Process of producing improved epoxy resin compositions

Polyglycidyl ethers of polyhydric phenols having an improved working time during curing with organic polybasic acid anhydrides to hard resins (see Group IV (a)) are obtained by reacting a polyhydric phenol with an epihalohydrin in an alkaline medium using proportions such that the resulting ether has an average number of epoxy groups per molecule greater than 1, and washing the product with water acidified to an extent such that the pH of the water during the washing does not exceed 5.5 and then washing with water to remove residual acid. The aqueous acid washing is said to cause a physical change in the structure of the glycidyl ether. This washing is preferably preceded by a washing with water to remove lower alcohols, alkali metal salts and excess alkali. Examples describe the preparation of polyglycidyl ethers from epichlorhydrin and 2,2 - bis - (4 - hydroxyphenyl) propane wherein aqueous caustic soda is added portionwise to the reaction mixture at 50-92 DEG C.; the reaction mixture is thereafter washed with distilled water, then with water containing formic, acetic, sulphuric or hydrochloric acid at a pH of 2.7 to 5.2 and finally with distilled water and dried. Other polyhydric phenols mentioned are alkylated or non-alkylated resorcinols, catechols, pyrogallols and hydroquinones, 4,41-dihydroxybenzophenone, 1:1 - bis - (4 - hydroxyphenyl) ethane and condensation products of phenols, such as phenol or cresol, with aldehydes, e.g. formaldehyde.ALSO:Polyglycidyl ethers which give an improved working time in curing to a hard resinous mass with the usual acid curing agents, e.g. polybasic acid anhydrides, are obtained by reacting polyhydric phenols with epihalohydrins in the presence of alkali in such proportions that the average number of epoxy groups per molecule in the ether is greater than one, washing the product with water to remove lower alcohols, alkali metal salts and excess alkali and further washing with water acidified to the extent that the washing water does not exceed a pH value of 5.5, preferably 2-4.5, the excess acid being removed by a final washing with water. The washing with strong acid is sated to cause a physical change in the structure of the product. A solution of 152 gs 2.2-bis(4-hydroxyphenyl) propane in 402 gs 9 per cent NaOH is heated to 50 DEG C. and 101.8 gs epichlorhydrin added, the temperature rising to 72 DEG C. in 9 mins. and being then increased to 92 DEG C. for 20 mins. after which a further 82.8 gs NaOH solution are ad