Water Repellent finish
If a fabric allows air but prevents water to pass through itself it is known as Water Repellent finish'Requirement
The fabric should not become unnecessarily
stiff and harsh
Method
(A) Using metallic salt
PROCESS
Pad toe fabric with metallic
salt: like Aluminium Acetate or lead acetate
Passing the padded fabric
through Soap like sodium acetate
If necessary a little
quantity of wax may be added. This method is not permanent
(B) Using silicon emulsion
They impart not only water
repellency but also soft handle and improved draping qualities.
PROCESS
Pad - Dry - Cure
If necessary Resin may be added
in conjunction with silicone
Catalyst should be added for permanent durable
finish.
E.g., for catalyst, Organo
Metallic salts They are added just before the application The pad bath contains
Silicone, Resin, Emulsifier and a Catalyst
(C) The velan pf process
It imparts water
repellency and a soft attractive finish
It is fast to washing,
boiling soap solution, dry cleaning etc
It is a compound of
Quaternary Ammonium Salt with Pyridine Base and a compound is formed with
cellulose in the presence of Sodium acetate.
PROCESS
Pad - Dry - Cure Soaping – Rinse
Padding : 6 % Velan PF + % Sodium acetate at 35
Drying 60 - 70°C
Curing 120°C for 2 – 3 mines.
Soaping - Soap - 0.2 %
Soda - 0.1 %
Temp. 35°C
Time 1 to 2 min.
Any soap or other detergent
left in the material will reduce its apparent Water repellency
(D) Using waxes Emulsion
It gives a soft handle and gloss to the
fabric.
PROCESS Pad –Dry - Cure
Preparation of Pad bath
Preparation of Pad bath
Take wax emulsion + 3 to 4
times of water temperature 40-50°C
↓
↓
Stir
↓
↓
Dilute to desired concentration
It can be used along with
stiffening or binding agents
Durable water Repellency
Stearoxy Methyl Pyridium Chloride is popularly
used for durable water repellent finish. Methylol Stearamide, Methylated
Methylol Melamine can also be used.
A catalyst should also, be
added. They chemically react with the fibres and produce durable repellent
finish.
PROCESS
Pad -Dry - Cure
For synthetics the following chemicals are
added
Zirconium type pyridinium compounds Silicones
Fluro carbons.