A method for preparing flame-retardant flexible polyurethane foam

Abstract

This invention discloses a method for preparing a flame-retardant flexible polyurethane foam in the field of flame-retardant materials and their preparation technology, comprising the following steps: (1) firstly modifying the surface of a flexible polyurethane foam with amino-modified carbon nanotubes; (2) then grafting phytic acid onto the surface of the flexible polyurethane foam modified with the amino-modified carbon nanotubes, thereby obtaining a flame-retardant flexible polyurethane foam. The invention utilizes the acid and alkali corrosion resistance of the amino-modified carbon nanotubes and the high reactivity of the phosphate and amino groups of phytic acid, firstly modifying the surface of a flexible polyurethane foam (FPUF) with amino-modified carbon nanotubes to form a protective layer and endowing it with multiple reactive sites; then, grafting phytic acid onto the amino-modified carbon nanotubes through a salt-forming reaction, constructing an organic-inorganic hybrid surface flame-retardant coating on the surface of the flexible polyurethane foam (FPUF), thereby obtaining a flame-retardant flexible polyurethane foam with high flame-retardant properties.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant materials and preparation thereof, and particularly relates to a method for preparing flame retardant soft polyurethane foam. Background Art

[0002] Flexible polyurethane foam (FPUF) is widely used in automotive and aircraft seat cushions, building insulation, and soundproof exterior walls due to its low density, high specific strength, good resilience, sound absorption, and breathability. However, FPUF plastics pose fire safety risks due to their high hydrocarbon content, large surface area, and porous structure, making them flammable. In particular, during combustion, FPUF not only has a high heat release rate and large amount of heat released, resulting in rapid flame propagation and difficulty in extinguishing, but is also often accompanied by melt dripping and toxic fumes, which can easily cause serious fire accidents and pose a significant threat to people's lives and property. Therefore, improving the flame retardancy of FPUF is of paramount importance.

[0003] According to the time division of combustion, the thermal decomposition and combustion of FPUF includes four stages: heating, pyrolysis, ignition, and combustion. The termination of any of these four stages can play a flame retardant role. Currently, the following three methods are commonly used to achieve the purpose of flame retardancy: (1) Improving the thermal stability of FPUF and inhibiting its thermal decomposition behavior; (2) Condensed phase flame retardancy: Improving the carbonization ability and carbonization quality of FPUF, preventing the transfer of heat, and isolating combustible decomposition products and oxygen; (3) Gas phase flame retardancy: Introducing substances that can capture H· and OH· free radicals to terminate the transmission of the combustion reaction. In fact, because FPUF has a porous structure, low density, and a large specific surface area, coupled with a large number of hydrocarbon segments, condensed phase flame retardancy is quite difficult, and gas phase flame retardancy is often the main method. Halogenated flame retardants can effectively improve the flame retardancy of FPUF by generating free radicals to terminate the combustion chain reaction, but they produce a lot of smoke and release toxic and corrosive gases during combustion, which limits their wide application. Phosphorus-based flame retardants overcome the defects of halogen-containing flame retardants and have the characteristics of high flame retardancy, low smoke, low toxicity, and no corrosive gas production. They can be used as a better substitute for halogen-based flame retardants for flame retardant FPUF.

[0004] Phytic acid (PA), also known as inositol hexaphosphate, is abundant in plant tissues such as legumes, grains, and oilseeds. It is biocompatible, environmentally friendly, non-toxic, and readily available. Phytic acid contains a unique inositol hexaphosphate structure and a phosphorus content of up to 28 wt%, making it an effective biomass-based phosphorus flame retardant. However, phytic acid is highly acidic and, when used directly in flame-retardant FPUFs, corrodes their structure and severely impairs their mechanical properties. Therefore, how to rationally utilize phytic acid to improve the flame retardancy of FPUFs while maintaining excellent resilience is an urgent issue. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a flame retardant flexible polyurethane foam, so as to ensure that the prepared flame retardant flexible polyurethane foam has both good flame retardant properties and resilience properties.

[0006] A method for preparing a flame-retardant flexible polyurethane foam in this solution comprises the following steps:

[0007] (1) First, the surface of soft polyurethane foam is modified with amino-modified carbon nanotubes;

[0008] (2) Phytic acid is then grafted onto the surface of the soft polyurethane foam modified with amino-modified carbon nanotubes to obtain a flame-retardant soft polyurethane foam.

