JPH01197476A - Production of aromatic polycarboxylic acid anhydride - Google Patents

Abstract

PURPOSE:To readily obtain the title compound which is a raw material for polyimides, etc., at a low cost without requiring expensive dehydrating agents and using special steps, by thermally dehydrating hydrous wet crystals of diphenyl sulfone-3,3',4,4'-tetracarboxylic acid. CONSTITUTION:Hydrous wet crystals of diphenyl sulfone-3,3',4,4'-tetracarboxylic acid is dehydrated, preferably at 110-250 deg.C, especially 150-230 deg.C under ordinary or reduced pressure to afford the aimed compound. The above-mentioned raw material diphenyl sulfone-3,3',4,4'-tetracarboxylic acid is obtained by, e.g., oxidizing the corresponding methyl substitution product with nitric acid or dichromic acid or catalytically oxidizing the above-mentioned substitution product with air. The raw material must be used in the form of the hydrous wet crystals. The moisture content in the wet crystals is preferably about 5-80wt.%, especially about 10-66wt.% expressed in terms of the wet basis.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aromatic polycarboxylic anhydride, more specifically, an aromatic polycarboxylic anhydride useful as a raw material for polyimide, polyamide, polyester, etc. The present invention relates to a method for producing diphenylsulfone-3,3=,4°4-1-tetracarboxylic dianhydride.

[Prior Art] Conventionally, methods for producing aromatic polycarboxylic acid anhydrides include anhydration using acetic anhydride, melting and dehydration, and wet thermal dehydration in a solvent such as diphenyl ether. It has been known.

However, all of these methods have their own problems and are not satisfactory.

That is, in the method using acetic anhydride, acetic acid remains in the obtained acid anhydride, and when various derivatives are manufactured using such acid anhydride as a raw material, the remaining acetic acid may have an adverse effect. It tends to affect Furthermore, aromatic polycarboxylic acids generally have a high melting point, and the acid anhydride obtained by melting and dehydration is colored, requiring a separate purification step. Furthermore, in the wet thermal dehydration method (U.S. Pat. No. 3,106.568), 22
Since a high temperature of 0° C. or higher is required and it is difficult to remove the high boiling point solvent used from the acid anhydride, the process becomes complicated, such as the need to wash the product with a low boiling point solvent such as benzene.

[Problem to be solved by the invention] We used diphenylsulfone-3,3''.

4.4--Tetracarboxylic acid is hereinafter abbreviated as rDsTcJ. ) to anhydride to give diphenylsulfone-3,3'
,4,4-tetracarboxylic dianhydride (rDSD)
It will be abbreviated as AJ. ).As a result of intensive research to develop an industrially advantageous manufacturing method that is economical, does not require the use of expensive dehydrating agents such as acetic anhydride, and has little coloring of the product, DSTC It has been found that unlike carboxylic acids, it is possible to anhydride the hydrous wet crystals by simply heating and dehydrating them at a relatively low temperature without requiring any special process for anhydration.

The present invention was made based on this knowledge, and an object of the present invention is to provide a novel and industrially useful method for producing SDA.

[Means for Solving the Problems] The method for producing DSDA according to the present invention is characterized by heating and dehydrating hydrated wet crystals of DSTC.

The DSTC according to the present invention can be obtained, for example, by subjecting the corresponding methyl substituted product to nitric acid oxidation, dichromic acid oxidation, or catalytic air oxidation.

This DSTC must be used in the form of water-containing wet crystals, and specifically, those obtained from a reaction system containing water can be used as is, and those obtained from a reaction system that does not contain water can be used directly. is used as a raw material after being recrystallized in a water-containing solvent.

The type of such recrystallization solvent and the water content of the solvent are not particularly limited as long as the desired effect is achieved. Suitable solvents include water-compatible solvents such as acetic acid, formic acid, methanol, isopropanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, and diglyme.

The water content in the wet crystals is preferably about 5 to 80% by weight in wet terms, particularly about 10 to 60% by weight. If the amount is less than this, it will be difficult to achieve the desired level of dehydration, while if it is more than this, it will take a long time for dehydration, which tends to be industrially disadvantageous.

The heating temperature is preferably about 110 to 250°C, particularly about 150 to 230'C.

If the temperature is lower than this, the dehydration rate is slow and it is economically disadvantageous; if the temperature is higher than this, the product tends to be colored.

The pressure conditions during heating are preferably normal pressure or reduced pressure, and reduced pressure is particularly recommended because the heating time can be shortened.

Although the heating time can be appropriately selected depending on the water content of DSTC, it is usually about 1 to 20 hours.

Heating may be performed with the DSTC standing still, or
It may be carried out while stirring or flowing.

[Example] The present invention will be described in detail below with reference to Examples.

Example 1 3.3-. 137 g (0.5 mol) of 4,4-tetramethyldiphenylsulfone were added to an acetic acid solution containing 20 mmol of cobalt bromide, 5 mmol of manganese acetate, and 20 mmol of hydrogen bromide, respectively, at an air pressure of 50 ml.
/ctA at 180°C for 1 hour. After cooling, the precipitated DSTC crystals were filtered off and recrystallized from water. 40
Wet crystal 1009 containing % by weight of water was placed in a stainless steel dish and dehydrated by heating at 180'C for 3 hours under reduced pressure of 1 to 2 mm Hg to obtain 54.0 g of DSDA. The acid anhydride content of this product was 99.7%, and the melting point was 287°C (literature value 286-287°C).

Here, the above acid anhydride amount (%) was determined by calculating the percentage of [2×(hydric acid value of product - earth acid value of product)] with respect to the theoretical acid value of DSDA.

Example 2 100 g of wet crystals of DSTA obtained in Example 1 were mixed with 1 to 2 Ir.
Dehydrated by heating at 200°C for 1 hour under reduced pressure of unHg.
．． A DSDA of 89 was obtained. The amount of acid anhydride in this product is 99.
8%, and the melting point was 287°C.

Example 3 3.3-. 4. Add 525 g of 60% nitric acid to 137 g (0.5 mol) of 4”-tetramethyldiphenylsulfone,
The reaction was carried out under pressure at 200'C for 6 hours. After cooling, the precipitated DSTC crystals were filtered off and washed thoroughly with water. The obtained crystals contained 50% water by weight. This wet crystal 1009 was heated to 180 mL under reduced pressure of 1 to 2 IwnHQ.
The mixture was dehydrated by heating at 100°C for 4 hours to obtain a DSDA of 44.59. This product has an anhydrous Mffl of 99.5% and a melting point of 287.
It was ℃.

Comparative Example 1 100 g of wet crystals of DSTC obtained in Example 1 were mixed under normal pressure for 1
After drying at 00°C for 6 hours, DSTC with a moisture content of 2% by weight was
"l" was obtained.
Heated at 80'C for 3 hours. The amount of acid anhydride in the obtained product was 2.5%.

[Effects of the Invention] According to the method of the present invention, DSDA can be obtained easily and inexpensively without using expensive dehydrating agents or high-boiling point solvents.

Patent applicant: Shin Nihon Rika Co., Ltd.

Claims (1)

[Claims] 1. When producing diphenylsulfone-3,3',4,4'-tetracarboxylic dianhydride, the hydrous wet crystals of diphenylsulfone-3,3',4,4'-tetracarboxylic acid are heated and dehydrated. A method for producing diphenylsulfone-3,3',4,4'-tetracarboxylic dianhydride, characterized in that: