Process for dyeing textile materials based on polyamide

Abstract

An improved process for dyeing polyamide without the formation of stripes involves including, in the aqueous dyeing bath, a group of anionic leveling agents, a cationic weak complexing agent, an organic sulfur-containing reducing compound and a detergent and dispersing agent, along with suitable dyestuff.

Description

FIELD OF INVENTION

The present invention relates to dyeing of textiles and, more particularly, to a new process for dyeing textile articles made of polyamide in aqueous medium. The invention produces polyamide textile articles having a perfectly homogeneous and uniform dyeing, free from significant stripe defects.

BACKGROUND

The process according to the invention relates very particularly to a substantial improvement of the productivity of the classical dyeing apparatus, for it permits a great increase of the quantity of textile materials to be dyed, a particularly appreciable reduction of the dyeing times and a decrease in the classically used dyeing temperature.

The difficulties inherent in the dyeing of polyamides in various forms, such as fibers in the flock condition, continuous threads, fiber yarns, fabrics, knit or woven manufactured articles, are well known, these difficulties being apparent in the form of stripes on the fabric, or else heterogeneous shades, which make these textiles unsuitable for sale. For many years there have been suggested numerous dyeing processes in aqueous mediums for these textile materials to reduce, or even to try to eliminate these particularly troublesome strip defects.

Thus, in order to make dyeing of polyamide materials homogeneous, it was first proposed to dye them with acid dyestuffs, acid chrome dyestuffs or else metalliferous dyestuffs in the presence of an anionic leveling compound. The recommended bath temperature was between 90.degree.C. and 130.degree.C., permitting either a dyeing at the boil at atmospheric pressure, or a dyeing in an autoclave under a suitable elevated pressure. Whatever the improvements brought to the removal of this stripe defect, the efficiency of such a process was still greatly insufficient.

It was later recommended to dye polyamide fibers at temperatures lower than the temperatures at which dyestuffs ascend to the textile materials. The dyeing was carried out in an aqueous bath containing, as dyestuff carriers, a low percentage of a mixture of amides coming from monocarboxylic aliphatic acids and primary or secondary amines containing at least a lower hydroxyalkyl group. Moreover, such a mixture contained anionic dispersants and an agent for swelling the fibers. Although a more homogeneous shade was provided by this operation, the stripe defect was, however, latent, for it was reduced without being effectively removed (French Pat. No. 1,522,041).

Other processes have also been suggested, including those proposing new combinations of known means. French Pat. No. 1,185,750 discloses a process for dyeing polyamide textile materials at a temperature of at least 100.degree.C., in an acidified bath containing one or several suitable dyestuffs, an anionic leveling agent and a cationic weak complexing agent, which does not precipitate in the presence of the anionic components of the bath. This process allows one to obtain homogeneous dyeings, with good fastness, but such process does not ensure complete elimination of the stripe defect.

It has been recommended to improve this latter dyeing process by introducing a reducing agent containing sulfur in its composition; this process limits polyamide yellowing, an oxidation phenomenon resulting from the aqueous treatment at a high temperature. Thus, fading of the colors by this yellowing and degradation of dyed material were thereby avoided (French Pat. No. 1,313,937). This last improvement has indeed provided better results than those previously obtained, but it was once again noted that the stripe defect, though lessened, was persistent.

SUMMARY

In view of the main before-mentioned drawback and of the impossibility of obtaining polyamide textile materials free from stripes after dyeing, it is an object of the present invention to overcome the drawbacks of the prior art to eliminate the stripe defect, to provide better dyed polyamides, and to provide an improved polyamide dyeing procedure.

Accordingly, a new process for dyeing polyamide textile articles is provided which results in excellent dyeing homogeneity, which inevitably removes the stripe defect and which increases the productivity of the dyeing apparatus in very large proportions.

