Abstract: An improved process for producing by interfacial reaction, a high solids an aqueous slurry of microcapsules is disclosed. Typical interfacial reaction involves the steps of emulsifying an oil phase containing the material to be encapsulated plus an oil-soluble, film-forming polyisocyanate in a continuous aqueous phase containing an emulsifying polymer under high shear conditions until the desired droplet size is obtained and then, under low shear conditions, adding a polyamine solution followed by an elevated temperature reaction sufficient to complete hardening of the polyurea capsule walls. The improvement of the invention comprising the introduction of a reaction period at elevated temperature between emulsification and polyamine addition, said reaction period permitting capsules of 10 microns or less average diameter to be made at greater than 40% by weight solids without agglomeration or resultant excess viscosity.

Abstract: A process is disclosed for performing encapsulation, en masse, by an in situ polymerization reaction to yield capsule wall material. The polymerization comprises a reaction between melamine and formaldehyde and/or polycondensation of monomeric methylol melamine or etherified methylol melamine, or a low molecular weight polymer thereof, in an aqueous vehicle and the reaction is conducted in the presence of negatively-charged, carboxyl-substituted polyelectrolyte material and certain salts, both dissolved in the vehicle. The disclosed encapsulation process permits the manufacture of microcapsules with more impermeable walls and/or lower capsule batch viscosities.

Abstract: This invention relates to paper, or like sheet material, having a coating comprising minute, liquid-containing, pressure-rupturable capsules, and also larger, non-rupturable kaolin-containing stilt capsules arranged in interspersion and in close juxtaposition. In the preferred embodiment the smaller capsules contain a liquid marking agent. The capsules, large and small, are interspersed as to size, and are closely spaced on the sheet, so that an intentional impact directed on a small area of the coating will crush substantially all of the small capsules in the area and result in the release of liquid marking agent, whereas a casually applied pressure will rupture relatively few of the small capsules in the area. The marking liquid may be a colorless chromogenic color reactant. The small capsules on a sheet containing said marking liquid may be associated with other color forming materials on said sheet, or alternatively said color forming materials may be contained on another contacting sheet.