DE69734980T2 - METHOD AND DEVICE FOR PREPARING SOFT TISSUE PAPER - Google Patents

Description

background the invention

It There are many characteristics of tissue products, such as bath and tissue Facial tissue which is desirable in making a final product Attributes that make it suitable and intended for the product Purpose, must be considered. improved Softness of the product has long been a major task, and this is a particularly significant factor in the success of Premium products. In general, the main components of the Softness stiffness and volume (density), with lower stiffness and coarser Volume (lower density) generally the perceived softness improve.

While improved Softness for all types of tissue products desirable is, it is a special challenge, softness improvements in uncreped, air-dried arches. By air drying provides a relatively non-compressive method of removal of water from a lane ready by passing hot air through the lane until it is dry. Even more accurate is a wet-laid Transferred web of the forming material to a coarse, highly permeable through-air drying fabric and held on the through-air dryer until dryness is reached is. The resulting dry web is softer and bulkier than a conventionally dried uncreped bow with fewer bindings be formed and because the web is less compressed. Therefore There are advantages in eliminating the Yankee dryer and the production of an uncreped through-air dried product. uncreped air-dried sheets feel However, compared to their creped counterparts typically but relatively hard and rough. This is partly due to the inherently high level Stiffness and strength of a Uncreped bow, but is partly due to the roughness of the through-air drying substance to which the wet web is adapted and on which it is dried.

Therefore There is a shortage and need for a procedure in the department and an apparatus for producing improved tissue products Softness, and in particular uncreped, through-air dried Tissue products with improved softness.

WHERE 95/00706 A relates to a method for producing a soft tissue sheet, which forms an aqueous Suspension of fibers for paper formation, mechanical processing suspension, dilute the aqueous Suspension of ruffled Fibers to a consistency of about 0.5% or less, applying the diluted one aqueous Suspension on a forming fabric to form a wet web, draining the wet web to a consistency of about 20 to about 30 percent, Transfer the dehydrated Path from the forming agent to a through-air drying fabric and Through-air drying of the web to a final dryness.

US-A-5,048,589 reveals towels or wipes, which are manufactured according to one A process comprising the steps of: (1) forming a Ingredient input from cellulosic fibers, water and a chemical Binding agent, (2) application of the substance input to a moving, with holes Treadmill moving at a speed which up to about 10% less than the first one with openings provided treadmills, creating a fibrous web on the moving treadmill is formed, (3) non-compressing Dry the fiber web to remove the water from the fiber web and (4) removing the dried fibrous web from the moving, provided with openings Treadmill.

Summary the invention

It has now been discovered that an improved uncreped throughdried web can be made by dewatering the web to greater than about 30 percent consistency prior to transferring the wet web from a forming fabric to one or more intermediate transfer materials at a lower speed before the web is transferred to a through-air dryer for final drying of the web. In particular, it has surprisingly been found that increasing the consistency of the uncreped throughdried web prior to the point of differential speed transfer results in: (1) better tensile strengths in both the machine direction and cross machine directions, resulting in improved runnability of the web; and improved runnability of the web; and (2) reduced modulus, ie, improved softness, when the tensile strength is adjusted to the normal value. This discovery allows the production of lower modulus tissue products at given tensile strengths, as compared to tissue products undergoing differential speed transfer at lower consistencies.

One particularly preferred means by which the web is more than drained about 30 percent consistency includes an air press which is just upstream of the differential speed transfer is arranged. While under Pressure fluid jets in combination with a vacuum device already previously discussed in the patent literature, such devices are in the Tissue production not been widely used. In principle, this seems to be the fact to lie that previously was not recognized that draining the Train to more than about 30 percent consistency before differential speed transfer to the improved product properties identified herein to lead would. Furthermore It is believed that the discouragement to such equipment to use the difficulties of actual implementation, including disintegration the tissue web, leaks of pressurized fluid, seal and / or cloth wear and the like. The im air press used in these methods overcomes these difficulties and provides a convenient device for achieving the desired Consistency before the speed differential transformer ready.

In order to In one aspect, the invention relates to a method of manufacturing a soft tissue sheet. The method includes the following Steps: Apply an aqueous Suspension of papermaking fibers on a continuous forming material, to form a wet web; Draining the wet web up to a consistency of about 20 to about 30 percent; additionally dewatering the wet web using non-compressing dehydrating agents up to a consistency of more than about 30 percent, transfer the additional dehydrated Train on a transfer material which is moving at a speed from about 10 to about 80 percent slower than the forming material moves; Transferring the web to a through-air drying agent; and through-air drying the train to a final Dryness.

The Air press is desirable a pressure differential over the wet web of about 35 to about 60 inches of mercury ready. This can be achieved in part by an air plenum chamber of the air press which is a fluid pressure on one side of the wet web from about 5 to about 60 pounds per square inch, and more particularly from about 5 to about 30 pounds per square inch. The pressurized Fluid may be air at ambient temperature, heated air, steam or the like be. Overall, the air press can be set up in such a way Wet web consistency of about 3 and preferably about 5 Percent increase. Optional steam showers can used in front of the air press to create a post-air press consistency to increase.

One Another aspect of the invention relates to an air press for dewatering a wet track. In one embodiment For example, the air press includes an air plenum chamber having a plenum chamber cover with a lower surface includes, and a vacuum box, which has a vacuum box cover includes, wherein an upper surface the vacuum box cover in close proximity to the lower surface of the Plenumkammerabdeckung is arranged. The air press also includes a means for feeding pressurized fluid to the air plenum chamber and a Means for applying vacuum to the vacuum box. Side sealing elements the air press are set up so that they are in contact with the air plenum chamber and the vacuum box stand to escape to minimize pressurized fluid. The side sealing elements are attached to one of air plenum chamber and the vacuum box and are in great Close to Side seal contact surfaces arranged, which from the other of Luftplenumkammer and vacuum box are defined. The side sealing elements are arranged to bend in sealing contact with the side seal contact surface, when exposed to pressurized fluid for sealing effectiveness to reinforce.

optional For example, the air press may include a position control mechanism which is arranged to keep the Luftplenumkammer in close proximity to the vacuum box. In particular, the position control mechanism preferably comprises a rotatably mounted lever which is attached to the Luftplenumkammer and a counterweight cylinder attached to the lever is. The position control mechanism is set up, the lever to turn to pressure changes within the plenary chamber. In this way the air plenum chamber is in the next one Near or is in contact with the substances which are between the Move air plenum chamber and the vacuum box through, without the Clamp fabrics in between.

