Title of Invention

A PROCESS FOR THE PREPATION OF DURABLE AND HIGHLY CONDUCTING THERMOPLASTIC POLYESTER FIBER OR YARN

Abstract A process for the preparation of highly conducting thermoplastic polyester fiber or monofilament or multifilament yarn with high durability by carrying out vapor phase oxidation of pyrrole on the surface of the thermoplastic polyester fiber or monofilament or multifilament yarn to form uniform coat of polypyrrole which is chemically bound to the surface of the fiber by passing pyrrole vapors onto the surface along with nitrogen gas; said thermoplastic polyester fiber or monofilament or multifilament yarn comprising a dopant such as alkali metal salts of substituted sulfonic acid as a co-monomer in the polyester backbone. A conducting thermoplastic fiber or monofilament or multifilament yarn has a uniform coating of conducting polypyrrole of around 0.1 to 5.0 % of the total weight of thermoplastic fiber or monofilament or multifilament yarn with electrical conductivity in the range of 10 –6 to 10 –9 S/cm. A conducting thermoplastic fiber, monofilament and / or multifilament yarn is used in applications in the field of static dissipation, EMI-shielding, composite structure and military applications.
Full Text FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
A process for preparing conducting thermoplastic polyester fibers, monofilaments or
multifilament yarn and products thereof.
2 APPLICANT
(a) Name : Reliance Industries Limited
(b) Nationality: Indian company incorporated under the Companies Act
1956
(c) Address : Reliance Technology Centre, B-4 MIDC Industrial Area,
Patalganga-410220, Dist- Raigad, Maharashtra, India.
3. INVENTORS
(a) Name : Nadkarni Vikas Madhusudan
(b) Nationality: Indian
(c) Address : A18 Garden Estate, Off D P Road, Aundh, Pune -411007,
Maharashtra, India.
(a) Name : Venkatachalam Subbiah
(b)Nationality : Indian
(c) Address : A1/6:1 Sneh Co-op Housing Society, Sector 19 A, Nerul, Navi Mumbai - 400706, Maharashtra - India
(a)Name : Labde Jayprakash Vinayak
(b)Nationality: Indian
(c) Address : B-19/10, Best Nagar, Sanman Society, Goregaon(West), Mumbai- 400104, Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention :

Technical Field Of The Invention
The invention relates to a process for preparing conducting thermoplastic polyester fiber, monofilament or multifilament yarn by vapour phase oxidation of pyrrole on the surface of thermoplastic polyester comprising a dopant such as sodium salt of substituted sulfonic acid in their backbone and in the presence of oxidizing agent.
The invention also relates to a highly conducting thermoplastic polyester fiber, monofilament and multifilament yarn with high durability.
The invention also relates to a use of a highly conducting thermoplastic polyester fiber, monofilament and multifilament yarn with high durability in the field of static dissipation, EMI-shielding, composite structures and military applications.
Background And Prior Art
Electrically conducting polymers are well known in the prior art. One of the oldest route for synthesis of conducting polymers consists of mixing or blending of a conductive powder such as carbon black, silver particles, or even silver or gold coated particles with polymer melt prior to extrusion of fibers which are used to make yarn or fiber. However to achieve fiber with reasonable conductivity, very high amount of powder or particles is required to be added in polymer melt. The particles of the powder or silver or gold coated particles necessarily should touch each other in order to obtain desired conductivity. The use of powder or particles in higher concentration may also adversely alter the properties of the fiber during extrusion and thus affecting physical properties of the fabric or yarn.
The conducting or antistatic fabric is also manufactured by incorporating conductive carbon fiber or carbon filled nylon or polyester fibers in fabric. Alternatively the fabric is coated with metals such as copper, nickel or noble
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metal but the manufacturing process involves complicated steps and it is industrially non-viable as it requires expensive catalysts such as palladium or platinum.
Use of Polypyrrole for achieving electrical conductivity is very well documented in "Handbook of conductive polymers" vol 1, pages-266-291 by G. Bryan Street of IBM Research laboratories. According to the above-mentioned article polypyrrole can be produced by electrochemical process or chemical oxidation by ferric chloride or any other oxidizing agent. But the films produced by these methods are insoluble in organic or inorganic solvents.
US 4,803,096 describes a method for imparting electrical conductivity in textile materials. The textile material is dipped in an aqueous solution of an oxidatively polymerizable compounds selected from pyrrole compound and aniline compound and oxidizing agent capable of oxidizing the pyrrole to a polymer in the presence of counter ion which imparts electrical conductivity to the polymer when fully formed. The pyrrole and aniline compound oxidized and adsorbed on the surface of the textile to form conductive polymer on the surface, making the textile electrically conductive. The pyrrole concentration in the aqueous solution is from 0.01 to 5 gm per liter. The chloride counter ions released from ferric chloride acts as doping agent and the polypyrrole formed in liquid phase oxidation is doped with the chloride counter ions. Instead of chloride counter ions, anions such as benzene or toluene sulfonate ions of naphthalene- 2-sulfonate or 1-5 -naphthalene disulfonate are added for doping the polypyrrole. A variety of doping agents or counter ions is disclosed in the prior arts. Modification over the above process is disclosed in US 4,877,646 and US 4,981,718 where the rate of oxidizing reaction is controlled by using weak complexing agent for ferric ions and by using vanadyl compound as an oxidizing agent respectively. These processes require high concentration of dopant or counter ion in the aqueous solution in order to achieve high conductivity in the textile.
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H Kuhn et al in their US 5,108,829 describe a process for preparing an electrically conductive textile material. In this process, the textile material is brought in contact with an aqueous solution of pyrrole, oxidizing agent and a dopant such as anthraquinone-2-sulfonic acid in an amount sufficient to impart electrical conductivity to polymer. Polymer is formed on the surface of the textile material and gets adsorbed on it. Antraquinone-2-sulfonic acid and pyrrole is used in the amount from 1:2 to 2.5:1. The aqueous solution consists of pyrrole in the amount from 0.01 to 15 gms.
The same authors have revealed in their publication in Textile Chemist and Colorist', Vol 29, No 12 p17-21 that chemical polymerization in presence of ferric salts yields superior products over other oxidizing agents like H2O2 or alkali persulfates. To get oxidized and doped form of polypyrrole at least 2.3 moles of iron salt are necessary. The polymerization is typical of a second order autocatalytic reaction with rate constant 1.3 x 10 "1 M"1 sec"1 and the rate is considerably slower if no fiber is present with rate constant 3.2 x 10 *2 M"1 sec'1. The reactions go well at relatively low concentrations preferably 0.01 to 0.02 moles/lit of the monomer.
