VC finished products, including pipes, fittings, profiles and so on. In addition, the profile material is being used as an outdoor construction material, and the request for the weather resistance function of the product is higher; the cross section of the time-sharing fruit is complicated, and the request for the formulation processing function is also relatively mean. Those who have decided to formulate the profiled material are very complicated. Take u-PVC profile as an example. In addition to the main material PVC, it generally includes a compound wave agent (including wave agent, smoothing agent, ultraviolet light collector, anti-oxidant, etc.) and resistance. Punching modifiers (such as CPE probably AIM), processing aids (ACR), titanium dioxide (TiO2), fillers (often using calcium carbonate), etc. , the material types are generally more than ten kinds. On the other hand, from the processing technology, following the popularization of extruder technology, the twin-screw extruder with strong plasticizing power has replaced the single-screw extruder. Whether the u-PVC profile warping pipe is indirectly extruded from the inclusion powder into the final product through the twin-screw extruder. Because the consumption of twin-screw extrusion omits the key to extrusion and extrusion outside of single-screw extrusion, the quality of the inclusions will affect the quality of the previous period. Good. Those who have made strict requests for the quality of the ingredients. Therefore, how to superstitiously mix and monitor the quality of the mixed mixture is a matter that must be faced as a finished consumer. This article will take the superstitious profile formulation as an example to discuss the role of the mixing process, and analyze how to monitor the quality of the mixture.
The effect of the mixture is based on the mixing of the u-PVC formula. Generally, the mixing of the cold-mixed warfare is two stages, and the mixed ingredients are called wet mix. The so-called cold mixing refers to the mixing process of freezing the inclusions to the softening temperature or above the softening temperature, while the cold mixed cold mixture is outside the cold mixing pot, and the coldness of the hair is sprayed through the leaves at low speed. Through the cold mixing pot jacket, the outside of the cold but the water is taken away until the material is lowered to the set temperature to a high process. The wet mix that is mixed with cold and cold mixed water needs to be used for a while after being "cooked". There are four aspects to the cold-mixed warfare: the first is to make the components of the material in the space evenly distributed, to obtain the certain uniformity, which is obvious that the components play a sufficient role; the second is through the process of cold mixing Therefore, the PVC particles have a process from the original state to the micro-melting of the fracture to the consolidation of the de novo, so that the wet mixing material obtains a certain pre-plasticizing motive, from the description of the inclusion form, that is, the necessary degree of separation for hunting The third is to make the wet mixture after the mixing process, clear the small particle size component, so that the overall particle size of the wet mixture is distributed relative to the larger and more concentrated, the appearance of the wet mix is improved. Density warfare activity, there is a wave of transportation that is only conducive to wet mixing, whether to improve the quality of production at the same time; the fourth is through the process of cold mixing, to eliminate the low-volatility components outside the material, to eliminate those components The impact on the quality of the material produced. The goal of standing the wet mix is to eliminate the static electricity generated outside the mixing process and further improve the apparent density war activity of the wet mix.
Taking the common profile material as an example, the formulation of the outer PVC and CPE is a large particle size (uniform particle size Dav is 150-200 μm), and the composite wave agent will be broken into small particles after the particles are in the form of tablets. However, before the mixing, it is improved to the level of calcium carbonate and titanium dioxide (10μm or higher). The processing aid ACR has a small particle size, but the formulation has a long content and the melting point is lower than the cold mix. The temperature will be melted outside the cold mixture. The small particle size component that really needs to be considered outside this formula is calcium carbonate and titanium dioxide.
The cold source outside the cold mixing process is generally the frictional cold generated by the high-speed shearing of the stirring blade. The detailed transformation process of the shape of the material outside the cold mixing process is: the high-speed mixer has a high effect, and the absolute proportion of PVC particles is broken by high-speed shearing action, and the specific surface area of PVC particles increases to form a strong electrostatic adsorption effect; On the other hand, the low-melting smoothing agent and processing aid outside the formula will gradually melt outside the temperature recovery process, adhere to the PVC particles, and act as a binder between the inorganic particles of PVC; PVC pellets are gradually shrinking after the initial rupture, and when the temperature is higher than the glass transition temperature (Tg) of 87 °C, the PVC particles gradually soften from the outside to the inside, and reach a certain degree of pre-plasticization. Soft or even micro-melting PVC particles are also conducive to the adhesion of small-sized inorganic particles. The effect of all the fruit complexes is: following the mixing process, the small particle size component of the calcium carbonate and titanium dioxide outside the formula The particles will gradually adhere and be embedded around the PVC particles, so that the particle size of the PVC particles will gradually decrease from the cracking, and the shape of the CPE outside the formula will change to different PVC. The small particle size component outside the formula gradually disappears, and the blend with the different particle size eventually becomes a powder with a relatively large particle size.