In another embodiment, the air press includes an air plenum chamber including a plenum chamber cover having a lower surface and means for supplying pressurized fluid to the air plenum chamber. The air press also includes a vacuum box having a Va includes a vacuum box cover having an upper surface disposed in close proximity to the lower surface of the plenum chamber cover, and means for applying vacuum to the vacuum box. An arm pivotally mounted to the air plenum chamber includes first and second portions, wherein the first portion of the arm is at least partially disposed within the air plenum chamber. A sealing rod is formed from or mounted on the first portion of the arm. The air press also includes means for pivoting the arm in response to fluid pressure within the air plenum chamber.

In this embodiment the seal rod portion of the rotatable arm functions as one End seal to prevent the escape of pressurized fluid between to avoid the Luftplenumkammer and the vacuum box. The sealing rod may be due to fabric irregularities or wrong alignment of the supporting structure. The end seals, which are also called cross machine direction or CD seals be designated, improve the storage of the pressurized Fluids and lead thus to a more efficient operation of the air press. The loading the end seals are controlled to contact the sealing rod with the underneath. lying, to maintain moving material, without excessive wear to cause the substance.

The improved results can without loss in terms of efficiency. The present method and the present devices are suitable at web speeds to be used, which are commercially useful. For example The former can be controlled at speeds of at least about 10 meters per second (2000 feet per minute (fpm)) and even stronger preferably at speeds of at least about 20 meters per Second (4000 fpm) to move.

Of the intermediate Transfer substance or the intermediates Transfer materials move at a slower speed as the forming material during the transfer to give the bow stretch. If the speed differential is increased between the Formierstoff and the slower transfer substance (which sometimes referred to as a "negative train" or "express transfer"), will be the train during The transfer also increased the transfer. The transfer substance can relatively smooth and dense compared to the coarse weave of a typical Durchlufttrocknungsstoffs. Preferably, the transfer substance as fine as he used from a practical point of view can be. Taking up the railway is achieved by the present of ankles on the surface of the transfer substance. additionally It may be advantageous if one or more of the transfers of the wet web, with or without the presence of a transfer fabric using "fixed gap" or "kiss" transfers which the substances simultaneously converge and diverge, which is hereafter will be described in detail. Such transfers not only avoid any significant densification of the web while it is in a wet, bond-forming state, but It has also been observed that when combined with a differential speed transfer and / or a smooth Transfer material used, the surface of the web and a final dry Smooth bow.

The Speed difference between the forming agent and the transfer material may be from about 10 to about 80 percent or more, preferably from about 10 to about 35 percent, and even more preferably about 15 to about 25 percent, with the transfer substance being the slower substance is. The optimal speed differential is of a variety depend on factors including of the particular type of product being manufactured. As before mentioned, is the increase the strain imparted to the web is proportional to the speed differential. For a uncreped, through-air dried, three-layered wipe with a basis weight for example, generates about 20 grams per square meter per layer a speed differential in the manufacture of each layer from about 20 to about 25 percent between the former and one individual transfer material an elongation in the final product of about 15 to about 20 percent.

The Elongation can be applied to the web using a single differential speed transfer or two or more differential speed transfers of the wet Lane be given before drying. This can be one or more transfer substances be used. The amount of stretch given to the web It can handle one, two, three or more differential speed transfers be split.

The transfer is preferably carried out in such a way that the resulting "sandwich" (which consists of the forming material / the web / the transfer substance) exists for as short a time as possible. In particular, it only exists at the leading edge of the vacuum jaw or transfer jaw slot which is used to effect the transfer. In fact, the former and the former converge and diverge Transfer material at the front edge of the vacuum slot. The intent is to minimize the distance over which the web is in simultaneous contact with both fabrics. Simultaneous convergence / divergence has been found to be the key element in eliminating macrof calls, thereby increasing the smoothness of the resulting tissue or other product.

In In practice, the simultaneous convergence and divergence of the two Fabrics only occur at the leading edge of the vacuum slot, though one enough greater Convergence angle between the two substances is maintained, while these approach the leading edge of the vacuum slot, and if there is a sufficiently large divergence angle upright between the two fabrics on the downstream side of the vacuum slot is obtained. The minimum convergence and divergence angles are about 0.5 degrees and larger, in particular about 1 degree or greater, in particular about 2 degrees or greater and even more specific about 5 degrees or greater. The convergence and divergence angles can be the same or different. Larger angles provide a wider margin of error while ready for operation. A suitable range is about 1 degree to about 10 degrees. Simultaneous convergence and divergence is achieved when the vacuum baking is set up so that the trailing edge the vacuum slot is sufficiently reset relative to the leading edge is to allow the substances to diverge immediately when passing over the Lead the leading edge of the vacuum slot. This becomes clearer by reference described on the figures.

If one uses the machine in such a way that the substances initially one have fixed distance to compression of the web during the To minimize transfers further, the distance should be between the Substances equal or greater as the thickness or gage of the Web, so that the web is not significantly compressed, though it is transferred at the leading edge of the vacuum slot.

improved smoothness is achieved by using the air press upstream of the differential speed transfer. This is most preferred in combination with a section of carrier at a fixed distance used following drying. Calendering the web is not necessary to desired Grade of smoothness to achieve, but further editing of the arc, such as through Calendering, embossing or creping may be beneficial to further the sheet properties to improve.

