Characteristics for metallocene-polyethylene film
Metallocene polyethylene is a type of polyethylene that results from the reaction with a metallocene catalyst, called metallocene. MPE is a more stable and uniformly distributed composition than LLDPE made with the Ziegler-Natta conventional catalyst. This allows for high strength, good transverse and longitudinal uniformity, and low molecular weight. It has a narrow molecular distribution and very low levels of low molecular-weight substances. This makes it good for anti-chemical extraction, dirt-repellent properties, low viscosity and lower film viscosity. Also, there are less crystal points because the film does not contain high molecular-weight substances. MPE film is very strong in physical and mechanical properties. These include puncture resistance, impact resistance and high tensile strengths. MPE film has excellent heat sealing properties. The sealing temperature is low and the range of heat melting points is large. The heat sealing time is shorter, the quality of the seal is high, and the possibility of leakage or fracture is reduced. MPE film is also non-toxic, tasteless and does not alter food nutrition. It preserves food flavor. It is widely used in high-performance packaging films due to its ease of opening, packaging and other properties. LLDPE films can migrate and oxidize when they are not treated with a lubricant. Heat seal seals that have been exposed to acid, alkali, or strong surfactants may break down and cause fouling. mPE film offers many benefits over traditional LDPE, LLDPE and PP. Films cannot match it. It is slowly replacing traditional packaging materials, and will be a very prominent position in the packaging industry because of its outstanding performance.
High quality packaging using metallocene-polyethylene film
Material selection and formula creation
The production cost of mPE films is very low because of the technology and equipment required for the film blowing process. To produce high-performance packaging materials, the production process employs mPE/LLDPE blend extrusion blow molding. This reduces overall costs, lowers melt viscosity and decreases the torque transmitted by the screw. This allows for mass production of thin films. The production rate for high-performance packaging film is usually 60% for mPE and 40% or LLDPE/LDPE. This allows for the best cost, production process, and performance.
Control of the manufacturing process for mPE film in high performance packaging
Metallocene polyethylene resin is unique in its molecular weight distribution. This polymer can be processed differently to traditional materials. To ensure that thin metallocene film production runs smoothly, it is important to control and monitor the conditions of the manufacturing process in order to stabilize product quality.
1. Production process: Although mPE film can be produced in the same way as regular PE film, the control of process conditions is quite different. The technological process is approximately as follows: dosing-mixing-extrusion-inflation-cooling-coronation-pulling-winding-checking-packing.
2. Blow Molding Process Control: Due to the higher price of metallocene resin than other PE resins, mPE can be combined with LLDPE (or general purpose LDPE) resins to lower costs. The extruder's feeding section is where the raw material is placed. Once the resin has reached the melting stage, the viscosity and torque are transmitted through the screw to increase motor current. Poor control can cause malfunctions or stoppages, which will lead to an increase in temperature. The film's melt will cause the thrust to be unstable. It will also break the film, cause the film to burst, and affect the film's uniformity thickness and width. The film's plasticization will suffer from a lower temperature. There will be many crystallization points and poor transparency. The film's mechanical properties will also decrease. Quality will drop to a hard and rough level. Mixing with other films can lead to a variety of problems, including localized shrinkage, delamination and poor heat sealing. The mPE blow molding process should be guided by the law of low-high, medium, and high temperature extrusion. This ensures that the melt was plasticized properly, the output was stable, and the pull and winding were consistent. To ensure that the feed section is kept at a low temperature, and strong draft, and the temperature in the compression section rise quickly to pre-melt and reduce the reaction of melt to excessive torque caused by the increase in viscosity, the melt must enter the homogenization section. To facilitate heat transfer, maintain stable viscous flow, and to ensure that the melt flows through the strainer, the cooling method should be chosen. It will form a strong, tubular film that prevents melt breakage, and provides a solid foundation for subsequent traction or cooling.
