Dewatering element for dewatering a fibrous web

Abstract

The invention relates to a dewatering element (1) for dewatering a fibrous web and comprises a wear body (3) having a sliding surface (4) and is characterized in that the wear body (3) is in the form of a ceramically reinforced polymer substrate. The dewatering element can be advantageously produced and recycled.

Description

[0001] DRAINAGE ELEMENT FOR DRAINING A FIBRE WEB

[0002] The invention relates to a dewatering element for dewatering a fibrous web guided on a fabric over the dewatering element, comprising a wear body that forms a sliding surface, wherein, for dewatering the fibrous web, the fabric can be guided over the wear body in direct contact with the sliding surface. The invention further relates to a dewatering device for use in a machine for producing the fibrous web, in particular a paper or pulp web, comprising the dewatering element according to the invention.

[0003] To produce a fibrous web, in particular a paper or pulp web, a fibrous suspension is formed and fed via a headbox to the sheet forming unit of the machine. In the sheet forming unit, the fibrous web is formed from the suspension by dewatering. For this purpose, the suspension is guided onto a clothing, which in turn is guided over the various dewatering elements, such as dewatering bars, or dewatering devices, such as a forming shoe or a dewatering table. This ensures direct contact between the clothing and the dewatering element, with the dewatering element forming a sliding surface for the clothing. The typically high machine or clothing speeds of e.g. 2000 m / min and the abrasive effect of the clothing moving relative to the dewatering elements result in high demands on the dewatering elements.On the one hand, the frictional resistance of the sliding surface should be minimal to achieve the lowest possible frictional power. On the other hand, wear on the sliding surface of the drainage elements should be minimal to ensure the longest possible service life of the covering and the drainage elements.

[0004] Dewatering elements that allow an optimal compromise between frictional resistance and wear are known from the prior art. EP4101977, for example, discloses a scraper bar. This is made of metal or plastic and is equipped with a plurality of wear elements made of a wear-resistant material, in particular ground ceramic plates, on the upper side facing the screen belt. The wear elements are mounted on a support bar and arranged in a row along the longitudinal extent of the scraper bar. EP4101977 further states that scraper bars, which can be up to 12 m long, must be manufactured precisely to the respective width of the paper machine and therefore must be produced individually. This design has the disadvantage that it is expensive, results in long delivery times, and cannot be produced in stock.

[0005] The aim of the invention is a dewatering element whose wear body can be easily produced, wherein the wear body can be easily adapted to the respective width of the paper machine and, in particular, can be easily constructed as a single piece across the entire width of the dewatering element. A further aim of the invention is a dewatering element wherein the valuable materials contained in the wear body are easily recycled after use and can be reused, in particular, in the production of wear bodies for dewatering elements.

[0006] This is achieved according to the invention in that the wear body is designed as a ceramic-reinforced polymer substrate, wherein ceramic particles are incorporated into the polymer substrate. The wear body is thus designed as a polymer substrate, wherein ceramic particles are incorporated into the polymer substrate, which bring about the ceramic reinforcement of the polymer substrate. A covering guided over the wear body is in direct contact with the wear body via the sliding surface. The ceramic reinforcement of the polymer substrate, i.e. the particles incorporated in the polymer substrate, bring about the high resistance to abrasion. In particular, a higher ceramic proportion in the wear body allows for an improvement in abrasion resistance or wear resistance. In accordance with the definition of a ceramic, the ceramic particles are made of a material with a crystalline or crystalline / amorphous structure or microstructure.The design of the wear body as a polymer substrate is advantageous in itself, since the polymer substrate imparts improved strength, in particular impact resistance, and improved toughness, or reduced brittleness, to the wear body. In particular, the polymer substrate imparts the advantageously low coefficient of friction and thus low frictional resistance, wherein the polymer substrate fills the cavities between the ceramic particles and enables the formation of a substantially smooth sliding surface of the wear body. The article according to the invention thus has a synergistic effect. The positive effects, such as the high abrasion resistance of the inherently low impact-resistant ceramic particles, overlap with the positive effects of the polymer substrate, such as the improved impact resistance of the wear body and in particular the formation of low frictional resistance.The wear body according to the invention advantageously allows for repairs, in particular by patching up local defects. Such local defects are formed, for example, as breakouts. For repair, the local defect is simply treated with the ceramic-reinforced polymer substrate, or the breakout is closed. Furthermore, a simple design of the wear body is possible. Likewise, there are no significant restrictions regarding the achievable width of the drainage body, which allows a one-piece design of the wear body or drainage element. In particular, the labor-intensive construction of the wear body from a plurality of flat-ground ceramic plates, known primarily from the prior art, can be eliminated. The solution according to the invention also advantageously allows for the recycling of the wear body.The application of appropriately high temperatures leads to the decomposition or degradation of the polymer substrate of the wear body, and the ceramic particles are released or made available again as a valuable material. This is particularly advantageous because this thermal decomposition of the wear body does not adversely change its properties. In particular, it eliminates the need to grind the wear bodies to be recycled, thus ensuring that the grain size distribution and particle diameter of the ceramic particles are not adversely affected.

