Preparation method of organically modified hydrotalcite-based flame retardant for paper

The invention discloses a preparation method of an organically modified hydrotalcite-based flame retardant for paper. The preparation method comprises the following steps: (1) dissolving a magnesium salt and an aluminum salt in water to obtain a mixed salt solution, and dissolving sodium hydroxide and sodium carbonate in water to obtain a mixed alkali solution; (2) adding the mixed alkali solutionand the mixed salt solution to a reaction vessel slowly and dropwise by using a constant-pressure funnel, during which the pH value of the solution in the reaction vessel is maintained around a rangeof 10-11, and stirring for reaction for 1.0 hour after the dropwise addition is finished; (3) raising the temperature to 80 DEG C, adding a cationic polymer to the reaction vessel, stirring for reaction at a constant temperature of 80 DEG C for 1.0 hour, then adding a coupling agent dissolved in ethanol and stirring for reaction for 2.0 hours, and stopping stirring and holding temperature for 18hours; and (4) naturally co