HK1034549A - Method for making tissue sheets on a modified conventional wet-pressed machine - Google Patents

Description

Method for making tissue using an improved conventional wet press

Background

The present invention relates generally to a method of making a paper product. And more particularly to a method of making a cellulosic web of high bulk and high absorbency on an improved conventional wet press.

There are generally two methods for making raw paper for paper products such as paper towels, napkins, towels, wipes, or the like. These processes are commonly referred to as wet-pressing and throughdrying. Although both methods may be the same at the front and back ends of the process, there is a significant difference in the manner in which water is removed from the wet web after initial formation.

More specifically, in the wet-pressing process, a newly formed, wet fabric is typically transferred to a papermaking felt and then pressed against the surface of a steam-heated Yankee dryer while still supported by the felt. As the fabric is transferred to the yankee dryer surface, water is extracted from the web and absorbed by the felt. The dewatered fabric, typically having a consistency of about 40%, is then dried on the hot surface of a Yankee steam dryer. The fabric is then creped to become soft and unfolded into the final sheet. One disadvantage of the wet-pressing process is that the pressing step increases the density of the fabric, thereby reducing the bulk and absorbency of the paper sheet. Subsequent creping steps can only partially restore these desirable sheet properties.

In the through-drying process, a newly formed fabric is first dewatered by vacuum and then transferred to a relatively porous fabric belt, and heated air is passed through the fabric to effect non-compressive drying. The resulting web is then transferred to a yankee dryer for creping. Since the web is substantially dry when it is transferred to the yankee dryer, the density of the web is not significantly increased by the transfer. Moreover, the throughdrying paper sheet inherently has a relatively low density because it is dried while the fabric is supported on the throughdrying fabric. Disadvantages of the throughdrying process are the high operating energy consumption and the high capital costs of the throughdrying machine.

Since most existing tissue making machines use old wet-pressing methods, it is of utmost importance for the manufacturer to find ways to modify existing wet-presses to produce consumer-acceptable low-density products, while at the same time the cost of modification is not high. Of course, it is possible to re-adapt the wet press to a throughdrying configuration, but this is generally not used due to the cost. Many complex and costly variations are necessary to provide a through-air dryer and its associated equipment. Accordingly, there is great interest in trying to improve existing wet presses without significantly changing the design of the wet press.

In U.S. patent 5,230,776 issued to Andersson et al at 7/27, 1993, a simple method for producing softer, more bulky tissue by modifying the wet press is described. This patent discloses replacing the felt with a perforated belt of the wire type and sandwiching the fabric between the forming wire and the perforated belt near the press roll. Additional dewatering devices such as steam blowpipes, blow nozzles and/or separate press felts are also disclosed which may be included within the confines of the sandwich structure to further increase the dry solids content prior to the yankee drying cylinder. These additional drying means are said to allow the modified wet press to run at a speed at least substantially equal to the speed of the through-air dryer.

It is important to reduce the moisture content of the fabric entering the yankee dryer to maintain the speed of the machine and prevent blistering or lack of adhesion of the fabric. See us patent 5,230,776, in which a separate press felt is used, it is however possible to increase the density of the fabric in the same way as in a conventional wet press. Thus, the increase in density due to the individual press felt will have a negative impact on the fabric bulk and absorbency.

Moreover, the air jets used to dewater the fabric are themselves ineffective in water removal or energy efficiency. It is known in the art to blow air over a sheet of paper to dry it, which is used in a yankee dryer hood for convection drying. However, in a yankee hood, a substantial portion of the air emitted by the nozzle does not penetrate through the fabric. Thus, if not heated to a high temperature, most of the air is wasted and not used to effectively remove the water. In a yankee dryer hood, the air is heated to 900 degrees fahrenheit and allowed to dwell for a long period of time to effect drying.

Thus, what is lacking and needed in the art is a practical method of making tissue having higher bulk and higher absorbency than throughdried paper using an improved conventional wet press.

Summary of The Invention

It has been found that wet-pressed tissue can be made with bulk and absorbency properties equivalent to similar throughdried products while maintaining reasonable equipment productivity. In particular, wet-pressed cellulosic webs can be made by vacuum dewatering the wet web to a consistency of up to about 30 percent and then noncompressively dewatering the paper to a consistency of 30 percent to 40 percent using an integral sealed air press. The sheet is then preferably transferred to a "molding" fabric belt in place of the conventional wet-pressed felt, in order to more closely conform the fabric belt to the contours of the wet web, or to impart a more three-dimensional nature to the wet web. The wet web is then preferably pressed against a Yankee dryer while being supported and dried by the mold fabric belt. The resulting products have higher wet bulk and absorbency than conventional wet pressed towel and towel products, and the same wet bulk and absorbency as existing throughdried products.

As used herein, "non-press dewatering" and "non-press drying" refer to dewatering or drying processes, respectively, that remove water from a cellulosic web without involving a nip press or other step that results in a significant increase in the density of or pressing against a portion of the web during drying or dewatering.

In the present process the wet fabric is wet molded to improve the three dimensional characteristics and absorbency of the fabric. As used herein, "wet-molded" tissue refers to: the tissue thus formed is conformed to the surface contour of the molding fabric at a consistency of from about 30% to about 40% and then dried by a thermally conductive drying means, such as a heated drying cylinder, distinct from other drying means, such as a through-air dryer, prior to optional additional drying means.

"molded fabric belts" suitable for the purposes of the present invention include, without limitation, papermaker's fabrics which exhibit an effective open area, or three-dimensional surface contour, which is sufficient to provide the fabric with a large amount of deflection in the Z-direction. Such fabric belts comprise a single layer, multiple layers or composite permeable structures. Preferred fabric belts have at least some of the following characteristics: (1) on the side of the molding fabric strip that is in contact with the wet web (top surface), the number of Machine Direction (MD) strands per inch (mesh) is from 10 to 200 (3.94 to 78.74 per cm) and the number of Cross Direction (CD) strands per inch (count) is also from 10 to 200 (3.94 to 78.74 per cm). Strand diameters are typically less than 0.050 inches (1.27 mm); (2) the distance between the highest point of the MD nodes and the highest point of the CD nodes is from about 0.001 to about 0.02 or 0.03 inches (0.025mm to about 0.508mm or 0.762mm) on the top surface. Between these two peaks there are knuckles formed by MD or CD strands to give the paper a three-dimensional peak/valley appearance configuration during the wet molding step; (3) on the top side, the length of the MD knuckles is equal to or greater than the length of the CD knuckles; (4) if the fabric strip is a multi-layer structure, it is preferred that the bottom layer have a finer mesh than the top layer to control the depth of fabric penetration and maximize retained fibers; and (5) may impart a certain geometric pattern to the fabric strip that is visually pleasing, such pattern typically repeating every 2 to 50 warp yarns.

Accordingly, in one aspect, the present invention relates to a method for making a cellulosic web, the steps of the method comprising: (a) depositing an aqueous suspension of papermaking fibers onto an endless forming fabric to form a wet fabric; (b) dewatering the wet web to a consistency of about 30 percent or greater using a non-compressive dewatering device adapted to cause a pressurized fluid to flow substantially through the web at a gauge pressure of about 5 pounds per square inch gauge or greater due to the integral seal with the wet web; (c) transferring the wet web to a molding fabric; (d) pressing the dewatered and molded web against a heated drying cylinder surface to at least partially dry the web; and (e) drying the fabric to a final dryness.

In another aspect, the present invention relates to a method of making a cellulosic web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers onto an endless forming fabric to form a wet fabric; (b) dewatering the wet web to a consistency of about 10% to about 30%; (c) supplementally dewatering the wet web to a consistency of from about 30% to about 40% using an air press adapted to cause a pressurized fluid to flow substantially through the web at a gauge pressure of about 5psig or greater due to the integral seal formed between the air plenum and the collection device; (d) transferring the wet web to a molding fabric belt to provide the web with a molded structure and a bulk of about 8 cc/g or greater; (e) pressing the dewatered and molded web against the surface of a heated drying cylinder with a fabric belt to maintain the web in a molded configuration and a bulk of about 8 cc/g or greater; and (f) drying the fabric to a final dryness.

In another aspect, the present invention relates to a method of making a cellulosic web, the method comprising the steps of: (a) depositing an aqueous suspension of papermaking fibers onto an endless forming fabric to form a wet fabric; (b) sandwiching the wet web between a pair of fabric belts, at least one of which is a three-dimensional molded fabric belt; (c) passing the sandwiched wet web structure between an air plenum and a collection device with the three-dimensional molding fabric belt disposed between the wet web and the collection device, the air plenum and collection device being operatively associated and adapted to create a pressure differential across the wet web of about 30 inches of mercury or greater and a pressurized fluid flow of about 10 standard cubic feet per minute or greater through the wet web per square inch; (d) dewatering the warm fabric to a consistency of about 30% or greater with a flow of pressurized fluid; (e) pressing the dewatered web against the surface of a heated drying cylinder with a fabric belt; and (f) drying the fabric to a final dryness.

The terms "integrally sealed" and "integrally sealed" as used herein refer to: a relationship between the air plenum and the wet web, the air plenum being in operative communication with and in indirect contact with the web such that about 85% or more of the air supplied to the air plenum flows through the web when the air plenum is operated at a pressure differential across the web of about 30 inches of mercury or greater; and a relationship between the air plenum and the collection device, the air plenum being in operative communication with and in indirect contact with the web and the collection device, whereby about 85% or more of the air supplied to the air plenum flows through the web and into the collection device when the air plenum and the collection device are operated at a pressure differential across the web of about 30 inches of mercury or greater.

The air press is capable of dewatering a wet web to a very high consistency, primarily due to the high pressure differential created across the web and the resulting air flow through the web. In particular embodiments, for example, the air pressure device may increase the consistency of the web by about 3% or more, particularly about 5% or more, such as from about 5% to about 20%, more particularly about 7% or more, such as from about 7% to 20%. Thus, the consistency of the wet web exiting the air press can be about 25% or greater, about 26% or greater, about 27% or greater, about 28% or greater, about 29% or greater, and desirably about 30% or greater, particularly about 31% or greater, more particularly about 32% or greater, such as from about 32% to 42%, particularly about 33% or greater, even more particularly about 34% or greater, such as from about 34% to 42%, and still more particularly about 35% or greater.

