Process for the production of a water-containing gel

A process for the production of a cross-linked water-containing gel insoluble in water is disclosed in which an aqueous polyvinyl alcohol solution is dispersed in a medium non-mixable with water and irradiated with ionizing radiation. Ultra-fine particles or granules of the gel are obtained by irradiating a suitable medium into which the polyvinyl alcohol has been dispersed by employing a high speed mixer. Suitable mediums are unlimited although aromatic hydrocarbon is preferred due to its stability with regard to radiation. To induce the cross-linking reaction, ionizing radiation at a preferred dose of 6 x 106 roentgen may be obtained from a Co-60 source or particle accelerator. In an example, 100ml of an aqueous solution consisting of 8g of polyvinyl alcohol dissolved in 100g of water was added to 400ml of toluene and dispersed in a mixer at a stirring speed of 140 rpm. The dispersed liquid was then irradiated for five minutes by an electron beam from a linear accelerator (8.2MeV; 45μA) while undergoing agitation. Following separation, a cross-linked polyvinyl water-containing gel insoluble in hot water was obtained at a yield of 64% and having an average gel diameter of 4.8mm. (Owens, K.J.)