JPH05294892A - Production of naphthalenedicarboxylic acid - Google Patents

Abstract

PURPOSE:To efficiently produce high-purity naphthalenedicarboxylic acid good in hue at a good recovery ratio by simply purifying crude naphthalenedicarboxylic acid containing an impurity and a coloring component without using a large amount of an alkali or an acid and water. CONSTITUTION:Crude naphthalenedicarboxylic acid is dissolved in a mixed solvent of an amine with an alcohol and then crystallized to provide a naphthalenedicarboxylic acid amine salt, which is then heated at a temperature above the boiling point of the amine to afford the objective naphthalenedicarboxylic acid, having >=99% purity and good in hue.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing high-purity naphthalenedicarboxylic acid. Naphthalene dicarboxylic acid is polyethylene naphthalate (PEN resin)
It is a compound useful as a raw material for high-performance resins such as.

[0002]

BACKGROUND OF THE INVENTION Naphthalenedicarboxylic acid is generally produced, for example, by oxidizing dialkyl-substituted naphthalene such as dimethylnaphthalene and diisopropylnaphthalene with molecular oxygen in the presence of cobalt, manganese and bromine. .. The crude naphthalenedicarboxylic acid obtained by this method contains impurities such as trimellitic acid and a coloring substance, and therefore requires a purification step.

Conventionally, as a method for purifying naphthalenedicarboxylic acid, crude naphthalenedicarboxylic acid is dissolved in an alkaline aqueous solution, subjected to treatments such as oxidation, hydrogenation and decolorization by adsorption, and then acidified to obtain a high purity. A method for obtaining naphthalenedicarboxylic acid is known (Japanese Patent Application Laid-open No. 48-4848).
-68554, JP-B-52-20993, JP-A-50-
105639, 160248, etc.). However, all of these methods use a large amount of alkali and acid, and thus have a problem that a large amount of inorganic salt and waste water are generated.

Further, the crude naphthalene dicarboxylic acid is mixed with N,
A method has been disclosed in which an organic solvent selected from N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc) and dimethylsulfoxide (DMSO) is used, followed by recrystallization after treatment with activated carbon (Japanese Patent Application Laid-Open No. S60-12069). 62
-230747). However, when the present inventors performed purification by the above method, when the recovery of naphthalenedicarboxylic acid was increased, the hue was hardly improved (see Comparative Examples 6 and 7). Furthermore, those organic solvents have high boiling points and it is difficult to recover the solvent.
There were problems such as high toxicity.

On the other hand, after dissolving crude 2,6-naphthalenedicarboxylic acid in an aqueous solution of a specific alkylamine such as dimethylamine, the amine is distilled off from the aqueous solution to obtain 2,6-
A method of purifying by precipitating naphthalenedicarboxylic acid has been disclosed (JP-A-50-142542). However, according to this method, (1) the amines are precipitated by recovering by distillation, so that only specific amines that can be distilled off can be used. (2) Since these amines azeotrope with water, a large amount of There are drawbacks such as water being distilled out together, and (3) the recovery rate is low because the amine cannot be completely removed from the aqueous solution.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing naphthalene dicarboxylic acid having a high purity and a good hue with a high recovery rate.

[0007]

The present invention is a method for producing high-purity naphthalenedicarboxylic acid, which comprises heating an amine salt of naphthalenedicarboxylic acid to a temperature not lower than the boiling point of the amine. <Naphthalenedicarboxylic acid amine salt> The naphthalenedicarboxylic acid amine salt used in the method of the present invention is not particularly limited. It can be suitably obtained by crystallization by.

(Di-substituted naphthalene) As the di-substituted naphthalene, there are two substituents such as an alkyl group, an acyl group, a formyl group, a hydroxyalkyl group and a hydroperoxyalkyl group which can be converted into a carboxyl group by an oxidation reaction. It is a di-substituted naphthalene. The positions of the two substituents may be positions other than two adjacent carbons, specifically, positions other than 1,2-position and 2,3-position, and particularly preferably 2,6-position. 2nd, 7th place.

(Crude naphthalene dicarboxylic acid) The above di-substituted naphthalene compounds are oxidized with molecular oxygen such as air in the presence of a catalyst such as heavy metal or bromine in a solvent such as aliphatic lower monocarboxylic acid or water. Thus, crude naphthalenedicarboxylic acid is obtained. Examples of the aliphatic lower monocarboxylic acid solvent include formic acid, acetic acid, propionic acid, butyric acid, valeric acid and bromoacetic acid. Among them, acetic acid is most preferable, and diluted with other solvent such as water or aromatic hydrocarbon. It may have been done.

The amount of the solvent used is not particularly limited, but is preferably 0.5 to 10 relative to the starting dialkylnaphthalene.
The weight is preferably 1 to 6 times by weight. Examples of the cobalt compound and the manganese compound used as the catalyst include, for example, formic acid of cobalt and manganese, acetic acid, propionic acid, oxalic acid, aliphatic carboxylic acid salts such as maleic acid, alicyclic carboxylic acid salts such as naphthenic acid, and benzoic acid. ,
In addition to aromatic carboxylic acid salts such as terephthalic acid, naphthoic acid and naphthalenedicarboxylic acid, inorganic compounds such as hydroxides, oxides, carbonates and halides can be mentioned. Of these, acetate and bromide are preferable.

The cobalt compound and the manganese compound are used as a mixture, and the mixing ratio thereof is 99: 1 to 1:99, preferably 9: cobalt: manganese (atomic ratio).
The range is from 7: 3 to 3:97. The amount of cobalt and manganese used is 0.2 to 10% by weight as the total amount of cobalt and manganese atoms with respect to the aliphatic carboxylic acid solvent.
It is preferably in the range of 0.4 to 5% by weight.

Examples of the bromine compound contained in the catalyst component include inorganic bromine compounds such as molecular bromine, hydrogen bromide and hydrobromide, and methyl bromide, ethyl bromide, bromoform, ethylene bromide and bromo. An organic bromine compound such as acetic acid can be exemplified. The amount of the bromine compound used is such that the amount of bromine atoms is 0.1 to the total number of moles of cobalt and manganese atoms contained in the aliphatic carboxylic acid solvent.
The amount is 10 times by mole, preferably 0.2 to 5 times by mole.

The reaction temperature is usually 100 to 300 ° C., and the pressure is an oxygen partial pressure in the gas phase of 0.2 to 10 kg / c in absolute pressure.
Pressures such as m ² are preferred. After completion of the reaction, the reaction solution is cooled to about room temperature and the precipitated solid is recovered to obtain crude naphthalenedicarboxylic acid. The crude naphthalenedicarboxylic acid thus obtained has a purity of 90% or more, generally 95 to 99%, and usually exhibits a light brown to brown color, but is used as it is in the next crystallization step. Alternatively, the crystallization may be performed after washing with a reaction solvent or the like. In some cases, the purity is 99% or more, such as activated carbon or DM
It is also possible to improve the hue by crystallizing naphthalenedicarboxylic acid after treatment with SO or the like.

Examples of the (amine) amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-propylamine, isopropylamine and diisopropylamine. , Triisopropylamine, n-butylamine, di-
n-butylamine, tri-n-butylamine cypyridine, n-hexylamine, di-n-hexylamine, tri-n-hexylamine, cyclohexylamine, dicyclohexylamine, tricyclohexylamine, n-
Octylamine, di-n-octylamine, tri-n-
Octylamine, ethylenediamine, N-methylethylenediamine, N, N-dimethylethylenediamine, N,
N'-dimethylethylenediamine, N, N, N'-trimethylethylenediamine, N, N, N ', N'-tetramethylethylenediamine, 1,2-diaminopropane,
1,3-diaminopropane, N-methyl-1,2-diaminopropane, N-methyl-1,3-diaminopropane, N, N-dimethyl-1,2-diaminopropane,
N, N-dimethyl-1,3-diaminopropane, N,
N, N'-trimethyl-1,2-diaminopropane,
N, N, N'-trimethyl-1,3-diaminopropane, N, N, N ', N'-tetramethyl-1,2-diaminopropane, N, N, N', N'-tetramethyl-
Aliphatic amines such as 1,3-diaminopropane, monoethanolamine, diethanolamine, triethanolamine and glycine and their derivatives; alicyclic amines such as piperidine, N-methylpiperidine, hexamethyleneimine and N-methylhexamethyleneimine ; And the like.

Of these, alkylamines having 30 or less carbon atoms are preferable. These amines can be used either individually or as a mixture of two or more kinds at an arbitrary ratio. The naphthalenedicarboxylic acid amine salt can be easily obtained by dissolving the above-mentioned crude naphthalenedicarboxylic acid in a mixed solvent of amine and alcohol for crystallization.

Examples of the (alcohol) alcohol include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isoptyl alcohol, sec-butyl alcohol, t-butyl alcohol, n-amyl alcohol, Isoamyl alcohol, sec-amyl alcohol, t-amyl alcohol, neopentyl alcohol,
Aliphatic chain type monoalcohols such as hexyl alcohol, pentyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol; cyclopentyl alcohol,
Alicyclic monoalcohol such as cyclohexyl alcohol;
Ethylene glycol, 1,2-propylene glycol,
Aliphatic chain diols such as 1,3-propylene glycol; 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,2-cyclohexanediol,
Alicyclic diols such as 1,3-cyclohexanediol and 1,4-cyclohexanediol; aliphatic polyols such as glycerin and pentaerythritol; and the like.

These alcohols can be used either individually or as a mixture of two or more kinds in an arbitrary ratio. The mixing ratio of amines and alcohols is 1:99 to 99: 1 by weight, preferably 5:95.
˜95: 5.

The amount of the mixed solvent of amines and alcohols used may be an amount sufficient to dissolve the crude naphthalene dicarboxylic acid at the temperature at which the dissolution operation is performed, and the mixing ratio of amines and alcohols and Since it varies depending on the temperature at which it is dissolved, it cannot be specified unconditionally, but it is usually in the range of 0.5 to 100 times by weight, preferably 1 to 50 times by weight, with respect to the crude naphthalenedicarboxylic acid. If the amount of the mixed solvent is less than the above range, a sufficient crystallization effect cannot be obtained, and even if it is used in excess of the above range, the crystallization effect does not change and the amount of solvent used increases, which is rather uneconomical. Is. The higher the melting temperature, the better, but usually room temperature to
It is carried out at 350 ° C, preferably 60 to 250 ° C. The pressure at this time is not particularly limited.

(Crystallization Operation) The crystallization operation is performed in the following procedure. That is, the crude naphthalene dicarboxylic acid is dissolved in a predetermined amount of mixed solvent, and if there is insoluble matter, the insoluble matter is removed by filtration. At this time, it may be treated with activated carbon or the like. When treating with activated carbon, a predetermined amount of activated carbon is added to a mixed solvent in which crude naphthalene dicarboxylic acid is dissolved, and the mixture is heated and stirred, and then the crude naphthalene dicarboxylic acid is dissolved in a column filled with activated carbon even in a batch treatment of filtering. Either the method of passing the mixed solvent may be used.

Then, if necessary, a predetermined amount of the mixed solvent may be recovered by an operation such as distillation and the solution may be concentrated. Then, the mixed solvent in which the crude naphthalenedicarboxylic acid is dissolved is cooled, and the precipitated amine salt of naphthalenedicarboxylic acid is filtered and recovered. The cooling temperature is lower than the melting temperature by 30 ° C. or more, and is −30 to 100 ° C., preferably −20.
It is in the range of -60 ° C. The mother liquor of the mixed solvent after filtering the precipitated amine salt of naphthalenedicarboxylic acid contains impurities and coloring substances, but usually does not undergo any special treatment, or is purified as necessary and repeatedly crystallized. Can be used for.

<Production of naphthalenedicarboxylic acid> By heating the separated crystallization product above the boiling point of the amine to recover the amine forming a salt with naphthalenedicarboxylic acid, a purified naphthalenedicarboxylic acid can be obtained. The pressure at the time of heating may be normal pressure or reduced pressure, and heating / recovering may be performed while introducing an inert gas such as nitrogen or argon.

The heating temperature is not lower than the boiling point of the amine used for crystallization at the pressure during the heating operation and lower than the thermal decomposition temperature of naphthalene dicarboxylic acid (about 280 ° C.). When the boiling point of the amine is higher than 280 ° C., the boiling point is lowered under reduced pressure to heat the amine. When heating the separated crystallization product,
The boiling point at the pressure during the heating operation is equal to or higher than the heating temperature,
It is also possible to disperse in a solvent other than amine and heat.

The solvent may be any solvent as long as it has a boiling point higher than the heating temperature and is inert to amines and naphthalenedicarboxylic acids, and examples thereof include aliphatic hydrocarbons such as liquid paraffin, alkylbenzenes, alkylnaphthalenes, Examples thereof include aromatic hydrocarbons such as alkyl biphenyl, ethers such as biphenyl ether, and esters. Since naphthalenedicarboxylic acid does not dissolve in most solvents and is solid in the above-mentioned solvent, purified naphthalenedicarboxylic acid can be obtained by collecting amines by heating and then filtering.

[0024]

The naphthalene dicarboxylic acids are N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO).
It dissolves to some extent in pyridine, but hardly dissolves in other organic solvents and water. Therefore, it hardly dissolves in amines and alcohols alone (Comparative Example). However, when a mixed solvent of amines and alcohols is used, surprisingly, the solubility of naphthalenedicarboxylic acids is dramatically improved, and the temperature dependence of the solubility becomes extremely large, Crystallization purification of the crude naphthalene dicarboxylic acid is very easy.

[0025]

Industrial Applicability By using the method of the present invention, a crude naphthalene dicarboxylic acid containing impurities and a coloring component obtained by an oxidation reaction of a crude naphthalene dicarboxylic acid, for example, a dialkyl naphthalene, has a high purity and a good hue. It is possible to effectively produce naphthalenedicarboxylic acid with a high recovery rate.

[0026]

EXAMPLES The present invention will be described in detail below with reference to Examples and Comparative Examples. The purity of naphthalenedicarboxylic acid was measured by high performance liquid chromatography. In addition, as for the hue, 10 g of a 25% methylamine aqueous solution was added to 1 g of the sample.
It was dissolved in ml, and the absorbance at a wavelength of 500 nm (hereinafter abbreviated as OD) was measured using a 10 mm quartz cell and evaluated by the value.

<Example 1> (1) 200 g of acetic acid and 9 parts of cobalt acetate / tetrahydrate were placed in a 500 ml titanium autoclave equipped with a reflux condenser, a gas introduction pipe, a raw material feed pump, a back pressure regulator and an induction stirrer. 0.4 g (37.5 mmol), manganese acetate / tetrahydrate 9.2 g (37.5 mmol), ammonium bromide 7.
4 g (75.0 mmol) and pyridine 5.9 g (7
5.0 mmol) was charged, and the inside of the reaction system was replaced with nitrogen,
The pressure in the system was adjusted to 30 kg / cm ² GP with a back pressure regulator. Heat the inner temperature to 200 ° C and add 4N of air.
It was supplied so that the internal pressure was kept at 30 kg / cm ² GP at 1 / min. When the system became stable, 79.6 g (375 mmol) of 2,6-diisopropylnaphthalene was continuously supplied over 4 hours. After the end of the supply of 2,6-diisopropylnaphthalene, the supply of air was continued for 1 hour while maintaining the system temperature at 200 ° C. and 30 kg / cm ² GP.

After completion of the reaction, the autoclave was cooled to room temperature, the precipitated solid matter was collected by filtration, and washed with 40 g of acetic acid. When the solid was dried, it was a light brown solid 67.2.
g was obtained. The yield of this crude 2,6-naphthalenedicarboxylic acid was 80.6%, and the purity was 97.2%. The OD was 3.44.

(2) In a 200 ml flask, the crude 2,6-naphthalenedicarboxylic acid 1 obtained in (1) above was added.
0.9 (50 mmol) g, 11.0 g of methanol, and 10.6 g (105 mmol) of triethylamine were charged and dissolved by heating in an oil bath at 80 ° C. Next, a column with a jacket filled with 4 g of activated carbon was kept warm at 70 ° C., the above-mentioned mixed solution was passed at LHSV = 1.0 hr ⁻¹ , and further 2 g of methanol was passed. Solution 3 recovered
1.8 g was cooled to room temperature, and the precipitated crystals were filtered.
At this time, the collected filtrate was 12.6 g. When 18.8 g of the separated crystals was put into a flask and heated and stirred at 120 ° C. for 2 hours while flowing nitrogen, 9.1 g of purified 2,6-naphthalenedicarboxylic acid was obtained. The recovery rate is 84.2%, the purity is 99.5%, and the OD is 0.0.
It was 52.

<Example 2> In a 200 ml flask, 10.9 g (50 mmol) of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1) and 11.0 methanol.
g and 10.6 g (105 mmol) of triethylamine were charged and dissolved by heating in an oil bath at 80 ° C. next,
A column with a jacket pre-filled with 4 g of activated carbon was
Keep the temperature at 0 ° C., and mix the above solution with LHSV = 1.0 hr.
^-1 was passed, and further 2 g of methanol was passed. 32.0 g of the collected solution was cooled to room temperature, and the precipitated crystals were filtered. At this time, the recovered filtrate was 12.9 g.
The separated crystals (19.0 g) were placed in a flask and the pressure was 25 m.
When the mixture was stirred at 120 ° C. for 2 hours under reduced pressure of mHg,
9.0 g of purified 2,6-naphthalenedicarboxylic acid was obtained. Recovery rate is 83.9%, purity is 99.7%, O
D was 0.056.

Example 3 In a 200 ml flask, 10.9 g (50 mmol) of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1) and 11.0 methanol.
g and 10.6 g (105 mmol) of triethylamine were charged and dissolved by heating in an oil bath at 80 ° C. Then, the column with a jacket filled with 4 g of activated carbon in advance is
Keeping the temperature at ℃, LHSV = 0.5hr ^-1
Then, 2 g of methanol was further passed. 32.2 g of the collected solution was cooled to room temperature, and the precipitated crystals were filtered. At this time, the recovered filtrate was 13.0 g.

19.3 g of the separated crystals and 30 g of liquid paraffin were placed in a flask and stirred at 120 ° C. for 2 hours under a reduced pressure of 22 mmHg. After cooling the mixture to room temperature, the crystals were separated by filtration, rinsed with hexane and dried to obtain 9.2 g of purified 2,6-naphthalenedicarboxylic acid. The recovery rate was 85.0%, the purity was 99.9%, and the OD was 0.051.

<Comparative Example 1> In a 200 ml flask, 5.00 g of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1), 27.13 g of DMSO and 0.3 of activated carbon were added.
8 g was charged, heated and melted at 120 ° C. for 30 minutes, activated carbon was filtered, and rinsed with 8 g DMSO. Then DMSO
28.75 g was recovered by vacuum distillation. The DMSO remaining in the flask was 7.0 g, which corresponds to 1.4 times the weight of the crude 2,6-naphthalenedicarboxylic acid. The content of the flask was cooled to room temperature, the precipitated 2,6-naphthalenedicarboxylic acid was filtered, rinsed with 5 g of DMSO and then dried, and 3.76 g of purified 2,6-naphthalenedicarboxylic acid was obtained. The recovery rate is 75.2%,
The purity was 99.85% and the OD was 2.87.

Comparative Example 2 3.00 g of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1), 74.78 g of DMF and 0.45 of activated carbon were placed in a 200 ml flask.
g was charged, heated and dissolved at 120 ° C. for 30 minutes, activated carbon was filtered, and rinsed with 13 g of DMF. Then DMF8
1.6 g was recovered by vacuum distillation. The DMF remaining in the flask was 6.0 g, which corresponds to 2.0 times the weight of the crude 2,6-naphthalenedicarboxylic acid. The content in the flask was cooled to room temperature, the precipitated 2,6-naphthalenedicarboxylic acid was filtered, rinsed with 5 g of DMF and then dried to obtain 2.55 g of purified 2,6-naphthalenedicarboxylic acid. The recovery rate was 85.0%, the purity was 98.54%, and the OD was 1.62.

Comparative Example 3 A 200 ml flask was charged with 1.0 g of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1) and 60.0 g of methanol, and the mixture was heated to 80 ° C.
After heating and refluxing for 4 hours, the crude 2,6-naphthalenedicarboxylic acid was hardly dissolved.

Comparative Example 4 A 200 ml flask was charged with 1.0 g of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1) and 60.0 g of triethylamine,
After heating and refluxing at 80 ° C. for 4 hours, the crude 2,6-naphthalenedicarboxylic acid was hardly dissolved.

Comparative Example 5 A 200 ml flask was charged with 6.0 g of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1) and 60.0 g of triethanolamine, and the mixture was heated and dissolved at 100 ° C. for 30 minutes. did. The solution was cooled to room temperature, but no crystals were precipitated. Therefore,
Upon concentration by vacuum distillation, the solution gelled.

Comparative Example 4 A 200 ml flask was charged with 1.0 g of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1), 15.0 g of acetone, and 10.0 g of triethanolamine, and 80 After heating at reflux at 4 ° C. for 4 hours, the crude 2,6-naphthalenedicarboxylic acid was hardly dissolved.

Comparative Example 5 A 200 ml flask was charged with 6.0 g of the crude 2,6-naphthalenedicarboxylic acid obtained in Example 1 (1) and a 20% triethylamine aqueous solution 60.0.
g and charged and melted at 100 ° C. for 30 minutes. The mixed solution was cooled to room temperature, but no crystals were precipitated.

Claims (4)

[Claims] 1. A method for producing naphthalenedicarboxylic acid, which comprises heating an amine salt of naphthalenedicarboxylic acid to a temperature not lower than the boiling point of the amine. 2. The naphthalenedicarboxylic acid amine salt is obtained by crystallizing crude naphthalenedicarboxylic acid in a mixed solvent of amine and alcohol.
The manufacturing method according to the item. 3. The method according to claim 1, wherein the amine is an alkylamine having 30 or less carbon atoms. 4. The production method according to claim 1, wherein the heating is carried out in a solvent other than an amine having a boiling point higher than the heating temperature.