GB2138030A - Mixed dyeings on polyacrylonitrile/cotton fabrics - Google Patents

Abstract

Mixed polyacrylonitrile/cotton fabrics are dyed in a two-step one-bath process involving a first step in which the PAN fibres are dyed with basic dyes and a second step in which the cotton fibres are dyed with direct dyes, the second step being carried out at a lower temperature, at which the basic dyes used in the first step do not migrate. The resulting dyeings have good fastness properties which can be improved further by after treatment with certain fixing agents.

Description

SPECIFICATION Improvements in or relating to organic compounds This invention relates to a dyeing process for polyacrylonitrile/cellulose mixtures. It is known to dye mixed substrates of polyacrylon itrile and cellulose fibres in a single bath with basic and direct dyestuffs, but in general poor fastness properties are obtained. Better fast ness can be obtained by dyeing with basic and reactive dyes, but in this case a two-bath process must be used, and the whole dyeing process takes a considerable time.

It has now been found that it is possible to dye such fibre mixtures in a two-step single bath process, and thereby to obtain dyeings with good wet fastness properties in a short dyeing time.

According to the present invention, therefore, there is provided a two-step single-bath process for the dyeing of a fibrous substrate comprising a mixture of fibres dyeable with basic dyes and hydroxy group-containing fibres, said process comprising a first step of dyeing with a basic dyestuff and a second step of dyeing with a direct dyestuff, the second step being carried out at a temperature which is below the final temperature reached in the first step; and the basic dyestuff used in the first step and the second step temperature being selected such that there is no signifficant migration of the basic dyestuff from the fibres dyeable with basic dyes to the hydroxy group-containing fibres.Preferably the first step is carried out over a temperature range between 60"C and 105,C, such that the final temperature is in the range 95 1 05,C, the dyebath is then cooled to 75 90"C and the second step is carried out at temperatures in the range of 75-90'C, the basic dyestuffs used in the first step being such as do not migrate significantly at this temperature. Fibres dyeable with basic dyestuffs include polyacrylonitrile (PAN) e.g. Orion or Acrilan and polyacrylonitrile or polyester modified with anionic groups. The term polyacrylonitrile is used to include acrylonitrile homopolymer and also copolymers containing at least 50% wt. acrylonitrile. Fibres containing hydroxy groups include cellulose, e.g.

cotton and regenerated cellulose (viscose).

The fibre mixtures to be dyed according to the process of the invention preferably contain the two fibre types in ratios from 20:80 to 80:20 by weight, particularly 50:50. The process of the invention is oarticularly suitable for PAN/cotton knitted fabrics, which find use for examole in sportswear such as jogging suits.

In a preferred method for carrying out the invention, the PAN component is dyed in the first step in conventional manner by entering the mixed substrate into a dyebath at 5060"C, the dyebath being adjusted with acid, e.g. formic or acetic acid, to the desired pH, preferably 4-5, and containing, in addition to the basic dyestuff or mixture of basic dyestuffs, conventional dyeing assistants e.g. softeners, retarding agents, lubricants, etc., particularly anti-precipitants such as are commonly used in single bath dyeing of PAN-containing mixed substrates. The bath is then heated to 95-105"C and dyeing is carried out at this temperature for 50-90 minutes.

The dyebath is then cooled to a temperature in the range 75-90"C, at which the basic dyestuffs used in the first step will not significantly migrate, and the direct dyestuff or mixture of direct dyestuffs is added to the same bath, together with conventional dyeing assistants for the dyeing of cellulose with direct dyes, e.g. sodium chloride or sodium sulphate. No intermediate rinsing or drying of the substrate is necessary. Dyeing of the cellulosic component is then carried out at this temperature for 50-80 minutes.

Basic dyestuffs are those in which the number of protonisable or cationic groups in the molecule is at least one greater than the number of any anionic groups, e.g. sulphonic or carboxylic acid groups, which may be present. Basic dyestuffs may be used in metalffree or in metal complex form The dyestuffs used must be such as will not migrate significantly under the conditions of the second step. Migration properties of basic dyestuffs are generally well known, are described in the manufacturer's technical literature or may be readily determined by experiment, so that selection of suitable basic dyestuffs for use in the first step will be a routine matter for the man skilled in the art. Suitable basic dyestuffs having low migration are described for example in US Patent 4 273 707, British Patent Application 2 081 734A and European Patent Application 51 041.On the other hand, German Offenlegungsschrift 2 548 009 describes basic dyestuffs which migrate under mild conditions and which are not suitable for use in the process of the present invention.

The selection of the direct dyestuffs to be used in the second step is not critical, but it is preferred to use metal complex dyes, particularly copper complexes. Suitable direct dyestuffs are described for example in 8ritish Patent Applications Nos. 2 070 006A and 2 106 126A.

The wet fastness properties of the resulting dyeings can be improved further if the dyed substrate is after-treated with a fixing agent F, which is the product of reacting a mono- or polyffunctional primary or secondary amine with cyanamide, dicyanodiamide, guanidine or biguanidine; said product containing reactive hydrogen atoms bound to nitrogen; or with a fixing agent F2 which is the reaction product of fixing agent F1 with B) an N-methylol derivative of a urea, melamine, guanamine, triazinone, urone, carbamate or acid amide.lf fixing agent F2 is used, it is applied in the presence of C) a catalyst for the cross-linking of N-methyloi compounds of the type B) above, and a heat-curing step is subsequently carried out.

Fixing agents F, and F2 are known and are described in British Patent Application 2 070 006A, the contents of which are incorporated herein by reference. In this publication, fixing agent F, is referred to as intermediate product A), while fixing agent F2 is the product claimed in Claim 1 of the application. It should be noted however, that whereas British Patent Application 2 070 006A describes intermediate product A) as including the reaction product of ammonia with cyanamide or dicyandiamide, such products are not included within the scope of fixing agent F1, and their reaction products with N-methylol compounds B) are not included within the scope of fixing agent F2.

Suitable N-methylol compounds B) and catalysts C) are also described in the above British Patent Application. The preferred fixing agents F1 are the compounds described as preferred classes of intermediate product A) in the above British Patent Application particularly the reaction products of diethylene triamine or triethylenetetramine with dicyanodiamide (DCDA). The preparation of fixing agents F, is described for example in British Patent 657 753 and US Patent 2 649 354.Preferred fixing agents F2 are the preferred end products described in British Patent Application 2 070 006A, particularly the products obtained by reacting the preferred fixing agents F, with hydrolysis-resistant reactive resin precursors, e.g. N, N'-dimethylol-4, 5-dihy- droxyethylene urea, N, N '-dimethylol-4, 5-dime- thoxyethylene urea and their methyl and ethyl ethers, preferably in the presence of a catalyst, e.g. magnesium chloride.

The aftertreatment is carried out in conventional manner, preferably by exhaust application. Preferred conditions are a weakly acidic bath at a temperature from 50-80"C. The quantity of fixing agent to be used depends upon the depth of the dyeing, but in general quantities up to 3% based on the dry weight of the goods may be used. Preferably aftertreatment is carried out in the presence of an electrolyte, e.g. 3-10 g/l sodium chloride.

The fixing agent may also be applied by padding, spraying, dipping, foam application or other conventional processes. For example, the dyed goods can be impregnated with a bath containing 10-20 g/l of fixing agent F, or F2 and squeezed out to give a pick-up of 80% of the dry weight. The aftertreatment bath may also contain assistants such as softeners, wetting agents, waterproofing agents, agents to improve the hand of the goods, etc.

The process of the present invention gives dyeings on mixed fibre substrates which have good fastness properties, particularly wet fastness properties, even without an aftertreatment step. By means of this process, wash fastness may be obtained which does not decrease even after repeated washing at 50 60"C. This may be achieved either with or without an aftertreatment step, depending upon the dyestuffs used. Furthermore, where special effects are to be obtained by dyeing the two different fibres in different shades, dyeing by the process of the invention ensures that the two shades will remain clearly separated, no aftertreatment being necessary.

These good properties are obtained in a shorter dyeing time than the previous twobath method in which basic and reactive dyes are used, even when the aftertreatment time is taken into account.

The following Examples, in which all parts and percentages are by weight and all temperatures in degrees centigrade, illustrate the invention.

EXAMPLE 1 To 1 litre of water at 60 are added 0.5 parts sodium acetate and, after adjusting the pH to 4.5 with acetic acid, 0.15 parts CI.

Basic Yellow 82, 0.01 parts C.l. Basic Red 104 and 0.2 parts C.l. Basic Blue 3. 50 Parts of a PAN/cotton mixed fabric is entered into this dyebath (goods to liquor ratio 1:20), and the temperature is raised to 105 over 50 minutes and held at 105 for 35 minutes.

After cooling to 80 , there is added to the same bath 0.29 parts C.I. Direct Yellow 98, 0.55 parts C.l. Direct Green 68, 0.115 parts C.l. Direct Brown 103 and 15 parts sodium chloride. Dyeing is continued at 80 for 60 minutes, and the substrate is rinsed to give an olive dyeing with good wet fastness properties.

The wet fastness properties may be further improved by entering the dyed and rinsed substrate into 1 litre of an after-treatment bath containing 1 part of fixing agent F, prepared as described in paragraphs 1 and 2 of Example 1 of British Patent Application No. 2 070 006A, heating the bath to 60 over 20 minutes and treating for a further 20 minutes at 60 . After rinsing an olive dyeing is obtained which is characterised by good wet fastness properties, particularly high wash fastness, and which retains its good fastness properties after repeated washing at 50 .

EXAMPLE 2 Example 1 is repeated using the following dyestuffs instep 1, 0.015 parts Cl. Basic Yellow 82 and 0.2 parts of a conventional dyestuff mixture containing, together with a carrier, C.l. Basic Violet 14, C.I. Basic Green 4, C.i. Basic Blue 3 and C.l. Basic Yellow 82 : in step 2, 012 parts C.l. Direct Yellow 98, 0.15 parts C.l. Direct Red 83 and 0.9 parts C.l. Direct Blue 257. A navy blue dyeing with good fastness properties is obtained.

EXAMPLES 3-14 Example 1 is repeated using as the aftertreatment agent one of the fixing agents F2 described in Examples 1-12 of British Patent Application No. 2 070 006A. Not only are wet fastness properties further improved, but an improved crease resistance is obtained.

Claims (10)

1. A two-step single-bath process for the dyeing of a fibrous substrate comprising a mixture of fibres dyeable with basic dyes and hydroxy group-containing fibres, said process comprising a first step of dyeing with a basic dyestuff and a second step of dyeing with a direct dyestuff, the second step being carried out at a temperature which is below the final temperature reached in the first step; and the basic dyestuff used in the first step and the second step temperature being selected such that there is no signifficant migration of the basic dyestuff from the fibres dyeable with basic dyes to the hydroxy group-containing fibres.

2. A process according to Claim 1 in which the fibrous substrate is a blend of polyacrylonitrile and cotton in a weight ratio of from 20:80 to 80:20.

3. A process according to Claim 1 or Claim 2 in which the first step is carried out over a temperature range between 60 and 105"C such that the final temperature is in the range 95-105"C.

4. A process according to any one of the preceding claims in which after completion of the first step the dyebath is cooled to 75 90"C and the second step is carried out at temperatures in the range of 75-90"C.

5. A process according to Claim 4 in which in the first step the mixed fibrous substrate is entered into a dyebath at 50-60"C, adjusted to pH 4-5, and containing one or more basic dyestuffs optionally together with conventional dyeing assistants, the temperature is raised to 95-105"C and dyeing is carried out at this temperature for 50-90 minutes : the bath is then cooled to a temperature in the range of 75-90"C, and in the second step one or more direct dyestuffs is added to the bath, optionally together with conventional dyeing assistants, and dyeing is carried out at this temperature for 50-80 minutes.

6. A process according to any one of the preceding claims in which the dyed substrate is aftertreated either with a fixing agent F1 which is the product of reacting a mono- or polyfunctional primary or secondary amine with cyanamide, dicyanodiamide, guanidine or biguanidine; said product containing reactive hydrogen atoms bound to nitrogen; or with a fixing agent F2 which is the reaction product of fixing agent F, with B) an N-methylol derivative of a urea, melamine, guanamine, triazinone, urone, carbamate or acid amide.

7. A process according to Claim 6 in which fixing agent F, is the reaction product of diethylenetriamine or triethylenetetramine with dicyanodiamide.

8. A process according to Claim 6 in which fixing agent F2 is the product obtained by reacting a) the reaction product of diethylenetriamine or triethylenetetramine with dicyanodiamide with B) a hydrolysis-resistant reactive resin precursor in the presence of C) a catalyst for the cross-linking of N-methylol compounds of the type B) above.

9. A process for the dyeing of a mixed polyacrylonitrile/ cotton substrate, as described in any one of the Examples.

10. A fibrous substrate comprising a mixture of fibres dyeable with basic dyes and hydroxy group-containing fibres, dyed by a process according to any one of Claims 1-9.