Title of Invention	"A PROCESS FOR THE PREPARATION OF A NOVEL CONDUCTING FIBROUS COMPOSITE FOR ELECTROMAGNETIC INTERFERENCE (EMI) SHIELDING APPLICATIONS"
Abstract	A process for the preparation of a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications by loading the clean fibrous matrix, with a hetero aromatic monomer, capable of forming into conjugated polymeric structure in an amount in the range of 1-50% w/w in an organic solvent used is an amount of of 2-10 times w/w, optionally adding emulsifier in the range of 0.1 to 1% w/w either in vacuum or ultrasonics by known methods optionally in presence of monomer penetrating accessory, reacting the monomer loaded fibrous matrix, with any oxidising agent in the range of 0.5 to 8 moles per mole of monomer, washing the polymeric matrix, with water followed by drying by known method to get the conducting polymeric fibrous composite.

Title of Invention

"A PROCESS FOR THE PREPARATION OF A NOVEL CONDUCTING FIBROUS COMPOSITE FOR ELECTROMAGNETIC INTERFERENCE (EMI) SHIELDING APPLICATIONS"

Abstract

A process for the preparation of a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications by loading the clean fibrous matrix, with a hetero aromatic monomer, capable of forming into conjugated polymeric structure in an amount in the range of 1-50% w/w in an organic solvent used is an amount of of 2-10 times w/w, optionally adding emulsifier in the range of 0.1 to 1% w/w either in vacuum or ultrasonics by known methods optionally in presence of monomer penetrating accessory, reacting the monomer loaded fibrous matrix, with any oxidising agent in the range of 0.5 to 8 moles per mole of monomer, washing the polymeric matrix, with water followed by drying by known method to get the conducting polymeric fibrous composite.

