CPP is a polypropylene (PP) film produced by a cast extrusion process in the plastics industry. This kind of film is different from BOPP (bidirectional polypropylene) film and belongs to non-oriented film. Strictly speaking, CPP films only have a certain orientation in the machine direction (MD) direction, mainly due to the nature of the process. By rapidly cooling on the cold casting roll, excellent clarity and smoothness are formed on the film. -Compared with other films such as LLDPE, LDPE, HDPE, PET, PVG, etc., the cost is lower and the output is higher. Although some PP films are produced by a casting process and used in the sanitary field or as synthetic paper containing fillers and other additives, the term CPP film generally refers to high-definition films suitable for applications such as lamination, metallization, and packaging. . Current use and potential use Current uses of CPP include: clothing, knitwear and floral packaging Bags; pouches; outer packaging; documents and photo album films; food packaging; and metalized films suitable for barrier packaging and decoration. Potential uses include: blister packaging (replaces PVC); food outer packaging; candy outer packaging (twisted film); pharmaceutical packaging (infusion bags); replaces PVG in areas such as photo albums, folders, and documents; synthetic paper; adhesive tape ; Report cover; business card holder; ring file and standing bag composite material. CPP film is so attractive because of its low cost and price advantage compared to PET, LLDPE, LDPE and other materials. Compared with LLDPE, the 5% ~ 10% price difference plus 2% density difference is the attraction. Furthermore, due to the inherent rapid cooling properties of the cast film, excellent smoothness and transparency can be formed. For packaging applications that require higher clarity, this feature makes PP film the material of choice. It can provide transparent windows to make the contents clearly visible, especially suitable for the flexible packaging market. After corona treatment, it is easy to use various processes for printing. This feature improves the final appearance of the film. CPP has excellent heat resistance. Since the PP softening point is about 140 ° C, this type of film can be used in hot filling, cooking bags, aseptic packaging and other fields. In addition, it has excellent acid resistance, alkali resistance and grease resistance, making it the first choice material in the field of bread product packaging or laminate materials. Its food contact safety, excellent demonstration performance, will not affect the flavor of the food inside, and can choose different grades of resin to obtain the desired characteristics. According to GMAI estimates, the global demand for thermoplastics in 2001 was 135.7 million tons, with PP accounting for 22% of the total polymer consumption. Western Europe, North America and Asia are the main consumer regions of polypropylene, accounting for 78% of the total global demand. Among them, Japan, Southeast Asia, China and South Korea alone accounted for 39% of the total global demand for PP. According to the forecast of the US market research agency Freedonia Group, as of 2002, the total demand for PP film in the US had an average annual growth rate of 4.5%, reaching 671,500 tons. However, most of the above films are BOPP films. Food packaging is expected to account for 85% of this demand. In the United States, CPP films are not as popular as in other regions, but recently they have not expanded their use in laminates. According to Borealis figures, the Western European PP market is expected to reach 8.1 million tons. The market size of CPP film in 2003 is expected to reach 423,000 tons, the main application areas are laminates and food packaging. Cast PP thin films, especially metallized grades, are extremely advantageous in the Asian food packaging market. For example, the amount of CPP film used in Japan was as high as 120,000 tons in 1997. In Latin America, GPP films have also begun to be well-received by the market, and have become more and more widely used. According to the prediction of Freedonia Group, the packaging PP is about 400,000 tons. For the future, the development trend of CPP film will be: -The market share increased, and the market share of PVC, PS and PE decreased accordingly; Production equipment CPP film production equipment can use single-layer casting extrusion line, or a more flexible complete 3-layer production line. The type and specifications of the equipment are determined by the intended product and film end use. The single-layer line has a small investment and is suitable for the production of films, laminate films and adhesive films for flower packaging and other uses. The coextrusion line has excellent flexibility and can be combined to produce homopolymer and copolymer PP grade structures. For the co-extrusion line, there are also two options: the combination of two extruders can produce ABA structure, but there are certain limitations; the combination of three extruders has a wider production range and can produce a single layer The structure (AAA), or the surface layer uses the same material (ABA) or different materials (ABC) co-extruded structure. Most modern production lines with competitive advantages for the production of CPP films often involve industry-standard 3-layer co-extrusion. Normally, a large extruder (100 mm or 150 mm) capable of producing an expanded structure layer is often used to produce the core layer. The surface layer is fed by a small extruder (60 mm or 90 mm), which can achieve good sealing or better performance during metallization. The co-extrusion technology is used because it can mix different grades of PP and improve the sealing characteristics. The use of more expensive additives on the surface layer helps to reduce costs, and the core layer can use recycled materials. If the special PP grade is used for the surface layer, the lamination performance