Waterborne Resins Used in Surface Coatings

Water soluble resins will not be considered further. Two distinct types of waterborne acrylics find use in surface coatings, namely  

Acrylic emulsions used in surface coating applications are almost invariably polymerised in water as described in Chapter II. 

It is also possible, but much less common, to produce a waterborne acrylic from a water insoluble acrylic by converting hydrophobic groups to hydrophilic pendent groups. For example, esters, amides or nitrile groups can be hydrolysed or unsaturated groups oxidised. 

Carboxyl containing acrylic polymers are often stabilised in aqueous solutions by adding ammonia or amines to form salts. These amines or ammonia can be largely driven off after film formation. However, even after the loss of the neutralising agent, the films remain water sensitive and some form of crosslinking is necessary for water maximum resistance. 

The most useful crosslinking agents are the N-methylol group containing resins such as the urea or melamine formaldehyde resins and the phenol formaldehyde resins which react with hydroxyl or carboxyl groups on the polymer. 

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