Preparation method and application of ternary flame-retardant-heat-conducting integrated auxiliary agent with self-loaded heat-conducting channels

Abstract

The application discloses a preparation method and application of a ternary flame-retardant-heat-conducting integrated additive with a self-loaded heat-conducting channel. Flake boron nitride and spherical alumina are activated, and the activated boron nitride and alumina are carried on acicular microcrystalline cellulose by a chemical grafting method to obtain a ternary heat-conducting agent. Meanwhile, taking polyphosphoric acid as an acid source, melamine as a gas source and pentaerythritol as a main carbon source, the activated ternary heat-conducting agent is modified by a flame-retardant method to obtain a ternary flame-retardant-heat-conducting additive. The ternary flame-retardant-heat-conducting additive can not only realize effective contact among heat-conducting media, but also provide a polyurethane adhesive with an oriented three-dimensional heat-conducting channel when the additive is added into the polyurethane adhesive, so that the heat conductivity of the adhesive is remarkably improved. Meanwhile, the introduction of the intumescent flame retardant can effectively inhibit the melt dripping of the polyurethane adhesive, and the polyurethane adhesive is endowed with high efficient flame-retardant performance, so that the flame-retardant-heat-conducting integration is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adhesives, and particularly relates to a preparation method and application of a ternary flame-retardant-heat-conducting integrated adjuvant with self-loaded heat-conducting channels. BACKGROUND

[0002] Polyurethane (PU) adhesives have excellent bonding properties and are widely used in aerospace, wood decoration, automobile sealant, synthetic leather, paint, building materials, electronics, and other fields. Although polyurethane adhesives have excellent properties, they are combustible materials. Polyurethane adhesives will almost instantly catch fire when exposed to a flame, and will release a large amount of heat, smoke, and toxic gases such as carbon monoxide and hydrogen cyanide during combustion. Therefore, the use of flame retardants is crucial for the fire safety of polyurethane adhesives, especially in the field of electronic packaging. Electronic components themselves generate heat, and the thermal conductivity of polyurethane adhesives is usually only 0.15~0.3 W / (m∙K), which has almost no heat conduction effect, and cannot effectively conduct the heat generated by electronic components, which not only reduces the reliability and service life of electronic devices, but also easily leads to the combustion of adhesives due to the accumulation of heat. Therefore, how to prepare a polyurethane adhesive with flame retardancy and high heat dissipation efficiency has become an increasingly urgent problem.

[0003] Microcrystalline cellulose is a natural source of material, which is widely available and has low cost. Microcrystalline cellulose has a unique orientation, with cellulose chains in the crystalline region arranged in a highly ordered manner, forming parallel crystalline structures that are less likely to deform or break during heat transfer, and can form stable heat conduction paths. The cellulose chains in the crystalline region interact through hydrogen bonds, allowing heat to be more effectively transferred within these regions. The surface of microcrystalline cellulose usually contains hydroxyl (-OH) functional groups, which can chemically react with other materials such as polymers or fillers. Through chemical modification, other functional groups can be introduced to adjust the properties of microcrystalline cellulose to meet specific application requirements.

[0004] Boron nitride has high thermal conductivity, low density, and high dielectric strength. The addition of boron nitride can significantly reduce the dielectric constant of the composite material, making it have excellent performance in electrical insulation. At the same time, the excellent thermal conductivity and chemical stability of boron nitride can effectively enhance the thermal conductivity of the composite material, and the addition of an appropriate amount of boron nitride in the composite resin can promote the conduction of heat within the material.

[0005] Alumina has the characteristics of high hardness, high melting point and high thermal conductivity. As a filler added to polymers, coatings, adhesives and sealants, alumina can improve the mechanical properties, wear resistance and corrosion resistance of the materials. Alumina filler can also be used for packaging and heat dissipation materials of electronic devices, which can improve the heat dissipation effect of electronic devices, protect the circuit board and improve its reliability. The present application aims to synthesize a polyurethane adhesive with high thermal conductivity and flame retardant performance, which has wide application prospect in various fields, especially in the field of electronic packaging. SUMMARY

[0006] The present application aims to provide a preparation method and application of a ternary flame-retardant-thermal-conductive integrated additive with self-loaded thermal-conductive channels. The obtained additive is added to polyurethane adhesive, which has high thermal conductivity, good thermal stability, high flame retardant efficiency and anti-dripping advantages.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A preparation method of a ternary flame-retardant-thermal-conductive integrated additive with self-loaded thermal-conductive channels, comprising the following steps:

