Some Guidelines On Fatliquoring

Fatliquoring is the last of the wet processes involved in the manufacture of leather. Working conditions vary from tannery to tannery. Thus to ensure that fatliquors give generally uniform & consistent results under varying conditions we would like to offer a few guidelines on their use. These guidelines could help the Tanner to get the best results out of a given set of fatliquors.

1. The preparation of the fatliquor emulsion which is to be fed into the drum containing the leather plays an important part in determining the manner in which the fatliquor will exhaust and is deposited in the leather. In tanning operations the preparation of emulsion itself is often a neglected operation resulting in variations in fatliquoring which are difficult to interpret. Anionic fatliquors are designed to produce 'Oil in Water' emulsions & not ' Water in Oil' emulsions. In order to produce such emulsions the fatliquor should be added to a minimum of four times its own volume of water at not more than 60o C. If however, water is added to the fatliquor there is a possibility of 'phase inversion' taking place i.e., the formation of ' Water in Oil' emulsion which on subsequent dilution-addition to the drum - may break and cause fat deposition on the surface of the leather. Thus instead of adding fatliquor to only small volumes of water it may be more advisable to add fatliquor directly to the drum in undiluted form. However, when fatliquoring is to done under extreme conditions like picking & tanning, the fatliquor should be diluted prior to its addition to the drum.
   
   
2. Temperatures are also an important factor as many fatliquors contain coupling agents, which are generally volatile and at high temperatures may escape from the system and reduce the stability of the emulsions.
   
   
3. Emulsions stability could also be impaired if prepared emulsions are allowed to stand for a long time before use. They should be used as soon as possible. Use of live steam to heat emulsions should be avoided since local superheating may effect the emulsion stability. If it is necessary water should be heated with steam and then oil added to it.
   
   
4. When a blend of fatliquors is to be used they should be mixed together first & then emulsified. Separate emulsions of individual fatliquors will not give the same fatliquoring effect as would a blend of fatliquors emulsified together.
   
   
5. Care should be taken to balance the ratio of deep penetrating fatliquors to surface lubricating types in a manner so as to achieve the desired lubrication throughout the cross-section of leather.
   
   
6. As far as possible soft water should be used for fatliquoring. For a desired degree of softness one may have to use 10-15% more fatliquor if, instead of soft water, hard water is used.
   
   
7. Overstabilizing the system by using excess of emulsifiers along with the fatliquors can result in poor bath exhaustion & wastage of fatliquors. This should be avoided.
   
   
8. Strict control over the initial pH of the fatliquoring bath & the final pH of the exhaust bath should be maintained so as to achieve uniform fat content & fat distribution in leather and to avoid many fat splitting problems.
   
   
9. For the best results ideal rotational speed of the fatliqioring drum should be around 12-16 R.P.M.