MXPA98010086A - Weaving materials that exhibit a behavior in the form of elastic, softness and texture similar to the t - Google Patents

Abstract

The present invention relates to a soft weft material that exhibits an elastic behavior along at least one axis, when subjected to an applied elongation and subsequently released. The weft material includes a stretchable network having a plurality of first regions and a plurality of second regions of the same material composition. One stop of the first regions extend in a first direction while the rest extend in a second direction perpendicular to the first direction to interconnect one another. The first regions form a border that completely surrounds the second regions. The second regions include a plurality of rib-shaped elements lifts

Description

TRAMA MATERIALS THAT EXHIBIT A BEHAVIOR IN THE FORM OF ELASTIC. SOFT AND SIMILAR TEXTURE TO THE FABRIC FIELD OF THE INVENTION The present invention relates to weft materials, and more particularly, to such weft materials which exhibit an elastic behavior in response to an applied elongation and subsequently released, along at least one axis. The present invention also relates to weft materials that are soft, similar in texture to the fabric, and simple. The present invention is further related to the weft materials wherein the inherent properties of a given weft material, for example the strength of resistance exerted by the weft material at an applied elongation can be modified. Additionally, resistance forces in stages, lateral contraction, and / or direction of the elastic behavior of conventional weft materials can also be modified and / or provided, as desired in the weft materials of the present invention. invention. The weft materials of the present invention have a wide range of potential uses as durable articles such as disposable articles, but are particularly well suited for use in disposable absorbent articles such as sanitary napkins, bandages, pantiliners, disposable diapers, incontinence briefs and Similar.

BACKGROUND OF THE INVENTION Absorbent articles such as sanitary napkins, pantiliners, disposable diapers, incontinence briefs, and bandages, are designed to absorb and retain fluid and other discharges from the human body, and to prevent staining of the body and clothing. Typically, most absorbent articles are made of materials that will not easily stretch under the forces to which the absorbent article is normally subjected when used. The inability of the materials comprising the absorbent article to stretch when subjected to normal forces of use, causes the absorbent article to have certain disadvantages. A disadvantage is the lack of comfort for the user. The user should ideally be able to notice a difference between an absorbent article that stretches to conform the user's body with the movements of the user and an item that fails to stretch. For example, a conventional sanitary napkin of the prior art does not move with the user's undergarments, thus causing the sanitary napkin to bypass, which can cause a degree of discomfort to the wearer. By allowing all or part of the sanitary napkin to stretch under conditions and forces of normal use, the sanitary napkin will be allowed to better conform to the wearer's undergarment and remain in place even when the wearer moves. Various attempts have been made to make one or more components of the absorbent articles capable of stretching in response to relatively low utilization forces.

Typical solutions of the prior art adhere to the addition of traditional elastics such as natural or synthetic rubber. For example, traditional elastics have been secured to portions of the topsheet and / or the backsheet of the absorbent articles, such as the waist portion of a disposable diaper, to provide a better fit and total comfort for the wearer. However, traditional elastics are expensive and require a certain degree of handling and handling during assembly. Although traditional elastics provide a degree of stretch to the absorbent article, the materials to which the traditional elastic is secured are typically not normally considered elastic or stretchable. Therefore, the traditional elastics added must be pre-stretched before being secured to the material or the material must be subjected to mechanical processing, for example, rolled with ring, to permanently lengthen the material to the limit beyond its initial length not stressed and allow the added traditional elastic to be effective. Otherwise, the traditional elastic added is limited by the material and is made inoperable. An example of an absorbent article having a weft material that has been subjected to further processing to allow the weft material to more easily extend with the added traditional elastic member is disclosed in U.S. Patent No. 5,151,092, issued to Buel et al. on September 29, 1992, and hereby incorporated herein by reference. The Buell patent discloses an operation that pretenses a backsheet so that the backsheet will be, at the time of mechanical stretching, permanently elongated and will not fully return to its original, undistorted configuration. Buel teaches that a traditional elastic member must be added to the pre-tensioned backsheet material for the invention to be operable. Buel also reports that a pre-stressed back sheet improves the extension and shrinkage of the traditional elastic member added. Accordingly, it is an object of the present invention to provide weft materials, in particular plastic films, which exhibit an "elastic" behavior in the direction of applied elongation without the use of additional traditional elastics. As used herein, the term "in elastic form" describes the behavior of the weft materials which when subjected to an applied elongation, extend the weft materials in the direction of the applied elongation, and when the elongate is released. Applied elongation the weft materials return, to a substantial degree, to their unstressed condition. Although these weft materials exhibiting an elastic-like behavior have a broad spectrum of utility, for example, durable-looking articles, disposable-looking articles, protective or covering materials such as tapestries, wrap-around materials to form complexes and the like, these are well suited for use as a top sheet, a back sheet and / or an absorbent core in an absorbent article. It is another object of the present invention to provide plastic films exhibiting a texture, softness in the form of a fabric.

BRIEF DESCRIPTION OF THE INVENTION The present invention pertains, in a preferred embodiment, to a weft material, preferably to a plastic film, which exhibits a performance in the form of an elastic in response to an applied elongation and subsequently released without the addition of traditional elastic materials such as rubber. synthetic or natural. In addition, the plastic films of the present invention are extremely soft, of texture similar to the fabric and sensillos. The films of this invention provide a barrier against the liquid, and still have the appearance and feel of woven and non-woven fabrics, making them especially suitable for use as a backsheet on a disposable absorbent article, such as a disposable sanitary napkin or towel. Alternatively, the film can be selectively perforated to meet the demands of breathable films. Another behavior in the form of elastic that can be exhibited is an elongation and recovery with a definite and sudden increase in the elongation of the strength of resistance, where this definitive and sudden increase in the strength of resistance restricts the additional elongation against the forces of relatively small elongation. The definitive and sudden increase in the elongation of the resistance force is referred to as a "force wall". As used herein, the term "strength wall" refers to the behavior of the resistance force of a weft material during elongation, where at some point in the elongation, other than the unstressed or starting point, the strength that resists the applied elongation suddenly increases. After reaching the force wall, the additional elongation of the weft material is only achieved through an increase in the elongation force to overcome the superior strength of the weft material. The weft material of the present invention includes a stretchable network comprising a plurality of first regions and a plurality of second regions, which are composed of the same material composition. A part of the first regions extend in a first direction while the rest of the first regions extend in a second direction perpendicular to the first direction. The first regions that extend in the perpendicular directions intersect with each other. The first regions form a border that completely surrounds the second regions. The first regions are oriented relative to an elongation axis, such that they will undergo a deformation substantially at the molecular and geometric level in response to an axial elongation applied in a direction substantially parallel to the elongation axis before a portion The substantial region of the second region undergoes any deformation of substantial molecular level. The second regions initially suffer a substantially geometric deformation in response to an applied elongation.