The mPE film process requires cooling. Because the melt extrusion temperature for mPE resins is higher than that of traditional LLDPE and the crystallization temperatures are lower than LLDPE it is important to heat transfer to the melt over time. For heat dissipation, the double-layer air rings should be used according to process requirements. A proper inflation ratio will help to cool the film bubble and improve film orientation. It will also ensure uniform thickness. It is best to maintain a 1.8-3.5 inflation ratio in mPE film production. The freeze line height should be at 2D (D is diameter of machine head) so that all-round film quality can be assured.
3. Equipment requirements: The MPE resin is injected into the extruder and the material is extruded to melt. The material is extruded until it reaches the melting stage. This causes the melt viscosity to increase sharply and friction to increase, which results in an increase of screw torque. The extruder's driving section bears a heavy load to transmit pressure. This increases the current through the main machine. When choosing equipment, you need to ensure that it has enough drive power to handle the high torque and load during production. The control of acceptable process conditions can help increase the main engine's load within a specific range. This will ensure that production runs smoothly.
The key to producing mPE films is the choice of the screw length to extruder's screw diameter ratio. A good screw length to diameter ratio will produce high-quality mPE films. It can also help reduce waste and provide other benefits. There is currently no consensus regarding the technical parameters of the screw that is used for the processing of MPE films. However, the extruder screw must have enough extrusion pressure to ensure sufficient shearing action within the compression section. After entering the homogenizing sectionsand, the shear must decrease to release the mold and relax the melt. To ensure quality and yield of mPE films, the typical screw length-to-diameter ratio is between 25:1 & 32:1.
Because of their outstanding properties, metallocene polyethylene material are used extensively in food packaging and industrial packaging. Major suppliers of metallocene are constantly upgrading their technology and developing new generation metallocene material. They strive to achieve a balance between performance, rigidity and heat sealing. Different metallocene catalysts have different properties, so users can choose the right metallocene material for their specific product needs.
Characteristics for metallocene-polyethylene film
Metallocene polyethylene is a type of polyethylene that results from the reaction with a metallocene catalyst, called metallocene. MPE is a more stable and uniformly distributed composition than LLDPE made with the Ziegler-Natta conventional catalyst. This allows for high strength, good transverse and longitudinal uniformity, and low molecular weight. It has a narrow molecular distribution and very low levels of low molecular-weight substances. This makes it good for anti-chemical extraction, dirt-repellent properties, and low film viscosity. Also, there are less crystal points because the film does not contain high molecular-weight substances. MPE film is very strong in physical and mechanical properties. These include puncture resistance, impact resistance and high tensile strengths. MPE film has excellent heat sealing properties. The sealing temperature is very low, heat sealing temperature range wide, peak value of melting point low, heat sealing time is reduced, sealing quality is good and leakage and fracture are greatly reduced. MPE film is also non-toxic, tasteless and does not alter food nutrition. It preserves food flavor. It is widely used in high-performance packaging films due to its ease of opening, packaging and other properties. LLDPE films can migrate and oxidize when they are not treated with a lubricant. Heat seal seals that have been exposed to acid, alkali, or strong surfactants may break down and cause fouling. mPE film offers many benefits that traditional LDPE and LLDPE films cannot match, such as PP, EVA, and so on. Because of its outstanding performance, mPE film is slowly replacing traditional packaging materials.
Application of metallocene polyethylene film in high quality packaging
Material selection and formula development
Since mPE resin has certain technology and equipment requirements in the film blowing process, the production cost of mPE film is limited. The production process uses mPE/LLDPE blending extrusion blow molding to obtain packaging materials with excellent performance, which reduces the overall cost of the film, reduces the melt viscosity, and reduces the torque transmitted to the screw, thereby reducing the driving load Allows the mass production of thin films . When the production rate of high performance packaging film is generally 60% for mPE and 40% for LLDPE or LDPE, its cost, production process and performance reach the ideal state.
Process control of mPE film for high performance packaging
Due to its special molecular weight distribution and composition, metallocene polyethylene resin determines that the processing technology and even the equipment for processing this polymer is different from traditional materials. In the production process of thin metallocene films, it is necessary to ensure the normal operation of the equipment and strictly control the process conditions in order to achieve the goal of stabilizing product quality.
