| As an important branch of functional polymer materials,water-soluble polymers are widely used in various types of water-based products or water-based industrial processes by virtue of their complex and versatile properties and environmentally friendly characteristics.In many important applications,water-soluble polymers need to be dissolved in water to form dilute solutions in order to be used,therefore,the dissolution rate is a very important property parameter for water-soluble polymers.At present,water-soluble polymers are mainly prepared by aqueous polymerization in industry,and the obtained polymer gel products are post-processed to obtain dry powder products,which are slow to dissolve due to the need to undergo the swelling process.The water-soluble polymer products obtained by emulsion polymerization are in the form of latex particles,which have better solubility properties.However,emulsion polymerization requires the use of large amounts of surfactants,which can significantly increase production costs and may have toxic effects on the environment or living organisms.Pickering emulsions are emulsions stabilized with ultra-fine solid particles,which can avoid the use of surfactants.Thus,the use of Pickering emulsion polymerization for the preparation of water-soluble polymers is a possible method for achieving the preparation of low-cost,high-safety,fast-soluble water-soluble polymer products.Calcium carbonate is one of the most common inorganic compounds in nature,with the advantages of wide source,low price,environmental friendly,good stability,easy to prepare,etc.,it is very suitable for large-scale industrial application of Pickering emulsions.In this paper,we first prepared a water-in-oil Pickering emulsion using stearic acid modified hydrophobic calcium carbonate particles and investigated in detail the effects of the amount of particles,oil-water ratio,emulsification temperature,and the type of ions in the aqueous phase on the properties of this Pickering emulsion.The experimental results showed that the minimum value of the amount of calcium carbonate particles in the emulsification process was 2 wt%and the optimum amount was 5 wt%.When the amount of particles was fixed relative to the dispersed phase,the change of oil-water ratio did not affect the emulsion droplet size and its distribution,but directly determined the volume and fluidity of the emulsion.Different types of Pickering emulsions could be obtained by adjusting the wettability of calcium carbonate particles.Raising the emulsification temperature is beneficial to enhance the polydispersity of emulsions,and high internal phase emulsions with 80%of the dispersed phase volume can be produced at emulsification temperatures higher than 30℃.The presence of Na+in the aqueous phase will reduce the stability of emulsions,leading to easier coalescence and deformation of droplets,while Ca2+can directly lead to the phase inversion of the emulsions,and the cationic monomers acryloyloxyethyl trimethyl ammonium chloride(DAC)will promote droplet aggregation.Subsequently,cationic polyacrylamide flocculant P(AM-DAC)was prepared by polymerization of calcium carbonate-stabilized water-in-oil Pickering emulsion by introducing acrylamide(AM)and DAC into the water phase.The microscopic images showed that the product was in the form of latex particles with an average particle size of 100 μm,and the infrared spectra confirmed that the product was a copolymer of AM and DAC.The solubility test showed that the product was completely soluble in pure water within 10 min under magnetic stirring at 500 rpm,exhibiting excellent solubility properties.The polymerization system was optimized by single-factor experiments,and the relative molecular mass of the resulting product was up to 9.27 dL/g in terms of intrinsic viscosity.Further flocculation experiments on diatomaceous earth suspensions showed that the product exhibited the best flocculation performance at a dosage of 40 mg/L,which was better than that of commercially dry powder products of the same cationic degree. |
PDF Full Text Request