Flame-retardant modified polyurethane and method for producing the same

Abstract

The application provides a flame-retardant modified polyurethane and a preparation method thereof, comprising the following steps: preparing MXene nanosheets with a two-dimensional sheet structure; modifying the MXene nanosheets by using dopamine hydrochloride to prepare a PDA / Mxene flame retardant; adding the PDA / Mxene flame retardant into a polyurethane foaming system containing polyether polyol and polymethylene polyphenyl polyisocyanate, and obtaining the flame-retardant modified polyurethane through a heating and curing reaction. The modified flame-retardant polyurethane has extremely excellent flame-retardant and smoke-suppressing performance. Compared with pure polyurethane, the maximum reduction rates of PHRR, THR, PSPR and TSP of the flame-retardant modified polyurethane are 24.5%, 46.0%, 29.5% and 20.9% respectively, and meanwhile, the melting and dripping phenomenon of the flame-retardant modified polyurethane disappears during combustion, and the fire safety performance is greatly improved. In addition, the addition of the PDA / Mxene flame retardant does not affect the inherent performance of the polyurethane, and the mechanical performance and thermal insulation performance of the polyurethane are not affected.

Description

Technical Field

[0001] This application belongs to the field of polyurethane foam material technology, and more specifically, relates to a flame-retardant modified polyurethane and its preparation method. Background Technology

[0002] Polyurethane foam (PU) is increasingly used in various fields such as mattresses, furniture cushioning, refrigeration technology and appliances, construction and building industries, automotive industry, packaging, and sporting goods due to its comfort, cost-effectiveness, energy efficiency, and potential environmental friendliness. However, the flammable and combustible nature of polyurethane limits its application range.

[0003] Currently, common flame retardant methods for polyurethane include additive flame retardancy, reactive flame retardancy, and coating flame retardancy. Among these, additive flame retardancy is widely used in modern industrial production due to its low cost and ease of operation. Additive flame retardants can be divided into two types: inorganic and organic. Inorganic flame retardants mainly include flame retardant systems such as aluminum hydroxide, magnesium hydroxide, silicon-based, and antimony trioxide, while organic flame retardants are mainly halogen-based, nitrogen-based, and phosphorus-based. Inorganic flame retardants are cheaper, have good thermal stability, and produce fewer toxic gases during combustion, but they suffer from poor mechanical properties, high filler requirements, and poor compatibility with the substrate. Organic flame retardants have high flame retardant efficiency, good compatibility with the substrate, and low filler requirements, but they produce a large amount of smoke and toxic gases during combustion. Among these, halogen-based flame retardants are widely used in polymer flame retardant modification due to their high flame retardant efficiency, but they release harmful substances such as dioxins and hydrogen halides during combustion, seriously endangering human health and the ecological environment. Summary of the Invention

[0004] The purpose of this application is to provide a flame-retardant modified polyurethane and its preparation method, so as to solve the technical problems of polyurethane being flammable and combustible in the prior art.

[0005] To achieve the above objectives, a first aspect of this application provides a method for preparing flame-retardant modified polyurethane, comprising the following steps: Preparation of MXene nanosheets with a two-dimensional layered structure; PDA / Mxene flame retardant was prepared by modifying the MXene nanosheets with dopamine hydrochloride. The PDA / Mxene flame retardant was added to a polyurethane foam system containing polyether polyol and polymethylene polyphenyl polyisocyanate, and the flame-retardant modified polyurethane was obtained by heating and curing reaction.

[0006] Furthermore, the preparation of the MXene nanosheets includes the following steps: Prepare lithium fluoride / hydrochloric acid solution; Ti3AlC2MAX powder was added to the lithium fluoride / hydrochloric acid solution, and the solution was heated, washed with water, ultrasonically dispersed, centrifuged, and the supernatant was collected to obtain the MXene nanosheets.

[0007] Furthermore, the preparation of the PDA / Mxene flame retardant includes the following steps: The MXene nanosheets were dispersed in Tris buffer at pH 8.5, followed by the addition of dopamine hydrochloride and stirring.

[0008] Furthermore, the amount of the PDA / Mxene flame retardant added accounts for 1%-3% of the total mass of the polyurethane foam system.

