Studies on Stability and Viscosity of Polymer/Polyether Polyols Suspension
|Keywords||Grafted polyether polyol Dispersion polymerization Particle size and particle size distribution Viscosity Styrene Acrylonitrile|
Graft polyether polyols, also known as the polymer polyol (POP), is a polyether polyol (PPG or PEG) as the parent, and graft copolymerized with the unsaturated monomer such as styrene, acrylonitrile kinds of the modified polyether; widely used in high-bearer soft foam and semi-rigid polyurethane (PU) production. Because of its use the Graft from and Graft through a graft polymerization method, the formation of the polyether polyol is a continuous phase of styrene-acrylonitrile copolymer is a solid particulate phase dispersed suspension. It is this special composition, it was obtained a PU foam basis polyether conferred while maintaining the toughness, and the introduction of the rigidity of the vinyl copolymer. However, in terms of POP's own preparation, or want to have dispersed stable polyurethane foam production applications, the characteristics of high and low viscosity solids. Master POP system dispersion stability and viscosity variation of the production of important guiding significance. -2 - Ethylhexanoate, tert-amyl (tert-Amylperoxy-2-ethylhexanoate, L575), azobisisobutyrate methyl ester (dimethyl 2,2 '-azobis (2-methylpropionate), respectively peroxide. AIBME) as initiator, the graft copolymer of acrylonitrile and styrene polyether medium to obtain a range of different experimental conditions the graft polyether polyol products, in-depth study of the various factors of polymerization products Reap Trail and stability law, thereby influencing factors on the viscosity of the suspension system model and graft polyether polyols (POP) viscosity comprehensive study. First, the impact POP polymerization system dispersion stability, particle size and particle size distribution of the factors. The effects of the type and concentration of the macromer, monomers St / AN ratio, the monomer polyether ratio of the chain transfer agent concentration, reaction temperature, the initiator type and concentration, reaction time, and a semi-continuous polymerization process factors on the system performance impact. The results show that the dispersion polymerization mechanism POP polymerization system was the reaction of the initial system of homogeneous, with the reaction, the particle phase precipitation from the system, and there are different allocation of the two-phase monomer and reaction sites experienced continuous phase - dispersed phase - Continuous phase transition; macromer is a decision on the stability of the system and affect the system the number of nucleation, multi-branched, high molecular weight macromer is conducive to the stability of the dispersion. Same species macromonomer along with its concentration increases, the obtained particle size of the POP products reduced viscosity and graft ratio exhibit liter relationship after the first drop, the inflection point at the minimum required amount of stabilizer is synthesized POP; monomer increased ratio of St ratio significantly improve product color and particle stability, and the particle size increases, the viscosity decreases, but relatively lower reaction rate and the rate of monomer conversion; monomer polyether and chain transfer agent concentration increases will increase the particle size, the particle size distribution becomes wider, and the monomer conversion rate slightly decreased. Monomer polyethers increase Bizeng Ambassador system solid holdup, and the concentration of the chain transfer agent is increased to make the system to decrease in molecular weight, the graft ratio increases, enhanced stability of the system; have a greater impact of reaction temperature on reaction rate and stability, low temperature is conducive to the reaction to the continuous phase transfer, so that the graft ratio increases, but likely to cause particle aggregation, while too high a temperature and easy to cause system implosion, the polymerization system of this study, a suitable reaction temperature is 90-100 ° C. The type and concentration of the initiator on the particle size of the system has been in stable dispersion required initiator concentration of not less than 1% variation with the variation of the conversion rate of the particle size of the reaction time match ; in a semi-continuous process, the feeding rate is increased significantly cause the particle size distribution becomes wider, the macromer in the process of semi-continuous feed and a chain transfer agent added to the system was stabilized to play a decisive role, the two substances at the same time semi-continuous addition in order to obtain a stable, monodispersed system. Secondly, viscosity was measured under different solid holdup experiments of different particle size and particle size distribution of POP products, effects of different viscosity model of graft polyether polyols (POP), the viscosity of the system fit and carried out on the the Quemada model parameters consistent with this suspension system fitted to obtain the relationship of the the parameter k0 right particle size and particle size distribution; corresponding research and then the relative viscosity of the relationship of temperature, base polyether viscosity and POP. Viscosity and solid holdup, particle size and particle size distribution, temperature, basic polyether viscosity relational: Finally, we study the influence of shear rate on the rheological behavior of the suspension system. The suspension system of the graft polyether polyols (POP) is not sensitive to shear in the rate of 30% or less of solids, was Newtonian behavior; When solids rate exceeds 30%, there are significantly shear thinning - shear-thickening - shear thinning phenomenon; viscosity on the shear sensitivity of the suspension is not only be increased with the increase in solids holdup, and increase with the particle size distribution becomes wider.