U.S. patent application number 13/777306 was filed with the patent office on 2013-08-29 for production of dyed cotton fibers.
This patent application is currently assigned to CELANESE INTERNATIONAL CORPORATION. The applicant listed for this patent is Celanese International Corporation. Invention is credited to Greg MOAKES, Harrie SCHOOTS.
Application Number | 20130219635 13/777306 |
Document ID | / |
Family ID | 47827481 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130219635 |
Kind Code |
A1 |
SCHOOTS; Harrie ; et
al. |
August 29, 2013 |
PRODUCTION OF DYED COTTON FIBERS
Abstract
In a method of dyeing and finishing cotton fibers, emulsion
copolymer treated cotton fibers are prepared by contacting the
fibers with an emulsion copolymer and curing the copolymer under
conditions to chemically anchor the emulsion copolymer to the
cotton and thereby form copolymer-treated cotton fibers. The
copolymer-treated cotton fibers are then contacted with a dye
material under conditions sufficient to affix at least a portion of
the dye material to the copolymer component of the
copolymer-treated cotton fibers and produce dyed cotton fibers.
Thereafter, the dyed cotton fibers are treated with a
surfactant-stabilized aqueous acrylic polymer dispersion to give
the fibers a worn or vintage character.
Inventors: |
SCHOOTS; Harrie; (League
City, TX) ; MOAKES; Greg; (Carrollton, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Celanese International Corporation; |
|
|
US |
|
|
Assignee: |
CELANESE INTERNATIONAL
CORPORATION
Irving
TX
|
Family ID: |
47827481 |
Appl. No.: |
13/777306 |
Filed: |
February 26, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61604980 |
Feb 29, 2012 |
|
|
|
Current U.S.
Class: |
8/552 |
Current CPC
Class: |
D06P 1/16 20130101; D06P
1/54 20130101; D06P 1/22 20130101; D06P 1/5257 20130101; D06P 1/525
20130101; D06P 3/6033 20130101; D06P 5/137 20130101; D06P 5/02
20130101; D06P 1/5221 20130101; D06P 3/60 20130101; D06P 3/6025
20130101; D06P 5/158 20130101 |
Class at
Publication: |
8/552 |
International
Class: |
D06P 5/13 20060101
D06P005/13 |
Claims
1. A method of dyeing and finishing cotton fibers, which method
comprises: (a) preparing emulsion copolymer treated cotton fibers
by contacting the fibers with an emulsion copolymer and curing the
copolymer under conditions to chemically anchor the emulsion
copolymer to the cotton and thereby form copolymer-treated cotton
fibers; b) contacting said copolymer-treated cotton fibers with a
dye material under conditions sufficient to affix at least a
portion of said dye material to the copolymer component of said
copolymer-treated cotton fibers and produce dyed cotton fibers; and
then (c) treating the dyed cotton fibers with a
surfactant-stabilized aqueous acrylic polymer dispersion.
2. The method according to claim 1, wherein the treating (c) is
conducted at a temperature of 25.degree. C. to 80.degree. C. for a
period of at least 5 minutes.
3. The method according to claim 1, wherein the treating (c) is
conducted at a temperature of 30.degree. C. to 60.degree. C. for a
period of 15 to 45 minutes.
4. The method according to claim 1, wherein the acrylic polymer
dispersion employed in (c) is diluted to about 0.05 to about 0.3%
solids.
5. The method according to claim 1, wherein the acrylic polymer
employed in (c) is produced from a monomer composition comprising
one or more (meth)alkyl acrylate monomers wherein the alkyl group
has from 1 to 12 carbon atoms.
6. The method according to claim 5, wherein the monomer composition
comprises butyl acrylate, methyl methacrylate, ethyl acrylate or a
mixture thereof.
7. The method according to claim 5, wherein the monomer composition
further comprises from 5 to 20% by weight, such as from 5 to 10% by
weight, of acrylonitrile based on the total weight of monomers in
the composition.
8. The method according to claim 1, wherein the surfactant
stabilizer for the acrylic polymer comprises an anionic
surfactant.
9. The method according to claim 1 and further comprising: (d)
stone washing the dyed cotton fibers at a temperature of 10.degree.
C. to 80.degree. C. for a period of less than 30 minutes.
10. The method according to claim 9, wherein the stone washing is
conducted at a temperature of 25.degree. C. to 50.degree. C. for a
period of 15 minutes to 30 minutes.
11. The method according to claim 1, wherein the dye material is a
disperse or vat dye.
12. The method according to claim 1, wherein the emulsion copolymer
employed in (a) is selected from vinyl ester-based, acrylic-based,
styrene/acrylic-based and styrene/butadiene-based emulsion
copolymers and mixtures thereof.
13. The method according to claim 1, wherein emulsion copolymer
employed in (a) is a vinyl ester-based copolymer selected from
vinyl acetate-ethylene copolymers, vinyl acetate-vinyl versatate;
vinyl acetate-acrylic copolymers, and combinations of said
copolymer types.
14. The method according to claim 1, wherein the emulsion copolymer
employed in (a) is a vinyl acetate-ethylene copolymer comprising
from 60 wt % to 95 wt % of vinyl acetate and from 5 wt % to 40 wt %
of ethylene, based on total monomers therein.
15. The method according to claim 1, wherein the emulsion copolymer
employed in (a) is an acrylic emulsion copolymer which comprises at
least two different types of (meth)acrylate co-monomers.
