Liquid alkali for reactive dyeing of textiles

A liquid alkali composition for use in fiber reactive dyeing of cotton and cotton blended fabrics or the like. The liquid alkali is a water-based solution of an alkali metal hydroxide and an alkali metal silicate. Preferably the composition is an aqueous mixture of potassium hydroxide and sodium silicate. In the most preferred embodiment the composition includes 35 wt % potassium hydroxide at a 45 wt % concentration, 25 wt % sodium silicate at 50.degree. Baume, 5 wt % of a borate, and the balance water. The resulting solution has a high enough pH to achieve reaction between the dye and fiber but is sufficiently buffered to achieve this reaction slowly so that the fiber reactive dyes fix in a level, uniform fashion.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates generally to the dyeing of textiles and, more 
particularly, to a liquid alkali for use in fiber reactive dyeing of 
cotton and cotton blended fabrics. 
(2) Description of the Prior Art 
Fiber reactive dyes were first introduced in the mid 1950's. Since that 
time they have become a dominant factor in dyeing cotton, regenerated 
cellulose and blends. These dyes can also be used to dye acrylics, nylon, 
silk, wool and blends of these fibers. Fiber reactive dyes are easy to 
apply and produce brilliant shades, fastness, penetration and leveling. 
Fiber reactive dyes are anionic in nature and react chemically with the 
fiber. The dyes include a chromophore to give color to the dye and a 
reactive group to form a chemical bond with the fiber. There may also be a 
substitutent or solubilizing group which provides additional dyeing 
characteristics such as solubility, substantivity, migration, washing off, 
etc. Fiber reactive dyes react in the presence of alkali to form a strong 
covalent chemical bond between a carbon atom of the dye molecule and an 
oxygen atom of the hydroxyl group in the cellulose. This step is called 
"fixing". 
No single alkali system has worked on all classes of reactive dyes due to 
the differences in the rate of hydrolysis of each dye. Of all the alkali 
systems, the liquid phosphate system described in U.S. Pat. No. 4,555,348, 
issued to Moran, and sold under the tradename "Alkaflo" by Sybron 
Chemicals of Birmingham, N.J., works almost universally. But Alkaflo is 
high in phosphorus which can contribute to environmental problems. 
Also, if the reaction mixture is too "hot" or alkaline, such as is seen 
with pure sodium hydroxide, the sensitive-type reactive dyes will 
hydrolyze with the water in the dyebath and form a nonreactive pigment 
that has no effect on the fabric color. Furthermore, as fashions have 
changed, the need to mix reactive dyes of different chemistries in the 
same shade and the necessity of developing a universal alkali system for 
cold pad batch dyeing that does not contain phosphorus has become more 
important. 
One attempt at producing a phosphorus-free liquid alkali was recently 
introduced and is being sold under the tradename "REMOL FB". REMOL FB is 
available from Hoechst Celanese of Somerville, N.J. According to its 
Material Safety Data Sheet, REMOL FB contains a mixture including 
potassium hydroxide and sodium silicate. However, test dyeings indicated 
that, like pure sodium hydroxide, REMOL FB is too "hot" for many classes 
of dyestuffs. 
Thus, there remains a need for a liquid, phosphorus-free, alkali for use in 
fiber reactive dyeing of cotton and cotton blended fabrics which has the 
clean dyeing properties of a phosphorus-based system such as Alkaflo but 
is not as "hot" as earlier alkali hydroxide/silicate mixtures. 
SUMMARY OF THE INVENTION 
The present invention is directed to a liquid alkali for use in dyeing of 
cotton and cotton blended fabrics. The liquid alkali is a water-based 
solution of an alkali metal hydroxide and an alkali metal silicate. 
Preferably the composition is an aqueous mixture of potassium hydroxide 
and sodium silicate. In the most preferred embodiment the composition 
includes 35 wt % potassium hydroxide at a 45 wt % concentration, 25 wt % 
sodium silicate at 50.degree. Baume, 5 wt % of a borate, and the balance 
water. The resulting solution has a high enough pH to achieve reaction 
between the dye and fiber but is sufficiently buffered to achieve this 
reaction slowly so that the fiber reactive dyes fix in a level, uniform 
fashion. 
Accordingly, one aspect of the present invention is to provide a liquid 
composition for use in reactive dyeing of cotton and cotton blended 
fabrics or the like. The composition includes: (a) an alkali metal 
hydroxide; (b) an alkali metal silicate; (c) sodium metaborate or sodium 
perborate; and (d) the balance water. 
