Timing spraying

Spray time for 448 g suspension Drying time after coating (45 °C). 

This value is dependent on both the total amount of pesticide applied and the spray time, as can be seen in the derivation of the equations. It does not differentiate between droplets that would be deeply inspired ( 5ju) or those which would merely impinge upon the nasal pharyngeal passage and then be swallowed ( < 50p but > 5jj). ... 

In addition to these calculated estimates of absorption, a specific estimate of absorbed dose can be made by measuring the metabolites of the pesticide in urine. For pesticides on which good data exist on metabolic excretion, it appears that this method is very sensitive. In a study conducted on orchardists (7), metabolites were detected in the urine samples of all workers, and a statistically significant correlation was found between the total 48 hour metabolite output and the total amount of pesticide sprayed. In contrast the same study indicated that the correlation between urinary output and the total spray time was not significant. This supports the point mentioned earlier that it seems reasonable to presume that exposure is related to the total amount available for contact, and that correlating exposure with the spray time may be misleading. 

Microprocessors that control processing improve the precision of the product (Chapter 3). It optimizes the process by controlling the machine cycle based on temperature and time, rather than time alone by using an infrared thermometer to monitor the mold s outer temperature. The molding cycle data for the oven and cooling chambers can be stored for different products and recalled when needed. Cycle time, oven temperature, major and minor axis speeds, fan and water spray times are typical of functions under complete computer control. 

The experiments were performed in a lab-scale plant with sample sizes of about 200 - 400 g powder and in a small pilot plant with sample sizes of 1 - 3 kg powder. Depending on the nozzles (orifices 0,4 / 0,5 /1,0 mm, spraying angles 30° and 90°), the kind of PEG (MW 1500/4000/8000/35000) and on pressure (100-250 bar) and temperature (45 - 70 °C) the spraying times reached from about 45 s to 180 s. The obtained particles were characterised by Scanning Electron Microscopy, Differential Scanning Calorimetry and by granulometric analysis. The results can be summarised as follows ... 

Faster Film Coating Operations Cellulose is insoluble and does not increase viscosity. Dispersions with higher solid content can therefore be used and total spraying time is significantly decreased. 

The recommended formulation is displayed (Table 9) and includes predicted film thickness, opacity, and cracking propensity. Standard machine settings and process details also are displayed with warnings if the total spray time is judged to be excessive. This is normally printed for inclusion in a laboratory notebook or file. If required and in particular if reformulation is likely to be necessary, the data may be stored in a database for future reference. 

Spray pressure Spraying time Drying time ... 

Spraying time (continuously) Drying after spraying... 

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