Raw material storage and pretreatment.
The raw materials for shoe soles are usually formulated in the form of a combination of three components A, B and C, with polyol, isocyanate and catalyst as the main ingredients, supplied for sale. Their storage periods at room temperature and under sealed conditions are 6 months, 3 months and 6 months respectively. During the storage period, attention should be paid to moisture-proof, avoiding light, forbidding exposure to sunlight and rain, and should pay attention to ventilation. Beyond the shelf life, before use must be analyzed and a small sample of foam test to check whether the failure. Raw materials should be heated and melted before use.
If color matching is required, color paste should be added to component A, and need to be fully stirred before use, so that it is evenly dispersed; catalyst component is usually added to component A in the production plant, but because of organic catalysts are prone to hydrolysis, and sometimes also because of the production conditions and environments around the world are not consistent, the catalyst can be used as a separate component to facilitate the regulation of catalysts are to be added to the component A before use, stirring The catalyst should be added to component A before use and stirred for at least 10~20min before adding component A to the working tank of the foaming machine.
The correctness of the distribution ratio of raw material group is the most critical condition to ensure the quality of products, therefore, the daily production must test and check the accuracy of the measuring ratio of the foaming machine. In the new addition of raw materials or metering pump error fluctuations, especially pay attention to the group distribution ratio measurement monitoring and checking. Foaming machine on the measurement of raw materials is mostly based on volume, its volume and viscosity, and even the temperature are directly related, so in the production of raw materials must be strictly controlled by the pressure, temperature in the predetermined range, otherwise, it will seriously affect the accuracy of the component measurement.
Sole molds are usually made of aluminum alloy and steel, and in recent years, the use of resin molds is very common. The mold cavity pattern must be clear, and special attention should be paid to the design of the deeper concave-convex pattern in the mold design, which must be conducive to the discharge of air bubbles, avoiding acute concave-convex pattern, which should be changed to a rounded transition if necessary.
The best angle should be about 45° parallel to the bending direction. Previously, it was thought that the finished sole should not be too thick, generally 6~8mm, usually not more than 12mm; but now the casting of soles with a thickness greater than 12mm has been fully mastered.
When adding inserts such as wooden cores, the cores must be dry. The temperature of the mold should be controlled at 45~55℃.
According to the shape and density requirements of the sole, the injection amount of foaming material should be adjusted appropriately. When pouring high heel soles, the heel part should be raised appropriately when installing the mold. When pouring, the heel can be poured after part of the material is poured in the front part (so that the foam center is not concentrated in one point), and the injection amount should be 40%~70%; when pouring flat shoes, the foot part of the mold should be lifted upward slightly. The mold should be adjusted at a proper angle on the production line, and the tilting angle of the mold should be adjusted accordingly to the shape of the sole, so as to avoid the surface of the sole from producing defects such as cavities and air bubbles.
The molding time of polyurethane soles is generally 5~7min, at this time, the performance of polyurethane soles has not yet reached the best degree, and it is not allowed to exert too much force when demolding. After demoulding, the semi-finished products should be placed at room temperature for 1 day, and the mold release agent adhered to the surface of the products should be cleaned up within 24h, so as to facilitate the processing treatment after color spraying.