Polyacrylonitrile copolymer spinning liquid and preparation method thereof

Abstract

The invention relates to a polyacrylonitrile copolymer spinning liquid and a preparation method thereof, wherein the polyacrylonitrile copolymer spinning liquid is high in isotacticity, and the distribution of copolymer units is uniform. According to the preparation method, bifunctional monomer itaconic acid monoester or itaconic acid monoamide is selected, wherein the reactivity ratio of bifunctional monomer itaconic acid monoester or itaconic acid monoamide is close to the reactivity ratio of acrylonitrile; and binary copolymerization is completed in a tubular reactor provided with a static mixer component, so that the isotacticity of acrylonitrile units in the polyacrylonitrile copolymer spinning liquid is increased effectively, formation sequence distribution of the copolymer units in the polyacrylonitrile copolymer spinning liquid is stabilized, and the process of polymerization is controlled smoothly. The isotacticity of the acrylonitrile units in the polyacrylonitrile copolymer spinning liquid is 28 to 35%, dynmaic viscosity is 200 to 800Pa.S, and molecular weight distribution is 1.5 to 2.2.

Description

technical field [0001] The invention belongs to the field of polyacrylonitrile preparation, in particular to a polyacrylonitrile copolymer spinning solution with high isotacticity and uniform distribution of copolymerization units and a rapid and stable preparation method thereof. Background technique [0002] Carbon fiber has the characteristics of high specific strength, high specific modulus, heat resistance, corrosion resistance, fatigue resistance, and creep resistance. It is a high-performance fiber material and has been widely used in aerospace, national defense construction, sports and leisure products, and medical equipment. and construction industries. Polyacrylonitrile-based carbon fiber has outstanding mechanical properties and is a hot spot in carbon fiber research and industrialization in recent years. The key to restricting the development of polyacrylonitrile-based carbon fibers is the quality of polyacrylonitrile precursors, and to obtain high-quality polya...

AI Technical Summary

Problems solved by technology

However, the widely used comonomer itaconic acid and unsaturated carboxylic acid ester (unsaturated amide) has a large difference in reactivity ratio with acrylonitrile, which belongs to a non-ideal copolymerization system, and serious copolymer composition will occur during the polymerization process. Migration, the instantaneous composition of the product is very different from the concentration ratio of the monomer feed, and the composition of the copolymers generated successively is also inconsistent. The final polymerization product is actually composed of a "blended" polyacrylonitrile stock solution containing different amounts of copolymerized chain segments. Using this The raw silk spun from this kind of stock solution has poor uniformity in microscopic physical structure and chemical reactivity, which will have an adverse effect on the performance of carbon fiber

[0004] Polyacrylonitrile used for carbon fiber in China is mostly prepared by solution polymerization with azo initiators, and batch polymerization is adopted. Due to the intense heat release of acrylonitrile polymerization and the high viscosity of the system in the later stage of polymerization, mass transfer and heat transfer are caused. Difficult, the reaction is difficult to control, so that the molecular weight distribution of polyacrylonitrile is broadened, the composition distribution is uneven, and the gel content increases, which significantly affects the improvement of subsequent fiber performance; The main reaction is an unsteady process with concentrated heat release and large viscosity changes. It is difficult to provide a reasonable stirring form that takes into account the low viscosity and fast heat release at the beginning of the polymerization and the high viscosity and slow heat release in the later stage of polymerization. The chain transfer reaction of the solvent is not conducive to the preparation of high molecular weight polymers; secondly, the gel effect is prone to occur in the stage of high conversion rate and high viscosity, resulting in large changes in the molecular weight and composition of the polymerization stock solution, and a wide distribution; moreover, the viscosity is extremely high in the late stage of polymerization , resulting in the difficulty of stirring and mixing the materials in the kettle, the difficulty of removing the heat from the materials in the kettle, and the phenomenon of implosion prone to occur, so the production of the polymerization stock solution is difficult to carry out stably

The precursors spun from this copolymer have poor stability in terms of microscopic physical structure and chemical reactivity, which adversely affects the stable production and performance of carbon fibers

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