Surface-active polymer and its use in a water-in-oil emulsion

#The present invention relates to a surface-active polymer with an excellent ability to stabilise a water-in-oil macroemulsion. The polymer contains a large hydrocarbon group linked via two ester bonds to two hydrophilic alkyleneoxy chains with a molecular weight of from 500 to 1,200 that are each monoetherified with an alkyl group containing 1-3 carbon atoms. The macroemulsion, hereinafter referred to as emulsion, can be used for instance in cosmetics, dry cleaning preparations, metal working compositions, and fuels for internal combustion engines and for heating.

#There is a general desire to be able to prepare a water-in-oil emulsion which is stable for a long period of time. Such an emulsion can be used for example in cosmetic formulations, in dry cleaning preparations, and in metal working compositions. It is also desired to use water-in-oil emulsions as fuels in order to limit the pollution resulting from the combustion of oil. It is well-known that the combustion of oil causes the formation of essential amounts of carbon monoxide, nitrogen oxides, uncombusted parts of the oil, and soot. The addition of a suitable amount of water will reduce this pollution without reducing the combustion yield. The general disadvantage of the existing water-in-oil fuels is that their stability is unsatisfactory and can cause operational disturbances.

#The prior art contains a large number of suggestions of how to improve the stability and the homogeneity of water-in-oil emulsions. Some of the art advocates adding a derivative of a polyisobutylene succinic acid (PIBSA) or its anhydride (a PIBSA derivative) as a stabilising and emulsifying agent. For instance, WO 01/51593 describes a water-in-oil emulsion which contains a PIBSA derivative, where said derivative, with one long-chain alkyl via an ester or ether bond, is obtainable by reacting a polyisobutylene succinic anhydride with a polyethylene glycol compound. Further, WO 02/094889 discloses emulsifiers which comprise a half-ester of PIBSA, where the ester group contains at least one group selected from OH, NH2 and/or NH3+. DE 10321734 also describes a half-ester of PIBSA, but here the ester group is obtained by reacting PIBSA, its anhydride or acid chloride, with a polyglycol mono-(low alkyl)ether. In EP 1491561 an ester compound is also disclosed, which ester is obtained by esterifying a PIBSA compound with a polyol, such as penta(ethylene glycol), pentaerythritol or glycerol.

#A succinic diester polymer of formula I was produced in the following manner. Polyisobutylene (number average molecular weight of about 910) in an amount of 100 g, maleic anhydride in an amount of 98 g, and xylene in an amount of 20 g were introduced into a reactor. After replacement of the air in the reactor with nitrogen, the temperature was raised to 195° C. and kept there for 24 hours. After removal of maleic anhydride by filtration at 20° C., the yield of polyisobutylene succinic anhydride was determined by anhydride titration to be above 60%, calculated on the conversion of polyisobutylene. The polyisobutylene succinic anhydride obtained from the above reaction was then added to another vessel in an amount of 549 g and further reacted with 494 g of a monomethyl ether of a polyethylene glycol having a molecular weight of about 750, in the presence of 3 g of xylene. The reaction was performed at 220° C. for 8 hours under continuous removal of the water formed during the reaction. Thereupon the temperature was raised to 240° C. and the azeotrope of xylene and water was distilled off at 20 mbar. After cooling to about 100° C. the reaction mixture was filtered under pressure. The reaction mixture obtained contained a succinic polymer of formula I, wherein L represents a polyisobutylenyl group of a number average molecular weight of about 910, R1 and R2 are methyl groups, and A1 and A2 are poly(ethyleneoxy) chains with an average molecular weight of about 750. The HLB value was 12.4. This succinic diester polymer is hereinafter referred to as Succinic Polymer I.

#In a similar manner the following succinic diester polymers according to the invention were produced.

#Succinic Polymer II. This is a succinic diester polymer in accordance with formula I wherein L represents a polyisobutylenyl group with a number average molecular weight of about 910, R1 and R2 are methyl groups, and A1 and A2 are poly(ethyleneoxy) chains with an average molecular weight of about 1,200. The diester has a HLB value of 14.4.