An additive for mixing insulating oil and use thereof

Abstract

This invention discloses an additive for mixed insulating oil and its application, relating to the technical field of insulating oil additives. The additive provided by this invention comprises the following components in parts by weight: 1-2 parts of component A and 1 part of component B; wherein component A comprises polymethyl methacrylate, and component B comprises at least one of polyisobutylene and styrene-acrylonitrile copolymer. In the additive provided by this invention, the polymethyl methacrylate molecular chain contains both polar ester groups and non-polar long alkyl side chains, which can act as a compatibilizer, but its intrinsic high-temperature stability is limited. Therefore, this invention requires the addition of at least one of polyisobutylene and styrene-acrylonitrile copolymer, so that after the additive is added to the insulating oil, it can form an interpenetrating network or a tightly associated system in the microstructure, thereby maximizing the improvement of the flash point of the mixed insulating oil.

Description

Technical Field

[0001] This invention relates to the field of insulating oil additives, and more specifically, to an additive for mixing insulating oils and its application. Background Technology

[0002] A power transformer is an electrical device used for converting electrical energy, playing a crucial role in the power system. Insulating oil, the liquid medium used for insulating and cooling the transformer, directly affects its operating performance and service life. To ensure the safe operation of the transformer, it is usually necessary to increase the flash point of the insulating oil by adding additives and adjusting the oil distribution ratio.

[0003] Currently, the main insulating oil used in transformers is mineral oil, which is difficult to degrade after aging, posing a significant environmental impact. With societal development, higher demands are being placed on the environmental friendliness of insulating oils. Therefore, in recent years, the application of synthetic or natural ester-based insulating oils, which are renewable and have higher degradability, in transformers has been increasing. Ester-based insulating oils can be directly injected into newly commissioned transformers, and existing mineral oil transformers can also have their mineral oil replaced using ester-based insulating oils. However, when replacing old mineral oil transformers with ester-based insulating oils, a mixture of the two types of insulating oil often occurs. Studies have shown that after replacing mineral oil transformers with synthetic ester-based insulating oil, the transformer generally still contains 1-5 wt% mineral oil.

[0004] Currently, technologies for improving the flash point of insulating oils are almost exclusively limited to single types of insulating oils, resulting in unclear effects of additives on the performance of ester-based insulating oils mixed with a small proportion of mineral oil. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an additive for mixing insulating oils and its application.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution: An additive for mixing insulating oils, comprising the following components in parts by weight: Component A 1-2 parts, Component B 1 part; Component A includes polymethacrylate, and component B includes at least one of polyisobutylene and styrene-acrylonitrile copolymer.

[0007] The additive provided in this application contains polymethyl methacrylate (PMMA) with both polar ester groups and non-polar long alkyl side chains in its molecular chain. The polar ester groups can form strong dipole-dipole interactions and hydrogen bonding with the ester groups in synthetic or natural ester insulating oil molecules, giving PMMA excellent compatibility and thickening network effect in mixed insulating oil matrices containing ester oils. Simultaneously, its non-polar alkyl side chains are well compatible with residual mineral oil (hydrocarbon) molecules in the mixed insulating oil. This amphiphilic structure allows PMMA to act as a bridge between the ester oil and mineral oil phases, effectively suppressing the escape of low molecular weight volatiles in the mixed system, thereby increasing the flash point of the mixed mineral oil. However, while PMMA has good compatibility when used alone, its high-temperature stability is limited. Therefore, the inventors of this application have discovered through experiments that compounding PMMA with at least one of polyisobutylene and styrene-acrylonitrile copolymer can further improve the flash point of the insulating oil. Polyisobutylene possesses excellent chemical inertness and sealing properties. Its dense, long-chain structure can fill the gaps in the polymer network formed by polymethyl methacrylate, further blocking the volatilization pathways of small-molecule hydrocarbon gases. The styrene-acrylonitrile copolymer contains a rigid benzene ring structure (styrene segment) and a highly polar cyano group (acrylonitrile segment). The benzene ring provides thermal stability and rigid support, while the cyano group enhances the interaction with the ester groups in polymethyl methacrylate. Therefore, only by using polymethyl methacrylate as the matrix to construct a main network compatible with the mixed insulating oil, and then introducing polyisobutylene for "gap filling" or styrene-acrylonitrile copolymer for "reinforcement," forming an interpenetrating network or a tightly associated system in the microstructure, can the flash point of the mixed insulating oil be maximized. Without the addition of polymethyl methacrylate, neither polyisobutylene nor styrene-acrylonitrile copolymer can independently form a uniform and stable anti-volatilization network in the mixed insulating oil.

[0008] As a preferred embodiment of the additives for mixing insulating oils according to the present invention, the polymethacrylate includes polymethyl methacrylate.

[0009] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polymethacrylate has a weight-average molecular weight of 20,000-100,000 g / mol.

[0010] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polymethacrylate has a melt index of 5-15 g / 10 min at 190°C and 2.16 kg.

[0011] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polyisobutylene has a weight-average molecular weight of 1000-2500 g / mol.

[0012] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polyisobutylene has a melt index of 10-30 g / 10 min at 200°C and 2.16 kg.

[0013] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the styrene-acrylonitrile copolymer is prepared by copolymerizing 70-80 wt% styrene and 20-30 wt% acrylonitrile.

[0014] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the styrene-acrylonitrile copolymer has a weight-average molecular weight of 150,000-200,000 g / mol.

[0015] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the styrene-acrylonitrile copolymer has a melt index of 1-10 g / 10 min at 220°C and 10 kg.

[0016] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, component B comprises polyisobutylene and styrene-acrylonitrile copolymer in a mass ratio of (2.5-5):(0-2.5).

[0017] The present invention also protects the use of the above-mentioned additives for use in mixed insulating oils, the mixed insulating oils including mineral oils and ester-based insulating oils.

[0018] As a preferred embodiment of the application described in this invention, the mineral oil includes No. 25 transformer oil (compliant with GB2536-90), and the ester insulating oil includes at least one of synthetic ester insulating oil and natural ester insulating oil.

[0019] As a preferred embodiment of the application described in this invention, the synthetic ester insulating oil includes pentaerythritol ester insulating oil.

[0020] As a preferred embodiment of the application described in this invention, the natural ester insulating oil includes glyceryl triester insulating oil.

[0021] As a preferred embodiment of the application described in this invention, the mixed insulating oil comprises mineral oil and ester insulating oil in a mass ratio of (1-5):(95-99).

[0022] As a preferred embodiment of the application described in this invention, the additive for mixing insulating oil has a mass ratio of (0.1-1):100 with the mixed insulating oil.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The additive for mixed insulating oil provided by this invention can increase the flash point of the insulating oil without affecting its insulating function. The acid value of the mixed insulating oil after adding the additive is ≤0.04mg KOH / g, the dielectric loss is ≤0.004%, and the flash point is increased to above 251℃. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] <Terminology Definition> The term "polymethacrylate" refers to a known polymeric organic compound obtained by reacting methacrylate monomers. Examples of methacrylate monomers suitable for obtaining polymethacrylates are alkyl methacrylates and cycloalkyl methacrylates, such as ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, ethylhexyl methacrylate, 3,3,5-trimethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, cyclopentyl methacrylate, and isobornyl methacrylate. The general formula for polymethacrylate is shown below: ; In the formula, R can be at least one of ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, ethylhexyl, 3,3,5-trimethylhexyl, stearyl, lauryl, cyclopentyl, and isobornyl.

[0026] The term "polyisobutylene" (PIB) refers to a polymer obtained by cationic polymerization of isobutylene, which is a typical saturated linear polymer. The main molecular chain does not contain double bonds or long branches, and its structural unit is -(CH2-C(CH3)2)-, which contains no asymmetric carbon atoms, and the structural units are connected in a regular sequence from head to tail.

[0027] The term "acrylonitrile-styrene copolymer" (SAN or AS resin) is a colorless and transparent thermoplastic resin obtained by copolymerization of acrylonitrile and styrene. It is obtained by suspension polymerization of acrylonitrile and styrene as raw materials, and can also be initiated by thermal initiator or obtained by emulsion polymerization.

[0028] The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0029] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0030] In this application, a list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0031] In the following description, all figures disclosed in this application are approximate values, regardless of whether the terms "about" or "approximately" are used in conjunction. They may vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a range of values ​​with a lower limit (RL) and an upper limit (RU) is disclosed, any values ​​falling within that range are specifically disclosed. Specifically, the following values ​​within this range are specifically disclosed: R = RL + k * (RU - RL), where k is a variable with a 1% increment from 1% to 100%, i.e., k is 1%, 2%, 3%, 4%, 5%, ..., 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any range of values ​​defined by the two R values ​​as defined above are also specifically disclosed.

