High-temperature-resistant acrylate modified polyurethane composite material and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant acrylate modified polyurethane composite material and a preparation method thereof, and belongs to the technical field of high polymer materials, the preparation method of the composite material comprises the following steps: (1) preparing a-NCO-terminated polyurethane prepolymer; (2) mixing the-NCO-terminated polyurethane prepolymer with a hydroxyl-containing methacrylate monomer, carrying out heat preservation reaction, neutralizing, dispersing and emulsifying to obtain a waterborne polyurethane dispersion; and (3) dropwise adding a mixture consisting of a mixed monomer, alpha-methyl styrene and an initiator into the dispersion, carrying out in-situ polymerization reaction for 2-5 hours, cooling, filtering and discharging to obtain the high-temperature-resistant acrylate modified polyurethane composite material. The composite material has excellent rigidity-toughness balance and heat resistance: through chemical modification, the coating hardness of the material can reach 4H while the flexibility is maintained; by introducing alpha-methyl styrene, the initial decomposition temperature can reach 245 DEG C to the maximum extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular materials, and in particular to a high-temperature-resistant acrylate modified polyurethane composite material and a preparation method thereof. BACKGROUND

[0002] Polyurethane (PU) materials are widely used in the fields of coatings, adhesives, sealants and elastomers due to their excellent wear resistance, flexibility and mechanical properties. However, the main chain of traditional polyurethane materials contains a large number of ester bonds, ether bonds and urethane bonds, which leads to a long-term use temperature usually lower than 80℃, a low heat distortion temperature, and easy softening and decomposition in high-temperature environments, resulting in a sharp decline in performance. This defect seriously limits the use of polyurethane in high-temperature application fields such as automobile engine compartments, electronic device heat insulation and aerospace materials.

[0003] Currently, the improvement of the heat resistance of polyurethane mainly adopts physical blending or simple core-shell structure modification methods. However, these methods have problems such as poor compatibility and phase separation, leading to unstable material performance. At the same time, the traditional modification methods have limited improvement of heat resistance, and often sacrifice the original flexibility of the material. In addition, many modification methods rely on organic solvents, which do not meet the current green and environmentally friendly development trend.

[0004] Although α-methylstyrene (AMS) homopolymer has a glass transition temperature as high as 175℃, it is a highly potential heat-resistant modification monomer, but it has not been applied to polyurethane modification, especially through in-situ polymerization to construct a fine network structure to achieve the synergistic improvement of heat resistance and mechanical properties.

[0005] Therefore, it has become an urgent need of the industry to develop a new composite material with excellent heat resistance, high hardness, good toughness and excellent processability, and has significant economic value. SUMMARY

[0006] Therefore, the present application provides a high-temperature-resistant acrylate modified polyurethane composite material and a preparation method thereof to solve the problems in the prior art.

[0007] In order to achieve the above purpose, the present application provides the following technical scheme: According to a first aspect of the present application, a preparation method of a high-temperature-resistant acrylate modified polyurethane composite material is provided, comprising the following steps: (1) Under the protection of inert gas, polyol, hydrophilic chain extender and polyisocyanate monomer are mixed, and under the action of catalyst, a polyurethane prepolymer with terminal -NCO group is prepared by reacting at 70-85℃ for 2-4h. During the reaction process, a proper amount of acetone can be added to adjust the viscosity of the system to ensure smooth stirring according to the change of viscosity; (2) The temperature of the terminal -NCO group-containing polyurethane prepolymer prepared in step (1) is reduced to below 60°C, and a hydroxyl-containing methacrylate monomer is added, and the reaction is maintained for 1-2 h; after the reaction is completed, the temperature of the system is reduced to 40-50°C, and a neutralizing agent is added for neutralization for 20 min; subsequently, deionized water is added for emulsification and dispersion under high-speed shearing at a speed of 1000-1200 r / min, to obtain a water-based polyurethane dispersion; (3) A mixture composed of a mixed monomer, alpha-methyl styrene (AMS), and an initiator is added dropwise to the water-based polyurethane dispersion obtained in step (2), the temperature of the system is raised to 70-80°C, and in-situ polymerization is performed for 2-5 h; after the reaction is completed, the system is cooled to room temperature, and after filtration, the product is discharged, to obtain a high-temperature-resistant acrylate-modified polyurethane composite material.

[0008] Further, the molar ratio of isocyanate (-NCO) groups contained in the polyisocyanate monomer to hydroxyl (-OH) groups contained in the polyol and the hydrophilic chain extender in step (1) is 1.1-2.1.

