Analysis of quality problems in extrusion molding of PVC double-wall corrugated pipes
DATE：2022/9/28 8:59:20 / READ： / SOURCE：This station
Analysis of quality problems in extrusion molding of PVC double-wall corrugated pipes
Check whether the flow rate of the two layers of molten material extruded from the tube blank tool mouth is consistent. The leeching quality of the raw material and the speed of the molten material are synchronized, that is, the rotation of the screw should be stopped immediately, the diameter plug and the cooling water jacket should be installed; then the corrugated forming machine should be moved to the mouth end of the mold; compressed air should be injected into the tube blank and connected to cooling water; at the same time start the operation of the corrugated forming machine
⑤ Pay attention to check and adjust the coordination between the corrugated forming machine and the speed of the die extruding the tube blank, and adjust the compressed air pressure to make the corrugation on the outer layer of the tube complete.
⑥ Check the forming quality of the corrugated pipe, adjust the mandrel to align the screw, and properly correct the uniformity of the provincial wall thickness.
⑦ Note that the temperature control of the cooling water should not exceed 10°C, and the high temperature of the cooling water will increase the difficulty of forming the double-wall corrugated pipe.
Analysis of quality problems in extrusion molding of PVC double-wall corrugated pipes
(1) The corrugated shape of the outer surface of the pipe is irregular
The quilt forming mold with two open molds is ideal to help the street. Ying Yaxin adjusted the two Huahuan Rings due to the Taiyixing Speedy Camp and the two half of the Hushou machine to be correctly aligned. Xiyu's semi-opening mold drive energy bar purchase is serious: there is a lot of accumulation during the operation of the same industry, and the working speed of the screw of the powder extruder is unstable, which makes the amount of material out of the bridge inconsistent. big. The hemp in the screw movement system should be overhauled. The pressure of the compressed air is unstable, which causes a large gap in the shape of the lines in the blow molding. The stable air supply pressure should be adjusted. The temperature of the melt used for forming the tube blank is too high, making it difficult to form the melt. The melt temperature should be appropriately reduced.
(2) The temperature of the melted material on the surface of the tube is low, and the plasticization of the raw material is not comprehensive. The machine and mold should be appropriately improved.
the process temperature of the tool. The cooling water temperature is too high, and the cooling water temperature should be lowered. The length of the straight section of the return tube blank setting is insufficient, and the sizing pressure is small, so the quality of the mold structure should be improved.
(3) The pipe is brittle
①The proportion of calcium carbonate added in the raw material formula for forming pipes is too high or the addition of lubricants
Whether the proportion of people in the first family is unreasonable, the government should enter the formula. Appropriately add some acrylic resin to the raw material
Reto arming and cutting aids to improve the gel rate of the melt.
Port: Transport phase to tube
②The content of moisture or impurities in the raw materials exceeds the standard, and the raw materials should be dried or replaced.
Running work.
③Insufficient pressure in the mold for forming the tube blank makes the quality of the tube wall poor. The specific structure of the speed of each blank of the mold should be improved.
④The temperature control of the molten material of the forming tube is unstable, and the high or low temperature of the molten material is the same as the screw, and it is easy to make the tube brittle after being shaped properly. It is necessary to pay attention to the temperature of the plasticized molten material.
The difference is too big. Analysis on the problem of high cooling capacity
(4) The adhesion between the inner and outer walls of the double-wall corrugated pipe is poor
① The temperature of the molten material in the forming mold is low, and the temperature of the forming mold should be appropriately increased. If the proportion of lubricant in the raw material is too large, the amount of lubricant added should be appropriately reduced.
③ The cooling of the broken tube is too fast, and the two layers of material are not welded firmly. Pay attention to appropriately slow down the speed of the tube blank cooling plastic extrusion process worker.
(5) There are longitudinal scratches on the inner wall of the tube
Scratches should be trimmed or the residual material on the working surface of the mandrel should be removed. Add the amount of agent, remove the residual material on the cooling and setting sleeve
(6) There are cracks or corrugations on the inner wall of the pipe
When the air pressure of 4 is used for forming, it will be the point of encirclement that the strength will not be enough to form a killing pattern or wave pattern on the wall. The compression in the E-No. 5 I-type school tool should be properly adjusted, and the grid material at the junction of the sub-streaming silver-textured beam should have a low degree of baking ring, which is easy to produce pear patterns. The pressure path of the inner structure of the machine to the grid material should be appropriately improved.
5.4.8 Polyvinyl chloride foam pipe
Vegetable paper vinyl foam tube is a new product in PVC pipes developed in recent years. This foam tube has two structural forms. The first type is a low-foaming polyvinyl chloride tube with a crust, the other type is that the middle core is a foam layer, and the inner and outer skins are a rigid polyethylene layer, as shown in Figure 5-33. 5:4.8.1 Polyvinyl chloride skinned low foaming camp PVC skinned low foaming pipe and polyvinyl chloride core layer foamed pipe Vinyl chloride rigid ordinary plastic pipe has many phases of cross-sectional structure Indication of the same points: extrusion molding raw materials, extruding 1-outer PVC hard layer; 2-PVC core layer molding equipment and production process route basic foam layer; 3-Inner layer PVC hard layer is the same, the difference is The only difference is that a certain proportion of foaming agent is added to the formula of the raw material combination. During the extrusion molding process, due to the slightly longer straight part of the mandrel in the molding die and some changes in the process conditions, the inner and outer walls of the tube are thick, forming a low-foaming polyvinyl chloride pipe with low polyvinyl crust. The performance of the foamed tube is basically the same as that of the general PVC hard tube: but this tube has the characteristics of low density, easy three-time processing, and easy price comparison. Zhuang B is (tri-salt or di-salt, lake lotion (Sinandianu or stearic acid, etc., its material (European acid, CaCO,) other additives (acrylic resin ACR, 5~10 chlorinated polyethylene CPE) And methacrylate-butadiene-styrene copolymer MBS, etc.) made in Chizhou (ammonia and two-purpose combined AC) 0.5 on the political joint parts, polyethylene to the skin low foaming section of the spelling molding: The basic technique used to find out the big reason is that you only have the wrong plumber of the molding tool at different intersections. The meat is too swayed. At present, the machine uses double learning rods and I can use parallel twin screws to make it sweet. (The screen can be rotated), twin-screw extruder.
