Aqueous dye solutions

Details Aqueous dye solutions Aqueous dye solutions

2001-04-17

2003-12-09

Einsmann, Margaret (Department: 1751)

Bleaching and dyeing; fluid treatment and chemical modification

Organic additive for dye composition, dye composition...

Ureas, thioureas, pseudoureas, or pseudothioureas

C008S598000, C008S681000, C008S684000, C008S688000, C008S919000

Reexamination Certificate

active

06660048

ABSTRACT:

The present invention relates to aqueous dye solutions of red disazo dyes, processes for their preparation and their use for dyeing paper.
The use of concentrated aqueous solutions of dyes has gained importance in recent years, in particular because of the advantages such solutions have over dyes in powder form. By using solutions, the difficulties associated with dust formation are avoided and the users are freed from the time-consuming and often difficult dissolving of the dye powder in water. The use of concentrated solutions has furthermore been stimulated by the development of continuous dyeing processes for paper, since in these processes it is advantageous to introduce the solution directly into the hollander or to add it at any other suitable point in the papermaking.
For some dyes, for example the dyes of the formula (1) defined below, formulation of concentrated dye solutions in free acid form presents difficulties, however, since deposits occur in the concentrated solutions during storage, especially at temperatures below room temperature, and these deposits cannot be dissolved again at all or can be dissolved only with an additional expenditure of work. Furthermore, concentrated solutions which are suitable as a commercial form should give clear solutions comprising about 1 to 3% by weight of dye, without a precipitate, when diluted for preparation of the dyebath, and this should also apply in the widest possible pH range.
Concentrated aqueous dye solutions in free acid form of certain dyes of the formula (1) defined below are known. However these solutions additionally contain considerable amounts of 3-chloro-2-hydroxypropyl trimethylammonium chloride or diethylene glycol monobutyl ether, both of which are undesirable.
The present invention was based on the object of providing suitable concentrated solutions in free acid form for the dyes of the formula (1) defined below which do not contain either a quaternary ammonium halide or a glycol- or diglycol ether. It has now been found that the dye solutions described below meet the requirements imposed in an outstanding manner. The present invention therefore relates to A) concentrated aqueous dye solutions comprising
a) at least 5% by weight, based on the weight of the solution, of a red dye of the formula
in which
R and R
1
independently of one another are each hydrogen, Cl, methyl or methoxy,
R
2
and R
3
independently of one another are each hydrogen, methyl or methoxy,
R
4
and R
5
independently of one another are each hydrogen or C
1
-C
4
alkyl,
A is an unbranched or branched alkylene radical, which can be interrupted by O, and
R
6
and R
7
independently of one another are each hydrogen or C
1
-C
6
alkyl, or in which
R
6
and R
7
, together with the N atom bonded to them, form a substituted or unsubstituted 5-, 6-or 7-membered ring, which can contain further heteroatoms,
b) formic acid or a C
1
-C
4
alkylcarboxylic acid,
c) a solubilizing agent,
d) water and, if appropriate,
e) further additives, or
B) concentrated aqueous dye solutions comprising
a) at least 5% by weight, based on the weight of the solution, of a red dye of the formula (1),
b) formic acid or a C
1
-C
4
alkylcarboxylic acid,
c) water and, if appropriate,
d) further additives, with the condition that the solutions comprise no solubilizing agent and
less than 0.1% by weight of alkali metal halide, based on the total weight of the solution.
The present invention preferably relates to the dye solutions of group A).
In the dyes of the formula (1), R and R
1
are preferably each H, methyl or methoxy, H being particularly preferred.
R
2
and R
3
are preferably each H.
R
4
and R
5
are preferably each methyl or, in particular, hydrogen.
Radicals A are, in particular, C
2
-C
6
alkylene radicals, in which the alkylene chain is straight or branched or can also be interrupted by bridge members, for example —O—, or in which the alkylene chain is substituted, for example by OH.
