助悬剂对硫酸钡混悬剂性能的影响

利用Hōppler流变粘度计研究了10种胶的流变学性质,确定了它们的流型。粘度较小的胶多属塑性流体如聚乙烯吡咯烷酮、阿拉伯胶、白芨胶、羟丙基甲基纤维素、甲基纤维素等,所配硫酸钡混悬剂贮存时易结块。粘度较大的胶多为膺塑性流型如羟乙基纤维素、西黄蓍胶、羧甲基纤维素钠等,所配制剂不结块易分散,但后两种胶所配制剂流动性较差。用羟乙基纤维素300作助悬剂产品流动性很好并且不结块容易再分散,是较理想的助悬剂。发现电解质六偏磷酸钠与柠檬酸钠配合应用(前者1%,后者0.8%)可以产生触变胶,保存时为凝胶,振摇后转变为流动性较好的溶胶。用沉降曲线法研究了各种混悬剂配方的抗胃液性能,结果认为六偏磷酸钠较柠檬酸钠抗胃液的能力为强,并证明酸性胃液(pH1～2.5)有强的絮凝作用,碱性胃液(pH8)对硫酸钡混悬剂没有显著的影响。

EFFECTS OF SUSPENDING AGENTS ON THE PROPERTIES OF BARIUM SULFATE SUSPENSIONS

Rheological studies of 10 different natural gums and cellulose derivatives as well as of the suspensions prepared from them were made using the Hoppler's Rheoviscometer, and their flow types have been determined.Suspensions with suspending agents of the plastic flow type (eg PVP, PVA, Acacia, hydroxypropylmethylcellulose, and methyl cellulose) with low viscosity were easy to cake on aging, while those with the pseudoplastic flow type suspending agents were not. Hydroxyethylcellulose (pseudoplastic flow) as a suspending agent produced better fluidity as well as better redispersibility on aging.Most of the barium sulfate suspensions (130%) were of the dilatant flow type. Suspensions containing methylcellulose, hydroxypropylmethylcellulose, tragacanth and sodium carboxymethylcellulose (0.1, 0.2, 0.15 and 0.3%) exhibited thixotropic properties, but did not form thixotropic gels.It was found that proper combined use of electrolytes in suspensions (1% sodium hexametaphosphate 0.8～1.2% sodium citrate)resulted in thixotropic gels, which turn to sols with good fluidity on shaking.Gastric fluid flocculating resistance of barium sulfate suspensions were studied by sedimentation method. Gastric fluids of different pH obtained from patients were mixed with barium sulfate suspensions and sedimentation curves were produced on an automatic recording sedimentation balance (KCY type). The results showed that:1. Suspensions containing sodium hexametaphosphate are more stable than those containing sodium citrate whatever suspending agents were used.2. Gastric fluid of pH 8 (alkalinity due to back-flow of the duodenal fluid) do not cause flucculation, on the other hand the gastric fluid of pH 1～2.5, caused remarkable flocculation.