Overview of the hottest metal packaging materials

2022-09-22
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Summary of metal packaging materials (5)

VII. Aluminum for metal packaging

1. Characteristics of aluminum packaging materials

aluminum is another kind of packaging metal materials other than steel. In addition to the excellent barrier, air tightness, moisture resistance and shading inherent in metal materials, it also has the following characteristics:

(1) light weight. Aluminum is a light metal with a specific gravity of 2.7, about 1/3 of iron. Therefore, aluminum packaging has the advantage of light weight and can save transportation costs

(2) good processing performance. Aluminum has excellent ductility and drawing performance, so aluminum cans are two-piece cans drawn at one time. Aluminum can be made very thin, and can also be used for packaging in the form of aluminum foil and aluminum plating

(3) aluminum does not rust in air and steam, and its surface is bright and beautiful. It does not need to be plated with a metal protective layer, but it can resist acid, alkali and salt media after surface coating

(4) tasteless and odorless, which does not affect the flavor quality of the packaging. In addition, it is free of sulfide and heavy metal pollution, which is particularly important for the packaging of food, pharmaceuticals and cosmetics

(5) it is easy to recycle, and aluminum cans can be recycled, thereby reducing costs and energy consumption. At present, the main controversy on aluminum packaging in the international market is that the production energy consumption of aluminum is too high, which increases the packaging cost. The solution to this problem is to strengthen the recycling of aluminum cans. Because aluminum packaging has a series of advantages mentioned above, the application of aluminum packaging is in the ascendant now

aluminum materials for packaging are mainly used in three forms: aluminum plate, aluminum foil and aluminum coated film. Aluminum plate is mainly used to make aluminum packaging containers, such as cans, basins, bottles and hoses. Aluminum foil is mostly used to make the barrier layer of multi-layer composite packaging materials, and the aluminum foil composite film is used for food packaging (mainly soft packaging), cigarette packaging, medicine, detergent, cosmetics and other packaging. Aluminized film is another form of composite material, which is a new type of composite flexible packaging material. It uses a special process to coat a very thin layer of metal aluminum on the surface of packaging plastic film or paper (one side or two sides). This aluminized film composite material is mainly used for vacuum packaging of food, such as fast food, snacks, meat, agricultural products, etc., as well as packaging, decoration and trademark materials of cigarettes, drugs, alcohol, cosmetics, etc

2. Aluminum and aluminum alloy sheet for packaging

(1) aluminum plate

aluminum is a kind of light metal, which is very stable in the atmosphere and has excellent processing performance. It is a kind of metal widely used. Since 1930, aluminum has been used to make packaging containers. Because aluminum packaging containers are convenient to process, light and durable, and have good protective performance, they are widely used in packaging products, and the consumption is also large. At present, the countries that produce more aluminum in the world include the United States, Europe and other countries. About 7-10% of the aluminum produced each year, with a total of 600000 tons, is used for product packaging. Aluminum packaging containers are made of pure aluminum or aluminum alloy plates

the strength of aluminum alloy (mainly aluminum magnesium and aluminum manganese alloys) plates is higher than that of pure aluminum. Since aluminum is not corrosion resistant to acid, alkali and salt, aluminum plates must be coated before use. The production process of aluminum sheet is: cast aluminum → hot rolling → cold rolling → annealing → cold rolling → heat treatment → leveling → passivation treatment (forming alumina film) → coating → aluminum sheet

aluminum plate is mainly used to make aluminum packaging containers, such as cans, boxes, bottles, etc. In addition, aluminum plate is a special material for making easy to open cans because of its good processability

(2) aluminum punching and cupping

aluminum plate is a new type of can making material with excellent processing performance, but it is difficult to weld, so aluminum plates are made into two-piece cans formed by punching and drawing at one time. At present, the speed of aluminum can production line can reach more than 120~150 years/min. The aluminum can is light and beautiful, the outer wall is not rusty, the can body is seamless and does not leak, and it is made of a single metal, with good protection performance. It is used in fish and meat cans without vulcanization spots, and as beer and beverage cans without flavor changes. One disadvantage of aluminum cans is that they have low strength and are easy to be dented, but as long as the transportation packaging is improved, this problem can be solved better

at present, aluminum cans are widely used in Europe and America, accounting for about 1/3 of metal cans. They are mainly used for beer and beverage cans with large sales volume, which are generally made into easy to open cans. Some of the spray cans in non food packaging are aluminum cans. Soon there will be fierce competition between aluminum cans and traditional tin cans

