EP1251203B1 - Shoe press belt - Google Patents

Abstract

The shoe press belt, as a roller mantle to extract water from a wet web or provide a calendered surface finish, is composed of a pliable and impermeable elastomer layer and a textile reinforcement layer. The elastomer layer (9a) is of soft rubber with a hardness of 5-100 P and J, and preferably 20-50 P and J and especially 35 P and J. The rubber layer has blind drillings (9d). The textile layer (9b) is of modified glass fibers, carbon fibers and/or high tensile synthetic fibers

Description

The invention relates to a shoe press belt according to the preamble of claim 1.

Such a shoe press belt, which is also referred to in German as Preßmantel, is used in paper, board or tissue machines for extensive dewatering of the respective product (wet press) or for finishing the surface (calender) (see, eg EP 0 939 162 A2 ). The corresponding wet presses or calenders have an extended press nip ("Preßnip") and are therefore also referred to as shoe presses.

In its press nip comes the shoe press belt or the press cover on its back (bottom) with the actual press shoe in sliding contact and must therefore have on this page excellent sliding properties. On its front side (upper side), the shoe press belt comes into contact with a dewatering felt (and via this indirectly with the respective product) or - in the case of a calender - also directly with the product, which is pressed by a rotating roller.

In addition to the mentioned sliding properties of the back it comes here on the liquid impermeability of the Belts Neither water from the product or dewatering felt should reach the press shoe, nor may any lubricant enter the product or felt from it. In addition, certain elasticity and bending properties are required.

Shoe press belts are known in various designs from the prior art.

That's how it describes EP 0 420 372 B1 a generic shoe press belt with a base fabric in the form of an endless loop with inside and outside, smooth polymer resin coating, which makes the fabric impermeable to liquids and gives it a uniform thickness. As the polymer resin which forms the elastomer, here is called polyurethane.

From the DE 50 20 005 C1 is another band for use in paper machines, especially in wet presses with extended press nip (shoe presses), known. The tape has a smooth, liquid-impermeable belt layer on the back side and a carrier web and a fiber layer attached thereto on the front side.

Also from the DE 42 02 731 A1 a generic press cover for a shoe press is known which comprises an elastomeric jacket material and two layers of reinforcing threads. For the specification of the jacket material, reference is here made, on the one hand, to a swellable material and, on the other hand, to polyurethane.

From the WO 95/16820 is a paper machine fabric - especially a shoe press belt - described, in which a carrier fabric is provided with a polymer coating, which tixotropic material (for example, aramid or silica glass). As a base material is also specifically called polyurethane.

Finally, out of the DE 44 38 354 A1 another Preßmantel of elastomeric material known, in which a substantially parallel to the surface extending fabric layer of a high-strength material - such as aramid fibers - is embedded.

In contrast to these known solutions, the invention is based on the object of providing a shoe press belt with further improved service properties, in particular optimized elasticity properties and advantageous multi-dimensional curvature behavior, in order to achieve a smooth machine run with low drive power and a high overall running time.

This object is achieved by a shoe press belt with the features of claim 1. As a result of the invention, an improved wet press or calender for paper, board and tissue production is also provided.

The invention includes the basic idea of forming the shoe press belt with an elastomer layer of a very soft and conformable (and also reasonably inexpensive) elastomer, whereby it can be given an unusually low bending moment and a low overall modulus of elasticity. The combination of these advantageously adjusted parameters results in the achievement of the abovementioned, in several aspects improved performance properties.

According to the invention, the soft rubber elastomer layer of the belt comprises a highly abrasion resistant rubber compound of a plurality of rubber compositions. These compositions are particularly homogeneously mixed in the compound.

By selecting the specific composition or compositions, an adjustment of the hardness of the soft rubber layer according to the needs of the particular application, ie according to the customer, possible. The hardness is preferably in the range between 20 and 50 P + J, in a currently regarded as a standard variant execution at about 35 P + J.

