Corrugated board adhesive molding each step has a direct relationship with the adhesive bonding mechanism. The nature of starch is due to the fact that the starch molecules contain hydroxyls that are prone to chemical reactions, so the starch can react chemically with many substances. In starch molecules, hydrogen bonds can form between hydroxyl groups on adjacent segments,
This increases the stability of the starch granules in the solution. In the process of using starch, it is always the first to destroy the granule structure to cause swelling of the granules, so that the starch molecules hydrate and dissolve. It is called gelatinization of starch. The whole process of bonding is done on core paper with sufficient heat and humidity. The adhesive applied to the peak gradually wets, diffuses, and penetrates into the paper fiber structure. At this point, the raw meal will rapidly gel and mature under the action of high temperature and finally reach full cure. When the five bonding steps of the corrugated cardboard bonding mechanism described above are synchronized, the best bonding effect will be obtained. If the adhesive gel is too fast, it will cause the glue to spread and infiltrate insufficiently to assemble on the surface of the cardboard and condense into crystals, causing false sticking of the cardboard; if the adhesive gel is too slow, there will be a lot of glue spread and penetration On the sides of the peak application line, white lines appear, and raw starch loses its viscosity due to its inability to ripen, resulting in poor adhesion of the cardboard.
Thus, finding the gel point of the adhesive will be the key to solving the adhesive effect of the paperboard. Due to the structural differences between single-sided and double-sided machines, it was decided that the adhesive formulation should be different. Under normal circumstances, single-side machine should choose the formula with low viscosity and high gel point; while the double-sided machine should choose formula with higher viscosity and lower gel point to meet the need of cardboard adhesive forming. The reason is: on the noodle machine, due to its unique sizing mechanism, it is decided that the bonding process is to be formed under high temperature and high speed, and the glueing-permeating-phase-bonding needs to be completed in an instant. Bonding—Fixing and other five adhesive forming steps require that the adhesive of a single-sided machine should be of low viscosity and high gel point in order to facilitate penetration and adhesion of the glue in a very short time. On the double-sided machine, due to a long time, and the glue application mechanism is cold sizing, the double-sided machine bonding process is to complete the adhesive molding at room temperature, requiring the double-sided machine adhesive to be higher viscosity, Lower gel point for slow diffusion, gelling and bonding. Under normal circumstances, single and double-sided machine adhesive quality requirements are shown in Table 1.
The data in Table 1 is not static. As the steam pressure and production speed provided by the equipment and the moisture content of the base paper are constantly changing during the production process, it is necessary to adjust it in a timely manner to meet the needs of various steps in adhesive forming in order to achieve the best Adhesion effect.
