Adhesive as well as preparation method and application thereof

Abstract

The invention discloses an adhesive as well as a preparation method and application thereof. The adhesive is prepared from the following raw materials: a polyether / polyester diol compound, polytrifluoropropyl methyl siloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane, alicyclic isocyanate, a flame retardant, a functional filler, a chain extender, a catalyst and a diluent. The polyether / polyester diol compound comprises polytetrahydrofuran diol (PTMG) and polycarbonate diol (PCDL); the flame retardant is a halogen-free flame retardant, the functional filler comprises silane coupling agent modified boron nitride nanosheets and modified aluminum oxide microspheres, and the modified aluminum oxide microspheres are phosphorylated aluminum oxide. According to the scheme, the comprehensive performance of the adhesive is remarkably improved through a multi-component collaborative innovative design.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to an adhesive and a preparation method and application thereof. Background Art

[0002] With the rapid development of 5G communications, new energy vehicles, and the Internet of Things (IoT), electronic devices are evolving toward higher frequencies, higher power densities, and smaller sizes, significantly increasing the severity of their operating environments. As the "protective armor" of electronic modules, potting materials must simultaneously meet complex requirements such as efficient heat dissipation, long-term weather resistance, process adaptability, and environmental compliance. While traditional epoxy resins, silicones, and polyurethane potting materials each have their own advantages, they all face significant technical bottlenecks:

[0003] 1. The contradiction between thermal conductivity and reliability is prominent

[0004] Inefficient thermal management: Conventional polyurethane potting compounds rely on micron-sized fillers such as aluminum oxide (Al2O3) or silicon dioxide (SiO2) to improve thermal conductivity. However, their disordered stacking results in generally low thermal conductivity, making it difficult to meet the requirements of high-power scenarios such as IGBT modules.

[0005] Filler-matrix interface defects: High addition of inorganic fillers can easily cause phase separation, resulting in a decrease in mechanical strength and mismatch in the coefficient of thermal expansion (CTE), and accelerating interface debonding under temperature-changing conditions.

[0006] 2. Shortcomings in weather resistance restrict long-term protection

[0007] Failure due to wet heat aging: The ester group in the polyurethane molecular chain is easily hydrolyzed and broken. After the double 85 test (1000h), the volume resistivity drops significantly, causing the risk of leakage current.

[0008] Yellowing due to UV radiation: Aromatic isocyanate residues (such as TDI and MDI) cause the material to yellow rapidly under outdoor UV radiation, affecting the signal stability of precision devices such as optical sensors.

[0009] 3. The challenge of balancing environmental protection and performance

[0010] Dependence on toxic flame retardants: To achieve high flame retardancy, traditional solutions often use halogenated flame retardants. However, their decomposition products contain dioxins, which makes it difficult to meet environmental protection requirements.

[0011] Hidden dangers of VOC release: Traditional solvent-based polyurethane potting adhesives contain high levels of residual volatile organic compounds (VOCs) such as toluene and xylene, which can easily lead to excessive pollutants in the airtight space inside electronic equipment.

[0012] Therefore, the current polyurethane potting compound faces the core contradictions of "high thermal conductivity and high stability cannot be achieved at the same time, long-term protection and rapid curing are difficult to balance, and environmental protection and superior performance restrict each other". These technical bottlenecks have become the key shackles restricting the high-quality development of the industry. Summary of the Invention

[0013] The present invention aims to solve at least one of the technical problems in the prior art. To this end, the present invention provides an adhesive.

[0014] The present invention also provides a method for preparing the adhesive.

[0015] The present invention also provides the application of the adhesive.

[0016] According to one aspect of the present invention, an adhesive is proposed, comprising the following raw materials: a polyether / polyester diol compound, polytrifluoropropylmethylsiloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane, an alicyclic isocyanate, a flame retardant, a functional filler, a chain extender, a catalyst, and a diluent, wherein the polyether / polyester diol compound comprises polytetramethylene glycol (PTMG) and polycarbonate diol (PCDL); the flame retardant is a halogen-free flame retardant, and the functional filler comprises boron nitride nanosheets modified with a silane coupling agent and modified alumina microspheres, wherein the modified alumina microspheres are phosphated alumina.