[0009] The working principle and beneficial effects of this solution: The present invention provides a method for preparing environmentally friendly flame-retardant flexible polyurethane foam based on surface treatment. This method is characterized by utilizing the acid and alkali corrosion resistance of amino-modified carbon nanotubes and the high reactivity of phosphate and amino groups of phytic acid. First, amino-modified carbon nanotubes are used to surface-modify flexible polyurethane foam (FPUF) to form a protective layer and impart multiple reactive sites. Phytic acid is then grafted onto the amino-modified carbon nanotubes through a salt-forming reaction, constructing an organic-inorganic hybrid surface flame-retardant coating on the surface of the flexible polyurethane foam (FPUF), thereby producing a flame-retardant flexible polyurethane foam with high flame retardancy. This preparation process is simple, can be applied on a large scale, and uses green and renewable raw materials. Furthermore, the prepared flame-retardant flexible polyurethane foam still has good resilience.

[0010] Furthermore, in step (1), the specific process of modifying the surface of the soft polyurethane foam with amino-treated carbon nanotubes is as follows: ultrasonically dispersing the amino-treated carbon nanotubes in a mixed solution of ethanol and water to obtain a mixed system; then immersing the soft polyurethane foam in the mixed system and pressing it 3 to 20 times to allow the liquid to fully penetrate into the pores of the soft polyurethane foam, and then taking it out and drying it.

[0011] Furthermore, in step (1), the volume ratio of ethanol to water in the mixed solution is (0.2-5):1. Wherein, (0.2-5):1 means that for every 1 mL of water in the mixed solution, 0.2-5 mL of ethanol is required to be mixed therewith.

[0012] Furthermore, in step (1), the ratio of the amount of the amino-modified carbon nanotubes to the mixed solution is (0.1-1 g):500 mL, wherein (0.1-1 g):500 mL means that the amount of the amino-modified carbon nanotubes to be added is 0.1-1 g per 500 mL of the mixed solution.

[0013] Furthermore, in step (1), the drying temperature of the soft polyurethane foam after being immersed in the mixed system is 40 to 90°C.

[0014] Furthermore, in step (2), the specific process of grafting phytic acid is as follows: the flexible polyurethane foam modified with amino carbon nanotubes is immersed in a phytic acid solution for reaction for 4 to 10 hours, and then taken out and dried.

[0015] Furthermore, in step (2), the concentration of the phytic acid solution is 0.5 to 3 wt%.

[0016] Furthermore, in step (2), the drying temperature is 40-90°C.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The soft polyurethane foam (FPUF) is first modified with amino-treated carbon nanotubes with acid and alkali resistance to form a protective layer, which can overcome the corrosion and damage of the strong acidity of phytic acid on the skeleton structure of the soft polyurethane foam (FPUF), maintain the excellent mechanical properties of the soft polyurethane foam (FPUF), and make it have good rebound performance;

[0019] (2) The salt-forming reaction characteristics of phytic acid and amino-modified carbon nanotubes were fully utilized to construct an organic-inorganic hybrid flame-retardant coating on the surface of flexible polyurethane foam (FPUF), which significantly improved the flame retardant properties of the flame-retardant flexible polyurethane foam;

[0020] (3) The phytic acid used is a highly efficient and environmentally friendly biomass flame retardant, and the preparation process is simple and easy to achieve mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a photo of the vertical combustion performance test of the flame retardant flexible polyurethane foam (flame retardant FPUF) prepared in Example 1;

[0022] Figure 2 This is the HRR curve of the cone calorimetry test of the flame retardant flexible polyurethane foam (flame retardant FPUF) prepared in Example 1;

[0023] Figure 3 This is the THR curve of the cone calorimetry test of the flame retardant flexible polyurethane foam (flame retardant FPUF) prepared in Example 1;

[0024] Figure 4 This is the stress-strain curve of the cyclic compression test of the flame-retardant flexible polyurethane foam (flame-retardant FPUF) prepared in Example 1;

[0025] Figure 5 This is the HRR curve of the cone calorimetry test of flexible polyurethane foam;

[0026] Figure 6 This is the THR curve of the cone calorimetry test for flexible polyurethane foam. DETAILED DESCRIPTION

[0027] The present invention is described in detail below through examples, and the technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any combination of the specific implementation methods.