The process according to the present invention involves dyeing polyamide textile materials at suitable temperature and acidity, in an aqueous bath containing, in addition to the suitable dyestuff(s):

a. a group of anionic leveling agents;

b. a cationic weak complexing agent;

c. an organic sulfur-containing compound, with a reducing action, which compound prevents a decrease of the mechanical qualities, a yellowing and/or a hardening of the textile material during the treatment;

d. a detergent and dispersing agent, which agent avoids the separation or the flocculation of the bath, and promotes a better circulation of the bath through the textile material.

For a better understanding of the invention, possible embodiments thereof will now be described, it being understood that these embodiments are intended as merely exemplary and in no way limitative.

DETAILED DESCRIPTION

In accordance with the present invention one obtains dyed polyamide textile materials having a very homogeneous shade on which the stripe defect is not apparent, and a suitable shade level, the process being carried out at a temperature lower than 100.degree.C. By combination of various elements, including the utilization of important adjuvants in the dyeing bath, the present invention provides a synergistic effect so as to obtain, for the first time, an operation which not only provides an eminently satisfactorily dyed polyamide textile, but a process which is highly efficient from a cost standpoint. Besides the use of lower than normal temperatures, conventional dyestuffs and a particular pH profile over given temperature values, the process utilizes a dyeing bath which contains in combination at least two anionic leveling agents, a cationic weak complexing agent, an organic sulfur-containing reducing compound, and a detergent and dispersing agent.

The group of anionic leveling agents comprises at least two components which possess the capability of temporarily fixing on the active dye sites of the textile materials, thus preventing the dyestuffs from too quickly taking up the sites which are ultimately meant for them.

The first anionic leveling agent B.sub.1 has the formula: R (A).sub.n R', in which R and R' are sulfonated benzene or naphthalene rings the same or different; A is a radical selected from CH.sub.2, SO.sub.2 or NH; and n is an integer from 0 to 4. For instance, a preferred material is sodium .alpha. .alpha.' di-naphthylmethane-.beta. .beta.' disulfonate.

The second anionic leveling agent B.sub.2 is a salt of an organic acid of the alkyl-aryl-sulfonic type, or else a polyalkylaryl sulfonic acid salt, in which the aryl radical is a benzene or naphthalene ring, the neutralizing ion being selected from the group consisting of an alkali metal, NH.sub.4 ion or an amine, such as for instance ammonium dodecylbenzene sulfonate, or sodium tetrapropylbenzene sulfonate, etc.

The cationic weak complexing agent is generally a product resulting from the condensation of ethylene oxide on an aromatic amine or else on a long-chain fatty amine, such as for instance the stearylamine oxyethylated with 8 moles of ethylene oxide. Its function is to temporarily complex the dyestuffs in the dyeing bath, and thus the equilibrium of the complex must be capable of being destroyed by an increase in the bath temperature, and the freed dyestuffs can thus slowly replace the anionic leveling agents on the dye active sites of the textile materials.

The sulfur-containing organic compound, which is known to be an active reducing agent in the treatments of polyamide textile articles, is preferably thio-urea or a derivative thereof with an N-alkyl substituted, such as N-mono-methyl thio-urea. The sulfur-containing organic compound may be selected from known compounds for this purpose (e.g. French Pat. No. 1,313,937).

The detergent and dispersing agent, which keeps the dyeing bath in a homogeneous state and makes easier the penetration and the circulation of the bath inside the textile materials during the treatment, is a mixture of C.sub.8 to C.sub.20 fatty alcohols, which are oxyethylated and sulfated, such as for instance ethoxylated and sulfated stearylic alcohol.

The various before-mentioned agents used in the process of the invention are introduced in the dyeing bath in proportions expressed in weight of dry material per volume unit of bath. For instance the anionic leveling agent belonging to the group B.sub.1 is introduced in a quantity from 0.10 g/liter to 1.50 g/liter of bath in such a way that the said agent is present in the bath in a proportion from 1.5 to 2 percent of the weight of textile materials to be dyed.

