U.S. patent application number 10/889209 was filed with the patent office on 2005-01-20 for production of cotton warp yarns having inverse denim effect.
This patent application is currently assigned to DyStar Textilfarben GmbH & Co. Deutschland KG. Invention is credited to Bock, Alexander, Schrott, Wolfgang, Sutsch, Franz.
Application Number | 20050011013 10/889209 |
Document ID | / |
Family ID | 33461942 |
Filed Date | 2005-01-20 |
United States Patent
Application |
20050011013 |
Kind Code |
A1 |
Schrott, Wolfgang ; et
al. |
January 20, 2005 |
Production of cotton warp yarns having inverse denim effect
Abstract
The present invention relates to a process for producing cotton
warp yarns having an inverse denim effect, which comprises using an
indigo dyeing range to perform a dyeing step whereby the cotton
warp yarn is through-dyed with indigo in one pass at a dyeing
temperature of 30 to 90.degree. C. and an indigo concentration of
5-500 g/l and a subsequent bleaching step whereby the indigo is
selectively decolorized on the surface of the cotton warp yarn.
Inventors: |
Schrott, Wolfgang;
(Ludwigshafen, DE) ; Sutsch, Franz;
(Rodersheim-Gronau, DE) ; Bock, Alexander;
(Darmstadt, DE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ, LLP
P O BOX 2207
WILMINGTON
DE
19899
US
|
Assignee: |
DyStar Textilfarben GmbH & Co.
Deutschland KG
Frankfurt am Main
DE
|
Family ID: |
33461942 |
Appl. No.: |
10/889209 |
Filed: |
July 12, 2004 |
Current U.S.
Class: |
8/115.51 |
Current CPC
Class: |
D06P 5/153 20130101;
D06P 1/22 20130101; D06P 5/155 20130101; D06P 5/156 20130101 |
Class at
Publication: |
008/115.51 |
International
Class: |
D06M 010/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2003 |
DE |
DE 103 32 164.0 |
Claims
1. A process for producing cotton warp yarns having an inverse
denim effect, which comprises using an indigo dyeing range to
perform a dyeing step whereby the cotton warp yarn is through-dyed
with indigo in one pass at a dyeing temperature of 30 to 90.degree.
C. and an indigo concentration of 5-500 g/l and a subsequent
bleaching step whereby the indigo is selectively decolorized on the
surface of the cotton warp yarn.
2. A process according to claim 1 that utilizes indigo in the form
of a solution of leuco indigo.
3. A process according to claim 2, wherein the leuco indigo has
been produced from indigo by catalytic hydrogenation.
4. A process according to claim 1 wherein the process is further
carried out in the presence of a wetting agent.
5. A process according to claim 4, wherein the wetting agent is
used in amounts of 5 to 50 g/l.
6. A process according to claim 1, wherein the bleaching step is
effected by means of a bleaching bath which contains potassium
permanganate as bleaching agent.
7. A process according to claim 1, wherein the bleaching step is
effected by means of a bleaching bath which contains a
thickener.
8. A process according to claim 1, wherein the through-dyeing of
the cotton warp yarn in the dyeing step is followed by rinsing with
water, bleaching with permanganate, another rinse and a subsequent
treatment with a bisulfite solution and the cycle of bleaching,
rinsing and treating with bisulfite is repeated at least once.
9. A process according to claim 1, wherein the bleaching step is
followed by a third step whereby the cotton warp yarn surface
decolorized in the bleaching step is treated with a pigment
suitable for cotton.
10. A textile article comprising cotton warp yarns dyed by a
process according to claim 1.
11. A process according to claim 3, wherein the process is further
carried out in the presence of a wetting agent.
12. A process according to claim 11, wherein the wetting agent is
used in amounts of 10 to 25 g/l.
13. A process according to claim 1, wherein said indigo
concentration is 10-50 g/l.
14. A process according to claim 1, wherein said indigo is a
pre-reduced indigo.
15. A process according to claim 14, wherein the pre-reduced indigo
is produced from an indigo without the use of a reducing agent.
16. A process according to claim 2, wherein the temperature is from
50 to 70.degree. C.