As used herein, the "transfer substance" is a substance which between the forming section and the drying section of the web-making process is arranged. Suitable transfer substances are those papermaking materials, which has a high fiber support index Provide and provide a good vacuum seal to the Fabric / bow contact during to maximize the transfer of the forming material. The substance can a relatively smooth surface contour have to keep the track smoothness but it has to be enough Have texture to pick up the web and make contact during one To maintain urgent transfers. Finer fabrics can one higher Generate degree of elongation in the web, which for some product applications desirable is.

transfer materials include single-ply, multi-ply, or composite pervious structures. Preferred substances have at least one of the following characteristics on: (1) On the side of the transfer material which is in contact with the wet web is (the top), is the number of strands in Machine direction (MD) per centimeter (grid) between 4 to 80 (10 to 200 per inch) and the number of strands in the cross machine direction (CD) per centimeter (count) also from 4 to 80 (10 to 200 per inch). The strand diameter is typically less than 0.2 mm (0.050 inches); (2) on the top is the distance between the highest point of the ankle in Machine direction and the highest Point of the ankle in the cross-machine direction from about 25 microns to about 0.5 or 0.75 mm (about 0.001 to about 0.02 or 0.03 inches). Between these two Can level ankle either through MD or CD strands be formed, which of the topography a three-dimensional Lend characteristic; (3) on the top, the length of the MD knuckles is the same or longer as the length the cd ankle; (4) if the fabric is made in a multi-layer construction, it is preferred that the lower layer be made of a finer mesh is as the top layer to control the depth of the web penetration and fiber retention to maximize; and (5) the fabric can be made such that he shows certain geometric patterns which are pleasing to the eye are and which are typically between every 2 to 50 yarn nodes to repeat.

specific suitable transfer agents include, for example, those which manufactured by Asten Forming Fabrics, Inc., Appleton, Wisconsin and are designated as numbers 934, 937, 939 and 959. Special Transfer materials that can be used also include those described in U.S. Pat U.S. Patent 5,429,686 which issued July 4, 1995 Chiu et al. and incorporated herein by reference is. The void volume of the transfer substance may be equal or less be as the stuff from which the web is transferred.

The Forming and Formierverfahren and the approach can conventional As he is well known, he is a papermaking industry. Such forming methods include Fourdrinier, roof converters (such as a suction roll), gap converters (such as twin-wire converters, Halbmondumformer) or the like. Forming fabrics or fabrics can also conventional, with the finer weaves with greater fiber support being preferred are to produce a smoother arc or a smoother trajectory. Head boxes, which are used to apply the fibers to the forming fabric, can be divided into layers or not be divided into layers.

The The method disclosed herein may be applied to any tissue web what are orbits for making facial tissue, bath tissue, Paper towels, Napkins or the like. Such tissue webs can be single-layered Products or multi-ply products, such as two-ply, three-ply, four-ply or more. Single-ply products are due to their lower manufacturing costs advantageous while of Many consumers prefer multi-ply products. In multilayered Products it is not necessary that all layers of the product the same, provided that at least one layer according to this Invention is formed. The tracks can be stacked or uncoated, and the web forming fibers can Any fibers which are suitable for papermaking.

suitable Basis weights for this Tissue webs can from about 5 to about 70 grams per square meter (gsm), preferably from about 10 to about 40 gsm, and even more preferably about 20 to about 30 gsm amount. For a single-ply bath tissue has a basis weight of about 25 gsm prefers. For a two-ply tissue has a basis weight of about 20 gsm per layer preferred. For a three-ply tissue has a basis weight of about 15 gsm per layer preferred. Generally, higher basis weight webs are needed a lower air flow to the same operating pressure in the Air plenum chamber upright. The width of the slots of the Air presses are preferably adjusted so that the system of to disposal standing air capacity being adjusted, with wider slots for heavier basis weight webs be used.

The Drying process may be any non-compressive drying process which tends to be the volume or the thickness of the wet ones Web, including without limitation through-air drying, Infrared radiation, microwave drying or the like. by virtue of its commercial availability and practicality Through air drying is a well known and preferred means to non-compressive drying of the web. Suitable through-air drying agents include without limitation Asten 920A and 937A and Velostar P800 and 103A. The Durchlufttrocknungsstoffe can also include those disclosed in U.S. Patent 5,429,686 which, on July 4, 1995 Chiu et al. was granted. The train is preferably dried to a final dryness without creping, because creping tends to cause the web volume and thickness are reduced.

During the underlying mechanism was not fully understood it is clear that the transfer fabric and the through-air drying fabric separate and independent posts to the final Can afford bowing properties. For example, the surface smoothness of a Bow, as determined by a sensory panel, over one wide range by change the transfer substances in the same through-air drying fabric manipulated become. Webs, which according to the present Method and were produced with the present device, tend to be very two-sided if they are not calendered. Non calendered webs can but with smooth / rough sides are joined to the outside, as required by special product shapes.

numerous Features and advantages of the present invention will become apparent from the following description will become apparent. In the description will refer to the attached Drawings which show preferred embodiments of the invention illustrate. Such embodiments represent not the full scope of the invention. Therefore, reference to the claims specified herein be taken to interpret the full scope of the invention to be able to.

Short description the drawings

1 Fig. 4 representatively shows a schematic diagram of the process flow illustrating a method and apparatus according to the present invention for producing uncreped throughdried sheets.

2 Fig. 4 representatively shows an enlarged plan view of an air press from process flow di agramm of 1 ,

3 Fig. 4 representatively shows a side view of Figs 2 shown air press, wherein sections are broken away and shown in section for purposes of illustration.

4 FIG. 4 representatively shows an enlarged sectional view taken generally from the plane of the line 4-4 in FIG 3 is seen from.

5 Representatively shows an enlarged sectional view similar 4 but generally from the level of line 5-5 in 3 seen.

6 Fig. 4 representatively shows a side view of an alternative sealing system for the air press, which is shown in Figs 2 and 3 is shown, with parts broken away for purposes of illustration and shown in section.

7 Fig. 4 representatively shows an enlarged side view of a vacuum transfer jaw which is shown in Figs 2 is shown.

8th Representatively shows an enlarged side view similar 7 which, however, illustrates the simultaneous convergence and divergence of substances at a leading edge of the vacuum slot.

9 Figure 12 is a generalized plot of a loading / extension curve for tissue illustrating the determination of the MD slope.

detailed Description of the invention

The Invention will now be in greater detail described with reference to the figures. Similar elements in different Figures became the same for consistency and simplicity Numeral given. In all embodiments, which shown are, can with regard to casserole, formers, rail transfers, drying and creping a conventional papermaking apparatus and can be conventional Papermaking modes are used, all without Another understood by experts in the field of papermaking will be. Nevertheless, different are conventional Components are presented to provide the context in which the various embodiments of the present invention can be used.

An embodiment of a method and apparatus for making a tissue is representative of 1 shown. For the sake of simplicity, the various tensioning rollers, which are used schematically to define the plurality of fabric runs, are shown but not numbered. A paper making casserole 20 injected or brings an aqueous suspension of papermaking fibers 21 on a continuous formliner 22 which is a forming roll 23 emotional. The forming material 22 allows partial dewatering of the newly formed, wet web 24 to a consistency of about 10 percent.

