A melt processable green bio-based flame retardant polyvinyl alcohol composite

Abstract

The application belongs to the field of flame-retardant materials, and discloses a green bio-based flame-retardant polyvinyl alcohol composite material which can be melt-processed, and the core is that a high-thermal-stability green bio-based flame retardant CADCM is synthesized by taking cytidine-5'-phosphate and cardanol as raw materials, and then the flame retardant is compounded in a polyvinyl alcohol (PVA) base material through an efficient melt processing process to obtain the target composite material. The method can significantly improve the flame-retardant performance and mechanical performance of the PVA material under the premise of ensuring good melt processability of the PVA material, and the bio-based flame-retardant PVA composite material has the advantages of environmental protection, processing adaptability and comprehensive performance, thereby providing an efficient and feasible technical path and innovative idea for widening the practical application scenarios of the PVA material in the fields of functional packaging film, environment-friendly plastic products and the like.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials, specifically relating to a green bio-based flame retardant polyvinyl alcohol composite material that can be melt-processed. Background Technology

[0002] Driven by the concept of green and sustainable development, researchers are actively exploring and applying new environmentally friendly polymer materials. Among them, polyvinyl alcohol (PVA), due to its non-toxic, high transparency, and biodegradable properties, has shown great application potential in functional packaging films, environmentally friendly plastic products, and other fields, attracting widespread attention from the industry.

[0003] Currently, there are two main technical approaches for PVA film preparation: solution casting and melt processing. Solution casting has lower requirements for the thermal stability of functional fillers, but the molding process involves solvent evaporation, resulting in high energy consumption and long production cycles, leading to low production efficiency and high production costs, making it difficult to meet the needs of large-scale industrial production. In contrast, melt processing has the advantages of high efficiency and speed, making it more suitable for large-scale industrial production. However, its application is limited by the inherent thermal properties of PVA material—PVA's melting temperature is approximately 230 ℃, while its decomposition temperature range is 200-250 ℃. The close proximity of these two temperatures results in a narrow processing window and also places higher demands on the thermal stability of functional fillers.

[0004] To broaden the processing window of PVA, the industry often introduces plasticizers to expand its melting and decomposition temperature range and improve its thermal processing performance. However, PVA itself is a flammable material with a limiting oxygen index (LOI) of only about 19%, and it also exhibits dripping during combustion. While the introduction of plasticizers may aid processing, it can further exacerbate the dripping problem during combustion, posing a significant fire hazard. Therefore, improving the flame retardant properties of PVA is a crucial prerequisite for its industrial application.

[0005] Currently, research on flame-retardant PVA composites mainly focuses on solution casting, while research on melt processing methods for preparing flame-retardant PVA composites is relatively scarce. Commonly used flame retardants such as ammonium polyphosphate and phytic acid exhibit excellent flame-retardant effects in solution casting systems, but their applicability under melt processing conditions is poor: the initial decomposition temperature of phytic acid is generally lower than the 160℃-210℃ range required for PVA melt processing, and its insufficient thermal stability leads to premature decomposition during processing, failing to exert its flame-retardant effect and potentially hindering PVA processing and molding; although ammonium polyphosphate possesses high thermal stability, the acidic substances generated within the system during PVA melt processing accelerate the high-temperature dehydration and carbonization of the PVA matrix, rendering the material unprocessable.

[0006] In summary, flame-retardant fillers used in melt-processing PVA composites must simultaneously meet three core requirements: high thermal stability, absence of acidic sources, and good compatibility with the PVA matrix. Insufficient compatibility can easily lead to filler agglomeration, thereby reducing the mechanical properties of the material. Therefore, developing a halogen-free flame retardant with high thermal stability, good compatibility, and environmental friendliness, and using a melt-processing strategy to prepare flame-retardant polyvinyl alcohol films, is of significant practical importance for promoting the efficient application of PVA materials in the context of green and sustainable development. Summary of the Invention

[0007] To address the problems of poor compatibility of flame retardants and inadequate compatibility between fillers and matrix in existing technologies, this invention provides a melt-processable green bio-based flame-retardant polyvinyl alcohol composite material. The core of this invention lies in synthesizing a high thermal stability green bio-based flame retardant CADCM and then incorporating it into a PVA matrix through an efficient melt processing process, ultimately obtaining a PVA composite material that combines excellent flame retardant properties, good mechanical properties, and processability.

