Synthesis Of Li-polyisoprene Rubber And Preparation Of Its Latex

Li-polyisoprene rubber has high purity,small odour and low ash content,which can be called the purest polyisoprene.What's more,its molecular structure and performance is the closest to nature rubber,so it can replace nature rubber and be applied in the fields of medical care fields to solve the protein allergy problem of nature latex.(1)At the first part of the article,using n-butyl lithium as initiator,cyclohexane as solvent,effects of initiator concentration,polymerization temperature,concentration of monomer and the reaction conversion on the microstructure of polyisoprene was studied during anionic polymerization of isoprene.The results shows that: the lower polymerization temperature,initiator concentration,polymerization temperature and the higher reaction conversion were benifit to the high Cis-1,4 structure formed.The content of Cis-1,4 structure of polyisoprene reached 89.8% and its Mn=20.6 ten thousand,Mw/Mn=2.0 at the point of m(Ip)/m(cyclohexane)=l:3,n(n-Bu Li)/n(Ip)=0.32×10-3 at 50? for 4h.(2)Based on rare earth-polyisoprene,the stability differences of rare earth-polyisoprene rubber by different emulsifying formula and process was studied and confirm the emulsifier formula and process.The results shows that,the optimal emulsifying method of Ln-IR: using a oil-water ratio of 1 by weight and the emusifying agent of 3% by weight of water phase contains disproportionated potassium rosinate and SDBS with the ratio of 1.5:1,Span80 is used as the co-emulsifier and its dosage is 0.1% of the emusifying agent,polyethylene glycol 6000 is used as the stabilizer and its dosage is 0.05% by weight of water phase;The coarse emulsion is distilled at 73~75? under normal pressure first and then by vacuum distillation to remove solvent with a stirring speed of 150~200rpm and the temperature is 73~75?,the dilute latex is centrifuged 10 minutes on 5000~7000 rpm,the size of dilute Ln-IRL is 200~300nm,the solid content of concentrated latex is 58%~67%.(3)Using the optimal emulsion condition of rare earth-polyisoprene to emulsifying Li-polyisoprene and then further optimized,the emulsifying effectiveness by different dosage of emulsifier and oil-water ratio.The results shows that,the optimal emulsifying method of Li-IR: using a oil-water ratio of 1 by weight and the emusifying agent of 3%~5% contains disproportionated potassium rosinate and SDBS with the ratio of 1.5:1,Span80 is used as the co-emulsifier and its dosage is 0.3%~0.5%,PAAS or polyethylene glycol 6000 is used as the stabilizer and their dosage is 0.03%,0.05% respectively,all reagent dosage are accounted by weight of water phase;The coarse emulsion is distilled at 73~75? with a stirring speed of 150 rpm,the dilute latex is centrifuged 10 minutes on 6000 rpm,the size of dilute Li-IRL is 400~700nm,the solid content of concentrated latex is 60~65%.