After formation of the Formierstoff carries 22 the wet track 24 to one or more vacuum or suction boxes 28 which can be used to additionally drain the wet web 24 provide while on the forming fabric 22 is held. In particular, several vacuum boxes 28 used to the web 24 to dewater to a consistency of about 20 to about 30 percent. The illustrated Fourdrinier converter is particularly useful for making the heavier basis weight sheets useful as wipes and towels, although other formers such as twin-wire converters, crescent converters, and the like may be used instead. Hydron needling as disclosed, for example, in U.S. Patent No. 5,137,600, which issued to Barnes et al. can be optionally used to increase the volume of the web.

Stronger dewatering of the wet web 24 is thereafter provided by suitable additional non-compressive dehydrating agents, for example selected from the group consisting of air press, infrared drying, microwave drying, ultrasonic drying, through air drying and displacement drains. In the illustrated embodiment, the additional non-compressible dewatering agent comprises an air press 30 which is described in greater detail hereinafter. The air press 30 raises the consistency of the wet web 24 desirably more than about 30 percent, in particular more than about 31 percent, in particular more than about 32 percent and in particular more than about 33 Percent. In particular embodiments, the wet web 24 when exiting the air press 30 and before the subsequent transfer, a consistency of about 31 to about 36 percent. In particular embodiments, the air press increases 30 the consistency of the wet web 24 at least about 3 and preferably at least about 5 percent.

Desirable is a support material 32 in front of the air press 30 in contact with the wet track 24 brought. The wet track 24 is between the support material 32 and the forming material 22 sandwiched and thus assisted during the pressure drop, which by the air press 30 is produced. Fabrics for use as a prop 32 include almost any fabric, including forming fabric, such as Albany International 94M.

The wet track 24 is then from the Formierstoff 22 on a transfer material 36 which moves at a slower rate than the forming fabric to impart increased elongation to the web. The transfer is preferably with the assistance of vacuum transfer baking 37 as explained below with reference to 7 and 8th described. The surface of the transfer material 36 is relatively smooth to the wet web 24 To give smoothness. The openness of the transfer substance 36 , as determined by its hollow volume is relatively low and can be approximately equal to that of Formierstoff 32 or even lower.

The transfer material 36 moves over rollers 38 and 39 before the wet web 24 on a through-air drying agent 40 is transferred, which moves at about the same speed, or if desired at a different speed. The transfer is accomplished by the vacuum transfer jaws 42 , which may be the same as that used for the previous transfer. The train 24 is dried to a final dryness while the web has a through-air dryer 44 to be led.

Before the dried sheet on a roll 48 is wound up for subsequent conversion into the final product form, it may be passed through one or more optional fixed spacing material gaps which are between support materials 52 and 53 are formed. The volume or gauge of the web 50 can be controlled by Stoffprägespalte, which between roles 54 and 55 . 56 and 57 and 58 and 59 are formed. Suitable supporting agents for this purpose are Albany International 84M or 94M and Asten 959 or 937, which are all relatively smooth fabrics with a fine pattern. Gap spacings between the different pairs of rolls may range from about 0.001 inches to about 0.02 inches (0.025-0.51 mm). As shown, the proppant portion of the machine is designed to do so. and is operated with. a series of fixed pitch columns which serve to control the gauge of the web and which can replace or supplement off-line calendering. Alternatively, a roller calendering apparatus may be used to achieve a final gauge or to supplement off-line calendering.

The air press 30 is in greater detail through the top view of 2 and the side view of 3 the latter comprising broken away portions for purposes of illustration. The air press 30 generally includes an upper air plenum chamber 60 in combination with a lower vacuum or suction box 62 , The terms "upper" and "lower" are used herein to facilitate reference to and understanding of the drawings and are not intended to limit the manner in which the components are oriented to one another. The sandwich from the wet tissue web 24 between the forming material 22 and the support material 32 runs between the air plenum chamber 60 and the vacuum box 62 therethrough.

The illustrated air plenum chamber 60 is set up, a supply of pressurized fluid through air distributor 64 which are operatively connected to a source of pressurized fluid, such as a compressor or blower (not shown). The air plenum chamber 60 is with a plenum cover 66 equipped, which has a lower surface 67 which, during use, is in close proximity to the vacuum box 62 is arranged and in close proximity to or in contact with the support material 32 is arranged ( 3 ). The plenum cover 66 is with slots 68 ( 5 ) formed perpendicular to the machine direction over substantially the entire width of the wet web 24 extend to passage of pressurized fluid from the Luftplenumkammer 60 to allow through the fabrics and the wet web.

The vacuum box 62 is operatively connected to a vacuum source and fixedly secured to a support structure (not shown). The vacuum box 62 includes a cover 70 with an upper surface 72 , about which the Formierstoff 22 emotional. The vacuum box cover 70 is with a pair of slots 74 ( 3 and 5 ), which is the arrangement of the slots 68 in the plenum chamber cover 66 correspond. The pressurized fluid dehydrates the wet web 24 by the pressurized fluid from the air plenum chamber 60 in and through the vacuum box 62 is pulled.

The fluid pressure within the air plenum chamber 60 is preferably maintained at about 5 pounds per square inch (psi) (0.35 bar) or more, and more preferably within the range of about 5 to about 30 psi (0.35 to 2.07 bar), such as about 15 psi ( 1.03 bar). The fluid pressure within the air plenum chamber 60 is preferably monitored and controlled to a predetermined value.

The lower surface 67 the plenum cover 66 is preferably slightly curved to facilitate trajectory control. The surface 67 is to the vacuum box 62 curved, ie curved about an axis which on the side of the vacuum box of the web 24 is arranged. The curvature of the lower surface 67 allows a change in the angle of the combination of the support material 32 , the wet track 24 and the Formierstoffs 22 which results in an overall downward force on the vacuum box 62 against the entry of air from outside seals and the wet web 24 supported during the dewatering process. The bend angle allows the loading and unloading of the air press 30 as it is necessary from time to time, based on process conditions. The required angle change depends on the pressure difference between the pressure and vacuum sides, and is preferably above 5 degrees, and more preferably in the range of 5 to 30 degrees, typically about 7.5 degrees.