Effect of mixing process on mixing motive
1. The feeding procedure and its influence on the mixing motive According to the synergistic effect of the various materials, the participation of various materials outside the formula should be participated in stages. The proper feeding procedure is to take the PVC at low speed and stir at high speed; after the high-speed stirring starts, the temperature rises to 60 °C and participates in the wave agent to take the soap wave volatility agent (for the composite granular wave agent suitable for taking PVC isochronous participation); 80 ° C degree At the time of the arrangement, the processing aid, the inner smoothing agent, the pigment and the impact modifier are involved (if the smoothing agent is in the presence of the wave agent, the different wavering agent participates separately); when the temperature rises to 100 ° C, it participates in the wax, etc. External smoothing agent; at 110 ° C, participate in calcium carbonate to take inorganic substances such as titanium dioxide. At the beginning, take the PVC to take the wave agent, whether to fully exert the fluctuation effect of the wave agent on PVC; the inner smoothness is late to participate in the gelation of the beginning of the material; then participate in the processing aid, impact modifier, etc. to facilitate the PVC The inclusion of the external slip agent is to prevent the external slip agent from affecting the separation of the friction between the materials; the inorganic particles such as calcium carbonate and titanium dioxide are initially involved, and on the one hand, the inorganic filler is prevented from being sucked by the smoothing agent. On the other hand, the wear of those softer particles for the mixing equipment is also eliminated. Such a feeding procedure will make all the mixes more superstitious. However, such a feeding method is complicated, the request for the manipulation of the equipment is higher, and the other mixing time is significantly delayed, so that the mixing is subject to high drop. Therefore, when it comes to real consumption, it is not long for manufacturers to fulfill all the materials and materials that are put into the mixing process at different times. According to the lesson, the materials are mixed at the same time, and only the suitable mixing process, the wet mix can also be very poor.
2. The effect of cold mixing and cold mixing temperature on mixing motives As mentioned above, the cold mixing temperature must be higher than the glass transition temperature of PVC. The detailed setting value should be determined according to whether the target of the cold mix can be reached. If the cold mixing temperature is low, the first is that the small particle size component of the wet mixture is still not long. The wet mixture is difficult to produce static electricity, which is beneficial to the activity, and even the pipeline transportation process is difficult to present the material layering. Signs, tension affects the quality of the material; secondly, the degree of pre-plasticization of the wet mix is sufficient, which is conducive to the poor plasticization degree of the early consumption, the data function of the product is affected; the third is the moisture outside the material, etc. When the volatiles are removed, the precipitation will increase outside the pre-processing, and the product will be difficult to exhibit bubbles, or even degradation, and the product will be affected by the tension. If the cold mix temperature is too high, the pre-plasticization of the wet mix is too high, and the wave agent is too much when it is being mixed, which affects the data of the process control products in the early stage of consumption, and even affects the product. Weather resistance. The setting of the cold mixing temperature depends only on the shape of the wet mixture itself, and it is necessary to properly mediate according to the plasticizing power of the extruder in the pre-war period. Generally, the proportion of small particle size components outside the formula is relatively high. It is presumed that the plasticizing power of the extruder in the early stage is sufficient, and the temperature of the cold mixing should be higher. vice versa. The general condition is high, and the cold mixing temperature setting of the u-PVC profile formulation is at 120 °C. The setting of the cold mixing temperature is set at 40 to 45 °C according to the general lesson. If the temperature of the cold mix is too high, the wet mix will be stored in the cold, but it will be stored in the outer part of the material, which will affect the quality of the residual material, and will be degraded by the wavy agent, wet mix and even pink. The cold mixing temperature is too low, which is beneficial to improve the mixing compliance.
3, the impact of feed quality on the quality of the mixture When mixing the material quality of each pot is generally 55 to 75% of the clean space of the cold mix. If the quality of the mixture is too long, there will be enough friction during the cold mixing, and the temperature of the wet mixture will rise rapidly. When there is only a delay in the cold, the borrower can lose too much volatility; the quality of the mixture is too much. Then the material is light and difficult to mix and symmetry, water and gas are difficult to exhaust, and ultimately affect the quality of the wet mix.