WO2012013778A1 - Fibrous web formed on a structured fabric - Google Patents

Fibrous web formed on a structured fabric

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Publication number
WO2012013778A1
WO2012013778A1 PCT/EP2011/063093 EP2011063093W WO2012013778A1 WO 2012013778 A1 WO2012013778 A1 WO 2012013778A1 EP 2011063093 W EP2011063093 W EP 2011063093W WO 2012013778 A1 WO2012013778 A1 WO 2012013778A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
fabric
pattern
structured
weave
web
Prior art date
Application number
PCT/EP2011/063093
Other languages
French (fr)
Inventor
Scott Quigley
Original Assignee
Voith Patent Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

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Classifications

    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F11/00Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
    • D21F11/006Making patterned paper
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00Wet end of machines for making continuous webs of paper
    • D21F1/0027Screen-cloths
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/02Patterned paper
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/002Tissue paper; Absorbent paper

Abstract

The invention relates to a fibrous web including a fibrous construct having at least one formed surface feature, the surface feature including a topographical pattern reflective of a weave pattern in a fabric used in a papermaking machine, the fabric including a single layer of yarns arranged in a repeating weave pattern, each weave pattern including a plurality of warp yarns substantially oriented in a machine direction (MD) defining MD yarns, and a plurality of weft yarns substantially oriented in a cross machine direction (CD) defining CD yarns, the MD yarns each having at least one long float within the weave pattern, each long float being adjacent to at least one other long float of an MD yarn, the weave, pattern being a plain weave apart from the long floats.

Description

FIBROUS WEB FORMED ON A STRUCTURED FABRIC

BACKGROUND OF THE INVENTION

Cross Reference To Related Applications

[0001] This is a division of U.S. patent application serial no. 12/847,519, entitled

"STRUCTURED FABRIC", filed July 30, 2010, which is incorporated herein by reference.

1, Field of the Invention

[0002] The present invention relates generally to papermaking, and relates more specifically to a fibrous web formed on a structured fabric employed in papermaking,

2. Description of the related art.

[0003] In a conventional papermaking process, a water slurry, or suspension, of cellulosic fibers (known, as the paper "stock") is fed into a gap between two endless woven wires that travels between two or more rolls. At least one of the wires are often referred to as a "structured fabric" thai provides a papermaking surface on the upper surface of its upper run which operates as a filter to separate the cellulosic fibers of the paper stock from the aqueous medium, thereby forming a wet paper web. The aqueous medium drains through mesh openings of the structured fabric, known as drainage holes, by gravity or vacuum located on the lower surface of the upper run (i.e.. the "machine side") of the fabric.

[0004] After leaving the forming section, the paper web is transferred to a press section of the paper machine, where it is passed through the nips of one or more pairs of pressure rollers covered with another fabric, typically referred to as a "press felt." Pressure from the rollers removes additional moisture from the web; the moisture removal is often enhanced by the presence of a "bait" layer of the press felt. The paper is then transferred to a dryer section for further moisture removal. After drying, the paper is ready for secondary processing and packaging. [0005] Typically, papermakers' fabrics are manufactured as endless belts by one of two basic weaving techniques. In the first of these techniques, fabrics are flat woven by a flat weaving process, with their ends being joined to form an endless belt by any one of a number of well- known joining methods, such as dismantling and reweaving the ends together (commonly known as splicing), or sewing on a pin-seamable flap or a special foldback on each end, then reweaving these into pin-seamable loops. A number of auto-joining machines are available, which for certain fabrics may be used to automate at least part of the joining process. In a flat woven papermakers' fabric, the warp yarns extend in the machine direction and the filling yarns extend in the cross machine direction.

[0006] In the second basic weaving technique, fabrics are woven directly in the form of a continuous belt with an endless weaving process. In the endless weaving process, the warp yarns extend in the cross machine direction and the filling yarns extend in the machine direction. Both weaving methods described hereinabove are well known in the art, and the term "endless belt" as used herein refers to belts made by either method.

[0007] Effective sheet and fiber support are important considerations in papermaking, especially for the forming section of the papermaking machine, where the wet web is initially formed. Additionally, the structured fabrics should exhibit good stability when they are run at high speeds on the papermaking machines, and preferably are highly permeable to reduce the amount of water retained in the web when it is transferred to the press section of the paper machine. In both tissue and fine paper applications (i.e., paper for use in quality printing, carbonizing, cigarettes, electrical condensers, and the like) the papermaking surface comprises a very finely woven or fine wire mesh structure. [0008] In a conventional tissue forming machine, the sheet is formed flat. At the press section, 100% of the sheet is pressed and compacted to reach the necessary dryness and the sheet is further dried on a Yankee and hood section. The sheet is then, creped and wound-up, thereby producing a flat sheet.

