Polypropylene filament
DATE：2022/10/21 8:44:49 / READ： / SOURCE：This station
Polypropylene filament
b. The raw materials in the hopper are "bridged" and the feeding is discontinuous.c. The fit clearance between the barrel and the screw is too large, and the amount of backflow material is large.
④ The surface color of silk is inconsistent
a. The barrel was not cleaned up when replacing raw materials.
b. The color matching is uneven.
c. The raw materials are plasticized unevenly in the barrel.
d. The temperature of water in the tank is unstable.
⑤ The silk surface is not bright or dark
a. The design of the spinneret hole is unreasonable or the hole surface is not smooth.
b. The barrel temperature control is too high.
⑥ Frequent wire breakage during drafting
a. The filter screen is broken and there are many impurities in the silk.
b. The heating temperature of drafting wire is low or the heating time is short.
c. The selection of raw material brand is unreasonable, and the drawing ratio is too large.
d. The guide roller in the water tank has large resistance or the working surface of the pressure screw is rough.
9.2 Polypropylene wire
Polypropylene monofilament is a kind of plastic filament with good acid and alkali resistance, low density, strong abrasion resistance, heat resistance and electrical insulation. Because of its low water absorption, the monofilament is mostly used to weave fishing nets and ropes; Secondly, it is used to replace cotton, hemp and brown to weave various hats and seat cushions; In addition, it is also used in aquaculture, chemical industry, shipbuilding, medical treatment, agriculture and people's daily life.
(1) The raw material for polypropylene monofilament extrusion is mainly isotactic polypropylene resin. Special resin for wire forming shall be selected as far as possible, such as T30S produced by Sinopec Qilu Petrochemical Co., Ltd., T30S (powder) produced by Tianjin Petrochemical Company and C30S produced by Fushun Petrochemical Company.
(2) Equipment conditions Polypropylene monofilament extrusion molding production line is shown in Figure 9-2. The equipment on the production line mainly includes single screw extruder, forming die, cooling water tank, traction and stretching device, pressure screw, heat treatment device and coiling device. The structure, working mode and function of each device and the structure and working requirements of each device of auxiliary machine for PE wire forming are identical. The extrusion molding process of polypropylene monofilament is to put polypropylene resin into the barrel of the single screw extruder. After plasticizing and melting, the rotating screw is pushed into the molding die, and the molten material is sprayed out of the spinneret hole of the die to form a filament. After cooling and shaping, the monofilament is made into finished products through heating, stretching, shaping, heat treatment and coiling. Its production process and equipment
As shown in Figure 9-5.
Figure 9-5 Schematic Diagram of Polypropylene Monofilament Extrusion Molding Production Line
1 - Extruder; 2 - Forming mould; 3 - Water tank; 4-drafting device; 5 - Oven; 6 - Second drafting device; 7 - Hot water tank; 8 - Winder
(3) Forming process
① The plasticizing temperature of raw materials in the barrel of the extruder (from the feeding section to the homogenizing section) is 180~200 ℃, 210~240 ℃, 250~270 ℃.
② The temperature of the die spinneret is 270~300 ℃.
③ The temperature of wire cooling and setting water in the water tank is 20~40 ℃.
④ Wire drawing preheating temperature 130~150 ℃; The drawing ratio is 7~8 times.
⑤ The temperature of heat treatment water after wire drawing is 100 ℃, and the running speed of wire is about 3% slower than that during wire drawing.
(4) Key points of process operation
① Isotactic polypropylene resin for polyfilament. The selection of the melt flow rate in the raw material should not be too high. If the MFR value is too high, the melt flow is very good, and the operation of extrusion molding wire is difficult; However, the MFR value cannot be too low, the melt flow rate is low, the melt fluidity is poor, and there are many broken ends when drawing the wire, even the wire cannot be produced.
② The temperature of raw materials in the plasticizing process gradually rises in the barrel of the extruder, but the temperature from the melt to the spinneret of the molding die should be slightly lower.
③ The distance between the spinneret and the cooling water level in the cooling setting tank shall be adjusted according to whether the specifications of the ortho benzene wire after stretching meet the requirements. It should also be noted that if the distance is too large, the silk will contact the air for too long, and the strength will decrease due to the oxidation of the silk.
④ The immersion length of the wire in the cooling and setting water tank shall not be less than 1m
⑤ If the wire blank is immersed in hot water for stretching, the length of the water tank shall be 2~3m, and the distance from the input steam pipe to the wire stretching point shall not be less than 150mm
⑥ Attention shall be paid to the influence of the temperature of water in the heating water tank on the quality of polypropylene wire during wire drawing; When the temperature of the heated water is 100 ℃ and the drawing ratio is 6-7 times, the tensile strength of the finished yarn is about 0.45N/dtex; When the heating temperature of the drawn wire is 130 ℃ and the elongation ratio of the stretched stearic acid phthalocyanine blue is 10 times, the tensile strength of the finished wire is about 0.65N/dtex.
⑦ The drawing temperature of PP preform shall not exceed 150 ℃, and the common value of drawing ratio is 6-8 times.
⑧ During equipment maintenance, attention shall be paid to the accuracy maintenance of the spinneret. The working surface of the spinneret hole shall be kept smooth, free of residue and scratches. During disassembly, it is not allowed to knock with a hammer, and handle with care to prevent deformation.
⑨ For ordinary polypropylene wire without special requirements, heat treatment is not required.
The quality requirements of polypropylene monofilament are the same as those of PE monofilament, which shall comply with QB/T2356-1998 standard.
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