Preparation method and application of high-efficiency low-toxicity flame retardant

Abstract

The invention discloses a preparation method and application of a high-efficiency and low-toxicity flame retardant, and relates to the technical field of flame retardant synthesizing.According to the method, phosphorus oxychloride and diethylene glycol react to generate an intermediate, then a modified catalyst is used for catalyzing the ring-opening addition reaction of the intermediate and epoxypropane, a polyphosphate framework is constructed in an oriented mode, and the high-efficiency and low-toxicity flame retardant is obtained. Finally, a high-quality flame retardant product is obtained through a post-treatment procedure. According to the invention, a supported modified catalyst system is adopted, gallium trichloride and other Lewis acid catalysts are uniformly anchored on the surfaces of chitosan, mordenite, alpha-cyclodextrin, lignin or shellac and other carriers through coordination, and the catalytic selectivity and reaction efficiency are significantly improved. The flame retardant prepared by the preparation method has the advantages of efficient flame retardance, high product purity and low toxicity.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of flame retardant synthesis, in particular to a preparation method and application of a high-efficiency low-toxicity flame retardant. BACKGROUND

[0002] In recent years, the global environmental governance system has been continuously improved, and countries have successively introduced strict regulations to limit the use of traditional halogen-containing flame retardants. The core problem of these flame retardants is that they are prone to release corrosive and highly toxic gases during combustion, which not only seriously harms human health, but also exacerbates environmental pollution and rescue difficulties at the fire scene. As a key category of phosphorus-containing flame retardants, dialkyl phosphate esters have been widely used in plastic processing, rubber modification, coating preparation and other industrial fields due to their excellent flame retardant efficiency, reliable thermal stability and good adaptability to various polymer substrates, becoming one of the core additives for improving the safety performance of polymer materials.

[0003] Under this background, the research and application of green and environmentally friendly flame retardants have become the core direction of industry transformation. Phosphorus-containing flame retardants gradually become the preferred category to replace traditional halogen-containing flame retardants due to their high efficiency and low smoke and low toxicity. Among them, chlorinated alkyl phosphate esters further strengthen the flame retardant effect through the synergistic flame retardant effect of phosphorus and chlorine elements in the molecular structure, effectively reducing the smoke and toxic gas release during combustion, which meets the current development concept of giving equal weight to environmental protection and safety, and the market application demand shows a continuous growth trend.

[0004] However, the current mainstream preparation process of chlorinated alkyl phosphate esters is still mainly based on traditional solvent method. This process generally uses benzene compounds or halogenated hydrocarbons as reaction media. This preparation process not only has strong volatility, high toxicity and non-degradability, but also causes serious air, water and soil pollution through volatilization, emission and other ways during production. At the same time, the raw material phosphorus oxychloride is chemically active and easily hydrolyzed with water to generate ineffective by-products and cause raw material loss, so strict water control of the reaction system is required, increasing the difficulty and cost of production operation; the ring-opening addition reaction of propylene oxide is a key step in the preparation process, which has high requirements for the activity and selectivity of the catalyst. However, the current catalysts generally have problems such as uneven dispersion of active sites and easy agglomeration and deactivation during the reaction, which directly leads to low product yield and insufficient purity, and easily causes side reactions such as molecular crosslinking and carbon chain rupture, further damaging the molecular structure integrity of the product and reducing the product quality.

[0005] In particular, in the production process of electronic and electrical precision components, the polymer material used needs to be added with a flame retardant to meet the fire safety standard, and such components are usually used in the internal part of smart phones, notebook computers and other precision electronic equipment, which has a closed working environment, a small space and is in a long-term power-on heating state. If the purity of the flame retardant is insufficient, the impurities in it will affect the mechanical properties and insulation properties of the polymer material, which may cause the components to crack, insulation failure and other problems during use, causing equipment failure and even safety hazards; if the water content exceeds the standard, it will cause bubbles, pinholes and other defects in the internal part of the polymer material, and may also accelerate the hydrolysis aging of the material, shorten the service life of the component; as a by-product with potential toxicity, if the residual TCPP in the flame retardant exceeds the standard, it will be slowly released during the long-term use and heating of the electronic equipment, which not only pollutes the environment, but also may cause chronic harm to human health through breathing, contact and other ways. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of high-efficiency low-toxicity flame retardant, and the flame retardant prepared by the method has good purity and low TCPP content.

[0007] In a first aspect, the present application provides a preparation method of high-efficiency low-toxicity flame retardant, which adopts the following technical scheme: A preparation method of high-efficiency low-toxicity flame retardant, comprising the following steps: S1, mixing phosphorus oxychloride, diethylene glycol and a first solvent, heating and stirring to obtain an intermediate; S2, adding a first solvent, a modified catalyst and propylene oxide to the intermediate in step S1, and passing in an inert gas, heating and stirring to obtain a multi-mixed product; S3, distilling the multi-mixed product in step S2, recycling the distillate, collecting the residue to obtain a primary mixed product; S4, centrifuging the primary mixed product in step S3, recycling the solid, retaining the liquid to obtain a primary product; washing and drying the primary product to obtain the high-efficiency low-toxicity flame retardant; The first solvent is a lactam compound; the modified catalyst is prepared by loading a catalyst active component on a carrier rich in hydroxyl and carboxyl polar groups.

[0008] By employing the above technical solution, in step S1, the phosphoryl chloride group in phosphorus oxychloride reacts with the hydroxyl groups at both ends of the diethylene glycol molecule to generate a phosphorus- and oxygen-containing intermediate. In step S2, the modified catalyst support is combined with the active catalyst component, effectively dispersing the active sites. The residual hydroxyl groups in the catalytic intermediate undergo a ring-opening addition reaction with the epoxy groups of propylene oxide, directionally constructing a polyphosphate ester framework. The synergistic effect of the phosphorus-oxygen bond and carbon chain in this structure is the core mechanism for the product's high-efficiency flame retardancy. Distillation and centrifugation steps remove low-boiling-point impurities and solid residues, respectively, and enable the recycling and reuse of raw materials. Subsequent washing and drying further remove residual moisture and trace impurities. The selective catalytic effect of the modified catalyst significantly reduces the formation of toxic byproducts such as TCPP. The molecular structure design of the product improves flame retardancy efficiency while reducing toxicity. The overall process, through a combination of functional group-directed reactions, catalytic regulation, and stepwise steps, achieves the goal of efficient, low-toxicity, and environmentally friendly preparation.

[0009] Optionally, the modified catalyst in step S2 includes: a catalyst and a support; the mass ratio of the catalyst to the support is 1:(0.4-10).

[0010] By adopting the above technical solution, the polar functional groups such as hydroxyl and carboxyl groups contained in the support can form stable coordination bonds with the active components of the catalyst, uniformly anchoring the catalyst on the support surface and avoiding local reaction imbalance caused by the aggregation of active sites. This mass ratio ensures that the support sufficiently disperses the catalyst, maximizing the exposure of active sites, while avoiding excessive shielding of active sites or the introduction of impurities by the support. The modified catalyst can catalyze the directional reaction between intermediates and propylene oxide, inhibit the formation of byproducts such as TCPP, improve product purity and flame retardant efficiency, and ensure the core performance of low toxicity and stability of the product.

[0011] Optionally, the carrier is any one of chitosan, mordenite, α-cyclodextrin, lignin, and shellac.

[0012] By employing the above technical solutions, both chitosan and lignin are natural bio-based carriers, possessing excellent biocompatibility and environmental friendliness. Their surfaces are rich in polar functional groups such as hydroxyl and carboxyl groups, enabling stable coordination with the active components of the catalyst. Lignin has a more rigid structure and slightly better anchoring stability for the active components, while chitosan is easier to dissolve and disperse, offering greater flexibility in compatibility. Mordenite, as an inorganic carrier, has a regular pore structure and a large specific surface area, which not only efficiently disperses active sites and prevents aggregation but also possesses excellent thermal and chemical stability, allowing it to adapt to more demanding reaction conditions. α-Cyclodextrin's unique advantage lies in its cavity structure, which can precisely encapsulate and anchor the active components of the catalyst, significantly improving catalytic selectivity and reducing side reactions. Shellac, with its excellent film-forming properties, can form a protective film on the catalyst surface, effectively reducing the loss of active sites, while its surface polar groups ensure stable coordination with the active components.

[0013] Optionally, the catalyst is any one of aluminum trichloride, indium trichloride, and gallium trichloride.

[0014] By employing the above-mentioned technical solutions, aluminum trichloride, indium trichloride, and gallium trichloride are all highly efficient Lewis acid catalysts that can precisely catalyze the ring-opening addition reaction between the residual hydroxyl group of the intermediate and the epoxy group of propylene oxide, thus directionally constructing a polyphosphate ester framework. Among them, aluminum trichloride exhibits strong catalytic activity and readily available raw materials, making it suitable for conventional reaction conditions; indium trichloride and gallium trichloride demonstrate superior stability and stronger catalytic selectivity, and can further suppress the formation of toxic byproducts. Indium trichloride exhibits a milder catalytic reaction and good compatibility with the reaction system; gallium trichloride, on the other hand, demonstrates outstanding performance in balancing activity and selectivity.

[0015] Optionally, the preparation method of the modified catalyst includes the following steps: The catalyst is added to the second solvent, then the support is added, the mixture is stirred, refluxed, filtered, washed, and dried under vacuum to obtain the modified catalyst; the second solvent is an alcohol.

[0016] By employing the above technical solution, the second solvent can fully dissolve the catalyst, providing a uniform environment for its interaction with the support. The stirring and reflux processes enhance the contact between the two, promoting the formation of stable coordination bonds between the polar functional groups such as hydroxyl and carboxyl groups on the support surface and the active components of the catalyst, thus achieving uniform anchoring of active sites. The filtration and washing steps effectively remove unbound free catalyst and impurities, avoiding interference with active sites or an increase in side reactions in subsequent reactions. Vacuum drying thoroughly removes moisture and residual solvent from the system, preventing moisture from damaging the bonding stability between the catalyst and the support, while maximizing the exposure of active sites. The overall process gives the modified catalyst better dispersibility, stability, and catalytic selectivity, providing a reliable guarantee for the targeted execution of the target reaction.

[0017] Optionally, the mass ratio of phosphorus oxychloride to diethylene glycol is 1:(0.6-0.9).

[0018] By employing the above technical solution, this mass ratio ensures a complete and directional reaction between the phosphoryl chloride group of phosphorus oxychloride and the hydroxyl groups at both ends of diethylene glycol. This ratio range allows for precise matching of the functional groups of both materials, avoiding side reactions caused by an excess of one raw material. It prevents incomplete reaction and residual phosphoryl chloride groups when diethylene glycol is insufficient, and also prevents excess hydroxyl groups from interfering with subsequent ring-opening addition reactions when diethylene glycol is excessive. This allows for the directional generation of a phosphorus- and oxygen-containing intermediate with a uniform structure, providing a stable precursor for the subsequent construction of the polyphosphate ester framework and ensuring the efficient formation of the flame-retardant core structure.

[0019] Optionally, the mass ratio of the intermediate, propylene oxide, and modified catalyst is 1:(1.12-2):(0.05-0.1).

[0020] By employing the above technical solution, this mass ratio enables precise matching of the functional groups of the intermediate and propylene oxide, and the amount of modified catalyst ensures that propylene oxide is present in sufficient quantity to undergo a ring-opening addition reaction with the intermediate. Sufficient propylene oxide can drive the reaction to proceed completely towards the formation of the polyphosphate ester framework, thereby suppressing side reactions. Simultaneously, a reasonable ratio ensures the regular formation of the polymer structure, laying the structural foundation for the product's highly efficient flame-retardant properties.

[0021] Optionally, the heating temperature in step S1 is 30-50℃; the heating temperature in step S2 is 135-150℃; and the centrifugation speed in step S4 is 400-800 rpm, and the centrifugation time is 10-30 min.

[0022] By adopting the above technical solution, step S1 at this temperature can gently drive the directional reaction between phosphoryl chloride groups and hydroxyl groups, ensuring the formation of intermediates while avoiding excessive reaction or decomposition of phosphorus oxychloride caused by high temperatures, thus reducing byproducts. In step S2, this temperature can activate the activity of epoxy groups, matching the catalytic activity range of the modified catalyst, promoting the efficient ring-opening addition of residual hydroxyl groups in the intermediate with propylene oxide, while simultaneously promoting the directional construction of the polyphosphate ester skeleton, ensuring reaction completeness and product structural regularity; furthermore, this centrifugation speed and time can better achieve solid-liquid separation.

[0023] Optionally, the stirring rate in steps S1 and S2 is 300-600 rpm; the stirring time in step S1 is 3-5 h; and the stirring time in step S2 is 4-6 h.

[0024] By adopting the above technical solution, the stirring rate can enhance the reaction efficiency between reactants, so that the raw materials can fully contact and be evenly dispersed, providing sufficient collision opportunities for functional group reactions; the stirring time in step S1 is sufficient to ensure that the phosphoryl chloride group and hydroxyl group fully react to generate a structurally uniform intermediate, avoiding raw material residue; the stirring time in step S2 matches the reaction time of the ring-opening addition reaction, promoting the directional construction of the polyphosphate ester skeleton.

[0025] A method for preparing a high-efficiency, low-toxicity flame retardant and its application in the fields of polyurethane flexible foam materials and electronic and electrical equipment.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. Compared with existing technologies, the modified catalyst prepared by combining the support and the catalyst can achieve stable coordination between the polar functional groups on the support surface and the active components of the catalyst, realizing uniform anchoring and dispersion of active sites and avoiding local reaction imbalance caused by the aggregation of active sites. It can precisely catalyze the directional ring-opening addition reaction of intermediates and propylene oxide, effectively suppress the formation of toxic byproducts such as TCPP, while improving the conversion rate of raw materials and reducing ineffective losses; 2. Compared with existing technologies, the synergistic effect of the raw material preparation process and the modified catalyst can significantly improve the overall performance of flame retardants. Reasonable raw material ratio and reaction condition control, combined with the highly selective catalysis of the modified catalyst, can directionally construct a well-structured polyphosphate ester skeleton and enhance the synergistic flame retardant effect of phosphorus and chlorine. The subsequent stepwise purification process such as distillation and centrifugation, combined with catalytic control, can effectively remove impurities and moisture, reduce TCPP residue, and finally obtain a high-purity, low-toxicity flame retardant product. Attached Figure Description

[0027] Figure 1 This is the infrared absorption spectrum of Example 7. Detailed Implementation

[0028] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this application are commercially available products: Gallium trichloride, part number: CD128349, Codow; Mercerized zeolite, product number: T22818-500g, Yuan Ye; Lignin, product number: HY-W250112, MedChemExpress (MCE); The commercially available products were purchased from Daihachi Chemical Industry Co., Ltd. in Japan. Example 1

[0029] A method for preparing a high-efficiency, low-toxicity flame retardant includes the following steps: The first step is to prepare the modified catalyst.

[0030] 1 kg of gallium trichloride was added to 200 mL of 50 wt% ethanol solution (second solvent) to obtain the first mixture. 0.4 kg of α-cyclodextrin was added to the first mixture to obtain the second mixture. The second mixture was stirred at 500 rpm and refluxed for 24 h, then cooled to 25 °C to obtain the third mixture. The third mixture was filtered to obtain a solid, which was washed twice each with 1.5 kg of chloroform and 1.5 kg of diethyl ether. The product from the final ether wash was dried at 40 °C and 0.08 MPa vacuum for 24 h to obtain the modified catalyst.

[0031] The second step is to prepare a highly efficient and low-toxicity flame retardant.

[0032] 10 kg of phosphorus oxychloride, 8 kg of diethylene glycol, and 8 kg of N-ethylpyrrolidone (the first solvent) were mixed to obtain a fourth mixture. The fourth mixture was heated to 40°C and stirred at 500 rpm for 4 hours to obtain an intermediate.

[0033] 10 kg of N-ethylpyrrolidone, 0.77 kg of modified catalyst, and 15 kg of propylene oxide were added to 10 kg of intermediate to obtain a fifth mixture. Nitrogen gas was introduced into the fifth mixture, and the mixture was heated to 140 °C and stirred at 500 rpm for 5 h to obtain a multi-mixed product.

[0034] The mixed products were then distilled at 210℃ for 6 hours, and the distillate was recovered. The distillate was then adsorbed onto activated carbon for 2 hours and reused. The residue after distillation was collected to obtain the initial mixed product. The initial mixed product was centrifuged at 500 rpm for 20 minutes, and the solid was recovered. It was washed twice with N-ethylpyrrolidone and purged with nitrogen at 110℃ for 2 hours for reuse. The liquid after centrifugation was retained to obtain the primary product. The primary product was washed twice with water, then twice with 2wt% sodium hydroxide solution, and finally once with water. The primary product after the final water wash was dried at 60℃ and 0.08 MPa vacuum for 24 hours to obtain the high-efficiency, low-toxicity flame retardant. Example 2

[0035] The difference between Example 2 and Example 1 is that 0.4 kg of α-cyclodextrin in Example 1 is replaced with 2.5 kg of α-cyclodextrin. Example 3

[0036] The difference between Example 3 and Example 1 is that 0.4 kg of α-cyclodextrin in Example 1 is replaced with 5 kg of α-cyclodextrin. Example 4

[0037] The difference between Example 4 and Example 1 is that 0.4 kg of α-cyclodextrin in Example 1 is replaced with 10 kg of α-cyclodextrin. Example 5

[0038] The difference between Example 5 and Example 3 is that 5 kg of α-cyclodextrin in Example 3 is replaced with 5 kg of mordenite. Example 6

[0039] The difference between Example 6 and Example 3 is that 5 kg of α-cyclodextrin in Example 3 is replaced with 5 kg of lignin. Example 7

[0040] The difference between Example 7 and Example 3 is that 0.4 kg of α-cyclodextrin in Example 3 is replaced with 0.4 kg of shellac. Example 8

[0041] The difference between Example 8 and Example 3 is that 0.4 kg of α-cyclodextrin in Example 3 is replaced with 0.4 kg of chitosan. Comparative Example 1

[0042] The difference between Comparative Example 1 and Example 1 is that the 0.4 kg α-cyclodextrin in Example 1 is replaced with 0.1 kg α-cyclodextrin. Comparative Example 2

[0043] The difference between Comparative Example 2 and Example 3 is that 5 kg of α-cyclodextrin in Example 3 was replaced with 5 kg of montmorillonite. Comparative Example 3

[0044] The difference between Comparative Example 3 and Example 7 is that unmodified gallium trichloride was used in Comparative Example 3. Comparative Example 4

[0045] The high-efficiency, low-toxicity flame retardant in Comparative Example 4 is a commercially available product.

[0046] Test Example 1 Product purity test: The purity of the high-efficiency and low-toxicity flame retardants prepared in Examples 1-8 and Comparative Examples 1-4 was tested by high performance liquid chromatography-evaporative light scattering detection (HPLC-ELSD). The test results are shown in Table 1.

[0047] Moisture test: Automatic micro-moisture analyzer; adjust the instrument according to the instrument manual and set it aside. Use a 100μL precision micro-syringe to draw 60μL of sample, turn on the measurement button of the automatic micro-moisture analyzer, inject the sample, and after the titration is completed, read the value and calculate the moisture content of the sample. The test results are shown in Table 1.

[0048] TCPP content test: The TCPP content of the products prepared in Examples 1-8 and Comparative Examples 1-4 was tested by gas chromatography-mass spectrometry (GC-MS), and the test results are shown in Table 1.

[0049]

[0050] A comparative analysis of Examples 1-4 and Comparative Example 1 revealed that the product prepared in Example 3 exhibited better overall performance in terms of product purity, moisture content, and TCPP content. This performance difference is likely due to the different mass ratio of catalyst to support. The mass ratio of catalyst to support can regulate the dispersion of catalyst active sites and the reaction microenvironment, thus influencing the overall product performance. As the dispersion medium for the catalyst, insufficient support can lead to catalyst agglomeration and uneven distribution of active sites. This not only reduces the selectivity of the target reaction and promotes the formation of the byproduct TCPP, but also generates more impurities due to intense local reactions, reducing product purity. Furthermore, a small amount of support has limited adsorption capacity and cannot effectively remove moisture generated in the reaction system, resulting in increased moisture content. When the amount of support is appropriate, uniform dispersion of catalyst active sites can be achieved, enhancing the directional catalytic effect of the target reaction and reducing side reactions. Sufficient support surface area can also efficiently remove moisture and some impurities from the system through physical adsorption, synergistically improving product purity. If the amount of support is too high, excessive support can easily create a shielding effect on the active sites, reducing catalytic efficiency. Furthermore, trace impurities adsorbed by the support itself may be introduced into the system, slightly degrading product purity and moisture control. Therefore, the catalyst-to-support mass ratio in Example 3 is optimal, resulting in better overall performance of the product prepared in Example 3.

[0051] Comparative analysis of Examples 5-8 and Comparative Example 2 revealed that the product prepared in Example 7 exhibited better overall performance in terms of purity, moisture content, and TCPP content. This performance difference may be attributed to the use of different carriers. Shellac possesses a dense cross-linked network structure and abundant polar functional groups. The hydroxyl and carboxyl groups on its molecular chain can form stable coordination with gallium trichloride, uniformly anchoring and dispersing the catalyst's active sites, preventing local reaction imbalances caused by active site aggregation. Simultaneously, its porous structure exhibits strong adsorption selectivity, accurately capturing moisture and TCPP precursors in the reaction system, significantly reducing impurity residues. While chitosan contains amino and hydroxyl coordination groups, its linear structure has less steric hindrance, resulting in slightly poorer dispersion stability of active sites compared to shellac. Furthermore, its wider pore size distribution leads to slightly weaker selective adsorption capacity for moisture and byproducts. Mordenite, with its regular microporous molecular sieve structure, provides some space for active site dispersion, but its strong hydrophobic properties result in weak interaction with polar catalysts. Furthermore, its microporous structure is easily blocked by reaction intermediates, leading to decreased water removal efficiency. Lignin, with its amorphous and loose structure, has a small specific surface area and low surface functional group activity, making it difficult to effectively disperse catalysts. It is also prone to degradation, generating trace impurities, and has limited adsorption capacity, making it unable to effectively control moisture and byproduct content. While montmorillonite's layered structure can support catalysts, its weak interlayer forces lead to easy delamination during the reaction, causing catalyst loss and aggregation. Moreover, its surface adsorption is primarily physical adsorption, resulting in poor adsorption stability for moisture and byproducts, ultimately degrading product performance. Therefore, the product prepared using shellac in Example 7 exhibits better performance.

[0052] A comparative analysis of Example 7 and Comparative Example 3 revealed that the product prepared in Example 7 exhibited better overall performance. This performance difference is likely due to the catalyst modification in Example 7, which was absent in Comparative Example 3. The core difference between catalyst modification and non-modification lies in the regulation of active sites and the system's purification capacity. Unmodified gallium trichloride is prone to aggregation, resulting in uneven distribution of active sites, poor catalytic selectivity, and a tendency to trigger side reactions that generate TCPP. Furthermore, it cannot adsorb moisture within the system, leading to a higher level of impurities and moisture residue. After modification with shellac, shellac can anchor and uniformly disperse catalytic active sites through coordination, enhancing the directionality of the target reaction and inhibiting the formation of byproducts. Simultaneously, the polar functional groups and porous structure of shellac can adsorb moisture within the system, reducing impurity residue and thus improving product purity while lowering moisture and TCPP content.

[0053] A comparative analysis of Example 7 and Comparative Example 4 revealed that the product prepared by this method exhibits better overall performance than commercially available products. This method utilizes specific products and preparation methods to prepare the modified catalyst. The cross-linked network and polar functional groups of shellac can uniformly anchor catalytic active sites, enhancing the directionality of the target reaction, inhibiting the formation of TCPP products, and simultaneously efficiently adsorbing moisture and impurities within the system. Commercially available products likely employ unmodified catalytic systems, where catalyst aggregation leads to poor catalytic selectivity, numerous side reactions, and a lack of targeted impurity and moisture removal control during preparation, resulting in higher levels of impurities, moisture, and TCPP residues in the product.

[0054] Test Example 2 According to the amendments to Annex II of the EU RoHS Directive 011 / 65 / EU (EU) 2015 / 863 - lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, polybrominated diphenyl ethers, di(2-ethylhexyl) phthalate, butyl benzyl phthalate, dibutyl phthalate and diisobutyl phthalate, the product prepared in Example 7 met the requirements.

[0055] Based on the European Chemicals Agency's candidate list of Substances of Very High Concern (SVHCs) for authorization consideration published as of June 27, 2024 (in accordance with EU Regulation 1907 / 2006 REACH), 241 SVHCs were screened and tested. The product prepared in Example 7 passed the test.

[0056] Based on the European Chemicals Agency's list of substances of very high concern (SVHCs) (in accordance with EU Regulation 1907 / 2006 REACH), 11 potential SVHCs were screened. The product prepared in Example 7 passed the test.

[0057] Analysis was performed using ICP-OES / AAS, UV-Vis, and GC-MS. The test results are shown in Table 2.

[0058]

[0059]

[0060] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing a high-efficiency, low-toxicity flame retardant, characterized in that, Includes the following steps: S1. Phosphorus oxychloride, diethylene glycol and the first solvent are mixed, heated and stirred to obtain an intermediate; S2. Add the first solvent, modified catalyst, and propylene oxide to the intermediate in step S1, introduce an inert gas, heat, and stir to obtain a mixed product. S3. Distill the mixed product from step S2, recover the distillate, collect the residue, and obtain the initial mixed product. S4. Centrifuge the initial mixture from step S3, recover the solids and retain the liquid to obtain the initial product; wash and dry the initial product to obtain the high-efficiency and low-toxicity flame retardant. The first solvent is a lactam compound; the modified catalyst is prepared by loading the catalyst active component onto a support rich in hydroxyl and carboxyl polar groups.

2. The method for preparing the high-efficiency, low-toxicity flame retardant according to claim 1, characterized in that, The modified catalyst in step S2 includes: a catalyst and a support; the mass ratio of the catalyst to the support is 1:(0.4-10).

3. The method for preparing the high-efficiency, low-toxicity flame retardant according to claim 2, characterized in that, The carrier is any one of chitosan, mordenite, α-cyclodextrin, lignin, and shellac.

4. The method for preparing the high-efficiency, low-toxicity flame retardant according to claim 2, characterized in that, The catalyst is any one of aluminum trichloride, indium trichloride, and gallium trichloride.

5. The method for preparing the high-efficiency, low-toxicity flame retardant according to claim 1, characterized in that, The method for preparing the modified catalyst includes the following steps: The catalyst is added to the second solvent, then the support is added, the mixture is stirred, refluxed, filtered, washed, and dried under vacuum to obtain the modified catalyst; the second solvent is an alcohol.

6. The method for preparing the high-efficiency, low-toxicity flame retardant according to claim 1, characterized in that, The mass ratio of phosphorus oxychloride to diethylene glycol is 1:(0.6-0.9).

7. The method for preparing the high-efficiency, low-toxicity flame retardant according to claim 1, characterized in that, The mass ratio of the intermediate, propylene oxide, and modified catalyst is 1:(1.12-2):(0.05-0.1).

8. The method for preparing the high-efficiency, low-toxicity flame retardant according to claim 1, characterized in that, The heating temperature in step S1 is 30-50℃; the heating temperature in step S2 is 135-150℃; the centrifugation speed in step S4 is 400-800 rpm, and the centrifugation time is 10-30 min.

9. The method for preparing the high-efficiency, low-toxicity flame retardant according to claim 1, characterized in that, The stirring rate in steps S1 and S2 is 300-600 rpm; the stirring time in step S1 is 3-5 h, and the stirring time in step S2 is 4-6 h.

10. The application of a high-efficiency, low-toxicity flame retardant prepared by the method described in any one of claims 1-9 in the fields of polyurethane flexible foam materials and electronic and electrical equipment.

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