Waterproof corrugated cardboard characteristics and processing method
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In recent years, with the improvement of people's living standards, the requirements for the packaging of goods have become higher and higher. As a packaging container for goods, corrugated boxes not only ensure the safe transportation of goods, but also can beautify goods, increase added value, and promote sales. In particular, in recent years, various new types of printed moisture-proof cardboard boxes have been printed on the market. It has greatly improved the product quality of the packaging carton, and fundamentally solved the problem of the carton packaging being damp, mildewed and vulnerable. The demand for carton with waterproof performance is increasing, especially in the packaging of vegetables, food, home appliances and industrial products. In particular, the use of water-resistant cartons for export products has grown rapidly, greatly contributing to the development of corrugated box manufacturing. Waterproof cardboard function and waterproof coating Introduction Waterproof cardboard is a general term for cardboard that has the strength to resist water damage. It is usually made by applying a layer of waterproof coating on corrugated cardboard and drying it. The waterproof coating is quickly dried and formed into a film after being coated on a carton. The film has high transparency and good gloss, and the coating film is smooth and non-blocking, and has no effect on the carton printing ink. After the corrugated carton is coated with waterproof coating, the surface of the carton can be enhanced in wear resistance, scratch resistance, high strength, strong water resistance, good moisture resistance, and can beautify and long-term protection of the carton. effect.
At present, domestic waterproof coatings mainly include: oil-soluble, alcohol-soluble and water-soluble waterproof coatings. Compared with these three waterproof coatings, the water-soluble and moisture-proof performance of water-soluble waterproof coatings is superior to oil-soluble and alcohol-soluble waterproof coatings. Water-soluble carton waterproofing coatings are usually water-based emulsions formed by paraffin and oxidized polyethylene as the main film-forming substances and blended with dispersants, stabilizers, thickeners, brighteners, conditioners, water and other additives. . Its outstanding advantages are: non-toxic and tasteless, good resistance to water penetration, not easy to burn, good stability, good adaptability to cold and hot temperature difference. It has the characteristics of safe use, low price, excellent waterproof and moisture resistance, and convenient use (spray, coating and brush).
This is because when the corrugated box is taken out of the freezer, the package is cooler than the outside. Just as cold water is poured into the cup in the summer, the same phenomenon of water droplets on the surface of the cup is the same as dew point. Generally, the dew on the surface of the corrugated cardboard can be absorbed by the linerboard in a short time, which increases the moisture of the carton and reduces the strength of the carton. The use of hydrophobic paperboard can turn dew into water droplets and prevent penetration into the interior without reducing the strength of the board. However, if it is placed outside for a long time, or repeatedly taken out by the freezer, because the hydrophobic treatment is only processed on the surface of the cardboard, the hydrophobic effect is gradually reduced, the water is increased, and the strength of the corrugated board is lowered after a certain period of time. For consistency. On the other hand, since the surface of the paperboard is subjected to hydrophobic processing, the surface abrasion resistance of the linerboard is greatly increased, and it is possible to prevent the cardboard boxes from rubbing each other many times during the circulation, and the surface of the cardboard is peeled off and the paper ends are generated. Water-resistant corrugated cardboard (water-retaining corrugated cardboard) Water-resistant corrugated cardboard is also known as water-retaining corrugated cardboard, which is in contact with water for a long time and does not substantially pass water. On the other hand, although water immersion can be prevented, the water resistance of the corrugated board will disappear once the water enters it.
In the corrugated board bonding process, the water-resistant waterproof coating is applied to the surface of the sheet by spray coating or roll coating to impart good water resistance to the paperboard. If the paper is coated on both sides, the paperboard is more waterproof. A representative method of making such corrugated cardboard is the curtain coating method. As shown in Fig. 1, the curtain method is a method in which a molten waterproof coating is sprayed down into a film curtain to pass a corrugated cardboard (or a corrugated cardboard box already printed) to form a coating film on the surface of the corrugated cardboard. Both sides can be processed on both sides by one or two curtain film installations.
The corrugated cardboard produced by this method can sufficiently prevent the water from being infiltrated from the surface, and the processing cost is also low, but the water cannot be prevented from immersing from the corrugated cardboard section. This corrugated board is generally used for packaging aquatic products. In addition to being used for waterproofing, corrugated cardboard has a soft waterproof layer on its surface, and is sometimes used for packaging of furniture, pianos, precision machinery and the like that are easily damaged. The strong water-resistance corrugated cardboard corrugated cardboard is soaked in water for a long time after processing, and the strength is not greatly reduced, which is called strong water-resistant corrugated cardboard. In other words, paper products have the disadvantage of being weakened by water, but the water resistance is still strong water-resistant corrugated cardboard after processing. There are two manufacturing methods, one is a one-time processing method: that is, the base paper is rendered water-resistant at the papermaking stage; and the secondary processing method is a processing method that imparts water resistance at the manufacturing stage of the corrugated board.
One-time processing method is a method of combining water-resistant linerboard and water-resistant corrugated base paper with water-resistant binder and processing to make corrugated board. Because of the water resistance of the base paper with water resistance, it is moderately water-resistant and highly water-resistant. The corrugated board produced is also moderately water-resistant and highly water-resistant. There are two secondary processing methods for secondary processing, namely coating method and dipping method. The coating method refers to a roll coater installed on a corrugated board machine, and the paraffin wax is applied to the liner board and the corrugated board, and then bonded. After the corrugated base paper is applied to the hot plate, the adhesive coating is sprayed on the corrugated base paper; sometimes, in order to improve the water resistance of the corrugated cardboard end face, the corrugated cardboard is also placed in front of the corrugated board cutter. Both ends of the slit are sprayed with a waterproof coating. The dipping method is to make the paperboard through the molten waterproof coating dipping tank, so that the waterproof coating penetrates the surface of the paper, and then the cardboard is sent to the drying section, and is subjected to hot air heating above 105 ° C, so that the surface of the cardboard is adsorbed with the waterproof coating, after cooling, The waterproof coating is fixed on the surface of the cardboard to make the cardboard waterproof. When the impregnation method is used, when the impregnation amount of the waterproof coating reaches 40% to 50% of the weight of the base paper, the strength of the paperboard can be greatly improved, but when used for general linerboard, the color of the cardboard becomes black.