EP3662107A1

EP3662107A1 - Press jacket and use thereof, and press roll and shoe press

Info

Publication number: EP3662107A1
Application number: EP18731427.3A
Authority: EP
Inventors: Delphine DELMAS DR.; Hermann Reichert; Michael WOKUREK DR.; Uwe Matuschczyk
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2017-07-31
Filing date: 2018-06-13
Publication date: 2020-06-10
Also published as: JP2020528972A; CN110998020B; WO2019025065A1; DE102017117227A1; JP7044864B2; CN110998020A; US20210131034A1

Abstract

The invention relates to a press jacket, comprising at least a first and a second polymer layer, wherein, seen with respect to the longitudinal axis of the press jacket, a first polymer layer is the radially outermost polymer layer thereof and, seen in the radial direction of the press jacket, has a thickness that is at most 60% of the overall thickness of the press jacket, wherein the first polymer layer comprises channels or holes, which are incorporated in the radially outermost lateral surface thereof and the depth of the channels or holes, seen in the radial direction of the press jacket, have a depth that corresponds at most to 95% of the thickness of the first polymer layer.

Description

Press cover and its use, as well as press roller and shoe press

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

There are enormous demands on the press shell in terms of its stability, namely with regard to surface hardness, resistance to pressure, temperature and hydrolysis. The press cover is also exposed during operation strong Biegewechselbelastungen. When entering the shoe rim - seen in the direction of rotation of the press jacket in front of the press nip - first takes a bend under a relatively small radius. This goes immediately into an opposite bend when passing through the press nips. When leaving the other shoe edge, ie - seen in the direction of rotation of the press jacket after the press nip - again an opposite bending. This deformation of the press jacket during entry and exit is also referred to as Alternate. It is readily apparent that the tendency of the press jacket, especially at this point to break, is very high due to the high mechanical stress. Accordingly, many measures are known from the prior art, which should increase the stability of the press jacket. The press cover must therefore be sufficiently flexible to allow it to pass around the shoe, it must be sufficiently stiff so that it does not deform or compress too much in the nip under the press load, and it must be sufficiently wear resistant. Press jackets therefore consist of a single-layer or multi-layer polymer layer, preferably of polyurethane, in which reinforcement threads in the form of loops or woven fabrics can be embedded.

The present invention relates to such initially mentioned, generic objects.

Multilayer press sleeves known from the prior art tend, during normal operation, to premature failure as a result of a - often only local - detachment of one of the polymer layers. This leads in practice to unplanned stoppages of the pressing device and thus to increased, costly downtime.

Generic press jackets have become known inter alia from US 2009/0038770 A1 and DE 102015217941 A1.

It is accordingly an object of the invention to provide a press cover which avoids the disadvantages of the prior art. In particular, a detachment of the individual polymer layers should be avoided, the service life of such a press jacket should be increased, and the downtimes of a press device equipped with such a press cover should be reduced.

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

The inventors have recognized that a detachment of the individual polymer layers can be avoided if the individual polymer layers exactly match one another are coordinated. This is the case when the thickness of the radially outermost polymer layer of a multilayer press jacket is altogether between at least 5 and at most 60%, preferably at most 55% of the total thickness of the press jacket, ie the thickness of all polymer layers. The values mentioned are meant to be inclusive. Although the mechanism of action could not be clarified conclusively, the inventors noticed that in such a thickness ratio, a press cover can be specified, which has a particularly low delamination tendency of the individual polymer layers during operation of the press. This knowledge is initially independent of the material used in the press jacket.

The advantages of the invention are particularly satisfactorily met if, in addition to the stated thickness ratio of the radially outermost polymer layer with respect to the entire press cover, grooves or bores are also provided in the radially outermost polymer layer. This is especially true when a certain ratio of the depth of such grooves or holes is chosen with respect to the thickness of the radially outermost polymer layer. Thus, the depth of the grooves or holes may be at least 35%, preferably at least 50% and at most 95% of the thickness of the radially outermost polymer layer.

Furthermore, the inventors have recognized that in addition to the two measures of the thickness and depth ratio of a delamination can be prevented by the fact that the first and the second polymer layer are performed differently in terms of their hardness. In this case, a difference of 1 to 6 Shore is sufficient, namely when the second polymer layer is made less hard than the first polymer layer.

If, according to the present invention, thickness or depth is used, then the greatest spatial extent is meant which is measured in the radial direction, ie perpendicular to the longitudinal axis of the press jacket. With total thickness is seen in a cross-section perpendicular to the longitudinal axis of the press jacket the To understand vertical distance between the radially outermost and radially innermost circumferential surface.

