| 摘要 |
The present invention provides particular phenol/formaldehyde resoles which are especially useful as foamable resins, and further provides cellular phenolic products having physical properties which are especially attractive for end-use application as construction foam. The resoles are characterized by a particular relationship between their viscosity and water content, expressed as the area bounded by certain points on a plot of resole viscosity on a logarithmic scale, as a function of water content of the resole, the particular area depending upon the mole ratio of formaldehyde-to-phenol at which the resole has been condensed. It has been found that phenol-formaldehyde resoles having the defined viscosity/water relationship are capable of providing phenolic foam having acceptable foam processability, a foam density from about 1.90 to about 3.70 pounds per cubic foot and, within this foam density range, a good balance of friability resistance and compressive strength, that is, a friability of less than 35 percent weight loss and a compressive strength of at least 20 pounds per square inch. Preferred resoles within the invention are foamable to phenolic foam having a reduced tendency to punk as well as the aforementioned desirable combination of foam processability and mechanical properties.
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