Amphiphilic branched polymer / phosphoric acid flame retardant salifying complex modified damp-heat-resistant polyurethane

Abstract

The invention provides amphiphilic branched polymer / phosphoric acid flame retardant salt-forming complex modified damp-heat-resistant polyurethane, which is prepared by the following steps: reacting branched polyethyleneimine with aldehydes, evaporating and drying to obtain a Schiff base structure after the reaction is ended, reacting with DOPO in a solvent to prepare and synthesize an amphiphilic branched polymer with a hydrophobic DOPO shell, and utilizing an electrostatic interaction principle to prepare the amphiphilic branched polymer / phosphoric acid flame retardant salt-forming complex modified damp-heat-resistant polyurethane with the hydrophobic DOPO shell and the amphiphilic branched polymer / phosphoric acid flame retardant salt-forming complex modified damp-heat-resistant polyurethane. The preparation method comprises the following steps: forming a complex with a phosphoric acid flame retardant, carrying out solution blending on the complex and thermoplastic polyurethane, and carrying out spray drying to obtain the modified polyurethane material. The modified polyurethane has the advantages of favorable flame retardancy, favorable heat and humidity resistance, favorable compatibility and certain transparency.

Description

Technical Field

[0001] This invention relates to the field of chemical materials, and in particular to the preparation of an electrostatic complex of an amphiphilic branched polymer / phosphate-based flame retardant and its application in moisture- and heat-resistant polyurethane materials. Background Technology

[0002] Thermoplastic polyurethane (TPU) boasts stable chemical properties and excellent mechanical properties, making it widely applicable in aerospace and the booming new energy sector. With societal development, TPU elastomers have played a vital role across various fields. However, the presence of carbon (C) and hydrogen (H) elements in TPU makes it flammable, significantly limiting its applications. Therefore, adding flame retardants is crucial for addressing TPU's flammability. Due to its hydrophilic nature, water molecules easily penetrate the material, disrupting hydrogen bonds and lowering its glass transition temperature, leading to partial degradation. Some commonly used flame retardants are highly hydrophilic; their addition significantly reduces TPU's resistance to damp heat, and they are also prone to water loss. Furthermore, some commonly used flame retardants have poor compatibility with TPU, drastically reducing its transparency and mechanical strength.

[0003] Phosphorus and nitrogen-containing flame retardants are the most widely used. Their main components are organic compounds containing phosphorus or nitrogen. 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 flammability of the polymer. Nitrogen-containing flame retardants, on the other hand, absorb heat from the polymer during decomposition and produce non-flammable gases, diluting the flammable material to achieve a combustion concentration. Among various phosphorus-containing flame retardants, phosphate-based flame retardants have the most readily available sources and the lowest cost. If their strong hygroscopic weakness can be overcome, they will be advantageous for use in cost-conscious civilian polyurethane products.

[0004] Tertiary amine groups can form strong electrostatic interactions with carboxylic acid, sulfonic acid, and phosphoric acid groups, an interaction commonly used in layer-by-layer coating technology. This patent draws upon this principle. The shell-core structure of amphiphilic hyperbranched polyethyleneimine allows its internal tertiary amine groups to interact strongly with phosphoric acid-based flame retardants, thus enabling complexation, while the outer shell provides hydrophobic shielding. Furthermore, combining hyperbranched polyethyleneimine with phosphoric acid-based flame retardants can create a phosphorus-nitrogen synergistic flame-retardant effect.

[0005] Based on the above considerations, this invention provides a method for preparing low-cost flame-retardant thermoplastic polyurethane at low temperatures by encapsulating a low-cost phosphoric acid flame retardant with a shell-core structured amphiphilic hyperbranched polyethyleneimine to obtain a complex. The modified polyurethane exhibits excellent flame-retardant properties and resistance to damp heat. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing an electrostatic complex of an amphiphilic branched polymer and a phosphoric acid flame retardant, and its application in moisture- and heat-resistant polyurethane materials. A flame-retardant complex of an amphiphilic branched polymer and a phosphoric acid flame retardant was prepared using a salt-forming reaction and a corresponding phase transfer method, and then used for the modification of polyurethane.

