Glass, columns transition

Scotts technology (17) uses fluid-bed (Wurster column) technology to apply polymeric coatings to a number of fertilizer substrates including urea, potassium nitrate, potassium sulfate, and monoammonium phosphate (MAP). The coating material is appHed as a water-borne latex onto the fluidized substrate. As the substrate is fluidized with warm air (40—50°C), water is driven off and the latex coalesces into a continuous film around the fertilizer particle. The particular latex compositions used have selected glass-transition and blocking temperatures, which enable quick removal of the water before the soluble fertilizer core dissolves. This obviates the need to use precoats prior to the latex appHcation. 

A mixture of dimethyl terephthalate (0.495 mol), 5-sodiosulfoisophthalic acid (0.005 mol), ethylene glycol (1.0 mole), and titanium tetraisopropoxide (100 ppm) was placed in a 500-ml flask equipped with an inlet for nitrogen, a metal stirrer, and a short distillation column. The flask was placed in a heated metal bath and the contents heated at 185°C for 2 hours, 200°C for 2 hours, and then up to 250°C under high vacuum for 2 hours. The temperature was finally increased to 270°C and a vacuum of 0.45 mmHg maintained for for 2 hours to remove unreacted diol. A high melt viscosity polymer was obtained with a glass transition temperature of 77°C with an inherent viscosity of 0.77 dl/g. 

The only reported-study on heat transfer is by Weekman and Myers.105 They measured wall-to-bed heat-transfer coefficients in a cocurrent air-water downward flow through a packed column. Three types of packings. 0.65-cm alumina spheres, 0.475-cm glass spheres and 0.38-cm TCC beads were examined. The heat-transfer coefficients were much higher than those observed for single-phase liquid flow. The transition from homogeneous to pulsed flow corresponded to an increase of... 

Under reduced pressure, water can be distilled off from 30% hydrogen peroxide by using a column, and a solution of up to 90% hydrogen peroxide can thus be obtained. All the all-glass apparatus for such a distillation must be scrupulously clean and free of organic materials and transition metals and their compounds. The 90% hydrogen peroxide is a clear colorless liquid (mp -11 °C, bp 140 °C dec, 1.393, ng 1.3998 [124 ). 

Since the temperature control required is not very stringent, it is possible to place the detector and the column in a well-insulated oven, the temperature of which is controlled by the amount of heat supplied. A Transite box wound with nichrome wire and insulated with glass wool has been found to be quite satisfactory. For carefully cen-... 

Demonstration of Instant Equilibration (Zf = 0). Data were gathered for several n-alkanes at various gas flow rates and column temperature of 100 C using a column coated with polyisobutylene (PIB). Under these conditions PIB is far above its glass transition temperature (Tg) and equilibration of probe and polymer is expected to be instantaneous. 

Overview. The capillary column IGC technique was used to determine the partition coefficients and diffusion coefficients of a number of solvents (methanol, acetone, methyl acetate, ethyl acetate, propyl acetate, benzene, toluene, and ethylbenzene) in poly(methyl methacrylate). Measurements below the glass transition temperature were obtained for the PMMA/methanol system. 

---