Characteristics and processing methods of waterproof corrugated board
In recent years, with the improvement of people's living standards, the requirements for the outer packaging of commodities have become higher and higher. Corrugated cardboard boxes, as outer packaging containers for commodities, can not only ensure the transportation safety of commodities, but also beautify commodities, increase added value, and promote sales. In particular, in recent years, various new types of moisture-proof glazing cartons with beautiful prints have appeared on the market. To a large extent, the product quality of the packaging carton has been improved, and the problem of moisture, mildew, and damage of the carton packaging has been fundamentally solved. At present, the demand for carton boxes with waterproof performance is constantly increasing, especially in the packaging of vegetables, food, home appliances, and industrial products. In particular, the volume of water-resistant carton used for export products has increased rapidly, which has greatly promoted the development of the corrugated carton manufacturing industry. The function of waterproof cardboard and the introduction of waterproof coating The waterproof cardboard refers to the general name of the cardboard that has the strength to resist the damage of the carton by water. It is generally made by coating a layer of waterproof coating on corrugated cardboard and drying it. The waterproof coating is quickly dried and formed into a film after being painted on the carton. The film layer has high transparency and good gloss. 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 and good moisture resistance, which can beautify and protect the carton for a long time. effect.
At present, domestic waterproof coatings mainly include: oil-soluble, alcohol-soluble and water-soluble waterproof coatings. Compared with the three waterproof coatings, the gloss and moisture resistance of water-soluble waterproof coatings are better than oil-soluble and alcohol-soluble waterproof coatings. Water-soluble carton waterproof coating is usually a water-based emulsion formed by combining paraffin wax and oxidized polyethylene as the main film-forming substances, together with dispersants, stabilizers, thickeners, brighteners, regulators, 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-proof performance, and convenient use (both spray, paint and brush).
This is because when the corrugated box is taken out of the freezer, the packaging is cooler than the outside. Just as cold water is poured into the cup in the summer, the phenomenon of water droplets on the surface of the cup is the same. This is the dew point phenomenon. Generally, the dew on the surface of 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 change dew into water droplets and prevent penetration into the interior, without reducing the strength of the paperboard. However, if it is left outside for a long time, or repeatedly taken in and out by the freezer, because the hydrophobic treatment is only processed on the surface of the cardboard, the hydrophobic effect gradually decreases, the moisture increases, and after a certain period of time, the strength of the general corrugated cardboard decreases. For consistency. On the other hand, due to the hydrophobic processing on the surface of the cardboard, the surface abrasion resistance of the lined cardboard is greatly increased, which can prevent the cartons from rubbing against each other multiple times during the circulation process, peeling the cardboard surface and producing paper dust. Water-resistant corrugated paperboard (water-proof corrugated paperboard) Water-resistant corrugated paperboard is also called water-resistant corrugated paperboard. This kind of paperboard is in contact with water for a long time and basically does not let water pass through. On the other hand, although it can prevent water from entering, once the water enters, the water resistance of the corrugated cardboard will all disappear.
During the bonding process of corrugated cardboard, the water-resistant waterproof coating is applied on the surface of the sheet of paper by spraying or roller coating, so that the cardboard has good water resistance. If each paper is coated on both the front and back sides, the waterproof performance of the cardboard is better. The representative method of manufacturing such corrugated board is the curtain coating method. As shown in Figure 1, the so-called curtain method is a method of allowing molten waterproof coating to be sprayed downwards in the form of a film curtain, allowing corrugated cardboard (or a corrugated cardboard box that has been printed) to pass, and forming a coating film on the surface of corrugated cardboard (It can be processed on both sides by one pass or two curtain installations)
Corrugated paperboard manufactured by this method can fully prevent water from immersing from the surface, and the processing cost is relatively low, but it cannot prevent water from immersing from the cross-section of the corrugated paperboard. This kind of corrugated cardboard is generally used for packaging aquatic products. In addition to waterproofing, due to the soft waterproof layer on the surface of corrugated cardboard, it is sometimes used for packaging furniture, pianos, precision machinery and other items that are easy to bruise. Strong water-resistant corrugated paperboard Corrugated paperboard is soaked in water for a long time after being processed, and the strength is not greatly reduced is called strong water-resistant corrugated paperboard. In other words, paper products have the disadvantage of becoming weak when exposed to water, but after processing, they still have strong water resistance (Water resistance). There are two manufacturing methods, one is the primary processing method: that is, the base paper is endowed with water resistance in the papermaking stage; and the secondary processing method: the processing method that is endowed with water resistance in the corrugated board manufacturing stage.
One-time processing method One-time processing method is a method of combining corrugated paperboard with water-resistant paperboard and corrugated base paper and then using a water-resistant adhesive to produce corrugated paperboard. Because the water resistance of the base paper with water resistance is divided into medium water resistance and high water resistance, the corrugated board produced also has two kinds of medium water resistance and high water resistance. Secondary processing method There are two secondary processing methods, namely coating method and dipping method. Coating method The coating method refers to installing a roll coating machine on the corrugated board machine, applying paraffin to the liner board and the corrugated board, and then bonding. After coating the adhesive on one side of the corrugated base paper before entering the hot plate, spray the waterproof coating on the corrugated base paper; sometimes in order to improve the water resistance of the end surface of the corrugated board, the corrugated board must be placed before the paper cutter of the corrugated board machine Spray water-repellent paint on the incisions at both ends. The dipping method is to make the paperboard pass through the molten waterproof paint dipping tank, so that the waterproof paint penetrates the surface of the paper, and then send the paperboard to the drying section, and be heated by hot air above 105 ℃ to allow the surface of the paperboard to absorb the waterproof paint. The waterproof coating is fixed on the surface of the cardboard, so that the cardboard has good waterproofness. Using the impregnation method When the additional amount of impregnation of the waterproof coating reaches 40% to 50% of the weight of the base paper used, the strength of the paperboard can be greatly improved, but when it is used for general noodle paperboard, the color of the paperboard will become black.
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