Study On The Synthesis And Key Influencing Factors Of Nylon 66 And Nylon MXD6

The nylon material has been widely concerned and applied in automobile,clothing,electronic and electrical,aerospace,cosmetics and packaging materials since industrialization because of the excellent mechanical properties,oil resistance,wear resistance,chemical resistance and electrical insulation,etc.Although the domestic nylon 66 industry makes some breakthroughs after years of development,there are also some shortcomings.For example,the nylon 66 with the low and medium viscosity generally produced by domestic enterprises has great limitations in the field of application,and the nylon 66 with the high viscosity has higher relative molecular mass and better properties than ordinary nylon66.In addition,the special nylon including the nylon MXD6 is monopolized by foreign countries for long time,which also limits its application and promotion.In this work,the synthesis and key influencing factors of the highviscosity nylon 66 and the special nylon MXD6 are adequately researched.Starting from the synthesis process of nylon 66 salt,the salt formation process is explored and optimized,and the high purity nylon 66 salt is prepared by the method of segmental drop addition.The infrared analysis is used to research the pre-polymerization process of nylon 66 salt,and a series of influencing factors,such as polymerization temperature,time,pressure,p H value of nylon salt solution and catalyst dosage,are identified for the polymerization process of the nylon 66 and resin properties by measuring the structural changes of polymer resin,the content changes of nylon 66 salt in resin,the relative viscosity and characteristic viscosity of the resulting products,which achieves the viscosity control of nylon 66.More importantly,the optimum polymerization conditions are determined,and the pre-polymerization temperature,pre-polymerization time,prepolymerization pressure,p H value of salt solution,catalyst dosage correspond to 210 °C,1 h,1.8 MPa,7.7,0.1 wt%,respectively,realizing the preparation and molecular weight control of high-viscosity nylon 66.Moreover,the relationship between the torque of the synthesis device and the viscosity and molecular weight of the nylon 66 is established,which provides a feasible regulation method and data reference for the actual production of nylon 66 products.A series of products with a viscosity range from 2.8 to 4.7 are prepared through observing torque changes and stop the reaction in time,satisfying the application needs of nylon 66 products for different applications and providing an important guidance for the development of domestic high-quality multi-grade nylon 66 products.The salt formation and condensation process of nylon MXD6 are explored and optimized,and the nylon MXD6 products are successfully prepared.The optimal pre-polymerization process including prepolymerization temperature of 210 °C and pre-polymerization time of 1 h is determined.In compared with the S6001,S6007 and S6121 products of the Mitsubishi Gas,the nylon MXD6 products with three different viscosities prepared by controlling the torque basically meet the viscosity requirements of different grades of products.