Full Text	The present invention relates to a process for the preparation of a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications. More particularly, the composite of the present invention has potential applications in electronic industry for electromagnetic interference (EMI) shielding purpose. As reported by Sathyamurthy (Electronics for you, p-43, May, 1998), in the wake of the rapid development of electronic apparatus, electromagnetic interference (EMI) has been a matter of much concern among the researchers. It is generated by an electronic equipment, which radiates electromagnetic waves affecting the normal functioning of another electronic equipment. The components of the electromagnetic wave, transmitted in the radio frequency (r-f) range by an electronic equipment, whether intended or not intended to transmit, originate r-f signals. EMI in the r-f range consists of undesirable r-f signals superimposed upon a desired signal. The unwanted EMI generated by an electronic apparatus can adversely affect, as an external source of interference, the functioning of another electronic apparatus. For example, high density multifunctional computers are controlled by pulses whose spectra are distributed over a wide range. Although these pulses are necessary for the operation of the computer, the high frequency electromagnetic waves, which are radiated, are likely to interfere with the functioning of the surrounding electronic apparatus resulting in noises. It is therefore important to protect electronic apparatus from EMI. Necessary care has also to be taken to ensure that the equipment itself does not become a source of EMI. This is how the concept of shielding the EMI has come into play. It is possible to achieve the EMI shielding with the help of some shielding materials, which can either reflect the electromagnetic waves tansmitted by an equipment, thereby preventing its further propagation, or absorb the same. The shielding capability of a material is defined as the proportion of attenuation of the electromagnetic waves incident upon a substance. As reported by Yasufuku (Institution of Electrical Engineering & Electronics Electrical Insulation, 6, 21,1990), it has been the usual practice to use metallic sheets for the purpose of housing information related apparatus like computers, video camera, word processors. Usually highly conducting metals like copper or aluminium, have conventionally been in use for partial covering of the electronic component to ensure that the induced r-f is neutralised. The major limitation of using metal for the purpose of EMI shielding is that due to the lack of flexibility of the metals, the area of contact between the shielding material and the equipment to be shielded is likely to be obviously less resulting in the reduction of the efficiency of shielding. Moreover, the use of metals increases not only the cost of the resulting product, but also its weight. Attention has therefore been shifted, in the realm of EMI shielding applications, to the thermoplastic polymers, which have of late been been getting much prominence due to the flexibility, versatility for design and low cost. Many electronic devices that inherently transmit a r-f signal are enclosed in housing made of polymer. But since these polymeric materials are non-conducting in nature for electricity, it is necessary to incorporate electrical conductors for using them as shielding materials. Unfilled polymeric material offer very little attenuation of r-f energy. Systems that would enable polymeric materials to attenuate r-f energy by using fillers or by applying a metallic plate to the surface of the plastic part, are incorporated in the housing for both component and device. Different methods have been in practice to prepare flexible metal-polymer composite, which may be used in the form of sheet, gasket, ohring etc. for the purpose of EMI shielding. The simplest method is to carry out electroplating. Thus, ABS (Acrylonitrile-butadiene-styrene) polymer can be electroplated or vacuum metallized with metals like copper, aluminium etc. for using as EMI shielding material. As reported in the Encyclopedia of Polymer science & Engineering, vol. 14, & supplementary volume, edited by Kohlmetz et al, Wiley Inter Science, New York, p-340,1989, electroconducting composite may also be prepared by mixing a thermoplastic resin with various metallic fillers, as detailed below and moulding the resulting mixture to a desired shape. Glass fibre is plated with nickel and the resulting nickel plated glass fiber is mixed with polycarbonate. The resulting mixture is moulded to form a composite with high level of electrical conductivity, suitable for using as EMI shielding material. Similarly polyester, incorporated with metallic fibers can form a good electroconducting composite. Different grades of cabon fibres may also be used for conductive applications. About 30-40% wAv, of carbon fibre on polymeric resin is used to make composite for EMI application depending on the geometry of the component to be shielded and the type of polymer used. The carbon fibre is first coated with a metal. Nickel coated carbon fibre is made by coating with 0.5 µm layer of nickel. This produces a fibre with diameter of 8 µm Various other metals like silver, gold, brass and copper may also be used for making the fibre. Nickel provides the best combination of electrical and physical properties and economics. 10-15% w/w, of nickel'may be loaded onto the carbon fibre to use the end product as EMI shielding material. Another option of making composites is to use stainless steel fibres, which are able to produce exceptional electrical properties even at a very low loading in the range of 5-10% w/w on the polymer weight primarily due to their high conductivity and aspect ratio. Stainless steel fibres of required dimension are made by pulling the fibres from a rod. The fibres of required diameter are chopped to get tow chopped fibres and formed into concentrates by coating the fibres with various thermoplastic compatible binders like polyester, polycarbonate etc. These thermoplastic polymer coated fibres are subjected to injection moulding to convert the same into composites of desired shape like sheets, ohring etc. This, however, necessitates very careful processing of the material, because stainless steel fibres are highly sensitive to the shear involved in injection moulding. Moreover, the complications of the sequential steps and the control parameters involved in the process render the process a costly one. Aluminium flakes may also be used as additives while preparing the conducting composites. 