| 摘要 |
PURPOSE:To efficiently obtain the subject molded product improved in thermal stability such as a high-quality film free from discoloration and fish-eyes by molding in a molten state a PVA-based resin having each specific aqueous solution viscosity and methanol solubles. CONSTITUTION:A polyvinyl alcohol-based resin <=10cps in the 4wt.% aqueous solution viscosity at 20 deg.C and <=5wt.% in methanol solubles is dried under a vacuum at 50 deg.C for 12hr and then heated to 220 deg.C into a melt, which is in turn, pelletized using a small-sized, twin-screw extruder. Thence, the resulting pellets are fed into a conventional extruder equipped with an inflation die with a screw bore diameter of 40mm, L/D of 28 and number of revolutions of 29rpm to carry out melt molding at a screw compressive part maximum temperature of 220 deg.C and delivery port temperature of 200 deg.C, thus obtaining the molded product improved in thermal stability such as a high-quality film having the above-mentioned advantages. |