[0008] To solve the technical problem, the present invention adopts the following technical solution:

[0009] This invention first discloses a green bio-based flame retardant, wherein the flame retardant is denoted as CADCM, which is generated by reacting cytidine-5'-phosphate with cashew nut shell extract. The specific preparation method of the green bio-based flame retardant includes the following steps:

[0010] Weigh 0.01 mol of cashew nut phenol (CARD), add 140~160 mL of anhydrous ethanol and stir to dissolve to obtain a cashew nut phenol solution;

[0011] Weigh 0.01 mol of cytidine-5'-phosphate (CMP), add 70–90 mL of deionized water, and place in an oil bath at 50–60 °C. Stir until dissolved, then add 0.02 mol of formaldehyde (FA), and continue stirring for 0.2–0.5 h. Next, add the cashew phenol solution, raise the oil bath temperature to 110–120 °C, and continue stirring for 4–4.5 h. After the reaction is complete, cool to room temperature, filter and collect the product, wash with a mixture of anhydrous ethanol and deionized water (ethanol to water volume ratio range 1.5–2:1), and finally dry in an oven at 50–60 °C for 20–24 h to obtain the product CADCM. The reaction formula is as follows: Figure 1 As shown.

[0012] This invention further discloses a melt-processable, green, bio-based, flame-retardant polyvinyl alcohol (PVA) composite material. This composite material is prepared by adding the aforementioned CADCM to a PVA base material via melt processing, and is designated as CADCM / PVA material. The PVA base material is composed of PVA, glycerol, ethylene glycol, antioxidant 1010, zinc stearate, calcium stearate, and caprolactam. In the composite material, the mass percentage of the PVA base material is 85%–92.5%, and the mass percentage of CADCM is 15%–7.5%.

[0013] Further, the composition of each raw material in the polyvinyl alcohol base material by weight is as follows: 77.5~78.5 parts polyvinyl alcohol, 10.5~11.5 parts glycerol, 6.5~7.5 parts ethylene glycol, 0.45~0.55 parts antioxidant 1010, 0.45~0.55 parts zinc stearate, 0.45~0.55 parts calcium stearate, and 2.45~2.55 parts caprolactam.

[0014] The preparation method of the CADCM / PVA material of the present invention includes the following steps:

[0015] Step 1: Take polyvinyl alcohol, glycerin, ethylene glycol, antioxidant 1010, zinc stearate, calcium stearate and caprolactam, pour them into a high-speed mixer and mix for 10-15 minutes to obtain polyvinyl alcohol base material;

[0016] Step 2: After mixing the polyvinyl alcohol base material and flame retardant CADCM evenly, add it to a mixer heated to 165~170 ℃ and mix for 2~3 minutes. Take out the mixed product.

[0017] Step 3: Place the compounded product in a flat vulcanizing machine and hot-press it at 170~175 ℃ for 1~2 min to form a sheet sample, thus obtaining CADCM / PVA material.

[0018] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0019] 1. This invention uses cytidine-5'-phosphate and cashew nut shellac as base materials to synthesize the bio-based flame retardant CADCM, avoiding the defects of traditional flame retardants from the source. It solves the problems of insufficient thermal stability and premature decomposition and failure of phytic acid flame retardants at PVA melt processing temperatures, and overcomes the problems of ammonium polyphosphate easily generating acidic substances and accelerating the high-temperature dehydration and carbonization of PVA. CADCM has excellent thermal stability (reaching 239℃ at 5% thermal weight loss) and good compatibility with the PVA matrix, avoiding filler agglomeration, providing a highly adaptable green flame retardant solution for PVA melt processing flame retardant modification. At the same time, its preparation process is simple, the reaction cycle is short, and the raw materials are renewable. Compared with traditional flame retardants, it requires less addition and has high flame retardant efficiency, significantly reducing production costs and environmental impact.

[0020] 2. CADCM, through a gas-phase-condensed-phase synergistic flame retardant mechanism, can significantly improve the limiting oxygen index and vertical burning rating of PVA composites, greatly reduce the peak heat release and total heat release, effectively suppress combustion dripping, and completely solve the fire safety hazard of decreased flame retardant performance of PVA after plasticizing modification. At the same time, as a rigid filler, CADCM can form multiple hydrogen bonds with the hydroxyl groups on the PVA molecular chain, strengthen the interfacial interaction, and improve the tensile strength and elastic modulus of PVA composites while improving flame retardant performance, breaking through the bottleneck of "flame retardant enhancement inevitably leads to a decrease in mechanical properties" in traditional flame retardant modification.

[0021] 3. This invention employs a melt processing technology to prepare composite materials, which significantly improves production efficiency and reduces energy consumption compared to solution casting, thus meeting the needs of large-scale industrial production. The CADM / PVA composite material prepared by this invention possesses excellent processing adaptability, high flame retardancy, superior mechanical properties, and green environmental protection characteristics, providing a feasible path for its large-scale application in functional packaging films, environmentally friendly plastic products, and other fields. Attached Figure Description

[0022] Figure 1 The reaction formula is for the reaction of cytidine-5'-phosphate and cashew nut alcohol to produce CADCM.

[0023] Figure 2 Infrared spectra of cytidine-5'-phosphate, cashew phenol, and CADCM.

[0024] Figure 3 The XPS spectra of CMP and CADCM are shown below: (a) is the full spectrum of CMP and CADCM; (b) is the N 1s spectrum of CMP; and (c) is the N 1s spectrum of CADCM.

[0025] Figure 4 This is a graph showing the TGA and DTG curves for CADCM.

[0026] Figure 5 The bar chart shows the limiting oxygen index of the samples obtained in comparative examples and Examples 1-4.

[0027] Figure 6 This is a diagram of the vertical combustion experiment process of the sample obtained for comparison.

[0028] Figure 7 The diagram shows the vertical combustion experiment process of the samples obtained in Examples 1-4.

[0029] Figure 8 The bar chart shows the mechanical properties of the samples obtained in comparative examples and Examples 1-4. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0031] The polyvinyl alcohol used in the following examples is model 1788.

[0032] Example 1

[0033] This embodiment prepares flame-retardant polyvinyl alcohol composite material according to the following steps:

[0034] 1. Preparation of CADCM

[0035] Weigh 0.01 mol of cashew phenol into a beaker, add 150 mL of anhydrous ethanol and stir to dissolve, obtaining a cashew phenol solution. Weigh 0.01 mol of cytidine-5'-phosphate into a three-necked flask, add 80 mL of deionized water, place in a 60 ℃ oil bath and stir until dissolved, then add 0.02 mol of formaldehyde and continue stirring for 0.5 h. Add the cashew phenol solution, raise the oil bath temperature to 120 ℃, and continue stirring for 4 h. After the reaction is complete, cool to room temperature, filter and collect the product, wash three times with a mixture of anhydrous ethanol and deionized water (volume ratio of anhydrous ethanol to deionized water is 15:8), and finally dry in a 50 ℃ oven for 24 h to obtain the product CADCM.

[0036] Figure 2 The figures show the infrared spectra of cytidine-5'-phosphate (CMP), cashew nut shell extract (CARD), and CADCM. It can be seen from the figures that in the FTIR spectrum of CMP, at 3573 cm⁻¹... -1 and 3453 cm -1 The double characteristic peak at 3330 cm⁻¹ is due to the NH stretching vibration of the amino group (-NH₂). In the CARD FTIR spectrum, this peak is at 3330 cm⁻¹. -1 The broad peaks around 2922 cm⁻¹ are due to the stretching vibrations of the phenolic hydroxyl groups. -1and 2850 cm -1 The absorption peak at 1590 cm⁻¹ is due to the asymmetric and symmetric vibrations of CH in the aliphatic chain. -1 and 1461 cm -1 The absorption peak at 2922 cm⁻¹ is attributed to the C=C stretching vibration of the benzene ring skeleton. In the FTIR spectrum of CADM, it can be observed that after CMP forms a benzoxazine ring with cashew phenol and formaldehyde, the double characteristic peak of -NH₂ in CMP disappears, and a new peak appears at 2922 cm⁻¹. -1 and 2850 cm -1 Both asymmetric and symmetric vibrational peaks of CH in the cashew phenol fatty chain appear at 1590 cm⁻¹. -1 and 1461 cm -1 A C=C stretching vibration peak of the cashew phenol benzene ring skeleton appears at 1109 cm⁻¹. -1 The absorption peak at 1049 cm⁻¹ is attributed to the asymmetric tensile vibration of the CNC. -1 The peaks at the point are attributed to the symmetric stretching vibration of COC. The appearance of these absorption peaks and the disappearance of the -NH2 double characteristic peak in CMP can preliminarily infer the successful synthesis of CADCM.

