Thermally conductive tpu film

Abstract

The application discloses a kind of heat-conducting TPU films, the application increases the adsorption site of boron nitride surface by introducing amino group on the surface of boron nitride, which is conducive to subsequent adsorption of copper ions, then using hydrazine hydrate to reduce copper ions, copper nanoparticles are formed on the surface and interlayer of hexagonal boron nitride, forming a heat-conducting path, further improving the thermal conductivity of hexagonal boron nitride;Then the copper-loaded boron nitride is immersed in 2-mercaptobenzimidazole solution, the lone pair electrons of heteroatoms such as N and S in 2-mercaptobenzimidazole and the large pi bond of benzene ring can form coordination bond with copper atoms, forming an organic film on the surface of copper, improving the bonding force between copper-loaded boron nitride and TPU;At the same time, the mercapto group in 2-mercaptobenzimidazole can react with the double bond in vinyltriethoxysilane, enhancing the bonding force between the heat-conducting layer and the intermediate layer, and further improving the overall mechanical properties of the heat-conducting TPU film.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive materials technology, specifically to a thermally conductive TPU film. Background Technology

[0002] In recent years, microelectronic integration and assembly technologies have developed rapidly, with electronic devices and components becoming increasingly miniaturized and multifunctional. Their operating frequencies have increased dramatically, leading to a rapid accumulation of heat and a continuous rise in ambient temperature. If this accumulated heat cannot be dissipated in time, it will significantly affect the reliability of the equipment and components, shortening their lifespan. Therefore, ensuring stable and efficient operation of equipment and components, timely heat dissipation has become a pressing issue in the field of microelectronic packaging. Currently, the common approach is to use thermally conductive materials with high thermal conductivity to dissipate heat promptly, thereby ensuring the normal operation of instruments and equipment.

[0003] TPU, thermoplastic polyurethane elastomer rubber, is a new type of organic polymer synthetic material that can replace rubber or soft polyvinyl chloride (PVC) materials. Its excellent wear resistance and resilience are superior to ordinary polyurethane, and its aging resistance is better than rubber. It can be said that TPU is the most ideal material to replace PVC and PU, and is internationally recognized as a new type of polymer material. Its molecular structure consists of alternating rigid blocks obtained from the reaction of diisocyanate and chain extenders, and flexible segments obtained from the reaction of diisocyanate and macromolecular polyols. TPU possesses excellent high tensile strength, high tear strength, toughness, and aging resistance, and has been widely used in medical and health, electronic and electrical appliances, and sporting goods.

[0004] TPU has a lower thermal conductivity than other synthetic and natural insulation materials, and is widely used in the field of insulation materials. However, for applications with high requirements for heat transfer performance, TPU must be modified to obtain high thermal conductivity. For example, Chinese patent document CN201810829286.2 discloses a method for preparing a high thermal conductivity modified TPU film. By using solution polymerization, a modified graphene oxide solution and a catalyst are added to the TPU raw material to obtain a high thermal conductivity modified TPU film. Although the addition of modified graphene oxide improves the thermal conductivity of TPU to a certain extent, it still cannot meet the actual application requirements. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a thermally conductive TPU film, wherein the prepared TPU film has uniform thickness and excellent mechanical and thermal conductivity properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A thermally conductive TPU film, wherein the thermally conductive TPU film is composed of a thermally conductive layer one, an intermediate layer and a thermally conductive layer two, wherein, by weight, the thermally conductive layer one and the thermally conductive layer two are both made of the following raw materials: 80-100 parts of polyether-type TPU, 40-50 parts of thermally conductive filler, 1-5 parts of silicone lubricant, and 0.5-1 parts of antioxidant; the intermediate layer is made of the following raw materials: 90-100 parts of polyether-type TPU, 15-25 parts of thermally conductive filler, 0.1-2 parts of silicone lubricant, and 4-8 parts of vinyltriethoxysilane.