[0032] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated.

[0033] Throughout this specification, references to "implementation," "partial implementation," "one implementation," "some implementations," "another enumerated method," "specific method," or "partial method" mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment.

[0034] I. Additives for mixing insulating oils To address the problem of insufficient flash point in existing ester-based insulating oils containing a small proportion of mineral oil, this application provides an additive for mixing insulating oils, comprising the following components in parts by weight: Component A 1-2 parts, Component B 1 part; Component A includes polymethacrylate, and component B includes at least one of polyisobutylene and styrene-acrylonitrile copolymer.

[0035] The additive provided in this application contains polymethyl methacrylate (PMMA) with both polar ester groups and non-polar long alkyl side chains in its molecular chain. The polar ester groups can form strong dipole-dipole interactions and hydrogen bonding with the ester groups in synthetic or natural ester insulating oil molecules, giving PMMA excellent compatibility and thickening network effect in mixed insulating oil matrices containing ester oils. Simultaneously, its non-polar alkyl side chains are well compatible with residual mineral oil (hydrocarbon) molecules in the mixed insulating oil. This amphiphilic structure allows PMMA to act as a bridge between the ester oil and mineral oil phases, effectively suppressing the escape of low molecular weight volatiles in the mixed system, thereby increasing the flash point of the mixed mineral oil. However, while PMMA has good compatibility when used alone, its high-temperature stability is limited. Therefore, the inventors of this application have discovered through experiments that compounding PMMA with at least one of polyisobutylene and styrene-acrylonitrile copolymer can further improve the flash point of the insulating oil. Polyisobutylene possesses excellent chemical inertness and sealing properties. Its dense, long-chain structure can fill the gaps in the polymer network formed by polymethyl methacrylate, further blocking the volatilization pathways of small-molecule hydrocarbon gases. The styrene-acrylonitrile copolymer contains a rigid benzene ring structure (styrene segment) and a highly polar cyano group (acrylonitrile segment). The benzene ring provides thermal stability and rigid support, while the cyano group enhances the interaction with the ester groups in polymethyl methacrylate. Therefore, only by using polymethyl methacrylate as the matrix to construct a main network compatible with the mixed insulating oil, and then introducing polyisobutylene for "gap filling" or styrene-acrylonitrile copolymer for "reinforcement," forming an interpenetrating network or a tightly associated system in the microstructure, can the flash point of the mixed insulating oil be maximized. Without the addition of polymethyl methacrylate, neither polyisobutylene nor styrene-acrylonitrile copolymer can independently form a uniform and stable anti-volatilization network in the mixed insulating oil.

[0036] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the mass ratio between component A and component B can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or within any range of two of the above values.

[0037] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polymethacrylate may include at least one of polyethyl methacrylate, polypropyl methacrylate, polyisopropyl methacrylate, polybutyl methacrylate, polyisobutyl methacrylate, polytert-butyl methacrylate, polypentyl methacrylate, polyhexyl methacrylate, polyethylhexyl methacrylate, poly(3,3,5-trimethylhexyl methacrylate), stearyl methacrylate, polylauryl methacrylate, polycyclopentyl methacrylate, and polyisoborneol methacrylate.

[0038] As a preferred embodiment of the additives for mixing insulating oils according to the present invention, the polymethacrylate includes polymethyl methacrylate.

[0039] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polymethacrylate has a weight-average molecular weight of 20,000-100,000 g / mol.

[0040] For example, the weight-average molecular weight of the polymethacrylate may be 20,000 g / mol, 25,000 g / mol, 30,000 g / mol, 35,000 g / mol, 40,000 g / mol, 45,000 g / mol, 50,000 g / mol, 55,000 g / mol, 60,000 g / mol, 65,000 g / mol, 70,000 g / mol, 75,000 g / mol, 80,000 g / mol, 85,000 g / mol, 90,000 g / mol, 95,000 g / mol, 100,000 g / mol, or within the range of any two of the above values.

[0041] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polymethacrylate has a melt index of 5-15 g / 10 min at 190°C and 2.16 kg.

