JP2023086184A - Method for producing phosphate compound - Google Patents

Abstract

To provide a method for producing a phosphate from highly safe and easy-to-handle raw material.SOLUTION: A method for producing a phosphate compound includes reacting an ammonium phosphate salt compound selected from the group consisting of ammonium orthophosphate salts, ammonium phosphonate salt, and ammonium phosphinate salts with an organic silane having an alkoxy group or an aryloxy group or a siloxane compound having an alkoxy group or an aryloxy group under heating conditions in an organic solvent where the ammonium phosphate salt compound dissolves.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a method for producing a phosphate ester compound using a phosphate such as orthophosphoric acid.

Phosphate ester (PO(OR) ₃ ), which is one of the organic phosphorus compounds, is a chemical product with various physical properties depending on the structure of the organic group R in the ester moiety.It is used as a flame retardant, plasticizer, stabilizer, etc. It is used properly according to the purpose. With the recent technological innovation in the automobile industry and the electronic parts industry, the performance required for resins is becoming more sophisticated year by year, and the development of phosphate ester compounds as resin additives and the improvement of their production methods are eagerly desired.

As a general industrial production method of phosphoric acid ester, there is a method of reacting a halide of phosphoric acid with an alcohol to convert halogen such as Cl (chlorine) to OR (carbon-based substituent). However, using a phosphoric acid halide as a raw material is not preferable from the viewpoint of safety. Therefore, as a method for producing a safer phosphate ester, the following Patent Document 1 discloses that orthophosphoric acid (PO(OH) ₃ ), which is inexpensive and readily available, is used as a starting material, and orthophosphoric acid and an alkoxy group or an aryloxy group are combined. It discloses a technique for producing a phosphate ester compound in a one-step reaction from an organic silane or siloxane compound possessed by the present invention.

Japanese Patent Application Laid-Open No. 2021-143139

In the technique described in Patent Document 1, phosphoric acid, which is a raw material, can be said to be a relatively safe compound compared to halides. It can not be said. In addition, since phosphoric acid is highly deliquescent and is usually distributed in the market as an aqueous solution, there is also the problem that it is heavy, bulky, and difficult to handle.
An object of the present invention is to solve such problems, and to provide a method for producing a phosphate ester using raw materials that are highly safe and easy to handle.

As described above, phosphoric acid is highly deliquescent and is used in the form of an aqueous solution. And organic silanes such as alkoxysilanes readily undergo hydrolysis and polycondensation in the presence of water and acids. As described in Patent Document 1, when an aqueous phosphoric acid solution and an organic silane such as alkoxysilane are used as raw materials in a method for producing a phosphate ester, the organic silane is easily affected by water, making it difficult to control the reaction. It is conceivable that However, the present inventors focused on an ammonium phosphate salt that is solid, contains almost no water, is excellent in handling, is also used as a fertilizer, is highly safe, and is easily available, and has completed the present invention. .

