Title of Invention	CONDUCTING POLYMER PAINTS AND COATING COMPOSITION FOR THE CORROSION PROTECTION OF IRON
Abstract	A process for the preparation of conducting polymer acrylic resin which can be used by applying to the surface of steel a coating of acrylic paint containing conducting polymer as pigments alongwith other constituents. The invention relates to synthesis of copolymer of aniline and substituted aniline comprising of sec. butyl aniline, o-phenetidine, o-ethyl aniline and o-toluidine. The copolymer of aniline and substituted aniline are synthesized in the presence of acid free environment and are embedded on fillers titanium oxide and are mixed with resin in appropriate ratio. In the present case a coating of copolymer mixed with other materials acrylic resin which is applied on the surface for the corrosion protection of iron and mild steel against hostile environment like saline water comprising NaCI, MgCI2, BaCI2 and so on.

Title of Invention

CONDUCTING POLYMER PAINTS AND COATING COMPOSITION FOR THE CORROSION PROTECTION OF IRON

Abstract

A process for the preparation of conducting polymer acrylic resin which can be used by applying to the surface of steel a coating of acrylic paint containing conducting polymer as pigments alongwith other constituents. The invention relates to synthesis of copolymer of aniline and substituted aniline comprising of sec. butyl aniline, o-phenetidine, o-ethyl aniline and o-toluidine. The copolymer of aniline and substituted aniline are synthesized in the presence of acid free environment and are embedded on fillers titanium oxide and are mixed with resin in appropriate ratio. In the present case a coating of copolymer mixed with other materials acrylic resin which is applied on the surface for the corrosion protection of iron and mild steel against hostile environment like saline water comprising NaCI, MgCI2, BaCI2 and so on.

