Application of CPP film for the hottest food packa

2022-08-16
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Application of CPP film for food packaging II

production equipment

CPP film production equipment can adopt single-layer casting and extrusion line, or a more flexible complete set of three-layer production line. The type and specification of the equipment are determined by the expected production products and the end use of the film

the investment of single-layer line is small, which is suitable for the production of film, laminated film and adhesive film for flower packaging and other purposes. The coextrusion line has excellent flexibility and can combine to produce PP grade materials of homopolymer and copolymer. For coextrusion line, there are also two options: the combination of two extruders can produce ABA structure, but there are some limitations; With the combination of three extruders, the production range is wider, and it can produce single-layer structure (AAA), or coextrusion structure with the same material (ABA) or different materials (ABC) on the surface

used in the production of expanded microspheres exhibited by the company. CPP films have the characteristics of low density, light weight and good resilience. Most modern production lines with competitive advantages often involve industry standard three-layer coextrusion. Generally, large extruders (100 mm or 150 mm) that can produce expanded structural layers are often used to produce core layers. The surface layer is fed by a small extruder (60mm or 90mm), which can obtain good sealing or better performance during the metallization process

coextrusion technology is adopted because it can mix PP of different grades, which can improve the sealing characteristics. Only using expensive additives on the surface layer can help reduce costs, and recycled materials can be used in the core layer. If the surface layer adopts special PP grade, the lamination performance can be improved, and its pinhole amount is also small

compared with CPE (cast polyethylene) film, the production requirements of CPP film are higher and more complex. Therefore, the requirements of clarity and thickness uniformity should be considered when configuring the equipment. It can be said that automatic die head is the key to ensure thickness uniformity. However, the cold casting roll and plastic casting device must ensure uniform cooling in order to ensure the effect of automatic die. The successful design can ensure closer contact between the melt extract and the cold casting roll, and produce film products with higher definition

after corona treatment, the temperature must also be controlled in order to transport the base material and avoid wrinkles and defects. At the same time, the coiler must be properly designed to ensure the accurate coiling of materials, otherwise the materials will shrink after aging, and it is easy to adhere when multi-layer films are formed. CCP coils are rolled in air gap mode. At the same time, the film feeding roller should also be used to control the coil hardness more accurately

the automatic die head and the whole process computer control can ensure the uniformity of the processing process and reduce the impact of external variables on the film quality. At the same time, the reasonable screw design and automatic temperature control can more accurately control the melting of materials and avoid the formation of condensate particles on the surface of the film

trend of processing equipment

due to the complexity of the production process, high-speed extrusion cannot be achieved in the CPP production process. Although great improvements have been made in recent years, the production speed is still low compared with other products such as stretched films. Since the quality of the film mainly depends on the optical properties and the number of condensates, it is necessary to reduce the speed and improve the quality in order to obtain better benefits. If the speed is accelerated, the cooling time will be shortened and more air will be sandwiched between the film and the cold casting roll, which conflicts with market expectations. In order to solve these problems, improved softening box and vacuum box have been developed. As a stopgap measure, some manufacturers began to adopt wider production lines to increase capacity and reduce the proportion of leftover materials in total output. Now, the production line that produces CPP with a width of 4.0 meters to 4.5 meters will list the items that need to be revised for the electronic universal experimental machine one by one today. It is not uncommon for the production line to produce the main roll of film. The industry has been committed to improving the design of the coiler, so as to accurately control the coiling conditions and ensure that the coil meets the specifications

The main components of the CPP extrusion line include:

- mixing system

- extruder (usually 3 sets)

- feeding head and automatic die head

- softening vacuum dual-purpose box

- casting device

- nuclear tester

- processing station

- coiler

- recycling system

- integrated control system

materials and film properties

the development of new materials will continue to affect the CPP market and promote market growth. Prominent trends include:

1 Develop new PP grades

2. New catalytic technology is adopted to form different material structures (developed by Borealis and Basell), such as high crystalline PP, random multiphase copolymer, super flexible PP, high melt strength PP, etc

3. Metallocene based PP, developed by Exxon, Dow and other companies, has excellent processability, high definition, good stiffness, excellent sealing performance, low extract content and low volatile content

exxon revealed that compared with the traditional Ziegler Natta grade, metallocene based PP is easier to draft during high-speed processing. CPP films can also be produced through various combinations, generally using the following structure:

layer a: copp (the interior of the random sensor is generally resistance strain gauge copolymer PP)

layer B: homopolymer PP

layer C: copp (low sealing initiation temperature, smoothing agent and anti adhesion additive)

different materials (random copolymer PP or homopolymer PP) can be selected for each layer, depending on the desired effect and end use. For example, if the film is used for metallization, lamination or cooking, the same formula but different grades can be used

metallized films are required to have excellent optical properties. For 20 micron (1 mil) 3-layer coextruded films, the haze value should not exceed 2%. For laminated films and cooking films, the haze value is 2.5% and 5% respectively, but it is required to have double sealing strength

for the kink film used in candy packaging, the most important characteristics are the retention or memory of dead folds and kinks. Other uses such as IV solution bags can adopt a three-layer structure, and one of the surface layers should adopt high crystalline grade to ensure heat resistance and moisture barrier; The core layer can be soft PP, and the other surface layer can be high sealing random copolymer pp. the next work plan of the unit elected as the vice president of the automotive lightweight Green Technology Alliance (the "China carbon fiber and composite industry alliance" initiated by the Ministry of industry and information technology of China) was reported. Vy Chen, Executive Secretary General of apimc, and Mr. Cao Du, executive chairman of ialta met with Mr. Xue Zhongming, chairman of Sinoma during the meeting

the new PP grade and technology have opened up a broad application field for the industry, and even replace other traditional materials

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