[0009] In an ATMOS™ system, a sheet is formed on a structured or molding fabric and the sheet is further sandwiched between the structured or molding fabric and a dewatering fabric. The sheet is dewatered through the dewatering fabric and opposite the molding fabric. The dewatering talies place with airflow and mechanical pressure. The mechanical pressure is created by a permeable belt and the direction of air flow is from the permeable belt to the dewatering fabric. This can occur when the sandwich passes through an extended pressure nip formed by a vacuum roll and the permeable belt. The sheet is then transferred to a Yankee by a press nip. Only about 25% of the sheet is slightly pressed by the Yankee while approximately 75% of the sheet remains unpressed for quality. The sheet is dried by a Yankee/Hood dryer arrangement and then dry creped. In the ATMOS™ system, one and the same structured fabric is used to carry the sheet from the headbox to the Yankee dryer. Using the ATMOS™ system, the sheet reaches between about 35 to 38% dryness after the ATMOS™ roll, which is almost the same dryness as a conventional press section. However, this advantageously occurs with almost 40 times lower nip pressure and without compacting and destroying sheet quality. Furthermore, a big advantage of the ATMOS™ system is that it utilizes a permeable belt which is highly tensioned, e.g., about 60 k.N/m. This belt enhances the contact points and intimacy for maximum vacuum dewatering. Additionally, the belt nip is more than 20 times longer than a conventional press and utilizes airflow through the nip, which is not the case on a conventional press system. [0010] Actual results from trials using an ATMOS™ system have shown that the caliper and bulk of the sheet is 30% higher than the conventional through-air drying (TAD) formed towel fabrics. Absorbency capacity is also 30% higher than with conventional TAD formed towel fabrics. The results are the same whether one uses 100% virgin pulp up to 100% recycled pulp. Sheets can be produced with basis weight ratios of between 1.4 to 40 g/m2. The ATMOS™ system also provides excellent sheet transfer to the Yankee working at 33 to 37% dryness. A key aspect of the ATMOS™ system is that it forms the sheet on the molding fabric and the same molding fabric carries the sheet from the headbox to the Yankee dryer. This produces a sheet with a uniform and defined pore size for maximum absorbency capacity.

[0011] U.S. patent application Ser. No. 1 1/753,435 filed on May 24, 2007, the disclosure of which is hereby expressly incorporated by reference in its entirety, discloses a structured fabric for an ATMOS™ system. The fabric utilizes an at least three float warp and weft structure which, like the prior art fabrics, is symmetrical in form.

[0012] U.S. Pat. No, 5,429,686 to CHIU et ah, the disclosure of which is hereby expressly incorporated by reference in its entirety, discloses structured forming fabrics which utilize a load-bearing layer and a sculptured layer. The fabrics utilize impression knuckles to imprint the sheet and increase its surface contour. This document, however, does not create pillows in the sheet for effective dewatenng of TAD applications, nor does it teach using the disclosed fabrics on an ATMOS™ system and/or forming the pillows in the sheet while the sheet is relatively wet and utilizing a hi-tension press nip.

[0013] U.S. Pat. No. 6,237,644 to HAY et al., the disclosure of which is hereby expressly incorporated by reference in its entirety, discloses structured forming fabrics which utilize a lattice weave pattern of at least three yarns oriented in both, warp and weft directions. The fabric essentially produces shallow craters in distinct patterns. This document, however, does not teach using the disclosed fabrics on an ATMOS™ system.

[0014] What is needed in the art is an efficient effective single layer fabric weave pattern to be used in a papermaking machine.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a fibrous web including a fibrous construct having at least one formed surface feature. The surface feature including a topographical pattern reflective of a weave pattern in a fabric used in a papermaking machine. The fabric including a single layer of yams arranged in a repeating weave pattern, each weave pattern including a plurality of warp yarns substantially oriented in a machine direction (MD) defining MD yarns; and a plurality of weft yarns substantially oriented in a cross machine direction (CD) defining CD yarns. The MD yarns each having at least one long float within the weave pattern. Each long float being adjacent to at least one other long float of an MD yarn. The weave pattern being a plain weave apart from the long floats.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0016] Fig. 1 shows a repeating weave pattern having a square shape of a top side or paper facing side of an embodiment of a structured fabric of the present invention, each indicating a location where a warp MD yarn passes over a weft CD yarn; [0017] Fig. 2 shows the weave pattern of the structured fabric of Fig. 1 ;

