مقدمة عن آلات حقن رغوة البولي يوريثان - أنظمة تخزين المواد، والتركيب، والتحكم في درجة الحرارة

Molding is one of the key production processes for polyurethane foam products. In this process, various liquid materials are accurately metered by a dosing pump and thoroughly mixed by a mixing head before being injected into molds. The materials react and cure inside the enclosed mold, forming products that match the shape of the mold cavity. Due to differences in raw materials and processing methods, molding can produce soft, rigid, semi-rigid foams, and foams with hard skins. Depending on the physical property requirements, the application range of polyurethane foam injection machines is vast, leading to rapid development and increasing market presence of various molded foam products.

Basic Components of a Polyurethane Foam Injection Machine Production Line

A polyurethane foam injection machine production line typically consists of multiple core units, including material storage, formulation and temperature control systems, metering systems, mixing systems, molds and transportation systems, mold temperature control systems, control systems, and exhaust systems. Depending on the product, some production lines also include auxiliary units for post-processing and curing.

Material Storage, Formulation, and Temperature Control Systems

Material storage tanks are typically reaction kettles equipped with mixing functions and jackets or coils for heating or cooling. These tanks are usually made of stainless steel. If carbon steel reaction kettles are used, the inner surface must be coated with a corrosion-resistant layer to protect against the corrosion from polyols and isocyanates. The working material tanks in polyurethane foam injection machines are generally small (ranging from 300 to 500 liters) and are used to supply materials directly to the dosing pumps. Most factories now use pre-mixed system materials, eliminating the need for on-site mixing. If manufacturers need to mix polyols and isocyanates on-site, larger formulation kettles should be set up to mix the components evenly before supplying them to the working material tank.

To ensure continuous production and maintain stable material temperatures, working material tanks are typically equipped with independent temperature control systems and automatic level control and replenishment features. This ensures a steady supply of raw materials and stable material temperatures, minimizing temperature fluctuations during the production process to meet process requirements.

For low-pressure polyurethane foam injection machines, polyol and isocyanate components can be stored in atmospheric pressure tanks, while high-pressure polyurethane foam injection machines require pressure tanks rated for 0.4-0.6 MPa, using dry nitrogen or air to pressurize the dosing pumps. If auxiliary blowing agents are needed during production, the corresponding requirements for the material tanks should be determined based on the type of auxiliary blowing agent used.

Most molding production lines are equipped with independent material temperature control systems that regulate the material temperature via a cooling and heating water system. This system includes jackets or coils designed for the material storage tanks, and heat exchangers are typically installed in the return pipelines to improve temperature control efficiency and maintain stable material temperatures.

In the production of some rigid foam and reaction injection molding products, gas is often introduced into the polyol component to improve distribution, reduce product density, minimize or eliminate the need for auxiliary blowing agents, or improve the stability of filler dispersion. The common methods for gas infusion are direct mechanical dispersion and collision mixing dispersion. Figure 1 shows the process flow of direct mechanical gas dispersion. In this method, a circulation pump sends the polyol to the gas dispersion tank, where a stirrer disperses the gas into the polyol under pressure. The stirring ensures uniform gas distribution. A density measuring device monitors density changes, and the control system adjusts the air compressor and stirring speed to maintain a stable gas content that meets process requirements.

Figure 1: Flow Diagram of Mechanical Gas Dispersion Process