How does plastic packaging effectively control glue viscosity control?

The effect of glue viscosity on quality

Polyurethane dry composite adhesives with a solid content of more than 70% have been applied in foreign markets since the 1980s. This kind of glue can maintain a very low viscosity when it is sized at a solid content of 40% or more. It is popular in the market because of its reduced solvent usage, low cost, environmental friendliness and excellent performance. Today, we have noticed that 50% solid content dry composite adhesives still have a large share in the domestic market, which indicates that our dry and plastic packaging manufacturers have further understanding of this aspect.

In dry compounding, the control of the amount of adhesive applied is very important, which greatly affects the quality of the composite. If the amount of glue is too small, the adhesive can not form a film continuously, and spots appear, which affects the appearance quality of the composite material, and the adhesion is poor, which reduces the retort resistance and heat seal strength of the composite material; the amount of glue is too much, not only wastes the adhesive The film will be wrinkled and hardened, tunneling phenomenon will occur, the opening property will be deteriorated, and the amount of glue applied will be too much. The solvent is difficult to volatilize, and too much solvent remains in the glue layer, which will generate odor.

The amount of glue applied should be determined according to the type of substrate, the use of the composite, and the printing conditions. An important process technology for the amount of glue applied is the viscosity control of the glue. Usually, when we talk about glue, we always say how the solid content or concentration of glue, as well as the peel strength and various resistance after compounding. In fact, the status of the glue should also have the following indicators:

1. The transfer rate of glue;

2. The transparency of the glue;

3. The state after the glue has been transferred.

These include: the number and size of white and white spots, the number and size of crystal points and crystal points, and the number and size of "glue points" and "glue points".

The prepared adhesive must meet the operating viscosity of the machine (the viscosity is best when the viscosity is controlled for 15~20s), and the high concentration operation should be selected as much as possible under the condition that the adhesive viscosity is allowed. High concentration operation can reduce residual solvents and save solvent costs. However, the premise is that there must be a suitable wire roller to ensure the proper amount of dry glue. Generally, the high temperature resistant cooking film bag has a dry glue amount of 4.5 to 5.0 g/m2. Therefore, when the binder concentration is high, a shallow mesh roll can be selected, provided that a proper amount of dry glue is ensured. The net roll for processing retort packaging is generally selected from 80 to 100 lines, and the starting speed is 70~100 m/min.

When selecting an adhesive, it is best to choose a binder with a high solid content, which can generally be used at a higher solid content (working concentration is 35% to 45%) to ensure the amount of sizing, reduce the amount of ethyl ester, and reduce production. Cost and increase production efficiency. Gaoding Fine Chemicals produces general-purpose polyurethane adhesive CX-2022/CA-875LT (optimal use concentration is 40%~45%) and 125°C high temperature cooking glue CX-2522/CA-775LT (optimal use concentration is 30 %~35%) is available for purchase.

It doesn't matter which viscosity cup is used for a business, as long as it provides the operator with the necessary instructional data to achieve the goal.