JPS6368535A - Purification of p,p'-alkylbiphenols - Google Patents

Abstract

PURPOSE:To obtain readily the titled white, high-purity compound useful especially as a raw material for resins, by treating the titled compound containing diphenoquinones with sodium dithionite in a hydrous organic solvent having compatibility with water in an inert gas atmosphere. CONSTITUTION:A p,p'-alkylbiphenol containing diphenoquinones, obtained by oxidation coupling of an alkylphenol, is reduced with 0.1-50wt% based on the crude alkylbiphenol of sodium dithionite in a hydrous organic solvent (preferably hydrous methanol, hydrous acetone, hydrous THF, especially hydrous methanol) in an inert gas atmosphere and the diphenoquinones are readily removed to give a white, high-purity alkylbiphenol industrially advantageously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for obtaining highly pure p,p'-alkylbiphenols. p,p'-alkylbiphenols are used as various chemical intermediates, monomers for producing copolymers,
It is useful as an antioxidant and a petroleum product stabilizer, and high-purity reeds are in demand, especially as raw materials for resins.

[Conventional technology]

As a method for producing p,p'-alkylbiphenols, for example, a method of t-il coupling of alkylphenols in an organic solvent (U.S. Pat. No. 4,180,686, British Patent No. GG2,047,232) ) is known, but in this method it is difficult to stop the oxidative coupling at the biphenol stage, and the main products are diphenoquinone and polyphenylene ether. Furthermore, a method of oxidative coupling of alkylphenols using a copper amine complex as a catalyst in an aqueous solvent (JP-A-53-65-8
No. 34), the biphenols obtained by washing the obtained oxidative coupling product with an organic solvent are yellow solids because they entirely contain a small amount of nophenoquinones.

Even if a small amount of these diphenoquinones is contained, they are markedly colored and difficult to separate and remove, so it is not easy to obtain white high-purity biphenols.

[Problem that the invention seeks to solve]

Biphenols are solid at room temperature, have a high melting point, and are difficult to purify by distillation, and there is no suitable solvent and it is difficult to completely remove diphenoquinones by recrystallization.
If kept, purification method by replacing solvent (JP-A-59-98
No. 027) has been proposed, but it requires distillation removal of a large amount of solvent and the operation is complicated. The present invention uses crude alkylbiphenols including diphenoquinones obtained by oxidative coupling of alkylphenols.
The object of the present invention is to provide a method for easily removing diphenoquinone gold and obtaining white, highly pure alkylbiphenol gold that is industrially advantageous.

[Means for solving problems]

The present invention is characterized in that p,p'-alkylbiphenols including diphenoquinones are treated with sodium dithionite in a water-containing organic solvent that is compatible with water and under an inert gas atmosphere. This is a method for purifying alkyl biphenols.

The p,p'-alkylbiphenols that are the object of the present invention are compounds represented by the general formula obtained by oxidative coupling of alkylphenols, such as 3.3', 5°5'
The position is methyl group, ethyl group, n-propyl group, 1-propyl group, r-butyl group, isobutyl group, 160-butyl group, t-butyl group, r-amyl group, isoamyl group, a@a
-7 Substituted with mil group, t-amyl group, etc., p, p'
-It is a biphenol and contains diphenoquinone at- as an impurity. The content of diphenoquinone varies depending on the reaction conditions of oxidative coupling, but is usually 5.
Heavy fk- or less, generally 1! The amount is less than or equal to 0.5% by weight, preferably less than 0.5% by weight.

Examples of organic solvents that are compatible with water used in the present invention include organic solvents that are compatible with water in any proportion, specifically, aliphatic lower alcohols such as methanol, ethanol, n-glopanol, and isoglopanol, and acetone. Ketones such as
THF, cyclic nityl compounds such as 1,3-dioxane, 1,4-dioxane, etc., DMF', DMS
O etc. are exemplified.

Among these, methanol, acetone and THF are preferred - methanol is particularly preferred.

The solvent can be used alone or in a mixed system of two or more. Alternatively, one to which water has been added in advance may be used.

The amount of solvent used to dissolve crude alkyl biphenols is
Since it varies depending on the type of alkylbiphenol and the processing temperature, it cannot be specified as a rule, but those with low solubility of alkylbiphenol are approximately 30 parts by weight per 1 part by weight of alkylbiphenol, and those with high solubility are approximately 30 parts by weight per 1 part by weight of alkylbiphenol. 5 parts by weight or more is preferred. When the treatment is carried out in a pressurized system at a higher temperature, the amount of solvent used can be smaller than the above amount.

In the method of the present invention, the obtained NFC solution is subjected to a reduction treatment using sodium dithionite under an inert gas atmosphere in a water-containing state. The amount of water should be within a range that dissolves the p, p'-alkylbiphenols and sodium dithionite, and is usually added as an aqueous solution of sodium dithionite. The amount of sodium dithionite used in the present invention depends on the amount of diphenoquinones contained in the alkylbiphenols, but is at least 0.1% by weight to 50% by weight based on the crude alkylbiphenols.
A weight percent range is preferred.

It is usually sufficient for the treatment temperature to range from 0° C. to the boiling point of the solvent used, but if the entire treatment is carried out in a pressurized system, no problem will arise even if the treatment is carried out at a temperature exceeding the boiling point of the solvent.

Since the treatment time varies depending on the treatment temperature, it is difficult to define it uniformly, but one hour or less is usually sufficient.

The product can be isolated by precipitating it by adding water or a solvent with a low ability to dissolve alkyl biphenols to a solution that has undergone the entire treatment with sodium dithionite, or by precipitating the product by adding water or a solvent with a low ability to dissolve alkyl biphenols to the solution that has undergone the entire treatment with sodium dithionite, or by precipitating the product by adding water or a solvent with a low ability to dissolve alkyl biphenols to the solution that has already been treated with sodium dithionite. High purity white alkyl biphenols can be easily obtained by removing the solvent by distillation and then adding water or a solvent with a low ability to dissolve the alkyl biphenols to precipitate the alkyl biphenols.

