REGENERATED ANIONIC CELLULOSE FIBER

Field of Invention

The present disclosure relates to a regenerated anionic cellulose fiber and a continuous process for production of said regenerated anionic cellulose fiber.

Background

Regenerated cellulose fibers, such as viscose, are commonly unable to uptake cationic or basic dyes due to absence of active anionic functionality. Additionally, cellulose fibers or fabrics suffer from poor wash fastness towards basic dyes due to negligible attraction of dyes with almost neutral cellulosic hydroxyl groups. It is however desirable to use cationic dyes considering that they have numerous advantages over reactive dyes. Dyeing of cellulose fibers with reactive dyes requires large amounts of dye and inorganic salt, leading to large amount of effluents including excess dye and salt. On the other hand, the dyeing process with cationic or basic dyes requires much lower dye as compared to reactive dyes and is salt and soda free. Further, dyeing process with cationic or basic dyes enables achieving up to hundred percent dye bath exhaustion. This not only reduces environmental pollution but also reduces the cost of dyeing. Additionally, cationic dyes provide brighter shades with high tinctorial value and color depth compared to reactive dyes on cellulose fibers with the same concentration of dyes.

Researchers have attempted to enable uptake of cationic or basic dyes by regenerated cellulosic fibers by introducing anionic functionality thereon.

Japanese Patent No. 158263/1996 discloses modifying cellulose fibers with an insoluble polymer obtained by cross-linking a dihydroxy-diphenylsulfone-sulfonate condensate with epoxy compounds having at least two epoxy groups in the molecule.

US4722739A discloses production of a crosslinked cellulosic fabric. Said fabric is composed of a sufficient amount of N-methylol crosslinking agent and amino acid to give the fabnc smooth drying properties and affinity for both cationic and anionic dyestuffs, especially basic and direct dye classes.

US 5902355 discloses cationic dyeable cotton, wool or regenerated cellulosics modified by insoluble polymer which is obtained by crosslinking dihydroxy diphenyl sulfone sulfonate condensate by a combination of two water soluble epoxy compounds for several hours before mixing to cellulose dope. Additionally, post dyeing treatment with tannic acid and tartar emetic in multistage application process was necessary to reach satisfactory wash fastness properties.

US 4722739 discloses direct and basic dyeable cellulosic fabrics which has been crosslinked with N-Methylol crosslinking agents such as l,3-Dimethylol-4,5- dihydroxyethyleneurea (DMDHEU) or Dimethylol propyl carbamate in presence of amino acids. Entire modification was carried out in fabric stage and basic dye concentration was maintained at as high as 5% with salt content up to 20%, making the process uneconomical and non-ecofriendly.

US4218366 discloses condensation product of 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfonesulfonic acid and a lower aliphatic aldehyde as a dye fixing agent for polyamide fibers.

EP055044B1 discloses synthetic fixing agent comprising of a condensate of bisphenol-A and formaldehyde for cationic dyes on polyamide materials, such as nylon.

S. Nag, N. Waghmare, V. Juikar, “Fabrication of Poly (Methacrylic Acid) functionalized cellulosic Fibers with Cationic Dye Uptake Capacity for Textile Applications” IRJET, 5 (12), 161-167, 2018 discloses inclusion of anionic polymers like poly (methacrylic acid) in viscose by in-situ polymerization and grafting of methacrylic acid onto viscose fiber. Summary

A regenerated anionic cellulose fiber is disclosed. Said regenerated anionic cellulose fiber comprises of a regenerated cellulose fiber crosslinked with a modifier, wherein said modifier has a structural formula I: wherein,

X=H, SO ₃ Na m= 10-80 n= 15-100

A continuous process for preparing a regenerated anionic cellulose fiber. Said process comprising treating cellulose in a viscose dope with a modifier in an amount of 0.5-20 % by weight of cellulose to obtain modifier bonded regenerated cellulose fibers, said modifier having a structural formula I: wherein,

X=H, SO ₃ Na m= 10-80 n= 15-100 followed by curing of the modifier bonded regenerated cellulose fibers at a temperature between 90-170°C.

Brief Description of Drawings

Figure 1 illustrates the mechanism of incorporating anionic functionality in regenerated cellulose fibers, in accordance with an embodiment of the present invention.

Figure 2 shows the Nitric oxide inhibition ability of test materials- 100% control fabric and 100% anionic functional fabric obtained from fibers in Examples CE1 and 1 respectively.

Figure 3 shows the anti-oxidant activity of the test material- 100% control fabric and 100% anionic functional fabric obtained from fibers in Examples CE1 and 1 respectively, as % increase in GSH levels.

Detailed Description

For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the disclosed composition and method, and such further applications of the principles of the disclosure therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof. Reference throughout this specification to “one embodiment” “an embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

In its broadest scope, the present disclosure relates to a regenerated anionic cellulose fiber. Said regenerated anionic cellulose fiber comprises of regenerated cellulose fiber bonded with a modifier. Said modifier has a structural formula I: wherein,

X=H, SO ₃ Na m= 10-80 n= 15-100

“Bonded” herein refers to bonds such as hydrogen bonding, covalent bonding and non-covalent interactions.

In accordance with an aspect, said modifier is a water soluble resol type copolymer which is a condensation product of bisphenol-S (4,4'-dihydroxydiphenylsulfone or 4,4'- dihydroxydiphenylsulfonesulfonate), phenolsulfonic acid and formaldehyde. In accordance with another embodiment, said modifier has a molecular weight ranging between 10000 and 45000 Da, wherein higher molecular weight is preferable. In accordance with an embodiment, said modifier consisting of a resol type copolymer of bisphenol-S, phenolsulfonic acid and formaldehyde is obtained from commercial sources such as that sold under trademark “SZ-9904” by Nagase-OG Colors & Chemicals Co Ltd., Japan.

In accordance with an embodiment, said regenerated anionic cellulose fiber comprises the modifier in an amount ranging between 0.5-20% by weight of cellulose fiber, and preferably 1-10% by weight of cellulose fiber.

Each repeat unit of said modifier comprises of three hydroxyl groups and one sulfonate group. The hydroxyl group present in cellulose fiber forms hydrogen bonds with hydrogen of multiple hydroxyl groups present in repeat units of bisphenol S and phenolsulfonic acid. The sulfonate group present in the modifier introduces anionic functionality in the regenerated cellulose fibers, which serves as binding site for cationic dye and metals.

In accordance with an embodiment, to improve the binding of modifier with the cellulose fiber, crosslinking agents are used. The regenerated anionic cellulose fiber comprises the crosslinking agent in an amount ranging between 0.5-7% by weight of cellulose fiber, and preferably between 1-3% by weight of cellulose fiber. Said crosslinking agents include those that react through their active methylol groups to form covalent bonds with hydroxyl group of cellulose fiber and phenolic ring of the modifier. Figure 1 illustrates the mechanism of incorporating anionic functionality in cellulose fibers using a crosslinking agent, in accordance with an embodiment of the present invention. In accordance with an embodiment, crosslinking agents are selected from a group consisting of l,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) (sold under trademark “Fixapret CP” from BASF), modified DMDHEU (sold under trademark “Synotex ACR” from Shubhan inks, or “Fixapret CL”, “Fixapret F-ECO plus” from BASF), N,N-dimethyl-4,5-dihydroxyethyleneurea or DMeDHEU (sold under trademark “Fixapret NF” from BASF), Cyclic urea derivative (sold under trademark “Stabitex ZF plus” from Pulcra), methylated high imino melamine resins (sold under trademark “Cymel 327/328/385” from Allnex). The degree of crosslinking and extent of hydrogen bond network can be varied by varying the concentration of modifier and crosslinking agent. The covalent bond formed by the crosslinking agent with the cellulose and the modifier increases the stability of modifier on the cellulose chains as well as the wash fastness of the regenerated cellulose fiber. Also, it improves the stability of anionically modified cellulose fibers when subjected to scouring treatments with other fibers such as polyester, cationic dyeable polyester, nylon, acrylic, cotton at high temperature of 85- 130 °C.

A continuous process for preparing said regenerated anionic cellulose fiber is also disclosed. Said process comprises: a. treating cellulose in a viscose dope with a modifier in an amount of 0.5-20 % by weight of cellulose to obtain modifier bonded regenerated cellulose fibers, said modifier having a structural formula I:

. I wherein,

X=H, SO ₃ Na m= 10-80 n= 15-100 b. curing the modifier bonded regenerated cellulose fibers at a temperature between 90-170°C.

In accordance with an embodiment, treatment in step (a) is carried by introducing the modifier in the viscose dope immediately before spinning the viscose dope to form regenerated cellulose fibers. In accordance with an aspect, said modifier is added to the viscose dope in an amount of 0.5-20 % of the weight of cellulose (o.w.c), and preferably between 1-10% of the weight of cellulose.

In accordance with an aspect, curing of the regenerated cellulose fibers is carried out at a temperature between 90-170 °C, and preferably between 110-145 °C.

In accordance with an embodiment, regenerated cellulose fibers obtained in step (a) are additionally treated with a crosslinking agent in an amount of 0.5-7% by weight of cellulose, and a curing agent in an amount of 0.01-3% by weight of cellulose, before curing. The regenerated cellulose fibers bonded with the modifier is treated with the crosslinking agent and the curing agent in spin finish treatment zone of a typical viscose fiber manufacturing set up.

In accordance with an embodiment, crosslinking agents are selected from a group consisting of l,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) (sold under trademark “Fixapret CP” from BASF), modified DMDHEU (sold under trademark “Synotex ACR” from Shubhan inks, or “Fixapret CL”, “Fixapret F-ECO plus” from BASF), N,N-dimethyl-4,5-dihydroxyethyleneurea or DMeDHEU (sold under trademark “Fixapret NF” from BASF), Cyclic urea derivative (sold under trademark “Stabitex ZF plus” from Pulcra), methylated high imino melamine resins (sold under trademark “Cymel 327/328/385” from Allnex). The degree of crosslinking and extent of hydrogen bond network can be varied by varying the concentration of modifier and crosslinking agent. The concentration of crosslinking agent is maintained such that formaldehyde on fiber remains within allowed Oeko-tex limits. In accordance with an embodiment, the crosslinking agent is used in low concentrations ranging between 1 - 140 g/L, and preferably between 7.5 - 80g/L. In accordance with an exemplary embodiment, the crosslinking agent is used in concentrations ranging between 7.5 - 40 g/L.

Curing agents are used so that lower reaction temperature is required and to accelerate the crosslinking of the crosslinking agent with the cellulose fiber and the modifier. In accordance with an embodiment, said curing agent is selected from a group consisting of magnesium chloride, calcium chloride, zinc chloride, citric acid, tartaric acid, zinc nitrate and titanium dioxide. Said curing agent is used in an amount in a range of 0.01 to 3% by weight of cellulose fiber. In accordance with yet another embodiment, curing agent is selected from a group consisting of Methane sulfonic acid (MSA), paratoluene sulfonic acid (PTSA) and amino blocked-PTSA catalysts. Said curing agent is used in an amount in a range of 0.002 to 0.5% by weight of cellulose fiber. Other suitable curing agents may be from the group of compounds containing 2 or more epoxy groups as aqueous formulation, where pH is maintained towards slightly alkaline with inorganic alkali.

Curing of the regenerated cellulose fibers with the crosslinking agent in presence of curing agent is carried out at a temperature between 90-170 °C, and preferably between 110-145 °C to induce covalent crosslinking. It was also found that higher temperature (> 145°C) gives better curing effect in lesser exposure time due to extensive covalent bond formation in addition to hydrogen bonded network and hence results in irreversible fixation (Figure 1). This curing at high temperature also results in one- self crosslinking of the modifier itself, which helps in withstanding higher temperatures during downstream processes of blend dyeing with acrylic or cationic dyeable polyester.

Examples:

In order that this invention may be better understood, the following examples are set forth. These examples are for the purpose of illustration only and the exact compositions, methods of preparation and embodiments shown are not limiting of the invention, and any obvious modifications will be apparent to one skilled in the art.

Also described herein are method for characterizing the dyed fibers, formed using embodiments of the claimed process.

Characterization methods:

1. Dye bath exhaustion (DBE): DBE was measured by UV-Visible spectroscopic method. Calibration curves of absorbance vs concentration was made for each dyes, which is a straight line passing through origin following BEER LAMBERT law. Using the calibration curve for each dyes, the residual dye concentration in dye bath post dyeing operation was measured and converted into dye bath exhaustion in percentage of initial dye concentration.

2. Color strength measurement: Color strength or tinctorial value of a dyed fiber is represented by K/S (K- absorption coefficient of colorant, and S -scattering coefficient of colorant). The sliver of dyed fiber is evaluated for reflectance in a color spectrophotometer, and Kulbelka-Munk theory gives the following relation between reflectance (R) and absorbance.

