Bleaching and dyeing; fluid treatment and chemical modification – Forming – shaping – or reshaping with dyeing process or product
Patent
1993-10-15
1997-07-29
Lieberman, Paul
Bleaching and dyeing; fluid treatment and chemical modification
Forming, shaping, or reshaping with dyeing process or product
8538, 8654, 8657, 8673, 8918, 8921, D01F 200, D06P 362
Patent
active
056517947
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to dyeing and has particular reference to the dyeing of cellulosic elongate members, particularly cellulosic fibres. It has further particular reference to the dyeing of cellulosic fibres spun from a solution containing cellulose or a cellulose compound.
BACKGROUND ART
Cellulosic fibres formed by spinning a solution or dope are well known. Cellulosic fibres of the viscose type have been manufactured for many years by dissolving sodium cellulose xanthate in caustic soda to form a syrup-like spinning solution known as viscose and commonly referred to as a spinning dope. The spinning dope is spun by extruding it through fine holes into a coagulating bath of sulphuric acid and salts which neutralise the alkaline content of the viscose dope and regenerate the original cellulose as continuous filaments. If the orifice through which the viscose dope is extruded is an elongate slit it is possible to manufacture a thin sheet of cellulose. If the orifice is annular it is possible to manufacture a tube of cellulose.
Such cellulosic regenerated elongate members are extremely well known.
In more recent years it has been proposed to manufacture cellulosic regenerated elongate material by forming a true solution of cellulose in a solvent such as a tertiary amine N-oxide. The tertiary amine N-oxide cellulose solution is then extruded into a water bath to dissolve out the amine oxide and to re-form the cellulose in a continuous filament or strip or tube depending on the shape of the orifice through which the material has been extruded.
DISCLOSURE OF THE INVENTION
It has now been discovered that such cellulosic regenerated material may be dyed by a route which in its most preferred form involves very low pollution levels, is very economic and is very quick.
The cellulose solution may be a solution of cellulose in an amine oxide solvent. Examples of such amine oxides are tertiary amine N-oxides such as N-methylmorpholine N-oxide, N,N-dimethylbenzylamine N-oxide, N,N-dimethylethanolamine N-oxide, N,N-dimethylcyclohexylamine N-oxide and the like. The use of amine oxides in processes for dissolving cellulose is disclosed in U.S. Pat. Nos. 3,447,939, 3,508,941 and 4,246,221, the contents of which are included herein by way of reference.
By the present invention there is provided a method of dyeing a cellulosic regenerated elongate member which includes the steps of: of: water to form an elongate extrudate from which either: member, or cellulosic material and thereby form the cellulosic regenerated elongate member, and that the cellulosic regenerated elongate member is dyed with at least one cationic direct dye after formation but prior to first drying.
A cationic direct dye comprises a long planar molecule containing positively charged groups. The long planar shape to the molecule enables it to lie closely alongside the cellulose molecule and to bond to the molecule by means of van der Waal's forces and hydrogen bonding. The positively charged groups on the dye can bond with O.sup.- ions on the cellulose molecule.
It appears that dyeing the cellulosic member, particularly fibre, after it has been formed but before it has been first dried (herein "never-dried cellulosic material") produces unique and improved properties in the material compared to products which are dyed after first drying. There is also considerable energy saving and saving in chemicals to be achieved, as well as enhanced uniformity of the dyed material.
In addition to treatment of the never-dried cellulosic material with the cationic direct dye, a subsequent treatment with an anionic direct dye may be used to produce further bleed-fastness characteristics by reaction between the anionic and cationic dye molecules.
The present invention also provides a cellulosic regenerated elongate member which has been dyed with a cationic direct dye whilst still in the never-dried condition.
The pH of the solution for the cationic direct dye may for example be pH 3, pH 4, pH 4.5, pH 5, pH 6, pH 7, pH 8, pH 9, or pH 10. The dyestu
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patent: 5277857 (1994-01-01), Nicholson et al.
Trotman, E.R, Dyeing and Chemicial Technology of Fibres, 6th Edition no month available 1984, pp. 353-357.
Derwent Abstract No. 80-286,75C of Russian Patent 679,657 (Aug. 15, 1979).
Courtaulds PLC
Einsmann Margaret
Lieberman Paul
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