Damp-heat-resistant and high-temperature-resistant polyurethane structural adhesive and preparation method thereof

Abstract

The invention discloses a damp-heat-resistant and high-temperature-resistant polyurethane structural adhesive which comprises a component A and a component B. The component A comprises the following components in parts by mass: 3-5 parts of fluorine-containing polyether polyol, 25-45 parts of polyether polyol, 10-20 parts of mica powder, 40-80 parts of heat-conducting filler, 2-5 parts of a chain extender and 1-3 parts of a coupling agent; the component B is prepared from 35 to 55 parts of isocyanate, 0.3 to 0.7 part of catalyst and 1 to 2 parts of tackifier. The polyurethane structural adhesive disclosed by the invention has excellent humidity and heat resistance, high temperature resistance, electrical insulation property and heat-conducting property, and the problem that the adhesive property of the polyurethane structural adhesive is reduced in a high-temperature and high-humidity environment is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal conductive structural adhesives, and particularly relates to a moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive and a preparation method thereof. Background Art

[0002] Polyurethane structural adhesives, due to their excellent bonding properties, good elasticity, and mechanical strength, are widely used in aerospace, automotive, electronics, and new energy sectors. In particular, in new energy vehicle power batteries, high-power electronic modules, and various outdoor electrical devices, polyurethane structural adhesives must not only provide reliable structural connections but also meet multiple functional requirements, including thermal conductivity, electrical insulation, and long-term environmental stability.

[0003] However, the polyurethane structural adhesives in the prior art have obvious deficiencies in terms of moisture and heat resistance and high temperature resistance:

[0004] 1. Aging issues related to humidity and heat are prominent. Traditional polyether and polyester-based polyurethane structural adhesives are prone to hydrolysis in high-temperature and high-humidity environments, resulting in a decrease in molecular weight and destruction of the cross-linking network. This, in turn, manifests as a sudden drop in mechanical strength and adhesive failure, seriously impacting product lifespan and safety. Reliability in humidity and heat is particularly critical in safety-critical applications, such as power batteries.

[0005] 2. Poor high-temperature resistance. Conventional polyurethane structural adhesives are prone to thermal oxidative degradation in long-term high-temperature environments, which intensifies molecular chain breakage, leading to shrinkage, cracking, and brittleness of the adhesive layer. These adhesives are unable to meet the structural stability requirements of modern electronic and electrical equipment under high-temperature conditions.

[0006] 3. Poor interfacial compatibility. In highly filled thermally conductive polyurethane structural adhesives, the interface between the inorganic filler and the organic polyurethane matrix is not firmly bonded. Under the influence of a hot and humid environment, micropores and interfacial delamination are easily formed, which not only leads to a decline in mechanical properties, but also increases thermal resistance and reduces thermal conductivity.

[0007] Therefore, the development of a polyurethane structural adhesive with excellent moisture and heat resistance, high temperature resistance and high thermal conductivity has important practical value and broad market prospects for meeting the stringent requirements of high-end fields such as new energy vehicle battery systems and high-power electronic devices. Summary of the Invention

[0008] Based on the above-mentioned prior art, the present invention provides a moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive and a preparation method thereof. The polyurethane structural adhesive of the present invention has excellent moisture-heat resistance, high-temperature resistance, electrical insulation performance and thermal conductivity, and solves the problem of decreased bonding performance of polyurethane structural adhesives in high temperature and high humidity environments.

[0009] The technical solution adopted to achieve the above-mentioned purpose of the present invention is:

[0010] A moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive comprises a component A and a component B. Component A comprises, in parts by mass, 3-5 parts of a fluorinated polyether polyol, 25-45 parts of a polyether polyol, 10-20 parts of mica powder, 40-80 parts of a thermally conductive filler, 2-5 parts of a chain extender, and 2-4 parts of a coupling agent; and component B comprises 35-55 parts of an isocyanate, 0.3-0.7 parts of a catalyst, and 1-2 parts of a tackifier.

[0011] Furthermore, the functionality of the fluoropolyether polyol is 2-4 and the average molecular weight is 2000-4000.

[0012] Furthermore, the fluoropolyether polyol is a mixture of polyoxypropylene diol and polyoxypropylene triol, and the mass ratio of polyoxypropylene diol to polyoxypropylene triol is 2-3:2-3.

[0013] Furthermore, the preparation method of the fluorinated polyether polyol is as follows:

[0014] 1. Dissolve potassium hydroxide in methanol to prepare a potassium hydroxide solution with a mass concentration of 0.1-0.2 wt%;

[0015] 2. Add trimethylolpropane to the reactor, then add potassium hydroxide solution, seal the reactor, evacuate and remove residual water vapor, and then fill with nitrogen for protection;

[0016] 3. Heat to 50-60°C while stirring, then slowly add 75-85% by weight of propylene oxide over 4-6 hours;

[0017] 4. Evenly mix the remaining propylene oxide and 2,2,3,3-tetrafluoropropylene oxide to obtain a mixed solution. Slowly drop the mixed solution into the reactor under nitrogen protection for 2-3 hours. After the dropwise addition is completed, continue stirring and reacting at 50-60°C for 2-4 hours;

[0018] 5. After the reaction is completed, cool to below 40°C, add methanol, stir to neutralize potassium hydroxide, then let stand, filter to obtain a filtrate;

[0019] 6. The filtrate is distilled under reduced pressure at 90–100°C, followed by vacuum degassing for 1–2 hours, and then cooled naturally to room temperature to obtain a slightly yellowish transparent viscous liquid, which is the fluorinated polyether polyol;

[0020] The molar ratio of trimethylolpropane, propylene oxide, 2,2,3,3-tetrafluoropropane oxide and sodium hydroxide is 1:12-18:0.8-1.5:0.017-0.034.

[0021] Furthermore, the thermally conductive filler is selected from at least one of aluminum oxide, boron nitride, silicon oxide and magnesium hydroxide.

[0022] Furthermore, the chain extender is selected from at least one of 1,4-butanediol, ethylene glycol, glycerol, butanediol and 1,6-hexanediol.

[0023] Furthermore, the catalyst is at least one of dibutyltin dilaurate, stannous octoate, zinc octoate and bismuth tricyclohexanoate.

[0024] Furthermore, the isocyanate is selected from 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

[0025] Furthermore, the coupling agent is selected from at least one of γ-glycidyloxypropyltrimethoxysilane, tetraisopropyl titanate, tetrabutyl titanate, acetylacetonate and 3-aminopropyltriethoxysilane.

[0026] Furthermore, the tackifier is selected from at least one of phenolic resin, modified rosin resin, petroleum resin and polyamide resin.

[0027] A method for preparing a moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive comprises the following steps:

[0028] S1. Mix mica powder, thermal conductive filler, and coupling agent uniformly, add 8-12% by weight of polyether polyol to disperse, heat to 60-80°C, stir at 60-80°C for 1-2 hours, and then dry to obtain a modified inorganic mixture;

[0029] S2. The remaining polyether polyol, fluorinated polyether polyol, and chain extender are stirred uniformly, and then the modified inorganic mixture is slowly added while being dispersed at high speed. After the mixture is dispersed and mixed uniformly, vacuum degassing is performed at 50-60°C to obtain component A.

[0030] S3. Add a catalyst and a tackifier to the isocyanate while stirring. After stirring evenly, component B is obtained.

[0031] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0032] 1. The present invention fluorinates polyether polyol to develop a fluorinated polyether polyol with good hydrophobicity and good chemical stability. A small amount of fluorinated polyether polyol is used to replace polyether polyol. The fluorinated polyether polyol has good hydrophobicity and chemical stability and can reduce the adsorption and penetration of water by polyurethane structural adhesive. At the same time, mica powder is added. The mica powder has an interlayer structure, which makes it resistant to water permeability and has a certain hydrophobicity. After modification with a coupling agent, its water permeability and hydrophobicity are significantly enhanced. The modified mica powder and fluorinated polyether polyol work synergistically, significantly enhancing the high temperature and high humidity resistance of the polyurethane structural adhesive, thereby significantly improving the stability of the polyurethane structural adhesive in high temperature and high humidity environments.

[0033] 2. The present invention adds mica powder, which has an interlayer structure. When combined with thermally conductive fillers, it can enhance the thermal conductivity of the polyurethane structural adhesive, reduce the amount of thermally conductive fillers used, and thus improve the processing performance, toughness and curing speed of the polyurethane structural adhesive.

