Preparation method of trimethylol melamine

The invention discloses a preparation method of trimethylol melamine. The preparation method comprises the following steps: feeding a formaldehyde solution into a reaction kettle according to a mole ratio of melamine : formaldehyde : water of 1:(2.5-3.5):(8-30), and adding water and melamine in sequence for reaction by adjusting temperature and rotating speed. Compared with the conventional process, the preparation method has the advantages that the synthesis process is simple, and raw materials are readily available and easy to separate and purify; due to the reduction of raw material components, the production cost of trimethylol melamine is greatly reduced, the conversion rate of melamine is increased, and the formaldehyde content is reduced; meanwhile, resources are also saved, production of wastewater is reduced, and the environment is protected.