Polymerization method capable of effectively controlling phase transformation in PPTA (poly-p-phenylene terephthamide) synthesis process

Abstract

The invention relates to a polymerization method capable of effectively controlling the phase transformation in a PPTA (poly-p-phenylene terephthamide) synthesis process. The polymerization method comprises the following steps of firstly dissolving LiCl in a solvent NMP (N-methyl-2-pyrrolidone) under the condition of nitrogen atmosphere protection, then adding comonomer p-phenylenediamine, terephthaloyl chloride and trace comonomer, adding acid absorbent pyridine, stirring so as to completely dissolve the acid absorbent pyridine, then adding PPD ((Para Phenylene Diamine), stirring so as to completely dissolve the PPD, then feeding condensing oil bath, maintaining the temperature of the condensing oil bath at -15 DEG C to -5 DEG C, adding TPC (Thymolphthalein Complexone) in three times, and stirring so as to fully react the TPC, thus obtaining modified PPTA resin, wherein the logarithmic viscosity number of the modified PPTA resin is in the range of 5.0-8.0, and the trace comonomer is a diamine monomer containing a flexible chain structure. The polymerization method is a method of effectively increasing the molecular weight by using the phase transformation; and according to the method, the phase transformation time of transforming a liquid phase into a solid phase can be delayed in the polymerization process, so that the molecular weight is effectively increased and the turbidity of a liquid crystal spinning solution is improved.

Description

technical field [0001] The invention relates to a polymerization method for controlling phase transition in the synthesis process of PPTA, in particular to a polymerization method for controlling phase transition in the synthesis process of PPTA which effectively delays the phase transition time. Background technique [0002] Aramid fibers can be roughly divided into poly-m-phenylene isophthalamide fiber (referred to as meta-aramid fiber), poly-para-phenylene terephthalamide fiber (referred to as para-aramid fiber) and heterocyclic aromatic polyamide fiber. Amide fiber (referred to as aramid fiber III) and other varieties. Because aramid fibers have the characteristics of ultra-high modulus, high strength, high temperature resistance, and light weight, they are widely used in aerospace, military clothing, and material reinforcement. However, due to the high rigidity of PPTA molecular chains, strong hydrogen bonds between molecular chains, tight packing and high crystallizat...

AI Technical Summary

Problems solved by technology

[0003] Chinese Patent No. CN101851809A The content of comonomer added in this patent is relatively large, and the molar ratio of comonomer to p-phenylenediamine is 30-100mol%. The amount of addition will change the mechanism of comonomer after entering the system. After a large amount of comonomer enters the system, it seriously damages the regularity of the system. The solvent is easy to diffuse into the molecular chain, but at the same time, its own properties also have a great impact on the system. PPTA resin itself is a relatively rigid molecular chain. A large number of comonomers will destroy this system, resulting in a large drop in mechanical properties

[0004] Chinese Patent No. CN102070781A This patent uses four monomers for copolymerization, introduces 4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenyl sulfide as the third monomer, and introduces m-phenylene Diformyl chloride is the fourth monomer, so the whole polymerization process will be relatively complicated, and the amount of monomer introduced in this patent is relatively large, which will also seriously damage the previous polyterephthaloyl terephthalate Amine system, so the performance will be greatly affected