LYOCELL FILAMENT DENIM
The invention relates to a denim fabric as it is used for clothes (1). The fabric is made from weft yarns (4) and warp yarns (6). At least one of the warp yarns and the weft yarns contains or consists of lyocell filaments (8). The resulting material combines high mechanical strength against wear and tear with superior softness, smoothness and luster. Furthermore, the denim according to the invention is bleachable. The denim according to the invention represents a new class of denim alongside existing cotton denims and denims with a silk component.
The invention relates to a Denim fabric.
Denim is a fabric which is usually woven from cotton as a warp-faced textile having a twill pattern. A very common denim fabric is indigo-dyed denim, in which only the warp is dyed. The weft stays white. The core of the warp, however, remains undyed, which results in fading characteristics which are typical for denim. Due to the warp-faced weaving, denim is colored—typically indigo—on the outside and white—uncolored—on the inside.
Although cotton is a fiber which is highly resistant and therefore able to undergo even aggressive finishing, its mechanical properties and its haptic qualities are not ideal and give denim only a small range of capabilities.
Therefore, it was tried in the past to improve the qualities for denim by at least partly replacing the cotton by silk and/or man-made fibers and filaments. One such example is the addition of Elastane for increasing elasticity. Typically up to 3% elastane may be added; more elastane is detrimental to longevity.
Man-made continuous filament yarns are widely used in the textile industry to produce fabrics with a distinct character compared to fabrics produced from yarns made using staple fiber. A continuous filament yarn is one in which all of the fibers are continuous throughout any length of the yarn. A continuous filament yarn will commonly consist of 20 to 200 or more individual fibers which are all parallel to each other and the axis of the yarn when produced. The yarn is produced by extruding a solution or melt of a polymer or a polymer derivative and then winding the yarn produced onto a bobbin or reel or by forming a cake by centrifugal winding.
Synthetic polymer continuous filament yarns are common. For example, nylon, polyester and polypropylene continuous filament yarns are used in a wide variety of fabrics. They are produced by melt spinning a molten polymer through a spinneret with a number of holes corresponding to the number of fibers required in the yarn produced. After the molten polymer has started to solidify, the yarn may be drawn to orient the polymer molecules and improve the properties of the yarn.
Continuous filament yarns can also be spun from cellulose derivatives such as cellulose diacetate and cellulose triacetate by dry spinning. The polymer is dissolved in a suitable solvent and then extruded through a spinneret. The solvent evaporates quickly after extrusion causing the polymer to precipitate in the form of a yarn. The newly produced yarn may be drawn to orient the polymer molecules.
Continuous filament yarns can further be produced from cellulose using the viscose process. Cellulose is converted to cellulose xanthate by reaction with sodium hydroxide and carbon disulphide and then dissolved in a sodium hydroxide solution. The cellulose solution, commonly called viscose, is extruded through a spinneret into an acid bath. The sodium hydroxide is neutralized causing the cellulose to precipitate. At the same time, the cellulose xanthate is converted back to cellulose by reaction with the acid. The newly formed fiber is drawn to orient the cellulose molecules, washed to remove reactants from the fiber and then dried and wound onto a bobbin. In earlier versions of this process, the wet yarn was collected into a cake using a centrifugal winder—a Topham Box. The cake of yarn was then dried in an oven before winding onto a bobbin.
Continuous filament cellulose yarns are also produced using the cupro process. Cellulose is dissolved in a solution of cuprammonium hydroxide. The resulting solution is extruded into a water bath where the cuprammonium hydroxide is diluted and the cellulose precipitates. The resulting yarn is washed, dried and wound onto a bobbin.
Cellulosic continuous filament yarn produced by either the viscose or the cupro process can be made into fabrics by weaving. Fabrics produced are used for a variety of applications including linings for women's apparel and menswear.
Fabrics made from continuous filament cellulose yarns are good at moisture handling to enhance the comfort of the wearer. They do not generate static electricity as readily as fabrics made using continuous filament synthetic yarns.
Fabrics made from currently available continuous filament cellulose yarns generally have poor physical properties. The dry strength and the tear strength are poor compared to fabrics made from synthetic polymers such as polyester. The wet strength is much lower than the dry strength due to interactions between the cellulose and water. The abrasion resistance is low. The interactions with water also soften the cellulose causing the fabrics made from the yarn to be unstable when wetted. This is particularly problematic when washing these materials in a household washing machine.
Due to these deficiencies, the products which were originally made using continuous filament cellulose yarns are now made mainly by synthetic polymer continuous filament yarns such as polyester and nylon.