The advantages according to the invention are achieved particularly well if polyurethane is preferably used, as in the case of a press jacket according to one of claims 6 to 8.

When it is mentioned according to the invention that something is made of a fabric, it is meant that it is made partly or wholly of such a fabric.

For the purposes of the invention is meant by a pressing device, for example, a shoe press, for example, for dewatering or treatment, such as smoothing a fibrous web. The shoe press comprises a shoe press roll and a counter roll which together form or define a press nip. The shoe press roll further comprises a rotating press cover and a stationary pressing element, the so-called press shoe. The latter is supported on a supporting, also standing yoke - for example via hydraulic pressing elements - and is pressed against the rotating press cover. The press cover rotates relative to the fixed press shoe and yoke and is thereby pressed in the press nip against the counter roll. Press shoe and yoke are arranged radially inside the press jacket. By the term standing is meant that the pressing element does not rotate relative to the shoe press roll or the counter roll, but translational - on the counter roll to and away from her, preferably in the radial direction - and thus can move relative to the counter roll. In addition to the fibrous web and the press jacket, one or more press felts circulating endlessly in the circumferential direction and / or further endless circulating press bands can be guided through the press nip of the shoe press. Of course, such a shoe press may comprise more than one press nip. For the purposes of the invention, a fibrous web is to be understood as a scrim of fibers, such as wood fibers, synthetic fibers, glass fibers, carbon fibers, additives, additives or the like. So can the fibrous web be designed for example as a paper, cardboard or tissue web. It may essentially comprise wood fibers, with small amounts of other fibers or additives and additives may be present. Depending on the application, this is left to the skilled person.

Under a press cover in the context of the invention is a band, tube or a coat to understand the / as shown, together with a fibrous web is passed through the press nip of a shoe press. For dewatering the fibrous web, the radially outermost surface (polymer layer) of the press jacket can come into contact with a press felt during normal operation, from which the fibrous web to be dewatered is directly carried. Depending on the embodiment of the pressing device, e.g. To smooth this of the press cover in normal operation also come into direct contact with the fibrous web. The press cover is designed as a circumferentially continuous around its longitudinal axis, closed jacket (hose). At its axial ends it is - viewed in the width direction (along the longitudinal axis) - open. Thus, the press cover can be held at these axial ends of two lateral clamping disks to form the shoe press roll. Instead of the guide through the two side clamping discs, the press cover, as is the case with open shoe presses, can be guided over the press shoe and a plurality of guide rollers. Regardless of whether the press cover is guided by the clamping disks or the guide rollers, the press shoe (or the guide rollers) comes into contact with a part of the radially innermost surface of the press cover (temporarily). The radially outermost surface of such a press jacket, e.g. the radially outermost polymer layer thereof may be provided with grooves and / or blind bores.

The press cover may be partially or completely made of a polymer. In this case, a pourable, curable, preferably elastomeric polymer such as polyurethane can be used as the polymer. The polymer can thus be adjusted as cast elastomer. By polymer layer is meant a layer comprising or entirely made of such a castable, curable, preferably elastomeric polymer. The polymer layer may preferably be a hardened layer produced in one piece by primary shaping. In other words, this is a monolithic urgeformt, so produced by eg casting. The term one-piece also includes cases in which the one layer was again made by casting the polymer from multiple layers of the same material. However, this only insofar as these layers are essentially no longer visible after curing, but a single, preferably uniform layer results. The same applies accordingly for the finished press cover.

When providing a plurality of polymer layers, these can be arranged one above the other in the radial direction, at least in sections over the width of the press jacket. At least in sections over the width of the press jacket means that the press cover is, for example, only one layer at its axial ends, whereas it is formed two or more layers between the axial ends. However, the polymer layers can also extend over the entire width of the press jacket. Also, the thickness of the press jacket - and thus the thickness of the individual polymer layers - in a section through the longitudinal axis thereof vary in sections along the longitudinal axis. Thus, for example, the radially outermost polymer layer in the region of the width edges of the press jacket may be smaller than in the middle of the press jacket. In other words, in the region of the width edges, the radially outermost polymer layer may be less thick than a radially inner or radially innermost polymer layer. Preferably, exactly one, two or three polymer layers are provided. These may be identical in polymer or vary in hardness or stoichiometry of the prepolymer. A total thickness of the finished press jacket in a section through the longitudinal axis of the same measured in the radial direction may be 5 to 10 mm, preferably 5 to 7, particularly preferably 5 to 6 mm. According to the invention, when a single layer is provided, the press cover may be made of a single cast, ie monolithically, so that the single layer has the thickness just mentioned. A finished press cover according to the invention is one whose at least one polymer layer cured and possibly finished, so for the purpose mentioned in eg a shoe press is ready for use. Analog is meant by finished polymer layer, a layer which has cured.

