PRESS COVER AND USE THEREOF

Abstract

A press cover or jacket includes at least one first polymer layer. The polymer layer contains or has been produced from a polyurethane, and the polyurethane has been formed from a prepolymer and a crosslinker. The prepolymer is a reaction product of naphthalene 1,5-diisocyanate or phenylene 1,4-diisocyanate and at least one polyol selected from a polycarbonate polyol, a polytetramethylene ether glycol, polyether polycarbonate polyol or mixtures thereof. A press using the press cover is also provided.

Claims

1-15. (canceled)

16. A press cover, comprising: at least one first and one second polymer layer each containing or being formed of a polyurethane, said polyurethane being formed from a prepolymer and a crosslinker; said prepolymer of said first polymer layer being a reaction product of naphthalene 1,5-diisocyanate as an isocyanate and at least one polyol selected from a polycarbonate polyol, a polyether polycarbonate polyol or mixtures of a polycarbonate polyol and a polyether polycarbonate polyol.

17. The press cover according to claim 16, wherein said prepolymer of said second polymer layer is a reaction product of: naphthalene 1,5-diisocyanate as an isocyanate and polytetramethylene ether glycol as a polyol, or phenylene 1,4-diisocyanate, diphenylmethane 4,4-diisocyanate, toluene 2,4-diisocyanate or 3,3-dimethyl-4,4-biphenylene diisocyanate as an isocyanate and a polyol or polytetramethylene ether glycol.

18. The press cover according to claim 17, wherein said first polymer layer is a radially outermost polymer layer relative to a longitudinal axis of the press cover.

19. The press cover according to claim 18, which further comprises a third polymer layer being a radially innermost layer relative to the longitudinal axis of the press cover, said second polymer layer being disposed between said third polymer layer and said first polymer layer in radial direction, and said third polymer layer including a prepolymer being a reaction product of: naphthalene 1,5-diisocyanate as an isocyanate and polytetramethylene ether glycol as a polyol, or phenylene 1,4-diisocyanate, diphenylmethane 4,4-diisocyanate, toluene 2,4-diisocyanate or 3,3-dimethyl-4,4-biphenylene diisocyanate as an isocyanate and a polyol or polytetramethylene ether glycol.

20. A press cover, comprising: a single polymer layer, said single polymer layer containing or being formed of a polyurethane, said polyurethane being formed of a prepolymer and a crosslinker; and said prepolymer being a reaction product of naphthalene 1,5-diisocyanate or phenylene 1,4-diisocyanate as an isocyanate and at least one polyol selected from a polycarbonate polyol, a polytetramethylene ether glycol, polyether polycarbonate polyol or mixtures of a polycarbonate polyol, a polytetramethylene ether glycol and a polyether polycarbonate polyol.

21. A press cover, comprising: at least one first and one second polymer layer each including or being formed of a polyurethane, said polyurethane being formed of a prepolymer and a crosslinker; said prepolymer of said first polymer layer being a reaction product of phenylene 1,4-diisocyanate, naphthalene 1,5-diisocyanate, diphenylmethane 4,4-diisocyanate, toluene 2,4-diisocyanate or 3,3-dimethyl-4,4-biphenylene diisocyanate as isocyanate, and at least one polyol selected from a polycarbonate polyol, a polyether polycarbonate polyol or mixtures of a polycarbonate polyol and a polyether polycarbonate polyol; and said prepolymer of said second polymer layer being a reaction product of naphthalene 1,5-diisocyanate as an isocyanate and polytetramethylene ether glycol as a polyol.

22. The press cover according to claim 21, wherein said first polymer layer is a radially outermost polymer layer relative to a longitudinal axis of the press cover.

23. The press cover according to claim 22, which further comprises a third polymer layer being a radially innermost layer relative to the longitudinal axis of the press cover, said second polymer layer being disposed between said third polymer layer and said first polymer layer in radial direction, and said third polymer layer including a prepolymer being a reaction product of naphthalene 1,5-diisocyanate as an isocyanate and polytetramethylene ether glycol as a polyol.

24. The press cover according to claim 21, wherein said crosslinker includes: butane-1,4-diol, hydroquinone 1,4-bis(2-hydroxyethyl) ether, 4,4-methylenebis(3-chloro-2,6-diethylaniline), an aliphatic or aromatic amine, an aliphatic or aromatic diamine, an alkanolamine, ethylenediamine, 2,2,4-trimethylhexane-1,6-diamine, 2,4,4-trimethyl-hexane-1,6-diamine, hexamethylenediamine, diethyltoluenediamine, 4,4-diaminodicyclohexylmethane, dimethylthiotoluenediamine, monoethanolamine as components or mixtures of said components.

25. The press cover according to claim 19, wherein said crosslinker of said radially outermost polymer layer includes butane-1,4-diol or at least one amine, said crosslinker of said radially innermost polymer layer includes at least one amine, and said respective amines are an aromatic or aliphatic amine, an aromatic or aliphatic diamine or an alkanolamine.

26. The press cover according to claim 23, wherein said crosslinker of said radially outermost polymer layer includes butane-1,4-diol or at least one amine, said crosslinker of said radially innermost polymer layer includes at least one amine, and said respective amines are an aromatic or aliphatic amine, an aromatic or aliphatic diamine or an alkanolamine.

27. The press cover according to claim 25, wherein said crosslinker includes a component selected from at least one polyol or bifunctional polyol having a molecular weight of between 1000 and 4000 g/mol.

28. The press cover according to claim 27, wherein said molecular weight of said component is between 1200 to 3500 g/mol.

29. The press cover according to claim 27, wherein said component is polyester polyol or polycaprolactone polyol; polyether polyols or polytetramethylene ether glycol, polypropylene glycol, polyethylene glycol, polyhexamethylene ether glycol, polycarbonate polyol, polyether carbonate polyol, polybutadiene polyol, perfluoropolyether polyol, silicone polyol or mixtures of said polyols.

30. The press cover according to claim 26, wherein said crosslinker includes a component selected from at least one polyol or bifunctional polyol having a molecular weight of between 1000 and 4000 g/mol.

31. The press cover according to claim 30, wherein said molecular weight of said component is between 1200 to 3500 g/mol.

32. The press cover according to claim 30, wherein said component is polyester polyol or polycaprolactone polyol; polyether polyols or polytetramethylene ether glycol, polypropylene glycol, polyethylene glycol, polyhexamethylene ether glycol, polycarbonate polyol, polyether carbonate polyol, polybutadiene polyol, perfluoropolyether polyol, silicone polyol or mixtures of said polyols.

33. The press cover according to claim 16, wherein said NDI-based prepolymer for production of said at least one polymer layer has an NCO content of 4% to 20% by weight.

34. The press cover according to claim 33, wherein said NCO content is 5% to 14% by weight.

35. The press cover according to claim 21, wherein said NDI-based prepolymer for production of said at least one polymer layer has an NCO content of 4% to 20% by weight.

36. The press cover according to claim 35, wherein said NCO content is 5% to 14% by weight.

37. The press cover according to claim 16, wherein a ratio of an amount of isocyanate actually used in said prepolymer to a calculated stoichiometric amount of isocyanate is between 0.8 and 1.2 for production of said at least one polymer layer.

38. The press cover according to claim 21, wherein a ratio of an amount of isocyanate actually used in said prepolymer to a calculated stoichiometric amount of isocyanate is between 0.8 and 1.2 for production of said at least one polymer layer.

39. The press cover according to claim 19, wherein at least one of a modulus of elasticity or a hardness of said first polymer layer is greater than a corresponding modulus of elasticity or hardness of at least one of said second or third polymer layer.

40. The press cover according to claim 23, wherein at least one of a modulus of elasticity or a hardness of said first polymer layer is greater than a corresponding modulus of elasticity or hardness of at least one of said second or third polymer layer.

41. A press or shoe press for the treatment of a fibrous material web, a paper web, a cardboard web, a tissue web or a pulp web, the press or shoe press comprising a press cover according to claim 16.

42. A press or shoe press for the treatment of a fibrous material web, a paper web, a cardboard web, a tissue web or a pulp web, the press or shoe press comprising a press cover according to claim 20.

43. A press or shoe press for the treatment of a fibrous material web, a paper web, a cardboard web, a tissue web or a pulp web, the press or shoe press comprising a press cover according to claim 21.

Description

[0036] The invention is elucidated in detail hereinafter with reference to the drawings without restriction of generality. The drawings show:

[0037] FIG. 1 a schematic side view as a partial section of a shoe press with a press cover in a working example of the present invention.

[0038] FIGS. 2a, 2b and 2c working examples of a press cover formed in accordance with the invention, each viewed in a section through the longitudinal axis thereof;

[0039] FIG. 3 a highly schematic diagram of the performance of the process of the invention in a side view of an apparatus for production of the press cover.

[0040] FIG. 1 shows a shoe press 10 which, in the present context, comprises a press roll of the invention, such as a shoe press roll 12, and an opposing roll 14. Shoe press roll 12 and opposing roll 14 are arranged parallel to one another with regard to their longitudinal axes. Together, they form or bound such a nip 22.

[0041] While the opposing roll 14 here consists of a roll of cylindrical configuration that rotates about its longitudinal axis, the shoe press roll 12 is composed of a shoe 16, a stationary yoke 18 that bears it, and a press cover 20. Shoe 16 and yoke 18 are in a fixed arrangement in relation to the opposing roll 14 or the press cover 20. This means that they do not rotate. The shoe 16 is supported here by the yoke 18 and pressed onto the radially innermost surface of the press cover 20 that revolves relative thereto via hydraulic press elements (not shown). The press cover 20 that surrounds shoe 16 and yoke 18 in circumferential direction rotates here about its longitudinal axis in the opposite sense from the opposing roll 14. Owing to the concave configuration of the shoe 16 on its side facing the opposing roll 14, the result is a comparatively long nip 22.

[0042] The shoe press 10 is especially suitable for dewatering of fibrous material webs 24. In the operation of the shoe press, a fibrous material web 24 is guided through the press gap 22 with one or two press felts 26, 26. In the present case, there are exactly two press felts 26, 26 that accept the fibrous material web 24 between them in a sandwich-like manner. In the course of passage through the nip 22, the press felts 26, 26 exert a pressure indirectly on the fibrous material web 24 in the nip 22. This is accomplished in that the radially outermost surface of the opposing roll 14 on the one hand and the radially outermost surface of the press cover 20 come into direct contact with the corresponding press felts 26, 26. The liquid exiting from the fibrous material web 24 is temporarily absorbed by the press felt(s) 26, 26 and any recesses provided in the press cover surface (not shown). After leaving the nip 22, the liquid absorbed by the depressions of the press cover 20 is spun off before the press cover 20 enters the press gap 22 again. In addition, the water absorbed by the press felt 26, 26 can be removed by suction elements after departure from the press gap 22.

[0043] The press cover shown in FIG. 1 may, as shown in the figures that follow, be executed in accordance with the invention.

[0044] FIGS. 2a, 2b and 2c show different alternatives of the common concept of the invention in a partial cross section, not to scale, through the longitudinal axis 20 of the finished press cover 20. The distance of the longitudinal axis 20 from the radially innermost surface of the corresponding polymer layer is likewise not shown to scale.

[0045] FIG. 2a shows a press cover 20 in the first alternative of the invention with a single polymer layer 20.1. In the present context, a reinforcing structure 20 has been embedded into the single polymer layer 20.1. This is indicated by the hatched circles that may be textile areal or linear structures such as fibers. The reinforcing structure is fully embedded into the polymer layer 20.1, meaning that the reinforcing structure 20 does not extend beyond the bounds of the polymer layer 20.1.

[0046] The first polymer layer 20.1 has been formed here from polyurethane which is produced from a prepolymer and a crosslinker. The prepolymer is a reaction product of naphthalene 1,5-diisocyanate (NDI) or phenylene 1,4-diisocyanate (PPDI) as isocyanate and at least one polyol selected from a polycarbonate polyol, a polytetramethylene ether glycol (PTMEG), polyether polycarbonate polyol or mixtures of these.

[0047] FIGS. 2b and 2c each show, as a modification of FIG. 2a, a multilayer press cover 20. For instance, according to FIG. 2b, which corresponds to an embodiment of the second alternative of the invention, exactly two polymer layers are provided, namely a first 20.1 and a second 20.2. In the present case, the first polymer layer 20.1 is simultaneously the radially outermost polymer layer of the press cover 20. On the other hand, the second polymer layer 20.2 is simultaneously the radially innermost polymer layer of the press cover 20. As shown, a reinforcing structure 20 may have been provided in the second polymer layer 20.2. In the present case, the first and a second polymer layer 20.1, 20.2 have been produced from a polyurethane. The latter is obtainable from a prepolymer and a crosslinker. According to the second alternative, the prepolymer of the first polymer layer 20.1 is a reaction product of naphthalene 1,5-diisocyanate (NDI) and at least one polyol. The latter is selected from a polycarbonate polyol, a polyether polycarbonate polyol or mixtures of the two.

[0048] On the other hand, the prepolymer of the second polymer layer 20.2 is a reaction product of naphthalene 1,5-diisocyanate (NDI) and at least one polytetramethylene ether glycol (PTMEG). Alternatively, this may have been produced from a phenylene 1,4-diisocyanate (PPDI), diphenylmethane 4,4-diisocyanate (MDI), toluene 2,4-diisocyanate (TDI) or 3,3-dimethyl-4,4-biphenylene diisocyanate (TODI) and a polyol. The latter may, for example, be polytetramethylene ether glycol (PTMEG).

[0049] For the rest, the statements already made for FIG. 2a are applicable.

[0050] FIG. 2c shows a three-layer press cover with a first polymer layer 20.1the radially outermost here, a radially innermost, third polymer layer 20.3, and a second polymer layer 20.2 arranged between the two in a sandwich-like manner. The arrangementas also in the diagram of FIG. 2bis viewed proceeding from the longitudinal axis 20 of the press cover 20 in the radial direction thereof. In the present case, only in the second polymer layer 20.2 is a (single) reinforcing structure 20 provided. This could of course also be different, and so such a reinforcing structure 20 could alternatively or additionally also be disposed in the first polymer layer 20.1 and/or the third polymer layer 20.3. Here too, the first and second polymer layer 20.1, 20.2 have each been produced from or contain such a polyurethane. The corresponding prepolymer of the first polymer layer 20.1 here may be a reaction product of phenylene 1,4-diisocyanate (PPDI), NDI, TODI, TDI or diphenylmethane 4,4-diisocyanate (MDI) or a mixture of the two. The corresponding at least one polyol may be selected from a polycarbonate polyol, a polyether polycarbonate polyol or mixtures thereof. The prepolymer of the second and third polymer layers 20.2, 20.3 here is a reaction product of naphthalene 1,5-diisocyanate (NDI) and at least one polytetramethylene ether glycol (PTMEG).

[0051] In respect of the embodiment of FIG. 2d, moreover, the statements already made for FIGS. 2a and 2b are applicable.

[0052] The use of the polyurethane in at least one of the polymer layers 20.1, 20.2, 20.3 of the three alternatives of the invention guarantees the particularly high stability of the press cover 20 with regard to the mechanical and dynamic properties such as stability, surface hardness, resistance to pressure, temperature and hydrolysis, and low swelling. These properties lead to a prolonged lifetime of the press cover 20 in operation.

[0053] FIG. 3 shows, in a highly schematic side view, an apparatus for production of a press cover 20 of the invention. The apparatus in the present context has exactly one cylindrical winding mandrel 4, with application here, for example, of a starting material 20 in spiral form to the radially outermost cover surface thereof. After embedding into the polymer, the starting material 20 forms the reinforcing structure 20 of the finished press cover 20 of the invention.

[0054] The diagram shows an initial stage of the production process. In the present case, for this purpose, one end of the starting material 20 has been secured to a polymer disposed at the outer extent of the winding mandrel 4. Apart from the schematic diagram shown, it would also be possible for one end of the starting material 20 to lie on or have been applied to the winding mandrel 4, i.e. directly, without initial provision of a polymer between starting material 20 and winding mandrel 4. The starting material 20 here may be a textile fabric or linear structure.

[0055] The winding mandrel 4 is mounted so as to be rotatable about its longitudinal axis 20, which corresponds to the longitudinal axis of the press cover to be produced. Longitudinal axis 20 runs at right angles here into the plane of the drawing. A casting material, such as castable, curable elastomeric polymer, e.g. polyurethane, is applied via a conduit 5 through a casting nozzle 6 downward onto the radially outermost cover surface of the winding mandrel 4 or onto the starting material 20. Such a casting material may be chosen, for example, with respect to its pot life and viscosity such that it does not drip off the winding mandrel 4 in the course of casting. During this period, the winding mandrel 4 is rotated about its longitudinal axis in the direction of the arrow. Simultaneously with this rotation, the casting nozzle 6 is guided parallel to and along the longitudinal axis 20 relative to the winding mandrel 4 by means of a suitable guide (not shown in detail in FIG. 3). Simultaneously with the casting application of the casting material, the starting material 20 is unrolled and wound on the rotating winding mandrel 4, for example to give windings. It is possible here for the casting material to get through the starting material 20 through to the winding mandrel 4. The polymer in this example, after the curing step, forms a first, preferably elastomeric polymer layer 20.1 of the press cover, which is the radially innermost here, of which FIG. 3 shows just part.

[0056] The casting material exiting from the casting nozzle 6 is a mixture of a prepolymer and a crosslinker. The former is provided from a prepolymer vessel (not shown) in which it is stored or stirred up. The prepolymer may comprise an isocyanate of the invention and a polyol. It may be present in the prepolymer vessel, for example, in the form of a prepolymer of the substances just mentioned.

[0057] The crosslinker may be provided in a crosslinker vessel. The crosslinker may comprise BDO, HQEE, MCDEA, at least one diamine, such as an aromatic or aliphatic diamine or alkanolamine, EDA, 2,2,4-trimethylhexane-1,6-diamine, 2,4,4-trimethylhexane-1,6-diamin, HMDA, DETDA, 4,4-diaminodicyclohexylmethane or DMTDA. In principle, mixtures of the aforementioned substances would also be conceivable. The crosslinker may alternatively comprise a further component, such as at least one polyol and/or else a catalyst. The crosslinker with its corresponding components may be stirred up directly in the crosslinker vessel. It is, however, also conceivable that the apparatus comprises a corresponding individual vessel for each of the components that is connected to the crosslinker vessel in a flow-conducting manner via conduits (not shown), in order to produce the crosslinker of the invention in the crosslinker vessel.

[0058] Prepolymer vessel and crosslinker vessel are assigned to the apparatus for production of a press cover 20. They are connected via conduits (likewise not shown) in a flow-conducting manner to a mixing chamber (not shown) connected upstream of the casting nozzle 6 in flow direction. The prepolymer/crosslinker mixture is thus produced upstream of and outside the casting nozzle 6, i.e. mixed in the mixing chamber. Irrespective of the production of the mixture, this is then applied to the surface of the winding mandrel 4 to form the at least one polymer layer 20.1 of the press cover 20.

[0059] By means of such a continuous casting operation, which is also known as rotary casting, a continuous press cover 20 that forms an intrinsically closed cylinder about its longitudinal axis 20 is thus gradually produced over the width of the winding mandrel 4, the internal circumference of which corresponds essentially to the outer circumference of the winding mandrel 4.

[0060] In principle, it would be conceivable to wind the starting material 20 onto more than one winding mandrel 4 shown in FIG. 3. For example, it would be possible to provide two winding mandrels that could be arranged in parallel at a distance from one another with regard to their longitudinal axes. Alternatively, it would also be conceivable to apply the polymer to the radially inner cover surface of the winding mandrel 4 as well, for example in the manner of spinning.

[0061] Irrespective of the embodiment addressed, the finished press cover 20 is finally removed from the at least one winding mandrel 4.

[0062] As shown in the figures, the press cover 20 takes the form according to the invention. This means that the at least one polymer layer has been produced (partly or completely) from a polyurethane. The polyurethane here has been formed from a prepolymer of the inventionwhich is a reaction product of at least one polyol with an isocyanateand a crosslinker. The crosslinker comprises, for example, the components mentioned at the outset. The former may also include further components known to the person skilled in the art.