JPS6163634A - Production of oxydibanzoic acid - Google Patents

Abstract

PURPOSE:When dimethyl diphenyl ether is oxidized with molecular oxygen in a catalyst consisting of a cobalt salt and bromine in a solvent of a lower fatty acid, the concentration of a phenol and water are specified in the reaction system to produce the titled compound with high reproducibility. CONSTITUTION:When dimethyl diphenyl ether of formula I is oxidized with molecular oxygen in a solvent of a lower fatty acid such as acetic acid, in the presence of a catalyst consisting of a cobalt salt such as cobalt acetate, cobalt propionate, cobalt benzoate, or cobalt naphthenate and bromine to give an oxydibenzoic acid which is used as a starting material for polyamide or polyester resins and shown in formula II, the amount of a phenol of formula III (R1, R2 are H, lower alkyl) is set to less than 600ppm and water, to 1-10wt% to enable industrially stabilized production of the objective compound with high reproducibility and high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing oxydibenzoic acid, more specifically,
The present invention relates to a method for producing oxydibenzoic acid by oxidizing dimethyl diphenyl ether with molecular oxygen in a solvent.

Oxydibenzoic acid is useful as a raw material for polyamide resins, a raw material for polyester resins, or various synthetic intermediates. Polyamide produced using oxydibenzoic acid has excellent properties such as strength and heat resistance.

(Prior Art) A method for oxidizing dimethyl diphenyl ether with molecular oxygen in a fihmrJ medium in the presence of a catalyst consisting of a cobalt salt and bromine includes a FRAM7L, 78,327°OA
581408i; GB, 951.192. O
A 615571r; US 5,139.452; O
The method described in A 61 6961 f etc. is known.

However, when carrying out the reaction using these existing synthetic methods, the time required for the reaction, reaction results, etc. vary widely depending on the reaction conditions and starting materials, making it difficult to produce oxydibenzoic acid on an industrial scale. It is difficult to manufacture stably.

(Problems to be Solved by the Invention) The purpose of the present invention is to provide a method for producing oxydibenzoic acid by oxidizing dimethyl diphenyl ether in a stable manner with good reproducibility by eliminating the instability of the existing synthetic methods described above. It is to be.

(First Means to Solve the Problem) As a result of various studies on the reaction of dimethyl diphenyl ether in a lower fatty acid solvent in the presence of cobalt salt and bromine, the inventor found that If the amount of impurities in the reaction system is kept below a certain value and the amount of water coexisting in the reaction system is controlled within a certain range, the reaction will always proceed stably and with good reproducibility, and the reaction results will also improve. The present invention was completed based on this discovery.

That is, in the present invention, when dimethyl diphenyl ether is oxidized with molecular oxygen in a lower fatty acid solvent in the presence of a catalyst consisting of a cobalt salt and bromine to produce oxydibenzoic acid, the phenolic compound present in the reaction system is
+)[)m or less, and the reaction is carried out while keeping the amount of water present in the reaction system in the range of 1 to 10 wt%.

The method of the invention is carried out in liquid lower fatty acids. Acetic acid is often used as a lower fatty acid solvent.

Appropriate amounts of a cobalt salt and a bromine compound used as a catalyst are added to a lower fatty acid solvent and reacted. As the cobalt salt, cobalt acetate, cobalt propionate, cobalt benzoate, cobalt naphthenate, etc. are often used. The concentration of cobalt salt in the solvent is 0.05-0.5 rrL61
A range of /l is preferred.

As the bromine compound, hydrobromic anhydride is often used, and the amount of the bromine compound used is preferably equivalent to or about 1.2 times the equivalent of the cobalt used. The oxidizing agent used in the method of the present invention is molecular oxygen, and oxygen gas or air is used. When using oxygen gas, use normal pressure or slightly pressurized (1,1 to 1
．． 5 kg/cut), the reaction proceeds satisfactorily. In addition, even when air is used as the oxidizing agent, oxidation can be carried out at normal pressure, but it is usually preferable to carry out the reaction under a pressure of about 2 to 10 to 9.

The temperature at which the reaction is carried out is 90-150°C. The time required for the reaction is 2 to 1 when the reaction is carried out in batches.
It is 0 hours.

etc. are often used. These chemicals are often produced, for example, by reacting paracresol sodium salt and parachlorotoluene as shown in the following formula.

The produced dimethyl diphenyl ether is isolated by a conventional method such as distillation under reduced pressure, and used as a raw material in the method of the present invention.

Dimethyl diphenyl ether usually contains 10 to 5
The oxidation reaction is carried out at a concentration of 0 wt %.

A phenolic compound represented by (representing a class alkyl group) is mixed. When a 4,4' monolith is used as a raw material, para-cresol is often mixed into the starting material, and when a 3,4' monolith or a 6,3' monolith is used, a metacresol is often mixed into the starting material.

In the method of the present invention, the amount of these impurities present in the reaction system is kept below a specific concentration and the reaction is carried out.

That is, the concentration of the phenolic compound in the reaction system during the reaction is 600 ppm or less, more preferably 500 ppm or less.
Keeping the VC below pm is necessary for the reaction to run smoothly and reproducibly.

Large amounts of phenolic compounds exceeding 600 ppm1
(If the oxidation reaction is too long, the oxidation reaction will hardly proceed, or there will be an abnormally long induction period, resulting in unfavorable results such as a decrease in reaction yield.Also, when the reaction is repeatedly carried out, each reaction However, there are wide variations in the time required for the reaction and the yield, making it difficult to carry out on an industrial scale.If the reaction is carried out while keeping the phenolic compound content below 600 ppm, the time required for each reaction will be reduced. The yield is also constant and the yield is high, making it possible to operate on an industrial scale.

Furthermore, the reaction can be carried out while maintaining the amount of water present in the reaction system, that is, the lower fatty acid solvent, in the range of 1 to 1 Qwt%.
It is necessary for the reaction to proceed efficiently and to obtain the target product in good yield.

This water is water mixed in as an impurity in lower fatty acids,
and water of crystallization of cobalt salts, for example (0H3Coo
)2Co・4H20, water produced by the oxidation reaction, and water content in the oxidizing agent, etc., is less than 1wt% or exceeds 1Qwt%, the reaction rate decreases, and the reaction Yield decreases.

(Action and Effect) According to the method of the present invention, the reaction always proceeds with good reproducibility,
The reaction yield is also high, and oxydibenzoic acid can be produced industrially and stably.

(Example〕 Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 is used as a reactor and heated to a predetermined temperature from the outside in an oil bath.

Acid-resistant cobalt s, 9. so% hydrogen bromide vinegar solution s, s
y, 200 ml of acetic acid! , 25.9 g of pure 4,4'-dimethyldiphenyl ether were charged to the reactor. Water present in the reaction system, ie, m: i'+f2 solvent, was 2.8 wt% at the start of the reaction. A trace amount of para-cresol was added in various amounts as an impurity to the above-mentioned reaction system and reacted.

The reaction was carried out at 110° C. by blowing atmospheric pressure oxygen gas. When oxysifthalic acid is generated by the reaction, it is precipitated as a white powder from the acetic acid solvent. The progress of the reaction was traced by sampling a small amount of the reaction solution using high-liquid chromatography to determine the product.

The yield was calculated. The results are shown in Table-1.

Table 1 Example 2 Using the same apparatus and reaction method as in Example 1, 5,4'-dimethyldiphenyl ether was added as a starting material into an acetic acid solvent to carry out an oxidation reaction. As for impurities and phenolic compounds in the acetic acid solvent, metacresol SO ppm is dissolved.

The reaction was carried out by changing the water content at the start of the reaction to (Φ). The results are shown in Table 21C.

Table-2

Claims (1)

[Scope of Claims] 1) Dimethyl diphenyl ether represented by the general formula (numerical formula, chemical formula, table, etc.) is oxidized with molecular oxygen in a lower fatty acid solvent in the presence of a catalyst consisting of cobalt salt and bromine. When producing oxydibenzoic acid represented by the formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ There are general formulas ▲ Numerical formulas, chemical formulas, tables, etc. that are present in the reaction system ▼ (R_1 and R_2 are hydrogen atoms or lower alkyl A method for producing oxydibenzoic acid, which is characterized in that the reaction is carried out by keeping the amount of a phenolic compound represented by (representing a group) below 600 ppm, and by keeping the amount of water present in the reaction system in the range of 1 to 10 wt%. .