Study on CPP of the hottest polypropylene salivati

2022-09-19
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Research on polypropylene drooling film (CPP) II

2. Domestic casting production lines have begun to appear

with the development of CPP product market, domestic plastic processing machinery manufacturers began to aim at the broad demand market of CPP production line. Accessories: 40X40X10mm clamp for stretching, m8x connection Φ The salivation production line was launched with 5 pieces ≥ 50mm in length. Due to the difference in the mastery of CPP casting technology and theory, and the limitation of capital and machining level, the quality of the production film fluctuated greatly, and the stability of the production line was relatively poor. At present, the existing problems are as follows:

(1) solve the waste edge recycling problem of salivation line

from an economic point of view, the scrap of salivary film needs to be recycled, but simply crushing the scrap back to the central layer through a full set of product design and development, due to the change of feed density, it is easy to cause the extruder to work unstable, which may affect the thickness of the film or the normal film formation. If the scrap is re granulated or added in proportion, it will not only increase the operation intensity, but also easily produce film crystal points due to pollution

(2) strengthen the research on the salivation processing technology of polypropylene, master the influence of polypropylene melting, coextrusion flow process, film-forming process and processing temperature on PP crystallization, and reasonably design the extruder, coextrusion die head and salivation quenching area, especially in the process of forming but some special steel can only be supplied from overseas or the United States, through the die head, electrostatic blank holder, pneumatic edge holder, air knife, air box The reasonable design of vacuum box can produce high-quality salivary film

(3) improve the automation of the production line, especially the need to increase the automatic adjustment system of film thickness to ensure the stability of film thickness; The reasonable design of the drag point of the production line, try to reduce the tension shape of the film and improve the flatness of the film; To improve the winding quality of the winding machine, it is necessary not only to ensure that the winding can be changed normally during high-speed production, but also to automatically adjust the winding tension in the set mode

although the current domestic CPP casting production line has a total production capacity of only 20000 ~ 30000 tons, with the continuous improvement of domestic casting equipment, which can only meet common national standards with more software on the market, it will have a far-reaching impact on China's CPP film processing industry

1.3 production of special materials for casting film in China:

in recent years, with the strengthening of the consumer market, the application field of CPP has been expanding and the development speed is fast. However, the special materials for salivation film are more dependent on imported materials than BOPP film materials and iPP film materials, and the annual import volume accounts for about 60% of the total usage. The varieties of CPP special materials in China are relatively single. The producers include Shanghai Petrochemical Co., Ltd., Beijing Yanshan Petrochemical Company and PetroChina Daqing Petrochemical Company. The production varieties are homopolymer polypropylene, binary random copolymer polypropylene and ternary copolymer polypropylene. The specific brands are f800e (binary random copolymer polypropylene), f800eps (ternary copolymer polypropylene), f800df (binary random copolymer polypropylene, fc801 (homopolymer polypropylene) Fc801m (homopolymer polypropylene for aluminum plating), c1608 (homopolymer polypropylene), c4608 (binary random copolymer polypropylene), X37F (homopolymer polypropylene), etc., can be applied to the core layer of ordinary composite film, semi digested film and aluminum plating film. However, PP resin for aluminum coating, PP resin for high-temperature cooking film and some polypropylene raw materials with special properties still need to be imported

2. Production varieties of salivary film in China:

at present, three-layer coextrusion salivary line is the main equipment for CPP production in China. The structure of three-layer coextrusion salivary film can generally be divided into three layers: heat sealing layer, core layer and corona layer. The range of material selection is wider than that of single-layer film. Materials that meet the requirements of each layer can be selected separately to endow the film with different properties and uses. Among them, the heat sealing layer should be heat sealed, which requires low heat sealing temperature and good openness of the material; The core material determines the mechanical properties of the film; After surface treatment (mainly corona treatment), the corona layer has appropriate surface tension for printing, compounding or metallization. The material of this layer has certain requirements for the addition of additives, with the surface wetting tension of the film. With the increasing market demand, casting film products are also being updated day by day. CPP varieties that have been produced in China are:

(1) vacuum aluminizing film

CPP film has good performance of blocking water vapor transmission, but poor performance of blocking oxygen transmission. After high vacuum aluminizing, the oxygen resistance of the film has also been greatly improved. The aluminized products have excellent shading, decoration, barrier and other unique properties, and have good adaptability in post-processing such as printing and compounding, and can meet the use requirements of heat resistance, chemical resistance, wear resistance, oxygen resistance, high barrier and so on. The different materials selected for the aluminum coating have a great impact on the fastness and gloss of the aluminum coating. The peel strength of ordinary VMCPP and BOPP after extrusion is less than 0.3n/15mm, and the peel strength of high-strength vacuum aluminum coating film after aluminum coating and BOPP after extrusion is greater than 0.5N/15mm

(2) ordinary composite film

can be directly dry compounded with BOPET film, BOPP film, etc. for packaging fast food and tea, etc. According to the different heat sealing temperature, it can be divided into ordinary heat sealing film (heat sealing temperature 135 ℃), low-temperature heat sealing film (heat sealing temperature 120 ~ 130 ℃) and ultra-low temperature heat sealing film (heat sealing temperature lower than 120 ℃). By selecting different heat sealing layer materials, the heat sealing temperature of CPP can be reduced to below 90 ℃

(3) cooking film

is compounded with barrier films such as PA, aluminum foil, etc. it is used to package products that need high-temperature cooking and disinfection, usually foods containing oil or soup. Semi cooking film (SCP) can withstand 121 ℃ for 40 minutes, and high temperature cooking film (RCP) can withstand sterilization above 135 ℃

(4) film for packaging

CPP film for packaging can be used separately for the outer packaging of food, clothing, sanitary napkins, flowers, etc. after printing and bag making. According to needs, the film has high transparency, antistatic and customer specified friction coefficient

(5) films with other special properties:

① CPP matting film

the surface gloss of CPP matting film is ≤ 10%, which has the surface optical effect of frosted glass. After printing, the color is saturated, the hand feeling is comfortable, and the appearance is elegant. It can be used for heat sealing or compounding. It is suitable for packaging high-grade sanitary napkins and food

② highly transparent super flexible film

by using coextrusion and blending technology, metallocene polyethylene is introduced into CPP film, so that cast polypropylene film has high transparency, high impact resistance, extremely soft handle, excellent puncture resistance and low temperature resistance. It is suitable for the packaging of high-grade clothes, T-shirts and underwear, and can also be used for other heavy packaging

③ CPP solvent resistant barrier film

using the solvent resistance of polyolefin materials, special barrier packaging design is adopted, so that the flexible packaging is applied to the packaging of pesticides such as emulsifiable concentrates. The usual flexible packaging structure is CPP//Al//BOPET and CPP//Pet aluminized//BOPET

④ CPP antistatic film

CPP antistatic film can be divided into hygroscopic antistatic film and permanent antistatic film

hygroscopic antistatic agents are usually added with precipitation type antistatic agents. Their antistatic properties are greatly affected by air humidity. This product can reduce the static electricity generated in the packaging process

the permanent antistatic film uses the permanent antistatic agent and adopts the methods of coextrusion, blending, coating or evaporation to make the CPP film have permanent antistatic properties. Under vacuum conditions, the surface resistivity is less than 1010 Ω/mouth to prevent electrostatic products, which can be suitable for the packaging of various electronic components

⑤ CPP kink film

pvc kink film has been widely used in kink packaging of candy, chocolate and other food and decorative products. Due to the safety problems of PVC film packaging, it is only a matter of time for non-toxic CPP kink film to replace PVC kink film. According to varieties, CPP kink film can be divided into heat sealing type, aluminum plating type and printing type

⑥ CPP extruded film

LDPE can be directly used for extrusion compounding with other film materials, which not only ensures the fastness of extrusion compounding, but also reduces the cost of extrusion compounding

at present, CPP's new product development mainly focuses on ultra-low temperature heat sealing film, cold resistant film, high temperature cooking film, etc. Some special-purpose films such as synthetic paper, antibacterial film, microporous breathable film and biodegradable film are also in the process of development and application. (to be continued)

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