The preparation of polyvinyl alcohol modified liquid with excellent performance is one of the key technologies for polyvinyl alcohol coating. Recent Chinese patents have disclosed a large number of preparation methods for polyvinyl alcohol modified coating liquid. . Some patented technologies are introduced as follows:
1. Acetalization cross-linking modification
Polyvinyl alcohol is pre-crosslinked by acetalization, coated on the polyethylene film and dried The dry film can be used as a barrier film with excellent performance and as an adhesive for lamination with polyethylene films, thus simplifying the lamination process, eliminating the need for special adhesives, and reducing the production cost of composite films.
2. Methanol and amino resin modification
Polyvinyl alcohol is modified with a mixture of methanol, amino resin, acidic catalyst and water, and then coated on the base film. After drying, a coating film is obtained.
3. Use additives such as condensation catalysts, defoaming agents, viscosity reducers, anti-skinning agents and anti-adhesive agents to modify them
Using polyvinyl alcohol as raw material, catalyzed After condensation, additives are added to form a coating, and the coating is applied to the base film to form a high-barrier coating film. After partial catalytic condensation of the polyvinyl alcohol macromolecular chain, the force of intramolecular hydrogen bonds is reduced and the water resistance is greatly improved, thereby solving the problem of the polyvinyl alcohol coating losing its barrier properties in the wet state.
4. Modify with additives such as defoaming agent, waterproofing agent and nano-intercalation agent
Mix polyvinyl alcohol, defoaming agent, water and waterproofing agent in proportion. Heat and stir to 90~100℃ until the polyvinyl alcohol is completely dissolved, then keep warm and cool, then add the layered intercalation agent in proportion, stir for 2~3 hours, and filter with a 150~200 mesh sieve to obtain polyvinyl alcohol. Coating fluid.
5. Modify using regulators, nano-inorganics, cross-linking agents, catalysts, surfactants and anti-solidification agents
Use a polyvinyl alcohol, regulator, When the modified coating liquid composed of nano-inorganic substances, cross-linking agents, catalysts, surfactants and anti-solidification agents is coated on the base film, the leveling, adhesion and uniformity are greatly improved. At the same time, the barrier properties of the coating liquid to oxygen and other gases are also greatly improved after it is dried and formed into a film.