U.S. patent number 3,929,408 [Application Number 05/420,975] was granted by the patent office on 1975-12-30 for process for dyeing textile materials based on polyamide.
This patent grant is currently assigned to Soprosoie. Invention is credited to Jean-Bernard Chaux, Georges Ravet.
United States Patent |
3,929,408 |
Ravet , et al. |
December 30, 1975 |
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.
Inventors: |
Ravet; Georges (Champagne au
Mont d'Or, FR), Chaux; Jean-Bernard (Tassin la
Demi-Lune, FR) |
Assignee: |
Soprosoie (Courbevoie,
FR)
|
Family
ID: |
9108514 |
Appl.
No.: |
05/420,975 |
Filed: |
December 3, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Dec 6, 1972 [FR] |
|
|
72.44078 |
|
Current U.S.
Class: |
8/585; 8/602;
8/589; 8/924 |
Current CPC
Class: |
D06P
1/625 (20130101); D06P 1/6076 (20130101); D06P
1/628 (20130101); D06P 1/0096 (20130101); D06P
1/60 (20130101); D06P 1/96 (20130101); D06P
1/6491 (20130101); D06P 1/622 (20130101); D06P
1/613 (20130101); Y10S 8/924 (20130101) |
Current International
Class: |
D06P
1/44 (20060101); D06P 1/60 (20060101); D06P
1/607 (20060101); D06P 1/00 (20060101); D06P
1/649 (20060101); D06P 1/96 (20060101); D06P
1/64 (20060101); D06P 1/613 (20060101); D06P
1/62 (20060101); D06P 005/04 () |
Field of
Search: |
;8/169,173,178R,41B |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3232695 |
January 1966 |
Robin et al. |
3478376 |
November 1969 |
Daeuble et al. |
|
Primary Examiner: Jacobs; Lewis T.
Attorney, Agent or Firm: Browdy and Neimark
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.
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.
* * * * *