Organic compounds -- part of the class 532-570 series – Organic compounds – Azo
Reexamination Certificate
2000-12-05
2002-05-28
Powers, Fiona T. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Azo
C534S638000, C534S797000, C534S802000, C534S817000, C534S829000, C534S840000, C534S845000, C106S031470, C106S031510, C106S031520
Reexamination Certificate
active
06395885
ABSTRACT:
This invention relates to dyes, to inks and to their use in ink jet printing (“IJP”). IJP is a non-impact printing technique in which droplets of ink are ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate.
There are many demanding performance requirements for dyes and inks used in IJP. For example they desirably provide sharp, non-feathered images having good water-fastness, light-fastness and optical density. The inks are often required to dry quickly when applied to a substrate to prevent smudging, but they should not form a crust over the tip of an ink jet nozzle because this will stop the printer from working. The inks should also be stable to storage over time without decomposing or forming a precipitate which could block the fine nozzle.
There is a growing demand for wide format prints which are prepared using ink jet printing. Wide format prints are often located outdoors, for example on advertising billboards, where they may be exposed to sunlight for long periods of time. It is therefore desirable that the prints exhibit a high light-fastness to minimise fading.
We have found that lithium salts of anionic dyes exhibit a surprisingly high light-fastness particularly when the dyes are incorporated into inks for use in ink jet printers. We have also found that when lithium is used in conjunction with sodium as cations in anionic dyes, the dyes exhibit a surprisingly high aqueous solubility and a high light-fastness.
According to a first aspect of the present invention there is provided the use of lithium as a cation for an anionic dye to enhance the light-fastness of the dye.
The lithium cation may be used as the sole cation for the anionic dye or in combination with other cations. For example, the lithium cation may be used together with another alkali metal cation (preferably potassium and especially sodium cations), with ammonium or with a quaternary ammonium cation.
The light-fastness of the dye generally increases as the proportion of lithium cations in the total pool of cations increases. Preferably, at least 20 mole %, more preferably at least 50 mole %, still more preferably at least 60 mole % of the cations in the anionic dye are lithium cations. In one embodiment substantially all of the cations in the dye are lithium cations.
In a second embodiment the lithium is used in combination with sodium as a cations for the anionic dye. We have found that the mixed lithium/sodium salts provide anionic dyes with a high light-fastness and a high aqueous solubility. Preferably the molar ratio of lithium to sodium cations in the anionic dye is from 1:4 to 99:1, more preferably from 1:4 to 3:1 and especially from 1:3 to 1.5:1, more especially from 1:2 to 1:1. This preferred ratio of lithium to sodium cations provides an anionic dye which exhibits an unexpectedly high light-fastness and water-fastness compared to the individual sodium and lithium salts of the dye.
When lithium is used in combination with sodium as the cations for an anionic dye preferably and at least 20 mole % of the total cations in the dye are lithium.
Preferably the anionic dye is a water-soluble anionic dye. Preferred water-soluble anionic dyes are water-soluble anionic direct, reactive and acid dyes, more preferably water-soluble anionic azo, bis azo and tris azo dyes which preferably contain one group, more preferably two or more groups, selected from carboxy, sulpho and phosphono.
It is especially preferred that the water-soluble anionic dye contains at least as many carboxy groups as sulpho groups.
According to a second aspect of the present invention there is provided a dye selected from C.I. Reactive Red 180, C.I. Acid Red 52 and a dye having one of the Formulae (1) to (9), wherein the dye is in the lithium salt form:
wherein:
R
1
and R
2
each independently is C
1-4
-alkyl;
each R
3
independently is alkoxy, —OH, —Cl or amino;
R
4
and R
5
each independently is C
1-4
-alkoxy;
R
6
is H or hydroxyethyl;
R
7
is —OH, —Cl, or C
1-4
-alkoxy;
R
8
is —COOH, —SO
3
H or —PO
3
H
2
;
R
9
and R
10
each independently is methyl or ethyl;
p is 1 or 2;
n is 0 or 1;
q and w each independently is 1 or 2;
a and b each independently is 1 or 2; and
each t independently is 1 or 2.
