GB2122225A - After-treatment of dyeings: afterchroming - Google Patents

Abstract

The fastness properties of a dyestuff on a hydroxy group- containing substrate are improved by applying to the substrate, preferably as an aftertreatment, A) the product of reacting a mono- or polyfunctional primary or secondary amine with cyanamide, dicyandiamide (DCDA), guanidine or biguanidine, or ammonia with cyanamide or DCDA; and, simulataneously or subsequently, B) a trivalent chromium salt. The process can advantageously be applied to the direct dyeing of cotton.

Description

SPECIFICATION Improvements in or relating to organic compounds This invention relates to a process for improving the fastness properties of dyes on a hydroxy group-containing substrate.

It is known that the product of reacting a mono- or poly- functional primary or secondary amine with cyanamide, dicyandiamide (DCDA), guanidine or biguanidine; or ammonia with cyanamide or DCDA may be used as a fixing agent to improve the wet fastness of dyes and optical brighteners, particularly direct dyes, on a hydroxy group-containing substrate, for example cotton.

This fixing agent is preferably used as an aftertreatment agent. It may be applied by padding, but preferably is applied from an exhaust bath.

It has now been found that the fastness properties of the resulting dyeings are further improved by treatment with a metal capable of forming a co-ordination complex with the above fixing agents, in particular with a trivalent chromium salt.

Accordingly, the present invention provides a process for improving the fastness properties of a dyestuff on a substrate comprising hydroxy group-containing fibres by applying to the substrate A) the product of reacting a mono- or poly functional primary or secondary amine with cyanamide, dicyandiamide (DCDA), guanidine or biguanidine; or ammonia with cyanamide or DCDA; and, simultaneously or subsequently, B) a trivalent chromium salt.

Preferably the process is an aftertreatment process, that is, A) and B) are applied simultaneously or sequentially to a substrate which is already dyed or printed.

The invention further provides an aftertreatment agent for a dyed, printed or brightened substrate comprising hydroxy group-containing fibres, which agent comprises a mixture of components A) and B).

Component A) is preferably the reaction product of a polyalkylene polyamine with cyanamide, DCDA or guanidine, more preferably with DCDA. The polyamine is preferably of formula I RRN+ZXAnZNRR in which each R independently is hydrogen or a C1~,O alkyl group unsubstituted or mono substituted with hydroxy, C14 alkoxy or cyano, n is a number from 0 to 100 Z, or each Z independently when n > O, is C23 alkylene or -CH2CHOHCH2- and X, or each X independently when n > 1, is -NR where R is as defined above, provided that the amine of formula I contains at least are reactive -NH- or -NH2 group.

More preferably each R is hydrogen, n is 0 to 4, X is NH or -NCH3- and Z, or each Z independently when n > O, is C23 alkylene.

Particularly preferred compounds are diethylene triamine, triethylene tetramine, tetraethylene pentamine, 2-aminoethyl-3-aminopropylamine, dipropylene triamine and N, N-bis-(3-aminopropyl)methylamine.

Components A) are known, and may be prepared by the methods described for example in British patent 657 753, US patent 2 649 354 and British published application 2 070 006A.

Suitably the amine, in free base or salt form, is reacted with the other starting material in the absence of water at elevated temperatures optionally in the presence of a non-aqueous solvent. Preferably the reaction is carried out in the absence of a solvent at a temperature of 140-1 600 C, and for most combinations of reagents, ammonia is evolved. The reagents are preferably reacted in a molar ratio of 0.1 to 1 mole of cyanamide, DCDA, guanidine or biguanidine per mole of reactive -NH or -NH2 groups, and when DCDA is reacted with a polyalkylene polyamine, the molar ratio of the reactants is more preferably from 2:1 to 1:2, particularly about 1:1.

The products A) are near-colourless viscous liquids or solids which are basic in character, water-soluble either in the free base or salt form, and contain reactive hydrogen atoms bonded to nitrogen. They may be used as fixing agents in free base or acid addition salt form, and may be used with basic, direct or reactive dyes, preferably direct and reactive dyes on cellulosic substrates.

Basic dyes include those having acid groups in addition to basic or cationic groups, e.g. those dyes disclosed in US Patent 4 273 707, British Application No. 2081734 and European Application No. 51 041.

The product is substantive to dyed cellulosic fibres and may therefore be applied, e.g. to cotton, from an exhaust bath, preferably under weak acid conditions at temperatures from room temperature to 1000C, preferably from 50800C. Approx. 1-3% of A) is normally used (by weight based on the dry weight of substrate), depending on the depth of shade. The bath may also contain from 3-10 g/l of sodium chloride to counteract any tendency to dye migration. The bath is preferably adjusted to a pH of 4-4.5. The product A) may also be applied by padding, e.g. as a 10-20 g/l solution padded at 80% pickup.

Component A) may be used as a fixing agent either alone or as a mixture with one or more additional cationic fixing agents, which preferably also have substantivity to dyed cotton. An example of such a further cationic fixing agent is the reaction product of a polyalkylene polyamine with epichlorohydrin as described in British Patent No. 1 396 195. A suitable mixture for example contains 1 part by weight of the reaction product of diethylenetriamine with DCDA and 2 parts by weight of the reaction product of the same amine with epichlorohydrin.

Although this treatment gives improved wash fastness for direct and reactive dyeings, it may be found that for heavy shades the wash-fastness falls short of what is desired. A further improvement is obtained by the use of a trivalent chromium salt B), which may be added to the padding liquor containing A) or added to the same exhaust bath as A) either initially or, which is preferred, after A) has become wholly or partly exhausted onto the substrate. Alternatively the chromium salt may be applied from a separate bath or by padding, dipping, spraying etc. in a subsequent treatment step.

Any water soluble inorganic or organic chromic salt may be used as component B), for example chromic sulphate, fluoride or acetate, or chrome alum(potassium chromium sulphate). The chromium salt is preferably at least partially basic, suitably up to 50% basic. A suitable salt is commercial chromium acetate 'D' (=dyeing quality), containing 28-30% chromic acetate (4850% basic), 25-27% chromic sulphate (4850% basic), 34-36% sodium sulphate and 910% water by weight.

The quantity of chromium salt used will depend upon the depth of the dyeings and the quantity of A) employed. Thus 13% shades of many direct dyeings on cotton may be treated with approx. 1-5% of A) and 0.55% of chromic salt, whereby the weight of chromic salt is suitably from50-1 00% of the weight of A) employed. More preferably approx. 3% of A) and 2% chromic acetate (commercial) are employed.

Unless otherwise stated, the above percentages are based upon the dry weight of substrate, The treatment with chromic salt is preferably carried out at mildly acid pH, preferably pH 44.5, and at temperatures of 60-800C preferably about 700C, for at least 30 minutes. Preferably the chromic salt is added to the bath after the substrate has been treated with A) for at least 20 minutes.

The substrate is finally rinsed and dried; other treatment steps such as the application of softeners, anti-static agents etc. being also possible.

The resulting dyeings and printings have improved wash fastness compared with those obtained without the use of chromic salt. Light fastness is not affected, and there is no change of shade, except in the case of some yellow dyeings where a slight greening of the ground shade of the cotton may occur.

The following Examples, in which all temperatures are in degrees Centigrade, illustrate the invention.

Example 1 A dyeing of 1.2% of the dyestuff of Example 1 of British Patent No. 1 354 790 on unbleached unmercerized cotton interlock fabric is obtained by conventional methods. The dyed fabric is rinsed, squeezed dry, and added to an aftertreatment bath at 20-250C containing 3.0% (based on dry weight of substrate) of the solid neutralized reaction product of diethylene triamine and DCDA prepared as described in the first part of Example 1 of British Patent Application No. 2070006A, 5.0 g/l common salt and 1.0 acetic acid, and having a pH of 4.0 to 4.5.

The goods to liquor ratio is 1:20. The temperature is raised to 700C over 1 5 minutes and held at 700C for 20 minutes.

To the bath is then added 2.0% (1 g/l) commercial chromium acetate 'D', of the composition stated above, and treatment is continued at 700C for a further 30 minutes.

Finally the fabric is ringed and dried. The resulting dyeing has better wet fastness properties than one obtained by repeating the process without the addition of chromic acetate.

Example 2 A bleached cotton cretonne fabric is dyed to 3% shade with the dyestuff of Formulal V11l of British Patent Application No. 2070006 rinsed and squeezed dry. The dyed fabric is added to an aftertreatment bath at 200C containing 3.0% of the fixing agent described in Example 1 and 10 gIl of common salt. The goods to liquor ratio is 1:20.

The bath is heated to 600C over 1 5 minutes, held at 600C for 20 minutes then 2.0% chromium acetate is added and treatment continued for 20 minutes. Finally the fabric is rinsed, squeezed and dried on a frame at 1 200C for 1 minute.

Improved wash fastness properties are obtained.

Example 3 The dyeing described in Example 2 is treated with 3.0% of the fixing agent of Example 1 and 10 g/l of common salt at a goods to liquor ratio of 1:20. The bath is heated from 200C to 600C over 10-15 minutes, then held at 600C for 20 minutes. Finally the fabric is cold rinsed and squeezed dry.

In a second aftertreatment bath the treated fabric is then added to a 1 g/l solution of chromic acetate at a goods to liquor ratio of 1:20, the pH being adjusted to 4.0-4.5 by addition of 0.25 ml/l of 60% acetic acid. The fabric is treated for 1 5 minutes at 200C then cold rinsed, squeezed dry and dried at 1 200C for 1 minute. Improved wet fastness properties are obtained.

Examples 4, 5 Examples 2 and 3 are repeated, using in place of the fixing agent of Example 1 a mixture of 1 part by weight of this fixing agent and 2 parts by weight of the reaction product of diethylene triamine and epichlorohydrin, prepared as described in Example 1 of British Patent No.

1 396 195. Good result are obtained.

Claims (3)

Claims

1. A process for improving the fastness properties of a dyestuff on a substrate comprising hydroxy group-containing fibres by applying to the substrate A) the product of reacting a mono- or poly functional primary or secondary amine with cyanamide, dicyandiamine (DCDA), guanidine or biguanidine; or ammonia with cyanamide or DCDA; and, simultaneously or subsequently, B) a trivalent chromium salt.

2. An aftertreatment agent for a dyed-or printed substrate comprising hydroxy groupcontaining fibres, which agent comprises a mixture of components A) and B), defined in Claim 1.

3. A process for improving the fastness properties of a direct dyestuff on cotton as described in any one of the Examples.