Amino Resin: Definition, Raw Materials, Applications

3rd January 2024
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What is amino resin?

Amino resins are resins formed by the condensation of compounds containing amino groups, such as urea, melamine, or benzoguanamine, with formaldehyde and alcohols.

Amino resins have been the primary cross-linking agents in the coating industry for over sixty years. The discovery of butanol-modified urea-formaldehyde resins in the 1930s marked the beginning of the application of amino-alcohol-acid bake coatings. In the early 1940s, melamine formaldehyde resins were invented, producing amino coatings with superior overall performance and driving the rapid development of amino resins in the coating industry. In the 1960s, benzoguanamine formaldehyde resins were invented, and their use as cross-linking agents resulted in coatings with excellent chemical resistance and initial gloss, expanding the application of amino coatings.

Raw materials of amino resin

The synthesis of amino resins involves fundamental raw materials such as amino compounds (primarily urea, melamine, benzoguanamine), aldehydes (mainly various specifications of formaldehyde), and alcohols (mainly aliphatic monohydric alcohols like methanol, butanol, isobutanol, ethanol, isopropanol, etc.).

Amino resins are classified based on the type of amino compound used. When urea is used, it is termed urea-formaldehyde resin (UF), and when melamine is employed, it is called melamine formaldehyde resin (MF).

The product of the reaction between amino compounds and formaldehyde contains a significant amount of methyl groups, exhibiting strong polarity and insolubility in organic solvents. Due to poor compatibility with other types of resins, amino resins used in coatings require modification with alcohols. After etherification, amino resins can undergo cross-linking reactions with compatible resins, resulting in coatings with practical value.

Raw-materials-of-amino-resin

Applications of amino resin

Amino resins are multifunctional polymers. If used alone in coatings, the resulting film may have poor adhesion, high hardness, and become brittle. Amino resins can react with polymers containing hydroxyl or carboxyl groups, making them suitable as cross-linking agents for various coating base resins, including alkyd resins, acrylic resins, saturated polyester resins, and epoxy resins.

Coatings cross-linked with amino resins as curing agents exhibit excellent gloss, color retention, hardness, chemical resistance, water resistance, and weather resistance. Therefore, amino resin coatings find widespread applications in industries such as automotive, construction machinery, steel furniture, household appliances, and pre-coated metal. When catalyzed by acid, amino resin coatings can significantly lower baking temperatures, making them suitable for two-component wood coatings and automotive repair coatings.

  • Amino&Alkyd Resin

The baked coating produced by amino and alkyd resin is the earliest and most widely used. The resulting film exhibits excellent hardness, gloss, water and weather resistance. This coating is commonly applied in the painting of light industrial products such as automobiles, bicycles, washing machines, sewing machines, small household appliances, and decorative components for lighting fixtures.

applications of Amino&Alkyd Resin

  • Amino&Polyester Resin

Polyester resin is a linear-structured polymer synthesized from polyols and polyacids. The resin structure contains hydroxyl and carboxyl groups, allowing cross-linking with amino resins to produce high-performance coatings. Due to the diverse structures of polyols and polyacids, various resins can be synthesized to meet different performance requirements for coatings. Therefore, baking paint made of amino-saturated polyester resins is primarily applied in the coil coating.

  • Amino&Acrylic Resin

Acrylic resin, with hydroxyl and carboxyl functional groups in its structure, forms films through cross-linking with amino resins. The coatings produced are predominantly employed in industries such as automotive, motorcycle, coil coating, and ink. These coatings exhibit excellent characteristics, including fullness, gloss, hardness, weather resistance, and chemical resistance.

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