JP2003073359A - Method for refining isoquinoline - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for efficiently distilling/refining isoquinoline from the exhaust gas and waste liquid recovered from a polyimide production process. SOLUTION: In distilling/isolating the isoquinoline from the waste solution discharged from the polyimide production process and comprising the isoquinoline, organic acids and reactive high-boiling materials, this method for refining the isoquinoline comprises the steps of (1) carrying out distillation at <=150 deg.C in the region where both the isoquinoline and the organic acids are present inside the distillation column, and (2) carrying out distillation at <=200 deg.C in the regiom where the reactive high-boiling materials are present inside the distillation column.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying isoquinoline from a solution containing isoquinoline.

[0002]

2. Description of the Related Art Isoquinoline (hereinafter referred to as IQ) is obtained by distillation from coal tar derived from high temperature carbonization of coal.
It is obtained by an extraction method, a crystallization method or the like. For example, JP-A-200
In 0-14633, IQ is roughly separated from the bitumen coal tar by distillation, followed by acid extraction,
Crystallization treatment, purification distillation, and further crystallization treatment were performed to obtain purified IQ having a purity of at least 97% by weight.

In addition to being used as a raw material for various pharmaceutical products, IQ is used as a curing agent in the process of producing a polyimide film. Waste liquid and exhaust gas containing IQ in the polyimide film manufacturing process may be discarded or incinerated, but if the IQ discharged from the process can be recovered and reused, its merit is great.

[0004]

The problem to be solved by the present invention relates to a purification method for efficiently recovering IQ from a solution containing IQ.

[0005] Conventionally, since IQ is derived from high temperature carbonization of coal, it is a substance stable to heat, and it is considered that it is unlikely to be modified even when heated to a high temperature. In recovering and reusing the IQ discharged from the sample, it was attempted to liquefy and recover the gas containing various organic solvents discharged from the heat treatment step of the polyimide film, and to distill and purify IQ from the recovered solution.

However, in the distillation operation usually considered, it was observed that the yield of the target component (IQ) was unexpectedly low and that the solution became highly viscous to make the distillation operation difficult.

[0007]

In view of the above situation, as a result of various studies on causes of reduction in IQ yield, it was found that IQ reacts with an organic acid at high temperature as shown in Reference Example 1. . Moreover, as a result of various studies on the cause of the thickening and solidifying phenomenon of the solution, it was discovered that the high boiling point component thickens and solidifies at high temperature. The present invention provides a method for purifying IQ with good yield by removing these factors that inhibit IQ purification, and specifically provides the following purification method.

(1) A method for purifying isoquinoline, wherein the temperature in the distillation column is set to 200 ° C. or lower in batch distillation for isoquinoline isolation from a solution containing isoquinoline and a reactive high-boiling substance.

(2) In continuous distillation using a distillation apparatus composed of at least two distillation columns for isoquinoline isolation from a solution containing isoquinoline and a reactive high-boiling substance, the boiling point of isoquinoline is higher than that of isoquinoline. A method for purifying isoquinoline, characterized in that the temperature in the distillation column in the first column for recovering low substances and the second column for recovering isoquinoline from the top of the column is set to 200 ° C. or lower.

(3) In batchwise distillation for isoquinoline isolation from a solution containing isoquinoline and an organic acid, the temperature in the distillation column is kept at 150 ° C. or lower until the amount of isoquinoline in the overhead distillate exceeds 30% by weight. A method for purifying isoquinoline, which comprises:

(4) In continuous distillation using a distillation apparatus composed of at least two distillation columns for isoquinoline isolation from a solution containing isoquinoline and an organic acid, a substance having a boiling point lower than that of isoquinoline is removed from the top of the column. A method for purifying isoquinoline, wherein the temperature in the distillation column of the first column to be recovered is set to 150 ° C. or lower.

(5) isoquinoline, a reactive high-boiling point component,
In batch distillation for isolating isoquinoline from a solution containing an organic acid, the temperature in the distillation column is set to 150 ° C or lower until isoquinoline in the overhead distillate exceeds 30% by weight, and 200 ° C or lower thereafter. A method for purifying isoquinoline, comprising:

(6) Isoquinoline, a reactive high boiling point component,
In a continuous distillation using a distillation apparatus comprising at least two distillation columns for isolating isoquinoline from a solution containing an organic acid, distillation of the first column for recovering a substance having a boiling point lower than that of isoquinoline from the top of the column A method for purifying isoquinoline, wherein the temperature in the column is 150 ° C. or lower and the temperature in the distillation column in the second column for recovering isoquinoline from the top of the column is 200 ° C. or lower.

In each of the above methods, when the reactive high-boiling substance is the reactive high-boiling substance contained in the waste liquid collected from the polyimide manufacturing process or the liquefaction recovery solution of the exhaust gas, and the composition of the organic acid is C _n H _{2n + 1} COOH (n = 0,
The case where the organic acid is represented by 1, 2) is mentioned as a typical embodiment of the present invention.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION One of the present invention provides a method for purifying isoquinoline from a solution containing a reactive high-boiling substance in addition to isoquinoline.

The reactive high-boiling substance is typically a high-boiling substance contained in a waste liquid discharged from a polyimide film manufacturing process or a liquefied and recovered solution of exhaust gas, and the boiling point at atmospheric pressure is that of isoquinoline. A substance which can react with itself or isoquinoline at a temperature above (242 ° C.) and above 200 ° C. is specifically mentioned.

When isoquinoline is purified from a solution containing such a reactive high-boiling substance, the temperature in the distillation column is preferably 200 ° C. or lower in batch distillation. Further, in continuous distillation using a distillation apparatus composed of at least two distillation columns, a first column for recovering a substance having a lower boiling point than isoquinoline from the top of the column, and
It is preferable that all the temperatures in the distillation column in the second column for recovering isoquinoline from the column top are set to 200 ° C. or lower.
This is because when the temperature exceeds 200 ° C., the solution becomes highly viscous and the distillation operation becomes difficult.

The present invention also provides a method for purifying isoquinoline from a solution containing an organic acid in addition to isoquinoline.

Examples of the organic acid include carboxylic acids and phenols, and in particular, C _n H _{2n + 1} COOH (which is often contained in the waste liquid discharged from the manufacturing process of the polyimide film or the liquefied and recovered solution of exhaust gas). n = 0, 1, 2)
The purification method of the present invention is preferably used when the organic acid is represented by

When isoquinoline is purified from a solution containing such an organic acid, in batch distillation, the temperature in the distillation column is set to 150 until the isoquinoline in the overhead distillate exceeds 30% by weight. It is preferable that the temperature is not higher than ° C.
Further, in continuous distillation using a distillation apparatus composed of at least two distillation columns, the temperature in the distillation column of the first column for recovering a substance having a boiling point lower than that of isoquinoline from the top of the column is set to 150 ° C. or lower. It is preferable. These temperatures are 1
This is because if the temperature exceeds 50 ° C., a reaction between isoquinoline and an organic acid occurs, which easily leads to a decrease in yield.

As described above, when the solution of isoquinoline contains a reactive high-boiling substance, a temperature of 200 ° C. or lower is preferable, and when an organic acid is contained, 150 ° C. or lower is preferable. When both the high-boiling substance and the organic acid are contained and the boiling point of the organic acid is lower than the boiling point of IQ, the following method is effective.

That is, in the batch distillation, the temperature in the distillation column is set to 150 ° C. or lower until the isoquinoline in the top distillate exceeds 30% by weight, and thereafter set to 200 ° C. or lower. Further, in continuous distillation using a distillation apparatus composed of at least two distillation columns, the temperature in the distillation column of the first column for recovering a substance having a lower boiling point than isoquinoline from the top of the column is set to 150 ° C. or lower, The temperature in the distillation column in the second column for recovering isoquinoline from the top of the column is set to 200 ° C or lower.

By such a purification method, isoquinoline can be isolated in good yield from a solution containing isoquinoline, a reactive high-boiling point component, and an organic acid.

As described above, the waste liquid discharged from the polyimide film manufacturing process and the liquefied recovery solution of the exhaust gas are
Reactive high-boiling substances and organic acids are included, but the manufacturing process of the polyimide film referred to here is JP-A-11-
Reference can be made to Japanese Patent Laid-Open No. 000930, Japanese Patent Laid-Open No. 2000-191806, and the like.

That is, in the process for producing a polyimide film, polyimide is polymerized in an organic polar solvent such as dimethylformamide (hereinafter referred to as DMF) or dimethylacetamide, and then acetic anhydride which is a dehydrating agent and IQ which is an agent. Mix and cast on endless belt. Use the endless belt to measure the imidization ratio of the film, residual volatile content, etc.
The film is mainly chemically imidized by gradually heating to about ℃. The exhaust gas from the process at this time mainly contains acetic anhydride, acetic acid generated by hydrolysis of acetic anhydride, DMF and the like.

After that, the film is thermally imidized by gradually raising the temperature to a maximum temperature of about 600 ° C. in a hot air oven or a far infrared oven. At this time, IQ mainly evaporates and vaporizes.
In addition, the organic solvent, etc. introduced into the process exhaust gas is thermally
It contains tar-like high-boiling substances that are produced by chemical action. Exhaust gas containing these components is liquefied and collected from the exhaust gas by a condenser, a scrubber, etc., and then supplied to the distillation of the present invention. The recovered solvent is sent to the distillation step, and IQ purification in the present invention is carried out in the distillation step.

Hereinafter, an example of an embodiment of IQ purification by batch distillation according to the present invention will be described. In addition to IQ, water and D
The purification of IQ from the solution recovered from the process for producing a polyimide film containing MF, acetic acid and a reactive high-boiling substance will be described in more detail as an example.

The apparatus for carrying out the distillation of the present invention may be a distillation apparatus having a theoretical plate number of 5 or more, preferably 10 or more, and the reflux ratio is 0.1 or more, preferably 0.5 or more. Is good.

In the main distillation, water, DMF and acetic acid are first distilled alone or as a mixed composition thereof. This is called the initial stage of distillation. After that, a solution containing IQ as a main component is distilled out. The initial distillation is performed until the IQ content in the distillate composition exceeds 30% by weight, and the IQ content in the distillate composition is 30%.
The time from when the content exceeds the weight% is the middle stage of distillation. After that, the IQ content in the distillate decreases, and other high-boiling substances start to distill. The IQ content in the distillate is set as the middle stage of distillation until the IQ content in the distillate exceeds 30% by weight and becomes 30% by weight again.
The time from when the content falls below 30% by weight is the latter stage of distillation.

If the temperature at the bottom of the column is higher than 150 ° C. at the initial stage of distillation, IQ reacts with acetic acid and the like, and the quality of IQ is altered to lower the yield. Also, the temperature at the bottom of the column is 200 ° C in the middle of the distillation.
If it is higher, IQ is remarkably deteriorated and the yield is extremely lowered. Therefore, it is advantageous to operate the column bottom temperature at 150 ° C. or lower, preferably 120 ° C. or lower at the initial stage of distillation, and after distilling the light-boiling components, raise the temperature to 200 ° C., preferably about 180 ° C.

Further, if distillation is carried out under normal pressure, it is not preferable because the heating medium temperature of the reboiler part for heating the solution needs to be high. Therefore, it is preferable to carry out distillation under reduced pressure. For example, it is advantageous that the operating pressure is 0.01 MPa or less, preferably 0.004 MPa or less. Further, the pressure during distillation may be operated so as to be constant, or the temperature at the top of the distillation column may be changed as an index.

Next, an example of an embodiment of IQ purification by continuous distillation according to the present invention, which comprises at least two distillation columns, will be described.

The solvent recovered from the process is first supplied to the first column. A liquid rich in components having a boiling point lower than IQ is distilled from the top of the first column, and IQ and a tar-like reactive high-boiling substance having a boiling point higher than IQ are obtained from the bottom of the column. Then, the bottoms of the first tower is supplied to the second tower, a liquid rich in IQ is obtained as a distillate from the top of the second tower, and other high-boiling substances are obtained from the bottom of the tower.

In the distillation operation in the first column, if the temperature in the column exceeds 150 ° C., the IQ is deteriorated and the IQ yield decreases, so the internal temperature of the first column is preferably 150 ° C. Is preferably operated at a temperature not exceeding 120 ° C.

In the second tower, the temperature inside the tower is 200 ° C.
If it exceeds, the solution is solidified in the reboiler section, and the distillation operation becomes difficult. Therefore, it is preferable to operate at a column temperature of 200 ° C or lower, preferably 180 ° C or lower.

If the above temperature conditions are to be achieved under normal pressure, it is necessary to raise the temperature of the heat medium in the reboiler section, which is not preferable. Therefore, the operating pressure of both the first tower and the second tower is 0.01 MPa or less, preferably 0.004 M.
It is advantageous that the pressure is Pa or less.

Next, a specific example of an embodiment of the present invention and an example of an apparatus in continuous distillation using two distillation columns will be described.
FIG. 1 is a conceptual diagram of an apparatus composed of two distillation columns.
Reference numerals 1 and 2 are first and second distillation columns, respectively, 3, 4 are reboilers, and 5 and 6 are condensers. When performing the distillation operation under reduced pressure, the vacuum pump 7 can be used. As the main piping, 8 is the supply of the recovered solvent as the raw material, 9 and 10 are the overhead vapor, and 1
1,12 is the overhead reflux, 13,14 is the overhead distillation, 17,1
8 is non-condensed gas exhaust, 15 is the first distillation column bottom delivery to the second distillation column supply, 16 is bottom delivery, and 19 is exhaust gas.

Although the embodiments of the present invention have been described above, the present invention may be carried out alone or in combination with other steps, and the embodiments are not limited.

[0039]

Example (Reference Example 1) IQ, DMF and acetic acid were mixed at various ratios and heated at 100 ° C. for 100 hours.
The presence / absence of Q and the change in viscosity were measured. The results are shown in Table 1. The units in the following tables are expressed in% by weight.

[0040]

[Table 1]

Example 1 Polyimide Manufacturing Process Single distillation was carried out using the solvent recovered from the exhaust gas. Charge the IQ solution recovered from the process exhaust gas into the flask at the bottom of the tower,
The distillate was sampled while heating the content liquid at an operating pressure of 0.004 MPa. The experiment was terminated when the amount of vapor became small and the distillation of the liquid stopped from the top of the column. As a result, 78.8% by weight of the input IQ could be recovered. Table 2 shows the experimental results. In the table, diacetylamide is described as DMAc.

[0042]

[Table 2]

(Example 2) Polyimide manufacturing process A packed column type batch distillation distillation was carried out using a solvent recovered from exhaust gas. As the distillation column, a glass experimental device having 20 theoretical plates with Raschig ring as a packing material was used. The IQ solution recovered from the process exhaust gas was charged into the flask at the bottom of the column, and the content liquid was heated at an operating pressure of 0.004 MPa. In the total reflux state, 1 hour after the temperature of the parietal recirculation became steady, the extraction was started from the parietal region at a reflux ratio of 1.0, and then 50 ml of distillate was used as a guide over time. Sampled. The experiment was terminated when the amount of vapor became small and the distillation of the liquid stopped from the top of the column. As a result, 65.0% by weight of the input IQ could be recovered. The liquid viscosity of the distillation residue at this time was measured by an E-type viscometer and found to be 60 ° C.
Was 1 Pa · s, and sufficient fluidity was obtained.
Table 3 shows the composition of each fraction.

[0044]

[Table 3]

(Comparative Example 1) Under the conditions described in Example 1, distillation was carried out while maintaining the solution temperature at 225 ° C. As a result, 75.3% of the input IQ was recovered. Table 4 shows the experimental results.

[0046]

[Table 4]

(Comparative Example 2) An experiment was conducted by changing the temperature condition of the bottom of the column by using the same experimental apparatus as in Example 2 and keeping the operating pressure at atmospheric pressure. As a result, the input IQ is 58.
2% by weight could be recovered. At this time, the distillation residue had poor fluidity at 160 ° C. Table 5 shows the composition of each fraction.

[0048]

[Table 5]

[0049]

By carrying out the distillation according to the method of the present invention, the isoquinoline can be recovered from the exhaust gas and the waste liquid of the polyimide manufacturing process without degrading the isoquinoline and reducing the efficiency of the distillation due to the increase in the viscosity of the solution. .

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a continuous distillation apparatus composed of two distillation columns.

[Explanation of symbols]

1,2: Distillation tower 3, 4: Reboiler 5,6: Condenser 7: Vacuum pump 8: Raw material supply 9,10: overhead vapor 11, 12: Tower top circulation 13, 14: Distillation from the top of the tower 15: First distillation column bottom payout to second distillation column supply 16: Tower bottom payout 17, 18: Non-condensing gas exhaust 19: Exhaust gas

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Claims (8)

[Claims] 1. A method for purifying isoquinoline, wherein the temperature in the distillation column is set to 200 ° C. or lower in batch distillation for isoquinoline isolation from a solution containing isoquinoline and a reactive high-boiling substance. 2. In continuous distillation using a distillation apparatus comprising at least two distillation columns for isoquinoline isolation from a solution containing isoquinoline and a reactive high-boiling substance, the boiling point of isoquinoline is lower than that of isoquinoline. First column for recovering substances, and second column for recovering isoquinoline from the top of the column
A method for purifying isoquinoline, wherein the temperature in the distillation column in the column is set to 200 ° C. or lower. 3. In batch distillation for isoquinoline isolation from a solution containing isoquinoline and an organic acid, the temperature in the distillation column is kept at 150 ° C. or lower until the isoquinoline in the overhead distillate exceeds 30% by weight. A method for purifying isoquinoline, which is characterized in that 4. In a continuous distillation using a distillation apparatus composed of at least two distillation columns for isoquinoline isolation from a solution containing isoquinoline and an organic acid, a substance having a boiling point lower than that of isoquinoline is recovered from the top of the column. The method for purifying isoquinoline, wherein the temperature in the distillation column of the first column is 150 ° C. or lower. 5. In batchwise distillation for isoquinoline isolation from a solution containing isoquinoline, a reactive high-boiling point component, and an organic acid, 30% by weight of isoquinoline in the overhead distillate is obtained.
The method for purifying isoquinoline is characterized in that the temperature in the distillation column is set to 150 ° C. or lower until the temperature exceeds, and the temperature is set to 200 ° C. or lower thereafter. 6. A continuous distillation using a distillation apparatus comprising at least two distillation columns for isoquinoline isolation from a solution containing isoquinoline, a reactive high-boiling point component, and an organic acid, and isoquinoline from the top of the column. The temperature in the distillation column of the first column for recovering a substance having a lower boiling point is set to 150 ° C. or lower, and the temperature in the distillation column in the second column for collecting isoquinoline from the top of the column is set to 200 ° C. or lower. A method for purifying isoquinoline. 7. The reactive high-boiling substance is a reactive high-boiling substance contained in a waste liquid collected from a polyimide manufacturing process or a liquefaction and recovery solution of exhaust gas, according to any one of claims 1, 2, 5, and 6. Method for purifying isoquinoline. 8. The composition of the organic acid is C _n H _{2n + 1} COOH (n
= 0, 1, 2), The method for purifying isoquinoline according to claim 3, 4, 5, or 6.