In principle, it is conceivable that the press cover has a reinforcing structure. By the term reinforcing structure in the sense of the invention is meant an enhancement of the at least one layer containing or consisting of the polymer, ie the polymer layer. In this case, the reinforcing structure can be completely embedded in the polymer layer so that the reinforcing structure does not go beyond the boundary of the polymer layer. In other words, the polymer layer plays the role of a matrix surrounding the reinforcing structure and bonding to the matrix as a result of adhesion or cohesive forces. Such a reinforcing structure can textile line structures -. As yarns or threads - and / or textile fabrics - such. Woven, knitted, knitted, braided, or scrim - and made from an appropriate starting material, e.g. be produced by winding. Starting material is understood to be that material or semifinished product by means of which the reinforcing structure of the finished press jacket according to the invention is produced.

The term "at most" refers to an interval closed on the right-hand side, which encompasses all values between greater than 0 and the maximum specified value (maximum value). Is e.g. the term of "at the most 5" means the interval between (including or greater) 0.01 and (including or exactly) 5.

The invention also relates to a press roll, such as a shoe press roll, for a shoe press for dewatering a fibrous web, wherein the press roll has at least one press jacket according to the invention. The invention also relates to a shoe press for dewatering a fibrous web, preferably a paper, board, tissue or pulp web, comprising a press roll and a counter roll, which together form or define a nip, wherein the press roll comprises a rotating press cover, wherein the press cover is formed according to the invention.

Finally, the invention relates to the use of a press jacket according to the invention for a press, such as shoe press for dewatering a fibrous web, preferably a paper, board, tissue or pulp web.

The invention will be explained in more detail below with reference to the drawings without limiting the generality. In the drawings show:

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

Shoe press with a press cover according to a

Embodiment of the present invention.

Embodiments of a press jacket in each case seen in a section through the longitudinal axis thereof; a highly schematic representation of an apparatus for producing the press jacket in a side view.

FIG. 1 shows, in a partially sectioned, schematic side view, a shoe press 10, which in the present case comprises a press roll according to the invention, such as a shoe press roll 12, and a counter roll 14. Shoe press roll 12 and counter roll 14 are arranged with respect to their longitudinal axes parallel to each other. Together they form or limit a nip 22. While the counter-roller 14 here consists of a cylindrical roller which rotates about its longitudinal axis, the shoe press roller 12 consists of a shoe 16, a stationary yoke 18 carrying it and a press cover 20 composed. Shoe 16 and yoke 18 are fixedly arranged with respect to the counter-roller 14 and the press cover 20, respectively. That means they do not rotate. In this case, the shoe 16 is supported by the yoke 18 and pressed by means not shown, hydraulic pressing elements to the radially innermost surface of the relatively encircling press jacket 20. The press jacket 20 which surrounds the shoe 16 and the yoke 18 in the circumferential direction, rotates about its longitudinal axis in the opposite direction of rotation to the counter-roller 14. Due to the concave configuration of the shoe 16 on its side facing the counter-roller 14, a comparatively long nip 22 results.

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

In another, not shown in the figures embodiment of the invention can be dispensed with the press felts 26, 26 '. In such a case, the fibrous web 24 on the one hand with the press cover 20 and on the other hand with the counter-roller 14, which together form a press nip, in direct contact. The latter can then be designed as a heated drying cylinder. The press cover shown in Figure 1, as shown in the following figures, be executed according to the invention. FIGS. 2 a and 2 b show different embodiments of the invention in a cross section through the longitudinal axis 20 'of the finished press jacket 20 which is not to scale, in part illustrated. The distance between the longitudinal axis 20 'to the radially innermost surface of the corresponding polymer layer of the press jacket 20 is also not shown to scale.

According to FIG. 2a, exactly two polymer layers are provided, namely a first 20.1 and a second 20.2. In the present case, however, the second polymer layer 20.2 is at the same time the radially innermost polymer layer of the press jacket 20. Both polymer layers 20.1, 20.2 adjoin one another directly in the radial direction, ie. there is no intermediate layer between these two.

As shown, a reinforcing structure 20 "may be provided in the second polymer layer 20.2 In the present case, a reinforcing structure 20" is embedded in the single polymer layer 20.1. This is indicated by the hatched circles, which may be textile area or line formations such as fibers. The reinforcement structure 20 "is completely embedded in the second polymer layer 20.2, which means that the reinforcement structure 20" does not extend beyond the boundaries of the polymer layer 20.2.

