Compositions: coating or plastic – Coating or plastic compositions – Marking
Patent
1998-11-17
2000-09-05
Klemanski, Helene
Compositions: coating or plastic
Coating or plastic compositions
Marking
106 3143, 106 3158, C09D 1102
Patent
active
061136778
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a colouring agent, particularly to an ink or to a printing ink. Moreover, the invention relates to a printing process or writing process with the application of a colouring agent, particularly with the application of an ink or printing ink, onto a material or support, respectively, by means of a per se known printing device or writing device. The invention finally also relates to a process for manufacturing a colouring agent.
Colouring agents, in particular inks or printing inks, are known since a long time. Already at times when colouring agents still were manually applied to suitable media like parchment, paper etc., but also in recent times, when the application of colouring agents was carried out manually or mechanically by means of suitable printing devices, for example by means of ink jet printers, there was a problem in that such inks were not water-resistant after drying on the medium onto which they were applied, in particular in such cases where intensive, water-soluble dyes were used for colouring. Signs applied onto suitable media as paper etc. by means of heretofore known colouring agents, particularly by inks or printing inks, are blurred when coming into contact with humidity, sweat or even with water or aqueous solutions. This is a disadvantage not only for inks applied by means of fountain pens, but also for inks applied, for example, by ink jet printers used in word processing, in modern printing systems etc. The solubility of such colouring agents in water results from the introduction of polar, salt-forming groups into the dye molecule. A good solubility in water usually is obtained, if several polar, salt-forming groups are present in the dye molecule and if the counter-cation of said salt-forming group(s) is a sodium ion.
On the other hand, a good solubility of said colouring agents in water is desired, since the colouring agents are provided for use in the form of aqueous solutions or at least in the form of solutions at least predominantly containing water as the solvent. Numerous colouring molecules, however, are non polar or at least poorly soluble in aqueous media, not considering their polar side groups conferring solubility. It is a frequently occurring consequence when storing or using such inks that the colouring agent(s) precipitate, leaving an aqueous phase which is more or less depleted of the colouring substance. The supernatant above said precipitated solid is unsuitable as a colouring agent. In addition, there is a high risk that the precipitated solid(s) clog(s) the conduits supplying the colouring agent in said writing or printing devices.
It was the object of the invention to provide a colouring agent, in particular an ink or a printing ink which is water-based and does not precipitate from an aqueous solution during storage or use even under unfavorable conditions, which, however, becomes insoluble after drying on a medium or material onto which it is applied in the course of printing or writing.
It was another object of the invention to provide a printing method by which a water-insoluble print can be generated on a suitable medium. It was also an object of the invention to provide a writing method resulting into water-insoluble letters or drawings on a suitable medium.
Finally, it was also an object of the invention to provide an economically acceptable and reproducible process for manufacturing a colouring agent or printing ink, respectively, which method may be conducted under industrially applicable conditions so as to obtain a stable colouring agent or printing ink.
Surprisingly, it was found that the solubility of the colouring agent in water or the re-dissolvability of the colouring agent in water or aqueous solutions can be controlled depending upon the pH value of the aqueous medium. Thereby, a means is provided by which the solubility of the colouring agent can be adapted to the conditions constrained by the soluble dye specifically used.
The colouring agent according to the invention may be an ink as normally used in per
REFERENCES:
patent: 5462592 (1995-10-01), Murakami et al.
patent: 5518534 (1996-05-01), Pearlstine et al.
Derwent abstract of JP05/148437, Jun. 1993.
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