| abstract |
A one-step, in-situ, process for producing a high solids content emulsion or dispersion of partially or totally crosslinked urea formaldehyde or melamine formaldehyde resin droplets or particles, by forming a reaction mixture of (i) aqueous formaldehyde (formalin), (ii) at least one water-soluble protective colloid, (iii) water and (iv) optionally a surfactant, and mixing the reaction mixture in a reaction vessel; optionally adjusting the initial pH of the reaction mixture according to a desired value as needed; adding (a) urea, substituted urea, or a mixture thereof, or (b) melamine, substituted melamine, or a mixture thereof, to the reaction mixture; and heating the reaction mixture to a temperature at which condensation takes place between the (a) urea, substituted urea, or the mixture thereof, or (b) melamine substituted melamine, or the mixture thereof, and the formaldehyde to form a urea formaldehyde or melamine formaldehyde resin, and holding the reaction mixture at that temperature or a higher temperature, under mixing, for a period of time sufficient to achieve a desired degree of crosslinking in said urea formaldehyde or melamine formaldehyde resin; and cooling the reaction mixture. The droplet or particle size of the resulting resin dispersion can be controlled and adjusted by way of the present technique to the application requirements. |