Preparation method of hard closed-cell polyimide foam

Abstract

The invention relates to a preparation method of hard closed-cell polyimide foam and belongs to the field of a preparation technology of a polymer polyimide foam material. The preparation method of the invention comprises the following steps: adding aromatic dianhydride into a polar solvent, and esterfying by adding an excessive amount of micromolecular fatty alcohol to obtain a solution A; addingdiamine, a foam stabilizer and an end-capping reagent into the solution A, reacting for 0.5-3 h to obtain a solution B, drying the solution B to remove the polar solvent, and crushing to obtain a precursor powder; placing the precursor powder into an open vessel and putting the open vessel with the precursor powder into a pressure vessel, vacuum-pumping to remove air and introducing CO2, heating,pressurizing, and finally cooling naturally and releasing pressure to obtain crosslinked polyimide foam. According to the method, nontoxic, odorless, non-combustible and cheap CO2 which is easily available is used as foaming gas. The preparation method is novel and has a wide application system.

Description

technical field [0001] The invention relates to a preparation method of rigid closed-cell polyimide foam, which belongs to the technical field of preparation of polymer polyimide foam materials. Background technique [0002] Polyimide foam has excellent flame retardancy, high temperature resistance, and open flame resistance, and is a type of high-performance foam material. Compared with other types of foamed plastics, it does not produce harmful gases during use, has a low density, a wide range of performance adjustments, and is easy to install and disassemble. It has been widely used abroad as a heat insulation and noise reduction material. [0003] The patent US3249561 of DuPont Company of the United States first disclosed a preparation method of polyimide foam. In this patent, a dehydrating agent is added to the polyamic acid solution, and then an acid that can generate gas is added. After foaming and solidification, polyimide foam is obtained. , however, the cell size ...

AI Technical Summary

Problems solved by technology

[0003] The patent US3249561 of DuPont Company of the United States first disclosed a preparation method of polyimide foam. In this patent, a dehydrating agent is added to the polyamic acid solution, and then an acid that can generate gas is added. After foaming and curing, polyimide foam is obtained. , however, the cell size of the foam produced by this method is not uniform and the chemical blowing agent can remain in the foam

U.S. Patent US4900761 discloses a method for preparing polyimide foam by polyester ammonium salt powder, but the products prepared by this method are mostly open-cell flexible foam with poor mechanical properties

Chinese patent CN101402743A discloses a method for preparing polyimide foam, which is mixed in proportion by aromatic dianhydride, low-molecular alcohol, catalyst, surfactant, etc. to form a solution of foam precursor in a polar solvent, and then mixed with Isocyanate is mixed and foamed, and polyimide foam is obtained by further microwave treatment and heat treatment. This kind of foam is also mostly low-density open-cell flexible foam with low mechanical properties and easy slag drop

In addition, although the soft polyimide foam with open-cell structure meets the needs of high temperature resistance and light weight in the aerospace field, its compression resistance is not ideal

[0004] Chinese patent CN102127225A discloses a method for preparing rigid foam by one-step method to improve foam compressive strength, which mainly involves injecting mixed liquid A and liquid B into a mold, then sealing, shaping and imidizing in microwave. The method has higher requirements on the mold used, and the mold needs to be resistant to high pressure and can be used in a microwave field; when the foam prepared by this method is unloaded, it is very easy to crack due to a large amount of gas discharge; although the above foam resistance The compressive strength is improved, but the above foams are mostly open-cell foams, which are prone to moisture absorption and frosting on the surface when used for a long time in a low temperature environment

U.S. Patent No. 6,235,803 discloses a method for preparing rigid closed-cell polyimide foam by the precursor microsphere method, which is mainly to pre-foam the prepolymer powder to form a microsphere intermediate, and then fill it into the mold and re-expand it. Although the foam obtained by this method has a high closed cell rate and good uniformity, the adhesion between the microspheres is not easy to control, so the mechanical properties of the foam are poor.

Chinese patent CN102964834A discloses a new method for preparing rigid foam using an end-capping agent. It mainly prepares low molecular weight precursor powder or low molecular weight polyimide, and then heats for crosslinking reaction. At the same time, A part of the gas is released during crosslinking to form a rigid closed-cell polyimide foam. The polyimide foam prepared by this method has better mechanical properties, but the system has high requirements for the selectivity of the end-capping agent, and only reduced Bornene dianhydride is used as an end-capping agent, and the selection range of the system is narrow, and this method mostly uses α-isomeric biphenyl anhydride as the main dianhydride, and the cost is extremely high, so its application is limited to a certain extent