By adding the present method to the dehydration step of an integrally sealed air press, a significant improvement over the prior methods described above can be obtained. First, and most importantly, a sufficiently high consistency is obtained so that the process can be operated at industrially useful speeds. As used herein, "high speed operation" or "industrial use speed" of a tissue machine refers to a machine speed in feet per minute that is at least the same as any one of the following values or ranges: 1,000; 1,500; 2,000; 2,500; 3,000; 3,500; 4,000; 4,500; 5,000; 5,500; 6,000; 6,500; 7,000; 8,000; 9,000; 10,000, and a range having any of the above values as an upper and lower limit. Moreover, molding the sheet at high consistency significantly improves the ability of the sheet to maintain its three-dimensionality and, thus, the final caliper of the sheet. As used herein, the term "textured" or "three-dimensional" as applied to the surface of a fabric strip, felt or uncalendered paper web means that the surface is not substantially smooth or coplanar. In addition, existing machine configurations are suitable for the rush transfer step, which results in a significant increase in bulk and absorbency over existing wet-pressing processes.

An optional steam jet or the like may be used before the air press to increase the consistency of the post air press and/or to improve the cross-machine direction moisture profile of the web. Moreover, higher consistencies can be obtained when the machine speed is slower and the residence time in the air press is longer.

The pressure differential across the wet web provided by the air press can be 25 inches of mercury or more, such as from about 25 to about 120 inches of mercury, particularly about 35 inches of mercury or more, such as from about 35 to about 60 inches of mercury, and more particularly from about 40 to about 50 inches of mercury high. The pressure differential can be achieved in part by maintaining a fluid pressure on one side of the wet web of greater than 0 to about 60 pounds per square inch gauge (psig), specifically greater than 0 to about 30psig, more specifically about 5psig or greater, for example about 5 to about 30psig, and still more specifically from about 5 to about 20psig, through the gas plenum of the air press. The collection means of the air press is preferably used as a vacuum box operating at 0 to about 29 inches of mercury vacuum, particularly 0 to about 25 inches of mercury vacuum, particularly greater than 0 to about 25 inches of mercury vacuum, and more particularly from about 10 to about 20 inches of mercury vacuum, for example about 15 inches of mercury vacuum. The collection means is preferably, but not necessarily, integrally sealed with the gas plenum and evacuated so that it acts as a collection means for air and liquid. The pressure levels in the gas plenum and the collection means are preferably monitored and controlled to predetermined levels.

It is apparent that the pressurized fluid used within the air press is sealed from the ambient air to create a substantial air flow through the fabric that results in a significant de-watering pressure of the air press. The flow of pressurized fluid through the air pressure device is suitably from about 5 to about 500 standard cubic feet per minute (SCFM) per square inch of the open area, particularly about 10SCFM or greater per square inch of the open area, for example from about 10 to about 200SCFM per square inch of the open area, more particularly about 40SCFM per square inch of the open area, for example from about 40 to about 120SCFM per square inch of the open area. Desirably, 70% or more, particularly 80% or more, and more particularly 90% or more of the pressurized fluid supplied to the air plenum is drawn through the wet web into the vacuum box. For purposes of the present invention, the term "standard cubic feet per minute" refers to cubic feet per minute measured at 14.7 pounds per square inch absolute and 60 degrees Fahrenheit ((F)).

The terms "air" and "pressurized fluid" are used interchangeably herein to refer to any gaseous substance used within an air pressure device for dewatering fabrics. The gaseous substance suitably comprises air, steam or the like. Preferably, the pressurized fluid comprises air having an ambient temperature, or a heated gas that is a gas that is raised to a temperature of about 300 ° F or less, particularly about 150 ° F or less, by a method that is solely pressurized.

The wet web is preferably adhered to the surface of a yankee dryer or other heated dryer in a manner that retains a substantial portion of the texture formed by the pretreatment, particularly the texture formed by molding on a three-dimensional fabric belt. The conventional method for producing wet-pressed crepe paper is not suitable for this purpose because in the conventional method, a press roll is used to dewater the web and uniformly press the web into a dense and flat state. For the purposes of the present invention, conventional substantially smooth press felts are replaced by textured materials such as apertured fabric belts, and preferably throughdrying fabric belts. The web of towels produced according to the process of the present invention preferably has a bulk of about 8 cubic centimeters per gram (cc/g) or greater, more preferably about 10cc/g or greater, and more preferably about 12cc/g or greater, after being molded on a three-dimensional fabric belt, and is maintained after being pressed on a heated drying cylinder with a textured foraminous fabric belt.

At best, a significantly reduced press pressure can be used as compared to conventional tissue making methods. Preferably, the area of maximum load applied to the fabric should be about 400psi or less, particularly about 350psi or less, more particularly about 150psi or less, for example between about 2 and about 50psi, and most particularly about 30psi or less, across any 1 square inch area surrounding the point of maximum pressure, on average. The pressing pressure in pounds per linear inch (pli) measured at the point of maximum pressure is preferably about 400pli or less, and particularly about 350pli or less. The application of the three-dimensional fabric structure to the cylindrical dryer with low pressure helps to maintain a substantially uniform density of the dried fabric. This helps to achieve a substantially uniform density of the fabric by effectively dewatering the fabric using a non-compressive device prior to attachment to the yankee dryer, and by selecting a foraminous fabric belt to have the fabric abut the dryer, which is relatively free of high stiffness protuberances that may exert high localized pressure on the fabric. The fabric strip is preferably treated with an effective amount of a fabric strip release agent to promote separation of the fabric from the fabric strip once the fabric is against the dryer surface.

The absorbency of a tissue can be characterized by its absorbent capacity and its rate of absorption. As used herein, "absorbent capacity" is the maximum amount of distilled water that a paper can absorb, expressed as grams of water per gram (unit sample paper). More specifically, the absorbency of a sample paper sheet can be measured as a sample cut into a dry paper sheet having a weight of approximately 0.01 grams for 4 inches by 4 inches (101.6 by 101.6 mm). The sample was dropped onto the surface of a distilled water tank at room temperature and left in the tank for 3 minutes. The sample is then removed using tongs or tweezers and hung vertically with three-pronged tongs to drain excess water. Each sample may be drained for 3 minutes. The sample is then placed on the weighing pan by placing the weighing pan under the sample and releasing the three-pronged clamp. The wet sample weight was approximately 0.01 grams. The absorption capacity is the wet weight of the sample minus the dry weight (amount of water absorbed) divided by the dry weight of the sample. At least 5 representative samples of each product can be measured and the results averaged.

The "absorption rate" is the time it takes for the product to completely wet out in distilled water. The absorption rate was determined by dropping a paper pad consisting of 20 sheets of paper, each measuring 2.5 inches by 2.5 inches (63.5 by 63.5mm), onto the surface of a distilled water tank having a temperature of 30 ℃. The time elapsed from the moment the sample hit the water until it was completely wetted out (as determined visually) is the absorption rate in seconds.

The method is suitable for use in the manufacture of a variety of absorbent products including facial tissues, bath tissues, towels, napkins or wipes or the like. For the purposes of the present invention, the term "tissue" or "tissue product" is generally used to describe the structure of such products, while the term "cellulosic web" is used to broadly refer to a web comprising or consisting of cellulosic fibers, regardless of the finished structure.

Many fiber types may be employed in the present invention including hardwood or softwood, straw (wheat straw), flax, milkweed seed wool fibers, abaca, hemp fibers, kenaf fibers, bagasse, cotton, reed or similar materials. All known papermaking fibers including bleached or unbleached fibers, naturally occurring fibers (including wood and other cellulosic fibers, cellulose derivatives, and chemically stiffened or crosslinked fibers), or synthetic fibers (synthetic papermaking fibers including certain forms of fibers made from polypropylene, acrylic, aramid, acetate, and the like), virgin and recycled or recycled fibers, hardwood and softwood, and fibers that have been mechanically pulped (e.g., groundwood), chemically pulped (including but not limited to kraft and sulfite pulping processes), thermomechanically pulped, chemithermomechanically pulped, or the like can be used. Mixtures of any subset of the above or related types of fibers may be used. The fibers may be prepared in a number of advantageous ways known in the art. Useful methods for preparing the fibers include dispersion to impart flexibility and improve drying properties as disclosed, for example, in U.S. patent 5,348, 620 published at 9/20 of 1994 and U.S. patent 5,501, 768 published at 3/26 of 1996, both of which are invented by m.a. hermans et al.

Chemical additives may also be used and may be added to the virgin fibers, the fiber pulp suspension, or to the fabric during or after production. Such additives include opacifiers, pigments, moisturizing enhancers, drying enhancers, emollients, lubricants, humectants, virucides, bactericides, buffers, waxes (waxes), fluoropolymers, odor control materials and deodorants, zeolites, dyes, fluorescent dyes or bleaches, fragrances, separators, vegetable and mineral oils, heat retention agents, adhesives, superabsorbents, surfactants, moisturizing agents, uv blockers, antimicrobials, detergents, bactericides, preservatives, rue extract, vitamin E, or similar additives. The chemical additives need not be added uniformly, but may vary at different locations and from one side of the towel to the other. Hydrophobic materials deposited on portions of the surface of the fabric may be used to enhance the performance of the fabric.

One or more headboxes may be used. The headbox or headboxes may be layered so that a multi-layer structure may be created by a single headbox jet during fabric formation. In a particular embodiment, the fabric is made with a stratified or layered headbox so that short fibers are preferentially deposited on one side of the fabric for improved softness, and longer fibers are then deposited on the other side of the fabric or on the inner layers for a three or more layer fabric. The fabric is preferably formed on an endless loop of an apertured forming fabric belt, which loop allows fluid drainage and partial dewatering of the fabric. Multiple primary fabrics from multiple headbox can be layered or mechanically or chemically joined in wet condition to form a multi-layered single fabric.

The many features and advantages of the invention are apparent from the following specification. In the following description, preferred embodiments of the present invention are explained with reference to the drawings. These examples do not represent the full scope of the invention. Accordingly, the claims hereof are to be construed as embracing the full scope of the invention.

Detailed description of the drawings

FIG. 1 typically shows a process flow diagram of the process of the present invention for making a high bulk and high absorbency cellulosic web.

Figure 2 typically shows a process flow diagram of another method of the present invention.

FIG. 3 typically shows a process flow diagram of yet another method of the present invention.

Fig. 4 representatively illustrates an enlarged end view of an air pressure device used in the method of fig. 1-3, with the air plenum seal of the air pressure device in a raised position relative to the wet web and the vacuum box.

Fig. 5 representatively illustrates a side view of the air pressure device of fig. 4.

FIG. 6 representatively shows an enlarged cross-sectional view taken generally in the plane of line 6-6 of FIG. 4 with the sealing device loaded against the web.

FIG. 7 representatively illustrates an enlarged cross-sectional view, similar to FIG. 6, taken generally in the plane of line 7-7 of FIG. 4.

Fig. 8 representatively illustrates a perspective view, partially broken away and in section, of several components of an air plenum seal device disposed against a fabric strip for purposes of illustration.

Fig. 9 representatively illustrates an enlarged cross-sectional view of another seal configuration of the air pressure device of fig. 4.

Fig. 10 representatively illustrates an enlarged schematic view of a sealing cross-section of the air pressure device of fig. 4.

Detailed description of the invention

The present invention will now be described in detail with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. For simplicity, the different tensioning rollers used to define the several paths of travel of the fabric belt are shown schematically, but not numbered. For stock preparation, the headbox, forming fabric belt, fabric transfer, creping and drying can use different conventional papermaking equipment and operations. Nevertheless, in order to provide a background description that may be used with embodiments of the present invention, specific conventional components are shown.

The method of the present invention can be carried out using the apparatus shown in FIG. 1. A primary paper web 10 forming a papermaking fiber slurry is deposited from a headbox 12 in an endless loop of an apertured forming fabric belt 14. The consistency and flow rate of the slurry determine the basis weight of the dry fabric, which is preferably between about 5 and about 80 grams per square meter (gsm), and more preferably between about 8 and about 40 gsm.

The primary fabric 10 is partially dewatered while carried on the forming fabric 14 by foils, suction boxes and other devices (not shown) as is known in the art. The conventional method of dewatering tissue prior to the drying cylinder of the present invention may result in insufficient removal of water in order to achieve high speed operation, thus requiring an auxiliary dewatering device. In the illustrated embodiment, air press 16 is used to non-compressively dewater fabric 10. The air press 16 is shown to include a pressurized air plenum 18 disposed on the fabric 10, a water and fluid collection device in the form of a vacuum box 20 disposed below the forming fabric 14 and in operative communication with the pressurized air plenum, and a support fabric 22. The wet web 10 is sandwiched between the forming fabric 14 and the support fabric 22 as it passes through the air press 16 so as to seal against the web without damaging the web.

The air press provides a substantial rate of moisture removal that enables a drying level of over 30% to be achieved before the fabric is attached to the yankee dryer, preferably without substantial press dewatering. Several embodiments of the air pressure device 16 will be described in more detail below. Other suitable examples are disclosed in U.S. patent application No. 08/647, 508, entitled "method and apparatus for making soft tissue" to m.a. hermans et al, 1996, 5/14, which is hereby incorporated by reference.

After the air press 16, the wet web 10 is further run with the forming fabric belt 14 until it is transferred to the textured and apertured fabric belt 24 with the aid of vacuum transfer shoes 26 at the transfer station. The transfer may be a rush transfer using appropriately designed slide rails, fabric belt positioning and vacuum levels such as disclosed in the following patent documents: U.S. patent application serial No. 08/790, 980 to Lindsay et al, entitled "method for improving rush transfer to produce high bulk without giant folding"; U.S. patent application serial No. 08/709,427 to Lindsay et al, filed on day 9/6 of 1996 entitled "process for producing high bulk tissue webs using nonwoven substrates"; us patent No. 5, 667, 636 to s.a. engel et al, published 1997, 9/16; and U.S. patent No. 5,607,551 to t.e.farrington, jr. et al, issued 3/4/1997; these patent documents are incorporated herein by reference. In rush transfer operations, the textured fabric belt 24 travels at a substantially slower speed than the forming fabric belt 14, with a speed differential of about 10% or greater, specifically about 20% or greater, and more specifically between about 15% and about 60%. Rush transfer desirably eliminates tenting from the microscopic level and increases longitudinal stretch without decreasing strength.

The textured fabric strip 24 may comprise a three-dimensional throughdrying fabric strip such as disclosed in U.S. patent 5429686 to k.f. chiu et al, published 7, 4, 1995, which is incorporated herein by reference, or the textured fabric strip 24 may comprise other woven, textured fabric or nonwoven fabric strips. The textured fabric strip 24 may be treated with a fabric strip release agent such as a silicon or hydrocarbon mixture to later separate the wet fabric from the fabric strip. The fabric tape release agent may be sprayed onto the textured fabric tape 24 prior to collecting the fabric. Once disposed on the textured fabric strip 24, the fabric 10 may be molded against the fabric strip using vacuum pressure or light pressure (not shown), although vacuum force is used to mold at the transfer shoe 26 during acquisition, which may properly mold the paper.

The wet web 10 on the textured web 24 is then pressed against the cylindrical dryer 30 by a press roll 32. The drum dryer 30 is equipped with a steam hood or yankee dryer hood 34. The hood typically utilizes jets of heated air at a temperature of about 300 ° F or more, particularly about 400 ° F or more, more particularly about 500 ° F or more, and most particularly about 700 ° F or more, the jet direction being directed from a nozzle or other flow passing device towards the web of towels so that the gas jet has a maximum velocity or partial average velocity in the hood of one of the following levels: about 10 meters per second (m/s) or greater, about 50m/s or greater, about 100m/s or greater, about 250m/s or greater.

The wet web suitably has a fiber consistency of about 30% or greater, preferably about 35% or greater, for example between about 35% and about 50%, and more preferably about 38% or greater when secured to dryer 30. Upon removal from dryer 30, the dryness of the fabric increases to about 60% or greater, specifically about 70% or greater, more specifically about 80% or greater, even more specifically 90% or greater, and most specifically between about 90% and about 98%. The fabric may be partially dried on a heated drying cylinder and wet creped at a consistency of about 40% to about 80% and then dried (post-dried) to a consistency of about 95% or greater. Non-conventional hood and impingement systems may be used as an alternative or in addition to the yankee dryer hood 34 to enhance the dryness of the web of towels. Additional cylindrical dryers or other drying equipment, in particular non-extrusion dryers, can be used after the first cylindrical dryer. Suitable post-drying equipment includes one or more cylindrical dryers such as yankee and empty can dryers, through-air dryers or any other commercial drying equipment. Alternatively, the molded fabric may be fully dried and dry creped on a heated drying cylinder. The dryness of the heated drying cylinder depends on such factors as the speed of the fabric, the size of the dryer, the amount of moisture in the fabric, etc.

The resulting dried fabric 36 is drawn or delivered from the dryer, such as by creping blade 28, and then wound onto roll 38. The interfacial control mixture 40 is shown as being sprayed from a spray tube 42 onto the surface of the rotary drum dryer 30 before the wet web 10 comes into contact with the dryer surface. As an alternative to spraying directly onto the dryer surface, the interfacial control mixture may be applied directly to the wet fabric or dryer surface by gravure printing, or may be incorporated into the aqueous fibrous slurry suspension in the wet end of the paper machine. When located on the dryer surface, the fabric 10 may also be chemically treated, such as by printing or spraying a solution directly onto the dryer fabric, including the addition of a solvent to promote separation from the dryer surface.

Interfacial control mixture 40 may include a conventional creping adhesive and/or a dryer release agent for wet-pressing and creping operations. An interfacial control mixture, disclosed in U.S. patent application entitled "method for producing low density elastic webs" by f.g. draucke et al, which is not known in the application number and filed on even date herewith, may also be used to remove the wet web 10 from the dryer surface without creping at the same time.

Figure 2 shows another alternative embodiment in which a primary paper web 10 in the form of a papermaking fiber slurry is deposited from a headbox 12 onto an endless loop of an apertured forming fabric belt 14. On forming fabric 14, primary fabric 10 is partially dewatered by vacuum box 46 or other suitable means. The air press 16 is used to noncompressively dewater and also to transfer the fabric 10 to the textured foraminous fabric belt 24. The gas pressure device 16 includes a pressurized gas plenum 18 disposed in operable communication with a vacuum box 20. As it passes through the air press 16, the wet fabric 10 is sandwiched between the forming fabric 14 and a textured fabric belt 24, the textured fabric belt 24 being disposed between the wet fabric and the vacuum box 20.

The wet web 10 on the textured web 24 is then pressed against the cylindrical dryer 30 by a press roll 32. The drum dryer 30 is equipped with a steam hood or yankee dryer hood 34. The resulting dried web 36 is drawn or delivered from the dryer without creping and then wound onto a roll 38. The angle at which the fabric is pulled from the dryer surface, measured at the point of separation in the tangential direction to the dryer surface, is suitably from about 80 to about 100 degrees, although the angle may vary at different operating speeds.

The interfacial control mixture 40 is sprayed from the spray tube 42 onto the surface of the rotary drum dryer 30 in the form of a spray. For example, the interplanar control mixture may include a mixture of polyvinyl alcohol, sorbitol and Hercules M1336 polyglycol added to an aqueous solution having a dosage of less than 5% solids by weight, between 50 and 75 mg/M. The amounts of adhesive compound and release agent must be balanced to bond the web so that it is not lifted further into the hood so that the web can be pulled from the dryer without creping.

The embodiment shown in fig. 2 provides an enhanced degree of wet molding, since the air press 16 is used to mold fabric onto the textured fabric strip 24. The air press is positioned at the interface between forming fabric 14 and textured fabric 24 so that a separate support fabric slide 22 (fig. 1) is not necessary. Forming fabric 14 and textured fabric 24 preferably move at the same speed as the embodiment of fig. 2. In machine configurations, fabrics are rush transferred and wet molded at industrial use speeds, which is beneficial for inverting the fabric or otherwise changing the location of the relative weakness of the fabric with respect to the textured fabric strip. The technique of turning and moving the fabric is not known in the application number and is filed on even date herewith and is disclosed in U.S. patent application entitled "low density elastic fabrics and methods of making such fabrics" to s.l. chen et al, which is hereby incorporated by reference.

Another alternative embodiment is shown in fig. 3. This embodiment is the same as the embodiment of fig. 2, except that the wet web 10 on the textured web 24 is transferred to the cylindrical dryer 30 using two transfer rolls 48. As a result, the fabric 10 is wound onto the dryer and the textured fabric strip 24 is held against the cylindrical dryer 30 for a predetermined span before the dryer hood 34 to improve drying and bonding performance. The textured fabric strip 24 preferably allows the fabric to be wrapped around the yankee dryer 30 for a limited distance of about 6 inches or more, such as between about 12 and about 40 inches, and more preferably at least about 18 inches, in the machine direction on the surface of the cylindrical dryer. The distance the fabric strip is wrapped around the dryer is preferably less than the entire distance the fabric contacts the dryer, and in particular, the fabric strip is separated from the fabric before the fabric enters the dryer hood 34. The length of the fabric tape wrap depends on the roughness of the fabric tape. Either or both of the rollers 48 may be loaded against the surface of the cylindrical dryer to improve the degree of drying, paper molding, and adhesive bonding. Alternatively, either or both rolls may be unloaded to avoid any additional compression of the fabric.

Wrapping the fabric strip over a predetermined span of the drying cylinder as provided in the embodiment of fig. 3 may enhance retention of the three-dimensional structure of the web, wherein the web remains in contact with the textured fabric strip 24 while the web is dried to a higher consistency. The machine configuration of fig. 3 is particularly desirable when the textured fabric strip 24 is relatively open or moving. Figure 3 shows the removal of the web from the yankee dryer with a creping blade 28.

Fig. 4-7 illustrate an air press 200 for dewatering a wet web 10. The gas pressure device 200 generally includes an upper gas plenum 202 that is integrated with a lower collection device in the form of a vacuum tank 204. The wet web 10 moves in the machine direction 205 between the air plenum and the vacuum box as the wet web 10 is sandwiched between the upper 206 and lower 208 support belts. The air plenum and the vacuum box are operatively coupled to one another such that pressurized fluid supplied to the air plenum moves through the wet web and is removed or exhausted through the vacuum box.

Each continuous web 206 and 208 moves over a series of rollers (not shown) to guide, drive and stretch the webs in a manner well known in the art. The stretch of the fabric strip is adjusted to a predetermined value, suitably from about 10 to about 60 pounds per linear inch (pli), particularly from about 30 to about 50pli, and most preferably from about 35 to about 45 pli. Fabric strips that can be used to convey the wet web 10 through the air press 200 include almost any fluid permeable fabric strip, such as Albany International 94M, Appleton Mills 2164B, or the like.

Fig. 4 shows an end view of the air press 200 across the width of the wet web 10, while fig. 5 shows a side view of the air press in the machine direction 205. In both figures, several components of the air plenum 202 are shown in a raised or retracted position relative to the wet web 10 and the vacuum box 204. In the collapsed position, the pressurized fluid may not be effectively sealed. In the present invention, the "retracted position" of the air pressure device means that the components of the air plenum 202 do not impinge on the wet web and the support web.

The gas plenum 202 and vacuum box 204 are shown mounted in a suitable frame structure 210. The illustrated frame structure includes upper and lower support plates 211 separated by a number of vertically oriented support bars 212. The gas plenum 202 defines a chamber 214 (fig. 7), the chamber 214 being adapted to receive pressurized fluid that is supplied through one or more suitable air tubes 215 that are operatively connected to a source of pressurized fluid (not shown). Accordingly, vacuum box 204 defines a plurality of vacuum chambers (described below in connection with fig. 7) that are preferably operatively connected to low and high vacuum sources via suitable fluid conduits 217 and 218 (fig. 5, 6 and 7), respectively. The moisture that is removed from the wet web 10 is then separated from the air stream. Various fasteners used to mount components of the pneumatic device are shown but not numbered.

Fig. 6 and 7 show enlarged cross-sectional views of the air pressure device 200. In these figures, the air press is shown in an operating position in which the components of the air plenum 202 are lowered into a colliding relationship with the wet web 10 and the support webs 206 and 208. It has been found that the degree of impact results in a proper sealing of the pressurized fluid with minimal contact force and thus reduces webbing wear as will be described in more detail below.

The air plenum 202 includes a stationary member 202 fixedly mounted to the frame structure 210, and a sealing device 260 movably mounted with respect to the frame structure and the wet web. In addition, the entire gas plenum is movably mounted relative to the frame structure.

With particular reference to fig. 7, the stationary part 220 of the gas plenum includes a pair of upper bearing means spaced apart from one another and disposed below the upper bearing plate 211. The upper bearing means defines outer surfaces 224 that face each other and partially define plenum chamber 214 therebetween. The upper bearing means also defines a lower surface 226 facing the vacuum box 204. In the illustrated embodiment, each lower surface 226 defines an elongated recessed portion 228 in which the upper pneumatic loading tube is fixedly mounted. The upper pneumatic loading tube 230 is suitably centered in the cross direction and preferably extends the full width of the wet web.

The stationary component 220 of the gas plenum 202 also includes a pair of lower support devices 240, the pair of lower support devices 240 being spaced apart from each other and vertically spaced apart from the upper support device 222. The lower bearing apparatus defines a top surface 242 and an outer surface 244. The top surface 242 faces directly toward the bottom surface of the upper bearing assembly 222 and, as shown, defines an elongated recessed portion 246 in which a lower pneumatic loading tube 248 is fixedly mounted. The lower pneumatic loading tube 248 is suitably centered in the cross direction and suitably extends over about 50% to 100% of the width of the wet web. In the illustrated embodiment, the lateral support plate 250 is fixedly coupled to the outer surface 224 of the lower bearing assembly and serves to stabilize the sealing assembly 260 against vertical movement.

Referring additionally to fig. 8, the sealing device 260 includes a pair of transverse seals referred to as spaced CD seals 262 (fig. 6-8), a plurality of carriers 263 (fig. 8) connected to the CD seals, and a pair of longitudinal seals referred to as MD seals 264 (fig. 6 and 8). The CD seal 262 is vertically movable relative to the stationary member 220. An optional but desirable bracket 263 is fixedly mounted to the CD seal to provide structural support so as to move vertically with the CD seal. In the machine direction 205, MD seals 264 are disposed between the upper support devices 222 and between the CD seals 262. As described in detail below, portions of the MD seal may move vertically relative to the stationary member 220. In the cross direction, the MD seal is disposed near the edges of the wet web 10. In one particular embodiment, the MD seal is movable in the cross direction in order to accommodate the range of possible wet web widths.

The illustrated CD seal 262 includes a main upstanding wall portion 266, a transverse flange 268 projecting outwardly from a top 270 of the wall portion, and a sealing disc 272 (fig. 7) mounted on an opposite bottom 274 of the wall portion. In this way, the outwardly projecting flanges 268 form opposed upper and lower control surfaces 276 and 278 that are substantially perpendicular to the direction of movement of the seal. The wall portion 266 and the flange 268 may comprise separate components as shown or a single component.

As described above, the components of the sealing device 260 are vertically movable between a retracted position, shown in fig. 4 and 5, and an operating position, shown in fig. 6 and 7. In particular, wall portion 266 of CD seal 262 is disposed within and slidable relative to position control plate 250. The amount of vertical movement is determined by the ability of lateral flange 268 to move between bottom surface 226 of upper support apparatus 222 and top surface 242 of lower support apparatus 240.

The vertical position of the transverse flange 268 and the CD seal 262 are controlled by actuating the pneumatic loading tubes 230 and 248. The loading tube is operatively connected to a pneumatic source and a control system (not shown) for the pneumatic means. Activation of upper load tube 230 may generate a downward force on upper control surface 276 of CD seal 262, causing flange 268 to move downward until it contacts top surface 242 of lower support device 240, or to stop moving under an upward force generated by the tension in lower load tube 248 or the fabric strip. Retraction of the CD seal 262 is accomplished by activating the lower loading tube 248 and deactivating the upper loading tube. In this condition, lower load tube presses upward on lower control surface 278, causing flange 268 to move toward the bottom surface of upper bearing assembly 222. Of course, the upper and lower loading tubes may be operated at different pressures to move the CD seal. Another means for controlling the vertical movement of the CD seal may include other types of connections such as pneumatic cylinders, hydraulic cylinders, bolts, jacks, mechanical connectors, or other suitable means. Suitable loading tubes are available from Seal Master corporation of Kent, Ohio.

As shown in FIG. 7, a pair of bridge span plates 279 span the gap between upper bearing assembly 222 and CD seal 262 to prevent pressurized fluid from escaping. Thus, the bridge plate defines a portion of the plenum chamber 214. The bridge span plate may be fixedly mounted on the outer surface 224 of the upper bearing means and may slide relative to the inner surface of the CD seal or vice versa. The bridge span plate may be made of a fluid permeable semi-rigid low friction material such as LEXAN, a metal plate or the like.

The function of the sealing panel 272 is combined with other features of the air press to minimize the escape of pressurized fluid longitudinally between the air plenum 202 and the wet web 10. Further, the sealing sheet is preferably formed in such a manner as to reduce the amount of wear of the fabric belt. In a particular embodiment, the sealing plate is made of an elastomeric plastic compound, ceramic, coated metal substrate or the like.

