CN113832778A - Preparation method of heat-conducting insulating paper based on nano silicon nitride modification - Google Patents

Preparation method of heat-conducting insulating paper based on nano silicon nitride modification Download PDF

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CN113832778A
CN113832778A CN202110592103.1A CN202110592103A CN113832778A CN 113832778 A CN113832778 A CN 113832778A CN 202110592103 A CN202110592103 A CN 202110592103A CN 113832778 A CN113832778 A CN 113832778A
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silicon nitride
nano silicon
paper
drying
pulp
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CN113832778B (en
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刘捷丰
张镱议
张恒
李毅
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Guangxi University
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/18—De-watering; Elimination of cooking or pulp-treating liquors from the pulp
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
    • D21D1/02—Methods of beating; Beaters of the Hollander type
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
    • D21H17/69—Water-insoluble compounds, e.g. fillers, pigments modified, e.g. by association with other compositions prior to incorporation in the pulp or paper

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Abstract

According to the preparation method of the heat-conducting insulating paper based on the modification of the nano silicon nitride, before the modification of the nano silicon nitride, the nano silicon nitride is dried for the second time, so that the moisture content in the nano silicon nitride can be reduced to the greatest extent, and the modification effect is better; adopts silane coupling agent KH-550 to nano silicon nitride (Si)3N4) The particles are subjected to surface treatment, and the modified nano silicon nitride particles are used for modifying the insulating paper, so that nano particles can be prevented from agglomerating, and the heat conductivity coefficient of the paper is greatly improved; modified nano silicon nitride (Si)3N4) Filling-inThe insulating paper has the advantages that the electrical insulating property of the insulating paper can be enhanced on the premise of ensuring the strength of the insulating paper, the heat conductivity coefficient of the paper can be greatly improved, and the application of the insulating paper in the field of heat conduction materials is expanded; strictly selecting materials, wherein the content of iron in the modified nano silicon nitride is below 8ppm, so that the situation that the breakdown field intensity of the insulating paper is reduced due to overhigh content of iron in the modified nano silicon nitride is avoided.

Description

Preparation method of heat-conducting insulating paper based on nano silicon nitride modification
Technical Field
The invention relates to the technical field of insulating paper processing, in particular to a preparation method of heat-conducting insulating paper based on nano silicon nitride modification.
Background
Oil-filled transformers are a core component in power systems, and their insulation performance is determined by their internal insulation. The internal insulation of the oil-immersed transformer is composite insulation consisting of insulating paper and transformer oil. The mechanical strength and the insulating property of the insulating paper are irreversibly reduced under the influence of factors such as aging and the like in the long-term operation process, so the service life of the insulating paper directly determines the service life of the transformer.
A large amount of heat can be generated inside the oil-immersed transformer in the operation process, and impurities generated in the transformer due to long-term operation can be deposited on the insulating paper, so that the thermal resistance of the insulating paper is further increased, and poor heat dissipation is caused. The heat build-up will cause the insulation paper temperature to rise, accelerating the cellulose aging, resulting in a reduction of the insulation paper lifetime and ultimately the transformer lifetime. Therefore, in order to improve the heat-conducting property of the insulating paper and reduce the aging degree of the insulating paper caused by local overheating, the development of the novel insulating paper with high heat-conducting property has great scientific value and economic benefit.
