FI116300B - Method for Thick Pulp Printing on a Paper or Board Machine and Similar Thickness Pulp for Paper or Board Machine - Google Patents

Description

116300

METHOD FOR SACRING PAPER ON PAPER OR BOARD MACHINE AND SIMILAR PAPER ON OR PAPERBOARD MACHINE

The present invention relates to a process for pulping on a paper or board machine, wherein the pulp is fed substantially symmetrically to two web forming wires between successive rolls of supporting roll, wherein the resulting pulp layer is then pre-pressed with the web forming web to separate . The invention also relates to a corresponding pulp web for a paper or board machine.

Nowadays, paper machine webs are so-called guitar webs in which the web is formed between two rolls supporting the forming wire. The mass is fed from the lip of the headbox over the free space to the puncture between two web forming wires. Between the forming fabrics, water is removed from the pulp, after which the web is subjected to actual compression.

20

With these friction and other strips, it is only possible to make a single layer web. If several layers are to be applied to the web, it is necessary to place ·· «several strips in a row. In other words, the '' · · '' formed web is fed with pulp by a second stripper to form a double-layered web. Another way is to connect the webs formed with different * 'strips only later. However, the final product formed by the methods described i is uneven. different types and poor bonding between layers, which make it difficult to print *, <· 30 paper and diminish paper durability. In addition, • »i has a low pulp consistency. Many more: stripers, and especially their web forming fabrics, require a lot of installation space. and maintenance.

Finnish Publication No. 69329 discloses a paper machine web other than the above, in which the pulp is fed to the forming wire by a slider member between the supporting rolls 2 116300. After the feeding, the pulp formed is pre-compressed. This removes water from the pulp and forms a web, which is further subjected to actual compression and further processing. The pre-pressed web is removed from the forming fabric 5, after which a second pulp layer can be applied to the same forming fabric. Thereafter, the formed webs are joined and led to a compression to form a double web. The second mass layer may also be applied to the surface of the first web.

The layers formed with this strip also remain at least partially separate, even in the final product. In addition, the layers are different, which reduces the quality of the final product. In practice, the layers overlap. Further, the present web is poorly suited for thick stock web, mainly because of the structure of the sliding member.

FI patent number 48212 discloses a device for making multilayer fibrous webs. The apparatus comprises two symmet-20 wire sections which form a wedge-shaped, downwardly sloping. . fluid space. The slurry is guided onto the wire by its horizontal portion via a feed tube or box. The slurry solid fed to the wires is thus compressed between the suction press rolls.

25 DE Application No. 1904962 discloses a twin-wire machine having two wires of symmetrically identical construction.

In the case of wires moving towards each other, fiber boxes are formed in the headboxes, where they form a web at the junction.

I The arrangement is intended to increase the uniformity of the various sides of the paper web 30.

It is an object of the invention to provide a novel process for forming a pulp in a paper or board machine which can be formed. . multilayer and semi-symmetrical but weakly 35 columns. It is also an object of the present invention to provide a new paper or board machine viscous pulp web which is 3116300 simpler than the prior art but which can use different consistency pulps. Characteristic features of the process of the present invention are set forth in the appended claim 1. Accordingly, the characteristic features of the viscous web 5 according to the invention are disclosed in the appended claim 6. In the process of the invention, several pulp layers are formed and pre-pressed simultaneously. This will result in a more consistent and durable end product. The method allows for a more versatile adjustment of the striping, thus applying 10 methods to different masses. At the same time, the properties of the final product can be further influenced. The strip according to the invention can simply and safely produce a multilayer web, whereby the final product can be obtained with a high basis weight. Correspondingly, the need for dewatering capacity can be reduced by using a thickener which can be kept sufficiently mixed with the web forming wire by the inventive stripper. In addition, the web requires significantly less installation space than currently used web browsers.

The invention will now be described in detail with reference to the accompanying drawings, which illustrate some embodiments of the invention, in which: Figure 1 is a schematic drawing of a high-density pulverizer according to the invention,

Figure 2 is a schematic drawing of a part of the pulp feed point of a high-density pulp web according to the invention, Figure 3 is a modification of the embodiment of Figure 2;

Figures 5a-b illustrate structural applications of the lip channel of the viscous pulp strip according to the invention, *. . Figure 6 shows a modification of the high-pulp stripper of Figure 1.

'* 35 4 116300

Figure 1 shows a high-density web according to the invention. In addition to the paper machine, the viscous web according to the invention, later more simply, the web can also be used in conjunction with other machines such as board machines. The web is intended to form a web of viscous pulp having a headbox consistency of greater than 1.5%. In practice, the consistency can be up to more than 5%, more usually 2-4%. The use of thick pulp plays a major role in the dewatering capacity of a papermaking machine, since a conventional papermaking machine uses pulp with a headbox consistency of typically 0.5 to 1%.

The stripper includes a web forming web 10 and a track 11 adapted to support it, comprising a plurality of rolls 12-15. In addition, the web has a head box 17 15 for supplying a thick mass to the web forming web 10 with slider elements 16. According to the invention, the pulp is fed to the web forming web 10 by a portion of the successive rolls 12 and 13 of the roll 11. The ribbon also has a pre-compression nip 18 formed after said headbox 17, which is comprised of two opposed arms. The pre-compression nip 18 may also consist of a shoe press nip in which one roll 12 is rigid and the other is ·; 'elastic shoe roll 12' (Figure 6). The shoe roll is also called '** ·) long nip roll. The web forming web and the 25 pulp fed to it are arranged to pass through the pre-compression nip to form the web * · '*. The web is actually compressed by a press section on which the web 33 is moved by means of a pick-up roll 20 (Figure 2).

: According to the invention, the forming fabric 10 includes two h .. · 30 at least a portion of the facing forming fabric • 21. Later, the forming fabric is more simply referred to as the · · · · fabric. In addition, one of the rolls 12 carrying the wires 21 carrying the wires 21 is arranged opposite one another. to form a pre-compression nip 18. Correspondingly, headbox 35 17 includes two sliding members 16 for forming a thick web 19 on both web forming wires 21 prior to pre-pressing 116300 nips 18 arranged to form one web 33 of the thick web (Figure 2). With this structure, the thick mass can be fed substantially symmetrically to two wires. In this case, both surfaces of the final product are identical. In practice, the layers are opposed, unlike in known strippers where the layers are overlapping (except for FI48212 and DE1904962). In addition, the individually formed symmetrical viscous mass layers are pre-pressed against each other in the pre-compression nip to form a single web. Due to the structure of the ribbon 10, the layers of pulp are pre-compressed simultaneously, whereby the finished web also becomes symmetrical in surface and structure. For clarity, the pulp layers 19 and web 33 are shown only in Figure 2.

Figures 2 and 3 show in more detail the pulp feed point. The pulp, later simpler, is fed by a headbox 17 which includes a slider 16 adapted to match the wire 21, the lip 22 of the slider 16 is discharged at high speed, so that the wire 21 is held tight to maintain the distance 20 between the slider 16 and the wire 21.

. . Stability is also enhanced by the arrangement of wire 21 on rolls 12 and • # «* * ;. * 13 between the arc. According to the invention, the sliding member is • · ·) * arranged against the wire so that the wire forms a sliding member • * · '· * · [at an angle β of 100-170 °, more preferably 140-160 °.

Further, the wire 21 surface of the slide member 16 is preferably '·' · curved. The tension of the wire 21 is adjusted, for example, by moving the rollers 14 • · · • »* ··· '. Generally, the wire tension is 3 to 15 kN / m.

Correspondingly, the curve of the wire 21 is adjusted by moving the rolls 13 preceding the feed point. In Fig. 3, the respective rolls 13 are further apart 30 than in Fig. 2, whereby the angle formed by the wire 21 at the slide member 16 increases. For functionally similar parts, the same reference numerals are used.

\. The operation of the stripper can be further adjusted by changing the feed angle of the pulp 35. According to the invention, the pulp is fed per wire at an angle α of 10 ° to 80 °, more preferably 50 ° to 60 °.

6116300

At a relatively steep angle, a uniform but dynamic spreading of the mass on the wire is achieved. Further, the pulp feed rate can be adjusted by changing the pulp feed rate. According to the invention, the pulp is fed to the wire at a speed of 5 to 80%, more preferably 10 to 40% lower than the wire speed. In this case, the wire moving faster than the pulp provides internal shear to the pulp, which slows down the flocculation of the fibers.

