Clothes and their use in tissue machines

Abstract

The invention relates to a clothing, in particular a felt, for use in a machine for producing a cotton paper web, comprising a base structure having a textile structure with MD yarns and at least one layer of nonwoven fibers, characterized in that the MD yarns completely or predominantly have a diameter of between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm, and the linear density of the MD yarns is greater than 37%, in particular between 37% and 45%. The invention also relates to a machine and a method for producing a cotton paper web using such a clothing.

Description

[0001] The invention relates to a clothing for a machine for producing a tissue paper web, as well as to a machine and a method for producing a tissue paper web by means of such a clothing.

[0002] The production of tissue or toilet paper is still a market that is growing sharply. The machines usually used in the production of tissue paper are described in EP 1 167 115 B1. As in papermaking in general, a fibrous material suspension is also applied on the wire clothing or between two wire clothings, and dewatered by suction. After this, the fibrous web is further dewatered in the press, and then further thermally dried. Here, the fibrous web is transported to the press on the water-absorbing wire clothing. The water pressed out from the web is absorbed by the wire clothing and removed from the wire clothing again after the fibrous web is removed. This is achieved by means of a suction box, i.e., the so-called Uhle Box, as described in EP 2 602 387 B1 for example. Modern tissue machines are operated at very high production speeds, so that the residence time of the tissue paper web in the pressing nip is very short. Therefore, too little dewatering of the web in the press is usually a limiting factor that hinders the increase of the machine production speed.

[0003] The object of the present invention is therefore to propose a machine and a method for operating the machine which ensure improved dewatering of a tissue paper web.

[0004] The object of the present invention is also to propose a modification of existing systems which can be implemented without effort or with only low effort.

[0005] Another object of the invention is to specify a clothing which allows a significantly improved dewatering of a tissue paper web.

[0006] This technical problem is completely solved according to the invention by a clothing, a machine and a method. In the description there are other advantageous features according to the design of the invention.

[0007] In terms of a clothing, the technical problem is solved by a clothing, in particular a felt, for use in a machine for producing a cotton paper web. The clothing comprises a base structure which has or consists of a woven textile structure with MD yarns and CD yarns. In addition, the clothing comprises at least one layer of nonwoven fibers. According to the invention, the base structure consists of two endless fabric layers, wherein in both fabric layers the MD yarns completely or predominantly have a diameter between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm, and the linear density of the MD yarns is greater than 37%, in particular between 37% and 45%, wherein two fabric loops are connected to one another by sewing with needles to one or more nonwoven layers.

[0008] In this context, the term “completely or predominantly” is to be understood as meaning that at least 90%, preferably 95%, in particular all of the MD yarns have a diameter within the stated range.

[0009] The term “wire diameter” is used within the scope of this application. This term is clearly defined for circular wires.

[0010] For monofilaments having a shape other than circular, or also for threads formed from a plurality of monofilaments, the diameter of the thread is to be understood as the diameter of the smallest circle which encloses the cross section of the thread.

[0011] To determine the linear density of an MD yarn, the number of threads per length unit is multiplied by the diameter and the resulting value is divided by the length unit.

[0012] Thus, at 10 threads / cm and a thread diameter of 0.40 mm, a thread density of 10*0.4 mm / 10 mm=40% is obtained.

[0013] By combining fine MD yarns with a high MD yarn density, the basic structure can take on some of the functionality that is otherwise assumed by one or more nonwoven layers in the clothing, such as pressure equalization. The basic structure achieves a hitherto unachievable uniform pressure distribution through the felt. Tests by the applicant have surprisingly shown that clothing, in particular felt, with such a basic structure can be achieved with fewer nonwoven covering layers. This is not only ecologically advantageous due to the saved nonwoven layers, but also achieves improved dewatering when used in a tissue machine. With thinner felts, for example, in addition to Uhle Box dewatering, nip dewatering can also be achieved in the press of a tissue machine.

[0014] In a preferred embodiment, the basic structure consists of two endless or endless fabric layers, wherein in both fabric layers the MD yarns completely or predominantly have a diameter between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm, and the linear density of the MD yarns is greater than 37%, in particular between 37% and 45%. This can be a double-layer fabric or two separate fabric layers.

[0015] In a preferred embodiment, it can be provided that the textile structure is formed by a flat fabric, wherein the warp threads of the weaving machine are the MD threads of the clothing. The flat fabric can have a plain weave, for example.