Another aspect of the present invention is to provide a liquid composition 
for use in reactive dyeing of cotton and cotton blended fabrics or the 
like. The composition including: (a) about 30 to 40 wt % of an alkali 
metal hydroxide; (b) about 10 to 40 wt % of an alkali metal silicate; and 
(c) the balance water. 
Another aspect of the present invention is to provide a liquid composition 
for use in reactive dyeing of cotton and cotton blended fabrics or the 
like. The composition includes: (a) about 30 to 40 wt % of an alkali metal 
hydroxide; (b) about 10 to 40 wt % of an alkali metal silicate; (c) up to 
about 5 wt % of sodium metaborate or sodium perborate borax and (d) the 
balance water. 
These and other aspects of the present invention will become apparent to 
those skilled in the art after a reading of the following description of 
the preferred embodiment when considered with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the preferred embodiment, the process for preparing the liquid alkali 
composition of the present invention includes the following steps: Into a 
mixer containing 40 parts by weight water add 35 parts by weight potassium 
hydroxide at a 45 wt % concentration and stir. Then add 25 parts by weight 
sodium silicate at 50.degree. Baume and stir. Stir until uniform and 
transfer the mixture into a suitable container. 
The liquid alkali of the present invention is added to the dyebath in a 
range of from 2 to 10 gms/l . The concentration of dyes in the dyebath 
range up to 5 wt %. Sodium sulfate or other salt ranges between about 80 
to 100 gms/l. 
The resulting solution has a high enough pH to achieve reaction between the 
dye and fiber but is sufficiently buffered to achieve this reaction slowly 
so that the fiber reactive dyes fix in a level, uniform fashion. 
Dyeings were made using various ratios of 45 wt % potassium hydroxide and 
50.degree. Baume sodium silicate and compared to conventional dyeing 
procedures and additives. Color yield was measured relative to a control 
having a value of 100%. The criteria for suitability was about .+-.10% of 
the control. The results are shown below in Examples 1-49. 
EXAMPLES 1-7 
Conventional reaction dyeings of cotton fabrics were made to determine the 
red dye yield of the candidate materials. The dye selected was a mixture 
of 3.50% Cibacron.TM. Scarlet F-3G and 1.50% Cibacron.TM. Red F-B. These 
dyes are available from Ciba-Geigy Corporation of Ardsley, N.Y. These dyes 
were chosen because they are sensitive to high alkalinity, i.e., they dye 
weak when too much alkalinity is used because of hydrolysis. The dyebath 
included 80 gms/l of sodium sulfate. Dyeing took place at 140.degree. F. 
for 40 minutes. The liquid alkali was added at 3 gms/l. The liquor ratio 
was 20 to 1. All color yield measurements are in comparison to a 
conventional dyebath containing 10 gms/l soda ash. 
TABLE 1 
______________________________________ 
Red Dye Trial Results 
Example Composition Suitable Yield 
______________________________________ 
1 potassium hydroxide 
35% Y +1.36% 
sodium silicate 
10% 
balance water 
2 potassium hydroxide 
35% Y +0.75% 
sodium silicate 
25% 
balance water 
3 potassium hydroxide 
35% Y +4.31% 
sodium silicate 
40% 
balance water 
4 potassium hydroxide 
35% Y +3.94% 
sodium silicate 
60% 
balance water 
5 potassium hydroxide 
10% Y -3.46% 
sodium silicate 
25% 
balance water 
6 potassium hydroxide 
50% N -13.76% 
sodium silicate 
25% 
balance water 
7 potassium hydroxide 
75% N -12.11% 
sodium silicate 
25% 
balance water 
______________________________________ 
EXAMPLES 8-14 
Conventional reaction dyeings of cotton fabrics were made to determine the 
green dye yield of the candidate materials. The dye selected was a mixture 
of 4.00% Procion.TM. Turquoise HA, 0.10% Procion.TM. Blue HERD and 0.80% 
Procion.TM. Yellow HE-6G. These dyes are available from ICI America of 
Wilmington, DE. The dyebath included 100 gms/l of sodium sulfate. Dyeing 
took place at 175.degree. F. for 40 minutes. The liquid alkali was added 
at 2 gms/l. The liquor ratio was 20 to 1. All color yield measurements are 
in comparison to a conventional dyebath containing 20 gms/l soda ash. 
