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DYE FIXING AGENT
DFA is an excellent dye fixing agent and is widely used as fixing agent for direct & reactive dyestuffs on cellulose fiber. DFA is also used for improving the rubbing fastness of the direct colours to light and washing.
Specification :-
Physical appearance : slightly yellowish fluid.
Ionic character : cationic
Chemical composition : Nitrogen containing condensation product
Ph : 1% solution has a ph of 5.5 – 6.0.
Solubility : Can be diluted with water to any desired concentration. Clear solutions are obtained.
Reaction in aqueous : Slightly acidic solution.
Stability : Dye Fixing Agent is not susceptible to sulphate ions i.e. the presence of sodium sulphate, copper sulphate, or other sulphates cause no inconvenience. Moreover this product is resistant to salts contained in hard water, chlorides and acids. Alkalies may impair its stability.
Storage Stability : Suitable for prolonged storage
Compatibility : DFA being cationic in character reacts with anionic product and undesirable compound may be found when such products are simultaneously present in the after treatment baths. Care should be taken to check compatibility through circumstances. DFA is compatible with non-ionic and cationic auxiliaries.
APPLICATION:
(A) For improving the wet fastness properties of direct and reactive dyes. DFA is ideally suited to improve the fastness to water, perspiration and wet finishing of dyeing and prints, produce with direct dyes on cotton and re-generated cellulose.
DFA does not cause any significant change in the shade or a reduction in fastness to light. A preliminary test is recommended in case where these are of critical importance. The handle of the goods is affected a little repellency, the rewetting of goods treated with it remain virtually unimpaired.
PROCESS: To ensure optimum improvement in fastness properties in medium shades produced with direct dyes and reactive dyes 2 - 4 % on an average of DFA calculated on the weight of the goods is required. The quantity is somewhat reduced in case of pale shades. An after treatment with 1 – 2 % DFA is often sufficient to produce considerable improvement in the wet fastness properties.
To ensure a uniform after treatment on the jig or on dyeing machines DFA may be added in several portions. In continuous process on the padding mangle it is applied for solutions containing 10 – 25 g.p.l calculated on the starging batch. The goods are dried immediately.
(B) Suggestions for usage in consumption with reactive dyes: Very often it is not possible to ensure a through final washing off to completely remove the hydrolyzed reactive dye which has just been rendered to react and from a bond with the cellulose fiber on which it is applied. However, the hydrolyzed reactive dye can be taken up by cellulose fiber substantively leading to initial coloration of washing liquor at the hands of the end user.
DFA effectively prevents such initial bleeding in home washing by fixing the hydrolyzed reactive dye substantively taken up by the cellulose fiber thus elimination a possible future complaint.
Future, many types of reactive dyes are susceptible to an acid of alkaline hydrolysis depending on the reactive system of the dye in spite of a through final washing off being effect at the processing plant.
This occours during storage of goods processed with all possible care and leading to a subsequent bleeding white laundering at home on account of the hydrolysis of dye fibre bond.
A treatment with DFA of material processed with reactive dyes offers the processor a safe guard against such undesirable occurrences.
A treatment with 1 g/l to 3 g/l of DFA at room temperature for 10-15 minutes followed by through rinsing is often adequate.
(C) Stripping: If re-dyeing is necessary to rectify faults pre-stripping of DFA may be carried out in a bath containing 2-4 parts Formic Acid (85%) per 1000 Parts liquor at near oil for 30 minutes followed by through rinsing. Re-dyeing may then be carried out followed by dye fixing treatment.
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