DESC:The disclosure relates to a process for preparing spun cellulosic fibers. Specifically, the disclosure relates to a process for preparing low-fibrillating spun cellulosic fibers. The disclosure also relates to spun cellulosic fibers.

BACKGROUND
The most commonly used technology to manufacture cellulosic fibers commercially is the viscose rayon process, which is known since 1890’s. The process involves derivatization by carbon disulfide, dissolution in alkali and precipitation in an acidic solution to manufacture viscose, high wet modulus and modal fibers. The next commercial process called the Lyocell process involves the use of direct solvent, N-methyl morpholine N-oxide (NMMO) and precipitation in a low solvent concentration aqueous bath to manufacture cellulosic fibers. The lyocell process uses dry jet wet spinning to prepare cellulosic fibers with conditioned and wet tenacity greater than viscose fibers. In terms of cellulose dissolution, ternary system of NMMO, cellulose and water has a very narrow solution window. Additionally the NMMO system is thermally unstable. From fiber properties point of view, in spite of good tensile properties, the fibers showed high fibrillation.
Ionic liquid (IL) have emerged as alternative solvent to NMMO in the last decade due to its adjustable polarity by mere exchange of cation and anion, enhancing the capacity to dissolve cellulose. Other advantages of IL include low melting temperatures (<100oC), less impurity content and negligible vapor pressure.
Broadly, cellulose solution is spun by two methods - dry jet wet spinning for cellulose solution in NMMO and wet spinning for viscose solution. For dry jet wet spinning, the polymer solution is spun through an air gap into the precipitating bath. The filament in the air gap is not precipitated and needs to be stabilized by air flow. A slight air flow disturbance can lead to fusion of neighboring filament leading to fused and poor quality fibers. The air gap length is also critical for the fiber properties; too short length leads to even higher fibrillation and too long a length leads to lower orientation owing to chain relaxation (*”Handbook of Fiber Chemistry” by Menachem Lewin, pg. 691-692, 2007). Whereas in wet spinning, the cellulose solution exits the spinneret into the coagulation bath where the coagulation or precipitation process stabilizes the spinning filament. Thus, it is easy to handle the filament in terms of processability and low-fibrillation in case of wet spinning unlike dry jet wet spinning.
The fibers spun by wet spinning of cellulose solution in ionic liquids also shows fibrillation tendency. Prior art reports several approaches to arrest fibrillation in wet spinning process, by using a) additives in cellulose-ionic liquid solvents, b) protic solvent(s) mostly water and also glycols and other alcohols in solution system (US8,163,215) c) protic solvent(s) like glycerol and/or 1,2-propanediol in coagulation bath (US 2010/0256352). But incorporation of the additives in solution or in coagulation bath poses additional load on recycling as the additive, solvent and non-solvent have to separate for the process to be economical.
Chinese patent application no CN 103205015 discloses cellulose aerogel, prepared by regenerating cellulose dissolved in ionic liquid using multiple coagulation baths having gradient concentration of ionic liquid from high to low. Another document, CN 103421202 also discloses a method of producing a high strength cellulose material by coagulating cellulose dissolved in ionic liquid in multiple baths having gradient concentration of ionic liquid from high to low. The process disclosed in this document specifically requires pressing of the cellulose material after each coagulation step to improve cellulosic material strength. Though these documents disclose the use of multiple baths for coagulating or regenerating cellulose, both are silent with regard to the process parameters that are required for preparing low-fibrillating cellulosic fibers.
Therefore, the need exists for a process for preparing low-fibrillating cellulosic fiber which can avoid the use of additives and solvents and further downstream processing.

OBJECTS:
It is therefore an object of this invention to propose a process for manufacturing low-fibrillating cellulosic fiber, which provides control over fibrillation properties of the cellulosic fiber.
It is a further object of this invention to propose a process for manufacturing low-fibrillating cellulosic fiber, which avoids the use of additives in solution or in the coagulation bath.
Another object of this invention is to propose a process for manufacturing low-fibrillating cellulosic fiber, which is simple and cost-effective.
These and other objects of the invention will be apparent to a person in the art on reading the ensuing description.