In a particularly preferred embodiment, the second region is composed of a plurality of raised rib-shaped elements. As used herein, the term "rib-shaped element" refers to an enhancement, recess, or combination thereof having a major axis and a minor axis. The major axes of the rib-shaped elements are preferably oriented substantially perpendicular to the axis of the applied elongation. The major axis and the minor axis of the rib-shaped elements can each be linear, curvilinear or a combination of linear and curvilinear. The rib-shaped elements allow the second region to undergo a "substantially geometric deformation", which results in significantly lower resistance forces to an applied elongation than that exhibited by the "deformation at the molecular level" and "geometric deformation" of the first region. As used in this, the term "deformation at the molecular level" refers to the deformation that occurs at a molecular level and that is not discernible to the naked eye. That is, although one may be able to discern the effect of deformation at the molecular level, for example, the elongation of the material of the weft, one is not able to discern the deformation that allows or causes this to happen. This is in contrast to the term "geometric deformation". As used herein, the term "geometric deformation" refers to the deformations of the weft material that are generally discernible to the naked eye when the material of the weft or articles that modalize the weft material are subjected to a elongation applied. Types of geometric deformation include, but are not limited to, bending, unfolding and rotation. In another preferred embodiment, the weft material of the present invention exhibits at least two significantly different stages of resistance force to an elongation applied along at least one axis, when subjected to an elongation applied in one direction substantially parallel to the axis. The material of the frame includes a tensable network having at least two different regions. One of the regions is configured in such a way that it will exhibit resistance forces in response to an axial elongation applied in a direction substantially parallel to the axis before a substantial part of the other region develops any applied elongation resistance force. At least one of the regions has a surface path length that is greater than that of the other region as measured parallel to the axis, while the material is in an unstressed condition. The region exhibiting the largest surface path length includes one or more rib-shaped elements, which extend beyond the plane of the other region. The weft materials exhibiting first applied elongation resistance forces until the elongation of the weft material is sufficient to cause a substantial part of the region having the largest surface path length, between the applied elongation axis , (ie, it becomes substantially coplanar with the applied elongation axis), after which the material of the screen exhibits second strengths of additional elongation resistance. The force of total resistance to elongation is greater than the first strength of resistance to elongation provided by the first region. Preferably, the first region has a first surface path length, L1, as measured substantially parallel to the axis of elongation while the material of the screen is in a non-stressed condition. The second region has a second surface path length, L2, as measured substantially parallel to the axis of the elongation while the frame is in a non-stressed condition. The first surface path length, L1, is smaller than the second surface path length, L2. The first region preferably has an elastic modulus, E1, and a cross-sectional area, A1. The first region itself produces a strength of resistance, P1, due to the deformation at the molecular level in response to an applied axial elongation, D. The second region preferably has an elastic modulus, E2, and a cross-sectional area, A2 . The second region produces a resistance force, P2, due to the geometric deformation in response to the applied axial elongation, D. The resistance force, P1, is significantly greater than the resistance force, P2, while (L1 + D) is less than L2. Preferably, when (L1 + D) is less than L2, the first region provides an initial resistance force, P1, in response to the applied axial elongation, D, substantially satisfying the equation P1 = (A1 x E1 x D) / L1. When (L1 + D) is greater than L2, the first and second regions provide a combined total resistance force, PT, to the applied axial elongation, D, satisfying the equation: PT = (A1xE1xD) + (A2xE2x L1 + D-L2) L1 L2 In another preferred embodiment, the weft material exhibits a Poisson lateral contraction effect of less than about 0.4 to 20% elongation as measured perpendicular to the elongation axis. As used herein, the term "Poisson's lateral contraction effect" describes the lateral contraction behavior of a material that is being subjected to an applied elongation. Preferably, the weft material exhibits a Poisson lateral contraction effect less than about 0.4 to 60% elongation as measured perpendicular to the elongation axis. Preferably, the surface path length of the second region is at least about 15% greater than that of the first region as measured parallel to the axis of elongation, while the material of the screen is in an unstressed condition. More preferably, the surface path length of the second region is at least 30% approximately greater than that of the first region as measured parallel to the axis of the elongation while the frame is in an unstressed condition.

BRIEF DESCRIPTION OF THE DRAWINGS Although the specification concludes with the claims that particularly state and distinctly claim the subject matter that is considered to form the present invention, it is believed that the invention will be better understood from the following description, which is taken in conjunction with the accompanying drawings. , where similar designations are used to designate substantially identical elements, and in which: Figure 1 is a simplified plan view illustration of a prior art sanitary napkin, with portions cut away to more clearly show the construction of the towel sanitary Figure 2 is a simplified plan view illustration of a disposable diaper of the prior art, with portions cut away to more clearly show the structure of the construction of the disposable diaper; Figure 3 is a plan view illustration of a preferred embodiment of a material of the polymeric web of the present invention; Figure 4 is an exemplary graph of the behavior of the strength of resistance versus the elongation percentage of a weft material of the present invention, as shown in Figure 3, and a base material of the weft, i.e. which does not include first and second regions, of similar composition of material; Figure 5 is a plan view illustration of a polymeric weft material of Figure 3, in a stressed condition corresponding to stage I, on the force-elongation curve illustrated in Figure 4; Figure 6 is an exemplary graph of the elastic hysteresis behavior of the weft material of the present invention, which is graphically represented by the curve 720 in Figure 4, when the weft material is subjected to a hysteresis test at 60 ° C. hundred; and Figure 7 is a simplified perspective view of a preferred apparatus used to form the weft materials of the present invention, with a portion of the apparatus being inclined to expose the teeth.