[0018] Fig. 3 shows a repeating weave pattern having a square shape of a top side or paper facing side of another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yarn;

[0019] Fig. 4 shows the weave pattern of the structured fabric of Fig. 3;

[0020] Fig. 5 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yarn;

[0021] Fig. 6 shows the weave pattern of the structured fabric of Fig. 5;

[0022] Fig. 7 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yarn;

[0023] Fig. 8 shows the weave pattern of the structured fabric of Fig. 7;

[0024] Fig. 9 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yarn;

[0025] Fig. 10 shows the weave pattern of the structured fabric of Fig. 9;

[0026] Fig. 1 1 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yarn;

[0027] Fig. 12 shows the weave pattern of the structured fabric of Fig. ! 1 ;

[0028] Fig. 13 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yarn;

[0029] Fig. 14 shows the weave pattern of the structured fabric of Fig. 13;

[0030] Fi g. 15 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each "X" indicating a location where a warp MD yarn passes over a weft CD yarn;

[0031] Fig. 16 shows the weave pattern of the structured fabric of Fig. 15;

[0032] Fig. 17 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yarn;

[0033] Fig. 18 shows the weave pattern of the structured fabric of Fig. 17;

[0034] Fig. 19 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each "X" indicating a location where a warp MD yarn passes over a weft CD yarn;

[0035] Fig. 20 shows the weave pattern of the structured fabric of Fig. 19;

[0036] Fig. 21 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each ^X" indicating a location where a warp MD yarn passes over a weft CD yarn;

[0037] Fig. 22 shows the weave pattern of the structured fabric of Fig. 21 ;

[0038] Fig. 23 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yam;

[0039] Fig. 24 shows the weave pattern of the structured fabric of Fig. 23; [0040] Fig. 25 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location, where a warp MD yarn passes over a weft CD yarn;

[0041] Fig, 26 shows the weave pattern of the structured fabric of Fig. 25;

[0042] Fig. 27 shows a repeating weave pattern having a square shape of a top side or paper facing side of yet another embodiment of a structured fabric of the present invention, each 'X' indicating a location where a warp MD yarn passes over a weft CD yarn;

[0043] Fig. 28 shows the weave pattern of the structured fabric of Fig. 27;

[0044] Fig. 29 illustrates a schematic cross-sectional view of an embodiment of an ATMOS™ papermaking machine;

|0045] Fig. 30 illustrates a schematic cross-sectional view of another embodiment of an ATMOS™ papermaking machine;

[0046] Fig. 31 illustrates a schematic cross-sectional view of another embodiment of an ATMOS™ papermaking machine;

[0047] Fig. 32 illustrates a schematic cross-sectional view of another embodiment of an ATMOS™ papermaking machine;

[0048] Fig. 33 illustrates a schematic cross-sectional view of another embodiment of an ATMOS™ papermaking machine;

[0049] Fig. 34 illustrates a schematic cross-sectional view of another embodiment of an ATMOS™ papermaking machine;

[0050] Fig. 35 illustrates a schematic cross-sectional view of another embodiment of an ATMOS™ papermaking machine; and [0051] Fig. 36 illustrates a schematic cross-sectional view of another embodiment of an ATMOS™ papermaking machine.

[0052] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0053] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in move detail than is necessary for the fundamental understanding of the present invention, and the description is taken with the drawings maliing apparent to those skilled in the art how the forms of the present invention may be embodied in practice.

[0054] The present invention relates to a structured fabric for a papermaking machine, a former for manufacturing a paper web, and also to a former which utilizes the structured fabric, and in some embodiments a belt press, in a papermaking machine.

[0055] The present invention also relates to a twin wire former ATMOS™ system which utilizes the structured fabric which has good resistance to pressure and excessive tensile strain forces, and which can withstand wear/hydrolysis effects that are experienced in an ATMOS™ system. The system may also include a permeable belt for use in a high tension extended nip around a rotating roll or a stationary shoe and a dewatering fabric for the manufacture of premium tissue or towel grades. The fabric has key parameters which include permeability, weight, caliper, and certain compressibility.

