What is water Repellent finish

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

It is a Chemical and Property giving finish. The finish should not affect the fastness properties of dyed goods and feel strength etc of the fabric

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

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.