In cold chain packaging and e-commerce packaging, the most demanding is that the carton is required to have various functional uses such as waterproof, moisture-proof and fresh-keeping. The following small series will introduce you to the process and use of some functional corrugated cardboard.
1, hydrophobic corrugated cardboard
Also known as water-repellent corrugated cardboard, when it is exposed to water for a short time, the surface of the processed paperboard causes the water to splash into water droplets, preventing water from penetrating into the cardboard interior.
Generally, the processing method of the hydrophobic corrugated cardboard is coating processing, and the commonly used coatings are hydrophobic agents such as paraffin, silicone and varnish. The varnish has low viscosity and good permeability, but excessive penetration into the paper will reduce the hydrophobic effect. Therefore, it is best to first brush a starch slurry on the surface of the paperboard before applying the varnish, and then apply the varnish after drying the film. The effect is better. In addition, the water resistance of the base paper can be improved by adding an appropriate amount of water-resistant auxiliaries, such as urea-formaldehyde resin, melamine formaldehyde resin, polyvinyl butyral, to the starch paste of the papermaking process. The waterproof coating can be applied directly to the surface of the corrugated board during processing.
The paraffin wax is applied to both surfaces of the corrugated cardboard, and the corrugated core is spray coated, so that the corrugated cardboard with higher hydrophobic property can be obtained, and the patent name is M/R corrugated cardboard.
The hydrophobic corrugated board is suitable for packaging dry powdery articles, especially the powder which is easy to agglomerate after water absorption. It is also suitable for packaging goods that often enter and leave the cold storage. It is easy to dew on the wall after being taken out of the cold storage, and the ordinary corrugated cardboard will be quickly absorbed. The compressive strength is reduced, and the carton cannot be crushed by the stacking pressure. The hydrophobically processed paperboard does not significantly reduce the compressive strength before the dewdrop evaporates, and can effectively protect the commodity.
2, cover corrugated cardboard
Also known as waterproof or water-retaining corrugated cardboard, its surface is almost impervious to water for a long time, but it cannot be immersed in water, otherwise it will lose its waterproof performance. The result is similar to ordinary corrugated board, which is mainly related to its processing technology.
The curtain corrugated board is usually used for curtain coating method, that is, the molten synthetic resin or paraffin mixture flows down from the hopper mouth, and is coated on the horizontally running corrugated cardboard to form a resin film or a wax film on the surface of the cardboard. Good water retention. If necessary, circulate the film once on the other side to obtain double-sided waterproof performance.
Covered corrugated cardboard is used to package salted products, frozen foods and fruit and vegetable products. Because of the soft paraffin layer on the surface of corrugated cardboard, it is also suitable for packaging high-gloss furniture, pianos, safes and precision machines. .
3, water resistant corrugated cardboard
Corrugated board paper whose strength is not significantly reduced after soaking in water for a long time is called water-resistant corrugated board. There are two kinds of equipment and processes for producing water-resistant corrugated cardboard, and its processing principle is similar to that of impregnation. Water resistant corrugated board can be used to measure its water resistance. The so-called water resistance is to immerse corrugated cardboard in water (20 ± 2 ° C tap water) 30mm, soak for 1h, and then test its bursting strength and edge strength, the residual strength should be no less than 75% of the standard strength (before water immersion). Water-resistant corrugated boxes are used to carry live fish, seafood and a class of goods with very high water content.
Corrugated cardboard after waterproof processing not only has good waterproof and moisture resistance, but also has high compressive strength. The following table lists the relative compressive strength properties of several waterproof corrugated cardboard and ordinary corrugated under different conditions.
4, fresh corrugated cardboard
The process of preserving corrugated cardboard is to adopt a special processing technology to make the carton pack fresh fruits and vegetables. It has the effect of reducing the water loss of the contents, inhibiting the growth of bacteria, and absorbing the bad gas in the tank. Make fruits and vegetables get better preservation effect.
Generally, the production methods of fresh corrugated cardboard are: clip-molding type, composite type, foaming type and mixed type.
The clip-molding type is to sandwich the plastic film soaked with the antibacterial agent and the preservative in the corrugated cardboard, and then apply the preservative in the corrugated box. This corrugated box can not only effectively prevent the evaporation of water, but also To adjust and control the temperature, keep the contents of the box fresh.
The composite type combines the aluminum-plated wrap film with the inner surface of the corrugated carton, so that the inside of the box has the function of absorbing ethylene gas, preventing evaporation of water, and reflecting radiant heat to prevent the temperature inside the box from rising. In turn, it plays a role in preservation.
The foaming type combines foam and corrugated cardboard, and its preservation effect is superior to the former two methods. It is good in suppressing evaporation of water, controlling heat resistance and air tightness.
The mixed corrugated board is made by adding a porous ethylene gas absorbing powder to the cardboard or coating a special ceramic powder capable of emitting a certain wavelength of infrared ray on the base paper. The carton produced by the paperboard can activate some molecules in the fruit and vegetable products, enhance the function of resisting microbial erosion, and improve the process effect of the fresh-keeping packaging.
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