16. The method according to claim 1, wherein the emulsion copolymer
employed in (a) is an acrylic emulsion copolymer comprising ethyl
acrylate and butyl acrylate co-monomers.
17. The method according to claim 1, wherein the emulsion copolymer
employed in (a) comprises from 0.1 wt % to 10 wt %, based on total
monomers in the copolymer, of one or more ethylenically unsaturated
cross-linking co-monomers having at least one amide, epoxy, or
alkoxysilane group.
18. The method according to claim 1, wherein the emulsion copolymer
employed in (a) comprises from 0.1 wt % to 10 wt %, based on total
monomers in the copolymer, of one of more multifunctional external
cross-linking co-monomers selected from diallyl adipate, triallyl
cyanurate, butanediol diacrylate, allyl methacrylate, and
combinations of said cross-linking co-monomers.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of the filing date of
U.S. Provisional Application No. 61/604,980 filed Feb. 29, 2012,
the entire contents of which are incorporated herein by
reference
FIELD
[0002] The present development relates to the production of dyed
cotton fibers, in which the dyed product is imparted a
"stone-washed", vintage or worn appearance.
BACKGROUND
[0003] Up until the present cotton fibers in the form of yarns and
fabrics have generally been dyed with reactive, direct, sulfur,
vat, or mordant dyes. Currently the industry prefers reactive
dyeing for apparel as reactive dyes provide the brightest colored
cotton of all the dyes. Water-soluble reactive dyes, which also
provide dyeing results with good fastness-to-washing properties,
can be used to dye or print hydrophilic cellulose fibers such as
cotton fibers. In such procedures, the cellulose fiber --OH groups
which are accessible on the fiber surface react with the
fiber-reactive groups of the reactive dyes, forming a covalent
fiber/dye bond.
[0004] Dyeing of cotton with reactive dyes gives good color
fastness. However, reactive dyes are strongly hydrophilic leading
to process inefficiencies and high costs due to the necessity of
using long dyeing times with salt additions and alkali, thus
allowing for the sensitive needs of reactives for high pH and high
temperature conditions. Reactive dyes which do not react with
cotton cellulose in the dyeing step eventually react with water and
hydrolyze. This hydrolyzed dye must be removed from the cotton
surface after dyeing with an after-soaping step to improve
crockfastness and washfastness properties.
[0005] Another dye class commonly employed for the coloring of
fabrics comprises disperse dyes, which are mainly used for the
dyeing of polyester, but can also be used to dye nylon, cellulose
acetate and acrylic fibers. Given their lack of affinity or
substantivity for cellulose, disperse dyes cannot be readily used
to dye cotton fibers and fabrics. However, some attempts have been
made to provide procedures for dyeing modified cotton fibers, e.g.,
fabrics, with disperse dyes. For example, U.S. Patent Publication
No. 2006/0048308 discloses a method of dyeing or printing
cellulose-containing fiber materials using disperse dyes. Such a
method comprises pre-treating the cellulose fiber material with a
water-soluble or dispersible polyester resin and a water-soluble or
dispersible acrylic binder. The polyester resin is fixed, for
example, to cotton fabric with the acrylic binder and strong
cross-linkers (e.g., melamine) via a pretreatment bath. The
polyester impregnated fabric is then dyed with an aqueous dye bath
containing disperse dye at a temperature of 130.degree. C. under
elevated pressure conditions.
[0006] In our co-pending U.S. Patent Application published as
US2012/0246842 A1 on Oct. 4, 2012 we have described a method for
dyeing cotton fibers, which method comprises: (a) contacting a
plurality of cotton fibers with a cellulose-reactive emulsion
copolymer in order to provide a combination of emulsion copolymer
and fibers; (b) curing the combination of emulsion copolymer and
fibers in order to chemically anchor the emulsion copolymer to the
cotton fibers via reaction of at least some cellulose-reactive
monomers within said copolymer with cellulose hydroxyl moieties
within the cotton fibers, to thereby form copolymer-treated cotton
fibers; and thereafter (c) contacting the copolymer-treated cotton
fibers with a disperse dye material under conditions which are
sufficient to affix at least a portion of said disperse dye
material to the copolymer component of said copolymer-treated
cotton fibers.
[0007] In addition, in our co-pending U.S. Patent Application
published as US2013/0000057 A1 on Jan. 3, 2013 we have described a
method for preparing indigo-dyed denim fabric, which method
comprises: (a) preparing emulsion copolymer-treated warp yarn by
contacting cotton yarn with a cellulose-reactive emulsion copolymer
and thereafter curing the emulsion copolymer; (b) weaving or
knitting the emulsion copolymer-treated cotton warp yarn into denim
fabric along with untreated cotton yarn as the weft yarn to thereby
prepare greige denim fabric having emulsion copolymer-treated
cotton warp yarn in the warp direction only; and thereafter (c)
contacting the greige denim fabric with an aqueous dispersion of an
indigo dyestuff material under conditions sufficient to
preferentially color the outer cross-sectional portions of the
emulsion copolymer-treated warp yarn to a greater extent than the
indigo dyestuff material colors the outer cross-sectional portions
of the untreated cotton weft yarn, to thereby provide indigo-dyed
denim fabric having a non-uniformly colored appearance.
