When many commodities (or products) are subjected to external moisture during storage and transportation, mold, moisture, deterioration, rust, etc. may occur and the quality of the product may be impaired. Such as crisp food, medicine, precision instruments and meters, etc., the quality will drop after being affected by moisture. Therefore, it is necessary to apply moisture-proof packaging to those products whose moisture absorption will be affected.
The role of moisture-proof packaging is to slow or block the speed of moisture entering the package through high-moisture packaging materials or to absorb moisture that penetrates into the package with a desiccant to maintain the moisture content of the product and obtain a certain shelf life. At present, general moisture-proof packaging uses moisture-proof moisture-proof paper packaging or plastic film packaging to obtain certain moisture-proof packaging requirements, but for the expansion-proof foods or other high-grade goods with high moisture-proof requirements, desiccants must also be enclosed to ensure the flavor of the food or Brittleness and other quality requirements.
Moisture-proof packaging materials refer to packaging materials that cannot pass or hardly penetrate water vapor. Commonly used moisture-proof packaging materials are paper, plastics, metals, glass, ceramics and so on. In addition to the functions of ordinary packaging materials, moisture-proof packaging materials have a special requirement in moisture-proof packaging that the moisture permeability is low. The lower the moisture permeability of the moisture-proof material, the better the moisture resistance. Common moisture-proof paper packaging materials are moisture-proof cellophane, paraffin paper, polyethylene processing paper, asphalt waterproof paper, polyethylene processing paper, aluminum-plastic composite moisture-proof paper, moisture-proof corrugated cardboard, etc. Various moisture-proof materials are generally added in unbleached sulphate chemical pulp or coated on the surface of paper with various moisture-proof chemicals, such as carbonamide resin, latex, polyamide resin and asphalt, paraffin wax, etc. Therefore, the functional characteristics and environmental performance of moisture-proof papers are greatly affected by moisture-proof drugs. Moisture-proof bag paper is used to manufacture paper bags for packaging bulk products, inorganic fertilizers, daily discharged waste, and other goods under high-humidity transport conditions.
1, moisture-proof cellophane
Cellophane, also known as "celluloid", also known as transparent paper, it is as transparent as glass, bright, is a decorative advanced packaging paper. Since its inception in 1908, its unique non-toxic, tasteless, anti-static and other special properties are widely used in food, medicine, sanitary packaging and decoration and other fields.
Cellophane is made of natural fibers such as wood pulp and cotton pulp and made into a film by the adhesive method. It is crisp, transparent, non-toxic and tasteless. Its molecular chain has a wonderful micro-permeability that allows the product to "breathe" like eggs through the pores on the skin, which is very beneficial to the preservation and preservation of the commodity; for oily, alkaline and organic Solvents have strong resistance; no static electricity, no self-absorption of dust, adapt to mechanical high-speed packaging and bag making.
Moisture-resistant glass paper is made by adding chemicals with moisture resistance during the papermaking process, such as polyethylene, polyvinylidene chloride (K-type coating), vinyl acetate copolymer (MST-type coating), etc. Based on the addition of a certain moisture resistance, suitable for packaging of food, meat and machine tools.
Since moisture-proof cellophane is derived from natural fibers, it can absorb water and be decomposed in the garbage, so as not to cause environmental pollution. The moisture-proof cellophane coating process using polyethylene and K-type coating is not only less contaminating, easy to handle, but also economical. Given the potential hazards of using plastics for food packaging, traditional plastic food packaging is facing the fate of being phased out in many developed countries. Instead, new-type packaging, moisture-proof cellophane, will show its strong vitality.
2, polyethylene processing paper
Polyethylene processing paper is a composite of kraft paper and high density polyethylene or low density polyethylene. It has the tough and strong characteristics of kraft paper, and at the same time, it has the superior dielectric properties, moisture resistance, good mechanical strength and impact resistance of polyethylene materials. It can maintain soft and chemical stability at low temperatures, and can resist certain concentrations. And temperature of the acid, alkali, salt solution and various organic solvents corrosion. Polyethylene processing paper, especially high density polyethylene processing paper, is an excellent high-grade moisture-proof packaging material, and its moisture resistance is better than PVC processing paper and asphalt paper.
The kraft paper in the polyethylene processing paper raw material is completely non-polluting to the environment. The polyethylene layer in the paper is also very easy to age in the atmosphere, especially under sunlight. Experiments have shown that natural cracking can occur after two years. Low density polyethylene Aging is faster, so the load on the environment is relatively small.
