GB648844A - Improvements in heat-reactive resin-impregnated sheets for adhesive purposes - Google Patents

Abstract

A composition for impregnating paper to make "film glue" comprises an aqueous solution having a pH value between 7 and 9 of a permanently fusible dihydroxybenzene-aldehyde resin and hexamethylene tetramine. The dihydroxybenzene may be resorcinol, catechol, or hydroquinone, and the aldehyde may be formaldehyde, acetaldehyde, paraldehyde, propionaldehyde, a butyl aldehyde, furfuraldehyde, a dialdehyde such as glyoxal or a mixture such as formaldehyde and butyl aldehyde. A minor amount of the dihydroxybenzene may be replaced by phenol, cresylic acid, or xylenol. The resins described in Specification 582,448 may be used. A resorcin-formaldehyde resin is made by heating resorcin and formaldehyde solution up to 100 DEG C., adding further formaldehyde with stirring, adding oxalic acid, and refluxing for 5 minutes. Water is added, the reaction mass may be cooled, and the pH value adjusted to between 7 and 9 by addition of alkali such as sodium, potassium, lithium, or ammonium hydroxide or carbonate. The resulting solution may be stored for months without deterioration, and for use in impregnating paper, is made heat-reactive by adding an aqueous solution of hexamethylenetetramine. The Specification as open to inspection under Sect. 91 comprises also the use, instead of a dihydroxy benzene, of secondary alkyl resorcins, resorcin ethers such as monomethyl resorcin ether, resorcin esters such as resorcin disulphonic esters, and trihydroxy-benzenes such as pyrogallol and phloroglucinol. This subject-matter does not appear in the Specification as accepted.