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Overview of the development of modern international flexible packaging equipment

1 introduction

as we all know, only after giving products proper packaging, can they become commodities. Therefore, packaging is an important guarantee in the circulation process of transferring products from producers to consumers without changing the quality

in modern society, unit consumer goods tend to be miniaturized, so the volume and weight of packaging will develop towards miniaturization. Table 1 lists the development of flexible packaging of various materials from 2000 to 2003. Among them, the decrease of cellophane is due to the replacement of PP film - this trend is still continuing

Table 1 development trend of world flexible packaging materials from 2000 to 2003

material name 2000 (%) 2003 (%) percentage increase (%). Paper 100104 + 4 cellophane aluminum foil 100102 + 2 polyethylene (PE) film 100152 + 52 polypropylene (PP) film 100136 + 36 polyester (PET) film 100200 + 100 polyamide (PA) film 100128 + 28

2 development overview of flexible packaging and its production equipment

various products have different requirements for flexible packaging materials, such as sufficient mechanical strength, Barrier performance to various media (such as water, water vapor and other gases), good hot pressing (or cold pressing) sealing performance, and good processing performance

various commonly used flexible packaging materials have their own characteristics, which can be selected according to different occasions. Such as the rigidity of paper; Rigidity and heat resistance of cellophane; PE and PP thermal sealing, mechanical strength and moisture resistance; Mechanical strength, heat resistance, odor barrier and film size stability of pet; The best light, moisture and odor resistance of aluminum foil. Figure 1 shows the use of various flexible packaging materials in the world in 2003

because a single material is often difficult to meet the needs of products, people combine the films of more than two materials to obtain better comprehensive properties. And extend the life of goods. The general trend is that the composite structure is becoming more and more complex. The most common composites are listed in Table 2. In addition, vacuum metal coating is also developing rapidly

Table 1 development trend of flexible packaging materials in the world from 2000 to 2003

composite materials packaged products bopp/cast PP film

BOPP/metallized layer

Pet/PE

PA/PE

paper/pe

paper/aluminum/pe

Pet/aluminum/pe noodles, macaroni, etc.

fast food

cosmetics, dairy products

meat, dairy products

flour, rice flour

instant food, medicine

coffee

is opposite to composite materials, The other extreme of development is to reduce costs, only seek short-term protection, and use a large number of single-layer films. The average use of flexible packaging for various products around the world is roughly shown in Figure 2

when oil return is not allowed, environmental problems have attracted more and more public attention. The flexible packaging industry is required to adopt new technologies, new structures, new processes and new materials to reduce the emission of dust, gas and solid waste, reduce the consumption of materials and energy, and reuse, recycle and reuse, that is, the so-called 4R (reduce, reuse, recover, recycle) principle

in order to obtain satisfactory results, the flexible packaging industry continues to make efforts from the following three aspects: A. developing new machines suitable for different products; B. Develop new flexible packaging materials; C. Train well-trained employees who are familiar with equipment and materials. This paper mainly discusses the development of flexible packaging equipment

the process route of flexible packaging production is basically: printing → compounding → slitting → bag making or wrapping. Modern machines generally adopt advanced technologies such as computer control. Satisfactory results can also be obtained when raw materials have defects such as fracture, insufficient flatness, unstable tension, irregular shrinkage and tensile deformation

when developing new machines, the direction of efforts is as follows: ① the materials that can be processed are as thin as possible, and at present, they have been processed 2 Seal cover 5 μ Printing machine of mpet film; ② The consumption of materials and inks shall be minimized; ③ Low energy consumption; ④ Use the amount of waste solvent to feed air pollution; ⑤ Try to reduce the downtime of changing the printing plate; ⑥ Able to cope with the different properties of various printing materials

the key to solve the problem is often: the transmission of reel material from the unwinding part to the winding part, tension control system and air/heat control

3 gravure printing machine and flexographic printing machine

printing is one of the most important processes in flexible packaging processing. Modern flexible packaging printing basically adopts gravure printing and flexographic printing

3.1 metal templates are used for gravure printing. Therefore, the dot will not expand with the increase of printing pressure. As the material belt always contacts along the template surface of the engraving cylinder, as long as you pay attention to the maintenance of the doctor blade system, you can avoid blurred images

the time for replacing printing plates of modern gravure printing machines is greatly shortened. For example, it takes only 30 minutes for an 8-color intaglio printer to replace the printing plate, including cleaning, adjustment, color matching and registration, while it takes 90 minutes for an 8-color CI flexographic printer to complete the same work

gravure printing machine can also handle 2.5 μ M PET film, 5 μ M aluminum foil and other ultra-thin materials. In addition, the extended dryer on the gravure printing machine can be used for cold sealing, heat sealing, hot melt waxing, wire slitting, wire molding, wire cutting indentation and wire compounding

the maximum number of printing packages can reach 10 ~ 12 groups, and as long as enough space is reserved, the color deck can also be expanded after installation, which is flexible

the main factor restricting the development of gravure printing machine is that the cost of printing cylinder is relatively expensive, and it also requires a lot of storage space and storage equipment

now, due to the application of electronic laser engraving technology and computer, it can be made according to user requirements. The technology is quite mature and the cost is greatly reduced, which is about 1/3 of the original carving cost. The cost of laser engraving gravure cylinder and laser engraving flexo cylinder is quite close

another problem of gravure printing is that the material strip must be completely dry after printing from one color deck before entering the next color deck, that is, the so-called "wet on dry". This leads to large energy consumption, large registration accuracy control, and increased difficulty in registration accuracy control

3.2 flexible printing adopts elastic template. The so-called "dot enlargement phenomenon" often occurs due to elastic deformation after the template is pressed. In order to reduce this phenomenon, the adjustment of the printing machine is particularly important. The printing effect will be significantly different with different operators in different shifts. When printing small text patterns, some people think that flexographic printing cannot achieve satisfactory results

now this phenomenon has undergone a fundamental change. With the development of photosensitive resin, the deformation phenomenon can be significantly reduced by using some solvents. The computer-controlled laser engraving technology can produce a super 300 line textured roller with a computer-controlled color deck, which greatly reduces or even eliminates the phenomenon of dot enlargement. Compared with gravure printing, the printing effect has been difficult to distinguish

and flexographic printing allows the printing of the second color on the semi dry ink of the first color, that is, the so-called "wet on wet". In this way, the drying length between the two printing color groups can be greatly shortened, so it is possible to configure 8 ~ 10 printing color groups around a common central impression cylinder, so as to ensure high overprint accuracy and print extensible films

since the contact pressure between the inking roller and the printing plate, and between the printing plate and the material belt is required to be as small as possible, modern flexographic printing machines have high operation accuracy and are equipped with fine-tuning mechanisms. The eccentricity of a six color central imprinting cylinder is 0.125 ~ 0.1mm. Ao Hong, deputy secretary of the Party group and deputy general manager of the half color high-speed aluminum group, attended the ceremony. The thickness difference of the printing plate is less than 0.2mm, and the runout between the inking roller and the printing plate is 0.2 ~ 0.33mm

the repetition length is limited by the gear. At present, the maximum number of printing colors is 8, and it must be an even number

4 compounding machine

the compounding technology basically includes liquid coating compounding, metal vacuum spraying, extrusion compounding, wet compounding and dry compounding. Wet composite requires drying volatile solvents, so there must be a porous material in the composite film that can be breathable