[0056] The structured fabric of the present invention is illustrated in Figs, 1-28. Fig. 1 depicts a weave pattern 10 from a top pattern view of the web facing side of the fabric (i.e., a view of the papermaking surface). The numbers 1 -20 shown on the bottom of the pattern identify the warp, machine direction (MD) yarns while the right side numbers 1 -20 show the weft, cross-direction (CD) yarns. The symbol X illustrates a location where a warp yarn passes over a weft yam and an empty box illustrates a location where a warp yarn passes under a weft yarn. As shown in Fig. 1 , the areas that are shaded indicate long float warp yarns, which float over at least two weft yarns. The shaded areas form a MD float pattern, while the non-shaded areas represent a plain weave pattern. In a like manner the weave patterns of Figs. 3, 5, 7, 9, 11 , 13, 15, 17, 19, 21 , 23, 25, and 27 illustrate other embodiments of the present invention.

[0057] Fig. 2 illustrates the weave pattern of the MD yarns relative to the CD yarns with the CD yarns being represented in each line as the numbers, with the line being the pattern, of the MD yarn. Each line representing the MD yarn identified along the left side of the Fig. In a like manner Fig. 4 corresponds to Fig 3 and so on with the even numbered figures through Fig, 28, corresponding to the odd numbered figure that is numerically one Jess than the even numbered Fig.

[0058] The embodiments shown in Figs. 1 -28 are illustrative of the invention and the invention is not limited to the weave patterns shown therein.

[0059] The fabric of Figs. 1 -28 illustrates a repeating weave pattern square of the fabric that encompasses twenty MD w rp yarns (yarns 1 -20 numbered along the bottom of each pattern) and twenty weft yarns (yarns 1-20 that are numbered along the right side of each pattern). There are long floats of the MD warp yarns over the weft yams, with the long float being over at least two weft yarns, and in most patterns over at least three weft yarns. Although in some patterns the MD warp yarn float is over at least four or even over at least five weft yarns.

[0060] Where the MD warp yarns have there long float they are always adjacent to at least one other MD warp yarn that is also undergoing a long float. The float beginning and ending are offset in the MD by one weft yarn position. The contiguous adjacent MD warp yarns form an MD yarn float pattern, with at least one being present in each weave pattern 10. The MD yarn float patterns are replicated in weave pattern 10, and includes mirror-image or reflected MD yarn float patterns. The MD yarn float patterns can be symmetrical or asymmetrical. For example, in Fig. 1 there is one MD yarn float pattern having a float over five weft yarns that is only four MD yarns wide and there is another MD yarn float pattern having a float over five weft yarns that is five MD yarns wide. So, while the patterns are similar and are a reflection of each other, they are also asymmetrical.

[0061] Looking at Fig, 3, there are MD yarn float patterns that are mirror-images and are symmetrical. The MD yarns float over three weft yarns and are three MD yarns wide. In each case apart from the MD yarn float patterns the weave of the single layer fabric is a simple weave pattern. In many cases the plain weave pattern surrounds the MD yarn float patterns. In some weave patterns, such as those of Figs. 17 and 1.9, the simple weave patterns appear surrounded by MD yarn float patterns.

[0062] The parameters of the structured fabric shown in Figs. 1 -28 can have a mesh (number of warp yarns per inch) and a count (number of weft yarns per inch) of any amount. The single- layered fabric should have a high permeability value due to the nature of a single layer fabric and the way it is woven. Regarding yarn dimensions, the particular size of the yarns is typically governed by the mesh of the papermaking surface and the yarn size can be selected based upon the intended use. Fabrics employing these yarn sizes may be implemented with polyester yarns or with a combination of polyester and nylon yarns.

[0063] The structured fabric can also be treated and/or coated with an additional polymeric material that is applied by, e.g., deposition. The material can be added cross-linked during processing in order to enhance fabric stability, contamination resistance, drainage, wearability, improve heat and/or hydrolysis resistance and in order to reduce fabric surface tension. This aids in sheet release and/or reduced drive loads. The treatment/coating can be applied to

impart/improve one or several of these properties of the fabric. As indicated previously, the topographical pattern in the paper web can be changed and manipulated by use of different single -layer weaves. Further enhancement of the pattern can be attained by adjustments to the specific fabric weave by changes to the yarn diameter, yarn counts, yarn types, yarn shapes, permeability, caliper and the addition of a treatment or coating etc. In addition, a printed design, such as a screen-printed design, of polymeric material can be applied to the fabric to enhance its ability to impart an aesthetic pattern into the web or to enhance the quality of the web. Finally, one or more surfaces of the fabric or molding belt can be subjected to sanding and/or abrading in order to enhance surface characteristics.

