Boxed milk is a large variety of fresh milk packaging. Liquid milk of various preservation methods has almost boxed milk. What is the manufacturing process of this kind of packaging? What are the requirements of liquid milk for this kind of packaging? This article will briefly introduce the four aspects of packaging materials, hygiene requirements and preservation, printing and packaging and recycling.
Packaging Materials
The packaging box for liquid milk is made of composite materials. Typical composite materials are composed of the following four materials or several of them.
Polyethylene (hereinafter abbreviated as PE) - the sealing layer, acts as a barrier to moisture and bacteria;
Cardboard - used to improve the hardness and strength of the box, and have a light protection effect;
Aluminum foil - with excellent oxygen barrier and dark performance;
EVOH Efficient Barrier Layer - an alternative to aluminum foil, is also used to block oxygen and protect from light.
Hygienic requirements and preservation
Fresh milk uses different box-making materials depending on the shelf life. The structure of the short-term fresh-keeping milk box requiring refrigeration is relatively simple, and the PE/cardboard/PE composite material is generally used; the aseptic filling milk box for long-term storage in a normal temperature environment is constructed of a material of PE/cardboard/adhesive layer. / Aluminum foil / adhesive layer / PE, or PE / cardboard / EVOH / adhesive layer / PE-type composite material.
Printing and forming
Advantages of flexographic printing: Printing methods for dairy packaging are offset, gravure and flexo. In the past, the proportion of offset printing was relatively high. In recent years, with the progress of flexo printing technology and the improvement of the quality of flexo printing, the proportion of flexo printing in packaging has continuously increased. Compared with gravure and offset printing, flexo printing has many characteristics.
Short product replacement time: If the BHS unit type flexo press, replace a sleeve plate less than 2 minutes, the preparation time for changing the printing color in one unit is 8-10 minutes, replace an anilox roller (or sleeve) The time is less than 3 minutes.
Strong drying capability: Drying ability is very important for water-based inks, especially for field printing. The drying device of each unit can be individually controlled by frequency conversion. The heating medium can be gas, hot oil or electric heat. Flexo presses are generally equipped with a UV curing device to facilitate the application of UV inks.
Gearless transmission: The gearless transmission technology has many advantages. One is that the diameter of the roller can be changed arbitrarily and continuously without changing gears as in the past; the other is that printing rolls of different sizes can be printed using the same diameter roller; The third is to facilitate the compensation of different thicknesses of cardboard or plates of different thicknesses.
Easy to monitor: Advanced flexo presses, such as the BHS Flexo press control and display system, can detect and display various data required for production, and can store job production process data for easy reuse. The system can monitor the machine in real time and display the fault point. The operator can handle the fault according to the instructions. For complex faults, remote diagnosis can also be implemented by the manufacturer via the network.
Convenient for changing paper: If the BHS flexo printing machine adopts a docking method, it does not need laps, which can reduce paper waste. Because it is a zero-speed continuation of paper, the operation is simple and the efficiency is high. And before the machine shuts down, all anilox rollers will be automatically clutched to avoid damage to each roller unit. Easy on-line processing: Flexo presses are generally multi-unit, and the last unit can be used for (water-based or UV) coating. When in-line die-cutting and indentation are required, circular press die cutting can be used, or flat pressurizing can also be used. Flat die cutting. After die cutting, the arrangement of the transfer can be changed for convenience of collection, for example, from two rows to four rows during die cutting, which reduces the speed of collection.
Dairy packaging box printing and post-press processing features: different uses of the packaging in the printing process there are some differences. The packaging box used for short-term preservation is PE/cardboard/PE, which is directly printed on the PE material during printing. For the long-lasting packaging box, it needs to be printed on the cardboard because of the need for high-temperature treatment. The PE was compounded onto the paperboard using an extrusion compounding method.
There are two kinds of molding methods for the packaging box. One is to arrange the in-line die-cutting and indentation unit behind the printing machine. At the same time, the printing, indentation and die cutting are completed, and then sent to the folder-gluer; the other is the roll-to-roll printing. The method is used for filling lines after slitting into narrow rolls. Shanghai International Paper Co., Ltd. is a large-scale enterprise that produces fresh milk packaging boxes. They use two BHS 9-color flexo printing machines, which are produced on-line with round press die cutting machines and indentation units. UV inks are used to print PE/cardboard. The packaging box of the /PE material has a printing width of 820 mm and a production speed of 250 m/min.
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