Full Text	FIELD OF INVENTION The present invention relates to the a process for the preparation of conducting polymer coating composition for the corrosion protection of iron based surfaces. More particularly the invention relates to a copolymer of aniline and substituted aniline synthesized in the absence of acidic environment and a process for the preparation of the said copolymer and subsequent paint formulations for the corrosion protection of iron. BACKGROUND OF INVENTION The corrosion of iron and mild steel is an enormous problem throughout the world. Giving an anticorrosion treatment to articles of iron and materials containing iron is considered essential for durability of the articles due to hostile environmental parameters of humidity, salinity of water etc. Many kinds of treatment, paints and coatings have been developed over the years to address this problem. For a coating to protect iron against corrosion, it should restrict access of water, oxygen and other oxidants to the iron surface. In some instances, corrosion inhibitors such as zinc coatings or organic amines are used. Recently much interest has been shown in the use of conductive polymers in corrosion protection of articles made from iron or mild steel. These articles maybe such as huge ships used for marine transport. Reference may be made to "Corrosion-Protective Coatings from Electrically Conductive Polymers", Proceedings from Technology 2001, San Jose, California, wherein Thompson et al disclose conductive polymer coatings for the protection of iron surfaces from corrosion. These coatings involved electrically conducting forms of several polymers, including polyaniline which had been appropriately doped with additives serving as electron acceptors to increase conductivity of the polymer. These polymers were used by applying undoped chemically prepared polymers to the steel surface and subsequent doping of the coated surface to the conductive state. Doped polyaniline was converted to a non-conducting emeraldine base which was dissolved in an organic solvent such as, N-methyl-pyrrolidinone (NMP) and coated on steel after which the coating was doped to the conducting state. The dopants used were tosylate ions, zinc nitrate and tetracyanoethylene. After doping, a top coat of standard fully cured epoxy was applied to provide abrasion resistance. In this disclosure the coating of the polymer dissolved in NMP is affected for curing by heating to a temperature of at least 95°C. The use of high temperature with NMP as the solvent is highly undesirable as during high temperature treatment, the NMP releases toxic gases. This work reported a corrosion barrier coating for steel made from an electrically conducting polymer which resists the transfer of electrons from iron to the oxidizing environment. The coating was said to have two layers: an undercoat of polyaniline on steel surface and an epoxy top coat for durability. The bilayer coating was reported to be more effective in resisting corrosion than a coating with epoxy alone. Reference may be made to US Patent 5441772, wherein a method of protecting carbon steel substrates from corrosion environments is provided by a coating of emeraldine base which has been chemically prepared and cast onto the substrate from NMP solution. The coating also includes other polymers such as polyimides, epoxies and urethane linked diisocyanates, among others. This invention also suffers from the disadvantage of the use of NMP which uses high temperature treatment for effecting a protective coating. Reference may be made to US Patent 5441772, wherein a method of protecting carbon steel substrates from corrosion environments by a coating of emeraldine base which has been chemically prepared and cast onto the substrate from NMP solution is disclosed. The coating also includes other polymers such as polyimides, epoxies and urethane linked diisocyanates, among others. In this patent disclosure, emeraldine base is dissolved in N-methyl pyrrolidinone which is then applied on carbon steel substrates. A temperature of 80-90°C is required to evaporate the NMP solution resulting in toxic NMP vapours. Reference may be made to US Patent 5853621,wherein an anti corrosion paint of the type comprising one or more polymeric binders dispersed in liquid medium with an effective amount of non-conductive conjugated polymers is disclosed. In this patent disclosure, polyaniline is mixed with a dispersant from Daniel Products in a solvent propylene glycol methyl ether acetate and aromatic naptha 100. Reference may be made to US Patent 5922466, wherein the development of a composite comprising a metal substrate and a corrosion protecting layer on at least one major surface, a composition comprising a thermoset or thermoplastic polymeric matrix and a conductive filler component comprising polyaniline, and other conducting polymers has been disclosed. In this patent, a composition of thermoplastic or thermoset polymeric matrix along with polyaniline is applied on iron substrate. For thermoplastic coating, a temperature ranging from 100-200°C is required which is the melting point of the polymeric material. This blend is then applied on the iron surface. In this case firstly, the temperature needed is very high and secondly, this type of process is not suitable for industrial applications because the coating can be applied only when it is in the melt stage and once the temperature lowers down, solidification will start leading to the requirement of again raising the temperature to desired level to effect the coating. Reference may be made to US Patent 6015613, wherein a method of forming corrosion inhibition multilayer coatings is disclosed. When the coating is bonded to a substrate, it forms an inter layer between the metal and substrate. The laminates serve to protect the metal surface from corrosion in acid, salt and alkaline corrosive environments. In the said patent disclosure, C1018 steel electrodes are brush coated with a dispersion of polyaniline and poly(butylmethylacrylate) in butyrolactone. The coating coupons are allowed to dry at 60°C in an air convection oven. An epoxy topcoat of Carboline 890 was then applied at 60°C. In this case, only a dispersion of polyaniline in solvent is used which may not spread uniformly on the surface and once the surface is exposed to hostile atmosphere, corrosion rate may be accelerated. Reference may be made to US Patent 6239251, wherein a method of forming low molecular weight oligomers of aniline based compounds are disclosed which are end fictionalized and capable of being reacted with other monomeric species to form a variety of copolymers. In this patent, aniline is polymerized in the presence of 1,4-phenylenediamine, 1,4-aminodiphenyl amine, n.n'diphenylhydrazine, benzidine and the like. The coating of the above copolymer is prepared by dissolving the copolymer in dimethylformamide (DMF) and then combining with epoxy resin in the form of bisphenol-A-diglycidyl ether. Curing is done at 120°C for 1 hour. The temperature required for curing in the disclosure is 120°C. OBJECTIVES OF THE INVENTION The main objective of the present invention is to provide a process for the preparation of conducting polymer coating composition useful for corrosion protection of iron and mild steel, which obviates the drawbacks as, mentioned above. Another objective of the present invention is to provide a process for the preparation of conducting polymer coating composition in acid free condition. Another objective of the present invention is to provide a process for the preparation of copolymer of aniline and substituted aniline synthesized in the absence of acidic conditions which can be useful for the prevention of corrosion of iron and mild steel in hostile saline atmosphere. Yet another object of the present invention is to provide a single coat of conducting polymer coating for the anti corrosive coating. BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated in figures 1-2 of the drawing accompanying this specification: Figure 1: represents a graph showing impedance plots of paint coated steel in 3 % NaCI after salt spray exposure. Fig. 2: represents impedance plots of paint with copolymer coated sample in 3 % NaCI. SUMMARY OF THE INVENTION Accordingly, the present invention provides a process for the preparation of conducting polymer coating composition for the corrosion protection of iron based surfaces. The present invention provides a process for the synthesis of copolymer of aniline and substituted aniline in aqueous medium in the temperature range of 0 to 5°C, and stirring the said mixture, adding an oxidant like cupric fluoroborate slowly drop by drop to the said mixture at a temperature in a range of 0 to 5°C, stirring the reaction mixture for a period in a range of 4-6 hours, filtering the said reaction mixture after the completion of the polymerization, washing thoroughly the said mixture with good quality water, filtering the precipitate and drying the polymer at a temperature in the range of 50-60°C under vacuum. In an embodiment of the present invention a process for the preparation of conducting polymer coating composition useful for corrosion protection of iron and mild steel comprising of: (a) a conducting copolymer of aniline and substituted aniline in the range of 1-30 weight% (b) resin in the range of 10-30 weight %, and (c) filler materials in the range of 10 -35 % .wherein said process comprising the steps: a. mixing of aniline and substituted aniline monomers at temperature ranging between 0°C 5°C; b. adding an oxidant slowly drop by drop to the reaction mixture as obtained in step (a) at a temperature in the range of-5 to 5°C; c. stirring the reaction mixture as obtained in step (b) for a period in a range of 4-6 hours at temperature ranging between 0°C to 5°C; d. filtering the reaction mixture as obtained in step (c) to obtain a precipitate of copolymer; e. washing the precipitate of copolymer as obtained in step (d) with water till the colour of the filtrate is colourless; f. drying the copolymer as obtained in step (e) at a temperature in a range of 50-60°C under vacuum; g. mixing the copolymer as obtained in step (f) with resin and filler materials for 30 to 60 minutes to obtain the conducting polymer coating composition. In another embodiment of the present invention the substituted aniline used in step (a) is selected from the group consisting of sec. butyl aniline, o-phenetidine, ethyl aniline and o-toluidine. In another embodiment of the present invention acrylic resin used in step (g) is PRL166. In another embodiment of the present invention the filler materials used in step (g) are selected from the group consisting of titanium oxide (anatyse), talc, silica and aluminum stearate. In another embodiment of the present invention the oxidant used in step (b) is selected from the group consisting of cupric fluoroborate, cupric phosphate, cupric sulphate, cupric chloride. In another embodiment of the present invention the ratio of mixture of aniline and substituted aniline is in the range 1.0 :1.0 to 0.01. In another embodiment of the present invention the mol ratio of (aniline and substituted aniline) and oxidant ranges from 1.0: 1.0 mole to 0.01. In another embodiment of the present invention polymerization of aniline and substituted aniline occurs free from acidic conditions. In another embodiment of the present invention coating composition is applied to pretreated iron based surface for the corrosion protection against hostile environment like saline water comprising NaCI, MgCl2, BaCl2. In another embodiment of the present invention the pretreatment of iron based surface by conventional known means is done such as buffing, chemical cleaning. DETAILED DESCRIPTION OF THE INVENTION The process of preparation of conducting polymer is described herewith. Monomer aniline and monomer o-phenetidine (substituted aniline) are taken in a glass reaction vessel containing aqueous/methanol solution at 0°C. This reaction mixture is stirred and aqueous solution of the oxidant is added drop wise. The oxidant may be cupric tartarate, cupric tetrafluoroborate, cupric sulphate, cupric chloride, cupric phosphate and the like. More preferably cupric fluoroborate is taken. The reaction mixture is stirred preferably for 4 hours, till a greenish precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with good quality water and preferably distilled water though de-ionized water may also be suitably used, till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at about 55°C. The resultant copolymer was used as a pigment which is mixed with acrylic resin and coated on iron electrode to study its behavior as a corrosion preventive coating in saline water. Electrochemical impedance measurements were carried out to determine the resistance of the coating after immersion in 3% NaCI. Organic compounds and polymers inhibit corrosion by absorbing at the metal surfaces. Modes of absorption depend on the chemical structure of the molecule like presence of pi-bonds or available lone pair of electrons, type of metal surfaces, electrochemical potential at the metal solution surface and complexation of molecules with metal ions neutralizing corrodant. In case of conducting polymer coating, adsorption takes place via functionalized nitrogen atoms of polymer nucleus oriented towards the metal surface and through the delocalized pi-electrons with the aromatic rings parallel to the electrode surface. The novelty of the present invention is the synthesis of conducting copolymer of aniline with o-phenetidine, o-toluidine, o - ethyl aniline and the like free from acidic conditions. The novelty of the invention lies in eliminating the use of toxic heavy elements like chromium, lead in the coating methods. Both these novelties are realized due to the inventive step of preparation of copolymer of aniline and substituted aniline like o-phenetidine by oxidation. The following examples are given by way of illustration of the working of the invention in actual practice and should not be construed to limit the scope of the present invention in any way. Example 1 Preparation of Copolymer 0.05 mole of aniline (4.65 ml) and 0.05 mole of o-phenetidine (6.85 ml) are taken in a reaction vessel containing 1.0 It of distilled water kept at 0°C ±1.0°C. The reaction mixture is stirred and drop wise aqueous solution of 0.1 mole of cupric fluoroborate (23.7 gms) of the oxidant is added in one hour time. The reaction mixture is stirred for 4 hours, till a greenish precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at 55°C with constancy of temperature maintained to within 1° C. The 30 % acrylic stock solution has to be prepared first. The corresponding wt% of individual ingredients have to be taken, premixed and then added to the acrylic stock solution with calculated amount (given in Table 1) using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards as given in Table 2. The formulated paints were tested for the following physical properties as per the ASTM Standards: a. Density (ASTM D 1475) b. Viscosity (ASTM D 1200) c. Volume solids (ASTM D 5201) d. Fineness of Dispersion (ASTM D 1210) For Painted Panels: a. Dry film thickness (ASTM D 1400) b. Impact resistance (ASTM G 14) c. Adhesion (ASTM D 4541) d. Flexibility (ASTM D 522) e. Abrasion Resistance (ASTM D 4060) The impedance measurements of these coatings were carried out after 1 day, 2 day, 5 day, 12 day, 30th day and 60th day and corresponding