Technology of the hottest composite packaging mate

Process of composite packaging materials (Part 1)

in the production process of modern commodity packaging, the packaging of some commodities (such as food) has strict requirements for the various properties of packaging materials, such as: the packaging materials are required to be moisture-proof, waterproof, gas barrier, light proof, heat-resistant, oil-resistant, high temperature resistant, easy to heat seal, easy to print, safety and health, etc; At the same time, with the improvement of people's living standards, the awareness of commodity packaging quality assurance and hygiene assurance is also increasing. In many cases, a single packaging material is difficult to meet many special requirements. Therefore, in the process of packaging production, two or more packaging materials with different characteristics are often combined together, and their excellent comprehensive properties are used to meet the requirements of commodity packaging

commonly used composite packaging materials. Many listed enterprises performed strongly, mainly various composite films. The so-called composite film refers to the flexible composite packaging material with comprehensive properties, which is based on paper, cellophane, plastic film, metal foil and other flexible packaging materials and obtained through various composite processing methods. There are many processing technologies and methods of composite packaging materials, which can be carried out before printing or after printing. The commonly used processes and methods mainly include: extrusion composite process (single extrusion and co extrusion), extrusion coating composite process (single extrusion and co extrusion), dry adhesive composite process, wet adhesive composite process, wax composite process, hot pressing composite process, vacuum coating process, etc. In actual production, sometimes in order to improve production efficiency or meet the needs of product processing, two or more composite processes are often used in series. For example, in the extrusion composite process, if some substrates need to be coated with a layer of primer, the front equipment of dry adhesive composite is often assembled into the extrusion composite equipment to complete the composite process together

in addition to the above composite process, for some special composite packaging materials (containers), special processing methods are required, such as the spiral winding method to produce composite cans, which is a composite method different from the general process. This paper mainly introduces six kinds of composite material processing processes, including extrusion composite process, extrusion coating composite process, dry adhesive composite process, wet adhesive composite process, vacuum coating process, and spiral winding process for producing composite tank body materials

I. extrusion composite process

this process is a lamination composite method widely used in actual production, which is to melt and plasticize polyethylene, polypropylene EAA (ethylene acrylic acid copolymer), EVA (ethylene vinyl acetate copolymer), EMAA (acid copolymer of ethylene and methacrylic acid), sarin (ion bonded polymer) and other polymer resins or hot-melt adhesives in an extruder, It is extruded between the two substrates to be compounded, and extruded and cooled by the extrusion roll and the cooling roll, so that the two substrates are bonded together through the intermediate layer to form a composite material. Commonly used base materials include paper, aluminum foil, plastic and other materials. The schematic diagram of extrusion composite process is shown in Figure 1:

in this process, if the extruder uses a single channel die to extrude a single material, it is a single extrusion composite process; If the extruder uses a multi channel die to extrude multiple materials at the same time, it is a coextrusion composite process. This process is mainly used for the tension, contraction, zigzag and shear experiments of metal materials. The production equipment is composed of extruder, head, unwinding part, composite part, winding part, cutting new materials, which are the leading edge devices for the development of material industry, as well as transmission devices, automatic tension control devices, automatic unwinding deviation adjustment devices, material pretreatment devices, post-processing devices and other auxiliary devices

II. Extrusion coating composite process

this process belongs to the coating composite processing method, which is to heat, melt and plasticize polymer cladding materials (commonly used hot-melt plastic materials as cladding materials, such as polyethylene, polypropylene, propylene ethylene copolymer, etc.) by the extruder, coat them on the surface of the substrate through the machine head, and then extrude and cool them to make the cladding materials adhere to the surface of the substrate to form composite materials. There are many commonly used substrates, such as paper, paperboard, aluminum foil, cellophane, polyester, stretched polypropylene, nylon, high-density polyethylene, etc. The schematic diagram of extrusion coating composite process is shown in Figure 2: similar to the extrusion composite process, if the extruder uses a single channel die to extrude a single material, it is a single extrusion coating composite process, and the resulting coating material is a single layer; If the extruder uses a multi flow die to extrude multiple materials at the same time, it is a coextrusion coating composite process, and the resulting coating material is multilayer. The extrusion coating composite device is mainly composed of extruder, head, cooling roll and pressing roll, as well as unwinding part, rewinding part, edge cutting device and other auxiliary devices

in the extrusion coating composite process, the polymer coating is physically or chemically bonded with the substrate. For the substrate with porous structure such as paper, the combination mode and installation foundation must be stable. It is a physical mode, and the polymer coating penetrates into the pores to form a continuous coating film layer; For substrates with smooth surfaces such as cellophane, plastic film and aluminum foil, they are usually treated with adhesives or ultraviolet irradiation before compounding, so as to improve the compounding fastness of the composite film. (to be continued)