Weapons: Wet weather cartons will no longer soften

Recently, there are more rains in many provinces and cities in China. The biggest weakness of traditional corrugated boxes is their poor strength. In humid environments, cartons tend to absorb moisture and reduce their strength. This article mainly describes how to make the surface of the corrugated cardboard box moisture-proof, and even if it encounters wet weather, the carton will not be softened by moisture.

corrugated paper

Corrugated board has a temporary waterproof function after being treated with a temporary water repellent during the production process. That is, when the water falls on it for a short period of time, it is not wetted with water droplets, which can prevent water from penetrating the cardboard. In most carton factories, the “water extraction agent” is mainly used to damp-proof the carton.

Pulling agent waterproof principle

Is a wax emulsion, the solid content is generally 48% to 51%, its greatest feature is that when used in about 30 times the water can be diluted, and then coated on the surface of the forming corrugated board, after about l50 °C temperature Dry, 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.

Disadvantages of water picker

However, the adhesion of wax to paper fibers is not good, especially when the water extractant is diluted 30 times, its solid content is only 1.5-1.7, and only a very thin layer of paper surface fiber is covered with wax and friction is encountered. If the carton is subjected to friction during handling or stacking, this waterproof surface will often be rendered useless. 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. Demulsification and precipitation.

Not suitable for: corrugated cartons that require a cold store, corrugated cartons that need to be stored in a high-humidity environment, and corrugated cartons that require shipping.

Special reminder: Different grades of water picking agent, its raw materials and preparation process is often different, with some differences in the water ratio, use this water ratio is very important to grasp, use the water ratio is too high, the degree of pull will be significantly reduced, Waterproof effect is not achieved; the water ratio is too low, often forming dark waxy oil spots on the cardboard surface, impairing the appearance of the cardboard.

corrugated paper

The so-called long-term water repellent treatment is a treatment that is almost impervious even when it is in contact with water for a long time. In China, for a long period of time, the water repellent treatment of the carton uses this method. The carton is painted by hand. Layer waterproofing agent, bright, good strength, good water resistance, and will 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, we must start from three aspects:

Coatings are not volatile.

A nontoxic, water-soluble, volatile solvent can be properly added to accelerate the rate of evaporation of water.

Change the operation mode 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°C, and some are as high as 180°C. General thermoplastic polymer coatings are already sticky at this temperature, and the cardboard coated with this kind of paint is often caused by heat when passed through a hot plate. Sticky, pull the paper and even pull the surface.

However, a new type of corrugated cardboard waterproof coating can overcome this disadvantage. 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 surface of the paper 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.

HDPE Pet Waste Bag

Hdpe Pet Waste Bag,Pet Waste Bag,Dog Poop Bag,Pet Dog Poop Waste Bag Set

Taizhou Jinchi Sanitary Product Co., Ltd , https://www.tzjcpetwastebag.com