[0034] 3. The present invention combines modified mica powder with fluorinated polyether polyol, which reduces the amount of fluorinated polyether polyol used, and can reduce the problems of poor toughness, poor adhesion, slow curing speed, reduced strength and high cost caused by excessive use of fluorinated polyether polyol.

[0035] 4. The present invention adds mica powder, which has good electrical insulation properties and further improves the electrical insulation properties of the polyurethane structural adhesive.

[0036] 5. The present invention adds mica powder. Both mica powder and fluorinated polyether polyol have good weather resistance, which significantly enhances the weather resistance of the polyurethane structural adhesive. BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION

[0037] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0038] Example 1

[0039] 1. Preparation of fluorinated polyether polyols

[0040] ① Weigh 1.5 g of potassium hydroxide, add 100 mL of anhydrous methanol, and stir to completely dissolve to obtain a KOH methanol solution with a concentration of 0.15 wt%.

[0041] ② Take 134g of trimethylolpropane (TMP) and put it into a dry 500mL stainless steel reactor with stirring and temperature control device, add KOH methanol solution, cover the reactor, pass nitrogen, evacuate (below -0.08MPa), heat to 50℃, maintain for 10 minutes to remove residual moisture in the liquid, stop evacuation, and continue to pass nitrogen protection.

[0042] ③. Start stirring, heat to 55°C, and slowly add 700g of propylene oxide into the reactor using a syringe pump. The addition time should be controlled within about 4 hours. During the addition process, maintain a slight positive pressure of nitrogen to prevent propylene oxide from being exposed to the air.

[0043] ④. Mix the remaining propylene oxide and 110g of 2,2,3,3-tetrafluoropropylene oxide and stir evenly to obtain a mixed solution. Maintain the temperature in the reactor at 50-60°C and a nitrogen atmosphere. Slowly add the mixed solution dropwise to the reactor over a period of about 2 hours. After the addition is complete, continue stirring and reacting for 2 hours.

[0044] ⑤. After the reaction stops, lower the temperature to 40°C. Add 100 mL of anhydrous methanol to the resulting mixture and stir evenly with a glass rod to neutralize excess KOH. After settling, filter using a Buchner funnel or filter paper to remove generated inorganic salts and impurities. Collect the filtrate.

[0045] ⑥ Transfer the filtrate to a vacuum distillation apparatus and distill under reduced pressure at 100°C to remove methanol and volatile solvents. After the solvent is completely removed, strip the solution under vacuum for 1–2 hours to obtain a slightly yellow, transparent, viscous product, which is the fluorinated polyether polyol.

[0046] 2. Preparation of component A:

[0047] ①, 15kg mica powder, 60kg alumina and 2kg tetraoctyloxybis (dilauryl phosphite) titanate (CAS No.: 68585-68-2) were mixed and stirred at 300rpm until uniformly mixed, 1.75kg polyoxypropylene glycol and 1.75kg polyoxypropylene triol were added, and stirring was continued at 300rpm until uniformly dispersed, heated to 70°C, stirred at 70°C for 1.5h, and then dried to obtain a modified inorganic mixture;

[0048] ②. Mix 15.75 kg of polyoxypropylene diol, 15.75 kg of polyoxypropylene triol, 4 kg of fluorinated polyether polyol and 3.5 kg of 1,4-butanediol, stir evenly, then slowly add the modified inorganic mixture while stirring and dispersing at a speed of 2000 rpm. After mixing evenly, vacuum degassing is performed at 55°C to obtain component A;

[0049] 3. Preparation of component B:

[0050] 0.5 kg of dibutyltin dilaurate and 1.5 kg of thermoplastic phenolic resin (Wuxi Akeli) were added to 40 kg of 4,4'-diphenylmethane diisocyanate while stirring at 1000 rpm. After stirring evenly, component B was obtained.

[0051] 4. Preparation of moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive:

[0052] Component A and component B are mixed in a volume ratio of 1:1 to obtain the moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive.

[0053] Example 2

[0054] The preparation method of the moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive of this embodiment is the same as that of Example 1, except that the formula ratio of this embodiment is different.

