Universal Dissolution Steps (Applicable to Most Conventional Grades)
For conventional, unmodified polyvinyl alcohol, the safest and most reliable method is "cold-water dispersion, followed by thermal dissolution":
Cold-Water Addition to Prevent Agglomeration: While stirring continuously, slowly and evenly add the polyvinyl alcohol into room-temperature water. Avoid dumping it all at once; otherwise, the surface of the powder or granules will rapidly swell and wrap around the dry core inside, forming difficult-to-dissolve "fish-eyes" or lumps.
Heating and Dissolution: Once uniformly dispersed, begin heating. For conventional high-hydrolysis grades (such as the 88 and 99 series), it is typically necessary to heat the mixture to 90°C–95°C and maintain stirring at this temperature for 30 minutes to 2 hours until completely dissolved.
Note: For certain special grades with lower degrees of hydrolysis (such as the L series, with a degree of hydrolysis around 70%), dissolution can sometimes be achieved at 70°C–80°C. Always refer to the product technical data sheet for specifics.
Key Differences Between Granules and Powder
Although the steps are identical, physical form dictates operational nuances:
Powder: Theoretically dissolves faster, but is extremely prone to agglomeration. When feeding, ensure it is sprinkled slowly and widely, or pre-wet and disperse it with a small amount of cold water before adding the rest of the water and heating. Patent data shows that untreated regular powder typically requires heating at 95°C for 30 minutes to dissolve completely.
Granules: Relatively less prone to dusting and agglomeration, but penetrating through to complete dissolution usually takes longer than powder. It requires ensuring sufficient heating temperature and stirring time to allow water to fully penetrate the interior of the granules.
Special Cases to Keep in Mind
There are surface-treated or modified "instant-dissolving" polyvinyl alcohol powders available on the market. These products improve water penetration through specialized processes (such as adding porogens) and may dissolve in just a few minutes to ten-odd minutes of stirring at 40°C–60°C. If you are using this type of product, follow the parameters provided by your supplier and do not blindly heat it to 95°C.