High-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries and preparation method

Abstract

The invention relates to the technical field of polyurethane structural adhesives and discloses a high-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries and a preparation method thereof. The polyurethane structural adhesive comprises, in parts by weight, 100 parts by weight of castor oil, 10-30 parts by weight of polyether polyol, 10-30 parts by weight of polyester polyol, 10-20 parts by weight of plasticizer, 2-4 parts by weight of chain extender, 1-3 parts by weight of dibutyltin dilaurate, 10-30 parts by weight of phosphorus-modified magnesium hydroxide, and 15-30 parts by weight of phosphorus-containing diisocyanate. The polyurethane structural adhesive is prepared by utilizing the phosphorus-containing diisocyanate twice. Experimental verification shows that the polyurethane structural adhesive has high strength and excellent flame-retardant properties, and has very important application value in the field of new energy lithium batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane structural adhesives, in particular to a high-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries and a preparation method thereof. Background Art

[0002] Due to the rapid development of new energy vehicles, new energy lithium batteries are one of the most critical components of new energy vehicles. As a power source, they directly affect the performance of new energy vehicles such as cruising range, safety, and service life. Structural adhesives are an indispensable part of lithium batteries. At present, lithium batteries may burn or even explode under abuse, which affects people's life and property safety to a certain extent. Structural adhesives can provide safety and reliability to a certain extent. Therefore, improving the flame retardant properties of structural adhesives for lithium batteries is a hot topic of current research.

[0003] 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) has an active hydrogen on the phosphorus in its molecular structure, allowing it to undergo addition reactions with unsaturated compounds to form a series of derivatives. Introducing the phosphaphenanthrene structure into these compounds results in excellent flame retardancy. This invention utilizes DOPO and magnesium hydroxide as raw materials to produce a high-strength, flame-retardant polyurethane structural adhesive. This adhesive addresses the poor flame retardancy and strength characteristics of current polyurethane structural adhesives for lithium batteries, and has significant application value in the field of new energy lithium batteries. Summary of the Invention

[0004] The purpose of the present invention is to overcome one or more deficiencies in the prior art and provide a high-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries. The polyurethane structural adhesive prepared by this method has been verified to have excellent flame retardant properties and mechanical properties through experiments.

[0005] In order to achieve the above object, a technical solution adopted by the present invention is:

[0006] A high-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries, the polyurethane structural adhesive being composed of the following raw materials in parts by weight: 100 parts by weight of castor oil, 10-30 parts of polyether polyol, 10-30 parts of polyester polyol, 10-20 parts of plasticizer, 2-4 parts of chain extender, 1-3 parts of dibutyltin dilaurate, 10-30 parts of phosphorus-modified magnesium hydroxide, and 10-30 parts of phosphorus-containing diisocyanate;

[0007] The preparation method of the polyurethane structural adhesive is as follows:

[0008] S1. Under a nitrogen atmosphere, add dried ultrafine magnesium hydroxide and phosphorus-containing diisocyanate to a toluene solvent, perform ultrasonic dispersion, heat to 80-90°C, stir and react for 6-10 hours. After the reaction is completed, cool to room temperature, wash with toluene, and dry to obtain phosphorus-containing modified magnesium hydroxide;

[0009] S2. Add castor oil, polyether polyol, polyester polyol and plasticizer into a planetary mixer, dehydrate at 120°C for 3 hours, cool to 50°C, add chain extender, dibutyltin dilaurate and phosphorus-modified magnesium hydroxide, mix evenly, heat to 70-80°C, react for 2-4 hours, and finally add phosphorus-containing diisocyanate, stir and mix evenly to obtain a high-strength flame-retardant polyurethane structural adhesive.

[0010] Preferably, in S1, the mass amount of phosphorus-containing diisocyanate is 1.5-3 times the mass amount of ultrafine magnesium hydroxide.

