DE1145630B - Process for the preparation of antioxidant, alkyl-substituted bis (4-hydroxyphenyl) sulfides - Google Patents

Description

Process for the preparation of antioxidant, alkyl-substituted bis (4-hydroxyphenyl) sulfides The process according to the invention for the preparation of antioxidant alkyl-substituted bis (4-hydroxyphenyl) sulfides consists in using a phenol of the general formula in which R denotes an alkyl group with 3 to 4 carbon atoms branched on the a carbon atom and R 'denotes an alkoxy group with 1 to 4 carbon atoms or an alkyl group with 1 to 4 carbon atoms, to be reacted with sulfur monochloride or sulfur dichloride in a manner known per se, the obtained Compounds, optionally with 1 or 2 equivalents of free sulfur, per equivalent of phenol nucleus, are reacted further.

The compounds prepared according to the invention have the formula in which R and R 'have the meanings given above and x is an integer from 1 to 3.

Examples of compounds according to the invention are: Bis- (3,5 -ditert. -butyl -4-hydroxyphenyl) sulfide, bis- (3-methyl - 5- isopropyl - 4 - hydroxyphenyl) - sulfide, bis - (3 - ethyl - 5 - sec-butyl-4-hydroxyphenyl) - sulfide, bis - (3.5 - diisopropyl - 4 - hydroxyphenyl) sulfide, bis (3 -methyl-5-tert-butyl- 4-hydroxyphenyl) - sulfide, bis- (3-n-butoxy-5-tert-butyl-4-hydroxyphenyl) -sulfide, bis- (3-methoxy-5-sec. -butyl-4-hydroxyphenyl) sulfide, bis - (3 -n -propyl - 5-tert-butyl-4-hydroxyphenyl) disulfide, bis (3-methyl-5-tert-butyl-4-hydroxyphenyl) trisulfide.

The alkyl radicals represented by R in the above formula include the isopropyl, tert-butyl and sec-butyl radical. It was found that Compounds containing these residues are extremely effective antioxidants in synthetic hydrocarbon polymers. It turned out that connections in the formula R denotes a tert-butyl or isopropyl radical, outstanding qualities as antioxidants for saturated hydrocarbon polymers. Particularly preferred compounds are those in which x is in the formula given above the value 1 is assigned, d. H. Bis-phenol sulfides, in which the phenol rings are in the 3,5-position are disubstituted. Of these compounds are bis (3-methyl-5-tert-butyl-4-hydroxyphenyl) sulfide and bis- (3,5-di-tert-butyl-4-hydroxyphenyl) sulfide because of their low content Cost price and its outstanding antioxidant effect the most preferred.

The compounds can be prepared by the following methods. It can be either sulfur monochloride, S2Cl2, or sulfur dichloride, sich, with the Parent phenol are implemented. If a compound with two or three the phenolic rings connecting sulfur atoms is desired, so the product of the reaction of sulfur chloride and phenol are further reacted with free sulfur. For the preparation of a particular compound of the invention, namely bis (3,5-di-tert-butyl-4-hydroxyphenyl) sulfide, a special procedure is applicable. This connection is created during implementation of sulfur dichloride with 2,6-di-tert-butylphenol, but it has been shown that she can also be produced by a process which involves the conversion of an alkali salt of 2,6-di-tert-butylphenol with sulfur dichloride. This manufacturing method cannot be used for the other bis-phenol sulfides as the phenol starting materials do not form any alkali metal salts which are chemically equivalent to the salt of 2,6-di-tert.-butylphenol.

The compounds obtainable according to the invention are useful as antioxidants the bis (2-methyl-5-tert-butyl-4-hydroxyphenyl) sulfide known from British patent specification 780 289 considerably superior, as has been determined on the basis of comparative tests.

The following examples illustrate the process according to the invention to make the connections.

All parts are parts by weight.

Example 1 4920 parts of 2-methyl-6-tert-butylphenol were in 2700 Parts dissolved low-boiling petroleum ether. The mixture was placed in a reaction vessel introduced with stirring device and devices for external cooling. Then were with stirring, 1545 parts of sulfur dioxide in 750 parts of low-boiling petroleum ether added in the following way: The reaction vessel was kept at 15 to 17 "C, while the sulfur dichloride solution was slowly added.

