Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
2002-04-26
2004-04-13
Drodge, Joseph (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S651000, C210S710000, C008S527000, C008S636000, C008S648000, C162S072000, C162S076000
Reexamination Certificate
active
06719906
ABSTRACT:
The present invention relates to a process for the preparation of solutions of anionic organic compounds, to the solutions so prepared and to the use of such solutions. In this context, anionic organic compounds are understood to be, especially, dyes and fluorescent whitening agents and also intermediates for the preparation thereof.
In recent years, the use of concentrated aqueous solutions, for example of dyes and fluorescent whitening agents, has gained in importance, that being the case because of the advantages that such solutions have over the corresponding powder forms. The use of solutions avoids the difficulties associated with dust formation and frees the users from the time-consuming, and often difficult, task of dissolving the powder in water. The use of concentrated solutions has also been encouraged by the development of continuous processes for dyeing or whitening paper because it is advantageous in those processes for the solution to be introduced directly Into the hollander or added at some other suitable point in paper manufacture.
In the case of a number of dyes and fluorescent whitening agents, however, formulating concentrated solutions presents difficulties because the concentrated solutions, especially when they still comprise significant amounts of inorganic salts, tend to gel. It is then not practically possible for such gels to be purified and/or desalted by filtering off and washing.
Furthermore, on storage, especially at temperatures below room temperature, there are often formed in the concentrated solutions deposits which either cannot be redissolved at all or can be redissolved only by carrying out additional work. Moreover, if concentrated anionic dye or fluorescent whitening agent solutions are to be suitable as commercial forms, they should, on being diluted to produce the dyebaths, yield clear solutions containing about from 1 to 3% by weight of dye or fluorescent whitening agent without a precipitate, and that should also be the case over a pH range that is as wide as possible.
The present Invention Is based on the problem of providing suitable concentrated solutions of such dyes and fluorescent whitening agents and also intermediates for the preparation thereof in which the mentioned difficulties do not occur.
It has now been found that, by means of the process described hereinbelow, it is possible to prepare, simply and economically, concentrated solutions that excellently meet the demands made. The process represents a simple and economical method for converting anionic organic compounds present in a poorly soluble salt form into a readily soluble form by temporarily converting particular or all acid groups Into the acid form and subsequently neutralising them using suitable bases.
The present invention accordingly relates to a process for the preparation of concentrated solutions or suspensions of anionic organic compounds, which process comprises
a) acidifying an aqueous solution or dispersion of an anionic organic compound that comprises salts and/or impurities, to a pH of 4.5 or less, if the pH is above that value, so that
b) the anionic organic compound becomes insoluble in water and precipitates out in the form of the free acid,
c) bringing the suspension, by means of micro- or ultra-filtration, to a salt content of less than 2% by weight, based on the total weight of the retained material, with
d) optional washing out of the salts with water at a pH of less than 4.5,
e) then optionally washing with water until acid-free, then
f) increasing the concentration so that the content of anionic organic compound is from 5 to 50% by weight, and
g) optionally dissolving the anionic organic compound by addition of a suitable base.
Anionic organic compounds are to be understood as being especially dyes and fluorescent whitening agents and intermediates for the preparation thereof.
Suitable dyes for the process according to the invention are anionic dyes that are stable and insoluble in water at pH values of less than 4.5. Such dyes may belong to any desired class. They are, for example, dyes containing at least one sulfonic acid group and/or carboxylic acid group from the following classes of dyes: metal-free or metal-containing mono-, bis- and poly-azo dyes, pyrazolone, thioxanthone, oxazine, stilbene, formazan, anthraquinone, nitro. methine, triphenylmethane, xanthone, naphthazarine, styryl, azastyryl, naphthoperinone, quinophthalone and phthalocyanine dyes. Such dyes may contain one or more fibre-reactive groups in the molecule.
Preference is given to azo dyes containing at least one sulfo group and, amongst those, especially the so-called azo direct dyes, for example those referred to in The Colour Index, Third Edition, Volume 2 (The Society of Dyers and Colourists, 1971). A further preferred dass is that of the so-called stilbene dyes.
Special preference Is given to dyes that are suitable for the dyeing of paper and, amongst those, especially the dyes of formula
wherein KK is the radical of a coupling component.
KK is preferably a coupling component of formula
wherein
Y
1
and Y
2
are each independently of the other ═O, ═NH or ═N—C
1
-C
4
alkyl,
Y
3
is ═O, ═S, ═NR or ═N—CN, R being hydrogen or C
1
-C
4
alkyl, and
R
1
and R
2
are each independently of the other hydrogen, unsubstituted or substituted alkyl or unsubstituted or substituted phenyl.
In formula (2) above, only one tautomeric form is indicated for the coupling component, but the formula is intended also to encompass the other tautomeric forms.
When R
1
and/or R
2
is/are an unsubstituted or substituted alkyl group, it is to be understood as being, for example, methyl, ethyl, n- or iso-propyl, n-, sec- or tert-butyl, straight-chain or branched pentyl or hexyl or cyclohexyl; the said radicals may be mono- or poly-substituted, for example by OH, C
1
-C
4
alkoxy or by C
1
-C
4
hydroxyalkoxy.
Examples of suitable substituted alkyl radicals are: methoxymethyl, ethoxymethyl, ethoxy-ethyl, ethoxypropyl, n-propoxymethyl, butoxyethyl and 2-hydroxyethoxypentyl.
When R
1
or R
2
is unsubstituted or substituted phenyl, the lafter may be mono- or poly-substituted, for example by C
1
-C
4
alkyl, C
1
-C
4
alkoxy, halogen, e.g. fluorine, chlorine or bromine, or by nitro.
R
1
and R
2
are preferably hydrogen or C
1
-C
4
alkyl.
Y
1
and Y
2
are preferably ═O or ═NH; furthermore, Y
1
and Y
2
are preferably the same.
Y
3
is preferably ═O, ═S, ═NH or ═N—CN, especially ═NH.
The dyes of formula (1) are known or can be synthesised in a manner known per se.
The stibene dyes are complex dye mixtures which result from the condensation of 4-nitro-toluene-2-sulfonic acid with itself or with other aromatic compounds. Their structure is defined by the mode of preparation. Suitable stilbene dyes are, for example, those described in The Colour Index, Third Edition, Volume 4 (The Society of Dyers and Colourists, 1971) under the constitution numbers from 40.000 to 40.510.
Suitable dyes for the process according to the invention are preferably Direct Yellow 11 and its derivatives Direct Yellow 6 and Direct Orange 15, which derivatives are obtainable by means of reductive sub-steps additionally incorporated into the synthesis.
Suitable fluorescent whitening agents for the process according to the invention are sulfo- and/or carboxy-group-containing whitening agents of various classes, for example bis(triazinylamino)stilbenes, bis(triazolyl)stilbenes, bis(styryl)biphenyls and bis(benzofuranyl)biphenyls, bis(benzoxalyl) derivatives, bis(benzimidazolyl) derivatives, coumarin derivatives and pyrazoline derivatives.
For example, the process according to the invention is suitable for the preparation of concetrgted solutions of the following fluorescent whitening agents:
Suitable intermediates for the process according to the invention are especially anionic intermediates that are used for the synthesis of dyes or of fluorescent whitening agents.
They are, especially, aromatic sulfonic acids that also carry one or more further substituents,
Hoffmann Martina
Käser Adolf
Kaufel Rainer
Lautenbach Holger
Malisz Jacek
Ciba Specialty Chemicals Corporation
Drodge Joseph
Mansfield Kevin T.
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