三甲基硅基甲基纤维素的合成及膜的富氧性能

引言 在分离膜研究与发展的历史上,天然高分子是最早使用和进行改性的膜材料.纤维素及其衍生物具有原料丰富易得、成本低、无污染、成膜性好等优点,至今仍作为常用的膜分离材料1].由于纤维素中存在大量的羟基和强的分子间氢键,氧透过性能并不理想,因此很少将纤维素直接用作气体分离尤其是氧氮分离的膜材料.近来,有专利报道对纤维素进行改性修饰,在羟基上连上含硅的基团如三甲基硅基,可以获得好的富氧性能2].但由于该反应属于非均相反应,这一制备方法的实施和验证有困难.本文选用能够溶于有机溶剂的甲基纤维素(MC)为原料,以六甲基二硅胺烷(HMDS)作为三甲基硅基化试剂,通过均相反应很容易地制备了具有较高的取代度和良好的有机溶剂溶解性能的三甲基硅基甲基纤维素(TMS-MC).经溶液浇铸成膜,对其富氧性能研究后发现,与甲基纤维素膜相比,该膜的透氧系数和氧氮分离系数分别得到显著改善.

Synthesis of trimethylsilyl methylcellulose and oxygen-enriching properties of membranes

To improve oxygen-enriching properties of cellulose derivative membranes, trimethylsilyl methylcellulose (TMS-MC) with degree of substitution (DS) of 1.12 was synthesized by using methylcellulose with DS of 1.80 as raw material and hexamethyldisilazane as reactant in a homogeneous reactive system.The chemical structures of TMS-MC were characterized with FT-IR and ¹H NMR.The product samples were fairly soluble in ordinary organic solvents such as tetrahydrofuran, chloroform, xylene, toluene, and so on.The gas separation membranes were prepared by casting a xylene solution of TMS-MC on a sheet of PET.It was found that the oxygen permeation properties of the TMS-MC membrane were improved and an obvious increase in separation factor was obtained especially.Comparing with methylcellulose, for example, the permeability coefficient and separation factor of the TMS-MC membrane increased from 2.5 Barrer and 2.41 to 23.85 Barrer and 5.42 at 20℃, respectively.