Papierfabrik August Koehler Ag

Pelikan Aktiengesellschaft

Gunter Pietsch

Karl-Heinz Schrader

The invention relates to a process for producing microcapsules by microencapsulating hydrophobic oils, particularly with substances contained therein, in which the hydrophobic oil is mixed, accompanied by vigorous stirring, into an aqueous medium containing a dispersion-stabilizing compound. The resulting oil-in-water dispersion is acid adjusted, aminoplastic capsules are formed in the conventional manner and the aqueous fraction of the aqueous medium is removed in the usual way. The aqueous medium contains a water-soluble, cationic compound such that it forms a dispersion-stabilizing compound in interaction with the water-soluble, anionic, sulphonated melamine-formaldehyde precondensate. The microcapsules obtained according to this process can be obtained economically without agglomerate formation in the form of dry single capsules e.g. by spray drying the aqueous capsule dispersion obtained. The invention also permits the encapsulation of random substances in dissolved and/or finely dispersed form.

Microcapsules and microcapsule production process

A description is given of a process for microencapsulating hydrophobic oils with color reactants of color reaction sytems dissolved therein, a cationized melamine/formaldehyde precondensate being precipitated in ultra-fine suspension from its acid aqueous solution, accompanied by vigorous stirring and by modifying the solubility conditions, said suspension is mixed under vigorous stirring with a hydrophobic oil containing the color reactants in dissolved form, the oil-in-water dispersion obtained is adjusted acid and an aqueous solution of a water-soluble, nonionic melamine/formaldehyde precondensate is added, accompanied by stirring, for forming the microcapsule envelope. For stabilizing the oil-in-water dispersion, the pH-value of the acid, aqueous solution of a cationized melamine/formaldehyde precondensate which, in the weak acid, neutral and alkaline, aqueous use range is present in insoluble, cationizable form, is raised in the absence of water-soluble, organic polymers by the addition of Bronsted bases and accompanied by vigorous stirring to such an extent that the cationizable melamine/formaldehyde precondensate is precipitated in ultra-fine suspension as a result of the modified solubility conditions. The possible elimination of the water-soluble, organic polymers is economically advantageous.

Process for microencapsulating hydrophobic oils, the microcapsules

A process for microencapsulating hydrophobic oils with color reactants, dissolved therein, of color reaction systems by reacting a water-soluble non-ionic melamine/formaldehyde precondensate and a water-soluble polymer in an oil-in-water dispersion for forming the capsule envelope is described. The special feature of this process is that, for stabilizing the oil-in-water dispersion, an aqueous solution of a cationic melamine/formaldehyde precondensate and the aqueous solution of a water-soluble polymer are mixed with vigorous stirring, a solid precipitating as a very fine suspension in the mixture, the mixture thus obtained and containing the very finely suspended solid is mixed with ther oil, containing the color reactant in solution, with vigorous stirring, the oil-in-water dispersion thus obtained in acidified and an aqueous solution of a water-soluble non-ionic melamine/formaldehyde precondensate is added with stirring, in order to form the capsule envelope. The use of the cationic melamine/formaldehyde precondensate leads to the precipitation of a very finely suspended reaction product thereof, whereby all the reaction systems in the course of the process are stabilized. Excellent capsules can be obtained without formation of agglomerates. The invention also relates to the microcapsules obtainable by the above process and to their advantageous use in color reaction recording systems.

Microcapsules containing oils and soluble color reaction components,

The invention relates to an aqueous ink for writing, drawing, or marking, which has as a dispersion stabilizer a degradation product of gelatin made by enzymatic action of a protease. The process of the invention is carried out by subjecting an aqueous gelatin solution to degradation by an enzyme, then inhibiting the enzyme, such as by heating to 90 degrees C. or above, before the degradation has proceeded to products which no longer have activity as dispersion stabilizers. Subsequently, colorants such as pigments can be added along with other desired additives.

Growing community of inventors

Isernhagen, Germany

Gunter Pietsch