[0016] The textile structure can advantageously consist of or include a woven fabric, a leno weave, a scrim or a knit.

[0017] When using a fabric as a base structure, it should be noted that a round fabric is usually used for the base structure of the clothing. This round fabric is rotated 90° to be loaded into the machine. The weft threads of the loom thus become the MD threads of the clothing, and the warp threads become the CD threads.

[0018] As an alternative to this, a flat fabric is used.

[0019] Paul Sudre in EP 0 425 523 B1 describes the principle of producing a seamed clothing with the aid of a flat fabric.

[0020] However, it is also possible to use a flat fabric with the length of the clothing to be produced and to connect the two end ends to each other. This also forms an endless fabric structure that can be used as a base structure or part of a base structure.

[0021] Since in a clothing the length in the machine direction (or longitudinal direction) is usually significantly greater than the width in the CD direction (or transverse direction) and the width of the weaving machine is large enough for the width of the machine, the desired flat fabric can be produced most easily by weaving a sufficiently long piece, wherein the warp threads then become the MD threads in the clothing. A 90° rotation as in a circular fabric is not necessary. This is very advantageous for a clothing according to one aspect of the invention. In a weaving machine, the warp threads can in principle be arranged arbitrarily close to one another, while two adjacent weft threads must therefore be spaced apart from one another so that, for example, in a plain weave, the warp threads alternate between each weft thread pair from top to bottom or vice versa from bottom to top. Due to this necessary spacing of the weft threads and the 90° rotation, such MD thread densities cannot be achieved or can only be achieved with great difficulty with conventional circular fabrics when using very fine threads. In a flat fabric, on the other hand, the warp threads used as MD threads can be arranged arbitrarily close to one another, thereby making it relatively easy to produce a clothing having the properties described in the invention.

[0022] When a flat fabric is used in the infrastructure, it can be made endless in an advantageous embodiment by connecting the ends at the ends. The connection can be realized in particular by welding. Ultrasonic welding and laser welding, in particular laser transmission welding, have proven to be suitable welding methods. If necessary, it can be advantageous to connect the two end ends by means of a connecting element. This can be, for example, one or more threads arranged in the CD direction and connected, in particular welded, to the MD threads at the two ends.

[0023] In an advantageous embodiment, it can be provided that the basic structure consists of two endless flat fabrics. The two fabric rings can then be combined into a double-layer structure. The two fabric rings can then be connected to one another, for example by sewing with a needle, with one or more nonwoven layers. As an alternative or in addition, other types of connection can also be provided, for example sewing or welding the two layers.

[0024] The basic structure can consist of a textile structure or can also include other elements. The basic structure can in particular also have other textile structures, such as other fabrics.

[0025] Different materials can be used for the MD yarns. Polyamides, such as PA6, PA6.6, are suitable, but also other polymers, such as PET. If CD yarns are present, these CD yarns can consist of the same or different polymers.

[0026] It can be provided that all MD yarns are of the same type. However, it is also possible to use MD yarns of different types. This can, for example, influence the fiber fixation or the dimensional stability. The MD yarns are advantageously monofilaments.

[0027] There are also different possibilities when selecting CD yarns. In addition to monofilaments, multifilaments or twisted yarns can also be used.

[0028] A suitable twisted wire can consist of 4 or 6 filaments. The filaments used can have a diameter of 0.15 to 0.25 mm. For example, a 0.2x2x2 twisted wire is very suitable.

[0029] In an advantageous embodiment, all CD yarns can be designed as twisted yarns. Here, all CD yarns can be composed of the same twisted yarns. Alternatively, different twisted yarns can also be used.

[0030] Also may be advantageous, both use twisted yarn and also use monofilament as CD yarn.Preferably, about 50% or more CD yarns are designed as twisted yarns.

[0031] In a preferred embodiment, twisted yarn and monofilament can be alternately set to CD yarn. In this case, if for example, separate CD yarn must be removed in order to form seam loops due to technical reasons, the twisted yarn share of CD yarn is 50% or slightly less than 50%.

[0032] In an advantageous embodiment, the clothing can have one or more nonwoven layers. The one or more layers can be arranged on the paper side and / or the running side of the clothing.

