Preparation of polybenzoxazole

Abstract

The invention relates to a preparation method of polybenzoxazole, which comprises the steps: 4, 6-Diaminoresorcinol / terephthalic acid composite salt is added into a polyphosphoric acid solution containing a certain amount of phosphoric anhydride and fully blended and dissolved directly at a temperature of 30 DEG C to 80 DEG C under the protection of inert gases, thereby preparing the polyphosphoric acid solution of 4, 6-Diaminoresorcinol / terephthalic acid composite salt which carries out a reactive extrusion polymerization to obtain the polybenzoxazole with twin screws. The invention directly mixes the 4, 6-Diaminoresorcinol / terephthalic acid, phosphoric anhydride and polyphosphoric acid to prepare into solution which carries out twin-screw polymerization without needing to carry out pre-polymerization, thus greatly shortening the polymerization time, saving time and increasing the production efficiency.

Description

technical field [0001] The invention relates to a preparation method of polybenzoxazole, and the prepared polymer has wide application prospects in the fields of high-performance composite materials, body armor, flame-retardant materials and the like. The invention belongs to the technical field of high-performance fiber material preparation. Background technique [0002] Polybenzoxazole (PBO) fiber - the abbreviation of cis-polyparaphenylene benzobisoxazole (PBO) fiber. The fiber has a 575kg / cm 2 Tensile strength and 28000kg / cm 2 The main performance indicators such as the initial modulus, the limiting oxygen index LOI value of 68, and the decomposition temperature of 650 ° C are among the highest among organic and inorganic fibers at present. 1.4 times, and the specific gravity is 1.52-1.55g / cm 2 Only 1 / 5 of steel. Due to its superior performance, it has been regarded as a new generation of superfibers for advanced structural composite materials such as aerospace and ...

AI Technical Summary

Problems solved by technology

There are following deficiencies in the method: the first: a large amount of hydrogen chloride gas will be released in the process of removing hydrochloric acid by 4,6-diaminoresorcinol hydrochloride, and these gases will be in the viscous reaction solution A large amount of foam is generated in the medium, thereby reducing the stirring efficiency of the reaction system

Second: Hydrogen chloride is a highly corrosive gas, which makes the reaction very demanding on equipment materials, and the degassing process takes up a lot of time, usually about 10-20 hours

Third: in the process of dehydrochlorination gas, a large amount of foam produced makes 4,6-diaminoresorcinol hydrochloride adhere to the reactor wall, destroying the equimolar ratio of the two monomers, serious Affects the final molecular weight of the polymer

The 4th, it is very difficult to completely remove hydrochloric acid in the prior art, so phosphorus pentoxide usually adopts the mode of distributive addition, in order to be easy to degassing, must make the temperature of reaction system raise, yet, under high temperature condition It will lead to more side reactions, which is not conducive to the increase of molecular weight

US5089591 and US5219981 reported that the PBO polymerization reaction is divided into two stages. The first stage is the pre-polymerization reaction in the polymerization reactor, the temperature is between 70-150 ° C, and the time is about 20 hours. The second stage is through the gear The pump transports the pre-polymerization product to the post-polymerization reaction in the twin-screw. The disadvantages of this method are: first, the pre-polymerization reaction takes 15-20 hours, and the polymerization time is still very long; second, the viscosity of the pre-polymerization reaction product is very high , needs gear pump to send to the twin-screw for post-polymerization reaction, which is unfavorable for the automatic continuous polymerization reaction

Images