Patent Application
20250043461
The present invention relates to a lyocell fiber comprising a matting agent, the use of said lyocell fiber for the production of a textile fabric and a textile fabric comprising said lyocell fiber.
Cotton is the most widely used natural cellulosic fiber for the production of textile fabrics. Although cotton is a very resistant fiber and can be subjected to aggressive and harsh treatments (e.g., denim laundry, etc.), its mechanical and haptic properties (e.g., handfeel, softness, etc.) are not always ideal in some applications.
Cellulosic man-made fibers can completely or partially replace cotton fibers in many applications. Suitable cellulosic man-made fibers in this regard include regenerated cellulose fibers such as viscose and modal or solvent-spun cellulosic fibers such as lyocell. Lyocell fibers are particularly suitable as a replacement for cotton due to their mechanical properties (such as high strength) and other properties (e.g., moisture management, grip, etc.). Especially in terms of handfeel and softness, lyocell fibers are regarded as superior to cotton. Lyocell fibers, however, have a high gloss which is undesirable for certain applications or for fashion reasons.
It is known from the prior art (WO 2010/144925 A1), that the gloss or sheen of lyocell fibers can be reduced by incorporating TiO2 as a matting agent into the lyocell spinning mass. However, TiO2 is very hard and abrasive, leading to high wear on the parts of the spinning apparatus. To achieve strong matting effects, a large amount of TiO2 needs to be incorporated in the fibers, thus, increasing the wear and reducing the lifetime of the expensive equipment even further.
Therefore, the invention has the object of providing a lyocell fiber which has a similar appearance to cotton, while retaining its mechanical strength and other properties, such as handfeel, softness, etc., that can be produced cost-efficiently.
The invention achieves the stated object in that the matting agent may contain between 2 wt.-% and 5 wt.-% BaSO4 and less than 1 wt.-% TiO2, with respect to fiber weight, whereby the matting agent is incorporated in the fiber matrix in the form of particulates.
By incorporating 2 to 5 wt.-% BaSO4 particulates in the fiber matrix, the disadvantages of the prior art can be overcome.
Furthermore, the present invention also solves the stated object by using the inventive fiber for the production of a textile fabric according to claim 6.
Even further, the present invention solves the stated object by providing a textile fabric according to claim 8 and a textile artic according to claim 14.
Preferred embodiments of the invention are set out in the dependent claims.
The embodiment variants of the invention are described in more detail below with reference to the drawings:
According to a first embodiment of the invention, the matting agent comprises between 2 wt.-% and 5 wt.-% BaSO4 and less than 1 wt.-% TiO2, whereby the matting agent is incorporated in the fiber matrix in the form of particulates. The wt.-%-values of BaSO4 and TiO2 are specified with respect to the fiber weight.
Due to the soft, non-abrasive mechanical properties of BaSO4, the wear on all parts of the spinning device can be reduced, thus, increasing the service life of the spinning device. Furthermore, it has been found, that a combination of a low amount of TiO2 (less than 1 wt.-%) and 2 to 5 wt.-% BaSO4 leads to a strong matting effect in the fibers, which results in an appearance similar to cotton. Even after dyeing the fibers, the matting effect still remains, rendering the inventive fibers suitable for all kinds of textile applications, such as denim fabrics and the like. While the desired matting effect can be achieved by the inventive fibers, the softness and handfeel, known from textiles made from lyocell fibers, as well as the mechanical properties remain essentially unchanged. Thus, a lyocell fiber with matte appearance can be provided without sacrificing the mechanical fiber properties, which can also be produced cost-efficiently.
In a preferred embodiment of the invention, the matting agent comprises between 3 wt.-% and 5 wt.-% BaSO4 and between 0.5 wt.-% and 0.9 wt.-% TiO2, with respect to the fiber weight. By reducing the amount of TiO2 to less than 0.9 wt.-%, the abrasive effect on the spinning machine parts can be minimized, while providing a strong matting effect in combination with 3 to 5 wt.-% BaSO4.
In an even further preferred embodiment, the matting agent comprises between 3.5 wt.-% and 4.5 wt.-% BaSO4, more preferably between 3.8 wt.-% and 4.2 wt.-% BaSO4, and between 0.6 wt.-% and 0.8 wt.-% TiO2, with respect to the fiber weight.
