Iron oxide red is a class of red inorganic pigments with wide applications. Now through different methods to improve its application performance is to reduce its industrial use and reduce industrial costs of the main way, mainly by improving the production process to control the α -Fe2O3 crystal shape, particle morphology and particle size and surface modification of its application performance to improve its application performance. The preparation of composite materials with inexpensive minerals as nuclei and iron oxide red particles as coatings is one of the effective ways. In this study, the composite powder materials with calcined diatomaceous earth as the nucleus and iron oxide red as the coating in the wet grinding system were prepared by mechanical chemical method using the mechanical chemical method as the raw materials, and the optimal process conditions for the preparation of composite pigments were determined by designing orthogonal tests, and the pigment properties of the composite powders prepared under the optimized conditions were characterized and analyzed.
Experimental instruments
Media agitation mill, 2L, Xeno zirconia beads, TLJ-2 type electric booster agitator,
Sample preparation process
An orthogonal experiment of 4 factors (dispersant dosage, iron oxide red ratio, compounding time and grinding speed) of 4 levels was designed. Firstly, under the condition of slurry concentration of 50%, Xeno zirconia beads/ material mass ratio of 5:1, stirring speed of 1200r/min and appropriate amount of dispersant, mechanically crushed calcined diatomaceous earth for 3h. Subsequently, iron oxide red is weighed according to the ratio of iron oxide red set by the experiment and dispersed for 30 min under the condition of 50% concentration of slurry and appropriate amount of dispersant. The dispersed iron oxide red slurry and Xeno zirconia beads were added to the calcined diatomaceous earth mechanical force activation system for compounding. Finally, the xeno zirconia beads are sifted into composite powders, dried and scattered for testing.
Sample performance characterization
Samples prepared by orthogonal tests are characterized by the hiding force to determine the optimal process conditions. The particle morphology of calcined diatomaceous earth and calcined diatomite/iron oxide red composite powder sample prepared under optimized conditions was characterized by S-3500N scanning electron microscope (SEM), and the pigment properties of the composite powder prepared under optimized conditions were characterized by covering power, oil absorption and pigment Lab value (USing SP60 Lab colorimeter).
Results and discussion of the 3.1 orthogonal test
The results of the quadrature test of the 4-factor 4 level and the analysis of the range are shown in Table 1. According to the analysis of Table 1, the significant order of the influence of various factors on the hiding power of the composite powder is: the iron oxide red ratio> the composite time> the amount of dispersant used> the grinding speed. The optimal process parameters for the preparation of calcined diatomaceous earth/iron oxide red composite powder are: the amount of dispersant is 0.9%, the proportion of iron oxide red is 60%, the composite time is 120min, and the grinding speed is 1300r/min. Since the iron oxide red ratio is 40% and 60%, the impact of the two on the application effect (hiding force) of the composite powder is very similar, so the proportion of iron oxide red is 40% from the cost point of view. Since the impact of the grinding speed on the hiding force is extremely small, the speed of 1200r/min is selected from the perspective of effective utilization of the instrument. The optimal process parameters for the preparation of calcined diatomaceous earth/iron oxide red composite powder were 0.9% of the dispersant, 40% of the iron oxide red ratio, 120min of the composite grinding time, and 1200r/min of grinding speed.
Optimize your experiment
Calcined diatomaceous earth/iron oxide red composite powder is prepared according to the optimization conditions obtained above. The particle morphology of calcined diatomaceous earth and iron oxide red composite powder ground for 3h is shown in Figure 2. The comparison of pigment properties of composite powder and iron oxide red is shown in Table 2. From Figure 2a, it can be seen that after wet mechanical grinding, the calcined diatomaceous earth particles are refined to less than 5 μm, and the pore structure is basically destroyed. From Figure 2b, it can be found that a large number of spherical fine particles are evenly adsorbed on the surface of the calcined diatomaceous earth particles after crushing. Combined with Figure 1b, it can be seen that the spherical fine particles coated on the surface of the calcined diatomaceous earth particles are iron oxide red.
According to Table 2, the ratio of the hiding power and oil absorption of calcined diatomaceous earth/iron oxide red composite powder prepared under optimized conditions to the corresponding data of iron oxide red pigments were 1.04 and 1.20, respectively. The results of the determination of the Lab value of the pigments of the two showed that compared with the iron oxide red pigments, the brightness (L value) of the composite powder was increased by 3.5%, the redness (a value) was increased by 4.9%, and the color difference between the two was 2.86. This shows that the composite powder material with similar properties to iron oxide red pigment was obtained by mechanical chemical method
conclusion
Studies have shown that the use of mechanical force chemistry in the wet grinding system can prepare a nuclei-shell type calcined diatomaceous earth/iron oxide red composite powder uniformly coated with iron oxide red particles. The significance of each influencing factor in the preparation of composite powder is: the proportion of iron oxide red> the composite time> the amount of dispersant used> the grinding speed.
2. The optimized process parameters for the preparation of composite powder by mechanical chemical method are: the amount of dispersant is 0.9%, the proportion of iron oxide red is 40%, the composite grinding time is 120min, and the grinding speed is 1200r/min. The ratio of calcined diatomaceous earth/iron oxide red composite powder to iron oxide red pigment prepared under this condition was 1.04 and 1.20, respectively, and the brightness and redness of the former were increased by 3.5% and 4.9%, respectively. This paper provides a composite powder with pigment properties similar to that of iron oxide red pigment by mechanodynamic chemical method.