MULTI-PLANE DEWATERING FABRIC

Abstract: A dewatering fabric for the press section of a paper making machine is described having improved dewatering characteristics, improved resistance to compaction, and enhanced ability to bridge cavities, such as grooves or holes, in press section rolls. The fabric includes at least two distinct layers of flattened monofilament warp yarns at a high fill factor, and at least one layer of weft yarns. Advantageously, the fabric is constructed to provide long exposed floats of one of the distinct layers of warp yarns on the paper side of the fabric. The fabric may be used alone, with a paper side batt, or with a batt on both sides.

Description: MULTI-PLANE DEWATERING FABRIC This invention relates to dewatering fabrics used in the press section of a papermaking machine. It is particularly concerned with a press section fabric including multiple distinct layers of flattened monofilament warp yarns configured to provide improved roll nip pressure uniformity, reduced paper marking, increased paper dewatering and enhanced compaction resistance. Pressure non-uniformity in a press nip can arise from two sources: a) the press rolls themselves, which may be grooved or drilled to provide void space for the water expressed from the web in the nip; and b) the press fabric itself, which, due to its woven structure (or other reasons) transmits press nip pressures unevenly. In different situations, either of these two sources may be the dominant source of non-uniformity and hence of paper marking or low dewatering. In some cases, for example, the pattern of the grooves of the press roll can be seen clearly in the finished paper, while in other cases, the marks of the woven structure of the fabric can be seen. Sometimes both marks are present. The first proposal to use flattened monofilament warp yarns in a press section fabric was by Miller et al., U.S. 4,414,263. Miller et al. advocated using flattened monofilament yarns with a relatively low aspect ratio in an otherwise conventional weave. Variations on the Miller et al. fabric which are proposed by Stanley, U.S. 4,973,512 and U.S. 5,023,132. An improved fabric using flattened monofilament warp yarns is described by Jackson, WO 91/04374. In the Jackson fabric, a flattened monofilament warp yarn with a somewhat higher aspect ratio is used at a high fill factor, in a weave pattern which provides long exposed floats of flattened monofilament warp yarns on the paper side of the fabric. This weave construction provides a relatively flat, smooth, almost platform-like surface on the paper side of the fabric. This relatively flat surface transfers the meclianical loads imposed by the press section rolls from the press fabric to the paper web in a way that provides improved pressure uniformity. The maximum benefit of a Jackson press section fabric appears to be obtained in a weave design that includes a single layer of weft yarns. In this type of fabric, the maximum float length for the flat warp yarns can be achieved, thereby imparting the maximum smoothness and pressure uniformity to the fabric. However, it has now been found that a fabric containing a single layer of weft yarns as described by Jackson has certain disadvantages. In particular, it seems not to be entirely suitable for configurations in which at least one of the press rolls has cavities, such as grooves or holes in its surface. It appears that such a thin fabric when used in a press felt is unable to bridge these roll cavities adequately, and pressure non-uniformity on the paper web results. If a double weft yarn layer fabric design is used, as is described by Jackson, in order to bridge the press roll cavities better, the amount of flattened monofilament warp yarns which can be exposed on the paper side of the fabric is not as high as can be exposed for a single weft yarn fabric design. This is because the flattened monofilament warp yarns follow a generally diagonal path within the fabric when they interweave with the bottom weft yarns. This limits the length of float that can be exposed on the paper side of the fabric. Thus there has been found to be a balance between enhanced pressure uniformity on the paper side of the fabric, and press roll cavity bridging on the press roll side of the fabric. If a double weft yarn layer fabric is used there is the further disadvantage that the peak pressure in the roll nip is not as high as is obtained with a single layer fabric, and therefore a double weft yarn layer fabric will dewater the sheet of paper less. This invention seeks to overcome these problems and to provide an improved fabric of the type described by Jackson which provides better roll cavity bridging characteristics and better pressure uniformity. Further, this invention also seeks to enhance the compaction resistance of the fabric. Additionally, this invention seeks to provide a fabric in which these improvements can be realised without losing the ability to have long exposed floats of flattened