Mixing ingredients is an important part of the producti […]
Mixing ingredients is an important part of the production of PVC profiles. The mixing process is not only the mechanical mixing between the components, but also the process of friction and collision between the components, and the materials are continuously heated and gradually gelled. Therefore, the quality of the dry blend directly affects the physical properties and chemical properties of the PVC profiles. . Foreign experts believe that a good mixer can make up for the poor plasticizing extruder, but even the best extruder can not make up for the shortage of the mixer, the importance of the mixer. In the mixer, the material is raised from normal temperature to 120 ° C in a short time by self-friction. Over time, the wear of the mixer is very large.
According to experience, in the case of raw materials, formulations, equipment and processes, sampling on a 6m long profile, the cooling impact test results of the profiles are very different: 8 samples are intact, 1 sample has Small cracks, and one sample showed a hole. After investigation, it is determined that the material is not uniformly mixed, and the small amount of the auxiliary agent is not well dispersed. This problem was solved after replacing the hot mix paddle. The visual performance of the mixer wear is that the noise is large, harsh, and the mixing time is prolonged from the general 8-10min to more than 15min.
After a long period of observation and comparison, the maximum density and maximum gelation of the PVC particles are obtained. The hot mixing temperature should be controlled at about 115 ° C, the mixing time is 8-10 min each time, and the feeding amount is 60 of the volume of the mixing machine. About %, this effect is ideal. In the winter, the speed of the mixer can be increased. In summer, the speed of the mixer should be lowered. Through such adjustments, work efficiency can be ensured and the mixing time can be controlled. In order to obtain satisfactory plasticizing quality of PVC materials, the processing precision and assembly accuracy of the screw and barrel are also important factors. High assembly precision and optimized extrusion process can better guarantee the quality of PVC profiles. Therefore, it is necessary to regularly check the axial clearance and radial clearance of the screw and the barrel, and adjust it in time if it does not meet the requirements.
