A nitrogen-phosphorus high-synergistic dual-function flame retardant, a high-efficiency flame-retardant beta-crystal polypropylene material, and a preparation method and application thereof

Abstract

The application discloses a kind of nitrogen phosphorus high synergistic dual-function flame retardant, efficient flame-retardant beta-crystal polypropylene material and preparation method and application, and flame retardant is composed of polybasic phosphate, modified polymer and chitosan, and modified polymer is polyphosphate modified phytic acid-melamine supramolecular polymer.The preparation method of flame retardant is: phytic acid-melamine supramolecular polymer is prepared using ion complexation, polyphosphate is added to modify, and modified polymer is obtained;Using the self-assembly effect between chitosan and modified polymer under electrostatic driving, chitosan-coated modified polymer core-shell material is obtained;Multi-element phosphorus salt is immobilized in chitosan-coated modified polymer core-shell material to obtain nitrogen phosphorus high synergistic dual-function flame retardant.The flame retardant can realize the high flame retardance and high beta crystal nucleation rate of PP material.The bio-based proportion in flame retardant is as high as 70% or more, which makes up for the problem that traditional polymer flame retardant is highly dependent on petrochemical raw materials, and reduces pollution in production.

Description

Technical Field

[0001] This invention relates to a nitrogen-phosphorus synergistic bifunctional flame retardant, a high-efficiency flame-retardant β-crystalline polypropylene material, its preparation method and application, and belongs to the field of flame retardant technology. Background Technology

[0002] Polypropylene (PP), as a semi-crystalline thermoplastic resin, boasts advantages such as low cost, mature processing technology, and high heat resistance, making it a crucial raw material for national economic and scientific and technological progress. However, PP's low low-temperature impact strength, poor thermal stability, flammability, and poor low-temperature toughness severely hinder its application in building materials, industrial sectors, and injection molding. Flame retardants, as functional additives, impart flame-retardant properties to PP by influencing the combustion process and combustion products, while nucleating agents significantly affect the structure and properties of PP by influencing its crystal morphology and grain size. Therefore, modifying PP by adding flame retardants and nucleating agents to generate PP with high flame retardancy and a microcrystalline structure is the most economical and effective means to achieve high-performance PP.

[0003] Among commonly used flame-retardant materials, intumescent flame retardants (IFRs) have attracted widespread attention due to their advantages such as smoke suppression, halogen-free properties, anti-drip properties, and non-toxicity. In IFRs, the acid source, when heated, produces inorganic acids that play a dehydrating role. As the temperature rises, an esterification reaction also occurs between the carbon source and the inorganic acid. Furthermore, the water vapor generated during the reaction and the non-flammable gases produced by the gas source accumulate on the material surface, forming a dense carbon layer that provides thermal and oxygen insulation, preventing further degradation of the polymer matrix and the escape of flammable gases, thus preventing flame spread. Therefore, the introduction of IFRs into PP not only improves flame-retardant performance but also ensures environmental benefits, better meeting my country's requirements for the development of environmentally friendly products.

[0004] Polypropylene (PP) can be classified into five crystal forms: smectic δ-crystalline, monoclinic α-crystalline, triclinic γ-crystalline, hexagonal β-crystalline, and pseudo-hexagonal. The addition of β-crystalline nucleating agents can induce the transformation of PP's α-crystalline form into β-crystalline, effectively improving the impact strength of PP at both room temperature and low temperatures. Therefore, selecting appropriate nucleating agents to increase the β-crystalline nucleation rate in PP is the most effective means to improve its low-temperature impact strength and low-temperature toughness.

[0005] Chinese invention patent CN115246860A discloses a method for preparing and using phosphorus-nitrogen intumescent flame retardant nanosheets. The first step involves a nucleophilic substitution reaction between hexachlorocyclotriphosphazene and acetaminophen to obtain an intermediate product. Subsequently, a deamidation reaction is carried out under alkaline conditions, followed by a salt-forming reaction with phytic acid to obtain phosphorus-nitrogen intumescent flame retardant nanosheets. To improve the product's thermal stability, this patent introduces acid anhydrides, which affects the product's flame retardant effect and ultimately limits its application range.

[0006] Chinese invention patent CN115678574A discloses a single-component intumescent flame retardant, its preparation method, and its application. First, ammonium polyphosphate, starch, and water are mixed evenly. Then, a melamine derivative and p-toluenesulfonic acid are added to obtain a mixture. During heating and stirring, a suitable crosslinking agent and additives are compounded, followed by specific in-situ polymerization to prepare the flame retardant. The flame retardant prepared by this patented technology exhibits low flame retardant performance, failing to achieve the desired effect, and the complex preparation process limits its application.

[0007] Chinese invention patent CN114561043B discloses a polypropylene nucleating agent composition and its preparation method and application. This patent utilizes the synergistic effect of sodium 2,2'-methylene-bis(4,6-di-tert-butylphenoxy)phosphate, calcium stearate, and bis(dioctyloxypyrophosphate)ethylene titanate to improve the dispersibility of phosphate metal salts. However, the transparency, α-crystal nuclei perfection, and regularity of PP are severely affected by the holding pressure time during injection molding, leading to defects in the crystallization process and affecting the low-temperature impact strength.

[0008] Chinese invention patent CN115678161A discloses a composite nucleating agent composition and its application. This composition comprises organophosphates, aromatic diamide nucleating agents, nano-calcium carbonate, and graphene. Using graphene as a base, it forms an interwoven crystalline network of α and β-crystalline polymers to improve the rigidity and toughness of the polymer, achieving a balanced stiffness and toughness while maintaining transparency. However, this patent uses multiple nucleating agents in combination, making their interactions difficult to predict. Extensive design and experimental work is required to determine the composition of the composite nucleating agent and its applicable range.

[0009] In summary, there is an urgent need for a nitrogen-phosphorus synergistic bifunctional flame retardant, a highly efficient flame-retardant β-crystalline polypropylene material, its preparation method, and its application. Summary of the Invention

[0010] This invention addresses the problems of low low-temperature impact strength, poor thermal stability, and flammability in polypropylene modified with existing flame retardants by providing a nitrogen-phosphorus synergistic dual-functional flame retardant. This flame retardant can simultaneously achieve dual-functional modification of flame retardancy and microcrystalline structure.

[0011] In addition, the present invention also provides a method for preparing the flame retardant.

[0012] Furthermore, this invention also provides applications of this flame retardant.

[0013] Meanwhile, the present invention also provides a high-efficiency flame-retardant β-crystalline polypropylene material modified with a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0014] Meanwhile, this invention also provides a method for preparing highly efficient flame-retardant β-crystalline polypropylene materials.

[0015] Meanwhile, this invention also provides applications of highly efficient flame-retardant β-crystalline polypropylene materials.

[0016] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0017] A nitrogen-phosphorus synergistic bifunctional flame retardant includes a supported flame retardant, the carrier being a core-shell composite of a chitosan-coated modified polymer, the loading being a polyphosphate, and the modified polymer being a polyphosphate-modified phytic acid-melamine supramolecular polymer.

[0018] A method for preparing a nitrogen-phosphorus synergistic bifunctional flame retardant includes the following steps:

[0019] Step a: Melamine is added to a reaction vessel, and deionized water is added at a mass ratio of melamine to deionized water of 1:100-250 to obtain a melamine aqueous solution. Then, phytic acid aqueous solution with a mass fraction of 50wt%-70wt% is added to the melamine aqueous solution at a mass ratio of phytic acid aqueous solution to melamine of 1:8-12. The reaction is carried out at 60-95℃ for 0.5-3 hours to obtain a phytic acid-melamine supramolecular polymer emulsion. Then, polyphosphate is added to the phytic acid-melamine supramolecular polymer emulsion at a mass ratio of polyphosphate to melamine of 1:2.5-5. The reaction is carried out at 70-90℃ for 4-6 hours. After standing, the mixture is filtered, washed with anhydrous ethanol until neutral, and dried at 60-95℃ for 12-24 hours to obtain the modified polymer.

[0020] Step b: Prepare an aqueous solution of organic acid with a mass fraction of 1wt% to 3wt%. Add chitosan at a mass ratio of chitosan to the aqueous solution of organic acid of 1:90 to 120, and stir at room temperature for 1 to 2 hours to obtain a chitosan solution. Add modified polymer at a mass ratio of modified polymer to chitosan solution of 1:150 to 300, stir, and react at 20 to 40°C for 2 to 4 hours. Add polyphosphate at a mass ratio of modified polymer to polyphosphate of 1:0.5 to 1.2, stir, and react at 40 to 65°C for 5 to 8 hours. Cool, filter, wash with distilled water until neutral, and dry at 50 to 80°C for 12 to 24 hours to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0021] Polyphosphate is one of the following: ammonium polyphosphate, sodium hexametaphosphate, and sodium tripolyphosphate.

[0022] The polyphosphate is one of zinc phytate, calcium phytate, or manganese phytate; the organic acid is acetic acid or citric acid.

[0023] A high-efficiency flame-retardant β-crystalline polypropylene material modified with a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0024] The high-efficiency flame-retardant β-crystalline polypropylene material has a β-crystalline content of 69.8%–76.2%, a heat distortion temperature of 115–120℃, a crystallization temperature of 129–133℃, and a notched impact strength of 44.4–48.7 KJ / m². 2 It has a UL-94 flame retardancy rating of V-1 to V-2 and a LOI of 29.4% to 32.9%.

[0025] The preparation method of high-efficiency flame-retardant β-crystalline polypropylene material includes the following steps: adding nitrogen-phosphorus high-synergistic dual-functional flame retardant to polypropylene at an addition amount of 10wt% to 20wt%, mixing evenly, melting and blending at 160 to 200℃, and finally cooling and granulating to obtain high-efficiency flame-retardant β-crystalline polypropylene material.

[0026] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in flame retardant materials, including high-efficiency flame retardant β-crystalline polypropylene materials.

[0027] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in modified polypropylene.

[0028] Application of high-efficiency flame-retardant β-crystalline polypropylene materials in flame-retardant products.

[0029] Flame retardant products include flame retardant building materials, flame retardant industrial products, and flame retardant injection molded products.

[0030] The reaction principle of this invention is as follows:

[0031] Phytic acid-melamine supramolecular polymer (MPA) was prepared by ionic complexation, and modified with polyphosphate to obtain modified polymer (A-MPA). A chitosan-coated modified polymer core-shell material was obtained by electrostatically driven self-assembly between chitosan polymer (CS) and modified polymer (A-MPA). A nitrogen-phosphorus synergistic bifunctional flame retardant was obtained by immobilizing polyphosphates in the chitosan-coated modified polymer core-shell material.

[0032] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0033] 1. The nitrogen-phosphorus high synergistic bifunctional flame retardant leverages the synergistic effect between the components in the flame retardant. While improving flame retardant performance, it also improves the crystallization characteristics of PP polymer, simultaneously enhancing the flame retardancy and low-temperature impact resistance of PP materials. This avoids the problem of uneven distribution of multi-component modifiers in PP materials and poor synergistic reinforcement effect.

[0034] 2. Based on imparting high flame retardant properties to PP, the nitrogen-phosphorus synergistic bifunctional flame retardant constructed in this invention is beneficial for leveraging the gas-condensation coexistence flame retardant mechanism, thereby improving flame retardant efficiency. Specifically:

[0035] a) Initial combustion stage: The polyphosphates immobilized in this nitrogen-phosphorus synergistic bifunctional flame retardant have a polyhydroxy structure, which promotes charring in the initial combustion stage. In addition, the metal cations in the polyphosphates can also play a significant role in in-situ catalytic charring, mainly in that the metal cations in the polyphosphates are directly linked to the PO structure, which can capture phosphorus-oxygen bonds and catalyze the generation of various cross-linked structures, thereby forming a high-quality char layer as a protective barrier, but it is not enough to prevent the polymer from continuing to burn.

[0036] b) Mid-combustion stage: As the temperature rises, the structural units of chitosan dehydrate and break down. The H2O released during this process helps to dilute some of the flammable gases.

[0037] c) Late Combustion Stage: The pyrolysis products of the modified polymer are mainly phosphoric acid and cross-linked char layer. During combustion, it also releases non-flammable gases such as NH3 and CO2 to reduce the concentration of flammable gases and promote the formation of porous char layer. In addition, the POC bonds in the modified polymer break, generating phosphorus-oxygen free radicals in the gas phase to capture active hydrogen and hydroxyl free radicals during the pyrolysis of polypropylene substrate, inhibiting further cracking and combustion of the PP main chain.

[0038] 3. Based on improving the low-temperature impact strength and low-temperature toughness of PP, the nitrogen-phosphorus synergistic bifunctional flame retardant constructed in this invention uses polyphosphates as nucleating agents and chitosan as a carrier. Through the interaction between the functional groups on the surface of chitosan and the nucleating agent, the nucleating agent is highly dispersed on its surface. At the same time, by utilizing the compatibility between chitosan and PP, the dispersibility of the nucleating agent in the PP matrix is ​​improved, further inducing PP to form oriented, regularly arranged and uniformly distributed microspheres, increasing the effective nucleation sites of PP, inducing the transformation of PP α crystal form to β crystal form, improving the β crystal form nucleation rate, and playing a better crystallization control role, thereby improving the impact strength and toughness of PP at low temperatures.

[0039] 4. This invention uses a bio-based structure to construct a nitrogen-phosphorus synergistic bifunctional flame retardant. The synthesis method of the target product is relatively simple and energy-efficient. The synthesis process does not require the addition of a catalyst and does not involve high-temperature and high-pressure reactions.

[0040] This invention discloses a nitrogen-phosphorus synergistic bifunctional flame retardant and its preparation method, comprising a polyphosphate, a modified polymer, and chitosan, wherein the modified polymer is a polyphosphate-modified phytic acid-melamine supramolecular polymer. The preparation method of this flame retardant is as follows: phytic acid-melamine supramolecular polymer is prepared using ionic complexation; polyphosphate is added for modification to obtain the modified polymer; self-assembly driven by electrostatic interaction between chitosan and the modified polymer yields a chitosan-coated modified polymer core-shell material; polyphosphate is then immobilized into the chitosan-coated modified polymer core-shell material to obtain the nitrogen-phosphorus synergistic bifunctional flame retardant. Applying this flame retardant to the modification of PP materials achieves high flame retardancy and high β-crystal nucleation rate in PP materials. The bio-based content of the flame retardant is over 70%, overcoming the problem of traditional polymer flame retardants' high dependence on petrochemical raw materials and reducing pollution during production. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the reaction principle of the present invention;

[0042] Figure 2 The images shown are scanning electron microscope images of the intermediate products during the preparation of the nitrogen-phosphorus highly synergistic bifunctional flame retardant in Example 1 of this invention. Among them: a is phytic acid-melamine supramolecular polymer (MPA), b is zinc phytate (PA-Zn), c is ammonium polyphosphate (APP), d is modified polymer (A-MPA), e is intermediate product A-MPA@CS, and f is nitrogen-phosphorus highly synergistic bifunctional flame retardant (A-MPA@CS / PA-Zn).

[0043] Figure 3 The infrared spectra of each intermediate product in the preparation process of the nitrogen-phosphorus synergistic bifunctional flame retardant in Example 1 of this invention are shown.

[0044] Figure 4 The thermogravimetric analysis (TG) spectra of each intermediate product during the preparation of the nitrogen-phosphorus synergistic bifunctional flame retardant in Example 1 of this invention. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0046] Example 1

[0047] This embodiment provides a method for preparing a nitrogen-phosphorus highly synergistic bifunctional flame retardant, the specific steps of which are as follows:

[0048] First, 1g of melamine was dissolved in 220g of deionized water, and then 0.1g of phytic acid aqueous solution (70wt%) was added. The mixture was reacted at 80℃ for 3h to obtain a phytic acid-melamine supramolecular polymer emulsion (MPA). Then, 0.25g of ammonium polyphosphate (APP) was added to the emulsion, and the mixture was reacted at 84℃ for another 6h. After standing, the mixture was filtered, and washed several times with 30g of anhydrous ethanol until the filtrate was neutral. The mixture was then dried at 75℃ for 18h to obtain the modified polymer (A-MPA).

[0049] Next, 1g of chitosan (CS) was added to 100g of acetic acid aqueous solution (1.5wt%) and stirred at room temperature for 1h to obtain a chitosan solution. Then, 0.2g of modified polymer was added to 30g of chitosan solution and stirred. The mixture was reacted at 20℃ for 4h, and then 0.1g of zinc phytate (PA-Zn) was added. The mixture was reacted at 60℃ for another 7h. After cooling and filtration, the mixture was washed with 20g of distilled water until neutral and dried at 80℃ for 12h to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant (A-MPA@CS@PA-Zn).

[0050] A nitrogen-phosphorus synergistic bifunctional flame retardant is a supported flame retardant. The carrier is a core-shell complex of a chitosan-coated modified polymer, the loading material is a polyphosphate (zinc phytate), and the modified polymer is a phytic acid-melamine supramolecular polymer modified with ammonium polyphosphate.

[0051] A high-efficiency flame-retardant β-crystalline polypropylene material modified with a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0052] The preparation method of high-efficiency flame-retardant β-crystalline polypropylene material includes the following steps: adding nitrogen-phosphorus high-synergistic dual-functional flame retardant to polypropylene at an addition amount of 10wt%, mixing evenly, melting and blending at 160℃, and finally cooling and granulating to obtain high-efficiency flame-retardant β-crystalline polypropylene material.

[0053] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in flame retardant materials, including high-efficiency flame retardant β-crystalline polypropylene materials.

[0054] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in modified polypropylene.

[0055] Application of high-efficiency flame-retardant β-crystalline polypropylene materials in flame-retardant products.

[0056] Flame retardant products include flame retardant building materials, flame retardant industrial products, and flame retardant injection molded products.

[0057] Example 2

[0058] This embodiment provides a method for preparing a nitrogen-phosphorus highly synergistic bifunctional flame retardant, the specific steps of which are as follows:

[0059] First, dissolve 2g of melamine in 500g of deionized water, then add 0.25g of phytic acid aqueous solution (50wt%) and react at 95℃ for 2h to obtain a phytic acid-melamine supramolecular polymer emulsion. Then add 0.8g of sodium tripolyphosphate to the emulsion and continue the reaction at 70℃ for 4.5h. After standing, filter and wash several times with 30g of anhydrous ethanol until the filtrate is neutral. Dry at 60℃ for 14h to obtain the modified polymer.

[0060] Next, 2g of chitosan was added to 180g of citric acid aqueous solution (3wt%) and stirred at room temperature for 2h to obtain a chitosan solution. Then, 0.8g of modified polymer was added to 160g of chitosan solution and stirred. The mixture was reacted at 40℃ for 2h, and then 0.96g of calcium phytate was added. The mixture was reacted at 65℃ for another 8h. After cooling and filtration, the mixture was washed with 20g of distilled water until neutral and dried at 60℃ for 16h to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0061] A nitrogen-phosphorus synergistic bifunctional flame retardant is a supported flame retardant. The carrier is a core-shell complex of a chitosan-coated modified polymer, the loading material is a polyphosphate (calcium phytate), and the modified polymer is a sodium tripolyphosphate-modified phytic acid-melamine supramolecular polymer.

[0062] A high-efficiency flame-retardant β-crystalline polypropylene material modified with a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0063] The preparation method of high-efficiency flame-retardant β-crystalline polypropylene material includes the following steps: adding nitrogen-phosphorus high-synergistic dual-functional flame retardant to polypropylene at an addition amount of 10wt%, mixing evenly, melting and blending at 170℃, and finally cooling and granulating to obtain high-efficiency flame-retardant β-crystalline polypropylene material.

[0064] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in flame retardant materials, including high-efficiency flame retardant β-crystalline polypropylene materials.

[0065] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in modified polypropylene.

[0066] Application of high-efficiency flame-retardant β-crystalline polypropylene materials in flame-retardant products.

[0067] Flame retardant products include flame retardant building materials, flame retardant industrial products, and flame retardant injection molded products.

[0068] Example 3

[0069] This embodiment provides a method for preparing a nitrogen-phosphorus highly synergistic bifunctional flame retardant, the specific steps of which are as follows:

[0070] First, dissolve 3g of melamine in 300g of deionized water, then add 0.25g of phytic acid aqueous solution (65wt%) and react at 60℃ for 0.5h to obtain a phytic acid-melamine supramolecular polymer emulsion. Then add 0.6g of sodium hexametaphosphate to the emulsion and continue the reaction at 90℃ for 4h. After standing, filter, and wash several times with 30g of anhydrous ethanol until the filtrate is neutral. Dry at 95℃ for 12h to obtain the modified polymer.

[0071] Next, 1.5g of chitosan was added to 180g of acetic acid aqueous solution (1wt%) and stirred at room temperature for 1.2h to obtain a chitosan solution. Then, 0.5g of modified polymer was added to 150g of chitosan solution and stirred. The mixture was reacted at 30℃ for 3h, and then 0.5g of manganese phytate was added. The mixture was reacted at 50℃ for another 5.5h. After cooling and filtration, the mixture was washed with 20g of distilled water until neutral and dried at 50℃ for 24h to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0072] A nitrogen-phosphorus synergistic bifunctional flame retardant is a supported flame retardant. The carrier is a core-shell complex of a chitosan-coated modified polymer, the loading material is a polyphosphate (manganese phytate), and the modified polymer is a sodium hexametaphosphate-modified phytic acid-melamine supramolecular polymer.

[0073] A high-efficiency flame-retardant β-crystalline polypropylene material modified with a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0074] The preparation method of high-efficiency flame-retardant β-crystalline polypropylene material includes the following steps: adding nitrogen-phosphorus high-synergistic dual-functional flame retardant to polypropylene at an addition amount of 15wt%, mixing evenly, melting and blending at 185℃, and finally cooling and granulating to obtain high-efficiency flame-retardant β-crystalline polypropylene material.

[0075] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in flame retardant materials, including high-efficiency flame retardant β-crystalline polypropylene materials.

[0076] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in modified polypropylene.

[0077] Application of high-efficiency flame-retardant β-crystalline polypropylene materials in flame-retardant products.

[0078] Flame retardant products include flame retardant building materials, flame retardant industrial products, and flame retardant injection molded products.

[0079] Example 4

[0080] This embodiment provides a method for preparing a nitrogen-phosphorus highly synergistic bifunctional flame retardant, the specific steps of which are as follows:

[0081] First, dissolve 3g of melamine in 300g of deionized water, then add 0.25g of phytic acid aqueous solution (65wt%) and react at 60℃ for 0.5h to obtain a phytic acid-melamine supramolecular polymer emulsion. Then add 0.6g of ammonium polyphosphate to the emulsion and continue to react at 90℃ for 4h. After standing, filter, and wash several times with 30g of anhydrous ethanol until the filtrate is neutral. Dry at 95℃ for 24h to obtain the modified polymer.

[0082] Next, 1.5g of chitosan was added to 180g of citric acid aqueous solution (1wt%) and stirred at room temperature for 1.2h to obtain a chitosan solution. Then, 0.5g of modified polymer was added to 150g of chitosan solution and stirred. The mixture was reacted at 30℃ for 3h, and then 0.5g of manganese phytate was added. The mixture was reacted at 50℃ for another 5.5h. After cooling and filtration, the mixture was washed with 20g of distilled water until neutral and dried at 50℃ for 18h to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0083] A nitrogen-phosphorus synergistic bifunctional flame retardant is a supported flame retardant. The carrier is a core-shell composite of chitosan-coated modified polymer, the loading material is a polyphosphate (manganese phytate), and the modified polymer is a phytic acid-melamine supramolecular polymer modified with ammonium polyphosphate.

[0084] A high-efficiency flame-retardant β-crystalline polypropylene material modified with a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0085] The preparation method of high-efficiency flame-retardant β-crystalline polypropylene material includes the following steps: adding nitrogen-phosphorus high-synergistic dual-functional flame retardant to polypropylene at an addition amount of 20wt%, mixing evenly, melting and blending at 200℃, and finally cooling and granulating to obtain high-efficiency flame-retardant β-crystalline polypropylene material.

[0086] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in flame retardant materials, including high-efficiency flame retardant β-crystalline polypropylene materials.

[0087] Application of a nitrogen-phosphorus synergistic bifunctional flame retardant in modified polypropylene.

[0088] Application of high-efficiency flame-retardant β-crystalline polypropylene materials in flame-retardant products.

[0089] Flame retardant products include flame retardant building materials, flame retardant industrial products, and flame retardant injection molded products.

[0090] Example 5

[0091] This embodiment provides a method for preparing a nitrogen-phosphorus highly synergistic bifunctional flame retardant, the specific steps of which are as follows:

[0092] First, dissolve 2g of melamine in 500g of deionized water, then add 0.25g of phytic acid aqueous solution (50wt%) and react at 95℃ for 2h to obtain a phytic acid-melamine supramolecular polymer emulsion. Then add 0.8g of sodium tripolyphosphate to the emulsion and continue the reaction at 70℃ for 4.5h. Let it stand, filter, and wash several times with 30g of anhydrous ethanol until the filtrate is neutral. Dry at 60℃ for 12h to obtain the modified polymer.

[0093] Next, 2g of chitosan was added to 180g of acetic acid aqueous solution (3wt%) and stirred at room temperature for 2h to obtain a chitosan solution. Then, 0.8g of modified polymer was added to 160g of chitosan solution and stirred. The mixture was reacted at 30℃ for 2h, and then 0.96g of manganese phytate was added. The mixture was reacted at 40℃ for another 5h. After cooling and filtration, the mixture was washed with 20g of distilled water until neutral and dried at 60℃ for 14h to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0094] Example 6

[0095] This embodiment provides a method for preparing a nitrogen-phosphorus highly synergistic bifunctional flame retardant, the specific steps of which are as follows:

[0096] First, 1g of melamine was dissolved in 220g of deionized water, and then 0.1g of phytic acid aqueous solution (70wt%) was added. The mixture was reacted at 80℃ for 3h to obtain a phytic acid-melamine supramolecular polymer emulsion. Then, 0.25g of sodium hexametaphosphate was added to the emulsion, and the mixture was reacted at 84℃ for another 6h. After standing, the mixture was filtered, and washed several times with 30g of anhydrous ethanol until the filtrate was neutral. The mixture was then dried at 75℃ for 15h to obtain the modified polymer.

[0097] Next, 1g of chitosan was added to 100g of citric acid aqueous solution (1.5wt%) and stirred at room temperature for 1h to obtain a chitosan solution. Then, 0.2g of modified polymer was added to 30g of chitosan solution and stirred. The mixture was reacted at 30℃ for 2h, and then 0.1g of zinc phytate was added. The mixture was reacted at 60℃ for another 7h. After cooling and filtration, the mixture was washed with 20g of distilled water until neutral and dried at 80℃ for 16h to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0098] Example 7

[0099] This embodiment provides a method for preparing a nitrogen-phosphorus highly synergistic bifunctional flame retardant, the specific steps of which are as follows:

[0100] First, 1g of melamine was dissolved in 220g of deionized water, and then 0.1g of phytic acid aqueous solution (70wt%) was added. The mixture was reacted at 80℃ for 3h to obtain a phytic acid-melamine supramolecular polymer emulsion. Then, 0.25g of sodium hexametaphosphate was added to the emulsion, and the reaction was continued at 84℃ for 6h. After standing, the mixture was filtered, and washed several times with 30g of anhydrous ethanol until the filtrate was neutral. The filtrate was then dried at 75℃ for 14h to obtain the modified polymer. Second, 1g of chitosan was added to 100g of citric acid aqueous solution (1.5wt%), and stirred at room temperature for 1h to obtain a chitosan solution. Then, 0.2g of the modified polymer was added to 30g of chitosan solution, stirred, and reacted at 30℃ for 2h. Then, 0.1g of calcium phytate was added, and the reaction was continued at 60℃ for 7h. After cooling and filtration, the mixture was washed with 20g of distilled water until neutral and dried at 80℃ for 12h to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0101] Comparative Example 1

[0102] The zinc phytate in Example 1 was replaced with pentaerythritol, as follows: First, 1g of melamine was dissolved in 220g of deionized water, and then 0.1g of phytic acid aqueous solution (70wt%) was added. The mixture was reacted at 80°C for 3h to obtain a phytic acid-melamine supramolecular polymer emulsion. Then, 0.25g of ammonium polyphosphate was added to the emulsion, and the mixture was reacted at 84°C for 6h. After standing, the mixture was filtered, and washed several times with 30g of anhydrous ethanol until the filtrate was neutral. The mixture was then dried at 75°C for 18h to obtain the modified polymer. Next, 1g of chitosan was added to 100g of acetic acid aqueous solution (1.5wt%) and stirred at room temperature for 1h to obtain a chitosan solution. Then, 0.2g of modified polymer was added to 30g of chitosan solution and stirred. The mixture was reacted at 20℃ for 4h, and then 0.1g of pentaerythritol was added. The mixture was reacted at 60℃ for another 7h. After cooling and filtration, the mixture was washed with 20g of distilled water until neutral and dried at 80℃ for 12h to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

[0103] Then, the flame retardant is added to polypropylene at a dosage of 10 wt%, mixed evenly, melt-blended at 160°C, and finally cooled and granulated to obtain flame-retardant modified polypropylene high-efficiency flame-retardant β-crystalline polypropylene material.

[0104] Comparative Example 2

[0105] The immobilization of calcium phytate on the core-shell composite of chitosan-coated modified polymer in Example 2 is omitted, and the remaining steps are the same as in Example 2; then, the flame retardant is added to polypropylene at an addition amount of 10 wt%, mixed evenly, melt-blended at 170°C, and finally cooled and granulated to obtain flame-retardant modified polypropylene high-efficiency flame-retardant β-crystalline polypropylene material.

[0106] Comparative Example 3

[0107] The modification of phytic acid-melamine supramolecular polymer by sodium hexametaphosphate in Example 3 is omitted, and the remaining steps are the same as in Example 3; then, the flame retardant is added to polypropylene at an addition amount of 15 wt%, mixed evenly, melt-blended at 185°C, and finally cooled and granulated to obtain flame-retardant modified polypropylene high-efficiency flame-retardant β-crystalline polypropylene material.

[0108] Comparative Example 4

[0109] The chitosan coating of the modified polymer and the immobilization of manganese phytate in Example 4 are omitted, and the remaining steps are the same as in Example 4; then the flame retardant is added to the polypropylene at an addition amount of 20 wt%, and after being mixed evenly, it is melt-blended at 200°C, and finally cooled and granulated to obtain the flame-retardant modified polypropylene high-efficiency flame-retardant β-crystalline polypropylene material.

[0110] The flame-retardant modified polypropylene prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to performance testing. Specifically, the limiting oxygen index was tested using an oxygen indexer 1600 according to GB / T2406-2009; the flammability was tested using a horizontal and vertical flammability tester CZF-5A according to UL94 standards; the impact strength was tested using a digital display simplified support impact testing machine XJJS-50 according to GB / T18743.1-2022; the heat distortion temperature was tested using a heat distortion temperature measuring instrument HDT / V-111 according to GB / T 1634.2-2004; and the crystallization temperature was tested using a differential scanning calorimeter DSC-600 according to GB / T 19466.3-2004. The content of β-crystal form in the polypropylene material was calculated using the Turner-Jone empirical formula.

[0111] The specific test results are shown in Table 1 below:

[0112] Table 1: Physical property test results of PP materials prepared in Examples 1-4 and Comparative Examples 1-4

[0113]

[0114]

[0115] Table 1 shows the flame retardancy, mechanical properties, heat distortion temperature, and crystallization temperature of the polypropylene modified with the above-mentioned nitrogen-phosphorus synergistic bifunctional flame retardant. It can be seen that the flame-retardant modified polypropylene of the present invention possesses excellent flame retardant properties and good mechanical properties.

[0116] Data from Example 1 and Comparative Example 1 show that replacing zinc phytate with pentaerythritol worsened the flame retardant properties of the polypropylene material. The LOI value decreased from 29.4% to 28.3%, the flame retardant rating decreased from UL 94V-1 to UL 94V-0, and the notched impact strength decreased from 45.3 KJ / m.2 It dropped to 29.4 KJ / m 2 The flame retardant and mechanical properties of polypropylene materials both decreased. The crystallization temperature of polypropylene decreased from 118℃ to 109℃, the heat distortion temperature decreased from 132℃ to 119℃, and the β-crystal nucleation rate decreased from 69.8% to 18.7%. This indicates that, compared to pentaerythritol, the zinc phytate immobilized on the core-shell composite of the chitosan-coated modified polymer significantly improved the β-crystal nucleation rate in polypropylene materials, and had a beneficial effect on the heat distortion temperature and crystallization temperature.

[0117] Data from Example 2 and Comparative Example 2 show that omitting the "immobilization of calcium phytate on the core-shell composite of chitosan-coated modified polymer" deteriorates the flame retardant properties of the polypropylene material. The LOI value decreases from 29.6% to 25.3%, the flame retardant rating decreases from UL 94V-1 to UL 94V-0, and the notched impact strength decreases from 48.7 KJ / m. 2 It dropped to 27.4 KJ / m 2 The flame retardant and mechanical properties of polypropylene materials both decreased. The crystallization temperature of polypropylene materials decreased from 120℃ to 107℃, the heat distortion temperature decreased from 133℃ to 115℃, and the β-crystal nucleation rate decreased from 71.1% to 17.9%. This indicates that the immobilization of calcium phytate on the core-shell composite significantly improved the β-crystal nucleation rate in polypropylene materials, and had a beneficial effect on the heat distortion temperature and crystallization temperature.

[0118] Data from Example 3 and Comparative Example 3 show that omitting the modification of phytic acid-melamine supramolecular polymer with sodium hexametaphosphate resulted in a deterioration in the flame retardant properties of the polypropylene material. The LOI value decreased from 31.7% to 25.4%, and the flame retardant rating dropped from UL94V-2 to UL 94V-0. This indicates that the modification of phytic acid-melamine supramolecular polymer with sodium hexametaphosphate significantly improved the flame retardant properties of polypropylene. The simply supported notched impact strength decreased from 44.6 KJ / m. 2 It dropped to 27.9 KJ / m 2 Furthermore, the heat distortion temperature and crystallization temperature of polypropylene materials also decreased. In addition, omitting the modification of phytic acid-melamine supramolecular polymers by sodium hexametaphosphate, it can be seen that the crystallization temperature, heat distortion temperature, and β-crystal nucleation rate of polypropylene all decreased. This indicates that the modification of phytic acid-melamine supramolecular polymers by sodium hexametaphosphate also plays a role in improving the β-crystal nucleation rate in polypropylene materials.

[0119] The difference between Example 4 and Comparative Example 4: The chitosan coating of the modified polymer and the immobilization of manganese phytate in Example 4 are omitted. Data from Example 4 and Comparative Example 4 show that omitting the "chitosan coating of the modified polymer and the immobilization of manganese phytate on the core-shell composite obtained after chitosan coating" deteriorates the flame retardant properties of the polypropylene material. The LOI value decreases from 32.9% to 28.7%, the flame retardant rating decreases from UL 94V-2 to UL 94V-0, and the notched impact strength decreases from 44.4 KJ / m. 2 It dropped to 21.7 KJ / m 2 The flame retardant and mechanical properties of polypropylene materials both decreased. Furthermore, omitting the steps of "coating the modified polymer with chitosan and immobilizing manganese phytate on the core-shell composite obtained after chitosan coating," it can be seen that the crystallization temperature, heat distortion temperature, and β-crystal nucleation rate of polypropylene all decreased, by 14℃, 17℃, and 55.7%, respectively. This indicates that "coating the modified polymer with chitosan and immobilizing manganese phytate on the core-shell composite obtained after chitosan coating" plays a beneficial role in improving flame retardant properties, mechanical properties, and β-crystal nucleation rate.

[0120] Figure 1 This is a schematic diagram of the reaction principle of the present invention.

[0121] Figure 2 The images show scanning electron microscope (SEM) images of the intermediate products during the preparation of the nitrogen-phosphorus synergistic bifunctional flame retardant in Example 1. As can be seen from the images, after modification with ammonium polyphosphate, the layered MPA mainly exhibits an irregular cubic morphology characteristic of ammonium polyphosphate. However, unlike ammonium polyphosphate, the surface of the modified A-MPA is relatively rough. After layer-by-layer assembly and immobilization, the deposition of zinc phytate particles on the outer layer of the prepared A-MPA@CS@PA-Zn is clearly visible, indicating the successful preparation of the nitrogen-phosphorus synergistic bifunctional flame retardant.

[0122] Figure 3 The figures show the infrared spectra of the intermediate products during the preparation of the nitrogen-phosphorus synergistic bifunctional flame retardant in Example 1. It can be seen from the figures that the infrared spectrum of A-MPA@CS@PA-Zn is significantly different from that of A-MPA@CS, and is closer to the infrared spectrum of PA-Zn at 3100 cm⁻¹. -1 A distinct -NH4 group appeared on the left and right sides. + The vibration peak is at 1500 cm⁻¹ -1 A distinct vibrational peak of -P=O appeared on the left and right sides, at 1100 cm⁻¹. -1 The presence of distinct -PO vibration peaks on the left and right sides indicates that zinc phytate was successfully immobilized on A-MPA@CS.

[0123] Figure 4The figures show the thermogravimetric (TG) spectra of various intermediate products during the preparation of the nitrogen-phosphorus synergistic bifunctional flame retardant in Example 1. The figures show that the modification with ammonium polyphosphate significantly improved the thermal stability of MPA, while also increasing the char residue. After treatment with the synergist polyphosphate, compared to A-MPA, its initial thermal stability was slightly reduced, but the thermal stability in the later stages and the final char residue were significantly improved.

[0124] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0125] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0126] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A nitrogen-phosphorus highly synergistic bifunctional flame retardant, characterized in that, This includes a supported flame retardant, wherein the carrier is a core-shell composite of a modified polymer coated with chitosan, the loading is a polyphosphate, and the modified polymer is a polyphosphate-modified phytic acid-melamine supramolecular polymer; the polyphosphate is ammonium polyphosphate, sodium hexametaphosphate, or sodium tripolyphosphate, and the polyphosphate is zinc phytate, calcium phytate, or manganese phytate; the mass ratio of polyphosphate to melamine in the preparation of the modified polymer is 1:2.5–5, and the mass ratio of the modified polymer to the polyphosphate is 1:0.5–1.2; the preparation method of the nitrogen-phosphorus synergistic bifunctional flame retardant is as follows: phytic acid-melamine supramolecular polymer (MPA) is prepared by ion complexation, and then modified with polyphosphate to obtain the modified polymer (A-MPA). By utilizing the electrostatically driven self-assembly between chitosan (CS) and modified polymer (A-MPA), a chitosan-coated modified polymer core-shell material was obtained; and a nitrogen-phosphorus synergistic bifunctional flame retardant was obtained by immobilizing polyphosphates in the chitosan-coated modified polymer core-shell material.

2. The preparation method of the nitrogen-phosphorus synergistic bifunctional flame retardant according to claim 1, characterized in that, Includes the following steps: Step a: Melamine is added to a reaction vessel, and deionized water is added at a mass ratio of melamine to deionized water of 1:100-250 to obtain a melamine aqueous solution. Then, phytic acid aqueous solution with a mass fraction of 50wt%-70wt% is added to the melamine aqueous solution at a mass ratio of phytic acid aqueous solution to melamine of 1:8-12. The reaction is carried out at 60-95℃ for 0.5-3h to obtain a phytic acid-melamine supramolecular polymer emulsion. Then, polyphosphate is added to the phytic acid-melamine supramolecular polymer emulsion at a mass ratio of polyphosphate to melamine of 1:2.5-5. The reaction is carried out at 70-90℃ for 4-6h, allowed to stand, filtered, washed with anhydrous ethanol until neutral, and dried at 60-95℃ for 12-24h to obtain the modified polymer. Step b: Prepare an aqueous solution of organic acid with a mass fraction of 1wt%–3wt%. Add chitosan at a mass ratio of chitosan to the aqueous solution of organic acid of 1:90–120, and stir at room temperature for 1–2 hours to obtain a chitosan solution. Add modified polymer at a mass ratio of modified polymer to chitosan solution of 1:150–300, stir, and react at 20–40°C for 2–4 hours. Add polyphosphate at a mass ratio of modified polymer to polyphosphate of 1:0.5–1.2, stir, and react at 40–65°C for 5–8 hours. Cool, filter, wash with distilled water until neutral, and dry at 50–80°C for 12–24 hours to obtain a nitrogen-phosphorus synergistic bifunctional flame retardant.

3. The preparation method according to claim 2, characterized in that, The polyphosphate is ammonium polyphosphate, the polyphosphate is zinc phytate, and the organic acid is acetic acid.

4. The preparation method according to claim 3, characterized in that: In step a, the amounts of melamine, deionized water, 70wt% phytic acid aqueous solution, and ammonium polyphosphate added are 1g, 220g, 0.1g, and 0.25g, respectively; the phytic acid-melamine reaction is carried out at 80℃ for 3h, and after adding ammonium polyphosphate, the reaction is carried out at 84℃ for 6h; in step b, 1g of chitosan is added to 100g of 1.5wt% acetic acid aqueous solution, and 30g of the resulting chitosan solution is added to 0.2g of modified polymer, reacted at 20℃ for 4h, and then 0.1g of zinc phytate is added, reacted at 60℃ for 7h, cooled, filtered, washed with 20g of distilled water until neutral, and dried at 80℃ for 12h.

5. A high-efficiency flame-retardant β-crystalline polypropylene material, characterized in that, The material comprises polypropylene and 10wt% to 20wt% of the nitrogen-phosphorus synergistic bifunctional flame retardant of claim 1; the material has a β-crystal content of 69.8% to 76.2%, a heat distortion temperature of 115 to 120°C, a crystallization temperature of 129 to 133°C, and an LOI of 29.4% to 32.9%.

6. The method for preparing the high-efficiency flame-retardant β-crystalline polypropylene material according to claim 5, characterized in that, The nitrogen-phosphorus synergistic bifunctional flame retardant is added to polypropylene at an addition amount of 10wt% to 20wt%, mixed evenly, melt-blended at 160 to 200°C, and then cooled and granulated to obtain the high-efficiency flame-retardant β-crystal polypropylene material.

7. The application of the nitrogen-phosphorus synergistic bifunctional flame retardant of claim 1 as both a flame retardant and a β-crystal nucleating agent in polypropylene materials.

8. The application according to claim 7, characterized in that, The amount of the nitrogen-phosphorus synergistic bifunctional flame retardant added to the polypropylene material is 10wt% to 20wt%.

9. The application of the high-efficiency flame-retardant β-crystalline polypropylene material according to claim 5 in flame-retardant products.

10. The application according to claim 9, characterized in that, The flame-retardant products include flame-retardant building materials, industrial flame-retardant products, or injection-molded flame-retardant products.

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