I. Introduction to aluminum materials
Aluminum is a resource-rich white light metal, and aluminum production worldwide is second only to steel. Its application in the packaging industry ranks first among non-ferrous metals. Aluminum is used as a packaging material, and aluminum sheets, aluminum blocks and aluminum foils, and aluminized films are generally used. Aluminum sheets are usually used as canning materials or capping materials; aluminum blocks are used to make cans for extrusion forming and thinning and drawing; aluminum foils are generally used for moisture-proof inner packaging or composite materials and flexible packaging.
The packaging plates are all rust-proof aluminum alloys. Manganese and magnesium mainly play the role of improving material strength and improving processing properties; copper can also improve the strength of materials, and at the same time reduce the insolation performance and processing properties; add zinc, especially in When copper and magnesium are added in the same day, the heat treatment effect is better, but the corrosion resistance and workability are degraded; the addition of silicon mainly reduces the melting point of aluminum, improves the strength and melt activity, and lowers the coefficient of thermal expansion. Aluminum foil is made from a thickness of 0.4-4). A 7mm (more 0.5mm) industrial pure aluminum sheet is made of a flexible metal thinner that has been subjected to multiple cold rolling and thinning.
Experts believe that the new market share of aluminum materials will also make new progress with the promotion of so-called active packaging. Due to the application of new technologies for the development of aluminum products, the demand for aluminum materials will further expand in the future.
Second, the characteristics of aluminum materials
Compared to other packaging materials, aluminum materials have the following advantages:
(1) The density of aluminum is very small, 2.7 g/cm, which is only 35% of steel. This makes the container easy to achieve weight reduction. The surface of aluminum naturally produces a dense film of aluminum oxide, which prevents the oxidation from proceeding further.
(2) Aluminum is non-toxic and tasteless, and meets the hygienic standards for packaged foods.
(3) The aluminum surface has high gloss, is easy to color, and has good printing effect.
(4) The easy opening of the open cover made of aluminum is better than that of the tin plate.
(5) Aluminum has excellent reflection and conductivity properties for light and heat, and can improve the effect of food can heating sterilization and low temperature treatment.
(6) The mechanical properties of aluminum can be kept constant at low temperatures, and are especially suitable for the packaging of frozen foods.
(7) The composite film made of aluminum foil is completely airtight and opaque, and can effectively protect the food inside. Aluminum foil can also improve the strength of the aluminum-plastic composite film.
(8) Waste can be recycled and reused, which not only saves energy but also prevents pollution caused by waste and meets environmental protection requirements.
However, there are some shortcomings in aluminum materials, mainly including:
(1) The production of aluminum is much more energy-efficient than tinplate and TFS, so the price is expensive.
(2) Aluminum is a non-magnetic material, so the original equipment that uses magnetic suction materials must be modified.
(3) Aluminum materials have poor corrosion resistance and should not be used for foods that are acidic, alkaline, and salty.
(4) The aluminum material is soft, and has lower strength than tinplate. It is easily deformed and scratched by collision during manufacturing and transportation.
(5) Aluminum is difficult to weld, so it can only be manufactured by stamping or bonding.
Some of the shortcomings of aluminum can now be compensated by compounding with other materials. For example, aluminum foil combined with paper or plastic can increase its rigidity and tensile strength; to overcome the shortcoming of low rigidity of thin-walled aluminum can, a small amount of liquid nitrogen can be filled before closing the container, and the internal pressure generated by liquid nitrogen vaporization can be increased. The rigidity and compressive properties of the container; the aluminum foil coated with nitrocellulose and modified polyolefin not only improves the chemical properties of the aluminum foil, maintains a good printed appearance, but also provides heat to consistency.
Third, the application of aluminum materials in packaging
1 aluminum anti-theft cap
Most of China's current packaging of liquor, wine, medicinal liquor and beverages are still based on glass bottles. About 50% of the bottle caps are made of aluminum-made anti-theft caps. China's anti-theft caps will grow at a rate of 10% per year. By 2010, the amount of anti-theft caps will reach 15 billion, and about 60,000 tons of aluminum strips will be needed. There are nearly 200 aluminum cap production factories in China, with an annual design capacity of about 9 billion pieces, including 30 production lines with a production capacity of more than 5 billion pieces, which can produce nearly 100 kinds of bottle caps. Aluminum caps are often machined on highly automated lines, so the strength, elongation and dimensional deviation of the material are critical, otherwise cracks or creases can occur during deep drawing. In order to ensure the easy printing after the cap is formed, the surface of the cap plate is required to be flat, without rolling marks, scratches and stains. Generally, the alloy materials used are 8001-HI4, 3003-H16 and the like. The material specification generally has a thickness of 0.20~43.23mm, a tolerance of ±0.1%, and a width of 449-796mm. The production of aluminum bottle caps can be carried out by hot rolling or continuous casting and rolling, respectively, and cold rolling. Production practice shows that the hot rolled billet is superior to the cast billet in the use effect of the anti-theft cap.
2 aluminum plastic blister packaging
At present, health foods and pharmaceutical tablets and capsules are increasingly popular in the form of blister packs, which are also known as blister packs, referred to as PTP (PressThrough Packaging). The aluminum foil used in the blister packaging is a sealing material which is densely packed on a medicinal plastic polyvinyl chloride (PVC) rigid sheet, so it is also called a lid material. Almost all products requiring opaque or high-barrier composites in modern packaging use aluminum foil as a barrier layer. This is because aluminum foil has a highly dense metal crystal structure, which can completely block any gas, so it is widely used. It is expected that the packaging for pharmaceutical blister materials will account for 60%~70% of the tablets and capsules of future pharmaceuticals. It is one of the best pharmaceutical packaging materials for the current development prospects.
