JP3235914B2 - Method for producing 4,5-dichlorophthalic acid or a salt thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a phthalocyanine dye or a pigment useful as a raw material for functional polymers and the like.
The present invention relates to a method for producing 5-dichlorophthalic acid or a salt thereof.

[0002]

2. Description of the Related Art 4,5-Dichlorophthalic acid or a salt thereof is represented by the following general formula (1)

Embedded image (Wherein, A represents hydrogen or a metal such as sodium or potassium), which is obtained by chlorinating phthalic acid with chlorine. Regarding the chlorination method of phthalic acid for the purpose of producing dichlorophthalic acid, German Patent No. 725,605 describes a method of reacting phthalic acid with chlorine in an aqueous solvent in the presence of a caustic alkali. .

However, according to this method, a large amount of isomers of 4,5-dichlorophthalic acid and trichlorophthalic acid, which is a perchlorinated product, are produced in a large amount in the reaction system, so that 4,5-dichlorophthalic acid is produced in a high yield. It is difficult to obtain good and high purity. This is because, during the process of chlorination of phthalic acid, 3,4-dichlorophthalic acid, 3,6-dichlorophthalic acid, or trichlorophthalic acid, which is an isomer other than the target 4,5-dichlorophthalic acid, Inevitably by-product,
In particular, the target product 4,5-dichlorophthalic acid and the by-product 3,3
This is because it is extremely difficult to separate 4-dichlorophthalic acid and trichlorophthalic acid. The method for producing 4-chlorophthalic acid is described in JP-A-56-455.4.
There are many reports in Japanese Patent Publication No. 38 and the like, but these reports focus on suppressing by-products of dichlorophthalic acid and do not suggest the present invention.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a process for producing 4,5-dichlorophthalic acid by chlorinating phthalic acid or a salt thereof with chlorine. It is intended to obtain a high purity.

[0005]

Means for Solving the Problems In view of the above points, the present inventors have proposed an improvement in a phthalic acid chlorination method.
As a result of intensive studies, the present invention has been achieved. That is, the present invention provides 4-chlorophthalic acid or a salt thereof by reacting phthalic acid or a salt of phthalic acid with chlorine in an aqueous solvent in the presence of a caustic alkali or caustic alkali salt to produce 4-chlorophthalic acid or a salt thereof. Alternatively, a crystal mainly composed of a salt thereof is separated, and then the separated crystal is controlled in a water solvent in the presence of a caustic alkali or a caustic salt at a temperature of 20 to 100 ° C and a pH of 4 to 13. While increasing the temperature or adding caustic and reacting with chlorine to form 4,5-dichlorophthalic acid or a salt thereof, the main component of which is 4,5-dichlorophthalic acid or a salt thereof This is a method for producing 4,5-dichlorophthalic acid or a salt thereof for separating crystals.

Hereinafter, the present invention will be described in detail. In the reaction of the present invention, phthalic acid is dissolved in an aqueous solvent in the presence of a caustic alkali,
Chlorination with chlorine first produces 4-chlorophthalic acid,
Next, 4,5-dichlorophthalic acid is used.
Since the inside of the reaction system is acidic or weakly alkaline, phthalic acids may exist in the form of a salt, and caustic alkali may also exist in the form of a salt. However, it is easier to understand phthalic acid, chlorophthalic acid, caustic alkali, etc., including the salt, and therefore, in the following description, the term may be used to include the salt. In the present invention, first, phthalic acid is chlorinated in the first step to obtain a crystal mainly containing 4-chlorophthalic acid or a salt thereof, and in the second step, it is chlorinated to obtain 4,5-dichlorophthalic acid or A crystal mainly composed of the salt is obtained.

[First Step] As the first step, generally, the above-mentioned JP-A-56-45438 and JP-A-Hei.
Although the method for producing 4-chlorophthalic acid described in JP-A-129,143 and the like can be employed, the following conditions are preferable. As the raw material phthalic acid used in the present invention, not only phthalic acid, but also phthalic anhydride, phthalic acid salts, phthalic imides, and the like which can be phthalic acid or a salt thereof in a reaction system can be used. The caustic used in the first step has a function of neutralizing hydrogen chloride generated by the reaction and a function of increasing the solubility of phthalic acids. As the caustic alkali, sodium hydroxide and potassium hydroxide are suitable. When phthalic anhydride is used, the amount of the caustic alkali used is in the range of 1 to 4 moles, and the pH is adjusted to be in the range of 4 to 13.
Even if the pH is slightly high at the beginning of the reaction, there is no problem because chlorine or hydrochloric acid generated by the reaction is neutralized, but if the pH is too high, the loss of chlorine increases. If the pH is too low, the reaction rate will decrease.

The amount of water as a solvent is usually about 2 to 30 times, preferably about 3 to 6 times the weight of phthalic acid. If the amount of water is too small, the slurry concentration becomes high, causing problems such as difficulty in stirring. If it is too large, problems such as deterioration of the yield occur. The reaction temperature is usually 20-80 ° C, preferably 30-70 ° C. Also,
The required amount of chlorine is usually 1 to 2 moles relative to phthalic acid, and this is blown into the reaction system in the state of chlorine gas. If unreacted phthalic acid is present, it is better to blow in excess. The reaction time is generally 1 to 12 hours. If the pH drops during the reaction, caustic may be added.

After completion of the reaction, the mixture is cooled to precipitate crystals, and the crystals are separated by means such as filtration. Acid precipitation or salting out may be performed to increase the recovery rate of the crystals. In particular, if cooling is used in combination with acid precipitation or salting out, the recovery rate increases. Examples of the acid used for the acid precipitation include hydrochloric acid, sulfuric acid, and the like, and the pH at this time may be adjusted to 0.5 to 7, preferably about 3 to 6. Examples of the salt used for salting out include potassium chloride, sodium chloride, and sodium sulfate.
The amount is usually 0.5 to 10% by weight based on the amount of the reaction solution. The temperature for the separation is usually 5 to 75 ° C, preferably 1 to 75 ° C.
0-40 ° C.

The crystals separated by filtration, centrifugation or the like are used in the second step as they are or after washing and drying as necessary. The crystals obtained here are in a state excluding water and sodium chloride, that is, in phthalic acids composed of phthalic acid and its derivatives, 4-chlorophthalic acid is 50% by weight or more, preferably 60% by weight or more,
The content of phthalic acid is 22% by weight or less, the amount of 3-chlorophthalic acid is 12% by weight or less, and the amount of dichlorophthalic acid is 15% by weight or less, preferably 10% by weight or less.
This value is a value obtained by converting a salt such as a phthalate into an acid such as phthalic acid. Note that the crystals used in the second step may contain water or salts such as sodium chloride, so that it is not necessary to perform purification to specifically remove them, but it is necessary to purify them by washing, recrystallization, etc. Or a disodium salt or an acid anhydride.

[Second Step] In the second step, the crystals mainly containing 4-dichlorophthalic acid or its salt obtained in the first step are treated with chlorine in an aqueous solvent in the presence of caustic alkali or caustic salt. To form 4,5-dichlorophthalic acid. This reaction can be carried out generally under the same conditions as in the first step, but is preferably carried out under the following conditions.

The caustic alkali used in this reaction is preferably sodium hydroxide, potassium hydroxide or the like. The amount of the caustic alkali used is usually about 0.1 to 20 times the weight of phthalic acids in the crystal, and the pH is 4 to 10%. It is preferable to set the range to 13. Water as a solvent is usually about 3 to 30 times the weight of the crystal. Usually, it is about 0.1 to 2 times the weight of phthalic acids in the crystal, and this is preferably blown in as chlorine gas. The reaction time is usually about 1 to 24 hours. When chlorine gas is blown in and the reaction proceeds, the pH of the reaction system decreases, and crystals are deposited. When the crystals are deposited, the reaction speed is extremely reduced, and the reaction is stopped.

Therefore, in the present invention, the reaction temperature is increased sequentially or the reaction proceeds by adding caustic alkali. However, if the reaction temperature is increased from the beginning of the reaction, the production of trichlorophthalic acid increases. Therefore, it can be said that it is preferable to keep the temperature within the above-mentioned temperature range at the initial stage of the reaction, at a relatively low temperature, and to gradually increase the temperature in accordance with the progress of the reaction. Also, if a large amount of caustic is added from the beginning of the reaction, not only the loss of caustic but also the loss of chlorine will occur, so the pH should be kept a little lower within the above range, and the chlorine gas should be kept within this range. It can be said that it is better to add caustic according to the blowing amount. In addition, the addition amount of the above-mentioned caustic alkali means the total amount when caustic alkali is added. When raising the temperature or adding caustic alkali, the blowing of chlorine gas may be temporarily interrupted, or may be performed continuously or intermittently without interruption.

There is a close relationship between the reaction temperature, the amount of caustic used, and the quality of the product. When the reaction temperature is high, the content of impurities such as trichlorophthalic acid increases. However, the amount of caustic used is reduced, and the content of inorganic salts in the product is reduced. On the other hand, when the reaction temperature is low, the reverse is true. Therefore, it is possible to select more appropriate reaction conditions depending on the intended quality of 4,5-dichlorophthalic acid. This chlorination
Stop at or near the point where the yield of 4,5-dichlorophthalic acid is highest.

After completion of the reaction, the mixture is cooled to precipitate crystals, and the crystals are separated by means such as filtration. Acid precipitation or salting out may be performed to increase the recovery rate of the crystals. In particular, if cooling is used in combination with acid precipitation or salting out, the recovery rate increases. Examples of the acid used for the acid precipitation include hydrochloric acid, sulfuric acid, and the like, and the pH at this time is preferably adjusted to 0.5 to 8, preferably about 3 to 7. Examples of the salt used for salting out include potassium chloride, sodium chloride, and sodium sulfate.
The amount is usually 0.5 to 10% by weight based on the amount of the reaction solution.
It is. The temperature at the time of separation is usually 5 to 80C, preferably 10 to 45C.

The crystals separated by filtration, centrifugation or the like can be washed with water as necessary to increase the purity. The purity can also be increased by adding 0.1 to 3 times the amount of water to the reaction solution and performing filtration or the like. Further, if necessary, the purity can be further increased by recrystallization or the like. A product containing usually 70% by weight or more of the 4,5-dichlorophthalic acid thus obtained, excluding water and inorganic salts such as sodium chloride, is obtained.

When phthalic acid is chlorinated, the 4-position and 5-position are preferentially substituted due to the orientation thereof, and at this time, those substituted at 3-position are also produced. And, since this 3-position substitution product is unsubstituted at the 4- and 5-positions which are more active,
It is likely to preferentially produce 3,4- or 3,5-disubstituted products, and furthermore, these di-substituted products still have an active unsubstituted 4- or 5-position, so that trichlorophthalic acid can be used. Also easy to generate. Most of these other isomers or trichlorophthalic acid are difficult to separate because there is no large difference in solubility from the target product, 4,5-dichlorophthalic acid. When the crystals mainly containing 4-chlorophthalic acid formed in the first step are separated as in the present invention, the amount of 3-chlorophthalic acid is drastically reduced, whereby the formation of the 3,4- or 3,5-disubstituted product is reduced. Not only is the production reduced, but the production of trichlorophthalic acid is also reduced. In addition, by controlling the reaction temperature and pH within a certain range, it is possible to suppress the by-products of by-products and to smoothly carry out the reaction.

[0018]

The present invention will be specifically described below based on examples and comparative examples.

Examples 1 to 4 [First step] In a 2,000 ml four-necked flask equipped with a chlorine blowing pipe, an exhaust gas pipe and a thermometer, 1,300 m of water was placed.
l, 375 g of 48% sodium hydroxide solution and 300 g of phthalic anhydride were charged and dissolved by stirring.
At 0 ° C., chlorine gas was introduced at a rate of 1.0 g / min for 4 hours,
Reacted. After completion of the reaction, 84 g of sodium chloride was added, cooled to room temperature, and filtered to obtain wet crystals having the following composition. The weight of phthalic acids is a value obtained by converting the weight of a salt such as a phthalate into an acid such as phthalic acid, and the yield is the theoretical yield of 4-chlorophthalic acid with respect to phthalic anhydride. Rate. Total weight: 752 g, moisture: 316.6 g, NaCl content: 3
0.8 g, phthalic acid: 67.7 g, monochlorophthalic acid: 339.1 g (4-monochlorophthalic acid: 294.
0 g, 3-monochlorophthalic acid: 45.1 g), dichlorophthalic acid: 71.4 g, and the yield: 72.4%.

[Second step] Water 5 was placed in a 1,000 ml five-necked flask equipped with a chlorine blowing pipe, an exhaust gas pipe and a thermometer.
20 ml, 13.5 g of a 48% sodium hydroxide solution, and 188 g of the wet crystals obtained in the first step were charged,
After stirring and dissolving, at 60 ° C., 0.35 chlorine gas was added.
The reaction was conducted at a rate of g / min for 2 hours. About one hour after the start of the reaction, precipitation of crystals started. At this point, the introduction of chlorine gas was temporarily stopped, and the temperature was raised. After about 1 hour, the reaction temperature shown in Table 1 was reached, and then the amount shown in Table 1 was adjusted so that the pH became 4.5 to 9.0. Of a 48% sodium hydroxide solution was added dropwise, and 0.35 g / chlorine gas was added while maintaining the reaction temperature.
After introducing for 2 hours at a speed of 30 minutes,
Add 5 ml of 5% hydrochloric acid, cool to 20 ° C., filter,
The obtained crystal was dried at 100 ° C. to obtain the desired crystal of 4,5-dichlorophthalic acid. About the obtained object,
From the data obtained by high performance liquid chromatography, the composition and the yield were examined by the area percentage. Table 1 shows the results.

COMPARATIVE EXAMPLE 325 ml of water was placed in a 500 ml five-necked flask equipped with a chlorine blowing pipe, an exhaust gas pipe, a thermometer and a dropping funnel.
93.8 g of sodium hydroxide solution and phthalic anhydride 7
After charging 5 g and dissolving by stirring, chlorine gas was introduced at 60 ° C. at a rate of 0.25 g / min for 4 hours to cause a reaction (corresponding to the first step in the above example). To the obtained reaction solution, 6.8 g of a 48% sodium hydroxide solution was added, and after raising the temperature to the reaction temperature in about 1 hour, the pH was adjusted to 4.5 to 9.0.
48% sodium hydroxide solution in the amount shown in Table 1 was added dropwise so that
After introducing at a rate of 5 g / min for 3.2 hours, the mixture was cooled to 30 ° C., 25 ml of 35% hydrochloric acid was added, the mixture was cooled to 20 ° C., filtered, and the obtained crystals were dried at 100 ° C. (Corresponding to the second step in the above example). The composition and yield of the obtained target product were examined by area percentage from data obtained by high performance liquid chromatography. Table 1 shows the results.

[0022]

[Table 1]

[0023]

According to the method of the present invention, phthalic acid or a salt thereof is chlorinated with chlorine to produce 4,5-dichlorophthalic acid with high yield and high purity.

────────────────────────────────────────────────── (5) References JP-A-2-237958 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 51/363 C07C 51/43 C07C 63 / 72

Claims (1)

(57) [Claims] 1. A method for producing 4-chlorophthalic acid or a salt thereof by reacting phthalic acid or a salt of phthalic acid with chlorine in an aqueous solvent in the presence of a caustic alkali or a caustic alkali salt to produce 4-chlorophthalic acid or a salt thereof. The crystals containing the salt as a main component are separated, and the separated crystals are then controlled in a water solvent in the presence of a caustic alkali or a caustic salt at a temperature of 20 to 100 ° C. and a pH of 4 to 13 while controlling. After increasing the temperature or adding caustic alkali and reacting with chlorine to produce 4,5-dichlorophthalic acid or a salt thereof, a crystal containing 4,5-dichlorophthalic acid or a salt thereof as a main component And a method for producing 4,5-dichlorophthalic acid or a salt thereof.