CN115427616A - Spun-dyed cellulosic fibers - Google Patents

Abstract

The present invention relates to cellulosic fibers containing an incorporated oxidized form of indigo pigment, wherein the fibers are made according to the modal process, exhibit a tenacity (conditioned) of at least 29cN/tex, and a wet modulus of at least 5cN/tex/% according to BISFA. Furthermore, the invention relates to the manufacture and use of such fibres in fabrics.

Description

Spun-dyed cellulosic fibers

The present invention relates to cellulosic fibres containing an incorporated oxidised form of indigo pigment, wherein the fibres are made according to the modal process and exhibit a tenacity (conditioned) of at least 29cN/tex as measured according to BISFA at an elongation of 5%, and a wet modulus of at least 5cN/tex/% as measured according to BISFA. Furthermore, the invention relates to the manufacture and use of such fibers in fabrics and garments (footwear and the like).

Prior Art

Natural or man-made cellulosic fibers and articles made therefrom, such as yarns or fabrics, can be dyed using a variety of dyes. The most common type of dye used is a reactive dye, wherein the dye chemically reacts with hydroxyl groups on the cellulose molecules that make up the fiber. This results in covalent bonds which impart high fastness properties to this type of dye. Reactive dyes are most commonly used because of their high fastness and full color range. In addition to reactive dyes, the cellulose fibers may also be colored with other dye types, such as direct dyes, vat dyes or sulfur dyes.

One of the most important vat dyes is indigo (CI vat blue 1).

Indigo is used to colour the yarn which is then used to produce indigo denim fabric. The spun warp yarns are first made into a beam (beam) and then dyed with indigo (CI vat blue 1) before being woven into a fabric. Preparation of the yarn is typically a simple scouring to remove any impurities, but may include such chemical treatments as caustic soda. Indigo can be applied by a variety of methods, but most are applied to the yarn by rope or slasher application.

Indigo dyes are insoluble in water and are therefore first converted to the soluble, so-called "leuco" form using an alkaline reducing system of sodium hydroxide and sodium dithionite. In the case of cellulose, this leuco indigo has a low substantivity, so that only light shades of depth can be obtained by the exhaust process. Thus, indigo is applied in a series of impregnations, with intermediate mudjacking and atmospheric oxidation. By repeating this process, the dyes are applied layer by layer to the substrate (substrate) to obtain a deep dyeing property with relatively low rub fastness.

In rope dyeing, the cellulose warp yarns extend in the form of ropes along the extent. The set of yarns is typically 300-400 warp yarns (ends), known as a rope or cord. In slasher dyeing, the warp yarns are spread apart flat and aligned parallel to each other. Indigo can also be dyed batchwise or in the form of fabrics, usually continuously. Skein batch dyeing of yarns can be carried out in a tank in repeated short dips followed by squeezing and atmospheric oxidation, although these applications are far less common.

The most common denim comes from colored warp yarns, while the weft yarns remain white. As a result of the warp-faced twill weave, one side of the woven fabric is dominated by blue warp yarns and the other side by white weft yarns. The indigo dyeing process, in which the core of the warp yarn remains white, produces the marked fading characteristics of denim.

Other vat dyes and sulfur dyes may also be used to color the yarn or fabric.

Dyes used to color cellulosic fibers and articles made therefrom are generally not used to color fibers (e.g., viscose, modal) during fiber spinning. The incorporation of reactive dyes into the spin dope used to produce lyocell fibres has been found to adversely affect the stability of the process and is unacceptable for reasons of process safety.

Indigo dyed denim has some properties which are to some extent and disadvantageous for some requirements (although they are indeed very popular with others): since the dye is present only on the outer surface of the cotton fiber, the rubbing fastness and washing fastness are poor. Denim articles show a wash-off effect (wash-down effect) after washing and laundry treatment (bleaching, oxidation, etc.) due to the loss of indigo.

