Study On The Polymerization And Spinning Of Poly (M-phenyleneisophthalamide)

As a new variety of polyamide poly (m-phenyleneisophthalamide) (PMIA) fiber was first prepared in 1962. Because of its excellent thermal and textile-like properties, the fibers and papers made from it have been widely used in industrial and clothes applications. After all it plays an irreplaceable role in the filed of high temperature resistance fiber.With the increasing requirement of high temperature resistance fiber, PMIA is fully developed. The main producers of PMIA fibers are in USA and Japan. Now in China, facing market demand of 1200t/a, there are only two companies having capability not more than 500t/a with poor fiber performance. This thesis is a part of the 2003 key project of JiangSu province. We've done a great deal of research work on polymerization and spinning of PMIA fibers.Firstly, the effects of reaction concentration, reaction temperature, reaction time, water content of solvent and monomers molar ratio on the low-temperature-solution condensation polymerization between meta-phenylenediamine(MPD) and isophthaloyl chloride(IPC) in N,N- dimethylacetamide solvent system were investigated. PMIA with inherent viscosity higher than 1.8 were obtained. The optimal conditions were: monomer concentration of 0.8~l.lmol/l,initial reactor temperature under -10℃, the IPC/MPD mole ratio of 1.002-1.005,the polymerization time of 60-70 minutes.Secondly, in order to improve productivity the twin-screw extruded was introduced in the process as the main reactor, which was the innovation of this thesis. By using it, semi-continuous polymerization process with advantages of high efficiency was achieved. By the mean time, polymerization time was decreased from 60 minutes for intermittent process to less than 30 minutes, and the relative molecular weight of the polymer was also increased. The optimal rotation speed of twin-screw was 100rpm.Thirdly, rheology properties, coagulability and stability of the dope were studied. We had obtained some important parameters such as non-Newton exponent, viscous activation energy, structural viscosity index, etc. These research works provided important foundation for the subsequent spinning process.At last, the wet-spinning process including coagulation, wet drawing, washing, dry drawing and heat setting was explored. Structure and properties of fibers during the spinning process were also studied. Under the optimal process fibers with tenacity of 3.3cN/dtex, X-ray crystalline of 40-50% were prepared.The innovation points of this thesis are:1. The semi-continuous condensation polymerization with twin-screw extrusion as main reactor was first introduced in the preparing of PMIA dope. The results showed that it can greatly decrease the polymerization time, meanwhile the resulted polymers had an inherent viscosity of 1.85, which was 3% higher than that obtained by intermittent ways. This method revealed a new prospect of industrialization of PMIA.2. The process from polymerization to spinning was developed on the lab scale instrument. PMIA fibers with favorable performance were prepared. These works was a great help to establishment of pilot plant.