FORM 2
The Patents Act 1970,
(39 of 1970)
&
The Patents Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
POROUS FIBRES AND PROCESS FOR PREPARING THE SAME
RELIANCE INDUSTRIES LIMITED
an Indian Company
of 3rd Floor, Maker Chamber-IV, 222, Nariman Point,
Mumbai400 021, Maharashtra, India.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

This application is a patent of addition to Indian Patent Application No. 2071/MUM/2011 filed on July 20, 2011, the entire contents of which, is specifically incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to porous fibres and a process for preparing the same.
BACKGROUND
Synthetic fibres especially polyester, polypropylene and nylon have been always competing with natural fibres such as cotton for its natural feel and dull look which is frequently termed as 'cotton look' and natural feel. The synthetic feel and shining luster of synthetic fibres make them less appealing for use in garments and hence natural fibres could not be replaced by synthetic fibres. In commercial production of synthetic textile fibres, additives such as Ti02, BaS04 and the like are added to avoid the smooth glossy luster.
Salt leaching method is commonly used in bio-medical applications wherein porous scaffolds are made from compounded Salt/polymer composite after boiling in suitable solvent. This method, which allows the preparation of porous structures with regular porosity, has been used to prepare porous DBC (di-butyryl-chitin) scaffolds employing excess salt crystals that can easily be dissolved as a porogen in water.
British Patent No. 1099676 discloses a method of making a microporous film which includes forming a spreadable mixture of a synthetic polymeric plastics working material, a finely divided removable solid filler and a solvent for the working material, forming a

coating of the mixture in the form of a film on a support, removing the solvent by evaporation, leaching out the filler with a liquid The particle size of the removable filler is not greater than 50 microns. It particularly discloses spreading of NaCl solution on a substrate such as polyvinyl chloride, polymethyi methacrylate, polystyrene, a polyamide, an olefin co-polymer and a nitrile rubber followed by leaching out by a suitable solvent.
Japanese Patent No. 7118432 discloses a method to produce a porous polyester film useful as label or poster having excellent opacity and drawability by extruding polyester and inorganic particles.
United States Patent No. 4244689 discloses a method of preparation of tooth root implant by adding sodium chloride to a powdered acrylic polymer. The mixture is moistened by liquid monomer and poured into a mould followed by polymerization. Then the solidified implant is removed from the mould and the salt is leached out by boiling water to impart porosity. Pore size achieved is in the range of 50-400 microns.
WO 1989000842 discloses use of crystalline salts such as sodium chloride to introduce porosity in polymethacrylates to make synthetic bony-tissue like material. Sodium chloride particles of size 50 to 200 mu are added to a monomer which is then polymerized to form a hydrophilic polymeric material. The resulting material is contacted with a sufficient amount of an aqueous solution to dissolve the crystals, thereby forming a polymerized microporous material having micropores of about 50 to 200 mu in diameter at the locations where the crystals had previously been.

None of the prior art documents disclose a simple salt leaching process for the preparation of nano-porous synthetic fibers/fabric.
Our co-pending Indian Patent Application 2071/MUM/2011 discloses a simple salt leaching process for the preparation of nano-porous synthetic fibers/fabric having pores of about 50 nm to about ]000 nm in diameter to impart dullness and cotton-like feel to synthetic fibers/fabric without using dulling agents like T1O2. The process disclosed in Indian Patent Application 2071/MUM/2011 involves incorporation of inorganic salt such as NaCl during the polymerization which is then subsequently removed to form nano-porous synthetic fibers/fabric.
However, it was found that the presence of salt which acts as a nucleating agent causes rapid crystallization resulting into yarn breakage during spinning and winding, Accordingly, it is desired to develop a simple process which can reduce the rate of crystallization and improve the spinning performance of synthetic polymer composition.
OBJECTS OF THE PRESENT INVENTION
It is an object of the present invention to provide a simple salt leaching process for the preparation of nano-porous synthetic fibers/yarn/fabric.
It is another object of the present invention to provide a simple process for the preparation of nano-porous synthetic fibers/yarn/fabric which imparts natural feel and cotton look to the synthetic fibres prepared.

It is still another object of the present invention to provide a simple process for the preparation of nano-porous synthetic fibers/yarn/fabric which avoids or reduce the use of dulling agents such as Ti02 and BaS04.
It is yet another object of the present invention to provide nano-porous synthetic fibers/yarn/fabric which has improved properties such as dyeability and water absorption.
It is a further object of the present invention to provide a process which improves the spinnability of the polymer during the preparation of nano-porous synthetic fibers/yarn/fabric.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1(a) illustrates fibres of example 1 with inorganic salt particles entrapped therein;
Fig. 1(b) illustrates porous fibres of example 1;
Fig. 2(a) illustrates film of example 2 with inorganic salt particles entrapped therein;
Fig. 2(b) illustrates control film of example 2;
Fig. 3(a) illustrates fibres of example 2 with inorganic salt particles entrapped therein;
Fig. 3(b) & 3(c) illustrates porous fibres of example 2,
Fig. 4 (a) illustrates DSC thermogram of PET sample;
Fig. 4 (b) illustrates DSC thermogram of PET with 0.5 % NaCl and 2 % IPA sample
(present invention); and
Fig. 4 (c). illustrates DSC thermogram of PET with 0.5 % NaCl sample.

SUMMARY
In accordance with one aspect of the present invention there is provided a porous synthetic fiber/yarn derived from a polyester/co-polyester, said polyester/co-polyester comprising repeating units derived from isophthalic acid, wherein the diameter of the pores in the fiber is about 50 nm to about 700 nm.
In accordance with another aspect of the present invention there is provided a process for the preparation of synthetic fiber/yarn as claimed in claim 1, said process comprising the following steps:
synthesizing a molten polymer comprising isopthalic acid as a co-monomer and at least one inorganic salt; said inorganic salt being introduced during synthesizing through a vehicle;
subjecting the molten polymer to at least one method selected from the group consisting of direct spinning and indirect spinning to obtain a fiber/yarn; and removing the inorganic salt particles from the fiber/yarn by at least one method selected from the group consisting of treating the fiber/yarn with boiled water and dyeing the fiber/yarn to obtain porous fiber/yarn having pores of about 50 nm to about 700 nm in diameter. Typically, the inorganic salt is at least one selected from the group consisting of sodium chloride, potassium chloride and calcium chloride, potassium carbonate, sodium carbonate, nitrates of inorganic compounds, thermally stable water soluble compounds and mixtures thereof.

In accordance with one of the embodiments of the present invention, the process comprises the following steps:
- preparing a molten polymer by mixing at least two different dicarboxylic acids or ester thereof and at least one diol in a reactor to obtain a mixture followed by esterifying the mixture to obtain a pre-polymer, the molar ratio of the total dicarboxylic acid or ester thereof to the total diol being 1:1.8 to 1:2 and at least one of the dicarboxylic acid being essentially isophthalic acid;
- subjecting the pre-polymer to polymerization at a temperature of about 270 to about 290 °C to achieve IV. of about 0.6 dl/gm;
incorporating at least one inorganic salt dispersed in a vehicle either before or during
or after any method step selected from the group consisting of mixing, esterifying and
polymerization;
subjecting the molten polymer to direct spinning to obtain fiber/yarn with inorganic
salt particles entrapped therein; and
removing the inorganic salt particles from the fiber/yarn by at least one method
selected from the group consisting of treating the fiber/yarn with boiled water and
dyeing the fiber/yarn to obtain porous polyester fiber/yarn having pores of about 50
nm to about 700 nm in diameter.
In accordance with another embodiment of the present invention, the process comprises the following steps:
a. preparing a molten polymer by mixing at least two different dicarboxylic acids or ester thereof and at least one diof in a reactor to obtain a mixture

followed by esterifying the mixture to obtain a pre-polymer, the molar ratio of the total dicarboxylic acid or ester thereof to the total diol being 1:1.8 to 1:2 and at least one of the dicarboxylic acid being essentially isophthalic acid;
b. subjecting the pre-polymer to polymerization at a temperature of about 270 to
about 290 °C to obtain amorphous chips of I.V. of about 0.6 dl/gm;
c. incorporating at least one inorganic salt dispersed in a vehicle either before or
during or after any method step selected from the group consisting of mixing,
esterifying and polymerization;
d. converting the amorphous chips into fiber/yarn with inorganic salt particles
entrapped therein; and
e. removing the inorganic salt particles from the fiber/yarn by at least one
method selected from the group consisting of treating the fiber/yarn with
boiled water and dyeing the fiber/yarn to obtain porous polyester fiber/yarn
having pores of about 50 nm to about 700 nm in diameter.
Typically, the method step (d) comprises the following steps:
crystallizing the amorphous chips at a temperature of about 110 C to about 170°C to obtain crystallized Polyethylene terephthalate (PET) chips;

