Preparation Of Fluorinated Cationic Guar Gum And Research On The Properties

Fluorinated hydrophobically associating cationic guar gum(FCGG) is determined as the water-soluble polymers with a small part of fluorinated hydrophobic groups in the molecular chain of cationic guar gum by Chemical reaction. Because of the favorable thickening, heat, shear resistance and gel breaking compared with guar gum(GG), FCGG is expected to become a new generation of water-soluble polymeric materials used in the oil industry, especially in the field of secondary and tertiary oil recovery fracturing.In this paper, a novel fluorinated surface-active monomer(FSM) that based on isophorone diisocyanate(IPDI) and Hexafluoroisopropyl alcohol(FOH) was synthesized, then the fluorinated hydrophobically associating cationic guar gum(FCGG) was copolymerized with FSM and cationic guar gum(CGG). The optimum reaction condition was determined by detecting isocyanatopropyl content and The structure of FCGG was characterized by infrared spectroscopy(FT-IR), nuclear magnetic resonance fluorine spectrum(19F-NMR) and X-ray diffraction(XRD). In addition, the hydrophobically associating property of FCGG was investigated by rheometer, fluorometry spectrum, ultraviolet spectrum and dynamic laser scattering(DLS). The influence of hydrophobic association to viscosity, temperature resistance, shear, modulus and other properties of FCGG were also reported. The gel was formed by mixturing FCGG with organic borate cross-linker(JL) to study its shear resistance, temperature resistance, gel modulus and gel breaking performance.The results show that, FSM was completely generated by the condition that n(IPDI):n(FOH) =1:1, acetone as the solvent, the dibutyltin dilaurate as catalyst and the dosage was 0.015-0.02wt%, reaction temperature was 80℃and the time was 4h. After that, the FCGG was synthesized successfully when n(CGG):n(FSM)=1:1, the dibutyltin dilaurate as catalyst and the dosage was 0.020-0.025wt%,reaction temperature was 70℃and reaction time was 6h.FCGG solution appeared a significant change as the change of cation substitution degree(DS). The hydrophobic association of FCGG was more obvious if the DS increased. This is because DS increased, fluorocarbon hydrophobic groups were more introduced in Macromolecules, and associate each other forming more hydrophobic micro area.namely, hydrophobic association was more obvious. The apparent viscosity tests suggested, with the increase of FCGG concentration, apparent viscosity was showing obvious rising, and there had a sudden increase phase. Fluorescence spectroscopy suggested, with the increase of FCGG concentration, Fluorine carbon chain increased rapidly and formed more hydrophobic micro area, hydrophobic association was more obvious, which enhanced the FCGG’s intermolecular forces. On the apparent, its viscosity increased. Modulus test and power law model suggested, with the increase of DS, FCGG produced more physical cross-linking structure, then the viscoelastic property of solution increased and formed gel, which suggested that hydrophobic groups self-assembly behavior lead to apparent viscosity increase. Not until the apparent viscosity of FCGG increased to a certain degree, did the apparent viscosity of FCGG begin to decrease with the increase of shear rate and temperature. The higher DS was, the more obvious the apparent viscosity increase. UV and UV scattering measurements showed that, hydrophobic group in FCGG solution had more hydrophobic micro area compared with CGG, which made UV absorption increase. DLS showed FCGG aggregate size distribution broadened and became more dispersed by measuring the particle size, which reflected its association with the strong hydrophobic properties.Macromolecular network structure was formed by FCGG with organic borate cross-linker(JL), the gel was viscoelastic apparently. The jelly performance of the mixture of FCGG and organic borate cross-linker(JL) were studied through the rheometer. The results showed that, the FCGG gel had greatly improved in the shear resistance and temperature resistance areas compared with GG and CGG, its viscosity was still greater than 100 m Pa·s when it was sheared in the 170s-1 at 50℃ for 60 min, however viscosity of GG and CGG was 50 m Pa·s. As the temperature increased, FCGG viscosity decreased slowly, its viscosity dipped occur at 85℃. Compared with the GG and CGG gel, FCGG temperature resistance had been improved. The gel breaking performance results showed the water-air interfacial tension, water-oil interfacial tension of the filtrate of FCGG was less than GG and CGG, it was helpful to decrease fluid friction and reduce water formation damage on the ground, the amount of its residue was significantly lower than GG.