Indicators for measuring the quality of adhesives

The bonding strength of corrugated cardboard depends mainly on the quality of the adhesive and the sizing quality of the corrugated cardboard production line.

Quality of adhesive

The quality of the adhesive mainly depends on the quality of the adhesive manufacturing process and the quality of the raw materials used. The main raw material used for the adhesive is starch, and corn starch above industrial grade one is generally used. If a lower-grade starch is used, due to its poor processing fineness, more impurities such as protein and fat, it will consume more caustic soda, making the adhesive unstable, and the bonded corrugated cardboard is easy to absorb moisture, and the adhesive It is easy to produce gels with larger starch granules and impurities as the core, making the fluidity worse.

Solid content, initial viscosity, viscosity, gelatinization temperature, etc. are important indicators to measure the quality of adhesives:

1. Solid content

The solid content of the adhesive should be determined according to the accuracy of the equipment, the running speed and the actual situation of the base paper. Once the speed of the high-speed wide-width corrugated cardboard production line reaches more than 200 meters per minute, the solid content of the adhesive must be high. Water and starch The ratio is usually between 2.5: 1-3: 1. The higher the solid content of the adhesive, the lower the moisture. The smaller amount of glue can ensure the adhesion of corrugated cardboard; and the moisture change during the processing of corrugated cardboard is small, which can reduce the warpage of corrugated cardboard. If the equipment of the enterprise is low in accuracy, slow in speed, and the base paper is easy to penetrate, the solid content of the adhesive should be lower, otherwise it will cause quality problems such as degumming of corrugated cardboard, crystallization of paste line and line explosion.

2. Initial adhesion

The initial adhesion is the key to ensure the adhesion of corrugated cardboard and increase the speed of the vehicle. In the production of corrugated cardboard, increasing the preheating area of ​​the base paper, or adding crosslinking agents when making the adhesive, and adding borax in the main body and the carrier tank, and increasing the solid content of the adhesive can all coat the adhesive. After a short period of time began to produce adhesion, and its adhesion can destroy paper fibers.

3. Viscosity

The lower the viscosity of the adhesive, the better the fluidity. The fluidity of the adhesive determines the permeability of the adhesive, the uniformity of the glue, and the amount of glue, which directly affects the speed of the vehicle, the adhesion of the cardboard, the flatness and strength of the cardboard. In addition, it is not that the higher the proportion of starch in the adhesive, the worse the fluidity; the high solid content adhesive can also maintain a very low viscosity by adjusting the formulation process. In general, the viscosity of the adhesive during circulation is reduced every time it passes through the circulation pump. At this time, the newly prepared adhesive should be mixed and used.

4. Pasting temperature

The gelatinization temperature refers to the initial temperature required to turn the starch adhesive into a paste. The adhesive gelatinization temperature is a key factor for maintaining high-speed production. The problem of adhesive gelatinization temperature is solved, except by adjusting the caustic soda In addition to the amount and method of heating, appropriate addition of some additives can also play the same effect. The gelatinization temperature cannot be too low, otherwise it will cause the adhesive to gelatinize during the cycle and affect the fluidity of the adhesive. The gelatinization temperature of the adhesive should be adjusted according to seasonal changes. In winter, the gelatinization temperature can be adjusted to 55-60 ° C, and in summer, the gelatinization temperature can be adjusted to 61 ° C-66.

Sizing quality of corrugated board production line

In the European and American countries, the most important one for the quality of corrugated boxes is the inspection of the width of the corrugated cardboard adhesive line. The standard sizing is accurate, the adhesive is applied evenly and smoothly on the entire corrugated peak, the contour of the glue line is clear, and there is no adhesive projected laterally from the corrugated, there is no trace of drag glue.

Poor sizing is mainly related to the equipment status, adhesive quality and base paper quality of the corrugated board production line.

Common quality problems caused by poor sizing are mainly manifested in the following aspects:

1. Drip glueing

There is dirt on the glue roller, such as paper dust, starch agglomerates and other foreign objects, or there is a blockage of foreign objects at the mesh on the surface of the roller, which causes the glue roller to not be glued smoothly. If it falls, the amount of glue on Lengfeng will be insufficient when glue is applied, and there will be intermittent drops of glue. The corrugated cardboard surface will show traces of layering of face paper and core paper, and the compressive strength, edge pressure strength and adhesive strength of the carton will be reduced.

When the gap between the upper rubber roller and the lower corrugated roller is too wide, the upper rubber roller cannot contact the lower corrugated roller, and there is not enough adhesive on the corrugated peak.

2. Adhesive lateral ejection

The viscosity of the adhesive is too high; when it is too low or the content of borax is too high, it is easy to produce lateral ejection of the adhesive when the production line is running at high speed. And compressive strength will be reduced.

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