Bleaching and dyeing; fluid treatment and chemical modification – Organic additive for dye composition – dye composition... – Carboxylic acid or salt thereof
Patent
1996-03-29
2000-02-15
Einsmann, Margaret
Bleaching and dyeing; fluid treatment and chemical modification
Organic additive for dye composition, dye composition...
Carboxylic acid or salt thereof
8137, 8542, 8929, 8930, 8924, D06P 1653
Patent
active
060247703
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process to improve the resistance to stains on yarns on the basis of silk, wool, polyamide, polyester, polyacrylonitrile, natural and artificial cellulosic fibres and in general all other synthetic fibres which can be dyed, by which the resistance of the dyed fibres against stains, especially coloured stains, is increased, whilst at the same time also other improved characteristics are obtained.
By "yarns" has to be understood, yarns whether greige (raw) or processed, yarns unfinished or finished, bright as well as dull, in yarn form or processed to fabric, felt, knitwear, non-woven, carpets, rugs, etc. To simplify matters, in this description yarn in which form whatsoever will be called "substrate".
Removal of stains, coloured or not, from a substrate, is still a very delicate problem, as there could remain traces or spots either by discoloration or coloration of the original substrate caused by the stain or by the detergents which affect the dyestuff of the substrate. This is especially the case for stains caused by products containing persistant dyestuffs or pigments for instance present in coffee, tea, wine, fruit juices, inks. . .
The purpose of this invention is to propose a process by which the resistance of a coloured or uncoloured substrate against stains of any nature is considerably improved and which at the same time improves the antistatic behaviour, as well as the resistance to soiling, house-mite and oxidative bleaching agents.
It is known (C.A. Vol. 97 (1982) 7.704 U) that tannin is used to fix dyestuff after the dyeing process. On the other hand it is also known from the swimwear industry, to treat coloured nylon fabric with extractions of gallotannin to improve the colour fastness to chlorine. This was based on the fact that the additional treatment of coloured nylon fabric with gallotannin extractions caused a migration of the dyes in the fibre whereby the gallotannin is fixed on the fibre. This provides a certain resistance to discoloration of the substrate by products containing chlorine. However this treatment has no known effect on coloured stains, and is not at all effective. for stains caused by other oxidative bleaching agents.
During extensive research in this field, it has now surprisingly been demonstrated that the resistance of coloured or uncoloured substrate to stains is considerably improved when the substrate is treated during the dyeing process with an aqueous solution containing up to 5% tannic acid by a pH lower than 6.
The term "dyeing process" as used in this description and claims is to be understood in a broad sense and means any or more steps in the sequence of steps applied to a substrate to give this substrate its coloured and finishing characteristics, whereby this sequence of steps can be done in one or more treatments.
It has been found that this treatment is very effective against stains caused by dyes of natural or synthetic origin with anionic, cationic, metalcomplex or disperse nature.
That the tannic acid would improve the discoloration caused by chlorine, could be expected by the man skilled in the art, but that this treatment would be efficient against coloured stains, could not be predicted.
According to the invention, the substrate, in acid medium, is treated with a solution containing 5 to 50 gram tannic acid per litre water and preferably between 25 to 35 g/l.
These concentrations and proportions are not critical, though it has been noticed that higher concentrations hardly influence the result but could cause a yellowing of the substrate.
Tannic acid is a compound derived for several centuries from nutgalls and has a structure of polygalloylglucose or polygalloylquinic acid.
The term "tannic acid" as used in this description and claims should be understood in a broad sense, and covers products containing tannic acid, such as for instance gallotannin.
In fact tannic acid is a mixture of compounds consisting of a glucose-chain which is several times substituted with gallic acid or trihydroxy-3,4,5-benzoic-acid-1. Substitut
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C. C. Cook et al., "The Effect of Some Aromatic Hydroxy Compounds on the Adsorption of Anionic Dyes by Nylon 6", Textile Res J. 47, 244 (1977) pp. 244-249, 1977.
Chemical Abstracts vol. 97 (1982) abstract 7704u, (Kane-) Kanebo et al, Studies on the mechanism of dye fixation. Part 10. Effect of aftertreatment with tannic acid on the fixation of disperse, acid, direct and basic dyes, Ogasawara, et al.
Einsmann Margaret
N.V. Denderland-Martin
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