In order to adapt the breaking strength of the belt to the high stresses, a fiber reinforcement or a composite material is incorporated in the elastomer layer. This textile reinforcing component is preferably formed according to the current state of knowledge as a scrim in the circumferential and / or longitudinal direction of the belt. Also, a design as a staple fiber fleece of short fibers - as an independent reinforcing layer or in combination with a further reinforcement, for example, the mentioned thread scrim, - appears to be useful. The use of a fabric as a reinforcing layer is possible.

In particular, modified glass fibers or carbon fibers, but in particular high-strength plastic fibers, can be used as reinforcing material. In the case of the latter, particular consideration is given to polyester and polyamide copolymers or aramid. In adaptation to customer requirements, combinations or mixtures of these materials can also be used appropriately.

The reinforcing layer is preferably incorporated close to the back in the elastomer-textile composite, on the one hand not to affect the rubber-elastic behavior on the front of the belt and on the other hand the lowest possible bending moment at the shoe curvature and at the belt ends and thus overall the intended optimization of the multi-dimensional curvature behavior to ensure.

In this sense, the total thickness of the Belts (in accordance with the elasticity and strength properties of the individual materials) in particular in the range between 5 and 10 mm, by default at about 7.5 mm, is selected.

The front of the belt can be made smooth, which will be particularly useful when used in a calender. But it can - especially for use in a wet press - also have a pronounced structure. At present, a structure with recesses in the form of blind holes appears to be preferred. These can be formed in particular approximately cylindrical and isolated from each other. But there are also structures with interconnected recesses, groove structures or similar. applicable.

Depending on the specific conditions of use, the open cross-sectional area of the structured front (ie, the total area of the recesses) suitably accounts for 10 to 50% of the frontal total area of the belt. For conventional wet press applications, an area fraction of the apertures of about 20% appears appropriate. The recesses have in particular lateral dimensions in the range between 0.5 and 5 mm, in particular between 1 and 3 mm. Their depth is suitably in the same range.

According to a further essential aspect of the invention, the shoe press belt has a significantly reduced stiffness compared to conventional Belts or - converted to the cross-section - bending stress. Thus, to achieve a deflection of 15 mm in a three-point bending test on a 30 mm wide and 5 mm thick specimen on two 100 mm spaced pads force is preferably 17 N or less, in particular 13 N or less, and the Bending stress is below 110 N / cm ² and in particular below 90 N / cm ² . In a practically preferred embodiment of the belt according to the invention, a force of 11 N and a bending stress of 70 N / cm ^{2 were} measured.

With such elasticity, it contributes significantly to the saving of drive power and smooth running of the respective wet press or calender, without the other hand, significant restrictions on the life would have to be taken into account. On the contrary, the reduced deformation-dependent material stresses even positively influence the running or service life of the belt.

Fig. 1

eine schematische Längsschnittdarstellung des Naßpressenabschnitts einer Papiermaschine und

Fig. 2

eine vereinfachte Querschnittsdarstellung einer Ausführungsform des erfindungsgemäßen Schuhpressenbelts einer solchen Naßpresse.

Moreover, advantages and expediencies result from the dependent claims and the following, sketch-like description of an exemplary embodiment with reference to the figures. From these show:

Fig. 1

a schematic longitudinal sectional view of the wet press section of a paper machine and

Fig. 2

a simplified cross-sectional view of an embodiment of the invention Schuhpressenbelts such a wet press.

1 shows a detail of the press nip of a wet press 1 of a paper machine with an extended press nip (shoe press). A press shoe 5 is disposed opposite a press shoe 3, and in the press nip 7 formed between both, a paper web 13 is dewatered between a shoe press belt 9 sliding on the press shoe 3, a press felt 11 and the surface of the press roll 5.

The shoe press belt 9 must on the one hand have an elasticity and flexibility which ensures the best possible contact with the curved surface of the press shoe 3 and the uniform application of an elastic pressure to the paper web 13 (via the press felt 11). On the other hand, it must be designed sufficiently stable in order to be able to cope with the high continuous load (tensile, compressive and Schwingungsbeansrpuchung) in the press nip 7 over an economically acceptable life. The hardness of the soft rubber is in the standard version at 35 P + J, but can be varied according to customer requirements by appropriate variation and mixture of rubber compositions within wide limits. The soft rubber can be used at operating temperatures above 100 ° C in continuous operation and can withstand temperature peaks of up to approx. 130 ° C.

