What is retannage?
Before the tanned leather is finished, it is first retanned, dyed and fatliquored. It may also be extended in a special operation to make the tough old cow hide into a soft and supple material.
Syntans – synthetic organic compounds – were originally developed as a substitute for vegetable tanning materials, which were sometimes in short supply. Today, syntan retannage is no longer the "poor relation" of the retanning methods, and syntans form an independent product group.
The term "syntan" covers a wide range of products with different chemical and technical properties that are used either alone or in combination with vegetable tanning materials as tanning materials, retanning materials and auxiliaries. Synthetic tanning materials give leather that has good fastness properties and is economical to produce, too.
Red, blue, yellow….. leather can be dyed in all conceivable colors and shades. LANXESS offers leather manufacturers a wide range of anionic powder and liquid dyestuffs and cationic liquid dyestuffs. Drum dyeing is one of the most important dyeing processes. It can be carried out, for example, in milling drums, automatic dyeing units with Y-shaped drums or in mixers. To obtain the desired results, the drum load, speed, drumming time and float temperature have to be adapted to suit the particular properties of the leather.
Finally, the leather is treated with fatliquoring agents to make it softer and more supple. The fatliquoring method used depends on the type of leather and the preceding tannage.
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