With the development of nanotechnology, the enhancement of various properties of modified polymers by using nanoparticles has become a research hotspot in recent years. Nano silicon nitride (Si)3N4) The insulating heat-conducting filler has high heat conductivity and good oxidation resistance, and has very low dielectric constant and dielectric loss, so that the insulating heat-conducting filler is very ideal. Mixing nano Si3N4The material is filled into the cellulose insulating paper, which is beneficial to reducing the gaps among cellulose molecular chains and reducing the thermal resistivity. Therefore, the present invention uses nano Si3N4As heat-conducting insulating filler and cellulose as raw materials, adopts silane coupling agent KH-550 as surface modifier,the nano particles are prevented from agglomerating, and the novel high-thermal-conductivity electrical insulation paper is manufactured by a wet papermaking technology.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide the preparation method of the heat-conducting insulating paper based on the modification of the nano silicon nitride, which not only meets the requirements of the transformer on the mechanical strength and the insulating property of the insulating paper, but also can improve the heat-conducting property of the insulating paper and reduce the aging degree of the insulating paper caused by local overheating.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating raw pulp paper to 80-100 ℃, and soaking the raw pulp paper in deionized water at 80-100 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a pulping machine for pulping treatment and dewatering to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into an oven with the temperature of 90-110 ℃ for primary drying, wherein the drying time is 25-35 min, and obtaining primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 80-85 ℃ to obtain dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to be alkalescent by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.4-0.6 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 3.5-4.5 times of the volume of the mixed solution into the three-neck flask; putting the three-neck flask into a water bath kettle, heating and stirring for 25-35 min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride;
(7) mixing the paper pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), stirring for 25-30 min, and fully mixing to obtain a paper pulp mixed solution;
(8) and (4) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming, and squeezing and drying to obtain the nano silicon nitride modification-based heat-conducting insulating paper.
Further, heating the raw pulp paper to 90 ℃ in the step (1), and soaking the raw pulp paper in deionized water at 90 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp.
Further, the wet paper pulp prepared in the step (1) is added into a wary beater to be beaten in the step (2), the beating degree is controlled to be 45 DEG SR, and the wet paper pulp is dewatered to obtain paper pulp.
Further, the nano silicon nitride is placed into an oven with the temperature of 100 ℃ for primary drying in the step (4), and the drying time is 30min, so that primary dried nano silicon nitride is obtained; and (3) carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 83 ℃ to obtain the dried nano silicon nitride.
Further, in the step (5), adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to 7.1-7.4 by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethanol is 0.5 g.
Further, in the step (6), dried nano silicon nitride is added into the surface modifier prepared in the step (5), and the mixture is uniformly stirred to obtain a mixed solution, wherein specifically, the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 15-25 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 3.5-4.5 times of the volume of the mixed solution into the three-neck flask; and (3) putting the three-neck flask into a water bath kettle, heating and stirring for 25-35 min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain the modified nano silicon nitride.
Furthermore, the particle size of the modified nano silicon nitride in the step (6) is 15-30 nm, and the content of iron in the modified nano silicon nitride is below 8 ppm.
Furthermore, the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension in the step (7) is 0.015-0.3 g.
Furthermore, in the step (7), 0.005-0.008 g of sulfonated nano graphite powder is added to every 1000ml of pulp mixed liquor.
Further, performing primary drying on the pressed and formed wet paper sheet in the step (8) at the temperature of 55-85 ℃, wherein the drying time is 7-12 min, and thus obtaining a primary dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 80-85 ℃, wherein the drying time is 5-8 min, so as to obtain a secondary dried paper sheet; and (3) drying the paper sheet subjected to secondary drying for three times at the temperature of 75-85 ℃ until the moisture content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
According to the preparation method of the nano silicon nitride modified heat-conducting insulating paper, before the nano silicon nitride is modified, the nano silicon nitride is dried for the second time, so that the moisture content in the nano silicon nitride can be reduced to the greatest extent, and the nano silicon nitride with low water content is placed in the silane coupling agent KH-550 modification liquid for modification, so that the modification effect is better; adopts silane coupling agent KH-550 to nano silicon nitride (Si)3N4) The particles are subjected to surface treatment, and the modified nano silicon nitride particles are used for modifying the insulating paper, so that nano particles can be prevented from agglomerating, and the heat conductivity coefficient of the paper is greatly improved; modified nano silicon nitride (Si)3N4) The filled insulating paper has the advantages that the electric insulating property of the filled insulating paper can be enhanced on the premise of ensuring the strength of the filled insulating paper, the heat conductivity coefficient of the paper can be greatly improved, and the application of the filled insulating paper in the field of heat conduction materials is expanded.
The invention relates to a method for preparing heat-conducting insulating paper based on nano silicon nitride modificationThe preparation method comprises strictly selecting materials, wherein the content of iron in the modified nano silicon nitride is below 8ppm, so that the situation that the breakdown field intensity of the insulating paper is reduced due to overhigh content of iron in the modified nano silicon nitride is avoided; to further prevent modification of nano silicon nitride (Si)3N4) Agglomeration is carried out, the dispersibility of the modified nano silicon nitride is improved, a dispersing agent can be added into the paper pulp mixed liquor in the step (7), and the inventor surprisingly finds that when the sulfonated nano graphite powder is added into the paper pulp mixed liquor, the modified nano silicon nitride (Si) can be prevented3N4) Agglomeration can effectively improve the tensile strength of the insulating paper; the moisture content in the insulating paper can be reduced to below 0.5% by carrying out three times of drying treatment on the squeezed and formed wet paper, and the three times of drying treatment also enables the insulating paper to be subjected to physical change, so that the water absorption performance of the insulating paper is effectively reduced.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The following examples may help one skilled in the art to more fully understand the present invention, but are not intended to limit the invention in any way.
According to the preparation method of the nano silicon nitride modified heat-conducting insulating paper, the raw pulp paper can be cut into pieces during wet paper pulp, and then the paper pulp is soaked in hot water; the particle size of the modified nano silicon nitride is 15-30 nm, specifically, after the modified nano silicon nitride is prepared, the modified nano silicon nitride is ground to 15-30 nm; the dosage of the nano silicon nitride in the step (4) of the following example is 2 g; in the following example, the wet paper sheet obtained by the sheet former was pressed by a press vulcanizer in the step (8) to obtain a press-formed wet paper sheet; the virgin pulp paper mentioned in the following examples refers to insulating paper;
the invention relates to a preparation method of heat-conducting insulating paper modified based on nano silicon nitride, wherein the volume fraction of ethanol in absolute ethyl alcohol is more than 99.5%; the density of the used ammonia water is 0.91g/cm for carrying out dry cultivation; the silane coupling agent KH-550 is chemically pure; the used sulfonated nano graphite powder is modified nano graphite powder which is subjected to surface modification by sodium dodecyl sulfate under the ultrasonic oscillation condition;
the invention relates to a preparation method of heat-conducting insulating paper modified based on nano silicon nitride.A used ultrasonic dispersion instrument is a Wujie Reian JRA-1000MF type constant-temperature closed ultrasonic reactor; the vacuum drying apparatus is a vacuum drying oven with a vacuum pump.
Example 1
A preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating the raw pulp paper to 80 ℃, and soaking the raw pulp paper in 80 ℃ deionized water at constant temperature for more than 4 hours to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a Bulboli beater for beating treatment, controlling the beating degree at 45 DEG SR, and dehydrating to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into a drying oven with the temperature of 90 ℃ for primary drying, wherein the drying time is 25min, and obtaining primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 80 ℃ to obtain dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to 7.1 by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.4 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution, wherein the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 15 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 3.5 times of the volume of the mixed solution into the three-neck flask; placing the three-neck flask into a water bath kettle, heating and stirring for 25min, performing condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride; the particle size of the modified nano silicon nitride is 15-30 nm, and the content of iron in the modified nano silicon nitride is below 8 ppm;
(7) mixing the pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), wherein the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension is 0.015g, stirring for 25min, and fully mixing to obtain a pulp mixed solution; 0.005g of sulfonated nano graphite powder is also added into every 1000ml of paper pulp mixed liquid;
(8) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming and squeezing, and drying the squeezed and formed wet paper sheet for one time at the temperature of 55 ℃ for 7min to obtain a once-dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 80 ℃ for 5min to obtain a secondary dried paper sheet; and (3) drying the paper sheet subjected to secondary drying for three times at the temperature of 75 ℃ until the water content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
Example 2
A preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating the raw pulp paper to 100 ℃, and soaking the raw pulp paper in deionized water at 100 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a Bulboli beater for beating treatment, controlling the beating degree at 45 DEG SR, and dehydrating to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into a drying oven with the temperature of 110 ℃ for primary drying, wherein the drying time is 35min, and obtaining primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 85 ℃ to obtain dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to 7.4 by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.6 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution, wherein the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 25 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 4.5 times that of the mixed solution into the three-neck flask; placing the three-neck flask into a water bath kettle, heating and stirring for 35min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride; the particle size of the modified nano silicon nitride is 15-30 nm, and the content of iron in the modified nano silicon nitride is below 8 ppm;
