EP3402924A1

EP3402924A1 - Dryer fabric

Info

Publication number: EP3402924A1
Application number: EP16816648.6A
Authority: EP
Inventors: Anas ALIAS; Matthias Schmitt; Wan Zeti Zafina WAN AHMAD NATHRI; Syahrul Ramadhan AHMAD KAMAL ARIFFIN
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2016-01-12
Filing date: 2016-12-15
Publication date: 2018-11-21
Also published as: CN108474177A; WO2017121571A1; US20190003118A1; DE102016200230A1

Abstract

The invention relates to a dryer fabric for use in a drying section of a machine which produces and/or processes a fibrous web, in particular paper, cardboard, tissue or nonwoven machine, having machine direction threads which are arranged next to one another in the machine transverse direction and are woven with machine transverse direction threads which are arranged next to one another in the machine direction to form a single-layer woven fabric with an air permeability in the range from 40 cfm to 330 cfm, wherein the machine direction threads and the machine transverse direction threads have a flattened cross-sectional shape with a ratio of width to height of greater than 1, and wherein each of the machine direction threads, during weaving with the machine transverse direction threads, runs over and/or under a maximum of three, preferably a maximum of two machine transverse direction threads which are arranged directly next to one another. The invention is characterized in that the number of machine direction threads per 10 cm, as viewed in the machine transverse direction, is in the range from 170 to 200, and the degree of filling of the machine direction threads is in the range from 90% to 110%.

Description

dryer

The invention relates to a dryer fabric according to the preamble of patent claim 1.

Dryer screens must meet a variety of requirements. For example, dryer fabrics for use at the beginning of a dryer section must have a low air permeability in order to keep evaporation controlled in a controlled manner and thus to prevent too rapid evaporation associated with damage to the still moist and thus sensitive paper. Furthermore, dryer fabrics must be designed to reduce soils that are difficult to clean, such as sticky deposits, a small inner, i.e., small amount, of dirt. not directly accessible, have volume, which is often achieved by web designs with only short Fadenflottierungen. Further, it has been found advantageous to dry fabrics of flat formed machine direction yarns and cross machine direction yarns since they have a smoother surface on the paper and / or running side and therefore may be less susceptible to fouling than round machine direction yarns and cross machine direction yarns.

In the prior art low-permeability dryers in the range of up to 330 cfm where the flat machine direction yarns are juxtaposed in the cross-machine direction and interwoven with machine-directional, flat-formed cross-machine direction yarns to form a single-ply fabric and in which the machine direction threads when weaving with the cross-machine direction yarns form only relatively short Fadenflottierungen, ie the machine direction threads extend during weaving with the cross-machine direction yarns over and / or under a maximum of three, in particular a maximum of two directly juxtaposed

Cross-machine direction yarns, the machine direction yarns often have little chance of dodging, especially when compared to fabrics having relatively long yarn floats of machine direction yarns and high air permeabilities. This small "dodge" may result in twisting and / or sliding of the machine direction yarns, particularly in fabrics where the machine direction yarns have been woven with low yarn tensions In particular, it is difficult to provide dry fabrics with low permeability and low tendency to fouling and good cleanability.

It is therefore the object of the invention to provide dryer fabrics with low permeability and low tendency to fouling and good cleanability, in which the machine direction threads have a lower tendency to twist and / or superimposing than in the known from the prior art drying fabrics.

The object is achieved by a dryer fabric with the features of patent claim 1. By providing a dryer fabric having a density of machine direction yarns in the range of 160 to 185 per 10 cm and a degree of filling of the machine direction yarns in the range of 90% to 15%, on the one hand, a dryer fabric is provided, in which the air permeability is set in a wide lower range can and in which a twisting and / or superimposing the machine direction threads is effectively prevented or greatly reduced.

If, for the purposes of the present invention, a flattened cross-sectional shape of a thread is mentioned, then this means a cross-sectional shape deviating from the circular shape of the respective thread (s). The corresponding thread should therefore not be circular in cross section or have no purely cylindrical shape. Nevertheless, the cross-sectional shape may have circular arcs or sections thereof. The terms flattened and deviating from the circular shape are understood in each case according to the present invention as a synonym. A corresponding cross-section is perpendicular to the longitudinal extent of the thread, which corresponds to the machine direction in a machine direction yarn and the machine direction in a machine direction yarn. In other words, the cross-sectional shape corresponds to the outer contour of the thread in the corresponding cross-sectional plane.

Is in accordance with the invention of width or height, then in the mentioned cross-section, the measured from the cross-sectional plane spanned in each case the largest

Extension of the outer contour of the thread meant. You could also say that the width of the X-axis and the height of the Y-axis of a Cartesian coordinate system in said cross-sectional plane corresponds. In that case the length of the thread would coincide with the corresponding Z-axis. The degree of filling in the context of the present invention is calculated according to the following formula:

Filling degree in% = A x W / 100mm x 100, with

A = number of machine direction threads per 100 mm in the cross machine direction, B = width of a machine direction thread in mm Advantageous embodiments and further developments of the invention are specified in the subclaims.