Denim laundry various methods are used to impart various effects to denim fabrics, such as bleaching, abrasion and fading appearance. Historically, bleaching chemicals such as hydrogen peroxide, hypochlorite and permanganate have been used primarily. The latest sustainable options for denim laundry are laser and ozone treatment. The laser sublimates the dye from the surface of the fabric to present a faded and used appearance and marks certain design patterns. Ozone gas is used to bleach denim garments due to its high oxidation potential.

Another very big drawback is the dyeing process of ordinary denim products: dyeing with indigo is carried out on the yarn. This process is not only very expensive, but also can severely contaminate the environment, especially the waste water of dye plants.

One approach to solving this problem is to incorporate indigo pigment in its oxidized (i.e. blue) form, of natural or synthetic origin, or other dye types that mimic the color and laundry washing effect of indigo, into viscose during spinning. Such fibers are sold under the name "viscose indigo". Viscose indigo, however, has a relatively low mechanical strength, especially in the wet state. Thus, viscose indigo fiber is typically blended with a significant amount of polyester fiber. Garments made using such blended yarns exhibit some significant disadvantages: due to the high synthetic fiber content, the wearing comfort is reduced compared to garments containing 100% cellulose fibers. Furthermore, it may be desirable to dye the polyester fiber component; however, this type of fiber requires a different type of dye, which is not suitable for cellulose.

Problem(s)

In view of the prior art, a problem to be solved is to provide a fiber which is suitable for making denim look but shows improved rub fastness while providing good wearing comfort for garments made therefrom.

Description of the invention

It is an object of the present invention to provide cellulosic fibers containing an incorporated oxidized form of indigo pigment, wherein the fibers are made according to the modal process and exhibit a tenacity (conditioned), also referred to as "force to break", of at least 29cN/tex as measured by BISFA at an elongation of 5%, and a wet modulus of at least 5cN/tex/% as measured by BISFA. Both properties were measured according to the method described in the BISFA brochure "Testing methods videos, model, lyocell and acetate stage fibers and tows",2004 edition. In a preferred embodiment of the invention, the fibers according to the invention comply with the requirements for modal fibers according to BISFA (see BISFA terminology, 2009 edition), which comprises: these mechanical properties depend on the titer of the fiber. This means that a fiber according to the invention of 1.3dtex will show a tenacity (conditioned) of at least 31.4 cN/tex and a wet modulus (wet) of at least 4.39 cN/tex/% at an elongation of 5%. A fiber according to the invention of 1.5 dtex at an elongation of 5% will exhibit a tenacity (conditioned) of at least 30.61 cN/tex and a wet modulus (wet) of at least 4.8 cN/tex/%.

Preferably, the indigo pigment contains a very low aniline content of less than 50ppm, preferably less than 25ppm, even more preferably less than 20ppm.

Preferably, the fibers according to the invention contain 0.5 to 4.0% (w/w) of indigo pigment, especially preferably 1.8 to 3.0% (w/w), relative to the total weight of the oven dried fibers. Lower indigo pigment content does not provide sufficiently deep fiber color and higher indigo pigment content reduces the mechanical strength of the fiber.

The fibers can be made by a process similar to the FR pigmented cellulose fiber process disclosed in AT287905B as follows: viscose with a cellulose content of 4 to 7%, a NaOH content of 5 to 10%, a carbon disulphide content of 36 to 42% (calculated with respect to the cellulose) and a modifier content of 1 to 5% (calculated with respect to the cellulose) is prepared. It shows a spinning gamma value of 50 to 68, a spinning viscosity of 50 to 120 ball drop seconds; and an alkali ratio of viscose ready for spinning (= cellulose concentration/alkali content) of 0.7 to 1.5. The oxidized form of the indigo pigment with very low aniline content is incorporated during spinning in the form of a pigment concentrate dispersion in an amount suitable to obtain a final concentration of the indigo pigment in the fiber of 0.5% to 4.0% (w/w), particularly preferably 1.8% to 3.0% (w/w), relative to the total weight of the absolutely dry fiber. The viscose containing indigo is extruded through a spinning nozzle into a spinning bath exhibiting a temperature of 34 to 48 ℃ and a spinning bath concentration of: h ₂ SO ₄ =68-90g/l, Na ₂ SO ₄ =90-160g/l, ZnSO ₄ =30-65g/l. The coagulated strands were drawn from the spinning bath at a speed of 15 to 60 m/min. The coagulated drawn wire was further thoroughly cleaned and cut into pieces having a fineness of 1.3dtex and a fineness of 38mmShort fibers of length. For the examples in this patent, these fibers are hereinafter referred to as "modal indigo".

