Patent GB-431945-A (GB)
Title: Improvements in or relating to the manufacture of polynuclear phenols
IPC: C10L1/183
Filed: 1934-01-18
Abstract: Polynuclear phenols are prepared by condensing phenol or its homologues with an aldehyde or ketone in the presence of an acid condensing medium, e.g. sulphuric acid, and an acid-soluble boron compound.  The products are dihydroxy-di-or-tri-arylalkanes.  Di (4-hydroxy-phenyl) dimethylmethane is best prepared by using phenol and acetone in theoretical proportions, 4 to 5 mols of sulphuric acid per mol of phenol, an acid concentration of 65--70 per cent and by keeping the temperature in the early stages at 25--35 DEG  C., and later at 45--55 DEG  C.  About 0,5--5 per cent of boric acid, based on the weight of phenol, is sufficient. Efficient stirring is necessary.  For example, 4,4 mols H2SO4 (diluted to 70 per cent) per mol of phenol and 2,3 per cent boric acid may be used, the reagents being heated for 6 hours at 45--50 DEG  C., and then for 12 hours at 55--60 DEG  C. The temperature may range up to 65 DEG  C., the ratio of phenol to acetone may vary somewhat, the molar ratio of sulphuric acid to phenol may vary from about 2 : 1 to 6 : 1, and the acid concentration from 65--75 per cent by weight.  o- or m-cresol, o-butyl-or o-chloro-phenol may replace phenol, and acetaldehyde, benzaldehyde, n-butyraldehyde, methylethylketone, dipropyl ketone, or cyclohexanone may replace acetone.  Hydrochloric acid may replace the sulphuric acid and, in place of boric acid, borax, sodium metaborate or perborate, or boron oxide may be used.  The products may be employed in making synthetic resins, as anti-oxidants and polymerization inhibitors for motor spirit, paints and varnishes, as insecticides, (either as the phenol or its salts), or dye intermediates, or can be nitrated to form explosives, or sulphonated to give wetting dispersing or emulsifying agents.  An example describes the preparation of di (4-hydroxyphenyl) dimethylmethane the molar ratio of phenol, acetone and sulphuric acid (67,5 per cent) being 1,0 : 0,5 : 4,33, 1,75 per cent boric acid being used.  The acetone is added to the molten phenol, the mixture cooled to 25 DEG C., and the boric acid dissolved in sulphuric acid added.  The mixture is refluxed at 30--35 DEG  C., for 15 hours with stirring, the temperature then being raised to 50 DEG  C., for 12 hours.  The product is filtered and washed with a little water, suspended in water, 10 per cent NaOH added until basic to litmus (pH at least 7), washed with water, and phenol removed by steam distillation after adding hydrochloric acid until acid to Congo red.  The product is cooled while stirring, filtered, washed, and dried.  The Specification as open to inspection under Sect. 91 comprises also the preparation of sulphones using sulphur trioxide in place of the aldehyde or ketone.  This subject-matter does not appear in the Specification as accepted.ALSO:Polynuclear phenols, obtained by condensing phenol or its homologues with an aldehyde or ketone, are used as anti-oxidants and polymerization inhibitors for motor spirit, paints, and varnishes.  They can be sulphonated to form dispersing or emulsifying agents.  The Specification as open to inspection under Sect. 91 comprises also the sulphones obtained with sulphur trioxide in place of the aldehyde or ketone.  This subject-matter does not appear in the Specification as accepted.