1. Abstract


The basis for this article arises from a question by a prominent Turkish producer:


"The rinsing and washing processes in my dyehouse are too long. Is there any way that we can utilise our existing machinery to improve the efficiency and reduce the rinsing time without compromising fastness properties? Our machine supplier is telling us that the latest Jet dyeing machines automatically reduce the washing off time. Is this true?"


In this article Mr. Steve Moorhouse, Technical Director of Dyehouse Solutions International., responds:


2. Article


The rinsing process can be shortened as follows:


Various people (machinery suppliers or chemical suppliers for example) will try to convince you that it is simple, and that only one approach holds the key. It is upto the concerned person to decide whether or not that opinion derives from a "vested interest". Experience wise, the objective should be not only to shorten the rinsing process time, reduce the number of rinse baths, but to do so without any compromise to the safety of the process or to the level "Right First Time" production.


Thus, many chemical suppliers will seek to convince that the number of rinses after bleaching and before dyeing can be reduced by the use of a peroxide killer. But this is only true if the modified rinsing process leaves the substrate "Fit for Dyeing". Peroxide is only one of the potentially harmful residual chemicals which must not be carried forward into the dyebath. If the use of a peroxide killer leads to a reduced number of rinse baths, will that reduced number still be sufficient to remove residual alkali ?

In our experience not necessarily so. See Case Study 1.


Thus also, the number of rinse baths after dyeing can easily be reduced. But what is the effect on critical wash-fastness? See Case Study 2.


There is no doubt whatsoever that machinery suppliers have made great strides in the last decade to shorten rinsing process times considerably with such techniques as CCR (Combined Cooling & Rinsing) and Smart Rinsing.


Much reliance on machinery should not be placed without taking full consideration of a full understanding of all the critical success factors involved.


So far as machinery developments are concerned, attempts are made in this article to give an independent review without any vested interest of any kind.


2.2 Case Studies


Shortening rinse processes with Improvements in Quality and Safety

To emphasise the importance of Quality and safety we pose two very simple, but "biting" questions.

a) Consider two processes A and B


Process

Time

A

6 hours

B

8 hours


Which process is the shorter?


b) Consider two processes A and B


Process

Time

Production Result

A

6 hours

Wrong Shade, Unlevel, Fails fastness Spec

B

8 hours

Right Shade, Level,

Passes highest Retail Spec.


Which Process is the shorter?


Let us now consider two case studies to illustrate the point.