PVC low foaming board
DATE：2022/3/10 8:43:48 / READ： / SOURCE：This station
PVC low foaming board
Since the 1980s, with the digestion and absorption of imported technology, the production of rigid polyvinyl chloride (R-PVC) products, such as R-PVC pipes, plates and profiles, has developed rapidly in the country. R-PVC low foaming board produced by twin-screw extruder is a foreign product developed in the 1970s. It has the characteristics of flat and bright, no paint, corrosion resistance, no mildew and moth proof; Its impact strength and tensile strength can be compared with pine; It is superior to wood in moisture-proof, heat insulation and sound insulation; It can be sawed, planed, cut, perforated, screwed and glued like wood. It consumes less man hours than wood, which can reduce the labor intensity of operators and facilitate the formation of mechanized processing. Antirust paper coater www.handern.com comThis example introduces the production process of R-PVC low foaming board with different thickness. 1 Material selection and formula design
(1) The main raw materials are pvc-xs type, Azodicarbonamide (AC), tribasic lead sulfate, dibasic lead stearate, dibasic lead phosphite, lead stearate, chlorinated polyethylene (CPE) dioctyl phthalate (DOP), calcium stearate, stearic acid, liquid paraffin, polyethylene wax (PE wax), titanium dioxide (rutile) light calcium carbonate. (2) Formula different thick PVC hair board production formula different thickness R-PVC low foaming board production formula raw material quality 1 Formula 2 Formula 3 pvc-xs type (low viscosity) 100 Azodicarbonamide (AC) 0.60 0.68 100 100 tribasic lead sulfate 2.5 2.5 0.70 2 The main equipment is mixing equipment, twin-screw extruder, three roller calender, cutting machine, etc. 3. Preparation process: AC foaming agent and other "PVC resin] high speed hot mixing - low speed cold mixing - twin screw extrusion - three roller calendering, fixed length cutting - traction sawing 4 Precautions and process control (1) hot / cold mixing process of materials. The extrusion of R-PVC low foaming plate directly uses the mixed powder of PVC and all additives, which requires the appropriate hot / cold mixing process. Only by dispersing and mixing all the raw materials such as PVC, foaming agent and stabilizer, can we create conditions for smooth extrusion foaming. Domestic high-speed kneaders are generally not equipped with low-speed cold kneading devices, which not only makes it difficult to feed continuously, but also affects the mixing, dispersion and cooling effect of multi-component materials. The preparation of R-PVC low foaming plate material is completed in the imported V30 mixing unit by using the hot / cold mixing process. Compared with the general mixing process limited to thermal stripping, this hot / cold mixing process has many advantages. The prize leaf of the high-speed mixer passes each component at a high speed of 400 ~ 800 / / min
When mixing, the materials rise along the wall of the mixing chamber due to the action of centrifugal force, and then fall to the center of the mixing chamber after touching the baffle. In this way, the mixing cycle can be repeated, and the materials of each component can be evenly dispersed. The friction heat between materials and between materials and chamber wall can make the materials reach the end temperature quickly. The speed of the low-speed cold mixer is 40R / min, and the jacket device has the circulating flow of cooling water. The materials are mixed evenly again under the slow mixing of the paddles, and the materials are cooled and become loose through the heat exchange of the mixing chamber wall, which effectively prevents the decomposition of the materials due to overheating and promotes the vacuum suction transportation. At the same time, the capacity of the mixing chamber of the mixer is three times that of the mixing chamber of the hot mixer, which can fully meet the feed of continuous extrusion of low foaming plates com
The mixing and feeding mode of each component material of R-PVC low foaming board should be added in sections according to the sequence of hot mixing and cold mixing. The operation steps and temperature control are as follows. 1) Hot mixed feeding. PVC and DOP are mixed at high speed, and stabilizer is added after the material temperature reaches 85 ℃; After 95 ℃, add impact toughening agent; At 100 ℃, add titanium dioxide and filler: after 110 ℃, add internal and external lubricants. The end temperature of hot mixing is (115 ± 5) ℃, and the corresponding time is 7 ~ 8min. 2) Mixed feeding. Put the materials reaching the end temperature of hot mixing into the cold mixer, add AC foaming agent, mix and stir at low speed, cool to 40 ℃ and discharge. If the one-time addition method is adopted, it will affect the uniform dispersion of the above additives in PVC resin, and it is easy to cause material caking and "fish eyes". In particular, once AC foaming agent condenses in the material, it is very unfavorable to extrusion foaming and product performance. (2) Process characteristics of conical twin-screw and its speed and cooling control two conical screws rotating in different directions are combined with each other and placed in the barrel with two holes intersecting into a "∞" shaped section. The diameter of the large and small head of the screw is 130mm / 80mm, the effective length of the screw is 1665mm, and the maximum speed of the screw is 36.4r/min. Compared with ordinary single screw and parallel twin screw, the process characteristics of conical twin screw are mainly shown in the following three aspects: first, the conical screw is fully mixed and plasticized evenly; Second, the conical twin-screw has good exhaust effect; third, the conical twin-screw has high conveying efficiency. Antirust paper coater www.handern.com com
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