Press cover for a press roller or conveyor belt

Abstract

The present invention relates to a press jacket for a press roller, in particular for a press roller of a shoe press for dewatering a fibrous web, in particular a paper, cardboard, tissue or pulp web, or a conveyor belt, in particular for a machine for producing or treating a fibrous web, in particular a paper, cardboard or tissue machine, wherein the press jacket or the conveyor belt comprises at least one polyurethane-containing layer, wherein the polyurethane is formed by reacting a prepolymer and a crosslinking component, wherein the prepolymer is a reaction product of an isocyanate component and a polyol component, wherein the isocyanate component contains phenylene diisocyanate (PPDI), and wherein the crosslinking component contains bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 4,4'-methylenebis(2-ethylaniline) (MBOEA).

Description

[0001] The present invention relates to a press jacket for a press roller, in particular for a press roller of a shoe press for dewatering a fibrous web, especially a paper, cardboard, tissue or pulp web, or a conveyor belt, in particular for a machine for producing or treating a fibrous web, in particular a paper, cardboard or tissue machine, wherein the press jacket or the conveyor belt comprises at least one polyurethane-containing layer. The present invention further relates to a method for producing such a press jacket or conveyor belt, a corresponding press jacket, and a corresponding conveyor belt.

[0002] Press rollers are used in a variety of presses, for example, in the form of shoe rollers in shoe presses, which are primarily used for dewatering fibrous webs such as paper webs. Such shoe presses consist of a shoe roller and a counter roller with a press gap between them. Shoe rollers comprise a stationary, i.e., non-rotating, pressing element, namely the shoe, and a flexible press sleeve that surrounds the shoe. The shoe is typically supported by a yoke and pressed against the surrounding press sleeve by hydraulic pressing elements. An oil film is usually built up between the shoe and the press sleeve for lubrication.Due to the concave design of the shoe on its side opposite the counter roller, a comparatively long press gap results, which is about 20 times longer than that of conventional presses consisting of two rotating rollers.

[0003] During the operation of the shoe press, a fiber web, along with one or two press felts, is guided through the press gap. The liquid that escapes from the fiber web due to the pressure exerted on it within the press gap, containing dissolved and undissolved compounds such as fibers, fiber fragments, fillers, and / or additives in addition to water, is temporarily absorbed by the press felt and by recesses provided in the surface of the press jacket. After exiting the press gap, the liquid absorbed by the press jacket is flung off before the jacket re-enters the press gap. Additionally, the water absorbed by the press felt is removed by suction elements after exiting the press gap.Due to the comparatively long press gap resulting from the concave design of the shoe, this type of shoe press achieves significantly better dewatering of the fiber web compared to a press consisting of two rotating rollers, thus allowing for a correspondingly shorter subsequent thermal drying time. This results in a particularly gentle dewatering of the fiber web.

[0004] The press shell of such a shoe press must ideally meet a variety of requirements to achieve optimal results. Firstly, it must be flexible enough to be guided around the shoe. Simultaneously, it must be sufficiently hard and rigid to prevent excessive deformation under the pressing force in the press gap. Furthermore, the press shell must exhibit high wear resistance, good abrasion resistance, low swelling in water, and other properties such as high resistance to crack initiation, good resistance to crack propagation, high elongation at break, and high breaking strength.

[0005] To at least partially meet these diverse requirements, such press jackets are typically made of fiber-reinforced polyurethane, i.e., a composite material in which a fiber mat or woven fabric is embedded in a polyurethane matrix. Both single-layer and multi-layer press jackets are known.

[0006] WO 2023 / 117201 A1 discloses a press jacket for a shoe press, wherein the press jacket comprises at least one polyurethane-containing layer, the polyurethane being the reaction product of a prepolymer and a crosslinking component. While the prepolymer is a reaction product of an isocyanate component and a polyol component, wherein the isocyanate component contains 1,3-xylylene diisocyanate (m-XDI) and / or 1,3-bis(isocyanatomethyl)cyclohexane (mH6XDI), optionally in a mixture with another isocyanate compound, such as phenylene diisocyanate (PPDI), and the polyol component contains at least one polycarbonate polyol, the crosslinking component preferably contains an aromatic diamine, in particular bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA), as the crosslinking agent.To produce the polyurethane, the prepolymer and the crosslinking component are first provided, before both are mixed together and applied to a surface, such as the surface of a winding mandrel, via a casting device having a casting nozzle.

[0007] However, a disadvantage of this known or similar process is that the mixing of the prepolymer and the crosslinking component, as well as the casting of the mixture thus produced, is prone to errors, especially if the isocyanate component contains higher amounts of phenylene diisocyanate (PPDI) or even consists of PPDI. This is because polyurethane particles can form in the mixing head during the mixing of the prepolymer and the crosslinking component, the casting nozzle can become clogged due to premature crosslinking of the prepolymer during the casting of the mixture of prepolymer and crosslinking component, or dripping or the formation of defects such as gaps, bubbles or holes can occur.

