GB795278A - Improvements relating to the manufacture of liquid synthetic resins for the stiffening of leather parts of footwear and to a process for stiffening such leather parts - Google Patents

Abstract

A solution of pH 3.0-5.5 of a resin of the resole type prepared from an hydroxy benzene or substituted hydroxy benzene and formaldehyde is used for hardening leather. The specified resole is prepared from one mol. of phenol and two mols. of formaldehyde and the condensation is carried so far that the viscosity of the resole at a concentration of 59 \sB 1 per cent by weight in ethyl alcohol is 200-400 centipoises at 25 DEG C. Specified solvents are alcohols, ketones, esters, hydrocarbons, water and mixtures of these. Specified acidifying agents are formic acid, paratoluene sulphonic acid and mixtures of these. Concentration of resole in solvent may be 60 per cent or less. In Example (1) the resin solution is prepared by condensing one mol. of phenol with two mols. of formaldehyde in an aqueous medium, adjusting the pH to 8.5-9.0 and refluxing at 97 DEG C. for 40 minutes followed by dehydration under vacuum at below 65 DEG C. until a sample of the resin solution resulting dissolved in industrial ethyl alcohol to a concentration of 59 \sB 1 per cent by weight yields a solution of viscosity 200-400 centipoises at 25 DEG C. This resin is then diluted with industrial ethyl alcohol to a resin concentration of 60 per cent by weight and formic acid added to give a pH of 4.5. In Example (2) a resin prepared as in Example (1) is dissolved in industrial ethyl alcohol and the pH adjusted to 3.5 by adding a mixture of equal parts of formic acid and paratoluene sulphonic acid and the resin concentration adjusted to 30 \sB 1 per cent by weight with a viscosity of less than 10 centipoises.