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More and more books are using EVA hot melt adhesive for binding process. Almost all of them are used in large, medium, and small processing plants across the country. There will still be an upward trend in the future. This is because using this adhesive results in fast book publishing speed, short cycle time, aesthetically pleasing books, and eliminates several processes. But often because printing factories are eager to get started and strive for more processing, they overlook the scientific nature of the environment and conditions for using hot melt adhesive, resulting in many problems during the processing. The following points are provided for users’ reference:
EVA hot melt adhesive is a type of thermoplastic adhesive. The opening time after application is affected by indoor temperature and humidity. Generally, the indoor (i.e. workshop) temperature should be kept constant. The appropriate temperature should be between 15-26 ℃, and the humidity should be maintained at around 50%. However, it is understood that very few units in the country that use hot melt adhesive can meet this requirement. Therefore, when hot melt adhesive is used in many areas, there are too many bubbles in summer, making it difficult to cure and cool down. In winter, the adhesive solidifies, the cooling time is shortened, the bonding is not firm or sticky, and the book breaks after pasting. In other regions, due to high humidity, the book behind the cover is not properly shaped and cannot be cut, etc. These phenomena are directly related to the temperature and humidity in the workshop. So the requirement is:
（1） Enterprises with better conditions should install temperature control equipment and humidity measuring instruments in workshops that use wireless adhesive equipment to ensure normal temperature and humidity.
（2） Efforts should also be made in other aspects to create conditions for scientific and standardized management and production. In the absence of these conditions, the following principle can be temporarily followed: when the temperature is high in summer, the temperature of the hot melt adhesive should be lowered by about 10 ℃, so that the opening and curing time of the adhesive can basically meet reasonable requirements.
（3） Books that have undergone wireless bonding processing should be stored in a warehouse or workshop at a temperature of 1-45 ℃. And it is strictly prohibited to store them on walls, heating systems (in winter), windows, and outdoors for a long time. Avoid moisture or overheating that can cause deformation of the paper, alter the adhesive, and result in irreparable losses.
Preventive Measures:
EVA hot melt adhesive is different from regular cold melt adhesive. According to its characteristics, the following points must be mastered and noted during use:
1、 Understand and master the various models and technical performance (including technical parameters) of each hot melt adhesive model. Different types of hot melt adhesives have different opening and curing times. Especially, it is necessary to strictly distinguish the use of summer glue and winter glue. When the temperature is different, the opening and curing time will also change.
2、 When using hot melt adhesive, do not heat it directly with an open flame. Be sure to use isolation oil for heating (the boiling point of water should reach 100 ℃), or use a sealed electric heating plate.
3、 Solid EVA hot melt adhesive must be preheated with a preheating device before being released into the working adhesive box of the adhesive solution. The preheating time is usually around 2 hours. When using glue, do not directly mix solid glue blocks (i.e. glue that has not been preheated) into the glue box to prevent poor fluidity of the glue or uneven application of partially melted glue on the back of the book.
4、 The amount of glue in the preheating glue pot should be controlled properly. If too much is used, the glue will melt one by one, causing deterioration and aging, reducing viscosity, and affecting adhesion.
5、 The entire bonding process must be completed within the opening time of the hot melt adhesive. If the machine is stopped due to a malfunction, the books in the book folder must be removed in a timely manner, and the book core must not stay above the glue wheel.
6、 When repairing wireless glue binding equipment for a long time, the preheating glue and working glue pot should be turned off to prevent glue aging.
7、 The temperature of the molten colloid should be strictly controlled within the range of use.
8、 Regularly clean the pre coating glue pot and the working glue pot, keep the glue pot clean, prevent impurities from accumulating in the glue, affect the temperature control accuracy, and even cause the temperature controller to malfunction, resulting in glue burning. Under normal production and operation conditions, preheated glue pots should be cleaned every 3 months. The work glue pot (used for gluing) should be cleaned every half month. A cleaning system for glue pots should be established to facilitate implementation.
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