[0037] Figure 3 The XPS spectra of CMP and CADCM are shown in the figure. As shown, CADCM contains four elements: C, N, P, and O, which is consistent with elemental composition. Furthermore, the N 1s spectrum of CMP shows three peaks: -NH2 (402.5 eV), NC (401.0 eV), and -C=NH (399.9 eV), while the N 1s spectrum of CADCM shows only two peaks: NC (400.9 eV) and -C=NH (399.8 eV). This indicates that the characteristic peak of -NH2 in CMP at 402.5 eV has disappeared, further demonstrating the successful preparation of the flame retardant CADCM.

[0038] Figure 4 The figure shows the TGA and DTG curves of CADCM. As shown, the pyrolysis of CADCM mainly has two stages: the first stage, between 230 and 420 °C, primarily involves the decomposition of phosphate groups, nitrogenous bases, ribose moieties, and long-chain alkyl groups. Phosphate groups dehydrate and decompose to form pyrophosphates, while nitrogenous bases and ribose moieties decompose to produce small molecules (such as furfural, NH3, CO2, and CO). Long-chain alkyl groups crack to produce hydrocarbons (such as alkanes and alkenes). The second stage, between 520 and 580 °C, mainly involves the further carbonization of the residues from the first stage. Simultaneously, the temperature at which CADCM loses 5% of its weight (T...) is also shown. 5% With a temperature of 239℃, it exhibits good thermal stability and can be used to prepare flame-retardant PVA materials via melt processing, which has practical application significance.

[0039] 2. Preparation of flame-retardant polyvinyl alcohol composite materials

[0040] 78 g of PVA1788, 11 g of glycerin, 7 g of ethylene glycol, 0.5 g of antioxidant 1010, 0.5 g of zinc stearate, 0.5 g of calcium stearate, and 2.5 g of caprolactam were weighed out sequentially and mixed in a high-speed mixer for 10 min to obtain the PVA base material. 46.25 g of PVA base material and 3.75 g of flame retardant CADCM were weighed out and mixed evenly. This mixture was then added to a Banbury mixer heated to 165 ℃ and kneaded for 2 min. The kneaded product was then removed. The kneaded product was placed in a flat vulcanizing machine and hot-pressed at 170 ℃ for 1 min to form a sheet sample, thus obtaining the CADCM / PVA material.

[0041] Example 2

[0042] In this embodiment, CADCM / PVA material was prepared using the same method as in Example 1, except that the mass of PVA base material and flame retardant CADCM in step 2 was 45 g and 5 g, respectively.

[0043] Example 3

[0044] In this embodiment, CADCM / PVA material was prepared using the same method as in Example 1, except that in step 2, the mass of PVA base material and flame retardant CADCM were 43.75 g and 6.25 g, respectively.

[0045] Example 4

[0046] In this embodiment, CADCM / PVA material was prepared using the same method as in Example 1, except that the mass of PVA base material and flame retardant CADCM in step 2 were 42.5 g and 7.5 g, respectively.

[0047] Comparative Example

[0048] In this embodiment, blank PVA material was prepared using the same method as in Example 1, except that the mass of PVA base material and flame retardant CADCM in step 2 was 50 g and 0 g, respectively.

[0049] The properties of the CADCM / PVA materials and blank PVA materials obtained in the above embodiments and comparative examples were tested using the following methods:

[0050] Limiting Oxygen Index (LOI): Tested using an HC-2C oxygen index meter from Nanjing Jiangning Analytical Instrument Co., Ltd., in accordance with ASTM D2863 standard.

[0051] Vertical flammability rating: The CZF-3 vertical flammability tester from Jiangning Analytical Instruments Co., Ltd. of China was used to conduct the test according to the ASTM D4804-14 standard. In the vertical flammability test, the first ignition and the second ignition are the core steps for evaluating the flame retardant performance of the material: (1) First ignition: After the sample is fixed vertically, the sample is ignited from the bottom with a specified flame. After 10 seconds, the flame is removed, and the timing is started. The flame burning time and whether there are molten droplets igniting the degreased cotton are recorded. (2) Second ignition: After the flame of the first ignition is extinguished, the sample is immediately ignited again with the same flame and held for 10 seconds. After the flame is removed, the timing is started, and the second flame burning time is recorded. Finally, the vertical flammability rating (UL-94) of the material is determined by combining the burning time of the two ignitions and the molten droplet situation.

