| 摘要 |
Aminoplast resin pigments for paper making comprise large surface area (>5m2/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.
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