2. Chain Mercerizer:

In order to make up for the shortcomings of the roller mercerizing machine, a clip stenter is used for post-mercerization treatment, in which a widthwise tension is applied then most alkali is showered off the fabric kept on the stenter, followed by thorough alkali removal and neutralization using an open-width washing machine.In this machine a heavy padding mangle is used for the application of alkaline solution in the 2 dip/2 nip method, with sufficient time allowed for penetration and swelling of the fabric in a timing cylinder, instead of undergoing an operation using so many rollers and so much solution as in roller mercerization, to ensure reduced use of the alkali. 

It is to be noted that all the fabric mercerizing process involve 4 steps:

i) Impregnation with caustic soda solution

ii) Stabilisation (first rinsing stage under tension)

iii) Washing in open width washing range

iv) Neutralising 

Recipe for mercerizing fabric:

Caustic soda: 20-23% (48-52 ^oTw) or (28-30 ^oBe)

Temperature: approx 20^oC

Time: 30-45 seconds

Machine Feature:

In a chain mercerizer, the cotton fabric is padded with two number of 3 bowl padding mangle, the troughs of which containing the required concentration of caustic soda and wetting agent. Between the two impregnation, the fabric goes around a set of dummy rolls (for timing and swelling), which are driven by fabric movement. The two squeezing nips of the padding mangle run at different speeds, the second one running fastest than the first one, in order to maintain the required tension in the warp way. 

After impregnation, the fabric is fed into the clips of a stenter, where it is stretched in the weft direction to the required dimensions. The alkali in the fabric is rinsed out with sprays situated over the stenter, initially with hot water and then with cold water. Thoroughly and even washing out to the order of less than 60 gpl of caustic soda remaining in the fabric. Until then the tension should not be released. Then the fabric is washed thoroughly in an open width washing range and neutralised. Here a counter current washing system is employed, wherein fresh water is introduced at the delivery end of the machine and the first wash liquor that the cloth meets in the stenter is slightly alkali concentration.