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1、7/2/2019,1,PATENT LEATHER,Singapore Technical Workshop January 28th - February 1st , 2008,7/2/2019,2,Sensual requirement for crust,Tightness : for smooth article is absolutely required. In case of “Naplack” some looseness is preferred. Softness : following the last trend, must be very soft Fullness
2、: it is extremely important, mainly in the belly part Selection grade : depending on the article, low grade is welcomed,7/2/2019,3,Crust Physical Requirement,Dyestuff Migration : must be applied best grade Fatliquor : 1) Mineral Oils must be avoided 2) Surface feel of oils must be dry 3) Must be fre
3、e of spew 4) Fastness to UV although the thickness of finishing is thick but cannot stop UV Syntan and resin : need to be care for the lightfastness,7/2/2019,4,Others,Crust must be dried in a proper way (keeping some relative humidity) otherwise leather will be shrunken while impregnation. Buffing p
4、roperty need to be good in order to avoid un-uniform buff. Flesh side must be buffed prior to grain buff Water absorption of crust should be not too fast and not too slow ( need to choose proper fatliquor),7/2/2019,5,PU Patent,Solvent-borne Polyurethane concept & SU-8250,7/2/2019,6,Polyurethanes Def
5、inition,Polyurethanes, often known as PU, are a very large and varied family of versatile and useful engineering materials. In a chemical point of view an “urethane” is the esther of a carbamic acid R NH CO O R and PU are polymers which contain urethane groups ( - NH CO O - ) produced by reaction of
6、 a polyol with an isocyanate (polycondensation),7/2/2019,7,PU - Chemistry,Reaction of Isocyanates with active hydrogen compounds: When an isocyanate react with an alcohol a urethane is formed R-NCO + R-OH R-NH-CO-O-R Isocyanate + Alcohol Urethane If the active hydrogen compound is a primary amine, i
7、t is formed a substituted urea : R-NCO + R-NH2 R-NH-CO-NH-R Isocyanate + Amine Substituted urea,7/2/2019,8,SU - 8250,SU-8250 is a solvent borne polyurethane with NCO reactive groups, based on TDI (Toluene di-isocyanate or 2,4-diisocyanate-1-methyl-benzene) SU-8250 reaction where TDI react with a pol
8、yol : NCO-Ar-NCO + HO-R-OH-(O-OC-HN-R-NH-CO-O-R-)n Diisocyanate + Polyol Polyurethane SU-8250 SU-8255,7/2/2019,9,SU - 8250,There is a second possible reaction between SU-8250 with active hydrogen and when it react with moisture an urea is formed : R-NCO + H-OH R-NH-CO-NH-R SU-8250 + Humidity Urea,7/
9、2/2019,10,Application,Pre-treatment of crust, means impregnation, is very important and a resin with good solvent resistance is required (RI-171). After ageing and vacuum, rebuffing has to be done with particular care Base coat is also extremely important and use of our RU-3957 is highly recommended
10、. Fillers containing stearine must be avoided! A combination of FI-1261 and FI-65 is recommended.,7/2/2019,11,Application,By curtain coater apply the mix of SU-8250 / SU-8255 with a ratio 48/52 and viscosity 23-25” Ford cup 4. Curtain coater should be a gravimetric one with a mechanical pump (in ord
11、er to avoid presence of air) with filters Kuno 10-25 micron, for black and clear application, and filter Kuno 25-50 micron, if white is concerned. Quantity to be applied : a) 12 g/sq.ft. on small skins b) 18-20 g/sq.ft. on sides For airless application, reduce viscosity to 15-17”,7/2/2019,12,Working
12、 Condition,Curtain Coater Room : 1) Floor and wall in ceramic (always clean) 2) Pressurized air 3) Air filter 50 micron 4) Change air 6-8 times per hour 5) Working temperature 18-22 Centigrades 6) Relative humidity 50-60%,7/2/2019,13,Working Condition,First Phase Drying : 1) Time about 8-10 hours 2) Change air 10-12 times per hour 3) Temperature 40-45 Centigrade 4) Relative humidity 20-30% Second Phase Drying : 1) Time about 8-10 hours 2) Change air 15-20 times per hour 3) Temperature 45 Centigrade 4) Increase relative humidity up to 70-80%,7/2/2019,14,
