EVA hot melt adhesives for printed materials

What are the forms of VA hot melt adhesive?
A: EVA hot-melt adhesives suitable for binding are generally divided into high-speed adhesives and low-speed adhesives. High-speed adhesives cure quickly and are suitable for high-speed linkage production lines. Low-speed adhesives cure at a slightly slower speed and are suitable for use in ordering machines. According to the difference of paper, it also divides the use of glue for copperplate paper and general bookprint paper, and also has the distinction between the book back glue (glue on the back of the book) and the side glue (glue on the glue stick) to suit different strengths and needs.

Why use EVA hot melt adhesive to warm up?
A: Because EVA hot melt adhesives require very strict temperature control and fluid uniformity (ie, fluidity) when used, if the solid hot melt adhesive is not preheated, direct use will result in: (1) reduction And destroy the normal temperature in the work of the plastic pot, there is no adhesion or page, hole-shaped and other unqualified products; (2) non-uniform colloidal, destroy its fluidity, resulting in the book page is not adhesive or uneven coating, book back uneven (glue The granular coating is applied to the back of the book), and the eyelet shape and the like. Therefore, EVA hot melt adhesive must be warmed up before use.

How to preheat EVA hot melt adhesive?
Answer: When preheating, the plastic block is put into the preheated plastic pot first, heated and melted to a certain temperature, and then heated into the working plastic pot before being used. There are two kinds of preheating methods: one is to preheat with an oil bath, that is, to directly preheat with a jacketed pan, and the other is to use a hot plate to preheat, that is, a method of directly heating the preheated pan with a hot plate device. The warm-up time is usually 2 hours. The preheating temperature should not be lower than the use temperature or 5-10°C higher than the use temperature, leaving room for cooling caused by the input.

What is the appropriate preheat temperature of EVA hot melt adhesive?
A: The preheating temperature of EVA hot melt adhesive should be the same as the use temperature or slightly higher 5-10°C, because the cooling phenomenon sometimes occurs in the plastic transfer, so the temperature can be slightly higher, but can not be lower than this range, because the glue temperature A drop in the pull value at low time affects the bond strength and wastes glue.

What is the opening time of EVA hot melt adhesive?
A: The open time of the hot melt adhesive refers to the time when the glue is applied to the adherend and can be stuck. This time is generally 7-13 seconds. In other words, during processing, the book block must be clamped and fixed with the cover in order to obtain a good adhesion effect.

What is the curing time of EVA hot melt adhesive?
Answer: The curing time of the hot melt adhesive refers to the time that the adhesive is solidified after the adhesive is applied. This time is basically the same as the open time, which is usually 7-14 seconds. In other words, after the cover and the book block are glued and clamped, the glue cannot solidify or peel off.

What is the cooling hardening time of EVA hot melt adhesive?
A: The cooling hardening time of EVA hot melt adhesive refers to the time that can be cut after the book is glued, glued, and solidified; this time should generally be guaranteed in 3 minutes, that is, only after 3 minutes, the book can be cooled and hardened before the finished product can be finished. The cutting, otherwise there will be deformation, sticky knife and other quality problems.

EVA hot melt adhesives should pay attention to which temperature when using?
Answer: The temperature of EVA hot-melt adhesive softening point (ie melting point of glue block), pre-adhesive and adhesive coating should be understood. The softening point should be 80°C and 5°C. The pre-adhesive temperature should be the same as or slightly higher than the coating temperature. The coating temperature should be controlled according to the technical parameters of the rubber, and the range should be ±5°C. In special cases, it can be 10%. °C.

What is the relationship between the use temperature of EVA hot melt adhesive and the bond strength of books?
A: According to the data, it is shown that the tensile strength of the hot melt adhesive can reach 8.83±0.04N/cm when the sizing is performed on ordinary book paper and the adhesive temperature is 170°C; when the adhesive temperature rises to 180°C, the pull test is performed. The value dropped to 7.33 soil 0.03N/cm; when the glue temperature dropped to 155°C, the pull value was only 5.22% soil 0.25N/cm. It can be seen that the temperature of the hot melt adhesive is directly related to the binding strength and tensile strength of the book, so the temperature of the hot melt adhesive must be controlled within a certain range in order to achieve the desired adhesive effect.

