Application and development of the hottest vacuum

2022-08-16
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Application and development of vacuum aluminized biaxially stretched polyester film

when it comes to vacuum aluminized film, people naturally think of packaging. Although the use of vacuum aluminizing film is no longer limited to packaging, it is undeniable that the packaging industry is still the largest market for vacuum aluminizing film. To this end, first from the application of packaging

first, aluminum foil and vacuum aluminum coating

the introduction of vacuum aluminum coating began with aluminum foil. Aluminum foil used on flexible plastic packaging is generally 6 ~ 20 μ M thickness. Aluminum foil has silver luster. Printing transparent ink directly on aluminum foil can have unique metallic luster. Aluminum foil has good shading, gas and humidity resistance, good thermal conductivity and electromagnetic shielding. The most prominent is the barrier performance of aluminum foil, which can completely block gas and moisture on the premise of sufficient thickness. Therefore, aluminum foil is an indispensable material in the flexible plastic packaging substrate film, and is widely used in drug packaging and food packaging, especially in the flexible packaging of drugs, cosmetics and other high-end products that need high-temperature cooking and relatively long storage time. However, aluminum foil has a fatal defect - after bending, aluminum foil is easy to produce cracks, which affects the barrier property of aluminum foil. At the same time, aluminum foil is expensive. In the 1980s, a new technology vacuum aluminizing was introduced. Since then, more and more people began to replace aluminum foil with vacuum aluminum coating without affecting the quality requirements, so as to reduce the packaging cost

the so-called vacuum aluminum plating refers to that under high vacuum, once aluminum is liquefied, it vaporizes immediately, and then it is cooled and stacked on the surface of plastic film to form an aluminum plating layer with good metallic luster and a thickness of about 300 ~ 600 angstroms. The thickness of the aluminized layer is also expressed by light transmission, optical density or square resistance. Vacuum aluminum coating is generally BOPP, BOPET, BOPA, CPP and other materials with good temperature resistance and mechanical processing performance. In this way, the vacuum aluminum coating has both mechanical and physical properties similar to the substrate and barrier properties similar to aluminum foil

although vacuum can reduce the weight by 30%, there is still a certain gap between the barrier performance of aluminum coating and aluminum foil. In fact, due to the good flexibility of vacuum aluminum coating, the problem of greatly reducing the barrier performance caused by the bending and cracking of aluminum foil can be avoided. In some cases, vacuum aluminum coating composite packaging has better barrier performance than aluminum foil composite packaging. Therefore, vacuum aluminum coating has replaced a large part of the aluminum foil market in flexible packaging products with certain barrier requirements

II. Progress in aluminized film and barrier packaging technology

in recent years, with the intensification of competition in the flexible packaging industry, people are not only concerned about the barrier effect of packaging, but also about the performance price ratio of packaging materials. More and more new technologies are introduced into the production of film. The processing enterprises of vacuum aluminized film also take various ways to improve the barrier performance of materials or reduce costs, Try to improve the market share of vacuum aluminized film. According to the market demand, Foshan DuPont Hongji Film Co., Ltd. has successively developed special polyester film

(1) the high oxygen barrier film 8231

is coated to improve the oxygen barrier ability of biaxially stretched polyester film. It can buffer the strong vibration and impact produced by high-speed vehicles. The oxygen resistance of 8231 film is similar to BOPA. If vacuum aluminum plating is combined, the oxygen resistance of the product will be greatly improved

(2) pretreatment film for aluminizing 121

when untreated or corona treated polyester film is aluminized in vacuum, the thickness of aluminum layer generally does not exceed 350 angstroms, which is mainly because the peel strength will decrease significantly with the increase of aluminum layer thickness. 121 film is a chemically treated film. Its surface is coated with a coating to improve the adhesion between the aluminum coating and polyester film, which enhances the adhesion of the aluminum coating. The thickness of the aluminum coating can be increased from the conventional 350 Angstroms to 500 Angstroms, or even 680 angstroms. Thus, the barrier performance of vacuum aluminized film is greatly improved, as shown in Table 4

with the continuous development of the packaging industry, many new processing technologies and applications have been widely adopted in recent years. For example, in order to improve production efficiency, extrusion coating has been introduced to many packaging companies, while the traditional vacuum aluminized products, due to their low adhesion strength between the aluminized layer and the film, cause the aluminized layer to crack and peel off under the high temperature coating, resulting in a sharp decline in the yield of products. For another example, jelly food is more popular in China. The original vacuum aluminized products are not suitable for the process of jelly food processing, that is, they must be boiled at 85 ℃ before leaving the factory. In this process, the separation between the traditional thin film and the aluminized layer is easy to occur. Foreign polyester film manufacturers have also tried to use coating treatment to enhance the adhesion strength of aluminum layer. However, most of these manufacturers use (NA) sulfonated polyester chemicals that are very sensitive to moisture for coating pretreatment. Therefore, the adhesion strength of the aluminum layer in the humid environment is not high, or even all of it is lost. Our 121 coating pretreatment film can not only greatly improve the peel strength of aluminum layer under normal conditions, but also maintain excellent peel performance in wet environment. Due to its outstanding performance in this regard, our products have been widely recognized by customers, as shown in Figure 1

