Reactive flame-retardant polyol, preparation method and application thereof in high-strength high-resilience tear-resistant and durable flame-retardant polyurethane soft foam

Abstract

The application relates to the technical field of flame-retardant polyols and applications thereof, and discloses a reaction-type flame-retardant polyol, a preparation method and application of the reaction-type flame-retardant polyol in high-strength high-resilience tear-resistant long-lasting flame-retardant polyurethane soft foam, the reaction-type flame-retardant polyol has the following structure: wherein the structure of R includes any one of three structures, and n is any number in 2-4; based on the structure design, the reaction-type flame-retardant polyol is introduced into the polyurethane soft foam, so that the prepared polyurethane soft foam has excellent comprehensive performances such as high strength, high resilience, tear resistance and high flame retardancy, and can meet the requirements of safety, comfort and mechanical properties of materials in more extensive application fields.

Description

Technical Field

[0001] This invention relates to the field of flame-retardant polyols and their application technology, specifically to a reactive flame-retardant polyol, its preparation method, and its application in high-strength, high-resilience, tear-resistant, durable flame-retardant polyurethane flexible foam. Background Technology

[0002] Flexible polyurethane foam (FPUF) is characterized by high resilience, low density, and environmental friendliness, and is widely used in furniture cushioning, car seat cushioning, sound insulation, and packaging materials. However, as an open-cell organic polymer foam, FPUF has a large surface area and good air permeability, making it highly flammable. The limiting oxygen index (LOI) of untreated FPUF is typically around 16-18%, which releases a large amount of heat, smoke, and toxic gases in a fire, seriously threatening people's lives, property, and safety. Therefore, improving the flame retardant properties of FPUF is crucial for its safe application.

[0003] Currently, there are two main approaches to impart flame retardancy to polymer matrices: one is to introduce flame-retardant structures into the matrix through chemical reactions; the other is to add flame retardants through physical blending. From the perspective of economics and process feasibility, the application of additive flame retardants is more common. However, they usually require a high addition amount to achieve the desired flame retardant effect, which often damages the mechanical properties of the material. Furthermore, flame retardants tend to migrate to the surface over time, leading to a decrease in flame retardant durability. Therefore, developing reactive flame retardants that can form chemical bonds with the matrix has become a key direction for simultaneously improving the flame retardancy and mechanical properties of polyurethane foam.

[0004] For example, Chinese patent CN102167791B discloses a polyurethane flexible foam with durable flame retardancy and high pressure sag hardness. This is achieved by simultaneously introducing phosphorus-based and halogen-based polyols to improve the flame retardancy of the polyurethane flexible foam. However, the introduction of halogen-based flame retardants causes the material to release large amounts of smoke and toxic gases during combustion, seriously endangering human health and polluting the environment. Another example is Chinese patent application CN116675825A, which discloses a reactive flame-retardant polyurethane flexible foam with a phosphate ester structure and its preparation method. This method obtains a flame-retardant polyurethane flexible foam with a phosphate ester structure through the reaction of diethanolamine and phytic acid. Using PADEA as a raw material to prepare polyurethane flexible foam improves its flame retardant properties, but does not improve tensile strength, tear resistance, and resilience. Another example is Chinese patent application CN107501509A, which discloses a phosphorus-nitrogen synergistic flame-retardant polyurethane flexible foam. This foam is prepared by using 4,4'-[1,4-phenyl-diethyl bisphosphite-dimethylimino)]diphenol as a reactive flame retardant. The modified foam exhibits significantly improved flame retardant properties, tear resistance, and compressive strength. However, due to the large rigid structure in the polyol, the foam's resilience decreases considerably.

[0005] Therefore, designing and synthesizing a halogen-free reactive flame-retardant polyol and introducing it as a key component into the FPUF system to achieve synergistic improvement in flame-retardant and mechanical properties is of great significance for the functionalization and high performance of FPUF. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a reactive flame-retardant polyol, which has the following structure:

[0007] ;

[0008] The structure of R includes , , Any of the three structures, where n is any number from 2 to 4.

[0009] A method for preparing the aforementioned reactive flame-retardant polyol includes the following steps:

[0010] Step S1: Diphenylphosphine, paraformaldehyde, and diethanolamine are dissolved in chloroform and reacted. After cooling to room temperature, the crude product is obtained by filtration and rotary evaporation. The crude product is then dissolved in dichloroform and further purified by multiple extractions with deionized water, saturated saline solution, and saturated sodium bicarbonate solution. The product is then dried with anhydrous sodium sulfate and concentrated by rotary evaporation. Finally, it is dried in a vacuum oven at -0.1 MPa and 100-110°C for 18-20 hours to obtain a reactive flame-retardant polyol intermediate.

