Phenol - aldehyde polymers formation

Oglialoro modification of, 708 Perkin triangle, 108, 218f Kon modification of, 109 Peroxides, detection of, in ether, 163 removal from diethyl ether, 163 removal from isopropyl alcohol, 886 Petroleum ether, purification of, 174 Phenacetin, 996, 997 1 10-Phenanthroline, 991, 992 p-Phenetidine, 997, 998 Phenetole, 665,670 Phenobarbitone, 1003,1004,1005 Phenol, 595, 613 Phenol aldehyde polymers, 1016 formation of, 1022 Phenolphthalein, 984, 985 action as indicator, 984 ... 

Some of the most familiar reactions falling into the polycondensation class are those leading to polyamides derived from dicarboxylic acids and diamines, polyesters from glycols and dicarboxylic acids, polyurethanes from polyols and polyisocyanates, and polyureas from diamines and diisocyanates. Similar polymer formations utilizing bifunctional acid chlorides with polyols or polyamines also fall into this class. The condensations of aldehydes or ketones with a variety of active hydrogen compounds such as phenols and diamines are in this group. Some of the less familar polycondensation reactions include the formation of polyethers from bifunctional halogen compounds and the sodium salts of bis-phenols, and the addition of bis-thiols to diolefins under certain conditions. 

The reaction conditions, particularly the acidity and the temperature, have a profound effect on the character of the resultant products. In general, three stages can be identified formaldehyde addition to phenol, prepolymer formation below 100°C, and crosslinking at temperatures above 100°C. The reactions between phenols and aldehydes were first described by Bayer, who also obtained the first patent on the preparation of methylolphenols. The first kinetic studies in alkaline media were reported by Lederer and Manasse. The first patents on resin produc s were issued to Smith, for an ebonite and wood substitute, and to Blumer, for a shellac substitute. However, not until Baekeland s famous heat and pressure patent did phenolic resins become prominent and widely used polymers. 

Amino Rosins. Amino resins are the reaction product of an aldehyde with a compound containing an amino (—NH2) group (see Amino Resins). Both urea and melamine react with formaldehyde, first by addition to form methy-lol compounds, and then by condensation to form cross-linked polymers through methylene bridge and methylene ether formation. The cross-linking reactions are exothermic and produce water and formaldehyde as volatile products in reactions similar to resole phenolics, illustrated in equation 3. Urea-formaldehyde and melamine-formaldehyde account for the bulk of the amino resins. Their characteristics include water solubility and unlimited colorability with dyes and pigments. Applications include decorative high pressure phenolic laminates, adhesives in the laminated wood and furniture industries, and as an additive to textile fabrics to impart wash and wear properties. 

A classical example of tiie formation of a network polymer is the polycondensation of phenols with aldehydes. The reaction between phenol and formaldehyde in the absence of a catalyst is very slow and hence in all commercial s)mthesis, catalysts are always added to... 

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