FORM 2
THE PATENT ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION:
Method to minimize loss of N-Methyl-Morpholine N-Oxide (NMMO) in cellulosic fibre
manufacturing process.
APPLICANT:
Aditya Birla Science and Technology Company Pvt. Ltd., Plot number 1 and 1-A/1, Taloja,
MIDC, Taluka- Panvel, District- Raigad- 410208, Maharashtra, India,
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes this invention and the manner in which it is
to be performed.

FIELD OF THE INVENTION
This Invention relates to a method to minimize loss of N-Methyl-Morpholine N-Oxide (NMMO) from resin effluent in the cellulosic fibre manufacturing process. Specifically, the disclosure relates to the method for reducing loss of NMMO in the regeneration effluents generated post treatment of a spin bath solution in ion-exchange resin systems during Lyocell fibre manufacturing process.
BACKGROUND OF THE INVENTION
Lyocell fibre manufacturing process is an eco-friendly process and an environmentally benign alternative to the viscose fibre manufacture process, for the production of high end cellulose fibres. A conventional method for producing Lyocell fibres includes following four steps: mixing, dissolving, spinning, and washing. The Lyocell process uses a direct solvent, N-Methyl-Morpholine N-Oxide (NMMO), in the production of Lyocell fibres to dissolve cellulose from pulp resulting in formation of cellulose dope. This cellulose dope is spun into cellulosic fibres leaving behind a spent NMMO solution. During spinning, various impurities associated with the cellulose dope leach out in the spent NMMO solution. The impurities usually include inorganic cations and anions, hemicellulosic impurities obtained from the pulp and degraded cellulosic impurities. To economise the process, spent NMMO solution (referred hereinafter as spin bath NMMO solution), is recovered and recycled after purifying it. The process of purification of the spin bath NMMO solution includes removing impurities derived from pulp, other raw materials used in the process, impurities leached out from metallic equipment, and/or impurities that may have been formed by degradation reactions.
The known purification process to remove ionic impurities employs use of ion-exchange resin systems. Here, an anion and cation resins are used. The anion resin carries a positive charge and hence adsorbs impurities carrying a negative charge. On the other hand,

the cation exchange resin has a negative charge and adsorbs impurities carrying a positive charge. Since NMMO carries a slight positive charge, it has a tendency to get adsorbed on the cation resin.
Generally, after completion of one purification cycle of spin bath NMMO solution, the feed of spin bath NMMO solution is stopped and the resins in the ion-exchange resin systems are regenerated as the capacity of the ion-exchange resins to adsorb impurities starts decreasing after one purification cycle of spin bath NMMO solution. The regeneration of both anion and cation resins used in the ion-exchange resin systems is done after every purification cycle of the spin bath NMMO solution.
A major drawback of regenerating the cation resin after every purification cycle is that as the cation resin adsorbs a significant amount of NMMO, the regeneration of cation resin after every purification cycle leads to loss of NMMO in an effluent generated post purification of the spin bath solution. Since NMMO is a very expensive solvent, even a small amount of loss of NMMO during the process makes the entire Lyocell process costly. Additionally, the adsorbed NMMO on the cation resin cannot be washed by water and has to be removed with regeneration chemicals such as HC1 which in turn contributes to higher COD in the effluent stream which has to be treated in the Effluent Treatment Plant.
Thus, there is a need for an efficient method to minimize loss of NMMO in an effluent generated during regeneration cycle. There is also a need of a method which reduces generation of COD in effluent and also leads to decrease in time of regeneration cycle.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a method to minimize loss of N-Methyl-Morpholine N-Oxide (NMMO) in an effluent generated during regeneration cycle of ion-

exchange resin systems during a Lyocell fibre manufacturing process, the spin bath being operably connected with the ion-exchange resin systems, the method comprising:
a) first passing the spin bath NMMO solution through an anion exchange resin system and then a cation resin exchange system for one purification cycle till outlet conductivity of solution reaches 15 µS/cm;
b) regenerating the anion exchange resin but not regenerating the cation exchange resin when one purification cycle is completed;
c) passing the spin bath NMMO solution first through the anion exchange resin and then through the cation exchange resin for second purification cycle;
d) regenerating the anion exchange resin but not the cation exchange resin when the second purification cycle of spin bath NMMO solution is completed; and
e) repeating steps a) to d) for at least four-five spin bath NMMO purification cycles.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, there is provided a method for minimizing loss of N-Methyl-Morpholine N-Oxide (NMMO) in resin effluent during the Lyocell fibre manufacturing process.
In accordance with the present invention, during the Lyocell fibre manufacturing process, a spin bath NMMO solution is used containing around 20-22% of NMMO in it. During the spinning of the cellulosic dope, NMMO tends to get contaminated with various impurities. In order to reuse this NMMO, it has to be purified. During the purification of the spin bath NMMO solution, the ionic impurities are removed in an ion-exchange resin system containing both anion and cation exchange resins. Preferably, the amount of cation resin used in the ion

exchange resin system is one fourth to the amount of anion resin used in the ion exchange resin system.
The impurities can either be metal impurities such as calcium, magnesium, sodium, etc. containing a positive charge or anionic impurities such as sulphate, thio-sulphate, nitrate, etc. There are also some colour impurities which are formed due to the addition of additives in the solution. When the purification process starts, the impurities containing a positive charge are adsorbed on the cation exchange resin system and the impurities containing a negative charge are adsorbed on the anion exchange resin system. NMMO carries a slightly positive charge and tends to get adsorbed on the cation resin of the ion exchange resin system.
According to an embodiment of the present invention, the spin bath NMMO solution is sent for purification during which the solution is first passed through an anion exchange resin and then through a cation exchange resin. The solution is continued to be passed for one purification cycle of the spin bath NMMO solution. Preferably, the purification cycle of the spin bath NMMO solution is continued till the conductivity of the outlet NMMO solution from resin system reaches 15 µS/cm (micro Siemens per centimetre). Once the conductivity of the outlet NMMO solution from resin system reaches 15 µS/cm, the anion resin from the ion exchange resin system is regenerated. Preferably, the capacity of the cation resin is not exhausted and it is not regenerated after the first purification cycle of the spin bath NMMO solution. In the second purification cycle of spin bath NMMO solution, it is passed through anion resin first and then through cation resin of ion exchange resin system. Again, once the conductivity of the outlet NMMO solution from resin system reaches 15 µS/cm, the anion resin is regenerated. Preferably, the capacity of the cation resin of the ion exchange resin system is not exhausted after the second purification cycle and hence they are not regenerated even after the second purification cycle of the spin bath NMMO solution. In the third purification cycle

of spin bath NMMO solution, it is passed through anion resin and then through cation resin of the ion exchange resin system. Once the conductivity of the outlet NMMO solution reaches 15 µS/cm, the anion resin is regenerated. In an embodiment, the capacity of the cation resin of the ion exchange resin system is not exhausted after the third purification cycle and hence it is not regenerated even after the third purification cycle of the spin bath NMMO solution. Preferably, the anion resin of the ion exchange resin system is regenerated during the third purification cycle of spin bath NMMO solution. Preferably, the cation resin is not regenerated for four to five purification cycles of spin bath NMMO solution. Preferably, the spin bath NMMO solution is operably connected with the ion-exchange resin systems.
Since NMMO carries a slight positive charge, it has a tendency to get adsorbed on the cation resin of the ion exchange resin system. With passage of time, a significant amount of NMMO gets adsorbed on the cation resins of the cation exchange resin system.
According to an embodiment, after every purification cycle, where only anion resin of the ion exchange resin system is regenerated, the adsorption of NMMO on the cation resin decreases as it gets replaced by other stronger cations from the spin bath NMMO solution.
According to an embodiment, as the number of purification cycles increase where same cation resin is used, the cationic metal impurities, which carries a stronger charge on them than NMMO and therefore a stronger affinity towards the cation resin, replace the already adsorbed NMMO on the cation resin of the ion exchange resins leading to further reduction in loss of NMMO in the effluent fonrted during regeneration of the cation resin.
Preferably, the overall performance of the ion exchange resin system during four-five purification cycles does not change significantly without regeneration of cation resin. Preferably, without regeneration of cation resin for 4-5 cycles, there is a significant reduction in loss of NMMO, generation of effluent and time of regeneration of ion exchange resin system,

