温度和盐浓度对Cr^(3+)与HPAM交联反应速率及冻胶脱水率的影响

Effects of Temperature and Salt Concentration on Cross-Linking Reaction Rate of Cr^(3+)and HPAM and Dehydration Rate of Hydrogel

针对过交联造成的冻胶堵剂脱水问题,通过实验建立了一种可以具体表征交联反应过程的方法,即采用分光光度法测定Cr^(3+)浓度以表征Cr^(3+)交联剂的反应速率。考察了交联反应过程中交联剂Cr^(3+)的反应量、冻胶脱水率的变化情况,研究了温度和盐浓度对Cr^(3+)与HPAM交联反应速率及冻胶脱水率的影响,并对交联速率与冻胶脱水的相互关系进行了分析。研究结果表明,温度升高后,Cr和聚合物羧基之间的反应速率加快,交联中间体——Cr多核羟基桥离子的形成速率也会加快;温度越高,Cr多核羟基桥离子的流体力学直径增大速度越快,从而使得Cr的交联反应速率越快。而增大无机盐浓度,有利于Cr多核羟基桥离子的形成,其流体力学直径达到最大值的时间显著缩短。因此,在温度和无机盐的影响下,交联反应过程中冻胶易出现交联速率过快的问题,交联过度会增加交联体系的密度,导致交联体系的保水能力降低,从而使冻胶脱水。本研究对探索抑制冻胶体系脱水的方法具有指导意义。

In order to solve the problem of dehydration of gel plugging agent caused by over crosslinking,a method was established to characterize the crosslinking reaction process,that is,the concentration of Cr^(3+)was determined by spectrophotometry to characterize the reaction rate of crosslinking agent Cr^(3+).The varying of the reaction amount of crosslinking agent Cr^(3+)and the dehydration rate of gel were investigated in the crosslinking reaction process,the effects of temperature and inorganic salt concentration on crosslinking reaction rate and gel dehydration rate were studied,and the relationship between crosslinking rate and gel dehydration rate was analyzed.It is shown that with the increase of temperature,the reaction rate between Cr and the carboxyl group of polymer HPAM is accelerated,and the formation rate of Cr polynuclear hydroxyl bridge ions is also accelerated.The higher the temperature,the faster the hydrodynamics diameter of Cr polynuclear hydroxyl bridge ions increases,which makes the crosslinking reaction rate of Cr faster.Increasing the concentration of inorganic salts is beneficial to the formation of Cr polynuclear hydroxyl bridge ions,and the time when the hydrodynamic diameter reaches the maximum value is significantly shortened.Therefore,under the influence of temperature and inorganic salts,the over crosslinking occurs in the cross-linking reaction process of Cr^(3+)and HPAM.Over crosslinking will increase the density of crosslinking system,resulting in the decrease of water holding capacity of crosslinking system,thus causing gel dehydration.This study has a guiding significance to explore the method of inhibiting the dehydration of gel system.