DETAILED DESCRIPTION OF THE INVENTION As used herein, the term "absorbent article" refers to devices that absorb and contain exudates from the body, and more specifically, refers to devices that are placed against or in proximity to, the body of the user, to absorb and contain the different exudates discharged from the body. The term "absorbent article" is intended to include diapers, catamenial pads, sanitary napkins, pantiliners, incontinence trunks, bandages and the like. The term "disposable" is used herein to describe absorbent articles that are not intended to be washed or otherwise restored or reused as an absorbent article (ie, they are intended to be disposed of after a single use, and preferably, to recycled, treated, or disposed of in another way that is compatible with the environment). Because of their single-use nature, low-cost construction materials and methods are highly desirable in disposable absorbent articles. Figure 1 is a plan view of a sanitary napkin 20 of the prior art, with parts of the structure which are cut away to show more clearly the construction of the sanitary napkin 20 and with the portion of the sanitary napkin 20 which is away from the user, that is, the external surface, oriented towards the observer. As used herein, the term "sanitary napkin" refers to an absorbent article that is worn by women, adjacent to the pudendal region, generally external to the urinary genital region, and which is intended to absorb and contain fluids. menstrual and other vaginal discharges from the user's body (for example, blood, menstruation and urine). As shown in Figure 1, the sanitary napkin 20 comprises a liquid-permeable upper sheet 24, a liquid-impermeable back sheet 26 bonded to the upper sheet 24, and an absorbent core 28 positioned between the upper sheet 24 and the back sheet 26. Although the top sheet, the backsheet and the absorbent core can be assembled in a variety of well-known configurations (including the so-called "tube" products or side flap products), the preferred configurations of sanitary napkins are generally described in U.S. Patent No. 4,950,264, issued to Osborn on August 21, 1990; Patent of the United States No. 4,425,130 issued to DesMarais on January 10, 1994; U.S. Patent No. 4,321,924, issued to Ahr on March 30, 1982; and U.S. Patent No. 4,589,876, issued to Van Tilburg on May 20, 1986. Each of these patents is hereby incorporated by reference. Figure 2 is a plan view of the prior art diaper 30 in its non-contracted, flat state (ie, with the contraction induced by the elastic pulled outward), with parts of the structure separated to more clearly show the construction of the diaper 30, and with the portion of the diaper 30 that contacts the wearer, the outer surface, facing the observer. As used herein, the term "diaper" refers to an absorbent article generally worn by infants and incontinent persons, which is worn around the wearer's lower torso. As shown in Figure 2, the diaper 30 comprises a liquid-permeable upper sheet 34, a liquid-impermeable backing sheet 36 attached to the upper sheet 34, an absorbent core 38 positioned between the upper sheet 34 and the backing sheet 36, elasticized side panels 40, elasticized leg cuffs 42, and an elastic waist feature 44, and a generally multiple fastening system designated 46. Although the diaper 30 can be assembled in a variety of well-known configurations, they are described generally the preferred diaper configurations in U.S. Patent No. 3,860,003, issued to Kenneth B. Buell on January 14, 1975; and in U.S. Patent No. 5,151,092 issued to Kenneth B. Buell et al. On September 29, 1992. Each of these patents is hereby incorporated by reference. Although the present invention will be described in the context of providing a "weft material", which exhibits an elastic behavior at an applied and subsequently released elongation, which is particularly well suited for use as a backsheet, a sheet In the case of a top and / or an absorbent core or a part thereof, in a disposable absorbent article such as a disposable diaper, sanitary napkin or bandage, the present invention is thus not limited to this application. It can be used in almost any application where a relatively low cost elastic weft material is desired, for example durable durable items, such as exercise clothing, disposable articles, elastic bandages, upholstery or other wear material. Wrap used to cover items with complex shape, etc. As used herein, the term "weft material" refers to a material in the form of a sheet or sheet, eg, a topsheet, a backsheet or an absorbent core, in a disposable absorbent article, or a material compound or laminate of two sheet-like materials and the like. The present invention can be practiced in major advantages in many situations where it is desirable to produce a weft material exhibiting an elastic behavior at an applied elongation and subsequent release, along at least one axis. The detailed description of a preferred structure and its use as a backsheet in a sanitary napkin or a disposable diaper will allow a person skilled in the art to easily adapt the present invention to other applications. Referring now to Figure 3, there is shown a preferred embodiment of a polymeric screen material 52 of the present invention. The weft material 52 is particularly well suited for use as a backsheet in an absorbent article, such as the sanitary napkin 20 of Figure 1 or the disposable diaper 30 of Figure 2. The weft material 52 has two centerlines, a longitudinal center line, which is also referred to hereinafter as an axis, line or direction "L" and a transverse or lateral center line, which is also referred to hereinafter as an axis, line or direction "T". The transverse center line "T" is generally perpendicular to the longitudinal center line "L". The raster material includes a "tensable network" of different regions. As used herein, the term "stretchable network" refers to a group of interconnected and interrelated regions that are capable of extending to some useful degree in a predetermined direction, providing the weft material with an elastic behavior, in response to an applied and subsequently released elongation. The tensable network includes a plurality of first regions 60 and a plurality of second regions 66. Frame material 52 includes transition regions 65 that are located at the interconnection between the first regions 60 and the second regions 66. The transition regions 65 they will exhibit complex combinations of the behavior of both the first region and the second region. It is recognized that each embodiment of the present invention will have transitional regions; however, the preferred embodiments of the present invention are greatly defined by the behavior of the weft material in different regions (e.g., the first regions 60 and the second regions 66). Accordingly, the following description of the present invention will refer to the behavior of the weft material in the first regions 60 and in the second regions 66, only, since it is not significantly dependent on the complex behavior of the weft material in the transition regions. 65. The weft material 52 has a first surface (facing the observer in Figure 3), and a second opposing surface (not shown). In the preferred embodiment shown in Figure 3, the tensable network includes a plurality of first regions 60, and a plurality of second regions 66. A portion of the first regions 60, indicated generally as 61, are substantially linear and extend in a first direction. The rest of the first regions 60, generally indicated as 62, are substantially linear and extend in a second direction that is substantially perpendicular to the first direction. Although it is preferred that the first direction be perpendicular to the second direction, other angular relationships between the first direction and the second direction may be suitable while the first regions 61 and 61 interconnect to each other. Preferably, the angles between the first and second directions vary from about 45 ° to about 135 °, with 90 ° being most preferred. The interconnection of the first regions 61 and 62 forms a boundary, indicated by the phantom line 63 in Figure 3, which completely encloses the second regions 66. Preferably, the width 68 of the first regions 60 is from about 0.01 inches to about 0.5 inches, and more preferably from about 0.03 inches to about 0.25 inches. However, other width dimensions may be suitable for the first regions 60. Because the first regions 61 and 62 are perpendicular to one another and equally spaced apart, the second regions have a square shape. However, other shapes for the second region 66 are suitable and can be achieved by changing the spacing between the first regions and / or aligning the first regions 61 and 62 with respect to one another. The second regions 66 have a first axis 70 and a second axis 71. The first axis 70 is substantially parallel to the longitudinal axis of the weft material 52, while the second axis 71 is substantially parallel to the transverse axis of the weft material 52 The first regions 60 have an elastic modulus E1 and a cross-sectional area A1. The second regions 66 have an elastic modulus E2 and a cross-sectional area A2. In the illustrated embodiment, a part of the weft material 52 has been "formed", such that the weft material 52 exhibits a strength of resistance along an axis, which in the case of the embodiment illustrated, is substantially parallel to the transverse axis of the weft, when subjected to an axial elongation applied in a direction substantially parallel to the transverse axis. As used herein, the term "formed" refers to the creation of a desired structure or geometry on the weft material, which will substantially retain the desired structure or geometry when not subjected to any externally applied elongation or force. A weft material of the present invention is comprised of a plurality of first regions and a plurality of second regions, wherein the first regions are visually distinct from the second regions. As used herein, the term "visually distinct" refers to the characteristics of the weft material that are readily discernible to the naked eye, when the weft material or the objects incorporating this weft material are subjected to normal use. As used herein, the term "surface path length" refers to a measurement along the topographic surface of the region in question, in a direction parallel to an axis. The method for determining the surface path length of the respective regions can be found in the Test Methods section stipulated in the following parts of the present specification. Methods for forming web materials of the present invention include, but are not limited to, enhancement by coupling plates or rolls, thermoforming, high pressure hydraulic forming, or casting. Although the entire part of the frame 52 has been subjected to a forming operation, the present invention can also be practiced by forming only a part thereof, for example, as will be described in more detail below. In the preferred embodiment shown in Figure 3, the first regions 60 are substantially planar. That is, the material inside the first regions 60 is substantially in the same condition before and after the forming step suffered by the frame 52. The second regions 66 include a plurality of raised rib-shaped elements 74. The elements in shape of rib 74 can be enhanced, sunk, or a combination thereof. The rib-shaped elements 74 have a first or major axis 76, which is substantially parallel to the longitudinal axis of the frame 52, and a second or minor axis 77 that is substantially parallel to the transverse axis of the frame 52. The elements in shape Rib 74 in the second region 66 may be separated from each other by unformed areas, essentially not engraved or sinking, or simply formed as separation areas. Preferably, the rib-shaped elements 74 are adjacent to each other and are separated by an unformed area less than 0.10 inches as measured perpendicular to the major axis 76 of the rib-shaped elements 74, and more preferably, the elements in rib shape 74 are contiguous, having no un-formed areas between them. The first regions 60 and the second regions 66 each have a "projected trajectory length". As used herein, the term "projected path length" refers to the length of a shadow of a region that would be launched by a parallel light. The projected trajectory length of the first region 60, and the projected trajectory length of the second region 66, are equal to one another. The first region 60 has a surface path length, L1, smaller than the surface path length, L2, of the second region 66, measured topographically in a parallel direction while the raster material is in a non-stressed condition. Preferably, the surface length of the second region 66 is at least about 15 percent greater than that of the first region 60, more preferably at least about 30 percent greater than that of the first region, and most preferably at least approximately 70 percent greater than that of the first region. In general terms, the longer the surface length of the second region, the greater the elongation of the weft material before finding the wall strength. The