Specifically, the present invention relates to a method for producing a phosphate ester compound of the following (1) to (6).
(1) an ammonium phosphate salt compound selected from the group _consisting of ammonium orthophosphate _, ammonium phosphonate, and ammonium phosphinate; an organosilane having an aryloxy group, or a siloxane compound represented by the general formula R′ _m (OR) _3-m SiOSiR′ _l (OR) _3-l and having an alkoxy group or an aryloxy group; A method for producing a phosphate ester compound, wherein the reaction is carried out under heating conditions in an organic solvent in which an acid ammonium salt compound is soluble.
In the above formula, R is a linear or branched alkyl group having 1 to 20 carbon atoms or an aryl group, and R' is a linear or branched alkyl group having 1 to 20 carbon atoms or an aryl group. where n is an integer of 3 or less including 0, m is an integer of 2 or less including 0, and l is an integer of 2 or less including 0. Note that R and R' may be the same or different from each other.
Since the ammonium phosphate salt compound is solid and contains almost no water, the target phosphate ester compound can be easily obtained without gelation in the reaction with an organic silane or the like. Further, the reaction can be promoted by dissolving the ammonium phosphate salt compound in an organic solvent. The reaction can be further accelerated by performing the reaction under heating conditions.
(2) The method for producing a phosphate ester compound according to (1) above, which is carried out in the absence of a catalyst. According to this configuration, it is possible to produce a phosphate ester compound by a simple method without using a catalyst.
(3) The method for producing a phosphate ester compound according to (1) or (2) above, wherein the reaction temperature under the heating condition is 100 to 250°C. According to this configuration, the optimal temperature conditions for the reaction can be achieved.
(4) The method for producing a phosphate ester compound according to any one of (1) to (3) above, using an aprotic polar solvent as the organic solvent. By using an aprotic polar solvent as the organic solvent, the ammonium phosphate compound is easily dissolved and the reactivity is improved.
(5) The method for producing a phosphate ester compound according to any one of (1) to (4) above, wherein the ammonium phosphate compound is an ammonium orthophosphate. According to this configuration, ammonium orthophosphate, which is inexpensive, readily available, and highly safe, can be used as a raw material.
(6) The method for producing a phosphate ester compound according to any one of (1) to (5) above, wherein the organic silane having an alkoxy group or an aryloxy group is tetraalkyl orthosilicate or tetraaryl orthosilicate. .

According to the present invention, it is possible to produce a phosphate ester compound in a one-step reaction using an ammonium phosphate salt compound, which is a solid, easy-to-handle, low-toxic, and easily available compound as a starting material.

In particular, orthophosphate ammonium salts such as ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) are also used as fertilizers and are readily available. It's also cheap. Therefore, by using an ammonium phosphate salt compound as a raw material for the production of phosphate ester compounds, it is possible to produce high-value-added phosphate esters that are used in various applications such as flame retardants, plasticizers, and stabilizers for various resins. It can be said that it is an industrially excellent method that can be produced at a low cost and has high productivity.

The present invention is characterized by producing a phosphate ester compound from an ammonium phosphate salt compound and an organic silane or siloxane compound having an alkoxy group or an aryloxy group.

The ammonium phosphate compound used as a starting material in the production method of the present invention is one ammonium phosphate compound selected from ammonium orthophosphate, ammonium phosphonate, and ammonium phosphinate. These ammonium phosphate compounds may be either hydrates or anhydrides, but anhydrides containing less water are preferred because they are less likely to gel upon reaction with organic silanes and the like.

A corresponding phosphate ester compound can be produced from any ammonium phosphate salt compound. A mixture of at least two of the three is obtained as a product (see formula (1) below). Similarly, when an ammonium phosphonate salt is used as a starting material, a mixture of phosphonic acid mono- and diesters is obtained (see formula (2) below), and when an ammonium phosphinate salt is used as a starting material, a phosphinic acid monoester (see formula (3) below) is obtained. ) is obtained as the product. The separation of each phosphoric acid ester compound can be carried out by operations such as distillation purification and silica gel chromatography.
As a raw material, ammonium orthophosphate is preferably used because it is readily available and inexpensive, but any ammonium phosphate compound can be used as a raw material to produce the corresponding phosphate ester.

（式（１）、式（２）及び式（３）中、Ｘは、アンモニウム（ＮＨ₄ ^＋）または水素（Ｈ）であって、少なくとも１つのＸはアンモニウムである。また、Ｒは炭素数１－２０の直鎖状または分岐したアルキル基、または、アリール基である。さらに、式（２）及び式（３）中、Ｙは、有機基または水素である。）

(In formula (1), formula (2) and formula (3), X is ammonium (NH ₄ ⁺ ) or hydrogen (H), and at least one X is ammonium. In addition, R is the number of carbon atoms 1 to 20 linear or branched alkyl group or aryl group.Furthermore, Y is an organic group or hydrogen in formulas (2) and (3).)

The ammonium phosphate salt compound used as a raw material is dissolved in an organic solvent before use. The above reaction proceeds only by mixing an ammonium phosphate compound with an alkoxy group- or aryloxy group-containing organosilane or siloxane compound in the presence of an organic solvent and heating the mixture. organic base) may be used.

