Elastic fabric and process of preparation

Abstract

In a woven fabric all warp and weft yarns are elastic, all weft and warp yarns have a stretchable core comprising a first elastic fiber and a second fiber that is less elastic than said first fiber, and the elasticity of the fabric in warp direction is at least 25% and elasticity of the fabric in weft direction (E.sub.weft) is at least 30%, preferably at least 40%.

Claims

1. A woven fabric comprising elastic warp yarns and elastic weft yarns, said elastic warp yarns and elastic weft yarns each having a stretchable core and an inelastic fibers sheath covering said core, said stretchable core including a first elastic fiber and a second fiber that is less elastic than said first elastic fiber, said woven fabric having an elasticity in warp direction of at least 25% (measured according to ASTM D3107-Stretch) and elasticity in weft direction of at least 40% (measured according to ASTM D3107-Stretch), and said elastic warp yarns having a twist level with a twist multiplier in the range of 2.5 to 6, wherein elasticity of the fabric in weft direction (E.sub.weft) is higher than the elasticity in warp direction (E.sub.warp) or wherein elasticity of the fabric in warp direction (E.sub.warp) is higher than elasticity in the weft direction (E.sub.weft).

2. The woven fabric according to claim 1, wherein the twist multiplier is in the range of 3.5 to 4.7.

3. The woven fabric according to claim 1, wherein: said first elastic fiber and said second fiber are intermingled with a number of connecting points within the range of 20 to 1000 twists per meter; said elasticity in said weft direction is greater than said elasticity in said warp direction; said second fiber comprises a PBT elastomultiester, a bicomponent PTT/PET or PTT/PBT, or nylon; and said first elastic fiber comprises a polyolefin elastomer or a polyurethane elastomer.

4. The woven fabric according claim 1, wherein said first elastic fiber is stretchable to at least 400% of an initial length of said first elastic fiber and said second fiber is stretchable to at least 20% of an initial length of said second fiber but is less stretchable than said first elastic fiber.

5. The woven fabric according to claim 1, wherein said woven fabric comprises denim.

6. A clothing article comprising a woven fabric comprising elastic warp yarns and elastic weft yarns, said elastic warp yarns and elastic weft yarns each having a stretchable core and an inelastic fibers sheath covering said core, said stretchable core including a first elastic fiber and a second fiber that is less elastic than said first elastic fiber, said woven fabric having an elasticity in warp direction of at least 25% (measured according to ASTM D3107-Stretch) and elasticity in weft direction of at least 40% (measured according to ASTM D3107-Stretch), and said elastic warp yarns having a twist level with a twist multiplier in the range of 2.5 to 6, wherein elasticity of the fabric in weft direction (E.sub.weft) is higher than the elasticity in warp direction (E.sub.warp) or wherein elasticity of the fabric in warp direction (E.sub.warp) is higher than elasticity in the weft direction (E.sub.weft).

7. The clothing article according to claim 6, wherein the twist multiplier lies in the range of 3.5 to 4.7 and said elasticity in weft direction is greater than said elasticity in warp direction.

8. The clothing article according to claim 6, wherein said first elastic fiber is stretchable to at least 400% of an initial length of said first elastic fiber and said second fiber is stretchable to at least 20% of an initial length of said second fiber, said second fiber being less stretchable than said first elastic fiber.

9. The clothing article according to claim 6, wherein: said first elastic fiber and said second fiber are intermingled with a number of connecting points within the range of 20 to 1000 twists per meter; said elasticity in said weft direction is greater than said elasticity in said warp direction; said second fiber comprises a PBT elastomultiester, a bicomponent PTT/PET or PTT/PBT, or nylon; and said first elastic fiber comprises a polyolefin elastomer or a polyurethane elastomer.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIGS. 1a and 1b show how the minimum warp elasticity required can be determined;

(2) FIG. 2 is a perspective schematic view of an exemplary embodiment of the fabric;

(3) FIG. 3 is a schematic view of the difference in the twist level of the warp yarn before weaving and in the finished fabric.