According to a particularly preferred embodiment of the invention, it is provided that the degree of filling of the machine direction yarns is in the range of 95% to 105%. As a result of this further restriction, the twisting and / or superimposing of the machine direction yarns can be increasingly prevented or reduced while the air permeability is low.

A specific embodiment of the invention provides that the machine transverse direction threads have a bone-shaped or lenticular cross-sectional shape. Applicant's experiments have further shown that the twisting and / or superimposing of the machine direction yarns can be further reduced if the ratio of width to height of the machine direction yarns is in the range of 1.7 to 1.9, a concrete embodiment of Figs Invention provides that the machine direction yarns have a height of 0.4 mm and a width of 0.6 mm.

In order to further reduce the tendency of the dryer fabric to become soiled, it is provided in particular that the majority (ie more than 50%), in particular the, ie all, machine direction yarns form groups of machine direction yarns arranged directly next to one another and the Machine direction threads of the respective group are woven side by side following the same weaving path with the cross-machine direction yarn. In this case, the groups can in particular be formed in each case from two or three directly adjacent machine direction threads. The inventive solution is particularly advantageous when each of the machine direction yarns passes over and / or under a single cross-machine direction yarn when weaving with the cross-machine direction yarns; in other words, when each of the machine direction yarns, when interweaving with the cross-machine direction yarns on the paper side, continuously crosses only a single cross-machine direction yarn and immediately adjacent to that single cross-machine direction yarn

Cross-machine direction yarns cross when the respective machine direction yarn runs on the machine side and / or when each of the machine direction yarns interweaves with the cross machine direction yarns on the machine side continuously only a single cross machine direction yarn and crosses the cross machine direction yarns immediately adjacent cross machine direction yarns when the respective machine direction yarns run on the paper side. A further development of the invention based thereon provides that the machine direction threads and the cross-machine direction threads are woven together in a plain weave.

Preferably, the density of the cross-machine direction yarns is in the range of 15 to 55 per 10 cm, which can be adjusted in particular the air permeability in the desired range.

According to a further embodiment of the invention it is provided that the machine transverse direction threads have a height in the range of 0.7 mm to 0.8 mm and a width of 1, 6 mm.

In particular, in order to increase the abrasion resistance of the dryer fabric according to the invention, it makes sense if the machine direction yarns and the cross-machine direction yarns are essentially made of PET. To increase the temperature resistance and the chemical resistance while substantially maintaining the abrasion resistance of the dryer fabric according to the invention, it may also be advantageous if between 40% and 60% of the MD yarns are essentially PET and between 60% and 40% of the MD yarns are essentially PPS and when the cross-machine direction yarns are substantially PET or where between 40% and 60% of the cross-machine direction yarns are substantially PET and between 60% and 40% of the cross-machine direction yarns are substantially PPS. For use at very high temperatures (eg> 150 ° C., for example in the case of oil-heated dryer sections), it is advantageous if between 40% and 60% of the machine direction yarns consist essentially of PPS and between 60% and 40% of the machine direction yarns PCTAs are and when the cross-machine direction yarns are substantially PCTA or where between 40% and 60% of the cross-machine direction yarns are essentially PCTA and between 60% and 40% of the cross-machine direction yarns are essentially PPS.

The highest temperature and hydrolysis resistance is achieved when the MD yarns are essentially PPS and the CMD yarns are essentially PPS or PCTA.

The term "substantially" is to be understood in the previous embodiments to the effect that the relevant material is present in more than 50% by weight, preferably more than 80% by weight, particularly preferably more than 95% by weight in the respective threads The invention will be further elucidated on the basis of schematic drawings

1 shows a dryer fabric according to the prior art in plan view,

Figure 2 shows an embodiment of a dryer according to the invention in

Top view and

3 shows the dryer fabric of Figure 2 in side view. 1 shows a dryer fabric 1 according to the prior art in plan view. The dryer fabric 1 comprises machine direction yarns 2 arranged next to one another in machine cross-linking CD, which are interwoven with cross-machine direction yarns 3 arranged next to one another in the machine direction MD to form a single-layer fabric with an air permeability in the range from 40 cfm to 330 cfm. The weave structure of the fabric is such that each of the machine direction yarns 2, when interweaving with the cross-machine direction yarns 3, extends above and / or below a maximum of three directly adjacent machine direction yarns 3. Specifically, the weave structure forms a plain weave. Further, the machine direction yarns 2 and the cross-machine direction yarns 3 have a flattened cross-sectional shape with a width to height ratio greater than one. Specifically, the machine direction yarns 2 have a height of 0.36 mm and a width of 0.67 mm. The cross-machine direction yarns 3 have a bone-shaped cross-sectional shape and a height of 0.8 mm and a width of 1.6 mm. As can further be seen, the machine direction yarns 2 form groups of two directly adjacent machine direction yarns 102, the machine direction yarns 2 of the respective group being woven side by side with the machine direction yarns 3 side by side along the same weaving path. The dryer fabric 1 shown in FIG. 1 has a degree of filling of the machine direction yarns of 16%. FIG. 1 further shows a location indicated by the reference numeral 4, on which a machine direction yarn 2a is slid over a machine direction yarn 2b, ie partially over it.

