that the press section comprises at least one metal belt press nip (N2; N3) 37) and the metal belt (301), and the lower surface of the fibrous web (W) is against the metal belt (301). Production line according to claim 1, characterized in that the metal belt (301) is heated by a heating means (302). Production line according to claim 1 or 2, characterized in that at least two metal belt press nipples (N2, N3) are formed on the press section, that the first metal belt press nip (N2) is formed between a suction press roll (37) and a central press roll (30). between the press felt (34) and the metal belt (301), and that a second metal belt press nip (N3) is formed between the shoe press roll (32) and the central press roll (30), wherein the fibrous web (W) is between the press felt (34) and the metal belt (301). 20175383 prh 06 -02- 2018 A production line according to any one of claims 1 to 3, characterized in that the press section (300) comprises at least one press felt (34) and at least one press nip (N1) in which water is discharged with the upper surface of the fibrous web (W) against the press felt (34). Production line according to one of Claims 2 to 4, characterized in that the temperature of the heated metal belt is 70-120 ° C. Production line according to one of claims 2 to 5, characterized in that the heating means (302) is a steam heating means or an infrared heating means. A production line according to any one of claims 1 to 6, characterized in that the drying section comprises a wire drying section (400) comprising at least one single wire drying group and that the wire drying section (400) is on the manufacturing line before the Yankee dryer (500). A production line according to any one of claims 1 to 7, characterized in that the drying section of the production line comprises a single-wire export drying section (550) comprising drying cylinders (59) after the Yankee dryer (500). Production line according to one of Claims 1 to 8, characterized in that the forming part comprises at least one forming unit (200) and one headbox (100) and that the forming unit (200) is a four-drier forming unit or a hybrid forming unit or Crescent type kit15. Production line according to one of Claims 1 to 9, characterized in that the Yankee dryer (500) comprises two rolls (52, 53), each of which forms a nip against the Yankee cylinder (50) and that one of the rolls (52,53) is smooth. 20 rolls and one of the rolls (52.53) is a grooved roll.