However, the quality of China's medicinal aluminum foil is far from the gap between imported aluminum foil. Judging from the actual situation reflected by several domestic enterprises producing PTP medicinal packaging, there are mainly two problems in the following aspects.
(1) The number of pinholes in medicinal aluminum foil is far below the requirement. Aluminum foil pinholes are defects in penetration performance, which affect the barrier properties of aluminum foils, especially for pharmaceutical packaging. It is easy to penetrate oxygen, water vapor and light to reduce the efficacy of drugs. In the national standard, the medicinal aluminum foil requires that the pinhole diameter is not more than 0.3 mm, and the diameter of 0.1 to 0.3 mm cannot be more than one/m2. At present, domestic aluminum foil rarely meets this standard.
(2) The thickness of the medicinal aluminum foil is uneven and the tensile strength is low. Due to the uneven thickness of the aluminum foil, it is easy to cause the coating amount of the adhesive in the mechanical coating process of the PTP aluminum foil to reach the standard coating amount range, thereby affecting the enthalpy strength of the aluminum foil and the polyvinyl chloride hard sheet. Due to the uneven thickness, the low tensile strength causes the foil to be broken after the tension is applied in the actual processing, which is not conducive to the normal production. These problems require the attention of the raw material manufacturers.
3 aluminum beverage cans
Currently. The development of aluminum beverage cans has three major features, namely, easy-open lids, special cans, self-heating/self-cooling beverage cans. For a long time, although metal packaging materials such as aluminum beverage cans have been challenged by tinplate and PET materials, due to their light weight and recyclable advantages, they are still one of the main forms of beverage packaging, which has not only been stably developed, but also It is also constantly developing and innovating.
Recently, the coin packaging company has successfully developed the EPOL (Easy Open Cover). The can lid is fused with a polymer-coated steel ring and a corrosion-resistant aluminum foil. It can be used in existing filling equipment. The aluminum foil cover can be opened safely and is suitable for the elderly and children. Due to the competition of PET bottles, the demand for aluminum cans for beverages in the Japanese market has gradually decreased in recent years. However, with the development of new aluminum cans, the demand for aluminum cans has started to rise again. At present, enterprises such as Wuzhong Stamping Industry, Dahe Can and Mitsubishi Materials have entered the production of aluminum cans, and aluminum can lids developed by the Chaiqi Manufacturing Plant have also been put on the market.
In order to complement the advantages of the two types of beverage packaging containers, PET bottles and aluminum cans, Japan Daiwa Can Co., Ltd. has taken the lead in the world to successfully develop new beverage packaging containers that can re-tighten metal cans. "New bottle metal cans (new bottles).
The new bottle is a new packaging container that has been developed beyond the existing two-piece can and three-piece can structural frame. It not only applies the current three-piece metal can composite technology, crimping technology, but also applies. The two-piece deep drawing forming technology is used to form the can body, and then the existing canned contents and the processing technology with the screw cap are used, thereby realizing the use of metal aluminum, and processing is formed into a bottle type and a diameter of 28 mm. A new metal bottle packaging container for the mouth. The new container combines the advantages of metal cans and PET bottles while overcoming the inherent shortcomings of both. Taking into account the environmental problems, the new bottle is made of a single metal aluminum alloy material, and the PET film material is compounded on the surface of the material, that is, the inner and outer surfaces of the can body; the inner surface of the bottom cover is also coated with composite PET. The film is coated with PET on the outer surface; the cap is coated with low density PET and the outer surface is applied by printing. This allows the inner layer of the new bottle to avoid contact with the contents, eliminating the need to use the various coatings traditionally used in metal cans. After the successful trial production of the new bottle, it was exhibited at the Australian Can Industry Exhibition in 2000 and won the grand prize of the exhibition in the name of the Japanese company. This technology is also very attractive internationally, and the demand for aluminum-PET cans will be further expanded in the future.
According to the investigation of the Japan Aluminum Can Recycling Association, as the four companies entered the production of aluminum cans, the sales volume of aluminum bottles in 2002 alone reached 1.5 billion, which is 2.5 times that of the previous year. Based on the increase of about 20%.
The beverage packaging market is one of the largest markets for the metal packaging market. In order to improve the brand effect, in addition to the use of aluminum silver white characteristics, the shape of aluminum cans is becoming more and more important, so manufacturers of metal forming equipment are also discussing aluminum can forming and embossing technology. As aluminum is easier to shape and achieve the required shape, researchers are exploring aluminum can reel expansion forming, spin forming and flow forming technology, which will be used first in beer cans in the near future.
The use of aluminum cans for beverages such as beer and soft drinks has increased the use of aluminum products, and other industries are currently considering the use of aluminum can products. According to information provided by the US Industrial Information Resources Corporation, more than a year ago, Japan’s largest aluminum can manufacturer, Dahe Aluminum Can Co., began producing aluminum cans for beer and tea companies. The company has produced 480 million aluminum cans in previous years. In addition, two other Japanese aluminum can manufacturers are expected to double their production of aluminum cans in the next two to three years. Aluminum cans are favored by the beverage industry because of their light weight and easy recycling. Recently, they have been popularized in other industries and have a tendency to replace glass and metal bottles.
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