According to the invention, the indigo pigment is incorporated into the entire cross-section of the fibre. That is, a photomicrograph of a cross-section of the fiber shows pigment distributed over the entire area of the cross-section, whereas conventionally dyed cellulosic fibers show only indigo pigment on the outer surface of the fiber. Surprisingly, the bleeding rate of the indigo pigment in the fiber according to the invention is significantly lower than the bleeding rate of the indigo pigment in viscose indigo.

Another aspect of the invention is the use of a fiber according to the invention as described above for the manufacture of fabrics (knits, wovens, seamless fabrics, etc.) having a denim appearance (obtained by laundry effects such as laser and ozone). Preferably, such colored fibers are used in the warp of a woven fabric, while the greige (i.e., undyed) fibers are used in the fill of the woven fabric to simulate a conventional denim fabric.

Such colored fibers may be used in the weft yarns, while the warp yarns may comprise the commonly used indigo-dyed cellulose fibers, in order to impart different aesthetic effects and wearing comfort to the consumer. In this product, the indigo-colored modal fiber is located on the skin side by imparting softness (i.e., comfort) to the modal fiber. Wash-off of the warp side will appear different from using the natural (i.e. undyed) fibers, resulting in a darker shade on the warp side.

Preferably, the fabric is a woven fabric having the appearance of denim comprising 40% to 100% (w/w) of the fibre according to the invention as described above.

In a preferred embodiment of the invention, the fabric exhibits a crock fastness according to ISO 105-X12:2016 4.0 to 5.0. Typical yarn dyed denim shows a crock fastness of about 3.0.

In a preferred embodiment of the invention, the fabric is a woven fabric. Preferably, the fabric contains 80% to 100% (w/w), preferably 95% to 100% (w/w), of the fibers according to the invention in the warp. This will give the typical denim appearance, especially a twill weave, where one side of the woven fabric is dominated by blue warp yarns and the other side by white weft yarns. The fabric may exhibit a shrinkage of less than 5.0% when washed according to ISO 6330 and tested according to Ö NORM ISO 3759.

In another preferred embodiment of the invention, the fabric is a knitted fabric. Preferably, the fabric exhibits a shrinkage of less than 12.0% when washed according to ISO 6330 and tested according to Ö NORM ISO 3759.

Yet another aspect of the present invention is a method of making a fiber according to the present invention, as described above, comprising the steps of:

a. preparing a modal spinning solution and preparing a modal spinning solution,

b. the indigo pigment is prepared in an oxidized form,

c. addition of indigo pigment to Modal spinning solution

d. Extruding the solution of step c into a coagulation bath according to the modal spinning process.

The pigments used in the process of the present invention can be manufactured, for example, according to WO 2004/024826 A2. Common modal spinning conditions as described in, for example, patent AT287905B or WO 2011/026159 A1 can be applied.

Preferably, the indigo pigment is added to the modal spinning solution in the form of a concentrate, the content of the indigo pigment in the concentrate suspension being, for example, 20% (w/w). For example, if a concentrate containing 20% (w/w) indigo pigment is used, in order to obtain 0.5% to 4.0% (w/w) indigo pigment in the final fiber, a concentrate suspension of 2.7% to 20.0% ((w/w) with respect to dissolved cellulose) must be added to the modal spinning solution.