However, there are problems with the synthetic yarns. Fabrics made using them do not have the moisture handling capability of fabrics made from cellulose yarns. Synthetic fabrics can generate static electricity. Some people find fabrics made from the synthetic yarns are much less comfortable to wear than silk. Further, fabrics made from synthetic yarns have poor washability, requiring dry cleaning to avoid excessive shrinkage.
Regarding the available denim fabrics, there is thus a need to create a denim fabric which has high moisture absorption, can be finished with a large variety of even aggressive agents, which is washable and soft.
This object is solved by a denim fabric that is made from weft yarns and warp yarns, wherein at least one of the weft yarns and the warp yarns contains or consists of lyocell filaments.
Such a lyocell filament denim withstands aggressive finishing agents. Further, the denim comprising or consisting of lyocell filament yarn is softer and smoother even than denim with a silk component. Thus, the inventive lyocell filament denim gives rise to a new class of fabrics with an entirely new set of properties. This is all the more surprising as it would have been expected from the properties of cotton yarn that—if at all—denim containing or consisting of lyocell staple fiber would be a replacement for cotton denim.
Lyocell is the generic name given to a type of cellulosic man-made fiber produced by a direct dissolution process. The lyocell process is described e.g. in U.S. Pat. No. 4,246,221 and WO 93/19230.
A slurry of wood pulp is formed with a solution of amine oxide in water. Water is then evaporated from the slurry in a thin film evaporator vessel. When the water level is reduced below a certain level, the cellulose forms a solution in the amine oxide. The resulting viscous liquid solidifies to a glassy solid below about 70° C. If maintained above this temperature, it can be pumped through a spinneret to form filaments which are then immediately immersed in water where the dilution of the amine oxide causes the cellulose to precipitate.
The spinneret used for extrusion of the amine oxide cellulose solution has a number of holes corresponding to the number of filaments required in the continuous filament yarn. After extrusion, the newly formed yarn is washed clean of amine oxide with a counter current flow of water. This washing may be done on self advancing reels on which water is introduced to wash the fiber. A finish may be applied to aid further processing and the yarn is dried. The washed and dried yarn is wound onto a bobbin.
In the lyocell process, cellulose in the form of wood pulp is the only raw material used. The wood pulp used comes from sustainable managed forests. The filaments produced are 100% cellulose and are the only output from the process. The amine oxide solvent is recovered from the washing water and reused to produce further filament. This recovery can be as high as 99.7%. As a result, the environmental impact of the lyocell process is very low. There are virtually no releases of gaseous or liquid emissions from the process and the filament produced is solvent free.
By contrast the viscose process uses carbon disulphide, sodium hydroxide, sulphuric acid and zinc sulphate. Hydrogen sulphide and carbon disulphide can be released from the process unless a great deal of care is taken. Sodium sulphate is produced as a by-product of the process.
The invention can be further improved by the following additional features, which can be combined independent of one another and which each exhibit a different technical effect.
The continuous filament lyocell yarns used to produce the products of the invention may be the as produced yarn in an untwisted state or may be twisted by rewinding. It may be a doubled yarn. It may be combined with another continuous filament yarn or staple fiber yarn by twisting the yarns together or by intermingling using for example an air jet.
The lyocell denim according to the invention contains preferably at least 10% lyocell filaments in at least one of the weft and the warp yarn. Preferably, the minimum overall content of lyocell filaments in the lyocell denim is above 10%. A content of more than 10% can improve the handfeel of the fabric significantly given the soft structure of a yarn containing or consisting of Lyocell filaments. Consequently, the total content of lyocell of at least 10% already gives a haptical impact independent of whether the Lyocell filament is used in warp or weft. Moreover, a blend of at least 10% lyocell filaments with other synthetic or cellulose filaments, e.g. with Viscose or Cupro filaments, or with Viscose or Cupro staple fibers, or wool and cotton improves the strength of the yarn. Finally, a blend of at least 10% lyocell filaments and synthetics improves the breathability and moisture management of the fabric significantly.
The dyeing and finishing procedures of the denim process are very demanding as the combine a strong chemical impact with a strong mechanical treatment of the fabric. Consequently, viscose and silk fibers cannot be used in these processes as they would not withstand this procedure. This is the reason why viscose and/or cupro staple fibers and filaments can only be used in a very small portion in combination with lyocell filaments or may even need to be replaced by lyocell filaments in another embodiment.
According to another preferred embodiment, the denim is bleached. In contrast to e.g. denims with a silk content, the lyocell filaments are capable of being treated by aggressive finishing agents such as chlorine bleach. Moreover, it has been surprisingly found that such an aggressive finishing agent, in particular chlorine bleach, softens the yarn containing or consisting of lyocell filaments, and thus actually improves softness and smoothness of the lyocell denim.