[0009] (1) Disperse the spherical alumina in Tris buffer solution for 30 min to obtain a spherical alumina suspension, add dopamine hydrochloride and stir at room temperature for 6 h, then add KH550 coupling agent and continue to stir at 60 °C for 5 h, then filter, wash and dry at 70-80 °C for 12-24 h to obtain activated spherical alumina thermal conductor;

[0010] (2) Disperse the flaky boron nitride in a mixed solution of Tris buffer solution and ethanol for 30 min to obtain a flaky boron nitride suspension, add dopamine hydrochloride and stir at room temperature for 6 h, then add KH550 coupling agent and continue to stir at 60 °C for 5 h, then filter, wash and dry at 70-80 °C for 12-24 h to obtain activated flaky boron nitride thermal conductor;

[0011] (3) Soak the microcrystalline cellulose in lye for 3 h, then freeze at-18 °C for 12 h, and then stir at room temperature to obtain a uniform microcrystalline cellulose suspension;

[0012] (4) Add the spherical alumina thermal conductor and flaky boron nitride thermal conductor obtained in steps (1) and (2) to the microcrystalline cellulose suspension obtained in step (3), and stir at room temperature for 2 h, then centrifuge, discard the supernatant, wash the precipitate with ethanol solution until neutral, and then add anhydrous ethanol to obtain a surface-activated ternary thermal conductor suspension;

[0013] (5) adding pentaerythritol into the phosphorus-containing acid, after magnetic stirring at 140 DEG C for 1.5 h, slowly adding the suspension of melamine and anhydrous ethanol, reducing the temperature to 80 DEG C and continuing to stir for 6 h, and after the reaction is completed, drying to obtain the flame retardant aid;

[0014] (6) uniformly dispersing the flame retardant aid obtained in step (5) in anhydrous ethanol, and then adding into the ternary heat-conducting agent suspension obtained in step (4) to continue stirring for 2 h, and then adding aluminum hydroxide to continue to react for 1 h, and after the reaction is completed, drying the reaction product to obtain the flame-retardant and heat-conducting integrated aid.

[0015] Further, the mass ratio of the dopamine hydrochloride to the flaky boron nitride and the spherical alumina is 1:5:5; the amount of the KH550 coupling agent is 2.5 mL per 1 g of dopamine hydrochloride.

[0016] Further, in step (3), the mass concentration of the lye is 5%, and the amount of the lye is 200 mL per 4 g of microcrystalline cellulose; the lye is one of sodium hydroxide and potassium hydroxide solution.

[0017] Further, in step (4), the mass ratio of the activated spherical alumina heat-conducting agent and the flaky boron nitride heat-conducting agent is 1:1-2:1; the total mass ratio of the microcrystalline cellulose and the heat-conducting agent is 15:(1-3); and the concentration of the ethanol solution is 60-95%.

[0018] Further, in steps (5) and (6), the molar ratio of the pentaerythritol, the phosphorus-containing acid, the melamine and the aluminum hydroxide is 1:2:2:2, and the phosphorus-containing acid is one or more of polyphosphoric acid, phosphoric acid and phytic acid.

[0019] Further, in step (6), the mass ratio of the flame retardant aid to the ternary heat-conducting agent is (2-5):15.

[0020] The application further provides a ternary flame-retardant and heat-conducting integrated aid prepared by the above method.

[0021] The application further provides an application of the above ternary flame-retardant and heat-conducting integrated aid in polyurethane adhesive, wherein the ternary flame-retardant and heat-conducting integrated aid is added into the polyurethane adhesive, and the amount of addition is 50-70% of the mass of the polyurethane adhesive.

[0022] The application compounding flaky boron nitride and spherical alumina, using acicular microcrystalline cellulose as an orientation channel, carries out surface activation treatment on the boron nitride and alumina, uses the chemical grafting method to carry on the loading on the acicular microcrystalline cellulose, forms the three-dimensional heat conduction channel with a certain orientation. Using the principle of flame retardant effect, using polyphosphoric acid as an acid source, melamine as a gas source, pentaerythritol as a main carbon source, combining grafting, coating method to modify the activated ternary heat conduction agent, through the simple physical blending method, the modified ternary flame-retardant-thermal integrated additive is added to the polyurethane adhesive to prepare a ternary efficient flame-retardant-thermal polyurethane adhesive with a heat conduction channel. Microcrystalline cellulose as the main "bridge", through the hydrogen bond between microcrystalline cellulose and other substances and the esterification reaction of polyphosphoric acid and hydroxyl, the heat conduction agent and the flame retardant realize chemical bonding, form an integrated flame-retardant-thermal additive, and finally obtain a flame-retardant-thermal integrated polyurethane adhesive. In addition, the unique structure of microcrystalline cellulose can also improve the poor mechanical properties of the composite material under a high inorganic filler content.

[0023] The beneficial effects of the application are as follows:

[0024] (1) The application uses spherical alumina and flaky boron nitride as a heat conduction medium, selects large particle size flaky aluminum nitride as the main medium for heat transfer, and uses small particle size spherical alumina to supplement the gap between flaky boron nitride. They have different shapes and sizes, and the combination of the two can effectively increase the contact area between the heat conduction agents. The introduction of acicular cellulose can provide an oriented channel network, so that the heat-conducting inorganic matter is orderly distributed, the utilization rate of the heat conduction additive is improved, and the heat transfer in the polyurethane adhesive is promoted. Therefore, the synergistic effect of the ternary heat conduction additive can greatly improve the thermal conductivity of the material. When the filling amount of the heat conduction additive is 55%, the thermal conductivity of the polyurethane adhesive can reach 2.28 W / M·K.

[0025] (2) The synthesized additive integrates flame retardation and heat conduction, has good compatibility with most resin matrices, and can be used as a modified additive for various resin matrices, providing a new method for multifunctional modification of resin materials. The introduction of microcrystalline cellulose promotes the mutual combination of heat conduction additives and flame retardant additives to some extent, forming a flame-retardant-thermal integrated additive and simplifying the processing technology of the material. In addition, cellulose can also be used as a carbon source for intumescent flame retardants to improve the carbonization rate and flame retardant performance of the material. The modified polyurethane adhesive can reach UL94 V-0 level in terms of flame retardant grade. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The synthesis process diagram of the ternary flame-retardant-thermal integrated additive of the application.

[0027] Figure 2The infrared spectrum of the ternary flame-retardant-thermal-conductive integrated adjuvant prepared in Example 1.

[0028] Figure 3 The scanning electron microscope image of the ternary flame-retardant-thermal-conductive integrated adjuvant prepared in Example 1.

[0029] Figure 4 The energy dispersive X-ray spectrum of the ternary flame-retardant-thermal-conductive integrated adjuvant prepared in Example 1.

[0030] Figure 5 The scanning electron microscope image of the carbon layer after the sample prepared in Application Example 1 was burned.

[0031] Figure 6 The scanning electron microscope image of the carbon layer after the sample prepared in Application Example 2 was burned.

[0032] Figure 7 The scanning electron microscope image of the carbon layer after the sample prepared in Application Comparative Example 1 was burned.

[0033] Figure 8 The scanning electron microscope image of the carbon layer after the sample prepared in Application Comparative Example 2 was burned.

[0034] Figure 9 The scanning electron microscope image of the carbon layer after the sample prepared in Application Comparative Example 3 was burned. DETAILED DESCRIPTION

[0035] In order to make the content described in the present application more convenient to understand, the technical solutions described in the present application will be further described below in combination with specific embodiments, but the present application is not limited thereto.

[0036] Example 1

[0037] In a beaker, 200 mL of deionized water was poured, 1.2 g of tris(hydroxymethyl)aminomethane was slowly added, and the system was titrated to pH = 8.5 using a hydrochloric acid solution to prepare a Tris buffer solution with pH = 8.5. Then, 10 g of spherical alumina with a particle size of about 5-6 µm was slowly added to the Tris buffer solution and ultrasonically dispersed for 30 min to obtain a preliminarily dispersed and activated alumina suspension. 2 g of dopamine hydrochloride was weighed and slowly poured into the above suspension. After stirring at 300 rpm and room temperature for 6 h, 5 mL of KH550 coupling agent was added, and the stirring was continued at 60 °C for 5 h. Finally, the mixture was suction filtered and washed with deionized water, and dried at 70 °C for 12 h to obtain the activated spherical alumina thermal-conductive adjuvant.

[0038] In another beaker, 600 mL of deionized water was poured, 1.2 g of tris(hydroxymethyl)aminomethane was slowly added to prepare a Tris buffer solution with pH = 8.5, then 200 mL of absolute ethanol was mixed, 8 g of flaky boron nitride with a particle size of about 25 µm was slowly added to the above solution, and ultrasonic dispersion was carried out for 30 min to obtain a flaky boron nitride suspension after preliminary dispersion and activation; 1.6 g of dopamine hydrochloride was weighed and slowly poured into the above suspension, and after stirring at room temperature for 6 h at 300 rpm, 4 mL of KH550 coupling agent was added, and the stirring was continued at 60 °C for 5 h; finally, the mixture was suction filtered, washed with deionized water and absolute ethanol, and dried at 70 °C for 12 h to obtain the activated flaky boron nitride heat-conducting additive.

