Freeze-thaw, vacuum drying

U) Special problems arise in drying photographs. Mass drying via freeze-thaw vacuum drying is possible if the emulsion has not been degraded by microbiological attack. 

Sludge cake from vacuum filters, because of its pasty nature, cannot be readily spread on land as a fertilizer or soil conditioner. It must be further air-dried. At some plants the sludge cake is stockpiled on the plant site over winter. Freezing, thawing and air drying result in a material which breaks up readily. 

Poly(ethyl methacrylate) (Cellomer Associates) was vacuum dried at 50 C. The molecular weight (M ) was determined to be 3.3 X 10 from its intrinsic viscosity in ethyl acetate.— Chloroform (spectral grade) and deuterochloroform (MSD Isotopes) were used as received. Prior to sample preparation the solvent was degassed using five freeze-thaw cycles. The solvent was vacuum distilled onto the polymer In a 12 nm NMR tube, and sealed. 

In order to obtain poly(styrene-vinylbenzyl chloride) copolymer, a mixture of 10.4g (0.1 mol) styrene, 7.6 g (0.05 mol) vinylbenzyl chloride (mixture of 60% meta isomer and 40% para isomer) and 90 mg benzoyl peroxide was used. Polymerization was carried out in degassed (three cycles of freeze-thaw under high vacuum) sealed ampules at 60°C. The polymer was precipitated with excess methanol, filtered, and dried. 

Carry out the freeze-thaw-degassing procedure in the same time vacuum and purge the vessel with dry argon or nitrogen to ensure all oxygen is removed from the... 

Miller, D.P., Anderson, R.E., De Pablo, J.J. Stabilization oflactate dehydrogenase following freeze-thawing and vacuum-drying in the presence of trehalose and borate. Pharm. Res. 15,1215—1221, 1998... 

Freeze/thaw/vacuum dry with controlled heat assistance... 

B) Freeze/thaw/vacuum drying technique is particularly effective with catalogs and journals containing coated paper (4). 

Shoulberg, reporting on his experience with freeze/thaw/vacuum drying experiments only (9), observes ... 

Freeze-Thaw, Vacuum Drying (1A, IB). The frozen books were laid with the spine vertical on metal shelves inside a large chamber. A controlled amount of heat was applied to the shelves to thaw the ice and to allow the water to evaporate. A vacuum was established to remove the water from the books. Progress in removing water from the books was checked by noting the return of the book s weight to its original value. 

Freeze-Thaw, Vacuum Drying (2). The frozen books were arranged separately in a horizontal position on the shelves of a small freezer dryer. The temperature of the shelf was set above freezing and held constant to supply energy for thawing the ice and evaporating the water. A vacuum to remove the water vapor was applied until the book became dry. 

How do these freeze-thaw, vacuum-dry processes compare with the traditional approaches of drained-air and interleave-air drying The... 

Freeze-thaw vacuum, inter leave-air, and solvent extraction processes offer the greatest potential in drying these types of coated- and uncoated-paper books after they have been wetted and frozen. The drained-air, vacuum-air cycle, vacuum, microwave, and dielectric drying processes work well on uncoated paper, but they fail to dry books containing this type of coated paper. Small and large units for freeze-thaw, vacuum drying have been used successfully to remove water from these frozen coated and uncoated books. 

Cool the Schlenk tube under argon down to -78°C (dry ice-isopropanol slush bath), and then admit the tube to a vacuum (c. 0.1 mmHg). Pump for 60 s, then admit argon gas and allow the apparatus to warm up to room temperature. Repeat this freeze-thaw process twice more. Heat the stirred mixture at 160°C under argon for 2 h. An abundant yellow precipitate of the molybdenum tricarbonyl complex develops. 

Copolymerization of I with styrene. A glass ampoule was charged with 1.45g (5m mol) of 1,0.53g (5m mol) of styrene, and 33 mg of AIBN (2 mol %) dissolved in 2.0 ml of dioxane. The ampoule was sealed under vacuum after a freeze-thaw cycle and the copolymerization was carried out at 58°C for 3 hours. The jelly-like polymer mixture was dissolved in NMP and the polymer was isolated by precipitation into methanol. After drying in vacuo, 1.76g (89%) of a white fibrous polymer were collected. The polystyrene equivalent molecular weight (Mw) is 1.3 x 10 by GPC. 

All reactions and sample preparations are carried out in an inert-atmosphere enclosure under dry nitrogen. Solvents and reagents are dried in the following manner. Benzene, tetrahydrofuran, and n-pentane are freshly distilled from lithium aluminum hydride pyridine is distilled over barium oxide and tetramethylethylenediamine is distilled over calcium hydride. Solvents used in preparing nmr and infrared samples are degassed by a freeze-thaw technique. Nmr spectra are obtained with torch-sealed nmr tubes. The commercial transition metal carbonyl complexes are recrystallized and vacuum-dried before use. Glassware is routinely flame-dried. 

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