25-40% w/w, of aluminium flakes is mixed with thermoplastic polymer binder and the mixture is moulded to desired shape to produce composites. The main limitation of aluminium polymer composite is that the impact resistance of the final product is very low. Moreover, higher loading of aluminium on the polymer adds to cost. Thus to summarise, the major drawbacks associated with the hitherto known composites may be enumerate as follows. i) Preparation of the composite involves a lot of sequential steps, whereby the conventional polymerisation is followed by external incorporation of metals and moulding , thereby involving more time and cost. ii) Since polymeric materials are likely to degrade at high temperature, only those polymers, which can withstand very high temperature involved in metallisation and subsequent moulding, can be selected for preparing the composites. iii) Metalised polymers may degrade on ageing due to the oxidation of metals, thereby reducing the shelf life of the resulting composite. iv) The composite involves materials of unmatched mechanical properties, exhibited by metals and polymeric materials, thereby posing great concern in respect of its mechanical strength. v) Incorporation of metal into the polymer obviously increases the specific gravity of the resulting product. The main objective of the present invention is to provide a process for the preparation of a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications, which obviates the drawbacks stated above. Another objective of the present invention is to provide a simple, economical process to prepare conducting fibrous composite. Still another objective of the invention is to prepare the conducting fibrous composite without necessitating rise of temperature. Yet another objective of the invention is to prepare flexible and light-weight conducting fibrous composite with good shelf life. Still another objective of the invention is to avoid the use of metal as the conducting material. Yet another objective of the invention is to make use of industrial waste fibres to prepare the composite. Still another objective of the present invention is to provide a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications. Accordingly , the present invention provides a process for the preparation of a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications, which comprises i) loading the clean fibrous matrix, with a hetero aromatic monomer, capable of forming into conjugated polymeric structure in an amount in the range of 1-50% w/w in an organic solvent used is an amount of of 2-10 times w/w, optionally adding emulsifier in the range of 0.1 to 1% w/w either in vacuum or ultrasonics by known methods optionally in presence of monomer penetrating accessory, ii) reacting the monomer loaded fibrous matrix, as formed in step (i), with any oxidising agent in the range of 0.5 to 8 moles per mole of monomer, iii) washing the polymeric matrix, as formed in step (ii), with water followed by drying by known method to get the conducting polymeric fibrous composite. In an embodiment of the present invention, the fibrous matrix used may be leather, leather splits, leather cuttings, leather trimmings, leather board, textile materials, paper boards. In another embodiment of the present invention, the method used for cleaning of the fibrous matrix may be brushing, vacuum cleaning. In yet another embodiment of the present invention, the monomer used may be pyrrole, substituted pyrroles,alkyl thiophene, either individually or in combination. In still another embodiment of the present invention, the emulsifier used may be sodium lauryl sulphate, glycerol, n-butanol. In yet another embodiment of the present invention, the amount of emulsifier used may be in the range of 0.1-1% w/w, on the monomer. In still another embodiment of the present invention, the solvent used may be such as acetone, ethyl methyl ketone, chloroform, methylene chloride. In yet another embodiment of the present invention, the amount of solvent used may be in the range of 2-10 times w/w, on the monomer. In still another embodiment of the present invention, the amount of monomer solution/emulsion may be in the range of 1-50% w/w, on the fibrous matrix. In yet another embodiment of the present invention, the monomer penetrating accessory used may be such as vacuum, ultrasonics. In still another embodiment of the present invention, the oxidising agent used may be such as ferric chloride, ammonium persulphate, potassium persulphate. In yet another embodiment of the present invention, the amount of oxidising agent used may be in the range of 0.5-8 moles per mole of monomer. In still another embodiment of the present invention, drying may be effected by air drying, vacuum drying. Accordingly, the present invention provides a novel conducting fibrous composite prepared by the process as described above. The surface of the fibrous matrix is cleaned by known method. Monomer, capable of forming into conjugated polymeric structure either in aqueous or in non aqueous medium, is either dissolved in 2-10 times w/w, of a solvent to prepare a monomer solution or emulsified in aqueous phase in the presence of an emulsifier, amounting in the range of 0.1-1% w/w, on the monomer. The cleaned fibrous matrix is then treated with 1-50% w/w, of the monomer mixture, optionally in the presence of a monomer penetrating accessory, to load the monomer onto the fibrous matrix. This monomer loaded matrix is reacted with 0.5-8 moles of an oxidizing agent per mole of the monomer to facilitate the polymerization of the monomer onto the fibrous matrix. The temperature of reaction is kept at 25°C.and the reaction is continued for a time period of 1-3 hrs. The resultant product is washed in water and then dried by known method to get the conducting fibrous composite. The minimum polymer to matrix ratio is maintained in such a way as 1:10 in order to achieve the composite to be conducting. The novelty and inventive step of the present invention lies not only in selecting low cost fibrous matrix, which includes 3-dimensional structures like leather ensuring better shape retention of the final product, but also in providing an economical method to polymerise the selected monomer onto the fibrous matrix itself, unlike the conventional processes, where a conducting material is incorporated into a preformed polymeric material involving additional processes like compounding and moulding, to prepare flexible, light-weight electro conducting fibrous composite for effective EMI shielding purpose, thereby suggesting a method to utilize the industrial wastes, which would otherwise have created disposal problem, for preparing value added products to extract wealth out of waste. This following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention. Example 1 280 gms of chrome leather splits of 3 mm thickness were taken in a tray and were cleaned by vacuum cleaner. 6.6 g of pyrrole was taken in a flask attached with a stirrer and 50 ml of water along with 0.2 g of sodium lauryl sulphate were added to it while stirring the contents for 3 hrs to form an emulsion. The cleaned leather splits were then dipped in this emulsion and were subjected to mild vacuum of 800 m bar to facilitate the loading of the monomer emulsion in the splits. After a period of 30 minutes, the leather splits were taken out of the flask and the volume of the remaining liquid in the flask was noted to be 44 ml. 18g of ferric chloride was dissolved in 50 ml of water taken in another beaker. The emulsion loaded leather splits were taken in a tray and the ferric chloride solution was poured on it. The contents were stirred occasionally. After a period of 3 hrs, the resulting leather composite was taken out of the tray and washed well in running water. The product was finally dried by air drying at 30°C to get the conducting leather composite, which may be used for EMI shielding application. Example 2 Sole leather trimmings with a thickness of 3 mm, weighing 250 gms, were taken in a tray and were cleaned by vacuum cleaner. 