In a further embodiment the BaSO4 particulates may have a particle size distribution defined by an x50 lower than 1.5 μm and an x99 lower than 4 μm.
In an even further embodiment, the TiO2 particulates may have a particle size distribution defined by an x50 lower than 1 μm and an x99 lower than 2 μm.
In the context of the present invention, the x50-value represents the mean particle size of the particle size distribution, while the x99-value represents the particle size, where 99% of all particles are smaller than x99.
Particle size distribution can be measured on the fiber via photomicrography in combination with digital image analysis.
The matting agent is added to the cellulose solution (i.e., the lyocell spinning mass) prior to spinning of the fibers. Therefore, the matting agent is preferably added to the spinning mass in the form of a suspension, where BaSO4 and optionally TiO2 particulates are dispersed in water beforehand with the help of a dispersion device. By supplying the particulates in the form of above-mentioned particle size distributions, a very even distribution of the particulates in the spinning mass and subsequently in the fibers is possible.
It has been found, that adding BaSO4 particulates as specified above to the spinning mass resulted in a uniform distribution of the particulates in the fibers, leading to lyocell fibers with strong mechanical properties (e.g., high tenacity). The particulates thereby have been found to be predominately arranged in the center of the fiber core. A weakening of the fiber structure, increased fibrillation or abrasive properties on the fiber surface could not be observed. Thus, an improved matted lyocell fiber with high mechanical strength may be provided.
Advantageously the inventive lyocell fibers exhibit a titer from 1.1 dtex to 2.5 dtex, preferably from 1.3 dtex to 2.0 dtex.
Furthermore, the inventive lyocell fibers as described above may advantageously be used for the manufacture of a textile fabric.
According to one embodiment of the invention, the manufacture of the fabric comprises spinning a yarn using the lyocell fiber and dyeing at least a part of the yarn, more particularly with an indigo dye.
When dyeing lyocell fibers or fabrics made thereof, in particular with indigo dyes (indigo dyestuff), the natural shine of the fibers is further increased. Lyocell fibers have a natural shine due to the intrinsic fiber properties (e.g., smooth cross-section). The combination of lyocell fibers with brilliant colors (e.g., indigo, reactive, direct, or other dye-colors) bring about a shiny fabric surface. As indigo lyocell fabrics have more sheen than indigo cotton fabrics, a matte version of such lyocell denim fabrics is sought after in the fashion industry.
In the present invention, the term “denim” refers to a category of fabrics, which are not only characterized by the weave- or binding type but show a characteristic combination of properties. While for traditional denim fabrics a twill weave was used, other types of textile bindings (such as canvas or satin weave) have also become established in the modem textile industry. However, all denim fabrics are characterized by a robust woven fabric with dyed warp yarns and undyed weft yarns, whereby the warp is surface dyed, but the core of the warp remains undyed, which results in fading characteristics typical for denim. Due to the warp-faced weaving, denim is colored on the outside and white (i.e., undyed) on the inside. Thereby, preferably indigo dyes are used for dyeing the warp.
A very common denim fabric is a woven fabric in which the warp contains indigo dyed cotton yarn while the weft contains undyed cotton yarn. Variations in denim fabric are however limitless e.g.: the weft yarn may contain dyed fiber (e.g., spun-dyed), the indigo dyed warp yarn can be overdyed with sulfur dyes, etc.
Alternative denim fabrics are also limitless, such as knit fabrics (e.g., circular, flat, or seamless knits) containing indigo dyed cotton yarn. Alternative to cotton, other cellulosic yarns (such as lyocell, modal, viscose, etc.) can also be used for indigo dyeing. Denim fabrics have the ability to get wash-down/used look during garment laundries (ozone, laser, etc.) thanks to indigo and other dischargeable dyestuffs.
By using the inventive fiber for spinning a yarn and subsequently dyeing at least part of the yarn, the advantages of the inventive fiber may be fully utilized. In particular, it has been found that the inventive fibers provide a matte appearance similar to cotton, even after dyeing. This is further demonstrated on behalf of several examples below.
In one embodiment of the invention, the first and second yarn may be interweaved to form a woven fabric, where the first yarn is a warp, and the second yarn is a weft or vice-versa.
In particular, the woven fabric may be a twill fabric, a canvas fabric, a statin fabric, or the like.
In a further embodiment, the woven fabric may be a 2/1 twill fabric with a basis weight between 100 g/m2 and 300 g/m2, preferably between 150 g/m2 and 250 g/m2, more preferably between 175 g/m2 and 225 g/m2. The warp having between 20 and 60 ends/cm, preferably between 30 and 50 ends/cm, more preferably between 32 and 48 ends/cm. The weft having between 10 and 35 picks/cm, preferably between 15 and 30 picks/cm, more preferably between 18 and 28 picks/cm. Such a twill fabric may show excellent opacity and matte properties in both undyed and dyed state (using a wide variety of different dyes). Further, such fabric shows a high smoothness and softness, comparable to standard lyocell fibers.
In a further embodiment, the second yarn also comprises lyocell fibers according to any of claims 1 to 5. In an alternative embodiment, the second yarn can also comprise cotton fibers or other cellulosic fibers, such as man-made cellulosic fibers, or synthetic fibers, such as polyester, etc.
In a further embodiment, the fabric has a wrinkle recovery rate of 60% or greater. The wrinkle recovery rate is measured according to the standard AATCC 202-2020 (American Association of Textile Chemists and Colorists) using a Phabrometer.
In a further embodiment, the textile fabric has an opacity of 0.75 or greater, more preferably of 0.8 or greater.
In a preferred embodiment, the fabric is a denim fabric, and the first yarn comprises an indigo dye on its surface. Due to the matted effect of the inventive fibers, denim fabrics made of said fibers have a solid matte effect, which can remain even after dyeing the fabrics with indigo dyestuff. Thus, the inventive fiber is perfectly suited for the application in indigo textiles, such as denim.
In another preferred embodiment, the first and or second yarn are reactive dyed, direct dyed or vat dyed. Besides dyeing with indigo dyestuff, the advantages of the inventive fibers are also obtained when dyeing with reactive dyes, direct dyeing or dyeing with vat dyes.
Such fabrics as described above may advantageously be used in textile articles, such as jeans, shirts, t-shirts, dresses, trousers, jackets, or the like.
In the following, the invention is further demonstrated on examples of textiles made from the inventive lyocell fibers.
For the evaluation of the fiber properties, the textile fabrics are compared with equivalent fabrics made from standard (unmatted) lyocell fibers and cotton fibers.
In a first example a white undyed woven twill fabric was produced from a lyocell (CLY) fiber containing approx. 4 wt.-% BaSO4 and approx. 0.75 wt.-% TiO2 as matting agent according to the present invention (furthermore referred to as “CLY Matte twill fabric”).
The BaSO4 particulates exhibited a particle size distribution characterized by: x10=0.42 μm, x16=0.56 μm, x50=1.09 μm, x84=1.78 μm, x90=2.05 μm and x99=3.46 μm. The TiO2 particulates exhibited a particle size distribution characterized by: x10=0.15 μm, x16=0.18 μm, x50=0.44 μm, x84=0.93 μm, x90=1.08 μm and x99=1.49 μm.
The lyocell fiber thereby had a titer of 1.7 dtex and a staple length of 38 mm.
Fabric construction was a 2/1 twill with a basis weight of approx. 200 g/m2, warp: 38 ends/cm, weft: 20 picks/cm. Yarn properties were approx. Ne 20 for warp and Ne 24 for weft.
For comparison, a standard lyocell fiber with a titer of 1.3 dtex and a staple length of 38 mm was used to produce a 2/1 twill fabric with properties as defined above (referred to as “CLY Std. twill fabric”).
Furthermore, for comparison, a cotton 2/1 twill fabric with properties as defined above was produced (referred to as “Cotton twill fabric”).
In a second example, a denim woven twill fabric was produced from a lyocell fiber containing the same amounts and characteristics of matting agents as specified in Example 1 (referred to as “CLY Matte denim fabric”).
The lyocell fiber also had a titer of 1.7 dtex and a staple length of 38 mm.
Fabric construction was a 2/1 twill with a basis weight of approx. 200 g/m2, warp: 42 ends/cm, weft: 25 picks/cm. The warp has been indigo-dyed and the weft is left undyed.
