FI107745B - Flerskiktsformare - Google Patents

Description

107745

multi-layer

Flerskiktsformare 5

The present invention relates to a multilayer web comprising two web forming units, each comprising a web forming and dewatering zone limited by a head box and an immediately subsequent, forming and draping wire, and a plurality of dewatering means, means for forming webs of interlacing webs. and in tap water fluidized portions comprising means for introducing water drained from the pulp suspension into the tap water tank and means for introducing tap water from the tap water tank into a pulp suspension to be fed. At least one of the forming units headbox is a multilayer headbox, at least one of the forming units headbox is a multilayer headbox having two layers of mass composition of different composition adapted to be fed to overlapping layers.

Multilayer webs are generally made either by using a multilayer carton from which all the web layers are simultaneously injected into a two-wire former, or by a plurality of sequentially or parallel-connected web formers. By means of leaching units, whereby the various layers of the web are either dewatered step by step on one another or on separate wires, whereby, after partial dewatering, they are joined together.

♦ · '. ···. Layering a printing paper web in a manner where all three layers are formed at the same time can • easily result in poor film purity, whether it is the deposition of paper additives, filler or fiber. Particularly when drying, the drying process may result in poor and inadequate coverage of the surface layers. In addition, it is difficult to adjust the middle layer formation, which prevents the requirement for sheet flatness for printing papers • 107745 2. Another major problem is the mixing of the water used to dilute the various layers. Especially when it is desired to cover the surface layers of the middle layer with a lower fiber quality and purity, the mixing of the waters may "eat" the quality and potential cost savings that may be achieved.

From DE-A-44 01 761 there is known a method for producing a multilayer paper containing at least two different pulp suspensions, either by means of a multilayer headbox or by combining layers made by flat wire technology. The first pulp suspension is mainly drained through the first wire and the second pulp suspension is mainly drained through the second wire, whereby the wastewater discharged through the first or second wire is collected in separate containers for further return to the first or second pulp suspension. In the manufacture of a three-layered web, the stripped tap water 15 is introduced into the pulp suspension for the outer layers of the web, and the stripped tap water is discharged into the pulp suspension for the middle layer of the sheet. When dewatering from the middle layer only through the surface layers, filtrates of different composition from different layers will inevitably mix with each other, and further, the purity of the layer will be affected.

• · t · »» t · • · · Γ *. FI Patent Application 950336 discloses a multi-layer reformer suitable for the manufacture of a one-sided web, wherein one of the two layers of the web is made by means of a kiteformer and the other is made by the wire and the tap water of both stripping units. . The same publication also describes a multiplicative symmetric • ·. ··· structure. rosin formation by means of two parallel or successive · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Separation of tap water is not necessary because for symmetry reasons, it is necessary to use the same mass suspension composition for 30 different layers.

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The object of the invention is to minimize the problems associated with the prior art by developing a multilayer concept which achieves good layer purity of the multilayer film and enables selective control of tap water.

To achieve these and later objects, the multilayer grid according to the invention is characterized in that the tap water system comprises two tap water tanks, and a possible single layer web forming unit associated with means for guiding tap water drained through a screen covering wire to a first tap water reservoir, and a first tap water reservoir comprising means for introducing tap water to a plurality of fluid suspensions and a second layer.

* ·· * 20 • · • · * * * *. In the solution according to the invention, the central idea is to lay one or two layers at a time and, in a suitable process step, to combine either two layers or one double layer and one single layer into one. . ^ in the thickness direction to a symmetrical three-layer web. When the web comprising the middle layer and the * * ♦ 25 two surface layers is formed in a stepwise manner in accordance with the invention, it is avoided that the middle layer has to be drained by the surface. through the layers. The invention also enables selective destruction of tap water.

