Difficulties and solutions caused by temperature changes in summer printing of self-adhesive labels
1. Problems caused by temperature changes
The high humidity in the summer environment will cause many troubles to self-adhesive printing companies. If not solved in time, it may cause significant losses. Common problems with the use of self-adhesive labels caused by humidity include:
1.1 Curling during printing
Self-adhesive label printing mostly uses UV ink. After drying with UV lamps, the moisture in the self-adhesive material will evaporate quickly. Due to the different shrinkage rates of the surface paper and the bottom paper of the self-adhesive material after water loss, it is easy to cause the material to curl, which is particularly obvious when printing film-type self-adhesive materials.
This is because the surface material of film-type self-adhesive materials is a film, and the bottom paper is paper. The surface material will not lose water when baked by UV lamps, while the bottom paper will shrink rapidly due to water loss, causing the material to curl downward. At this time, if the environmental humidity of the printing workshop is low, the bottom paper cannot replenish moisture from the environment in time, and the problem of material curling cannot be improved, which will seriously affect production efficiency.
If the humidity in the printing workshop is controlled at a relatively appropriate level, although the material will lose water quickly after being baked by UV lamp, the workshop environment can replenish water in time, the material will not have serious curling phenomenon, and the production efficiency will not be greatly affected. It can be seen that it is very necessary to reasonably control the humidity of the workshop in summer.
1.2 Curling after cutting
Many self-adhesive labels need to be cut into single sheets. Sometimes we will find that the labels will curl quickly after being cut into single sheets, resulting in unqualified packaging. In theory, the tension of the self-adhesive label material has been fully released after die-cutting and waste discharge, and there should be no serious curling after cutting into single sheets. So, what exactly causes this?
This phenomenon is often caused by improper material selection and improper environmental humidity control. There are many types of self-adhesive material base paper, such as about 60g of Glazin base paper, about 95g of coated base paper, about 120g of cardboard, etc. In principle, it is not recommended to use self-adhesive materials with a base paper less than 80g to cut labels into single sheets. This is because this base paper is too thin and is sensitive to environmental humidity. When the humidity fluctuates greatly, this type of base paper will also stretch or shorten with the change of environmental humidity, resulting in severe curling of the self-adhesive material after die-cutting, and this situation will also occur during scrapping.
The best solution to this problem is to choose a material with a higher gram weight as the base paper. The higher the gram weight of the base paper, the less deformation it will suffer from the influence of environmental humidity, and it is easier to ensure the flatness of the label after it is cut into a single sheet.
1.3 Changes in the tension of raw materials
In summer, the problem of loose or tight rolls of raw materials is often encountered. This situation often occurs when the raw materials are taken out for use after being stored in the warehouse for a period of time, and even cannot be used in severe cases.
This is because the air humidity changes greatly in summer, and the tension of the adhesive material changes after water loss or water absorption, causing the raw material to be loosely wound or too tight. Some materials, especially film adhesive materials, will also be caused by the protrusion of the core of the material during use.
Therefore, in summer, we should try to maintain the lowest inventory of adhesive materials, reduce inventory cycles, strengthen warehouse management, and implement "first in, first out". Generally, there will be no obvious changes in materials within 7-10 days of arrival, and the longest cycle should not exceed 15 days.
2 Label wrinkling and bulging
Summer is the peak season for labeling failures of self-adhesive labels, among which wrinkling and bulging are common problems after labeling paper self-adhesive labels. So, what are the reasons for label wrinkling and bulging?
2.1 Water loss during processing
During the processing of self-adhesive materials, the self-adhesive materials on the paper surface will lose some moisture after being baked by UV lamps, resulting in extremely low moisture content in the finished labels. However, when end users use them, they often open the package and directly label them. After the label is affixed, it will absorb moisture in the air and expand, forming wrinkles or bulges in the expanded area.
To avoid this problem, the best way is to add water to the self-adhesive material during processing. A humidifier can be placed at the equipment winding station to replenish moisture for the material base paper. Enterprises with conditions are best to install a temperature and humidity control system in the workshop to ensure the normal moisture content of the label products.
2.2 Improper storage
Usually, after the self-adhesive labels are printed, they are packaged in plastic bags or wrapped in heat shrink film, which essentially isolates them from the outside environment. But in summer, it often rains, and the air humidity rises suddenly after the rain. If the labels are affixed at this time, the labels will easily absorb moisture in the air and swell, causing wrinkles and bulging.
Therefore, when storing finished products with self-adhesive labels in summer, it is necessary to pay attention and try to open the packaging 24 hours before labeling, so that the labels and the labeled objects are placed in the same environment for 24 hours, which is conducive to balancing the humidity of the two and ensuring the quality of labeling. Especially when the labeled object is a corrugated box, this operation must be done well to ensure the effectiveness of the labeling.
