The correct selection and use of the hottest gravu

The correct selection and use of gravure printing materials (Part 2)

4) liquid packaging

the so-called liquid packaging film is the packaging film whose content is liquid. According to the printing method, it can be divided into surface printing liquid packaging film and internal printing liquid packaging film

surface printing liquid packaging film generally adopts three-layer coextrusion or five layer coextrusion PE film (black-and-white film, milky white film, matte film, packaging machine 'target=u blank> transparent film), which is mainly used for liquid packaging of milk, soybean milk, soy sauce, vinegar, etc. and frozen packaging of frozen meat food. The liquid packaging film needs to undergo uniform corona treatment before printing. The third treatment surface: the critical surface tension of uniform thickness should reach 40 ~ 41 dyne. Common inner printing liquid packaging films such as milk film packaging can choose biaxially oriented polypropylene (BOPP), matting polypropylene (BOPP), polyethylene terephthalate (PET) as the substrate, and high-strength metallocene polyethylene as the laminating substrate. For three-layer composite, PET film can be used for printing, and aluminum foil or pet aluminized film can be used for the middle layer because of their good barrier performance, and then metallocene polyethylene with good heat sealing and high strength can be compounded. For liquid packaging such as cosmetics and pesticides, including the impact blade and the centering film for clamping the sample anvil, pet is selected as the printing surface material, aluminum foil or pet aluminized film is selected as the middle layer, and metallocene polyethylene is used as the third layer. Common lamination combination methods: PET film/pet aluminized film/metallocene polyethylene film or PET film/aluminum foil/metallocene polyethylene film. Pet has high mechanical strength, strong toughness and excellent dimensional stability, so it is often used as the surface layer of liquid packaging film. When printing pet substrate, the surface tension of the printing surface is required to reach more than 50 dyne, and the pet aluminized film in the middle layer of the composite film should be corona treated on both sides

5) cooking packaging

the so-called cooking packaging is the packaging that puts the contents in a steam boiler at 120 ℃ for cooking for 40 minutes without broken bags. The commonly used structures are pa/pe, pa/cpp, pet/al/cpp

polyamide (PA) is commonly known as nylon. Nylon film is OPA or CPA film made of nylon 6 resin after biaxial stretching. It has high strength, can maintain high modulus and stiffness in a wide temperature range, and has many advantages such as high oxygen barrier, puncture strength, tear strength, high temperature resistance and printability. Nylon film also has high transparency and safety. Based on these advantages, nylon film has been widely used in food packaging, pharmaceutical packaging and industrial packaging. For example, put 12 μ PA of M and 30 ~ 80 μ M of CPP or PE, in which nylon has puncture resistance, high impact strength and high temperature stability, while other resins such as polyethylene and non stretched polypropylene have excellent heat sealing and barrier properties. The composite product has good cold storage, good corrosion resistance, puncture resistance, gas resistance and fragrance retention, and can be cooked at high temperature. The disadvantage is that it is easy to absorb moisture. After absorbing moisture, the barrier and strength will decrease, the adhesion of ink will decrease, and the film will wrinkle. Therefore, it should be stored in a dry place and pay attention to the change of humidity in the printing environment

in modern packaging, aluminum foil is used in many advanced composite materials that require light tightness. Aluminum foil is made of electrolytic aluminum with a purity of more than 99.5% by calendering. Compared with paper, plastic film and other materials, aluminum foil has the advantages of good barrier, strong air tightness, moisture-proof and waterproof, strong protection of contents, excellent thermal conductivity and shading. At the same time, it is non-toxic, and can be compounded with paper, plastic film and other materials, which is convenient for printing and coloring. Therefore, aluminum foil is a packaging material that cannot be replaced at present, and has a wide range of uses. The thickness of aluminum foil used in composite materials is usually 7 ~ 9 μ m. In practical use, in addition to being used as chocolate and medicine packaging, the thickness should be selected according to different contents. There are four widths of aluminum foil produced in China, which are 10 ~ 39mm, 39 ~ 130mm, 130 ~ 220mm and 220 ~ 600mm respectively. There are 18 kinds of thickness, of which the thinnest is 5 μ m. The thickest is 200 μ m。 Aluminum foil should be pretreated before printing, that is, coated with a layer of shellac coating or nitrocellulose to improve the adhesion of ink

bopp/al/ldpe is used for barrier light proof or vacuum flexible packaging, in which BOPP is pretreated for internal printing, coated with polyurethane adhesive, and mixed with aluminum foil (thickness 10 ~ 30 μ m) For the first time, the color printing pattern is more shiny and dazzling after being contrasted with silver white aluminum foil. Next, the adhesive is coated on the other side of the aluminum foil and then compounded with polyethylene substrate (thickness 30 ~ 100 μ m) After curing, shaping and cutting, t-sealing, three side sealing, h-sealing and other bag making, or directly sent to the food, drugs, cosmetics and other packaging lines for automatic high-speed continuous packaging. LDPE used for bonding with Al face shall undergo surface activation treatment. In the above process, BOPP can be replaced by more crisp pet, while LDPE can be replaced by CPP. Example 12 μ M pet is used to measure the tensile strength of paper, paperboard and other similar thin sheet materials by dry composite method and 7 ~ 14 μ M aluminum foil composite, and then composite 30 ~ 80 μ M CPP, the composite product has the characteristics of gas resistance, moisture resistance, fragrance retention, high mechanical strength, cooking and low temperature refrigeration, and is mainly used for the packaging of baked goods, meat products, cream, etc

the above introduces the selection of several common packaging materials. In actual production, we will encounter various types of packaging. In the selection of materials, we should not only consider the beauty of the packaging, but also consider the characteristics and packaging methods of the contents of the packaging. What kind of materials should be selected for what type of packaging. Never "change the cat for the Prince". If there is any mistake in choosing materials, the loss after packaging will be incalculable. Therefore, printers are required to understand the characteristics and special requirements of the contents of the package before packaging, and then pay more attention to the selection of materials. For new product development, it is required to do a good job of testing first, and then mass production. Remember, only when everything is ready can we make high-quality products with flexible packaging. Author Shi Peiqin, Shandong Linyi Xingda company color printing factory

source: Printing World

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