17. A process according to claim 1, wherein the dyeing is conducted
at a pH from 10.5 to 13.5.
18. A process according to claim 12, wherein the wetting agent is
fatty alcohol ethoxylate, alkanesulfonate, sulfonsuccinate, alkyl
phosphate, paraffin, hydrocarbon or mixtures thereof.
19. A process according to claim 12, wherein the wetting agent is a
salt of phosphoric esters.
20. A process according to claim 6, wherein said potassium
permanganate is used in an amount from 20 to 50 g/l.
Description
[0001] The present invention concerns a process for producing
indigo-dyed cotton warp yarns which have an inverse denim effect
and also textile articles comprising such cotton warp yarns.
[0002] Denim refers to a relatively coarse woven cotton fabric
which was originally used for robust workwear, but today is used
particularly for manufacturing fashionable jeans articles. The warp
yarns needed to produce denim can be dyed with indigo or else with
sulfur dyes, especially sulfur black, although dyeing to blue with
indigo is greatly predominant.
[0003] Traditionally, the warp yarn is dyed with indigo as a rope
or as a warp yarn sheet on specific dyeing ranges which consist of
a combination of one or more troughs with squeeze rolls and a
subsequent skying sector. The reduced dye is applied in the troughs
and oxidized in the skying sector (see for example Technical
Information TI/T 017 d from BASF AG dated June 1995, title:
Continuous dyeing with indigo).
[0004] The dyeing is typically carried out in a dyebath at room
temperature or slightly elevated temperatures of about
20-35.degree. C., a pH of about 10.5 to 14 and an indigo
concentration of about 0.5 to 10 g/l. Wetting agents in a
concentration of about 0.1 to 5 g/l can be used as well. A redox
potential in the dyebath is maintained by using an excess of
hydrosulfite reducing agent in amounts of about 0.1 to 5 g/l. The
yarn contact time with the dyebath is generally 8 to 30 seconds per
pass. Dyeing in multiple passes, i.e., the repeated application of
dye from the dyebath by dipping with subsequent squeezeoff in the
dyeing trough and the following skying, makes it possible to
achieve deeper shades (see for example ITB Veredlung 2/90, title:
Indigo-Frberei: Verfahrens-und maschinentechnische Losungen,
author: Dipl. Ing. L. Haas).
[0005] German Patent Application DE 196 29 985 describes
single-pass dyeing wherein, to overcome the low affinity of indigo,
the dyebath additionally has added to it salt in the form of sodium
chloride in order that an electrolyte concentration of 200 to 350
g/l may be set.
[0006] These processes all produce a so-called ring dyeing, i.e.,
the fiber is dyed at the surface only, leaving the interior of the
fiber, the core, undyed. Ring dyeing makes it possible to endow
made-up denim articles with a high-contrast appearance in
particular washing and/or bleaching processes through a wash-down
of the initially dark blue fabric. An example is the familiar
stone-wash effect, which is achieved by washing the made-up article
with enzymes and pumice stones.
[0007] However, jeans fashion is now demanding articles which no
longer exhibit this wash-down effect or modifications achieved
utilizing this effect. On the contrary, the demand is for articles
which turn darker in washing or other treatment operations rather
than lighter. These articles are so to speak to behave inversely to
conventionally dyed denim.
[0008] Prior art ring-dyed denim cannot provide such effects.
[0009] There is consequently a need for a process for producing
inverse denim that shall be economical in that it should not
require additional cost and an inconvenience on the part of dyers,
but should be simple to carry out, ideally in dyers' existing
dyeing equipment.
[0010] The present invention, then, provides such a process.
[0011] The present invention relates to a process for producing
cotton warp yarns having an inverse denim effect, which comprises
using an indigo dyeing range to perform
[0012] a dyeing step whereby the cotton warp yarn is through-dyed
with indigo in one pass at a dyeing temperature of 30 to 90.degree.
C. and an indigo concentration of 5-500 g/l and
[0013] a subsequent bleaching step or etching step, etching here to
be understood as meaning a treatment of a dyed surface wherein the
dye is locally destroyed, as described by M. Peter, H. K. Rouette
in "Grundlagen der Textilveredlung" page 633 et seq., whereby the
indigo is selectively decolorized on the surface of the cotton warp
yarn. This selective decolorization can in principle be carried out
oxidatively or reductively, oxidative decolorization being
preferred.