[0042] For example, the melt index of the polymethacrylate at 190°C and 2.16 kg can be 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, 10 g / 10 min, 11 g / 10 min, 12 g / 10 min, 13 g / 10 min, 14 g / 10 min, 15 g / 10 min, or within any two of the above values.

[0043] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polyisobutylene has a weight-average molecular weight of 1000-2500 g / mol.

[0044] For example, the weight-average molecular weight of the polyisobutylene can be 1000 g / mol, 1100 g / mol, 1200 g / mol, 1300 g / mol, 1400 g / mol, 1500 g / mol, 1600 g / mol, 1700 g / mol, 1800 g / mol, 1900 g / mol, 2000 g / mol, 2100 g / mol, 2200 g / mol, 2300 g / mol, 2400 g / mol, 2500 g / mol, or within any two of the above values.

[0045] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the polyisobutylene has a melt index of 10-30 g / 10 min at 200°C and 2.16 kg.

[0046] For example, the melt index of the polyisobutylene at 200°C and 2.16 kg can be 10 g / 10 min, 11 g / 10 min, 12 g / 10 min, 13 g / 10 min, 14 g / 10 min, 15 g / 10 min, 16 g / 10 min, 17 g / 10 min, 18 g / 10 min, 19 g / 10 min, 20 g / 10 min, 21 g / 10 min, 22 g / 10 min, 23 g / 10 min, 24 g / 10 min, 25 g / 10 min, 26 g / 10 min, 27 g / 10 min, 28 g / 10 min, 29 g / 10 min, 30 g / 10 min, or within any two of the above values.

[0047] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the styrene-acrylonitrile copolymer has a weight-average molecular weight of 150,000-200,000 g / mol.

[0048] For example, the weight-average molecular weight of the styrene-acrylonitrile copolymer may be 150,000 g / mol, 155,000 g / mol, 160,000 g / mol, 165,000 g / mol, 170,000 g / mol, 175,000 g / mol, 180,000 g / mol, 185,000 g / mol, 190,000 g / mol, 195,000 g / mol, 200,000 g / mol, or within the range of any two of the above values.

[0049] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, the styrene-acrylonitrile copolymer has a melt index of 1-10 g / 10 min at 220°C and 10 kg.

[0050] For example, the melt index of the styrene-acrylonitrile copolymer at 220°C and 10 kg can be 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, 10 g / 10 min, or within any two of the above values.

[0051] As a preferred embodiment of the additive for mixing insulating oil according to the present invention, component B comprises polyisobutylene and styrene-acrylonitrile copolymer in a mass ratio of (2.5-5):(0-2.5).

