The influence of polyethylene wax on the production process of U-P V C pipe, PV C pipe is widely used in agricultural irrigation, urban sewage discharge and other fields. The formula of UPVC pipe determines the properties and processing of the product. The design of pV C formula is mainly the design of heat stabilizer, which is true for soft products. The hardness of products can be achieved by adjusting the amount of plasticizer used, with very little external embellishing agent,***** to add a small amount of stearic acid or stone wax that can be. Solid metal soaps can even be used without external lubricant. But for hard P V C formula design, the difficulty and the main content of formula design is the proportion of internal and external lubricant and the total amount of the design. The amount of lubricant can not be less, more will not do, and the proportion of internal and external lubricant is more important, try to tube the total amount is enough, but the proportion is out of adjustment, also can not continue to produce a suitable product. The most influential factor in formula design and production process control is the choice and dosage of lubricant.

1, lubricant characteristics

Lubricant is defined as an additive designed to improve the fluidity and demoulding of plastics during molding and thus improve the performance of products. A good lubricant should meet the following requirements: good dispersion performance, appropriate compatibility with resin, good thermal stability, does not cause color drift, does not affect product performance, non-toxic, inexpensive. Lubricants according to the function of classification, can be divided into internal lubrication and external lubrication, but there is no strict boundary between internal and external lubricants, are relative, often a lubricant.

It does both. There is a certain compatibility between the lubricant and the resin, it can reduce the cohesion between the resin molecular chain, reduce the melt viscosity weaken the internal friction between the polymer, prolong the processing time, improve the fluidity and improve the role of transparency. External lubricant and resin compatibility is poor, it is attached to the surface of molten resin, processing machinery surface, mold surface, the formation of lubrication molecular layer, so as to reduce the friction between resin and processing equipment. Therefore, lubricants with long molecular carbon chains can make the distance between the two friction surfaces longer and have greater lubrication effect.

2. The influence of lubricant in the mixing process

Lubricating agent is not used in large quantities, so the influence of mixing current and mixing time is not very large. In the formulation of HARD tube, the lubricant can be increased or decreased under the condition that the RESIN, calcium carbonate and stabilizer remain unchanged. The mixing current and mixing time hardly changed. Filling agent, especially C aC O, has the greatest influence on mixing current and mixing time, as shown in Figure 1. It can be seen from Figure 1 that the mixing current decreases gradually with the increase of C aC O. The main reason is that the flow of C aC O is better, especially the flow performance is better at high temperature. Therefore, in the process of mixing, due to the addition of CaC O, the friction between PV C particles, PV C particles and the machine surface is reduced, and the total friction is reduced. The more CaC O is added, the more obvious the effect is.

3, lubrication body system on the production of processed products

The addition of lubricant has little effect on the mixture, but it plays a very important role in the control of extrusion process. Because the basic principle of the extruder is to heat the resin at 9I temperature and the rotation of the screw on the material's shear friction with the same, so that the resin into a melting state, and then through the mold molding, The heat required to produce PV C hard tubes comes from two parts: one is external heating; Two is between materials and materials, materials and screw and barrel between the shear friction. And the main is between materials and materials, materials and screw and cylinder between the shear friction, the use of slippery agent is to adjust the material sub sub between the use of force and material and machine surface friction force, so slippery agent on the quality of the product, The process temperature control plays an important role in the production process.

Internal lubricants promote plasticizing and reduce plasticizing torque, while external lubricants delay plasticizing and prevent resin melts from sticking to the metal surface of the processing equipment. Therefore, the plasticizing time of resin mixture can be controlled by adjusting the proportion of internal and external lubricant, so that it can meet the plasticizing rate required by specific processing equipment and technology. If the shear force of the processing equipment is too large, the production of friction heat is too much, in the processing of the easier decomposition of the resin, it is necessary to reduce the processing temperature, in order to avoid the resin internal overheating caused by decomposition. But resin is a poor conductor of heat, reduce the effect of heating temperature alone is limited, and the most reliable method is to reduce resin viscosity to radically reduce friction heat generation, and the appropriate scale up the internal and external lubricant can reduce the dosage of resin melt viscosity, also make the lubrication system can guarantee specific processing equipment and process requirement, can continuously produce qualified plastic products. On the contrary, the shear force of processing equipment is small, and the amount of internal and external lubricant can be appropriately reduced, which can also meet the requirements of specific equipment. In the production process,***** the use of internal and external lubricants is appropriate, in order to economically and continuously produce high-quality products, if the use of internal and external lubricants is unbalanced, even if other conditions meet the technological requirements, it can not be normal production, will inevitably cause the decline of internal quality and appearance. If the internal lubrication is excessive and the external lubrication is insufficient, it will cause premature plasticization, which not***** increases energy consumption, but also sticks to the surface of processing equipment, local overheating and thermal degradation, so that the product quality decreases, the waste product rises, and the shutdown rate also rises. Insufficient internal lubrication and excessive external lubrication will make the products brittle and reduce the mechanical properties and secondary processing properties. If the internal and external lubrication effects are insufficient, the melt viscosity and adhesion will increase, which is more likely to cause local decomposition, which will seriously affect the product quality and increase the downtime. Excessive internal and external lubrication not***** wastes lubricants but also causes the same consequences as excessive external lubrication and mechanical properties decline.

4. Adjustment of lubricant in actual production

In the process of our experiment, the problem of internal and external lubrication balance was also obvious. At the beginning of the experiment, we***** added 4.5 parts of stabilizer and 0.2 parts of carbon black to the formula, because the stabilizer was a compound stabilizer, and the lubrication system had been prepared. Moreover, when the C aCO3 was 6 parts, We used 4.5 parts stabilizer and 0.2 parts carbon black, and all the indicators of pipe quality and external appearance were qualified. Therefore, when C aC O3 was increased to 8 parts, we still borrowed the ratio of 6 parts, and the temperature of plasticizing section could not be controlled during the experiment. In many experiments, the temperature of the plasticized section is 10 ℃ higher than the set value, and the mechanical properties of the tube are not fit for the standard. The main reason is that the slippery body system does not fit. Because in C aC O3, it is 6 parts, although the formula makes good use, but when the light calcium increases to 8 parts, the friction between the material and the screw and the barrel is much larger than that of the light calcium in 6 parts, so the material in the plasticized section of the screw shear friction force is too large. The rubbing heat produced is too high, so that the material is too plasticized, which affects the quality of the product. And when the lubrication system is not adjusted, the paste often appears because the temperature of the screw plasticizing section is high, which brings great difficulties to our actual test. Through the analysis of the above experimental phenomena, we judged that the external lubrication was not sufficient. Therefore, under the condition that the main body formula remained unchanged, we added paraffin wax and CPE to the formula, and the temperature of plasticized section did not lose control in the experiment with the adjusted formula. Finally, through the adjustment of the process temperature, all the properties of the pipe are qualified, and the ratio is PV C: 100 after adjustment; Light calcium carbonate: 8; Stabilizer: 4. 5; C P E: 5; Stearic acid: 2.5; Paraffin: 3.5.

5. Conclusion

Through the large amount of theoretical analysis and experimental summary, we can understand that the key to the formulation design of PV C hard tube lies in the adjustment of the smooth body system in the formula. Now in many manufacturers in order to reduce the low production cost, in the formula added a large amount of light calcium. Due to the addition of light calcium increases the material and screw and barrel shear friction, this time the slippery body system is more important,***** the type and proportion of internal and external lubricant is appropriate, in order to effectively control the shear friction heat, the production of qualified products.