JPH0859555A - Method for purifying dimethyl 4,4-biphenyldicarboxylate - Google Patents

Abstract

PURPOSE: To efficiently purify the subjective compound while avoiding restriction on equipment due to distillation at high temperatures and preventing decomposition reaction of decarbonylation, etc., by dissolving crude crystals in a specific high-boiling point solvent and then carrying out crystallization the compound. CONSTITUTION: This purifying method comprises dissolving crude crystals of dimethyl 4,4'-biphenyldicarboxylate (DM-BDC) in a solvent selected from a compound of formula I (X, Y and Z are each H, a 1-4C alkyl, etc.), formula II (W is O, S, etc.), formula III (X, Y and Z are H, NO3 , etc.) and formula IV (X and Y are each H or Cl, etc.) and tetralin and decalin, preferably at 130-180 deg.C and filter the solution, removing insoluble content such as residue of metal catalyst or unreacted raw material, etc., and crystallzing DM-BDC. Furthermore, examples of a compound of formula I, a compound of formula II, a compound of formula III and a compound of formula IV are biphenyl, dipenyl ether, naphthalene and nitrobenzene, respectively.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for purifying dimethyl 4,4'-biphenyldicarboxylate (hereinafter referred to as DM-BDC) to high purity.

[0002]

2. Description of the Related Art DM-BDC is a compound useful as a raw material for highly functional polymers such as liquid crystal compounds.

As a method for purifying DM-BDC, there is a method by distillation. However, this method is DM-B
Since the melting point of DC is as high as 217 ° C., it is necessary to carry out distillation at a considerably high temperature, and a special distillation apparatus corresponding to the high melting point is required. Since the number of plants equipped with such a special distillation apparatus is limited, this purification method by distillation cannot be universally carried out. Further, during such a refining operation at a high temperature, a decomposition reaction such as decarboxylation of DM-BDC itself may occur.

A method for purifying DM-BDC by recrystallization is also known. However, DM-BDC is almost insoluble in general recrystallization solvents such as ketones such as acetone, alcohols such as methanol, low boiling aromatic hydrocarbons such as toluene, and 100 ° C in chlorobenzene and the like. Since it only dissolves with a solubility of around several% in the vicinity, the production efficiency is extremely low.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention avoids the restrictions on the equipment due to distillation at high temperature and prevents decomposition reactions such as decarboxylation, and DM-BDC with high production efficiency.
The main object is to provide a method capable of purifying

[0006]

DISCLOSURE OF THE INVENTION As a result of intensive studies conducted by the present inventor in view of the above problems of the prior art, DM
In the case of performing the heating dissolution operation in a specific high-boiling-point solvent capable of heating up to around the melting point (217 ° C.) of BDC, DM is much higher in solubility than the conventionally used dissolution by chlorobenzene or the like. -We have found that it can dissolve BDCs.

That is, the present invention provides the following DM-BDC.
The following method (1), (2), (3), (4), (5) and (6) is used to provide crude crystals of dimethyl 1.4,4′-biphenyldicarboxylate. A method for purifying dimethyl 4,4′-biphenyldicarboxylate, which comprises dissolving in a solvent comprising at least one compound represented by the formula (1), filtering and removing insolubles, and then crystallizing;

[0008]

[Chemical 13]

{In the formula (1), X, Y and Z are
All are the same or different from each other and represent H, a C ₁ -C ₄ alkyl group, Br and a NO ₃ group. ｝

[0010]

Embedded image

{In the formula (2), W is O, S, C
Represents O, CH ₂ and NH. ｝

[0012]

[Chemical 15]

{In formula (3), X, Y and Z are
All identical or 2 or more or different and represent H, alkyl group of C ₁ -C _4, Cl, Br, and NO ₃ groups. ｝

[0014]

Embedded image

[0015]

[Chemical 17]

[0016]

Embedded image

{In the formula (6), X and Y are the same or different and are H, a C ₁ -C ₄ alkyl group, Cl,
Represents Br, NO ₃ group and NH ₂ group. } A crude crystal of dimethyl 4,4'-biphenyldicarboxylate is prepared from at least one of the compounds represented by the following formulas (1), (2), (3), (4), (5) and (6). Which is characterized in that it is dissolved in the following solvent, the insoluble matter is removed by filtration, the impurities are adsorbed and removed, and then crystallization is carried out.
Method for purifying dimethyl'-biphenyldicarboxylate;

[0018]

[Chemical 19]

{In the formula (1), X, Y and Z are
All are the same or different from each other and represent H, a C ₁ -C ₄ alkyl group, Br and a NO ₃ group. ｝

[0020]

Embedded image

{In formula (2), W is O, S, C
Represents O, CH ₂ and NH. ｝

[0022]

[Chemical 21]

{In formula (3), X, Y and Z are
All identical or 2 or more or different and represent H, alkyl group of C ₁ -C _4, Cl, Br, and NO ₃ groups. ｝

[0024]

[Chemical formula 22]

[0025]

[Chemical formula 23]

[0026]

[Chemical formula 24]

{In the formula (6), X and Y are the same or different and each represents H, a C ₁ -C ₄ alkyl group, Cl,
Represents Br, NO ₃ group and NH ₂ group. } The method according to the above item 1 or 2, wherein the crude crystal of dimethyl 3,4,4′-biphenyldicarboxylic acid is a crude crystal obtained by methyl-esterifying 4,4′-biphenyldicarboxylic acid.

The method according to item 1 or 2 above, wherein the crude crystals of dimethyl 4,4,4'-biphenyldicarboxylate are crude crystals obtained by coupling methyl parachlorobenzoate or methyl parabrombenzoate.

The crude crystals of dimethyl 4,4'-biphenyldicarboxylic acid are crude crystals obtained by methyl-esterifying 4,4'-biphenyldicarboxylic acid chloride or 4,4'-biphenyldicarboxylic acid bromide. The method according to item 1 or 2 above.

From the viewpoint of operation, the solvent used in the present invention is preferably liquid in the temperature range handled, and more preferably liquid at room temperature. Specific examples of the compound used as the solvent in the present invention are as follows.

I. A compound represented by the formula (1); biphenyl, monoethylbiphenyl, diethylbiphenyl, triethylbiphenyl, monoisopropylbiphenyl, diisopropylbiphenyl, triisopropylbiphenyl,
Nitrobiphenyl, bromobiphenyl, dibromobiphenyl, etc.

II. Compounds represented by formula (2); diphenyl ether, diphenyl sulfide, diphenyl ketone, diphenylmethane, diphenylamine.

III. A compound represented by the formula (3): naphthalene, monomethylnaphthalene, dimethylnaphthalene,
Trimethylnaphthalene, monoethylnaphthalene, diethylnaphthalene, triethylnaphthalene, monoisopropylnaphthalene, diisopropylnaphthalene, triisopropylnaphthalene, nitronaphthalene, chloronaphthalene, dichloronaphthalene, bromonaphthalene, dibromonaphthalene and the like.

IV. A compound represented by the formula (4): tetralin.

V. A compound represented by the formula (5); decalin.

VI. A compound represented by the formula (6): VIII. Compounds represented by formula (8): nitrobenzene, dichlorobenzene, aniline, nitrotoluene, chlorotoluene and the like.

These solvents may be used alone,
Alternatively, two or more kinds may be mixed and used.

The DM-BDC crude crystal targeted by the present invention is irrespective of the production method thereof, for example, crude crystal obtained by methyl esterifying 4,4'-biphenyldicarboxylic acid, methyl parachlorobenzoate or Crude crystals obtained by coupling methyl parabromide benzoate, 4,
4'-biphenyldicarboxylic acid chloride or 4,4
It is all crude crystals such as crude crystals obtained by methyl-esterifying'-biphenyldicarboxylic acid bromide.

The amount of the solvent used for the DM-BDC crude crystal depends on the type and purity of the crude crystal due to the difference in the production method,
Although it varies depending on the type of solvent itself, the temperature at the time of dissolution, etc., it is usually about 0.5 to 20 times the weight of the crude crystal. If the amount of the solvent used is too large, the purification efficiency will not be sufficiently improved, whereas if it is too small, a sufficient purification effect will not be achieved.

The temperature at which the DM-BDC crude crystals are dissolved is determined mainly by the boiling point of the solvent used, but is usually 100.
C. to the boiling point of the solvent, more preferably in the range of about 130 to 180.degree.

The filtration of the solution in which DM-BDC is dissolved is carried out by using a filter press or the like according to a conventional method. By this filtration, for example, a part of the metal catalyst used in the coupling reaction and unreacted 4,4 used as a raw material
It is possible to remove'-biphenyldicarboxylic acid and the like.

The filtrate after filtration is subjected to a crystallization treatment to crystallize the purified DM-BDC. The most common crystallization method is so-called "recrystallization method" in which the purified product is crystallized by cooling the filtrate, but crystallization may be performed by adding a solvent having low DM-BDC solubility.

In the present invention, if necessary, DM-B
After filtering the solution in which DC is dissolved, the filtrate is further subjected to adsorption treatment with activated carbon, activated carbon fibers or the like to adsorb and remove impurities, whereby a higher degree of purification can be performed. The adsorption treatment can be performed by either a fixed bed system or a fluidized bed system. By this adsorption treatment, it is possible to remove a small amount of dissolved impurities and minute impurities that could not be removed by the filtration in the previous step.

[0044]

According to the method of the present invention which uses a specific solvent, it is possible to efficiently perform a high degree of purification of DM-BDC by crystallization without using a special apparatus such as a distillation equipment corresponding to a high melting point. You can do it.

[0045]

EXAMPLES Examples and comparative examples will be shown below to further clarify the features of the present invention.

In the following, the compositions of crude crystals and purified crystals were analyzed by gas chromatography. The metal content was analyzed by the atomic absorption method.

Example 1 4,4'-biphenyldicarboxylic acid (hereinafter referred to as BDCA) was methyl-esterified with methanol at 120 ° C. in the presence of a sulfuric acid catalyst to give DM-BDC 83.1%, 4,4.
'-Biphenyldicarboxylic acid monomethyl ester (hereinafter referred to as MM-BDC) 3.1% and BDCA 13.8
Crude crystals having a composition of 10% were obtained.

15.0 g of the obtained crude crystals and monoisopropylbiphenyl (51% of 4-isopropylbiphenyl,
30 g of 3-isopropylbiphenyl (49%) was placed in a flask equipped with a reflux tube and heated to 180 ° C. to dissolve the crude crystals.

Next, the obtained solution is retained at a particle size of 2.5 μm.
After filtering at 180 ° C. using a filter of m, the filtrate was cooled to room temperature while stirring, and the precipitated crystals were separated by filtration and dried. As a result, 11.9 g of white purified crystals were obtained.

The composition of this purified crystal was DM-BDC9.
9.5%, MM-BDC 0.5%, BDCA trace amount, and DM-BDC recovery rate was 95.0%.

The results of this example and the following examples are collectively shown in Table 1 below.

Example 2 DM-BDC crude crystals were purified in the same manner as in Example 1 except that nitrobenzene was used instead of monoisopropylbiphenyl. As a result, white purified crystals 11.9.
g was obtained.

Example 3 Instead of monoisopropylbiphenyl, diisopropylbiphenyl (4,4'-diisopropylbiphenyl 30
%, 3,4'-diisopropylbiphenyl 70%), and DM-BDC crude crystals were purified in the same manner as in Example 1. As a result, 11.5 g of white purified crystals
was gotten.

Example 4 DM-BD was carried out in the same manner as in Example 1 except that o-dichlorobenzene was used instead of monoisopropylbiphenyl.
Purification of C crude crystals was performed. As a result, white purified crystal 1
1.6 g was obtained.

[0055]

[Table 1]

From the results shown in Table 1, the excellent effects of the present invention are clear.

Examples 5 to 11 DM-BDC crude crystals were purified in the same manner as in Example 1 except that the following compounds were used as the solvent.

Example 5 ... Diphenyl ether Example 6 ... Diphenylamine Example 7 ... Methylnaphthalene (α-form 45% + β-form 5)
5%) Example 8: Isopropylnaphthalene (α-form 18% + β)
-Body 82%) Example 9 ... Tetralin Example 10 ... Decalin Example 11 ... Aniline The results of these Examples are collectively shown in Table 2 below.

[0059]

[Table 2]

Example 12 Methyl p-chlorobenzoate was coupled with metallic zinc and a nickel catalyst to give DM-BDC 95.2%, M.
Crude crystals having a composition of 0.7% M-BDC and 4.1% unknown components were obtained. This crude crystal further contains Zn3.5% and N
i 2.0%.

15.0 g of this crude crystal and 3 parts of nitrobenzene
0 g was put in a flask equipped with a reflux tube, and heated to 180 ° C. to dissolve the crude crystals.

Next, the obtained solution was retained at a particle size of 2.5 μm.
After filtering at 180 ° C. using a filter of m, 1 g of granular coconut husk activated carbon was added to the filtrate and heated at 180 ° C. for 1 hour. Then, the filtrate was filtered again at 180 ° C. to remove the activated carbon, the filtrate was cooled to room temperature while stirring, and the precipitated crystals were separated by filtration and dried. As a result, 12.9 g of white purified crystals were obtained.

The composition and metal content of the obtained purified crystal are shown in Table 2.

[0064]

[Table 3]

From the results shown in Table 3, it is clear that the purification effect of DM-BDC is further improved by adsorbing with activated carbon.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C07C 67/14 67/343 67/52

Claims (5)

[Claims] 1. A crude crystal of dimethyl 4,4′-biphenyldicarboxylate is prepared from the following formulas (1), (2), (3), (4),
Dissolving in a solvent consisting of at least one of the compounds (5) and (6), filtering off the insolubles, and then crystallizing the dimethyl 4,4'-biphenyldicarboxylate. Purification method; {In the formula (1), X, Y and Z are all the same or different in two or more, and are H, a C ₁ -C ₄ alkyl group, B
Represents r and NO ₃ groups. } [Chemical formula 2] {In the formula (2), W represents O, S, CO, CH ₂ and NH. } [Chemical formula 3] {In the formula (3), X, Y and Z are all the same or different in two or more, and are H, a C ₁ -C ₄ alkyl group, C
It represents 1, Br and NO ₃ groups. } [Chemical 4] [Chemical 5] [Chemical 6] {In the formula (6), X and Y are the same or different and are H, a C _{1 to} C ₄ alkyl group, Cl, Br, NO ₃
Group and NH ₂ group. ｝ 2. A crude crystal of dimethyl 4,4′-biphenyldicarboxylate is prepared from the following formulas (1), (2), (3), (4),
Dissolved in a solvent consisting of at least one of the compounds (5) and (6), filtered to remove insolubles, adsorbed and removed impurities, and then crystallized. Method for purifying dimethyl'-biphenyldicarboxylate; {In the formula (1), X, Y and Z are all the same or different in two or more, and are H, a C ₁ -C ₄ alkyl group, B
Represents r and NO ₃ groups. } [Chemical formula 8] {In the formula (2), W represents O, S, CO, CH ₂ and NH. } [Chemical 9] {In the formula (3), X, Y and Z are all the same or different in two or more, and are H, a C ₁ -C ₄ alkyl group, C
It represents 1, Br and NO ₃ groups. } [Chemical formula 10] [Chemical 11] [Chemical 12] {In the formula (6), X and Y are the same or different and are H, a C _{1 to} C ₄ alkyl group, Cl, Br, NO ₃
Group and NH ₂ group. ｝ 3. The method according to claim 1, wherein the crude crystals of dimethyl 4,4′-biphenyldicarboxylic acid are crude crystals obtained by methyl esterifying 4,4′-biphenyldicarboxylic acid. 4. The method according to claim 1 or 2, wherein the crude crystal of dimethyl 4,4'-biphenyldicarboxylate is a crude crystal obtained by coupling methyl parachlorobenzoate or methyl parabromobenzoate. 5. A crude crystal of dimethyl 4,4′-biphenyldicarboxylic acid is a crude crystal obtained by methyl esterifying 4,4′-biphenyldicarboxylic acid chloride or 4,4′-biphenyldicarboxylic acid bromide. The method according to claim 1 or 2.