[0008] Dyed cotton products are subjected to a variety of post
treatments to improve their physical and/or visual properties. One
such post treatment is stone-washing in which the dyed material is
imparted a "worn" appearance by partial removal of dye in a manner
to yield a material having areas which are lighter in color
(sometimes referred to as "highs and lows" or a vintage character)
and softer in texture. Traditionally, stone washing is effected by
washing the dyed material at 60 to 70.degree. C. for about 60
minutes in a commercial washing machine together with pumice
stones, water and a surfactant. However, conventional stone washing
suffers from a number of defects in that, for example, not only
does stone washing damage the fabric but also the pumice stones are
expensive and tend to abrade during the process. Moreover,
particulate abrasion by-products can cause significant processing
and equipment problems. Particulate pumice must be manually removed
from processed clothing items because it tends to accumulate in
pockets, on interior surfaces, in creases and in folds. In the
stone washing machine, the stones can cause overload damage to
electric motors, mechanical damage to transport mechanisms and
washing drums and can significantly increase the requirements for
machine maintenance. The pumice stones and particulate material can
clog machine drainage passages and can clog drains and sewer lines
at the machine site. These problems can add significantly to the
cost of doing business and to the purchase price of the goods.
Moreover, although other abrasive materials, such as diatomaceous
earth, have been used instead of pumice stones, these in general
have proved less effective in generating the required distressed
appearance.
[0009] To avoid the problems of mechanical stone washing, it is
known to try to achieve the same distressed appearance by the use
of chemical agents, particularly enzymes. For example, U.S. Pat.
No. 5,006,126 discloses a method of introducing localized areas of
variation and color density into the surface of dyed cellulosic
fabric by contacting the fabric with an aqueous composition
consisting essentially of: (a) water; (b) at least 25 wt-% of a
cellulase enzyme and at least 1,500 CMC units of cellulase enzyme
per liter of aqueous composition; and (c) a buffer that can
maintain the pH of the aqueous solution at about the cellulase
enzyme optimum pH. However, although this treatment is said to give
a variation in color density that is substantially the same as that
produced by conventional pumice stone processing, enzymes digest
the underlying cellulosic fabric thereby decreasing its strength.
In addition, enzymatic processes are generally difficult to
control.
[0010] There is therefore a need for a process for producing dyed
fabrics with a worn or distressed appearance which reduces or
obviates the need for mechanical stone washing.
[0011] According to the present invention, it has now been found
that if an emulsion treated and dyed material, such as disclosed in
U.S. Publications Nos. US2012/0246842 and US2013/0000057, is
subjected to a specific post treatment with an acrylic emulsion
composition, the material can be given the desired "worn"
appearance characteristic of stone washing either without or with a
much reduced stone washing treatment.
SUMMARY
[0012] In one aspect, the invention resides in a method of dyeing
and finishing cotton fibers, which method comprises:
[0013] (a) preparing emulsion copolymer treated cotton fibers by
contacting the fibers with an emulsion copolymer and curing the
copolymer under conditions to chemically anchor the emulsion
copolymer to the cotton and thereby form copolymer-treated cotton
fibers;
[0014] b) contacting said copolymer-treated cotton fibers with a
dye material under conditions sufficient to affix at least a
portion of said dye material to the copolymer component of said
copolymer-treated cotton fibers and produce dyed cotton fibers; and
then
[0015] (c) treating the dyed cotton fibers with a
surfactant-stabilized aqueous acrylic polymer dispersion.
[0016] Generally, the treating (c) is conducted at a temperature of
25.degree. C. to 80.degree. C., such as 30.degree. C. to 60
.degree. C., for a period of at least 5 minutes, such as 15 to 45
minutes.
[0017] Typically, the acrylic polymer dispersion employed in (c) is
diluted to about 0.05 to about 0.30 wt % solids, preferably to
about 0.05 to about 0.15 wt % solids.
[0018] In one embodiment, the acrylic polymer is formed from a
monomer composition comprising one or more (meth)alkyl acrylate
monomers wherein the alkyl group has from 1 to 12 carbon atoms.
Optionally, the monomer composition further comprises from 5 to 20%
by weight, such as from 5 to 10% by weight, of acrylonitrile based
on the total weight of monomers in the composition.
[0019] Conveniently, the surfactant stabilizer for the acrylic
polymer comprises an anionic surfactant.
[0020] In one embodiment, the method further comprises (d) stone
washing the dyed cotton fibers at a temperature of 10.degree. C. to
80.degree. C., such as 25.degree. C. to 50.degree. C., for a period
of less than 30 minutes, for example for 15 to 30 minutes.
[0021] Generally, the emulsion copolymer employed in (a) is
selected from vinyl ester-based, acrylic-based,
styrene/acrylic-based and styrene/butadiene-based emulsion
copolymers and mixtures thereof.
[0022] In one embodiment, the emulsion copolymer employed in (a) is
a vinyl acetate-ethylene copolymer comprising from 60 wt % to 95 wt
% of vinyl acetate and from 5 wt % to 40 wt % of ethylene, based on
total monomers therein.
[0023] In another embodiment, the emulsion copolymer employed in
(a) is an acrylic emulsion copolymer which comprises at least two
different types of (meth)acrylate co-monomers, for example ethyl
acrylate and butyl acrylate co-monomers.
[0024] Conveniently, the emulsion copolymer employed in (a)
comprises from 0.1 wt % to 10 wt %, based on total monomers in the
copolymer, of one or more ethylenically unsaturated cross-linking
co-monomers having at least one amide, epoxy, or alkoxysilane
group.
