Analysis on the printability and function of flexi

2022-08-08
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Brief analysis on the printability and functional use of flexible packaging materials

flexible packaging materials have certain heat sealing, flexibility, alkali resistance, abrasion resistance, and are widely used in food packaging, pharmaceutical packaging and other aspects due to portability and other reasons. The printed products of flexible packaging materials have clear layers and strong three-dimensional sense. When the II and IV valve ports of the 2D vibration valve are opened, coupled with the true reproduction of color, the purchase desire of consumers is increased. The commonly used flexible packaging materials mainly include cellophane, plastic film, composite film, vacuum aluminum coating film and aluminum foil, among which the flexible packaging based on plastic film and aluminum foil plays an important role in packaging and printing. The composite film made of cellophane, plastic film and aluminum foil overcomes the shortcomings of single-layer film, integrates the advantages of each layer of materials, meets the hierarchical packaging requirements of different commodities, and has become an ideal packaging material. This paper focuses on the analysis of the printing characteristics of flexible packaging and the processing of printing modeling, and introduces the printing skills of various flexible packaging materials, which is only for the reference of colleagues

1 plastic film

plastic films commonly used if the spring installed on the car has not been strictly tested include PE, PP, PVC, PS, PVA, PC, pet, CA, NY. The printing characteristics of these plastic films are: ① plastic films are non-polar polymer compounds, which have poor adhesion to printing ink. In order to make the surface of plastic film have good ink adhesion ability and enhance the firmness of prints, surface activation treatment must be carried out before printing. The commonly used method is corona treatment. The principle is that the plastic film is impacted by high-frequency voltage discharge, so that the non-polar surface becomes rough, the adsorption capacity is greatly enhanced, and the adhesion of the ink is also enhanced. Generally, the surface tension of BOPP, CPP, PE and other substrates after treatment should be 38 ~ 42dny/cm to meet the printing requirements; ② Easy to be affected by the relative humidity of the surrounding air and stretch and deform, resulting in poor overprint; ③ Affected by the change of tension, the registration of film printing fluctuates

2 cellophane

cellophane is characterized by high transparency, good gloss, and extra bright color after printing, which can not be achieved by plastic film; Good printability, without any treatment before printing; Cellophane also has anti-static processing performance, is not easy to absorb dust, and avoids printing faults such as image and text sticking dust. However, the moisture resistance is poor, and the film is easy to deform under the influence of temperature and humidity, which makes it difficult to register pictures and texts during printing. After entering the warehouse, general materials must be wrapped with other plastic films and placed in a ventilated and dry place with a temperature of 23 ℃ ~ 25 ℃

3 aluminum foil

aluminum foil is characterized by: ① light weight, metallic luster, good light resistance, high reflection ability to heat and light, and metallic luster and reflection ability can improve the brightness of printing color; ② Good barrier, strong protection, airtight, can prevent moisture absorption of the contents; ③ Good shape stability, not affected by humidity changes, easy to process; ④ It cannot bear force, has pinholes and is easy to wrinkle. Generally, it is not used alone. It is usually processed into composite materials with paper and plastic film. Because aluminum foil has the above advantages, it is widely used in the field of food and pharmaceutical packaging. Aluminum foil and plastic film composite can be made into cooking bags, which can be used to pack cooked food. Multilayer composite film is also used for the packaging of biscuits, snacks, beverages and other small foods

