An adhesive, its preparation method and use

Abstract

The application discloses an adhesive and a preparation method and application thereof. The adhesive comprises the following raw materials: a polyether / polyester diol compound, a polytrifluoropropyl methyl siloxane, a polydimethylsiloxane, a perfluorooctyltrimethoxysilane, an alicyclic isocyanate, a flame retardant, a functional filler, a chain extender, a catalyst and a diluent. The polyether / polyester diol compound comprises a polytetrahydrofuran diol (PTMG) and a polycarbonate diol (PCDL); the flame retardant is a halogen-free flame retardant; the functional filler comprises a silane coupling agent modified boron nitride nanosheet and a modified alumina microsphere; and the modified alumina microsphere is a phosphorylated alumina. The application scheme is designed through multi-component synergistic innovation, and the comprehensive performance of the adhesive is remarkably improved.

Description

TECHNICAL FIELD

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

[0002] With the rapid development of 5G communication, new energy vehicles and Internet of Things technology, electronic devices are evolving towards high frequency, high power density and miniaturization, and the working environment is becoming more severe. Encapsulation materials, as the "protective armor" of electronic modules, need to meet the complex requirements of efficient heat dissipation, long-term weather resistance, process adaptation and environmental compliance. Although traditional epoxy resin, silicone and polyurethane encapsulation materials have their own advantages, they all have significant technical bottlenecks:

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

[0004] Low efficiency heat management: conventional polyurethane encapsulation glue often relies on alumina (Al2O3) or silicon dioxide (SiO2) micrometer fillers to improve thermal conductivity, but the disordered stacking of these fillers leads to a generally low thermal conductivity, which is difficult to meet the needs of high-power scenarios such as IGBT modules.

[0005] Filler-matrix interface defects: high addition of inorganic fillers can easily cause phase separation, leading to a decrease in mechanical strength and a mismatch in coefficient of thermal expansion (CTE), accelerating the interface peeling under temperature changes.

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

[0007] Wet heat aging failure: the ester group in the polyurethane molecular chain is prone to hydrolysis and chain scission, and the volume resistivity decreases significantly after 1000h of double 85 test, leading to the risk of leakage current.

[0008] Ultraviolet irradiation yellowing: the residual aromatic isocyanate (such as TDI, MDI) causes the material to yellow quickly under outdoor ultraviolet irradiation, affecting the signal stability of precision devices such as optical sensors.

[0009] 3. Environmental protection and performance balance problem

[0010] Dependence on toxic flame retardants: to achieve high flame retardant grade, traditional solutions often use halogen-based flame retardants, but their decomposition products contain dioxin-like substances, which are difficult to meet environmental protection requirements.

[0011] VOC release risk: the residual amount of volatile organic compounds (VOC) such as toluene and xylene in traditional solvent-based polyurethane encapsulation glue is high, which can easily lead to pollution of the internal airtight space of electronic equipment.

[0012] Therefore, the current polyurethane pouring sealant is faced with the core contradictions of "high thermal conductivity and high stability being incompatible, long-term protection and rapid curing being difficult to balance, environmental protection and superior performance being mutually restricted", and these technical bottlenecks have become the key shackles restricting the high-quality development of the industry. SUMMARY

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

[0014] The present application also proposes a preparation method of the above-mentioned adhesive.

[0015] The present application also proposes the application of the above-mentioned adhesive.

[0016] According to an aspect of the present application, an adhesive is proposed, comprising the following raw materials: a polyether / polyester diol compound, a polytrifluoropropyl methyl siloxane, a polydimethylsiloxane, a 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 polytetrahydrofuran diol (PTMG) and polycarbonate diol (PCDL); the flame retardant is a halogen-free flame retardant, the functional filler comprises boron nitride nanosheets modified by a silane coupling agent and modified alumina microspheres, and the modified alumina microspheres are phosphorylated alumina.

[0017] The adhesive according to the embodiments of the present application has at least the following beneficial effects: the present application scheme significantly improves the comprehensive performance of the adhesive through multi-component synergistic innovation design. Specifically, compared with the prior art, the adhesive of the present application scheme has the following advantages:

[0018] 1) Balanced rigid and flexible polyether soft segment blending system: through the blending of polytetrahydrofuran diol (PTMG) and polycarbonate diol (PCDL), the precise control of the rigidity and flexibility of the molecular chain is realized. PTMG ensures that the adhesive has excellent low-temperature toughness, and the ester group structure of PCDL promotes the orientation arrangement of the thermal conductive filler along the stress field direction to form an ordered thermal conductive path. This design not only avoids the interface stress concentration caused by the over-hardness of the material, but also prevents the decrease of the thermal conductive efficiency caused by the disordered stacking of the filler, thereby providing a material basis for heat dissipation of high-power devices.