6.6 g of pyrrole was taken in a flask attached with a stirrer and 50 ml of acetone was added to it while stirring the contents for 3 hrs to form a solution. The cleaned leather trimmings were then immersed in this solution and were kept in an ultrasonic bath to facilitate the penetration of the monomer solution in the leathers. After a period of 30 minutes, the leather trimmings were taken out of the flask and dried at 30°C for 15 min. 18g of ferric chloride was dissolved in 50 ml of water taken in another beaker and the leather trimmings were added to that. The contents were stirred occasionally. After a period of 2 hrs, the resulting leather composites were taken out of the beaker and washed well in running water. The products were finally dried by air drying at 30°C to get the conducting leather composite, which may be used for EMI shielding application. Example 3 lOOgms of cloth trimmings were taken in a tray and were cleaned by brush. 4.4g of pyrrole was taken in a flask attached with a stirrer and 3.6g of 3-methyl thiophene was added to it. 50 ml of chloroform was then added to the flask while stirring the contents for 2.5 hrs to form a solution. The cleaned cloth trimmings were then immersed in this solution, which was kept in an ultrasonic bath to facilitate the penetration of the monomer solution in the cloth. After a period of 30 minutes, the cloth was taken out of the flask and air-dried at 30°C for 15 min. 45g of ammonium per sulphate was dissolved in 100 ml of water taken in another beaker and the cloth was added to that. The contents were stirred occasionally. After a period of 2 hrs, the resulting textile composite was taken out of the beaker and washed well in running water. The product was finally dried by air drying at 30°C to get the conducting textile composite, which may be used for EMI shielding application. Example 4 lOOgms of paper board materials were taken in a tray and were cleaned by brush. 4.4g of pyrrole was taken in a flask attached with a stirrer and 3.6g of 3-methyl thiophene was added to it. 50 ml of chloroform was then added to the flask while stirring the contents for 2.5 hrs to form a solution. The cleaned paper boards were then immersed in this solution, which was kept in an ultrasonic bath to facilitate the penetration of the monomer solution in the paper board material. After a period of 30 minutes, the paper board was taken out of the flask and air-dried at 30°C for 15 min. 45g of ammonium per sulphate was dissolved in 100 ml of water taken in another beaker and the paper boards was added to that. The contents were stirred occasionally. After a period of 2 hrs, the resulting paper board composite was taken out of the beaker and washed well in running water. The product was finally vacuum dried to get the conducting paper board composite, which may be used for EMI shielding application. Example - 5 280gms of rejection grade chrome leather materials were taken in a tray and were cleaned by brush. Octyl thiophene was then prepared by the following method. 12g of magnesium was dried in nitrogen for 10 min. and cooled in icebath. 300 ml of dry diethyl ether was then added to the beaker containing the metal and 60g of octyl chloride was added to the same over a period of 1 hr with continuous stirring. After a period of 3 hrs., the contents were refluxed for 24 hrs. in a water bath. Then the contents were alowed to cool down to 30°C and 0.lg of nickel catalyst was added to the mixture. 82g of bromo thiophene was then added to the above mixture, which was then refluxed for 48 hrs. The contents were then neutralised to pH 8 using dilute hydrochloride acid. The resulting mixture was extracted with ether and the ether layer was evaporated to dryness. The resulting liquid obtained was purified using silica gel column to get pure octyl thiophene. 9.3 g of octyl thiophene monomer was dissolved in 50 ml of methylene chloride taken in a beaker and the solution was poured into a tray. The cleaned chrome leather materials were then added to the tray and were allowed to immerse in the octyl thiophene monomer solution. After 4 hrs, the leathers were taken out of the tray. 40 gms of potassium persulphate was dissolved in 100 ml of water taken in another beaker and the octyl thiophene loaded leathers were added to that solution. The contents were stirred occasionally. After a period of 3.5 hrs, the resulting leather composites were taken out of the beaker and washed well in running water. The product was finally vacuum dried to get the conducting leather composite, which may be used for EMI shielding application. The advantages of the present invention are the following. 1 .The process of the present invention is very simple and economical. 2 Metallic component has been avoided to ensure that the process provides an economical process to prepare composite with desirable characteristics. 3. Industrial waste fibres like leather splits, trimmings, textile cuttings etc. are used as the fibrous matrix to ensure that the wastes, which create disposal problem for the industry, can be converted into value added products. 4.There is no stringent control of temperature, pH etc. ensuring that the process is very simple to operate. 5. The resulting composite is flexible, light-weight and has a long shelf life. 6. Three dimensional materials like leather are selected as the fibrous matrix in the present invention ensuring better shape retention for the final composite product. We Claim: 1. A process for the preparation of a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications, which comprises i) loading the clean fibrous matrix, with a hetero aromatic monomer, capable of forming into conjugated polymeric structure in an amount in the range of 1-50% w/w in an organic solvent used is an amount of of 2-10 times w/w, optionally adding emulsifier in the range of 0.1 to 1% w/w either in vacuum or ultrasonics by known methods optionally in presence of monomer penetrating accessory, ii) reacting the monomer loaded fibrous matrix, as formed in step (i), with any oxidising agent in the range of 0.5 to 8 moles per mole of monomer, iii) washing the polymeric matrix, as formed in step (ii), with water followed by drying by known method to get the conducting polymeric fibrous composite. 2. A process, as claimed in claim 1,wherein the fibrous matrix used is leather, leather splits, leather cuttings, leather trimmings, leather board, textile materials, paper boards. 3. A process, as claimed in claims l&2,wherein the method used for cleaning of the fibrous matrix is brushing, vacuum cleaning. 4. A process, as claimed in claims 1 to 3, wherein the organic solvent used is acetone, ethyl methyl ketone, chloroform, methylene chloride. 5. A process, as claimed in claims 1 to 4, wherein the monomer used is pyrrole, substituted pyrroles,alkyl thiophene, either individually or in combination. 6. A process, as claimed in claims 1 to 5, wherein the emulsifier used is sodium lauryl sulphate, glycerol, n-butanol. 7. A process, as claimed in claims 1 to 6, wherein the oxidising agent used is ferric chloride, ammonium persulphate, potassium persulphate. 8. A process, as claimed in claims 1 to 7, wherein drying is effected by air drying, vacuum drying. 9. A process for the preparation of a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications, substantially as herein described with reference to the examples.