[0008] The object of the present invention is therefore to provide a press jacket or conveyor belt comprising at least one polyurethane-containing layer, wherein the polyurethane is based on phenylene diisocyanate (PPDI) as an isocyanate compound and is formulated in such a way that it can be easily cast and cured into the desired shape before crosslinking without complications such as clogging of the mixer and / or the casting device or the formation of defects.

[0009] According to the invention, this problem is solved by providing a press jacket for a press roller, in particular for a press roller of a shoe press for dewatering a fibrous web, in particular a paper, cardboard, tissue or pulp web, or a conveyor belt, in particular for a machine for producing or treating a fibrous web, in particular a paper, cardboard or tissue machine, wherein the press jacket or the conveyor belt comprises at least one polyurethane-containing layer, wherein the polyurethane is formed by reacting a prepolymer and a crosslinking component, wherein the prepolymer is a reaction product of an isocyanate component and a polyol component, wherein the isocyanate component contains phenylene diisocyanate (PPDI), and wherein the crosslinking component contains bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 4,4'-methylenebis(2-ethylaniline) (MBOEA).

[0010] Surprisingly, it was found within the scope of the present invention that a layer of polyurethane based on phenylene diisocyanate (PPDI) as an isocyanate compound can be formed simply and reliably without complications, such as clogging of the mixer and / or the casting device, by mixing the appropriate PPDI-based prepolymer and the crosslinking component and by casting the mixture thus produced into the desired shape, if the crosslinking component contains 4,4'-methylenebis(2-ethylaniline) (MBOEA) in addition to bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA).

[0011] According to the invention, the crosslinking component contains a mixture of bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 4,4'-methylenebis(2-ethylaniline) (MBOEA). Particularly good results are obtained when the crosslinking component contains, based on 100 wt% of the crosslinking component, 10 to 80 wt% MCDEA and 0.1 to 10 wt% MBOEA, more preferably 20 to 70 wt% MCDEA and 0.1 to 8 wt% MBOEA, and most preferably 30 to 60 wt% MCDEA and 0.1 to 6 wt% MBOEA.

[0012] In a further development of the inventive concept, it is proposed that the crosslinking component, in addition to MCDEA and MBOEA, contains at least one polyol. For the purposes of this invention, polyols are understood to be all alcohols having at least two hydroxyl groups. Particularly good results are obtained if the crosslinking component contains, based on 100 wt% of the crosslinking component, 20 to 80 wt% and preferably 35 to 65 wt% of at least one polyol, wherein the at least one polyol is selected from the group consisting of polycarbonate polyols, polyether polycarbonate polyols, polyether polyols, and mixtures thereof.

[0013] According to a preferred embodiment, the crosslinking component comprises at least one polyether polyol, preferably a polyalkylene ether polyol, particularly preferably a poly-C1-10 alkylene ether polyol, and most preferably a poly-C3-6 alkylene ether polyol. Suitable examples of polyether polyols are those selected from the group consisting of polytetramethylene ether glycol (PTMEG), polypropylene glycol (PPG), polyethylene glycol (PEG), polyhexamethylene ether glycol, and mixtures thereof. Polytetramethylene ether glycol (PTMEG) is particularly preferred.

[0014] According to a particularly preferred embodiment, the crosslinking component comprises at least one polycarbonate polyol. Particularly good results are obtained with a polycarbonate polyol according to the general formula (I): H-(OR 1< -OC(O)) n1 -OH (I), wherein R 1< is selected from linear C 1 -C 20 alkylene groups and branched C 1 -C 20 alkylene groups, and n 1 is an integer of at least 2. Preferably, the polycarbonate polyol according to the general formula (I) has as R 1< a linear C 4 -C 14 alkylene group or a branched C 4 -C 14 alkylene group, particularly preferably a linear C 4 -C 10 alkylene group, most preferably a linear C 4 -C 7 alkylene group, and most preferably a Cs or C 6 alkylene group. Furthermore, it is preferred that n 1 in the general formula (I) is an integer between 3 and 100, particularly preferably between 7 and 30 and most particularly preferably between 10 and 25.

[0015] It is equally preferred that the crosslinking component, instead of at least one polycarbonate polyol according to general formula (I) or in addition to at least one polycarbonate polyol according to general formula (I), contains as a polyol at least one polycarbonate polyol according to general formula (II): H-(OR 2< -OC(O)) n2 -OR 3< -OC(O)) n3 -OH (II), wherein R 2< and R 3< are different from each other and are independently selected from linear C 1 -C 20 alkylene groups and branched C 1 -C 20 alkylene groups, and n 2 and ns are, independently of each other, an integer of at least 1. Preferably, the polycarbonate polyol according to general formula (II) has as R 2< and R 3< , independently of each other, a linear C 4 -C 14 alkylene group or branched C 4 -C 14 alkylene group, particularly preferably a linear C 4 -C 10 alkylene group and most preferably a linear C 5 -C 7 alkylene group.In general formula (II), it is most preferred that one of R2< and R3< is a C5 alkylene group and the other of R2< and R3< is a C6 alkylene group. Furthermore, it is preferred that n2 and n3 in general formula (II) are each an integer between 2 and 50, particularly preferably between 3 and 15, and most preferably between 5 and 13.

