Abstract: The electrostatic steric hindrance and steric effect are the dominant factors for the resistance to reunion of nanometer calcium carbonate.According to the resistance to reunion mechanism,mechanic shearing effect to the dispersion of nanometer calcium carbonate was analyzed.It is found that nanometer calcium carbonate can be dispersed when the speed rate is up to 5 000 r/min,but the dispersed solution is unstable and easy to layer under the standing state.The dispersion effect of polyalcohol to nanometer calcium carbonate was analyzed.It is found that average grain size of nanometer calcium carbonate is 35.7 nm and distribution of grain size is from 20 nm to 50 nm,when concentration of polyalcohol is 90 kg/m³.The steric effect is the dominant mechanism.When concentration of biopolymer XC is 6 kg/m³,average grain size of nanometer calcium carbonate is 24.1 nm,distribution of grain size is from 15 nm to 35 nm.The solution is white and heavy viscous emulsion with good stability and no layering.Reduction of surface tension and steric effect are the dominant mechanisms for keeping the system stable.The analysis on the effects of the organic and inorganic dispersants acting with XC on the nanometer calcium carbonate shows that the compound dispersant is complement in advantage of reducing Van der Waals attraction and surface tension.The compound effect can make the dispersion of grain size getting better.

Key words: nanometer calcium carbonate, electrostatic steric hindrance, steric effect, mechanical shear, dispersant, dispersion mechanism, drilling fluid

摘要： 静电位阻和空间位阻是纳米碳酸钙抗团聚的两个主要因素。根据其抗团聚机理,分析了机械剪切对纳米碳酸钙的分散作用。结果表明,单纯采用高速搅拌,转速需达到5000r/min以上才能分散纳米碳酸钙,但溶液不稳定,静置后易分层。分析了聚合醇SD-301对纳米碳酸钙的分散作用后发现,聚合醇加量为90kg/m³时,纳米碳酸钙粒子平均值最小(35.7nm),分布范围为20~50nm,空间位阻是其主要作用机理;生物聚合物XC加量为6kg/m³时,纳米碳酸钙分散平均粒径为24.1nm,分布范围为15~35nm,其分散溶液为白色黏稠乳状液,稳定性好,静置时不分层。降低表面张力和空间位阻是保持纳米碳酸钙分散体系稳定的主要机理。对有机分散剂、无机分散剂与XC共同作用对纳米碳酸钙影响的分析结果表明:复合分散剂能使高分子类、无机和有机类分散剂优势互补,在降低颗粒之间范德华引力的同时,也降低了介质水的表面张力,这两方面共同作用使颗粒的润湿分散效果更佳。

关键词: 纳米碳酸钙, 静电位阻, 空间位阻, 机械剪切, 分散剂, 分散机理, 分散规律, 钻井液