[0028] It is important to note that this embodiment is intended solely to further illustrate the present invention and is not to be construed as limiting the scope of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the above disclosure are also considered to fall within the scope of the present invention. It should be emphasized that the substrate dimensions described in the specific embodiments herein are merely for the purpose of describing the present invention in detail and are not intended to limit the present invention.

[0029] The present invention provides a method for preparing a flame-retardant flexible polyurethane foam, the process steps and conditions of which are as follows (the parts of materials used in the following examples are all parts by weight unless otherwise specified):

[0030] Example 1

[0031] A method for preparing a flame-retardant flexible polyurethane foam comprises the following steps:

[0032] First, 0.62 g of amino-modified carbon nanotubes (CNT-NH2) were ultrasonically dispersed in a mixed solution of 3100 mL of ethanol and water, where the volume ratio of ethanol to water was 1:1.

[0033] Then, a flexible polyurethane foam (FPUF) measuring 310 mm × 100 mm × 20 mm was immersed in the above mixture and pressed ten times, each pressing lasting 0.5 to 1 minute. After the liquid fully penetrated the pores of the FPUF, the foam was removed and dried at 90°C to obtain CNT-NH2-modified foam.

[0034] Finally, the CNT-NH2 modified foam prepared above was immersed in a 1% phytic acid (PA) solution for 6 hours, taken out, and dried at 90°C to obtain a flame retardant flexible polyurethane foam (FPUF / CNT-NH2-PA).

[0035] Performance testing:

[0036] (1) Limiting oxygen index (LOI) test

[0037] The limiting oxygen index test is a common method for evaluating the flame retardancy of modern materials. It determines the minimum oxygen concentration required for the material to burn stably in a nitrogen-oxygen mixture. This patent uses a JF-3 oxygen index tester based on ASTM D2863-97. The test specimens are 150 mm × 10 mm × 10 mm in size. Each set of specimens is tested three times, and the average result is taken. The evaluation criteria for the test results are shown in Table 1.

[0038] Table 1 Limiting oxygen index rating table

[0039]

[0040] According to the measurement, the LOI value of the flame-retardant flexible polyurethane foam prepared in Example 1 is 27.6%, which reaches the level of flame-retardant materials.

[0041] (2) Vertical burning level test

[0042] This patent uses a CZF-3 vertical combustion apparatus to test the flame retardant properties of samples in accordance with the UL-94 test standard (TB117-2000). The sample size is 304.8mm×76.2mm×12.7mm.

[0043] The vertical burning test shows that the flame retardant flexible polyurethane foam prepared in Example 1 passes the UL-94V-0 grade. Figure 1 shown.

[0044] (3) Cone Calorimeter (CC) test

[0045] CC is a combustion behavior research instrument designed based on the principle of oxygen consumption. It characterizes the combustion behavior of materials by measuring combustion parameters such as ignition time (TTI), heat release rate (HRR), total heat release (THR), smoke product rate (SPR), and total smoke production (TSP). It is currently recognized as the most ideal small combustion performance test instrument. The CC test of the sample in this patent was carried out using the cone calorimeter of Kunshan Modis Combustion Technology Instrument Co., Ltd., with an irradiation power of 35kW / m 2 , the sample size is 100mm×100mm×10mm.

[0046] The cone calorimetry test showed that the peak HRR of the flame retardant flexible polyurethane foam prepared in Example 1 was reduced from 496.9 to 299.5 kW / m2 (see Appendix Figure 2 ), THR decreased from 19.63 to 17.02MJ / m2 (see attached Figure 3 ).

[0047] (4) Rebound test

[0048] The resilience of the flame-retardant FPUF was tested by cyclic compression. This patent uses a universal testing machine (CMT6202, MTS Systems Co., Ltd.) for testing, with a sample size of 2 cm × 2 cm × 2 cm, a compression speed of 50 mm / min, and 100 cyclic compression cycles.

