JPH0971591A - Metallic salt of bis-2,6-dimethylphenyl hydrogenphosphates and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject new compound useful as an additive, etc., capable of improving the flame retardance, smoke preventing properties and stability of resins by reacting 2,6-dimethylphenols with a phosphorus oxyhalide in the presence of a Lewis acid catalyst and then reacting the resultant compound with a metallic hydroxide. SOLUTION: This metallic salt of new bis-2,6-dimethylphenyl hydrogenphosphates represented by formula I [M is a bivalent metal such as magnesium, zinc or tin; R1 to R4 are each H or a 1-6C alkyl; Me is methyl; (n) is an integer of 0-3]. The metallic salt has a high purity and is useful as an additive to thermoplastic or thermosetting resins and capable of improving the flame retardance, smoke preventing properties, low hazard, weather and hydrolytic resistances, heat stability and plasticity. The compound is obtained by reacting 2,6-dimethylphenols with a phosphorus oxyhalide in the presence of a Lewis acid catalyst, providing a phosphorohalogenide represented by formula II (X is chlorine or bromine) and then reacting the resultant compound with a metallic hydroxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel metal salt of bis-2,6-dimethylphenylhydrogen phosphates which is useful as an additive for resins and a method for producing the same. The metal salt of bis-2,6-dimethylphenylhydrogen phosphates of the present invention has a high purity and is flame retardant, smoke proof, as an additive of a thermoplastic resin or a thermosetting resin,
Improves low toxicity, weather resistance, hydrolysis resistance, heat stability and plasticity.

[0002]

2. Description of the Related Art Thermoplastic resins or thermosetting resins are used in a wide range of our daily lives both indoors and outdoors. These resins are not only safe, but are desired to have properties suited to various applications.
Additives are usually used according to their use.

For example, since resin is an organic substance, heat,
It deteriorates due to light, oxygen, water, microorganisms, etc., and its characteristics cannot be retained for a long time. In particular, when the resin is used outdoors, the deterioration is remarkable.
In order to prevent the deterioration of the resin, generally, a stabilizer such as a phosphorous acid ester, an organic acid metal salt, a hindered amine, etc. is added in addition to an ultraviolet absorber and an antioxidant.

Although the ultraviolet absorber has excellent chemical stability, it is often colored and it is difficult to apply it to a light-colored resin. In addition, it is very expensive, and its stabilizing effect against deterioration of the resin is small. The antioxidant improves the weather resistance of the resin, but it is also often colored and is not suitable for addition to a light-colored resin.

The phosphite ester can be improved in heat resistance, weather resistance, transparency and the like when used in combination with a phosphite metal salt, but it is easily hydrolyzed and volatilizes easily at high temperature or for a long time. . The metal salt of an organic acid has a function of substituting an unstable chlorine atom and neutralizing hydrogen chloride during resin processing, and has a great effect of improving thermal stability, but this also has a problem such as coloring.

Hindered amine is not volatile and is excellent in thermal stability, but is less effective for chlorine-containing resins and the like. As described above, the additive for improving weather resistance improves the weather resistance, hydrolysis resistance, light resistance, etc. of the additive itself because the additive itself is deteriorated or decomposed by heat, light, water, etc. Has been desired. From such a viewpoint, it has recently been found that an organic phosphate metal salt is effective as an additive for improving weather resistance.

However, the conventional organophosphate metal salt having a chain hydrocarbon group can improve weather resistance when used in a vinyl chloride resin, etc., but has a low lubricity and is difficult to process during resin processing. Besides generating frictional heat, it is not always good in thermal stability. In addition, these organic phosphoric acid ester metal salts are relatively easily hydrolyzed, and have drawbacks in coloring and blooming property.

On the other hand, the organic phosphoric acid ester metal salt having an aromatic group is excellent in hydrolysis resistance and thermal stability as compared with the organic phosphoric acid ester metal salt having a chain hydrocarbon group,
Good weather resistance. Further, since it has good compatibility and plasticity with resins, it is useful as a nucleating agent for resins, a flame retardant and the like. However, it has the drawback of being poor in coloring, blooming and hydrolysis resistance.