1. Production process: The production process of mPE film is basically the same as ordinary PE film, but the control of the process conditions is different. The technological process is approximately as follows: dosing-mixing-extrusion-inflation-cooling-coronation-pulling-winding-checking-packing.
2. Blow Molding Process Control: Because the current price of metallocene PE resin is higher than ordinary PE resin, mPE is combined with LLDPE or general purpose LDPE resin to reduce costs. When the raw material is dosed into the feeding section of the extruder, the resin is in the melting stage, and the viscosity rises sharply, and the torque is transmitted through the screw to increase the motor current. If the control is poor, it will cause stoppage or other phenomena, and the temperature of the material in the machine will rise accordingly. When the melt comes out of the mold, the thrust will be unstable, the film will be broken, the film will break, and the film bubble will be unstable, which will affect the film width and uniformity thickness. If the temperature is lowered, the plasticization of the film will be poor, there will be many crystallization points, the transparency will be poor, the mechanical properties of the film will decrease, and the quality of the film will be hard and rough. When mixed with other films, a number of problems arise, such as localized shrinkage, delamination, and poor heat sealing effect. Therefore, the mPE blow molding process is best to follow the law of low, high, medium and medium temperature extrusion process, so that the melt is plasticized pevenly, the output was stable, the pull and winding were normal. Thus, the feeding section must be kept at a low temperature to ensure timely feeding and strong draft; the temperature must rise rapidly in the compression section to pre-melt the resin and reduce the reaction of the melt to excessive torque due to the increase in viscosity; the melt enters the homogenization section. The cooling method must be chosen to facilitate the transfer of more heat buildup, maintain a stable viscous flow state of the material, and ensure a balanced flow of the melt through the strainer. , form a strong tubular film, prevent melt breakage and provide a good basis for subsequent traction and cooling.
Cooling is also a very important part of mPE film processing. Since the melt extrusion temperature of mPE resin is higher than traditional LLDPE, and the crystallization temperature is lower than LLDPE, it is especially important to transfer heat to the melt over time. The double-layer air ring should be used for timely heat dissipation according to process requirements. An appropriate inflation ratio helps to cool the film bubble, improve the balanced film orientation, and also ensure film thickness uniformity. In the production process of mPE film, it is better to keep the inflation ratio within 1.8-3.5, and the freeze line height should be controlled at about 2D (D is the die diameter of the machine head), so that the all-round quality of the film can be guaranteed.
3. Equipment requirements: After the MPE resin enters the extruder, the material is extruded until melting. When the material enters the middle stage of melting, the melt viscosity increases sharply, and the friction of the material increases, resulting in an increase in screw torque. In order to transmit pressure, the driving part of the extruder bears a large load, which increases the current of the main machine. Therefore, when choosing equipment, it is necessary to select equipment with sufficient drive power to withstand the torque and loads that occur during production. In the production process, control of reasonable process conditions can also improve the load on the main engine within a certain range and ensure normal production.
Choosing the screw length to screw diameter ratio of the extruder is also the key to mPE film production equipment. Choosing a reasonable screw length to diameter ratio can produce high quality mPE film, and at the same time, can ensure the realization of production capacity, thereby reducing waste and receiving certain benefits. At present, there is no consensus on the technical parameters of the screw used in the processing of MPE film, but the extruder screw must have sufficient extrusion pressure so that the screw has sufficient shearing action in the compression section; after entering the homogenizing sectionand, the shear must be reduced to relax the melt and quickly transfer heat, and quickly release the mold to stabilize production capacity. Typically, screw length to diameter ratios are between 25:1 and 32:1 to ensure mPE film yield and quality.
Metallocene polyethylene materials are widely used in food and industrial packaging due to their excellent properties. Major metallocene suppliers are also actively upgrading their technologies, developing new generation metallocene materials and striving to achieve a balance in performance, rigidity, processing, heat sealing and other aspects. The properties of metallocenes produced with different metallocene catalysts also differ, and users can choose suitable metallocene materials according to their product requirements.