[0052] Combustion performance: The test was conducted using a cone calorimeter from Suzhou Zhengbiao Combustion Testing Technology Service Co., Ltd., China, in accordance with ISO5660-1:2002 standard.

[0053] Mechanical properties: The tensile testing machine of Shenzhen Ruigeer Instrument Co., Ltd. was tested in accordance with the standard GB / T 1040.3-2006.

[0054] Table 1 shows the limiting oxygen index (LOI), vertical flammability rating (UL-94), peak heat release rate (pHRR), total heat release (THR), ignition time (TTI), tensile strength, and modulus of elasticity for the comparative examples and samples obtained in Examples 1-4. Figure 5 , Figure 6 , Figure 7 and Figure 8 The following are bar charts showing the limiting oxygen index, vertical combustion test process, and mechanical properties of the thin film samples obtained in comparative examples and Examples 1-4, respectively.

[0055] Table 1

[0056]

[0057] As shown in the table and figures above, introducing CADCM into the polyvinyl alcohol matrix via a high-efficiency melt processing method significantly improves the limiting oxygen index and vertical flammability of the composite material, while substantially reducing the peak heat release ratio (pHRR) and total heat release (THR). This indicates that the CADCM prepared in this invention can effectively exert its flame-retardant effect under melt processing conditions, significantly improving the flame-retardant performance and fire safety of polyvinyl alcohol composite materials. Furthermore, the tensile property data demonstrate that CADCM exhibits good dispersibility and compatibility within the polyvinyl alcohol matrix, enhancing both flame-retardant properties and the material's mechanical properties.

[0058] The above embodiments are typical embodiments of the present invention and are not intended to limit the present invention in any way. Any adjustments and modifications made by those skilled in the art to the described technical solutions, as long as they do not deviate from the inventive concept, should fall within the protection scope of the present invention.

Claims

1. A green bio-based flame retardant, characterized in that: The flame retardant is decadealkylbenzoxazinylcytidine-5'-phosphate, generated by the reaction of cytidine-5'-phosphate and cashew phenol, denoted as CADCM. The structural formula of CADCM is shown below: 。 2. A method for preparing the green bio-based flame retardant according to claim 1, characterized in that, Includes the following steps: Weigh 0.01 mol of cashew phenol and add 140-160 mL of anhydrous ethanol and stir to dissolve to obtain a cashew phenol solution; Weigh 0.01 mol of cytidine-5'-phosphate, add 70-90 mL of deionized water, place in an oil bath at 50-60 ℃ and stir until dissolved. Add 0.02 mol of formaldehyde and continue stirring for 0.2-0.5 h. Then add the cashew phenol solution, heat the oil bath to 110-120 ℃, and continue stirring for 4-4.5 h. After the reaction is complete, cool to room temperature, filter and collect the product, wash with a mixture of anhydrous ethanol and deionized water, and finally dry in an oven at 50-60 ℃ for 20-24 h to obtain the product CADCM.

3. A melt-processable, green, bio-based, flame-retardant polyvinyl alcohol composite material, characterized in that: The composite material is prepared by adding the green bio-based flame retardant described in claim 1 to a polyvinyl alcohol base material through melt processing, and is denoted as CADCM / PVA material; in the composite material, the mass percentage of polyvinyl alcohol base material is 85%~92.5%, and the mass percentage of CADCM is 15%~7.5%; The polyvinyl alcohol base material comprises the following components by weight: 77.5-78.5 parts polyvinyl alcohol, 10.5-11.5 parts glycerol, 6.5-7.5 parts ethylene glycol, 0.45-0.55 parts antioxidant 1010, 0.45-0.55 parts zinc stearate, 0.45-0.55 parts calcium stearate, and 2.45-2.55 parts caprolactam.

4. A method for preparing the melt-processable green bio-based flame-retardant polyvinyl alcohol composite material according to claim 3, characterized in that, Includes the following steps: Step 1: Take polyvinyl alcohol, glycerin, ethylene glycol, antioxidant 1010, zinc stearate, calcium stearate and caprolactam, pour them into a high-speed mixer and mix for 10-15 minutes to obtain polyvinyl alcohol base material; Step 2: After mixing the polyvinyl alcohol base material and flame retardant CADCM evenly, add it to a mixer heated to 165~170 ℃ and mix for 2~3 minutes. Take out the mixed product. Step 3: Place the compounded product in a flat vulcanizing machine and hot-press it at 170~175 ℃ for 1~2 min to form a sheet sample, thus obtaining CADCM / PVA material.

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