Novel flame retardant fiber and preparation method thereof

The invention belongs to the technical field of carbon materials and discloses a novel flame retardant fiber and a preparation method thereof. The preparation method comprises the following steps: (1) adding water to a pulp with beating degree of 28-70 DEG SR to adjusted into a slurry with concentration of 1-10%; (2) adding aluminum chloride solution with mass fraction of 3-15% into the slurry in the step (1), and stirring for reaction; and (3) adding sodium hydroxide solution into the mixed solution after reaction in the step (2), reacting, and washing with water to obtain the flame-retardant fiber. The aluminum chloride solution and slurry are mixed, so that the aluminum ions penetrate into the cell cavities of the fiber; the sodium hydroxide is added after the reaction, so that aluminium ions combine with hydroxide to form aluminum hydroxide, which is precipitated in fiber cell cavities. The novel flame-retardant fiber has flame-retardant effect by aluminum hydroxide dehydration heat absorption, solves the problem of low retention of aluminum hydroxide added to the fiber in a filling way, and also improves the problem of paper strength decrease due to filling.