Preferably, the multilayer web according to the invention comprises two die-forming units which form two partial webs, at least one of which is a double-layered web. For this purpose, at least one of the web forming units has a headbox as a multilayer headbox, into which two pulp suspensions of different fiber, additive and / or filler composition are fed into different layers to form a two-layer sub-web. The tap water drained through the wires of said web forming unit is led to different water circulations so that the tap water from different pulp suspensions of different chemical and solids composition is recycled to the pulp suspension from which the said tap water is derived.

Preferably, the two-wire zone of the two forming units consists of identical or similar elements disposed in a mirror image relative to one another, whereby the partial webs become similar in structure and the structure of the multilayer web becomes symmetrical.

Naturally, the multilayer web material of the invention can also be used to produce an asymmetric web structure, for example, by making one of the partial webs monolayer and / or using different web thicknesses or mass compositions and / or providing different web forming units ... with different dewatering elements.

After the forming units, the partial webs are led together as the residual wires of the carrier wires and joined together by the common run of said wires.

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In the following, the invention will be described with reference to the figures in the accompanying drawings, in which details, however, are not intended to be narrowly limited.

Fig. 1 shows a multilayer web which produces two double-layered sub-webs to be joined together to form a three-ply web and a tap water circulation.

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Figure 2 shows a modification of a multilayer ribbon in which one of the sub-webs to be manufactured is a single-layer and the tap water circulation of the ribbon.

Figure 3 shows another multilayer web according to the invention.

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Figure 4 shows a third multilayer web according to the invention.

Fig. 1 shows a web forming part suitable for the manufacture of, for example, a three-layer paper or board web W, the middle layer of which has a different fiber, additive and / or filler composition than the surface and bottom layers of the web. The web forming part preferably comprises two web forming units, preferably of similar parts, each of which is made of a sub-web W 1, W 2, which contains one of the surface layers of the three-ply web W and a part of its middle layer. After felting, the partial webs Wi, W2 y-15 are aligned with each other.

The first web forming unit comprises a carrier fabric 12 and a covering fabric 11 bounding a two wire web forming and dewatering zone, and a multilayer headbox 10, into which two mass suspensions M 1 and M 2 of different compositions are introduced. The pulp suspension streams are fed from the headbox 10 to the strainer formed between the wires 12 and 11, and in the region of the double wire zone, dewatering is performed on both forming wires 11 and 12 on the former roll 13, the track placed on both sides • · ♦. ·: ·. dewatering units 14 and 15 and transfer suction box 16. In addition, the purpose of the transfer simulation is to ensure that the partial web Wj, after the twin-wire zone, is released from the covering wire 11 and follows the supporting wire 12.

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The second web forming unit, respectively, comprises a carrier wire 22 covering • · '. ···. a wire 21, a double-layered headbox 20, and a dewatering member in the two-wire belt zones 23, the dewatering units 24 and 25 on both sides of the web, and the transfer suction box 26. The construction of the second web forming unit The 107745 6 sections are preferably disposed such that they form a mirror image of the structure of the first web forming unit.

After the end of the two-wire zones, the partial webs W1 and 5 W2 formed by co-located twin-wire formers are led by the supporting wires 12,22 to the suction roll 30, over which the two wires 12,22 are curved. During the joint run of the wires 12 and 22, the partial webs W1 and W2 are joined to each other by the clamping force exerted by the wires 12,22 and the negative pressure acting on the transfer suction roll 30 in the underpressure zone. The resulting multilayer web W resulting from the joining 10 continues to pass along the pickup point supported by the wire 22, from which the transfer felt 31 passing over the pickup roll 32 captures the web W for further feed to the press section of the paper machine.

The pulp feed system of each web forming unit comprises a multi-layered headbox 10.20, into which superfluous layers are provided with pulp suspension flows M 1 and M 2, which preferably have different fiber, additive and / or filler compositions. In both kiteformers, the first pulp suspension M1 is fed to the backing wire 12.22 and the second pulp suspension ... M2 is fed to the covering wire 11.21. When the thus formed partial webs W1 · · ·! ** 20 and W2 are joined together, the layers formed against their respective wires 11 and 21, containing the second pulp suspension M2, are joined together to form the middle layer of the three-layer web W and the first pulp suspension M] · · • ·, ·; ·, The prepared layers remain as the surface layers of the web W.

