Current Situation and Development of Offset Blanket

Published: 23rd April 2010
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    In 1982, the former State Economic Commission, set up a printing technology and equipment co-ordination team, under the leadership of Comrade Fan Mu Han developed a 'laser photo-typesetting, electronic color separation, offset printing, binding interaction "with 16 character development policies for China's development of printing technology and equipment played a major guiding role in making offset printing prospered. Offset Printing Blanket (hereinafter referred to as Blanket) is the offset printing, a very important but essential to the printing equipment and printing technology with the continuous development of right its varieties, the quality has also been put forward new demands. In the offset printing blanket play an intermediary role, based on a blank part of the "water dredging oil", while the graphic part of the "pro-oil hydrophobic" in principle, plate The ink on the part of the first delivered to the blanket, and then the ink from the blanket as faithfully as possible transfer to the substrates. the early 60s, China's printing press blanket used on all rely on imports. since 1960 by the Shanghai Printing Equipment Factory trial out of the first piece of blanket (general field blankets), the general blanket has gone through more than 40 years, has basically all the ground at present blanket import substitution for the printing speed of 4000 / hour or so presses.





Common Blanket generally off (915cm × 915cm × 1.85mm) and a souvenir sheet (1200cm × 1200cm × 1.85mm) two kinds of specifications, the structure of four-bonded cotton after (Tu natural mortar between each floor ), coated with ink solvent-resistant synthetic rubber slurry.





Blanket is a fine rubber products, it is to faithfully printed version of the graphic part of the absorption of the ink transferred to the substrates (typically for all types of paper), and its printing plate on a blank portion of another by the Run version of Roller brushing the wet syrup in advance to ensure that it does not stick ink, so the rubber surface must be resistant to ink, solvent (for printing plate when Kaishi blanket), acid and alkali synthetic rubber, while the four-layer blanket Inter have a good bond strength, but also to give blanket certain degree of flexibility, the general kinds of natural rubber as the main rubber design a reasonable formula. As a general offset printing, ink transferred to the paper up process is a certain pressure, through the blanket with an embossed roller to complete the reverse operation, coupled with the completion of the general color printing at least yellow, goods, blue, black four color, advanced 6-color printing, and even 8-color, to ensure that accurate overprint require blanket must ensure that sufficient tension (Blanket is the tension on the drum) and a good constant load elongation, to ensure that the printing blanket the process will not become ever longer and caused network deformation, writing imaginary ills of hair.





   In addition, the blanket must also have a good overall flatness of the surface can not have any size adhesive impurities in order to ensure uniform ink delivery, picture level, clear, sharp clear text. Thus, the overall design of Blanket involves chemistry, polymer chemistry, and textile and many other fields, especially as a blanket at the end of frame materials, cloth, in its weaving process is designed to be spinning cotton yarn, cotton weaving expertise, special finishing process, meridional (ie, blanket wrapped in rollers direction) to maintain a certain degree of elongation deformation of the textile industry in a very special technical requirements for products.





With the rapid development of printing technology, in particular, to keep the multi-color printing, high-speed (web, double-sided printing) direction, for supporting the blanket of the development must be compatible with. The original blanket has far can not meet the general needs of the printing, air-cushion-type compressible blanket (hereinafter referred to as air-cushion blanket) came into being. The so-called air-cushion blanket is a layer near the surface of the second floor at the end of the next layer of cloth in between the very fine closed-cell rubber sponge layer, so that the whole blanket is extremely good resistance to compression deformation and the instantaneous elastic recovery in order to ensure high speed printing in the case of smooth (developed to the two-color printing, four color, six-color, eight-color machines, web presses, and the speed has exceeded 10000 / hour, or even to 60000 / h).





Blanket on the ground in the printing process of engagement with the embossing cylinder (whose internal structure does not exist compression layer) produces shear stress, so that blanket the surface of rubber rollers in contact with both sides of the resulting expansion of the phenomenon (or convex hull), thus affecting the printing quality . The air-cushion blanket contact with the drum, the compression of its inner layer of the contraction in the vertical direction, so that shear stress is absorbed, the expansion will not produce the phenomenon, which not only guarantee the smooth progress of high-speed printing, but also ensure that the Indian goods quality.





The printing process to be completed depends on a certain degree of printing pressure, and offset printing presses on the pressure given by regulating the blanket cylinders and the gap between the impression cylinder to achieve. Traditional gravure and letterpress printing because of its special requirements, its silk printing pressure is generally in the 40, while the printing speed of 5 1000 / hour offset printing, the printing pressure is generally about 25 wires, but the printing speed in a 10000 / hour or more, especially in web-fed presses, which print at speeds up to 60000 / hour or more, such a high printing speed must require its printing pressure of about 10 wires in order to enable the printing smoothly, the resulting pairs of air-cushion Blanket's technical performance requirements even higher. At present, only the United States, Japan, Germany, Britain and several other industrialized countries have air-cushion blanket manufacturing plant.





