GB683169A - The manufacture of thermosetting aminoplastic molding compositions in granular form - Google Patents

Abstract

Granular aminoplast moulding materials are made by heating an aminoplast moulding powder to 45-80 DEG C. while maintaining it in a loose and uncompacted condition, feeding the heated powder directly to a briquetting machine and forming briquettes at a pressure of 5000-25,000 pounds per square inch, having a surface/volume ratio (measured in inch units) of less than 10 : 1, and granulating the briquettes while hot to form granules which will pass an 8-10 mesh screen and of which the major portion will not pass an 80 mesh screen. The preferred temperature is 70-80 DEG C., the powder preferably being agitated while being heated. The preferred briquetting pressure is 10,000-15,000 pounds per square inch. A revolving cutter blade type granulator may be used for granulating the briquettes. Examples of the production of urea-formaldehyde and melamine-formaldehyde granular moulding materials are given, the briquette sizes varying from 9 X 5 X 3/4 inches to discs 1 inch diameter X 3/8 inch thick. The granules give good and uniform mouldings either directly or after preforming. The preparation of urea-formaldehyde and melamine - formaldehyde resins and moulding powders is described. Hardening agents referred to are phthalic acid or anhydride, maleic acid, diammonium phosphate and triethanolamine phthalate. The compositions may be buffered with alkaline materials such as free urea, melamine or hexamethylene tetramine.