DETAILED DESCRIPTION

(4) The present invention relates to a woven fabric having elastic warp yarns and elastic weft yarns. The woven fabric of the present invention is characterised in that it has an elasticity, i.e. it can be stretched, in warp direction of at least 25%, preferably at least 30%, measured according to ASTM D3107 MODIFIED (Stretch) after 3 home wash. Preferably, elasticity of the fabric in weft direction (E.sub.weft) is higher than the elasticity of the fabric in warp direction (E.sub.warp) Alternatively, elasticity in weft direction (E.sub.weft) is at least 30%, preferably at least 40%, most preferably above 45% measured according to ASTM D3107 MODIFIED (Stretch) after 3 home wash, and elasticity of the fabric in warp direction (E.sub.warp) is higher than the elasticity of the fabric in weft direction (E.sub.weft)

(5) In view of the fact that the woven fabric of the present invention is elastic in both warp and weft direction, it can be defined as a “bi-stretch” woven fabric. As used herein, “E.sub.weft” and “E.sub.warp” respectively refer to the percentage of stretch in weft and in warp, measured according to ASTM D3107 MODIFIED (Stretch) after 3 home wash.

(6) As used herein, the term “elastic yarn” refers to a yarn comprising an elastomeric fiber, covered by a wrap, i.e. a core-spun yarn, and which provides characteristics of elasticity to the woven fabric.

(7) Suitable fibers for the elastic filament are: polyurethanic fibers such as elastane (e.g. Lycra, dorlastan), spandex (RadicciSpandex Co), lastol (Dow Chemical XLA).

(8) Suitable fibers for the less elastic, control, filament are: polyamides such as nylon (e.g., nylon 6, nylon 6,6, nylon 6,12 and the like), polyester, polyolefins such as polypropylene and polyethylene, mixtures and copolymers of the same, PBT and bicomponent filaments namely elastomultiesters such as PBT/PET and PTT/PET filaments. Suitable staple fibers for the sheath are polyester fibers, cotton, cotton blended, regenerated cellulose fibers, cotton synthetic fibers, all type of animal hair blends and natural fibers, preferably cotton fibers, that can be dyed.

(9) Preferred elastic yarns for the present invention are disclosed in WO2012/06248; for all these yarns, when the two filaments of the core are twisted, the twisting number is at least 20 twist per meter, preferably at least 200 twists per meter, more preferably 300 to 600 twists/meter, to result in the two filaments elongating and retracting as a single filament.

(10) As previously mentioned, the elasticity of the fabric in warp direction (E.sub.warp) is at least 25% (ASTM D3107 MODIFIED (Stretch) after 3 home wash), and elasticity of the fabric in weft direction (E.sub.weft) is higher than the elasticity in warp direction (E.sub.warp) or the elasticity of the fabric in weft direction (E.sub.weft) is at least 30% (ASTM D3107 MODIFIED (Stretch) after 3 home wash), and elasticity of the fabric in warp direction (E.sub.warp) is higher than the elasticity in weft direction (E.sub.weft)

(11) According to preferred embodiments of the present inventions, the elasticity in warp direction is preferably at least 30% more preferably at least 40% according to ASTM D3107 MODIFIED (Stretch) after 3 home wash.

(12) Due to the fact that E.sub.weft is higher than E.sub.warp or E.sub.warp is higher than E.sub.weft, the comfort level of the bi-stretch fabric of the invention is improved. This improvement is obtained because, when E.sub.warp is lower than, the warp yarns of the bi-stretch fabric can provide a better support against the gravity; at the same time, a higher E.sub.weft allows a better shaping of the body in vertical direction and when E.sub.warp higher than E.sub.weft, allows a better shaping of the body in horizontal direction.

(13) In a preferred embodiment, an elastic woven fabric, according to the present invention, has an elasticity in the warp direction (E.sub.warp) comprised in the range of 25% to over 75%, preferably 25% to 90%, more preferably 30% to 90%, most preferably 30% to 60%, according to ASTM D3107 MODIFIED (Stretch) after 3 home wash), and the elasticity in the weft direction (E.sub.weft) comprised in the range of 30% to over 150%, preferably 30% to 150%, more preferably 50% to 140%, measured according to ASTM D3107 MODIFIED (Stretch) after 3 home wash).

