| 摘要 |
Provided are a modified diphenylmethane diisocyanate (MDI) biuret curing agent and preparation method thereof, the curing agent being prepared by reacting dibasic alcohol, water and MDI in an organic solvent; the molar ratio between the dibasic alcohol and the MDI is 0.05-0.2:1; the molar ratio between the water and the remaining MDI is 1: 3-3.2. The preparation method comprises the steps of: firstly, using the dibasic alcohol to modify a part of MDI, dividing the metered water into multiple parts, and adding the water by multiple times; after adding the first part of water, reacting firstly under 70-100°C, then heating up to 120-140°C for reaction; secondly, lowering the temperature to 70-100°C, adding the second part of water; and repeating the above processes until all the metered water is added, to produce the MDI curing agent with partial biuret structure. The curing agent has a clear and transparent appearance, is mainly used as the curing agent of polyurethane coating and adhesive agent, and has a higher NCO percentage and a slower curing speed than that of common MDI prepolymer curing agents. |
