JPH0476991B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of the Invention] The present invention relates to an improvement in a method for producing high purity biphenyltetracarboxylic dianhydride by heating and anhydrifying biphenyltetracarboxylic acids. [Background of the Invention] It is already well known that aromatic polyimides having excellent properties as heat-resistant resins can be industrially advantageously produced by using biphenyltetracarboxylic dianhydride as a raw material. Biphenyltetracarboxylic dianhydride is o-
O-phthalic acid diester such as dimethyl phthalate is dimerized using a palladium-based catalyst, purified, crystallized, and hydrolyzed to produce biphenyltetracarboxylic acid, and then the biphenyltetracarboxylic acid is heated to a high temperature. It can be obtained by making it anhydrous. To anhydride the above-mentioned biphenyltetracarboxylic acid by heating it to a high temperature, for example, under a nitrogen atmosphere and a reduced pressure of 100 to 500 mmHg,
A method of heating to 0.degree. C. is described in Japanese Patent Publication No. 57-15098. However, according to the research of the present inventor, when aromatic polyimide is synthesized by copolymerizing aromatic diamines and biphenyltetracarboxylic dianhydride obtained by the conventional method as described above, polymerization It has been found that there is a problem in that the viscosity of the reaction solution is not sufficiently high and a high molecular weight aromatic polyimide cannot be obtained. [Object of the Invention] The present invention provides monomer raw materials useful as one of the monomer raw materials for producing high molecular weight aromatic polyimide.
It is an object of the present invention to provide a method that can industrially advantageously produce high-purity biphenyltetracarboxylic dianhydride. [Summary of the Invention] The present inventor has discovered that even if aromatic polyimide is synthesized by copolymerizing aromatic diamines and biphenyltetracarboxylic dianhydride obtained by a conventional method, the viscosity of the polymerization reaction solution remains low. We investigated the reasons why the temperature did not rise to a sufficiently high level. As a result, when the amount of biphenyltricarboxylic acid (hereinafter simply referred to as tricarboxylic acid) that is mixed as an impurity in biphenyltetracarboxylic dianhydride increases, the increase in the viscosity of the polymerization reaction solution is inhibited. It was found that the formation of high molecular weight aromatic polyimides was hindered. Then, by carrying out the heating operation including the anhydration step under specific heating conditions, high purity biphenyltetracarboxylic dianhydride with a significantly reduced amount of tricarboxylic acid mixed in is obtained,
It has been found that a high molecular weight aromatic polyamide can be obtained when such high purity biphenyltetracarboxylic dianhydride is copolymerized with an aromatic diamine. This invention was already announced in June 1986.
It was filed on the 25th as Japanese Patent Application No. 159246/1983. As a result of further research into a method for obtaining biphenyltetracarboxylic dianhydride with a low amount of biphenyltricarboxylic acid, the inventors have discovered that the progress of the process of heat-treating biphenyltetracarboxylic acid to anhydride. At the same time, an inert gas such as nitrogen gas is brought into contact with the reaction mixture while flowing, and by-product tricarboxylic acid is removed from the reaction mixture by accompanying the flowing inert gas, thereby reducing the amount of tricarboxylic acid mixed in. It has been newly discovered that highly purified biphenyltetracarboxylic dianhydride with significantly reduced purity can be obtained. Therefore, the present invention provides a method for producing biphenyltetracarboxylic dianhydride by anhydrating biphenyltetracarboxylic acid by heat-treating it at an anhydration temperature of 250°C or higher under normal pressure or reduced pressure. The anhydration operation is carried out by contacting the reaction mixture at a temperature of 250 to 300°C for 8 to 40 hours with an inert gas flowing at a flow rate of 2 to 20 Nm ^{3 /} hour per 1 m 3 of biphenyltetracarboxylic acid as a raw material. , a method for producing high-purity biphenyltetracarboxylic dianhydride, characterized in that the process is carried out while removing by-produced biphenyltricarboxylic acid from the reaction mixture. [Detailed Description of the Invention] In the present invention, high purity biphenyltetracarboxylic dianhydride can be produced as follows. Biphenyltetracarboxylic acid, which is a raw material for high-purity biphenyltetracarboxylic dianhydride, is o-
It can be obtained by dimerizing an o-phthalic acid di-lower alkyl ester such as dimethyl phthalate and then hydrolyzing this. Biphenyltetracarboxylic acid obtained by dimerization of di-lower alkyl o-phthalate is usually
It is a mixture of three types of isomers: 3,3',4,4'-isomer, 2,2',3,3'-isomer, and 2,3,3',4'-isomer, and the above-mentioned biphenyl The tetracarboxylic acid crystal is preferably in a crystalline state in which one of these three types is separated from the other two types.