[0016] The crosslinking component preferably contains, based on 100 wt.% of the crosslinking component, 10 to 80 wt.% and particularly preferably 35 to 65 wt.% of at least one polyol according to general formula (I) and / or at least one polyol according to general formula (II).

[0017] According to an alternative embodiment of the present invention, the crosslinking component comprises at least one polyether polycarbonate polyol. Suitable examples are polyether polycarbonate polyols analogous to the general formula (I), wherein R<1 is a linear C1-C20 alkylene ether group or a branched C1-C20 alkylene ether group, preferably a linear or branched C4 alkylene ether group, or (II), wherein each of R1, R2, and R3 independently is a linear C1-C20 alkylene ether group or a branched C1-C20 alkylene ether group, preferably a linear C4-C14 alkylene ether group or a branched C4-C14 alkylene ether group, particularly preferably a linear C4-C10 alkylene ether group, and most preferably a linear C4-C7 alkylene ether group.Most preferably, R1 is a linear Cs or C6 alkylene ether group, one of R2 and R3 is a C5 alkylene ether group, and the other of R2 and R3 is a C6 alkylene ether group. Furthermore, it is preferred that n2 and n3 are as specified with reference to general formulas (I) and (II).

[0018] Particularly good results are obtained when the weight-averaged molecular weight of the at least one polycarbonate polyol contained in the crosslinking component is 700 to 4,000 and preferably 1,000 to 3,000 g / mol.

[0019] In a further development of the inventive concept, it is proposed that the crosslinking component contains 0.1 to 10 wt.% and preferably 1 to 6 wt.% of at least one alkylene carbonate, based on 100 wt.% of the crosslinking component. Particularly good results are obtained when the crosslinking component contains propylene carbonate as the alkylene carbonate. The addition of an alkylene carbonate, such as propylene carbonate or ethylene carbonate, to the crosslinker in the production of a polyurethane-containing mold shell is unusual. This is because it is normally used as a solvent in the plastics industry for purposes outside of polyurethane production. Surprisingly, it was found that the prepolymer-crosslinker mixture exhibited a lower viscosity with an optimal pot life. This allows the resulting, initially low-viscosity polymer to penetrate the reinforcing structure (e.g., made of threads) particularly well before it solidifies as a result of curing.Even particularly rough substrates can be coated. In both cases, air bubbles can escape very effectively. This contributes to the production of virtually bubble-free press jackets using rotational molding, enabling polymer layers up to 40 mm thick – which can be produced monolithically in a single coating pass.

[0020] According to the invention, the isocyanate component from which the prepolymer is formed by reaction with the polyol component contains phenylene diisocyanate (PPDI). Particularly good results are obtained if the isocyanate component, based on 100 wt% of the isocyanate component, contains at least 90 wt%, preferably at least 95 wt%, and most preferably at least 99 wt% PPDI, and most preferably consists entirely of PPDI.If the isocyanate component does not consist of PPDI, the isocyanate component may contain one or more other isocyanate compounds, such as, in particular, one or more selected from the group consisting of 1,3-xylylene diisocyanate (m-XDI), 1,3-bis(isocyanatomethyl)cyclohexane (mH6XDI), toluene-2,4-diisocyanates (TDI), methylenediphenyl diisocyanates (MDI), hexamethylene diisocyanates (HDI), 1,5-naphthalene diisocyanates (NDI), isophorone diisocyanates (IPDI), 3,3'-dimethyl-4,4'-biphenyl diisocyanate (TODI), and mixtures of two or more of the aforementioned compounds. However, as explained above, it is particularly preferred that the isocyanate component consists entirely or at least almost entirely of PPDI.

[0021] With regard to the composition of the polyol component, which consists of one or more polyols, the present invention is not particularly limited. Particularly good results are obtained if the polyol component contains at least one polyol selected from the group consisting of polycarbonate polyols, polyether polycarbonate polyols, polyether polyols, and mixtures thereof. Preferably, the sum of the aforementioned polyols in the polyol component, based on 100 wt.% of the polyol component, is at least 80 wt.%, more preferably at least 90%, particularly preferably at least 95%, most preferably at least 98%, and most preferably 100 wt.%.

[0022] According to a preferred embodiment, the polyol component contains at least one polyether polyol. Preferably, the at least one polyether polyol is a polyalkylene ether polyol, more preferably a poly-C1-10 alkylene ether polyol, and most preferably a poly-C3-6 alkylene ether polyol. Suitable examples of polyether polyols are those selected from the group consisting of polytetramethylene ether glycol (PTMEG), polypropylene glycol (PPG), polyethylene glycol (PEG), polyhexamethylene ether glycol, and mixtures thereof. The polyether polyol polytetramethylene ether glycol (PTMEG) is particularly preferred.

[0023] According to a particularly preferred embodiment, the polyol component contains at least one polycarbonate polyol as the polyol. For the purposes of the present invention, polycarbonate polyol refers to all polyols that contain at least one carbonate group as a functional group in addition to hydroxyl groups. Preferably, the polycarbonate polyol contains terminal hydroxyl groups, and particularly preferably, the polycarbonate polyol is a diol containing carbonate groups. According to an illustrative, but not limiting, embodiment, the polycarbonate polyol contains only carbonate groups as functional groups in addition to terminal hydroxyl groups. In particular, the at least one polycarbonate polyol contained in the polyol component can be a polycarbonate homopolyol, a polycarbonate copolyol, or a mixture thereof, regardless of whether it contains one or more further functional groups in addition to the hydroxyl and carbonate groups.

[0024] According to a first particularly preferred embodiment of the present invention, the polyol component comprises at least one polycarbonate polyol according to the general formula (I): H-(OR 1< -OC(O)) n1 -OH (I), wherein R 1< is selected from linear C 1 -C 20 alkylene groups and branched C 1 -C 20 alkylene groups, and n 1 is an integer of at least 2. For the purposes of the present invention, an alkylene group is understood to be a C n H 2n hydrocarbon group, i.e., a hydrocarbon group with two terminal radicals.

[0025] Particularly good results are obtained when in the general formula (I) n 1 is an integer between 3 and 100, preferably between 7 and 30 and most preferably between 10 and 25.

[0026] Preferably, R<1> in the general formula (I) is selected from linear C4-C14 alkylene groups and branched C4-C14 alkylene groups, particularly preferably from linear C4-C10 alkylene groups, and most preferably from linear C4-C7 alkylene groups. Most preferably, R1 in the general formula (I) is a C5 alkylene group or a C6 alkylene group.

[0027] According to a second particularly preferred embodiment of the present invention, the polycarbonate polyol contains two or more different alkylene groups, in particular two, three, or four different alkylene groups. For example, the polycarbonate polyol can have a first C1-C20 alkylene group A, such as a linear Cs alkylene group, and a second C1-C20 alkylene group B, different from the first, such as a linear C6 alkylene group. The two groups can then be arranged alternately, in blocks, or randomly, for example ABAB, AAAB, AABB, BBAA, ABBB, or BAAA.

[0028] A preferred example of such a polycarbonate polyol is a polycarbonate polyol according to the general formula (II): H-(OR 2< -OC(O)) n2 -OR 3< -OC(O)) n3 -OH (II), wherein R 2< and R 3< are different from each other and are independently selected from linear C 1 -C 20 alkylene groups and branched C 1 -C 20 alkylene groups, and n 2 and ns are, independently of each other, an integer of at least 1.

[0029] In particular, good results are obtained if in the general formula (II) n 2 and ns, independently of each other, are an integer between 3 and 100, preferably between 4 and 15 and most preferably between 5 and 15.

[0030] Preferably, in the general formula (II), R2< and R3< are different from each other and independently selected from linear C4-C14 alkylene groups and branched C4-C14 alkylene groups, particularly preferably from linear C4-C10 alkylene groups and most preferably from linear C4-C7 alkylene groups. Most preferably, one of R2< and R3< is a C5 alkylene group and the other of R2< and R3< is a C6 alkylene group.

[0031] In a further development of the inventive concept, it is proposed that the weight-averaged molecular weight of the at least one polycarbonate polyol contained in the polyol component be 500 to 4,000 and preferably 700 to 3,000 g / mol. The molecular weight can be determined by gel permeation chromatography against a polystyrene standard. However, according to the present invention, it is preferred to determine the weight-averaged molecular weight of the structural units via the hydroxyl number, i.e., via the amount of potassium hydroxide in milligrams that is equivalent to the amount of acetic acid bound during the acetylation of 1 g of substance. The hydroxyl number can be determined by back titration according to DIN 53240 and is expressed in mg KOH / g. The weight-averaged molecular weight can then be determined, for example, in the case of diols, by dividing 112,200 by the hydroxyl number.

[0032] According to a particularly preferred embodiment of the present invention, the polyol component contains, based on 100 wt.% of the polyol component, at least 50 wt.%, more preferably at least 80%, particularly preferably at least 90%, most preferably at least 98%, and most preferably 100 wt.% of one or more polycarbonate polyols. The polyol component may contain one or more polycarbonates with general formula (I), one or more polycarbonates with general formula (II), or a mixture of polycarbonate(s) with general formula (I) and polycarbonate(s) with general formula (II).Particularly good results are obtained when the polyol component consists essentially of one or more polycarbonates of general formula (I), of one or more polycarbonates of general formula (II), or of a mixture of polycarbonate(s) of general formula (I) with polycarbonate(s) of general formula (II), i.e., at least 95 wt.%, more preferably at least 99 wt.%, and most preferably 100 wt.% of one or more polycarbonates of general formula (I), one or more polycarbonates of general formula (II), or a mixture of polycarbonate(s) of general formula (I) with polycarbonate(s) of general formula (II).

