The quality of the adhesive is a key factor affecting the adhesive strength of the corrugated box. In the adhesive used for export cartons, the relevant standards stipulate that no sodium silicate (Baubulin) should be used, and starch adhesives or other equivalent adhesives should be used.
Corn starch adhesives are commonly used in export cartons. The preparation methods are hot and cold. Because most manufacturers use the cold method, the cold method is used as an example: The adhesive is made by chemical reaction from water, starch, sodium hydroxide and a small amount of borax, etc. Not the same, usually in the case of water ratio of 1:5, according to the different starch origin and quality, by gradually adding sodium hypochlorite, corn starch, sodium hydroxide, borax (the chemicals must be dissolved and diluted to the required concentration), Mix evenly and several times to prepare the ideal adhesive. Therefore, the preparation procedure and the preparation method have a direct influence on the quality of the bonding, and some ingredients even have a great influence. E.g:
1. The protein content of starch does not exceed 0.5%. Excessive protein content tends to coagulate and reduce viscosity.
2. The amount of borax accounts for about 0.5% of the total amount. Too little or too much will cause the bond strength to decrease. Too few binders are too thin, causing too high permeability to run corrugated board; too much can make the binder rubbery and lose adhesion.
3. Sodium hydroxide acts as a pasting agent to decompose water-insoluble starch molecules and form a homogeneous, transparent, viscous starch paste. However, the amount of sodium hydroxide must be strictly controlled, the amount is too much, too alkaline will damage the paper fiber, and when the relative temperature in the air is large, the cartons will absorb yellowing and degumming; too little, will cause Starch oxidation time is too long, starch paste is uneven, viscosity decreases. The pH of the formulated adhesive should be between 7.5 and 8.5.
4. The concentration of sodium hydroxide (dissolved and diluted to 10%) has a great influence on the quality of the binder. The concentration is too high. When the gelatinization reaction is intense, the reaction is strongly saccharified. There was a phenomenon of gum on the cardboard, which caused the cardboard to open and the adhesive strength decreased.
In addition, the binder material addition process and time, stirring uniformity, seasonal temperature changes, reaction time, water quality and other factors on the joint temperature changes, the length of the reaction time, water quality and other factors have a certain quality of the adhesive Impact. If the oxidation reaction temperature is too high, the oxidation reaction rate will increase. If other conditions do not change, the quality of the resulting adhesive will decrease. If using the hot method, the preparation process of the adhesive is somewhat different.
