Synthesis Of Star-shaped Polyisoprene By Coupling Method And Preparation Of Its Latex

Star-branched polyisoprene has unique branched structure. Because of its unique branched structure, Star-branched polyisoprene and its copolymers have been studied for a long time due to their lower solution, bulk viscosities and less shear sensitivity, to achieve the unity of physical/mechanical properities and processability. Conventional latex and viscosity index improver are based on linear-polymer, can not replace natural rubber latex and high-performance viscosity index improver. Therefore from the structure improvement of base rebber, preparation of the star-shaped polyisoprene and star-poly(butadiene-isoprene) random copolymer, preparation of latex and viscosity index improver replace natural rubber latex is of great significance.Based on the idea of molecular design, using the method of living anionic polymerization, cyclohexane as solvent, n-butyllithium as initiator, DVB(m-DVB and p-DVB) as coupling agent, synthesis of linear-polyisoprene and star-shaped polyisoprene, results show that with the same amount of m-DVB and p-DVB, m-DVB has a higher coupling agent than p-DVB; m-DVB/living chains=3.0, has the highest coupling agent; coupling agent and branching degree decreases with increasing of the molecular weight of linear-arm; with the increase of coupling time the coupling agent and branching agent increase; when the coupling time is 24 hours, single-arm is one hundard, copling agent can reach 92.1% and branching degree is 8.1; coupling agent can improve with adding coupling agent by several times; cyclohexane is a better slvent the hexane for the preparation of star-shaped polyisoprene and isoprene copolymers. With home-made epoxy polybutadiene(Mn=2000,epoxy degree=21%) as coupling agent, the experimental results show that linear-chain is 1.0x105, coupling agent/activity chain=1.0, coupling reaction time is 24 hours, coupling efficiency can reach 65.4% and branching degree is 6.3.Preparation of star-shaped poly(butadiene-isoprene) random copolymer, linear-arm is 7x104, m-DVB/living chain-3.0, coupling reaction time is 24 hours, coupling efficiency can reach 93.2%,branching degree can reach 8.3.Based on linear-polyisoprene(Mn=9.8x105), examines the emulsifying condition and process, with the main emulsifying sulfonate and disproportionated rosin acid potassium, the results show that:the dostage of main emulsimer is 2.0%-4.0%, and SDBS:K=1:4, auxiliary emulsifier is span-80, dostage of 0.03% of water mass fraction, water phase:oil pahse=1:1, the pH is 10-11 of water phase, adjust the rotation speed is 200 rpm to 400 rpm, to form the largest distillation liquid level.The application of the emulsion system and formula of optimal to emulsifying star-shaped polyisoprene, when the main emulsifier SDBS:K=1:1, emulsifying power is 6250rpm and 3750 rpm; K-PAM as the stabilizer, no emulsion breaking and less solvent demusification, latex particle size between 800nm to 900nm, solid content is 60%-65% which is close to the kraton360 latex.