The lyocell denim according to the invention has a superior softness. An indirect measure for softness is the TS7 value as determined by a TSA tissue softness analyzer. According to one embodiment, the denim according to the invention has a TS7 value of no more than 8 in the fixed state, i.e. before garment wash. Moreover, a TS7 value of no more than 6 can be obtained with the inventive denim after garment wash, and even after bleaching.
The TSA also yields another parameter, the TS750 value, which is correlated to smoothness. Preferably, the denim according to the invention in the fixed state has a TS750 value of no more than 120. A TS750 value of no more than 120 may also be maintained after garment wash and/or after bleaching.
With the above-indicated smoothness and/or softness, the denim according to the invention has higher smoothness and/or softness than a cotton denim and an even partly superior softness and/or smoothness to denim with silk yarn.
Preferably, the denim also has high mechanical resilience. For example, the denim may score at least 15,000 cycles to hole formation in a Martindale abrasion test in the fixed state, i.e. before garment wash. In another embodiment, the denim may score 8,000 cycles to hole formation after garment wash and/or after bleaching. This indicates that the denim according to the invention can be used for textiles that are subject to strong wear.
The outer face of the denim, i.e. the warp face of the denim, may, in another embodiment, have a pilling grade of no worse than 5 in the fixed state, i.e. before garment wash, and/or no worse than 5 after garment wash and no worse than 5 after bleaching.
Yarn strength of the denim in the at least one, warp and/or weft, direction in which the lyocell filament yarn is used is preferably at least 20 cN/tex, more preferably at least 25 cN/tex, in the fixed state cond. 20/65 and/or at least 10 cN/tex, preferably at least 20 cN/tex in the wet state. After garment wash, the yarn strength in the at least one, warp and/or weft, direction in which the lyocell filament yarn is used was preferably at least 4.5 cN/tex, more preferably at least 5 cN/tex cond. 20/65, and preferably at least 3, preferably at least 7 cN/tex wet. After bleaching, yarn strength in the at least one, warp and/or weft, direction in which the lyocell filament yarn is used, is at least 2 cN/tex, preferably at least 3 cN/tex. cond. 20/65, and preferably at least 2 cN/tex, more preferably at least 5 cN/tex wet.
Yarn elongation of the weft and/or warp yarn which contains or consists of lyocell filaments may be at least 4% after fixation and/or at least 2% after garment wash and/or at least 1% after bleaching.
The hairiness of the denim according to the invention may have a grade of no worse than 4 after garment wash and of no worse than 3 after bleaching on the warp face, i.e. the outer face of the denim.
The fiber splice of the denim according to the invention may have a grade of no worse than 4 before and/or after fixation and/or of no worse than 4.5 after garment wash and/or of no worse than 4.5 after bleaching.
All the above parameters qualify the denim according to the invention as a fabric suitable for an extremely wide range of denim applications. The combination of softness, smoothness and luster, on the one hand, and the mechanical properties such as wear resistance and yarn strength, on the other, present a unique combination for denims.
The specific hand as determined by a Handle-O-Meter in the direction of the warp and/or weft yarns that contain or consist of lyocell filaments is at least 4 mN m2 g−1 after garment wash and/or at least 3 mN m2 g−1 after bleaching. These values indicate a high smoothness and flexibility of the inventive denim.
The luster of the warp and/or weft yarn containing, preferably consisting of, lyocell filaments may be at least 20% reflection. This allows creating a denim having high gloss.
The invention also relates to a garment, in particular a garment of women's apparel, and/or menswear, such as jackets, coats, blouses, dresses and pants, in which a lyocell denim as described above is used.
Further, the invention relates to the use of a yarn containing or consisting of lyocell filaments in a denim fabric.
Moisture regain of the fabric as measured according to ASTMD 1909 is an indicator for the comfort level. Mulberry silk has 11% of moisture regain and offers one of the best comfort levels of all fabrics with respect to moisture regain. The lyocell filament yarn and/or denim according to the invention preferably has a moisture regain of at least 13% which results in a similar or even better comfort than mulberry silk.
The lyocell filament denim of the invention may be of any style, weave or finish that is suitable for production with a continuous filament yarn and results in a denim comparable to cotton. The lyocell filament denim may be constructed as plain weave, twill, satin, sateen, hopsack, cord and fancy weaves. Fabrics may be woven using any loom suitable for weaving continuous filament yarns including shuttle looms, rapier looms, projectile looms or ribbon looms.
