JP3625504B2 - High purity biphenyltetracarboxylic dianhydride and process for producing the same - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a high-purity biphenyltetracarboxylic dianhydride (hereinafter referred to as BPDA) and a method for producing the same. Specifically, the present invention relates to a high-purity BPDA having a very low content of insoluble fine particles and a method for producing the same.
[0002]
[Prior art]
BPDA is a useful compound as a raw material for producing an aromatic polyimide, which is attracting attention as a heat resistant resin. Aromatic polyimide using BPDA is either a method of producing by a polymerization reaction of BPDA and aromatic diamine, or a method of ring-closing imidization of polyamic acid obtained by polymerization of BPDA and aromatic diamine at a low temperature near room temperature. Can be manufactured.
[0003]
Aromatic polyimide using BPDA has a large application in the field of electronic materials. In recent years, with the advancement of functions of electronic material products, high performance has been required for aromatic polyimides used as films and varnishes as well. In particular, various improvements have been studied for higher performance with respect to heat resistance, insulation, gas barrier properties, and the like, which are characteristics of aromatic polyimide. For example, typical applications of aromatic polyimides using BPDA include gas separation membranes and flexible printed circuit boards. In these fields of application, however, there are issues to be addressed as membrane functions become more sophisticated and substrates become more functional. As a result, there is an increasing demand for improving defects in films and molded products.
[0004]
Conventionally, depending on the use of an organic compound, the inclusion of insoluble fine particles may be extremely disliked. For example, if insoluble fine particles are mixed in BPDA, which is a raw material for aromatic polyimide, due to these production processes and other reasons, it naturally remains in the product polymer as it is. Insoluble fine particles include (a) those mixed in the production process and (b) those mixed in the process of handling the organic compound after production. Specific examples of (a) include those derived from catalysts, catalyst carriers, metal powders, packing powders, and other manufacturing equipment. Specific examples of (b) handle products. It is a fine powder such as dust floating in the atmosphere.
[0005]
The inventors have found that there is some correlation between the specific characteristics of the aromatic polyimide and the content of insoluble fine particles in a special region for unknown reasons. That is, when the content of the insoluble fine particles in a special region is below a certain level, the specific characteristics of the above-mentioned aromatic polyimide can be greatly improved, that is, the particle size is in the range of 5 to 30 μm. It was found that various defects occur when the content of insoluble fine particles is 1 × 10 ⁴ or more per gram. For example, if the use of aromatic polyimide is for fibers, it will cause thread breakage during spinning, and if the use is for film, it will cause fish eyes, pinholes, etc. When the application is a varnish, fish eyes are generated, and when the application is a gas separation membrane, the separation characteristics are deteriorated.
[0006]
In order to eliminate the disadvantages derived from these insoluble fine particles, generally, a method of removing the insoluble fine particles by installing a filter during the process of producing the aromatic polyimide is taken. The life of this filter depends on the filter material, usage conditions, and usage time, but it is often governed by the insoluble particulate content in the liquid to be treated. The production cost is unavoidable due to the fact that the product becomes short-lived, the productivity and yield decrease, and the frequent replacement of expensive filters is necessary. In any case, it is strongly desired to reduce insoluble fine particles in the raw material.
[0007]
BPDA can be obtained by heating biphenyltetracarboxylic acid (hereinafter referred to as BTC) to a temperature range of 150 to 250 ° C. and subjecting it to a dehydration ring-closing reaction. From the standpoint of coloring, a satisfactory level cannot be obtained. Therefore, a method has been proposed in which crude BPDA obtained by heating BTC is volatilized by heating to a temperature of 250 to 400 ° C. under reduced pressure, and then the vapor of this volatilized BPDA is cooled and recovered as purified crystals. (See Japanese Patent Publication No. 4-37078).
However, the method described in this publication may fail to satisfy the insoluble fine particle content level required for the raw material for producing aromatic polyimide, and can stabilize the high-purity BPDA with extremely low insoluble fine particle content and Therefore, development of a manufacturing method has been desired.
[0008]
[Problems to be solved by the invention]
In view of the above situation, the present inventors have intensively studied to provide a high-purity BPDA and an industrially advantageous production method thereof. As a result, as described above, specific characteristics of aromatic polyimide and insoluble fine particles in a special region The reason is unknown for the body content, but it was found that there is some correlation, and the present invention was completed.