Likewise the proportions of the anionic leveling agent belonging to the group B.sub.2 may vary advantageously from 0.15 g/liter to 2 g/liter, but are preferably chosen from 0.25 g/liter to 0.50 g/liter of bath. The cationic weak complexing agent is used in quantities varying from 0.10 g/liter to 1.50 g/liter of bath. The sulfur-containing organic compound is used in very low quantities, varying from 0.0045 g/liter to 0.06 g/liter of bath, and the detergent and dispersing agent is added to the bath in quantities varying from 0.25 g/liter and 1 g/liter of bath.

The temperature during dyeing is at least 80.degree.C. and at most 130.degree.C. However, it is preferably between 85.degree.C. and 100.degree.C., i.e., at a temperature which remains, practically, considerably lower than the temperature recommended in the processes of the prior art. In addition to the fact that the dyeing temperature is lower, the rate of the bath temperature increase may be quickened, this obtaining dyeing qualities never reached till now.

The acidic conditions of the bath are equally important. It is very easy, thanks to the present process, to adjust the acidity conditions according to the various stages of the increase of the bath temperature the pH is between 7 and 8 when the temperature is lower than 80.degree.C., then it is lowered to between 3 and 7 when the temperature reaches the adequate value for dyeing, that is to say when the temperature is preferably between 80.degree.C. and 100.degree.C.

The process according to the invention is advantageously carried on according to the following mode: After dissolution in water at room temperature of the various above-described agents, according to the preferred proportions, the resultant bath is introduced in the dyeing vat, which has been previously fitted with the textile materials. The bath pH is then adjusted to a neutral or slightly basic value, either by introduction of an organic acid usually used, such as acetic acid, or by an alkaline agent normally used in this field.

The treatment of the textile begins at room temperature, then the bath is gradually heated at a rate of temperature increasing preferably between 0.5.degree.C. and 4.degree.C. per minute to the desired intermediate temperature, such as 40.degree.C. under normal pressure. It is during this first period of time that the temporary fixation of the anionic leveling agents on the dye active sites of the textile materials is carried out.

At the end of this first stage, the dyestuffs, which have been dissolved in a given quantity of water, are introduced into the bath in which the textile materials are residing. The dyestuffs are then sequestered by the weak cationic complexing agent, which prevents them from ascending onto the textile materials quickly and in an irregular way. The bath ratio can advantageously vary from 1/4 to 1/50 by volume. The dyestuffs are selected from the conventional group consisting of simple acid dyestuffs and soluble or dispersed metalliferous dyestuffs normally used for dyeing polyamides.

At the conclusion of introducing the dyeing solution into the bath, the bath is then gradually heated from the intermediate temperature to the dyeing temperature of 85.degree.C.-90.degree.C., according to a rate varying from 0.5.degree.C. to 4.degree.C. per minute, but preferably from 0.8.degree.C. to 1.2.degree.C. per minute. This dyeing temperature is then maintained for about 15 minutes.

Due to the increasing of the bath temperature for the intermediate value to the dyeing temperature, the complex which retains the dyestuffs is destroyed and the dyestuffs are thus freed to come to the active dye sites of the textile materials by taking the place of the anionic leveling agents.

The pH of the dyeing bath is then lowered to a value between 3 and 7 in acidity scale, by introducing any conventionally used acid, preferably an organic acid, in one bath, but preferably in several batches, the introduction time of the acid varying from 15 to 60 minutes according to the type of acidic dyestuffs used. Whereas, in the processes described in the prior art, the necessary quantity of acid was introduced at the beginning of the dyeing operation, in the present process the acid is gradually and fractionally added during the above described later stage of the operation.

After addition of the acid, the circulation of the dyeing bath is maintained for 15 to 60 minutes, then it is cooled and discharged, and the dyed textile materials are then washed.

The total duration of dyeing is established according to the degree of dyestuff exhaustion from the bath, this exhaustion being measured by the coloration of a sample taken out of the bath. Likewise the rate of the increase of the bath temperature can be determined with respect to samplings systematically achieved during dyeing, the colorations of which are evaluated by the colorimeter.

