Polyurethane prepolymer as well as preparation method and application thereof

Abstract

The invention provides a polyurethane prepolymer as well as a preparation method and application thereof. The polyurethane prepolymer is prepared from the following raw materials in parts by weight: 10 to 80 parts of perfluorodiol and 20 to 90 parts of isocyanate. The content of NCO in the polyurethane prepolymer is 15 to 23 weight percent. The isocyanate comprises liquefied diphenylmethane diisocyanate and / or long-chain fatty acid modified diisocyanate. The polyurethane prepolymer has better temperature resistance and moisture resistance and longer skinning time, can be used as a curing agent of a polyurethane adhesive and can be better applied to assembly of a battery pack.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a polyurethane prepolymer used in new energy power batteries, and a preparation method and application thereof. Background Art

[0002] With the rapid advancement of new energy technologies, sales and demand for new energy vehicles are also rapidly increasing. Batteries, motors, and electronic controls are key components in determining the performance of new energy electric vehicles, with batteries being the core component. Due to the compact size of batteries, heat must be channeled into a cooling system. Furthermore, during the use of electric vehicles, they are inevitably subject to vibration, thermal shock, and other factors. Therefore, the power battery is the "heart" of new energy vehicles, and adhesives are the "muscle membrane" that enables this "heart" to maintain its enduring power.

[0003] Adhesives are widely used in the production of power batteries and their systems. Adhesives are primarily used in the assembly of prismatic cells in power batteries, playing a critical role in ensuring long-lasting, stable, efficient, and safe operation. During battery assembly, adhesives strengthen the connection between the cell and the pack casing, enhancing the structural strength and stability of the entire battery pack. Furthermore, the use of thermally conductive adhesives can dissipate heat generated by the cell during operation to external heat sink components, helping to maintain the battery pack's operating temperature within a suitable range. Furthermore, adhesives can provide additional protection, such as shockproofing, waterproofing, and flame retardancy, thereby enhancing the overall safety of power batteries. Compared to traditional mechanical fastening methods, such as bolting, adhesives simplify production lines, improve efficiency, and enable lighter battery pack designs, contributing to improved energy efficiency and range for electric vehicles.

[0004] Currently, two-component polyurethane adhesives are widely used in power battery assembly. These adhesives can consist of a polyurethane curing agent and a polyol compound. They offer excellent properties such as adjustable working time, high bond strength, and excellent bond quality. However, as technological requirements for new energy batteries continue to increase, the industry is also placing higher demands on polyurethane adhesives. Because temperature and humidity resistance are crucial to battery life, polyurethane curing agents must meet temperature and humidity resistance tests exceeding 2000 hours. However, most current polyurethane curing agents fail to meet the long-term temperature and humidity resistance requirements for high safety and stability required by new energy batteries. Furthermore, pack assembly not only requires connecting numerous cells or battery packs in series and parallel but also requires the installation of a battery management system (BMS), thermal management system, and housing. Polyurethane adhesives are required for numerous bonding processes. Pack assembly requires exposure to humidity for a certain period of time, and current polyurethane curing agents are prone to rapid skinning when exposed to air during pack assembly, making them extremely unsuitable for use in the new energy power battery industry. Summary of the Invention

[0005] Based on the above problems, the purpose of the present invention is to provide a polyurethane prepolymer and its preparation method and application, which has better temperature and moisture resistance and longer skinning time, can be used as a curing agent for polyurethane adhesives and can be better used in pack assembly.

[0006] To achieve the above objectives, the present invention provides, in a first aspect, a polyurethane prepolymer comprising, by weight, 10 to 80 parts perfluorodiol and 20 to 90 parts isocyanate, wherein the polyurethane prepolymer has an NCO content of 15 to 23 wt.%, and the isocyanate comprises liquefied diphenylmethane diisocyanate and / or a long-chain fatty acid-modified diisocyanate.

[0007] The present invention uses perfluorodiol to synthesize a polyurethane prepolymer. The fluorine atoms in the perfluorodiol have extremely strong electronegativity and can form strong C-F bonds. Therefore, the perfluorodiol exhibits extremely high hydrophobicity and oleophobicity. In addition, the melting point and boiling point of the perfluorodiol are relatively high, and it can remain stable even in high-temperature environments. The prepared polyurethane prepolymer does not undergo chemical changes during the assembly of the pack and the use of new energy vehicles, even in high-temperature and high-humidity hot and humid environments. Its excellent heat and humidity resistance meets the application requirements of the new energy power battery field. The isocyanate includes liquefied diphenylmethane diisocyanate and / or long-chain fatty acid modified diisocyanate. The selected isocyanate has low activity in the reaction with water vapor, and the synthesized polyurethane prepolymer has low water vapor activity under standard conditions. In addition, the NCO content in the polyurethane prepolymer obtained by controlling the reaction of the perfluorodiol and the specific isocyanate is 15-23wt.%. The high NCO content has low water vapor sensitivity, so the polyurethane prepolymer is used as an adhesive curing agent and also has long moisture sensitivity. Therefore, during the pack assembly process, it can avoid being exposed to the air and causing skinning faster.

