MXPA00010786A - Webs having deactivable expansion obstruction means - Google Patents

Abstract

The present invention relates to web materials which can be used in the production of large quantities of articles which are assembled from, inter alia, continuously fed web materials. In particular, the present invention teaches web materials which are expandable by a predetermined elongation after the expandability of the web material has been activated externally. To provide this functionality, the web materials comprise at least one longitudinal expansion means and at least one deactivatable expansion obstruction means. Another object of the present invention is the process for making such web materials comprising the step of incorporating longitudinal expansion means and deactivatable expansion obstruction means into the web material.

Description

TRAPS THAT HAVE DISSOLVABLE EXPANSION OBSTRUCTION MEDIA FIELD OF THE INVENTION The present invention relates to weft materials that can be used in the production of large quantities of articles that are assembled from, inter alia, continuously fed weft materials. In particular, the present invention relates to those weft materials that are capable of expanding by a predetermined elongation after the wearer has activated the ability to extend the weft material.

BACKGROUND Weft materials are well known in the prior art, especially for use in the industrial manufacture of large quantities of discrete articles. The weft materials typically have a two-dimensional configuration with the longitudinal dimension being substantially greater than the transverse dimension. Usually, the longitudinal dimension of a weft material is also substantially greater than the length of the weft material part actually used in the production of a discrete simple article. During the manufacturing process, the weft material is supplied in longitudinally continuous form and then cut into discrete pieces during the manufacturing process. For many applications, it is preferable to use weft materials that are capable of longitudinally expanding without losing their functionality. These weft materials are especially useful when they are attached to elements of varying sizes or placement. The expansion capacity of the weft material allows them to adapt to a new size or position of the element to which they are fixed. In some cases, it is desirable that the expansion of the weft material be limited to a certain elongation. Said need arises when its uses the weft material to guide or limit the increase or movement of the fixed element as described above. It can also be advantageous when the moment of expansion of the weft material can be determined externally. This specific need exists, for example, when the moment of increase or movement of the fixed element must be controlled. In U.S. Patent Nos. 5,518,801 issued to Chappell, No. 5,650,214 issued to Anderson, and in No. 5,691, 035 issued to Chappell, weave materials are disclosed which exhibit performance in the form of elastic. Specifically, these weft materials having an elongation and recovery with a defined and sudden element in the elongation of strength resistance are described where this sudden and definite increase in the strength of resistance restricts the further elongation against the relatively small elongation forces . Although progress has been made towards a weft material that is capable by a predetermined amount, this expansion can only be started by increasing the tension on the weft material. However, there remains the problem of providing a weft material that can be easily expanded by a predetermined amount after the expansion capacity has been activated externally during use. The present invention is a weft material comprising a longitudinal dimension, a transverse dimension substantially less than the longitudinal dimension, at least one longitudinal expansion means, and at least one deactivatable means of obstructing the expansion. It is a further object of the present invention to provide said weft material which additionally has a relative elastic modulus reduction of at least 50%, preferably at least 70%, still more preferably at least 90%, when subjected to the expansion clog test disabled. It is a further object of the present invention that said weft material comprises a plurality of longitudinally spaced longitudinally extending means at fixed distances. It is a further object of the present invention to provide said weft material which additionally has a plurality of longitudinal expansion means, the minimum distance between the transversely juxtaposed edges delimiting two adjacent longitudinal expansion means being D1 and the maximum distance between the two transversely delimiting edges of a longitudinal expansion means being D2, wherein the ratio of D1 to D2 is therefore minus two preferably at least three. It is a further object of the present invention to provide said weft material comprising a region having a relative expansion capacity after deactivation of at least 50%, preferably at least 100%, more preferably at least 150% according to the expansion test after deactivation. It is a further object of the present invention to provide said weft material in which the deactivating means for obstructing the expansion are capable of being deactivated by a cutting device, being cut in at least two parts, being cut out of the weft material, by electromagnetic radiation, by adding a deactivating agent, or by applying a longitudinal tension to the weft.

