Preparation of low molecular weight polyhydroxyl compounds

Claim 1

In a process for the preparation of mixtures of low molecular weight polyhydroxyl compounds and hydroxyl aldehydes and hydroxy ketones by condensation of formaldehyde in the presence of compounds of divalent lead as catalysts and in the presence of co-catalysts containing a mixture of hydroxy aldehydes and hydroxy ketones, at a reaction temperature of from 70° to 110° C., the improvement which comprises (1) condensing aqueous formalin solutions and/or paraformaldehyde dispersions containing from 20 to 65% by weight of formaldehyde in the presence of: (a) soluble or insoluble lead (II) salts or divalent lead attached to a high molecular weight resinous carrier; and (b) a co-catalyst comprising a mixture of hydroxy aldehydes and hydroxy ketones obtainable by condensation of formaldehyde, which mixture contains at least 75% by weight of C 3 -C 6 -compounds and is characterized by the following molar ratios: compounds having 3 carbon atoms/compounds having 4 carbon atoms from 0.5:1 to 2.0:1; compounds having 4 carbon atoms/compounds having 5 carbon atoms from 0.2:1 to 2.0:1; compounds having 5 carbon atoms/compounds having 6 carbon atoms from 0.5:1 to 5.0:1; (2) maintaining the pH of the reaction solution at from 6.0 to 7.0 by controlled addition of inorganic or organic base until from 10 to 60% by weight of the starting material has undergone reaction, (3) thereafter, lowering the pH of the reaction solution by from 0.5 to 3.0 units to a pH of from 4 to 6, (4) continuing the reaction at a pH of from 4.0 to 6.0, and (5) stopping the self-condensation of formaldehyde hydrate by cooling and/or by inactivation of the lead catalyst by means of acids when the residual formaldehyde content in the reaction mixture is from 0 to 10% by weight of formaldehyde and thereafter removing the catalyst in the known manner.