[0009] Further, the polyisocyanate monomer is at least one selected from toluene diisocyanate (TDI), p-phenylene diisocyanate (PPDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and xylylene diisocyanate (XDI).

[0010] Further, the mixed monomer in step (3) is composed of a soft monomer and a hard monomer, and the mass ratio of the soft monomer to the hard monomer is 1:(2.4-3); the initiator includes, but is not limited to, potassium persulfate (KPS) or ammonium persulfate (APS).

[0011] Further, the soft monomer is at least one selected from n-butyl acrylate (BA) and isooctyl acrylate (EHA), and the hard monomer is at least one selected from methyl methacrylate (MMA) and styrene (St).

[0012] Further, the addition amount of the alpha-methyl styrene (AMS) in step (3) accounts for 5%-40% of the total mass of the mixed monomers.

[0013] Further, the addition amount of the alpha-methyl styrene (AMS) in step (3) accounts for 15%-30% of the total mass of the mixed monomers.

[0014] Further, the amount of the hydroxyl-containing methacrylate monomer added in step (2) is 4%-10% of the total mass of the terminal -NCO group-containing polyurethane prepolymer, and the hydroxyl-containing methacrylate monomer is at least one selected from hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA) and hydroxyethyl methacrylate (HEMA).

[0015] Further, the mass ratio of the polyol, the hydrophilic chain extender and the polyisocyanate monomer added in step (1) is (50-70):(4-6):(20-22), and the amount of the catalyst added is 0.04%-0.07% of the total mass of the terminal -NCO group-containing polyurethane prepolymer.

[0016] Further, the mass ratio of the polyol, the hydrophilic chain extender and the polyisocyanate monomer added in step (1) is 50:4:22, and the amount of the catalyst added is 0.066% of the total mass of the terminal -NCO group-containing polyurethane prepolymer.

[0017] Further, the polyol includes but is not limited to polyether polyol (PPG, such as DL-1000), polytetramethylene ether glycol (PTMG) or polybutylene adipate glycol (PBA); the hydrophilic chain extender includes but is not limited to dimethylol propanoic acid (DMPA) or dimethylol butanoic acid (DMBA); the catalyst includes but is not limited to dibutyltin dilaurate (DBTDL); and the neutralizing agent includes but is not limited to diethylamine (DEA), triethanolamine (TEA) or 2-amino-2-methyl-1-propanol (AMP).

[0018] According to a second aspect of the present application, the high-temperature-resistant acrylate-modified polyurethane composite material prepared by the preparation method can be used as a main film-forming material or a matrix resin of a composite material.

[0019] Compared with the prior art, the present application has the following advantages: The high-temperature-resistant acrylate-modified polyurethane composite material provided by the present application introduces an acrylate monomer containing α-methyl styrene (AMS) into a polyurethane matrix for copolymerization through an in-situ polymerization technology, thereby constructing a stable interpenetrating polymer network (IPN) structure. This method introduces a rigid acrylate segment into a flexible polyurethane network through chemical modification, thereby significantly improving the surface hardness of the coating while still maintaining good toughness. In addition, the -NCO groups or -OH groups in the polyurethane can form strong hydrogen bonds or chemical bonds with the surface of the substrate, and the introduction of the acrylate further optimizes the polarity and wettability of the polymer, thereby enhancing the interfacial bonding force. The composite material has the following outstanding advantages: (1) Thermal resistance is significantly improved: By introducing high glass transition temperature (Tg) of alpha-methylstyrene (AMS) monomer, the thermal stability of the coating film is significantly improved, and the initial decomposition temperature (T d5% ) can reach up to 245℃, which is 27-63℃ higher than that of traditional polyurethane.

[0020] (2) Synergistic enhancement of toughness and rigidity: While retaining the good toughness of polyurethane, the introduction of rigid acrylate segments through chemical modification allows the hardness of the coating film to increase by up to 3H, and the hardness of AUPU-3 (Example 3) and AUPU-4 (Example 4) can reach 4H.

[0021] (3) Stable structure and excellent adhesion: In-situ polymerization technology promotes the uniform dispersion and physical entanglement of two phases (polyurethane phase and acrylate phase) at the microscale, effectively avoiding phase separation and ensuring the stability and reliability of the material structure. Specifically, AUPU-1 to AUPU-6 (Examples 1-6) all achieve the optimal 0-level adhesion, significantly outperforming physical blending (Blend-C).

[0022] (4) Environmental friendliness and process compatibility: Developed based on a water-based system, the volatile organic compound (VOC) content is low, meeting strict environmental regulations and sustainable development trends. The in-situ polymerization process adopted is stable, highly adaptable, and easy to scale up, making it particularly suitable for fields with stringent requirements for heat resistance and environmental friendliness, such as high-performance coatings, industrial adhesives, and electronic packaging materials. DETAILED DESCRIPTION

[0023] The following specific examples illustrate the embodiments of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosed content. Obviously, the described examples are part of the embodiments of the present application, not all. Based on the examples in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] According to the first aspect of the present application, a preparation method of a high-temperature-resistant acrylate-modified polyurethane composite material is provided, comprising the following steps: (1) Under the protection of inert gas, polyol, hydrophilic chain extender and polyisocyanate monomer are mixed, and under the action of catalyst, the reaction is carried out at 70-85℃ for 2-4h to prepare NCO-terminated polyurethane prepolymer. During the reaction process, appropriate amount of acetone can be added to adjust the viscosity of the system to ensure smooth stirring according to the change of viscosity; (2) The temperature of the terminal -NCO group-containing polyurethane prepolymer prepared in step (1) is reduced to below 60°C, and a hydroxyl-containing methacrylate monomer is added, and the reaction is maintained for 1-2 h; after the reaction is completed, the temperature of the system is reduced to 40-50°C, and a neutralizing agent is added for neutralization for 20 min; then deionized water is added for emulsification and dispersion under high-speed shearing at a speed of 1000-1200 r / min, to obtain a water-based polyurethane dispersion; (3) A mixture composed of a mixed monomer, alpha-methyl styrene (AMS) and an initiator is added dropwise to the water-based polyurethane dispersion obtained in step (2), the temperature of the system is raised to 70-80°C, and in-situ polymerization is carried out for 2-5 h; after the reaction is completed, the system is cooled to room temperature, and after filtration, the product is discharged, to obtain a high-temperature-resistant acrylate-modified polyurethane composite material.

[0025] Further, the molar ratio of the isocyanate (-NCO) groups contained in the polyisocyanate monomer to the hydroxyl (-OH) groups contained in the polyol and the hydrophilic chain extender in step (1) is 1.1-2.1.

[0026] Further, the polyisocyanate monomer is selected from at least one of toluene diisocyanate (TDI), p-phenylene diisocyanate (PPDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and xylylene diisocyanate (XDI).

[0027] Further, the mixed monomer in step (3) is composed of a soft monomer and a hard monomer, and the mass ratio of the soft monomer to the hard monomer is 1:(2.4-3); the initiator includes but is not limited to potassium persulfate (KPS) or ammonium persulfate (APS).

[0028] Further, the soft monomer is selected from at least one of n-butyl acrylate (BA) and isooctyl acrylate (EHA), and the hard monomer is selected from at least one of methyl methacrylate (MMA) and styrene (St).

[0029] Further, the addition amount of alpha-methyl styrene (AMS) in step (3) accounts for 5%-40% of the total mass of the mixed monomers.

[0030] Further, the addition amount of alpha-methyl styrene (AMS) in step (3) accounts for 15%-30% of the total mass of the mixed monomers.

[0031] Further, the addition amount of the hydroxyl-containing methacrylate monomer in step (2) is 4%-10% of the total mass of the terminal -NCO group-containing polyurethane prepolymer, and the hydroxyl-containing methacrylate monomer is selected from at least one of hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA) and hydroxyethyl methacrylate (HEMA).

[0032] Further, the mass ratio of the polyol, the hydrophilic chain extender and the polyisocyanate monomer in step (1) is (50-70):(4-6):(20-22); the amount of the catalyst added accounts for 0.04%-0.07% of the total mass of the polyurethane prepolymer with terminal -NCO groups.

[0033] Further, the mass ratio of the polyol, the hydrophilic chain extender and the polyisocyanate monomer in step (1) is 50:4:22; the amount of the catalyst added accounts for 0.066% of the total mass of the polyurethane prepolymer with terminal -NCO groups.

[0034] Further, the polyol includes but is not limited to polyether polyol (PPG, such as DL-1000), polytetramethylene ether glycol (PTMG) or polybutylene adipate-1,4-diol (PBA); the hydrophilic chain extender includes but is not limited to dimethylol propionic acid (DMPA) or dimethylol butyric acid (DMBA); the catalyst includes but is not limited to dibutyltin dilaurate (DBTDL); the neutralizing agent includes but is not limited to diethylamine (DEA), triethanolamine (TEA) or 2-amino-2-methyl-1-propanol (AMP).

[0035] According to the second aspect of the present application, the high-temperature-resistant acrylate-modified polyurethane composite prepared by the preparation method can be used as a main film-forming material or a matrix resin of a composite material. Example 1

[0036] A preparation method of a high-temperature-resistant acrylate-modified polyurethane composite: (1) Synthesis of polyurethane prepolymer with terminal -NCO groups: Under nitrogen protection, 50 g of DL-1000, 4 g of DMPA, 22 g of IPDI and 0.05 g of DBTDL were added to a 500 mL four-necked flask equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen inlet tube; the temperature of the system was raised to 80°C, the temperature was kept constant, and the reaction was stirred for 3 h; during the reaction, appropriate amount of acetone was added according to the change of viscosity to adjust the viscosity of the system to ensure smooth stirring; after the reaction, the -NCO content was monitored by di-n-butylamine titration method, and the polyurethane prepolymer with terminal -NCO groups was obtained when the -NCO content reached the theoretical value; (2) Introduction of double bond into polyurethane prepolymer: The temperature of the system was reduced to 55°C, 5 g of HEMA was added to the polyurethane prepolymer with terminal -NCO groups obtained in step (1), the temperature was kept constant, and the reaction was stirred for 1.5 h; (3) Neutralization and emulsification: After the reaction, the temperature of the system was reduced to 45℃, 3.0g TEA was added for neutralization for 20min; 120g deionized water was added under high speed shearing at 1200r / min for 30min to obtain a dispersion; (4) In-situ polymerization of acrylate: After the reaction, a mixture composed of mixed monomers (consisting of 15g MMA, 10g AMS and 5g BA) and 0.5g APS solution (prepared by dissolving 0.5g APS in 5g deionized water) was added dropwise to the dispersion obtained in step (3); the temperature of the system was increased to 75℃, the temperature was kept constant, and the reaction was stirred for 4h; (5) Post-treatment: After the reaction, the system was cooled to room temperature, and the acetone was removed by distillation under reduced pressure. After filtration, an acrylate-modified polyurethane composite with a solid content of about 41% was obtained, which was denoted as AUPU-1. Example 2

[0037] A method for preparing a high-temperature-resistant acrylate-modified polyurethane composite: (1) Synthesis of NCO-terminated polyurethane prepolymer: Under nitrogen protection, 70g PTMG 1000, 4g DMPA, 20g HDI and 0.04g DBTDL were added to a 500mL four-necked flask equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen inlet tube; the temperature of the system was increased to 75℃, the temperature was kept constant, and the reaction was stirred for 3.5h; during the reaction, appropriate amount of acetone was added according to the change of viscosity to adjust the viscosity of the system to ensure smooth stirring; after the reaction, the-NCO content was monitored by di-n-butylamine titration method, and the NCO-terminated polyurethane prepolymer was obtained when the-NCO content reached the theoretical value; (2) Introduction of double bond into polyurethane prepolymer: The temperature of the system was reduced to 50℃, and 4g HEA was added to the NCO-terminated polyurethane prepolymer obtained in step (1), and the reaction was stirred for 2h at constant temperature; (3) Neutralization and emulsification: After the reaction, the temperature of the system was reduced to 45℃, 3.0g TEA was added for neutralization for 20min; 120g deionized water was added under high speed shearing at 1200r / min for 30min to obtain a dispersion; (4) In-situ polymerization of acrylate: After the reaction, a mixture composed of mixed monomers (composed of 10 g of MMA, 8 g of AMS and 12 g of BA) and 0.8 g of an APS aqueous solution (prepared by dissolving 0.8 g of APS in 8 g of deionized water) was added dropwise to the dispersion obtained in step (3); the temperature of the system was raised to 78°C, the temperature was kept constant, and the reaction was stirred for 3.5 h; (5) Post-treatment: After the reaction, the system was cooled to room temperature, and the acetone was removed by distillation under reduced pressure. After filtration, an acrylate-modified polyurethane composite material with a solid content of about 41% was obtained, which was recorded as AUPU-2. Example 3

