A good degreasing system for sheep and lamb skins is one of the major points for producing a quality garment article. Some raw pelts, which are currently pickled in the country of origin, can contain up to 50% of natural fats. This natural fat has to be dispersed and removed as much as possible. However, traditional white spirit solvent degreasing is not an eco-friendly system. It should be replaced for environmental and performance reasons.
TFL has developed a new aqueous degreasing system, which uses BORRON® SE, as a degreaser and emulsifier and SELLATAN® PFD liq., as pretanning agent.
When compared to other degreasing processes, the following advantages can be noticed:
- practically complete degreasing/dispersion of natural fats
- shrinkage temperatures can be significantly higher than 70°C
- washing at 45°C
- very white pretanned skin
- high safety and consistency in use
- good dyeability
which implies a better quality of the garment article is achieved.
This new degreasing system avoids the following disadvantages of other systems:
- fixation of fat stains
- yellowing due to oxidation of excess fat left in the skin
- shrinking effect
- yellow colour with other pretanning systems involving for example glutaraldehyde
- low shrinkage temperature with mono-aldehydes
- reversible pretanning with for example aluminium-based systems.
The measurement of the fat content in skins is typically made by Soxhlet extraction. The result is a fat content value in %, which does not give any indication of the natural fat distribution in the skin. One of the major claims against the use of white spirit is the poor dispersing effect, which often results in an incomplete removal of the fat, e.g. from the firmer parts, along the back bone. When the tanner sees the result of the poor natural fat dispersion it is too late and the final article needs to be re-worked.
To show the excellent degreasing and dispersing effect of BORRON® SE, a special pink dye (Red Sudan IV) which fixes only to the fat, was added before washing:
