CN-122012165-A - Synthetic ester insulating oil based on alkyl chain length grading and star-comb composite branching synergistic regulation and preparation method thereof

CN122012165ACN 122012165 ACN122012165 ACN 122012165ACN-122012165-A

Abstract

The invention discloses synthetic ester insulating oil based on alkyl chain length grading and star-comb composite branching cooperative regulation and control and a preparation method thereof, and relates to the technical field of insulating materials of power equipment. The preparation method comprises the steps of carrying out gradient mixing fatty acid esterification on polyalcohol and C8-C12 to obtain a gradient main chain ester intermediate, carrying out vacuum grafting on the intermediate and branched acid to obtain star-branched ester, carrying out transesterification on the star-branched ester and branched alcohol to obtain star-comb-shaped composite branched ester, and compounding the composite branched ester and an additive to obtain the finished product. The insulating oil solves the problem that the low pour point and low-temperature viscosity of the traditional oil cannot be considered, improves extreme low-temperature adaptability, insulating property and thermal stability, is suitable for high-cold areas and direct-current transmission equipment, has the advantages of readily available raw materials and environment-friendly process, can replace the traditional mineral insulating oil, and provides key technical support for stable operation of power equipment in extreme environments.

Inventors

WANG FEIPENG
LI SHI
LI JIAN
HUANG ZHENGYONG
LI CHANGHENG
ZHANG YINGFAN

Assignees

重庆大学

Dates

Publication Date: 20260512
Application Date: 20260204

Claims (7)

1. The preparation method of the synthetic ester insulating oil is characterized by comprising the following steps of: (1) The main chain construction, namely, in a protective atmosphere, carrying out esterification reaction on polyalcohol and C8-C12 gradient mixed fatty acid under the action of a catalyst, and monitoring the acid value to be less than or equal to 2.5 mg KOH/g to obtain an ester intermediate with a gradient main chain; (2) The star-branched chain construction, namely mixing the ester intermediate with the gradient main chain with branched acid, adding a catalyst, carrying out grafting reaction under the vacuum condition, and monitoring the acid value to be less than or equal to 1.2 mg KOH/g to obtain star-branched ester; (3) The construction of comb-shaped branched chains, namely mixing star-shaped branched esters with branched alcohols, carrying out transesterification under the action of a catalyst, and monitoring that the conversion rate of the branched alcohols is more than or equal to 95 percent to obtain star-comb-shaped composite branched esters; (4) Compounding, namely uniformly mixing the star-comb composite branched ester and the additive to obtain the synthetic ester insulating oil; In step (1), the polyol is selected from pentaerythritol or trimethylolpropane; In the step (1), the C8-C12 gradient mixed fatty acid is a mixture of C8 fatty acid, C10 fatty acid and C12 fatty acid in a molar ratio of 4:3:3; in the step (2), the molar ratio of the ester intermediate with the gradient main chain to the branched acid is 1:4; in step (2), the branched acid is selected from isooctanoic acid or pivalic acid; In step (3), the branched alcohol is selected from 2-ethylhexanol or 3, 5-dimethylheptanol; in the step (3), the molar ratio of the star-branched ester to the branched alcohol is 1:3; The catalyst in the step (1) is p-toluenesulfonic acid or concentrated sulfuric acid, the catalyst in the step (2) is selected from tetrabutyl titanate or stannous oxide, and the catalyst in the step (3) is a Ziegler type catalyst.
2. The preparation method according to claim 1, wherein in the step (1), the esterification reaction is carried out at a temperature of 150-170 ℃ for a time of 5-7 hours, in the step (2), the grafting reaction is carried out at a temperature of 175-185 ℃ for a time of 4-5 hours, and in the step (3), the transesterification reaction is carried out at a temperature of 200-220 ℃ for a time of 3-4 hours.
3. The preparation method according to claim 2, wherein the esterification reaction adopts a sectional heating mode, pre-esterification is carried out for 2 hours at 150 ℃, and then the temperature is raised to 160-170 ℃ for continuous reaction for 4 hours.
4. The method of claim 1, wherein the additives include one or more of antioxidants, charge inhibitors, light stabilizers, and defoamers.
5. The method of claim 4, wherein the antioxidant in step (4) comprises di-t-butyl-p-cresol, the charge inhibitor comprises benzotriazole, the light stabilizer comprises a hindered amine light stabilizer, and the defoamer comprises a silicone-based defoamer.
6. A synthetic ester insulating oil obtained by the production process according to any one of claims 1 to 5.
7. Use of the synthetic ester insulating oil according to claim 6 in electrical equipment.

Description

Synthetic ester insulating oil based on alkyl chain length grading and star-comb composite branching synergistic regulation and preparation method thereof Technical Field The invention relates to the technical field of insulating materials of power equipment, in particular to synthetic ester insulating oil based on alkyl chain length grading and star-comb composite branching cooperative regulation and control and a preparation method thereof. Background With the development of power systems to high voltage, large capacity and extreme environmental adaptability, the performance requirements of insulating oil serving as a core insulating and heat dissipating medium of power equipment are increasingly severe. Although the traditional mineral insulating oil has good dielectric strength and thermal stability, the traditional mineral insulating oil has poor biodegradability, insufficient low-temperature fluidity (the pour point is generally higher than-30 ℃), fire hazard exists, and the comprehensive requirements of high-cold areas (such as polar regions, plateaus and the like) and direct-current transmission equipment on the low-temperature starting performance, environmental protection performance and safety of an insulating medium are difficult to meet. In recent years, synthetic ester insulating oils have been considered as an important direction to replace mineral oils due to their biodegradability, high fire point (> 300 ℃) and excellent thermo-oxidative stability, yet they still face significant challenges in pour point control at extremely low temperatures. The primary problems of the existing synthetic ester oil are inherent contradiction between molecular structure and pour point, namely that short-chain esters (such as partial pentaerythritol esters) can lower the pour point below-50 ℃, but the rigidity of the molecules is enhanced to lead to the steep rise of low-temperature viscosity and the deterioration of fluidity, and long-chain or branched esters can improve viscosity-temperature characteristics, and the unordered branched chains are easy to reduce molecular stacking resistance, so that the pour point is raised to be above-40 ℃. Meanwhile, the pour point is regulated and controlled by adopting single means such as fixed chain length or random branching in the prior art, the synergistic effect of alkyl chain length grading (such as main chain/side chain differential design) and branched chain space configuration (such as symmetrical/asymmetrical branching and branched chain position optimization) is neglected, so that low-temperature fluidity and thermal stability are difficult to consider, and extreme environment suitability is seriously insufficient, namely, the electric equipment in alpine regions requires that insulating oil still keeps fluidity below-60 ℃, the pour point of the existing synthetic ester oil is only up to-60 ℃ at the minimum, and the pour point is realized by relying on a pour point depressant, which can possibly introduce impurities and degrade dielectric properties, and in addition, in DC power transmission equipment, the traditional ester oil is easy to cause space charge accumulation under long-term electric field stress due to insufficient matching of molecular polarity and steric hindrance, and insulation aging is accelerated. In summary, the prior art cannot realize the synergistic optimization of pour point, viscosity-temperature characteristics, dielectric properties and thermal stability of the synthetic ester insulating oil through the precise design of a molecular layer, and a synthetic ester insulating oil design and preparation method based on the precise design of a molecular topological structure are needed. Disclosure of Invention The invention aims to provide synthetic ester insulating oil based on alkyl chain length grading and star-comb composite branching cooperative regulation and control and a preparation method thereof, so as to solve the problems in the prior art. In order to achieve the above object, the present invention provides the following solutions: the invention provides a preparation method of synthetic ester insulating oil, which comprises the following steps: (1) The main chain construction, namely, in a protective atmosphere, carrying out esterification reaction on polyalcohol and C8-C12 gradient mixed fatty acid under the action of a catalyst, and monitoring the acid value to be less than or equal to 2.5 mg KOH/g to obtain an ester intermediate with a gradient main chain; (2) The star-branched chain construction, namely mixing the ester intermediate with the gradient main chain with branched acid, adding a catalyst, carrying out grafting reaction under the vacuum condition, and monitoring the acid value to be less than or equal to 1.2 mg KOH/g to obtain star-branched ester; (3) The construction of comb-shaped branched chains, namely mixing star-shaped branched esters with branched alcohols, carrying out transesterification under the action