Benzylic Ether-Type Foams

Materials for Benzylic Ether-Type Foams. Resin (Benzylic Ether-Type Resin). Bem lic ether-type resins can be prepared by reacting phenols and aldehydes in nonaqueous phase in the presence of metallic catalysts. For representative production conditions and for resultant resin properties, refer to Table 58 (15). 

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In manufacturing phenolic foams, a blowing agent such as R-113 (trichlorotrifluoroethane) is evaporated by using an exothermic reaction (Equation 7), and the blowing agent is included in the polymer. The reaction involved in forming the benzylic ether-type foam is shown below. Similarly, this foam will finally form a network polymer as do resol-type foams. 

Figure 57. Foaming processes for resol-type and benzylic ether-type foam.

Foaming Characteristics. When producing resol-type and benzylic ether-type foams, the index expresses apparent reactivity. Following are the foaming times ... 

For making sandwich panels both the resol-type and benzylic ether-type foams can be used. These sandwich panels are used as building materials (partition panels, ceiling panels, wall panels, panels for clean rooms, door panels, panels for prefabricated refrigeration storehouses, etc.). 

The cost of raw materials for use in phenolic foams is low, but since this foam has the weak points listed above, it cannot exceed polyurethane foam in cost performance. Resol-type foams and benzylic ether-type foams use chlorofluorocarbon (CFC) as a foamimg agent. It is necessary to develop a new foaming agent which does not destroy the ozone layer in the atmosphere. When these problems are solved phenolic foam applications will make further rapid progress. 

Benzylic ether type Figure 55. Classification of phenolic foams. 

In the resol type, phenol and formaldehyde react in the presence of a basic catalyst and provide a liquid type resol to which an acid catalyst and blowing agent are added and the foam is then molded. In forming the resol a method is available for obtaining a benzylic ether-type liquid oligomer by reacting phenol and formaldehyde in nonaqueous phase. 

Foaming Process of Resol-Type Foam. The foaming processes for phenolic foam of both the resol type and benzylic-ether type are the same as those for rigid polyurethane foams. The block-foaming process (slab foaming), pouring process, continuous-laminate process, and spray process are used. See Figure 57. 

A research program to have benzylic ether-type resin react with polyisocyanate for producing polyurethane or urethane-modified poly-isocyanurate foam is being promoted. A foam which has intermediate properties between phenolic foam and polyurethane foam can be produced. 

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