Development of amino resins for emulsion paint formulation: effect of aldelhydic group and degree of substitution
AbstractIn our continuous effort to develop a paint binder from amino resins, amino resins from different aldehydic groups were synthesized to produce urea, formaldehyde (UF), urea acetaldehyde (UA), urea
proparaldehyde (UP) and urea butaldehyde (UB) at different degree of substitution (Mono – tetra). Some physical properties of these resins were evaluated. The viscosity, gel time, density and refractive index
of the resins (except UB) were found to increase with increase in alkyl length of the aldehydic group while turbidity (except UF) increased with increase in alkyl length of the aldehydic group. On the other
hand, melting point and moisture uptake decreases with increase in alkyl length of the aldehydic group. In the case of the degree of substitution the viscosity, turbidity, melting point and moisture uptake
increases with increase in the degree of substitution while the gel time and refractive index were found to decrease with increase in the degree of substitution. However, an initial rise followed by a gradual
fall was recorded for density for the different degree of substitution for all the resins. Samples for UF and UA with the exception of monoethylol urea were too hard brittle and has low water resistance while
those of UP and UB resins were too soft and remained as semi solid in the cured state at room temperature (30oC). This result indicates that these resins cannot be used alone as paint binder.
However, monoethylol urea seems to have sieved itself out as a compromise candidate who is neither brittle nor too soft. A comparison of monoethylol urea with some physical properties of some
convectional paint binders present it as a potential binder which may be used in the coating industry.