weft material exhibits a modified "Poisson's lateral contraction effect" substantially less than that of an otherwise identical base web of a composition of similar material, ie, a web having no first and second regions. The method for determining the Poisson's lateral contraction effect of a material can be found in the Test Methods section stipulated in the following parts of the present specification. Preferably, the Poisson's lateral contraction effect of the frames of the present invention is less than about 0.4 when the web is subjected to an elongation of about 20 percent. Preferably, the frames exhibit a Poisson lateral contraction effect less than about 0.4 when the raster is subjected to an elongation of about 40, 50, or even 60 percent. More preferably, the Poisson's lateral contraction effect is less than about 0.3, when the frame is at an elongation of 20, 40, 50 or 60 percent. The Poisson's lateral contraction effect of the frames of the present invention is determined by the amount of the web material that is occupied by the first and second regions, respectively. As the area of the weft material occupied by the first region increases, the Poisson's lateral contraction effect also increases. Conversely, as the area of the web material occupied by the second region increases, the Poisson's lateral contraction effect decreases. Preferably, the area percentage of the weft material occupied by the first region is from about 2 percent to about 90 percent, and more preferably from about 5 percent to about 50 percent. Prior art weft materials having at least one layer of an elastomeric material will generally have a lateral contraction effect of Large Poisson, that is, "will form a neck" as they elongate in response to an applied force. The weft materials of the present invention can be designed to moderate, if not substantially eliminate the Poisson lateral contraction effect. For the weft material 52, the direction of the applied axial elongation, D, indicated by the arrows 80 in Figure 3, is substantially perpendicular to the first axis 76 of the rib-shaped elements 74. This is because the elements in rib shape 74 are able to unfold or deform geometrically in a direction substantially perpendicular to their first axis 76, to allow extension in the weft 52. In Figure 4, an exemplary graph of a strength-elongation force curve is shown. 720 of a weft material generally similar to the weft material 52 shown in Figure 3, together with a curve 710 of a base weft material of similar composition. The method for generating the resistance-elongation strength curves can be found in the Test Methods section stipulated in the following parts of the specification. Referring now to the force-elongation curve 720 of the formed web of the present invention, there is a lower substantially linear initial force against the elongation step I designated 720a, a transition zone designated 720b indicating the encounter of the wall force, and a substantially linear stage II designated 720c, exhibiting a substantially higher force versus elongation behavior. As seen in Figure 4, the formed web exhibits a different elongation behavior in the two steps when it is subjected to an elongation applied in a direction parallel to the transverse axis of the web. The strength of resistance exerted by the weft formed at the applied elongation is significantly lower in the region of stage I (720a) against the region of stage II (720c) of curve 720. In addition, the resistance force exerted by the The pattern formed at the applied elongation, as illustrated in step I (720a) of curve 720, is significantly smaller than the resistance force exerted by the base web, as illustrated in curve 710 within the limits of elongation of the step I. When the formed web is subjected to another applied elongation, and enters into step II (720c), the strength of resistance exerted by the formed web increases, and approaches the strength of resistance exerted by the basic web. The strength of resistance to the elongation applied for the elongation of stage I (720a) of the formed web is provided by the deformation at the molecular level of the first region of the formed web, and the geometric deformation of the second web region. the formed plot. This is in contrast to the strength of resistance to an applied elongation that is provided by the base web, illustrated in the curve 720 of Figure 4, which results from the deformation at the molecular level of the entire web. The weft materials of the present invention can be designed to produce virtually any strength of strength in stage I that is less than that of the base weft material, by adjusting the percentage of the weft surface that is comprised of the first weights. and second regions, respectively. The force-elongation behavior of stage I can be controlled by adjusting the width, the cross-sectional area, and the spacing of the first region, and the composition of the base frame. Referring now to Figure 5, as the frame 52 is subjected to an applied axial elongation, D, indicated by the arrows 80 in Figure 5, the first regions 60, which have the shortest path length, L1 , provides most of the initial resistance force, P1, as a result of deformation at the molecular level, at the applied elongation, corresponding to stage I. While in stage I, the rib-shaped elements 74 of the second regions 66 are undergoing geometric deformation, or unfolding, and offer a minimum resistance to the applied elongation. Furthermore, the shape of the second regions 66 changes as a result of the movement of the lattice structure formed by the interconnection of the first regions 61 and 62. Accordingly, as the lattice 52 is subjected to the applied elongation, the first regions 61 and 62 undergo geometric deformation or unfolding, thereby changing the shape of the second regions 66. The second regions are extended or elongated in a direction parallel to the direction of the applied elongation, and crush or shrink in a direction perpendicular to the direction of the applied elongation. . In the transition zone (720b) between stages I and II, the rib-shaped elements 74 are becoming aligned with (i.e., coplanar with) the applied elongation. That is, the second region 66 is exhibiting a change from geometric deformation to deformation at the molecular level. This is the principle of the wall of force. In step II, the rib-shaped elements 74 of the second region 66 are substantially aligned with (ie, coplanar with), the axis of the applied elongation (i.e., the second region has reached its limit of geometric deformation), and they begin to resist another elongation by means of deformation at the molecular level. The second region 66 now contributes, as a result of the deformation at the molecular level, with a second resistance force, P2, to another applied elongation. In the sanding stage first regions 61 and 62 have also reached their limit of geometric deformation and resist another elongation mainly through deformation at the molecular level. The resistance to elongation forces illustrated in stage II by both of the deformation at the molecular level of the first regions 60 and the deformation at the molecular level of the second regions 66, provide a total resistance force, PT, which is greater than the force of resistance illustrated in stage I, which is provided by the deformation at the molecular and geometric level of the first regions 60 and the geometric deformation of the second regions 66. In accordance with the foregoing, the inclination of the force curve elongation in stage II, is significantly greater than the inclination of the force-elongation curve in stage I. The resistance force P1 is substantially greater than the resistance force P2 when (L1 + D) is less than L2. Although (L1 + D) is smaller than L2, the first region 64 provides an initial resistance force, P1, which generally satisfies the equation: P1 = (A1xE1xD) L1 When (L1 + D) is greater than L2, the first and second regions provide a combined total resistance force, PT, to the applied elongation, D, which generally satisfies the equation: PT (A1xE1xD) + (A2xE2x L1 + D-L2 L1 L2 The maximum elongation that occurs while in stage I is considered to be the "stretch available" of the formed web material. The available stretch corresponds to the distance over which the second region undergoes geometric deformation. The available stretch can be determined effectively by inspection of the force-elongation curve 720, as shown in Figure 4. The approximate point at which there is an inflection in the transition zone between stage I and stage II, is the percentage of elongation of the "stretch available" point. The range of available stretch can vary from approximately 10 percent to 100 percent; this range of elongation is often found to be of interest in the disposable absorbent articles, and can largely be controlled by the degree to which the length of the surface trajectory L2 in the second region exceeds the length of the surface trajectory L1 in the first region, and by the composition of the base film. The term "available stretch" is not intended to imply a limit to the elongation to which the weft of the present invention can be subjected, since there are applications where an elongation beyond the available stretch is desired. Curves 730 and 735 of Figure 6 show the elastic hysteresis behavior exhibited by the weft material of the present invention. Curve 730 represents the response to an applied and released elongation during the first cycle, and curve 735 represents the response to an applied and released elongation during the second cycle. The force relaxation during the first cycle 731, and the establishment or deformation percentage 732, is illustrated in Figure 6. Note that a significant recoverable elongation, or useful elasticity, is exhibited at relatively low forces over multiple cycles, ie, this means that the weft material can expand and contract easily to a considerable degree. The method to generate the elastic hysteresis behavior can be found in the Test Methods section in the next part of the specification. When the weft material is subjected to an applied elongation, the weft material exhibits an elastic-like behavior as it extends in the direction of the applied elongation, and returns to its substantially unstressed condition, once the stiffening is removed. applied elongation, unless the raster material extends beyond the point of performance. The weft material is capable of undergoing multiple cycles of applied elongation without losing its ability to recover in a substantial manner. In accordance with the foregoing, the weft material may be returned to its substantially unstressed condition, once the elongation or applied force is removed. Although the weft material can be extended in an easy and reversible manner in the direction of the applied axial elongation, in a direction substantially perpendicular to the first axis 76 of the rib-shaped elements 74, the weft material does not spread as easily in a direction substantially parallel to the first axis 76 of the rib-shaped elements 74. The formation of the rib-shaped elements allows the rib-shaped elements to deform geometrically in a direction substantially perpendicular to the first or major axis 76 of the ribs. Rib-shaped elements, while deformation is required substantially at the molecular level to extend in a direction substantially parallel to the first axis of the rib-shaped elements. The amount of applied force required to extend the frame, it depends on the composition and cross-sectional area of the weft material, and the width and spacing of the first regions, requiring the first narrower and more widely spaced regions of lower applied extension forces to achieve the desired elongation for a composition and given cross-sectional area. The depth and frequency of the rib-shaped elements 74 can also be varied to control the available stretch of a weft of the present invention. The available stretch or elongation is increased if for a given number of rib-shaped elements, the height or the degree of deformation and departure on the rib-shaped elements is increased. In a similar manner, the stretching or elongation available is increased if, for a given height or degree of deformation, the frequency of the rib-shaped elements is increased. There are several functional properties that can be controlled through the application of the present invention. There is the strength of resistance exerted by the weft material against the applied elongation, and the available stretch of the weft material before it finds the strength wall. The strength of resistance that is exerted by the weft material against an applied elongation is a function of the material (eg, composition, molecular structure and orientation, etc.) and cross-sectional area and the percentage of the projected surface area of the material plot that is occupied by the first region. The largest extent of the percentage of the weft material by the first region, the strength of resistance greater than the weft material will exert against an elongation applied by a material composition and given cross-sectional area.