[0008] Specifically, the preparation method of the thermally conductive filler is as follows:

[0009] S1. Add hexagonal boron nitride powder to sodium hydroxide solution and stir at 40-80℃ for 2-3 hours. Then filter, wash and dry to obtain pretreated boron nitride powder.

[0010] S2. Disperse the pretreated boron nitride powder in deionized water, then add polyethyleneimine and epichlorohydrin to it, heat and stir to react. After the reaction is completed, filter, wash and dry to obtain modified boron nitride.

[0011] S3. Add the modified boron nitride to the copper sulfate solution and disperse it by ultrasonication for 1-2 hours. Then add hydrazine hydrate dropwise and react at a constant temperature of 60-70℃ for 4-6 hours. After the reaction is completed, filter, wash and dry to obtain copper-loaded boron nitride.

[0012] S4. Immerse copper-loaded boron nitride in a 2-mercaptobenzimidazole solution at room temperature for 2-3 hours. After treatment, filter and dry to obtain composite modified boron nitride.

[0013] S5. 40-60 parts of composite modified boron nitride and 50 parts of polyether-type TPU are blended and mixed, and then granulated by a granulator to obtain the thermally conductive filler.

[0014] Specifically, in step S2, the mass ratio of pretreated boron nitride powder, polyethyleneimine, and epichlorohydrin is 6-10:4-8:3-5, and more preferably 7-8:5-6:4-5.

[0015] Specifically, in step S2, the heating and stirring reaction temperature is 50-80℃. In some embodiments of the present invention, it can be selected as 50℃, 60℃, 70℃, or 80℃. The heating and stirring reaction time is 3-5h. In some embodiments of the present invention, it can be selected as 3h, 4h, or 5h.

[0016] Specifically, in step S3, the mass ratio of modified boron nitride, copper sulfate solution, and hydrazine hydrate is 5-10:100:6-12, more preferably 6-8:100:8-10; wherein the mass fraction of copper sulfate solution is 10-15%, and in some embodiments of the present invention, it can be selected as 10%, 11%, 12%, 13%, 14%, or 15%.

[0017] Specifically, in step S4, the mass ratio of copper-loaded boron nitride to 2-mercaptobenzimidazole is 5-8:1-2. In some embodiments of the present invention, it can be selected as 5:1, 5:2, 6:1, 6:2, 7:1, 7:2, 8:1, or 8:2.

[0018] Specifically, the antioxidant is selected from one or more of antioxidant 168, antioxidant 1098, and antioxidant 1010.

[0019] Specifically, the thickness of the first thermally conductive layer is 0.05-0.1 mm, and in some embodiments of the present invention, it can be selected as 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, or 0.1 mm; the thickness of the intermediate layer is 0.1-0.3 mm, and in some embodiments of the present invention, it can be selected as 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, or 0.3 mm; the thickness of the second thermally conductive layer is 0.05-0.1 mm, and in some embodiments of the present invention, it can be selected as 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, or 0.1 mm.

[0020] The present invention also provides a method for preparing the above-mentioned thermally conductive TPU film, comprising the following steps: placing the raw materials of thermally conductive layer one, intermediate layer and thermally conductive layer two in a high-speed mixer according to the weight parts, stirring and mixing evenly to obtain the first thermally conductive layer mixed raw material, the intermediate layer mixed raw material and the second thermally conductive layer mixed raw material; then feeding the obtained mixed raw materials of each film layer into the three feeding hoppers of the three-layer co-extrusion equipment, wherein the intermediate layer mixed raw material is fed into the feeding hopper of the middle single screw extruder of the three-layer co-extrusion equipment, and the first thermally conductive layer mixed raw material and the second thermally conductive layer mixed raw material are fed into the feeding hoppers of the two side single screw extruders of the three-layer co-extrusion equipment, respectively, extruded through the three-layer co-extrusion die head, cast and formed, and then pressed together by the embossing roller and the pressure roller and shaped and cured by the cooling roller to obtain the thermally conductive TPU film.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The thermally conductive TPU film prepared by the present invention is a composite of thermally conductive layer one, intermediate layer and thermally conductive layer two. The overall thickness of the prepared TPU conductive film is uniform. At the same time, the prepared thermally conductive TPU film has good mechanical properties and thermal conductivity, and has broad economic and social benefits.