[0007] The polymer substrate of the drainage element is advantageously designed as a duromer. Duromers are plastics that, once cured, can no longer be deformed by heating or other means. This is particularly advantageous for the application according to the invention, since considerable amounts of heat can be introduced into the wearing body as a result of the frictional power transferred from the covering to the drainage element. The polymer substrate designed as a duromer thus allows the dimensional stability and operational strength to be maintained at typical operating temperatures or design temperatures of drainage elements. Duromers can be permanently thermally stable up to a temperature of <=100°C, advantageously <=80°C, i.e. they do not exhibit any softening. After the duromers have cured, however, further machining can be carried out by machining.In general, thermosets are characterized by high mechanical strength, although these strength properties are essentially unaffected by temperature. In particular, thermosets allow for very good incorporation of ceramic particles because they have an advantageously high adhesive force and are therefore an optimal polymer substrate. In particular, the polymer substrate designed as a thermoset gives the wear body an advantageously low coefficient of friction and thus low frictional resistance. In addition, a particularly simple design of the wear body is possible, e.g. by producing the wear body using a casting process, in particular a vacuum casting process. Casting can take place at room temperature, for example. The wear body produced in this way already has very smooth surfaces after casting, which means that post-processing of the surfaces is unnecessary or only necessary to a minimal extent.Manufacturing using a casting process also allows for considerable flexibility in the feasible geometry of the wear body. This allows for easily creating curved geometries, such as the ledges in forming shoes. Likewise, localized defects in the wear body can be effectively repaired using a casting process.

[0008] Likewise advantageously, the wear body of the drainage element is produced from a ceramic-reinforced polymer synthetic resin, in particular epoxy resin, in particular using a casting process. The substrate is formed from the synthetic resin, with a vacuum casting process being particularly advantageous. Casting can take place, for example, at room temperature. Synthetic resins are, for example, precursors, i.e. prepolymers, for the formation of thermosets. Advantageously, these precursors are liquid or soluble and can be easily mixed with fillers, in particular ceramic particles. This makes it possible to easily form the wear body, in particular by shaping the wear body using a casting process, wherein the synthetic resin is cast together with the incorporated ceramic particles. Typically, the prepolymers are polymerized and crosslinked with the aid of hardeners and possibly catalysts.The use of an epoxy resin system as a polymer resin is particularly advantageous, as this allows for advantageous integration of the ceramic particles. When mixed with a hardener, the epoxy resin system reacts to form a thermoset, exhibiting advantageous mechanical properties and temperature resistance after curing.

[0009] A favorable embodiment of the invention is characterized in that the mass fraction of the ceramic particles in the ceramic-reinforced polymer substrate is 60%-99%, in particular 70%-98%, and particularly advantageously 80%-96%. A higher mass fraction of the ceramic particles is associated with greater wear resistance of the wear body. A higher polymer substrate fraction, in turn, is advantageous with regard to the impact resistance and toughness of the wear body. The mass fraction of the ceramic particles in the wear body is capped to ensure homogeneous integration of the ceramic particles into the polymer substrate.

[0010] A further advantageous embodiment of the invention is characterized in that the incorporated ceramic particles are formed from Si carbide, Si nitride, Al oxide, Zr oxide, or zirconium dioxide-reinforced aluminum oxide. These specific ceramics are particularly favorable in terms of their wear resistance. Advantageously, all ceramic particles in a wear body consist of the same specific ceramic. Equally advantageously, ceramic particles made of different specific ceramics can be present in a wear body.

