| 摘要 |
Stable, clear polymethylolphenol solutions are prepared by heating at 60-100 DEG C. and at a pH of 7.0-9.5, 4-10 mols. of monomeric formaldehyde as a 58-65 per cent. aqueous solution with 1 mol. of phenol containing not more than 20 per cent. of water until the free formaldehyde content of the mixture is below 35 per cent. and cooling the solution to below 30 DEG C. The formaldehyde is kept monomeric by maintaining it at 80 DEG C. from the time of its preparation until the time of its use. A number of examples are given and are compared with results achieved with different conditions. The pH of the cooled solution may be adjusted to 4.5-6.8 for greater stability. The solutions may be made more viscous by heating them at 70-100 DEG C. at a pH of 7.0-9.5. Urea, phenol or other similar resin-forming ingredients (a list is given) may be added before or after bodying. The products may be thermoset by heating at 120-175 DEG C. Examples are given of the use of the solutions, with the addition of urea and phenol, as adhesives for plywood. The adhesive solutions before thermosetting may be mixed with walnut shell flour and ammonium chloride as a hardening catalyst. The products may also be set in the cold. The solutions are stated to be useful for many other purposes for which resin-forming solutions are conventionally employed. Specification 641,703 is referred to.ALSO:Stable, clear polymethylol phenol solutions are prepared by heating, at 60-100 DEG C. and at a pH of 7.0-9.5, 4-10 mols. of monomeric aqueous formaldehyde of 58-65 per cent strength with 1 mol. of phenol containing not more than 20 per cent water, until the free formaldehyde content of the mixture is below 35 per cent and cooling the solution to below 30 DEG C. The formaldehyde is kept monomeric by maintaining it at 80 DEG C. from the time of its preparation until the time of its use. The pH of the cooled solutions may be adjusted to 4.5-6.8 for greater stability. Specification 641,703 is referred to.
|
