Application of packaging materials for the hottest

2022-08-12
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Application of fast food packaging materials II

4. Full plastic barrier composite packaging materials

(1) high barrier full plastic composite packaging materials

industrialized high barrier full plastic composite packaging materials. The commonly used barrier resins are polyvinylidene chloride (PVDC), ethylene vinyl alcohol copolymer (EVOH), aromatic nylon MXD6, etc. They can not only produce packaging materials with good transparency and high barrier, but also their thermoplastic properties can be co extruded. With the extensive use of modern computer and communication technology, the required composite packaging materials can be directly produced from plastic pellets, and cleaner production can be implemented. Because of their thermoformability, they can be deep drawn and processed into containers of the desired shape

polyvinylidene chloride is a variety with outstanding advantages and disadvantages. It is the only polymer commonly used in the packaging field that has a high barrier to oxygen and water vapor at the same time. Although its molding performance is worse than that of ordinary general thermoplastic, under specific molding conditions, it can not only produce single-layer flat film and pipe film, but also produce multi-layer coextrusion composite film by coextrusion method, but also by lotion (or solution) coating method, with relatively low cost Polyvinylidene chloride coating containing high barrier packaging materials, therefore, polyvinylidene chloride has been regarded as one of the most promising barrier packaging materials. However, the environmental adaptability and thermal stability of PVDC are very poor, and the waste packaging can not be recycled through melting granulation. And it is not easy to decompose, and will not be absorbed by nature and return to nature; During incineration, toxic and harmful substances such as hydrogen chloride and dioxin will be produced. Although through people's efforts, the tail gas absorption incinerator can effectively treat the hydrogen chloride generated during its incineration, so far, no effective treatment method has been found for the strong carcinogen dioxin, so people have questioned the use of polyvinylidene chloride packaging materials. If there is no major breakthrough in the disposal technology of packaging waste, the application prospect of polyvinylidene chloride in packaging is not optimistic

ethylene vinyl alcohol copolymer has the same high oxygen resistance as polyvinylidene chloride. Although its ability to block water vapor is poor, it can be compounded with polyolefins such as polyethylene to produce composite materials with high water vapor barrier. Its molding performance is very excellent. It can be processed and molded by conventional thermoplastic processing technology and equipment, and has excellent environmental adaptability. It can be recycled by melting granulation, and heat energy can be recovered by incineration. During incineration, only carbon dioxide and water are produced without any substances harmful to human health and the natural environment. However, due to its high price, its application is greatly limited. Although the progress of coextrusion process and equipment in recent years has reduced the barrier layer in the composite to 5%-15% of the total thickness, creating better conditions for the promotion and application of ethylene vinyl alcohol copolymer packaging materials, it is still limited to those occasions with high added value and other packaging materials are not competent. The large-scale application of vinyl alcohol ethylene copolymer still needs a substantial reduction in its cost

the oxygen resistance of aromatic nylon MXD6 under standard conditions is slightly lower than that of ethylene vinyl alcohol copolymer, but after cooking treatment, the time required to restore the original high oxygen resistance is much shorter than that of ethylene vinyl alcohol copolymer. At the same time, it also has good molding processing and environmental adaptability, so it is recommended for food packaging requiring cooking processing. At present, the main obstacle to its application is also the cost

(2) barrier all plastic composite packaging material

it is expected to bring huge market value. At the end of 2014, barrier all plastic composite packaging materials, which are widely used at present, are composites with polyester (PET) and nylon (PA6) as barrier layers. Although they have only medium oxygen resistance, and the oxygen permeability is about 100cm3/(m2.24h. O.1mpa), they can meet the needs of many food packaging. They all have good adaptability to environmental protection, and have a major advantage of low cost compared with the above high barrier materials. Therefore, they have strong market competitiveness and are widely used

polyester, polyethylene terephthalate, is mainly used in plastic flexible packaging materials, which are various composite flexible packaging materials based on biaxially stretched films. In addition to barrier property, polyester film also provides good mechanical strength. Biaxial tensile film has high strength and can be made very thin, so the mass per unit area is very small. At the same time, in recent years, the price of polyester resin has decreased significantly. Polyester pressure resistant blasting experimental machine is mainly used for pressure resistant and blasting of heat exchange equipment such as heaters, coolers, evaporators, condensers, etc. the cost per unit area of polyester film is relatively low. The flexible packaging material with polyester film as the barrier layer has become one of the preferred substrates for barrier composite packaging materials, which is widely used

