Application of starch adhesive for cardboard production line

At present, the adhesives used in automated cardboard production lines (or single-sided machines) at home and abroad are commonly referred to as “raw rubber”. The so-called "raw gum" means that there is no adhesive force at room temperature, and only when the high temperature on the paper heats the matured rubber, it has adhesive force. The production method mainly uses starch (mainly corn starch, and also other starches such as tapioca starch, wheat starch, etc.), and is made into adhesive by two-step method. The disadvantage of this type of pure starch adhesive is that the strength and hardness of the paperboard produced is not high, the moisture resistance is poor, and it is not water resistant.

The optimum viscosity of the automated cardboard production line (or single-sided machine) adhesives should be controlled between 45-95 seconds (measured with 4 cups), and of course between 30-300 seconds. In fact, manufacturers use a variety of habits, different formulations, the viscosity of the glue used is very different, the minimum viscosity of about 30 seconds, the largest in about 300 seconds. Why is the best viscosity between 45-95 seconds? This is because, if the viscosity is too small, the rubber roller is not glued, and when it is compounded on both sides, the penetration is too fast; the viscosity is too large, the fluidity is poor, the coating is uneven, and the penetration ability is not strong. Both of these conditions can cause poor adhesion. Therefore, in practical use, the viscosity of the glue should be controlled within a suitable viscosity range.

So how to adjust the viscosity of the glue? First of all, it should be understood what is the main factor affecting the size of the gel, and how it affects it. The influencing factors and impacts are as follows:

First, the amount of carrier starch (or rubber powder), the viscosity of large; carrier starch (or powder) with less, small viscosity.

Second, the total water added, the viscosity is small; total water, viscosity.

Third, the use of borax, viscosity, large amount; low viscosity, low viscosity.

Fourth, the glue, the longer the mixing time, the smaller the viscosity; the shorter the stirring time, the greater the viscosity. In addition, under the same stirring time, the faster the speed of the mixer is, the smaller the viscosity is.

5. The use of caustic soda at a level below 3.5% of the total starch has little effect on the viscosity of the glue. If the amount of caustic soda is too large, the viscosity of the glue is extremely large and forms a mass that cannot be used.

Sixth, the viscosity of starch itself is also different. Starch contains branched and amylose starches, with a large amount of amylopectin and a large viscosity; amylopectin is less in viscosity and has a smaller viscosity. Different origins and different varieties of corn, containing amylopectin different, the processed starch viscosity is very small.

Usually, for an enterprise, the equipment for making glue must be certain, and the speed of the mixer must be constant. Due to the constraints of the production line, the moisture content of the glue used is basically the same, that is, the total water inflow is constant, and the amount of borax is also not used. Change, in this way, in the actual gluing process, only need to increase or reduce the amount of carrier starch, to master the appropriate mixing time, you can arbitrarily adjust the viscosity of the glue, so that it is within the optimum viscosity range. If there is a change in the viscosity of the starch itself, it is only necessary to increase or decrease the amount of the carrier starch, so that the viscosity of the glue can be kept substantially constant.

When people talk about the viscosity of glue, it's easy to confuse it with good adhesion. Adhesive viscosity and adhesiveness are two different things. Viscosity and adhesion are two completely different concepts. In the case of adhesives for paperboard production lines, the viscosity of the glue does not substantially affect the bond strength in the larger range of viscosity. It is by no means the higher the viscosity of the glue, the higher the bond strength, and the opposite is the good flowability, ie the viscosity. It is used in small and large-scale high-speed automatic production lines, and the adhesive effect is better.

Different papers have different requirements for the viscosity of the glue, the paper is rough, easy to penetrate, and the glue with a slightly higher viscosity is used; the paper is fine and the glue with a lower viscosity is used. In particular, imported “cow cardboard” uses high-permeability plastics.

In different seasons, the temperature and humidity are different, and the requirements for glue are different. If the temperature is dry, the total amount of water should be appropriately increased; when the temperature is low, the amount of water should be appropriately reduced. When the amount of water is changed, the amount of the corresponding carrier starch should be appropriately changed so as to keep the viscosity of the glue substantially constant. The viscosity of the glue mentioned here is basically the same, which does not mean that the formula of the glue is not changed. On the contrary, the glue formulation should be appropriately adjusted according to different paper, season, and viscosity of the starch itself, but it is not suitable for large adjustment. Absolutely not changing the West is not science. Different batches of starch may have different viscosity levels. If necessary, the formula should also be adjusted. It is only necessary to increase or decrease the amount of carrier starch.

In short, the glue makers should make out the principle of glue making, and flexibly apply it according to actual needs. The glue viscosity can be arbitrarily adjusted to meet the actual needs of board production. China Packaging News