What is the relationship between the temperature of EVA hot melt adhesive and the texture of the book paper?
Answer: Due to the different textures of the paper, the thermal conductivity and reaction of the colloid are different, which can cause the curing and cooling speed of the glue to change. In the case of coated paper and book paper, the inorganic matter contained in the coated paper is about 10 times higher than that of the paper. The inorganic material has good thermal conductivity. It can speed up the curing and cooling speed of hot melt adhesives. When the glue temperature is also 170°C, the tensile test value can reach 8.83N/cm on the book paper, while the pull value of the coated paper can only reach 1.86 earth, 0.11N/cm (65g/m2 paper) and 1.46N. /cm (100g/m2 paper). Obviously, the different paper textures will change the use temperature of hot melt adhesives in order to achieve good adhesive fastness.

What environment and conditions are required for using EVA hot melt adhesives?
A: EVA hot melt adhesive is a kind of hot-melt adhesive material. It can only be used under the scientifically standardized environment and conditions to achieve the desired effect of this adhesive material.
(1) Temperature and humidity requirements for production plants
The opening time and curing time of the EVA hot melt adhesive are affected by the temperature and humidity in the working room. Generally, the temperature in the working chamber is maintained at a constant temperature of 17-27°C (21-26°C in foreign countries); the relative humidity is kept at 50°C. %about.
(2) The storage conditions of the finished product of the wireless bindery requires that the warehouse or factory building of the finished product should be guaranteed to have a temperature of 1-40°C; it is prohibited to stack it against the wall for long periods of time, by the window. By heating and outdoor, to prevent the paper from damp or heat, damage the internal water after deformation, adhesive changes, resulting in irreparable damage.
(3) Strengthen management Due to changes in the use of materials, the requirements for the press-binding shop are becoming more and more stringent. First, management personnel should pay attention to the necessary environment and conditions for the use of hot-melt adhesive materials, ensure the reliability of processing quality, and gradually move toward the specification. produce.

What should you pay attention to when using EVA hot melt adhesive?
Thermoplastic EVA hot melt adhesives differ greatly from cold glues. According to its characteristics, the following matters must be observed when using:
(1) The technical performance (technical parameters) of various types of EVA hot melt adhesives should be known and mastered. Different types of hot melt adhesives have different melting point, opening, curing, cooling time, etc., and different changes will occur.
(2) Use EVA hot melt adhesive, avoid direct heating with open flame, must use jacketed oil pan heating (the boiling point of water should be 100 °C) or use a sealed hot plate heating device hot glue.
(3) The solid hot melt adhesive must be preheated with a preheating device before use. After being qualified, the solid hot melt adhesive can be released into a plastic working plastic box for use. The preheating time is generally 2 hours. It is forbidden to directly incorporate the solid rubber block in the working plastic box to destroy the homogeneity of the colloidal temperature.
(4) The amount of glue in the preheated glue pan must be properly grasped, not too much, and the amount of glue added can not be used up, causing the colloids to melt and turn, making it deteriorated and aged, and the viscosity lowering; it is also not possible to add too little and not enough Causes the waiting for melting to affect normal production.
(5) During the open time of the hot melt adhesive (ie, within 7-14 seconds), the entire adhesive clamping process must be completed; in case of shutdown, the book block in the book holder is about to be glued or glued onto the rubberizing wheel. The finished coated book block (without the cover) should be removed immediately and must not be used.
(6) During the long-term repair phase of the Binder, the preheating glue pan and the work glue pan should be closed to prevent the colloids from melting and aging without using any melt.
(7) EVA hot melt adhesive colloid application temperature must be implemented according to technical parameters, strictly controlled within the scope of use, can not arbitrarily change the use of plastic temperature, under special circumstances, the maximum allowable error ± (5-10) °C.
(8) The preheated glue pot and the working glue pot should be regularly cleaned to ensure the cleanness of the glue pot and prevent the impurities in the glue solution from depositing and depositing, affecting the accuracy of the temperature control. When the temperature is too severe, it will cause the failure of the thermostat and cause the colloid smoke, Burning phenomenon.

Source: hc360 Huicong Print Channel

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