EP1357223B1 - Paper machine clothing and process for making the same - Google Patents

Abstract

In a paper-making process a first paper web is de-watered by a second dewatering web made of porous paper. The second web has a layer of longitudinal strips (3) and a layer of transverse (4) strips which cross each other at intersections (8). An Independent claim is also included for a process of making commensurate porous paper web.

Description

The invention relates to a porous dryer fabric for the dryer section of a paper machine with a scrim consisting of at least one layer of longitudinal yarns and at least one layer of transverse yarns crossing the longitudinal yarns, wherein the longitudinal and transverse yarns are interconnected in the region of crossing points. The invention further relates to a process for producing a porous dry sieve for the dryer section of a paper machine in which a scrim of thermoplastic material is produced by arranging at least one layer of longitudinal yarns and at least one layer of transverse yarns intersecting the longitudinal yarns. and transverse threads are interconnected in the region of crossing points.

Dryer fabrics are long and wide belts which circulate in the dryer section of a paper machine and with which the paper web is transported through the dryer section. In the dryer section, the paper web and the dryer fabric are passed over heated rollers, whereby further dewatering of the paper web is carried out, in this case, it is better to say drying.

The textile thread structures are formed primarily as tissue. In addition, so-called scrims are known in which the threads are not integrated with each other, so they are not interwoven or meshed. US Pat. No. 3,097,413 A discloses a papermachine fabric which comprises a scrim consisting of a layer of longitudinal threads which run parallel and at a distance from each other and are not connected to one another. On the situation, a non-woven fabric is applied, which includes the longitudinal threads and is needled with these.

However, such a paper machine clothing has only a low transverse strength. Therefore, one has proceeded to combine the longitudinal thread layer with a transverse thread layer (DE 1 802 560 A, EP 0 394 293 B). Initially, modules consisting of a thread layer and a needled nonwoven fabric are formed and these modules are brought together and re-needled. This production method is not suitable for paper machine clothing, which consist only of a thread structure. For this case, US 4,555,440 A proposes to connect the individual thread layers by binding threads together.

In the case of the aforementioned papermachine clothing, in particular the resistance to displacement between the individual layers and thus the dimensional stability is unsatisfactory. As far as binding threads are used, these foreign bodies represent and complicate the manufacturing process considerably. To eliminate these disadvantages proposes the US 5,888,915 A a generic dryer before, in which the layers of longitudinal and transverse threads are placed directly on each other and fused together at the crossing points by heating in an oven. The prerequisite for this, however, is that bicomponent filaments are used in which the filament core has a higher melting temperature than the filament sheath. The fusion takes place by heating to a temperature above the melting point of the thread sheath and below the melting point of the thread core.

Due to the direct connection of the threads of the individual layers, the dimensional stability of the paper machine clothing is improved. The disadvantage, however, is that special threads, namely bicomponent threads, must be used, which are expensive and whose material properties can not always be optimally adjusted to the conditions in the respective section of the paper machine.

In WO 99/64670 a press felt for the press section of a paper machine is disclosed in which the carrier may be formed as a scrim with at least one layer longitudinal threads and at least one layer of longitudinal threads crossing transverse threads and in which the threads using a water-soluble polymer, for example PVAL, interconnected. The threads may consist of the water-soluble material. Instead, the compound can also be prepared by means of a layer of water-soluble material. With the use of the press felt in the paper machine, the water-soluble Material dissolved out and thereby the permeability of the press felt produced.

EP 0 922 806 A2 describes a liquid-impermeable shoe press belt which has a u.a. Also has a carrier designed as a thread carrier within a plastic layer enclosing the carrier. For the initial stabilization of the yarn layer - similar to US 5,888,915 A1 - two-component threads are used, which are fused together by heating. Alternatively, the threads are coated after production of the netting with a chemical material, whereby the threads are connected to each other at the crossing points. Then the scrim is coated with the plastic material.

FR 1 571 179 A discloses a papermachine fabric with a scrim consisting of a layer of longitudinal yarns and two layers of transverse yarns enclosing this layer. To connect the longitudinal and the transverse threads, all three layers are initially placed one above the other. Thereafter, continuous adhesive beads are applied on both sides of the longitudinal threads, which have connection between the transverse threads with the longitudinal threads and go over the transverse threads, so that the threads are at the crossing points without adhesive bond to each other.

