The dry lamination method is to coat a layer of solvent based adhesive on the plastic film (the adhesive consists of one-component hot-melt adhesive and two-component reactive adhesive), and the solvent is evaporated and dried through the drying channel of the laminating machine, and then bonded with other composite materials in the hot pressing state to form a smooth composite material. The composite film integrates the excellent properties of each layer of film, such as moisture resistance, barrier property, heat resistance and heat sealing property, so as to meet the packaging needs of various commodities. What needs to be added is that in the drying process in the drying channel, the cleaner the solvent in the adhesive is required to volatilize, the better. Because if the solvent does not volatilize clean, its volume will gradually increase after winding. The gradual accumulation of residual solvents will leave tiny pinholes on the cooled composite materials. Such tiny pinholes are what we call bubbles, which seriously affect the quality of products and even fail to meet the requirements of customers, resulting in product scrapping. Bubbles are easy to occur in the composite products using one-component hot-melt adhesive, of course, two-component reactive adhesive is not excluded. The volatilization degree of solvent is related to many factors, such as the temperature of drying channel, the speed of machine speed, indoor temperature and humidity, and even the adhesive itself. In practical work, we should be able to judge and distinguish accurately, so as to solve the problem.
1. The influence of oven temperature is divided into three areas: evaporation zone, hardening zone and odor elimination zone. The energy consumption in the three regions is almost equal, so it should be adjusted at any time according to the condition of the substrate to be compounded. Generally speaking, the temperature in the evaporation zone should be controlled at 50-60 ℃, the temperature in the hardening zone should be controlled at 70-80 ℃, and the temperature in the odor removal zone should be controlled at 80-100 ℃. Only when the substrate runs smoothly and the tension between the composite and the substrate is appropriate, can there be a smooth composite. With proper temperature control, the solvent volatilization in the adhesive is favorable.
2. The influence of machine speed, indoor temperature and humidity also indirectly affects solvent volatilization. In practical work, it is necessary to master the machine speed and solvent evaporation speed. If the machine speed is too fast, it is not conducive to solvent volatilization, thus affecting the amount of residual solvent. If the machine speed is too slow, the production efficiency will be reduced. At the same time, the longitudinal and transverse extension of the substrate should be considered to prevent distortion and deformation. The temperature of compound workshop should be controlled at 25 ℃ and the relative temperature should be controlled at 50% - 60%.
3. The relationship between two-component reactive adhesive and bubbles. Two component adhesives are mainly polyurethane adhesives, and two-liquid reactive adhesives are more commonly used. At present, our factory uses pu-1950 main agent produced by Zhejiang Huangyan Huaguang resin Co., Ltd., and the binder ratio is main agent: curing agent: ethyl acetate = 1:0.2:1.7. The curing time is generally 24-48 hours. Experience tells us that if the curing time is not enough, there will be small bubbles, and even affect the peel fastness. The preparation of two-component adhesive must be stirred evenly, so that the curing agent is full of activity and evenly dispersed, which is conducive to affinity with printing substrate and reduce bubbles. The temperature of curing chamber should be controlled at 50-60 ℃. Our factory operation is more regular, indoor clean, good environment, which is to reduce the bubble factor.
4. In dry lamination, unqualified cots are also the cause of bubbles. It is very important to choose the top cot and the hot pressing roller. The cot should be fine, smooth and free of small pits and lines. The pressure of hot pressing roller is also related to the generation of bubbles. The requirements must be compact and adjustable according to the actual situation. The bubble is also related to the roller. It is hot in summer, and it is easy to block the anilox roller when using the two-component adhesive for a long time, so pay attention to cleaning. Our factory uses the powerful film remover produced by Shanghai Shenda Technology Co., Ltd. for cleaning, and the effect is good. In addition, the amount of glue is too small, the concentration is too thin is also the cause of bubbles, at this time, increase the amount of glue. The bubble can be eliminated by increasing the concentration ratio. In winter, if the indoor air-conditioning device is not installed, the temperature is low, the humidity is less than 40%, and the adhesive dispersion is not good, which will also lead to bubbles. At this time, the prepared adhesive can be preheated for 1-2 hours to obtain satisfactory results. However, attention must be paid to safety, and special personnel shall be assigned to take care of the preheating.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.

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