Ethylene backbone polymers in combination with ester polymers having long alkyl side chains are low viscosity distillate fuel cold flow improvers

Claim 1

A light middle distillate fuel oil having a viscosity in the range of about 1.6 to 7.5 centistokes at 100°F boiling in the range of 250° to 750°F, which has been improved in its low temperature flow properties by about 0.002 to 0.5 wt. % based on the weight of the total composition, of a synergistic flow improving mixture of 0.5 to 10 parts by weight of an oil soluble ethylene backbone middle distillate pour point depressing polymer having a molecular weight in the range of about 500 to 50,000 per part by weight of an oil soluble long side chain ester-containing polymer operable as a residua flow improver and having a molecular weight in the range of about 1000 to 100,000, wherein said ethylene backbone pour point depressant is selected from the group of polymers consisting of: 1. chlorinated polyethylene containing about 10 to 30 wt. % chlorine, 2. copolymers consisting essentially of 3 to 40 molar proportions of ethylene with a molar proportion of C 3 to C 16 alpha monoolefin, and 3. copolymers consisting essentially of 3 to 40 molar proportions of ethylene with a molar proportion of an ethylenically unsaturated alkyl ester of the formula: ##EQU5## wherein R 1 is hydrogen or methyl, R 2 is a --OOCR 4 or --COOR 4 group wherein R 4 is hydrogen or a C 1 to C 16 alkyl group, and R 3 is hydrogen or --COOR 4 ; wherein said long side chain ester containing polymer is characterized by at least 25 wt. % of the polymer being straight chain C 18 -C 44 alkyl groups extending from ester linkages, said long chain ester polymer being selected from the group consisting of: A. polyester condensation product of 0.8 to 1.6 molar proportions of an alkenyl or alkyl succinic anhydride or its corresponding acid containing a linear hydrocarbon group of 16 to 44 carbon atoms with 0.8 to 1.2 molar proportions of a polyol containing 2 to 6 hydroxy groups and a total of 2 to 12 carbon atoms, and 0.7 to 2.2 molar proportions of a C 20 to C 44 saturated aliphatic monocarboxylic acid; B. addition polymers comprising moieties of long side chain unsaturated esters represented by the formula: ##EQU6## wherein R 1 is hydrogen or a C 1 to C 5 alkyl group, R 2 is a --OOCR 4 or --COOR 4 group wherein R 4 is a C 20 to C 44 straight chain alkyl group, and R 3 is hydrogen or --COOR 4 ; and C. polymers of about equi-molar proportion of C 18 to C 46 mono alpha aliphatic olefin with an unsaturated C 4 to C 10 dicarboxylic acid or anhydride and esterified with about 0.5 to 1.0 molar proportion of C 20 to C 40 linear, saturated, alcohol; said synergistic flow improving mixtures being polymer combinations of: (1) and (B); (2) and (A); (3) and (A); and (3) and (C).