Acid and alkali resistant heat-conducting insulating sheet based on PI film and preparation method thereof

Abstract

The invention discloses an acid and alkali resistant heat-conducting insulating sheet based on a PI film and a preparation method thereof, and relates to the technical field of heat-conducting insulating sheet preparation. The acid and alkali resistant heat-conducting insulating sheet based on the PI film comprises the PI film and a heat-conducting rubber material layer compounded on the PI film, and the heat-conducting rubber material layer is prepared from the following raw materials in parts by weight: 60-100 parts of nitrile rubber buna, 20-100 parts of chloroprene rubber, 1-3 parts of zinc oxide, 2-8 parts of sulfur, 0.4-1.0 part of an accelerant, 400-600 parts of modified aluminum oxide, 12-18 parts of a tackifier, 0.1-1 part of an antioxidant, 10-30 parts of white carbon black and 10-30 parts of a plasticizer. According to the acid and alkali resistant heat-conducting insulating sheet based on the PI film and the preparation method thereof, the tackifier is added, so that the adhesive force between the heat-conducting rubber layer and the PI film is improved; by adding the nitrile rubber buna and the chloroprene rubber, the heat-conducting insulating sheet with good adhesive force and acid and alkali resistance is provided.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive insulating sheet preparation technology, and in particular to an acid and alkali resistant thermally conductive insulating sheet based on PI film and its preparation method. Background Technology

[0002] Thermally conductive insulating sheets are materials with both thermal conductivity and insulation functions. They can effectively conduct heat and prevent current leakage, operate stably in high-temperature environments, and have a certain degree of flexibility and durability. They are commonly used in fields such as heat dissipation for new energy vehicle batteries, electronic devices, or home radiators such as PTC water heaters.

[0003] Conventional thermally conductive insulating sheets typically use PI film (polyimide film) or fiberglass cloth as the substrate, with a thermally conductive material coated or calendered onto the PI film or fiberglass cloth. This thermally conductive material generally consists of silicone, thermally conductive fillers, and other additives. However, the low surface energy of the PI film, and issues related to the acid and alkali resistance and breakdown voltage of the coating and PI film, reduce the performance of the thermally conductive insulating sheet and affect its heat dissipation effect.

[0004] Therefore, in order to solve the problems of low surface energy of PI film and improve the acid and alkali resistance and breakdown voltage resistance of coating and PI film, this invention provides an acid and alkali resistant thermally conductive insulating sheet based on PI film and its preparation method. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an acid and alkali resistant thermally conductive insulating sheet based on a PI film and its preparation method.

[0006] Specifically, the following technical solutions are included: In a first aspect, an acid and alkali resistant thermally conductive insulating sheet based on a PI film is provided, comprising a PI film and a thermally conductive adhesive layer laminated on the PI film, wherein the thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 60-100 parts of nitrile rubber, 20-100 parts of chloroprene rubber, 1-3 parts of zinc oxide, 2-8 parts of sulfur, 0.4-1.0 parts of accelerator, 400-600 parts of modified alumina, 12-18 parts of tackifier, 0.1-1 part of antioxidant, 10-30 parts of silica, and 10-30 parts of plasticizer.

[0007] Preferably, the nitrile rubber is 60-80 parts by weight and the chloroprene rubber is 20-40 parts by weight.

[0008] Furthermore, the tackifier is one or both of vinyl tackifiers and hydrogen-containing tackifiers.

[0009] Preferably, the tackifier is a vinyl tackifier.

[0010] Furthermore, the accelerator is one or more of the following: aldehyde amine accelerators, guanidine accelerators, thiuram accelerators, thiazole accelerators, dithiocarbamate accelerators, xanthate accelerators, thiourea accelerators, and sulfenamide accelerators.

[0011] Preferably, the aldehyde-amine accelerator is vulcanization accelerator H (hexamethylenetetramine), the guanidine accelerator is vulcanization accelerator D (diphenylguanidine), the thiuram accelerator is vulcanization accelerator TT (tetramethylthiuram disulfide), the thiazole accelerator is vulcanization accelerator M (2-mercaptobenzothiazole), the dithiocarbamate accelerator is vulcanization accelerator ZDMC (zinc dimethyl dithiuramate), the xanthate accelerator is vulcanization accelerator ZBX (zinc dibutyl dithiuramate), the thiourea accelerator is vulcanization accelerator NA-22 (2-mercaptoimidazoline), and the sulfenamide accelerator is vulcanization accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide).

[0012] Preferably, the accelerator is a thiuram-based accelerator, specifically TMTD (tetramethylthiuram disulfide).

[0013] Furthermore, the antioxidant is selected from one or more of the following: peroxide decomposition type antioxidants, free radical scavenging type antioxidants, and metal deactivation type antioxidants.

[0014] Preferably, the antioxidant is selected from one or more of zinc dialkyl dithiophosphate, zinc dialkyl dithiocarbamate, N-phenyl-α-naphthylamine, alkylphenthiazide, benzotriazole derivatives, and mercaptobenzothiazide derivatives.

[0015] Preferably, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 168, antioxidant 1520, antioxidant 1726, antioxidant 126, antioxidant 245, antioxidant 1076, and antioxidant B255.

[0016] Preferably, the antioxidant is BHT (2,6-di-tert-butyl-p-cresol).

[0017] Furthermore, the plasticizer is selected from one or more of the following: aliphatic diester plasticizers, phthalate plasticizers, polyphenolic acid ester plasticizers, benzoate plasticizers, polyol ester plasticizers, chlorinated hydrocarbon plasticizers, epoxy plasticizers, citrate plasticizers, and polyester plasticizers.

[0018] Preferably, the phthalate plasticizers include phthalate plasticizers and terephthalate plasticizers.

[0019] Preferably, the plasticizer is dioctyl phthalate.

[0020] Furthermore, the thickness of the PI film is 25–125 μm.

[0021] Preferably, the PI film thickness is 38 μm.

[0022] Furthermore, the sulfur is selected from one or more of powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.

[0023] Preferably, the sulfur is powdered sulfur.

[0024] Furthermore, the median particle size D50 of the zinc oxide is 0.3–1.5 μm.

[0025] Furthermore, the silica is one or both of fumed silica and precipitated silica.

[0026] Preferably, the silica is fumed silica.

[0027] In a second aspect, a method for preparing an acid and alkali resistant thermally conductive insulating sheet based on a PI film according to the first aspect is provided, comprising the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix for 20 min at a speed of 20-40 r / min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 20-40 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at a speed of 20-40 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 20-40 r / min and a temperature of 20-40°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 20-40 r / min and a temperature of 20-40°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0028] Preferably, in step S6, the calendering composite is made by calendering the thermally conductive adhesive and the PI film through a five-roll calender at a temperature of 130-150°C, a roll speed of 4-10 r / min, and a linear speed of 0.6-1.0 m / min to produce an insulating sheet; the insulating sheet is then wound up and calendered again through a five-roll calender at a temperature of 130-150°C, a roll speed of 4-10 r / min, and a linear speed of 0.6-1.0 m / min to produce an acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0029] In step S4, the temperature is maintained at 20-40°C to prevent premature reaction due to excessively high temperature.

[0030] The beneficial effects of this invention are as follows: This invention improves the adhesion between the thermally conductive adhesive layer and the PI film by adding a tackifier that reacts with sulfur to generate free radicals; and by adding nitrile rubber and chloroprene rubber, it provides a thermally conductive insulating sheet with good adhesion and resistance to acids and alkalis. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the acid and alkali resistant thermally conductive insulating sheet structure based on PI film according to Embodiment 1 of the present invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0035] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0036] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0037] To better understand the technical content of the present invention, the technical solution of the present invention will be further introduced and explained below with reference to specific embodiments.

[0038] In this embodiment / comparative example, the PI film thickness is 38 μm (Ningbo Jinshan New Material Co., Ltd., 36MT38). The nitrile rubber used is NBR3604 from Lanzhou Chemical Company of China National Petroleum Corporation. The chloroprene rubber used is MT-40 from Denka Co., Ltd. of Japan. The sulfur used is powdered sulfur (Qingdao Luchuan Chemical Co., Ltd.). The accelerator used is TMTD (tetramethylthiuram disulfide), from Ningbo Aicam New Material Co., Ltd. The zinc oxide used (Foshan Jingge New Material Co., Ltd., GD-S003A) has a median particle size D50 of 1.0 μm. The tackifier used is a vinyl tackifier (Guangzhou Tianjiang High-Tech Materials Co., Ltd., TJ-C006). The antioxidant used is BHT (2,6-di-tert-butyl-p-cresol), from Bayer. The silica used is fumed silica (Cabot, LM150). The plasticizer used is dioctyl phthalate (BASF, DOP). The modified alumina used is BAK-5 from Ya'an Baitu High-tech Materials Co., Ltd.

[0039] Example 1 An acid and alkali resistant thermally conductive insulating sheet based on a PI film includes a PI film and a thermally conductive adhesive layer laminated on the PI film. The thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 70 parts nitrile rubber, 30 parts chloroprene rubber, 2 parts zinc oxide, 4 parts sulfur, 0.5 parts accelerator, 500 parts modified alumina, 16 parts tackifier, 0.3 parts antioxidant, 20 parts silica, and 20 parts plasticizer. Figure 1 This is a schematic diagram of the acid and alkali resistant thermally conductive insulating sheet structure based on PI film according to Embodiment 1 of the present invention.

[0040] The method for preparing the acid and alkali resistant thermally conductive insulating sheet based on PI film includes the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix at 30 r / min for 20 min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 30 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at 30 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 30 r / min and a temperature of 30°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 30 r / min and a temperature of 30°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film. The thermally conductive adhesive and the PI film are calendered using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to form an insulating sheet. The insulating sheet is then wound up and calendered again using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0041] Example 2 An acid and alkali resistant thermally conductive insulating sheet based on a PI film includes a PI film and a thermally conductive adhesive layer laminated on the PI film. The thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 60-80 parts nitrile rubber, 20-40 parts chloroprene rubber, 1-3 parts zinc oxide, 2-8 parts sulfur, 0.4-1.0 parts accelerator, 400-600 parts modified alumina, 12-18 parts tackifier, 0.1-1 part antioxidant, 10-30 parts silica, and 10-30 parts plasticizer.

[0042] The method for preparing the acid and alkali resistant thermally conductive insulating sheet based on PI film includes the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix at 30 r / min for 20 min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 30 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at 30 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 30 r / min and a temperature of 30°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 30 r / min and a temperature of 30°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film. The thermally conductive adhesive and the PI film are calendered using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to form an insulating sheet. The insulating sheet is then wound up and calendered again using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0043] Example 3 An acid and alkali resistant thermally conductive insulating sheet based on a PI film includes a PI film and a thermally conductive adhesive layer laminated on the PI film. The thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 60-80 parts nitrile rubber, 20-40 parts chloroprene rubber, 1-3 parts zinc oxide, 2-8 parts sulfur, 0.4-1.0 parts accelerator, 400-600 parts modified alumina, 12-18 parts tackifier, 0.1-1 part antioxidant, 10-30 parts silica, and 10-30 parts plasticizer.

[0044] The method for preparing the acid and alkali resistant thermally conductive insulating sheet based on PI film includes the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix at 30 r / min for 20 min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 30 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at 30 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 30 r / min and a temperature of 30°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 30 r / min and a temperature of 30°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film. The thermally conductive adhesive and the PI film are calendered using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to form an insulating sheet. The insulating sheet is then wound up and calendered again using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0045] Example 4 An acid and alkali resistant thermally conductive insulating sheet based on a PI film includes a PI film and a thermally conductive adhesive layer laminated on the PI film. The thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 60-80 parts nitrile rubber, 20-40 parts chloroprene rubber, 1-3 parts zinc oxide, 2-8 parts sulfur, 0.4-1.0 parts accelerator, 400-600 parts modified alumina, 12-18 parts tackifier, 0.1-1 part antioxidant, 10-30 parts silica, and 10-30 parts plasticizer.

[0046] The method for preparing the acid and alkali resistant thermally conductive insulating sheet based on PI film includes the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix at 30 r / min for 20 min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 30 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at 30 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 30 r / min and a temperature of 30°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 30 r / min and a temperature of 30°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film. The thermally conductive adhesive and the PI film are calendered using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to form an insulating sheet. The insulating sheet is then wound up and calendered again using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0047] Example 5 An acid and alkali resistant thermally conductive insulating sheet based on a PI film includes a PI film and a thermally conductive adhesive layer laminated on the PI film. The thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 60-80 parts nitrile rubber, 20-40 parts chloroprene rubber, 1-3 parts zinc oxide, 2-8 parts sulfur, 0.4-1.0 parts accelerator, 400-600 parts modified alumina, 12-18 parts tackifier, 0.1-1 part antioxidant, 10-30 parts silica, and 10-30 parts plasticizer.

[0048] The method for preparing the acid and alkali resistant thermally conductive insulating sheet based on PI film includes the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix at 30 r / min for 20 min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 30 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at 30 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 30 r / min and a temperature of 30°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 30 r / min and a temperature of 30°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film. The thermally conductive adhesive and the PI film are calendered using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to form an insulating sheet. The insulating sheet is then wound up and calendered again using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0049] Example 6 An acid and alkali resistant thermally conductive insulating sheet based on a PI film includes a PI film and a thermally conductive adhesive layer laminated on the PI film. The thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 60-80 parts nitrile rubber, 20-40 parts chloroprene rubber, 1-3 parts zinc oxide, 2-8 parts sulfur, 0.4-1.0 parts accelerator, 400-600 parts modified alumina, 12-18 parts tackifier, 0.1-1 part antioxidant, 10-30 parts silica, and 10-30 parts plasticizer.

[0050] The method for preparing the acid and alkali resistant thermally conductive insulating sheet based on PI film includes the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix at 30 r / min for 20 min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 30 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at 30 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 30 r / min and a temperature of 30°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 30 r / min and a temperature of 30°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film. The thermally conductive adhesive and the PI film are calendered using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to form an insulating sheet. The insulating sheet is then wound up and calendered again using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0051] Example 7 An acid and alkali resistant thermally conductive insulating sheet based on a PI film includes a PI film and a thermally conductive adhesive layer laminated on the PI film. The thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 60-80 parts nitrile rubber, 20-40 parts chloroprene rubber, 1-3 parts zinc oxide, 2-8 parts sulfur, 0.4-1.0 parts accelerator, 400-600 parts modified alumina, 12-18 parts tackifier, 0.1-1 part antioxidant, 10-30 parts silica, and 10-30 parts plasticizer.

[0052] The method for preparing the acid and alkali resistant thermally conductive insulating sheet based on PI film includes the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix at 30 r / min for 20 min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 30 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at 30 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 30 r / min and a temperature of 30°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 30 r / min and a temperature of 30°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film. The thermally conductive adhesive and the PI film are calendered using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to form an insulating sheet. The insulating sheet is then wound up and calendered again using a five-roll calender at a temperature of 140°C, a roll speed of 7 r / min, and a linear speed of 0.8 m / min to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

[0053] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the acid and alkali resistant thermally conductive insulating sheet based on PI film does not contain an adhesive, while all other conditions are the same.

[0054] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the acid and alkali resistant thermally conductive insulating sheet based on PI film does not contain chloroprene rubber and the weight of nitrile rubber is 100 parts; all other conditions are the same.

[0055] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the acid and alkali resistant thermally conductive insulating sheet based on PI film does not contain nitrile rubber and the weight of chloroprene rubber is 100 parts; all other conditions are the same.

[0056] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the weight of the tackifier in the acid and alkali resistant thermally conductive insulating sheet based on PI film is 20 parts, while all other conditions are the same.

[0057] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that the weight of nitrile rubber in the acid and alkali resistant thermally conductive insulating sheet based on PI film is 50 parts, while all other conditions are the same.

[0058] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the weight of neoprene rubber in the acid and alkali resistant thermally conductive insulating sheet based on PI film is 10 parts, while all other conditions are the same.

[0059] Comparative Example 7 The only difference between Comparative Example 7 and Example 1 is that the tackifier in the acid and alkali resistant thermally conductive insulating sheet based on PI film is a phenolic resin tackifier (specifically tert-butylphenolic resin, SP-1068), while all other conditions are the same.

[0060] Comparative Example 8 Compared with Example 1, Comparative Example 8 differs only in that the nitrile rubber and neoprene rubber in the acid and alkali resistant thermally conductive insulating sheet based on PI film are replaced with equal parts by weight of silicone (specifically methyl vinyl silicone), and all other conditions are the same.

[0061] Performance testing Examples 1-7 and Comparative Examples 1-8, based on PI film, were tested for thermal resistance, breakdown voltage, solvent resistance, coating hardness, and acid and alkali resistance. The test results are shown in Tables 1-2 below. Thermal resistance was tested according to ASTM D5470. Breakdown voltage was tested according to ASTM D149. Solvent resistance (70N base oil) was tested at 70℃ for 6 months to measure thickness change. Coating hardness was tested using a Newton's pen; the absence of exposed PI film indicates good adhesion and scratch resistance. Acid and alkali resistance was tested according to HG / T 2181-2009 to measure thickness change.

[0062] Table 1. Performance test results of acid and alkali resistant thermally conductive insulating sheets based on PI film in Examples 1-7 Table 2. Performance test results of acid and alkali resistant thermally conductive insulating sheets based on PI film for Comparative Examples 1-8 As shown in Tables 1 and 2, the acid and alkali resistant thermally conductive insulating sheet based on PI film of the present invention not only has low thermal resistance, but also good adhesion between the thermally conductive layer and PI, with no exposed PI film, and also possesses acid and alkali resistance. In contrast, the performance test results of the acid and alkali resistant thermally conductive insulating sheet based on PI film prepared with missing components (Comparative Examples 1-3) or with component weight parts outside the scope of the present invention (Comparative Examples 4-6) are poor. Furthermore, the performance test results of the acid and alkali resistant thermally conductive insulating sheet based on PI film prepared using a tackifier not specified in the present invention (Comparative Example 7) are also poor.

[0063] In summary, this invention provides an acid and alkali resistant thermally conductive insulating sheet based on a PI film and its preparation method. The formulation uses a blend of nitrile rubber (NBR) and chloroprene rubber (CR) as the matrix, combining the oil resistance of NBR with the weather resistance and flame retardancy of CR. A high proportion (400-600 parts) of modified alumina is added as a thermally conductive filler, along with a vulcanization system (zinc oxide, sulfur, accelerator), reinforcing agent (silica), tackifier, antioxidant, and plasticizer, to form the final thermally conductive rubber compound (layer). Modified alumina is the core thermally conductive medium, and its high addition ensures the formation of thermal conduction pathways. Sulfur vulcanization, combined with zinc oxide and various optional accelerators, achieves cross-linking and curing of the rubber. Tackifier, antioxidant, plasticizer, and silica are used to improve adhesion, heat aging resistance, processing flexibility, and reinforcement, respectively. In the preparation method, the rubber base materials (nitrile rubber and chloroprene rubber) are first mixed with the antioxidant. Plasticizer, silica, tackifier, and thermally conductive filler (modified alumina) are added sequentially and thoroughly mixed and dispersed. In the final stage, vulcanizing agents (zinc oxide, sulfur) and accelerators are added at a low temperature (20-40℃) to prevent premature vulcanization (scorching). After adding the accelerator, a vacuum (-0.08 MPa) is applied to remove air bubbles and ensure the compactness of the rubber compound. Finally, the thermally conductive rubber compound is laminated with a PI film via calendering.

[0064] Therefore, the innovation of this invention lies in: 1. Functional integration: It cleverly combines the excellent insulation and high temperature resistance of PI film with a specially designed acid and alkali resistant rubber thermal conductive layer (thermal conductive rubber material), which solves the problem that a single material cannot simultaneously meet the requirements of insulation, thermal conductivity and corrosion resistance.

[0065] 2. Synergistic formulation: The NBR / CR rubber blend system provides a foundation for acid and alkali resistance; the high-filler modified alumina ensures thermal conductivity; the specific vulcanization system and processing technology ensure the processing feasibility and final product performance under high filler conditions.

[0066] 3. Ingenious process design: The step-by-step mixing and low-temperature sulfur addition process effectively solves the problems of mixing difficulties, high viscosity and easy early sulfurization caused by high thermal conductivity filler, thus improving production stability and product uniformity.

[0067] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An acid- and alkali-resistant thermally conductive insulating sheet based on a PI film, characterized in that, The material includes a PI film and a thermally conductive adhesive layer laminated on the PI film. The thermally conductive adhesive layer is composed of the following raw materials in parts by weight: 60-100 parts nitrile rubber, 20-100 parts chloroprene rubber, 1-3 parts zinc oxide, 2-8 parts sulfur, 0.4-1.0 parts accelerator, 400-600 parts modified alumina, 12-18 parts tackifier, 0.1-1 part antioxidant, 10-30 parts silica, and 10-30 parts plasticizer.

2. The acid and alkali resistant thermally conductive insulating sheet based on PI film according to claim 1, characterized in that, The tackifier is one or both of vinyl tackifiers and hydrogen-containing tackifiers.

3. The acid and alkali resistant thermally conductive insulating sheet based on PI film according to claim 1, characterized in that, The accelerator is one or more of the following: aldehyde amine accelerator, guanidine accelerator, thiuram accelerator, thiazole accelerator, dithiocarbamate accelerator, xanthate accelerator, thiourea accelerator, and sulfenamide accelerator.

4. The acid and alkali resistant thermally conductive insulating sheet based on PI film according to claim 1, characterized in that, The antioxidant is selected from one or more of the following: peroxide decomposition type antioxidants, free radical scavenging type antioxidants, and metal deactivation type antioxidants.

5. The acid and alkali resistant thermally conductive insulating sheet based on PI film according to claim 1, characterized in that, The plasticizer is selected from one or more of the following: aliphatic diester plasticizers, phthalate plasticizers, polyphenolic ester plasticizers, benzoate plasticizers, polyol ester plasticizers, chlorinated hydrocarbon plasticizers, epoxy plasticizers, citrate plasticizers, and polyester plasticizers.

6. The acid and alkali resistant thermally conductive insulating sheet based on PI film according to claim 1, characterized in that, The thickness of the PI film is 25–125 μm.

7. The acid and alkali resistant thermally conductive insulating sheet based on PI film according to claim 1, characterized in that, The sulfur is selected from one or more of powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.

8. The acid and alkali resistant thermally conductive insulating sheet based on PI film according to claim 1, characterized in that, The median particle size D50 of the zinc oxide is 0.3–1.5 μm.

9. The acid and alkali resistant thermally conductive insulating sheet based on PI film according to claim 1, characterized in that, The silica mentioned is one or both of fumed silica and precipitated silica.

10. A method for preparing an acid and alkali resistant thermally conductive insulating sheet based on a PI film according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Place the nitrile rubber, chloroprene rubber and antioxidant in a mixer and mix for 20 min at a speed of 20-40 r / min; S2. Add the plasticizer and silica in the specified weight proportions, and continue to knead at a speed of 20-40 r / min for 20 min; S3. Add the specified amount of thickener and modified alumina, and knead at a speed of 20-40 r / min for 40 min; S4. Add the zinc oxide and sulfur in the specified weight proportions, and knead for 20 minutes at a speed of 20-40 r / min and a temperature of 20-40°C. S5. Add the accelerator in the specified weight proportions, mix at a speed of 20-40 r / min and a temperature of 20-40°C for 10 min, then vacuum to a vacuum degree of -0.08 MPa to prepare a thermally conductive adhesive. S6. The thermally conductive adhesive obtained in step S5 is calendered and laminated with the PI film to obtain the acid and alkali resistant thermally conductive insulating sheet based on the PI film.

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