It was surprisingly found that the fibers according to the invention also have a much lower bleed rate than other dope-dyed modal fibers. The color penetration of modal indigo is also lower than viscose indigo, while the mechanical textile properties of modal fibers are much higher compared to viscose fibers.

Furthermore, it has surprisingly been found that if an indigo pigment in oxidized form is incorporated into the cellulose rayon according to the invention, it is very stable in its typical blue color, whereas if it is applied to, for example, cotton using the conventional denim indigo dyeing process, the dye is very sensitive to oxidation.

Denim laundry

With the aid of a conventional hypochlorite bleaching treatment (e.g. 2g/l soda, 3g/l sodium hypochlorite; 30min at 30 ℃, warm and cold water rinse, 0.8g/l H) which is commercially used in denim laundry ₂ O ₂ Dechlorination at 40 ℃ for 30min, rinsing with warm or cold water) and a powerful hydrogen peroxide bleaching treatment (e.g. 4g/l hydrogen peroxide, 4g/l sodium hydroxide, 90 ℃ for 30min, followed by neutralization (1 g/l acetic acid)), little effect was observed.

Increasing the hypochlorite concentration (4 g/l sodium hypochlorite, 40 ℃,10min, then neutralizing (3 g/l sodium thiosulfate, 30 ℃,10 min)) may have a slight effect. However, such treatment is not recommended in view of the large amount of chemicals used in order to produce very little effect on the product.

However, denim laundry conditions using permanganate (e.g., 4g/l potassium permanganate, 40 ℃,10min, then neutralized (2 g/l metabisulfite, 40 ℃,10 min) are very effective for removing indigo in dope dyed modal indigo products.

Local bleaching with potassium permanganate also produced significant visual results by spraying 20g/l potassium permanganate solution and drying in air (or 80 ℃ in a tenter dryer) and then washing the fabric in sodium dithionite solution (1-4 g/l) at 40 ℃ for 20 minutes.

Significant visible results were also obtained on the fibers according to the invention by ozone treatment (50% G2Lab machine, ozone gas concentration: 45 gr/Nm3, 15min,30min or 45 min) and laser marking (using Jeanologia machine), for example 40-150 tpx (per pixel time).

Household clothes washing machine

The domestic laundry washing of conventional denim articles (water and detergents) results in the loss of indigo dye from the fabric, because of the fading phenomenon that occurs after each washing cycle. Therefore, conventional denim products do not have color retention (color retentions) after home laundry washing.

Indigo dye trapped in dope dyed modal indigo fibre is not lost in home laundry washing. Our study showed that 30 home laundry washes did not result in color loss of the dope dyed modal indigo garments, and thus color retention was demonstrated. In the home laundry wash test, a commercial home laundry detergent (Fewa Color) was used and spun dyed modal indigo garments (knitted and woven) were washed at 40 ℃ and plate or drum dried.

Short fading, wash-off or similar appearance of dope dyed modal indigo products can only be produced by commercial denim laundering (laser, ozone, permanganate, etc.). This garment effect/appearance will be maintained over the consumer life of the garment as the indigo will not be removed with the home laundry wash. This property distinguishes indigo spun-dyed modal products from conventionally dyed indigo dyed products on the market.

Preferred uses of the fibers according to the invention are:

denim-type woven fabric structure, in particular having an areal weight of more than 100 g/m ² The denim fabric of (1).

Woven type fabric structure, light weight fabric, especially having an areal weight of more than 80 g/m ² Shirts, dresses, etc

Knitwear, including seamless, particularly tops, bottoms, undergarments, and other garments, shoes, bags, and the like, made of or containing textile fabrics.

In all these applications, modal indigo shows much better properties than viscose indigo, since it has a lower shrinkage and a higher strength. In all these applications, the low bleed tendency of the fibers according to the invention may be an advantage.

The invention will now be illustrated by way of examples. These examples are not intended to limit the scope of the present invention in any way. The invention also includes any other embodiments based on the same inventive concept.