[0033] Preferably, the weight of the blanket is 750 g / m 2 Up to 1250g / m 2 Between, especially at 900g / m2 Up to 1100g / m 2 In special cases, the weight can be as high as 1400g / m 2 This refers to the total weight of the base structure and the nonwoven layer, if present.

[0034] It is very advantageous for the invention if the weight proportion of the nonwoven layer corresponds to a maximum weight proportion of the basic structure, in particular to a maximum of 2 / 3 of the weight proportion of the basic structure.

[0035] In felts used to make tissue paper, the weight share of nonwoven fibers is usually greater than the weight share of the base structure. The nonwoven fibers are usually 60% of the total weight and the base structure is 40% of the total weight.

[0036] Since, for the clothing proposed here, part of the functionality of the nonwoven layer is assumed by the base structure due to the combination of the MD yarn density and the MD yarn diameter, it is possible to reduce the amount of nonwoven fibers. This makes it possible to achieve a lighter and thinner felt.

[0037] In a preferred embodiment, the clothing can have a thickness of 3.5 mm or less, preferably a thickness between 2.5 mm and 3 mm. For this purpose, the thickness is determined at a pressure of 0.1 MPa.

[0038] In addition, the relative proportion of nonwoven fibers in the overall clothing is reduced. Thus, for example, a felt can be used in which the base structure and the nonwoven layer each account for 50% by weight. The base structure can even account for a larger proportion of the weight of the felt. If 60% of the total weight comes from the base structure and only 40% from the nonwoven fibers, the weight proportion of the nonwoven layer is only equivalent to 2 / 3 of the weight proportion of the base structure. In addition, during the service life of the clothing, the nonwoven layer is greatly compressed, thereby reducing important clothing properties, such as permeability. Since the proportion of nonwoven fibers in the overall clothing is small, these losses caused by the compression of the nonwoven fibers are smaller and the performance of the clothing remains within a tolerable range for a longer time.

[0039] However, it may also be advantageous if the paper side of the clothing has a certain amount of nonwoven fibers. This amount should not be less than 10% of the total weight of the clothing. It is also advantageous here if at least the upper side of the contact paper of the clothing is provided with nonwoven fibers having a fineness of between 11 and 22 dtex.

[0040] The nonwoven fabrics can consist of any suitable material, in particular polyamide, but also of elastomers such as thermoplastic polyurethane (TPU), melt fibers, bicomponent fibers or mixtures thereof.

[0041] In terms of the machine, the technical problem is solved by a machine for producing a tissue paper web, which comprises a press device with at least one press nip. In this case, the machine has at least one clothing according to one aspect of the invention. During operation of the press device, this clothing passes through the at least one press nip together with the tissue paper web.

[0042] Cotton paper is usually made of cellulose and is a very light paper. The mass per unit area is usually 15g / m 2 Up to 30g / m 2 However, 10g / m 2 Or 5g / m 2 The value is greater than 30g / m 2 The same is possible with paper.

[0043] In an advantageous embodiment, the machine comprises a so-called crescent former.Thus, the fibrous web can be conveyed after initial dewatering in the former, usually on a clothing, such as a felt, to a pressing device, in which further dewatering is achieved in a press nip.

[0044] The press preferably has a long nip, in particular a shoe nip. Compared to a roll nip which is also possible, the web stays in the nip for a longer time. This makes it possible, in particular, to use lower pressing pressures. This is important in the production of tissue paper, since the web volume remains unchanged, which is an important quality parameter in tissue paper.

[0045] It may also be advantageous if the press has a wastewater collector, which is provided for collecting water removed from the tissue web in the at least one pressing nip. By using a felt according to one aspect of the invention, the dewatering power of the press can be increased, in particular in a long nip or a shoe nip, by performing nip dewatering in addition to the usual Uhle Box dewatering. In this case, water (or a water-air mixture) from the tissue web is not only pressed into the wire cloth, but also passes through the wire cloth. This water enters the environment after the pressing nip as splash water or spray, while the rest of the pressed water is further conveyed together with the wire cloth to the usually downstream Uhle Box. The splash water may also flow forwards in the opposite direction of the web's running direction. This partial dewatering is referred to as nip dewatering. In order to prevent contamination of the press or uncontrolled wetting of the environment, it is advantageous if one or more wastewater collectors are provided in the press. The wastewater collector is arranged so that the splash water can be collected and transported away.