(7) mixing the pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), wherein the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension is 0.3g, stirring for 30min, and fully mixing to obtain a pulp mixed solution; 0.008g of sulfonated nano graphite powder is also added into every 1000ml of paper pulp mixed liquor;
(8) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming and squeezing, and drying the squeezed and formed wet paper sheet for one time at the temperature of 85 ℃ for 12min to obtain a once-dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 85 ℃ for 8min to obtain a secondary dried paper sheet; and drying the paper sheet subjected to secondary drying for three times at the temperature of 85 ℃ until the moisture content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
Example 3
A preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating the raw pulp paper to 90 ℃, and soaking the raw pulp paper in deionized water at 90 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a Bulboli beater for beating treatment, controlling the beating degree at 45 DEG SR, and dehydrating to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into a drying oven with the temperature of 100 ℃ for primary drying for 30min to obtain primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 83 ℃ to obtain dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to 7.2 by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.5 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution, wherein the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 20 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 4 times that of the mixed solution into the three-neck flask; placing the three-neck flask into a water bath kettle, heating and stirring for 30min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride; the particle size of the modified nano silicon nitride is 15-30 nm, and the content of iron in the modified nano silicon nitride is below 8 ppm;
(7) mixing the pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), wherein the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension is 0.03g, stirring for 28min, and fully mixing to obtain a pulp mixed solution;
(8) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming, squeezing, and drying the squeezed and formed wet paper sheet for one time at the temperature of 65 ℃ for 8min to obtain a once-dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 82 ℃ for 6min to obtain a secondary dried paper sheet; and drying the paper sheet subjected to secondary drying for three times at the temperature of 80 ℃ until the moisture content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
Example 4
A preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating the raw pulp paper to 90 ℃, and soaking the raw pulp paper in deionized water at 90 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a Bulboli beater for beating treatment, controlling the beating degree at 45 DEG SR, and dehydrating to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into a drying oven with the temperature of 100 ℃ for primary drying for 30min to obtain primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 83 ℃ to obtain dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to 7.2 by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.5 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution, wherein the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 20 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 4 times that of the mixed solution into the three-neck flask; placing the three-neck flask into a water bath kettle, heating and stirring for 30min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride; the particle size of the modified nano silicon nitride is 15-30 nm, and the content of iron in the modified nano silicon nitride is more than 10 ppm;
(7) mixing the pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), wherein the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension is 0.03g, stirring for 28min, and fully mixing to obtain a pulp mixed solution; 0.006g of sulfonated nano graphite powder is also added into every 1000ml of paper pulp mixed liquor;
(8) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming, squeezing, and drying the squeezed and formed wet paper sheet for one time at the temperature of 65 ℃ for 8min to obtain a once-dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 82 ℃ for 6min to obtain a secondary dried paper sheet; and drying the paper sheet subjected to secondary drying for three times at the temperature of 80 ℃ until the moisture content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
Example 5
A preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating the raw pulp paper to 90 ℃, and soaking the raw pulp paper in deionized water at 90 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a Bulboli beater for beating treatment, controlling the beating degree at 45 DEG SR, and dehydrating to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into a drying oven with the temperature of 100 ℃ for primary drying for 30min to obtain primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 83 ℃ to obtain dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to 7.2 by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.5 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution, wherein the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 20 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 4 times that of the mixed solution into the three-neck flask; placing the three-neck flask into a water bath kettle, heating and stirring for 30min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride; the particle size of the modified nano silicon nitride is 15-30 nm, and the content of iron in the modified nano silicon nitride is below 8 ppm;
(7) mixing the pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), wherein the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension is 0.03g, stirring for 28min, and fully mixing to obtain a pulp mixed solution; 0.006g of sulfonated nano graphite powder is also added into every 1000ml of paper pulp mixed liquor;
(8) and (4) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming, squeezing and drying for one time to obtain the heat-conducting insulating paper based on nano silicon nitride modification.
Example 6
A preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating the raw pulp paper to 90 ℃, and soaking the raw pulp paper in deionized water at 90 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a Bulboli beater for beating treatment, controlling the beating degree at 45 DEG SR, and dehydrating to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into a drying oven with the temperature of 100 ℃ for primary drying for 30min to obtain primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 83 ℃ to obtain dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to 7.2 by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.5 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution, wherein the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 20 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 4 times that of the mixed solution into the three-neck flask; placing the three-neck flask into a water bath kettle, heating and stirring for 30min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride; the particle size of the modified nano silicon nitride is 15-30 nm, and the content of iron in the modified nano silicon nitride is below 8 ppm;
(7) mixing the pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), wherein the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension is 0.03g, stirring for 28min, and fully mixing to obtain a pulp mixed solution; 0.006g of sulfonated nano graphite powder is also added into every 1000ml of paper pulp mixed liquor;
(8) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming, squeezing, and drying the squeezed and formed wet paper sheet for one time at the temperature of 65 ℃ for 8min to obtain a once-dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 82 ℃ for 6min to obtain a secondary dried paper sheet; and drying the paper sheet subjected to secondary drying for three times at the temperature of 80 ℃ until the moisture content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
Comparative example 1
A preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating the raw pulp paper to 90 ℃, and soaking the raw pulp paper in deionized water at 90 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a Bulboli beater for beating treatment, controlling the beating degree at 45 DEG SR, and dehydrating to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) putting the nano silicon nitride into an oven with the temperature of 100 ℃ for primary drying, wherein the drying time is 80min, and obtaining dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to 7.2 by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.5 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution, wherein the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 20 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 4 times that of the mixed solution into the three-neck flask; placing the three-neck flask into a water bath kettle, heating and stirring for 30min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride; the particle size of the modified nano silicon nitride is 15-30 nm, and the content of iron in the modified nano silicon nitride is below 8 ppm;
(7) mixing the pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), wherein the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension is 0.03g, stirring for 28min, and fully mixing to obtain a pulp mixed solution; 0.006g of sulfonated nano graphite powder is also added into every 1000ml of paper pulp mixed liquor;
(8) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming, squeezing, and drying the squeezed and formed wet paper sheet for one time at the temperature of 65 ℃ for 8min to obtain a once-dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 82 ℃ for 6min to obtain a secondary dried paper sheet; and drying the paper sheet subjected to secondary drying for three times at the temperature of 80 ℃ until the moisture content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
Comparative example 2
A preparation method of heat-conducting insulating paper based on nano silicon nitride modification comprises the following steps:
(1) heating the raw pulp paper to 90 ℃, and soaking the raw pulp paper in deionized water at 90 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a Bulboli beater for beating treatment, controlling the beating degree at 45 DEG SR, and dehydrating to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into a drying oven with the temperature of 100 ℃ for primary drying for 30min to obtain primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 83 ℃ to obtain dried nano silicon nitride;
(5) mixing the pulp suspension liquid prepared in the step (3) with the dried nano silicon nitride prepared in the step (4), wherein the addition amount of the dried nano silicon nitride in each 1000ml of pulp suspension liquid is 0.03g, stirring for 28min, and fully mixing to obtain a pulp mixed liquid; 0.006g of sulfonated nano graphite powder is also added into every 1000ml of paper pulp mixed liquor;
(6) injecting the pulp mixed liquor prepared in the step (5) into a paper sheet former for dehydration forming, squeezing, and drying the squeezed and formed wet paper sheet for one time at the temperature of 65 ℃ for 8min to obtain a once-dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 82 ℃ for 6min to obtain a secondary dried paper sheet; and drying the paper sheet subjected to secondary drying for three times at the temperature of 80 ℃ until the moisture content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
The properties of the thermal conductive and insulating paper modified based on nano silicon nitride prepared in the above examples 1 to 6 and comparative examples 1 to 2 were verified:
firstly, detecting the relative dielectric constant of the heat conduction and insulation paper based on the modification of the nano silicon nitride, which is prepared in the embodiments 1-6 and the comparative examples 1-2, according to GB/T1409-; relative dielectric constant calculation formula:
εr=Cx/CO；
secondly, detecting the breakdown field intensity of the heat-conducting insulating paper based on the modification of the nano silicon nitride, which is prepared in the embodiments 1-6 and the comparative examples 1-2, according to GB1408.1-2006 insulating material electrical strength test method;
thirdly, the tensile strength of the heat-conducting and insulating paper modified based on the nano silicon nitride, which is prepared in the embodiments 1 to 6 and the comparative examples 1 to 2, is detected, and the experimental conditions are as follows: the temperature is 20 ℃, and the relative humidity is 65%;
fourthly, detecting the moisture content of the heat conduction and insulation paper based on the modification of the nano silicon nitride, which is prepared in the embodiments 1 to 6 and the comparative examples 1 to 2, wherein a testing instrument is a paper moisture tester;
the results of the tests of examples 1 to 6 and comparative examples 1 to 2 are shown in tables 1 to 4 below.
TABLE 1
Serial number Relative dielectric constant at 20 deg.C
Example 1 1.21
Example 2 1.23
Example 3 1.25
Example 4 1.29
Example 5 1.22
Example 6 1.15
Comparative example 1 1.42
Comparative example 2 1.63
TABLE 2
Sequence of Number (C) Breakdown field strength of 0 day of aging time （kV.mm-1） Breakdown field strength with aging time of 5 days （kV.mm-1） Breakdown field of aging time 10 days Strong (kV.mm-1) Breakdown field of 15 days of aging time Strong (kV.mm-1) Breakdown field of aging time 20 days Strong (kV.mm-1) Breakdown field of aging time 25 days Strong (kV.mm-1)
Practice of Example 1 64 61 58 54 50 46
Practice of Example 2 64 62 57 43 51 48
Practice of Example 3 62 58 55 51 49 45
Practice of Example 4 57 56 52 49 45 41
Practice of Example 5 59 55 53 48 46 40
Practice of Example 6 67 65 60 57 54 52
Comparison of Example 1 52 48 43 41 38 35
Comparison of Example 2 45 41 38 35 31 28
TABLE 3
Serial number Longitudinal direction of tensile strength（N） Tensile Strength longitudinal (N)
Example 1 104.6 52.5
Example 2 101.7 50.8
Example 3 79.5 32.3
Example 4 103.5 50.2
Example 5 102.9 51.4
Example 6 107.9 55.6
Comparative example 1 100.8 50.3
Comparative example 2 99.7 48.7
TABLE 4
Sequence of Number (C) Aging time 0 day water content Amount (%) Aging for 5 days and moisture content Amount (%) Aging for 10 days and moisture content Amount (%) Aging for 15 days and moisture content Amount (%) Aging for 20 days and moisture content Amount (%) Aging for 25 days and moisture content Amount (%)
Practice of Example 1 ≤0.5 ≤0.8 ≤1.12 ≤1.81 ≤2.45 ≤3.05
Practice of Example 2 ≤0.5 ≤0.8 ≤1.12 ≤1.81 ≤2.45 ≤3.05
Practice of Example 3 ≤0.5 ≤0.8 ≤1.12 ≤1.81 ≤2.45 ≤3.05
Practice of Example 4 ≤0.5 ≤0.8 ≤1.12 ≤1.81 ≤2.45 ≤3.05
Practice of Example 5 ≤0.5 ≤1.32 ≤2.55 ≤3.46 ≤4.23 ≤4.89
Practice of Example 6 ≤0.5 ≤0.8 ≤1.12 ≤1.81 ≤2.45 ≤3.05
Comparison of Example 1 ≤0.5 ≤0.5 ≤1.12 ≤1.81 ≤2.45 ≤3.05
Comparison of Example 2 ≤0.5 ≤0.8 ≤1.12 ≤1.81 ≤2.45 ≤3.05
According to the detection results, the preparation method of the nano silicon nitride modified heat-conducting insulating paper disclosed by the invention has the advantages that before the nano silicon nitride is modified, the nano silicon nitride is dried for the second time, so that the moisture content in the nano silicon nitride can be reduced to the greatest extent, and the nano silicon nitride with low water content is placed in the silane coupling agent KH-550 modification liquid for modification, so that the modification effect is better; adopts silane coupling agent KH-550 to nano silicon nitride (Si)3N4) The particles are subjected to surface treatment, and the modified nano silicon nitride particles are used for modifying the insulating paper, so that nano particles can be prevented from agglomerating, and the heat conductivity coefficient of the paper is greatly improved; modified nano silicon nitride (Si)3N4) The filled insulating paper has the advantages that the electrical insulating property of the filled insulating paper can be enhanced on the premise of ensuring the strength of the filled insulating paper, the heat conductivity coefficient of the paper can be greatly improved, and the application of the filled insulating paper in the field of heat conduction materials is expanded; strictly selecting materials, wherein the content of iron in the modified nano silicon nitride is below 8ppm, so that the situation that the breakdown field intensity of the insulating paper is reduced due to overhigh content of iron in the modified nano silicon nitride is avoided; to further prevent modification of nano silicon nitride (Si)3N4) Agglomeration is carried out, the dispersibility of the modified nano silicon nitride is improved, a dispersing agent can be added into the paper pulp mixed liquor in the step (7), and the inventor surprisingly finds that when the sulfonated nano graphite powder is added into the paper pulp mixed liquor, the modified nano silicon nitride (Si) can be prevented3N4) Agglomeration can effectively improve the tensile strength of the insulating paper; the moisture content in the insulating paper can be reduced to below 0.5% by carrying out three times of drying treatment on the squeezed and formed wet paper, and the three times of drying treatment also enables the insulating paper to be subjected to physical change, so that the water absorption performance of the insulating paper is effectively reduced.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (10)

1. A preparation method of heat-conducting insulating paper based on nano silicon nitride modification is characterized by comprising the following steps:
(1) heating raw pulp paper to 80-100 ℃, and soaking the raw pulp paper in deionized water at 80-100 ℃ for more than 4 hours at constant temperature to obtain wet paper pulp;
(2) adding the wet paper pulp prepared in the step (1) into a pulping machine for pulping treatment and dewatering to obtain paper pulp;
(3) adding deionized water and the paper pulp prepared in the step (2) into a fluffer, and fluffing the paper pulp into a paper pulp suspension;
(4) placing the nano silicon nitride into an oven with the temperature of 90-110 ℃ for primary drying, wherein the drying time is 25-35 min, and obtaining primary dried nano silicon nitride; carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 80-85 ℃ to obtain dried nano silicon nitride;
(5) adding absolute ethyl alcohol and a silane coupling agent KH-550 into a container, uniformly mixing, and adjusting the pH value of the solution to be alkalescent by using ammonia water to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethyl alcohol is 0.4-0.6 g;
(6) adding dried nano silicon nitride into the surface modifier prepared in the step (5), and uniformly stirring to obtain a mixed solution; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 3.5-4.5 times of the volume of the mixed solution into the three-neck flask; putting the three-neck flask into a water bath kettle, heating and stirring for 25-35 min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain modified nano silicon nitride;
(7) mixing the paper pulp suspension prepared in the step (3) with the modified nano silicon nitride prepared in the step (6), stirring for 25-30 min, and fully mixing to obtain a paper pulp mixed solution;
(8) and (4) injecting the pulp mixed liquor prepared in the step (7) into a paper sheet former for dehydration forming, and squeezing and drying to obtain the nano silicon nitride modification-based heat-conducting insulating paper.
2. The method for preparing the nano silicon nitride modified heat conducting and insulating paper according to claim 1, wherein in the step (1), the raw pulp paper is heated to 90 ℃, and is soaked in deionized water at 90 ℃ for more than 4 hours at constant temperature, so as to obtain wet pulp.
3. The method for preparing the nano silicon nitride modified heat-conducting insulating paper as claimed in claim 1, wherein the wet pulp prepared in the step (1) is added into a wary beater to be beaten in the step (2), the beating degree is controlled to be 45 ° SR, and the wet pulp is dewatered to obtain the pulp.
4. The preparation method of the nano silicon nitride modified heat-conducting insulating paper according to claim 1, wherein in the step (4), the nano silicon nitride is placed in an oven with the temperature of 100 ℃ for primary drying, and the drying time is 30min, so that primary dried nano silicon nitride is obtained; and (3) carrying out vacuum drying on the primarily dried nano silicon nitride under the conditions that the vacuum degree is-0.06 MPa and the drying temperature is 83 ℃ to obtain the dried nano silicon nitride.
5. The preparation method of the nano silicon nitride modified heat-conducting insulating paper as claimed in claim 1, wherein in the step (5), absolute ethyl alcohol and a silane coupling agent KH-550 are added into a container and uniformly mixed, and ammonia water is used for adjusting the pH value of the solution to 7.1-7.4, so as to obtain a surface modifier; the addition amount of the silane coupling agent KH-550 in each 100ml of absolute ethanol is 0.5 g.
6. The preparation method of the nano silicon nitride modified heat-conducting insulating paper based on the claim 1 is characterized in that in the step (6), the dried nano silicon nitride is added into the surface modifier prepared in the step (5) and is uniformly stirred to obtain a mixed solution, and specifically, the addition amount of the dried nano silicon nitride in each 100ml of the surface modifier is 15-25 g; adding the mixed solution into a clean empty three-neck flask, and adding absolute ethyl alcohol with the volume 3.5-4.5 times of the volume of the mixed solution into the three-neck flask; and (3) putting the three-neck flask into a water bath kettle, heating and stirring for 25-35 min, then carrying out condensation reflux treatment on the mixed solution, and drying the nano silicon nitride modified by the surface modifier to obtain the modified nano silicon nitride.
7. The preparation method of the nano silicon nitride modified heat-conducting insulating paper as claimed in claim 1, wherein the particle size of the modified nano silicon nitride in the step (6) is 15-30 nm, and the content of iron in the modified nano silicon nitride is below 8 ppm.
8. The method for preparing the thermal conductive and insulating paper based on the modification of the nano silicon nitride as claimed in claim 1, wherein the addition amount of the modified nano silicon nitride in each 1000ml of pulp suspension in the step (7) is 0.015-0.3 g.
9. The preparation method of the nano silicon nitride modified heat-conducting insulating paper as claimed in claim 1, wherein 0.005-0.008 g of sulfonated nano graphite powder is further added to each 1000ml of the pulp mixed liquid in the step (7).
10. The preparation method of the nano silicon nitride modified heat-conducting insulating paper as claimed in claim 1, wherein in the step (8), the pressed and formed wet paper sheet is subjected to primary drying at the temperature of 55-85 ℃, and the drying time is 7-12 min, so as to obtain a primary dried paper sheet; putting the paper sheet subjected to primary drying into a vacuum degree of-0.06 MPa, and performing secondary drying at a drying temperature of 80-85 ℃, wherein the drying time is 5-8 min, so as to obtain a secondary dried paper sheet; and (3) drying the paper sheet subjected to secondary drying for three times at the temperature of 75-85 ℃ until the moisture content of the paper sheet is below 0.5%, thus obtaining the nano silicon nitride modification-based heat conduction insulating paper.
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