WO2021058165A1

WO2021058165A1 - 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

Info

Publication number: WO2021058165A1
Application number: PCT/EP2020/070406
Authority: WO
Inventors: Delphine Delmas
Original assignee: Voith Patent Gmbh
Priority date: 2019-09-26
Filing date: 2020-07-20
Publication date: 2021-04-01
Also published as: EP4034706A1; CN114450447A; JP2022550082A; DE102019125908A1; US20220372701A1

Abstract

The invention relates to a press cover comprising at least one polymer layer, wherein the at least one polymer layer comprises or is produced from at least one thermoplastic elastomer in the form of a copolymer. Furthermore, the invention also relates to the use of a press cover of this type in a shoe press, to a shoe press of this type, and to a press roll, in each case comprising a press cover of this type. Finally, the invention also relates to 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.

Description

PRESSED COAT, ITS USE AND USE OF A THERMOPLASTIC ELASTOMER IN THE FORM OF A COPOLYMER FOR A POLYMER LAYER OF A PRESSED COAT

The invention is based on a press cover, in particular for a press device for treating a fibrous web, e.g. for smoothing or dewatering it, in detail according to the independent claims. The invention also relates to a shoe press and the use of a press jacket in such and to a machine comprising such a shoe press, in detail according to the independent claims. Press devices such as shoe presses have long been part of modern paper machines. They essentially comprise a stationary shoe (also called a press shoe), which extends in a cross-machine direction, and a press cover that encircles the stationary shoe. The latter is deformable and essentially assumes a tubular shape in operation. The shoe is shaped in such a way that it forms a press nip (press nip) with a counter roller. The press nip is defined by the contact surface of the counter roll in the shoe. The shoe is designed to be movable and can be moved to the counter roll.

Enormous demands are made on the press jacket with regard to its stability, namely with regard to surface hardness, resistance to pressure, temperature and hydrolysis. The press jacket is also exposed to strong alternating bending loads during operation. When entering the edge of the shoe - seen in the direction of rotation of the press jacket in front of the press nip - there is initially a bend under a relatively small radius. This immediately turns into a bend in the opposite direction when passing through the press nip. When it runs out at the other edge of the shoe, that is - after the press nip as seen in the direction of rotation of the press jacket - there is again a counter-bending. This deformation of the press jacket when it runs in and out is also referred to as a change nip. It is easy to see that the tendency of the press jacket to break, especially at this point, is very great due to the high mechanical stress. Accordingly, many measures are known from the prior art that the stability of the

Press jacket should increase. The press cover must therefore be sufficiently flexible so that it can be guided around the shoe, it must be sufficiently rigid so that it does not deform or compress too much in the nip under the press load, and it must be sufficiently wear-resistant. Press jackets therefore consist of a single or multi-layer polymer layer, preferably made of polyurethane, in which reinforcing threads in the form of scrims or fabrics can be embedded.

The present invention relates to such generic objects mentioned at the outset.

Although press sleeves known from the prior art have sufficient flexibility and at the same time sufficient rigidity, their chemical resistance, in particular to water and oil, their abrasion resistance, their resistance to cracking and crack growth and their swelling behavior are in need of improvement.

It is accordingly the object of the invention to provide a press jacket which avoids the disadvantages of the prior art.

The object is achieved by the features of the independent claims. Particularly preferred and advantageous embodiments of the invention are given in the subclaims.

The inventor has recognized that the object according to the invention is achieved if a thermoplastic elastomer (TPE) in the form of a copolymer is used for a polymer layer of the press jacket.

Thermoplastic elastomers are - according to the definition of the Wikipedia article of the same name, last edited on July 22, 2019 at 11:13 a.m. - materials in which elastic polymer chains are embedded in thermoplastic material. They can be processed in a purely physical process in a combination of high shear forces, the action of heat and subsequent cooling. Conventional elastomers, on the other hand, are chemically wide-meshed network molecules. The cross-links cannot be broken without decomposition of the material. Although no chemical crosslinking is necessary, for example through a time-consuming and temperature-intensive vulcanization as is the case with elastomers, the parts produced have rubber-elastic properties due to their special molecular structure. Renewed exposure to heat and shear forces leads to melting and deformation of the material.

For the purposes of the invention, copolymers are polymers which are composed of two or more different types of monomer. According to the Wikipedia article mentioned at the beginning, thermoplastic elastomers are divided into copolymers and elastomer alloys. Copolymers are used either as random or block copolymers. The former consist of a crystallizing (and thus physically crosslinking) main polymer such as B. polyethylene, the degree of crystallization by a randomly installed along the chain comonomer such. B. vinyl acetate is reduced to such an extent that the crystallites (= the hard phase) in the finished material (EVA in the example) no longer have direct contact. As in conventional elastomers, they then act as isolated cross-linking points. In block copolymers, the hard and soft segments are sharply separated in one molecule (e.g. SBS, SIS). With TPEs, the material separates into a continuous and a discontinuous phase below a certain temperature. As soon as the latter falls below its glass transition temperature Tg (the Tg of the continuous phase is significantly below the later application temperature), it again acts as a crosslinking point. Elastomer alloys, on the other hand, are polyblends, i.e. mixtures

(Mixture) of finished polymers, i.e. the plastic consists of several types of molecules. Different mixing ratios and additives result in tailor-made materials (for example polyolefin elastomer made of polypropylene (PP) and natural rubber (NR) - depending on the proportions, they cover a wide range of hardnesses). The thermoplastic elastomer is preferably a segmented block copolymer. Such a thermoplastic polyether-ester block copolymer (COPE or TPE-E) and / or a thermoplastic copolyamide elastomer (COPA or TPE-A) can be. The two polymers mentioned can be alternatives to conventional polyurethanes or thermoplastic polyurethanes (TPU). The soft segments are formed by the polyol. For the hard segments of COPE, polyesters, polybutylenetephtalates, polyethylene terephthalates, methyl terephthalates, poly (butylene 2,6 napthalene dicarboxylate, poly (butylene-co-isophthalate or aromatic polycarbonates) can be used. For COPA, polyamides can be used as hard segments Polyether polyols, for example polytetramethylene glycol, polycarbonate polyols, polyether polycarbonate polyols, polycaprolactone polyols are particularly suitable polyols for the invention. In principle, it would be conceivable to use a polyol blend, i.e. an elastomer alloy between the thermoplastic copolymers mentioned and a thermoplastic elastomer to use urethane-based (TPU) for the at least one polymer layer of the press jacket When, according to the invention, it is said that something is made of a material, that means that it is partly or completely made of such a material.

The press jacket or the at least one polymer layer can be produced partially or completely from a polymer. A pourable, curable, preferably elastomeric polymer such as polyurethane can be used as the polymer. The polymer can consequently be set as a cast elastomer.

By polymer layer is meant a layer which comprises such a pourable, curable, preferably elastomeric polymer or is produced entirely from it. The polymer layer can preferably be a cured layer produced in one piece by primary molding. In other words, it is primordial monolithic, that is produced by, for example, casting. The term “one-piece” also includes cases in which the one layer was again produced from several layers of the same material when the polymer was cast. However, this is only insofar as these layers are essentially no longer visible after curing, but rather a single, preferably uniform layer results. The same applies accordingly to the finished press jacket.

When a plurality of polymer layers are provided, these can be arranged one above the other as seen in the radial direction - at least in sections over the width of the press jacket. At least in sections across the width of the press jacket means that the press jacket is, for example, only single-layered at its axial ends along the longitudinal axis of the press jacket, whereas it has two or more layers between the axial ends. However, the polymer layers can also extend over the entire width of the press jacket. The thickness of the press jacket - and thus the thickness of the individual polymer layers - can also vary in sections along the longitudinal axis in a section through its longitudinal axis. For example, the radially outermost polymer layer in the area of the width edges of the press jacket can be smaller than in the middle of the press jacket. In other words, the radially outermost polymer layer can be less thick in the region of the width edges than a radially inner or radially innermost polymer layer. Precisely one, two or three polymer layers are preferably provided. These can be identical in terms of their polymer or vary in terms of their hardness or stoichiometry of the prepolymer. A total thickness of the finished press jacket in a section through its longitudinal axis, measured in the radial direction, can be 5 to 10 mm, preferably 5 to 7, particularly preferably 5 to 6 mm. According to the invention, when a single layer is provided, the press jacket can be made from only one cast, ie monolithically, so that the single layer has the thickness just mentioned. A finished press jacket within the meaning of the invention is one whose at least one polymer layer is cured and possibly finally processed, that is to say for the is ready for use in a shoe press, for example. Similarly, a finished polymer layer means a layer that has cured.

A reinforcing thread within the meaning of the invention is understood to be a pliable, textile line structure that has a dominant extension and uniformity in its longitudinal direction. When fiber is mentioned, a single, endless fiber in the manner of a monofilament is meant. If, on the other hand, a fiber bundle is spoken of in the sense of the invention, it is not a question of monofilaments but, in turn, a single thread, such as a twisted thread or yarn, that is a bundle of continuous fibers or monofilaments. The fiber bundles themselves can be made from fibers twisted together.

The definition that at least the longitudinal threads are produced as reinforcing threads according to the invention means that only the longitudinal threads are designed in this way or, in addition, the longitudinal threads and at least one further circumferential thread are produced in this way. If, for example, a scrim of circumferential and longitudinal threads is preferably present, this means that at least the longitudinal threads are designed according to the invention. The term reinforcement structure in the context of the invention means reinforcement of the at least one layer containing or consisting of the polymer - that is to say the polymer layer. The reinforcement structure can be completely embedded in the polymer layer, so that the reinforcement structure does not go beyond the delimitation of the polymer layer. In other words, the polymer layer takes on the role of a matrix which surrounds the reinforcement structure and binds to the matrix as a result of adhesive or cohesive forces. Such a reinforcement structure can be textile line structures - z. B. yarns or twisted threads - and / or textile fabrics - such. B. fabrics, knitted fabrics, knitted fabrics, braids or scrims - comprise and can be produced from a corresponding starting material, for example by winding. In other words, a single reinforcing thread according to the invention is, considered in and of itself, a textile line structure. Several such reinforcing threads can be designed, for example, as longitudinal and / or circumferential threads be that they together form a textile fabric. The at least one reinforcement thread, which is embedded in the at least one polymer layer, then represents the reinforcement structure of the press jacket or its polymer layer. Starting material is understood to mean that material or semi-finished product by means of which the reinforcement structure of the finished press jacket according to the invention is produced, i.e. in the present case the at least a reinforcement thread.

The reinforcement thread or the reinforcement structure can be produced from a polymer or comprise such a polymer. Polymers are polyester, polyethylene naphthalate or polyamides, such as aramids. The materials of the at least one polymer layer and the at least one reinforcement thread or reinforcement structure embedded therein thus differ.

In the context of the invention, a press device is, for example, a shoe press, e.g. for dewatering or treatment, such as smoothing a

Meant fiber web. The shoe press comprises a shoe press roll and a counter roll, which together form or delimit a press nip. The shoe press roll further comprises a revolving press cover and a standing press element, the so-called press shoe. The latter is supported on a load-bearing, also standing yoke - for example via hydraulic ones

Press elements - and is pressed against the surrounding press jacket. The press jacket rotates relative to the stationary press shoe and yoke and is thereby pressed against the counter roll in the press nip. The press shoe and yoke are arranged radially inside the press jacket. The term is understood to mean that the press element does not rotate relative to the shoe press roll or the counter roll, but can move in a translatory manner - towards the counter roll and away from it, preferably in the radial direction thereof - and thus relative to the counter roll. In addition to the fibrous web and the press cover, one or more press felts running continuously in the circumferential direction and / or further continuously running press belts can be guided through the press nip of the shoe press. Such a shoe press can of course comprise more than one press nip. For the purposes of the invention, a fibrous web is to be understood as meaning a scrim or tangle of fibers, such as wood fibers, plastic fibers, glass fibers, carbon fibers, additives, additives or the like. For example, the fibrous web can be designed as a paper, cardboard or tissue web. It can essentially comprise wood fibers, small amounts of other fibers or also additives and additives being able to be present. Depending on the application, this is left to the specialist.

