A transparent and UV-resistant flame-retardant polyvinyl alcohol film and its preparation method

Abstract

The present invention discloses a transparent and UV-resistant flame-retardant polyvinyl alcohol film and a preparation method thereof. The film is prepared by adding N-(2-aminoethyl)-P-methylphosphonamidomethyl ester and nano-TiO2 to polyvinyl alcohol to form a film. The N-(2-aminoethyl)-P-methylphosphonamidomethyl ester is a phosphorus-nitrogen-containing transparent liquid flame retardant prepared by reacting ethylenediamine with dimethyl methylphosphonate. According to the method of the present invention, the mechanical properties and flame retardant properties of the polyvinyl alcohol film can be significantly improved while maintaining the basic transparency of the film. In addition, the addition of a small amount of nano-TiO2 gives the polyvinyl alcohol film certain UV resistance. The high-performance flame-retardant polyvinyl alcohol film prepared by the present invention can be used in the packaging field, especially in the packaging of high-end textiles, and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the field of flame retardant materials, and in particular relates to a transparent and UV-resistant flame retardant polyvinyl alcohol film and a preparation method thereof. Background Art

[0002] Plastic films such as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) are widely used today, but they all suffer from non-biodegradability and pose significant environmental risks. Polyvinyl alcohol (PVA), a non-toxic, highly transparent, and biodegradable polymer, has gained increasing attention and holds promise for applications in packaging and agricultural films. However, PVA's low limiting oxygen index (LOI), at approximately 19%, makes it a flammable polymer and presents significant safety concerns. Therefore, improving the flame retardancy of PVA is crucial. The most direct approach is to modify the PVA matrix with flame retardants. However, the addition of most existing flame retardants can negatively impact the mechanical properties and transparency of PVA films. Therefore, developing flame-retardant PVA films while maintaining both transparency and mechanical properties is crucial. Summary of the Invention

[0003] Based on the shortcomings of the above-mentioned prior art, the present invention provides a transparent and UV-resistant flame-retardant polyvinyl alcohol film and a preparation method thereof, aiming to prepare a flame-retardant polyvinyl alcohol material with excellent comprehensive performance by compounding a phosphorus-nitrogen flame retardant system ETDM and nano-TiO2 and adding them to polyvinyl alcohol.

[0004] In order to solve the technical problem, the present invention adopts the following technical solution:

[0005] The present invention first discloses a phosphorus-nitrogen-containing transparent liquid flame retardant, which is prepared by reacting ethylenediamine (EDA) with dimethyl methylphosphonate (DMMP) to produce N-(2-aminoethyl)-P-methylphosphonamidomethyl ester (denoted as ETDM), i.e., a phosphorus-nitrogen-containing transparent liquid flame retardant. The preparation method is as follows: ethylenediamine and dimethyl methylphosphonate are mixed in a molar ratio of 5 to 10:1, stirred in an oil bath at 100 to 120°C for 1 to 1.5 hours, and then excess ethylenediamine is removed using a vacuum rotary evaporator at 75 to 85°C to obtain the product ETDM (a light yellow oil). The reaction formula is as follows: Figure 1 shown.

[0006] The present invention further discloses a transparent, UV-resistant, flame-retardant polyvinyl alcohol film, which is prepared by compounding the aforementioned ETDM and nano-TiO2 into polyvinyl alcohol, referred to as an ETDM / TiO2 / PVA film. The composition of the raw materials, by weight, is as follows: 90-100 parts polyvinyl alcohol, 9-9.5 parts ETDM, and 0.5-1 part nano-TiO2.

[0007] The preparation method of the ETDM / TiO2 / PVA film of the present invention is as follows:

[0008] Add polyvinyl alcohol to deionized water, and stir in an oil bath at 95-100° C. until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution;

[0009] Add nano-TiO2 powder into an appropriate amount of deionized water and disperse it evenly with ultrasound to obtain nano-TiO2 dispersion;

[0010] Adding nano-TiO2 dispersion and ETDM to the polyvinyl alcohol solution, stirring in an oil bath at 85-95° C. for 0.5-1 h to obtain a membrane solution;

[0011] The obtained membrane liquid was poured onto a polytetrafluoroethylene membrane, allowed to stand at room temperature for 70 to 72 hours, and then dried in an oven at 35 to 45°C for 20 to 24 hours to obtain an ETDM / TiO2 / PVA film.

