Damp-heat-resistant flame-retardant polyurethane and host-guest chemical preparation method thereof

Abstract

The invention provides damp-heat-resistant flame-retardant polyurethane and a host-guest chemical preparation method thereof, hyperbranched polyethyleneimine reacts with aldehydes to obtain a Schiff base structure, and then an organic hydrogen phosphate compound reacts with the Schiff base structure to synthesize a phosphorus-containing hydrophobic shell-hydrophilic core hyperbranched polymer. A phosphate flame retardant is embedded in the obtained amphiphilic hyperbranched flame-retardant polymer to form a flame-retardant complex by utilizing a host-guest coated hydrophilic-hydrophobic interaction principle, and the complex is blended with polyurethane to obtain a modified polyurethane material. The modified polyurethane can effectively inhibit precipitation of phosphate flame retardants, so that the material has excellent flame retardance and humidity and heat resistance, and a flame-retardant complex of the flame-retardant polyurethane has good compatibility with the polyurethane, so that the material has good transparency.

Description

Technical Field

[0001] This invention relates to the field of chemical materials, and in particular to a method for preparing a flame-retardant and moisture-resistant thermoplastic polyurethane material. Background Technology

[0002] Thermoplastic polyurethane (TPU) is lightweight, easy to process, and has relatively stable mechanical and chemical properties, offering advantages such as heat resistance, corrosion resistance, high strength, and high toughness. However, due to its high carbon and hydrogen content, most polyurethane materials are flammable, significantly limiting the application of TPU resins in various fields. Therefore, flame retardants are needed to improve its flame retardancy. However, the addition of flame retardants exposes their hydrophilicity, further degrading the hygrothermal performance of TPU resins. Thermoplastic polyurethane (TPU) suffers from severe defects under high humidity and high temperature conditions. Due to its inherent hydrophilicity, water molecules easily penetrate the material, disrupting hydrogen bonds and lowering its glass transition temperature, leading to partial degradation. The addition of flame retardants further increases hydrophilicity, exacerbating the performance degradation. With societal development, TPU elastomers play a vital role in various fields, particularly in the booming new energy and aerospace sectors. Therefore, improving the resistance to hygrothermal aging and flame retardancy of TPU has become crucial.

[0003] Adding flame retardants to thermoplastic polyurethane is the most direct method to improve its flame retardant properties. Phosphorus- and nitrogen-based halogen-free flame retardants are widely used. The main components of these flame retardants are phosphorus or nitrogen-based organic compounds. The good flame retardant effect of phosphorus and nitrogen-based flame retardants is primarily due to the fact that phosphorus compounds can undergo dehydration and carbonization to form a protective carbon layer, thereby reducing the polymer's flammability. Nitrogen-based flame retardants, on the other hand, can absorb heat from the polymer during decomposition and produce non-flammable gases, diluting the flammable material to a concentration suitable for combustion.

[0004] Common salt flame retardants have poor compatibility with polyurethane systems, making them prone to migration and loss. This leads to the modified polyurethane absorbing water easily, resulting in a significant decrease in its resistance to damp heat. According to the review article CurrentOrganic Chemistry, 2011, 15(1): 2-26, amphiphilic hyperbranched polymers with a core-shell structure have a strong hydrophilic core and a strong hydrophobic shell. By utilizing the hydrophilic-hydrophobic interaction and the corresponding phase transfer method, inorganic salts can be embedded inside the polymer, extracted from the aqueous phase into the organic phase, and then the solvent in the organic phase is evaporated to obtain the complex.

[0005] This invention provides a flame-retardant and moisture-resistant thermoplastic polyurethane material and its host-guest chemical preparation method. Branched polyethyleneimine and aldehydes are reacted in a solvent to obtain a Schiff base structure, which is then reacted with an organophosphorus compound to obtain a phosphorus-containing amphiphilic hyperbranched polymer. Utilizing the host-guest encapsulation principle and employing hydrophilic-hydrophobic interactions and corresponding phase transfer methods, a phosphate flame retardant is embedded within this two-part hyperbranched flame-retardant polymer to form a complex. This complex is then blended with polyurethane to obtain the modified polyurethane material. The modified polyurethane exhibits excellent flame-retardant and moisture-resistant properties. The flame-retardant complex has good compatibility with polyurethane, resulting in a completely transparent modified polyurethane. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a flame-retardant and moisture-resistant thermoplastic polyurethane material and its host-guest chemical preparation method. A flame-retardant complex of an amphiphilic branched polymer and a flame retardant is prepared using hydrophilic-hydrophobic interactions and a corresponding phase transfer method.