[0017] The adhesive according to the embodiments of the present invention has at least the following beneficial effects: The present invention significantly improves the overall performance of the adhesive through the innovative design of multi-component collaboration. Specifically, compared with the prior art, the adhesive of the present invention has the following advantages:

[0018] 1) A balanced rigidity and flexibility polyether soft segment blend system: By blending polytetramethylene glycol (PTMG) with polycarbonate diol (PCDL), precise control of molecular chain rigidity and flexibility is achieved. PTMG ensures the adhesive's excellent low-temperature toughness, while the ester structure of PCDL promotes the alignment of thermally conductive fillers along the stress field, forming an orderly thermal conduction path. This design avoids interfacial stress concentration caused by excessively rigid materials and prevents disordered filler stacking that reduces thermal conductivity, providing a material foundation for heat dissipation in high-power devices.

[0019] 2) Fluorosilicone Synergistic Hydrophobic System: The introduction of polydimethylsiloxane (PDMS) segments and perfluorooctyltrimethoxysilane creates a dual hydrophobic barrier. PDMS blocks water penetration through its low surface energy, while perfluorooctyltrimethoxysilane migrates to the surface to form a fluorocarbon layer, further enhancing its resistance to wet heat aging. After 1000 hours of double 85°C testing (85°C / 85% RH), the volume resistivity retention rate is ≥90%, significantly superior to traditional polyurethane adhesives (typically <70%).

[0020] 3) UV stabilization and anti-yellowing technology: The use of alicyclic isocyanate eliminates UV-sensitive conjugated double bonds, thus inhibiting photo-induced yellowing from the root.

[0021] 4) Three-dimensional thermal conductive network and CTE matching technology: A two-dimensional-three-dimensional synergistic thermal conductive network is constructed by compounding boron nitride (BN) nanosheets modified with silane coupling agents with phosphorylated aluminum oxide (Al2O3) microspheres. BN nanosheets provide a high thermal conductivity path in the plane, phosphorylated Al2O3 fills the gaps and forms a three-dimensional network. At the same time, the phosphorus element is covalently bonded to the polyurethane matrix (forming a POC bond), solving the problem of thermal expansion coefficient (CTE) mismatch between the filler and the matrix. In addition, phosphorylated aluminum oxide also has a flame retardant effect. When burned, it can release phosphoric acid, promote the formation of a carbon layer, synergistically enhance the flame retardant effect, and no harmful substances such as dioxins are released.

[0022] 5) Low VOC emission: No need to use too much organic solvent, low VOC emission.

[0023] According to some embodiments of the present invention, the adhesive comprises the following raw materials in parts by weight:

[0024]

[0025] According to some embodiments of the present invention, the polyether / polyester diol compound comprises 20-30% by weight of polycarbonate diol (PCDL). Controlling the mass ratio of polyether diol compound to polyester diol compound can better balance rigidity and toughness and reduce the tendency of phase separation.

[0026] According to some embodiments of the present invention, the number average molecular weight of the polycarbonate diol is 1000 to 2500 Da.

[0027] According to some embodiments of the present invention, the number average molecular weight of the polytetrahydrofuran diol is 600 to 2000 Da.

[0028] According to some embodiments of the present invention, the number average molecular weight of the polydimethylsiloxane is 3000 to 5000 Da.

[0029] According to some embodiments of the present invention, the polydimethylsiloxane is selected from hydroxy polydimethylsiloxane. The use of PDMS containing terminal hydroxyl groups enables it to be better anchored in the network during the prepolymerization reaction.

[0030] According to some embodiments of the present invention, the alicyclic isocyanate includes at least one of isophorone diisocyanate and hexamethylene diisocyanate.

[0031] According to some embodiments of the present invention, the average particle size of the boron nitride nanosheets modified with the silane coupling agent is between 300 and 500 nm. The particle size of the filler is controlled to achieve better dispersion stability.

[0032] According to some embodiments of the present invention, the average particle size of the modified alumina microspheres is 2 to 5 μm.

[0033] According to some embodiments of the present invention, the mass ratio of the silane coupling agent-modified boron nitride nanosheets to the modified alumina microspheres is 3-4:5-6.

[0034] According to some embodiments of the present invention, the flame retardant includes a gas phase flame retardant and a condensed phase flame retardant, which has dual flame retardancy in both gas and condensed phases, has excellent flame retardancy, and burns without toxic smoke.

[0035] According to some embodiments of the present invention, the gas-phase flame retardant includes at least one of carbonates (such as calcium carbonate, sodium carbonate, sodium carbonate, potassium carbonate or magnesium carbonate, etc.), ammonium salts, organic phosphates, ammonium polyphosphates, boric acid amines, melamine salts, dicyandiamide, dicyandiamide formaldehyde resin or chlorinated paraffin.

[0036] According to some embodiments of the present invention, the condensed phase flame retardant includes at least one of zinc borate, silicon oxide, aluminum oxide, copper oxide, magnesium hydroxide, aluminum hydroxide, copper hydroxide, cobalt hydroxide, chromium hydroxide, zinc hydroxide, aluminum silicate, calcium silicate, clay powder, feldspar powder or talc.

[0037] According to some embodiments of the present invention, the flame retardant further comprises a bio-based flame retardant. Adding the bio-based flame retardant further enhances the flame retardant effect, and improves the flame retardant efficiency through catalytic carbonization, thereby achieving V0 flame retardancy.

[0038] According to some embodiments of the present invention, the bio-based flame retardant includes at least one of an amine-modified adenosine triphosphate flame retardant and a chitosan derivative.

[0039] According to some embodiments of the present invention, the chain extender includes a diol or a diamine monomer.

[0040] According to some embodiments of the present invention, the chain extender includes but is not limited to one or more of 1,4-butanediol, neopentyl glycol, diethylaminoethanol, ethylenediamine, and N,N-dihydroxy(diisopropyl)aniline.

[0041] According to some embodiments of the present invention, the catalyst is selected from at least one of bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, pentamethyldipropylenetriamine, and an environmentally friendly polyurethane organic bismuth catalyst. Selecting a catalyst with moderate catalytic activity promotes gel formation while preventing excessive gelation from affecting filler orientation.

[0042] According to some embodiments of the present invention, the diluent includes hydroxyethyl methacrylate (HEMA). HEMA, a reactive diluent, is used to reduce viscosity and allows casting at room temperature.

[0043] According to another aspect of the present invention, a method for preparing an adhesive is provided, comprising the following steps:

[0044] The polyether / polyester diol compound, polytrifluoropropylmethylsiloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane and alicyclic isocyanate are subjected to prepolymerization reaction to obtain a prepolymer; functional fillers, chain extenders, flame retardants, catalysts and diluents are prepared according to the formula to obtain the product.

[0045] According to some embodiments of the present invention, the prepolymerization reaction temperature is 75 to 85° C., and the reaction time is 1 to 3 hours.

[0046] According to some embodiments of the present invention, the functional filler is dispersed in the prepolymer during use, specifically by the following steps: the functional filler is mixed with the prepolymer and uniformly mixed at 1000-3000 rpm. The dispersion can be achieved using a high-speed shear disperser or other device.

[0047] According to some embodiments of the present invention, when used, a chain extender, a flame retardant, a catalyst and a diluent are added to a prepolymer in which a functional filler is dispersed, and then the prepolymer is poured and cured.

[0048] According to some embodiments of the present invention, the curing process is as follows: curing at room temperature for 20 to 28 hours, and then curing at 75 to 85° C. for 3 to 8 hours.

[0049] According to yet another aspect of the present invention, an electronic product is provided, wherein the raw materials for preparing the electronic product include the above-mentioned adhesive.

[0050] According to some embodiments of the present invention, the electronic products include capacitors, modules, sensors, controllers, charging guns, soft-pack lithium batteries, coils, small transformers, or wiring harnesses. The adhesives of the present invention provide reliable all-weather, all-scenario protection, injecting long-lasting vitality into electronic products.

[0051] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the concept of the present invention and the technical effects produced in conjunction with the embodiments, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. Unless otherwise specified, the test methods used in the embodiments are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials obtained from commercial channels. Unless otherwise specified, the same parameter in each embodiment has the same value. The embodiments described below are exemplary and are only used to explain the present invention, and are not to be understood as limitations of the present invention.

[0053] In the description of the present invention, reference to the term "some embodiments" or the like indicates that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0054] In the description of the present invention, if there is a description of first, second, etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0055] Example

[0056] This example provides an adhesive, which is prepared from polyether / polyester diol compounds, polytrifluoropropylmethylsiloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane, alicyclic isocyanate, flame retardant, functional filler, chain extender, catalyst and diluent raw materials. The polyether / polyester diol compounds include polytetramethylene glycol (PTMG) and polycarbonate diol (PCDL); the flame retardant is a halogen-free flame retardant, and the functional filler includes boron nitride nanosheets modified with a silane coupling agent and modified alumina microspheres, and the modified alumina microspheres are phosphated alumina.

[0057] The preparation process of silane coupling agent modified boron nitride nanosheets is as follows:

[0058] Add boron nitride nanosheets (mass-to-volume ratio: 3 g / 100 mL) to water and ultrasonically disperse (under 800 W for 2 h) to obtain a boron nitride dispersion (milky white, uniformly dispersed, and free of precipitation).

[0059] To the above dispersion, a silane coupling agent (γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 15% of the boron nitride nanosheets) was added, along with ethanol (a volume ratio of ethanol to water of 7:3). The pH of the system was adjusted to approximately 4.5. The mixture was stirred at 800 rpm and allowed to react at 65±2°C for 4 hours, maintaining the pH below 5.5. After the reaction, the mixture was centrifuged at 8000 rpm for 15 minutes, washed three times with alternating ethanol and water, dried, and ground. The resulting silane-coupling-agent-modified boron nitride nanosheets had an average particle size of 450 nm.

[0060] Modified alumina microspheres are coated with a phosphate coupling agent. The preparation process is as follows:

[0061] Alumina microspheres were dried in an oven to remove surface adsorbed water. A pyrophosphate coupling agent (Shin-Etsu Chemical, Japan, KR-38S) was added to a mixture of isopropyl alcohol and water, and the pH was adjusted to approximately 4.5. The mixture was stirred at 300 rpm and allowed to react at 75 ± 2°C for 3 hours. After the reaction, the mixture was centrifuged at 8000 rpm for 15 minutes, washed three times with isopropyl alcohol, dried, and ground to obtain the modified alumina microspheres with an average particle size of 4.5 μm.

[0062] The volume ratio of isopropanol to water in the mixed solution is 9:1; the mass fraction of the pyrophosphate coupling agent in the final solution is 5%, and the hydrolysis is stirred at room temperature for 30 minutes to fully hydrolyze the coupling agent to generate phosphate groups.

[0063] The specific formulas of the embodiments and comparative examples are shown in Table 1 below:

[0064] Table 1

[0065]

[0066]

[0067] Test case performance test

[0068] A polyether / polyester diol compound, polytrifluoropropylmethylsiloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane, and alicyclic isocyanate are prepolymerized to obtain a prepolymer. The functional filler is dispersed in the prepolymer using the following steps: the functional filler and prepolymer are mixed under an inert atmosphere (N2 or Ar, etc.) at 3000 rpm for 15 minutes. A high-speed shear disperser or other device can be used to achieve uniform dispersion and mixing. A chain extender, flame retardant, catalyst, and diluent are added to the prepolymer containing the functional filler. The mixture is stirred for 10 minutes until homogeneous, then poured (at room temperature) and cured.