FIG. 2 shows an embodiment of a dryer fabric 101 according to the invention in plan view and FIG. 3 shows the dryer fabric 101 of FIG. 2 in a side view. In the following, only the differences to the dryer fabric of FIG. 1 will be discussed. Furthermore, the reference numerals of Figures 2 and 3 correspond to the same components as those of Figure 1 only have these increased by 100 number. In the dryer fabric 101 of Figs. 2 and 3, the number of machine direction yarns 102 per 10 cm in machine direction CD is in the range of 170 to 200 and the filling degree of the machine direction yarns 102 is 104%. Further, the width to height ratio of the machine direction yarns 102 is in the range of 1.7 until 19. Specifically, the machine direction yarns 102 have a height of 0.4 mm and a width of 0.6 mm. In addition, the number of cross-machine direction yarns 103 per 10 cm in the machine direction MD is in the range of 15 to 55 per 10 cm.

Claims

claims

1 . Dryer fabric for use in a dryer section of a machine producing and / or processing a fibrous web, in particular a paper, board, tissue or nonwoven machine with machine direction threads arranged side by side in the cross machine direction, with machine crosswise adjacent machine direction yarns to form a single-layer fabric having an air permeability in the range of 40 cfm to 330 cfm, the machine direction yarns and the cross-machine direction yarns having a flattened cross-sectional shape with a width to height ratio greater than 1, and wherein each of the machine direction yarns interweaves with the cross-machine direction yarns above and / or under a maximum of three, preferably a maximum of two directly adjacent machine transverse direction threads runs,

characterized in that

The number of machine direction yarns per 10 cm in the cross machine direction is in the range of 160 to 185, and the degree of filling of the machine direction yarns is in the range of 90% to 15%.

2. Drying machine according to claim 1, characterized in that the degree of filling of the machine direction yarns in the range of 95% to 1 1 1%.

3. Drying screen according to claim 1 or 2, characterized in that the

Cross-machine direction yarns have a bone-shaped or lenticular cross-sectional shape.

4. Drying screen according to one of the preceding claims, characterized in that the ratio of width to height of the machine direction yarns in the range of 1, 7 to 1, 9 is.

5. drying fabric according to claim 4, characterized in that the

Machine direction threads have a height of 0.4 mm and a width of 0.6 mm.

6. dryer fabric according to any one of the preceding claims, characterized in that the machine direction yarns form groups of groups of directly adjacent machine direction yarns and the machine direction yarns of the respective group are woven side by side the same weaving path with the machine transverse direction yarns.

A dryer fabric according to any one of the preceding claims, characterized in that each of the machine direction yarns passes over and / or under a single cross machine direction yarn when weaving with the cross machine direction yarns.

8. drying fabric according to claim 7, characterized in that the

Machine direction yarns and the cross-machine direction yarns are woven together in a plain weave.

A dryer fabric according to any one of the preceding claims, characterized in that the number of cross machine direction yarns per 10 cm in the machine direction is in the range of 15 to 55 per 10 cm.

A dryer fabric according to any one of the preceding claims, characterized in that the cross machine direction yarns have a height in the range of 0.7 mm to 0.8 mm and a width of 1.6 mm.

11. The dryer screen according to claim 1, wherein the machine direction threads and the cross-machine direction threads are substantially made of PET.

The dryer fabric according to any one of the preceding claims 1 to 10, characterized in that between 40% and 60% of the machine direction yarns are substantially PET and between 60% and 40% of the machine direction yarns are substantially PPS and the machine direction yarns are substantially PET or that between 40% and 60% of the cross-machine direction yarns are essentially PET and between 60% and 40% of the cross-machine direction yarns are essentially PPS.

A dryer fabric according to any one of the preceding claims 1 to 10, characterized in that between 40% and 60% of the machine direction yarns are substantially PPS and between 60% and 40% of the machine direction yarns are essentially PCTA and the machine direction yarns are essentially PCTA or that between 40% and 60% of the cross-machine direction yarns are essentially PCTA and between 60% and 40% of the cross-machine direction yarns are essentially PPS.

14. Drying screen according to one of the preceding claims 1 to 10, characterized in that the machine direction yarns are substantially of PPS and the cross-machine direction yarns substantially of PPS or PCTA.