In the packaging of modern commodities, the packaging of some goods (especially food) has strict requirements on various properties of packaging materials, such as moisture-proof, waterproof, barrier gas, light, heat, oil, and resistance. High temperature, easy heat seal, easy to print and so on. Tong Yi's packaging materials are difficult to meet a number of requirements. Therefore, in the packaging production process, two or more packaging materials with different characteristics are often combined together to make use of their excellent overall performance to achieve the commodity packaging. Claim.
Commonly used composite materials are mainly composite films. The term “composite film†refers to a flexible composite material that is made of flexible packaging materials such as paper, cellophane, plastic film, and metal foil, and is applied to a variety of composite processing methods such as coating, lamination, and coextrusion. Composite packaging materials. There are various processing methods and methods for composite packaging materials, which can be processed before printing or can be processed after printing. In many cases, in order to prevent the packaged goods (especially foods) from directly contacting the printing ink layer, one or more layers of other materials are often laminated on the ink layer side after printing to prevent the direct flow of the goods and the ink layer. The purpose of contact, while taking advantage of the comprehensive properties of multiple materials in the composite layer, to better protect the goods.
The commonly used processes and methods for post-press composite processing of packaging materials are: extrusion compounding process (single extrusion and co-extrusion, extrusion-laminating process), extrusion coating process ( There are two kinds of single extrusion and co-extrusion, which belong to the coating composite processing method, dry adhesive bonding technology, wet adhesive bonding technology, wax composite technology, and hot pressing composite technology (the above four are coating- Laminated composite method), straight hollow coating process. In actual production, sometimes two or more composite processes are often used in series in order to increase the production efficiency or the need for product processing. For example, in an extrusion compounding process, if certain substrates need to be coated with a layer of primer Materials, often the dry-glue compound front assembly is assembled into the extrusion compounding device to complete the compounding process. Here, we mainly introduce five kinds of composite materials processing technology, such as extrusion composite process and vacuum coating process.
First, extrusion composite process. This process is a laminating and compounding method widely used in practical production. It is a polymer resin or hot melt adhesive such as polyethylene, polypropylene, EAA (ethylene-acrylic acid copolymer), Sarin (ionic bond polymer), etc. The agent, after being melt-fused by an extruder, is extruded into two substrates to be composited and bonded together through an intermediate layer to form a composite material. Commonly used substrates include paper, aluminum foil, plastics, and other materials.
In this process, if the extruder uses a single runner die to extrude a single material, it is a single extrusion composite process. The process mainly produces equipment from the extruder, head, unwinding part, composite part, winding part, trimming device and transmission device, tension automatic control device, automatic reeling device, material pretreatment device, post-processing Device and other auxiliary devices.
Second, extrusion coating composite process. The process belongs to a coating composite processing method, which is a method of applying a polymer cladding material (usually a hot-melt plastic material as a cladding material, such as polyethylene, polypropylene, propylene-ethylene copolymer, etc.) by an extruder for heating and melting and plasticizing. The head is applied to the surface of the substrate to form a composite material. There are many commonly used substrates, such as paper, cardboard, aluminum foil, cellophane, polyester, stretched polypropylene, nylon, high density polyethylene, and the like.
Similar to the extrusion compounding process, if the extruder uses a single runner die to extrude a single material, it is a single extrusion coating composite process. The resulting cladding material is a single layer; if the extruder uses a multi-passage die The head, while extruding multiple materials at the same time, is a co-extrusion coating process, and the resulting coating material is multi-layered. Extrusion coating composite device, mainly composed of extruder, head, cooling roller and pressure roller, in addition to unwinding part, winding part, trimming device and other auxiliary devices.
Extrusion coating composite process, physical or chemical bonding between the polymer coating and the substrate. For paper and other porous structure of the substrate, the bonding method is a physical way, the polymer coating penetrates into the pores to form a continuous coating film layer; for cellophane, plastic film, aluminum foil and other smooth surface of the substrate, usually used before compounding Adhesive agent or UV irradiation is applied to improve the composite fastness of the composite film.
Third, dry adhesive composite technology. Dry-process adhesive compounding, also called dry-laid compounding, is a process in which the adhesive layer material coating liquid (binder) is uniformly coated on the first-layer substrate by a coating device (strength On the surface of the large composite substrate material, the solvent in the adhesive layer material coating solution (binder) is completely volatilized through a hot tunnel, and then compounded with the second layer substrate by warming and pressurizing, and then rolled and trimmed. Limited to coils to complete composite processing. Dry-glue compounding not only publishes the fit between plastic films (such as polypropylene and polyethylene, polyester and polyethylene, nylon and polyethylene, etc.), but also composites plastic film with aluminum foil and paper ( Such as two-way stretching of polypropylene, aluminum foil and polyethylene three-layer composite, glass paper, aluminum foil and polyethylene three-layer composite, etc.).
This kind of process is a kind of coating-laminating compounding method. The adhesive used is made of extremely volatile organic solvents and is an extremely important one in a variety of composite processes. Its production equipment is mainly Unwinding part, gluing part, drying part, compound part, winding part, etc.
Fourth, wet adhesive composite process. Wet method adhesive compounding, also called wet laminating compounding, is a process in which the first layer of substrate (such as plastic film, aluminum foil, etc.) is first coated with adhesive material by a coating device, and is in a wet state The second layer of substrate (such as paper, cellophane, etc.) is extruded together through a composite device, and then dried by hot drying to remove the solvent, so that the two layers of the substrate are compounded together and then rolled into a roll after trimming. Material, complete the composite processing.
This kind of process is also a kind of coating-laminating compounding method. The binding materials used are mostly water-based viscose liquids or emulsions, mainly polyvinyl alcohol, sodium silicate, starch, polyvinyl acetate. , Ethylene-vinyl acetate copolymers, polyacrylates, natural resins, etc. This process is commonly used in the production of composite materials for paper and aluminum foil, and has the advantages of simple operation, low binder usage, low cost, fast compounding speed, and no residual solvent. The production equipment is similar to the dry glue adhesive composite equipment, except that the drying sequence (or location) is different. Many wet glue adhesive composite equipments can be dry glued and compounded after simple modification.
Fifth, vacuum coating process. The vacuum coating process is a composite processing method of packaging materials that is different from other methods. Commonly used is the vacuum aluminum film process, in the high vacuum conditions, the use of vacuum evaporation method, the polyester, oriented nylon and other plastic film surface, plating a very thin layer of aluminum metal film, in order to improve the plastic Film decorating and barrier properties. Compared with the production of aluminum foil composite materials, it has the advantages of less aluminum consumption, short production process, less total energy consumption and lower composite production cost.
The process is produced in a closed vacuum chamber under high vacuum conditions. The closed vacuum chamber is connected to the high vacuum system. The vacuum chamber is equipped with a supporting device for the base material roll, a cooling drum, a coated composite material take-up device, and a vapor deposition device. The substrate is supported by the supporting device and gradually spreads after being pulled by the guide roller, the cooling drum and the coiling device. The aluminum material in the electric heating crucible is heated and heated to evaporate into aluminum metal vapor particles, and the heat shielding plate is Flying out of the opening and reaching the surface of the plastic film substrate that passes through the surface of the cooling drum, the metal aluminum vapor particles are cooled and condense on the surface of the substrate, gradually forming a uniform metal aluminum film layer, which is wound into a coil by a coiling device, and is completed. The entire process. Films produced by vacuum aluminum plating can be directly applied to the packaging of foods and other commodities, and other composite processing can also be performed to further improve the performance of composite packaging materials. (Liu Zunzhong, Beijing Institute of Graphic Communication) ("China Packaging News")