[0011] An advantageous embodiment of the invention is characterized in that the ceramic particles have a diameter, in particular measured by laser diffraction according to ISO 13320:2020, of less than 1.5 mm and in particular less than 1 mm, and the diameter of the ceramic particles is most frequently between 0.1 mm and 0.4 mm and in particular between 0.2 mm and 0.3 mm. Excessively large diameters of the ceramic particles should be avoided, since larger particles break off more easily from the polymer substrate or the sliding surface during operation. The ceramic particles are preferably polydisperse, wherein a mixture of ceramic particles with different diameters is present.Polydisperse ceramic particles can be embedded particularly well in the polymer substrate, whereby a high space filling by the ceramic particles in the polymer substrate is possible and a low mass fraction of the polymer substrate in the wear body allows a secure integration of the ceramic particles into the wear body.

[0012] A further advantageous embodiment of the invention is characterized in that the dewatering element is designed for use in a machine for producing the fibrous web, in particular a paper or pulp web. The dewatering element is preferably designed as a bar, in particular as a scraper bar, dewatering bar, forming bar, or as a covering, in particular as a screen table covering, former covering, suction bar covering, wet vacuum covering, separating vacuum covering, felt vacuum covering or as a perforated plate for dewatering. Typically, the dewatering element or the bar extends over the entire working width of the clothing or the working width of the machine. The dewatering elements can also be arranged in the machine direction, i.e. in the direction of movement of the clothing, in which case a plurality of dewatering elements is arranged transversely to the machine direction to form a dewatering device, in particular a forming shoe.

[0013] In an advantageous embodiment of the dewatering element, the wear body is designed as a single piece, in particular across the working width of the clothing. The working width of the machine essentially corresponds to the working width of the clothing or the width of the fibrous web. A single-piece design of the wear body across the entire working width of the clothing is advantageous because the modular design of the wear body using ceramic plates, as known from the prior art, is very complex and labor-intensive and can be omitted. This single-piece production across the working width is made possible by designing the wear body as a ceramic-reinforced polymer substrate, whereby the wear body can be manufactured as a single piece across the entire working width, in particular using a casting process.

[0014] In a further advantageous embodiment of the drainage element, the wear body is divided into parts across the working width of the covering. To form the drainage element, the parts of the wear body are arranged in a row. The division of the wear body or the drainage element allows for easier delivery of the drainage element from the production site to the place of use. By designing the wear body as a ceramic-reinforced polymer substrate, it is easily possible to divide the wear body into longer parts. Preferably, the drainage element comprises a wear body, wherein the wear body is divided across the working width of the covering into a maximum of 10 parts, more advantageously into a maximum of 8 parts, and particularly advantageously into a maximum of 6 parts. The parts of the wear body are advantageously connected by adhesive bonding and / or form-fitting.The positive-lock connection can be achieved, in particular, by interlocking the wear body parts. The combination of adhesive bonding and positive locking allows for a particularly resilient connection of the wear body parts.

[0015] In an advantageous embodiment of the invention, the wear body of the drainage element is additionally designed as a support strip for being received in a frame. In the prior art, ceramic elements or plates are constructed to form a wear body which is connected to a support strip. The drainage element thus conventionally designed can be received in a frame via the support strip. Due to the inventive design of the wear body as a ceramic-reinforced polymer substrate, the wear body can be manufactured very easily and, in particular, complex geometries, such as for the design of the wear body as a support strip, can be realized simply and cost-effectively. In particular, the wear body can be manufactured using a casting process, which means there are hardly any restrictions with regard to shaping.

[0016] In an equally advantageous embodiment of the invention, the drainage element comprises, in addition to the wear body, a support strip, in particular made of fiber-reinforced plastic or a polymer substrate. The formation of support strips from fiber-reinforced plastic is advantageous. Advantageously, however, the support strip can also be made of the polymer substrate, whereby the incorporation of ceramic particles into the support strip can be omitted. This offers the advantage that the polymer substrate has good strength, in particular impact resistance, and good toughness, or reduced brittleness. The wear body and support strip can be connected by positive and / or non-positive engagement. Non-positive engagement can be achieved, for example, by gluing, whereby a combination of positive and non-positive engagement results in a particularly resilient connection.In a particularly preferred embodiment, the wear body is applied to the support bar in a casting process - forming a positive and / or force fit.