[0025] Conveniently, the emulsion copolymer employed in (a)
comprises from 0.1 wt % to 10 wt %, based on total monomers in the
copolymer, of one of more multifunctional external cross-linking
co-monomers selected from diallyl adipate, triallyl cyanurate,
butanediol diacrylate, allyl methacrylate, and combinations of said
cross-linking co-monomers.
DETAILED DESCRIPTION
[0026] Described herein is method of producing dyed cotton fibers,
whether in the form of yarn, fabric or garments, which not only
allows the use of disperse dyes in the dying operation but also
employs a post treatment step which imparts to the fibers the
"worn" or "vintage" appearance characteristic of stone washing
either without or with a much reduced stone washing treatment. In
addition, the post treatment step has little or no adverse effect
on the integrity of the cotton fibers unlike most existing chemical
methods of duplicating the stone washing process.
[0027] Cotton Fibrous Material
[0028] Cotton is a fluffy staple fiber that grows in a boll, or
protective capsule, around the seeds of cotton plants. The chemical
composition of cotton is generally about 91% cellulose and 7.85%
water with the balance being protoplasm, pectins, waxes fatty
substances and mineral salts.
[0029] Cotton fiber is generally spun into yarn or thread and used
to make a soft, breathable textile fabric. "Textiles" and like
terminology refer to yarns, fabrics, sewing threads, finished
garments and so forth. Fabrics may be knit or woven fabrics made of
cotton fibrous material. Garments may be apparel and industrial
garments. The terms "fabrics" and "textiles" also include home
goods such as linens, drapery, and upholstery (automotive, boating,
airline included) made of the cotton fibrous materials described
herein.
[0030] It is well known that cotton fibers can be combined with
other fiber types when fashioned and used in the form of yarns,
fabrics, textiles and garments. Typically cotton can be combined
with other natural fiber types such as silk, linen, wool, angora
and mohair. It is also well known that cotton can also be combined
with synthetic and semi-synthetic fiber types such as polyester
fibers, aramid fibers, polyamide (nylon) fibers, acrylic
(acrylonitrile) fibers, spandexes, rayons, Tencel and cellulose
acetate fibers. The cotton fibrous materials which are dyed and
treated by the method described herein can contain minor amounts
(less than 50 wt %) of fiber types other than cotton. However, the
best dyeing results obtained using the method described herein are
achieved when the yarns, fabrics, textile, garments, etc., contain
no fibers other than cotton. Accordingly, preferred for use in the
method herein are yarns, fabrics, textiles and garments which are
100% cotton.
[0031] Emulsion Copolymer Pretreatment
[0032] In the present process, the cotton fibrous material is
contacted, prior to dyeing, with a selected type of emulsion
copolymer. Such emulsion copolymers include those which have
conventionally been used as textile finishing agents. Such emulsion
copolymers include those described in detail in U.S. Patent
Publication No. 2011/0005008, which is incorporated by reference
herein in its entirety.
[0033] Suitable types of emulsion copolymers for use in the present
process include vinyl ester-based, acrylic-based,
styrene/acrylic-based or styrene/butadiene-based emulsion
copolymers. The emulsions are generally aqueous emulsions. Such
copolymers typically can also contain minor amounts of
cross-linking or emulsion stabilizing co-monomers. Such co-monomers
can, for example, in and of themselves or in combination with
external cross-linking agents, make the emulsion copolymers used
herein cellulose-reactive during the curing step described
below.
[0034] One preferred type of emulsion copolymer comprises the vinyl
ester-based copolymers selected from vinyl acetate-ethylene
copolymers, vinyl acetate-vinyl versatate; vinyl acetate-acrylic
copolymers, and combinations of these copolymer types. Vinyl
acetate-ethylene (VAE) emulsion copolymers are well-known. Such VAE
copolymers useful herein can comprise from about 60 wt % to about
95 wt % of vinyl acetate and from about 5 wt % to about 40 wt % of
ethylene, based on total monomers therein. More preferably, VAE
copolymers will comprise from about 70 wt % to about 90 wt % of
vinyl acetate and from about 8 wt % to about 15 wt % of ethylene,
based on total monomers therein.
[0035] Another preferred type of emulsion copolymer for use in the
method herein comprises acrylic emulsion copolymers made of acrylic
ester co-monomers. The alkyl acrylates that can be used to prepare
the acrylic ester copolymer emulsions include alkyl acrylates and
alkyl methacrylates containing 1 to 12, preferably 1 to 10 carbon
atoms in the alkyl group. The polymer backbone in the acrylic ester
copolymer can be either hydrophilic or hydrophobic and it can
comprise polymerized soft monomers and/or hard monomers. The soft
and hard monomers are monomers which, when polymerized, produce
soft or hard polymers, or polymers in between. Preferred soft
acrylic ester monomers are selected from alkyl acrylates containing
2 to 8 carbon atoms in the alkyl group and include ethyl acrylate,
propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. The
hard acrylic ester monomers are selected from alkyl methacrylates
containing up to 3 carbon atoms in the alkyl group and from
non-acrylic monomers such as styrene and substituted styrenes,
acrylonitrile, vinylchloride, and generally any compatible monomer
the homopolymer of which has a Tg above 50.degree. C. Preferred
acrylic ester monomers are selected from alkyl acrylates and
methacrylates containing 1 to 12 carbon atoms in the alkyl group,
especially ethyl acrylate and butyl acrylate.