This type of adhesive bond between the layers of the yarn layer of the paper machine clothing has significant disadvantages. So considerable quantities of glue are necessary to produce the adhesive beads along all longitudinal threads, especially since a relatively thick adhesive application is necessary to make the connection. In addition, the strength of the compound in the region of the crossing points is not satisfactory, ie the strength of the yarn layer is not particularly high. In addition, the adhesive beads are completely exposed and thus subject to the risk to go under the moist-warm conditions in the paper machine on the surface in a slightly sticky state. Dirt particles or fibers are then deposited on them, ie the scrim is dirty. The adhering dirt particles can even lead to a deterioration in the quality of the paper web.

The invention has the object of providing a dryer fabric in such a way that with him regardless of the type of threads, a high dimensional stability can be achieved. A second object is to provide a method for the production thereof.

The first object is achieved in that the longitudinal and transverse threads are formed as flat threads and connected to each other at points of intersection point adhesive. The basic idea of the invention is therefore to connect the surfaces of the longitudinal and transverse threads, which are opposite one another at the points of intersection, over which they normally rest against one another by means of adhesive. Since flat threads are used according to the invention, faces are located at the crossing points, over which the threads are glued together in terms of area. The dryer fabric according to the invention is characterized by high dimensional stability and low cost of production when using Einkomponentenfäden. It is therefore no longer dependent on bicomponent yarns, although the basic idea of the invention also includes such threads, but can use Einkomponentenfäden and still realize a high dimensional stability. Under Einkomponentenfäden are to be understood as such threads, which consist of a homogeneous material, wherein the material may also be a copolymer, provided that only homogeneity is given.

Compared with woven and knitted fabrics, the dryer fabric according to the invention has the advantage of high flexibility with regard to the number of layers, the thread density and the choice of material. In addition, no elaborate textile machines, such as weaving and knitting machines required for the production, which also limits the width of the drying wires to be produced on them. Such a limitation does not exist with thread plies, i. they can be made in practically any width. In addition, in the case of suture, it is possible to dispense with the heat setting necessary for fabrics, if the threads have previously been sufficiently thermally treated.

Suitable adhesives are, in particular, hot melt adhesives whose melting temperature is below that of the filaments, diffusion adhesives, contact adhesives and / or reaction adhesives.

In an embodiment of the invention it is provided that the longitudinal and transverse threads are additionally positively connected at intersections, wherein the compound in each case from a recess in the one thread and a protruding bordering projections on the crossing thread or at the intersection points aligned recesses and these passing pins, eg Studs or rivets of plastic or metal, may consist. Such a positive connection supports the adhesive bond and gives even more strength.

It is particularly preferred to form the flat threads with a rectangular cross-section. As a suitable width for the longitudinal and transverse threads, a range of 2 to 20 mm, preferably 8 to 12 mm, has been found. The thickness should be between 0.3 to 2 mm, preferably 0.6 to 1.2 mm, wherein the transverse threads should have at most the same thickness as the longitudinal threads.

In order to ensure sufficient permeability to water or steam, in particular in the case of very wide flat threads, passage openings can be provided in the longitudinal and / or transverse threads. Due to their size and number, the permeability can be controlled arbitrarily, whereby the possibility exists to make the permeability across the width of the dryer screen different, eg in the middle higher than in the edge regions or vice versa. The through holes may be formed as round holes or elongated slots.

The dryer fabric according to the invention can have any number of layers, wherein in each case one layer with longitudinal threads and one layer with transverse threads alternate, ie in each case are adjacent to one another. An expedient number are two or three layers, wherein in the former case preferably a lower Längsfadengelege is combined with an upper Querfadengelege and in the latter case, a layer with transverse threads is enclosed on both sides of a respective layer of longitudinal threads. In this way, a longitudinal structure is formed at the top and bottom. Of course, there is the possibility to proceed vice versa, so that there is a transverse structure at the top and bottom by the transverse threads present there.

The permeability of the dryer fabric can also be adjusted within wide limits, for example, by the width dimensions of the longitudinal and / or transverse threads and / or their thread density. In this case, it is also possible to arrange the longitudinal threads in at least one layer in such a way that they have a different thread density in the middle region than in the edge regions, in particular in the middle region a lower one than in the edge regions.

With the thread scrim according to the invention, eyelets can also be produced in a simple manner on the end faces of the drying wire by folding over longitudinal threads to form loops, in order to form a plug wire seam with them. This can be done in such a way that end pieces of longitudinal threads of a first layer at the end faces of the Dry sieve with the formation of loops on the side facing away from this layer of the situation with transverse threads and attached to a plurality of these transverse threads, preferably at least five transverse threads, are attached. However, the attachment can also be made on the longitudinal threads themselves. The fixation can be done in both cases positively, for example by means of bolts or rivets made of plastic or metal.