[0014] The process of the invention thus ideally provides a
colorless product which can be modified to be dark blue by removing
the colorless ring and laying the colored core bare.
[0015] An indigo dyeing range in the realm of the present invention
is a range which consists of one dyeing trough or a combination of
multiple dyeing troughs with squeeze rolls and subsequent skying
sectors (see for example ITB Veredlung 2/90, title: Indigo-Frberei:
Verfahrens-und maschinentechnische Losungen, author: Dipl. Ing. L.
Haas).
[0016] Any commercially available indigo may be used. Indigo is
preferably used in amounts of 10-50 g/l and more preferably in
amounts of 20 to 40 g/l.
[0017] It is particularly advantageous to use pre-reduced indigo to
carry out the process of the invention. The pre-reduced indigo used
is ideally produced from indigo without use of reducing agent, such
as sodium dithionite for example, but by catalytic hydrogenation.
It is most advantageous to use indigo in the form of a leuco indigo
solution as described for example in EP 1 097 184 B1 and offered on
the market by DyStar Textilfarben GmbH & Co. Deutschland
KG.
[0018] To stabilize leuco indigo, i.e., to back-reduce leuco indigo
which has become oxidized in the dyebath, it is preferable to use a
hydrosulfite excess of 0.1 to 5 g/l and more preferably 0.2 to 2
g/l. It will be appreciated that in lieu of the hydrosulfite it is
possible to use other suitable reducing agents, for example glucose
or hydroxyacetone, or else combinations of various reducing agents
such as glucose/hydrosulfite.
[0019] The temperature at which the process of the invention is
carried out is preferably 30-90.degree. C. and more preferably in
the range from 50 to 70.degree. C.
[0020] The process of the invention can be carried out with or
without wetting agent, but preferably it is carried out in the
presence of a wetting agent. Examples of suitable wetting agents
are anionic wetting agents, for example fatty alcohol ethoxylate,
alkanesulfonate, sulfosuccinate, alkyl phosphate or paraffins and
hydrocarbons or else mixtures thereof, and most preference is given
to using salts of phosphoric esters. The amounts in which the
wetting agents mentioned are used are preferably in the range from
5 to 50 g/l and more preferably in the range from 10 to 25 g/l.
[0021] Dyebath pH in the process of the invention is preferably in
the range from 10.5 to 13.5.
[0022] The process of the invention surprisingly leads in just one
pass to yarns which are through-dyed, i.e., dyed in the core as
well in the surface region. The contact time with the dyebath is
preferably 8 to 30 seconds and more preferably 15 to 20 seconds.
The subsequent skying takes preferably 90 to 130 seconds and more
preferably 100 to 110 seconds.
[0023] The dyeing step is followed by a bleaching step wherein the
indigo is selectively decolorized on the surface of the cotton warp
yarn, leaving the core of the yarn unchanged.
[0024] Useful bleaching agents include all systems which oxidize
indigo, for example hypochlorites, such as sodium hypochlorite or
permanganate. But preference is given in particular to
permanganate, which exists for example in the form of an alkali
metal salt and more preferably in the form of potassium
permanganate. Very particular preference is given to a bleaching
bath which contains potassium permanganate in an alkaline medium,
the potassium permanganate being used in amounts which are
preferably from 5 to 100 g/l and more preferably from 20 to 50
g/l.
[0025] The pH is preferably in the range from 8 to 10 and can be
set for example with NaOH, for example with 38.degree. B NaOH.
[0026] It is preferable to adjust the bleaching bath to a viscosity
of about 12 to 50 seconds measured using a Ford cup (DIN 53211-4)
and more preferably 25 to 45 seconds by means of viscosity
moderators. Useful viscosity moderators include for example
rheological additives such as: polyvinylcaprolactam,
polyvinylpyrrolidone and also copolymers thereof, polyetherpolyol,
associative thickeners, polyurea, polyurethane, sodium alginates,
modified galactomannans, polyetherurea, polyurethane, nonionic
cellulose ethers.