[0011] The structural formula of the reactive flame-retardant polyol intermediate is as follows:

[0012] ;

[0013] Step S2: Under a nitrogen atmosphere, the reactive flame-retardant polyol intermediate is mixed with triethylamine in chloroform, and then added to a dichlorodimethylsilane / chloroform solution under ice bath conditions for a first reaction. Finally, a diol / chloroform solution is added for a second reaction. After cooling to room temperature, the mixture is purified. The purification steps are the same as in S1 to obtain the reactive flame-retardant polyol.

[0014] Preferably, in step S1, the molar ratio of diphenylphosphine, paraformaldehyde, and diethanolamine is 1:(1-2):(0.8-1.2).

[0015] Preferably, in step S1, the reaction conditions are: under a nitrogen atmosphere, at 50-60°C for 14-16 hours.

[0016] Preferably, in step S2, the molar ratio of the reactive flame-retardant polyol intermediate, dichlorodimethylsilane, and diol is 1:2:(1-1.2); the diol includes any one of 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol.

[0017] Preferably, in step S2, the first reaction conditions are: reacting in an ice bath for 2 hours, then heating to 55-60℃ and continuing the reaction for 3-4 hours; the second reaction conditions are: reacting at 55-60℃ for 4-6 hours.

[0018] A high-strength, high-resilience, tear-resistant, durable flame-retardant polyurethane flexible foam comprising the aforementioned reactive flame-retardant polyol, comprising the following components by weight:

[0019] 85-95 parts of polyether polyol;

[0020] 5-15 parts of reactive flame-retardant polyol;

[0021] 2.5-3.5 parts of chemical foaming agent;

[0022] Crosslinking agent 0.2-0.6 parts;

[0023] Catalyst 1.0-1.8 parts;

[0024] Foam stabilizer 0.4-0.8 parts;

[0025] 2.6-3.0 parts of pore-opening agent;

[0026] 60-80 parts of isocyanate.

[0027] Preferably, the number-average molecular weight of the polyether polyol is 4000-6000 g / mol, and the functionality of the polyether polyol is 2-4.

[0028] Preferably, the chemical foaming agent comprises water; the crosslinking agent comprises at least one of glycerol, diethanolamine, and triethanolamine; and the catalyst comprises at least one of the following: environmentally friendly organic bismuth catalyst AUCAT-1001E (Guangzhou Yourun Synthetic Materials Co., Ltd.), environmentally friendly organic bismuth zinc catalyst BX-EM14 (Guangzhou Yourun Synthetic Materials Co., Ltd.), environmentally friendly organic bismuth zinc catalyst BX-EM23 (Guangzhou Yourun Synthetic Materials Co., Ltd.), N,N-dimethylcyclohexylamine, N-methylmorpholine, and triethylenediamine.

[0029] Preferably, the foam stabilizer includes at least one of silicone oil L-580, silicone oil L-3639, and silicone oil Y-10366; the cell opener includes at least one of ZLY-1900, GK-150, and KF-28.

[0030] Preferably, the isocyanate includes at least one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), modified diphenylmethane diisocyanate (MDI-2412), polyphenylmethane polyisocyanate (pMDI), 1,5-naphthalene diisocyanate (NDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI).

[0031] A method for preparing the high-strength, high-resilience, tear-resistant, durable, flame-retardant polyurethane flexible foam includes the following steps:

[0032] Step 1: Mix the polyether polyol, reactive flame-retardant polyol, chemical foaming agent, crosslinking agent, catalyst, foam stabilizer, and cell opener according to the above weight ratio, and stir at 1500-3000 r / min for 3-5 min to obtain component A; wherein, the reactive flame-retardant polyol is heated to 40°C before use. Preheat at 80℃ for 10 minutes 20 minutes;

[0033] Step 2: Use isocyanate as component B;

[0034] Step 3: Mix component A and component B at a speed of 1500-3000 r / min, stir and foam, cure at 60-80℃ for 24-28 hours, and then mature at room temperature for 24 hours.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] This invention discloses a reactive flame-retardant polyol that reacts chemically with isocyanate to become a structural component of a polyurethane matrix, thereby effectively preventing the migration of flame-retardant components and ensuring that the material has long-term stable flame-retardant properties.

[0037] The reactive flame-retardant polyol of this invention is designed with a side chain containing a flame-retardant rigid benzene ring structure. While maintaining the flexibility of the main chain conformation, it has little impact on the chain segment mobility. It ensures that the material has high strength and tear resistance while maintaining high elasticity and flexibility. Furthermore, the tertiary amine structure where the nitrogen atom is located has high polarity, which increases the intermolecular forces between chain segments and helps to improve the strength and tear resistance of the material. Moreover, the side chain flame-retardant structure can preferentially break at a lower temperature than the main chain flame-retardant structure, releasing the active free radical scavenger more rapidly, thereby further improving the flame-retardant performance of the material.

[0038] In the molecular structure of the reactive flame-retardant polyol of the present invention, the rigid phosphorus-nitrogen flame-retardant unit and the flexible siloxane are connected by a long-chain alkane flexible spacer segment. The spacer segment can regulate the phase separation behavior between the rigid flame-retardant unit and the siloxane segment, thereby regulating the flexibility of the molecular chain. The synergistic effect of the above segments not only improves the mechanical strength and flame retardancy of the polyurethane flexible foam material, but also improves its resilience and dimensional stability.

[0039] In summary, based on the above structural design, through the synergistic flame-retardant effect of phosphorus, nitrogen, and silicon elements, combined with the combined action of rigid benzene rings, tertiary amine structures, and flexible siloxane segments, and by inserting long-chain alkane flexible spacers between the rigid phosphorus and nitrogen flame-retardant units and the flexible siloxane segments, the phase separation behavior between the rigid flame-retardant units and the siloxane segments is controlled to further regulate the flexibility of the molecular chains. This results in a polyurethane flexible foam with high tensile strength, tear resistance, high compressive strength, high dimensional stability, high resilience, and long-lasting flame retardancy, which can meet the safety, comfort, and mechanical performance requirements of a wider range of application fields. Attached Figure Description

[0040] Figure 1 This is the structural formula of the reactive flame-retardant polyol of the present invention; wherein, the structure of R includes , , Any of the three structures, where n is any number from 2 to 4;

[0041] Figure 2 This is the structural formula of the reactive flame-retardant polyol intermediate of the present invention;

[0042] Figure 3 The Fourier transform infrared spectra of the reactive flame-retardant polyol intermediate and the reactive flame-retardant polyol prepared in this invention are shown. Detailed Implementation

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely illustrated below. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] This embodiment discloses a method for preparing a reactive flame-retardant polyol, including the following steps:

[0046] Step S1: Dissolve 0.3 mol diphenylphosphine, 0.45 mol paraformaldehyde and 0.3 mol diethanolamine in 200 mL of chloroform and react at 60 °C for 14 hours under a nitrogen atmosphere. After cooling to room temperature, purify the product (the specific purification steps are: obtain crude product by filtration and rotary evaporation, then dissolve crude product in dichloroform and further purify by multiple extractions with deionized water, saturated saline solution and saturated sodium bicarbonate solution, then dry with anhydrous sodium sulfate, then concentrate the product by rotary evaporation, and then dry it in a vacuum oven at -0.1 MPa and 110 °C for 18 hours to obtain a reactive flame-retardant polyol intermediate).

[0047] Step S2: Under a nitrogen atmosphere, 0.3 mol of the reactive flame-retardant polyol intermediate was mixed with 1.0 mol of triethylamine in 200 mL of chloroform. Then, under ice bath conditions, the mixture was added to 150 mL of dichlorodimethylsilane / chloroform solution, wherein the concentration of dichlorodimethylsilane in the dichlorodimethylsilane / chloroform solution was 4 mol / L. After reacting for 2 hours, the temperature was gradually increased to 55 °C and the reaction was continued for another 4 hours. Subsequently, 50 mL of 1,5-pentanediol / chloroform solution was added to the system, wherein the concentration of 1,5-pentanediol in the 1,5-pentanediol / chloroform solution was 6.6 mol / L, and the reaction was continued for 5 hours. After cooling to room temperature, the mixture was purified using the same purification steps as in S1 to obtain the reactive flame-retardant polyol.

[0048] Example 2

[0049] This embodiment discloses a method for preparing high-strength, high-resilience, tear-resistant, durable, and flame-retardant polyurethane flexible foam, including the following steps:

[0050] Step 1: Mix the polyether polyol with a number average molecular weight of 5000 g / mol and a functionality of 3, the reactive flame-retardant polyol prepared in Example 1, water, glycerol, environmentally friendly organic bismuth zinc catalyst BX-EM23, triethylenediamine, silicone oil L-580 (foam stabilizer), and KF-28 (cell opener) in the specified proportions, and stir at 3000 r / min for 3 min to obtain component A; wherein, the reactive flame-retardant polyol is preheated at 60°C for 15 minutes before use;

[0051] Step 2: Use modified diphenylmethane diisocyanate (MDI-2412) as component B;

[0052] Step 3: Mix component A and component B at a speed of 3000 r / min, stir, and then inject into a mold for foaming. Cure at 80°C for 24 hours, and then cure at room temperature for 24 hours to obtain high-strength, high-resilience, tear-resistant, durable, and flame-retardant polyurethane flexible foam.

[0053] Examples 3-4

[0054] Compared with Example 2, Examples 3-4 adjusted the amount of reactive flame-retardant polyol added during the preparation of component A, while keeping other conditions unchanged.

[0055] Comparative Example 1

[0056] This comparative example discloses a method for preparing a reactive flame-retardant polyol, comprising the following steps:

[0057] Step S1: Dissolve 0.3 mol diphenylphosphine, 0.45 mol paraformaldehyde and 0.3 mol diethanolamine in 200 mL chloroform, react at 60 °C for 14 hours under nitrogen atmosphere, cool to room temperature and purify to obtain a reactive flame-retardant polyol intermediate.

[0058] Step S2: Under a nitrogen atmosphere, 0.33 mol of reactive flame-retardant polyol intermediate and 1.0 mol of triethylamine were mixed in 200 mL of chloroform. Then, 200 mL of reactive flame-retardant polyol intermediate / chloroform solution containing 0.3 mol of dichlorodimethylsilane was added at 55 °C. The mixture was reacted for 5 hours, cooled to room temperature, and purified to obtain reactive flame-retardant polyol.

[0059] Comparative Example 2

[0060] This comparative example discloses a method for preparing a reactive flame-retardant polyol, comprising the following steps:

[0061] Step S1: Dissolve 0.3 mol diphenylphosphine, 0.45 mol paraformaldehyde and 0.3 mol diethanolamine in 200 mL chloroform, react at 60 °C for 14 hours under nitrogen atmosphere, cool to room temperature and purify to obtain a reactive flame-retardant polyol intermediate.

[0062] Step S2: Under a nitrogen atmosphere, 0.3 mol of the reactive flame-retardant polyol intermediate was mixed with 1.0 mol of triethylamine in 200 mL of chloroform, and then added to 150 mL of dichlorodimethylsilane / chloroform solution under ice bath conditions. The concentration of dichlorodimethylsilane in the dichlorodimethylsilane / chloroform solution was 4 mol / L. After reacting for 2 hours, the temperature was gradually increased to 55 °C and the reaction was continued for another 4 hours. Subsequently, 50 mL of 1,3-propanediol / chloroform solution was added to the system. The concentration of 1,3-propanediol in the 1,3-propanediol / chloroform solution was 6.6 mol / L, and the reaction was carried out for 5 hours. After cooling to room temperature, the mixture was purified to obtain the reactive flame-retardant polyol.

[0063] Comparative Example 3

[0064] This comparative example discloses a method for preparing a reactive flame-retardant polyol, comprising the following steps:

[0065] Step S1: Dissolve 0.3 mol diphenylphosphine, 0.45 mol paraformaldehyde and 0.3 mol diethanolamine in 200 mL chloroform, react at 60 °C for 14 hours under nitrogen atmosphere, cool to room temperature and purify to obtain a reactive flame-retardant polyol intermediate.

[0066] Step S2: Under a nitrogen atmosphere, 0.3 mol of the reactive flame-retardant polyol intermediate was mixed with 1.0 mol of triethylamine in 200 mL of chloroform, and then added to 150 mL of dichlorodimethylsilane / chloroform solution under ice bath conditions. The concentration of dichlorodimethylsilane in the dichlorodimethylsilane / chloroform solution was 4 mol / L. After reacting for 2 hours, the temperature was gradually increased to 55 °C and the reaction was continued for another 4 hours. Subsequently, 50 mL of 1,4-butanediol / chloroform solution was added to the system. The concentration of 1,4-butanediol in the 1,4-butanediol / chloroform solution was 6.6 mol / L, and the reaction was carried out for 5 hours. After cooling to room temperature, the mixture was purified to obtain the reactive flame-retardant polyol.

[0067] Comparative Example 4

[0068] This comparative example discloses a method for preparing a reactive flame-retardant polyol, comprising the following steps:

[0069] Step S1: 0.3 mol dimethyl methylphosphonate, 0.6 mol diethanolamine and 2 ml tetrabutyl titanate were subjected to transesterification reaction at 150 °C for 6 hours under nitrogen atmosphere. After cooling to room temperature, the mixture was purified to obtain a reactive flame-retardant polyol intermediate.

[0070] Step S2: Under a nitrogen atmosphere, 0.3 mol of the reactive flame-retardant polyol intermediate was mixed with 1.0 mol of triethylamine in 200 mL of chloroform, and then added to 150 mL of dichlorodimethylsilane / chloroform solution under ice bath conditions. The concentration of dichlorodimethylsilane in the dichlorodimethylsilane / chloroform solution was 4 mol / L. After reacting for 2 hours, the temperature was gradually increased to 55 °C and the reaction was continued for another 4 hours. Subsequently, 50 mL of 1,5-pentanediol / chloroform solution was added to the system. The concentration of 1,5-pentanediol in the 1,5-pentanediol / chloroform solution was 6.6 mol / L, and the reaction was continued for 5 hours. After cooling to room temperature, the mixture was purified to obtain the reactive flame-retardant polyol.

