Efficient pet direct processing by multi screw extruder
Through different cylinder and screw combinations, the co directional parallel twin screw extruder can meet the wide mixing demand of almost all kinds of plastics in the market, and it has become the most rapidly developed and widely used mixing technology in the market.
At the same time, in order to meet the processing demand of higher filling volume, domestic and foreign suppliers have developed various disc extruders, reciprocating screw extruders and different combinations of multi screw extruders. In recent years, multi screw extruder has gradually become a force of rapid development in the mixing market to meet the direct processing demand of sensitive materials.
Multi screw new technology emerges in endlessly
In recent years, different manufacturers and research institutes have developed new models such as inverted triangle arrangement three screw extruder, one word arrangement three screw extruder, one word arrangement four screw extruder, Mrs multi screw extruder, and the combination of multi screw extruder and single screw or twin screw extruder The direct machining system plays a special role in different fields.
Beijing University of chemical technology has independently developed a fully engaged three screw extruder with inverted triangle arrangement. According to the introduction, the newly developed three screw extruder has the advantages of low energy consumption, high output, good mixing and dispersion quality. It can obtain the dispersion effect better than the conventional twin screw extruder with a small aspect ratio, and has excellent exhaust performance. There is no overflow at the exhaust port, which can effectively reduce the loss of raw materials and energy in the production process. In this project, the error correction technology of end face combination is proposed and used for the first time to realize the smooth transition in the process of combination of different screw elements and ensure the interchangeability of screw elements.
Based on the national key scientific and technological research project and "863" project undertaken by the National Engineering Research Center of polymer new molding equipment of South China University of technology, TDM series parallel three screw dynamic mixing extruder is developed. The three screws of the extruder mesh in a "one" shape and rotate in the same direction at high speed. Under the action of the vibration force field, the axial meshing clearance between the main screw and the two auxiliary screws changes periodically, which makes the materials subject to strong shearing, extrusion, kneading and grinding, so as to make the materials better homogenized and dispersed. Compared with the traditional parallel twin-screw dynamic mixing extruder, there is one more high shear zone, which can realize high-yield extrusion, and the production capacity is close to twice of that of the twin-screw extruder with the same screw diameter; due to the increase of specific surface area and the improvement of surface renewal rate, the devolatilization efficiency is also greatly improved. This series of machine adopts the same direction parallel combination three screw structure and introduces the vibration force field into melting, plasticizing, mixing and mixing. It has unique advantages of high filling, high dispersion, high output and low energy consumption.
The latest developed multi screw mixing system Mrs extruder was introduced by gneuss in k2007 and Chinaplas in 2008. Mrs system consists of a single screw drum. According to different specifications, there are 8-10 screw grooves on the screw drum. In these grooves are respectively equipped with conveying screws which are parallel to the axis of the extruder. These small screws are driven by a set of planetary gear system and rotate reversely with the main screw. Using this system to achieve significant exchange effect. These small grooves are opened on the screw drum, and 30% of them are open type, which can optimize the melt entry and easy to discharge. In addition, due to the fact that all parts contacting the melt can be controlled separately, the extremely accurate melt temperature control can be realized.
The Mrs extruder includes a single screw drum for significant exchange.
According to the introduction, the unique system components and structure of Mrs make its possible devolatilization area far higher than that of the commonly used extrusion system. For example, the free surface of the melt produced by the Mrs system in vacuum can be 25 times more than that of the co rotating twin screw extruder.
Compared with the traditional multi screw extruder, Mrs system has many obvious differences. In Mrs system, each screw has its own bearing support. This means that 8-10 small screws are parallel to each other. The ring extruder is usually composed of several two engaged screws, while the planetary screw is in the form of several screws engaged with the barrel and the main screw respectively. Both of these technologies are only limited open areas and are very sensitive to impurities in materials. And these impurities are often inevitable in the processing of recycled materials.
Technovel, a Japanese extruder manufacturer, exhibited a fully meshed contract rotating four screw extruder on k2007. The device is arranged in one word. The kzwfr series four screw extruder developed by technovel (patent pending) is mainly used in traditional processing methods, such as the processing of materials that can not be processed by single screw or even twin screw, according to the field personnel of technovel. According to the introduction, the equipment can reduce the heat generation of materials in the processing process, extend the residence time of materials, improve the exhaust function, improve the feed performance, and has better dispersion performance, which can realize stable precision extrusion, and save energy and space.
Pet directly processed into a hot spot
The wide application of PET material in the field of packaging makes the application of recycled PET become the focus of the market. The moisture contained in the processing of PET materials is easy to cause thermal degradation of the materials, which makes the mechanical properties and optical properties reduced. Different manufacturers have developed a variety of advanced processing schemes for pet direct processing and recycled PET direct processing. Among them, the multi screw extruder seems to be the most concerned technology in the industry.
Better than traditional APET sheet direct processing technology
The transparent PET sheet used in packaging industry should not only eliminate the pollution of external substances and dust, but also make sure that the distribution of color agents is highly uniform, the intrinsic viscosity is at least 0.74g/dl, and the crystallinity is more than 40%. In order to meet these strict requirements, sheet manufacturers adopt various processing methods.
