Grinding Of Talc Research Articles

Foam in grinding and role of ground mineral in its stability

AbstractSurfactants are usually used as grinding aids. However, surfactant foaming during the grinding process is rarely mentioned in the literature with no clarification of its effect on the grinding process. In this paper, the generation of foam during the grinding of talc and quartz, as two different minerals in their hardness and hydrophobicity, was observed in the presence of sodium dodecyl sulfonate (SDS). The effect of generated foam on the fineness of ground product under different grinding conditions such as solids%, grinding time, and pulp pH was investigated. The results indicated that the foam was formed during the grinding of both minerals. The foam volume depends not only on the presence of surfactant but also on the characteristics of the mineral along with grinding conditions. The foam was intense and more stable particularly at pH 10 and high solid content (i.e., 60% solids) in the case of talc due to its fineness and hydrophobicity that result in bubbles stabilization. Remarkably, there is no foam at acidic pH due to the high ionic strength that leads to bubble instability. Most importantly, the presence of surfactant foams improves the size reduction process by providing more dispersion of particles, as one of the grinding aid mechanisms, due to particle‐particle and particle‐SDS repulsive electrostatic forces.

Ultrafine dry grinding of talc by planetary mill: effects of operating conditions

Ultrafine grinding is required in most industrial applications of talc. In this work, a planetary mill was used to produce a d50 product of less than 5 μm. The effects of grinding time, media size, mill filling, rotational speed, and media-to-powder ratio, as the main grinding parameters, were initially investigated by the one-variable-at-a-time strategy. In addition, the statistical design method was applied to optimize and correlate the d90 and d50 of the ground product to the media-to-talc percentage and grinding time, being the most significant variables for talc grinding in a planetary mill. The results indicate that the ball size significantly affects the product fineness up to a certain ball size (i. e., 4 mm), after which the product becomes coarser. At the same time, lower mill filling and higher mill rpm yield finer products. The agglomeration of particles under dry conditions is the main constraint to size reduction below certain limits. The maximum size reduction obtained in grinding with the 85 % media-to-powder ratio, 30 % mill filling, and higher rotational speed (300 rpm) during 30 min grinding cycles was 14.6 μm and 4.5 μm for d90 and d50 of the ground product, respectively.

Dry grinding of talc in a stirred ball mill

The aim of this work was to investigate micro fine size dry grindability of talc in a stirred ball mill. The effects of various parameters such as grinding time, stirrer speed, powder filling ratio and ball filling ratio were investigated. Alumina balls were used as grinding media. Experiments were carried out using the 24 full factorial design. The main and interaction effects were evaluated using the Yates method. Test results were evaluated on the basis of product size and surface area.

Mechanochemical polymerization of styrene initiated by the grinding of layered clay minerals

The polymerization of styrene mechanochemically initiated by the grinding of talc was performed by using a vibrating ball mill. Talc used was one of layered clay minerals as well as montmorillonite. The effect of the grinding of talc on the polymerization of the styrene was investigated by characterizing the polymer formed and talc ground. The results revealed that of all the experiments we have performed thus far, styrene most abundantly polymerized by grinding of talc. The polymerization of styrene was closely related to the total surface area of the ground talc. The products obtained were the composites of talc particles and resulting polymer attached to the particle surface. From the analysis of the molecular weight distribution of the polymer, it was suggested that the polymerization of the styrene proceeded with two types of cationic active species which were produced by the grinding of layered clay minerals. Mechanochemical polymerization is expected to be one of the more promising production processes of polymeric nanocomposites when layered clay minerals can be ground to finer nanometer sized-particles.

湿式粉砕におけるタルクの剥離および物性変化の定量と抑制

Delamination and changes in the physico-chemical properties in the grinding of talc were studied using a multi-ring media grinding machine. Products were characterized by SEM, specific surface area, St and aspect ratio, As, determined from the Heywood diameter and thickness measured by a confocal scanning laser microscope. The change in the physico-chemical properties were examined by thermogravimetry and X-ray diffractometry. As and St increase with the increasing rate of revolution. The former levels off at above ca. 1000min-1, while the latter keeps increasing. When the St of products exceeds three times that of the starting material, the crystal structure and the physico-chemical properties of talc change remarkably, indicating the change from the delamination region to the size reduction region. The change between these two operational regions is shown to be controlled by selecting the grinding condition.

タルクの乾式粉砕における昇華性固体の助剤効果

タルクの乾式粉砕における昇華性固体の助剤効果

Multistage wet grinding of talc: relation between physico-chemical parameters of the filler and mechanical properties of filled polypropylenes

Three talc samples of different mineralogical composition were wet-ground with an increasing number of grinding cycles. On each sample the particle size analysis, X-ray diffraction spectra, infrared spectra and nitrogen adsorption isotherms were carried out. In parallel, three mechanical properties of talc-filled polypropylenes were determined. A statistical analysis based on normalized principal component analysis and multiple partial linear regression was then carried out in order to determine correlations between the physico-chemical parameters of the fillers and the mechanical properties of polypropylene composites. The results show that this approach is valid only if the samples are separated according to their mineralogical composition. On the basis of this first analysis, an “industrial” model based on easily obtainable parameters is proposed. It is very satisfactory for talc-rich samples. For more chloritic ores, some other parameters have to be measured to enhance the quality of the models. The approach proposed in the present study seems then very promising.

減圧下での高速衝撃粉砕

The grinding of talc was carried out under reduced pressure using a hammer screen mill which was putting into a vacuumn vessel. The effect of the pressure of the atmosphere on the grinding efficiency was investigated experimentally. The grinding conditions were from 0.08 to 93.3kPa in the vacuum vessel.Finer products were obtained as the pressure of the atmosphere decreased. In particular, the particle size of the products was greatly influenced when the pressure of the atmosphere was less than 2.67kPa. The ratio of the incremental specific surface area produced by grinding less than 2.67kPa to that at 93.3kPa has a tendency to increase with decreasing particle size. On the other hand, the influence of the opening size of the screen on the size distribution of products at 0.08kPa was recongized. Therefore, grinding under a reduced peesure, where the friction drag of the air effect is negligible, is expected to be useful for improving grinding efficiency.