Waterproofing the surface of the carton, in addition to protecting the package from water soaking, is mainly to prevent the water from infiltrating the box itself. After the carton is wetted by water, the compressive strength and bursting resistance of the case will be greatly reduced, which will seriously affect the quality of the package.
The surface of the carton is treated with water, usually by applying a waterproof agent. According to the effect of the waterproof agent, the treatment method of the waterproof carton can be divided into: temporary waterproof treatment and permanent waterproof treatment.
I. Temporary water repellent treatment Corrugated board has a temporary waterproof function after it is treated with a temporary water repellent during the production process. According to the interpretation of JIS Z 1537--1989: When water falls on it for a short period of time, it does not become wet and it prevents water from penetrating the cardboard. Temporary water repellent treatment cardboard technology has been applied in all major carton factories in China for the past ten years. This water repellent was originally introduced from Japan and its text surface was "water pick-up agent." This type of paint was used on fabric fibers early on and was later used for cardboard processing. Therefore, most tree carton manufacturers use the name of the picking agent.
Pulling agent is a wax emulsion, the solid content is generally :48 ~ 51%, its most prominent feature is that it can be diluted with about 30 times of water in use, and then coated on the surface of the forming corrugated board, after 150 oC The temperature is left and right to dry, and the surface fiber of the paper is coated with vinegar and has a low surface tension to form a surface layer that does not wet the water. When it encounters water, the water does not infiltrate on the cardboard, forming a drop of water and falling down, thereby achieving a waterproof effect. 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 1.5~1.7, and only a thin layer of paper surface fiber is covered with wax. In addition, wax size in wax emulsions is generally larger than that of common polymer emulsions, and it is difficult to penetrate deep into the paper fiber. Simultaneously, the water pick-up agent is generally sensitive to a class of chemicals such as alum, and is often fast on the surface of paper. The emulsion breaks down and precipitates, so most of the wax particles in the puller are only present on a thin layer of paper. Under the effect of external friction, the wax is easily rubbed off, leaving no wax-wrapped fibers, and the waterproof effect is greatly reduced. In order to enhance the adhesion of the wax to the paper fiber, there are often rosin derivatives or carboxylated polymer emulsions in the water pick-up agent, which have good adhesion to the paper fiber, wax and good compatibility. In this way, their addition promotes the adhesion of the wax to the paper fiber, and at the same time, if the wax is modified, such as oxidizing and basifying it, similar effects are achieved, so that the adhesion of the wax to the paper fiber can be increased. However, it must be pointed out that the increase in these measures, the concentration of the water picking agent formed at this concentration is still not a waterproof film, so when it comes to friction, such as carton handling, stacking process friction, often Make this waterproof surface useless. This is why the type of carton coated with water is defined as a temporary waterproof carton.
Currently, picking agents have been widely used in some carton factories and have become a basic process. This is primarily due to its price and machineability. Second, it maintains the true nature of the paper and coincides with the current return to nature. Third, there is no adverse effect on the recycling of cartons. Fourth, its waterproof effect is fully qualified for general use. However, it must be pointed out that cartons used in some special environments, such as cartons that need frozen containers, require cartons that are stored in high-humidity environments, cartons that require shipping, and care should be taken when using a water remover. In actual practice, cartons that have been coated with water-drawing agents have been found. After being taken out of the frozen warehouse, the cartons have been deformed, causing economic disputes. Therefore, when recommending what kind of waterproof treatment, customers should fully consider the use environment of the customer's carton.
In addition, different brands of water extraction agent, its raw materials and preparation process is often different, with some differences in the water ratio, it is very important to use this appropriate water ratio, the water ratio is too high, the degree of extraction will be significantly reduced, Not waterproof; water ratio is too low, often forming dark waxy oil spots on the cardboard surface, damaging the appearance of the cardboard.
Second, long-term waterproof treatment The so-called long-term waterproof treatment, according to the JISZ1537--1989's statement: "even if prolonged contact with water is almost impermeable" treatment.
