Application of heat shrink labels in the beverage industry
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First, Introduction
In recent years, the annual output of Chinese beverages has shown a trend of increasing year by year, maintaining a growth rate of 10% to 20% per year. It can be said that the beverage industry is one of the fastest growing industries in the food industry. Various beverage production giants have rushed to the beverage market. Uniform, Huiyuan, Master Kong, Pepsi, Coca-Cola, Nongfu Spring, Robust, Yinlu, etc. have launched their latest beverages. The beverage industry is so hot that it is used in beverage packaging, and it has naturally benefited as a heat-shrinkable label that highlights the brand image.
Heat shrinkable labels are part of the label market and are used in heat shrink packaging. They are now experiencing rapid growth and market share is expanding. It is estimated that the annual growth rate can be maintained at around 15%, far exceeding the annual growth rate of 5% in the ordinary label market, and the development potential is huge, which has become the biggest bright spot in the label industry.
As the name implies, a heat shrink label is a film label printed on a plastic film or plastic tube with a special ink. During the labeling process, when heated (about 70 ° C), the shrink label will quickly follow the outside of the container. The contour shrinks and fits snugly against the surface of the container. These types of labels are not new products in the field of labels. They have been widely used since the early 1990s, but they have the unique advantage of being able to match the packaging of goods, so they are very popular in the packaging market. Another reason why shrink film packaging and shrink labels are popular is that their images have a three-dimensional effect, giving people a rich imagination, attracting the interest of many customers and consumers, thus opening up a broad market.
Second, the characteristics of heat shrinkable labels
1. Heat shrinkable label advantages
1.1The heat shrinkable film has high transparency, so the label has bright color and good gloss.
1.2 can be produced on a large scale, is a label that is independent of the production of the product.
1.3 The heat shrinkable film is close to the product after shrinking, and the package is compact and can display the appearance of the product, and the packaged product is beautiful. For example, the milk doll of Hangzhou Wahaha Group and the fermented yoghurt of the probiotic probiotics use heat shrink labels. The uniquely shaped shaped bottle is covered with a pattern designed to fit the bottle, which is full of interest and can capture the children's favor for the first time.
1.4 shrink film has good wear resistance and high strength, ensuring the weight of the contents. The printing belongs to the film printing (the image is in the film sleeve), which can protect the imprint and the label has better wear resistance.
1.5 heat shrink packaging process and equipment is relatively simple, heat sealing is good, labeling does not require the use of adhesives.
1.6 Nowadays, the beverage container has a unique shape and a personalized design, and the heat-shrinkable film label can clearly show the outer surface contour of the beverage container. The heat shrinkable film is close to the product and compact in packaging, and can be applied to the packaging of irregular products; the excellent adaptability to the bottle body is the reason why Xiamen Yinlu chooses to shrink the label. Most of the silver herons use shrink labels. The picture on the left shows:
1.7 heat shrinkable film as a label saves forest resources, reduces costs, is hygienic, and is easy to use.
2. Disadvantages of heat shrinkable film labels
2.1 It is necessary to consider that the shrinkage rate of the graphic image is the same as the shrinkage rate of the shrink film, so that it can be accurately reproduced.
2.2 The ink used in the label printing of heat shrinkable film must also have a certain shrinkage rate in order to accurately reproduce the graphic.
2.3 Because the heat shrinkable film label must be shrunk during the printing process, and the barcode can only be read accurately, it must undergo strict design and printing quality control. Otherwise, the pattern shrinkage will cause the barcode quality to be unqualified or unreadable. .
2.4 The printing suitability of most heat shrinkable films is not very good, and prepress pretreatment is required.
Third, the choice of materials
Affecting the quality of heat-shrinkable labels In addition to the control of the printing process, materials are decisive, so choosing the right material is key. So how to choose?
1. Material thickness. The thickness of the film material is determined according to the application field, cost, film properties, shrinkage properties, printing process, and labeling process requirements of the heat shrinkable label. It is generally required that the film thickness of the shrink film label should be 30 to 70 μm, and the conventional film specifications are 40 μm and 50 μm.
2. Material shrinkage rate. The shrinkage of the film is generally required to be within the range of application, and the transverse (TD) shrinkage is higher than the longitudinal (MD) shrinkage. The transverse shrinkage of commonly used materials is 50% to 52% and 60% to 62%, and 90% in special cases. The longitudinal shrinkage rate is required to be 6% to 8%. When making a shrink film label, try to choose a material with a small longitudinal shrinkage.
3. Environmental protection of materials. The materials used for the heat shrinkable film are mainly various thermoplastic films. Originally based on PVC shrink film, with the continuous development of market demand, PVC (polyvinyl chloride) shrink film is gradually reduced, and various PE, PP, PET (polyester), PETG (modified polyester), PVDC, OPS Multi-layer co-extruded heat shrinkable films such as (oriented polystyrene), OPP, and POF have developed rapidly and become the mainstream in the market. They have their own characteristics in terms of shrinkage characteristics and environmental protection.
Fourth, the classification of materials
1.PVC (polyvinyl chloride): PVC shrink film has good transparency and high shrinkage, between 40% and 60%, and its cost is low, tensile strength is high, temperature shrinkage range is large, and heat source is The requirements are not high, and the main processing heat source is hot air, infrared light or a combination of the two. However, the PVC shrink film is environmentally friendly, PVC is difficult to recycle, and produces toxic gas when burned, which is not conducive to environmental protection and has been banned in Europe and Japan. However, in China, because the environmental protection requirements are not very high, PVC is still the most important material in the field of heat shrinkable labels. The heat shrinkable label of PVC material has a market share of 80% in the domestic beverage industry.
2. PET film (polyester): PET film is an internationally recognized environmentally friendly heat shrinkable film material. Its technical indicators, physical properties, application range and usage methods are close to PVC heat shrinkable film, which is the current advanced one-way shrink film. Its transverse shrinkage rate is 70%, its longitudinal shrinkage is less than 3%, and it is non-toxic and non-polluting. It is the most ideal material to replace PVC.
3.PETG (modified polyester): Among various types of shrink film, PETG film has the highest environmental protection and shrinkage rate of 78% and can adjust the shrinkage rate in advance. PETG shrink film has a large market share, about 15 %~20%. However, the raw material cost is high, the shrinkage rate is too large, and it is limited in use.
4. OPS (Oriented Polystyrene): This is a widely used alternative to PVC film. It has good shrinkage performance of up to 65% and is also environmentally friendly. Compared with PVC shrink film, 0PS shrink film is environmentally friendly; 0PS shrink film is cheaper and more economical than PETG shrink film. The current market share of 0PS shrink film is 5%, and it still maintains a rapid growth momentum.
5. PE (polyethylene): Polyethylene is recognized as a non-toxic material, especially suitable for commodity labels in food, pharmaceutical, beverage and other industries. It can be made into a heat-shrinkable label with high transparency, good processing performance, high strength and environmental protection. However, due to its very stable non-polar properties, printability is poor and surface treatment must be performed. This limits its large-scale application to a certain extent.
6.0PP: OPP film has a low shrinkage rate, and its main application is in the field of shrink-surround label. At the same time, the quality is low and the price is very competitive, accounting for about 18% to 20% of the market. In order to improve the scratch resistance of the ink layer and better protect printed images, OPP is suitable for containers that require low shrinkage and are close to cylindrical. The difference between OPP and the other substrates mentioned above is that it is designed for the ring can.
Fifth, the printing process of the heat shrinkable film label
1. Prepress processing.
As a heat shrinkable film label, shrinkage deformation is unavoidable in the printing process, sometimes even more serious, and the shrinkage deformation in different directions and positions may be different. Therefore, how to design the shrinkage and deformation error of graphics and barcodes before printing is the difference between making shrink labels different from other printed materials. Here's a brief analysis of how to deal with it.
1.1 Prepress treatment of heat shrinkable film.
In theory, it is believed that to obtain good printability on a plastic film, the surface tension of the film should be higher than the surface tension of the ink, and the surface should have a certain roughness to form an adsorption force.
In the plastic film, polyolefins such as PP and PE film are non-polar polymer materials, which have stable chemical properties and small surface tension, which is lower than the tension of the ink. Poor adhesion to ink. While some films have surface tension and ink tension equivalent or higher, their surface is smooth, and the adsorption of the surface of the pore-free pores is small. At the same time, the antistatic agent of the antistatic agent added to the various films in the synthetic resin also affects. The surface properties of the film deteriorate the printability. Therefore, there are some printing suitability problems in most shrink films. Therefore, in order to improve the printability of the film surface, it is necessary to pretreat the surface of the film having poor printing performance to improve surface tension and surface adsorption. Commonly used methods are corona treatment, plasma treatment, chemical treatment, coating treatment, and the like.
1.2 label image size determination.
Firstly, according to the thickness of the shrink film, the transverse shrinkage of the film and the allowable shrinkage in each direction after packaging, the deformation error allowed after the shrinkage deformation, etc., to determine the size of the image on the shrink label to ensure shrinkage deformation. The latter pictures can be accurately restored.
1.3 flat design of heat shrinkable label.
The flat design of the shrink label needs to take into account the shape of the container. The designer of the prepress department needs to correct the deformation of some parts of the label, and try not to place the key image in a place with high shrinkage. In addition, it is also possible to work with the container manufacturer to make the density of the container suitable. Proper shrinkage is provided, both in smaller areas and in larger sizes.
2. Printing process
At present, the printing of heat shrinkable film labels is mainly gravure printing, using solvent-based inks, because the gravure printing plate has high precision, the printing quality of gravure printing on the film is the best in all printing, the ink layer is thick and strong, and the graphic Rich in layers. Moreover, the printing plate has a high printing durability and is suitable for long-running, and the printing volume of the label is often large, so gravure is more suitable. However, the gravure printing plate is complicated, the cycle is long, the cost is high, and it is easy to be polluted. Followed by flexible layout printing, with the development of flexographic plate making and printing technology, the printing color is clear and clear, with thick and high gloss of gravure, and the use of water-based ink for flexo printing is beneficial to environmental protection, so the environmental protection requirements are improved and flexible. The printing will have a larger application. In addition, offset printing and digital printing also have a range of applications to meet the specific needs of customers.
Although the heat shrinkable label in China is developing very fast and is not as sought after as other labels, the heat shrinkable label is not as popular as the sticker because of its large occupancy, because it does not have many obstacles that are difficult to overcome. Attracting the curiosity of the printing industry; in addition, the overall low level of heat shrink labels, the limitations in market expansion and process development, is also the reason why it is not good. However, with regard to the current application status of heat shrinkable labels, the use of such labels will be more and more, but the form will not change, only the materials will be improved, more environmentally friendly, and the future trend will be environmentally friendly. Direction development.