Status and development of label environmentally friendly materials and printing processes
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As an indispensable business card in the circulation of goods, the label has received universal attention from all walks of life and commodity manufacturers. Self-adhesive labels, in-mold labels, heat-shrink labels, anti-counterfeit labels, digital labels, R F I D electronic labels, etc. are widely used in the market. At the same time, with the growing popularity of sustainable development, low carbon, energy saving, emission reduction, environmental protection and green printing have become one of the top priorities of the current printing industry, and environmentally friendly labels have become the mainstream of future label development.
First. Environmentally friendly materials for label printing
The need for label environmental protection undoubtedly puts higher requirements on the printed materials of label printing. For label printing substrates, from the original fiber paper and single film material to synthetic paper, composite paper, multi-layer modified film material. The transition, in response to the requirements of the label function and quality, is also more environmentally friendly. For the label printing ink, it is also required to be non-toxic and non-volatile, easy to deink when recycled, and the ink product can be degraded.
1. Printing material
①Environmentally friendly synthetic paper.
Synthetic paper does not contain the components of fiber paper, but has the writing and printing properties of fiber paper. It is a new type of three-layer composite material that is formed by mechanical processing using P P as the base material and adding fillers and additives. Synthetic paper processing is a process in which P P particles and filler materials are mixed and melt-extruded into a film, which is longitudinally stretched and then combined with two upper and lower surface layers, and then transversely stretched and cooled to obtain a product. Synthetic paper consists of three layers of film with different stretching effects. The middle layer is stretched in two directions, with high tensile strength and rigidity, while the upper and lower films are only stretched laterally, producing dense micropores. The light is scattered and becomes white and opaque. With the unevenness and whiteness characteristics of the fiber paper, it has good writing and printing suitability. Synthetic paper has the advantages of anti-transparent, anti-mildew, solvent resistance, high whiteness and high-quality reproduction. It is suitable for making labels inside the film. It can be recycled at the same time as the packaging container. It is smokeless and has no odor when burned. It is a green packaging material.
② composite paper.
The composite paper for labeling is often a type of printing material composed of coated paper based on a coated paper or a layer of non-paper material. Among them, aluminized paper is a common type in label printing. Aluminized paper is coated with a layer of aluminum powder on the coated paper, which is well compounded with the paper, and then uniformly coated with a layer of coating on the aluminum coating to improve the printability of the surface. Composite paper has strong tear strength, gorgeous appearance, easy recycling, and is suitable for wine labels.
③ Environmentally friendly membrane materials.
P E T and O P S are currently widely used in the manufacture of heat shrink sleeves. The heat shrink sleeve is a sleeve label and is a film label printed on a plastic film or plastic tube using a special ink. This label can be recycled and has significant advantages in terms of cost savings and environmental protection. From everyday life, we can also clearly feel that the market for heat shrinkable sleeves is expanding, covering almost all retail industries. Domestic suppliers of PET are mainly SKC in South Korea, Fuwei in Shandong and other suppliers. OPS suppliers are mainly in Japan, where the factory is located in Shanghai and Guangdong Huaye, etc., which are the fastest growing labels in East China and South China. , can achieve convenient procurement.
With the shortage of timber resources, for a large developing country, the huge amount of commodities has forced us to restrict the amount of label printing fiber paper, so the amount of paper is getting smaller and the amount of film is getting larger and larger. The limitations of the film's printability and post-processing performance make the technology hotspots turn to multi-layer film compounding to achieve the printing and environmental characteristics of fiber paper.
2. Environmentally friendly ink
Ink is the key to reflecting the source, content, nature, and function of the product in the label. The types of label printing environmentally friendly inks are also under constant development and research.
① U V ink.
UV inks use the radiant energy of the spectrum to achieve ink drying, low VOC emissions, low environmental pollution, high ink solid content, and high color density; as long as the UV film is not irradiated, the ink film is basically dry, so it is not necessary to end the production task. Cleaning the ink path, the reasonable loss of ink is small.