[0009] Further, adding the PDA / Mxene flame retardant to the polyurethane foam system containing polyether polyol and polymethylene polyphenyl polyisocyanate includes the following steps: The PDA / Mxene flame retardant was added to component A containing polyether polyol and ultrasonically dispersed evenly. Weigh out component B containing polymethylene polyphenyl polyisocyanate; Mix component A and component B evenly with stirring.

[0010] Furthermore, component A also contains water, silicone oil, dibutyltin dimethylsiloxane, and triethylenediamine.

[0011] Furthermore, the ripening reaction is carried out at a temperature of 60 °C.

[0012] Furthermore, the ripening reaction takes 1 hour.

[0013] A second aspect of this application also provides a flame-retardant modified polyurethane obtained by the above preparation method, wherein the flame-retardant modified polyurethane contains a PDA / Mxene flame retardant.

[0014] Furthermore, the amount of the PDA / Mxene flame retardant added accounts for 1%-3% of the total mass of the polyurethane.

[0015] Compared with the prior art, this application has the following technical effects: This application discloses a method for preparing a flame-retardant modified polyurethane using a one-step foaming process. The method combines a PDA / Mxene flame retardant with foaming raw materials, and after curing, produces a novel flame-retardant modified polyurethane. The preparation method is simple. The method involves pre-exfoliating the easily aggregated Ti3AlC2MAX to prepare two-dimensional MXene nanosheets with good dispersion properties. Simultaneously, dopamine hydrochloride is used to modify the MXene nanosheets to prepare the PDA / Mxene flame retardant. With only 3 wt% of this PDA / Mxene flame retardant, the flame-retardant modified polyurethane achieves extremely excellent flame-retardant and smoke-suppressing properties. Compared to pure polyurethane, the maximum reductions in PHRR, THR, PSPR, and TSP of the flame-retardant modified polyurethane in this application are 24.5%, 46.0%, 29.5%, and 20.9%, respectively. Furthermore, the melting and dripping phenomenon during combustion of the flame-retardant modified polyurethane disappears, significantly improving fire safety performance. Furthermore, the addition of PDA / Mxene flame retardant does not affect the inherent properties of polyurethane itself; its mechanical and thermal insulation properties remain unaffected. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating a method for preparing a PDA / Mxene flame retardant is provided in this application embodiment. Figure 2 These are mechanical property test diagrams of the polyurethane materials prepared in Examples 1-3, Comparative Examples 1 and 2 of this application; Figure 3 (a) XRD patterns of Ti3AlC2 MAX, MXene, PDA / MXene, PU, ​​MP-PU-1, PMP-PU-1, PMP-PU-2 and PMP-PU-3 provided in the embodiments of this application. Figure 3 (b) Fourier transform infrared spectra of Ti3AlC2MAX, MXene, PDA / MXene, PU, ​​MP-PU-1, PMP-PU-1, PMP-PU-2 and PMP-PU-3 provided in the embodiments of this application; Figure 4 Scanning electron microscope (SEM) images of Ti3AlC2 MAX (a), MXene (b, c) and transmission electron microscope (TEM) images of MXene (d, e) and PDA / MXene (f, g) provided for embodiments of this application; Figure 5 Elemental scan analysis chart of PMP-PU-3 provided for implementation of this application; Figure 6 The HRR (a), THR (b), SPR (c), and TSP (d) curves of pure PU, MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3 provided in the embodiments of this application are respectively. Figure 7 Digital photographs of the combustion behavior and char residue of pure PU, MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3 at different times, provided for embodiments of this application. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0020] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0021] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as µg, mg, g, or kg.

[0022] This application provides a novel flame-retardant modified polyurethane and its preparation method. The preparation of the novel flame-retardant modified polyurethane in this application mainly consists of two steps: first, the synthesis of flame retardant PDA / Mxene; and second, the preparation of polyurethane foam by simply mechanically mixing PDA / Mxene flame retardant with polyether polyol N330 and polymethylene polyphenyl polyisocyanate (PAPI) as foaming raw materials.

[0023] In this embodiment, Ti3AlC2MAX (titanium aluminum carbide) is first exfoliated to prepare MXene nanosheets with a two-dimensional layered structure. These nanosheets are then compounded with dopamine hydrochloride (PDA) to prepare a PDA / MXene flame retardant. On one hand, PDA possesses excellent adhesive properties and structural stability, enabling it to form encapsulation or protective coatings on the surface of nanomaterials. On the other hand, PDA contains abundant active groups such as amines and imines, which helps enhance the compatibility between nanomaterials and polymer materials.

[0024] This application discloses a novel flame-retardant modified polyurethane preparation method using a one-step foaming process. The method combines a PDA / Mxene flame retardant with foaming raw materials, and after curing, prepares the novel flame-retardant modified polyurethane. The preparation method is simple. In this application, the method pre-exfoliates the easily aggregated Ti3AlC2MAX to prepare two-dimensional MXene nanosheets with good dispersion properties. Simultaneously, dopamine hydrochloride is used to modify the MXene nanosheets to prepare a PDA / Mxene flame retardant. With only 3 wt% of this PDA / Mxene flame retardant, the flame-retardant modified polyurethane achieves extremely excellent flame-retardant and smoke-suppressing properties. Compared to pure polyurethane, the maximum reductions in PHRR, THR, PSPR, and TSP of the flame-retardant modified polyurethane in this application are 24.5%, 46.0%, 29.5%, and 20.9%, respectively. Furthermore, the melting and dripping phenomenon during combustion of the flame-retardant modified polyurethane disappears, significantly improving fire safety performance. Furthermore, the addition of PDA / Mxene flame retardant does not affect the inherent properties of polyurethane itself; its mechanical and thermal insulation properties remain unaffected.

[0025] The following examples illustrate a flame-retardant modified polyurethane and its preparation method according to embodiments of this application.

[0026] Example 1 Example 1 of this application provides a flame-retardant modified polyurethane and its preparation method, including the following steps: (1) Preparation of PDA / Mxene flame retardant First, 2 g of lithium fluoride was dissolved in 40 mL of hydrochloric acid solution (9M), and then 2 g of Ti3AlC2MAX powder was slowly added. The mixture was then heated in an oil bath for 48 h (37 °C), followed by repeated centrifugation and washing with deionized water until the supernatant was neutral. The resulting precipitate was dispersed in anhydrous ethanol, sonicated for 1 h, and then centrifuged to remove excess ethanol. Finally, the precipitate was further sonicated in deionized water (1 h) and centrifuged at 3500 rpm for 25 min. The upper dispersion was collected and freeze-dried to obtain monolayer or few-layer MXene powder.

[0027] Next, 1 g of the prepared MXene powder was added to 400 mL of Tris buffer (pH=8.5), mechanically stirred, and ultrasonically dispersed for 1 h to mix thoroughly. Compared with water, Tris buffer can resist the influence of external acids and alkalis on the experiment, achieving better preparation results. Then, 0.8 g of dopamine hydrochloride was added and stirred continuously for 9 h. The mixture was then washed with deionized water by centrifugation until neutral, and the resulting precipitate was vacuum dried overnight to obtain polydopamine-modified MXene powder. A schematic diagram of the specific preparation of the PDA / MXene flame retardant is attached. Figure 1 .

[0028] (2) Preparation of flame-retardant modified polyurethane PDA / MXene-PU-1 (PMP-PU-1) First, a certain amount of PDA / Mxene black powder flame retardant was added to 30 g of polyether polyol (N330), mechanically stirred, and ultrasonically dispersed for 3 h to ensure thorough mixing. Then, the mixture was poured into a disposable plastic cup and 0.9 g of deionized water, 0.27 g of silicone oil (L580), and 0.03 g of dibutyltin dibutylsilicate (C) were added. 32 H 64 O4Sn), 0.024 g triethylenediamine (C6H 12 N2), vigorously stir and mix thoroughly, label as component A. Simultaneously, weigh 13 g of polymethylene polyphenyl polyisocyanate (PAPI) into another disposable plastic cup, label as component B. To achieve ideal experimental results, the substances in component A need to be dispersed independently in solution before mixing with component B. Then, stir rapidly to ensure uniform mixing of components B and A, pour the mixture into a mold for reaction, let it stand at room temperature for 5 min until the foam shape stabilizes, and then place it in an oven at 60 ℃ for 1 h to fully cure, thus obtaining flame-retardant modified polyurethane foam PMP-PU-1. The amount of PDA / Mxene flame retardant added accounts for 1% of the total mass of the polyurethane foam system.

