Polyamic acid slurry as well as preparation method and application thereof

Abstract

The invention relates to polyimide slurry as well as a preparation method and application thereof. The polyamide acid slurry comprises the following components: amino-terminated polyamide acid, composite resin and inorganic filler. A polyimide film prepared from the polyamide acid slurry still keeps good adhesive force and insulating property after working in a high-temperature and high-humidity environment, and is very suitable for preparing a water-cooling plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyimide materials, and more particularly, to a polyamic acid slurry and a preparation method and application thereof. BACKGROUND

[0002] Polyimide (PI) is a high-performance organic polymer widely used in aerospace, electronics, automotive industry and other fields. The water-cooled plate of the power battery of the electric vehicle is mainly used for heat dissipation to ensure the normal operation and safety of the battery pack. Since the water-cooled plate is usually made of metal, the water-cooled plate needs to be insulated to avoid short circuit of the battery pack. Polyimide has excellent high-temperature resistance and certain insulation, and is often used as an insulating material on the surface of the water-cooled plate substrate.

[0003] The main ways to form a polyimide film on the surface of the water-cooled plate include film pasting and slurry coating and curing to form a film. The patent with publication number CN118755422A forms a polyimide film on the water-cooled plate substrate by pasting a film, but the cost of pasting a film is high, and the performance of the glue used for pasting a film is high.

[0004] The slurry coating and curing to form a film can well avoid the above shortcomings, but the slurry coating and curing to form a film also has problems: the thermal stress between the polyimide and the metal substrate due to the different coefficients of thermal expansion (CTE) in the high-temperature working environment of the water-cooled plate, and the adhesion of the polyimide to the water-cooled plate substrate decreases after a period of use.

[0005] In addition, although the polyimide itself has good high-temperature resistance, it still faces challenges in the high-temperature and high-heat scenario of the water-cooled plate: the polyimide is more easily penetrated by water in a high-temperature and high-humidity environment, resulting in a decrease in the insulation performance of the polyimide.

[0006] Therefore, new technology needs to be developed to solve the problems of the adhesion of the polyimide film to the metal substrate and the decrease in the insulation performance of the polyimide film caused by the working conditions of the water-cooled plate when the polyimide film is used as an insulating material for the water-cooled plate. SUMMARY

[0007] The primary object of the present application is to overcome the problem of the significant decrease in the insulation performance and adhesion of the existing polyimide material for the water-cooled plate under the working conditions, and to provide a polyamic acid slurry.

[0008] A further object of the present application is to provide a preparation method of the polyamic acid slurry.

[0009] A further object of the present application is to provide the application of the above-mentioned polyamic acid slurry in the preparation of a water-cooled plate.

[0010] A further object of the present application is to provide a water-cooled plate.

[0011] It is a further object of the present application to provide a method for preparing the water-cooled plate.

[0012] The above objects of the present application are achieved by the following technical solutions. A polyamide acid slurry comprises the following components: an end-amino-containing polyamide acid, a composite resin, and an inorganic filler. The composite resin comprises a polytetrafluoroethylene resin and an acrylic resin.

[0013] The present application adds an inorganic filler to the polyamide acid slurry, which provides a basis for the mechanical properties and heat resistance of the polyamide acid slurry after film formation.

[0014] The present application further adds a composite resin comprising a polytetrafluoroethylene resin and an acrylic resin; the acrylic resin has certain film-forming ability and adhesion, and it can react with the end-amino group in the polyamide acid through the carboxyl group during the film formation process of the polyamide acid slurry, thereby improving the uniformity of the polyimide molecular weight and the high-temperature and high-humidity resistance of the polyimide. The lubricity of the polytetrafluoroethylene resin can make the inorganic filler well dispersed during the film formation process and make the acrylic resin easily react with the polyamide acid, so that the adhesion of the polyimide film under high temperature and high humidity will not decrease significantly. In addition, the good hydrophobicity of the polytetrafluoroethylene resin makes the polyimide not easily penetrated by water molecules in high temperature and high humidity, thereby keeping the insulation performance of the polyimide film good. Therefore, the polyimide film made of the polyamide acid slurry still maintains good insulation performance and adhesion to the substrate after working in a high-temperature and high-humidity environment, and is very suitable for preparing a water-cooled plate.