After adding about 45010 of the sulfur dichloride, a white color fell Solid substance that made the reaction mass extremely viscous and the temperature Allowed to rise to about 18 "C. At this point, there were another 1200 parts of petroleum ether added so that the reaction mixture could be easily stirred. In accordance with the further addition of sulfur dichloride further solvent was introduced at periodic intervals, around the reaction mass in a sufficiently liquid state to carry out the stirring to keep. In the course of the addition of sulfur dichloride, a total of 2400 parts became lower boiling point Petroleum ether also brought in. After the addition of sulfur dichloride is complete the reaction mass was heated to 28 ° C. with stirring and a further 1 hour between 28 and 30 "C held.

Then the reaction mass was cooled to 10 "C and 1/2 hour at this temperature was maintained, after which it was filtered. The dry pressed solid substance was then slurried with petroleum ether and the mixture filtered again and pressed dry.

There were thus 3800 parts of bis (3-methyl-5-tert-butyl-4-hydroxyphenyl) sulfide obtained from m.p. 124 to 125 "C, which corresponds to a yield of 71010.

Example 2 A solution of 34 parts of freshly distilled sulfur dichloride in about 25 parts of petroleum ether was slowly stirring a solution of 123.6 Parts of 2,6-di-tert-butylphenol in 60 parts of petroleum ether are added. Here gave half of the sulfur dichloride was added slowly at 20 to 25 ° C. and the mixture was heated then under reflux, it then cooled to 25 "C and gave the remaining sulfur dioxide slowly to. The mixture was then refluxed for 99 hours.

After removal of the solvent and volatile constituents in the The remaining brownish-black oil was vacuum distilled and the residue crystallized fractionally from methanol. The third Crystallization Fraction provided 5 parts of bis- (3, 5-di-tert-butyl-4-hydroxyphenol) -suffid vom F. = 138 to 140 "C.

Analysis: Calculated ..... 5 7.24%; found . . . .. S 7.5 ° / 0.

The methanol solution from which the bis- (3,5-di-tert-butyl-4-hydroxyphenyl) sulfide was obtained, it was left to stand for a long time, whereby a further 2 parts crystallized Material were obtained. Recrystallization of this material from 95 above methanol yielded bis (3,5-di-tert-butyl-4-hydroxyphenyl) trisulfide in the form of yellow crystals from F. = 129 to 130 "C.

Analysis: Calculated ... ... 5. s 18.97%; found . . .. 5 19.0 0 / o.

Example 3 360 parts of freshly distilled o-tert-butylguaiacol from Bp 6.5 = 117 to 121 "C were stirred in a reaction vessel with a low boiling point Diluted petroleum ether and at 10 to 15 "C with 103 parts of sulfur dichloride, too diluted with low-boiling petroleum ether, slowly added. After the addition of sulfur dichloride is complete the reaction mixture was warmed to 30 "C and about 2 days at room temperature ditched. The reaction mixture was then first with water, then washed with aqueous sodium bicarbonate solution and again with water and washed over calcium sulfate dried. After drying and removing the solvent in vacuo (0.1 mm Hg) at 95 ° C., 230 parts of bis (3-methoxy-5-tert-butyl-4-hydroxyphenyl) disulfide were obtained obtained as a residue.

Analysis: Calculated ... .. 5 1 5,201o; found ... . .. SI 5.70 / o.

Example 4 The procedure described in Example 1 is followed however, after the addition of the sulfur dichloride, the reaction mixture contains 960 parts of sulfur and thus receives bis (3-methyl-5-tert.-butylffihydroxyphenyl) disulfide of melting point 84 up to 86.5 "C in good yield.

Claims (2)

PATENT CLAIMS: 1. Process for the preparation of antioxidant, alkyl-substituted bis (4-hydroxyphenyl) -sufflden, characterized in that a phenol of the general formula in which R is an alkyl radical with 3 to 4 carbon atoms branched on the a-carbon and R 'is an alkoxy radical with 1 to 4 carbon atoms or an alkyl radical with 1 to 4 carbon atoms, is reacted with sulfur monochloride or sulfur dichloride in a manner known per se. 2. Further development of the method according to claim 1, characterized in that that the product obtained contains 1 or 2 equivalents of free sulfur, per equivalent Phenolic nucleus, is implemented. Publications considered: German Patent No. 753 626; French Patent No. 824600; U.S. Patent No. 2,605,288, 2,670,383; British Patent No. 780289.