Full Text

The present invention relates to a process for the preparation of a novel conducting fibrous composite for electromagnetic interference (EMI) shielding applications. More particularly, the composite of the present invention has potential applications in electronic industry for electromagnetic interference (EMI) shielding purpose. As reported by Sathyamurthy (Electronics for you, p-43, May, 1998), in the wake of the rapid development of electronic apparatus, electromagnetic interference (EMI) has been a matter of much concern among the researchers. It is generated by an electronic equipment, which radiates electromagnetic waves affecting the normal functioning of another electronic equipment. The components of the electromagnetic wave, transmitted in the radio frequency (r-f) range by an electronic equipment, whether intended or not intended to transmit, originate r-f signals. EMI in the r-f range consists of undesirable r-f signals superimposed upon a desired signal. The unwanted EMI generated by an electronic apparatus can adversely affect, as an external source of interference, the functioning of another electronic apparatus. For example, high density multifunctional computers are controlled by pulses whose spectra are distributed over a wide range. Although these pulses are necessary for the operation of the computer, the high frequency electromagnetic waves, which are radiated, are likely to interfere with the functioning of the surrounding electronic apparatus resulting in noises. It is therefore important to protect electronic apparatus from EMI. Necessary care has also to be taken to ensure that the equipment itself does not become a source of EMI. This is how the concept of shielding the EMI has come into play. It is possible to achieve the EMI shielding with the help of some shielding materials, which can either reflect the electromagnetic waves tansmitted by an equipment, thereby preventing its further propagation, or absorb the same. The

shielding capability of a material is defined as the proportion of attenuation of the electromagnetic waves incident upon a substance.
As reported by Yasufuku (Institution of Electrical Engineering & Electronics Electrical Insulation, 6, 21,1990), it has been the usual practice to use metallic sheets for the purpose of housing information related apparatus like computers, video camera, word processors. Usually highly conducting metals like copper or aluminium, have conventionally been in use for partial covering of the electronic component to ensure that the induced r-f is neutralised.
The major limitation of using metal for the purpose of EMI shielding is that due to the lack of flexibility of the metals, the area of contact between the shielding material and the equipment to be shielded is likely to be obviously less resulting in the reduction of the efficiency of shielding. Moreover, the use of metals increases not only the cost of the resulting product, but also its weight.
Attention has therefore been shifted, in the realm of EMI shielding applications, to the thermoplastic polymers, which have of late been been getting much prominence due to the flexibility, versatility for design and low cost. Many electronic devices that inherently transmit a r-f signal are enclosed in housing made of polymer. But since these polymeric materials are non-conducting in nature for electricity, it is necessary to incorporate electrical conductors for using them as shielding materials. Unfilled polymeric material offer very little attenuation of r-f energy. Systems that would enable polymeric materials to attenuate r-f energy by using fillers or by applying a metallic plate to the surface of the plastic part, are incorporated in the housing for both component and device.

Different methods have been in practice to prepare flexible metal-polymer composite, which may be used in the form of sheet, gasket, ohring etc. for the purpose of EMI shielding. The simplest method is to carry out electroplating. Thus, ABS (Acrylonitrile-butadiene-styrene) polymer can be electroplated or vacuum metallized with metals like copper, aluminium etc. for using as EMI shielding material.
As reported in the Encyclopedia of Polymer science & Engineering, vol. 14, & supplementary volume, edited by Kohlmetz et al, Wiley Inter Science, New York, p-340,1989, electroconducting composite may also be prepared by mixing a thermoplastic resin with various metallic fillers, as detailed below and moulding the resulting mixture to a desired shape.
Glass fibre is plated with nickel and the resulting nickel plated glass fiber is mixed with polycarbonate. The resulting mixture is moulded to form a composite with high level of electrical conductivity, suitable for using as EMI shielding material. Similarly polyester, incorporated with metallic fibers can form a good electroconducting composite. Different grades of cabon fibres may also be used for conductive applications. About 30-40% wAv, of carbon fibre on polymeric resin is used to make composite for EMI application depending on the geometry of the component to be shielded and the type of polymer used. The carbon fibre is first coated with a metal. Nickel coated carbon fibre is made by coating with 0.5 µm layer of nickel. This produces a fibre with diameter of 8 µm Various other metals like silver, gold, brass and copper may also be used for making the fibre. Nickel provides the best combination of electrical and physical properties and economics. 10-15% w/w, of nickel'may be loaded onto the carbon fibre to use the end product as EMI shielding material.

