Aqueous ink compositions

Details Aqueous ink compositions Aqueous ink compositions

1999-03-30

2001-03-13

Klemanski, Helene (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Marking

C534S753000, C534S794000

Reexamination Certificate

active

06200371

ABSTRACT:

This invention relates to inks and to their use in ink jet printing.
Ink jet printing methods involve printing an image onto a substrate using ink droplets emitted from a small nozzle without bringing the nozzle into contact with the substrate. Over recent years ink jet printers have become popular because they are quieter and more versatile than impact printers, for example conventional basket typewriters are noisy and the images they can print are restricted to the shapes moulded onto the end of each mechanical lever. The most popular ink jet printers are the thermal and piezoelectric.
The requirements for inks used in ink jet printers include:
i) they should not clog the small nozzle from which they are emitted, or form a blocking crust over the end,
ii) the resultant image should have good water-fastness so that it does not smudge excessively on contact with sweat or water,
iii) the image should also have a good light-fastness so that it does not fade quickly on exposure to daylight,
iv) they should dry quickly on paper and give discrete, sharp images,
v) they should have good storage stability, and
vi) they should have a high colour strength to give intensely coloured images.
WO91/06608 describes aqueous inks containing a polyester, water, a pigment and a wax. Whilst these inks are useful in printing presses, the pigments they contain require intensive and expensive milling to make them fine enough to pass through ink jet printer heads and the pigments have a tendency to settle out from the ink on standing for long periods. Furthermore, images formed from inks containing insoluble pigments are generally opaque and dull, particularly in the magenta shade area, limiting their usefulness on overhead projector slides.
There is a need for inks which are suitable for both thermal and piezo IJP, have high colour strength and produce images having a high light-fastness and water-fastness when printed on a substrate.
According to the present invention there is provided an ink comprising water, a water-dissipatable polymer and a dye of the Formula (1):
wherein:
R
1
is optionally substituted alkyl or optionally substituted aryl;
R
2
is H, optionally substituted alkyl or optionally substituted aryl;
R
5
is H or optionally substituted alkyl; and
R
3
and R
4
are each independently optionally substituted alkyl or optionally substituted aryl, or R
3
and R
4
together with the CH group to which they are attached from an optionally substituted 5- or 6- membered ring.
R
1
is preferably optionally substituted alkyl, more preferably optionally substituted C
1-4
-alkyl, especially C
1-4
-alkyl.
R
2
is preferably H or optionally substituted alkyl, more preferably optionally substituted alkyl, especially optionally substituted C
1-8
-alkyl, more especially C
1-6
-alkyl.
Preferably R
3
and R
4
are each independently optionally substituted alkyl, or R
3
and R
4
together with the CH group to which they are attached form an optionally substituted 5- or 6- membered ring.
When R
3
or R
4
is optionally substituted alkyl it is preferably optionally substituted C
1-8
-alkyl, more preferably C
1-6
-alkyl, especially C
2-4
-alkyl.
When the group —CHR
3
R
4
forms a 5- or 6-membered ring the ring is preferably a cyclohexyl or cyclopentyl ring.
Examples of preferred groups represented by —CHR
3
R
4
include prop-2-yl, but-2-yl, pent-2-yl, pent-3-yl, hex-2-yl, hex-3-yl, hept-2-yl, cyclopentyl and cyclohexyl.
R
5
is preferably H or C
1-4
-alkyl, more preferably H or methyl, especially H.
The optional substituents which may be present on R
1
, R
2
, R
3
, R
4
and R
5
are preferably selected from C
1-4
-alkoxy, especially methoxy; halo, especially Cl, Br or F; C
1-4
-alkyl, especially methyl; nitro; cyano; —OCO(C
1-4
-alkyl); —CO
2
(C
1-4
-alkyl); optionally substituted amino, especially —NR
a
R
b
wherein R
a
and R
b
are each independently H, C
1-4
-alkyl or C
1-4
-alkyl substituted by hydroxy, carboxy or sulpho.
In a preferred embodiment R
1
is C
1-4
-alkyl, R
2
is C
1-8
-alkyl, R
3
and R
4
are each independently C
1-4
-alkyl and R
5
is H.
A further feature of the invention provides dyes of Formula (1), as defined above.
Dyes of Formula (1) may be prepared by reacting the corresponding dye having a H atom on the pyrazole nitrogen atom with chloracetonitrile, preferably under alkaline conditions. The dye having a H atom on the pyrazole nitrogen atom may be prepared by diazotising a compound of Formula (2) and coupling the resultant diazonium salt to a compound of Formula (3):
wherein R
1
, R
2
, R
3
and R
4
are as hereinbefore defined.
The diazotisation is preferably performed at a temperature below 6° C., e.g. −5° C. to +5° C. Typically sodium nitrite is used as the diazotising agent and the process is performed in the presence of dilute mineral acid, for example dilute hydrochloric acid.
The water-dissipatable polymer preferably bears ionised carboxy and/or sulphonate groups, especially ionised sulphonate groups, because these assist water dissipatability of the polymer. Such groups can be chain pendant and/or terminal.
The water-dissipatable polymer is preferably a water-dissipatable polyester. The water-dissipatable polyester can be prepared using conventional polymerisation procedures known to be effective for polyester synthesis. Thus, it is well known that polyesters contain carbonyloxy (i.e —C(═O)—O—) linking groups and may be prepared by a condensation polymerisation process in which an acid component (including ester-forming derivatives thereof is reacted with a hydroxyl component. The acid component may be selected from one or more polybasic carboxylic acids, e.g. di- and tri-carboxylic acids or ester-forming derivatives thereof, for example acid halides, anhydrides or esters. The hydroxyl component may be one or more polyhydric alcohols or phenols (polyols), for example, diols, triols, etc. (It is to be understood, however, that the polyester may contain, if desired, a proportion of carbonylamino linking groups —C(═O)—NH— (i.e. amide linking groups) by including an appropriate amino functional reactant as part of the “hydroxyl component”; such as amide linkages). The reaction to form a polyester may be conducted in one or more stages. It is also possible to introduce in-chain unsaturation into the polyester by, for example, employing as part of the acid component an olefinically unsaturated dicarboxylic acid or anhydride.
Polyesters bearing ionised sulphonate groups may be prepared by using at least one monomer having two or more functional groups which will readily undergo an ester condensation reaction (e.g. carboxyl groups, hydroxyl groups or esterifiable derivatives thereof) and one or more sulphonic acid groups (for subsequent neutralisation after polyester formation) or ionised sulphonate groups (i.e. neutralisation of the sulphonic acid groups already having been effected in the monomer) in the synthesis of the polyester. In some cases it is not necessary to neutralise sulphonic acid groups since they may be sufficiently strong acid groups as to be considerably ionised in water even without the addition of base. Often, the sulphonic acid or ionised sulphonate containing monomer is a dicarboxylic acid monomer having at least one ionised sulphonate substituent (thereby avoiding any need to effect neutralisation subsequent to polyester formation). (Alternatively, alkyl carboxylic acid ester groups may be used in place of the carboxylic acid groups as ester-forming groups). Such a monomer will therefore be part of the acid component used in the polyester synthesis.
Preferred polybasic carboxylic acids which can be used to form the polyester have two or three carboxylic acid groups. For example, one can use C
4
to C
20
aliphatic, alicyclic and aromatic compounds having two or more carboxy groups and their ester forming derivatives (e.g. esters, anhydrides and acid chlorides), and dimer acids such as C36 dimer acids. Specific examples include adipic acid, fumaric acid, maleic acid, succinic acid, itaconic acid, sebacic acid, nonanedioic acid, deca

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