[0049] The test shows that the cyclic compression stress-strain curve of the flame retardant soft polyurethane foam prepared in Example 1 is similar to that of pure FPUF, and after 100 cycles of compression, it can still recover to its original shape, indicating that the flame retardant soft polyurethane foam prepared maintains good mechanical properties. Figure 4 shown.

[0050] Example 2

[0051] A method for preparing a flame-retardant flexible polyurethane foam comprises the following steps:

[0052] First, 0.31 g of amino-modified carbon nanotubes (CNT-NH2) were ultrasonically dispersed in a mixed solution of 3100 mL of ethanol and water, where the volume ratio of ethanol to water was 1:1.

[0053] Then, a flexible polyurethane foam (FPUF) with a size of 310 mm × 100 mm × 20 mm was immersed in the above mixed system and pressed several times to allow the liquid to fully penetrate the pores of the FPUF. After that, it was taken out and dried at 90 ° C to obtain CNT-NH2 modified foam;

[0054] Finally, the CNT-NH2 modified foam prepared above was immersed in a 1% phytic acid (PA) solution for 6 hours, taken out, and dried at 90°C to obtain a flame retardant flexible polyurethane foam (FPUF / CNT-NH2-PA).

[0055] After testing, the LOI value of the flame retardant foam is 25.4%; the vertical burning test shows that the flame retardant foam passes the UL-94V-0 grade.

[0056] Example 3

[0057] A method for preparing a flame-retardant flexible polyurethane foam comprises the following steps:

[0058] First, 0.62 g of amino-modified carbon nanotubes (CNT-NH2) were ultrasonically dispersed in a mixed solution of 3100 mL of ethanol and water, where the volume ratio of ethanol to water was 1:1.

[0059] Then, a flexible polyurethane foam (FPUF) with a size of 310 mm × 100 mm × 20 mm was immersed in the above mixed system and pressed several times to allow the liquid to fully penetrate the pores of the FPUF. After that, it was taken out and dried at 90 ° C to obtain CNT-NH2 modified foam;

[0060] Finally, the CNT-NH2 modified foam prepared above was immersed in a 1.5% mass fraction phytic acid (PA) solution for 6 hours, taken out, and dried at 90°C to obtain a flame retardant flexible polyurethane foam (FPUF / CNT-NH2-PA).

[0061] After testing, the LOI value of the flame retardant foam is 28.2%; the vertical burning test shows that the flame retardant foam passes the UL-94V-0 grade.

[0062] Example 4

[0063] A method for preparing a flame-retardant flexible polyurethane foam comprises the following steps:

[0064] First, 0.62 g of amino-modified carbon nanotubes (CNT-NH2) were ultrasonically dispersed in a mixed solution of 3100 mL of ethanol and water, where the volume ratio of ethanol to water was 2:1.

[0065] Then, a flexible polyurethane foam (FPUF) with a size of 310 mm × 100 mm × 20 mm was immersed in the above mixed system and pressed several times to allow the liquid to fully penetrate the pores of the FPUF. After that, it was taken out and dried at 90 ° C to obtain CNT-NH2 modified foam;

[0066] Finally, the CNT-NH2 modified foam prepared above was immersed in a 1% phytic acid (PA) solution for 6 hours, taken out, and dried at 90°C to obtain a flame retardant flexible polyurethane foam (FPUF / CNT-NH2-PA).

[0067] After testing, the LOI value of the flame retardant foam is 27.8%; the vertical burning test shows that the flame retardant foam passes the UL-94V-0 grade.

[0068] Example 5

[0069] A method for preparing a flame-retardant flexible polyurethane foam comprises the following steps:

[0070] First, 0.93 g of amino-modified carbon nanotubes (CNT-NH2) were ultrasonically dispersed in a mixed solution of 3100 mL of ethanol and water, where the volume ratio of ethanol to water was 2:1.

[0071] Then, a flexible polyurethane foam (FPUF) with a size of 310 mm × 100 mm × 20 mm was immersed in the above mixed system and pressed several times to allow the liquid to fully penetrate the pores of the FPUF. After that, it was taken out and dried at 90 ° C to obtain CNT-NH2 modified foam;

[0072] Finally, the CNT-NH2 modified foam prepared above was immersed in a 1% phytic acid (PA) solution for 6 hours, taken out, and dried at 90°C to obtain a flame retardant flexible polyurethane foam (FPUF / CNT-NH2-PA).