TABLE 2 
______________________________________ 
Green Dye Trial Results 
Example Composition Suitable Yield 
______________________________________ 
8 potassium hydroxide 
35% N +15% 
sodium silicate 
10% 
balance water 
9 potassium hydroxide 
35% N +20% 
sodium silicate 
25% 
balance water 
10 potassium hydroxide 
35% Y +6% 
sodium silicate 
40% 
balance water 
11 potassium hydroxide 
35% Y +9% 
sodium silicate 
60% 
balance water 
12 potassium hydroxide 
10% N -22% 
sodium silicate 
25% 
balance water 
13 potassium hydroxide 
50% N +20% 
sodium silicate 
25% 
balance water 
14 potassium hydroxide 
75% N +10% 
sodium silicate 
25% 
balance water 
______________________________________ 
EXAMPLES 15-21 
A second group of reaction dyeings of cotton fabrics identical to Examples 
8-14 were made to determine the green dye yield of the candidate materials 
for liquid alkali added at 5 gms/l. The liquor ratio was 20 to 1. All 
color yield measurements are in comparison to a conventional dyebath 
containing 20 gms/l soda ash. 
TABLE 3 
______________________________________ 
Green Dye Trial Results (con't) 
Example Composition Suitable Yield 
______________________________________ 
15 potassium hydroxide 
35% N +17% 
sodium silicate 
10% 
balance water 
16 potassium hydroxide 
35% N +18% 
sodium silicate 
25% 
balance water 
17 potassium hydroxide 
35% N +11% 
sodium silicate 
40% 
balance water 
18 potassium hydroxide 
35% Y +5% 
sodium silicate 
60% 
balance water 
19 potassium hydroxide 
10% Y +4% 
sodium silicate 
25% 
balance water 
20 potassium hydroxide 
50% Y -4% 
sodium silicate 
25% 
balance water 
21 potassium hydroxide 
75% Y -5% 
sodium silicate 
25% 
balance water 
______________________________________ 
EXAMPLES 22-28 
A third group of reaction dyeings of cotton fabrics identical to Examples 
8-14 were made to determine the green dye yield of the candidate materials 
for liquid alkali added at 10 gms/l. The liquor ratio was 20 to 1. All 
color yield measurements are in comparison to a conventional dyebath 
containing 20 gms/l soda ash. 
TABLE 4 
______________________________________ 
Green Dye Trial Results (con't) 
Example Composition Suitable Yield 
______________________________________ 
22 potassium hydroxide 
35% Y +1% 
sodium silicate 
10% 
balance water 
23 potassium hydroxide 
35% Y -2% 
sodium silicate 
25% 
balance water 
24 potassium hydroxide 
35% Y -3% 
sodium silicate 
40% 
balance water 
25 potassium hydroxide 
35% Y -4% 
sodium silicate 
60% 
balance water 
26 potassium hydroxide 
10% Y +6% 
sodium silicate 
25% 
balance water 
27 potassium hydroxide 
50% N -15% 
sodium silicate 
25% 
balance water 
28 potassium hydroxide 
75% N -26% 
sodium silicate 
25% 
balance water 
______________________________________ 
EXAMPLES 29-35 
Conventional reaction dyeings of cotton fabrics were made to determine the 
blue dye yield of the candidate materials. The dye selected was a mixture 
of 3.00% Remazol.TM. Turquoise R-P and 0.50% Remazol.TM. Blue R-W. These 
dyes are available from Hoechst Celanese of Summerville, N.J. The dyebath 
included 100 gms/l of sodium sulfate. Dyeing took place at 160.degree. F. 
for 40 minutes. The liquid alkali was added at 2 gms/l. The liquor ratio 
was 20 to 1. All color yield measurements are in comparison to a 
conventional dyebath containing 5 gms/l soda ash and 2 gms/l caustic 50%. 
TABLE 5 
______________________________________ 
Blue Dye Trial Results 
Example Composition Suitable Yield 
______________________________________ 
29 potassium hydroxide 
35% N -10% 
sodium silicate 
10% 
balance water 
30 potassium hydroxide 
35% N -25% 
sodium silicate 
25% 
balance water 
31 potassium hydroxide 
35% N -29% 
sodium silicate 
40% 
balance water 
32 potassium hydroxide 
35% N -28% 
sodium silicate 
60% 
balance water 
33 potassium hydroxide 
10% N -57% 
sodium silicate 
25% 
balance water 
34 potassium hydroxide 
50% N -13% 
sodium silicate 
25% 
balance water 
35 potassium hydroxide 
75% Y -1% 
sodium silicate 
25% 
balance water 
______________________________________ 
EXAMPLES 36-42 
A second group of reaction dyeings of cotton fabrics identical to Examples 
29-35 were made to determine the blue dye yield of the candidate materials 
for liquid alkali added at 7 gms/l. The liquor ratio was 20 to 1. All 
color yield measurements are in comparison to a conventional dyebath 
containing 5 gms/l soda ash and 2 gms/l caustic 50%. 
