Nitrogenous copolymers, their preparation and use as additives for improving the pour properties of hydrocarbon middle distillates

A copolymer of average number molecular weight of about 400 to 50,000 comprising:

• (a) 5-60% by mole of recurrent units (A) deriving from alpha olefins of 2-36 carbon atoms complying with the general formula:
• ##STR15## wherein R.sup.1 is a hydrogen atom or a lower alkyl group of 1-4 carbon atoms and R.sup.2 is a hydrogen atom or an alkyl group of 1-30 carbon atoms,
• (b) 10-70% by mole of recurrent units (B) deriving from unsaturated dicarboxylic compounds complying with one of the general formulas:
• ##STR16## wherein R.sup.3 is a hydrogen atom or a lower alkyl group of 1-4 carbon atoms, X is an oxygen atom or an .dbd.N--R.sup.4 group in which R.sup.4 is a monovalent organic radical deriving from a compound containing a primary amine group complying with one of the general formulas:
• ##STR17## wherein R is a monovalent aliphatic radical of 1-30 carbon atoms, Z is selected from the oxygen atom --O-- and --NR.sup.15 -- groups wherein R.sup.15 is a hydrogen atom or a monovalent aliphatic radical of 1-30 carbon atoms, n is an integer from 2 to 4, m is an integer from 1 to 4 or may be zero when Z is --NH--, R.sup.14 is a divalent aliphatic radical of 2-30 carbon atoms, each of G and L, identical or different, is an --OH, --OR.sup.1 or --NHR.sup.4 group, in which R.sup.1 and R.sup.4 are defined as precedingly, and each of R.sup.5 and R.sup.6, identical or different, is a hydrogen atom or a lower alkyl group of 1-4 carbon atoms, at least one of them being a hydrogen atom,
• (c) 10-70% by mole of recurrent units (C) deriving from unsaturated esters of 1,2-diols, complying with the general formula:
• ##STR18## wherein each of R.sup.7 and R.sup.10, identical or different, is hydrogen atom or a lower alkyl group of 1-4 carbon atoms, R.sup.8 is a divalent aliphatic radical of 1-30 carbon atoms, q is zero or 1, R.sup.9 is a monovalent aliphatic radical of 2-30 carbon atoms, and R.sup.11 is a hydrogen atom, a lower alkyl group of 1-4 carbon atoms or a lower acyl radical of 1-4 carbon atoms, and
• (d) 0-60% by mole of recurrent units (D) deriving from acrylic compounds complying with the general formula:
• ##STR19## wherein R.sup.12 is a hydrogen atom or a lower alkyl radical of 1-4 carbon atoms, Y is a --OH, --NHR.sup.4 or --OR.sup.13 wherein R.sup.4 is defined as above and R.sup.13 is an alkyl radical of 1-30 carbon atoms, at least one of the recurrent units (A), (B), (C) and/or (D) of said copolymer containing at least 12 carbon atoms, and at least 10% of the recurrent units of said copolymer being recurrent units (B) of imide type, conforming with the above general formulas wherein X is an .dbd.N--R.sup.4 group.