An organic silane having an alkoxy group or an aryloxy group, or a siloxane compound having an alkoxy group or an aryloxy group is used to produce a phosphate ester from an ammonium phosphate salt compound as a raw material. In this specification, organosilanes are represented by the general formula R' _n Si(OR) _4-n , and siloxane compounds are represented by the general formula R' _m (OR) _3-m SiOSiR' _l (OR) _3-l. expressed. In the above formula, R is a linear or branched alkyl group having 1 to 20 carbon atoms or an aryl group, and R' is a linear or branched alkyl group having 1 to 20 carbon atoms, or It is an aryl group, where n is an integer of 3 or less including 0, m is an integer of 2 or less including 0, and l is an integer of 2 or less including 0. Note that R and R' may be the same or different from each other. Examples of organic silanes having an alkoxy group include tetraalkyl orthosilicate, monoalkyltrialkoxysilanes, dialkyldialkoxysilanes, etc., in which alkyl is a linear or branched alkyl having 1 to 20 carbon atoms. The alkyl group may contain heteroatoms. Of the tetraalkyl orthosilicates, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, and tetrapentyl orthosilicate, in which the alkyl has 1 to 5 carbon atoms, are particularly preferably used.

The organic silane having an aryloxy group is preferably tetraaryl orthosilicate, and the siloxane compound is preferably an organic siloxane compound in which R or R' is an alkyl group or an aryl group, particularly hexaalkoxydisiloxane.
Although the aryl group is not particularly limited, phenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group. etc. are exemplified.

When tetraalkyl orthosilicate is used, the molar ratio (equivalent) of the orthosilicate compound is preferably in the range of about 1 to 10, more preferably in the range of 3 to 5. be. If one tetraalkyl orthosilicate is consumed to esterify one OH group or OX group of the ammonium phosphate compound, the range of 3 to 5 can be said to be a suitable range. In addition, when showing a numerical range in this specification, an upper limit and a lower limit shall be included.

In addition, the organic solvent used for the reaction may be an organic solvent in which the ammonium phosphate salt compound dissolves, but an aprotic polar solvent is preferable so that the ammonium phosphate salt compound is easily dissolved. For example, acetonitrile (CH ₃ C≡N), acetone (CH ₃ C(=O)CH ₃ ), ethers (e.g., diethyl ether, tetrahydrofuran, etc.), sulfoxide solvents such as dimethyl sulfoxide (CH ₃ ) ₂ SO (DMSO), N-methylacetamide, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone, N-methyl-2-piperidone, hexamethylphosphoric triamide [(CH ₃ ) Amide solvents such as _2N ] _3P =O(HMPA) are suitable, and dimethylformamide or dimethylacetamide is particularly preferred in terms of good yields and few by-products due to decomposition of the solvent. .

The reaction of the present invention is preferably carried out, for example, by adding appropriate amounts of an organic solvent and tetraalkyl orthosilicate to the ammonium phosphate compound in a reaction vessel in an air atmosphere, and heating and stirring the sealed reaction mixture. The amount of the organic solvent is sufficient as long as it dissolves the ammonium phosphate compound, and the reaction can be accelerated by heating.

The reaction temperature under the heating conditions of the present invention may be about 100°C to 250°C, more preferably 150°C to 200°C from the viewpoint of reactivity. For example, when the reaction is carried out at a temperature of about 200° C., if an aprotic polar solvent having a boiling point of 150° C. to 200° C. is used as the organic solvent, the reaction will be conducted under reflux conditions. By carrying out the reaction under such conditions, the temperature is maintained at the boiling point of the reaction solution (organic solvent), which facilitates temperature control and increases the reproducibility of the reaction. Examples of such aprotic polar solvents include dimethylformamide, dimethylacetamide, and dimethylsulfoxide.
Any reaction time can be adopted depending on the scale of production and the amount of phosphoric acid ester to be produced, but the reaction can be carried out in about 1 to 24 hours.

The product produced by the reaction is cooled to room temperature, washed and neutralized with water, an alkaline aqueous solution or an acidic aqueous solution as necessary, and then subjected to a purification process to produce a product. Vacuum distillation, silica gel column chromatography, and the like can be applied as the purification step.

An example of the production method of the present invention will be described below using examples, but the present invention is not limited to these examples. In addition, % of a yield shows mol%.

(Example 1)
In an air atmosphere, put 23.0 mg (0.2 mmol) of ammonium dihydrogen phosphate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in a screw cap test tube, and add 2.0 mL of dimethylformamide (N,N-dimethylformamide: DMF). After adding 0.18 mL (0.8 mmol) (4 equivalents) of tetraethyl orthosilicate (manufactured by Tokyo Chemical Industry Co., Ltd.), the mixture was sealed, heated at 200 ° C. (reflux state), and stirred (1200 rpm). . After 24 hours, the reaction mixture was returned to room temperature, 31.3 μL of dimethyl phenylphosphonate (manufactured by Tokyo Chemical Industry Co., Ltd.) as an internal standard substance was added, and ³¹ P{ ¹ H} NMR was analyzed using a nuclear magnetic resonance spectrometer (Bruker AVANCE 600 spectrometer). , 243 MHz) to determine the yield of the desired phosphate ester.

The above reaction is shown in the following formula (4). As shown in the formula (4), the products were monoethyl orthophosphate 1, diethyl orthophosphate 2, and triethyl orthophosphate 3, and mixtures of two or more of these were produced by the reaction. Further, 26.4 mg (0.2 mmol) of diammonium hydrogen phosphate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was also used to produce a phosphate ester under the same conditions as above.

Table 1 shows the yield (%) of each phosphoric acid ester 1-3. The total yield of each phosphoric acid ester 1 to 3 is the yield of the entire phosphoric acid ester. From the results in Table 1, in the case of ammonium dihydrogen phosphate (Sample 1), the overall yield was 94%. The yield of 3 was 93%, and diethyl orthophosphate 2 was below the detection limit. In the case of diammonium hydrogen phosphate (Sample 2), the overall yield was 99%, and the breakdown was as follows: the yield of monoethyl orthophosphate 1 was 5%, and the yield of diethyl orthophosphate 2 was 5%. was 60%, and the yield of triethyl orthophosphate 3 was 34%.

From the above results, it was confirmed that the use of an ammonium phosphate salt compound as a starting material yields a phosphate ester with a high yield of 94% or more. Further, in the following examples, attention was paid to orthophosphoric acid triethyl ester 3 in which all OH groups and OX groups were esterified, and ammonium dihydrogen phosphate (sample 1) in which the yield of orthophosphoric acid triethyl ester 3 was high was used. was used for further investigation.

(Example 2)
In Example 2, among the conditions of Example 1, the type of organic solvent (DMF), the heating temperature, and the type of tetraalkyl orthosilicate (tetraethyl orthosilicate) were changed, and the other conditions were the same as those of Example 1 (sample A phosphoric acid ester was produced under the same conditions as in 1).
Specifically, sample 3 uses dimethylacetamide (N,N-dimethylacetamide: DMAc) as an organic solvent, sample 4 uses a heating temperature of 150° C., and sample 5-8 uses tetraalkyl orthosilicate, Tetrapropyl orthosilicate (manufactured by Tokyo Chemical Industry Co., Ltd.), Tetrabutyl orthosilicate (manufactured by Tokyo Chemical Industry Co., Ltd.), Tetraisopropyl orthosilicate (manufactured by Tokyo Chemical Industry Co., Ltd.), Tetraisobutyl orthosilicate (separately synthesized product) Four equivalents were used to prepare the phosphate ester. A reaction formula is shown in the following formula (5). Table 2 shows the yield of each phosphoric acid ester of 1 to 3. Tetraisobutyl orthosilicate was produced from isobutyl alcohol and silicon tetrachloride by the following method.

After putting 37.3 mg (0.306 mmol) (0.01 equivalent) of 4-dimethylaminopyridine (DMAP) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) into a three-necked flask, the atmosphere was replaced with argon. 125 ml of methylene chloride (CH ₂ Cl ₂ ) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 11.6 ml (125 mmol) (4.1 equivalents) of isobutyl alcohol (iBuOH) (manufactured by Tokyo Chemical Industry Co., Ltd.) are placed in a three-necked flask. ) and 17.5 ml (125 mmol) (4.1 equivalents) of triethylamine (Et ₃ N) (manufactured by Sigma-Aldrich Japan LLC) were sequentially added, and the mixture was immersed in ice water to cool. Then, 3.5 ml (30.6 mmol) (1 equivalent) of silicon tetrachloride (SiCl ₄ ) (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise over 45 minutes, followed by stirring for 3 hours while cooling. After that, the ice bath was removed, the temperature was returned to normal temperature, and the stirring was continued for 2 more days. Next, precipitated solids in the reaction mixture were filtered with a filter, the filtered material was rinsed with methylene chloride, and the collected filtrate was concentrated with an evaporator. was precipitated.

Then, the precipitated solid was further filtered, and the filter cake was washed with hexane (30 ml×2 times, 20 ml×1 time). Furthermore, the final filtrate was collected, washed with ultrapure water (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) (100 ml x 2 times), and magnesium sulfate (MgSO ₄ ) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added. Dehydration drying treatment was performed using After that, magnesium sulfate is removed by filtration, and the residue is distilled through solvent concentration (initial distillation: ~103°C/8~10mmHg, main distillation: 103~106°C/8~10mmHg) to obtain the final product, tetra orthosilicate. Isobutyl was obtained.

From the above results, it was confirmed that a high yield was stably obtained when DMF was used as the organic solvent. It was also confirmed that when tetraalkyl orthosilicate was used as the organic silane, stable high yields could be obtained for various alkyls.

The method for producing a phosphate ester compound of the present invention is an excellent production method that can use various ammonium phosphate salts as starting materials and can produce a phosphate ester compound in a one-step reaction without using a catalyst. be.
Moreover, there is concern about the future depletion of phosphorus resources worldwide, and the recycling of phosphorus resources discharged from industries, such as sewage sludge and incineration ash, has become an important issue. For example, if phosphorus in sewage is recovered, it can be converted into chemical products to have added value. A method for direct conversion to a phosphate ester may become an important technology in the future for sustainable development.

Claims (6)

an ammonium phosphate compound selected from the group consisting of ammonium orthophosphate, ammonium phosphonate, and ammonium phosphinate;
an organic silane represented by the general formula R' _n Si(OR) _4-n and having an alkoxy group or an aryloxy group, or an organic silane having the general formula R' _m (OR) _3-m SiOSiR' _l (OR) _3-l and a siloxane compound having an alkoxy group or an aryloxy group,
A method for producing a phosphate ester compound, wherein the ammonium phosphate compound is dissolved in an organic solvent under heating conditions.
In the above formula, R is a linear or branched alkyl group having 1 to 20 carbon atoms or an aryl group, and R' is a linear or branched alkyl group having 1 to 20 carbon atoms or an aryl group. where n is an integer of 3 or less including 0, m is an integer of 2 or less including 0, and l is an integer of 2 or less including 0. 2. The method for producing a phosphoric acid ester compound according to claim 1, which is carried out in the absence of a catalyst. 3. The method for producing a phosphate ester compound according to claim 1, wherein the reaction temperature under the heating condition is 100 to 250.degree. 4. The method for producing a phosphate ester compound according to any one of claims 1 to 3, wherein an aprotic polar solvent is used as the organic solvent. 5. The method for producing a phosphate ester compound according to any one of claims 1 to 4, wherein the ammonium phosphate compound is an ammonium orthophosphate. 6. Production of the phosphate ester compound according to any one of claims 1 to 5, wherein the organic silane having an alkoxy group or an aryloxy group is tetraalkyl orthosilicate or tetraaryl orthosilicate. Method.