JPH0796511B2 - Method for producing aralkyl ether - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing high-purity aralkyl ether. More specifically, in a method for producing an aralkyl ether by reacting aralkyl dichloride and a lower alcohol in the presence of an alkaline substance, the aralkyl dichloride and the lower alcohol are reacted, and then contacted with sodium bisulfite. It is a method for producing aralkyl ether.

Aralkyl ether is an important substance as a raw material of a phenol aralkyl resin (trade name: Zyloc), which is excellent in heat resistance, particularly resistance to oxidative deterioration.

[Prior Art] Aralkyl ethers are susceptible to autoxidation and transform into aromatic aldehydes during storage. Further, when an aralkyl ether is produced by reacting an aralkyl dichloride with an alcohol, an impurity contained in the aralkyl dichloride, for example, α, α, α′-trichloroxylene produces an alkoxymethylbenzaldehyde (aromatic aldehyde) as a by-product, and At present, aromatic aldehydes have a boiling point close to that of aralkyl ethers, making it difficult to purify and producing high-purity aralkyl ethers.

Since this aromatic aldehyde makes it difficult to control the molecular weight during resin production and adversely affects the hue, it has been desired to establish an industrial production method of aralkyl ether having a higher purity than ever before.

[Problems to be Solved by the Invention]

An object of the present invention is to provide an industrial production method of aralkyl ether containing no aromatic aldehyde.

[Means for solving the problem]

The present inventors have earnestly studied to achieve the above-mentioned object, and arrived at the present invention.

That is, the present invention is a method for producing an aralkyl ether by reacting aralkyl dichloride and a lower alcohol in the presence of an alkaline substance, characterized in that after reacting the aralkyl dichloride and the lower alcohol, it is contacted with sodium bisulfite. And a method for producing aralkyl ether.

Hereinafter, the present invention will be described in more detail.

Examples of the aralkyl dichloride referred to in the present invention include α, α′-dichloro-p-xylene, α, α′-dichloro-o-xylene and α, α′-dichloro-m-xylene. This α, α'-dichloroxylene is p-
It is produced by a chlorination reaction of xylene or o-xylene or m-xylene. For example, p-xylene or o-
It can be produced by reacting xylene or m-xylene with molecular chlorine under irradiation of light or in the presence of a peroxide radical generator or an azo radical generator. The chlorination reaction of xylene is a sequential reaction, and it is generally well known that the product can be controlled by the molar ratio of chlorine to xylene. α, α'-dichloroxylene has a molar ratio of chlorine to xylene of about 2, and is contained in the largest amount in the reaction mass. However, in order to increase the yield of α, α'-dichloroxylene, the molar ratio should be increased. It is also possible to reduce the boiling point to 2 or less and to recycle low boiling components. In order to take out α, α'-dichloroxylene from such a reaction mass, generally, a distillation method or a crystallization method can be adopted, but the reaction mass can be used as it is without purification.

The lower alcohol used in the present invention is methanol,
They are ethanol, 1-propanol and 2-propanol. The lower alcohol may be at least the number of moles of chlorine contained in α, α'-dichloroxylene, but industrially 1.5 times or more is suitable.

The alkaline substance is lithium hydroxide, lithium carbonate, sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, calcium hydroxide or calcium carbonate. These alkaline substances are usually used alone, but may be used as a mixture of two or more kinds. The alkaline substance may be used in the form of a solid having a high purity or an aqueous solution having a low purity. The alkaline substance may be at least more than the number of moles of chlorine contained in α, α′-dichloroxylene.

In the present invention, a method of preliminarily mixing α, α′-dichloroxylene and a lower alcohol and then sequentially adding an alkaline substance, or a method of preliminarily mixing a lower alcohol and an alkaline substance and then successively adding α, α′-dichloroxylene. Alternatively, a method of simultaneously adding α, α′-dichloroxylene, a lower alcohol and an alkaline substance is adopted. The reaction temperature can be arbitrarily selected within the range of 0 to 200 ° C., and the reaction pressure is usually atmospheric pressure or pressurized. For example, it is industrially advantageous to utilize the heat of reaction between α, α′-dichloroxylene and a lower alcohol, and to control the temperature to the boiling point of the lower alcohol under normal pressure by refluxing the lower alcohol.

As the aralkyl ether obtained as described above,
For example, α, α′-dimethoxy-p-xylene, α,
α'-dimethoxy-o-xylene, α, α'-dimethoxy-m-xylene, α, α'-diethoxy-p-xylene, α, α'-diethoxy-o-xylene, α, α'-
Diethoxy-m-xylene, α, α′-di (1-propoxy) -p-xylene, α, α′-di (1-propoxy) -o-xylene, α, α′-di (1-propoxy)
-M-xylene, α, α'-di (2-propoxy) -p
-Xylene, α, α'-di (2-propoxy) -o-xylene, α, α'-di (2-propoxy) -m-xylene. As the aromatic aldehyde which is an impurity, p-methoxymethylbenzaldehyde, o-methoxymethylbenzaldehyde, m-methoxymethylbenzaldehyde, p-methylbenzaldehyde, o-methylbenzaldehyde, m-methylbenzaldehyde, p-
Ethoxymethylbenzaldehyde, o-ethoxymethylbenzaldehyde, m-ethoxymethylbenzaldehyde, p
Typical examples are -1-propoxymethylbenzaldehyde, o-1-propoxymethylbenzaldehyde, m-1-propoxymethylbenzaldehyde, p-2-propoxymethylbenzaldehyde, o-2-propoxymethylbenzaldehyde and m-2-propoxymethylbenzaldehyde. It is an example.