Another option of making composites is to use stainless steel fibres, which are able to produce exceptional electrical properties even at a very low loading in the range of 5-10% w/w on the polymer weight primarily due to their high conductivity and aspect ratio. Stainless steel fibres of required dimension are made by pulling the fibres from a rod. The fibres of required diameter are chopped to get tow chopped fibres and formed into concentrates by coating the fibres with various thermoplastic compatible binders like polyester, polycarbonate etc. These thermoplastic polymer coated fibres are subjected to injection moulding to convert the same into composites of desired shape like sheets, ohring etc. This, however, necessitates very careful processing of the material, because stainless steel fibres are highly sensitive to the shear involved in injection moulding. Moreover, the complications of the sequential steps and the control parameters involved in the process render the process a costly one.
Aluminium flakes may also be used as additives while preparing the conducting composites. 25-40% w/w, of aluminium flakes is mixed with thermoplastic polymer binder and the mixture is moulded to desired shape to produce composites. The main limitation of aluminium polymer composite is that the impact resistance of the final product is very low. Moreover, higher loading of aluminium on the polymer adds to cost. Thus to summarise, the major drawbacks associated with the hitherto known composites may be enumerate as follows.
i) Preparation of the composite involves a lot of sequential steps, whereby the conventional polymerisation is followed by external incorporation of metals and moulding , thereby involving more time and cost.

ii) Since polymeric materials are likely to degrade at high temperature, only those
polymers, which can withstand very high temperature involved in metallisation and
subsequent moulding, can be selected for preparing the composites.
iii) Metalised polymers may degrade on ageing due to the oxidation of metals, thereby
reducing the shelf life of the resulting composite.
iv) The composite involves materials of unmatched mechanical properties, exhibited by
metals and polymeric materials, thereby posing great concern in respect of its mechanical
strength.
v) Incorporation of metal into the polymer obviously increases the specific gravity of the
resulting product.
The main objective of the present invention is to provide a process for the preparation of a
novel conducting fibrous composite for electromagnetic interference (EMI) shielding
applications, which obviates the drawbacks stated above.
Another objective of the present invention is to provide a simple, economical process to
prepare conducting fibrous composite.
Still another objective of the invention is to prepare the conducting fibrous composite
without necessitating rise of temperature.
Yet another objective of the invention is to prepare flexible and light-weight conducting
fibrous composite with good shelf life.
Still another objective of the invention is to avoid the use of metal as the conducting
material.
Yet another objective of the invention is to make use of industrial waste fibres to prepare
the composite.

Still another objective of the present invention is to provide a novel conducting fibrous
composite for electromagnetic interference (EMI) shielding applications.
Accordingly , the present invention provides a process for the preparation of a novel
conducting fibrous composite for electromagnetic interference (EMI) shielding
applications, which comprises
i) loading the clean fibrous matrix, with a hetero aromatic monomer, capable of
forming into conjugated polymeric structure in an amount in the range of 1-50% w/w in
an organic solvent used is an amount of of 2-10 times w/w, optionally adding emulsifier
in the range of 0.1 to 1% w/w either in vacuum or ultrasonics by known methods
optionally in presence of monomer penetrating accessory,
ii) reacting the monomer loaded fibrous matrix, as formed in step (i), with any oxidising
agent in the range of 0.5 to 8 moles per mole of monomer,
iii) washing the polymeric matrix, as formed in step (ii), with water followed by drying
by known method to get the conducting polymeric fibrous composite.
In an embodiment of the present invention, the fibrous matrix used may be leather,
leather splits, leather cuttings, leather trimmings, leather board, textile materials, paper
boards.
In another embodiment of the present invention, the method used for cleaning of the
fibrous matrix may be brushing, vacuum cleaning.
In yet another embodiment of the present invention, the monomer used may be pyrrole,
substituted pyrroles,alkyl thiophene, either individually or in combination.
In still another embodiment of the present invention, the emulsifier used may be sodium
lauryl sulphate, glycerol, n-butanol.

In yet another embodiment of the present invention, the amount of emulsifier used may be
in the range of 0.1-1% w/w, on the monomer.
In still another embodiment of the present invention, the solvent used may be such as
acetone, ethyl methyl ketone, chloroform, methylene chloride.
In yet another embodiment of the present invention, the amount of solvent used may be in
the range of 2-10 times w/w, on the monomer.
In still another embodiment of the present invention, the amount of monomer
solution/emulsion may be in the range of 1-50% w/w, on the fibrous matrix.
In yet another embodiment of the present invention, the monomer penetrating accessory
used may be such as vacuum, ultrasonics.
In still another embodiment of the present invention, the oxidising agent used may be such
as ferric chloride, ammonium persulphate, potassium persulphate.
In yet another embodiment of the present invention, the amount of oxidising agent used
may be in the range of 0.5-8 moles per mole of monomer.
In still another embodiment of the present invention, drying may be effected by air drying,
vacuum drying.
Accordingly, the present invention provides a novel conducting fibrous composite
prepared by the process as described above.
The surface of the fibrous matrix is cleaned by known method. Monomer, capable of
forming into conjugated polymeric structure either in aqueous or in non aqueous medium,
is either dissolved in 2-10 times w/w, of a solvent to prepare a monomer solution or
emulsified in aqueous phase in the presence of an emulsifier, amounting in the range of
0.1-1% w/w, on the monomer.

