Outdoor high-efficiency flame retardant additive and preparation method thereof

Abstract

This invention relates to a high-efficiency outdoor flame retardant additive, its preparation method, and its application, belonging to the field of polymer material additives technology. This high-efficiency flame retardant additive has N,N'-di(3-aminopropyl)-1,2-ethylenediamine as its main chain, linked with dialkoxy-monochlorotriazine, containing six N-cyclohexyloxy hindered amine groups, with a purity ≥99.5% and a total yield ≥80%. It is prepared from 2,2,6,6-tetramethylpiperidone nitroxide radical, cyclohexane, etc., via N-cyclohexyloxylation, reductive amination, N-acylation, and nucleophilic substitution reactions. Adding 0.5~3.0 wt% of this stabilizer to polypropylene materials can impart UL-94 VTM-0 flame retardancy and excellent photothermal stability. Furthermore, the preparation process is low-cost and environmentally friendly, solving the technical problems of easy deactivation of hindered amines, functional separation of additives, and low yield in traditional synthesis processes. It is suitable for polypropylene fibers, films, nonwoven fabrics, and other polyolefin products.

Description

Technical Field

[0001] This invention relates to an outdoor high-efficiency flame retardant additive, its preparation method and application, belonging to the field of flame retardant material technology. It is particularly suitable for outdoor polymer materials such as polypropylene, polyethylene, and engineering plastics that need to simultaneously meet the requirements of flame retardancy, anti-photoaging and weather resistance. It can be applied to the modification of outdoor pipes, sunshade materials, outdoor engineering components and other products. Background Technology

[0002] With the widespread application of polymer materials in construction, transportation, outdoor facilities and other fields, the safety hazards caused by their flammability are becoming increasingly prominent. In outdoor use scenarios, materials also need to withstand complex environmental factors such as ultraviolet radiation, high temperature and humidity, and wind and rain erosion, which puts forward comprehensive requirements for flame retardancy, aging resistance, weather resistance and low migration.

[0003] Polyolefin materials are widely used in automotive interiors, photovoltaic encapsulation, architectural films, and nonwoven fabrics due to their low cost and excellent processing performance. However, polyolefin materials are flammable and release a large amount of heat and smoke when burning, so they need to be modified to be flame-retardant. At the same time, polyolefin materials are susceptible to aging and degradation under ultraviolet light and heat-oxidation when used outdoors, so light stabilizers need to be added to improve weather resistance.

[0004] Hindered amine light stabilizers (HALS) are the mainstream UV stabilizers for polyolefin materials. However, traditional HALS are mostly NH-type high-alkalinity tetramethylpiperidine derivatives. When used in combination with halogenated or phosphorus-containing flame retardants, the acidic substances produced by the decomposition of the flame retardant during processing or use can react with HALS to form ammonium salts with no light-stabilizing activity. These ammonium salts easily migrate to the material surface, leading to a significant decrease in the material's UV resistance. Furthermore, traditional polymeric additives are mostly designed for single functions. Adding flame retardants and light stabilizers separately can easily result in poor compatibility and insufficient synergy, affecting the overall performance of the material.

[0005] N-substituted alkoxy hindered amines (NORs), as low-alkaline non-reactive light stabilizers, can effectively avoid deactivation caused by acidic substances. Furthermore, studies have found that they also possess flame-retardant properties, providing a new direction for the development of halogen-free, environmentally friendly, and multifunctional polymeric additives. However, the current synthesis of NOR-type hindered amines suffers from cumbersome processes, low raw material conversion rates, difficulty in impurity control, and large emissions of waste. Therefore, developing a high-yield, high-purity, low-cost process for preparing N-alkoxy hindered amines with both flame-retardant and light-stabilizing functions, and achieving domestic substitution, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an outdoor high-efficiency flame retardant additive and its preparation method. This high-efficiency flame retardant additive combines high flame retardancy with long-term photothermal stability, low alkalinity, halogen-free, low smoke, good compatibility with polyolefin materials, and excellent extraction resistance. Its preparation process uses inexpensive cyclohexane as an alkylating agent, optimizes reaction parameters, improves product yield and purity, reduces production costs, and is equipped with a complete environmental protection system to meet industrial emission standards. The low addition amount of this stabilizer can significantly improve the flame retardancy and aging resistance of polyolefin materials, meeting the application requirements of outdoor polymer materials.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: An outdoor high-efficiency flame retardant additive, with N,N'-bis(3-aminopropyl)-1,2-ethylenediamine (tetraamine) as the main chain, is linked to a diekoxy-chlorotriazine unit in the molecule, contains 6 N-cyclohexyloxy hindered amine groups, and has a molecular weight of 2261. This stabilizer is a white granular substance with the following physicochemical properties: purity ≥99.5%, total yield ≥80%, melting range 108~123℃, flash point >110℃, and vapor pressure of 1×10⁻⁻⁻⁻⁻⁶ at 20℃. 4 Pa, dynamic viscosity at 20℃: 85~90 mPa・s, water solubility at 20℃: <40 ppb, 1% weight loss temperature: 260℃, 10% weight loss temperature: 285℃; this stabilizer has low alkalinity, does not interact with hindered amine light stabilizers, can be melt-processed, and will not reduce the ductility and mechanical properties of polyolefin materials.