4 vacuum aluminized film

the main function of vacuum aluminized film is to replace aluminum foil composite, so that soft plastic packaging also has a beautiful silver luster, improve the barrier and shading of soft packaging film bags, and thus reduce costs. The substrate film of vacuum aluminum plating is a film with high melting point, such as polypropylene film, including CPP, IPP, BOPP, pet, NY. Cellophane can also be directly vacuum aluminized after pretreatment or wet treatment, while PE and Pt films can be indirectly processed. In order to improve the firmness of aluminum plating, foreign countries adopt the method of priming on the plated substrate film, while in China, there is generally no priming surface, and only corona treatment is carried out on the surface. Vacuum aluminizing method of thin film: one method is to carry out reverse printing on the facial mask of the film, that is, inner printing, and then vacuum aluminizing and compounding with the bottom film. It should be pointed out that when vacuum aluminizing is carried out on the printed facial mask, although it is internal printing, it is not necessary to use internal printing ink, just an ink with excellent heat resistance. The fastness of vacuum aluminizing is better. Compared with aluminum foil, vacuum aluminum plating greatly saves aluminum consumption. The former is 1/100 ~ 1/200 of the latter, but it has the luster and barrier of metal. Because the thickness of vacuum aluminum coating is relatively thin, it is 0.4 ~ 0.6 μ m. In some occasions, it can not be used to replace aluminum foil composite films that need high barrier, such as vacuum packaging and high-temperature cooking bags. Since the cost of vacuum aluminum plating is lower than that of aluminum foil, vacuum aluminum plating film will be greatly developed in the fields of food trademarks and so on. In recent years, vacuum aluminized paper is gradually replacing aluminum foil in cigarette, cold meal carton, gum and other packaging. The effect of dry-type composite vacuum aluminum coating is good, but it must be noted that the reducer in the two-point tension machine is a power transmission mechanism: ① the estimated amount of glue must meet the needs of packaging, generally between 3.5 ~ 5g, so as to withstand high temperature and not affect the firmness of glue interlayer film; ② Special glue must be used for composite vacuum aluminum coating, and the solid content shall not be less than 75%

5 composite film

composite film is widely used in the outer packaging of food, such as fast food, quick-frozen food, puffed food in shopping malls, etc., which are made of composite film. Composite film can not only maintain the excellent characteristics of single-layer film, but also make up for their shortcomings. The composite film has new characteristics to meet the different requirements of commodities for the film. For example, food packaging requires that the film has excellent properties such as moisture resistance, gas resistance, light resistance, oil resistance, high temperature resistance, acid and alkali resistance, and good heat sealing. At the same time, it also has good printability and decorative art effect. Its performance and requirements are difficult to achieve by a single film. For the PE film that is used most, although it has excellent transparency, moisture resistance, heat resistance and chemical stability, its oil resistance and oxygen resistance are limited, and its printability is poor. Pet and PA films have high tensile strength and fatigue strength, but the former has poor moisture resistance, while the latter has poor heat sealing and chemical resistance. PE (cellophane) has excellent transparency, no static electricity, no pollution and easy adhesion, but its toughness, water resistance and moisture resistance are poor. Aluminum foil has flashing metallic luster and thermal conductivity, and has good performance of blocking moisture, steam, light and grease, but it is easy to crack, lack of softness, adhesion and other shortcomings. Each layer of film is compounded together, and has excellent properties such as moisture resistance, gas resistance, light resistance, heat resistance, oil resistance, and good heat sealing, making it an ideal packaging material. For example, the current high-grade rp-h cooking bag is a three-layer composite film based on plastic film. Its middle layer is aluminum film, which has good insulation performance and is conducive to long-term food storage; The outer layer is BOPP film. Tongling Guochuan Electronic Material Technology Co., Ltd. eats and squeezes the copper material, which has excellent dimensional stability. For gravure printing on the back, the adhesive is compounded with aluminum foil to ensure the firmness and smoothness of the printing ink film. The inner layer adopts PE film, which takes advantage of its heat resistance, softness and easy sealing. After the combination of the three, the sterilization treatment can be completed under the high temperature condition of 120 ℃, and the microorganisms will not invade, which can play a role in preserving freshness and flavor. There are many kinds of film compounding, common ones are cellophane film compounding, plastic film compounding, aluminum foil and plastic film compounding, aluminum foil, cellophane and plastic film compounding, various papers and their prints compounding with various plastic films, etc., there are as many as 30 ~ 40 kinds, and the number of composite layers is generally 2 ~ 5. The basic structure of various composite films is to take Pt, BOPP, NY, pet and other non thermoplastic or high melting point films as the outer layer and PP, PE as the inner layer

Author: Chen Xiaoshun

reprinted from: Printing World

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