The lyocell denim fabrics produced using continuous filament lyocell yarns can have aesthetics and appearance similar to a fabric produced from continuous filament viscose yarn, but have significantly better physical properties. The higher strength and modulus of the yarn result in improved fabric breaking strength, tear strength, abrasion resistance and stability. The wet fabric properties are also superior.
The lyocell denim 2 comprises weft yarns 4 and warp yarns 6, which may be twisted. At least one of the weft yarns 4 and the warp yarns 6 contains or consists of lyocell filaments.
An example of a warp and/or weft yarns 6, 4 with at least one lyocell filament 8 is shown in
To investigate the quality of the lyocell filament denim according to the invention over silk, samples were prepared and compared to comparative examples made from denim consisting of or containing cotton. For denim, bottom is the benchmark, against which any denim using yarn from man-made fibers or filaments has to compete in the market. The samples of the inventive lyocell filament denim are compared to comparative examples using the following tests:
Tests
A Martindale abrasion test according to DIN EN ISO 12947-2;
a Martindale pilling test according to DIN EN ISO 12945-2;
washing shrinkage according to DIN EN ISO 5077; from the absolute values of the shrinkage in both samples direction the sum was taken as a combined shrinkage;
fastness to rubbing according to ISO 105 X12;
AATCC durable press rating according to DIN EN ISO 15487;
air permeability according to DIN EN ISO 9237;
fastness according to DIN EN 20105-A02;
yarn strength in the warp and weft according to DIN EN ISO 2062,
moisture regain according to ASTMD 1909,
luster of the yarns was determined at an angle of 45° according to EN 14086-01/2003,
luster of the fabrics was determined at an angle of 75° according to TAPPI T480.
For the end consumer, it is important how the look of a fabric changes after washing. To assess this the surface aspects hairiness, pilling and fiber splice were determined according to the following tests:
The tests were carried out by 3 persons in a dark room in which a color assessment cabinet “Multilight Datacolor” of Variolux with daylight lamps D65 was provided. The lamps were mounted on an upper side of the cabinet.
For testing hairieness, the test sample was held oblique by the test person and the hairiness was graded between best (grade 5, no hairiness) and worst (grade 1, long protruding fibers up to 2 mm).
The number of pillings (hairy knots on the fabric surface) was assessed using reference samples (knits K3 or K2, or wovens W3 or W2) of EMPA Standard SN 198525 analogous to DIN EN ISO 12 945-2. The reference samples are graded with 1 to 5 and are compared to the test samples. Grade 5 corresponds to a denim having no pillings. The more pillings there are on the surface of the test samples the worse the grade gets. The worst grade is 1.
Fiber splice is created if fibrillic fibers are moved to the surface by scouring. The fibrillic fibers are brushlike ends with stick out if the scoured sample is analyzed under a microscope. For measuring fiber splice, a microscope SM with an X10 eyepiece of UHL Technische Mikroskope was used. For a smooth surface which showed no fibrilles, grade 5 was given. If there was a dense fur of long, curved fiber ends that were partly detached from the surface, grade 1 was given.
In all three tests, intermediate grades were possible.
If samples were subjected to washing, washing was performed according to DIN EN ISO 6330. Tests to assess parameters in the dry state are performed in the conditioned state 65/20. All standards mentioned in this application are included by reference in their entirety.
Samples were prepared as follows. Hereby, weight was determined according to DIN EN 12127. Yarn count in the weft and warp was performed in accordance with DIN 53820-3.
An overview of the material and the properties of samples 1, 2, 3, 5 and 6, which concern a lyocell filament denim, and comparative samples 4 and 7, which concern the benchmark cotton, against which samples 1, 2, 3 5 and 65 are tested, is given in Table 1.
Samples 1, 2, 3, 5 and 6, and Comparative Samples 4 and 7
Sample 1 was a denim 1857-A, in which the warp consisted of bright, untwisted yarn having dtex 500f300 that was made of lyocell filaments. The weft yarn consisted of cotton yarn having a core of Lycra T400. This resulted in a fabric having 70% lyocell yarns, 20% cotton, 8% elastomultiester and 2% elastane. The denim had a weight of 343 g m−2.
Sample 2 was a denim 978-150-814 containing 33% lyocell filaments and 67% cotton. The weight was 143 g m−2. The warp was made of cotton ring yarn Z. The weft was made from yarn dtex 150f90.