[0011] Preferably, the preparation method of the phosphorus-containing diisocyanate is:

[0012] (1) Add iminodipropionic acid and 4-dimethylaminopyridine to chloroform solvent, stir and mix evenly, then add diphenylphosphinyl chloride, add triethylamine under nitrogen protection, stir and disperse, heat to 70-80°C, react for 20-35h, and after the reaction is completed, wash with deionized water, dry, filter, and rotary evaporate to obtain intermediate 1;

[0013] (2) Under nitrogen protection, add intermediate product 1, epoxybutene, and tetrabutylammonium bromide to N,N-dimethylformamide solvent, stir and mix evenly, heat to 80-90°C, react for 24-30 hours, and after the reaction is completed, distill under reduced pressure, wash with deionized water, and dry to obtain intermediate product 2;

[0014] (3) Add DOPO to toluene solvent, stir to dissolve, then add intermediate product 2, heat to 100-120°C, react for 6-10 hours, cool to room temperature after the reaction, filter, wash with deionized water, and dry to obtain intermediate product 3;

[0015] (4) Add the intermediate product 3 and isophorone diisocyanate to N,N-dimethylformamide solvent, stir and mix evenly, heat to 60-75°C, add dibutyltin dilaurate, react for 3-6 hours, and after the reaction is completed, distill under reduced pressure, wash with deionized water, and dry to obtain phosphorus-containing diisocyanate.

[0016] More preferably, in (1), the molar ratio of iminodipropionic acid to diphenylphosphinyl chloride is 1:1-1.2.

[0017] Further preferably, in (2), the molar ratio of the intermediate product 1 to epoxybutene is 1:2-2.4.

[0018] Further preferably, in (3), the molar ratio of DOPO to intermediate 2 is 2-2.5:1.

[0019] Further preferably, in said (4), the molar ratio of the intermediate product 3 to isophorone diisocyanate is 1:2.2-2.5.

[0020] The reaction mechanism of the present invention is as follows: the present invention utilizes iminodipropionic acid and diphenylphosphinoyl chloride to undergo a substitution reaction under the catalysis of 4-dimethylaminopyridine to obtain an intermediate product 1, utilizes the carboxyl structure contained therein to undergo a ring-opening reaction with epoxybutene to obtain an intermediate product 2, and then undergoes an addition reaction with DOPO to obtain an intermediate product 3, which reacts with isophorone diisocyanate under the initiation catalysis of dibutyltin dilaurate to obtain a phosphorus-containing diisocyanate, and finally, the intermediate product is mixed with castor oil, polyether polyol, polyester polyol, plasticizer, etc. to react to obtain a high-strength flame-retardant polyurethane structural adhesive.

[0021] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0022] 1. magnesium hydroxide is an inorganic material with a large amount of hydroxyl groups on its surface. It is therefore very easy to agglomerate and difficult to disperse in an organic matrix. The present invention reacts it with phosphorus-containing diisocyanates, and the hydroxyl groups on the surface of magnesium hydroxide react with the -NCO groups in the phosphorus-containing diisocyanates to form carbamates, which are organicized to increase their compatibility with organic substances and are evenly dispersed in organic matrices. The carbamates formed are hydrogen bonded with strong polar groups such as carbamate groups, isocyanate groups, and ester groups to produce more cross-linking sites. When subjected to external force, magnesium hydroxide can not only act as a stress concentration point to absorb more external force, but also the cross-linked network structure thus formed can absorb and disperse more external force, further improving the mechanical properties of the structural adhesive. In addition, since the structure prepared by the present invention contains more polar groups, it can produce stronger chemical links such as hydrogen bonds with the surface of the coated substrate, thereby improving the peel strength of the structural adhesive.

[0023] 2. Magnesium hydroxide is an excellent inorganic flame retardant. It can decompose and dehydrate at high temperatures, and reduce the temperature of the matrix material by absorbing heat through decomposition. In addition, the water vapor produced by high-temperature decomposition can form a water vapor film on the surface of the matrix material to isolate external oxygen. In addition, a layer of non-flammable oxides will be formed and attached to the surface of the matrix material. Introducing it into the structural adhesive can effectively improve the flame retardant properties of the structural adhesive. The structural adhesive prepared by the present invention also has a large number of phosphorus-containing structures, which can produce strong acidic substances by thermal decomposition, have a strong dehydration effect, promote the carbonization of the material, and form a dense carbon layer on the surface of the matrix material, which hinders the transport of materials and the transfer of energy. It forms an organic-inorganic flame retardant structure with magnesium hydroxide, and the two synergistically flame retardant, jointly improving the flame retardant properties of the material. The structural adhesive prepared by the present invention has been confirmed to have excellent flame retardant effect, mechanical properties and peel strength through experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the reaction route of phosphorus-containing diisocyanates. DETAILED DESCRIPTION

[0025] The following is a further detailed description of the high-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries and its preparation method in conjunction with specific examples. These examples are only for comparison and explanation purposes, and the present invention is not limited to these examples.

[0026] Example 1: (1) Add 0.1 mol of iminodipropionic acid and 1 mmol of 4-dimethylaminopyridine to chloroform solvent, stir and mix evenly, then add 0.12 mol of diphenylphosphinoyl chloride, add 0.01 mol of triethylamine under nitrogen protection, stir and disperse, heat to 75°C, react for 35 hours, and after the reaction is completed, wash with deionized water, dry, filter, and rotary evaporate to obtain intermediate 1.

[0027] (2) Under nitrogen protection, 80 mmol of intermediate product 1, 170 mmol of epoxybutene, and 1.2 mmol of tetrabutylammonium bromide were added to N,N-dimethylformamide solvent, stirred and mixed evenly, heated to 85 °C, and reacted for 30 h. After the reaction was completed, vacuum distillation was performed, the mixture was washed with deionized water, and dried to obtain intermediate product 2.

[0028] (3) Add 70 mmol of DOPO to toluene solvent, stir and dissolve, then add 30 mmol of intermediate product 2, heat to 110 °C, react for 8 h, and after the reaction is completed, cool to room temperature, filter, wash with deionized water, and dry to obtain intermediate product 3.

[0029] (4) 80 mmol of the intermediate product 3 and 200 mmol of isophorone diisocyanate were added to N,N-dimethylformamide solvent, stirred and mixed evenly, and heated to 65 °C. 0.8 mmol of dibutyltin dilaurate was added thereto and reacted for 3 h. After the reaction was completed, the mixture was evaporated under reduced pressure, washed with deionized water, and dried to obtain phosphorus-containing diisocyanate.

[0030] (5) Under nitrogen atmosphere, 4 g of dried ultrafine magnesium hydroxide and 6 g of phosphorus-containing diisocyanate were added to toluene solvent, ultrasonically dispersed, heated to 85 °C, and stirred for 10 h. After the reaction, cooled to room temperature, washed with toluene, and dried to obtain phosphorus-containing modified magnesium hydroxide.

[0031] (6) Add 50g of castor oil, 5g of polyether polyol (PPG400), 10g of polyester polyol (PBA-3000), and 8g of plasticizer DIDP into a planetary mixer, dehydrate at 120℃ for 3h, cool to 50℃, add 1g of chain extender BDO, 1.5g of dibutyltin dilaurate, and 5g of phosphorus-modified magnesium hydroxide, mix well, heat to 75℃, react for 4h, and finally add 10g of phosphorus-containing diisocyanate and stir to mix well to obtain a high-strength flame-retardant polyurethane structural adhesive.

[0032] Example 2: (1) Add 0.1 mol of iminodipropionic acid and 1.2 mmol of 4-dimethylaminopyridine to chloroform solvent, stir and mix evenly, then add 0.12 mol of diphenylphosphinoyl chloride, add 0.08 mol of triethylamine under nitrogen protection, stir and disperse, heat to 70°C, react for 35 hours, and after the reaction is completed, wash with deionized water, dry, filter, and evaporate to obtain intermediate 1.