[0027] The bleaching step is carried out at 15 to 90.degree. C. and
preferably at room temperature. The contact time with the bleaching
bath is preferably 10 to 30 seconds and more preferably 12 to 20
seconds.
[0028] In a preferred embodiment of the process according to the
invention, the through-dyeing of the cotton warp yarn in the dyeing
step is followed by rinsing with water, bleaching with
permanganate, another rinse and a subsequent treatment with a
bisulfite solution and the cycle of bleaching, rinsing and treating
with bisulfite is repeated at least once.
[0029] It is particularly advantageous for there to be four to six
cycles of bleaching, rinsing and treating with bisulfite.
[0030] An intervening drying between dyeing step and bleaching can
be used to further enhance the ring effect achieved by the
bleaching.
[0031] The rinsing between bleaching bath and bisulfite bath can be
carried out in 1 to 3 passes and be associated with a skying of 0
to 120 seconds.
[0032] The bisulfite bath preferably contains 10 to 100 g/l and
more preferably 20 to 50 g/l of bisulfite. The bisulfite bath can
likewise be followed by a skying of 0 to 120 seconds.
[0033] It is a particular advantage to dyers that the dyeing step
of the process according to the invention is complete after just
one pass. This is because this leaves dyers with the option of
using the other dyeing troughs of the indigo dyeing range which are
not needed for dyeing to carry out the subsequent bleaching step
with or without rinsing and with or without bisulfite treatment.
Thus, the equipment needs to be modified only minimally, if at
all.
[0034] The cotton warp yarns dyed by the process of the invention
can be subjected to further treatment steps to obtain certain
effects and then be conventionally woven up and processed into
textile articles for the consumer, such as garments in
particular.
[0035] However, it is also possible for the dyed and
surface-bleached cotton warp yarns to be processed into textile
articles without further treatment and, if desired, only then to
undertake further treatment steps, i.e., to modify the already
made-up merchandise. It is of course similarly possible to subject
not only the dyed and bleached cotton warp yarns but also the
textile articles produced therefrom to further treatment steps.
[0036] The cotton warp yarns dyed by the process of the invention
can of course also be woven up, and further processed into articles
for the consumer, in admixture with further materials. Blends with
elastane may be mentioned by way of example.
[0037] The inverse denim effect of the cotton warp yarns dyed and
bleached according to the invention can be made visible, for
example, by removing the undyed outer ring of the yarn through
washing or some other mechanical stressor and the dark-dyed core
coming to light as a result.
[0038] In a further implementation of the process according to the
invention, the cotton warp yarn surface decolorized in the
bleaching step is stabilized in a third step. Thus, the inverse
denim effect can be reinforced by treating the surface with for
example TiO.sub.2 in the presence of binders, such as acrylate
copolymer or polyurethane. In the same way, the surface can be
modified not just to be white but also to be colored, for example
with colored pigments, such as vat dyes in pigment form, or else
disperse dyes.
[0039] It is of course also possible for the third step mentioned
not to be carried out until after the cotton warp yarn has been
woven up, for example on the final made-up textile product.
[0040] The present invention also provides textile articles
comprising cotton warp yarns dyed by the process of the invention.
Examples of such textile articles are denim fabrics which have not
been made up, but in particular garments such as pants, skirts,
shirts, jackets, etc. or other textile type articles.
[0041] The examples which follow illustrate the invention. The
parts in the table examples are by weight.
EXAMPLE 1
[0042] A) Dyeing Step
[0043] A commercially available unpretreated dry cotton warp yarn
was dyed from a dyeing liquor of the following composition:
[0044] 20 g/l of indigo as commercially available DyStar Indigo Vat
40% solution
[0045] 2 g/l of hydrosulfite (BASF Hydrosulfit konz.)
[0046] 20 g/l of wetting agent (Primasol NF)
[0047] The pH of the liquor was 13.
[0048] The yarn was dyed at 50.degree. C. in the course of a dip
time of 25 seconds. The subsequent skying took 120 seconds.
[0049] This was followed by two rinses with water at 20.degree.
C.
[0050] A through-dyed yarn having a high level of applied indigo
was obtained. A dye analysis of the dyed yarn revealed a level of
5.8%.
