Ethylene oligomers Extractives

Various on-line SFE-SFC applications for the analysis of polymer additives and oligomers have been reported, such as additives in PE [121] polymer additives and oligomers in PP nylon pellets and PEEK granules [15] and oligomers in PET films [103], PS [122] and PMMA [123], sometimes in quantitative fashion [15,103]. SFE-SFC has identified the cyclic trimer tris-(ethylene terephthalate) in commercially available PET film [103]. Also, SFE-SFC extraction and... 

HTE liquid polymers were synthesized by cationic ring-opening polymerization of epichlorohydrin (ECH) in the presence of water or ethylene glycol (EG) as a modifier (1). Cyclic oligomers were removed by extraction. After extraction, the liquid polymers were essentially free from cyclic oligomers as determined by gel permeation chromatography (GPC) (Figure 1). 

This silane polymer was found to be virtually insoluble in carbon dioxide at pressure and temperature levels up to 552 bar (8,000 psia) and 120°C, respectively. Additionally, it was difficult to solubilize in supercritical ethylene and ethane at the same conditions. Supercritical propane proved to be a better solvent, and the extraction of the low molecular weight oligomers was accomplished at conditions of 483 bar (7,000 psia) and 120°C. 

This patent is concerned primarily with the polymerization of ethylene at conditions high above its critical temperature and pressure. The Krase and Lawrence patent covers polymerization but it also describes the separation of various oligomers by stagewise pressure reduction. The multistep sequence results in a lower energy recycle/separation process which produces discreet fractions of polyethylene of different molecular weight. A portion of the example and process operation is excerpted from the patent to point out once more that supercritical fluid extraction and separation have been known and understood for 40 to 50 years. 

Wang et al. extracted cellulose nanofibres from soybean stock by chemo-mechanical treatments with diameter ranging from 50-100 nm and size of -1000 nm (2007). The cellulose nano fibers were dispersed in polymeric matrix of poly (vinyl alcohol) (PVA) and polyethylene (PE) by addition of dispersant ethylene-aciylic oligomer. The soya bean stock based PVA films showed an increase of 4-5 fold in tensile strength. 

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