(3) aluminum tubes and aluminum tube packaging

extruded hoses try to prevent the general election act of the executive seat from passing. About 2/3 of the packaging containers are aluminum tubes, which are mainly used for the packaging of toothpaste, cosmetics, ointments, etc. Aluminum tube used in food packaging is a new and simple packaging method, which is popular in Europe and Australia. Aluminum tubes are especially suitable for filling semi liquid or paste food, such as sauce, meat, such as rubber and plastic, metal processing, paint and ink, personal care, packaging, medicine, food and beverage, automobile and renewable energy, such as sauce, cream, honey, concentrated food and flavored food. Aluminum tube packaging not only has the characteristics of light weight, excellent protective performance, good strength, not easy to break and easy to carry, but also has the advantages of easy opening, extrusion and folding, easy storage of food after eating, longer time to maintain freshness than bottles and cans, no freezing treatment, and convenient use. Therefore, it is popular with consumers and is used in the packaging of military food and aerospace food

aluminum tubes are generally made of 99% pure aluminum for extrusion and crimping. The outer surface can be printed and decorated, and the inner wall is coated with organic resin coatings, such as epoxy resin, phenolic resin, vinyl resin, etc., which can further improve the corrosion resistance and prevent the cracking of aluminum tubes during curling

the production method of aluminum tubes is to punch aluminum plates with a certain thickness with a precision blanking punch, blanking them into small disc blanks, annealing them, and then impact them on a 100~350t extruder to extrude them, so that the disc blanks extend outward into tubes along a certain length and diameter, and finally achieve a certain hydraulic universal testing machine. What are the common maintenance methods? Please see the introduction below. The formed aluminum tube should also be heat treated to eliminate the work hardening effect, so as to avoid cracking during extrusion and curling. Finally, paint the inner wall of the aluminum tube, dry it, and decorate and print it on the surface of the tube

aluminum tubes vary in size, with a diameter of 15~50mm and a length of 40~200mm. Its length is determined by the thickness of the disc blank

3. Aluminum foil and aluminum foil composites

(1) aluminum foil

aluminum foil is the most used metal foil for packaging. Aluminum foil is calendered from electrolytic aluminum or aluminum alloy plates with purity of 99.3~99.9%, and the thickness is less than 0.2mm. Generally, aluminum foil is used in combination with other packaging materials as a barrier layer to improve its barrier performance. In production, in order to reduce the packaging cost, we hope to reduce the thickness of aluminum foil as much as possible, but when the aluminum foil is too thin, needle shaped holes will be generated, which will degrade the barrier performance. Therefore, efforts must be made to improve the production technology of aluminum foil to minimize the incidence of pinholes. The number of pinholes can be measured according to their air permeability and moisture permeability data. In addition, aluminum foil is not required to have high mechanical properties while maintaining a certain softness to reduce cracking

industrial aluminum foil produced in China now has four width ranges and eighteen different thicknesses. Its series products are as follows (table 10):

table 10 specification series of aluminum foil (unit: mm)

aluminum foil width 10~39mm 39~130mm 130~220mm 220~600mm

aluminum foil thickness 0.005 0.0075 0.010 0.012 0.014 0.016 0.020 0.025 0.030

0.040 0.050 0.070 0.080 0 0 0.100 0.120 0.150 0.200

mechanical properties of aluminum foil The relationship between thickness and moisture permeability is shown in Table 11 and table 12 respectively

Table 11 mechanical properties of aluminum foil with different thickness

thickness (mm) tensile strength (MPA) elongation (%)

0.0075~0.011 30~100 0.5

0.012~0.04 30~100 2.0~0.5

0.05~0.20 30~100 3.0~0.5

table 12 relationship between thickness of aluminum foil and moisture permeability

thickness of aluminum foil (mm) moisture permeability (g/m224h)

0.007~0.008 7

0.008~0.010 5

0.010~0.015 2.5

0.015~0.020 1.0

0.020~0.025 0

aluminum foil is thin, but as a packaging material, it has the following advantages:

① light weight, which is conducive to reducing transportation costs

② good barrier and shading. It is moisture-proof, airtight and has fragrance retention performance, and can prevent moisture absorption, oxidation, volatilization and deterioration of packaging materials

③ good heat resistance, stable shape at high and low temperatures, and can be used as a baking container

④ it is highly protective, so that the packaging is not easy to be damaged by bacteria, molds and insects

⑤ good reflection and gloss of light. It has high reflective ability to heat and light, and its reflectivity is 83~85%, so the exhibition effect is excellent

⑥ good mechanical performance, which can meet the use of automatic packaging machinery

⑦ good secondary processing, molding and embossing

⑧ good adaptability for printing and compounding. Easy to color, easy to fit with paper, plastic, etc

⑨ it is non-toxic and not easy to cause public hazards

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