JPS5854146B2 - Method for isomerizing methyl↓-delta↓-4↓-tetrahydrophthalic anhydride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for isomerizing methyl-delta-4-tetrahydrophthalic anhydride, and more particularly, to a method for isomerizing methyl-delta-4-tetrahydrophthalic anhydride.
This invention relates to a novel isomerization method for heat-treating tetrahydrophthalic anhydride.

Methyl-delta-4-tetrahydrophthalic anhydride (hereinafter abbreviated as Me-Δ'-THPA) has been widely used as a curing agent for epoxy V resins and as a component of unsaturated polyester resins.

However, this compound is solid at room temperature, which is a major drawback as an epoxy resin curing agent, which is often required to be in a liquid state for handling.

Therefore, methods have been developed to obtain liquid materials by isomerizing Me-Δ'-T HP A. US Patent No. 2
959599), silica-alumina, acidic ion exchange resin (Japanese Patent Publication No. 43-13455), and the like are known.

All of these methods generate structural isomers by shifting the position of the double bond in the cyclohexene ring, and lower the melting point by eutectic melting of each structural isomer.

On the other hand, a method for sterically geometric isomerizing Me-Δ'-THPA without causing movement of the double bond is also known.

For example, 3-Me-Δ'-THPA includes cis-3-methyl-4-cyclohexene-cis, cis-2-dicarboxylic anhydride (melting point 63°C), trans-3-methyl-4
-Cyclohexene-cis, cis-2-dicarboxylic anhydride (melting point 41'C), cis-3-methyl-4-cyclohexene-cis, trans-1,2-dicarboxylic anhydride (melting point 133°C) and trans-3 Four geometric isomers of -methyl-4-cyclohexene-cis, trans-1,2 dicarboxylic anhydride (melting point 121'C) are known (Journal of American Chemical Society VOL).

72, pp. 1678-1681, April 1950).

Also, in that document, cis-3-methyl-4-cyclohexene-cis, cis-cysto-2-dicarboxylic acid anhydride with a melting point of 63°C was heat-treated at 175°C for 4 hours in the presence of dibutylaniline to obtain an isomer with a melting point of 30°C. Although there have been reports of experimental examples in which mixtures were obtained, there have been no reports of obtaining liquid products through geometric isomerization, and the reality is that there is little knowledge about the catalysts used in the reaction.

The main objective of the present invention is to use a novel catalyst to
It is an object of the present invention to provide a method for isomerizing THPA, and a further object is to provide an isomerization method that enables the production of a liquid isomer mixture.

Therefore, these objects of the present invention are based on Me-△4-THPA
in the presence of alkaline earth metal oxides at 130-300℃
This is achieved by heat treatment.

Me-Δ:'-THPp used in the present invention.

is 3-Me-△'-T HP A, 4-Me-△4-
THPA or a mixture thereof, and these compounds can be easily obtained, for example, by subjecting 1,3-pentadiene, isoprene, or a mixture thereof and maleic anhydride to a Diels-Alder reaction.

Among these compounds, 3-Me-Δ'-THPAO
4-Me-Δ' THPA is more likely to cause isomerization than 4-Me-Δ'-Me-△'-THPAO~80
It is advantageous to use % by weight, even in the range from 5 to 75% by weight.

In the present invention, such Me-Δ'-THPA is heat-treated in the presence of a basic metal oxide, thereby progressing isomerization.

Specific examples of alkaline earth metal oxides that can be used include calcium oxide, magnesium oxide, strontium oxide, barium oxide, etc. Among them, calcium oxide is preferred in terms of reactivity and stability of the catalyst itself. Awarded.

In the present invention, Me-Δ'-THPA is used at temperatures of 130 to 300°C, preferably 150 to 2.0°C in the presence of a catalyst of usually 1 part by weight or more, preferably 5 parts by weight or more per 100 parts by weight of Me-Δ'-THPA.
The reaction is carried out at a temperature of 50°C.

At this time, as the reaction temperature decreases, the isomerization rate decreases, and conversely, as the reaction temperature decreases, the product becomes colored.

Other reaction conditions are not particularly limited, but
o in an atmosphere of a gas inert to the reaction such as nitrogen or argon,
It is appropriate to react for about 1 to 30 hours, preferably about 1 to 10 hours.

The reaction format may be patch or continuous, and any method such as fixed bed or fluidized bed may be used; however, in cases where metal oxides are mixed in a liquid isomer mixture, The metal oxide can be easily separated by one filtration.

According to the method of the present invention, by appropriately selecting reaction conditions such as the amount of catalyst used, reaction temperature, and reaction time, it is possible to obtain an isomer mixture with an excellent hue of Gardner color number 2 or less without distillation. I can do it.

However, if some coloration occurs or if a more transparent product is desired, the color can be easily removed by distillation.

In addition to the reaction conditions as described above, the starting material M
By appropriately controlling the composition of e-Δ4-THPA, it is possible to obtain a liquid isomer mixture at 20°C or even 0°C.
When using a mixture of 50% by weight and 30 to 50% by weight of 4-Me-Δ'-THPA, a liquid isomer mixture can be obtained even at temperatures below -10°C.

The isomer mixture thus obtained is used as a component of unsaturated polyester and is extremely useful as a curing agent for epoxy gamma resin.

The present invention will be explained in more detail with reference to Examples below.

Note that all parts in the examples are based on weight.

Example 1 A 500 ml separable flask with a stirrer had a melting point of 61°C.
Gardner color number 1 or less 3-Me-△4THPA100
After charging 10 parts of calcium oxide and 10 parts of calcium oxide, the reaction was carried out at 200° C. for 3 hours in a nitrogen atmosphere, and then the catalyst was removed by filtration.

The product obtained was Gardner 1, even though no distillation was performed, and had a melting point of 10°C.

In addition, when analyzed by nuclear magnetic resonance spectroscopy, it was confirmed that no movement of the double bond of the cyclohexene ring occurred, and that the geometric isomer was an earth group.

When the same treatment was performed in the absence of a catalyst, the melting point was 4.
The temperature was 6°C.

Example 2 A reaction was carried out in the same manner as in Example 1 except that 4-Me-△4-THPA with a melting point of 64°C and Gardner 1 or less was used instead of 3-Me-△'-THPA. , a product with a Gardner color number of 1 and a melting point of 59° C. was obtained.

For comparison, the reaction was carried out in the absence of a catalyst, and the melting point of the product was 64°C.

11 Example 3 3-Me-Δ4-THPA, 4-M6-Δ4-THPA
and various alkaline earth metal oxides in the proportions shown in Table 1, and the reaction was carried out in the same manner as in Example 1.

The properties of the obtained product are shown in Table 1.

This result shows that any basic metal oxide exhibits good catalytic activity.

Also, 3-Me-△'-THPA and 4-Me-△4-T
It can be seen that when HP A is used in combination, a product with an even lower melting point is obtained.

Example 4 - Ward? p
3-Me-△'-THPA 60 parts, 4-Me-△4
- 40 parts of THPA and a predetermined amount of 0 calcium were charged, and a reaction was carried out according to the predetermined reaction conditions listed in Table 2.

The results are shown in Table 2. In addition, 3-Me-Δ'-TH
The melting point of a mixture of 60 parts of PA and 40 parts of 4-Me-Δ4-THPA was 35°C.

From this result, it can be seen that when the reaction temperature is high, a liquid isomer mixture is obtained, but when the reaction temperature is ioo°C, almost no isomerization occurs.

Claims (1)

[Scope of Claims] 1. Methyl-delta-4-tetrahydrophthalic anhydride, characterized in that methyl-delta-4-tetrahydrophthalic anhydride is heat-treated at 130 to 300°C in the presence of an alkaline earth metal oxide. Acid isomerization method. 2 Methyl-delta-4-tetrahydrophthalic anhydride is 3-methyl-delta-4-tetrahydrophthalic anhydride 1
20% by weight of 4-methyl-delta-4-tetrahydrophthalic anhydride.