[0007] The objective of this invention is achieved through the following technical solution: a heat-resistant flame-retardant polyurethane and its host-guest chemical preparation method, comprising the following steps: (1) Add 1~5 g of hyperbranched polyethyleneimine and 1~8 g of aldehydes, and stir at 90~120 °C for 12~48 h; after the reaction is completed, precipitate and dry to obtain hyperbranched polyethyleneimine / aldehyde Schiff base; (2) Add 1~5g of hyperbranched polyethyleneimine / aldehyde Schiff base, 1~6g of organophosphorus compound and 50~150ml of the first solvent, and stir at 50~80℃ for 12~48h; after the reaction is completed, centrifuge the precipitate and remove the first solvent by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) Dissolve the obtained hydrophobic shell-hydrophilic core host and phosphate flame retardant in the second solvent and aqueous solution respectively. Mix the two phases and stir at high speed for a few minutes. After standing, take the solvent phase and evaporate to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is heated and mixed with thermoplastic polyurethane at 140~250℃. The final product is a transparent and uniform flame-retardant thermoplastic polyurethane material. The mass ratio of host-guest complex to thermoplastic polyurethane is less than 50%.

[0008] Furthermore, the aldehydes mentioned are salicylaldehyde, phenylformaldehyde, phenylacetaldehyde, 3-phenylpropanal, and o-propenyloxybenzene. Formaldehyde, p-methoxybenzaldehyde, or halogenated benzaldehyde, but not limited to these.

[0009] Furthermore, the organophosphorus compound is one or more of diphenylphosphine, diphenylphosphine, dibutylphosphine, and phenylbutylphosphine, but is not limited thereto.

[0010] Furthermore, the flame retardant is one or more of sodium tripolyphosphate, ammonium polyphosphate, sodium dihydrogen phosphate, and disodium hydrogen phosphate, but is not limited thereto.

[0011] Furthermore, the first solvent is one or more of toluene, xylene, dichloromethane, chloroform, N,N-dimethylformamide, or N,N-dimethylacetamide, but is not limited thereto.

[0012] Furthermore, the second solvent is a solvent that is immiscible with water, such as chloroform, dichloromethane, or toluene, but is not limited to these.

[0013] The advantages of this invention are: This invention involves reacting aromatic aldehydes with polyethyleneimine, grafting organophosphorus compounds to provide a hydrophobic shell, and then encapsulating phosphate flame retardants with hyperbranched polymers to form flame-retardant complexes, which are then added to thermoplastic polyurethane. Due to its good compatibility with thermoplastic polyurethane, a highly transparent material can be obtained, the flame retardant properties of the composite material can be improved, and the resistance to damp heat can be significantly enhanced. Attached Figure Description

[0014] Figure 1 The images show the proton NMR spectrum of the polyethyleneimine / aldehyde Schiff base polymer prepared in Example 1 and the proton NMR spectrum of the hyperbranched polymer matrix with a phosphorus-containing hydrophobic shell and hydrophilic core. Figure 2 The infrared spectra of the polyethyleneimine / aldehyde Schiff base polymer prepared in Example 1 and the infrared spectra of the hyperbranched polymer matrix with a phosphorus-containing hydrophobic shell and hydrophilic core are shown. Figure 3 This is a flowchart of the experimental process; Figure 4 The water absorption test of the flame-retardant thermoplastic polyurethane materials prepared in Examples 3-6 at 80°C for 168 hours; Figure 5 These are the flame retardant test results of the modified polyurethane materials in Examples 3, 4, 5, and 6. Figure 6 This is a photograph of the modified polyurethane sheet from Example 5. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] Example 1 (1) Add 1g of branched polyethyleneimine and 1g of salicylaldehyde, and stir at 90℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base. (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1g of dibutylphosphine and 150ml of toluene, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove the toluene by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and sodium tripolyphosphate were dissolved in chloroform and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of the host-guest complex to the thermoplastic polyurethane is less than 50%. Example 2

[0017] (1) Add 5g of branched polyethyleneimine and 8g of salicylaldehyde, and stir at 120℃ for 48h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base. (2) Add 5g of branched polyethyleneimine / aldehyde Schiff base, 6g of diphenylphosphine and 150ml of xylene solvent, and stir at 80℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove xylene by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and sodium tripolyphosphate were dissolved in chloroform and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of the host-guest complex to the thermoplastic polyurethane is less than 50%. Example 3

[0018] (1) Add 2g of branched polyethyleneimine and 3.76g of salicylaldehyde, and stir at 85℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of diphenylphosphine oxide and 100ml of chloroform solvent, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove the chloroform by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and sodium tripolyphosphate were dissolved in chloroform and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of the host-guest complex to the thermoplastic polyurethane is 5%. Example 4

[0019] (1) Add 2g of branched polyethyleneimine and 3.76g of salicylaldehyde, and stir at 85℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of diphenylphosphine oxide and 100ml of chloroform solvent, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove the chloroform by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and sodium tripolyphosphate were dissolved in chloroform and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of host-guest complex to thermoplastic polyurethane is 10%. Example 5

[0020] (1) Add 2g of branched polyethyleneimine and 3.76g of salicylaldehyde, and stir at 85℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of diphenylphosphine oxide and 100ml of chloroform solvent, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove the chloroform by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and sodium tripolyphosphate were dissolved in chloroform and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is heated and mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of host-guest complex to thermoplastic polyurethane is 15%. Example 6

