Solution method for synthesizing butyl rubber

The invention relates to a solution method for synthesizing butyl rubber. A mixture of C4-C8 monoolefine monomers and C4-C14 polyene hydrocarbon monomers is taken as a raw material, and in a system that hexane and chloromethane are solvents, polymerization reaction is initiated by an initiating system to prepare butyl rubber polymer, wherein the reaction pressure is normal pressure, the reaction temperature ranges from 0 to -90DEG C, and the initiating system has the concentration of 0.01-0.001mol/L, and is prepared by dissolving a main initiator, namely deionized water and a coinitiator, namely aluminum alkyl dihalide by using a polar solvent CH2Cl2 for mixing, and adding alkylol amines; the molar ratio of the coinitiator to the main initiator is 1:1-10:1, and the molar ratio of a third component to the main initiator is 1:10-1:25; and the adding amount of the mixed solvent is 1 to 50 times volume of the polymerization monomers. According to the method, reaction is mild, polymerization temperature is improve