Ultra white PVC rigid pipe
DATE：2022/3/1 8:37:18 / READ： / SOURCE：This station
Ultra white PVC rigid pipe
1. Material selection and formula design(1) Raw material selection in the well-known VC product processing formula, in addition to selecting the appropriate brand of PVC resin, there must be heat stabilizer, processing aid, lubricant and impact modifier. According to the processing and use requirements of different products, plasticizer, antioxidant, antistatic agent and pigment are also required.
1) PVC resin. Because the product has very high requirements for whiteness, the thermal stability of the resin itself is very important. Therefore, the resin with K value of about 65 should be selected. Through the control experiment, the effect of S-65 (Formosa Plastics), tk-1001 (Japan) and tl-1000 (Tianjin lejin) is good and can meet the requirements. Due to the strict color requirements of the product, the resins of different manufacturers should be trial produced before mass production, otherwise the color is inconsistent.
2) Heat stabilizer. Although the product is exported to European and American markets, there are no special requirements for heat stabilizers, so lead stabilizers are selected as heat stabilizers for production. The selection of heat stabilizer is a very key step in production. Therefore, a series of experiments have been done. Basic formula (mass parts): 100 parts of pvc0 4 parts of external lubricant and 0.8 parts of internal lubricant. The formula was extruded on sjsz-45 twin-screw extruder. Through the comparison of various heat stabilizers, p-210d (domestic) and 2.0 parts of trisodium salt + 2.0 parts of lead stearate were selected.
3) Lubricants. Lubricant is actually a stabilizer, which is characterized by reducing the destructive effect of mechanical stress during PVC processing. It can be achieved by adjusting the flow performance of components, so as to reduce internal friction and heat released during mechanical operation. Because the processing temperature is reduced, the forming process of PVC material or its products can be carried out evenly and rapidly. Especially when the components are in contact with the metal, the degradation of PVC can be reduced by preventing the components from adhering to the metal surface of the processing equipment. In addition, it can make the various components added to the components easier to distribute and improve the appearance of the products. Due to the importance of lubricants to the product, internal and external lubricants were carefully selected. Polyethylene wax is selected as the external lubricant, which has stable chemical properties and excellent electrical properties; Butyl stearate is selected as the internal lubricant, but it only has excellent lubrication effect in the initial stage and poor continuous lubrication in the medium term. It needs to be added with stearic acid (because stearic acid has good lubrication in the middle and later stages)
4) Paint. PVC resin is yellow after plasticization. In order to achieve extra white, titanium dioxide needs to be added, and domestic anatase type can be used. The general dosage is about 3.0 parts, but only adding titanium dioxide is not enough, and an appropriate amount of whitening agent must be added.
5. The color change is not easy to adjust.
(2) The square design is based on two lead systems. 1 formula (the same below): pvc100; Composite stabilizer, 4.0 phr; Light calcium carbonate, 8.0 parts; Polyethylene wax, 0.2 parts; Butyl stearate, 2.0 parts; Stearic acid, 0.4 parts; Titanium dioxide, 3.0 parts; Appropriate amount of whitening agent.
2: VC100 copies; Three salts, 2.0 parts; Lead stearate, 2.0 parts; Polyethylene wax. 0.4 parts: light calcium carbonate, 8.0 parts; Butyl stearate, 2.0 parts; Stearic acid, 0.4 parts; Titanium dioxide. 3.0 parts; Appropriate amount of whitening agent.
2. Main equipment
SRL high and low speed mixer Zhangjiagang light industrial machinery factory; Sjsz-45 twin screw extruder.
3. Preparation process
(1) Process flow: PVC + powdered additives → high speed mixer - low speed mixer → extrusion → cooling and setting → cutting → packaging.
(2) Production process
1) PVC and various additives are added into the high-speed mixer according to the formula for kneading. The kneading temperature is about 95 ℃ and the kneading time is 10 min. then they are stirred and cooled in the low-speed mixer and discharged at 45 ℃.
2) The combined materials can be directly added into sjsz-45 extruder for molding, and the operating temperatures of each zone are 165 ℃, 170 ℃, 175 ℃, 180 ℃ and 200 ℃ in turn.
3 static production, which comes out of the extruder, after vacuum cooling and shaping, it can be coated with antistatic agent by external coating method.
In addition, trial production should be carried out for PVC resins from different manufacturers in production, otherwise the color is difficult to be consistent; The influence of heat stabilizer on whiteness is the most critical, and great attention should be paid to the selection of heat stabilizer.
Author：admin