1) Things that can cross-link PVA include: inorganic substances such as sodium sulfate, zinc sulfate, boric acid (borax, etc.), as well as polybasic organic acids and aldehyde compounds. Heating can also mature polyvinyl alcohol. "Fine Chemical Technology" Chemical Industry Press
2) PVA insolubilizing agent: water-soluble amine-formaldehyde condensate, such as dimethylurea, trimethylmelamine, dimethylethylurea, dimethylurea, Aldehydes, polyvalent metal salts or complexes; industrial formaldehyde resin is suitable as an insolubilizing agent for cross-linked polyvinyl alcohol, and is used together with acid catalysts such as ammonium nitrate, which mostly requires heating; insolubilizing agents for metal compounds include: dichromate, nitric acid Chromium, chromium complexes, copper ammonia hydroxide and organic titanates need to be heated; Sodium sulfate and potassium sulfate in "Water-Soluble Polymers" Chemical Industry Press
1) edited by Yan Ruixuan It is discussed as a precipitating agent in the book "Water-Soluble Polymers"!