PVA coated high barrier film
PVA-coated high barrier film is made by coating nano-inorganic PVA on polyethylene film and printing, which solves the technical bottleneck of poor barrier performance of three-layer polyethylene film at present without greatly increasing the cost. In 2008, after three years' efforts and independent innovation, the researchers of Cangzhou Jinlong Plastic Co., Ltd. finally took the lead in bringing the product with national patent-PVA coated high barrier milk film to the market. Its oxygen barrier rate is less than 2cm3/(m2.24h.0. 1mpa), and its barrier performance is not only obviously better than that of EVOH five-layer extruded film, but also the packaging cost is greatly reduced, which not only ensures all the quality requirements of packaged products for aseptic packaging, but also greatly reduces the cost of aseptic packaging in food processing enterprises, and solves the technical bottleneck of poor barrier performance of the current three-layer polyethylene extruded film.
PVDC (polyvinylidene chloride)
PVDC resin is often used as composite material or monomer material and extruded film sheet, and it is the most widely used high barrier packaging material, in which the amount of PVDC coating film is very large. PVDC coating is based on polypropylene (OPP), polyethylene terephthalate (PET) and so on. Due to the high softening temperature of pure PVDC, close to its decomposition temperature, poor compatibility with general plasticizers, it is difficult to thermoform and directly apply. The actual PVDC films are mostly polymers of vinylidene chloride (VDC) and vinyl chloride (VC), and films made of methyl acrylate (HA) with excellent barrier properties.
PVDC (polyvinylidene chloride) is characterized by low permeability, barrier property and chemical resistance. China PVDC was developed with the introduction of sausage processing technology.
In 2002, the domestic output of PVDC was about 20,000 tons. At present, it has been widely used in moisture-proof packaging of food, cigarettes, beverages and chemical, pharmaceutical, electronic, military and other industries.
Single-layer PVDC film is formed by bi-directional stretch blow molding, which has shrinkage, barrier and water resistance, does not decompose under microwave heating, and is widely used as household fresh-keeping film. Multi-layer extrusion of PVDC with synthetic resins such as polyethylene (PE), polypropylene (PP) and polystyrene (HIPS) is used for vacuum dairy products, jam and other packaging, which has good tensile properties and is suitable for large-capacity packaging. The composite sheet of PVDC, polyethylene and polyvinyl chloride (PVC) is suitable for the packaging of hygroscopic and volatile drugs. At present, many domestic scientific research units and manufacturers focus on the composite membrane technology of PVDC and other resins and the high temperature resistance technology of the composite membrane.
PVDC is used in various substrates, such as polyethylene, polypropylene, polyvinyl chloride, polyamide (PA), polyethylene terephthalate (PET) and so on. Taking biaxially oriented polypropylene as an example, after coating, the oxygen permeability decreased by 1000 times and the water permeability decreased by 3 times. The coating can be single-layer or multi-layer. Generally, a single layer coating of 2.5μm can play a good barrier effect.
Ethylene/vinyl alcohol * * * polymer
EVOH has always been the most widely used high barrier material. The film types of this material are not only inextensible, but also biaxial stretching, aluminum evaporation, gluing and so on. In biaxial stretching, there is heat-resistant stretching for aseptic packaging products.
The barrier performance of EVOH depends on the ethylene content. Generally speaking, when the ethylene content increases, the gas barrier property decreases, but it is easy to process.
EVOH is characterized by excellent gas barrier and machinability, as well as excellent transparency, luster, mechanical strength, flexibility, wear resistance, cold resistance and surface strength.
In the field of packaging, EVOH is made into the middle barrier layer of composite film, which is used for all hard packaging and soft packaging; Used for aseptic packaging, hot pot and retort pouch in food industry, packaging dairy products, meat, canned fruit juice and condiments; In non-food fields, it is used for packaging solvents, chemicals, air-conditioning structural parts, gasoline tank linings, electronic components, etc. In food packaging, EVOH plastic containers can completely replace glass and metal containers. Many domestic aquatic products companies use PE/EVOH/PA/RVOH/PE five-layer extruded film to vacuum package seafood. While accelerating the research of EVOH composite film, the tensile orientation of EVOH is also being studied abroad. The gas barrier performance of the new EVOH membrane is three times that of the existing high-performance non-stretch EVOH membrane. In addition, EVOH can also be used as a barrier material to be coated on other synthetic resin packaging materials to enhance the barrier performance.
Nylon packaging material
Nylon packaging material has always used "nylon 6". However, the air tightness of "nylon 6" is not ideal. There is a kind of nylon (MKD6) condensed from m-dimethylamine and adipic acid, which is 0/0 times more airtight than "Nylon 6" and has good transparency and puncture resistance. Mainly used for high barrier packaging film and food soft packaging with high barrier requirements. Its food hygiene has also been approved by the FDA.
As a kind of film, its biggest feature is that its barrier performance will not decrease with the increase of humidity. In Europe, due to the outstanding environmental problems, as a substitute product of PVDC film, MXD6 nylon is widely used. A new biaxially oriented film composed of MXD6 nylon and EVOH is a kind of nylon film with high barrier property. The compounding method includes multilayer compounding, and mixing and stretching MXD6 nylon and EVOH***.
Inorganic oxide coating
The so-called coating made of SIOx (silicon oxide) on other substrates has attracted more and more attention from the market. In addition to silicon oxide coating, there is also aluminum oxide vapor deposition film. Its air tightness is the same as that of the silicon oxide coating obtained by the same method.
In recent years, multilayer composite, * * mixing, * * polymerization and evaporation technologies have developed rapidly. High barrier packaging materials such as ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC), polyamine (PA), polyethylene terephthalate (PET) and silicone vapor-deposited film have been further developed, among which the following products are more noticeable: MXD6 polyamide packaging materials; Silicon oxide evaporation film, etc.