The heavy-duty packaging carton is made of moisture-proof, in addition to protecting the packaging from water soaking, it is mainly to prevent water from infiltrating the box itself. Because the compressive strength and burst resistance of the carton body will be greatly reduced after the carton is soaked in water, which will seriously affect the quality of the packaging. Heavy-duty packaging cartons are made of moisture-proof, usually by coating waterproofing agent to solve the problem. Therefore, according to the function of the waterproofing agent, the method of making the moisture-proof carton can be divided into: temporary waterproofing treatment and long-term waterproofing treatment.
Heavy-duty packaging cartons are temporarily waterproofed after being treated with temporary waterproofing agents during the production process. According to the interpretation of JISZ1537-: When water falls on it for a short time, it will not wet into water droplets, which can prevent water from penetrating the cardboard. Temporary waterproofing agent processing cardboard technology has been applied in major carton factories in China in the past ten years. This kind of water repellent was originally introduced from Japan, and its Japanese text is called “water repellent”.
This kind of coating was used on fabric fibers in the early days, and then used for the treatment of cardboard. Therefore, most tree carton factories use the name of water-drawing agent. The water-drawing agent is a wax emulsion, the solid content is generally: 48%-51%, its biggest feature is that it can be diluted with about 30 times of water during use, and then coated on the surface of the corrugated cardboard being formed. Drying at a temperature of about 150°C, the fibers on the surface of the paper have low surface tension due to the wrapping of vinegar, forming a surface layer that is not wettable to water. When it encounters water, the water does not infiltrate the cardboard, forming water droplets to roll off, so as to achieve the effect of waterproofing. However, the adhesion of wax to paper fibers is not good, especially when the water-drawing agent is diluted 30 times, its solid content is only 1.5, and only a very thin layer of fiber on the surface of the paper is covered by wax. In addition, since the particle size of wax in wax emulsions is generally larger than that of ordinary polymer emulsions, it is difficult to penetrate deep into the paper fibers. At the same time, water-drawing agents are generally sensitive to chemicals such as alum and tend to be fast on the paper surface. Demulsification and precipitation of rice, so most of the wax particles in the water-drawing agent only exist in a very thin layer on the paper. Under the action of external friction, the wax is easily rubbed off, exposing the wax-free fiber, and the waterproof effect is greatly reduced. In order to enhance the adhesion of wax to paper fibers, rosin derivatives or carboxylated polymer emulsions are often used in water-drawing agents. They have good adhesion to paper fibers and good compatibility with wax. In this way, their addition can promote the adhesion of the wax to the paper fiber, and at the same time, if the wax is modified, such as oxidizing and basicizing it, it also has a similar effect, which can increase the adhesion of the wax to the paper fiber. However, it must be pointed out that even with the addition of these measures, the water-drawing agent at such a concentration is still not a waterproof film. Therefore, when friction is encountered, such as the friction during the handling and stacking of cartons, it will often Make this waterproof surface useless. This is why this type of carton coated with water-drawing agent is designated as a temporary waterproof carton. At present, water-drawing agents have been widely used in some carton factories and have become a basic process. This is mainly due to the following four aspects: the price and machine coatability of the water-drawing agent; the water-drawing agent maintains the original color of the paper and is in line with the current mainstream return to nature; the water-drawing agent has no adverse effect on the recycling of cartons; The water-proof effect of the water agent is fully competent for the use of general cartons. However, it must be pointed out that the cartons used in some special environments, such as cartons that need to be frozen, cartons that need to be stored in high humidity environments, and cartons that need to be shipped by sea, should be cautious when using water-drawing agents. In practice, there have been cases of cartons coated with water-drawing agent. After being taken out of the freezer, the cartons were deformed, causing economic disputes. Therefore, when recommending what waterproofing treatment customers should use, full consideration should be given to the environment in which the customer’s cartons are used.
In addition, the raw materials and preparation processes of different brands of water-drawing agents are often different, and there are some differences in the water ratio. It is important to master the appropriate water ratio when using it. If the water ratio is too high, the drawability will be significantly reduced, and the waterproof effect will not be achieved; if the water ratio is too low, dark waxy oil spots are often formed on the cardboard surface, which damages the appearance of the cardboard.
5 factors that affect the compressive strength of cartons
Carton compressive strength is the most important quality index required for many commodity packaging. During the test, the corrugated carton is placed between two pressure plates and pressed to the pressure when the carton is crushed, which is the carton compressive strength.
1. Quality of raw materials
The base paper is the decisive factor in determining the compressive strength of the carton, which can be seen from the kellicutt formula. However, the influence of other conditions in the production process of corrugated board cannot be ignored, such as the amount of adhesive, the change of flute height, impregnation, coating, and composite processing.
carton made of corrugated cardboard with too high moisture content, or stored in a humid environment for a long time, will reduce its compressive strength. Fiber is a kind of strong water absorption. In the rainy season and when the humidity in the air is high, the moisture balance between the moisture in the cardboard and the atmospheric environment is very important.
3. Box type
box type refers to the type of box and the size ratio of the same type of box, they have a significant impact on the compressive strength. Some carton boxes are made of double-layer corrugated cardboard, and their compressive strength is significantly higher than that of single-layer boxes of the same specification; under the same conditions, the higher the box, the worse the stability and the lower the compressive strength.
4. Printing and perforation
Printing will reduce the compressive strength of the carton. For products that require ventilation, opening holes on the surface of the box or punching the handle holes on the side of the box will reduce the strength of the carton, especially if the opening area is large, and the effect is more obvious.
5. Processing process deviation
In the process of box making, improper wire crimping, deep grooves, weak bonding, etc. will also reduce the compressive strength of the box.
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