JPH0819020B2 - Method for purifying 3,3 ', 5,5'-tetraalkyl-4,4'-biphenol - Google Patents

Description

TECHNICAL FIELD The present invention relates to 3,3 ′, 5,5′-tetraalkyl-4, containing impurities of diphenoquinones and polyphenylene ethers.
The present invention relates to a method of purifying 4'-biphenol to obtain high-purity 3,3 ', 5,5'-tetraalkyl-4,4'-biphenol (hereinafter sometimes abbreviated as alkyl biphenols).

Alkyl biphenols are useful as various chemical intermediates, copolymer monomers, antioxidants, and petroleum product stabilizers, and particularly high-purity resin raw materials are required.

As a conventional method for producing alkylbiphenols, for example, a method of oxidative coupling of alkylphenols in an organic solvent (US 4,180,686, UK 2,047,232), or
A method for oxidative coupling of alkylphenols using a copper amine complex as a catalyst in an aqueous solvent (JP-A-53-65).
No. 834) is known, but the alkylbiphenols obtained by these methods are yellow solids containing diphenoquinones and polyphenylene ethers. Even if the diphenoquinones are contained in a small amount, the coloring is remarkable.

Alkyl biphenols are solid at room temperature, have a high melting point, are difficult to purify by distillation operation, and there is no suitable solvent, and it is difficult to remove and purify diphenoquinones and polyphenylene ethers by recrystallization. It was not easy to obtain white highly pure alkyl biphenols.

For example, a method for purifying 4,4'-biphenol by substituting a solvent has been proposed (JP-A-59-98027), but it is necessary to remove a large amount of solvent by distillation, and the operation is complicated. Is.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention is more easily and industrially advantageous than crude alkylbiphenols containing impurities such as diphenoquinones and polyphenylene ethers obtained by oxidative coupling of alkylphenols. The present invention aims to provide a purification method for obtaining white high-purity alkyl biphenols.

Means for Solving the Problems That is, the present invention provides a crude 3,3 ′, 5,5′-tetraalkyl containing 0.01 to 5% by weight of diphenoquinones and 0.1 to 10% by weight of polyphenylene ethers as impurities. −
4,4'-biphenols in a mixed solvent of a lower alcohol and an aromatic hydrocarbon in a weight ratio of 1: 0.1 to 10 at 80 ° C or higher, 1
It is characterized in that high-purity 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenols are precipitated by heating to a temperature of less than 50 ° C. and then cooling, and this precipitate is recovered. The present invention provides a method for purifying crude 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol.

The crude alkylbiphenols (crude 3,3 ', 5,5'-tetraalkyl-4,4'-biphenols) to be purified according to the present invention are obtained by oxidative coupling of 2,6-dialkylphenols. It is obtained, and usually contains 0.01 to 5% by weight of diphenoquinones and 0.1 to 10% by weight of polyphenylene ethers as impurities.

As the 2,6-dialkylphenols, the 2,6-position of phenol is methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group,
It is alkylphenols substituted with an alkyl group having 1 to 4 carbon atoms such as t-butyl group.

In the present invention, a mixed solvent of a lower alcohol and an aromatic hydrocarbon is used as the solvent. As the lower alcohol, methanol, ethanol, n-propanol,
Examples of the aromatic hydrocarbon include i-propanol and the like, and examples of the aromatic hydrocarbon include benzene, toluene, xylene, ethylbenzene and the like. The mixed solvent is usually added separately, but a mixed solvent prepared in advance may be used.

When the heat treatment with a solvent is carried out only with a lower alcohol, not only the recovery of alkylbiphenols is lowered, but also the amount of polyphenylene ethers remaining is large, and a high-purity product cannot be obtained. On the other hand, when the aromatic hydrocarbon is used alone, a large amount of the aromatic hydrocarbon must be used in order to obtain a high-purity product, and the disadvantages in industrial implementation cannot be avoided.

The weight ratio of the aromatic hydrocarbon to the lower alcohol in the mixed solvent used is in the range of 0.1 to 10, preferably 1 to 5
Range. When the weight ratio is less than 0.1, the recovery rate is lowered, and when it exceeds 10, it is necessary to use a large amount of solvent in order to obtain a highly pure product.