Sample 3 was a denim 1857-8, in which the warp consisted of bright untwisted yarn of 100% lyocell filaments, the yarn having a linear mass density of dtex 500f300. The weft was a 100% polyester yarn with an ELAS core of Lycra T400. This resulted in a denim having 356 gm−2 and 70% lyocell, 28% polyester and 2% elastane.
Sample 6 was a denim 1857-CNF containing 70% lyocell, 28% cotton and 2% elastane. Warp consisted of a lyocell filament yarn having 556 dtex. Weft was made from dull cotton ring yarn with an elastane core.
Sample 5 was a denim 978-100-814 of 45% lyocell and 55% cotton. Warp consisted of cotton ring yarn Z and weft consisted of lyocell yarn dtex 100f 60. The material weight was 128 g m−2.
Comparative Sample 4 was a denim 840-814 made from 59% cotton and 41% silk, where the warp yarn was made of cotton and the weft yarn was made from silk. This resulted in a denim that had high softness and smoothness, and a luster. The weight was 171 g m−2.
Comparative Sample 7 was denim 435-4047 consisting of 98% cotton and 2% elastene. Warp was made from cotton ring yarn and weft from cotton ring yarn with a dull elastane core.
Samples 1 to 3 and 6 were benchmarked against comparative sample 7 with respect to washability, resistance against finishing agents, smoothness, softness and luster.
Samples 2 and 5 were benchmarked against comparative sample 4, to compare a lyocell warp denim against a cotton warp denim as both featured the same weft material.
The samples and comparative samples underwent the following finishing steps. After each finishing step, the samples and comparative examples were tested.
Fixation
First, samples 1, 3 and 4 and comparative samples 7 were fixed for 45 seconds at 195° C. and then tested. The results of these tests are summarized in Table 2.
Garment Wash
Samples 1, 2, 3, 5, 6 and comparative samples 4 and 7 were garment-washed as follows.
Fibrillation was carried out with a liquor ratio of 1:60 with 2.5 kg fabric and 150 l liquor at 22 rpm for 20 minutes at 60° C. with maximum heating rate in 2 g/l Persoftal L, 2 g/l soda and 0.3 g/l Lavasperse KDS conc.
Then, the liquor was cooled down to 40° C. and rinsed cold with 300 l, then rinsed warm with 150 l for 5 minutes at 50° C., where heating started right at the beginning of the rinsing, and then again rinsed cold with 300 l.
After rinsing, enzyme washing was carried out at a liquor ratio of 1:60 again with 2.5 kg fabric and 150 l liquor at 22 rpm. The liquor contained 2 g/l Persoftal L, 3 g/l Peristal E and 0.3 g/l Lavasperse KDS conc. The pH value was controlled to be between pH 4.5-5. After heating to 55° C. at the maximum heating rate, the pH value was checked. At pH 5.5, 2 g/l Perizym 2000 were added before adding the enzyme and then the material was processed at 55° C. for 55 minutes. Then the material was heated to 85° C. and treated at 85° C. for 15 minutes.
The liquor was then drained and the material rinsed as follows: First, cold rinsing with 300 l, then warm rinsing with 150 l, where the heating started with the filling of the second rinsing step. Warm rinsing continued for 5 minutes at 50° C. Finally, cold rinsing took place with 300 l.
Reviving took place at a liquor ratio of 1:60 as above using 2% Tubingal RGH, 1% Tubingal RWM, 3 g/l Peristal E at 15 minutes and 40° C. after heating at the maximum rate.
The liquor was then drained and the material was tumble-dryed for 50 minutes at 80° C. and then allowed to cool down for 20 minutes.
After that, the samples and comparative examples were tested as described above. The results are summarized in Table 3.
Strong Bleach
For a final series of tests, samples 1, 2, 3, 5, 6 and comparative samples 4 and 7 were bleached as follows:
Pre-scouring took place at a liquor ratio of 1:60 with 2.5 kg of fabrics and 150 l of liquor. For prewashing, 2 g/l Persoftal L, 0.5 g/l NaOH 100% (1 g/l NaOH 50%) and 0.2 g/l Lava Sperse KDS conc. were used. Pre-scouring was carried out for 20 minutes at 60° C. (maximum heating rate).
After that, cooling down to 40° C. and then cold rinsing with 300 l took place.
Bleaching took place at a liquor ratio of 1:60 and 15 rpm, cold, for 30 minutes, again with 2.5 kg fabrics and 150 l liquor containing 2 g/l Soda and 0.4 g/l Lava Sperse KDS conc. The pH value was checked and maintained at pH 10. As bleaching agent, 3 g/l active chlorine (20 ml/l bleaching lye solution 150 g/l) was used.
The liquor was then drained and the material was cold-rinsed with 300 l and warm rinsed with 150 l as above.
