Curing Behavior of Waterborne Paint Containing Catalyst Encapsulated in Micelle

Abstract

This research has studied the feasibility of fabricating a catalyst that activates at 80 °C to ensure the curing performance of two-pack isocyanate curable paints, while remaining inactive at 40 °C to ensure storage stability and pot life. The research examined whether the added dibutyl tin dilaurate (DBTL) provided a catalytic function for curing the waterborne paint, which remains almost inactive at 40 °C and activates at 80 °C or higher. It was confirmed that the use of a non-ionic surfactant with a hydrophilic-lipophilic-balance (HLB) of between 13 and 14 resulted in rapid curing at a temperature of 80 °C or higher, thereby demonstrating catalytic properties. The results also show that the viscosity of the paint remained virtually unchanged after exposure for 1 h at 40 °C. This wass presumed to be the result of the DBTL, which was constrained by the micelles up to a temperature of 70 °C, breaking down the micelles at a temperature of 80 °C or higher. It was also confirmed that the catalytic switching properties were not obtained at a lower or higher HLB. It was found that selecting the non-ionic surfactant by HLB can control the activating temperature of the catalytic properties.

Effects of Organic Solvent on Curing Behavior and Storage Stability for Waterborne Paint Containing Catalyst Encapsulated in Micelles

“…The oleic-acid-type surfactant Nonion E-212 (a product of Nichiyu, Tokyo, Japan; hereafter referred to as E-212) was used. It can activate the catalytic function at approximately 80 • C, as previously reported [16], as a nonionic surfactant that develops a switching function in the production and extinction of micelles. This was dissolved in deionized water to a concentration of 20 wt% to form a transparent aqueous solution.…”

“…The increase in MW with increasing temperature up to the maximu thought to be due to stronger hydrophobic interactions of surfactant mol consequent micelle growth, as described above. On the other hand, the decr with increasing temperature above the maximum value may indicate tha released, which is accompanied by shrinkage of the micelles [16]. • with DBTL 〇 without DBTL The MW (closed triangle) of the aqueous solution with DBTL and PrOH and (closed square) of the aqueous solution with DBTL and 2EhOH are shown in F associated with data from Figure 5.…”

“…We focus on the possibility of encapsulating catalysts in surfactant micelles. As a result, it is found that the 2-pack isocyanate waterborne paint (without organic solvents) containing DBTL and encapsulated in advance in nonionic surfactant micelles with hydrophilic-lipophilic balance of 13-14 releases DBTL with the collapse of the micelles at 80 • C or higher for the rapid progress of curing, while at the same time the viscosity levels of the paint before and after standing at 40 • C for 1 h remain almost the same [16].…”

“…Paints were prepared by mixing the above aqueous solution with an acrylic emulsion and polyisocyanate. The acrylic emulsion [16] with a glass transition temperature of 20 • C (calculated value obtained from the glass transition temperature of acrylic monomer) and a hydroxyl value of 150 (same as above) was synthesized. A water-dispersible polyisocyanate Burnock DNW5500 (a product of DIC Corporation, Tokyo, Japan) was mixed to obtain a 1:1 molar ratio of hydroxyl groups to isocyanate groups in the acrylic emulsion.…”

“…The increase in M W with increasing temperature up to the maximum value is thought to be due to stronger hydrophobic interactions of surfactant molecules and consequent micelle growth, as described above. On the other hand, the decrease in M W with increasing temperature above the maximum value may indicate that DBTL is released, which is accompanied by shrinkage of the micelles [16].…”