What is Suzhou multi-layer blow molding processing

Multi layer blow molding is a Suzhou blow molding processing technology developed to meet the special requirements of packaging containers such as airtightness and corrosion resistance in certain industries such as pharmaceuticals, food, and cosmetics. Its basic process principles are the same as those of single-layer product blow molding technology, mainly including co extrusion blow molding and injection molding blow molding.

When using co extrusion method, multiple extrusion sails are used to simultaneously squeeze different resins into multi-layer machine heads to form multi-layer concentric product preforms, which are then blow molded. When using injection molding for blow molding. Then, a layer is first injected onto the male mold, and the mold cavity is changed to inject on the first layer to form the second layer. This process is repeated to form a multi-layer product blank, followed by blow molding. Multilayer systems that have been adopted in industry include polyamide/polyolefin, polystyrene/polyacrylonitrile/polypropylene, polyolefin/polyvinyl chloride, etc

Multi layer blow molding is a technology that uses two or more extruders to melt and mix the same or different types of plastics in different extruders, then composite and extrude them in the same head, and blow mold to manufacture multi-layer hollow containers.

Suzhou multi-layer blow molding processing is developed on the basis of injection molding blow molding and extrusion blow molding, with little difference in process, except that the product wall is not a single layer but multiple layers. The multi-layer structures used include nylon/polyolefin, polyvinyl alcohol/polyolefin, polyethylene/polyvinyl chloride/polyethylene, polystyrene/polyacrylonitrile/polypropylene, etc.

Multi layer blow molded containers are mainly designed to meet the increasing demand for airtightness in cosmetics, pharmaceuticals, and food packaging. Therefore, the raw materials and layers of multi-layer containers should be selected according to the needs. Two types of plastic two-layer structures, two types of plastic three-layer structures, three types of plastic four layer structures, or four types of plastic four layer structures can be used. The more levels there are, the higher the technical requirements.

The key to multi-layer blow molding is to control the fusion bonding between the resin layers, and there are two bonding methods. The first method is to mix resin with adhesive properties, which can reduce the number of layers while maintaining a certain strength. The second method is to add a layer of adhesive material, which requires the purchase of an extruder for extruding the adhesive material, making the equipment and operation more complex.

Suzhou multi-layer blow molding is a process of directly blowing or stretching multi-layer preforms to form multi-layer hollow containers. Multi layer preforms are co extruded by multiple extruders and then blow molded, known as co extrusion blow molding; If a multi-layer billet is formed by injection molding and then blown, it is called co injection blow molding.

The use of multi-layer composite technology is usually based on the following considerations:

(1) By placing a small amount of resin with excellent barrier properties but high cost in the middle layer of a multi-layer structure, the barrier performance of the container can be improved and the shelf life can be extended at a relatively low cost.

(2) Recycling resources and reducing costs. For example, recycled materials can be placed in the middle layer, or a layer of resin mixed with expensive colorants or UV resistant materials can be placed on the outer layer to reduce costs.

(3) Other functional needs. Including optical effects, tactile effects, and usage effects generated by the combination of materials with different properties.

In short, the ultimate goal of multi-layer composite is to optimize the combination of different functional materials, complement each other's strengths and weaknesses, and enhance the value of the product. The materials used include the same type of material, as well as materials with significant differences in chemical structure. In the latter case, an adhesive is required to increase the interlayer bonding force. However, significant differences in the rheological behavior of different materials will increase the difficulty of the process.

The typical application of multi-layer blow molded products in Suzhou is the packaging of milk, natural fruit juice, tea drinks, tomato sauce, carbonated soft drinks, beer, seasonings, and cosmetics that require high barrier performance.