monofilament warp yarns on the paper side of the fabric. These improvements are obtained by incorporating into the fabric at least two distinct layers of flattened monofilament warp yarns, and at least one layer of weft yarns. One layer of flattened monofilament warp yarns provides the long exposed floats generally on one side of the fabric. Further, if a double weft yarn layer construction is used, the other warp yarn layer(s) can be utilised to maintain good separation between the upper and lower weft yarn layers (that is, the weft yarn layers adjacent the paper side and the press roll side of the fabric, respectively) without having to diminish in any way the amount of long exposed flattened monofilament warp yarn floats on the paper side of the fabric. The separation thereby obtained between two weft yarn layers enhances fabric compaction resistance and available void volume. We have found that fabrics woven according to this invention reduce marking by both the press rolls and -the press fabric, and the exact configuration of the two layers of flat warps can be adjusted for these different circumstances. If the press roll grooves are the main source of non-uniformity, it may be beneficial to locate the long floats close to the roll surface. In other cases, the long floats may be beneficially located nearest the paper side surface of the fabric. In the fabrics of this invention, the term "warp yarn" is used to designate the warp on the weaving loom, that is the set of yarns that travel from the warp beam through the heddles of the loom, and which form the shed through which the weft yarn is passed. If a fabric of this invention is woven as an endless loop, the flattened monofilament warps lie in the cross- machine direction of the paper making machine. It is known to weave an endless loop incorporating a seam, or to insert a seam later, in order to facilitate installation in a press section. Alternatively, if a fabric of this invention is woven as a "flat" fabric, as a continuous run, and then joined into the required endless loop with a suitable seam, the flattened monofilament warps lie in the machine direction of the paper making machine. Thus, in a first broad aspect this invention provides a woven dewatering fabric, for the press section of a papermaking machine, having a first side and a second side, one of which constitutes the paper side of the fabric, and the other of which constitutes the press roll side of the fabric, and having long exposed floats of flattened monofilament warp yarns on the first side of the fabric, wherein: (i) the aspect ratio of the flattened monofilament warp yarns is at least 1.5:1; (ii) the fabric weave includes at least two distinct layers of warp yarns each including flattened monofilament warp yarns, one of which provides the exposed first side floats; (iii) the fabric weave further includes at least one layer of weft yarns; and (iv) the fill factor for each of the distinct layers including flattened monofilament warp yarns is at least 45%. Preferably, the long exposed floats on the first side of the fabric satisfy a definition for 'float ratio* similar to the one given by Jackson, WO 91/04374, modified to fit the fabrics of this invention. For the fabrics of this invention it is preferred that the long exposed floats on the first side of the fabric satisfy a float ratio formula x/y, wherein: (i) "x" represents the number of weft yarns in a weft yarn layer on the first side of the fabric in a single weave pattern repeat which are on the inside of the fabric with respect to a particular flattened monofilament warp yarn, and supporting that warp yarn; and (ii) "y" represents the total number of weft yarns in the weft yarn layer on the first side of the fabric in a single weave pattern repeat; and wherein for a majority of the first side exposed floats of flattened monofilament warp yarns: (iii) x is greater than one; and (iv) x is greater than one-half of y. In some applications, it is possible to use the fabrics of this invention in a press roll section without a porous layer, such as a needled fibrous batt, attached thereto. Conveniently, a porous layer, such as a fibrous batt, can be attached to the paper side, or to both the paper side and the press roll side, of the fabric. Preferably, the flattened monofilament warp yarns making up each of the distinct layers of warp yarns are situated substantially vertically above one another in the woven fabric. The invention will now be discussed by way of reference to the attached Figures in which: Figures 1, 2 and 3 show a single weft yarn layer fabric; Figures 4 through 11 show alternative weave patterns; Figures 12 and 13 show a weave pattern incorporating a binder tie yarn; Figures 14, 15 and 16 show fabrics carrying porous layers; and Figure 17 shows the face of a fabric. In Figure 1 is shown a single weft yarn layer fabric according to this invention. The fabric as shown includes three layers of yarns: (i) an upper, side A, set of flattened