Introduction of different types of corrugated board processing

In some commodity packaging, corrugated boxes are required to have waterproof, rust-proof, freshness-preserving, flame-retardant and other properties, which are not available in ordinary corrugated cardboard, and therefore require further processing.

(a) waterproof corrugated cardboard

In a high temperature environment, the moisture content of the product package or the product itself is too high, such as the use of ordinary corrugated cardboard boxes will reduce the compressive strength of the carton. According to the use requirements, different methods can be used to improve the waterproof performance of corrugated board, mainly hydrophobic corrugated cardboard and water-resistant corrugated cardboard.

1, hydrophobic corrugated cardboard

Also known as water repellent corrugated cardboard. When exposed to water for a short time, the surface of the paperboard is processed so that the water splashes out as water droplets to prevent water from penetrating into the interior of the paperboard.

(1) Hydrophobic board processing method

The processing method of general hydrophobic corrugated paperboard is to perform coating processing. Commonly used coatings include paraffin, silicone, and varnish. The varnish has low viscosity and good permeability, but too much penetration into the paper will reduce the hydrophobic effect. Therefore, it is better to brush a starch slurry on the surface of the cardboard before painting the varnish. In addition, the addition of a suitable amount of water-resistant additives, such as urea-formaldehyde resin, melamine-formaldehyde resin, and polyvinyl butyral, can improve the water resistance of the coating. During processing, the waterproof coating can be applied directly to the surface of the corrugated cardboard, and paraffin can be applied to both surfaces of the corrugated cardboard during the production process. The corrugated core is spray coated, so that a corrugated cardboard with higher hydrophobicity can be obtained. The patent name is M/R corrugated cardboard.

(2) Use of hydrophobic corrugated cardboard

Hydrophobic corrugated paperboard is suitable for packaging dry powdered articles, especially powders that are easy to agglomerate after absorbing water. It is also suitable for packaging goods that often enter and exit the cold storage. After being taken out of a cold storage, it is easy to form condensation on the wall of the box. Common corrugated cardboard will absorb quickly. The reduction in compressive strength causes the carton to withstand the stacking pressure and crush. The hydrophobically processed cardboard will not significantly reduce the compressive strength before dew evaporation, and can effectively protect the goods.

2, water-blocking corrugated cardboard

Also known as waterproof or waterproof corrugated cardboard. Its surface is in contact with water for a long time and is almost impermeable to water. However, it cannot be immersed in water, otherwise it will lose its waterproof performance. The result is similar to ordinary corrugated cardboard, which is mainly related to its processing technology.

(1) Water-blocking corrugated board processing method

Water-blocking corrugated paperboard is commonly used curtain coating method, that is to say the molten synthetic resin or paraffin mixture flows from the hopper mouth into a film-like shape and is coated on a horizontally running corrugated cardboard. The surface of the paperboard is formed with a resin film or a wax film. Good water retention performance. If necessary, cover the membrane once again on the other side to obtain double-sided waterproof performance.

(2) Use of water-blocking corrugated cardboard

Water-blocking corrugated cardboard is used for packaging salted products, frozen foods, and fruit and vegetable products. Because corrugated cardboard has a soft paraffin layer, it is also suitable for high-gloss finish furniture, pianos, safes and precision machines. .

3, water-resistant corrugated cardboard

The corrugated board with its strength not significantly reduced after being soaked in water for a long time is called a water-resistant corrugated board, and its processing principle is similar to the impregnation processing.
(1) Immersion solution

Paraffin or neoprene synthetic rubber, polyphenylene butadiene, chloroprene, polyhydrosiloxane, chromium difluoroacetate, etc.

(2) Immersion wax

The automatic paper feeding machine continuously feeds the corrugated board into a paraffin wax dipping tank at a temperature of 90 to 100° C. The dipping time is 5 to 10 s. The adjustment is performed according to the amount of paperboard and the number of layers, so that the wax liquid penetrates the corrugated paperboard as a degree.

(3) Heat drying

The corrugated cardboard removed from the wax bath removes the excess wax and is then slowly moved in a hot oven at 110-130°C, further allowing the wax liquid to penetrate the inside of the paperboard while allowing the excess wax liquid to flow away.

(4) Cooling

The dipping wax paperboard removed from the hot air chamber is forced to cool at room temperature to solidify the wax liquid. After the above processing, the corrugated board has good water resistance. The instrument can be used to measure its water resistance. The so-called water resistance is to corrugated board into the water (20 ± 2 °C tap water) 30mm, soak 1h, and then test its burst strength and side pressure strength, the required residual strength is not less than the standard strength (before water) 75%. Water-resistant corrugated cartons are used for the shipment of live fish, seafood and very high moisture content products. The waterproof corrugated paperboard not only has good waterproof and moisture resistance, but also has improved compressive strength.

The method of keeping fruits and vegetables fresh is to reduce water loss, inhibit biological respiration and bacterial growth, and remove the ethylene gas that causes them to age and ripen. Preservation of corrugated cardboard is the first step in the process.

1, clip type

The plastic film soaked with the antibacterial agent and the preservative is sandwiched in a corrugated paperboard, and then the inner surface of the corrugated paperboard is coated with a CTM preservative, the components of which are the phytohormone and its derivatives, tropolone and its Derivatives (such as hinokitiol) and terpene ethers. This type of corrugated board prevents moisture from evaporating, maintains the freshness of the merchandise inside the box, and also regulates and controls the temperature.

2. Compound type

The aluminum-coated cling film is laminated on the inner surface of the corrugated cardboard. This composite film has the function of absorbing ethylene gas. The aluminized film can prevent moisture from evaporating, reflect radiant heat, and prevent the temperature inside the box from rising.

3, foam type

The combination of foam and corrugated fiber has a better preservation effect than ordinary and sandwich-type corrugated cardboard.

1 The moisture permeability is 1/20 of that of ordinary corrugated cardboard. It is not easy to cause fruit and vegetable contraction due to evaporation of water.

2 Because of low thermal conductivity and good thermal resistance, no sharp temperature fluctuations will occur in the box.

3 Because of its low air permeability, it can adjust the storage atmosphere.

Using the above-mentioned three kinds of corrugated cardboard cartons, the fresh-keeping effect of cauliflower was evaluated. As a result, the oxygen content in foam-type fresh-keeping corrugated cardboard boxes gradually decreased, the carbon dioxide concentration increased, and the respiration and growth of cauliflower were suppressed. Corrugated cardboard cauliflowers have been deprived of oxygen, and although they have less flowering, they have suffered from diseases and insect pests and have strong offensive odors. The atmosphere in the ordinary carton is almost the same as the atmosphere, and the cauliflower turns yellow and deteriorates.

4, mixed type

In the manufacture process of corrugated board inner paper, porous ethylene gas absorption powder is added to prevent ripening; special ceramic powders capable of emitting infrared rays with a wavelength of 6-14 μm can also be coated on the base paper. This kind of powder can emit infrared rays at normal temperature, which can not only activate the relevant molecules in the fruit, increase the ability to resist microbial erosion, but also activate the enzyme and increase the sweetness of the fruit. For peach, grape, bayberry and other fresh packaging effect.

(III) Anti-static Corrugated Cardboard

The anti-static packaging of electronic components, integrated circuits and electronic fuses is very important. The application of carbon powder and laminated aluminum foil on the surface of corrugated cardboard, and the addition of metal fibers or carbon fibers in the production process of boxboard can all produce anti-static corrugated cardboard.

In addition there are deodorant, non-slip and other corrugated cardboard, suitable for packaging related products. (Text: Sun Ling)