The demand for chrome- and metal free leathers is increasing.
Vegetable tanneries are more and more asked to make fashionable leathers with the properties similar to those of chrome leather. The trend is to produce smooth and tight-grained leathers with a very soft handle. If possible the leathers must be milled. This means that the classic, stiff vegetable leather is less in demand. The demand is also for articleds dyed in brilliant shades with a good fixation. To be able to meet these demands the process needs to be controlled right from the pickle stage. The first part of the process is a pretannage.
Pretannage
The pretannage is done with a glutardialdehyde and a combination of SYNTAN SA and SYNTAN WT. The amount of glutardialdhyde is the main parameter for setting the softness. The amounts used can vary from 0.8% to 2.4%. Working without aldhydes is possible but it gives a tenser and rougher-feeling grain.
SYNTAN SA and SYNTAN WT have the following advantages when used during pretannage:
neck wrinkles become less visible
neck wrinkles are smoothened
dyeings are more uniform.
Main tannage
For main tannage every metal-free tanning agent is possible.
It is necessary to add some fatliquor during this process:
as a lubricant between the hides
for softness
After tanning the leathers are horsed up for a minimum of one night before sammying and shaving.
Fatliquoring
For softness and a round handle we chose the following combination:
SYNTHOL WP = for strong fullness and roundness
SULPHIROL EG 60 = softens the leather without looseness
POLYOL AK = gives a silky touch and keeps the grain elastic.
For optimum fixation the running time of acid is of great importance. It should not be less than 30 minutes.
The leathers are very well set and strongly vacuum dried. Right vacuum drying is a condition for maximum grain smoothness.
REÇETE-BÜYÜTMEK İÇİN TIKLAYIN
Hiç yorum yok:
Yorum Gönder