[0052] For example, component B may include 2.5 parts polyisobutylene, 2.6 parts polyisobutylene, 2.7 parts polyisobutylene, 2.8 parts polyisobutylene, 2.9 parts polyisobutylene, 3 parts polyisobutylene, 3.1 parts polyisobutylene, 3.2 parts polyisobutylene, 3.3 parts polyisobutylene, 3.4 parts polyisobutylene, 3.5 parts polyisobutylene, 3.6 parts polyisobutylene, 3.7 parts polyisobutylene, 3.8 parts polyisobutylene, 3.9 parts polyisobutylene, 4 parts polyisobutylene, 4.1 parts polyisobutylene, 4.2 parts polyisobutylene, 4.3 parts polyisobutylene, 4.4 parts polyisobutylene, 4.5 parts polyisobutylene, 4.6 parts polyisobutylene, 4.7 parts polyisobutylene, 4.8 parts polyisobutylene, 4.9 parts polyisobutylene, and 5 parts polyisobutylene, or... Polyisobutylene and styrene-acrylonitrile copolymers with a mass ratio of 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, and 3.4:1 (by mass ratio) are used in the following copolymers: Polyisobutylene and styrene-acrylonitrile copolymers in a mass ratio of 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4:1, 4.1:1, 4.2:1, and 4.3:1 respectively. The following copolymers have a mass ratio of 4.4:1:polyisobutylene-styrene-acrylonitrile (POI), 4.5:1:POI), 4.6:1:POI), 4.7:1:POI), 4.8:1:POI), 4.9:1:POI), 5:1:POI), 2.5:1.5:POI), 2.6:1.5:POI), and 2.7:1:POI).The following are the copolymers of polyisobutylene and styrene-acrylonitrile in a mass ratio of 5:1:5:2.8:1.5:2.9:1.5:3.1:1.5:3.2:1.5:3.3:1.5:3.4:1.5:3.5:1.5:3.6 ...5:1.5:3.6:1:3.5:1.5:3.6:1:3.5:1.5:3.6:1:3.5:1.5:3.6:1:3.5:1:3.5:1.5:3.6:1:3.5:1:3.5:1:3.6:1:3.5:1:3.5:1:3.6:1:3.5:1:3.5:1:3.6:1:3.5:1:3.5:1:3.5:1 The following are examples of polyisobutylene and styrene-acrylonitrile copolymers with mass ratios of 3.5:1:5, 3.7:1.5, 3.8:1.5, 3.9:1.5, 4:1.5, 4.1:1.5, 4.2:1.5, 4.3:1.5, 4.4:1.5, and 4.5:1.5. Polyisobutylene and styrene-acrylonitrile copolymers with a mass ratio of 0.5:1.5, 4.6:1.5, 4.7:1.5, 4.8:1.5, 4.9:1.5, 5:1.5, 2.5:2, 2.6:2, 2.7:2, and 2.8:2 are mentioned in the original text. Polyisobutylene and styrene-acrylonitrile copolymers in a mass ratio of 2.9:2, 3:2, 3.1:2, 3.2:2, 3.3:2, 3.4:2, 3.5:2, 3.6:2, 3.7:2, and 3.The following are the copolymers with a mass ratio of 8:2 (polyisobutylene and styrene-acrylonitrile), 3.9:2 (polyisobutylene and styrene-acrylonitrile), 4:2 (polyisobutylene and styrene-acrylonitrile), 4.1:2 (polyisobutylene and styrene-acrylonitrile), 4.2:2 (polyisobutylene and styrene-acrylonitrile), 4.3:2 (polyisobutylene and styrene-acrylonitrile), 4.4:2 (polyisobutylene and styrene-acrylonitrile), 4.5:2 (polyisobutylene and styrene-acrylonitrile), 4.6:2 (polyisobutylene and styrene-acrylonitrile), and 4.7:2 (polyisobutylene and styrene-acrylonitrile). - Acrylonitrile copolymer, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 4.8:2, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 4.9:2, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 5:2, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 2.5:2.5, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 2.6:2.5, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 2.7:2.5, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 2.8:2.5, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 2.9:2.5, polyisobutylene and styrene-acrylonitrile copolymer with a mass ratio of 3:2.5 The following are examples of copolymers containing polyisobutylene and styrene-acrylonitrile in a mass ratio of 3.1:2.5: 3.2:2.5: 3.3:2.5: 3.4:2.5: 3.5:2.5: 3.6:2.5: 3.7:2.5: 3.8:2.5: 3.9:2.5: 3.9:2.5: 3.1:2.5: 3.1:2.5: 3.1:2.5: 3.1:2.5: 3.1:2.5: 3.2 ... Polyisobutylene and styrene-acrylonitrile copolymers in a mass ratio of 4:2.5, 4.1:2.5, 4.2:2.5, 4.3:2.5, 4.4:2.5, 4.5:2.5, 4.6:2.5, 4.7:2.5, and 4.8:2.5.A 5:5 mass ratio of polyisobutylene to styrene-acrylonitrile copolymer, a polyisobutylene to styrene-acrylonitrile copolymer with a mass ratio of 4.9:2.5, and a polyisobutylene to styrene-acrylonitrile copolymer with a mass ratio of 5:2.5.

[0053] II. Mixed insulating oil The present invention also protects the use of the above-mentioned additives for use in mixed insulating oils, the mixed insulating oils including mineral oils and ester-based insulating oils.

[0054] As a preferred embodiment of the application described in this invention, the mineral oil includes No. 25 transformer oil (compliant with GB2536-90), and the ester insulating oil includes at least one of synthetic ester insulating oil and natural ester insulating oil.

[0055] As a preferred embodiment of the application described in this invention, the synthetic ester insulating oil includes pentaerythritol ester insulating oil.

[0056] As a preferred embodiment of the application described in this invention, the natural ester insulating oil includes glyceryl triester insulating oil.

[0057] As a preferred embodiment of the application described in this invention, the mixed insulating oil comprises mineral oil and ester insulating oil in a mass ratio of (1-5):(95-99).

[0058] For example, the mass ratio of mineral oil to ester insulating oil in the mixed insulating oil can be 1:95, 1:96, 1:97, 1:98, 1:99, 2:95, 2:96, 2:97, 2:98, 2:99, 3:95, 3:96, 3:97, 3:98, 3:99, 4:95, 4:96, 4:97, 4:98, 4:99, 5:95, 5:96, 5:97, 5:98, 5:99, or within the range of any two of the above values.

[0059] As a preferred embodiment of the application described in this invention, the additive for mixing insulating oil has a mass ratio of (0.1-1):100 with the mixed insulating oil.

[0060] For example, the mass ratio of the additive used to mix the insulating oil to the mixed insulating oil can be 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.35:100, 0.4:100, 0.45:100, 0.5:100, 0.55:100, 0.6:100, 0.65:100, 0.7:100, 0.75:100, 0.8:100, 0.85:100, 0.9:100, 0.95:100, 1:100, or within any two of the above values.

[0061] III. Examples The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way.

[0062] Unless otherwise specified, all reagents, materials, and instruments used in the following examples and comparative examples are commercially available. Furthermore, unless otherwise specified, "parts" and "%" refer to mass measurements.

[0063] The raw material information used in some of the embodiments and comparative examples is as follows: Transformer oil No. 25: purchased from Shell.

[0064] Pentaerythritol ester insulating oil: MIDEL 7131 synthetic ester insulating oil.

[0065] Glyceryl triester insulating oil: Cargill FR3 natural ester insulating oil.

[0066] Polymethyl methacrylate-1: Polymethyl methacrylate, weight average molecular weight 35000 g / mol, melt index 10 g / 10 min at 190℃ and 2.16 kg. Purchased from Aladdin, grade P742581.

[0067] Polymethacrylate-2: Polypropyl methacrylate, weight average molecular weight 35000 g / mol, melt index 10 g / 10 min at 190℃ and 2.16 kg. Purchased from Aladdin, grade P477445.

[0068] Polymethyl methacrylate-3: Polymethyl methacrylate, weight average molecular weight 50,000 g / mol, melt index 15 g / 10 min at 190℃ and 2.16 kg. Purchased from Aladdin, grade P434524.

[0069] Polymethyl methacrylate-4: Polymethyl methacrylate, weight average molecular weight 120,000 g / mol, melt index 2 g / 10 min at 190℃ and 2.16 kg. Purchased from Aladdin, grade P434521.

[0070] Polymethyl methacrylate-5: Polymethyl methacrylate, weight average molecular weight 10000 g / mol, melt index 20 g / 10 min at 190℃ and 2.16 kg. Purchased from Aladdin, grade P141443.

[0071] Polyisobutylene-1: weight-average molecular weight 2400 g / mol, melt index 20 g / 10 min at 200℃ and 2.16 kg. Purchased from Aladdin, grade P304883.

[0072] Polyisobutylene-2: weight-average molecular weight 1300 g / mol, melt index 15 g / 10 min at 200℃ and 2.16 kg. Purchased from Aladdin, grade P304882.

[0073] Polyisobutylene-3: weight-average molecular weight ~300 g / mol, melt index of 35 g / 10 min at 200℃ and 2.16 kg. Purchased from Puyang Hengtai Petrochemical Co., Ltd., grade HT-03.

[0074] Polyisobutylene-4: weight-average molecular weight 6700 g / mol, melt index 5 g / 10 min at 200℃ and 2.16 kg. Purchased from Shanghai Zhenzhun Biotechnology Co., Ltd., brand name PIB6000.

[0075] Styrene-acrylonitrile copolymer-1: prepared by copolymerization of 75 wt% styrene and 25 wt% acrylonitrile, with a weight-average molecular weight of 165,000 g / mol and a melt index of 8 g / 10 min at 220℃ and 10 kg. Purchased from Aladdin, grade P434451.

[0076] Styrene-acrylonitrile copolymer-2: prepared by copolymerization of 70 wt% styrene and 30 wt% acrylonitrile, with a weight-average molecular weight of 185,000 g / mol and a melt index of 1 g / 10 min at 220℃ and 10 kg. Purchased from Aladdin, grade P434452.

[0077] Polyisoprene-grafted-maleic anhydride: weight-average molecular weight 25000 g / mol, melt index 10 g / 10 min at 190℃ and 2.16 kg. Purchased from Aladdin, grade P478273.

[0078] Ethylene-vinyl acetate copolymer: weight average molecular weight 35000 g / mol, melt index 18 g / 10 min at 190℃ and 2.16 kg. Purchased from Aladdin, grade P301636.

[0079] Polyisoprene: weight-average molecular weight 38,000 g / mol, melt index 10 g / 10 min at 200℃ and 5.0 kg. Purchased from Aladdin, grade P485890.

[0080] Ethylene alcohol-ethylene copolymer: weight average molecular weight 3000 g / mol, melt index 1.6 g / 10 min at 190℃ and 2.16 kg. Purchased from Kuraray Co., Ltd., grade EVAL F101.

[0081] Examples 1-6 and Comparative Examples 1-2 This embodiment and comparative example provide a series of additives for mixing insulating oils, and the specific component mass parts are shown in Table 1.

[0082] Table 1. Example 7 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polymethacrylate-1 with an equal mass of polymethacrylate-2.

[0083] Example 8 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polymethacrylate-1 with an equal mass of polymethacrylate-3.

[0084] Example 9 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polymethacrylate-1 with an equal mass of polymethacrylate-4.

[0085] Example 10 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polymethacrylate-1 with an equal mass of polymethacrylate-5.

[0086] Example 11 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polyisobutylene-1 with an equal mass of polyisobutylene-2.

[0087] Example 12 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polyisobutylene-1 with an equal mass of polyisobutylene-3.

[0088] Example 13 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polyisobutylene-1 with an equal mass of polyisobutylene-4.

[0089] Example 14 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace styrene-acrylonitrile copolymer-1 with an equal mass of styrene-acrylonitrile copolymer-2.

[0090] Comparative Example 3 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polymethacrylate with an equal mass of polyisoprene-grafted-maleic anhydride.

[0091] Comparative Example 4 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polymethacrylate with an equal mass of ethylene-vinyl acetate copolymer.

[0092] Comparative Example 5 An additive for mixing insulating oils, which differs from Example 4 only in that: Replace polymethacrylate-1 with an equal mass of styrene-acrylonitrile copolymer-1.

[0093] Comparative Example 6 An additive for mixing insulating oils, which differs from Example 5 only in that: Replace polymethacrylate-1 with an equal mass of polyisobutylene-1.

[0094] Comparative Example 7 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace polyisobutylene with an equal mass of polyisoprene.

[0095] Comparative Example 8 An additive for mixing insulating oils, which differs from Example 1 only in that: Replace the styrene-acrylonitrile copolymer with an equal mass of ethylene alcohol-ethylene copolymer.

[0096] Performance testing I. Basic Effect Test of Additives: Insulating oil sample preparation: The additives obtained from the examples and comparative examples were mixed with the mixed insulating oil at a mass ratio of 0.7:100. The mixed insulating oil contained 97 wt% MIDEL 7131 synthetic ester insulating oil and 3 wt% No. 25 mineral oil.

[0097] Flash point test: According to GB / T 261-2021 "Determination of flash point - Binski-Martin closed cup method", the insulating oil is heated in a closed container, and a mixture of oil gas and air is formed above the oil surface. The mixture is then brought into contact with an open flame, and the lowest temperature at which a flash (instantaneous combustion) first occurs is the flash point.

[0098] Acid value test: Tested according to GB / T 264-1983.

[0099] Dielectric loss test: Tested according to IEC60247 at a temperature of 90℃.

[0100] The results of the above performance tests are shown in Table 2 below: Table 2. According to Table 2 above, the additive for mixed insulating oil provided by the present invention can improve the flash point of the insulating oil without affecting its insulating function. The acid value of the mixed insulating oil after adding the additive is ≤0.04mg KOH / g, the dielectric loss is ≤0.004%, and the flash point is increased to above 251℃.

[0101] According to Examples 1-5, when component B contains both polyisobutylene and styrene-acrylonitrile copolymer, it has a better effect on improving the flash point of insulating oil.

[0102] According to Examples 7-14, the selection of components with appropriate molecular weights is beneficial to further improve the flash point of the insulating oil.

[0103] According to Comparative Examples 1-2, an inappropriate ratio of components A and B will lead to a decrease in flash point, affecting the safety of the resulting insulating oil during use.

[0104] According to Comparative Examples 3-8, if the selected components are not suitable, or if only component B is added, the flash point cannot be effectively increased.

[0105] II. Exploration of Applicable Systems for Additives The additives provided by this invention were added to different mixed insulating oil systems in different amounts to investigate the effect of the addition amount on the flash point and its effect on improving the flash point of different mixed insulating oil systems, as shown in Examples 1-5.

[0106] Example of an effect 1. The additive obtained in Example 1 was mixed with a mixed insulating oil at a mass ratio of 0.7:100. The mixed insulating oil contained 97 wt% MIDEL 7131 synthetic ester insulating oil and 3 wt% No. 25 mineral oil.

[0107] Example of effect 2. The additive obtained in Example 1 was mixed with a mixed insulating oil at a mass ratio of 0.7:100, wherein the mixed insulating oil contained 97 wt% Cargill FR3 natural ester insulating oil and 3 wt% No. 25 mineral oil.

[0108] Example of an effect 3. The additive obtained in Example 1 was mixed with a mixed insulating oil at a mass ratio of 0.7:100. The mixed insulating oil contained 99 wt% MIDEL 7131 synthetic ester insulating oil and 1 wt% No. 25 mineral oil.

[0109] Example of an effect 4. The additive obtained in Example 1 was mixed with a mixed insulating oil at a mass ratio of 0.7:100, wherein the mixed insulating oil contained 90 wt% MIDEL 7131 synthetic ester insulating oil and 10 wt% No. 25 mineral oil.

[0110] Example of an effect: 5. The additive obtained in Example 1 was mixed with a mixed insulating oil at a mass ratio of 1.2:100. The mixed insulating oil contained 97 wt% MIDEL 7131 synthetic ester insulating oil and 3 wt% No. 25 mineral oil.

[0111] The flash point of the insulating oil obtained in the above example was tested according to Part 1, and the results are shown in Table 3 below: Table 3. As can be seen from Table 3 above, the additive provided by the present invention has an excellent effect on increasing the flash point of ester insulating oil mixed with a small proportion of mineral oil, and can increase the flash point of the insulating oil to above 260°C.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An additive for mixing insulating oils, characterized in that, The components include the following parts by weight: Component A 1-2 parts, Component B 1 part; Component A includes polymethacrylate, and component B includes at least one of polyisobutylene and styrene-acrylonitrile copolymer.

2. The additive for mixing insulating oil as described in claim 1, characterized in that, Includes at least one of the following (1)-(2): (1) The polymethacrylate includes polymethyl methacrylate; (2) The styrene-acrylonitrile copolymer is prepared by copolymerizing 70-80 wt% styrene and 20-30 wt% acrylonitrile.

3. The additive for mixing insulating oil as described in claim 1 or 2, characterized in that, Includes at least one of the following (1)-(2): (1) The weight-average molecular weight of the polymethacrylate is 20,000-100,000 g / mol; (2) The melt index of the polymethacrylate at 190℃ and 2.16kg is 5-15 g / 10 min.

4. The additive for mixing insulating oil as described in claim 1, characterized in that, Includes at least one of the following (1)-(2): (1) The weight-average molecular weight of the polyisobutylene is 1000-2500 g / mol; (2) The melt index of the polyisobutylene at 200℃ and 2.16kg is 10-30 g / 10 min.

5. The additive for mixing insulating oil as described in claim 1 or 2, characterized in that, Includes at least one of the following (1)-(2): (1) The weight-average molecular weight of the styrene-acrylonitrile copolymer is 150,000-200,000 g / mol; (2) The melt index of the styrene-acrylonitrile copolymer at 220℃ and 10kg is 1-10 g / 10 min.

6. The additive for mixing insulating oil as described in claim 1, characterized in that, Component B includes polyisobutylene and styrene-acrylonitrile copolymer in a mass ratio of (2.5-5):(0-2.5).

7. The use of the additive for mixed insulating oil according to any one of claims 1-6 in mixed insulating oil, characterized in that, The mixed insulating oil includes mineral oil and ester-based insulating oil.

8. The application as described in claim 7, characterized in that, The mineral oil includes No. 25 transformer oil, and the ester insulating oil includes at least one of synthetic ester insulating oil and natural ester insulating oil.

9. The application as described in claim 8, characterized in that, The mixed insulating oil comprises mineral oil and ester insulating oil in a mass ratio of (1-5):(95-99).

10. The application as described in claim 7, characterized in that, The additive used for mixing insulating oil has a mass ratio of (0.1-1):100 with the mixed insulating oil.

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