PRESS COVER, THE USE THEREOF, AND THE USE OF A THERMOPLASTIC ELASTOMER IN THE FORM OF A COPOLYMER FOR A POLYMER LAYER OF A PRESS COVER

Abstract

A press cover is formed with at least one polymer layer. The at least one polymer layer includes or is formed of at least one thermoplastic elastomer in the form of a copolymer. There is also disclosed the use of a press cover of this type in a shoe press, a shoe press of this type, and a press roll, in each case having a press cover of this type. Finally, there is also disclosed the use of a thermoplastic elastomer in the form of a copolymer, for at least one polymer layer of a press cover for a shoe press for the treatment of a fibrous web.

Claims

1-14. (canceled)

15. A press cover for a press for the treatment of a fibrous material web, the press cover comprising: at least one polymer layer, said at least one polymer layer being formed of, or comprising, at least one thermoplastic elastomer being a copolymer.

16. The press cover according to claim 15, wherein said at least one thermoplastic elastomer is a segmented block copolymer.

17. The press cover according to claim 15, wherein said at least one thermoplastic elastomer is a thermoplastic copolyester elastomer.

18. The press cover according to claim 15, wherein said at least one thermoplastic elastomer is a thermoplastic copolyamide elastomer.

19. The press cover according to claim 15, wherein said at least one polymer layer comprises an embedded reinforcing structure, being at least one reinforcing thread.

20. The press cover according to claim 19, wherein said at least one reinforcing thread consists of a polymer selected from the group consisting of polyester, polyethylene naphthalate, and polyamide.

21. The press cover according to claim 20, wherein said at least one reinforcing thread is an aramid thread.

22. The press cover according to claim 19, wherein said at least one reinforcing thread comprises of a polymer selected from the group consisting of polyester, polyethylene naphthalate, and polyamide.

23. The press cover according to claim 19, wherein said at least one reinforcing thread is one or more longitudinal threads which, running in a longitudinal direction of the press cover, are arranged at a spacing distance and parallel to one another over a circumference of the press cover.

24. The press cover according to claim 23, wherein at least one further reinforcing thread is a circumferential thread which runs within said at least one polymer layer along a helical line in the circumferential direction of the press cover.

25. The press cover according to claim 24, wherein said reinforcing threads that are longitudinal threads and said at least one further reinforcing thread that is configured as circumferential thread form a scrim with one another, with said longitudinal threads being arranged radially within said at least one circumferential thread, as viewed in relation to the longitudinal axis of the press cover.

26. The press cover according to claim 19, wherein said at least one polymer layer is one of a plurality of polymer layers and at least one polymer layer, in relation to the longitudinal axis of the press cover, is a radially inner or innermost polymer layer, and an additional polymer layer is a radially outermost layer in relation to the longitudinal axis of the press cover.

27. The press cover according to claim 26, wherein said at least one polymer layer is one of exactly two polymer layers and a radially inner polymer layer is a radially innermost polymer layer of the press cover.

28. A press roll for a shoe press for treating a fibrous material web the press roll comprising at least one press cover according to claim 15.

29. A shoe press for treating a fibrous material web, the shoe press comprising a press roll and an opposing roll, which together form or delimit a press nip, said press roll including a circulating press cover according to claim 15.

30. The shoe press according to claim 29, configured for treating a paper, cardboard, tissue, or pulp web,

31. The press cover according to claim 15 configured for use in a shoe press for treating a fibrous material web.

32. The shoe press according to claim 29, configured for treating a paper, cardboard, tissue, or pulp web.

33. In a press cover for a shoe press for treating a fibrous material web, the press cover having at least one polymer layer, the improvement which comprises the at least one polymer layer being a thermoplastic elastomer in the form of a copolymer.

34. The improved press cover according to claim 33, wherein the copolymer is a segmented block copolymer, being a thermoplastic copolyester elastomer and/or a thermoplastic copolyamide elastomer.

Description

[0033] Without limitation of its general nature, the invention is elucidated in more detail below with reference to the drawings. In the drawings

[0034] FIG. 1 shows, in partial section, a schematic side view of a shoe press having a press cover according to an exemplary embodiment of the present invention.

[0035] FIGS. 2a and 2b show embodiments of a press cover in each case seen in a section through its longitudinal axis;

[0036] FIG. 3 shows a highly schematic representation of an apparatus for producing the press cover, in a side view.

[0037] FIG. 1 shows in partial section a schematic side view of a shoe press 10, which presently comprises a press roll of the invention, such as shoe press roll 12, and an opposing roll 14. In terms of their longitudinal axes, shoe press roll 12 and opposing roll 14 are arranged parallel to one another. They together form a nip 22 or delimit such a nip.

[0038] While the opposing roll 14 here consists of a cylindrically configured roll rotating about its longitudinal axis, the shoe press roll 12 is assembled from a shoe 16, a stationary yoke 18 supporting said shoe, and a press cover 20. Shoe 16 and yoke 18 are in a fixed, stationary arrangement relative to the opposing roll 14 and the press cover 20, respectively. This means that they do not rotate. The shoe 16 is supported by the yoke 18 and is pressed onto the radially innermost surface of the press cover 20, circulating relative to it, by way of hydraulic press elements, which are not shown. The press cover 20, which surrounds shoe 16 and yoke 18 in the circumferential direction, rotates about its longitudinal axis in the opposite direction of rotation to the opposing roll 14. Because of the concave configuration of the shoe 16 on its side facing the opposing roll 14, a comparatively long nip 22 is obtained.

[0039] The shoe press 10 is suitable more particularly for the dewatering of fibrous material webs 24. In the operation of the shoe press, a fibrous material web 24 is guided with one or two press felts 26, 26′ through the press gap 22. In the present case there are exactly two press felts 26, 26′, which accommodate the fibrous material web 24 between them in the manner of a sandwich. On passage through the nip 22, a pressure is exerted indirectly in the nip 22 on the fibrous material web 24 by the press felts 26, 26′. This takes place through the radially outermost surface of the opposing roll 14, on the one hand, and the radially outermost surface of the press cover 20 coming into direct contact with the corresponding press felts 26, 26′. The liquid emerging from the fibrous material web 24 is taken up temporarily by the press felt or felts 26, 26′ and by any depressions (not shown) provided in the press cover surface. Following departure from the nip 22, the liquid taken up by the depressions in the press cover 20 is thrown off, before the press cover 20 enters the press gap 22 again. Moreover, following departure from the press gap 22, the water taken up by the press felt 26, 26′ can be removed using suction elements.

[0040] In a further embodiment of the invention, not shown in the figures, it is possible to omit the press felts 26, 26′. In such a case, the fibrous material web 24 is in direct contact with the press cover 20 on the one side and with the opposing roll 14 on the other side, these components together forming a press nip. The latter roll may in this case be configured as a heated drying cylinder.

[0041] The press cover shown in FIG. 1 may be configured in accordance with the invention, as shown in the following figures.

[0042] FIGS. 2a and 2b show different embodiments of the invention, in a partially illustrated cross section, not to scale, through the longitudinal axis 20′ of the completed press cover 20. The distance of the longitudinal axis 20′ from the radially innermost surface of the corresponding polymer layer of the press cover 20 is likewise shown not to scale.

[0043] In accordance with FIG. 2a there are precisely two polymer layers, a first 20.1 and a second 20.2. In the present case, the first polymer layer 20.1 is likewise the radially outermost polymer layer of the press cover 20. Conversely the second polymer layer 20.2 is likewise the radially innermost polymer layer of the press cover 20.

[0044] As shown, there may be a reinforcing structure 20″ in the second polymer layer 20.2. This structure presently is completely embedded in the polymer layer 20.2. This is indicated by the shaded circles, which may be textile sheetlike or linear structures such as fibers. This means that the reinforcing structure 20″ does not extend beyond the confines of the polymer layer 20.2.

[0045] The reinforcing structure 20″ here comprises a plurality of reinforcing threads 21 serving as longitudinal thread 21.1. These threads are arranged running with distance in parallel to one another in the longitudinal direction of the press cover 20 over its circumference. Additionally here there is at least one further reinforcing thread 21 provided as a circumferential thread 21.2, which preferably runs in the form of a helical line in the circumferential direction of the press cover within the same polymer layer 20.1, 20.2, 20.3 in which the longitudinal threads 21.1 are also arranged. The longitudinal threads 21.1 and the circumferential thread 21.2 form with one another a scrim, in such a way that the longitudinal threads 21.1 are arranged radially within the at least one circumferential thread 21.2—as viewed in relation to the longitudinal axis 20′ of the press cover 20.

[0046] FIG. 2b, in a modification relative to FIG. 2a, shows a three-layer press cover. This cover comprises a first—here radially outermost—polymer layer 20.1, a radially innermost, third polymer layer 20.3, and a second polymer layer 20.2 sandwiched between these other two layers. The arrangement is as viewed—in the same way as for the illustration in FIG. 2a— in the radial direction of the press cover 20, starting from its longitudinal axis 20′. Presently there is only a (single) reinforcing structure 20″ provided in the second polymer layer 20.2. This could of course also be different, and so, alternatively or additionally, there could be a reinforcing structure 20″ of this kind arranged in the first polymer layer 20.1 and/or in the third polymer layer 20.3, as well.

[0047] In the present case, one of the polymer layers 20.1, 20.2 or 20.3 shown in FIGS. 2a and 2b may comprise or be made of a thermoplastic elastomer of the invention in the form of a copolymer. This could be the case, for example, for the radially innermost and/or the radially outermost polymer layer. The remaining polymer layers in that case could be made of a polyurethane. The latter is obtainable, for example, from a prepolymer and a crosslinker. The respective prepolymer itself is obtainable by reaction of an isocyanate with a polyol.

[0048] FIG. 3, in a highly schematic side view, shows an apparatus for producing a press cover 20 of the invention. The apparatus presently has precisely one cylindrical winding mandrel 4; here, a starting material 20″, for example, is applied spirally to the radially outermost circumferential surface of said mandrel. After embedding into the polymer, the starting material 20″″ forms the reinforcing structure 20″ of the completed press cover 20 of the invention.

[0049] The illustration shows an initial stage of the production process. For this purpose, in the present case, one end of the starting material 20′″ is secured on a polymer which is arranged on the outer periphery of the winding mandrel 4. Aside from the schematic illustration shown, the end of the starting material 20′″ could also lie or be applied directly, in other words without mediation, on the winding mandrel 4, without a polymer being provided initially between starting material 20′″ and winding mandrel 4. The starting material 20′″ in this case may be a textile sheetlike structure or linear structure.

[0050] The winding mandrel 4 is mounted so as to be rotatable about its longitudinal axis 20′, which corresponds to the longitudinal axis of the press cover being produced. Longitudinal axis 20′ here runs perpendicularly into the plane of the drawing. Via a conduit 5, a casting material, such as castable, curable elastomeric polymer, here polyurethane for example, is applied through a casting nozzle 6 from above onto the radially outermost circumferential surface of the winding mandrel 4 or onto the starting material 20′″. A casting material of this kind may be selected in terms of its pot life and viscosity, for example, such that it does not drip down from the winding mandrel 4 during casting. During this process, the winding mandrel 4 is rotated about its longitudinal axis in the direction of the arrow. Concurrently with this rotation, the casting nozzle 6 is guided via a suitable guide, not shown further in FIG. 3, parallel to the longitudinal axis 20′, along that axis in a relative manner on the winding mandrel 4. At the same time as the casting material is poured on, the starting material 20′″ is unwound and is wound onto the rotating winding mandrel 4 to form coils. The casting material here may pass through the starting material 20′″ as far as the winding mandrel 4. In this example, after the curing step, the polymer forms a radially innermost and preferably elastomeric polymer layer, corresponding to the polymer layer 20.2 of the press cover from FIG. 2a, of which only a part is shown in FIG. 3.

[0051] The casting material emerging from the casting nozzle 6 is presently a mixture of a prepolymer and a crosslinker. The former is provided from a prepolymer container, not shown, in which it is stored or prepared by stirring. The prepolymer is the reaction product of an isocyanate and a polyol. In the prepolymer container it may be present, for example, in the form of a prepolymer of the substances just stated.

[0052] The crosslinker may be provided in a crosslinker container.

[0053] Prepolymer container and crosslinker container are assigned to the apparatus for producing a press cover 20. They have a flow-conducting connection, via conduits which are likewise not shown, to a mixing chamber (not shown) which is upstream of the casting nozzle 6 in the flow direction. The prepolymer-crosslinker mixture is therefore produced upstream and outside of the casting nozzle 6, i.e. it is mixed in the mixing chamber. Irrespective of the production of the mixture, it is then applied to the surface of the winding mandrel 4 to form the at least one polymer layer of the press cover 20.

[0054] In principle it would be conceivable for two or more casting nozzles 6 to be provided. These nozzles could be connected via corresponding conduits to separate prepolymer containers and crosslinker containers, in order independently of one another for different polymers as well to be supplied to the plurality of casting nozzles 6. In that case the casting nozzles 6 could be arranged with distance from one another along the longitudinal axis of the press cover 20, to produce multiple polymer layers 20.1, 20.2, 20.3 simultaneously by concurrent delivery of the polymer from the casting nozzles 6, in one casting.

[0055] By means of a continuous casting operation of this kind, also known as rotational casting, therefore, a continuous cylindrical-tubular press cover 20 which is intrinsically closed about its longitudinal axis 20′ is gradually produced over the width of the winding mandrel 4, the internal circumference of said cover 20 corresponding substantially to the outer circumference of the winding mandrel 4.

[0056] In principle it would be conceivable to wind the starting material 20′″ onto more than the one winding mandrel 4 shown in FIG. 3. It would be possible, for example, to provide two winding mandrels, which could be arranged with distance from one another and parallel in terms of their longitudinal axes. Alternatively it would also be conceivable for the polymer to be applied to the radially inner circumferential surface of the winding mandrel 4 as well, in a centrifugal manner, for example. Irrespective of the embodiment addressed, the completed press cover 20 is finally taken off from the at least one winding mandrel 4.

[0057] Although not illustrated in the figures, the reinforcing structure 20″ of the at least one polymer layer 20.1, 20.2 could also be constructed of a plurality of starting materials 20′″ placed one above another in the radial direction and each running in the longitudinal axis direction and in the circumferential direction of the press cover 20.

[0058] The structure of a corresponding polymer layer, which contains or comprises a thermoplastic elastomer in the form of a copolymer, may be produced analogously with such an apparatus. In this case the thermoplastic elastomer is applied over the circumference of the winding mandrel 4, if this is the radially innermost polymer layer of the press cover. Alternatively or additionally, the elastomer may be applied to a polymer layer already produced from polyurethane, in order then to constitute the radially outermost polymer layer of the press cover. The thermoplastic elastomer of the invention may be applied as a polymer layer by means, for example, of an extrusion process.