[0036] The emulsion copolymer will frequently contain, in addition
to the main co-monomers, minor amounts of co-monomers which can
provide cross-linking with both cellulose hydroxyl moieties within
the cotton fibers and cross-linking within the copolymer itself.
Such cross-linking co-monomers are unsaturated so as to polymerize
into the copolymer backbone and will also contain at least one
functional group containing nitrogen, oxygen or silicon atoms.
[0037] Thus the emulsion copolymers herein can comprise from about
0.1 wt % to about 10 wt %, based on total monomers in the
copolymer, of one or more ethylenically unsaturated cross-linking
co-monomers having, for example, at least one amide, epoxy, or
alkoxysilane group. Examples of such suitable self cross-linking
co-monomers include N-methylol (meth)acrylamide and esters therof,
N-vinylpyrrolidinone, dimethylaminoethyl acrylate, glycidyl
acrylate, glycidyl methacrylate, allyl glycidyl ether, vinyl
glycidyl ether, acryloxy-propyltri(alkoxy)silanes,
methacryloxypropyltri(alkoxy)silanes, vinyltrialkoxysilanes,
vinylmethyldialkoxysilanes and combinations of these cross-linkable
co-monomers.
[0038] The emulsion copolymer can also contain, in addition to the
main co-monomers and self cross-linking co-monomers, minor amounts
of multifunctional external cross-linking co-monomers. Thus the
copolymers used herein can optionally comprise from about 0.1 wt %
to about 10 wt %, based on total monomers in the copolymer, of one
of more of these multifunctional cross-linking co-monomers.
Examples of suitable multifunctional cross-linking co-monomers
include diallyl adipate, triallyl cyanurate, butanediol diacrylate,
allyl methacrylate and combinations thereof.
[0039] Suitable cellulose-reactive emulsion copolymers can be
prepared in conventional fashion using known emulsion
polymerization techniques and raw materials. In general, such
emulsion copolymers can be prepared by polymerizing appropriate
co-monomers in appropriate amounts in an aqueous reaction mixture
using conventional polymerization initiators and catalysts and
conventional polymerization conditions. The copolymer emulsions so
prepared can be stabilized with suitable emulsifiers (surfactants)
and/or protective colloids.
[0040] Pretreating the cotton fibers with the emulsion copolymers
initially involves contacting the fibers with the aqueous emulsion
at a temperature of 40.degree. C. to 60.degree. C. so that the
insoluble emulsion copolymer is deposited or "exhausted" onto the
cotton fibers, substantially without reaction with the fibers. Such
contact generally involves immersion of the cotton fibrous material
in a treatment bath which can be made by diluting an aqueous
emulsion copolymer dispersion to a solids content of from about 2
wt % to about 10 wt %, more preferably from about 3 wt % to about 6
wt %. Such treatment baths will also have a pH of from about 3 to
about 7, more preferably from about 5 to about 7.
[0041] Yarn can be treated with saturating liquors (called "pad
baths") with a nip roll squeeze after each bath saturation. Yarn
can also be treated in "package" form with the saturating liquor.
Woven goods can be pad bath finished in continuous stenter (open
width) frames or with batch processes such as, piece dyeing, jet,
beck, jigger or paddle machines. Knit goods can be processed in the
same machinery (both continuous and batch) as woven, just under
different conditions. For garments, industrial garment washing
machines may be used. Optional application methods include manual
processes such as spraying or manual wet add-on techniques.
[0042] In one embodiment, cotton fabric can be contacted with the
emulsion copolymer-containing treatment bath in a continuous
padding operation run at a pad pressure of from about 0.3 bar to
about 2.5 bar and at a pad speed of from about 0.25 to about 1
m/minute. More preferably, such a continuous padding operation can
be run at a pad pressure of from about 0.9 bar to about 1.1 bar and
at a pad speed of from about 0.3 to about 0.6 m/minute. (Commercial
production speeds can be considerably higher, for example from
about 10 to about 30 meters/minute.)
[0043] Regardless of the method of application selected,
application and processing conditions should be selected such that
the cotton fibrous material has a substantially uniform
distribution of the emulsion copolymer associated with it. The
fiber/copolymer combination will generally contain from about 1 wt
% to about 10 wt %, more preferably from about 3 wt % to about 6 wt
%, of the copolymer on a dry basis.
[0044] After the fiber/copolymer combination has been formed, this
combination is subjected to curing conditions which are effective
to chemically anchor the emulsion copolymer to the cotton fibrous
material via reaction of the copolymer with at least a portion of
the hydroxyl moieties of the cellulose component of the cotton
fibers. Such chemical reaction can occur via a cross-linking
mechanism with the cross-linkable co-monomers which will generally
form part of the emulsion copolymer as hereinbefore described.
Curing of the fiber/copolymer combination also will generally
promote some self-cross-linking of the copolymer within the fibrous
cotton materials as well.
[0045] Curing conditions for the fiber/copolymer combination will
generally involve subjecting the combination to elevated
temperatures of from about 140.degree. C. to about 165.degree. C.
for a period (dwell time) of from about 0.2 to about 4 minutes.
More preferably, the fiber/copolymer combination can be cured by
using temperatures of from about 145 .degree. C. to about 155
.degree. C. for a period (dwell time) of from about 0.3 to about 1
minute. In addition to anchoring the copolymer to the cellulose
hydroxyl groups of the cotton fibers, curing of the fiber/copolymer
combination will also generally serve to remove water from this
combination. Thus curing of the fiber/copolymer combination can
serve to partially or even substantially completely dry the
fiber/copolymer combination prior to the dyeing step of the method
herein.
[0046] The treating of the cotton fibrous material with the
emulsion copolymer and the subsequent curing of the fiber/copolymer
combination serves to provide chemically modified,
copolymer-treated cotton fibrous material. Such copolymer-treated
cotton fibers can then be dyed using the dyes and dyeing conditions
hereinafter described.
[0047] Optional Denim Fabric Formation
[0048] In one embodiment, cotton warp yarn, after the copolymer
emulsion pretreatment described above and either before or after
being dyed, is incorporated into cotton denim fabric with untreated
weft or fill yarn, that is yarn that has not been modified by the
emulsion copolymer treatment. In practice, not all of the warp yarn
needs to be emulsion copolymer-treated cotton yarn and not all of
the weft yarn needs to be untreated cotton yarn. Generally, at
least 50% of the warp yarn in the resultant greige denim fabric
should be emulsion copolymer-treated cotton yarn and at least 50%
of the weft yarn should be untreated cotton yarn. Preferably,
however, substantially all of the warp yarn in the fabric should be
emulsion copolymer-treated cotton yarn and substantially all of the
weft yarn should be untreated cotton yarn.
[0049] Cotton warp and weft yarns can be fashioned into cotton
denim fabrics in accordance with the methods herein by any
conventional technique known for the preparation of such denim
fabrics. The method herein is compatible with cotton denim fabrics
having a wide range of fabric basis weights. Cotton denim fabrics
will typically have a basis weight ranging from about 3 to about 10
oz/yd.sup.2.
[0050] Weaving is a common method for making cotton yarn into
cotton denim fabrics. The woven cotton denim fabrics which can be
indigo dyed in accordance with the dyeing methods described
hereinafter include, for example, those of a basic weave, satin
weave, twill weave, ripstop weave or basket weave. Denim fabrics
are most commonly of the twill weave type.
[0051] Cotton yarns can also be knitted to provide a variety of
denim knit fabric types prior to being dyed in accordance with the
dyeing method herein. Denim knit cotton fabrics will generally be
of the warp type, including tricot knits or raschel knits.
[0052] Dyeing Process
[0053] After curing, the emulsion copolymer-treated cotton fibers
are contacted with a dye material under conditions sufficient to
affix at least a portion of said dye material to the copolymer
component of said copolymer-treated cotton fibers and produce dyed
cotton fibers.
[0054] Any known dye material can be used in the dyeing step but,
in one preferred embodiment, the dye is a disperse dye. Disperse
dyes are insoluble in water and were originally developed for the
dyeing of cellulose acetate and are water-insoluble. They are
generally finely ground in the presence of a dispersing agent
(surfactant) and are sold as a paste or spray-dried and sold as a
powder.
[0055] Suitable disperse dyes for use in the dyeing method herein
are those described under "Disperse Dyes" in the Colour Index, 3rd
edition (3rd revision 1987 inclusive of Additions and Amendments up
to No. 85). Such dyes include, for example, carboxylic acid
group-free and/or sulfonic acid group-free nitro, amino,
aminoketone, ketoninime, methine, polymethine, diphenylamine,
quinoline, benzimidazole, xanthene, oxazine and coumarin dyes and
especially anthraquinone and azo dyes, such as mono- or di-azo
dyes. Such disperse dyes are also those described in detail in U.S.
Patent Publication No. 2006/0048308. That '308 patent document, and
especially its disclosure of the several structural formulas for
disperse dye materials disclosed therein, is incorporated herein by
reference.
[0056] The preferred types of disperse dye materials useful herein
include the quinoline dyes, the anthraquinone dyes and the azo
dyes. The dyeing method herein is equally useful with disperse dyes
whether they are classified as high energy dyes, medium energy dyes
or low energy dyes. Useful disperse dyes which can be used herein
also include dyes which are especially formulated for to serve as
automotive dyes, lightfast dyes or fluorescent dyes.
[0057] Generally, the copolymer-treated cotton fibers will be
contacted with the disperse dye material by immersing the fibers in
a dye liquor in the form of an aqueous dispersion of the disperse
dye material. The aqueous dye liquor can contain, for example, from
about 0.01 wt % to about 15 wt % of the disperse dye material. More
preferably, the aqueous dye liquor can contain from about 0.5 wt %
to about 5.0 wt % of the disperse dye material. The lower
concentrations of the dye in the dye liquor are useful for tinting
operations. Higher dye concentrations in the dye liquor, of course,
produce dyed cotton fibers, yarns, fabrics and garments having more
intense color.
[0058] The aqueous dye liquor will generally be contacted with the
cotton fibrous material to be dyed at temperatures of from about
65.degree. C. to about 100.degree. C., more preferably from about
80.degree. C. to about 95.degree. C. Under such dyeing liquor
temperature conditions, it is possible to carry out the dyeing step
of the method herein at atmospheric pressure. Dyeing liquor pH will
generally range from about 3 to about 8, more preferably from about
4 to about 7.