[0033] (2) Under nitrogen protection, 80 mmol of intermediate product 1, 192 mmol of epoxybutene, and 1 mmol of tetrabutylammonium bromide were added to N,N-dimethylformamide solvent, stirred and mixed evenly, heated to 85 °C, and reacted for 25 h. After the reaction was completed, vacuum distillation was performed, the mixture was washed with deionized water, and dried to obtain intermediate product 2.

[0034] (3) Add 75 mmol of DOPO to toluene solvent, stir and dissolve, then add 30 mmol of intermediate product 2, heat to 115 °C, react for 10 h, and after the reaction is completed, cool to room temperature, filter, wash with deionized water, and dry to obtain intermediate product 3.

[0035] (4) 80 mmol of the intermediate product 3 and 180 mmol of isophorone diisocyanate were added to N,N-dimethylformamide solvent, stirred and mixed evenly, and heated to 75 °C. 0.5 mmol of dibutyltin dilaurate was added thereto and reacted for 6 h. After the reaction was completed, the mixture was evaporated under reduced pressure, washed with deionized water, and dried to obtain phosphorus-containing diisocyanate.

[0036] (5) Under nitrogen atmosphere, 4 g of dried ultrafine magnesium hydroxide and 8 g of phosphorus-containing diisocyanate were added to toluene solvent, ultrasonically dispersed, heated to 85 °C, and stirred for 10 h. After the reaction, the mixture was cooled to room temperature, washed with toluene, and dried to obtain phosphorus-modified magnesium hydroxide.

[0037] (6) Add 50g of castor oil, 10g of polyether polyol (PPG400), 15g of polyester polyol (PBA-3000), and 10g of plasticizer DIDP into a planetary mixer, dehydrate at 120℃ for 3h, cool to 50℃, add 2g of chain extender BDO, 1g of dibutyltin dilaurate, and 8g of phosphorus-modified magnesium hydroxide, mix well, heat to 80℃, react for 2h, and finally add 12g of phosphorus-containing diisocyanate and stir to mix well to obtain a high-strength flame-retardant polyurethane structural adhesive.

[0038] Example 3: (1) Add 0.1 mol of iminodipropionic acid and 1.5 mmol of 4-dimethylaminopyridine to chloroform solvent, stir and mix evenly, then add 0.1 mol of diphenylphosphinoyl chloride, add 0.012 mol of triethylamine under nitrogen protection, stir and disperse, heat to 80°C, react for 20 hours, and after the reaction is completed, wash with deionized water, dry, filter, and rotary evaporate to obtain intermediate product 1.

[0039] (2) Under nitrogen protection, 80 mmol of intermediate product 1, 160 mmol of epoxybutene, and 1.4 mmol of tetrabutylammonium bromide were added to N,N-dimethylformamide solvent, stirred and mixed evenly, heated to 85 °C, and reacted for 30 h. After the reaction was completed, vacuum distillation was performed, the mixture was washed with deionized water, and dried to obtain intermediate product 2.

[0040] (3) Add 75 mmol of DOPO to toluene solvent, stir and dissolve, then add 30 mmol of intermediate product 2, heat to 120 °C, react for 6 h, and after the reaction is completed, cool to room temperature, filter, wash with deionized water, and dry to obtain intermediate product 3.

[0041] (4) 80 mmol of the intermediate product 3 and 176 mmol of isophorone diisocyanate were added to N,N-dimethylformamide solvent, stirred and mixed evenly, and heated to 60 °C. 0.6 mmol of dibutyltin dilaurate was added thereto and reacted for 4 h. After the reaction was completed, the mixture was evaporated under reduced pressure, washed with deionized water, and dried to obtain phosphorus-containing diisocyanate.

