JP3087993B2 - Method for producing aromatic polyamic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high molecular weight aromatic polyamic acid from biphenyltetracarboxylic dianhydride obtained by dehydrating biphenyltetracarboxylic acid.

[0002]

2. Description of the Related Art It is well known that aromatic polyimides having excellent properties as heat-resistant resins can be produced industrially advantageously by using biphenyltetracarboxylic dianhydride as a raw material. That is, an aromatic polyimide is generally obtained by cyclizing (imidizing) a polyamic acid obtained by polymerization (copolymerization) of biphenyltetracarboxylic dianhydride and an aromatic diamine at a low temperature around normal temperature. ing. And biphenyltetracarboxylic dianhydride dimerizes o-phthalic acid diesters such as o-dimethyl phthalate using a palladium-based catalyst,
Biphenyltetracarboxylic acid is obtained through purification, crystallization, hydrolysis, and other steps, and the biphenyltetracarboxylic acid is heated to a high temperature to be dehydrated.

[0003] The above-mentioned method of dehydrating biphenyltetracarboxylic acid by heating it to a high temperature includes, for example, 100 to 50 mmHg under a reduced pressure of normal pressure to 40 mmHg in a nitrogen atmosphere.
The method of heating at 0 ° C. is described in JP-B-57-15098.
No., published in Japanese Unexamined Patent Publication No. As a method for purifying biphenyltetracarboxylic dianhydride, a method for purifying crude biphenyltetracarboxylic dianhydride by heating and recovering the same is disclosed in JP-A-61-249977.
No., published in Japanese Unexamined Patent Publication No. Further, a method of obtaining biphenyltetracarboxylic dianhydride with less coloring by heating biphenyltetracarboxylic acid at a low concentration using an acetic anhydride solvent and anhydrating the same is disclosed in JP-A-62-11.
No. 6572.

[0004]

According to the study of the present inventors, it has been reported that an aromatic polyamic acid is produced by copolymerizing with an aromatic diamine using a biphenyltetracarboxylic dianhydride obtained by a known method. It has been found that there is a problem that the viscosity of the polymerization reaction solution is not sufficiently high, and a high molecular weight aromatic polyamic acid cannot be obtained. Accordingly, an object of the present invention is to provide a method for producing a high molecular weight aromatic polyamic acid (and furthermore, an aromatic polyimide).

[0005]

Means for Solving the Problems The present inventors have proposed a polymerization reaction for producing an aromatic polyamic acid by polymerizing biphenyltetracarboxylic dianhydride obtained by a known method and an aromatic diamine. The reason why the viscosity of the liquid did not become sufficiently high was examined. As a result, when the amount of biphenyltricarboxylic acids (biphenyltricarboxylic acid and / or anhydride) mixed as impurities in biphenyltetracarboxylic dianhydride (reaction product) increases, the viscosity of the polymerization reaction solution increases. Has been found to be impeded, ie the production of high molecular weight polyamic acids has been impeded.

Accordingly, the present inventor has repeated studies on a method for obtaining a biphenyltetracarboxylic dianhydride-containing product having a low content of biphenyltricarboxylic acids, and as a result,
By dehydrating biphenyltetracarboxylic acid under specific heating conditions, a product containing less than 0.15% by weight (particularly less than 0.1% by weight) of mixed biphenyltricarboxylic acids (mixed amount) ( Crystal) can be obtained, and the use of biphenyltetracarboxylic dianhydride, in which the content of biphenyltricarboxylic acids is extremely reduced as described above, as a raw material enables the production of a high molecular weight aromatic polyacic acid. And completed the present invention.

[0007] The present invention relates to a biphenyltetracarboxylic dianhydride obtained by dehydration of biphenyltetracarboxylic acid, wherein the total content of biphenyltricarboxylic acid and its anhydride is less than 0.15% by weight (particularly, (Preferably less than 0.1% by weight) of a biphenyltetracarboxylic dianhydride and an aromatic diamine in a method for producing a high molecular weight aromatic polyamic acid.

The above-mentioned high-purity biphenyltetracarboxylic dianhydride containing an extremely small amount of biphenyltricarboxylic acid and its anhydride is obtained by crystallizing biphenyltetracarboxylic acid under an inert gas atmosphere (usually, usually Under reduced pressure or reduced pressure), and then heat-treated at a dehydration temperature of 250 ° C. or higher to produce biphenyltetracarboxylic dianhydride, before the temperature is raised from 80 ° C. to the dehydration temperature. The heat treatment was performed at an average heating rate of 50 ° C /
The heating is carried out at a temperature not higher than the time to remove the adhering water and water of crystallization adhering to the crystal, and then heating the preheated crystal at an anhydrous temperature of 250 to 300 ° C. for at least 3 hours. It can be easily produced by treating and dehydrating. In the above-mentioned manufacturing method, the pre-heating treatment is such that the crystal is heat-treated and the temperature is raised to 130 ° C. so that the average heating rate is not higher than 30 ° C./hour, and the attached water is mainly removed from the crystal. In the first step, the crystal is subjected to a heat treatment to increase the temperature from 130 ° C. to the dehydration temperature so that the average rate of temperature rise does not become higher than 50 ° C./hour. Preferably, a second step to be performed is included.

The biphenyltetracarboxylic dianhydride containing an extremely small amount of biphenyltricarboxylic acid used in the method for producing an aromatic polyamic acid according to the present invention can be obtained by anhydrification of a known biphenyltetracarboxylic acid or by a known method. It cannot be obtained by an industrial purification method of the dehydrated crude biphenyltetracarboxylic dianhydride. For example, the mixed amount (total content of biphenyltricarboxylic acids) of biphenyltetracarboxylic dianhydride obtained by the method described in JP-A-61-249977 and the method described in JP-A-62-116572. ) Is usually 0.5% by weight or more.

The high-purity biphenyltetracarboxylic dianhydride (high-purity crystal) used in the method for producing an aromatic polyamic acid of the present invention can be produced as follows. Biphenyltetracarboxylic acid crystals, which are raw materials for high-purity biphenyltetracarboxylic dianhydride-containing products,
It can be obtained by dimerizing an o-phthalic acid di-lower alkyl ester such as o-dimethyl phthalate and then hydrolyzing it. Biphenyltetracarboxylic acid obtained by dimerization of o-phthalic acid di-lower alkyl ester is usually 3,3 ′, 4,4′-isomer,
It is a mixture of three isomers of 2 ', 3,3'-isomer and 2,3,3', 4'-isomer, and the above-mentioned biphenyltetracarboxylic acid crystal is obtained by adding any one of these three kinds to the other. It is desirable that the material be separated and purified from the two types. In particular, biphenyltetracarboxylic acid is 3,3 ', 4,4
Desirably, it is a 4'-form.

In the method for producing high-purity biphenyltetracarboxylic dianhydride, when performing the above-mentioned dehydration heat treatment, first, the pre-heat treatment during the temperature rise from about 80 ° C. to the dehydration temperature is averaged. In order to prevent the heating rate from becoming higher than 50 ° C./hour, preferably, the heating is performed at an average heating rate of 45 ° C./hour or less for at least one hour to remove the attached water and the crystallization water attached to the crystals. In addition, 8
The heating conditions for raising the temperature to 0 ° C. are not particularly limited. However, the above preheating treatment is particularly preferably performed at an average heating rate of about 0.01 to 28 ° C / hour and at least 0.5 hour, particularly preferably, so that the average heating rate is not higher than 30 ° C / hour. Is a first step of heat-treating the crystal for about 1 to 5 hours to raise the temperature to about 130 ° C., and removing and drying the crystal mainly by evaporation of attached water, and an average heating rate of 50 ° C. / Especially preferably, the average heating rate is 10 to 45 ° C. so as not to become higher than the time.
/ Hour, at least 0.5 hour, particularly preferably 1 to
6 hours, heat-treat the dried crystals as described above,
The temperature is increased from about 130 ° C. to the dehydration temperature, and the pretreatment for reproducibly dehydrating the crystal is performed in two steps including a second step of mainly removing water of crystallization from the crystal. desirable.

That is, when the first step of the preheating treatment is performed on the crystal, at about 80 to 130 ° C., the adhering water retained or adsorbed in the voids between the crystal particles is evaporated. Drying of the crystals occurs which is gradually removed. Further subsequently, when the second step described above is performed on the dried crystals, at about 130-anhydrous temperature, the coordination within the crystals or the intermolecular force between the crystals and water molecules As the bound crystal water is gradually removed from the crystal, removal of water that hinders dehydration
Drying is sufficiently performed.

If the preheating treatment of heating the biphenyltetracarboxylic acid from about 80 ° C. to the dehydration temperature is performed at an average heating rate higher than 50 ° C./hour, the removal and drying of the adhering water and crystallization water are insufficient. This is not preferable because it becomes difficult to maintain the dehydration temperature uniformly over the entire crystal when the crystal is subjected to the dehydration heat treatment. When the dehydration temperature cannot be maintained uniformly, the entire crystal is heated unevenly, the temperature becomes extremely high locally, and the crystal sinters. In addition, the dehydration itself is not uniformly performed, and the formation of biphenyltricarboxylic acid by decarboxylation tends to occur.

The second step in the pre-heating treatment is to heat the first half from about 130 ° C. to 170 ° C. at an average heating rate of about 40 ° C.
Per hour or less for at least 0.5 hour, the second half of which is from about 170 ° C. to the dehydration temperature at an average heating rate of 50 ° C.
/ Hour or less.

In the dehydration step, the crystal subjected to the preheating treatment is stirred, if necessary, under an atmosphere of an inert gas (preferably nitrogen gas) free of an active gas such as oxygen. 3) 250-300 under normal pressure or reduced pressure, preferably reduced pressure from normal pressure to 40 mmHg
It is carried out by subjecting to a heat treatment at a dehydration temperature of ° C, preferably 255-290 ° C, for at least 3 hours, preferably 5-40 hours, particularly preferably 10-30 hours.

In the above-mentioned method, the crystal from which water has been sufficiently removed by the pre-heating treatment of the biphenyltetracarboxylic acid crystal is subjected to the dehydration heating treatment as described above, whereby the adjacent pair of carboxyl groups of the biphenyltetracarboxylic acid is treated. Each one of the water molecules is dehydrated from the group and condensation is performed to form the anhydride ring of the carboxyl group, resulting in biphenyltetracarboxylic dianhydride. In addition, biphenyltricarboxylic acids (eg, 3,3 ′, 4-biphenyltricarboxylic acid, 3,4,4′-biphenyltricarboxylic acid, or acid anhydrides thereof) by-produced in the dehydration step or the like are sublimated. Is removed from the crystals of biphenyltetracarboxylic dianhydride.

In carrying out the above-described production method, pressurized steam or a heat medium as a heat source is circulated as a heat source in the space inside the rotating blades of the agitator or in the jacket covering the outer wall of the reaction vessel, to obtain biphenyltetracarboxylic acid. What is necessary is just to perform the pre-heating treatment and the dehydration heating treatment of the crystals of, for example,
When the pressurized steam and the heat-resistant heat medium are used in combination, it is preferable to use different heat sources for the inside of the jacket and the gap inside the rotary blade. The preheat treatment is preferably performed using pressurized steam. For example, the pressurized steam used for the first preheat treatment has a steam pressure of 1.0 to 5
kg / c〓, particularly preferably 1.1 to 3 kg / c〓. Dehydration treatment, for example, liquid or vapor of an aromatic compound such as alkylbenzene, alkylnaphthalene, alkyldiphenyl, diphenylether, hydrogenated triphenyl, dibenzyltoluene, or liquid of a mineral oil such as a paraffinic mineral oil or an alkylaromatic mineral oil It is preferable to use a heat-resistant heat medium consisting of

When the pre-heating treatment and the dehydration heating treatment of the crystal are carried out by using the same kind of heat-resistant heat medium having a different temperature, the temperature can be raised continuously, and the heat treatment can be carried out step by step in each heat treatment step. In addition, each time the type of the heat medium changes, it is separated into a different portion provided in the reaction tank (for example, a gap portion of a rotating blade of a stirring device, a jacket covering an outer wall of the reaction tank, etc.). There is no need to supply. The heat source may be electric energy such as an electric resistance heater or an infrared heater as long as uniform heating in each heat treatment can be performed and the rate of temperature rise can be controlled.

The above-obtained biphenyltetracarboxylic dianhydride has a biphenyltricarboxylic acid content (mixed amount) of less than 0.15% by weight (based on the product). By doing, 0.
It is less than 1% by weight.

The method for producing an aromatic polyamic acid according to the present invention is characterized in that a high-purity biphenyltetracarboxylic dianhydride with a small amount of biphenyltricarboxylic acid obtained by the above method is used as a raw material. . That is, when such a high-purity biphenyltetracarboxylic dianhydride and an aromatic diamine are copolymerized by a known method, the viscosity of the polymerization reaction solution increases, and a high-molecular-weight aromatic polyamic acid is produced.

[0021] The viscosity of the polymerization reaction solution is usually indicated by logarithmic viscosity. The logarithmic viscosity is given by the following formula: Which is highly correlated with the molecular weight of the polyamic acid (and polyimide).

The logarithmic viscosity (measurement temperature) is obtained by copolymerizing a biphenyltetracarboxylic dianhydride produced as described above, in which the content of the biphenyltetracarboxylic acid is reduced, with an aromatic diamine by a known method. 3
0 ° C., concentration; 0.5 g (polymer) / 100 mL solvent,
Solvent: N-methyl-2-pyrrolidone) is 2.5 to 7.0.
And further, a high molecular weight polyamic acid in the range of 3.0 to 5.0 can be obtained.

[0023]

【Example】

[Example 1] A built-in disk type stirring device having a rotating blade with a horizontal rotating shaft in which a gap through which pressurized steam or a heat-resistant heat medium can flow is built in, and pressurized steam or a heat-resistant heat medium is incorporated. 280 kg of purified 3,3 ', 4,4'-biphenyltetracarboxylic acid crystals are placed in a reaction vessel (dryer) whose outer wall is almost covered with a jacket for distributing the nitrogen gas, and placed under a nitrogen gas atmosphere. The first step of the pre-heating treatment is carried out at a normal pressure while stirring at a pressure of 2 kg / cm ² G through both the rotating blades and the jacket to remove water adhering to the crystals.
The temperature was raised from 100 ° C. to 100 ° C. at an average rate of 30 ° C./hour, and then maintained at a temperature of 100 ° C. for about 1 hour.

Subsequently, the second step of the preheating treatment is switched so that pressurized steam of 6 kg / cm ² G flows through the rotating blades and the jacket to remove water of crystallization of the crystals. The temperature was raised from 100 ° C. to 130 ° C. at an average rate of 25 ° C./hour.
For 2 hours. Next, the reaction mixture was heated to 280 ° C. under an average temperature rising condition of 35 ° C./hour. The preheated crystals in the reaction vessel are maintained at a dehydration temperature of 280 ° C. for 20 hours while being stirred in an atmosphere of nitrogen gas, to thereby prepare 3,3 ′, 4,4′-biphenyltetracarboxylic acid. The acid was dehydrated to yield 247 kg of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride. Next, 300 m equipped with a stirrer and nitrogen flow pipe
に Into a three-necked flask,
11.76 g of 3 ', 4,4'-biphenyltetracarboxylic dianhydride, 8.00 of diaminodiphenyl ether
g and 177.84 g of N-methyl-2-pyrrolidone
Was charged and stirred at 30 ° C. for 5.5 hours in a nitrogen atmosphere to measure the viscosity of the polymerization reaction solution when the aromatic polyamic acid was synthesized, and the logarithmic viscosity was calculated from the above equation. Table 1 shows the results of dehydration and the logarithmic viscosity of the polymerization reaction solution.

Example 2 A heat-resistant heat medium of various temperatures was circulated through a jacket of a reaction tank, and no other heat source was used. The first step of the pre-heating treatment was performed by raising the temperature from about 80 ° C. to 100 ° C. at an average rate of 25 ° C./hour, and then maintaining the temperature at 100 ° C. for 1 hour. continue,
In the second step (first half) of the pre-heating treatment for removing water of crystallization of crystals, the temperature is raised from 100 ° C. to 150 ° C. at an average rate of 25 ° C./hour, and then maintained at 150 ° C. for 2 hours. I did it. Furthermore, the second step of the preheating treatment (second half)
The temperature was raised from 150 ° C. to the dehydration temperature of 280 ° C. at an average rate of 35 ° C./hour. Example 1 was repeated except that the dehydration treatment was performed at 280 ° C. for 20 hours.
Using the same reaction tank and raw materials as those used in Example 1, an anhydrous reaction was performed under the same reaction conditions as in Example 1, and
3 ', 4,4'-biphenyltetracarboxylic acid was dehydrated to produce 247 kg of 3,3', 4,4'-biphenyltetracarboxylic dianhydride. Next,
Using 3 ′, 4,4′-biphenyltetracarboxylic dianhydride, an aromatic polyamic acid was synthesized in the same manner as in Example 1, and the logarithmic viscosity of the polymerization reaction solution was calculated. Table 1 shows the results of dehydration and the logarithmic viscosity of the polymerization reaction solution.

Example 3 The first step of the preheating treatment for the crystals in the reaction vessel was carried out by raising the temperature from about 80 ° C. to 130 ° C. continuously by using a heat-resistant heat medium at 20 to 25 ° C.
Per hour at an average rate of temperature rise, and then the second step of the preheating treatment is performed by raising the temperature from 130 ° C. to 280 ° C. continuously with a heat-resistant heat medium at 30 to 35 ° C./hour. Example 1 was repeated using the same reactor and raw materials as in Example 1 except that the heating was performed at an average temperature rising rate, and finally, the crystals were maintained at 280 ° C. for 20 hours to carry out the dehydration heat treatment.
Under the same reaction conditions as described in
3 ′, 4,4′-biphenyltetracarboxylic acid was dehydrated to produce 247 kg of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. Next,
Using 3 ′, 4,4′-biphenyltetracarboxylic dianhydride, an aromatic polyamic acid was synthesized in the same manner as in Example 1, and the logarithmic viscosity of the polymerization reaction solution was calculated. Table 1 shows the results of dehydration and the logarithmic viscosity of the polymerization reaction solution.

[Comparative Example 1] Using the same reaction vessel and raw materials as in Example 1, a high-temperature heat-resistant heat medium was passed through the jacket of the reaction vessel to carry out each heat treatment. Example 1 except that the temperature was raised from 80 ° C. to 280 ° C. in one step in 2 hours (average rate of temperature increase 100 ° C./hour), and then the crystal was maintained at 280 ° C. for 5 hours.
Under the same reaction conditions as described in
246 kg of 3 ', 4,4'-biphenyltetracarboxylic dianhydride were produced. Next, these 3,3 ', 4
Using 4'-biphenyltetracarboxylic dianhydride,
An aromatic polyamic acid was synthesized in the same manner as in Example 1, and the logarithmic viscosity of the polymerization reaction solution was calculated. Table 1 shows the results of dehydration and the logarithmic viscosity of the polymerization reaction solution.

Table 1 Total Acid Dehydration Ratio Triacid Logarithmic Viscosity (%) (%) (%) ──────────────────────────────── Example 1 100 100 0.06 4.0 Example 2 100 100 0.06 4.0 Example 3 100 100 0.07 3.8 Comparative Example 1 99.0 99.0 0.3 2.3 ──────────────────

Total acid: The content of biphenyltetracarboxylic dianhydride in the dehydrated product. Dehydration ratio: The production ratio of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride to the raw material. Triacid: the content of biphenyltricarboxylic acids in the product. (Measurement temperature: 30 ° C., concentration: 0.5 g (polymer) / 1)
00 mL solvent, solvent: N-methyl-2-pyrrolidone)

From the above results, it can be seen that the use of the biphenyltetracarboxylic dianhydride containing an extremely small amount of the biphenyltricarboxylic acid of the present invention makes it possible to obtain a high-viscosity (ie, high molecular weight) aromatic polyamic acid from a known aromatic polyamic acid. It can be seen that it can be produced by a polymerization reaction with a diamine.
On the other hand, when the biphenyltricarboxylic acid is used in an amount of 0.2% by weight or more of the biphenyltetracarboxylic dianhydride specified in the present invention, the viscosity of the obtained aromatic polyamic acid is clearly reduced and is high. It is also apparent that it is difficult to obtain one having a molecular weight.

[0031]

The biphenyltricarboxylic acid of the present invention and the biphenyltetracarboxylic dianhydride having an extremely low content of less than 0.15% by weight of the acid anhydride are polymerized with aromatic diamines by a known method. Thereby, a high molecular weight aromatic polyamic acid can be obtained.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Genji Koga 1978-10 Ogushi, Obe-shi, Ube-shi, Yamaguchi Ube Industries, Ltd. Ube Chemical Factory (56) References JP-A-60-81154 (JP, A) JP 38-5997 (JP, B1) JP-B 39-30060 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 73/10

Claims (2)

(57) [Claims] 1. A biphenyltetracarboxylic dianhydride obtained by dehydrating biphenyltetracarboxylic acid, wherein the total content of biphenyltricarboxylic acid and its anhydride is less than 0.15% by weight. A method for producing a high molecular weight aromatic polyamic acid, comprising polymerizing an acid dianhydride and an aromatic diamine. 2. The biphenyltetracarboxylic dianhydride used as the biphenyltetracarboxylic dianhydride has a total content of less than 0.1% by weight of biphenyltricarboxylic acid and its anhydride. 2. The method for producing an aromatic polyamic acid according to 1.