Water-soluble polyurethane for wood lacquer and preparation method thereof

The invention discloses water-soluble polyurethane for the wood lacquer and a preparation method thereof. The water-soluble polyurethane comprises the following raw materials in parts by weight: 165-175 parts of polycarbonate diol, 131-132 parts of isophorone diisocyanate, 0.4-0.6 part of catalyst, 16.5-17.5 parts of dihydromethyl propionic acid, 2.7-3 parts of dihydroxyacetone, 18.5-19.5 parts of 1,4-butanediol, 4-5 parts of acetone, 12.5-13 parts of triethylamine, 6-7 parts of ethylenediamine, 628-638 parts of deionized water and 5-6 parts of adipic acid dihydrazide. The preparation method adopts the preparation technology combining the acetone method with pre-polymer dispersion method, thus effectively reducing the dosage of acetone and increasing the molecular weight of the generated polyurethane; and when the prepared water-soluble polyurethane dispersion forms a film, with the volatilization of water and the reduction of the pH value, the self-crosslinking reactions of ketonic carbonyl and hydrazide group can be performed, thus the after crosslinking density of the film can be increased and the hardness and water resistance of the the film can be increased.