Novel crystal form D of Retigabine and preparation method thereof

The invention relates to the field of medicinal chemistry, in particular to a novel crystal form D of N-(2- amino-4-(4- fluoro benzyl amino) phenyl) ethyl carbamate (Retigabine) and a preparation method of the novel crystal form D. The invention provides X-ray powder diffraction characteristic absorption peaks and DSC (differential scanning calorimetry) endothermic transition peaks of the novel crystal form. The novel crystal form D of the Retigabine is characterized in that the crystal has characteristic absorption peaks at angles of (2 theta) 5.18 DEG, 10.60 DEG, 13.22 DEG, 13.98 DEG, 15.70DEG, 18.26 DEG, 20.46 DEG, 21.40 DEG, 22.22 DEG, 22.58 DEG, 23.06 DEG, 24.44 DEG, 24.82 DEG, 27.38 DEG and 28.28 DEG under the X-ray powder diffraction and the DSC endothermic transition of the novelcrystal form is at a temperature of 60-70 DEG C. The novel crystal form D of the Retigabine is thin in grain size (the average grain size is 20-35 mum and normal distributed), and can be used for medicinal preparation producti