UV inkjet printing, which combines the advantages of inkjet printing technology and UV curing technology, is a new technology developed at the end of the 20th century. It has the ability to print on rigid and flexible materials, high production efficiency, and image resolution of printed products. High, durable, and low-cost advantages make it a good application prospect. In the field of digital printing inks, according to I nfo T rends, the sales of solvent-based inks will be reduced from 900 million US dollars to 600 million US dollars from 2000 to 2004, with an average annual compound growth rate of - 9 %; sales of UV inkjet inks will increase from the current $360 million to $800 million in 2014. At present, ink manufacturers' research on UV inks for green packaging (such as food, pharmaceuticals, packaging for daily use, etc.) focuses on the topic of how to reduce the migration of harmful substances, such as the replacement of what is now commonly used with large molecular weight photoinitiators. A small molecular weight photoinitiator that meets environmental requirements in ink formulations.
② water-based inks.
As a new type of packaging printing material, water-based ink is mainly a solvent compared with oil-soluble ink. Printing with water-based ink does not need to be diluted with any organic solvent, and only water can be used. Therefore, water-based ink has no V O C emission problem. At present, water-based inks are not only used more in label printing, but also in the printing industry. Of course, it should also be noted that problems such as long drying time and limited color saturation of the ink are required to be noted.
③ Soybean environmental ink.
Soybean eco-friendly ink uses soybean oil to replace the mineral oil in the ink. The soy oil-based ink made by the company replaces the common petroleum-based ink, which can better avoid the pollution of the product. Since the content of mineral oil is partially replaced by soybean oil, the oleic acid in the vegetable oil is relatively more than the conventional ink, and the emulsification rate of the ink is increased to some extent, so that the ink is produced under actual printing conditions. Printing is unstable. Therefore, it is necessary to select a resin with good water resistance as much as possible in selecting a resin to prevent excessive emulsification.
④ edible inks.
As a special ink, edible inks are widely used in food and pharmaceutical industries, such as DNA and anti-counterfeiting inks synthesized by DNA and edible inks, in addition to traditional inks. It is safe and does not cause any harm to the human body. It is mainly used in the pharmaceutical industry, such as printing of capsules, film-coated tablets, sugar-coated tablets, etc., only need to check the DNA password mark on the capsule to verify its authenticity. The colorant is an edible pigment, and the binder is generally composed of an oil and an auxiliary agent thereof, and the oil is an edible vegetable oil, and the solvent may be a liquid sugar. The printing method of the edible ink is basically the same as that of the conventional printing in the prepressing stage, and the printing method is mainly the ink jet type and the silk screen type. In the printing process, when selecting the drying method and condition parameters of the ink and the thickness of the ink layer, the characteristics of the ink itself should be considered on the one hand, and the characteristics of the food or the medicine itself should be emphasized on the other hand. At present, the exploration around edible inks is mainly reflected in the selection of raw materials. How to choose the materials with better printing color rendering and safer use is the problem to be solved at present.
In order to make the information on the label lasting, clear, and difficult to erase, it is necessary to fully match the ink with the label substrate, and the ink has good printability. In terms of achieving environmental labeling, it is also necessary to consider the actual use of the label and select a suitable environmentally friendly ink depending on the substrate. For example, labels on outdoor air conditioners need to consider performance requirements such as light fastness and rain resistance; labels on detergents need to consider performance requirements such as water resistance, acid and alkali resistance, and soap resistance. In addition, when using synthetic paper and film substrate for printing, it is necessary to test the adhesion fastness, scratch resistance and folding resistance of the selected UV ink, so as to prevent the ink layer from falling off and fading after the label is used, thereby causing Secondary pollution.
At the same time, the environmentally friendly ink used in the PET shrink film is similar to the PVC shrink film, but the surface adhesion of the white ink needs to be confirmed. This is because the surface adhesion of the white ink to the PET shrink film is higher than that of the PVC shrink film, and the other colors are basically the same. OPS shrink film is the most environmentally friendly film material to date, it should use environmentally friendly inks with completely alcohol-soluble acrylic resin, and the surface solvent resistance of OPS shrink film is much lower than that of PVC and PET shrink film, so it must be selected. Environmentally friendly ink for OPS shrink film. In more specific cases, it is necessary to gradually find a solution in actual production.
Second, environmental label printing process
1. Flexographic printing
Compared to embossing, Flexo uses environmentally friendly inks to achieve true environmentally friendly printing. In the United States, flexo printing is the mainstream technology for label printing, and 80% of self-adhesive labels use flexo printing. In Europe, flexo and embossing are half of each in self-adhesive label printing. In China, embossing technology is very mature in the label market, and currently has a higher market share than flexo printing. However, the development of flexo printing is very fast, and it has an absolute advantage in label printing. This is due to the continuous improvement and improvement of its process technology, which is reflected in the following aspects:
① The direct plate-making technology of flexo printing, especially the screening technology, has made a breakthrough, which has greatly improved the printing quality of flexo printing, especially in dealing with the gradation of delicate level to the net.
② Compared with embossing, flexo printing uses a short ink supply system of anilox roller, so that flexo printing requires almost no adjustment of ink color when preparing for adjustment, and no official ink supply. The change causes chromatic aberration and causes waste, which also has an advantage in yield.
③ Flexo printing is suitable for all combinations of printing methods, and is the most inclusive and malleable in all printing methods.
④ Flexo has an advantage in dealing with short runs.
At present, flexo printing has achieved a very high degree of standardization, and the operation is simple and convenient. The anilox roller ink transfer method also ensures the high consistency of the colors of different batches of printing, which is unmatched by other printing methods. Although the flexo dots are not as delicate as the embossing because of the plate material, the flexo printing has an advantage in terms of overall printing quality. In China, flexo printing is still in its infancy and there is a lot of room for improvement. At present, domestic customers are more likely to choose the printing method from the perspective of cost. When the customer's environmental awareness and quality awareness are improved overall, they will be more inclined to spend more to ensure quality. At that time, the advantages of flexo printing will be highlighted. . In the long run, with the improvement of flexographic plate making technology and the reduction of plate making costs, flexo printing will gradually show certain advantages in the printing of short-run jobs. At that time, flexo printing will definitely replace embossing. , become the mainstream technology of label printing.
2. Digital printing
Digital printing has also become an environmentally friendly label printing process due to the elimination of the plate making process. At the same time, it can realize on-demand printing, improve production efficiency, increase the anti-counterfeiting function of label printing, and realize the individualized demand, while the printing width is basically unlimited. Digital label printing can easily realize graphic printing and variable data printing to meet the ever-changing needs of the market, mainly in the following aspects:
① Adopt digital production, reduce production cost, print on demand, no waste, and realize both long and short versions, expand the business scope of the enterprise, and the whole process can be completed by one person, improving production efficiency.
② The anti-counterfeiting function of the product can be realized by means of spot color printing, micro-text printing, bar code printing and watermarking.
③ Improve the accuracy of label printing, and print high-precision images with resolutions of 2,400 d p i and 2,300 lines/inch.
④ The printing range and service range are expanded to print on any material including leather, glass, wood, stone, etc., to meet the needs of different fields.
⑤ Adaptable to the production environment, the overall design process ensures that it can operate freely in various industrial production environments.
The growing demand for personalized products in the market and the shortening of the launch cycle of new products have contributed to the development of on-demand digital printing. According to survey statistics, 45 percent of label printers believe that on-demand printing will be a very important factor; 6 7 percent of label printers believe that short-run production capacity will be a very important survival factor; 4 0 is expected in the next few years % of the label production will be digitally printed.
Third, the conclusion
The growing demand for green environmental protection also places demands on a wide range of labels. Grasping the development direction of environmental labeling materials and printing technology, developing and developing environmentally friendly materials and printing methods will be the day to advocate green and environmentally friendly life, and the focus of the label industry that is more widely used.