Talking about the basic situation of composite flexible packaging
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Types of substrates for composite flexible packaging
Composite flexible packaging is easy to sell and use. Composite films, such as paper/plastic composite films, plastic/plastic composite films, aluminum/plastic composite films, etc., are made by compounding various substrates (mainly paper, plastic film, aluminum foil). The main position of these substrates is a plastic film.
Different substrates have different roles in the composite film, according to which the substrate can be divided into: base film. Mainly confers the basic packaging requirements of the composite film, such as certain mechanical strength, barrier properties, transparency, etc.; functional layer film, giving the composite film special functions, such as high barrier properties, gas selective transmission, etc.; heat sealing The adhesive layer film enables the composite film to be heat-sealed and bonded. Generally, the composite film is mostly divided and referred to by its base film, and a polypropylene composite film, a polyester composite film, a nylon composite film, and the like are added.
Almost all plastic films can be used as packaging materials, but for composite film substrates, they are mainly large-sized varieties such as polyethylene (PE), polypropylene (PP), polyester (PET), and nylon ( PA-6, PA-66), etc., as well as a variety of functions (barrier properties, etc.), such as polyvinylidene chloride copolymer (PVDC). Ethylene and ethylene acid copolymer (EVOH), ionomers, and the like. These substrates (plastic film) can be divided into calendered film, blown film, cast film (CPE, CPP), biaxially stretched film (BOPP, BOPET, BOPA), co-extruded composite film, etc. according to the forming process; The barrier properties are classified into very high barrier properties (such as PVDC, EVOH), excellent barrier properties (such as BOPA, BOPET, acrylonitrile copolymer), and general barrier properties (such as CPE, CPP, BOPP).
Physical properties of composite flexible packaging substrates and their applications
Which kinds of substrates are used to form a composite film for composite flexible packaging depends on the nature, state and packaging requirements of the packaged product. As far as we know, there are many types of goods or products that can be packaged in composite flexible packaging, such as beverages, juices and jams, oil stains, dried foods such as biscuits and dried vegetables, and powdered items such as tea and milk powder. Pharmaceutical products and supplies, meat products, hardware, etc., their traits and packaging requirements are different, some require preservation, some require preservation, some require transparency, some require higher strength, and so on. Therefore, a thorough understanding of the basic physical properties of the substrate must be made.
For the physical properties of the substrate, please refer to the Handbook of Packaging Materials and Containers published by Guangdong Science and Technology Press. Regarding the composition and packaging application of the composite film, in the "Packaging Materials and Container Handbook", pp. 258-261, the composition and packaging application of the BOPP composite film, the BOPET composite film and the BOPA composite film are provided in more detail.
In addition to the packaging requirements, the processability and economy (packaging cost) of the substrate must also be considered. The following is an example. Dry food packaging such as instant noodles and biscuits, outer packaging of audio tapes, video tapes, cigarettes, etc., small packages such as candy, because of the requirements of moisture-proof, anti-fouling, tightening, etc., and the packaging cost is low, the price is low. A biaxially oriented polypropylene film (BOPP) is suitable for a composite film of a base film. In addition to a lower price, BOPP is more important in that the water vapor transmission rate is low.
Tea, coffee, milk powder, etc., require moisture protection and sufficient fragrance. Therefore, it is more appropriate to use a BOPET-based composite film with good gas barrier properties and high fragrance. If higher barrier properties and resistance are required. For UV, a layer of aluminum foil or a vacuum evaporated aluminum film is required.
Meat products, such as sausage, ham, etc., require preservation, antiseptic and certain moisturizing. The composite film with nylon film as the base film is a suitable soft packaging material because the nylon film has good oxygen barrier property and large water. Gas transmission rate.
The packaging of liquids such as beverages, juices, oil stains and shampoos requires packaging to be resistant to extrusion, so substrates with good strength, such as BOPET, BOPA, etc., should be used. In addition, packaging for foods such as beverages and juices is required to be fresh. , anti-corrosion, etc., so we must also consider the barrier properties of the substrate, BOPET, BOPA can meet the requirements.
For the packaging of foods or articles that have been cooked, a base film with good strength, such as BOPET, BOPA, and a heat-sealing adhesive film with good heat-bonding strength and resistance to cooking, such as cast polypropylene film (CPP), should be selected. ), cast polyethylene film (CPE). Of course, the composite film made of them can be further made into a retort package after being cooked, and it depends on the type of adhesive (currently using polyurethane adhesive) and quality, as well as the technical level of the manufacturing process.
Development of new composite substrates for flexible packaging
The development of the new substrate includes two aspects: a film of a new plastic variety and a new film developed by modification of the existing composite flexible packaging substrate. New plastic film is expected to be used in composite flexible packaging substrates, including polycarbonate (PC), poly(ethylene-2,6-naphthalate) (PEN), poly-4-methyl-l-pentene (TPX) and so on. PC film has been produced by casting method in China; the thickness can be 20μm. The TPX film is resistant to boiling water cooking and non-toxic. The most important feature is that it has a large difference in the transmission rate between nitrogen and oxygen. It is especially suitable for the packaging of meat and vegetables. It has high heat resistance and can be used in cooking bags.
The new substrate developed by modification has an isophthalic acid modified polyester film, and the barrier property of the film is improved compared with the unmodified one; there are new film varieties developed by blending or additive technology, such as high transparency. Polyester film and polypropylene film, matt and white polypropylene film.
In addition, the development of new substrates using new post-processing techniques has yielded new results in recent years, such as vacuum evaporation of silica on BOPET films to improve barrier properties, or the addition of a small amount of titanium during vacuum evaporation of aluminum to improve evaporation. The appearance and packaging effect of the aluminum film.