Patent ID: 9505910
Filing Date: 2016-11-29
CPC Classification: C07C,C08G,C08K,C09D

Claim Text:
1. A preparation method of modified diphenylmethane diisocyanate (MDI) biuret curing agent, comprising the steps of: a, adding MDI and an organic solvent in a reaction kettle, stirring uniformly, adding dehydrated dibasic alcohol for reaction at a room temperature for 0.5˜2 hours, then heating up to 60° C., reacting at 60˜90° C. for 1˜4 hours to obtain an MDI-modified product; b, adding water by multiple times, wherein a molar ratio between the water and remaining MDI after the first step of the reaction is 1:3˜3.2, wherein the water is added within a range from 4 to 10 times; controlling the temperature in the reaction kettle within 70˜100° C., dropwise adding a first part of the water, and reacting for 0.5˜2 hours, then heating up to 120˜140° C. , and reacting for 0.5˜2 hours; lowering the temperature to 70˜100° C., dropwise adding a second part of the water, repeating the above process until all the water is added, reacting for 0.5˜2 hours, heating up to 120˜140° C. and reacting for 1˜5 hours; and c, lowering the temperature to 60° C., adding the organic solvent according to the product solid content requirements, stirring uniformly, and discharging to obtain the modified MDI biuret curing agent; the feeding ratios of each reactant in the curing agent are as follows: in the first step of the reaction, the molar ratio between the dibasic alcohol and the MDI is 0.05˜0.2:1; and in the second step of the reaction, the molar ratio between the water and the remaining MDI after the first step of the reaction is 1:3˜3.2, wherein the mole number of the remaining MDI after the first step of the reaction is the difference of subtracting two times of the mole number of the dibasic alcohol from the MDI mole number fed in the first step of the reaction; the product indexes of the curing agent are as follows: wherein the following contents are weight percentages: (1) solid content: 50˜75%; and (2) NCO content: 12˜18%, counted in terms of total solid.