The present invention can be achieved by reacting aralkyl dichloride with a lower alcohol and then contacting with sodium bisulfite. It is particularly effective to contact with sodium hydrogen sulfite immediately after the reaction of the aralkyl dichloride and the lower alcohol, during the removal of excess lower alcohol, or after the removal of the lower alcohol by distillation.

Sodium bisulfite is effective both as a solid and an aqueous solution, but in the case of a solid due to contact time and the like, it is more effective to add water having a solubility or higher and dissolve it. About 35% of the aqueous solution is usually on the market, but it may be diluted if necessary.

Sodium bisulfite is preferably used in a molar amount of 2 to 50 times that of the aromatic aldehyde which is an impurity. More preferably,
It is 3 to 40 times the molar amount. If the above upper limit is exceeded, sodium bisulfite will be used more than necessary, which is not preferable. If it is less than the lower limit, the effect of removing the aromatic aldehyde is insufficient, which is not preferable.

The temperature at which sodium bisulfite is brought into contact is preferably 40 ° C. or lower. More preferably, it is 35 ° C or lower. When the amount exceeds the above upper limit, the effect of removing the aromatic aldehyde is insufficient, which is not preferable. Further, the effect does not change even if they are contacted at a temperature lower than necessary.

In the present invention, stirring is usually performed. The pressure is preferably normal pressure or increased pressure. The contact time may vary depending on the excess ratio of sodium bisulfite, the reaction temperature, the shape and capacity of the reactor, the type and the number of agitators of the agitator, the reaction mass amount of aralkyl dichloride and lower alcohol, and cannot be specified unconditionally, The effect is sufficient if they are contacted for 10 minutes or more.

As a method for recovering only high-purity aralkyl ether after bringing the aromatic aldehyde contained in the aralkyl ether into contact with sodium hydrogen sulfite, the following method can be employed. Excess methanol or ethanol or 1-propanol or 2-propanol is removed by distillation or the like to separate the layers, and the aqueous layer is removed, so that the aromatic aldehyde is not mixed in the aralkyl ether. Furthermore, high-purity aralkyl ether can be produced by removing other impurities by distillation purification.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 A chlorinated reaction mass obtained by blowing gaseous chlorine into p-xylene under irradiation of a high pressure mercury lamp was purified by distillation to obtain α,
α'-dichloro-p-xylene 95.5%, α, α, α'-
Trichloro-p-xylene 3%, α, α-dichloro-p
-Distillation mixture containing 1% xylene and 0.5% other impurities 2
I got 00g. To 100 g of this, 200 g of methanol and 200 g of 25% sodium hydroxide were added, and the mixture was reacted under reflux of methanol for 3 hours. The salt was removed by filtration, the methanol was removed by a rotary evaporator, and the mixture was cooled to room temperature. With hydrochloric acid
After adjusting the pH to 4, 20 g of a 35% aqueous solution of sodium hydrogen sulfite was added, stirred for 20 minutes, and then allowed to stand in a separating funnel for 5 minutes. After removing the lower layer, the upper layer was purified by a plate distillation column. The purity of α, α'-dimethoxy-p-xylene measured by gas chromatography was 99.5%. Also, p-methoxymethylbenzaldehyde is 0.05
%Met.

Comparative Example 1 α, α′-dimethoxy-p-xylene was synthesized and purified in the same manner as in Example 1 except that the remaining 100 g of the chlorinated product distilled and purified in Example 1 was used and sodium bisulfite was not added. did. As a result, α, α ′ with a purity of 98.6%
Only dimethoxy-p-xylene was obtained. Moreover, 0.8% of p-methoxymethylbenzaldehyde was contained.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, the present invention is an excellent method capable of industrially removing an aromatic aldehyde which is present in an aralkyl ether and which makes it difficult to control the molecular weight during resin production and adversely affects the hue of the resin. Moreover, sodium bisulfite is inexpensive and advantageous in terms of cost.

Claims (2)

[Claims] 1. A method for producing an aralkyl ether by reacting an aralkyl dichloride with a lower alcohol in the presence of an alkaline substance, which comprises reacting the aralkyl dichloride with the lower alcohol and then contacting with sodium bisulfite. And a method for producing aralkyl ether. 2. The method according to claim 1, wherein the aralkyl ether is α, α′-dimethoxy-p-xylene.