JPH07118200A - Production of naphthalenedicarboxylic acid - Google Patents

Abstract

PURPOSE:To effectively crystallization-purify crude naphthalenedicarboxylic acid into the highly pure product having a good color tone with a small volume of a solvent. CONSTITUTION:1-15wt.% of water is added to the solvent mixture of an amine compound with an alcohol compound. Crude naphthalene- dicarboxylic acid is dissolved in the solvent mixture, cooled and crystallized to purify the naphthalenedicarboxylic acid.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing naphthalenedicarboxylic acid. In particular, the present invention relates to a method for purifying crude naphthalthalenedicarboxylic acid by crystallization. Naphthalenedicarboxylic acid is a compound useful as a raw material for highly functional resins such as polyethylene naphthalate (PEN resin).

[0002]

2. Description of the Related Art Naphthalenedicarboxylic acid can be produced, for example, by oxidizing dialkylnaphthalenes such as dimethylnaphthalene and diisopropylnaphthalene with molecular oxygen in the presence of cobalt, manganese and bromine. However, since the crude naphthalenedicarboxylic acid obtained by these methods contains impurities such as trimellitic acid and a coloring substance, a purification step is required. Conventionally, as a method for purifying naphthalenedicarboxylic acid, a crude naphthalenedicarboxylic acid is dissolved in an alkaline aqueous solution, subjected to treatment such as oxidation or hydrogenation, and decolorization by adsorption. Methods for obtaining the same are known (JP-A-48-68554, JP-A-48-49747, JP-A-50-105639, 16).
No. 0248, etc.). However, these methods
Since both use a large amount of alkali and acid, there is a problem that a large amount of inorganic salt and waste water are generated.

Further, crude naphthalene dicarboxylic acid is mixed with N,
A method is disclosed in which an organic solvent selected from N-dimethylformamide, N, N-dimethylacetamide and dimethylsulfoxide (DMSO) is used for dissolution, treated with activated carbon and then recrystallized (JP-A-62-23074).
7 publication). However, these organic solvents have problems that they have high boiling points, it is difficult to recover the solvents, and they are highly toxic.

Further, a method has been proposed in which a crude naphthalenedicarboxylic acid is dissolved in an aqueous solution of a specific alkylamine such as dimethylamine and then the amine is distilled off from the aqueous solution to precipitate the naphthalenedicarboxylic acid. (Japanese Patent Laid-Open No. 50-142542). However, in this method, (1) the amine is precipitated by recovering it by distillation, so that only a specific amine that can be distilled off can be used. (2) Since these amines azeotrope with water, a large amount of water is distilled off together, and (3) the amine cannot be completely removed from the aqueous solution, so that the recovery rate is low. there were. On the other hand, a method has also been proposed in which crude naphthalenedicarboxylic acid is dissolved in a mixed solvent of amines and alcohols and crystallized to obtain naphthalenedicarboxylic acid with high recovery and high purity and good hue (Japanese Patent Application Laid-Open No. Hei 5). No. 155807).

[0005]

The object of the present invention is to obtain a high recovery of naphthalene dicarboxylic acid having a high purity and a good hue by cooling and crystallization from a crude naphthalene dicarboxylic acid using a mixed solvent of amines and alcohols. When purifying with
An object of the present invention is to provide a production method which is capable of efficiently producing naphthalenedicarboxylic acid with a smaller amount of solvent used and has excellent production efficiency.

[0006]

According to the present invention, crude naphthalenedicarboxylic acid obtained by oxidizing dialkylnaphthalene is dissolved in a mixed solvent of amines and alcohols and crystallized by cooling operation. In this case, the present invention provides a method for producing naphthalenedicarboxylic acid, characterized in that 1 to 15% by weight of water is present in the mixed solvent.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention is described in more detail below. (Crude naphthalenedicarboxylic acid) The crude naphthalenedicarboxylic acid used in the method of the present invention is not particularly limited, but for example, dialkylnaphthalene compounds may be used in a solvent such as an aliphatic lower monocarboxylic acid or water with cobalt, manganese and Mention may be made of crude naphthalenedicarboxylic acids obtained by oxidation with molecular oxygen in the presence of bromine. The crude naphthalene dicarboxylic acid obtained by such an oxidation reaction has a purity of 90% or more, generally 95 to 99%.
Although it usually has a light brown to brown color, it may be directly used in the method of the present invention, or may be used in the method of the present invention after washing with a reaction solvent or the like. In some cases, the purity is 99% or more, such as activated carbon,
The hue of naphthalenedicarboxylic acid after the preliminary purification treatment with dimethyl sulfoxide (DMSO) or the like can be further improved by the method of the present invention.

Examples of the (amine) amines include aliphatic amines and their derivatives, alicyclic amines and aromatic amines. Specifically, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, di-n-
Examples include propylamine, tri-n-propylamine, isopropylamine, diisopropylamine, triisopropylamine and the like. These amines may be used alone or in a mixture of two or more kinds at an arbitrary ratio.

Examples of (alcohol) alcohols include aliphatic chain monoalcohols, alicyclic monoalcohols, aliphatic chain diols, alicyclic diols, and aliphatic polyols. Specific examples include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol and the like. These alcohols can be used either individually or as a mixture of two or more kinds at an arbitrary ratio.

(Mixed solvent) In the method of the present invention, when a crude naphthalene dicarboxylic acid is dissolved in a mixed solvent of the above amines and alcohols for crystallization, a predetermined amount of water is allowed to exist in the mixed solvent. To do. The mixing ratio of amines and alcohols is 5:95 to 95: 5, preferably 1 by weight.
The range is 0:90 to 90:10. The ratio of water present in the mixed solvent varies depending on the amines and alcohols used and the ratio thereof, but is usually in the range of 1 to 15 preferably 1 to 10% by weight. If the amount of water in the mixed solvent is less than the above range, the effect of improving the solubility of naphthalenedicarboxylic acid by the addition of water cannot be obtained, and if more than the above range is added, the solubility of naphthalenedicarboxylic acid and its temperature This is unsuitable because the dependency is reduced, and as a result, the amount of purified naphthalenedicarboxylic acid recovered per unit amount of solvent is reduced as compared with the case where water is not added. In addition, the water present in the mixed solvent may be either water contained in the crude naphthalenedicarboxylic acid brought to the purification step due to washing after the oxidation step, or water newly added to the mixed solvent. Good. The amount of water in the mixed solvent can be controlled usually by adjusting the amount of water added to the mixed solvent, but if necessary, it can be controlled by a reverse osmosis membrane, a molecular sieve or the like.

The amount of the mixed solvent used may be an amount sufficient to dissolve the crude naphthalenedicarboxylic acid at the temperature at which the dissolution operation is carried out, but in order to increase the recovery amount of the purified naphthalenedicarboxylic acid per unit solvent amount. In, a saturated amount is preferable, since it depends on the amines and alcohols to be used and the mixing ratio thereof, the amount of water in the mixed solvent, and the temperature at which they are dissolved, it cannot be unconditionally specified, but usually,
It is in the range of 1 to 10 times by weight, preferably 1 to 5 times by weight, with respect to the crude naphthalene dicarboxylic acid. If the mixed solvent amount 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 it is uneconomical because the amount of solvent used increases. .

(Crystallization operation) The crystallization operation is performed in the following procedure. That is, the crude naphthalenedicarboxylic acid is dissolved in a predetermined amount of a mixed solvent of amines, alcohols and water,
If there is insoluble matter, the insoluble matter is removed by filtration.
In addition, when coloring is remarkable, decolorization treatment is performed with activated carbon or the like.
The melting temperature cannot be unconditionally specified because it varies depending on the amines and alcohols used, the proportion thereof, the amount of water in the mixed solvent, and the amount of crude naphthalenedicarboxylic acid, but it is saturated at the boiling point of the mixed solvent or below at which the crude naphthalenedicarboxylic acid can be dissolved It may be higher than the melting temperature, and is usually performed in the range of 10 to 100 ° C. The pressure at this time is not particularly limited.

When treating with activated carbon, a predetermined amount of activated carbon is added to a mixed solvent of crude naphthalene dicarboxylic acid,
Either a batch treatment in which the mixture is heated and stirred and then filtered, or a mixed solvent in which a crude naphthalene dicarboxylic acid is dissolved is passed through a column filled with activated carbon. Then, if necessary, the solvent may be recovered by distillation or the like, 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 separated by filtration, centrifugation or the like. The cooling temperature is lower than the melting temperature, preferably 10 ° C. or more lower than the melting temperature, and usually in the range of 0 to 90 ° C.

The crystals of the amine salt of naphthalenedicarboxylic acid obtained by crystallization and filtration are the amines used in crystallization,
Since not only alcohols and water but also impurities are attached, it is preferable to wash with the amine used for crystallization. The amount of amine used for washing is in the range of 0.5 to 20 times by weight, preferably 0.5 to 5 times by weight, of the naphthalenedicarboxylic acid amine salt obtained by crystallization and filtration. By heating and drying the obtained crystals of the amine salt of naphthalenedicarboxylic acid in a nitrogen stream at a temperature not lower than the boiling point of the amine at the pressure during the heating operation and not higher than the thermal decomposition temperature (280 ° C.) of naphthalenedicarboxylic acid, a high purity is obtained. Thus, naphthalenedicarboxylic acid having a good hue can be obtained. The drying temperature is usually in the range of 100 to 200 ° C.

[0015]

The naphthalenedicarboxylic acids are soluble in N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide and pyridines to some extent, but are hardly soluble in other organic solvents and water. Therefore, it hardly dissolves in amines and alcohols alone. However, when a mixed solvent of amines and alcohols is used, the solubility of naphthalenedicarboxylic acids is drastically improved, and the temperature dependence of the solubility becomes extremely large. Crystallization purification can be easily performed. further,
When water is added to the mixed solvent in an amount of 1 to 15% by weight during crystallization and purification with a mixed solvent of the above amines and alcohols, the solubility of naphthalenedicarboxylic acid is further improved, and per unit solvent amount The amount of purified naphthalenedicarboxylic acid recovered can be increased, and crystallization purification can be efficiently performed with a small amount of solvent used.

[0016]

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, the hue of naphthalenedicarboxylic acid is 2g for 1g of sample.
Dissolve in 10 ml of 5% methylamine solution, and use a 10 mm quartz cell to absorb light with a wavelength of 500 nm (hereinafter referred to as OD).
(Abbreviated as) is evaluated by the measured value.

(Reference example) 50 having a reflux condenser, a gas introduction pipe, a raw material liquid feed pump, a back pressure regulator and an induction stirrer
In a 0 ml titanium autoclave, 200 g of acetic acid, 9.4 g (37.5 mmol) of cobalt acetate / tetrahydrate, 9.2 g (37.5 mmol) of manganese acetate / tetrahydrate, and 7.4 g (75.5) of ammonium bromide. 0 mmol) and 5.9 g (75.0 mmol) of pyridine were charged, the inside of the reaction system was replaced with nitrogen, and the system pressure was adjusted to 30 kg / cm ² with a back pressure regulator.
It became G. The inner temperature was heated to 200 ° C., and air was supplied at 4 Nl / min so that the inner pressure was kept at 30 kg / cm ² G. When the system is stable 2, 6
79.6 g (375 mmol) of diisopropylnaphthalene were fed continuously over 4 hours. After the supply of 2,6-diisopropylnaphthalene was completed, the inside of the system was heated to 200 ° C., 30 k
The air supply was continued for 1 hour while maintaining g / cm ² G.
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. The solid was dried to obtain 67.2 g of a light brown solid. The yield of this crude 2,6-naphthalenedicarboxylic acid was 80.6.
%, And the purity was 97.2%. Also, the OD is 3.
It was 44.

(Example 1) 22 g of crude naphthalenedicarboxylic acid obtained in Reference Example, 25 (boiling point 65 ° C.) 25
g, triethylamine (boiling point 90 ° C.) 25 g, and water 3 g were charged in a 200 ml flask and dissolved by heating in a water bath at 60 ° C. to obtain a saturated solution state. Next, the jacketed column filled with 4 g of activated carbon was kept warm at 60 ° C., the above-mentioned mixed solution was passed at SV = 1.0 hr ⁻¹ , and further 10: 25: 25: 3 mixed solvent of methanol, amine and water was added. It was passed through. 82 g of the collected solution was cooled to 20 ° C. in cold water, and the precipitated crystals were separated by filtration to give 38 g of triethylamine.
Washed with. The recovered crystals weighed 38 g, and the mixture of the filtrate and the washing liquid weighed 82 g. 38 g of the recovered crystals was dried in a 150 ° C. dryer for 4 hours while flowing nitrogen, and 16 g of 2,6-naphthalenedicarboxylic acid was obtained. Recovery rate 73%, purity 99.4%, OD 0.05
8. The amount of purified naphthalenedicarboxylic acid recovered per unit amount of solvent was 30 g-purified NDCA / 100 g-solvent.

(Example 2) 18 g of crude naphthalenedicarboxylic acid obtained in Reference Example, 25 (boiling point 65 ° C.) 25
g, triethylamine (boiling point 90 ° C.) 25 g, and water 6 g were charged into a 200 ml flask, and dissolved by heating in a 60 ° C. water bath (saturated solution state). Next, the jacketed column filled with 4 g of activated carbon was kept warm at 60 ° C., the above-mentioned mixed solution was passed through at SV = 1.0 hr ⁻¹ , and further a mixed solvent of methanol, amine and water was mixed at 25: 25: 6. It passed. 81 g of the collected solution was cooled to 20 ° C. in cold water, the precipitated crystals were separated by filtration, and washed with 32 g of triethylamine. The recovered crystals were 32 g, and the mixed liquid of the filtrate and the washing liquid was 81 g. When 32 g of the collected crystals were dried in a dryer at 150 ° C. for 4 hours while flowing nitrogen, 13 g of 2,6-naphthalenedicarboxylic acid was obtained. Recovery rate 72%, purity 99.5%, OD 0.055,
The amount of purified naphthalenedicarboxylic acid recovered per unit amount of solvent was 23 g-purified NDCA / 100 g-solvent.

Comparative Example 1 10 g of the crude naphthalenedicarboxylic acid obtained in Reference Example, 25 g of methanol and 25 g of triethylamine were placed in a 200 ml flask and dissolved by heating in a hot water bath at 60 ° C. (saturated solution state). Next, activated carbon 4
keep the jacketed column filled with g at 60 ° C,
The above-mentioned mixed solution was passed at SV = 1.0 hr ⁻¹ , and then 10 g of a 1: 1 mixed solvent of methanol and amine was passed. 68 g of the collected solution was cooled to 20 ° C. in cold water, the precipitated crystals were separated by filtration, and washed with 20 g of triethylamine. The recovered crystals were 20 g, and the mixed liquid of the filtrate and the washing liquid was 68 g. 20 g of the recovered crystals were dried in a 150 ° C. dryer for 4 hours while flowing nitrogen, and 8 g of 2,6-naphthalenedicarboxylic acid was obtained. Recovery rate 80%, Purity 99.5%, OD 0.050,
The amount of purified naphthalenedicarboxylic acid recovered per unit amount of solvent was 16 g-purified NDCA / 100 g-solvent.

Comparative Example 2 14 g of the crude naphthalenedicarboxylic acid obtained in Reference Example, 25 g of methanol, 25 g of triethylamine and 13 g of water were placed in a 200 ml flask and dissolved by heating in a hot water bath at 60 ° C. (saturated solution state).
Next, a jacketed column packed with 4 g of activated carbon was
The temperature was kept at 0 ° C., the above mixed solution was passed through at SV = 1.0 hr ⁻¹ , and further methanol, amine, water, 25:25:
13 g of mixed solvent was passed through. 84 g of collected solution
Was cooled to 20 ° C. in cold water, the precipitated crystals were filtered off, and washed with 26 g of triethylamine. The recovered crystals weighed 26 g, and the mixture of the filtrate and the washing liquid weighed 84 g. The recovered crystals (26 g) were charged under a nitrogen flow of 150
When dried for 4 hours in a ℃ dryer, 10 g of 2,6-
Naphthalenedicarboxylic acid was obtained. Recovery rate 71%, purity 99.3%, OD 0.053, recovery amount of purified naphthalenedicarboxylic acid per unit solvent amount was 16 g-purified N
DCA / 100 g-solvent.

[0022]

EFFECTS OF THE INVENTION According to the method of the present invention, a crude crystal of naphthalene dicarboxylic acid containing impurities and a coloring component obtained by an oxidation reaction of dialkylnaphthalene is cooled with a mixed solvent of amines and alcohols. When the naphthalene dicarboxylic acid with high purity and good hue is purified with high recovery by precipitation, it can be efficiently produced with a small amount of solvent.

Claims (1)

[Claims] 1. A crude naphthalenedicarboxylic acid obtained by oxidizing a dialkylnaphthalene is dissolved in a mixed solvent of amines and alcohols, and when this is crystallized by a cooling operation, in the mixed solvent. The method for producing naphthalenedicarboxylic acid is characterized in that 1 to 15% by weight of water is present in the mixture.