[0012] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0013] 1. The present invention utilizes ethylenediamine and dimethyl methylphosphonate to react to prepare a phosphorus-nitrogen-containing transparent liquid flame retardant, which has high flame retardant efficiency and requires a small amount of addition during application, thus overcoming the shortcomings of traditional flame retardants, which have high addition amounts and low flame retardant efficiency. The preparation method is simple, has a short cycle, and is low in cost.

[0014] 2. The present invention adds ETDM and nano-TiO2 to polyvinyl alcohol to prepare a flame-retardant polyvinyl alcohol film. On the one hand, the phosphorus- and nitrogen-containing flame retardant ETDM prepared by the present invention and nano-TiO2 can produce a synergistic effect, achieving excellent flame retardant effects through gas-phase and condensed-phase flame retardancy; on the other hand, both the flame retardant ETDM and nano-TiO2 can produce hydrogen bonds with the polyvinyl alcohol matrix, have good compatibility in the polyvinyl alcohol matrix, and can improve the mechanical properties of the polyvinyl alcohol composite material. In addition, because nano-TiO2 has good ultraviolet absorption, while improving the flame retardant and mechanical properties of the composite material, it also gives the composite material a certain degree of ultraviolet resistance. The method of the present invention overcomes the problem that the addition of traditional flame retardants affects the mechanical properties or transparency of the material. The high-performance flame-retardant polyvinyl alcohol film prepared by the present invention can be used in the packaging field, especially in high-end textile packaging, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The reaction formula for the reaction of ethylenediamine and dimethyl methylphosphonate to produce ETDM.

[0016] Figure 2IR spectra of ethylenediamine, dimethyl methylphosphonate and ETDM.

[0017] Figure 3 This is the H NMR spectrum of ETDM.

[0018] Figure 4 Figure 2 is the NMR phosphorus spectra of DMMP and ETDM.

[0019] Figure 5 The figure is a histogram of the limiting oxygen index of the composite materials obtained in the comparative example and examples 1-4.

[0020] Figure 6 The figure is a bar graph showing the mechanical properties of the composite materials obtained in the comparative example and examples 1-4.

[0021] Figure 7 The UV absorbance graphs of the composite materials obtained in the comparative example and examples 1-4 are shown. DETAILED DESCRIPTION

[0022] The technical solutions of the present invention are described clearly and completely below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0023] The polyvinyl alcohol used in the following examples is model 1799.

[0024] Example 1

[0025] In this embodiment, a flame-retardant polyvinyl alcohol film is prepared according to the following steps:

[0026] 1. Preparation of ETDM

[0027] 48.6 g of ethylenediamine and 9.9 g of dimethyl methylphosphonate were added to a 250 mL three-necked flask, and the mixture was stirred in an oil bath at 110°C for 1.2 h. The excess ethylenediamine was then removed using a vacuum rotary evaporator at 85°C to obtain the ETDM product (pale yellow oil).

[0028] Figure 2 The infrared spectra of ethylenediamine (EDA), dimethyl methylphosphonate (DMMP) and ETDM are shown in the figure. It can be seen from the figure that in the Fourier transform infrared spectrum of EDA, 3289 cm -1 and 3361 cm -1 The absorption peak at 1604 cm corresponds to the absorption peak of NH -1 The absorption peak at 2854 cm corresponds to the bending vibration of NH. -1 and 2956 cm -1The absorption peaks at 1189cm correspond to the symmetric stretching vibration and asymmetric stretching vibration of -OCH3. -1 The peak at 1178 cm corresponds to the swing of -OCH3. -1 The PN characteristic peak appears at . In addition, it can be found that the intensity of the -OCH3 characteristic peak is weaker than that of DMMP. Therefore, it can be preliminarily inferred that ETDM was successfully synthesized.

[0029] Figure 3 is the H NMR spectrum of ETDM, Figure 4 is the NMR phosphorus spectrum of DMMP and ETDM. Figure 3 As shown in the hydrogen spectrum, ETDM has a short broad peak near 4.5 ppm, which is caused by the hydrogen on the imine group. Figure 3 The calculated ratios of proton numbers under different chemical environments are consistent with the theory; in addition, Figure 4 The phosphorus spectra show chemical shifts of 33.0 ppm and 19.8 ppm for DMMP and ETDM, respectively, indicating a change in the chemical environment of phosphorus. This suggests that DMMP and ethylenediamine successfully reacted to form the flame retardant ETDM.