Dechlorination was performed with 2 ml/l hydrogen peroxide 50% for 30 minutes at 40° C.
Then cold rinsing with 300 l, warm rinsing with 150 l for 5 minutes at 50° C. (heating started with the rinsing), and cold rinsing with 300 l was performed.
Then, enzyme washing, followed by rinsing and reviving and tumble drying took place as follows:
After rinsing, enzyme washing was carried out at a liquor ratio of 1:60 again with 2.5 kg fabric and 150 l liquor at 22 rpm. The liquor contained 2 g/l Persoftal L, 3 g/l Peristal E and 0.3 g/l Lavasperse KDS conc. The pH value was maintained between pH 4.5-5. After heating to 55° C. at the maximum heating rate, the pH value was checked. before adding the enzyme and then the material was processed at 55° C. for 55 minutes. Then the material was heated to 85° C. and treated at 85° C. for 15 minutes.
The liquor was then drained and the material rinsed as follows: First, cold rinsing with 300 l, then warm rinsing with 150 l, where the heating started with the filling of the second rinsing step. Warm rinsing continued for 5 minutes at 50° C. Finally, cold rinsing took place with 300 l.
Reviving took place at a liquor ratio of 1:60 as above using 2% Tubingal RGH, 1% Tubingal RWM, 3 g/l Peristal E at 15 minutes and 40° C. after heating at the maximum rate.
Then, the samples and comparative examples were tested as above. The results of these tests are summarized in Table 4.
RESULTS
From Tables 1 to 4, the following is apparent: Comparing samples 2 and 5 to comparative sample 4, the tenacity of the lyocell filament both wet and dry according to the invention is significantly higher than the tenacity of the silk denim of comparative sample 4. Further, yarn strength and yarn elongation both dry and wet are superior in all lyocell filament denims compared to non-lyocell filament cotton denims as exemplified in comparative sample 4 and 7.
Further, it has been demonstrated that lyocell filament denim—as does cotton—withstands even aggressive finishing agents such as chlorine bleach that destroys silk.
With respect to pilling, hairiness and fiber splice, the lyocell filament denim is at least comparable to if not better by one grade than cotton denim before and after garment wash and after bleaching. Further, the lyocell filaments are not subject to the fibrillation that occurs with cotton after washing.
Although cotton still has higher yarn strength before and after garment wash and after the bleaching, yarn strength of the inventive lyocell filament denim is still very good. In particular, the yarn strength of the lyocell filament denim is paired with luster, softness and smoothness that are all superior to cotton denim and can only be achieved with a denim containing silk. However, the latter cannot be bleached.
This becomes clear from the following tests, in which the softness and smoothness are analyzed using the TSA Tissue Software Analyzer (TSA Test), a Handle-O-Meter, and a handfeel panel.
The TSA Test
The TSA test was carried out to verify that the haptic qualities of the lyocell filament denim of samples 1 to 5 are at least equal if not superior to the haptic qualities of the silk denim of comparative sample 4.
The two predominant haptic qualities that are improved by using silk in denim are softness and smoothness. To assess these characteristics objectively, the TSA test was carried out.
The TSA test is described in SchloBer et al., “Griffbeurteilung von Textilien mittels Schallanalyse”, Meilland Textilberichte, 1/2102, p. 43-45, in the emtec publication Gruner, “A new and objective measuring technique to analyze the softness of tissue” (2012), in the TSA Operating Instructions, and in “Neue and Objektive Messtechnik für Softness-Analyse” in avr-Allgemeiner Vliesstoff Report 5/2015, p. 99-101. Originally developed to measure softness and smoothness of tissues and non-wovens using sound spectra, it has been adapted to also evaluate the softness and smoothness of woven fabrics.
The TSA test was performed using a TSA Tissue Softness Analyzer device of emtec electronics GmbH, Leipzig, Germany, and the software ESM which is shipped with the TSA. The TSA measures a sound spectrum which results from pressing and rotating a star-like body against a sample fabric with a defined force. For testing, the fabric is clamped around its perimeter and unsupported otherwise, in particular opposite the rotating body. In the TSA test performed here, the software and its evaluation algorithm was not used. Instead, the sound pressure as measured by the TSA at 7 kHz (TS7) was taken as an objective indirect measure of softness and the sound pressure at 750 Hz (TS750) in the sound spectrum measured by the TSA was taken as an objective indirect measure of smoothness. The sound pressure is automatically given by the TSA as dB V2 rms, where V is the rotational velocity of the rotating body. Using these values directly avoided any problems that may have arisen due to the EMS algorithm having been developed for tissue, and not for woven fabrics. A total of four probes was subjected to the TSA test for each sample.
