Paste solution for poor adhesion problems

The carton industry is very regional, with seasonal and environmental conditions in different regions, and the source of the base paper is different. In the same region, the speed, shape, and pasting systems of different manufacturers' equipment are all different; the quality of the paste-making personnel is also uneven. Qi. The quality of paste must meet the requirements of different manufacturers and the special requirements of individual customers. Therefore, the formulation of the paste is more difficult to be exactly the same. However, the principle of paste-making, the mechanism of adhesion, and the solution to poor adhesion are the same. In this paper, we will mainly explain the pasting principle, the bonding mechanism of corrugated cardboard, and the paste solution to the common problems of poor adhesion.
Paste principle:
Natural starch is a linear polymer compound formed by linking dehydrated D-glucose through α-1,4 oxime linkages. The viscosity of natural starch is high, and the liquidity is poor. It is easy to precipitate and stratify, and can not be used directly as a binder. Its structure contains a large number of hydrophilic hydroxyls and is not hydrophobic in nature.
During the paste-making process, the starch linear polymer is broken into fine particles by chemical action by adding NaOH, so that the starch molecules can more easily penetrate into the base paper. When NaOH is added in a proper amount, too much, the gelatinization temperature will decrease, and the paste will instead cause the water to lose its viscosity; if too little, the paste will be easily precipitated and the paste gelatinization temperature will be high.
The borax added during the paste-making process is a complexing agent, which forms the network-like structure of the starch molecule particles after chain scission and has a cross-linking and viscosity-increasing effect, which is favorable for improving the initial adhesion and accelerating the drying speed. The addition of borax is appropriate. When it is too much, the gel phenomenon occurs easily, the film is brittle, and the pressure lines are easy to burst; too little, the complexation is not enough and the adhesion is poor, causing cardboard degumming and running.
The addition of the resin bridge bridging agent in the paste is mainly to increase the adhesive strength, so that the paperboard has a certain hydrophobic function. The stabilizer is mainly to stabilize the viscosity of the paste to prevent the paste from deteriorating and losing its viscosity. At present, the fully automatic paste making system used in the market mainly uses the effect of physical and mechanical shear stress to make the starch molecular particles finer and increase the permeability and stability of the paste.
Adhesion mechanism:
Although the bonding process of corrugated board is an instantaneous process, it is microscopically divided into the following steps:

Fully Adhesive Poor Paste Solution When poor adhesion occurs, the first thing to do is to analyze the diagnosis on-site, whether it is poor adhesion or poor adhesion. Is the order stuck poorly before or after, or is the individual order stuck badly? In order to determine the main cause of poor adhesion, and on-site adjustment and solution. Avoid all problems of poor adhesion attributed to the problem of adhesives.
However, there are only a few phenomena that have the same phenomenon. The causes and solutions of poor bonding are different.
Tearing cardboard, there is no paste on the peak or lack of paste, generally the operation and process gap adjustment issues. At the same time to check the viscosity of the paste is appropriate to avoid blocking the pipe, resulting in pulp-free pulp;
Tearing cardboard, there is a paste on the peak and the amount of pulp is appropriate. At this point, observe the gelatinization of the paste.
A. If the surface paste is white, it means that the paste is not gelatinized during the bonding process, and thus there is no tackiness, resulting in poor adhesion. Explain that the temperature or steam pressure at the production site is not enough, or the speed is too fast. Or the pasting temperature of the paste is too high, causing poor adhesion under normal production conditions. In this case, if only happens by chance, the general adjustment operation can be solved. If it happens frequently, the gelatinization temperature of the paste must be adjusted to the factory's production conditions (vehicle speed, steam pressure, etc.).
B. If the surface paste is cooked, it is likely that the paste is gelatinized too early, and the paste has not sufficiently penetrated into the base paper fiber and should be pasted on the surface to cause false adhesion or degumming. At this point, it is necessary to analyze whether the speed is too slow, whether the temperature is too high, the degree of sizing of the base paper, and the sizing method. When the operation cannot be adjusted, it is necessary to analyze whether the gelatinization temperature of the paste is too low, and adjust the paste formulation and the gelatinization temperature appropriately. For the adhesion of surface applied collagen paper, the permeability of the paste is stronger.
In short, the occurrence of such adhesion problems, as well as other types of paperboard adhesion problems such as blistering, dew-cursing, and poor local adhesion, have a lot to do with production operations and equipment performance. But no matter what kind of poor adhesion, corrugated board production site technology and management personnel must be familiar with the principle of paste, and adhesion mechanism, but also need to understand the characteristics of the company's original paper, corrugated shape, speed, steam pressure and temperature and other process parameters And equipment characteristics. Never change, there is no problem that cannot be solved.