Production Process Of Polyurethane Material For Sole

Polyurethane (PU) microporous elastomer sole materials were industrialized in Europe in the late 1960s, entered the U.S. market in the 1970s, and developed rapidly in the world since the 1980s. The sole made of microporous polyurethane elastomer has the characteristics of high strength, good elasticity, comfort, wear resistance, folding resistance, oil resistance, corrosion resistance, light weight, slip resistance, etc. It can cushion the impact of the ground, and can be made into different colors and varieties of soles. The main varieties include leather shoes, cross-country ski shoes, sandals, slippers, sports shoes, travel shoes, anti-static and oil resistant safety shoes, etc.

Production process:

1. Preparation of PU sole solution

The stock solution can be divided into polyester type and polyether type. Polypropylene glycol system was developed in the early years, but now it is mostly polyester system. Due to different properties, the preparation methods are also different.

Prepolymer method or semi prepolymer method is usually used to prepare polyester PU sole stock solution, which can be made into two or three components generally. Component A is composed of some polyester, chain extender, foam homogenizer and foaming agent, and is obtained by static degassing after mixing 40e~70e. In the all water foaming system, the foaming agent is water, and the water content in component A must be determined, which is generally about 0.4%. Component B is isocyanate terminated prepolymer prepared by reaction of part of polyester polyol with isocyanate. The relative molecular weight of polyester should be 1500~2000. In isocyanate, the ratio of pure MDI to liquefied MDI is 19B1. During the reaction, 1/10000 inhibitor must be added to prevent the occurrence of side reaction. Holding at a certain temperature for 2h~3h is enough, of which) NCO% is controlled at about 19%. Component C is a catalyst (added to component A is a two-component stock solution). The three component system is suitable for two-color, low hardness sports shoes and low-density sandals. When using, mix component A and component C evenly first, and then mix with component B. It is characterized by small reduction of viscosity and reactivity, small change of product hardness and size, and good molding stability. Polyether type stock solution is usually prepared by one-step method. Component A is obtained by fully mixing polyether polyol, chain extender, foaming agent, catalyst and foam homogenizer in the mixer; Component B is modified isocyanate or liquefied MDI. Polyester glycol can endow the sole with high strength, abrasion resistance, strong adhesion with the upper and other characteristics. Polyether type sole overcomes the shortcomings of poor water resistance and low temperature elasticity of polyester type sole, and has good formability. While giving excellent low temperature flexibility and elasticity, it can keep the physical and mechanical properties of the sole basically unchanged. However, under the condition of low density, polyester soles have poor dimensional stability, while polyether soles have good dimensional stability but low mechanical properties under the same density. Therefore, in the water foaming system, the mechanical strength and wear resistance of products can be improved by mixing two alcohols in a certain proportion. This work has been reported in foreign literature, for example, the poly (ether 2-ester) polyol of MipolurPE2PolidolA [2] is a mixed polyol containing both ether and ester, and the performance of its sole material is between polyester and polyether. Domestic scholars have also done some work. Zha Liusheng and others have improved by mixing characteristic amounts of polyester polyols with domestic polyether as the main raw material, and synthesized poly (ester 2 ether) foam sole material. Its physical and mechanical properties are better than GB10508289 indicators, and its cost is 10%~15% lower than that of pure polyester PU sole material [3].

2. PU sole forming process

PU soles include unit soles, all polyurethane boots, direct upper injection soles, hard soles and the middle layer of soles, and other whole shoe and composite soles. The soles, uppers or uppers of all polyurethane boots are made of PU. Among them, the all polyurethane shoes made of microporous PU elastic system have soft boots, wear-resistant soles, oil resistance and chemical corrosion resistance. The whole shoe is light, warm and comfortable. PU soles are generally molded by low-pressure casting or high-pressure casting, and a few are also molded by injection molding. The process flow is shown in Figure 1. The molding equipment is sole casting machine. The normal pressure pouring equipment for polyester PU molding is mainly composed of pouring machine, circular or rotary table drying channel and other devices. In the PU sole stock solution, components A and B are both liquid, and the mixing reaction is intense, so in the molding process, the accurate measurement of equipment and the mixing uniformity of components are two important factors that directly affect the product performance. For the two-color sole, the two-color casting machine is used for molding. Generally, the mold with an additional intermediate plate is used for secondary pouring and heating curing.