JP2821654B2 - Flame retardant insulating oil containing orthophosphate ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to orthophosphoric acid ester le relates to a flame-retardant insulating oil having free <br/>.

[0002]

2. Description of the Related Art Oil called insulating oil is used in electric devices such as power cables, transformers, and condensers. In general, highly refined mineral oil is widely used, but its use is flammable and its use entails a fire hazard. Therefore, from the viewpoint of disaster prevention, it is required that insulating oil of electric equipment installed in an urban area be nonflammable or nonflammable.

Hitherto, polychlorinated biphenyls (PCB) have been put to practical use for such uses, but their accumulated toxicity has been a problem, and their use has been banned altogether.
Currently, orthophosphate esters such as tricresyl phosphate (hereinafter, referred to as "TCP") and trixylenyl phosphate (hereinafter, referred to as "TXP") have been proposed as alternatives to PCBs.

[0004] It is widely known that by adding a small amount of such orthophosphate ester to a synthetic resin or the like, the resin can be made flame-retardant, so that there is no problem in flame retardancy. However, the above TCP and TXP have a volume resistivity value,
The electrical properties such as relative dielectric constant and dielectric loss tangent do not reach the level required for insulating oils, and are not satisfactory for use as insulating oils.

[0005]

In view of this situation, the present inventor has developed a novel insulating oil having excellent flame retardancy and excellent electrical properties such as volume resistivity, relative permittivity and dielectric loss tangent. We have been working hard to develop it. As a result, it has been found that the specific orthophosphate represented by the following general formula (1) has excellent flame retardancy and excellent electrical properties required as an insulating oil. The present invention has been completed based on such findings.

That is, the present invention relates to the general formula

[0007]

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Wherein R ¹ and R ² are the same or different and represent a lower alkyl group. R ³ represents a hydrogen atom or a lower alkyl group. R ⁴ represents a phenyl group which may have a lower alkyl group as a substituent or an alkyl group which may have a halogen atom as a substituent. n shows the integer of 1-3. To contain orthophosphoric acid ester le represented by] according to the flame retardant insulating oil according to claim.

In the present specification, examples of the lower alkyl group include a methyl group, an ethyl group, an n-propyl group and an is
An o-propyl group, an n-butyl group, a tert-butyl group and the like can be mentioned. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the phenyl group which may have a lower alkyl group as a substituent include a phenyl group, a cresyl group, and a xylyl group. Examples of the alkyl group which may have a halogen atom as a substituent include a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a 2-ethylhexyl group, a 1-chloroethyl group, and a 2-chloroethyl group.

Specific examples of the orthophosphate represented by the above general formula (1) include, for example, di (2,6-dimethylphenyl) phenyl phosphate, di (2,6-dimethylphenyl) cresyl phosphate, (2,6-dimethylphenyl) xylyl phosphate, di (2,6-dimethylphenyl) isopropyl phosphate,
6-dimethylphenyl) 2-ethylhexyl phosphate, di (2,4,6-trimethylphenyl) cresyl phosphate, 2,6-dimethylphenyldiphenylphosphate, 2,6-dimethylphenyldicresylphosphate, 2,6-dimethylphenyl Dixylyl phosphate, 2,6-dimethylphenyl diisopropyl phosphate, 2,6-dimethylphenyl di (2-ethylexyl) phosphate, 2,4,6-trimethylphenyl dicresyl phosphate and the like can be mentioned. Among these, di (2,6-dimethylphenyl) cresyl phosphate is particularly preferred.

[0011] orthophosphoric acid ester represented by the general formula (1) may, eg be phosphorus oxychloride in the general formula

[0012]

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Wherein R ¹ , R ² and R ³ are as defined above. And a general formula R ⁴ OH, wherein R ⁴ is as defined above. And a hydroxy compound represented by the following formula:

In the insulating oil of the present invention, the orthophosphate represented by the above general formula (1) may be used alone or in combination of two or more.

In the present invention, the orthophosphate represented by the above general formula (1) can be used as it is as a flame-retardant insulating oil. For example, transformer oil, condenser oil,
For applications such as cable oil, the orthophosphoric ester can be used as it is as a flame-retardant insulating oil. Particularly, for applications such as transformers that require a cooling effect due to the flow of the insulating oil, the orthophosphoric acid ester is used. The acid ester may be diluted with another low-viscosity insulating oil or the like before use. Examples of the low-viscosity insulating oil include, for example, mineral oil, alkylbenzene, aliphatic ester oil and the like, as well as orthophosphate esters and the like which do not correspond to the above general formula (1) such as TCP and TXP. In the case of diluting with such a low-viscosity insulating oil, the dilution ratio varies depending on the flame retardancy, viscosity and the like for which the insulating oil is required, but cannot be determined unconditionally, but is generally about 20 times or less, preferably 0.1 times or less. -10
It is better to dilute about twice.

In the present invention, if necessary, an antioxidant and the like may be appropriately added for the purpose of improving stability.

[0017]

EXAMPLES The present invention will be further clarified with reference to Production Examples and Examples below, but the present invention is not limited to these Production Examples and Examples.

Production Example Synthesis of di (2,6-dimethylphenyl) cresyl phosphate A four-necked flask was equipped with a stirrer, a thermometer, a dropping funnel, and a condenser connected to a water scrubber. Dimethylphenol, 20 g
Of xylene and 1.5 g of magnesium chloride were heated and mixed. When the temperature of the reaction solution reached 120 ° C., 153 g of phosphorus oxychloride was added over about 2 hours. The hydrogen chloride gas generated at this time was led to a water scrubber. After the addition of phosphorus oxychloride was completed, the temperature of the reaction solution was gradually raised to 180 ° C., and the mixture was aged at the same temperature for 2 hours. The reaction solution was cooled to room temperature, 108 g of cresol was added, and the temperature was gradually raised to 230 ° C.
Aging was performed under reduced pressure of 0 mmHg to complete the reaction.
After washing the reaction solution with hydrochloric acid and water to remove the catalyst,
After dehydration, 396 g of a crude product was obtained. The crude product was distilled to obtain 357 g of a purified product as a pale yellow oil.

The composition of the product was determined by liquid chromatography [HL
C-802UR, manufactured by Tosoh Corporation], 95.2% of di (2,6-dimethylphenyl) cresyl phosphate, tris (2,6-dimethylphenyl)
It was a mixture of 2.2% phosphate, 2.5% 2,6-dimethylphenyldicresyl phosphate and 0.1% tricresyl phosphate. This product is called "DX
"CP".

FIG. 1 shows an infrared absorption spectrum of the product.

Examples Di (2,6-dimethylphenyl) phenyl phosphate (hereinafter referred to as "DXPP"), DXCP and 2,6-dimethylphenyldiphenyl phosphate (hereinafter referred to as "XDPP") produced according to the above-mentioned production examples. The electrical properties (volume resistivity, dielectric loss tangent and relative dielectric constant) and flammability of the sample were examined. The results are shown in Table 1 in comparison with those of TCP and TXP.

[0022]

[Table 1]

[0023]

The orthophosphoric ester of the present invention represented by the general formula (1) is nonflammable, and has a volume specific resistance,
In terms of electrical properties such as relative permittivity and dielectric loss tangent, the insulating oil has a performance that can sufficiently satisfy the specifications of the insulating oil, and the industrial value of the insulating oil is extremely high.

[Brief description of the drawings]

FIG. 1 is an infrared absorption spectrum of a product obtained in a production example.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-105436 (JP, A) JP-A-64-9265 (JP, A) JP-A-63-2955663 (JP, A) JP-A-62 1787 (JP, A) JP-A-56-59787 (JP, A) JP-A-56-59786 (JP, A) JP-A-55-157592 (JP, A) JP-A-55-1557591 (JP, A) JP 54-3014 (JP, A) US Patent 4,556,684 (US, A) US Patent 3,863,613 (US, A) US Patent 4,914,144 (US, A) European Patent Application Publication 7460 (EP, A) West German Patent Application Publication 2929099 (DE, A1) Clin. Immunol. Immu nopathol. (1988), Vol. 49, No. 1, pp. 41-52 (58) Fields investigated (Int. Cl. ⁶ , DB name) C07F 9/09 C10M 137/04 C10N 40:16 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A compound of the general formula [Wherein, R ¹ and R ² are the same or different and represent a lower alkyl group. R ³ represents a hydrogen atom or a lower alkyl group.
R ⁴ represents a phenyl group which may have a lower alkyl group as a substituent or an alkyl group which may have a halogen atom as a substituent. n shows the integer of 1-3. ]
Characterized by containing an orthophosphate represented by the formula
Flame retardant insulating oil .