Process And Apparatus For Manufacture of Processable Polyvinyl Alcohol

1 . 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 98% or more;

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 primary outlet, the components being arranged to apply a shearing force to the polymer while the polymer is conveyed by the components from the inlet through a reaction zone to the outlet;

one or more secondary inlets located downstream from the primary inlet for introducing reactants comprising a processing aid and a plasticizer to the chamber to form a reaction mixture;

wherein the plasticizer is selected from the group consisting of the following compounds and mixtures thereof:

(a) sugar alcohols selected from the group consisting of: diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, and mixtures thereof;

polyols selected from the group consisting of: pentaerythritol, dipentaerythritol, and mixtures thereof;

(b) diols selected from the group consisting of: methyl pentanediol, 1,2-propanediol, 1,4-butanediol, 2-hydroxy-1,3-propanediol, 3-methyl-1,3-butanediol, 3,3-dimethyl-1,2-butanediol, and mixtures thereof;

(c) glycols selected from the group consisting of: polyethylene glycol 300, polyethylene glycol 400, alkoxylated polyethylene glycol, and mixtures thereof;

(d) caprolactam, tricyclic trimethylolpropane formal, rosin esters, euricamide, and mixtures thereof;

wherein the blending chamber comprises a plurality of heated regions arranged so that the mixture is subjected to a temperature profile whereby the temperature increases from the inlet to the outlet;

a secondary outlet located between the reaction zone and primary outlet arranged to allow removal of processing aid from the chamber;

reacting the processing agent, plasticizer and polymer in the reaction zone to form plasticized polymer; and

allowing the plasticized polymer to pass from the primary outlet.

2 . A method as claimed in claim 1 wherein the plasticizer is selected from the group consisting of: sugar alcohols selected from the group consisting of: diglycerol, triglycerol, fructose, ribose, xylose, D-mannitol, triacetin, and mixtures thereof;

polyols selected from the group consisting of: pentaerythritol, dipentaerythritol, and mixtures thereof.

3 . A method as claimed in claim 1 wherein the plasticizer is selected from the group consisting of: diols selected from the group consisting of: methyl pentanediol, 1,2-propanediol, 1,4-butanediol, 2-hydroxy-1,3-propanediol, 3-methyl-1,3-butanediol, 3,3-dimethyl-1,2-butanediol, and mixtures thereof.

4 . A method as claimed in claim 1 wherein the plasticizer is selected from the group consisting of: glycols selected from the group consisting of: polyethylene glycol 300, polyethylene glycol 400, alkoxylated polyethylene glycol, and mixtures thereof.

5 . A method as claimed in claim 1 wherein the plasticizer is selected from the group consisting of: caprolactam, tricyclic trimethylolpropane formal, rosin esters, euricamide, and mixtures thereof.

6 . A method as claimed in claim 1 wherein the polyvinyl alcohol polymer has a degree of hydrolysis of 93 wt % to 98 wt %.

7 . A method as claimed in claim 6 wherein the polyvinyl alcohol polymer has a degree of hydrolysis of 93 wt % to 97 wt %.

8 . A method as claimed in claim 7 wherein the polyvinyl alcohol polymer has a degree of hydrolysis of 93 wt % to 95 wt %.

9 . A method as claimed in claim 1 , wherein the polyvinyl alcohol polymer comprises a lower viscosity polymer and a higher viscosity polymer, wherein both polymers have the same degree of hydrolysis.

10 . A method as claimed in claim 1 wherein the processing aid is water.

11 . A method as claimed in claim 1 wherein the plasticizer comprises two or more polyols selected from the group consisting of:

dipentaerythritol, methyl pentanediol, triacetin, 2-hydroxy-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, tricyclic trimethylolpropane formal, D-mannitol, triglycerol; and xylose.

12 . A method as claimed in claim 1 wherein the plasticizer comprises one or more compounds selected from the group consulting of caprolactam and alkoxylated polyethylene glycol.

13 . A method as claimed in claim 1 wherein the plasticizer is selected from the group consisting of: dipentaerythritol, triacetin, methyl pentanediol, rosin esters and mixtures thereof.

14 . A method as claimed in claim 1 wherein the reactants further comprise a reactive stabilizer selected from the group consisting of: sodium stearate, potassium oleate, sodium benzoate, calcium stearate, stearic acid, dimethyl propionic acid and mixtures thereof.

15 . A method as claimed in any claim 11 , wherein the amount of the reactive stabilizer is from 0.2 wt % to 5 wt %.

16 . A method as claimed in claim 15 , wherein the amount of the reactive stabilizer is from 0.5 wt % to 3 wt %.

17 . A method as claimed in claim 16 , wherein the amount of the reactive stabilizer is from 0.5 wt % to 2 wt %.

18 . A method as claimed in claim 17 , wherein the amount of reactive stabilizer is from 0.5 wt % to 1.5 wt %, preferably 1 wt %.