[0033] According to an alternative embodiment of the present invention, the crosslinking component comprises at least one polyether polycarbonate polyol. Suitable examples are polyether polycarbonate polyols analogous to the general formula (I), wherein R<1 is a linear C<1-C<20 alkylene ether group or a branched C<1-C<20 alkylene ether group, preferably a linear or branched C4 alkylene ether group, or (II), wherein each of R<1, R<2, and R<3, independently of one another, is a linear C1-C20 alkylene ether group or a branched C1-C20 alkylene ether group, preferably a linear C4-C14 alkylene ether group or a branched C4-C14 alkylene ether group, particularly preferably a linear C4-C10 alkylene ether group, and most preferably a linear C4-C7 alkylene ether group.Most preferably, R1 is a linear Cs or C6 alkylene ether group, one of R2 and R3 is a C5 alkylene ether group, and the other of R2 and R3 is a C6 alkylene ether group. Furthermore, it is preferred that n1, n2, and n3 are as specified with reference to general formulas (I) and (II).

[0034] Particularly good results are obtained when the press jacket or conveyor belt comprises at least one polyurethane-containing layer, wherein the polyurethane is formed by reacting a prepolymer and a crosslinking component, wherein the prepolymer is a reaction product of an isocyanate component and a polyol component, wherein: i) the crosslinking component, based on 100 wt.% of the crosslinking component, contains 10 to 80 wt.% bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 0.1 to 10 wt.% 4,4'-methylenebis(2-ethylaniline) (MBOEA) and preferably 20 to 70 wt.% MCDEA and 0.1 to 8 wt.% MBOEA, ii) the crosslinking component also contains, based on 100 wt.% of the crosslinking component, 20 to 80 wt.% and preferably 35 to 65 wt.%-% of at least one polycarbonate polyol according to general formula (I): H-(OR 1< -OC(O)) n1 -OH (I), wherein R 1< is a linear Cs or C 6 alkylene group and n 1 is an integer of at least 2, and / or at least one polycarbonate polyol according to general formula (II): H-(OR 2< -OC(O)) n2 -OR 3< -OC(O)) n3 -OH (II), wherein one of R 2< and R 3< is a C 5 alkylene group and the other of R 2< and R 3< is a C 6 alkylene group, and n 2 and ns, independently of each other, are an integer of at least 1, iii) the isocyanate component, based on 100 wt% of the isocyanate component, contains at least 90 wt% phenylene diisocyanate (PPDI) and preferably consists of PPDI, and iv) the Polyol component, based on 100 wt.% of the polyol component, to at least 90 wt.%, preferably to at least 98 wt.% and particularly preferably to 100 wt.%.-% is composed of at least one polycarbonate polyol according to general formula (I): H-(OR 1< -OC(O)) n1 -OH (I), wherein R 1< is selected from linear C 1 -C 20 alkylene groups and branched C 1 -C 20 alkylene groups and preferably a linear Cs or C 6 alkylene group and n 1 is an integer of at least 2 and / or is composed of at least one polycarbonate polyol according to general formula (II): H-(OR 2< -OC(O)) n2 -OR 3< -OC(O)) n3 -OH (II), wherein R 2< and R 3< are different from each other and are independently selected from linear C 1 -C 20 alkylene groups and branched C 1 -C 20 alkylene groups and preferably one of R 2< and R 3< is a C 5 alkylene group and the other of R 2< and R 3< is a The C6 alkylene group, as well as n2 and ns, are independently of each other integers of at least 1.

[0035] Preferably, the H / NCO ratio of the polyurethane is between 1.1 and 0.85.

[0036] To further increase abrasion resistance, an additive such as silicone oil can also be added to the polyurethane in an amount of 0.1 to 3 wt.% and preferably 0.5 to 1.5 wt.%, based on the total weight of the polyurethane.

[0037] Furthermore, it is preferred if the polyurethane layer of the press jacket or the conveyor belt comprises only a polyurethane, i.e., a polyurethane formed only from a prepolymer by reaction of the prepolymer with a crosslinking component.

[0038] The press jacket or conveyor belt according to the invention can be single-layered or multi-layered. In a multi-layered design, at least the outermost or innermost layer is composed of the polyurethane described above.

[0039] In a further development of the inventive concept, it is proposed to design the press jacket or the conveyor belt in multiple layers, wherein the outermost or innermost layer is composed of the polyurethane described above and the remaining layer(s) are composed of one or more other polyurethanes, wherein the polyurethane of an inner layer forms the matrix in which a fiber mat or a fiber fabric is embedded.