The process of dyeing according to the invention can be applied to continuous or discontinuous polyamide fibers in various forms such as flock, ribbons, finished clothes, cards, bobbins, hanks, fabrics and so on. It is equally carried out on woven, knitted, and non-woven textile materials, which are rolled on a perforated roller, enabling the circulation of the dyeing bath through such fabrics, or which are placed in bundles either in an apparatus for dyeing with circulation, or in a rotative perforated drum. The process is normally applied to materials containing either all nylon fibers or sufficient nylon fibers with other fibers such that the problem of striping normally occurs.

The process for dyeing according to the invention can be effected in any vat commonly used and adapted to the textile materials to be dyed, fitted with the heating and cooling elements necessary for the various operation, as with the apparatus for control and thermal regulation. Among the known apparatus can be mentioned drum machines, paddle machines, becks for fabrics or yarns, special machines for dyeing of textured jerseys, autoclaves, etc.

The following examples illustrate the application of the process to the dyeing of polyamide textile materials without limitating the scope of the invention.

EXAMPLE 1

So as to show the synergy brought about in the present process, several dyeing tests were achieved on polyamide textile materials based on polyamide.

These tests were carried out each time with a warp and weft fabric web of continuous polyamide 66 yarn, the weight of which was 350 kg and the length of which about 3,500 m, this web being effected by stripes when dyed according to usual processes.

The dyeing conditions, applied in each test, were the following:

The dyeing was made in a three-color dyeing, and the used quantity of dyestuff was expressed in weight in relation to the polyamide weight.

______________________________________ C.I. Orange Acid 3 1 % C.I. Red Acid 57 0.6 % C.I. Blue Acid 72 1 % ______________________________________

The dyeing apparatus was an autoclave with a bath circulation by means of a pump. The differential pressure of utilization was 2 bars, measuring the pressure drop during the passage of the dyeing bath through the fabric, and the bath ratio was 1/15 by volume.

Dyeing began at 20.degree.C. in the presence of the various agents as indicated below, then the bath was gradually heated 10 minutes to reach 40.degree.C; at this temperature the dyestuffs were introduced, and the bath pH was 7. Then the temperature was brought to 90.degree.C. after 60 minutes of further heating, kept at this value for 45 minutes, during which the pH of the dyeing bath was rapidly brought to 4 by additions in progressive quantities of acetic acid. The bath was then cooled and its concentration was maintained for 15 minutes; then the bath was discharged, and the dyed textile material was washed, then dried.

The above-mentioned conditions were systematically reproduced in the tests, the results of which are indicated hereinafter.

COMPARATIVE TEST 1--1

Tests of dyeing at a temperature lower than 100.degree.C. with only one anionic leveling agent, a cationic weak complexing agent and an organic sulfur-containing compound (leveling agent B.sub.2 and detergent and dispersant agent omitted).

The proportions of the various agents in the dyeing bath were the following:

anionic leveling agent from 0.20 g/liter sodium dinaphthyl methane : to disulfonate 1.25 g/liter cationic weak complexing agent from 0.20 g/liter (stearylamine oxyethylated with : to 8 moles of ethylene oxide) 1.25 g/liter organic sulfur-containing from 0.01 g/liter compound (thio-urea) : to 0.05 g/liter.

Though the proportions of the various agents were increased, the warp and weft polyamide 66 fabrics were badly plain and striped, but the shade was satisfactory.

COMPARATIVE TEST 1-2

Tests of dyeing at a temperature lower than 100.degree.C. with two anionic leveling agents, a weak cationic complexing agent and an organic sulfur-containing compound (detergent and dispersing agent omitted).

The proportions of the various agents in the dyeing bath were varied between the following values.

first anionic leveling agent (sodium dinaphthylmethane : 0.20 g/liter to disulfonate) 1.25 g/liter second anionic leveling agent (ammonium dodecylbenzene sulfonate) : 0.20 g/liter to 1.80 g/liter cationic complexing agent (stearylamine oxyethylated with 8 : 0.20 g/liter to moles of ethylene oxide) 1.25 g/liter organic sulfur-containing compound (thio-urea) : 0.01 g/liter to

The warp and weft polyamide 66 fabrics still presented a lack of leveling with visible stripes, but the level of shade was satisfactory.

