Three-component polyurethane molding is an innovative solution in sole production which increases operational properties of the footwear and improves its design. To reduce the weight and increase the flexibility of the footwear, two various types of thermoplastic polyurethane (TPU) and foamed polyurethane (PU) are applied in three-layer molding technology.
The process of forming the sole outer layer consists of several stages.
1. Thermoplastic polyurethane (TPU) is the granules which melt in an extruder, — and by spreading, fill the lower part of the pressing mold accurately repeating the tread pattern.
2. The shoe upper layer, drawn tight over the last, is lowered into the pressing mold without without tightly adjoining the formed two-color TPU layer. Further, PU is injected into the pressing mold. The foamed PU is a thermoreactive liquid polymer that is initially in the liquid state. The polymer changes into a solid state under the high temperature conditions and, by expanding, fills the space between the shoe upper and the TPU outer layer which is inside the pressing mold.
3. At the final stage the sole rises to the foortwear top in the injection unit under the established temperature modes and the sole is finally formed, whose properties considerably exceed the properties of a thermoelastoplastic (TEP) and polyvinylchloride (PVC) sole.
Different types of molding units and German equipment DESMA with special sets of programs for density control of the obtained sole, product weight control, control cycles of chemical processes are used for the complex molding processes that take place at «Vostok-Service» Group of Companies.
Our shoemakers use hi-tech additional equipment: robots for roughing and dispersion of release agents and the equipment for injection of dyes.
Complex three-layer molding processes contribute to the production of the soles with the excellent performance characteristics and design, allow decreasing the footwear weight and increasing the flexibility of the product.