can be improved, and the amount of pinholes is also small. Compared with GPE (cast polyethylene) film, CPP film production requirements are higher and more complex. Therefore, when configuring the equipment, the requirements of clarity and thickness uniformity should be considered. It can be said that the automatic die is the key to ensure the thickness uniformity. However, the cold casting rolls and casting equipment must ensure uniform cooling in order to ensure the effect of the automatic die. The successful design can ensure that the melt extract and the cold casting roll are in closer contact, producing a thinner film product with higher definition. After corona treatment, the temperature must also be controlled to facilitate the transport of the base material and avoid the formation of wrinkles and defects. At the same time, it must be properly designed into a roll machine to ensure that the material is accurately rolled, otherwise the material will shrink after aging and it is easy to adhere when the multilayer film is formed. CCP coils are wound in air gap mode. At the same time, the film feed roller should also be used to control the coil hardness more accurately. The use of automatic die head and full computer control can ensure that the processing flow is uniform and reduce the impact of external variables on the quality of the film. At the same time, the reasonable screw design and automatic temperature control can control the material melting more accurately and avoid the formation of condensate on the film surface. Due to the complex production process, high-speed extrusion cannot be achieved during the CPP production process. Although Song has made great improvements in recent years, the production speed is still slow compared to other products such as stretched films. Since the quality of the film is mainly determined by the optical characteristics and the number of condensed particles, it is necessary to reduce the speed and improve the quality in order to obtain better benefits. If the speed is increased, the cooling time will be shortened, and more air will be caught between the film and the cold casting roll, which conflicts with market expectations. To solve these problems, improved softening boxes and vacuum boxes have been developed. As a stopgap measure, some producers have begun to use wider production lines to increase capacity and reduce the proportion of scrap in total output. Nowadays, production lines that produce 4.0 to 4.5 meters wide CPP film main rolls are not uncommon. The industry has been committed to improving the design of the coiling machine in order to accurately control the coiling conditions and ensure that the coils meet the specifications. The main components of CPP extrusion line include: -Hybrid system Material and film properties The development of new materials will continue to affect the CPP market and promote market growth. Highlighted trends include: 1. Development of new PP grades. Exxon revealed that compared to the traditional Ziegler-Natta grade, when metallocene-based PP is used, it is easier to draw during high-speed processing. CPP film can also be produced through various combinations, generally adopt the following structure: Layer A: CoPP (random copolymer PP) Different materials (random copolymer PP or homopolymer PP) can be used 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. Metalized films are required to have excellent optical properties. For a 20-micron (1 mil) 3-layer coextruded film, the haze value cannot exceed 2%. For laminated films and cooking films, the haze values ​​are 2.5% and 5%, respectively, but it is required to have double the sealing strength. For twisted films used in candy packaging, the most important characteristics are dead folds and twist retention or memory. For other purposes such as IV solution bags, a 3-layer structure can be used, and one of the surface layers should be of high crystalline grade to ensure heat resistance and moisture barrier; the core layer can be made of soft grade PP, and the other surface can be made of high Random random copolymer PP. The new PP grades and technologies have opened up broad application fields for the industry, and even replaced other traditional materials. (Battenfield Gloucester Engineering Co., Ltd.) GlazeKing Ceramics TechnologyCo.,Ltd. , http://www.maglazekingceramics.com
The main characteristics of CPP film include:
-Higher stiffness than PE film.
-Excellent barrier to moisture and odor.
-Multi-function, can be used as composite base film.
-It can be metallized.
-As a food and commodity packaging and outer packaging, it has an excellent demonstration, so that the product can still be clearly seen under the packaging.
Market size
-Co-extrusion structure is widely used in application fields with higher requirements;
-Improvement of sealing characteristics;
-Processing problems such as fouling can be solved;
-Increased production efficiency in areas such as film production, auxiliary operations, and end use;
-Enhanced metal adhesion;
-PP increases market share in non-traditional markets such as desserts, salads, frozen food can lids, fruit pulps, snacks, candy pouches, peeling structures, and twisted films;
-As a low-cost alternative to bread, biscuits, pasta products, snacks, and other less demanding packaging fields, it replaces BOPP film.
Processing equipment trends
-Extruder (usually 3 sets)
-Feeding head and automatic die head
-Softening-vacuum dual-use box
-Casting device
-Nucleometer
-Processing station
-Coiler
-recycling system
-Integrated control system
2. Adopt new catalytic technology 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 companies such as Exxon and Dow, has excellent processability, high definition, excellent stiffness, excellent sealing performance, low extractables content and low volatile content.
Layer B: Homopolymer PP
Layer C: CoPP (low sealing initiation temperature, slip agent and anti-blocking additive)