Again, for comparison, a standard lyocell fiber with a titer of 1.3 dtex and a staple length of 38 mm and a cotton fiber were both used to produce denim fabrics (referred to as “CLY Std. denim fabric” and “Cotton denim fabric”) with properties as defined above.
First, the matte property of the fabrics of Examples 1 and 2 were evaluated visually by conducting an internal survey and, second, by analyzing the CIELCh color space (the CIELCh color space is defined by the International Commission on Illumination).
In
The white cotton twill fabric is perceived by 43% of people as dull (1) and by 41% of people as more or less dull (2). 0% of people perceived the cotton twill fabric as shiny (5).
The inventive matted lyocell twill fabric according to Example 1 is perceived by 43% of people as neither dull nor shiny (3) and by 22% of people as more or less dull (3). 7% perceived it as dull (1), while 10% perceived it as shiny (5).
The standard lyocell twill fabric is perceived by 47% of people as more or less shiny (4) and by even 12% as shiny (5). 0% considered the standard lyocell fabric as dull (1).
This survey clearly shows that the inventive fiber produces a solid matting effect when used to manufacture a twill fabric. Although cotton is perceived as even more dull, a significant improvement over standard lyocell fabrics can be discerned.
In
Similar to what has been described above, a significant improvement in matting effect of the inventive fiber can be discerned from the survey results. In the denim fabrics according to Example 2, the effect is even more pronounced as for the white twill fabric according to Example 1. While for the standard lyocell denim fabric, the shine is increased due to the dyeing, the inventive matted lyocell fiber retains its dull or matte effect even after dyeing with indigo, making the appearance overall more similar to cotton.
In the following, the matte properties of Example 1 and Example 2 fabrics are analyzed by means of CieLCh color space. All measurements are performed using a D65 light source under 100 angle.
The L*C*h color space is preferred by some industry professionals because its system correlates well with how the human eye perceives color. It has the same diagram as the L*a*b* color space but uses cylindrical coordinates instead of rectangular coordinates.
In this color space, L indicates lightness, C represents chroma, and h is the hue angle. The value of chroma C is the distance from the lightness axis L and starts at 0 in the center. Hue angle starts at the +a axis and is expressed in degrees (e.g., 0° is +a, or red, and 900 is +b, or yellow).
The L-axis describes the lightness (luminance) of the color. Positive L means that product has lighter color. Negative L means that product has darker color.
The C-axis describes the chroma of a color. Higher values mean brighter color and lower value means duller color.
The h-axis describes the wrinkle hue.
In Table 1, the CieLCh-Values for inventive lyocell matte, lyocell std. and cotton denim fabrics according to Example 2 are presented. The values are represented as A-values with respect to the lyocell std. values as a reference. From said A-values, changes in the parameters can be easily discerned.
From Table 1, it becomes obvious, that the lyocell matte denim fabric according to the present invention has less chroma (ΔC=−0.53), thus is duller, than the denim fabric from standard lyocell fibers.
For further evaluation, the white twill fabrics according to Example 1 were dyed with either red, black, and blue reactive dyestuffs, blue, green, and orange direct dyes, or yellow and red vat dyes at same dyeing conditions but at separate dyebaths, so that fiber property was the only differing parameter. Table 2 shows CieLCh values of lyocell matte, lyocell standard and cotton fabrics, respectively for the different dyes. Higher L-values of inventive lyocell matte fabric for almost all dyes/colors than for lyocell standard fabric proves less lightness/shininess of matte lyocell compared to standard lyocell. Dyed cotton fabric was found to have least lightness/shininess compared to matte lyocell and standard lyocell.
The test was carried out on the sample on the right side of the goods (marked by the weaver). 10 measurements per angle setting were carried out on the sample material on a non-reflective background (black spectrometer paper). The measurements were made longitudinally, diagonally, and transversely to the warp/weft direction of the material. The sample was air-conditioned at 20° C., 65% relative humidity for at least 24 h prior to the measurements.
The higher the value given in
As can be clearly seen from
A similar observation can be made for denim fabrics according to Example 2 as depicted in
Furthermore, the opacity of fabrics using the lyocell fiber containing matting agents according to the present invention is analyzed.