The present invention provides biphenyltetracarboxylic acid with 3,
It can be particularly advantageously applied when it is a 3', 4, 4'-configuration. After the above-mentioned purified biphenyltetracarboxylic acid is purified, it is further preliminarily heat-treated to obtain
It may be one in which adhering water and crystal water contained in the crystals have been removed. When carrying out the dehydration operation of the present invention, a reaction tank equipped with an inert gas introduction pipe, an exhaust pipe, and a stirring device is generally used. The anhydrification of biphenyltetracarboxylic acid is carried out by (1) contacting the reaction mixture with an inert gas (preferably nitrogen gas) in the absence of active gases such as oxygen, with stirring if necessary, and (2) with constant stirring. Under pressure or reduced pressure, preferably normal pressure ~ 40mm
Under reduced pressure of Hg, (3) at an anhydration temperature of 250 to 300°C, preferably 255 to 280°C, and (4) by heat treatment for 8 to 40 hours, preferably 10 to 30 hours. Let's do it. In the present invention, the heat treatment is preferably carried out over a sufficient period of time to substantially completely anhydride biphenyltetracarboxylic acid and to sublimate and remove secondary biphenyltricarboxylic acids, It is preferable to carry out the treatment within the above-mentioned time range. In the present invention, by heat-treating biphenyltetracarboxylic acid as described above, one water molecule is dehydrated from each adjacent pair of carboxyl groups of biphenyltetracarboxylic acid, and the anhydride ring of the carboxyl group is dehydrated. A condensation to form is carried out. As a result, biphenyltetracarboxylic dianhydride is produced, and biphenyltricarboxylic acid (e.g., 3,3',4-biphenyltricarboxylic acid, 3,4,4'-biphenyltricarboxylic acid) is produced as a by-product. , or acid anhydrides thereof) are removed from the biphenyltetracarboxylic dianhydride accompanied by an inert gas. Note that tricarboxylic acid may exist as an impurity in biphenyltetracarboxylic acid as a raw material, and in this case, at least a portion of the tricarboxylic acid is removed from the reaction mixture accompanied by an inert gas. be done. In the present invention, the operation of bringing the reaction mixture into contact with a flowing inert gas can be carried out, for example, by introducing an inert gas into the upper part of the reaction tank and touching the upper surface of the reaction mixture and the vapor of the reaction mixture with the flowing inert gas. A method such as contacting with a certain inert gas can be used. The inert gas that comes into contact with the reaction mixture and is accompanied by tricarboxylic acid is discharged from an exhaust system such as an exhaust pipe, but in this case it is desirable to heat the exhaust system. If the exhaust system is not heated, the tricarboxylic acid that sublimes and accompanies the inert gas may cool in the exhaust system, solidify, and flow back into the reaction tank. Heating is a preferred embodiment. The heating temperature of the exhaust system such as the exhaust pipe may be within a temperature range at which the biphenyltricarboxylic acids do not solidify, but it is preferably within the range of 200 to 350°C. The heating method for the exhaust system is not particularly limited, and can be carried out, for example, by covering almost the entire length of the exhaust pipe from the reaction tank to the exhaust port with a jacket and flowing a heat medium through the jacket. The flow rate of the inert gas was 1 m ³ of biphenyltetracarboxylic acid during the above-mentioned anhydration heat treatment.
The amount needs to be in the range of 2 to 20 Nm ³ /hour (apparent capacity). By flowing an inert gas into the reaction tank in an amount within the above range, the sublimation of the biphenyltricarboxylic acid is promoted, thereby making it easier to remove the tricarboxylic acid. It is desirable that the inert gas be heated to a temperature range of 200 to 350° C. without significantly cooling the atmosphere inside the reaction tank, and then introduced into the reaction tank. If an inert gas is introduced into the reaction tank without heating, some of the biphenyltricarboxylic acid that is in the gaseous state will sublimate and solidify, increasing the amount of biphenyltricarboxylic acid mixed in the product. be. The inert gas to be introduced can be heated, for example, by covering the introduction pipe with a jacket and flowing a heat medium through it in the same way as heating the exhaust pipe. For example, the heating of the reaction tank, exhaust pipe, etc.
Heat-resistant heat-resistant liquids or vapors of aromatic compounds such as alkylbenzenes, alkylnaphthalenes, alkyl diphenyls, diphenyl ethers, hydrogenated triphenyls, and dibenzyltoluenes, or mineral oil liquids such as paraffinic mineral oils and alkyl aromatic mineral oils. Preferably, this is carried out using a medium. The heat source may be electrical energy such as an electric resistance heater or an infrared heater, as long as the temperature in each heat treatment of the present invention can be controlled within the requirements of the manufacturing method of the present invention. The biphenyltetracarboxylic dianhydride obtained as described above usually has a biphenyltricarboxylic acid content of less than 0.1% by weight, and by selecting the heat treatment conditions, the content of biphenyltricarboxylic acids can be reduced to 0.08% by weight.
