Discussion On The Production Process Of PVC Foam Board

　　PVC foam board is carried out under very unstable conditions, such as the viscosity rise and expansion of the melt. Under the same temperature and shear force conditions, the viscosity of PVC resin containing a foaming agent is lower than that of PVC resin without a foaming agent, the foaming process is unstable, and the stability of melt viscosity is improved. During the extrusion process of PVC foam board products, lubricants have a great influence on melt fluidity, mold release performance, and the mixing and distribution of foaming gas. After the melt enters the mold cavity, through reasonable lubrication and coordination, a product with uniform density, uniform thickness, smooth surface, and the uniform surface can be formed.

　　Given the above characteristics, according to the production process of PVC foam board, in the extrusion production process of foam products, it is necessary to comprehensively consider the influence of formula, process, equipment, and other factors. The key is to grasp the following three key factors: (1) The balance between the maximum foaming rate of the melt and the cells; the discharge balance of the die lip; the matching of the stripping speed and the drawing speed of the slab.

　　When the feeding speed is constant, the feeding speed is too fast, the shear heat rises too fast, the melt is easy to degrade and changes color, the strength is reduced, and the foaming efficiency is reduced, the produced foam board will have quality defects such as light bands and dark bands. Small size, easy plasticization of the melt, low foaming rate, easy to cause no-load operation of the extruder, and affect the service life of the extruder. The matching of drawing speed and drawing speed. In the actual production process, if the shape of the mold is regular, or slightly expanded and straightened, it indicates that the extrusion speed and the pulling speed match well. When the casting speed and the casting speed are too fast, the decomposition degree of the foaming agent is closely related to the gas nucleus ratio when the melt is released from the mold, and the residence time of the melt in the machine is too short, and the decomposition degree of the foaming agent is small, to increase the air-core ratio and increase the foaming speed, the drawing speed and the drawing speed should be appropriately reduced.

　　If the plate speed is too fast or the traction speed is too slow, the foaming efficiency will be reduced, the product density will be too high, the resistance of the tractor will be increased, and the surface of the product will appear horizontal waves, which will lead to blockage of the shaping die in severe cases; the demoulding speed of the slab Too slow or pulling too fast. Under the strong traction force, the foaming of the product is hindered, the foaming rate is also reduced, the surface of the plate is distorted, and the dimensional change rate is high. After the product is cooled and shaped, there are still many internal stresses that cannot be released, affecting its strength and performance, and even streaks, wrinkles or collapse appear in low-pressure parts. Generally speaking, in the case of constant slab ejection speed, appropriately increasing the pulling speed can slow down the resistance of the die lip and significantly increase the product density.

　　In short, in the extrusion production of the WPC foam board factory, the process parameters affecting foaming and skinning are complementary, and it is difficult to achieve the desired effect only by adjusting a certain parameter.