Bleaching and dyeing; fluid treatment and chemical modification – Confined gas phase superatmospheric pressure dyeing process
Reexamination Certificate
2001-02-09
2003-09-16
Einsmann, Margaret (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Confined gas phase superatmospheric pressure dyeing process
C008S529000, C008S543000, C008S917000, C008S918000
Reexamination Certificate
active
06620211
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for dyeing textile material with one or more fibre-reactive disperse dyestuffs in a supercritical or almost critical fluid, which textile material is selected from the group consisting of silk, wool and cellulose, combinations thereof and combinations of one or more thereof with synthetic fibres.
BACKGROUND OF THE INVENTION
A dyeing method of this type for dyeing wool and wool-containing fabrics is known from the article “Wolle färben ohne Wasser. Möglichkeiten und Grenzen überkritischer Fluide” in DWI Reports 122 (1999). In this article, it is stated that modification of supercritical carbon dioxide with water, although increasing the solubility of a conventional wool dyestuff in the supercritical fluid and considerably increasing the dyeing, causes damage to the fibres at dyeing temperatures of over 100° C. An increase in the temperature is desirable in order to raise the dyeing rate. Fibre-reactive disperse dyestuffs are not subject to the problem of a (too) low solubility. It is reported that the most important advantage of fibre-reactive disperse dyestuffs is that the washfastness and fastness to rubbing are good.
The dyeing of textile materials in a supercritical fluid per se is already known from DE-A1-39 06 724. In this known method according to DE-A1-39 06 724, a supercritical fluid which contains one or more dyestuffs is made to flow onto and through a textile substrate which is to be treated. The type of fluid is in this case selected as a function of the dyeing system, which system is determined by the type of dyestuff and the type of textile material. Optionally modified polar (dipolar) supercritical fluids or mixtures thereof are selected for polar dyeing systems, such as water-soluble reactive dyestuffs, acid dyestuffs and basic dyestuffs. One example of a modifying agent for changing the polarity of supercritical CO
2
is water, so that the dyestuff used dissolves better in the supercritical fluid. Nonpolar fluids are used for nonpolar dyeing systems, such as disperse dyestuff systems. For textile materials which contain both nonpolar and polar fibres and are therefore dyed using different types of dyestuffs, it is proposed in DE-A-39 06 724 for these materials to be dyed in a plurality of steps, each step using a system of dyestuff and supercritical fluid which is suitable for one type of fibre. CO
2
as nonpolar supercritical fluid gives good results for dyeing textile materials made from the synthetic fibres of polyester and acetate using disperse dyestuffs, as is also described DE-A1-43 32 219. It is assumed that carbon dioxide dissolves in hydrophobic fibres of the textile material, such as the abovementioned polyester and acetate fibres, with the result that these fibres swell (cf. EP-B1-0 222 207, in which this effect is described), so that the uptake of the disperse dyestuff is improved. However, the above technique cannot readily be used for hydrophilic fibres, such as wool, silk and cellulose (cotton, viscose) fibres, with the conventional water-soluble acid or reactive dyestuffs or with disperse dyestuffs. To make it possible to dye textile materials which contain wool, silk or cellulose, if desired in combination with synthetic fibres such as polyamide fibres or polyester fibres, for this purpose it is proposed in the abovementioned DE-A1-43 32 219 for the textile materials to be pretreated with a hydrophobic finishing agent (“Ausrüstmittel”) prior to the dyeing in supercritical CO
2
with a disperse dyestuff. This pretreatment can be carried out as a separate step by bringing the textile material Into contact with an aqueous solution of the finishing agent, if desired with heating, after which the pretreated textile material is thoroughly pressed and dried under conditions which are such that the hydrophobic finishing agent cures or crosslinks with the fibre. The pretreatment with the finishing agent may also be carried out directly in an autoclave in an atmosphere of supercritical CO
2
. However, the washfastness and fastness to rubbing of textile materials which have been pretreated in this way and dyed are lower than the fastnesses which are required and can be achieved with the conventional acid or reactive dyestuffs which have been dissolved in water. This shortcoming is described in DE-A1-44 22 707. Incidentally, it is pointed out here that acid and alkaline dyestuffs do not form a covalent bond, but rather a much weaker ionic bond. When textile which has been dyed with dyestuffs of this type is rinsed or washed, contamination is released on account of the poor fixation of the dyestuffs to the textile. According to the dyeing method which is described in this latter application, for dyeing cellulose-containing substrates with fibre-reactive disperse dyestuffs in supercritical CO
2
, the substrate is previously modified with compounds which contain amino groups, with the result that even and colourfast colours with good washfastness and fastness to rubbing are obtained. The fibre-reactive disperse dyestuffs used are dyestuffs which in addition to the fibre-reactive group do not contain any group which makes them soluble in water, and the fibre-reactive group itself is not or does not comprise a group which makes the dyestuff soluble in water. The term “fibre-reactive” in general refers to those molecule parts which can react and form a covalent bond with hydroxyl groups, for example of cellulose, or with amino and thiol groups, for example of wool and silk, of synthetic polymers, such as polyamides, and with amine-treated cellulose. The dyestuff therefore reacts with the fibres, so that a covalent bond is formed between the dyestuff and the fibre. A fibre-reactive disperse dyestuff of this type can be well fixed in cellulose and polyester materials on the basis of the chemical structure. However, the fixation of the dyestuff in polyester material is based on the penetration of the dyestuff into swollen polyester fibres, the dyestuff being mechanically “anchored” in the fibre when the swelling is eliminated at the end of the dyeing process. In the method described in the examples of DE-A1-44 22 707, a cotton-containing fabric is pretreated in accordance with a procedure which is known from EP-A1-0 546 476 and is then dried, after which the supercritical dyeing is carried out in an autoclave in which a dyestuff and a quantity of solid CO
2
are placed.
Currently, an increasing number of textile materials are being demanded and developed which are composed of different materials, for example purely of natural fibre materials, such as 80% cotton with the addition of 20% silk or wool, or combinations of natural fibre materials of this type with synthetic fibre materials, such as polyester and polyamide.
It has therefore been found that there is still a need for improvements and/or simplifications to the methods for dyeing textile materials in a supercritical fluid, in particular for combined textile materials which contain natural fibres, in particular based on cellulose (cotton, viscose).
It is an object of the present invention to provide a relatively simple and inexpensive method for dyeing a wide range of materials which contain at least one of the textile materials cellulose, wool or silk using one or more fibre-reactive disperse dyestuffs, resulting in colourfastnesses and washfastnesses which are comparable to or better than those achieved with reactive dyestuffs which are normally used for dyeing in water.
SUMMARY OF THE INVENTION
According to the invention, to this end the method of the type described in the introductory part is characterized in that the relative humidity of the fluid is in the range from 10-100% during dyeing.
The term supercritical fluid is understood as meaning a fluid in which the pressure and/or the temperature is/are above the critical pressure and/or critical temperature which is/are characteristic of the fluid in question. Examples of supercritical fluids which can possibly be used include, inter alia, CO
2
, N
2
O, the lower alkanes, such as ethane
Gerritsen Jan Willem
Gooijer Hendrik
Veugelers Wilhelmus J. T.
Woerlee Geert Feye
Einsmann Margaret
Hoffmann & Baron , LLP
Stork Prints B.V.
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