The cleaned fibrous matrix is then treated with 1-50% w/w, of the monomer mixture, optionally in the presence of a monomer penetrating accessory, to load the monomer onto the fibrous matrix. This monomer loaded matrix is reacted with 0.5-8 moles of an oxidizing agent per mole of the monomer to facilitate the polymerization of the monomer onto the fibrous matrix. The temperature of reaction is kept at 25°C.and the reaction is continued for a time period of 1-3 hrs. The resultant product is washed in water and then dried by known method to get the conducting fibrous composite. The minimum polymer to matrix ratio is maintained in such a way as 1:10 in order to achieve the composite to be conducting.
The novelty and inventive step of the present invention lies not only in selecting low cost fibrous matrix, which includes 3-dimensional structures like leather ensuring better shape retention of the final product, but also in providing an economical method to polymerise the selected monomer onto the fibrous matrix itself, unlike the conventional processes, where a conducting material is incorporated into a preformed polymeric material involving additional processes like compounding and moulding, to prepare flexible, light-weight electro conducting fibrous composite for effective EMI shielding purpose, thereby suggesting a method to utilize the industrial wastes, which would otherwise have created disposal problem, for preparing value added products to extract wealth out of waste. This following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention.
Example 1
280 gms of chrome leather splits of 3 mm thickness were taken in a tray and were cleaned by vacuum cleaner. 6.6 g of pyrrole was taken in a flask attached with a stirrer and 50 ml

of water along with 0.2 g of sodium lauryl sulphate were added to it while stirring the contents for 3 hrs to form an emulsion. The cleaned leather splits were then dipped in this emulsion and were subjected to mild vacuum of 800 m bar to facilitate the loading of the monomer emulsion in the splits. After a period of 30 minutes, the leather splits were taken out of the flask and the volume of the remaining liquid in the flask was noted to be 44 ml. 18g of ferric chloride was dissolved in 50 ml of water taken in another beaker. The emulsion loaded leather splits were taken in a tray and the ferric chloride solution was poured on it. The contents were stirred occasionally. After a period of 3 hrs, the resulting leather composite was taken out of the tray and washed well in running water. The product was finally dried by air drying at 30°C to get the conducting leather composite, which may be used for EMI shielding application.
Example 2
Sole leather trimmings with a thickness of 3 mm, weighing 250 gms, were taken in a tray and were cleaned by vacuum cleaner. 6.6 g of pyrrole was taken in a flask attached with a stirrer and 50 ml of acetone was added to it while stirring the contents for 3 hrs to form a solution. The cleaned leather trimmings were then immersed in this solution and were kept in an ultrasonic bath to facilitate the penetration of the monomer solution in the leathers. After a period of 30 minutes, the leather trimmings were taken out of the flask and dried at 30°C for 15 min.
18g of ferric chloride was dissolved in 50 ml of water taken in another beaker and the leather trimmings were added to that. The contents were stirred occasionally. After a period of 2 hrs, the resulting leather composites were taken out of the beaker and

washed well in running water. The products were finally dried by air drying at 30°C to get the conducting leather composite, which may be used for EMI shielding application.
Example 3
lOOgms of cloth trimmings were taken in a tray and were cleaned by brush. 4.4g of pyrrole was taken in a flask attached with a stirrer and 3.6g of 3-methyl thiophene was added to it. 50 ml of chloroform was then added to the flask while stirring the contents for 2.5 hrs to form a solution. The cleaned cloth trimmings were then immersed in this solution, which was kept in an ultrasonic bath to facilitate the penetration of the monomer solution in the cloth. After a period of 30 minutes, the cloth was taken out of the flask and air-dried at 30°C for 15 min.
45g of ammonium per sulphate was dissolved in 100 ml of water taken in another beaker and the cloth was added to that. The contents were stirred occasionally. After a period of 2 hrs, the resulting textile composite was taken out of the beaker and washed well in running water. The product was finally dried by air drying at 30°C to get the conducting textile composite, which may be used for EMI shielding application.
Example 4
lOOgms of paper board materials were taken in a tray and were cleaned by brush. 4.4g of pyrrole was taken in a flask attached with a stirrer and 3.6g of 3-methyl thiophene was added to it. 50 ml of chloroform was then added to the flask while stirring the contents for 2.5 hrs to form a solution. The cleaned paper boards were then immersed in this solution, which was kept in an ultrasonic bath to facilitate the penetration of the monomer

