FORM 2 THE PATENTS ACT, 1970 (39 of 1970) As amended by the Patents (Amendment) Act, 2005 The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2005 COMPLETE SPECIFICATION (See section 10 and rule 13) TITLE OF THE INVENTION Biodegradable, non-carcinogenic, vegetable oil pour point depressants and processes for the preparation thereof. APPLICANTS Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company. INVENTOR Chaudhari Sushil Ekanath of Crompton Greaves Ltd, Conition Monitoring & Diagnostic Centre, CG Global R&D Centre, Kanjur (E), Mumbai 400042, Maharashtra, India, an Indian National. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the nature of this invention and the manner in which it is to be performed: TECHNICAL FIELD OF THE INVENTION This invention relates to biodegradable, non-carcinogenic, vegetable oil pour point depressants, dialkyl ester of poly-(alkyl recinoleate -co-maleic anhydride) of formula (I): -CH ■CH- CH2 to C22 straight chain aliphatic alkyl group; and represents the number of repeating units. having pour point depressant activity in vegetable oil; the process comprising: a) esterifying ricinoleic acid with C10 to C22 aliphatic alcohol in the molar ratio of 1.5:1 in the presence of an organic solvent and sulphuric acid catalyst at 110°C to 140°C under azeotropic conditions to obtain an alkyl ester of ricinoleic acid; b) co-polymerizing the alkyl ester of ricinoleic acid with a double re-crystallized maleic anhydride in the 1:1 molar ratio under inert atmosphere and in the presence an organic solvent and a free radical initiator like benzoyl peroxide or azobisisobutyronitrile (AIBN) at 50°C to 75°C to obtain a poly-(alkyl recinoleate -co-maleic anhydride) co-polymer; and c) diesterifying the co-polymer with Q0 to C22 aliphatic alcohol in the molar ratio of 1:2 at 110° C to 140° C in the presence of an organic solvent and an acid catalyst like para-toluene sulfonic acid or sulphuric acid or combination thereof. 9. The process as claimed in claim 8 wherein the C10 to C22 aliphatic alcohol used is selected from behenyl alcohol, decyl alcohol, dodecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol and benyl alcohol. 10.The process as claimed in claim 8 wherein, the organic solvent is selected from toluene, benzene or xylene. 11 .A vegetable oil comprising dialkyl ester of poly-(alkyl recinoleate -co-maleic anhydride) having general formula (I) : Formula (I) wherein R' and R" represents C,0 to Cu straight chain aliphatic alky! group; and n represents the number of repeating units. having pour point depressant activity in vegetable oil.