[0055] The moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive of this embodiment includes component A and component B. Component A includes: 3 kg of fluorinated polyether polyol, 22.5 kg of polyoxypropylene glycol, 22.5 kg of polyoxypropylene triol, 20 kg of mica powder, 80 kg of aluminum oxide, 5 kg of 1,4-butanediol, and 3 kg of tetraoctyloxybis(dilaurylphosphite) titanate; component B includes: 55 kg of 4,4'-diphenylmethane diisocyanate, 0.3 kg of dibutyltin dilaurate, and 2 kg of thermoplastic phenolic resin.

[0056] Example 3

[0057] The preparation method of the moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive of this embodiment is the same as that of Example 1, except that the formula ratio of this embodiment is different.

[0058] The moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive of this embodiment includes component A and component B. Component A includes: 5 kg of fluorinated polyether polyol, 12.5 kg of polyoxypropylene glycol, 12.5 kg of polyoxypropylene triol, 10 kg of mica powder, 40 kg of aluminum oxide, 2 kg of 1,4-butanediol, and 1 kg of tetraoctyloxybis(dilaurylphosphite) titanate; component B includes: 35 kg of 4,4'-diphenylmethane diisocyanate, 0.7 kg of dibutyltin dilaurate, and 1 kg of thermoplastic phenolic resin.

[0059] Comparative Example 1

[0060] The preparation method of the polyurethane structural adhesive in this comparative example is the same as that in Example 1, except that the formula ratio of this comparative example is different.

[0061] The moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive of this embodiment includes component A and component B. Component A includes: 4 kg of fluorinated polyether polyol, 12.5 kg of polyoxypropylene glycol, 12.5 kg of polyoxypropylene triol, 40 kg of aluminum oxide, 2 kg of 1,4-butanediol, and 1 kg of tetraoctyloxybis(dilaurylphosphite) titanate; component B includes: 35 kg of 4,4'-diphenylmethane diisocyanate, 0.7 kg of dibutyltin dilaurate, and 1 kg of thermoplastic phenolic resin.

[0062] Comparative Example 2

[0063] The preparation method of the polyurethane structural adhesive in this comparative example is the same as that in Example 1, except that the formula ratio of this comparative example is different.

[0064] The moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive of this embodiment includes component A and component B. Component A includes: 12.5 kg of polyoxypropylene glycol, 12.5 kg of polyoxypropylene triol, 15 kg of mica powder, 40 kg of aluminum oxide, 2 kg of 1,4-butanediol, and 1 kg of tetraoctyloxybis(dilaurylphosphite) titanate; component B includes: 35 kg of 4,4'-diphenylmethane diisocyanate, 0.7 kg of dibutyltin dilaurate, and 1 kg of thermoplastic phenolic resin.

[0065] Comparative Example 3

[0066] The preparation method of the polyurethane structural adhesive in this comparative example is the same as that in Example 1, except that the formula ratio of this comparative example is different.

[0067] The moisture-resistant, heat-resistant and high-temperature resistant polyurethane structural adhesive of this embodiment includes component A and component B. Component A includes: 12.5 kg of polyoxypropylene glycol, 12.5 kg of polyoxypropylene triol, 40 kg of aluminum oxide, 2 kg of 1,4-butanediol, and 1 kg of tetraoctyloxybis(dilaurylphosphite) titanate; component B includes: 35 kg of 4,4'-diphenylmethane diisocyanate, 0.7 kg of dibutyltin dilaurate, and 1 kg of thermoplastic phenolic resin.

[0068] The polyurethane structural adhesives prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests:

[0069] Thermal conductivity: Thermal conductivity was measured according to ASTM D5470.

[0070] High humidity and heat aging: Aging in a humidity and heat aging chamber at 85°C and 85% humidity for 1000 hours. Shear strength of the structural adhesive was tested before and after humidity and heat aging in accordance with GB / T 7124-2008.

[0071] Volume resistivity: refer to GB / T10064 standard to test volume resistivity.

[0072] The test results are shown in Table 1 below:

[0073]

[0074] As can be seen from Table 1, the present invention prepares a fluorinated polyether polyol by fluorinating the side chain of polyoxypropylene triol. A small amount of fluorinated polyether polyol is used instead of polyether polyol, and mica powder is added. The fluorinated polyether polyol resists high temperature and high humidity corrosion by improving the chemical stability and hydrophobicity of the molecule, and the mica powder blocks the penetration of external water vapor and oxygen through physical barrier effect. The two can synergistically significantly enhance the weather resistance of polyurethane structural adhesive in high temperature and high humidity environments, with complementary mechanisms and superimposed effects.