[0038] A method for preparing a high-temperature-resistant acrylate-modified polyurethane composite material: (1) Synthesis of a polyurethane prepolymer with a terminal -NCO group: Under nitrogen protection, 50 g of PBA 1000, 6 g of DMPA, 20 g of IPDI and 0.05 g of DBTDL were added to a 500 mL four-necked flask equipped with a mechanical stirrer, a thermometer, a condenser and a nitrogen inlet tube; the temperature of the system was raised to 85°C, the temperature was kept constant, and the reaction was stirred vigorously for 2.5 h; after the reaction, the -NCO content was monitored by di-n-butylamine titration, and when the -NCO content reached the theoretical value, a polyurethane prepolymer with a terminal -NCO group was obtained; (2) Introduction of double bonds into the polyurethane prepolymer: The temperature of the system was reduced to 60°C, 7 g of HEMA was added to the polyurethane prepolymer with a terminal -NCO group obtained in step (1), the temperature was kept constant, and the reaction was stirred for 1 h; (3) Neutralization and emulsification: After the reaction, the temperature of the system was reduced to 45°C, 4.5 g of TEA was added and neutralized for 20 min; 140 g of deionized water was added under high-speed shearing at a speed of 1200 r / min, and emulsified for 30 min to obtain a dispersion; (4) In-situ polymerization of acrylate: After the reaction, a mixture composed of mixed monomers (composed of 15 g of MMA, 12 g of AMS and 3 g of BA) and 0.5 g of an APS solution (prepared by dissolving 0.5 g of APS in 10 g of deionized water) was added dropwise to the dispersion obtained in step (3); the temperature of the system was raised to 75°C, the temperature was kept constant, and the reaction was stirred for 4 h; (5) Post-treatment: After the reaction, the system was cooled to room temperature, and the acetone was removed by distillation under reduced pressure. After filtration, an acrylate-modified polyurethane composite material with a solid content of about 41% was obtained, which was recorded as AUPU-2. Example 4

[0039] A preparation method of a high-temperature-resistant acrylate-modified polyurethane composite material (1) Synthesis of polyurethane prepolymer with terminal -NCO group: Under nitrogen protection, 50 g of DL-1000, 4 g of DMBA, 22 g of HDI, and 0.05 g of DBTDL were added to a 500 mL four-necked flask equipped with a mechanical stirrer, a thermometer, a condenser, and a nitrogen inlet tube; the temperature of the system was raised to 80°C, and the temperature was kept constant, and the reaction was stirred for 3 h; during the reaction, appropriate amount of acetone was added according to the change of viscosity to adjust the viscosity of the system and ensure smooth stirring; after the reaction, the -NCO content was monitored by di-n-butylamine titration method, and when the -NCO content reached the theoretical value, the polyurethane prepolymer with terminal -NCO group was obtained; (2) Introducing double bond into polyurethane prepolymer: The temperature of the system was reduced to 55°C, 5 g of HEA was added to the polyurethane prepolymer with terminal -NCO group obtained in step (1), and the temperature was kept constant, and the reaction was stirred for 1.5 h; (3) Neutralization and emulsification: After the reaction, the temperature of the system was reduced to 45°C, 3.0 g of DEA was added and neutralized for 20 min; 120 g of deionized water was added under high-speed shearing at a speed of 1200 r / min, and emulsified for 30 min to obtain a dispersion; (4) In-situ polymerization of acrylate: After the reaction, a mixture composed of mixed monomers (composed of 15 g of MMA, 10 g of AMS, and 5 g of EHA) and 0.5 g of KPS solution (prepared by dissolving 0.5 g of KPS in 5 g of deionized water) was added dropwise to the dispersion obtained in step (3); the temperature of the system was raised to 75°C, and the temperature was kept constant, and the reaction was stirred for 4 h; (5) Post-treatment: After the reaction, the system was cooled to room temperature, and the acetone was removed by reduced pressure distillation, and the acrylate-modified polyurethane composite material with a solid content of about 41% was obtained after filtration, which was recorded as AUPU-4. Example 5

[0040] A preparation method of a high-temperature-resistant acrylate-modified polyurethane composite material (1) Synthesis of polyurethane prepolymer with terminal -NCO group: Into a 500 mL four-necked flask equipped with a mechanical stirrer, thermometer, condenser and nitrogen inlet tube, 50 g of DL-1000, 4 g of DMPA, 22 g of MDI and 0.05 g of DBTDL were added under nitrogen protection; the temperature of the system was raised to 80°C, the temperature was kept constant, and the reaction was stirred for 3 h; during the reaction, appropriate amount of acetone was added according to the change of viscosity to adjust the viscosity of the system and ensure smooth stirring; after the reaction was completed, monitoring was performed by di-n-butylamine titration method, and after the -NCO content reached the theoretical value, a polyurethane prepolymer with terminal -NCO groups was obtained; (2) Introducing double bonds into the polyurethane prepolymer: The temperature of the system was reduced to 55°C, 5 g of HPA was added to the polyurethane prepolymer with terminal -NCO groups obtained in step (1), the temperature was kept constant, and the reaction was stirred for 1.5 h; (3) Neutralization and emulsification: After the reaction was completed, the temperature of the system was reduced to 45°C, 3.0 g of TEA was added and neutralized for 20 min; 120 g of deionized water was added under high-speed shearing at a speed of 1200 r / min, and emulsified for 30 min to obtain a dispersion; (4) In-situ polymerization of acrylate: After the reaction was completed, a mixture composed of a mixed monomer (composed of 10 g of MMA, 5 g of St, 10 g of AMS and 5 g of BA) and 0.5 g of APS solution (prepared by dissolving 0.5 g of APS in 5 g of deionized water) was added dropwise to the dispersion obtained in step (3); the temperature of the system was raised to 75°C, the temperature was kept constant, and the reaction was stirred for 4 h; (5) Post-treatment: After the reaction was completed, the system was cooled to room temperature, acetone was removed by reduced pressure distillation, and a polyurethane-acrylate composite material with a solid content of about 41% was obtained after filtration, which was recorded as AUPU-5. Example 6

