ABSTRACT
It IS possible to form cyclic compounds with -CH2-and/or -CH20CH2bridges, depending on the reaction conditions. When the methylol phenol compound is condensed under essentially neutral conditions using sufficiently high temperature to eliminate water, but not so high as to cause elimination of formaldehyde, a cyclic resin is obtained having 4-8 phenolic units (almost exclusively an even number of units rather than odd) bridged by ether-containing linkages, -CH20CH2-. However, since it is practically impossible to entirely exclude the elimination of formaldehyde, some of the bridging will be means of methylene groups -CH2-·
l. Formation of urea and formaldehyde mixture in molar ratio 1:2 at 80850C
4. Establishing the pH within the range of 5.8-6.5, urea addition until a urea:CH20 molar ratio of 1:1 to 1:1.3 is reached, and reducing temperature to 50°C
-CH20H + H+ =--CH2-0-H =--CH2 + H20 (19) +
+ + -H+ -CH2 + -CH20H =-CH2-0-H -CH2-0-CH2-
[34]. Depending on the formulation and reaction conditions, open pore urea-
Open pore urea-formaldehyde structures have unique properties, and their spherical and pore sizes can be controlled to make them suitable for many applications. Filtration structures, chromatographic columns, porous urea-formaldehyde pigmented polystyrene, smog dispersal agents, moisture retentive fertilizers, fruit coatings, and porous polymer-bound multicomponent corrosion inhibitors have been prepared. Development of technologies based on open pore urea-formaldehyde structures is a distinct possibility.
