What are the applications of multi-layer blow molding processing in Shanghai

Multi layer blow molding is a Shanghai blow molding process that uses injection molding or extrusion to produce multi-layer preforms for the production of hollow products. The obtained product has the characteristics of isolating oxygen, carbon dioxide, and moisture, and also has advantages such as chemical resistance, but the cost is relatively high. It can be used as a beverage bottle, fuel tank, and container for chemicals.

Shanghai multi-layer blow molding processing generally uses co extrusion method to produce preforms, which are then blown to obtain products. For example, in the manufacture of pesticide bottles, PA-6 can be used as the inner layer, high molecular weight polyethylene as the outer layer, and ionic resin as the adhesive for the middle layer; On the equipment, if a storage cylinder mouth mold is used, three extruders can be used to plasticize PA-6, ion type resin, and HMWPE into their respective storage cylinders; When pressure is applied to the pistons of the three storage cylinders, the materials converge at the mold mouth to form a three-layer billet, which is then inflated, cooled and shaped to obtain a hollow product.

If the melting point of the polyamide resin used is 220 ℃, the selected HMWPE should have sufficient melt strength at 225-230 ℃. The polyamide adheres to the surface of polyethylene through an adhesive, and the elongation of the preform mainly depends on the molecular weight of polyethylene. However, blow molding of polyamide requires high polymerization degree resin, or viscosity increase through grafting and cross-linking to reduce sagging.

Since its production began in 1973, plastic fuel tanks for automobiles have accounted for 90% of the market share in 2000. In terms of fuel tank materials, there has been a shift from single-layer high molecular weight polyethylene products to multi-layer extruded hollow products.

For example, a 6-layer co extruded blow molded fuel tank using ethylene vinyl alcohol copolymer (EVOH) as a barrier layer has a 24-hour hydrocarbon leakage of 0.1g. During the 6-layer co extrusion, the material structure is: HDPE/adhesive/EVOH/adhesive/recycled/HDPE; The share (%) of each layer is 38/2/3/2/43/12. Due to the poor heat resistance of EVOH, continuous extrusion process can only be used. In order to fully utilize the unit composed of 6 extruders and minimize waste, two sets of blow molding molds can be configured, and two 6-axis robotic arms can be used to respectively transport the preforms and take away the products.

In terms of co extrusion blow molding equipment, Rikufec, a German company, produced the world's largest three-layer co extrusion blow molding equipment for Spanish customers in 2000, model GBMS4000/A300/Coex3, with a discontinuous operating system featuring a 300L annular pushing pressure die; A extrusion molding machine with an extrusion capacity of 1500kg and a clamping force of 5000kN, with template sizes ranging from 405mm to 3350mm, can produce products with a volume of up to 25m3.