Commonly used plastic films are: PE, PP, PVC, PS, PVA, PC, PET, CA, NY. The printing characteristics of these plastic films are:
1. The plastic film is a non-polar polymer compound, which has poor adhesion to the printing ink. In order to make the surface of the plastic film have good ink adhesion ability and enhance the firmness of the printing product, the surface activation treatment is performed before printing;
2. The hygroscopicity is mostly caused by the relative humidity of the surrounding air and the telescopic deformation, resulting in poor overprinting;
3. Influenced by the change of tension. In the printing process, in the range of the allowable strength of the film, the elongation increases with the increase of the tension, which brings difficulties to the accuracy of the color printing overlay.
4. The surface is smooth, there are no hair pores, ink layer is not easy to fix or fixed firmly, after the first color is printed, it is easy to be the next color overprinted ink stick out, so that the pattern and text are incomplete, resulting in defects;
5. The surface oil layer seeps out. The film made by adding additives can easily seep out during the printing process, forming an oily layer, ink layer, paint or other adhesive on the surface of the film, and it is not easy to bond firmly on the surface of such film;
6. Since the plastic film is a non-polar material, there are no pores, the ink is not easy to dry, these characteristics are not conducive to printing, so the plastic film must be surface treatment before printing.
The characteristics of cellophane are: high transparency and strong gloss. After the printing of graphic and text, the color is exceptionally bright, which is beyond the reach of the plastic film; the printability is good; no treatment is required before printing, and the cellophane also has antistatic treatment performance. Difficult to absorb dust, to avoid the printing of text and other troubles. However, the moisture-proof property is poor, and the film is easily deformed due to the influence of temperature and humidity, resulting in difficulty in registering the image when printed.
The characteristics of aluminum foil are:
1. Light weight, with metallic luster, good light-reflecting ability to heat and light, metallic luster and reflection ability can increase the brightness of printing color;
2. Good insulation, strong protection, impermeable to gas and water vapor, to prevent the contents from absorbing moisture and gasification, and not easily invaded by bacteria and insects;
3. Good shape stability, not affected by changes in humidity. Easy to process, can be printed on aluminum foil, color difference, embossing, surface coating, lacquer painting, etc.;
4 can not be forced, no sealing properties, pinholes and wrinkles and other phenomena, so under normal circumstances are not used alone, usually with paper, plastic film processed into composite materials, to overcome the lack of sealing defects, which Isolation and other advantages have also been fully utilized.
Aluminum foil is widely used in the food and pharmaceutical packaging fields. Aluminum foil and plastic film are combined to effectively use high-temperature cooking and complete shading. It can be used as a cooking bag to package cooked foods. Multi-layer composite films are also used. For biscuits, snacks, drinks and other small food packaging.
Vacuum aluminum film
Compared with aluminum foil, vacuum aluminum plating greatly saves the amount of aluminum. The former is only 1/100 to 1/200 of the latter, but it has metallic luster and insulation. Due to the relatively thin thickness of vacuum aluminum plating, only O. 4O. 6Î¼m, can not be used to replace aluminum foil composite films that require high barrier properties, such as vacuum packaging and high temperature cooking bags. The cost of vacuum aluminum plating is lower than that of aluminum foil, and it will be greatly developed in the fields of food trademarks, etc. In recent years, vacuum aluminum-plated paper is gradually replacing aluminum foil in the packaging of cigarettes, cold food cartons, and chewing gum.
The main role of vacuum aluminum coating film is to replace the aluminum foil composite, so that soft plastic packaging also has a beautiful silver-white gloss, improve the barrier properties of soft packaging film bag shading, thereby reducing costs. The vacuum-plated substrate film is a polypropylene film with a relatively high melting point, including CPP, IPP, and BOPP. The PET film, NY film, and paper can also be directly vacuum-plated after pretreatment or conditioning. PE film, PT can use indirect aluminum plating process. In order to provide the fastness of aluminum plating, foreign countries adopt the method of coating the bottom layer on the substrate film to be plated, while the domestic generally has no bottom coating surface, and corona treatment is only performed on the surface. There are two kinds of vacuum aluminum plating methods for thin films, which can be reverse-printed on the surface film of the thin film, that is, printed inside, and then vacuum-aluminized and then composited with the backing film. It can also be reverse printed on the MASK, and then dry-composite with the vacuum-aluminized base film. The bottom film of the latter must be CPP or IPP, which has good heat resistance and can be heat-sealed.
When the vacuum aluminum plating is performed on the printed mask, although it is printed on the inside, it is not necessary to use the ink on the back, and it is only necessary that the ink has excellent heat resistance. If the printed material is dark after vacuum aluminum plating, the desired gloss is lost because the ink is poor in heat resistance. Vacuum aluminizing on the printed surface, since the adhesive resin in the ink is a good undercoat, the fastness of the aluminized is better, especially when the full-print version is in the field, the aluminized layer has better fastness.
There are many kinds of composite films. The common ones are the compounding of cellophane and plastic film, the compounding of plastic film and plastic film, the compounding of aluminum foil and plastic film, the compounding of aluminum foil, glass, paper and plastic film, various papers and their prints and The compounding of plastic film, etc., is as many as 30 to 40, and the composite layer is generally 25 layers. The basic structure of various composite films is a non-thermoplastic or high-melting point film such as PT, BOPP, NY, PET, etc., as the outer layer, and PP, PE as the inner layer for comprehensive application. The commonly used composite film structure has a lot of uses. When selecting the composite film, the printing performance must be taken into account in order to obtain a beautiful trademark pattern.
Composite films are widely used in food packaging, such as shopping malls of fast food, frozen foods, puffed foods. These are made of composite film, which can not only maintain the excellent characteristics of single-layer films, but also have their own deficiencies. After compounding, they have new characteristics to meet the different requirements of the products for the film. For example, food packaging requires the film to be moisture-proof. Anti-gas, anti-light, oil resistance, high temperature resistance, heat sealability and other excellent performance, but also has a good printability and decorative arts effect, performance and requirements are difficult to achieve a single film. The PE film that is most widely used has excellent transparency, moisture resistance, heat resistance, and chemical stability, but its oil resistance and oxygen resistance are limited, and printability is poor. PET and PA films have high tensile strength and fatigue strength, but the former has poor moisture resistance, and the latter has poor heat sealability and chemical resistance. PE has excellent transparency, no static electricity, no pollution, and easy adhesion, but its toughness, water resistance and moisture resistance are all poor. Aluminium foils have scintillating metallic luster and thermal conductivity properties, and have good moisture barrier, vapor, light emission, and grease properties, but have drawbacks such as easy breakage, lack of flexibility, and lack of thermal adhesiveness.
Each layer of thin desert compound together, at the same time with moisture, gas, light, heat, oil, heat sealing and other fine properties, become an ideal packaging material. For example, the current high-grade RP-H cooking bag is a three-layer composite film with a plastic film as the base material. Its middle is aluminum foil and has good insulation properties, which is good for food storage for a long period of time. The outer layer is made of BOPP film. Excellent dimensional stability, back gravure printing, compounding with aluminum foil with adhesive to ensure the firmness and smoothness of printing color. The inner layer uses PE film to take advantage of its heat-resistance, softness, and easy sealing. After the three components are compounded, they can withstand high-temperature sterilization at 120Â°C, and the microorganisms will not be immersed in it.
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