resistance of the coatings were noted. Table 1: The ratios of ingredients to be taken for premixing Table 2: The physical properties of the formulated paint composition Table 3: Impedance behaviour of Copolymer of aniline & o-ethoxy aniline-NA as Top coated sample in 3 % NaCI (Table Removed) Example -2 0.05 M of aniline (4.65 ml) and 0.05 M of sec. butylaniline (7.46 ml) are taken in a reaction vessel in 1.0 Itr of distilled water and is kept at 0°C. The reaction mixture is stirred and drop wise aqueous solution of oxidant, cupric chloride (0.1 mole, 17.04 gms) is added. The reaction mixture is stirred for 4 hours, till a brownish green precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at 50°C. 30 % acrylic resin stock solution (PRL166, Pidilite, India. Ltd.) is prepared first. The corresponding wt% of individual ingredients have to be taken, premixed and then added to the acrylic solution with the required calculated amount. The ingredients containing 15 % of copolymer 35 % of titanium oxide (anatyse), 20 % of talc, 20 % of silica and 10 % of aluminum state were premixed and added in the acrylic resin solution using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards. The impedance measurements of these coatings were carried out after 1 day, 7 day, 14 day, 35th day and 60th day and corresponding resistance of the coatings were noted. Table 4: Impedance parameters of copolymer incorporated coating on Steel in 3 % NaCI (Table Removed) Example -3 0.05 M of aniline (4.65 ml) and 0.05 M of o-toluidine (5.35 ml) are taken in a reaction vessel in 1.0 Itr of distilled water and is kept at 0°C. The reaction mixture is stirred and drop wise aqueous solution of oxidant, cupric chloride (0.1 mole, 17.04 gms) is added. The reaction mixture is stirred for 4 hours, till a brownish green precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at 50°C. 30 % acrylic resin stock solution (PRL166, Pidilite, India. Ltd.) is prepared first. The corresponding wt% of individual ingredients have to be taken, premixed and then added to the acrylic solution with the required calculated amount. The ingredients containing 15 % of copolymer 35 % of titanium oxide (anatyse), 20 % of talc, 20 % of silica and 10 % of aluminum state were premixed and added in the acrylic resin solution using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards. The impedance measurements of these coatings were carried out after 1 day, 2 day, 5 day, 12 day, 30th day and 60th day and corresponding resistance of the coatings were noted. EXAMPLE 4 0.05 M of aniline (4.65 ml) and 0.05 M of o-ethyl aniline (6.05 ml) are taken in a reaction vessel in 1.0 Itr of distilled water and is kept at 0°C. The reaction mixture is stirred and drop wise aqueous solution of oxidant, cupric chloride (0.1 mole, 17.04 gms) is added. The reaction mixture is stirred for 4 hours, till a brownish green precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at 50°C. 30 % acrylic resin stock solution (PRL166, Pidilite, India. Ltd.) is prepared first. The corresponding wt% of individual ingredients have to be taken, premixed and then added to the acrylic solution with the required calculated amount. The ingredients containing 15 % of copolymer 35 % of titanium oxide (anatyse), 20 % of talc, 20 % of silica and 10 % of aluminum state were premixed and added in the acrylic resin solution using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards. The impedance measurements of these coatings were carried out after 1 day, 2 day, 5 day, 12 day, 30th day and 60th day and corresponding resistance of the coatings were noted. Preparation of Acrylic resin coating without containing the copolymer Example-5 An acrylic resin (30 %) (PRL166, Pidilite, India. Ltd.) containing filler materials like titanium oxide (anatyse) 35 %, talc 20 %, silica (20%) and aluminum stearate (10 %) was prepared using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards Table 5). The impedance measurements of these coatings were carried out after 1 day, 2 day, 5 day, 12 day, 25th day and 60th day and corresponding resistance of the coatings were given in Table 6. Table 5: Properties of the paint/ paint film Table 6: Impedance behaviour of Top coated (Blank) sample in 3 % NaCI (Table Removed) Advantages: The main advantage of carrying the above studies was to see how the conducting polymer polyaniline and its copolymer synthesized without using acidic medium affects the corrosion inhibition behavior of iron & mild steel in saline water conditions. Usually, polyaniline is synthesized in the presence of inorganic acid or organic acid medium by oxidant like ammonium persulphate, potassium persulphate, FeCl3, etc. However, in the present case, aniline and the copolymers of aniline are synthesized using cupric fluoroborate and copper phosphate in distilled water without the use of any inorganic or organic acid. And when these pigments are used in the conventional acrylic resins, then a better corrosion inhibition response was obtained. WE CLAIM: 1. A process for the preparation of conducting polymer coating composition useful for corrosion protection of iron and mild steel comprising of: (a) a conducting copolymer of aniline and substituted aniline in the range of 1-30 weight% (b) resin in the range of 10-30 weight %, and (c) filler materials in the range of 10 -35 % .wherein said process comprising the steps: a. mixing of aniline and substituted aniline monomers in the ratio in range between 1.0 : 1.0 to 0.01 at temperature ranging between 0°C 5°C; b. adding an oxidant slowly drop by drop to the reaction mixture as obtained in step (a) at a temperature in the range of-5 to 5°C; c. stirring the reaction mixture as obtained in step (b) for a period in a range of 4-6 hours at temperature ranging between 0°C to 5°C; d. filtering the reaction mixture as obtained in step (c) to obtain a precipitate of copolymer; e. washing the precipitate of copolymer as obtained in step (d) with water till the colour of the filtrate is colourless; f. drying the copolymer as obtained in step (e) at a temperature in a range of 50-60°C under vacuum; g. mixing the copolymer as obtained in step (f) with resin and filler materials for 30 to 60 minutes to obtain the conducting polymer coating composition. 2. A process as claimed in claim 1, wherein the substituted aniline used in step (a) is selected from the group consisting of sec. butyl aniline, o-phenetidine, ethyl aniline and o-toluidine. 3. A process as claimed in claim 1, wherein acrylic resin used in step (g) is PRL166. 4. A process as claimed in claim 1, wherein the filler materials used in step (g) are selected from the group consisting of titanium oxide (anatyse), talc, silica and aluminum stearate. 5. A process as claimed in claim 1, wherein the oxidant used in step (b) is selected from the group consisting of cupric fluoroborate, cupric phosphate, cupric sulphate, cupric chloride. 6. A process as claimed in claim 1 of step (b), wherein the mol ratio of (aniline and substituted aniline) and oxidant ranges from 1.0:1.0 mole to 0.01. 7. A process as claimed in claim 1, wherein polymerization of aniline and substituted aniline occurs free from acidic conditions. 8. A process as claimed in claim 1, wherein coating composition is applied to pretreated iron based surface for the corrosion protection against hostile environment like saline water comprising NaCI, MgCl2, BaCl2. 9. A process as claimed in claims 1, wherein the pretreatment of iron based surface by conventional known means is done such as buffing, chemical cleaning. 10. A process for the preparation of conducting polymer coating composition substantially as herein described with reference to the examples and drawing accompanying this specification