〔Example〕

The present invention will be explained in more detail below by way of practical examples.

Example 1 Yellow-green 3.3',5.5'-tetramethyl-4,4'
- 500 ml of crude di-and-droxydiphenyl product (containing 0.09% of 1-tetramethyldiphenoquinone) - Dissolved by heating in 7000 g of methanol under a stream of nitrogen. Add sodium dithionite 3 (ltloo) to this solution.

Above the aqueous solution of No. 9 dissolved in water, under refluxing methanol, No. 1
Heat and stir for nine hours. After cooling to room temperature, 10kl? of water was added to precipitate crystals, filtered, collected, and dried to yield white 3.3',5.5'-tetramethyl-4,4'-dihydroxydiphenyl 462! ! (Tetramethyldiphenoquinone 0.001 weight or less, recovery rate 92.4%) t' was obtained.

Example 2 In Example 1, in place of methanol, 5o
The same operation as in Example 1 was carried out except that oo and vt were used. .001 weight or less, recovery rate 91.2%) was obtained.

Example 3 In Example 1, THFsoo was used instead of methanol.
The same operation as in Example 1 was carried out except that oJi't- was used, and 453 g of white 3.3',5.5'-tetramethyl-4,4'-di and droxydiphenyl<tetramethyl Diphenoquinone 0.001i! 1 (quantity less than 1, recovery rate 90.6%) was obtained.

Example 4 Yellow-green 3. gi, 5,5'-tetra-t-butyl-
500 g of 4,4'-dihydroxydiphenyl crude product (containing 0.16% of tetra-t-butyldiphenoquinone) was heated and dissolved in 5000 g of methanol under a nitrogen stream. An aqueous solution of 50 & 1000 g of sodium dithionite dissolved in water was added to this solution, and the mixture was heated and stirred for 1 hour under methanol reflux. After cooling to room temperature, water was added at 10 o'clock to precipitate crystals, which were collected by filtration and dried to give white 3,3',5,5'-tetra-1-
Butyl-4,4'-dihydroxydiphenyl 468! i
(Tetra-t-butyldiphenoquinone 0.001 weight)
The following results were obtained with a recovery rate of 93.6 cm.

Comparative Example 1 Yellow-green 3.3',5.5'-tetramethyl-4,4'
-Dihydroxydiphenyl crude product XOOg (containing 0.09% by weight of tetramethyldiphenoquinone) was heated and dissolved in methyl isobutyl lactone x401 under a nitrogen stream. To this solution was added an aqueous solution of 200!L of sodium thione powder dissolved in water, and the mixture was heated and stirred at 70°C for 1 hour. After cooling to room temperature, the aqueous layer was separated and removed, and the organic layer
a, add toluene to precipitate crystals, collect by filtration, and dry to give a yellow 3.3', 5.5'-
Tetramethyl-4,4'-dihydroxydiphenyl 90
3g (tetramethyldiphenoquinone 0.04 g
Contains es, recovery rate 90.3'%)? Obtained. The obtained crystals remained colored even after purification.

Comparative Example 2 Yellow-green 3.3',5.5'-tetramethyl-4,4'
-Dihydroxydinophenyl crude product 100! ? (Containing 0.09% by weight of tetramethyldiphenoquinone) t-Methanol 1400.9
The mixture was heated and dissolved. Add 6 sodium dithionite to this solution.
．． An aqueous solution dissolved in 1200 g of water was added to the mixture, and the mixture was heated and stirred for 1 hour while refluxing methanol. After cooling to room temperature, 2001 water was added to precipitate crystals, filtered and collected, and dried to give yellow 3,3',5,
91.5.9% of 5'-tetramethyl4.4'-dihydroxydiphenyl (containing 0.05% by weight of tetramethyldiphenol, recovery rate 91.5%) was obtained. The obtained crystals remained colored even after 'ffIfJ1.

Comparative Example 3 Yellow-green 3.3',5.5'-tetramethyl-4,4'
-Dihydroxydiphenyl crude product 10 (1 (containing 0.09% by weight of tetramethyldiphenoquinone) t'' was heated and dissolved in 1400 g of methanol under a nitrogen stream, then gradually cooled and crystals were precipitated at 0°C. Precipitation The resulting crystals were collected by filtration and dried to give yellow 3.3' crystals.5.
5'-tetramethyl-4,4'92,4To) was obtained. The obtained crystals remained colored even after purification.

Comparative Example 4 Yellow-green 3.3',5.5'-tetramethyl-4,4'
-Dihydroxydiphenyl crude product (25 g) (tetramethylnoaenoki 2F 0.09 475, 9ffi catalyst (5% supported on alumina support) 9 rad) was placed in a 1.5-inch glass-slit autoclave with 10 g and the container was sealed. Hydrogen gas was introduced from the gas introduction tube at 5ψ-, and the mixture was stirred vigorously at 70°C for 5 hours. All the catalyst was separated from the reaction mixture, crystals were precipitated, collected by filtration, and dried to give yellow 3.
．． 3'.

5,5'-tetramethyl-4,4'-dihydroquine diphenyl 2 1. 99 (containing 0.02% by weight of tetramethyldiphenoquinone, recovery rate 87.6%) was obtained.

The obtained crystals remained colored even after purification.

Claims (1)

[Claims] A p,p'-alkylbiphenol characterized by treating p,p'-alkylbiphenols including diphenoquinones with sodium dithionite in a water-containing organic solvent that is compatible with water and in an inert gas atmosphere. refining methods.