Reduction clearing of polyester textiles

Details Reduction clearing of polyester textiles Reduction clearing of polyester textiles

1999-01-22

2004-05-04

Einsmann, Margaret (Department: 1751)

Bleaching and dyeing; fluid treatment and chemical modification

Cleaning or laundering

C008S110000, C008S588000, C008S592000, C008S602000, C008S142000, C008S922000

Reexamination Certificate

active

06730132

ABSTRACT:

The present invention describes a process for reduction clearing dye or printed polyester textiles. It further relates to mixtures useful as aftertreatment compositions in the process of the invention, its preferred components and its preferred use form and quantity.
In vat dyeing, cellulosic textiles are customarily dyed by converting suitable dyes by reduction in a strongly alkaline medium into their soluble leuco form, which, after penetrating the fiber, is converted back into the insoluble dye by atmospheric oxidation. The reductant used is usually sodium dithionite, but the use of sulfinates is known too, from GB-3-829 177, for related printing applications. Mixtures of dithionite with sulfinates or sulfonates are described in U.S. Pat. No. 3,265,459, U.S. Pat. No. 3,645,665 and U.S. Pat. No.3,798,172 as useful reductants for cellulose dyeing.
By contrast, polyester textiles are exclusively dyed in an acidic medium. The method employed is the high temperature exhaust process, the thermosol process or the superheated steam fixation process. In the first process, the textile is dyed in a dyebath in a pressure vessel at a pH of about 3-6 and a temperature of about 120-140° C. This treatment causes the disperse dye to diffuse into the plasticized polyester fiber to form a molecular dispersion in the polymer matrix. The completion of the dyeing step is usually followed by a preclear with fresh water and finally by an alkaline reduction clear in a wash bath, for which purpose it is customary to use sodium dithionite and caustic soda in aqueous solution.
In the thermosol and superheated steam fixation processes, too, the preclear is followed by alkaline reduction clearing.
As in the high temperature exhaust process, in the thermosol and superheated steam fixation processes the aftertreatment used is predominantly an aqueous solution of caustic soda and sodium dithionite. The pH of the reduction clearing bath is therefore high, about 12-13. Wash baths which contain sodium hydroxymethanesulfinate (Rongalit®c, Superlite®c) optionally in mixtures with sodium hydroxymethanesulfonate or dithionite-formaldehyde condensates, and which in specific cases can also be rendered acidic by addition of strong organic or inorganic acids are described in JP-A-05 272 075-A, JP-A-02 300 391, JP-A-04 146 279, JP-A-01 028 090, JP-A-02 091 285, JP-A-57 006 188, JP-A-57 066 189, JP-A-60 162 889. However, these washing systems do not meet the high requirements demanded of aftertreatment compositions in respect of the achievement of high color fastnesses on polyester textiles.
Disadvantages of the traditional high temperature exhaust process are
high time, water and energy intensity through the pH change from acid to alkaline
high salt loadings in the dyehouse wastewater and dye residues which color the wastewater
high autoignition tendency of hydrosulfite in bulk, and
a relatively rapid exhaustion of the reductive wash bath through atmospheric oxidation.
The thermosol and the superheated steam fixation processes likewise have the disadvantage of insufficient air stability of the wash baths, so that accurate dosing of the reductant cannot be accomplished under plant conditions without analysis. As a consequence, it is not always possible to avoid incompletely destroyed dye residues staining the white ground.
It is an object of the present invention to provide a simplified process for dyeing polyester textiles—without a costly interim rinse and a separate clear—to save time, water and energy. Furthermore, colorless, low-salt wastewaters shall result, and the aftertreatment compositions to be used in the dyeing liquor or in the wash bath shall be simple to handle, high yielding, simple to meter and possessed of an effective clearing action.
We have found that this object is achieved by a process for reduction clearing dyed or printed polyester textiles, which comprises adding, to the acidic dyeing liquor or the wash bath, an aftertreatment composition comprising as components
