| abstract |
Sand or rock masses containing mineral oil are deoiled with a deoiling agent containing an aqueous solution of a water-soluble copolymer which is a random distribution of 5 to 60% of weight of units of the formula ##STR1## 2 to 40% by weight of units of the formula ##STR2## 38 to 93% by weight of units of the formula ##STR3## and partial hydrolysates thereof, wherein when R 1 is hydrogen, R 2 is hydrogen, methyl or ethyl, Y is --CO--NH--C(CH 3 ) 2 --CH 2 -- or a direct bond, and X.sup.⊕ is a cation; when R 1 and R 2 are identical or different, each is hydrogen, methyl, ethyl or, together are trimethylene, Y is --CO--NH--C(CH 3 ) 2 --CH 2 -- and X.sup.⊕ is a cation. |