Composite process of the hottest packaging materia

2022-07-26
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Packaging material composite process

in the process of modern commodity packaging, the packaging of some commodities (especially food) has strict requirements for various properties of packaging materials, such as moisture-proof, waterproof, gas barrier, light proof, heat-resistant, oil-resistant, high temperature resistant, easy to heat seal, easy to print, etc. Tong Yi's packaging materials are difficult to meet many 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 materials are mainly various composite films. The so-called composite film refers to a flexible composite packaging material with comprehensive properties, which is based on flexible packaging materials such as paper, cellophane, plastic film and metal foil. This polyurethane waterproof coating has attracted much attention in the construction field, and is obtained through coating, laminating, CO extrusion and other composite processing methods. There are many processing technologies and methods for composite packaging materials, which can be processed before printing or after printing. In many cases, in order to avoid the packaged goods (especially food) from directly contacting the printing ink layer, one or more layers of other materials are often compounded on one side of the printing ink layer after printing, so as to prevent the goods from directly contacting the printing ink layer. At the same time, the comprehensive properties of various materials in the composite layer are used to better protect the goods

the processes and methods commonly used for post press composite processing of packaging materials mainly include: extrusion composite process (including single extrusion and co extrusion, belonging to extrusion lamination processing method), extrusion coating composite process (including single extrusion and co extrusion, belonging to coating composite processing method), dry adhesive composite process, wet adhesive composite process, wax composite process Hot pressing composite process (the above four belong to coating lamination composite method), direct air coating process, etc. In actual production, sometimes in order to improve production efficiency or product processing needs, 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 backing material, the front equipment of dry adhesive composite is often assembled into the extrusion composite equipment to jointly complete the composite process. This paper mainly introduces five processing technologies of composite materials, such as extrusion composite technology and vacuum coating technology

I. extrusion composite process. This process is a laminating method widely used in actual production. It is to extrude polyethylene, polypropylene, EAA (ethylene acrylic acid copolymer), sarin (ionic bonded polymer) and other polymer resins or hot-melt adhesives through hot melting and plasticization in an extruder, and then extrude the two substrates to be compounded to form composite materials by bonding them together through an intermediate layer. Commonly used base materials include paper, aluminum foil, plastic and other materials

in this process, if the extruder uses a single channel die to extrude a single material, it is a single extrusion composite process. The main production equipment of this process is composed of extruder, head, unwinding part, composite part, rewinding part, edge cutting device, transmission device, automatic tension control device, automatic unwinding deviation adjustment device, material pretreatment device, post-treatment device 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 an extruder, and then coat them on the surface of the substrate through the machine head to form composite materials. There are many common substrates, such as paper, paperboard, aluminum foil, cellophane, polyester, stretched polypropylene, nylon, high-density polyethylene, etc

similar to the extrusion composite process, if the extruder uses a single channel die to extrude a single material, it is an extrusion coating composite process with the warming of the international market situation, and the resulting coating material is a single layer; If the extruder uses a multi channel die head to extrude multiple materials at the same time, it is a co extrusion coating composite process, and the resulting coating material is multi-layer. The extrusion coating compound device is mainly composed of an extruder, a machine head, a cooling roll and a pressing roll, as well as a unwinding part, a rewinding part, an edge cutting device and other auxiliary devices

extrusion coating composite process, the polymer coating is physically or chemically bonded with the substrate. For porous substrates such as paper, the bonding method is physical. Polymer coating Lubrizol can also provide X-ray identification with radiation impervious materials, which penetrate into the pores to form a continuous coating film layer; For the substrate with smooth surface such as cellophane, plastic film and aluminum foil, it is usually treated with adhesive or ultraviolet irradiation before compounding to improve the compounding fastness of the composite film

III. dry adhesive composite process. Dry adhesive compounding, also known as dry lamination compounding, the process is as follows: firstly, the adhesive layer material coating liquid (adhesive) is evenly coated on the surface of the first layer of substrate (composite base material with high strength) with a coating device, the solvent in the adhesive layer material coating liquid (adhesive) is completely volatilized through a hot drying channel, and then it is compounded with the second layer of substrate by heating and pressing, and rolled into coiled material after trimming to complete the compounding process. Dry adhesive compounding not only publishes the combination of plastic films (such as the combination of polypropylene and polyethylene, polyester and polyethylene, nylon and polyethylene), but also publishes the composite operator code * * between plastic films and aluminum foil and paper (such as the three-layer composite of biaxial stretching polypropylene, aluminum foil and polyethylene, and the three-layer composite of cellophane, aluminum foil and polyethylene)

this process is a kind of coating lamination composite method. The adhesive used in this process is prepared with highly volatile organic solvents. It is a very important kind of composite process. Its production equipment is mainly composed of unwinding part, gluing part, drying part, composite part, winding part, etc

IV. wet adhesive composite process. Wet adhesive compounding, also known as wet lamination compounding, is a process in which the first layer of base materials (such as plastic film, aluminum foil, etc.) are first coated with adhesive materials through the coating device, then extruded together with the second layer of base materials (such as paper, cellophane, etc.) through the compounding device in a wet state, and then dried through a hot drying channel to remove the solvent, so that the two layers of base materials are compounded together, and rolled into coiled materials after trimming, Finish compound machining

this process is also a coating lamination method. The bonding materials used are mostly viscose or emulsion with water as solvent, mainly including polyvinyl alcohol, sodium silicate, starch, polyvinyl acetate, ethylene vinyl acetate copolymer, polyacrylate, natural resin, etc. This process is commonly used in the production of paper and aluminum foil composite materials. It has the advantages of simple operation, less adhesive consumption, low cost, fast compounding speed, no residual solvent, etc. Its production equipment is similar to dry adhesive compounding equipment, but the drying sequence (or position) is different. Many wet adhesive compounding equipment can be used for dry adhesive compounding production after simple transformation

v. vacuum coating process. Vacuum coating process is a kind of composite processing method of packaging materials, which is different from other methods. Generally, vacuum aluminum coating process is commonly used. Under high vacuum conditions, a very thin metal aluminum coating is coated on the surface of polyester, directional nylon and other plastic films by vacuum evaporation, so as to improve the decoration performance and barrier performance of plastic films. Compared with the production of aluminum foil composites, it has the advantages of less aluminum consumption, shorter production process, less total energy consumption and lower composite production cost

the process is carried out in a closed vacuum chamber under high vacuum conditions. The closed vacuum chamber is connected with 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 coiling device, an evaporation device, etc. The base material is supported by the supporting device, and gradually loosens after being pulled by the guide roller, cooling drum and coiling device. The aluminum material for evaporation in the electric heating crucible is electrified and heated to evaporate into metal aluminum vapor particles, which fly out from the opening of the heat shield plate and reach the surface of the plastic film base material passing through the surface of the cooling drum. The metal aluminum vapor particles are cooled and condensed on the surface of the base material, gradually forming a uniform metal aluminum film, The whole process is completed by coiling into coils by coiling device. The film produced by vacuum aluminum plating can be directly applied to the packaging of food and other commodities, and can also be used for other composite processing to further improve the performance of composite packaging materials

(liuzunzhong, Beijing Institute of printing)

reprinted from: (China packaging daily)

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