The upper and lower surfaces 72 and 67 preferably have different radii of curvature. In particular, the radius of curvature of the lower surface is 67 desirably larger than the radius of curvature of the upper surface 72 so as to contact lines between the air plenum chamber 60 and the vacuum 62 at the front and rear edges 76 the air press 30 to build. Taking into account the position of the sandwich of the support material 32 and the forming material 22 and the loading and unloading mechanisms in a suitable manner, the radii of curvature of these surfaces can be reversed.

The leading and trailing edges of the air press 30 also can with end seals 78 ( 3 ) which at all times are in very close proximity to or in contact with the support material 32 being held. The end seals 78 minimize leakage of pressurized fluid between the air plenum chamber 60 and the vacuum box 62 in the machine direction. Suitable end seals 78 may be formed of elastic plastic joints or the like.

With additional reference to 4 and 5 is the air press 30 preferably with side sealing elements 80 equipped to reduce the loss of pressurized fluid along the side edges 82 avoid the air press. The side sealing elements 80 include a semi-rigid material which is adapted to deform or flex slightly when pressurized fluid from the air plenum chamber 60 is suspended. The illustrated side sealing elements 80 define a slot 84 for attaching to the vacuum box cover 70 using a clamp bar 85 and fasteners 86 or other suitable means. In cross section, each side seal element 80 L shape, with one leg 88 from the vacuum box cover 70 up into a side seal slot 89 which extends in the plenum chamber cover 66 is trained.

Pressurized fluid from the air plenum chamber 60 causes the legs 88 outwardly in sealing contact with the outer surface of the side seal slot 89 the plenum chamber cover 66 bend, as is in 4 and 5 is shown. Alternatively, the position of the side seal elements 80 be reversed so that it is firmly attached to the plenum chamber cover 66 are attached and come into sealing contact with contact surfaces, which through the vacuum box cover 70 (not shown) are defined. In any such alternative embodiments, it is desirable that the side seal element be urged into engagement with the seal contact surface by the pressurized fluid.

A position control mechanism 90 holds the air plenum chamber 60 In the next. Proximity to the vacuum box 62 and in contact with the prop 32 , The position control mechanism 90 includes a pair of levers 92 , which by cross pieces 93 are connected together and with suitable fasteners 94 ( 3 ) at the air plenum chamber 60 are attached. The ends of the levers 92 opposite the air plenum chamber 60 are rotatable on a shaft 96 assembled. The position control mechanism 90 also includes a counterweight cylinder 96 , which effectively has a fixed structural support 99 and one of the cross pieces 93 connects with each other. The counterweight cylinder 98 is set up to expand or retract and thereby cause the levers 92 around the shaft 96 turn, which causes the air plenum chamber 60 yourself to the vacuum box 62 approaching or moving away from him.

In operation, a control system causes the counterweight cylinder 98 to stretch enough that the end seals 78 in contact with the prop 32 Step and the side sealing elements 80 inside the side seal slots 89 be positioned. The air press 30 is activated so that pressurized fluid the Luftplenumkammer 60 fills and the semi-rigid side sealing elements 80 in sealing engagement with the plenum chamber cover 66 are forced. The pressurized fluid also creates an upward force tending to the air plenum chamber 60 away from the prop 32 to move. The control system controls operation of the counterbalance cylinder 98 to this upward force based on continuous measurement of the fluid pressure within the air plenum chamber 60 to be compensated by the pressure monitoring system. The end seals 78 They are thus very close to or in contact with the support material at all times 32 held. The control system compensates for random pressure drops or pressure spikes within the air plenum chamber 60 by proportionally lowering or increasing the force passing through the counterweight cylinder 98 is exercised. As a result, the end seals jam 78 the substances 32 and 22 not one that would otherwise lead to excessive wear of the fabrics.

An alternative sealing system for the air press 30 is representative in 6 shown. The air plenum chamber 100 is with a swivel arm 102 equipped with a sealing rod 104 defines or wears, which is adapted to, on the support material 32 across the width of the wet track 24 to drive to minimize leakage of pressurized fluid in the machine direction. While only one arm 102 in 6 is to be understood, that a second arm at the opposite end of the Luftplenumkammer 100 can be used and constructed in a similar manner. The sides of the air plenum chamber 100 can side seals 80 as related to 2 - 5 described or fixed to the vacuum box 62 be mounted to minimize or eliminate lateral leakage of pressurized fluid.

The swivel arm 102 desirably comprises a rigid material such as structural steel, graphite composites or the like. The arm 102 has a first section 106 at least partially within the air plenum chamber 100 is arranged, and a second section 108 , which is preferably arranged outside the Luftplenumkammer. The arm 102 is through a joint 110 pivotally attached to the Luftplenumkammer. A pressurized fluid impervious joint seal is on both the inner surface of a wall 114 the air plenum chamber 100 as well as the first section 106 attached to prevent escape of the pressurized fluid. The sealing rod 104 is preferably a separate element which is attached to the first section 106 is attached, and by contact with the pressurized fluid on the first portion to the support material 32 out (not in 6 shown) is urged. Suitable sealing rods 104 can be formed of a durable material with low resistance and low coefficient of friction, such as ceramic, heat-resistant polymers or the like.

A counterweight bubble 120 with an inflatable chamber 122 is with brackets 124 or other suitable means at the second section 108 of the arm 102 attached. The chamber 122 is operatively connected to a source of pressurized fluid, such as air, to inflate the chamber. The arm 102 and the bubble 120 are arranged so that the bladder, when inflated (not shown) against the outer surface of the wall 114 the air plenum chamber 100 pushes, which causes the arm around the joint 110 to pan. Alternatively, a mechanism using pressurized cylinders (not shown) may be used instead of the counterweight bladder as a means for pivoting the arm 102 be used.

A control system is set up, the bubble 120 proportional in response to the pressure of the fluid within the air plenum chamber 102 inflate or deflate them. For example, the control system is set up as the pressure within the plenum chamber increases 100 , the pressure inside or the inflation of the counterweight bladder 120 to raise so that the sealing rod 104 not overly down against the support material 32 excluded.

