Abstract: The present invention relates to a method of preparing a vinyl chloride-based polymer in a polymerization device including: a polymerization reactor; a reflux condenser connected to the polymerization reactor; and a recovery pipe connected to the reflux condenser, the method including: initiating a polymerization by adding a first vinyl chloride-based monomer and an initiator into the polymerization reactor; and recovering a second vinyl chloride-based monomer from the polymerization reactor through the recovery pipe, and performing a polymerization while adding a third vinyl chloride-based monomer into the polymerization reactor, wherein a content of the initiator is 0.105 to 0.110 parts by weight based on 100 parts by weight of a content of the first vinyl chloride-based monomer.

Abstract: The present invention provides a polyamic acid aqueous solution composition capable of polymerizing polyamic acid in water rather than in an organic solvent, as well as achieving a high imidization rate during low-temperature curing.

Abstract: The present application provides a polyamic acid aqueous solution composition prepared of a polyimide, wherein the composition enables the polymerization of hydrophobic-based monomers into a polyamic acid in water and is improved in transparency, eco-friendliness, storage stability, and the like when cured.