The liquid phase oxidation of pyrrole uses high concentration of pyrrole to obtain thicker coatings of polypyrrole, which is deposited as a particulate material on the fiber or fabric surface. Thus induces conductivity to the fiber or fabric surface. This deposit or particulate material may get eliminated or decomposed at the time of extrusion or downstream process or after repeated washing the coat get washed off. Hence the electrical conductivity achieved by this process is not durable.
The conductivity of polypyrrole coated fabrics or textile material decreases over the time by a controlled diffusion or a first order decay process. The rate of decay is depending on type of dopant anion used, the method of preparation and conditions of aging. The decay is significantly more rapid in the presence of air,
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particularly oxygen. Thus it indicates that the reaction of oxygen with the polymer backbone is responsible for a significant portion of the conductivity loss.
To prevent conductivity loss, US 5,833,884 reported the use of stabilizing agents like 2,4-dihydroxy benzophenone (DHBP). The use of stabilizing agent improves the stable conductivity of the polypyrrole coated textile fabric. But the increase in conductance and stability depend on the ratio of DHBP to pyrrole and the stabilizing agent does not get incorporated into the polymer hence leaching out or migration of DHBP would cause pollution or other environmental drawbacks.
Conductive polymer coated fabrics have the advantage of light weight, ease of manufacture, low cost and a wide range of surface conductivities as compared to that of metals and carbon coated products but have following drawbacks.
The major drawback of the process is that use of high concentration of dopant or counter ion in the aqueous reaction solution in order to achieve high levels of conductivity in the polymer coated fiber or fabric which causes adsorption of oxygen and carbon dioxide on the surface of the polymer thereby leading to poor stability of the conductivity on storage.
Another drawback is that polypyrrole is formed by the oxidation of pyrrole in the solution and then polypyrrole gets precipitated in solution, which gets coated on the surface of the textile material. Thus the process results into an unnecessary loss of pyrrole, which precipitates in the solution but does not get coated on the textile material and has to be separated from the bath by filtration. Thus the process needs removal or disposal of the excess amount of precipitated polypyrrole and hence it is not cost-effective and eco-friendly.
Another drawback is that after repeated washing of the textile material or fabric, the electrical conductivity in found to be decreased and hence not durable.
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Objects:
An object of the invention is to provide a process for the preparation of conductive thermoplastic polyester fiber, monofilament or multifilament yarn with high conductivity.
Another object of the invention is to provide a process for the preparation of conductive thermoplastic polyester fiber, monofilament or multifilament yarn where the conductivity is highly durable.
Another object of the invention is to provide a process for the preparation of conductive thermoplastic polyester fiber, monofilament or multifilament yarn with the above mentioned properties where the process is economical, cost-effective and eco-friendly.
Another object of the invention is to provide a process for the preparation of conductive thermoplastic polyester fiber, monofilament or multifilament yarn with the above mentioned properties where the process is simple, efficient and convenient to carry out.
Another object of the invention is to provide a use of a conducting thermoplastic polyester fiber, monofilament and multifilament yarn with high durability in the field of static dissipation, EMI-shielding, composite structures and military applications.
Detailed Description:
According to the invention there is provided a process for the preparation of highly conducting thermoplastic polyester fiber, monofilament and multifilament yarn with high durability, the process comprising
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a. Preparing a thermoplastic polyester fiber, monofilament and multifilament
yarn incorporating a dopant such as alkali metal salts of substituted
sulfonic acid as a co-monomer in the polyester backbone;
b. dipping the thermoplastic polyester fiber, monofilament and multifilament
yarn in a lower chain alcohol comprising a oxidizing agent such as ferric
chloride and a surfactant followed by drying the thermoplastic polyester
fiber, monofilament and multifilament yarn under nitrogen gas flow;
c. vapor phase oxidation of pyrrole on a surface of the thermoplastic
polyester fiber, monofilament and multifilament yarn to form uniform coat
of polypyrrole which is chemically bound to the surface of the fiber by
passing pyrrole vapors onto the surface along with nitrogen gas and
d. washing the thermoplastic polyester fiber, monofilament and multifilament
yarn with water followed by a lower chain alcohol followed by drying the
textile material or fabric under nitrogen gas flow.
The alkali salt of substituted sulfonic acid is lithium, potassium or sodium salt of substituted sulfonic acid. In one the embodiment, the alkali salt of substituted sulfonic acid used is sodium salt of 5-sulfo 1:3 isophthalic acid. But the sodium salts other isomers of substituted sulfonic acid namely 3-sulpho- or 4 -sulpho-1:3 isophthalic acid can also be incorporated as the co-monomer in the polyester backbone instead of sodium salt of 5-sulfo 1:3 isophthalic acid and electrical conductivity of the polyester can be further studied by adding different isomers of substituted sulfonic acid at different concentration. The sodium salt of 5-sulfo 1:3 isophthalic acid is incorporated as the co-monomer in the polyester backbone in the range of 1.5 to 7 %. Preferably, the sodium salt of 5-sulfo isophthalic acid is incorporated as the co-monomer in the polyester backbone in the range of 2.2 to 4.5 %. The lower chain alcohol comprising ferric chloride used is methanol. The lower chain alcohol comprising ferric chloride comprises 2 to 15% ferric chloride and surfactant. The surfactant used is any conventional surfactant. In the vapor phase oxidation, the surface of the thermoplastic polyester fiber, monofilament or multifilament yarn comprising a dopant such as
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sodium salt of substituted sulfonic acid in their backbone is exposed to the vapors of pyrrole for 10 sec to 200 sec, at a flow rate of nitrogen varying from 200 to 800 ml/min. In the vapor phase oxidation, the pyrrole vapors are diluted with nitrogen gas heated to 30 to 90° C. The conducting thermoplastic fiber or monofilament or multifilament yarn prepared according to the above invention has a uniform coat of conducting polypyrrole and found to be increased in weight after conductive coat, which is around 0.1 to 5.0 % of the total weight of thermoplastic fiber or monofilament or multifilament yarn.
According to the invention there is also provided a conducting thermoplastic fiber or monofilament or multifilament yarn with electrical conductivity is in the range of 10 "7 to10 "8 S/cm. The thermoplastic fiber or monofilament or multifilament yarn prepared by the above process shows the good conductivity even after 5-10 washes in cold water and hence the conducting textile material or fabric is showing stable electrical conductivity.
The invention uses thermoplastic fiber or monofilament or multifilament yarn comprising sulfonate moieties in its backbone which act as an in-situ dopant and oxidizes pyrrole on the surface of the fiber to form chemically bonded polypyrrole coating on the surface of each fiber or filament, which renders stable electrically conductivity even after repeated washings of the fiber. Therefore, there is no need for large quantity of dopants as used in the prior art. When the textile material or fabric is dipped in the methanol comprising ferric chloride, it gets adsorbed on the surface of the fiber of the textile material or fabric, which is further exposed to the minimum concentration of vapours of pyrrole in a diluted form with nitrogen gas. The reaction is carried out at room temperature by using minimum concentration of pyrrole and ferric chloride and using in-situ doping agent on the fiber. This helps to have a good control on the process conditions to achieve uniform conductive coating at the surface of the thermoplastic polyester fibers or monofilament or multifilament yarn. Thus there is no need to use excess of pyrrole or no unwanted precipitation of polypyrrole and hence no
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disposal problem. By controlling the process parameters, one can achieve uniform coating with a very low amount of pyrrole vapours on the surface of the thermoplastic polyester fibers, monofilament or multifilament yarn. Thus the process is cost-effective and economical. The process is also simple, easy, efficient and convenient to carry out.
Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.
Example 1:
The polyethylene terephthalate fibers comprising 4.2% (w/w) of sodium salt of 5-sulfo isophthalic acid as a comonomer was prepared by conventional polymerization technique. The yarn was prepared by using the fiber of polyethylene terephthalate by conventional process. The yarn of 0.05 gm was dipped in methanol consisting of 2. 5% of ferric chloride w/v and surfactant for 3 sec and the yarn was dried for 5 min under 25 LPM nitrogen gas. The vapour of pyrrole comprising 0.2-5cc pyrrole along with the nitrogen gas (200 cc/min) was passed over the surface of the yarn to form uniform coat of polypyrrole which was chemically bound to the surface of the yarn. The yarn was washed with water followed by methanol and dried under nitrogen gas flow. The electrical conductivity of the yarn was measured by using fluke meter.
Table 1. Effect of quantity of pyrrole on elcectrical conductivity with 4.2 w% in-situ dopant on the yarn

