Patent ID: 11866886
Assignee: BE RICH LIMITED
Field: Textile and paper machines (Mechanical engineering)
Classification: CPC D  Y | IPC D

Claim 5:
6. A biodegradable food-grade polyvinyl alcohol (PVA)-coated paper substrate, wherein the PVA-coated paper substrate is made by the method comprising the steps of:
providing a substrate, in which step a paper substrate is provided;
preparing a first coating material, in which step PVA with a degree of alkalization of 90%-100% and a molecular weight of 100,000-300,000 is rendered into an aqueous solution with a weight ratio of the PVA being 3%-15%;
preparing a second coating material, in which step sodium trimetaphosphate is rendered into an aqueous solution with a molar concentration of the sodium trimetaphosphate being 0.05-1 Mol/l;
forming a coating layer, in which step at least a surface of the paper substrate is coated with the first coating material to form at least one said coating layer;
forming a surface cross-linked layer, in which step the at least one coating layer is coated with the second coating material in order for the second coating material to cross-link with a surface of the at least one coating layer and thereby form at least one said surface cross-linked layer, with the at least one coating layer having a portion that is on an inner side of the at least one surface cross-linked layer and remains in a non-cross-linked state; and
drying, in which step the paper substrate, the at least one coating layer, and the at least one surface cross-linked layer are dried, wherein the at least one coating layer is formed by coating the at least a surface of the paper substrate with the first coating material at a coating amount of 1-10 g/m2.