[0039] 10 g of sodium hydroxide was weighed into 190 mL of deionized water to prepare a 5% sodium hydroxide solution, and 4 g of microcrystalline cellulose solid powder was added to the sodium hydroxide solution. After standing at room temperature for 3 h, a stable suspension was formed; the suspension was moved to a -18 °C environment and kept for 12 h to form a solid frozen material; it was moved to room temperature and thawed by mechanical stirring to form a uniform microcrystalline cellulose suspension.

[0040] 30 g of the activated spherical alumina heat-conducting additive and 30 g of the activated flaky boron nitride heat-conducting additive were slowly poured into the microcrystalline cellulose suspension, stirred at room temperature at 500 rpm for 2 h, then centrifuged at 9000 rpm for 10 min, the supernatant was discarded, and the precipitate was collected and washed with ethanol solutions with concentrations of 60%, 70%, 80%, 90%, and 95% in sequence until it was neutral. 600 mL of absolute ethanol was poured into the reaction system to obtain a surface-activated ternary heat-conducting agent suspension.

[0041] 14.3 g of pentaerythritol was added to 54.2 g of polyphosphoric acid, and stirred at 400 rpm at 140 °C for 1.5 h; 15 g of melamine was weighed into 600 mL of absolute ethanol to form a melamine-ethanol suspension, which was slowly added to the above pentaerythritol-polyphosphoric acid product, and the temperature was adjusted to 80 °C, and stirred at 500 rpm for 6 h. The product was moved to a 140 °C oven and dried for 24 h to obtain a flame retardant additive.

[0042] Take 8 g of flame retardant aid into 200 mL of anhydrous ethanol, disperse uniformly at 80 °C under 500 rpm magnetic stirring to obtain a suspension, slowly add the suspension into the surface-activated ternary thermal conductor suspension, after 2 h of magnetic stirring, add 2.35 g of aluminum hydroxide and continue magnetic stirring for 1 h. Move the product to a 80 °C oven and dry for 12 h to obtain the flame-retardant-thermal-conductive integrated aid.

[0043] Take 18.4 g of polybutylene adipate and place it in a three-necked flask, dehydrate at 80 °C for 3 h. Add 0.03 g of H8O2 type defoaming agent, 0.015 g of dibutyltin dilaurate and 3.1 g of 1,4-butanediol dropwise into the polybutylene adipate, and after 30 s of magnetic stirring at 80 °C under 500 rpm, slowly add the flame-retardant-thermal-conductive integrated aid 42 g, continue stirring for 30 s; after the system is uniformly stirred, slowly add 1.6 g of hexamethylene diisocyanate and continue stirring for 1 min to obtain a self-loaded thermal conduction channel ternary flame-retardant-thermal-conductive polyurethane adhesive.

[0044] Figure 2 The infrared spectrum of the ternary flame-retardant-thermal-conductive integrated aid prepared in Application Example 1 is shown in the figure. As can be seen from the figure, the hydroxyl stretching vibration in the structure of dopamine hydrochloride causes the activated boron nitride and aluminum oxide to appear obvious absorption wide peaks at 3380 cm -1 , 1630 cm -1 , which indicates that the boron nitride and aluminum oxide are successfully activated by dopamine hydrochloride. At the same time, the hydroxyl stretching vibration in the structure of microcrystalline cellulose also appears absorption wide peaks near 3380 cm -1 , 1630 cm -1 , and for the ternary flame-retardant-thermal-conductive integrated aid, the absorption wide peaks originally belonging to the hydroxyl stretching vibration in the structure of activated boron nitride and aluminum oxide and the structure of microcrystalline cellulose near 3380 cm -1 , 1630 cm -1 are actually weakened, indicating that the original hydroxyl functional group is consumed with the progress of the chemical reaction, and the absorption wide peak intensity is weakened. In addition, the C-H bending vibration and C-O-C (ether bond) stretching vibration peaks (1390 cm -1 and 1070 cm -1 ) in the structure of microcrystalline cellulose also appear in the infrared spectrum of the ternary flame-retardant-thermal-conductive integrated aid, which indicates that after the activation of boron nitride and aluminum oxide by dopamine hydrochloride, the chemical grafting reaction with microcrystalline cellulose can be successfully carried out. Figure 3 、 4 The scanning electron microscope and energy dispersive X-ray spectrum of the ternary flame-retardant-thermal-conductive integrated aid prepared in Application Example 1 are shown in the figures. As can be seen from the figures, the boron nitride and aluminum oxide are evenly distributed in the microcrystalline cellulose, and the surface of the microcrystalline cellulose is rough and uneven, which is the result of the chemical grafting reaction between the boron nitride and aluminum oxide activated by dopamine hydrochloride and the microcrystalline cellulose.Figure 3 It can be seen that the ternary flame-retardant-thermal conductive integrated additive is distributed in a network shape as a whole, which is due to the activated boron nitride and aluminum oxide, and the hydrogen bond effect between them and the microcrystalline cellulose, so that the thermal conductive inorganic matter can be distributed along the whisker structure of the microcrystalline cellulose with a certain orientation, and a three-dimensional network thermal conductive channel is constructed. And through the energy dispersive X-ray spectroscopy of the ternary flame-retardant-thermal conductive integrated additive Figure 4 It can be seen that the main C, N, P flame-retardant elements are also distributed along the network structure, which shows that the flame-retardant additive is successfully combined with the activated boron nitride and aluminum oxide at the molecular level.

[0045] Example 2

[0046] In a beaker, 200 mL of deionized water was poured, 1.2 g of tris (hydroxymethyl) aminomethane was slowly added, and the system was titrated to pH = 8.5 with hydrochloric acid solution to prepare a Tris buffer solution with pH = 8.5. Then 10 g of spherical aluminum oxide with a particle size of about 5-6 µm was slowly added to the Tris buffer solution and ultrasonically dispersed for 30 min to obtain a preliminary dispersed and activated aluminum oxide suspension. 2 g of dopamine hydrochloride was weighed and slowly poured into the above suspension. After stirring at 300 rpm at room temperature for 6 h, 5 mL of KH550 coupling agent was added and the stirring was continued at 60 °C for 5 h. Finally, the mixture was suction filtered and washed with deionized water, and dried at 70 °C for 12 h to obtain the activated spherical aluminum oxide thermal conductive additive.

[0047] In another beaker, 600 mL of deionized water was poured, 1.2 g of tris (hydroxymethyl) aminomethane was slowly added to prepare a Tris buffer solution with pH = 8.5, then 200 mL of absolute ethanol was added for mixing, 8 g of flaky boron nitride with a particle size of about 25 µm was slowly added to the above solution and ultrasonically dispersed for 30 min to obtain a preliminary dispersed and activated flaky boron nitride suspension. 1.6 g of dopamine hydrochloride was weighed and slowly poured into the above suspension. After stirring at 300 rpm at room temperature for 6 h, 4 mL of KH550 coupling agent was added and the stirring was continued at 60 °C for 5 h. Finally, the mixture was suction filtered and washed with deionized water and absolute ethanol respectively, and dried at 70 °C for 12 h to obtain the activated flaky boron nitride thermal conductive additive.

[0048] 10 g of sodium hydroxide was weighed into 190 mL of deionized water to prepare a 5% sodium hydroxide solution, and 4 g of microcrystalline cellulose solid powder was added to the sodium hydroxide solution. After standing at room temperature for 3 h, a stable suspension was formed. The suspension was moved to an environment of -18 °C and kept for 12 h to form a solid frozen material. It was moved to room temperature and thawed by mechanical stirring to form a uniform microcrystalline cellulose suspension.

[0049] Take 40 g of activated spherical alumina heat conduction aid and 20 g of activated flaky boron nitride heat conduction aid, slowly pour into the microcrystalline cellulose suspension, stir at room temperature for 2 h at 500 rpm, then centrifuge at 9000 rpm for 10 min, discard the supernatant, collect the precipitate, and wash with 60%, 70%, 80%, 90%, and 95% ethanol solution respectively until the system is neutral. Take 600 mL of absolute ethanol and pour it into the reaction system to obtain a surface-activated ternary heat conduction agent suspension.

[0050] Add 14.3 g of pentaerythritol to 54.2 g of polyphosphoric acid and stir at 400 rpm at 140 °C for 1.5 h. Take 15 g of melamine and pour it into 600 mL of absolute ethanol to form a melamine-ethanol suspension. Slowly add it to the above-mentioned pentaerythritol-polyphosphoric acid product and adjust the temperature to 80 °C. Stir at 500 rpm for 6 h. Dry the product in a 140 °C oven for 24 h to obtain a flame retardant aid.

[0051] Take 8 g of the flame retardant aid and pour it into 200 mL of absolute ethanol. Stir at 500 rpm at 80 °C until evenly dispersed. Slowly add the uniform suspension to the surface-activated ternary heat conduction agent suspension and stir magnetically for 2 h. Add 2.35 g of aluminum hydroxide and continue stirring magnetically for 1 h. Dry the product in an 80 °C oven for 12 h to obtain a flame-retardant-heat-conductive integrated aid.

[0052] Take 18.4 g of poly-1,4-butanediol adipate and place it in a three-necked flask. Dehydrate at 80 °C for 3 h. Add 0.03 g of H8O2 type defoamer, 0.015 g of dibutyltin dilaurate, and 3.1 g of 1,4-butanediol dropwise to the poly-1,4-butanediol adipate. Stir at 500 rpm at 80 °C for 30 s, then slowly add 42 g of the flame-retardant-heat-conductive integrated aid and continue stirring for 30 s. When the system is uniformly stirred, slowly add 1.6 g of hexamethylene diisocyanate and continue stirring for 1 min to obtain a self-loaded heat-conducting ternary flame-retardant-heat-conductive polyurethane adhesive.

[0053] Comparative Example 1

[0054] Take 18.4 g of polybutylene adipate and place it in a three-necked flask, and dehydrate it at 80 °C for 3 h. Add 0.03 g of H8O2 antifoaming agent, 0.015 g of dibutyltin dilaurate, and 3.1 g of 1,4-butanediol dropwise to the polybutylene adipate, and after stirring at 500 rpm for 30 s at 80 °C, slowly add 1.6 g of hexamethylene diisocyanate, and continue stirring for 1 min to obtain a polyurethane adhesive.

[0055] Comparative Example 2

[0056] Take 8 g of a flame-retardant aid and place it in 200 mL of anhydrous ethanol, and after uniformly dispersing it by stirring at 500 rpm at 80 °C, add 15 g each of activated spherical alumina and flaky boron nitride, and after stirring for 2 h, add 1.18 g of aluminum hydroxide, and continue stirring magnetically for 1 h. Move the product to an oven at 80 °C, and dry it for 12 h to obtain a binary flame-retardant heat-conducting aid.

[0057] Take 18.4 g of polybutylene adipate and place it in a three-necked flask, and dehydrate it at 80 °C for 3 h. Add 0.03 g of H8O2 antifoaming agent, 0.015 g of dibutyltin dilaurate, and 3.1 g of 1,4-butanediol dropwise to the polybutylene adipate, and after stirring at 500 rpm for 30 s at 80 °C, slowly add 42 g of the binary flame-retardant heat-conducting aid, and continue stirring for 30 s; after the system is uniformly stirred, slowly add 1.6 g of hexamethylene diisocyanate dropwise, and continue stirring for 1 min to obtain a binary heat-conducting polyurethane adhesive.

[0058] Comparative Example 3

[0059] Take 18.4 g of polybutylene adipate and place it in a three-necked flask, and dehydrate it at 80 °C for 3 h. Add 0.03 g of H8O2 antifoaming agent, 0.015 g of dibutyltin dilaurate, and 3.1 g of 1,4-butanediol dropwise to the polybutylene adipate, and after stirring at 500 rpm for 30 s at 80 °C, slowly add 8 g of a flame-retardant aid, 10 g of spherical alumina, 20 g of flaky boron nitride, and 4 g of microcrystalline cellulose, and continue stirring for 30 s; after the system is uniformly stirred, slowly add 1.6 g of hexamethylene diisocyanate dropwise, and continue stirring for 1 min to obtain a heat-conducting polyurethane adhesive.

[0060] Application Example 1

[0061] The self-loaded heat-conducting channel ternary flame-retardant-heat-conductive polyurethane adhesive obtained in Example 1 was hot-pressed by a flat vulcanizing machine to prepare flame-retardant performance test samples (length x width x thickness = 130 mm x 10 mm x 3.2 mm), mechanical property standard test samples, and heat-conducting performance test samples (length x width x thickness = 40 mm x 40 mm x 5 mm) for testing.

[0062] The results show that the vertical combustion test level of the sample can reach UL94 V-0 level, the LOI value is 35.3%, the elongation at break is 7.9%, the tensile strength is 45.1 MPa, the residual carbon rate of the flame-retardant sample after fully carbonizing at 600 °C in a muffle furnace is 54.1%, and the thermal conductivity is 2.28 W / m·k.

[0063] Application Example 2

[0064] The self-loaded heat-conducting channel ternary flame-retardant-heat-conductive polyurethane adhesive obtained in Example 2 was hot-pressed by a flat vulcanizing machine to prepare flame-retardant performance test samples (length x width x thickness = 130 mm x 10 mm x 3.2 mm), mechanical property standard test samples, and heat-conducting performance test samples (length x width x thickness = 40 mm x 40 mm x 5 mm) for testing.

[0065] The results show that the vertical combustion test level of the sample can reach UL94 V-0 level, the LOI value is 28.5%, the elongation at break is 8.4%, the tensile strength is 48.4 MPa, the residual carbon rate of the flame-retardant sample after fully carbonizing at 600 °C in a muffle furnace is 54.38%, and the thermal conductivity is 1.6 W / m·k.

[0066] Figure 5 、 6 The scanning electron microscope images of the carbon layers after combustion of the samples prepared in Application Examples 1 and 2, respectively. As can be seen from the images, a large amount of inorganic matter and residual carbon form a dense layered structure, and there are no large holes on the surface, indicating that it plays a role in blocking the heat source, and therefore has good flame-retardant performance.

[0067] Application Comparative Example 1

[0068] The polyurethane obtained in Comparative Example 1 was hot-pressed by a flat vulcanizing machine to prepare flame-retardant performance test samples (length x width x thickness = 130 mm x 10 mm x 3.2 mm), mechanical property standard test samples, and heat-conducting performance test samples (length x width x thickness = 40 mm x 40 mm x 5 mm) for testing.

[0069] The results show that the vertical burning test level of the sample is UL94 NR level, the LOI value is 18.2%, the elongation at break is 461.6%, the tensile strength is 12.35 MPa, the residual carbon rate of the flame-retardant sample is 0.2% after fully carbonizing at 600 °C in the muffle furnace, and the thermal conductivity coefficient is 0.23 W / m·k.

[0070] Figure 7 The scanning electron microscope image of the carbon layer after burning of the sample prepared in Comparative Example 1 is shown in the figure. As can be seen from the figure, the carbon layer is rough and has large holes, which cannot effectively block the heat source, and the ideal flame-retardant effect is not achieved.

[0071] Comparative Example 2

[0072] The polyurethane obtained in Comparative Example 2 is hot-pressed by a flat vulcanizing machine to prepare flame-retardant performance test samples (length x width x thickness = 130 mm x 10 mm x 3.2 mm), mechanical property standard test samples, and thermal conductivity performance test samples (length x width x thickness = 40 mm x 40 mm x 5 mm) for testing.

[0073] The results show that the vertical burning test level of the sample is only UL94 V-1 level, the LOI value is 26.8%, the elongation at break is 8.0%, the tensile strength is 10.6 MPa, the mechanical property decreases, the residual carbon rate of the flame-retardant sample is 52.1% after fully carbonizing at 600 °C in the muffle furnace, and the thermal conductivity coefficient is 1.53 W / m·k.

[0074] Figure 8 The scanning electron microscope image of the carbon layer after burning of the sample prepared in Comparative Example 2 is shown in the figure. As can be seen from the figure, only a partial layered structure is formed, and the carbon layer has many holes and is not smooth as a whole, which cannot effectively block the heat source, and the ideal flame-retardant effect is not achieved.

[0075] Comparative Example 3

[0076] The thermal conductive polyurethane adhesive obtained in Comparative Example 3 is hot-pressed by a flat vulcanizing machine to prepare flame-retardant performance test samples (length x width x thickness = 130 mm x 10 mm x 3.2 mm), mechanical property standard test samples, and thermal conductivity performance test samples (length x width x thickness = 40 mm x 40 mm x 5 mm) for testing.

[0077] The results show that the vertical burning test level of the sample is only UL94 V-1 level, the LOI value is 24.0%, the elongation at break is 1.1%, the tensile strength is 22.5 MPa, the mechanical property decreases, the residual carbon rate of the flame-retardant sample is 53.34% after fully carbonizing at 600 °C in the muffle furnace, and the thermal conductivity coefficient is 2 W / m·k.

[0078] Figure 9The scanning electron microscope image of the carbon layer after combustion of the sample prepared in application example 3 is shown for comparison. The inorganic matter and residual carbon are arranged sparsely, and there are large gaps between the inorganic matter and the residual carbon, which cannot effectively block the heat source, and the ideal flame-retardant effect is not achieved.

[0079] By comparing application examples 1-2 and application comparative examples 1-3, it can be seen that:

[0080] (1) The present application uses spherical alumina, flaky boron nitride and needle-like microcrystalline cellulose as three different shapes of heat conductors, uses needle-like microcrystalline cellulose as a channel, and uses spherical alumina and flaky boron nitride as the main heat conducting medium, thereby constructing a ternary three-dimensional heat conducting channel in the polyurethane adhesive. In terms of chemical modification, needle-like microcrystalline cellulose serves as the main chemical grafting "bridge" to effectively integrate the heat conductors and flame retardants into an integrated flame-retardant and heat-conducting additive.

[0081] (2) Different proportions of the two activated heat conducting media will greatly affect the thermal conductivity of the final polyurethane adhesive. A high proportion of boron nitride can significantly improve the thermal conductivity of the polyurethane adhesive, but at the same time, since the processability of boron nitride is lower than that of alumina, this will lead to a deterioration of the mechanical properties of the polyurethane adhesive to some extent when the proportion of boron nitride is increased.

[0082] (3) The thermal conductivity of the binary heat-conducting polyurethane adhesive is low, and the thermal conductivity coefficient is not high. The heat conducting medium cannot achieve efficient contact, and the material does not have a certain heat conducting orientation, so a high filler amount of the heat conductor is usually required to make the thermal conductivity coefficient of the product meet the qualified standard. Due to the large amount of additive filling, the mechanical properties of the composite material are greatly reduced. At the same time, the flame-retardant effect of the binary polyurethane adhesive is poor, and the overall carbon content of the material is insufficient, which cannot achieve effective combustion inhibition.

[0083] (4) Directly blending the ternary heat-conducting additive with the polyurethane adhesive can improve the thermal conductivity of the material to some extent, but since the heat conducting medium is not modified, the medium does not have targeting, and the contact area of the medium is small, so the thermal conductivity coefficient is not high. At the same time, the compatibility of the unmodified additive with the polyurethane is poor, and the mechanical properties of the final composite material are sharply reduced.

[0084] The above only describes the preferred embodiments of the present application, and any changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A method for preparing a self-supporting heat-conducting channel of a ternary flame-retardant-heat-conducting integrated adjuvant, characterized in that, It comprises the following steps: (1) dispersing the spherical alumina in Tris buffer solution for 30 min to obtain a spherical alumina suspension, adding dopamine hydrochloride and stirring at room temperature for 6 h, adding KH550 coupling agent and continuing to stir at 60 °C for 5 h, filtering, washing, and drying at 70-80 °C for 12-24 h to obtain activated spherical alumina heat conductor; (2) dispersing the flaky boron nitride in a mixed solution of Tris buffer solution and ethanol for 30 min to obtain a flaky boron nitride suspension, adding dopamine hydrochloride and stirring at room temperature for 6 h, adding KH550 coupling agent and continuing to stir at 60 °C for 5 h, filtering, washing, and drying at 70-80 °C for 12-24 h to obtain activated flaky boron nitride heat conductor; (3) soaking the microcrystalline cellulose in lye for 3 h, freezing at-18 °C for 12 h, and then stirring at room temperature to obtain a uniform microcrystalline cellulose suspension; (4) adding the spherical alumina heat conductor and flaky boron nitride heat conductor obtained in steps (1) and (2) to the microcrystalline cellulose suspension obtained in step (3), stirring magnetically at room temperature for 2 h, centrifuging, discarding the supernatant, washing the precipitate with ethanol solution until neutral, and then adding anhydrous ethanol to obtain a surface-activated ternary heat-conducting agent suspension; (5) adding pentaerythritol to a phosphorus-containing acid, stirring magnetically at 140 °C for 1.5 h, slowly adding a suspension of melamine and anhydrous ethanol, reducing the temperature to 80 °C and continuing to stir for 6 h, and then drying to obtain a flame-retardant aid; (6) uniformly dispersing the flame-retardant aid obtained in step (5) in anhydrous ethanol, adding it to the ternary heat-conducting agent suspension obtained in step (4) and continuing to stir for 2 h, and then adding aluminum hydroxide and continuing to react for 1 h, and then drying the reaction product to obtain a flame-retardant-heat-conducting integrated aid.

2. The production method according to claim 1, characterized by: 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 method of claim 1, wherein: In step (3), the mass concentration of the lye is 5%, and the amount used is 200 mL per 4 g of microcrystalline cellulose; the lye is one of sodium hydroxide and potassium hydroxide solution.

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

5. The method of claim 1, wherein: In steps (5) and (6), the molar ratio of pentaerythritol, phosphorus-containing acid, melamine, and aluminum hydroxide is 1:2:2:2; and the phosphorus-containing acid is one or more of polyphosphoric acid, phosphoric acid, and phytic acid.

6. The method of claim 1, wherein: In step (6), the mass ratio of flame-retardant aid to ternary heat-conducting agent is (2-5):

15.

7. The ternary flame-retardant-heat-conducting integrated aid prepared by the method of any one of claims 1-6.

8. Use of the ternary flame-retardant-thermally conductive integrated adjuvant according to claim 7 in polyurethane adhesives, characterized by the fact that: The ternary flame-retardant-heat-conducting integrated aid is added to the polyurethane adhesive, and the amount added is 50-70% of the mass of the polyurethane adhesive.

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