Full Text

FIELD OF INVENTION
The present invention relates to the a process for the preparation of conducting polymer coating composition for the corrosion protection of iron based surfaces. More particularly the invention relates to a copolymer of aniline and substituted aniline synthesized in the absence of acidic environment and a process for the preparation of the said copolymer and subsequent paint formulations for the corrosion protection of iron.
BACKGROUND OF INVENTION
The corrosion of iron and mild steel is an enormous problem throughout the world. Giving an anticorrosion treatment to articles of iron and materials containing iron is considered essential for durability of the articles due to hostile environmental parameters of humidity, salinity of water etc. Many kinds of treatment, paints and coatings have been developed over the years to address this problem. For a coating to protect iron against corrosion, it should restrict access of water, oxygen and other oxidants to the iron surface. In some instances, corrosion inhibitors such as zinc coatings or organic amines are used. Recently much interest has been shown in the use of conductive polymers in corrosion protection of articles made from iron or mild steel. These articles maybe such as huge ships used for marine transport.
Reference may be made to "Corrosion-Protective Coatings from Electrically Conductive Polymers", Proceedings from Technology 2001, San Jose, California, wherein Thompson et al disclose conductive polymer coatings for the protection of iron surfaces from corrosion. These coatings involved electrically conducting forms of several polymers, including polyaniline which had been appropriately doped with additives serving as electron acceptors to increase conductivity of the polymer. These polymers were used by applying undoped chemically prepared polymers to the steel surface and subsequent doping of the coated surface to the conductive state. Doped polyaniline was converted to a non-conducting
emeraldine base which was dissolved in an organic solvent such as, N-methyl-pyrrolidinone (NMP) and coated on steel after which the coating was doped to the conducting state. The dopants used were tosylate ions, zinc nitrate and tetracyanoethylene. After doping, a top coat of standard fully cured epoxy was applied to provide abrasion resistance. In this disclosure the coating of the polymer dissolved in NMP is affected for curing by heating to a temperature of at least 95°C. The use of high temperature with NMP as the solvent is highly undesirable as during high temperature treatment, the NMP releases toxic gases. This work reported a corrosion barrier coating for steel made from an electrically conducting polymer which resists the transfer of electrons from iron to the oxidizing environment. The coating was said to have two layers: an undercoat of polyaniline on steel surface and an epoxy top coat for durability. The bilayer coating was reported to be more effective in resisting corrosion than a coating with epoxy alone.
Reference may be made to US Patent 5441772, wherein a method of protecting carbon steel substrates from corrosion environments is provided by a coating of emeraldine base which has been chemically prepared and cast onto the substrate from NMP solution. The coating also includes other polymers such as polyimides, epoxies and urethane linked diisocyanates, among others. This invention also suffers from the disadvantage of the use of NMP which uses high temperature treatment for effecting a protective coating.
Reference may be made to US Patent 5441772, wherein a method of protecting carbon steel substrates from corrosion environments by a coating of emeraldine base which has been chemically prepared and cast onto the substrate from NMP solution is disclosed. The coating also includes other polymers such as polyimides, epoxies and urethane linked diisocyanates, among others. In this patent disclosure, emeraldine base is dissolved in N-methyl pyrrolidinone which is then applied on carbon steel substrates. A temperature of 80-90°C is required to evaporate the NMP solution resulting in toxic NMP vapours. Reference may be made to US Patent 5853621,wherein an anti corrosion paint of the type comprising one or more polymeric binders dispersed in liquid medium
with an effective amount of non-conductive conjugated polymers is disclosed. In this patent disclosure, polyaniline is mixed with a dispersant from Daniel Products in a solvent propylene glycol methyl ether acetate and aromatic naptha 100.
Reference may be made to US Patent 5922466, wherein the development of a composite comprising a metal substrate and a corrosion protecting layer on at least one major surface, a composition comprising a thermoset or thermoplastic polymeric matrix and a conductive filler component comprising polyaniline, and other conducting polymers has been disclosed. In this patent, a composition of thermoplastic or thermoset polymeric matrix along with polyaniline is applied on iron substrate. For thermoplastic coating, a temperature ranging from 100-200°C is required which is the melting point of the polymeric material. This blend is then applied on the iron surface. In this case firstly, the temperature needed is very high and secondly, this type of process is not suitable for industrial applications because the coating can be applied only when it is in the melt stage and once the temperature lowers down, solidification will start leading to the requirement of again raising the temperature to desired level to effect the coating. Reference may be made to US Patent 6015613, wherein a method of forming corrosion inhibition multilayer coatings is disclosed. When the coating is bonded to a substrate, it forms an inter layer between the metal and substrate. The laminates serve to protect the metal surface from corrosion in acid, salt and alkaline corrosive environments. In the said patent disclosure, C1018 steel electrodes are brush coated with a dispersion of polyaniline and poly(butylmethylacrylate) in butyrolactone. The coating coupons are allowed to dry at 60°C in an air convection oven. An epoxy topcoat of Carboline 890 was then applied at 60°C. In this case, only a dispersion of polyaniline in solvent is used which may not spread uniformly on the surface and once the surface is exposed to hostile atmosphere, corrosion rate may be accelerated. Reference may be made to US Patent 6239251, wherein a method of forming low molecular weight oligomers of aniline based compounds are disclosed which are end fictionalized and capable of being reacted with other monomeric species
to form a variety of copolymers. In this patent, aniline is polymerized in the presence of 1,4-phenylenediamine, 1,4-aminodiphenyl amine, n.n'diphenylhydrazine, benzidine and the like. The coating of the above copolymer is prepared by dissolving the copolymer in dimethylformamide (DMF) and then combining with epoxy resin in the form of bisphenol-A-diglycidyl ether. Curing is done at 120°C for 1 hour. The temperature required for curing in the disclosure is 120°C.