Referring particularly to fig. 6 and 8, the MD seals 264 are spaced apart from each other and are adapted to prevent the loss of pressurized fluid along the sides of the pneumatic device. Fig. 6 and 8 each show one of the MD seals 264, with the MD seal 264 being disposed in the cross direction adjacent to the edge of the wet web 10. As shown, each MD seal includes a cross support 280, an end deckle band 282 operably coupled to cross support 280, and a drive 284 for moving the end deckle band relative to the cross support. The cross-supports 280 are generally disposed adjacent the side edges of the wet web 10 and generally between the CD seal members 262. As shown, each cross support defines a downwardly directed channel 281 (FIG. 8) in which an end stop paper frame strip is mounted. In addition, each cross support defines an annular bore 283 within which the driver 284 is mounted.

The end deckle band 282 is movable relative to the cross support 280 due to the cylinder drive 284. A coupling 285 (fig. 12) couples the end stop frame strap to the output shaft of the cylinder drive. The couplers may include one or more inverted T-shaped rods so that the end paper frame strip may slide within the channel 281, for example for replacement.

As shown in FIG. 8, the cross supports 280 and end deckle bands 282 define slots to receive a fluid impermeable sealing band 286, such as an O-ring material or the like. The sealing band helps seal the plenum cavity 214 of the pneumatic device from leaks. The sealing tape slot is preferably widened at the interface between cross supports 280 and end paper frame tape 282 to accommodate relative movement between these components.

A bridge span plate 287 (fig. 6) is disposed between the MD seal 264 and the upper support plate 211 and is fixedly mounted thereto. The lateral portion of plenum chamber 214 (fig. 7) is defined by a bridge plate. A sealing means, such as a fluid impermeable gasket material, is preferably disposed between the bridge plate and the MD seal to allow relative movement thereof and to prevent loss of pressurized fluid.

Regardless of the vertical position of CD seal 262, drive 284 suitably provides for the controlled loading and unloading of end deckle band 282 against upper support fabric 206. The load can be precisely controlled to meet the necessary sealing force. The end deckle band may be retracted when it is not necessary to eliminate the entire end deckle and fabric band wear. Suitable drivers may be provided by Bimba, Inc. Alternatively, springs (not shown) may be used, thus holding the end deckle against the fabric strip, although the ability to control the position of the end deckle may be sacrificed.

Referring to fig. 6, each end deckle band 282 has a top surface or edge 290 disposed adjacent to link 285, an opposite bottom surface or edge 292, the bottom surface or edge 292 disposed in use in contact with webbing 206, and a side surface or edge 294, the side surface or edge 294 being immediately adjacent to CD seal 262. The bottom surface 292 is suitably shaped to match the curvature of the vacuum box 204. The bottom surface 292 is preferably shaped to conform to the curvature of the fabric strip impact at the location where the CD seal 262 impacts the fabric strip. Thus, the central portion 296 of the bottom surface is laterally surrounded longitudinally by spaced apart ends 298. The shape of central portion 296 generally conforms to the shape of the vacuum box, while the shape of end portions 298 generally accommodates the deflection of the fabric strip caused by CD seal 262. To prevent the protruding end 298 from wearing, the end deckle band is preferably retracted before the CD seal 262 is retracted. The end deckle bands are preferably made of a gas impermeable material which minimizes abrasion of the fabric bands. Specific materials suitable for the end deckle include polyethylene, nylon or the like.

The MD seal 264 is preferably movable in the cross direction so that it is preferably slidably disposed against the CD seal 262. In the illustrated embodiment, movement of the MD seal 264 in the cross direction is controlled by a threaded shaft or screw 305, which threaded shaft or screw 305 is held in place by a bracket 306 (fig. 8). Threaded shaft 305 passes through a threaded hole in cross support 280 and rotation of the shaft moves MD seal 264 along the shaft. Another means for moving the MD seal in the cross direction may also be used, such as a pneumatic device or the like. In an alternative embodiment, the MD seal is fixedly mounted to the CD seal so that the entire seal is raised and lowered together (not shown). In another alternative embodiment, cross supports 280 are fixedly mounted to the CD seal and the end deckle bands are adapted to move independently of the CD seal (not shown).

The vacuum box 204 includes a lid 300, the lid 300 having a top surface 302 over which the lower support fabric belt 208 travels. The vacuum chamber cover 300 and the sealing device 260 are preferably slightly curved to facilitate fabric handling. The illustrated vacuum chamber lid is provided with a first outer sealing slide 311, a first sealed vacuum zone 312, a first inner sealing slide 313, a series of four high vacuum zones 314, 316, 318 and 320 surrounding three inner slides 315, 317 and 319, a second inner sealing slide 321, a second sealed vacuum zone 322, and a second outer sealing slide 323 (fig. 7) along the longitudinal direction 205 from the front edge to the rear edge. Each of these tracks and zones preferably extends across the full width of the fabric in the cross direction. Each slide rail includes a top surface, preferably made of a ceramic material, to seat against the lower support fabric belt 208 without causing significant fabric belt wear. Suitable vacuum chamber covers and slides may be made of plastic, nylon, coated steel or the like and are available from JWI or IBS.

The four high vacuum regions 314, 316, 318 and 320 are channels within the lid 300 that are operably connected to one or more vacuum sources (not shown) to draw a higher vacuum level. For example, the high vacuum zone may operate at a vacuum of 0 to 25 inches of mercury, particularly about 10 to about 25 inches of mercury. As another illustrative example, the cover 300 may define a plurality of holes or other shaped openings (not shown) that are connected to a vacuum source to create a pressurized fluid flow through the fabric. In one embodiment, the high vacuum zone includes nozzles, each measuring 0.375 inch in the machine direction, that extend across the full width of the wet web. The residence time of exposure to the pressurized fluid stream at any given point on the web, in the illustrated embodiment the time across the nozzles 314, 316, 318, and 320, is suitably about 10 milliseconds or less, particularly about 7.5 milliseconds or less, more particularly about 5 milliseconds or less, such as about 3 milliseconds or less, and even about 1 millisecond or less. The number and width of the high pressure vacuum nozzles and the speed of the machine determine the residence time. The residence time selected depends on the type of fibers contained within the warm fabric and the desired amount of dewatering.

First and second sealed vacuum zones 312 and 322 may be employed to minimize loss of pressurized fluid from the pneumatic device. The sealed vacuum zones are channels within the lid 300 that are operably connected to one or more vacuum sources (not shown) that are desirably drawn to a lower vacuum level than the four high vacuum zones. In particular, the desired vacuum level for the sealed vacuum region is from 0 to about 100 inches of water vacuum.

The air pressure device 200 is preferably constructed so that the CD seal 262 is disposed within the sealed vacuum zones 312 and 322. In particular, the sealing plate 272 of the CD seal 262 on the front side of the gas pressure device is arranged in the longitudinal direction between the first outer sealing slide 311 and the first inner sealing slide 313, in particular in the middle between them. The rear sealing plate 272 of the CD seal is similarly arranged in the longitudinal direction between the second inner sealing slide 321 and the second outer sealing slide 323, in particular in the middle between them. As a result, the sealing device 260 can be lowered so that the CD seals deviate from the normal running trajectory of the wet web 10 and the web belts 206 and 208 toward the vacuum box, which is shown on a slightly enlarged scale in FIG. 7 for illustrative purposes.

The sealed vacuum zones 312 and 322 function to minimize the loss of pressurized fluid from the air press 200 across the width of the wet web 10. The vacuum within the sealed vacuum zones 312 and 322 draws pressurized fluid from the gas plenum 202 and ambient gas from outside the gas pressure device. As a result, a gas flow is introduced into the sealed vacuum region from outside the air pressure device, rather than the pressurized fluid leaking in the opposite direction. Due to the relative difference in vacuum between the high vacuum region and the sealed vacuum region, most of the pressurized fluid from the gas plenum flows into the high vacuum region rather than the sealed vacuum region.

In another embodiment, partially shown in fig. 9, neither or both of sealed vacuum zones 312 and 322 are evacuated. Instead, a deformable sealing frame 330 is disposed within the sealing zones 312 and 322 (only 322 shown) to prevent leakage of pressurized fluid in the longitudinal direction. In this case, the air press is sealed longitudinally by the sealing sheet 272 impinging on the fabric belts 206 and 208 and the wet web 10, and the fabric belts and wet web being disposed adjacent to or in contact with the deformable sealing deckle 330. The CD seal 262 hits the web and wet web and is disposed on the other side of the web and wet web by the deformable sealing deckle 330, where the profile is found to form a particularly effective air plenum seal.

The deformable sealing frame 330 preferably extends across the full width of the wet web to seal the front or back or both ends of the air press 200. The sealed vacuum zone may be disconnected from the vacuum source as the deformable sealed deckle is stretched across the full width of the fabric. A full width flexible seal frame is provided at the rear end of the air press and a vacuum or blow box is provided downstream of the air press to retain the fabric 10 on one of the fabric strips as they separate.

The flexible sealing frame 330 preferably comprises two materials, one material being a material that wears preferentially relative to the fabric strip 208, meaning that when the fabric strip and material are used, the material wears without significant wear of the fabric strip occurring, and the other material is elastic and deflects when impacted against the fabric strip. In either case, the deformable sealing deckle is preferably gas impermeable and preferably comprises a material having a high porosity, such as a closed cell membrane or the like. In one particular embodiment, the deformable sealing deckle includes a closed-cell membrane measuring 0.25 inches in thickness. Optimally, the deformable sealing frame itself wears to match the path of the fabric strip. The deformable sealing frame is preferably attached with backing plates 332 for structural support, such as aluminum rods.

In embodiments where a full width sealing deckle is not used, some sort of sealing means is required in the cross direction of the fabric. The above-described deformable sealing deckle or other suitable means known in the art may be used to block the flow of pressurized fluid from the wet web laterally outward through the web.

The degree of impingement of the CD seal in the upper support web 206 uniformly across the width of the wet web was found to be an important factor in forming an effective seal across the web. The degree of impact required has also been found to be a function of the maximum tension of the upper and lower support web 206 and 208, the pressure differential across the web and between the plenum 214 and the sealed vacuum zones 312 and 322, and the gap between the CD seal 262 and the vacuum chamber cover 300.

Referring additionally to the schematic of the rear seal portion of the air press shown in fig. 10, the minimum desired amount of impact, h (min), of the CD seal 262 in the upper support web 206 is found to be represented by the following equation:

h(min)=(T/W)*[cosh(Wd/T)-1]；

wherein T is the measured fabric strip tension in pounds per inch;

w is the pressure differential across the fabric measured in psi; and

d is the gap in the longitudinal direction measured in inches.

Figure 10 shows the rear CD seal 262 offsetting the upper support web 206 by the amount indicated by arrow "h". The maximum tension of the upper and lower support fabric belts 206 and 208 is indicated by arrow "T". The web tension is measured by a standard tension meter supplied by Huyck corporation or other suitable method. The gap between the sealing plate 272 of the CD seal and the second inner seal slide 321, measured in the longitudinal direction, is indicated by arrow "d". The gap "d" used to determine the degree of impact is the gap on the higher pressure differential side of the sealing plate 272, i.e., the gap toward the plenum, because the pressure differential on that side has the greatest effect on the fabric strip and the fabric position. Preferably, the gap between the sealing plate and the second outer slide 323 is almost the same as or even smaller than the gap "d".

Adjusting the vertical position of the CD seal 262 to the minimum degree of impingement as described above is a determining factor in the effectiveness of the CD seal. The loading force exerted on the sealing device 260 plays a minor role in determining the effectiveness of the seal and only needs to be adjusted to the amount needed to maintain the necessary degree of impact. Of course, the amount of fabric wear will adversely affect the commercial application of the air press 200. In order to achieve an effective seal while the fabric strip is substantially not worn, the degree of impact is preferably equal to or slightly greater than the minimum degree of impact. To minimize the non-uniformity of the wear of the webbing across its width, the force applied to the webbing is preferably kept constant in the cross direction. This can be achieved by either controlled and uniform loading of the CD seal or controlled location of the CD seal and uniform geometry of the impact of the CD seal.

In use, the control system lowers the sealing device 260 of the gas plenum 202 to an operating position. First, the CD seal 262 is lowered so that the sealing plate 272 hits the support web 206 to the extent described above. In particular, the pressures within the upper and lower load tubes 230 and 248 are adjusted to move the CD seal 262 downward until the movement is stopped by contact of the lateral flange 268 with the lower support device 240 or until the tension is balanced by the webbing. Second, the end deckle band 282 of MD seal 264 is lowered into contact with or into close proximity to the upper support fabric band. As a result, both the air plenum 202 and the vacuum box 204 are sealed against the wet web to prevent the pressurized fluid from escaping.

The air pressure device is then activated, whereupon the pressurized fluid fills the air plenum 202 and creates an air flow through the fabric. In the embodiment shown in fig. 7, high and low vacuums are applied to high vacuum zones 314, 316, 318, and 320 and sealed vacuum zones 312 and 322, respectively, to facilitate gas flow, sealing, and removal of water. In the embodiment of fig. 9, pressurized fluid flows from the air plenum to the high vacuum zones 314, 316, 318, and 320, and the deformable sealing deckle 330 laterally seals the air press. The pressure differential across the wet web and the air flow generated through the web effectively dewaters the web.

Many of the structural and operational features of the pneumatic device help to allow only a small escape of pressurized fluid with little wear of the fabric strip. Initially, the air press 200 uses a CD seal that hits the fabric strip and the wet fabric. The degree of impact is determined in order to optimize the effectiveness of the CD seal. In one embodiment, the air press utilizes sealed vacuum zones 312 and 322 to create ambient air that flows into the air press across the width of the wet web. In another embodiment, the deformable seal 330 is disposed within the sealed vacuum zones 312 and 322 opposite the CD seal. In either case, to minimize the need for precise alignment of mating surfaces between the gas plenum 202 and the vacuum box 204, the CD seal 262 is preferably disposed at least partially within the channel of the vacuum box cover 300. Furthermore, the sealing device 260 may be loaded against a stationary component, such as the lower bearing device 240 connected to the frame structure 210. As a result, the loading force of the gas pressure device is independent of the pressurized fluid pressure within the gas plenum. The fabric belt wear is minimized due to the use of the fabric belt low wear material and the lubrication system. Suitable lubricating systems may include chemical lubricants such as emulsified oil, a separating agent or other similar chemicals, or water. Typical lubricant application methods include spraying dilute lubricant, atomized solutions of water or gas, more concentrated felt wiping solutions in a uniform manner in the cross direction, or other methods known in the art for spray system applications.

The ability to operate at higher inflation pressures is seen to depend on the ability to prevent leakage. The presence of leaks can be detected by excessive air flow, increased operating noise, moisture dispersion, and in extreme cases, regular or irregular excursions within the wet fabric including holes and threads, etc., as compared to previous or anticipated operations. Maintenance is performed by calibrating or adjusting the sealing components of the pneumatic device to avoid leakage.

In an air press, uniform air flow in the cross direction is desirable to provide uniform dewatering of the fabric. Flow uniformity in the cross direction can be improved with mechanisms on the pressure and vacuum sides, such as tapered tubing, whose shape can be designed using computational fluid dynamics modeling. Since the basis weight and moisture content of the fabric cannot be made uniform in the cross direction, it is advantageous to use additional means to achieve uniform airflow in the cross direction, such as independently controlled areas with airflow regulators on the pressure or vacuum side to vary the airflow depending on the paper properties, a baffle to achieve a significant pressure drop in the airflow before wetting the fabric, or other directing means. Another method of controlling CD dewatering uniformity may also include external devices such as a regional control steam jet such as the Devrizer steam jet available from Honeywell-Measurex Systems of Dublin.

Examples of the present invention

The following examples are provided to facilitate a more detailed understanding of the invention. The particular amounts, ratios, components, and parameters are exemplary and not intended to specifically limit the scope of the present invention.

Example 1

A 12 inch wide tissue was produced on an experimental tissue machine having a 22 inch fabric belt width from a fiber pulp suspension comprising an unrefined 50: 50 fiber mixture of bleached kraft northern softwood fibers and bleached kraft eucalyptus fibers. The tissue was formed by depositing a stock suspension from each layer using a stratified, three-layer headbox to form a mixed sheet having a nominal basis weight of 19 gsm. The headbox sprays a stock suspension between two Raffinet Wire (Lindsay Wire)2164B forming fabric belts in a twin fourdrinier forming section with a suction roll former. To control the strength, Parez 631 NC containing 6% solids was added to the stock at a rate of 1000 ml/min prior to the forming process.

When deposited at a speed of 1000 feet per minute (fpm) between two forming fabric belts, the primary fabric is conveyed on four vacuum boxes operating at vacuum pressures approaching 11, 14, 13, and 19 inches of mercury vacuum, respectively. And the primary web, contained between the two forming fabric belts, passes through an air press comprising an air plenum and a collection box in operative communication and integrally sealed to each other. The gas plenum pressurizes the air to 15psi at about 150 degrees fahrenheit, while the collection box operates at about 11 inches of mercury vacuum. The paper was subjected to a final differential pressure of about 41.5 inches of mercury and to an airflow of 68 SCFM per square inch with a residence time of 7.5 milliseconds through four nozzles, each nozzle being 3/8 inches in length. The consistency of the fabric just before the air press is about 30% and the consistency when leaving the air press is about 39%.

The dewatered fabric was then conveyed using a vacuum pick-up shoe operating under a vacuum of about 10 inches of mercury on a three-dimensional fabric belt, which was a Lindsay Wire T-216-3 TAD fabric belt. Just prior to transfer from the forming fabric, a silicone emulsion in water is sprayed onto the paper side of the T-216-3 fabric for final transfer to the yankee dryer. The silicone resin was applied at a flow rate of 400 ml/min at 1.0% solids. The TAD fabric strip was then pressed against the surface of a yankee dryer, which had a conventional press roll operating at a maximum press pressure of 350 pli. The web was wrapped about 39 inches around the surface of the yankee dryer by a transfer roll which was removed or slightly moved away from the yankee dryer. The fabric was bonded to a yankee dryer using a binder mixture made of polyvinyl alcohol airsol 523 manufactured by Air Products and chemical company and sorbitol added to the water by Spraying Systems company at a flow rate of about 0.4 gallons per minute (gpm) and operating conditions of about 40 psig. The spray had a solids concentration of about 0.5 by weight percent. The sheet was creped as it was removed from the yankee dryer and had a final dryness of about 92% consistency, and the sheet was wound around a mandrel. The product was then converted into 2-ply bath tissue using standard techniques. The results of example 1 are shown in table 1 below.

Example 2

A 12 inch wide tissue was produced on an experimental tissue machine having a 22 inch fabric belt width from a fiber pulp suspension comprising an unrefined 50: 50 fiber mixture of bleached kraft northern softwood fibers and bleached kraft eucalyptus fibers. The tissue was formed by depositing a stock suspension from each layer using a stratified, three-layer headbox to form a mixed sheet having a nominal basis weight of 19 gsm. The headbox sprays a stock suspension between two Raffinet Wire (Lindsay Wire)2164B forming fabric belts in a twin fourdrinier forming section with a suction roll former. To control the strength, Parez 631 NC containing 6% solids was added to the stock at a rate of 1000 ml/min prior to the forming process.