SUMMARY
The disclosure relates to a process for preparing spun cellulosic fibers. The process includes preparing a solution of cellulose in an ionic liquid, spinning the solution of cellulose to obtain spun cellulosic fibers, passing the spun cellulosic fibers sequentially through at least three baths having ionic liquid, wherein the concentration of ionic liquid in the first bath is in a range of 40-85% w/w, maintained at a temperature in a range of 5?C to 60?C, and the concentration of ionic liquid in each bath is lower than the preceding bath, and imparting a stretch to the spun cellulosic fibers in the first bath in a range of 15% to 100%.
The disclosure also discloses spun cellulosic fibers having a fibrillation index of not more than 3, obtained from a process including preparing a solution of cellulose in an ionic liquid, spinning the solution of cellulose to obtain spun cellulosic fibers, passing the spun cellulosic fibers sequentially through at least three baths having ionic liquid, wherein the concentration of ionic liquid in the first bath is in a range of 40-85% w/w, maintained at a temperature in a range of 5?C to 60?C, and the concentration of ionic liquid in each bath is lower than the preceding bath and imparting a stretch to the spun cellulosic fibers in the first bath in a range of 15% to 100%.

DETAILED DESCRIPTION:
For the purpose of promoting an understanding of the principles of the invention, 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 invention is thereby intended, such alterations and further modifications in the disclosed process, and such further applications of the principles of the invention therein being contemplated as would normally occur to one skilled in the art to which the invention 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 invention 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 invention. 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.
A process for preparing spun cellulosic fibers is disclosed. Specifically, a process for preparing low-fibrillating spun cellulosic fibers is disclosed.
The process comprises of preparing a solution of cellulose in a solvent comprising an ionic liquid, spinning the solution of cellulose to obtain spun cellulosic fibers and passing the spun cellulosic fibers sequentially through at least two baths having ionic liquid such that the concentration of ionic liquid in the second bath is lower than that of the first bath.
The cellulose solution is prepared by dissolving cellulose pulp in the solvent comprising an ionic liquid. The dissolution of cellulose may be carried out by exposing the cellulose to the solvent at high temperature in a dissolving or mixing equipment such as a wiped film evaporator or a sigma mixer. In accordance with an aspect, cellulose pulp with alpha cellulose in the range of 80% to 97%, hemi-cellulose in the range of 3 to 20% and having a degree of polymerization in the range of 100 to 4000 may be used for the preparing the cellulose solution. The cellulose solution may be prepared such that the concentration of cellulose is in the range of 5-25%. The cellulose solution may further be passed through a non-woven metallic mesh filter.
The cellulose solution is then spun by passing through a spinneret die by a spinning pump to obtain spun cellulosic fibers. The spinning speeds and throughput of the cellulose solution are maintained such that a resulting fiber fineness of about 1 to 2 denier is obtained.
The process further comprises of passing the spun cellulosic fibers sequentially through at least three baths having ionic liquid such that the concentration of ionic liquid in the each bath is lower than the preceding bath. The concentration of ionic liquid in the first bath is in a range of 20 to 95 % w/w and preferably in the range of 40-85% w/w. The first bath is maintained at a temperature in a range of 5?C to 60?C. The spun cellulosic fibers are imparted a stretch in the first bath. The stretch imparted in the first bath is in a range of 15 % to 100%.
In accordance with an aspect, the spun cellulosic fibers are passed through multiple baths herein after described as “multiple bath arrangement” wherein the concentration of ionic liquid in each bath is lower than the preceding bath. The rate of decrease in concentration of ionic liquid between each bath may be linear. The number of baths in the multiple bath arrangement is in a range of 4 to 8.
In the multiple bath arrangement, the concentration of the ionic liquid in the first bath may be in the range of 20 to 95 % w/w and preferably in the range of 40-85% w/w. Additional increase in solvent concentration leads to fused fibers and lower concentration leads to lower stretchability of the spun cellulosic fibers. The concentration of the final bath is 1% ionic liquid or less. By reducing the concentration of the ionic liquid in the baths, one is able to control the rate of fiber regeneration, i.e. the regeneration kinetics and solvent-water diffusion rate, which leads to a stronger low-fibrillating cellulosic fiber structure.
The ionic liquid used includes but is not limited to 1-methyl-3-methylimidazolium acetate, 1-butyl-3-butylimidazolium acetate, 1-ethyl-3-ethylimidazolium propionate, 1-ethyl-3-ethylimidazolium octanoate or 1,3-disubstituted imidazolium salt. In accordance with an embodiment, the ionic liquid is a 1,3-disubstituted imidazolium salt of the formula I

