GB618093A - New and improved impregnating and adhesive compositions - Google Patents

Abstract

An adhesive comprises 3 : 5-xylenol, formaldehyde or a formaldehyde-liberating substance (e.g. paraformaldehyde, hexamethylenetetramine, dimethylol urea, and methylol melamines), and a thermosetting condensation of formaldehyde acid or phenol and/or m-cresol or mixtures of cresols containing not less than 40 per cent m-cresol, the molar proportion of formaldehyde or its equivalent to xylenol being 1 : 1 to 3 : 1 and the molar ratio of xylenol to the phenolic constituent of the condensate being 0.1 : 1 to 2 : 1. The condensates may be prepared in aqueous solution and may be partly dehydrated, or may be spray dried and dissolved in e.g. water, acetone or alcohol, xylenol and paraformaldehyde being then dissolved therein, and the mixture if desired, spray dried; or a powdered condensate may be mixed with xylenol and paraformaldehyde either dry or in solution, e.g. in water, acetone or methanol, in which an acidic substance may also be present. The preferred molar ratio of total formaldehyde to phenol (and/or cresol) plus xylenol is 2 : 1 to 2.5 : 1, and that of xylenol to phenol (and/or cresol) is 1 : 3. Fillers, e.g. wood flour, may be added. In examples: (1), (2) aqueous formaldehyde and phenol in a molar ratio of 2.2 : 1 are condensed in the presence of caustic soda; paraformalde and 3 : 5-xylenol in the molar ratio of 2.2 : 1 were dissolved in this condensate in such quantities that the molar ratio of xylenol to phenol was (1) 1 : 3, (2) 5 : 3, mixed with wood flour and used as a plywood adhesive; (3), (4) the condensate of example 1 was dehydrated to a viscous syrup, mixed with xylenol, paraformaldehyde, wood flour and p-toluene sulphonamide and used as a plywood adhesive. Specification 558,745 is referred to. Reference has been directed by the Comptroller to Specification 607,104.