Solvent drying methods

Special drying methods, such as superheated steam, solvent, vacuum, infrared radiation, and high frequency dielectric and microwave heating, are occasionally employed when accelerated drying is desired and the species being dried can withstand severe conditions without damage. None of these methods is of significant commercial importance. 

The solvent process involves treating phthalonitrile with any one of a number of copper salts in the presence of a solvent at 120 to 220°C [10]. Copper(I)chloride is most important. The list of suitable solvents is headed by those with a boiling point above 180°C, such as trichlorobenzene, nitrobenzene, naphthalene, and kerosene. A metallic catalyst such as molybdenum oxide or ammonium molybdate may be added to enhance the yield, to shorten the reaction time, and to reduce the necessary temperature. Other suitable catalysts are carbonyl compounds of molybdenum, titanium, or iron. The process may be accelerated by adding ammonia, urea, or tertiary organic bases such as pyridine or quinoline. As a result of improved temperature maintenance and better reaction control, the solvent method affords yields of 95% and more, even on a commercial scale. There is a certain disadvantage to the fact that the solvent reaction requires considerably more time than dry methods. 

Microspheres by solvent extraction method were obtained with rate of mixing equal 300 rev/s. Particles by spray drying were produced with spray dryer operated with an inlet temperature of 50°C and outlet temperature of 45°C. The air flow indicator was set at 700 and the aspirator at 5. The polymer solution (concentration 0.5% wt/v) was supplied at 10 mL/min. The concentrations of monomer, initiator, and surfactant in ring-opening dispersion polymerization leading to microspheres were as follows [Lc]o = 2.77 10 mol/L, [tin(II) 2-ethyUiexanoate]o = 4.9 10 mol/L, [poly(DA-CL)] = 1.6 g/L. 

The number average diameter of microspheres obtained from polymers synthesized, by emulsification of polymer solutions followed by solvent extraction and/or solvent evaporation methods, can be controlled by choosing the appropriate conditions at which particles are produced. However, by this method particles with 15 p,m and with D D > 1.9 are produced. Spray drying did not provide poly(L-Lc) particles with regular spherical shape. Direct synthesis of poly(L-Lc) microspheres by ring-opening polymerization with stepwise monomer addition can be used as a method of choice for the production of microspheres with diameters controlled to ca. 6 p.m and with diameter polydispersity parameter < 1.20. 

Spray drying—Spray drying is applicable to substances that are soluble in a convenient solvent. This method involves atomizing a solution to form a mist. Larger particles are removed by impaction. The remaining flow is mixed with solvent-free air to permit evaporation of solvent from the droplets. Residue particles of the solute are left behind as the solvent evaporates. 

Other semi-2-IPNs [52] processed by the freeze-drying method included IPN from 4,4 -bismaleimido diphenylmethane (BMI) and linear BTDA/3,4 -ODA polyamic acid that were dissolved in 1,3,5-trioxane (Fig. 16). The resulting semi-2-IPNs exhibited higher Tgs and reduced phase separation, and contained no plasticizing solvent. A comparison of unidirectional properties of composites prepared by the freeze-dry process to those by traditional solvent evaporation process is presented in Table 13. The freeze-drying method for the preparation of IPNs appears to be superior to previous technology. 

Quantitative Estimation by Sis Dry Method—Ae-saying.—The fourth sad last method of estimating the amount of gold in an ore or alloy, is by the use of fluxes and fire. It is therefore termed the dry method, and formerly even the separation of the silver was effected without a liquid solvent, by one or other of the dry processes described in connection with the operation of parting ou the large scale but now the agency of an acid solution is employed in the last part of the process. 

The final process of solvent removal, known as drying, can be conducted by two methods "air-dry and "water-dry . There is also a "continuous air-dry method , which is used in conjunction with "water-dry method ... 

Drying of Double-Base Solvent Propellants. If a volatile solvent, such as acetone, has been used to facilitate the gelatinization of NC with NG, the solvent must be removed for the same reason as described under Drying of Single-Base Propellants. Here the air-drying method is preferred to water-drying because the loss of NG, on evaporation in heated air, is not as great as the loss due to solubility of NG in water (Ref 1)... 

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