a) at least one compound of the formula (I)
 A
m
[(CR
1
R
2
)
m
SO
2
M]
p,q
  (I)
 where
A is NR
3
3−q
or OR
4
2−p
R
1
, R
2
, R
4
are each Hydrogen or C
1
-C
6
-alkyl
R
3
represents identical or different radicals selected from the group consisting of hydrogen, C
1
-C
20
-alkyl, C
3
-C
8
-cycloalkyl opt. substituted by from one to three C
1
-C
4
-alkyl radicals
M is the equivalent of an ammonium, alkali metal or alkaline earth metal ion
m is 0 or 1
p is 1 or 2
q is 1, 2 or 3
subject to the provisos that at least one of R
1
, R
2
, R
4
is C
1
-C
6
-alkyl when A is OR
4
2−p
and that, if m is 0:
p, q are each 2 and
the compound of he formula (I) is used together with sufficient acid acceptor to raise the pH of the dyeing liquor or of the wash bath by from 1 to 3 units,
b) optionally at least one compound of the formula (II)
A[(CR
1
R
2
)SO
3
M]
p,q
  (II)
 where A, R
1
, R
2
, R
3
, R
4
, M, p and q are each as defined for the formula (I), although the specific choice of these variables does not have to be the same for the compounds of the formulae (I) and (II)
c) and optionally further additives.
When the process of the invention is to be carried out with mixtures comprising ammonium, alkali metal or alkaline earth metal dithionites—where m in the formula (I) is 0, that is—the acid acceptors used are preferably ammonium, alkali metal or alkaline earth metal bicarbonate, carbonate, oxide, hydroxide, bisulfite, sulfite, hydrogenphosphate or phosphate, the use of the alkali metal and alkaline earth metal bicarbonates and carbonates being particularly preferred. Normally the sodium dithionite commercially available as “hydrosulfite” will be used. This sodium dithionite generally has a technical grade purity of more than 80%. Its use in the reduction clearing process described herein is preferred for cost reasons. However, special requirements may justify the use of other alkali metal and also alkaline earth metal or ammonium dithionites or mixtures thereof.
Suitable ammonium dithionites are not only NH
4
⊕
but also, for example, NL
4
⊕
compounds, wherein the substituents L represent identical or different radicals selected from the group consisting of hydrogen and C
1
-C
6
-alkyl in which nonadjacent CH and CH
2
groups may be replaced by N on the one hand or NH or O on the other and CH
3
groups by NH
2
or OH. Examples thereof are the mono-, di-, tri- and tetraethanolammonium compounds, but also the corresponding salts of ethylenediamine, diethylenetriamine and triethylenetetramine. It is also possible to use the salts of the condensation products of ammonia with diethylene glycol such as H
2
N(C
2
H
4
)O(C
2
H
4
)OH, HN[(C
2
H
4
)O(C
2
H
4
)(OH]
2
or N[(C
2
H
4
)O(C
2
H
4
)OH]
3
.
Suitable acid acceptors in addition to the aforementioned substances also include their mixtures. The only important criterion is to ensure a buffering of the acidic dyeing liquor by about 1-3 pH units in order that the reduction of excess dye by the dithionite may be ensured.
Normally, the desired pH change is ensured by the use of dithionites and acid acceptor in a weight ratio within the range from 3:1 to 1:1, which is why this mixing ratio is indeed preferred.
Depending on the specific requirements, it can also be sensible to add salts of complexing agents such as, for example, nitrilo-triacetic acid (NTA, N(CH
2
COOH)
3
), ethylenediaminetetraacetic acid (EDTA, [CH
2
N(CH
2
COOH)
2
]
2
), diethylenetriaminepentaacetic acid (DTPA, HOOCCH
2
N[(CH
2
)
2
N(CH
2
COOH)
2
]
2
), hydroxyethylethylenediamine triacetic acid (HEDTA, HO(CH
2
)
2
N(CH
2
COOH)(CH
2
)
2
N(CH
2
COOH
2
), propylenediaminetetraacetic acid (PDTA, (HOOCCH
2
)
2
N(CH
2
)
3
N(CH
2
COOH)
2
) or &bgr;-alaninediacetic acid ((HOOCCH
2
)
2
N(CH
2
)
2
COOH) as a buffer. These are marketed under the brandname of Trilon®, for example. It is also possible to use mixtures between these complexing agents alone or with other acid acceptors.
If, in addition, surfactants or

Affiliated with

Also associated with

Rating

Reduction clearing of polyester textiles does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Reduction clearing of polyester textiles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reduction clearing of polyester textiles will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3254482