The covered percentage of the weft material by the first region is determined in part, but entirely by the widths of the first regions and the spacing between the first adjacent regions. The available stretch of the weft material is determined by the surface length of the second region. The surface length of the second region was determined at least in part by the spacing of the rib-shaped elements, the frequency of the rib-shaped element, and the depth of formation of the rib-shaped elements as measured perpendicularly. to the plot material plane. In general, the largest of the surface path length of the second region, the largest stretch available from the raster material. In addition to the aforementioned elastic-like properties, a plastic film of the present invention is also characterized as being soft, textured and fabric-like, and simple in appearance. The soft, cloth-like, simple plastic film is also a barrier against the liquid, making it especially useful as a backsheet in a disposable absorbent article, such as a disposable diaper. Although all the frame material includes a tensable network of first and second regions, the present invention can also be practiced by providing specific parts of the frame with a tensable network comprised of first and second regions. It would be obvious to a person skilled in the art that all or part of a backsheet in a disposable absorbent article may include a network or tensile networks comprised of first and second regions. Although the weft material having a stretchable web of the present invention has been described as a backsheet or a part thereof in an absorbent article, in some embodiments it may be necessary to provide the topsheet and the absorbent core with a tensable network.

DEVELOPMENT METHOD Referring now to Figure 7, an apparatus 400 used to form the weft 52 shown in Figure 3 is shown. The apparatus 400 includes the interengage plates 401, 402. The plates 401, 402 include a plurality of teeth intergraded 403, 404, respectively. The plates 401, 402 are joined under pressure to form the weft of the present invention. The plate 402 includes toothed regions 407 and grooved regions 408. Within the serrated regions 407 of the plate 402, there are a plurality of teeth 404. The plate 401 includes the teeth 403 which mesh with the teeth 404 of the plate 402.

