High-temperature and high-humidity resistant polyurethane hot melt adhesive PUR and preparation method thereof

Abstract

The application discloses a high-temperature and high-humidity resistant polyurethane hot melt adhesive PUR and a preparation method thereof. The high-temperature and high-humidity resistant polyurethane hot melt adhesive PUR comprises the following components in parts by mass: 80-100 parts of polyether type polyurethane particles, 5-8 parts of hexagonal boron nitride nanosheets, 1-3 parts of hollow nanosilica, 3-5 parts of hydrazide-based capture agent, 1-2 parts of heat-activated microspherical epoxy resin, 0.5-1 part of zirconium aluminate, and 5-10 parts of hydrogenated terpene resin. The application utilizes multi-component synergy, simultaneously improves the high-temperature and high-humidity resistance of the polyurethane hot melt adhesive PUR, and solves the problems of softening failure of the adhesive layer caused by high temperature and molecular chain hydrolysis and peeling caused by high humidity in electronic device packaging.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging technology, and in particular to a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) and its preparation method. Background Technology

[0002] As electronic devices evolve towards higher performance and miniaturization, their operating temperature and humidity environments are becoming increasingly demanding. For example, automotive electronics must withstand the dual challenges of 85°C high temperature and 85% RH high humidity for extended periods, while the surface temperature of heat-generating components such as 5G chips can reach over 100°C. Polyurethane hot melt adhesive (PUR) is widely used in electronic packaging due to its flexibility and ease of processing; however, the stability of traditional PUR in high-temperature and high-humidity coupling environments has become a key bottleneck restricting device reliability.

[0003] Currently, the high temperature resistance or high humidity resistance of PUR can be improved by modification, but the two cannot be achieved at the same time. The reason is that improving heat resistance requires increasing the crosslinking density or introducing rigid segments, but this will reduce the mobility of molecular chains, forcing moisture to diffuse in a straight line along the rigid interface, which will accelerate hydrolysis. On the other hand, improving moisture resistance depends on hydrophobic groups, but this will weaken the interfacial adhesion between the adhesive layer and the metal / plastic substrate under high temperature conditions.

[0004] Therefore, there is a need for a novel polyurethane hot melt adhesive that can both suppress high-temperature softening and block the penetration of water molecules. Summary of the Invention

[0005] In view of this, this application provides a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) and its preparation method, which is used to solve the problem of how to simultaneously improve the high-temperature resistance and high-humidity resistance of polyurethane hot melt adhesive (PUR).

[0006] To achieve the above technical objectives, this application adopts the following technical solution:

[0007] In a first aspect, the present invention provides a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR), comprising the following components in parts by weight: 80-100 parts of polyether-type polyurethane particles, 5-8 parts of hexagonal boron nitride nanosheets, 1-3 parts of hollow nano-silica, 3-5 parts of acylhydrazine scavenging agent, 1-2 parts of thermally activated microsphere epoxy resin, 0.5-1 parts of zirconate aluminate, and 5-10 parts of hydrogenated terpene resin.

[0008] Preferably, the softening temperature of the thermally activated microsphere epoxy resin is 95-114℃.

[0009] Preferably, the acylhydrazide scavenger is sebacic acid dihydrazide.

[0010] Preferably, the mass ratio of sebacic acid dihydrazide to thermally activated microsphere epoxy resin is 1.5-2.5:1.

[0011] Preferably, the molar ratio of Zr to Al in the zirconium aluminate nanoclusters is 2-4:1.

[0012] Secondly, this application provides a method for preparing a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR), comprising the following steps:

[0013] S1. Polyether-type polyurethane particles are mixed with hydrogenated terpene resin after vacuum dehydration to obtain a dehydrated matrix;

[0014] S2. Boron nitride nanosheets and hollow nano-silica were added to the dehydrated matrix and then sheared under a vertical magnetic field to obtain a magnetic orientation composite.

[0015] S3. At a certain temperature, zirconium aluminate is added to the magnetic orientation composite and dispersed evenly. Then, hydrazide-based scavenging agent and thermally activated microsphere epoxy resin are added and mixed and extruded to obtain high-temperature and high-humidity resistant polyurethane hot melt adhesive PUR.

