CN119286428A

CN119286428A - Preparation method and application of a ternary flame retardant-thermal conductive integrated additive with a self-contained heat conduction channel

Info

Publication number: CN119286428A
Application number: CN202411588424.4A
Authority: CN
Inventors: 靳艳巧; 洪家辉; 熊雷; 陈清煌; 郑晶; 孙娜娜
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2024-11-08
Filing date: 2024-11-08
Publication date: 2025-01-10

Abstract

The present invention discloses a preparation method and application of a ternary flame-retardant and thermally conductive integrated auxiliary agent with a self-carrying heat-conducting channel. Flake boron nitride and spherical aluminum oxide are activated, and are carried on needle-shaped microcrystalline cellulose by a chemical grafting method to obtain a ternary thermal conductor. At the same time, polyphosphoric acid is used as an acid source, melamine is used as a gas source, and pentaerythritol is used as a main carbon source. The activated ternary thermal conductor is flame-retardantly modified by combining grafting and coating methods to obtain a ternary flame-retardant and thermally conductive auxiliary agent. The ternary flame-retardant and thermally conductive auxiliary agent in the present invention not only realizes effective contact between heat-conducting media, but also provides a three-dimensional heat-conducting channel with orientation for the polyurethane adhesive by adding the agent to the polyurethane adhesive, which significantly improves the thermal conductivity of the adhesive; at the same time, the introduction of the intumescent flame retardant can effectively suppress the melt droplets of the polyurethane adhesive, giving it efficient flame-retardant properties, thereby realizing flame-retardant and thermally conductive integration.

Description

Preparation method and application of ternary flame-retardant-heat-conducting integrated auxiliary agent of self-carrying heat-conducting channel

Technical Field

The invention belongs to the technical field of adhesives, and particularly relates to a preparation method and application of a ternary flame-retardant and heat-conducting integrated auxiliary agent of a self-carrying heat-conducting channel.

Background

Polyurethane (PU) adhesives have excellent adhesive properties and are widely applied to the fields of aerospace, wood decoration, automobile sealants, synthetic leather, paint, building materials, electronics and the like. Although the polyurethane adhesive has excellent performance, the polyurethane adhesive is a combustible material. The polyurethane adhesive can be almost instantaneously ignited when being exposed to flame, and can release a large amount of heat, smoke, carbon monoxide, hydrogen cyanide and other toxic gases during combustion. Therefore, the use of flame retardants is critical to the fire safety of polyurethane adhesives, especially in the field of electronic packaging. The electronic component has heating property, the heat conductivity coefficient of the polyurethane adhesive is only 0.15-0.3W/(m ∙ K) generally, the polyurethane adhesive has almost no heat conduction effect, heat generated by the electronic component cannot be effectively conducted out, the reliability and the service life of the electronic equipment can be reduced, and the adhesive is easy to burn when heat is accumulated. Therefore, it has become an urgent problem how to prepare a polyurethane adhesive having flame retardancy while efficiently radiating heat.

Microcrystalline cellulose is a natural source material, and has wide sources and low cost. Microcrystalline cellulose has unique orientation, cellulose chains in the structure are arranged in a highly ordered manner in a crystallization area to form a parallel crystallization structure, and the microcrystalline cellulose is not easy to deform or destroy the structure in the heat transfer process, so that a stable heat conduction path can be formed. Cellulose chains in the crystalline regions interact through hydrogen bonding, enabling heat to be transferred more efficiently within these regions. Microcrystalline cellulose typically contains hydroxyl (-OH) functional groups on its surface that can chemically react with other materials such as polymers or fillers. Through chemical modification, other functional groups can be introduced to regulate the performance of microcrystalline cellulose to adapt to specific application requirements.

Boron nitride has the characteristics of high thermal conductivity, low density, high dielectric strength and the like. The addition of boron nitride can significantly reduce the dielectric constant of the composite material, so that the composite material has excellent performance in the aspect of electrical insulation. Meanwhile, the boron nitride has excellent heat conductivity and chemical stability, the heat conduction characteristic of the composite material can be effectively enhanced, and the proper amount of boron nitride is added into the composite resin to promote the heat conduction in the material.

Alumina has the characteristics of high hardness, high melting point and high thermal conductivity. Alumina is added as a filler to polymers, paints, adhesives and sealants, which can improve the mechanical properties, wear resistance and corrosion resistance of the material. The alumina filler can also be used for packaging and heat dissipation materials of electronic devices, and can improve the heat dissipation effect of the electronic devices, protect circuit boards and improve the reliability of the circuit boards. The invention aims to synthesize the polyurethane adhesive with higher heat conduction efficiency and flame retardant property, and has wide application prospect in various fields, especially in the field of electronic packaging.

