Cooling Dispersion

Check for the presence of clear gels in the cooled, dispersed solution. 

A solution of palmitoyl chloride in dioxane was added dropwise to a cooled dispersion of sodium borohydride.The mixture was heated on the steam bath for a short time and then, after cooling, water was added. On distillation a yield of hexadecanol 87%, M.P. 49°C, B.P. 344°C. 

Preparation of DMS0-Soluble Starch-g-PAN Samples and Water-Soluble Starch-g-Polyacrylamide. Five grams of starch- -PAN (prepared by either ceric- or cobalt-60 initiation) was dispersed in 333 g of DMSO, and the dispersion was heated for 2 hr at 115°C. The cooled dispersion was then treated with ultrasound for 10 min to mechanically rupture gel particles and to render the polymer soluble (Branson Sonifier, Model S 125 ... 

Five grams of starch-g-polyacrylamide was dispersed in 333 ml of water and the mixture was heated for 4.5 hr at 95-100°C. The cooled dispersion was then treated with ultrasound, as described for starch-g-PAN in DMSO. The resulting solution was gravity-filtered through fluted Whatman 54 paper, and the filtrate was freeze-dried to give 4.4 g of polymer. To give a denser, more compact product, which might more closely resemble soluble starch-g-PAN, the freeze-dried polymer was dispersed in 20 ml of water, and the polymer was precipitated from the thick paste by addition of ethanol. The polymer was separated by filtration, washed with ethanol, and vacuum dried at 60°C. 

The cooled dispersion is either poured from the creased flask into a suitable container for further use or utilized directly in the dispersion flask (sodium hydride, synthesis 3). 

Fire Use dry chemical or carbon dioxide for small fires alcohol foam or polymer foam for large fires. Use water spray to keep fire-exposed containers cool, disperse vapors, and protect workers trying to stop the leak. Water spray may be used to fiush spills away from exposures. Wear goggles and self-contained breathing apparatus. 

A mixture of (I) (80.0 g 0.294 mole), potassium permanganate (196 g 1.24 moles) and 0.15 N aqueous sodium hydroxide solution (3000 ml) was stirred and maintained at 90-93for 4 hours. The reaction mixture was cooled and filtered to remove manganese dioxide. The alkaline purple filtrate was acidified with 12 N hydrochloric acid (140 ml), decolorized with sodium sulfite, and the clear solution extracted with ether (1.35 kg). The ether extract was dried (MgS04), filtered, the filtrate diluted with toluene (200 ml) and the resulting mixture concentrated at reduced pressure to a mass of white crystals. Dispersal of the white crystals in boiling toluene, followed by filtration of the cooled dispersion led to analytical white crystals of (II) 86.5g, 88.4% yield mp 183-185°C. 

Cool the flasks in cold water, and then titrate the contents of each with /i/.t a()H solution, using phenolphthalein as an indicator. Shake the contents of the flask A repeatedly during the titration in order to keep the fine crystals of acetanilide dispersed in the aqueous solution. 

Water clarification Water, cooling Water desalination Water dispersions Water drainage Water fastness Water fluoridation... 

Aqueous media, such as emulsion, suspension, and dispersion polymerization, are by far the most widely used in the acryUc fiber industry. Water acts as a convenient heat-transfer and cooling medium and the polymer is easily recovered by filtration or centrifugation. Fiber producers that use aqueous solutions of thiocyanate or zinc chloride as the solvent for the polymer have an additional benefit. In such cases the reaction medium can be converted directiy to dope to save the costs of polymer recovery. Aqueous emulsions are less common. This type of process is used primarily for modacryUc compositions, such as Dynel. Even in such processes the emulsifier is used at very low levels, giving a polymerization medium with characteristics of both a suspension and a tme emulsion. 

Complex Coacervation. This process occurs ia aqueous media and is used primarily to encapsulate water-iminiscible Hquids or water-iasoluble soHds (7). In the complex coacervation of gelatin with gum arabic (Eig. 2), a water-iasoluble core material is dispersed to a desired drop size ia a warm gelatin solution. After gum arabic and water are added to this emulsion, pH of the aqueous phase is typically adjusted to pH 4.0—4.5. This causes a Hquid complex coacervate of gelatin, gum arabic, and water to form. When the coacervate adsorbs on the surface of the core material, a Hquid complex coacervate film surrounds the dispersed core material thereby forming embryo microcapsules. The system is cooled, often below 10°C, ia order to gel the Hquid coacervate sheU. Glutaraldehyde is added and allowed to chemically cross-link the capsule sheU. After treatment with glutaraldehyde, the capsules are either coated onto a substrate or dried to a free-flow powder. 

Ko//M //s. When dispersion is requited ia exceedingly viscous materials, the large surface area and small mixing volume of roU mills allow maximum shear to be maintained as the thin layer of material passiag through the nip is continuously cooled. The roUs rotate at different speeds and temperatures to generate the shear force with preferential adhesion to the warmer roU. 

In the post-dispersion process, the soHd phenoHc resin is added to a mixture of water, cosolvent, and dispersant at high shear mixing, possibly with heating. The cosolvent, frequently an alcohol or glycol ether, and heat soften the resin and permit small particles to form. On cooling, the resin particles, stabilized by dispersant and perhaps thickener, harden and resist settling and agglomeration. Both resole and novolak resins have been made by this process (25). 

For products intended to remain stable dispersions for an extended period, a particle size of 2 p.m or less is desirable. A thickening agent is usuaUy added after the reaction has been completed and the mixture is cooled in order to prevent settling and agglomeration. Examples of thickeners are guar gum, xanthan gum, and hydroxyethylceUulose. The final products are generaUy between 40 and 50% soUds, with a viscosity of 1500 5000 mPa-s(=cP). 

Alkyl or aryl phosphonates, which contain a carbon—phosphoms bond, are comparatively more stable. They are of interest as antiscaling additives and corrosion inhibitors for cooling towers and heat exchangers (see Dispersants Water, industrial water treatment), surfactants (qv), sequestrants, and textile-treating agents. Trialkyl phosphites are usehil as esterification (qv) reagents. 

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