It is a further object of the present invention to provide said weft material in which the deactivating means of expansion obstruction are joints between the weft material bonds which are separated longitudinally apart along the surface contour. These joints can be thermal joints, adhesive bonds, mechanical fixation, tangled fiber. The configuration of the joints can be continuous or non-continuous in the transverse direction. The joints may be positioned near the longitudinally extending edges of the weft material. It is a further object of the present invention to provide this weft material comprising first surface, a second surface opposite to the first surface, a first concealed surface, and a second hidden surface opposite to the first concealed surface where the longitudinal expansion means it comprises at least one pair of a first transverse bend and a second transverse bend, the first transverse bend being secured by the deactivation means of obstructing the expansion such that at least part of the first surface conceals between the first bend edge and the second transverse bending edge is in contact with a part of the first hidden surface on the opposite side of the first transverse bending edge, the second transverse bending being secured by the deactivating means of expansion clogging in such a way that at least part of the second hidden surface between the first transverse bending edge and the second transverse bending edge is in contact with a part of the second hidden surface on the opposite side of the second transverse bending edge. It is a further object of the present invention to provide said weft material in which the longitudinal expansion means comprises a plurality of pairs of a first transverse fold secured and a second transverse bend secured.

It is a further object of the present invention to provide said weft material in which the longitudinal expansion means comprises a transversely corrugated region of the weft material. It is a further object of the present invention to provide a weft material comprising a first region and a second region wherein the first region has a higher basis weight than the second region. It is a further object of the present invention to provide said weft material having a deviation of the basis weight of less than 5% when subjected to the base weight deviation test. It is a further object of the present invention to provide a process for making a weft material comprising the steps of forming a weft, stabilizing a weft, incorporating a longitudinal expansion means in a weft, and incorporating the deactivation means of expansion clogging. in a plot. It is a further object of the present invention to provide a process for making a weft material wherein the steps of forming and stabilizing a weft proceeds to the step of incorporating the longitudinal expansion means and the deactivating means of obstructing the expansion in the weft . It is a further object of the present invention to provide said process for making a weft material wherein the step of incorporating the longitudinal expansion means and the deactivating means of obstructing the expansion in a web is intermediate to the step of forming a web and step to stabilize a plot. It is a further object of the present invention to provide said process for making a weft material wherein the step of incorporating the longitudinal expansion means into the weft material comprises at least one step selected from the group of: bending transversely a region of the material of weft, bending in z a region of weft material, bending accordion-like weft material.

It is a further object of the present invention to provide such a process for making a weft material wherein the step of incorporating the longitudinal expansion means into the weft material comprises at least one step selected from the group of: acrespar a region of the material of Weft, weave a region of the weft material, ring-roll a region of the weft material, or fold a region of the weft material. It is a further object of the present invention to provide said process for making a weft material wherein the step of incorporating the deactivation means of obstructing the expansion in the weft material utilizes bonding mechanisms of the adhesive bonding type. It is a further object of the present invention to provide a process for making a weft material wherein the step of incorporating the deactivating means of obstruction of the expansion in the weft material uses a joining mechanism selected from the group of: ultrasonic joint, joint thermal, pressure union, friction union, or autogenous union. It is a further object of the present invention to provide a process for making a weft material wherein the step of incorporating the deactivation means of obstructing the expansion in the weft material utilizes the attachment mechanism mechanically. It is a further object of the present invention to provide a process for making a weft material further comprising the steps of: unrolling the weft, longitudinally cutting the weft, and rewinding the weft, which is characterized in that the step of incorporating the weft longitudinal expansion means and the deactivating means of obstruction of the expansion in the weft material precedes the unwinding step, it is intermediate of the unwinding step and the rewinding step, or follows the step of rewinding.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to weft materials which are used in the production of large quantities of articles which are assembled from, inter alia, continuously fed weft materials. Preferably, these weft materials are supplied as a roll. The term "weft material" as used herein refers to a material in the form of a sheet, or a mixed or laminated material comprising two or more sheet materials. For example, a weft material may be a fibrous web, a non-fibrous web, a foam, or the like. The weft material of the present invention is essentially two-dimensional, that is, the thickness of the weft material is much smaller than its length and its transverse dimension. Additionally, the transverse dimension of the weft material is substantially less than its longitudinal dimension. The longitudinal dimension preferably exceeds the transverse dimension by a factor of 100, most preferably the longitudinal dimension of the weft material of the present invention is essentially infinite. In addition, the weft material of the present invention has a first external surface and a second external surface opposite the first surface. The weft material of the present invention may also comprise hidden surfaces including a first and a second concealed surface according to which the outer surface is connected thereto. At least part of each concealed surface is in contact with at least a part of one of another concealed surface such as after bending a conventional weft material. These hidden surfaces may become part of the respective external surface during the expansion of the weft material of the present invention.