[0023] (2) In this invention, hexagonal boron nitride powder is first added to sodium hydroxide solution for pretreatment. Then, polyethyleneimine is grafted onto the surface of boron nitride. By introducing amino groups, the adsorption sites on the surface of boron nitride are increased, which is beneficial for the subsequent adsorption of copper ions. Then, copper ions are reduced by hydrazine hydrate to form copper nanoparticles on the surface and between the layers of hexagonal boron nitride, forming a thermally conductive pathway and further improving the thermal conductivity of hexagonal boron nitride. Then, copper-loaded boron nitride is immersed in 2-mercaptobenzimidazole solution. The lone pair electrons of heteroatoms such as N and S in 2-mercaptobenzimidazole and the large π bond of the benzene ring can form coordinate bonds with copper atoms to form an organic film on the copper surface, which improves the bonding force between copper-loaded boron nitride and TPU. At the same time, the mercapto groups in 2-mercaptobenzimidazole can react with the double bonds in vinyltriethoxysilane, which enhances the bonding force between the thermally conductive layer and the intermediate layer, thereby improving the overall mechanical properties of the thermally conductive TPU film. Detailed Implementation

[0024] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0025] It should be noted that, unless otherwise specified, all chemical reagents involved in this invention were purchased through commercial channels.

[0026] The TPU resin used in this embodiment of the invention is 85A polyether-type TPU with hexagonal boron nitride CAS number: 10043-11-5 and particle size of 100nm.

[0027] Example 1

[0028] A method for preparing a thermally conductive TPU film includes the following steps:

[0029] The raw materials for thermally conductive layer one, intermediate layer and thermally conductive layer two are placed in a high-speed mixer according to the weight parts and mixed evenly to obtain the first thermally conductive layer mixture, intermediate layer mixture and second thermally conductive layer mixture. Then, the obtained mixtures of each film layer are fed into the three feeding hoppers of the three-layer co-extrusion equipment. The intermediate layer mixture is fed into the feeding hopper of the middle single screw extruder of the three-layer co-extrusion equipment, and the first thermally conductive layer mixture and the second thermally conductive layer mixture are fed into the feeding hoppers of the two side single screw extruders of the three-layer co-extrusion equipment. The mixture is extruded through the die head of the three-layer co-extrusion die, cast and formed at a die temperature of 175°C, and then pressed together by the embossing roller and pressure roller and shaped and cured by the cooling roller to obtain the thermally conductive TPU film.

[0030] The thickness of the first thermally conductive layer is 0.08 mm, and it is composed of the following raw materials in parts by weight: 80 parts of polyether-type TPU, 40 parts of thermally conductive filler, 3 parts of silicone lubricant, and 0.5 parts of antioxidant 168.

[0031] The thickness of the intermediate layer is 0.2 mm, and it is composed of the following raw materials in parts by weight: 90 parts of polyether-type TPU, 25 parts of thermally conductive filler, 1 part of silicone lubricant, and 6 parts of vinyltriethoxysilane.

[0032] The second thermally conductive layer has a thickness of 0.08 mm and is composed of the following raw materials in parts by weight: 80 parts of polyether-type TPU, 40 parts of thermally conductive filler, 3 parts of silicone lubricant, and 0.5 parts of antioxidant 168.

[0033] The preparation method of thermally conductive filler is as follows:

[0034] S1. Add 10g of hexagonal boron nitride powder to 100mL of 2mol / L sodium hydroxide solution, stir at 60℃ for 3h, and then filter, wash and dry to obtain pretreated boron nitride powder.

