tube and they are stirred and dissolved then 7 g of 2 2 39 bis n phenylamidinyl 2 2 39 azopropane dihydrochloride an azo type initiator containing cationic groups dissolved in 10 ml of distilled water is added the mixture is polymerized under stirring at 48 u00b0 52 u00b0 c while passing nitrogen gas therethrough 10 hours thereafter 7 g of said initiator dissolved in 10 ml of distilled water is further added to keep on with the polymerization heat generation ceases 5 hours thereafter so stirring is stopped and standing polymerization is continued at 50 u00b0 c u00b1 1 u00b0 c for additional 50 hours there is resultantly obtained a colorless and transparent viscous solution an aqueous solution of polymonoallylamine hydrochloride hereinafter referred to as resin a 1 solution although this solution can be immediately used as a drainage improving resin solution in this invention the solid polymer may be recovered from the solution by the following operation 415 g of said resin a 1 solution is added into approximately 5 liters of methanol to form a white precipitate of the polymer and this precipitate without dried is finely broken up in methanol and extracted with methanol for 15 hours by using a soxhlet extractor removing the unpolymerized monoallylamine hydrochloride the precipitate is dried under reduced pressure at 50 u00b0 c to obtain 265 g of the polymer yield 90 this polymer was identified as polymonoallylamine hydrochloride hereinafter referred to as resin a 1 by elementary analysis ir absorption spectral analysis and nmr spectral analysis the intrinsic viscosity.