One embodiment of the weft material of the present invention is a fibrous web, such as a tissue web, a non-woven web, a woven web, an interwoven web, or the like. These fibrous webs can be made from natural fibers (for example wood or cotton fibers), of synthetic fibers (for example, polyester or polypropylene fibers), or a combination of natural and synthetic fibers. The non-woven web materials can be, without being limited thereto, made by commonly referred processes such as spinning, spinning, melt blowing, carding and / or bonding with continuous air or calendering. The fibrous webs of the present invention can be absorbent or non-absorbent, liquid permeable, or liquid impervious. Another embodiment of the weft material of the present invention is the non-fibrous web such as a film. The non-fibrous web materials of the present invention may comprise 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 mixtures thereof with the above or other materials. Examples of other suitable polymeric materials that may also be used include, but are not limited to, polyesters, polyurethanes, compostable or biodegradable polymers, heat-shrinkable polymers, thermoplastic elastomers, metallocene catalyst-based polymers (e.g., INSITE ™ available from Dow Chemical Company and Exxact ™ available from Exxon), and respirable polymers. The non-fibrous web material may also be composed of an apertured film, macroscopically expanded three-dimensional formed film, absorbent or foam, filled composition, or laminates and / or combinations thereof.

The weft materials of the present invention may include laminates of the aforementioned materials. The laminates can be combined by any number of joining methods known to those skilled in the art. These joining methods include but are not limited to thermal bonding, adhesive bonding (using any of a number of adhesives including but not limited to sprayed adhesives, thermal melt adhesives, latex-based adhesives and the like), sonic bonding and extrusion lamination by means of which a polymeric film is emptied directly onto a substrate, and while still in a partially molten state, attached to a substrate side, or by depositing non-woven meltblown fibers directly onto a substrate. Alternatively, the weft material of the present invention can also comprise discretely distributed substances that are fixed to the weft material. An essential element of the weft material of the present invention is that it comprises at least one longitudinal expansion means. The term "longitudinal expansion means" as used herein refers to a means that allows the weft material to expand in the longitudinal direction by a predetermined amount. After this expansion, the weft material preferably exhibits a behavior under longitudinal tension similar to a conventional weft material. Preferably, the longitudinal expansion of a weft material of the present invention is irreversible, after the predetermined longitudinal expansion there is no contraction force pulling back the weft material to its unexpanded configuration. Generally, a region of the weft material whose perimeter coincides with the perimeter of the longitudinal expansion means may be characterized as having a longitudinal surface contour at least partially. As a result, the length of the longitudinal surface contour of this region of the weft material is substantially longer than the longitudinal distance of the two transverse edges that delimit the region. Specifically, the difference between the length of the surface contour and the longitudinal distance between the delimiting transverse edges is the predetermined length of accessible expansion for the region of the weft material comprising the longitudinal expansion means. The term "longitudinal surface contour length" as used herein refers to the length of a region of a weft material by which the length is measured along a possibly curved path that follows the longitudinal dimension of the surfaces external and hidden like these are connected to each other. A preferred embodiment of the longitudinal expansion means of the present invention is a double transverse bend, which upon unfolding allows the weft material to substantially increase its longitudinal dimension. A particularly preferred embodiment of the longitudinal expansion means of the present invention having a curved longitudinal surface contour is comprised in a weft material according to the present invention which is obtained by arranging a conventional precursor weft material in a transverse fold in z. The term "z-fold" as used herein refers to two transverse folds that are arranged such that the longitudinal cross-section of the weft material resembles the letter "z" when viewed from the side. Specifically, the first surface of the precursor web material between the first transverse bending and the second transverse bending are in close proximity to the first surface on the opposite side of the first transverse bending and the second surface of the precursor screening material between the first transverse bending and the second transverse bending is in close proximity to the second surface on the opposite side of the second transverse bending. The z-fold allows the weft to comprise a longitudinal expansion medium