The embodiment of the vacuum transfer baking 37 , which in the transfer substance section of the process ( 1 ) is clearer in 7 and 8th illustrated. The vacuum transfer baking 37 defines a vacuum slot 130 ( 7 ) connected to a vacuum source and having a length of "L" suitably from about 0.5 to about 1 inch (12.7-25.4 mm). For producing uncreped throughdried bath tissue, a suitable vacuum slot length is about 1 inch (25.4 mm). The vacuum slot 130 has a leading edge 132 and a trailing edge 133 , which are corresponding input casserole and outlet taps 134 and 135 of vacuum transfer baking 37 form. The trailing edge 133 of the vacuum slot 130 is relative to the leading edge 132 offset what by the different Orientation of the exit flow area 135 relative to the entrance casserole area 134 caused. The angle "A" between the levels of the entrance ramp area 134 and the exit flow area 135 may be about 0.5 degree or more, more preferably about 1 degree or more, and more specifically about 5 degrees or more, for sufficient separation of the forming material 22 and the transfer substance 36 as they converge and diverge.

8th also makes the wet tissue web 24 as they bake in the direction indicated by the arrows towards the vacuum transfer 37 emotional. Also the transfer material 36 moving at a slower speed approaches vacuum transfer baking 37 , The convergence angle between the two incoming substances is designated as "C". The divergence angle between the two substances is designated as "D". As shown, the two materials converge and diverge simultaneously at point "P", which is the leading edge 132 of the vacuum slot 130 equivalent. It is not necessary or desirable that the web be covered with both fabrics over the entire length of the vacuum slot 130 comes into contact to the transfer of the forming material 22 on the transfer substance 36 to effect. How out 8th obviously, neither the Formierstoff need 22 still the transfer material 36 to be deflected more than a small amount to perform the transfer, which can reduce fabric wear. Expressed in numbers, the change in direction of each substance can be less than 5 degrees.

As mentioned previously, the transfer material moves 36 at a lower speed than the forming material 22 , if more than one transfer material is used, the speed differential between the materials may be the same or different. Multiple transfer fabrics can provide flexibility in operation as well as a wide variety of fabric / speed combinations to influence the properties of the final product.

The height of the vacuum used for differential speed transfer may be from about 76 to about 381 mm (about 3 to about 15 inches) of mercury, preferably about 127 mm (about 5 inches) of mercury. Vacuum baking (negative pressure) may be supplemented or replaced by the use of positive pressure applying means from the opposite side of the web 24 to blow the web onto the next fabric in addition to or as a substitute for vacuuming it onto the next fabric. A vacuum roll or vacuum rolls may also be used to replace the vacuum jaw (s).

Examples

The the following EXAMPLES are attached, for a deeper understanding to impart the invention. The special amounts, proportions, Compositions and parameters should be and should be exemplary does not specifically limit the scope of the invention.

As With reference to the examples, tensile strength is used in the machine direction, stretch in the machine direction and tensile strength in transverse machine direction obtained by the TAPPI test method 494 OM-88 "tear resistance properties from paper and cardboard "under Using the following parameters: Crosshead speed is 10.0 inches / min. (254 mm / min.); maximum load is 10 pounds (4.540 g); Terminal span (the distance between the terminals, sometimes as the gauge length denotes) 2.0 inches (50.8 mm); and the sample width is 3 inches (76.2 mm). The Tensile test machine is a Sintech, model CITS-2000 of Systems Integration Technology Inc. of Stoughton, Massachusetts Division of MTS Systems Corporation, Research Triangle Park, North Carolina.

The stiffness of the sample sheets can be objectively represented by either the maximum slope of the machine direction (MD) / tissue extension (hereafter referred to as the "MD slope") curve or the machine direction stiffness (defined herein) also takes into account the final size of the tissue and the number of layers of the product. Determination of the MD slope will be hereinafter referred to 9 described. The MD slope is the maximum slope of the machine direction / strain curve for the tissue. The units for the MD slope are kilograms per 3 inches (7.62 centimeters). The MD stiffness is calculated by multiplying the MD slope by the square root of the quotient of the gauge block divided by the number of plies. The units of MD stiffness are (kilograms per 7.62 cm) micrometer ^0.5 ((kilograms per 3 inches) micrometer ^0.5 ).

9 Figure 12 is a generalized stress / strain curve for a tissue arc illustrating the determination of the MD slope. As shown, two points P1 and P2, the distance of which is exaggerated for purposes of illustration, are selected along the Belas expansion / expansion curve. The tensile strength tester is programmed (GAP [General Applications Program], version 2.5, Systems Integration Technology Inc., Stoughton, MA, a division of MTS Systems Corporation, Research Triangle Park, NC) as a linear regression for the points calculated, which were taken from P1 to P2. This calculation is repeatedly performed on the curve by adjusting the points P1 and P2 in a regular manner along the curve (described below). The maximum of these calculations is the maximum slope and is referred to herein as the MD slope when performed in the machine direction of the sample.

The Program of the tensile tester should be set up in such a way 500 points, such as P1 and P2 over two and a half inches (63.5 mm) Extension range be recorded. This provides a sufficiently high number of points in essence, any practical extension of the Surpass sample. At a crosshead speed of 10 inches per minute (254 mm / min.) This means one point every 0.030 seconds. The Program calculates slopes below these points by using the 10th point as the initial one Point (for example, P1) sets 30 points to the 40th point (for example P2) counts and perform a linear regression based on these 30 points. It stores the slope from this regression in an array. The Program counts then ten points up to the 20th point (which becomes P1) and repeat the procedure again (counts thirty points by then what the 50th point would be (which becomes P2) calculates the slope and saves it as well in the array). This procedure is used for the entire length of the Bow continued. The maximum slope is then considered the highest value selected from this array. The maximum pitch units are kg per three inch sample width. (Tension is natural dimensionless, as the length the extension by the length the terminal distance is shared. This calculation is done by the Test machine program considered.)

Examples 1-4. To illustrate the invention, a number of uncreped throughdried tissues were produced using the method substantially as described in U.S. Pat 1 is shown. Specifically, Examples 1-4 were all three-layer, single-ply bathtissues in which the outer layers comprised dispersed, debonded eucalyptus fibers, and the middle layer comprised refined northern softwood kraft fibers. Cenebra eucalyptus fibers were pulped at 10 consistency for 15 minutes and dehydrated to 30% consistency. The pulp was then introduced into a Maule Well Disperser. The disperser was operated at 160 ° F (70 ° C) with a power input of 2.2 HPD / T (1.8 kilowatt-days per tonne). After dispersing, a plasticizer (Witco C6027) in the amount of 7.5 kg per metric ton of dry fiber (0.75 weight percent) was added to the pulp.

