| With the difficulty of oil recovery increases,the performance requirements of oilfield chemical additives are also getting higher and higher.Hydrophobically associating polyacryla-mide HMPAM has a very important application prospect in this field due to its better viscoelasticity and shear resistance,especially for the field of enhanced recovery.At present,the synthesis of HMPAM mainly adopts the thermal initiation of polymerization,but thermal initiation is difficult to further increase the molecular weight of the polymer due to the limitation of its polymerization conditions,while the majority of conventional photoinitiat-ion remains in the qualitative research.In recent years,photoinitiated polymerization is gradually receiving the favor of researchers.However,the advantages of the photoinitiated polymerization process have not been fully exploited at present.Therefore,this paper proposes that the "on" and "off' of polymerization and the characteristics of local polymerization can be realized,Developed a new polymerization process to control the polymerization process,in order to achieve the purpose of improving the polymer molecular weight.The main research content of this article was as follows:(1)It is proposed to establish a theoretical model for controlling the periodic variation of free radical concentration in each microelement of the polymerization system through a multislit intermittent moving light source.By calculating the radiant energy reaching the liquid surface of the polymerization system and calculating the effective energy of photoinitiator decomposition absorption,a mathematical model for calculating the primary radical concentration of any microelement in the polymerization system was established according to the laws of photochemical reaction,and it had been proposed to calculate the concentration of primary radicals in each microelement based on the amount of initiator consumed,and the theory of regulating the change of free radical concentration of each microelement by the generated primary radical concentration and interval time.(2)Through the periodic variation of the free radical concentration of each microelement in the polymerization system,a multislit gaptype movable light source was designed.Through analysis of the calculation model of primary free radical concentration,A photoinitiated polymerization experimental instrument was designed and developed,which the intensity of the incident light is controlled by controlling the number of light bulbs are switched on and off,and the time of each microelement to receive light is controlled by changing the slit width and the moving speed of the light source,that is,controlling the energy radiated from the light source of each microelement,changes the width of the shading plate,ie,interval width,controll-ing the degree of decay of the free radical concentration in each microelement.(3)According to the symbol of the temperature change rate of the polymerization system,the polymerization process is divided into three stages,and the process of judging each polymerization stage based on the change of the temperature gradient of the polymerization system is proposed,and the process of automatically adjusting each polymerization process is acheived.The influences of photoinitiator decomposition rate constant,light source moving speed,slit width and spacing width on the molecular weight of synthesized polymers were investigated respectively,and an optimized experimental scheme for regulation was obtained:The ? stage,the induction period,should select light intensity 0.58mW/cm2,the speed of the light source was chosen to be 1 cm/s,the illumination time was 3s and the interval time was 3s.The concentration of primary radical generated in a single process was 0.205×10-5,mol/L.The ? stage,the polymerization period,should select light intensity 0.206 mW/cm2,the speed of the light source was chosen to be 0.1cm/s,the illumination time was 30s and the interval time was 30s.The concentration of primary radical generated in a single process was 1.46×10-5 mol/L.In ? stage,the latter stage of polymerization,should select light intensity 0.206 mW/cm2.the speed of the light source was chosen to be 0.1cm/s,the illumination time was 30s and the interval time was 30s.The concentration of primary radical generated in a single process was 1.46x 10-5 mol/L.(4)Based on a simple to complex research approach,the water-soluble hydrophobic monomer 2-acrylamido tetradecyl sodium sulfonate(NaAMC14S)was introduced into the hydrophobic modified polyacrylamide HMPAM.At the same time,according to the relationship of polymerization system temperature changes corresponding to the time,divided the reaction time into three stages according to the change of temperature slope in phase II.According to the mathematical model,the movement speed controls the generation amount of the primary radical concentration and interval time in a single process.The feasible way of adjusting polymerization process was explored by the combinatorial experiment of different moving speed at the ? stage.The apparent viscosity of synthetic polymers was respectively studied by constant speed,gradually decreasing speed,gradually increasing speed and first increase and then decrease the speed.The results show that gradually decreasing the moving speed of the light source is conducive to improve the polymer molecular weight and is the main way of regulation.(5)HMPAM-1 was synthesized by photoinitiator decomposition rate constants to regulate the polymerization process and HMPAM-3 was synthesized by modulating the periodical changes of free radical concentration at various stages,and synthesis of HMPAM-2 by direct radiation with a fixed light source.The characterization of the polymers by IR and 1HNMR confirmed that the synthesized polymers were the target product.The viscosity average molecular weight of each polymer was determined by capillary method under the condition of disassociation.The experimental results showed that the intrinsic viscosity of HMPAM-3 was higher than HMPAM-2,increased by 86.3%and increased by 22.7%compared with HMPAM-1.The Particle size distribution of each polymer was determined by dynamic light scattering(DLS)under the condition of disassociation.The experimental results showed that the particle size of HMPAM-3 was higher than HMPAM-1,increased by 32.9%and increased by one time compared with HMPAM-2.By measuring the viscosity of three 5000ppm polymerization solution,HMPAM-3 was higher than HMPAM-1,increased by 43.3%and increased by 71.0%compared with HMPAM-2.It further proves the superiority of the process of regulating the polymerization process by controlling the periodic variation of free radical concentration. |
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