Spinneret plate

Melt filtration systems are commonly employed in pigment master-batch production and in situations where the presence of defects in the compound may have a critical effect on its subsequent processing or properties. This is vitally important, for example, in fibre-spinning operations involving extrusion of polyester or polyamide through fine spinneret plates [162], and in minimizing breakdown of polymer cable insulation subjected to electrical stress [163]. 

Fiber processing, spinning, reaction A liquid polymer is extruded through a spinneret plate and encounters a chain extending cross-linking component producing a filament. 

There are many patents in the literature, mostly on static devices for melt-spinning multiple fibers with the islands in a sea configuration. This is usually done by a multiple series of flow-divider plates that take the initial side-side polymer flow (as in a heterofil spinner) and subdivide it and cross over the flow many times before the spinneret plate, so that each spun filament emerges with the desired structure. Some examples are further ideas of Okamoto [78] and Dugan [79]. More recently, the dissolvable matrix has been made of such materials as polylactic acid (already mentioned), thermoplastic starches, or water-soluble copolyesters. Good review articles on microfibers have been written by Robeson [80], Murata [81], and Isaacs [82]. 

The spinneret plate used in solution spinning is made of a soft corrosion resistant material, such as special grade stainless steel or platinum. It is usually thin with the diameter of individual spinneret holes in the range of0.025-0.05 mm and l/d ratio of 1. Both the diameter and length of the spinneret are much smaller than those used for melt spinning. This is because the viscosity of the polymer solution is significantly lower (3000-7000 cP) and a high back pressure is not... 

We have said little here about the proper selection of initial conditions for the thin filament equations. This issue has received some attention through the use of numerical methods like those described in the next chapter, which make it possible to link the shear and exit flow in the spinneret to the spinline. A related but more difficult problem that has received very little attention is the proper modeUng of heat transfer at the top of the spinline, where crossflow air is likely to be impeded by the geometry, and heat transfer from the metal spinneret plate might be important. 

Solution Filtration. The polymer solution, free of unacetylated ceUulose, rigid particle contaminants, and dirt, must pass through spinnerets with holes of 30—80 ]lni diameter. Multistage filtration, usuaUy through plate-and-frame filter presses with fabric and paper filter media, removes the extraneous matter before extmsion. Undesirable gelatinous particles, such as the hemiceUulose acetates from ceUulose impurities, tend to be sheared into smaller particles rather than removed. The solution is also aUowed to degas in hoi ding tanks after each state of filtration. 

The dark blue solution containing 5—10% of cellulose with a DP of 1000—2000 is filtered through a series of plate-and-frame filter presses using fine mesh metal screens to remove any particles that might block the spinneret holes. It is then deaerated under vacuum and stored ready for spinning. Unlike viscose dope, the cuprammonium cellulose [9050-09-3] solution is relatively stable. 

At the bottom of the pack the polymer exits into the air via a multiplicity of small holes through a thick plate of metal (the spinneret). The number of holes can... 

The spinneret passes the melt through a very large number of very small holes. It is a rectangular plate die, typically provided with 200 or... 

The spinneret is a type of die principally used in fiber manufacture. It is usually a metal plate with many small holes (or oval, etc.) through which a melt is pulled and/or forced. They enable extrusion of filaments of one denier or less. Conventional spinneret orifices are circular and produce a fiber that is round in cross section. They can contain from about 50 to 110 very small holes. A special characteristic of their design is that the melt in a discharge section of a relatively small area is distributed to a large circle of spinnerets. Because of the smaller distance in the entry region of the distributor, dead spaces are avoided, and the greater distance between the exit orifices makes for easier threading.143... 

Fleece can be made from polyethylene terephthalate (PET) bottles. The first step is to wash and then mechanically crush the bottles, shaping the plastic into small chips. The chips can then be heated and forced through tiny holes in a metal plate (called a spinneret), which forms fibers that harden as they cool to room temperature. These fibers are wound onto a spool as they are formed, and they can subsequently be stretched to improve their strength. Machines can then be used to texturize and cut the fibers to their desired length and be used to make fleece cloth for clothing, blankets, etc. 

In solution spinning process, the polymer is used as a solution by dissolving polymer in an appropriate solvent, whereas in the melt spinning process, the polymer is in the molten state. However, in both the cases, the polymer (either in the molten or in the solution form) is streamed through a spinneret, which is a special kind of plate with extremely fine holes for the fibers. The solution spinning may be of three types. 

The spin pump (metering pump) delivers the molten polymer to a spin pack, which consists of a top cap and a breaker plate to distribute polymer evenly, then into a filtration media and out of the spinneret. The filtration media contains either different layers of special sand, layers of different size of stainless steel screens, or sintered metals. In addition to removing the foreign particles, gel particles and undesirable conglomerate additives, filtration may also improve the polymer melt homogeneity due to its torturous path and high shear of the filtration media. 

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