[0064] The characteristics of the individual yarns utilized in the fabric of the present invention can vary depending upon the desired properties of the final papermakers' fabric. For example, the materials comprising yarns employed in the fabric of the present invention may be those commonly used in papermakers' fabric. As such, the yarns may be formed of polypropylene, polyester, nylon, or the like. The skilled artisan should select a yarn material according to the particular application of the final fabric. [0065] By way of non-limiting example, the structured fabric is a single-layered woven fabric which can withstand high pressures, heat, moisture concentrations, and which can achieve a high level of water resnoval and also mold or emboss the paper web. These characteristics provide a structured fabric appropriate for the Voith ATMOS™ papermaking process. The fabric preferably has a width stability and a suitable high permeability and preferably utilizes hydrolysis and/or temperature resistant materials, as discussed above. The fabric is preferably a woven fabric that can be installed on an ATMOS™ machine as a pre-joined and/or seamed continuous and/or endless belt. Alternatively, the structured fabric can be joined in the

ATMOS™ machine using, e.g., a pin-seam arrangement or can otherwise be seamed on the machine.

[0066] The invention also provides for utilizing the structured fabric disclosed herein on a machine for making a fibrous web, e.g., tissue or hygiene paper web, etc., which can be, e.g., a twin wire 4- a permeable belt ATMOS™ system. Referring again to the drawings, and more particularly to Figs. 29-35, there is a fibrous web machine including a headbox 22 that discharges a fibrous slurry between a forming fabric 26 and a structured fabric 28 having a weave pattern 10. It should be understood that structured fabric 28 is an embodiment of the structured fabric discussed above in connection with Figs. 1-28. Rollers 30 and 32 direct fabric 26 in such a manner that tension is applied thereto, against slurry 24 and structured fabric 28. Structured fabric 28 is supported by forming roll 34 which rotates with a surface speed that matches the speed of structured fabric 28 and forming fabric 26. Structured fabric 28 has peaks and valleys as defined by weave pattern 10, which give a corresponding structure to web 38 formed thereon. Structured fabric 28 travels in a web direction, and as moisture is driven from the fibrous slurry, structured fibrous web 38 takes form. The moisture that leaves the slurry travels through forming fabric 26.

[0067] The fibrous slurry is formed into a web 38 with a structure that matches the shape of structured fabric 28. Forming fabric 26 is porous and allows moisture to escape during forming. Further, water is removed through dewatering fabric 82, The removal of moisture through fabric 82 does not cause compression of web 38 traveling on structured fabric 28.

[0068] Due to the formation of the web 38 with the structured fabric 28 the pockets of the fabric 28 are fully filled with fibers. Therefore, at the Yankee surface 52 the web 38 has a much higher contact area, up to approximately 100%, as compared to the prior art because the web 38 on the side contacting the Yankee surface 52 is almost flat.

[0069] Referring to Fig. 29, there is shown an embodiment of the process where a structured fibrous web 38 is formed. Structured fabric 28 carries a three dimensional structured fibrous web 38 to an advanced dewatering system 50, past vacuum box 67 and then to a position where the web is transferred to Yankee dryer 52 and hood section 54 for additional drying and creping before winding up on a reel (not shown).

[0070] A shoe press 56 is placed adjacent to structured fabric 28, holding fabric 28 in a position proximate Yankee dryer 52. Structured fibrous web 38 comes into contact with Yankee dryer 52 and transfers to a surface thereof, for further drying and subsequent creping.

[0071] A vacuum box 58 is placed adjacent to structured fabric 28 to achieve improved solids levels, Web 38, which is carried by structured fabric 28, contacts dewatering fabric 82 and proceeds toward vacuum roll 60. Vacuum roll 60 operates at a vacuum level, of -0.2 to -0.8 bar with a preferred operating level of at least -0.4 bar. Hot air hood 62 is optionally fit over vacuum roll 60 to improve dewatering. [0072] Optionally a steam box can be installed instead of the hood 62 supplying steam to the web 38. The steam box. preferably has a sectionalized design to influence the moisture re-dryness cross profile of the web 38. The length of the vacuum zone inside the vacuum roll 60 can be from 200 mm to 2,500 mm, with a preferable length of 300 mm to 1 ,200 mm and an even more preferable length of between 400 mm to 800 mm. The solids level of web 38 leaving suction roll 60 is 25% to 55% depending on installed options. A vacuum box 67 and hot air supply 65 can be used to increase web 38 solids after vacuum roll 60 and prior to Yankee dryer 52. Wire turning roll 69 can also be a suction roll with a hot air supply hood. As discussed above, roll 56 includes a shoe press with a shoe width of 80 mm or higher, preferably 120 mm or higher, with a maximum peak pressure of less than 2.5 MPa. To create an even longer nip to facilitate the transfer of web 38 to Yankee dryer 52, web 38 carried on structured fabric 28 can be brought into contact with the surface of Yankee dryer 52 prior to the press nip associated with shoe press 56, Further, the contact can be maintained after structured fabric 28 travels beyond press 56.