In practice, the fibers begin to flocculate immediately upon contact with the wire 10. To achieve good bonding of the pulp layers, the pulp is fed to the wire as close as possible to the pre-pressing nip. Hereby, the fibers of the various pulp layers at least partially flocculate with each other, thereby preventing the formation of a clear boundary between the pulp layers in the web. Thus, the aforesaid distance 15 is formed between the rolls 12 and 13 of the roll 21 of the wire 21 in the running direction of the two wires 21. According to the invention, the distance between the respective rolls 12 and 13 is 500 - 4000 mm, more preferably 1500 - 3000 mm. The use of large rollers also contributes to the bonding of the mass layers. According to the invention, the roll 12 of the pre-compression nip 20 has a radius of curvature of 200 to 1000 mm. . more preferably 250 to 750 mm. Instead of a rotating roller, a curved sliding shoe with a simple radius of curvature can be used. The wires are guided against the sliding shoe to form a long functional 25-compression nipple between the wires. is used without the * * * · back roll, or a shoe press can be used as a pre-press nip, which due to its flexibility avoids possible cross-sectional problems.

Each sliding member 16 is supported by a paper or board machine structure 23. Suitably opposed sliding members 16 at the same time counteract the forces exerted by each other. Figure 2 also shows; · 'also provided with the slide member 16 and the lip passageway 22. According to the invention 35, the lip strip is adapted to move in the direction of the lip channel. In this case, the thickness of the pulp layer can simply be adjusted to 7116300. Generally, the adjusting movement is from 1 to 20 mm, which is sufficient to feed different masses at different thicknesses with a single web.

The pulp is thus fed to the wire 21 by a headbox 17 which, in addition to the sliding members 16, comprises a manifold 25 and a lip passageway 22 extending therefrom to the sliding member 16. According to the invention, the lip passageway has an average height of 2-10 mm, more preferably 3-6 mm. Thereby shear forces are applied to the mass flow, which, respectively, causes intense turbulence in the lip duct. This prevents the fibers from flocculating in the longer lip lip channel. In addition to the low lip channel 22, guiding elements 26 adapted to influence the mass flow can be provided on the inner surface of the lip channel 22. In Figures 5a and 5b, the control elements 15 are provided by special lip channel wall structures. The control elements may also be separate pieces to be attached to the lip duct (not shown). Even the inner surfaces of the lip duct may be replaceable.

Figure 3 shows another embodiment of a strip according to the invention. . lus. According to the invention, pulp and / or additive is fed before the pre-pressing between the wires. Preferably, the pulp is fed into the closing piston of the pre-press nip. In other words, the middle • * f '·' · [lip channel 22 is separated from the wires 21. With this strip, t * <· 25 simply provides a three-layer web. For example, the middle manifolds feed the unbleached recycled fiber h ·· * and the outermost manifolds bleached pulp to give the final product both a surface and an internal (»: symmetrical structure. By way of derogation from Fig. 3, the manifold may be positioned above the slides if necessary, whereby a third lip channel is formed at an advantageously short connection to the manifolds 25, whereby each of the 35 mass flows in the cross-machine direction is adjusted.

8 116300

As the pulp is fed to the open wire, water is removed from the resulting pulp layer. Preferably, at the feed point, the area between the rollers is closed and depressurized with a suitable shield 28, whereby the discharged water can be collected in a controlled manner. Separate dewatering means 29 may also be provided on the backside of the wire 21 5, which are based on vacuum in Figure 3. Vacuum can also be applied after the pre-pressing nip to guide the web to the right wire as the wires separate.

The dewatering ability can be further improved by using at least one press felt and / or shoe press in addition to the wires during pre-pressing. According to the invention, the moisture profile of the felt is further adjusted prior to pre-pressing. In this case, the transverse moisture profile of the forming paper board machine can still be influenced during pre-pressing. The adjustment is effected, for example, by a zone steam box 31 or the like. Similarly, the felt 30 may be reconditioned by scrubbers 32 located downstream of the pre-pressing nip 18. For a similar purpose, steam may also be supplied to the pre-pressing nip between the layers of pulp.