where,
R1 and R3 are each, independently of one another, an organic group having 1 to 20 carbon atoms;
R2, R4 and R5 are each, independently of one another, an H atom or an organic group having from 1 to 20 carbon atoms;
X is an anion, anion being at least one selected from the group consisting of a carboxylate anion of formula Ra-COO- wherein Ra is a alkyl group having 1 to 20 carbon atoms, preferably 1 to 9 carbon atoms, and phosphate anion of formula Rb-Rc-PO4- , Rb and Rc are alkyl groups having 1 to 20 carbon atoms, preferably having 1 to 5 carbon atoms; and n is 1, 2 or 3.
In accordance with an embodiment, R1 and R3 are same.
In accordance with an embodiment, X is diethyl phosphate.
The baths may further comprise at least 15% by weight of a protic solvent selected from the group consisting of water, methanol, ethanol, glycerol, n-propanol, iso-propanol, butanol, pentanol and mixtures thereof.
Optionally, both organic and inorganic additives may be employed in the first bath to further control the fibre properties. The organic additives may be selected from dimethyl formamide, dimethyl sulfoxide, dimethyl acetamide, dimethyl imidazole, N-methyl pyrrolidinone, valerolactam, caprolactam, pyrrolidinone, dimethyl propylene urea, sulfolane, acetyl acetone, and their mixtures thereof. The inorganic additives may be selected from sulfates, carbonates, chlorides and phosphates of lithium, sodium, potassium, barium, calcium, zinc, aluminum and their mixtures thereof.
Though the process described above is directed towards a wet spinning process, the teachings of the disclosure can equally be applied in dry-wet spinning where the spun cellulosic fiber is (1) stretched in the air-gap to attain the desired denier and (2) regenerated in at least three baths with reducing concentration of ionic liquids to attain the desired degree of fibrillation.
The disclosure also provides spun cellulosic fibers obtained by the above disclosed process. The spun cellulosic fibers obtained have a fibrillation index less than or equal to 3. The conditioned tenacity of the fibers is greater than 2.5 grams per denier. “Dry or conditioned tenacity” is defined as the fiber break measured in a controlled condition of about 65% relative humidity and about 25?C temperature.
The invention will now be explained in greater details with the help of the following non-limiting examples.

EXAMPLE 1 - 2:
Cellulose Solution Preparation: 440 g of 1-ethyl-3-methylimidazolium acetate (EMIMA) and 60 g cellulose pulp (Degree of Polymerization of 580) are introduced into jacketed glass vessel maintained at 90?C by jacketed thermal fluid. The mixing is carried out for 4 hours under vacuum to dissolve and remove air bubbles. The cellulose solution obtained is then used for fibre spinning.
Fiber Spinning: Cellulose solution was processed on wet spinning set up with multiple bath arrangement. The cellulose solution was passed through a non-woven metallic mesh filter of 10 micron pore size followed by a spinneret die of 80 micron diameter by a spinning pump into the multiple bath arrangement. Multiple bath arrangement includes five baths of varying concentration of ionic liquid as shown in Table 1. Spinning speeds and throughput of cellulose solution were maintained to obtain a resulting fiber fineness of 1.2 denier. The resulting spun cellulosic fibers were further washed in water and dried in air oven at 80?C for 30 minutes.
Measurement of fibrillation index (FI): The spun cellulosic fibers were cut to approximately 15 mm length and 20 mg fiber were added to 5 ml water and shaken at 30 Hz for 30 minutes. Average number of fibrils on each cellulosic fiber was counted by observing the fibrillated fiber on an optical microscope.
The fibrillation index (FI) was defined on the basis of the number of fibrils as follows: 1-5 fibrils, FI=1; 6-10 fibrils, FI=2; 11-20 fibrils, FI=3; 21-40 fibrils, FI=4; 41-80 fibrils, FI=5 and >80 fibrils, FI=6.

Table 1
Example 1 Example 2
Spinneret die 80 ?m/ 90 holes 80 ?m/ 90 holes
Spinning temperature 120?C 120?C
Solvent Ethyl Methyl Imidazole Acetate Ethyl Methyl Imidazole Acetate
Solvent Concentration, % Temperature Residence time, seconds Solvent Concentration, % Temperature in 0C Residence time, seconds
Bath 1 69% 20C 6.5 69% 20 6.5
Bath 2 - - - 45% 25 6.5
Bath 3 - - - 30% 25 6.5
Bath 4 - - - 15% 25 6.5
Bath 5 - - - 0% 25 6.5
FI >50 4

EXAMPLES 3 - 8:
Cellulose Solution Preparation: 880 g of 1-ethyl-3-methylimidazolium acetate (EMIMA) and 120 g cellulose pulp are introduced into a jacketed laboratory mixer maintained at 90?C by thermal fluid. The mixing is carried out for 4 hours under vacuum to dissolve cellulose and remove air bubbles. The cellulose solution is then used for fiber spinning.
Fiber Spinning: Cellulose solution was processed on a wet spinning set up with multiple bath arrangement. The cellulose solution at 120?C was passed through a non-woven metallic mesh filter of 10 micron pore size followed by a spinneret die of 80 micron diameter by a spinning pump into the multiple bath arrangement. Multiple bath arrangement included different number of baths containing ionic liquid with a concentration gradient. Spinning speeds and throughput of the cellulose solution were maintained to obtain a resulting fiber fineness of 1.2 denier. Solvent concentrations, temperatures and stretch percent distributions across the baths are shown in Table 2. The stretching of cellulosic fiber spun through the spinneret was effected using godet roll after each bath. The percent stretch was determined by subtracting the extrusion speed from the linear speed of each godet roll, dividing the remainder by the difference of linear speed of the last godet roll and extrusion speed, then multiplying the resultant value by 100. The resulting fibers were further washed in water and dried in air oven at 80?C for 30 minutes.
Measurement of fibrillation index (FI): the fibers were cut to approximately 15 mm length and 20 mg fiber were added to 5 ml water and shaken at 30 Hz for 30 minutes. Fibrillated fibers were observed under the optical microscope and the fibrils were counted on each fiber. The fibrillation index (FI) was defined on the basis of the number of fibrils as follows: 1-5 fibrils, FI=1; 6-10 fibrils, FI=2; 11-20 fibrils, FI=3; 21-40 fibrils, FI=4; 41-80 fibrils, FI=5 and >80 fibrils, FI=6. The fiber properties are illustrated in Table 2.
“Dry breaking elongation” is defined as the elongation measured in a controlled condition of 65% relative humidity and 25?C temperature.

Table 2

Pulp DP 653 587
% Cellulose 12
Spinning Temperature 110?C
Spinneret 90 holes/80 ?m
Concentration of IL (%)
Temperature (?C) % stretch Example 3 Example 4 Example 5 Example 6 Example 7 Example 8
Bath 1 20 97% 40% 71% 80% 69% 69% 69%
Bath 2 25 98% 54% 56% 75% 45% 60% 45%
Bath 3 25 100% 45% 47% 55% 30% 55% 30%
Bath 4 25 100% 35% 37% 40% 15% 50% 15%
Bath 5 25 100% 25% 28% 25% 1.5% 5% 4%
Bath 6 25 100% 15% 20% 12% -- -- --
Bath 7 25 100% 5% 8% 6% -- -- --
Bath 8 25 100% 0.5% 1% 2% -- -- --
Titer (denier) Filament breakage 1.2 Fused filament 1.2 1.2 1.2
Dry tenacity (gpd) 1.8 1.57 1.50 1.36
Dry breaking elongation (%) 9 8 8 9
FI 2 1 4 4

EXAMPLES 9 - 10
Cellulose solution was prepared by the same process as that describer in Examples 3-8 above. Cellulose solution was processed on a wet spinning set up with multiple bath arrangement. The cellulose solution at 120?C was passed through a non-woven metallic mesh filter of 10 micron pore size followed by a spinneret die of 80 micron diameter by a spinning pump into the multiple bath arrangement. Temperature of bath 1 for Example 9 was kept at 24?C whereas temperature of bath 1 for Example 10 was kept at 13?C. Other parameters including concentration of ionic liquid in baths and stretch percent was kept same for both Example 9 and 10.

Table 3
Pulp DP 653
% Cellulose 12
Spinning Temperature 110?C
Spinneret 90 holes/80 ?m
Temperature (?C)
Concentration of IL (%) % stretch Example 9 Example 10
Bath 1 66% 30% 24 13
Bath 2 60% 59% 25 25
Bath 3 55% 72% 25 25
Bath 4 50% 84% 25 25
Bath 5 39% 92% 25 25
Bath 6 26% 100% 25 25
Bath 7 12% 100% 25 25
Bath 8 1% 100% 25 25
Titer (denier) 1.2 1.2
Dry tenacity (gpd) <1.0 3.0
Dry breaking elongation (%) 7 7
FI 3 5

EXAMPLE 11- 13
Cellulose solution prepared in the same manner as that for Examples 3-8 was processed on a wet spinning set up with multiple bath arrangement. The cellulose solution at 120?C was passed through a non-woven metallic mesh filter of 10 micron pore size followed by a spinneret die of 80 holes per 90 micron diameter by a spinning pump into the multiple bath arrangement. As indicated in Table 4, the percent stretch applied was varied for examples 11 to 13. Other parameters such as concentration of ionic liquid in the baths and temperature of the baths were kept constant in all examples.

Table 4
Pulp DP 653
% Cellulose 12
Spinning Temperature 110?C
Spinneret 80 holes/90 ?m
% stretch
Concentration of IL (%) Temperature (?C) Example 11 Example 12 Example 13
Bath 1 75% 8 99% 39% 12%
Bath 2 40% 8 100% 93% 46%
Bath 3 0.5% 25 100% 100% 100%
Titer (denier) 1.2 1.2 Filament Breakage
Dry tenacity (gpd) <1.0 3.7
Dry breaking elongation (%) 8 8
FI 1 3

EXAMPLE 14 -17
Cellulose Solution Preparation: 880 g of different ionic liquids as listed in Table 5 and 120 g cellulose pulp are introduced into jacketed laboratory mixer maintained at 90?C by thermal fluid. The mixing is carried out for 4 hours under vacuum to dissolve cellulose and remove air bubbles. The cellulose solution is then used for fiber spinning.
Fiber Spinning: Cellulose solution was processed on a wet spinning set up with multiple bath arrangement. The cellulose solution at 120?C was passed through a non-woven metallic mesh filter of 10 micron pore size followed by a spinneret die of 80 micron diameter by a spinning pump into the multiple bath arrangement. Multiple bath arrangement includes seven baths where the concentration of ionic liquid in the each bath is lower than the preceding bath. Concentration of ionic liquid, temperatures and stretch distributions across the baths are shown in Table 5. Spinning speeds and throughput of cellulose solution were maintained to obtain a resulting fiber fineness of 1.2 denier. The resulting fibers were further washed in water and dried in air oven at 80?C for 30 minutes. The fiber properties are showed in Table 5.