[0040] Another object of the present invention is a method for manufacturing a press jacket or conveyor belt according to at least one of the preceding claims, comprising the following steps: a) Providing at least one rotatably mounted winding mandrel, b) Providing a crosslinking component composed as above, which contains bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 4,4'-methylenebis(2-ethylaniline) (MBOEA), c) Providing a prepolymer as the product of a reaction between an isocyanate component composed as above and a polyol component composed as above, wherein the isocyanate component contains phenylene diisocyanate (PPDI), d) Mixing the prepolymer and the crosslinking component to produce a polyurethane, e) Applying the prepolymer-crosslinking mixture to a surface of the winding mandrel to form at least one polymer layer of the press jacket or conveyor belt, f) Curing the at least one polymer layer, and g) Removing the press jacket or conveyor belt thus produced from the winding mandrel.

[0041] Furthermore, the present invention relates to a shoe press for dewatering a fibrous web, in particular a paper, cardboard, tissue or pulp web, which comprises a press roller and a counter roller which together form or limit a press gap (also called nip), wherein the press roller comprises a circumferential press jacket which is designed as described above.

[0042] Finally, the present invention relates to a machine for the production or treatment of a fibrous web, in particular a paper, cardboard or tissue machine, which comprises a conveyor belt designed as described above.

[0043] The present invention is described below by way of example only, using advantageous embodiments and with reference to the accompanying drawings.

[0044] This shows: Fig. 1: a schematic view of a shoe press with a press jacket according to an embodiment of the present invention and Fig. 2: a schematic view of a press section of a paper machine comprising a shoe press and a conveyor belt according to an embodiment of the present invention.

[0045] In the Fig. 1 Figure 10 shows a shoe press comprising a shoe roller 12 and a counter roller 14. While the counter roller 14 consists of a rotating, cylindrical roller, the shoe roller 12 is composed of a shoe 16, a stationary yoke 18 supporting it, and a press shell 20. The shoe 16 is supported by the yoke 18 and pressed against the rotating press shell 20 by hydraulic pressing elements (not shown). Due to the concave shape of the shoe 16 on its side opposite the counter roller 14, a comparatively long pressing gap 22 is created.

[0046] The shoe press 10 is particularly suitable for dewatering fibrous webs 24, such as paper webs. During operation of the shoe press, a fibrous web 24 with one or two press films 26, 26' is guided through the press gap 22. The liquid that escapes from the fibrous web 24 due to the pressure exerted on it in the press gap 22, containing dissolved and undissolved compounds such as fibers, fiber fragments, fillers, and / or additives in addition to water, is temporarily absorbed by the press felt(s) 26, 26' and by recesses (not shown) provided in the surface of the press jacket. After exiting the press gap 22, the liquid absorbed by the press jacket 20 is flung off before the press jacket 20 re-enters the press gap 22. In addition, the water absorbed by the press felt 26, 26' is removed by suction elements after leaving the press gap 22.

[0047] Due to the comparatively long press gap 22 on the side opposite the counter roller 14, resulting from the concave design of the shoe 16, a significantly better dewatering of the fiber web 24 is achieved with such a shoe press 10 compared to a press consisting of two rotating rollers, so that the subsequent thermal drying can be correspondingly shorter. In this way, a particularly gentle dewatering of the fiber web 24 is achieved.

[0048] In the Fig. 2 The figure shows a section of the press section of a paper machine, which includes a shoe press 10. The shoe press 10, as in the one shown in the figure, comprises Fig. 1In the illustrated embodiment, a shoe roller 12, comprising a press sleeve 20 and a press element or shoe 16, and a counter roller 14, wherein a press gap is formed between the shoe 16 and the counter roller 14. This part of the paper machine also includes two suction rollers 28, 28' and two deflection rollers 30, 30'. During operation of the paper machine, a felt 26, guided by the suction rollers 28, 28' and which picks up the fiber web 24 at the suction roller 28, is guided through the press gap. Furthermore, a conveyor belt or transfer belt 32, guided by the deflection rollers 30, 30', is guided through the press gap below the felt 26 carrying the fiber web 24. The transfer belt 32 takes the fiber web 24 from the felt 26 in the press gap and carries it out of the press gap via the deflection roller 30'.Due to the pressure exerted on the fiber web 24 in the press gap, liquid escapes from the fiber web. This liquid contains dissolved and undissolved compounds, such as fibers, fiber fragments, fillers, and / or additives, in addition to water. This liquid is temporarily absorbed by the felt 26 and by recesses provided in the press jacket surface. After exiting the press gap, the liquid absorbed by the press jacket 20 is flung off before the press jacket 20 re-enters the press gap. Furthermore, the water absorbed by the felt 26 after exiting the press gap is removed by suction elements provided on the suction roller 28'.Due to the comparatively long press gap resulting from the concave design of the shoe 16, such a shoe press achieves significantly better dewatering of the fiber web 24 compared to a press consisting of two rotating rollers, so that the subsequent thermal drying can be correspondingly shorter. In this way, a particularly gentle dewatering of the fiber web 24 is achieved.

[0049] The present invention is described below by way of example with reference to advantageous embodiments and the following purely illustrative and non-limiting examples. Example

[0050] Good results regarding the trouble-free castability of a polyurethane layer of a shoe press shell, whose prepolymer consisted of phenylene diisocyanate (PPDI) and a C 5 -C 6 -polycarbonate polyol, were achieved with a crosslinker which was composed of 45 wt% bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA), 49 wt% a C 5 -C 6 -polycarbonate polyol, 3 wt% 4,4'-methylenebis(2-ethylaniline) (MBOEA) and 3 wt% propylene carbonate.

[0051] A comparison sample using the same prepolymer and crosslinker components, except that Amicure 101®< was used instead of 4,4'-methylenebis(2-ethylaniline) (MBOEA), presented greater challenges during casting. Determining the precise amount of Amicure 101®< required to keep both dripping and the risk of defects such as gaps, bubbles, or holes in the polyurethane due to premature crosslinking to an acceptable level is difficult. Using 4,4'-methylenebis(2-ethylaniline) (MBOEA) instead of Amicure 101®< did not result in any problems with either dripping or defects, regardless of the required dosage. Reference symbol list

[0052] 10 Shoe press 12 Shoe roller 14 Counter roller 16 Shoe 18 Standing yoke 20 Press jacket 22 Press gap 24 Fiber web 26, 26' Press felt 28, 28' Suction rollers 30, 30' Deflection rollers 32 Conveyor belt / Transfer belt

Claims

1. Press jacket for a press roller, in particular for a press roller of a shoe press for dewatering a fibrous web, in particular a paper, cardboard, tissue or pulp web, or conveyor belt, in particular for a machine for producing or treating a fibrous web, in particular a paper, cardboard or tissue machine, wherein the press jacket or the conveyor belt comprises at least one polyurethane-containing layer, wherein the polyurethane is formed by reacting a prepolymer and a crosslinking component, wherein the prepolymer is a reaction product of an isocyanate component and a polyol component, wherein the isocyanate component contains phenylene diisocyanate (PPDI), and, wherein the crosslinking component contains bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 4,4'-methylenebis(2-ethylaniline) (MBOEA).

2. Press jacket or conveyor belt according to claim 1, characterized by the fact thatThe crosslinking component, based on 100 wt.% of the crosslinking component, contains 10 to 80 wt.% bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 0.1 to 10 wt.% 4,4'-methylenebis(2-ethylaniline) (MBOEA), preferably 20 to 70 wt.% MCDEA and 0.1 to 8 wt.% MBOEA and particularly preferably 30 to 60 wt.% MCDEA and 0.1 to 6 wt.% MBOEA.

3. Press jacket or conveyor belt according to claim 1 or 2, characterized by the fact that The crosslinking component, based on 100 wt.% of the crosslinking component, contains 20 to 80 wt.% and preferably 35 to 65 wt.% of at least one polyol, wherein the at least one polyol is selected from the group consisting of polycarbonate polyols, polyether polycarbonate polyols, polyether polyols and mixtures thereof.

4. Press jacket or conveyor belt according to claim 3, characterized by the fact that the crosslinking component as a polyol contains at least one polycarbonate polyol according to the general formula (I): H-(OR 1 -OC(O)) n1-OH (I), wherein R 1 from linear C1-C 20 -Alkylene groups and branched C1-C 20 -alkylene groups selected and preferably a linear Cs or C6 alkylene group and n1 is an integer of at least 2, and / or contains at least one polycarbonate polyol according to general formula (II): H-(OR 2 -OC(O)) n2 -OR 3 -OC(O)) n3 -OH (II), wherein R 2 and R 3 are different from each other and are independent of each other, consisting of linear C1-C 20 -Alkylene groups and branched C1-C 20 -Alkylene groups are selected and preferably one of R 2 and R 3 one C5 alkylene group and the other of R 2 and R 3 a C6 alkylene group, and n2 and ns, independently of each other, are an integer of at least 1.

5. Press jacket or conveyor belt according to at least one of the preceding claims, characterized by the fact thatThe crosslinking component, based on 100 wt.% of the crosslinking component, contains 0.1 to 10 wt.% and preferably 1 to 6 wt.% of at least one alkylene carbonate and preferably propylene carbonate.

6. Press jacket or conveyor belt of at least one of the preceding claims, characterized by the fact that the isocyanate component, based on 100 wt.% of the isocyanate component, contains at least 90 wt.%, preferably at least 95 wt.%, particularly preferably at least 99 wt.% 1,3-phenylene diisocyanate (PPDI) and most preferably consists of phenylene diisocyanate (PPDI).

7. Press jacket or conveyor belt according to at least one of the preceding claims, characterized by the fact thatthe polyol component contains at least one polyol selected from the group consisting of polycarbonate polyols, polyether polycarbonate polyols, polyether polyols and mixtures thereof, wherein the sum of the aforementioned polyols in the polyol component, based on 100 wt.% of the polyol component, is preferably at least 80 wt.%, more preferably at least 90%, particularly preferably at least 95%, most preferably at least 98% and most preferably 100 wt.%.

8. Press jacket or conveyor belt according to at least one of the preceding claims, characterized by the fact that The polyol component, based on 100 wt.% of the polyol component, contains at least 50 wt.%, more preferably at least 80%, particularly preferably at least 90%, most preferably at least 98% and most preferably 100 wt.% of one or more polycarbonate polyols.

9. Press jacket or conveyor belt according to at least one of the preceding claims, characterized by the fact thatthe polyol component contains at least one polycarbonate polyol according to the general formula (I): H-(OR 1 -OC(O)) n1 -OH (I), wherein R 1 from linear C1-C 20 -Alkylene groups and branched C1-C 20 -Alkylene groups selected and preferably a linear Cs or C6 alkylene group and n1 is an integer of at least 2.

10. Press jacket or conveyor belt according to at least one of the preceding claims, characterized by the fact that the polyol component contains at least one polycarbonate polyol according to general formula (II): H-(OR 2 -OC(O)) n2 -OR 3 -OC(O)) n3 -OH (II), wherein R 2 and R 3 are different from each other and are independent of each other, consisting of linear C1-C 20 -Alkylene groups and branched C1-C 20 -Alkylene groups are selected and preferably one of R 2 and R 3one C5 alkylene group and the other of R 2 and R 3 a C6 alkylene group, and n2 and ns, independently of each other, are an integer of at least 1.

11. Press jacket or conveyor belt according to claim 3, 4, 7, 8, 9 or 10, characterized by the fact that the weight-averaged molecular weight of the at least one polycarbonate polyol is 500 to 4,000 and preferably 700 to 3,000 g / mol.

12. Press jacket or conveyor belt according to at least one of the preceding claims, characterized by the fact that: i) the crosslinking component, based on 100 wt% of the crosslinking component, contains 10 to 80 wt% bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 0.1 to 10 wt% 4,4'-methylenebis(2-ethylaniline) (MBOEA) and preferably 20 to 70 wt% MCDEA and 0.1 to 8 wt% MBOEA, ii) the crosslinking component furthermore contains, based on 100 wt% of the crosslinking component, 20 to 80 wt% and preferably 35 to 65 wt% at least one polycarbonate polyol according to general formula (I): H-(OR 1 -OC(O)) n1 -OH (I), wherein R 1 a linear Cs or C6 alkylene group and n1 is an integer of at least 2, and / or contains at least one polycarbonate polyol according to general formula (II): H-(OR 2 -OC(O)) n2 -OR 3 -OC(O)) n3 -OH (II), wherein one of R 2 and R 3 one C5 alkylene group and the other of R 2 and R 3a C6 alkylene group, and n2 and ns are, independently of each other, an integer of at least 1, iii) the isocyanate component, based on 100 wt% of the isocyanate component, contains at least 90 wt% phenylene diisocyanate (PPDI) and preferably consists of PPDI, and iv) the polyol component, based on 100 wt% of the polyol component, is composed of at least 90 wt%, preferably at least 98 wt% and particularly preferably 100 wt% of at least one polycarbonate polyol according to the general formula (I): H-(OR 1 -OC(O)) n1 -OH (I), wherein R 1 from linear C1-C 20 -Alkylene groups and branched C1-C 20 -alkylene groups selected and preferably a linear Cs or C6 alkylene group and n1 is an integer of at least 2 and / or is composed of at least one polycarbonate polyol according to general formula (II): H-(OR 2 -OC(O)) n2 -OR 3-OC(O)) n3 -OH (II), wherein R 2 and R 3 are different from each other and are independent of each other, consisting of linear C1-C 20 -Alkylene groups and branched C1-C 20 -Alkylene groups are selected and preferably one of R 2 and R 3 one C5 alkylene group and the other of R 2 and R 3 a C6 alkylene group, and n2 and ns, independently of each other, are an integer of at least 1.

13. Method for producing a press jacket or conveyor belt. A press jacket or conveyor belt according to at least one of the preceding claims, comprising the following steps: a) providing at least one rotatably mounted winding mandrel, b) providing a crosslinking component containing bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA) and 4,4'-methylenebis(2-ethylaniline) (MBOEA), c) providing a prepolymer as the product of a reaction between an isocyanate component and a polyol component, wherein the isocyanate component contains phenylene diisocyanate (PPDI), d) mixing the prepolymer and the crosslinking component to produce a polyurethane, e) applying the prepolymer-crosslinking mixture to a surface of the winding mandrel to form at least one polymer layer of the press jacket or conveyor belt, f) curing the at least one polymer layer, and g) removing the press jacket or conveyor belt thus produced from the Winding mandrel.

14. Shoe press for dewatering a fibrous web, in particular a paper, cardboard, tissue or pulp web, comprising a press roller and a counter roller which together form or limit a press gap, wherein the press roller comprises a circumferential press jacket which is designed according to one of claims 1 to 12.

15. Machine for the production or treatment of a fibrous web, in particular a paper, cardboard or tissue machine, comprising a conveyor belt according to at least one of claims 1 to 12.

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