Abstract
A foamed fabric comprising filaments of closed-cell foam of cross-linked polymeric material is formed by integrating the filaments into a precursor textile and subsequently foaming the material at a foaming temperature at which the filaments expand. The foamed fabric can be used for protective garments, pads, mats and the like.
Claims
1. An unfoamed, woven precursor textile having a warp and a weft and comprising filaments of chemically cross-linked polymeric material, containing a chemical blowing agent, which, on subjecting to a foaming temperature of at least 150 C., expands by at least 5 times its volume to form a closed-cell foamed fabric.
2. The precursor textile according to claim 1, wherein the filaments are arranged in the warp.
3. The precursor textile according to claim 1, further comprising fibres of non-foamed material.
4. The precursor textile according to claim 3, wherein the filaments are present as at least 20% of the fabric by weight.
5. A foamed fabric formed by foaming of the precursor textile according to claim 1, having a net density of between 30 Kg/m.sup.3 and 100 Kg/m.sup.3.
6. The foamed fabric according to claim 5, having a first impact shock absorption value of greater than 25% force reduction (Fmax).
7. A foamed fabric formed by foaming the precursor textile according to claim 1, wherein the filaments extend out of a plane of the fabric in the form of open arches.
8. A foamed fabric formed by foaming the precursor textile according to claim 7, wherein during foaming the filaments expand and extend to form the open arches.
9. A foamed fabric formed by foaming the precursor textile according to claim 1, having a thickness of at least 5 mm and a weight of less than 1000 g/m.sup.2.
10. A garment, a garment portion, a mat, an underlay, a furnishing element or a seating element, comprising a precursor textile according to claim 1.
11. The precursor textile according to claim 1, further comprising other fibres of non-foamed materials, wherein the size of the cross sectional area of the filaments in an unfoamed state with respect to the other fibres is between 0.1x and 100x.
12. A foamed fabric formed by foaming the precursor textile according to claim 1, wherein the precursor textile expands at the foaming temperature by at least 5 times its volume.
13. A foamed fabric formed by foaming the precursor textile according to claim 1, wherein the precursor textile expands at the foaming temperature by at least 10 times its volume.
14. A foamed fabric formed by foaming the precursor textile according to claim 1, wherein the precursor textile expands at the foaming temperature by at least 20 times its volume.
15. The precursor textile according to claim 1, wherein the polymeric material is polyethylene, ethylene vinyl acetate or a blend thereof.
16. The precursor textile according to claim 1, wherein the cross-linked polymeric material ensures the precursor textile is stable to at least 180 C.
17. A foamed fabric comprising a woven textile having a warp and a weft and filaments of chemically cross-linked polymeric material, which have been foamed to form closed-cell foamed filaments that extend out of a plane of the fabric in the form of open arches.
18. The foamed fabric according to claim 17, wherein foaming takes place subsequent to forming the precursor textile into a further product.
19. An unfoamed, woven precursor textile having a warp and a weft and comprising filaments of chemically cross-linked polymeric material, containing a chemical blowing agent, which, on subjecting to a foaming temperature of at least 150 C., forms a closed-cell foamed fabric, wherein the weight of the filaments is between 10,000 dtex and 50,000 dtex.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The features and advantages of the invention will be appreciated upon reference to the following drawings of a number of exemplary embodiments, in which:
(2) FIG. 1 shows a perspective view illustrating the production of filaments of foamable polymeric material according to the invention;
(3) FIG. 2 shows in schematic view a weaving machine operational to integrate the filaments of FIG. 1 into a woven textile;
(4) FIG. 3 shows a plan view of part of the woven textile produced according to the invention in the machine of FIG. 2;
(5) FIG. 4 shows in schematic plan view a tenter oven in use in converting the textile of FIG. 3 into a foamed fabric;
(6) FIG. 5 shows a side elevation of the tenter oven of FIG. 4;
(7) FIG. 6 shows a perspective view of part of the foamed fabric produced in the tenter oven of FIG. 4;
(8) FIG. 7 shows a plan view of the foamed fabric of FIG. 6;
(9) FIG. 8 shows a perspective view of a portion of woven textile according to an alternative embodiment of the invention;
(10) FIG. 9 shows a perspective view of a foamed fabric formed from the textile precursor of FIG. 8;
(11) FIGS. 10A and 10B show in plan view a further alternative embodiment of a woven textile for producing a skewed fabric.
(12) FIGS. 11A and 11B show schematic perspective views of a shoulder pad confected from the precursor textile of FIG. 8; and
(13) FIG. 12 shows an alternative procedure for forming filaments of foamable polymeric material
DETAILED DESCRIPTION
(14) An exemplary procedure for forming filaments of foamable polymeric material is shown in perspective view in FIG. 1. According to the figure, an extruded, cross-linked sheet 10 of foamable material is fed from a roll 12 through a strip forming device or shredder 14. The sheet 10 is cross-linked PE available from Sekisui under the name Alveocel LUT 4501 1.3 mm. Other similar materials are available from Trocellen GmbH and appropriate procedures for forming such foamable cross-linked polymeric materials are disclosed in EP0476798. On passing through shredder 14, the sheet 10 is cut into multiple filaments 16, each having a width of 4 mm, which are subsequently wound together onto a spool 18. The wound strip has a dTex value of around 38 000.
(15) FIG. 2 shows in schematic view a weaving machine 20 operational to integrate the filaments 16 into a woven textile 22. A number of spools 18 produced according to the process of FIG. 1 are mounted for delivery of filaments 16 into the warp direction of machine 20 at a spacing of 1 cm. An additional beam 24 of 370 dTex PET warp threads 26 is mounted in the warp direction such that the filaments 16 repeat at a rate of one filament for every 27 warp threads. The beam 24 and weaving machine 20 have an active width of 2.1 meters. It will be understood that this configuration is merely exemplary and that other weaving structures can also be chosen as detailed below. In the weaving machine 20, a pair of PET weft threads 28, each of 1100 dTex are inserted by a projectile weft insertion device 30 from a reel 32 at a spacing of 54 threads/10 cm. The woven textile 22 is wound onto a textile roll 34 for subsequent processing.
(16) FIG. 3 is a plan view of a portion of the textile 22 produced in the machine 20. According to this weaving pattern, the filaments 16 are equally spaced on the frontside and the backside of the textile 22 in that respectively seven weft threads 28 pass over a given filament 16, followed by seven weft threads 28 passing beneath it. The warp threads 26 are woven in plain weave with the weft threads 28. The resulting textile 22 has a weight of 556 g/m.sup.2, comprising approximately 390 g/m.sup.2 of the filaments 16, 100 g/m.sup.2 of the warp threads 26 and 65 g/m.sup.2 weft threads 28.
(17) FIG. 4 shows in schematic plan view a tenter oven 40 being used in a finishing process on the textile 22 for the formation of a foamed fabric 42. The tenter oven 40 is shown in FIG. 5 in side elevation. According to FIGS. 4 and 5, the textile roll 34 is mounted to deliver the textile 22 to the tenter oven 40. To this end, the sides of the textile 22 are gripped by the tenter frame 44 which stretches the textile 22 laterally as it is carried through beneath heater 46. The heaters 46 subject the textile 22 to a foaming temperature of 190 C. for a time of 3 minutes as it is carried through the tenter oven at a speed of 3 meters per minute. During the heating phase, the blowing agent in the foamable polymeric filaments 16 is activated and the filaments 16 expand multiaxially. Because of the manner in which the textile 22 has been woven with equal numbers of weft threads 28 on both sides of the filaments 16, the filaments expand to form upstanding arches 48 extending above and below a base layer 50 formed by the warp and weft threads 26, 28. The foamed filaments 16 exhibit a net volume increase that is around eight times greater than prior to foaming. The overall gross increase in volume is somewhat greater due to the space occupied by the arches 48.
(18) A close up perspective view of part of the foamed fabric 42 is shown in FIG. 6 illustrating the upstanding arches 48 extending above and below the base layer 50.
(19) FIG. 7 shows a top elevation of the foamed fabric 42, which additionally illustrates the manner in which adjacent arches 48 engage against each other and partially fuse during the heating process to form bridges 54. These bridges 54 serve to stabilise the structure of the foamed fabric 42 making it 2-D stable and preventing skewing thereof. It will be understood that although in this aspect the structure of the precursor textile ensures that bridges 54 are formed after foaming, it is also possible to produce a foamed fabric without such bridges, whereby the foamed fabric remains a textile in that it remains deformable or skewable within the plane of the base layer.
(20) The foamed fabric 42, produced as described above was tested and exhibited exemplary properties. A number of tests were carried out on the foamed fabric 42 described above according to the methods outlines in the FIFA Handbook of Test methods January 2012 edition. The test sample achieved results for Vertical Deformation: 6.45 mm; Force Reduction 23.95%; Energy Restitution: 71.75% and Shock Absorption (first, second, third impact): 39.3%, 25.3%, 22.6%. Another similar sample of the foamed fabric 42 was subjected to water flow testing according to ASTM D4491 and achieved average flow meter readings of 1.59 g/m based on five sample locations (temperature correction factor: 0.9097; average sample thickness: 8.24 mm; permittivity: 0.898/s; permeability: 0.741 cm/s). Depending upon the fabric construction, it is expected that water flow rates of anywhere from 0.5 g/m to 5 g/m could easily be achievable.
(21) FIG. 8 shows in perspective view an aspect of a woven textile 122 for use as a precursor in the formation of a foamed fabric. In this example, the filaments 16 are woven in an asymmetric manner with respect to the weft threads 28 in what can be termed a satin weave. Thus, each filament 16 passes over three weft threads 28, and subsequently is captured under one weft thread 28. The weft threads 28 are in this case present as thread bundles or multi-strand threads. The remaining warp threads 26 are woven in a plain weave with respect to the weft threads 28.
(22) FIG. 9 shows the woven textile 122 of FIG. 8 in perspective view after it has been finished or foamed to form a foamed fabric 142. The foaming step can take place in the tenter oven 40 as described in relation to FIG. 4. As can be seen, the filaments 16 of foamable polymeric material have expanded to form arches 48, which in this case are upstanding only from the frontside of the base layer 50. At the backside of the foamed fabric 142 (in the figure, the lower side is designated as the backside), the filaments 16 have remained largely in the plane of the base layer 50. The relatively higher arches will collapse under a lower load than those of the embodiment of FIG. 6.
(23) FIG. 10A shows in plan view a further aspect of a woven textile 222 for use as a precursor in the formation of a foamed fabric. In this example, the foamable filaments 16 are oriented in the warp direction and are woven in a loose plain weave with further warp threads 26 and weft threads 28.
(24) In FIG. 10B, the woven textile 222 is subjected to a further processing step of skewing, whereby a force F is applied to distort the weave structure through an angle . Foaming takes place by application of heat as described above, while maintaining the force F. After completion of the foaming process, the resulting foamed fabric is stable in the skewed orientation due to the formation of bridges between adjacent arches as described above.
(25) FIG. 11A illustrates in perspective view a step in the confection of a protective shoulder pad using the precursor textile 122 of FIG. 8 that has been trimmed to an appropriate size. The weave of the precursor textile 122 is sufficiently loose that it can easily deform or drape to follow the contours of a mould or in this case a mannequin 60. The mannequin 60 with the precursor textile 122 is then subjected to heat treatment at the foaming temperature to expand the foam filaments 16. FIG. 11B shows the mannequin 60 after foaming has taken place. The foamed fabric 142 has expanded with the formation of foam arches 48 which are connected together, thus forming a resilient shoulder pad 62, which retains its shape even once removed from the mannequin. The shoulder pad 62 provides excellent cushioning and good ventilation due to its open structure. It will be understood that the same or similar procedure can be used to form fabric elements of many different shapes and forms as can be required.
(26) FIG. 12 shows an alternative procedure for forming filaments of foamable polymeric material. According to this embodiment, an extruder 312 delivers foamable PE extrudate 310 to a die-head 314, where it is extruded as filaments 316. The foamable PE includes suitable blowing and chemical cross-linking agents which are not activated at the extrusion temperature of 150 C. The filaments 316 are fed through a cooling bath 317 and subsequently wound onto spools 318. The un-foamed and un-crosslinked filaments may subsequently be integrated into woven precursor textiles as described above. After weaving, the filaments 316 can be cross-linked and foamed in a single step by exposure to heat at around 180 C. An advantage of the extruded filaments 316 is that they may be formed in a wide variety of cross-sectional shapes and weights according to the shape and size of the extruder die-head 314.
(27) Thus, the invention has been described by reference to certain aspects discussed above. It will be recognized that these aspects are susceptible to various modifications and alternative forms well known to those of skill in the art. In particular, the invention is not limited to any particular weave structures and as it can be seen, depending on the nature of the weave structure, the filaments can be guided to expand in a given manner to achieve a different resulting effect.
(28) Many modifications in addition to those described above can be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific aspects have been described, these are examples only and are not limiting upon the scope of the invention.
