| In the production process of architectural ceramics, the addition of dispersant is helpful to disperse the ceramic particles efficiently, and keep a good liquidity for ceramic slurry with a high solid content. Ceramic dispersant can improve the efficiency of ball-milling of ceramic slurry, and the quality of ceramics. Ceramic dispersant can also reduce the required water content in the ceramic slurry, and decrease energy consumption. At present, inorganic salt is generally used as ceramic dispersant, but it does not very well in grinding, and stability of ceramic slurry. Polymer dispersant can meet the requirement of ceramic slurry with high performance, but its high price limits its utility. This paper has investigated the effect of a series of polymer dispersant on property of ceramic slurry, and developed a novel lignin-based dispersants by chemical modification and compounding. The main research progress and achievements of this paper are as follows:(1) Effect of a series of polymer dispersants on the fluidity, apparent viscosity and solid content of ceramic slurry were intensively studied, and then four kinds of dispersants with good performance were screened out for further investigation. The four kinds of polymer dispersants were Naphthalene formaldehyde condensate (FDN), Dong-Guan high efficiency dispersant (GCL4-1), Aminosulfonic acid-based (ASP) and Modified aminosulfonic acid-based (ASL).(2) After investigating the applied performance of the four kinds of polymer dispersants incorporating with inorganic salts, two kinds of composite dispersants with good visbreaking performance were selected. The first composite dispersant was ASP incorporating with H and S, with the mass ratio of 1.0:1.0:5.0. When 69wt% ceramic slurry with dispersant dosage of 0.35% was used, the fluidity of ceramic slurry with ASP-H-S was 45.12s, which was 13.32s less than that of the reference dispersant. Here, the dispersant dosage is defined as the dispersant content in ceramic slurry, in mass of solid dispersant per unit mass of dry ceramic slurry. The reference dispersant is a mixture of sodium tripolyphosphate and water-glass with ratio of 2:5, which is widely used in the field of aechitectural ceramic slurry. The second composite dispersant was ASL incorporationg with T and S, with the mass ratio of 1.0:0.8:5.0. When 69wt% ceramic slurry with dosage of 0.34% was used, the fluidity of ceramic slurry with ASL-T-S was 53.50s, which was 4.94s less than that of the reference dispersant. The apparent viscosity of ceramic slurry with ASP-H-S, ASL-T-S and reference dispersant was 240.0 mpa.s, 246.5 mpa.s, and 288.5 mpa.s, respectively. After being set aside for 120min, the ceramic slurry with ASP-H-S, ASL-T-S, and the reference dispersant had a stability index of 3.32,3.39 and 3.95, respectively. In the meantime, the average particle size of the three ceramic slurries was 17.25μm,16.34μm and 16.27μm .(3) The pilot plant tests showed that the grinding properties of ASP-H-S and ASL-T-S were better than that of reference dispersant. After being milled for 7 hour, the ceramic slurry with ASP-H-S had 0.30 % residues on 250-mesh sieve, while that with the reference dispersant had 1.02% residues on 250-mesh sieve. The ceramic slurry with ASP-H-S had 1.04 % residues on 250-mesh sieve after being milled for 6 hour. Obviously, compared with the reference dispersant, these composite dispersants can increase grinding efficiency. The ceramic slurry with ASP-H-S, ASL-T-S, and the reference dispersant had a similar flexural strength. Their flexural strength was 2.53 MPa, 2.48 MPa, and 2.67 MPa, respectively.(4) To meet the requirement of ceramic dispersants with low-cost and high dispersive ability, a novel lignin-based dispersant LMA was prepared by co-polymerization of kraft lignin, phenol, sodium p-aminobenzene sulfonate, and formaldehyde. The optimum synthetic conditions were as follows: the molar ratio of kraft lignin, phenol, sodium p-aminobenzene sulfonate, and formaldehyde was 0.90: 1.00:1.26:2.50; the pH value of reaction solution was 10.4; the reaction time at 95℃was 3.0h ; the reactant concentration was in the range of 25wt% 33wt%. The fact that the kraft lignin was successfully modified to form LMA was proved by IR spectra.(5) The surface tension, adsorption ability, and the salt effect of LMA were studied. Surface tension of LMA solution was measured to be 49.92mN.m-1. The adsorption amount of LMA on ceramic particles was 1.1mg.g-1. When the inorganic salt (T) is added into LMA with the mass ratio of 1:1, the surface tension reduced to be 46.51mN.m- 1 . The adsorption amount of LMA on ceramic particles reduced to be 0.4mg.g-1 because of the competitive adsorption of salt. The adsorption amount of LMA on ceramic particles decreased with increasing salt content.(6) Lignin-based ceramic dispersant LMA-T-S was fabricated by mixing LMA, T, and S, and then the applied performance of LMA-T-S in architectural ceramic slurry was investigated. When 69wt% ceramic slurry with added dosage of 0.35% was used, the fluidity of ceramic slurry with LMA-T-S was 49.53s, which was 7.08s less than that of the reference dispersant. Obviously, the grinding, dispersion, and stabilization of LMA-T-S were better than that of reference dispersant. After being milled, the ceramic particles with LMA-T-S had an average size of 12.61μm, while the blank sample and reference dispersant had the average size of 19.47μm and 13.45μm. After being set aside for 60min, the ceramic slurry with LMA-T-S had the average size of 15.37μm, while that with the reference dispersant had the average size of 16.29μm. Through microscope with magnification of 1000, it was observed that the ceramic slurry with LMA-T-S had a smaller particle size than that with the reference dispersant. When 69wt% ceramic slurry with added dosage of 0.35% was used, the Zeta potential of the ceramic slurry with LMA-T-S was 38.89mv, which was 6.0 mv higher than that with reference dispersant. The rheological curve of the ceramic slurry with LMA-T-S showed that the viscosity was 232.3mpa.s when the solidity was 70wt%, indicating that LMA-T-S had a good visbreaking performance.
|
PDF Full Text Request