A shoe press belt 9 suitable for meeting these requirements is shown schematically in cross-section in FIG. 2. This shoe press belt 9 has as a base a soft rubber band 9a, near the back of a textile reinforcing layer 9b is provided with a scrim of carbon fibers or modified glass fibers or aramid fibers. The total thickness of the belt is 7.5 mm; in the area of the lateral lips 9c approx. 5 mm. In the Belt front are blind holes 9d with a diameter of 2.5 mm and a depth of 2 mm. The total area of the openings is 20% of the front surface of the Belt.

The embodiment of the invention is not limited to this example, but also in a variety of modifications - both in terms of the materials of the individual components as well as in terms of geometric dimensions - possible.

LIST OF REFERENCE NUMBERS

1

A press

3

Press shoe

5

press roll

7

press nip

9

nip press

9a

Soft rubber band

9b

textile reinforcement layer

9c

lip

9d

blind holes

11

press felt

13

paper web

Claims (13)

1. Shoe-press belt (9) of a wet press or a calender with an elongated press gap, especially for a paper, cardboard or tissue-making machine, with a flexible, liquid-impermeable elastomer layer (9a) and a textile reinforcement layer (9b),
   characterised in that
   the elastomer layer (9a) comprises soft rubber, in particular, a highly abrasion-resistant rubber compound made of several rubber and/or silicon rubber compositions, with a hardness within the range between 5 and 100 P+J.
2. Shoe-press belt according to claim 1,
   characterised in that
   the hardness of the elastomer layer (9a) is disposed within the range between 20 and 50 P+J, preferably at approximately 35 P+J.
3. Shoe-press belt according to any one of the preceding claims,
   characterised in that,
   in the operational condition, the textile reinforcement layer (9b) is integrated into the elastomer layer (9a) close to the rear side facing towards a press shoe (3) in such a manner that it brings about no substantial change in the rubber-elastic properties of the elastomer layer (9a) on its front side.
4. Shoe-press belt according to any one of the preceding claims,
   characterised in that
   the textile reinforcement layer (9b) comprises modified glass fibres, carbon fibres and/or high-strength synthetic fibres.
5. Shoe-press belt according to any one of the preceding claims,
   characterised in that
   the textile reinforcement layer (9b) comprises an arrangement of threads in the circumferential and/or longitudinal direction of the shoe-press belt (9).
6. Shoe-press belt according to any one of the preceding claims,
   characterised by
   an overall thickness within the range between 5 and 10 millimetres, especially approximately 7.5 millimetres.
7. Shoe-press belt according to any one of the preceding claims,
   characterised by
   a structured front side, especially provided with recesses (9d) in the manner of blind boreholes.
8. Shoe-press belt according to claim 7,
   characterised in that
   the recesses (9d) provide lateral dimensions and a depth within the region between 0.5 and 5 millimetres, especially between 1 and 3 millimetres.
9. Shoe-press belt according to claim 7 or 8,
   characterised in that
   the open cross-sectional surface of the structured front side occupies a portion between 10 and 50%, especially of approximately 20%, of the total area of the front side.
10. Shoe-press belt according to any one of the preceding claims,
    characterised in that,
    in a three-point bending test with test item 30 millimetres wide and 5 millimetres thick on two supports disposed at 100 millimetres distance, a force of 17 N or less, especially 13 N or less must be exerted in order to achieve a bending of 15 millimetres, and a bending stress of 110 N/cm² or less, especially of 90 N/cm² or less occurs.
11. Shoe-press belt according to claim 10,
    characterised in that
    in the three-point test, a force of 11 N must be applied and a bending stress of 70 N/cm² occurs.
12. Wet press with an elongated press gap of a paper, cardboard or tissue-making machine, with a shoe-press belt according to any one of the preceding claims.
13. Calender with an elongated press gap of a paper, cardboard or tissue-making machine with a shoe-press belt according to any one of claims 1 to 11.

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