JP2005220038A - Method for producing onium tetrakisacyloxyborate and its precursor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an onium tetrakis acyloxyborate and a precursor thereof useful as a curing agent for an epoxy resin, the raw material is inexpensive, easy to handle, the purification operation is simple, and the target product is produced in a high yield. Provide a way to do it.
An organic carboxylic acid and sodium borohydride are reacted to produce sodium tetrakisacyloxyborate. Also, sodium tetrakis acyloxyborate and onium salt are reacted to produce onium tetrakis acyloxyborate.
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Description

  The present invention relates to a method for producing onium tetrakis acyloxyborate useful as an epoxy resin curing catalyst and a precursor thereof.

  It is known that onium tetrakisacyloxyborate compounds such as tetra-substituted phosphonium tetraacyloxyborate serve as curing catalysts for epoxy resins and the like, and efficient production methods thereof have also been proposed (Patent Documents 1 and 2). . In the former proposal, a method of reacting a tetra-substituted phosphonium tetra-substituted borate with an organic acid has been disclosed, but there are problems such as high raw materials used or poor stability, and industrial availability. When using easy tetraphenylphosphonium tetraphenylborate as a raw material, it is a problem that benzene which requires careful handling is by-produced.

  In the latter proposal, a method is disclosed in which an amine salt of an organic carboxylic acid and boron trihalide are reacted to form a tetrakisacyloxyborate amine salt, and then an onium salt such as a tetra-substituted phosphonium salt is reacted. In this proposal, an amine salt is by-produced during the synthesis of the tetrakisacyloxyborate amine salt, so this separation and removal becomes essential, and the operation becomes complicated.

  The latter publication also shows that the reaction did not proceed when a potassium salt was used in the above reaction instead of the amine salt of the organic carboxylic acid. In addition, as a conventional technique for synthesizing tetrakisacyloxyborate compounds, a method of reacting triacetylborate and potassium acetate in the presence of acetic anhydride has been introduced (Non-Patent Document 1), and an additional test has been conducted. The product yield is shown to be low. It is also shown that the reaction did not proceed when aromatic carboxylic acid anhydride was used instead of acetic anhydride and potassium aromatic carboxylate was used instead of potassium acetate. Furthermore, tetraphenylphosphonium tetrakisacetoxyborate was obtained by the reaction of potassium tetrakisacetoxyborate and tetraphenylphosphonium bromide, but the yield was shown to be low.

JP-A-8-196911 JP 2001-261684 A I. G. Lewis, V.D. N. Prahotnik, Inorganic Chemistry Journal VOL. 13, 2050 (1968)

  The present inventor considered that onium tetrakisacyloxyborate is particularly useful as the above-mentioned curing catalyst among onium tetrakisacyloxyborate, and onium tetrakis that can be advantageously produced industrially. The synthesis method of acyloxyborate was examined. As a result, a two-stage production method via sodium tetrakis acyloxyborate has been found. Accordingly, an object of the present invention is to provide a method for producing onium tetrakisacyloxyborate and its precursor in a high yield, since the raw materials are inexpensive and easy to handle, and the purification operation is easy.

  That is, according to this invention, the manufacturing method of sodium tetrakis acyloxy borate characterized by making organic carboxylic acid and sodium borohydride react is provided. The present invention also provides a method for producing onium tetrakisacyloxyborate, characterized by reacting sodium tetrakisacyloxyborate and onium salt which can be produced in this manner. Furthermore, according to the present invention, sodium tetrakisaroyloxyborate which is a precursor of onium tetrakisaroyloxyborate useful as a curing catalyst among oniumtetrakisacyloxyborate is provided.

  The sodium borohydride used in the first invention is inexpensive, has moderate reactivity and stability, and is easy to handle. In addition, in the reaction of the first invention, high-purity sodium tetrakisacyloxyborate can be obtained in a high yield by a simple operation. Also in the reaction of the second invention, high-purity onium tetrakisacyloxyborate can be obtained in high yield from sodium tetrakisacyloxyborate under mild reaction conditions and simple purification operation. In particular, tetraphenylphosphonium tetrakisaroyloxyborate particularly useful as a curing catalyst for epoxy resins can be advantageously produced industrially.