Disclosure of Invention

The invention aims to provide a preparation method and application of a ternary flame-retardant and heat-conducting integrated auxiliary agent for a self-carried heat conducting channel, and the obtained auxiliary agent is added into a polyurethane adhesive, so that the polyurethane adhesive has the advantages of high heat conductivity, good heat stability, high flame-retardant efficiency, molten drop resistance and the like.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a preparation method of a ternary flame-retardant and heat-conducting integrated auxiliary agent of a self-carrying heat-conducting channel comprises the following steps:

(1) Dispersing spherical alumina in Tris buffer solution, performing ultrasonic treatment for 30 min to obtain spherical alumina suspension, adding dopamine hydrochloride, stirring for 6h at room temperature, dropwise adding KH550 coupling agent, continuously stirring for reacting for 5h at 60 ℃, performing suction filtration, washing, and drying for 12-24 h at 70-80 ℃ to obtain an activated spherical alumina heat-conducting agent;

(2) Dispersing flaky boron nitride in a mixed solution of Tris buffer solution and ethanol for ultrasonic treatment for 30min to obtain flaky boron nitride suspension, adding dopamine hydrochloride, stirring for 6h at room temperature, dripping KH550 coupling agent, continuously stirring for reaction for 5h at 60 ℃, carrying out suction filtration and washing, and drying for 12-24 h at 70-80 ℃ to obtain an activated flaky boron nitride heat-conducting agent;

(3) Soaking microcrystalline cellulose in alkali liquor for 3 h, freezing at-18 ℃ for 12: 12h, and stirring at room temperature to obtain uniform microcrystalline cellulose suspension;

(4) Adding the spherical alumina heat conducting agent and the flaky boron nitride heat conducting agent obtained in the step (1) and the step (2) into the microcrystalline cellulose suspension obtained in the step (3), magnetically stirring for 2 hours at room temperature, centrifuging, discarding the supernatant, washing the precipitate with ethanol solution to be neutral, and adding absolute ethanol to obtain a surface-activated ternary heat conducting agent suspension;

(5) Adding pentaerythritol into phosphoric acid, magnetically stirring at 140 ℃ for 1.5 h, slowly adding a suspension of melamine and absolute ethyl alcohol, reducing the temperature to 80 ℃ and continuously stirring for 6 h, and drying after the reaction is completed to obtain a flame retardant auxiliary;

(6) Uniformly dispersing the flame retardant auxiliary obtained in the step (5) into absolute ethyl alcohol, adding the absolute ethyl alcohol into the ternary heat conductive agent suspension obtained in the step (4), continuously stirring for 2h, adding aluminum hydroxide, continuously reacting for 1h, and drying the reactant after the reaction is finished to obtain the flame retardant-heat conductive integrated auxiliary.

Further, the mass ratio of the dopamine hydrochloride to the platy boron nitride to the spherical alumina is 1:5:5, and the dosage of the KH550 coupling agent is 2.5 mL for every 1 g dopamine hydrochloride.

Further, in the step (3), the mass concentration of the alkali liquor is 5%, the dosage of the alkali liquor is 200 mL for every 4 g microcrystalline cellulose, and the alkali liquor is one of sodium hydroxide and potassium hydroxide solution.

Further, in the step (4), the mass ratio of the activated spherical alumina heat conductive agent to the flaky boron nitride heat conductive agent is 1:1-2:1, the total mass ratio of microcrystalline cellulose to the heat conductive agent is 15 (1-3), and the concentration of the ethanol solution is 60-95%.

Further, the molar ratio of pentaerythritol, the phosphoric acid, the melamine and the aluminum hydroxide in the step (5) and the step (6) is 1:2:2:2, and the phosphoric acid is one or more of polyphosphoric acid, phosphoric acid and phytic acid.

Further, in the step (6), the mass ratio of the flame retardant auxiliary agent to the ternary heat conductive agent is (2-5) to 15.

The invention also provides the ternary flame-retardant and heat-conducting integrated auxiliary agent prepared by the method.

The application of the ternary flame-retardant and heat-conducting integrated auxiliary agent in the polyurethane adhesive is that the ternary flame-retardant and heat-conducting integrated auxiliary agent is added into the polyurethane adhesive, and the addition amount of the ternary flame-retardant and heat-conducting integrated auxiliary agent is 50-70% of the mass of the polyurethane adhesive.