[0019] 2) Fluorosilicon synergistic hydrophobic system: the introduction of polydimethylsiloxane (PDMS) segments and perfluorooctyltrimethoxysilane constructs a double hydrophobic barrier. PDMS blocks moisture penetration through low surface energy characteristics, and perfluorooctyltrimethoxysilane migrates to the surface to form a fluorocarbon layer, further enhancing the resistance to humid heat aging. After 1000 hours of double 85 test (85℃ / 85%RH), the volume resistivity retention rate is ≥90%, which is significantly better than that of traditional polyurethane adhesives (usually <70%).

[0020] 3) UV stabilization and anti-yellowing technology: using aliphatic isocyanate, eliminating the conjugated double bond sensitive to UV, and inhibiting photoyellowing from the root.

[0021] 4) Three-dimensional heat conduction network and CTE matching technology: through the modification of boron nitride (BN) nanosheets and phosphorylated alumina (Al2O3) microspheres by silane coupling agent, a two-dimensional-three-dimensional synergistic heat conduction network is constructed. BN nanosheets provide in-plane high thermal conductivity path, and phosphorylated Al2O3 fills the gap and forms a three-dimensional network, while the phosphorus element covalently bonds with the polyurethane matrix (forms P-O-C bond), solving the problem of mismatching of the thermal expansion coefficient (CTE) of the filler and the matrix. In addition, phosphorylated alumina also has a flame-retardant effect, which can release phosphoric acid when burning, promote the formation of carbon layer, and synergistically improve the flame-retardant effect without releasing harmful substances such as dioxin.

[0022] 5) Low VOC release: without using too much organic solvent, the VOC release is low.

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

[0024]

[0025] According to some embodiments of the present application, the mass fraction of polycarbonate diol (PCDL) in the polyether / polyester diol compound is 20-30%. Controlling the mass ratio of polyether diol compound and polyester diol compound better balances rigidity and toughness and reduces the tendency of phase separation.

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

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

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

[0029] According to some embodiments of the present application, the polydimethylsiloxane is selected from hydroxyl polydimethylsiloxane. Using PDMS containing terminal hydroxyl groups makes it better anchored in the network during the prepolymerization process.

[0030] According to some embodiments of the present application, the aliphatic isocyanate comprises at least one of isophorone diisocyanate and hexamethylene diisocyanate.

[0031] According to some embodiments of the present application, the average particle size of the silane coupling agent modified boron nitride nanosheet is 300-500 nm. Controlling the particle size of the filler makes it have better dispersion stability.

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

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

[0034] According to some embodiments of the present application, the flame retardant includes a gas phase flame retardant and a condensed phase flame retardant. The gas phase and condensed phase dual effect flame retardant has excellent flame retardant performance and is non-toxic smoke during combustion.

[0035] According to some embodiments of the present application, the gas phase flame retardant includes at least one of a carbonate salt (such as calcium carbonate, sodium carbonate, sodium carbonate, potassium carbonate, or magnesium carbonate, etc.), an ammonium salt, an organic phosphate salt, ammonium polyphosphate, amine borate, melamine salt, dicyandiamide, dicyandiamide formaldehyde resin, or chlorinated paraffin.

[0036] According to some embodiments of the present application, 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 powder.

[0037] According to some embodiments of the present application, the flame retardant further includes a bio-based flame retardant. Adding a bio-based flame retardant further improves the flame retardant effect, improves the flame retardant efficiency by catalyzing the formation of char, and achieves V0 level flame retardation.

[0038] According to some embodiments of the present application, 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 application, the chain extender includes a dihydric alcohol or a dihydric amine monomer.

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

[0041] According to some embodiments of the present application, the catalyst is selected from at least one of bismuth isooctoate, bismuth laurate, bismuth neodecanoate, pentamethyldipropylenetriamine, and polyurethane environmentally friendly organic bismuth catalyst. A catalyst with moderate catalytic activity is selected to promote gel formation and avoid too fast gelation affecting the orientation of the filler.

[0042] According to some embodiments of the present application, the diluent comprises hydroxyethyl methacrylate (HEMA). The active diluent HEMA is used to reduce viscosity, and the adhesive can be poured at room temperature.

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

[0044] The polyether / polyester diol compound, polytrifluoropropyl methyl siloxane, polydimethyl siloxane, perfluorooctyl trimethoxysilane and alicyclic isocyanate are subjected to a prepolymerization to obtain a prepolymer; the functional filler, chain extender, flame retardant, catalyst and diluent are prepared according to a formula, and the adhesive is obtained.

[0045] According to some embodiments of the present application, the prepolymerization temperature is 75-85℃, and the reaction time is 1-3h.

[0046] According to some embodiments of the present application, when used, the functional filler is dispersed in the prepolymer, and the dispersion is achieved by mixing the functional filler with the prepolymer and mixing uniformly at 1000-3000rpm. The high-speed shearing dispersion machine or other devices can be used for the dispersion.

[0047] According to some embodiments of the present application, when used, the chain extender, flame retardant, catalyst and diluent are added to the prepolymer in which the functional filler is dispersed, and then pouring and curing are performed.

[0048] According to some embodiments of the present application, the curing process is as follows: curing at room temperature for 20-28h, and then curing at 75-85℃ for 3-8h.

[0049] According to still another aspect of the present application, an electronic product is also provided, and the raw material for preparing the electronic product comprises the adhesive.

[0050] According to some embodiments of the present application, the electronic product comprises a capacitor, a module, a sensor, a controller, a charging gun, a soft-pack lithium battery, a coil, a small transformer or a wire harness. The adhesive of the present application can provide reliable protection in all-weather and all-scenarios, and can inject long-lasting vitality into the electronic product.

[0051] Additional aspects and advantages of the present application will be given in part in the following description, will become apparent in part from the following description, or will be learned by practice of the present application. DETAILED DESCRIPTION

[0052] The concept and the technical effects of the present application will be described clearly and completely in combination with the embodiments, so that the purpose, features and effects of the present application can be fully understood. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application. The test methods used in the embodiments are conventional methods unless otherwise specified. The materials and reagents used are commercially available unless otherwise specified. The same parameters have the same values in each embodiment unless otherwise specified. The following described embodiments are exemplary and are used to explain the present application, but cannot be understood as limiting the present application.

[0053] In the description of the present application, the description of the terms "some embodiments" and the like means that the specific features, structures, materials or characteristics described in combination with the embodiments or examples are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0054] In the description of the present application, 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 indicated technical features or the sequence of indicated technical features.

[0055] Embodiments

[0056] The present example provides an adhesive prepared from polyether / polyester diol compound, polytrifluoropropylmethylsiloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane, alicyclic isocyanate, flame retardant, functional filler, chain extender, catalyst and diluent raw materials, the polyether / polyester diol compound includes polytetrahydrofuran diol (PTMG) and polycarbonate diol (PCDL); the flame retardant is a halogen-free flame retardant, the functional filler includes silane coupling agent modified boron nitride nanosheet and modified alumina microsphere, and the modified alumina microsphere is phosphorylated alumina.

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

[0058] The boron nitride nanosheet (mass / volume ratio of 3 g / 100 mL) is added to water, ultrasonic dispersion (ultrasonic for 2 h under 800 W) to obtain a boron nitride dispersion (milky white, uniformly dispersed state, no precipitation);

[0059] To the above dispersion, a silane coupling agent (γ-(2,3-epoxypropoxy) propyl trimethoxysilane, added amount 15% of boron nitride nanosheet) was added, ethanol was added, the volume ratio of ethanol to water was 7:3, and the pH of the system was adjusted to about 4.5. Under stirring at 800 rpm, the reaction was carried out at 65±2℃ for 4h, and the pH of the system was controlled to be below 5.5 during the reaction. After the reaction was completed, centrifugal separation was carried out at 8000 rpm for 15 min, and the ethanol / water was alternately washed for 3 times, and then dried and ground to obtain the product. The average particle size of the obtained silane coupling agent modified boron nitride nanosheet was 450 nm.

[0060] The modified alumina microspheres were coated with phosphate coupling agent. The preparation process is as follows:

[0061] The alumina microspheres were dried in an oven to remove the surface adsorbed water; pyrophosphate coupling agent (Japan Shin Nittoku Chemical, KR-38S) was added to a mixed solution of isopropyl alcohol and water, and the pH was adjusted to about 4.5. Under stirring at 300 rpm, the reaction was carried out at 75±2℃ for 3h. After the reaction was completed, centrifugal separation was carried out at 8000 rpm for 15 min, and the isopropyl alcohol was washed for 3 times, and then dried and ground to obtain the product. The average particle size of the obtained modified alumina microspheres was 4.5μm.