A is preferably a radical of the formula —(CH
2
)
n
—, in which n is an integer from 2 to 6.
Particularly suitable radicals A are ethylene, n-propylene, iso-propylene or n-butylene. Among these, n-propylene is especially preferred.
R
6
and R
7
independently of one another are each linear or branched unsubstituted C
1
-C
6
alkyl, or C
1
-C
6
alkyl which is substituted, for example by OH or C
1
-C
4
alkoxy. The alkyl chains can also be interrupted, for example by —O—.
Preferably, R
6
and R
7
independently of one another are each unsubstituted C
1
-C
4
alkyl, and in an especially preferred embodiment R
6
and R
7
are identical and are each methyl or ethyl.
A 5-, 6- or 7-membered ring of R
6
and R
7
together with the N atom joining them is, in particular, a pyrrolidine, piperidine, morpholine or piperazine ring. The piperazine radical can be substituted on the N atom which is not bonded to the alkylene chain, for example by alkyl.
In the dyes of the formula (1), the sulfo group is preferably located in the m- or, in particular, in the p-position relative to the azo group.
Preferred concentrated solutions according to the invention comprise a dye of the formula
in which
m is 2, 4 or, in particular, 3, and
R
6
and R
7
are each C
1
-C
2
alkyl.
The concentration of the dye can vary within wide limits and is at least 5% by weight, preferably 6 to 15% by weight, in particular 8 to 10% by weight, based on the weight of the concentrated solution.
The alkylcarboxylic acid is, for example, acetic acid, propionic acid, butyric acid or valeric acid. Propionic acid and, in particular, acetic acid are preferred.
Suitable solubilizing agents are, for example, compounds of the following groups:
I) alkali metal or ammonium salts of C
1
-C
4
alkylcarboxylic acids,
II) low molecular weight acid amides,
III) low molecular weight lactams or lactones,
IV) alkanolamines or reaction products of ethylene oxide and/or propylene oxide with alkanolamines.
The solubilizing agents of group I) are, in particular, the sodium, potassium, lithium or ammonium salts of acetic acid or propionic acid. Sodium and ammonium acetate are particularly preferred. The solubilizing agents of group I) do not of course have to be employed in the form of the salts mentioned, but can also be prepared in the solutions from the corresponding bases and acids by neutralization.
Low molecular weight acid amides are, in particular, formamide, and especially urea. Suitable solubilizing agents of group III) are, for example, &ggr;-butyrolactam or &egr;-caprolactone, but in particular &ggr;-butyrolactone, or especially &egr;-caprolactam.
The solubilizing agents of group IV) are, for example, diethanolamine or triethanolamine, but in particular reaction products of 1 to 6 mol of ethylene oxide and/or propylene oxide with 1 mol of diethanolamine or triethanolamine. Particularly preferred compounds are those of the formula
in which
p is an integer from 1 to 6 and of the substituents R
8
and R
9
, one is hydrogen and the other is hydrogen or methyl.
Preferably, in the compounds of the formula (3), p is 1.
The solubilizing agents of group 1) are preferably present in an amount of 1 to 6% by weight, in particular 1 to 3% by weight, based on the weight of the solution.
The solubilizing agents of groups II), III) and IV) are preferably present in an amount of 3 to 20% by weight, in particular 6 to 15% by weight, based on the weight of the solution.
It is also possible to employ mixtures of solubilizing agents of one group or mixtures of solubilizing agents of different groups, for example mixtures of ammonium acetate and urea.
The C
1
-C
4
alkylcarboxylic acid is preferably employed in an amount of 3 to 20% by weight, in particular 6 to 15% by weight, based on the weight of the solution.
Further additives which can be present in the concentrated solutions according to the invention are organic solvents, for example dimethylsulfoxide, N-methylpyrrolidone, ethylene glycol, propylene glycol or glycerol, and boric acid.
The concentrated aqueous solutions of group A) according to the invention can be prepared, for example, by filtering the dy

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