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The basic spinning process of spunbonded and melt blown nonwovens includes the process that the polymer is melted into spinning melt, ejected from the spinneret hole at a certain temperature and pressure, cooled and drawn into filamentous fibers, then divided and laid on the netting device, and consolidated into nonwovens.
Among them, the process of melt extrusion from the spinneret hole is the beginning of the spinning process. The geometric size, structural shape and distribution density of the spinneret hole have a great influence on the spinning process.
Generally, the shape of the spinneret hole is circular, and the diameter of the hole is related to the viscosity of the melt. For the melt with high viscosity and poor fluidity, the spinneret hole with large pore size should be selected; The ratio of pore length (L) to pore diameter (d) (L / D) (hereinafter referred to as "length diameter ratio") has a great influence on the export expansion effect.
In spunbonded spinning system, when spinning PP raw material, the diameter of spinneret hole is generally between 0.30 ~ 0.60mm, and the length diameter ratio is 3 ~ 4; When spinning pet, PA and other raw materials, the diameter of spinneret hole is generally between 0.20 ~ 0.35mm, and the length diameter ratio is 2 ~ 2.5. When spinning coarse denier fiber, the diameter of spinneret hole is much larger than the above parameters, but the arrangement density of spinneret hole is relatively reduced.
The diameter of spinneret hole is larger and the length diameter ratio is larger, which is more favorable for stable spinning.
In melt blown spinning system, in order to reduce yarn breakage, it is required to reduce the export expansion as much as possible, so the length diameter ratio of spinneret hole should be increased as much as possible. For example, when spinning PP raw materials, the diameter of spinneret hole is generally between 0.3 ~ 0.4mm, and the length diameter ratio is 10 ~ 15. When the density of spinneret hole is high, a larger length diameter ratio should be used, which is much larger than that of spunbonded spinneret hole, At present, melt blown spinnerets with a length diameter ratio of spinneret holes greater than 50 can be manufactured.
