The process of forming the tread layer of the sole is carried out in several stages.
1. Thermoplastic polyurethane (TPU) — granules that melt in the extruder — as they melt, flow and fill the lower part of the mold, precisely reproducing the tread pattern.
2. The upper blank, pulled over a last, is lowered into the mold without fitting tightly against the formed two-color TPU layer. Then PU is injected into the mold. Foamed PU is a thermosetting polymer initially in a liquid state. Under the influence of high temperature this polymer solidifies and, expanding, fills the space between the footwear upper blank and the TPU tread layer inside the mold.
3. In the final stage, the sole is bonded to the shoe upper in the injection-molding unit under set temperature regimes and the final formation of the sole takes place, the properties of which significantly exceed those of soles made from thermoplastic elastomer (TPE) and polyvinyl chloride (PVC).
For complex molding processes at the footwear facilities of the Vostok-Service Group, German DESMA equipment is used, equipped with special programs that allow control of the density of the produced sole, monitoring of the product weight, and control of the cycles of chemical processes.
Our shoemaking operations also feature additional high-tech equipment: robots for roughening and spraying mold-release lubricants and equipment for injecting dyes.
Complex three-layer molding processes produce soles with excellent performance characteristics and design, contribute to a reduction in footwear weight, and increase the flexibility of the product.