Abstract A mixed solution of polyvinyl alcohol and gelatinized starch for manufacturing polyvinyl acetal porous articles is prepared by introducing forcedly at a constant rate a dispersion formed by adding starch particles or a suspension of starch particles to an aqueous solution of polyvinyl alcohol having a relatively low temperature to one end of a cylindrical heater provided with an inner stirrer and a heating means in the outer periphery, heating the cylindrical heater at a sufficient temperature to gelatinize the starch in the dispersion by the time the continuously flowing dispersion reaches the other end of the cylindrical heater and withdrawing the gelatinized dispersion continuously from the cylindrical heater.
A method as claimed in claim 1, in which the reaction solution is flowed onto an endless belt to form a layer thereon and heating the layer on the endless belt to effect an acetalization reaction and to form a spongy sheet.
Claim 2
Dependent Claim
28 words
The method as claimed in claim 1, wherein after the gelatinized dispersion is withdrawn from the heater, the gelatinized dispersion is cooled in a separate continuous type cooler.
Claim 3
Dependent Claim
17 words
The method as claimed in claim 3, wherein said continuous type cooler is a vacuum defoaming cooler.
Claim 4
Dependent Claim
17 words
The method as claimed in claim 3, wherein said continuous type cooler is a cylindrical heat exchanger.