• · • 1 · •> ·

The method and the strip according to the invention provide a multi-layer web in a simpler manner than before. In addition, • «<*”] can be used to feed pulps with a wide range of consistency. The basic product is symmetrical in structure. On the other hand, »♦» can easily be made into a web having different layers for different purposes. Regardless of the number of pulp layers, only one pre-compression is required, whereby the pulp layers simultaneously form a web.

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Claims (13)

A method for pulping in a paper or board machine, wherein the pulp is fed substantially symmetrically to two web forming wires (21) by a portion of successive rolls (12, 12 ', 13) of a supporting roller (11), whereupon the resulting pulp layer (19) is subsequently extruded. (21), wherein the separately formed pulp layers (19) are pre-pressed against the pre-compression nip (18) to form a single web (33), characterized in that the pulp is a pulp having a headbox consistency of more than 1.5% and fed to a forming web (21) by means of a sliding member (16) arranged in contact. 1 1 6300 Method according to Claim 1, characterized in that the thick mass is fed towards the forming fabric (21) at an angle α of 10 ° to 80 °, more preferably 50 ° to 60 °. Method according to Claim 1 or 2, characterized in that, before the pre-pressing, a thick mass and / or an additive is fed between the forming wires (21). • · • I I «t Method according to one of Claims 1 to 3, characterized in that, in addition to forming webs (21), at least one pressing felt (30) is used in the pre-pressing, the moisture profile of which is adjusted before the pre-pressing. Method according to one of Claims 1 to 4, characterized in that the thick pulp is fed to the forming fabric (21) at a rate which is 5 to 80%, more preferably 10 to 40% 'lower than the velocity of the forming fabric (21). * I A pulp web for a paper or board machine, intended to form a web (33) of pulp, which comprises a 116300 web forming web (10) and a plurality of rolls (12-15) adapted to support it. comprising a roller assembly (11), - a headbox (17) for supplying pulp to the forming fabric (10) with a portion of successive rollers 5 (12, 12 ', 13) of a supporting roller assembly (11), and - two opposed rollers (12, 12') a preformed nipple (18) formed after the headbox (17) and through which the forming web (10) and the pulp fed thereto are arranged to pass to form the web (10), which web forming web (10) comprises two web forming webs at least spaced apart; one of the two rolls (12, 12 ') of which is supported by one of the two supporting rollers (11), which is arranged to form a pre-pressing nip (18) arranged to form a (19) one web (33), characterized in that the headbox is adapted to a viscous pulp having a headbox consistency of more than 1.5%, and the headbox (17) comprises two slider members (16) fitted to the web forming web (10). (19) for forming on both web forming wires (21) 20 before the pre-pressing nip (18). A viscous web according to claim 6, characterized. characterized in that the partial distance is formed in the direction of travel of the two forming webs (21) of the web forming fabric (21), ·,: 25 successive rolls (12, 12 ', 13), with which rolls (12, 12', ···, 13) the distance between 500 and 4000, more preferably 1500 to 3000 mm. A viscose web according to claim 6 or 7, characterized in that the slider (16) is arranged at said Ί '30 distance against the forming fabric (21) such that the V * forming fabric (21) forms an angle β of 100 with the sliding member (16). 170 °, more preferably 140-160 °. > $ »>> ·» A viscose web 35 according to any one of claims 6 to 8, characterized in that the roll (12, 12) of the pre-pressing nip (18) has a radius of curvature of 200 to 1000 mm, more preferably 250 to 750 mm. A viscose web according to any one of claims 6 to 9, characterized in that the sliding member (16) comprises a lip channel (22) adapted to open on the forming fabric (21) having an average height of 2 to 10 mm, more preferably 3 to 6 mm. 5 A viscous web according to claim 10, characterized in that guide elements (26) adapted to influence the viscous mass flow are provided on the inner surface of the lip channel (22). 10 A viscose web according to Claim 10 or 11, characterized in that a lip strip (24) adapted to move in the direction of the lip channel (22) is arranged in connection with the sliding member (16) to limit the outlet side of the lip channel (22). 15 A high-mass web according to any one of claims 6 to 12, characterized in that one of the rolls (12, 12 ') of the pre-compression nip (18) is a long nip roll. f Hl I 116300