mono-filament warp yarns 1, 3, 5 & 7; (ii) a lower, side B, set of flattened monofilament warp yarns 2, 4, 6 & 8; and (iii) a single layer of weft yarns 1, 2, 3, 4, 5, 6, 7 & 8. SUBSTITU i E SHEET Each set of warp yarns is woven at a fill factor of at least 45%, and preferably of about 85%. Thus the combined fill factor for the two sets of warp yarns is greater than 90%, and preferably is about 170%. This high fill factor for the flattened monofilament warp yarns provides the improved pressure uniformity on the paper side, improved press roll cavity bridging on the press roll side, and enhanced compaction resistance of the fabric. Figures 2 and 3 show schematically the weave pattern for the fabric of Figure 1. In these and later figures three conventions are used; it can be seen that the yarns in Figure 1 are numbered to match Figures 2 and 3. First, in Figure 2 a filled-in square indicates that at that point a warp yarn passes over a weft yarn. Second, Figure 3 represents a cross section based on Figure 2 along the line of the warp yarn numbers given: thus in Figure 3 the warp yarns are numbers 1 & 2 from Figure 2, and the section in Figure 3 is the left-hand side of the diagram in Figure 2. Third, 'A' represents the first side and 'B' the second side, of the fabric. In all of these fabrics the side A includes the long exposed floats. Certain other features of the fabrics of this invention can be seen in Figure 1. First of all, only one set of yarns, 1, 3, 5 & 7, is exposed on the side A of the fabric. As shown, the two sets of warp yarns are substantially one over the other: thus warp yarn 1 is above warp yarn 2, and so on. This is largely a consequence of the fill factor used; generally, the higher the fill factor the better this correlation will be. It can also be seen that at some points in this single weft yarn layer fabric warp yarns from both sets pass the same side of particular weft yarn: warp yarns 1 and 2 both pass over the side A of weft yarn 2, and pass under the side B of weft yarn 8. Finally, as shown this fabric is effectively the same on both faces, as the weave SUBSTITUTE SHEET patterns for the two sets of warp yarns are mirror images of each other. This is not necessary, and the weave pattern adopted for the press roll side B can be different to that of the paper side A. In a fabric such as that in Figure 1 as the fabric is the same on both faces, it does not matter which of side A and side B is taken as the paper side of the fabric, and which is taken as the press roll side of the fabric. In these Figures as noted above the convention is adopted that the first side of the fabric, which includes the long exposed floats, is identified as side A. Generally, it is preferred that side A be the paper side of the fabric, but this is not necessary. The fabrics of this invention function adequately in some applications when side A is the press roll side of the fabric. The warp yarn weave pattern on the side A of the fabric preferably utilizes the long exposed float concepts described by Jackson in WO 91/04374. That is, the weave pattern includes long exposed floats of flattened monofilament warp yarns with an aspect ratio of at least 1.5:1 on the side A of the fabric but not necessarily on the side B of the fabric. These long exposed floats can be characterized by a "float ratio" expressed by the formula x/y as defined above. There is an upper limit to the float ratio, which is the point at which fabric integrity becomes questionable. For a fabric similar to that shown in Figure 1, this seems to occur at a float ratio of about 9/10. It also appears that if the values of x and y are both low, or if x is close to one half of y, then the dewatering properties of the fabric are impaired. The float ratio in a given fabric need not be constant either along a given flattened monofilament warp yarn, or for all of the flattened monofilament warp yarns in a given weave. Further, not all of the exposed floats of flattened monofilament warp yarns need have a float ratio in which SUBSTITUTE SHEET x is both greater than one, and greater than one half of y, although maximum benefit will be obtained if these restrictions are observed. As is shown in Figure 17, which shows only the side A of the fabric, a fabric can be woven with varying float ratios. From the top downwards in Figure 17 the float ratios are 7/8, 5/8, 6/8, 4/8, 6/8, 3/8 and 5/8. In a similar way the float length can be varied along a given flattened monofilament warp yarn, to provide in sequence a 1/2 unit, then a 5/6 unit, for example. In such a case the float ratio should be determined over the full length of the pattern repeat, and 1/2 combined with 5/6 in fact is 6/8. The warp yarn weave pattern on the side B of the fabric is not so restricted, as is shown in the weave designs of Figures 4 through 9. In each of these, whilst an adequate float ratio is maintained for -the set of warp yarns providing the side A long exposed floats, the path for the other warp