[0042] (5) Under nitrogen atmosphere, 4 g of dried ultrafine magnesium hydroxide and 10 g of phosphorus-containing diisocyanate were added to toluene solvent, ultrasonically dispersed, heated to 90 °C, and stirred for 6 h. After the reaction, cooled to room temperature, washed with toluene, and dried to obtain phosphorus-modified magnesium hydroxide.

[0043] (6) Add 50g of castor oil, 8g of polyether polyol (PPG400), 12g of polyester polyol (PBA-3000), and 10g of plasticizer DIDP into a planetary mixer, dehydrate at 120℃ for 3h, cool to 50℃, add 1.5g of chain extender BDO, 0.5g of dibutyltin dilaurate, and 5g of phosphorus-modified magnesium hydroxide, mix well, heat to 70℃, react for 3h, and finally add 15g of phosphorus-containing diisocyanate and stir to mix well to obtain a high-strength flame-retardant polyurethane structural adhesive.

[0044] Example 4: (1) Add 0.1 mol of iminodipropionic acid and 1.2 mmol of 4-dimethylaminopyridine to chloroform solvent, stir and mix evenly, then add 0.12 mol of diphenylphosphinoyl chloride, add 0.01 mol of triethylamine under nitrogen protection, stir and disperse, heat to 80°C, react for 24 hours, and after the reaction is completed, wash with deionized water, dry, filter, and evaporate to obtain intermediate 1.

[0045] (2) Under nitrogen protection, 80 mmol of intermediate product 1, 180 mmol of epoxybutene, and 1 mmol of tetrabutylammonium bromide were added to N,N-dimethylformamide solvent, stirred and mixed evenly, heated to 80 °C, and reacted for 26 h. After the reaction was completed, vacuum distillation was performed, the mixture was washed with deionized water, and dried to obtain intermediate product 2.

[0046] (3) Add 70 mmol of DOPO to toluene solvent, stir and dissolve, then add 30 mmol of intermediate product 2, heat to 100 °C, react for 10 h, and after the reaction is completed, cool to room temperature, filter, wash with deionized water, and dry to obtain intermediate product 3.

[0047] (4) 80 mmol of the intermediate product 3 and 180 mmol of isophorone diisocyanate were added to N,N-dimethylformamide solvent, stirred and mixed evenly, and heated to 65 °C. 0.6 mmol of dibutyltin dilaurate was added thereto and reacted for 5 h. After the reaction was completed, the mixture was evaporated under reduced pressure, washed with deionized water, and dried to obtain phosphorus-containing diisocyanate.

[0048] (5) Under nitrogen atmosphere, 4 g of dried ultrafine magnesium hydroxide and 12 g of phosphorus-containing diisocyanate were added to toluene solvent, ultrasonically dispersed, heated to 85 °C, and stirred for 8 h. After the reaction, cooled to room temperature, washed with toluene, and dried to obtain phosphorus-modified magnesium hydroxide.

[0049] (6) Add 50g of castor oil, 15g of polyether polyol (PPG400), 5g of polyester polyol (PBA-3000), and 5g of plasticizer DIDP into a planetary mixer, dehydrate at 120℃ for 3h, cool to 50℃, add 1g of chain extender BDO, 0.5g of dibutyltin dilaurate, and 15g of phosphorus-modified magnesium hydroxide, mix well, heat to 75℃, react for 4h, and finally add 10g of phosphorus-containing diisocyanate and stir to mix well to obtain a high-strength flame-retardant polyurethane structural adhesive.

[0050] Example 5: (1) Add 0.1 mol of iminodipropionic acid and 1.5 mmol of 4-dimethylaminopyridine to chloroform solvent, stir and mix evenly, then add 0.12 mol of diphenylphosphinoyl chloride, add 0.08 mol of triethylamine under nitrogen protection, stir and disperse, heat to 80°C, react for 28 hours, and after the reaction is completed, wash with deionized water, dry, filter, and evaporate to obtain intermediate 1.

