Title of Invention	"A PROCESS FOR THE PREPARATION OF PLOYANILINE SALT"
Abstract	The process for preparing polyaniline salt comprises in adding aniline in water hydrochloric acid in water. Ammonium persulphate is added to such a solution and the reaction is carried out at a first temperature of 5 to 10°C followed by a second temperature being the room temperature.

Full Text

The present invention relates to a process for the preparation of polyaniline salt/ more particularly to acidic polyaniline salt even more particularly to polyaniline hydrochloride and product thereof. The acidic polyaniline salt/ more particularly polyaniline hydrochloride is used as conducting polymer in the paints and coatings. The acidic polyanile salt also find application as the precursor for synthesis of emiridine base and doped conducting polymers/ more particularly conducting polymers doped with complex ions of transition metals. The acidic polyaniline salt/ more particularly polyaniline hydrochloriide salt is generally prepared by the process/ wherein the benzadine is formed as by product. A disadvantage of such a process is that benzadine thus formed is toxic in nature. Yet another disadvantage of such a process for preparation of polyaniline hydrochloride is that/ the reaction is performed at very low temperature/ viz. 0CC or lower/ which in turn is difficult to be controlled. A further disadvantagee is that by product/ such as low molecular weight polymers/ more particularly oligomers are also formed during the synthesis of main compound. Still another drawback of the known process for preparation of polyaniline hydrochloride is that such known processes comprises of removal of impurities, like by product, as stated herein above, by treatment with organic solvents and aqueous medium. This multistep treatment calls for drying of the final product under vacuum as additional step. Therefore, the existing method of preparation of polyaniline hydrochloride suffers from disadvantages and drawbacks as stated herein above and in addition from the disadvantages, viz. the process is time consuming, uneconomicaal, the by-product formed is toxic, and yield and purity of the final product is not good for industrial application. An object of this invention is to propose a process for preparation of polyaniline hydrochloride, which inturn results in higher yield of the final product preferably 90% or more. Another object of this invention is to propose a process for preparation of polyaniline hydrochloride which avoids the formation of by products, like toxic benzadine and low molecular weight polymers, viz. oligomers. Still another object of this invention is to propose a process for preparation of polyaniline hydrochloride and where the reaction is carried out above 0°C, which is relatively much easier to control and makes the process more convenient as compared to known such process, as described hereinabove. Yet another object of this invention is to propose a process for preparation of poly aniline hydrochloride, which avoids the additional step of treatment of reaction product with organic solvents for removal of by products and subsequently drying under vacuum, hence making the whole process a convenient and time saving process. A still further object of the present invention is to propose a process for preparation of polyaniline hydrochloride, wherein the final product can be oven dried or air dried and the whole process is completed in the same reaction vessel, and the final product is yielded in high purity. According to this invention there is provided a process for preparation of polyaniline salt, such as polyaniline hydrochloride, characterized in adding aniline to water followed by addition of hydrochloric acid in water and in the ratio of 0.7 mole to 1.0 mole, and subsequently adding ammonium persulphate to said solution, the ratio of aniline to ammonium persulphate being varied between 0.9 mole to 1.4 mole, the reaction being carried out at temperature more than 0°C and preferably between 5 to 10°C to get the desired product, and subsequently at room temperature, the precipitated product obtained from said reaction being washed and then dried. The method of preparation of polyaniline hydrochloride according to the present invention, and comprising of reactants in ratios described hereinabove has definite advantage over the known process of prior art, that no by product, like toxic benzadine and oligomers are formed even in traces, hence, making the process non-toxic, and the proposed process is characterized by its ease of operation and purity of the resulted product in addition to its higher yield. Accordingly, the process comprises of first mixing 0.9 to 1.1 mole of aniline with about 1 litre of water followed by addition of hydrochloric acid between 1.1-1.4 moles taken in 100-150 ml of water. The temperature of this reaction solution is controlled to 5°C by addition of ice cubes. To this solution 0.8 to 1.05 mole of ammonium persulphate again taken in 400-500 ml of water is added gradually with constant stirring. On complete addition of ammonium persulphate the temperature of reacting solution is maintained between 5-10 C for about two hours and then at room temperature for about 2.5 to 5.0 hours, preferably between 3-4 hours with constant stirring. The green coloured product thus formed is filtered through a buchner funnel using either a filter paper or polypropylen filter cloth and washed repeatedly with water. The resulted product is pure polyaniline hydrochloride with no by products as described herein above. The invention is illustrated but not limited by the following examples: EXAMPLE 1 One litre of aniline was added to 26 litre of distilled water in a bucket fitted with a stirrer and thermometer. To this 1.2 litre of hydrochloric acid was added with gradual addition of ice cubes to bring down the temperature to 5 degree celsius. On attaining the temperature of 5 degree celsius, 2.0 kg of ammonium persulphate was added gradually with constant stirring. The temperature of this reacting solution was maintained 5-10 degree celsius for two hours. The reaction is allowed to continue for further 3.5 hours at room temperature. The green coloured product was filtered through buchner funnel using polypropylene filter cloth. The synthesised polyaniline hydrochloride was washed with 1.5 litre of water until the pH of the filterate was 5.0. The air dried polyaniline hydrochloride having electrical conductivity of 8.0 s/cm, weighed 1.1 kg. The percentage yield was 91%. EXAMPLE 2 3.0 litres of aniline, 3.6 litres of HC1, and 6.0 Kg of ammonium persulate were reacted in a bucket according to example 1. The total amount of water used was 70 litres. The quantitative yield of polyaniline hydrochloride was 3.26 kg and percentage yield was 90%. EXAMPLE 3 100 ml of aniline, 125 ml of HC1, 200 g of ammonium persulphate were reacted in one litre flask according to example 1. The quantitive yield of synthesised polyaniline hydrochloride was 107 gm and percentage yield was 93%. The foregoing examples have illustrated that the proposed process is also suitable for industrial applications with good percentage yield and making the process highly economical and time saving. We Claims; 1. A process for preparation of polyaniline salt, such as polyaniline hydrochloride, characterized in adding aniline to water followed by addition of hydrochloric acid in water and in the ratio of 0.7 mole to 1.0 mole, and subsequently adding ammonium persulphate to said solution, the ratio of aniline to ammonium persulphate being varied between 0.9 mole to 1.4 mole, the reaction being carried out at temperature more than 0°C and preferably between 5 to 10°C to get the desired product, and subsequently at room temperature, the precipitated product obtained from said reaction being washed and then dried. 2. A process as claimed in claim 1, wherein the temperature of reaction of aniline and hydrochloric acid is maintained at 5°C, and that of reaction of ammonium persulphate with said reaction mixture is between 5-10°C. 3. A process as claimed in claim 1, wherein the said reaction is carried out for 2 hours at temperature between 5-10°C after additions of hydrochloric acid and ammonium persulphate and subsequently for 3-4 hours at room temperature. 4. A process as claimed in claim 1, wherein the precipitated product washed with water only, and dried either at 60-70°C in oven or air dried. 5. A process for preparation of polyaniline salt such as polyaniline hydrochloride substantially as herein described and illustrated in the examples.

Documents:

344-del-1996-abstract.pdf

344-del-1996-claims.pdf

344-del-1996-complete specification (granted).pdf

344-del-1996-correspondence-others.pdf

344-del-1996-correspondence-po.pdf

344-del-1996-description (complete).pdf

344-del-1996-form-1.pdf

344-del-1996-form-2.pdf

344-del-1996-form-3.pdf

344-del-1996-form-9.pdf

344-del-1996-gpa.pdf