[0016] Preferably, in step S2, the shearing is performed at 500 rpm for 20 minutes under a vertical magnetic field of 0.5-1T.

[0017] Preferably, in step S3, the temperature is 70-80℃.

[0018] Thirdly, this application provides a method for applying a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR), wherein after application, the adhesive is cured sequentially at 80-90℃ for 20 min, 95-114℃ for 10 min, and 60-80℃ for 24 h.

[0019] Fourthly, this application provides the application of high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) in the preparation of electronic device packages.

[0020] The beneficial effects of this application are as follows: This application solves the problem of adhesive layer softening failure caused by high temperature by using the rapid thermal conductivity of boron nitride combined with the high temperature repair of epoxy microspheres; solves the problem of molecular chain hydrolysis caused by high humidity by using the lateral water blocking of boron nitride combined with the water absorption of silica and the hydrolysis blocking of hydrazide; and solves the problem of adhesive layer softening failure caused by high temperature and molecular chain hydrolysis caused by high humidity in electronic device packaging by using the synergistic effect of multiple components. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] This invention provides a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR), comprising the following components in parts by weight: 80-100 parts of polyether-type polyurethane particles, 5-8 parts of hexagonal boron nitride nanosheets, 1-3 parts of hollow nano-silica, 3-5 parts of acylhydrazine scavenging agent, 1-2 parts of thermally activated microsphere epoxy resin, 0.5-1 parts of zirconate aluminate, and 5-10 parts of hydrogenated terpene resin.

[0023] In this application, polyether-type polyurethane particles are used as the matrix material. The ether bonds in their molecular chains have excellent flexibility and hydrolysis resistance. Their long molecular chains act like an "elastic net" to wrap other components (for example, TPU chains are adsorbed onto the h-BN surface through van der Waals forces to form a "coating-entanglement" structure), buffering thermal stress during temperature changes. However, pure polyurethane will soften and fail under high temperature conditions. In humid environments, ester bonds are easily hydrolyzed by water. Water molecules attack ester bonds to generate carboxyl groups, which further catalyze the breakage of surrounding ester bonds, forming a chain reaction (autocatalytic hydrolysis), ultimately leading to the powdering and detachment of the adhesive layer. Therefore, this application introduces hexagonal boron nitride nanosheets, which form a special "standing" arrangement structure under the action of a vertical magnetic field. This structure can quickly conduct heat in the vertical direction to rapidly dissipate heat from the chip, preventing heat accumulation and softening of the adhesive layer, thus solving the problem of high-temperature softening. It can also force water molecules to take a long detour in the horizontal direction, blocking water vapor penetration, thus solving the problem of humidity.

[0024] The porous structure of the nano-silica in this application adsorbs and penetrates water molecules, expands to fill gaps, locks in moisture, blocks water molecules from attacking the molecular chains of the adhesive layer, enhances the structural strength of the polyurethane hot melt adhesive, and mitigates the drawback of easy hydrolysis under high humidity and high heat conditions.

[0025] As those skilled in the art know, the humid environment in which electronic devices operate often contains acidic substances that catalyze the breakage of polyurethane molecular chains, producing -COOH. Simultaneously, acidic fragments further accelerate the hydrolysis of the material, creating a vicious cycle. The hydrazide-based scavenger in this application, with higher activity than water molecules, can preemptively capture -COOH, blocking the hydrolysis chain reaction. Thermally activated epoxy microspheres (which require heating to trigger the curing reaction compared to unactivated epoxy microspheres) soften and release epoxy groups upon reaching a critical temperature (95-114°C), reacting with the hydrazide groups to generate new crosslinking points. The damaged molecular chains are repaired using the hydrolysis byproduct -COOH.

[0026] The zirconium aluminate of this application can form a dense passivation film, blocking chloride ions in sweat or salt spray from corroding the circuit, further improving its resistance to high temperature and high humidity.