[0041] A method for preparing a high-temperature-resistant polyurethane-acrylate composite material: (1) Synthesis of polyurethane prepolymer with terminal -NCO groups: Into a 500 mL four-necked flask equipped with a mechanical stirrer, thermometer, condenser and nitrogen inlet tube, 50 g of DL-1000, 4 g of DMPA, 22 g of PPDI and 0.05 g of DBTDL were added under nitrogen protection; the temperature of the system was raised to 80°C, the temperature was kept constant, and the reaction was stirred for 3 h; during the reaction, appropriate amount of acetone was added according to the change of viscosity to adjust the viscosity of the system and ensure smooth stirring; after the reaction was completed, monitoring was performed by di-n-butylamine titration method, and after the -NCO content reached the theoretical value, a polyurethane prepolymer with terminal -NCO groups was obtained; (2) Introducing double bonds into the polyurethane prepolymer: The temperature of the system was decreased to 55°C, 5 g of HEMA was added to the terminal -NCO group-containing polyurethane prepolymer obtained in step (1), the temperature was kept constant, and stirring was performed for 1.5 h; (3) Neutralization and emulsification: After the reaction was completed, the temperature of the system was decreased to 45°C, 3.0 g of TEA was added, and neutralization was performed for 20 min; 120 g of deionized water was added under high-speed shearing at a rotation speed of 1200 r / min, and emulsification was performed for 30 min to obtain a dispersion; (4) In-situ polymerization of acrylate: After the reaction was completed, a mixture composed of a mixed monomer (consisting of 10 g of MMA, 2 g of EHA, 10 g of AMS, and 5 g of BA) and 0.5 g of an APS solution (prepared by dissolving 0.5 g of APS in 5 g of water) was added dropwise to the dispersion obtained in step (3); the temperature of the system was increased to 75°C, the temperature was kept constant, and stirring was performed for 4 h; (5) Post-treatment: After the reaction was completed, the system was cooled to room temperature, and acetone was removed by distillation under reduced pressure; after filtration, an acrylate-modified polyurethane composite material with a solid content of about 41% was obtained, which was recorded as AUPU-6.

[0042] Comparative Example 1: A preparation method of a traditional polyurethane material: (1) Synthesis of terminal -NCO group-containing polyurethane prepolymer: Under nitrogen protection, 50 g of DL-1000, 4 g of DMPA, 22 g of IPDI, and 0.05 g of DBTDL were added to a 500 mL four-necked flask equipped with a mechanical stirrer, a thermometer, a condenser, and a nitrogen inlet tube; the temperature of the system was increased to 80°C, the temperature was kept constant, and stirring was performed for 3 h; during the reaction, an appropriate amount of acetone was added according to the viscosity change to adjust the viscosity of the system and ensure smooth stirring; after the reaction was completed, the -NCO content was monitored by di-n-butylamine titration, and when the -NCO content reached the theoretical value, a terminal -NCO group-containing polyurethane prepolymer was obtained; (2) Introduction of double bonds into the polyurethane prepolymer: The temperature of the system was decreased to 55°C, 2.5 g of 1,4-butanediol (BDO) was added to the terminal -NCO group-containing polyurethane prepolymer obtained in step (1), the temperature was kept constant, and stirring was performed for 1.5 h; (3) Neutralization and emulsification: After the reaction was completed, the temperature of the system was decreased to 45°C, 3.0 g of TEA was added, and neutralization was performed for 20 min; 120 g of deionized water was added under high-speed shearing at a rotation speed of 1200 r / min, and emulsification was performed for 30 min to obtain a dispersion; (4) Post-treatment: After the reaction was completed, the system was cooled to room temperature, and acetone was removed by vacuum distillation. After filtration, a polyurethane material with a solid content of about 41% was obtained, denoted as PU-C.