Table 5
Examples 14 Examples 15 Examples 16 Examples 17
Solvent 1-methyl-3-methylimidazolium acetate 1-butyl-3-butylimidazolium acetate 1-ethyl-3-ethylimidazolium propionate 1-ethyl-3-ethylimidazolium octanoate
Pulp DP 587
Spinning Temperature 110?C
Spinneret 90 holes/80 ?m
% Cellulose 8 8 8 10
Temperature (?C) % stretch Concentration of IL (%) Concentration of IL (%) Concentration of IL (%) Concentration of IL (%)
Bath 1 25 97% 54% 46% 46% 73%
Bath 2 25 98% 45% 40% 38% 60%
Bath 3 25 100% 35% 30% 31% 40%
Bath 4 25 100% 35% 20% 22% 30%
Bath 5 25 100% 15% 10% 13% 20%
Bath 6 25 100% 5% 5% 6% 10%
Bath 7 25 100% 0.5% 0.6% 0.6% 0%
Titer (denier) 1.2 1.2 1.2 1.2
Dry tenacity (gpd) <1.0 <1.0 <1.0 <1.0
Dry breaking elongation (%) 7 8 6 7
FI 2 1 1 3

EXAMPLE 18-19
Cellulose solution was prepared by the same process as that describer in Examples 3-8 above. Cellulose solution was processed on a wet spinning set up with multiple bath arrangement. The cellulose solution at 110?C was passed through a non-woven metallic mesh filter of 10 micron pore size followed by a spinneret die of 90 micron diameter by a spinning pump into the multiple bath arrangement. Temperature of bath 1 for Example 18 was kept at 7?C whereas temperature of bath 1 for Example 19 was kept at 5?C as indicated in Table 6. Other parameters including concentration of ionic liquid in baths and stretch percent was kept same for both Example 18 and 19. Table 6 illustrates the fiber properties of the fibers obtained.

Table 6
Pulp DP 653
% Cellulose 10
Spinning Temperature 110?C
Spinneret 80 holes/90 ?m
Temperature (?C)
Concentration of IL (%) % stretch Example 18 Example 19
Bath 1 75% 45% 7 5
Bath 2 40% 95% 25 25
Bath 3 4% 100% 25 25
Titer (denier) 1.2 1.2
Dry tenacity (gpd) 3.4 3.6
Dry breaking elongation (%) 9 9
FI 3 4

EXAMPLE 20 -21
Cellulose solution prepared in the same manner as that for Examples 3-8 was processed on a wet spinning set up with multiple bath arrangement. The cellulose solution at 110?C was passed through a non-woven metallic mesh filter of 10 micron pore size followed by a spinneret die of 60 micron diameter by a spinning pump into the multiple bath arrangement. As indicated in Table 7, the percent stretch applied was varied for examples 20 to 21. Other parameters such as concentration of ionic liquid in the baths and temperature of the baths were kept constant in all examples.

Table 7
Pulp DP 653
% Cellulose 7
Spinning Temperature 110?C
Spinneret 150 holes/60 ?m
% stretch
Concentration of IL (%) Temperature (?C) Example 20 Example 21
Bath 1 67% 10 15 2
Bath 2 53% 10 31 18
Bath 3 45% 10 44 36
Bath 4 38% 10 56 55
Bath 5 24% 10 69 73
Bath 6 15% 10 87 82
Bath 7 6% 25 98 97
Bath 8 2% 25 100 100
Titer (denier) 1.2 1.2
Dry tenacity (gpd) 2.5 2.6
Dry breaking elongation (%) 8 7
FI 3 4
As shown in above tables, the cellulosic fibers produced in accordance with the process of the present disclosure have better mechanical properties and good fibrillation index than the corresponding product prepared by the conventional methods or prior-art methods. This is achieved due to the critical combination of ionic liquid concentration in the first bath, the temperature and stretch imparted to the spun cellulosic fibers in the first bath.