without losing its primarily two-dimensional configuration. Another preferred embodiment of the longitudinal expansion means of the present invention is a plurality of transverse folds which are in close proximity to each other., hereinafter called the accordion fold. The longitudinal expansion means of the present invention may also be but are not limited to regions of the weft material that are mechanically stressed, plicated, corrugated, "ring-rolled", or folded. The "ring rolling" process is described in U.S. Patent No. 4,517,714 issued to Sneed. All of these treatments have to be carried out in the transverse direction to make the weft material longitudinally expandable. A particularly preferred embodiment of the weft material of the present invention comprises a plurality of longitudinal expansion means which are spaced apart longitudinally allowing the weft material to expand locally at the positions of the longitudinal expansion means. An even more preferred embodiment comprises longitudinal expansion means at longitudinally equal distances to allow periodic local expansion of the weft material when it is converted. Another essential element of the weft material of the present invention which it comprises is at least one deactivable means of obstructing the expansion. The term "deactivation means of expansion clogging" as used herein refers to a means that is preventing the expansion of a weft material comprising a longitudinal expansion means. In addition, the deactivation means for blocking the expansion is designed so that it can be deactivated by an external deactivation device. After deactivation of the deactivating means of expansion obstruction, the longitudinal expansion means may be used to longitudinally expand the weft material at the position of the respective longitudinal expansion means. The term "external deactivation device" as used herein refers to any apparatus that is capable of acting directly or indirectly on the weft material, thereby removing at least one deactivatable means of expansion obstruction or at least not functional to a deactivating means of expansion obstruction. Generally, the deactivation means of the expansion of the present invention retain the delimiting transverse edges of a region of the weft material comprising a longitudinal expansion means at a distance less than the length of the longitudinal surface contour between the delimiting transverse edges. . Preferably, the tear-off means of obstructing the expansion prevents relative movement of the hidden surface regions of the weft material that are spaced apart along the longitudinal surface contour. This can be achieved by at least the partial direct connection or at least the indirect partial connection such as the edge joint. The deactivation means of the expansion of the present invention include but are not limited to adhesive bonding, ultrasonic bonding, heat bonding, pressure bonding, friction bonding, autogenous bonding or combinations of different bonding methods. The deactivating means for obstructing the expansion can also be mechanical fastening by means of a mechanical fastening device such as a bracket, or filament or by fiber entanglement. Alternatively, the tear-off means of expansion obstruction may be the region of the weft material with low or no longitudinal expansion capacity that is longitudinally disposed parallel to the longitudinally expandable region of the weft material. An embodiment of the external deactivation device may be, but is not limited to, a cutting device, an electromagnetic radiation emitting device, a heating device, a frame tensioning device, a deactivating agent dispensing device, or the like. A preferred embodiment of the deactivating means of obstruction of the expansion can be deactivated by electromagnetic radiation (visible infrared)., ultraviolet), or a deactivating agent (water, organic solvent, chemical agent). An even more preferred embodiment of the deactivation means for blocking the expansion is an adhesive bond that can be deactivated by electromagnetic radiation or by a deactivating agent. In another preferred embodiment of the weft material of the present invention, the deactivation means for obstructing the expansion are placed in proximity to the longitudinal edges of the weft material. Alternatively, the deactivation means for obstructing the expansion can be arranged in separate, isolated, apart positions. Preferably, the deactivation of the deactivation means for obstructing the expansion is achieved by cutting off the deactivating means of obstructing the expansion of the weft. Alternatively, the deactivation of the deactivation means for obstructing the expansion is achieved by cutting off the deactivation means of expansion clogging in at least two parts. In still another preferred embodiment of the weft material of the present invention, the deactivating means of clogging the expansion can be separated by applying a longitudinal tension to the weft material without tearing the entire weft. In this case, the tearing force of the deactivating means for obstructing the expansion must be substantially less than the tearing force of the weft material. In still another embodiment of the present invention, the mechanical fixation can be removed or rendered non-functional by an external deactivation device such as a cutting device. The deactivated expansion obstruction test disclosed in the present invention quantifies the ability of a weft material to expand more easily after deactivation of its expansion obstruction deactivation means. The parameter describing this capacity is the reduction of the relative elastic modulus exhibited while measuring two identical samples, one of them comprising the expansion obstruction means deactivated. When the weft material of the present invention is subjected to the expansion blocked deactivation test the reduction of the elastic modulus is preferably at least 50%, more preferably at least 75%, even more preferably at least 90% . A preferred embodiment of the present invention is a weft material comprising a first region and a second region where the second region has a higher basis weight than the first region. In an even more preferred embodiment of the weft material of the present invention, the second region comprises at least one longitudinal expansion means while the first region does not comprise a longitudinal expansion means. Still more preferably, the basis weight of the second region is chosen such that after expansion by means of the longitudinal expansion elements the basis weight of the second region is essentially similar to the basis weight of the first region. This property is measured using the base weight deviation test. Preferably, the deviation of the relative basis weight of the weft material of the present invention is less than 10%, more preferably less than 5%. The advantage of this particular embodiment is that after the expansion by the predetermined amount the weft material has an essentially uniform basis weight. Preferably, the base material of the present invention or at least one region thereof that is comprising at least one longitudinal expansion means has a relative expansion capacity after deactivation of at least 50%, more preferably at least less 100%, even more preferably at least 150%. This parameter describes the relative expansion capacity that the screen material of the present invention exhibits after the deactivation of the expansion obstruction means. The relative expansion capacity after deactivation is quantified with the expansion test after deactivation disclosed in this application. Another aspect of the present invention is the process for making a weft material according to the present invention. Alternately, the weft material of the present invention can also be obtained by modifying a conventional weft material. Preferably, the process of the present invention for making a weft material comprises the steps of (A) forming a weft material, (B) stabilizing the weft material, (C) incorporating the unexpanded longitudinal expansion means into the material. weft, (D) incorporating the deactivation means of expansion obstruction in the weft precursor material, and optionally, (E) unrolling the weft material, optionally, (F) longitudinally cutting the weft material, optionally, ( G) rewind the weft material. In this, the combination of incorporating the means of longitudinal expansion in a conventional precursor web with the incorporation of the deactivating means of obstruction of the expansion in order to avoid the expansion of the longitudinal expansion means allows the production of weft materials according to the invention. with the present invention. The order of the steps does not necessarily have to be in the previous order. It is possible to carry out step B at any point after step A, in particular after step D. Steps C and D can also be carried out intermediate to steps E and G or after step G. Preferably, the step of incorporating the longitudinal expansion means into the weft material is carried out by bending the weft transversely, even more preferably in a fold at zo in an accordion fold. Alternatively, the longitudinal expansion means are incorporated into the weft by pre-stretching at least partially the weft material to make it longitudinally expandable. The possible processes for this task are cornered, corrugated, "ring rolled", or folded. All of these treatments have to be carried out in the transverse direction to make the weft material longitudinally expandable. Preferably, the deactilable means of obstructing the expansion are incorporated into the weft material by joining the surfaces or edges that are spaced apart along the surface contour. These surfaces or edges have been brought in close proximity to each other by incorporating the longitudinal expansion means into the weft material. Possible methods to achieve these bonds include, but are not limited to, adhesive bonding, ultrasonic bonding, thermal bonding, pressure bonding, friction bonding, autogenous bonding or combinations of different bonding methods. Alternatively, the joints can be achieved by incorporating mechanical fastening devices such as brackets, wires, or the like, into the weft material. Another possibility for incorporating the deactivable means of obstructing the expansion in the weft material is the entanglement of the fibers of different surface regions or edge, for example, by stitching, hydroentanglement, or the like.

