The carton factory revealed that the corrugated cardboard has a temporary waterproof function after being treated with a temporary waterproof agent in the production process. When water falls on it for a short time, it will not get wet and form water droplets, which can prevent water from soaking through the cardboard. The temporary water repellent treatment cardboard process has been applied in major carton factories in my country in the past ten years. This waterproofing agent was originally introduced from Japan, and its Japanese literal is "water-pulling agent".
This coating was used in the early days on fabric fibers, and later in the treatment of cardboard. Therefore, most tree carton factories use the name of water-pulling agent. The water-removing agent is a wax emulsion with a solid content of 48% to 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. After 150 When it is dried at a temperature of about ℃, the surface fibers of the paper have low surface tension due to the wrapping of vinegar, forming a surface layer that is not wetted by water. When encountering water, water does not infiltrate on this cardboard, forming water droplets to roll off, thus achieving the effect of waterproofing. However, the adhesion of wax to paper fibers is not good, especially when the water-pulling agent is diluted 30 times, its solid content is only 1.5~, and only a thin layer of paper surface fibers is wrapped by wax. In addition, because the particle size of the wax in the wax emulsion is generally larger than that of the usual polymer emulsion, it is difficult to penetrate deep into the paper fibers. At the same time, the water-removing agent is generally sensitive to chemicals such as alum, and tends to be very fast on the surface of the paper. The rice is precipitated by demulsification, so most of the wax particles in the water-removing agent only exist in a very thin layer on the paper surface.
Under the action of external friction, the wax is easily rubbed off, exposing the fibers without wax wrapping, and the waterproof effect is greatly reduced. In order to enhance the adhesion of wax to paper fibers, there are often rosin derivatives or carboxylated polymer emulsions in the water-removing agent, which not only have good adhesion to paper fibers, but also have good compatibility with wax. In this way, their addition can promote the adhesion of the wax to the paper fibers, and at the same time, if the wax is modified, such as oxidation and matrixing, it also has a similar effect, which can increase the adhesion of the wax to the paper fibers. But it must be pointed out that even with these measures added, the water-pulling agent is still not a waterproof film layer at such a concentration. renders this waterproof surface useless. This is why such cartons coated with water repellent are designated as temporary waterproof cartons.