[0008] As a technical solution of the present invention, the liquefied diphenylmethane diisocyanate is carbodiimide-modified 4,4′-MDI.

[0009] As a technical solution of the present invention, the long-chain fatty acid-modified diisocyanate is a reaction product of a long-chain fatty acid and a diisocyanate.

[0010] As a technical solution of the present invention, the long-chain fatty acid includes palmitic acid or stearic acid.

[0011] As a technical solution of the present invention, the diisocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate and diphenylmethane diisocyanate.

[0012] As a technical solution of the present invention, the molecular weight of the perfluorodiol is 100-10000.

[0013] As a technical solution of the present invention, the perfluorodiol includes at least one of perfluoro-1,9-nonanediol, perfluoro-1,12-dodecanediol and perfluoro-1,10-decanediol.

[0014] A second aspect of the present invention provides a method for preparing a polyurethane prepolymer, comprising the steps of: removing water from a perfluorodiol in an oil bath, and then reacting the perfluorodiol with an isocyanate under vacuum and stirring. This preparation method is simple, incorporates perfluoro groups into the prepolymer, and the fluoro groups exhibit extremely excellent moisture and heat resistance, resulting in the synthesized prepolymer also exhibiting excellent moisture and heat resistance.

[0015] As a technical solution of the present invention, the reaction temperature is 60-80° C., the reaction time is 1-4 hours, and the stirring speed is 2000-4000 r / min.

[0016] A third aspect of the present invention provides the use of the aforementioned polyurethane prepolymer, or the polyurethane prepolymer prepared by the aforementioned method for preparing the polyurethane prepolymer, as a two-component polyurethane adhesive for power batteries. DETAILED DESCRIPTION

[0017] The polyurethane prepolymer of this invention, as a curing agent for polyurethane adhesives, exhibits excellent temperature and humidity resistance and a long skinning time. It can be used as an adhesive component in power batteries and systems, such as for bonding adjacent cells, bonding cells to battery casings, and as a thermally conductive coating for heat transfer. The polyurethane prepolymer can be cured with a polyol compound at room temperature to form a polyurethane adhesive, although curing can be accelerated by heating. The polyol compound can be castor oil, polyester polyol, or the like.

[0018] The polyurethane prepolymer of the present invention has low water vapor activity under standard conditions. The NCO content in the polyurethane prepolymer is 15-23 wt.%. For example, the NCO content can be, but is not limited to, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, 20 wt.%, 21 wt.%, 22 wt.%, or 23 wt.%. A high NCO content results in low water vapor sensitivity, resulting in a skinning time of ≥12 hours for the prepolymer under standard conditions. A standard environment refers to a temperature of 23°C ±2°C and a humidity of 50% ±5°C. A skinning time of ≥12 hours indicates that skinning will occur after more than 12 hours under standard conditions. Furthermore, the skinning time under standard conditions can be, but is not limited to, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, or 20 hours.

[0019] In parts by weight, the raw materials for preparing the polyurethane prepolymer include 10 to 80 parts of perfluorodiol and 20 to 90 parts of isocyanate. As an example, the weight proportion of perfluorodiol can be, but is not limited to, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, and 80 parts. The weight proportion of isocyanate can be, but is not limited to, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, and 90 parts.

[0020] The molecular weight of the perfluorodiol is 100 to 10,000. For example, the molecular weight of the perfluorodiol may be, but is not limited to, 100, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, or 10,000. The perfluorodiol includes at least one of perfluoro-1,9-nonanediol, perfluoro-1,12-dodecanediol, and perfluoro-1,10-decanediol.

[0021] The isocyanate includes liquefied diphenylmethane diisocyanate and / or a long-chain fatty acid-modified diisocyanate. The liquefied diphenylmethane diisocyanate is carbodiimide-modified 4,4′-MDI. The long-chain fatty acid-modified diisocyanate is the reaction product of a long-chain fatty acid and a diisocyanate. The long-chain fatty acid includes palmitic acid or stearic acid. The diisocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate.

[0022] The method for preparing a polyurethane prepolymer of the present invention comprises the steps of: removing water from a perfluorodiol in an oil bath, and then reacting the perfluorodiol with an isocyanate under vacuum and stirring. Removing water in an oil bath prevents the synthesized polyurethane prepolymer from containing moisture, which could lead to quality degradation or unstable performance. The oil bath temperature can be between 100°C and 120°C, and by way of example, can be, but is not limited to, 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C, 118°C, or 120°C. The reaction temperature is between 60°C and 80°C, and by way of example, can be, but is not limited to, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, or 80°C. The reaction time is between 1 and 4 hours, and by way of example, can be, but is not limited to, 1 hour, 2 hours, 3 hours, or 4 hours. The stirring speed is 2000~4000r / min. As an example, the speed can be but not limited to 2000r / min, 2200r / min, 2400r / min, 2600r / min, 2800r / min, 3000r / min, 3200r / min, 3400r / min, 3600r / min, 3800r / min, and 4000r / min.

[0023] In order to better illustrate the purpose, technical solutions and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0024] Example 1 The raw materials (by weight) for preparing the polyurethane prepolymer in this example include 30 parts perfluoro-1,9-nonanediol (molecular weight 412.1) and 136.6 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 110°C to remove water for 2 hours, then cooled to 70°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3000 rpm for 3 hours until the NCO content reaches 20 wt.%. The mixture is then cooled to 35°C and removed from the reactor.

[0025] Example 2 The raw materials (by weight) for preparing the polyurethane prepolymer in this example include 30 parts perfluoro-1,9-nonanediol (molecular weight 412.1) and 92.5 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 110°C to remove water for 2 hours, then cooled to 70°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3000 rpm for 3 hours until the NCO content reaches 17 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0026] Example 3 The raw materials (by weight) for preparing the polyurethane prepolymer in this example include 30 parts perfluoro-1,9-nonanediol (molecular weight 412.1) and 77.1 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 110°C to remove water for 2 hours, then cooled to 70°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3000 rpm for 3 hours until the NCO content reaches 15 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0027] Example 4 The raw materials (by weight) for preparing the polyurethane prepolymer in this example include 30 parts perfluoro-1,10-decanediol (molecular weight 462.1) and 205 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 120°C to remove water for 3 hours, then cooled to 80°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3500 rpm for 2 hours until the NCO content reaches 23 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0028] Example 5 The raw materials (by weight) for preparing the polyurethane prepolymer in this example include 30 parts perfluoro-1,10-decanediol (molecular weight 462.1) and 111 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 120°C to remove water for 3 hours, then cooled to 80°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3500 rpm for 2 hours until the NCO content reaches 19 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0029] Example 6 The raw materials (by weight) for preparing the polyurethane prepolymer in this example include 30 parts perfluoro-1,10-decanediol (molecular weight 462.1) and 66 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 120°C to remove water for 3 hours, then cooled to 80°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3500 rpm for 2 hours until the NCO content reaches 15 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0030] Example 7 The raw materials (by weight) for preparing the polyurethane prepolymer in this example include 30 parts perfluoro-1,9-nonanediol (molecular weight 412.1) and 148.2 parts long-chain fatty acid isocyanate (NCO content: 22%), which is the reaction product of palmitic acid and isophorone diisocyanate. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 110°C to remove water for 2 hours, then cooled to 70°C, and dimer acid diisocyanate is added. The mixture is reacted at a speed of 3000 rpm for 3 hours until the NCO content reaches 15 wt.%, then cooled to 35°C and removed from the kettle.

[0031] Comparative Example 1 The raw materials (by weight) for preparing the polyurethane prepolymer in this comparative example include 30 parts perfluoro-1,9-nonanediol (molecular weight 412.1) and 84.85 parts 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 110°C for 2 hours to remove water, then cooled to 70°C, 4,4'-MDI is added, and the mixture is reacted at 3000 rpm for 3 hours until the NCO content reaches 20 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0032] Comparative Example 2 The raw materials (by weight) for preparing the polyurethane prepolymer in this comparative example include 30 parts perfluoro-1,9-nonanediol (molecular weight 412.1) and 70.5 parts 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 110°C for 2 hours to remove water, then cooled to 70°C, 4,4'-MDI is added, and the mixture is reacted at 3000 rpm for 3 hours until the NCO content reaches 18 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0033] Comparative Example 3 The raw materials (by weight) for preparing the polyurethane prepolymer in this comparative example include 30 parts perfluoro-1,9-nonanediol (molecular weight 412.1) and 54.6 parts 4,4'-MDI. The preparation method is as follows: perfluoro-1,9-nonanediol is heated under vacuum at 110°C for 2 hours to remove water, then cooled to 70°C, 4,4'-MDI is added, and the mixture is reacted at 3000 rpm for 3 hours until the NCO content reaches 15 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0034] Comparative Example 4 The raw materials (by weight) for preparing the polyurethane prepolymer in this comparative example include 30 parts polyester diol (molecular weight 400) and 136 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: the polyester diol is heated under vacuum at 120°C to remove water for 3 hours, then cooled to 80°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3500 rpm for 2 hours until the NCO content reaches 20 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0035] Comparative Example 5 The raw materials (by weight) for preparing the polyurethane prepolymer in this comparative example include 50 parts polyester diol (molecular weight 400) and 117 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: the polyester diol is heated under vacuum at 120°C to remove water for 3 hours, then cooled to 80°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3500 rpm for 2 hours until the NCO content reaches 18 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0036] Comparative Example 6 The raw materials (by weight) for preparing the polyurethane prepolymer in this comparative example include 30 parts polyester diol (molecular weight 400) and 77.1 parts carbodiimide-modified 4,4'-MDI. The preparation method is as follows: the polyester diol is heated under vacuum at 120°C to remove water for 3 hours, then cooled to 80°C, carbodiimide-modified 4,4'-MDI is added, and the mixture is reacted at 3500 rpm for 2 hours until the NCO content reaches 15 wt.%. The mixture is then cooled to 35°C and removed from the kettle.