Opacity in the context of the present invention refers to the opacity or opaqueness of the investigated textiles. The opacity is indicated as a unitless number between 0 and 1 (or 0% and 100%), whereby perfect transparency is present at 0, which decreases with increasing value. At 1, the respective material is completely opaque.
In all measurements, opacity has been determined at a wavelength of 570 nm with a Konica Minolta CM600d spectrophotometer (Q425F168, Inv. No. 71559) including accessory set for calibration. Enclosed computer (laptop) with SpectramagicNX software was used for evaluation. Measurements have been calibrated using TQC-Test (Chart Art. No. VF2345 Batch No. 227270) and Green tile CM-A101GN.
Opacity values were determined with the above setup following NWSP060.4.R0.20 (defined for measuring opacity of nonwovens).
In Table 3, the measured opacity-values for undyed twill fabrics according to Example 1, as described above, are shown. Therein it can be discerned, that the twill fabric made from the inventive lyocell matte fibers has the highest opacity, similar to the twill fabric made from cotton. Both have a significantly higher opacity than the fabric made from lyocell std. fibers.
Furthermore, in Table 4, the measured opacity-values for single knit jersey fabrics (Ne 20/1 ring spun, 110 gsm) made from the lyocell matte fiber according to the invention and from lyocell standard fiber are shown, whereby the fabrics have been dyed with different dyes.
Dyeing of the fabrics was performed at different dye baths using the same recipes so that there is no difference between fibers regarding dye uptake.
As can be discerned from Table 4, colored jersey knit fabrics from lyocell matte fibers show consistently higher opacity values than similar jersey knit fabrics made from lyocell standard fibers.
In
In
The SEM images clearly show that the fiber surface is smooth without any visible defects caused by the incorporation of matting agents. This can also be discerned from the cross-section images, which show a smooth regular shape and cross-section without visible defects, as would be expected from lyocell fibers. Thus, the matting agent is finely dispersed in the fiber matrix and does not form agglomerations or the like.
Further, tensile strength and elongation of the lyocell matte fibers according to the invention and comparative lyocell standard fibers were tested according to the BISFA standard (“Testing methods for viscose staple fibers).
Strength- and elongation values of the fibers are shown in Table 5. Thereby it can be discerned, that lyocell matte fibers have fiber strength and elongation similar to lyocell standard fibers without matting agents. Only a 6% decrease in fiber strength can be observed.
Furthermore, the strength and elongation of yarns made from lyocell matte fibers according to the present invention and comparative lyocell standard and cotton fibers is evaluated. Yarn configurations for all fibers were: Ne 20 (Nm 34, 300 dtex), 661T/m. Strength- and elongation-values are given in Table 6, respectively.
From the values it can be clearly discerned, that yarn strength and elongation of the lyocell fibers containing matting agents still remain high and exceed that of cotton.
Softness and surface properties (roughness/smoothness) of undyed woven twill fabrics (Ne 20/1, 110 gsm) using the lyocell matte fiber (CLY Matte) according to the present invention and comparative fabric using standard lyocell fiber (CLY Std.) and cotton fiber were measured by a Tissue Softness Analyzer (TSA type B0458) device manufactured by Emtec Electronic (Germany). The analysis of fabrics by use of TSA is well known to the skilled person (see e.g.: Abu-Rous et al., J Fashion Technol Textile Eng 2018, S4).
The rotating part of the TSA generates noise while moving over the fabric surface, which is captured by a microphone and analyzed into its amplitude signals. In the resulting sonic spectrum, the signal peak (in dB V2 rms) at 750 Hz (TS750) is a measure for the fabric vibration under the rotating part and should correlate with fabric smoothness, while the peak at 6500 Hz (TS7) occurs through the vibration on the rotating part itself while moving above the fabric surface and is considered a measure for the softness of surface fibers. The lower the generated noise, the smoother resp. softer is the fabric (higher TS750 peak means higher roughness, lower TS7 peak means higher softness).
Thus, it is demonstrated, that the inventive lyocell fibers comprising the matting agent according to the claims can maintain the high softness and smoothness as usually expected for lyocell fibers.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21199580.8 | Sep 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/076890 | 9/28/2022 | WO |
