JPS6353173B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing alkyl monosubstituted hydroquinones. More specifically, the present invention relates to a method for producing a monosubstituted hydroquinone having an alkyl group having 5 or more carbon atoms in high yield. It has been known that monosubstituted hydroquinones having an alkyl group having 4 or less carbon atoms are useful as diol components of polyesters, particularly wholly aromatic polyesters. However, it is not known whether a polyester containing a monosubstituted hydroquinone having an alkyl group of 5 or more carbon atoms as a diol component and what kind of properties this polyester has are known. The present inventor has discovered that a wholly aromatic polyester containing monosubstituted hydroquinone with an alkyl group as the main diol component has excellent melt moldability and excellent mechanical properties.
It was discovered that it has thermal and chemical properties, and is useful as fibers, plastics, and other industrial materials. However, there is no known method for producing monosubstituted hydroquinone with an alkyl group, which is useful as a raw material for producing such polyester, industrially and in a high yield. As a method for producing monosubstituted hydroquinone having an alkyl group having 5 or more carbon atoms, for example, low temperature (approximately 15
A diisobutylene-containing glacial acetic acid solution cooled to
The resulting solution was gradually added dropwise to a glacial acetic acid solution in which hydroquinone had been dissolved, mixed, and left at room temperature for several days, then mixed with a large amount of water, left overnight, and then crystallized. A method for obtaining tertiary octylhydroquinone is known (J.Am.Chem.
Soc., Vol55P2571-2575). However, this method has a low yield of the desired product, and also requires the use of a large amount of solvent and the separation of the reaction product by contacting it with water together with a sulfuric acid catalyst.As a result, 1) a large amount of solvent is used; 2) Requires post-treatment of waste liquids containing strong acids such as sulfuric acid;
3) It has serious drawbacks as an industrial production method, such as the low yield of the desired product (52% at most) and the waste of hydroquinone. The present inventor has focused on the fact that the above-mentioned drawbacks can be significantly improved if the alkyl polysubstituted hydroquinone produced in large amounts in the above-mentioned alkylation reaction can be converted into alkyl mono-substituted hydroquinone at a high conversion rate, and has developed this conversion method. As a result of intensive study, we have arrived at the present invention. That is, the present invention is a method for producing alkyl monosubstituted hydroquinone, which is characterized by subjecting hydroquinone and alkyl polysubstituted hydroquinone to a heating reaction in the presence of a phosphoric acid catalyst. The alkyl polysubstituted hydroquinone used in the present invention has the following general formula: (However, in the formula, n is a number of 2, 3 or 4,
X is an alkyl group. ) is a compound represented by As X in the above general formula,

[Formula] (where R ₁ , R ₂ and R ₃ are each hydrogen, aliphatic hydrocarbon group, alicyclic hydrocarbon group or aromatic hydrocarbon group. However, R ₁ , R ₂
and R ₃ have a total carbon number of at least 4, but
Any two or more of R ₁ to _{R 3} are preferably aromatic hydrocarbon groups. Preferred examples of such alkyl include:
tertiary amyl, 1-methylbutyl, cyclohexyl, 1,1-dimethylbutyl, 1,1-dimethylpentyl, 1-ethyl 1-methylbutyl, 1,
1,3,3-tetramethylbutyl, benzyl, α
-Methylbenzyl, α,α-dimethylbenzyl, etc. In the present invention, the alkylpolysubstituted hydroquinone may be used alone or in a mixture of two or more. Furthermore, it goes without saying that the alkyl polysubstituted hydroquinone may contain a small amount of hydroquinone or alkyl monosubstituted hydroquinone. If the average value of n of such alkyl polysubstituted hydroquinone is taken as, the molecular formula of this alkyl polysubstituted hydroquinone is

It is expressed as [Formula]. The amount of alkyl polysubstituted hydroquinone used in the present invention is:

[Formula] Hydroquinone is preferably used at a ratio of (-1) x 0.5 to (-1) x 3 moles per mole. In particular, in order not to waste hydroquinone, hydroquinone is (-1) x It is preferably used in a ratio of 0.7 to (-1) x 1.5 mol, more preferably (-1) x 0.85 to (-1) x 1.25 mol. The phosphoric acid catalyst used in the present invention is 1 to 10 times the total weight of the alkyl polysubstituted hydroquinone and hydroquinone, more preferably 2 to 7 times, particularly 3 to 7 times the total weight of the alkyl polysubstituted hydroquinone and hydroquinone.
Preferably, the amount is 5 times the weight. The concentration of phosphoric acid catalyst is usually 75-110 in terms of H ₃ PO ₄ content.
% by weight. It is not necessary to use a particularly concentrated phosphoric acid catalyst, and a concentration of 100% or less is preferred from the viewpoint of operability during the reaction. Using too dilute a phosphoric acid catalyst will result in
This is not very preferable because it becomes impossible to raise the reaction temperature and the reaction takes a long time.
Therefore, taking both factors into consideration, the phosphate concentration is
80-100% is preferred. The reaction temperature is preferably a temperature at which the reaction proceeds smoothly and at which undesirable side reactions such as oxidation do not proceed significantly, that is, from 115 to 160°C, more preferably from 120 to 150°C. Further, the reaction time is, for example, about 1 to 3 hours at a reaction temperature of 150°C, and about 10 hours to at a reaction temperature of 120°C.
It is preferable to set the temperature to 15 hours, and those skilled in the art will be able to appropriately select other temperatures with reference to these examples. After carrying out the reaction in this manner, when the reaction mixture is allowed to stand still, the reaction mixture separates into two layers, and a layer containing alkyl monosubstituted hydroquinone is formed in the upper layer. The temperature at this time may be any temperature, for example, approximately the same as, slightly higher or lower than the reaction temperature. The desired alkyl-substituted hydroquinone can be obtained by separating this upper layer, washing it preferably with hot water until it becomes almost neutral, and then recrystallizing and/or distilling it. The present invention will be described below with reference to Examples. Example 1 110 g of hydroquine, 250 g of 2,5-di-tertiary amylhydroquinone, and 500 g of 89% phosphoric acid were charged into a three-necked flask, reacted at 140° C. for 3 hours, and then allowed to stand at the same temperature for 30 minutes. Upon standing, the reaction mixture separated into two layers. Separate the upper layer and add 500 ml of hot water.
ml three times, then dry, and then add 200ml of xylene.
Monoamylhydroquinone was obtained by reconsolidation using
Obtained 126g. Examples 2 to 4 The alkyl monosubstituted hydroquinones shown in Table 1 were prepared in the same manner as in Example 1, except that the alkyl polysubstituted hydroquinones shown in Table 1 were used instead of 2,5-ditertiary amylhydroquinone. Obtained.

【table】

Claims (1)

[Claims] 1. A method for producing alkyl monosubstituted hydroquinone, which comprises subjecting hydroquinone and alkyl polysubstituted hydroquinone to a heating reaction in the presence of a phosphoric acid catalyst.