Common external crosslinking agents for carboxyl containing water-based resins

The method of crosslinking modification of water-based resin by adding crosslinking agents can increase molecular weight and block hydrophilic groups after curing to form a network structure, greatly improving its water resistance and solvent resistance. At the same time, it reduces the sensitivity of the coating to temperature and solves the problem of hot adhesion and cold brittleness of acrylic resin coatings.

The commonly used external crosslinking agents for carboxyl containing water-based resins are:

1. Melamine formaldehyde crosslinking agent. This type of crosslinking agent has readily available raw materials, low product prices, and can be used as a room temperature crosslinking agent. The type of neutralizing agent and strong acid catalyst have a significant impact on the crosslinking temperature.

        2. Aziridine crosslinking agent. The reaction speed is fast and the effect is obvious, making it a relatively mature and effective room temperature crosslinking agent currently being studied. There is a significant tension in the structure of the aziridine ring, which has high activity and can react with carboxyl and hydroxyl groups at room temperature

        3. Polycarbodiimide (PCDI) crosslinking agent. This type of crosslinking agent has the advantages of low toxicity and high efficiency, which can improve the water resistance of the coating while maintaining its original characteristics. Its reaction rate with carboxyl groups is slow, and the crosslinking effect can only reach its optimal level after 4-5 days.

        4. Polyisocyanate crosslinking agents. Polyisocyanate crosslinked coatings have high glossiness, mechanical strength, and solvent resistance. Crosslinking is achieved by reacting the isocyanate group with high reactivity on the crosslinking agent molecule with the carboxyl group in the lotion.