If several reinforcement threads are preferably embedded as longitudinal threads and at least one reinforcement thread as circumferential thread, which surrounds the longitudinal threads in the circumferential direction, as a scrim in the polymer layer, the advantages according to the invention are fulfilled particularly well. Because a clutch is able to absorb local overloads particularly well. The advantages according to the invention are achieved particularly well if the press cover is constructed from preferably several polymer layers arranged one above the other in the radial direction. If two polymer layers are provided, then the radially inner one is that with the reinforcement structure according to the invention. This means that the reinforcement structure is only arranged in the radially innermost polymer layer. If three or more polymer layers are provided, then the reinforcement structure is preferably arranged in the second lowest polymer layer, that is to say in the one which lies radially above the radially innermost polymer layer.

The invention also relates to a press roll, such as a shoe press roll, for a shoe press for treating a fibrous web, characterized in that the press roll has at least one press cover according to one of the preceding claims.

The invention also relates to a shoe press for treating a fibrous web, preferably a paper, cardboard, tissue or cellulose web, comprising a press roll and a counter roll which together form a nip or limit, wherein the press roll comprises a revolving press cover, characterized in that the press cover is designed according to the invention.

The invention further relates to the use of a press jacket according to the invention for a press, such as a shoe press for treating a fibrous web, preferably a paper, cardboard, tissue or cellulose web.

The invention also relates to the use of a thermoplastic elastomer in the form of a copolymer, preferably a segmented block copolymer, which is preferably a thermoplastic copolyester elastomer (COPE) and / or a thermoplastic copolyamide elastomer (COPA), for at least one polymer layer of a press jacket for a Shoe press for treating a fibrous web. The invention is explained in more detail below with reference to the drawings without restricting the generality. In the drawings show:

Fig. 1 is a partially sectioned, schematic side view of a

Shoe press with a press cover according to an embodiment of the present invention.

2a and 2b, embodiments of a press jacket, each seen in a section through its longitudinal axis; Fig. 3 is a highly schematic representation of a device for

Production of the press jacket in a side view.

1 shows a partially sectioned, schematic side view of a shoe press 10, which in the present case comprises a press roll according to the invention, such as a shoe press roll 12, and a counter roll 14. Shoe press roll 12 and counter roll 14 are arranged parallel to one another with regard to their longitudinal axes. Together they form a nip 22 or delimit one. While the counter roll 14 here consists of a cylindrical roll rotating around its longitudinal axis, the shoe press roll 12 is composed of a shoe 16, an upright yoke 18 carrying it, and a press cover 20. Shoe 16 and yoke 18 are arranged in a fixed manner with respect to counter roll 14 and press cover 20, respectively. That means they don't rotate. In this case, the shoe 16 is supported by the yoke 18 and is pressed against the radially innermost surface of the press jacket 20, which is circumferential relative thereto, via hydraulic press elements (not shown). The press jacket 20, which surrounds the shoe 16 and yoke 18 in the circumferential direction, rotates about its longitudinal axis in the opposite direction of rotation to the counter roll 14. The concave design of the shoe 16 on its side facing the counter roll 14 results in a comparatively long nip 22.