[0017] The invention also relates to a dewatering device for dewatering a fibrous web in a machine for producing a paper or pulp web, wherein the dewatering device comprises at least one dewatering element according to the invention. In particular, the dewatering device can be designed as a forming shoe, forming table, suction box, in particular a wet suction box, separating suction box, felt suction device, flat suction device, etc. When forming a forming table, dewatering elements are typically designed, in particular, as strips transverse to the machine direction. A forming shoe is typically constructed from dewatering elements aligned in the machine direction, with a plurality of dewatering elements then being arranged transversely to the machine direction to form the dewatering device.

[0018] The invention will now be described by way of example with reference to the drawings.

[0019] Fig. 1 shows a machine for producing a paper or pulp web with dewatering devices and dewatering elements according to the state of the art.

[0020] Fig. 2 shows a drainage device with drainage elements according to the prior art.

[0021] Fig. 3 shows a drainage element according to the state of the art.

[0022] Fig. 4 shows a drainage element according to the invention.

[0023] Fig. 5 shows another drainage element according to the invention.

[0024] Fig. 1 shows a machine 5 for producing a paper or pulp web with dewatering devices 9 and dewatering elements 1 according to the prior art, wherein a Fourdrinier or fourdrinier wire former is shown. A fiber suspension is applied to a fabric 2 via a headbox 10 and is guided for dewatering over various dewatering devices 9, e.g., the screen table, dewatering boxes with strip-shaped dewatering elements, and dewatering boxes with pad-shaped dewatering elements. The dewatering of the fiber web takes place through the fabric 2, wherein the fabric 2 is in direct contact with the dewatering elements 1 and slides over the dewatering elements 1, wearing them down.

[0025] Fig. 2 shows a dewatering device 9 with dewatering elements 1 according to the prior art, wherein a dewatering box with strip-shaped dewatering elements 1 is shown. The fibrous web lying on the clothing 2 is guided over the dewatering elements 1 and dewatered in the process. The individual dewatering element 1 is designed here as a strip or dewatering strip and comprises a wear body 3 which forms a sliding surface 4, wherein the clothing 2 is guided in direct contact with the sliding surface 4 for dewatering the fibrous web. In the prior art, the wear bodies 3 are composed of sintered ceramic plates. The dewatering element 1 further comprises a support strip 8, wherein the dewatering element 1 is connected to a framework or the box via the support strip 8. The connection between the ceramic wear body 3 and the support strip 8 is made, for example, by gluing.

[0026] Fig. 3 shows a dewatering element 1 according to the prior art. The illustration covers the entire working width 6 of the machine or the fabric 2. Thus, in the prior art, the wear body 3 is formed as a sintered ceramic, with the wear body 3 being constructed in detail from individual ceramic plates 11, which are arranged in a row and connected.

[0027] Fig. 4 shows a drainage element 1 according to the invention, which is designed as a drainage strip. The wear body 3 is designed as a ceramic-reinforced polymer substrate, wherein ceramic particles are incorporated into the polymer substrate. In particular, the polymer substrate is designed as a duromer, wherein the wear body 3 is produced from a ceramic-reinforced polymer synthetic resin, in particular epoxy resin, using a casting process. The mass fraction of the ceramic particles in the ceramic-reinforced polymer substrate is advantageously 80%-96%. In addition to the wear body 3, the drainage element 1 comprises a support strip 8 for connecting the drainage element 1 to a framework (not shown). The support strip 8 can be made of fiber-reinforced plastic, but in particular also of the polymer substrate.The connection between the wear body 3 and the support bar 8 in the illustrated drainage element 1 is achieved by a positive and non-positive connection, with the positive connection being achieved via a dovetail joint. The wear body 3 is applied to the support bar 8 using a casting process, whereby the wear body 3 and the positive and non-positive connection with the support bar 8 are formed. The illustrated drainage element 1, and in particular the wear body 3, can be a single piece across the working width 6 of the covering or the machine, or can be divided into parts.

[0028] Fig. 5 shows a drainage element 1 according to the invention, which is also designed as a drainage strip. The drainage element 1 shown here differs from the embodiment shown in Fig. 4 in that the wear body 3 is also designed as a support strip 8 for reception in a frame. Advantageously, the drainage element 1 comprising the wear body 3 and the support strip 8 can thus be manufactured in a single manufacturing step, e.g., by a casting process. The drainage element 1 shown is advantageously one-piece across the working width 6 of the covering 2 or the machine 5, or divided into parts.