[0021] (1) Add 2g of branched polyethyleneimine and 3.76g of salicylaldehyde, and stir at 85℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of diphenylphosphine oxide and 100ml of chloroform solvent, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove the chloroform by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and sodium tripolyphosphate were dissolved in chloroform and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of host-guest complex to thermoplastic polyurethane is 20%. Example 7

[0022] (1) Add 1g of branched polyethyleneimine and 6.33g of salicylaldehyde, and stir at 85℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 2g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of phenyl butylphosphine and 100ml of N,N-dimethylacetamide solvent, and stir at 65℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove N,N-dimethylacetamide by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and sodium tripolyphosphate were dissolved in toluene and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of the host-guest complex to the thermoplastic polyurethane is less than 50%. Example 8

[0023] (1) Add 1g of branched polyethyleneimine and 4.66g of salicylaldehyde, and stir at 100℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 2g of branched polyethyleneimine / aldehyde Schiff base, 4.52g of dibutylphosphine and 100ml of toluene solvent, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove the toluene by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and disodium hydrogen phosphate were dissolved in toluene and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of the host-guest complex to the thermoplastic polyurethane is less than 50%. Example 9

[0024] (1) Add 1g of branched polyethyleneimine and 6.0g of salicylaldehyde, and stir at 100℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 4.52g of phenyl butylphosphine and 100ml of xylene solvent, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove xylene by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and disodium hydrogen phosphate were dissolved in dichloromethane and aqueous solution, respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex containing flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 170°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of the host-guest complex to the thermoplastic polyurethane is less than 50%. Example 10

[0025] (1) Add 1g of branched polyethyleneimine and 1.266g of salicylaldehyde, and stir at 100℃ for 24h; after the reaction is completed, precipitate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 2g of branched polyethyleneimine / aldehyde Schiff base, 4.52g of diphenylphosphine and 100ml of chloroform solvent, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove the chloroform by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) The obtained hydrophobic shell-hydrophilic core host and sodium dihydrogen phosphate were dissolved in toluene and aqueous solution respectively. The two phases were mixed and stirred at high speed for a few minutes. After standing, the solvent phase was taken and evaporated to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is mixed with thermoplastic polyurethane at 200°C. A transparent and uniform flame-retardant thermoplastic polyurethane material is finally obtained. The mass ratio of the host-guest complex to the thermoplastic polyurethane is less than 50%. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat-resistant, flame-retardant polyurethane and its host-guest chemical preparation method, characterized in that, Includes the following steps: (1) Add 1~5 g of hyperbranched polyethyleneimine and 1~8 g of aldehydes, and stir at 90~120 °C for 12~48 h; after the reaction is completed, precipitate and dry to obtain hyperbranched polyethyleneimine / aldehyde Schiff base; (2) Add 1~5g of hyperbranched polyethyleneimine / aldehyde Schiff base, 1~6g of organophosphorus compound and 50~150ml of the first solvent, and stir at 50~80℃ for 12~48h; after the reaction is completed, centrifuge the precipitate and remove the first solvent by rotary evaporation to obtain the hydrophobic shell-hydrophilic core body. (3) Dissolve the obtained hydrophobic shell-hydrophilic core host and phosphate flame retardant in the second solvent and aqueous solution respectively. Mix the two phases and stir at high speed for a few minutes. After standing, take the solvent phase and evaporate to obtain the host-guest complex of the flame retardant. (4) The host-guest complex containing the flame retardant is heated and mixed with thermoplastic polyurethane at 140~250℃. The final product is a transparent and uniform flame-retardant thermoplastic polyurethane material. The mass ratio of host-guest complex to thermoplastic polyurethane is less than 50%.

2. The heat-resistant flame-retardant polyurethane and its host-guest chemical preparation method according to claim 1, characterized in that, The aldehydes mentioned are salicylaldehyde, phenylformaldehyde, phenylacetaldehyde, 3-phenylpropanaldehyde, o-propenyloxybenzaldehyde, p-methoxybenzaldehyde, or halogenated benzaldehyde, but are not limited thereto.

3. The heat-resistant flame-retardant polyurethane and its host-guest chemical preparation method according to claim 1, characterized in that, The organophosphorus compound is diphenylphosphine, diphenylphosphine, dibutylphosphine, or phenylbutylphosphine, but is not limited to these.

4. The flame-retardant and moisture-resistant thermoplastic polyurethane material according to claim 1 and its host-guest chemical preparation method, characterized in that, The phosphate flame retardant is sodium tripolyphosphate, ammonium polyphosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, but is not limited to these.

5. The heat-resistant flame-retardant polyurethane and its host-guest chemical preparation method according to claim 1, characterized in that, The first solvent is toluene, xylene, dichloromethane, chloroform, N,N-dimethylformamide, or N,N-dimethylacetamide, but is not limited thereto.

6. The heat-resistant flame-retardant polyurethane and its host-guest chemical preparation method according to claim 1, characterized in that, The second solvent is a solvent that is immiscible with water, such as chloroform, dichloromethane, or toluene, but is not limited to these.

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