K/S = [{(1-R) ² /2R}J

Color strength of one dyed fiber is expressed as % of K/S of standard (which is 100)

Color Strength = [(K/S)batch / (K/S Standard] x 100

3. Measurement of colour fastness to washing: Colour fastness is the ability of fabrics/fibres to retain the dyes used to colour them. Colour fastness of dyed fibers was measured ISO: 105 C10-2006 at 45-50 °C. The multifiber fabric sandwiched with test fiber sample was treated with soap + soda ash solution at 1:50 MLR at 45-50 °C for 30 minutes, in a Dye master. Sample was removed and rinsed with cold water twice followed by drying at 105 °C. The rating is given on a scale of 5, wherein 5 = unchanged and 1 = major changes.

Comparative Example 1 (CE1): Dyeing of regenerated cellulose fibers (without anionic functionalization) with Basic Dyes-coracryl variants CGNX blue and C4G red (From Colourtex Industries Pvt. Ltd.)

Regenerated cellulose fibers were subjected to basic dyeing at 1:30 fiber to liquor ratio with a progressive rise of temperature from 25 to 65 °C at a rate of 1.4 °C /minute and then holding at 65 °C for 30-45minutes followed by cooling up to 40°C and further washing with 1 g/L phosphate free soap. The dye concentration was maintained as 1% on fiber weight basis and pH of dye bath is maintained in the range of 4.0-5 with acetic acid.

It was observed that dye pick up could not take place.

Comparative Example 2 (CE2): Dyeing of Acrylic fibers with Basic Dyes-coracryl variants CGNX blue and C4G red (From Colourtex Industries Pvt.Ltd.)

Acrylic fibers were subjected to basic dyeing at 1:30 fiber to liquor ratio with a progressive rise of temperature from 25 to 105 °C at a rate of 1.4 °C /minute and then holding at 105 °C for 30-45 minutes followed by cooling up to 40 °C and further washing with 1 g/L phosphate free soap. The dye concentration was maintained as 1% on fiber weight basis and pH of dye bath is maintained in the range of 4.0-5 with acetic acid.

Dye bath exhaustion was found to be about 98-100% for all dyes.

Example 1: Aqueous solution of the modifier- SZ 9904 (with 31-34% active) was added to viscose dope at 1-10% active by weight of cellulose, mixed thoroughly and spun into acidic coagulation bath, in a typical viscose fiber manufacturing set up. The regenerated fiber thus obtained is subjected to successive washing steps in a regular viscose fiber process, such as, hot water washing, dilute sulfuric acid wash at 90 °C, water wash at 60 °C, desulph wash at 90 °C, water wash at 60 °C followed by dilute acetic acid rinse and spin finish application. Post application of spin finish, fiber bed is squeezed to attain moisture content of 80-120% followed by curing at a temperature between 90-145°C.

The dried fibers were scoured at 90°C in sodium carbonate solution (l-3g/L) sodium hydroxide solution (l-2g/L), and subsequently dyed with various basic dyes (Coracryl red C4G or Coracryl cgnx blue) at 1% o.w.f. in an acidic bath at pH 4-5 in presence of Benzalkonium chloride as levelling agent, with a progressive rise of temperature from 25-60°C at 1.4deg/min, holding at 65°C for 30-45 min, followed by cooling to <35°C and washing with phosphate free soap and hot water. It was observed that dried fiber was free of smell.

Example 2 (With crosslinking agent and curing agent): Example 1 was repeated, except that the moving fiber bed was additionally treated in the spin finish treatment zone with various amount of crosslinking agent- modified DMDHEU (commercially available as “Synotex ACR”) along with curing agent- citric acid and magnesium chloride. Amount of citric acid and magnesium chloride were varied as per requirement of end pH of fiber. Treated fiber bed was squeezed to moisture content of 80-120% and dried at temperature of 120-150°C, preferably 130-145°C.

It was found that higher temperature than this is not feasible in continuous process and leaves possible chance of fiber yellowness and hence avoided. However, higher curing temperature gives better fixation with no other negative impact on fiber. The dried fibers were scoured at 90°C in sodium carbonate solution (l-3g/L) + sodium hydroxide solution (l-2g/L), and subsequently dyed with basic dye at 1% o.w.f. in an acidic bath at pH 4-5 in presence of Benzalkonium chloride as levelling agent, with a progressive rise of temperature from 25-60°C at 1.4deg/min, holding at 60°C for 30-45 minutes, followed by cooling to <35°C and washing with phosphate free soap and hot water. As shown in Table 1 below, Dye bath exhaustion was found to be more than 98% at 4% or higher active polymer (o.w.f) loading.