Non woven weft material folded in z This example is provided to demonstrate the principle of the present invention. A glued-blown spunbond nonwoven web material glued, available from Corovin GmbH of Peine, Germany, under the designation MD3000, consisting mainly of polypropylene fibers was cut into a longitudinal strip having a length of 20 mm. centimeters and a width of 2.54 centimeters. The weft material was arranged in a transverse fold in z by the following steps: At localized positions of 5 and 8 centimeters away from one of the transverse edges, the strip of the weft material was folded transversely. The transverse fold located at 8 centimeters was folded back over the weft material reaching approximately 2 centimeters away from the transverse edge. To secure the z-fold the longitudinal edges of the three layers forming the z-fold were heat-bonded to a depth of 1 millimeter applying a temperature slightly higher than the melting point of the fibers of the nonwoven web material. The final length of the strip with the z-fold of the weft material was 140 millimeters. The reduction of the elastic modulus of Example 1 was 99% when it was subjected to the expansion blocked deactivation test.

METHODS Elastic Module Test The elastic modulus test is used to measure the elastic modulus which is defined as the curve of the expansion tension versus the elongation curve relative to 0% relative elongation. Tests are performed on a standard stress-strain analysis apparatus such as Zwick Model 1445, available from Zwick GmbH & Co. of Ulm, Germany, which is interfaced with a Compaq Prolinea 466 computer available from Compaq Computer Corporation of Houston / Texas, USA, using Zwick software 7047.4b which is available from Zwick GmbH & Co. of Ulm, Germany. All essential parameters needed to test are entered into the program for each test. Also the entire data collection, data analysis and graphing are done using the program. The samples used for this test are 25.4 millimeters wide by 140 millimeters long with the long axis of the sample cut parallel to the longitudinal dimension of the weft material. The sample should be cut with a sharp die cutter or some suitable pointed cutting device designed to cut a sample of (25.4 +/- 1) millimeters wide. The sample must be cut in such a way that an area representative of the longitudinal expansion medium is represented. There will be cases (due to variations in any of the size or distance of the longitudinal expansion medium) in which it will be necessary to cut off any of the larger or smaller samples than what is suggested there. In this case, it is very important to note (along with any reported data) the sample size, whose area of the raster material was taken, and preferably includes a schematic diagram of the representative area used for the sample. Also, the results need to be calculated taking into account the different length. Three samples of a given material are tested. The clamps of the apparatus consist of air operated jaws designed to concentrate the total grip force along a single line perpendicular to the direction of the test stress having a flat surface of an opposite face from which a round half protrudes to minimize the slippage of the sample. The distance between the lines of the gripping force should be 100 millimeters as measured by a steel rule held under the jaws. This distance will be referred to from this as the "length of measurements". The sample is mounted on the jaws with its long axis perpendicular to the direction of the percent elongation applied. The crosshead speed is set at 500 millimeters per minute. The crosshead lengthens the sample until the sample breaks at which point the crosshead stops and returns to its original position (0% elongation). The elastic modulus measured by the apparatus for the three samples is averaged to obtain the final result.

Test of obstruction of the deactivatable expansion The blockage test of the deactivatable expansion is used to measure the relative reduction of the elastic modulus of a weft material. First, six identical samples of the raster material called A1, A2, A3, B1, B2, and B3 are prepared later, following the instructions given in the elastic modulus test. Each sample must comprise at least one longitudinal expansion means and at least one deactivating means of expansion obstruction. In the event that the sample size of the elastic modulus test is sufficient to satisfy this requirement, the elastic modulus test has to be modified to encompass sufficiently large weft material samples. Samples A1, A2 and A3 are subjected to the elastic modulus test. The resulting elastic moduli are averaged to obtain the elastic modulus EMA of the samples A1, A2 and A3. Then, the deactivation means for blocking the expansion comprised in samples B1, B2 and B3 are deactivated and the modified samples are subjected to the elastic modulus test. The resulting elastic moduli are averaged to obtain the EMB elastic modulus of samples B1, B2 and B3. Finally, the relative reduction of the elastic modulus is computed according to the formula (EMA - EMB) / EMA.

Proof of the deviation of the base weight This test is used to determine the uniformity of a weft material after the deactivation means of the expansion obstruction comprised in the weft material have been deactivated. Three identical samples of the subject web material are prepared, named samples A1, A2, and A3 hereinafter, according to the sample preparation described in the elastic modulus test. Each sample must comprise at least one longitudinal expansion means and at least one deactivating means of expansion obstruction. In the event that the sample size of the elastic modulus test is insufficient to meet that requirement, the elastic modulus test has to be modified to encompass sufficiently large samples of the weft material. The sample A1 is mounted on the jaws of a standard stress-strain measurement apparatus such as a Zwick model 1445, available from Zwick GmbH & Co. of Ulm, Germany, in accordance with the instructions of the elastic module test. Subsequently, sample A1 is expanded with an expansion voltage of 1 Newton per 0.0254 meters using the apparatus. Finally, five square pieces of the weft material having a surface area of (1 +/- 0.01) square centimeters are cut from the A1 frame. The positions in which the pieces are cut out should be chosen equally distributed along the longitudinal dimension of the sample A1 and should be centered with respect to the transverse direction. All parts of the weft material obtained in this way are weighed to the nearest microgram. The same procedure is carried out with samples A1 and A3. The relative deviation of the basis weight is obtained by dividing the standard deviation of the weights of the 15 pieces of the weft material by the average weight of the pieces.

