In order to meet the requirements of the ecological leather limited specification and the EU limited quota, we should first check the formaldehyde content of the leather produced now, and take corresponding measures. We must take corresponding measures to make use of formaldehyde as raw material, synthetic additives, retanning agents, aldehyde tanning agents, formaldehyde fixing agents, and some possible residual formaldehyde finishing materials, instead of using environmentally-friendly leather materials, we must use formaldehyde containing chemical materials instead of environmentally-friendly materials, and add formaldehyde cleaning agent (ammonium salt) to deal with them.

The intermediates of formaldehyde react with ammonia are unstable. The first step is addition reaction, then dehydration. The final trimer produces Sanya amino aldehyde, dissolves in water, and removes formaldehyde by washing.

The above shows that the elimination of free formaldehyde in leather can be treated by adding ammonium or ammonia water in the following processes according to the actual situation.

A and filling retanning period add 0.6%-1% or so ammonium salt; B and neutralization neutralizer can add ammonium salt 1% +; C, dyeing process before adding dye, add ammonia water, can adjust the pH value of dye solution, and eliminate free formaldehyde.