The most commonly used processing method is single screw extruder, which requires the raw materials to be dried thoroughly. The energy consumption of pre drying equipment is very high, so processors have been looking for alternative methods. One feasible way is to use a single screw extruder combined with an infrared dryer, which reduces energy consumption by 60% compared with the traditional processing method. In contrast, the third way is single screw extruder plus crystallizer, which can also reduce energy consumption, but it is mainly recommended for recycled material processing, because the quality of the final product is poor. The traditional type of single screw extruder has proved unsuitable for this application if it is not equipped with drying equipment because of its low surface area / volume ratio. From this point of view, multi screw extruder is very suitable, but due to its complexity, so far the market penetration is not high.
Pet without drying can be directly processed in co rotating twin screw extruder with high efficiency exhaust. When the initial moisture content of raw material is less than 4000ppm, this processing method can obtain excellent sheet quality. In particular, it is advisable to use this kind of equipment for high-yield extrusion lines between 1500 and 3000 kg / h, despite the significant increase in equipment investment.
The modified planetary screw and single screw are used to produce high quality APET sheet
Pattenfeld extrusion technology company has launched a new concept of economic single screw extruder, which is used to produce high-quality APET sheet. This new processing equipment is not only suitable for extrusion lines with production capacity of 800-1000kg / h, but also can retain the flexibility of processing, that is, it can process not only pet, but also PS or PP. The innovation of the equipment lies in the combination of modified planetary screw and single screw with high efficiency melt exhaust function. Although the equipment investment is similar to the traditional pre drying equipment of single screw extruder, the maintenance cost and energy consumption of this new technology are relatively lower.
Planetary screw has a long history in PVC processing. Its basic principle is that several planetary screws meshed by involute rotate around the central screw meshed and rotated in a similar way. Melt is transported in the process of meshing, and new surface is formed continuously. It can exhaust completely at a vacuum of about 5mbar, and the effect is very good. At the same time, the self-cleaning characteristics of the planetary screw segment can ensure a shorter and predetermined melt residence time, so it can minimize the thermal decomposition of polymer molecular chain. Through a large exhaust port, the multi-stage vacuum pump can completely pump out water gas and any by-products. The shorter single screw next to the planetary screw is used for pressure formation, and the polymer melt exhausted is delivered to the melt pump and die head.
The first extruder of this type has been installed and operated at a well-known pet thermoforming sheet manufacturer in Europe, with excellent performance. This equipment can process the original APET with an initial moisture content of 3000 ppm and 100% recycled bottle material.
Multi screw system for direct processing of PET film
MKF-Folien and ENTEX have jointly developed an optimized PET blending process, which can process different PET materials. The core of this technology is entex's patented technology, planetary extruder with vacuum system. As we all know, pet is very easy to hydrolyze in the process of processing, so it usually needs to carry out complex pre drying treatment, and the use of planetary extruder, together with its vacuum system and upstream processing, can realize the continuous processing of materials, at this time, pre drying is not a necessary work.
Entex introduced that in the practical application of mkf, the overall net capacity can be increased to 600-1000kg / h (gross capacity 1200kg / h). The quality of the film is the same as that of the traditional extrusion line. At the same time, other devolatilization components can be discharged during the processing.
Mrs 110 extruder, especially suitable for recycling PET
In addition, this system can avoid pet thermal degradation or thermal oxidation degradation due to the presence of moisture in other processing methods, and will not reduce the mechanical and optical properties of materials. Compared with the traditional pre drying method and the optimized method, the performance of the film IV value is equivalent.
Entex emphasizes that the materials used in the process of use can be easily controlled and have more advantages when using recycled materials. Plant operators can use recycled materials to immediately reproduce the high quality of the final product and complete material replacement. Because there is no need for pre drying and partial crystallization of the material, the energy consumption for PET film production is significantly reduced. It is reported that this technology can be used in virtually all pet extrusion applications.
Innovative Mrs extruder for pet direct processing
The purpose of Mrs devolatilization system was to optimize the devolatilization of polymer melt. Because of its larger polymer melt area, compared with the existing devolatilization system in the market, Mrs equipment or called Mrs extruder has more efficient devolatilization capacity. In addition, due to the continuous change of its surface area, high-speed opening or renewal can produce a larger free volume, so that when the gas is generated, it is easier to discharge.
Mrs110 extruder, especially suitable for recycling PET
With the integrated Mrs exhaust area, the recycled PET materials can be processed quickly and easily by single screw extruder without pre drying. In a specific processing application, a water ring pump can produce the required suction of 20-40mba. At the same time, the viscosity of the material can be increased. This makes the Mrs extruder particularly suitable for making PET sheet or packing belt from recycled PET material, such as bottle sheet. Therefore, it is not surprising that the first Mrs extruder is sold in this field.
According to ganos, because of the special advantages of Mrs system, it can be used for: dehydration or removal of residual monomers in the process of PC processing; removal of monomers and residual oligomers in the process of nylon processing; increasing the molecular weight of pet, PBT and PTT through polycondensation; removal of monomer styrene in ABS or San; reducing VOC of POM, PP, ABS and other materials used in automotive interior trim. In addition, it can also be used to introduce chemical or physical foaming agent or other components when manufacturing PS, PE, pet, PP and other foaming products. These are only a very small part of the fields where Mrs system can be applied.