Example 3 (Stability of anionic fiber at single bath dyeing like condition with cationic dyeable polyester (CDPET)): The scoured fibers obtained in Examples 1 and 2 were subjected to sequential dyeing steps of 60°C/40 minutes dyeing followed by 120°C/20 minutes dyeing in separate vials. Regular viscose staple fiber (VSF) and cationic dyeable polyester (CDPET) yarns were treated similarly as control experiments. Briefly, the dried fibers were scoured similarly at 90°C in sodium carbonate solution (1- 3g/L) + sodium hydroxide solution (l-2g/L), and subsequently dyed with basic dye at 1% o.w.f. in an acidic bath at pH 4-5 in presence of benzalkonium chloride as levelling agent, with a progressive rise of temperature from 45-60 °C, holding for 40 minutes at 60 °C and then increasing temperature to 120°C and holding for 20 minutes. Post cooling, washing with phosphate free soap and hot water were carried out. The dye bath exhaustion of the fiber obtained in Examples 1, 2 and 3 are listed in Table 1 (for Coracryl red C4G) and Table 2 (for Coracryl Cgnx blue) below.

Table 1: DBE in Coracryl red C4G - 1% o.w.f.

Table 2: DBE in Coracryl Cgnx blue - 1% o.w.f.

Table 3 shows colour strength of fiber when dyed with Coracryl red C4G - 1% o.w.f., as measured by Minolta spectrophotometer.

Table 3: Dyeing with Coracryl red C4G - 1% o.w.f.

Observation: It was observed that color strength of regenerated anionic cellulose 5 fiber was at least 17 times with 4% loading of modifier on fiber as compared to standard regenerated cellulose fiber or VSF. Crosslinking was found to have no negative impact on color strength. Table 4 shows colour strength of fiber when dyed with Cgnx blue - 1% o.w.f., as measured by Minolta spectrophotometer.

Table 4: Dyeing with Cgnx blue - 1% o.w.f.

Observation: It was observed that color strength of regenerated anionic cellulose fiber was at least 10 times with 4% loading of modifier on fiber as compared to standard regenerated cellulose fiber. Table 5 shows colour strength of fiber when dyed with with Coracryl red C4G - 1% o.w.f., at 60°C for 40 minutes and 120°C for 20 minutes Table 5: Dyeing at low -to-high temperature to represent single bath dyeing

Observation: It was observed that color strength of regenerated anionic cellulose fiber was at least 10 times with 4% loading of modifier on fiber, when dyed at higher temperature to mimic a polyester/acrylic like blend condition as compared to standard regenerated cellulose fiber.

It was found that the crosslinking agent resulted in high temperature stability (higher K/S) of the modifier inside fiber. Further, the K/S values of anionic VSF was found to be approaching that of acrylic fiber indicating that regenerated anionic cellulose fiber described here can be used for single bath dyeing with CDPET or acrylic fiber which requires high temperature dyeing condition. Table 6 shows the colour fastness results for various experiments at 45-50 °C.

Table 6: Results of Colour fastness

Observation: It was observed that acceptable degree of colour fastness to washing was obtained when concentration of modifier was at 2% and higher. Also, no staining was observed on multifabric. Example 4 (Measurement of cytotoxity and anti-oxidant activity): The in vitro cytotoxicity was performed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide) assay for a 100% control fabric and 100% anionic functional fabric obtained from fibers in Examples CE1 and 1 respectively, on human Keratinocyte (HaCaT) cell line to assess the toxicity on healthy cells. The same nontoxic concentration of test material at 25mg/mL of cell suspension was used to evaluate its modulatory effect and anti-oxidant activity against lipopolysaccharide (LPS) induced toxicity.

Preparation of test solution: 25mg/piece of test material (control and functional fabric) was weighed separately and autoclaved for sterilization. The control and functional fabric were further soaked in cell culture media for 10-15 minutes, before using in the treatment and analysis.

Cell line and Culture medium: Cell lines HaCaT was cultured in DMEM-HG media supplemented with 10% inactivated Fetal Bovine Serum (FBS), penicillin (100 lU/mE), streptomycin (100 g/mE) and amphotericin B (5 pg/mL) in a humidified atmosphere of 5% CO2 at 37°C until confluent. The cells were dissociated with TPVG solution (0.2% trypsin, 0.02% EDTA, 0.05% glucose in phosphate buffer saline (PBS). The stock cultures were grown in 25 cm ² culture flasks and all experiments were carried out in 96 well microtitre plates.

Cytotoxicity Studies: The monolayer cell culture was trypsinized and the cell count was adjusted to 2xl0 ⁵ cells/mL using medium containing 10% FBS. To each well of the 6 well microtitre plate, 2 mL of the diluted cell suspension was added. After 24 hours, when a partial monolayer was formed, the supernatant was flicked off followed by washing of the monolayer once with medium and 2 mL of cell culture media with the autoclaved test material (25 mg/mL) was added on to the partial monolayer in microtitre plates. The plates were then incubated at 37° C for 2 days in 5% CO2 atmosphere, and microscopic examination was carried out and observations were noted every 24 hours’ interval. After 48 hours, the solutions in the wells were discarded and 500 pL of MTT in PBS was added to each well. The plates were gently shaken and incubated for 3 hours at 37 C in 5% CO2 atmosphere. The supernatant was removed and 500 .L of DMSO was added and the plates were gently shaken to solubilize the formed formazan. The absorbance was measured using a microplate reader at a wavelength of 570 nm. The percentage growth inhibition was calculated and concentration of test sample needed to inhibit cell growth by 50% (CTC50) values is generated from the cytotoxic response for the cell line.

Measurement of Anti-Oxidant Activity: Reduced glutathione (GSH) is the highly available and low molecular weight thiol compound synthesized in cells. GSH plays important roles in protecting cells from oxidative damage caused by different agents synthesized inside or entering from external sources into the cells. It also protects from the toxicity of xenobiotic electrophiles, and maintains redox homeostasis.

For measurement of in vitro GSH activity of test material, following steps were performed:

Step I (LPS induction on HaCaT cell line): HaCaT cells were seeded into 6 well culture dishes at a cell population 2xl0 ⁵ cells/ml in DMEM with 10% FBS. After 24 hours, the cells were treated with a known non-toxic concentration of test materials along with lp.g/ml of lipopolysaccharide (LPS) and incubated at 37°C with 5% CO2 for 24 hours.

Step II (Estimation of GSH in cell supernatant by ELISA): After 24 hours of incubation the supernatant was collected and centrifuged at 500 g force for 10 minutes and stored at -80 °C until further use. Before estimation of the markers, the supernatants were brought to room temperatures and processed for markers GSH by ELISA kit method according to the manufacturer’s instructions.

Nitric Oxide Inhibition and its relevance: Many diseases are caused by oxidative stress and oxidative stress is initiated by free radicals, which seek stability through electron pairing with biological macromolecules such as proteins, lipids and DNA in healthy human cells and cause protein and DNA damage along with lipid peroxidation. NO (Nitric Oxide) is one such molecule which generates free radicals at higher concentrations and causes damage to cells. The test materials were tested for their ability to inhibit NO in vitro in HaCaT cell line.

Measurement of Nitric Oxide Inhibition: HaCaT cells were treated with test material (25 mg/mL) as described above and incubated for 24 hours and conditioned media collected was used for nitrite determination. Determination of nitrite as a biomarker for NO was carried out. In brief, equal volume (50 pL) of 0.1% N-l-napthylethylenediamine dihydrochloride prepared in water, 1% sulfanilamide prepared in 5% phosphoric acid and cell culture media were mixed in flat bottom 96-well plate incubated for 10-15 min. Colored end product was measured at 530 nm. Percentage of nitric oxide inhibition was calculated over control.

The results of antioxidant activity of test materials is tabulated in Table 7 and 8, below. Figure 2 shows the Nitric oxide inhibition ability of test materials and Figure 3 shows the antioxidant activity of the test material as % increase in GSH levels.

Table 7: Antioxidant effect of Test Materials as %NO inhibition

Table 8: Antioxidant effect of Test Materials as %increase in GSH Observations: Anti-inflammatory activity of the test materials is demonstrated by GSH increase in HaCaT cells. Control fabric only increased the GSH levels by 17.05% over the cell control whereas the functional fabric increased the levels of GSH by 87.20% over the cell control.

