CN110194918B

CN110194918B - Modified epoxy organic silicon high-thermal-conductivity insulating impregnating varnish and preparation method thereof

Info

Publication number: CN110194918B
Application number: CN201910558993.7A
Authority: CN
Inventors: 景录如; 刘晨; 吴斌; 张春琪; 崔益华; 许红雨; 张明玉
Original assignee: Oubang Science And Technology Suzhou Co ltd; Suzhou Taihu Electric Advanced Material Co ltd
Current assignee: Oubang Science And Technology Suzhou Co ltd; Suzhou Taihu Electric Advanced Material Co ltd
Priority date: 2019-06-26
Filing date: 2019-06-26
Publication date: 2020-07-03
Anticipated expiration: 2039-06-26
Also published as: CN111548699A; CN110194918A; CN111548699B; WO2020258620A1

Abstract

The invention discloses an insulating impregnating varnish and a preparation method thereof, wherein the insulating impregnating varnish comprises matrix resin, a diluent and a curing agent, the matrix resin is prepared by condensation reaction of modified epoxy resin and organic silanol with silicon hydroxyl, raw materials of the modified epoxy resin comprise epoxy resin, a vinyl monomer containing ester group and a hydrophobic hexagonal boron nitride nanosheet containing vinyl, the modified epoxy resin is prepared by polymerization reaction of the epoxy resin and the rest raw materials, and the boron nitride nanosheet is prepared by adopting a specific method: carrying out surface hydroxyl modification and freeze-thaw expansion treatment, and then carrying out boron nitride stripping and esterification modification catalysis by combining a specific compound one-pot method; preparation: mixing and stirring matrix resin, a diluent and a curing agent to obtain the resin; the insulating impregnating varnish disclosed by the invention has the advantages of stable product quality in batches during preparation and the like on the basis of high heat conductivity coefficient, low dielectric loss, high and low temperature impact resistance, good bonding strength, good permeability, high electric field strength and higher mechanical strength.

Description

Modified epoxy organic silicon high-thermal-conductivity insulating impregnating varnish and preparation method thereof

Technical Field

The invention belongs to the technical field of polymer composite materials and electricians, and particularly relates to a modified epoxy organic silicon high-thermal-conductivity insulating impregnating varnish and a preparation method thereof.

Background

The insulating impregnating varnish is mainly applied to the insulating impregnating treatment of motors, transformers and scattered-reactance winding coils, is used for filling gaps between coils and gaps between the coils and surrounding objects (such as iron cores, interlayer insulating filler strips, heat-shrinkable sleeves and the like), is used for bonding coil leads with leads and other objects, mainly plays a role in electrical insulation and bonding forming, improves the mechanical property, the electrical strength, the protective property and the like of the coils, and can also be used as an impregnating, coating or packaging material of electronic components.

Along with the development of large capacity, miniaturization and high efficiency of devices such as motor electrical appliances, the heat dissipation capacity of each part of the motor, particularly an insulating part, directly influences the temperature rise of the motor, if the temperature rise of the motor exceeds a limit value, insulation aging, coil breakdown and motor burnout can be caused, and if the insulation impregnating varnish has high heat-conducting performance and electrical insulation performance at the same time, the temperature rise of a motor winding can be effectively reduced, so that the volume of the motor is reduced, and the output force of the motor can be increased. In addition, with the rapid development of the current microelectronic integration technology and high-density assembly technology, whether heat can be dissipated in time in the working process of electronic components becomes a key limiting factor influencing the normal work and the service life of the electronic components, and the heat-conducting insulating impregnating varnish (resin) with high reliability, good heat dissipation and other excellent comprehensive properties is used as a coating or packaging material of a thermal interface to rapidly dissipate heat generated in the working process of the components so as to ensure the normal operation of electronic equipment. The development of a novel high-thermal-conductivity insulating material solves the problem of structural heat dissipation, and the improvement of the thermal conductivity of an insulating layer in a motor is one of important measures for improving the insulation of the motor and reducing the loss, which is one of the research hotspots of electric insulating materials in various countries in the world, but the existing insulating impregnating varnish has some problems more or less.

For example, chinese invention patent CN 101381583B discloses a high thermal conductivity silicone impregnating varnish, which is prepared by mixing three aluminum nitride powder bodies with different average particle sizes, high thermal conductivity and high insulation properties to prepare a mixed aluminum nitride powder filler, adding the mixed aluminum nitride powder filler into an organic silicone prepolymer, adding a catalyst and a curing agent, and performing conventional ball milling and mixing uniformly, wherein the particle size of the thermal conductive filler is 5-20 μm, and the use amount is more than 20%; also, for example, chinese patent CN 101864145A discloses a high thermal conductivity insulating impregnating resin for an air reactor and a preparation method thereof, the impregnating resin is prepared by stirring and heating inorganic powders such as epoxy resin, toughening agent, curing accelerator, silica micropowder, alumina powder, sericite powder and the like to 60-75 ℃ and then carrying out vacuum defoamation, and the usage amount of the thermal conductive filler is up to more than 45%; although the thermal conductivity coefficient of the insulating paint can reach 0.386-0.502W/(m.k) and 0.35-0.90W/(m.K) respectively, the mechanical property is influenced, the viscosity is greatly influenced, the permeability of the impregnating paint is reduced, the flowability is poor, the forming of an air-gap-free integral insulating structure is not facilitated, and the impregnating treatment is not facilitated; for another example, chinese patent CN102295878A discloses a filled heat-conducting insulating impregnating varnish, which is prepared by using surface-functionalized inorganic powder with high heat conductivity and high insulating property as a filler (specifically silane modification), adding the filler into modified epoxy resin, adding a dispersant, a peroxide initiator and an active diluent, and mixing, wherein although the heat conductivity of the heat-conducting impregnating varnish is greatly improved to 0.31-0.5W/(m · K), the heat-conducting impregnating varnish has non-uniform dispersion with a high probability during practical application, and has settlement phenomenon, nanoparticle aggregation, unstable product quality among batches, and influences the heat-conducting efficiency and the electromechanical properties of the product.

Meanwhile, the high-thermal-conductivity insulating impregnating varnish or resin is required to be applied to large and medium-sized high-voltage generator insulating systems or electronic components, so that not only is the thermal conductivity coefficient increased, but also low dielectric loss, high electric field strength, excellent toughness, high and low temperature impact resistance, good bonding strength and the like are required, and in addition, good permeability is required, and the conventional impregnating varnish is difficult to simultaneously meet the requirements.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an improved insulating impregnating varnish which has the advantages of stable product quality in batch preparation and the like on the basis of high heat conductivity coefficient, low dielectric loss, high and low temperature impact resistance, good bonding strength, good permeability, high electric field strength and higher mechanical strength.

The invention also provides a preparation method of the insulating impregnating varnish.