The shoe press 10 is particularly suitable for dewatering fibrous webs 24. When the shoe press is in operation, a fibrous web 24 with one or two press felts 26, 26 ′ is passed through the press nip 22. In the present case there are exactly two press felts 26, 26 'that sandwich the fibrous web 24 between them. When passing through the nip 22, a pressure is exerted indirectly in the nip 22 on the fibrous web 24 by the press felts 26, 26 '. This takes place in that the radially outermost surface of the counter roller 14 on the one hand and the radially outermost surface of the press jacket 20 come into direct contact with the corresponding press felts 26, 26 '. The liquid emerging from the fibrous web 24 is temporarily absorbed by the press felt (s) 26, 26 'and any depressions (not shown) provided in the press jacket surface. After leaving the nip 22, the liquid absorbed by the depressions of the press jacket 20 is thrown off before the press jacket 20 re-enters the press nip 22. In addition, the water taken up by the press felt 26, 26 ′ can be removed with suction elements after it has left the press nip 22.

In a further embodiment of the invention not shown in the figures, the press felts 26, 26 'can be dispensed with. In such a case, the Fibrous web 24 on the one hand with the press jacket 20 and on the other hand with the counter roll 14, which together form a press nip, in direct contact. The latter can then be designed as a heated drying cylinder. The press jacket shown in FIG. 1 can, as shown in the following figures, be designed according to the invention.

2a and 2b show different embodiments of the invention in a not to scale, partially shown cross section through the longitudinal axis 20 'of the finished press jacket 20. The distance between the longitudinal axis 20 'and the radially innermost surface of the corresponding polymer layer of the press jacket 20 is also not shown to scale.

According to FIG. 2a, exactly two polymer layers are provided, namely a first 20.1 and a second 20.2. In the present case it is the first polymer layer

20.1 at the same time the radially outermost polymer layer of the press jacket 20. On the other hand, the second polymer layer 20.2 is also the radially innermost polymer layer of the press jacket 20. As shown, a reinforcing structure 20 ″ can be provided in the second polymer layer 20.2 This is indicated by the hatched circles, which can be textile planar structures or line structures such as fibers. This means that the reinforcement structure 20 ″ does not extend beyond the boundaries of the polymer layer 20.2.

The reinforcement structure 20 ″ here comprises a plurality of reinforcement threads 21 serving as longitudinal threads 21.1. These are arranged in the longitudinal direction of the press jacket 20 over its circumference at a distance from and parallel to one another

21.2 is provided, which is preferably within the same polymer layer 20.1, 20.2, 20.3 in which the longitudinal threads 21.1 are also arranged, helically in The circumferential direction of the press jacket runs. The longitudinal threads 21.1 and the circumferential thread 21.2 form a scrim with one another, namely in such a way that the longitudinal threads 21.1 are arranged radially within the at least one circumferential thread 21.2 - viewed in relation to the longitudinal axis 20 'of the press jacket 20.

In a modification of FIG. 2a, FIG. 2b shows a three-layer press jacket. This comprises a - here radially outermost - first polymer layer 20.1, a radially innermost, third polymer layer 20.3 and a second polymer layer 20.2 sandwiched between these two. The arrangement relates - as also in the illustration in FIG. 2a - starting from the longitudinal axis 20 'of the press jacket 20, seen in its radial direction. In the present case, a (single) reinforcement structure 20 ″ is provided only in the second polymer layer 20.2. Of course, this could also be different so that, alternatively or additionally, such a reinforcement structure 20 ″ could also be arranged in the first polymer layer 20.1 and / or the third polymer layer 20.3.

In the present case, one of the polymer layers 20.1, 20.2 or 20.3 shown in FIGS. 2a and 2b can be produced from a thermoplastic elastomer according to the invention in the form of a copolymer or comprise such a copolymer. This could be the case, for example, for the radially innermost and / or the radially outermost polymer layer. The remaining polymer layers could then be made from a polyurethane. This is available, for example, from a prepolymer and a crosslinker. The respective prepolymer itself can be obtained by reacting an isocyanate with a polyol.

