Study On The Preparation Of Redispersible Latex Powder And Its Modification To Cement

Cementing engineering is the key link between drilling and oil resource exploitation.Because the high temperature and pressure environment,cement is easy to crack,which threatens the safety of cementing.It is necessary to improve the defects of cement,so we need add polymer to the cement slurry.Latex is a common cement toughening agent,which can improve the flexural strength of cement stone.The styrene-butadiene latex,acrylic latex,styrene-acrylic latex and ethylene-vinyl acetate copolymer can improve the toughness of cement to a certain extent.SBR latex has attracted much attention due to better temperature resistance,but the old SBR latex has poor dispersion in cement,is difficult to mix uniformly with cement slurry.And liquid latex is not conducive to industrial transportation,so the preparation of a redispersible styrene butadiene latex powder become a new research direction.In this paper,by designing the molecular structure,selecting two hydrophilic functional monomers: itaconic acid(IA)and sodium p-styrene sulfonate(SSS),to prepare styrene butadiene latex with core-shell structure.Then by spray drying,the powder is obtained,which solves the problem of liquid latex transportation.The performance of the latex powder was testde by infrared spectroscopy,thermal weight loss,particle size distribution,salt tolerance,and microscopic morphology characterization.The results showed that the latex powder was the target product,it has obvious core-shell structure and good performance redispersibility: the latex particles are stable and non-aggregated in water,their particle size distribution is uniform.The thermal weight loss temperature is 267.7 °C,and they can exist stably in a saturated salt solution.Three different latex powders were obtained by adding 1 %,3 %,and 5 % of IA.Three latex powders were characterized by UV spectroscopy and Zeta potential.The results showed that the stability of the latex powder increases along with IA addition.Afterwards,it was tested for free liquid content,sedimentation stability,fluidity,rheological properties,flexural strength,compressive strength,triaxial mechanical properties,pore size distribution,etc.The results showed that the addition of latexs can not only reduce the free liquid content,increase the settlement stability of the cement slurry,delay the hydration time of the cement,but also have a significant improvement on the fluidity and rheological properties of the cement.Compared with the original latex,the re-dispersed latex has less performance loss,can significantly improve the mechanical deformation ability of the cement stone,and the modulus of modified cement stone is as low as 3.16 GPa,has very excellent elasticity and toughness.The modified cement stone is characterized by the hydration heat release rate and X-ray diffraction,test data shows that the hydration time of the cement increases with the increase of the IA addition ratio.The interaction between styrene-butadiene latex and cement particles was studied by the microstructure characterization,adsorption capacity test characterization,and micro-morphology characterization.The results showed that the latex particles were filled in the cement stone through adsorption and complexation.The mesoporous pores are reduced in the pores,and a dense polymer film is formed on the surface of the cement stone,which makes the cement more dense.The modified cement has better fluidity and mechanical properties.