The Reactive Dyeing of Cellulosic Fibres

The present study is mainly directed at achieving high fixation
efficiency of reactive dyes on cotton in order to solve the remaining
problems with the use of this type of dyes, e.g. the necessity of using
expensive and time-consuming wash off procedure and of using high
concentration of electrolyte to exhaust the dyebath.
A number of ways to modify cotton have been sought to achieve the above
objectives. Modification of cotton with a polyamide epichlorohydrin (PAE)
resin and its derivatives was extensively studied; three simple
pretreatment methods have been proposed and mechanistic implications are
also discussed.
Light fastness of the dyeings produced on cotton modified with polymeric
compounds was compared to that achieved on cotton modified with low
molecular weight compounds. It is concluded that reduction of light
fastness of reactive dyeings always occurs on the former polymer modified
substrate whilst there is no such problem with the dyeings on the latter
substrate.
Modification of cotton with a specially synthesized low molecular weight
compound, 1,1-dimethyl-3-hydroxyl-1-azetidinium chloride (DMAC), and a
commercially available compound, Glytac A, were carried out and the
dyeability of the subsequent substrate was studied. The practical
importance of these methods and the mechanism of covalent bond formation
when using reactive dyes on these substrate are discussed.
A systematic study of introducing different amino groups into cotton via
reaction of cotton with N-methylol acrylamide followed by amination with
different amines was undertaken and the dyeing behaviour of reactive dyes
on the substrate produced was evaluated.
An unusual reaction was observed when further treating cotton which had
been pre-esterified with chloropropionyl chloride (CPC) in an aqueous
solution of amines. Amination under severe conditions led to substrates
which are dyeable with reactive dyes with good fastness properties but
amination under much milder conditions produced substrates which gave
the subsequent dyeings of poor wash fastness.
A method to determine the chlorine content in CPC cotton by ion-exchange
chromatography is discussed.
An alternative way to achieve dye-fibre covalent bonding was proposed:
cotton was activated first and then dyed with alkyl-amino dyes. The ways
of cotton activation, the methods to prepare alkyl-amino dyes and
activation agents are discussed. This approach not only imparts high
efficiency to the fibre-dye reaction but also avoids the problem of dye
hydrolysis.
The present study has thus far produced six papers which have been
published during the course of this project. The Journal names and the
other details about the publications were given as follows:
[1] S.M. Burkinshaw, X.P. Lei and D.M. Lewis, J.S.D.C., 105(1989)
391-398.
[2] D.M. Lewis and X.P. Lei, Text. Chem. and Col., 2J_(1989) 23-29.
[3] S.M. Burkinshaw, X.P. Lei, D.M. Lewis, J.R. Easten, B. Parton and
D.A.S. Phillips, J.S.D.C., J_06(1990) 307-315.
[4] X.P. Lei and D.M. Lewis, J.S.D.C., 106(1990)352-356.
[5] D.M. Lewis and X.P. Lei, J.S.D.C., 107(1991 )102-109.
[6] X.P. Lei and D.M. Lewis, Dyes and Pigments, in press.