SPECIFIC EMBODIMENTS ARE DESCRIBED BELOW
A process for preparing spun cellulosic fibers, comprising preparing a solution of cellulose in an ionic liquid, spinning the solution of cellulose to obtain spun cellulosic fibers, passing the spun cellulosic fibers sequentially through at least three baths having ionic liquid, wherein the concentration of ionic liquid in the first bath is in a range of 40-85% w/w, maintained at a temperature in a range of 5?C to 60?C, and the concentration of ionic liquid in each bath is lower than the preceding bath, and imparting a stretch to the spun cellulosic fibers in the first bath in a range of 15% to 100%.
Such process(es), wherein the spinning of cellulosic fibers is by wet spinning.
Such process(es), comprising passing the spun cellulosic fibers sequentially through multiple baths wherein the concentration of ionic liquid in each bath is lower than the preceding bath.
Such process(es), 3 wherein the number of baths is 4 to 8.
Such process(es), wherein the concentration of ionic liquid in the final bath is 1% w/w or less.
Such process(es), wherein the ionic liquid is a 1,3-disubstituted imidazolium salt of the formula I

where,
R1 and R3 are each, independently of one another, an organic group having 1 to 20 carbon atoms;

R2, R4 and R5 are each, independently of one another, an H atom or an organic group having from 1 to 20 carbon atoms;

X is an anion, anion being at least one selected from the group consisting of a carboxylate anion of formula Ra-COO- wherein Ra is a alkyl group having 1 to 20 carbon atoms, preferably 1 to 9 carbon atoms, and phosphate anion of formula Rb-Rc-PO4- , Rb and Rc are alkyl groups having 1 to 20 carbon atoms, preferably having 1 to 5 carbon atoms; and n is 1, 2 or 3.

Such process(es),, wherein R1 and R3 are same.
Such process(es), wherein X is diethyl phosphate.
Such process(es), wherein the baths further comprises at least 15% by weight of a protic solvent selected from the group consisting of water, methanol, ethanol, glycerol, n-propanol, iso-propanol, butanol, pentanol and mixtures thereof.
Such process(es), wherein the first bath further comprises additives selected from a group comprising dimethyl formamide, dimethyl sulfoxide, dimethyl acetamide, dimethyl imidazole, N-methyl pyrrolidinone, valerolactam, caprolactam, pyrrolidinone, dimethyl propylene urea, sulfolane, acetyl acetone, sulfates, carbonates, chlorides and phosphates of lithium, sodium, potassium, barium, calcium, zinc, aluminum and mixtures thereof.

FURTHER SPECIFIC EMBODIMENTS ARE DESCRIBED BELOW
Spun cellulosic fibers having a fibrillation index of not more than 3, obtained from a process comprising preparing a solution of cellulose in an ionic liquid, spinning the solution of cellulose to obtain spun cellulosic fibers, passing the spun cellulosic fibers sequentially through at least three baths having ionic liquid, wherein the concentration of ionic liquid in the first bath is in a range of 40-85% w/w, maintained at a temperature in a range of 5?C to 60?C, and the concentration of ionic liquid in each bath is lower than the preceding bath, and imparting a stretch to the spun cellulosic fibers in the first bath in a range of 15% to 100%.

Spun cellulosic fiber(s) having conditioned tenacity greater than 2.5 grams per denier.