When deposited at a speed of 1000 feet per minute (fpm) between two forming fabric belts, the primary fabric is conveyed on four vacuum boxes operating at vacuum pressures approaching 11, 14, 13, and 19 inches of mercury vacuum, respectively. And the primary web, contained between the two forming fabric belts, passes through an air press comprising an air plenum and a collection box in operative communication and integrally sealed to each other. The gas plenum pressurizes the air to 15psi at about 150 degrees fahrenheit, while the collection box operates at about 11 inches of mercury vacuum. The paper was subjected to a final differential pressure of about 41.5 inches of mercury and to an airflow of 68 SCFM per square inch with a residence time of 7.5 milliseconds through the four nozzles, each nozzle being 3/8 "in length. Of fabrics immediately before the air-pressure deviceThe consistency is about 30% and the consistency upon leaving the air pressure means is about 39%. The dewatered fabric was then flash-transferred using a vacuum pick-up shoe operating under a vacuum of about 10 inches of mercury on a three-dimensional fabric belt, a Lindsay Wire T-216-3 TAD fabric belt, which was conveyed at a speed 20% slower than the forming fabric belt. Just prior to transfer from the forming fabric, a silicone emulsion in water is sprayed onto the paper side of the T-216-3 fabric for final transfer to the yankee dryer. The TAD fabric strip was then pressed against the surface of a yankee dryer, which had a conventional press roll operating at a maximum press pressure of 350 pli. The web was wrapped about 39 inches around the surface of the yankee dryer by a transfer roll which was removed or slightly moved away from the yankee dryer. The fabric was bonded in a controlled manner to a Yankee dryer using an interplanar control mixture comprising, based on the active solids percentage, approximately 26% polyvinyl alcohol, 46% sorbitol and 28% Hercules M1336 polyglycol at 50 and 75mg/M²In between. The mixture was prepared as an aqueous solution of less than 5% solids by weight. The sheet is dried at approximately 90% consistency on a yankee dryer and then "peeled" from the yankee dryer by applying sufficient wrap tension to remove the sheet just prior to the creping blade. The paper sheet is then wound onto a mandrel without additional pressing. The product was then converted into 2-ply bath tissue using standard techniques. The results of example 2 are shown in table 1 below.

Example 3 (comparative example)

The paper is formed from a blend of bleached kraft northern softwood, bleached kraft eucalyptus and softwood BCTMP fibers in a blend ratio of 50: 40: 10 and is formed using an improved fourdrinier forming machine at an operating condition of about 3500 fpm. The final sheet, having a basis weight of about 20gsm, was transferred from the forming fabric to a standard wet-pressed felt (using a couch roll). The fabric was transferred to and onto a 15 foot Yankee dryer using standard techniques. The sheet was dried on a Yankee dryer using standard techniques and removed from the dryer at a consistency of about 95% with a creping blade. To further increase the caliper, the sheet is fed through an open draw to a second yankee dryer (which operates without the usual hood) and is adhered to the dryer using a latex adhesive. The sheet is then creped and wound on a mandrel. The product was then converted into 2-ply bath tissue using standard techniques. The process used in this example is known as the stand-alone re-creping process and is described in british patent documents GB2179949, GB2152961A, and GB2179953 BB. The results of example 3 are shown in table 1 below.

Example 4 (comparative example)

The paper is formed from a blend of bleached kraft northern softwood and bleached kraft eucalyptus fibers in a blend ratio of 65: 35. A paper sheet having a layered structure is formed using a twin-wire former, and eucalyptus fibers are on the outer side (air side) of the paper sheet. The paper sheet is dewatered to a consistency of approximately 27 percent using conventional vacuum dewatering techniques and then throughdried using standard techniques to a consistency of approximately 90 percent. The paper was then conveyed to a Yankee dryer, bonded using PVA as the binder, and dried to a consistency of 97%. The paper is then wound onto a mandrel. The product was then reformed into a two-ply bath tissue using standard techniques. The results of example 4 are shown in table 1 below.

TABLE 1

Test of	Unit of	EXAMPLE 1 inventive (creping)	EXAMPLE 2 inventive (without creping)	Example 3 comparative example	Example 4 comparative example
						Hardness of the roll	0.001”	104	140	134	178
Diameter of the roller	mm	126	128	125	125
						Number of sheets		253	180	280	198
Mandrel external diameter (Core OD)	mm	40	40	46	46
						Thickness (2kPa, 8 layers)	Micron meter	1667	2402	1288	1719
Strength in MD	g/3”	1739	1911	2285	1719
						Elongation at MD	％	14	13	22	15
CD Strength	g/3”	972	1408	718	700
						GMT	g/3”	1300	1640	1281	1097
Weight of oven-dried roll	g	133	95	158	106
						Absolute dry basis weight	g/m2	19.1	18.8	20.6	20.4
Absorption capacity	g	97.4	117.2	79.0	97.0
						Absorption capacity	g (water)/g (fiber)	11.8	14.1	10.8	11.0

The data in table 1 clearly shows that improvements in paper/roll performance can be obtained with the present invention. In creped form (example 1), the present invention produces a bath tissue product having a greater caliper than that of the tissue product, with a caliper ratio of 1667 microns to 1288 microns, than the caliper despite the additional re-creping step specifically employed to control (example 3) to increase the controlled bulk. Without the re-creping step, the caliper differential would be greater, since the re-creping step typically increases the caliper by more than about 30%. This additional thickness allows 27 sheets (from 280 counts to 253) to be removed while maintaining the same roll diameter from a roll performance standpoint. In fact, the rollers used in the present invention are more robust at the same roller diameter despite the reduced number of sheets (104 vs. 134, smaller numbers representing greater stiffness). Overall, the present invention allows the roll weight to be reduced from 158 grams to 133 grams (16%) while providing excellent roll performance.

The improvement in roll performance was even more pronounced when considering the uncreped example (example 2). Here, the number of sheets was reduced to 180 sheets while maintaining the roller diameter and hardness (in contrast, the number of sheets was 280 in the case of control). In this case, the weight of the roll is reduced by 40%.

Additionally, the product of the present invention is comparable to the creped throughdried product described in example 4. It is clear that the product has roughly equal properties in terms of roll bulk etc. In fact, the example of throughdrying shows a lower hardness, which means that the product of the invention is even better than the product of the throughdrying method.

Example 5

The paper was formed from a fiber blend of southern bleached kraft pine, bleached kraft northern softwood and bleached kraft eucalyptus in a blend ratio of 50: 30: 20 on a laboratory paper towel machine running at about 50 fpm. The finished sheet, having a basis weight of about 41 grams per square meter, is carried on a forming fabric and then transferred to a T-216-3 forming fabric. At the transfer point, the primary web passes through an air pressure device comprising an air plenum and a collection box in operative communication and (integral) sealed with each other. At this point, the sheet is dewatered from a consistency of approximately 10% for post forming to a consistency of 32-35%. The sheet is then conveyed to a Yankee dryer where it is conveyed to the Yankee dryer, which is bonded using polyvinyl alcohol sprayed through standard nozzles and dried to a 55% consistency. The paper is then transferred to a post-dryer for final drying and winding onto a mandrel. The final fabric is then embossed with a butterfly embossing pattern to obtain a final single ply paper towel product. The results of example 5 are shown in table 2 below.

Example 6

Bleached kraft southern softwood and softwood BCTMP fiber blend having a blend ratio of 65: 35 were formed into paper using a modified fourdrinier former operating at a machine speed of 250 fpm. The finished sheet, having a basis weight of approximately 50 grams per square meter, is transferred to a standard wet-pressed felt and conveyed to a Yankee dryer. The sheet is transferred to a yankee dryer using standard wet pressing techniques through a nip of press rolls. The paper was bonded to a dryer using polyvinyl alcohol and creped at approximately 55% consistency. The paper sheet is then fed through an open draw to a series of can dryers where the paper sheet is dried to approximately 95% consistency and wound onto a mandrel. The product was then converted into a layer of paper towel using standard techniques. The results of example 6 are shown in table 2 below.

Table 2 clearly shows the product advantages inherent in the present invention. Despite a 19% reduction in basis weight, the paper towels produced using the present invention have advantages in caliper and absorbency over large-scale wet creping control

TABLE 2

Experiment of	Unit of	EXAMPLE 5 invention	Example 6 (comparative example)
				Hardness of roll	Inch (L)	0.191	0.277
Diameter of roller	Inch (L)	5.3	5.0
				Number of sheets		80	85
Mandrel outside diameter	mm	42	37
				Thickness-10 pieces	Inch (L)	0.252	0.195
Strength in MD	g/3”	2934	2750
				Elongation at MD	％	13.2	7.8
CD Strength	g/3”	1420	1086
				Elongation of CD	％	8.1	7.3
GMT	g/3”	2041	1728
Unit weight	g/m2	41.3	50.9
				Absorption capacity	g	2.56	1.73
Absorption capacity	g (water)/g (fiber)	5.86	3.84

In addition, the products of the present invention have a higher CD stretch, such that the "tenacity" of the tissue in use is increased. As a final product, the rolls produced using the present invention have a larger diameter (5.3 inches to 5.0) and greater hardness (0.191 to 0.277). At the same time, the roll weight was reduced by 19% since the paper size and number of sheets were fixed.

Example 7

A fiber mixture of bleached kraft northern softwood and bleached kraft eucalyptus in a 50: 50 blend ratio was formed into paper using a forming apparatus and structure as described in example 1. In this case, the machine speed is 2500 fpm. The final sheet, having a basis weight of approximately 20 pounds per 2880ft2, was passed through four vacuum boxes of 19.8, 19.8, 22.6, and 23.6 inches of mercury, respectively. The final sheet is then transported through an additional integrated sealed dewatering system as described in example 1. The pneumatics were adjusted to maintain a pressure of 15psig within the gas plenum, and consistency was measured using front and back pneumatics samples. The results of example 7 are shown in table 3 below.

Example 8

The experiment of example 7 was repeated except that the gas pressure device was reconfigured to eliminate the integral seal between the gas plenum of the gas pressure device and the associated collection tank. In particular, the sealing load and the resulting impact of the transverse sealing sheet is reduced until the leakage between the gas plenum and the collection tank is evident. In this regard, the arrangement of the air plenum/collection box of the air press is set to a nominal 0.1 inch gap, although it is not possible to actually see the space between the air plenum and collection box as it is occupied by the web and paper. The gas flow into the gas plenum increases to the maximum gas flow that the compressor can provide and a subsequent dewatering consistency sample is taken. The results of example 8 are shown in table 3 below.

