Use of alkanolamine ester(s) of boric acid - in deliming in leather prodn. reducing evolution of hydrogen sulphide

摘要

Boric acid alkanolamine esters of formula B(OR)3 are used for deliming in leather prodn. R = H or gp. of formula (alkylene-O)n-(C(R1)H)m-NR2R3, or 2 R gps. together form gp. of formula (alkylene1)2 N-R3, or 3 R gps. together form gp. of formula -(alkylene1)3-N and at least 1 R is not H; alkylene is 2-6C; alkylene1 is 2-3C; R1 = H, Me or Et; R2 = H, 1-4C alkyl or Ph; R3 = H or 1-4C alkyl; n = 0-6; m = 2-10. ADVANTAGE - Evolution of H2S during deliming is limited. In an example, (A) a mixt. of 149g of tiethanolamine and 62g of orthoboric acid was heated at 80-83 deg. C, with removal of water at 25 mbars. The yield of triester was almost quantitative. (B) 100 pts. of steeped, delimed oxhide was soaked in a 50% bath contg 2% of the ester from (A), at 30 deg. C. After 30 mins., the pH was 8.9 and the H2S concn. was 140 ppm. After a further 60 mins., the hide was delimed, the H2S concn. was O and the pH was 9.2. The hides were clean and bright. Further treatment gave a soft, evenly dyed leather with very fine grain.