EP0544167B1 - Papermaking fabric, in particular dryer felt - Google Patents

Abstract

A paper machine cover with a textile web structure, e.g., a woven, knitted, or non-woven fabric, etc., is provided. The paper machine cover has flattened threads, whereby respectively the longer axis of the cross-section of these threads extends parallel to the plane of the paper machine cover. The flattened threads consist of monofilaments with an annular cross-section and/or multifilaments formed of individual filaments with an annular cross-section. The monofilaments or individual filaments of the multifilaments have an annular cross-section. These filaments are deformed plastically into the flattened cross-section at least in those areas where they extend parallel to the plane of the paper machine cover.

Description

The invention relates to a paper machine clothing, in particular dryer fabric, with or consisting of a textile fabric, for. B. a fabric, knitted fabric, scrim or the like, which has flattened threads in cross-section, wherein the longer axis of the cross-section of these threads extends parallel to the plane of the paper machine clothing.

Paper machine clothing is textile webs of very great length and considerable width, which are used for the formation and guidance as well as the transport of the paper web through the individual parts of the paper machine, essentially the sheet formation section, the press section and the dryer section. In this case, primarily fabrics are used as textile fabrics for the material web, the structure of which is specially adapted to the respective requirements in the individual batches of the paper machine. In some cases, these fabrics are also covered with needled fleece on one or both sides and needled to obtain felt-like surfaces. Instead of a woven fabric, other flat structures can also be used, for example warp knitted fabrics or scrims.

Monofilaments or multifilaments consisting of individual fibers are used for the flat structure of paper machine clothing. Thermoplastic polymers, in particular polyamides, polyesters or the like, are practically without exception suitable as materials for this. As a rule, the monofilaments or the individual fibers of the multifilaments are solid and have a diameter of 0.1 mm and above. The cross section is usually circular.

However, paper machine clothing with a flat structure which does not contain circular threads is known in the prior art (US Pat. No. 3,858,623). It has proven advantageous for use in the dryer section of a paper machine in particular to use flattened threads whose longer cross-sectional axis extends parallel to the plane of the paper machine clothing. It has primarily been proposed that only the longitudinal threads extending in the running direction of the paper machine clothing be flattened (cf., for example, US Pat. No. 2 0̸0 1233 123, US Pat. No. 3 139 119, US Pat. No. 3 545 70̸5, US Pat. No. 3 632 0̸68, US-PS 4 142 557, DE-OS 28 47 327, US-PS 4 351 874, GB-OS 2 0̸97 435). However, paper machine clothing is also known in which the longitudinal and transverse threads consist of flat wires, for example in metal thread beds (US Pat. No. 3,164,514, US Pat. No. 3,309,265), but also in metal fabrics (US Pat. No. 3,346,465). The same is also known for fabrics made of plastic threads (GB-PS 980-288).

The use of flattened threads has considerable advantages, particularly when used as a dryer fabric. The dryer fabric can be made thinner, which results in better heat transfer from the heating rollers to the paper web. In addition, the material density inside the dryer fabric is greater than when using circular threads, which reduces the air permeability. Too high air permeability has the consequence that considerable air movements take place through the dryer fabric, which can lead to fluttering of the dryer fabric.

The production of paper machine clothing with thread systems that contain flattened threads is difficult because the threads do not twist allowed to. The risk of twisting is particularly evident with weft threads. No useful proposals are known in the prior art on how the twisting of the threads can be prevented.

The invention is therefore based on the object to design a paper machine clothing of the type mentioned so that it is ensured that the flattened threads are always oriented so that the longer axis of the thread cross section extends parallel to the plane of the paper machine clothing. The invention further relates to a method for producing such a paper machine clothing.

This object is achieved according to the invention in that the flattened threads consist of monofilaments which are annular in cross section and / or of multifilaments which are formed from individual fibers which are annular in cross section, the monofilaments or individual fibers of the multifilaments which are annular in cross section at least in the areas in which they run essentially parallel to the plane of the paper machine clothing, are plastically deformed to the flattened cross section.

Such paper machine clothing can be produced according to the invention in such a way that hollow monofilaments and / or multifilaments with hollow fibers in cross section are used for the flat structure in cross-section and that the flat structure provided therewith or consisting thereof is subjected to such pressure and heat treatment that the Monofilaments or multifilaments are plastically deformed to the flattened cross-section at least in the areas in which they run essentially parallel to the plane of the paper machine clothing.

In this process, the formation of Fabric initially uses hollow monofilaments and / or multifilaments with hollow individual fibers, so that it does not matter in which orientation they are introduced or integrated into the fabric. The deformation to a flattened cross-section is then carried out by a pressure and heat treatment, for example by calendering, in that the finished thread system is passed between one or other pairs of heated rollers. As a result, the hollow monofilaments or the multifilaments with hollow individual fibers are plastically deformed and in this way obtain a flattened cross section. Normal machines can therefore be used for the production of the fabric. Due to the pressure and heat treatment, extremely thin paper machine coverings, in particular dryer fabrics, can be realized, which guarantee very good heat transfer and also have such a density within the thread system that the air permeability and thus the tendency to flutter is only slight. In addition, the weight of such paper machine clothing can also be reduced.

It is known to provide the thread system in the form of a fabric with hollow monofilaments in paper machine clothing. Such monofilaments were prior art, but were initially used in other fields of technology (see US Pat. No. 2,399,259 and US Pat. No. 3,772,137). According to US Pat. No. 4,251,588, a paper machine clothing equipped with such hollow filaments promises improved dimensional stability compared to solid monofilaments, particularly under deformation stresses such as occur in the press section, a higher degree of binding of the threads among one another, a longer lasting flexibility and overall an improved Lifespan. The use of hollow plastic weft threads can also be found in DE-OS 28 47 327.

In addition, it is known to use hollow fibers as supports for a treatment liquid in paper machine clothing (EP-A1 0̸ 191 231). This treatment liquid escapes through openings, for example at the end of the fibers, during operation of the paper machine clothing, in particular in order to achieve a cleaning effect. The fibers are parts of spun yarns, multifilaments or needled nonwovens.

When using hollow monofilaments, however, it has been expressly warned against flattening of the thread cross-sections (cf. US Pat. No. 4,251,588), which is why the hollow monofilaments described in this publication only have a small hollow volume of the order of 3 to 15% of the total cross-section .

In an embodiment of the invention it is provided that the monofilaments or fibers of the multifilaments, which are ring-shaped in cross section, are deformed in such a way that their inner sides abut one another, ie. H. are flattened as much as possible in order to achieve the thinnest possible thread system.

If the paper machine clothing consists of the textile fabric, use as a dryer fabric is particularly suitable. In principle, the invention can also be used for all other types of paper machine clothing. If the paper machine clothing is intended as a press felt, there is the possibility of needling the textile fabric with the flattened threads on one or both sides in a manner known per se with a nonwoven fabric, so that the covering is given a felt-like surface on one or both sides.

The ring-shaped monofilaments or multifilaments with ring-shaped individual fibers deformed according to the invention can in principle be introduced into the thread system both in the longitudinal and in the transverse direction. Significant advantages however, this is already achieved when these monofilaments or multifilaments run only in one direction of the paper machine clothing, specifically when the thread system is flat-woven, preferably in the transverse direction. Cross-sectionally round threads can then be used for the longitudinal direction. However, solid flat wires can also be used, since warp threads can be kept twist-free more easily than weft threads in a weaving machine.

Insofar as the paper machine clothing has or consists of a fabric formed as a fabric, it has proven to be advantageous that the fabric has the same weave on both sides, that is to say it is symmetrical in this respect.

An advantageous further development of the method according to the invention consists in using hollow monofilaments and / or hollow fibers for the multifilaments as starting material for the flat structure, which have a circular cross section on the outside and inside before they are plastically deformed. The orientation in which they are introduced into the thread system is then irrelevant.

According to the invention, hollow monofilaments or hollow individual fibers should also be used for the multifilaments, which have a free cross-sectional area that is between 20̸ and 80̸%, preferably 40̸ to 60̸% of the total cross-sectional area. With particularly thin-walled monofilaments or fibers, heavily flattened thread cross-sections can be achieved, the thin-walled area being limited by the forces to be absorbed in each case.

Figur (1)

einen teilweisen Längsschnitt durch eine Papiermaschinenbespannung parallel zu dessen Laufrichtung;

Figur (2)

einen teilweisen Querschnitt durch die Papiermaschinenbespannung gemäß Figur (1) in der Ebene A-A (Figur 1);

Figur (3)

einen teilweisen Querschnitt durch die Papiermaschinenbespannung gemäß Figur (1) in der Ebene B-B (Figur 1);

Figur (4)

einen teilweisen Längsschnitt durch die Papiermaschinenbespannung gemäß den Figuren (1) bis (3) nach einer Kalandrierbehandlung;

Figur (5)

einen Querschnitt durch die Papiermaschinenbespannung gemäß Figur (4) in der Ebene C-C (Figur 4);

Figur (6)

einen teilweisen Querschnitt durch die Papiermaschinenbespannung gemäß Figur (4) in der Ebene D-D (Figur 4).

