To obtain the above molded product excellent in weatherability, oxidation stability and transparency by mixing two reaction solutions which can react with each other by use of a Ziegler catalyst.

This molded product is obtained by bulk polymerization in a mold of a mixture composed of (A) a solution containing (i) a Ziegler catalyst and (ii) a polymerizable olefin monomer and (B) another solution containing (iii) a Ziegler catalyst acttivator and the component (ii). The component (i) is pref. a substance prepared by stabilizing a titanium halide with a phenolic compound (e.g. by stabilizing titanium tetrachloride with t-butylphenol). The component (iii) is pref. a substance prepared by stabilizing an alkylaluminum compound with a vinyl ether compound (e.g. by stabilizing diethylaluminum chloride with isobutyl vinyl ether).