The invention is characterized in that flaky boron nitride and spherical alumina are compounded, needle-shaped microcrystalline cellulose is used as an orientation channel, surface activation treatment is carried out on the boron nitride and the alumina, and the boron nitride and the alumina are carried on the needle-shaped microcrystalline cellulose by a chemical grafting method to form a three-dimensional heat conduction channel with certain orientation. According to the action principle of the flame retardant, polyphosphoric acid is used as an acid source, melamine is used as an air source, pentaerythritol is used as a main carbon source, the activated ternary heat-conducting agent is subjected to flame retardant modification by combining grafting and coating methods, and the modified ternary flame retardant-heat-conducting integrated auxiliary agent is added into the polyurethane adhesive in a simple physical blending mode to prepare the ternary high-efficiency flame retardant-heat-conducting polyurethane adhesive with heat conducting channels. The microcrystalline cellulose is used as a main bridge, and chemical bonding is realized between the heat conducting agent and the flame retardant through hydrogen bonding action between the microcrystalline cellulose and other substances and esterification reaction of polyphosphoric acid and hydroxyl, so that an integrated flame-retardant heat conducting auxiliary agent is formed, and finally the flame-retardant heat conducting integrated polyurethane adhesive is obtained. In addition, the unique structure of the microcrystalline cellulose can also improve the problem of poor mechanical properties of the composite material under the condition of higher inorganic filling quantity.

The invention has the beneficial effects that:

(1) According to the invention, spherical aluminum oxide and flaky boron nitride are used as heat conducting media, flaky aluminum nitride with large particle size is used as main media for heat transmission, gaps which are in contact with each other between flaky boron nitride are supplemented by spherical aluminum oxide with small particle size, the contact area between heat conducting agents can be effectively increased by compounding the spherical aluminum oxide and the flaky boron nitride with different shapes and sizes, and a channel network with orientation can be provided by introducing needle-shaped cellulose, so that heat conducting inorganic matters are orderly distributed, the utilization rate of heat conducting auxiliary agents is improved, and the heat transfer in the polyurethane adhesive is promoted. Therefore, the synergistic effect of the ternary heat conduction auxiliary agent can greatly improve the heat conductivity of the material, and when the filling quantity of the heat conduction auxiliary agent is 55%, the heat conductivity of the polyurethane adhesive can reach 2.28W/M ∙ K.

(2) The auxiliary agent synthesized by the invention integrates flame retardance and heat conduction, has better compatibility with most resin matrixes, can be used as a modified auxiliary agent for various resin matrixes, and provides a novel method for multifunctional modification of resin materials. The introduction of microcrystalline cellulose promotes the mutual combination of the heat conduction auxiliary agent and the flame retardant auxiliary agent to a certain extent, so that the flame retardant-heat conduction integrated auxiliary agent is formed, and the processing technology of the material is simplified. In addition, the cellulose can also be used as a carbon source of the intumescent flame retardant, the char yield and the flame retardant property of the material are improved, and the flame retardant grade of the modified polyurethane adhesive can reach UL 94V-0 grade.

Drawings

FIG. 1 is a diagram of a process for synthesizing a ternary flame retardant-thermally conductive integrated adjuvant of the present invention.

Fig. 2 is an infrared spectrum of the ternary flame retardant-heat conductive integrated auxiliary agent prepared in example 1.

FIG. 3 is a scanning electron microscope image of the ternary flame retardant-thermally conductive integrated auxiliary prepared in example 1.

FIG. 4 is an energy dispersive X-ray spectrum of the ternary flame retardant-thermally conductive integrated adjuvant prepared in example 1.

FIG. 5 is a scanning electron microscope image of a carbon layer after burning a spline prepared in example 1.

FIG. 6 is a scanning electron micrograph of a carbon layer after burning a spline prepared in application example 2.

FIG. 7 is a scanning electron micrograph of a carbon layer after burning a spline prepared in comparative example 1.

FIG. 8 is a scanning electron micrograph of a carbon layer after burning a spline prepared in comparative example 2.

FIG. 9 is a scanning electron micrograph of a carbon layer after burning a spline prepared in comparative example 3.

Detailed Description

In order to make the contents of the present invention more easily understood, the technical scheme of the present invention will be further described with reference to the specific embodiments, but the present invention is not limited thereto.

Example 1

Pouring 200 mL deionized water into a beaker, slowly adding 1.2 g Tris (hydroxymethyl) aminomethane, titrating the system to pH=8.5 by using a hydrochloric acid solution to prepare Tris buffer solution with pH=8.5, slowly adding spherical alumina with the particle size of 10 g of about 5-6 mu m into the Tris buffer solution, performing ultrasonic dispersion for 30min to obtain an alumina suspension after preliminary dispersion activation, weighing 2g dopamine hydrochloride, slowly pouring into the suspension, magnetically stirring for 6h at room temperature by 300 rpm, adding 5mL KH550 coupling agent, continuously stirring for 5 h at 60 ℃, finally performing suction filtration on the mixture, washing by using deionized water, and drying for 12 h at 70 ℃ to obtain the activated spherical alumina heat conduction auxiliary agent.

Pouring 600 mL deionized water into another beaker, slowly adding 1.2 g Tris (hydroxymethyl) aminomethane to prepare Tris buffer solution with pH of 8.5, adding 200 mL absolute ethyl alcohol to mix, slowly adding 8 g platy boron nitride with particle size of about 25 mu m into the solution, performing ultrasonic dispersion for 30 min to obtain platy boron nitride suspension after primary dispersion and activation, weighing 1.6 g dopamine hydrochloride, slowly pouring into the suspension, magnetically stirring for 6h at room temperature by 300 rpm, adding 4 mL KH550 coupling agent, continuously stirring for 5h at 60 ℃, and finally performing suction filtration on the mixture, washing by deionized water and absolute ethyl alcohol respectively, and drying for 12 h at 70 ℃ to obtain activated platy boron nitride heat conduction auxiliary agent.

10 G sodium hydroxide is weighed and poured into 190 mL deionized water to prepare sodium hydroxide solution with the mass concentration of 5%, 4 g microcrystalline cellulose solid powder is weighed and added into the sodium hydroxide solution, stable suspension is formed after standing for 3h at room temperature, the suspension is moved to the environment of-18 ℃ to keep 12 h, solid frozen matter is formed, and the suspension is moved to room temperature to be thawed through mechanical stirring, so that uniform microcrystalline cellulose suspension is formed.

Weighing 30 g of each of the activated spherical alumina heat conduction auxiliary agent and the activated flaky boron nitride heat conduction auxiliary agent, slowly pouring the mixture into a microcrystalline cellulose suspension, magnetically stirring the mixture at 500 rpm at room temperature for 2h, centrifuging the mixture by 9000 rpm, discarding supernatant after 10 min, collecting precipitate, washing the precipitate by using 60%, 70%, 80%, 90% and 95% ethanol solution successively until the precipitate is neutral, weighing 600 mL of absolute ethyl alcohol, and pouring the mixture into a reaction system to obtain the surface-activated ternary heat conduction agent suspension.

Adding 14.3 g pentaerythritol into 54.2 g polyphosphoric acid, magnetically stirring at 140 ℃ by 400 rpm for 1.5 h, weighing 15 g melamine, pouring the melamine into 600 mL absolute ethyl alcohol to form melamine-ethyl alcohol suspension, slowly adding the melamine-ethyl alcohol suspension into the pentaerythritol-polyphosphoric acid product, adjusting the temperature to 80 ℃, magnetically stirring at 500 rpm for 6 h, and transferring the product into a 140 ℃ oven for drying for 24h to obtain the flame retardant auxiliary agent.

8G of flame retardant auxiliary is weighed and poured into 200 mL of absolute ethyl alcohol, and is uniformly dispersed at 80 ℃ through 500 and rpm of magnetic stirring to obtain a suspension, the suspension is slowly added into the surface-activated ternary heat conducting agent suspension, after 2h of magnetic stirring, 2.35 g of aluminum hydroxide is added, and the magnetic stirring is continued for 1 h. And (5) transferring the product to an 80 ℃ oven for drying 12 h to obtain the flame-retardant and heat-conducting integrated auxiliary agent.

18.4 G Poly (1, 4-butylene adipate) was weighed into a three-necked flask and dehydrated at 80℃to 3 h. 0.03 g of H8O2 defoamer, 0.015 g dibutyl tin dilaurate and 3.1 g of 1, 4-butanediol are added into poly (1, 4-butanediol adipate) in a dropwise manner, after the mixture is magnetically stirred at 80 ℃ for 30 s by 500 rpm, the flame-retardant and heat-conducting integrated auxiliary agent 42 g is slowly added, the mixture is continuously stirred for 30 s, after the system is uniformly stirred, 1.6 g hexamethylene diisocyanate is slowly added in a dropwise manner, and the mixture is continuously stirred for 1 min, so that the ternary flame-retardant and heat-conducting polyurethane adhesive with a self-carrying heat conducting channel is obtained.

