Study On Heat-resistance Modification Of Carboxymethyl Cellulose

Carboxymethyl cellulose(CMC) was synthesized from natural cellulose through alkalization and etherization. It was widely used in drillings of oil and natural gas. The common CMC couldn't satisfy the need of exploitation in high-temperature and complex stratum, and it is urgent to develop CMC with better heat-resistance. The modification of CMC were studied in many ways, but studies on heat-resistance CMC were absent.After studying the mechanism on improving of heat-resistance of CMC, a approach of adding modifier in the CMC synthesis process was proposed to improve heat-resistance in this paper. Laws in modification technology/product structure/application properties were studied. CMC with better heat-resistance was prepared by using the optimized technology.CMC was synthesized in a 10L malaxator, adding triphenyl phosphate(TPP), borate or sodium silicate as the modifier. Influences of factors, such as the dose of TPP and water, alkalization time and way of adding sodium hydroxide, on the degree of substitution(DS), uniformity of substitution groups distribution and the viscosity were studied.. It found that adding of TPP in alkalization was one way to improve heat-resistance of CMC. The viscosity of 2wt% modified CMC solution increased with increasing the dose of TPP. While, the DS, distribution of DS and the resistance to salt solution and to acid solution decreased with increasing the dose of TPP. It also showed that rs and ra of modified CMC were lower than those of unmodified CMC, however, the viscosity values of modified CMC in 2wt% NaCl solution and 2wt% lactic acid solution were greater than those of unmodified CMC. The viscosity value of lwt% modified CMC in distilled water was 41mPas , however ,that of unmodified CMC was only 8.8mPas at 148.9 and 35.1MPa. The optimized recipe and synthesis conditions were obtained as follows: thedose of TPP was 8wt%, alkalization temperature 20 alkalization time 90min, the firstdose of sodium hydroxide was 2mol % and the second dose was 1.15mol%. Adding of sodium borate in etherification stage could also improve the heat-resistance of CMC. The viscosity was first increased and then decreased with the increasing of sodiumborate. ,DS and distribution of DS were improved. The optimized technology was gotten as follows: sodium borate was 8wt%,alkalization temperature 20 alkalization time 90min.The heat-resistance of CMC was also enhanced by adding sodium silicate in alkalization, and adding sodium borate in etherization in the synthesis of CMC. ra was decreased, but the viscosity was significant increased. The optimized technology was got: the dose of sodium silicate 10wt%,the dose of sodium borate was 6wt%, alkalization temperature20 alkalization time 90min, the first dose of sodium hydroxide was 2mol%, and thesecond dose was 1.15mol%.After comparing the properties of CMC synthesized through the above methods, CMC which was synthesized by adding TPP in alkalization stage had best heat-resistance, salt-resistance and acid-resistance properties.