Claims
- 1. A method for producing 1-naphthol-4-sulphonic acid in free acid form contaminated with less than 2% by weight of 1-naphthol-2-sulphonic acid, by sulphonating 1-naphthol in a solvent which is substantially inert towards the sulphonating agent and in which 1-naphthol-4-sulphonic acid has a solubility at a temperature >50.degree. C. of from 0.01 to 5.0% by weight, which comprises the step of separating the 1-naphthol-4-sulphonic acid from the reaction mixture by filtration at a temperature >50.degree. C. directly after completion of the sulphonation.
- 2. A method according to claim 1, in which the solvent is selected from halogenated aliphatic hydrocarbons and aromatic monocyclic hydrocarbons which are optionally nitrated or halogenated.
- 3. A method according to claim 1, in which the solvent is selected from benzene, toluene, xylene, nitrobenzene, nitrotoluene, monochlorobenzene, dichlorobenzenes, trichlorobenzenes, chloroform, trichloroethylene, 1,1,1- or 1,1,2-trichloroethane, tetrachloroethylene or 1,1,2,2-tetrachloroethane.
- 4. A method according to claim 1 in which the solvent is used in an amount from 2 to 20 times the amount of 1-naphthol.
- 5. A method according to claim 1, in which the sulphonating agent is chlorosulphonic acid.
- 6. A method according to claim 5, in which chlorosulphonic acid is added at a temperature from -20.degree. to +20.degree. C. in an excess from 5 to 20% by weight when the solvent is an aromatic monocyclic hydrocarbon.
- 7. A method according to claim 5, in which chlorosulphonic acid is added at a temperature >20.degree. C. in a stoichiometric amount or in an excess up to 5% by weight when the solvent is an halogenated or nitrated hydrocarbon.
- 8. A method according to claim 1, in which the reaction mixture is heated at a temperature >50.degree. C. after addition of the sulphonating agent.
- 9. A method according to claim 1, in which the reaction mixture is heated at a temperature from 60.degree. to 100.degree. C. after addition of the sulphonating agent.
- 10. A method according to claim 1, in which filtration of the reaction mixture is carried out at the same temperature at the reaction.
- 11. A method according to claim 1, in which filtration is carried out at a temperature from 60.degree. to 100.degree. C.
- 12. A method according to claim 1 in which the content of 1-naphthol-2-sulphonic acid in the final product is up to 0.5% by weight based on the weight of 1-naphthol-4-sulphonic acid.
- 13. A method according to claim 8 in which filtration of the reaction mixture is carried out at the same temperature as the reaction.
- 14. A method according to claim 9 in which filtration of the reaction mixture is carried out at a temperature of 60.degree.-100.degree. C.
- 15. A method according to claim 9 in which filtration of the reaction mixture is carried out at the same temperature as the reaction.
- 16. A method according to claim 13 in which the amount of solvent is 2 to 20 times the amount of 1-naphthol by weight.
- 17. A method according to claim 14 in which the amount of solvent is 2 to 20 times the amount of 1-naphthol by weight.
- 18. A method according to claim 14 in which the solvent is selected from the group consisting of benzene, toluene, xylene, nitrobenzene, nitrotoluene, monochlorobenzene, dichlorobenzene, trichlorobenzene, chloroform, trichloroethylene, 1,1,1- and 1,1,2-trichloroethane, tetrachloroethylene and 1,1,2,2-tetrachloroethane.
- 19. A method according to claim 14 in which the sulphonating agent is chlorosulphonic acid.
- 20. A method for producing 1-naphthol-4-sulphonic acid in free acid form contaminated with less than 2% by weight of 1-naphthol-2-sulphonic acid which comprises dissolving 1-naphthol in a solvent selected from the group consisting of aromatic monocyclic hydrocarbons, which may be nitrated or halogenated, and halogenated aliphatic hydrocarbons and in which 1-naphthol-4-sulphonic acid has a solubility of from 0.01 to 5.0%, by weight, at a temperature >50.degree. C., adding chlorosulphonic acid to the dissolved 1-naphthol in an amount ranging from stoichiometric to 20%, by weight, in excess of stoichiometric and at a temperature of -20.degree. to 120.degree. C., heating the resulting reaction mixture for 1-12 hours at a temperature >50.degree. C. after completing addition of the chlorosulphonic acid and, directly thereafter, filtering the reaction mixture at a temperature >50.degree. C. at which 1-naphthol-4-sulphonic acid has the said solubility in said solvent.
Parent Case Info
This application is a continuation-in-part of Application Ser. No. 597,172, filed Apr. 5, 1984 and now abandoned.
US Referenced Citations (4)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
597172 |
Apr 1984 |
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