Preparation of aminoplast resin particles
AssigneeImperial Chemical Industries PLC
InventorsRichard G. C. Henbest, John Harrison
Life of this patent
Estimating the term…
Abstract
Aminoplast resin pigments for paper making comprise large surface area (>5m.sup.2 /g) particles, preferably of size below 200 .mu.m, made from an aminoplast resin made by condensing formaldehyde with urea and/or melamine in the presence of 0.2 to 15 moles, per 100 moles of formaldehyde, or sulphite, phosphate, phosphite or borate radicals. The resin may be converted to the particulate form by gelling the resin in extended form by dilution with an aqueous acid, followed by drying, curing, and comminution of the gelled resin. To effect gelation in extended form the resin is preferably diluted to a resin solids content of less than 25% by weight by the addition of sufficient acid to cause gelation within 20 minutes.
Claims9
A process for the manufacture of particles suitable for use as pigments in paper making which comprises;
- (A) reacting in an aqueous medium urea, formaldehyde and a source of inorganic oxyacid radicals selected from the group consisting of sulphite, phosphate, phosphite, and borate radicals, said source being present in such a quantity that ther are 0.2 to 15 moles, per 100 moles of formaldehyde, of said oxyacid radicals, to form an aqueous urea-formaldehyde resin solution;
- (B) adding an aqueous acid to said resin solution, the amount of said acid being sufficient to cause said resin to gel in an extended form of a mass of high area particles lightly bonded together;
- (C) drying the resultant gelled resin mass;
- (D) curing said mass by heating at 100.degree. C. to 200.degree. C.;
- and
- (E) comminuting said cured gelled resin mass to powder form.
Dependencies are inferred from the claim text.