- drying the crystallized Polyethylene terephthalate (PET) chips at a temperature of about 110 to about 140°C to obtain PET chips having moisture level less than 40ppm; and
- extruding the Polyethylene terephthalate chips through at least one screw extruder at a temperature of about 270 to about 300°C to obtain fiber/yarn with inorganic salt particles entrapped therein,
Typically, the amount of inorganic salt is in the range of about 0.1 to about 10 % of the theoretical weight of the polyester.
Typically, the amount of isopthalic acid is about 1 to about 4 % of the theoretical weight of the polyester, preferably, 2 %.
Typically, the two different di-carboxylic acids are selected from the group consisting of terephthalic acid, isophthalic acid, adipic acid, glutaric acid and sebacic acid.
Typically, the diol is at least one selected from ethylene glycol, diethylene glycol, methylene glycol, propylene glycol, butanediol, 1,3 -propane diol and neopentyl glycol. Typically, the vehicle is at least one selected from the group consisting of monoethylene glycol and water.
Typically, the step of incorporating inorganic salt is carried out either before the polymerization or during the polymerization.

DETAILED DESCRIPTION
The drawbacks of known synthetic fibre/yarn are synthetic feel and shining luster. The
process of the present invention imparts natural feel and dull look ('cotton look') to the synthetic fibers.
The process of the present invention imparts natural feel and dull look ('cotton look') to the synthetic fibers by introducing nano and micro porosity on the fibre/yarn by a simple 'Salt-leaching method'. The salt-leaching method of the present invention involves incorporation of at least one inorganic salt into the synthetic fibres/yarn such as polyester at any stage before the polymerization or polycondensation step.
It is known that during the fibre spinning process molten polymer is extruded to a cold atmosphere which allows solidification and crystallization of the polymer. The polymer undergoes partial crystallization to form crystalline and amorphous phase. The spinnability, spinning rate or production speed is highly dependent on the rate of crystallization of the polymer in the quench zone.
The as-spun fibre drawability and draw ratio are highly related to the molecular mobility. During the high speed spinning process, above 2000m/min, elongational stress causes molecular rearrangement and orientation along the fibre axis. This also can induce crystallization. Fibre breakage may occur if the molecules are not mobile enough at this stage. If the molecules crystallize very fast immediately after extrusion, the mobile phase (amorphous) would be very less, giving rise to increased yarn tension and fibre breakage.

One particular problem associated with the salt leaching process for the preparation of nano-porous synthetic fibers/fabric disclosed in our co-pending Indian Patent Application 2071/MUM/2011 is poor spinning efficiency on account of the frequent yarn breakage during spinning of the PET/salt chips. This is attributed to the high rate of crystallization of the polyester because of the presence of the salt which acts as a nucleating agent. The present invention particularly addresses this problem.
In accordance with one aspect of the present invention there is provided a porous synthetic fiber/yarn derived from a polyester/co-polyester, said polyester/co-polyester comprising repeating units derived from isophthalic acid, wherein the diameter of the pores in the fiber is about 50 nm to about 700 ran.
In accordance with another aspect of the present invention, there is provided a process that results in improved spinning performance. The improvement in spinning performance is achieved by reducing the rate of crystallization of the polymer. The process of the present invention involves a method step of incorporation of isopthalic acid (IPA) as a co-monomer during the polymerization, which reduces the rate of crystallization of the polymer and which in turn improves the spinning efficiency.
The salt leaching method in accordance with the present invention is described herein
below.
Initially, slurry of at least one inorganic salt is prepared by dispersing the inorganic salt
into a vehicle. Typically, the inorganic salt is at least one selected from the group

consisting of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate and calcium chloride, nitrates of inorganic compounds, thermally stable water soluble compounds and mixtures thereof. Typically, the vehicle is selected from the group consisting of water, mono ethylene glycol and mixtures thereof. Preferably, the slurry of inorganic salt is prepared in mono ethylene glycol (MEG). The obtained slurry along with isopthalic acid as a co-monomer is then incorporated at any step of polymerization during the manufacture of fiber/yarn. Finally, the inorganic salt particles are removed from the fiber/yarn by at least one method selected from the group consisting of treating the fiber/yarn with boiled water and dyeing the fiber/yarn to obtain porous fiber/yarn having pores of about 50 nm to about 700 nm in diameter.
In accordance with another aspect of the present invention there is provided a process for
the preparation of a porous synthetic fiber/yarn prepared from polyester/co-polyester.
The process is described herein below:
Initially, a molten polymer containing isopthalic acid as a co-monomer and at least one
inorganic salt is synthesized wherein the inorganic salt is introduced during the synthesis
through a vehicle.
Typically, the inorganic salt is at least one selected from the group consisting of sodium
chloride, potassium chloride and calcium chloride, nitrates of inorganic compounds,
thermally stable water soluble compounds and mixtures thereof.
Typically, the vehicle is at least one selected from the group consisting of monoethylene
glycol and water. The molten polymer is then subjected to at least one method selected
from the group consisting of direct spinning and indirect spinning to obtain a fiber/yam.

Typically, the direct spinning process involves continuous polymerization and spinning which avoids the stage of formation of solid polymer pellets. The polymer melt is produced from the raw materials and then from the polymer finisher directly pumped to the spinning machines. Direct spinning is dedicated to high production capacity.
Typically, the indirect spinning is a batch process where the polymer is synthesized, solidified to pellets and later on re-melted to spin into fiber.
In the next step, the inorganic salt particles from the fiber/yam are removed by at least one method selected from the group consisting of treating the fiber/yarn with boiled water and dyeing the fiber/yarn to obtain porous fiber/yarn having pores of about 50 nm to about 700 nm in diameter.
In accordance with another embodiment of the present invention there is provided a process for the preparation of porous fiber/yam prepared from polyester/co-polyester, The process involves the following steps:
In the first step, slurry of at least one inorganic salt is prepared by dispersing the inorganic salt into a vehicle. Typically, the inorganic salt is at least one selected from the group consisting of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate and calcium chloride, nitrates of inorganic compounds, thermally stable water soluble compounds and mixtures thereof. Typically, the amount of the inorganic salt is about 0.1 to about 10 % of the theoretical weight of the polyester..

Typically, the vehicle is at least one selected from the group consisting of monoethylene glycol and water. Preferably, the slurry of inorganic salt is prepared in mono ethylene glycol.
In the next step, a molten polymer is prepared by mixing at least two dicarboxylic acids or esters thereof and at least one diol in a reactor to obtain a mixture. Typically, the two different dicarboxylic acids are selected from the group consisting of purified terephthalic acid, isophthalic acid, adipic acid, glutaric acid and sebacic acid.
Typically, the diol is at least one selected from ethylene glycol, diethylene glycol,
triethylene glycol, propylene glycol, butanediol, 1,3 -propane diol and neopentyl glycol.
Typically, the molar ratio of the total dicarboxylic acid or esters thereof to the total diol
ranges between 1:1.8 to 1:2.
The obtained mixture is esterifed to obtain a pre-polymer. The resultant pre-polymer is
then subjected to polymerization at a temperature of about 270 to about 290°C to achieve
I.V. of about 0.6 dl/gm.
Typically, the slurry of inorganic salt is incorporated either before or during or after the
mixing step.
Alternatively, the slurry of inorganic salt is incorporated either before or during or after
the esterifying step.
In accordance with another embodiment of the present invention the slurry of inorganic salt is incorporated either before or during or after the polymerization, preferably either before or during the polymerization.

The obtained molten polymer is subjected to direct spinning to obtain fiber/yarn with inorganic salt particles entrapped therein. Finally, the inorganic salt particles are removed from the fiber/yarn by at least one method selected from the group consisting of treating the fiber/yarn with boiled water and dyeing the fiber/yarn to obtain porous polyester/co-polyester fiber/yarn having pores of about 50 nm to about 700 nm in diameter.
In accordance with still another embodiment of the present invention there is provided a process for the preparation of porous fiber/yarn prepared from poiyester/co-poiyester. The process involves the following steps.
In the first step, slurry of at least one inorganic salt is prepared by dispersing the inorganic salt into a vehicle. Typically, the inorganic salt is at least one selected from the group consisting of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate and calcium chloride, nitrates of inorganic compounds, thermally stable water. soluble compounds and mixtures thereof. Typically, the amount of the inorganic salt is about 0.1 to about 10 % of theoretical weight of the polyester.
Typically, the vehicle is at least one selected from the group consisting of monoethylene glycol and water. Preferably, the slurry of inorganic salt is prepared in mono ethylene glycol.
In the next step, at least two different dicarboxylic acids or esters thereof and at least one diol are mixed in a reactor to obtain a mixture.

Typically, the two different di-carboxylic acids are selected from the group consisting of purified terephthalic acid, isophthalic acid, adipic acid, glutaric acid and sebacic acid.
Typically, the diol is at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, 1,3 -propane diol and neopentyl glycol. Typically, the molar ratio of the total dicarboxylic acid or ester thereof to the total diol ranges between 1:1.8 to 1:2.
The mixture is further esterified to obtain a pre-polymer which is then subjected to polymerization at a temperature of about 270 to about 290 °C to obtain amorphous chips of I.V. of about 0.6 dl/gm.
The prepared slurry of inorganic salt is incorporated either before or during or after the mixing step.
Alternatively, the slurry of inorganic salt is incorporated either before or during or after the esterifying step.
In accordance with another embodiment of the present invention the slurry of inorganic salt is incorporated either before or during or after the polymerization, preferably either before or during the polymerization.
The obtained amorphous chips are converted into fiber/yarn with inorganic salt particles entrapped therein.
In accordance with one embodiment of the present invention the amorphous chips are converted into fiber/yarn by using the following method steps.

