| 摘要 |
1,149,903. Phenolic urea resins; foundry cores. ASHLAND OIL & REFINING CO. 12 July, 1966 [30 July, 1965], No. 31314/66. Headings C3N and C3R. A resin product comprises a condensate of phenol (P), formaldehyde (F), and urea (U) having a molar ratio F/(P + U) of 2À85-3À4 and containing 9-12% by wt., based on the amount charged of urea. The product may have a viscosity Q to Z (Gardner-Holdt). The resin may be prepared by heating P, F and U in the prescribed ratios with an alkaline catalyst to a temperature sufficient to obtain a water tolerance of 300-500%, adding acid to reduce the pH to 4À0-7À0 and heating the resultant mixture to drive off the water. The resins may be used in preparing foundry cores using, e.g. 0À25-5% of the sand (e.g. Nugent lake sand) of a resin binder according to the invention. Other materials, e.g. iron oxide, wood, cereal or pitch may be present. |
