Fluidized-Bed Coating with Sodium Sulfate and PVA−TiO₂, 1. Review and Agglomeration Regime Maps

Abstract

This paper, and two associated papers Bach, P. Ind. Eng. Chem. Res. 2009, 48, 1905 and 1914, address the fluid-bed coating of placebo enzyme granules (i.e., sodium sulfate cores, with a size range of 400-500 µm) using two types of coatings: sodium sulfate and PVA-TiO 2 . The coating experiments were conducted in a medium-scale top-spray MP-1 fluid bed, and many rheological experiments were performed on the coating formulations to support the interpretation of the fluid-bed coating results. In this first part of the study, a thorough introduction to the inorganic salt and polymer film coating is provided, along with a presentation of the equipment and materials being used in this and the following papers. Results from agglomeration studies over a broad range of process conditions are presented, showing that the tendency toward agglomeration is always less for the salt coating process than for the polymer coating process, under similar process conditions. Based on the experimental results, an agglomeration regime map is suggested for each of the two types of coating solutions, based on values of the drying force and the coating solution spray rate.

Fluidized-Bed Coating with Sodium Sulfate and PVA−TiO2, 2. Influence of Coating Solution Viscosity, Stickiness, pH, and Droplet Diameter on Agglomeration

“…The agglomeration tendencies are statistical similar in the three experiments with coating solution G; the three agglomeration percentages are within the a range of (0.88%, as determined for the sieve equipment in the first part of this study. 2 The situation is different for the experiments with coating solution A, because there are significant differences between the agglomeration percentages. In accordance with expectations, the agglomeration tendency decreases as the mean droplet size decreases.…”

“…The three coating solutions were solutions A, B, and C, which were described in the first part of this series of reports. 2 Two coating experiments were performed for each coating solution for two sets of drying force/spray rate conditions, according to Table 3. Lastly, the influence of additives in the PVA-TiO 2 system will be tested.…”

“…The equipment and coating solutions used in the present paper may be found in the first part of this study. 2 …”

Controlled Release Fertilizers: A Review on Coating Materials and Mechanism of Release

“…On the other hand, in pan coating, a coating solution is sprayed to urea granules under air high temperature for drying purposes [ 88 ]. This often results in poor coating quality (defective porous layer) due to poor maintenance of the humidity level during production [ 89 ]. It was also reported that coating uniformity using this method is affected by particle size distribution, binder properties, the number of coating materials and drying temperature [ 27 ].…”

Flexible polyvinyl alcohol/2-hydroxypropanoic acid films: effect of residual acetyl moieties on mechanical, thermal and antibacterial properties

“…Modification of PVA with LA can have several benefits on resulting polymer material, including that esterification of PVA secondary hydroxyl groups with LA may decrease its hydrophilicity and PVA/LA interactions increase intermolecular spacing among PVA chains [15][16][17]. It means that LA acts in PVA systems as a plasticizer [5,[18][19][20], which is also interesting from a mechanical properties point of view.…”