In the first step, the amorphous chips are crystallized at a temperature of about 110 °C to about 170°C to obtain crystallized Polyethylene terephthalate (PET) chips. These crystallized Polyethylene terephthalate (PET) chips are then dried at a temperature of about 110 to about 140 C to obtain PET chips having moisture level less than 40ppm.
In the next step, the Polyethylene terephthalate chips are extruded through at least one screw extruder at a temperature of about 270 to about 300°C to obtain fiber/yarn with inorganic salt particles entrapped therein.
Finally, the inorganic salt particles are removed from the fiber/yarn by at least one method selected from the group consisting of treating the fiber/yarn with boiled water and dyeing the fiber/yarn to obtain porous polyester/co-polyester fiber/yarn having pores of about 50 nm to about 700 nm in diameter.
The invention will now be described in greater detail with the reference to the following examples, which are presented here for the purpose of illustration only and should not be construed as limitative of the scope of the present invention.
Example I;
Preparation of Polyester yarn containing 5% sodium chloride (as an additive) followed by
boiling the yarn to remove the additive particles in order to make the yarn porous.
Raw Material:
Bright Polyester Chips (IV-0.6 approx)
Sodium chloride (as an additive)
Procedure

1. PET Chips crystallization: Chips were crystallized at 140°C for 3-4 hrs.
2. Pulverization: The crystalized chips were pulverized.
3. Mixing with additive: Additive (5%) was crushed in a mixer and mixed with
the pulverized chips to obtain a mixture.
4. Drying: The mixture was kept in a vacuum oven at 170°C before spinning.
5. Single Screw Spinning: Some portion of this mixture was then fed to single
screw extruder to obtain filament yarn and rest was converted into chips.
6. Twin Screw Spinning: The chips were then passed to twin screw extruder for
better mixing of additives.
7. Crystallization: Chips obtained from twin screw extruder were further
crystallized at 140°C for 3-4 hrs
8. Drying: Crystallized chips were then dried in a vacuum oven at 170°C for a
day.
9. Single Screw Spinning: Yarn from these chips was spun in single screw
extruder.
10. Porous Yarn: Yarn obtained from twin screw spinning was then boiled in
water to remove the additive particles present in the yarn in order to make the
yarn porous. (Fig 1 (a) & (b))
Table 1: Characterization of Yarn

Initial Weight, gms Final Weight, gms Additive Loss, %
Twin Screw Yarn 2.8673 2.7940 54% of the initial amount
Imbibing results:

Yarn obtained from single screw spinning and Normal filament yarn were tested for imbibing of water, in which both yarn samples were imbibed in water and squeezed. The results are shown in table No. 2.
Table No. 2: Imbibing results

Type of Yarn Initial Weight, gins Final Weight, gms Imbibed, %
Norma] Filament Yarn 0.6503 1.2613 94
Single Screw Yarn 0.3126 0.9316 198
Moisture Regain (MR):
Yarn obtained from single screw spinning was compared for moisture regain with the
normal PRT filament yarn.
Results:
i) MR of Normal PET Filament Yarn: 0.54%
ii) MR of Single Screw Yarn: 1.05%
It was found that this process is associated with certain processing problems such as chocking of spinnerettes due to presence of salts (additives). Therefore, in order to overcome this processing problem, inventors of this invention attempted to utilize finer or nano/micro sized additive particles by in-situ polymerizing PET in the presence of additive instead of mixing the additives with ready made PET chips.
Example 2
In-situ polymerization of PET with an inorganic salt in 10 liter reactor

Reactor used: lab reactor with electrical heating (Capacity: 10L)
Inorganic salt used: 2.5 % NaCl
sodium chloride was first dispersed in monoethylene glycol (MEG) to obtain a
homogenous dispersion of sodium chloride in MEG. The obtained dispersion was
charged into a reactor containing purified terephthalic acid followed by esterification to
obtain a pre-polymer. During this reaction MEG gets consumed and water is produced.
The resulting pre-polymer was transferred to a poly condensation reactor and the reaction
was continued under vacuum. During this process the amount of MEG gets gradually
reduced followed by phase separation of sodium chloride which leads to formation of
fine homogeneous crystals of sodium chloride.
The reaction was stopped after the desired torque was obtained indicating the IV build up
(0.6 dl/g). The molten polymer was then converted into chips, crystallized at 140°C and
dried under vacuum at 120°C to obtain PET chips having a moisture level less than
40ppm.
The obtained polymer was greenish in colour and slightly rough in nature due to larger
particle size.
Spinning:
The spinning was carried out in a Brabender single screw extruder at 275°C under nitrogen atmosphere through multifilament spinneret holes.
Due to higher agglomeration, the fibres were very rough and there were chocking issues in the filter.