[0027] This application solves the problem of adhesive layer softening and failure caused by high temperature by using the rapid thermal conductivity of boron nitride combined with the high temperature repair of epoxy microspheres. It solves the problem of molecular chain hydrolysis and shedding caused by high humidity by using the lateral water blocking of boron nitride combined with the water absorption of silica and the hydrolysis blocking of hydrazide. It also solves the problem of poor moisture resistance under high temperature conditions and poor high temperature resistance under high humidity conditions by using the synergistic effect of multiple components.

[0028] In some embodiments, the softening temperature of the thermally activated microsphere epoxy resin is 95-114°C.

[0029] In this embodiment, if the softening point is too low, epoxy will be released during the mixing stage, causing the rubber compound to cross-link prematurely and become unusable; if it is too high, the repair will be delayed, and the electronic components will have already been overheated and damaged.

[0030] In some embodiments, the acylhydrazide scavenger is sebacate dihydrazide.

[0031] In some embodiments, the mass ratio of sebacic acid dihydrazide to thermally activated microsphere epoxy resin is 1.5-2.5:1.

[0032] In this embodiment, if there is too little hydrazide, it will not be able to capture all carboxyl groups, and the residual acid will accelerate hydrolysis; if there is too much, it will cause excessive cross-linking and make the adhesive layer brittle.

[0033] In some embodiments, the molar ratio of Zr to Al in the zirconium aluminate nanoclusters is 2-4:1.

[0034] In this embodiment, an excessively high or low zirconium-aluminum ratio will reduce the passivation film density.

[0035] This application provides a method for preparing a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR), comprising the following steps:

[0036] S1. Polyether-type polyurethane particles are mixed with hydrogenated terpene resin after vacuum dehydration to obtain a dehydrated matrix;

[0037] S2. Boron nitride nanosheets and hollow nano-silica were added to the dehydrated matrix and then sheared under a vertical magnetic field to obtain a magnetic orientation composite.

[0038] S3. At a certain temperature, zirconium aluminate is added to the magnetic orientation composite and dispersed evenly. Then, hydrazide-based scavenging agent and thermally activated microsphere epoxy resin are added and mixed and extruded to obtain high-temperature and high-humidity resistant polyurethane hot melt adhesive PUR.

[0039] In some embodiments, in step S2, the shearing is performed at 500 rpm for 20 min under a 0.5-1T vertical magnetic field.

[0040] In this embodiment, boron nitride rotates under the Lorentz force due to its diamagnetism. After shearing treatment, it can ensure that the boron nitride nanosheets are vertically oriented, which not only optimizes the thermal conductivity and water-blocking properties, but also avoids the stress concentration problem caused by filler agglomeration.

[0041] In some embodiments, the temperature in step S3 is 70-80°C.

[0042] In this embodiment, if the mixing temperature is too low, the components will be unevenly dispersed; if it is too high, the epoxy microspheres will be activated prematurely.

[0043] This application provides a method for applying a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR). After application, the adhesive is cured sequentially at 80-90℃ for 20 minutes, 95-114℃ for 10 minutes, and 60-80℃ for 24 hours.

[0044] In this application, polyurethane molecular chains are first induced to arrange themselves in an orderly manner at 80-90℃ to form initial physical cross-linking points; then the temperature is raised to 95-114℃ to trigger the repair function of epoxy microspheres (the curing temperature of the second stage is the same as the softening temperature of epoxy microspheres), repairing the molecular chain break points; finally, the temperature is maintained at 60-80℃ for 24 hours to allow zirconium aluminate sufficient time to migrate to the metal interface and form a complete protective film.

[0045] This application provides the application of high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) in the preparation of electronic device packages.

[0046] Raw material source:

[0047] Hexagonal boron nitride nanosheets: Xi'an Qiyue Biotechnology Co., Ltd., item number 52352;

[0048] Thermally activated microsphere epoxy resin: Guangzhou Zhuocen Chemical Co., Ltd., DER 6508 (softening point 95-105℃) or DER 6510HT (105-114℃);

[0049] Non-thermally activated microsphere epoxy resin: Guangzhou Zhuocen Chemical Co., Ltd., DER 6615 (softening point 78-86℃);

[0050] Hollow nano silica: Xi'an Ruixi Biotechnology, 100-300nm.

[0051] The following specific embodiments further illustrate this solution. Example

[0052] A high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) comprises the following components in parts by weight: 90 parts polyether-type polyurethane particles, 6 parts hexagonal boron nitride nanosheets, 2 parts hollow nano-silica, 4 parts sebacate dihydrazide, 1.5 parts thermally activated microsphere epoxy resin, 0.8 parts zirconate aluminate, and 5 parts hydrogenated terpene resin; the softening temperature of the thermally activated microsphere epoxy resin is 95-114℃.

[0053] A method for preparing high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) includes the following steps:

[0054] S1. Add 90 parts of polyether polyurethane granules and 5 parts of hydrogenated terpene resin to a twin-screw extruder with an aspect ratio of 40:1 and a temperature of 80°C. Mix and melt under a vacuum of -0.095MPa for 2 hours to ensure a moisture content of <0.02%. The melt is then water-cooled and pelletized to obtain uniform dehydrated matrix granules, which are then sealed and stored for later use.

[0055] S2. Add the dehydrated matrix particles to a mixer and melt them at 75°C and 50 rpm. Then add 6 parts of hexagonal boron nitride nanosheets and mix at 100 rpm for 5 minutes to avoid agglomeration. Add 2 parts of nano-silica and continue mixing for 10 minutes to ensure uniform dispersion. Then transfer the mixture to a magnetic field shearing device equipped with neodymium iron boron permanent magnets with a magnetic field strength of 0.8T and treat it at a shear rate of 500 rpm for 20 minutes to make the boron nitride nanosheets vertically aligned.

[0056] S3. Transfer the magnetic orientation composite to a planetary stirrer, add 0.8 parts of zirconium aluminate nanoclusters at 75°C and vacuum -0.09MPa, stir for 15 minutes until completely dispersed, then add 4 parts of sebacic acid dihydrazide, stir for 10 minutes, and finally add 1.5 parts of thermally activated epoxy microspheres, stir at 50 rpm for 5 minutes to avoid microsphere breakage, and after mixing evenly, extrude into strips through a single screw extruder at 80°C and die pressure of 5MPa, cool with water and then granulate to obtain the final hot melt adhesive product.

[0057] Application method of high temperature and high humidity resistant polyurethane hot melt adhesive PUR: Heat the hot melt adhesive particles to 85℃ to melt them, apply them to the electronic device packaging area (thickness 0.2mm), and cure using the following procedure: cure at 85℃ for 20 minutes, cure at 114℃ for 10 minutes, and cure at 70℃ for 24 hours.

[0058] Examples 2-5

[0059] A high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) is the same as in Example 1, except that the amount of hexagonal boron nitride nanosheets used is 3, 5, 8, and 10 parts respectively.

[0060] Comparative Example 1

[0061] A polyurethane hot melt adhesive (PUR) is the same as in Example 1, except that the magnetic field is removed in step S2.

[0062] Comparative Example 2

[0063] A polyurethane hot melt adhesive (PUR) is identical to that in Example 1, except that the thermally activated microsphere epoxy resin is replaced with an unthermally activated microsphere epoxy resin.

[0064] Comparative Example 3

[0065] A polyurethane hot melt adhesive (PUR) is identical to that in Example 1, except that the amount of sebacic acid dihydrazide used is 1.5 parts.

[0066] Comparative Example 4

[0067] A polyurethane hot melt adhesive (PUR) is identical to Example 1 except that the curing step of 70°C for 24 hours is omitted.

[0068] Testing and Evaluation

[0069] The high humidity resistance and high temperature resistance of the polyurethane hot melt adhesive PUR in different embodiments and comparative examples were tested using the following methods:

[0070] High-temperature creep resistance: A constant stress of 0.2 MPa was applied at 85℃, and the strain rate (%) was recorded after 100 h to evaluate the effect of high-temperature conditions on the material;

[0071] Humid heat aging: The interfacial bond strength decay rate was tested at 85℃ / 85% RH (measured every 24 hours for a total of 168 hours) to evaluate the impact of high temperature and high humidity conditions on the material's bonding performance.