When the film is formed between the plates 401, 402, the parts of the film that are placed inside the grooved regions 408 of the plate 402, and the teeth 403 on the plate 401, remain without deformations. These regions correspond to the first regions 60 of the weft 52 shown in Figure 3. The parts of the film placed between the toothed regions 407 of the plate 402 (which comprises the teeth 404), and the teeth 403 of the plate 401, is formed in an incremental and plastic manner, creating rib-shaped elements 74 in the second regions 66 of the weft material 52. The method for forming can be performed in a static mode, wherein a part discrete of a base film is deformed at the same time. Alternatively, the method for forming can be achieved by using a dynamic, continuous press to intermittently contact the moving web and form the base material in a weft material formed of the present invention. These and other suitable training methods for forming the weft material of the present invention are more fully described in U.S. Patent No. 5,518,801 issued to Chapell et al. On May 21, 1996, and is hereby Incoporated here by reference. The weft materials of the present invention can be composed of polyolefins such as polyethylenes, including linear low density polyethylene.

(LLDPE), low density polyethylene (LDPE), ultra low density polyethylene (ULDPE), high density polyethylene (HDPE), or polypropylene, and / or mixtures thereof with the above and other materials. Examples of other suitable polymeric materials that may also be used include, but are not limited to, polyester, polyurethanes, compost-forming or biodegradable polymers, and heat-shrinkable polymers, thermoplastic elastomers, metallocene-catalyzed based polymers (e.g., INSITE available from Dow Chemical Company and Exxact available from Exxon), and breathable polymers. The weft material may also be composed of synthetic woven material, synthetic mesh, non-woven material, apertured film, macroscopically expanded three-dimensional formed films, absorbent or fibrous absorbent materials, foams, filler composition, or laminates and / or combinations thereof. same. The non-woven materials can be made by, but not limited to, any of the following methods: bonded spinning, bonded spinning, melt-blown extrusion, carding and / or bonding by continuous air or calendering, with a bonded material bonded with fibers loosely linked that is the preferred modality. Although the weft material has been described as a single base layer of a substantially planar polymeric film, the present invention can be practiced equally well with other materials. Although the fluid impervious polymeric film exhibiting an elastic behavior in the direction of applied elongation may be suitable for use as a backing sheet in a disposable diaper or sanitary napkin, such a weft material would not work well as a sheet. superior in an absorbent article. Examples of other base materials from which the weft of the present invention can be made and which will effectively function as a fluid pervious top sheet in an absorbent article, include films with two-dimensional openings, and films formed with openings, macroscopically expanded , three-dimensional. Examples of films formed with openings, macroscopically expanded, three-dimensional, are described in U.S. Patent Number 3,929,135 issued to Thompson on December 30, 1975; U.S. Patent Number 4,324,246 issued to Mullane et al. on April 13, 1982; U.S. Patent Number 4,342,314 issued to Radel et al. on August 3, 1982; U.S. Patent Number 4,463,045 issued to Ahr et al. on July 31, 1984; and in the United States Patent Number ,006,394 issued to Baird on April 9, 1991. Each of these patents is incorporated herein by reference. The weft materials of the present invention may include laminates of the aforementioned materials. The laminates can be combined by any of a number of linking methods known to those skilled in the art. These link methods include, but are not limited to, thermal link; adhesive bonding (using any of a number of adhesives, including, but not limited to, spray adhesives, hot melt adhesives, latex-based adhesives, and the like); sonic link; and extrusion lamination, whereby, a polymer film is emptied directly onto a substrate, and while still in a partially molten state, it is bonded to one side of the substrate, or by depositing a non-meltblown spinning it is directly bonded to a substrate.