[0037] The polyurethane prepolymers prepared in Examples 1-7 and Comparative Examples 1-6 were reacted with modified castor oil A3941 (Shanghai Jingri) at a ratio of n(NCO):n(OH)=1:1 to prepare polyurethanes 1-13. The properties of polyurethanes 1-13 were tested, and the results are shown in Table 1.

[0038] Moisture sensitivity test: The skinning time of the prepolymer is measured in accordance with GB / T13477.5-2002 Test methods for building sealing materials Part 5: Test of surface drying time.

[0039] Double 85 shear strength test after aging: The polyurethane prepolymer and castor oil components were mixed evenly in proportion, and two pieces of 3003 aluminum materials without primer coating and surface treatment were bonded to each other to prepare shear test pieces. The shear test pieces were cured for 7 days in an environment of temperature (23±2)℃ and relative humidity (50±5)%RH, and then placed in a test chamber with temperature of 85℃ and relative humidity of 85%RH for a certain period of time. The shear strength was tested after being taken out and placed at room temperature for 24 hours, and the shear strength change rate before and after aging was calculated.

[0040] Table 1 Performance test results

[0041] The results in Table 1 show that polyurethane prepolymers prepared using perfluorodiols and specific isocyanates exhibit excellent temperature and humidity resistance and a prolonged skinning time. Furthermore, a performance comparison of polyurethanes 1 and 7 shows that the skinning time is longer when the perfluorodiol is perfluoro-1,9-nonanediol and the isocyanate is dimer acid diisocyanate. This is due to the lower reactivity of dimer acid diisocyanate to moisture. A comparison of polyurethanes 4-6 and 11-13 shows that perfluoroalcohols exhibit excellent moisture and temperature resistance and weathering resistance. This is because the fluorine atoms in perfluorodiols have extremely strong electronegativity, forming strong C-F bonds, resulting in extremely high hydrophobicity and oleophobicity. Furthermore, perfluoroalcohols can form a synergistic effect with specific isocyanates, resulting in a longer skinning time for the resulting prepolymers. Polyurethanes 1-13 show that, under the same conditions, a higher NCO content is associated with a longer skinning time.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polyurethane prepolymer, characterized in that: In parts by weight, the preparation raw materials include 10 to 80 parts of perfluorodiol and 20 to 90 parts of isocyanate, the NCO content in the polyurethane prepolymer is 15 to 23 wt.%, and the isocyanate includes liquefied diphenylmethane diisocyanate and / or long-chain fatty acid modified diisocyanate.

2. The polyurethane prepolymer according to claim 1, characterized in that The liquefied diphenylmethane diisocyanate is carbodiimide-modified 4,4′-MDI.

3. The polyurethane prepolymer according to claim 1, characterized in that The long-chain fatty acid-modified diisocyanate is a reaction product of a long-chain fatty acid and a diisocyanate.

4. The polyurethane prepolymer according to claim 3, characterized in that The long chain fatty acids include palmitic acid or stearic acid.

5. The polyurethane prepolymer according to claim 3, characterized in that The diisocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate and diphenylmethane diisocyanate.

6. The polyurethane prepolymer according to claim 1, characterized in that The molecular weight of the perfluorodiol is 100-10000.

7. The polyurethane prepolymer according to claim 1, characterized in that The perfluorodiol includes at least one of perfluoro-1,9-nonanediol, perfluoro-1,12-dodecanediol and perfluoro-1,10-decanediol.

8. The method for preparing a polyurethane prepolymer according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: after removing water from the perfluorodiol in an oil bath, reacting the perfluorodiol with the isocyanate under vacuum and stirring conditions.

9. The method for preparing a polyurethane prepolymer according to claim 8, characterized in that: The reaction temperature is 60-80° C., the reaction time is 1-4 hours, and the stirring speed is 2000-4000 r / min.

10. Use of the polyurethane prepolymer according to any one of claims 1 to 7, or the polyurethane prepolymer prepared by the method for preparing a polyurethane prepolymer according to any one of claims 8 to 9 as a curing agent for a two-component polyurethane adhesive for power batteries.

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