黄原胶的化学改性及溶液黏度特征

Chemical modification and solution viscosity characteristics of Xanthan gum

黄原胶-OH与马来酸酐发生酯化反应,合成了具有更好黏度特征的改性黄原胶MX。合成反应的最佳条件:XG与MA摩尔比1∶11,温度70℃,反应时间24h,产率57.7%。MX比XG有更好的的溶解分散性;当聚合物浓度由7g·L-1增至8g·L-1时,XG的黏度增加了240mPa·s,而MX70的黏度增加了582mPa·s;1.2%NaCl溶液中,2g·L-1MX70黏度为234mPa·s-1,而XG黏度为95mPa·s;3g·L-1的聚合物溶液,pH值为4时MX70、XG表观黏度分别为284、178mPa·s,pH值为11时MX70、XG表观黏度分别为262、152mPa·s;3g·L-1的聚合物溶液,温度从20℃增至80℃,表观黏度依次下降,但MX70黏度下降率比XG减少18.7%。与XG相比,改性后的黄原胶MX增溶性良好、溶液黏度明显提高、耐温耐盐性增强,对油田钻井液增黏剂的研究及应用具有重要的指导意义。

Xanthan gum-OH and maleic anhydride were esterified to produce the modified Xanthan gum MX with better viscosity characteristics. The best conditions for reaction are： molar ratio of XG and MA is 1：11; the temperature is 70℃ and reaction time 24h. MX has better solubleness and dispersity compared with XG. When the polymer coneentration increased from 7 to 8g·L^-1, the viscosity went up to 240mPa＇s, while MX70 viscosity in- creased 582mPa＇s; in the 1.2% NaCI solution, viscosity of 2g·L^-1 MX70 is 234mPa＇s, while XG 95mPa＇s. In the 3g·L^-1 aqueous solution, when pH=4, viscosity of MX70 is 284mPa＇s, while XG 178mPa＇s. when pH=l 1, viscosity of MX70 is 262mPa＇s, while XG 178mPa＇s; In the 3g·L^-1 aqueous solution, when the temperature increased from 20℃ to 80℃, the colloidal viscosity turned down in proper order. However, the scale of decrease of MX70 viscosity is 18.7% less than XG. The hydrotropy of modified Xanthan gum MX is good. And the solution viscosity has in- creased remarkably. The ability of temperature resistance and salt tolerance has also been strengthened. It is of great importance to the research and application of oilfield drilling fluid tackifier.