JPS5930709B2 - Method for producing isomerized liquid polycarboxylic acid anhydride - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing a liquid acid anhydride mixture.

Generally 4-methyl-△4-tetrahydrophthalic anhydride (
3-methyl- (hereinafter abbreviated as 4-methyl-△4-THPA)
Δ4-tetrahydrophthalic anhydride (hereinafter referred to as 3-methyl-Δ
It is known that a liquid anhydrous acid can be obtained by isomerizing the double bond in the molecule of methyl-THPA (such as 4-THPA) alone or in a mixture. , resin acids, palladium-based catalysts, etc. are known to be used.

When using a catalyst other than a palladium-based catalyst among the above isomerization catalysts, the mixed anhydride obtained by isomerizing 4-methyl-△4-THPA or 3-methyl-△4-THPA alone has a high freezing point and can be used at room temperature. Generally, only solid acids or acid anhydrides with melting points of a few degrees can be obtained.

For this improvement, 4-methyl-△4-THPA and 3-methyl-△4-THPA mixture were used as raw materials,
For example, a liquid acid anhydride is produced by mixing a third component such as hexahydrophthalic anhydride (hereinafter abbreviated as HHPA) and an isomerized product. When using a palladium catalyst, for example, as described in Japanese Patent Publication No. 44-458, a liquid acid anhydride mixture with a sufficiently low freezing point can be produced even if 4-methyl-Δ4-THPA is subjected to an isomerization reaction alone. However, during isomerization, a considerable disproportionation reaction occurs as a side reaction, and the side reaction product is methylhexahydrophthalic anhydride (hereinafter methyl-HH).
(abbreviated as PA) and methyl phthalic anhydride (hereinafter referred to as methyl-P)
A) is reported to be produced in considerable amounts, for example about 22-53% by weight. However, according to the inventor's study, the above-mentioned side reaction product methyl-HHPA
The isomerized methyl-THPA mixture, which contains a relatively small amount of such side reaction products, is affected by the above-mentioned Japanese Patent Publication No. 44-458. Compared to the acid anhydride mixture described in No.
It is extremely stable against moisture in the atmosphere, and is superior in that it absorbs almost no moisture.Furthermore, it has a lower viscosity and lower freezing point, so it has excellent stability and workability. It was found to be more excellent as a resin curing agent.

The present invention relates to methyl-HHP produced by the above disproportionation reaction.
Methyl-△ containing only a small amount of A and methyl-PA
As a result of extensive research aimed at producing a liquid acid anhydride mixture containing THPA as a main component and having low hygroscopicity and good low-temperature stability, it was discovered that this objective could be achieved by using a specific catalyst.

That is, the present invention provides a liquid acid anhydride containing methyl-Δ1-tetrahydrophthalic anhydride as a main component, which is characterized in that methyl-Δ4-tetrahydrophthalic anhydride is isomerized in the presence of a palladium catalyst and sulfur or a sulfur compound. It relates to a method for producing a mixture.

In the present invention, the raw material for the isomerization reaction is 4-methyl-△4-
Methyl-△ such as THPAl3-methyl-Δ4-THPA
4-THPA can be used alone or in the form of a mixture. In the present invention, the palladium catalyst can be used as a metal alone, but it is preferable that the palladium is supported in an amount of about 0.1 to 10% by weight, preferably about 1 to 5% by weight, on a carrier such as carbon, alumina, silica, or asbestos.

The sulfur or sulfur compound to be added can be either sulfur alone or an organic compound or an inorganic compound containing sulfur in the molecule, and exhibits excellent selectivity. Examples of the above-mentioned sulfur-containing organic compounds include ethyl mercaptan, benzyl mercaptan, lauryl mercaptan, dibutyl sulfide, benzyl sulfide, dibenzyl disulfide, dibenzyl trisulfide, thiophene 1,4-dithiodiene, and thiabenzene. In addition, examples of inorganic compounds containing sulfur include sodium sulfide, sodium sulfate, p
-Tolylmercaptan sodium salt, sodium p-toluenesulfonate, etc. can be mentioned.

Depending on the concentration used, sulfur or sulfur compounds can act as catalyst poisons that inhibit not only disproportionation reactions but also isomerization reactions, and the concentration added to the reaction system must be strictly controlled. . As a result of various studies on this point, we found that the appropriate amount of sulfur or sulfur compounds to be added to the reaction system is approximately 1 to 200 ppm in terms of S relative to the raw material methyl-Δ4-THPA, and that if the amount added is large, the isomerization reaction will occur. It has been found that if the addition amount is small, the selectivity will deteriorate. The method of carrying out the present invention is based on the raw material methyl-Δ4-THPA, 100%
Approximately 0.01 to 5 parts of palladium (in terms of pure content) and the aforementioned predetermined amount of sulfur or sulfur compound are used per 0 parts by weight (hereinafter all parts by weight).

