PROCESS FOR PREPARING BIPHENYL-2,2'-DIOLS

1 . Process comprising the process steps of:

a) adding sodium n-dodecyl sulfate,

b) adding a base,

c) adding a phenol of the formula (I):

where R 1 , R 2 , R 3 , R 4 are selected from:

—H, —(C 1 -C 12 )-alkyl, —O—(C 1 -C 12 )-alkyl, —(C 6 -C 20 )-aryl, —O—(C 6 -C 20 )-aryl:

wherein the alkyl groups and aryl groups cited may be substituted as follows:

substituted —(C 1 -C 12 )-alkyl groups, substituted —O—(C 1 -C 12 )-alkyl, substituted —(C 6 -C 20 )-aryl, substituted —O—(C 6 -C 20 )-aryl may have one or more substituents; the substituents are each independently selected from: —(C 1 -C 12 )-alkyl, —O—(C 1 -C 12 )-alkyl, halogen,

d) heating the reaction mixture of a) to c),

e) adding hydrogen peroxide to the reaction mixture,

f) cooling the reaction mixture so that the product (II) precipitates:

2 . Process according to claim 1 ,

where R 1 , R 2 , R 3 , R 4 are selected from:

—H, —(C 1 -C 12 )-alkyl, —O—(C 1 -C 12 )-alkyl.

3 . Process according to claim 1 , where R 2 and R 4 are each —H.

4 . Process according to claim 1 , where R 1 and R 3 are selected from:

—(C 1 -C 12 )-alkyl, —O—(C 1 -C 12 )-alkyl.

5 . Process according to claim 1 , where R 1 and R 3 are —(C 1 -C 12 )-alkyl.

6 . Process according to claim 1 , wherein the phenol (I) has the structure (3):

7 . Process according to claim 1 , wherein the base in process step b) is sodium hydroxide.

8 . Process according to claim 1 , wherein the heating in process step d) is carried out at a temperature in the range from 50° C. to 100° C.

9 . Process according to claim 1 , wherein the addition of hydrogen peroxide in process step e) is carried out by dropwise addition of a hydrogen peroxide solution.

10 . Process according to claim 1 , wherein the temperature set in process step d) is maintained during the addition of hydrogen peroxide.

11 . Process according to claim 1 , wherein the temperature set in process step d) is maintained over a period in the range from 10 minutes to 2 hours after the addition of hydrogen peroxide.

12 . Process according to claim 1 , comprising the additional process step f2):

f2) active cooling of the reaction mixture.

13 . Process according to claim 12 ,

wherein the active cooling is effected with the aid of an ice bath.

14 . Process according to claim 1 , comprising the additional process step g):

g) washing the precipitated product with water.