JPH0643372B2 - Method for separating and recovering 3,3 ', 4,4'-biphenyltetracarboxylic acid tetraester - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to highly pure 3,3 ′, 4,4′-from a reaction mixture produced by a dimerization reaction of o-phthalic acid diester.
The present invention relates to a method for efficiently separating and recovering biphenyltetracarboxylic acid tetraester.

BACKGROUND OF THE INVENTION Biphenyl tetracarboxylic acid tetraester is an o-phthalate such as dimethyl o-phthalate while solvent-free gas containing molecular oxygen is supplied to a reaction system in the presence of a catalyst containing a divalent palladium salt. It is already known that it can be obtained by dimerizing an acid diester.
-31148, 52-2906, and 57.
-15098, JP-A-56-46844, and JP-A-60-51151.

The reaction product obtained from the o-phthalic acid diester by the above method includes the main product 3,3 ′, 4,4′-biphenyltetracarboxylic acid tetraester (hereinafter referred to as s-B).
Abbreviated as PTT), 2,3,3 ′, 4′-biphenyltetracarboxylic acid tetraester (hereinafter a-B)
(Abbreviated as PTT), biphenyl tricarboxylic acid triester, high boiling point compound and the like. Among these reaction products, s-BPTT is very useful as a raw material for producing an aromatic polyimide having high heat resistance, and a technique for improving the selectivity to s-BPTT in the above dimerization reaction and the above From the reaction product mixture of s-BPTT
Techniques for recovering a high-yield have been conventionally studied.

As a method for highly efficiently recovering s-BPTT from a product by a dimerization reaction of o-phthalic acid diester, a biphenyltetracarboxylic acid tetraester mixture is once hydrolyzed into a biphenyltetracarboxylic acid, and then The method of separating and recovering 3,3 ', 4,4'-biphenyltetracarboxylic acid by fractional crystallization was the mainstream. The separation and recovery operation using such fractional crystallization operation is described in detail in the above-mentioned publication. That is,
3,3 ', 4,4'-biphenyltetracarboxylic acid tetraester (s-BPTT) and 2,3,3', 4'-biphenyltetracarboxylic acid tetraester (a-BPT)
T) is similar in solubility to a usual solvent, and both have a high boiling point and a similar boiling point. Therefore, s-BPTT and a-BPTT can be separated from each other in the ester form as they are. Since it was very difficult, a method of hydrolyzing the mixture to fractionally crystallize it in the form of carboxylic acids whose solubilities were separated from each other had been the object of development.

OBJECT OF THE INVENTION The present invention provides a highly pure 3,3 ', 4,4'-from the reaction mixture produced by the dimerization reaction of o-phthalic acid diester.
An object of the present invention is to provide a novel method for efficiently separating and recovering biphenyltetracarboxylic acid tetraester.

The present invention, in particular, directly without hydrolyzing the reaction product biphenyl tetracarboxylic acid tetraester,
It is an object of the present invention to provide a method capable of separating and recovering 3,3 ′, 4,4′-biphenyltetracarboxylic acid tetraester with high efficiency.

Further, the present invention provides an extremely high purity of 3,3 ', 4,4'.
-It is also an object of the present invention to provide biphenyl tetracarboxylic acid tetraester by a simple operation.

SUMMARY OF THE INVENTION The present invention is produced by supplying a gas containing molecular oxygen to an o-phthalic acid diester under heating without solvent in the presence of a catalyst containing a divalent palladium salt. 4,
4'-biphenyltetracarboxylic acid tetraester,
From a reaction product mixture obtained by removing a catalyst component and unreacted o-phthalic acid diester from a reaction mixture containing 2,3,3 ′, 4′-biphenyltetracarboxylic acid tetraester, biphenyltricarboxylic acid triester and a high boiling point product A method for separating and recovering high-purity 3,3 ', 4,4'-biphenyltetracarboxylic acid tetraester, wherein a reaction product mixture is formed under reduced pressure using a thin film evaporator to produce reaction products other than high boiling point products. A step of evaporating and recovering the substance, rectifying the reaction product recovered by evaporation using a rectification column,
A step of distilling off 2,3,3 ', 4'-biphenyltetracarboxylic acid tetraester and a biphenyltricarboxylic acid triester, and a distillation residual product (can solution) of the above rectification step is a top pressure of 5 Torr or less. A step of rectifying using a rectification column under a column bottom temperature of 320 ° C. or less to recover 3,3 ′, 4,4′-biphenyltetracarboxylic acid tetraester as a distillate. And a method for separating and recovering 3,3 ′, 4,4′-biphenyltetracarboxylic acid tetraester.

[Detailed Description of the Invention] As described above, the present invention provides a molecular structure of an o-phthalic acid diester under heating in the presence of a catalyst containing a divalent palladium salt in the substantially absence of a solvent. From the various reaction products formed when dimerizing the o-phthalic acid diester by supplying a gas containing oxygen,
The present invention provides a method for separating and recovering 3 ', 4,4'-biphenyltetracarboxylic acid tetraester in high yield.

The separation and recovery method of the present invention comprises removing a catalyst component and unreacted o-phthalic acid diester from a reaction mixture according to a known method, and then treating the reaction product mixture by at least two steps.
In this method, 3 ', 4,4'-biphenyltetracarboxylic acid tetraester is separated and recovered.

Hereinafter, the above two types of steps will be described in detail.

In the first step of the present invention, the reaction product mixture obtained by removing the catalyst component and the unreacted o-phthalic acid diester is heated under reduced pressure to obtain a high boiling point having a boiling point higher than that of s-BPTT. In this step, reaction products other than the products are evaporated and collected. That is, since a resinous substance or a similar high-boiling-point product produced by a complicated side reaction exists in the reaction product, an evaporation operation is performed for the purpose of separating this, and the target s-BPTT-containing evaporation recovery is carried out. Get things. In this evaporation operation, it is preferable to use an evaporation device that does not require the evaporation target to be kept at a high temperature for a long time in order to avoid decomposition of the target substance, s-BPTT, as much as possible. Therefore, the evaporation operation of the first step uses a known thin film evaporation device.

The second step is a reaction product having a boiling point lower than that of s-BPTT such as a-BPTT and biphenyltricarboxylic acid triester (hereinafter, simply referred to as “evaporated product obtained by the first step (reaction product recovered by evaporation)”). It is a step for removing low boiling point products) and is carried out using a rectification column. The rectification in the second step needs to be performed at a tower top pressure of 5 Torr or less and a tower bottom temperature of 320 ° C. or less.

As described above, by carrying out the rectification operation under severe conditions under high vacuum, it becomes possible to separate the low boiling point product from s-BPTT with high accuracy while avoiding the decomposition of s-BPTT.

The second step is further divided into a pre-stage for removing the low-boiling product and a post-stage for purifying s-BPTT by removing the accompanying high-boiling product from the first step.

The rectification conditions in the first stage of the second step are column top pressure of 0.1 to 3.
0 torr, tower top temperature 150-240 ° C, tower bottom pressure 2-1
It is preferable that the pressure is 0 torr and the bottom temperature is 250 to 320 ° C., and the top pressure is 0.5 to 1.5 torr, the top temperature is 180 to 240 ° C., the bottom pressure is 2 to 5 torr, and the bottom temperature is 2.
It is particularly preferable that the temperature is 80 to 320 ° C.

In order to operate in the above pressure range, the pressure loss of the packing of the rectification column is preferably 6 mmHg / m or less, and particularly preferably 3 mmHg / m or less.

By operating under the above-mentioned conditions, the bottom liquid obtained in the rectification column in the first stage of the second step contains s-BPTT having a sufficiently high purity. However, s-BPTT is an aromatic polyimide having excellent heat resistance. To use it as one of the raw material monomers,
Further, s-BPTT having a reduced content of biphenyl tricarboxylic acid triester is preferable. For this purpose, the above-mentioned bottom liquid is further rectified to obtain a distillate,
It is preferable to recover the 3 ', 4,4'-biphenyltetracarboxylic acid tetraester (second step after the second step).

The rectification conditions in the latter stage of the second step are column top pressure of 0.1 to 3.
0 torr, tower top temperature 180-320 ° C, tower bottom pressure 2-8
The tower temperature is preferably 260 to 320 ° C., the column top pressure is 0.5 to 1.5 torr, the column top temperature is 250 to 300 ° C., the column bottom pressure is 2 to 5 torr, and the column bottom temperature is 2.
It is particularly preferable that the temperature is 80 to 310 ° C.

In order to operate in the above pressure range, the pressure loss of the packing of the rectification column is preferably 6 mmHg / m or less, and particularly preferably 3 mmHg / m or less.

The packing used in the rectification towers in the first and second stages of the second step described above is preferably a net material composed of a special fine wire with a small pressure drop. As such a net material, Sulzer BX Packing (Sumitomo (Available from Heavy Machinery Co., Ltd.), ROMDOPAK (manufactured by Tsukishima Machinery Co., Ltd.),
And Dual Pack (manufactured by Nippon Kagaku Kikai Co., Ltd.), but Sulzer BX packing is preferable.

Next, the method for separating and recovering 3,3 ′, 4,4′-biphenyltetracarboxylic acid tetraester from the dimerization reaction product of the present invention will be described in more detail with reference to the accompanying drawings.

After the catalyst component is reduced and removed from the dimerization reaction solution by a known method and the unreacted o-phthalic acid diester is distilled off, the boiling point is lower than that of the high boiling point product in the thin film evaporator 1 of FIG. Distill all components. This distillate is s-BPTT,
It consists of a-BPTT, biphenyl tricarboxylic acid triester, and trace amounts of high boiling products. The above-mentioned distillate is introduced into the rectification column 3 via the conduit 2.

This rectification column processes the above-mentioned distillate under the above-mentioned pressure and temperature conditions to distill off compounds having a lower boiling point than s-BPTT, such as a-BPTT and biphenyltricarboxylic acid triester, to obtain s-BPTT. Is a main component, and is a step of collecting a can liquid in which a trace amount of high boiling point products and the like are mixed.

When carrying out the above-mentioned rectification step (first step of the second step), a plurality of rectification towers can be arranged in series, if desired, but two rectification towers are used in terms of equipment and cost. It is preferable.

That is, the distillate of the thin film evaporator 1 is first rectified in the rectification column 3, and by this rectification operation, a low boiling point product and a trace amount of s-BPTT are obtained, A bottom liquid containing s-BPTT as a main component is obtained at the bottom. Next, the distillate obtained at the top of the rectification column 3 is guided to the rectification column 5 by the conduit 4, and the rectification operation is further performed. By this rectification operation, substantially the low boiling point product is distilled off and separated, and the bottom liquid is piped.
Thus, the s-BPTT contained in the distillate of the rectification column 3 is efficiently recovered by refluxing to the rectification column 3.

In the rectification operation in the latter stage of the second step, the bottom liquid of the rectification column 3 is treated in the high boiling rectification column 8 under the above-mentioned pressure and temperature conditions,
It is a step of collecting the distillate as s-BPTT. On the other hand, the high boiling point compound and a small amount of s-BPTT obtained at the bottom of the high boiling rectification column 8 are refluxed to the thin film evaporator 1 to produce s-B.
Collect PTT. When performing the above-mentioned rectification step (second step of the second step), it is possible to arrange a plurality of high-boiling rectification towers in series if desired, but from the viewpoint of equipment and cost, two rectification towers are used for treatment. Preferably.

That is, the above-mentioned can liquid of the rectification tower 3 is first introduced into the rectification tower 8 by the guiding can 7 and rectified. By this rectification, s-BPTT is mainly distilled off from the top of the tower. Next, the distillate obtained at the top of the rectification column 8 is introduced into the rectification column 10 through the conduit 9, and the rectification operation is repeated. By this rectification operation, the desired highly pure s-BPTT can be obtained at the top of the column.

The bottom liquid of the rectification column 10 is a high boiling point product and s-BPTT.
Therefore, the bottom liquid is refluxed to the rectification column 8 through the conduit 11 to recover s-BPTT. The bottom liquid of the rectification column 8 is mainly composed of high-boiling products, but is slightly s-B.
Since it contains PTT, the bottom liquid is returned to the thin film evaporator 1 through the conduit 12 to recover s-BPTT.

The s-BPTT (3, separated and recovered by the method of the present invention,
3 ', 4,4'-biphenyltetracarboxylic acid tetraester) is hydrolyzed by a known method, for example, a method of hydrolyzing at high temperature and high pressure, or a method of hydrolyzing by adding an acid or an alkali. 3 ', 4, 4'
-Biphenyltetracarboxylic acid, which can be dehydrated by heating it to a higher temperature to give 3,3 ', 4,4' which is important as one of the monomer raw materials of aromatic polyimide having excellent heat resistance. Biphenyltetracarboxylic dianhydride can be obtained.

[Effects of the Invention] By utilizing the separation and recovery method of the present invention, s-BPTT can be separated and purified without causing thermal deterioration due to evaporation operation, etc. As compared with the method of separating isomers by crystallization, s-BPTT with high purity can be efficiently obtained continuously.

S-BPTT obtained by the separation and recovery method of the present invention
(3,3 ′, 4,4′-biphenyltetracarboxylic acid tetraester) has a high purity, and in particular, the mixed amount of biphenyltricarboxylic acid triester which is an obstacle to the polyimide formation reaction utilizing s-BPTT is 0.1. Since the content is very small, such as less than 1% by weight, the heat-resistant aromatic polyimide can be used as an ester or in the form of a derivative such as acid dianhydride (3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride). It can be used very advantageously in manufacturing.

Next, examples and comparative examples of the present invention will be shown.

[Example 1] O-dimethyl phthalate was reacted for 10 hours at 220 ° C under atmospheric pressure in the absence of a solvent in the presence of molecular oxygen using a catalyst composed of palladium acetate, o-phenanthroline and copper acetate to give a dihydrogenate. Quantified. The catalyst is reduced and removed, and unreacted o
-After recovering dimethyl phthalate, the mixture of the dimerization products is rectified in the step shown in the flow sheet in FIG.
Tetramethyl 3,3 ′, 4,4′-biphenyltetracarboxylic acid (s-BPTTM) was recovered as a distillate at the top of the rectification column 10. Each rectification column was packed with Sulzer BX packing. Table 1 shows the operating conditions of each rectification column.

Table 2 shows the composition of the distillate at the top of the rectification column 10 recovered by the above method.

Comparative Example 1 From the dimerization reaction product obtained in Example 1, the catalyst was removed in the same manner, unreacted dimethyl o-phthalate was recovered, and then the mixture evaporated by the thin film evaporator 1 was recovered. Instead of rectifying, the mixture (evaporation recovery product) and methanol were mixed with a line mixer at a ratio of 1: 4 (volume ratio), cooled at 25 ° C., crystallized, and centrifuged to obtain purified biphenyl tetra. Crystals of tetramethyl carboxylate were obtained.

The composition of the above-mentioned crystals is shown in Table 2.

[Brief description of drawings]

FIG. 1 is a flow sheet showing a separation / collection operation which is preferably adopted for carrying out the separation / collection method of the present invention. 1: thin film evaporator, 2: conduit, 3: rectification column, 4: conduit,
5: rectification tower, 6: conduit, 7: conduit, 8: rectification tower, 9: conduit, 10: rectification tower, 11: conduit, 12: conduit

Claims (1)

[Claims] 1. A 3,3 ′, 4 produced by supplying a gas containing molecular oxygen to an o-phthalic acid diester under heating without solvent in the presence of a catalyst containing a divalent palladium salt.
4'-biphenyltetracarboxylic acid tetraester,
From a reaction product mixture obtained by removing a catalyst component and unreacted o-phthalic acid diester from a reaction mixture containing 2,3,3 ′, 4′-biphenyltetracarboxylic acid tetraester, biphenyltricarboxylic acid triester and a high boiling point product A method for separating and recovering high-purity 3,3 ', 4,4'-biphenyltetracarboxylic acid tetraester, wherein a reaction product mixture is formed under reduced pressure using a thin film evaporator to produce reaction products other than high boiling point products. A step of evaporating and recovering the substance, rectifying the reaction product recovered by evaporation using a rectification column,
A step of distilling off 2,3,3 ′, 4′-biphenyltetracarboxylic acid tetraester and biphenyltricarboxylic acid triester; the distillation residual product of the above rectification step is a column top pressure of 5 Torr or less and a column bottom temperature. Rectifying using a rectification column under the condition of 320 ° C. or less to recover 3,3 ′, 4,4′-biphenyltetracarboxylic acid tetraester as a distillate. A method for separating and recovering 3,3 ', 4,4'-biphenyltetracarboxylic acid tetraester.