Process for the preparation of a formaldehyde-free synthetic tanning agent

A process for the preparation of synthetic organo-polymeric tanning agent used for tanning leather, said process comprising the steps of:

• (a) reacting an aromatic compound with sulfuric acid at a temperature in the range of 40 to 60° C. to obtain a sulfonized aromatic compound;
• (b) adding one or more organic ligands to the sulfonized aromatic compound of step (a) to obtain a mixture;
• (c) heating the mixture at a temperature in the range of 60 to 80° C.;
• (d) adding one or more multi-functional polymers to the mixture of step (c);
• (e) heating the mixture of step (d) at a temperature in the range of 40 to 100° C. to obtain a reaction mixture to form an organo polymeric matrix comprising sulfonized aromatic compound polymerized to the multi-functional polymer or polymers and wherein the organo-polymeric matrix does not comprise formaldehyde;
• (f) adding water to the reaction mixture to obtain a pH of between 3.0 to 3.5;
• (g) optionally, drying the reaction mixture to obtain the synthetic organo-polymeric tanning agent.