3 shows, in a highly schematic side view, a device for producing a press jacket 20 according to the invention. In the present case, the device has exactly one cylindrical winding mandrel 4, with a starting material 20 '", for example, being applied in a spiral to its radially outermost jacket surface. The starting material 20""After embedding in the polymer, it forms the reinforcement structure 20" of the finished press jacket 20 according to the invention. The illustration shows an initial stage of the manufacturing process. In the present case, one end of the starting material 20 '''is attached to a polymer which is arranged on the outer circumference of the winding mandrel 4. Apart from the schematic illustration shown, one end of the starting material 20''' could also be directly, that is, directly on rest or be applied to the winding mandrel 4 without initially providing a polymer between the starting material 20 '"and the winding mandrel 4. The starting material 20'" can be a flat textile structure or a linear structure. The winding mandrel 4 is rotatably mounted about its longitudinal axis 20 ', which corresponds to the longitudinal axis of the press jacket to be produced. Longitudinal axis 20 'here runs perpendicularly into the plane of the drawing. A casting material, such as a castable, curable elastomeric polymer, here for example polyurethane, is passed through a line 5 through a casting nozzle 6 from above onto the radially outermost circumferential surface of the winding mandrel 4 or onto the starting material 20 '" Pot life and viscosity are selected so that it does not drip down from the winding mandrel 4 during casting. During this time, the winding mandrel 4 is rotated in the direction of the arrow about its longitudinal axis. Simultaneously with this rotation, the pouring nozzle 6 is parallel via a suitable guide not shown in FIG relative to the longitudinal axis 20 'along this along the winding mandrel 4. Simultaneously with the pouring of the casting material, the starting material 20'"is unrolled and wound onto the rotating winding mandrel 4 to form coils. The casting material can pass through the starting material 20 '"to the winding mandrel 4. In this example, after the curing step, the polymer forms a radially innermost and preferably elastomeric polymer layer, which corresponds to the polymer layer 20.2 of the press jacket from FIG only a part is shown in FIG. 3.

The casting material emerging from the casting nozzle 6 is in the present case a mixture of a prepolymer and a crosslinker. The former is provided from a prepolymer container, not shown, in which it is stored or mixed. The prepolymer is the reaction product of an isocyanate and a polyol. By doing It can be in the form of a prepolymer made from the substances just mentioned, for example.

The crosslinker can be provided in a crosslinker container.

The prepolymer container and crosslinker container are assigned to the device for producing a press jacket 20. They are connected in a flow-conducting manner to a mixing chamber (not shown) connected upstream of the pouring nozzle 6 in the direction of flow via lines, which are likewise not shown. The prepolymer / crosslinker mixture is thus produced upstream and outside of the pouring nozzle 6, that is to say is mixed in the mixing chamber. Independently of the production of the mixture, it is then applied to the surface of the winding mandrel 4 in order to form the at least one polymer layer of the press jacket 20. In principle, it would be conceivable that two or more pouring nozzles 6 could be provided. These could be connected to separate prepolymer and crosslinker containers via corresponding lines in order to also supply different polymers to the majority of the pouring nozzles 6 independently of one another. The casting nozzles 6 could then be arranged along the longitudinal axis of the press jacket 20 at a distance from one another in order to produce several polymer layers 20.1, 20.2, 20.3 simultaneously in one cast by simultaneously applying the polymer from the casting nozzles 6.

By means of such a continuous casting process, which is also known as rotary casting, an endless, cylindrical tubular press jacket 20, which is closed around its longitudinal axis 20 'and whose inner circumference essentially corresponds to the outer circumference of the winding mandrel 4, is gradually produced over the width of the winding mandrel 4 . In principle, it would be conceivable to wind the starting material 20 '''on more than the one winding mandrel 4 shown in Fig. 3. For example, two winding mandrels could be provided which are parallel with respect to their longitudinal axes at a distance from one another could be arranged. Alternatively, it would also be conceivable to also apply the polymer to the radially inner lateral surface of the winding mandrel 4, for example in the manner of spinning. Regardless of the embodiment mentioned, the finished press cover 20 is finally removed from the at least one winding mandrel 4.

Although this is not shown in the figures, the reinforcement structure 20 ″ of the at least one polymer layer 20.1, 20.2 could also be made up of several starting materials 20 ″ ′, superposed in the radial direction, each running in the longitudinal axis direction and in the circumferential direction of the press jacket 20.