(14) In a preferred embodiment, the elastic woven fabric of the present invention has the elasticity in warp direction (E.sub.warp) of at least 25%, and the elasticity in weft direction (E.sub.weft) of at least 30% (ASTM D3107 MODIFIED (Stretch) after 3 home wash); in a more preferred embodiment, elasticity in warp direction (E.sub.warp) is at least 25% and elasticity in weft direction (E.sub.weft) is at least 40% (ASTM D3107 MODIFIED (Stretch) after 3 home wash).

(15) In a preferred embodiment, the elastic woven fabric of the present invention has the elasticity in weft direction (E.sub.weft) that is twice the elasticity in warp direction (E.sub.warp), preferably E.sub.weft is two to three times E.sub.warp Another advantage of the bi-stretch fabric of the present invention is that, providing high elasticity in both warp and weft direction, an improvement of recovery, and a reduction of the growth, is obtained.

(16) According to an exemplary embodiment, the improvement of the performance is obtained by the bi-stretch fabric of the present invention because it is more elastic than what people need in daily life. In this view, a normal daily use does not require the use of all elastic and elongation capacity of the fabric. Therefore the fabric of the invention will not be overstretched or stressed, thus avoiding damages and lacking of performance, such as lacking of recovery, growth increasing, and bagging.

(17) For example, in the so called “super-skinny” garments, the garment's cut is usually smaller than the normal body size. Therefore, just wearing super skinny garments, causes the stretching of the fabric which the garments are made of. In view of this fact, a normal use can cause overstretching of the fabric of the super-skinny garment, thus causing damages to the fabric and bagging, e.g. at knees and elbows. The bi-stretch fabric of the present invention allows to avoid these problems. In particular, these problems are avoided because the fabric of the invention is able to move with human skin, i.e. is able to move as human skin does.

(18) The elastic corespun yarn, in a preferred embodiments has an English cotton count ranging from 4 Ne to 150 Ne, preferably from 10 Ne to 80 Ne, more preferably 12 Ne to 60 Ne.

(19) The elastic woven fabric of preferred embodiments has a weight in the range of 3 oz/yard.sup.2 to 20 oz/yard.sup.2 after wash (according to ASTM D3776), preferably from 4 oz/yard.sup.2 to 15 oz/yard.sup.2, more preferably from 7 oz/yard.sup.2 to 14 oz/yard.sup.2.

(20) In a particularly preferred embodiment, the bi-stretch fabric of the present invention is a denim fabric.

(21) An elastic woven fabric according to the present invention can be produced by a process characterized by determining the minimum warp elasticity required, and weaving warp yarns and weft yarns, wherein said woven fabric is elastic in both warp and weft direction, characterized in that the elasticity of the fabric in warp direction is at least 25%, preferably at least 30% (ASTM D3107 MODIFIED (Stretch) after 3 home wash), and elasticity of the fabric in weft direction (E.sub.weft) is higher than the elasticity in warp direction (E.sub.warp). Preferably E.sub.weft>E.sub.warp, more preferably E.sub.weft≥2E.sub.warp, most preferably, the value of E.sub.weft is two to three times the value of E.sub.warp or the elasticity of the fabric in weft direction is at least 30%, preferably at least 40% (ASTM D3107 MODIFIED (Stretch) after 3 home wash), and elasticity of the fabric in warp direction (E.sub.warp) is higher than the elasticity in weft direction (E.sub.weft). Preferably E.sub.warp>E.sub.weft, more preferably E.sub.warp≥2E.sub.weft, most preferably, the value of E.sub.warp is two to three times the value of E.sub.weft.

(22) As mentioned, in a preferred embodiment of the invention, the fabric is not heat set, i.e. it does not undergo a thermal treatment to set its elasticity to a pre-set value. It was surprisingly found that when the elastic yarns of the invention are used, in particular the elastic yarns above disclosed by reference to WO2012/062480, the resulting fabric does not have to be heat-set to avoid the occurrence of problems such as curling and torqueing. However, as discussed above, a fabric according to the invention can optionally undergo a thermal treatment.

(23) Possible combinations of stretch values (elasticity) measured by ASTM D3107 (stretch) after three home washings, are 30-75; 33-35; 53-75; 27-65; 28-50; 35-100; 40-100 40-120, where the elasticity is given for warp-weft.

(24) Making reference to FIGS. 1A and 1B, the minimum warp elasticity required can be determined by measuring the variation in the distance between two benchmark points “A” 30 and “B” 40 taken at two opposite ends of a joint 20, such as an elbow, or a knee, along the axis of the limb 10, e.g. an arm or a leg, on the skin of the future user.

(25) For example, in order to make trousers, the determination will be carried out on a knee, namely above and below a knee; on the contrary, if the purpose is to obtain a fabric to make shirts, the minimum warp elasticity required will be determined on an elbow.

(26) In FIG. 1A, i.e. when the limb 10, for example an arm or a leg is unbent, two benchmarks “A” 30 and “B” 40 are taken at two opposite ends of a joint 20, such as an elbow, or a knee, along the axis of the limb 10, i.e. the arm or the leg.

(27) The distance between benchmark “A” 30 and benchmark “B” 40 when the limb, e.g. the arm or the leg, is unbent is, for example, of the value X. When the arm or the leg is bent, as shown in FIG. 1B, the distance, measured along the skin of the limb 10, i.e. along the skin of the leg or arm, between benchmark “A” 30 and benchmark “B” 40, taken at two opposite ends of a joint 20, increases to a value Y. The percentage of the variation of distance X to distance Y, is calculated with the formula (Y−X)/X. The result thus obtained, indicates the minimum warp elasticity required for a fabric according to the present invention.

(28) Therefore, in a preferred embodiment, the minimum warp elasticity required is at least of the value calculated using formula (Y−X)/X, wherein X is the distance between two benchmarks, i.e., making reference to FIGS. 1A and 1B, “A” 30 and “B” 40, taken at two opposite ends of a joint 20, along the axis of a limb 10, when the limb 10 is unbent, and Y is the distance between the same two benchmarks when the limb 10 is bent.

(29) The fabric of the present invention is woven in order to obtain an elastic woven fabric having E.sub.warp that is greater, preferably at least twice to value (Y−X)/X.

(30) In a most preferred embodiment, the warp elasticity E.sub.warp of the fabric of the present invention is 20%, preferably 30%, more preferably 40% higher than the value (Y−X)/X.

(31) Another object of the invention is a process for preparing an elastic woven fabric as above disclosed, characterized by determining the minimum warp elasticity required for said fabric, selecting an elastic yarn and a rigid yarn to be used at least in the warp yarns, and weaving warp yarns and weft yarns, wherein said woven fabric being elastic in both warp and weft direction, characterized in that the elasticity of the fabric in warp direction is at least 30% (ASTM D3107 MODIFIED (Stretch) after 3 home wash), and elasticity of the fabric in weft direction (E.sub.weft) is higher than the elasticity in warp direction

(32) (E.sub.warp).

(33) In the process, the minimum warp elasticity required for said fabric is calculated using formula (Y−X)/X, wherein X is the distance between two benchmarks taken at two opposite sides of a joint, along the axis of a limb, when the limb is unbent, and Y is the distance between the same two benchmarks when the limb is bent.

(34) FIG. 2 shows a woven fabric according to the invention. In FIG. 2 a woven fabric 50 has warp yarns 51 and weft yarns 52. In the core of a warp yarns 51, are present a first fiber 61 and a second fiber 62. In the same way, core fibers 63, comprising both first and second fibers, of weft yarns 52 are shown.

(35) As previously discussed, second fibers are less elastic than first fibers.

(36) In FIG. 2 is shown a particularly preferred embodiment of the woven fabric according to the invention that is a bi-directional stretch fabric. In a more preferred embodiment, said fabric is denim.