In front During formation, the softwood fibers became 3.2 for 30 minutes Percent consistency turns into mush while the dispersed, debonded Eucalyptus fibers were diluted to 2.5 percent consistency. The total weight of the layered sheet became 35% / 30% / 35 % for examples 1, 2 and 4 and in 33% / 34% / 33% for Example 3 among the dispersed ones Eucalyptus / Refined Softwood / Dispersed Eucalyptus Layers divided up. The middle layer was refined to levels which necessary to achieve target strength values while the outer layers Softness and volume provided. For additional drying and temporary wet strength to the middle layer was a reinforcing agent, Parez 631 NC, added.

These Examples used a four-layer Beloit Concept III headbox. The refined kraft material from northern softwood was used in used the two middle layers of the casserole to one single middle layers for to produce the three-layered product described. There was turbulence generating inserts, which offset from the disk about three inches (75 millimeters) and layer splitters, which are about six inches (150 millimeters) across the Slice out, used. The total disc opening was about 0.9 inches (23 millimeters) and the water flow in all four Casserole layers were comparable. The consistency of the material feed in the casserole was about 0.09 weight percent.

Of the resulting three-layer sheet was using on a converter Formed twin screen and suction forming roll, wherein the Formierstoffe Appleton Mills 2164-B fabrics were. The speed of the forming material was between 11.8 and 12.3 meters per second. The freshly educated Track was then made to a consistency of 25-26% using Vacuum sucked from under the former dehydrated without air press, and 32-33 % with air press, before being transferred to the transfer fabric, which moved at 9.1 meters per second (29-35% express transfer). The transfer fabric was Appleton Mills 2164-B. A vacuum baking, which about 6-15 Inches (150-380 Millimeters) mercury vacuum pulls, was used to the web to transfer to the transfer substance.

The Web was then transferred to a through-air dryer, which is at a speed of about 9.1 meters per second moving. There were Appleton Mills T124-4 and T124-7 through air dryers used. The railway was over a Honeycomb Durchluftdrockner transported, which at a Temperature of about 350 ° F (175 ° C) was operated, and to a final dryness of about 94-98% consistency dried.

The Sequence of preparation of the sample sheets was as follows: There were four rolls of bows prepared from Example 1. The consistency data, which is shown in Table 1 listed are based on two measurements, one at the beginning and one at the end the 4 rolls. The other data shown in Table 1 represent one Average based on 4 measurements, one per roll. The Air press was then started. Data immediately before and immediately after activation of the air press are shown in Table 3 (individual Data points). These data show that the air press is significant increases caused the tensile strength values. The procedure was then modified to reduce the tensile strengths to values which are comparable those of the bows from Example 1 were. After this process adjustment period were 4 rolls of bows of Example 2 (of this invention). Later, 4 rolls of the bows of Example 3 (of this invention) using a different one Durchlufttrocknungsstoffs and manufactured with activated air press. The Air press was shut down and the process adjusted to tensile strength values, which were comparable to those of the sheets of Example 3, again to get. Four rolls of the sheets of Example 4 were then made. The consistency data point for each example in Table 2 is an average value which is 2 measurements, one at the beginning and one at the end of each sentence of 4 rolls. The other data in Table 2 is based on a Average of 4 measurements per sample sheet, one per roll. In Table 2, the data of Example 4 is in the left column and the data of Example 3 shown in the right column to be consistent with tables 1 and 3 to stay what data without the air press in the left column and data with the air press in the right Show column.

Tabelle 2

Tabelle 3

Procedure Condition and Resulting Tissue Properties for Examples 1-4. As used in Tables 1-3 below, the column headings have the following meanings: "consistency @ rapid transfer" is the consistency of the web at the point of transfer from the forming fabric to the transfer fabric, expressed as percent solids; "MD Tensile Strength" is the machine direction tensile strength, expressed in grams per 3 inches (7.62 centimeters) of sample width; "CD tensile strength is the transverse machine direction tensile strength, expressed as grams per 3 inches (7.62 centimeters) sample width;" MD Elongation "is the machine direction stretch, expressed as percent elongation at sample failure;" MD Slope "is as defined above, expressed as kilograms per 3 inches (7.62 centimeters) of sample width "Final gauge" is the final gauge of an arc measured with a volume micron (TMI Model 49-72-00, Amityville, New York) with an anvil diameter of 4 1/16 inches (103.2 mm) and anvil pressure of 220 grams / square inch (3.39 kilopascals), expressed in microns; "MD Stiffness" is the machine direction stiffness factor as previously defined, expressed as (kilograms per 3 inches ) Micron ^0.5 ; "basis weight" is the finished basis weight expressed as grams per square meter; "TAD fabric" means through-air drying fabric; "refinement" is the power input to refine the middle layer expressed as kilowatts; "Rush" is the speed difference between the former and the slower transfer, divided by the speed of the transfer and expressed as a percentage; "HW / SW" is the distribution of the weight of hardwood (HW) and softwood (SW) fibers in the three-ply, single-ply tissues, expressed as a percentage of total fiber weight; and "Parez" is the amount of Parez 631 NC added expressed as kilograms per metric ton of the middle layer fibers. Table 1

Table 2

Table 3

As shown by the preceding examples, produces the air press significantly higher Consistencies upstream from the differential speed transfer, resulting in smoother arcs, such as it is shown by the lower modulus values. Preferably the modulus (MD stiffness) of tissue products is at least 20 percent smaller than that of a comparable tissue product, which without additional Drain to a consistency of more than about 30 percent. Further, the machine direction tensile strength is the tissue product at least 20 percent higher and the tensile strength of the tissue products in the cross-machine direction at least 20 percent higher than that of a comparable tissue product, which without additional Drain to a consistency of more than about 30 percent. additionally The stretch in the machine direction of tissue products is at least 17 percent higher than that of a comparable tissue product, which without additional Drain to a consistency of more than about 30 percent.

The The foregoing detailed description is for the purpose of illustration. Therefore, a number of modifications and changes can be made, without departing from the scope of the present invention. For example can alternative or optional features, as part of an embodiment are described, used to another embodiment to build. In addition, two can Names named components represent parts of the same structure. Furthermore, can various method and device arrangements as in PCT Patent Application Publication WO 95/00706 of January 5, 1995 and US Patent Application No. 08 / 330,166, filed October 27, 1994 by Engel et al. entitled "Method For Making Smooth Uncreped Throughdried Sheets "should be used Invention not to the specific embodiments which described were limited but only through the claims.