    Cushion Blanket general requirements for its overall flatness error of one wire, while the surface layer only in the 40 silk or less (general blanket flatness error can be about 4 wire, the surface layer of 60 wires or so), otherwise will result in network deformation, graphics and other ills level was not clear. Therefore, the design of air-cushion blanket used at the end of the four-layer fabric skeleton at the end of cloth to design all kinds of different thickness, in contact with the surface layer must be about the thickness of 15 silk muslin, in order to ensure blanket tension on the rotary at the end of cloth lines without exposing the structure, which will affect the printing quality of the end of the middle layer thickness of 25 silk cloth around the end of the final layer thickness of 35 silk cloth at the same time to give a good anti-compression air-cushion blanket instantaneous elastic deformation as well as the restorative, the key is (closed-cell) foam rubber sponge layer of the production. Throughout the development process of domestic and international air-cushion blanket abroad in the early 70s trial, and the domestic is 80 years since the mid-trial, until after the mid-90s, began to gradually put into operation a small volume. Closed-cell foam cushion layer of the system in general there are three ways to do (1) salting out method (2) Chemical foam Law (3) micro-sphere method.





Salting-out method, using a very fine MgSO4. Crystal mixing into rubber formulations, water for dialysis to be out after curing salt crystals, to keep a layer of very fine closed-cell layers. Taking into account its long production cycle, low efficiency, are generally less used.





Chemical blowing agent used is in a certain temperature and pressure conditions, the decomposition emit CO2, N2 and other gases, so as to match speed and rubber vulcanization, rubber cross-linked layer of the grid that contains the gas, resulting in closed-cell rubber sponge layer. Now, most of the air-cushion blanket factory at home and abroad have adopted this method of production.





Microsphere method is specially processed using a micro-sphere, be mixed with rubber formulations, in a certain temperature and pressure conditions, vaporization expansion, the formation of a highly uniform layer of closed-cell structure of the compression. Because the relationship between patent rights and other issues, only a few small factories abroad, using this method of production.





In the air-cushion blanket the entire production process, in addition to the end of fabric and design is very important formula, the vulcanization process in determining the quality of air-cushion blanket pros and cons of the more important factor. Domestic air-cushion blanket factory capable of producing a variety of conditions, are currently used drum traditional methods of curing vulcanizing machine cushion blanket, which is in the closed-cell foam cushion blanket layer uniformity as well as the delicate nature of the product as a whole flexibility have some negative impact. In addition, in order to ensure the air-cushion blanket to achieve excellent flatness, the product after vulcanization is subject to continuous grinding machine grinding. The process In addition to the above-mentioned purposes, there is a more important purpose is to give blanket the surface of certain plastic smoothness. People generally have a more one-sided view that blanket the surface of the more smooth as possible. In actual fact, of course, the more the surface is smooth, transfer to the printed version of the more complete network, but the concentration of the transfer ink printed version of the worse (dwell less), and because the printing speed faster and faster, in particular, web printing, rubber The more smooth the surface of cloth, its exclusive nature of paper the worse, and even affect the normal printing.





This shows that blanket the surface of grinding two purposes, first, to give an overall excellent flatness blanket, and second, giving it a certain degree of surface smoothness (smooth, but not the more the better) in order to meet the high-quality printing需要.





Cushion Blanket As a new printing presses has strong vitality is drawing attention to domestic and foreign manufacturers, especially domestic, according to incomplete statistics, the author, and now the domestic air-cushion blanket the needs of ordinary blanket ratio of 1:3 ordinary blanket or a larger share of possession, but the economically developed southern regions, such as Shenzhen, Guangdong, Fujian, air-cushion blanket with ordinary blanket has undergone a fundamental change in the ratio of basic to 4:1, with foreign advanced nations . Thus, with the rapid development of economic construction, printing technology, along the continuous development of air-cushion blanket demand will grow, and with UV (UV curing) printing, business forms printing, continuous printing of new technologies the emergence of varieties of air-cushion blanket, specifications have also put forward new demands. In addition, in order to maximize economic benefits to make quicker and more convenient exchange blanket, and in order to make blanket installed on the drum when the tension on the tension more uniform, and some blanket manufacturing factory in the blanket, on each blanket 2 are pre-loaded good aluminum splints to replace the old blanket when disassembly, with more than a dozen screws of iron splint.





In 1999, China Printing Equipment Industries Association of China's printing industry by 2010, the development of 28-character principle: "pre-press digital network-based, multi-color printing more efficient, diverse, after India and automation equipment, high-quality series." One of the equipment requested is present, China's equipment manufacturing goals. China's quality was still a blanket, the low-grade, at the end to achieve high-quality, but also more varieties of a single, can not form a series, this is the direction of the printing equipment production efforts.







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