[0073] After testing, the LOI value of the flame retardant foam is 28.3%; the vertical burning test shows that the flame retardant foam passes the UL-94V-0 grade.

[0074] Comparative Example 1

[0075] A method for preparing FPUF / PA comprises the following steps: soaking a flexible polyurethane foam (FPUF) with a size of 310 mm × 100 mm × 20 mm in a phytic acid (PA) solution with a mass fraction of 1% for 6 hours, taking it out, and drying it at 90° C. to obtain the FPUF / PA.

[0076] Comparative Example 2

[0077] A method for preparing FPUF / CNT-NH2 comprises the following steps: first, weighing 0.62 g of amino-modified carbon nanotubes (CNT-NH2) and ultrasonically dispersing them in a mixed solution of 3100 mL of ethanol and water, wherein the volume ratio of ethanol to water is 1:1;

[0078] Then, a flexible polyurethane foam (FPUF) with a size of 310 mm × 100 mm × 20 mm was immersed in the above mixed system and pressed ten times, with each pressing lasting 0.5 to 1 minute. After the liquid fully penetrated the pores of the FPUF, it was taken out and dried at 90°C to obtain a CNT-NH2-modified foam, namely FPUF / CNT-NH2.

[0079] Cone Calorimeter (CC) tests were performed on conventional flexible polyurethane foam (FPUF), FPUF / PA prepared in Comparative Example 1, FPUF / CNT-NH2 prepared in Comparative Example 2, and flame retardant flexible polyurethane foam (FPUF / CNT-NH2-PA) prepared in Example 1. The test results are shown in the attached figure. Figures 5-6 As shown in the accompanying figure, it can be seen that the flame retardant properties of the flame retardant soft polyurethane foam prepared by combining phytic acid with amino-modified carbon nanotubes are significantly improved.

[0080] The performance testing methods of the flexible polyurethane foams prepared in Examples 2 to 5 and Comparative Examples 1 to 2 are the same as those in Example 1 and will not be described again here.

Claims

1. A method for preparing a flame-retardant flexible polyurethane foam, characterized in that: The following steps are involved: (1) First, the surface of soft polyurethane foam is modified with amino-modified carbon nanotubes; (2) Phytic acid is then grafted onto the surface of the soft polyurethane foam modified with amino-modified carbon nanotubes to obtain a flame-retardant soft polyurethane foam.

2. The method for preparing a flame-retardant flexible polyurethane foam according to claim 1, wherein: In step (1), the specific process of modifying the surface of the soft polyurethane foam with amino-treated carbon nanotubes is as follows: ultrasonically dispersing the amino-treated carbon nanotubes in a mixed solution of ethanol and water to obtain a mixed system; then immersing the soft polyurethane foam in the mixed system and pressing it 3 to 20 times to allow the liquid to fully penetrate into the pores of the soft polyurethane foam, and then taking it out and drying it.

3. The method for preparing a flame-retardant flexible polyurethane foam according to claim 2, wherein: In step (1), the volume ratio of ethanol to water in the mixed solution is 0.2 to 5:

1.

4. The method for preparing a flame-retardant flexible polyurethane foam according to claim 3, wherein: In step (1), the ratio of the amount of the amino-modified carbon nanotubes to the mixed solution is 0.1-1 g:500 mL.

5. The method for preparing a flame-retardant flexible polyurethane foam according to claim 4, wherein: In step (1), the drying temperature of the soft polyurethane foam after being immersed in the mixed system is 40 to 90°C.

6. The method for preparing a flame-retardant flexible polyurethane foam according to any one of claims 1 to 5, characterized in that: In step (2), the specific process of grafting phytic acid is as follows: the flexible polyurethane foam modified with amino carbon nanotubes is immersed in a phytic acid solution for reaction for 4 to 10 hours, and then taken out and dried.

7. The method for preparing a flame-retardant flexible polyurethane foam according to claim 6, wherein: In step (2), the concentration of the phytic acid solution is 0.5-3 wt%.

8. The method for preparing a flame-retardant flexible polyurethane foam according to claim 7, wherein: In step (2), the drying temperature is 40-90°C.

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