yarns can be quite different. Figures 6 and 7 show a second fabric in which the warp yarn weave patterns are mirror images of each other, while in Figures 4, 5, 8 and 9 the patterns are quite different. The float ratio for side A of each of these weaves is: x y x y Figure 3 7 8 7/8 Figure 5 6 8 6/8 Figure 7 5 8 5/8 Figure 9 7 8 7/8 From these Figures and the derived float ratios it can be seen how the float ratio is calculated. In each case it is only the weft yarns supporting a warp yarn which are counted. In each of these Figures, as is indicated at X, there is a second warp yarn between the exposed float and a weft yarn: that weft yarn is taken to be supporting the warp yarn float. SUBSTITUTE SHEET The designs of Figures 4, 5, 6 and 7 have flattened monofilament warp yarns on both sides of the fabric providing good paper side pressure uniformity and good press roll venting cavity bridging. In Figures 8 and 9 the design has flattened monofilament warp yarn floats on the side A of the fabric, but unlike Figures 6 and 7 the second warp yarns are highly interlaced between each layer of weft yarns providing good paper side pressure uniformity and good compaction resistance. In the designs of Figures 4, 5, 8 and 9 (and also Figures 10 and 11, described below) the warp yarn sets have differing path lengths. Designs of this type may require the use of two, or more, warp yarn beams, as is well known to those skilled in the art of weaving. The designs illustrated are all interwoven so that the result is a single fabric. Figures 10 and 11 illustrates a design using two layers of weft yarns, and three layers of flattened monofilament warp yaπls 1, 2 and 3. As shown, the weave pattern for warp yarn 1, on the side A of the fabric and warp yarn 3, on the side B of the fabric, are essentially similar, but this is not necessary: the pattern for warp yarn 3 can be different. The third layer of warp yarns, 2, is interlaced into the weft yarns between the other two. Due to the high fill factors used for each warp yarn, in the woven fabric the three warp yarns lie substantially above each other. In this fabric the float ratio is 5/6. Figures 12 and 13 illustrate a fabric in which the two distinct layers of flattened monofilament warp yarns weave separately into the two sets of weft yarns. One set of flattened monofilament warp yarns weaves into the side A set of wefts (the even numbered ones) and the other set of flattened monofilament warp yarns weaves into the side B set of wefts (the odd numbered ones). Again, although the weave patterns shown are essentially SUBSTITUTE SHEET -li¬ the same for each set of flattened monofilament warp yarns, the pattern for side B need not be the same as that for side A. The float ratio is 5/6. These two layers are then joined together in the weave by the separate binder yarns Y. These separate binder yarns can be incorporated either in the warp yarn direction (as shown in Figure 13) or in the weft yarn direction (not shown). Generally binder yarns are small relative to the warp yarns or weft yarns, often serving only to hold the fabric together during weaving and subsequent processing, until a fiber batt layer is attached by needling thus binding the entire structure together. In some cases the binder yarns are soluble yarns and are removed by washing after needling. In other cases where no batt or other porous layer is used the binder yarns are stronger and withstand use in the press section, to keep the two layers of the fabric from separating. It is possible to use the fabrics of this invention on their own in a press section. As was noted above, cases where the fabric weave pattern is such that the fabric is essentially the same on both faces, whether side A or side B is the paper side of the fabric does not matter. But when an tmsymmetrical weave, such as that in Figure 5 or Figure 9 is used the fabric faces cease to be the same. In most applications it is preferred that side A, the first side which incorporates the long exposed floats of flattened monofilament warp yarns, is taken as the paper side of the fabric. Alternatively, as shown in Figure 14, 15, and 16, the fabrics of this invention may also be used with porous layers attached thereto. If only one layer is used, generally it will be attached to the paper side of the fabric, such as the layer 70 attached to side A of the fabric, or the layer 80 attached to side B of the fabric, in Figures 14 and 15. Two porous layers, as at 70 and 80 in Figure 16 may be attached one to each side of the fabric. Again although this seemingly makes both faces of the fabric the same, it SUBSTITUTE SHEET is still preferred that side A with the first set long exposed floats is the paper side of the fabric. Thus the single batt arrangement of Figure 14 is preferred rather than Figure 15. Typically a porous layer 70, 80 comprises a staple fiber batt, which is generally attached to the fabric by needle punching. If a batt is used, some thought should be given to the direction