| Acrylamide(AM)-acrylic acid(AA)-2-acrylamido-2-methylpropane sulfonic acid (AMPS) copolymer emulsion has been widely used as drag reducer in shale gas due to its well-known excellent anti-acid, anti-temperature, anti-salt and anti-shearing characteristics. However, polymer emulsion always exists the problem of poor storage stability. At present, principal methods to improve the stability of emulsion mainly including the optimization of the formulation of the polymerization system and the optimization of the process conditions. Therefore, systematic study for the formulation of the P(AM/AA/AMPS) system was conducted firstly by applying traditional inverse emulsion polymerization approach. Then, the emulsion prepared by transitional phase inversion (TPI) was applied to inverse emulsion polymerization. Thus, the stability of the polymer emulsion was investigated. Finally, the dynamics of the preparation process of P(AM/AA/AMPS) through TPI-inverse emulsion polymerization method was studied.In this dissertation, the traditional inverse emulsion polymerization was conducted firstly in a three-neck flask. Effects of several experimental factors including emulsifier types and amounts, the HLB value, initiator kinds and dosage, monomer concentration, oil-water ratio, nitrogen time, reaction temperature and reaction time on the intrinsic viscosity of the polymer, conversion rate of monomer as well as the stability of the emulsion were discussed systematically. Through single-factor tests and orthogonal experiments, the optimum synthesis condition was optimized and selected as follows:the monomer concentration was45%, HLB value of the emulsifier was6, the emulsifier(Span80/Tween80) dosage was8%, the initiator(V-50) dosage was1‰, the reaction temperature was45℃and the reaction time was4.5h. The structure of the polymer was characterized by applying infrared spectroscopic analysis. The results prove that the resultant polymer is AM/AA/AMPS terpolymer.The phase transition point was detected by applying TPI method to prepare emulsion, and then, the phase diagram of different monomer concentrations and different emulsifier amounts was made. Particle size of emulsion prepared by phase inversion point (TPI), direct emulsification methodl(DE1), direct emulsification method2(DE2), and catastrophic phase inversion (CPI) was contrastively discussed. The result indicates that emulsion prepared by TPI method possesses the smallest particle diameter. To make a comparative analysis, emulsion prepared by TPI method and emulsion prepared by DE1method were put in a glass reaction kettle with a capacity of1L to conduct inverse emulsion polymerization, considering particle diameter, stability, heat release, apparent viscosity and intrinsic viscosity [η] as investigation targets. The research shows that after polymerization, the TPI emulsion has a smaller droplet size as well as better mechanical stability, freeze-thaw stability, thermo stability and stewing stability. In addition, the highest temperature and the maximum viscosity value during the polymerization process of TPI are both lower than that of DE1, but the intrinsic viscosity value [η] of TPI is much higher. During the TPI inverse emulsion polymerization process in the glass reaction kettle, comparative study for five different blender (2-blade bending paddle,3-blade pitched agitator, flat paddle agitator, anchor and frame agitator, A、B、C、D and E respectively) was conducted regarding the polymerization exotherm, the product molecular weight, stability and particle size of the emulsion as investigation targets. The study find out that2-blade bending paddle is the most suitable blender for inverse emulsion polymerization, and the stewing stability time for the resultant polymer emulsion can be up to longer than90d. Besides, the Fluent simulation software was applied to simulate the flow field of blender A and blender D during the stirring process, from the velocity vector of A and D found:the flow field of A agitator had the radial and axial flow, and this is in favor of the mixing. The dispersion of A mixer to material is less affected by the density and viscosity of the system, and the simulation results were in good agreement with the experimental results, further verified the A mixer is more suitable for TPI-inverse emulsion polymerization. By further optimization of the formulation of the TPI inverse emulsion polymerization system, it turned out that the initiator dosage can be reduced to0.7%o, and by pouring into condensate water during the heat release period to reduce the system temperature, the polymer molecular weight can be increased effectively.Finally, effects of temperature, monomer concentration, initiator dosage and the emulsifier dosage on polymerization behavior were explored. The result indicate that the apparent activation energy of the system was83.42kJ/mol (Ea=83.42kJ/mol). Meanwhile, with the increase of reaction temperature [T], monomer concentration [M], the initiator dosage[I] and the decrease of the emulsifier dosage[S], the polymerization reaction rate Rp accelerated simultaneously. |
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