Less than 0.05% by weight, even less than 0.05% by weight. When such highly purified biphenyltetracarboxylic dianhydride and aromatic diamine are copolymerized by a known method, the viscosity of the polymerization reaction solution increases and a high molecular weight aromatic polyimide is produced. The viscosity of the polymerization reaction solution is usually expressed as logarithmic viscosity. Logarithmic viscosity is a value expressed by the following formula: Logarithmic viscosity=natural logarithm (solution viscosity/solvent viscosity)/solution concentration, and has a high correlation with the molecular weight of polyimide. In the case of copolymerization of biphenyltetracarboxylic dianhydride and aromatic diamines, the resulting aromatic polyimide has a logarithmic viscosity (measurement temperature: 30°C, concentration: 0.5 g/100 ml solvent (N-methyl-2 -pyrrolidone)) is usually 2.5 to 7.0, more preferably 3.0 to 5.0. [Effect of the invention] The high-purity biphenyltetracarboxylic dianhydride of the present invention has an extremely low amount of impurity biphenyltricarboxylic acid, and has a high purity by copolymerizing the anhydride and aromatic diamines. Aromatic polyimides of molecular weight can be obtained. Next, Examples and Comparative Examples of the present invention will be shown. Example 1 An inert gas inlet pipe and an exhaust pipe are attached, a disc-type stirring device is built in, and a jacket for circulating a heat-resistant heat medium is provided so that the inert gas inlet pipe, exhaust pipe, and outer wall of the reaction tank are almost completely covered. 280 kg (apparent volume: about 0.4 m ³ ) of purified crystals of 3,3',4,4'-biphenyltetracarboxylic acid are introduced into the covered reactor. Next, the reaction tank is heated, the raw materials are stirred at normal pressure, and the inert gas introduction pipe and exhaust pipe are heated to 300°C.
The contents of the reaction vessel ( ³ , 3', 4,
4′-biphenyltetracarboxylic acid) was maintained at an anhydration temperature of 280°C for 20 hours, thereby producing 3,3′,
4,4'-biphenyltetracarboxylic acid was anhydrified to produce 247 kg of 3,3',4,4'-biphenyltetracarboxylic dianhydride. Next, 300ml with a stirrer and nitrogen flow pipe attached.
In a three-neck flask were placed 11.76 kg of 3,3',4,4'-biphenyltetracarboxylic dianhydride obtained as described above and diaminodiphenyl ether.
8.00g and N-methyl-2-pyrrolidone
177.84 g was charged and stirred for 5.5 hours at 30° C. under a nitrogen atmosphere to synthesize aromatic polyimide. The viscosity of the polymerization reaction solution was measured, and the logarithmic viscosity was calculated from the above formula. The result of anhydration and the logarithmic viscosity of the polymerization reaction solution are
Shown in the table. Comparative Example 1 Except that after the gas in the reaction tank was once replaced with nitrogen gas, the flow of nitrogen gas was not carried out.
Anhydration was carried out using the same reactor and reaction conditions as in Example 1 to obtain 247 kg of 3,3',4,4'-biphenyltetracarboxylic dianhydride. Next, using this 3,3',4,4'-biphenyltetracarboxylic dianhydride, aromatic polyimide was synthesized in the same manner as in Example 1, and the logarithmic viscosity of the polymerization reaction solution was calculated. . The result of anhydration and the logarithmic viscosity of the polymerization reaction solution are
Shown in the table.

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Claims (1)

[Scope of Claims] 1. When biphenyltetracarboxylic acid is anhydrified by heat treatment under normal pressure or reduced pressure to produce biphenyltetracarboxylic dianhydride, the anhydration operation is performed by The reaction mixture is brought into contact with an inert gas flowing at a flow rate of 2 to 20 Nm ³ /hour per 1 m ³ of enyltetracarboxylic acid at a temperature of 250 to 300°C for 8 to 40 hours to produce biphenyltricarboxylic acid as a by-product. 1. A method for producing high-purity biphenyltetracarboxylic dianhydride, which is carried out while removing from a reaction mixture. 2. The method for producing high-purity biphenyltetracarboxylic dianhydride according to claim 1, wherein the inert gas that has come into contact with the reaction mixture is discharged from the reaction system using a heated discharge system. 3 The inert gas in contact with the reaction mixture is
The method for producing high-purity biphenyltetracarboxylic dianhydride according to claim 1, which comprises discharging from the reaction system using a discharging system heated at 350°C.