Paperboard book upset deformation is a technical problem commonly encountered in book printing enterprises. In this article, the author combines his own practical experience over the years to talk about his own views on this issue.
Analysis of the Causes of the Deformation of the Board Paper Book
Raw material
The structure of the gray board or the cardboard itself determines that it is easier to warp in production. The gray board or cardboard has a high density and a long fiber, and its water absorption has a great influence on the structure of the board. When water is absorbed, the fibers of the gray board or the cardboard may elongate, but due to the thickness of the gray board or the cardboard, the water absorption amount on both sides may be inconsistent, resulting in different elongation lengths of the gray board or the cardboard fiber, thereby making The gray board or cardboard is deformed. At the same time, when the water is lost, the fibers of the gray board or the cardboard will shrink, but the inconsistency of the water loss on both sides will lead to inconsistent fiber shrinkage and deformation. Although the gray board or cardboard will be deformed due to water absorption and water loss, from the author's many years of production experience, the deformation caused by water loss is more serious than the deformation caused by water absorption. In addition, different brands and different types of gray board or cardboard have different water absorption properties, and the deformation phenomenon is different in production.
2. Ambient temperature and humidity
The environmental temperature and humidity have a great influence on the production of cardboard paper. When the ambient temperature and humidity are lower than the water content of the paper, the paper will lose water, and the degree of water loss of each part of the paper is generally different, which causes the paper to warp and deform. When the ambient temperature and humidity are higher than the water content of the board, it will cause the board to absorb water, which will also cause the board to warp and deform. In these two cases, the degree of deformation is different. The deformation at the time of water loss is much larger than the deformation at the time of water absorption, so the curling deformation of the paperboard always occurs in the dry season in autumn and winter.
3. Production process
When producing a paper-based book, it is necessary to use a white latex shell or a pair of enamel. The white latex contains a lot of water. When the shell is on the upper shell or the crucible, a large amount of water will enter the board, but the moisture does not enter evenly. This leads to inconsistent water content in each part of the board, which leads to the occurrence of the board. Upset deformation.
4. Mode of operation
When producing hardcover books, some enterprises are automatic upper casings. Some enterprises are handmade upper shells. The upper shells are usually evenly coated with the upper shell, so that the water content of the paperboard is more uniform. At the same time, the adhesive used in the automatic upper shell of the machine is different from the adhesive used in the manual upper shell, that is, the solid content of the adhesive is different. The solid content of the adhesive used in the automatic upper shell of the machine is higher than that of the manual upper shell. The solid content of the adhesive is high, the water content is smaller, and it is more difficult to cause the curling deformation of the paperboard book.
5. Process design
No matter whether it is gray board or cardboard, there are lines. Therefore, when the shell is on the upper or opposite of the paper, it needs to be textured. A lot of production experience tells us that for hardcover books, you need to wear the upper shell; for the script, you need to confront the lines. If it does not follow the pattern, serious upset deformation will occur in the later stage of the finished paperboard.
The above is the main reason for the warping deformation of the board paper book in production. From the data obtained from mass production practice, it is ideal to control the water content of the board paper book within 8% to 12%, and the warping deformation phenomenon can be well controlled.
How to improve the curling deformation of the paperboard book
1. Proper selection of raw materials
Need to choose a gray board or cardboard with moderate tightness. The tightness is too small, the paper has strong water absorption, and is greatly affected by the environmental temperature and humidity. It is prone to deformation; the tightness is too large, and other quality problems will occur. In addition, when using, be sure to ensure that the pattern is smooth, that is, the texture of the gray board should be parallel to the direction of the spine. The two cardboards facing each other should be in the direction of the grain as far as possible (that is, the grain is parallel to the direction of the spine) to avoid the inconsistency of the grain. The paperboard book is upset and deformed. In the case of adhesives, try to use white latex with a large solid content and eliminate the mixing of two white latexes.
2. Suitable production environment
The production environment should be moderately stable, that is, the temperature should be controlled between 20 and 30 °C, and the humidity should be controlled at more than 45%. Every year from April to September, the air humidity is generally above 50%, and the temperature can be controlled at 20 to 30 °C. From October to March of the following year, because the ambient humidity is below 40%, or even lower, the quality problem of the paperboard curling deformation often occurs. When the humidity is too low, it is necessary to spray a certain amount of water in the air of the workshop to keep the air humidity above 45%.
3. Strictly control all aspects of production
Before producing the hardcover book, it is necessary to take out the gray board from the warehouse at least 24 hours in advance and place it in the production workshop. In the production of the material, the shell and the shell, the water content of the gray board before and after the process must be tested to ensure the water content of the gray board before and after the process. The water content is 8% to 12%. For the stencil paper, it is also necessary to take out the jam from the warehouse 24 hours in advance and place it in the production workshop. Before and after the confrontation, it is necessary to test the change of the moisture content of the cardboard. When the water content is higher than 12%, the paper jam needs to be dehumidified until it reaches 8% to 12%. When dehumidifying, it is necessary to fix the jam to prevent the jam from being deformed due to water loss during the dehumidification process. It should be emphasized that in each control step, the moisture content of the gray board or paperboard should be tested, and the test results should be recorded for later analysis and correction.
4. Emphasis on packaging and transportation
The transportation after packaging of the finished product is also very important. For domestic products, it is necessary to know the temperature and humidity of the customer's location and the temperature and humidity of the location of the factory in advance. If the temperature difference between the two is large, it is recommended to do shrink packaging treatment for the finished product; for foreign products, it is also necessary to know the environmental temperature of the customer's location in advance. Humidity, if it is shipping, also consider the temperature and humidity of the cabin during the shipping process. If it is produced from October to March of the following year, it is recommended to shrink the packaging of all finished products, and consider negotiating with the shipping company. Place the product in the position of the bilge.
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