The loop formation should expediently be done only with a part of the longitudinal threads, so that the two end edges mesh with their loops like a comb and thus can form a passageway for a pintle. Preferably, alternately at least one end piece should be turned over to form a loop and end at least one end piece without forming a loop on the respective outer transverse thread. In order that the permeability in this area is not impaired, longitudinal threads should be connected to the ends of the end pieces of longitudinal thread at the position with transverse threads adjacent second layer, i. these longitudinal threads butt against the end pieces, so do not overlap with them, so that it does not come in this area to a compression of longitudinal threads.

As for the material of the threads, there are basically no restrictions; it should have high tensile strength, low elongation and a high initial modulus. For example, PET, PA in all modifications, PPS, PEK, PEKK, elastic polyester, PBT or PTT or are suitable Combinations thereof. The threads can be armored, eg fiber-reinforced with glass fibers, carbon fibers and / or ceramic fibers, the fibers also being present as short cut fibers.

For use in the dryer section are primarily training in question, in which the dryer fabric consists solely of the scrim, which does not preclude that the scrim is additionally combined with other components, such as a nonwoven fabric.

For the preparation of the above-described drying wire, a method is proposed according to the invention, in which flat threads are used for the longitudinal and transverse threads and they are so connected with adhesive, that the adhesive remains exclusively between the opposite surfaces of the longitudinal and transverse threads in order to connect these surfaces.

According to a further feature of the invention, it is provided that the longitudinal and transverse threads are positively connected to each other at intersection points, for example by interlocking a respective projection on the one thread and a complementary recess on the crossing thread or by inserting a pin such as a bolt or a rivet, in aligned recesses in the threads. This further strengthens the connection at the crossing points.

Specifically, the production of the fabric layer can be made in such a way that initially longitudinal threads are clamped parallel to each other, for example, between two parallel thread trees, and then successively laid on these longitudinal threads individually or in groups transverse threads and glued together at the intersection points longitudinal and transverse threads, wherein In addition, a positive connection can be made by the fact that connecting bolts are pierced in aligned at the intersections holes or a projection on one thread is pressed into a complementary recess in the other thread.

If a felt is to be formed, one or both sides of a fiber layer should be applied to the fabric scrim and attached thereto. The attachment can be done by needling, gluing or melting.

It is understood that the transverse threads do not have to be perpendicular to the longitudinal threads, but that with the inventive method and scrim can be produced, in which the transverse threads extend obliquely to the longitudinal threads. In this case, two layers of transverse threads may be provided, in which the transverse threads of a layer crossing the longitudinal threads at a different angle than that of the other layer.

Figur 1

eine Draufsicht auf eine schematisch dargestellte Papiermaschinenbespannung;

Figur 2

eine Seitenansicht der Papiermaschinenbespannung gemäß Figur 1;

Figur 3

einen Querschnitt durch die Papiermaschinenbespannung gemäß den Figuren 1 und 2;

Figur 4

eine vergrößerte Seitenansicht der Papiermaschinenbespannung gemäß den Figuren 1 bis 3.

Figur 5

eine Draufsicht auf einen Teil einer Papiermaschinenbespannung mit zusätzlicher formschlüssiger Verbindung der Fäden;

Figur 6

eine teilweise Querschnitt durch die Papiermaschinenbespannung gemäß Figur 5;

In the drawing, the invention is illustrated by means of exemplary embodiments. Show it:

FIG. 1

a plan view of a schematically illustrated papermachine fabric;

FIG. 2

a side view of the papermachine fabric according to Figure 1;

FIG. 3

a cross section through the paper machine clothing according to Figures 1 and 2;

FIG. 4

an enlarged side view of the papermachine fabric according to Figures 1 to 3.

FIG. 5

a plan view of a part of a paper machine clothing with additional positive connection of the threads;

FIG. 6

a partial cross section through the paper machine clothing according to Figure 5;

The papermachine fabric 1 shown in FIGS. 1 to 4 consists of a scrim, the lower layer 2 of which is formed by longitudinal yarns-designated 3 by way of example. The longitudinal threads 3 have - as can be seen in particular from Figure 3 - rectangular cross section and the same distance from each other. For the manufacturing process they are - which is not visible here - wound with their left-hand ends on a thread tree. On the right side is - also not visible here - a second tree provided on the finished papermachine fabric 1 is wound. In this direction (arrow A), the papermachine clothing 1 moves.

On the pad 2 is a top layer 4 with mutually parallel transverse threads - for example, 5, 6, 7 called - launched. The transverse threads 5 have a wide distance - it corresponds essentially to the distance between the longitudinal threads 3 -, the transverse threads 6 a close distance in order to reduce the permeability of the paper machine clothing 1 and the transverse threads 7 also a close distance, but a substantially smaller width than the transverse threads 5, 6. It is understood that these differences are not present in an actual paper machine clothing, ie it is the same transverse threads with the same distance from each other for use. The illustration is intended merely to symbolize that the method according to the invention enables a very wide variety of types of longitudinal and transverse threads 3, 5, 6, 7 and thread densities. The same applies to the longitudinal threads 3, wherein here also the possibility is given to vary their distances across the width, for example to provide a lower thread density in the central region than in the two edge regions or vice versa.

For the production of the paper machine clothing 1, the longitudinal threads 3 are stretched between the two trees and then the transverse threads 5, 6, 7 placed over the longitudinal threads 3. This can be done by machine, for example, with a cross-plate device, as is known in principle from US-A-3,097,413. For the connection of the transverse threads 5, 6, 7 with the longitudinal threads 3, they are glued together at their crossing points - designated by way of example by 8 - via an adhesive layer - designated by way of example by 10. The adhesive is present at the crossing points point by point. The adhesive can be applied to the longitudinal and / or transverse threads 3, 5, 6, 7 pointwise or surface wise, the adhesive should be subsequently removed in the latter case, for example by means of a solvent which is applied to the finished paper machine clothing. In addition, can placed on the top layer 4 a plate, for example, a glass plate which presses the transverse threads 5, 6, 7 on the longitudinal threads 3 and so prevents a shift between the two until the adhesive bond has become firm.

Figures 5 and 6 show sections of another papermachine fabric 11 with a lower layer 12 of longitudinal threads - for example, denoted by 13 - and an upper layer 14 of transverse threads - designated by way of example 15. It is understood that a plurality of longitudinal threads 13 are present and that the transverse threads 15 extends over the entire width of the paper machine clothing 11.

Longitudinal and transverse threads 13, 15 here also have a rectangular cross-section, wherein the transverse threads 15 are flatter than the longitudinal threads 13. At the crossing points - exemplified by 16 - the longitudinal and transverse threads 13, 15 are positively connected to each other, via connecting bolts - For example, denoted by 17 -, respectively, each aligned holes - by way of example with 18, 19 - enforce in the longitudinal and transverse threads 13, 15. Instead, however, the connecting pins 17 may also be integrally formed on the longitudinal threads 13 or the transverse threads 15, so that only the respective other threads have holes into which the connecting pins 17 are then pressed.

The positive connection is used for additional fixing of the longitudinal and transverse threads 13, 15 at the crossing points 16 and supports the connection by means of adhesive layers - designated 20 by way of example -.

Claims (30)