In the present case, the first and a second polymer layer 20.1, 20.2, made of a polyurethane. This is available from a prepolymer and a crosslinker.

The thickness d of the first polymer layer 20.1, as viewed in the radial direction, is less than half the total thickness D of the entire according to the invention Press mantle 20, so the thickness of all polymer layers 20.1, 20.2 considered together.

FIG. 2b shows, in a modification to FIG. 2a, a three-layer press jacket. This comprises a - here radially outermost - first polymer layer 20.1, a radially innermost, third polymer layer 20.3 and a sandwiched between these two second polymer layer 20.2. The arrangement relates - as well as in the illustration of FIG. 2a - viewed from the longitudinal axis 20 'of the press jacket 20 in its radial direction. In the present case, a (single) reinforcing structure 20 "is provided only in the second polymer layer 20.2 Of course, this could also be different, so that alternatively or additionally such a reinforcing structure 20" could also be arranged in the first polymer layer 20.1 and / or the third polymer layer 20.3. Again, the first and the second polymer layer 20.1, 20.2 are each made of a polyurethane or contain such. This statement also applies analogously to FIG. 2a. Due to the fact that the thickness ratio d of the first polymer layer 20.1 according to the invention is also chosen with respect to the total thickness D of the press jacket 20, the result is a press jacket with which detachment of the individual polymer layers from one another is avoided.

3 shows a highly schematic side view of an apparatus for producing a press jacket 20 according to the invention. In the present case, the apparatus has exactly one cylindrical winding mandrel 4, in which case a starting material 20 "'is applied spirally on its radially outermost peripheral surface. "forms after embedding in the polymer, the reinforcing structure 20" of the finished press jacket 20 according to the invention. The diagram shows an initial stage of the manufacturing process. In the present case, for this purpose, one end of the starting material 20 "'on a polymer, which is arranged on the outer circumference of the winding mandrel 4, attached. Apart from the schematic representation shown, one end of the output mate neck 20 "could also rest directly on the winding mandrel 4 or be applied without initially providing a polymer between starting material 20"'and winding mandrel 4. The starting material 20 "'can be a textile fabric or a line structure.

The mandrel 4 is rotatably mounted about its longitudinal axis 20 ', which corresponds to the longitudinal axis of the press jacket to be produced. Longitudinal axis 20 'extends perpendicular to the plane of the drawing. Via a conduit 5, a pouring nozzle 6, such as pourable, curable elastomeric polymer, e.g. Polyurethane, from the top onto the radially outermost lateral surface of the winding mandrel 4 or onto the starting material 20 '' Such a casting material can be selected, for example, with regard to its pot life and viscosity such that it does not drip off the winding mandrel 4 during casting At the same time as this rotation, the casting nozzle 6 is guided along this along the winding mandrel 4 by a suitable guide, not further shown in Fig. 3, parallel to the longitudinal axis 20 ' Starting material 20 "'unrolled and wound on the rotating winding mandrel 4 to helices. In this case, the casting material can pass through the starting material 20 '' as far as the winding mandrel 4. In this example, after the hardening step, the polymer forms a radially innermost and preferably elastomeric polymer layer, which corresponds to the polymer layer 20.2 of the press jacket from FIG in Fig. 3, only a part is shown.

The pouring material emerging from the pouring nozzle 6 is a mixture of a prepolymer and a crosslinking agent. The former is provided from a prepolymer container, not shown, in which it is stored or stirred. The prepolymer may comprise an isocyanate of the invention and a polyol. In the prepolymer container, for example, it may be in the form of a prepolymer of the aforementioned substances. The crosslinker may be provided in a crosslinker tank. It is executed according to the invention.

Prepolymer containers and crosslinker containers are associated with the device for producing a press jacket 20. They are connected via lines also not shown in flow with one of the casting nozzle 6 in the flow direction upstream mixing chamber (not shown). The prepolymer crosslinker mixture is thus produced upstream and outside of the pouring nozzle 6, ie mixed in the mixing chamber. Regardless of the preparation of the mixture, this is then applied to the surface of the winding mandrel 4 to form the at least one polymer layer of the press jacket 20.

By means of such a continuous casting process, which is also known as rotational molding, an endless, about its longitudinal axis 20 'self-contained cylindrical tube-shaped press cover 20 is gradually produced over the width of the winding mandrel 4, whose inner circumference substantially corresponds to the outer circumference of the winding mandrel 4 ,

In principle, it would be conceivable to wind the starting material 20 "'on more than one winding mandrel 4 shown in Fig. 3. For example, two winding mandrels could be provided which could be arranged parallel to one another with respect to their longitudinal axes at a distance from one another Polymer also on the radially inner circumferential surface of the winding mandrel 4, for example, by the manner of spinning applied .Indeed of the mentioned embodiment, the finished press cover 20 is finally removed from the at least one winding mandrel 4.