In China, for a long time, the waterproof treatment of cartons is based on this approach. The carton is hand-painted with a waterproofing agent that is bright, strong, and has good water resistance and does not collapse after brushing. This type of water repellent is often solvent-based (or oily). It has a large physical damage to the operator and causes pollution to the environment. It is also unfavorable for the recycling of cartons and has rarely been used in recent years. Replaced by water-based or emulsion-type waterproof coatings. Aqueous emulsion waterproof coating can reach the requirement of being in contact with water for a long time and it is almost impervious to water. However, when the paint is applied by hand, if the paint contains a lot of water and the natural drying time is long, it will easily cause collapse or separation of the paper and the corrugated medium. . To solve these problems, the first coating has a high non-volatile content, and the second one can be suitably added with a non-toxic water-soluble volatile solvent to accelerate the evaporation speed of the water. The third is to change the way of manual brushing and use the method of machine coating and drying for production. For the existing waterproof coatings, the first two items have actually been adopted, and the third one is difficult to implement with the current paints. Therefore, the drying and forming temperature of corrugated board is generally around 150 oC, and some are as high as 180 oC. General thermoplastic polymer coatings are already sticky at this temperature, and the cardboard coated with this kind of paint is often caused by hair when passing through a hot plate. Sticky, pull the paper and even pull the surface. A new type of corrugated cardboard waterproof coating can overcome this shortcoming. This coating is a combination of a polymer emulsion and a wax emulsion. The polymer emulsion has good film forming property and water resistance, and the particle size of the emulsion is finer than that of the wax emulsion. After coating, the permeability to paper is stronger than that of the wax emulsion because of its poor compatibility with the wax. After the film is formed, the wax is precipitated from the polymer film, and most of the wax particles that are blocked by the paper fiber float on the surface fiber of the paper. When the corrugated paperboard is shaped into a heating plate, the phenomenon of stickiness on the paper surface is reduced due to the effect of the wax, and the paper surface will not be napped. At the same time, the polymer film will not be scratched under the protection of the wax, so that Cardboard can have a long-lasting waterproof effect. This coating also solves the problem of low efficiency of hand painting. At the same time, due to the presence of wax, it also acts as a matting agent, keeping the cardboard in its true colors. This type of paint is a water emulsion type, and the use of water-based inks for printing does not cause ink sticking. Finally, it must be pointed out that the main resin in this polymer emulsion is easily hydrolyzed by alkali, which is also convenient for paper recycling.
Third, the new progress of waterproofing The single paperboard waterproofing treatment is only one aspect of widening the carton application field. If considered together with water-resistant adhesives, such cartons can be used directly for fresh fruit and vegetables. If the waterproof coating has a certain reinforcing effect, and the application of the reinforcing adhesive, it should be advantageous for those cardboard boxes that are made of recycled cardboard boxes and staple fibers.
With the development of nanotechnology, an ultra-bipolar interface material appears. The structural principle is that the adsorbed gas atoms are stably present on the surface of the nanometer-sized concave surface, and have a stable gas film on the macroscopic surface, so that neither the oil nor the water can directly contact the surface of the material, and thus the material The surface exhibits double sparseness. Paper products, films, etc., treated with super-clear interface material technology, will obtain super-hydrophobic, super-oleophobic effect, which is a revolution in the waterproof treatment of carton.
The surface of the carton is treated with water, usually by applying a waterproof agent. According to the effect of the waterproof agent, the treatment method of the waterproof carton can be divided into: temporary waterproof treatment and permanent waterproof treatment.
I. Temporary water repellent treatment Corrugated board has a temporary waterproof function after it is treated with a temporary water repellent during the production process. According to the interpretation of JIS Z 1537--1989: When water falls on it for a short period of time, it does not become wet and it prevents water from penetrating the cardboard. Temporary water repellent treatment cardboard technology has been applied in all major carton factories in China for the past ten years. This water repellent was originally introduced from Japan and its text surface was "water pick-up agent." This type of paint was used on fabric fibers early on and was later used for cardboard processing. Therefore, most tree carton manufacturers use the name of the picking agent.
Pulling agent is a wax emulsion, the solid content is generally :48 ~ 51%, its most prominent feature is that it can be diluted with about 30 times of water in use, and then coated on the surface of the forming corrugated board, after 150 oC The temperature is left and right to dry, and the surface fiber of the paper is coated with vinegar and has a low surface tension to form a surface layer that does not wet the water. When it encounters water, the water does not infiltrate on the cardboard, forming a drop of water and falling down, thereby achieving a waterproof effect. 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 1.5~1.7, and only a thin layer of paper surface fiber is covered with wax. In addition, wax size in wax emulsions is generally larger than that of common polymer emulsions, and it is difficult to penetrate deep into the paper fiber. Simultaneously, the water pick-up agent is generally sensitive to a class of chemicals such as alum, and is often fast on the surface of paper. The emulsion breaks down and precipitates, so most of the wax particles in the puller are only present on a thin layer of paper. Under the effect of external friction, the wax is easily rubbed off, leaving no wax-wrapped fibers, and the waterproof effect is greatly reduced. In order to enhance the adhesion of the wax to the paper fiber, there are often rosin derivatives or carboxylated polymer emulsions in the water pick-up agent, which have good adhesion to the paper fiber, wax and good compatibility. In this way, their addition promotes the adhesion of the wax to the paper fiber, and at the same time, if the wax is modified, such as oxidizing and basifying it, similar effects are achieved, so that the adhesion of the wax to the paper fiber can be increased. However, it must be pointed out that the increase in these measures, the concentration of the water picking agent formed at this concentration is still not a waterproof film, so when it comes to friction, such as carton handling, stacking process friction, often Make this waterproof surface useless. This is why the type of carton coated with water is defined as a temporary waterproof carton.