[0008] The preparation method of the above-mentioned high-efficiency outdoor flame retardant additive uses 2,2,6,6-tetramethylpiperidone nitroxide radical, cyclohexane, n-butylamine, cyanuric chloride, and N,N'-di(3-aminopropyl)-1,2-ethylenediamine as raw materials, and synthesizes them through N-cyclohexyloxylation, reductive amination, N-acylation, and nucleophilic substitution reactions. The specific steps are as follows: (1) Synthesis of intermediate 1: Using 2,2,6,6-tetramethylpiperidone nitroxide radical as raw material, cyclohexane as alkylating agent, tert-butyl hydroperoxide (TBHP) as oxidant, and cuprous chloride as catalyst, N-cyclohexyloxylation was achieved through radical reaction; the reaction temperature was controlled at ≥40℃, the amount of cuprous chloride catalyst was 2~3wt%, the molar ratio of tert-butyl hydroperoxide to 2,2,6,6-tetramethylpiperidone nitroxide radical was 3.5:1, and the reaction time was 16h to obtain intermediate 1. The reaction yield of this step was 86%. (2) Synthesis of intermediate 2: The intermediate 1 obtained in step (1) is subjected to a reducing amination reaction with n-butylamine in a certain ratio to introduce an amino functional group and obtain an amino-containing intermediate 2. (3) Synthesis of intermediate 3: The intermediate 2 obtained in step (2) is subjected to N-acylation reaction with cyanuric chloride in a certain ratio to obtain dialkoxychlorotriazine intermediate 3; (4) Synthesis of target product: The intermediate 3 obtained in step (3) is subjected to nucleophilic substitution reaction with N,N'-bis(3-aminopropyl)-1,2-ethylenediamine in an optimized ratio. This reaction is a substitution reaction of the third chlorine atom on the cyanuric chloride molecule. It is carried out under high temperature conditions to overcome the steric hindrance effect, suppress the generation of mono- and di-substituted by-products, and improve the selectivity and purity of the target product. After separation, purification and granulation, an outdoor high-efficiency flame retardant additive is obtained.

[0009] The above-mentioned outdoor high-efficiency flame retardant additives are applied by adding the stabilizer to polypropylene materials at a ratio of 0.5~3.0wt%, and then processing them through twin-screw extrusion granulation, blow molding or spinning to prepare polypropylene fibers, non-woven fabrics, films or tapes. The optimal addition amount for preparing polypropylene films is 2.0wt%, and the addition amount for preparing polypropylene fibers and non-woven fabrics is 0.5~1.5wt%. Beneficial effects

[0010] The outdoor high-efficiency flame retardant additive of this invention is a monomolecular high molecular weight hindered amine containing 6 N-cyclohexyloxy hindered amine groups. It integrates flame retardant and photothermal stabilization functions. Its low alkalinity structure can avoid deactivation by acidic substances decomposed by flame retardants, solving the technical problem of activity loss when traditional hindered amine light stabilizers are compounded with flame retardants. Its molecular weight reaches 2261, which has excellent extraction resistance. It can play a long-term role in thin products such as films and fibers. It is halogen-free, low-smoke, non-toxic and odorless, meeting environmental protection requirements.

[0011] The preparation process of this invention uses inexpensive cyclohexane instead of traditional expensive alkylating reagents. Through single-factor experiments, the reaction temperature, catalyst dosage, oxidant molar ratio, and reaction time of intermediate 1 synthesis were optimized, and the optimal process parameters were determined, resulting in an intermediate 1 yield of 86% and a total target product yield of over 80%, far exceeding the 50% of existing technologies. The product purity is ≥99.5%, and it is white granular, which is superior to similar grayish-white products with a purity of 99% from abroad. Its 1% weight loss temperature reaches 260℃, and its thermal stability is better. At the same time, it significantly reduces raw material and production costs.

[0012] The preparation process of this invention effectively suppresses the formation of mono- and di-substituted byproducts by optimizing the temperature and molar ratio of the nucleophilic substitution reaction, thereby improving the selectivity and purity of the target product. The process route is simple and can achieve multi-scale step-by-step scale-up, from laboratory pilot-scale to stability experiments in a 5L reactor, pilot-scale scale-up in 50-100L, and finally to ton-scale industrial mass production. Moreover, it adopts a closed, pipelined, and automated production scheme, making the production process safe and controllable.

[0013] The preparation process of this invention is equipped with a complete environmental protection system. Wastewater treatment adopts a combination process of "physicochemical pretreatment + biochemical treatment", and tail gas is treated by a three-stage absorption and purification tower. Hazardous waste is managed in accordance with national standards. The discharge of waste gas, wastewater, and solid waste complies with the "Emission Standard of Pollutants for Petrochemical Industry" (GB 31571-2015), which solves the problem of large discharge of waste gas, wastewater, and solid waste in traditional synthesis processes and realizes green industrial production.

[0014] The stabilizer of this invention exhibits good compatibility with polyolefin materials, requiring only 0.5~3.0 wt% addition. It does not reduce the material's ductility or mechanical properties during melt processing. When added to polypropylene materials, it significantly improves their flame retardancy and UV aging resistance. A 2.0 wt% addition can achieve the highest UL-94 VTM-0 flame retardancy rating for polypropylene films. The heat release rate and total heat release are significantly reduced, and the loss of mechanical properties after UV aging is also significantly minimized. It can be widely used in polypropylene fibers, nonwoven fabrics, films, tapes, and other products, achieving domestic substitution, breaking the foreign technological monopoly, and possessing significant industrial application value.

[0015] The preparation process of this invention is simple to operate, and the process parameters of each step are easy to control. The stability of product performance is ensured by step-by-step pretreatment and segmented temperature-controlled melt blending. It is suitable for large-scale industrial production and can be widely used in the modification of various outdoor polymer materials such as polypropylene, polyethylene, and engineering plastics, with broad application prospects. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0017] Example 1: Synthesis of Intermediate 1 Using 2,2,6,6-tetramethylpiperidone nitroxide radicals as starting material, cyclohexane as the alkylating agent, tert-butyl hydroperoxide as the oxidant, and cuprous chloride as the catalyst, an N-cyclohexyloxylation radical reaction was carried out. The reaction temperature was controlled at 45℃, the amount of cuprous chloride catalyst was 3wt%, the molar ratio of tert-butyl hydroperoxide to 2,2,6,6-tetramethylpiperidone nitroxide radicals was 3.5:1, and the reaction time was 16 h. After the reaction, intermediate 1 was obtained by extraction, washing, drying, separation and purification. The yield of intermediate 1 was 86%, and its chemical structure was characterized by infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and mass spectrometry, which were consistent with the target structure.

[0018] Example 2: Synthesis of Intermediate 2 and Intermediate 3 Intermediate 1 obtained in Example 1 was added to a reaction vessel at a molar ratio of 1:1.2 with n-butylamine. Anhydrous ethanol was added as a solvent, and a reductive amination reaction was carried out at 80°C for 8 hours. After the reaction, the intermediate 2 containing an amino group was obtained by distillation, separation and purification. Its chemical structure was characterized to be consistent with the target structure. The above intermediate 2 and cyanuric chloride were added to a reactor at a molar ratio of 2:1 and N-acylation reaction was carried out under low temperature conditions for 6 hours. After the reaction was completed, the intermediate 3 was obtained by washing, filtering and drying. Its chemical structure was characterized to be consistent with the target structure.

[0019] Example 3 Synthesis of High-Efficiency Outdoor Flame Retardant Additive Intermediate 3 obtained in Example 2 was added to a reactor at a molar ratio of 3.2:1 with N,N'-bis(3-aminopropyl)-1,2-ethylenediamine. The mixture was heated to 120°C for a nucleophilic substitution reaction for 10 hours with a stirring rate of 300 r / min throughout. After the reaction, the mixture was desolvated, recrystallized, dried, and granulated to obtain a white granular N-alkoxy hindered amine flame retardant light stabilizer. The product was tested and found to have a purity of 99.6%, a total yield of 81%, a melting range of 109-122°C, a 1% weight loss temperature of 262°C, and a dynamic viscosity of 87 mPa·s at 20°C. All physicochemical properties met the requirements of this invention. Its chemical structure was characterized by infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and mass spectrometry, and was consistent with the target structure.