as more clearly shown in the experimental data. According to another embodiment, by not regenerating the cation resin of the ion exchange resin system for at least 4-7 cycles leads to reduction in the loss of NMMO in the resin effluent further reducing COD in the effluent generated post treatment of a spin bath NMMO solution.
EXAMPLES
Details of the method to minimize loss of N-Methyl-Morpholine N-Oxide in resin effluent in the Lyocell process according to the present disclosure are provided below.
Spin bath NMMO solution which contains 20% NMMO has been used for all trials. Both cationic and anionic resins used have been obtained from commercial sources.
Experimental Data 1:
a) Experimental set up containing glass columns with diameter of around 2.2 cm and
height of around 30 cm with outlet sample collection valve was taken. Peristaltic pump
was used to maintain constant flow rate. Cotton was used as membrane in glass column
to avoid carry-over of resin beads from said glass column. 30 ml of anion and 10 ml of
cation exchange resins were used.
b) In first cycle, anion exchange resin was regenerated with 4% of Sodium Hydroxide (NaOH) and cation exchange resin was regenerated with 4% Hydrochloric acid (HC1) (Regeneration as shown in table-1). In addition, the anion exchange resin was cleaned with 4% HC1.
c) From second to ninth cycle, only anion exchange resin was regenerated and cation exchange resin was used without regeneration.
d) Spin bath NMMO solution (feed) was passed through columns with 7-8 ml/min flow using peristaltic pump and samples were analysed after fraction of every 4-5 BV (BV=

bed volume of anionic resin) and sample of feed & outlet was collected for further analysis.
e) Conductivity of various fractions (BV) were measured. The ion exchange resin system was considered exhausted when the outlet conductivity of NMMO solution reached 15 µs/cm.
f) Column outlet sample at 15 µs/cm and spin bath NMMO solution as feed sample were analysed with Induced coupled plasma (ICP) for metal impurity detection. However, cation acid wash and overall composite sample of ninth cycle was also analysed with ICP as well as high pressure liquid chromatography (HPLC).
g) ICP analysis was done for detection of cationic impurities and HPLC analysis was done for NMMO.
Table 1: Regeneration of Lab resin columns In Experimental Data 1

Reagent Resin Volume of reagent, BV Water BV
HC1 4% Anionic 2-3 4-5
NaOH 4% Anionic 2-3 3-4
HC1 4% Cationic 2-3 3-4
Experimental Data 2:
a) The experimental set up consisted of three columns of fibre reinforced plastic (FRP) for resin beads. Pipeline connections for spin bath NMMO feed and for reagent chemicals were provided.
b) 75 litres anion exchange and 18.75 litres of cation exchange resins were used.
c) In the first cycle, anion exchange resin was regenerated with 4-5 % NaOH and cation exchange resin was regenerated with 4-5 % HC1 (Regeneration as shown in table-2)
d) From second to fifth cycle, only anion exchange resin was regenerate and cation exchange resin was used without regeneration.

e) Spin bath NMMO solution (feed) was passed through columns with 800-1500 L/h flow and samples were analysed after fraction of every 10 BV, The samples of feed and at outlet, at 15 µs/cm, were collected for further analysis.
Table 2: Regeneration of resin columns in Experiment data 2

In the present process, the quantum of effluent generated reduces by 10-20% while time of regeneration reduces substantially by 20-30%.
RESULTS: The following tables summarizes resin performance and analytical results -
Table 3: Results of Experiment Data 1

Total effluent Total effluent without
Volume Combined in regeneration of
of Water column normal Cationic Resin
reagent wash, water wash cycle (BV)
Regent Resin (BV) (BV) (BV) (BV)
HCl 5% Anionic- 2-3 4-5 3-4 16-19 13-15
NaOH

5% Anionic 2-3 3-4
HCL 5% Cationic 3-4 4-5

Experimental Data 1 ICP Analysis
No. of Cycle Flow BV/h Regeneration BV at 15 Conductivity Feed Conductivity Ca
of
Feed Ca at
exhaust Na of
Feed
PPM Na at
Exhaust PPM
1 15-16 Cation An on 56 136-138 1.4 1.4
2
An on 56
1.2 2
3
An on 56
3-4 1.6 2.1
4
An on 60
1.3 9-10 2.2
5
An on 60
1.5 2.6
6
An on 60
1.2 2.3
7
An on 56
__ j 2.6
8
An ton 60
1.4 2.7
9
An ton 60
1.7 2.2
• Resin performance in terms of BV was approximately same for first and ninth cycle, showing cation working efficiently till ninth cycle without regeneration.
• ICP results showing there was no leakage of Ca & Na for first & ninth cycle.

Table 4: Results of Experiment Data 2
• For cycle 1, in which feed conductivity was in the range of 100-104 µS/cm, feed BV was 140. However, for cycle 2, BV is 125. The decrease in the BV can be attributed to higher feed conductivity, i.e., 105-110 µS/cm

• In spin bath NMMO solution, only Ca and Na cationic impurities were detected. Other cationic impurities were marginal (< 1ppm), There was no significant difference for cationic impurities (Ca, Na) in the outlet for cycle 1 and cycle 3.
• On comparing cycles 2 and 4 (for which feed conductivity is the same), it was found that resin performance was the same. Also, there was no significant difference in the impurity content in the outlet at exhaust conductivity. Hence, resin performance has not changed even without regeneration of cationic resin.
• It was observed from cycles 1 and 5 that resin performance was decreased by 10% for cycle 5 as compared to cycle 1. This could be primarily because velocity was kept almost double in cycle 5 as compared to cycle 1. This has reduced the contact time of spin bath with resin

Opera ting conditions Regeneration Resin Performance
Cycle No. Flow BV/h Anion
Velocity
m/h Cation
Velocity
m/h Feed conductivity
µS/cm Cation Anion BV at
15 µS/cm Ca in Feed (ppm ) Ca at 15
µS/cm (ppm) Na in
Feed
(ppm) Na at 15 µS/cm
(ppm)
1 10 to 11 9 to 10 20 to 22 100-104 Yes Yes 140 2-3 1.7 8-10 1
2


110-115 No Yes 85
0.7
0.6
3


105-110 No Yes 125
0.6
0.7
4


110-115 No Yes 85
0.8
0.7
5 20 to 17 to 20 35 to 40 100402 No Yes 125
1
0.7

significantly. There was no significant difference for impurity content at the outlet for both cycles.
• Velocity was increased to check the effect on resin performance without cation regeneration at much higher velocity.
• Thus, considering the change in feed conductivity and feed velocity, there was no major change in resin performance from cycle 1 to cycle 5. Also, there was no significant difference in the cationic impurities at the outlet for these cycles.
Table 5: NMMO loss at washing streams for the experimental setup:

Cycle No. NMMO loss in effluent, ppm
Data 1 1 St 407
2nd to 9th 461
Data 2 1 St 609
2nd to 5th 243
• HPLC results showed that NMMO loss in overall effluent stream of first and subsequent cycles was in similar range or a lower range thus reducing overall NMMO loss as the
number of regeneration was reduced.
Table 6: NMMO loss estimation per ton of fibre production

Data 2 NMMO, ppm Total solution passed, m3 Total effluent generated /cycle BV Expected fiber, T NMMO loss, kg/Tf
Cycle 1 609 10.5 1648 0.38 3.27
Cycle 2 to 5 243 31.5 13-15 1.14 0.43
• On the basis of per ton production of fibre, NMMO loss had reduced from 3.27 kg to 0.43 kg, which is about 88% less.

INDUSTRIAL APPLICABILITY
The present invention discloses the method to minimize loss of N-Methyl-Morpholine N-Oxide (NMMO) in an effluent generated post treatment of a spin bath NMMO solution in ion-exchange resin systems during the Lyocell fibre manufacturing process.
It has been observed that by using the method of the present invention, the overall loss of NMMO used in the Lyocell fibre manufacturing process is reduced significantly and the efficiency of ion-exchange resin is improved. It is observed that on the basis of per ton production of fibre, NMMO loss is reduced from 3.27 kg to 0.43 kg, which is about 88% less by using the method described herein. Additionally, the method described herein reduces generation of effluent by around 11% and the overall time of regeneration cycle is reduced by 24%.
The invention is defined by the claims that follow.

We Claim:
1. A method to minimize loss of N-Methyl-Morpholine N-Oxide (NMMO) in an effluent
generated during regeneration cycle of ion-exchange resin systems during Lyocell fibre
manufacturing process, the spin bath being operably connected with the ion-exchange resin
systems, the method comprising:
a) passing the spin bath NMMO solution through an anion exchange resin system and
then a cation resin exchange system for one purification cycle till outlet conductivity of
solution reaches 15 µS/cm;
b) regenerating the anion exchange resin but not regenerating the cation exchange resin when one purification cycle is completed;
c) passing the spin bath NMMO solution first through the anion exchange resin system and then through the cation exchange resin system for second purification cycle;
d) regenerating the anion exchange resin but not the cation exchange resin when the
second purification cycle of spin bath NMMO solution is completed; and
e) repeating steps a) to d) for at least four-five spin bath NMMO purification cycles.
2. The method as claimed in claim 1, wherein the spin bath NMMO solution is passed through the anion exchange resin system and then the cation exchange resin system, for third purification cycle of the spin bath NMMO solution, when the spin bath NMMO solution reaches 15 µS/cm.
3. The method as claimed in claim 1, wherein adsorption of N-Methyl-Morpholine N-Oxide (NMMO) on the non-regenerated cation resin decreases with every purification cycle of the spin bath NMMO solution.

4. The method as claimed In claim 1, wherein the volume of cation exchange resin Is 25 % to 50% of anion exchange resin.