As shown in Fig. 3, the press cover 20 is executed according to the invention.

Although not shown in the figures, the reinforcing structure 20 "of the at least one polymer layer 20.1, 20.2 could also consist of a plurality of radially superimposed, each in the longitudinal axis direction and in Circumferential direction of the press jacket 20 extending starting materials 20 "'be constructed.

Claims

claims

1 . Press cover (20) comprising a plurality of polymer layers (20.1, 20.2), wherein a first polymer layer (20.1) with respect to the longitudinal axis (20 ') of the press cover (20) seen its radially outermost polymer layer and in the radial direction of the press cover (20) seen has a thickness which is at most 60% of the total thickness of the press jacket (20), wherein the first polymer layer (20.1) comprises grooves or bores which are introduced into the radially outermost lateral surface and the depth of the grooves or bores in the radial direction of the press jacket (20 ) have a depth which corresponds to at most 95% of the thickness of the first polymer layer (20.1).

2. Press cover (20) according to claim 1, characterized in that the thickness of the first polymer layer (20.1) at least 5%, preferably at most 55% of the total thickness of the press jacket (20).

3. Press cover (20) according to claim 1, characterized in that the depth of the grooves or holes at least 35%, preferably at least 50% of the thickness of the first polymer layer (20.1) corresponds.

4. Press cover (20) according to any one of claims 1 to 3, characterized in that press cover (20) comprises a second, with respect to the longitudinal axis (20 ') seen its radially innermost polymer layer (20.2).

5. Press cover (20) according to claim 4, characterized in that the first and second polymer layer (20.1, 20.2) each contain or are made of a polyurethane, and the polyurethane is formed from a prepolymer and a crosslinker, wherein the prepolymer of first polymer layer (20.1) from a reaction product

- 1, 4-phenylene diisocyanate (PPDI), naphthalene-1, 5-diisocyanate (NDI) or 3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI) and at least one Polyol is selected from a polyether polyol, polycarbonate polyol, a polyether-polycarbonate polyol, or

4,4'-diphenylmethane diisocyanate (MDI) and at least one polyol selected from a polycarbonate-polyol, a polyether-polycarbonate-polyol, or

- mixtures thereof.

6. Press cover (20) according to claim 5, characterized in that the prepolymer of the second polymer layer (20.2) is a reaction product of:

4,4'-diphenylmethane diisocyanate (MDI), toluene-2,4-diisocyanate (TDI) or naphthalene-1, 5-diisocyanate (NDI) and at least one polyol selected from a polyether polyol, or

- mixtures thereof.

7. Press cover (20) according to claim 5 or 6, characterized in that the crosslinker 1, 4-butanediol (BDO), 1, 4-hydroquinones bis (2-hydroxyethyl) ether (HQEE), 4,4'-methylene bis ( 3-chloro-2,6-diethylanilines) (MCDEA), diethyltoluenediamines (DETDA), dimethylthiotoluenediamines (DMTDA) or mixtures thereof.

8. Press cover (20) according to any one of the preceding claims, characterized in that the first and the second polymer layer (20.1, 20.2) seen in the radial direction adjacent to each other.

9. Press cover (20) according to any one of the preceding claims, characterized in that the hardness of the first polymer layer (20.1) is between 90 and 98 Shore A.

10. Press cover (20) according to any one of the preceding claims, characterized in that the hardness of the second polymer layer (20.2) is between 90 and 96 Shore A.

1 1. Press cover (20) according to one of the preceding claims, characterized in that the first and the second polymer layer (20.1, 20.2) differ in their hardness between 1 and 6 Shore A, wherein the second polymer layer (20.2) is less hard than the first Polymer layer (20.1).

12. Press roll, such as shoe press roll (12), for a shoe press (10) for treating a fibrous web (24), characterized in that the press roll has at least one press cover (20) according to one of the preceding claims.

Shoe press (10) for treating a fibrous web (24), preferably a paper, board, tissue or pulp web, comprising a press roll and a backing roll (14) together form or define a nip (22), wherein the Press roller comprises a rotating press cover, characterized in that the press cover (20) according to one of claims 1 to 1 1 is formed.

14. Use of a press jacket (20) according to any one of claims 1 to 1 1 for a press, such as shoe press (10) for treating a fibrous web (24), preferably a paper, board, tissue or pulp web.