Sulfur or a sulfur compound may be added directly as it is, or may be supported on the same carrier as palladium. In this case, the supporting ratio is preferably about 0.1 to 10% by weight. These raw materials, catalysts, etc. are charged into a reactor equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet, and heated to about 150-260°C, preferably about 160-260°C, in a nitrogen gas atmosphere.
Preferably, the isomerization reaction is carried out at 240°C for about 3 to 20 hours.

In the present invention, when 4-methyl-Δ4-TAPA is used as a raw material, 4-methyl-Δ1THPA is usually about 45 to 10
0% by weight, 4-methyl△4-THPA approximately 0-25% by weight
, 4-methylΔ2-THPA and 4-methyl-Δ3-T
Approximately 0-28% by weight as HPA mixture, 4-methyl-H
A liquid acid anhydride consisting of about 0 to 3% by weight of HPA and about 2% by weight or less of other components, and 3-methyl-△4-TH
When using PA as a raw material, 3-methyl-△1-THPA
About 40-100% by weight, 3-methyl-△4-THPA about 0-15% by weight, 3-methyl-△2-THPA and 3-
Approximately 0-38% by weight as methyl-Δ3-THPA mixture
, a trace amount of 3-methyl-HHPA, approximately 7% by weight of other components
A liquid acid anhydride consisting of:

In the present invention, as described above, a large amount of methyl-Δ1-THPA is produced through the isomerization reaction and becomes the largest component in the acid anhydride mixture, and at the same time, methyl-Δ1-THPA is produced through the isomerization reaction.
The amounts of HHPA and methyl-PA produced are small. The amount of methyl-Δ1-THPA produced may account for about 90 to 100% by weight of the mixture depending on the reaction conditions, and especially when the amount of methyl-Δ1-THPA is 55% by weight or more, especially about 60% by weight. % or more is preferred. On the other hand, the amount of the disproportionation reaction product in the present invention is small, as described above, and is usually about 1 to 7% by weight. The liquid acid anhydride, which is the object of the present invention, can be made into a product as it is by separating the catalyst from the reaction mixture by a filtration method or a sintering method.

Further, if necessary, it can be purified by distillation or the like. The present invention will be illustrated below with examples.

Examples 1 to 4 Raw material 3-methyl-Δ4-THPA or 4-methyl-Δ
A predetermined amount of a palladium catalyst supported on a 4-THPAI carrier and a sulfurized component were charged into 21 four-way flasks (equipped with a stirrer, a reflux condenser, and a gas inlet), and reacted in a nitrogen gas atmosphere to produce 3-methyl A liquid acid anhydride containing 4-methyl-Δ1-THPA or 4-methyl-Δ1-THPA as a main component is produced.

Table 1 shows the amount charged, reaction conditions, results, etc. 9 Examples 5 to 8 Isomerization was carried out in the same manner as in Example 1 using a catalyst in which palladium and a sulfur compound were supported on a carrier.

The amount charged, reaction conditions, results, etc. are shown in Table-2. Next table-
Comparison of the viscosity and water absorption of the acid anhydride mixture obtained by the method of the present invention as described in Section 3, the acid anhydride mixture described in Japanese Patent Publication No. 44-458, and 4-methyl-hexahydrophthalic anhydride. I conducted an experiment. Water absorption test (1) Water absorption diameter of acid anhydride mixture 54177! A sample of about 10 f was accurately weighed in a glass shear dish, and the sample was placed in a thermostatic chamber at a room temperature of 25° C. and a temperature of 50 to 60% to examine its change over time.

The results are shown in Figure 1. Note that A in FIG. 1 represents Example 1 and B
represents Example 2, C represents Example 3, D represents Example 4, E represents Example 5, F represents Example 7, G represents Comparative Example G, H represents Comparative Example H, and I represents Comparative Example I. Figure 1 shows that the anhydride mixture of the present invention has an extremely low water absorption rate and no dicarboxylic acid crystals precipitate, whereas the comparative example has a high water absorption rate and does not precipitate dicarboxylic acid crystals at 22 hours. Be looked at.

[Brief explanation of drawings]

FIG. 1 is a graph showing the water absorption properties of acid anhydride mixtures of the present invention and comparative examples.

Claims (1)

[Claims] 1. A liquid acid anhydride containing methyl-△^1-tetrahydrophthalic anhydride as a main component, which is characterized by isomerizing methyl-△^4-tetrahydrophthalic anhydride in the presence of a palladium catalyst and sulfur or a sulfur compound. Method of manufacturing the mixture.