As an example of solving the above problems, Japanese Patent Publication No.
JP-A-74616 discloses the combined use of a metal salt of an organic phosphoric acid ester and an epoxy compound, an organic phosphorous acid ester compound or a dibenzoylmethane compound. In particular, the weather resistance can be improved without adversely affecting the coloring property, blooming property and the like of the agricultural vinyl chloride film represented by vinyl chloride.

Further, Japanese Patent Application Laid-Open No. 63-305161 discloses a polyphenylene ether type composition containing Ca, Ba and Al salts of phosphoric acid ester having a phenyl group as a flame retardant.

[0011]

DISCLOSURE OF THE INVENTION The present invention solves the drawbacks of the prior art, and improves the coloring, flame retardancy, smoke resistance, low toxicity, weather resistance and hydrolysis resistance of thermoplastic and thermosetting resins. It is an object of the present invention to provide an additive having excellent properties, heat stability, plasticity and the like, and a method for producing the additive.

[0012]

[Means for Solving the Problems] The present inventors earnestly studied the additives for resins, especially the phosphates, and obtained the following findings. It has been found that the metal salt of the bis-2,6-dimethylphenylhydrogen phosphates of the present invention is particularly excellent in heat resistance and hydrolysis resistance as an additive for thermoplastic and thermosetting resins.

That is, according to the present invention, the general formula (I)

[0014]

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Wherein M is a divalent metal selected from magnesium, zinc and tin, R1, R2, R3 and R4
Are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, Me is a methyl group, and n is an integer of 0 to 3), and a metal salt of bis-2,6-dimethylphenylhydrogenphosphate is provided. To be done.

According to the present invention, 2,6-dimethylphenol and phosphorus oxyhalide are reacted under a Lewis acid catalyst to give a compound of the general formula (II)

[0017]

Embedded image

(Wherein X is a chlorine atom or a bromine atom, R5
And R6 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Me is a methyl group) to obtain a phosphorohalogenide, which is then reacted with a metal hydroxide. Bis-2,6-represented by the general formula (I)
Provided is a method for producing a metal salt of dimethylphenyl hydrogen phosphates.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION R1, R2 of the general formula (I),
R3 and R4 are each independently a hydrogen atom or a carbon number of 1 to
3 is an alkyl group. "C1-C3 alkyl group"
Examples thereof include linear or branched aliphatic hydrocarbon residues, and specific examples include methyl, ethyl, propyl, isopropyl and the like. Most preferred R1, R2, R3
And R4 is a hydrogen atom.

The metal M of the general formula (I) includes a divalent metal selected from magnesium, zinc and tin, and the metal salt of the general formula (I) can be obtained. Further, the coefficient n in the formula (I) varies depending on the type of metal salt,
Takes an integer value of ~ 3. Specific compounds belonging to the formula (I) include bis-2,6-dimethylphenylphosphate Mg salt, bis-2,6-dimethylphenylphosphate Zn salt, bis-2,6-dimethylphenylphosphate Sn salt and bis. -2,4,6-trimethylphenyl phosphate Mg salt, bis-2,4,6-trimethylphenyl phosphate Zn salt, bis-2,4,6-trimethylphenyl phosphate Sn salt, bis-2,3,6-trimethyl Phenyl phosphate Mg salt, bis-2,3,6
-Trimethylphenyl phosphate Zn salt, bis-2,
6-dimethyl-3-ethylphenyl phosphate Mg
Salt, bis-2,6-dimethyl-3-ethylphenyl phosphate Zn salt, bis-2,6-dimethyl-4-ethylphenyl phosphate Mg salt, bis-2,6-dimethyl-4-ethylphenyl phosphate Zn salt, Screw-2,
6-dimethyl-4-propylphenyl phosphate Mg
Salt, bis-2,6-dimethyl-4-propylphenylphosphate Zn salt, bis-2,6-dimethyl-4-isopropylphenylphosphate Mg salt, bis-2,6-
Dimethyl-4-isopropylphenyl phosphate Zn
Salt etc. are mentioned.

Out of the above compounds, when a bis-2,6-dimethylphenyl phosphate Mg salt or a bis-2,6-dimethylphenyl phosphate Zn salt is used as an additive in the resin, excellent effects are exhibited. preferable. The metal salt of bis-2,6-dimethylphenylhydrogenphosphate of the present invention can be produced, for example, by the following method. That is, 2,6-dimethylpheno-
It can be obtained by reacting a phosphorus compound with phosphorus oxyhalide under a Lewis acid catalyst to obtain a phosphorohalogenide represented by the general formula (II), and then reacting this with a metal hydroxide. Here, the substituent R5 of the general formula (II)
And the "alkyl group having 1 to 3 carbon atoms" of R6 has the same meaning as the "alkyl group having 1 to 3 carbon atoms" of the general formula (I).

