Characteristics of co-extrusion film

Characteristics of co-extrusion film

In the processing of the film, one raw material is extruded onto another film that has been made or different types of films have been made, and the adhesive is used to bond each other to form a multi-layer film. This product called a composite membrane. Co-extrusion film has most of the characteristics of composite film, but there is a difference, that is, all layers of co-extrusion film are extruded together at the same time, and the layers are bonded by hot melt without adhesive.

Most of the materials of the composite film are plastic, but paper, metal foil (usually aluminum) or fabric can also be used. All layers of coextruded film are extruded together at the same time, so there are no other non-plastic materials such as aluminum foil or paper.

The composite film can be delaminated under certain conditions, but the co-extrusion film will not, so under the action of tensile tension, there will be different forms of expression between the two; in addition, because the materials of the co-extrusion film are bonded together by hot melt, so When pinched hard, spherical air bubbles will be produced, but the composite film will not produce spherical air bubbles when pinched hard because it is bonded by adhesive.

Multi-layer co-extruded barrier film refers to a functional composite film obtained by extruding melts of resins with high barrier properties and other resins through a common die using multiple extruders. Multi-layer co-extrusion compounding is a green compound production process, especially for the current food packaging industry, the raw materials used are generally certified by the US food and health safety agency, and the raw materials are fed to each layer uniformly by a special delivery pipeline , There is no raw material exposure and no environmental pollution during the processing. Its conjunctive layer is made of modified LLDPE, which is non-toxic to the environment, food and human body, and there will be no traditional dry compounding, that is, the so-called solvent residue phenomenon, and no waste gas pollution; it is also different from dry compounding, Solvent-free lamination and general single-layer extrusion lamination process require a dry box for processing, so energy consumption is also less. In addition, the multi-layer co-extrusion composite process also has the following advantages. Nanjing Sumino Precision Machinery Co., Ltd. professional co-extrusion film and composite film production line

(1) Low cost

The multi-layer co-extrusion composite process uses a variety of resins with different functions, and only one process of blow molding can be used to make multi-functional composite film products, which can reduce production costs. In addition, under the condition of meeting the requirements of customers, the resin raw materials with required properties can be reduced to the minimum thickness, and the thinnest single layer can reach 2~3μm, which can greatly reduce the amount of expensive resin used, thereby reducing the cost of materials .

(2) Flexible structure

Multi-layer co-extrusion technology can combine various raw materials in different combinations, make full use of raw materials with different properties, and form one-time molding without being limited by market-related product specifications, and can effectively meet the needs of different packaging occasions. The more layers, The more flexible the structural design, the lower the cost.

(3) High composite performance

The co-extrusion composite process combines the melted adhesive and the base resin. The peel strength of this process is very high, usually up to 3N/15mm or more, and it cannot even be peeled off. It is suitable for general packaging materials. For products requiring high peel strength, thermal adhesive resin can be added for compounding, and the peel strength can reach 14N/15mm or even higher.

(4) Wide range of uses and broad use environment

Multi-layer co-extruded composite products can cover almost all packaging fields: food, daily chemical products, beverages, pharmaceuticals, protective films and even aerospace products, etc. At present, many dry composite products in China have adopted co-extruded composite materials abroad. craft. Toothpaste tubes that cannot be produced by the dry lamination process. Paper-plastic-aluminum composite products. Products such as aerospace are also realized by co-extrusion composite technology. With the in-depth research and continuous innovation of co-extrusion composite resins, processes and equipment, multi-layer co-extrusion composites will expand to a wider range.

First, the multilayer coextruded barrier film is a plastic film. In the field of plastic products, we usually refer to planar plastic products with a thickness of less than 0.2 mm as plastic films, those with a thickness between 0.2 and 0.7 mm as plastic sheets, and those with a thickness greater than 0.7 mm as plastic sheets. sheet.

Multilayer co-extruded barrier films should have certain gas barrier properties. The barrier property here refers to the shielding ability of plastic products (containers, films) to small molecule gases and odors. We usually use the gas transmission rate to measure the size of the barrier performance of plastic products.

General-purpose plastics such as PE and PP have relatively high gas transmission rate values, that is, poor gas barrier performance, while PA, PVDC, EVOH and other resin materials have much lower gas transmission rate values than general-purpose plastics, and better barrier performance. Therefore, we usually refer to multi-layer co-extruded films containing at least one resin material among PA, PVDC and EVOH as multi-layer co-extruded barrier films. Nanjing Sumino Seiko professional co-extrusion film and composite film production line

Multi-layer co-extrusion of PE, PA, TIE, EVOH and other resins can be used for vacuum packaging of dairy products, jams, meat products, etc.

The multi-layer co-extrusion film mostly adopts ABCBA5-layer symmetrical structure, with PA or EVOH as the barrier layer, and polyethylene as the heat-sealing layer. Adhesive resins are used to space the discrete barrier and heat seal layers. PA or EVOH is a resin that is extremely sensitive to humidity. It is protected by a polyethylene layer, and its excellent oxygen barrier performance has been fully exerted.

In general, the structure of a multilayer coextruded film depends on the functional requirements of the film. On the premise of meeting the process requirements, through the combination of different polymers, the functional requirements of packaging materials such as barrier, heat sealing, body strength, thermal puncture, environmental suitability, secondary processing characteristics, and extended storage and shelf life are met. From the analysis of functional requirements, the combination of five polymers is sufficient.

However, seven-layer, nine-layer, eleven-layer and even more-layer co-extrusion composite films have been applied in the market, making it a trend and developing rapidly. The structural design of co-extrusion film is gradually requiring to systematically achieve the ideal state integrating function, technology, cost, environmental protection, safety and secondary processing.

Nanjing Sumino Precision Machinery Co., Ltd. has a professional cast film production line. The company's main cast film production lines include: TPU hot melt adhesive film production line, CPP/CPE cast film production line, EVA solar energy packaging film production line, PE hygienic and breathable Film production line, PVDF cast film production line, PP three-dimensional film production line, medical blood purification film production line, multi-layer co-extruded barrier film production line, LLDPE stretch film production line, etc.