[0007] The objective of this invention is achieved through the following technical solution: a moisture-resistant polyurethane modified with an amphiphilic branched polymer / phosphate-based flame retardant salt complex, comprising the following steps: (1) Add 1~6g of branched polyethyleneimine and 1~8g of aldehyde, and stir at 90~120℃ for 12~36h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1~5g of branched polyethyleneimine / aldehyde Schiff base, 1~8g of DOPO (CAS: 35948-25-5) and 50~150ml of solvent, and stir at 50~80℃ for 12~48h; after the reaction is completed, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phosphoric acid flame retardant and stirred at high speed until all solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate flame retardant electrostatic complex is dissolved in alcohol or ketone to form a concentrated solution, which is then dried and recovered in a closed spray dryer to finally obtain a humid heat resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane is less than 50%.

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

[0009] Furthermore, the phosphoric acid-based flame retardant is phosphoric acid, phytic acid, pyrophosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, but is not limited to these.

[0010] Furthermore, the solvent is toluene, xylene, dichloromethane, chloroform, N,N-dimethylformamide, or N,N-dimethylacetamide, but is not limited thereto.

[0011] The advantages of this invention are: This invention improves the flame retardant properties of composite materials by forming a complex with a highly branched polymer through electrostatic interaction of a phosphoric acid flame retardant. At the same time, the reaction of aromatic aldehydes and polyethyleneimine induces a certain cross-linking reaction during combustion. Grafting with DOPO (CAS: 35948-25-5) enhances the hydrophobic shielding and flame retardancy of the flame retardant complex material. The composite material's resistance to damp heat is improved, and it also exhibits good compatibility with thermoplastic polyurethane. Attached Figure Description

[0012] Figure 1 The images show the 1H NMR spectrum of the polyethyleneimine / aldehyde Schiff base polymer prepared in Example 1 and the 1H NMR spectrum of the hyperbranched polymer matrix with hydrophobic shell and hydrophilic core. Figure 2 It is a complete experimental process flowchart; Figure 3 The water absorption test of the flame-retardant thermoplastic polyurethane materials prepared in Examples 3-6 at 80°C for 168 hours; Figure 4 These are the flame retardant test results of the modified thermoplastic polyurethane materials in Examples 3, 4, 5, and 6. Figure 5 This is a photograph of the modified thermoplastic polyurethane sheet from Example 4. Detailed Implementation

[0013] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Example 1

[0014] (1) Add 1g of branched polyethyleneimine and 1g of salicylaldehyde, and stir at 90℃ for 12h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1g of DOPO (CAS: 35948-25-5) and 50ml of chloroform, and stir at 80℃ for 48h; after the reaction is complete, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain a branched polymer with a hydrophobic shell and a hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phytic acid and stirred at high speed until all the solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in acetone to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was less than 50%. Example 2

[0015] (1) Add 6g of branched polyethyleneimine and 8g of salicylaldehyde, and stir at 120℃ for 36h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 5g of branched polyethyleneimine / aldehyde Schiff base, 8g of DOPO (CAS: 35948-25-5) and 150ml of xylene, and stir at 50℃ for 12h; after the reaction is completed, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phytic acid and stirred at high speed until all the solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in methyl ethyl ketone to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was less than 50%. Example 3

[0016] (1) Add 1g of branched polyethyleneimine and 1.9g of phenylformaldehyde, and stir at 90℃ for 24h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of DOPO (CAS: 35948-25-5) and 100ml of toluene, and stir at 70℃ for 24h; after the reaction is completed, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phytic acid and stirred at high speed until all the solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in acetone to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was 5%. Example 4

[0017] (1) Add 1g of branched polyethyleneimine and 1.9g of phenylformaldehyde, and stir at 90℃ for 24h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of DOPO (CAS: 35948-25-5) and 100ml of toluene, and stir at 70℃ for 24h; after the reaction is completed, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phytic acid and stirred at high speed until all the solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in acetone to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was 10%. Example 5

[0018] (1) Add 1g of branched polyethyleneimine and 1.9g of phenylformaldehyde, and stir at 90℃ for 24h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of DOPO (CAS: 35948-25-5) and 100ml of toluene, and stir at 70℃ for 24h; after the reaction is completed, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phytic acid and stirred at high speed until all the solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in acetone to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was 15%. Example 6

[0019] (1) Add 1g of branched polyethyleneimine and 1.9g of phenylformaldehyde, and stir at 90℃ for 24h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of DOPO (CAS: 35948-25-5) and 100ml of toluene, and stir at 70℃ for 24h; after the reaction is completed, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phytic acid and stirred at high speed until all the solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in acetone to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was 20%. Example 7

[0020] (1) Add 4g of branched polyethyleneimine and 6.33g of formaldehyde, and stir at 120℃ for 36h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 2g of branched polyethyleneimine / aldehyde Schiff base, 1.52g of DOPO (CAS: 35948-25-5) and 100ml of N,N-dimethylformamide, and stir at 80℃ for 36h; after the reaction is completed, centrifuge the precipitate, and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of sodium dihydrogen phosphate and stirred at high speed until all solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphate flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in acetone to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was less than 50%. Example 8

[0021] (1) Add 1g of branched polyethyleneimine and 6g of p-methoxybenzaldehyde or halobenzaldehyde, and stir at 90℃ for 12h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base. (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 4.52g of DOPO (CAS: 35948-25-5) and 150ml of N,N-dimethylacetamide, and stir at 80℃ for 48h; after the reaction is completed, centrifuge the precipitate, and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of sodium dihydrogen phosphate and stirred at high speed until all solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphate flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in methyl ethyl ketone to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was less than 50%. Example 9

[0022] (1) Add 1g of branched polyethyleneimine and 1.266g of salicylaldehyde, and stir at 90℃ for 12h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1g of branched polyethyleneimine / aldehyde Schiff base, 7.25g of DOPO (CAS: 35948-25-5) and 150ml of N,N-dimethylacetamide, and stir at 80℃ for 48h; after the reaction is completed, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phytic acid and stirred at high speed until all the solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate-based flame retardant electrostatic complex was dissolved in isopropanol to form a concentrated solution, which was then dried and recovered using a closed-loop spray dryer to finally obtain a heat-resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane was 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 moisture-resistant polyurethane modified with an amphiphilic branched polymer / phosphate-based flame retardant salt complex, characterized in that, Includes the following steps: (1) Add 1~6g of branched polyethyleneimine and 1~8g of aldehydes, and stir at 90~120℃ for 12~36h; after the reaction is completed, evaporate and dry to obtain branched polyethyleneimine / aldehyde Schiff base; (2) Add 1~5g of branched polyethyleneimine / aldehyde Schiff base, 1~8g of DOPO (CAS: 35948-25-5) and 50~150ml of solvent, and stir at 50~80℃ for 12~48h; after the reaction is completed, centrifuge the precipitate and remove the solvent by rotary evaporation to obtain the branched polymer with hydrophobic shell and hydrophilic core. (3) The obtained branched polymer solid with hydrophobic shell and hydrophilic core is placed in an aqueous solution of phosphoric acid flame retardant and stirred at high speed until all solids dissolve in water through electrostatic interaction. After evaporation, an amphiphilic branched polymer / phosphoric acid flame retardant electrostatic complex is obtained. (4) The obtained amphiphilic branched polymer / phosphate flame retardant electrostatic complex is dissolved in alcohol or ketone to form a concentrated solution, which is then dried and recovered in a closed spray dryer to finally obtain a humid heat resistant polyurethane powder material. The mass ratio of the complex to the thermoplastic polyurethane is less than 50%.

2. The moisture-resistant polyurethane modified with an amphiphilic branched polymer / phosphate-based flame retardant salt complex according to claim 1, characterized in that, The aldehydes mentioned are salicylaldehyde, phenylformaldehyde, phenylacetaldehyde, 3-phenylpropanaldehyde, o-propenyloxybenzene, formaldehyde, p-methoxybenzaldehyde, or halogenated benzaldehyde, but are not limited thereto.

3. The moisture-resistant polyurethane modified with an amphiphilic branched polymer / phosphate-based flame retardant salt complex according to claim 1, characterized in that, The phosphoric acid flame retardant is phosphoric acid, phytic acid, pyrophosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, but is not limited to these.

4. The moisture-resistant polyurethane modified with an amphiphilic branched polymer / phosphate-based flame retardant salt complex according to claim 1, characterized in that, The solvent is toluene, xylene, dichloromethane, chloroform, N,N-dimethylformamide, or N,N-dimethylacetamide, but is not limited thereto.

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