The correct use of EVA hot-melt adhesives and the opening of wireless perfect binding machines are a very important issue for bookbinding of printed books and periodicals. It is related to the product quality and social impact of books and periodicals in China, and is directly related to the benefits of factories and enterprises. In order to help each book binding and processing unit to correctly understand, use EVA hot melt adhesive, open the wireless binding machine, correctly handle the common quality problems of wireless binding, and ensure that the quality of the processed products meets the standard requirements. The following views are provided for peers reference.
1. VA hot melt adhesive and its use
EVA hot melt adhesive is one of the most used bonding materials for book connection in China, that is, the binding material for wireless binding; the reason for the largest amount is that it has many advantages and is suitable for fast book publishing, which can shorten the publishing cycle and adapt The fast-paced needs of modern society. The following is a brief introduction of EVA hot melt adhesive and correct use:
1. What is EVA hot melt adhesive
EVA hot melt adhesive is a meltable polymer that does not require solvents and does not contain water at 100% solids. It is a solid at room temperature, heated and melted to a certain extent to become a fluid with a certain viscosity, that is, an adhesive. . The melted EVA hot melt adhesive is light brown translucent or white adhesive. The composition of EVA hot melt adhesive is composed of basic resin (ethylene and vinyl acetate polymer), tackifier, viscosity regulator, antioxidant, cold resistance agent, heat resistance agent and so on.
2. Features of EVA hot melt adhesive
â‘ It is usually solid at normal temperature. When heated to a certain level, it melts into a liquid adhesive. Once it cools to below the melting point, it quickly becomes a solid (solidified after hardening) and is easy to store.
â‘¡ Fast curing, low pollution, strong adhesion, the adhesive layer has a certain flexibility, and a certain hardness, which is very suitable for the bonding of books and periodicals.
â‘¢ Re-sticky. When the glue is applied to the adherend and the glue layer is solidified or hardened, it can be heated, melted and softened to restore the shape of the glue and re-adhesion. Conducive to the recovery of defective products.
â‘£ Easy to use. Just put the hot-melt adhesive in the bath and heat it to melt it into a liquid adhesive with the desired viscosity, and apply it to the adhered object. After being neatly pressed, it can be cured in a few seconds, about 3 minutes It can reach the degree of hardening, cooling and drying, and can be cut into a book instantly.
Because EVA hot melt adhesive has the above characteristics, it is very suitable for the needs of modern high-speed linkage production.
3. Use of EVA hot melt adhesive
The EVA hot melt adhesives currently produced and used in China are generally classified into high-speed and low-speed adhesives for binding; high-speed adhesives cure slightly faster than low-speed adhesives. According to the different substances to be adhered, it is divided into different glues for offset paper and art paper; and there are adhesive glue (back book glue) and side glue glue mouth to adapt to the strength and needs of the adherend. It not only has a good bonding effect but also reduces costs.
Before using hot-melt adhesive, make preparations before use to ensure the normal work goes smoothly.
â‘ Rubber storage. Correctly select the type and type of glue according to the paper quality, and should decide how much glue to store according to the quantity used; too much glue storage will melt and cause waste, too little affects normal operation.
② Warm up. Before use, the solid rubber block must be preheated so that it can be melted into a liquid state. There are two preheating methods: one is to preheat with an oil bath, that is, to preheat with a jacketed melting pot; the other is to preheat with an electric heating plate, that is, to directly preheat in the preheating pot with an electric heating plate device. The preheating time is generally 2 hours. When the colloid reaches the required heating temperature and there is a certain good fluidity, the glue liquid is released into the working glue pot with a temperature of 160 ~ 180 ℃ through the constant temperature pipeline for the application of the book .
③ Adjust the temperature. According to the technical parameters of the adhesive, adjust the temperature of the adhesive. The temperature requirements of the glue are extremely strict, and it must be adjusted according to standard parameters. The glue temperature cannot be arbitrarily increased or decreased, and the normal fluid is destroyed. In special cases, the swimming volume is at most ± 10 ℃. When everything is ready, normal operation can begin.
4. Adhesion and adaptability of EVA hot melt adhesive
The adhesion of EVA hot-melt adhesive will vary with the temperature of the hot-melt adhesive heating, the difference and advantages of the material to be adhered, the width and depth of the milling back, the height of the rubber wheel and the adhesive Different binding speeds will result in different binding effects.
â‘ The relationship between the temperature of EVA hot melt adhesive and the viscosity and tensile force.
The softening point of EVA hot melt adhesive (when binding books and periodicals) should generally be above 80 ℃, that is, it can be softened and start to melt when heated to 80 ℃. This temperature and effect are only the temperature at which the hot-melt adhesive melts. It must be heated to a temperature of 130 ° C to 180 ° C before it can be used to bind books. Colloids that reach this temperature, regardless of viscosity or viscosity , Liquidity, etc., are suitable for the bonding of books and periodicals.
According to the measurement of foreign data, when the glue is applied on ordinary book paper, the tensile test value of hot melt adhesive can reach 8.83 ± 0.44N /? When the adhesive temperature is 170 ℃; when the adhesive temperature rises to 180 ℃, the hot melt adhesive The tensile test value will drop to 7.33 ± 0.33N / ?; conversely, when the adhesive temperature drops to 155 ℃, the tensile test value is only 5.22 ± 0.25N / ?. This shows that the temperature of the hot melt adhesive heating must be strictly controlled, not too high or too low (except for special cases). If the gel temperature is too high, although the fluidity and permeability of the colloid have increased (thin), the viscosity and bond strength have decreased, affecting the pulling force of the colloid; when the gel temperature is too low, the viscosity of the colloid has increased (thickened), but it has affected the flow of the gel The wettability and permeability of the coating on the back of the book will also reduce the tensile strength, consistency, and toughness of the hot melt adhesive, and even the phenomenon of non-sticking or loose bonding between the cover and the back of the book after the glue is applied. Therefore, the heating temperature of EVA hot melt adhesive must be strictly controlled within an optimal and appropriate range required by the technical parameters, in order to achieve the ideal adhesive temperature and reliability of bonding.
â‘¡ The relationship between different paper textures and gluing temperature
There are many types of papers used to make books and periodicals, and their textures are different. This is also directly related to the temperature when gluing. The different sizing temperatures of the paper are also different. This is not only the reason for the different paper fibers, but more importantly because of the different reflection of the thermal conductivity of the colloid due to the different properties of the paper and the changes in solidification and cooling rate. To. Take the thermal conductivity of coated paper, light coated paper (coated paper) and book paper (uncoated relief paper, etc.) as an example. The former solidifies and cools the glue much faster than the latter, because the coated paper contains The inorganic matter is about ten times higher than book paper (including letterpress, newsprint, etc.), and the inorganic matter has good thermal conductivity, which can accelerate the speed of curing and cooling hardening of the hot melt adhesive.
If the gluing temperature is 170 ℃, the tensile test value of hot-melt adhesive can reach the aforementioned tensile value of 8.83N /? On non-coated paper; while the coated test value of coated paper can only reach 1.86 ± 0.11 N /? (65g /? Paper) and 1.64N /? (100g /? Paper). The low value of the colloidal tensile force of the coated paper obviously does not meet the requirements of bonding. Therefore, to increase the tensile force after the coated paper is glued, the strength of the glue solution and the temperature of the glue must be increased. When the temperature of the glue is 180 ～ 190 ℃ (coated paper glue), the tensile force of the hot melt glue can reach 4.1 ～ 3.9N / ?. It can be seen that the use temperature of the hot melt adhesive should also vary depending on the texture of the paper materials of books and periodicals.
â‘¢ The relationship between the opening time of EVA hot-melt adhesive and the speed of wireless binding machine.
There are many types of wireless nailing machines, including high-speed, medium-speed and low-speed. High-speed 12,000 books / hour, 10000 books / hour, 8000 books / hour, etc., medium speeds are 6000 books / hour, 5000 books / hour, 3000 books / hour, etc., but they all belong to the category of linked production lines. Low-speed machines generally refer to stand-alone machines, such as disc binders, elliptical binders and long-type binders. The speed is generally 200 to 2000 books / hour.
In order to cooperate with different speeds, when using EVA hot-melt adhesive to bind books and periodicals, there are three periods (also called three points) in addition to the melting point, which must be strictly controlled and mastered.
A. Opening hours. Opening time refers to the time to apply glue to the adherend (back of the book or sticky mouth) to be adhered, generally 7 to 13 seconds. This time is the milling and conveying from the glue binding machine to the cover and book back The work process (including sticky paper jam) until the adhesive mouth is glued and clamped, that is, the equipment must complete this work within 13S during operation. If the equipment can not be completed within 13S during operation, the bonding effect is definitely not ideal, and there will be stickiness, empty back, page breaks, loose pages, etc. Therefore, the opening time of the hot melt should be selected according to the needs of the speed of the binding machine to determine which model is suitable.
B. Curing time. Curing time refers to the process of solidification of liquid adhesive. The curing time is generally 7 to 14 seconds, which is basically the same as the opening time. The user hopes that this time can be shortened, which is more conducive to the setting and cooling of the book.
Hardening time. Hardening time refers to the time for books and periodicals to stick and cool and set firmly to be cut. In addition to a certain opening and curing time, it is also required that the adhesive should be cooled and hardened (dried) as soon as possible so that the finished product can be cut smoothly. This time is required to be fast and accurate, especially for the processing glue of the wireless perfect binding linkage production line, because this production line is a linkage production line from the collating machine to the book cutting, and the work process of each part is according to the movement The beats are coherent with each other, therefore, the time for the book to be published after the cover has been shaped and transmitted to the cutting part must have certain regularity and accuracy to achieve the ideal effect after the book is cut. That is to say, the delivery time of the book should be ensured that when the book reaches the part under the cutter of the book cutter, the back of the book (sticky mouth) has reached the level of cooling hardening and drying, so that the quality of the finished product can be guaranteed. This time should generally be completed in 3 minutes, otherwise it will cause deformation of the back of the book, unstable dimensions, sticky knives, dirty books, etc. Therefore, the length of the conveyor belt of the book delivery conveyor of the linked production line should be selected according to the operating speed. The length of the common conveyor belt is about 45m. If the conveyor belt is equipped with a stacking device, it can be set at about 20m. In short, the book with the cover should be in It cools for about 3 minutes (min) during the transfer process and then reaches the position of the book cutter.Umbrella With Screen Mesh Netting
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