Examples

Example 1:production of indigo-containing spun-dyed modal fibers:

the incorporated cellulose fibers were made by a process similar to the FR pigmented cellulose fiber process disclosed in AT287905B as follows:

viscose with a cellulose content of 6%, a NaOH content of 7%, a carbon disulphide content of 39% (relative to the cellulose) and a modifier content of 3% (relative to the cellulose) was prepared. It showed a spinning gamma value of 57 and a spinning viscosity of 80 ball drop seconds. 2.3% (w/w) (referred to the cellulose content of the spinning solution) of an oxidized form of indigo pigment with a very low aniline content is incorporated during spinning in the form of a pigment concentrate which contains 20% (w/w) of the pigment. The viscose containing indigo was extruded through a spinning nozzle into a spinning bath exhibiting a temperature of 38 ℃ and a spinning bath concentration of: h ₂ SO ₄ =72g/l, Na ₂ SO ₄ =120g/l, ZnSO ₄ =60g/l. The coagulated strands were drawn from the spinning bath at a speed of 45 m/min. The solidified drawn wire was further thoroughly washed and cut into short fibers having a fineness of 1.58dtex and a length of 38mm. At 5% elongation, the tenacity (conditioned) was 32.1 cN/tex and the wet modulus (wet) was 5.5 cN/tex/%. The elongation at break was 15.5%. All mechanical properties were measured according to the method described in the BISFA brochure "Testing methods vision, model, lyocell and acetate stage fibers and tows",2004 edition. For the examples in this patent, these fibers are hereinafter referred to as "modal indigo".

Example 2: properties of the Fabric containing the fibers according to the invention and the Properties thereof

Using the fibers of example 1, three fabrics were prepared as follows; the yarn of fibers was spun by a rotor spinning machine:

2.a: denim bottom heavy fabric

Warp yarn: modal indigo yarn, ne 11

Weft yarn: cotton/elastic fiber (98%/2%) yarn, ne 15

3/1 RHT fabric structures; 7 warp yarns/cm, 20 weft yarns/cm

2.b: heavy shirt fabric

Warp yarn: modal indigo yarn, ne 24/1

Weft yarn: cotton, ne 15

2/1 RHT fabric structures; 185gsm

2.c: knitted jacket fabric

Modal indigo yarn Ne 24

A single jersey construction containing 2% spandex; 185gsm

These fabrics were subjected to several performance tests:

measurement according to ISO 105-X12:2016Fastness to rubbing(1 = worst; 5= best); see table 1:

table 1:

fabric	Dry matter	Wet
			2.b	4-5	4-5
2.c	4-5	4

Both fabrics containing the fibres according to the invention show very good rubfastness properties.

Determination of the resistance according to ISO 105-C10:2006Fastness to washing. The fabric was washed with white cotton and white modal fabric, respectively, and the dyeings evaluated on the color scale (1 = worst fastness; 5= best fastness);see table 2:

table 2:

	color of fabrics before washing	Dyeing of modal sliver	Dyeing of cotton sliver
				Denim	45	4-5	5
Knitting machine	4	5	5

Both fabrics containing the fibres according to the invention exhibit very good wash fastness properties.

After washing the samples according to ISO 6330Shrinkage ratio. The woven fabrics tested were the denim fabric of example 2.a containing modal indigo and the denim fabric made in the same manner, but the latter contained viscose indigo instead of modal indigo. The knit fabrics tested were the fabric of example 2.c containing modal indigo and the knit fabric made in the same manner, but the latter contained viscose indigo instead of modal indigo. Table 3 shows that: fabric displays containing modal indigo fibers according to the inventionGiving significantly lower shrinkage than comparable fabrics made using viscose indigo.

Table 3:

reduction rate [% ]]	Viscose indigo	Modal indigo blue
			Woven fabric	7.0	4.5
Knitted fabric	17.5	11.5

Example 3:yarn tenacity after denim bleaching process compared to viscose indigo

The modal indigo fibers of the invention were compared with commercially available viscose indigo fibers (obtained from Lenzing Aktiengesellschaft, lenzing/austria). The yarn is spun by a quick spinning machine, namely, a rotor spinning process is adopted. Yarn tenacity was measured before and after permanganate treatment in aqueous solution according to the following conditions: potassium permanganate at a concentration of 4g/l was added at 40 ℃ for 10min, followed by neutralization with 2g/l disodium metabisulfite (disodium metabisulphite) at 40 ℃ for 10min. Table 4 shows that: although the permanganate bleached viscose indigo degrades so that yarn strength and yarn elongation cannot be measured (yarn tears when clamped), the modal indigo shows satisfactory mechanical properties even after permanganate bleaching.

Table 4:

type of fiber	Viscose indigo	Viscose indigo	Modal indigo blue	Modal indigo blue
					Treatment of	Untreated with	Permanganate bleaching	Untreated	Permanganate bleaching
Yarn count [ dtex ]]	303	303	313	323
					Yarn Strength [ cN/tex ]]	9.5	It is impossible to	12.4	5.4
Elongation of the yarn [% ]]	12.5	It is impossible to use	9.6	5.6

Example 4:testing of fiber bleed

A Labomat apparatus with 500mL test tubes was used, which was run at 20 rpm. 200ml of deionized water were measured in a graduated cylinder and heated to 85 ℃ in a Labomat apparatus. 5g of fiber was added. The Labomat temperature was raised to 98 ℃ as quickly as possible. The sample was treated at 98 ℃ for 5 minutes and then cooled to 70 ℃ as quickly as possible. The liquid was transferred to a 100ml beaker and cooled to room temperature (i.e. 20 ℃) while the fibers were removed manually.

The resulting liquid was evaluated for bleeding using two methods:

photometric evaluation of the absorption of the resulting liquid at a wavelength of 480 nm.

Turbidity measurements using a turbidimeter according to ISO 7027-1; results are expressed in [ NTU ] = nephelometric turbidity units.

For each measurement, a test tube filled with pure water is required as a blank reference. The fibers tested were as follows:

modal indigo was obtained according to example 1. Viscose indigo, viscose black (spun-dyed) and modal black (spun-dyed) are commercially available products from Lenzing Aktiengesellschaft, lenzing/austria. All fibres used were staple fibres with a titre of 1.3 to 1.7 dtex and a cut length of 38 to 39mm.

Table 5:

	Abs [480nm]	turbidity [ NTU]
			Viscose black	0.0363	10.2
Viscose indigo	0.0495	22.4
			Modal black	0.1168	29.9
Modal indigo blue	0.0158	5.82

The results (table 5) show: although in dope dyed viscose fibres the transition from conventional pigments to indigo pigments leads to higher bleed, in dope dyed modal fibres the transition from conventional pigments to indigo pigments surprisingly leads to a significant reduction in bleed. This is particularly surprising since the basic chemistry of these two processes-the formation of cellulose xanthate and subsequent coagulation and regeneration of cellulose-is the same.

Example 5: theoretical model-based sustainability assessment

To assess the sustainability of the present invention, it was compared to three conventional denim dyeing methods. The three conventional methods of comparison are hereinafter referred to as method a, method B, and method C.

These comparisons were made by the sustainable development expert consultant company GAVILAN AD using expert software developed by Archroma under the name "One Way". The expert system has a built-in database containing information on all the resources (water, energy, CO2 produced, etc.) required to operate the various parts of the equipment (paddles, wash tanks, pre-dryers, drying cans, tenters, etc.) during the application. The expert program also calculates indirect resource requirements (e.g., energy depending on the type of fuel in the boiler, the heating system of the operating box-direct/indirect steam, the power required by the engine, etc.). "owf" means "fiber weight".

