In the implementation of solvent-free composite process, the "spot" of composite membrane is a common abnormal phenomenon. There are physical and chemical reasons for the formation of "spots". But the "points" caused by physical reasons and chemical reasons are different in terms of external appearance, formation mechanism and solutions.
1. "Points" produced by physical causes.
a. Characteristics 1
Irregular distribution, often ink layer thickness, the number of different areas is different. In severe cases, "snowflake" phenomenon can be observed in the light ink.
Cause analysis: the amount of glue is too small, the glue is not enough to fill the gap of the ink layer and the pit on the surface of the material. This "point" is actually a "void" formed by no glue.
Solution: increase the amount of glue.
b. Characteristic 2
Some "points" appear periodically in a fixed area of the pattern.
Cause analysis: coating part of a roller is not clean or there are mechanical defects, resulting in a specific area of the transfer of glue amount, and the formation of "point"
Solution: according to the repeated length, compare the circumference of each roller, find out the roller where the problem is, and clean up the foreign matter or repair the defect
Warm tips: through the following measures, usually can avoid the composite film due to insufficient glue or uneven coating caused by "dot".
1. Set the glue amount of various composite structures reasonably;
2. Pay attention to keep the rollers of the coating unit clean and clean the attached foreign matters in time;
3. Regularly check the surface condition of each roller in coating unit and replace the roller with defect in time;
4. Reasonably set the glue level in the glue storage tank, regularly observe the glue condition in the tank, and timely handle the abnormal phenomena such as deposit, viscosity and caking of mixed glue.

2. "Points" produced by chemical causes.

Features: the distribution is irregular, but the distribution is wide. Although the size of "points" is different, their shapes are often regular circles In wet weather, it is easy to appear when the material structure with good barrier property (such as aluminum coating) is compounded.
Cause analysis: the isocyanate (- NCO) component in the two-component solvent-free adhesive reacts with water in the air to generate carbon dioxide gas, because these gases can not be separated out from the composite membrane with good barrier property, and are accumulated between the composite membranes to form "points". So these dots are actually carbon dioxide "bubbles.".
Solution: through the following measures, the "bubble" caused by the reaction of water and glue in the air can be avoided.
1. Control the humidity of compound operation and curing environment, and control the relative humidity below 70%;
2. Regularly replace the desiccant in the rubber storage barrel of the rubber mixer to ensure the drying of the air in the rubber storage barrel;
3. After the glue packaging barrel (especially the curing agent component) is opened, if there is residual glue in it, it should be closed tightly in time and used up as soon as possible.
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. We uphold the integrity of cooperation, good quality, good service business philosophy, won the industry's approval, products sold to all over the world; welcome friends from all walks of life to inquire, visit our factory to investigate guidance and business negotiations.