How is polypropylene high-strength yarn produced, and what is the commonly used production process?
Polypropylene high-strength yarns are usually produced by melt spinning. The polypropylene resin is added to a vertical or horizontal screw extruder for heating and melting, extruded from a spinneret through a metering pump, and cooled into fibers in the air. The industry also uses the film split fiber method to produce split and film split fibers.
The characteristics of polypropylene high-strength yarn melt spinning are: ① Generally use single-head equal-pitch screw extruder. In order to adapt to the characteristics of high viscosity and poor fluidity of fiber-forming polypropylene melt, the screw compression ratio is larger, the smaller is 2.8, metering The segment is as short as possible, and the screw length-diameter ratio ranges from 20 to 26. ② Due to the large molecular weight, the melt temperature during spinning is generally higher than the melting point by ~ 130 ℃, and methods such as adding molecular weight regulators can also be used to reduce the spinning temperature. ③The crystallization speed is faster during the cooling molding process, and the cooling temperature should be slightly lower.
Polypropylene high-strength yarns are now short-spun or shrink-spun, that is, the distance of the cooling process after the melt exits the spinneret is very short, and the channel can be less than 1m. For example, the short-staple production line with an annual output of 1kt, from spinning, drawing, shaping, crimping to cutting and other processes, can be placed in a factory building with a height of 8m and a length of 30m, with less investment, high efficiency, and reduced cost.
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