[0073] Now, additionally referring to Fig. 30, there is shown yet another embodiment of the present invention, which is substantially similar to the invention illustrated in Fig. 29, except that instead of hot air hood 62, there is a belt press 64. Belt press 64 includes a permeable belt 66 capable of applying pressure to the machine side of structured fabric 28 that carries web 38 around vacuum roll 60. Fabric 66 of belt press 64 is also known as an extended nip press belt or a link fabric, which can run at 60 KN/m fabric tension with a pressing length that is longer than the suction zone of roll 60.

[0074] Preferred embodiments of the fabric 66 and the required operation conditions are also described in PCT/EP2004/053688 and PCT/EP2005/050198 which are herewith incorporated by reference. [0075] The above mentioned references are also fully applicable for dewatering fabrics 82 and press fabrics 66 described in the further embodiments.

[0076] Belt 66 is a specially designed extended nip press belt 66, made of, for example reinforced polyurethane and/or a spiral link fabric. Belt 66 also can have a woven construction. Such a woven construction is disclosed, e.g., in EP 1837439. Belt 66 is permeable thereby allowing air to flow there through to enhance the moisture removing capability of belt press 64. Moisture is drawn from web 38 through dewatering fabric 82 and into vacuum roll 60.

[0077] Referring to Fig. 31 , there is shown another embodiment of the present invention which is substantially similar to the embodiment shown in Fig. 30 with the addition of hot air hood 68 placed inside of belt press 64 to enhance the dewatering capability of belt press 64 in conjunction with vacuum roll 60.

[0078] Referring to Fig. 32, there is shown yet another embodiment of the present invention, which is substantially similar to the embodiment shown in Fig. 30, but including a boost dryer 70 which encounters structured fabric 28. Web 38 is subjected to a hot surface of boost dryer 70, and structured web 38 rides around boost dryer 70 with another woven fabric 72 riding on top of structured fabric 28. On top of woven fabric 72 is a thermally conductive fabric 74, which is in contact with both woven fabric 72 and a cooling jacket 76 that applies cooling and pressure to all fabrics and web 38. The pressing process does not negatively impact web quality. The drying rate of boost dryer 70 is above 400 kg/hr m2 and preferably above 500 kg/hr m2. The concept of boost dryer 70 is to provide sufficient pressure to hold web 38 against the hot surface of the dryer thus preventing blistering. Steam that is formed at the knuckle points of fabric 28 passes through fabric 28 and is condensed on fabric 72. Fabric 72 is cooled by fabric 74 that is in contact with cooling jacket 76, which reduces its temperature to well below that of the steam. Thus the steam is condensed to avoid a pressure build up to thereby avoid blistering of web 38. The condensed water is captured in woven fabric 72, which is dewatered by dewatering device 75. It has been shown that depending on the size of boost dryer 70, the need for vacuum roll 60 can be eliminated. Further, depending on the size of boost dryer 70, web 38 may be creped on the surface of boost dryer 70, thereby eliminating the need for Yankee dryer 52.

[0079] Referring to Fig. 33, there is shown yet another embodiment of the present invention substantially similar to the invention disclosed in Fig, 30 but with an addition of an air press 78, which is a four roll cluster press that is used with high temperature air and is referred to as a High Pressure Through Air Dryer (HPT AD) for additional web drying prior to the transfer of web 38 to Yankee dryer 52. Four-roll cluster press 78 includes a main roll, a vented roll, and two cap rolls. The purpose of this cluster press is to provide a sealed chamber that is capable of being pressurized. The pressure chamber contains high temperature air, for example, 150° C or higher and is at a significantly higher pressure than conventional TAD technology, for example, greater than 1.5 psi resulting in a much higher drying rate than a conventional TAD. The high-pressure hot air passes through an optional air dispersion fabric, throug web 38 and fabric structured 28 into a vent roll. The air dispersion fabric may prevent web 38 from following one of the cap rolls. The air dispersion fabric is very open, having a permeability that equals or exceeds that of fabric structured 28. The drying rate of the HPT AD depends on the solids content of web 38 as it enters the HPT AD. The preferred drying rate is at least 500 kg/hr m2, which is a rate of at least twice that of conventional TAD machines.