[0020] Example 4: Preparation and Performance Testing of Polypropylene Film The outdoor high-efficiency flame retardant additive obtained in Example 3 was added to polypropylene powder at a ratio of 2.0 wt%. After granulation by twin-screw extrusion (extrusion temperature 180~200℃), it was blow-molded into a polypropylene film with a thickness of 0.2 mm. At the same time, a pure polypropylene film without the added stabilizer was prepared as a blank control, and its performance was tested according to national standards. Flame retardant performance: According to GB / T 2406.2, the limiting oxygen index of this polypropylene film is 25.8%, while that of pure polypropylene film is 16.7%; according to GB / T 2408, the UL-94 vertical burning rating of this polypropylene film is VTM-0; according to ISO 5660 standard, the peak heat release rate of this polypropylene film is 59.8% lower than that of pure polypropylene film, and the total heat release is 62.7% lower than that of pure polypropylene film. UV aging resistance: The film was placed in an accelerated UV aging chamber with a UV wavelength of 334nm, a power of 0.83W / m², and a chamber temperature of 50℃. After irradiation for 20 days, the tensile strength was measured according to GB / T 1040, and the impact strength was measured according to GB / T1843. The tensile strength of the polypropylene film decreased by 11.3%, and the impact strength decreased by 13.1%, with no obvious yellowing on the surface; the tensile strength of the pure polypropylene film decreased by 18.3%, and the impact strength decreased by 36.9%, with obvious yellowing on the surface. Mechanical properties: The tensile strength and tear strength of this polypropylene film are slightly lower than those of pure polypropylene film, with a variation range of ≤5%, which has a limited impact on the mechanical properties of the matrix material.

[0021] Example 5: Preparation and performance testing of polypropylene fibers The outdoor high-efficiency flame retardant additive prepared in Example 3 was added to polypropylene powder at a ratio of 1.0 wt%, and polypropylene fibers were obtained by melt spinning (spinning temperature 220~240℃). The fibers were then woven into knitted socks. The flame retardant performance of the knitted socks was significantly improved after flame retardant performance testing. In addition, the fibers passed the conventional performance test and showed that they had good photothermal stability and extraction resistance. They were halogen-free, low-smoke, non-toxic and odorless.

[0022] This invention can be summarized in other specific forms that do not depart from the spirit or essential features of the invention. Therefore, in all respects, the above embodiments of the invention should be considered illustrative only and not limiting, while the claims define the scope of the invention. The foregoing description does not define the scope of the invention; therefore, any changes within the meaning and scope equivalent to the claims should be considered to be included within the scope of the claims.

Claims

1. An outdoor high-efficiency flame retardant additive, characterized in that, It has N,N'-bis(3-aminopropyl)-1,2-ethylenediamine as the main chain, with dicalkoxy-1,2-chlorotriazine linked in the molecule and containing 6 N-cyclohexyloxy hindered amine groups.

2. The preparation method of the outdoor high-efficiency flame retardant additive as described in claim 1, characterized in that, Using 2,2,6,6-tetramethylpiperidone nitroxide radical, cyclohexane, n-butylamine, cyanuric chloride, and N,N'-bis(3-aminopropyl)-1,2-ethylenediamine as raw materials, the following steps were performed to synthesize the following: 1) Synthesis of intermediate 1: 2,2,6,6-Tetramethylpiperidone nitroxide radical was prepared by N-cyclohexyloxylation reaction using cyclohexane as the alkylating agent, tert-butyl hydroperoxide as the oxidant, and cuprous chloride as the catalyst. The reaction conditions were: temperature ≥40℃, cuprous chloride dosage 2~3wt%, tert-butyl hydroperoxide to 2,2,6,6-tetramethylpiperidone nitroxide radical molar ratio 3.5:1, and reaction time 16h. 2) Synthesis of intermediate 2: intermediate 1 is prepared by reductive amination with n-butylamine; 3) Synthesis of intermediate 3: intermediate 2 is prepared by N-acylation reaction with cyanuric chloride; 4) Synthesis of the target product: Intermediate 3 is prepared by nucleophilic substitution reaction with N,N'-bis(3-aminopropyl)-1,2-ethylenediamine. This reaction is a substitution reaction of the third chlorine atom on the cyanuric chloride molecule and is carried out under high temperature conditions.

3. The preparation method of the outdoor high-efficiency flame retardant additive as described in claim 2, characterized in that, The amount of cuprous chloride used in step 1) is 3 wt%.

4. The application of the outdoor high-efficiency flame retardant additive as described in claim 1, characterized in that, The stabilizer is added to polypropylene materials at a ratio of 0.5 to 3.0 wt% for the preparation of polypropylene fibers, nonwoven fabrics, films, or tapes.