Extrusion Process of Monofilament Yarn

Monofee, as a monofilament yarn manufacturer with 35 years of production experience, provides monofilament yarns of various specifications for various purposes.

Overview

Polymer orientation is divided into uniaxial orientation and biaxial orientation. Monofilaments, flat yarns and other types of plastic products are produced by uniaxial orientation extrusion technology. Orientation stretching is carried out continuously. During the stretching process, the single fiber enters at a lower speed and is output at a higher speed. Due to the different entry and exit speeds, that is, the linear speeds of the two sets of drawing rollers, the single fiber is subjected to oriented stretching, and the parallel gaps between molecules are reduced to form a three-dimensional space neatly arranged lattice with a compact structure and high crystallinity, thereby increasing the tensile strength of the monofilament, reducing the elongation and reducing the fineness. The degree of stretching is generally expressed by the stretch ratio, which represents the ratio of the linear speeds of the two sets of rollers. The technical indicators of the monofilament fineness, relative tensile strength and elongation depend on the size of the stretch ratio.

Monofilament yarn is widely used in ropes, nets, tarpaulins, fishing lines, sewing yarns, bristles, racket strings, industrial fibers and other products. Many plastics can be produced by extrusion, mainly PA6, PA66, PET, TPU, TPEE, ETPEE, etc. At present, the speed of the monofilament production line is as high as 160m/min, and the number of monofilaments produced can reach 200.

Process and equipment

The production process of monofilament yarn has the following steps:
Extrusion, molding, cooling, water bath, stretching, hot air furnace, re-stretching, heat setting, winding

There are two production processes for monofilaments. One is the one-step stretching method, in which the monofilament blank is only stretched once; the other is the two-step stretching method, in which the monofilament blank is stretched twice. The one-step production line mainly produces monofilaments of materials such as PP, HDPE, and PA. The stretching temperature can be controlled by a water bath or a hot air furnace. The advantage of the water bath is that the heating efficiency is high, but the maximum temperature can only be 100℃, which is suitable for the processing of HDPE. The temperature of the hot air box can be adjusted to 210℃, which is suitable for the processing of PP and PA. The two-step production line mainly produces PET monofilaments. The first pre-stretching temperature is generally controlled at 70-90℃, and the second stretching temperature is generally 220-250℃, close to the melting point.

The monofilament yarn production line is mainly composed of an extruder, a mold, a cooling water tank, a hot air furnace, a stretching machine, a heat treatment device, a winder, etc. Usually the diameter of the monofilament is between 0.125 and 1.5 mm, and its cross-section differs by about 150 times, so the production line must have a large speed regulation range.

Product defect control factors

The quality defects of monofilament yarn in production are related to the following factors.

Extrusion part: raw material drying; feeding system; extruder temperature; screen changer type; mesh number or number of layers of the screen; selection of gear pump; head melt pressure.

Mold part: mold type; machine neck expansion angle; flow stabilization neck; spinneret hole number; spinneret hole distribution; spinneret hole diameter and length; mold-controlled flow channel without dead angle; mold temperature.

Cooling water tank: constant temperature system of cooling water tank; structure of cooling water tank; spacing of comb guides; cooling temperature; water temperature uniformity; overflow control; distance between die and water surface.

Hot air box: heating method; air duct structure; constant temperature of hot air box; length of hot air box; temperature in hot air box; fan air volume and air pressure; contact angle between hot air and monofilament; opening and closing of hot air box.

Stretching part: one-step method or two-step method; roller wrap angle; stretching force; roller arrangement method; application of slipping device; stretching ratio and adjustment; roller surface hardness and roughness; motor type and transmission method.

Winding part: tension control method; wire arrangement method; number of spindles; loading and unloading of spindles; spindle transmission system; single-strand or multi-strand winding; wire suction system.