3, moisture-resistant corrugated cardboard
Corrugated cardboard is one of the most widely used types of paperboard in packaging, especially for commodity packaging, and can be used instead of wooden crates and metal boxes. Corrugated cardboard is processed from corrugated base paper. First, the base paper is processed into a corrugated shape, and then the surface layer is bonded with adhesive from both sides to make the middle layer of the paperboard a hollow structure, so that the corrugated paperboard has higher strength, stiffness, hardness, pressure resistance, burst resistance, Extensibility and other properties are higher than that of ordinary cardboard. The cartons made from it are also firmer and are more conducive to protecting the packaged products. Moisture-resisting corrugated board is atomized with a paraffin liquid at a temperature of 130°C to 180°C. In moisture-resistant cardboard, the mass of paraffin wax is 30% to 45%. This kind of corrugated paperboard has higher moisture resistance and its strength is much higher than that of non-impregnated paperboard.
In recent years, due to the development of synthetic resins, a calcium plastic corrugated cardboard has been produced, which can overcome the disadvantages of some existing corrugated cardboards. It has the characteristics of moisture-proof, rain-proof, high strength, abundant material sources and more and more applications.
Calcium-plastic corrugated cardboard refers to plastic paper with calcified fillers. It is a kind of plastic packaging material, not a paper packaging material. Because it is compared with kraft corrugated paper, it is used to be called cardboard.
Whether it is kraft corrugated paper or calcium plastic corrugated paperboard, it has the features of light weight, high mechanical strength, good moisture resistance, etc. The cartons made have good folding properties, small storage space, low transportation costs, and can be used repeatedly for repeated use. Easy to recycle, it is an excellent green substitute for wood packaging.
4, Kraft board
Kraft boxboard is also called noodle board or kraft paperboard. The raw material ratio of the foreign production of kraft paperboard board is generally 100% natural kraft wood pulp, and a few kraft wood pulp noodles are used. The waste paper pulp is used as the core layer and the bottom layer. Because domestic wood resources are insufficient, 40% is adopted. 50% wood pulp noodle, with wheat straw pulp, rice straw pulp, mango chert pulp, bagasse pulp, waste pulp and other one or two mixed pulp as core layer and bottom layer.
Kraft boxboard is a premium cardboard for transport packaging. It is tougher than ordinary cardboard, very solid, has a high compressive strength, puncture strength and folding resistance, with good moisture resistance, good appearance and other characteristics, mainly used in the manufacture of foreign trade packaging cartons and domestic high-end products Packaging cartons.
In recent years, as the demand for packaging quality has gradually increased, some high-end products (such as high-grade alcoholic beverages, beverages, etc.) are gradually replacing the original gray-white board paper, natural kraft paper, etc. with the white-leaf kraft paperboard produced by all-wood pulp. The development is fast and the demand is large. Therefore, moisture-proof packaging required moisture-proof white kraft paperboard came into being.
The raw material for the production of white-faced kraft paperboard uses native sulphate coniferous wood pulp and part of the purchased wood pulp; all the batters use self-produced fully-bleached kraft pulp. The ratio of bottom paste to batter is 7:3. The slurry ratio can be adjusted according to different requirements in the actual production process.
5, moisture-proof flat adhesive paperboard
Flat-adhesive paperboard is a multi-layered material that is tightly bonded by two or more layers of flat-layer paperboard. Flat-adhesive paperboard can use different materials to adhere to the outer and inner layers, usually using lower-performance cardboard. The cardboard is glued with silica gel. The number of cardboard layers is determined according to the requirements of the cardboard box. The properties of the raw materials and their strength indicators should also be taken into account. Compared with corrugated paperboard, flat adhesive paperboard has higher strength index and higher pressure resistance.
Moisture-resistant flat adhesive paperboard is made of moisture-proof raw materials and moisture-proof glue, which can achieve certain requirements of moisture resistance. Some moisture-proof flat adhesive paperboards are treated with polyethylene on the surface. Usually, the outer layer of the rolled paperboard is pre-laminated with a polyethylene cover and then pressed against the paperboard at the press-bonding machine. In this way, it is possible to obtain a flat cover with one or both sides of a polyethylene cover. Adhesive paperboard. Due to the impermeability of the polyethylene layer, the adhesive with the cardboard must use the glue solution with the lowest water content, such as latex, polyvinyl acetate emulsion and hot melt adhesive. To improve the moisture resistance of dry-adhesive paperboard, it is also possible to coat the outer surface with a beeswax mixture. These adjuvants are non-toxic materials that do not cause chemical contamination.
Moisture-proof flat-glued cardboard box is mainly used for products requiring strong strength of the packing box under high humidity conditions, such as goods, vegetables, explosives, various spare parts, hardware products, etc., and transshipment packaging boxes for transportation products in cold regions. Wait.
Author/(Liu Guoxin)
Source: Shanghai Packaging
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