COMPARATIVE TEST 1-3

Tests of dyeing at a temperature lower than 100.degree.C. with only one anionic leveling agent, a cationic weak complexing agent, an organic compound and a detergent and dispersing agent (leveling agent B.sub.2 omitted).

The proportions of the various agents in the dyeing bath were between the following values:

anionic leveling agent 0.20 g/liter to (sodium dinaphthylmethanedi- : 1.25 g/liter sulfonate) cationic weak complexing agent 0.20 g/liter to (stearylamine oxyethylated with : 1.25 g/liter 8 moles of ethylene oxide) organic sulfur-containing compound : 0.01 g/liter to (thio-urea) 0.05 g/liter detergent and dispersing agent 0.25 g/liter to (mixture of fatty alcohols with : 1 g/liter 8 to 20 C. atms. oxyethylated and sulfated)

The warp and weft polyamide 66 fabrics presented an excellent shade, as well as a very satisfactory level of shade, but there were numerous and significant stripes.

EXAMPLE TEST 1-4

Tests of dyeing at a temperature lower than 100.degree.C. with two anionic leveling agents, a weak cationic complexing agent, an organic sulfur-containing compound and a detergent and dispersing agent.

The proportions of the various agents in the dyeing bath were between the following values:

first anionic leveling agent 0.20 g/liter to (sodium dinaphthylmethane : 1.25 g/liter disulfonate) second anionic leveling agent 0.20 g/liter to (ammonium dodecylbenzene : 1.80 g/liter sulfonate) weak cationic complexing agent (stearylamine oxyethylated with 0.20 g/liter to 8 moles of ethylene oxide) : 1.25 g/liter organic sulfur-containing : 0.01 g/liter to compound (thio-urea) 0.05 g/liter detergent and dispersing agent 0.25 g/liter to (mixture of fatty alcohols with : 1.25 g/liter 8 to 20 C. oxyethylated and sulfated)

The warp and weft fabrics made of polyamide 66 showed an excellent shade, a perfect leveling, and the absence of the stripe defect was particularly noticeable.

EXAMPLE 2

A fabric web made of polyamide 6, without torsion in warp and weft, having a weight of 180 kg. and a length of 2,000 m was dyed. The used autoclave was an apparatus having a volume of 900 liters, fitted with a circulation pump of 17 C.V. The web was rolled on a roller.

The bath ratio was 1/5, compared with conventional bath ratios from 1/10 to 1/15. The dyeing composition expressed in percent of dyestuffs related to the textile material to be dyed was the following:

brown Telon BST (Bayer) 2.5 % C.I. Orange Acid 67 0.360 % C.I. Orange Acid 51 0.085 %

The aqueous bath for dyeing contained the various agents according to the invention in the following proportions:

sodium dinaphthylmethane disulfonate : 0.95 g/liter ammonium dodecylbenzene sulfonate : 0.25 g/liter stearylamine oxyethylated with 8 moles of ethylene oxide : 0.95 g/liter thio-urea : 0.02 g/liter mixture of fatty alcohols in C.sub.8 .sub.- 20 oxyethylated and sulfated : 0.5 g/liter

The dyeing bath was quickly heated from room temperature to 40.degree.C. in 10 minutes. Then the dyestuffs were introduced into said bath at this temperature. The dyeing bath was then heated to 90.degree.C. in about 60 minutes, then kept at this temperature for 15 minutes. At this moment the dyeing bath was acidified by adding every 5 minutes first 200 ml. of acetic acid, then 400 ml., 1,000 ml. and at last 1,000 ml. of this same acid. The normal bath exhaustion was noted, after the concentration of the dyeing bath had been maintained for 15 minutes. The bath was then discharged, the material washed with water, and then dried.

