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Coated boxboard is a new type of packaging material that combines the advantages of both boxboard and whiteboard. It is coated with a layer of white (or colored) pigment on the surface of the Kraft board to make it look to the level of coated white board, and the inherent quality and physical properties of the Kraft board. It is not only suitable for small packaging boxes, but also for corrugated cartons as outer packaging.
According to the estimation of the manufacturer, the kraft box board is processed into a coated boxboard, and the profit per ton of coated box board can be profited by about 400 yuan, and it is generally self-produced base paper. The economic benefit is considerable. At the same time, due to the great potential of the market in China, the prospects for the production of coated boxboards are very promising.
Second, the production of coated boxboard in China in foreign countries, the coating boxboard has been widely used, and is replacing many other types of packaging cardboard. According to reports in the literature, before 1993, the sales volume of Mead and Manver, two American coated cartonboards, accounted for 55% of the U.S. market, and coating boxboards were established in Japan, Europe, and Hong Kong. Cut supply points, there are also some imports in our country. Currently, the outer packagings of Shanghai Shi Lang Ice Lotion and Beijing Wuxing Special Guobin Beer, which are currently on the market, all use small coated corrugated boxes made from imported coated cardboard.
In China, the production of coated boxboard has just started. In 1986, Tianjin's scientific research department began research and development of coated boxboard. In the 1990s, scientific research and production companies in Beijing and Fu Ning successively made a lot of research, achieved certain achievements, and effectively translated into productivity. Wuhan's machinery manufacturing enterprises in Hubei Province developed and produced supporting domestically produced equipment. Some production lines have been established throughout the country, especially in Hubei, Hunan, Tianjin, Shandong, Guangdong, Zhejiang, Sichuan and Shaanxi. According to statistics, in 1995, the output of all kinds of cardboard was 18.123 million tons, accounting for 57% of the total paper and board production of 15929.96 million tons, of which the output of coated white paperboard was 550,000 tons (including 1/3 of coated cardboard The total consumption of coated white paperboard was 980,000 tons, and the import volume was 440,000 tons. In the reform of the papermaking industry and the ten-year plan, it is pointed out that the key to adjusting the structure of whiteboard products is to increase the production of high-grade coated whiteboard and develop new varieties to replace imports. Its planning goal is: In 1995, the output of whiteboard was 600,000 tons, of which 300,000 tons was coated with white cardboard, accounting for 50%; In 2000, the whiteboard reached 800,000 tons, of which 500,000 tons was coated with white cardboard, accounting for 62% . In 1994, the consumption of white paperboard market reached 488,600 tons, domestically produced 339,700 tons (excluding exports of 0.19 million tons), the import volume was 0.15800 tons, and the consumption of coated white board was 822,200 tons, which accounted for the total consumption. 55%. This shows that the national production rate of white paperboard can not meet the needs of production development. At the same time, it shows that the market demand for coated white paperboard is much higher than that of ordinary white paperboard, which further confirms the trend of packaging to high-grade development. At present, domestically-manufactured domestically-manufactured home appliances and microcomputer-based corrugated cardboard boxes that have been sold on the domestic market have been manufactured in large quantities using coated cardboard. However, due to the late start of the production of coated boxboard in China, there are many problems in the technology and equipment, mainly improvement of the technical performance of the coated boxboard: how to adapt to the rapid absorption of water-soluble ink in the high-speed production line of corrugated boxes, box folding When the coating does not break, the corrugated box production line is changed from monochrome printing to color printing and so on. All these problems require the efforts of our management departments and production researchers to jointly solve the problems in technology and prices so as to promote this new type of packaging materials to meet market needs as soon as possible.
Third, coating box board production technology and coated paper, label paper, painted newspapers and coated white paperboard, coating boxboard also have to go through the paint configuration, coating method selection and finishing and other technical processes, different It is the coated paper board that is painted white (or color), so the coating should be thicker, the paint consumption should be greater, otherwise the natural surface is not easy to be covered, the smoothness and whiteness can not go up If the coating is too thick, it will bring about problems such as poor coating fastness, falling powder and frying lines. Therefore, the coating process of boxboard is more difficult than other coated products. According to the manufacturer's production experience, the technical requirements and processes for coating boxboard production are summarized as follows.