In the drawing, the invention is illustrated in more detail using an exemplary embodiment. Show it:

Figure (1)

a partial longitudinal section through a paper machine clothing parallel to its direction of travel;

Figure (2)

a partial cross section through the paper machine clothing according to Figure (1) in the plane AA (Figure 1);

Figure (3)

a partial cross section through the paper machine clothing according to Figure (1) in the plane BB (Figure 1);

Figure (4)

a partial longitudinal section through the paper machine clothing according to the figures (1) to (3) after a calendering treatment;

Figure (5)

a cross section through the paper machine clothing according to Figure (4) in the plane CC (Figure 4);

Figure (6)

a partial cross section through the paper machine clothing according to Figure (4) in the plane DD (Figure 4).

The dryer fabric (1) shown in the figures is intended for the dryer section of a paper machine. It consists of a fabric (2), which is only shown here by way of example in plain weave, with itself in the transverse direction, i. H. transverse threads (3, 4, 5) extending transversely to the intended running direction of the drying wire (1) and longitudinal threads (6, 7, 8, 9) extending along the running direction.

The transverse threads (3, 4, 5) run relatively straight through the body of the fabric (2) and are designed as solid monofilaments. For the longitudinal threads (6, 7, 8, 9) are annular in cross-section during the manufacture of the fabric (2) Hollow monofilaments have been used, as can be seen in particular from Figures (2) and (3). The longitudinal threads (6, 7, 8, 9) initially have a circular cross section on the inside and outside and tie in the cross threads (3, 4, 5).

After the weaving process, the fabric (2) is subjected to a calendering treatment by passing it between pairs of calendering rollers pressed against one another, this calendering treatment also being able to be carried out several times. Due to this calendering treatment, the flat sides of the fabric (2) are subjected to a simultaneous pressure and heat treatment. The consequence of this is that the longitudinal threads (6, 7, 8, 9) designed as hollow monofilaments are flattened, i.e. have an almost rectangular cross-section, the inside of the longitudinal threads (6, 7, 8, 9) coming to lie on top of one another, such as this is particularly clear from Figures (5) and (6).

As can be seen in the comparison of the figures (1) and (4), the thickness of the drying wire (1) is considerably reduced due to the flattening of the longitudinal threads (6, 7, 8, 9). The thickness could be reduced even further by using hollow monofilaments for the transverse threads (3, 4, 5).

Claims (10)

1. A paper-making machine covering, comprising or consisting of a planar textile formation, e.g. a woven fabric, knitted fabric, lay-up or the like, which has flattened filaments, wherein the longer axis of the cross-section of each of these filaments extends parallel to the plane of the paper-making machine covering, characterised in that the flattened filaments (6, 7, 8, 9) consist of monofilaments which are annular in cross-section and/or of multifilaments which are formed from individual fibres which are annular in cross-section, wherein the monofilaments or the individual fibres of the multifilaments which are annular in cross-section are plastically deformed to form the flattened cross-section, at least in the regions in which they run substantially parallel to the plane of the paper-making machine covering (1).
2. A paper-making machine covering according to claim 1, characterised in that the monofilaments (6, 7, 8, 9) or the individual fibres of the multifilaments which are annular in cross-section are deformed in such a way that their internal faces adjoin each other.
3. A paper-making machine covering according to either one of claims 1 or 2, characterised in that the planar textile formation is pinned to a fibrous web on one or both sides.
4. A paper-making machine covering according to claims 1 to 3, characterised in that the annular monofilaments or multifilaments comprising annular individual fibres only run in the transverse direction of the paper-making machine covering (1).
5. A paper-making machine covering according to any one of claims 1 to 4, characterised in that the paper-making machine covering (1) ) comprises or consists of a planar formation constructed as a woven fabric (2), and that the woven fabric (2) has an identical weave on both sides.
6. A process for producing a paper-making machine covering according to any one of claims 1 to 5, characterised in that hollow monofilaments (6, 7, 8, 9) and/or multifilaments having hollow individual fibres are used as a starting material for the planar textile formation, and that the planar formation provided therewith is subjected to a pressure- and heat-treatment such that the mono- or multifilaments are plastically deformed to form the flattened cross-section, at least in the regions in which they run substantially parallel to the plane of the paper-making machine covering.
7. A process according to claim 6, characterised in that hollow monofilaments (6, 7, 8, 9) and/or hollow individual fibres for the multifilaments which have a circular cross-section on the outside and on the inside are used as a starting material for the planar formation (2).
8. A process according to claim 7, characterised in that the hollow monofilaments (6, 7, 8, 9) or the individual fibres of the multifilaments have a free internal cross-sectional area which is between 20 and 80%, preferably 40 to 60%, of the total cross-sectional area.
9. A process according to any one of claims 6 to 8, characterised in that the hollow monofilaments or the multifilaments comprising hollow individual fibres are only introduced into the filamentary system (2) in the transverse direction of the paper-making machine covering (1).
10. A process according to any one of claims 6 to 9, characterised in that the filamentary system (2) is calendered for the pressure- and heat-treatment

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