| 摘要 |
This invention relates to the manufacture of foam from phenolic resins and to the foam so produced. In order to overcome some the the limitations of the prior art closed cell phenolic foams, we have developed a method of preparing closed cell foams from modified, low cost phenol formaldehyde resoles, which exhibit high closed cell contents, low friability and low thermal conductivity. This specification provides a foam competitive with urethane foams, which have an aged thermal conductivity of about 0.16K. or less, but which will not generate fumes as toxic as those of urethane. There is, provided a method of making a phenolic foam material comprising the steps of (1) preparing a base catalyzed phenol-formaldehyde resole having a mole ratio of phenol to formaldehyde of between 1:3 and 1:4.5 and containing substantially no free phenol but including residual formaldehyde; (2) neutralizing, concentrating and acidifying said the resole; (3) reacting with co-reactants consisting essentially of urea and resorcinol in an amount such that the molar ratio of combined urea and resorcinol to free formaldehyde in said resole is about 1:1, the ratio of urea to formaldehyde being selected so that in a test starting at ambient temperature a reaction temperature of 70 DEG to 75 DEG C. is reached during foaming within a period of 4 to 8 minutes, the urea being reacted first where urea and resorcinol are separately reacted with the resole; (4) (a) combining the product of step 3 with a surfactant in an amount sufficient to be effective as a cell stabilizer and (b) a blowing agent in an amount sufficient to form a foam; (5) initiating foam formation by adding to the mixture of step 4 a catalyst comprising an acidic material to reduce the pH of the mixture to below 4; (6) curing the mixture of step 5. |
