| 摘要 |
Low-color or white, dilutable condensation products of formaldehyde and phenol in molar ratios of 1.9-5.0:1, characterized by carbon-13 nuclear magnetic resonance spectra as having at least about 30 molar percent of the total formaldehyde content of the resin bound to phenol nuclei in benzyl formal groups of the form Ph-(CH2O)n-CH2OH wherein n>/=1, and less than about 40 molar percent of the total formaldehyde content of the resin bound to phenol nuclei in methylol groups of the form Ph-CH2OH, wherein Ph is a phenol nucleus. Phenol, water and an alkaline catalyst, limited to 0.5-2.2 moles of catalyst per 100 moles of phenol and preferably lithium carbonate, are mixed with formaldehyde at 1.9-5.0 formaldehyde to phenol ratios. The reaction mixture is heated at a uniform rate over 1 hour to reflux temperature and refluxed until a viscosity of 400-500 centipoise at 50-75% solids is attained. The mixture is cooled to 50 DEG C. and neutralized with acid to a pH of 3-7, preferably with citric acid. The resulting resin may be employed, without solvent dilution, to make resin-fiberglass laminates that have strengths comparable to polyester or epoxy laminates. The laminates have exceptional fire resistance and low smoke evolution when exposed to flame.
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