Currently, picking agents have been widely used in some carton factories and have become a basic process. This is primarily due to its price and machineability. Second, it maintains the true nature of the paper and coincides with the current return to nature. Third, there is no adverse effect on the recycling of cartons. Fourth, its waterproof effect is fully qualified for general use. However, it must be pointed out that cartons used in some special environments, such as cartons that need frozen containers, require cartons that are stored in high-humidity environments, cartons that require shipping, and care should be taken when using a water remover. In actual practice, cartons that have been coated with water-drawing agents have been found. After being taken out of the frozen warehouse, the cartons have been deformed, causing economic disputes. Therefore, when recommending what kind of waterproof treatment, customers should fully consider the use environment of the customer's carton.
In addition, different brands of water extraction agent, its raw materials and preparation process is often different, with some differences in the water ratio, it is very important to use this appropriate water ratio, the water ratio is too high, the degree of extraction will be significantly reduced, Not waterproof; water ratio is too low, often forming dark waxy oil spots on the cardboard surface, damaging the appearance of the cardboard.
Second, long-term waterproof treatment The so-called long-term waterproof treatment, according to the JISZ1537--1989's statement: "even if prolonged contact with water is almost impermeable" treatment.
In China, for a long time, the waterproof treatment of cartons is based on this approach. The carton is hand-painted with a waterproofing agent that is bright, strong, and has good water resistance and does not collapse after brushing. This type of water repellent is often solvent-based (or oily). It has a large physical damage to the operator and causes pollution to the environment. It is also unfavorable for the recycling of cartons and has rarely been used in recent years. Replaced by water-based or emulsion-type waterproof coatings. Aqueous emulsion waterproof coating can reach the requirement of being in contact with water for a long time and it is almost impervious to water. However, when the paint is applied by hand, if the paint contains a lot of water and the natural drying time is long, it will easily cause collapse or separation of the paper and the corrugated medium. . To solve these problems, the first coating has a high non-volatile content, and the second one can be suitably added with a non-toxic water-soluble volatile solvent to accelerate the evaporation speed of the water. The third is to change the way of manual brushing and use the method of machine coating and drying for production. For the existing waterproof coatings, the first two items have actually been adopted, and the third one is difficult to implement with the current paints. Therefore, the drying and forming temperature of corrugated board is generally around 150 oC, and some are as high as 180 oC. General thermoplastic polymer coatings are already sticky at this temperature, and the cardboard coated with this kind of paint is often caused by hair when passing through a hot plate. Sticky, pull the paper and even pull the surface. A new type of corrugated cardboard waterproof coating can overcome this shortcoming. This coating is a combination of a polymer emulsion and a wax emulsion. The polymer emulsion has good film forming property and water resistance, and the particle size of the emulsion is finer than that of the wax emulsion. After coating, the permeability to paper is stronger than that of the wax emulsion because of its poor compatibility with the wax. After the film is formed, the wax is precipitated from the polymer film, and most of the wax particles that are blocked by the paper fiber float on the surface fiber of the paper. When the corrugated paperboard is shaped into a heating plate, the phenomenon of stickiness on the paper surface is reduced due to the effect of the wax, and the paper surface will not be napped. At the same time, the polymer film will not be scratched under the protection of the wax, so that Cardboard can have a long-lasting waterproof effect. This coating also solves the problem of low efficiency of hand painting. At the same time, due to the presence of wax, it also acts as a matting agent, keeping the cardboard in its true colors. This type of paint is a water emulsion type, and the use of water-based inks for printing does not cause ink sticking. Finally, it must be pointed out that the main resin in this polymer emulsion is easily hydrolyzed by alkali, which is also convenient for paper recycling.
Third, the new progress of waterproofing The single paperboard waterproofing treatment is only one aspect of widening the carton application field. If considered together with water-resistant adhesives, such cartons can be used directly for fresh fruit and vegetables. If the waterproof coating has a certain reinforcing effect, and the application of the reinforcing adhesive, it should be advantageous for those cardboard boxes that are made of recycled cardboard boxes and staple fibers.
With the development of nanotechnology, an ultra-bipolar interface material appears. The structural principle is that the adsorbed gas atoms are stably present on the surface of the nanometer-sized concave surface, and have a stable gas film on the macroscopic surface, so that neither the oil nor the water can directly contact the surface of the material, and thus the material The surface exhibits double sparseness. Paper products, films, etc., treated with super-clear interface material technology, will obtain super-hydrophobic, super-oleophobic effect, which is a revolution in the waterproof treatment of carton.
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