[0059] The dyeing step of the method herein may be carried out
using either batch or continuous operations. If a batch method is
employed, the copolymer-treated cotton fibrous material can be
contacted with the dye liquor for a period of from about 0.25 to
about 3 hours, more preferably from about 0.5 to about 1.0 hour. In
batch operation, a dye liquor to fiber ratio of from about 30:1 to
about 3:1 can be used. More preferably, when cotton fibers are in
fabric form, liquor to fabric ratios of from about 20:1 to about
8:1 can be employed.
[0060] The aqueous dying liquor can optionally contain various
fiber and fabric treating adjuvants besides the disperse dye
material. Such adjuvants can include, for example, optical
brighteners, fabric softeners, antistatic agents, antibacterial
agents, anti-wrinkling agents, ironing aids, flame-retardants,
enzymes, UV stabilizers, anti-foaming agents, perfumes, and the
like.
[0061] In another preferred embodiment, the dye is a vat dye and in
particular an indigo dye generally known as Vat Blue 1. Unlike
conventional indigo dyeing processes, with the emulsion copolymer
treated fibers described herein, the dyeing can be conducted
without the indigo dye being converted to its reduced or leuco form
and at moderate pH values of from about 9 to less than about 12,
more preferably from about 10 to about 11. In addition, as in the
case of disperse dyes, indigo dyeing can be at temperatures of from
about 65.degree. C. to about 100.degree. C., more preferably from
about 80.degree. C. to about 95.degree. C., under at atmospheric
pressure.
[0062] Post Treatment
[0063] After dyeing, the dyed cotton fibers are rinsed with water
and then subjected to one or more post treatment steps to give the
material a stone-washed or vintage appearance. The first, and
optionally the only post-treatment step, involves treating the dyed
cotton fibers with a surfactant-stabilized aqueous acrylic polymer
dispersion. Suitable acrylic polymers are produced from monomer
compositions comprising one or more (meth)alkyl acrylate monomers
wherein the alkyl group has from 1 to 12 carbon atoms. Preferred
monomer compositions include butyl acrylate, methyl methacrylate,
ethyl acrylate and mixtures thereof. Optionally, the monomer
composition can contain from 5 to 20% by weight, such as from 5 to
10% by weight, of acrylonitrile based on the total weight of
monomers used to produce the acrylic polymer.
[0064] In addition, the monomer composition can contain from 1 to
10% by weight, such as from 1 to 5% by weight, of N-methylol
(meth)acrylamide and esters therof, N-vinylpyrrolidinone,
dimethylaminoethyl acrylate, glycidyl acrylate, glycidyl
methacrylate, allyl glycidyl ether, vinyl glycidyl ether,
acryloxy-propyltri(alkoxy)silanes,
methacryloxypropyltri(alkoxy)silanes, vinyltrialkoxysilanes,
vinylmethyldialkoxysilanes and combinations of these cross-linkable
co-monomers.
[0065] Suitable surfactants used to stabilize the acrylic polymer
dispersion are anionic surfactants, such as sodium, potassium, and
ammonium salts of linear aliphatic carboxylic acids of chain length
C.sub.12-C.sub.20, sodium hydroxyoctadecanesulfonate, sodium,
potassium, and ammonium salts of hydroxy fatty acids of chain
length C.sub.12-C.sub.20 and their sulfonation and/or sulfation
and/or acetylation products, alkyl sulfates, including those in the
form of triethanolamine salts, alkyl(C.sub.10-C.sub.20) sulfonates,
alkyl(C.sub.10-C.sub.20) arylsulfonates, dimethyl-dialkyl
(C.sub.8-C.sub.18) ammonium chloride, and their sulfonation
products, lignosulfonic acid and its calcium, magnesium, sodium,
and ammonium salts, resin acids, hydrogenated and dehydrogenated
resin acids, and their alkali metal salts, dodecylated sodium
diphenyl ether disulfonate, sodium lauryl sulfate, sulfated alkyl
or aryl ethoxylate with EO degree between 1 and 10, for example
ethoxylated sodium lauryl ether sulfate (EO degree 3) or a salt of
a bisester, preferably of a bis-C.sub.4-C.sub.18 alkyl ester, of a
sulfonated dicarboxylic acid having 4 to 8 carbon atoms, or a
mixture of these salts, preferably sulfonated salts of esters of
succinic acid, more preferably salts, such as alkali metal salts,
of bis-C.sub.4-C.sub.18 alkyl esters of sulfonated succinic acid,
or phosphates of polyethoxylated alkanols or alkylphenols.
[0066] In one embodiment, the surfactant-stabilized aqueous acrylic
polymer dispersion is Lyoprint PBA available from Huntsman.
[0067] Generally, the post-treatment with the surfactant-stabilized
aqueous acrylic polymer dispersion is conducted at a temperature of
25.degree. C. to 80.degree. C., preferably 30.degree. C. to
60.degree. C., for a period of at least 5 minutes, preferably 15 to
45 minutes. Generally, the acylic polymer dispersion is diluted
with water so as to contain from about 0.05 to about 0.30 wt %
solids, preferably from about 0.05 to about 0.15 wt % solids, most
preferably about 0.10 wt % solids.
[0068] After the acrylic emulsion post-treatment the material has a
natural looking "salt and pepper" effect characteristic of worn
garments. Although the reason for this result is not fully
understood it is believed that the surfactant-stabilized acrylic
polymer dispersion partially removes the dye from the emulsion
coated fibers without adversely effecting the underlying cotton
structure.
