How to choose retanning agent for napa cattle upper leather according to product requirements?

The properties and styles of various products are largely determined by retanning.  Therefore, what products are processed is the main basis for selecting retanning agents.  What principles should be followed in the selection of retanning agent for napa leather?  

1, Performance requirements of cattle napa upper leather.  

Softness is an important index of cattle napa upper leather, in addition to the requirement of tight grain, flat and fine, plump and elastic, like general upper leather.  

2. Selection of retanning agent.  

(1) In order to balance softness and firmness of grain, a large dose of chromium powder may be used for retanning before neutralization, in combination with more chrome-containing syntanning agents and aldehyde tanning agents, or polymer retanning agents may be used for retanning with chromium before neutralization to tighten grain to the maximum extent before neutralization.  

(2) Widely used in the neutralization process neutralizing and synthetic tanning agent with organic carboxylic acid salt, do both with a deep (and slightly long), and not with too intense, neutral pH value control in 4.5 or so, also can at the same time of adding neutralizing agent, adding 2% to 4% of acrylic polymer tanning agent, do both tightening grain, and does not cause feel stiff.  

(3) After neutralization, the filling should not be too heavy, and the proportion of resin tanning agent and synthetic tanning agent should be appropriately increased, and tannin extracts should be used less, especially those with strong convergence should be avoided.  

(4) Sometimes some waterproof fat-adding agent or some polymer softener with both tanning function and refueling function can be used to replace part of tannin extract and amino resin and other strong filling materials, can receive double effect that we get compacted grain surface, plump and elastic, and feel soft, grain surface meticulous.