Use of water-based adhesives

First, how to choose the rubber roller (net roller)? How much is suitable for glue?

The amount of glue on the water-based glue is small, so it is very important to choose the right glue roller. For water-based adhesives, the pits on the top rollers should be shallow, and the openings should be large so that the glue can contact the substrate with the largest surface area. This results in uniform coating, rapid drying, good composite appearance, and high peel strength. The appropriate network roller is the premise to ensure the amount of gluing and peeling strength, users should adjust according to the equipment conditions and compound speed. It is recommended to use a 180-line/inch to 200-line/inch electric carving roller. The pits communicate with each other and the depth of the pit is 32μ to 35μ. Always clean the rollers during use to prevent clogging, and re-chrome or sculpt a new cable roller after a period of use.

The suitable amount of glue is 1.6g/m2 to 2.4g/m2, which cannot be lower than 1.6g/m2, otherwise the peel strength cannot be guaranteed. If the amount of glue is too high, it will affect the drying of the glue, affect the leveling of the glue on the surface of the plastic film, thereby affecting the composite appearance and peel strength.

Second, high-speed composite bubbles, how to solve? Is it possible to add defoamer?

In order to catch up with production schedules and reduce costs, some manufacturers now have very fast speeds, some reaching 160m/min or more. For this compounding speed, water-based adhesives tend to produce more foam in the tank. If the continuous production lasts for several days, the foam will accumulate more and even overflow out of the tank. If you do not take certain measures at this time, it may lead to problems such as small amount of glue, low intensity, and appearance of white spots. The best solution is to put a uniform ink stick in the plastic tank to defoam. At the same time, the use of circulating glue to ensure that the plastic tank glue not too little. A plastic bucket for recycling should be used, so that if the foam in the plastic bucket can not be eliminated during a long period of operation, a spare plastic bucket can be used to apply glue, and the foam can be replaced after the foam in the original plastic bucket is eliminated.

YH620S products already contain defoamers, generally do not need additional anti-foaming agent, too much defoamer will affect the surface properties of the glue, thus affecting the composite appearance. The added defoamer will not mix well with the glue and will also affect the appearance of the composite.

Third, water-based plastic can be diluted with water?

At present, the market's water-based adhesives are mostly emulsion-based. The principle is that high-molecular polymers rely on emulsifiers to stably exist in water. Actually, it is a metastable state. Many external forces will cause the gel liquid to demulsify, and lose. effect. I do not recommend using water to dilute the glue, because dilution with water increases the surface tension of the glue and destroys the stability of the glue, resulting in delamination. In addition, dilution can alter the surface properties of the product, resulting in poor wetting and affecting the composite appearance.

Fourth, the use of water-based plastic compound, the appearance of some white spots, aging will disappear after a while, what is the reason? How to avoid this happening?

Water-based adhesives generally contain more than 50% of water and must be completely evaporated in a short period of time, requiring adequate temperature and wind speed. There are two reasons for the white appearance of the composite product. There are two reasons: First, the amount of glue is insufficient; second, the drying is not complete. The white spots that can disappear after a short period of ripening indicate that the drying is not complete, because ripening can further help the water to evaporate; otherwise, it indicates that the amount of glue is insufficient.

To avoid incomplete drying, the drying tunnel temperature and wind speed need to be adjusted. Drying temperature can be set to 70 °C ~ 80 °C 90 °C, but the author found that many of the actual temperature of the composite device is much lower than the set temperature, so conditions must be corrected to avoid too much error. The size of the wind speed is particularly important for the drying of water-based adhesives. It must be ensured that the wind speed reaches 6m/s or more, and the air outlet and air inlet of the equipment are often cleaned to prevent clogging. In addition, the temperature of the composite roll also affects the appearance of the composite, and also affects the initial tack, and the actual temperature of the composite roll must be above 50°C.

Fifth, the use of water-based adhesive composite film need to mature? Does aging for a period of time increase machine peel strength? Does a long-term high temperature aging affect it?

The YH620S compounded film generally does not require curing and can be slit at the next machine. Appropriate curing for a period of time can increase the peel strength because the molecular weight of the water-based glue is high, and it takes a certain time to level and reach a better strength. Therefore, it is better that the composite film is matured in a maturation chamber at 50°C for 1 h to 4 h when conditions permit. Prolonged high temperature (above 80°C) aging has a certain effect on the strength of the composite film because the water-based adhesive polymer cannot withstand high temperatures for a long time.

Six, water-based plastic will not affect the adhesion of ink on the film? Why does the appearance of a composite film printed with different inks vary greatly?

Water-based adhesives have good adaptability to aqueous inks and solvent-based inks. The occurrence of ink transfer generally depends on the quality of the ink. If the affinity of the ink to the film is poor, the adhesive may pull the ink off the film. This problem does not exist with good quality inks.

Ink contains different waxes, slip agents, defoamers, plasticizers, etc. These components will have a detrimental effect on the glue, which will affect the appearance of the compound. Therefore, after replacing the ink, the glue should be tested to avoid damage.

Reprinted from: China Packaging News Author/Chen Xiaofeng