PRACTICE OF NAPA SHEEPSKIN
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OBJECTIVE
Nappa leather or Napa leather is
a full-grain leather, typically dyed, made from unsplit kid-, lamb- or
sheep-skin by tanning with salts of chromium or aluminium sulfate, and noted
for softness and durability. It is often used in high-quality leather products
such as high-end furniture and accessories.
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OBSERVATION ABOUT LEATHER
We observed about the ovine hides before starting to
leather process. The ovine hides that coming from salted conservation was
extremely fragile and high hardness. The hair had broken off easily.We saw some
defect on the surface of ovines because
the bacterial effect given damage to the raw. Some area of the raw was cut and
the corners was needed trimmed. After the observation, we started to process
for napa.
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MAIN FORMULA
AND MODIFY FORMULA
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TECHNICAL
INFORMATION AND CHEMICALS USED
We got the leather after soaking
unhairing and fleshing operations.we started with deliming and bating
operations.we started with the skin
4000gr and %200 water and 0.15%
sodium bisulphite we were gona repeat same process but we didnt put water
again to get faster effect we putted
sodium bisulphite and ammonium sulfate after 60 minutes we measured Ph with
fenolftaleyn and we got the right pH;8.5 so we added pancreatic enzyme (RİNDECALİN
ON)to make bating operation. The aim of this products
hydrolized to epidermal structure for eliminate the hair, provided to
controlled swelling of hide and reveal to reactive amino and carboxyl groups of
collagen.We used to deliming agents for decrease the pH to 8,0-8,5 because the
pancreatic bating enzyme is working with 8,2 ph value. We didnt make the degreasing process cause of time wasnt
enough so we started pickling process we used 7% salt and 1.2%formic acid it
was a usual pickling operation.we got pH 3.7 at the end of pickle and drummed
at night.in tanning we used 33% basic chrome sulphate and electrolyte stable fatliquoring agent (ENSUL
AM 80)mainly includes sulphited fish oil it gives excellent softness ,round,
velvety, soft touch,very good fullness, improvement of the tear resistance high
exhaustion of the float, i. e. economic working without polluting the waste
waters,excellent inner softness.also we used magnesium oxide(PLEMETOL SBRZ) in
tanning magnesium oxide is used during basification and raises the pH of the
hide or skin to allow the chromium or aldehyde to chemically bind to the skin
protein.we finished tanning with pH 3.9.than we had splitting and we got 2235gr of tanned skin.we made
washing used acetic acid and tensioactives to clean leather.in retaning we used
synthetic tanning agent(TAMPOTAN EH) containing chromium powder that contains
12% chromium oxide, tanning synthetic substances that favorably influence the
quality and smoothness of many skins.and we used glutaraldehyde(RELUGAN GT 50) it
gives leather thin surface,rub and sweat and washing fastness properties all we
need in a napa leather.at the final we made basification with sodium formiat.we
made washings and used acetic acid and tensioactives to get beter results.we
made neutralising with sodum formiat and sodium bicarbonate and final ph was
6.5 as wanted.in dyeing and greasing we used acrilic resyn (RELUGAN RE) it
Improves the fullness and softness of retanned leathers without affecting the
typical chrometanned character of the leather.we gave 2% of dye in one time and
we used synthetic dispersant TAMOL M)to obtain homogenius dyeing.we used
concentrated lecithin(LİPSOL MSG) for leather softening agent with an extraordinarily
low offer which produces leather with very good softness.and we used synthetic
fatliquor possesses
excellent light fastness and resistance
to yellowing caused by heat or ageing. synthetic fatliquor will not
bleach or lighten anionic dyeings.and we used ester phosphorus (NEOPRİSTO SWF)its a very softening fatliquor and to fix
chemicals we used formic acid.
FINAL OBSERVATION AND CONCLUSIONS
The colour of the leather is
orange we looked fort he softness with our hands moving leather but we got some
breaking fibrils inside so it wasnt good softness as we want.thats can be cause
of salt conservation or cause of we didnt operate the degreasing
process.normally with sheep napa leathers industry prefers pickled
conservationed leathrs because pickled conservation leathers gives beter softness
cause of lytropic attack on the low pH.touch of leather was ruff eyesells were
open and superficial touch was dry we prefer wet touch.more or less we obtained
70% homogenius colour but intensity is not strong thats cause of our
formulation we used dye one time thats all.also we obtained flattness and
softness.
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BIBLIOGRAPHY
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