Stable Aqueous Melamine-Urea-Formaldehyde Resins

Stable Aqueous Melamine-Urea-Formaldehyde Resins [62] 

To a resin flask equipped with a mechanical stirrer and condenser are added 259.2 gm (3.2 moles) of 37% formaldehyde (inhibited with 13.2% methanol) and 4.4 gm (0.1 mole) of acetaldehyde. The pH is adjusted to 8.5 with aqueous sodium hydroxide and then simultaneously while stirring are added 50.4 gm (0.4 mole) of melamine and 60 gm (1.0 mole) of urea. The reaction mixture becomes warm (40 -50 C) and the temperature of the reaction is maintained at 50 C for about j hr after the melamine and urea go into solution. The pH of the resulting condensation is adjusted to about 10.5 and the solution is stable without precipitation for 32 days (250 cP at 25°C). 

Some additional preparations using this procedure are outlined in Tables XIII and XIV. 

Conditions same as Preparation 3-7. Data given in moles. 

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TABLE XIII Preparation of Stable Aqueous Melamine-Urea-Formaldehyde Resins [62]... 

Melamine-formaldehyde resins [9003-08-1], like urea resins, are used primarily for bonding wood. Because they are not particularly stable in aqueous solution, melamine-formaldehyde resins are marketed primarily in powder form. 

Formaldehyde is one ofthe most important basic chemical compounds [1]. Aqueous formaldehyde solutions are used as disinfection and conservation agents. It is an educt for the production of resins from phenol, urea, and melamin. Water-free formaldehyde is the raw material for polyoxymethylene, a dimensionally stable polymer. 

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