[0029] Example 2 The difference between this and Example 1 is that in step (2), the amount of PDA / Mxene flame retardant added accounts for 2% of the total mass of the polyurethane foam system, and other process conditions are the same, so flame-retardant modified polyurethane foam PMP-PU-2 is prepared.

[0030] Example 3 The difference between this and Example 1 is that in step (2), the amount of PDA / Mxene flame retardant added accounts for 3% of the total mass of the polyurethane foam system, and other process conditions are the same, so flame-retardant modified polyurethane foam PMP-PU-3 is prepared.

[0031] Comparative Example 1 The difference between this and Example 1 is that in step (1), dopamine hydrochloride was not used to modify MXene powder. Other process conditions were the same, and flame-retardant modified polyurethane foam MP-PU-1 was prepared.

[0032] Comparative Example 2 The difference between this and Example 1 is that no PDA / Mxene flame retardant is added in step (2), that is, pure polyurethane is prepared and pure PU is obtained.

[0033] The amounts of each substance used in Examples 1-3, Comparative Examples 1 and 2 of this application are shown in Table 1.

[0034] Table 1 sample N330 (g) PAPI (g) H2O (g) L580 (g) C32H64O4Sn (g) C6H12N2 (g) MXene (%) PDA / MXene (%) PU 30 13 0.9 0.27 0.03 0.024 0 0 MP-PU-1 30 13 0.9 0.27 0.03 0.024 1 0 PMP-PU-1 30 13 0.9 0.27 0.03 0.024 0 1 PMP-PU-2 30 13 0.9 0.27 0.03 0.024 0 2 PMP-PU-3 30 13 0.9 0.27 0.03 0.024 0 3 The mechanical properties of the polyurethane materials prepared in Examples 1-3, Comparative Examples 1 and 2 of this application were tested, and the test results are as follows: Figure 2 As shown, from Figure 2 As observed, compared to pure polyurethane (pure PU), adding PDA / Mxene flame retardant does not affect the mechanical properties of polyurethane itself. Figure 2 CFPU is a commercially available flexible polyurethane foam.

[0035] XRD and Fourier transform infrared spectroscopy analyses were performed on Ti3AlC2MAX, MXene, PDA / MXene, PU, ​​MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3, respectively. The results are as follows: Figure 3 As shown in (a) and 3(b). From Figure 3 (a) It can be seen that no impurity peaks appeared on the curves of PMP-PU-1, PMP-PU-2, and PMP-PU-3, and they all had MXene characteristic peaks, indicating that the flame-retardant modified polyurethane was successfully prepared. From Figure 3 (b) It is observed that the synthesized products PMP-PU-1, PMP-PU-2 and PMP-PU-3 contain polyurethane segments, indicating that the polyurethane foam was successfully synthesized.

[0036] Scanning electron microscopy and transmission electron microscopy analyses were performed on Ti3AlC2MAX, MXene, and PDA / MXene. The results are as follows: Figure 4 As shown, Figure 4Microstructures of the samples before and after etching and stripping, as observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). MXene exhibits an almost transparent sheet-like structure under TEM (d), indicating successful etching and the acquisition of layered MXene. Furthermore, compared to the smooth surface of MXene without a noticeable dark boundary layer (e), PDA / MXene clearly shows two boundary layers, one light and one dark (g), which mainly originate from the PDA organic coating adhering to the surface after dopamine self-polymerization.

[0037] Elemental scanning analysis was performed on the PMP-PU-3 implemented in this application, and the results are as follows: Figure 5 As shown, PMP-PU-3 contained C, N, and O elements belonging to pure PU, as well as Ti elements belonging to MXene, which were uniformly distributed. The elemental analysis results indicate that flame-retardant modified polyurethane PMP-PU-3 has been successfully prepared, and the modified particles are uniformly distributed inside the foam skeleton, providing a good foundation for the subsequent multifunctional application of the material.