The 2,6-dimethylphenols that can be used in the present invention include 2,6-dimethylphenol, 2,3,6-trimethylphenol and 2,4,6-.
Trimethylphenol, 2,6-dimethyl-3-ethylphenol, 2,6-dimethyl-4-ethylphenol, 2,6-dimethyl-4-propylphenol, 2,
6-Dimethyl-4-isopropylphenol and the like can be mentioned, and 2,6-dimethylphenol is particularly preferable.

Examples of the phosphorus oxyhalide that can be used in the present invention include phosphorus oxychloride and phosphorus oxybromide, and phosphorus oxychloride is particularly preferable. Further, as the Lewis acid catalyst, aluminum chloride,
Magnesium chloride, tin chloride, zinc chloride, copper chloride, ammonium chloride, titanium tetrachloride, antimony pentachloride, aluminum sulfate, magnesium sulfate, zinc sulfate, copper sulfate,
Examples thereof include ammonium sulfate, aluminum nitrate, magnesium nitrate, zinc nitrate, copper nitrate and ammonium nitrate, with aluminum chloride and magnesium chloride being particularly preferred.

The Lewis acid catalyst is used in an amount of 0.1 to 5.0% by weight of phosphorus oxyhalide, and particularly preferably,
It is 0.5 to 2.0% by weight. When the amount of the catalyst used is within this range, the reaction time is shortened, and removal from the product after the reaction becomes easy. The metal hydroxide that can be used in the present invention, magnesium hydroxide, zinc hydroxide,
Examples include tin hydroxide.

First, the reaction between 2,6-dimethylphenol and phosphorus oxyhalide is usually carried out at a temperature of 50 to 25.
It is carried out at 0 ° C, preferably 70 to 160 ° C. When the reaction temperature is in this range, the reaction time does not become long, and 2,
Sublimation of 6-dimethylphenol does not occur. Then, the hydrogen halide produced as a by-product is removed from the reaction system,
6-Dimethylphenyl phosphorohalogenide is obtained. At this time, the pressure in the reaction system may be reduced in order to allow the reaction to proceed.

Further, the obtained 2,6-dimethylphenylphosphorohalogenide is usually reacted with a metal compound or a metal hydroxide in the presence of a solvent at a temperature of 50 to 250 ° C, preferably 70 to 160 ° C. Then, a metal salt of bis-2,6-dimethylphenylhydrogen phosphate is obtained.
At this time, the phosphorohalogenide is used by heating and dissolving it in a solvent, and as the solvent, for example, toluene, xylene, hexane, mineral spirits or the like can be used.
Further, the metal compound or the metal hydroxide can be used as a suspension using water as a medium.

Further, the metal salt of bis-2,6-dimethylphenylhydrogen phosphates of the present invention is disclosed in Japanese Patent Application Laid-Open No.
It can also be produced by using the reaction of a phosphoric acid compound and water described in JP-A 1-210090. Further, the metal salt of bis-2,6-dimethylphenylhydrogen phosphates of the present invention is disclosed in JP-A-2-272048.
It can also be obtained by using the reaction of a phosphoric acid compound and an aqueous alkaline solution described in JP-A No.

The synthetic resin to which the metal salt of bis-2,6-dimethylphenylhydrogenphosphates of the present invention is added is not particularly limited. Examples of synthetic resins used in the present invention include thermoplastic resins and thermosetting resins. Specifically, as the thermoplastic resin,
For example, polyethylene resin, polypropylene resin, polymethylpentene resin, polybutene-1 resin, polystyrene resin, polymethacrylstyrene resin, polyphenylene ether resin, polyphenylene sulfide resin, polyacrylonitrile resin, polyamide (nylon) resin, polyethylene terephthalate resin, polybutylene terephthalate Resin, polycarbonate resin, polyvinyl alcohol resin, polyvinyl acetal resin, polyacetal resin, polyacrylate resin, polysulfone resin, hydroxybenzoic acid polyester resin, polyvinyl chloride resin,
Polyvinyl bromide resin, polyvinyl fluoride resin, polyvinyl acetate resin, polyvinylidene chloride resin, AS (acrylonitrile-styrene) resin, ABS (acrylonitrile-butadiene-styrene) resin, fluororesin, methacryl resin, acrylic resin, polycarbonate- ABS resin (alloy resin), vinyl chloride-styrene copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-isobutylene copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride -Chlorinated propylene copolymer, vinyl chloride-butadiene copolymer, vinyl chloride-isoprene copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer Polymer, vinyl chloride - vinyl acetate copolymer, vinyl chloride - ethylene - vinyl acetate terpolymer, vinyl chloride - styrene - maleic anhydride ternary copolymer, a vinyl chloride - styrene - acrylonitrile terpolymer, vinyl chloride -
Vinylidene chloride-vinyl acetate terpolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-maleic acid ester copolymer, vinyl chloride-methacrylic acid ester copolymer, vinyl chloride-acrylonitrile copolymer,
Acrylic ester-butadiene-styrene copolymer,
Methacrylic acid ester-butadiene-styrene copolymer and the like can be mentioned.

Examples of the thermosetting resin include polyurethane resin, phenol resin, melamine resin, urea resin, epoxy resin, silicone resin, diallyl phthalate resin,
Examples thereof include polyimide resin and unsaturated polyester resin. Among the above synthetic resins, especially polypropylene resin,
When the metal salt of the present invention is added to a polycarbonate resin, a methacrylic resin, an acrylic resin, an ABS resin, an unsaturated polyester resin, a polyvinyl chloride resin and the above various vinyl chloride copolymers, excellent effects are exhibited. For example, when added to vinyl chloride resin, weather resistance is improved. These synthetic resins can be used alone or as a mixture of two or more.

By adding the metal salt of the present invention, these synthetic resins are prevented from deterioration due to the action of heat, light, etc., and their quality is maintained for a long time. That is, the resin composition comprising the metal salt of the present invention and the synthetic resin is a stable resin composition in which the effect of the metal salt (the effect of preventing the deterioration of the synthetic resin due to the action of heat, light, etc.) is long-term sustainable. Is. The metal salt of the present invention may be added in an amount of 0.1 to 15% by weight, though it varies depending on the type of synthetic resin to be added.

Hereinafter, the present invention will be described more specifically by showing examples, but the present invention is not limited to these examples.

[0032]

【Example】

(Example 1) A 1-liter four-necked flask was equipped with a stirrer, a thermometer, an additional funnel, and a condenser equipped with a hydrogen chloride recovery device, and 366.1 g (3,6) of 2,6-dimethylphenol was placed in the flask. 0.000 mol), toluene 12.
2 g and magnesium chloride 2.3 g were filled, and the mixture was heated and stirred. When the temperature of the reaction solution reached 130 ° C, 230.7 g (1.50 mol) of phosphorus oxychloride was added. After the addition was completed, the temperature was gradually raised to 160 ° C., the generated hydrogen chloride was completely recovered, and bis-2,6-dimethylphenylphosphorochloridate was obtained.

The compound obtained was a pale yellow liquid and had a yield of 4
It was 83.0 g (yield 99.2%). In addition, the following results were obtained by elemental analysis. Elemental analysis Cl: 10.9%, P: 9.52% To this bis-2,6-dimethylphenylphosphorochloridate 162.2 g (0.50 mol) was added toluene 150.1 g, and the mixture was heated and stirred at 80 ° C. , Magnesium hydroxide 14.6 g (0.25 mol) and water 65.2 g
The solution dispersed in was added. After stirring at 80 ° C for 2 hours, water and toluene were distilled off, and the obtained crystals were washed with water and dried to obtain magnesium salt monohydrate of bis-2,6-dimethylphenylhydrogen phosphate. It was

The compound obtained was a white solid and had a yield of 14
The amount was 8.5 g (yield 91.0%). The following results were obtained from the elemental analysis and infrared absorption spectrum. Elemental analysis Measured value C: 58.8%, H: 5.8%, P: 9.5%, Mg: 3.8% Theoretical value C: 58.8%, H: 5.8%, P: 9.5%, Mg: 3.7% Infrared absorption spectrum O- H: 3600 to 3650, 3200 to 3400 cm ^-1 P = O: 1150 to 1350 cm ^-1 P-O- (C) aromatic: 905 to 995 cm ^-1

(Example 2) Bis-2,6-dimethylphenylphosphorochloridate (486.9 g, 1.50 mol) obtained in the same manner as in Example 1 was added to toluene (207.7 g).
Was added, and the mixture was heated with stirring, and at 95 ° C., 187.4 g of water (6.8 times the theoretical value) was added. After the addition was completed, the generated hydrogen chloride was completely recovered and dried to obtain bis-2,6-dimethylphenylhydrogen phosphate. The obtained compound was a white solid and had a yield of 457.5 g (yield 99.
6%). In addition, the following results were obtained by elemental analysis and acid value measurement. Elemental analysis P: 9.9% Acid value 183.0

Then, 169.8 g of toluene was added to 153.0 g (0.50 mol) of this bis-2,6-dimethylphenylhydrogen phosphate, and the mixture was stirred with heating to 80
14.6 g (0.25 mol) of magnesium hydroxide at ℃
Was added to 98.5 g of water to add a solution. After stirring at 80 ° C for 2 hours, water and toluene were distilled off, and the obtained crystals were washed with water and dried to obtain a magnesium salt monohydrate of bis-2,6-dimethylphenylhydrogen phosphate. .

The compound obtained was a white solid and had a yield of 15
The amount was 5.3 g (yield 95.2%). The following results were obtained from the elemental analysis and infrared absorption spectrum. Elemental analysis Measured value C: 58.8%, H: 5.8%, P: 9.5%, Mg: 3.8% Theoretical value C: 58.8%, H: 5.8%, P: 9.5%, Mg: 3.7% Infrared absorption spectrum O- H: 3600 to 3650, 3200 to 3400 cm ^-1 P = O: 1150 to 1350 cm ^-1 P-O- (C) aromatic: 905 to 995 cm ^-1

Example 3 To 153.1 g (0.50 mol) of bis-2,6-dimethylphenylhydrogen phosphate obtained by the same procedure as in Example 2 was added toluene 200.6.
g, heated and stirred, and at 80 ° C., sodium hydroxide 2
An aqueous solution in which 0.1 g (0.50 mol) was dissolved in 98.7 g of water was added. Then, 34.1 g of zinc chloride (0.
25 mol) was dissolved in 251.3 g of water, and an aqueous solution was added. After stirring at 80 ° C. for 2 hours, water and toluene were distilled off, and the obtained crystals were washed with water and dried to give bis-2,
A zinc salt of 6-dimethylphenyl hydrogen phosphate was obtained.

The compound obtained was a white solid and had a yield of 16
The amount was 4.6 g (yield 97.5%). The following results were obtained from the elemental analysis and infrared absorption spectrum. Elemental analysis Measured value C: 56.8%, H: 5.3%, P: 9.1%, Zn: 9.6% Theoretical value C: 56.8%, H: 5.3%, P: 9.2%, Zn: 9.7% Infrared absorption spectrum P = O: 1150 to 1350 cm ^-1 P-O- (C) aromatic: 905 to 995 cm ^-1

Example 4 To 162.3 g (0.50 mol) of bis-2,6-dimethylphenylphosphorochloridate obtained by the same operation as in Example 1 was added 204.3 g of toluene.
Was added, and the mixture was heated with stirring, and sodium hydroxide 2
An aqueous solution obtained by dissolving 0.1 g (0.50 mol) in 103.2 g of water was added. Then, 34.2 g of zinc chloride
An aqueous solution prepared by dissolving (0.25 mol) in 270.6 g of water was added. After stirring at 80 ° C for 2 hours, water and toluene were distilled off, and the obtained crystals were washed with water and dried to obtain a zinc salt of bis-2,6-dimethylphenylhydrogen phosphate.

The obtained compound was a white solid and had a yield of 16
It was 3.9 g (yield 97.0%). The following results were obtained from the elemental analysis and infrared absorption spectrum. Elemental analysis Measured value C: 56.8%, H: 5.3%, P: 9.1%, Zn: 9.6% Theoretical value C: 56.8%, H: 5.3%, P: 9.2%, Zn: 9.7% Infrared absorption spectrum P = O: 1150 to 1350 cm ^-1 P-O- (C) aromatic: 905 to 995 cm ^-1

(Example 5) [Hydrolysis stability test] Equipment used: Kyoshin Engineering Co., Ltd. pressure cooker type: HV-22DS slim type digital PID type: horizontal type <test tank evaporation generation tank separated type> chamber material : SUS 304

[Hydrolysis stability measurement test method] 200 m
About 25 to 35 g of a sample was placed in a 1-beaker, covered with a watch glass, kept at 120 ° C., 2 atm and saturated steam for 72 hours (3 days), then returned to normal pressure and cooled. After cooling, the weight and acid value were measured and compared with the acid value before the test, and the hydrolysis rate was determined from the following formula.

[0044]

[Equation 1]

Since the sample has a first stage neutralization point at pH 7 to 9 and a second stage neutralization point at pH 10 to 12, the second stage neutralization point is the acid value of the sample. did. However, for those having no neutralization point in the second stage, the neutralization point in the first stage was used as the acid value. Samples are bis-2,6-dimethylphenylhydrogen phosphate (DXPA) bisphenylhydrogen phosphate (DPPA) mono-2-ethylhexyl-2-ethylhexylphosphonate (PC-88A) bis-2-ethylhexyl hydrogen phosphate (D
P-8R) Bisisodecyl hydrogen phosphate (DP-10)
R) was used.

[Method of measuring acid value] In a 200 ml beaker,
About 2.0 to 2.8 g of the sample was put. Ethyl alcohol 1
00 ml was put into another beaker with a graduated cylinder, several drops of bromthymol blue (BTB) solution was added as an indicator, and N / 10 alcoholic potassium hydroxide solution was dropped to neutralize using a measuring pipette. The neutralized solution was poured into a beaker containing a sample, a rotor was inserted, and an automatic potentiometric titrator was used to perform titration with an N / 2 alcoholic potassium hydroxide solution. Since there is a difference in the weight of the sample before and after the test,
The sample weight used for the calculation of the acid value was calculated by the following formula.

[0047]

[Equation 2]

DXPA 24.29 in a 200 ml beaker
Put 77g, cover with watch glass, 120 ℃, 2atm,
After maintaining for 72 hours (3 days) under saturated steam, the pressure was returned to normal pressure and cooled. The weight after cooling was 24.2918 g, and the acid value was 181.22 and 181.98 before and after the test, respectively. From this, the hydrolysis rate was 0.207%. DP
The same test was performed for PA, PC-88A, DP-8R, and DP-10R. The results are shown in Table 1.

[0049]

[Table 1]

According to Table 1, DXPA has the best hydrolysis resistance, and the 2,6-dimethylphenyl group having a sterically hindered group at the 2,6 position improves the hydrolysis resistance. .

[0051]

The phosphoric acid ester metal salt having a 2,6-dimethylphenyl group thus obtained is excellent in heat resistance and hydrolysis resistance, particularly hydrolysis resistance. Further, when this is made into a metal salt, when it is added to a resin, deterioration due to the action of heat, light or the like is prevented, and a stable resin composition that is sustainable for a long period of time can be provided.

Therefore, the metal salt of the 2,6-dimethylphenylhydrogen phosphates of the present invention has properties such as flame retardancy, lubricity and releasability, and at the same time has excellent heat resistance, weather resistance and resistance to corrosion. It can be used as a hydrolyzable resin additive.

Claims (4)

[Claims] 1. A compound of the general formula (I) (In the formula, M is a divalent metal selected from magnesium, zinc and tin, R 1, R 2, R 3 and R 4 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, Me is a methyl group, n Is an integer of 0 to 3) and is a metal salt of bis-2,6-dimethylphenylhydrogenphosphate. 2. R1, R2, R3 and R of the general formula (I)
The metal salt according to claim 1, wherein 4 is a hydrogen atom. 3. A 2,6-dimethylphenol and a phosphorus oxyhalide are reacted under a Lewis acid catalyst to give a compound represented by the general formula (II): (In the formula, X is a chlorine atom or a bromine atom, R 5 and R 6 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, M
e is a methyl group) to obtain a phosphorohalogenide,
Next, this is reacted with a metal hydroxide, and bis-2 represented by the general formula (I) according to claim 1,
A method for producing a metal salt of 6-dimethylphenylhydrogenphosphate. 4. The method for producing a metal salt according to claim 3, wherein the Lewis acid catalyst is magnesium chloride.