Test Methods Length of the Surface Trajectory The measurements of the length of the trajectory of the material regions formed, will be determined by selecting and preparing representative samples of each different region, and analyzing these samples by means of analysis methods. of microscopic image. The samples will be selected to be representative of the surface geometry of each region. In general terms, transitional regions should be avoided, since they would normally contain characteristics of both the first and the second regions. The sample to be measured is cut and separated from the region of interest. The "measured edge" will be cut parallel to a specified axis of elongation. A stretch of unstressed sample of 1.27 centimeters, will be "marked in the caliber" perpendicular to the "measuring edge": while it is attached to the woven material, and then cut precisely and removed from the woven material. Then the measurement samples are mounted on the long edge of a microscope slide. The "measured edge" will extend slightly (approximately 1 millimeter) outwards from the edge of the slide. A thin layer of pressure sensitive adhesive is applied to the glass face edge to provide a suitable sample support element. For the highly formed sample regions, it has been found desirable to gently extend the sample in its axial direction (without imposing significant force) to simultaneously make contact and join the sample to the edge of the slide. This allows a better identification of the shore during the analysis of the image, and avoids possible "wrinkled" shore areas that require an analysis of additional interpretation. The images of each sample will be seen as "measured shore" views taken with the "edge on top" of the support slide, using suitable microscopic measuring elements of sufficient quality and application. The data presented here was obtained using the following equipment: Keyence VH-6100 video unit (20x lens), with video image prints made with a Sony Video printer Mavigraph unit. Video impressions were scanned by images with a Hewlett Packard ScanJet IIP scanner. The analysis of the image was on a Macintosh HCi computer, using the NIH MAC Image software version 1.45.

Using this equipment, initially a calibration image of a grid scale length of 1.27 centimeters is taken, with increment marks of 0.127 millimeters, to be used for establishing the calibration of the computer image analysis program. All the samples that are to be measured are taken video images, and they are printed on video image. Next, all video impressions are scanned into the image at 100 dpi (gray scale of level 256) in a suitable Mac image file format. Finally, each image file (including the calibration file) is analyzed using the Mac Image 1.45 computer program. All samples are measured with selected freehand line measurement tools. The samples are measured on both lateral edges, and the lengths are recorded. Simple film samples (thin and constant thickness) require only the measurement of one edge. The laminated and thick foam samples are measured on both lateral edges. The traces of the length measurement will be made along the full gauge length of a cut sample. In cases of highly deformed samples, multiple (partially overlapping) images may be required to cover the entire cut sample. In these cases, the selected characteristic features common to both overlapping images are used as "markers" to allow the readings of the image length to be joined but not overlap. The final determination of the path length for each region is obtained by priming the lengths of five (5) caliber samples of 1.27 centimeters separated from each region. Each "path length" of the gauge sample is to be the average of the surface path lengths of both lateral edges.

Poisson Lateral Contraction Effect The Poisson lateral contraction effect is measured on an Instron Model 1122, available from Instron Corporation of Canton, Massachusetts, which interfaces with a Gateway 2000 486 / 33Hz computer available at Gateway 2000 from N. Sioux City , South Dakota, using the TestWork R software, which is available from Sintech, Inc., of Research Triangle Park, North Carolina. All the essential parameters required for the test in the TestWorksTM software are entered for each test. The data collection is done through a combination of manual measurements of the sample width, and elongation measurements made with TestWorks ™. The samples used for this test are 2.54 centimeters wide by 10.16 centimeters long, with the long axis of the sample cut parallel to the direction of the first region of the sample. The sample should be cut with a sharp knife, or with a properly sharpened cutting device designed to cut an accurate sample 2.54 centimeters wide. It is important that a "representative sample" be cut, in such a way that an area representative of the symmetry of the global pattern of the deformed region is represented. There will be cases (due to variations in either the size of the deformed part or the relative geometries of the first and second regions) where it will be necessary to cut samples either larger or smaller than suggested herein. In this case, it is very important to note (along with any reported data) the size of the sample, which area of the deformed region was taken, and preferably to include a schematic of the representative area used for the sample. In general terms, an "aspect ratio" of (2: 1) must be maintained for the actual extended traction part (11: w1), if possible.

Five samples are tested. The fasteners of the Instron consist of air-operated fasteners designed to concentrate all clamping force along a single line perpendicular to the direction of elongation of the test, which has a flat surface and an opposite face from which half a round protrudes. No slippage should be allowed between the sample and the fasteners. The distance between the lines of the clamping force should be 5.08 centimeters, measured by a steel rule stopped at one side of the fasteners. This distance will be referred to from now on as the "gauge length". The sample is mounted on the fasteners with their long axis perpendicular to the direction of the applied elongation. An area representative of the geometry of the global pattern must be symmetrically centered between the fasteners. The crosshead speed is set at 25.4 centimeters per minute. The crosshead moves to the specified tension (measurements are made both at the 20 percent and 60 percent elongation). The width of the sample at its narrowest point (w2) is measured to be up to the nearest 0.508 millimeters, using a steel rule. The elongation in the direction of the applied extension is recorded up to the nearest 0.508 millimeters in the TestWorks software. The Poisson Lateral Contraction Effect (PLCE) is calculated using the following formula: PLCE = w2 - w1 w1 12 - 11 11 where: w2 = the width of the sample under an applied longitudinal elongation w., = the original width of the sample. I2 = the length of the sample under an applied longitudinal elongation I., = the original length of the sample (length of gauge).

Measurements are made in both the 20 percent and 60 percent elongation, using five different samples for each given elongation. The PLCE at a given percentage of elongation is the average of five measurements.