[0030] 2. Preparation of flame retardant polyvinyl alcohol film

[0031] 12 g of polyvinyl alcohol (PVA) and 108 g of deionized water were added to a three-necked flask and stirred in a constant-temperature oil bath at 100°C until the PVA was completely dissolved, yielding a 10 wt% PVA solution. 1.33 g of ETDM was added to the PVA solution and stirred in an 85°C oil bath for 0.5 h to obtain a membrane solution. The resulting uniform membrane solution was poured onto a polytetrafluoroethylene (PTFE) film mold and allowed to stand at room temperature for 70 h. The resulting film was then dried in a 40°C oven for 24 h to obtain an ETDM / PVA film.

[0032] Example 2

[0033] In this embodiment, the polyvinyl alcohol composite material is prepared according to the following steps:

[0034] 1. Preparation of ETDM

[0035] Same as Example 1.

[0036] 2. Preparation of flame retardant polyvinyl alcohol film

[0037] 0.07 g of nano-TiO2 powder was added into 10 g of deionized water and ultrasonicated for 15 min to disperse it evenly to obtain nano-TiO2 dispersion.

[0038] 12 g of polyvinyl alcohol (PVA) and 108 g of deionized water were added to a three-necked flask and stirred in a constant-temperature oil bath at 100°C until the PVA was completely dissolved, resulting in a 10 wt% PVA solution. 1.26 g of ETDM and a nano-TiO2 dispersion (containing 0.07 g of nano-TiO2) were added to the PVA solution and stirred in an 85°C oil bath for 0.5 h to obtain a film solution. The resulting uniform film solution was poured onto a polytetrafluoroethylene (PTFE) film mold and allowed to stand at room temperature for 70 h. The film was then dried in a 40°C oven for 24 h to obtain an ETDM / TiO2 / PVA film.

[0039] Example 3

[0040] In this embodiment, the polyvinyl alcohol composite material is prepared according to the following steps:

[0041] 1. Preparation of ETDM

[0042] Same as Example 1.

[0043] 2. Preparation of flame retardant polyvinyl alcohol film

[0044] 0.1 g of nano-TiO2 powder was added into 10 g of deionized water and ultrasonicated for 15 min to disperse it evenly to obtain nano-TiO2 dispersion.

[0045] 12 g of polyvinyl alcohol (PVA) and 108 g of deionized water were added to a three-necked flask and stirred in a constant-temperature oil bath at 100°C until the PVA was completely dissolved, resulting in a 10 wt% PVA solution. 1.23 g of ETDM and a nano-TiO2 dispersion (containing 0.1 g of nano-TiO2) were added to the PVA solution and stirred in an 85°C oil bath for 0.5 h to obtain a film solution. The resulting uniform film solution was poured onto a polytetrafluoroethylene (PTFE) film mold and allowed to stand at room temperature for 70 h. The film was then dried in a 40°C oven for 24 h to obtain an ETDM / TiO2 / PVA film.

[0046] Example 4

[0047] In this embodiment, the polyvinyl alcohol composite material is prepared according to the following steps:

[0048] 1. Preparation of ETDM

[0049] Same as Example 1.

[0050] 2. Preparation of flame retardant polyvinyl alcohol film

[0051] 0.13 g of nano-TiO2 powder was added into 10 g of deionized water and ultrasonicated for 15 min to disperse it evenly to obtain nano-TiO2 dispersion.

[0052] 12 g of polyvinyl alcohol (PVA) and 108 g of deionized water were added to a three-necked flask and stirred in a constant-temperature oil bath at 100°C until the PVA was completely dissolved, resulting in a 10 wt% PVA solution. 1.2 g of ETDM and a nano-TiO2 dispersion (containing 0.13 g of nano-TiO2) were added to the PVA solution and stirred in an 85°C oil bath for 0.5 h to obtain a film solution. The resulting uniform film solution was poured onto a polytetrafluoroethylene (PTFE) film mold and allowed to stand at room temperature for 70 h. The film was then dried in a 40°C oven for 24 h to obtain an ETDM / TiO2 / PVA film.

[0053] Comparative Example

[0054] This comparative example prepares a blank polyvinyl alcohol film:

[0055] Add 12 g of polyvinyl alcohol (PVA) and 108 g of deionized water to a three-necked flask. Stir in a 100°C oil bath until the PVA is completely dissolved, yielding a 10 wt% PVA solution. Pour the PVA solution onto a polytetrafluoroethylene (PTFE) film, let it sit at room temperature for 70 hours, and then dry it in a 40°C oven for 24 hours to obtain a PVA film.

[0056] The properties of the PVA films obtained in the above embodiments and comparative examples were tested as follows:

[0057] Limiting oxygen index instrument: HC-2C oxygen index instrument produced by Nanjing Jiangning Analytical Instrument Co., Ltd., the test conditions are in accordance with ASTMD2863.