When it was out of the autoclave, the fabric had an excellent shade and a perfect level absorption and it was free from the main stripe defect.

A sample of the same web, being 1,500 m long only, was dyed in the same autoclave and under identical working conditions, but in the absence of the second anionic leveling agent and of the detergent and dispersing agent. The thus dyed sample had a correct shade, but was badly plain and presented significant stripe defects.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is described in the specification.

Claims

What is claimed is:

1. A process for dyeing polyamide textile materials comprising:

forming an aqueous bath containing an admixture consisting essentially of 0.10 to 1.50 grams/liter of said bath of a first anionic leveling agent of the formula R A.sub.n R', in which R and R' are sulfonated benzene or naphthylene rings, A is CH.sub.2, SO.sub.2 or NH and n is an integer from 0 to 4; 0.15 to 2.0 grams/liter of said bath of a second anionic leveling agent of a salt of an organic acid of the alkylaryl-sulfonic type or the polyalkyl-aryl-sulfonic type; 0.10 to 1.5 grams/liter of said bath of a cationic weak complexing agent capable of sequestering polyamide dyestuffs at low temperatures; 0.0045 to 0.06 grams/liter of said bath of an organic sulfur-containing compound having a reducing activity; and 0.25 to 1.0 grams/liter of said bath of a detergent and dispersing agent capable of maintaining the aqueous bath in an homogeneous condition;

contacting said polyamide textile material with said aqueous bath at a neutral or slightly basic pH and at approximately room temperature;

heating said aqueous bath at a rate between 0.5.degree.C. and 4.degree.C. per minute to an intermediate selected temperature to effect temporary fixation of the anionic leveling agents on the dye active sites of said polyamide textile material;

adding at least one acid or soluble or dispersed metalliferous dyestuff normally used for dyeing polyamides to said aqueous bath, said dyestuff becoming sequestered at said temperature by the weak cationic complexing agent;

gradually heating said aqueous bath from said intermediate temperature to a dyeing temperature no greater than 130.degree.C. at a rate between 0.5.degree.C. and 4.degree.C. per minute, said increasing temperature serving to destroy the complex which retains the dyestuff and also serving to de-fix the anionic leveling agents from the dye active sites on the polyamide textile material;

lowering the pH of the aqueous bath to between 3 and 7 and maintaining said elevated dyeing temperature and said pH for about 15 to 60 minutes; and

removing the dyed textile material.

2. A process in accordance with claim 1 wherein said first anionic leveling agent is sodium .alpha.,.alpha. ' dinaphthyl methane-.beta. ,.beta.' disulfonate; said second anionic leveling agent is ammonium dodecylbenzene sulfonate or sodium tetrapropylbenzene sulfonate.

3. A process in accordance with claim 1 wherein said second anionic leveling agent salt of an alkyl aryl sulfonic or polyalkyl aryl sulfonic acid has a neutralizing ion selected from the group consisting of the alkali metals, ammonium or an amine.

4. A process in accordance with claim 1 wherein said cationic weak complexing agent is a condensation product of ethylene oxide on an aromatic amine or a long chain fatty amine.

5. A process according to claim 4 wherein said weak cationic complexing agent is stearyl amine oxyethylated with 8 moles of ethylene oxide.

6. A process in accordance with claim 1 wherein said organic sulfur containing compound is thiourea or an n-alkyl derivative thereof.

7. A process in accordance with claim 1 wherein said detergent and dispersing agent is an ethoxylated and sulfated mixture of fatty alcohols containing 8 to 20 carbon atoms.

8. A process in accordance with claim 1 wherein said second anionic leveling agent is present in an amount between 0.25 and 0.50 grams/liter of said bath.

9. A process in accordance with claim 1 wherein said final dyeing temperature is between 85.degree. and 100.degree.C.

10. A process in accordance with claim 1 wherein said process is carried out under normal pressure and said intermediate temperature is about 40.degree.C.