TABLE 6 
______________________________________ 
Blue Dye Trial Results (con't) 
Example Composition Suitable Yield 
______________________________________ 
36 potassium hydroxide 
35% Y +8% 
sodium silicate 
10% 
balance water 
37 potassium hydroxide 
35% Y +4% 
sodium silicate 
25% 
balance water 
38 potassium hydroxide 
35% Y -12% 
sodium silicate 
40% 
balance water 
39 potassium hydroxide 
35% N -16% 
sodium silicate 
60% 
balance water 
40 potassium hydroxide 
10% N -26% 
sodium silicate 
25% 
balance water 
41 potassium hydroxide 
50% Y -9% 
sodium silicate 
25% 
balance water 
42 potassium hydroxide 
75% N -13% 
sodium silicate 
25% 
balance water 
______________________________________ 
EXAMPLES 43-49 
A third group of reaction dyeings of cotton fabrics identical to Examples 
29-35 were made to determine the blue dye yield of the candidate materials 
for liquid alkali added at 10 gms/l. The liquor ratio was 20 to 1. All 
color yield measurements are in comparison to a conventional dyebath 
containing 5 gms/l soda ash and 2 gms/l caustic 50%. 
TABLE 7 
______________________________________ 
Blue Dye Trial Results (con't) 
Example Composition Suitable Yield 
______________________________________ 
43 potassium hydroxide 
35% Y -7% 
sodium silicate 
10% 
balance water 
44 potassium hydroxide 
35% Y +2% 
sodium silicate 
25% 
balance water 
45 potassium hydroxide 
35% N -16% 
sodium silicate 
40% 
balance water 
46 potassium hydroxide 
35% N -20% 
sodium silicate 
60% 
balance water 
47 potassium hydroxide 
10% N -27% 
sodium silicate 
25% 
balance water 
48 potassium hydroxide 
50% N -18% 
sodium silicate 
25% 
balance water 
49 potassium hydroxide 
75% N -29% 
sodium silicate 
25% 
balance water 
______________________________________ 
These results clearly show that the present invention, as shown in Example 
1-3, 22-24, and 36-38, will provide good color yield on various dyes, 
including alkali sensitive dyes for typical amounts of alkali of 3 to 10 
gms/l in the dyebath. The above examples also show that the present 
invention is an acceptable substitute for phosphorus-based alkali for 
reactive dyeing of cotton and cotton blended fabrics or the like. 
Accordingly, the amount of silicate in the present invention can be varied 
between a low of about 10 to a high of about 40 wt % of 50.degree. Baume 
with 25 wt % being most preferred. Similarly, the amount of 45 wt % 
concentration alkali metal hydroxide in the present invention varies 
between a low of about 30 to a high of about 40 wt % with 35 wt % being 
most preferred. Thus, the composition has the following properties: 
Appearance: Clear liquid 
1% pH: 12.2-12.4 
45 wt % Potassium Hydroxide: 30-40 wt % 
50.degree. Baume Sodium Silicate: 10-40 wt % 
This provides a liquid alkali product that can be used at between about 2 
to 10 gms/l in the dyebath. 
In the preferred embodiment, the process also included adding up to about 5 
wt % sodium metaborate or sodium perborate to the liquid alkali as a final 
step. The borates act as a buffer. The effect of the borate can best be 
seen in FIG. 1 which is a graphical representation of the titration curves 
for 1% solutions of liquid alkalis prepared according to the present 
invention. As can be seen, the liquid alkalis containing borates have a 
more gradual slope than the liquid alkali without borate. This more 
gradual slope has a slight drop in the high end of the pH curve but still 
has a high enough pH to achieve reaction between the dye and fiber. In 
addition, the alkali is better buffered to achieve this reaction slowly so 
that the fiber reactive dyes fix in a more level, uniform fashion. 
However, as shown above, the dyebath tests have shown that the mixture can 
be made without the borate and still provide satisfactory yield. 
Certain modifications and improvements will occur to those skilled in the 
art upon reading of the foregoing description. By way of example, sodium 
hydroxide could be used in place of potassium hydroxide. Also, carbonates 
are possible substitutes for the borates. It should be understood that all 
such modifications and improvements have been deleted herein for the sake 
of conciseness and readability but are properly within the scope of the 
following claims.