in which it is laid, since it is known that the batt fibers tend to be oriented substantially in the direction the batt is laid onto the base fabric. For the fabrics of this invention it is preferred that a batt is laid with a high degree of fiber orientation. There are, nevertheless, several options for the direction of orientation, relative to the direction of the long exposed floats in side A of the fabric, regardless of whether side A is or is not the paper side of the fabric. For a fabric with a single batt layer, the orientation can be substantially parallel to, or substantially perpendicular to, the side A exposed floats. For a fabric with two batt layers, one on each side of the fabric, the orientation of each batt independently can be substantially parallel to, or substantially perpendicular to, the side A exposed floats. Thus there are four options: both side A and side B batts oriented in the same direction, and either parallel or perpendicular to the side A exposed floats, or the side A and side B batts oriented substantially perpendicular to each other, and one of them - either side A or side B - parallel to the long exposed floats. In the fabric of this invention a high weft yarn fill, as well as a high flattened monofilament warp yarn fill of at least 45%, is recommended, in SUBSTITUTE SHEET order to minimize the space between the flattened warp yarn support points, such as the distance Z in Figure 3. The purpose of this high weft yarn fill is to reduce the bending of the flattened monofilament warp yarns in a direction at right angles to their plane in the fabric under the influence of the very high pressures exerted on the fabric in the press. Several variables affect the weft yarn fill factor in a given fabric. Some of these are: (a) the degree of openness required in the fabric; (b) the thickness of the flattened monofilament warp yarns; (c) the material used for the flattened monofilament warp yarns: a stiff material with a high elastic modulus deflects less than a soft one; and (d) the degree of softness of the weft yarns: a soft deformable weft yarn provides better support than a yarn which is hard and makes contact with the warp yarns along a thin line. In practice, it appears that the weft yarn spacing, as at Z in Figure 3, should be less than 8 times the flattened monofilament warp yarn thickness, and is preferably less than 5 times. Generally press fabrics are constructed from nylon onofilaments, with a nylon staple fiber batt, although polyester and other materials are sometimes used. It is preferred to use nylon for this invention, but this invention is not so limited. The distinct warp yarn layers in the fabric of this invention are woven from flattened monofilament yarns. In these flattened monofilament warp yarns, the aspect ratio, that is the ratio of width to thickness, should be at least 1.5:1. If the thickness is made too low, the filament becomes too thin and too flexible, and tends to transmit both knuckle markings from the fabric weave and any pattern of cavities in the press rolls to the paper. A suitable lower limit for the thickness appears to be at about 0.1 mm. If the aspect ratio is made too low it becomes difficult to control the weaving process and hence it is desirable that the aspect ratio be at least 1.5:1, and preferably at least 2.0:1. A desirable range for the aspect ratio is from about 4:1 to about 10:1. Currently available weaving equipment appears to be able to handle fibers with an aspect ratio of up to about 100:1. The fiber cross section also need not be simply substantially rectangular. It is also of advantage to use the grooved flattened monofilament warp yarns described by Jackson, WO 91/04374. In the preceding discussion of the figures it is assumed that all of the flattened monofilament waip yarns are the same. This is preferred, as it simplifies weaving, but it is not necessary. Warp yarns which are not flattened monofilaments can be included, but this is not recommended, especially in the paper side of the fabric. The dewatering capabilities of the fabric will likely be impaired, and the risk of paper marking enhanced. Consequently it is preferred that at least the majority, preferably substantially all, and most preferably all of the warp yarns are flattened monofilament yarns. It is also most convenient if the flattened monofilaments in each of the different layers of warp yarns are of substantially the same width and thickness. A fabric according to this invention can be woven either as a closed endless loop, or as a continuous run of fabric which is then seamed in some way to provide the required loop. In a closed loop fabric the flattened monofilament warp yarns He in the cross-machine direction, that is substantially at a right angle to the direction in which the paper web moves. In a continuous run of fabric, the flattened monofilament warp yarns lie in the machine direction of the fabric substantially parallel to the direction of movement of the paper web.

Claims: CLAIMS What is claimed is: 1. A woven dewatering fabric, for the press section of a papermaking machine, having a first side and a second side, one of which constitutes the paper side of the fabric, and the other of which constitutes the press roll side of the fabric, and having long exposed floats of flattened monofilament warp yarns on the first side of the fabric, wherein: (i) the aspect ratio of the flattened monofilament warp yarns is at least 1.5:1; (ii) the fabric weave includes at least two distinct layers of warp yarns each including flattened monofilament warp yams, only one of which provides the exposed first side floats; (iii) the fabric weave further includes at least one layer of weft yarns; and (iv) the fill factor for each of the distinct layers of flattened monofilament warp yarns is at least about 45%. _. A fabric according to claim 1 wherein the first side exposed floats of flattened monofilament warp yarns have a float ratio expressed by the formula x y, wherein (i) "x" represents the number of weft yarns in a weft layer on the first side of the fabric in a single weave pattern repeat which are on the inside of the fabric with respect to a particular flattened monofilament warp yarn, and supporting that warp yarn; and (ii) "y" represents the total number of weft yarns in the weft layer on the first side of the fabric in a single weave pattern repeat; and wherein for a majority of the first side exposed floats of flattened monofilament warp yarns: (iii) x is greater than one; and (iv) x is greater than one-half of y. 3. A fabric according to claim 1 including two distinct layers of flattened monofilament warp yarns. 4. A fabric according to claim 1 including three distinct layers of flattened monofilament warp yarns. 5. A fabric according to claim 1 including one layer of weft yarns. 6. A fabric according to claim 1 including two layers of weft yarns. 7. A fabric according to claim 3 further including one layer of weft yarns. 8. A fabric according to claim 3 further including two layers of weft yarns. 9. A fabric according to claim 4 further including two layers of weft yarns. 10. A fabric according to claim 1 wherein each distinct layer of flattened monofilament warp yarns is interlaced with a single set of weft yarns, which are joined together in the weave by a binder yarn. 11. A fabric according to claim 1 wherein the first side of the fabric, induding the long exposed floats, is the paper side of the fabric, and the second side is the press roll side of the fabric. 12. A fabric according to daim 1 wherein the second side of the fabric is the paper side of the fabric, and the first side, including the long exposed floats, is the press roll side of the fabric. 13. A fabric according to daim 11 further including a porous layer attached to the paper side of the fabric. 14. A fabric according to daim 12 further induding a porous layer attached to the paper side of the fabric. 15. A fabric according to daim 11 further including a porous layer attached to both the paper side and the press roll side of the fabric. 16. A fabric according to daim 12 further including a porous layer attached to both the paper side and the press roll side of the fabric. 17. A fabric according to claim 13 wherein the porous layer is a staple fiber batt. 8 A fabric according to claim 14 wherein the porous layer is a staple fiber batt. 19. A fabric according to claim 15 wherein the porous layers are staple fiber batts. 20. A fabric according to claim 16 wherein the porous layers are staple fiber batts. 21. A fabric according to claim 17 wherein the batt is attached by needle punching, and the batt fibers are oriented substantially in a direction perpendicular to the flattened monofilament warp yarns. 22. A fabric according to daim 17 wherein the batt is attached by needle punching, and the batt fibers are oriented substantially in a direction parallel to the flattened monofilament warp yarns. 23. A fabric according to claim 18 wherein the batt is attached by needle punching, and the batt fibers are oriented substantially in a direction perpendicular to the flattened monofilament warp yarns. 24. A fabric according to claim 18 wherein the batt is attached by needle punching, and the batt fibers are oriented substantially in a direction parallel to the flattened monofilament warp yarns. 25. A fabric according to claim 19 wherein the batts are attached by needle punching and the batt fibers are oriented substantially perpendicular to the flattened monofilament yarns. 26. A fabric according to claim 19 wherein the batts are attached by needle punching and the batt fibers are oriented substantially parallel to the flattened monofilament yarns. 27. A fabric according to claim 19 wherein the batts are attached by needle punching, and the batt fibers in the paper side batt are oriented in a direction substantially perpendicular to the flattened monofilament warp yarns, and the batt fibers in the press roll side are oriented in a direction substantially parallel to the flattened monofilament warp yarns. 28. A fabric according to claim 19 wherein the batts are attached by needle punching, and the batt fibers in the paper side batt are oriented in a direction substantially parallel to the flattened monofilament warp yarns, and the batt fibers in the press roll side are oriented in a direction substantially perpendicular to the flattened monofilament warp yarns. 29. A fabric according to claim 20 wherein the batts are attached by needle punching and the batt fibers are oriented substantially • perpendicular to the flattened monofilament yarns. 30. A fabric according to claim 20 wherein the batts are attached by needle punching and the batt fibers are oriented substantially parallel to the flattened monofilament yarns. 31. A fabric according to daim 20 wherein the batts are attached by needle punching, and the batt fibers in the paper side batt are oriented in a direction substantially perpendicular to the flattened monofilament warp yarns, and the batt fibers in the press roll side are oriented in a direction substantially parallel to the flattened monofilament warp yarns. 32. A fabric according to claim 20 wherein the batts are attached by needle punching, and the batt fibers in the paper side batt are oriented in a direction substantially parallel to the flattened monofilament warp yarns, and the batt fibers in the press roll side are oriented in a direction substantially perpendicular to the flattened monofilament warp yarns. 33. A fabric according to claim 2 wherein the float ratio is the same for all of the exposed floats. 34. A fabric according to claim 2 wherein the float ratio is not the same for all of the exposed floats. 35. A fabric according to claim 2 wherein the float ratio is no more than 9/10. 36. A fabric according to claim 2 wherein the float ratio is from 5/8 to 9/10. 37. A fabric according to claim 2 wherein the float ratio is from 3/4 to 7/8. 38. A fabric according to claim 1 wherein the fill factors for each of the distinct layers of warp yarn are the same. 39. A fabric according to claim 1 wherein the fill factors for each of the distinct layers of warp yarn are not the same. 40. A fabric according to claim 1 wherein the fill factor for at least one of the distinct layers of warp yarns is at least 60%. 41. A fabric according to claim 1 wherein the fill factor for at least one of the distinct layers of warp yarns is at least 80%. 42. A fabric according to claim 1 wherein the fill factor for at least one of the distinct layers of warp yarns is at least 85%. 43. A fabric according to claim 1 wherein all of the flattened monofilament warp yarns have the same aspect ratio. 44. A fabric according to claim 1 wherein all of the flattened monofilament warp yarns do not have the same aspect ratio. 45. A fabric according to claim 1 wherein at least one distinct layer of flattened monofilament warp yarns has an aspect ratio of at least about 2:1. 46. A fabric according to daim 1 wherein at least one distinct layer of flattened monofilament warp yarns has an aspect ratio of from at least about 4:1 to less than about 10:1. 47. A dewatering fabric according to daim 1 woven as a closed endless loop. 48. A dewatering fabric according to claim 47 including a seam. 49. A dewatering fabric according to daim 1 woven as a continuous run and seamed to provide a loop. 50. A fabric according to claim 1 wherein in at least the distinct layer of warp yarns providing the paper side long exposed floats the majority of the warp yarns are flattened monofilament yarns. 51. A fabric according to claim 1 wherein in at least the distinct layer of warp yarns providing the paper side long exposed floats substantially all of the warp yarns are flattened monofilament yarns. 52. A fabric according to claim 1 wherein in at least the distinct layer of warp yarns providing the paper side long exposed floats all of the warp yarns are flattened monofilament yarns. 53. A fabric according to claim 1 wherein in each of the distinct layers of warp yarns the majority of the warp yarns are flattened monofilament yarns. 54. A fabric according to claim 1 wherein in each of the distinct layers of warp yarns substantially all of the warp yarns are flattened monofilament yarns. 55. A fabric according to claim 1 wherein in each of the distinct layers of warp yarns all of the warp yarns are flattened monofilament yarns.

Inventors: JACKSON GRAHAM WILLIAM, JACKSON, GRAHAM, WILLIAM
Applicants: JWI LTD, JWI LTD.
Application year: 1991
Main classification: D21F7
IPC codes: D21F1, D21F7