[0035] S2. Disperse 6g of pretreated boron nitride powder in 100mL of deionized water, then add 4g of polyethyleneimine and 3g of epichlorohydrin to it, heat and stir at 60℃ for 4h, and after the reaction is completed, filter, wash and dry to obtain modified boron nitride.

[0036] S3. Add 5g of modified boron nitride to 100g of 10wt% copper sulfate solution, disperse ultrasonically for 1h, then add 6g of hydrazine hydrate dropwise, and react at 65℃ for 5h. After the reaction is complete, filter, wash and dry to obtain copper-loaded boron nitride.

[0037] S4. Immerse 6g of copper-loaded boron nitride in 100g of 2wt% 2-mercaptobenzimidazole solution for 3h at room temperature. After treatment, filter and dry to obtain composite modified boron nitride.

[0038] S5. 50 parts of composite modified boron nitride and 50 parts of polyether-type TPU are blended and mixed, and then granulated by a granulator to obtain the thermally conductive filler.

[0039] Example 2

[0040] A method for preparing a thermally conductive TPU film includes the following steps:

[0041] The raw materials for thermally conductive layer one, intermediate layer and thermally conductive layer two are placed in a high-speed mixer according to the weight parts and mixed evenly to obtain the first thermally conductive layer mixture, intermediate layer mixture and second thermally conductive layer mixture. Then, the obtained mixtures of each film layer are fed into the three feeding hoppers of the three-layer co-extrusion equipment. The intermediate layer mixture is fed into the feeding hopper of the middle single screw extruder of the three-layer co-extrusion equipment, and the first thermally conductive layer mixture and the second thermally conductive layer mixture are fed into the feeding hoppers of the two side single screw extruders of the three-layer co-extrusion equipment. The mixture is extruded through the die head of the three-layer co-extrusion die, cast and formed at a die temperature of 175°C, and then pressed together by the embossing roller and pressure roller and shaped and cured by the cooling roller to obtain the thermally conductive TPU film.

[0042] The thickness of the first thermally conductive layer is 0.08 mm, and it is composed of the following raw materials in parts by weight: 90 parts of polyether-type TPU, 40 parts of thermally conductive filler, 2 parts of silicone lubricant, and 0.8 parts of antioxidant 1098.

[0043] The thickness of the intermediate layer is 0.2 mm, and it is composed of the following raw materials in parts by weight: 100 parts of polyether-type TPU, 20 parts of thermally conductive filler, 1.5 parts of silicone lubricant, and 5 parts of vinyltriethoxysilane.

[0044] The second thermally conductive layer has a thickness of 0.08 mm and is composed of the following raw materials in parts by weight: 90 parts of polyether-type TPU, 40 parts of thermally conductive filler, 2 parts of silicone lubricant, and 0.8 parts of antioxidant 1098.

[0045] The preparation method of thermally conductive filler is as follows:

[0046] S1. Add 10g of hexagonal boron nitride powder to 100mL of 2mol / L sodium hydroxide solution, stir at 80℃ for 2h, and then filter, wash and dry to obtain pretreated boron nitride powder.

[0047] S2. Disperse 10g of pretreated boron nitride powder in 100mL of deionized water, then add 5g of polyethyleneimine and 4g of epichlorohydrin to it, heat and stir at 50℃ for 5h, and after the reaction is completed, filter, wash and dry to obtain modified boron nitride.

[0048] S3. Add 10g of modified boron nitride to 100g of 15wt% copper sulfate solution, disperse ultrasonically for 1h, then add 8g of hydrazine hydrate dropwise, and react at 60℃ for 6h. After the reaction is complete, filter, wash and dry to obtain copper-loaded boron nitride.

[0049] S4. Immerse 8g of copper-loaded boron nitride in 100g of 2wt% 2-mercaptobenzimidazole solution for 3h at room temperature. After treatment, filter and dry to obtain composite modified boron nitride.