For testing, a fabric sample of 11 cm diameter was clamped as required by the TSA device and tested without stretching.
Lower values of TS7 indicate higher softness and lower values of TS750 indicate higher value of smoothness.
Handle-O-Meter Tests
The Handle-O-Meter tests were carried out using a Handle-O-Meter testing device of Thwing-Albert Instrument Company, West Berlin, N.J., USA. Sample size was 10 cm×10 cm. The ¼ inch slot was used with a 1,000 g beam and a stainless steel surface. The tests were conducted on samples cond. 65/20.
In both the TSA and the Handle-O-Meter tests, only the right, outer side of the denim was considered. The results are summarized in Table 5.
As a result, the Handle-O-Meter yields two force measurements which are assigned to two orthogonal directions, a machine direction MD which in the chosen set-up corresponded to the warp direction and a cross direction CD which in the chosen setup corresponded to the weft direction. These forces are correlated to the stiffness and smoothness of the tested surface. The force is normalized with the bulk weight of the test sample, resulting in a specific hand in mN m2 g−1.
From Table 5, it follows that the cotton denim of comparative sample 7 s inferior regarding smoothness to samples 1, 3 and 6. Although these lyocell filament denims are stiffer than the cotton denim according to comparative sample 7 before garment wash, they are softer than comparative sample 7 after garment wash.
The silk denim of comparative sample 4 is less smooth then samples 2 and 5, in which lyocell endless filaments are used in the weft instead of silk. Further, the lyocell filament denim is softer than the silk denim of comparative sample 4 before finishing. After finishing, softness of samples 2 and 5 corresponds to the softness of comparative sample 4.
Thus, it can be concluded from the TSA and the Handle-O-Meter tests that the lyocell filament denim according to the invention combines indeed superior softness and smoothness with the capability of being bleached. In addition, the lyocell filament denim has high tenacity. This combination results in a new class of denim fabrics.
Handfeel Panel
To verify the results from the TSA and Handle-O-Meter tests, a handfeel panel was used. The panel was put together consisting of ten independent textile experts. The panel's task was to evaluate objectively the touch of the lyocell filament denim according to the invention in comparison to the comparative examples.
In order to obtain reproducible results independent of the panel members, the handfeel panel operated as follows:
All samples to be tested by the handfeel panel were provided in a format 17 cm×17 cm and were glued to carbon using a double-sided gluing tape approximately 2 cm from the border on the upper edge. The fabric sample was glued onto the cardboard with the right, warp-faced side facing to the front. It was oriented such that the weft direction was horizontal and the warp direction was vertical.
For evaluation of the handfeel a semantic grid was defined by providing contrasting pairs of descriptive adjectives for describing the handfeel. The term of the contrasting pairs which corresponded to the desired quality is considered “best”. Thus, for a fabric, in which smoothness was a desired quality, higher grades will be given than for the opposite quantity, coarseness. Grades ranged from 1 (worst) to 10 (best).
Further, it was prescribed how the evaluation should be done, e.g. by prescribing the motion of the hand over the fabric for assessing smoothness.
Reference sample fabrics of the same construction type (weave) with as close construction parameters as possible and, at the same time, significant differences in handfeel were pre-defined for each word pair. For example, a fabric being considered as having a reference coarseness and a fabric being considered as having a reference smoothness were given to the handfeel panel.
The grades for the respective reference fabrics were fixed at 2 and 8 respectively. Thus, the reference fabric for the worse quality of a word pair had by definition a grade 2 and the reference fabric for the better quality of a word pair a grade 8. Assigning the grades 2 and 8, respectively, allowed to expand the scale during the test if materials with a better or worse quality than the two reference materials were met. Thus, the reference material for coarseness was defined to have a grade 2 and the reference material for smoothness was defined to have a grade 8 in the coarseness-smoothness scale. All other materials which were then tested had to be graded by the handfeel panel relative to the reference material.
For testing the denim samples, the following semantic grid was used:
for assessing touch: cotton-like (grade 2) and silk-like (grade 8);
for assessing consistence: loose (grade 2) and compact (grade 8);
for assessing wearing sensation: stiff (grade 2) and flexible (grade 8);
for assessing surface: coarse (grade 2); and smooth (grade 8).
As reference material for grade 2, comparative sample 7 was used. As reference material for grade 8, comparative sample 4 was used for all word pairs.