TABLE 3

Test of	Unit of	Example 7	Example 8 (comparative example)
				Post dewatering consistency	％	34.2	32.1
Pre dewatering consistency	％	26.8	26.8
				Removed water content	1b. Water/1 b. fiber	0.81	0.61

As shown in table 3, any reduction in the overall seal level results in a significant loss of the dewatering capacity of the air press. In particular, when the integral seal is lost, nearly 25% or less of the water is removed (0.61 lb/lb to 0.81) even though the air plenum and collection box remain in significant contact with the fabric strip. The loss of 2% of the post dewatering consistency will translate into a nearly 10% speed reduction of the machine, which is limited due to drying limitations. This limitation is desirable on warm presses that are converted into structures of the present invention.

The previous tests attempted to illustrate the maximum possible results possible using known techniques such as those described in U.S. patent 5,230,776 to the Valmet Corporation. In practice, the apparatus does not necessarily operate as described above, due to the excessive noise that can be generated during the test and the jets of air generated by the non-integrally sealed dewatering apparatus. Although not specifically stated, in practice it is contemplated that the apparatus described in U.S. patent 5,230,776 may be operated at intervals of 1 inch or more, at which conditions dehydration is significantly reduced and would result in greater air consumption. In fact, this inefficiency results in more additional energy costs and reduced speed, and thus this technique is not suitable for commercial plants.

Example 9

A fiber blend of bleached kraft northern softwood and bleached kraft eucalyptus in a 50: 50 blend ratio was used to form a 20gsm sheet while running at 2000fpm speed, as described in example 1. The sheet was then vacuum dewatered using 4 vacuum boxes approaching vacuum levels of 18, 18, 17 and 21 inches, respectively. Vacuum box consistency samples were taken. The results are shown in Table 4.

Example 10

The experiment of example 9 was repeated, but with the addition of a steam "blow box" (Devroniczer) to increase dewatering. The steam box is not integrally sealed to the vacuum box and is intended to be similar to the device disclosed in us patent 5,230,776. Steam flow to the Devronizer was approximately every hour (300 pounds). And a consistency sample was taken to determine the increase due to the additional steam blow box. The results are shown in Table 4.

Example 11

The experiment of example 8 was repeated but the integrated sealed gas pressure unit of example 1 was added to the process. The air press was operated at 15psig feed pressure and a vacuum level of 17 inches of mercury. Furthermore, consistency samples were taken to determine the increase due to the additional integral sealed pneumatic device. The results are shown in Table 4.

TABLE 4

Serial number	Consistency%
		Example 9	24.2
Example 10	24.8
		Example 11	33.3

The data in table 4 clearly show that the use of an integral sealed air pressure device results in a greater consistency increase than the use of a steam blow box. The blow box increased the consistency by 0.6%, while the integrated sealed air pressure unit increased the consistency by an additional 8.5% on the basis of the consistency increase caused by the steam blow box. Since the paper had been dewatered to a consistency of 24.2% by passage through four vacuum boxes (example 9), it was not practical to add enough vacuum and/or steam blow boxes to raise the consistency to a level that could achieve commercially viable speeds. However, the addition of an integral seal air pressure device (example 11) increased the consistency to a level that could be achieved at commercial speeds with the improved wet press design.

The foregoing detailed description has been presented for purposes of illustration. Thus, many modifications and variations of the present invention are possible without departing from its spirit and scope. For example, alternative or alternative features that are part of one embodiment may be used to form other embodiments. In addition, two named components may represent portions of the same structure. Also, different alternative processes and equipment configurations may be used, such as, inter alia, stock preparation, headbox, forming fabric belt, fabric conveyor, creping, and drying. Thus, the invention should not be limited by the specific embodiments described, but by the claims and their equivalents.

Claims (32)

1. A method for making a cellulosic web, the steps of the method comprising:

(a) depositing an aqueous suspension of papermaking fibers onto an endless forming fabric to form a wet fabric;

(b) dewatering the wet web to a consistency of about 30 percent or greater using a non-compressive dewatering device adapted to cause a pressurized fluid to flow substantially through the web at a gauge pressure of about 5 pounds per square inch gauge or greater due to the integral seal formed by the non-compressive dewatering device with the wet web;

(c) transferring the wet web to a molding fabric;

(d) pressing the dewatered and molded web against the surface of a heated drying cylinder to at least partially dry the web; and

(e) the fabric is dried to a final dryness.

2. A method of making a cellulosic web, the method comprising the steps of:

(a) depositing an aqueous suspension of papermaking fibers onto an endless forming fabric to form a wet fabric;

(b) dewatering the wet web to a consistency of about 10% to about 30%;

(c) supplementally dewatering the wet web to a consistency of from about 30% to about 40% using an air press adapted to cause a pressurized fluid to flow substantially through the web at a gauge pressure of about 5psig or greater due to an integral seal formed between the air plenum and the collection device;

(d) transferring the wet web to a molding fabric belt to provide the web with a molded structure and a bulk of about 8 cc/g or greater;

(e) pressing the dewatered and molded web against the surface of a heated drying cylinder with a fabric belt to maintain the web in a molded configuration and a bulk of about 8 cc/g or greater; and

(f) the fabric is dried to a final dryness.

3. A method of making a cellulosic web, the method comprising the steps of:

(a) depositing an aqueous suspension of papermaking fibers onto an endless forming fabric to form a wet fabric;

(b) sandwiching the wet web between a pair of fabric belts, at least one of which is a three-dimensional molded fabric belt;

(c) passing the sandwiched wet web structure between an air plenum and a collection device with the three-dimensional molding fabric strip disposed between the warm web and the collection device, the air plenum and collection device being operatively associated and adapted to create a pressure differential across the wet web of about 30 inches of mercury or greater and a flow of pressurized fluid through the warm web of about 10 standard cubic feet per minute per square inch or greater;

(d) dewatering the wet web to a consistency of about 30% or greater with a pressurized fluid stream;

(e) pressing the dewatered web against the surface of a heated drying cylinder with a fabric belt; and

(f) the fabric is dried to a final dryness.

4. The method of claim 1, wherein the non-compressive dewatering device increases the consistency of the fabric by about 5% to about 20%.

5. The method of claim 2, wherein the web is additionally dewatered to a consistency of about 32 percent or greater.

6. The method of claim 5, wherein the web is additionally dewatered to a consistency of about 34 percent or greater.

7. The method of claim 1, 2 or 3, wherein the pressure differential across the fabric is about 30 inches of mercury or greater.

8. The method of claim 7 wherein the pressure differential across the web is from about 35 to about 60 inches of mercury.

9. The method of claim 1, 2 or 3, wherein the pressurized fluid is pressurized to about 5 to about 30 pounds per square inch gauge.

10. The method of claim 1, 2 or 3 wherein the collection means comprises a vacuum box that draws a vacuum of greater than 0 to about 25 inches of mercury.

11. The method of claim 2 or 3, wherein the residence time in the air pressure device is about 10 or less.

12. The method of claim 11, wherein the residence time in the air press is about 7.5 or less.

13. The method of claim 2 or 3, wherein the web travels at a speed of about 1000 feet per minute or greater and the consistency of the web increases about 5 percent or greater from entering the air press to exiting the air press.

14. The method of claim 2 or 3, wherein the web travels at a speed of about 2000 feet per minute or greater and the consistency of the web increases about 5 percent or greater from entering the air press to exiting the air press.

15. The method of claim 1 or 2, wherein the wet web is traveling at a speed of about 2000 feet per minute or greater.

16. The method of claim 2 or 3, wherein about 85% or more of the pressurized fluid supplied to the air plenum flows through the wet web.

17. The method of claim 16, wherein about 90% or more of the pressurized fluid supplied to the air plenum flows through the wet web.

18. The method of claim 1, 2 or 3, wherein the temperature of the pressurized fluid is about 300 degrees celsius or less.

19. The method of claim 18, wherein the temperature of the pressurized fluid is about 150 degrees celsius or less.

20. A method according to claim 2 or 3, characterized in that the heated drying cylinder comprises a dryer hood and that the fabric belt pressed against the drying cylinder is separated from the dryer hood before the fabric enters the dryer hood.

21. A method according to claim 2 or 3, characterized in that the web of fabric pressed against the drying cylinder is wound onto the drying cylinder by an amount which is less than the full distance of contact of the web with the drying cylinder.

22. A method according to claim 1, 2 or 3, wherein the web is transferred to the heated drying cylinder using a pair of transfer rolls which form an extended wrap of predetermined span.

23. The method of claim 22, wherein one or both of the transfer rolls are not loaded against the heated drying cylinder.

24. The method of claim 22, wherein one or both transfer rolls are loaded against a heated drying cylinder.

25. The method of claim 1 or 2, wherein the web is pressed against the drying cylinder with a pressing pressure of about 350 pounds per linear inch or less.

26. A method according to claim 2 or 3, characterized in that a release agent is added to the web pressed against the heated drying cylinder to facilitate the transfer of the moulding fabric.

27. A method according to claim 1 or 2, wherein the pressurized fluid stream transfers the fabric to the molding fabric.

28. A method according to claim 1 or 2, characterized in that the dewatered fabric is rush-transferred onto a fabric belt.

29. A method according to claim 2 or 3, wherein the web is removed from the heated drying cylinder without creping.

30. The method of claim 1, 2 or 3, wherein the web is dried to a consistency of about 95 percent or greater and thereafter creped.

31. The method of claim 1, 2 or 3, wherein the web is partially dried on the surface of a heated drying cylinder to a consistency of from about 40% to about 80%, wet creped, and then finally dried to a consistency of about 95% or greater.

32. An absorbent tissue made by the method of claim 1, 2 or 3.