Preferably, each of the web forming units produces similar sub-webs Wi, W2, but it is also possible to make sub-webs different. ***. for example, by changing the thickness of the various layers. The modification of the invention shown in Fig. 2, in which one of the partial webs Wj is · · · · · *, will be described in more detail below. a single layer.

• · • ♦ · 30 • • • • • i * • · · · «· 107745 7

In the two-wire zone of each web forming unit, water is dewatered through both the carrier wire 12,22 and the covering wire 11,21. In the solution according to the invention, these drained SiS-S4 webs are led to different containers 40,50 and circulating arrays so that the SiIs and S3s drained through both wires 12 and 22 carrying the web forming units 5, mainly from the first pulp suspension Mi the tap water S2 and S4 drained to the first tap water tank 40 and the respective screening wires 11 and 21, respectively, coming from the second pulp suspension M2 to the second tap water tank 50. The water of the first tap water tank 40 is fed to the streams 43 and 44 the water of the first pulp suspension M1 and the water of the second tap water tank 50 are conveyed along lines 53 and 54 to the second pulp suspension M2 to be fed to headboxes 10 and 20, respectively. Thanks to this arrangement, the tap water of different chemical and / or solid composition 15 is recycled to the pulp suspension from which the tap water is derived.

Fig. 2 shows a modification of the multilayer ribbon of Fig. 1. In the first web forming unit, a single layer interlayer Wj is produced which contains only the first pulp suspension Mi and thus forms a second · · *. the surface layers of the three-layer web W to be manufactured. In the second, the web form- ♦ · · • · ♦ ***. in the same manner as described in connection with Fig. 1, a double-layered web W2 comprising a first pulp suspension Mi is formed.

I .. a surface layer and a multi-layer web W made of a second pulp suspension M2

• · · 25 inner layers for the middle layer. In this case, both tap water Si and S2 of the first kiteformer are led along lines 41 and 45 to the first wire. passage through the second tuftformer carrying wire 22 through tap 42 into the first tap water 40 and through the covering wire through tap 52 into second tap water tank 50.

From the first tap water tank 40, water is led along line 43 to the first mass suspension Mi to be fed to the first headbox 10 and to the first mass suspension Mi to be fed to the second headbox 20 through 44. From the second tap water tank 50, water is led along the line 54 to the second pulp suspension M2 to be fed to the second headbox 20.

Fig. 3 shows another modification of the multilayer strip according to the invention. 1 and 2, the first web forming unit comprises a carrier wire 12 and a covering wire 11, between which a pulp suspension stream is fed from the headbox 10. The web is dewatered in the biaxial zone by means of a drawing roll 13, dewatering elements 14 and 15 disposed on both sides of the web, and a transfer suction roll 17 which also ensures that the web Wj after covering web 21, headbox 20, ήπιοί 5, dewatering roll 23, dewatering units 24 and 25, and transfer suction roll 27. Following the web-forming dewatering units 12 and 22, the webs 12 and 22 are brought into contact with one another by and the vacuum applied to them by the suction roll 30 is connected to each other to form a multilayer web W.

20 • · 1 · ·

At least one and possibly both of the web forming units »S <I" in Figure 3 are adapted to make a double-layered sub-web W1, W2 having two layers of different composition. Each of the sub-webs.

The wires drained through the various wires in the wires of the W1, W2 gritformer, as shown in Figures 1 and 2, are led to two separate tap water tanks (not shown) such that the wafers drained from the surface layers of the multilayer web. Si, S3 can be separated from the middle layers of the multilayer web, drainage water from S2, S4 and the various pulp suspensions can be recycled into the pulp suspension.