Polymer & Fibre characterization:
A small piece of the PET/sodium chloride chip was molten over a glass plant and converted in to a film (Fig. 2(a)). Similarly a control film also was made without sodium chloride content (Fig. 2(b)).
The fibres obtained after spinning were boiled in water and examined through scanning electron microscopy (Fig. 3(a), 3(b), 3(c)).
Example 3
In-situ polymerization of PET with an inorganic salt in 50 liter reactor Concept
The learning from the previous experiments was that the solubility of inorganic salt in
MEG is limited and in PET it is little. Therefore, in order to get homogeneous dispersion,
smaller concentration of additive has to be used. The smaller concentration provides
better spinnability and smaller voids after boiling the fibre.
Reactor used: Dow-therm heated lab reactor (capacity: 50 liter) to avoid the greenish
colour obtained in the electrically heated reactor.
Inorganic salt used: NaCl (0.5 % & 1.0 %)
Polymerization and spinning:
The polymerization method was similar to that in example 2, except that the concentration of the additive was 0.5 and 1% instead of 2.5 %. It was found that polymerization took place without any difficulty and the colour of the obtained polymer colour was normal. The polymer was then crystallized and dried before spinning.

The spinning was conducted in a pilot spinning machine. The conditions and mechanical characterization of the fibres are given in the following table (Table No. 3).
Table No. 3: Physical property Report of PET with sodium chloride salt Fibres

Sr. No. Trial No. Unit 93 94
1 Type NA FDY FDY
2 Polymer NA PET + 0.5% NaCl PET+1.0% NaCl
3 Draw Ratio NA 2.73 2.73
4 Winding Speed mpm 3000 3000
5 Denier/ fil. NA 300/144 300/144
6 Actual Denier NA 284.7 194.5 (FOF)
7 Tenacity gpd 2.8 2.5
8 Elongation % 44.8 43.4
* FDY:Fully Drawn Yarn Gloss measurement:
Knitted hose of control bright yarn, two test samples with 0.5 and 1% NaCl respectively and one control full dull yarn were prepared on knitting machine. Hose samples were boiled in water to remove additives and finishes. Hose was dried and ironed for measuring Gloss values. The results are shown in table No. 4
Table 4: Gloss Values

Angle ° Control Bright (0% NaCl) Test Sample 1 (0.5% NaCl) Test Sample 2 (l%NaCl) Full Dull control
20 1.43 1.3 1.14 1.05
60 5 4 2.82 2.05
85 0.53 1.6 0.64 0.25
From the results, it is found that the gloss values have significantly reduced with the increase in additive content. With 1% of additive level, the gloss values have reached

near to the values of control full dull fabric. Apart from gloss values, the feel of the fabric was very good and soft when inspected visually and by hand touch method.
Example 4
In-situ polymerization of PET with 0.5 % inorganic salt dissolved in water in 50 liter reactor.
The polymerization method was similar to that in example 2, except that i) the
concentration of the additive (NaCl) used was 0.5% instead of 2.5 %, ii) the additive was
dissolved in ~600ml water first, and iii) the additive dissolved in water was added to
reaction mixture either before the esterification or after the esterification.
It was found that the polymerization took place without any difficulties and the colour of
the obtained polymer was normal. The polymer was then crystallized and dried before
spinning.
The spinning was conducted in a pilot spinning machine. The conditions and mechanical
characterization of the fibres are given in the following table (Table No. 5)
Table 5: Physical property report

Sr. Trial No. Unit 107 108 109 110
No.
] Type NA POY POY POY POY
2 Polymer NA PET + PET + PET PET +
NaCl NaCl + NaCl
added after added NaCl added
esterification before esterification added before esterification
+
Ti02 MB added 0.03% before
esterification
With
RETllO
Spin