In the first invention, sodium tetrakisacyloxyborate is produced by reacting an organic carboxylic acid with sodium borohydride (NaBH ₄ ). Examples of organic carboxylic acids as raw materials include aliphatic carboxylic acids such as acetic acid, propionic acid, butyric acid and phenylacetic acid, alicyclic carboxylic acids such as cyclohexanecarboxylic acid, benzoic acid, p-toluic acid, m-toluic acid, Examples thereof include monocyclic aromatic carboxylic acids such as o-toluic acid and p-methoxybenzoic acid, and bicyclic aromatic carboxylic acids such as 1-naphthoic acid and 2-naphthoic acid. In the reaction of the first invention, even when a monocyclic or bicyclic aromatic carboxylic acid is used as a raw material, the corresponding sodium tetrakisacyloxyborate can be produced in high yield.

  The proportion of organic carboxylic acid and sodium borohydride used in the production of sodium tetrakisacyloxyborate is stoichiometric, that is, 4 moles of organic carboxylic acid per mole of sodium borohydride, or an excess of organic carboxylic acid. A ratio is preferable. When the proportion of the organic carboxylic acid used is less than the stoichiometric amount, the reaction product becomes a mixture of various acyloxyborates, and it becomes difficult to obtain high-purity sodium tetrakisacyloxyborate.

  The reaction of the first invention can be carried out without a solvent, but in order to suppress the rapid generation of hydrogen gas and appropriately control the reaction, it can be carried out in the presence of a solvent inert to the reaction. preferable. Preferred examples of the solvent that can be used for such purposes include aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and mesitylene. Although there is no restriction | limiting in particular in the usage-amount of a solvent, Usually, about 1-20 weight times of raw material organic carboxylic acid is suitable.

  The above reaction is preferably performed under conditions where the organic carboxylic acid is in a liquid state and sodium borohydride is dispersed in the reaction medium. This reaction is also preferably performed while removing by-produced hydrogen gas from the reaction system. The reaction temperature varies depending on the type of organic carboxylic acid, but is, for example, 50 to 200 ° C. If the temperature is set to a temperature at which the solvent is refluxed, the reaction can be easily adjusted. The reaction time varies depending on the reaction temperature, but is generally the time until generation of hydrogen gas is not recognized, and is usually about 1 to 20 hours.

  In the above reaction, hydrogen gas as a by-product can be easily removed from the reaction system by exhaust, so that no special operation is required in the purification process. That is, the reaction liquid is cooled as necessary to collect a solid crude product, which is washed with a solvent such as toluene and vacuum-dried to remove the unreacted organic acid and the remaining solvent, High purity sodium tetrakis acyloxyborate can be obtained with good yield.

  In the reaction of the second invention, sodium tetrakisacyloxyborate, which can be produced by the method as described above, is reacted with an onium salt such as a tetra-substituted phosphonium salt, a tetra-substituted ammonium salt, or a tri-substituted sulfonium salt to produce onium tetrakisua. Siloxyborate is produced. In these onium salts, the substituents are hydrocarbon groups such as alkyl groups, cycloalkyl groups, and aryl groups, and the salts are halides such as chlorides, bromides, and iodides. In view of the usefulness of the epoxy resin as a curing catalyst, the substituent is preferably an aryl group such as a phenyl group or a tolyl group, and chloride or bromide is preferably used in consideration of yield, cost, and the like. Particularly preferred are tetraaryl substituted phosphonium salts, especially tetraphenylphosphonium bromide.

  In the reaction between sodium tetrakisacyloxyborate and an onium salt, it is preferable to use 1 mol of the latter or a slight excess of the former with respect to 1 mol of the former in consideration of economy, yield, ease of purification, and the like. . That is, since this reaction is a reaction that produces a sodium salt as a by-product, it is most effective to separate and remove this by washing with water in the purification after completion of the reaction. In this case, both sodium tetrakisacyloxyborate and the product onium tetrakisacyloxyborate are sparingly soluble in water, so excessive use of sodium tetrakisacyloxyborate will contaminate the product, resulting in high purity. This is because it is difficult to obtain the desired object. If the onium salt is in excess, it is soluble in water, so there is no such problem and purification is easy.