(37) The bi-stretch fabric of the invention is suitable to produce clothing articles at least comprising it. For example, clothing articles that can comprise the elastic woven fabric of the present invention can be leggings, pants, T-shirts, sweaters, jackets and any other garment.

(38) The following table shows the advantages of a fabric according to the invention as far as growth of the fabric is concerned.

(39) TABLE-US-00001 TABLE 1 Growth for Growth for Growth for Required 80% elastic fabric 50% elastic fabric 20% elastic fabric elasticity % (ASTM D3107) (ASTM D3107) (ASTM D3107) 10 1 1 1 20 1.5 3 6 30 2 4 — 40 3 5 — 50 4 7 — 60 5 — — 65 5.5 — — 70 5.8 — — 75 7.5 — — 80 10 — —

(40) In the above table, the required elasticity is the elasticity determined or measured as previously discussed; e.g. it is known that the elasticity required for the fabric of a legging or skinny jeans is 20% when the actually fabric used has a 20% elasticity, the result would be a growth of the fabric with use and resulting bagging at the knees. Additionally, any holding and shaping power of the fabric would be decrease with time.

(41) If for the said legging or jeans garment the used fabric has elasticity of 50%, the growth will be only 3 or 1.5 if a fabric having 80% elasticity is used. Similarly, if the required elasticity is 50%, the use of a 50% elastic fabric will result in a growth of 7% of the fabric compared to a growth of 4% if a fabric having 80% elasticity is used.

(42) It is an advantage of the invention that the final garment using the invention can be customized to the final user's body structure; in fact, by measuring the required elasticity on the user's body as previously mentioned it is possible to select a garment having the elasticity that better suits the user's body characteristics.

(43) With reference to FIG. 3, a schematic view of the shrinking of a fabric, and of its effect on the warp yarn twist level is shown. In particular, on the left, the twist level of a warp yarn 51 at the beginning of the fabric production step is shown, while, on the right, the twist level of the same warp yarn 51 in the finished fabric is shown. For clarity, only the warp yarn 51 (and not the fabric) is shown. As mentioned, in order to obtain the desired twist level of the warp yarns in the finished fabric, the warp yarn 51 is produced with a low twist level, so that at the beginning of the fabric production the twist level of the warp yarn is lower than the final one.

(44) As before mentioned, in fact, when the fabric shrinks in the warp direction, the twist level of the warp yarn 51 in the fabric increases. The initial twist level is thus chosen so as to obtain the desired twist level at the end of the fabric production steps, taking into account the fabric elasticity in the warp direction, as well as the expected shrinkage of the fabric in the warp direction during the fabric production steps.

(45) Preferably, the twist level of the warp yarns 51 in the finished fabric is provided with a twist multiplier comprised between 2.5 and 6, more preferably between 3 and 5, most preferably between 3.5 and 4.7. According to a possible embodiment, to obtain such a desired twist level, the warp yarn is produced with a twist level having a twist multiplier comprised between 2.0 and 4.5, more preferably between 2.5 and 4.3, most preferably between 2.6 and 4. In other words, during the fabric production, the fabric shrinks and the twist level of the warp yarns increases, from the condition before weaving (e.g. having a twist multiplier between 2 and 4.5) with respect to the condition in the finished fabric.

(46) As mentioned before, preferably, the initial twist level of the warp yarn (before weaving) is chosen as a function of the shrinkage of the fabric, i.e. as a function of the initial length of the warp yarn (before weaving) and of the final length of the warp yarn (i.e. in the fabric). In other words, the initial twist level of the warp yarn can be determined with the following formula:
IT=DT*FL/IL

(47) wherein IT is the initial twist of the warp yarn, DT is the desired twist of the warp yarn in the fabric (i.e. the final twist level), FL is the final length of the warp yarn in the fabric, IL is the initial length of the warp yarn before being woven.

(48) As an example, if the fabric shrinks for 30% of its length (e.g. from 100 to 70 cm), the initial twist level is 30% smaller than the desired twist level in the finished fabric (e.g. the warp yarn has initially a twist multiple of 2.8 to obtain the a warp yarn with desired twist multiple 4.0 in the final fabric).