With the rapid development and innovation of polymer technology, more and more plastic products are used more and more widely in various industries. Large-scale applications of plastic products can be seen in aerospace, automobile, household appliances, daily use, medical treatment, food packaging, construction, ships and so on.
People have higher and higher requirements for products. They not only put forward higher requirements in terms of safety, environmental protection, humanization and appearance, but also require our color masterbatch to keep pace with the times and continuously improve the safety, quality and performance of products; It is precisely because our color masterbatch can just bring more environmentally friendly and safe colorful visual feast to our world, so color masterbatch is as indispensable as salt we must have when cooking.
Color masterbatch is a kind of color preparation product with high concentration and high efficiency. It is a polymer composite prepared by uniformly mixing pigment higher than constant and then loading it into resin through twin-screw extruder. There is no doubt that twin screw extruder is the best choice for color masterbatch processing.
In recent years, China has developed into the country with the fastest growth in the demand for color masterbatch. With the growth of China's production capacity, terminal products have higher and higher requirements for high concentration, ultra-high concentration and multifunctional color masterbatch. In order to solve the key technical problems in the process of color masterbatch processing in the past, the engineers of Nanjing KEYA solved the key technical bottlenecks such as improving the quality of color masterbatch products and reducing the waste of raw materials in the process of switching different color varieties through the innovative technical application of key components such as screw and cylinder of twin screw extruder.
KEYA's third generation HK series twin screw extruder gearbox- higher bearing capacity, more stable torque output and longer service life, guaranteeing the processing of color masterbatch.
The screw of HK series model has higher feeding capacity and can add more materials, that is, the filling rate of materials in the screw is greatly improved. As shown in Figure 1, h can be used to represent the thickness of material layer. The thicker the material, the higher the filling rate and the greater the output; v represents screw speed.
When the screw speed remains unchanged and the shear rate r decreases due to the increase of h, the shear rate of the screw to the material is reduced. As shown in Figure 2, the closer the material is to the outer circle, the higher the linear speed, the stronger the shear force, and the higher the material filling rate, so that the closer the material is to the small circle, and the shear rate decreases. At the same time, because the material filling rate is higher, The metal friction probability between screw and cylinder of twin screw extruder is reduced. It realizes lower energy consumption, higher product quality, longer equipment life and better stability.
In the process of material extrusion, if the final product has high requirements for impurity residue (such as film and XLPE cable), the screw needs to be pulled out for surface cleaning after being used for a period of time to prevent material carbonization and adhesion on the screw surface, especially in the process of color masterbatch operation, and it is often necessary to switch different colors and quickly replace raw materials.
In response to this kind of demand, Nanjing KEYA has developed a formula design for spraying wear-resistant lubricating layer on the screw surface: the surface hardness of the element reaches HV3500, the color is black gray, the coating thickness is 4.0-6.0 (UM), the maximum working temperature is 900 ℃ and the friction coefficient is 0.3. While improving the surface hardness, it also maintains good coating toughness, adhesion and lubricity. As shown in Figure 3 (the figure on the left shows a new screw element sprayed with lubricating layer on the surface, and the figure on the right shows a conventional 6542 screw element).
Over the years, the cylinder of twin-screw extruder has mainly adopted C-type bushing structure (Fig. 4) and integral bushing structure (Fig. 5) to adapt to the formulation operation of a variety of polymers; In the process of color masterbatch operation, due to the need to switch materials frequently, the joints in the cylinder will cause cross pollution of different colors.
As shown in Fig. 4, the C-type bushing has a joint between the sleeve and the sleeve that runs through the whole equipment, resulting in material residue and longer color switching process; As shown in Figure 5, it is the integral sleeve after the cylinder is removed at the masterbatch filling operation site. It can be seen that the inner bushing and the end faces of the cylinder are no longer on the same plane. The reason is that the thermal expansion coefficients of the cylinder body and the bushing are different after the cylinder is heated during the production process. Therefore, if the integral bushing structure is adopted, there is a joint between the cylinder and the cylinder; It will also lead to the residue of materials, especially for the operation materials whose final product is membrane, the disadvantages are particularly obvious; To solve the above problems, we developed a metal sintered wear-resistant cylinder (Fig. 6).
Adopting metal sintering technology is pioneering, which is to sinter the alloy powder on the surface of the splayed hole in the cylinder through a special process to form a uniform and dense alloy layer. The alloy layer not only solves the defects of the traditional scheme, but also has better corrosion and wear resistance and long service life, and effectively solves the problem of the splicing joint of the holes in the cylinder, and greatly improves the efficiency of switching different materials.
KEYA has developed a new cylinder cooling and heating structure. As shown in Figure 7, the cylinder adopts a new radial cooling water channel design and imported heating elements, which not only improves the temperature control efficiency, but also reduces the temperature difference distribution and thermal deformation of the cylinder, avoids the resulting local shear heat and hardware wear, and improves the service life of equipment and parts.
Reference test data: set the operating conditions of the twin-screw extruder (modification of most conventional materials): 70 ~ 80% of the time in zone 1~3 of the feeding section is in the full load heating state, and 20 ~ 30% of the time in zone 4~head; calculate according to the above working conditions: HK53, length diameter ratio 44, calculate according to 80% heating time of the first three cylinders and 30% heating time of the last seven cylinders, and 5000 hours of annual operation time:
Traditional full cast copper heater: 4.2x3x0.8x5000 + 4.2x7x0.3x5000 = 94500 kwh;
New heating rod: 2.8x3x0.8x5000 + 2.8x7x0.3x5000 = 63000kWh.
The technological innovation of KEYA's third generation HK series twin screw extruder has led the development trend of color masterbatch industry in terms of application scope, higher production capacity and lower energy consumption; The cross-border technical cooperation and application of twin-screw extruder and multi disciplines (powder alloy, metal cutting, heat treatment, ceramic heating, etc.) make HK series models more suitable for the processing and production of color masterbatch industry; The application of high torque and advanced control system makes the twin screw extruder highly stable and easy to operate, which provides a reliable guarantee for the continuous and stable production of users in color masterbatch industry
Tel: +86-25-52706155
E-mail: info@kymach.com
No.59 West Tianyuan Road, Jiangning, Nanjing, Jiangsu Province, China
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