[0062] In the mixed solution, the volume ratio of isopropyl alcohol to water was 9:1; the mass fraction of pyrophosphate coupling agent in the final solution was 5%, and the coupling agent was hydrolyzed for 30 min at room temperature to generate phosphate groups.

[0063] The specific formulations of each example and comparative example are shown in Table 1 below:

[0064] Table 1

[0065]

[0066]

[0067] Performance test of test example

[0068] A pre-polymer was obtained by pre-polymerization of a polyether / polyester diol compound, a polytrifluoropropylmethylsiloxane, a polydimethylsiloxane, a perfluorooctyltrimethoxysilane and a cycloaliphatic isocyanate; the functional filler was dispersed in the pre-polymer by the following steps: the functional filler was mixed with the pre-polymer under the protection of inert atmosphere (N2 or Ar can also be used), and the mixture was stirred at 3000 rpm for 15 min. A high-speed shearing disperser or other device can be used for dispersion and mixing. The chain extender, the flame retardant, the catalyst and the diluent were added to the pre-polymer with the dispersed functional filler, and the mixture was continuously stirred for 10 min until homogeneous, and then poured (at room temperature) and cured.

[0069] Curing process: room temperature (25℃±5℃) curing for 24h, then transfer into oven and curing at 80℃±2℃ for 4h.

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

[0071] 2. CTE: the test standard is ASTM E831 (TMA). Prepare 10±0.5mm long×5±0.5mm wide×3±0.1mm thick sample, use TMA instrument to test thermal expansion coefficient, and the temperature range is -40℃→150℃.

[0072] 3. Wet heat aging test: place the sample in 85℃ / 85%RH environment for 1000h, and test the volume resistivity change.

[0073] 4. UV aging test: use QUV accelerated aging box, irradiate for 1000h (60℃ light (8h)→50℃ condensation (4h)) at 340nm wavelength, and use color difference instrument to test color difference ΔE.

[0074] 5. Flame retardant performance test: carry out vertical burning test according to UL94 standard.

[0075] 6. VOC test: use headspace-gas chromatography-mass spectrometry (HS-GC-MS) to analyze the volatile organic content of the cured adhesive layer.

[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 by using the formulation of the embodiment of the present application has excellent thermal conductivity, CTE coefficient; at the same time, has excellent anti-wet heat and UV aging performance, and also has good flame retardant performance and low VOC.

[0080] The above has made a detailed description of the embodiment of the present application, but the present application is not limited to the above embodiment, and various changes can be made within the knowledge range possessed by those skilled in the art without departing from the purpose of the present application.

Claims

1. An adhesive, characterized in that: The adhesive comprises the following raw materials in parts by weight: 100 parts of polyether / polyester diol compound 8-10 parts of polytrifluoropropylmethylsiloxane 5-10 parts of polydimethylsiloxane 0.1-0.2 parts of perfluorooctyltrimethoxysilane 20-25 parts of alicyclic isocyanate 25-30 parts flame retardant 80-100 parts of functional filler 10-15 parts of chain extender 1-3 parts catalyst 20-25 parts diluent The polyether / polyester diol compounds include polytetrahydrofuran diol and polycarbonate diol; the flame retardant is a halogen-free flame retardant; and the functional filler includes silane coupling agent-modified boron nitride nanosheets and modified alumina microspheres, wherein the modified alumina microspheres are phosphorylated alumina.

2. The adhesive according to claim 1, characterized in that: The polyether / polyester diol compound contains 20-30% polycarbonate diol by mass.

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

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

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

6. The adhesive according to claim 1, characterized in that: The flame retardant includes gas-phase flame retardants and condensed-phase flame retardants.

7. A method for preparing an adhesive as described in any one of claims 1 to 6, characterized in that: Includes the following steps: A prepolymer is obtained by prepolymerizing polyether / polyester diol compounds, polytrifluoropropylmethylsiloxane, polydimethylsiloxane, perfluorooctyltrimethoxysilane, and alicyclic isocyanates; functional fillers, chain extenders, flame retardants, catalysts, and diluents are then formulated according to the recipe to obtain the final product.

8. An electronic product, characterized in that: The raw materials for manufacturing the electronic product include the adhesive as described in any one of claims 1 to 6.

9. The electronic product according to claim 8, characterized in that: The electronic products include capacitors, modules, sensors, controllers, charging guns, pouch lithium batteries, coils, small transformers, or wire harnesses.

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