Water-based coating process guidance

Oil film to be removed from the water-based film immediately

The water-based film is an effective method for processing the surface of the printed matter to improve the surface gloss, strength, aesthetic effect, temperature resistance, water resistance, and abrasion resistance of the printed matter and improve the quality of the printed material and the quality of the printed product. Therefore, the quality of the coated film is evaluated. Also need to examine the film brightness, strength, adhesion and other aspects.

The development of water-based laminating machine has made the water-based laminating technology widely used. The water-based wet laminating film has been favored by customers because of its high strength, high grade, easy recycling, and no pollution.
When the water-based laminating process was just promoted, due to the customer's lack of understanding of the process, concerns, and fear of problems, in view of this, had done a lot of trials beforehand for customers, such as: Hubei Xinhua printing factory, in order to test the water-based print After the film temperature resistance, moisture resistance, oil resistance and other properties, in the early use of the machine to do a relevant coating test, regardless of temperature, humidity, oil, can reach the film product requirements.

The lamination process is more complicated and the following points need to be noted in normal production:

â–  Printing powder

Because water-based glue can dissolve powder on the surface of the printed matter, when the snow-covered product appears, it is incomprehensible. In fact, the reason is simple. The water-based glue itself is also limited by the solubility. If the print dust is too large, the excess part cannot Completely dissolved by the glue, there will be a large area of ​​snow.

There are three ways to solve this situation:

1. Coordinate the process up and down, and minimize the dusting amount when printing;

2. The amount of glue should be increased appropriately to increase the ability of glue to dissolve and spray powder.

3. Spray the powder on the surface of the printed product before coating.

â–  Cleaning

Because the water-based film glue dries quickly, if it does not flow at rest, it will dry into rubber and become a solid block. If it is attached to the coating roller or the pressure roller, it will cause the local glue to be too small, or the local pressure will be too large when the pressure is applied. Therefore, the coating roller and the pressure roller should be kept clean during the lamination process.

If there is too much dust in the surrounding environment, there will be dry rubber and cut-off film fragments in the glue, and the covered product will have snowflakes. Therefore, attention should be paid to environmental sanitation. The glue should be used up to be sealed back to the plastic barrel or taken up. Pre-gel filtration method.

â– Discoloration of printed products

It mainly appears in large area printing gold and gilding products. This is due to chemical reactions between the chemically active elements of the glue and the gold powder.

The solution is: for gold products using special gold ink or special glue, or change the process, bronzing products after the first foil bronzing, many manufacturers use the latter process, the effect is very good.

â–  Paper and plastic separation

This phenomenon is easy to appear in full-page prints, because the surface of the ink layer is thick, the glue is difficult to wet, spread, infiltration, and bonding is not strong.

The solution is:

1. For such products, glue manufacturers are required to increase the solid content of the glue;

2. Appropriately increase the thickness of the glue layer;

3. Increase the ambient temperature during film coating and product drying;

4. Check if the glue is deteriorating, check the date of manufacture and shelf life of the glue;

5. Whether the film is over the shelf life, check whether the corona treatment of the film fails.

â– Deformation

There are several reasons for this situation:

1. The amount of glue is too large, because a large amount of glue will inevitably make the paper absorb moisture. Any paper will deform when it absorbs a lot of water. So in the absence of snow spots, minimize the amount of glue;

2. The film is stretched and deformed seriously. At this time, the tension of the film should be properly adjusted. As long as the film can be flattened and attached to the paper, the smaller the tension, the better.

3. Winding tension is too high. Under the premise of guaranteeing that the product can be rewinded onto the roll after the rewind, the smaller the rolling force, the better;

4. The temperature difference between the external environment of the film and the humidity is too great.

At present, there is also a kind of glue between the oiliness and the water in the country. The price is very cheap. It does not need to be dried and dried naturally after coating. The brightness and flatness of the product can meet the requirements, but it has strong Irritating odor, unstable quality. Can be used for low-end products. High-end products are recommended to use white green glue produced by regular manufacturers.

With the rapid development of the printing and packaging industry, waterborne coatings will have a broader perspective.

Source: China Packaging News