[0072] Water vapor permeability: measured at 38°C / 90% RH (ASTM E96), in g·mm / (m²·day), to assess the effect of high humidity conditions on the material.

[0073] The results are shown in Table 1.

[0074] Table 1 Test Results

[0075] ;

[0076] Examples 1-5 show that the vertical arrangement of boron nitride effectively enhances high-temperature rigidity, and the water vapor permeability decreases with increasing boron nitride content; Comparative Example 1 shows that disordered boron nitride completely loses its water-blocking ability, and its high-temperature modulus drops sharply; Comparative Example 2 shows that unactivated epoxy microspheres cannot be dynamically repaired, and their hydrolysis resistance decreases; Comparative Example 3 shows that insufficient hydrazide and residual carboxyl groups lead to local hydrolysis channels, resulting in poor high humidity and high temperature resistance.

[0077] This application solves the problem of adhesive layer softening and failure caused by high temperature by using the rapid thermal conductivity of boron nitride combined with the high temperature repair of epoxy microspheres. It solves the problem of molecular chain hydrolysis and shedding caused by high humidity by using the lateral water blocking of boron nitride combined with the water absorption of silica and the hydrolysis blocking of hydrazide. It also solves the problem of poor moisture resistance under high temperature conditions and poor high temperature resistance under high humidity conditions by using the synergistic effect of multiple components.

[0078] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR), characterized in that, The product comprises the following components in parts by weight: 80-100 parts polyether polyurethane particles, 5-8 parts hexagonal boron nitride nanosheets, 1-3 parts hollow nano-silica, 3-5 parts sebacic acid dihydrazide, 1-2 parts thermally activated microsphere epoxy resin, 0.5-1 part zirconate aluminate, and 5-10 parts hydrogenated terpene resin; the softening temperature of the thermally activated microsphere epoxy resin is 95-114℃; the polyurethane hot melt adhesive PUR is prepared by a step including shearing under a vertical magnetic field, and after application, it needs to undergo curing treatments sequentially at 80-90℃ for 20 min, 95-114℃ for 10 min, and 70℃ for 24 h. 2.The high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) according to claim 1, characterized in that, The mass ratio of sebacic acid dihydrazide to thermally activated microsphere epoxy resin is 1.5-2.5:

1. 3.The high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) according to claim 1, characterized in that, The molar ratio of Zr to Al in zirconium aluminate is 2-4:

1.

4. A method for preparing a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Polyether-type polyurethane particles are mixed with hydrogenated terpene resin after vacuum dehydration to obtain a dehydrated matrix; S2. Boron nitride nanosheets and hollow nano-silica are added to the dehydrated matrix, and then sheared under a vertical magnetic field to obtain a magnetic orientation composite. S3. At a certain temperature, zirconium aluminate is added to the magnetic orientation composite and dispersed evenly. Then, sebacic acid dihydrazide and thermally activated microsphere epoxy resin are added and mixed and extruded to obtain the high temperature and high humidity resistant polyurethane hot melt adhesive PUR.

5. The preparation method of the high-temperature and high-humidity resistant polyurethane hot melt adhesive PUR according to claim 4, characterized in that, In step S2, shearing is performed at 500 rpm for 20 minutes under a vertical magnetic field of 0.5-1T. 6.The preparation method of the high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) according to claim 4, characterized in that, In step S3, the temperature is 70-80℃.

7. A method of applying the polyurethane hot melt adhesive (PUR) resistant to high temperature and high humidity according to any one of claims 1-3, characterized in that, After applying the adhesive, cure at 80-90℃ for 20 minutes, 95-114℃ for 10 minutes, and 70℃ for 24 hours in sequence.

8. The application of a high-temperature and high-humidity resistant polyurethane hot melt adhesive (PUR) as described in any one of claims 1-3 in the preparation of electronic device packages.