Bleaching and dyeing; fluid treatment and chemical modification – Reactive dye composition – process – or product
Patent
1998-01-30
1999-11-02
Einsmann, Margaret
Bleaching and dyeing; fluid treatment and chemical modification
Reactive dye composition, process, or product
8549, 8602, 8604, 534631, 534634, 534641, D06P 1382, D06P 1384, C09B 62008, C09B 62651
Patent
active
059761970
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for dyeing substrates, to dyes and to compositions.
In conventional dyeing processes using water-soluble dyes, not all dye fixes to a substrate and, after dyeing, the dyehouse has the expensive problem of disposing of highly coloured solutions containing unfixed dye. For example, during normal exhaust dyeing some unfixed dye remains in the dyebath, whilst some only loosely adheres to textiles and has to be washed-off in the dyehouse to avoid later cross-staining of adjacent fibres during domestic washing. This can result in large volumes of coloured effluent which often contains considerable amounts of dissolved dye. There is a need for a dyeing process which results in colourless or weakly coloured effluent and, ideally, coloured textiles which require less or no washing after dyeing is complete. Such a process would make dyehouses more environmentally friendly and reduce their effluent disposal costs.
According to a first aspect of the present invention there is provided a process for the coloration of a substrate comprising applying thereto a water-soluble dye having at least two electrophilic groups and a nucleophilic agent having a molecular weight below 600 and at least one group selected from aliphatic primary amino groups and aliphatic secondary amino groups.
The dye and the nucleophilic agent may react together during the process to form a highly substantive species which has great affinity for the substrate. The precise mechanism is not fully understood, but the species might exist as some form of oligomer or polymer wherein the agent and dye are joined together by either covalent bonds formed between the electrophilic groups of the dye and aliphatic primary/secondary group(s) in the nucleophilic agent, or by anion-cation attraction between anionic groups in the dye (when present) and cationic protonated aliphatic primary and secondary amino groups. Possibly both of these mechanisms play a part in formation of the highly substantive species.
It is possible to select appropriate combinations of dyes and nucleophilic agents for use in the process by measuring how much dye is immobilised under exhaust dyeing conditions. Very high immobilisation under these conditions indicates that the dye and nucleophilic agent form the highly substantive species and this behaviour is reflected in other dyeing processes, e.g. printing, continuous and semi-continuous dyeing.
Preferably the dye and the nucleophilic agent used in the process are such that if they are applied to cotton by exhaust dyeing at least 90%, more preferably at least 95%, especially at least 97%, more especially from 99% to 100% of the dye is immobilised. This definition is not intended to limit processes of the invention to exhaust dyeing, but serves as a useful test for identifying combinations of dyes and nucleophilic agents which can react together and form a highly substantive species under a whole variety of different dyeing conditions.
The extent of immobilisation of the dye may be determined by dissolving 0.100 grammes ("W1") of dye in a dyebath containing 30 ml of water buffered at pH 7, adding 0.75 g of sodium sulphate and 5 g of cotton, heating to 95.degree. C. over one hour, maintaining the temperature at 95.degree. C. for one hour, then adding nucleophilic agent such that the ratio of electrophilic groups in the dye to the total amount of aliphatic primary amino groups and aliphatic secondary amino groups in the nucleophilic agent is 2:3, heating for one further hour at 95.degree. C., followed by removing the dyed cotton from the dyebath and stirring the dyed cotton for 15 minutes with each of (i) 50 ml of water containing 0.03 grammes of acetic acid, and (ii) three lots of 50 ml of boiling water, wherein the total weight in grammes of dye dissolved in the dyebath and washes is determined using a spectrophotometer ("W2") and the % immobilisation is given by the calculation:
When some combinations of dye and agent are heated under exhaust dyeing conditions in the presence of a substrate they form
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Brennan Colin Michael
Ebenezer Warren James
Hutchings Michael Gordon
Patel Prakash
Shawcross Andrew Paul
Einsmann Margaret
Zeneca Limited
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