Properties and Application of Amino Resin Adhesives and Binders

Presents a historical review of the development of urea and melamine resins. Urea resins are modified for better water resistance, gap-filling properties, faster clamping characteristics, and better wet strength in paper. Unmodified urea resins give excellent bonds in film thicknesses of about 7 mils. For gap-filling purposes, the resin is modified with benzyl alcohol or furfural alcohol which reduce shrinkage on curing. For imparting wet strength to paper, molecular size, constitution and ionic character, presence of electrolyte, and nature of the pulp are important. With anionic urea resins, some modification of treatment must be made usually involving co-treatment with alum. With cationic resins, modification is not necessary since there is ionic attraction. Molecular size is especially important. Regardless of resin type, the retention (and wet strength) increases as the molecular size of the resin increases up to a point, beyond which further increases in molecular size have no further effect. Melamine resins have excellent color stability, high heat resistance, and hardness. They are used especially for making decorative laminates.

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