[0046] With the aid of a clothing according to one aspect of the invention and, if appropriate, by the introduction of a water collector, the dewatering capacity of the press can be significantly increased even in existing tissue machines with very little effort.

[0047] In terms of method, the technical problem is solved by a method for producing a tissue paper web by using a machine according to one aspect of the invention.

[0048] It can advantageously be provided that in the press a portion of the dewatering takes place in the form of nip dewatering and that the water removed thereby is completely or partially collected by the waste water collector.

[0049] In particular, it can be provided that the nip dewatering accounts for more than 10%, in particular between 20% and 50%, of the total dewatering of the press.

[0050] It is particularly advantageous if the tissue machine is operated at a relatively high speed of more than 1200 m / min, in particular more than 1500 m / min or 1800 m / min. Especially at relatively high production speeds, too low a dry weight content after the press is a limiting factor for increasing the production speed. The method proposed here makes it possible to increase the dry weight content after the press, thereby making it possible to achieve relatively high production speeds in a stable manner.

[0051] The invention is explained in more detail below with reference to the schematic, not-to-scale drawings. In the drawings:

[0052] Figure 1 A tissue machine according to one aspect of the invention is shown.

[0053] Figure 1 A tissue machine 1 according to one aspect of the invention is shown. This typical design of a tissue machine 1 is used as an example to explain aspects of the solution described here. The invention is not limited to this embodiment. In this case, a fibrous stock suspension is applied to the clothing 2 or between the clothing 2 and the outer wire 22 via a headbox. In the former 20, initial dewatering is achieved by means of a suctioned forming roller 21, which is partially surrounded by the clothing 2. The former 20 is Figure 1 The crescent former is designed in the embodiment, but other types of formers are also possible. The produced fibrous material mat is then conveyed to a pressing device 30 supported by the clothing 2. Figure 1 In the embodiment, the pressing device 30 is designed as a shoe press 30. Here, the pressing nip 31 is arranged between the shoe roll 34 and the Yankee cylinder 41. The clothing 2 and the tissue paper web 3 pass through the pressing nip 31 together. After the pressing nip, the web 3 further runs on the surface of the Yankee cylinder 41. Here, a drying hood 42 is arranged on the Yankee cylinder 41. The web 3 is separated from the Yankee cylinder 41 by means of a crepe scraper 43 and further conveyed to the winding section 60. Figure 1As shown, a scanner 50 or other suitable measuring device 50 can also be provided before the winding section 60, by which important parameters of the fiber web 3, such as thickness, moisture or mass per unit area, are detected. If the scanner 50 is designed to be traversable, the transverse curves of these parameters can also be determined.

[0054] exist Figure 1 The clothing 2 of the machine 1 shown in the figure is advantageously a clothing according to one aspect of the invention. The clothing can advantageously comprise a base structure of a flat fabric, in particular a plain weave, which is made endless by connecting the ends at the ends, for example welding. The MD yarns of this base structure in the embodiment all have a diameter of between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm. The linear density of the MD yarns is greater than 37%, preferably between 37% and 45%, particularly preferably between 39% and 43%. The clothing 2 has a linear density of 750 g / m 2 Up to 1250g / m 2 Between, especially at 900g / m 2 Up to 1100g / m 2 , the nonwoven covering layer can be reduced in such a way that it only accounts for half the weight of the clothing or less. Since in the clothing 2 according to one aspect of the invention the base structure assumes part of the function of the nonwoven layer, the clothing can be designed to be very thin. Unlike the tissue paper machine 1 known from the prior art, when such a clothing 2 is used in a press nip 31, in particular a shoe press nip 31, dewatering of the nip can be achieved. This results in splashing water or spray, which usually occurs after the press nip 31, but may also occur before the press nip 31. In order to prevent contamination of the press 30 or uncontrolled wetting of the environment, it is advantageous to provide one or more waste water collectors 33 in the press device 30. Figure 1 In the embodiment, the waste water collector 33 is arranged after the press nip 31. As an alternative or in addition, a waste water collector 33 can also be arranged before the press nip 31. The waste water collector or collectors 33 absorb part of the water removed from the web 3 by the press nip dewatering. The rest is stored in the clothing 2 and transported away by the press nip 31. In order to remove this water from the clothing 2, a waste water collector 33 is arranged before the press nip 31. Figure 1 In the shown device, a suction box 32, the so-called Uhle Box 32, is arranged between the press nip 31 and the headbox 10. In the method according to one aspect of the invention, the share of the nip dewatering is more than 10% of the total dewatering of the press 30, in particular between 20% and 50%.

