Formaldehyde → Formaldehyde;phenol

Participants

Reaction Steps

Into a 4 liter resin flask equipped with a mechanical stirrer, reflux condenser and thermometer is placed 2000 gms (21.28 moles) USP phenol; 882 gms (15.28 moles) aqueous formaldehyde (52%); 200 gms water and 12 gms (0.10 mole) phosphoric acid (85%). The pH of the resulting mixture is 1.05. This mixture is then heated to reflux and refluxed a total of 5 hours. The free formaldehyde content of the mixture at this point is found to be 0.84%. At this point the reflux condenser is replaced with a distillation condenser and batch distilled under atmospheric pressure for one hour until the batch temperature reaches 160° C. At this point a mixture of 173 gms (3.0 moles) of 52% aqueous formaldehyde, mixed with 70 gms of water is slowly added to the mixture over a period of 36 minutes. During the addition, the batch temperature drops to 142° C. When all the aqueous formaldehyde has been added, the batch is held at 142°-150° C. for 15 minutes. Then the receiver on the distillation condenser is replaced with a vacuum receiver to allow completion of the batch under vacuum. The resin is then dehydrated to a batch temperature of 165° C. under vacuum of 28 inches of mercury. The vacuum is released and the resin discharged from the vessel to yield 2027 gms of product, which exhibits a gradient bar melting point of 223° F. and a glass transition temperature as measured by differential scanning calorimetry of 70° C. (158° F.). This resin is a non-curing Novolak as shown when tested on a hot plate at 330° F. However, when thoroughly blended with 10 parts per hundred (pph) of hexa, it has a set time of 24-25 sec. when heated at 330° F. (166° C.).

Provenance & Evidence