[0050] S5. 40 parts of composite modified boron nitride and 50 parts of polyether-type TPU are blended and mixed, and then granulated by a granulator to obtain the thermally conductive filler.

[0051] Example 3

[0052] A method for preparing a thermally conductive TPU film includes the following steps:

[0053] The raw materials for thermally conductive layer one, intermediate layer and thermally conductive layer two are placed in a high-speed mixer according to the weight parts and mixed evenly to obtain the first thermally conductive layer mixture, intermediate layer mixture and second thermally conductive layer mixture. Then, the obtained mixtures of each film layer are fed into the three feeding hoppers of the three-layer co-extrusion equipment. The intermediate layer mixture is fed into the feeding hopper of the middle single screw extruder of the three-layer co-extrusion equipment, and the first thermally conductive layer mixture and the second thermally conductive layer mixture are fed into the feeding hoppers of the two side single screw extruders of the three-layer co-extrusion equipment. The mixture is extruded through the die head of the three-layer co-extrusion die, cast and formed at a die temperature of 175°C, and then pressed together by the embossing roller and pressure roller and shaped and cured by the cooling roller to obtain the thermally conductive TPU film.

[0054] The thickness of the first thermally conductive layer is 0.08 mm, and it is composed of the following raw materials in parts by weight: 100 parts of polyether-type TPU, 40 parts of thermally conductive filler, 4 parts of silicone lubricant, and 1 part of antioxidant 168.

[0055] The thickness of the intermediate layer is 0.2 mm, and it is composed of the following raw materials in parts by weight: 95 parts of polyether-type TPU, 25 parts of thermally conductive filler, 1 part of silicone lubricant, and 8 parts of vinyltriethoxysilane.

[0056] The second thermally conductive layer has a thickness of 0.08 mm and is composed of the following raw materials in parts by weight: 100 parts of polyether-type TPU, 40 parts of thermally conductive filler, 4 parts of silicone lubricant, and 1 part of antioxidant 168.

[0057] The preparation method of thermally conductive filler is as follows:

[0058] S1. Add 10g of hexagonal boron nitride powder to 100mL of 2mol / L sodium hydroxide solution, stir at 40℃ for 3h, and then filter, wash and dry to obtain pretreated boron nitride powder.

[0059] S2. Disperse 10g of pretreated boron nitride powder in 100mL of deionized water, then add 8g of polyethyleneimine and 5g of epichlorohydrin to it, heat and stir at 80℃ for 3h, and after the reaction is completed, filter, wash and dry to obtain modified boron nitride.

[0060] S3. Add 8g of modified boron nitride to 100g of 15wt% copper sulfate solution, sonicate for 1h, then add 10g of hydrazine hydrate dropwise, and react at 60℃ for 6h. After the reaction is complete, filter, wash and dry to obtain copper-loaded boron nitride.

[0061] S4. Immerse 5g of copper-loaded boron nitride in 100g of 1wt% 2-mercaptobenzimidazole solution for 3h at room temperature. After treatment, filter and dry to obtain composite modified boron nitride.

[0062] S5. 60 parts of composite modified boron nitride and 50 parts of polyether-type TPU are blended and mixed, and then granulated by a granulator to obtain the thermally conductive filler.

[0063] Example 4

[0064] A method for preparing a thermally conductive TPU film includes the following steps:

[0065] The raw materials for thermally conductive layer one, intermediate layer and thermally conductive layer two are placed in a high-speed mixer according to the weight parts and mixed evenly to obtain the first thermally conductive layer mixture, intermediate layer mixture and second thermally conductive layer mixture. Then, the obtained mixtures of each film layer are fed into the three feeding hoppers of the three-layer co-extrusion equipment. The intermediate layer mixture is fed into the feeding hopper of the middle single screw extruder of the three-layer co-extrusion equipment, and the first thermally conductive layer mixture and the second thermally conductive layer mixture are fed into the feeding hoppers of the two side single screw extruders of the three-layer co-extrusion equipment. The mixture is extruded through the die head of the three-layer co-extrusion die, cast and formed at a die temperature of 175°C, and then pressed together by the embossing roller and pressure roller and shaped and cured by the cooling roller to obtain the thermally conductive TPU film.

[0066] The thickness of the first thermally conductive layer is 0.08 mm, and it is composed of the following raw materials in parts by weight: 85 parts of polyether-type TPU, 50 parts of thermally conductive filler, 5 parts of silicone lubricant, and 168 parts of antioxidant.

[0067] The thickness of the intermediate layer is 0.2 mm, and it is composed of the following raw materials in parts by weight: 90 parts of polyether-type TPU, 20 parts of thermally conductive filler, 0.8 parts of silicone lubricant, and 5 parts of vinyltriethoxysilane.

[0068] The thickness of the second thermally conductive layer is 0.08 mm, and it is composed of the following raw materials in parts by weight: 85 parts of polyether-type TPU, 50 parts of thermally conductive filler, 5 parts of silicone lubricant, and 1 part of antioxidant 168.

[0069] The preparation method of thermally conductive filler is as follows:

[0070] S1. Add 10g of hexagonal boron nitride powder to 100mL of 2mol / L sodium hydroxide solution, stir at 40℃ for 3h, and then filter, wash and dry to obtain pretreated boron nitride powder.

[0071] S2. Disperse 8g of pretreated boron nitride powder in 100mL of deionized water, then add 6g of polyethyleneimine and 5g of epichlorohydrin to it, heat and stir at 60℃ for 4h, and after the reaction is completed, filter, wash and dry to obtain modified boron nitride.

[0072] S3. Add 10g of modified boron nitride to 100g of 15wt% copper sulfate solution, disperse ultrasonically for 1h, then add 12g of hydrazine hydrate dropwise, and react at 60℃ for 6h. After the reaction is complete, filter, wash and dry to obtain copper-loaded boron nitride.

[0073] S4. Immerse 6g of copper-loaded boron nitride in 100g of 1wt% 2-mercaptobenzimidazole solution for 3h at room temperature. After treatment, filter and dry to obtain composite modified boron nitride.

[0074] S5. 50 parts of composite modified boron nitride and 50 parts of polyether-type TPU are blended and mixed, and then granulated by a granulator to obtain the thermally conductive filler.

[0075] Comparative Example 1

[0076] A method for preparing a thermally conductive TPU film includes the following steps:

[0077] The raw materials for thermally conductive layer one, intermediate layer and thermally conductive layer two are placed in a high-speed mixer according to the weight parts and mixed evenly to obtain the first thermally conductive layer mixture, intermediate layer mixture and second thermally conductive layer mixture. Then, the obtained mixtures of each film layer are fed into the three feeding hoppers of the three-layer co-extrusion equipment. The intermediate layer mixture is fed into the feeding hopper of the middle single screw extruder of the three-layer co-extrusion equipment, and the first thermally conductive layer mixture and the second thermally conductive layer mixture are fed into the feeding hoppers of the two side single screw extruders of the three-layer co-extrusion equipment. The mixture is extruded through the die head of the three-layer co-extrusion die, cast and formed at a die temperature of 175°C, and then pressed together by the embossing roller and pressure roller and shaped and cured by the cooling roller to obtain the thermally conductive TPU film.

[0078] The thickness of the first thermally conductive layer is 0.08 mm, and it is composed of the following raw materials in parts by weight: 80 parts of polyether-type TPU, 40 parts of thermally conductive filler, 3 parts of silicone lubricant, and 0.5 parts of antioxidant 168.

[0079] The thickness of the intermediate layer is 0.2 mm, and it is composed of the following raw materials in parts by weight: 90 parts of polyether-type TPU, 25 parts of thermally conductive filler, 1 part of silicone lubricant, and 6 parts of vinyltriethoxysilane.

[0080] The second thermally conductive layer has a thickness of 0.08 mm and is composed of the following raw materials in parts by weight: 80 parts of polyether-type TPU, 40 parts of thermally conductive filler, 3 parts of silicone lubricant, and 0.5 parts of antioxidant 168.

[0081] The thermally conductive filler is hexagonal boron nitride powder.

[0082] Comparative Example 2

[0083] A method for preparing a thermally conductive TPU film includes the following steps:

[0084] The raw materials for thermally conductive layer one, intermediate layer and thermally conductive layer two are placed in a high-speed mixer according to the weight parts and mixed evenly to obtain the first thermally conductive layer mixture, intermediate layer mixture and second thermally conductive layer mixture. Then, the obtained mixtures of each film layer are fed into the three feeding hoppers of the three-layer co-extrusion equipment. The intermediate layer mixture is fed into the feeding hopper of the middle single screw extruder of the three-layer co-extrusion equipment, and the first thermally conductive layer mixture and the second thermally conductive layer mixture are fed into the feeding hoppers of the two side single screw extruders of the three-layer co-extrusion equipment. The mixture is extruded through the die head of the three-layer co-extrusion die, cast and formed at a die temperature of 175°C, and then pressed together by the embossing roller and pressure roller and shaped and cured by the cooling roller to obtain the thermally conductive TPU film.

[0085] The thickness of the first thermally conductive layer is 0.08 mm, and it is composed of the following raw materials in parts by weight: 80 parts of polyether-type TPU, 40 parts of thermally conductive filler, 3 parts of silicone lubricant, and 0.5 parts of antioxidant 168.

[0086] The thickness of the intermediate layer is 0.2 mm, and it is composed of the following raw materials in parts by weight: 90 parts of polyether-type TPU, 25 parts of thermally conductive filler, 1 part of silicone lubricant, and 6 parts of vinyltriethoxysilane.

[0087] The second thermally conductive layer has a thickness of 0.08 mm and is composed of the following raw materials in parts by weight: 80 parts of polyether-type TPU, 40 parts of thermally conductive filler, 3 parts of silicone lubricant, and 0.5 parts of antioxidant 168.

[0088] The preparation method of thermally conductive filler is as follows:

[0089] S1. Add 10g of hexagonal boron nitride powder to 100mL of 2mol / L sodium hydroxide solution, stir at 60℃ for 3h, and then filter, wash and dry to obtain pretreated boron nitride powder.

[0090] S2. Disperse 6g of pretreated boron nitride powder in 100mL of deionized water, then add 4g of polyethyleneimine and 3g of epichlorohydrin to it, heat and stir at 60℃ for 4h, and after the reaction is completed, filter, wash and dry to obtain modified boron nitride.

[0091] S3. Add 5g of modified boron nitride to 100g of 10wt% copper sulfate solution, disperse ultrasonically for 1h, then add 6g of hydrazine hydrate dropwise, and react at 65℃ for 5h. After the reaction is complete, filter, wash and dry to obtain copper-loaded boron nitride.

[0092] S4. 50 parts of copper-loaded boron nitride and 50 parts of polyether-type TPU are blended and mixed, and then granulated by a granulator to obtain the thermally conductive filler.

[0093] The thermally conductive TPU films prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to performance tests. The thermal conductivity was tested according to GB / T 10295-2008, and the tensile strength and elongation at break were tested according to GB / T1040.3-2006. The tensile rate was 50 mm / min. The test results are shown in the table below:

[0094] Thermal conductivity (w / (mk)) Tensile strength (MPa) Elongation at break (%) Example 1 1.96 39.8 714 Example 2 1.92 40.4 756 Example 3 1.89 41.7 782 Example 4 2.01 39.5 699 Comparative Example 1 1.23 28.6 587 Comparative Example 2 1.87 32.1 645

[0095] Finally, it should be noted that the above embodiments do not limit the present invention in any way. Those skilled in the art can make modifications and improvements based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A thermally conductive TPU film, characterized in that, The thermally conductive TPU film is composed of a thermally conductive layer one, an intermediate layer, and a thermally conductive layer two. By weight, the thermally conductive layer one and the thermally conductive layer two are both made of the following raw materials: 80-100 parts of polyether-type TPU, 10-20 parts of thermally conductive filler, 1-5 parts of silicone lubricant, and 0.5-1 parts of antioxidant; the intermediate layer is made of the following raw materials: 90-100 parts of polyether-type TPU, 3-5 parts of thermally conductive filler, 0.1-2 parts of silicone lubricant, and 4-8 parts of vinyltriethoxysilane. The preparation method of the thermally conductive filler is as follows: S1. Add hexagonal boron nitride powder to sodium hydroxide solution and stir at 40-80℃ for 2-3 hours. Then filter, wash and dry to obtain pretreated boron nitride powder. S2. Disperse the pretreated boron nitride powder in deionized water, then add polyethyleneimine and epichlorohydrin to it, heat and stir to react. After the reaction is completed, filter, wash and dry to obtain modified boron nitride. S3. Add the modified boron nitride to the copper sulfate solution and disperse it by ultrasonication for 1-2 hours. Then add hydrazine hydrate dropwise and react at a constant temperature of 60-70℃ for 4-6 hours. After the reaction is completed, filter, wash and dry to obtain copper-loaded boron nitride. S4. Immerse copper-loaded boron nitride in a 2-mercaptobenzimidazole solution at room temperature for 2-3 hours. After treatment, filter and dry to obtain composite modified boron nitride. S5. 40-60 parts of composite modified boron nitride and 50 parts of polyether-type TPU are blended and mixed, and then granulated by a granulator to obtain the thermally conductive filler.

2. The thermally conductive TPU film according to claim 1, characterized in that, In step S2, the mass ratio of pretreated boron nitride powder, polyethyleneimine, and epichlorohydrin is 6-10:4-8:3-5.

3. The thermally conductive TPU film according to claim 1, characterized in that, In step S2, the heating and stirring reaction temperature is 50-80℃, and the heating and stirring reaction time is 3-5h.

4. The thermally conductive TPU film according to claim 1, characterized in that, In step S3, the mass ratio of modified boron nitride, copper sulfate solution and hydrazine hydrate is 5-10:100:6-12, and the mass fraction of copper sulfate solution is 10-15%.

5. The thermally conductive TPU film according to claim 1, characterized in that, In step S4, the mass ratio of copper-loaded boron nitride to 2-mercaptobenzimidazole is 5-8:1-2.

6. The thermally conductive TPU film according to claim 1, characterized in that, The antioxidant is selected from one or more of antioxidant 168, antioxidant 1098, and antioxidant 1010.

7. The thermally conductive TPU film according to claim 1, characterized in that, The thickness of the first thermally conductive layer is 0.05-0.1 mm, the thickness of the intermediate layer is 0.1-0.3 mm, and the thickness of the second thermally conductive layer is 0.05-0.1 mm.

8. A method for preparing a thermally conductive TPU film as described in any one of claims 1-7, characterized in that, The process includes the following steps: The raw materials for thermally conductive layer one, intermediate layer, and thermally conductive layer two are placed in a high-speed mixer according to their respective weight proportions and mixed evenly to obtain the first thermally conductive layer mixture, intermediate layer mixture, and second thermally conductive layer mixture. Subsequently, the obtained mixtures of each film layer are fed into the three feed hoppers of a three-layer co-extrusion equipment. The intermediate layer mixture is fed into the feed hopper of the middle single-screw extruder of the three-layer co-extrusion equipment, while the first and second thermally conductive layer mixtures are fed into the feed hoppers of the two side single-screw extruders of the three-layer co-extrusion equipment. The mixture is extruded through the three-layer co-extrusion die, cast, and then pressed together by embossing rollers and pressure rollers, and solidified by cooling rollers to obtain a thermally conductive TPU film.