Metal materials are one of the earliest traditional materials discovered and used by humans. In China and some developing countries, metal materials still dominate the material industry. Metal materials are one of the four major
Packaging materials. The main types of materials are steel, aluminum, and molding materials are thin plates and metal foils. With the development of modern metal container molding technology and metal plating technology, the development and application of green
Metal Packaging materials has become a development trend.
Performance Characteristics and Application of Metal Packaging Materials
Although the amount of metal materials in the packaging materials is not large, but because of its excellent overall performance, and rich resources, so the metal still maintains a strong vitality in the packaging field. Especially in the field of composite packaging materials found a place to use, to become the main barrier material layer in composite materials, such as the aluminum foil as the base material of the composite material and the successful application of metal composite film is a good proof. In general, metal packaging materials have the following characteristics:
1, metal materials, good ductility, easy processing, easy molding, molding effect is good. Mature processing technology, continuous, automated production and other characteristics. Such as the sheet can be stamping, rolling, stretching, welding made of different shapes and sizes of packaging containers; foil can be combined with plastics, paper, etc.; metal aluminum, gold, silver, chromium, titanium, etc. can also be plated in plastic film And on paper.
2, metal materials have excellent comprehensive protection performance and barrier properties. High metal strength, excellent mechanical properties, good barrier properties to light, gas and water, moisture resistance, fragrance protection, heat resistance, cold resistance, grease resistance and other properties greatly exceed the plastic, paper and other types of packaging materials, Can effectively protect the contents of the long-term, suitable for a variety of packaging requirements.
3, metal materials have a good decorating performance. The smooth and bright surface of metal materials, easy to print, has a good decorating performance, can improve the aesthetics and grade of the packaged objects. In addition, a variety of metal foils and metallized films are highly desirable brand materials.
4, metal materials easy to recycle and recycling, and conducive to lightweight design. The sources of metal packaging materials are abundant, and it is easy to promote lightweight design on the packaging so as to save materials and improve efficiency.
5, although the metal packaging materials have the above characteristics, but there are also deficiencies. The main reason is that the chemical stability is poor, and the corrosion resistance is not as good as that of plastics and glass. In particular, steel packaging materials are prone to corrosion. Therefore, metal packaging materials need to be covered with a layer of anti-corrosive substances, in order to prevent the contamination of goods by harmful substances from the outside world and the objects to be packaged.
6, the application of metal packaging materials. At present, the molding materials in metal packaging materials are mainly thin plates and aluminum foils. The former is a rigid material, such as transport packaging steel, tin plated steel plate, chrome plated steel plate, galvanized steel plate, usually directly to the barrel, cans; the latter is a flexible material, such as aluminum foil and aluminized film, generally taken The vacuum evaporation method is coated with a metal film on other materials to improve the barrier protection function of the package. Metal packaging used for transport packaging large containers, cans, barrels, containers, such as industrial product packaging containers, semi-finished food products in food powder, dairy products, oils and fats and chemical raw materials in liquid and solid material packaging; in sales The packaging is mainly applied to the packaging of sprays for foods, beverages, oils and some cosmetics, such as cans in beverages, cans in food and daily necessities, aluminum tube bags, metal platters, metal hoses, etc. Metal sealed containers and caps, liner bags, etc.
Environmental Performance Evaluation of Metal Packaging Materials
The metal packaging material is an excellent recyclable material, its easy recovery and excellent recyclability make the metal a kind of green packaging material with low environmental load. For example, metal packaging waste can be refurbished, recycled, recycled, or re-melted and cast into new aluminum or steel products. Therefore, as long as an effective recycling system is established, its waste will not cause pollution to the environment. These advantages stem from several special properties of the metal itself.
1, metal reusability. Metals have high physical properties and stability. They have little loss during use and the protective performance of the packaging is not affected. Therefore, they can be recycled and used repeatedly.
2, the remelting of metal. The metal material is composed of metal atoms. Even if it is heated, melted, or deformed, the metal will be in an atomic state and the quality will not change. That is, the scrap metal has remeltability. The physical and mechanical characteristics of scrap metal are basically the same as or similar to metal, and can be changed in physical form to reproduce the use value. In theory, scrap
Metal Can be recycled indefinitely, which is incomparable to other resources.
3, metal variability. In practical applications, metal materials go through various manufacturing processes not only as prototypes, but also as processing to improve metal properties. For recycling, various kinds of processing can be made into two types: processing processes that do not impair recycling recyclability, such as melting, solidification, and heat treatment; and processing that impairs recycling reproducibility, such as alloying, compounding, and the like.
4, metal binding energy. Since the metal binding energy after separation and extraction from oxides, sulfides, and other ores is low, that is, the ratio of metal remelting energy to metal extraction energy is particularly low, in this sense, the reused metal is called “energy carrying resource”. At the same time, this feature is undoubtedly conducive to recycling.
5. The comprehensive utilization of resources is good. Compared with other renewable resources, the amount of metal renewable resources generated is large, which has significant advantages for saving resources, reducing environmental pollution, reducing construction capital investment, and improving economic efficiency.
Therefore, in terms of the properties of the metal material itself, it is a kind of high-performance packaging material with perpetual reproducibility, and the use of the metal package has a relatively low environmental load. At present, aluminum foils and aluminum foils have become a better development direction for pre-barrier flexible packaging (such as
Food Packaging) because aluminum foil is easily recycled.
Ecological design of metal packaging materials
However, from the entire life cycle process, from mining, smelting, rolling steel (aluminum) panels, to making packaging, use, and disposal, metal packaging consumes a lot of resources and energy, especially for the environment. It will cause pollution. Therefore, we must vigorously promote clean production, improve backward production processes, and promote scientific production management so that the production of metal materials will minimize harm to the human body and the environment and pollution.
The ecological design of metal packaging is based on the environmental coordination of packaging materials and the reduction of environmental load at the design stage, on material resources (resource capacity), material composition, technology, structure and performance, recycling, ecological balance (environmental capacity), etc. Comprehensive considerations in all aspects will make the production of materials conducive to reducing the environmental load and facilitate the recycling of waste. It is not only difficult to post-process but also has high benefits. The current direction of ecological design of metal packaging materials is to pursue functional, safety, economical, and low environmental load. The most economical way for metal packaging materials to save resources and energy and reduce environmental load is the recyclability of materials and lightweight packaging. Therefore, the focus of the current study is to look at cyclic metal components and organizational design, packaging-specific material design, lightweight packaging and structural rationalization of the design and production of clean design.
1, recycled metal components and tissue design. The requirements for a highly recyclable metal design are that elements that are difficult to remove during recycling are not used; depleted elements are not used as much as possible; no toxic elements are used; and production methods that are difficult to separate during the recycling process are not used.
In order to satisfy the high performance, metal materials are realized by adding alloying elements and controlling the microstructures such as crystallization. However, after the metal is discarded and remelted after being discarded, it is generally difficult to remove the alloy elements and impurities, thereby reducing the recyclability. The current methods used in the recycling design are the high purity of metals and the easy addition of alloys to remove elements and the harmlessness of impurities. The ideal state for metal materials that can be recycled and recycled is high purity and “single composition”, but considering the practicability and economy of materials, it is generally required to minimize the addition of alloying elements, and the basic alloy system that can be recycled and recycled should be composed of pure metal as much as possible. Analogously, the easy addition of the alloy added element is the kind and the allowable amount of the second element that is required to be added without hindering the regeneration, the third element requires the addition of the minimum amount, and it is required that the added elements are not depleting elements and toxic elements. "Compositional singulation" means that if a composite material is used to strengthen and toughen the material, the single-composite material should also be used to make the process simpler during recycling, thereby reducing the environmental burden during the cycle.
In addition to alloy composition design, the methods used in the recyclable design process of metallic materials include methods for controlling metal structure and optimizing microstructure. The first method is to use a recyclable alloy method. It is a complex structure of soft phase and hard phase that is balanced by controlling the metallographic composition, that is, by controlling the rolling, heat treatment, and two-phase precipitation heat treatment techniques, and becomes an element that the metal does not inhibit the regeneration, and the electric furnace Remelting is possible without recycling back to the furnace. In addition to metal transformation hardening, crystal refinement and strengthening are all important means to ensure the material properties and make the material recyclable.
2, metal packaging special material design. Packing-specific material design is mainly aimed at packaging steel materials. Since tinplates used in the country mostly have no distinction in use, the quality of the steel cans and other containers often become unstable. The quality of metal packaging products and the problem of defective and defective products are largely related to the standard. At present, Europe has developed and produced special tinplates for packaging and put them into the market, so that the scope of application is more definite and specific, and the pertinence is strong. This has greatly promoted the stability of metal packaging quality and the rational allocation of metal materials in the entire society.
Developed countries such as Europe and the United States not only develop special tinplates, but also tailor-made steel plate materials for steel drums. This makes the material thickness, carbon content, hardness, and galvanized layer thickness more in line with the needs of the barrel making and canning industries. Can not be too high, suitable for
Packaging Can be made, the material size is determined according to need, corner scrap is almost zero, so that the quality of steel drums and other metal packaging, costs are the best, also consistent with the principle of appropriate packaging and packaging reduction .
3. Lightweight and structurally rational design of metal packaging containers. The purpose of this design is to make the thickness of the metal packaging material comply with the green packaging requirements, remove the redundant structure of the packaging and make the packaging structure meet the convenience of use and facilitate the recycling process. There are two ways: First, thinning materials. For example, China has been using 200mm steel drums made of 1.5mm~1.2mm thick steel sheets, so that steel drums can be reused many times. However, due to the need to refurbish old drums for cleaning and paint stripping prior to each use, a large amount of toxic and hazardous liquids and gases are discharged and the environment is polluted. Some foreign developed countries have taken the lead in adopting 0.8mm~1.0mm ultra-thin steel plates to produce 200 liters of steel drums. They are directly recycled and reused after use. They are not allowed to be used again. This eliminates environmental pollution, contributes to lightweight packaging, and reduces packaging. cost. The second is to improve and improve the structural design. For example, the closed steel drum structure has the problem of residue in the user's use, which not only results in a huge waste of contents, but also may cause pollution to the environment; steel drums with residues will also be used for recycling. Cause trouble, if refurbished, cleaning the steel barrel will bring more pollution. Some developed countries started to improve the structure of steel drums based on environmental protection, and developed several structures that do not leave residues, such as grooved drainage structures and streamlined dome-type steel bucket structures without leaving residues.
4, metal packaging materials clean production design. The clean production of metal packaging materials is to make the metal material processing process consume less resources and energy as much as possible, emit less waste, and be easy to recycle after being discarded. The clean production of metal materials, especially the major innovations in the process flow, is of great importance in reducing the environmental load of material production. Specifically, it should include the application of new technologies for production processes, waste management in production processes, and comprehensive treatment of wastes, etc., mainly to reduce the energy consumption per ton of steel, reduce the steel ratio, protect the environment, and save resources.