Hysteresis test The hysteresis test is used to measure the percentage of establishment and the percentage of force relaxation of a material. The tests are performed on an Instron Model 1 122, available from Instron Corporation of Canton, Mass., Which is interfaced with a Gateway 2000 486 / 33Hz computer available at Gateway 2000 from N. Sioux City, South Dakota, 57049, using the TestWorks ™ software that is available from Sintech, Inc., Research Triangle Park, North Carolina 27709. All essential parameters required for the test are entered into the TestWorks ™ software for each test (ie, Cross Head Speed, Percentage of Maximum Lengthening and Sustaining Times). Also, all data collection, data analysis, and graphing are done using the TestWorks ™ software. The samples used for this test are 2.54 centimeters wide by 10.16 centimeters long, with the long axis of the sample cut parallel to the direction of the maximum extensibility of the sample. The sample must be cut with an exact sharpening, or with a properly sharpened cutting device designed to cut an accurate sample 2.54 centimeters wide. (If there is more than one direction of extensibility of the material, the samples should be taken parallel to each direction of stretching.The sample should be cut in such a way as to represent an area representative of the symmetry of the overall pattern of the deformed region. due to variations in either the size of the deformed part or in the relative geometries of the first and second regions) where it will be necessary to cut samples larger or smaller than suggested here, in this case, it is very important Note (along with any reported data) the size of the sample, what area of the deformed region was taken, and preferably include a schematic of the representative area used for the sample Typically three separate samples are measured at a voltage of 20 percent, 60 percent, and 100 percent, for each material Three samples of a given material are tested in each percentage of elongation. The Instron consist of air-designed fasteners designed to concentrate all clamping force along a single line perpendicular to the direction of traction of the test, which has a flat surface and an opposite face from which it protrudes. half round, to minimize the slippage of the sample. The distance between the lines of the clamping force should be 5.08 centimeters, measured by a steel rule stopped at one side of the fasteners. This distance will be referred to from now on as the "gauge length". The sample is mounted on the fasteners with their long axis perpendicular to the direction of the percentage of elongation applied. The crosshead speed is set at 25.4 centimeters per minute. The crosshead is moved to the maximum percentage of elongation specified, and stops the sample at this elongation percentage for 30 seconds. After 30 seconds, the crosshead returns to its original position (0 percent elongation), and remains in this position for 60 seconds. Then the crossed head returns to the same maximum percentage of elongation that was used in the first cycle, subject for 30 seconds, and again it returns to zero. A graph of two cycles is generated.The percentage of force relaxation is determined by following the calculation of the force data from the first cycle: Force at Maximum% Elongation - Force after 30 seconds at x 100 =% Fza Sustain Relaxation Strength in the Maximum% Elongation (cycle 1) The establishment percentage is the elongation percentage of the second cycle sample, where the sample begins to resist elongation. The average percentage of force relaxation and the percentage of establishment for three samples, is reported for each value of maximum percentage of elongation tested.

Traction Test The tensile test is used to measure the force against the percentage of elongation, and the percentage of stretch available from a material. The tests are performed on an Instron, Model 1122, available from Instron Corporation of Canton, Mass., Which interfaces with a Gateway 2000 486 / 33Hz computer available at Gateway 2000 from N. Sioux City, South Dakota, using the TestWorks ™ software that is available from Sintech, Inc., Research Triangle Park, North Carolina. All the essential parameters necessary for the test are put into the TestWorks R software for each test. Also, all data collection, data analysis, and graphing are done using the TestWorks ™ software. The samples used for this test are 2.54 centimeters wide by 10.16 centimeters long, with the long axis of the sample cut parallel to the direction of the maximum extensibility of the sample. The sample must be cut with an exact sharpening, or with a properly sharpened cutting device designed to cut an accurate sample of 2.54 centimeters. (If there is more than one direction of extensibility of the material, the samples should be taken parallel to each one). The sample must be cut in such a way that an area representative of the symmetry of the global pattern of the deformed region is represented. There will be cases (due to variations in the size of the deformed part, or in the relative geometries of the first and second regions) where it will be necessary to cut samples larger or smaller than suggested herein. In this case, it is very important to note (along with any reported data) the size of the sample, what area of the deformed region was taken, and preferably to include a schematic of the representative area used for the sample. Three samples of a given material are tested. The fasteners of the Instron consist of air operated fasteners designed to concentrate all clamping force along a single line perpendicular to the direction of the test drive, which has a flat surface and an opposite face from which it protrudes. half round, to minimize the slippage of the sample. The distance between the lines of the clamping force should be 5.08 centimeters, measured by a steel rule stopped at one side of the fasteners. This distance will be referred to from now on as the "gauge length". The sample is mounted on the fasteners with their long axis perpendicular to the direction of the percentage of elongation applied. The crosshead speed is set at 25.4 centimeters per minute. The crossed head lengthens the sample until the sample is broken, at which point, the crossed head stops and returns to its original position (elongation of 0 percent). The percentage of stretch available is the point at which there is an inflection in the force-elongation curve, beyond which point there is a rapid increase in the amount of force required to lengthen the sample further. The average percentage of stretch available for three samples is recorded. Although particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications may be made, without departing from the spirit and scope of the invention. Accordingly, it is intended to cover in the appended claims, all changes and modifications that are within the scope of the present invention.

Claims (12)

1. CLAIMS 1. A soft weft material characterized by a plurality of first regions and a plurality of second regions that are composed of the same material composition, a part of said first regions extending in a first direction, while the rest of said first ones regions extend in a second direction perpendicular to said first direction to interconnect one another, said first regions forming a boundary completely surrounding the second regions, said second regions comprising a plurality of raised rib-shaped elements, said first regions suffering a deformation at the molecular and geometric level and said second regions initially suffering a substantially geometric deformation when the web is subjected to an elongation applied along at least one axis.
2. 2. A soft weft material exhibiting an elastic behavior along at least one axis, said weft material characterized by a plurality of first regions and a plurality of second regions, said first region and said second region being composed of the same composition of material and each having projected, unstressed trajectory length, a part of said first regions extending in a first direction while the rest of the first regions extend in a second direction perpendicular to said first direction for interconnect to each other, said first regions forming a boundary completely surrounding the second regions, said second regions comprising a plurality of elements in the form of raised rib, said first region undergoing a deformation at the molecular and geometric level and said second region initially suffering a substantial deformation The geometry is when the weft material is subjected to an elongation applied in a direction substantially parallel to said axis, said first region and said second region substantially returning to its projected, unstressed path length, when the applied elongation is released.
3. The weft material according to any of claim 1 or 2, wherein said first regions and said second regions are different from one another.
4. 4. The weft material according to any of the preceding claims, wherein the first region is substantially free of the rib-shaped elements. The weft material according to any of the preceding claims, wherein said rib-shaped elements have a major axis and a minor axis. The weft material according to claim 5, wherein said first region and said second region are composed of at least one layer of film material. The weft material according to any of the preceding claims, wherein the weft material is a backsheet in a disposable absorbent article. The weft material according to any of the preceding claims, wherein the weft material is a part of the backsheet in a disposable absorbent article. The weft material according to any of the preceding claims, wherein said weft material is a topsheet in a disposable absorbent article. The weft material according to any of the preceding claims, wherein said weft material is a part of a topsheet in a disposable absorbent article. The weft material according to any of the preceding claims, wherein said weft material is a laminate of two or more materials. The weft material according to any of the preceding claims, wherein said weft material exhibits a Poisson's lateral contraction effect less than about 0.4 to 60% elongation as measured perpendicular to said axis.