JPH01294668A - Production of polycarboxylic acid anhydride isomer - Google Patents

Abstract

PURPOSE:To obtain the subject compound with an industrially excellent process in high yield by removing the catalyst with an adsorbent such as silica-alumina compound in the isomerization of an unsaturated alicyclic 1,2-dicarboxylic acid anhydride in the presence of an amine catalyst. CONSTITUTION:A polycarboxylic acid anhydride isomer is produced by the steric isomerization of an unsaturated 1,2-dicarboxylic acid anhydride (e.g., 3- or 4-methyl- <4>-tetrahydrophthalic anhydride) in the presence of an amine catalyst (e.g., trimethylamine or 2-ethyl-4-methylimidazole). In the above process, the amine-based isomerization catalyst is removed with an adsorbent (e.g., active clay or synthetic aluminum silicate). The amount of the adsorbent is preferably about 0.05-3 pts.wt. per 100 pts.wt. of the isomer mixture of the polycarboxylic acid anhydride containing the amine compound. The obtained compound is useful as an epoxy resin hardener or a raw material for polyester resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing polycarboxylic acid anhydride isomers by stereoisomerization.

[Prior art and its problems] Unsaturated alicyclic 1,2-dicarboxylic acid anhydrides are widely used industrially as epoxy resin curing agents and polyester resin raw materials, and from the viewpoint of workability, they cannot be liquid at room temperature. Awarded.

It is generally well known that acid anhydrides that are liquid at room temperature can be obtained by stereoisomerizing unsaturated 1,2-dicarboxylic acid anhydrides alone or in mixtures. Various isomerization catalysts have been proposed as catalysts suitable for such stereoisomerization, specifically, alkali metal oxides (Japanese Patent Publication No. 58-54146), acidic ion exchange resins (Japanese Patent Publication No.
9-3997@), quaternary ammonium salt (Special Publication No. 1983)
-34476), phosphorus compounds (JP-A-55-339)
No.), amine compounds (Japanese Unexamined Patent Publication No. 151941/1983)
etc. are exemplified. Among these, amine compounds are
It has particularly excellent isomerization catalytic ability.

However, if the polycarboxylic anhydride isomer obtained using an amine compound as a catalyst is used as an epoxy resin curing agent without a purification process, it may absorb moisture during storage and open the anhydride group. It has been observed that there is a tendency for the product to deteriorate easily, and a purification step is essential to overcome this problem, but the conventional purification method using distillation has not been able to obtain isomers at a low yield.

In view of the current situation, the present inventors have conducted extensive studies with the aim of removing the catalyst without purification by distillation and obtaining polycarboxylic acid anhydride isomers in good yield. The inventors discovered that amine compounds are efficiently adsorbed by specific compounds, and that the intended purpose can be achieved by adsorption treatment using such compounds, and based on this knowledge, the present invention was completed. .

That is, an object of the present invention is to provide a novel method for producing polycarboxylic acid isomers in an industrially superior and high yield, which includes a step in which the amine-based isomerization catalyst can be easily removed. .

[Means for Solving the Problems] The method for producing polycarboxylic acid isomers according to the present invention comprises isomerizing an unsaturated alicyclic 1,2-dicarboxylic acid anhydride in the presence of an amine catalyst to obtain the corresponding stereoisomer. When producing isomers, the amine isomerization catalyst is adsorbed and removed using an adsorbent.

The unsaturated 1,2-dicarboxylic anhydride used as a raw material in the present invention is an unsaturated 1,2-dicarboxylic anhydride that can be stereoisomerized with an amine compound, and specifically, it is an unsaturated 1,2-dicarboxylic anhydride that can be stereoisomerized with an amine compound. The above-mentioned acid anhydrides having an alkyl nucleus having 1 to 8 carbon atoms, structural isomers thereof, and endomethylene groups are exemplified, and more specifically, 3-methyl-△4-tetrahydrophthalic anhydride and its structure Examples include isomers.

The isomerization catalyst may be any conventionally known amine compound, such as trimethylamine, triethylamine, tributylamine, dimethylethylamine,
Examples include aliphatic, alicyclic or aromatic amines such as triethanolamine, dimethylethylamine, methylethylpropylamine, dimethyllaurylamine, dimethylaniline and dibutylaniline, imidazoles such as 2-ethyl-4-methylimidazole, Usually acid anhydride 1
It is used in an amount of 0.01 to 2 parts by weight per 00 parts by weight.

The isomerization reaction may be carried out at a temperature of about 90 to 250°C for about 1 to 10 hours under an inert gas atmosphere.

Examples of suitable adsorbents according to the present invention include silica-alumina compounds.

Here, the silica-alumina compound has a composition containing silica and alumina, and is sufficient as long as it participates in the adsorption reaction and can achieve the intended purpose. Specifically, bentonite is used as a compound. , natural products such as pearlite, kaolin, zeolite, and activated clay, or other solid silicic acid-based substances derived from them that have similar properties, and artificially synthesized solids that have properties similar to the above-mentioned natural minerals. Examples include silicic acid-based substances. Among the above-mentioned silica-alumina compounds, compounds with high acidity are preferred, and activated clay, synthetic aluminum silicate, etc. are particularly recommended.

The adsorbent is preferably added in an amount of 0.01 to 5 parts by weight, preferably 0.01 to 5 parts by weight, per 100 parts by weight of the polycarboxylic anhydride isomer mixture containing the amine compound.
Although the amount is 0.5 to 3 parts by weight, it is possible to use an even lower concentration depending on the type of amine compound used as a catalyst.

A general processing method in the present invention is shown below.

That is, a predetermined amount of a raw material acid anhydride isomer mixture (containing an isomerization catalyst) and a predetermined amount of adsorbent are placed in a reactor equipped with a stirrer, a thermometer, a cooler, an inert gas inlet, and a pressure reduction port. Preparation, under inert gas or under reduced pressure if necessary.
The adsorption treatment is performed at a temperature of about 200°C, preferably room temperature to 150°C, for about 10 minutes to 5 hours. After the adsorption process is completed,
The adsorbent is separated by filtration or decanting to obtain the target acid anhydride containing less amine compounds.

In addition, other polyvalent carboxylic acid anhydrides, such as
Succinic anhydride, phthalic anhydride, trimellitic anhydride,
Pyromellitic anhydride, nadic anhydride, methyl nadic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tothicenylsuccinic anhydride, benzophenonetetracarboxylic anhydride, etc. It may be added before the isomerization reaction or before the adsorption treatment to form a liquid polycarboxylic acid anhydride with a lower freezing point.

The polycarboxylic acid anhydride according to the present invention can be used as an acid component of polyester, as well as for sealing electronic parts, casting electric parts,
It has excellent properties as a hardening agent for epoxy resins used as insulating materials such as impregnated varnish for motor coils.

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

The effectiveness of removing amine compounds was determined by measuring the nitrogen content using the Termuerne reaction coulometric titration method.

Example 1 Lauryl dimedium was added as an isomerization catalyst to 100 parts by weight of a mixed acid anhydride of 3-methyl-Δ4-tetrahydrophthalic anhydride/4-methyl-Δ4-tetrahydrophthalic anhydride-7/3 (weight ratio). 500 ppm of Lamine was added, and the mixture was stirred at a temperature of 180° C. for 3 hours to obtain 1 q of the isomer mixture. The nitrogen content present in this isomer mixture was 33 ppm. Activated clay was added to the isomerization mixture in an amount of 1% by weight based on the raw material acid anhydride as an adsorbent for the isomerization catalyst, and heated at 120° C. to 5 #
The mixture was treated under reduced pressure H';J for 1 hour. After that, this material was filtered under reduced pressure to remove 0.0% nitrogen. A carboxylic acid anhydride containing 1 ppm was obtained with a yield of 99%.

Example 2 An isomer mixture was treated according to Example 1, except that 2% by weight of synthetic aluminum silicate was used as an adsorbent based on the raw acid anhydride. As a result, a carboxylic acid anhydride with a nitrogen content of o, ippm was obtained. The product was obtained in 99% yield.

Example 3 200 ppm of triethylamine was added as an isomerization catalyst to 100 parts by weight of the same mixed acid anhydride as in Example 1, and the mixture was stirred at a temperature of 180°C for 6 hours to obtain an isomer mixture. Ta. The nitrogen content present in this isomer mixture was 28 ppm. Activated clay was added to the isomerization mixture as an adsorbent for the isomerization catalyst in an amount of 1% by weight based on the raw material acid anhydride, and the mixture was heated at 120° C. and treated under normal pressure for 1 hour. After filtering this product under reduced pressure, the nitrogen content is 0. 99 lppm of carboxylic acid anhydride
% yield.

Example 4 An isomer mixture was treated according to Example 3, except that 3% by weight of synthetic zeolite was used as an adsorbent based on the raw acid anhydride. As a result, a carboxylic acid anhydride with a nitrogen content of 0.5 ppm was obtained. Obtained with a yield of 99%.

Example 5 As a result of the same treatment as in Example 1 except that 3-methyl-Δ4-tetrahydrophthalic anhydride was used as the raw material acid anhydride, a 99% yield of carboxylic acid anhydride with a nitrogen content of 0.2 ppm was obtained. obtained at a rate.

Comparative Example 1 The yield of the isomer mixture containing 0.1 ppm of nitrogen obtained by single @ distillation of the isomer mixture obtained in Example 1 (nitrogen content a in acid anhydride = aappm) was 94 %Met.

Patent applicant: Shin Nippon Rika Co., Ltd.

Claims (1)

[Claims] 1. When unsaturated alicyclic 1,2-dicarboxylic acid anhydride is isomerized in the presence of an amine catalyst to produce the corresponding stereoisomer, the amine isomerization catalyst is adsorbed and removed using an adsorbent. A method for producing a polycarboxylic acid anhydride isomer, characterized by: