Process and apparatus for manufacture of processable polyvinyl alcohol

A method for manufacture of a plasticized polyvinyl alcohol polymer mixture, the method comprising the steps of:

• introducing into a mixing reactor a polyvinyl alcohol polymer comprising homopolymeric polyvinyl alcohol or a blend thereof having a degree of hydrolysis in the range of 93% to less than 98%;
• wherein the mixing reactor comprises a blending chamber having a primary inlet, a primary outlet and at least two inter-engaging components extending between the primary inlet and the primary outlet, the at least two inter-engaging components being arranged to apply a shearing force to the polyvinyl alcohol polymer while the polyvinyl alcohol polymer is conveyed by the at least two inter-engaging components from the primary inlet through a reaction zone to the primary outlet;
• one or more secondary inlets located downstream from the primary inlet for introducing reactants comprising water as a processing aid and a plasticizer to the blending chamber to form a reaction mixture;
• wherein the plasticizer comprises triacetin, and dipentaerythritol;
• wherein the blending chamber comprises a plurality of heated regions arranged so that the reaction mixture is subjected to a temperature profile whereby the temperature increases from the primary inlet to the primary outlet;
• a secondary outlet located between the reaction zone and the primary outlet arranged to allow removal of water from the blending chamber;
• reacting the water, the plasticizer and the polyvinyl alcohol polymer in the reaction zone to form the plasticized polyvinyl alcohol polymer mixture;
• and
• allowing the plasticized polyvinyl alcohol polymer mixture to pass from the primary outlet.