Press jacket for a shoe press

Abstract

The present invention relates to a press jacket for a press roll, in particular for a press roll of a shoe press for dewatering a fibrous web, in particular a paper, board, tissue or pulp web, wherein the press jacket comprises at least one layer containing polyurethane, wherein the polyurethane is formed by reacting a prepolymer and a cross-linking component, wherein the prepolymer is a reaction product of an isocyanate component and a polyol component, wherein i) the isocyanate component contains 1,4-cyclohexyl diisocyanate (CHDI) and / or phenylene diisocyanate (PPDI) in an amount of at least 50% by weight, and ii) the polyol component contains at least one homopolycarbonate polyol in an amount of at least 50% by weight.

Description

[0001] Pressing mantle for a shoe press

[0002] 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, wherein the press jacket comprises at least one polyurethane-containing layer. The present invention further relates to a corresponding press jacket.

[0003] 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.

[0004] 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.

[0005] 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 load in the press gap. Furthermore, the press shell must exhibit good thermal stability, high wear resistance, 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.

[0006] To at least partially meet these diverse requirements, such press jackets are typically made of fiber-reinforced polyurethane, 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 available. The polyurethane is usually formed by crosslinking a prepolymer, which is created by reacting an isocyanate component, containing, for example, methylenediphenyl diisocyanate (MDI) or phenylene diisocyanate (PPDI), with a polyol component containing one or more polyols, such as one or more copolycarbonate polyols. Such polyurethanes are easy to process because the copolycarbonate polyols have a comparatively low viscosity.However, copolycarbonate polyols lead to polyurethanes with properties that are not optimal for use in compression moldings. Furthermore, the processability of polyurethanes containing copolycarbonate polyols, particularly with regard to their viscosity, needs improvement.

[0007] The object of the present invention is therefore to provide 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, which has excellent mechanical properties and whose polyurethane component is easy to process.

[0008] According to the invention, this problem is solved by a press jacket according to claim 1. According to the invention, a press jacket is thus provided 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, wherein the press jacket 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 isocyanate component contains 1,4-cyclohexyl diisocyanate (CHDI) and / or phenylene diisocyanate (PPDI) in an amount of at least 50% by weight and ii) the polyol component contains at least one homopolycarbonate polyol in an amount of at least 50% by weight.This solution is based on the surprising finding that a layer of polyurethane – obtained by crosslinking a prepolymer formed from the reaction product of i) CHDI and / or PPDI and ii) a polyol component containing homopolycarbonate polyol – exhibits excellent mechanical properties and is excellently processable, and for these reasons is ideally suited as a material for 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.

[0009] According to the invention, the isocyanate component, from which the prepolymer has been formed by reaction with the polyol component, contains at least

[0010] 50 wt% 1,4-cyclohexyl diisocyanate (CHDI) and / or phenylene diisocyanate (PPDI). Preferably, the isocyanate component contains either CHDI or PPDI, but not both simultaneously. Particularly good results are obtained if the isocyanate component contains at least 80 wt%, preferably at least 90 wt%, more preferably at least 95 wt%, and most preferably at least 99 wt% CHDI or PPDI, and most preferably consists entirely of CHDI or PPDI.If the isocyanate component does not consist entirely of CHDI or PPDI, it may contain other common isocyanates, such as one or more isocyanates selected from the group consisting of toluene-2,4-diisocyanates (TDI), methylenediphenyl isocyanates (MDI), hexamethylenediisocyanates (HDI), 1,5-naphthalene diisocyanates (NDI), isophorone diisocyanates (IPDI), 1,3-xylylene diisocyanate (m-XDI), 1,4-xylylene diisocyanate (p-XDI), 1,3-bis(isocyanatomethyl)cyclohexane (m-HeXDI), 1,4-bis(isocyanatomethyl)cyclohexane (p-HeXDI), 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 CHDI or PPDI.To achieve particularly high hardness, an optimal modulus of elasticity, and excellent thermal stability, a further development of the invention proposes that the press jacket comprise at least one polyurethane-containing layer, the isocyanate component of which consists exclusively or at least predominantly of trans-CHDI. Accordingly, it is preferred that the CHDI contained in the isocyanate component of the press jacket containing the at least one polyurethane-containing layer is 51 to 100 mol% trans-CHDI, preferably 70 to 100 mol% trans-CHDI, and particularly preferably 90 to 100 mol% trans-CHDI. Most preferably, the isocyanate component of the press jacket containing the at least one polyurethane-containing layer consists of CHDI, of which 51 to 100 mol% is trans-CHDI, preferably 70 to 100 mol% trans-CHDI, and particularly preferably 90 to 100 mol% trans-CHDI, and thus contains no other isocyanate compound than CHDI.

[0011] According to the present invention, the polyol component of the press jacket containing the at least one polyurethane-containing layer contains at least one homopolycarbonate polyol in an amount of at least 50% by weight. For the purposes of this invention, polyols are understood to be all alcohols which have at least two hydroxyl groups and preferably a weight-averaged molecular weight of 500 to 10,000 g / mol. For the purposes of this invention, a homopolycarbonate polyol is defined as such a polyol which also contains carbonate groups but is composed of only one building block or monomer, which may be repeated.

[0012] The present invention is not particularly limited with regard to the composition of the at least one homopolycarbonate polyol contained in the polyol component. For the purposes of the present invention, homopolycarbonate polyol refers to all polyols that, in addition to hydroxyl groups, contain at least one carbonate group as a functional group, but are composed of only one building block or monomer, which may be repeated. Polyols can therefore contain, in addition to hydroxyl groups and carbonate group(s), at least one other functional group, such as one or more ether groups, i.e., be homopolyethercarbonate polyols. Preferably, the at least one polycarbonate polyol contained in the polyol component of the press jacket containing the at least one polyurethane-containing layer contains terminal hydroxyl groups, and particularly preferably, the homopolycarbonate polyol is a diol containing hydroxyl groups and optionally further functional groups.According to an illustrative, but not limiting, embodiment, the at least one homopolycarbonate polyol contains only carbonate groups as functional groups in addition to terminal hydroxyl groups.

[0013] According to the invention, the at least one homopolycarbonate polyol contained in the polyol component of the press jacket containing the at least one polyurethane-containing layer is a polycarbonate polyol according to the general formula (I):

[0014] HO-(R 1 -OC(O)O)mR 1 -OH (I),

[0015] in which R 1 selected from linear Ci-C2o alkylene groups and branched C1-C20 alkylene groups and n 1 is an integer of at least 2.

[0016] For the purposes of the present invention, an alkylene group is understood to be a CnH2n hydrocarbon group, i.e., a hydrocarbon group with two terminal radicals.

[0017] Good results are obtained especially when in the general formula (I) R 1 selected from linear Ce-C2o alkylene groups and branched C6-C20 alkylene groups, further preferably from linear Ce-Cu alkylene groups and particularly preferably from linear Ce-Ci2 alkylene groups.

[0018] In particular, R 1 An alkylene group with an even number of carbon atoms, i.e., a Cx alkylene group, where x is an even integer. Particularly good results are obtained with a Ce alkylene group, a Cs alkylene group, a Cw alkylene group, and a Ci2 alkylene group. R is most preferred. 1 in the general formula (I) a Ce alkylene group.

[0019] In a further development of the inventive concept, it is proposed that the weight-averaged molecular weight of the at least one homopolycarbonate polyol be 400 to 10,000 g / mol, more preferably 600 to 5,000 g / mol, and particularly preferably 700 to 4,000 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, in the case of diols for example by dividing 112,200 by the hydroxyl number.

[0020] To improve processability by reducing the viscosity of the polyol component, the invention further provides that the polyol component of the press jacket containing the at least one polyurethane-containing layer comprises two or more different homopolycarbonate polyols of general formula (I). Particularly good results are obtained when the polyol component of the press jacket containing the at least one polyurethane-containing layer comprises two or more different homopolycarbonate polyols according to general formula (I). Particularly good results are obtained when at least one of these homopolycarbonate polyols is used as R 1 contains a Ce alkylene group and another of these homopolycarbonate polyols as R 1a linear C7-C20 alkylene group, preferably a linear Cy-Cu alkylene group, more preferably a linear C7-Ci2 alkylene group, and particularly preferably a linear C7-C10 alkylene group. According to an alternative but equally advantageous embodiment of the present invention, it is provided that at least one of these homopolycarbonate polyols is configured as R 1 contains a Cs or Cw alkylene group and another of these homopolycarbonate polyols as R 1 a linear C12-16 alkylene group, and preferably that at least one of these homopolycarbonate polyols acts as R 1 contains a Cw alkylene group and another of these homopolycarbonate polyols as R 1 a linear Ci2 alkylene group.

[0021] Particularly preferred is that the polyol component contains two homopolycarbonate polyols according to the general formula (I), one of which is homopolycarbonate polyol as R 1contains a Ce alkylene group and the other homopolycarbonate polyol as R 1 contains a Cw alkylene group or a Cw alkylene group.

[0022] To achieve the aforementioned effects to a particularly high degree, the polyol component of the press jacket containing the at least one polyurethane-containing layer comprises exclusively or at least almost exclusively homopolycarbonate polyols. For this reason, according to a further particularly preferred embodiment of the present invention, the polyol component consists of at least 80 wt.%, more preferably at least 90 wt.%, particularly preferably at least 95 wt.%, most preferably at least 99 wt.%, and most preferably at least 100 wt.% of one or more homopolycarbonate polyols, and in particular of one or more homopolycarbonate polyols according to general formula (I).It is therefore highly preferred that the press jacket 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 consists of CHDI and / or PPDI and the polyol component consists of one or more homopolycarbonate polyols with the general formula (I).

[0023] According to an alternative embodiment of the present invention, the polyol component of the press jacket containing the at least one polyurethane-containing layer comprises 75 to 99 wt.%, and preferably 75 to 90 wt.%, of one or more homopolycarbonate polyols and 1 to 25 wt.%, and preferably 10 to 25 wt.%, of one or more polyethers. Preferred examples of polyethers are polytetramethylene glycol (PTMG), polyhexamethylene glycol (PHMG), polyoctamethylene glycol, polydecamethylene glycol, and any mixtures of two or more thereof. Particularly good results are obtained when the at least one polyether has a weight-averaged molecular weight of 100 to 10,000 g / mol, preferably 500 to 5,000 g / mol, particularly preferably 700 to 3,000 g / mol, and most preferably 700 to 2,500 g / mol. As described above, the one or more homopolycarbonate polyols preferably each have the general formula (I).

[0024] According to another alternative embodiment of the present invention, the polyol component of the press jacket containing the at least one polyurethane-containing layer comprises 75 to 99 wt.%, and preferably 75 to 90 wt.%, of one or more homopolycarbonate polyols and 1 to 25 wt.%, and preferably 10 to 25 wt.%, of one or more polyether carbonates. In this embodiment as well, it is preferred that the one or more homopolycarbonate polyols preferably each have the general formula (I). The polyether carbonate can be any compound containing at least one ether group and at least two carbonate groups.

[0025] Preferably, the prepolymer of the press jacket containing the at least one polyurethane-containing layer contains no free monomers or, if any, only minimal amounts of free monomers. Therefore, it is preferred that the prepolymer contains a maximum of 1 wt.%, preferably less than 0.5 wt.%, and particularly preferably less than 0.1 wt.% free monomers.

[0026] The present patent application is not particularly limited with regard to the composition of the crosslinking component of the press jacket containing at least one polyurethane-containing layer. For example, the crosslinking component can contain at least one diol and / or one diamine. The diol is preferably an aliphatic diol or an aromatic diol, whereas aliphatic diamines, cycloaliphatic diamines, and aromatic diamines are equally suitable as diamines.

[0027] Suitable examples of aliphatic diols suitable as crosslinking agents are those according to the general formula (II):

[0028] HO-(CH2)X-OH (II),

[0029] wherein x is an integer between 2 and 14. Particularly preferably, x is an integer of 2, 4, 6, 8, 10, 12 or 14 and most preferably of 2, 4 or 6.

[0030] Suitable examples of diols are 1,2-ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, N-N'-bis-(2-hydroxypropylaniline), hydroquinone bis-(2-hydroxyethyl) ether (HQEE), 1,3-bis(2-hydroxyethyl)resorcinol and any mixtures of two or more of the aforementioned compounds.

[0031] Suitable examples of aliphatic diamines suitable as crosslinking agents are diamines selected from the group consisting of ethylenediamine (EDA), 2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, hexamethylenediamine (HMDA) and mixtures thereof.

[0032] Suitable examples of aromatic diamines suitable as crosslinking agents are bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA), 4,4'-methylene-bis-(2-ethylbenzenamine) (MBOEA), 3,5-dimethylthio-2,4- or -2,6-toluenediamine (available under the trade name Ethacure 300) and diethyltoluenediamine (available under the trade name Ethacure 100).

[0033] A suitable example of cycloaliphatic diamines suitable as crosslinking agents is 4,4'-diaminodicyclohexylmethane, which is available under the trade name Amicure PACM.

[0034] The crosslinking component particularly preferentially contains MCDEA.

[0035] In addition to or instead of aliphatic diol and / or aromatic diol and / or aliphatic diamine and / or cycloaliphatic diamine and / or aromatic diamine, the crosslinking component may contain at least one alkanolamine, wherein the at least one alkanolamine is preferably a C1-6 alkylmonohydroxymonoamine and particularly preferably monoethanolamine. Furthermore, the crosslinking component may contain a polyol, wherein the polyol may be, for example, a polyether, a polycarbonate polyol, or a polyethercarbonate polyol. It may be a polyol that is also contained in the prepolymer. Suitable examples of polyethers are polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetrahydrofuran, polyhexamethylene glycol, polyoctamethylene glycol, and polydecamethylene glycol.

[0036] In addition, the crosslinking component can contain a triol.

[0037] Furthermore, it is preferred that the crosslinking component additionally contains at least one catalyst, which is preferably a tertiary amine compound and / or an organometallic compound. Particularly good results are obtained if the at least one catalyst is a tertiary amine compound selected from the group consisting of 1,4-diazabicyclo(2,2,2)octane (DABCO), also called triethylenediamine (TEDA), triethylamine, and mixtures thereof. Equally good results are obtained if the at least one catalyst contains an organometallic compound with a metal selected from the group consisting of bismuth, mercury, aluminum, zirconium, iron, calcium, sodium, potassium, lead, tin, titanium, and mixtures thereof. The at least one catalyst is particularly preferred to be 1,4-diazabicyclo(2,2,2)octane (DABCO) and / or a tin-based organometallic compound.

[0038] Preferably, the H / NCO ratio of the polyurethane is between 1.15 and 0.85.

[0039] To further increase abrasion resistance, an additive such as silicone oil can 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. Furthermore, it is preferred if the polyurethane layer of the press jacket comprises only one polyurethane.

[0040] The press-fit casing according to the invention can be single-layered or multi-layered. In a multi-layered configuration, at least the outermost layer is composed of the polyurethane described above.

[0041] In a further development of the inventive concept, it is proposed to design the press jacket in multiple layers, wherein the outermost layer is composed of the polyurethane described above and the inner 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.

[0042] Another object of the present invention is a shoe press for dewatering a fibrous web, in particular a paper, cardboard, tissue or cellulose web, which comprises a press jacket as described above.

[0043] Finally, the present invention relates to a method for producing a previously described press jacket, comprising the following steps: a) providing at least one rotatably mounted winding mandrel, b) providing a previously described crosslinking component, c) providing a prepolymer as the product of a reaction of a previously described isocyanate component containing CHDI and / or PPDI with a previously described polyol component,

[0044] d) Mixing the prepolymer and the crosslinking component to produce a polyurethane, e) Applying the prepolymer-crosslinking mixture to a surface of the winding dome to form at least one polymer layer of the press jacket,

[0045] f) Curing of at least one polymer layer and

[0046] g) Removing the press jacket produced in this way from the winding dome.

[0047] The present invention is described below by way of example only, using advantageous embodiments and with reference to the accompanying drawings.

[0048] This shows:

[0049] Fig. 1: a schematic view of a shoe press with a press jacket according to an embodiment of the present invention and

[0050] Fig. 2: a schematic view of a press section of a paper machine comprising a shoe press according to an embodiment of the present invention.

[0051] Figure 1 shows a shoe press 10 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 press gap 22 is created. The shoe press 10 is particularly suitable for dewatering fibrous webs 24, such as paper webs.During operation of the shoe press, a fiber web 24 with one or two press films 26, 26' is guided through the press gap 22. The liquid that escapes from the fiber 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 felts 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. Additionally, the water absorbed by the press felts 26, 26' is removed by suction elements after exiting the press gap 22.

[0052] 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.

[0053] Figure 2 shows a section of the press section of a paper machine, which includes a shoe press 10. As in the embodiment shown in Figure 1, the shoe press 10 comprises a shoe roller 12 having a press sleeve 20 and a press element or shoe 16, and a counter roller 14, with a press gap 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 receives the fiber web 24 on the suction roller 28, is guided through the press gap. In addition, a conveyor belt, guided by the deflection rollers 30, 30', is positioned below the felt 26, which carries the fiber web 24.The transfer belt 32 is guided through the press gap, taking the fiber web 24 from the felt 26 within the press gap and guiding it out of the press gap via the deflecting 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 surface of the press jacket. 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 is removed after exiting the press gap 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.

[0054] The present invention is described below by way of example only, with reference to advantageous embodiments and the following purely illustrative and non-limiting examples.

[0055] Example: The viscosities of two homopolycarbonates were compared with the viscosity of a mixture of the two homopolycarbonates and with the viscosity of a copolycarbonate polyol at 70°C and 80°C, with the results summarized in the following table.

[0056]

[0057] Viscosities were determined at 70°C and 80°C respectively using a Brookfield viscometer (spindle RV-04, speed 40 rpm).

[0058] The viscosity of the polycarbonate(s) used to produce the polyurethane is important because the viscosity of a prepolymer is strongly dependent on the viscosity of the polyol used, especially if this prepolymer is intended to contain few monomers, for example, for safety reasons. The results above show that it is advantageous to use one or more homopolycarbonate polyols with relatively long monomers, such as C10, in the production of the polyurethane prepolymer, as their viscosity is lower than that of Ce homopolycarbonate polyols or even lower than that of CsCe-based copolycarbonate polyols. Surprisingly, it was also found that the viscosity of a 50 / 50 mixture of two homopolycarbonate polyols is lower than the mathematical mean of the individual viscosities of the two homopolycarbonate polyols.

[0059] 10 shoe press

[0060] 12 shoe roller

[0061] 14 Counter roller

[0062] 16 shoes

[0063] 18 standing yoke

[0064] 20 Pressed jacket

[0065] 22 Press gap

[0066] 24 Fiber web

[0067] 26, 26' Pressed felt

[0068] 28, 28' suction rollers

[0069] 30, 30' deflection rollers

[0070] 32 T ransportband / T ransferband

Claims

Patent 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, wherein the press jacket 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 isocyanate component contains 1,4-cyclohexyl diisocyanate (CHDI) and / or phenylene diisocyanate (PPDI) in an amount of at least 50% by weight and ii) the polyol component contains at least one homopolycarbonate polyol in an amount of at least 50% by weight. wherein the at least one homopolycarbonate polyol has the general formula (I): HO-(R 1 -OC(O)O)mR 1 -OH (I), in which R 1selected from linear Ci-C2o alkylene groups and branched C4-C20 alkylene groups and n 1 an integer of at least 2, wherein the polyol component contains two or more different homopolycarbonate polyols according to the general formula (I), wherein i) at least one of these homopolycarbonate polyols is R 1 contains a Ce-alkylene group and another of these homopolycarbonate polyols as R 1 contains a linear C1-C2o alkylene group or ii) at least one of these homopolycarbonate polyols as R 1 contains a Cs or Cw alkylene group and another of these homopolycarbonate polyols as R 1 1. Contains a linear Ci2-16-alkylene group.

2. Pressed casing according to claim 1, characterized in that the isocyanate component contains CHDI or PPDI, but not a mixture of CHDI and PPDI.

3. Pressed casing according to claim 1 or 2, characterized in that the isocyanate component contains at least 80 wt.%, preferably at least 90 wt.%, more preferably at least 95 wt.% and particularly preferably at least 99 wt.% CHDI or PPDI and most preferably consists of CHDI or PPDI.

4. Pressed casing according to at least one of the preceding claims, characterized in that the CHDI contained in the isocyanate component is 51 to 100 mol% trans-CHDI, preferably 70 to 100 mol% trans-CHDI and particularly preferably 90 to 100 mol% trans-CHDI.

5. Pressed casing according to at least one of the preceding claims, characterized in that in the general formula (I) R 1 selected from linear Cs-C2o alkylene groups and branched Ce-C2o alkylene groups, preferably from linear Ce-Cu alkylene groups and particularly preferably from linear Cs-Ci2 alkylene groups, wherein R 1most preferably a Ce alkylene group, a Cs alkylene group, a Cw alkylene group or a Ci2 alkylene group, and most preferably a Ce alkylene group.

6. Pressed casing according to at least one of the preceding claims, characterized in that the weight-averaged molecular weight of the at least one homopolycarbonate polyol is 400 to 10,000 g / mol, preferably 600 to 5,000 g / mol, and particularly preferably 700 to 4,000 g / mol.

7. Pressed casing according to at least one of the preceding claims, characterized in that i) at least one of these homopolycarbonate polyols is used as R 1 contains a Ce alkylene group and another of these homopolycarbonate polyols as R 1 a linear C7-C14 alkylene group, preferably a linear C1-Ci2 alkylene group and particularly preferably a linear Cy-Cw alkylene group or ii) at least one of these homopolycarbonate polyols as R 1contains a Cw alkylene group and another of these homopolycarbonate polyols as R 1 contains a linear Ci2 alkylene group.

8. Pressed casing according to at least one of the preceding claims, characterized in that the polyol component consists of at least 80 wt.%, preferably at least 90 wt.%, particularly preferably at least 95 wt.%, most preferably at least 99 wt.% and most preferably at least 100 wt.% of one or more homopolycarbonate polyols.

9. Pressed casing according to at least one of the preceding claims, characterized in that the isocyanate component consists of CHDI or PPDI and the polyol component consists of one or more homopolycarbonate polyols with the general formula (I).

10. Pressed casing according to at least one of the preceding claims, characterized in that the polyol component contains 75 to 99 wt.% and preferably 75 to 90 wt.% of one or more homopolycarbonate polyols and 1 to 25 wt.% and preferably 10 to 25 wt.% of one or more polyethers, preferably polytetramethylene glycol (PTMG), polyhexamethylene glycol (PHMG), polyoctamethylene glycol, polydecamethylene glycol or any mixture of two or more thereof.

11. Pressed casing according to at least one of claims 1 to 7, characterized in that the polyol component contains 75 to 99 wt.% and preferably 75 to 90 wt.% of one or more homopolycarbonate polyols and 1 to 25 wt.% and preferably 10 to 25 wt.% of one or more polyether carbonates.

12. Press jacket according to at least one of the preceding claims, characterized in that the prepolymer contains a maximum of 1 wt.%, preferably less than 0.5 wt.% and particularly preferably less than 0.1 wt.% free monomers.

13. Pressed casing according to at least one of the preceding claims, characterized in that the crosslinking component contains at least one polyol, diol and / or diamine, preferably as the polyol a polyether polyol, a polycarbonate polyol or a polyether carbonate polyol or preferably a polyol, diol and / or diamine selected from the group consisting of polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetrahydrofuran, polyhexamethylene glycol, polyoctamethylene glycol, polydecamethylene glycol, 1,2-ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, ethylenediamine (EDA), 2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine, hexamethylenediamine (HMDA). N-N'-Bis-(2-hydroxypropylaniline), Hydroquinone bis-2-(hydroxyethyl) ether (HQEE), 1,3-Bis(2-hydroxyethyl)resorcinol, Bis(4-amino-2-chloro-3,5-diethylphenyl)methane (MCDEA), 4,4'-Methylene bis-(2-ethylbenzenamine) (MBOEA), 3,5-Dimethylthio-2,4- or -2,6-toluenediamine, diethyltoluenediamine, 4,4'-diaminodicyclohexylmethane or the crosslinking component contains any mixture of two or more of the aforementioned compounds.

14. Shoe press for dewatering a fibrous web, in particular a paper, cardboard, tissue or pulp web, which has a press jacket according to at least one of the preceding claims.

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