A continuously conducted process for the preparation of 3,3,5-trimethylcyclohexylidene bisphenol (BP-TMC) in the presence of a gaseous acidic catalyst, wherein the gaseous acidic catalyst comprises hydrogen sulfide and hydrogen chloride, comprising at least the following steps: either providing a separate first stream comprising: (i) 3,3,5-trimethylcyclohexanone (TMC-one), the TMC-one having a purity of at least 90 wt.-%, preferably of at least 95 wt.-%, more preferably of at least 98 wt.-%, and the TMC-one comprising less than 1 wt.-%, preferably less than 0.5 wt.-%, more preferably less than 0.2 wt.-%, most preferably less than 0.1 wt.-%, phenol, (ii) a gaseous acidic catalyst; providing a separate second stream comprising: (iii) phenol, (iv) further components; or providing a separate first stream comprising: (v) phenol, the phenol having a purity of at least 90 wt.-%, preferably of at least 95 wt.-%, more preferably of at least 99 wt.-%, most preferably of at least 99.9 wt.-%, and the phenol comprising less than 0.5 wt.-%, preferably less than 0.2 wt.-%, more preferably less than 0.1 wt.-%, most preferably less than 0.05 wt.-% TMC-one, (vi) a gaseous acidic catalyst; providing a separate second stream comprising: (vii) phenol, (viii) TMC-one, (ix) further components; and then (c) bringing together the first stream and the second stream in a reaction vessel to form a reaction mixture. providing a separate first stream comprising: (i) 3,3,5-trimethylcyclohexanone (TMC-one), the TMC-one having a purity of at least 90 wt.-%, preferably of at least 95 wt.-%, more preferably of at least 98 wt.-%, and the TMC-one comprising less than 1 wt.-%, preferably less than 0.5 wt.-%, more preferably less than 0.2 wt.-%, most preferably less than 0.1 wt.-%, phenol, (ii) a gaseous acidic catalyst; (i) 3,3,5-trimethylcyclohexanone (TMC-one), the TMC-one having a purity of at least 90 wt.-%, preferably of at least 95 wt.-%, more preferably of at least 98 wt.-%, and the TMC-one comprising less than 1 wt.-%, preferably less than 0.5 wt.-%, more preferably less than 0.2 wt.-%, most preferably less than 0.1 wt.-%, phenol, (ii) a gaseous acidic catalyst; providing a separate second stream comprising: (iii) phenol, (iv) further components; or (iii) phenol, (iv) further components; or providing a separate first stream comprising: (v) phenol, the phenol having a purity of at least 90 wt.-%, preferably of at least 95 wt.-%, more preferably of at least 99 wt.-%, most preferably of at least 99.9 wt.-%, and the phenol comprising less than 0.5 wt.-%, preferably less than 0.2 wt.-%, more preferably less than 0.1 wt.-%, most preferably less than 0.05 wt.-% TMC-one, (vi) a gaseous acidic catalyst; (v) phenol, the phenol having a purity of at least 90 wt.-%, preferably of at least 95 wt.-%, more preferably of at least 99 wt.-%, most preferably of at least 99.9 wt.-%, and the phenol comprising less than 0.5 wt.-%, preferably less than 0.2 wt.-%, more preferably less than 0.1 wt.-%, most preferably less than 0.05 wt.-% TMC-one, (vi) a gaseous acidic catalyst; providing a separate second stream comprising: (vii) phenol, (viii) TMC-one, (ix) further components; and then (vii) phenol, (viii) TMC-one, (ix) further components; and then (c) bringing together the first stream and the second stream in a reaction vessel to form a reaction mixture.