Molecular Design And Application Of Acrylic Copolymer Dispersant

Due to its excellent light absorption properties,Ti O₂ ultrafine powder is widely used in the white pigment and cosmetics industries.Ultrafine powder is extremely prone to particle agglomeration,which seriously affects the widespread use of Ti O₂.The need for uniformity of the particle size distribution of Ti O₂ and the dispersibility of the powder greatly contributes to the development of the dispersant.In recent years,regulations on the limitation of organic solvents in coatings and auxiliaries have greatly promoted the rapid development of the field of waterborne coatings.However,due to the high surface energy of the water itself,complete dispersion of the ultrafine Ti O₂ powder in the water environment is difficult to achieve.In this paper,two series of copolymer-modified dispersants were prepared by free radical copolymerization using a redox initiation system to test their structural properties.In the third part,the performance was compared with the mainstream dispersants at home and abroad.1.The methacrylic acid（MAA）as the main monomer,the acrylamide（AM）with closed Q-e value and the hydroxyethyl methacrylate（HEMA）as the secondary monomer were subjected to free radical copolymerization of redox aqueous solution to prepare the polymers.The polymers structure contain anionic anchoring group（-COO^-）、amide group and hydroxyl group which can exert a certain wetting action on the surface of the pigment filler particles.In this paper,the molecular structure of the series of polymers was characterized by infrared,nuclear magnetic,Abbe refractometer and static light scattering.Based on the ratio of polymer monomer,dispersant addition and group type,the viscosity of the suspension was determined by a rotary viscometer.The relationship between viscosity and variable was discussed.When the polymer monomer addition ratio is P[MAA-AM 20%-HEMA 5%（DP2-12）,the lowest dispersion viscosity is 500 cp,which is about 0.3%of the initial viscosity.The average particle size and particle size distribution of Ti O₂ particles in the suspension under the action of copolymerization modified dispersant were obtained by light scattering particle size analyzer.The results show that the copolymer-modified dispersant containing HEMA monomer effectively reduces the average particle size（330 nm）,only about 0.1%of the initial particle size,while making the particle size distribution narrower and tends to be single-distribution.The results of scanning electron microscopy（SEM）and transmission electron microscopy（TEM）showed that the addition of dispersant can significantly reduce the aggregation tendency of Ti O₂ particles and the particle distribution is more uniform.2.A series of polymer dispersants were prepared by copolymerization of free radical aqueous solution in redox initiation system,by using cheaper acrylic acid（AA）as the main monomer,AM and HEMA as sub-monomers.The polymers contain anionic anchoring group（-COO^-）、amide group and hydroxyl group which can exert a certain wetting action on the surface of the pigment filler particles.At the same time,maleic anhydride（MA）with a large difference in Q-e values was introduced to obtain a larger ion charge density in the polymer molecule.Based on the ratio of polymer monomer,dispersant addition and group type,the relationship between viscosity,particle size,SEM and TEM morphology and variables was discussed by comparing the dispersion of Ti O₂,particle size,SEM and TEM observation.When the polymer monomer ratio is P[AA-AM 20%-HEMA 5%]（DP3-12）,the minimum dispersed viscosity and average particle size of Ti O₂ are 200 cp and 307 nm,respectively（about0.1%of initial viscosity and particle size）.The results of SEM and TEM showed that the acrylic copolymer modified dispersant had better dispersion effect than methacrylic acid in dispersing Ti O₂.However,due to its low reactivity rate,MA has a heterogeneous polymerization of polymer molecules and even more residuals,which makes the dispersion performance worse.The structure of the series of polymers was characterized by infrared,nuclear magnetic,Abbe refractometer and static light scattering.The effects of molecular composition,polymer type and process on dispersion performance were studied by combining the molecular structure of the polymer.3.On the basis of the structural properties of the first two parts,the dispersion viscosity and high temperature anti-aging experiment of the dispersant prepared and the mainstream dispersant at home and abroad for the one-component（Ti O₂）and multi-component coating suspensions are discussed,by using the type and amount of dispersant as variables.Comparing the application performance of seven dispersants,such as water separation,heat storage stability,scrub resistance,color display performance and thixotropic index,DP3-12 surpassed some excellent imported dispersant products in terms of the scrub resistance and color display.