First, EVA hot melt adhesive and its use
EVA hot melt adhesive is the most widely used adhesive material for book connection in China at present, that is, adhesive material for wireless binding; The reason why it is used the most is because it has many advantages, which is suitable for publishing books quickly, shortening the publishing cycle and meeting the needs of the fast pace of modern society. Here is a brief introduction to EVA hot melt adhesive and its correct use:
1. What is EVA hot melt adhesive?
EVA hot melt adhesive is a solvent-free, waterless, 100% solid meltable polymer. It is a solid at room temperature, and when heated and melted to a certain extent, it becomes a flowable viscous liquid, that is, an adhesive. The melted EVA hot melt adhesive is a light brown translucent or white adhesive. EVA hot melt adhesive consists of basic resin (ethylene and vinyl acetate polymer), tackifier, viscosity regulator, antioxidant, cold-resistant agent and heat-resistant agent.
2.2 characteristics. EVA hot melt adhesive
① It is generally solid at room temperature, but it melts into a liquid adhesive when heated to a certain extent. Once cooled to below the melting point, it quickly becomes a solid (hardened solid), which is easy to preserve and store.
(2) Fast curing, little pollution, strong adhesion, and the adhesive layer has certain flexibility and hardness, which is very suitable for the bonding of books and periodicals.
③ Re-adhesion. When an adhesive solution is applied to an adherend, after the adhesive layer is cured or hardened, it can be heated and melted to soften, restore the shape of the adhesive body and re-adhere. Conducive to recycling defective products.
④ Easy to use. As long as the hot melt adhesive is put into a container for bath melting to form a liquid adhesive with the required viscosity, it can be bonded and solidified in a few seconds after being pressed neatly, and it can be hardened, cooled and dried in about 3 minutes, and can be cut into rolls immediately.
Due to the above characteristics, EVA hot melt adhesive is very suitable for modern high-speed linkage production.
3.3 Use. EVA hot melt adhesive
EVA hot melt adhesives produced and used in China are generally divided into high-speed and low-speed adhesives suitable for bonding; The curing speed of high-speed adhesive is slightly faster than that of low-speed adhesive. According to the different substances to be bonded, it is divided into offset paper and coated paper with different adhesives; There are two kinds of gluing: back gluing and side gluing, so as to meet the strength and needs of the adherend, achieve good bonding effect and reduce the cost.
When using hot melt adhesive, we should make preparations before using it to ensure the normal work goes smoothly.
① Glue storage. The type and model of glue should be correctly selected according to the quality of paper, and the dosage of glue should be determined according to the dosage; Too much glue melts in turn, causing waste, and too little affects normal operation.
② Preheating. Solid rubber blocks must be preheated before use, so that they can be melted into liquid first. There are two preheating methods: one is oil bath preheating, that is, jacket melting pot preheating; The other is preheating with electric heating plate, that is, preheating directly in a preheating pot with electric heating plate device. The preheating time is generally 2 hours. When the colloid reaches the required heating temperature and has a certain good fluidity, it is released into a working glue tank with the temperature of 160 ~ 180℃ through a constant temperature pipeline for smearing books.
(3) Temperature adjustment. Adjust the temperature of the adhesive according to the technical parameters of the adhesive. The temperature requirement of glue is very strict and must be set according to standard parameters. It is not allowed to raise or lower the temperature of glue at will, which will destroy the normal fluid. Under special circumstances, the maximum swimming capacity is 10℃. When everything is ready, it can run normally.
4.4 Adhesion and adaptability. EVA hot melt adhesive
The adhesion of EVA hot melt adhesive will get different adhesion effects due to the different heating temperature of hot melt adhesive, the different materials of the adherend, the width and depth of milling back, the height of gluing wheel and the different operation speed of gluing.
① ① ① Relationship between temperature, viscosity and tension of ①①EVA hot melt adhesive.
The softening point of EVA hot melt adhesive (when binding books and periodicals) should generally be above 80℃, that is, it can soften and melt when heated to 80℃. This temperature and function is only the melting temperature of hot melt adhesive. In order to bind books, the heating temperature should be raised to 130℃ ~ 180℃ before use. The colloid reaching this temperature, whether it is viscosity, viscosity or fluidity, is suitable for the adhesion of books and periodicals.
According to foreign data, the tensile test value of hot melt adhesive can reach 8.83 0.44 N/㎝ when the adhesive temperature is 170℃. When the glue temperature rises to 180℃, the tensile test value of hot melt adhesive will drop to 7.33 0.33 n/; On the contrary, when the glue temperature drops to 155℃, the tensile test value is only 5.22 0.25 n/. This shows that the melting and heating temperature of hot melt adhesive must be strictly controlled, neither too high nor too low (except in special circumstances). When the adhesive temperature is too high, although the fluidity and permeability of the adhesive increase (dilute), the viscosity and adhesive strength decrease, which affects the tensile force of the adhesive. When the glue temperature is too low, the viscosity of the glue will increase (thicken), but it will also affect the fluidity of the glue and the wettability and permeability of the back of the book, and at the same time reduce the tension, viscosity and toughness of the hot melt adhesive, and even the phenomenon that the cover and the back of the book do not adhere or are not firmly adhered after gluing. Therefore, the heating temperature of EVA hot melt adhesive must be strictly controlled in an optimal and appropriate range required by technical parameters in order to achieve ideal bonding temperature and bonding reliability.