[0015] If other fluororesins (such as polyvinylidene fluoride) are used instead of the polytetrafluoroethylene resin, the insulation performance and adhesion to the substrate of the polyimide film made of the polyamide acid slurry after working in a high-temperature and high-humidity environment will be significantly worse.

[0016] If methyl acrylate resin is used instead of the acrylic resin, the initial adhesion of the polyimide film made of the polyamide acid slurry to the substrate is not good, and the insulation performance and adhesion to the substrate of the polyimide film after working in a high-temperature and high-humidity environment will be significantly worse.

[0017] If only the polytetrafluoroethylene resin or only the acrylic resin is used, the insulation performance and adhesion to the substrate of the polyimide film made of the polyamide acid slurry after working in a high-temperature and high-humidity environment will be significantly worse.

[0018] If no composite resin is added, the insulation performance and adhesion to the substrate of the polyimide film made of the polyamide acid slurry after working in a high-temperature and high-humidity environment will be significantly worse.

[0019] Preferably, the polyamide acid slurry comprises the following components by weight: 10 parts of end-amino-containing polyamide acid, composite resin 1~3.5 parts, inorganic filler 3~9 parts.

[0020] The amount of the composite resin can be specifically 1, 1.5, 2, 2.5, 3 or 3.5 parts by weight; and the amount of the inorganic filler can be specifically 3, 4, 5, 6, 7, 8 or 9 parts by weight.

[0021] Preferably, the mass of the polyamide acid in the polyamide acid slurry accounts for at least 45% of the sum of the masses of the components in the polyamide acid slurry except the solvent.

[0022] In the present application, the mass ratio of the polytetrafluoroethylene resin and the acrylic resin can be 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2.0:1, 2.3:1, 2.5:1, 2.7:1, 3.0:1 or 3.2:1.

[0023] Preferably, the composite resin comprises polytetrafluoroethylene resin and acrylic resin with a mass ratio of (0.8~3.2):1.

[0024] More preferably, the composite resin comprises polytetrafluoroethylene resin and acrylic resin with a mass ratio of (2~3):1.

[0025] By controlling the mass ratio of the polytetrafluoroethylene resin and the acrylic resin within the range, the polyimide film made of the polyamide acid slurry has better retention of insulation performance after working in a high-temperature and high-humidity environment and better retention of adhesion to the substrate.

[0026] Preferably, the solid content of the polyamide acid slurry is 13~20 wt%.

[0027] Preferably, the solvent of the polyamide acid slurry comprises at least one of N-methyl pyrrolidone (NMP), dimethylacetamide (DMAC) or dimethylformamide (DMF), but is not limited thereto.

[0028] Preferably, the polyamide acid is a copolymer of diamine and dianhydride.

[0029] Both the diamine and the dianhydride commonly used in the art for synthesizing polyamide acid can be used in the present application.

[0030] More preferably, the diamine is at least one of aromatic diamine or aliphatic diamine.

[0031] Further preferably, the aromatic diamine is at least one of p-phenylenediamine, 1,3-bis(3-aminophenoxy)benzene, 4,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, p-aminophenyl p-aminobenzoate, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, or 4,4'-bis(3-aminophenoxy)benzophenone.

[0032] Further preferably, the aliphatic diamine is at least one of 1,3-cyclohexanedimethylamine.

[0033] More preferably, the dianhydride is at least one of an aromatic dianhydride or an aliphatic dianhydride.

[0034] Further preferably, the aromatic dianhydride is at least one of pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, or hydrogenated diphenyl anhydride.

[0035] Further preferably, the aliphatic dianhydride is at least one of hydrogenated pyromellitic dianhydride or cyclobutane tetracarboxylic dianhydride.

[0036] The polyamic acid containing terminal amino groups can be commercially available or self-made.

[0037] For self-made polyamic acid containing terminal amino groups, the diamine is generally used in excess relative to the dianhydride, so that the polyamic acid containing terminal amino groups can be obtained.

[0038] Preferably, the polyamic acid is prepared by reacting the diamine and the dianhydride at 0-30°C for 6-10 hours.

[0039] More preferably, the reaction is carried out in a solvent.

[0040] Further preferably, the solvent is at least one of N-methylpyrrolidone, dimethylacetamide, or dimethylformamide.

[0041] More preferably, the molar ratio of the diamine to the dianhydride is 100:95-99.