Finish
3 Winding Speed mpm 2600 2600 2600 2600
4 Denier/fil. NA 130/36 130/36 130/36 250/72
5 Actual Denier NA 122.9 126.8 120.5 234.6
6 Draw Tension g 16.0 15.9 15.6 33.1
7 Tenacity SPd 1.9 1.3 1.5 1.3
8 Elongation % 144.0 129.2 135.1 128.2
POY: Partially Oriented Yarn RET110: Code of the finish
Example 5 Slurry Route
540 g of additive (NaCl) and 1460g of MEG were mixed and milled in laboratory bead
mill, in recirculation mode for 1 hour, to obtain slurry of the additive (27%).
PET polymer containing 0.25% & 0.5% additive, were made by adding salt slurry (27%)
at the end of esterification. Polymerization was carried out as per standard method. This
PET polymer was used for making POY of 130x36 denier.
Texturising of POY was carried out followed by knitting and boiling the knitted hose in
water to remove soluble salt. Boiled hose showed dull look with a feel like a cotton
fibres. Dyed hose showed higher dye uptake compared to standard PTY hose.
The results are shown in table No. 6

Table 6: Physical Property Report

Sr. No. Trial No. Unit 145 146 147 148 149
1 Type NA POY POY POY POY POY
2 ARL Batch No. NA 90 90 91 92 93
3 Polymer NA NaCl
(0.25%) in MEG and milling NaCl
(0.25%) in MEG and milling NaCl
(0.50%) in MEG and milling NaCl
(0.25%)
in
Water NaCl (0.25%) in MEG
4 Winding Speed mpm 2900 2800 2900 2900 2800
5 Denier/ fil. NA 130/36 130/36 130/36 130/36 130/36
6 Actual Denier NA 125.75 127 127.05 126.85 124.8
7 Draw Tension g 29.7 25.25 26.15 33 25.55
8 Tenacity gPd 2.3 2.25 2.1 2.05 1.85
9 Elongation % 135 143.8 134.2 118.95 128.9
Table 7: Determination of additive present in the fibre

Sr. Trial Sample Na NaCl Ash
No. content (ppm) content (ppm) %
1 147 Additive (0.50%) in MEG and milling Before boiling 1268 3225 0.47
2
Additive (0.50%) in MEG and After 802 2040 0.18
milling boiling
Example 6: Preparation of Poly ester yarn without salt
Purified terephthalic acid and mono ethylene glycol were charged into reactor followed by esterification to obtain a pre-polymer. The resulting pre-polymer was transferred to a polycondensation reactor and the reaction was continued under vacuum.

The reaction was stopped after the desired torque was obtained indicating the IV build up
(0.6 dl/g). The molten polymer was then converted into chips, crystallized at 140°C and
dried under vacuum at 120°C to obtain PET chips having a moisture level less than
40ppm.
Spinning:
The spinning was carried out in a pilot spinning plant at 285CC through multifilament
spinneret holes.
Example 7: Preparation of polyester yarn with salt and 2 % IPA
Purified terephthalic acid, mono ethylene glycol along with IPA were charged into
reactor followed by esterification to obtain a pre-polymer. The resulting pre-polymer was
transferred to a polycondensation reactor where Sodium chloride slurry was added and
the reaction was continued under vacuum. During this process, the amount of MEG got
gradually reduced followed by phase separation of sodium chloride which lead to
formation of fine homogeneous crystals of sodium chloride.
The reaction was stopped after the desired torque was obtained indicating the IV build up
(0.6 dl/g). The molten polymer was then converted into chips, crystallized at 140°C and
dried under vacuum at 120°C to obtain PET chips having a moisture level less than
40ppm.
Spinning:
The spinning was carried out in a pilot spinning plant at 285°C through multifilament
spinneret holes.
Characterization of yarn from example 6 and 7

Sr. No. Trial No. Unit 1300 1299

1 Type NA FDY FDY
2 Polymer NA PET without salt and I PA PET with 1%
sodium chloride
and 2% IPA
3 Winding Speed mpm 3500 3500
4 Denier/ fil. NA 100/36 100/36
5 Actual Denier NA 99.5 100.8
6 Tenacity gpd 3.7 2.7
7 Elongation % 37.6 25.2
The yarn breakage was less compared to all previous experiments with NaCl
Technical Advancement:
■ The present invention provides a simple salt leaching process for the preparation of nano-porous synthetic fibers/yarn/fabric.
■ The process of the present invention imparts natural feel and cotton look to the synthetic fibres/yam/fabric.
■ The process of the present invention avoids the use of dulling agents such as TiC>2 and BaS04-
■ The present invention provides nano-porous synthetic fibers/yarn/fabric which has improved properties such as, dyeability and water absorption.
■ The present invention provides a process which improves the spinnability of the polymer during the preparation of nano-porous synthetic fibers/yarn/fabric.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the