Preferably n is 0.
Preferably p is 2. More preferably p is 2 and each —COOH is meta to the azo group (—N═N—) in Formula (1).
R
1
and R
2
are preferably methyl or ethyl, more preferably methyl. Preferably the —SO
3
H groups in Formula (2) are attached at the meta position relative to each azo group.
Preferably each t is 2. More preferably each t is 2 and the —COOH groups are at the 3- and 5-positions in each phenyl group in Formula (3). Preferably R
3
is —OH or C
1-4
-alkoxy, more preferably —OH or methoxy and especially —OH.
R
4
and R
5
are preferably methoxy.
Preferably a and b are 2, more preferably a and b are 2 and each —COOH is attached meta to each azo group (—N═N—) in Formula (5).
Preferably R
6
is hydroxyethyl, more preferably R
6
is hydroxyethyl and the —SO
3
H group on the phenyl ring is attached in the ortho position relative to the azo group.
Preferably R
7
is —OH.
Preferably R
8
is —COOH or —PO
3
H
2
. It is especially preferred that R
8
is meta to the azo group in Formula (9).
In view of the foregoing preferences, a preferred dye according to the second aspect of the present invention is the lithium salt of a dye having one of the Formulae (10) to (21):
It is especially preferred that the dye according to the second aspect of the present invention is selected from the lithium salt of a dye of the Formula (10), (11) and (12), because these dyes exhibit a particularly high light-fastness.
Preferably in this second aspect of the invention substantially all of the —COOH, —SO
3
H and —PO
3
H
2
groups shown in the dyes of the Formulae (1) to (21) are in the lithium salt form. Accordingly, in the dyes according to the second aspect of the invention preferably all the carboxy groups are present as —COOLi, all the sulpho groups are present as —SO
3
Li and all the phosphono groups are present as —PO
3
Li
2
.
The dyes of the Formulae (1) to (21) may be prepared by methods which directly result in the lithium salt. Alternatively the dyes may be prepared in the form of a salt with a cation other than lithium, for example the sodium or potassium salt, followed by conversion into the lithium salt using conventional techniques, preferably, reverse osmosis, nano-filtration, electrodialysis, dialysis, an ion exchange technique or by precipitating the dye in free acid form followed by neutralising with LiOH.
An example of a suitable technique for converting a dye in the form of a salt with a cation other than the lithium into its lithium salt comprises passing a solution of the alternative salt of a dye of Formula (1) to (21) through an acid loaded ion exchange resin to give the free acid form of the dye. A solution/suspension of the free acid form of the dye is then neutralised with a molar excess of lithium hydroxide to give the lithium salt.
The lithium salt of the dyes of Formula (1) may be prepared in the form of their sodium salts using an analogous process to that disclosed in Example 2 of EP 0 356 080. The sodium salt may then be converted to the lithium salt using any of the hereinbefore defined methods.
The lithium salt of the dye of Formula (2) may be prepared by diazotising a sulphoaniline (for example using NaNo
2
in dilute mineral acid at below 5° C.) and coupling with a compound of the formula:
wherein R
1
and R
2
are as hereinbefore defined, followed by conversion to the lithium salt as hereinbefore described. Certain dyes of Formula (2) are commercially available in the form of their sodium salts, for example C.I. Direct Yellow 132.
The lithium salt of the dye of Formula (3) may be prepared using an analogous process to that described in example 3 of PCT publication number WO 94/16021, followed by conversion into the lithium salt.
The lithium salt of the dye of Formula (4) may be prepared by condensing hydroxyethylamine with a chlorotriazine
Lavery Aidan Joseph
Meyers John Parker
Watkinson Janette
Avecia Limited
Powers Fiona T.
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