A process for purifying Maleic Anhydride Modified graft polyolefin comprises adding an aqueous solution of alkali metal hydrox ide to a solution of a maleic anhydride graft polyolefin contain ing unreacted maleic anhydride and dissolved in an organic solvent at a temperature from 80°C to 160°C.
Thereby precipi tating Maleic Anhydride Modified graft polyolefin particles to make a W/O emulsion; stirring the W/O emulsion while maintaining the temperature within the above temperature range for less than 2 hours; adding further aqueous solution of alkali metal hydroxide to the W/O emulsion to change it into an O/W emulsion; and separating and washing the maleic anhydride graft polyolefin particles with water.
An organic solvent having no affinity for water and with a boiling point not lower than 80°C can be used, which simpli fies the recovery of the solvent; moreover unreacted maleic anhydride is changed into water-soluble maleic anhydride salt, but grafted maleic anhydride groups in the modified polyolefin can be prevented from changing into alkali metal salt, by using a solution of inexpensive alkali metal hydroxide in a specific concentration, which provides maleic anhydride graft polyolefin with good adhesion.