[0071] Comparative Example 5

[0072] This comparative example discloses a method for preparing a reactive flame-retardant polyol, comprising the following steps:

[0073] Step S1: 0.3 mol benzylphosphonate diethyl ester, 0.6 mol diethanolamine and 2 ml tetrabutyl titanate were subjected to transesterification reaction at 150 °C for 6 hours under nitrogen atmosphere. After cooling to room temperature, the mixture was purified to obtain a reactive flame-retardant polyol intermediate.

[0074] Step S2: Under a nitrogen atmosphere, 0.3 mol of the reactive flame-retardant polyol intermediate was mixed with 1.0 mol of triethylamine in 200 mL of chloroform, and then added to 150 mL of dichlorodimethylsilane / chloroform solution under ice bath conditions. The concentration of dichlorodimethylsilane in the dichlorodimethylsilane / chloroform solution was 4 mol / L. After reacting for 2 hours, the temperature was gradually increased to 55 °C and the reaction was continued for another 4 hours. Subsequently, 50 mL of 1,5-pentanediol / chloroform solution was added to the system. The concentration of 1,5-pentanediol in the 1,5-pentanediol / chloroform solution was 6.6 mol / L, and the reaction was continued for 5 hours. After cooling to room temperature, the mixture was purified to obtain the reactive flame-retardant polyol.

[0075] Comparative Example 6

[0076] Compared with Example 2, Comparative Example 6 used the reactive flame-retardant polyol prepared in Comparative Example 1 in the preparation of component A, while other conditions remained unchanged.

[0077] Comparative Example 7

[0078] Compared with Example 2, Comparative Example 7 used the reactive flame-retardant polyol prepared in Comparative Example 2 in the preparation of component A, while other conditions remained unchanged.

[0079] Comparative Example 8

[0080] Compared with Example 2, Comparative Example 8 used the reactive flame-retardant polyol prepared in Comparative Example 3 in the preparation of component A, while other conditions remained unchanged.

[0081] Comparative Example 9

[0082] Compared with Example 2, Comparative Example 9 used the reactive flame-retardant polyol prepared in Comparative Example 4 in the preparation of component A, while other conditions remained unchanged.

[0083] Comparative Example 10

[0084] Compared with Example 2, Comparative Example 10 used the reactive flame-retardant polyol prepared in Comparative Example 5 in the preparation of component A, while other conditions remained unchanged.

[0085] Comparative Example 11

[0086] Compared with Example 2, Comparative Example 11 used the reactive flame-retardant polyol intermediate prepared in Example 1 instead of the reactive flame-retardant polyol prepared in Example 1 during the preparation of component A, while all other conditions remained unchanged.

[0087] Comparative Example 12

[0088] Compared with Example 2, Comparative Example 12 used the additive flame retardant DMMP (dimethyl methylphosphonate) instead of the reactive flame retardant polyol prepared in Example 1 during the preparation of component A, while other conditions remained unchanged.

[0089] Comparative Example 13

[0090] Compared with Example 2, Comparative Example 13 used the additive flame retardant DOPO (9,10) in the preparation of component A. Dihydrogen 9 Oxygen 10 Phosphorus phenanthrene 10 The oxide was used instead of the reactive flame-retardant polyol prepared in Example 1, and all other conditions remained unchanged.

[0091] Comparative Example 14

[0092] Compared with Example 2, Comparative Example 14 did not add the reactive flame-retardant polyol prepared in Example 1 during the preparation of component A, and all other conditions remained unchanged.

[0093] In the above examples and comparative examples, the environmentally friendly organic bismuth zinc catalyst BX-EM23 was from Guangzhou Yourun Synthetic Materials Co., Ltd.; the foam stabilizer silicone oil L-580 was from Momentive Corporation of the United States; the cell opener KF-28 was from Jiangsu Zhongshan Chemical Co., Ltd.; and the modified diphenylmethane diisocyanate MDI-2412 was from Huntsman Corporation of the United States.

[0094] In Examples 2-4 and Comparative Examples 6-14 above, the raw materials and their amounts (by weight) in the preparation process of high-strength, high-resilience, tear-resistant, durable, and flame-retardant polyurethane flexible foam are shown in Table 1:

[0095] Table 1

[0096]

[0097] Experimental Example

[0098] 1. Fourier transform infrared spectroscopy analysis was performed on the reactive flame-retardant polyol intermediate and the reactive flame-retardant polyol prepared in Example 1 of the present invention;

[0099] Test results as follows Figure 3 As shown, Figure 3 This is the Fourier transform infrared spectrum of the reactive flame-retardant polyol intermediate and the reactive flame-retardant polyol prepared by this invention. The spectrum is shown at 2313 cm⁻¹. -1 The disappearance of the characteristic peak attributed to the PH bond of diphenylphosphine oxide indicates that the PH bond reaction is complete; the reactive flame-retardant polyol intermediate and the reactive flame-retardant polyol have peaks at 3283 cm⁻¹. -1 and 3372cm -1 A broad characteristic peak was generated at 2847 cm⁻¹, indicating the formation of -OH groups. -1 2937cm -1 The characteristic peak at 793 cm⁻¹ indicates the generation of -CH₂ groups; simultaneously, the reactive flame-retardant polyol at 793 cm⁻¹... -1 The characteristic peaks at the point indicate the formation of Si-C bonds; the characteristic peaks of specific groups in the figure show that the reactive flame-retardant polyol intermediate and reactive flame-retardant polyol prepared in this embodiment were successfully synthesized.

[0100] II. Test specimens were prepared from the high-strength, high-resilience, tear-resistant, durable, and flame-retardant polyurethane flexible foams prepared in Examples 2-4 and Comparative Examples 6-14, and the performance of each test specimen was tested according to the following standards:

[0101] (1) Tensile strength test: Tested according to ISO 1798-2008 standard, at a rate of 500 mm / min;

[0102] (2) Elongation at break test: Tested according to ISO 1798-2008 standard, at a rate of 500 mm / min;

[0103] (3) Tear strength test: Tested according to ISO 8067-2008 standard, at a rate of 100 mm / min;

[0104] (4) Compression strength test: Tested according to ISO 3386-2015 standard, at a rate of 100 mm / min;

[0105] (5) Compression set test: Tested according to ISO 1856-2018 standard;

[0106] (6) Resilience test: Tested according to ISO 8307-2018 standard;

[0107] (7) Limiting oxygen index test: Tested according to ISO 4589-2017 standard;

[0108] (8) Accelerated thermal aging limiting oxygen index test: Tested according to ISO 2440-2025 standard.

[0109] The test results for the above performance tests are shown in Table 2:

[0110] Table 2

[0111]

[0112] As shown in Table 2, introducing the reactive flame-retardant polyol of the present invention into the structure of the polyurethane matrix as a reactant can endow polyurethane flexible foam with excellent comprehensive properties such as high strength, high resilience, tear resistance and high flame retardancy.

[0113] A comparison of Examples 3-4 with Example 2 shows that as the amount of reactive flame-retardant polyol added increases, the strength and tear resistance of the polyurethane foam first increase and then decrease. This is because the rigid benzene ring structure and tertiary amine structure of the reactive flame-retardant polyol can enhance the strength and tear resistance of the foam when an appropriate amount is introduced. However, excessive introduction of reactive flame-retardant polyol can cause local stress concentration due to the rigid benzene ring structure, which reduces the strength and tear resistance of the foam. Meanwhile, the elongation at break, resilience, and dimensional stability gradually decrease because the increased rigidity restricts the movement of molecular chains. At the same time, it can be seen that the synergistic flame-retardant effect of phosphorus, nitrogen, and silicon elements is enhanced with the increase of the amount of reactive flame-retardant polyol added.

[0114] As can be seen from the comparison between Comparative Example 6 and Comparative Examples 7-8 and Example 2, the lack of a flexible long-chain spacer between the rigid flame-retardant unit and the flexible siloxane chain segment results in poor mechanical properties, dimensional stability and resilience of the polyurethane flexible foam. This is because the rigid flame-retardant unit is directly connected to the flexible siloxane, resulting in poor microphase separation between the hard and soft segments, making it easier to form a "microphase mixture" structure. The flexible siloxane is suppressed by the adjacent rigid structure, which severely restricts the movement of the molecular chain. At the same time, the lack of stress buffering and transition between the rigid and flexible parts makes it easier to form stress concentration points.

[0115] A comparison of Comparative Examples 7-8 with Example 2 shows that, compared to 1,3-propanediol and 1,4-butanediol, the polyurethane flexible foam prepared using reactive flame-retardant polyols synthesized from 1,5-pentanediol exhibits improved performance in all aspects except for flame retardancy. This is because the spacer segments of 1,3-propanediol and 1,4-butanediol are shorter than those of 1,5-pentanediol, resulting in insufficient spatial distance between the rigid flame-retardant units and the flexible siloxane segments. This leads to a lack of transition between the rigid and flexible segments, incomplete microphase separation, and "adhesion" between the rigid and flexible segments, affecting the overall performance of the polyurethane flexible foam. In contrast, 1,5-pentanediol has the optimal spacer segment length, resulting in the best microphase separation. In addition to its structural integrity, the longer flexible segments in 1,5-pentanediol provide greater spatial freedom, which helps release internal stress, reduces stress concentration caused by the introduction of rigid units, and optimizes interfacial compatibility, ensuring stress transition between rigid and flexible segments. The reduced flame retardancy of the polyurethane flexible foam in Example 2 is due to the shorter average distance between phosphorus, nitrogen, and silicon flame retardant units in the reactive flame retardant polyol synthesized from 1,3-propanediol and 1,4-butanediol. During combustion, the flame retardant elements are released more concentratedly, further enhancing the synergistic flame retardant effect between phosphorus, nitrogen, and silicon. However, overall, its flame retardancy is not significantly different from that of 1,3-propanediol and 1,4-butanediol.

[0116] A comparison of Comparative Examples 9-10 and Example 2 shows that the introduction of the biphenyl ring structure in the reactive flame-retardant polyol of Example 2 significantly improves the strength and tear resistance of the polyurethane flexible foam. Furthermore, the elongation at break and resilience of Example 2 are superior to those of Comparative Example 10. This is attributed to the presence of a rigid flame-retardant structure in the side chain of the flame-retardant polyol in Example 2, which has minimal interference with the conformation and flexibility of the main chain, allowing the main chain to maintain high chain segment mobility. In contrast, the rigid flame-retardant structure in Comparative Example 10 is located in the polyol main chain, which, while contributing to improved strength, severely restricts chain segment mobility. Additionally, the flame retardancy of Example 2 is superior to that of Comparative Example 10 because the side chain... Compared to the main chain flame-retardant structure, the flame-retardant structure usually breaks preferentially at lower temperatures, allowing for faster release of active free radical scavengers. In Comparative Example 9, dimethyl methylphosphonate was used as the phosphorus-containing component. Compared to Comparative Example 10 and Example 2, dimethyl methylphosphonate lacks a benzene ring structure. The benzene ring structure can enhance the rigidity of polyurethane flexible foam, thereby improving the strength and tear resistance of polyurethane flexible foam. At the same time, as an excellent char precursor, the benzene ring structure is more easily cross-linked and aromatized during combustion, and forms a denser and continuous char layer with substances such as polyphosphoric acid produced by the decomposition of phosphorus-containing groups. This effectively isolates heat and oxygen, improving the flame-retardant performance of polyurethane flexible foam.

[0117] As can be seen from the comparison between Comparative Example 11 and Example 2, the introduction of flexible siloxane segments into the rigid phosphorus-nitrogen flame-retardant unit of the reactive flame-retardant polyol, and the use of long-chain alkanes as spacer segments to regulate the phase separation behavior between them and the rigid flame-retardant unit, effectively solves the problem of a significant reduction in the resilience and dimensional stability of polyurethane flexible foam caused by the introduction of rigid structure. At the same time, the synergistic flame-retardant effect of phosphorus, nitrogen and silicon elements further improves the flame retardancy of polyurethane flexible foam. Therefore, the polyurethane flexible foam prepared in Example 2 has comprehensive excellent properties such as high strength, high resilience, tear resistance and long-lasting flame retardancy.

[0118] A comparison of Comparative Examples 12-14 with Example 2 shows that the halogen-free reactive flame-retardant polyol of the present invention can effectively improve the long-lasting flame retardancy of polyurethane flexible foam. Simultaneously, it can be observed that, compared to unmodified polyurethane flexible foam, the strength, tear resistance, and resilience of polyurethane flexible foam using dimethyl methylphosphonate as a flame retardant are all reduced. This is because dimethyl methylphosphonate, as a low-viscosity small-molecule liquid, acts as an inert, non-reactive diluent in polyurethane flexible foam, physically isolating and diluting the polar groups in the molecules, reducing intermolecular forces. Furthermore, dimethyl methylphosphonate... Methyl ester has poor compatibility with the polyurethane matrix, forming weak interfacial regions at the microscopic level. These regions become stress concentration points under stress, accelerating material failure. Furthermore, its addition dilutes the density of chemical crosslinking points, interfering with the formation of hard segment micro-regions and disrupting the microphase separation structure between the elastic soft segments and the strength-enhancing hard segments in the foam. While polyurethane flexible foams using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as a flame retardant show some improvement in strength and tear resistance, this molecule contains rigid and large planar fused rings that are difficult to rotate. Furthermore, adding this substance to polyurethane flexible foam easily leads to agglomeration, severely restricting the conformational changes of the soft segments. This results in a significant decrease in the elongation at break, dimensional stability, and resilience of the prepared polyurethane flexible foam. However, after adding the reactive flame-retardant polyol described in this invention, compared with unmodified polyurethane flexible foam and polyurethane flexible foam prepared with additive flame retardants, the tensile strength, elongation at break, tear resistance, compressive strength, and flame retardant properties of the resulting material are significantly improved. The resilience is also better than that of polyurethane flexible foam prepared with additive flame retardants (dimethyl methylphosphonate, 9,10-dihydro-9-oxa-10- The performance of phosphorus-phenanthrene-10-oxide was significantly improved. This is because the reactive flame-retardant polyol described in this invention has a much higher interfacial compatibility compared to the two additive flame retardants mentioned above, avoiding the destruction of the microphase separation structure between the soft and hard segments. Furthermore, through the synergistic flame-retardant effect of phosphorus, nitrogen, and silicon elements, combined with the combined action of rigid benzene rings, tertiary amine structures, and flexible siloxane segments, and by inserting long-chain alkane flexible spacers between the rigid phosphorus and nitrogen flame-retardant units and the flexible siloxane segments, the phase separation behavior between the rigid units and the siloxane segments is regulated, thereby improving the overall performance of the material.

