Moisture-proof packaging technology and application of new materials

Market's new demand for waterproof tide of carton

In recent years, with the improvement of people's living standards, the demand for outer packaging of goods has become higher and higher. Corrugated cartons as packaging containers for goods, not only to ensure the safety of the transport of goods, but also play a role in beautifying the goods, increase the added value, and promote sales. In particular, in recent years, various kinds of beautifully-printed moisture-proof glazing cartons appearing on the market have greatly improved the product quality of the packaging cartons, and fundamentally solved the problem of carton packaging susceptible to moisture, mildew, and vulnerability. . After the corrugated box is damp or subjected to grease penetration, the strength will rapidly decrease. The shape and stiffness will change due to moisture. Because the carton is subjected to water infiltration, the compressive strength and bursting resistance of the box will be greatly reduced, which will seriously affect the quality of the packaging. For example, in an environment with 95% relative humidity, the corrugated carton loses 2/3 of its original intensity, and the corrugated carton will collapse. The current market demand for carton with waterproof performance is continuously increasing, especially in the application of vegetables, food, household appliances and industrial products. In particular, the rapid increase in the use of water-resistant cartons for export products has greatly promoted the development of the corrugated box manufacturing industry.

Waterproof paperboard refers to a generic name for paperboard that has resistance to water destroying its strength. Corrugated boxes are used for moisture-proof production. In addition to protecting the packaging from water, it is mainly to prevent the water from infiltrating the box itself.

The development of moisture-proof and waterproof corrugated cardboard is of concern. Because the corrugated paper box absorbs moisture or absorbs water, the stacking strength will be greatly reduced, which has become an important issue to be solved by cartons manufacturing enterprises. The most commonly used method is to apply a water remover on the raw paper. The earliest use of tung oil was applied to the carton to achieve waterproof and moisture proof effects. Chitosan is impregnated with acetic acid solution and treated with acetic anhydride, converted into chitin, and applied to the original paper also has good moisture-proof and waterproof effects. Using paraffin, microcrystalline wax, polyethylene wax, beeswax, white wax, carnauba wax, montan wax and other animal and plant waxes, emulsified and coated on paperboard can also be moisture-proof and waterproof. Because of its low cost, it is currently the most used method. . However, this method has poor surface scratch resistance and low gloss, and can be obtained by adding a thermosetting polymer such as a propylene-based polymer, a phenolic resin, an epoxy resin, an amino resin, a polyamide, a polyurethane, and a poly(vinyl chloride). The composite structure of the water drawing agent used to impregnate the cardboard, can greatly improve the cardboard waterproof and moisture resistance. Waxed corrugated cardboard is not conducive to recycling, the EU has begun to limit the use. Another kind of water pick-up agent is made of chromium trioxide in propanol-hydrochloric acid solution, and it is made by compounding with stearic acid. It has both anti-mold and anti-fouling properties. There are currently different formulations of water picking agents on the market. If resin, starch or plastic moisture-proof agents are added to the paper pulp as moisture-proof paper, naturally the production of cartons is the most convenient. Although some raw paper costs are added, the total cost is still cost-effective. Japan's Toyo Steel Co., Ltd. has developed a pure iron foil 0.02mm to 0.05mm thick, galvanized, nickel or tin anti-rust treatment, and kraft paper, polyethylene film extrusion compounded into a composite cardboard, for the production of Cartons are not only waterproof and moisture-proof, but also can shield electromagnetic waves and anti-static electricity. They are particularly suitable for the packaging of aquatic products, fruits and vegetables, electronic instruments, semiconductor devices and electromechanical products. After the aluminum-clad polyvinyl chloride film is compounded with kraft paper to make a carton, it also has waterproof and moisture-proof functions.

Moisture-proof packaging technology

Air humidity is an important factor causing corrosion and deterioration of commercial products. The harm of wetness to industrial products and other items is mainly manifested in the corrosion of metal products and the occurrence of moldy deliquescence of non-metal products. Some organic materials swell, deform, and foam on the surface after moisture absorption, which not only affects the appearance but also degrades the mechanical properties. In order to prevent the articles from being exposed to moisture during production, transportation, storage, and use, the protective packaging used for the qualitative change is called moisture-proof packaging.

The moisture resistance of packaging materials or containers depends primarily on the moisture permeability of the material or container. The moisture permeability of packaging materials refers to the weight of water vapor per unit area. The moisture permeability of packaging materials is related to the type of material, processing method and material thickness. In order to improve the moisture resistance of packaging materials and reduce their moisture permeability, multiple layers of different soft materials are often used for compounding to make composite films. The moisture permeability of common packaging materials and composite packaging materials is shown in the table below.

There are four general moisture-proof packaging methods: The first is to prevent the moisture content of the packaged moisture-containing product from losing moisture, to ensure the stability of the product's performance, and to use a moisture-proof packaging material with a certain moisture permeability for packaging; the second is to prevent the packaged product from being packaged. The moisture is absorbed by moisture, and a certain amount of desiccant is placed in the packaging container so as to absorb the moisture brought into the packaging during the packaging and keep the humidity within a certain range. Commonly used desiccants are: silica gel, molecular sieve, activated alumina and so on. This method requires the container to be sealed so that the interior space of the container is isolated from the outside air. This method is applicable to small and medium-sized packages. The third method is to detect and control the humidity of the controlled space continuously or intermittently, so as to keep the humidity of the controlled space within a certain range and achieve the purpose of drying and sealing the materials and equipment. . This method is suitable for moisture-proof packaging of large products (such as large-scale instruments, automobiles, airplanes, etc.), and can be controlled by cyclic drying, condensation, and dehumidification; the fourth method is to prevent moisture by vacuuming in a sealed packaging container. purpose.