[0029] The present invention offers numerous advantages. The dewatering element according to the invention, in particular its wear body, can be produced simply and with little labor-intensiveness, wherein the wear body can be manufactured for the respective width of the paper machine and in particular can be produced in one piece over the entire width of the clothing or machine. There is also great flexibility with regard to the realizable geometry of the wear body. Curved geometries can thus be easily realized, e.g. by a casting process. In particular, the invention is characterized by a synergistic effect, wherein a wear body designed as a ceramic-reinforced polymer substrate advantageously has high resistance to abrasion and also has improved strength, in particular impact resistance, improved toughness or reduced brittleness, and a low coefficient of friction orIt has low frictional resistance. Local defects in the wear body can also be easily repaired. Furthermore, the valuable materials contained in the wear body, i.e., the ceramic particles, are easily recycled after use without adversely affecting the ceramic particles. The ceramic particles can then be reused in the manufacture of wear bodies for drainage elements.

[0030] Reference symbol

[0031] (1 ) Drainage element

[0032] (2) Covering

[0033] (3) Wear body (4) Sliding surface

[0034] (5) Machine

[0035] (6) Working width

[0036] (7) Part

[0037] (8) Support bar (9) Drainage device

[0038] (10) Headbox

[0039] (11 ) Ceramic plate

Claims

Patent claims 1. Dewatering element (1) for dewatering a fibrous web guided on a fabric (2) over the dewatering element (1), comprising a wear body (3) which forms a sliding surface (4), wherein for dewatering the fibrous web the fabric (2) can be guided over the wear body (3) in direct contact with the sliding surface (4), characterized in that the wear body (3) is designed as a ceramic-reinforced polymer substrate, wherein ceramic particles are incorporated into the polymer substrate.

2. Dewatering element (1) according to claim 1, wherein the dewatering element (1) is designed for use in a machine (5) for producing the fibrous web and the dewatering element (1) is designed as a strip, in particular a scraper strip, dewatering strip, forming strip or as a covering, in particular as a sieve table covering, former covering, suction bar covering, wet vacuum covering, separating vacuum covering, felt vacuum covering or as a perforated plate for dewatering.

3. Drainage element (1) according to one of the preceding claims, wherein the wear body (3), in particular over a working width (6) of the covering (2), is in one piece.

4. Drainage element (1) according to one of claims 1 to 2, wherein the wear body (3) is divided into parts (7) over a working width (6) of the covering (2) and the parts (7) of the wear body (3) are arranged in a row to form the wear body (3).

5. Drainage element (1) according to claim 4, wherein the parts (7) of the wear body (3) are connected by gluing and / or by positive locking, in particular in the form of positively interlocking parts (7) of the wear body.

6. Drainage element (1) according to one of the preceding claims, wherein the wear body (3) is also designed as a support strip (8) for receiving in a frame.

7. Drainage element (1) according to one of claims 1 to 5 with a support strip (8) in particular made of fiber-reinforced plastic or polymer substrate, wherein the wear body (3) and the support strip (8) are form- and / or are connected in a force-locking manner and the support strip (8) is designed to be received in a frame.

8. Drainage element (1) according to claim 7, wherein the wear body (3) is applied to the support strip (8) in a casting process.

9. Drainage element (1) according to one of the preceding claims, wherein the incorporated ceramic particles are formed from Si carbide, Si nitride, Al oxide, Zr oxide or zirconium dioxide-reinforced aluminum oxide.

10. Drainage element (1) according to one of the preceding claims, wherein the ceramic particles have a diameter, the diameter of the ceramic particles is less than 1.5 mm and in particular less than 1 mm and the diameter of the ceramic particles is most often between 0.1 mm and 0.4 mm and in particular between 0.2 mm and 0.3 mm.

11. Drainage element (1) according to one of the preceding claims, wherein the polymer substrate is formed as a duromer.

12. Drainage element (1) according to one of the preceding claims, wherein the wear body (3) is made of a ceramic-reinforced polymer resin, in particular epoxy resin, in particular using a casting process.

13. Drainage element (1) according to one of the preceding claims, wherein the mass fraction of the ceramic particles in the ceramic-reinforced polymer substrate is 60% - 99%, in particular 70% - 98% and particularly advantageously 80% - 96%.

14. Dewatering device (9) for use in a machine (5) for producing the fibrous web, in particular a paper or cellulose web, comprising at least one dewatering element (1) according to one of claims 1 to 13.

15. Dewatering device (9) according to claim 14, wherein the dewatering device (9) is designed as a forming shoe, screening table, suction box, in particular wet suction box, separating suction box, felt suction device, flat suction device, etc.

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