Manufacture of moisture-proof carton box--making method (below)

(III) Manufacturing method of waterproof cardboard

1, hydrophobic corrugated cardboard

The so-called hydrophobic corrugated paperboard is a surface of a processed paperboard when it is exposed to water for a short time, so that the water condenses into water droplets and splashes to prevent water from entering. In the papermaking process, in order to increase the water resistance of the base paper, papermaking water repellents may be added into the pulp, or surface sizing may be performed to impart water resistance to the base paper. In the production of linerboards in paper mills, the papermaking water-repellent agent is applied to the surface of the calender of the papermaking machine for coating. In the manufacture of corrugated paperboards, papermaking water-repellent agents are coated on a corrugated board machine with a roll coater, or papermaking water-repellent agents are sprayed on the paperboard surface with a spraying device.

Hydrophobic corrugated cardboard is commonly used for the packaging of vegetables, fruits and aquatic products. According to the different packaging materials and circulation conditions, it is divided into two types: water repellency on the surface and inside of the carton and hydrophobicity on the surface of the box. For example, corrugated cardboard with hydrophobic treatment on the surface of the box will be taken out into the freezer and then taken out after a period of time. Generally, dew will be produced on the surface of the corrugated cardboard.

This is because when the cardboard box is taken out of the freezer, the package is cooler than the outside. Just as the cold water is poured into the cup during the summer, the phenomenon of water droplets on the surface of the cup is the same. This is the dew point phenomenon. The dew on the surface of corrugated board can be absorbed by the liner board in a short time, increasing the moisture of the cartons and reducing the strength of the cartons.

The use of hydrophobic cardboard can turn dew into water droplets and prevent penetration into the interior, without lowering the strength of the cardboard. However, if it is left outside for a long time or it is repeatedly taken in and taken out by a freezer, because the hydrophobic treatment is only processed on the surface of the cardboard, the effect of the vegetable and water is gradually reduced, and the water content is increased by i = a given time and the ordinary corrugated cardboard The intensity drops to =. On the Other hand, because the surface of the paperboard is subjected to hydrophobic processing, the surface abrasion resistance of the linerboard is greatly increased, which can prevent the carton from rubbing against each other several times during the circulation process, and the paperboard surface is peeled off and paper ends are generated.

2, water-resistant corrugated board (water retaining corrugated cardboard)

Water-resistant corrugated paperboard is also called water-repellent corrugated paperboard. The paperboard is in contact with water for a long time and basically does not allow water to pass through. If, on the other hand, water is prevented from immersing, the water resistance of the corrugated board will disappear once water enters it.

In the bonding process of corrugated cardboard, a water-resistant waterproof coating is applied to the surface of the paper by spraying or roller coating, so that the paperboard has good water resistance. If there is coating on both sides of each sheet, the waterproof performance of the cardboard is better.

A typical method for producing such a corrugated cardboard is a curtain coating method. As shown in Fig. 1, the so-called curtain method is a method of spraying a molten waterproof paint into a thin film curtain to pass a corrugated cardboard (or already printed corrugated cardboard box) and forming a coating film on the surface of the corrugated cardboard ( Pros and cons can be processed on both sides by once or by installing two film units.)

The corrugated paperboard manufactured by this method can fully prevent water from immersing into the surface and the processing cost is also low, but it cannot prevent the water from infiltrating through the cross section of the corrugated cardboard. This kind of corrugated cardboard is generally used for packaging aquatic products. In addition to being used for waterproofing, corrugated cardboard has a soft waterproof layer on the surface, and is sometimes used for the packaging of easily bumped furniture, pianos, and precision machinery.

3, strong water-resistant corrugated cardboard

Corrugated board is treated with water-repellent corrugated paperboard after being processed for a long time. The strength is not greatly reduced. In other words, paper products have the disadvantage of becoming weaker in water, but strong water-resistance corrugated paperboards are still processed with strong water resistance (W ate rresistance).

There are two kinds of manufacturing methods. One is a one-time processing method: that is, water resistance is given to the base paper at the papermaking stage; and there is a secondary processing method that is a processing method that imparts water resistance during the manufacturing stage of corrugated cardboard.

One-time processing

The primary processing method is a method of forming a corrugated paperboard by combining a water-resistant linerboard and a water-resistant corrugated base paper and then using a water-resistant adhesive. Because of the water resistance of the base paper with water resistance, the water resistance of the base paper is medium, high water resistance and high water resistance. The corrugated board produced is also medium in water resistance and highly resistant to water.

Secondary processing

There are two kinds of secondary processing methods, namely coating method and impregnation method.

Coating method

The coating method refers to installing a roll coater on a corrugated board machine, applying paraffin wax to the linerboard and corrugated cardboard, and then bonding. After the corrugated paper is applied to the hot plate, it is coated with adhesive on one side, and then the waterproof coating is sprayed on the corrugated paper; sometimes, in order to improve the water resistance of the corrugated board, the corrugated board is also used before the paper cutting machine of the corrugated board machine. Spray on the two ends of the waterproof coating.

Dipping method

Impregnation method is to make the board through the molten waterproof coating impregnated tank, so that the waterproof coating soaked the surface of the paper, and then send the cardboard into the drying section, subjected to hot air heating above 105 °C, so that the cardboard surface adsorption waterproof coating, after cooling, waterproof coating It is fixed on the surface of the board, so that the board has good water resistance. When the impregnation method is used, when the impregnation amount of the waterproof coating reaches 40%-50% of the weight of the base paper, the strength of the cardboard can be greatly improved. However, when used for general linerboard, the color of the cardboard will become black.

Author: Institute of Paper Engineering, Shaanxi University of Science Chen Chang Liu Xiaoxia