JPH09192506A - Removing method of catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a highly heat-stable and high-quality ester phosphate to be produced in a high yield by mixing a crude ester phosphate obtained through a chemical reaction with an aqueous solution of hydrogen phosphate salt, and allowing the deposition and separation of a magnesium component as a precipitate of hydrogenphosphate salt. SOLUTION: A method for removing a catalyst is such that, in the presence of a magnesium chloride catalyst, crude ester phosphate obtained through the chemical reaction of phosphor oxyhalogenide with an alcohol and/or a phenol is mixed with an aqueous solution of phosphoric acid or a water soluble hydrogen phosphate salt with a concentration of 0.3mol/liter or more, and a magnesium component is caused to deposit as a precipitate of hydrogenphosphate salt, and the precipitate thus produced is separated. In addition, the precipitate and the ester from which the precipitate forming liquid is removed are further cleaned with hot water to remove the residual components e.g. halogen such as chlorine or hydrogenphosphate ion in the precipitate liquid, and then is dehydrated and dried. Thus it is possible to obtain a highly heat-stable product not containing a catalytic metal component and an inorganic halogen component.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flame retardant for resins,
The present invention relates to a method for cleaning and purifying phosphate ester, which is widely used as a plasticizer, an antioxidant, an additive for lubricating oil, and the like. More specifically, it relates to a method for completely removing magnesium and chlorine from a phosphoric acid ester obtained by reacting phosphorus oxyhalide with alcohols and / or phenols in the presence of a magnesium chloride catalyst.

[0002]

2. Description of the Related Art The phosphoric acid ester to which the present invention is applied is, for example, a compound represented by the following general formulas (2) and (3).

[0003]

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[0004]

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(In the formula, R1 to R4 are the same or different and each represents an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxyalkyl group, an alkylaryl group, an aryl group, an alkoxyaryl group or a hydroxyaryl group. A polyhydric alcohol residue or a phenol residue is represented, and n is an integer of 1 or more and approximately 30.) As a method for producing a phosphoric acid ester, phosphorus oxyhalide, such as phosphorus oxychloride, alcohols and / or A method of heating and dehydrochlorinating a phenol is well known. Above all, phosphorus oxyhalide and phenols are used for the production of phosphoric acid ester having an aryl group, which has excellent thermal stability and is widely used as a flame retardant for resins, plasticizers, antioxidants, additives for lubricating oils, etc. Since the reaction rate is low, a method of accelerating the reaction using a Lewis acid catalyst such as aluminum chloride or magnesium chloride has been widely adopted industrially. In particular, for the production of the phosphoric acid ester oligomer represented by the above general formula (3), magnesium chloride, which has high reaction selectivity and produces less ester monomer and less gelation, is exclusively used as a catalyst. The amount of magnesium chloride used for the synthesis of the phosphoric acid ester is usually in the range of 0.1 to 10 mol% with respect to the phosphorus oxyhalide. Both the magnesium content and the inorganic chlorine content are in the range of several tens to several thousands ppm.

Since these magnesium and inorganic chlorine components cause troubles during use, such as causing mold corrosion and mold contamination during mixing with resin or during molding, they are removed by a purification process. I have to do it. In particular, the magnesium content, which is a residual amount of only a few tens of ppm, remarkably deteriorates the thermal stability of the product, so that it is necessary to completely remove it.

As a refining step, a vacuum distillation method is adopted for relatively low molecular weight phosphoric acid esters. However, since the alkyl phosphate ester has a low thermal decomposition temperature and the aryl phosphate ester has a high boiling point, in any case, decomposition of the product due to heating is likely to occur, resulting in a decrease in yield. For crystallizing phosphoric acid ester such as triphenyl phosphate, purification by a recrystallization method is effective, but there are problems that the applicable phosphoric acid ester is limited, the yield of the product is reduced, and the waste solvent is treated.