[0051] (2) Under nitrogen protection, 80 mmol of intermediate product 1, 192 mmol of epoxybutene, and 0.8 mmol of tetrabutylammonium bromide were added to N,N-dimethylformamide solvent, stirred and mixed evenly, heated to 90 °C, and reacted for 24 h. After the reaction was completed, vacuum distillation was performed, the mixture was washed with deionized water, and dried to obtain intermediate product 2.

[0052] (3) Add 60 mmol of DOPO to toluene solvent, stir and dissolve, then add 30 mmol of intermediate product 2, heat to 110 °C, react for 8 h, and after the reaction is completed, cool to room temperature, filter, wash with deionized water, and dry to obtain intermediate product 3.

[0053] (4) 80 mmol of the intermediate product 3 and 200 mmol of isophorone diisocyanate were added to N,N-dimethylformamide solvent, stirred and mixed evenly, and heated to 65 °C. 0.6 mmol of dibutyltin dilaurate was added thereto and reacted for 5 h. After the reaction was completed, the mixture was evaporated under reduced pressure, washed with deionized water, and dried to obtain phosphorus-containing diisocyanate.

[0054] (5) Under nitrogen atmosphere, 4 g of dried ultrafine magnesium hydroxide and 12 g of phosphorus-containing diisocyanate were added to toluene solvent, ultrasonically dispersed, heated to 80 °C, and stirred for 10 h. After the reaction was completed, the mixture was cooled to room temperature, washed with toluene, and dried to obtain phosphorus-modified magnesium hydroxide.

[0055] (6) Add 50g of castor oil, 10g of polyether polyol (PPG400), 15g of polyester polyol (PBA-3000), and 6g of plasticizer DIDP into a planetary mixer, dehydrate at 120℃ for 3h, cool to 50℃, add 1g of chain extender BDO, 1g of dibutyltin dilaurate, and 15g of phosphorus-modified magnesium hydroxide, mix well, heat to 80℃, react for 3h, and finally add 15g of phosphorus-containing diisocyanate and stir to mix well to obtain a high-strength flame-retardant polyurethane structural adhesive.

[0056] Comparative Example 1: This comparative example differs from Example 1 in that in step (6), isophorone diisocyanate is used instead of phosphorus-containing diisocyanate.

[0057] Comparative Example 2: The difference between this comparative example and Example 1 is that in step (6), phosphorus-modified magnesium hydroxide is not contained.

[0058] The 90° peel strength (aluminum / aluminum) was measured using a microcomputer-controlled electronic universal testing machine with reference to GJB446-1988 standard.

[0059] The polyurethane structural adhesive was cured in an environment of 25°C and 50% relative humidity for 7 days, and the tensile strength was tested according to GB / T528-2009.

[0060] Table 1: Strength test data of polyurethane structural adhesive

[0061] Peel strength / (N / cm) Tensile strength / MPa Example 1 38.8 9.6 Example 2 43.2 11.0 Example 3 46.9 12.1 Example 4 51.3 15.4 Example 5 48.2 13.1 Comparative Example 1 32.4 7.4 Comparative Example 2 30.1 6.8

[0062] It can be seen from the table that the polyurethane structure prepared by the present invention has higher strength.

[0063] Refer to GB / T2408-2008 to test the flame retardant properties of polyurethane structural adhesive.

[0064] Table 2: Flame retardant performance data of polyurethane structural adhesive

[0065] Flame retardant grade Example 1 V-0 Example 2 V-0 Example 3 V-0 Example 4 V-0 Example 5 V-0 Comparative Example 1 V-1 Comparative Example 2 V-1

[0066] It can be seen from the table that the polyurethane structural adhesive prepared by the present invention has good flame retardant effect, and the organic-inorganic synergistic flame retardant effect is better.