[0075] At the same time, the addition of mica powder can improve the thermal conductivity of polyurethane structural adhesive and reduce the amount of thermal conductive filler added.

Claims

1. A polyurethane structural adhesive that is resistant to moisture, heat and high temperature, characterized by: The invention comprises component A and component B. Component A comprises, by mass, 3-5 parts of fluorinated polyether polyol, 25-45 parts of polyether polyol, 10-20 parts of mica powder, 40-80 parts of thermal conductive filler, 2-5 parts of chain extender, and 1-3 parts of coupling agent; and component B comprises 35-55 parts of isocyanate, 0.3-0.7 parts of catalyst, and 1-2 parts of tackifier.

2. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, characterized in that: The functionality of the fluoropolyether polyol is 2-4 and the average molecular weight is 2000-4000.

3. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 2, characterized in that: The fluoropolyether polyol is a mixture of polyoxypropylene diol and polyoxypropylene triol, and the mass ratio of polyoxypropylene diol to polyoxypropylene triol is 2-3:2-3.

4. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, wherein the preparation method of the fluorinated polyether polyol is as follows: 4.

1. Dissolve potassium hydroxide in methanol to prepare a potassium hydroxide solution with a mass concentration of 0.1-0.2 wt%; 4.

2. Add trimethylolpropane to the reactor, followed by potassium hydroxide solution, seal the reactor, evacuate and remove residual water vapor, and then fill with nitrogen for protection; 4.

3. Heat to 50-60°C while stirring, then slowly add 75-85% by weight of propylene oxide dropwise for 4-6 hours; 4.

4. Evenly mix the remaining propylene oxide and 2,2,3,3-tetrafluoropropylene oxide to obtain a mixed solution. Slowly add the mixed solution dropwise to the reactor under nitrogen protection for 2-3 hours. After the addition is complete, continue stirring and reacting at 50-60°C for 2-4 hours; 4.

5. After the reaction is completed, cool to below 40°C, add methanol, stir to neutralize the potassium hydroxide, then let stand, filter, and obtain a filtrate; 4.

6. Distill the filtrate under reduced pressure at 90–100°C, then perform vacuum degassing for 1–2 hours. Cool naturally to room temperature to obtain a slightly yellowish, transparent, viscous liquid, which is the fluorinated polyether polyol. The molar ratio of trimethylolpropane, propylene oxide, 2,2,3,3-tetrafluoropropane oxide and sodium hydroxide is 1:12-18:0.8-1.5:0.017-0.

034.

5. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, characterized in that: The thermally conductive filler is selected from at least one of aluminum oxide, boron nitride, silicon oxide and magnesium hydroxide.

6. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, characterized in that: The chain extender is selected from at least one of 1,4-butanediol, ethylene glycol, glycerol, butanediol and 1,6-hexanediol.

7. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, characterized in that: The catalyst is at least one of dibutyltin dilaurate, stannous octoate, zinc octoate and bismuth tricyclohexanoate.

8. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, characterized in that: The isocyanate is selected from 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

9. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, characterized in that: The coupling agent is selected from at least one of γ-glycidyloxypropyltrimethoxysilane, tetraisopropyl titanate, tetrabutyl titanate, acetylacetonate and 3-aminopropyltriethoxysilane.

10. The moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, characterized in that: The tackifier is selected from at least one of phenolic resin, modified rosin resin, petroleum resin and polyamide resin.

11. A method for preparing the moisture-heat-resistant and high-temperature-resistant polyurethane structural adhesive according to claim 1, characterized in that The steps include: S1. Mix mica powder, thermal conductive filler, and coupling agent uniformly, add 8-12% by weight of polyether polyol to disperse, heat to 60-80°C, stir at 60-80°C for 1-2 hours, and then dry to obtain a modified inorganic mixture; S2. The remaining polyether polyol, fluorinated polyether polyol, and chain extender are stirred uniformly, and then the modified inorganic mixture is slowly added while being dispersed at high speed. After the mixture is dispersed and mixed uniformly, vacuum degassing is performed at 50-60°C to obtain component A. S3. Add a catalyst and a tackifier to the isocyanate while stirring. After stirring evenly, component B is obtained.

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