1. Porous dryer screen (1, 11) for the drying section of a paper machine, comprising a filament lay-up made of at least one layer (2, 12) of longitudinal filaments (3, 13) and at least one layer (4, 14) of transverse filaments (5, 6, 7; 15) which cross the longitudinal filaments (3, 13), wherein the longitudinal and transverse filaments (3, 13; 5, 6, 7; 15) are joined to each other in the region of crossing points (8, 16), characterised in that the longitudinal and transverse filaments (3, 13; 5, 6, 7; 15) are formed as flat filaments and are joined to each other via an adhesive (10, 20) present as spots.
2. Dryer screen according to claim 1, characterised in that the adhesive (10, 20) is a hot-melt adhesive, a diffusion adhesive, a contact adhesive and/or a reaction adhesive.
3. Dryer screen according to claim 1 or 2, characterised in that the longitudinal and transverse filaments (3, 13; 5, 6, 7; 15) are additionally positively attached to each other at crossing points (8, 16).
4. Dryer screen according to claim 3, characterised in that each joint consists of an aperture in one filament and of a projection, which fits suitably therein, on the crossing filament.
5. Dryer screen according to claim 3, characterised in that each joint consists of mutually aligned apertures (18, 19) in the filaments (13, 15) and of a pin (17) which passes through the latter.
6. Dryer screen according to any one of claims 1 to 5, characterised in that the longitudinal and transverse filaments (3, 13; 5, 6, 7; 15) comprise a rectangular cross-section.
7. Dryer screen according to claim 6, characterised in that the longitudinal and transverse filaments (3, 13; 5, 6, 7; 15) have a width of 2 to 20 mm, preferably 8 to 12 mm.
8. Dryer screen according to any one of claims 1 to 7, characterised in that the longitudinal filaments (3, 13) have a width in their middle region which differs from that in their edge regions.
9. Dryer screen according to any one of claims 6 to 8, characterised in that the longitudinal and transverse filaments (3, 13 ; 5, 6, 7; 15) have a height of 0.3 to 2 mm, preferably 0.6 to 1.2 mm.
10. Dryer screen according to any one of claims 6 to 9, characterised in that the transverse filaments (5, 6, 7; 15) have a thickness which as a maximum is the same as that of the longitudinal filaments (3).
11. Dryer screen according to any one of claims 1 to 10, characterised in that the longitudinal and/or transverse filaments comprises passageway openings.
12. Dryer screen according to any one of claims 1 to 11, characterised in that at least three layers are present, wherein a layer comprising longitudinal filaments and a layer comprising transverse filaments are adjacent in each case.
13. Dryer screen according to claim 12, characterised in that each layer comprising transverse filaments is surrounded on both sides by a layer of longitudinal filaments.
14. Dryer screen according to any one of claims 1 to 12, characterised in that at least one layer comprising longitudinal filaments has a filament density in its middle region which differs from that in its edge regions.
15. Dryer screen according to any one of claims 1 to 14, characterised in that end pieces of longitudinal filaments (3, 13) are wrapped round and fixed to the end faces of the paper machine clothing (1, 11) with the formation of loops.
16. Dryer screen according to claim 15, characterised in that the end pieces are fixed to transverse filaments (5, 6, 7; 15) on the side, which is remote from the layer (2, 12) comprising the longitudinal filaments (3, 13), of the layer (4, 14) comprising transverse filaments (5, 6, 7; 15).
17. Dryer screen according to claim 15, characterised in that the end pieces are fixed to the longitudinal filaments (3, 13) themselves.
18. Dryer screen according to any one of claims 15 to 17, characterised in that non-loop-forming end pieces of longitudinal filaments (3, 13) are each fixed to the last transverse filaments (5, 6, 7; 15) on the end face of the paper machine clothing (1).
19. Dryer screen according to any one of claims 15 to 18, characterised in that, alternately, at least one end piece is wrapped round with the formation of a loop, and at least one end piece ends at the outer edge of the last transverse filament (5, 6, 7; 15) on the end face of the paper machine clothing (1).
20. Dryer screen according to either one of claims 15 or 19, characterised in that longitudinal filaments of a second layer comprising longitudinal filaments, which is seated against the layer comprising transverse filaments, adjoin the ends of the end pieces.
21. Dryer screen according to any one of claims 1 to 17, characterised in that the longitudinal and/or transverse filaments (3, 13; 5, 6, 7; 15) consist of PET, PA in all modifications, PPS, PEK, PEEK, an elastic polyester, PBT or PTT or a combination thereof.
22. Dryer screen according to any one of claims 1 to 21, characterised in that the longitudinal and/or transverse filaments (3, 13; 5, 6, 7; 15) are fibre-reinforced.
23. Dryer screen according to any one of claims 1 to 22, characterised in that a fibrous layer is provided on at least one side.
24. A method of producing a porous dryer screen (1, 11) for the drying section of a paper machine, wherein a filament lay-up is produced by arranging at least one layer (2, 12) of longitudinal filaments (3, 13) and at least one layer (4, 14) of transverse filaments (5, 6, 7; 15), which cross the longitudinal filaments (3, 13), one above the other, and joining the longitudinal and transverse filaments (3, 13; 5, 6, 7; 15) to each other in the region of crossing points (8, 16), characterised in that flat filaments are used for the longitudinal and transversal filaments (3, 13; 5, 6, 7; 15) and that they are joined by adhesive, so that the adhesive remains exclusively between the mutually opposite faces of the longitudinal and transverse filaments (3, 13; 5, 6, 7; 15) for the purpose of joining said faces.
25. A method according to claim 24, characterised in that the longitudinal and transverse filaments (3, 13; 5, 6, 7; 15) are additionally positively attached to each other at crossing points (8, 16).
26. A method according to claim 24 or 25, characterised in that longitudinal filaments (3, 13) are firstly clamped parallel to each other, and that transverse filaments (5, 6, 7; 15) are then laid, individually or in groups, successively on said longitudinal filaments (3, 13) and are fixed to the longitudinal filaments (3, 13), and that the filament lay-up is conveyed in a longitudinal direction and is then rolled up.
27. A method according to claim 26, characterised in that transverse filaments (5, 6, 7; 15) are also fixed, simultaneously or later, to the other side of the longitudinal filaments (3, 13).
28. A method according to claim 26 or 27, characterised in that temporary fixing is effected by the additional application of weight.
29. A method according to any one of claims 24 to 28, characterised in that the layers (2, 12; 4, 14) are temporarily pressed on to each other at the crossing points (8, 16) for fixation.
30. A method according to any one of claims 24 to 29, characterised in that a fibrous layer is applied to one or both sides of the filament lay-up and is fixed thereto.

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