Time in sec for whichNirogen (containingpyrrole vapours) ispassed throughchamber Amount of Pyrrole(gm) passed through chamber Amount ofPyrrole (gm)deposited onknitted yarn Conductivity(S/cm)For 2.5% (w/v) OAin methanol
10 0.0011 0.0004 5.1x10-8
20 0.0033 0.0011 1.4x10-7
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50 0.0052 0.0016 1.8x10-7
100 0.00103 0.002 2.0x10-7
150 0.0168 0.0025 6.1x10-7
The fiber/ monofilament or multifilament yarn prepared according to the invention may find applications in static dissipation, EMI-shielding, composite structures and military applications. Some of the military applications include materials with conductivity gradients, such as edge cards and layered structures such as Jaumann absorbers and Salisbury screens.
Dated this the 10 day of April ) 2006
For Reliance Industries Limited
Dr Vikas Madhusudan Nadkarni Director(Research and Technology)
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Documents:

563-mum-2006-abstract(10-4-2007).pdf

563-MUM-2006-ABSTRACT(16-6-2009).pdf

563-MUM-2006-ABSTRACT(9-4-2009).pdf

563-mum-2006-abstract(granted)-(3-2-2011).pdf

563-MUM-2006-CANCELLED PAGES(9-4-2009).pdf

563-mum-2006-claims(10-4-2007).pdf

563-MUM-2006-CLAIMS(16-6-2009).pdf

563-MUM-2006-CLAIMS(9-4-2009).pdf

563-MUM-2006-CLAIMS(CANCELLED PAGES)-(16-6-2009).pdf

563-mum-2006-claims(granted)-(3-2-2011).pdf

563-mum-2006-claims(marked copy)-(9-4-2009).pdf

563-MUM-2006-CLAIMS(MARKED)-(9-4-2009).pdf

563-mum-2006-correspondence 1(8-10-2010).pdf

563-mum-2006-correspondence(10-4-2007).pdf

563-MUM-2006-CORRESPONDENCE(15-1-2010).pdf

563-MUM-2006-CORRESPONDENCE(16-6-2009).pdf

563-MUM-2006-CORRESPONDENCE(8-10-2010).pdf

563-MUM-2006-CORRESPONDENCE(9-4-2009).pdf

563-mum-2006-correspondence(ipo)-(4-2-2011).pdf

563-mum-2006-correspondence-received.pdf

563-mum-2006-description (provisional).pdf

563-mum-2006-description(complete)-(10-4-2007).pdf

563-MUM-2006-DESCRIPTION(COMPLETE)-(16-6-2009).pdf

563-MUM-2006-DESCRIPTION(COMPLETE)-(9-4-2009).pdf

563-mum-2006-description(granted)-(3-2-2011).pdf

563-mum-2006-form 1(10-4-2006).pdf

563-MUM-2006-FORM 1(16-6-2009).pdf

563-MUM-2006-FORM 1(9-4-2009).pdf

563-mum-2006-form 13(9-4-2009).pdf

563-mum-2006-form 18(13-8-2007).pdf

563-mum-2006-form 2(16-6-2009).pdf

563-mum-2006-form 2(9-4-2009).pdf

563-mum-2006-form 2(complete)-(10-4-2007).pdf

563-mum-2006-form 2(granted)-(3-2-2011).pdf

563-MUM-2006-FORM 2(TITLE PAGE)-(16-6-2009).pdf

563-MUM-2006-FORM 2(TITLE PAGE)-(9-4-2009).pdf

563-mum-2006-form 2(title page)-(complete)-(10-4-2007).pdf

563-mum-2006-form 2(title page)-(granted)-(3-2-2011).pdf

563-mum-2006-form 2(title page)-(provisional)-(10-4-2006).pdf

563-MUM-2006-FORM 26(16-6-2009).pdf

563-MUM-2006-FORM 3(9-4-2009).pdf

563-mum-2006-form 5(10-4-2007).pdf

563-MUM-2006-FORM 8(9-4-2009).pdf

563-mum-2006-form-1.pdf

563-mum-2006-form-2.doc

563-mum-2006-form-2.pdf

563-mum-2006-form-3.pdf

563-mum-2006-specification(amended)-(9-4-2009).pdf


Patent Number 245849
Indian Patent Application Number 563/MUM/2006
PG Journal Number 06/2011
Publication Date 11-Feb-2011
Grant Date 03-Feb-2011
Date of Filing 10-Apr-2006
Name of Patentee RELIANCE INDUSTRIES LTD.
Applicant Address Reliance Technology Centre, B-4 MIDC Industrial Area, Patalganga 410220, Dist Raigad,
Inventors:
# Inventor's Name Inventor's Address
1 NADKARNI VIKAS MADHUSUDAN A 18 GARDEN ESTATE, OFF D P ROAD, AUNDH, PUNE 411007,
2 VENKATACHALAM SUBBIAH B-19/10, Best Nagar Sanman Society Goregaon(W) Mumbai 400104 Maharashtra, India
3 LABDE JAYAPRAKASH VINAYAK B-19/10, Best Nagar Sanman Society Goregaon (W) Mumbai 400104 Maharashtra, india
PCT International Classification Number B05D 5/12
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA