Trisphenol process

#This invention relates to new trisphenols based on p-isopropenylphenol and to a process for their preparation.

#It is known that p-isopropenylphenol is converted into the dimers (I) and (II) in accordance with the following equation when mildly heated, or even at 25.degree. C, if it is dissolved in a solvent. ##STR1## In the presence of strong acids such as hydrochloric acid, sulphuric acid or phosphoric acid, these dimers are in equilibrium with the carbonium ion of the monomer (III). When reacted with phenol, they are therefore generally not converted into trisphenol (IV) but into bisphenol A ##STR2##

#Even when an attempt is made to reduce the reactivity of the dimers by acylating the phenolic hydroxyl groups, the products obtained under the usual reaction conditions used for alkylating phenols with the aid of acid catalysts are almost exclusively acyl derivatives of bisphenol A. For example monoacetyl bisphenol A (VI) is obtained when the diacetate of dimeric p-isopropenylphenol (V) is reacted with phenol at 50.degree. C while hydrogen chloride is introduced: ##STR3##

#A solution of 268 g (1 mol) of dimeric p-isopropenylphenol with a melting point of 131.degree. C in 500 ml of acetic acid anhydride and 1 ml of pyridine is heated under reflux for 2 hours. Excess acetic acid anhydride is then removed at reduced pressure together with the glacial acetic acid formed, and the reaction product is distilled off as a viscous liquid at 178.degree. to 182.degree. C/0.08 Torr. n.sub.D.sup.20 = 1.549. Yield 342 g = 97% of theoretical.

#A stream of anhydrous hydrogen chloride is introduced into a solution of 176 g (0.5 mol) of the diacetyl compound prepared according to (a) above, in 470 g (5 mol) of phenol and 300 ml of methylene chloride at 0.degree. C in the course of 6 hours until the solution is saturated. The hydrogen chloride, solvent and excess phenol are then removed by heating at reduced pressure to a reaction temperature of up to 200.degree. C. 227 g of residue are obtained. High vacuum distillation yields 36 g of monoacetyl bisphenol A at between 195 .degree. to 210.degree. C/0.04 Torr and 190 g of a 2,4-di-(4'-acetoxyphenyl)-2-(4"-hydroxyphenyl)-4-methyl-pentane fraction at 250.degree. to 270.degree. C/0.04 Torr. Yield: 85% of the theory.

#By boiling in excess 2N sodium hydroxide solution until a clear solution is obtained, acidification with dilute acetic acid, dissolving the trisphenol in ethyl acetate and removing the solvent, trisphenol of the formula given below is obtained in the form of a hard resin. The melting point is between 150.degree. and 152.degree. C after recrystallisation from ethylene chloride. ##STR8##