[0069] Although the post-treatment with the surfactant-stabilized
acrylic polymer dispersion will often be sufficient to provide the
required vintage appearance to the cotton product, it may in some
cases be desirable to precede this post treatment with a mechanical
stone washing treatment. In this case, however, the duration and
severity of the mechanical stone washing treatment can be
significantly reduced as compared with a conventional stone washing
process. For example, in the present process, stone washing is
conveniently conducted at a temperature of 10.degree. C. to
80.degree. C., preferably 25.degree. C. to 50.degree. C., for a
period of less than 45 minutes, for example for 15 minutes to 30
minutes without the addition of caustic. In contrast, conventional
stone washing treatments require temperatures of 75.degree. C. to
95.degree. C. for periods of 60 minutes to 90 minutes at pH values
of 8 to 11.
[0070] The invention will now be more particularly described with
reference to the following non-limiting Examples.
EXAMPLE 1
Garment Exhaust Pretreatment with Garment Exhaust Dyeing and Batch
Post treatment
[0071] Cotton garments prepared for dyeing are added to a garment
washing machine, which is filled with water at a 20:1 liquor ratio,
or 20 parts water for each part fabric. The machine is run at low
(25 to 40) RPM for 5 minutes at ambient temperature for wetting of
the garments. A 50% solids acrylic copolymer emulsion (composed of
89% ethyl acrylate, 8% acrylonitrile and 3% N-methylolacrylamide
(NMA)) is added to create a 10% diluted solids solution. The bath
temperature is ramped at 5.degree. F./min to 160.degree. F.
(71.degree. C.) while running at low RPM and the machine is run at
this temperature for 1 hour. The bath temperature is then ramped
down to 140.degree. F. (60.degree. C.) and the water is removed.
Complete extraction of the garments is effected for 30 seconds at
400 RPM and the garments are then removed from the washing machine
for drying/curing.
[0072] Curing of the emulsion copolymer is completed on the dry
garments at 120.degree. C. to 150.degree. C. for about 20
seconds.
[0073] The dried and cured garments are then exhaust dyed in the
same garment washing machine used for the emulsion pretreatment
again with the machine being filled with water to a 20:1 liquor
ratio. The water is adjusted to a 4 pH with acetic acid and the
machine is run for 5 minutes with low RPM to rewet the garments.
The desired mixture and concentration of disperse dye is
solubilized in hot water as is conventional in the art of handling
dry disperse dyestuffs for use in wet processing of polyester. This
dissolved dye is added to the machine after the wetting step and
the resultant exhaust dye bath is ramped to 95.degree. C. at a ramp
rate of about 5.degree. F./min. The exhaust bath is retained at
this temperature for 60 minutes, after which the bath temperature
is ramped down to 140.degree. F. (60.degree. C.) at 5.degree.
F./min before bath is removed. The machine is then filled with
fresh water, ramped to 40.degree. C. for rinsing, and cycled at
this temperature for 15 minutes. The first rinse bath is then
removed, whereafter the machine is again filled with fresh water
and rinsed for 15 minutes with 25.degree. C. water. The second
rinse bath is then removed and the garments are transferred to a
stone-washing machine.
[0074] The stone-washing machine is filled with the garments and
water at a 15:1 liquor ratio. Pumice stones (preferably 2-4 cm
diameter stones) are added to the machine at about 2 parts stone to
1 part cotton. The stone-washing machine at is run at 25 to 40 RPM
for 30 minutes at 30.degree. C. The garments are now ready for post
treatment
[0075] The stone-washed garments are placed in a garment washing
machine and water is added to a 20:1 liquor ratio. 10 g/L
Lyoprint.RTM. PBA (Huntsmann) is added to the bath and the machine
is run at low RPM for 20 minutes at 60.degree. C. bath temperature.
After 20 minutes the bath is cooled to 30.degree. C. and a softener
package, 2% owg Siligen N-AP softener (BASF), is added to the bath.
The softener package is run for 5 minutes, after which the water is
removed. The garments are dried at 80.degree. C. and are then ready
for conditioning and packaging for delivery.
EXAMPLE 2
Continuous Pretreatment with Continuous Dyeing
[0076] This Example employs circular knit or tubular fabric that
has been pretreated by bleaching and biofinishing (enzyme) for
whitening and wettability and run through a slitter to make it
"open width", or flat. This flat fabric is run through a pad bath
made of an 8% diluted solid solution of the acrylic copolymer
emulsion used in Example 1. The saturated cotton is then squeezed
between pad rolls at a pressure to generate a wet pick up of
approx. 95% to 105%. The cotton is then dried in a stenter frame at
230.degree. F. (110.degree. C.). The dried cotton is doffed in roll
form at the end of the line and returned through another drying
stenter for curing at 300.degree. F. (149.degree. C.) for about 60
seconds. The fabric is collected and is ready for pad dyeing.
[0077] The pretreated cotton roll is then sent through a disperse
dye bath and passed between pad rolls with wet pick up and dye bath
concentration adjusted for desired depth of shade. The disperse dye
is prepared in the same way as in Example 1 before being added to
the pad trough. The fabric is then dried at 230.degree. F.
(166.degree. C.) or at acceptable production temperature. The
fabric is then sent for production and stonewashing/post treatment
using the same process as described in Example 1 above.
* * * * *