[0080] Advantages of the HPTAD process are in the areas of improved sheet dewatering without a significant loss in sheet quality and compactness in size and energy efficiency.

Additionally, it enables higher pre- Yankee solids, which increase the speed potential of the invention. Further, the compact size of the HPTAD allows for easy retrofitting to an existing machine. The compact size of the HPTAD and the fact that it is a closed system means thai it can be easily insulated and optimized as a unit to increase energy efficiency,

[0081] Referring to Fig. 34, there is shown another embodiment of the present invention. This is significantly similar to the embodiments shown in Figs. 30 and 33 except for the addition of a two-pass HPTAD 80. In this case, two vented rolls are used to double the dwell time of structured web 38 relative to the design shown in Fig. 33. An optional coarse mesh fabric may be used as in the previous embodiment. Hot pressurized air passes through web 38 carried on structured fabric 28 and onto the two vent rolls. It has been shown that depending on the configuration and size of the HPTAD, more than one HPTAD can be placed in series, which can eliminate the need for roll 60.

[0082] Referring to Fig. 35, a conventional twin wire former 90 may be used to replace the crescent former shown in previous examples. The forming roll can be either a solid or open roll . If an open roll is used, care must be taken to prevent significant dewatering through the structured fabric to avoid losing basis weight in the pillow areas. The outer forming fabric 93 can be either a standard forming fabric or one such as that disclosed in U.S. Pat. No. 6,237,644. The inner fabric 91 should be a structured fabric that is much coarser than the outer forming fabric 90. For example, inner fabric 91 may be similar to structured fabric 28. A vacuum roll 92 may be needed to ensure that the web stays with structured fabric 91 and does not go with outer wire 90. Web 38 is transferred to structured fabric 28 using a vacuum device. The transfer can be a stationary vacuum shoe or a vacuum assisted rotating pick-up roll 94. The second structured fabric 28 is at least the same coarseness and preferably coarser than first structured fabric 1. The process from this point is the same as the process previously discussed in conjunction with Fig. 30. The registration of the web from the first structured fabric to the second structured fabric is not perfect, and as such some pillows will lose some basis weight during the expansion process, thereby losing some of the benefit of the present invention. However, this process option allows for running a differential speed transfer, which has been shown to improve some sheet properties. Any of the arrangements for removing water discussed above as may be used with the twin wire former arrangement and a conventional TAD.

[0083] Referring to Fig. 36 there is illustrated another ATMOS™ system having many elements as discussed above. The ATMOS™ system of Fig 36, is further described in WO 2010/069695 having a priority date of December 19, 2008. Belt press 64 constitutes a first pressing zone where web 38 is pressed. Web 38 proceeds to a second pressing zone 65 where web 38 is pressed again.

[0084] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fail within the limits of the appended claims.

