| Vinyl chloride (VC)-acrylonitrile (AN) copolymer fibers, obtained by dry or wet spinning process, have the advantages of both polyacrylonitrile fibers and polyvinyl chloride fibers, such as lightweight, warmth, weather resistance and chemical resistance et al. Moreover, VC-AN copolymer fibers have good flame-resistance performance because of the introduction of VC. Industrially, it's difficult to obtain well dissolved copolymer, so VC/AN copolymerization and copolymer's soluble property in acetone solvent were mainly studied to find an optimal process for preparing well dissolved VC-AN copolymer.VC-AN copolymer composition was determined through the measurement of Cl-content in the method of oxygen-flask combustion. The soluble property of copolymer in acetone solvent was determined by continuous extraction for 24 hours.VC-AN copolymer was prepared by suspension polymerization. The reactivity ratios of VC and AN were calculated through YBR method as rVC=0.041 and rAN=3.65. The influence of AN feed time on copolymer composition was studied. Molecular weight and its distribution of VC-AN copolymer were studied on the change of polymerization temperature and comonomer feed mode. Soluble properties of the copolymers synthesized under different conditions were compared. The results showed that reducing AN feeding speed or raising reaction temperature could improve copolymer's soluble property.VC/AN emulsion copolymerization and solubility of copolymers influenced by initial monomer feed ration, amount of initiator as well as polymerization temperature was studied. The results showed that the monomer activity of AN was much greater than that of VC. AN conversion reached the maximum value after reacting for 4 hours and almost only VC polymerized subsequently. This resulted in VC-AN copolymer composition's dramatical change over time and copolymer's Cl-content changed from 20% to 40%. As the reaction proceeding, the proportion of AN in copolymerization system decreased, and copolymer's solubility in acetone increased. But the solubility value was no more than 45%.Monomer feed ratio has significant influence on copolymer composition and solubility. As the proportion of AN increased in copolymerization system, VC copolymerization rate increased and the conversion within 2 hours also increased from 5% to 15%. While AN conversion remained at a relatively high level and changed unsignificantly. VC-AN copolymer composition corresponded to initial monomer feed composition, and Cl-content increased with the amount of VC monomer. Solubility of copolymer was mainly determined by initial monomer feed ratio, so when VC:AN changed from 9:1 to 8:2, the copolymer solubility droped from all-dissolved to only 20% dissolved.Potassium Persulfate (KPS) and Sodium Bisulfite (SBS) were used as initiator. When no SBS was introduced, the initiating efficiency was low. Adding a small amount of SBS could significantly accelerate the reaction, however, the ratio of oxidant and reductant in the initiating system should be maintained approximately stable. The copolymer could be all dissolved only except the condition that no SBS was added.Increasing the polymerization temperature would accelerate both AN and VC polymerization, but because of AN's high activity, higher temperature was not conducive to the stability of the comonomers proportion and control of the copolymerization process. Cl-content of copolymer increased as the polymerization temperature increased. Solubility of copolymer was less affected by temperature, so when maintaining the monomer feed ratio all-dissolved copolymer could be always obtained.In industry, emulsion breaking and washing are important processes for VC-AN copolymer producing. Al2(SO4)3 was used as demulsifier after different kinds of metal salts solution were studied. The washing process of copolymer emulsion was also studied by the method of measuring liquid conductivity of the washed solution. |
PDF Full Text Request