Process for retanning leather with acrylic-based oligomers

摘要

The invention relates to oligomers containing structural units of the formulae ##STR1## wherein X.sub.1 is --CN, --COOR.sub.1, --OOCR. sub.2 or - -CONHR.sub.3, Y.sub.1 is --COOH or --COOM.sub.2, Y.sub.2 is -- CONH.sub.2, --CH.sub.2 OH, --OCH.sub.3 or --OC.sub.2 H.sub.5, each of Z. sub.1, Z.sub. 2 and Z.sub.3 is hydrogen, methyl or ethyl, each of M.sub.1 and M.sub.2 is an amine cation, an ammonium cation or an alkali metal cation, and each of R.sub.1, R.sub.2 and R.sub.3 is C.sub.1 -C.sub.8 alkyl, C.sub.1 - C.sub.8 -hydroxyalkyl or alkoxyalkyl containing altogether at most 8 carbon atoms, fatliquoring the treated leather and drying it, and, if appropriate, additionally dyeing said treated leather before or after it has been fatliquored.PPThese oligomers are suitable for use as tanning agents in a process for retanning chrome- tanned leather. The oligomers are prepared by copolymerizing comonomers of the acrylic acid series corresponding to the structural units of the indicated formulae, in the presence of sulfite or hydrogen sulfites of the formulae SO.sub.3 (M).sub.2 or HSO.sub.3 M, and have an average molecular weight of at most 14,000.