In order to solve the technical problems, the invention adopts the following technical scheme: the insulating impregnating varnish comprises a matrix resin, a diluent and a curing agent, wherein the matrix resin is prepared by condensation reaction of a modified epoxy resin and an organic silanol with a silicon hydroxyl group, raw materials of the modified epoxy resin comprise an epoxy resin, a vinyl monomer containing an ester group and a hydrophobic hexagonal boron nitride nanosheet containing a vinyl group, and the modified epoxy resin is prepared by polymerization reaction of the epoxy resin and the rest raw materials; the hydrophobic hexagonal boron nitride nanosheet containing the vinyl group is prepared by the following method:

(1) carrying out surface hydroxylation modification on the hexagonal boron nitride to prepare hydroxylated hexagonal boron nitride;

(2) carrying out freeze-thaw expansion treatment on the hydroxylated hexagonal boron nitride prepared in the step (1) to prepare expanded hydroxylated hexagonal boron nitride;

(3) mixing and stirring the expanded hydroxylated hexagonal boron nitride prepared in the step (2) and a compound shown in a formula (I) in a first solvent to obtain a first mixed solution, adding an unsaturated acid and/or unsaturated anhydride and a second solvent into the obtained first mixed solution, and reacting to prepare the hydrophobic hexagonal boron nitride nanosheet containing the vinyl group;

wherein R is₀Is C_1-6Alkyl group of (1).

According to some preferred aspects of the present invention, the ester group-containing vinyl monomer is a combination of one or more selected from compounds represented by formula (ii):

in the formula, R₁Is C_1-10Alkyl of R₂、R₃Are each independently hydrogen or C_1-10Alkyl groups of (a); c_1-10The alkyl group of (a) includes methyl, ethyl, propyl, isopropyl, butyl, pentyl, isopentyl, neopentyl, hexyl and the like.

According to some particular aspects of the invention, in formula (II), R₂And R₃At least one of which is hydrogen.

More preferably, the ester group-containing vinyl monomer is at least two selected from the group consisting of compounds represented by formula (ii). According to a particular aspect of the invention, the vinyl monomer containing an ester group is a combination of methyl Methacrylate (MAA) and Butyl Acrylate (BA).

According to some preferred aspects of the present invention, the epoxy resin is a bisphenol type epoxy resin.

According to some preferred and specific aspects of the present invention, the bisphenol type epoxy resin is a combination of one or more selected from compounds represented by formula (iii):

in the formula: r₄is-C (CH)₃)₂-、-CH₂-or-S (O)₂N is an integer selected from 0 to 10, i.e. n can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. According to a particular aspect of the invention, the epoxy resin is epoxy E-51 and/or epoxy E-44.

According to some preferred aspects of the present invention, in the process of preparing the hydrophobic hexagonal boron nitride nanosheets containing vinyl groups, the epoxy resin, the hydrophobic hexagonal boron nitride nanosheets containing vinyl groups, and the vinyl monomer containing ester groups are fed in a mass ratio of 1: 0.05-0.1: 0.15-0.4. More preferably, the feeding mass ratio of the epoxy resin, the hydrophobic hexagonal boron nitride nanosheets containing vinyl groups and the vinyl monomer containing ester groups is 1: 0.05-0.085: 0.18-0.32.

According to some preferred aspects of the present invention, the polymerization reaction is conducted at a temperature of 100 ℃ and 120 ℃. More preferably, the polymerization reaction is carried out at a temperature of 105 ℃ and 115 ℃.

According to some specific aspects of the present invention, in step (1), the hydroxylated hexagonal boron nitride is prepared by: mixing hexagonal boron nitride with a sodium hydroxide aqueous solution, and stirring and reacting at the temperature of 90-150 ℃ to prepare the boron nitride-based catalyst.

In some embodiments of the present invention, in step (1), the hexagonal boron nitride is obtained from a commercially available product with a purity of 99% or more and a particle size of about 2 to 5 μm.

According to some specific and preferred aspects of the present invention, in the step (1), the temperature is achieved by means of heating by an oil bath.

According to some specific aspects of the invention, in the step (1), after the stirring reaction, a step of washing with distilled water is further included until the washing is neutral, and drying is performed to obtain the hydroxylated hexagonal boron nitride.

According to some preferred aspects of the present invention, in step (2), the freeze-thaw expansion process is operated in the following manner: preparing the hydroxylated hexagonal boron nitride prepared in the step (1) into an aqueous solution, freezing the obtained aqueous solution at a first set temperature, then unfreezing the aqueous solution to a second set temperature, and circularly freezing and unfreezing the aqueous solution for multiple times to prepare the expanded hydroxylated hexagonal boron nitride; wherein the first set temperature is-50 to-5 ℃, and the second set temperature is 10 to 30 ℃. More preferably, the first set temperature is-45 to-15 ℃, and the second set temperature is 18 to 28 ℃.

According to some specific aspects of the invention, in the step (2), the mass fraction of the aqueous solution is 5-20%.

According to some specific aspects of the invention, in the step (2), the freezing time is 1-8 h.

According to some specific aspects of the present invention, in the step (2), the number of the cycles is 4 to 12.

According to some specific and preferred aspects of the present invention, in step (3), R is as described in formula (I)₀And may be methyl, ethyl, propyl, butyl or pentyl.

According to some preferred aspects of the present invention, in the step (3), the mixing and stirring are performed at a temperature of 60 to 78 ℃. More preferably, in the step (3), the mixing and stirring are carried out at a temperature of 65 to 75 ℃. In some embodiments of the present invention, the mixing and stirring may be performed by using ultrasonic waves, and the mixing and stirring may be performed under water bath heating to control the temperature.

According to some preferred aspects of the present invention, in the step (3), the reaction occurring in the second solvent is performed at a temperature of 80 to 120 ℃ in the presence of an inert gas. More preferably, in the step (3), the reaction in the second solvent is performed at a temperature of 85 to 115 ℃. Wherein the inert gas comprises nitrogen, argon and the like.

According to some preferred aspects of the present invention, in the step (3), the mixing and stirring are controlled to be performed in an anhydrous environment. In some embodiments of the present invention, the raw materials and the moisture in the environment can be separated by refluxing and water separation, so that the mixing and stirring can be carried out in a water-free environment.

According to some preferred aspects of the invention, in the step (3), the feeding mass ratio of the compound shown in the formula (I) to the expanded hydroxylated hexagonal boron nitride is 6-12: 1.

According to some preferred aspects of the invention, the feeding mass ratio of the unsaturated acid and/or unsaturated anhydride to the expanded hydroxylated hexagonal boron nitride is 0.05-0.5: 1.

According to some preferred aspects of the invention, the first solvent is cyclohexane and the second solvent is ethyl acetate.

According to some preferred aspects of the invention, the unsaturated acid is linoleic acid and/or methacrylic acid and the unsaturated anhydride is itaconic anhydride and/or maleic anhydride.

The method for preparing the hydrophobic hexagonal boron nitride nanosheet containing the vinyl is different from the prior art, the stripping and hydrophobic modification of the boron nitride nanosheet can be carried out in one pot without separating an intermediate, the compound shown in the formula (I) can be reused, the high yield of the hydrophobic hexagonal boron nitride nanosheet containing the vinyl is realized, the modification is thorough, almost no unmodified boron nitride nanosheet exists, and further the industrial batch production can be realized.

According to some preferred aspects of the present invention, in preparing the base resin, the charge mass ratio of the modified epoxy resin to the silicone alcohol having a silicon hydroxyl group is 1: 0.15-0.35. More preferably, in the preparation of the matrix resin, the charging mass ratio of the modified epoxy resin to the organic silanol having a silicon hydroxyl group is 1: 0.20-0.35.

According to some preferred aspects of the invention, the condensation reaction is carried out in the presence of a catalyst at 120-180 ℃ and the mass ratio of the catalyst to the modified epoxy resin is 0.005-0.015: 1.

According to some preferred aspects of the invention, the catalyst is cobalt naphthenate.

In some preferred embodiments of the present invention, the matrix resin is prepared by the following method: adding the modified epoxy resin and the xylene solution of the organic silanol into a reactor, slowly heating to 140-160 ℃, carrying out reflux reaction for 45min, gradually removing the solvent until the solid content reaches 80-88%, adding a catalyst, continuing to carry out water diversion and reflux reaction until the viscosity reaches 80-100sec (coating a 4# cup, 25 ℃), cooling to 110-130 ℃, removing the solvent in the reaction system through reduced pressure distillation, and filtering to obtain the matrix resin.

According to some particular aspects of the invention, the mass fraction of the organosilanol in the xylene solution of organosilanols is between 40 and 60%. According to a particular aspect of the invention, the mass fraction of the organosilanol in the xylene solution of organosilanols is 50%.

According to some preferred aspects of the present invention, the organosilanol having a silicon hydroxyl group is a compound represented by the formula:

in the formula, e, f, g, h, i and q are respectively and independently numbers between 0 and 20, and e, h and i are not 0 at the same time, e, f and g are not 0 at the same time, g is 0 and q is not 0; r¹，R²，R³Independently methyl, vinyl or phenyl.

According to some preferred aspects of the present invention, in the above-mentioned structural formula of the silanol having a silicon hydroxyl group, the total number of moles of the phenyl group, the methyl group and the vinyl group connected to the Si atom is 1.30 to 1.70, and the proportion of the phenyl group to the total number of moles of the phenyl group, the methyl group and the vinyl group connected to the Si atom is 18 to 50%; the mass content of the vinyl in the organic silanol is 0.5-10%.

According to some preferred aspects of the present invention, the above-mentioned organosiliconate having a silicon hydroxyl group has a temperature index of 180 to 220 ℃ according to a secant method and a molecular weight of 500 to 8000 according to a GPC method.

According to some preferred and specific aspects of the present invention, the silanol having a silicon hydroxyl group is one or more selected from the group consisting of TH-1# (R/Si ═ 1.50, Ph/R ═ 0.43, Vi mass% ═ 4.1) of new electrical materials, suzhou taihu lake electrical materials, TH-2# (R/Si ═ 1.58, Ph/R ═ 0.35, Vi mass%: 0.6) of new electrical materials, suzhou taihu lake electrical materials, TH-3# (R/Si ═ 1.50, Ph/R ═ 0.35, Vi mass% 3.2) of new electrical materials, suzhou taihu lake electrical materials, each of which can be prepared according to the method of ZL 201310090271.6. In the above, R/Si represents the total number (molar number) of groups of methyl, phenyl and vinyl groups bonded to Si atoms in the silicon compound; the ratio (molar ratio) of phenyl groups to all (methyl, phenyl, vinyl) groups in the number of groups bonded to the Si atom is represented by Ph/R; the Vi mass fraction% represents the proportion (mass percentage) of vinyl groups in the silicon.

According to some specific aspects of the invention, the diluent is polypropylene glycol diglycidyl ether or neopentyl glycol diglycidyl ether or a combination of both.

According to some specific aspects of the invention, the curing agent is methyl tetrahydrophthalic anhydride or methyl hexahydrophthalic anhydride or a combination of both.

According to some preferred aspects of the present invention, in the insulating impregnating varnish, the charging mass ratio of the matrix resin, the diluent and the curing agent is 1: 0.05-0.25: 0.35-0.7. More preferably, in the insulating impregnating varnish, the mass ratio of the base resin, the diluent and the curing agent is 1: 0.05-0.20: 0.35-0.60.

The invention provides another technical scheme that: the preparation method of the insulating impregnating varnish comprises the following steps:

(a) preparing hydrophobic hexagonal boron nitride nanosheets containing vinyl;

(b) carrying out polymerization reaction on epoxy resin, the hydrophobic hexagonal boron nitride nanosheet containing the vinyl group prepared in the step (a) and the residual raw materials in a third solvent in the presence of an initiator to generate the modified epoxy resin;

(c) condensing the modified epoxy resin prepared in the step (b) with an organic silanol having a silicon hydroxyl group to prepare the matrix resin;

(d) and (c) mixing the matrix resin prepared in the step (c) with a diluent and a curing agent to prepare the insulating impregnating varnish.

According to some specific aspects of the invention, in step (b), the initiator is dibenzoyl peroxide (BPO).

According to some specific aspects of the invention, in step (b), the third solvent is n-butanol.

According to some specific aspects of the present invention, specific embodiments for preparing the modified epoxy resin are: (i) uniformly mixing epoxy resin, a third solvent and an initiator of 1/4, placing the mixture into a four-neck flask connected with a condensate pipe and nitrogen, adding the hydrophobic hexagonal boron nitride nanosheet containing the vinyl prepared in the step (a), and heating the mixture in an oil bath to 85-95 ℃ for 10-60min at constant temperature;

(ii) heating to about 100 ℃ and 120 ℃, simultaneously dropwise adding the ester group-containing vinyl monomer solution in which the 3/4 initiator is dissolved by using a constant-pressure dropping funnel, slowly dropwise adding, reacting for 3-4h under the condition of heat preservation after dropwise adding, and then distilling under reduced pressure to remove the third solvent (which can be recycled) to obtain the product.

According to some particular aspects of the invention, in step (d), the mixing is carried out at a temperature of 20-50 ℃; and/or, the mixing time is 30-60 min.

Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages:

according to the invention, the epoxy resin is modified through polymerization reaction by innovatively adopting an ester-containing vinyl monomer and a vinyl-containing hydrophobic hexagonal boron nitride nanosheet, so that the boron nitride nanosheet is in covalent bond connection with the epoxy resin, the addition amount of the vinyl-containing hydrophobic hexagonal boron nitride nanosheet is very small, and then the modified epoxy resin and the organic silanol with a silicon hydroxyl group are subjected to condensation reaction to prepare the specific matrix resin, so that the problems of difficult uniform dispersion and sedimentation caused by physical filling adopted for realizing high heat conduction of the conventional impregnating varnish are effectively solved, and the impregnating varnish has the advantages of stable product quality in batches during preparation and the like on the basis of high heat conductivity coefficient, low dielectric loss, high and low temperature impact resistance, good bonding strength, good permeability, high electric field strength and higher mechanical strength;

meanwhile, as the crude product of the modified boron nitride nanosheet obtained by modifying the boron nitride nanosheet in the prior art contains the unmodified boron nitride nanosheet and is difficult to realize effective separation, the modified boron nitride nanosheet directly obtained in the prior art is not ideal in performance in all aspects after epoxy resin is modified, the hydrophobic hexagonal boron nitride nanosheet containing the vinyl is prepared by adopting a specific method, specifically, surface hydroxyl modification and freeze-thaw expansion treatment are adopted, and then the catalysis of boron nitride stripping and esterification modification is carried out by combining a specific compound shown in the formula (I), so that on one hand, the stripping and hydrophobic modification by a one-pot method are realized, an intermediate is not required to be separated, on the other hand, the compound shown in the formula (I) can be repeatedly used, the yield is high, the cost is greatly saved, on the other hand, the purity of the crude product of the hydrophobic hexagonal boron nitride nanosheet containing the vinyl is high, almost no unmodified boron nitride or boron nitride nanosheets exist, and further the modified epoxy resin can be directly used in the preparation process of the modified epoxy resin, so that the properties of the matrix resin prepared after the modified epoxy resin is subjected to condensation reaction with organic silanol with silicon hydroxyl groups are not influenced, and the gain effect is realized.

Drawings

FIG. 1 is a Transmission Electron Micrograph (TEM) of vinyl-containing hydrophobic hexagonal boron nitride nanosheets prepared in example 3, with the left and right being at different magnifications;

FIG. 2 is an Atomic Force Microscope (AFM) image of hydrophobic hexagonal boron nitride nanoplates containing vinyl groups prepared in example 3;

fig. 3 is an XRD spectrum of the hydrophobic hexagonal boron nitride nanosheet containing vinyl group prepared in example 3.

Detailed Description

The present invention will be described in further detail with reference to specific examples. It is to be understood that these examples are for the purpose of illustrating the general principles, essential features and advantages of the present invention, and the present invention is not limited by the following examples. The implementation conditions used in the examples can be further adjusted according to specific requirements, and the implementation conditions not indicated are generally the conditions in routine experiments. The raw materials used in the examples are all commercially available commercial products. In the following examples, all starting materials are essentially obtained commercially or prepared by conventional methods in the art, unless otherwise specified.

Example 1

A compound of formula (Ia) (i.e. R in formula (I))₀Propyl) preparation: 15.8g (0.073mo1) of N-butylpyridinium bromide ([ bpy ] was weighed out]Br) and 8g (0.073mo1) (sodium tetrafluoroborate) NaBF₄Adding 100mL of acetone as a solvent into a plastic washing bottle, magnetically stirring, condensing and refluxing at room temperature, reacting for 12h, standing, performing vacuum filtration, discarding a white solid NaBr to obtain a pale yellow clear filtrate, adding 100mL of dichloromethane into the pale yellow clear filtrate, precipitating a white precipitate, performing vacuum filtration, concentrating the filtrate by rotary evaporation to remove acetone and dichloromethane in the filtrate, and collecting a yellow oily liquidVacuum drying at 60 deg.C for 8 hr to obtain compound [ bpy ] of formula (Ia)]BF₄13.8g, yield 85.2%;

example 2

A compound of formula (Ib) (i.e. R in formula (I))₀Methyl group): 28.2g (0.15mol) of bromo-N-ethylpyridine were added to a Erlenmeyer flask containing 50mL of acetone, and 16.5g (0.15mol) of NaBF was added₄Magnetically stirring for 10h at room temperature, filtering, performing rotary evaporation, removing volatile acetone, and vacuum drying to obtain white solid compound represented by formula (Ib) 25.16g, yield 86.5%, m.p.53.2-53.6 deg.C;

example 3

The embodiment provides a preparation method of modified epoxy resin and the modified epoxy resin prepared by the method, wherein the modified epoxy resin comprises the following raw materials: epoxy resin E-5180 g, hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl, methyl Methacrylate (MAA)13g and Butyl Acrylate (BA)7 g. The solvent adopted in the preparation process is 25g of third solvent, namely n-butanol, and the initiator is 4g of dibenzoyl peroxide (BPO).

The preparation method specifically comprises the following steps:

(a) preparing a hydrophobic hexagonal boron nitride nanosheet containing vinyl:

(1) the method for preparing the hydroxylated hexagonal boron nitride by carrying out surface hydroxylation modification on the hexagonal boron nitride comprises the following specific implementation modes: adding 50g of hexagonal boron nitride (hBN with the purity of more than or equal to 99 percent and the particle size of 2-5 microns) into a 1000ml three-mouth reaction bottle, then adding the hexagonal boron nitride into a prepared 5mol/L sodium hydroxide aqueous solution, mechanically stirring for 10 hours under the oil bath heating condition at about 100 ℃, washing the obtained mixture with distilled water for multiple times until the filtrate is neutral, and drying to obtain 49.5g of hydroxylated hexagonal boron nitride (hBN-OH);

(2) performing freeze-thaw expansion treatment on the hydroxylated hexagonal boron nitride prepared in the step (1) to prepare expanded hydroxylated hexagonal boron nitride, wherein the specific implementation mode is as follows: preparing a 10% distilled water solution from the hydroxylated hexagonal boron nitride (hBN-OH) product prepared in the step (1), freezing the distilled water solution in a freezer at the temperature of about-25 ℃ for 5 hours, then unfreezing the distilled water solution to room temperature, and performing freeze-thaw cycle for 6 times to obtain 49.1g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH), wherein the surface hydroxyl number of the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) is determined to be 0.0209 mmol/g;

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2) and 250mL of cyclohexane, putting the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) and the cyclohexane into 1000mL of three-neck flask with a stirrer and a reflux water separator, heating the three-neck flask to reflux, gradually removing water in a system by a refluxing solvent, cooling the temperature to 80 ℃ when no water is evaporated in the reflux water separator, adding 237g of the prepared compound shown in the formula (Ia), putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, carrying out ultrasonic stirring reaction for 24 hours, then adding 12g of linoleic acid and 50mL of ethyl acetate, introducing nitrogen, heating the mixture to 100 ℃ for 4 hours, cooling the mixture to 65 ℃, carrying out vacuum filtration, cleaning a filter cake twice by using a toluene/acetone (1:1 volume ratio) mixed solution, then carrying out filtration, adding the mixture into 500mL of a toluene/isopropanol mixed solution to form a micro-nano dispersion solution, centrifuging at a rotating speed of 8000r/min, taking the upper suspension, filtering, and drying (140 ℃) to obtain 14.4g of the hydrophobic hexagonal boron nitride nanosheet M-BNNSs (formula (IV-1)) containing vinyl, wherein the yield is 57.3%;

the yield is calculated as follows:

：m_M-BNNSsthe obtained hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl has the mass g; : w_P-BNOHIs the mass g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH); n is_P-BNOH: the surface hydroxyl content of the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) is mmol/g; m_ma: molecular weight of modifier (unsaturated acid or unsaturated anhydride), in this case linoleic acid: 280.44g/mol, based on the following examplesIn the same manner.

TEM images of the measured products As shown in FIGS. 1(a) (b) (c), TEM images of single exfoliated M-BNNSs were visible on the porous carbon mesh, exhibiting the transparent effect of single layer M-BNNSs, and showing the lateral dimension of 2-3 μ M, and superimposed images of crimp of few-layer M-BNNSs at the side, which was caused by the test environment at 200KV electron microscope and the number of clearly visible crimp of BNNS was 7, were measured using HRTEM (high definition Transmission Electron microscope) FIG. 1(d), demonstrating that single-layer or few-layer M-BNNSs were obtained by the present invention. As shown in fig. 2: a typical Atomic Force Microscope (AFM) image of M-BNNSs deposited on a mica substrate from an ethanol/water dispersion is shown, showing a flake height of 3nm, which also reveals the nature of the exfoliated M-BNNSs. The XRD patterns of the original hexagonal boron nitride and the hydrophobic hexagonal boron nitride nanosheets M-BNNSs containing the vinyl are measured, diffraction peaks (002), (100), (101), (102), (004), (104), (110) and (112) shown in the XRD contrast patterns are consistent with the standard peaks of the hexagonal boron nitride XRD, and the hydrophobic hexagonal boron nitride nanosheets containing the vinyl and obtained by stripping are also proved to be free of other impurities. In addition, we can see from the figure that the (002) peak is shifted to a small angle direction and the peak is relatively enhanced, which all indicate that the modified hexagonal boron nitride (002) face after exfoliation is more exposed and the face spacing becomes larger, indicating that boron nitride has been well exfoliated.

Cooling the filtrate subjected to vacuum filtration to below 25 ℃, standing and layering for 4h, and performing simple rotary evaporation treatment on the lower layer liquid (namely the compound shown in the formula (Ia)), so that the lower layer liquid can be used as a stripping agent and a catalyst for the next cycle again, thereby being repeatedly used; the upper layer after standing and layering is a mixed solvent and can be recycled after vacuum distillation treatment;

the structural formula of the formula (IV-1) is shown as follows, and only shows a schematic structure of covalent connection after one hydroxyl group on the boron nitride nanosheet reacts with linoleic acid, and other hydroxyl groups on the boron nitride nanosheet can also react with linoleic acid and then be covalently connected:

(b) preparation of modified epoxy resin

(b-1) uniformly mixing epoxy resin E-51, n-butanol and 1/4 BPO, placing the mixture in a four-neck flask connected with a condensate pipe and nitrogen, adding the hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl and shown in the formula (IV-1) and prepared, and heating the mixture in an oil bath to 90 ℃ for constant temperature for 30 min;

(b-2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 108g of modified epoxy resin (formula V-1), wherein the synthetic route is shown as follows:

x, y and z are independently integers between 1 and 25, and n is an integer selected from 0 to 10; specifically, the epoxy value of the above-mentioned E51 epoxy resin used is 0.51, and then the average molecular weight of this epoxy resin should be 200/0.51 ═ 392.16;

represents the average number of n, which is the same in the examples below when E51 epoxy resin is used;

the monomers MAA and BA and the hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl and shown in the formula (IV-1) prepared by the method can be copolymerized and polymerized, and the active site is grafted and copolymerized at one position only by way of example, so that the method can graft the hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl and shown in the formula (IV-1) onto an epoxy resin molecule in a copolymerization way, and hybrid toughening modification of epoxy by inorganic boron nitride is realized; meanwhile, the hydrophobic hexa-type vinyl-containing epoxy resin shown in formula (IV-1) in the modified epoxy resin shown in formula V-1Three nonsequential copolymerization of the boron nitride nanosheet, MAA and BA are grafted onto an epoxy resin matrix, the formula V-1 only provides an exemplary grafting mode, and likewise, the following embodiments all exemplarily provide schematic structures of the hydrophobic hexagonal boron nitride nanosheet containing the vinyl group and the modified epoxy resin.

Example 4

The embodiment provides a preparation method of modified epoxy resin and the modified epoxy resin prepared by the method, wherein the epoxy resin comprises the following raw materials: epoxy resin E-5180 g, hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl, methyl Methacrylate (MAA)13g and Butyl Acrylate (BA)7 g. In the preparation process, 25g of n-butanol serving as a third solvent is adopted, and 4g of dibenzoyl peroxide (BPO) serving as an initiator is adopted.

The preparation method specifically comprises the following steps:

(a) preparing a hydrophobic hexagonal boron nitride nanosheet containing vinyl:

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2) and 250mL of cyclohexane, putting the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) and the cyclohexane into 1000mL of three-neck flask with a stirrer and a reflux water separator, heating the three-neck flask to reflux, gradually removing water in a system by a refluxing solvent, cooling the temperature to 80 ℃ when no water is evaporated in the reflux water separator, adding 218g of the prepared compound shown in the formula (Ib), putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, carrying out ultrasonic stirring reaction for 24 hours, then adding 12g of linoleic acid and 50mL of ethyl acetate, introducing nitrogen, heating the mixture to 100 ℃ and carrying out reflux reaction for 4 hours, cooling the mixture to 65 ℃, carrying out vacuum filtration, cleaning a filter cake twice by using a toluene/acetone (1:1 volume ratio) mixed solution, then carrying out filtration, adding the mixture into 500mL of a toluene/isopropanol mixed solution to form a micro-nano dispersion solution, centrifuging at a rotating speed of 8000r/min, taking the upper suspension, filtering and drying (140 ℃) to obtain 14.5g of the hydrophobic hexagonal boron nitride nanosheet M-BNNSs formula (IV-1) containing vinyl, wherein the yield is 57.7%;

the structure only shows a schematic structure of covalent connection after one hydroxyl on the boron nitride nanosheet reacts with linoleic acid, and other hydroxyl on the boron nitride nanosheet can also react with linoleic acid and then be covalently connected;

(b) preparation of modified epoxy resin:

(b-2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under the condition of heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 108.1g of the modified epoxy resin.

Example 5

The embodiment provides a preparation method of modified epoxy resin and the modified epoxy resin prepared by the method, wherein the modified epoxy resin comprises the following raw materials: epoxy resin E-4485g, hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl, methyl Methacrylate (MAA)13g and Butyl Acrylate (BA)7 g. The solvent adopted in the preparation process is 25g of third solvent, namely n-butanol, and the initiator is 4g of dibenzoyl peroxide (BPO).

The preparation method specifically comprises the following steps:

(a) preparing a hydrophobic hexagonal boron nitride nanosheet containing vinyl:

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2) and 250mL of cyclohexane, putting the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) into 1000mL of three-neck flask with a stirrer and a reflux water separator, heating the three-neck flask to reflux, gradually removing water in a system by a refluxing solvent, cooling the temperature to 80 ℃ when no water is evaporated in the reflux water separator, adding 237g of the prepared compound shown in the formula (Ia), putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, carrying out ultrasonic stirring reaction for 24 hours, then adding 4g of methacrylic acid and 50mL of ethyl acetate, introducing nitrogen, heating the mixture to 100 ℃ for 4 hours, cooling the mixture to 65 ℃, carrying out vacuum filtration, cleaning a filter cake twice by using a toluene/acetone (1:1 volume ratio) mixed solution, then filtering the mixture, adding the mixture into 500mL of toluene/isopropanol mixed solution to form a micro-nano dispersion solution, centrifuging at a rotating speed of 8000r/min, taking the upper suspension, filtering, and drying (140 ℃) to obtain 14.3g of the hydrophobic hexagonal boron nitride nanosheet M-BNNSs (formula (IV-2)) containing vinyl, wherein the yield is 57.1%;

the structural formula of the formula (IV-2) is shown as follows, and only shows a schematic structure of covalent connection after one hydroxyl group on the boron nitride nanosheet reacts with methacrylic acid, and other hydroxyl groups on the boron nitride nanosheet can also react with methacrylic acid and then be covalently connected:

(b) preparing modified epoxy resin:

(b-1) uniformly mixing epoxy resin E-44, n-butanol and 1/4 BPO, placing the mixture in a four-neck flask connected with a condensate pipe and nitrogen, adding the hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl and shown in the formula (IV-2) and prepared, and heating the mixture in an oil bath to 90 ℃ for constant temperature for 30 min;

(b-2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 113.5g of the modified epoxy resin (formula V-2), wherein the synthetic route is as follows:

x, y and z are independently numbers between 1 and 25, and n is an integer selected from 0 to 10; the epoxy value of the E44 epoxy resin used above is 0.44, and the average molecular weight of the epoxy resin should be 200/0.44-454.55;

represents the average number of nIn the following examples, n is the same when E44 epoxy is used.

Example 6

The preparation method specifically comprises the following steps:

(a) preparing a hydrophobic hexagonal boron nitride nanosheet containing vinyl:

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2) and 250mL of cyclohexane, putting the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) and the cyclohexane into 1000mL of three-neck flask with a stirrer and a reflux water separator, heating the three-neck flask to reflux, gradually removing water in a system by a refluxing solvent, cooling the temperature to 80 ℃ when no water is evaporated in the reflux water separator, adding 218g of the prepared compound shown in the formula (Ib), putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, carrying out ultrasonic stirring reaction for 24 hours, then adding 4g of methacrylic acid and 50mL of ethyl acetate, introducing nitrogen, heating the mixture to 100 ℃ for 4 hours, cooling the mixture to 65 ℃, carrying out vacuum filtration, cleaning a filter cake twice by using a toluene/acetone (1:1 volume ratio) mixed solution, then filtering the mixture, adding the mixture into 500mL of toluene/isopropanol mixed solution to form a micro-nano dispersion solution, centrifuging at a rotating speed of 8000r/min, taking the upper suspension, filtering, and drying (140 ℃) to obtain 14.5g of the hydrophobic hexagonal boron nitride nanosheet M-BNNSs (formula (IV-2)) containing vinyl, wherein the yield is 57.9%;

(b) preparing modified epoxy resin:

(b-2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under the condition of heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 113.7g of the modified epoxy resin.

Example 7

The preparation method specifically comprises the following steps:

(a) preparing a hydrophobic hexagonal boron nitride nanosheet containing vinyl:

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2) and 250mL of cyclohexane, putting the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) and the cyclohexane into 1000mL of three-neck flask with a stirrer and a reflux water separator, heating the three-neck flask to reflux, gradually removing water in a system by a refluxing solvent, cooling the temperature to 80 ℃ when no water is evaporated in the reflux water separator, adding 237g of the prepared compound shown in the formula (Ia), putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, carrying out ultrasonic stirring reaction for 24 hours, then adding 5g of itaconic anhydride and 50mL of ethyl acetate, introducing nitrogen, heating the mixture to 100 ℃ for 4 hours, cooling the mixture to 65 ℃, carrying out vacuum filtration, cleaning a filter cake twice by using a toluene/acetone (1:1 volume ratio) mixed solution, then filtering the mixture, adding the mixture into 500mL of toluene/isopropanol mixed solution to form a micro-nano dispersion solution, centrifuging at 8000r/min, collecting upper suspension, filtering, and oven drying (140 deg.C)14.8g of hydrophobic hexagonal boron nitride nanosheet M-BNNSs (formula (IV-3)) containing vinyl, wherein the yield is 59.1%; the structural formula of the formula (IV-3) is shown as follows, and only shows a schematic structure of covalent connection after one hydroxyl group on the boron nitride nanosheet reacts with itaconic anhydride, and other hydroxyl groups on the boron nitride nanosheet can also react with itaconic anhydride and then be covalently connected:

(b) preparing modified epoxy resin:

(b-1) uniformly mixing epoxy resin (E-51), n-butanol and 1/4 BPO, placing the mixture into a four-neck flask connected with a condensate pipe and nitrogen, adding the prepared hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl shown in the formula (IV-3), and heating in an oil bath to 90 ℃ for constant temperature for 30 min;

(b-2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 108.9g of the modified epoxy resin (formula V-3), wherein the synthetic route is as follows:

x, y and z are independently numbers between 0 and 25 and are not 0, and n is an integer selected from 0 to 10;

example 8

The preparation method specifically comprises the following steps:

(a) preparing a hydrophobic hexagonal boron nitride nanosheet containing vinyl:

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2) and 250mL of cyclohexane, putting the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) and the cyclohexane into 1000mL of three-neck flask with a stirrer and a reflux water separator, heating the three-neck flask to reflux, gradually removing water in a system by a refluxing solvent, cooling the temperature to 80 ℃ when no water is evaporated in the reflux water separator, adding 218g of the prepared compound shown in the formula (Ib), putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, carrying out ultrasonic stirring reaction for 24 hours, then adding 5g of itaconic anhydride and 50mL of ethyl acetate, introducing nitrogen, heating the mixture to 100 ℃ for 4 hours, cooling the mixture to 65 ℃, carrying out vacuum filtration, cleaning a filter cake twice by using a toluene/acetone (1:1 volume ratio) mixed solution, then filtering the mixture, adding the mixture into 500mL of toluene/isopropanol mixed solution to form a micro-nano dispersion solution, centrifuging at a rotating speed of 8000r/min, taking the upper suspension, filtering and drying (140 ℃) to obtain 14.7g of the hydrophobic hexagonal boron nitride nanosheet M-BNNSs (formula (IV-3)) containing vinyl, wherein the yield is 58.7%; the structural formula of the formula (IV-3) is shown as follows, and only one hydroxyl on the boron nitride nanosheet is shown after being reacted with itaconic anhydrideThe valence-linked schematic structure, other hydroxyl groups on the boron nitride nanosheet can also be covalently linked after reaction with itaconic anhydride:

(b) preparing modified epoxy resin:

and (b-2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant-pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under the condition of heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 108.8g of the modified epoxy resin.

Example 9

The preparation method specifically comprises the following steps:

(a) preparing a hydrophobic hexagonal boron nitride nanosheet containing vinyl:

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2) and 250mL of cyclohexane, putting the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) and the cyclohexane into 1000mL of three-neck flask with a stirrer and a reflux water separator, heating the three-neck flask to reflux, gradually removing water in a system by a refluxing solvent, cooling the temperature to 80 ℃ when no water is evaporated in the reflux water separator, adding 237g of the prepared compound shown in the formula (Ia), putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, carrying out ultrasonic stirring reaction for 24 hours, then adding 4.5g of maleic anhydride and 50mL of ethyl acetate, introducing nitrogen, heating the mixture to about 100 ℃, carrying out reflux reaction for 4 hours, cooling the mixture to 65 ℃, carrying out vacuum filtration, cleaning a filter cake twice by using a toluene/acetone (1:1 volume ratio) mixed solution, then filtering the mixture, adding the mixture into 500mL of toluene/isopropanol mixed solution to form a micro-nano dispersion solution, centrifuging at a rotating speed of 8000r/min, taking the upper suspension, filtering, and drying (140 ℃) to obtain 14.8g of the hydrophobic hexagonal boron nitride nanosheet M-BNNSs (formula (IV-4)) containing vinyl, wherein the yield is 59.1%;

the structural formula of the formula (IV-4) is shown as follows, only a schematic structure of covalent connection after one hydroxyl group on the boron nitride nanosheet is reacted with maleic anhydride is shown, and other hydroxyl groups on the boron nitride nanosheet can also be covalently connected after the other hydroxyl groups are reacted with maleic anhydride:

(b) preparation of modified epoxy resin:

(b-1) uniformly mixing epoxy resin E-44, n-butanol and 1/4 BPO, placing the mixture in a four-neck flask connected with a condensate pipe and nitrogen, adding the prepared hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl shown in the formula (IV-4), and heating in an oil bath to 90 ℃ for constant temperature for 30 min;

(b-2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 113.9g of the modified epoxy resin (formula V-4), wherein the synthetic route is as follows:

x, y and z are independently numbers between 1 and 25, and n is an integer selected from 0 to 10.

Example 10

The preparation method specifically comprises the following steps:

(a) preparing a hydrophobic hexagonal boron nitride nanosheet containing vinyl:

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2) and 250mL of cyclohexane, putting the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) and the cyclohexane into 1000mL of three-neck flask with a stirrer and a reflux water separator, heating the three-neck flask to reflux, gradually removing water in a system by a refluxing solvent, cooling the temperature to 80 ℃ when no water is evaporated in the reflux water separator, adding 218g of the prepared compound shown in the formula (Ib), putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, carrying out ultrasonic stirring reaction for 24 hours, then adding 4.5g of maleic anhydride and 50mL of ethyl acetate, introducing nitrogen, heating the mixture to 100 ℃ for 4 hours, cooling the mixture to 65 ℃, carrying out vacuum filtration, cleaning a filter cake twice by using a toluene/acetone (1:1 volume ratio) mixed solution, then filtering the mixture, adding the mixture into 500mL of toluene/isopropanol mixed solution to form a micro-nano dispersion solution, centrifuging at a rotating speed of 8000r/min, taking the upper suspension, filtering and drying (140 ℃) to obtain 14.7g of the hydrophobic hexagonal boron nitride nanosheet M-BNNSs (formula (IV-4)) containing vinyl, wherein the yield is 58.7%;

(b) preparation of modified epoxy resin:

(b-1) uniformly mixing epoxy resin (E-44), n-butanol and 1/4 BPO, placing the mixture into a four-neck flask connected with a condensate pipe and nitrogen, adding the prepared hydrophobic hexagonal boron nitride nanosheet (M-BNNSs) containing vinyl shown in the formula (IV-4), and heating in an oil bath to 90 ℃ for constant temperature for 30 min;

(b-2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under the condition of heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 113.8g of the modified epoxy resin.

Comparative example 1

The embodiment provides a modified epoxy resin, which comprises the following raw materials: epoxy resin E-4485g, hydrophobic hexagonal boron nitride nanosheet (M-BNNSs)6g, methyl Methacrylate (MAA)13g and Butyl Acrylate (BA)7 g. The solvent adopted in the preparation process is 25g of third solvent, namely n-butanol, and the initiator is 4g of dibenzoyl peroxide (BPO).

The preparation method comprises the following steps:

preparing a hydrophobic hexagonal boron nitride nanosheet:

(1) preparing hydroxylated hexagonal boron nitride, and specifically implementing the following steps: adding 50g of hexagonal boron nitride (hBN with the purity of more than or equal to 99 percent and the particle size of 2-5 microns) into a 1000ml three-mouth reaction bottle, then adding the hexagonal boron nitride into a prepared 5mol/L sodium hydroxide aqueous solution, mechanically stirring for 10 hours under the oil bath heating condition at about 100 ℃, washing the obtained mixture with distilled water for multiple times until the filtrate is neutral, and drying to obtain 49.5g of hydroxylated hexagonal boron nitride (hBN-OH);

(2) the preparation method of the expanded hydroxylated hexagonal boron nitride comprises the following specific steps: preparing a 10% distilled water solution from the hydroxylated hexagonal boron nitride (hBN-OH) product prepared in the step (1), freezing the distilled water solution in a freezer at the temperature of about-25 ℃ for 5 hours, then unfreezing the distilled water solution to room temperature, and performing freeze-thaw cycle for 6 times to obtain 49.1g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH), wherein the surface hydroxyl number of the expanded hydroxylated hexagonal boron nitride (P-hBN-OH) is determined to be 0.0209 mmol/g;

(3) taking 25g of expanded hydroxylated hexagonal boron nitride (P-hBN-OH) prepared in the step (2), adding 250mL of mixed solvent (toluene/cyclohexane is 1:1), putting the mixed solvent into 1000mL of three-neck flask with a stirrer, heating to reflux, gradually removing water in the system from the refluxing solvent, cooling to 80 ℃ after no water is evaporated from a reflux water separator, adding polyethylene glycol

Putting the reactor into an ultrasonic cleaner, controlling the water temperature to be about 70 ℃, ultrasonically stirring and reacting for 24 hours, then cooling to 65 ℃, precipitating for 30min, and decompressing and pumping out the solvent;

(4) then adding 12g of linoleic acid into the obtained precipitate, adding 100mL of mixed solvent (toluene/cyclohexane is 1:1), introducing nitrogen, heating to about 120 ℃, carrying out reflux reaction for 8h, cooling to 65 ℃, carrying out vacuum filtration, washing a filter cake twice by using toluene/acetone (1:1 volume ratio) mixed solution, then filtering, adding the filter cake into 500mL of toluene/isopropanol mixed solution to form micro-nano dispersion, carrying out centrifugal treatment at a rotating speed of 8000r/min, taking upper-layer suspension, filtering and drying (140 ℃) to obtain 9.0g of hydrophobic hexagonal boron nitride nanosheets (M-BNNSs), wherein the yield is 35.8%;

(II) preparing modified epoxy resin:

(1) uniformly mixing epoxy resin E-44, n-butanol and BPO (bisphenol A) of 1/4, placing the mixture in a four-neck flask connected with a condensate pipe and nitrogen, adding the prepared hydrophobic hexagonal boron nitride nanosheet, and heating in an oil bath to 90 ℃ for 30min at constant temperature;

(2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant-pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under the condition of heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 113.6g of modified epoxy resin.

Comparative example 1 is different from the present invention in that the compound represented by formula (I) of the present invention is not used for exfoliation and esterification, resulting in the need for two steps to carry out the reaction and doubling of the synthesis time. The obtained hydrophobic hexagonal boron nitride nanosheet product contains unmodified hexagonal boron nitride nanosheets and is not easy to separate. Therefore, the prepared modified epoxy resin contains independent unmodified hexagonal boron nitride nanosheets, and the performance of the impregnating varnish product is influenced.

Comparative example 2

Directly using a commercially available hexagonal boron nitride nanosheet, wherein the raw materials of the modified epoxy resin comprise: epoxy resin E-4485g, commercially available hexagonal boron nitride nanosheets (M-BNNSs)6g, methyl Methacrylate (MAA)13g and Butyl Acrylate (BA)7 g. The solvent adopted in the preparation process is 25g of third solvent, namely n-butanol, and the initiator is 4g of dibenzoyl peroxide (BPO).

The preparation method specifically comprises the following steps:

(1) uniformly mixing epoxy resin E-44, n-butanol and BPO (bisphenol A) of 1/4, placing the mixture in a four-neck flask connected with a condensate pipe and nitrogen, adding a commercially available hexagonal boron nitride nanosheet (M-BNNSs), and heating the mixture in an oil bath to 90 ℃ for 30min at constant temperature;

(2) heating to about 110 ℃, simultaneously dropwise adding a mixed monomer (MAA and BA) solution dissolved with 3/4BPO initiator by using a constant-pressure dropping funnel, slowly dropwise adding for about 30min, reacting for 3-4h under the condition of heat preservation after dropwise adding, and then distilling under reduced pressure to remove n-butyl alcohol (which can be recycled) to obtain 113.8g of modified epoxy resin.

The difference between the comparative example 2 and the invention is that the boron nitride nanosheet sold in the market is directly doped into the acrylic ester grafted epoxy resin system, and the thermal conductivity, the electrical property of the impregnating varnish, the bonding force and the like are far lower than those of the invention because the unmodified boron nitride nanosheet is poor in compatibility with the epoxy resin.

Examples 11 to 18 and application examples 1 to 2

The embodiments provide an insulating impregnating varnish, which comprises a matrix resin, a diluent and a curing agent, wherein the matrix resin is prepared by the following method: adding modified epoxy resin and a dimethylbenzene solution of organic silanol with a silicon hydroxyl group (the mass fraction of the organic silanol is 50%) into a reactor, slowly heating to 150 +/-3 ℃, carrying out reflux reaction for 45min, gradually removing the solvent until the solid content reaches 85%, adding a catalyst cobalt naphthenate, continuously carrying out water diversion and reflux reaction until the viscosity reaches 90sec (coating a 4# cup and carrying out 25 ℃) after 65 wt% of the solvent is removed, cooling to 120 +/-3 ℃, removing the solvent in the reaction system through reduced pressure distillation, and filtering to obtain the matrix resin.

Preparing insulating impregnating varnish: mixing the prepared matrix resin with diluent and curing agent at room temperature, and stirring for 60 min.

The following organosilols having a silicon hydroxyl group are selected from TH-1# (R/Si ═ 1.50, Ph/R ═ 0.43, Vi mass% ═ 4.1) of new electrical materials, suzhou taihu lake, and TH-2# (R/Si ═ 1.58, Ph/R ═ 0.35, Vi mass% ═ 0.6) of new electrical materials, suzhou taihu, and TH-3# (R/Si ═ 1.50, Ph/R ═ 0.35, Vi mass%: 3.2) of new electrical materials, suzhou taihu, and can be prepared by the method described in 201310090271.6.

Examples 11-18 and application examples 1-2 used starting materials and amounts as shown in table 1 below:

TABLE 1

Performance testing

The insulating impregnating varnishes obtained in the above examples 11 to 18 and comparative examples 1 to 2 were subjected to the following performance tests (performance test sample curing process conditions: 140 ℃/2h +170 ℃/10h), see in particular table 2.

TABLE 2

The above embodiments are merely illustrative of the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the content of the present invention and implement the invention, and not to limit the scope of the invention, and all equivalent changes or modifications made according to the spirit of the present invention should be covered by the scope of the present invention.

Claims

1. An insulating impregnating varnish comprises a matrix resin, a diluent and a curing agent, and is characterized in that the matrix resin is prepared by condensation reaction of a modified epoxy resin and an organic silanol with a silicon hydroxyl group, raw materials of the modified epoxy resin comprise an epoxy resin, an ester group-containing vinyl monomer and a hydrophobic hexagonal boron nitride nanosheet containing a vinyl group, the modified epoxy resin is prepared by polymerization reaction of the epoxy resin and the rest raw materials, and the feeding mass ratio of the epoxy resin, the hydrophobic hexagonal boron nitride nanosheet containing the vinyl group and the ester group-containing vinyl monomer is 1: 0.05-0.1: 0.15-0.4;

the hydrophobic hexagonal boron nitride nanosheet containing the vinyl group is prepared by the following method:

wherein R is₀Is C_1-6Alkyl groups of (a);

the epoxy resin is one or more of the compounds shown in the formula (III):

in the formula: r₄is-C (CH)₃)₂-、-CH₂-or-S (O)₂N is 1, 2, 34, 5, 6, 7, 8, 9 or 10.

2. The insulation impregnating varnish according to claim 1, wherein said vinyl monomer containing ester group is one or more selected from the group consisting of compounds represented by formula (ii):

in the formula, R₁Is C_1-10Alkyl of R₂、R₃Are each independently hydrogen or C_1-10Alkyl group of (1).

3. The insulating impregnating varnish according to claim 1, wherein said polymerization reaction is carried out at a temperature of 100 ℃ and 120 ℃.

4. The insulating impregnating varnish according to claim 1, wherein, in step (1), said hydroxylated hexagonal boron nitride is prepared by: mixing hexagonal boron nitride with a sodium hydroxide aqueous solution, and stirring and reacting at the temperature of 90-150 ℃ to prepare the boron nitride-based catalyst; and/or, in the step (2), the freeze-thaw expansion treatment is operated in the following mode: preparing the hydroxylated hexagonal boron nitride prepared in the step (1) into an aqueous solution, freezing the obtained aqueous solution at a first set temperature, then unfreezing the aqueous solution to a second set temperature, and circularly freezing and unfreezing the aqueous solution for multiple times to prepare the expanded hydroxylated hexagonal boron nitride; wherein the first set temperature is-50 to-5 ℃, and the second set temperature is 10 to 30 ℃.

5. The insulation impregnating varnish according to claim 1, wherein in the step (3), the mixing and stirring are carried out at a temperature of 60 to 78 ℃, the reaction in the second solvent is carried out at a temperature of 80 to 120 ℃ in the presence of an inert gas, and the mixing and stirring are controlled to be carried out in an anhydrous environment; and/or in the step (3), the feeding mass ratio of the compound shown in the formula (I) to the expanded hydroxylated hexagonal boron nitride is 6-12: 1, the feeding mass ratio of the unsaturated acid and/or unsaturated anhydride to the expanded hydroxylated hexagonal boron nitride is 0.05-0.5: 1, the first solvent is cyclohexane, the second solvent is ethyl acetate, the unsaturated acid is linoleic acid and/or methacrylic acid, and the unsaturated anhydride is itaconic anhydride and/or maleic anhydride.

6. The insulation impregnating varnish according to claim 1, wherein in the preparation of the matrix resin, the charging mass ratio of the modified epoxy resin to the silicone alcohol having a silicon hydroxyl group is 1: 0.15-0.35; and/or, the condensation reaction is carried out at the temperature of 120-180 ℃ in the presence of a catalyst, and the mass ratio of the catalyst to the modified epoxy resin is 0.005-0.015: 1.

7. The insulation impregnating varnish according to claim 1, wherein said diluent is polypropylene glycol diglycidyl ether or neopentyl glycol diglycidyl ether or a combination of both, and said curing agent is methyl tetrahydrophthalic anhydride or methyl hexahydrophthalic anhydride or a combination of both; and/or in the insulating impregnating varnish, the mass ratio of the base resin, the diluent and the curing agent is 1: 0.05-0.25: 0.35-0.7.

8. A method for preparing an insulation impregnating varnish according to any one of claims 1 to 7, characterized in that it comprises the following steps:

(a) preparing hydrophobic hexagonal boron nitride nanosheets containing vinyl;