OBJECTIVES OF THE INVENTION
The main objective of the present invention is to provide a process for the
preparation of conducting polymer coating composition useful for corrosion
protection of iron and mild steel, which obviates the drawbacks as, mentioned
above.
Another objective of the present invention is to provide a process for the
preparation of conducting polymer coating composition in acid free condition.
Another objective of the present invention is to provide a process for the
preparation of copolymer of aniline and substituted aniline synthesized in the
absence of acidic conditions which can be useful for the prevention of corrosion
of iron and mild steel in hostile saline atmosphere.
Yet another object of the present invention is to provide a single coat of
conducting polymer coating for the anti corrosive coating.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is illustrated in figures 1-2 of the drawing accompanying
this specification:
Figure 1: represents a graph showing impedance plots of paint coated steel in 3
% NaCI after salt spray exposure.
Fig. 2: represents impedance plots of paint with copolymer coated sample in 3
% NaCI.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a process for the preparation of conducting polymer coating composition for the corrosion protection of iron based surfaces. The present invention provides a process for the synthesis of copolymer of aniline and substituted aniline in aqueous medium in the temperature range of 0 to 5°C, and stirring the said mixture, adding an oxidant like cupric fluoroborate slowly drop by drop to the said mixture at a temperature in a range of 0 to 5°C, stirring the reaction mixture for a period in a range of 4-6 hours, filtering the said reaction mixture after the completion of the polymerization, washing thoroughly the said mixture with good quality water, filtering the precipitate and drying the polymer at a temperature in the range of 50-60°C under vacuum.
In an embodiment of the present invention a process for the preparation of conducting polymer coating composition useful for corrosion protection of iron and mild steel comprising of: (a) a conducting copolymer of aniline and substituted aniline in the range of 1-30 weight% (b) resin in the range of 10-30 weight %, and (c) filler materials in the range of 10 -35 % .wherein said process comprising the steps:
a. mixing of aniline and substituted aniline monomers at temperature ranging between 0°C 5°C;
b. adding an oxidant slowly drop by drop to the reaction mixture as obtained in step (a) at a temperature in the range of-5 to 5°C;
c. stirring the reaction mixture as obtained in step (b) for a period in a range of 4-6 hours at temperature ranging between 0°C to 5°C;
d. filtering the reaction mixture as obtained in step (c) to obtain a precipitate of copolymer;
e. washing the precipitate of copolymer as obtained in step (d) with water till the colour of the filtrate is colourless;
f. drying the copolymer as obtained in step (e) at a temperature in a range of 50-60°C under vacuum;
g. mixing the copolymer as obtained in step (f) with resin and filler materials for 30 to 60 minutes to obtain the conducting polymer coating composition.
In another embodiment of the present invention the substituted aniline used in
step (a) is selected from the group consisting of sec. butyl aniline, o-phenetidine,
ethyl aniline and o-toluidine.
In another embodiment of the present invention acrylic resin used in step (g) is
PRL166.
In another embodiment of the present invention the filler materials used in step
(g) are selected from the group consisting of titanium oxide (anatyse), talc, silica
and aluminum stearate.
In another embodiment of the present invention the oxidant used in step (b) is
selected from the group consisting of cupric fluoroborate, cupric phosphate,
cupric sulphate, cupric chloride.
In another embodiment of the present invention the ratio of mixture of aniline and
substituted aniline is in the range 1.0 :1.0 to 0.01.
In another embodiment of the present invention the mol ratio of (aniline and
substituted aniline) and oxidant ranges from 1.0: 1.0 mole to 0.01.
In another embodiment of the present invention polymerization of aniline and
substituted aniline occurs free from acidic conditions.
In another embodiment of the present invention coating composition is applied to
pretreated iron based surface for the corrosion protection against hostile
environment like saline water comprising NaCI, MgCl2, BaCl2.
In another embodiment of the present invention the pretreatment of iron based
surface by conventional known means is done such as buffing, chemical
cleaning.
DETAILED DESCRIPTION OF THE INVENTION
The process of preparation of conducting polymer is described herewith. Monomer aniline and monomer o-phenetidine (substituted aniline) are taken in a
glass reaction vessel containing aqueous/methanol solution at 0°C. This reaction mixture is stirred and aqueous solution of the oxidant is added drop wise. The oxidant may be cupric tartarate, cupric tetrafluoroborate, cupric sulphate, cupric chloride, cupric phosphate and the like. More preferably cupric fluoroborate is taken. The reaction mixture is stirred preferably for 4 hours, till a greenish precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with good quality water and preferably distilled water though de-ionized water may also be suitably used, till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at about 55°C. The resultant copolymer was used as a pigment which is mixed with acrylic resin and coated on iron electrode to study its behavior as a corrosion preventive coating in saline water.
Electrochemical impedance measurements were carried out to determine the resistance of the coating after immersion in 3% NaCI.
Organic compounds and polymers inhibit corrosion by absorbing at the metal surfaces. Modes of absorption depend on the chemical structure of the molecule like presence of pi-bonds or available lone pair of electrons, type of metal surfaces, electrochemical potential at the metal solution surface and complexation of molecules with metal ions neutralizing corrodant.
In case of conducting polymer coating, adsorption takes place via functionalized nitrogen atoms of polymer nucleus oriented towards the metal surface and through the delocalized pi-electrons with the aromatic rings parallel to the electrode surface.
The novelty of the present invention is the synthesis of conducting copolymer of aniline with o-phenetidine, o-toluidine, o - ethyl aniline and the like free from acidic conditions. The novelty of the invention lies in eliminating the use of toxic heavy elements like chromium, lead in the coating methods. Both these novelties are realized due to the inventive step of preparation of copolymer of aniline and substituted aniline like o-phenetidine by oxidation.
The following examples are given by way of illustration of the working of the invention in actual practice and should not be construed to limit the scope of the present invention in any way.
Example 1
Preparation of Copolymer
0.05 mole of aniline (4.65 ml) and 0.05 mole of o-phenetidine (6.85 ml) are taken in a reaction vessel containing 1.0 It of distilled water kept at 0°C ±1.0°C. The reaction mixture is stirred and drop wise aqueous solution of 0.1 mole of cupric fluoroborate (23.7 gms) of the oxidant is added in one hour time. The reaction mixture is stirred for 4 hours, till a greenish precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at 55°C with constancy of temperature maintained to within 1° C. The 30 % acrylic stock solution has to be prepared first. The corresponding wt% of individual ingredients have to be taken, premixed and then added to the acrylic stock solution with calculated amount (given in Table 1) using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards as given in Table 2. The formulated paints were tested for the following physical properties as per the ASTM Standards:
a. Density (ASTM D 1475)
b. Viscosity (ASTM D 1200)
c. Volume solids (ASTM D 5201)
d. Fineness of Dispersion (ASTM D 1210) For Painted Panels:
a. Dry film thickness (ASTM D 1400)
b. Impact resistance (ASTM G 14)
c. Adhesion (ASTM D 4541)
d. Flexibility (ASTM D 522)
e. Abrasion Resistance (ASTM D 4060)
The impedance measurements of these coatings were carried out after 1 day, 2 day, 5 day, 12 day, 30th day and 60th day and corresponding resistance of the coatings were noted. Table 1: The ratios of ingredients to be taken for premixing
Table 2: The physical properties of the formulated paint composition
Table 3: Impedance behaviour of Copolymer of aniline & o-ethoxy aniline-NA as Top coated sample in 3 % NaCI
(Table Removed)
Example -2
0.05 M of aniline (4.65 ml) and 0.05 M of sec. butylaniline (7.46 ml) are taken in a reaction vessel in 1.0 Itr of distilled water and is kept at 0°C. The reaction mixture is stirred and drop wise aqueous solution of oxidant, cupric chloride (0.1 mole, 17.04 gms) is added. The reaction mixture is stirred for 4 hours, till a brownish green precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at 50°C. 30 % acrylic resin stock solution (PRL166, Pidilite, India. Ltd.) is prepared first. The corresponding wt% of individual ingredients have to be taken, premixed and then added to the acrylic solution with the required calculated amount. The ingredients containing 15 % of copolymer 35 % of titanium oxide (anatyse), 20 % of talc, 20 % of silica and 10 % of aluminum state were premixed and added in the acrylic resin solution using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards. The impedance measurements of these coatings were carried out after 1 day, 7 day, 14 day, 35th day and 60th day and corresponding resistance of the coatings were noted.
Table 4: Impedance parameters of copolymer incorporated coating on Steel in 3 % NaCI
(Table Removed)
Example -3
0.05 M of aniline (4.65 ml) and 0.05 M of o-toluidine (5.35 ml) are taken in a reaction vessel in 1.0 Itr of distilled water and is kept at 0°C. The reaction mixture is stirred and drop wise aqueous solution of oxidant, cupric chloride (0.1 mole, 17.04 gms) is added. The reaction mixture is stirred for 4 hours, till a brownish green precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at 50°C. 30 % acrylic resin stock solution (PRL166, Pidilite, India. Ltd.) is prepared first. The corresponding wt% of individual ingredients have to be taken, premixed and then added to the acrylic solution with the required calculated amount. The ingredients containing 15 % of copolymer 35 % of titanium oxide (anatyse), 20 % of talc, 20 % of silica and 10 % of aluminum state were premixed and added in the acrylic resin solution using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards. The impedance measurements of these coatings were carried out after 1 day, 2 day, 5 day, 12 day, 30th day and 60th day and corresponding resistance of the coatings were noted.
EXAMPLE 4
0.05 M of aniline (4.65 ml) and 0.05 M of o-ethyl aniline (6.05 ml) are taken in a reaction vessel in 1.0 Itr of distilled water and is kept at 0°C. The reaction mixture is stirred and drop wise aqueous solution of oxidant, cupric chloride (0.1 mole, 17.04 gms) is added. The reaction mixture is stirred for 4 hours, till a brownish green precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The precipitate so obtained is vacuum dried at 50°C. 30 % acrylic resin stock solution (PRL166, Pidilite, India. Ltd.) is prepared first. The corresponding wt% of individual ingredients have to be taken, premixed and then added to the acrylic
solution with the required calculated amount. The ingredients containing 15 % of copolymer 35 % of titanium oxide (anatyse), 20 % of talc, 20 % of silica and 10 % of aluminum state were premixed and added in the acrylic resin solution using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards. The impedance measurements of these coatings were carried out after 1 day, 2 day, 5 day, 12 day, 30th day and 60th day and corresponding resistance of the coatings were noted.
Preparation of Acrylic resin coating without containing the copolymer
Example-5
An acrylic resin (30 %) (PRL166, Pidilite, India. Ltd.) containing filler materials like titanium oxide (anatyse) 35 %, talc 20 %, silica (20%) and aluminum stearate (10 %) was prepared using an attritor for 30 minutes. The formulated paint was characterized for its physical properties such as specific gravity; viscosity, drying time and dry film thickness as per ASTM standards Table 5). The impedance measurements of these coatings were carried out after 1 day, 2 day, 5 day, 12 day, 25th day and 60th day and corresponding resistance of the coatings were given in Table 6.
Table 5: Properties of the paint/ paint film
Table 6: Impedance behaviour of Top coated (Blank) sample in 3 % NaCI
(Table Removed)
Advantages: The main advantage of carrying the above studies was to see how the conducting polymer polyaniline and its copolymer synthesized without using acidic medium affects the corrosion inhibition behavior of iron & mild steel in saline water conditions. Usually, polyaniline is synthesized in the presence of inorganic acid or organic acid medium by oxidant like ammonium persulphate, potassium persulphate, FeCl3, etc. However, in the present case, aniline and the copolymers of aniline are synthesized using cupric fluoroborate and copper phosphate in distilled water without the use of any inorganic or organic acid. And when these pigments are used in the conventional acrylic resins, then a better corrosion inhibition response was obtained.

