Processes of Urethane Foam Preparation

Processes of Urethane Foam Preparation. Urethane foams can be prepared by the one-shot process, semi-prepolymer (quasi-prepolymer) process or prepolymer process. The one-shot fnrocess is most commonly used. The semi-prepolymer process is sometimes preferred because of the advantages of easy processing, stabilized-foam rise and lower exotherm. 

The one-shot process is used for flexible and rigid foams. In the case of slabstock foams, the ingredients are separately supplied to the mixing head. In order to adjust viscosity and mixing accuracy, some of the ingredients, such as polyol and tin catalyst, water and amine catalyst, are pre-mixed. 

Two-component premix systems are widely used for different foam systems because these systems can be supplied in two kinds of drums. In addition, the machines for foam preparation can be of simple structure, and their handling and maintenance are easy. 

The semi-prepolymer systems have the same advantages as the one-shot, two-component premix systems. 

In contrast to the non-frothing process, the frothing process is conducted under pressurized mixing. The frothing process is further classified into the following three processes (a) R-12 (CFC-12 process (25) (b) Thermal Froth process (157) and (c) Chemical Froth process (157). 

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