(3) film for gold and silver paperboard g film

the film for gold and silver paperboard requires that the composite product has a smooth surface, bright appearance and mirror (metal) reflection effect. At the same time, it must also have good processing performance and cannot wrinkle in the process of aluminum plating. For the purpose of ensuring easy processing of products, the traditional vacuum aluminum plating base film makes the surface roughness of the film larger, and the high brightness requirements required for this purpose cannot be formed in aluminum plating. The gloss of G film used for this purpose is increased from the conventional 120 to the level of 140 ~ 150, which has been widely praised by customers

III. other applications of aluminized products

Application of aluminum spraying (aluminum transfer)

aluminum spraying (aluminum transfer) is a technology developed to adapt to the situation that some products with low melting point and high moisture content cannot be directly evaporated in vacuum aluminizing machine. The process can be divided into four steps: aluminizing polyester film, gluing on the aluminized layer, compounding with paper, and stripping by evaporation. This product has a better concept of environmental protection. Some time ago, the State Administration of tobacco expressly stipulated that paper plastic composite products should not be used as cigarette packaging, and aluminum spray paper is recommended. There are also some disadvantages in this product, that is, the product can not achieve the bright appearance effect of paper plastic composite products for the time being

use of anodized (bronzing)

due to the many production processes for this purpose, it must undergo several high-temperature processing:

the processing process of anodized is: upper release layer - upper color layer - vacuum aluminum plating - upper adhesive layer - rewinding

when using anodized products, metal foil or pigment is hot stamped on printed matter or other substrate with the help of a certain pressure and temperature. Therefore, there are high requirements for the mechanical and physical properties, high temperature resistance and dimensional stability of the substrate. The most commonly used substrate for this purpose is 12 to 15 micron biaxially stretched polyester film. The products after hot stamping have special metallic luster and luxurious and magnificent natural color, which can produce a strong contrast on the screen of printed matter, thus making the printed matter produce a gorgeous and eye-catching effect; In addition, the objects of hot stamping include not only printed matter and paper, but also plastic, leather, cotton and other surfaces. Electrochemical aluminum products have been widely used in the decoration market and packaging market

purpose of capacitor

the product after vacuum aluminizing is of double-layer structure. The aluminized layer has good conductivity, and plastic film is an excellent insulating material. Therefore, thin film capacitors of different sizes can be produced by special aluminum plating and winding together. At present, the films used in this field are mainly biaxially oriented polypropylene film and biaxially oriented polyester film. With the rapid development of household appliance industry, such applications are also increasing. Due to its high dielectric constant, biaxially stretched polyester film is very suitable for small capacitors, and is more suitable for the production of small electrical capacitors. At present, the thinnest polyester film for capacitors in the world has reached 0.7 to 0.9 microns, while the thickness that can be officially mass produced in China is 3.5 microns. For the time being, only Foshan DuPont Hongji Film Co., Ltd. can produce it

laser anti-counterfeiting application

this application requires the film to have good brightness, stiffness, mechanical and physical properties and high temperature resistance. The raw material used is generally biaxially stretched polyester film with a thickness of 25 microns to 36 microns. Its basic principle is to conduct special molding treatment on the film of vacuum aluminized display equipment to avoid glare and other phenomena that affect the transmission of information, so as to make the aluminized film produce holographic effect, so as to achieve the purpose of anti-counterfeiting. With the further improvement of self-protection awareness of domestic enterprises, more and more customers begin to adopt such methods to protect their products from infringement. On the other hand, in order to further improve the effect and clarity of holography, higher requirements are put forward for the vacuum aluminum coating used for this purpose, such as the requirements for brightness. In order to ensure good processing performance, more additives are added to the traditional polyester film. The surface of the film is rough, the haze is high (about 3%), and the brightness of the products after vacuum aluminizing is not enough. Foshan DuPont Hongji Film Co., Ltd. has invested a lot of human and material resources to successfully develop a vacuum aluminized base film with a haze of less than 1%, which has been recognized and praised by customers

vacuum aluminized biaxially stretched polyester film is also widely used in other fields because of its excellent performance in various aspects, such as

· excellent decorative performance, which can be used as decorations in textiles or clothes by 2020, such as gold and silver silk and gold and silver pieces commonly used in clothes

· good shielding effect, which can be used as wire winding film or anti-static packaging

· it has a good reflection effect on light, and is very suitable for use as heat proof material and agricultural reflection film

source: packaging magazine

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