[0067] The present invention uses the above-described embodiments to illustrate a high-strength, flame-retardant polyurethane structural adhesive for new energy lithium batteries and its preparation method. However, the present invention is not limited to these embodiments, nor does it necessarily rely on these embodiments for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for various raw materials in the present invention, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. High-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries, characterized by: The polyurethane structural adhesive is composed of the following raw materials in parts by weight: 100 parts by weight of castor oil, 10-30 parts of polyether polyol, 10-30 parts of polyester polyol, 10-20 parts of plasticizer, 2-4 parts of chain extender, 1-3 parts of dibutyltin dilaurate, 10-30 parts of phosphorus-modified magnesium hydroxide, and 10-30 parts of phosphorus-containing diisocyanate; The preparation method of the phosphorus-containing diisocyanate is: (1) Add iminodipropionic acid and 4-dimethylaminopyridine to chloroform solvent, stir and mix evenly, then add diphenylphosphinyl chloride, add triethylamine under nitrogen protection, stir and disperse, heat to 70-80°C, react for 20-35h, and after the reaction, wash with deionized water, dry, filter, and rotary evaporate to obtain intermediate 1, wherein the molar ratio of iminodipropionic acid to diphenylphosphinyl chloride is 1:1-1.2; (2) Under nitrogen protection, the intermediate product 1, epoxybutene, and tetrabutylammonium bromide are added to N,N-dimethylformamide solvent, stirred and mixed evenly, heated to 80-90°C, and reacted for 24-30 hours. After the reaction is completed, the mixture is distilled under reduced pressure, washed with deionized water, and dried to obtain the intermediate product 2. The molar ratio of the intermediate product 1 to epoxybutene is 1:2-2.4; (3) Add DOPO to toluene solvent, stir to dissolve, then add intermediate product 2, heat to 100-120°C, react for 6-10 hours, cool to room temperature after the reaction, filter, wash with deionized water, and dry to obtain intermediate product 3. The molar ratio of DOPO to intermediate product 2 is 2-2.5:1; (4) Add the intermediate product 3 and isophorone diisocyanate to N,N-dimethylformamide solvent, stir and mix evenly, heat to 60-75°C, add dibutyltin dilaurate thereto, react for 3-6 hours, and after the reaction is completed, distill under reduced pressure, wash with deionized water, and dry to obtain phosphorus-containing diisocyanate. The molar ratio of the intermediate product 3 to isophorone diisocyanate is 1:2.2-2.5; The preparation method of the phosphorus-containing modified magnesium hydroxide is: Under a nitrogen atmosphere, dry ultrafine magnesium hydroxide and phosphorus-containing diisocyanate are added to a toluene solvent, ultrasonically dispersed, heated to 80-90°C, stirred and reacted for 6-10 hours. After the reaction is completed, cooled to room temperature, washed with toluene, and dried to obtain phosphorus-containing modified magnesium hydroxide.

2. The method for preparing the high-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries according to claim 1, characterized in that: The following steps are involved: S1. Under a nitrogen atmosphere, add dried ultrafine magnesium hydroxide and phosphorus-containing diisocyanate to a toluene solvent, perform ultrasonic dispersion, heat to 80-90°C, stir and react for 6-10 hours. After the reaction is completed, cool to room temperature, wash with toluene, and dry to obtain phosphorus-containing modified magnesium hydroxide; S2. Add castor oil, polyether polyol, polyester polyol and plasticizer into a planetary mixer, dehydrate at 120°C for 3 hours, cool to 50°C, add chain extender, dibutyltin dilaurate and phosphorus-modified magnesium hydroxide, mix evenly, heat to 70-80°C, react for 2-4 hours, and finally add phosphorus-containing diisocyanate, stir and mix evenly to obtain a high-strength flame-retardant polyurethane structural adhesive.

3. The method for preparing the high-strength flame-retardant polyurethane structural adhesive for new energy lithium batteries according to claim 2, characterized in that: In S1, the mass amount of phosphorus-containing diisocyanate is 1.5-3 times the mass amount of ultrafine magnesium hydroxide.

Images