[0119] The above results indicate that the reactive flame-retardant polyol synthesized in this invention can significantly improve the strength and tear resistance of polyurethane flexible foam and endow it with good long-lasting flame retardancy. At the same time, it solves the problem that the introduction of rigid structure leads to a significant reduction in the resilience of polyurethane flexible foam. The prepared polyurethane flexible foam has comprehensive excellent properties such as high strength, high resilience, tear resistance and long-lasting flame retardancy, and has high application value in a variety of fields.

[0120] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A reactive flame-retardant polyol, characterized in that, The reactive flame-retardant polyol has the following structure: ； The structure of R in the formula includes , , Any of the three structures, where n is any number from 2 to 4.

2. A method for preparing the reactive flame-retardant polyol as described in claim 1, characterized in that, Includes the following steps: Step S1: Diphenylphosphine oxide, paraformaldehyde and diethanolamine are dissolved in chloroform, reacted, cooled to room temperature and purified to obtain a reactive flame-retardant polyol intermediate; Step S2: Under a nitrogen atmosphere, the reactive flame-retardant polyol intermediate is mixed with triethylamine in chloroform, and then added to a dichlorodimethylsilane / chloroform solution under ice bath conditions for a first reaction. Finally, a diol / chloroform solution is added for a second reaction. After cooling to room temperature, the mixture is purified to obtain the reactive flame-retardant polyol.

3. The method according to claim 2, characterized in that, In step S1, the molar ratio of diphenylphosphine, paraformaldehyde, and diethanolamine is 1:(1-2):(0.8-1.2).

4. The method according to claim 2, characterized in that, In step S1, the reaction conditions are: under a nitrogen atmosphere, at 50-60°C for 14-16 hours.

5. The method according to claim 2, characterized in that, In step S2, the molar ratio of the reactive flame-retardant polyol intermediate, dichlorodimethylsilane, and diol is 1:2:(1-1.2); the diol includes 1,5-pentanediol.

6. The method according to claim 2, characterized in that, In step S2, the first reaction conditions are: react in an ice bath for 2 hours, then raise the temperature to 55-60℃ and continue the reaction for 3-4 hours; the second reaction conditions are: react at 55-60℃ for 4-6 hours.

7. A high-strength, high-resilience, tear-resistant, durable flame-retardant polyurethane flexible foam comprising the reactive flame-retardant polyol of claim 1, characterized in that, By weight, it comprises the following components: 85-95 parts of polyether polyol; 5-15 parts of reactive flame-retardant polyol; 2.5-3.5 parts of chemical foaming agent; Crosslinking agent 0.2-0.6 parts; Catalyst 1.0-1.8 parts; Foam stabilizer 0.4-0.8 parts; 2.6-3.0 parts of pore-opening agent; 60-80 parts of isocyanate.

8. The high-strength, high-resilience, tear-resistant, durable, flame-retardant polyurethane flexible foam according to claim 7, characterized in that, The chemical foaming agent includes water; the crosslinking agent includes at least one of glycerol, diethanolamine, and triethanolamine; and the catalyst includes at least one of AUCAT-1001E, BX-EM14, BX-EM23, N,N-dimethylcyclohexylamine, N-methylmorpholine, and triethylenediamine.

9. The high-strength, high-resilience, tear-resistant, durable, flame-retardant polyurethane flexible foam according to claim 7, characterized in that, The isocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, modified diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

10. A method for preparing the high-strength, high-resilience, tear-resistant, durable, flame-retardant polyurethane flexible foam as described in claim 7, characterized in that, Includes the following steps: Step 1: Mix the polyether polyol, reactive flame-retardant polyol, chemical foaming agent, crosslinking agent, catalyst, foam stabilizer, and cell opener according to the weight ratio described in claim 7, and stir at a speed of 1500-3000 r / min for 3-5 min to obtain component A; wherein, the reactive flame-retardant polyol is heated to 40 °C before use. Preheat at 80℃ for 10 minutes 20 minutes; Step 2: Use isocyanate as component B; Step 3: Mix component A and component B at a speed of 1500-3000 r / min, stir and foam, cure at 60-80℃ for 24-28 hours, and then mature at room temperature for 24 hours.

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