Claims

WHAT IS CLAIMED IS:
1. A fibrous web, comprising:
a fibrous construct having at least one formed surface feature, said surface feature including a topographical pattern reflective of a weave pattern in a fabric used in a papermaking machine, the fabric including:
a single layer of yarns arranged in a repeating weave pattern, each said weave pattern including:
a plurality of warp yams substantially oriented in a machine direction (MD) defining MD yarns; and
a plurality of weft yarns substantially oriented in a cross machine direction (CD) defining CD yarns, said MD yarns each having at least one long float within said weave pattern, each said long float being adjacent at least one other long float of an MD yarn, said weave pattern being a plain weave apart from said long floats.
2. The fibrous web of claim 1, wherein within said weave pattern said long floats that are adjacent to each other form at least one MD float pattern within said weave pattern.
3. The fibrous web of claim 2, wherein within, said weave pattern said at least one MD float pattern is a plurality of MD float patterns.
4. The fibrous web of claim 3, wherein within said weave pattern said plurality of MD float patterns are each one of identical and mirror imaged.
5. The fibrous web of claim 4, wherein within said weave pattern each of said plurality of MD float patterns are surrounded with said plain weave,
6. The fibrous web of claim 4, wherein within said weave pattern each of said plurality of MD float patterns touch each other forming a continuous MD float pattern with said plain weave defining the balance of said weave pattern.
7. The fibrous web of claim 1 , wherein within said weave pattern each said long float floats across at least 3 CD yarns.
8. The fibrous web of claim 7, wherein within said weave pattern each said long float floats across at least 4 CD yarns.
9. The fibrous web of claim 8, wherein within said weave pattern each said long float floats across at least 5 CD yarns.
10. The fibrous web of claim 1 , wherein the papermaking machine is an ATMOS™ papermaking machine that includes:
a dewatering fabric, a fibrous web is dewatered through the dewatering fabric, the dewatering fabric and the fabric being on opposite sides of the fibrous web; and
a permeable belt in contact with a portion of the fabric, there being an airflow in a direction such that the airflow first passes through said permeable belt, then the fabric, then the fibrous web, then said dewatering fabric.
1 1. A fibrous web obtainable by a process in a papermaking machine, the process comprising the steps of:
discharging a fibrous slurry between a forming fabric and a structured fabric; and removing moisture from said fibrous slurry through at least one of said forming fabric and said structured fabric to thereby form the fibrous web, said structured fabric being a single layer structured fabric of yarns arranged in a repeating weave pattern, a fibrous web being formed between said forming fabric and said structured fabric, each said weave pattern including:
a plurality of warp yarns substantially oriented in a machine direction (MD) defining MD yarns; and
a plurality of weft yarns substantially oriented in a cross machine direction (CD) defining CD yarns, each of said MD yarns having at least one long float within said weave pattern, each said long float being adjacent at least one other long float of an MD yarn, said weave pattern being a plain weave apart from said long floats.
12. The process of claim 1 1, wherein within said weave pattern said long floats that are adjacent to each other form at least one MD float pattern within said weave pattern.
13. The process of claim 12, wherein within said weave pattern said at least one MD float pattern is a plurality of MD float patterns.
14. The process of claim ] 3, wherein within said weave pattern said plurality of MD float patterns are each one of identical and mirror imaged.
15. The process of claim 14, wherein within said weave pattern each of said plurality of MD float patterns are surrounded with said plain weave.
16. The process of claim 14, wherein within said weave pattern each of said plurality of MD float patterns touch each other forming a continuous MD float pattern with said plain weave defining the balance of said weave pattern.
17. The process of claim 1 1 , wherein within said weave pattern each said long float floats across at least 3 CD yarns.
18. The process of claim 1 1 , wherein the papermaking machine is an ATMOS 1 M papermaking machine including a permeable belt in contact with a portion of said single layer structured fabric, the fibrous web being between said single layer structured fabric and said forming fabric, there being an airflow in a direction such that the airflow first passes through said permeable belt, then said single layer structured fabric, then the fibrous web, then said forming fabric.
19. A fibrous web obtainable by a process in a papermaking machine, the process comprising the steps of:
discharging a fibrous slurry between a forming fabric and a structured fabric; and removing moisture from said fibrous slurry through at least one of said forming fabric and said structured fabric to thereby form the fibrous web, the fibrous web having at least one surface feature, said surface feature including a topographical pattern reflective of a weave pattern in said structured fabric used in a papermaking machine, said structured fabric including a single layer of yarns arranged in a repeating weave pattern, each said weave pattern including:
a plurality of warp yarns substantially oriented in a machine direction (MD) defining MD yarns; and
a plurality of weft yarns substantially oriented in a cross machine direction (CD) defining CD yarns, said MD yarns each having at least one long float within said weave pattern, each said long float being adjacent at least one other long float of an MD yarn, said weave pattern being a plain weave apart from said long floats,
20. The process of claim 19, wherein within said weave pattern said long floats that are adjacent to each other form at. least one MD float pattern within said weave pattern.
21 . The process of claim 19, wherein the papermaking machine is an ATMOS™ papermaking machine including a plurality of pressing zones through which the fibrous web travels.
PCT/EP2011/063093 2010-07-30 2011-07-29 Fibrous web formed on a structured fabric WO2012013778A1 (en)

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US12847519 US20120024489A1 (en) 2010-07-30 2010-07-30 Structured fabric
US12/847,519 2010-07-30
US12/969,806 2010-12-16
US12969806 US20120024486A1 (en) 2010-07-30 2010-12-16 Fibrous web formed on a structured fabric

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US20120024486A1 (en) 2012-02-02 application
US20120024489A1 (en) 2012-02-02 application
US20120024487A1 (en) 2012-02-02 application
WO2012013773A1 (en) 2012-02-02 application

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