Bleaching and dyeing; fluid treatment and chemical modification – Process of printing permanently on substrate – other than... – Resist or reserve
Reexamination Certificate
2000-10-03
2002-12-17
Delcotto, Gregory (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Process of printing permanently on substrate, other than...
Resist or reserve
C008S445000, C008S478000, C008S495000, C008S532000, C008S554000, C008S552000
Reexamination Certificate
active
06494924
ABSTRACT:
The present invention relates to precipitated, water-insoluble dyes in colloidally disperse form, to a process for preparing them and to their use.
Pigments and disperse dyes are the most important representatives of the group of water-insoluble dyes. It is frequently necessary, in the case of disperse dyes even essential, to use them in colloidally disperse form. The colloidally disperse form is particularly important when the dyes are used in ink-jet printing, a widely used process, for the contactless printing of various print media, for example paper, film, photopaper and textiles. To obtain a colloidally disperse form, the dye crystals are generally mechanically comminuted, for example by grinding. A decisive disadvantage of grinding is that metallic attritus or attritus from the grinding media ends up in the dye powder and can lead to major problems in the use of the dye powder. For example, ink-jet printing nozzles may be damaged or blocked.
Pigments and disperse dyes in colloidally disperse form have to be stabilized against recrystallization, agglomeration and flocculation. U.S. Pat. No. 5,531,816 proposes a waterborne ink-jet ink composition comprising at least one deagglomerated pigment having a particle size within the range from 5 nm to 1 &mgr;m, at least one water-insoluble organic compound and at least one amphiphilic compound. The amphiphile solubilizes the water-insoluble organic compound in the aqueous phase in the form of small droplets. The pigment is dispersed in the droplets of the water-insoluble organic compound and so maintained in the deagglomerated state.
DE 27 32 500 A describes a process for preparing water-dispersible, pulverulent disperse dyes by spray drying a solution of the dyes in formic acid, formamide, N-methylformamide, butyrolactone or ethylene glycol. The solution may further comprise dispersants, surfactants and protective colloids. The dye powder obtained consists of particles in the nanoparticle range.
Prior art dye particles all have a relatively broad particle size distribution, which is why the brilliance of the color leaves something to be desired. In addition, prior art dye particles are highly crystalline and have a nonuniform particle shape.
It is an object of the present invention to provide water-insoluble dyes in colloidally disperse form which have a narrow particle size distribution. In addition, the dye particles shall be substantially spherical and amorphous.
It has now been found that this object is achieved, surprisingly, by dye particles obtained by precipitation from a solution of the dye in a water-miscible organic solvent.
The present invention accordingly provides precipitated, water-insoluble or sparingly water-soluble dyes in colloidally disperse form having an average particle size within the range from 5 nm to 5 &mgr;m and having a particle size distribution width (variance) of less than 50% (both measured by quasi-elastic light scattering and evaluation by the cumulant method; cf. Bruce J. Berne and Robert Pecora, “Dynamic Light Scattering”, John Wiley & Sons, Inc. 1976, p. 196f.).
The average particle size is preferably within the range from 5 nm to 1 &mgr;m, especially within the range from 5 nm to 500 nm. The width of the particle size distribution is preferably less than 40%.
The dye particles of the invention possess only a small crystalline content by virtue of the process used for preparing them. The crystallinity is preferably not more than 30%, especially not more than 10%. Particularly preferably, the particles are present in completely amorphous form.
In addition, preferably not less than 80%, especially not less than 90%, of the dye is present in the form of spherical particles.
Because of their narrow particle size distribution, the dyes of the invention provide a cleaner color, and hence greater brilliance, in paper and photo printing in particular. In addition, they also provide higher color strength.
The dyes of the invention further exhibit advantageous viscosity characteristics and are simple to apply to fibers because of their high amorphous content.
Preference according to the invention is given to water-insoluble or sparingly water-soluble azo, anthraquinone, quinophthalone, methine and azamethine dyes.
The dye particles of the invention can be prepared by two different methods, by
A) precipitating it from a solution in a water-miscible organic solvent, or
B) preparing an oil-in-water emulsion from a solution of the dye in a water-immiscible organic solvent and precipitating the dye particles by stripping off the solvent.
Method A) (Water-miscible Solvent)
To produce the dye particles of the invention, the coarsely crystalline dye particles are initially dissolved in a suitable water-miscible organic solvent. Which solvent is used depends on the solubility properties of the dye. In principle, all water-miscible (which also includes those solvents which are miscible with water only to a proportion of not less than about 10% by weight) organic solvents are usable. In general, thermally stable solvents of this type are used. Suitable solvents are:
1. mono- and polyalcohols such as methanol, ethanol, n-propanol, isopropanol, glycol, glycerol, propylene glycol, polyethylene glycols, etc.;
2. ethers, such as tetrahydrofuran, dioxane, 1,2-propanediol 1-n-propyl ether, 1,2-butanediol 1-methyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, etc.;
3. esters, such as methyl acetate, monoesters of ethylene glycol or propylene glycols with acetic acid, butyrolactone, etc.;
4. ketones, such as acetone or methyl ethyl ketone;
5. amides, such as formamide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and hexamethylphosphoramide;
6. sulfoxides and sulfones, such as dimethyl sulfoxide and sulfolane;
7. alkanecarboxylic acids, such as formic acid or acetic acid.
Preference is given to the solvents recited above under 1 to 5, especially methanol, ethanol, n-propanol, isopropanol, 1,2-butanediol 1-methyl ether, 1,2-propanediol 1-n-propyl ether, dimethylacetamide, N-methylpyrrolidone or acetone.
The amount of solvent depends on the dye to be dissolved. In general, it is desirable to keep the amount of solvent used to a minimum.
The coarsely crystalline dyes are generally dissolved at elevated temperature, since the solubility is too low at room temperature or below. The dissolving is preferably effected at from 50 to 300° C., especially at from 100 to 300° C. If the boiling point of the solvent is too low, the dissolving may also be effected under superatmospheric pressure, for example at a pressure of up to 50 bar.
The precipitating of the dye particles in colloidally disperse form is then effected by adding water to the solution of the dye in the water-miscible organic solvent. The temperature at which the precipitating step takes place is not critical. Advantageously, water of from 0 to 50° C. is added to the hot solution of the dye.
The water preferably comprises at least one protective colloid in order that the reagglomeration of the colloidally disperse particles may be prevented. Protective colloids used include the natural or synthetic polymers customarily used for this purpose. Useful natural or semisynthetic protective colloids include for example gelatin, including fish gelatin, starch or starch derivatives, such as dextrins, pectin, gum arabic, casein, caseinate, alginates, cellulose and cellulose derivatives, such as methylcellulose, carboxymethylcellulose, hydroxypropylcellulose or hydroxypropylmethylcellulose.
Useful synthetic protective colloids are water-soluble homo- or copolymers, which can be neutral polymers, cationic polymers or anionic polymers. Similarly, complexes of polycationic and polyanionic polymers and also coacervates are contemplated.
The polymers are polymerized from monomers having hydrophilic groups and optionally comonomers having hydrophobic groups, the ratio between hydrophilic and hydrophobic groups being chosen in such a way that the copolymer is water-soluble.
Suitable hydrophilic monomers include for example N-vinyllactams, s
Auweter Helmut
Bohn Heribert
Heger Robert
Horn Dieter
Siegel Bernd
BASF - Aktiengesellschaft
Delcotto Gregory
Elhilo Eisa
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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