scope of the invention, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We Claim:
1. A porous synthetic fiber/yarn derived from a polyester/co-polyester, said polyester/co-polyester comprising repeating units derived from isophthalic acid, wherein the diameter of the pores in the fiber is about 50 nra to about 700 ran".
2. A process for the preparation of synthetic fiber/yarn as claimed in claim 1, said
process comprising the following steps:
a. synthesizing a molten polymer comprising isopthalic acid as a co-
monomer and at least one inorganic salt; said inorganic salt being
introduced during synthesizing through a vehicle;
b. subjecting the molten polymer to at least one method selected from the
group consisting of direct spinning and indirect spinning to obtain a
fiber/yarn; and
c. removing the inorganic salt particles from the fiber/yarn by at least one
method selected from the group consisting of treating the fiber/yarn
with boiled water and dyeing the fiber/yarn to obtain porous fiber/yarn
having pores of about 50 run to about 700 nm in diameter.
3. The process as claimed in claim 2, wherein the inorganic salt is at least one selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, potassium carbonate, sodium carbonate, nitrates of inorganic compounds, thermally stable water soluble compounds and mixtures thereof.
4. The process as claimed in claims 2, said process comprising the following steps:

a. preparing a molten polymer by mixing at least two different dicarboxylic
acids or ester thereof and at least one diol in a reactor to obtain a mixture
followed by esterifying the mixture to obtain a pre-polymer, the molar ratio of
the total dicarboxylic acid or ester thereof to the total diol being 1:1.8 to 1:2
and at least one of the dicarboxylic acid being essentially isophthalic acid;
b. subjecting the pre-polymer to polymerization at a temperature of about 270 to
about 290 °C to achieve I.V. of about 0.6 dl/gm;
c. incorporating at least one inorganic salt dispersed in a vehicle either before or
during or after any method step selected from the group consisting of mixing,
esterifying and polymerization;
d. subjecting the molten polymer to direct spinning to obtain fiber/yarn with
inorganic salt particles entrapped therein; and
e. removing the inorganic salt particles from the fiber/yarn by at least one
method selected from the group consisting of treating the fiber/yarn with
boiled water and dyeing the fiber/yarn to obtain porous polyester fiber/yarn
having pores of about 50 nm to about 700 nm in diameter.
5. The process as claimed in claim 2, said process comprising the following steps:
a. preparing a molten polymer by mixing at least two different dicarboxylic acids or ester thereof and at least one diol in a reactor to obtain a mixture followed by esterifying the mixture to obtain a pre-polymer, the molar ratio of the total dicarboxylic acid or ester thereof to the total diol being

1:1.8 to 1:2 and at least one of the dicarboxylic acid being essentially isophthalic acid;
b. subjecting the pre-polymer to polymerization at a temperature of about
270 to about 290 °C to obtain amorphous chips of I.V. of about 0.6 dl/gm;
c. incorporating at least one inorganic salt dispersed in a vehicle either
before or during or after any method step selected from the group
consisting of mixing, esterifying and polymerization;
d. converting the amorphous chips into fiber/yarn with inorganic salt
particles entrapped therein; and
e. removing the inorganic salt particles from the fiber/yarn by at least one
method selected from the group consisting of treating the fiber/yarn with
boiled water and dyeing the fiber/yarn to obtain porous polyester
fiber/yarn having pores of about 50 nm to about 700 nm in diameter.
6. The fiber/yarn as claimed in claim 5, wherein the method step (d) comprises the following steps:
- crystallizing the amorphous chips at a temperature of about 110 °C to about 170°C to obtain crystallized Polyethylene terephthalate (PET) chips;

- drying the crystallized Polyethylene terephthalate (PET) chips at a temperature of about 110 to about 140 C to obtain PET chips having moisture level less than 40ppm; and
- extruding the Polyethylene terephthalate chips through at least one screw extruder at a temperature of about 270 to about 300°C to obtain fiber/yarn with inorganic salt particles entrapped therein.
7. The process as claimed in any of the preceding claims, wherein the amount of
inorganic salt is in the range of about 0.1 to about 10 % of the theoretical weight of the polyester.
8. The process as claimed in any of the preceding claims, wherein the amount of isopthalic acid is about 1 to about 4 % of the theoretical weight of the polyester, preferably, 2 %.
9. The process as claimed in claim 4 and 5, wherein said two different di-carboxylic acids are selected from the group consisting of terephthalic acid, isophthalic acid, adipic acid, glutaric acid and sebacic acid.
10. The process as claimed in claim A and 5, wherein the diol is at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, 1,3 -propanediol andneopentyl glycol.

11. The process as claimed in any of the preceding claims, wherein the vehicle is at least one selected from the group consisting of monoethylene glycol and water.
12. The process as claimed in claim 4 and 5 wherein the step of incorporating inorganic salt is carried out either before the polymerization or during the polymerization.