shrink film manufacturing process
In this article, we will talk about the shrink film manufacturing process. Shrink films have provided excellent conditions for storage, packaging, and easy moving and transportation of products. Gradually, due to its unique features such as flexibility, lightness, ease of use, and reasonable price, this product has found a unique position in the packaging industry in the packaging of products such as cans, bottles, canned goods, and also small boxes. Please be with us till the end of the article.
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Shrink film
Shrink film is a type of packaging produced from a thin layer of a transparent and flexible polymer that sticks to food containers and products to create a tight seal. Plastic ensures products’ health by protecting against air, preventing moisture absorption, and increasing their useful life.
Plastics are synthetic polymers made from giant molecules produced from the combination of thousands of tiny molecules of the same type in a long chain. These small molecules are known as monomers; combining them is called polymerization. Natural polymers include familiar materials such as silk, rubber, and cotton.
Shrink film manufacturing process
To shape the granules and use them in the production of multi-layer films, it is necessary to melt them using an extruder. The extruder does the melting of these granules.
1- Extrude:
The extruder consists of a cylinder with a nozzle and includes feeding, melting, metering, and mixing areas. In this industry, single extruders are used, and depending on the machine’s capacity, the extruder’s dimensions can be different. As an example of the Shrink film manufacturing process, we explained below.
The diameter of the spiral is from 45 to 300 mm. Extruders are usually designed with a capacity of 50-2000 kg/h, and the length to the diameter of the spiral L/D is between 28 and 33. The L/D used in different polymers varies according to the type and properties of the polymer. Commonly, L/D is used around 30. An electric element system or an oil system can heat the wall of the extruder or cylinder. The fed granules move forward due to the rotation of the spiral. And the temperature of the granule increases at this time. As a result of the temperature of the wall and the temperature caused by friction, the polymer gradually softens. In the end, it will be completely melted and uniform. In producing multiple films, multiple extruders are used for the final result. After the granules are dissolved, the resulting melt is transferred to the blower to form a film. A set of several extruders is used to produce the film in several layers. The number of extruders in the system equals the number of layers in the final film. The simultaneous use of several extruders and the production of a multi-layer film makes it possible to use several polymers in this film’s production simultaneously. The design of the extruder output is such that all the extruders are connected to a mold. On that mold, a separate output is considered for each extruder. The molten material from the exits is finally placed on each other and becomes a multi-layered film.
2- Blowing air:
The next step in the Shrink film manufacturing process is air blowing. After the granule melts, the resulting melt comes out of the end part of the extruder. An aeration system is used to form the polymers in the form of bubbles. By using cool air blowing and shaping the molten polymer, the molten film becomes solid and is formed. Figures 4-a and 4-b show the general process of single-layer film production and the formation of the film from the polymer melt, respectively. During the application of cold air, the film is somewhat stretched so that in addition to increasing the length, its appearance is increased to some extent, and its final strength is increased. In the end, the created film is assembled on the roll.
As it is clear from the name of this product, the process consists of three stages: forming, filling the film with another product (using the film for packaging), and finally, packaging the created film.
3- Forming stage:
The created circular polymer film is continuously removed from the system. Due to this film’s uniform and continuous release, it could be used for packaging. This way, after leaving the forming method, the film is filled with a specific product by the weighing machine. This product can be food or anything else that needs packaging. After the desired film is filled with the product to a specific size, the packaging and cutting operations are performed. It’s the third step in the Shrink film manufacturing process.
4- Packaging:
After distributing the product in the package, a specific volume of the film needed for packaging the product is determined, and the film is cut into exact dimensions and packaged. The packaging is such that a particular area is installed to open this package.
5- Shrink film printing process:
In the last step of the Shrink film manufacturing process, a part of the shrink wrap film passes through a six-color flexographic printing machine before packaging. It is printed according to the customer’s order and the desired product. The capacity of this printer is 60 kilos per hour, and the rest of the produced film will be packaged. This process is to strengthen the promotional aspect of the product.
Shrink film uses
Today, nylon polyethylene films are mixed with daily life and have many applications.
The Shrink film is used in different applications according to the number of layers and the type of polymer used. These films are often used for packaging and storing food, agricultural products, medical equipment, chemicals, and general and military purposes.
These films can also produce layers with different properties, such as low permeability. These films can replace CPP and BOPP polypropylene films used for packaging.
In this article, we tried to introduce the shrink film manufacturing process. Please share your comments and suggestions with us. We hope this article was useful for you.