[0055] List of Reference Numerals

[0056] 1 Tissue Machine

[0057] 2 Net carpet

[0058] 3 Cotton paper

[0059] 10 headbox

[0060] 20 Shaper

[0061] 21 Forming roller

[0062] 22 Extranet

[0063] 30 Pressing device

[0064] 31 Pressing Nip

[0065] 32 Suction box "Uhle Box"

[0066] 33 Wastewater collector

[0067] 34 Shoe Roller

[0068] 40 Drying device

[0069] 41 Yankee

[0070] 42 Hood

[0071] 43 Crepe Scraper

[0072] 50 Scanner

[0073] 60 Winding unit

Claims

1. A clothing (2) for use in a machine (1) for producing a cotton paper web (3), comprising a base structure consisting of a woven textile structure with MD yarns and CD yarns, and comprising at least one layer made of nonwoven fibers, characterized in that The basic structure consists of two endless fabric layers, wherein in both fabric layers the MD yarns completely or mostly have a diameter between 0.25 mm and 0.45 mm and the linear density of the MD yarns is greater than 37%, wherein the two fabric rings are connected to one another by sewing with needles with one or more nonwoven layers.

2. The clothing (2) according to claim 1, characterized in that The basic structure consists of two fabric layers which are produced endlessly.

3. The clothing (2) according to claim 1, characterized in that The net blanket (2) is felt.

4. The clothing (2) according to claim 1, characterized in that The MD yarns completely or mostly have a diameter between 0.3 mm and 0.35 mm, and the linear density of the MD yarns is between 37% and 45%.

5. The clothing (2) according to claim 2, characterized in that The textile structure is a flat fabric, wherein the warp threads of the weaving machine provide the MD threads of the clothing and the flat fabric is produced endlessly by connecting the end-side ends.

6. The clothing (2) according to claim 5, characterized in that The connection is achieved by welding.

7. The clothing (2) according to claim 1, characterized in that At least some of the CD yarns are designed to be twisted.

8. The clothing (2) according to claim 7, characterized in that 50% or more of the CD yarns are designed to be twisted yarns.

9. The clothing (2) according to claim 1, characterized in that The clothing (2) has a thickness of 3.5 mm or less.

10. The clothing (2) according to claim 9, characterized in that The clothing (2) has a thickness between 2.5 mm and 3 mm.

11. The clothing (2) according to claim 1, characterized in that The weight of the blanket is 750g / m 2 Up to 1250g / m 2 between.

12. The clothing (2) according to claim 11, characterized in that The weight of the blanket is 900g / m 2 Up to 1100g / m 2 between.

13. The clothing (2) according to claim 1, characterized in that The weight proportion of the nonwoven layer corresponds at most to the weight proportion of the basic structure.

14. The clothing (2) according to claim 13, characterized in that The weight proportion of the nonwoven layer corresponds to a maximum of 2 / 3 of the weight proportion of the basic structure.

15. A machine (1) for producing a tissue paper web (3), comprising a pressing device (30) having at least one pressing nip (31), characterised in that The machine (1) has at least one clothing (2) according to one of claims 1 to 14, and the clothing (2) passes through the at least one press nip (31) during operation of a press device (30).

16. The machine (1) according to claim 15, characterized in that The pressing nip (31) is a long nip (31).

17. The machine (1) according to claim 16, characterized in that The pressing nip (31) is a shoe nip.

18. The machine (1) according to claim 15 or 16, characterized in that The pressing device (30) has a waste water collector (33) which is arranged to collect water removed from the tissue paper web (3) in the at least one pressing nip (31).

19. A method for producing a tissue paper web (3), wherein: A machine (1) according to any one of claims 15 to 18 is used for producing a tissue paper web.

20. The method according to claim 19, characterized in that In the pressing device (30), a part of the dewatering is achieved in the form of nip dewatering, and the water thus dewatered is completely or partially collected by a waste water collector (33).

21. The method according to claim 20, characterized in that The dewatering in the nip area accounts for more than 10% of the total dewatering amount of the pressing device (30).

22. The method according to claim 21, characterized in that The nip dewatering accounts for between 20% and 50% of the total dewatering of the pressing device (30).

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