Solid, particulate tanning agent preparations

A pre-mix tanning material for producing a tanning agent product, the tanning material comprising a mixture of:

• a) 10 to 99 wt% of at least one compound containing carbamoylsulphonate groups, wherein the at least one compound comprises reaction products formed from a reaction between organic polyisocyanates and bisulphite or disulphite, and the organic polyisocyanate is a polyisocyanate having an NCO functionality of 1.8 to 2.5 and a molecular weight is less than 400 g/mol;
• and
• b) 1 to 90 wt% of at least one organic tanning agent selected from the group consisting of syntans, resin tanning agents, polymeric retanning agents, and vegetable tanning agents,
• wherein the pre-mix tanning material is a spray-dried, solid, particulate material.