Preparation method of polyimide

Abstract

The invention discloses a preparation method of polyimide. The method comprises the following steps: ensuring that dianhydride and diamine are reacted in an ionic liquid according to a molar ratio of1 to 1, mixing an obtained prepolymer solution with water-soluble acrylic resin and saturated polyester resin solution with the molar ratio of 2 to 1, ensuring that reaction is performed for 1 to 2h at 80 to 120 DEG C, feeding an organic solvent to perform backflow, mixing the obtained premixed solution with methanol or deionized water, precipitating, filtering and drying, and dissolving the obtained prepolymer powder into a polar solvent; curing the prepolymer glue solution on a flat plate, performing curing for 1h at 80 DEG C, performing curing for 2h at 100 DEG C, performing curing for 3h at 150 DEG C, performing curing for 2h at 200 DEG C, performing curing for 1h at 230 DEG C, and cooling the prepolymer glue solution to a room temperature so as to obtain a polyimide film. According tothe method, through the blending and curing of the prepolymer solution, the water-soluble acrylic resin and the saturated polyester resin solution, a polyimide material with good heat resistance andheat stability and small thermal expansion coefficient is obtained.

Description

technical field [0001] The invention relates to the technical field of polymer materials. More particularly, the present invention relates to a kind of preparation method of polyimide. Background technique [0002] Polyimide has excellent mechanical properties, heat resistance, low temperature resistance, flame retardancy, solvent resistance and electrical properties. It can be used as a structural composite material and is widely used in aerospace, aviation, precision machinery, microelectronic devices and Transparent conductive film, TFT substrate and flexible printed circuit substrate, etc. [0003] Polyimide is usually synthesized in two steps: the first step is the formation of polyamic acid (PAA) by dianhydride and diamine in a polar aprotic reaction solvent; the second step is the thermal imidization of PAA to poly There are mainly the following problems in the preparation process of imide: due to the rigid chain characteristics, polyimide has a high melting tempera...

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Problems solved by technology

[0003] Polyimide is usually synthesized in two steps: the first step is the formation of polyamic acid (PAA) by dianhydride and diamine in a polar aprotic reaction solvent; the second step is the thermal imidization of PAA to poly There are mainly the following problems in the preparation process of imide: due to the rigid chain characteristics, polyimide has a high melting temperature and a large thermal expansion coefficient, and at the same time, it has poor solubility and is not easy to process; traditional polyimide The formed film is generally hard, brittle, and insufficient in strength, and there are still defects in the microelectronics industry that reduce the linear expansion coefficient and mechanical strength; due to the formation of intramolecular and intermolecular charge transfer complexes (CTC) and electronic polarization Traditional PI films are often yellow or dark brown, which cannot meet the requirements of optical waveguide materials in the communication field, alignment films of liquid crystal displays, flexible transparent conductive substrates, etc. for the transparency of PI films in the optical field.

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