solution in the paper board material. After a period of 30 minutes, the paper board was taken out of the flask and air-dried at 30°C for 15 min.
45g of ammonium per sulphate was dissolved in 100 ml of water taken in another beaker and the paper boards was added to that. The contents were stirred occasionally. After a period of 2 hrs, the resulting paper board composite was taken out of the beaker and washed well in running water. The product was finally vacuum dried to get the conducting paper board composite, which may be used for EMI shielding application.
Example - 5
280gms of rejection grade chrome leather materials were taken in a tray and were cleaned by brush. Octyl thiophene was then prepared by the following method. 12g of magnesium was dried in nitrogen for 10 min. and cooled in icebath. 300 ml of dry diethyl ether was then added to the beaker containing the metal and 60g of octyl chloride was added to the same over a period of 1 hr with continuous stirring. After a period of 3 hrs., the contents were refluxed for 24 hrs. in a water bath. Then the contents were alowed to cool down to 30°C and 0.lg of nickel catalyst was added to the mixture. 82g of bromo thiophene was then added to the above mixture, which was then refluxed for 48 hrs. The contents were then neutralised to pH 8 using dilute hydrochloride acid. The resulting mixture was extracted with ether and the ether layer was evaporated to dryness. The resulting liquid obtained was purified using silica gel column to get pure octyl thiophene.
9.3 g of octyl thiophene monomer was dissolved in 50 ml of methylene chloride taken in a beaker and the solution was poured into a tray. The cleaned chrome leather materials

were then added to the tray and were allowed to immerse in the octyl thiophene monomer
solution. After 4 hrs, the leathers were taken out of the tray.
40 gms of potassium persulphate was dissolved in 100 ml of water taken in another beaker
and the octyl thiophene loaded leathers were added to that solution. The contents were
stirred occasionally. After a period of 3.5 hrs, the resulting leather composites were
taken out of the beaker and washed well in running water. The product was finally vacuum
dried to get the conducting leather composite, which may be used for EMI shielding
application.
The advantages of the present invention are the following.
1 .The process of the present invention is very simple and economical.
2 Metallic component has been avoided to ensure that the process provides an economical
process to prepare composite with desirable characteristics.
3. Industrial waste fibres like leather splits, trimmings, textile cuttings etc. are used as the fibrous matrix to ensure that the wastes, which create disposal problem for the industry, can be converted into value added products.
4.There is no stringent control of temperature, pH etc. ensuring that the process is very simple to operate.
5. The resulting composite is flexible, light-weight and has a long shelf life.
6. Three dimensional materials like leather are selected as the fibrous matrix in the present
invention ensuring better shape retention for the final composite product.

We Claim:
1. A process for the preparation of a novel conducting fibrous composite for
electromagnetic interference (EMI) shielding applications, which comprises
i) loading the clean fibrous matrix, with a hetero aromatic monomer, capable of forming into conjugated polymeric structure in an amount in the range of 1-50% w/w in an organic solvent used is an amount of of 2-10 times w/w, optionally adding emulsifier in the range of 0.1 to 1% w/w either in vacuum or ultrasonics by known methods optionally in presence of monomer penetrating accessory,
ii) reacting the monomer loaded fibrous matrix, as formed in step (i), with any oxidising agent in the range of 0.5 to 8 moles per mole of monomer,
iii) washing the polymeric matrix, as formed in step (ii), with water followed by drying by known method to get the conducting polymeric fibrous composite.
2. A process, as claimed in claim 1,wherein the fibrous matrix used is leather, leather
splits, leather cuttings, leather trimmings, leather board, textile materials, paper boards.
3. A process, as claimed in claims l&2,wherein the method used for cleaning of the
fibrous matrix is brushing, vacuum cleaning.
4. A process, as claimed in claims 1 to 3, wherein the organic solvent used is acetone,
ethyl methyl ketone, chloroform, methylene chloride.
5. A process, as claimed in claims 1 to 4, wherein the monomer used is pyrrole,
substituted pyrroles,alkyl thiophene, either individually or in combination.
6. A process, as claimed in claims 1 to 5, wherein the emulsifier used is sodium lauryl
sulphate, glycerol, n-butanol.

7. A process, as claimed in claims 1 to 6, wherein the oxidising agent used is ferric
chloride, ammonium persulphate, potassium persulphate.
8. A process, as claimed in claims 1 to 7, wherein drying is effected by air drying,
vacuum drying.
9. A process for the preparation of a novel conducting fibrous composite for
electromagnetic interference (EMI) shielding applications, substantially as herein
described with reference to the examples.

Documents:

1283-del-1999-abstract.pdf

1283-del-1999-claims.pdf

1283-del-1999-correspondence-others.pdf

1283-del-1999-correspondence-po.pdf

1283-del-1999-description (complete).pdf

1283-del-1999-form-1.pdf

1283-del-1999-form-19.pdf

1283-del-1999-form-2.pdf

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Patent Number

215470

Indian Patent Application Number

1283/DEL/1999

PG Journal Number

11/2008

Publication Date

14-Mar-2008

Grant Date

27-Feb-2008

Date of Filing

23-Sep-1999

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	NARAYANA SASTRI SOMANATHAN	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020, INDIA.

PCT International Classification Number

B32B 5/12

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA