IE52997B1 - Stretched fabric material - Google Patents

Abstract

Fabric material is formed utilising a basic fabric taken from the loom and comprising stretchable warp yarns and weft yarns. In accordance with the present invention, the basic fabric is stretched to stretch the stretchable yarns by as much as twice their original length and the yarns are set in this stretched condition. The fabric can be cold or hot drawn, and the stretchable yarns preferably comprise plastics tape e.g. polypropylene. The weft and warp yarns may be heat bonded at their interstices, and a further preferred feature is that the weft yarns have longitudinal zones of weakness which results in the weft yarns splitting into individual strips on warp stretching. An additional base sheet or film may be employed. The inventive fabrice material provides considerably increased cover without substantial increase of cost, and the strength and stability of the fabric will be increased.

Description

The present invention relates to woven fabric material and particularly fabric material including yams of nylon, polyester, polypropylene, polyethylene or other stretchable fabric materials,, Advantageously such yams extend longitudinally in the woven fabric material „ According to one aspect ©2 the present invention, there is provided a method of treating woven fabric material which comprises stretchable warp or weft yarns, the treatment comprising the steps of stretching the fabric, to stretch said stretchable warp ©r weft yams and simulfc^ aneously to split the yams which extend transversely to the stretchable yams, said splitting being continuous or intermittent along the length of the said transversely extending yarns, and setting the stretchable yarn in the stretched condition to obtain a stretched fabric material having substantially increased area.

The yams may be stretched cold or may be heated 5 to their softening point prior to stretching.

Preferably, the stretchable yam comprises synthetic resinous plastics yam.

The stretched yams can be stretched to at least 30% of the original length and preferably to at least twice the original length.

According to another aspect of the present invention there is provided a method of manufacturing a fabric material comprising the steps of forming a woven base fabric of warp and weft yams, said warp yams comprising stretchable yams while said weft yams include longitudinally extending zones of weakness, stretching the base fabric to stretch said stretchable warp yams, said warp stretching serving to split said weft yams into spaced strips, and setting the stretch20 able warp yams in the stretched condition, to obtain a stretched fabric material having substantially increased area. ssss? Methods in accordance with the present invention give advantages over a standard woven materials namely;1. An increase in the area of fabric for a given quantity of material. 2. A reduction in the weight of the stretched warp or weft yarn. 3. Greater strength of fabric (in grammes/dtex) in the stretched direction. 4. An increase in width in the weft yarn may be achieved, resulting in an increase in cover in the fabric for a given quantity of yarn.

. A bond between the warp and weft elements of the fabric may be achieved to a variable degree.

According to a further aspect of the present 15 invention there is provided a woven fabric material comprising warp yams and weft yams, the weft yams being intermittently split and the intermittently split portions of the weft yams being separated into a plurality of strips having gaps there-between.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows a base fabric used in this embodiment of the present invention, and Fig. 2 shows the base fabric of Fig, 1 treated In accordance with the present invention.

Referring to Figs. 1 and 2, base fabric material 1 comprises a woven construction of warp yams 2 and weft yams 3, which yams 2, 3 are formed from flat polypropylene tape. The warp is a 111 tex tape produced with a stretch orientation ratio of 6:1 for example, while the weft tape 3 is a 111 tex tape with a stretch orientation ratio of 7 to 1 and which has been produced with localised weakened areas 4 running in the longitudinal directions by means of fibrillation, embossing or other methods. Thirty-nine threads per 10 cms can be provided in the warp direction and thirty-nine threads per 10 cms in the weft direction. Fig. 1 shows the fabric in the initial unstretched condition. The basic fabric 1 is now tensioned and heated to approximately 160°C at which temperature the polypropylene yams become softened. With the temperature controlled at the desired value of 160°C approximately, the fabric 1 is stretched in the warp direction (see arrow X in Fig. 2) to twice its original length. It is important to control the fabric temperature within particular limits e.g. + 2°C for satisfactory results and the particular temperature selected will depend on the material of the yam and other factors, such as the type of yam bond desired. The warp yam 2 experiences a weight reduction from 111 tex to 56 tex.

However, due to the increased orientation of the warp yam 2, the tenacity of the yam, as expressed in gms/dtex, will be increased and the extension of the yam at breaking load will be reduced. The weft yam 3 will not be 53997 fa stretched longitudinally. However, due to the appropriate temperature applied to the fabric 1 and the tension and stretching which occurs in the process, the warp and weft yams 2, 3 in the fabric will bond together at their intersections 5. The degree of bonding may be adjusted by varying the conditions of temperature, tension and stretch. During the heating and stretching in the warp direction X and because of the bond achieved at the intersections 5 of warp and weft yams 2, 3, the weft tape 3 will be extended in its crosswise direction. Also because it has been weakened in the longitudinally extending direction it will tend to split along these weak sones or points 4 continuously or intermittently (depending on degree and form of weakening) into strips 6, which strips 6 will be pulled apart (see Fig. 2) thus retaining to a degree the effective cover of the weft tapes 3 despite their now being situated in the fabric at 19¾ threads per 10 cats instead of the original 39 threads per 10 cms. As can be seen, the individual gaps 7 in the stretched fabric are smaller than would be the case if the weft yam did not split: this gives more effective cover. If the weft tapes are not weakened longitudinally their width may be extended by the disturbing of the molecular structure during the heat and stretch process resulting in a possible reduction in tensile strength. If however the longitudinally weakened weft tape splits into a series of narrow strips 6 during the heat and stretch process the molecular orientation is not disturbed and the tensile strength is maintained.

Ultimately, on cooling the fabric, a permanent bond is achieved at the warp/weft intersections 5 resulting in a high degree of fabric stability with a satisfactoryretention of cover and strength.

The advantages to be gained from producing the fabric in this form can be listed as follows:1. For every one square metre produced on the loom (i.e. as in Fig. 1), two square metres of finished fabric will result (Fig. 2) 2. If fabric can be produced with a resultant warp tex of 56 from an initial warp tex of 111, then this will result in a cheaper yam cost per kilo in the fabric, as it is normal for the lower tex yams to be more expensive per kilo than the higher tex yams 3. The resultant strength of the fabric in grammes/dtex in the warp direction will be greater after stretching than that of the fabric in the unstretched condition (Fig. 1) The resultant strength of the fabric 1 in the weft direction in grammes/dtex is maintained despite crosswise extension of the weft tapes 3.

It will be appreciated that a base fabric 1 containing tapes (2, 3) of yams of other synthetic or natural materials of differing construction width, orientation ratio, polymer or fibre base and situated in the base fabric with different settings of tapes or yarns per 10 cm, provided the tapes or yams used can be extended if necessary by the percentage required under the selected conditions of temperature and direction of base fabric stretch.

It will also be appreciated that in this embodiment the stretch may be applied to the base fabric in the longitudinal direction, or in both the longitudinal and transverse directions in varying degrees from 1% upwards.

One commercial end use for the fabric described in this embodiment would be as a material for packing purposes, particularly for production of bags and sacks where good cover, strength and stability of the fabric is desirable at a low cost.

In a modification, weft yam for example in the form of tapes may be used which do not have the longitudinally extending weakened zones.

Claims (9)

1. A method of treating woven fabric material which comprises stretchable warp or weft yams, the treatment comprising the steps of stretching the fabric to stretch 5 said stretchable warp or weft yams and simultaneously to split the yams which extend transversely to the stretchable yams, said splitting being continuous or intermittent along the length of the said transversely extending yams, and setting the stretchable yam in the 10 stretched condition to obtain a stretched fabric material having substantially increased area.

2. A method of manufacturing a fabric material comprising the-steps of forming a woven base fabric of warp and weft yams, said warp yams comprising stretchable yams 15 while said weft yams include longitudinally extending zones of weakness, stretching the base fabric to stretch said stretchable warp yams, said warp stretching serving to split said weft yams into spaced strips, and setting the stretchable warp yams in the stretched condition, to 20 obtain a stretched fabric material having substantially increased area.

3. A method as claimed in Claim 1 or Claim 2, wherein the stretchable yam comprises synthetic resinous plastics yam.

4. A method as claimed in Claim 2, wherein the weft yam comprises synthetic resinous plastics yarn, said longitudinally extending zones of weakness being provided by yam fibrillation or embossing. 55. A method of treating a fabric material wovenfrom tapes of synthetic resinous plastics material, the treatment comprising the steps of heating the fabric to a raised temperature at which the synthetic resinous plastics material will soften, stretching the fabric 10 longitudinally whilst at the raised temperature to extend the warp tapes longitudinally while simultaneously producing longitudinally extending splits in the weft tapes due to a lateral extension, of the weft tapes, and cooling the stretched fabric material while the warp 15 tapes are longitudinally extended to produce a dimensionally stable fabric material having gaps between strips formed in the weft tapes by splitting thereof and a substantially greater surface area than the fabric material immediately after weaving. 20 6. A method as claimed in any one of the preceding claims, wherein the stretchable yam is stretched and set with a length increase of at least 30% of the original length. 7. A method as claimed in Claim 6, wherein said length 25 increase is at least equal to the original length. 8. A method according to any one of the preceding claims wherein the warp yams or tapes are bonded to the weft yams or tapes. 9. A method of making a stretched fabric material

5. Substantially as hereinbefore described with reference to the accompanying drawings.

6. 10. Fabric material made by the method of any one of the preceding claims,

7. 11. A woven fabric material comprising warp yams and 10 weft yams, the weft yams being intermittently split and the intermittently split portions of the weft yams being separated into a plurality of strips having gaps there-between.

8. 12. A woven fabric material according to Claim 11 wherein 15 the warp and weft yams are bonded together at their intersections.

9. 13. Fabric material substantially as hereinbefore described with reference to and as illustrated in Figure 2 of the accompanying drawings.