[0042] Preferably, the specific surface area of the polytetrafluoroethylene resin is ≥7.5 m 2 / g.

[0043] More preferably, the specific surface area of the polytetrafluoroethylene resin is 7.5-70 m 2 / g.

[0044] Preferably, the number average molecular weight of the polytetrafluoroethylene resin is 5000-10000; specifically, it can be 5000, 6000, 7000, 8000, 9000, or 10000.

[0045] Preferably, the acrylic resin has a number average molecular weight of 1000-50000; specifically, 1000, 2000, 4000, 5000, 8000, 10000, 15000, 20000, 25000, 30000, 35000, 40000, 45000 or 50000.

[0046] Preferably, the inorganic filler is at least one of mullite, talcum powder, mica, silicon dioxide, aluminum oxide or boron nitride.

[0047] More preferably, the inorganic filler is aluminum oxide and boron nitride in a mass ratio of 2-4:6-8.

[0048] Preferably, the inorganic filler is at least one of a nano-sized inorganic filler (such as an average particle size of 50-500 nm) or a micro-sized inorganic filler (such as an average particle size of 20-100 μm).

[0049] Preferably, the polyamic acid slurry further comprises other auxiliary agents 0-1 parts.

[0050] More preferably, the other auxiliary agent is at least one of a dispersing agent, a defoaming agent, a coupling agent or a leveling agent.

[0051] Further preferably, the dispersing agent is used in an amount of 0.2-0.4 parts, including but not limited to an alkyl ammonium salt of a high molecular copolymer.

[0052] Further preferably, the defoaming agent is used in an amount of 0.05-0.1 parts, including but not limited to a silicone defoaming agent.

[0053] Further preferably, the coupling agent is used in an amount of 0.2-0.4 parts, including but not limited to 3-aminopropyl triethoxysilane.

[0054] Further preferably, the leveling agent is used in an amount of 0.05-0.1 parts, including but not limited to a silicone leveling agent.

[0055] The preparation method of the polyamic acid slurry comprises the following steps: Mixing the components to obtain the polyamic acid slurry.

[0056] The application of the polyamic acid slurry in the preparation of a water-cooled plate is also within the protection scope of the present application.

[0057] A water-cooled plate comprises a water-cooled plate substrate and a polyimide film formed from the polyamic acid slurry.

[0058] Preferably, the water-cooled plate substrate is an aluminum plate (such as a 6061 aluminum alloy plate).

[0059] Preferably, the thickness of the polyimide film is 50-200 μm.

[0060] The preparation method of the water-cooled plate comprises the following steps: The polyamide acid slurry is coated on the surface of the water-cooled plate substrate, and then cured to obtain the water-cooled plate.

[0061] Preferably, the curing process comprises the following steps: first, heat preservation at 120-180℃ for 0.5-2 hours, then heat preservation at 230-270℃ for 1-3 hours, and finally heat preservation at 280-400℃ for 1-3 hours.

[0062] Compared with the prior art, the present application has the following advantages: The polyamide acid slurry of the present application is prepared by adding inorganic fillers and composite resins, and the polyimide film prepared therefrom still maintains good insulation performance and adhesion to the substrate after working in a high-temperature and high-humidity environment, and is very suitable for preparing water-cooled plates. DETAILED DESCRIPTION

[0063] In order to more clearly and completely describe the technical solutions of the present application, the present application is further described in detail below through specific examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application, and various changes can be made within the scope of the present application.

[0064] Some reagents selected for the embodiments and comparative examples of the present application are described as follows: Polyamide acid: self-made, the self-making process comprises the following steps: adding 4,4'-diamino diphenyl ether (ODA) into NMP, stirring at room temperature for half an hour, then adding pyromellitic dianhydride (PMDA), and stirring at low temperature (5℃) in a nitrogen atmosphere for 8h to obtain polyamide acid containing terminal amino groups; wherein the solid content of the polyamide acid is 16%, and the viscosity is 1000P. The molar ratio of 4,4'-diamino diphenyl ether to pyromellitic dianhydride is 100:98; Polytetrafluoroethylene resin 1#: Japan Daikin, model number M-18F; Polytetrafluoroethylene resin 2#: USA Sowei, model number L206F; Acrylic resin 1#: BASF, model number HPD 196 MEA AP, solid content 38%; when preparing the composite resin or the polyamide acid slurry, the amount of the acrylic resin is the amount of solid after conversion according to the solid content; Acrylic resin 2#: Young Sun, model number AC 6038, solid content 40%; when preparing the composite resin or the polyamide acid slurry, the amount of the acrylic resin is the amount of solid after conversion according to the solid content; Other fluororesin 1#: polyvinylidene fluoride, manufacturer: France Arkema, model number HSV900; Other resin 1#: methyl acrylate resin, Kanos, solid content 40%; when it is used to make composite resin or polyamide acid slurry, the amount of solid after conversion according to solid content is used; Composite resin 1#: polytetrafluoroethylene resin 1# and acrylic resin 1# are mixed in a mass ratio of 2:1 to obtain; Composite resin 2#: polytetrafluoroethylene resin 1# and acrylic resin 1# are mixed in a mass ratio of 1:1 to obtain; Composite resin 3#: polytetrafluoroethylene resin 1# and acrylic resin 1# are mixed in a mass ratio of 3:1 to obtain; Composite resin 4#: polytetrafluoroethylene resin 1# and acrylic resin 2# are mixed in a mass ratio of 2:1 to obtain; Composite resin 5#: polytetrafluoroethylene resin 2# and acrylic resin 1# are mixed in a mass ratio of 2:1 to obtain; Composite resin 6#: other fluororesin 1# and acrylic resin 1# are mixed in a mass ratio of 2:1 to obtain; Composite resin 7#: polytetrafluoroethylene resin 1# and other resin 1# are mixed in a mass ratio of 2:1 to obtain; Inorganic filler 1#: alumina, average particle size 100 nm, manufacturer is Chao Tai, model is FLG3; Inorganic filler 2#: boron nitride, average particle size 50 μm, manufacturer is Chao Tai, model is JL-GBN-50; Inorganic filler A#: inorganic filler 1# and inorganic filler 2# are mixed in a mass ratio of 3:7 to obtain; Silane coupling agent: 3-aminopropyl triethoxysilane, commercially available; Dispersant: alkyl ammonium salt of high molecular copolymer, BYK-9076, BYK; Leveling agent: silicone leveling agent, BYK-310, BYK; Defoaming agent: silicone defoaming agent, BYK-1789, BYK; The polyamide acid slurries of the examples and comparative examples of the present application are prepared by the following preparation method: According to the formula, each component is taken, the composite resin, the silane coupling agent, the dispersant, the polyamide acid are mixed, then the leveling agent and the defoaming agent are added, and the solvent NMP is added to adjust the solid content of the system to 15wt%, and the polyimide slurry is obtained.

[0065] Examples 1~9 Examples 1~9 provide a series of polyamide acid slurries, and the formula is shown in Table 1 (if a component (such as polyamide acid) is a dispersion or a liquid before mixing, the amount of the component in Table 1 refers to the amount of solid after conversion according to solid content).

[0066] Formulation of Examples 1-9 (parts by weight)

[0067] Comparative Examples 1-5 Comparative Examples 1-5 provide a series of polyamic acid slurries, the formulations of which are shown in Table 2 (if a component is a dispersion or solution before mixing, the amount thereof in Table 2 refers to the amount of solid of the component after conversion according to solid content).

[0068] Table 2 Formulation of Comparative Examples 1-5 (parts by weight)

[0069] Performance test The polyamic acid slurries of Examples 1-9 and Comparative Examples 1-5 were used to prepare water-cooled plates, in the following manner: the polyamic acid slurry was automatically sprayed (spray gun caliber 1.2 mm, pressure 0.3 MPa) on a substrate, and was first incubated at 80°C for 30 min, and then was subjected to stepwise curing: incubation at 150°C for 1 h, at 250°C for 2 h, and at 300°C for 1 h under a nitrogen atmosphere, to form a polyimide film with a thickness of 100 μm on the substrate, to obtain a water-cooled plate. The substrate was 6061 aluminum alloy (thermal conductivity 167 W / (m·K), tensile strength 290 MPa).

[0070] The prepared water-cooled plate was subjected to the following tests: (1) Shear strength: the adhesion was characterized by shear strength; the initial shear strength was tested according to GB / T 7124-2008; after 1000 h of double 85 test, the shear strength after double 85 test was tested according to GB / T 7124-2008; (2) Leakage current: the initial leakage current was tested according to GB / T 1408.1-2016; after 1000 h of double 85 test, the leakage current after double 85 test was tested according to GB / T 1408.1-2016; the smaller the leakage current, the better the insulation performance.

[0071] The performance of the polyimide slurries of the examples and comparative examples was determined according to the above-mentioned test methods, and the test results are shown in Table 3.

[0072] Table 3 Performance test results of the polyimide slurries of the examples and comparative examples

[0073] From Table 3, it can be seen that: The water-cooled plate made of the polyamide acid slurry of embodiments 1-7 has a shear strength of 10.8 MPa or above after the double 85 test, and a shear strength retention rate (the shear strength after the double 85 test divided by the initial shear strength) of 90% or above; the leakage current is still ≤175 mA / m 2 The degree of increase is 7% or less; indicating that the polyamide acid slurry of the present application can maintain good adhesion to the substrate and insulation performance in a high-humidity and high-temperature environment after film formation.

[0074] Comparative Example 1 uses other fluororesins instead of polytetrafluoroethylene, and the polyamide acid slurry made into a polyimide film has significantly decreased adhesion to the substrate and poor insulation performance after the double 85 test. Comparative Example 2 uses other resins instead of acrylic resins, and the polyamide acid slurry made into a polyimide film has good initial insulation performance, but significantly decreased adhesion to the substrate and poor insulation performance after the double 85 test. Comparative Examples 3 and 4 separately add polytetrafluoroethylene and acrylic resins, respectively. The polyamide acid slurry of Comparative Example 3 made into a polyimide film has good initial insulation performance, but poor insulation performance and adhesion to the substrate after the double 85 test. The polyamide acid slurry of Comparative Example 4 made into a polyimide film has poor adhesion to the substrate and insulation performance after the double 85 test. Comparative Example 5 does not add composite resins, and the polyamide acid slurry made into a polyimide film has significantly decreased adhesion to the substrate and poor insulation performance after wet heat aging.

[0075] Obviously, the above embodiments of the present application are merely exemplary and are not intended to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. It is not necessary or possible to exhaust all embodiments. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A polyamic acid slurry, characterized in that, It includes the following components: amino-terminated polyamic acid, composite resin, and inorganic filler; The composite resin includes polytetrafluoroethylene resin and acrylic resin.

2. The polyamic acid slurry according to claim 1, characterized in that, The components include the following parts by weight: 10 parts of polyamic acid containing terminal amino groups, 1-3.5 parts of composite resin, Inorganic filler 3-9 parts.

3. The polyamic acid slurry according to claim 1, characterized in that, The composite resin comprises polytetrafluoroethylene resin and acrylic resin in a mass ratio of (1~3):

1.

4. The polyamic acid slurry according to claim 1, characterized in that, The solid content of the polyamic acid slurry is 13~20wt%.

5. The polyamic acid slurry according to claim 1, characterized in that, The polyamic acid is a copolymer of diamine and dianhydride.

6. The polyamic acid slurry according to claim 1, characterized in that, The number average molecular weight of the polytetrafluoroethylene resin is 5000~10000.

7. The polyamic acid slurry according to claim 1, characterized in that, The number average molecular weight of the acrylic resin is 1000~50000.

8. The polyamic acid slurry according to claim 1, characterized in that, The inorganic filler is at least one of silicon dioxide, aluminum oxide, or boron nitride.

9. The polyamic acid slurry according to claim 1, characterized in that, The polyamic acid slurry also includes 0.1 to 1 part of other additives.

10. A method for preparing the polyamic acid slurry according to any one of claims 1 to 9, characterized in that, Includes the following steps: The components are mixed to obtain the polyamic acid slurry.

11. The use of the polyamic acid slurry according to any one of claims 1 to 9 in the preparation of water-cooled plates.

12. A water-cooled plate, characterized in that, It includes a water-cooled plate substrate and a polyimide film formed from the polyamic acid slurry according to any one of claims 1 to 9.

13. The method for preparing the water-cooled plate according to claim 12, characterized in that, Includes the following steps: The polyamic acid slurry according to any one of claims 1 to 9 is applied to the surface of the water-cooled plate substrate and cured to obtain the water-cooled plate.

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