An object of the present invention is to provide a high-purity biphenyltetracarboxylic dianhydride (hereinafter referred to as BPDA) and an industrially advantageous production method thereof.
[0009]
[Means for Solving the Problems]
The biphenyltetracarboxylic dianhydride for polyimide according to the present invention is characterized in that the content of insoluble fine particles having a size of 5 to 30 μm is 2 × 10 ³ or less per 1 g .
[0012]
Hereinafter, the present invention will be described in detail.
In the present invention, the insoluble fine particles refer to those having a size of 5 to 30 μm mixed in the raw material and product due to the cause of the above (a) or (b). These sizes, numbers, etc. can be easily confirmed and counted by a particle size image processing apparatus, for example, an apparatus capable of enlarging and counting fine particles such as GX-10 manufactured by Mitsubishi Chemical Corporation.
[0013]
In the method of the present invention, BPDA obtained by a dehydration ring-closing reaction of BTC containing an insoluble fine particle of a specific amount or less or crude BPDA containing an insoluble fine particle of a specific amount or less is volatilized, and then the volatile component is cooled. Then, a method of recovering as crystals is adopted.
[0014]
In order to carry out the method of the present invention using BTC containing a specific amount or less of insoluble fine particles, first, the BTC crystal is heated to a temperature of 150 to 250 ° C. under reduced pressure to cause a dehydration ring closure reaction. The produced BPDA is volatilized by heating under normal pressure or reduced pressure, and then the volatile component is cooled and recovered as crystals (hereinafter simply referred to as “first method”). Further, in order to carry out the method of the present invention using crude BPDA containing a specific amount or less of insoluble fine particles, the crude BPDA is heated and volatilized under reduced pressure, and the volatile matter is cooled and recovered as crystals ( Hereinafter, it is simply referred to as “second method”).
[0015]
The BTC and crude BPDA used in the present invention are not particularly limited in these production methods, and may be produced by any method. BTC and crude BPDA are limited to BTC and crude BPDA in which the content of insoluble fine particles having a size of 5 to 30 μm is 7 × 10 ⁴ or less per 1 g. In order to obtain a high-purity BPDA in which the content of insoluble fine particles is 7 × 10 ⁴ or less per gram of crude BPDA and the content of insoluble fine particles is at the target level, it is necessary to repeat volatile purification operations. In addition, productivity and yield are extremely lowered, which is not preferable.
[0016]
BTC is usually obtained by hydrolyzing tetramethyl biphenyltetracarboxylate obtained by dehydration dimerization reaction of dimethyl o-phthalate in an aqueous medium in the presence of an acid catalyst. In addition, 4-halophthalic acid obtained by halogenating phthalic anhydride is subjected to dehalogenation dimerization reaction in an aqueous medium in the presence of an alkali, a reducing agent, and a Pd catalyst to obtain a biphenyltetracarboxylic acid tetraalkali metal salt. This can also be obtained by neutralizing with a mineral acid. The BTCs thus obtained are essentially all 3,4,3 ′, 4′-isomers.
[0017]
The BTC obtained by the above method can be used as a raw material compound of the “first method” of the present invention. The content of insoluble fine particles having a size of 5 to 30 μm must be 7 × 10 ⁴ or less per 1 g, but usually BTC containing 5 × 10 ³ to 7 × 10 ⁴ per 1 g used. For this purpose, the liquid raw material and solvent to be used need to pass through a filter to remove insoluble fine particles. Similarly, the reaction solution from which the solid catalyst has been removed must be passed through a filter and adjusted so that the content of insoluble fine particles is 7 × 10 ⁴ or less per gram. The filter used at this time varies depending on conditions, but for example, a filter having a pore diameter of 1 μm is used in combination of one stage or a plurality of stages in series.
[0018]
A crude BPDA is produced using the BTC prepared by the above method as a raw material. In order to obtain BPDA using BTC as a raw material, in accordance with a known method, for example, in a liquid medium such as 2 to 10 times by weight of acetic anhydride or decalin, heating to a temperature range of 100 ° C. to the boiling point of the liquid medium is performed. It can be easily obtained by reacting.
The crude BPDA thus obtained can be used as a raw material compound of the “second method” of the present invention. The content of insoluble fine particles having a size of 5 to 30 μm contained in the crude BPDA must be 7 × 10 ⁴ or less per 1 g, but usually 5 × 10 ³ to 7 × 10 ⁴ per 1 g. The containing BPDA is used. For this purpose, the liquid raw material and solvent to be used need to pass through a filter to remove insoluble fine particles.
[0019]
The dehydration ring closure reaction of the “first method” of the present invention will be described in detail. When BTC is heated to a temperature of 150 to 250 ° C. under normal pressure or reduced pressure, for example, in the range of 10 ² to 10 ⁵ Pa, crude BPDA is obtained. can get. In this case, the raw material BTC can be used in a wet state. In this case, adhering water and further crystal water are removed by evaporation in the course of temperature rising, and then a dehydration ring-closing reaction occurs. These series of reactions are carried out while purging the adhering water, crystal water and water generated by the dehydration ring closure reaction outside the reaction system, so that the reaction rate is improved, so that an inert gas is passed at normal pressure, or It is preferable to carry out under reduced pressure.
The time required for the dehydration ring-closing reaction varies depending on the heating rate, heating temperature, degree of reduced pressure, and the presence or absence of attached water, but can usually be selected in the range of 0.5 to 10 hours.
[0020]
The “second method” of the present invention will be described in detail. When the crude BPDA obtained by the above method is heated and volatilized, and the volatilized BPDA is cooled, high-purity BPDA with an extremely low content of insoluble fine particles is obtained as crystals. It precipitates and can be easily recovered. The volatilization operation of the crude BPDA is preferably performed while heating under reduced pressure. If the heating temperature is too low, BPDA cannot be volatilized efficiently, and if it is too high, BPDA is thermally decomposed. According to the experiments by the present inventors, it was found that the temperature should be 300 to 400 ° C., preferably 300 to 350 ° C. under a reduced pressure of 4000 Pa or less, preferably 2700 Pa or less.
[0021]
When crude BPDA with a high content of insoluble fine particles is volatilely purified, most of the insoluble fine particles remain as residues in the distillation kettle. The insoluble fine particles in the purified product increase. Therefore, when crude BPDA with a high content of insoluble fine particles is used, it is necessary to frequently extract the residue of the distillation pot, and the productivity and yield are extremely lowered. When crude BPDA with a low content of insoluble fine particles is used as a raw material, there is no need to frequently extract the residue in the distillation kettle even when performing a volatile refining operation in a batch system, which improves both productivity and yield. .
[0022]
If the crude BPDA contains insoluble fine particles, if the crude BPDA contains volatilized BPDA, if the volatilization rate is high, the insoluble fine particles are mixed with the vapor that volatilizes and mixes with the volatile purified product. It is preferable to select an appropriate volatilization rate.
[0023]
The cooling temperature of the volatilized BPDA is usually 200 ° C. or lower, preferably 100 ° C. or lower. This cooling method can be performed by various methods, but is usually performed by a drum-type rotary cooler disposed at the tip of a gas pipe directly connected to a gas phase portion of a container for performing a volatilization operation, for example, an evaporation kettle or the like. Is preferred. The BPDA adhering to the drum type rotary cooler is easily and continuously scraped by a suitable scraper and recovered as flakes.
[0024]
The BPDA thus obtained has a high purity of insoluble fine particles of 5 to 30 μm in size of 2 × 10 ³ or less per gram, and is suitable as a raw material for producing aromatic polyimide, In addition, an aromatic polyimide having excellent insulation and gas barrier properties can be obtained.
And the gas separation membrane manufactured from the aromatic polyimide which used said high purity BPDA as a raw material has very few membrane defects, and exhibits the separation characteristic outstandingly excellent compared with the conventional product. Furthermore, it is preferable that the film obtained by the reaction of BPDA having an insoluble fine particle content of 1 × 10 ² or less per 1 g and an aromatic diamine has remarkably improved gas barrier properties. On the other hand, the film obtained by the reaction of 2 × 10 ⁴ BPDA and aromatic diamine per gram of insoluble fine particles was poor in insulation and could not be used as a flexible printed board.
[0025]
【Example】
EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not limited to the following description examples, unless the meaning is exceeded.
In the following examples, solvent preparation, sample preparation, and insoluble fine particle counting were performed according to the following procedure.
<Preparation of solvent>
In a class 100 clean bench, reagent-grade N-methylpyrrolidone was passed through a filter having a mesh size of 0.2 μm to remove insoluble particles having a size of 0.2 μm or more.
[0026]
<Sample adjustment>
First, in a class 100 clean bench, about 1 g of a sample is precisely weighed into a cleaned and dried glass bottle, 200 ml of the above N-methylpyrrolidone is added thereto, and the mixture is placed in an ultrasonic cleaner for about 3 hours. The washer was turned on to dissolve the sample. Subsequently, this solution was passed through a filter having a coarseness of 0.4 μm to separate insoluble fine particles.
<Counting insoluble fine particles>
In a Class 1000 clean room, the number of insoluble fine particles on the filter was measured using a particle size image processing apparatus {manufactured by Mitsubishi Chemical Corporation, GX-10}. The number of insoluble fine particles measured was corrected with the sample weight and converted to the number per 1.0 g of the sample.
[0027]
[Example 1]
A vertical cylindrical reactor equipped with a stirrer, a jacket, a condenser, a thermometer, and an inert gas supply port was charged with 100 parts by weight of BTC containing 2 × 10 ⁴ insoluble fine particles having a size of 5 to 30 μm per gram. . While stirring the reactor contents, heating to 215 ° C. under normal pressure, passing nitrogen gas at a rate of 2 m ³ / hour, purging the generated water, and continuing the dehydration ring closure reaction for 10 hours, Obtained. Subsequently, the temperature was raised to 300 ° C. and held at this temperature for 5 hours to melt the crude BPDA.
[0028]
The melt of crude BPDA was transferred to a vertical cylindrical evaporation kettle equipped with a jacket and evaporated (volatilized) under the conditions of 305 ° C. and 230 Pa. The evaporated BPDA was brought into contact with the surface of a drum-type rotary cooler disposed at the end of a gas pipe directly connected to the gas phase portion of the evaporation kettle, and was cooled and deposited. The BPDA crystals adhering to the drum surface were continuously scraped by a scraper and recovered as flakes. After pulverizing this flake, 80 parts by weight of purified BPDA was obtained.
When the number of insoluble fine particles having a size of 5 to 30 μm in the purified BPDA was counted, it was 400 per 1 g, which was much smaller than that of the insoluble fine particles in the raw BTC.
[0029]
[Example 2]
In the example described in Example 1, the raw material was operated in the same procedure as in Example 1 except that the raw material was replaced with BTC containing 5 × 10 ⁴ insoluble fine particles having a size of 5 to 30 μm.
The number of insoluble fine particles having a size of 5 to 30 μm in the obtained BPDA was 1000 per 1 g, which was significantly smaller than that of the insoluble fine particles in the raw material BTC.
[0030]
[Comparative Example 1]
In the example described in Example 1, the raw material was operated in the same procedure as in the same example except that BTC containing 1.5 × 10 ⁵ insoluble fine particles having a size of 5 to 30 μm per 1 g was used. .
The number of insoluble fine particles having a size of 5 to 30 μm in the obtained BPDA was 3500 per 1 g, exceeding 2 × 10 ³ per 1 g of the target value.
[0031]
【The invention's effect】
The present invention has the following particularly advantageous effects, and its industrial utility value is extremely large.
1. A high-purity BPDA having a content of insoluble fine particles having a size of 5 to 30 μm according to the present invention of 2 × 10 ³ or less per 1 g is produced by reacting this with an aromatic diamine to produce a polyimide. When it is processed into a gas separation membrane, a product with few membrane defects can be obtained.
2. According to the method of the present invention, a high-purity BPDA with an extremely low content of insoluble fine particles can be easily produced.
3. When the crude BPDA having a content of insoluble fine particles of a specific amount or less is used as a raw material by the method of the present invention, it is not necessary to frequently extract the residue in the distillation kettle even when the batch operation is performed. Yield is greatly improved.

Claims (1)

A biphenyltetracarboxylic dianhydride for polyimide, wherein the content of insoluble fine particles having a size of 5 to 30 μm is 2 × 10 ³ or less per 1 g.