Benzoguanamine, and Melamine Resins for Coatings

The first amino resins used in coatings were partially butylated, polymeric urea-formaldehyde (UF) resins introduced in the late 1920s. Melamine-formaldehyde (MF) resins followed in 1935. In 1960 a range of fully alkylated, predominantly 

Properties. Alkylated amino resins can be classified into two general classes (1) polymeric, partially alkylated resins which have a lower solids content and (2) the more monomeric, fully and partially alkylated products which have a higher solids content. 

Typical polymeric, partially alkylated amino resins are butylated or isobutylated condensates with an average degree of polymerization between 3 and 8 and a combined formaldehyde content of 1.4-1.8 per amino group [2.147]-[2.149]. The hydroxymethyl (methylol) groups are partially alkylated (degree of alkylation 40-80%). 

The final resin has a solids content of ca. 50-65 %, and a combination of functional sites of different reactivity [2.148]. The solvents most commonly used are aromatic hydrocarbons and alcohols. 

Fully alkylated amino resins require strong acid catalysis for fast and/or low-temperature cross-linking. Their catalysis mechanism is different from that of partially alkylated resins which respond to weak acid catalysts or general acid catalysis. A fully alkylated melamine resin catalyzed by a strong acid catalyst is a faster curing (cross-linking) agent than a partially butylated amino resin. 

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