Processing slush

As with the so-called slush process, slush skins, which are manufactured in the spray or casting method, are inserted into a back-foaming mold in a second work step and are back-foamed there with a PU foam and connected with a carrier. When the part geometry allows, an effort should be made to design the mold to allow to spray and then back-foam or back-inject in the same mold. 

Seafood. Sorbates are used to extend the shelf life of many seafood products, both fresh and processed (103,104). For smoked or dried fish, an instantaneous dip in 5 wt % potassium sorbate or a 10-minute dip in 1.0 wt % potassium sorbate prior to drying or smoking inhibits the development of yeast and mold (105,106). For fresh fish, sorbates can be incorporated at approximately 0.5 wt % into the ice, refrigerated seawater, or ice-water slush in... 

R. O. Voth, J. D. Siegworth, J. F. Welch and M. J. Hi2a, Process Design Criteria, Data and Metrology Related to Slush Hydrogen Technology, NASA Tech. Memo 1006, NASA Langley Res. Cntr.,Mar., 1987. 

In recent years rotational casting methods have made the slush moulding process virtually obsolete. In these processes an amount of material equal to the weight of the finished product is poured into a mould. The mould is then closed and rotated slowly about two axes so that the paste flows easily over the cavity walls in an oven at about 200-250°C. When the compound has gelled, the moulds are cooled and the moulding removed. Compared with the slush moulding process there is no wastage of material, little flash, and more even wall thickness. Completely enclosed hollow articles such as playballs are most conveniently made. 

GC-TEA Analysis. A Bendix model 2200 GC and Thermo Electron model 502 TEA were used. The GC injector temperature was 210 C. The TEA pyrolysis furnace was operated at 450 C and the cold trap was held at -150 C in isopentane slush. Oxygen flow to the ozonator was 20 cc/min and indicated pressure was 1.5 torr at a helium flow rate of 20 cc/min. TEA output was processed by a digital integrator (Spectra Physics System I). 

Into a size 6A porcelain boat (88 X 13 X 10 mm.) is placed 10.0 g. (0.0113 mol) of Ag2ReBr6 (as much as 15 g. may be processed readily), and the boat is positioned near the sealed end of a 25 X 300 mm. Pyrex tube fitted with an inner 29/44 S.T. sleeve joint. The tube is connected to a mechanical vacuum pump (capable of reducing the pressure to ca. 50 p) via either a trap cooled by liquid nitrogen or a trap cooled by a Dry Ice-isopropyl alcohol slush, which is in turn connected to an 11-mm. Vycor combustion tube packed with copper gauze and maintained at 600° by means of a furnace. (Either protective system between the tube and the pump will serve to remove bromine, one of the reaction products.)... 

Injection is by far the most used moulding process but compression and compression-transfer are used for specific cases. Rotomoulding is specifically used for polyethylene and a few other powdered resins. Slush moulding is broadly used for automotive dashboards. Generally ... 

Solution polymerizafion. Highly exothermic reactions can be handled by this process. The reaction is carried out in an excess of solvent that absorbs and disperses the heat of reaction. The excess solvent also prevents the formation of slush or sludge, which sometimes happens in the bulk process when the polymer volume overtakes the monomer. The solution process is particularly useful when the polymer is to be used in the solvent, say like a coating. Some of the snags with this process its difficult to remove residual traces of solvent, if that s necessary the same is true of catalyst if any is used. This process is used in one version of a low-pressure process for high-density polyethylene and for polypropylene. 

The sequence of operations (assuming the initial solid is not air sensitive) would be to load the sample tube with a weighed amount of reactive compound and the stirrer, to attach this tube to the tensimeter, and to pump out the air in the tensimeter. The sample tube is cooled to liquid nitrogen temperature and solvent is then condensed into the sample tube from a storage container on the vacuum line. The main valve on the tensimeter is then closed and the sample container allowed to warm so the solid may dissolve, perhaps with the aid of the stirrer. A constant temperature slush bath is next placed around the sample tube as illustrated in Fig. 9.5 and an initial pressure measurement is taken on the manometer. Next, the first alloquot of the reactive gas is transferred from a storage bulb elsewhere on the vacuum system into the calibrated bulb using the techniques outlined in Section 5.3.G (the bubbler manometer shown in Fig. 9.5 is used for the pressure determination required for this process). This gas is con-... 

They can be processed by techniques commonly used for thermoplastics, such as extrusion, injection molding, rotational molding, dip, slush molding, and powder and fluidized bed coating,16 and can be expanded into foams.17 Compression and transfer molding of FEP resins can be done, but with some difficulty. Extrusion of PEP is used for primary insulation or cable jackets and for tubing and films. 

During the mixing process, tremendous amounts of solvent fumes are likely to be given off along with condensed water from the air. Therefore, the original preparation of a slush bath should be done in a fume hood. Once the slush bath begins to reach equilibrium, the amount of vapors leaving the Dewar decreases and it is safe to remove the bath from the fume hood. 

The crude product which collects in the —196° trap is purified as follows The volatile material in the —196° trap is allowed to warm slowly to room temperature as it distills through a cold-temperature ( — 63°) slush bath (chloroform) into a —196° trap, the distillation being repeated six times on the —63° fraction. Pure product collects in the —63° trap. If the used SiHjBr is condensed onto the partly reacted K[C5H5] remaining after these operations, and a similar purification process is employed, 0.60 g (6.2 mmol 95% yield) of product is obtained. Anal. Calcd. for C5H8Si C, 62.42 H, 8.38 Si, 29.19. Found C, 62.70 H, 8.62 Si, 28.81. 

The mold may be split or one-piece. The finished part is removed either by splitting the mold or, in the case of a one-piece mold, by collapsing the part with a vacuum. This process can be very labor intense. However it is also automated requiring relatively no labor. Automatic systems fill molds with plastisol carried by conveyor belts through an oven as it is being slushed (the mold is put into a control motion pattern). The plastisol can gel repeatedly to a thickness of 0.06 in. (15.2 mm). The excess plastisol is poured out of the mold and automatically returned to the main tank for reprocessing. The molds proceed to another oven where curing is completed. 

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. 

PVC plastisol compounds can be manipulated into shapes, or applied to fabrics in the ungelled state by either simple flow techniques or by very low pressure processes. The main techniques are spreading, dipping, spraying and rotational and slush moulding. 

The material which stopped in the —196° trap is then warmed slowly to room temperature while distilling through a —130° trap ( -pentane slush) into a — 196° trap. The material (CHsSiCI3) which stops in the —130° trap is cooled to —196° and again warmed to room temperature and allowed to distill through a — 130° trap into a —196° trap. This process may be represented as follows ... 

About 2 ml. of the methyl iodide solution is added to the stirred mixture, and after about 10 seconds, the stopcock is opened for a minute. This process is repeated until the dimethyl sulfoxide solution is colorless. The crude methylphosphine which collects in the liquid-nitrogen-cooled trap is then purified by fractional condensation in traps cooled to —112° (CS2 slush), — 130° (n-pentane slush), and —196° (liquid nitrogen). The material which collects in the —112 and —196° traps is discarded. About 0.009 mole (75% yield) of purified methylphosphine collects in the —130° trap. 

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