Dispersant

Details Dispersant Dispersant

2001-04-24

2004-01-20

Niland, Patrick D. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C106S031010, C106S031130, C106S031250, C523S160000, C523S161000, C524S507000, C524S590000, C524S591000, C524S839000, C524S840000, C525S123000, C525S127000, C525S455000, C528S044000, C528S065000, C528S085000

Reexamination Certificate

active

06680355

ABSTRACT:

The present invention relates to a dispersant and to its use for dispersing pigments and for preparing an inkjet printing ink.
A dispersant is a substance which facilitates the dispersing of particles in a medium by lowering the interfacial tension between the two components. Dispersants are generally surface-active materials having an anionic, cationic or nonionic structure. The presence of a dispersant substantially reduces the dispersing energy required. Dispersed solids may have a tendency to reagglomerate after the dispersing operation, owing to mutual attraction forces. The use of dispersants also counteracts the reagglomeration tendency of the solids.
The dispersant used has to meet particularly high requirements when used for dispersing pigments, such as color or magnetic pigments. Inadequate dispersing manifests itself as increased viscosity in liquid systems, loss of brilliance and hue shifts. Particularly good dispersion of the color pigment is required in the case of inks for use in inkjet printers so as to ensure unimpeded passage of the color pigment particles through the nozzles of the print head which are frequently only a few micrometers in diameter. In addition, pigment particle agglomeration and the associated blockage of the printer nozzles has to be avoided in the standby periods of the printer.
Polymeric dispersants contain in one part of the molecule so-called anchor groups (an anchor group block) which sorb onto the solid to be dispersed. In a spatially separate part of the molecule, polymeric dispersants have a polymer chain which sticks out and whereby solid particles are made compatible with the dispersion medium, or stabilized (stabilizer block). Polymeric dispersants based on polyfunctional isocyanates, a polymeric compound and compounds bearing dispersing groups are described for example in DE-A-21 25 065, WO 97/12923, DE-A-36 41 581, WO 95/30045 and EP-A-0 742 238. In general, the anchor groups have to be specifically adapted to the solid to be dispersed, for example different color pigments, since otherwise the anchor groups may desorb and the dispersion may become unstable in the course of the formulation of the end product or in the course of storage. The need for individual adaptation of the dispersant to the pigment is disadvantageous. It has also been determined that the inkjet inks used hitherto are in need of improvement with regard to their optical density when used for printing cellulosic substrates.
It is an object of the present invention to provide a dispersant which provides stable dispersions with a large number of pigments of differing constitutions and leads to inkjet inks having improved optical density when used for printing cellulosic substrates.
We have found that this object is achieved by a polymeric dispersant obtainable by reacting
(i) a di- or polyfunctional isocyanate with
(ii) an HX-terminated polymeric compound, where X is COO, O, S or NR
1
and R
1
is H or C
1
-C
6
-alkyl; and either
(iii) an HY-terminated homopolymer of a monomer selected from the group consisting of N-vinylamides, N-vinyllactams and vinyl- or allyl-substituted nitrogenous heterocycles or copolymer of one or more of the monomers mentioned and optionally further monomers, where Y is COO, O, S or NR
2
and R
2
is H or C
1
-C
6
-alkyl; or
(iv) an HY-functional organic phosphonic ester, where Y is as defined above.
The polymeric dispersant of the invention is accordingly obtainable through reaction of three mandatory components, namely a di- or polyisocyanate to act as point of attachment; a polymer compound (hereinafter referred to as stabilizer block) terminated at one end by an isocyanate-reactive group; and an anchor group block, which can be either a homo- or copolymer of a selected nitrogenous monomer or an organic phosphonic ester, which each possess an isocyanate-reactive group. The terms stabilizer block and anchor group block have been introduced for ease of reference in the description part which follows. In general, it is the anchor group block which becomes sorbed onto the solid to be dispersed. In an individual case, however, the relationships may also be different.
