Development trend of the hottest paper packaging a

2022-08-04
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The development trend of paper packaging and its new printing technology (Part 2)

3.3 gravure printing technology

(1) Gravure Engraving Technology and digital proofing

traditional gravure includes engraving gravure, etching gravure and photographic gravure, among which engraving gravure includes manual engraving gravure and electronic circle engraving gravure. Modern electronic engraving gravure has the advantages of advanced technology, low plate making cost, high and stable plate making quality, wide application range and environmental protection. It occupies a leading position in gravure plate making

modern electronic engraving systems do not need to input information through the scanning unit. All image data, equipment driving parameters and other information are transmitted to the electronic engraving equipment in digital form. The key technologies of electronic engraving system include driving circuit technology, digital signal processor application technology, AC servo technology, high-frequency electromagnet technology, etc

intelligent and high-frequency engraving technology is the main development direction of gravure electronic engraving system. The intelligent engraving system includes automatic trial engraving, automatic quick crossing over the non engraving area, automatic replacement of the cylinder, etc. Engraving frequency is the bottleneck that affects the efficiency of electric engraving system. Therefore, the development of higher frequency electromagnetic engraving head has always been the main research direction of electric engraving system manufacturers

gravure proofing has analog mode and digital mode. The gravure proofing machine is made by simulating the principle of gravure printing machine. The ink is transferred to the substrate through the rolling action between the embossing cylinder and the gravure cylinder to form a clear pattern. The digital proofing machine adopts inkjet and electronic imaging proofing. Using digital technology to obtain high-resolution eye tone samples directly on heat transfer materials can effectively reflect the fine level. Although the sample color of digital proofing is difficult to achieve the color reproduction effect of transparency and concentration of gravure printing ink. However, digital proofing has the characteristics of high production efficiency, reliability and convenience, which is an important trend in the future

(2) improvement of gravure printing inks

with the enhancement of people's awareness of environmental protection, more and more attention has been paid to the environmental pollution caused by traditional solvent based inks. With the technological progress of the new generation of water-soluble polymers, water-based inks have been successfully applied to the gravure printing process of paper packaging products such as cigarette packets and wine labels, realizing toluene free ink printing and avoiding the pollution of solvent-based inks to the environment and operators. Water based ink has shown great influence and significant growth potential on the packaging market, which is the development direction of the ink industry. Water based glazing oil will also gradually replace solvent based glazing oil

in Europe and the United States, more than 90% of printing enterprises use water-based inks that are non-toxic to human body and pollution-free to the environment to print tobacco and wine boxes, medicine boxes, food boxes and packaging boxes (boxes) of daily necessities, avoiding harm to the ecological environment. In the field of gravure printing abroad, it has become an inevitable trend for water-based ink to replace solvent based ink

the water-based intaglio aluminum box ink also has the functions of automatic algorithm generation and automatic editing of experimental reports; The volatile and dry heat curing ink, which greatly facilitates the debugging and system redevelopment, is mainly composed of film-forming substances, colorants, additives and cosolvents. Film forming material is the key part to determine the physical properties of ink. Water soluble acrylic resin and water-soluble self crosslinking lotion colorants are often used as basic materials with alkali resistance. This water-based gravure printing ink has the characteristics of non-toxic, tasteless, good transfer performance and adhesion fastness, and is suitable for rotary gravure printing

(3) advanced technology of gravure printing equipment

most foreign advanced gravure printing machines use sleeve impression cylinder and plate roller direct drive technology. The sleeve type imprinting cylinder has the advantages of rapid replacement of the cylinder, and there is no need to break the material belt when replacing the imprinting cylinder, so the waste of materials can be reduced. The plate cylinder of each printing unit is directly driven by a separate motor to realize longitudinal registration during the stamping process, and a stepping motor is commanded to move to control horizontal registration. The main advantages of the independent drive are that it does not need the mechanical transmission shaft and the registration compensation roller mechanism, the number of mechanical parts is reduced, and the length of the material belt is shortened. Therefore, it is conducive to improving the printing quality and printing speed

the quick replacement, positioning and installation system can effectively reduce the auxiliary time of the device and improve the work efficiency. At present, foreign advanced gravure printing machines use pneumatic installation of doctor blade fixing clip, printing device, trolley rapid positioning installation and other devices to realize the rapid replacement of live parts

3.4 silk screen printing refresh technology

silk screen printing has the characteristics of thick ink layer, rich picture and text layers, strong three-dimensional sense and wide range of printing materials. Its application in high-grade tobacco, wine and food packaging cartons is gradually increasing. The use of UV silk ink to print sanding, refraction, ice flowers, wrinkles and other effects on cigarette boxes has greatly stimulated consumers' desire to buy. However, due to the low printing speed, slow ink curing speed, difficult to control the printing quality and large consumption of printing materials, the flat press and flat wire printing method can not meet the needs of cigarette carton scale and mass production. The high-speed rotary silk printing production line is adopted, which has the advantages of high printing speed, high productivity, stable printing quality and low consumption. It has changed the traditional flat press flat silk printing, manual paper supply and ink supply, and is suitable for high-speed automatic and large-scale mass production of exquisite folding cartons

the nickel metal round wire printing plate, built-in doctor blade and automatic ink supply system are used for web rotary wire printing. The doctor blade transfers the printing ink from the round wire plate to the substrate surface supported by the embossing cylinder. How to use the steel strand relaxation testing machine in the whole printing process? From paper feeding, ink supply, printing color registration, UV drying bath, etc. are fully automatic controlled by computer. The round screen printing plate is made of 100% nickel non-woven fabric material. Its holes are formed by electroforming. The whole surface is flat and thin to ensure the stability and precision of the imprinting. It is suitable for large format rotary printing. The maximum speed can reach 125m/min. The silk can be reused for 15 times. Therefore, the web rotary silk printing can not only meet the requirements of special effects such as sanding and ice flower printing, but also online hot stamping holographic anti-counterfeiting marks, embossing and die-cutting forming, which is easy to realize high-speed automatic printing of cartons

the environmental friendly UV screen printing imitating metal etching ink is mainly composed of oligomer (i.e. UV curing resin), active diluent (i.e. photosensitive crosslinking monomer), photoinitiator (polymerization) and additive. It is printed on gold and silver card paper. The UV screen printing imitation metal etching ink solidifies rapidly under the irradiation of UV light, and the surface of the printed matter has a frosting effect

under the external light irradiation, the photopolymerization initiator in UV ink absorbs photons of a certain wavelength, excites them to the excited state, and forms free radicals or ions. Then, through the transfer of energy between molecules, polymers such as polymeric prepolymers and photosensitive monomers become excited states, resulting in charge transfer complexes; Complexation can continuously crosslink the scaffold and solidify the film. UV ink selectively absorbs ultraviolet photons. The dryness of UV ink is affected by the total energy of UV light source and the energy distribution of different wavelengths. Solving the matching of UV ink and UV light source is conducive to accelerating the drying speed of ink, improving labor productivity and energy utilization, and reducing production costs

4. Surface finishing and forming processing technology

4.1 water-based glazing and UV glazing

the coating process is simple and cheap. However, the coated paper is difficult to be recycled, non degradable and easy to cause white pollution. Long term use will also endanger the health of workers. Therefore, the traditional instant coating adhesive materials will be replaced by high-quality environmental friendly new adhesives. Glazing can not only enhance the surface brightness and protect the printed text, but also does not affect the recycling of paper, which can save resources and protect the environment. Therefore, it is widely used in the surface processing of paper packaging prints. Glazing paint mainly includes solvent glazing oil, water-based glazing oil, UV glazing oil, etc. Due to the poor effect of solvent varnish, and is not conducive to environmental protection, the scope of application is greatly limited

with water as the solvent, water-based polishing oil is non-toxic and tasteless, eliminating the harm to human body and environmental pollution. It has the characteristics of fast dry bath speed, stable performance, good wear resistance of polishing surface, wide post press processing adaptability, good heat sealing performance, safe and reliable use, and has been paid more and more attention by food, medicine, tobacco carton packaging and printing enterprises

uv glazing relies on UV irradiation to cause chemical reaction inside the UV coating and complete the curing process. Due to the role of UV, UV glazing is instantly dry, and there is no solvent volatilization during curing, which will not cause environmental pollution. The printing products using UV varnish have high surface gloss, heat resistance, wear resistance, water resistance and light resistance. However, due to the high price of UV varnish and high requirements on machine performance, it is only used for the polishing of high-grade cartons at present

4.2 hot stamping technology

in the fierce market competition, in order to increase the added value of products and carry out packaging anti-counterfeiting more effectively, more and more packaging cartons adopt hot stamping technology. Hot stamping includes ordinary hot stamping, cold hot stamping, concave convex hot stamping and holographic hot stamping. The commonly used ordinary hot stamping processes include flat hot stamping and circular hot stamping. Because circular hot stamping is line contact, it has the characteristics of extensive hot stamping substrate, suitable for large-area hot stamping and high hot stamping precision, and is widely used

hot stamping does not require heated metal plates, but uses printing adhesives to transfer metal foil. Cold hot stamping process is a promising new process with low cost, energy saving and high production efficiency

concave convex hot stamping (also known as three-dimensional hot stamping) is the use of modern engraving technology to make the upper and lower matching female and male molds. The hot stamping and embossing processes are completed at one time, which improves the production efficiency. The molds made by electric engraving can have curved surface transition, which can achieve the three-dimensional relief effect that is difficult to be achieved by molds made by general corrosion method. With the appearance of concave convex hot stamping, the hot stamping and embossing processes are completed at the same time, reducing the process and waste products caused by inaccurate overprint

holographic identification uses computer technology to change the amplitude and frequency of the grating, making its effect more brilliant and clear than the color of the calculated pattern. If the electronic universal testing machine is used as a copy of the original due to the high frequency of the fixture, a large number of holograms will be lost, so as to achieve the purpose of anti-counterfeiting. Holographic identification can not only have very good anti-counterfeiting performance, but also make special numbers or words into holographic identification according to customers' needs. It is more and more widely used in high-end carton packaging

4.3 die cutting technology

(1) die cutting plate and its processing technology

die cutting plate material: in addition to the multi-layer wood plywood plate commonly used in China, durama and sandwich are also popular abroad. The life of the die-cutting plate mainly depends on the quality of the tangent knife and the number of tool changes. Fiber plastic plate and sandwich steel plate not only have high precision, but also overcome the shortcomings of multi-layer wood plywood plate which is easily affected by humidity and temperature changes; And the number of tool changes is 3 times and 6 times more than that of multi-layer wood glued version respectively. In foreign countries, in addition to high-pressure water jet grooving for fiber plastic plates, multi-layer wood plywood plates and sandwich steel plates are generally made by laser cutting square calligraphy

die cutting plate laser cutting system die cutting plate laser cutting system is composed of laser machining head, computer aided design (CAD) software, computer numerical control device (CNC), workbench, etc. Through the workbench and

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