INDUSTRIAL APPLICABILITY
The process as disclosed provides a simple and cost effective process for preparing low-fibrillating spun cellulosic fibers using ionic liquids as solvents. The process is such that the low-fibrillating spun cellulosic fibers can be obtained without the use of additives in the coagulation bath. As no additives are used further downstream processing is not required to be carried out during the process of preparing spun cellulosic fibers, making the process cost effective and environmentally friendly. Multiple parameters including concentration of ionic liquid in first bath, nature of cellulose, stretch imparted, temperature of first bath, concentration of ionic liquid in last bath have been factored in arriving at the present process. Specifically, the parameters of concentration of ionic liquid in first bath, temperature of the first bath and stretch imparted in the first bath have been devised to provide improved cellulosic fibers with low fibrillation.
,CLAIMS:We Claim:

1. A process for preparing spun cellulosic fibers, comprising:
preparing a solution of cellulose in an ionic liquid;
spinning the solution of cellulose to obtain spun cellulosic fibers;
passing the spun cellulosic fibers sequentially through at least three baths having ionic liquid;
wherein the concentration of ionic liquid in the first bath is in a range of 40-85% w/w, maintained at a temperature in a range of 5?C to 60?C, and the concentration of ionic liquid in each bath is lower than the preceding bath; and
imparting a stretch to the spun cellulosic fibers in the first bath in a range of 15% to 100%.

2. A process as claimed in claim 1 wherein the spinning of cellulosic fibers is by wet spinning.

3. A process as claimed in claim 1 comprising passing the spun cellulosic fibers sequentially through multiple baths wherein the concentration of ionic liquid in each bath is lower than the preceding bath.

4. A process as claimed in claim 3 wherein the number of baths is 4 to 8.

5. A process as claimed in claim 1 wherein the concentration of ionic liquid in the final bath is 1% w/w or less.

6. A process as claimed in claim 1 wherein the ionic liquid is a 1,3-disubstituted imidazolium salt of the formula I

where,
R1 and R3 are each, independently of one another, an organic group having 1 to 20 carbon atoms;

R2, R4 and R5 are each, independently of one another, an H atom or an organic group having from 1 to 20 carbon atoms;

X is an anion, anion being at least one selected from the group consisting of a carboxylate anion of formula Ra-COO- wherein Ra is a alkyl group having 1 to 20 carbon atoms, preferably 1 to 9 carbon atoms, and phosphate anion of formula Rb-Rc-PO4- , Rb and Rc are alkyl groups having 1 to 20 carbon atoms, preferably having 1 to 5 carbon atoms; and n is 1, 2 or 3.

7. A process as claimed in claim 6, wherein R1 and R3 are same.

8. A process as claimed in claim 6, wherein X is diethyl phosphate.
9. The process as claimed in claim 1, wherein the baths further comprises at least 15% by weight of a protic solvent selected from the group consisting of water, methanol, ethanol, glycerol, n-propanol, iso-propanol, butanol, pentanol and mixtures thereof.

10. A process as claimed in claim 1 wherein the first bath further comprises additives selected from a group comprising dimethyl formamide, dimethyl sulfoxide, dimethyl acetamide, dimethyl imidazole, N-methyl pyrrolidinone, valerolactam, caprolactam, pyrrolidinone, dimethyl propylene urea, sulfolane, acetyl acetone, sulfates, carbonates, chlorides and phosphates of lithium, sodium, potassium, barium, calcium, zinc, aluminum and mixtures thereof.

11. Spun cellulosic fibers having a fibrillation index of not more than 3, obtained from a process comprising:
preparing a solution of cellulose in an ionic liquid;
spinning the solution of cellulose to obtain spun cellulosic fibers;
passing the spun cellulosic fibers sequentially through at least three baths having ionic liquid;
wherein the concentration of ionic liquid in the first bath is in a range of 40-85% w/w, maintained at a temperature in a range of 5?C to 60?C, and the concentration of ionic liquid in each bath is lower than the preceding bath; and
imparting a stretch to the spun cellulosic fibers in the first bath in a range of 15% to 100%.

12. Spun cellulosic fibers as claimed in claim 11 having conditioned tenacity greater than 2.5 grams per denier.

Dated this 29th day of April, 2013

Aparna Kareer
Of Obhan & Associates
Agent for the Applicant
Patent Agent No. 1359