[0069] Curing process: Curing at room temperature (25℃±5℃) for 24 hours, then transfer to an oven and cure at 80℃±2℃ for 4 hours.

[0070] 1. Thermal conductivity test: Prepare a 3±0.1mm thick standard sample, use a laser thermal conductivity meter to test the thermal diffusivity, and calculate the thermal conductivity. The test standard is ASTM E1461.

[0071] 2. CTE: The test standard is ASTM E831 (thermomechanical analysis, TMA). Prepare a sample with a length of 10±0.5mm, a width of 5±0.5mm, and a thickness of 3±0.1mm. Use a TMA instrument to test the thermal expansion coefficient at a temperature range of -40℃→150℃.

[0072] 3. Humidity and heat aging test: Place the sample in an 85℃ / 85%RH environment for 1000h and measure the change in volume resistivity.

[0073] 4. UV aging test: Use QUV accelerated aging chamber, 340nm wavelength irradiation for 1000h (60℃ light (8h) → 50℃ condensation (4h)), and use colorimeter to measure color difference ΔE.

[0074] 5. Flame retardant performance test: vertical burning test is carried out in accordance with UL94 standard.

[0075] 6. VOC test: Use headspace gas chromatography-mass spectrometry (HS-GC-MS) to analyze the volatile organic compound content of the glue layer after curing.

[0076] The test results are shown in Table 2 below:

[0077] Table 2

[0078]

[0079] As can be seen from Table 2, the adhesive prepared using the formulation of the embodiment of the present invention has excellent thermal conductivity and CTE coefficient; at the same time, it has excellent resistance to moisture and heat and UV aging, and also has good flame retardant properties and low VOC.

[0080] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the scope of the present invention.

Claims

1. An adhesive, characterized in that: The invention comprises the following raw materials: polyether / polyester diol compounds, polytrifluoropropylmethylsiloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane, alicyclic isocyanate, flame retardant, functional filler, chain extender, catalyst and diluent, wherein the polyether / polyester diol compounds include polytetramethylene glycol and polycarbonate diol; the flame retardant is a halogen-free flame retardant; the functional filler includes boron nitride nanosheets modified with a silane coupling agent and modified alumina microspheres, and the modified alumina microspheres are phosphated alumina.

2. The adhesive according to claim 1, characterized in that: The adhesive comprises the following raw materials in parts by weight:

3. The adhesive according to claim 1, wherein: The mass proportion of polycarbonate diol in the polyether / polyester diol compound is 20-30%.

4. The adhesive according to claim 1, characterized in that: The number average molecular weight of the polycarbonate diol is 1000-2500 Da; and / or the number average molecular weight of the polytetramethylene glycol is 600-2000 Da; and / or the number average molecular weight of the polydimethylsiloxane is 3000-5000 Da.

5. The adhesive according to claim 1, characterized in that: The polydimethylsiloxane is selected from hydroxy polydimethylsiloxane.

6. The adhesive according to claim 1, characterized in that: The average particle size of the boron nitride nanosheets modified by the silane coupling agent is 300-500 nm; and / or the average particle size of the modified alumina microspheres is 2-5 μm.

7. The adhesive according to claim 1, characterized in that: The flame retardant includes a gas phase flame retardant and a condensed phase flame retardant.

8. A method for preparing the adhesive according to any one of claims 1 to 7, characterized in that: The steps include: The polyether / polyester diol compound, polytrifluoropropylmethylsiloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane and alicyclic isocyanate are subjected to prepolymerization reaction to obtain a prepolymer; functional fillers, chain extenders, flame retardants, catalysts and diluents are prepared according to the formula to obtain the product.

9. An electronic product, characterized in that: The raw materials for preparing the electronic product include the adhesive according to any one of claims 1 to 7.

10. The electronic product according to claim 9, characterized in that: The electronic products include capacitors, modules, sensors, controllers, charging guns, soft-pack lithium batteries, coils, small transformers or wiring harnesses.

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