Expansion test after deactivation The expansion test after deactivation is used to measure the relative expandability of a weft material from which the deactivable means of expansion obstruction comprised in the weft material are deactivated. First, three identical samples of the raster material, called B1, B2 and B3 are prepared here later, following the instructions given in the elastic module test. Each sample must comprise at least one longitudinal expansion means and at least one deactivating means of expansion obstruction. In the event that the sample size of the elastic modulus test is sufficient to satisfy this requirement, the elastic modulus test has to be modified to encompass sufficiently large samples of the weft material.

The deactivable means of obstructing the expansion of samples B1, B2, and B3 are deactivated. After this, the same procedure as for sample A1 is carried out for samples B1, B2 and B3 to measure the relative elongation under an expansion tension of 1 Newton per 0.0254 meters. The resulting relative elongation is averaged obtaining the relative expansion capacity after deactivation. Although the test methods described above are useful for many of the screen materials of the present invention, it is recognized that the test method can be modified to encompass some of the more complex web materials within the scope of the present invention.

Claims (15)

1. A weft material having a longitudinal dimension, and a transverse dimension substantially less than the longitudinal dimension, and comprising at least one longitudinal expansion means characterized in that the weft material further comprises at least one deactivating means of expansion obstruction. .

A weft material according to claim 1, wherein the weft material has a relative reduction of elastic modulus of at least 50% when subjected to the expansion blocked deactivation test.

3. A weft material according to claim 1, wherein the deactivating means of expansion obstruction is located in a region that has a relative expansion capacity after deactivation of at least 50% when subjected to the expansion test after deactivation.

4. A weft material according to claim 1, wherein the weft material comprises a plurality of longitudinal expansion means separated at fixed distances.

A weft material according to claim 4, wherein the minimum longitudinal distance between the juxtaposed transversely delimiting edges of two adjacent longitudinal expansion means is D1, and the maximum longitudinal distance between the two transversely delimiting edges of a medium of Longitudinal expansion is D2 where the ratio of D1 to D2 is at least two.

A weft material according to claim 1, wherein the deactivating means of the expansion obstruction are junctions between the regions of the weft material which are separated longitudinally apart along the surface contour.

7. A weft material according to claim 6, wherein the bonds are continuous in the transverse direction.

8. A weft material according to claim 6, wherein the seams are not continuous in the transverse direction.

A weft material according to claim 1, comprising a first surface and a second surface wherein said longitudinal expansion means comprises at least one pair of first transverse bending and a second transverse bending, the first transverse bending being secured by the deactivating means of obstructing the expansion such that at least part of said first surface hidden between the first transverse bending edge and said second transverse bending edge is in contact with a part of the first surface concealed on the side opposite the first transverse bending edge, the second transverse bending being secured by the deactivating means of obstructing the expansion such that at least a part of the second surface conceals between the first transverse bending edge and said second edge of transverse bending is in contact with a part of dich a second hidden surface on the opposite side of the second edge of transverse bending.

10. A weft material according to claim 1, comprising a first region and a second region wherein the first region has a greater weight than the first region.

11. A process for making a plot material comprising the steps of: - forming a plot; - stabilize the plot; - incorporate means of longitudinal expansion in the frame; incorporate deactivable means of obstructing the expansion in said frame.

A process for making a weft material according to claim 11, wherein the steps of forming and stabilizing a weft precede the step of incorporating the longitudinal expansion means and the deactivating means of obstructing the expansion in the weft .

A process for making a weft material according to claim 11, wherein the step of incorporating the longitudinal expansion means and the deactivating means of obstructing the expansion in a weft is intermediate to the step of forming a weft already said step to stabilize a plot.

14. A process for making a raster material according to claim 11, wherein the step of incorporating the longitudinal expansion means into the weft material comprises at least one step selected from the group of: - transversely folding a region of the weft material; - bending in z a region of the weft material; - folding said raster material into accordion.

15. A process for making a weft material according to claim 11, further comprising the steps of: unrolling said weft, longitudinally cutting the weft, rewinding the weft, characterized in that the step of incorporating the longitudinal expansion means and the deactivable means of obstructing the expansion in the weft material precede the step of unwinding said weft.