Coating method, drying process, principle of double-sided adhesive coating process and method to improve the adhesion between adhesive and substrate

Double-sided tape is a roll-shaped adhesive tape made of paper, cloth, and plastic film as the base material, and then uniformly coated with elastomer pressure-sensitive adhesive or resin-type pressure-sensitive adhesive on the above-mentioned base material. Adhesive and release paper (film) are composed of three parts.

Coating method

1 recoating

After the glue on the release paper is dried in an oven, it is bonded to the laminated material so that the glue is transferred to the laminated material. Suitable for double-sided tapes, single-sided label tapes and foam substrate tapes.

Features:

▶The thickness of the adhesive film is uniform, and the total thickness of the tape depends on the thickness deviation of the laminated material;

▶The finished tape or the process needs to be peeled off;

▶The maximum temperature of the oven can be controlled to 120°C when using release paper.

2Straight coating

Adhesive is directly coated on the substrate and wound, also known as winding from the back. Suitable for packaging tape and re-peelable tape.

Features:

▶The glue easily penetrates into the inside of the substrate, and the adhesion is good;

▶The total thickness of the tape is the same, and when the material is deviated, the thickness of the adhesive layer changes exactly in the reverse direction;

▶Drying speed and temperature depend on the type of substrate.

Drying process and principle

Drying means that the adhesive is coated on the substrate, and the moisture and solvent in the adhesive are volatilized at a certain speed to obtain a dry film. The drying process is an important part of the production of tape, which has a great impact on product quality. During the drying process, the heat and the substance are changing at the same time. The initial drying stage is mainly the heat continuously passing into the adhesive from the air, so that the solvent continuously diffuses from the inside of the adhesive layer to the surface, and reaches a saturated state on the surface. This period is called constant rate drying.

The moving speed of the substance depends on how much heat is transferred to the adhesive. After the solvent vaporizes on the surface, the drying enters the rate reduction stage. The surface temperature of the adhesive rises in a short time and enters a higher temperature oven. The bottom solvent gradually diffuses through the surface film. If the initial temperature is too high, the surface film is too high. Early hardening will affect the volatilization of the internal solvent vapor. When the temperature is higher than the boiling point of the solvent, the solvent gas in the adhesive layer will expand and cause foaming problems, which will eventually affect the cohesive strength of the adhesive layer, so it is frequently required to monitor Whether there is foaming on the rubber surface. At the same time, confirm whether the smell of the glue is too heavy. On the other hand, check whether the thickness of the glue layer is normal and whether the drying effect is sufficient.

The coating method, drying process and principle of the double-sided adhesive coating process and how to improve the adhesion between the adhesive and the substrate

Variation trend of drying speed and drying time (illustration)

Excessive amount of residual solvent will cause the initial adhesion of the tape to be large, and the performance of the tape will change easily after aging. At the same time, it will increase the peelability of the release paper. For use, too much solvent will affect the adherend or the printed layer with poor solvent resistance. Excessive medium odor has an impact on the working environment. The drying effect of the adhesive mainly depends on the heat transfer. In order to achieve sufficient heat supply, the hot air circulation of the oven must be ensured. Therefore, it is necessary to regularly check and clean the filter of the oven.

Take-up

The design of the coiling part needs to consider tension control. The tension of the base material during coiling changes with the diameter of the coil, and shows a gradual decrease. Generally, the slope is used to adjust to reduce the tension downward trend, which can overcome the air pressure when the coil is too loose. For the problem of rolling when entering and over-tightening, the coiling part is designed with a special driving device and a pressing device. When producing single-layer release paper double-sided tapes and PE protective film tapes, if air is involved, there will be pattern-like marks on the surface of the adhesive layer. If there are bubbles on the appearance of the protective film tape, the application range of the product will be limited ( Products with high appearance requirements cannot be used), and the air entrained by the double-sided tape (with moisture in the air) will affect the cross-linking effect of L-45 hardeners, and will cause the product's adhesion performance to decline (especially if the air humidity is too high) Time), so it is best to use the compression shaft to eliminate air entrapment during rewinding.

Double-sided tape peeling method

In the production of the second process of double-sided tape, the glue is applied by peeling paper (engineering paper) and then transferred to the first process product and then peeled off. In order to achieve the smoothness of the adhesive surface and avoid horizontal wrinkles, it is necessary to consider which type of paper to use The route is more reasonable. When the peelability of the first engineering surface is relatively small or the adhesive layer is thin and easy to deform, when the engineering paper is used for peeling, especially when the winding tension is too large, the adhesive layer is easy to be pulled up and enter the air, so use The tape direction peeling is more reasonable, and reducing the winding tension can improve the problem of the adhesive layer being pulled up. For example, in the production of foam double-sided tape, in order to avoid wrinkling of engineering paper, the method of peeling the tape down in advance can also be used. However, it is easier to control the peeling of general double-sided tape using engineering paper direction.