[0043] Comparative Example 2: A method for preparing a polyurethane-acrylate blend: (1) Synthesis of polyurethane prepolymers with -NCO end groups: Under nitrogen protection, 50g DL-1000, 4g DMPA, 22g IPDI, and 0.05g DBTDL were added to a 500mL four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and nitrogen inlet tube. The system temperature was raised to 80℃ and maintained at that temperature for 3 hours with stirring. During the reaction, an appropriate amount of acetone was added dropwise to adjust the viscosity of the system according to the viscosity change, ensuring smooth stirring. After the reaction was completed, the di-n-butylamine titration method was used to monitor the reaction. Once the -NCO content reached the theoretical value, the polyurethane prepolymer with -NCO groups was obtained. (2) Introducing double bonds into polyurethane prepolymers: The system temperature was lowered to 55℃, and 5g HEMA was added to the polyurethane prepolymer with terminal-NCO groups obtained in step (1). The temperature was kept constant and the reaction was stirred for 1.5h. (3) Neutralization and emulsification: After the reaction was completed, the system temperature was lowered to 45℃, and 3.0g of TEA was added for neutralization for 20min. Under high-speed shearing at 1200r / min, 120g of deionized water was added, and the emulsification reaction was carried out for 30min to obtain the dispersion. (4) Physical blending of polyurethane and acrylate: After the reaction is complete, 30g of commercially available styrene-acrylic emulsion is added dropwise to the dispersion obtained in step (3), and mechanical blending is continued for 1 hour; (5) Post-processing: After the reaction was completed, the system was cooled to room temperature, and acetone was removed by vacuum distillation. After filtration, a polyurethane-acrylate blend with a solid content of about 41% was obtained, denoted as Blend-C.

[0044] Test example: Using a coating stick, the samples from Examples 1-6 (acrylate-modified polyurethane) and Comparative Examples 1 and 2 (conventional polyurethane) were uniformly coated onto a standard tinplate to form a 200 μm wet film. The coated samples were then placed in a 120°C forced-air drying oven for 1 hour of continuous drying and curing. After curing, the samples were cured under standard conditions of 23±2°C and 50±5% relative humidity for 24 hours, followed by various performance tests. The specific test items are as follows: Thermal stability test: The test was performed on a STA409PC instrument from NETZSCH, Germany, under the following conditions: heating from 30 to 600 °C at a rate of 10 °C / min under a nitrogen flow of 25 mL / min, recording the weight loss of the sample, and taking the temperature at which the mass loss was 5% (T d5% ) as the evaluation index.

[0045] Hardness test: Refer to GB / T 6739-2022 “Pigments and Dopes - Determination of Film Hardness by Pencil Method”; Adhesion test: Refer to GB / T 9286-2021 “Pigments and Dopes - Crosshatch Test for Paint Films”.

[0046] The following table shows the performance test results of the coating films formed by the samples in Examples 1-6 and Comparative Examples 1 and 2: From the experimental data in the above table, compared with the traditional polyurethane (PU-C) in Comparative Example 1 and the polyurethane-acrylate blend (Blend-C) in Comparative Example 2, the acrylate-modified polyurethanes (AUPU-1 to AUPU-6) in Examples 1-6 all showed significant advantages in the thermal stability, hardness and adhesion of the coating films, as follows: In terms of thermal stability, the initial decomposition temperature (T d5% ) of the coating films of AUPU-1 to AUPU-6 (Examples 1-6) was increased by 27-63 °C compared with the PU-C (Comparative Example 1) coating film and by 14-50 °C compared with the Blend-C (Comparative Example 2) coating film, which indicated that the chemical modification significantly improved the thermal stability of the material. This was mainly due to the network structure formed by chemical bonding, which could more effectively inhibit the chain segment movement in the initial stage of thermal decomposition. Among them, the coating film formed by AUPU-3 in Example 3 had the best thermal stability, with a T d5% as high as 245 °C.

[0047] In terms of coating film hardness, the hardness of the coating films of AUPU-1 to AUPU-6 (Examples 1-6) was increased by 2-3H compared with the PU-C (Comparative Example 1) coating film and by 1-2H compared with the Blend-C (Comparative Example 2) coating film. This result indicated that through chemical modification, rigid acrylate segments were effectively introduced into the flexible polyurethane network, which improved the surface hardness while taking into account the material toughness. Among them, the hardness of the coating films of AUPU-3 in Example 3 and AUPU-4 in Example 4 both reached the highest 4H.