The structure of a corresponding polymer layer which comprises or contains a thermoplastic elastomer in the form of a copolymer can be produced analogously with such a device. 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 jacket. Alternatively or additionally, it can be applied to a polymer layer already made from polyurethane in order to then represent the radially outermost polymer layer of the press jacket. The thermoplastic elastomer according to the invention can be applied as a polymer layer, for example, by an extrusion process.

Claims

1. Press jacket comprising at least one polymer layer (20.1, 20.2, 20.3), wherein the at least one polymer layer (20.1, 20.2, 20.3) comprises at least one thermoplastic elastomer in the form of a copolymer or is made from such.

2. Press jacket according to claim 1, characterized in that the thermoplastic elastomer is a segmented block copolymer.

3. Press jacket according to claim 1 or 2, characterized in that the thermoplastic elastomer is a thermoplastic copolyester elastomer (COPE).

4. Press jacket according to one of claims 1 to 3, characterized in that the thermoplastic elastomer is a thermoplastic copolyamide elastomer (COPA). 5. Press cover according to one of claims 1 to 4, characterized in that a reinforcing structure (20 ") is embedded in the at least one polymer layer (20.1, 20.2, 20.3), the reinforcing structure (20") at least one reinforcing thread (21) includes.

6. Press cover according to claim 1 or 5, characterized in that several polymer layers are provided and the at least one polymer layer (20.1,

20.2, 20.3) in relation to the longitudinal axis (20 ') of the press jacket (20) is the radially inner or innermost polymer layer (20.1) and, in addition, a further one, seen in relation to the longitudinal axis (20') of the press jacket (20) radially outermost polymer layer (20.2) is provided.

7. Press cover according to claim 6, characterized in that exactly two

Polymer layers (20.1, 20.2) are provided and the radially inner

Polymer layer (20.2) is at the same time the radially innermost polymer layer of the press jacket (20). 8. Press jacket according to one of claims 1 to 7, characterized in that the at least one reinforcing thread (21) is made from a polymer or comprises one, a polyester, polyethylene naphthalate or polyamide, such as aramid, being selected as the polymer.

9. Press cover according to one of claims 1 to 8, characterized in that one or more reinforcing threads (21) are provided as longitudinal threads (21.1) which extend in the longitudinal direction of the press cover (20) over the circumference of the press cover (20) at a distance and are arranged parallel to each other.

10. Press cover according to one of claims 1 to 9, characterized in that at least one further reinforcing thread (21) is provided as a circumferential thread (21.2), which preferably runs helically in the circumferential direction of the press cover within the polymer layer (20.1, 20.2, 20.3) and preferably the reinforcing threads (21) designed as longitudinal threads (21.1) and the at least one further reinforcing thread (21) designed as circumferential threads (21.2) form a scrim with one another, preferably in such a way that the longitudinal threads (21.1) radially inside the at least one circumferential thread (21.2) - in relation to the longitudinal axis (20 ') of the press jacket - are arranged.

11. Press roll, such as shoe press roll (12), for a shoe press (10) for

Treatment of a fibrous web (24), characterized in that the

Press roll has at least one press cover (20) according to one of the preceding claims.

12. Shoe press (10) for treating a fibrous web (24), preferably a paper, cardboard, tissue or cellulose web, comprising a press roll and a counter roll (14) which together form or delimit a nip (22), the Press roll comprises a revolving press cover, characterized in that the press cover (20) is designed according to one of Claims 1 to 10. 13. Use of a press jacket (20) according to one of claims 1 to 10 for a press, such as a shoe press (10) for treating a fibrous web (24), preferably a paper, cardboard, tissue or cellulose web. 14. Use of a thermoplastic elastomer in the form of a copolymer, preferably a segmented block copolymer, which is preferably a thermoplastic copolyester elastomer (COPE) and / or a thermoplastic copolyamide elastomer (COPA), for at least one polymer layer (20.1, 20.2, 20.3) a press jacket for a shoe press (10) for treating a fibrous web (24).