Claims (26)

A method of making a soft tissue sheet, comprising the steps of: applying an aqueous suspension of papermaking fibers to a continuous forming fabric ( 22 ) to a wet web ( 24 ) to build; Dewatering the wet web ( 24 ) to a consistency of 20 to 30 percent; Transferring the web onto a transfer fabric ( 36 ), which moves at a speed which is 10 to 80 percent lower than that of the forming material ( 22 ); Transfer the web ( 24 ) to a through-air drying substance ( 40 ); and through-air drying of the web to a final dryness, characterized in that the wet web ( 24 additionally dewatered to a consistency of greater than 30 percent using a non-compressing dehydrating agent before being applied to the transfer material ( 36 ) is transferred. The method of claim 1, wherein the non-compressive dehydrating agent is selected from the group consisting of an air press ( 30 ), Infrared drying, microwave drying, ultrasonic drying, through air drying, and displacement drainage. The method of claim 1, wherein the non-compressing dehydrating agent comprises an air press ( 30 ). Method according to claim 3, wherein the air press ( 30 ) the consistency of the wet web ( 24 ) increased by at least 3 percent. Method according to one of claims 3 or 4, wherein the air press ( 30 ) an air plenum chamber ( 60 ), and fluid pressure within the air plenum chamber (FIG. 60 ) within the range of 34 to 207 kPa (5 to 30 pounds per square inch). Method according to one of claims 3 to 5, wherein the air press ( 30 ) provides a pressure difference across the wet web of 889 to 1524 mm (35 to 60 inches) of mercury. Method according to one of claims 3 to 6, wherein the air press ( 30 ) the wet web ( 24 ) drained to a consistency of more than 31 percent. Method according to claim 7, wherein the air press ( 30 ) the wet web ( 24 ) drained to a consistency of more than 32 percent. Method according to one of claims 3 to 6, wherein the air press ( 30 ) the wet web ( 24 ) drained to a consistency of 31 to 36 percent. Method according to one of claims 3 to 9, wherein the wet web ( 24 ) between the forming material ( 22 ) and a support material ( 32 ) is embedded when passing through the air press ( 30 ) is transported. Method according to one of the preceding claims, wherein dewatering of the wet web ( 24 ) to a consistency of 20 to 30 percent using multiple vacuum boxes ( 62 ) is carried out. Method according to one of the preceding claims, wherein the forming material ( 22 ) moves at a speed of at least 10 m / s (2,000 feet per minute). Tissue product, available by the method according to one of the preceding claims, wherein the stiffness of the tissue product in the machine direction at least 20 percent less than that of an identical tissue product to which it is added dehydration treatment up to a consistency of more than 30 percent is missing. The tissue product of claim 13, wherein the tear resistance of the tissue product in the machine direction is at least 20 percent higher than that of an identical tissue product to which it is added to the additional drainage treatment up to a consistency of more than 30 percent is missing. The tissue product of any of claims 13 or 14, wherein the tear strength of the tissue product in the cross machine direction is at least 20 percent higher than that of an identical tissue product which lacks the additional dewatering treatment to a consistency of more than 30 percent. Tissue product according to one of claims 13 to 15, wherein the elongation of the tissue product in the machine direction is at least 17 percent higher is considered to be that of an identical tissue product to which it is attached additional dehydration treatment up to a consistency of more than 30 percent is missing. Air press ( 30 ) for dewatering a wet web ( 24 ) comprising: an air plenum chamber ( 60 ), comprising a plenum chamber cover ( 66 ) with a lower surface ( 67 ); a means for supplying pressurized fluid to the air plenum chamber ( 60 ); a vacuum box ( 62 ), comprising a vacuum box cover ( 70 ) with an upper surface ( 72 ) in close proximity to the lower surface ( 67 ) of the plenum chamber cover ( 66 ) is arranged; means for applying vacuum to the vacuum box; and side seals ( 80 ) arranged to communicate with the air plenum chamber ( 60 ) and the vacuum box ( 62 ) in order to minimize leakage of the pressurized fluid, the side seal elements ( 80 ) at one of the air plenum chambers ( 60 ) and the vacuum box ( 62 ) are positioned in close proximity to side seal contact surfaces defined by the other of the air plenum chamber (FIGS. 60 ) and the vacuum box ( 62 ) are defined; the side sealing elements ( 80 ) are adapted to flex into sealing contact with the side seal contact surface when exposed to pressurized fluid. Air press according to claim 17, wherein the side sealing elements ( 80 ) on the vacuum box cover ( 70 ) and the plenum chamber cover ( 66 ) Sealing slots and the side sealing contact surfaces are defined. Air press according to claim 17, further comprising end seals ( 78 ) attached to the plenum chamber cover ( 66 ) are mounted. Air press according to one of claims 17 or 19, further comprising a position control mechanism ( 90 ) which is adapted to the air plenum chamber ( 60 ) in close proximity to the vacuum box ( 62 ) to keep. Air press according to claim 20, wherein the position control mechanism ( 90 ) a rotatably mounted lever ( 92 ), which at the Luftplenumkammer ( 60 ) and a counterweight cylinder ( 98 ) which is arranged to move the lever ( 92 ) to turn. Air press according to claim 20, further comprising a control system which is adapted to operate the counterweight cylinder (10). 98 ) in response to measurements of fluid pressure within the air plenum chamber ( 60 ). Air press according to claim 17, 18 or 19, wherein the upper and lower surfaces of the vacuum box ( 62 ) are curved out. Air press according to claim 23, wherein the upper ( 72 ) and lower surface ( 67 ) have different radii of curvature. Air press according to claim 17, comprising: an arm ( 102 ), which pivotably at the Luftplenumkammer ( 100 ) and a first ( 106 ) and a second ( 108 ) Section, the first section ( 106 ) at least partially in the interior of the air plenum chamber ( 100 ) is arranged and a sealing rod ( 104 ); and a means for pivoting the arm ( 102 ) in response to fluid pressure within the air plenum chamber ( 100 ). Air press according to claim 25, further comprising a hinge seal ( 112 ), which is impermeable to pressurized fluid and both at the air plenum chamber ( 100 ) as well as the first section ( 106 ) is attached.