Method for synthesizing special resin for polypropylene cast film

The invention relates to a method for synthesizing special resin for a randomly copolymerized polypropylene cast film. A second generation domestic loop pipe polypropylene device is used for synthesis, CS-2 catalyst/propylene is 0.02-0.03 g/kg, and hydrogen gas and ethylene are uniformly added into two loop pipes; triethyl aluminum/propylene is 0.14-0.24 kg/t, triethyl aluminum/electron donor is 1-8 kg/kg, the densities of a first loop pipe polymerization reactor and a second loop pipe polymerization reactor are controlled at 530-580 kg/m , the concentration of hydrogen gas is controlled at 1200-1500 ppm, ethylene/propylene is 18-20 kg/t, and the melt flow rate of powder is 11-14 g/10 min; additives comprise an antioxidant, a neutralizing agent, an antiblocking agent and a slipping agent; the melt flow rate value of a product is 6-9 g/10 min, and the content of ethylene is 3.6-4.0%.