Synthesis Of Modified Acrylic Water-based Dispersants For Preparation Of Praseodymium-doped Zirconium Silicate And Aluminum Cobalt Oxide Pigments In Waterborne Ceramic Inks

The existing ceramic inks are mainly volatile organic solventborne,which affect the ecological environment and human being health.Recent developments on waterborne ceramic inks have become popular,in which the synthesis and application of effective water-based polymer dispersants are particularly critical.Water-based polymer dispersants have the flexible structure,controllable molecular weight and steric hindrance effect as well,and can change the molecular weight and molecular structure according to the corresponding application.These water-based polymer dispersants can be used in various fields like ceramic pigment grinding and dispersion,dye dispersion,scale inhibition,washing,water treatment and sliding water-based lubrication for steel making.The objectives of this dissertation mainly were to a)synthesize different types of water-based polymer dispersants with the functions of grinding aid and dispersion via the modification of(meth)acrylic monomers,b)apply the synthesized water-based polymer dispersants for wet ultrafine grinding of ceramic inorganic pigment(i.e,praseodymium-doped zirconium silicate,Pr-ZrSiO4 and cobalt aluminate,CoAl2O4)particles in a sirred bead mill and dispersion of the particles in waterborne inks,and c)clarify the mechanisms of ultrafine grinding and dispersion of ceramic pigment particles via the related experiments,physical and chemical characteriztions,and mathematical simulation analysis.In addition,waterborne ceramic inks with proper viscosity,surface tension and density were prepared in the presence of water-based polymer dispersant,and some inkjet printing effects of the waterborne ceramic inks were simulated and the color properties of the waterborne ceramic inks on the surface of a ceramic tile by screen-printing and thermal transfer calcinations were determined.The main research contents and results of this dissertation are as follows:(1)I,V and S series of water-based polymer dispersants containing different functional groups and epoxy ester modified acrylic water-based resin were synthesized via an aqueous radical polymerization method.In addition,two kinds of water-based diblock polymer dispersants(i.e.,PMA-b-S and PV-b-G)were also synthesized by reversible addition-fragmentation chain transfer polymerization(RAFT)methods.The molecular weight and functional groups structure of the synthesized dispersants were characterized by 1H nuclear magnetic resonance(1H-NMR),Fourier transform infrared spectroscopy(FT-IR)and gel permeation chromatography(GPC).The results show that the target water-based polymer dispersants with a suitable molecular weight can be obtained by controlling the polymerization conditions(2)Aqueous suspensions with submicron-sized ceramic pigment Pr-ZrSiO4 and CoAl2O4 particles were prepared via wet ultrafine grinding in a stirred bead mill in the presence of different polymer dispersants(i.e.,I series,V series and S series)or aqueous polymer dispersants containing different molecular weights,respectively.All the samples were characterized by particle size analysis,scanning electron microscopy(SEM)and X-ray diffraction(XRD).The results show that submicron-sized Pr-ZrSiO4 pigment particles with narrower size distribution(d50=334 nm,n=2.61)are produced after the micron-sized particles(d50=8849 nm,n=1.32)are wet ground for 90 min in the presence of 2 wt.%sodium polyacrylate-2-acrylamide-2-methylpropanesulfonate-hydroxyethyl methacrylate(PASH2)as a modified water-based polymer dispersant with an appropriate molecular weight.Similarly,submicron-sized CoAl2O4 pigment particles with narrower size distribution(d50=340 nm,n=2.62)can be obtained after the micron-sized particles of(d50=5199 nm;n=0.86)are wet ground under the same grinding conditions in the presence of 2 wt.%of sodium polymethylmethacrylate-acrylate-2-acrylamide-2-methylpropanesulfonate-hydroxyeth-ylmeth acrylate copolymer as a modified water-based polymer dispersant with an appropriate molecular weight(PMASH1).Based on the adsorption amount of dispersant,rheological properties,adsorption thermodynamics and kinetics analysis,zeta potential measurement and interparticle potential energy calculation,dispersants PASH2 and PMASH1 can produce more effective hydrogen bonding,thus being readily adsorbed on the particle surface for wetting,effectively improving the rheological properties(i.e.,viscosity)of the aqueous suspension to be ground,and favoring the breakage of ceramic pigment particles.In addition,steric hindrance repulsive energy between the particles is generated due to carbon chains of the polymer dispersant adsorbed on the particle surface.Besides,the presence of carboxylic acid groups(-COO-)and sulfonic acid groups(-SO3-)in dispersants PASH2 and PMASH1 can also provide a strong charge density for the particles and generate the interparticle electrostatic repulsive energy.The selection function Si and the breakage function Bi,j for pigment particles in ultrafine grinding from a discrete(breakage)population balance model(PBM)were analyzed.The results show that the breakage mechanism of Pr-ZrSiO4 and CoAl2O4 pigment particles ground in stirred bead mill in the presence of water-based polymer dispersant PASH2 or PMASH1 is mainly due to the compressive and shear stresses between beads in grinding(3)The dispersion stabilities of submicron-sized Pr-ZrSiO4 particles in aqueous suspension at different parameters were investiaged by a standing sedimentation method for 24 h.The results show that a 35 wt.%aqueous suspension of submicron-sized Pr-ZrSiO4 particles with a narrow particle size distribution can be dispersed at pH value of 7 in the presence of 3 wt.%of a suitable molecular weight dispersant PASG1.Based on the results analyzed by FTIR,adsorption thermodynamics and kinetics and zeta potential measurement,dispersant PASG1 has more adsorption group(i.e.,-OH and-CO-NH-),can be adsorbed on the particle surface through hydrogen bonding.This is conducive to enhancing the steric hindrance effect between the particles.Also,carboxylic acid group(-COO-)and sulfonic acid group(-SO3-)in dispersant PASG1 can provide more charge density,thus having the more intense interparticle electrostatic repulsion energy.These interparticle repulsive energies against the van der Waals attractive energy can promote the particles dispersion and stable in the suspension effectively.In addition,the dispersion/aggregation behavior of submicron sized Pr-ZrSiO4 particles at different amounts of PASG1 addition,particle solid contents and particle size distributions was predicted by a modified PBM.The results show that the predicted data are similar to the experimental results,indicating that the modified PBM model can be used to predict the dispersion/aggregation behavior of ceramic pigment particles indense aqueous suspensions(4)The dispersion of submicron-sized Pr-ZrSiO4 or CoAl2O4 pigment particles in aqueous suspensions in the presence of three random copolymer dispersants,two diblock polymer dispersants(i.e.,PMA-b-S and PV-b-G)and dispersants PMA-b-S and PV-b-G mixed in different mass ratios was investigated via 840 h standing sedimentation and centrifugal sedimentation,respectively.The samples were characterized by particle size analysis,adsorption amount deterimination,zeta potential measurement and X-ray photoelectron spectroscopy.The results show that the submicron sized pigment particles in the aqueous suspension have a superior dispersion stability with in standing sedimentation for 840 h or centrifugal sedimentation in the presence of 5 wt.%of diblock polymer dispersants PMA-b-S and PV-b-G in a mass ratio of 9:1.Furthermore,waterborne ceramic inks with submicron-sized Pr-ZrSiO4 or CoAl2O4 pigment particles were prepared by using 5 wt.%of diblock polymer dispersants PMA-b-S and PV-b-G in a mass ratio of 9:1,water-soluble solvents,anti-settling agent,anti-foaming agent,wetting and leveling agent,water-based resin and other additives.The inkjet printing characterizations(i.e.,Re,We and Oh evaluation parameters)of waterborne ceramic inks prepared were predicted by a semi-empirical model The predicted results show that the waterborne ceramic inks with appropriate viscosities(i.e.,13.4 and 19.0 mPa.s),surface tensions(i.e.,38 and 39 mN/m)and densities(i.e.,1250 and 1450 kg/m3)can satisfy the inkjet printing requirements.Besides,the waterborne ceramic inks were also decorated on a ceramic tile by screen-printing and low-temperature calcination of thermal transfer films,respectively.The results show that the waterborne ceramic inks decorated on a ceramic tile have a color rendering effect,indicating that the waterborne ceramic inks prepared have a promising application prospectThis dissertation finally gave the major conclusions based on the experimental results obtained and the corresponding basic analysis.The prospects for future studies and application of water-based polymer dispersants in waterborne ceramic inks were also proposed.