Synthesizeaqueous polyurethane catalyst. Generally, diisocyanate and oligomer diol (or polyol) are first synthesized Pre-react with the chain extender to prepare a certain molecular weight prepolymer or high molecular weight polyurethane resin, and then use phase transfer method to dissolve or emulsify it in water. The synthesis methods of water-based polyurethane catalysts mainly include the following.
(1) Prepare end-NCO polyurethane prepolymer from oligomer diol, diisocyanate and small molecule chain extender, or prepare high molecular weight polyurethane in organic solvent, and then emulsify emulsified under the action of agents and high shear forces.
(2) Prepare polyurethane or prepolymer from low and medium molecular weight polyoxyethylene glycol as the raw material of oligomer diol, and diisocyanate (and chain extender), and then disperse it in water.
3) Use chain extenders containing carboxyl groups, sulfonic acid groups or tertiary amino groups to prepare polyurethane or its prepolymer, neutralize it to make ionic polyurethane and emulsify it. Depending on the specific situation, neutralization can be performed before or at the same time as emulsification, and the emulsification process of the prepolymer can be used for amine chain extension.
(4) Preparation of polyurethane-urea-polyamine (PUUA). PUUA is emulsified in a dilute acid aqueous solution, or the adduct of PUUA and epichlorohydrin (ECH) is emulsified in an acidic aqueous solution. Or the adduct of PUUA and ECH reacts with lactone or sultone, and is emulsified in an alkaline aqueous solution to obtain an anionic polyurethane emulsion.
(5) Make polyurethane carry hydrophilic hydroxymethyl groups. The method of introducing methylol is to use the reaction between the amino group of polyurethane and formaldehyde, or the reaction of an NCO-containing polyurethane prepolymer with excess triethanolamine.
(6) First prepare a terminal NCO prepolymer containing hydrophilic chain extender segments or groups such as PEO, and then react with sodium bisulfite alcohol aqueous solution and emulsify. The prepolymer can still be Reacts with blocking agents such as ketoxime or caprolactam and emulsifies in water to form blocked polyurethane emulsion.
The above is the synthesis method of water-based polyurethane catalyst. I hope it will be helpful to everyone.