traditional PET film does not have heat sealing performance. When bag making is required, a layer of heat sealing material must be processed and compounded in advance. The process is complex, which will not only increase the production cost, but also reduce some characteristics, such as transparency. In order to overcome the defect that PET film cannot be heat sealed, foreign countries have developed a new multi-layer co extrusion biaxial tensile pet product with heat sealing property

nylon is polyamine, which is also a medium and good barrier plastic packaging material. Its barrier property is equivalent to that of pet. The permeability of non stretched PA film is slightly greater than that of PET film, while that of stretched PA film is lower than that of PET film. Nylon film has two obvious characteristics. One is its outstanding puncture resistance, so it is especially suitable for vacuum packaging of food with bone; The second is that nylon is easy to absorb moisture, and the barrier performance can be significantly reduced after being affected by moisture. Therefore, for commodities with high barrier requirements for packaging materials, polyolefin resin should be compounded on both sides of the nylon layer for protection

using multi-layer coextrusion technology has become an effective means to improve the barrier property of nylon composite film. In order to improve the barrier property of CO extruded composite film, it has been increased from the original layer to more than 7 layers. When the multi-layer coextrusion film is equipped with a moving beam, it will stop automatically; When there are more than two barrier layers, it can avoid the decline of barrier performance caused by the dislocation of defects in the production process. When nylon and EVOH are used together, the effect is more obvious

generally speaking, the use of high barrier packaging materials for processed food helps to extend the shelf life of food, so people pay great attention to high barrier packaging. However, it must be pointed out that the shelf life of food depends not only on the barrier of packaging materials, but also on many factors such as the formula composition of food, food production and processing technology, and the sanitary conditions of production sites. Generally, the market price of high barrier packaging materials is significantly higher than that of ordinary barrier and low barrier packaging materials. It is not advisable to unilaterally pursue the high barrier of packaging materials, which is also the reason why high, medium and low barrier packaging materials can coexist

III. easy to open packaging materials

with the arrival of social aging, there is a tendency to reduce the peel strength of packaging and adopt easy to open packaging. Recently, in the process of diversification, there has also been a change in the past, which only pursued the easy unsealing performance of cover materials. In addition to cover materials, for example, the need for easy unsealing of bags has also increased, and there has been an easy unsealing face to face sealing. This kind of sealing surface can be unsealed by hand without the use of pliers and knives

the easy opening of convenience food is usually achieved through the application of easy opening film. The so-called easy to open film is a kind of film that can be heat sealed. After the film is heat sealed, the sealing has good sealing performance. During the storage and transportation of commodities, it can effectively prevent the leakage of contents and the pollution of contents by external substances, and has a reliable protection function for commodities; When the goods need to be taken out, the sealing part can be peeled off to take out the packaged goods conveniently

easy to open film generally adopts multi-layer composite structure, with at least main layer and heat sealing layer. The function of the main layer is to give the film rigidity, tensile and tear strength, and have a high melting point to facilitate sealing. The heat sealing layer, also known as the adhesive layer, provides reliable sealing and easy stripping. Obviously, the selection of heat sealing layer is crucial to the performance of easy to open film. The material of heat sealing layer can be special adhesive or special formula. When the requirements are not high, general resin of specific brand can also be used

for example, the adhesion of special functional polymers depends on the micro dispersion of non adhesive resin (differential dispersion occurs at the interface through the action of heat and pressure during heat sealing), and the micro control of the differential dispersion of non adhesive resin is used to control the sealing strength, so as to achieve the purpose of easy opening

easy to open packaging materials have been actually used in China. If the covering film of frozen small packaging basically adopts easy to open packaging materials, it is also used in bottled yogurt. But generally speaking, this kind of material with excellent performance is not widely used in China at present. The resin production enterprises have no special resin supply for easy unsealing, and completely rely on imported special resins. The varieties of easy opening materials that can be provided in China are single, which are basically limited to the cover materials for containers such as PS and pp. the varieties of easy opening packaging materials for face-to-face opened bags have not been industrialized yet, while in some industrial developed countries such as Japan, there are already serial products available. (to be continued)

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