  In the above reaction, since sodium tetrakis acyloxyborate and onium salt are both solid at room temperature, it is preferable to carry out the reaction by dissolving them in a solvent and adding them dropwise. The dripping may be performed on either the sodium tetrakis acyloxyborate solution or the onium salt solution, and there is no need for heating. After completion of the dropping, the reaction can be completed by stirring the reaction solution at 15 to 30 ° C. for about 30 minutes.

  As a solvent that can be used for such a purpose, a solvent having a very high boiling point should not be used for separation and removal under reduced pressure after completion of the reaction. It is also desirable to dissolve the raw material sodium tetrakisacyloxyborate and onium salt and use a solvent that is sparingly soluble in the product onium tetrakisacyloxyborate. When such a solvent is used, since the reaction solution is suspended quickly after the dropping, the production of the target product can be visually observed, and the product can be easily separated. Examples of solvents that can be used include cyclic ethers such as tetrahydrofuran, ketones such as methyl isobutyl ketone, esters such as ethyl acetate, and halogenated hydrocarbons such as dichloromethane. The amount of the solvent used is arbitrary, but it is economical to make it usually in the range of about 1 to 20 times the weight of the raw material.

  In order to recover the target onium tetrakis acyloxyborate from the suspension obtained by the reaction, first, the solvent is removed under reduced pressure, and then the solid content obtained by washing with water may be dried under reduced pressure. The removal of the solvent is preferably performed as completely as possible, otherwise the remaining solvent may dissolve the target product and reduce the yield slightly. By the water washing, the sodium salt and unreacted onium salt by-produced by the reaction can be removed as an aqueous solution. By the simple method as described above, onium tetrakisacyloxyborate can be obtained in good yield from sodium tetrakisacyloxyborate. In particular, high-purity tetra-substituted phosphonium tetrakisaroyloxyborate can be obtained in high yield from sodium tetrakisaroyloxyborate and a tetra-substituted phosphonium salt.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this Example.

[Example 1]
A 500 ml flask equipped with a Dimroth condenser was charged with 100 ml of toluene, 10.38 g (85 mmol) of benzoic acid and 0.76 g (20 mmol) of sodium borohydride, heated to 75 ° C. and stirred for 1 hour. The hydrogen gas generated at this time was removed out of the system. Next, the reaction solution was heated to 110 ° C. and stirred for 1 hour to complete the reaction.

  After cooling the reaction solution, the cake obtained by filtration was washed with toluene, and dried under vacuum to obtain 9.74 g of sodium tetrabenzoate borate (yield 94% based on sodium borohydride).

  2.59 g (5 mmol) of sodium tetrabenzoate borate thus obtained was placed in a 100 ml flask, and 20 ml of acetone was added and dissolved. To this was added dropwise a solution of 2.14 g (5.1 mmol) of tetraphenylphosphonium bromide dissolved in 10 ml of methanol at room temperature. At this time, the reaction solution was suspended. After completion of the dropwise addition, this was stirred at room temperature for 30 minutes.

  After completion of the reaction, the solvent was removed from the reaction solution under reduced pressure, and 30 ml of water was added to the resulting crude cake and stirred for 30 minutes. This was filtered to remove sodium bromide as a reaction by-product as an aqueous solution, and the cake was washed with water and dried under vacuum heating to give 3.96 g of tetraphenylphosphonium tetrabenzoate borate (sodium tetrabenzoate). Yield 95% based on acid borate).

[Example 2]
A 500 ml flask equipped with a Dimroth condenser was charged with 100 ml of toluene, 13.94 g (81 mmol) of 1-naphthoic acid and 0.76 g (20 mmol) of sodium borohydride, heated to 75 ° C. and stirred for 1 hour. . The hydrogen gas generated at this time was removed out of the system. Next, the reaction solution was heated to 110 ° C. and stirred for 1 hour to complete the reaction.

  After cooling the reaction solution, the cake obtained by filtration was washed with toluene and dried in vacuo to obtain 12.72 g of sodium tetrakis (1-naphthoyloxy) borate (yield 89% based on sodium borohydride). Obtained.

  3.59 g (5 mmol) of sodium tetrakis (1-naphthoyloxy) borate thus obtained was placed in a 100 ml flask and dissolved in 20 ml of acetone. To this was added dropwise a solution of 2.14 g (5.1 mmol) of tetraphenylphosphonium bromide dissolved in 10 ml of methanol at room temperature. At this time, the reaction solution was suspended. After completion of the dropwise addition, this was stirred at room temperature for 30 minutes.

  After completion of the reaction, the solvent was removed from the reaction solution under reduced pressure, and 30 ml of water was added to the resulting crude cake and stirred for 30 minutes. This was filtered to remove sodium bromide as a reaction by-product as an aqueous solution, and the cake was washed with water and dried under vacuum heating to obtain 5.00 g of the target product tetraphenylphosphonium tetrakis (1-naphthoyloxy) borate ( The yield was 97% based on sodium tetrakis (1-naphthoyloxy) borate).

As an example of the analysis results, the sodium tetrakis (1-naphthoyloxy) borate obtained in Example 2 was subjected to spectroscopic analysis by ¹¹ B-NMR, and the deuterated dimethyl sulfoxide was set to 0 ppm with an aqueous phosphoric acid solution as an external reference. Was measured as a measurement solvent. The NMR chart is shown in FIG. As shown in FIG. 1, a single singlet appears at a chemical shift value of 1.82 ppm, and it is clear that the product is a single component boron compound.

Further, tetraphenylphosphonium tetrakis (1-naphthoyloxy) borate of Example 2 was identified by ¹¹ B-NMR and mass spectrometry. The analysis results are shown below.

^The measurement by ¹¹ B-NMR was performed using a deuterated dimethyl sulfoxide as a measurement solvent with an aqueous phosphoric acid solution set to 0 ppm with an external reference. The NMR chart is shown in FIG. As shown in FIG. 2, a single singlet was shown at a chemical shift value of 1.82 ppm, indicating that the product was a single component boron compound.

  In mass spectrometry, positive ions and negative ions were measured by a field desorption method (FD) and a fast electron impact method (FAB), respectively. In the positive ion mode, a peak having a mass number of 339 indicating a tetraphenylphosphonium ion is detected (FIG. 3), and in the negative ion mode, a mass number of 695 indicating a parent ion of a tetrakis (1-naphthoyloxy) borate part. Were detected (FIG. 4).

  Differential thermal analysis (DSC) was also measured and had a sharp endotherm at 241 ° C., indicating that the product was of high purity (FIG. 5).

It is drawing which shows the ¹¹ B-NMR chart of sodium tetrakis (1-naphthoyloxy) borate prepared in Example 2. 1 is a drawing showing an ¹¹ B-NMR chart of tetraphenylphosphonium tetrakis (1-naphthoyloxy) borate prepared in Example 2. FIG. It is drawing which shows the mass spectrometry (positive ion mode) chart of the said tetraphenylphosphonium tetrakis (1-naphthoyloxy) borate. It is drawing which shows the mass spectrometry (negative ion mode) chart of the said tetraphenylphosphonium tetrakis (1-naphthoyloxy) borate. It is drawing which shows the differential thermal analysis (DSC) chart of the said tetraphenylphosphonium tetrakis (1-naphthoyloxy) borate.

Claims (6)

  A process for producing sodium tetrakisacyloxyborate, which comprises reacting an organic carboxylic acid with sodium borohydride.   The method for producing sodium tetrakisacyloxyborate according to claim 1, wherein the organic carboxylic acid is an aromatic carboxylic acid.   A process for producing onium tetrakisacyloxyborate, characterized by reacting sodium tetrakisacyloxyborate with an onium salt.   The method for producing onium tetrakisacyloxyborate according to claim 3, wherein the sodium tetrakisacyloxyborate is sodium tetrakisaroyloxyborate.   The method for producing onium tetrakisacyloxyborate according to claim 3 or 4, wherein the onium salt is a tetra-substituted phosphonium salt. Sodium tetrakisaroyloxyborate.

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