[0048] In terms of adhesion, the coating films of AUPU-1 to AUPU-6 (Examples 1-6) all exhibited the best 0-grade adhesion, stable and excellent performance. In contrast, the adhesion of the coating film of PU-C (Comparative Example 1) was 1-grade, and the adhesion of the coating film of Blend-C (Comparative Example 2) was only 2-grade. This phenomenon confirms that the -NCO groups or hydroxyl groups in the polyurethane prepolymer can form strong hydrogen bonds or chemical bonds with the surface of the substrate, and the introduction of acrylate further optimizes the polymer polarity and wettability, thereby enhancing the interfacial bonding. The adhesion of the coating film of the polyurethane-acrylate blend (Blend-C) is poor, which may be related to poor compatibility between the two phases, decreased cohesive strength, and weak interfacial bonding.

[0049] Although the present application has been described in detail with general description and specific examples above, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of the present application claimed.

Claims

1. A method for preparing a high-temperature resistant acrylate-modified polyurethane composite material, characterized in that, Includes the following steps: (1) Under the protection of inert gas, polyol, hydrophilic chain extender and polyisocyanate monomer are mixed and reacted at 70-85℃ for 2-4h under the action of catalyst to obtain polyurethane prepolymer with terminal -NCO group; (2) The temperature of the polyurethane prepolymer with NCO end groups obtained in step (1) is lowered to below 60°C, and a monomer containing hydroxymethyl methacrylate is added. The reaction is kept at the temperature for 1-2 hours. After the reaction is completed, the temperature of the system is lowered to 40-50°C, and a neutralizing agent is added for neutralization for 20 minutes. Then, deionized water is added under high-speed shear at a speed of 1000-1200 r / min for emulsification and dispersion to obtain an aqueous polyurethane dispersion. (3) Add a mixture of mixed monomers, α-methylstyrene and initiator to the waterborne polyurethane dispersion obtained in step (2), raise the system temperature to 70-80℃, and carry out in-situ polymerization reaction for 2-5 hours; after the reaction is completed, cool the system to room temperature, filter and discharge to obtain high temperature resistant acrylate modified polyurethane composite material.

2. The preparation method of the high-temperature resistant acrylate-modified polyurethane composite material as described in claim 1, characterized in that, The molar ratio of the isocyanate groups in the polyisocyanate monomer in step (1) to the hydroxyl groups in the polyol and hydrophilic chain extender is 1.1-2.

1.

3. The method for preparing the high-temperature resistant acrylate-modified polyurethane composite material as described in claim 2, characterized in that, The polyisocyanate monomer is selected from at least one of toluene diisocyanate, terephthalic diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and phenyl diisocyanate.

4. The method for preparing the high-temperature resistant acrylate-modified polyurethane composite material as described in claim 1, characterized in that, The mixed monomers in step (3) consist of soft monomers and hard monomers, and the mass ratio of the soft monomers to the hard monomers is 1:(2.4-3).

5. The method for preparing the high-temperature resistant acrylate-modified polyurethane composite material as described in claim 4, characterized in that, The soft monomer is selected from at least one of n-butyl acrylate and isooctyl acrylate, and the hard monomer is selected from at least one of methyl methacrylate and styrene.

6. The method for preparing the high-temperature resistant acrylate-modified polyurethane composite material as described in claim 1, characterized in that, The amount of α-methylstyrene added in step (3) accounts for 5%-40% of the total mass of the mixed monomers.

7. The method for preparing the high-temperature resistant acrylate-modified polyurethane composite material as described in claim 6, characterized in that, The amount of α-methylstyrene added in step (3) accounts for 15%-30% of the total mass of the mixed monomers.

8. The method for preparing the high-temperature resistant acrylate-modified polyurethane composite material as described in claim 1, characterized in that, The amount of hydroxymethyl methacrylate monomer added in step (2) is 4%-10% of the total mass of the polyurethane prepolymer with terminal -NCO groups, and the hydroxymethyl methacrylate monomer is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxyethyl methacrylate.

9. The method for preparing the high-temperature resistant acrylate-modified polyurethane composite material as described in claim 1, characterized in that, In step (1), the mass ratio of the polyol, hydrophilic chain extender and polyisocyanate monomer added is (50-70): (4-6): (20-22); the amount of catalyst added is 0.04%-0.07% of the total mass of the polyurethane prepolymer with terminal -NCO groups.

10. The high-temperature resistant acrylate-modified polyurethane composite material prepared by the preparation method according to any one of claims 1-9.

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