[0051] B) Bleaching Step
[0052] The dyed yarn obtained as per A) was dyed with potassium
permanganate (20 g/l) at a temperature of 25.degree. C. and a pH of
8.5. The contact time with the bleaching bath was 18 seconds.
[0053] The yarn was then led directly into a bath of 30 g/l of
hydrosulfite (pH: 8.5, temperature: 25.degree. C.) and subsequently
rinsed at 20.degree. C. The cycle of bleaching, treating with
hydrosulfite and rinsing was subsequently repeated twice.
EXAMPLE 2
[0054] A yarn dyed as per step A) of example 1 was treated at a
temperature of 25.degree. C. with a bath containing
[0055] 200 g/l of thickener (Monagum, 10%)
[0056] 150 g/l of etching agent (Magnatrop W),
[0057] 80 g/l of moisture donor (tzverstrler HN),
[0058] 10 g/l of aqueous sodium hydroxide solution and
[0059] 150 g/l of Rongalit C
[0060] for 17 seconds, interveningly dried and steamed at
102.degree. C. for 1 minute. This was followed by washing off at
60.degree. C. and then at 20.degree. C.
EXAMPLE 3
Dyeing Example at Size Application
[0061] A yarn treated as per steps A) and B) of example 1 was
interveningly dried on a contact dryer and then treated at a
temperature of 30.degree. C. with a size bath containing
[0062] 200 g/l of binder (Perapret PU),
[0063] 30 g/l of thickener (Primasol AMK),
[0064] 100 g/l of white pigment (Acramin Wei.beta. DRN 01)
[0065] and subsequently set on a contact dryer.
EXAMPLE 4
Dyeing Example at Size Application
[0066] A yarn treated as per steps A) and B) of example 1 was
interveningly dried on a contact dryer and then treated at a
temperature of 30.degree. C. with a size bath containing
[0067] 200 g/l of starch ether
[0068] 350 g/l of titanium dioxide
[0069] 300 g/l of binder (Perapret PU)
[0070] 100 g/l of Imperon Orange K-G (C.I. Pigment Yellow 5)
[0071] and subsequently set on a contact dryer.
EXAMPLE 5
Dyeing Example at Size Application
[0072] A yarn treated as per steps A) and B) of example 1 was
interveningly dried on a contact dryer and then treated at a
temperature of 30.degree. C. with a size bath containing
[0073] 200 g/l of starch ether
[0074] 300 g/l of binder (Perapret PU)
[0075] 50 g/l of Indanthren Gelb 5.degree. GF-D (C.I. Vat Yellow
46)
[0076] and subsequently set on a contact dryer.
EXAMPLE 6
Dyeing Example at Size Application
[0077] A yarn treated as per steps A) and B) of example 1 was
interveningly dried on a contact dryer and then treated at a
temperature of 30.degree. C. with a size bath containing
[0078] 200 g/l of starch ether
[0079] 400 g/l of titanium dioxide
[0080] 300 g/l of binder (Perapret PU)
[0081] 150 g/l of Dianix Gelb P6G fl. (C.I. Disperse Yellow
114)
[0082] and subsequently set on a contact dryer.
[0083] The table examples which follow describe further embodiments
of the process of the invention. They are carried out similarly to
the abovementioned examples 1 to 3.
1 Bleaching example Aftertreatment example Product 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 Potassium 5 50 30 permanganate Sodium
hypochlorite 20 10 Sodium persulfate 30 10 Inorganic salt 40 Starch
ether 20 40 20 40 200 200 200 Acrylate copolymer 50 50 50 30
Moisture donor 80 Reducing agent 150 30 Sodium bisulfite 30 20 30
Titanium dioxide 100 400 350 Polyurethane 200 300 300 300 Colored
pigment* 100 200 Temperature (.degree. C.) 30 40 25 30 25 60 50 25
40 40 40 40 30 30 30 pH 11 11.2 12 11 10.6 6.5 11.5 6.5 8.5 8.5 8.5
6.5 6.5 8 8 8 *colored pigment here refers not only to pigment dyes
but also to vat dyes, which are present in their oxidized form, as
a pigment, but also disperse dyes.
* * * * *