The assumptions made for methods A, B and C are as follows:

the general assumption for all four methods, i.e. including the modal indigo treatment according to the invention:

-length of warp to dyeing: 10000m

-weight: 2190 Kg

-denim product type: lightweight (7 Oz/Yd, namely about 235 g/m)

25 ℃ for all process steps

The processes a-B-C comprise spun yarns before indigo dyeing, whereas spun yarns after indigo dyeing of spun-dyed modal indigo fibers covering fibers according to the invention.

Additional assumptions for method a (conventional indigo yarn dyeing) are as follows:

indigo concentration (standard commercial form of granulated indigo): 4% owf (dark tone)

The dyeing process of the indigo yarn comprises prewetting, temperature bleaching (2 boxes), cold bleaching (1 box), indigo dyeing (6 boxes) and rinsing (3 boxes).

Additional assumptions for method B (pre-reduced indigo yarn dyeing) are as follows:

pre-reduced liquid indigo, 4% owf (dark tone) under nitrogen to prevent its oxidation

The dyeing process of the indigo yarn comprises prewetting, temperature bleaching (2 boxes), cold bleaching (1 box), indigo dyeing (3 boxes) and rinsing (3 boxes).

Additional assumptions for method C (low water usage sulfur dyeing) are as follows:

non-indigo dye concentrations adjusted for laboratory and batch comparison dyeing: 12% prereduced sulfur dye

The application of non-indigo dyes allows for a pre-preg step, rather than the conventional pre-wetting for indigo.

-caustic dip, temperature bleaching (2 boxes), sulphur dyeing (2 boxes), curing bath (2 boxes), rinsing (3 boxes).

When the spun-dyed modal indigo fiber production process according to the invention is compared with the other dyeing processes A to C, the process according to the invention has significant savings in terms of water, chemicals, electricity, heat and waste water (see Table 6: savings achieved with indigo spun-dyed modal according to the invention compared with processes A, B and C). Modal indigo fibers do not require the heat energy required to dry conventionally dyed yarns.

TABLE 6

Compared with the saving of the invention	Method A	Method B	Method C
				Water (W)	99.5 %	99.5 %	99.1 %
Chemical product	87.4 %	81 %	83.7 %
				Electric power	99.96 %	99.96 %	99.96 %
Waste water	99.5 %	99.5 %	99.1 %
				Heat generation	100%	100%	100%

Claims (11)

1. Cellulosic fibres containing indigo pigment in incorporated oxidised form, characterised in that the fibres are made according to the modal process and exhibit a tenacity (conditioned) of at least 29cN/tex and a wet modulus according to BISFA of at least 5 cN/tex/%.

2. The fiber of claim 1, wherein the indigo pigment is incorporated into the entire cross-section of the fiber.

3. Use of the fiber of claim 1 for the manufacture of a fabric having the appearance of denim.

4. A textile fabric having the appearance of denim, characterized in that it contains from 40% to 100% (w/w) of the fiber according to claim 1.

5. The fabric of claim 4, which exhibits crockfastness according to ISO 105-X12:2016 4.0 to 5.0.

6. The fabric of claim 4, which is a woven fabric.

7. A fabric according to claim 6, comprising 80% to 100% (w/w), preferably 95% to 100% (w/w) of the fibres according to claim 1 in the warp.

8. The fabric of claim 6, which exhibits a shrinkage of less than 5.0% when washed according to ISO 6330 and tested according to Ö NORM ISO 3759.

9. The fabric of claim 4, which is a knit fabric.

10. The fabric of claim 9 which exhibits a shrinkage of less than 12.0% when washed according to ISO 6330 and tested according to Ö NORM ISO 3759.

11. A method for making a fibre according to claim 1, characterised in that it comprises the following steps:

a. preparing a Modal spinning solution

b. Preparation of indigo pigment in oxidized form

c. Addition of indigo pigment to Modal spinning solution

d. Extruding the solution of step c into a coagulation bath according to the modal spinning process.