As with dry laminating process, solvent-free laminating process is a relatively common anomaly in the implementation of laminating film “point”. The causes of “point” are physical and chemical. But the physical causes of the “point” and chemical causes of the “point” whether from the external appearance, formation mechanism and solution are different. Therefore, this “point” is not the other “point”, should be carefully screened and treated separately, can not be “the same”.

1, physical causes of the “point”.
a, characterized by a performance:
Distribution of irregular, often different thickness of the ink layer in different areas of the number of different. Serious, light ink can be observed at the “snowflake” phenomenon.
Reason analysis: the amount of glue is too small, the coated glue is not enough to fill the gap in the ink layer in the composite film and the pits on the surface of the material. This “point” is actually no glue and the formation of the “gap”.
Solution: increase the amount of glue.

b, characterized by two:
Some of the “points” periodically focus on repeated in the pattern of a fixed area.
Reason analysis: coating part of a roller is not clean or mechanical defects, resulting in a specific area of the amount of glue transfer bad, and the formation of the “point”.

Solution: According to the length of the periodic recurrence, compare the circumference of the rollers, find out where the problem is the roller, and clean up the foreign matter or repair the defects.

Warm reminder: Through the following measures, usually can avoid the laminating film appear due to insufficient amount of glue or glue unevenly caused by the “point”.

1、Reasonable setting of various composite structure of the amount of glue;
2, pay attention to keep the coating unit rollers clean, clean up the adhering foreign matter in time;
3, often check the coating unit roller surface conditions, timely replacement of the surface has defective roller;
4、Reasonably set the glue level in the storage tank, and often observe the status of the glue in the tank, and deal with the abnormal phenomena such as the mixture of glue siltation, viscosity, lumps and so on in time.

2, chemical reasons for the “point”.

Characteristics of performance: irregular distribution, but the distribution of a wide range of “points” although the size is not the same, but its shape is often a relatively regular round ...... in wet weather, the barrier is good (such as aluminized film) is easy to appear in the material structure of the composite.

Reason analysis: two-component solvent-free adhesive isocyanate (-NCO) components react with water in the air to generate carbon dioxide gas, because these gases can not be precipitated from the barrier good composite film, silt collection in the formation of composite film between the “point”. Therefore, these spots are actually carbon dioxide “bubbles”.

Solution: Through the following measures, you can usually avoid the composite film due to the water in the air and glue reaction caused by the “bubble”.

1, control composite operation, curing environment humidity, general relative humidity control below 70%;
2, regular replacement of the glue mixing machine storage barrel desiccant, to ensure that the storage barrel of dry air;
3, glue drum (especially curing agent components) after opening, if there is residual glue, should be closed tightly in time, and as soon as possible will be used up residual glue.

Warm tips: According to the experience of some of our customers, relatively independent closed operating space is conducive to the control of relative humidity.