The Problem and Solution of "Overflow" in Summer Printing of Adhesive Stickers
The adhesive layer in the self-adhesive label material has a certain fluidity, which is greatly affected by temperature. Generally, the higher the ambient temperature, the stronger the fluidity of the adhesive. Once the fluidity of the glue becomes stronger, it is easy to overflow. Especially during the production process of roll to roll self-adhesive labels, the material is affected by the machine operating tension and winding tension. If the fluidity of the adhesive becomes stronger at this time, it is more likely to overflow under the action of tension. There are several common overflow phenomena, which will be analyzed one by one below.
1. Material end face or section overflow
The majority of self-adhesive label materials are rolled materials, with a small amount being cut into single sheets. In summer, under the influence of high temperatures, both forms of adhesive label materials are more prone to adhesive overflow. Among them, roll shaped adhesive label materials are mainly characterized by adhesive overflow on the two end faces of the roll, while cutting individual adhesive label materials is mainly characterized by adhesive overflow on the cut surface.
Once the adhesive label material overflows, it can be very troublesome to handle. Because the overflowing glue will stick to the lower layer of material, causing the material to not unwind and print properly. When the roll like material with adhesive overflow on the end face is printed on the machine, the adhesive on both sides will accumulate on the guide roller of the equipment while passing the paper. Over time, if the accumulated adhesive is too thick, it is easy to tear the material and must be stopped for processing, greatly increasing production losses. The edges of single sheets of material with adhesive overflow on the cutting surface may stick together, causing faults such as double sheets, multiple sheets, skewed paper feeding, and even paper jamming during equipment operation.
Therefore, in summer, production enterprises of adhesive label materials must take preventive measures when cutting to avoid problems caused by material overflow. Firstly, it is necessary to clean the cutting tools in a timely manner. Clean up the accumulated glue on the surface of the cutting tool in a timely manner to avoid excessive adhesion to the material surface due to the accumulation of glue. At the same time, it is necessary to strictly control the cutting tension. At present, many slitting machines use sliding friction shafts for winding, and the tension of each roll is controllable. At the same time, the machine's winding tension control system can adjust the tension taper in real time based on the material's winding diameter, ensuring that the material can run at the most suitable tension without loosening the winding, avoiding end face overflow caused by excessive winding tension.
In addition, after the material is cut off from the machine, baby powder can also be evenly applied to both ends of the material. This small powder can have a certain sealing effect on the cut surface of the adhesive material, greatly reducing the possibility of adhesive overflow on the material end face. After cutting, the material for cutting single sheets can be coated with small powder like talcum powder on four sections to reduce the possibility of glue overflow. However, it should be noted that since most of the material for cutting single sheets is used for offset printing, the powder dosage should be strictly controlled. If the dosage is too high, it may cause white spots during subsequent printing.
If the printing enterprise finds that there is glue overflow on the end face of the self-adhesive label material, it can use silicone oil spray or release agent to evenly spray on the end face of the material if the glue overflow is not serious. If the glue overflow is serious, it can no longer be unwrapped normally, it can only replace the material again.
2 Die cutting overflow
The main reason for the overflow of die-cutting glue is also due to the high temperature in summer, which increases the fluidity of the glue and causes the overflow under the squeezing effect of the die-cutting blade. So, what should I do if there is a mold cutting overflow during summer production?
Firstly, it is necessary to improve the temperature and humidity environment of the production workshop as much as possible. Generally speaking, the temperature of the printing workshop is controlled between 20 ℃~25 ℃, and the relative humidity is controlled between 50%~60%. In order to meet this requirement for environmental temperature and humidity, many printing companies have installed temperature and humidity control systems.
In addition, some self-adhesive label materials with particularly strong adhesive fluidity or thickened adhesive are prone to adhesive overflow problems, especially in winter and summer. Therefore, when die-cutting such materials in summer, it is recommended to first freeze the materials and immediately print the die-cutting online after taking them out before production, which can effectively avoid the problem of adhesive overflow during die-cutting.
3. The finished product label overflows after being cut flat
Some self-adhesive label products need to be cut into flat sheets. Generally, after cutting flat sheets, they are packaged in dozens of hundreds of sheets. In the summer, it is common to encounter the problem of glue overflow when the cut flat sheets of labels are placed for a period of time. Once there is an overflow, it can cause the upper and lower labels to stick together, and sometimes the bottom paper of the upper label will peel off the lower label, causing inconvenience for end users.
The main reason for this problem is that hundreds of processed finished product labels are stacked together, which can cause squeezing. In addition, the high temperature in summer increases the fluidity of the glue, leading to overflow under the squeezing pressure. Therefore, in the summer, it is recommended that printing companies reduce the number of sheets per label to avoid extrusion and overflow caused by excessive stacking of labels. At the same time, try to store the finished label products in a cool and dark place, and do not accumulate too much inventory at once. The inventory time should not be too long to avoid glue overflow problems.
4. Improper storage leading to glue overflow
Improper storage leads to adhesive overflow in summer, and some film type adhesive labels have experienced adhesive overflow problems after being placed for a period of time. Labels with adhesive overflow will make a crackling sound when unrolled, and if the label area is small, it is easy to be peeled off by the bottom paper of the label. This overflow problem is often caused by the harsh storage environment in the warehouse, where the temperature and humidity cannot be controlled. Therefore, when storing self-adhesive label products, especially film type self-adhesive label products, in summer, it is necessary to control the temperature and humidity of the warehouse within an appropriate range, and generally refer to the temperature and humidity requirements of the printing workshop. If this is not possible, it is necessary to separate a small room in the warehouse and install air conditioning to store the expensive label products separately.
During printing, various environmental factors such as temperature, humidity, dust level, and the presence or absence of light will affect the quality of printed products in various processes.
Packaging printing methods mainly based on flexographic printing and gravure printing are more sensitive to changes in ambient temperature and humidity. Excessive temperature and low humidity are not conducive to the drying of inks (especially water-based inks), causing quality defects such as paste and fuzzing. Excessive dust content can also cause quality defects such as inaccurate printing on the actual layout of printed products.
Therefore, in the printing process and various processes of processing printed products, it is necessary to ensure constant environmental temperature and humidity, reduce dust in the air, and ensure stable quality of the final printed product.