Fig. 2 is an infrared spectrogram of the ternary flame retardant-heat conductive integrated auxiliary agent prepared in application example 1. As can be seen from the graph, the stretching vibration of the hydroxyl groups in the dopamine hydrochloride structure causes the activated boron nitride and aluminum oxide to have obvious absorption broad peaks at 3380 cm ^-1、1630 cm^-1, which indicates that the boron nitride and aluminum oxide are successfully activated by the dopamine hydrochloride. Meanwhile, the absorption broad peak appears near 3380 cm ^-1、1630 cm^-1 in the microcrystalline cellulose structure, and for the ternary flame-retardant and heat-conducting integrated auxiliary agent, the absorption broad peak originally belonging to the activated boron nitride and aluminum oxide structure near 3380 cm ^-1、1630 cm^-1 and caused by the hydroxyl telescopic vibration existing in the microcrystalline cellulose structure is weakened instead, which indicates that the original hydroxyl functional group is consumed along with the progress of chemical reaction, and the absorption broad peak strength is weakened. In addition, C-H bending vibration and C-O-C (ether bond) stretching vibration peaks (1390 cm ^-1 and 1070 cm ^-1) in the microcrystalline cellulose structure also appear in the infrared spectrogram of the ternary flame-retardant-heat-conducting integrated auxiliary agent, so that the boron nitride and the aluminum oxide can smoothly perform chemical grafting reaction with microcrystalline cellulose after being activated by dopamine hydrochloride. Fig. 3 and 4 are respectively a scanning electron microscope image and an energy dispersion X-ray spectrum image of the ternary flame retardant-heat conductive integrated additive prepared in application example 1. As can be seen from fig. 3, the ternary flame retardant-heat conduction integrated auxiliary agent is integrally distributed in a net shape, and because the activated boron nitride and aluminum oxide generate hydrogen bond action with microcrystalline cellulose, heat conduction inorganic matters can be distributed along the whisker structure of the microcrystalline cellulose with certain orientation, and a three-dimensional net-shaped heat conduction channel is constructed. And as can be seen from the energy dispersion X-ray spectrum chart 4 of the ternary flame retardant-heat conductive integrated auxiliary agent, the main C, N, P flame retardant elements are also distributed along the veins of the network structure, which shows that the flame retardant auxiliary agent is successfully chemically combined with activated boron nitride and aluminum oxide on the molecular level.

Example 2

Pouring 200 mL deionized water into a beaker, slowly adding 1.2 g Tris (hydroxymethyl) aminomethane, titrating the system to pH=8.5 by using a hydrochloric acid solution to prepare a Tris buffer solution with pH=8.5, slowly adding 10 g spherical alumina with the particle size of about 5-6 mu m into the Tris buffer solution, performing ultrasonic dispersion for 30min to obtain an alumina suspension after preliminary dispersion activation, weighing 2g dopamine hydrochloride, slowly pouring into the suspension, magnetically stirring for 6 h at room temperature by 300 rpm, adding 5mL KH550 coupling agent, continuously stirring for 5h at 60 ℃, finally performing suction filtration on the mixture, washing by using deionized water, and drying for 12 h at 70 ℃ to obtain the activated spherical alumina heat conduction auxiliary agent.

Adding 600 mL deionized water into another beaker, slowly adding 1.2 g Tris (hydroxymethyl) aminomethane to prepare Tris buffer solution with pH of 8.5, adding 200mL absolute ethyl alcohol to mix, slowly adding 8 g platy boron nitride with particle size of about 25 mu m into the solution, performing ultrasonic dispersion for 30 min to obtain platy boron nitride suspension after primary dispersion and activation, weighing 1.6 g dopamine hydrochloride, slowly pouring into the suspension, magnetically stirring at room temperature for 6 h by 300: 300 rpm, adding 4mL KH550 coupling agent, continuously stirring at 60 ℃ for 5: 5 h, and finally performing suction filtration on the mixture, washing by deionized water and absolute ethyl alcohol respectively, and drying at 70 ℃ for 12: 12 h to obtain activated platy boron nitride heat conduction auxiliary agent.

10 G sodium hydroxide is weighed and poured into 190 mL deionized water to prepare sodium hydroxide solution with the mass concentration of 5%, 4g of microcrystalline cellulose solid powder is weighed and added into the sodium hydroxide solution, stable suspension is formed after standing for 3 h at room temperature, the suspension is moved to the environment of-18 ℃ to keep 12h, solid frozen matter is formed, and the suspension is moved to room temperature to be thawed through mechanical stirring, so that uniform microcrystalline cellulose suspension is formed.

Weighing activated spherical aluminum oxide heat conduction auxiliary agent 40 g and activated platy boron nitride heat conduction auxiliary agent 20 g, slowly pouring the spherical aluminum oxide heat conduction auxiliary agent 40 and the activated platy boron nitride heat conduction auxiliary agent 20 g into a microcrystalline cellulose suspension, magnetically stirring the mixture at 500 rpm at room temperature for 2h, centrifuging the mixture at 9000rpm for 10 min, discarding supernatant, collecting precipitate, washing the precipitate by using ethanol solution with concentration of 60%, 70%, 80%, 90% and 95% successively until the system is washed to be neutral, weighing absolute ethanol 600 mL, and pouring the anhydrous ethanol 600 mL into a reaction system to obtain a surface-activated ternary heat conduction agent suspension.

8 G flame retardant auxiliary is weighed and poured into 200 mL absolute ethyl alcohol, and is uniformly dispersed by 500 and rpm magnetic stirring at 80 ℃, the uniform suspension is slowly added into the surface-activated ternary heat conductive agent suspension to be magnetically stirred for 2h, and then 2.35 g aluminum hydroxide is added to continue magnetic stirring for 1 h. And (5) transferring the product to an 80 ℃ oven for drying 12 h to obtain the flame-retardant and heat-conducting integrated auxiliary agent.

Comparative example 1

18.4 G Poly (1, 4-butylene adipate) was weighed into a three-necked flask and dehydrated at 80℃to 3 h. 0.03 g of H8O2 defoamer, 0.015 g g of dibutyltin dilaurate and 3.1 g of 1, 4-butanediol are added dropwise to the poly (1, 4-butanediol adipate), after magnetic stirring is carried out at 80 ℃ by 500: 500 rpm for 30: 30 s, 1.6: 1.6 g hexamethylene diisocyanate is slowly added dropwise, and stirring is continued for 1: 1 min, so that the polyurethane adhesive is obtained.

Comparative example 2

8 G flame retardant auxiliary is weighed and poured into 200mL absolute ethyl alcohol, after being uniformly dispersed by magnetic stirring at 500rpm at 80 ℃, the activated spherical aluminum oxide heat conduction auxiliary and flaky boron nitride heat conduction auxiliary are added into the mixture, 15 g are respectively added, after stirring for 2h, 1.18 g aluminum hydroxide is added, and magnetic stirring is continued for 1 h. And (5) transferring the product to an 80 ℃ oven for drying 12h to obtain the binary flame-retardant heat-conducting auxiliary agent.

18.4 G of poly (1, 4-butylene adipate) was weighed into a three-necked flask and dehydrated at 80℃to 3 h. Dropwise adding 0.03 g of H8O2 defoamer, 0.015 g dilaurate-dibutyl tin and 3.1 g of 1, 4-butanediol into poly (1, 4-butanediol adipate), magnetically stirring at 80 ℃ by 500 rpm for 30 s, slowly adding 42g of binary flame retardant heat conduction auxiliary agent, continuously stirring for 30 s, slowly dropwise adding 1.6 g hexamethylene diisocyanate, continuously stirring for 1 min after the system is uniformly stirred, and obtaining the binary heat conduction polyurethane adhesive.

Comparative example 3

18.4 G of poly (1, 4-butylene adipate) was weighed into a three-necked flask and dehydrated at 80℃to 3 h. 0.03 g of H8O2 defoamer, 0.015 g dibutyl tin dilaurate and 3.1 g of 1, 4-butanediol are added into poly (1, 4-butanediol adipate) in a dropwise manner, after the mixture is magnetically stirred at 80 ℃ by 500: 500 rpm for 30: 30 s, a flame retardant auxiliary agent 8 g, spherical alumina 10: 10 g, flaky boron nitride 20: 20 g and microcrystalline cellulose 4: 4 g are slowly added, the mixture is continuously stirred for 30: 30 s, and after the system is uniformly stirred, hexamethylene diisocyanate 1.6: 1.6 g is slowly added in a dropwise manner, the mixture is continuously stirred for 1:1 min, so that the heat-conducting polyurethane adhesive is obtained.

Application example 1

The ternary flame-retardant-heat-conducting polyurethane adhesive for self-supporting heat-conducting channels obtained in example 1 was hot-pressed by a flat vulcanizing machine to prepare flame-retardant performance test bars (length×width×thickness=130 mm ×10mm ×3.2 mm), mechanical performance standard test bars and heat-conducting performance test sample blocks (length×width×thickness=40 mm ×40 mm ×5× 5 mm) for testing.

The results show that the vertical burning test grade of the sample can reach UL 94V-0 grade, the LOI value is 35.3%, the elongation at break is 7.9%, the tensile strength is 45.1 MPa, the carbon residue rate of the flame-retardant sample bar after being fully carbonized in a muffle furnace at 600 ℃ is 54.1%, and the heat conductivity coefficient is 2.28W/m ∙ k.

Application example 2

The ternary flame-retardant-heat-conducting polyurethane adhesive for self-supporting heat-conducting channels obtained in example 2 was hot-pressed by a flat vulcanizing machine to prepare flame-retardant performance test bars (length×width×thickness=130 mm ×10 mm ×3.2 mm), mechanical performance standard test bars and heat-conducting performance test sample blocks (length×width×thickness=40 mm ×40mm ×5× 5 mm) for testing.

The results show that the vertical burning test grade of the sample can reach UL 94V-0 grade, the LOI value is 28.5%, the elongation at break is 8.4%, the tensile strength is 48.4 MPa, the carbon residue rate of the flame-retardant sample bar after being fully carbonized in a muffle furnace at 600 ℃ is 54.38%, and the heat conductivity coefficient is 1.6W/m ∙ k.

FIGS. 5 and 6 are scanning electron micrographs of carbon layers after burning of the bars prepared in application examples 1 and 2, respectively. The graph shows that a large amount of residual inorganic matters and carbon residue form a compact lamellar structure, and a large amount of large holes are not formed on the surface, so that the flame retardant coating has a good flame retardant property.

Comparative example 1 was used

The polyurethane obtained in comparative example 1 was hot-press molded by a press vulcanizer to prepare flame retardant property test bars (length×width×thickness=130 mm ×10mm ×3.2 mm), mechanical property standard test bars and heat conductive property test bars (length×width×thickness=40 mm ×40 mm ×5× 5 mm) for testing.

The results showed that the test specimens had a vertical burn test rating of UL94 NR rating, an LOI value of 18.2%, an elongation at break of 461.6%, a tensile strength of 12.35 MPa, a char residue after adequate carbonization of the flame retardant spline in a muffle furnace at 600 ℃ of 0.2% and a thermal conductivity of 0.23W/m ∙ k.

FIG. 7 is a scanning electron microscope image of a carbon layer after spline combustion prepared by comparative example 1. As can be seen from the figure, the carbon layer is coarse and has large holes, so that the heat source cannot be effectively blocked, and the ideal flame-retardant effect is not achieved.

Comparative example 2 was used

The polyurethane obtained in comparative example 2 was hot-press molded by a press vulcanizer to prepare flame retardant property test bars (length×width×thickness=130 mm ×10mm ×3.2 mm), mechanical property standard test bars and heat conductive property test bars (length×width×thickness=40 mm ×40 mm ×5× 5 mm) for testing.

The results showed that the vertical burn test rating of the test specimen was only UL 94V-1, the LOI value was 26.8%, the elongation at break was 8.0%, the tensile strength was 10.6 MPa, the mechanical properties were lowered, the carbon residue ratio after the flame-retardant spline was sufficiently carbonized in a muffle furnace at 600 ℃ was 52.1%, and the thermal conductivity was 1.53W/m ∙ k.

FIG. 8 is a scanning electron microscope image of a carbon layer after spline burning prepared in comparative application example 2. As can be seen from the figure, only a partial layered structure is formed, the holes of the carbon layer are more, the whole carbon layer is uneven, a heat source cannot be effectively blocked, and an ideal flame-retardant effect is not achieved.

Comparative example 3 was used

The heat conductive polyurethane adhesive obtained in comparative example 3 was hot-press molded by a press vulcanizer to prepare flame retardant property test bars (length×width×thickness=130 mm ×10 mm ×3.2 mm), mechanical property standard test bars and heat conductive property test bars (length×width×thickness=40 mm ×40 mm ×5 mm) for testing.

The results show that the vertical burning test grade of the sample is only UL 94V-1, the LOI value is 24.0%, the elongation at break is 1.1%, the tensile strength is 22.5 MPa, the mechanical property is reduced, the carbon residue rate of the flame-retardant spline after being fully carbonized in a muffle furnace at 600 ℃ is 53.34%, and the heat conductivity coefficient is 2W/m ∙ k.

FIG. 9 is a scanning electron microscope image of the carbon layer after spline burning prepared in comparative application example 3. The arrangement of the inorganic matters and the carbon residue is sparse, and a large gap exists between the inorganic matters and the carbon residue, so that a heat source cannot be well blocked, and an ideal flame-retardant effect is not achieved.

The comparison of application examples 1-2 and application comparative examples 1-3 can be seen:

(1) The invention refers to three different shapes of heat conductive agents of spherical alumina, platy boron nitride and acicular microcrystalline cellulose, wherein the acicular microcrystalline cellulose is used as a channel, the spherical alumina and the platy boron nitride are used as main heat conductive media, and a ternary three-dimensional heat conductive channel is built in the polyurethane adhesive. In the aspect of chemical modification, needle-shaped microcrystalline cellulose is taken as a main chemical grafting 'bridge', so that the heat conducting agent and the flame retardant can be effectively combined into a whole, and a flame-retardant and heat conducting integrated auxiliary agent is generated.

(2) The difference in the proportions of the two activated heat transfer mediums will affect the thermal conductivity of the final polyurethane adhesive to a greater extent. The high proportion of boron nitride can obviously improve the heat conductivity coefficient of the polyurethane adhesive, but at the same time, as the processability of the boron nitride is lower than that of aluminum oxide, the mechanical property of the polyurethane adhesive is deteriorated to a certain extent when the proportion of boron nitride is improved.

(3) The binary heat-conducting polyurethane adhesive has lower heat-conducting property, low heat-conducting coefficient, high-efficiency contact of heat-conducting medium can not be realized, and certain heat-conducting orientation does not exist in the material, so that a higher filling quantity of the heat-conducting agent is generally required to enable the heat-conducting coefficient of the product to reach the qualified standard, and the mechanical property of the composite material is greatly reduced due to filling of a large amount of auxiliary agents. Meanwhile, the binary polyurethane adhesive has poor flame retardant effect, and the overall carbon content of the material is insufficient, so that the combustion inhibition effect cannot be effectively realized.

(4) The ternary heat conduction auxiliary agent is directly blended with the polyurethane adhesive, so that the heat conduction performance of the material can be improved to a certain extent, but the heat conduction medium is not modified, no targeting is generated between the mediums, so that the contact area of the medium is small, and the heat conduction coefficient is not high. Meanwhile, the unmodified auxiliary agent has poor compatibility with polyurethane, and the mechanical property of the final composite material is drastically reduced.

The foregoing description is only of the preferred embodiments of the invention, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A method for preparing a ternary flame retardant and heat conducting integrated additive for a self-supporting heat conducting channel, characterized in that it comprises the following steps:

(1) Spherical alumina was dispersed in Tris buffer and ultrasonicated for 30 min to obtain a spherical alumina suspension. Dopamine hydrochloride was added and stirred at room temperature for 6 h. KH550 coupling agent was added dropwise and stirred at 60 °C for 5 h. The mixture was filtered and washed, and then dried at 70-80 °C for 12-24 h to obtain an activated spherical alumina thermal conductor.

(2) Dispersing flake boron nitride in a mixed solution of Tris buffer and ethanol and ultrasonicating for 30 min to obtain a flake boron nitride suspension, adding dopamine hydrochloride and stirring at room temperature for 6 h, adding KH550 coupling agent dropwise and continuing to stir at 60 °C for 5 h, filtering, washing, and drying at 70-80 °C for 12-24 h to obtain an activated flake boron nitride thermal conductor;

(3) Soaking microcrystalline cellulose in an alkaline solution for 3 h, freezing it at -18 °C for 12 h, and then stirring it at room temperature to obtain a uniform microcrystalline cellulose suspension;

(4) adding the spherical alumina thermal conductor and the flake boron nitride thermal conductor obtained in step (1) and step (2) to the microcrystalline cellulose suspension obtained in step (3), magnetically stirring at room temperature for 2 hours, centrifuging, discarding the supernatant, washing the precipitate with an ethanol solution until it is neutral, and adding anhydrous ethanol to obtain a surface-activated ternary thermal conductor suspension;

(5) Add pentaerythritol to the phosphorus-containing acid, stir magnetically at 140 °C for 1.5 h, slowly add the suspension of melamine and anhydrous ethanol, lower the temperature to 80 °C and continue stirring for 6 h. After the reaction is completed, dry to obtain a flame retardant additive;

(6) The flame retardant additive obtained in step (5) is uniformly dispersed in anhydrous ethanol, and then added to the ternary thermal conductive agent suspension obtained in step (4) and stirred for 2 h. Aluminum hydroxide is then added and the reaction is continued for 1 h. After the reaction is completed, the reactant is dried to obtain a flame retardant-thermal conductive integrated additive.

2. The preparation method according to claim 1, characterized in that the mass ratio of dopamine hydrochloride to flaky boron nitride and spherical alumina is 1:5:5; and the amount of KH550 coupling agent used is 2.5 mL per 1 g of dopamine hydrochloride.

3. The preparation method according to claim 1, characterized in that: the mass concentration of the alkali solution in step (3) is 5%, and the amount thereof is 200 mL per 4 g of microcrystalline cellulose, and the alkali solution is one of sodium hydroxide solution and potassium hydroxide solution.

4. The preparation method according to claim 1 is characterized in that: in step (4), the mass ratio of the activated spherical alumina thermal conductor to the flaky boron nitride thermal conductor is 1:1-2:1; the total mass ratio of microcrystalline cellulose to the thermal conductor is 15:(1-3); and the concentration of the ethanol solution is 60-95%.

5. The preparation method according to claim 1, characterized in that the molar ratio of pentaerythritol, phosphorus-containing acid, melamine and aluminum hydroxide in step (5) and step (6) is 1:2:2:2, and the phosphorus-containing acid is one or more of polyphosphoric acid, phosphoric acid and phytic acid.

6. The preparation method according to claim 1, characterized in that: in step (6), the mass ratio of the flame retardant auxiliary agent to the ternary thermal conductor is (2-5):15.

7. The ternary flame retardant-thermal conductive integrated auxiliary agent prepared by the method according to any one of claims 1 to 6.

8. An application of the ternary flame retardant and thermal conductive integrated additive as claimed in claim 7 in a polyurethane adhesive, characterized in that the ternary flame retardant and thermal conductive integrated additive is added to the polyurethane adhesive in an amount of 50-70% of the mass of the polyurethane adhesive.