The chemical nature of the stabilizer block is not particularly critical. In general, it is preferable for the polymeric compound to be water-soluble or water-swellable. The polymeric compound therefore preferably possesses hydrophilicizing structural elements, such as ether, ester or amide groups. The polymeric compound is terminated at one end by an isocyanate-reactive group. Preferably, there are no further isocyanate-reactive groups along the chain. Preferred polymeric compounds are compounds of the general formula
R
3
—M
n
—XH
where
R
3
is hydrogen, linear or branched C
1
-C
28
-alkyl, linear or branched C
2
-C
28
-alkenyl, linear or branched C
2
-C
28
-alkynyl or the residue of a singly or multiply unsaturated polymerization initiator or of a chain regulator,
M represents identical or different polymerized units of monomers selected from the group consisting of &agr;,&bgr;-ethylenically unsaturated mono- or dicarboxylic acids; unsubstituted or hydroxyl-, C
1
-C
6
-alkoxy-, polyalkyleneoxy- or halogen-mono- or -polysubstituted C
1
-C
20
-(cyclo)alkyl or C
7
-C
20
-aralkyl esters, amides, nitriles or anhydrides of &agr;,&bgr;-ethylenically unsaturated mono- or dicarboxylic acids; vinyl or allyl esters of aliphatic or aromatic carboxylic acids; vinyl or allyl ethers; ethylenically unsaturated sulfonic acids or sulfonic acid derivatives; halogenated or unhalogenated ethylenically unsaturated aliphatic C
2
-C
20
hydrocarbons; aromatic ethylenically unsaturated compounds and compounds polymerizable to form polyphosphacenes; or is
where
R
4
, R
5
, R
6
and R
7
are independently H, C
1
-C
6
-alkyl, C
6
-C
20
-aryl, —CH
2
-Cl or —CH
2
—OH, and R
8
, R
9
and R
10
are independently a C
2
-C
20
-alkylene, C
6
-C
10
-arylene or C
7
-C
20
-aralkylene group, and
n is an integer between 0 and 10,000, preferably ≧2, especially ≧3, particularly preferably within the range from 30 to 1000, and
X is as defined above.
The polymeric compound may be prepared by anionic, cationic or preferably free-radical polymerization of ethylenically unsaturated monomers. Suitable monomers are &agr;,&bgr;-ethylenically unsaturated mono- or dicarboxylic acids, such as acrylic acid, methacrylic acid, cinnamic acid, maleic acid, fumaric acid or itaconic acid; optionally hydroxyl-, C
1
-C
6
-alkoxy-, polyalkyleneoxy- or halogen-substituted C
1
-C
20
-(cyclo)alkyl esters, amides, nitriles or anhydrides of &agr;,&bgr;-ethylenically unsaturated mono- or dicarboxylic acids, such as methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, stearyl(meth)acrylate, lauryl(meth)acrylate, cyclohexyl(meth)acrylate, benzyl(meth)acrylate, trifluoromethyl(meth)acrylate, hexafluoropropyl(meth)acrylate, tetrafluoropropyl(meth)acrylate, polypropylene glycol mono(meth)acrylates, polyethylene glycol mono(meth)acrylates; vinyl or allyl esters of aliphatic or aromatic carboxylic acids, e.g., vinyl acetate, vinyl propionate, vinyl butanate, vinyl hexanoate, vinyl octanoate, vinyl decanoate, vinyl stearate, vinyl palmitate, vinyl crotonate, divinyl adipate, divinyl sebacate, 2-vinyl 2-ethylhexanoate, vinyl trifluoroacetate; allyl acetate, allyl propionate, allyl butanate, allyl hexanoate, allyl octanoate, allyl decanoate, allyl stearate, allyl palmitate, allyl crotonate, allyl salicylate, allyl lactate, diallyl oxalate, allyl stearate, allyl succinate, diallyl glutarate, diallyl adipate, diallyl pimelate, diallyl cinnamate, diallyl maleate, diallyl phthalate, diallyl isophthalate, triallyl benzene-1,3,5-tricarboxylate, allyl fluoroacetate, allyl perfluorobutyrate, allyl perfluorooctanoate; ethylenically unsaturated sulfonic acids and sulfonic acid derivatives, such as vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, their esters and halides, vinyl benzenesulfonate, 4-vinylbenzenesulfonamide; vinyl or allyl ethers, such as vinyl

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