② The relationship between different textures of book paper and gelatinizing temperature.
There are many kinds of paper for making books and periodicals, and the texture is different, which is also directly related to the temperature when gluing. Different sizing temperatures of paper are different, which is not only due to different paper fibers, but also due to different paper properties, different responses to colloid thermal conductivity and changes in curing and cooling rates. Take the thermal conductivity of coated paper, lightweight coated paper (coated paper) and book paper (uncoated letterpress paper). ) for example. The former can cure and cool the glue faster than the latter, because the inorganic content of coated paper is about ten times higher than that of book paper (including embossed paper, newsprint, etc.). ), and inorganic substances have good thermal conductivity, which can speed up the curing and cooling hardening of hot melt adhesives.
If the coating temperature is 170℃, the tensile test value of hot melt adhesive can reach the aforementioned tensile value of 8.83 N/㎝ on uncoated paper; The tensile test values of coated paper can only reach1.860.11n/(65g/paper) and1.64n/(100g/paper). The colloidal tension value of coated paper is so low that it obviously can't meet the bonding requirements. Therefore, in order to improve the tensile value of coated paper after sizing, it is necessary to improve the strength of glue solution and sizing temperature. When the sizing temperature is 180 ~ 190℃ (coated paper adhesive), the tensile force of hot melt adhesive can reach 4. 1 ~ 3.9N/. It can be seen that the use temperature of hot melt adhesive should also change according to the texture of paper materials of books and periodicals.
③ ③ The relationship between the opening time of ③③EVA hot melt adhesive and the running speed of wireless binding machine.
At present, there are many kinds of wireless nailing machines, including high speed, medium speed and low speed. High speed 12000 copies/hour, 10000 copies/hour, 8000 copies/hour, etc. , and medium-speed 6000 copies/hour, 5000 copies/hour, 3000 copies/hour, etc. , but they all belong to the category of linkage production line. Low-speed machine generally refers to a single machine, such as disc binding machine, oval binding machine, long nail binding machine, etc., and the speed is generally 200 ~ 2000 books/hour.
In order to cooperate with different machine speeds, there are still three periods (also called three points) when using EVA hot melt adhesive to bond books and periodicals, which must be strictly controlled and mastered.
A. business hours. Glue-opening time refers to the time when glue is applied to the adherend (back or mouth) to be pasted, which is usually 7 ~ 13 seconds. This time is the working process (including paper jam) from the beginning of gluing to the bonding and clamping of the cover and back mouth after the back milling and conveying of the binding machine, that is, the equipment must complete this work within 13 seconds during operation. If the equipment can't be completed within 13S during operation, the bonding effect will definitely be unsatisfactory, and there will be loose bonding, empty back, pages falling into rolls and scattered pages. Therefore, the opening time of hot sol should be determined according to the speed of binding machine.
B. curing time. Curing time refers to the solidification process of liquid adhesive. The curing time is usually 7 ~ 14 seconds, which is basically consistent with the opening time. Users hope that this time can be shortened, which is more conducive to the finalization and cooling of books.
Hardening time. Hardening time refers to the time for cutting books and periodicals after they are pasted, cooled and shaped firmly. 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 requirement is fast and accurate, especially for the processing glue of the wireless binding linkage production line, because this production line is a linkage production line from the collator to the book cutter, and the working processes of each part are interrelated according to the movement rhythm. Therefore, after putting the cover on the book and sending it to the book cutting part, the time of publishing the book should have certain regularity and accuracy, so as to achieve the ideal effect after cutting the book. That is to say, the delivery time of the book should ensure that when the book reaches the position under the knife of the book cutter, the back (sticky mouth) of the book has reached the degree of cooling, hardening and drying, so as to ensure the quality of the cut finished product. This time usually takes 3 minutes to complete, otherwise the back of the book will be deformed, the size will be unstable, the knife will stick and the book will be dirty. Therefore, the conveyor belt length of the book conveying device in the linkage production line should be selected according to the running speed. Generally, the length of conveyor belt is about 45m. If there is a stacking device, the conveyor belt can be set at about 20m. In short, the book whose cover is wrapped should be cooled for about 3 minutes (min) before reaching the book cutter.
Look for these companies: National Starch, Henkel, Nanhai Adhesive Industry Co., Ltd.: Zhu: 1330 1323236.