• · ··· • · 30 • · • 4 · 2 • · 1 3 ··>% 107745 9

Fig. 4 shows a modification of a multilayer ribbon, in which the partial webs W1 and W2 are formed in two web forming units, which correspond exactly to those shown in Fig. 3, whereby also their tap water circulation is as described above. The webs W1, W2 are joined after the forming units by a common run of carrier wires 12 and 22, which in this embodiment is longer than in Fig. 3, extending over the air suction roll 33 and terminating in the transfer suction box 34 located inside the lower wire 22.

Many variations of the invention are possible within the scope of the following claims.

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Claims (7)

A multi-layered web comprising: - two web forming units, each comprising a web forming and dewatering zone bounded by a headbox (10,20) 5 and immediately followed by a carrier wire (12,22) and a covering wire (11,21). and a plurality of web forming and dewatering members (13-17,23-27), means (12,22,30) for interconnecting sub-webs (W1, W2) formed by web forming units to form a multilayer web (W), 10. a tap water system comprising 41,42,45,51,52) for transferring water (Si - S4) drained from the pulp suspension (Mi, M2) through the wire (11,12,21,22) to the tap water tank (40,50) and the organs (43,44,53). 54) for supplying tap water from a wire water tank (40,50) to a head box (10,20) to be fed to a pulp suspension (M 1, M 2), and 15 to at least one of the web forming units as a headbox (10,20) overlapping two layers of a different composition (M 1, M 2) for the preparation of a two-layer partial web (W 1, W 2), characterized in that the ···, 20 - tap water system comprises two tap water tanks (40.50), * · · · · - each web forming unit is provided with means (41.42) for leading the screened wire (12.22) through the screened water (Si, S3) to the first wire? ···; . J water tank (40), «·: * · *: - the bilayer web forming unit comprises means for: * Γ: passing 25 (51,52) of screened water (S2, S4) to a second tap water tank (50) ) and a possible single-layer web forming unit are connected to a first forming tap water (S) through the wire (11) covering the organs (45) to the first tap water tank (40), and • ·: ***: 30 - means (43,44) associated with the first tap water reservoir (40) for a mass suspension (Mi) for conducting tap water to the surface layers of the multilayer web (W) • 107745 11 and a second tap water tank (50) associated with means (53.54) for conducting the tap water into the middle layer layers of the multilayer web (W) (M2). A multilayer web as claimed in claim 1, characterized in that both web forming units are provided with a headbox (10,20) having two layers of a different composition composition (W1, M2) for supplying two layers of a two layer web (W1, M2). 10 The multilayer web as claimed in claim 1 or 2, characterized in that the two-wire zone of the two forming units consists of identical or similar elements (10-16,20-26) disposed in a mirror image relative to each other. 15 The multilayer web as claimed in any one of claims 1 to 3, characterized in that the web forming units are followed by a common run of the carrier wires (12.22) by which the webs (Wi, W2) are arranged to be joined together. 20 • · ** i ... ; ·, 5. The multilayer web according to claim 4, characterized in that the members «· ·. for connecting the partial webs (Wi, W2) comprise carrier wires • · · «« ·. : (12,22) a common running roll (30,33) over which both wires • are (12.22) adapted to curve, and means (30,34) for applying a negative pressure ♦ 1 · 2; 25 sex in the web (W). A multi-layer fabric according to claim 5, characterized in that the carrier 3; a transfer suction roller (30) is provided for the common run of the conventional wires (12,22). • · • · 30 • · • · · · · * 1 · 2 • · · 3 · 107745 12 A multilayer fabric according to claim 5, characterized in that a transfer suction box (34) downstream of the roll (33) is imaged for the common run of the carrier wires (12,22). · * * ♦ ♦ ♦ ♦ ♦ ♦ »» »» »» »» »» »» »» · · 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 77 77 77 77 77 77 77 77 77 77 107745 13