The test material also showed significant reduction of NO (Nitric Oxide) compared to the control cells. Control fabric reduced the NO by 5.77% over the control cells, whereas the functional fabric scavenged the NO radicals by 56.65% over the cell control.

The fabric obtained from regenerated anionic cellulose fiber demonstrated good antioxidant (anti-ageing) properties compared to the control fabric at the tested conditions.

Industrial Applicability

The disclosed regenerated anionic cellulose fibers are dyeable with cationic or basic dyes and provides a dyeing process having upto 100% dye bath exhaustion, similar to acrylic fibers or CDPET. The said fiber has 10-17 times higher color strength as compared to standard regenerated cellulose fiber, when dyed with cationic dyes under salt and soda free conditions.

The high average molecular weight of the modifier provides for extensive hydrogen bonding ability with cellulose fiber thereby enhancing the fixing in between the cellulose chains. Use of crosslinking agent makes this fixing of modifier on the cellulose chains irreversible. At high temperature curing condition, the modifier can one-self crosslink to result in a fiber/yarn/fabric that can withstand high temperature downstream processes.

Said regenerated cellulose fibers are capable of cationic/basic dyeing in a salt and soda free environment unlike reactive dyeing process of standard cellulose fibers which requires 14-30 g/L soda and 45-80 g/L salt. Also, no dye fixing agent is necessary on fabric produced from such regenerated anionic cellulose fiber which eliminates the load for downstream processes. Thus, the present regenerated anionic cellulose fibers have significantly low carbon footprint and is environment friendly.

Said regenerated anionic cellulose fiber can be extensively used in single bath dyeing process with other cationic dyeable fibers such as polyesters, wools or acrylics. The single bath dyeing for blends comprising of acrylics, wool or cationic dyeable polyesters can be carried out at fiber, yarn or fabrics stage. This provides significant savings in terms of energy, cost and cumbersome process as compared to regular multi- step dyeing comprising of blends. Additionally, single bath dyeable blends of wool or acrylic fibers with regenerated cellulose fibers of present process improves the skin feel in terms of softness due to cellulose content, in rough and scaly wool or acrylics. Said regenerated cellulose fiber is stable at that high temperature dyeing condition of CDPET or acrylic. Said regenerated anionic cellulose fiber provides enormous opportunities for melange applications in knits or wovens in combination with regular viscose staple fiber, optically white viscose staple fiber, modal, acrylic, polyester or print applications such as saree/dress material.

Said regenerated anionic cellulose fiber has a pH in range of 5-7. Thus, the fiber exhibits skin pH balancing benefits, and finds application in face masks etc.

Said regenerated anionic cellulose fiber exhibits improved antioxidant properties. At a given concentration, said fiber demonstrates significant GSH increase and NO (nitric oxide) inhibition in human Keratinocyte (HaCaT) cell line, as compared to unmodified fiber. In accordance with an embodiment, said regenerated anionic cellulose fiber at a concentration of 25 mg/mL exhibits a 50-100% increase in GSH levels as compared to control fiber, in in human Keratinocyte (HaCaT) cell line. In accordance with an embodiment, said regenerated anionic cellulose fiber at a concentration of 25 mg/mL exhibits a 25-50% NO inhibition as compared to control fiber, in in human Keratinocyte (HaCaT) cell line. Additionally, said regenerated anionic cellulose fiber was found to be non-toxic to various cell lines, such as Human dermal Fibroblast (HDF) cell line. The disclosed process of preparing said regenerated anionic cellulose fibers is a continuous process. It is cost effective and environmentally sustainable. The dyeing process requires upto 50% less dyes and does not require salt and soda. It also provides brighter shades with high tinctorial value and color depth when compared to conventional reactive dyeing on cellulose fibers with the same concentration of dyes. Additionally, said process is an epoxy free process for fabricating cationic dyeable regenerated cellulose fibers. Hence, the present process provides an economically viable dyeing process. The disclosed regenerated anionic cellulose fiber finds applications such as: (1) to make hygiene fabrics/wipes such as indoor upholstery, curtains, hospital fabrics and carpets as can prevent bacterial growth, (2) for removal of cationic water soluble agents, (3) removal of heavy metal ions from water bodies, (4) preparing fabric with skin natural pH balance, (5) removal of ammonia, amine derivatives or other harmful indoor gases from air and hence as filter materials for air purification, (6) preparing water soaking pads for meat industry.