The difference between the overall structure and the structure of the mold for rigid PVC pipes is that the straight section of the core-like shape is slightly longer than that of the die for forming the low-profile e-pipe.
Straight quality: When necessary, compressed air can be blown into the tube blank, which is also for political advancement or supplementation
The quality of the crust on the inner wall of the foam tube.
(3) The raw materials for forming the PVC crusted low-foaming pipe in the molding process should be noted in the order of adding the materials during mixing: ① First, add the PVC resin, stabilizer and lubricating flower to the mixer in sequence, and stir 30min, stop the mixer heating when the temperature of the raw material reaches about 110°; ②Add the foaming agent and nucleating agent (i.e. filler) to the blender and stir for 10min; ③Put the evenly mixed raw materials into the cold hair# In the machine, the temperature of the cooling and stirring material is below 40 ° C;
Using a single screw extruder to extrude and form a crusted low-foaming tube, the process temperature is Br-160 seven for barrel feeding, 170~180°C in the plasticizing section, and 175~-185°C in the homogenizing section. Forming mold 10~1805, mandrel discharge end 140~150°C•
(1) Selection of raw materials
The main raw material in the molding material of the polyvinyl nitride core foam tube is the suspension method polyethylene resin, but the fluidity and formability of the inner and outer skin layers of the core foam tube and the foam core during free molding are different. , so choose the flag of PVC resin. There are also some differences. In general, SC5 type Pve grease is used in the material formulation of the inner and outer skin layers, and sG7 or SC8 type PvC resin is used for the foamed core layer. Similarly, in order to meet the needs of production and process, a certain proportion of stabilizers, lubricants and other auxiliary materials should be added to the formula, and a foaming agent should be added to the formula of the foamed core layer. The inner and outer skin layers of the polyvinyl chloride core layer foam tube (white) The reference formula of the molding materials is as follows (mass parts).
Polyvinyl chloride (PVC SG5) styrene-a methylbenzene core layer foam is sold from the synthetic type carrier structure is softer than the teaching. For example, because (e, it is because the folding machine is used to spell out the inner and outer skin layers of the forming tube) layer, and then combined and composited into the core layer. The raw material in the forward-running core layer is foamed under the temperature system that is connected between the die and the sizing sleeve. Figure 534: Two extruders feed and extrude the core layer foam tube with composite mold structure example; 2 one core rod; one middle set; 4 one mold body; 5 one pipe material composite shunt Cone; 6-the inner and outer skin layer material separation chain; 1-core layer material distribution cone, 8-core layer coupling; 9-inner and outer layer coupling feed port "down"-inner and outer skin layer baking material feeding port, feeding口"I"-Flute-feed Extrusion Technician's Manual for Foamed Core Layers
(3) Forming process
①Production and molding process sequence of polyvinyl fluoride core layer foamed tube local language. Production and molding process sequence Milk XPG foaming core layer materials are measured according to the formula: high-speed mixing of raw materials, two raw materials, temperature barriers, one heat, physical and chemical, one phase, multi-phase synthesis, vacuum cooling, setting, vacuum spray cooling water tank, one year of introduction, one cutting, one Inspector pool
How to deal with the raw material of the raw material, the polyethylene core layer, the raw material of the tube
(4) Erye Wang Ai is to mix all kinds of raw materials in the station speed mud machine to meet the performance requirements of PVC core. It is stipulated in the polychloride that according to the jade production material and even under a certain temperature, it can be evenly diagnosed and separated, so that the mixed raw material can meet the next production process and the production process requirements of the extruder. There is a foaming agent added in the molding material formula of the PVC core layer foam pipe, so when the raw materials are mixed, the polyvinyl fluoride should be removed—stabilizer—modifier—nucleating agent—two-way agent—foaming agent— A sequence of colorants added to the mixing chamber of the mixer, with
Properties Vicat softening temperature/° tensile yield strength, elongation at break/% The material can achieve a relatively uniform dispersion. The temperature of the raw materials in the high-speed mixer should be as far as 110C, and then transferred to the cold mixer to cool down and stir until the temperature of the material drops to about 4o0 before feeding the extruder. The hot mixing of raw materials, cooling and stirring time should not work
③ Process temperature of extruder forming core layer foam tube
The temperature control of the extrusion molding process of the polyvinyl chloride core layer foam tube is basically the same as the temperature control of the extrusion molding process of other molded polyvinyl chloride pipes. The temperature of the extruder is controlled within the range of 140~200C,
The difference is ≥ the temperature of the forming mold is controlled within the range of 170~195°C. However, due to the polyethylene roller core
The viscosity of the polyvinyl chloride resin used for the inner and outer skin layers of the raw materials for the molding of the layered foam pipe is high.
The viscosity of the polyethylene resin used for the foam core layer, so the temperature of the extruder for extruding the inner and outer skin layers
The temperature is controlled to be about 10°C higher than that of the extruded foam core extruder to meet the original requirements.
plasticizing process temperature requirements.
(4) Quality requirements The quality requirements of the polyvinyl chloride core foam pipe for drainage should meet the
GB/T 16800-1997 National Standard.
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