The solubility of PVA is different with polymerization degree and alcoholysis degree
The solubility of PVA is different with the degree of polymerization and alcoholysis degree. Here should pay special attention is partial alcoholysis PVA can soluble at normal temperature, the solubility temperature dependency is small. But full alcoholysis PVA has very small solubility at low temperature, the solubility temperature dependency is big. Moreover,when put polyving akohol PVA in the dissolving tank, the surface of polyving akohol particle is in half-soluble condition,which cause the particles stick with each other and to form big lumps.
Considering above points, we should take following soluble operation methods for different types of polyvinyl alcohol PVA. Firstly add 15-25℃ water into the solution tank, string and adding polyvinyl alcohol PVA at the same time. At this temperature, the fully hydrolyzed PVA almost insoluble, therefore no lumps or clay domain.
When polyvinyl alcohol PVA adding finished, start to heat, increasing the temperature while stir.If we blow in 1.5kg/cm vapor, and do as the above method. When temperature reaches requested humidity, it is almost totally soluble.
Partially hydrolyzed Polyvinyl Alcohol is a type of PVA has relative high solubility at low temperature. When been added into water, its surface will be in half-soluble condition quickly, and the particles are easy to stick and form lumps. The higher polymerization degree, and the easier to form big lumps. To prevent the forming of lumps and easy for soluble, we must pay more attention to the conditions of water, adding speed and temperature.
The temperature should be lower than 25℃.
The adding speed should be slow, and prevent too PVA one time.
The temperature should not increase immediately after adding PVA. We should stir it with the original temperature in 10-15 minutes. After the lumps dispersing and start to increase the temperature.
To short the dissolving time, it is best to increase the temperature to 95℃.For Polyvinyl Alcohol with polymerization lower than 500,it will dissolve quickly