[0058] Vertical combustion apparatus: CZF-3 vertical combustion apparatus produced by China Jiangning Analytical Instrument Co., Ltd. The vertical combustion test standard is tested in accordance with ASTM D4804-14.

[0059] Cone calorimeter: China Suzhou Zhengbiao Analytical Instrument Co., Ltd. The test conditions were in accordance with ISO5660-1:2002.

[0060] Tensile testing machine: Shenzhen Ruige Instrument Co., Ltd., testing conditions are in accordance with GB / T 1040.3-2006.

[0061] UV-Vis-NIR spectroscopy: Spectroscopy was performed on a Solid-Spec-3700 UV-Vis-NIR spectrometer (Solid-Spec-3700, Japan). The spectral range was 220–800 nm. Barium sulfate powder was used as the background.

[0062] Table 1 shows the limiting oxygen index (LOI), vertical burning rating (UL-94), peak heat release rate (pHRR), total heat release rate (THR), time to ignition (TTI), elongation at break, and tensile strength of the films obtained in the comparative example and Examples 1-4. Figure 5 、 Figure 6 and Figure 7 The limiting oxygen index histogram, mechanical property histogram and ultraviolet absorbance graph of the films obtained in the comparative example and examples 1-4 are respectively.

[0063] Table 1. Performance test data of polyvinyl alcohol film

[0064]

[0065] The data in the table and accompanying figures show that the addition of ETDM and nano-TiO2 significantly improves the limiting oxygen index of the polyvinyl alcohol film, enhances the vertical combustion rating, and significantly reduces the peak heat release rate (pHRR) and total heat release rate (THR). This indicates that the flame retardant ETDM prepared in this invention, combined with a small amount of nano-TiO2, can significantly enhance the flame retardant and safety properties of polyvinyl alcohol composites. The tensile data also demonstrates that the addition of the flame retardant ETDM and a small amount of nano-TiO2 exhibits good compatibility within the polyvinyl alcohol matrix, effectively enhancing the mechanical properties of the polyvinyl alcohol composite. Furthermore, due to the UV absorption capacity of nano-TiO2, the composite not only improves its flame retardancy and mechanical properties but also imparts a degree of UV resistance.

[0066] The above embodiments are typical embodiments of the present invention and are not intended to limit the present invention. Any adjustments and modifications to the described technical solutions made by those skilled in the art shall fall within the scope of protection of the present invention as long as they do not deviate from the concept of the invention or exceed the scope defined by the claims.

Claims

1. A transparent and UV-resistant flame-retardant polyvinyl alcohol film, characterized by: Ethylenediamine is reacted with dimethyl methylphosphonate to generate N-(2-aminoethyl)-P-methylphosphonamide methyl ester ETDM, which is a transparent liquid flame retardant containing phosphorus and nitrogen; 9 to 9.5 parts of the ETDM and 0.5 to 1 part of nano-TiO2 are compounded and added to 90 to 100 parts of polyvinyl alcohol to prepare a transparent and UV-resistant flame-retardant polyvinyl alcohol film, which is recorded as ETDM / TiO2 / PVA film.

2. The transparent and UV-resistant flame-retardant polyvinyl alcohol film according to claim 1, characterized in that: The preparation method of ETDM is as follows: ethylenediamine and dimethyl methylphosphonate are mixed in a molar ratio of 5 to 10:1, stirred and reacted in an oil bath at 100 to 120°C for 1 to 1.5 hours, and then excess ethylenediamine is removed by a vacuum rotary evaporator at 75 to 85°C to obtain the product ETDM.

3. A method for preparing the transparent and UV-resistant flame-retardant polyvinyl alcohol film according to claim 1 or 2, characterized in that: Add polyvinyl alcohol to deionized water, and stir in an oil bath at 95-100° C. until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution; Add nano-TiO2 powder into an appropriate amount of deionized water and disperse it evenly with ultrasound to obtain nano-TiO2 dispersion; Adding nano-TiO2 dispersion and ETDM to the polyvinyl alcohol solution, stirring in an oil bath at 85-95° C. for 0.5-1 h to obtain a membrane solution; The obtained film liquid was poured onto a polytetrafluoroethylene mold, allowed to stand at room temperature for 70 to 72 hours, and then dried in an oven at 35 to 45°C for 20 to 24 hours to obtain the ETDM / TiO2 / PVA film.

4. The preparation method according to claim 3, wherein: The mass concentration of the polyvinyl alcohol solution is 8-12%.

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