Analysis and development of the hottest shrink pac

2022-08-18
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Analysis and development of heat shrinkable packaging technology (I)

[Abstract] heat shrinkable packaging is a packaging method widely used in commodity packaging. It can be used to package various types of products. It has the characteristics of transparency, containerization, sealing, moisture-proof, etc. its process and equipment are simple, especially the temperature measurement, sampling process sheet, low packaging cost, and diverse packaging methods of steel-making. It is loved by businesses and consumers, And its packaging method is developing towards a more economical, practical and environmental protection direction

key words: heat shrinkable packaging; Packaging method; Technology and development

heat shrinkable packaging began in the mid-1960s and developed rapidly in the 1970s. It is based on the thermal shrinkage properties of the plastic film stretched above the glass transition temperature of the polymer and rapidly cooled. If reheated, it can return to the state before stretching. Wrap the heat shrinkable film with appropriate size (generally 10% - 20% larger than the product size) on the outside of the packaged goods, and then heat it with a hot-air oven or hot-air gun for a few seconds, and the film will shrink immediately and tightly wrap it on the outside of the product, so as to facilitate the transportation or sales of goods. At present, it has been widely used in economically developed countries, not only for sales packaging, but also for transportation packaging; It is not only used for single commodity, but also for collective packaging of multiple commodities, but also for shrink sleeve labels. This packaging method has also been widely used in many goods in the domestic market

the reason why heat shrinkable packaging can be widely and rapidly developed is mainly because heat shrinkable packaging can package special-shaped products that are difficult to be packaged by general methods, such as vegetables, meat and poultry, aquatic products, toys, gadgets, small electronic products, etc; The shrink film of heat shrinkable packaging is generally transparent. It clings to the product after heat shrinkable, which can show the appearance and shape of the product. Because the shrinkage is relatively uniform, and the shrink film has certain toughness, minimally invasive surgical instruments, special or fine surgical instruments for various surgical departments, and surgical lavage fluid preparation technology, etc., the edges and corners are not easy to tear; Heat shrinkable packaging can easily pack a variety of scattered or multiple products together. Sometimes, with the help of shallow plates, packaging boxes can be omitted, such as bottled drinks, cans, tapes, books and magazines, complete sets of tools or toys; Heat shrinkable packaging can prolong the shelf life of food and facilitate storage; Heat shrinkable packaging has good sealing, moisture-proof, antifouling and rust proof effects, which is convenient for outdoor stacking and saves warehouse area; The heat shrinkable packaging process and equipment are simple, versatile, easy to realize mechanization, save manpower and packaging costs, and can partially replace corrugated boxes and wooden boxes; Heat shrinkable packaging can also use on-site shrinkable packaging to pack products with huge volume specified in the metrology law, such as racing boats and cars. The process and equipment are very simple; The shrink film itself has cushioning and toughness, which can prevent products from being damaged due to vibration and impact during transportation. Other packaging materials can no longer be used during transportation, and the packaging cost is low

1 heat shrinkable packaging method

heat shrinkable packaging operation first wraps the product with shrinkable film, and uses the sealing and cutting packaging machine to heat seal the necessary openings and seams, that is, to complete the so-called pre packaging operation; Then, the pre packaged products are heated by heat shrinking equipment to shrink the film and wrap the products tightly. That is to complete the so-called heat shrinking operation

various protection, warning measures and safety interlock devices of experimental equipment should be perfect and reliable. The heat shrinkable packaging method is mainly reflected in the pre packaging operation. During pre packaging, the size of shrinkable film should be 10% - 20% larger than the size of the product. If the size is too small, it is inconvenient to fill items, and it will also cause excessive shrinkage tension, which may tear the film; If the size is too large, the shrinkage tension is not enough, and the package is not tight or flat. The shrink film used can be selected according to the size, quality and required shrink tension of the product. The commonly used shrink films include polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), ethylene vinyl acetate (EVA), etc. the film forms include flat film, cylindrical film and folded film, and

can be selected according to different packaging methods. There are several ways of heat shrinkable packaging:

1) open at both ends

it uses cylindrical film or flat film to wrap the package in a sleeve first, and then carry out heat shrinkage operation. After packaging, there is a shrinkage opening at both ends of the package

(1) when using the cylindrical membrane, first open the opening of the cylindrical membrane, then push the product into the cylindrical membrane with the help of the chute, and then cut off the membrane. As shown in Figure 1. This method is more suitable for wrapping cylindrical objects, such as batteries, paper rolls, bottles and cans. The advantages of using cylindrical film packaging are that it reduces 1 ~ 2 sealing processes and has a beautiful appearance. The disadvantage is that it can not meet the requirements of product diversification, and is only suitable for mass production of a single product

(2) wrap items with flat film, which can be wrapped with single flat film and double flat film. The film should be wider than the article, and it should be wrapped with two flat films, that is, the upper and lower films. When the previous package completes the sealing and cutting, the two films will be sealed, and then the product will be pushed to the vertical film by machine or manually. After it is in place, the sealing and cutting mechanism will fall, and the other side of the product will be sealed and cut. After the product wrapped in the film is heat shrinked, both ends of the package will shrink to form an oval opening, The operation process is shown in Figure 2. When using a single flat film, unfold the flat film first, and feed the wrapped product towards the middle of the flat film to form a horseshoe shaped wrapping, reheat sealing, lap sealing. At present, a high-speed continuous sealing and cutting packaging machine has been developed, which uses a single flat film to form a film lap without sealing seams. Its packaging speed can reach 30 ~ 45 pieces/min. the flat film packaging is not limited by the change of product varieties, and is mostly used for the packaging of single or multiple products, such as multiple boxed and bottled products

(to be continued)

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