Method for producing polyalkylene oxide

A method for producing a polyethylene polyalkylene oxide, comprising

• step 1 of performing a polymerization reaction of an ethylene oxide in the presence or absence of a chain transfer agent to obtain a high-molecular-weight polyethylene oxide;
• and
• step 2 of irradiating the high-molecular-weight polyethylene oxide obtained in step 1 with radiation to obtain a polyethylene oxide;
• wherein
• the amount of the chain transfer agent when used is less than 300 mass ppm relative to the ethylene oxide, and
• the high-molecular-weight polyethylene oxide obtained in step 1 has a viscosity at 25° C. in a 1 mass % aqueous solution of 7500 mPa·s or more,
• the viscosity at 25° C. in a 1 mass % aqueous solution of the high-molecular-weight polyethylene oxide being a value measured by the following method:
• 6 g of the high-molecular-weight polyethylene oxide and 125 mL of isopropanol are added to a 1 L beaker;
• while the mixture is stirred at 300 to 400 rpm using a stirring blade, 594 g of ion-exchange water is added, followed by stirring for one minute;
• subsequently, the stirring speed is changed to 60 rpm, and stirring is continued for an additional 3 hours to obtain a 1% aqueous solution of polyethylene oxide;
• the aqueous solution is kept at 25° C., and the viscosity is measured using a rotational viscometer;
• and the obtained value is referred to as the viscosity at 25° C. in a 1% aqueous solution.