WE CLAIM:
1. A process for the preparation of conducting polymer coating composition useful for corrosion protection of iron and mild steel comprising of: (a) a conducting copolymer of aniline and substituted aniline in the range of 1-30 weight% (b) resin in the range of 10-30 weight %, and (c) filler materials in the range of 10 -35 % .wherein said process comprising the steps:
a. mixing of aniline and substituted aniline monomers in the ratio in range between 1.0 : 1.0 to 0.01 at temperature ranging between 0°C 5°C;
b. adding an oxidant slowly drop by drop to the reaction mixture as obtained in step (a) at a temperature in the range of-5 to 5°C;
c. stirring the reaction mixture as obtained in step (b) for a period in a range of 4-6 hours at temperature ranging between 0°C to 5°C;
d. filtering the reaction mixture as obtained in step (c) to obtain a precipitate of copolymer;
e. washing the precipitate of copolymer as obtained in step (d) with water till the colour of the filtrate is colourless;
f. drying the copolymer as obtained in step (e) at a temperature in a range of 50-60°C under vacuum;
g. mixing the copolymer as obtained in step (f) with resin and filler materials for 30 to 60 minutes to obtain the conducting polymer coating composition.
2. A process as claimed in claim 1, wherein the substituted aniline used in step (a) is selected from the group consisting of sec. butyl aniline, o-phenetidine, ethyl aniline and o-toluidine.
3. A process as claimed in claim 1, wherein acrylic resin used in step (g) is PRL166.
4. A process as claimed in claim 1, wherein the filler materials used in step (g) are selected from the group consisting of titanium oxide (anatyse), talc, silica and aluminum stearate.
5. A process as claimed in claim 1, wherein the oxidant used in step (b) is selected from the group consisting of cupric fluoroborate, cupric phosphate, cupric sulphate, cupric chloride.
6. A process as claimed in claim 1 of step (b), wherein the mol ratio of (aniline and substituted aniline) and oxidant ranges from 1.0:1.0 mole to 0.01.
7. A process as claimed in claim 1, wherein polymerization of aniline and substituted aniline occurs free from acidic conditions.
8. A process as claimed in claim 1, wherein coating composition is applied to pretreated iron based surface for the corrosion protection against hostile environment like saline water comprising NaCI, MgCl2, BaCl2.
9. A process as claimed in claims 1, wherein the pretreatment of iron based surface by conventional known means is done such as buffing, chemical cleaning.
10. A process for the preparation of conducting polymer coating composition substantially as herein described with reference to the examples and drawing accompanying this specification

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Patent Number

277928

Indian Patent Application Number

537/DEL/2010

PG Journal Number

51/2016

Publication Date

09-Dec-2016

Grant Date

06-Dec-2016

Date of Filing

09-Mar-2010

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	DHAWAN SUNDEEP KUMAR	NATIONAL PHYSICAL LABORATORY, DR. KS KRISHNAN MARG, NEW DELHI-110012
2	SADAGOPAN SATHIYANARAYANAN	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE
3	SULTHAN SYED AZIM	CENTRAL ELECTROCHEMICAL RESEARCH INSTITUTE
4	SAINI PARVEEN	NATIONAL PHYSICAL LABORATORY
5	S RAHDAKRISHNAN	NATIONAL PHYSICAL LABORATORY

PCT International Classification Number

B01D15/36;

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA