JP5831241B2 - Method for producing liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride - Google Patents

Description

  The present invention is useful as an epoxy resin curing agent and the like, and is liquid at room temperature, 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride (hereinafter referred to as liquid 1,2,4-cyclohexanetricarboxylic acid-1,2). In particular, the present invention relates to a production method for efficiently and industrially producing liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride. .

  In recent years, high-intensity blue LEDs and white LEDs have been developed, and their application has been expanded to bulletin boards, full-color displays, mobile phone backlights, and the like. Conventionally, a thermosetting resin composition comprising an epoxy group-containing compound and an acid anhydride curing agent has been used as a sealing material for a photoelectric conversion element such as an LED because of its excellent colorless transparency. As a curing agent for an epoxy group-containing compound used in such a photoelectric conversion element, an alicyclic acid anhydride such as methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride is generally used. Among them, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, etc., which are liquid at room temperature, are mainly used because of their ease of handling.

As a conventional method for producing 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride, a molecular form is obtained using a rhodium catalyst in which trimellitic acid is supported on activated carbon having a surface area of 940 m ² / g or more in a polar solvent. After hydrogenation with hydrogen, cis, cis-1,2,4-cyclohexanetricarboxylic acid obtained by recrystallization using tetrahydrofuran and / or acetonitrile as a solvent is dehydrated using an anhydrous reagent such as acetic anhydride. And a 1,2,4-cyclohexanetricarboxylic acid alkyl ester obtained by nuclear hydrogenation by heating a trimellitic acid alkyl ester in the presence of a noble metal-based hydrogenation catalyst and an aliphatic alcohol. Alternatively, 1,2,4-cyclohexanetri obtained by hydrolysis in dimethyl sulfoxide solvent Although a method for dehydrating and ring-closing rubonic acid (Patent Document 2) is disclosed, the obtained 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride is in a solid state at room temperature (hereinafter referred to as the following). Solid form 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride).

Conventional solid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride is difficult to handle and is often used after being dissolved in a solvent, but the operation is complicated and a drying step is required. The environment may be adversely affected.
1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride is expected to be used in various applications such as a resin for a sealing material of an optical semiconductor because it is excellent in colorless transparency and the like. , 2,4-cyclohexanetricarboxylic acid-1,2-anhydride is difficult to handle and its use is limited.

In recent years, 1,2,4-cyclohexanetricarboxylic acid and / or solid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride is heated and melted to obtain liquid 1,2,4-cyclohexanetricarboxylic acid- It has been found that 1,2-anhydrides can be obtained (Patent Document 3). This easy-to-handle liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride can be used for raw materials such as paints, adhesives, molded products, optical semiconductor encapsulant resins, curing agents, polyimide resins, etc. It is useful as a modifier, plasticizer, lubricant oil raw material, medical / agrochemical intermediate, paint resin raw material, toner resin and the like, and its application is expanding.

According to Patent Document 3, when solid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride is used as a raw material, isomerization proceeds by heating and melting, and trans, represented by the formula (1), A mixture of trans-1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride and cis, cis-1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride represented by the formula (2) is obtained. It has been shown to be liquid.


Further, when 1,2,4-cyclohexanetricarboxylic acid is used as a raw material, dehydration simultaneously proceeds in addition to isomerization by heating and melting, and in the same manner as described above, trans, trans-1, A mixture of 2,4-cyclohexanetricarboxylic acid-1,2-anhydride and cis, cis-1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride represented by the formula (2) was obtained, It has been shown to be.

  However, since 1,2,4-cyclohexanetricarboxylic acid and solid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride are solid, they are difficult to handle and are inferior in industrial productivity. In particular, when 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride is used as a raw material, the step of dehydrating 1,2,4-cyclohexanetricarboxylic acid using a dehydrating agent such as acetic anhydride; Since the process of isomerizing the obtained anhydride by heating and melting is necessary, the number of processes increases.

  On the other hand, when the inventors tracked the case of using 1,2,4-cyclohexanetricarboxylic acid as a raw material according to Patent Document 3, the liquid 1,2,4-cyclohexanetricarboxylic acid having a dehydration rate of 95% shown in this document was used. Acid-1,2-anhydride is poor in storage stability, and during storage and mixing with alicyclic dicarboxylic acid anhydride, crystals gradually precipitate, and eventually the whole becomes a white solid, and It was found that a dehydration rate of 98% or more is necessary to enhance the storage stability. In addition, it has been found that the heating and melting method disclosed in Patent Document 3 requires a large heating time to increase the dehydration rate to more than 95%, and the productivity is extremely low on an industrial scale. Increasing the dehydration rate is not only for improving the storage stability, but also for improving the performance of the subsequent liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride as various polymer raw materials and additives. Is important to.

US Pat. No. 5,412,108 JP-A-8-325196 International Publication No. 2005/049597

  An object of the present invention is to provide a method for industrially efficiently producing a liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride having a high dehydration rate.

  As a result of intensive studies on the heating and melting step in order to solve the above-mentioned problems, the inventors of the present invention obtained a formula (2) during the reaction when 1,2,4-cyclohexanetricarboxylic acid was dehydrated and isomerized by heating and melting. 1) In addition to the two isomers represented by the formula (2), it was discovered that there are four isomers in total, two isomers. Furthermore, as a result of detailed examination of the dehydration and isomerization behavior of these four isomer mixtures, the ratio of the four isomers is governed by the dehydration rate, and the higher the dehydration rate, the more the formula (1), the formula It turned out that the ratio of the isomer shown by (2) increases, and conversely, the ratio of other isomers increases as the dehydration rate decreases. The other two isomers decrease as the dehydration rate increases and almost disappears when the dehydration rate is 99% or more. A mixture of the two isomers represented by the formulas (1) and (2) is obtained. It turns out that it is obtained. Although these four isomer ratios change, that is, the isomerization reaction rate itself is relatively fast, the isomer ratio is governed by the dehydration rate, so if the dehydration progresses slowly, the apparent isomerization rate also slows. Become. From this, it was found that the time required for isomerization can be greatly shortened by promoting dehydration, and the present invention has been achieved.

That is, the present invention is as follows.
Production of liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride, characterized in that 1,2,4-cyclohexanetricarboxylic acid is heated and melted at a liquid temperature of 180 ° C. or higher and a pressure of 10,000 Pa or lower. Method.

According to the present invention, liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride having a high dehydration rate can be produced industrially efficiently.

  As a production method of 1,2,4-cyclohexanetricarboxylic acid used as a raw material in the present invention, a method of directly hydrogenating trimellitic acid, a method of hydrolyzing trimellitic acid and then hydrolyzing it, an alkali metal trimellitic acid There is a method of hydrolyzing the salt after hydrogenation, and any of the 1,2,4-cyclohexanetricarboxylic acid obtained by any method can be used for the liquid 1,2,4-cyclohexanetricarboxylic acid-1,2- of the present invention. It can be used as a raw material for anhydrides. Since the obtained 1,2,4-cyclohexanetricarboxylic acid is obtained in a reaction solution mixed with a solvent, a catalyst or a hydrolysis product, one obtained by removing the solvent, catalyst or hydrolysis product from the reaction solution is used. For example, the direct hydrogenation reaction solution obtained by filtering the catalyst may be concentrated to dryness to remove the solvent. The reaction solution may be concentrated to reduce the melting amount of 1,2,4-cyclohexanetricarboxylic acid and be obtained by crystallization. Alternatively, 1,2,4-cyclohexanetricarboxylic acid or 1,2,4-cyclohexanetricarboxylic acid obtained by crystallization by adding a poor solvent for 1,2,4-cyclohexanetricarboxylic acid to the reaction solution may be used.

  In the present invention, 1,2,4-cyclohexanetricarboxylic acid is heated and melted under conditions that promote dehydration. In order to promote the dehydration, a method of promoting the removal of generated water outside the system in the dehydration reaction such as increasing the liquid temperature at the time of heating and melting or decreasing the pressure is preferable. In addition, a dehydration accelerator such as acetic anhydride may be added during heating and melting.

  When the liquid temperature is less than 180 ° C, dehydration is difficult to proceed, so a temperature of 180 ° C or higher is preferable, 190 ° C or higher is more preferable, and 210 ° C or higher is more preferable. On the other hand, when heated above 300 ° C., the liquid is colored and deteriorated remarkably, so that it is preferably 300 ° C. or lower, and more preferably 280 ° C. or lower. As a heating method of the heating and melting reactor, a jacket type, an internal coil type, an external heat exchanger type, or the like can be used, and these may be combined.

  The lower the pressure in the heated melt reactor, the more the dehydration is promoted. Specifically, it is preferably 10,000 Pa or less, and more preferably 5000 Pa or less. On the other hand, when the pressure is lowered below 500 Pa, 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride is also entrained in the water and distilled, so it is preferable that the pressure be 500 Pa or higher. When heating and melting is performed in a batch system, if the pressure reduction operation is started after the liquid temperature has risen, dehydration occurs rapidly, and the water vapor is violently foamed, causing problems such as loss of internal liquid and clogging. It is more preferable to reduce the pressure to a predetermined pressure from the start of heating.

  By promoting dehydration, the time for heating and melting can be greatly shortened. As a result, not only the industrial production efficiency can be improved, but also liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride can be obtained with less coloring. In addition, by providing a step of distilling and purifying liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride after the heating and melting step, liquid 1,2,4-cyclohexanetricarboxylic having a better color value. Acid-1,2-anhydride can be obtained. At this time, the color value (Hazen) of cyclohexanetricarboxylic anhydride which is liquid at room temperature is 100 or less, preferably 50 or less. This color value (Hazen) can be measured with a spectral colorimeter or the like. The distillation method may be either a batch method or a continuous method, but a method having a small heat history is preferable in order to suppress decomposition of the target product and generation of high boiling components. Further, simple distillation may be used, but the number of stages may be added. The distillation pressure is preferably 2000 Pa or less, and more preferably 1000 Pa or less. By setting it as the said pressure, decomposition | disassembly of a target object and the production | generation of a high boiling component can be suppressed.

  Since the liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride of the present invention is liquid at room temperature, it can be industrially advantageously used in various applications. Further, when the anhydride is used as a curing agent, the epoxy resin can be cured without using a curing accelerator, which is industrially useful. Further, the liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride of the present invention can be purified by distillation to have a good color value, and is useful as an optical application. That is, the liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride of the present invention is used for light-receiving elements such as LEDs and semiconductor lasers, photoconductive elements, photodiodes, solar cells, phototransistors, and photothyristors. Insulating and sealing materials for photoelectric conversion elements such as optical coupling elements such as elements, photocouplers and photointerrupters, adhesives such as liquid crystals, resins for optical modeling, and surface coating agents such as plastic, glass and metal, and decoration It can also be used for applications that require transparency of materials and the like. Furthermore, the liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride according to the present invention is a liquid crystal display device (LCD), a solid-state imaging device (CCD), an electroluminescence (EL) device, etc. It can also be used as a curing agent for a thermosetting resin composition that can be suitably used in a coating solution for a protective film.

  The thermosetting resin composition using the liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride of the present invention is 2 mm or more by a conventionally known method such as potting, casting, filament winding, stacking tank and the like. It can also be applied to insulation sealing and moldings with a thickness of. Specifically, mold transformer, mold transformer (current transformer (CT), zero-battery transformer (ZCT), instrument transformer (PT), installed instrument transformer (ZPT)), gas switching Parts (insulation spacers, support insulators, operation rods, sealed terminals, bushings, insulation columns, etc.), solid insulation switch parts, overhead distribution line automation equipment parts (rotary insulators, voltage detection elements, general capacitors, etc.), underground distribution lines Equipment parts (moulded transformers, power transformers, etc.), power capacitors, resin insulators, insulation seals for heavy electrics such as coils for linear motor cars, impregnating varnishes for various rotating equipment coils (generators, motors, etc.) ) And the like. Also, insulating sealing resins used in low-electric fields such as flyback transformers, ignition coils, potting resins such as AC capacitors, transparent sealing resins such as LEDs, detectors, emitters and photocouplers, film capacitors, and impregnating resins for various coils. Can also be used.

  The liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride of the present invention is used for various FRP molded products, various coating materials, adhesives, and decorative materials as other uses that do not necessarily require laminates or insulation. Curing agent of thermosetting resin composition used for materials, raw materials and modifiers such as polyimide resin, polyamideimide resin, polyamide resin, polyester resin, alkyd resin, plasticizer and lubricating oil raw material, medical and agrochemical intermediate, It can be used as a resin material for paints, a resin for toners, and the like.

  EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

The anhydrous ratio was determined by measuring the amounts of 1,2,4-cyclohexanetricarboxylic acid and 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride using GPC. The measurement conditions for GPC are shown below.
Model: SHODEX GPC-101
Detector: RI (refractive index)
Column: SHODEX KF-801 × 2, KF-802.5, KF-803L
Column temperature: 40 ° C
Carrier: Dehydrated THF (with stabilizer)
Carrier flow rate: 1 ml / min
Sample preparation: 0.5 wt% sample / dehydrated THF

The isomer ratio was calculated by methylating the sample with BF ₃ / MeOH (methanol), obtaining the amounts of each of the four isomers by GC, and calculating the ratio. For esterification, 0.05 g sample, 10 ml of BF ₃ / MeOH reagent and one boiling stone were placed in a φ25 × 150 mm screw test tube, set in a block heater at 150 ° C. and esterified for 6 minutes, then allowed to cool. did. After allowing to cool, 20 ml of ion exchange water and 5 ml of chloroform were added, a screw cap was attached, the test tube was shaken, and the esterified sample was extracted into the chloroform layer. Further, the chloroform layer was washed with 20 ml of 0.2N-Na ₂ CO ₃ aqueous solution and twice with 20 ml of ion-exchanged water, and then the chloroform layer was subjected to GC analysis. The GC conditions are shown below.
Model: HP 6890
Detector: FID
Column: Capillary column DB-1 (length 30 m, inner diameter 530 μm, film thickness 1.5 μm)
Column temperature: 200 ° C. → 300 ° C. (initial time 10 min, heating rate 7 ° C./min)
Carrier: He
Sample injection volume: 1 μL
Split ratio: 11: 1
The obtained isomer ratio is in the form of {isomer represented by formula (1): isomer represented by formula (2): other isomer (1): other isomer (2)} in this example. Indicated.

[Reference example]
When the ratio of isomers to the dehydration rate at a liquid temperature of 230 ° C. was examined, the following ratio was obtained.
{Isomer represented by formula (1): Isomer represented by formula (2): Other isomer (1): Other isomer (2)} =
Dehydration rate 0%: 11: 16: 24: 49
Dehydration rate 50%: 36: 28: 13: 23
Dehydration rate 70%: 43:35: 7:15
Dehydration rate 90%: 51:40: 2: 7
Dehydration rate 99%: 56: 44: 0: 0

The isomers represented by the formulas (1) and (2) rise linearly with an increase in the dehydration rate. On the other hand, other isomers decrease linearly with an increase in dehydration rate, and almost no longer exist at a dehydration rate of 99% or more. This ratio is almost constant regardless of the rate of dehydration. If the dehydration rate is determined, the isomer ratio is also determined. That is, it can be said that the isomer ratio is a thermal equilibrium system with respect to the dehydration rate.

[Example 1]
A 1-L four-necked flask (reactor) equipped with a thermocouple and stirrer was charged with 700 g of cis, cis-1,2,4-cyclohexanetricarboxylic acid crystals, and the inside of the flask was used with a vacuum pump and a vacuum controller. At 1333 Pa and heated with a mantle heater controlled at 230 ° C. In about one hour after the start of heating, 1,2,4-cyclohexanetricarboxylic acid crystals melted. The liquid temperature at this time was 180 degreeC. After confirmation of melting, stirring was started, and the control of the heating control device was switched from mantle heater temperature control to liquid temperature control, and the liquid temperature was controlled to 230 ° C. About 15 minutes after melting, the liquid temperature reached 230 ° C. At this point, the dehydration rate was 96% and the isomer ratio was 14: 80: 3: 3. After 1 hour, the dehydration rate exceeded 99%, and isomerization proceeded rapidly. After 2 hours, the isomerization was completed with 56: 44: 0: 0, which is a steady ratio at a dehydration rate of 99% or more. Liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride was obtained in a total operation time of about 4 hours on a 1 L flask scale.

[Example 2]
A 3 m ³ SUS316 reactor equipped with a thermocouple and a heating medium jacket was charged with 500 kg of cis, cis-1,2,4-cyclohexanetricarboxylic acid crystals, and the reactor was maintained at 1333 Pa while maintaining 230 in the jacket. A heating medium at 0 ° C. was supplied and heated. Crystals melted about 8 hours after the start of heating. The liquid temperature at this time was about 190 ° C. Thereafter, when the internal solution was sampled at 18 hours, the dehydration rate was 99% or more and the isomer ratio was 56: 44: 0: 0. Liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride was obtained in a total operating time of 26 hours on an industrial scale.

[Comparative Example 1]
According to Patent Document 3, heating and melting were performed in the same manner as in Example 1 except that nitrogen was passed at 100 ml / min during heating and melting, and the inside of the reactor was set to normal pressure (about 100,000 Pa). As a result, about 2 hours until the crystals melted, the dehydration rate was 80% and the isomer ratio was 48: 37: 5: 10 even 3 hours after the liquid temperature reached the predetermined temperature. Since the progress of the dehydration was slow, the isomerization was not completed due to the influence. When this was continued, the dehydration rate reached 99% after 7 hours, and the isomer ratio was 56: 44: 0: 0, and the isomerization was completed. About 12 hours of operation time was required on a 1 L flask scale.

[Comparative Example 2]
According to Patent Document 3, heating and melting were performed in the same manner as in Example 2 except that nitrogen was passed at 30 L / min during heating and melting, and the inside of the reactor was set to normal pressure. As a result, about 12 hours until the crystals melted, the dehydration rate was 50% and the isomer ratio was 36: 28: 13: 23 even 20 hours after the liquid temperature reached the predetermined temperature. Since the progress of the dehydration was slow, the isomerization was not completed due to the influence. On the industrial scale, isomerization was not completed even over a total of about 32 hours, and liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride was not obtained.

[Comparative Example 3]
The reason for the slow progress of dehydration and isomerization in Comparative Example 1 was that there was a possibility that the flow rate of nitrogen to be circulated at the time of heating and melting was insufficient. Heating and melting were carried out in the same manner as in Example 1 (normal pressure in the reactor). As a result, about 2 hours until the crystals melted, the dehydration rate was 67% and the isomer ratio was 45: 35: 6: 14 even 3 hours after the liquid temperature reached the predetermined temperature. Since the progress of the dehydration was slow, the isomerization was not completed due to the influence. When this was continued, the dehydration rate reached 99% after 7 hours, and the isomer ratio was 56: 44: 0: 0, and the isomerization was completed. By increasing the nitrogen flow rate, there was a slight effect on the progress of dehydration and isomerization at 3 hours after the liquid temperature rose, but the operation time until completion of isomerization was not shortened. It was.

[Comparative Example 4]
The reason for the slow progress of dehydration and isomerization in Comparative Example 1 was that the liquid temperature at the time of heating and melting was 230 ° C., which was considered to be 20 ° C. lower than the liquid temperature 250 ° C. shown in Patent Document 3, Heating and melting were performed by the same operation as in Comparative Example 1 (normal pressure in the reactor) except that the liquid temperature was 260 ° C. As a result, about 1.5 hours until the crystals melted, the dehydration rate was 95% and the isomer ratio was 54: 42: 1: 3 even 3 hours after the liquid temperature reached the predetermined temperature. Two hours later, the isomerization was completed after reaching a dehydration rate of 99%. The total operation time was about 6.5 hours, which was shorter than that of Comparative Example 1, but took 2.5 hours more than that of Example 1. The liquid 1,2,4-cyclohexanetricarboxylic acid-1,2-anhydride obtained was colored dark brown because the high temperature of 260 ° C. was maintained for a long time.

[Comparative Example 5]
Heating and melting were performed in the same manner as in Example 1 except that the pressure in the reactor was changed to 40000 Pa. As a result, it took about 1.5 hours until the crystals melted, and after 3 hours from the time when the liquid temperature reached the predetermined temperature, the dehydration rate was 84% and the isomer ratio was 50: 40: 3: 7. It was 7 hours after the completion of isomerization when the degree of dehydration reached 99%. The total operation time was about 11.5 hours, which was not significantly different from Comparative Example 1. At a reduced pressure of about 40,000 Pa, dehydration and isomerization were not promoted so much.

Example 3
Heating and melting were performed in the same manner as in Example 1 except that the pressure in the reactor was set to 10,000 Pa. As a result, dehydration and isomerization were completed about 1.5 hours until the crystals melted, and about 6.5 hours after the liquid temperature reached a steady state. The operation time was about 8 hours in total, and a time shortening effect was seen as compared with Comparative Example 1.

Example 4
Heating and melting were performed in the same manner as in Example 1 except that the pressure in the reactor was 5000 Pa. As a result, dehydration and isomerization were completed about 1.3 hours until the crystals melted, and about 4.7 hours after the liquid temperature reached a steady state. The total operation time was about 6 hours, and an effect of shortening the time was further observed as compared with Example 3.

[Comparative Example 6]
The flask was equipped with a condenser, and heat-melting was carried out in the same manner as in Comparative Example 1, except that the dehydration rate was intentionally suppressed by returning water produced by the dehydration into the system. As a result, the dehydration rate was 45% and the isomer ratio was 35: 26: 13: 26 even 3 hours after reaching the predetermined temperature. Even after 7 hours, the dehydration rate was 73%, the isomer ratio was 46: 35: 6: 13, and even after 6 hours, the dehydration rate was 95% and the isomer ratio was 53: 41: 2: 4. there were. Thus, since the isomer ratio is governed by the dehydration rate, if the dehydration is intentionally suppressed, the progress of the isomerization is also slowed.

Claims (2)

Liquid 1,2,4-cyclohexanetricarboxylic acid-1,2- characterized in that 1,2,4-cyclohexanetricarboxylic acid is heated and melted at a liquid temperature of 180 ° C. or higher and 300 or lower and a pressure of 500 Pa or higher and 10,000 Pa or lower. Method for producing anhydride. The production method according to claim 1, wherein a dehydration accelerator is added during heating and melting.