Preparation method of poly-p-phenylene benzobisoxazole fiber

Abstract

The invention relates to a preparation method of poly-p-phenylene benzobisoxazole fiber, which is an improvement to the existing salt-forming method. The present invention is that terephthalic acid and 4,6-diaminoresorcinol hydrochloride are neutralized by acid and alkali to directly generate 4,6-diamino-1,3-resorcinol / terephthalic acid composite salt, remove 80-90% of the water in the system by filtration, the compound salt does not need to be further washed and dried, and polyphosphoric acid and phosphorus pentoxide are directly added for polymerization to prepare a poly-p-benzobisoxazole prepolymer. Then the prepolymer is subjected to twin-screw continuous post-polymerization, filtration and defoaming, and directly enters spinning equipment for spinning, water washing, drying and winding to obtain poly-p-phenylene benzobisoxazole fibers. The invention can greatly save time, omit the hydrogen chloride removal process, and increase the continuity of the production process.

Description

technical field [0001] The invention relates to a preparation method of polymer fibers, in particular to a preparation method of poly-p-phenylene benzobisoxazole fibers. Background technique [0002] PBO fiber is the abbreviation of polyparaphenylene benzobisoxazole (PBO) fiber. The fiber has main performance indicators such as 5.8GPa tensile strength and 280GPa modulus, 68 LOI value and 650℃ decomposition temperature, and has good environmental stability, all of which belong to the current performance of organic and inorganic fibers. Most, its specific strength is about 12-14 times that of steel, its specific modulus is 1.4 times that of steel, and its specific gravity is 1.54-1.56g / cm 3 Only 1 / 5 of steel. Due to its superior performance, it has been regarded as a new generation of super fiber for the preparation of advanced structural composite materials in aerospace and military fields since its appearance. At present, PBO uses 4,6-diaminoresorcinol hydrochloride and te...

AI Technical Summary

Problems solved by technology

[0005] 1. During the dehydrochlorination process of 4,6-diaminoresorcinol hydrochloride, a large amount of hydrogen chloride gas will be released, and these gases will generate a large amount of foam in the viscous reaction liquid, thereby reducing the agitation of the reaction system Efficiency; a large amount of foam produced makes 4,6-diaminoresorcinol hydrochloride adhere to the reactor wall, which easily destroys the balance of the ratio of polymer raw materials, thus making the final molecular weight of the prepared polymer poor in repeatability

[0006] 2. Hydrogen chloride is a strong corrosive gas, which makes the reaction have high requirements for equipment materials, and the degassing process takes a lot of time

[0007] 3. It is difficult to completely remove hydrogen chloride in the prior art. In order to facilitate degassing, the temperature of the reaction system needs to be raised. However, under high temperature conditions, side reactions will increase, which is not conducive to the increase of polymer molecular weight.

The disadvantages of this method are: first, 4,6-diaminoresorcinol hydrochloride is relatively easy to oxidize, so when preparing its aqueous solution, it needs to be protected with anaerobic water and nitrogen; second, it needs to be neutralized by acid and alkali It needs to be filtered and washed later. This process makes the prepared 4,6-diaminoresorcinol / terephthalate easily exposed to air and oxidized, and needs to be dried under vacuum conditions, which is time-consuming and labor-intensive. Obviously Increased process difficulty

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