The panel was instructed to assess the above characteristics as follows:
To evaluate touch, the sample card had to be taken up with one hand and the fabric was allowed to fold down. Then, the handfeel panel members were asked to grip into the pending fabric in such a way that the right (warp-faced) side of the denim touched the palm;
Consistence describes whether the fabric gives a feel of having a more open or more dens weaving. The sample card was put on table before the individual handfeel panel members. The fabric was taken up with both hands and kneading and stretching the fabric.
Wearing sensation is determined by again lifting the sampe card with one hand and allow the fabric to fold down. The sample card is then shaken to evaluate the falling pattern of the fabric. Then, the fabric is gripped by the free hand for further assessment.
Finally, for the judging the surface feel the cardboard lying was put on a table. The warp-faced surface was assessed by moving the palm of the hand in warp direction and in weft direction.
For each sample fabric and each word pair, the average across the evaluations by the individual handfeel panel members and the deviation from the mean was calculated. The average was used to assess and rank the samples. A summary of the results is given in Table 6.
Luster
Luster of individual yarns usable in a lyocell denim according to the invention was measured using a glossmeter. The results in % reflection of incident light are given in Table 7. For measuring the luster of yarns, they were wound on wrap-over cardboard and luster was measured according to EN 14086-01/2003 at 45°. The luster of fabrics was determined according to TAPPI T480 at 75°. The viewing angle was directed along the yarn direction for measuring yarn luster.
Samples 1, 3, 7, 8 were yarns made from 100% bright lyocell filaments having the linear mass densities indicated in Table 7.
Samples 2, 4, 5, 6 are comparative samples.
Sample 3 had a far superior luster to all other samples and the comparative examples. The luster of samples 1 and 6 was comparable to the denim of comparative sample 7, containing silk.
Luster of the yarn usable for denim was at least 20% reflection.
Thus it can be concluded that the inventive lyocell filament denim also combines a superior luster with resistance against aggressive finishing agents.
Claims
1. A lyocell denim made from weft yarns and warp yarns, wherein at least one of the weft yarns and the warp yarns contains or consists of lyocell filaments.
2. The lyocell denim according to claim 1, wherein the denim is bleached.
3. The lyocell denim according to claim 1, wherein the denim has a TS7 value of no more than 6 in a TSA test in the fixed state and/or after garment wash and/or after bleaching.
4. The lyocell denim according to claim 1, wherein the denim has a TS750 value of no more than 100 in the fixed state and/or after garment wash and/or after bleaching.
5. The lyocell denim according to claim 1, wherein the yarn strength of the yarns containing or consisting of lyocell is at least 25 cN/tex after fixation and/or at least 4.5 cN/tex after garment wash and/or at least 2 cN/tex after bleaching.
6. The lyocell denim according to claim 1, wherein the denim scores at least one at least 15,000 cycles to hole formation in a Martindale abrasion test in the fixed state and 8,000 cycles to hole formation in a Martindale abrasion test after garment wash and/or after bleaching.
7. The lyocell denim according to claim 1, wherein the warp face of the denim has a pilling grade of no worse than 5 in the fixed state and/or no worse than 5 after garment wash and no worse than 5 after bleaching in a Martindale pilling test.
8. The lyocell denim according to claim 1, wherein the yarn elongation of at least one of the warp and weft yarn containing the lyocell filaments is at least 4% after fixation and/or at least 2% after garment wash and/or at least 1% after bleaching.
9. The lyocell denim according to claim 1, wherein the of the denim on the warp face has a hairiness grade no worse than 4 after garment wash and no worse than 3 after bleaching.
10. The lyocell denim according to claim 1, wherein the fiber splice of the denim has a grade of no worse than 4 before and/or after fixation and/or no worse than 4.5 after garment wash and/or no worse than 4.5 after bleaching.
11. The lyocell denim according to claim 1, wherein the specific hand in the direction of the warp and/or weft yarns that combine or consist of lyocell filaments is at least 4 mN m2 g−1 after garment wash and/or at least 3 mN m2 g−1 after bleaching.
12. The lyocell denim according to claim 1, wherein the yarn consisting of or containing lyocell filaments has a luster of at least 20% reflection.
13. A garment comprising a lyocell denim according to claim 1.
14. A yarn comprising lyocell filaments in a denim fabric.
Type: Application
Filed: Sep 20, 2018
Publication Date: Sep 17, 2020
Inventors: Susanne Carls (4860 Lenzing), Martin Neunteufel (New Territories, Hong Kong), Dieter Eichinger (8280 Fürstenfeld), Christoph Schrempf (4701 Bad Schallerbach), Mohammad Abu-Rous (1110 Wien)
Application Number: 16/649,201