The amount of solvent used varies depending on the heating temperature and cannot be specified in a uniform manner. However, it is preferably in the range of 3 parts by weight or more and less than 10 parts by weight with respect to 1 part by weight of alkylbiphenols. Is not at a satisfactory level, and if it is more than this level, the efficiency and the recovery rate of alkylbiphenol decrease, which is a disadvantage in industrial practice.

The heating temperature is preferably in the range of 80 ° C. or higher and lower than 150 ° C. When the temperature is lower than this, the removal of impurities, particularly diphenoquinones, is not sufficient, and when the temperature is higher than this, the effect of raising the temperature is can not see.

The heating time is preferably at least 5 minutes or more at a predetermined temperature.

The heat treatment is carried out in an inert gas atmosphere, and the treatment pressure is carried out under a spontaneously generated pressure at the heating temperature, although it depends on the mixing ratio of the solvent used.

After the heat treatment, the treatment mixture is cooled to cause precipitation and precipitation as high-purity alkylbiphenols which are the target substance in the crude alkylbiphenols, and the precipitates are isolated by filtration or centrifugation.

Examples Hereinafter, the present invention will be described more specifically with reference to Examples.

Example 1 100 g of yellow-green 3,3 ', 5,5'-tetraalkyl-4,4'-biphenol crude product (tetramethyldiphenoquinone 0.09
%, Containing polyphenylene ether 0.85%), toluene 30
0 g and 100 g of methanol were placed in a glass autoclave (1), and heated and stirred at 140 ° C. for 30 minutes in a nitrogen atmosphere.

Then, after cooling the content, the solid content was collected by filtration and dried to obtain 92.3 g of white 3,3 ', 5,5'-tetramethyl-4,4'-biphenol. (Tetramethyldiphenoquinone 0.001% or less, polyphenylene ether 0.05%, recovery rate 92.3%).

Example 2 The same operation as in Example 1 was carried out except that 100 g of isopropanol was used in place of methanol in Example 1, and white 3,3 ′, 5,5′-tetramethyl- 4,4 ′
93.1 g of biphenol were obtained. (Tetramethyldiphenoquinone 0.001% or less, polyphenylene ether 0.05%,
Recovery rate 93.1%).

Example 3 In Example 1, mixed xylene was used instead of toluene.
The same operation as in Example 1 was carried out except that 400 g was used to obtain 92.8 g of white 3,3 ', 5,5'-tetramethyl-4,4'-biphenol. (Tetramethyldiphenoquinone
0.001% or less, polyphenylene ether 0.06%, recovery rate 9
2.8%).

Comparative Example 1 The same operation as in Example 1 was carried out except that only 400 g of methanol was used as the solvent in Example 1, and white 3,3 ′, 5,5′-tetramethyl-4 was obtained. 77.2 g of 4,4'-biphenol was obtained. (Tetramethyldiphenoquinone 0.001% or less, polyphenylene ether 0.60%, recovery rate 77.2%).

Comparative Example 2 The same operation as in Example 1 was carried out except that only 800 g of toluene was used as the solvent in Example 1, and 3,3 ′, 5,5′-tetramethyl-4,4 was used. ′ -Biphenol
Although 91.5 g was obtained, it was light yellow in color. (Tetramethyldiphenoquinone 0.01%, polyphenylene ether
0.03%, recovery rate 91.5%).

Claims (1)

[Claims] 1. 0.01-5% by weight of diphenoquinones and
Crude 3,3 ', 5,5'-tetraalkyl-4,4'-containing 0.1 to 10% by weight of polyphenylene ethers as impurities
Biphenols are heated to a temperature of 80 ° C or higher and lower than 150 ° C in a mixed solvent of a lower alcohol and an aromatic hydrocarbon in a ratio of 1: 0.1 to 10 by weight, and then cooled to obtain highly pure 3,3.
Precipitation of 3 ', 5,5'-tetraalkyl-4,4'-biphenols and recovery of the precipitate,
A method for purifying 3,3 ', 5,5'-tetraalkyl-4,4'-biphenol.