1. Technical requirements for base paper a. The boxboards used for coating are generally grades B and C, but they must meet the technical requirements specified in GB 13024-91, in which the folding resistance and the lateral ring pressure strength index can be better than the specified requirements to ensure that after coating Basic strength requirements;
b. Surface smoothness: due to the rough surface of the board, the traces of the felt, poor smoothness, and poor uniformity, it is difficult to apply the coating process. The shape coating, that is, the state of the surface of the base paper, is still in a state after being coated, and does not have the effect of filling and filling like the blade coating, that is, it is difficult to make up for the defects caused by the unevenness of the cardboard when the brush is used. Therefore, the cardboard with good formation, smooth surface, and low dust should be selected so that the coating can be saved during the coating process, the cost can be reduced, and the quality can be guaranteed;
c. The surface of the cardboard box should be neat and clean, and should not be stained with oil. The paint cannot cover the oil stains.
d. Boxboards should not be too stiff, and the sizing degree should not exceed 0.5mm. Although there are sizing agents in the coating formulation, proper sizing is still required for the cardboard raw paper. Otherwise, some components in the coating may be excessively infiltrated during the coating process, causing undesirable results. However, if the amount of glue is too large, it will affect the adhesion of the paint and the base paper;
e. The sulphate wood pulp is best for the dried pasta. The use of wheat straw pulp noodle box board and bamboo pulp with large brittleness, short fibers, and extraneous cells should be used as little as possible because the water absorption during coating is so large that the moisture will migrate into the paperboard too quickly, which will cause the coating surface to be rough and difficult to obtain delicate. Appearance; boxboard with imported OCC pulp can also be used;
2. Basic requirements for coating performance The coating of coated carton board uses a water-soluble paint, which consists of rubber, pigments, auxiliaries and water, but it has its own characteristics.
a. Solid content of paint is high, generally 50 to 60%
b. The coating should be divided into a surface layer and a primer. The composition of the two layers is different.
c. The proportion of rubber is large.
3. Coating method and combination process selection a. The choice of coating methods Most of the domestic kraft linerboards are noodle kraft linerboards, with 15 to 20% sulphate coniferous wood pulp as the top layer, 80% or more used corrugated cardboard pulp and waste cement sack pulp. The core bottom layer and the core bottom layer are mostly made of AOCC pulp and cotton stalk pulp. The paper machine also uses multi-net multi-cylinder rotary screen machines. Most of the production lines do not have the conditions for quantitative, moisture, and thickness control with microcomputers, and the production process of boxboards. The condition factors, such as vertical ration, banner quantification and thickness difference, poor uniformity and rough surface, should not be applied with a blade coater. Because of the low wet strength of the cardboard and the large amount of coating, metal bar coaters are not suitable. The use of an improved air knife applicator provides greater flexibility and adaptability to coating concentration, coating weight, and vehicle speed.
b. Combination Process Selection The combination of coating processes is diverse and should be selected based on the actual conditions of the base paper and the coating target. Cardboard coating is generally one-sided coating. If the coating amount is low, after the brushing, it is easy to expose the photochromic lens. The uneven coating results in pinholes and pits, which directly affect the glossiness and printability after brushing. Therefore, 2 or 3 coating methods are adopted to ensure that the coating amount is above 18g/m2, the water absorption of the base paper is reasonably controlled, and the formation of the coating pinhole is reduced, and then the back coating, finishing, brushing and gloss polishing are applied. Light, coiling and other processes can be completed.
(1) Necessity of back coating Because domestic kraft paperboard is basically noodle boxboard, there are differences in the three-layer surface pulp core and the pulping process conditions. When the surface is coated, it is dried without tension. One of the dry layers of coated cardboard. Therefore, the bottom surface is wetted and the chrome-plated glossy cylinder dries. The cardboard can be restored to flatness and the coating is lighted.
(2) The effect of polishing is applied to the glossy cylinder. Drying is the first finishing process after the cardboard is coated. The second step is polishing. The effect of polishing is to increase the gloss and smoothness of the gloss, but the whiteness will decrease. This is because polishing destroys the coating and changes light refraction. In order to ensure a certain amount of whiteness, the cardboard to be polished can be pre-remedyed in terms of coating amount and coating formulation.
(3) The effect of glossy calendering The gloss calendering also belongs to finishing. The polished coated boxboard is further finished with gloss calendering to further improve the smoothness and surface strength of 25 to 50%, while eliminating dust obstacles.
At present, domestic manufacturers have also developed color coated cardboard to meet the packaging needs of different commodities. Compared with white coating box board, it has the advantages of bright paper, eye-catching, strong sense of gloss, etc.; at the same time, it can be used to make the process of adding full-color printing and bottoming in the process of making water box to reduce the cost.
The brushed light-coated boxboard is a kind of packaging board that can be brushed and coated on the boxboard, and the paper mechanically press light to coat the coated surface of the board with a brush, thereby forming a glossy film on the board coating. It is mainly used for middle and high-grade packaging and decoration, in order to beautify the goods and improve the product quality, such as the packaging of export goods, cosmetics, toys, Chinese and Western medicines.
Fourth, the development trend of coating box board production technology Since the production of coated boxboard has just started, the user has not fully recognized. Furthermore, if the manufacturer uses high-grade base paper in production, the cost will be high, and the use of low-grade base paper will make the quality difficult to pass, and the new coating boxboard production line and the coating technology used will be difficult to improve in a short time. Therefore, experts have proposed that the current production technology of coated boxboard will have the following trends:
1. The raw paperboard used for coating should be turned to a long wire or laminated board machine for production. At present, several such production lines have been built in China, and production practices have proven its advantages.
2. The single mode of air knife coating should be broken, and the mixing process of air knife coating and blade coating should be turned. In foreign countries, the advanced production line is using the production process of the front scraper coating head and the back two scraper coating heads, which can achieve the purpose of uniform appearance;
3. Cancel calender sizing;
4. Increase the back coating, especially for low-thickness paperboards of 0.25-0.5mm;
5. The best coating process for the coloured linerboard is a flat precoating with a high solids content;
Although the history of the production of coated cardboard is relatively short, there are still many problems, and there is a considerable gap compared with developed countries. However, as long as everyone works together to solve the technical problems, I believe that in a relatively short period of time The production level and quality of coated boxboard will take a new step to promote the development of the packaging industry.
(Wu Jianzhi)
Talking about the Development Trend of Coated Carton Board in China
First, the production and development prospects of coated boxboard With the development of China's national economy and the improvement of people's material living standards, especially since the reform and opening up, the total amount of export goods has been increasing, and the quality and variety of packaging board have also been higher. The request. As we all know, the important role of packaging is to protect the goods while promoting sales. In order to arouse the desire of consumers to purchase and increase the attractiveness of products to consumers, manufacturers pay more attention to the appearance quality of cartons and cartons, and require that cardboard have better strength, higher glossiness, smoothness, and exquisite packaging and printing. effect. At present, China's commercial packaging paperboard mainly includes yellow cardboard, boxboard, ordinary white paperboard and coated white paperboard. Coated white paperboard has good printing performance, which has been widely used in China. However, due to its stiffness and low strength, it is only suitable for use as a box for light goods, and its use is subject to certain restrictions. The kraft boxboard, however, has good stiffness and high strength but has a low surface smoothness and unsightly appearance. In color printing. Therefore, the development of a new type of packaging material that satisfies the packaging and decorating of goods, has sufficient strength, and is suitable in price is already an urgent need for domestic shopping malls.