On the other hand, for a phosphoric acid ester having a high boiling point such as the polyphosphoric acid ester represented by the general formula (3), a vacuum distillation method cannot usually be used, and a metal component and a chlorine component are exclusively converted into a water phase by hot water or alkaline water. A washing and purifying method is employed in which the extract is extracted and removed. However, according to the research conducted by the present inventors, the magnesium content in the crude phosphoric acid ester is present in the form of magnesium chloride, and a part thereof is present in the form of an organic metal such as a salt of phosphoric acid ester. Things turned out. Of these, the former, along with the coexisting inorganic chlorine, can be removed relatively easily by washing with hot water, while the latter has a strong affinity with esters and is hardly extracted into the aqueous phase, and the thermal stability of the product is high. The latter has a stronger effect of lowering the heat resistance, and it is difficult to secure product physical properties such as thermal stability only by washing with hot water.

In washing with alkaline water, a compound in which a trace amount of by-products such as monoesters and diesters are complexed with ions derived from catalysts and washing water such as alkali and alkaline earth metals acts as a surfactant. Therefore, emulsification occurs and it becomes difficult to separate the phosphoric acid ester and the washing water. In order to solve this problem, a method of hydrolyzing by-products such as monoesters and diesters is adopted.
For example, JP-A-51-108021 describes a method of decomposing a by-product with an oxidizing agent and then washing with alkaline water. However, in the presence of alkali, the phosphoric acid ester undergoes significant hydrolysis, the yield of the product decreases, and a large amount of alcohols, phenols and organic phosphorus compounds migrate to the aqueous phase, making wastewater treatment difficult.

On the other hand, Japanese Patent Laid-Open No. 46-5514 discloses that
A method using aminoalkylenephosphonic acid and salts thereof as a cleaning improver is described. However, this cleaning improver is difficult to obtain and, as a result of being distributed in both the water phase and the oil phase, causes problems of wastewater treatment and reduction of heat resistance of the product.

[0011]

DISCLOSURE OF THE INVENTION The present invention provides a method for removing a magnesium component derived from a catalyst, which is capable of easily producing a high-quality phosphate ester which is not corrosive and has good thermal stability in a high yield. The purpose is to provide.

[0012]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that when a cleaning solution containing a hydrogen phosphate group at a specific concentration or higher is used, the entire amount of magnesium is precipitated as a hydrogen phosphate salt. The inventors have found that the phosphoric acid ester and water can be easily separated because they can be separated by filtration and can be separated by filtration, and no emulsification occurs in the mixing process, thus completing the present invention.

That is, the present invention is as follows.
1. A crude phosphoric acid ester obtained by reacting phosphorus oxyhalide with alcohols and / or phenols in the presence of a magnesium chloride catalyst is soluble in phosphoric acid or water at a concentration of 0.3 mol / liter or more. A method for removing a catalyst, which comprises mixing an aqueous solution of hydrogen phosphate and precipitating a magnesium component as a precipitate of hydrogen phosphate, and then separating the formed precipitate. 2. The method for removing the catalyst according to 1 above, wherein the phosphoric acid ester is a phosphoric acid ester oligomer alone or a mixture represented by the following general formula (1), or a mixture of a phosphoric acid ester oligomer and a triaryl phosphate.

[0014]

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(In the formula, n is an integer of 1 to 10, and Ar1,
Ar2, Ar3 and Ar4 are phenyl groups or have 1 carbon atom
To 4 are aryl groups in which 1 to 5 alkyl groups are substituted, and may be the same or different. Further, when n ≧ 2, a plurality of Ar4 may be the same or different.
R is a divalent aromatic group represented by the following formula. )

[0016]

[Chemical 6]

(In the formula, A represents a bond, divalent S, a sulfone group, or a C ₁ -C ₄ alkylidene group or an alkylene group.) First, the crude phosphoric acid ester to be purified in the present invention will be described. . The phosphoric acid ester of the present invention is a monovalent and / or phosphorus oxyhalide in the presence of a magnesium chloride catalyst.
Alternatively, it is a compound or a mixture of compounds obtained by reacting a polyhydric alcohol and / or a phenol.

Examples of the phosphorus oxyhalide, which is a raw material for the phosphoric acid ester, include phosphorus oxychloride and phosphorus oxybromide, and phosphorus oxychloride is particularly preferable. Examples of monohydric alcohols include n-propyl alcohol and n-
Butyl alcohol, isobutyl alcohol, n-pentyl alcohol, isopentyl alcohol, neopentyl alcohol, n-hexyl alcohol, n-octyl alcohol, 2-ethylhexyl alcohol, isooctyl alcohol, nonyl alcohol, decyl alcohol,
Dodecyl alcohol, tridecyl alcohol, hexadecyl alcohol, octadecyl alcohol, oleyl alcohol, cyclopentyl alcohol, cyclohexyl alcohol, benzyl alcohol, 2-phenylethyl alcohol, 3-phenylpropyl alcohol, methoxyethyl alcohol, ethoxyethyl alcohol, propoxyethyl alcohol, Isopropoxyethyl alcohol, butoxyethyl alcohol, isobutoxyethyl alcohol, amyloxyethyl alcohol, hexoxyethyl alcohol, cyclohexoxyethyl alcohol, octoxyethyl alcohol, 2-ethylhexoxyethyl alcohol, desiloxyethyl alcohol, dodecyloxy. Ethyl alcohol, benzyloxyethyl alcohol, methoxy B pills alcohol, ethoxy-propyl alcohol, butoxy propyl alcohol, cyclohexoxy propyl alcohol, 2-ethylhexoxide propyl alcohol, octoxy propyl alcohol,
Methoxybutyl alcohol, 3-methoxybutyl alcohol, cyclohexoxybutyl alcohol, 2-ethylhexoxybutyl alcohol, benzyloxybutyl alcohol, methoxycyclohexyl alcohol, butoxycyclohexyl alcohol, etc., and some or all of the hydrogen atoms of these compounds Examples include compounds substituted with a halogen atom.

Examples of the monohydric phenols include phenol, m-cresol, p-cresol, 2,6-xylenol, 2,4-xylenol, 3,5-xylenol, 2,4,6-trimethylphenol, 4- Ethylphenol, 2-methyl-4-ethylphenol, 4-propylphenol, 4-isopropylphenol, 4-
Butylphenol, 4-isobutylphenol, 4-t
-Butylphenol, 4-hexylphenol, nonylphenol, 4-decylphenol, 4-cyclohexylphenol, 3,5-di-t-butylphenol, 1
-Naphthol, 2-naphthol, 5,6,7,8-tetrahydro-2-naphthol, m-phenylphenol,
p-phenylphenol, p-benzylphenol, p
-Cumylphenol, m-methoxyphenol, m-butoxyphenol, m-cyclohexoxyphenol, and the like, and compounds in which some or all of the hydrogen atoms of these compounds are replaced with halogen atoms.

Examples of the polyhydric alcohols include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, isopropylene glycol, butylene glycol, hexylene glycol, cyclohexylene glycol, 1,3,5-hydroxypentyltriol and trimethylol. Propane, glycerin, diglycerin, pentaerythritol, etc.,
And compounds in which some or all of the hydrogen atoms of these compounds are replaced with halogen atoms.

Examples of polyphenols include hydroquinone, resorcinol, catechol, bisphenol A, bisphenol F, bisphenol S, m-phenylphenol, p-phenylphenol, phloroglucinol, hydroxyhydroquinone, 1,3,6-naphthalene. Examples include triol and the like, and compounds in which some or all of the hydrogen atoms of these compounds are replaced with halogen atoms.

The crude phosphoric acid ester to be purified, which is obtained by reacting these alcohols and / or phenols with phosphorus oxyhalide, has the general formula (2)

[0023]

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In addition to the phosphoric acid triester represented by the general formula (3)

[0025]

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The oligomer type polyphosphoric acid ester represented by Examples of the phosphoric acid triester represented by the general formula (2) include tributyl phosphate,
Tris (2-ethylhexyl) phosphate, trioctylphosphate, tris (butoxyethyl) phosphate, trisdichloropropylphosphate, tris (β-chloropropyl) phosphate, tris (tribromoneopentyl) phosphate, dibutylphenylphosphate, di (2- Ethylhexyl) phenyl phosphate, butyl diphenyl phosphate, octyl diphenyl phosphate, 2-ethyl hexyl diphenyl phosphate, 2-ethyl hexyl dicresyl phosphate, 2-ethyl hexyl (o-chlorophenyl) phosphate, nonyl diphenyl phosphate, butoxy ethyl diphenyl phosphate, octoxy butyl diphenyl phosphate , Butoxyethyl di (o-chlorophenyl) phosphate, Liphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, trixylenyl phosphate, xylenyl diphenyl phosphate, chlorophenyl diphenyl phosphate, tris (isopropylphenyl) phosphate, isopropylphenyl diphenyl phosphate, tris (dibromophenyl) phosphate, tris ( Tribromophenyl) phosphate, naphthyldiphenylphosphate, cumylphenyldiphenylphosphate, biphenyldiphenylphosphate, tris (biphenyl)
Examples thereof include phosphate and nonylphenyldiphenylphosphate.

In the polyphosphate represented by the general formula (3), a part of the substituents of the phosphate triester represented by the general formula (2) is replaced with a residue of a polyhydric alcohol and / or a polyvalent alcohol. Compounds substituted and cross-linked with residues of phenols, such as ethylene glycol bis (dibutyl phosphate), butylene glycol bis {di (2-ethylhexyl) phosphate}, ethylene glycol bis (diphenyl phosphate), P, P 'diphenol bis ( Diphenyl phosphate), resorcinol bis (dimethyl phosphate), resorcinol bis (diphenyl phosphate), resorcinol bis {di (2,6 xylyl) phosphate}, resorcinol bis {di (p-chlorophenyl) phosphate}, hydroquinone bis (diphenyl phosphate), B Phenol A bis (diphenyl phosphate), bisphenol A bis (dicresyl phosphate), bisphenol F bis (diphenyl phosphate), bisphenol S bis (diphenyl phosphate), tetrabromobisphenol A bis (diphenyl phosphate), poly (ethylene glycol-butyl phosphate) ), Poly {butylene glycol- (2-ethylhexyl) phosphate}, poly (ethylene glycol-phenyl phosphate), poly (resorcinol-phenyl phosphate), poly {resorcinol-
(2,6 xylyl) phosphate}, poly {resorcinol- (p-chlorophenyl) phosphate}, poly (hydroquinone-phenyl phosphate), poly (bisphenol A-phenyl phosphate), poly (bisphenol A-cresyl phosphate), poly ( Examples thereof include bisphenol F-phenyl phosphate) and poly (bisphenol S-phenyl phosphate).

Particularly, the polyphosphoric acid ester represented by the following general formula (1) requires a magnesium chloride catalyst in order to increase the yield of the product, and a purification method other than washing cannot be applied. An emulsion is likely to be formed during washing, and the effect of the present invention is particularly remarkable.

[0029]

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(In the formula, n is an integer of 1 to 10, and Ar1,
Ar2, Ar3 and Ar4 are phenyl groups or have 1 carbon atom
To 4 are aryl groups in which 1 to 5 alkyl groups are substituted, and may be the same or different. Further, when n ≧ 2, a plurality of Ar4 may be the same or different.
R is a divalent aromatic group represented by the following formula. )

[0031]

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(In the formula, A represents a bond, a divalent S, a sulfone group, or a C ₁ -C ₄ alkylidene group and an alkylene group.) Next, the principle of magnesium precipitation formation in the present invention will be described below. Show.

[0033]

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(In the formula, R represents the same or different substituents of the phosphoric acid ester. The hydrogen phosphate ion HPO ₄ ²⁻ is added as phosphoric acid of the washing liquid component or as a water-soluble hydrogen phosphate salt. Magnesium hydrogen phosphate is pure MgH
Not only PO ₄ .xH ₂ O, but also a complex salt with the hydrogen phosphate salt used for cleaning. ) An equilibrium relationship is established between the partition of Mg ²⁺ ions in the ester phase and the aqueous phase and between the ions in the aqueous phase and the precipitated magnesium hydrogen phosphate. Since the solubility product of magnesium hydrogen phosphate is constant, the solubility of magnesium hydrogen phosphate decreases as the concentration of hydrogen phosphate ions in the wash water increases, the concentration of Mg ²⁺ ions in the aqueous phase decreases, and the equilibrium shifts to the right. The extraction of magnesium from the ester phase and the formation of precipitate proceed. Therefore, in order to remove magnesium contained in the ester as a precipitate, it is essential to increase the concentration of hydrogen phosphate ions in the wash water, specifically, 0.3 mol / mol
It is necessary to have liters or more, preferably 0.5 mol / liter or more. There is no upper limit to the concentration, but even if it is too thick, the effect does not change, and the density of washing water approaches that of the ester,
It is usually used at 2 mol / liter or less because separation after washing becomes difficult. By using an aqueous solution containing phosphoric acid or a phosphate soluble in water at the above concentration (hereinafter, abbreviated as "precipitate forming solution"), the whole amount of magnesium contained in the ester can be precipitated as a precipitate, and at the same time the emulsion is mixed at the time of mixing. The washing water and the phosphoric acid ester can be completely separated in a short time by the stationary separation without the occurrence of liquefaction.

The components of the precipitation-forming liquid include phosphoric acid and, for example, disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium ammonium hydrogen phosphate, etc. In addition to the phosphates and their mixtures,
A mixture of phosphoric acid and an alkali such as sodium hydroxide, potassium hydroxide or aqueous ammonia can be used.

There is no particular limitation on the amount of the precipitate-forming liquid used with respect to the crude phosphoric acid ester to be washed, but the effect does not change even if it is used in a large amount, and if it is too small, it becomes difficult to uniformly mix the two, and the precipitate is formed. The reaction lowers the concentration of hydrogen phosphate ions in the precipitate-forming liquid, which is not preferable. Usually, it is used in an amount of 0.3 to 2 times, and more preferably 0.5 to 1 times, the weight of the crude phosphoric acid ester.

There are no particular restrictions on the mixing conditions of the crude phosphoric acid ester and the precipitate-forming liquid, and static mixers, line mixers and the like can be used in addition to the ordinary tank type mixer. The operating temperature is the viscosity of the ester and the mixing state during stirring,
Also, in consideration of the precipitation formation rate, it is usually selected in the range of 50 to 100 ° C. The precipitate formation is almost completed in about 15 minutes if sufficient stirring is performed, but it is preferable to set the stirring time to 1 hour or more in order to age the precipitate and form large particles that are easily separated.

The mixture in which the precipitate has been formed may be separated and removed from the ester and then separated from the ester, or the precipitate may be removed after the aqueous phase is removed by static separation or the like. The method for removing the precipitate is not particularly specified, but for example, a filtration method, a centrifugal separation method or the like can be adopted. The filtration method includes
It is possible to use a filter cloth commonly used in industry, or a filter made of natural or synthetic fiber, ceramic, metal or the like. The collection particle size of the filter is preferably in the range of 0.2 to 10 μm, because if it is large, fine particles cannot be captured, and if it is small, clogging easily occurs and the processing speed decreases.
The range of 0.5 to 5 μm is more preferable. In order to improve the filtration efficiency, it is also preferable to use a filter aid such as diatomaceous earth, cellulose or perlite.

For the centrifugal separation method, a batch type, disc ball type, screw decanter type device or the like which is commonly used in industry can be used. It is also preferable to use a special disc ball type or screw decanter type device to separate the three components of precipitation, ester and aqueous phase at once. The ester from which the precipitate and the precipitate-forming liquid have been separated is further washed with hot water or the like according to a known method to remove residual halogen such as chlorine and the components of the precipitate-forming liquid such as hydrogen phosphate ion, and then dehydrated and dried. As a result, it is possible to obtain a product that does not contain a catalytic metal component and an inorganic halogen component and has excellent thermal stability.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described with reference to Examples. First, the evaluation method of phosphoric acid ester is shown below. 1. Composition of phosphate ester: GPC method column Tosoh TSKgel G2000HXL 2
Hon Tosoh TSKgel G3000HXL 1 in-line solvent THF flow = 1 ml / min Detector UV λ = 254 nm Sample THF 1000-fold diluted 5 μl Absolute calibration curve method 2. Quantification of magnesium content: ICP method device Seiko JY-38PII type sample MIBK 500-fold diluted (crude phosphate) 30-fold diluted (purified product) Quantitative method Absolute calibration curve method 3. Quantification of chlorine content: potentiometric titration method with silver nitrate Device manufactured by Kyoto Denshi, AT-200 type sample Approximately 0.2 g of ester (crude phosphate ester), approximately 5 g
3. (Purified product) is dissolved in 200 ml of acetone, and 4 ml of acetic acid is added as an electrolyte. Thermal stability: TGA 300 ° C weight loss rate device Rigaku TAS-300 TG-DT
A sample 20 ± 10 mg D5mm * H2.5mm Aluminum sample pan Measurement conditions 50 ° C → (temperature increase 100 ° C / min) → 300 ° C 1
Time holding Measurement atmosphere Helium gas 100 ml / minute flow Weight reduction rate (wt% / hr) for 20 minutes from 40 minutes to 60 minutes after the start of temperature increase Table 1 shows the crude phosphate ester used in the examples. The method for synthesizing the crude phosphoric acid ester will be described below. <Synthesis of Crude Phosphate A> Bisphenol A456.
4 g (2.0 mol), phosphorus oxychloride 768.1 g (5.
0 mol), and anhydrous magnesium chloride 2.8 g (0.0
15 mol) was charged into a 2000 ml four-necked flask equipped with a stirrer / reflux tube, and the mixture was stirred at 70 to 120 ° C. under a nitrogen stream for 5 minutes.
Allowed to react for hours. After the reaction, while maintaining the reaction temperature,
The flask was depressurized to 100 mmHg or less with a vacuum pump, and unreacted phosphorus oxychloride was collected with a trap. The flask was then cooled to room temperature and 752 g of phenol (8.0
Mol) was added, and the mixture was heated to 100 to 170 ° C. and reacted for 5 hours. The crude phosphoric acid ester A was depressurized to 10 mmHg or less at the same temperature to distill off unreacted phenols.
1297 g was obtained. <Synthesis of Crude Phosphate Ester B> 220.5 g (2.0 mol) of resorcinol instead of bisphenol A, and 865.0 g (8.0 m-cresol instead of phenol).
(100 mol) of crude phosphoric acid ester B was obtained by the same method as in the synthesis of crude phosphoric acid ester A described above, except that the amount (mol) was used.

[0041]

Example 1 100 g of crude phosphoric acid ester A was placed in a 300 ml separa flask equipped with a stirrer, a baffle, and a reflux device, and as a precipitate forming solution, 50 g of 0.5 mol / liter dipotassium hydrogen phosphate aqueous solution and 0.5 mol / liter. Add 50 liters of an aqueous solution of sodium dihydrogen phosphate and stir for 3 hours at 80 ° C.
Stirred for hours. Stop stirring and keep the temperature at 30
The mixture was allowed to stand for a minute and the ester phase and the aqueous phase were separated. The colorless and transparent aqueous phase was removed by decantation, and the ester phase was filtered using filter paper (# 131 manufactured by Advantech) to remove the solid content. The recovered ester was returned to the flask, 100 g of distilled water was added, the mixture was stirred at 80 ° C. for 30 minutes, and then allowed to stand for 30 minutes to separate an aqueous phase. The same washing was performed twice more, and then vacuum drying was performed to remove water, and 98 g of a purified product was obtained. Table 2 shows the evaluation results.

[0042]

Example 2 The catalyst was removed in the same manner as in Example 1 except that 100 g of the crude phosphoric acid ester B was used instead of the crude phosphoric acid ester A to obtain 97 g of a purified product. Table 2 shows the evaluation results.

[0043]

Example 3 By the same method as in Example 1, except that 0.015 mol of dipotassium hydrogen phosphate and 0.015 mol of sodium dihydrogen phosphate were dissolved in distilled water to make 100 ml as a precipitate forming liquid. To remove the catalyst,
96 g of purified product was obtained. Table 2 shows the evaluation results.

[0044]

Example 4 The catalyst was removed in the same manner as in Example 1 except that 70 g of 0.5 mol / liter phosphoric acid was used as the precipitate-forming liquid to obtain 98 g of a purified product. Table 2 shows the evaluation results.

[0045]

Example 5 As a precipitate forming liquid, 0.04 mol of phosphoric acid and 0.02 mol of sodium hydroxide were dissolved in distilled water to prepare 100
The catalyst was removed in the same manner as in Example 1 except that an aqueous solution (ml) was used to obtain 98 g of a purified product. Table 2 shows the evaluation results.

[0046]

Comparative Example 1 The same procedure as in Example 1 was carried out except that 50 g of a 0.2 mol / liter aqueous solution of dipotassium hydrogen phosphate and 50 g of a 0.2 mol / liter aqueous solution of sodium dihydrogen phosphate were used as the precipitate forming liquid. To remove the catalyst,
96 g of purified product was obtained. Table 2 shows the evaluation results.

[0047]

Comparative Example 2 Purification was carried out in the same manner as in Example 1 except that 100 g of distilled water was used instead of the precipitate forming liquid to obtain 94 g of a purified product. No precipitate was formed.
Table 2 shows the evaluation results.

[0048]

Comparative Example 3 The catalyst was removed in the same manner as in Example 1 except that 100 g of a 0.5 mol / liter sodium hydroxide aqueous solution was used in place of the precipitate forming liquid, and 87
g purified product was obtained. No precipitate was formed and the collected aqueous sodium hydroxide solution was colored orange yellow and had a strong phenol odor. Table 2 shows the evaluation results.

[0049]

COMPARATIVE EXAMPLE 4 The procedure of Example 1 was repeated except that 100 g of a 0.1 mol / liter aqueous solution of sodium hydroxide was used in place of the precipitate-forming liquid, and the mixture was stirred and mixed with the ester to give a creamy product. It was not possible to separate the two phases by placing. The aqueous phase separated by the centrifugal sedimentation method was colored orange-yellow and had a phenol odor.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

According to the present invention, the magnesium and chlorine components used as catalysts can be removed from the crude phosphoric acid ester without causing hydrolysis of the ester, and high-quality phosphoric acid excellent in thermal stability can be obtained. Since the ester can be obtained in a high yield, it is industrially very useful.

[Brief description of the drawings]

FIG. 1 is a TGA weight loss curve of purified phosphate ester products obtained in Examples and Comparative Examples.

[Explanation of symbols]

 1 TGA heating loss curve of the purified product of Example 1 2 TGA heating loss curve of the purified product of Example 3 3 TGA heating loss curve of the purified product of Comparative Example 4 TGA heating loss curve of the purified product of Comparative Example 5 Temperature Showing curve

Claims (2)

[Claims] 1. A crude phosphoric acid ester obtained by reacting phosphorus oxyhalide with alcohols and / or phenols in the presence of a magnesium chloride catalyst is used to prepare phosphoric acid or phosphoric acid at a concentration of 0.3 mol / liter or more. A method for removing a catalyst, which comprises mixing an aqueous solution of hydrogen phosphate soluble in water, precipitating a magnesium component as a precipitate of hydrogen phosphate, and separating the formed precipitate. 2. The method for removing a catalyst according to claim 1, wherein the phosphoric acid ester is a phosphoric acid ester oligomer alone or a mixture represented by the following general formula (1), or a mixture of the phosphoric acid ester oligomer and a triaryl phosphate. Embedded image (In the formula, n is an integer of 1 to 10 and is Ar1, Ar2, Ar
3, Ar4 is a phenyl group or an aryl group in which 1 to 5 alkyl groups having 1 to 4 carbon atoms are substituted, and may be the same or different. Further, when n ≧ 2, a plurality of Ar4 may be the same or different. R is a divalent aromatic group represented by the following chemical formula 2. ) (In the formula, A is a bond, divalent S, a sulfone group or C ₁ to
Alkylidene group C _4, an alkylene group. )