[0038] The combustion performance of the polyurethane materials prepared in Examples 1-3, Comparative Examples 1 and 2 of this application was tested. The combustion process of the polyurethane foam samples was recorded using a cone calorimeter (FTT Company, UK) according to the ISO 5660 standard test method. The sample size was 100 mm × 100 mm × 10 mm, and the radiative heat flux during the test was 35 kW / m². 2 The combustion behavior of the samples was further tested using an FAA-PCFC micro calorimeter (Micro Cone Calorimeter, UK). The samples were heated and decomposed in a nitrogen atmosphere, from room temperature to 750℃ at a heating rate of 1℃ / s. Parameters such as HRR and THR were calculated based on the oxygen consumption principle. The results are as follows: Figure 6 As shown. The combustion behavior of polyurethane foam was further observed through direct combustion experiments, and digital images of each stage of the foam sample combustion process were recorded, such as... Figure 7 As shown.

[0039] Figure 6 (a) shows the HRR (heat release rate) curves for pure PU, MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3. Figure 6 (b) shows the THR (Total Heat Release) curves for pure PU, MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3. Figure 6 (c) shows the SPR (smoke release rate) curves for pure PU, MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3. Figure 6(d) shows the TSP (Total Flue Gas Emission) curves for pure PU, MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3.

[0040] Figure 7 Digital photographs of the combustion behavior and char residue of pure PU, MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3 at different times. From Figure 7 As observed, neither the pure PU nor the flame-retardant modified PU obtained through foaming exhibited melt detachment during the entire combustion process, and the blocky structure was almost entirely preserved. Furthermore, the combustion time was significantly extended. Specifically, pure PU, MP-PU-1, PMP-PU-1, PMP-PU-2, and PMP-PU-3 were completely burned after 76 s, 85 s, 92 s, 93 s, and 96 s of ignition, respectively. The combustion time of the flame-retardant modified PU gradually increased, with PMP-PU-3 extending by 20 s. Simultaneously, the melt dripping phenomenon of the prepared flame-retardant modified PU foam material completely disappeared.

[0041] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing flame-retardant modified polyurethane, characterized in that, Includes the following steps: Preparation of MXene nanosheets with a two-dimensional layered structure; specifically, the preparation of the MXene nanosheets includes the following steps: Prepare lithium fluoride / hydrochloric acid solution; Ti3AlC2MAX powder was added to the lithium fluoride / hydrochloric acid solution, and the solution was heated, washed with water, ultrasonically dispersed, centrifuged, and the supernatant was collected to obtain the MXene nanosheets. The MXene nanosheets were modified with dopamine hydrochloride to prepare a PDA / MXene flame retardant; specifically, the preparation of the PDA / MXene flame retardant includes the following steps: The MXene nanosheets were dispersed in Tris buffer at pH 8.5, then dopamine hydrochloride was added and the mixture was stirred to react. The PDA / Mxene flame retardant is added to a polyurethane foaming system containing polyether polyol and polymethylene polyphenyl polyisocyanate, and a flame-retardant modified polyurethane is obtained by heating and curing reaction; specifically, the addition of the PDA / Mxene flame retardant to the polyurethane foaming system containing polyether polyol and polymethylene polyphenyl polyisocyanate includes the following steps: The PDA / Mxene flame retardant was added to component A containing polyether polyol and ultrasonically dispersed evenly. Weigh out component B containing polymethylene polyphenyl polyisocyanate; Mix component A and component B evenly with stirring.

2. The method for preparing a flame-retardant modified polyurethane as described in claim 1, characterized in that, The amount of PDA / Mxene flame retardant added accounts for 1%-3% of the total mass of the polyurethane foam system.

3. The method for preparing a flame-retardant modified polyurethane as described in claim 1, characterized in that, Component A also contains water, silicone oil, dibutyltin dilaurate, and triethylenediamine.

4. The method for preparing a flame-retardant modified polyurethane as described in claim 1, characterized in that, The ripening reaction is carried out at a temperature of 60 °C.

5. The method for preparing a flame-retardant modified polyurethane as described in claim 4, characterized in that, The ripening reaction takes 1 hour.

6. The flame-retardant modified polyurethane prepared by the method for preparing flame-retardant modified polyurethane according to any one of claims 1-5, characterized in that, The flame-retardant modified polyurethane contains PDA / Mxene flame retardant.

7. The flame-retardant modified polyurethane as described in claim 6, characterized in that, The amount of PDA / Mxene flame retardant added accounts for 1%-3% of the total mass of polyurethane.

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