Spinning Plate

The spinning assembly can be round or rectangular. It contains a filter package on top of a supporting/distribution plate. The spinning plate is the bottom of the spinning assembly. 

For production of fibers, usually having diameters of 10-30 pm, very fine filtration is necessary. The rule of thumb is that particles of more than one-third of the eventual fiber diameter will cause interruptions of the spinning or drawing process and should therefore be removed. The particles that must he removed can be solid (catalyst remnants, dust) or gel-like (not fully melted or crossfinked polymer). Solid particles can more easily be removed than gel particles. Pigments or delustrants may be added to the spinning melt. Note that these must almost be submicronic and should easily pass any filter. 

Filtration can be applied in all stages of the process in a central filter in the polymer melt line, or at the end of the line, in the spinning assembly. Central filters are common in large-scale melt-spinning processes, for example, staple fiber production. Two parallel filters may be used to enable filter deaning without interruption 

Spinning assemblies always contain filters. In many cases it is the only place where filtration takes place, but there may also be a combination of prefiltration 

Filter packages are usually a stack of screens, going from coarse to fine in the streamline direction, on top of a support plate with holes for further distribution of the flow. Screens are plain-weave, or sometimes twill-weave, steel wire fabrics. Their fineness is indicated in mesh (threads per inch), openings per cm, or pore size in microns. For example, 325 mesh = 16 800 opening s cm 40 pm. 500 mesh (25 pm) filtration is common in melt spinning. For even finer filtration, steel nonwoven materials are used, with a filter fineness going down to 5 pm. 

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A number of producers have begun to utilize large rectilinear spinnerettes in Heu of multiple small individual ones. In effect, the spinning plate is slightly wider than the desired web and a continuous curtain of filaments is formed providing uniformity from point to point relative to multiple side by side spinnerettes in a block. 

In general, once the curtain of filaments has been produced, it is necessary to attenuate the filaments in order to provide strength and resistance to deformation. The most commonly practiced approach is to utilize a single slot, which is at least the width of the curtain, at a point below the spinning plate and above the laydown screen. There are two practical approaches taken. The first utilizes the injection of low pressure air at a point above the slot so that the fibers attain sufficient acceleration in the slot to provide adequate draw (22) (Fig. 7). The second utilizes a low pressure vacuum below a venturi to provide the pressure differential requited for sufficient acceleration and resulting attenuation (30). 

It is important that the mold be dynamically balanced and securely locked in place on the spinning plate. The safety guards around the equipment must be capable of retaining the mold if it comes loose from the spinning plate. The polyurethane mixture must be carefully added to the center of the mold. If it hits the edge of the inlet, strands of "fairy floss-like" polyurethane may be formed. 

Pellet cells by spinning plates at 500g, 3 min, 4°C. Aspirate off the supernatant taking care not to disturb the pellet and wash cells three times with 200 pL FACS buffer/well. 

A Solution of methyl l-methoxy-2,3-benzo-8,9,10-trinorborna-2,5-diene-l-carboxylate (8,5 mg, 0.37 mmol) and acetophenone (1 drop) in benzene (40 mL) was deoxygenated by bubbling Nj into the mixture for 20 min. Irradiation was carried out in a Rayonet reaetor equipped with 3500 A lamps for 75 min, the solvent was removed on a rotary evaporator under vacuum, and the product was purified by spinning-plate chromatography (5% EtOAc in petroleum ether) yield 85 mg (100%). 

Top 384, 1,536 washer/aspirator for gentle, tangential washing of poorly adherent cells on tissue culture plates mid rapidly spins plate (15 s) to collect all pL volumes into the bottom of wells and avoid hang-ups of microdrops... 

Spin plate in Vspin for 15 s mealed sohaian to bottom of walli... 

Spin plate invmed on a paper towel at 30g for 30 s to remove any remaining waste. 

Typical procedure. l-Cyano-6-methoxy-benzonorbornadiene 1429 [1087] A solution of TMS-PP was first prepared by refluxing phosphorus pentoxide (2 g) and hexame-thyldisiloxane (5 mL) in dichloromethane (10 mL) for 1 h. The cooled solution was filtered to remove undissolved materials. This TMS-PP solution (5.5 mL) was then mixed with the appropriate carboxamide (134 mg, 0.332 mmol) in dichloromethane (2 mL) and the resulting mixture was heated at reflux temperature for 6 h. It was then cooled to room temperature, and diluted with dichloromethane and water. The organic phase was separated, and the aqueous layer was extracted with dichloromethane. The combined dichloromethane solutions were dried and concentrated to leave a colorless oil. Pure 1429 was obtained by spinning-plate chromatography on silica gel (eluting with 2.5% ethyl acetate in petroleum ether) 112 mg (91%). 

The bottom of the assembly is the spinning plate 5-30 mm thick. The number of holes varies enormously. A hosiery yarn may have one or three filaments, a carpet yarn 60 filaments, an industrial yarn 350 filaments. For low filament numbers per... 

It is impossible to manufacture 200-500 pm holes in a melt-spinning plate, which must be 5-30 mm thick to withstand the high spinning pressure. Moreover, such a long narrow hole would give too high a pressure drop. In practice there is always a backhole (pre-channel, counterbore), with a diameter of 2-3 mm. The actual spinning capillary is usually short, with an I/D ratio of only 1-2. 

For the design of polymer lines, filter packs and spinning plates, rheological data are required to make the proper calculations. Fiber polymer melts have a fairly common rheological behavior they are viscoelastic and shear thinning. 

The process concerns the production of an industrial yam with a titer of 1670 dtex f 325. We assume that spinning holes are used with a diameter of 500 pm and an L/D ratio of 1.5 there are 325 holes per spinning plate. There are eight spinning bundles per extmder. The spinning speed is 800 m min and the spun yarn is immediately drawn five times on the same machine (an integrated process) and then wound with a speed of 4000 m min h... 

Most acrylic production is for staple fiber. Huge spinning plates with up to 60 000 holes are used, and tow drawing and crimping are included in the process. Drawing takes place in a hot-water bath, which is possible because the wet glass transition temperature is about 75°C. The above-mentioned porosity of acrylics is used to control luster. Dried yams are very lustrous but can be made dull again by a hot wet treatment. 

Besides keeping the temperature at a low level, molecular distillation holds only a small volume of the liquid at the evaporation temperature and thereby reduces the thermal degradation. The spinning-plate type of still is particularly effective in this respect because of the thin film obtained. 

Centrifugal casting (or spinning) Plates, cathodic tubes... 

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