What are the classification and common materials of flexible packaging?

Packaging, an integral part of merchandise. "Package" embodies the practical function of packaging design, wrapping commodities with appropriate materials and techniques to achieve the protection function of commodities; "packaging" embodies the artistic beauty of packaging, which refers to beautifying and decorating commodities and realizing the function of selling commodities.

Plastic packaging refers to packaging in plastic. Plastic is a synthetic or natural polymer resin as the main material. After adding various additives, it has ductility under a certain temperature and pressure, and can fix its shape after cooling.

Flexible packaging is defined as: flexible packaging refers to packaging that can change the shape of the container after filling or removing the contents. Various bags, boxes, sleeves, packages, etc. made of paper, aluminum foil, fiber, plastic film and their composites are all flexible packaging. Plastic flexible packaging has many advantages, such as light texture, easy portability, strong impact resistance, good barrier properties, easy printing, low cost, and can be used for microwave heating, etc.

Classification by material: laser aluminized film composite paper material, laser transfer paper material, paper composite material, aluminum composite material, plastic composite material, fabric composite material, etc.

According to the form of packaging: three-side seal, mandarin duck bag, middle seal, organ bag, stand-up bag, zipper bag, eight-side seal, straw bag, special-shaped bag, cover material, label, etc.

Classification by production process: dry composite film, extrusion (co-extrusion) composite film, solvent-free composite film, coating film, etc.

Classification by function: high barrier film bags, cooking film bags, antistatic film bags, antibacterial film bags, anti-fog film bags, vacuum film bags, chemical-resistant film bags, deoxidation packaging film bags, modified atmosphere packaging film bags, etc.

1. LDPE, LLDPE resin and film
Production of simple two-layer or book-layer composites. Such as extrusion compounded BOPP/PE, paper/PE, pp/PE; dry compounded BOPP/PE, PET/PE, BOPP/AL/PE, PET/AL/PE, etc. Among them, LDPE resins and films are often A certain proportion of LLDPE is blended to enhance its strength and stiffness. Mainly used in the packaging of instant noodles, biscuits, mustard and other foods. General coating grade LDPE resins are: IC7A, L420, 19N430, 7500, etc.; blown film grade LDPE resins are: Q200, Q281, F210-6, 0274, etc.; LLDPE resins are: 218w, 218F, FD21H, etc.

2. CPP film, CPE film
With the introduction of a new generation of flexible packaging equipment and casting equipment, the scope of package contents has been further expanded. Some puffed food, cereal and other packaging bags have higher requirements for transparency, and boiled and high-temperature sterilization products have been in the market one after another. The requirements for materials have also increased accordingly, and the inner layer materials dominated by LDPE and LLDPE can no longer meet the requirements of the above products. Produced by casting method with good heat sealability. CPP with oil resistance, transparency, aroma retention, and special low-humidity heat-sealing and high-temperature cooking properties is widely used in packaging. The aluminized CPP developed on this basis is also widely used because of its metallic luster, beautiful appearance and barrier properties. And the CPE film produced by the casting method is further used because of its unidirectional tearability, low temperature heat sealing and good transparency.

3. MLDPE resin
With the continuous development and change of the packaging market, there are more and more special requirements for packaging. DOW Chemical Company in the United States has produced metallocene polyethylene MLDPE by metallocene catalyzed polymerization. Such as APFINITY, POP1880, 1881, 1840, 1450 and other resins. Then Exxon in the United States. Mitsui in Japan and Philips in the United States have also successively produced MLLDPE. Such as Exxon's EX-CEED350D60, 350D65, Mitsui Petrochemical's E-VOLVE SP0540, SP2520, Philips MPACT D143, D139 and so on. Since MLLDPE has good blendability and ease of processing with LDPE and LLDPE, MLLDPE can be mixed in blown film or cast processing, and the mixing ratio can be from 20% to 70%. This type of film has good tensile strength, impact strength, good transparency, and good low temperature heat sealing and anti-pollution properties, and its composite material as the inner layer is widely used in frozen, refrigerated food, shampoo, Oil, vinegar, soy sauce, detergent, etc. It can solve the packaging speed, breakage, leakage and penetration of the above products in the process of packaging production and transportation.

4. Inner layer material of cover film
Liquid packaging cups for jelly, juice, yogurt, fruit milk, soup, etc. Bottle, whose main material is HDPE. PP, PS, etc. The cover film of this package should consider not only the shelf life, but also the heat sealing strength between the cover film and the cup, as well as the convenience of consumers - easy tearing. To achieve this particularity, the inner layer material can only form the interface bonding strength with the cup, but cannot completely penetrate and fuse together. Modified EVA resin is generally used. Such as the United States DuPont APPEEL53007. TOPCO L-3388 from Toyo Japan, LOTRYL 20MA 08 from France, WT231 from HIRO.DINE from Japan, etc. Its structure can be: PET/PE/HM, BOPA/PE/HM, PET/VMPET/PE/HM, PET/AL/PE/HM, paper/PE/AL/PE/HM. For the cover film and the bottom cup that are required to be firmly covered and not torn apart, the material of the bottom cup is generally required to be consistent with the material of the inner layer of the cover film, so that the two materials can be completely fused when they are heat-sealed. For example, for HDPE cups, the inner layer material of the cover film is: LDPE or EAA; for PP cups, the inner layer of the cover film is CPP film; for PET bottles, we have found a coated modified PET film as a heat sealing layer, Capped pesticide PET bottles with satisfactory results.

5. Co-extruded film
Films produced by blending single-layer LDPE or LDPE with other resins have single performance and cannot meet the packaging requirements of modern article development. Therefore, co-extruded films produced by co-extrusion blown film or co-extrusion casting equipment have improved overall performance. . For example, the comprehensive properties of the film, such as mechanical strength, heat sealing performance, heat sealing temperature, barrier property, opening property, and anti-pollution property, are improved, and its processing cost is reduced, so it is widely used. Such as the hot melt adhesive film of H layer co-extrusion blown film: PE/HM, cable film PE/EAA, low temperature heat sealing film of MLLDPE, cover film of EVA, antistatic film, slip film. Co-extruded CPP, unmodified PP/heat-sealable PP, etc. Three-layer, five-layer nylon co-extruded film, five-layer, seven-layer EVOH, PVDC high-barrier film are also constantly developing and widely used.

The development of the inner layer film of composite flexible packaging materials, from LDPE, LLDPE, CPP, MLLDPE, to the current large-scale use of co-extruded films, basically realizes the functionalization and personalization of packaging, and meets the quality assurance, processing performance, transportation of packaging contents. ,Storage conditions. With the continuous introduction of new materials and the improvement of inner layer film production technology and equipment, the inner layer film of composite flexible packaging materials is bound to develop rapidly and promote food.